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Sensors, Volume 8, Issue 10 (October 2008), Pages 6125-6790

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Editorial

Jump to: Research, Review

Open AccessEditorial Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology
Sensors 2008, 8(10), 6125-6131; doi:10.3390/s8106125
Received: 25 September 2008 / Accepted: 26 September 2008 / Published: 1 October 2008
Cited by 2 | PDF Full-text (457 KB) | HTML Full-text | XML Full-text
Abstract Editorial note concerning the "Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology" special issue. Full article

Research

Jump to: Editorial, Review

Open AccessArticle Modelling Spatial and Temporal Forest Cover Change Patterns (1973-2020): A Case Study from South Western Ghats (India)
Sensors 2008, 8(10), 6132-6153; doi:10.3390/s8106132
Received: 13 August 2008 / Revised: 20 September 2008 / Accepted: 21 September 2008 / Published: 1 October 2008
Cited by 13 | PDF Full-text (1548 KB) | HTML Full-text | XML Full-text
Abstract
This study used time series remote sensing data from 1973, 1990 and 2004 to assess spatial forest cover change patterns in the Kalakad-Mundanthurai Tiger Reserve (KMTR), South Western Ghats (India). Analysis of forest cover changes and its causes are the most challenging [...] Read more.
This study used time series remote sensing data from 1973, 1990 and 2004 to assess spatial forest cover change patterns in the Kalakad-Mundanthurai Tiger Reserve (KMTR), South Western Ghats (India). Analysis of forest cover changes and its causes are the most challenging areas of landscape ecology, especially due to the absence of temporal ground data and comparable space platform based data. Comparing remotely sensed data from three different sources with sensors having different spatial and spectral resolution presented a technical challenge. Quantitative change analysis over a long period provided a valuable insight into forest cover dynamics in this area. Time-series maps were combined within a geographical information system (GIS) with biotic and abiotic factors for modelling its future change. The land-cover change has been modelled using GEOMOD and predicted for year 2020 using the current disturbance scenario. Comparison of the forest change maps over the 31-year period shows that evergreen forest being degraded (16%) primarily in the form of selective logging and clear felling to raise plantations of coffee, tea and cardamom. The natural disturbances such as forest fire, wildlife grazing, invasions after clearance and soil erosion induced by anthropogenic pressure over the decades are the reasons of forest cover change in KMTR. The study demonstrates the role of remote sensing and GIS in monitoring of large-coverage of forest area continuously for a given region over time more precisely and in cost-effective manner which will be ideal for conservation planning and prioritization. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Fabrication and Optimization of a Nanoporous Platinum Electrode and a Non-enzymatic Glucose Micro-sensor on Silicon
Sensors 2008, 8(10), 6154-6164; doi:10.3390/s8106154
Received: 27 August 2008 / Revised: 24 September 2008 / Accepted: 26 September 2008 / Published: 1 October 2008
Cited by 34 | PDF Full-text (377 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, optimal conditions for fabrication of nanoporous platinum (Pt) were investigated in order to use it as a sensitive sensing electrode for silicon CMOS integrable non-enzymatic glucose micro-sensor applications. Applied charges, voltages, and temperatures were varied during the electroplating of [...] Read more.
In this paper, optimal conditions for fabrication of nanoporous platinum (Pt) were investigated in order to use it as a sensitive sensing electrode for silicon CMOS integrable non-enzymatic glucose micro-sensor applications. Applied charges, voltages, and temperatures were varied during the electroplating of Pt into the formed nonionic surfactant C16EO8 nano-scaled molds in order to fabricate nanoporous Pt electrodes with large surface roughness factor (RF), uniformity, and reproducibility. The fabricated nanoporous Pt electrodes were characterized using atomic force microscopy (AFM) and electrochemical cyclic voltammograms. Optimal electroplating conditions were determined to be an applied charge of 35 mC/mm2, a voltage of -0.12 V, and a temperature of 25 °C, respectively. The optimized nanoporous Pt electrode had an electrochemical RF of 375 and excellent reproducibility. The optimized nanoporous Pt electrode was applied to fabricate non-enzymatic glucose micro-sensor with three electrode systems. The fabricated sensor had a size of 3 mm x 3 mm, air gap of 10 µm, working electrode (WE) area of 4.4 mm2, and sensitivity of 37.5 µA•L/mmol•cm2. In addition, it showed large detection range from 0.05 to 30 mmolL-1 and stable recovery responsive to the step changes in glucose concentration. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Two Improvements of an Operational Two-Layer Model for Terrestrial Surface Heat Flux Retrieval
Sensors 2008, 8(10), 6165-6187; doi:10.3390/s8106165
Received: 1 September 2008 / Revised: 27 September 2008 / Accepted: 28 September 2008 / Published: 1 October 2008
Cited by 28 | PDF Full-text (840 KB) | HTML Full-text | XML Full-text
Abstract
In order to make the prediction of land surface heat fluxes more robust, two improvements were made to an operational two-layer model proposed previously by Zhang. These improvements are: 1) a surface energy balance method is used to determine the theoretical boundary [...] Read more.
