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Sensors, Volume 9, Issue 3 (March 2009), Pages 1295-2221

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Open AccessArticle Role of SAM Chain Length in Enhancing the Sensitivity of Nanopillar Modified Electrodes for Glucose Detection
Sensors 2009, 9(3), 1295-1305; doi:10.3390/s90301295
Received: 27 January 2009 / Revised: 24 February 2009 / Accepted: 24 February 2009 / Published: 26 February 2009
Cited by 18 | PDF Full-text (464 KB) | HTML Full-text | XML Full-text
Abstract
In this report, alkanethiol self assembled monolayers (SAM) with two different chain lengths were used to immobilize the functionalizing enzyme (glucose oxidase) onto gold nanopillar modified electrodes and the electrochemical processes of these functionalized electrodes in glucose detection were investigated. First, the [...] Read more.
In this report, alkanethiol self assembled monolayers (SAM) with two different chain lengths were used to immobilize the functionalizing enzyme (glucose oxidase) onto gold nanopillar modified electrodes and the electrochemical processes of these functionalized electrodes in glucose detection were investigated. First, the formation of these SAMs on the nanopillar modified electrodes was characterized by the cyclic voltammetry and electrochemical impedance spectroscopy techniques, and then the detection sensitivity of these functionalized electrodes to glucose was evaluated by the amperometry technique. Results showed that the SAM of alkanethiols with a longer chain length resulted in a higher degree of surface coverage with less defect and a higher electron transfer resistance, whereas the SAM of alkanethiols with a shorter chain length gave rise to a higher detection sensitivity to glucose. This study sheds some new insight into how to enhance the sensing performance of nanopillar modified electrodes. Full article
Open AccessArticle Observing and Studying Extreme Low Pressure Events with Altimetry
Sensors 2009, 9(3), 1306-1329; doi:10.3390/s90301306
Received: 29 December 2008 / Revised: 1 February 2009 / Accepted: 24 February 2009 / Published: 26 February 2009
Cited by 2 | PDF Full-text (1438 KB) | HTML Full-text | XML Full-text
Abstract
The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant [...] Read more.
The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant along-track sea surface height (SSH) signal: the case of tropical cyclone Isabel is presented here. The S- and C-band measurements are used because they are less impacted by rain than the Ku-band, and new sea state bias (SSB) and wet troposphere corrections are proposed. More accurate strong altimeter wind speeds are computed thanks to the Young algorithm. Ocean signals not related to atmospheric pressure can be removed with accuracy, even within a Near Real Time context, by removing the maps of sea level anomaly (SLA) provided by SSALTO/Duacs. In the case of Extra-Tropical Depressions, the classical altimeter processing can be used. Ocean signal not related to atmospheric pressure is along-track filtered. The sea level pressure (SLP)-SLA relationship is investigated for the North Atlantic, North Pacific and Indian oceans; three regression models are proposed allowing restoring an altimeter SLP with a mean error of 5 hPa if compared to ECMWF or buoys SLP. The analysis of barotropic simulation outputs points out the regional variability of the SLP/Model Sea Level relationship and the wind effects. Full article
(This article belongs to the Special Issue Ocean Remote Sensing)
Open AccessArticle An Electromagnetically Excited Silicon Nitride Beam Resonant Accelerometer
Sensors 2009, 9(3), 1330-1338; doi:10.3390/s90301330
Received: 26 January 2009 / Revised: 16 February 2009 / Accepted: 23 February 2009 / Published: 26 February 2009
Cited by 13 | PDF Full-text (228 KB) | HTML Full-text | XML Full-text
Abstract
A resonant microbeam accelerometer of a novel highly symmetric structure based on MEMS bulk-silicon technology is proposed and some numerical modeling results for this scheme are presented. The accelerometer consists of two proof masses, four supporting hinges, two anchors, and a vibrating [...] Read more.
A resonant microbeam accelerometer of a novel highly symmetric structure based on MEMS bulk-silicon technology is proposed and some numerical modeling results for this scheme are presented. The accelerometer consists of two proof masses, four supporting hinges, two anchors, and a vibrating triple beam, which is clamped at both ends to the two proof masses. LPCVD silicon rich nitride is chosen as the resonant triple beam material, and parameter optimization of the triple-beam structure has been performed. The triple beam is excited and sensed electromagnetically by film electrodes located on the upper surface of the beam. Both simulation and experimental results show that the novel structure increases the scale factor of the resonant accelerometer, and ameliorates other performance issues such as cross axis sensitivity of insensitive input acceleration, etc. Full article
Open AccessArticle Study of Interactions between Metallothionein and Cisplatin by using Differential Pulse Voltammetry Brdicka´s reaction and Quartz Crystal Microbalance
Sensors 2009, 9(3), 1355-1369; doi:10.3390/s90301355
Received: 8 October 2008 / Revised: 14 February 2009 / Accepted: 17 February 2009 / Published: 26 February 2009
Cited by 19 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text
Abstract
Treatment strategies for tumour diseases are progressively focusing on personalization of medicine. However, this focus requires methods revealing the early general biological mechanisms, including the formation anti-cancer drugs’ resistance. The low molecular mass protein metallothionein is thought to be the crucial for [...] Read more.
Treatment strategies for tumour diseases are progressively focusing on personalization of medicine. However, this focus requires methods revealing the early general biological mechanisms, including the formation anti-cancer drugs’ resistance. The low molecular mass protein metallothionein is thought to be the crucial for the formation of resistance in tumour treatment based on the platinum-cytostatics. The interactions between metallothionein (MT) and cisplatin were determined by the adsorptive transfer stripping technique coupled with the differential pulse votlammetry Brdicka´s reaction. The signals related to the MT-cisplatin complex appeared at -0.9 V. The formation of this complex depended on the time of interaction between cisplatin and MT. The complex formation was consequently confirmed by quartz crystal microbalance analyses. The formation of this complex was detectable even after a 20 s long interaction. Moreover, we detected presence of MT-cisplatin complex in the blood of male rats treated with this drug. Full article
Open AccessArticle Scaling-up Transformation of Multisensor Images with Multiple Resolutions
Sensors 2009, 9(3), 1370-1381; doi:10.3390/s90301370
Received: 18 October 2008 / Revised: 27 December 2008 / Accepted: 11 February 2009 / Published: 26 February 2009
Cited by 7 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
For scaling up low resolution multispectral images (LRMIs) with high resolution panchromatic image (HRPI), intensity-hue-saturation (IHS) can produce satisfactory spatial enhancement but usually introduces spectral distortion in the fused high resolution multispectral images (HRMIs). In this paper, to minimize this problem, we [...] Read more.
For scaling up low resolution multispectral images (LRMIs) with high resolution panchromatic image (HRPI), intensity-hue-saturation (IHS) can produce satisfactory spatial enhancement but usually introduces spectral distortion in the fused high resolution multispectral images (HRMIs). In this paper, to minimize this problem, we present a generalized intensity modulation (GIM) by extending the IHS transform to an arbitrary number of LRMIs, which uses the information of the spectral response functions (SRFs) of the multispectral and panchromatic sensors. Before modulation, the generalized intensity is enhanced by injecting details extracted from the HRPI by means of empirical mode decomposition. After the enhanced generalized intensity is substituted for the old one, the HRMIs are obtained through the GIM. Quickbird images are used to illustrate the superiority of this proposed method. Extensive comparison results based on visual analysis and Wald’s protocol demonstrate that the proposed method is more encouraging for scaling up the LRMIs with the HRPI spectrally and spatially than the tested fusion methods. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Robust Design of SAW Gas Sensors by Taguchi Dynamic Method
Sensors 2009, 9(3), 1394-1408; doi:10.3390/s90301394
Received: 31 December 2008 / Revised: 23 February 2009 / Accepted: 27 February 2009 / Published: 27 February 2009
Cited by 13 | PDF Full-text (451 KB) | HTML Full-text | XML Full-text
Abstract
This paper adopts Taguchi’s signal-to-noise ratio analysis to optimize the dynamic characteristics of a SAW gas sensor system whose output response is linearly related to the input signal. The goal of the present dynamic characteristics study is to increase the sensitivity of [...] Read more.
This paper adopts Taguchi’s signal-to-noise ratio analysis to optimize the dynamic characteristics of a SAW gas sensor system whose output response is linearly related to the input signal. The goal of the present dynamic characteristics study is to increase the sensitivity of the measurement system while simultaneously reducing its variability. A time- and cost-efficient finite element analysis method is utilized to investigate the effects of the deposited mass upon the resonant frequency output of the SAW biosensor. The results show that the proposed methodology not only reduces the design cost but also promotes the performance of the sensors. Full article
(This article belongs to the Special Issue Piezoelectric Sensors for Determination of Analytes in Solutions)
Open AccessArticle Automated Directional Measurement System for the Acquisition of Thermal Radiative Measurements of Vegetative Canopies
Sensors 2009, 9(3), 1409-1422; doi:10.3390/s90301409
Received: 9 January 2009 / Revised: 25 February 2009 / Accepted: 3 March 2009 / Published: 3 March 2009
Cited by 7 | PDF Full-text (464 KB) | HTML Full-text | XML Full-text
Abstract
The potential for directional optical and thermal imagery is very large. Field measurements have been performed with a goniometer on which thermal instruments were attached. In order to reduce dynamical effects the goniometer was adjusted to run in automated mode, for zenith [...] Read more.
The potential for directional optical and thermal imagery is very large. Field measurements have been performed with a goniometer on which thermal instruments were attached. In order to reduce dynamical effects the goniometer was adjusted to run in automated mode, for zenith and azimuthal direction. Directional measurements were performed over various crops with increasing heterogeneity. The improvements to the goniometer proved successful. For all the crops, except the vineyard, the acquisition of the directional thermal brightness temperatures of the crops went successfully. The large scale heterogeneity of the vineyard proved to be larger then the goniometer was capable of. The potential of directional thermal brightness temperatures has been proven. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Real Time Monitoring of Temperature of a Micro Proton Exchange Membrane Fuel Cell
Sensors 2009, 9(3), 1423-1432; doi:10.3390/s90301423
Received: 3 February 2009 / Revised: 27 February 2009 / Accepted: 2 March 2009 / Published: 3 March 2009
Cited by 8 | PDF Full-text (1101 KB) | HTML Full-text | XML Full-text
Abstract
Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature [...] Read more.
Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature inside the fuel cell. Experimental results demonstrate that temperature was generally linearly related to resistance and that accuracy and sensitivity were within 0.5 °C and 1.68×10-3/°C, respectively. The best experimental performance was 9.37 mW/cm2 at an H2/O2 dry gas flow rate of 30/30 SCCM. Fuel cell temperature during operation was 27 °C, as measured using thermocouples in contact with the backside of the electrode. Fuel cell operating temperature measured in situ was 30.5 °C. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Sink-oriented Dynamic Location Service Protocol for Mobile Sinks with an Energy Efficient Grid-Based Approach
Sensors 2009, 9(3), 1433-1453; doi:10.3390/s90301433
Received: 26 November 2008 / Revised: 25 February 2009 / Accepted: 26 February 2009 / Published: 3 March 2009
Cited by 18 | PDF Full-text (564 KB) | HTML Full-text | XML Full-text
Abstract
Sensor nodes transmit the sensed information to the sink through wireless sensor networks (WSNs). They have limited power, computational capacities and memory. Portable wireless devices are increasing in popularity. Mechanisms that allow information to be efficiently obtained through mobile WSNs are of [...] Read more.
Sensor nodes transmit the sensed information to the sink through wireless sensor networks (WSNs). They have limited power, computational capacities and memory. Portable wireless devices are increasing in popularity. Mechanisms that allow information to be efficiently obtained through mobile WSNs are of significant interest. However, a mobile sink introduces many challenges to data dissemination in large WSNs. For example, it is important to efficiently identify the locations of mobile sinks and disseminate information from multi-source nodes to the multi-mobile sinks. In particular, a stationary dissemination path may no longer be effective in mobile sink applications, due to sink mobility. In this paper, we propose a Sink-oriented Dynamic Location Service (SDLS) approach to handle sink mobility. In SDLS, we propose an Eight-Direction Anchor (EDA) system that acts as a location service server. EDA prevents intensive energy consumption at the border sensor nodes and thus provides energy balancing to all the sensor nodes. Then we propose a Location-based Shortest Relay (LSR) that efficiently forwards (or relays) data from a source node to a sink with minimal delay path. Our results demonstrate that SDLS not only provides an efficient and scalable location service, but also reduces the average data communication overhead in scenarios with multiple and moving sinks and sources. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
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Open AccessArticle Waveform Analysis of UWB GPR Antennas
Sensors 2009, 9(3), 1454-1470; doi:10.3390/s90301454
Received: 13 February 2009 / Revised: 23 February 2009 / Accepted: 24 February 2009 / Published: 3 March 2009
Cited by 10 | PDF Full-text (1922 KB) | HTML Full-text | XML Full-text
Abstract
Ground Penetrating Radar (GPR) systems fall into the category of ultra-wideband (UWB) devices. Most GPR equipment covers a frequency range between an octave and a decade by using short-time pulses. Each signal recorded by a GPR gathers a temporal log of attenuated [...] Read more.
Ground Penetrating Radar (GPR) systems fall into the category of ultra-wideband (UWB) devices. Most GPR equipment covers a frequency range between an octave and a decade by using short-time pulses. Each signal recorded by a GPR gathers a temporal log of attenuated and distorted versions of these pulses (due to the effect of the propagation medium) plus possible electromagnetic interferences and noise. In order to make a good interpretation of this data and extract the most possible information during processing, a deep knowledge of the wavelet emitted by the antennas is essential. Moreover, some advanced processing techniques require specific knowledge of this signal to obtain satisfactory results. In this work, we carried out a series of tests in order to determine the source wavelet emitted by a ground-coupled antenna with a 500 MHz central frequency. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Identification of Earthquake Induced Damage Areas Using Fourier Transform and SPOT HRVIR Pan Images
Sensors 2009, 9(3), 1471-1484; doi:10.3390/s90301471
Received: 3 January 2009 / Revised: 20 February 2009 / Accepted: 28 February 2009 / Published: 3 March 2009
PDF Full-text (6245 KB) | HTML Full-text | XML Full-text
Abstract
A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to [...] Read more.
A devastating earthquake with a magnitude of Mw 7.4 occurred on the North Anatolian Fault Zone (NAFZ) of Turkey on August 17, 1999 at 00:01:39 UTC (3:01 a.m. local time). The aim of this study is to propose a new approach to automatically identify earthquake induced damage areas which can provide valuable information to support emergency response and recovery assessment procedures. This research was conducted in the Adapazari inner city, covering a 3 × 3 km area, where 11,373 buildings collapsed as a result of the earthquake. SPOT high resolution visible infrared (HRVIR) Pan images obtained before (25 June 1999) and after (4 October 1999) the earthquake were used in the study. Five steps were employed to conduct the research and these are: (i) geometric and radiometric correction of satellite images, (ii) Fast Fourier Transform (FFT) of pre- and post-earthquake images and filtering the images in frequency domain, (iii) generating difference image using Inverse Fast Fourier Transform (IFFT) pre- and post- earthquake images, (iv) application of level slicing to difference image to identify the earthquake-induced damages, (v) accuracy assessment of the method using ground truth obtained from a 1/5,000 scale damage map. The total accuracy obtained in the research is 80.19 %, illustrating that the proposed method can be successfully used to automatically identify earthquake-induced damage areas. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Early Forest Fire Detection Using Radio-Acoustic Sounding System
Sensors 2009, 9(3), 1485-1498; doi:10.3390/s90301485
Received: 27 January 2009 / Revised: 17 February 2009 / Accepted: 27 February 2009 / Published: 3 March 2009
Cited by 12 | PDF Full-text (626 KB) | HTML Full-text | XML Full-text
Abstract
Automated early fire detection systems have recently received a significant amount of attention due to their importance in protecting the global environment. Some emergent technologies such as ground-based, satellite-based remote sensing and distributed sensor networks systems have been used to detect forest [...] Read more.
Automated early fire detection systems have recently received a significant amount of attention due to their importance in protecting the global environment. Some emergent technologies such as ground-based, satellite-based remote sensing and distributed sensor networks systems have been used to detect forest fires in the early stages. In this study, a radio-acoustic sounding system with fine space and time resolution capabilities for continuous monitoring and early detection of forest fires is proposed. Simulations show that remote thermal mapping of a particular forest region by the proposed system could be a potential solution to the problem of early detection of forest fires. Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
Open AccessArticle Detection of Activities by Wireless Sensors for Daily Life Surveillance: Eating and Drinking
Sensors 2009, 9(3), 1499-1517; doi:10.3390/s90301499
Received: 12 January 2009 / Accepted: 20 February 2009 / Published: 3 March 2009
Cited by 13 | PDF Full-text (794 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces a two-stage approach to the detection of people eating and/or drinking for the purposes of surveillance of daily life. With the sole use of wearable accelerometer sensor attached to somebody’s (man or a woman) wrists, this two-stage approach consists [...] Read more.
This paper introduces a two-stage approach to the detection of people eating and/or drinking for the purposes of surveillance of daily life. With the sole use of wearable accelerometer sensor attached to somebody’s (man or a woman) wrists, this two-stage approach consists of feature extraction followed by classification. At the first stage, based on the limb’s three dimensional kinematics movement model and the Extended Kalman Filter (EKF), the realtime arm movement features described by Euler angles are extracted from the raw accelerometer measurement data. In the latter stage, the Hierarchical Temporal Memory (HTM) network is adopted to classify the extracted features of the eating/drinking activities based on the space and time varying property of the features, by making use of the powerful modelling capability of HTM network on dynamic signals which is varying with both space and time. The proposed approach is tested through the real eating and drinking activities using the three dimensional accelerometers. Experimental results show that the EKF and HTM based two-stage approach can perform the activity detection successfully with very high accuracy. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle A Novel Energy-Efficient MAC Aware Data Aggregation Routing in Wireless Sensor Networks #
Sensors 2009, 9(3), 1518-1533; doi:10.3390/s90301518
Received: 4 January 2009 / Revised: 24 February 2009 / Accepted: 2 March 2009 / Published: 4 March 2009
Cited by 9 | PDF Full-text (235 KB) | HTML Full-text | XML Full-text
Abstract
Embedding data-aggregation capabilities into sensor nodes of wireless networks could save energy by reducing redundant data flow transmissions. Existing research describes the construction of data aggregation trees to maximize data aggregation times in order to reduce data transmission of redundant data. However, [...] Read more.
Embedding data-aggregation capabilities into sensor nodes of wireless networks could save energy by reducing redundant data flow transmissions. Existing research describes the construction of data aggregation trees to maximize data aggregation times in order to reduce data transmission of redundant data. However, aggregation of more nodes on the same node will incur significant collisions. These MAC (Media Access Control) layer collisions introduce additional data retransmissions that could jeopardize the advantages of data aggregation. This paper is the first to consider the energy consumption tradeoffs between data aggregation and retransmissions in a wireless sensor network. By using the existing CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) MAC protocol, the retransmission energy consumption function is well formulated. This paper proposes a novel non-linear mathematical formulation, whose function is to minimize the total energy consumption of data transmission subject to data aggregation trees and data retransmissions. This solution approach is based on Lagrangean relaxation, in conjunction with optimization-based heuristics. From the computational experiments, it is shown that the proposed algorithms could construct MAC aware data aggregation trees that are up to 59% more energy efficient than existing data aggregation algorithms. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessCommunication Synthesis, Binding and Fluorescence Studies of Bis-2-amidopyrrole Receptors for Bis-carboxylate Anions
Sensors 2009, 9(3), 1534-1540; doi:10.3390/s90301534
Received: 12 February 2009 / Revised: 27 February 2009 / Accepted: 2 March 2009 / Published: 4 March 2009
Cited by 7 | PDF Full-text (123 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The ditopic neutral receptors 1 and 2 were synthesized for the recognition and sensing of bis-carboxylates. They are based on pyrrole and amide groups as hydrogen-bond donors to bind the oxoanions of the guests. Among the obtained results, the selectivity for glutarate [...] Read more.