In order to make the prediction of land surface heat fluxes more robust, two improvements were made to an operational two-layer model proposed previously by Zhang. These improvements are: 1) a surface energy balance method is used to determine the theoretical boundary lines (namely ‘true wet/cool edge’ and ‘true dry/warm edge’ in the trapezoid) in the scatter plot for the surface temperature versus the fractional vegetation cover in mixed pixels; 2) a new assumption that the slope of the Tmf curves is mainly controlled by soil water content is introduced. The variables required by the improved method include near surface vapor pressure, air temperature, surface resistance, aerodynamic resistance, fractional vegetation cover, surface temperature and net radiation. The model predictions from the improved model were assessed in this study by in situ measurements, which show that the total latent heat flux from the soil and vegetation are in close agreement with the in situ measurement with an RMSE (Root Mean Square Error) ranging from 30 w/m2~50 w/m2,which is consistent with the site scale measurement of latent heat flux. Because soil evaporation and vegetation transpiration are not measured separately from the field site, in situ measured CO2 flux is used to examine the modeled λEveg. Similar trends of seasonal variations of vegetation were found for the canopy transpiration retrievals and in situ CO2 flux measurements. The above differences are mainly caused by 1) the scale disparity between the field measurement and the MODIS observation; 2) the non-closure problem of the surface energy balance from the surface fluxes observations themselves. The improved method was successfully used to predict the component surface heat fluxes from the soil and vegetation and it provides a promising approach to study the canopy transpiration and the soil evaporation quantitatively during the rapid growing season of winter wheat in northern China. Full article
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Open AccessCommunication Analyzing Land Use/Land Cover Changes Using Remote Sensing and GIS in Rize, North-East Turkey
Sensors 2008, 8(10), 6188-6202; doi:10.3390/s8106188
Received: 19 August 2008 / Revised: 21 September 2008 / Accepted: 19 September 2008 / Published: 1 October 2008
Cited by 27 | PDF Full-text (1154 KB) | HTML Full-text | XML Full-text
Abstract
Mapping land use/land cover (LULC) changes at regional scales is essential for a wide range of applications, including landslide, erosion, land planning, global warming etc. LULC alterations (based especially on human activities), negatively effect the patterns of climate, the patterns of natural [...] Read more.
Mapping land use/land cover (LULC) changes at regional scales is essential for a wide range of applications, including landslide, erosion, land planning, global warming etc. LULC alterations (based especially on human activities), negatively effect the patterns of climate, the patterns of natural hazard and socio-economic dynamics in global and local scale. In this study, LULC changes are investigated by using of Remote Sensing and Geographic Information Systems (GIS) in Rize, North-East Turkey. For this purpose, firstly supervised classification technique is applied to Landsat images acquired in 1976 and 2000. Image Classification of six reflective bands of two Landsat images is carried out by using maximum likelihood method with the aid of ground truth data obtained from aerial images dated 1973 and 2002. The second part focused on land use land cover changes by using change detection comparison (pixel by pixel). In third part of the study, the land cover changes are analyzed according to the topographic structure (slope and altitude) by using GIS functions. The results indicate that severe land cover changes have occurred in agricultural (36.2%) (especially in tea gardens), urban (117%), pasture (-72.8%) and forestry (-12.8%) areas has been experienced in the region between 1976 and 2000. It was seen that the LULC changes were mostly occurred in coastal areas and in areas having low slope values. Full article
(This article belongs to the Special Issue Remote Sensing of Land Surface Properties, Patterns and Processes)
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Open AccessArticle GACEM: Genetic Algorithm Based Classifier Ensemble in a Multi-sensor System
Sensors 2008, 8(10), 6203-6224; doi:10.3390/s8106203
Received: 20 April 2008 / Revised: 22 September 2008 / Accepted: 26 September 2008 / Published: 1 October 2008
Cited by 6 | PDF Full-text (475 KB) | HTML Full-text | XML Full-text
Abstract
Multi-sensor systems (MSS) have been increasingly applied in pattern classification while searching for the optimal classification framework is still an open problem. The development of the classifier ensemble seems to provide a promising solution. The classifier ensemble is a learning paradigm where [...] Read more.