The ditopic neutral receptors 1 and 2 were synthesized for the recognition and sensing of bis-carboxylates. They are based on pyrrole and amide groups as hydrogen-bond donors to bind the oxoanions of the guests. Among the obtained results, the selectivity for glutarate over succinate is particularly interesting.Compound 1 behaves as a PET fluorescence sensor for glutarate. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Improving Measurement of Forest Structural Parameters by Co-Registering of High Resolution Aerial Imagery and Low Density LiDAR Data
Sensors 2009, 9(3), 1541-1558; doi:10.3390/s90301541
Received: 27 November 2008 / Revised: 2 February 2009 / Accepted: 3 February 2009 / Published: 4 February 2009
Cited by 17 | PDF Full-text (1001 KB) | HTML Full-text | XML Full-text
Abstract
Forest structural parameters, such as tree height and crown width, are indispensable for evaluating forest biomass or forest volume. LiDAR is a revolutionary technology for measurement of forest structural parameters, however, the accuracy of crown width extraction is not satisfactory when using [...] Read more.
Forest structural parameters, such as tree height and crown width, are indispensable for evaluating forest biomass or forest volume. LiDAR is a revolutionary technology for measurement of forest structural parameters, however, the accuracy of crown width extraction is not satisfactory when using a low density LiDAR, especially in high canopy cover forest. We used high resolution aerial imagery with a low density LiDAR system to overcome this shortcoming. A morphological filtering was used to generate a DEM (Digital Elevation Model) and a CHM (Canopy Height Model) from LiDAR data. The LiDAR camera image is matched to the aerial image with an automated keypoints search algorithm. As a result, a high registration accuracy of 0.5 pixels was obtained. A local maximum filter, watershed segmentation, and object-oriented image segmentation are used to obtain tree height and crown width. Results indicate that the camera data collected by the integrated LiDAR system plays an important role in registration with aerial imagery. The synthesis with aerial imagery increases the accuracy of forest structural parameter extraction when compared to only using the low density LiDAR data. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Using a LIDAR Vegetation Model to Predict UHF SAR Attenuation in Coniferous Forests
Sensors 2009, 9(3), 1559-1573; doi:10.3390/s90301559
Received: 16 December 2008 / Revised: 23 January 2009 / Accepted: 5 March 2009 / Published: 6 March 2009
Cited by 3 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
Attenuation of radar signals by vegetation can be a problem for target detection and GPS reception, and is an important parameter in models describing vegetation backscatter. Here we first present a model describing the 3D distribution of stem and foliage structure based [...] Read more.
Attenuation of radar signals by vegetation can be a problem for target detection and GPS reception, and is an important parameter in models describing vegetation backscatter. Here we first present a model describing the 3D distribution of stem and foliage structure based on small footprint scanning LIDAR data. Secondly we present a model that uses ray-tracing methodology to record detailed interactions between simulated radar beams and vegetation components. These interactions are combined over the SAR aperture and used to predict two-way attenuation of the SAR signal. Accuracy of the model is demonstrated using UHF SAR observations of large trihedral corner reflectors in coniferous forest stands. Our study showed that the model explains between 66% and 81% of the variability in observed attenuation. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
Open AccessArticle Metal-Organic Frameworks for Sensing Applications in the Gas Phase
Sensors 2009, 9(3), 1574-1589; doi:10.3390/s90301574
Received: 19 February 2009 / Revised: 4 March 2009 / Accepted: 5 March 2009 / Published: 6 March 2009
Cited by 156 | PDF Full-text (329 KB) | HTML Full-text | XML Full-text
Abstract
Several metal-organic framework (MOF) materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O2, CO2 [...] Read more.
Several metal-organic framework (MOF) materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O2, CO2, C3H8, NO, H2, ethanol and methanol in the gas atmosphere and under different test gas humidity conditions. Different sensor configurations were studied in a frequency range of 1 Hz -1 MHz and time-continuous measurements were performed at 1 Hz. The materials did not show any impedance response to O2, CO2, C3H8, NO, or H2 in the gas atmospheres, although for some materials a significant impedance decrease was induced by a change of the ethanol or methanol concentration in the gas phase. Moreover, pronounced promising and reversible changes in the electric properties of a special MOF material were monitored under varying humidity, with a linear response curve at 120 °C. Further investigations were carried out with differently doped MOF materials of this class, to evaluate the influence of special dopants on the sensor effect. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Open AccessCommunication Ultra-Fast Low Concentration Detection of Candida Pathogens Utilizing High Resolution Micropore Chips
Sensors 2009, 9(3), 1590-1598; doi:10.3390/s90301590
Received: 9 January 2009 / Revised: 26 February 2009 / Accepted: 2 March 2009 / Published: 9 March 2009
Cited by 3 | PDF Full-text (539 KB) | HTML Full-text | XML Full-text
Abstract
Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the [...] Read more.
Although Candida species are the fourth most common cause of nosocomial blood stream infections in the United States, early diagnostic tools for invasive candidemia are lacking. Due to an increasing rate of candidemia, a new screening system is needed to detect the Candida species in a timely manner. Here we describe a novel method of detection using a solid-state micro-scale pore similar to the operational principles of a Coulter counter. With a steady electrolyte current flowing through the pore, measurements are taken of changes in the current corresponding to the shape of individual yeasts as they translocate or travel through the pore. The direct ultra-fast low concentration electrical addressing of C. albicans has established criteria for distinguishing individual yeast based on their structural properties, which may reduce the currently used methods’ complexity for both identification and quantification capabilities in mixed blood samples Full article
(This article belongs to the Section Biosensors)
Open AccessCommunication Development of a Novel Method for in vivo Determination of Activation Energy of Glucose Transport Across S. cerevisiae Cellular Membranes. A Biosensor-like Approach
Sensors 2009, 9(3), 1599-1608; doi:10.3390/s90301599
Received: 12 December 2008 / Revised: 21 January 2009 / Accepted: 6 March 2009 / Published: 9 March 2009
Cited by 1 | PDF Full-text (112 KB) | HTML Full-text | XML Full-text
Abstract
Whereas biosensors have been usually proposed as analytical tools, used to investigate the surrounding media pursuing an analytical answer, we have used a biosensor-like device to characterize the microbial cells immobilized on it. We have studied the kinetics of transport and degradation [...] Read more.
Whereas biosensors have been usually proposed as analytical tools, used to investigate the surrounding media pursuing an analytical answer, we have used a biosensor-like device to characterize the microbial cells immobilized on it. We have studied the kinetics of transport and degradation of glucose at different concentrations and temperatures. When glucose concentrations of 15 and 1.5 mM were assayed, calculated activation energies were 25.2 and 18.4 kcal mol-1, respectively, in good agreement with previously published data. The opportunity and convenience of using Arrhenius plots to estimate the activation energy in metabolic-related processes is also discussed. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A Tabu Search WSN Deployment Method for Monitoring Geographically Irregular Distributed Events
Sensors 2009, 9(3), 1625-1643; doi:10.3390/s90301625
Received: 28 January 2009 / Accepted: 24 February 2009 / Published: 9 March 2009
Cited by 20 | PDF Full-text (415 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we address the Wireless Sensor Network (WSN) deployment issue. We assume that the observed area is characterized by the geographical irregularity of the sensed events. Formally, we consider that each point in the deployment area is associated a differentiated [...] Read more.
In this paper, we address the Wireless Sensor Network (WSN) deployment issue. We assume that the observed area is characterized by the geographical irregularity of the sensed events. Formally, we consider that each point in the deployment area is associated a differentiated detection probability threshold, which must be satisfied by our deployment method. Our resulting WSN deployment problem is formulated as a Multi-Objectives Optimization problem, which seeks to reduce the gap between the generated events detection probabilities and the required thresholds while minimizing the number of deployed sensors. To overcome the computational complexity of an exact resolution, we propose an original pseudo-random approach based on the Tabu Search heuristic. Simulations show that our proposal achieves better performances than several other approaches proposed in the literature. In the last part of this paper, we generalize the deployment problem by including the wireless communication network connectivity constraint. Thus, we extend our proposal to ensure that the resulting WSN topology is connected even if a sensor communication range takes small values. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle Data Base Design with GIS in Ecosystem Based Multiple Use Forest Management in Artvin, Turkey: A Case Study in Balcı Forest Management Planning Unit
Sensors 2009, 9(3), 1644-1661; doi:10.3390/s90301644
Received: 11 December 2008 / Revised: 25 February 2009 / Accepted: 2 March 2009 / Published: 10 March 2009
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Abstract
In Turkey, the understanding of planning focused on timber production has given its place on Multiple Use Management (MUM). Because the whole infrastructure of forestry with inventory system leading the way depends on timber production, some cases of bottle neck are expected [...] Read more.
In Turkey, the understanding of planning focused on timber production has given its place on Multiple Use Management (MUM). Because the whole infrastructure of forestry with inventory system leading the way depends on timber production, some cases of bottle neck are expected during the transition period. Database design, probably the most important stage during the transition to MUM, together with the digital basic maps making up the basis of this infrastructure constitute the main point of this article. Firstly, the forest management philosophy of Turkey in the past was shortly touched upon in the article. Ecosystem Based Multiple Use Forest Management (EBMUFM) approaches was briefly introduced. The second stage of the process of EBMUFM, database design was described by examining the classical planning infrastructure and the coverage to be produced and consumed were suggested in the form of lists. At the application stage, two different geographical databases were established with GIS in Balcı Planning Unit of the years 1984 and 2006. Following that the related basic maps are produced. Timely diversity of the planning unit of 20 years is put forward comparatively with regard to the stand parameters such as tree types, age class, development stage, canopy closure, mixture, volume and increment. Full article
(This article belongs to the Special Issue Remote Sensing of Land Surface Properties, Patterns and Processes)
Open AccessCommunication Development of an Electrogenerated Chemiluminescence Biosensor using Carboxylic acid-functionalized MWCNT and Au Nanoparticles
Sensors 2009, 9(3), 1662-1677; doi:10.3390/s90301662
Received: 4 February 2009 / Revised: 4 March 2009 / Accepted: 6 March 2009 / Published: 9 March 2009
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Abstract
A COOH-F-MWCNT-Nafion-Ru(bpy)32+-Au-ADH electrogenerated chemi-luminescence (ECL)electrode using COOH-functionalized MWCNT (COOH-F-MWCNT) and Au nanoparticles synthesized by the radiation method was fabricated for ethanol sensing. A higher sensing efficiency for ethanol for the ECL biosensor prepared by PAAc-g-MWCNT was measured [...] Read more.
A COOH-F-MWCNT-Nafion-Ru(bpy)32+-Au-ADH electrogenerated chemi-luminescence (ECL)electrode using COOH-functionalized MWCNT (COOH-F-MWCNT) and Au nanoparticles synthesized by the radiation method was fabricated for ethanol sensing. A higher sensing efficiency for ethanol for the ECL biosensor prepared by PAAc-g-MWCNT was measured compared to that of the ECL biosensor prepared by PMAc-g-MWCNT, and purified MWCNT. Experimental parameters affecting ethanol detection were also examined in terms of pH and the content of PAAc-g-MWCNT in Nafion. Little interference of other compounds was observed for the assay of ethanol. Results suggest this ECL biosensor could be applied for ethanol detection in real samples. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessArticle Least Square Regression Method for Estimating Gas Concentration in an Electronic Nose System
Sensors 2009, 9(3), 1678-1691; doi:10.3390/s90301678
Received: 14 December 2008 / Revised: 7 March 2009 / Accepted: 10 March 2009 / Published: 10 March 2009
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Abstract
We describe an Electronic Nose (ENose) system which is able to identify the type of analyte and to estimate its concentration. The system consists of seven sensors, five of them being gas sensors (supplied with different heater voltage values), the remainder being [...] Read more.
We describe an Electronic Nose (ENose) system which is able to identify the type of analyte and to estimate its concentration. The system consists of seven sensors, five of them being gas sensors (supplied with different heater voltage values), the remainder being a temperature and a humidity sensor, respectively. To identify a new analyte sample and then to estimate its concentration, we use both some machine learning techniques and the least square regression principle. In fact, we apply two different training models; the first one is based on the Support Vector Machine (SVM) approach and is aimed at teaching the system how to discriminate among different gases, while the second one uses the least squares regression approach to predict the concentration of each type of analyte. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Noise Reduction for CFA Image Sensors Exploiting HVS Behaviour
Sensors 2009, 9(3), 1692-1713; doi:10.3390/s90301692
Received: 18 December 2008 / Revised: 4 March 2009 / Accepted: 9 March 2009 / Published: 10 March 2009
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Abstract
This paper presents a spatial noise reduction technique designed to work on CFA (Color Filtering Array) data acquired by CCD/CMOS image sensors. The overall processing preserves image details using some heuristics related to the HVS (Human Visual System); estimates of local texture [...] Read more.
This paper presents a spatial noise reduction technique designed to work on CFA (Color Filtering Array) data acquired by CCD/CMOS image sensors. The overall processing preserves image details using some heuristics related to the HVS (Human Visual System); estimates of local texture degree and noise levels are computed to regulate the filter smoothing capability. Experimental results confirm the effectiveness of the proposed technique. The method is also suitable for implementation in low power mobile devices with imaging capabilities such as camera phones and PDAs. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
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Open AccessCommunication Humidity Sensitivity of Multi-Walled Carbon Nanotube Networks Deposited by Dielectrophoresis
Sensors 2009, 9(3), 1714-1721; doi:10.3390/s90301714
Received: 22 January 2009 / Revised: 10 March 2009 / Accepted: 10 March 2009 / Published: 11 March 2009
Cited by 47 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an investigation on the humidity sensitivity of deposited multi-walled carbon nanotube (MWCNT) networks using ac dielectrophoresis (DEP) between interdigitated electrodes (IDEs). MWCNTs dispersed in ethanol were trapped and enriched between IDEs on a Si/SiO2 substrate under a positive [...] Read more.
This paper presents an investigation on the humidity sensitivity of deposited multi-walled carbon nanotube (MWCNT) networks using ac dielectrophoresis (DEP) between interdigitated electrodes (IDEs). MWCNTs dispersed in ethanol were trapped and enriched between IDEs on a Si/SiO2 substrate under a positive DEP force. After the DEP process, the ethanol was evaporated and the MWCNT network on a substrate with IDEs was put into a furnace for repeated thermal annealing. It was found that the resistance stability of the network was effectively improved through thermal annealing. The humidity sensitivity was obtained by measuring the resistance of the MWCNT network with different relative humidity at room temperature. The experimental results show the resistance increases linearly with increasing the relative humidity from 25% to 95% RH with a sensitivity of 0.5%/%RH. The MWCNT networks have a reversible humidity sensing capacity with response time and recovery time of about 3 s and 25 s, respectively. The resistance is dependent on temperature with a negative coefficient of about -0.33%/K in a temperature range from 293 K to 393 K. Full article
Open AccessArticle CMOS Image Sensor with a Built-in Lane Detector
Sensors 2009, 9(3), 1722-1737; doi:10.3390/s90301722
Received: 16 February 2009 / Revised: 8 March 2009 / Accepted: 11 March 2009 / Published: 12 March 2009
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Abstract
This work develops a new current-mode mixed signal Complementary Metal-Oxide-Semiconductor (CMOS) imager, which can capture images and simultaneously produce vehicle lane maps. The adopted lane detection algorithm, which was modified to be compatible with hardware requirements, can achieve a high recognition rate [...] Read more.
This work develops a new current-mode mixed signal Complementary Metal-Oxide-Semiconductor (CMOS) imager, which can capture images and simultaneously produce vehicle lane maps. The adopted lane detection algorithm, which was modified to be compatible with hardware requirements, can achieve a high recognition rate of up to approximately 96% under various weather conditions. Instead of a Personal Computer (PC) based system or embedded platform system equipped with expensive high performance chip of Reduced Instruction Set Computer (RISC) or Digital Signal Processor (DSP), the proposed imager, without extra Analog to Digital Converter (ADC) circuits to transform signals, is a compact, lower cost key-component chip. It is also an innovative component device that can be integrated into intelligent automotive lane departure systems. The chip size is 2,191.4 x 2,389.8 mm, and the package uses 40 pin Dual-In-Package (DIP). The pixel cell size is 18.45 x 21.8 mm and the core size of photodiode is 12.45 x 9.6 mm; the resulting fill factor is 29.7%. Full article
(This article belongs to the Special Issue Image Sensors)
Open AccessArticle Quantitative Assessment of Desertification Using Landsat Data on a Regional Scale – A Case Study in the Ordos Plateau, China
Sensors 2009, 9(3), 1738-1753; doi:10.3390/s90301738
Received: 2 December 2008 / Revised: 4 January 2009 / Accepted: 6 February 2009 / Published: 12 March 2009
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Abstract
Desertification is a serious threat to the ecological environment and social economy in our world and there is a pressing need to develop a reasonable and reproducible method to assess it at different scales. In this paper, the Ordos Plateau in China [...] Read more.
Desertification is a serious threat to the ecological environment and social economy in our world and there is a pressing need to develop a reasonable and reproducible method to assess it at different scales. In this paper, the Ordos Plateau in China was selected as the research region and a quantitative method for desertification assessment was developed by using Landsat MSS and TM/ETM+ data on a regional scale. In this method, NDVI, MSDI and land surface albedo were selected as assessment indicators of desertification to represent land surface conditions from vegetation biomass, landscape pattern and micrometeorology. Based on considering the effects of vegetation type and time of images acquired on assessment indictors, assessing rule sets were built and a decision tree approach was used to assess desertification of Ordos Plateau in 1980, 1990 and 2000. The average overall accuracy of three periods was higher than 90%. The results showed that although some local places of Ordos Plateau experienced an expanding trend of desertification, the trend of desertification of Ordos Plateau was an overall decrease in from 1980 to 2000. By analyzing the causes of desertification processes, it was found that climate change could benefit for the reversion of desertification from 1980 to 1990 at a regional scale and human activities might explain the expansion of desertification in this period; however human conservation activities were the main driving factor that induced the reversion of desertification from 1990 to 2000. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Optimal Spectral Domain Selection for Maximizing Archaeological Signatures: Italy Case Studies
Sensors 2009, 9(3), 1754-1767; doi:10.3390/s90301754
Received: 7 January 2009 / Revised: 10 March 2009 / Accepted: 10 March 2009 / Published: 12 March 2009
Cited by 8 | PDF Full-text (924 KB) | HTML Full-text | XML Full-text
Abstract
Different landscape elements, including archaeological remains, can be automatically classified when their spectral characteristics are different, but major difficulties occur when extracting and classifying archaeological spectral features, as archaeological remains do not have unique shape or spectral characteristics. The spectral anomaly characteristics [...] Read more.
Different landscape elements, including archaeological remains, can be automatically classified when their spectral characteristics are different, but major difficulties occur when extracting and classifying archaeological spectral features, as archaeological remains do not have unique shape or spectral characteristics. The spectral anomaly characteristics due to buried remains depend strongly on vegetation cover and/or soil types, which can make feature extraction more complicated. For crop areas, such as the test sites selected for this study, soil and moisture changes within near-surface archaeological deposits can influence surface vegetation patterns creating spectral anomalies of various kinds. In this context, this paper analyzes the usefulness of hyperspectral imagery, in the 0.4 to 12.8 mm spectral region, to identify the optimal spectral range for archaeological prospection as a function of the dominant land cover. MIVIS airborne hyperspectral imagery acquired in five different archaeological areas located in Italy has been used. Within these archaeological areas, 97 test sites with homogenous land cover and characterized by a statistically significant number of pixels related to the buried remains have been selected. The archaeological detection potential for all MIVIS bands has been assessed by applying a Separability Index on each spectral anomaly-background system of the test sites. A scatterplot analysis of the SI values vs. the dominant land cover fractional abundances, as retrieved by spectral mixture analysis, was performed to derive the optimal spectral ranges maximizing the archaeological detection. This work demonstrates that whenever we know the dominant land cover fractional abundances in archaeological sites, we can a priori select the optimal spectral range to improve the efficiency of archaeological observations performed by remote sensing data. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Fabricating an Amperometric Cholesterol Biosensor by a Covalent Linkage between Poly(3-thiopheneacetic acid) and Cholesterol Oxidase
Sensors 2009, 9(3), 1794-1806; doi:10.3390/s90301794
Received: 16 December 2008 / Revised: 2 March 2009 / Accepted: 13 March 2009 / Published: 13 March 2009
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Abstract
In this study, use of the covalent enzyme immobilization method was proposed to attach cholesterol oxidase (ChO) on a conducting polymer, poly(3-thiopheneacetic acid), [poly(3-TPAA)]. Three red-orange poly(3-TPAA) films, named electrodes A, B and C, were electropolymerized on a platinum electrode by applying [...] Read more.