Multi-sensor systems (MSS) have been increasingly applied in pattern classification while searching for the optimal classification framework is still an open problem. The development of the classifier ensemble seems to provide a promising solution. The classifier ensemble is a learning paradigm where many classifiers are jointly used to solve a problem, which has been proven an effective method for enhancing the classification ability. In this paper, by introducing the concept of Meta-feature (MF) and Trans-function (TF) for describing the relationship between the nature and the measurement of the observed phenomenon, classification in a multi-sensor system can be unified in the classifier ensemble framework. Then an approach called Genetic Algorithm based Classifier Ensemble in Multi-sensor system (GACEM) is presented, where a genetic algorithm is utilized for optimization of both the selection of features subset and the decision combination simultaneously. GACEM trains a number of classifiers based on different combinations of feature vectors at first and then selects the classifiers whose weight is higher than the pre-set threshold to make up the ensemble. An empirical study shows that, compared with the conventional feature-level voting and decision-level voting, not only can GACEM achieve better and more robust performance, but also simplify the system markedly. Full article
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Open AccessArticle Mesoporous Silicon with Modified Surface for Plant Viruses and Their Protein Particle Sensing
Sensors 2008, 8(10), 6225-6234; doi:10.3390/s8106225
Received: 1 April 2008 / Revised: 1 September 2008 / Accepted: 1 September 2008 / Published: 1 October 2008
Cited by 5 | PDF Full-text (395 KB) | HTML Full-text | XML Full-text
Abstract
Changes in electric parameters of a mesoporous silicon treated by a plasma chemical etching with fluorine and hydrogen ions, under the adsorption of NEPO (Nematodetransmitted Polyhedral) plant viruses such as TORSV (Tomato Ringspot Virus), GFLV (Grapevine Fan Leaf Virus) and protein macromolecule [...] Read more.
Changes in electric parameters of a mesoporous silicon treated by a plasma chemical etching with fluorine and hydrogen ions, under the adsorption of NEPO (Nematodetransmitted Polyhedral) plant viruses such as TORSV (Tomato Ringspot Virus), GFLV (Grapevine Fan Leaf Virus) and protein macromolecule from TORSV particles are described. The current response to the applied voltage is measured for each virus particle to investigate the material parameters which are sensitive to the adsorbed particles. The peculiar behaviors of the response are modeled by the current-voltage relationship in a MOSFET. This model explains the behavior well and the double gate model of the MOSFET informs that the mesoporous silicon is a highly sensitive means of detecting the viruses in the size range less than 50 nm. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle APEX - the Hyperspectral ESA Airborne Prism Experiment
Sensors 2008, 8(10), 6235-6259; doi:10.3390/s8106235
Received: 28 April 2008 / Revised: 10 September 2008 / Accepted: 23 September 2008 / Published: 1 October 2008
Cited by 37 | PDF Full-text (1280 KB) | HTML Full-text | XML Full-text
Abstract
The airborne ESA-APEX (Airborne Prism Experiment) hyperspectral mission simulator is described with its distinct specifications to provide high quality remote sensing data. The concept of an automatic calibration, performed in the Calibration Home Base (CHB) by using the Control Test Master (CTM), [...] Read more.
The airborne ESA-APEX (Airborne Prism Experiment) hyperspectral mission simulator is described with its distinct specifications to provide high quality remote sensing data. The concept of an automatic calibration, performed in the Calibration Home Base (CHB) by using the Control Test Master (CTM), the In-Flight Calibration facility (IFC), quality flagging (QF) and specific processing in a dedicated Processing and Archiving Facility (PAF), and vicarious calibration experiments are presented. A preview on major applications and the corresponding development efforts to provide scientific data products up to level 2/3 to the user is presented for limnology, vegetation, aerosols, general classification routines and rapid mapping tasks. BRDF (Bidirectional Reflectance Distribution Function) issues are discussed and the spectral database SPECCHIO (Spectral Input/Output) introduced. The optical performance as well as the dedicated software utilities make APEX a state-of-the-art hyperspectral sensor, capable of (a) satisfying the needs of several research communities and (b) helping the understanding of the Earth’s complex mechanisms. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Switzerland)
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Open AccessArticle A New Method to Define the VI-Ts Diagram Using Subpixel Vegetation and Soil Information: A Case Study over a Semiarid Agricultural Region in the North China Plain
Sensors 2008, 8(10), 6260-6279; doi:10.3390/s8106260
Received: 4 September 2008 / Revised: 17 September 2008 / Accepted: 27 September 2008 / Published: 7 October 2008
Cited by 18 | PDF Full-text (576 KB) | HTML Full-text | XML Full-text
Abstract
The VI-Ts diagram determined by the scatter points of the vegetation index (VI) and surface temperature (Ts) has been widely applied in land surface studies. In the VI-Ts diagram, dry point is defined as a pixel with maximum Ts and minimum VI, [...] Read more.