In this study, use of the covalent enzyme immobilization method was proposed to attach cholesterol oxidase (ChO) on a conducting polymer, poly(3-thiopheneacetic acid), [poly(3-TPAA)]. Three red-orange poly(3-TPAA) films, named electrodes A, B and C, were electropolymerized on a platinum electrode by applying a constant current of 1.5 mA, for 5, 20 and 100 s, respectively. Further, 1-ethyl-3-(3-dimethylamiopropyl)carbodiimide hydrochloride (EDC‧HCl) and N-hydroxysuccinimide (NHS) were used to activate the free carboxylic groups of the conducting polymer. Afterwards, the amino groups of the cholesterol oxidase were linked on the activated groups to form peptide bonds. The best sensitivity obtained for electrode B is 4.49 mA M-1 cm-2,with a linear concentration ranging from 0 to 8 mM, which is suitable for the analysis of cholesterol in humans. The response time (t95) is between 70 and 90 s and the limit of detection is 0.42 mM, based on the signal to noise ratio equal to 3. The interference of species such as ascorbic acid and uric acid increased to 5.2 and 10.3% of the original current response, respectively, based on the current response of cholesterol (100%). With respect to the long-term stability, the sensing response retains 88% of the original current after 13 days. Full article
Open AccessArticle Leeches as Sensor-bioindicators of River Contamination by PCBs
Sensors 2009, 9(3), 1807-1820; doi:10.3390/s90301807
Received: 23 February 2009 / Revised: 10 March 2009 / Accepted: 11 March 2009 / Published: 13 March 2009
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Abstract
The aim of the study was to evaluate the use of leeches of the genus Erpobdella as a means of assessing polychlorinated biphenyl contamination of watercourses. The River Skalice, heavily contaminated with PCBs, was selected as a model. The source of contamination [...] Read more.
The aim of the study was to evaluate the use of leeches of the genus Erpobdella as a means of assessing polychlorinated biphenyl contamination of watercourses. The River Skalice, heavily contaminated with PCBs, was selected as a model. The source of contamination was a road gravel processing factory in Rožmitál pod Třemšínem from which an estimated 1 metric ton of PCBs leaked in 1986. Levels of PCB were measured in leeches collected between 1992 to 2003 from 11 sites covering about 50 km of the river (the first sampling site upstream to the source of contamination and 10 sites downstream). The PCB indicator congeners IUPA no. 28, 52, 101, 118, 138, 153, and 180 were measured. Levels were highest at the four sampling sites nearest the source of pollution. The highest values of PCB congeners were found in 1992. PCB content decreased from 1992 to 2003 and with distance from the source. The study indicated that leeches of the genus Erpobdella are a suitable bioindicator of contamination in the surface layer of river sediments. Full article
Open AccessArticle An Evaluation of Relative Damage to the Powertrain System in Tracked Vehicles
Sensors 2009, 9(3), 1845-1859; doi:10.3390/s90301845
Received: 21 January 2009 / Revised: 25 February 2009 / Accepted: 11 March 2009 / Published: 13 March 2009
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Abstract
The objective of this study was to improve the reliability of the endurance test for the powertrain system of military tracked vehicles. The measurement system that measures the driving duty applied to the powertrain system caused by mobility on roads consists of [...] Read more.
The objective of this study was to improve the reliability of the endurance test for the powertrain system of military tracked vehicles. The measurement system that measures the driving duty applied to the powertrain system caused by mobility on roads consists of eight analog channels and two pulse channels, including the propeller shaft output torques for the left and right sides. The data obtained from this measurement system can be used to introduce a new technology that produces the output torque of a torque converter and that can be applied to analyze the revolution counting for the endurance and road mobility in the front unit and represent the relative fatigue damages analysis technique and its results according to the driven roads through a cumulative fatigue method. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Thiopental and Phenytoin as Novel Ionophores for Potentiometric Determination of Lead (II) Ions
Sensors 2009, 9(3), 1860-1875; doi:10.3390/s90301860
Received: 20 January 2009 / Revised: 23 February 2009 / Accepted: 9 March 2009 / Published: 13 March 2009
Cited by 7 | PDF Full-text (160 KB) | HTML Full-text | XML Full-text
Abstract
Two novel polymeric membrane sensors for the analysis of Pb(II) have been developed based ontwo therapeutic drugs, thiopental (TP) and phenytoin (PT) as two new ionophores and potassium tetrakis(p-chlorophenyl) borate (KTpClPB) as a lipophilic additive, in plasticized PVC [...] Read more.
Two novel polymeric membrane sensors for the analysis of Pb(II) have been developed based ontwo therapeutic drugs, thiopental (TP) and phenytoin (PT) as two new ionophores and potassium tetrakis(p-chlorophenyl) borate (KTpClPB) as a lipophilic additive, in plasticized PVC membranes. The sensors show a Nernstian response for Pb(II) ions over the wide concentration ranges of 1×10-2 - 7×10-6 M and 1×10-2 - 8×10-6 M for the sensors based on thiopental and phenytoin, respectively. The proposed sensors have a fast response time and can be used for more than nine weeks without any considerable divergence in potentials. The sensors exhibit comparatively good selectivity with respect to alkaline, alkaline earth and some transition and heavy metal ions. They were employed for direct determination of lead in solder alloys and in galena rocks with a good agreement with the obtained results by atomic absorption spectroscopy. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Sea Clutter Reduction and Target Enhancement by Neural Networks in a Marine Radar System
Sensors 2009, 9(3), 1913-1936; doi:10.3390/s90301913
Received: 18 December 2008 / Revised: 16 February 2009 / Accepted: 11 March 2009 / Published: 16 March 2009
Cited by 20 | PDF Full-text (2130 KB) | HTML Full-text | XML Full-text
Abstract
The presence of sea clutter in marine radar signals is sometimes not desired. So, efficient radar signal processing techniques are needed to reduce it. In this way, nonlinear signal processing techniques based on neural networks (NNs) are used in the proposed clutter [...] Read more.
The presence of sea clutter in marine radar signals is sometimes not desired. So, efficient radar signal processing techniques are needed to reduce it. In this way, nonlinear signal processing techniques based on neural networks (NNs) are used in the proposed clutter reduction system. The developed experiments show promising results characterized by different subjective (visual analysis of the processed radar images) and objective (clutter reduction, target enhancement and signal-to-clutter ratio improvement) criteria. Moreover, a deep study of the NN structure is done, where the low computational cost and the high processing speed of the proposed NN structure are emphasized. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Vibration and Fluorescence Spectra of Porphyrin- CoredBis(methylol)-propionic Acid Dendrimers
Sensors 2009, 9(3), 1937-1966; doi:10.3390/s90301937
Received: 21 October 2008 / Revised: 27 February 2009 / Accepted: 16 March 2009 / Published: 16 March 2009
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Abstract
Bis-MPA dendron-coated free-base tetraphenylporphyrin and zinc-tetraphenyl-porphyrin (TPPH2 and TPPZn) were studied in comparison with simple porphyrins (H2P, ZnP) by theoretical simulation of their infrared, Raman and electronic absorption spectra, as well as fluorescense emission. Infrared and fluorescence spectra of [...] Read more.
Bis-MPA dendron-coated free-base tetraphenylporphyrin and zinc-tetraphenyl-porphyrin (TPPH2 and TPPZn) were studied in comparison with simple porphyrins (H2P, ZnP) by theoretical simulation of their infrared, Raman and electronic absorption spectra, as well as fluorescense emission. Infrared and fluorescence spectra of the dendrimers were measured and interpreted along with time-resolved measurements of the fluorescence. The 0-1 emission band of the dendron substituted TPPZn was found to experience a "heavy substitution"-effect. The 0-1 vibronic emission signal is associated with a longer decay time (approx. 7 - 8 ns) than the 0-0 emission (approx. 1 - 1.5 ns). The former contributed with more relative emission yield for larger dendron substituents, in agreement with the appearance of steady-state emission spectra showing increased contribution from the 0-1 vibronic fluorescence band at 650 nm. No such substitution effect was observed in the electronic or vibrational spectra of the substituted free-base variant, TPPH2. Vibration spectra of the parent porphyrins (H2P, ZnP, TPPH2 and TPPZn) were calculated by density functional theory (DFT) using the B3LYP/6-31G** approximation and a detailed analysis of the most active vibration modes was made based on both literature and our own experimental data. Based on the results of theoretical calculations the wide vibronic bands in the visible region were assigned. The vibronic structure also gave a qualitative interpretation of bands in the electronic absorption spectra as well as in fluorescence emission depending on the size of dendrimer substitution. From the results of time-dependent DFT calculations it is suggested that the TPPZn-cored dendrimers indicate strong vibronic interaction and increased Jahn-Teller distortion of the prophyrin core for larger dendrimer generations. Specifically, this leads to the entirely different behaviour of the emission spectra upon substitution of the TPPH2 and TPPZn variants, which was also experimentally observed. Since TPPH2 is originally of lower symmetry the specific distortion upon dendron substitution is not expected to the same extent, which also was in agreement with the experimental findings. Full article
(This article belongs to the Special Issue Dendritic Sensors: From Dendrimer Molecules to Dendritic Cells)
Open AccessArticle Implementation of 3D Optical Scanning Technology for Automotive Applications
Sensors 2009, 9(3), 1967-1979; doi:10.3390/s90301967
Received: 9 February 2009 / Revised: 3 March 2009 / Accepted: 9 March 2009 / Published: 17 March 2009
Cited by 7 | PDF Full-text (428 KB) | HTML Full-text | XML Full-text
Abstract
Reverse engineering (RE) is a powerful tool for generating a CAD model from the 3D scan data of a physical part that lacks documentation or has changed from the original CAD design of the part. The process of digitizing a part and [...] Read more.
Reverse engineering (RE) is a powerful tool for generating a CAD model from the 3D scan data of a physical part that lacks documentation or has changed from the original CAD design of the part. The process of digitizing a part and creating a CAD model from 3D scan data is less time consuming and provides greater accuracy than manually measuring the part and designing the part from scratch in CAD. 3D optical scanning technology is one of the measurement methods which have evolved over the last few years and it is used in a wide range of areas from industrial applications to art and cultural heritage. It is also used extensively in the automotive industry for applications such as part inspections, scanning of tools without CAD definition, scanning the casting for definition of the stock (i.e. the amount of material to be removed from the surface of the castings) model for CAM programs and reverse engineering. In this study two scanning experiments of automotive applications are illustrated. The first one examines the processes from scanning to re-manufacturing the damaged sheet metal cutting die, using a 3D scanning technique and the second study compares the scanned point clouds data to 3D CAD data for inspection purposes. Furthermore, the deviations of the part holes are determined by using different lenses and scanning parameters. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle LULC Classification and Topographic Correction of Landsat-7 ETM+ Imagery in the Yangjia River Watershed: the Influence of DEM Resolution
Sensors 2009, 9(3), 1980-1995; doi:10.3390/s90301980
Received: 19 December 2008 / Revised: 17 February 2009 / Accepted: 9 March 2009 / Published: 17 March 2009
Cited by 14 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
DEM-based topographic corrections on Landsat-7 ETM+ imagery from rugged terrain, as an effective processing techniques to improve the accuracy of Land Use/Land Cover (LULC) classification as well as land surface parameter retrievals with remotely sensed data, has been frequently reported in the [...] Read more.
DEM-based topographic corrections on Landsat-7 ETM+ imagery from rugged terrain, as an effective processing techniques to improve the accuracy of Land Use/Land Cover (LULC) classification as well as land surface parameter retrievals with remotely sensed data, has been frequently reported in the literature. However, few studies have investigated the exact effects of DEM with different resolutions on the correction of imagery.Taking the topographic corrections on the Landsat-7 ETM+ images acquired from the rugged terrain of the Yangjiahe river basin (P.R. China) as an example, the present work systematically investigates such issues by means of two commonly used topographic correction algorithms with the support of different spatial resolution DEMs. After the pre-processing procedures, i.e. atmospheric correction and geo-registration, were applied to the ETM+ images, two topographic correction algorithms, namely SCS correction and Minnaert correction, were applied to assess the effects of different spatial resolution DEMs obtained from two sources in the removal of topographic effects and LULC classifications. The results suggested that the topographic effects were tremendously reduced with these two algorithms under the support of different spatial resolution DEMs, and the performance of the topographic correction with the 1:50,000-topographic-map DEM was similar to that achieved using SRTM DEM. Moreover, when the same topographic correction algorithm was applied the accuracy of LULC classification after topographic correction based on 1:50,000-topographic-map DEM was similar as that based on SRTM DEM, which implies that the 90 m SRTM DEM can be used as an alternative for the topographic correction of ETM+ imagery when high resolution DEM is unavailable. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Sensory Properties and Color Measurements of Dietary Chocolates with Different Compositions During Storage for Up to 360 Days
Sensors 2009, 9(3), 1996-2016; doi:10.3390/s90301996
Received: 30 December 2008 / Revised: 4 March 2009 / Accepted: 11 March 2009 / Published: 17 March 2009
Cited by 12 | PDF Full-text (884 KB) | HTML Full-text | XML Full-text
Abstract
In this work sensory characteristics (appearance – color, brilliance, shape and surface; texture – structure, break, firmness and chewiness; aroma – odor and taste) of dietary chocolates of different compositions were evaluated, in parallel with color parameter measurements. Color was determined instrumentally on the top and bottom surfaces, using a "MINOLTA" Chroma meter CR 400 thristimulus colorimeter. Sensory evaluation was performed by a group of experienced panelists immediately after the production (0 – 30 days), and then after 90, 180, 270 and 360 days of storage under ambient conditions (t = 18 – 20°C). Results were statistically analyzed by the two-factorial analysis of variance (MANOVA) and with the LSD – test. It was concluded that the storage time up to one year had statistically highly significant (p < 0.01) effects on the sensory attributes of chocolate, as well as on instrumentally measured color parameters. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle GPS Velocity and Strain Rate Fields in Southwest Anatolia from Repeated GPS Measurements
Sensors 2009, 9(3), 2017-2034; doi:10.3390/s90302017
Received: 17 December 2008 / Revised: 13 March 2009 / Accepted: 16 March 2009 / Published: 17 March 2009
Cited by 8 | PDF Full-text (1281 KB) | HTML Full-text | XML Full-text
Abstract
Southwestern Turkey is a tectonically active area. To determine kinematics and strain distribution in this region, a GPS network of sixteen stations was established. We have used GPS velocity field data for southwest Anatolia from continuous measurements covering the period 2003 to [...] Read more.
Southwestern Turkey is a tectonically active area. To determine kinematics and strain distribution in this region, a GPS network of sixteen stations was established. We have used GPS velocity field data for southwest Anatolia from continuous measurements covering the period 2003 to 2006 to estimate current crustal deformation of this tectonically active region. GPS data were processed using GAMIT/GLOBK software and velocity and strain rate fields were estimated in the study area. The measurements showed velocities of 15-30 mm/yr toward the southwest and strain values up to 0.28-8.23x10-8. Results showed that extension has been determined in the Burdur-Isparta region. In this study, all of strain data reveal an extensional neotectonic regime through the northeast edge of the Isparta Angle despite the previously reported compressional neotectonic regime. Meanwhile, results showed some small differences relatively with the 2006 model of Reilinger et al. As a result, active tectonic movements, in agreement with earthquake fault plane solutions showed important activity. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Spatial Forecast of Landslides in Three Gorges Based On Spatial Data Mining
Sensors 2009, 9(3), 2035-2061; doi:10.3390/s90302035
Received: 17 December 2008 / Revised: 25 February 2009 / Accepted: 26 February 2009 / Published: 18 March 2009
Cited by 14 | PDF Full-text (825 KB) | HTML Full-text | XML Full-text
Abstract
The Three Gorges is a region with a very high landslide distribution density and a concentrated population. In Three Gorges there are often landslide disasters, and the potential risk of landslides is tremendous. In this paper, focusing on Three Gorges, which has [...] Read more.
The Three Gorges is a region with a very high landslide distribution density and a concentrated population. In Three Gorges there are often landslide disasters, and the potential risk of landslides is tremendous. In this paper, focusing on Three Gorges, which has a complicated landform, spatial forecasting of landslides is studied by establishing 20 forecast factors (spectra, texture, vegetation coverage, water level of reservoir, slope structure, engineering rock group, elevation, slope, aspect, etc). China-Brazil Earth Resources Satellite (Cbers) images were adopted based on C4.5 decision tree to mine spatial forecast landslide criteria in Guojiaba Town (Zhigui County) in Three Gorges and based on this knowledge, perform intelligent spatial landslide forecasts for Guojiaba Town. All landslides lie in the dangerous and unstable regions, so the forecast result is good. The method proposed in the paper is compared with seven other methods: IsoData, K-Means, Mahalanobis Distance, Maximum Likelihood, Minimum Distance, Parallelepiped and Information Content Model. The experimental results show that the method proposed in this paper has a high forecast precision, noticeably higher than that of the other seven methods. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle Fabrication and Characterization of a Tunable In-plane Resonator with Low Driving Voltage
Sensors 2009, 9(3), 2062-2075; doi:10.3390/s90302062
Received: 19 February 2009 / Revised: 14 March 2009 / Accepted: 18 March 2009 / Published: 18 March 2009
Cited by 22 | PDF Full-text (647 KB) | HTML Full-text | XML Full-text
Abstract
This study presents the fabrication and characterization of a micromechanical tunable in-plane resonator. The resonator is manufactured using the commercial 0.35 µm complementary metal oxide semiconductor (CMOS) process. The resonator is made of aluminum, and the sacrificial layer is silicon dioxide. The [...] Read more.
This study presents the fabrication and characterization of a micromechanical tunable in-plane resonator. The resonator is manufactured using the commercial 0.35 µm complementary metal oxide semiconductor (CMOS) process. The resonator is made of aluminum, and the sacrificial layer is silicon dioxide. The post-process involves only one maskless etching step using an etchant to remove the sacrificial layer. The resonator includes three parts: a driving part to provide a driving force, a sensing part that is used to detect a change in capacitance when the resonator is vibrating, and a tuning part that changes the resonant frequency of the resonator. The main advantages of the tunable resonator are a low driving voltage and compatibility with the CMOS process. The resonant frequency of the resonator can be changed upon applying a dc voltage to the tuning part. To reduce the driving voltage, the driving part is designed as comb-finger rows. Experimental results show that the resonator has a resonant frequency of about 183 kHz and a driving voltage of 10 V; the resonant frequency increases 14 kHz when a tuning voltage of 30 V is applied. The resonator has a maximum frequency–tuning ratio of 7.6%. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessArticle Optimization of a PVC Membrane for Reference Field Effect Transistors
Sensors 2009, 9(3), 2076-2087; doi:10.3390/s90302076
Received: 20 February 2009 / Revised: 9 March 2009 / Accepted: 12 March 2009 / Published: 19 March 2009
Cited by 8 | PDF Full-text (190 KB) | HTML Full-text | XML Full-text
Abstract
For the miniaturization of ISFET sensing systems,the concept of a REFET with low ion sensitivity is proposed to replace the conventional reference electrodes through the arrangement of a quasi reference electrode and a differential readout circuit. In this study, an ion-unblocking membrane [...] Read more.
For the miniaturization of ISFET sensing systems,the concept of a REFET with low ion sensitivity is proposed to replace the conventional reference electrodes through the arrangement of a quasi reference electrode and a differential readout circuit. In this study, an ion-unblocking membrane was used as the top layer of a REFET. To optimize the REFET performance, the influences of the silylating process, different plasticizers, and the composition of the PVC cocktails were investigated. A low sensitivity (10.4 ± 2.2 mV/pH) and high linearity (99.7 ± 0.3 %) in the range from pH 2.2 to pH 11.6 was obtained for the REFET with a 60˚wt.% DNP/(DNP + PVC) membrane. To evaluate the long term stability, the drift coefficient was estimated, and for the best REFET, it was –0.74 mV/h. Two criteria for assessing the lifetime of REFETs were used, namely the increase in pH sensitivity to a value higher than 15 mV/pH and the degradation of linearity below 99 %. For the best REFET, it was approximately 15 days. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Availability and End-to-end Reliability in Low Duty Cycle MultihopWireless Sensor Networks
Sensors 2009, 9(3), 2088-2116; doi:10.3390/s90302088
Received: 17 November 2008 / Revised: 6 March 2009 / Accepted: 16 March 2009 / Published: 20 March 2009
Cited by 13 | PDF Full-text (367 KB) | HTML Full-text | XML Full-text
Abstract
A wireless sensor network (WSN) is an ad-hoc technology that may even consist of thousands of nodes, which necessitates autonomic, self-organizing and multihop operations. A typical WSN node is battery powered, which makes the network lifetime the primary concern. The highest energy [...] Read more.
A wireless sensor network (WSN) is an ad-hoc technology that may even consist of thousands of nodes, which necessitates autonomic, self-organizing and multihop operations. A typical WSN node is battery powered, which makes the network lifetime the primary concern. The highest energy efficiency is achieved with low duty cycle operation, however, this alone is not enough. WSNs are deployed for different uses, each requiring acceptable Quality of Service (QoS). Due to the unique characteristics of WSNs, such as dynamic wireless multihop routing and resource constraints, the legacy QoS metrics are not feasible as such. We give a new definition to measure and implement QoS in low duty cycle WSNs, namely availability and reliability. Then, we analyze the effect of duty cycling for reaching the availability and reliability. The results are obtained by simulations with ZigBee and proprietary TUTWSN protocols. Based on the results, we also propose a data forwarding algorithm suitable for resource constrained WSNs that guarantees end-to-end reliability while adding a small overhead that is relative to the packet error rate (PER). The forwarding algorithm guarantees reliability up to 30% PER. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle Metabolic Discrimination of Select List Agents by Monitoring Cellular Responses in a Multianalyte Microphysiometer
Sensors 2009, 9(3), 2117-2133; doi:10.3390/s90302117
Received: 7 January 2009 / Revised: 15 March 2009 / Accepted: 17 March 2009 / Published: 23 March 2009
Cited by 23 | PDF Full-text (248 KB) | HTML Full-text | XML Full-text
Abstract
Harnessing the potential of cells as complex biosensors promises the potential to create sensitive and selective detectors for discrimination of biodefense agents. Here we present toxin detection and suggest discrimination using cells in a multianalyte microphysiometer (MMP) that is capable of simultaneously [...] Read more.
Harnessing the potential of cells as complex biosensors promises the potential to create sensitive and selective detectors for discrimination of biodefense agents. Here we present toxin detection and suggest discrimination using cells in a multianalyte microphysiometer (MMP) that is capable of simultaneously measuring flux changes in four extracellular analytes (acidification rate, glucose uptake, oxygen uptake, and lactate production) in real-time. Differential short-term cellular responses were observed between botulinum neurotoxin A and ricin toxin with neuroblastoma cells, alamethicin and anthrax protective antigen with RAW macrophages, and cholera toxin, muscarine, 2,4-dinitro-phenol, and NaF with CHO cells. These results and the post exposure dynamics and metabolic recovery observed in each case suggest the usefulness of cell-based detectors to discriminate between specific analytes and classes of compounds in a complex matrix, and furthermore to make metabolic inferences on the cellular effects of the agents. This may be particularly valuable for classifying unknown toxins. Full article
(This article belongs to the Special Issue Toxin Sensors)
Open AccessArticle EROD and MROD as Markers of Cytochrome P450 1A Activities in Hepatic Microsomes from Entire and Castrated Male Pigs
Sensors 2009, 9(3), 2134-2147; doi:10.3390/s90302134
Received: 21 February 2009 / Revised: 18 March 2009 / Accepted: 19 March 2009 / Published: 23 March 2009
Cited by 23 | PDF Full-text (166 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, we characterized the kinetic parameters of 7-ethoxy-resorufin O-deethylation (EROD) and 7-methoxyresorufin O-demethylation (MROD) in hepatic microsomes from entire and castrated male pigs. Validation parameters of an HPLC-based method to analyse EROD and MROD activities are also [...] Read more.
In the present study, we characterized the kinetic parameters of 7-ethoxy-resorufin O-deethylation (EROD) and 7-methoxyresorufin O-demethylation (MROD) in hepatic microsomes from entire and castrated male pigs. Validation parameters of an HPLC-based method to analyse EROD and MROD activities are also described. Eadie-Hofstee plot analysis demonstrated a biphasic kinetic of EROD, indicating that at least two forms of cytochrome P450 are involved in this reaction. MROD followed monophasic kinetic, suggesting that a single enzyme, or enzymes with similar affinities, is responsible for the reaction. Inhibitory effects of α-naphthoflavone (ANF), ellipticine and furafylline were studied using microsomes from entire and castrated male pigs. ANF is a known inhibitor of both cytochrome P450 1A1 and 1A2 (CYP1A1 and CYP1A2); the presence of ANF in the incubations resulted in the inhibition of both EROD and MROD activities in porcine liver microsomes. EROD activities in porcine liver microsomes were also inhibited by selective CYP1A1 inhibitor ellipticine, but not by CYP1A2 inhibitor furafylline. MROD activities were strongly inhibited by ellipticine and to a much lesser extent by furafylline. Further studies are needed to evaluate substrate specificities of porcine CYP1A1 and CYP1A2. Full article
Open AccessArticle Automatic Exudate Detection from Non-dilated Diabetic Retinopathy Retinal Images Using Fuzzy C-means Clustering
Sensors 2009, 9(3), 2148-2161; doi:10.3390/s90302148
Received: 29 January 2009 / Revised: 19 March 2009 / Accepted: 20 March 2009 / Published: 24 March 2009
Cited by 68 | PDF Full-text (286 KB) | HTML Full-text | XML Full-text
Abstract
Exudates are the primary sign of Diabetic Retinopathy. Early detection can potentially reduce the risk of blindness. An automatic method to detect exudates from low-contrast digital images of retinopathy patients with non-dilated pupils using a Fuzzy C-Means (FCM) clustering is proposed. Contrast [...] Read more.
Exudates are the primary sign of Diabetic Retinopathy. Early detection can potentially reduce the risk of blindness. An automatic method to detect exudates from low-contrast digital images of retinopathy patients with non-dilated pupils using a Fuzzy C-Means (FCM) clustering is proposed. Contrast enhancement preprocessing is applied before four features, namely intensity, standard deviation on intensity, hue and a number of edge pixels, are extracted to supply as input parameters to coarse segmentation using FCM clustering method. The first result is then fine-tuned with morphological techniques. The detection results are validated by comparing with expert ophthalmologists’ hand-drawn ground-truths. Sensitivity, specificity, positive predictive value (PPV), positive likelihood ratio (PLR) and accuracy are used to evaluate overall performance. It is found that the proposed method detects exudates successfully with sensitivity, specificity, PPV, PLR and accuracy of 87.28%, 99.24%, 42.77%, 224.26 and 99.11%, respectively. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Electromechanical Characteristic Analysis of Passive Matrix Addressing for Grating Light Modulator
Sensors 2009, 9(3), 2162-2175; doi:10.3390/s90302162
Received: 23 January 2009 / Revised: 5 March 2009 / Accepted: 19 March 2009 / Published: 24 March 2009
Cited by 1 | PDF Full-text (1206 KB) | HTML Full-text | XML Full-text
Abstract
AGrating Light Modulator (GLM) based on Micro-Electro-Mechanical Systems (MEMS) is applied in projection display. The operating principle of the GLM is introduced in this paper. The electromechanical characteristic of the passive matrix addressing GLM is studied. It was found that if the [...] Read more.
AGrating Light Modulator (GLM) based on Micro-Electro-Mechanical Systems (MEMS) is applied in projection display. The operating principle of the GLM is introduced in this paper. The electromechanical characteristic of the passive matrix addressing GLM is studied. It was found that if the spring constant is larger, both the response frequency and the driving voltage are larger. Theoretical analysis shows that the operating voltage and the pull-in voltage of the GLM are 8.16 and 8.74 V, respectively. When an all-selected pixel in a m×n array is actuated by a voltage V0, the voltages of the half-selected pixel in row and column are V0(m-1)/(m+n-1) and V0(n-1)/(m+n-1), respectively, and the voltage of the non-selected pixel is V0/(m+n-1). Finally, the experimental results indicate that the operating voltage and the pull-in voltage are 7.8 and 8.5V respectively, and the response frequency of the GLM is about 7 kHz. The crosstalk in a 16×16 GLM array is validated by the experiment. These studies provide a theoretical basis for improving the GLM driver. Full article
Open AccessArticle Development of a Novel, Ultra-rapid Biosensor for the Qualitative Detection of Hepatitis B Virus-associated Antigens and Anti-HBV, Based on “Membrane-engineered” Fibroblast Cells with Virus-Specific Antibodies and Antigens
Sensors 2009, 9(3), 2176-2186; doi:10.3390/s90302176
Received: 3 February 2009 / Revised: 16 March 2009 / Accepted: 25 March 2009 / Published: 25 March 2009
Cited by 14 | PDF Full-text (180 KB) | HTML Full-text | XML Full-text
Abstract
A novel miniature cell biosensor detection system for the detection of Hepatis B virus (HBV)-associated antigens and anti-HBV is described. The biosensor is based on “membrane-engineered” Vero fibroblast cells immobilized in an alginate matrix. The membrane-engineering process involved the electroinsertion of anti-HBV [...] Read more.
A novel miniature cell biosensor detection system for the detection of Hepatis B virus (HBV)-associated antigens and anti-HBV is described. The biosensor is based on “membrane-engineered” Vero fibroblast cells immobilized in an alginate matrix. The membrane-engineering process involved the electroinsertion of anti-HBV specific antibodies (anti-HBs, anti-HBe) or antigens (HBsAg) in the membranes of the Vero cells. The attachment of a homologous antigen to the electroinserted antibody (or, respectively, of the antibody to the electroinserted antigen) triggered specific changes to the cell membrane potential that were measured by appropriate microelectrodes, according to the principle of the Bioelectric Recognition Assay (BERA). The sensor was used for screening 133 clinical blood serum samples according to a double-blind protocol. Considerably higher sensor responses were observed against HBV-positive samples, compared with responses against negative samples or samples positive for heterologous hepatitis viruses such as Hepatitis C (HCV) virus. Detection of anti-HBs antibodies was made possible by using a biosensor based on immobilized Vero cells bearing the respective antigen (HBsAg). The observed response was rapid (45 sec) and quite reproducible. Fluorescence microscopy observations showed that attachment of HBV particles to cells membrane-engineered with anti-HBs was associated with a decrease of [Ca2+]cyt. The perspectives for using the novel biosensor as a qualitative, rapid screening, high throughput assay for HBV antigens and anti-HBs in clinical samples is discussed. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessArticle Measurement and Evaluation of Finger Tapping Movements Using Log-linearized Gaussian Mixture Networks
Sensors 2009, 9(3), 2187-2201; doi:10.3390/s90302187
Received: 6 November 2008 / Revised: 18 March 2009 / Accepted: 18 March 2009 / Published: 26 March 2009
Cited by 11 | PDF Full-text (1172 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a method to quantitatively measure and evaluate finger tapping movements for the assessment of motor function using log-linearized Gaussian mixture networks (LLGMNs). First, finger tapping movements are measured using magnetic sensors, and eleven indices are computed for evaluation. After [...] Read more.
This paper proposes a method to quantitatively measure and evaluate finger tapping movements for the assessment of motor function using log-linearized Gaussian mixture networks (LLGMNs). First, finger tapping movements are measured using magnetic sensors, and eleven indices are computed for evaluation. After standardizing these indices based on those of normal subjects, they are input to LLGMNs to assess motor function. Then, motor ability is probabilistically discriminated to determine whether it is normal or not using a classifier combined with the output of multiple LLGMNs based on bagging and entropy. This paper reports on evaluation and discrimination experiments performed on finger tapping movements in 33 Parkinson’s disease (PD) patients and 32 normal elderly subjects. The results showed that the patients could be classified correctly in terms of their impairment status with a high degree of accuracy (average rate: 93:1 § 3:69%) using 12 LLGMNs, which was about 5% higher than the results obtained using a single LLGMN. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle Determination of Lactoferrin and Immunoglobulin G in Animal Milks by New Immunosensors
Sensors 2009, 9(3), 2202-2221; doi:10.3390/s90302202
Received: 29 December 2008 / Revised: 20 March 2009 / Accepted: 24 March 2009 / Published: 26 March 2009
Cited by 20 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
Two different immunosensors, recently developed for the determination of antibacterial proteins (lactoferrin and immunoglobulin G) in buffalo milk and in other commercial animal milks samples, were used in the present study. The aim was to propose these immunosensor methods for routine control [...] Read more.
Two different immunosensors, recently developed for the determination of antibacterial proteins (lactoferrin and immunoglobulin G) in buffalo milk and in other commercial animal milks samples, were used in the present study. The aim was to propose these immunosensor methods for routine control of important diet products, such as cow and goat milks, and in particular buffalo milk. To this end we employed two different kinds of immunosensors: one for the analysis of immunoglobulin G (IgG), the other was a new amperometric immunosensor for lactoferrin analysis. Lactoferrin and IgG immunosensors were also used for the determination of lactoferrin and immunoglobulin G in buffalo milk on different days of lactation. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)

Review

Jump to: Research

Open AccessReview Toxin Detection by Surface Plasmon Resonance
Sensors 2009, 9(3), 1339-1354; doi:10.3390/s9031339
Received: 3 November 2008 / Revised: 19 January 2009 / Accepted: 20 February 2009 / Published: 26 February 2009
Cited by 52 | PDF Full-text (178 KB) | HTML Full-text | XML Full-text
Abstract
Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, [...] Read more.
Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, e.g. liquid chromatography and mass spectrometry (LC-MS), in order to detect as low concentrations as possible. Surface plasmon resonance (SPR) is one of the new biophysical methods which enables rapid toxin detection. Moreover, this method was already included in portable sensors for on-site determinations. In this paper we describe some of the most common methods for toxin detection, with an emphasis on SPR. Full article
(This article belongs to the Special Issue Toxin Sensors)
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Open AccessReview Fabrication and Structural Design of Micro Pressure Sensors for Tire Pressure Measurement Systems (TPMS)
Sensors 2009, 9(3), 1382-1393; doi:10.3390/s90301382
Received: 21 January 2009 / Revised: 17 February 2009 / Accepted: 22 February 2009 / Published: 27 February 2009
Cited by 13 | PDF Full-text (392 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we describe the design and testing of a micro piezoresistive pressure sensor for a Tire Pressure Measurement System (TPMS) which has the advantages of a minimized structure, high sensitivity, linearity and accuracy. Through analysis of the stress distribution of [...] Read more.
In this paper we describe the design and testing of a micro piezoresistive pressure sensor for a Tire Pressure Measurement System (TPMS) which has the advantages of a minimized structure, high sensitivity, linearity and accuracy. Through analysis of the stress distribution of the diaphragm using the ANSYS software, a model of the structure was established. The fabrication on a single silicon substrate utilizes the technologies of anisotropic chemical etching and packaging through glass anodic bonding. The performance of this type of piezoresistive sensor, including size, sensitivity, and long-term stability, were investigated. The results indicate that the accuracy is 0.5% FS, therefore this design meets the requirements for a TPMS, and not only has a smaller size and simplicity of preparation, but also has high sensitivity and accuracy. Full article
Open AccessReview Gas Sensors Based on Electrospun Nanofibers
Sensors 2009, 9(3), 1609-1624; doi:10.3390/s90301609
Received: 4 February 2009 / Revised: 24 February 2009 / Accepted: 6 February 2009 / Published: 9 March 2009
Cited by 159 | PDF Full-text (729 KB) | HTML Full-text | XML Full-text
Abstract
Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun [...] Read more.
Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
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Open AccessReview Scale Issues in Remote Sensing: A Review on Analysis, Processing and Modeling
Sensors 2009, 9(3), 1768-1793; doi:10.3390/s90301768
Received: 18 December 2008 / Revised: 7 March 2009 / Accepted: 12 March 2009 / Published: 13 March 2009
Cited by 65 | PDF Full-text (167 KB) | HTML Full-text | XML Full-text
Abstract
With the development of quantitative remote sensing, scale issues have attracted more and more the attention of scientists. Research is now suffering from a severe scale discrepancy between data sources and the models used. Consequently, both data interpretation and model application become [...] Read more.
With the development of quantitative remote sensing, scale issues have attracted more and more the attention of scientists. Research is now suffering from a severe scale discrepancy between data sources and the models used. Consequently, both data interpretation and model application become difficult due to these scale issues. Therefore, effectively scaling remotely sensed information at different scales has already become one of the most important research focuses of remote sensing. The aim of this paper is to demonstrate scale issues from the points of view of analysis, processing and modeling and to provide technical assistance when facing scale issues in remote sensing. The definition of scale and relevant terminologies are given in the first part of this paper. Then, the main causes of scale effects and the scaling effects on measurements, retrieval models and products are reviewed and discussed. Ways to describe the scale threshold and scale domain are briefly discussed. Finally, the general scaling methods, in particular up-scaling methods, are compared and summarized in detail. Full article
(This article belongs to the Section Remote Sensors)
Open AccessReview A Review on Direct Electrochemistry of Catalase for Electrochemical Sensors
Sensors 2009, 9(3), 1821-1844; doi:10.3390/s90301821
Received: 20 January 2009 / Revised: 3 March 2009 / Accepted: 13 March 2009 / Published: 13 March 2009
Cited by 30 | PDF Full-text (1184 KB) | HTML Full-text | XML Full-text
Abstract
Catalase (CAT) is a heme enzyme with a Fe(III/II) prosthetic group at its redox centre. CAT is present in almost all aerobic living organisms, where it catalyzes the disproportionation of H2O2 into oxygen and water without forming free [...] Read more.
Catalase (CAT) is a heme enzyme with a Fe(III/II) prosthetic group at its redox centre. CAT is present in almost all aerobic living organisms, where it catalyzes the disproportionation of H2O2 into oxygen and water without forming free radicals. In order to study this catalytic mechanism in detail, the direct electrochemistry of CAT has been investigated at various modified electrode surfaces with and without nanomaterials. The results show that CAT immobilized on nanomaterial modified electrodes shows excellent catalytic activity, high sensitivity and the lowest detection limit for H2O2 determination. In the presence of nanomaterials, the direct electron transfer between the heme group of the enzyme and the electrode surface improved significantly. Moreover, the immobilized CAT is highly biocompatible and remains extremely stable within the nanomaterial matrices. This review discusses about the versatile approaches carried out in CAT immobilization for direct electrochemistry and electrochemical sensor development aimed as efficient H2O2 determination. The benefits of immobilizing CAT in nanomaterial matrices have also been highlighted. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
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Open AccessReview Applications of SAR Interferometry in Earth and Environmental Science Research
Sensors 2009, 9(3), 1876-1912; doi:10.3390/s90301876
Received: 23 September 2008 / Revised: 10 December 2009 / Accepted: 12 March 2009 / Published: 13 March 2009
Cited by 24 | PDF Full-text (305 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides a review of the progress in regard to the InSAR remote sensing technique and its applications in earth and environmental sciences, especially in the past decade. Basic principles, factors, limits, InSAR sensors, available software packages for the generation of [...] Read more.
This paper provides a review of the progress in regard to the InSAR remote sensing technique and its applications in earth and environmental sciences, especially in the past decade. Basic principles, factors, limits, InSAR sensors, available software packages for the generation of InSAR interferograms were summarized to support future applications. Emphasis was placed on the applications of InSAR in seismology, volcanology, land subsidence/uplift, landslide, glaciology, hydrology, and forestry sciences. It ends with a discussion of future research directions. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))

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