The VI-Ts diagram determined by the scatter points of the vegetation index (VI) and surface temperature (Ts) has been widely applied in land surface studies. In the VI-Ts diagram, dry point is defined as a pixel with maximum Ts and minimum VI, while wet point is defined as a pixel with minimum Ts and maximum VI. If both dry and wet points can be obtained simultaneously, a triangular VI-Ts diagram can be readily defined. However, traditional methods cannot define an ideal VI-Ts diagram if there are no full ranges of land surface moisture and VI, such as during rainy season or in a period with a narrow VI range. In this study, a new method was proposed to define the VI-Ts diagram based on the subpixel vegetation and soil information, which was independent of the full ranges of land surface moisture and VI. In this method, a simple approach was firstly proposed to decompose Ts of a given pixel into two components, the surface temperatures of soil (Tsoil) and vegetation (Tveg), by means of Ts and VI information of neighboring pixels. The minimum Tveg and maximum Tsoil were then used to determine the wet and dry points respectively within a given sampling window. This method was tested over a 30 km × 30 km semiarid agricultural area in the North China Plain through 2003 using Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) and MODerate-resolution Imaging Spectroradiometer (MODIS) data. The wet and dry points obtained from our proposed method and from a traditional method were compared with those obtained from ground data within the sampling window with the 30 km × 30 km size. Results show that Tsoil and Tveg can be obtained with acceptable accuracies, and that our proposed method can define reasonable VI-Ts diagrams over a semiarid agricultural region throughout the whole year, even for both cases of rainy season and narrow range of VI. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Crime Scene Reconstruction Using a Fully Geomatic Approach
Sensors 2008, 8(10), 6280-6302; doi:10.3390/s8106280
Received: 14 August 2008 / Revised: 15 September 2008 / Accepted: 7 October 2008 / Published: 8 October 2008
Cited by 5 | PDF Full-text (1434 KB) | HTML Full-text | XML Full-text
Abstract
This paper is focused on two main topics: crime scene reconstruction, based on a geomatic approach, and crime scene analysis, through GIS based procedures. According to the experience of the authors in performing forensic analysis for real cases, the aforesaid topics will [...] Read more.
This paper is focused on two main topics: crime scene reconstruction, based on a geomatic approach, and crime scene analysis, through GIS based procedures. According to the experience of the authors in performing forensic analysis for real cases, the aforesaid topics will be examined with the specific goal of verifying the relationship of human walk paths at a crime scene with blood patterns on the floor. In order to perform such analyses, the availability of pictures taken by first aiders is mandatory, since they provide information about the crime scene before items are moved or interfered with. Generally, those pictures are affected by large geometric distortions, thus - after a brief description of the geomatic techniques suitable for the acquisition of reference data (total station surveying, photogrammetry and laser scanning) - it will be shown the developed methodology, based on photogrammetric algorithms, aimed at calibrating, georeferencing and mosaicking the available images acquired on the scene. The crime scene analysis is based on a collection of GIS functionalities for simulating human walk movements and creating a statistically significant sample. The developed GIS software component will be described in detail, showing how the analysis of this statistical sample of simulated human walks allows to rigorously define the probability of performing a certain walk path without touching the bloodstains on the floor. Full article
(This article belongs to the Special Issue GIS Crime Mapping)
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Open AccessArticle A Multivariate Model for Coastal Water Quality Mapping Using Satellite Remote Sensing Images
Sensors 2008, 8(10), 6321-6339; doi:10.3390/s8106321
Received: 11 September 2008 / Revised: 27 September 2008 / Accepted: 6 October 2008 / Published: 10 October 2008
Cited by 8 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
his study demonstrates the feasibility of coastal water quality mapping using satellite remote sensing images. Water quality sampling campaigns were conducted over a coastal area in northern Taiwan for measurements of three water quality variables including Secchi disk depth, turbidity, and total [...] Read more.
his study demonstrates the feasibility of coastal water quality mapping using satellite remote sensing images. Water quality sampling campaigns were conducted over a coastal area in northern Taiwan for measurements of three water quality variables including Secchi disk depth, turbidity, and total suspended solids. SPOT satellite images nearly concurrent with the water quality sampling campaigns were also acquired. A spectral reflectance estimation scheme proposed in this study was applied to SPOT multispectral images for estimation of the sea surface reflectance. Two models, univariate and multivariate, for water quality estimation using the sea surface reflectance derived from SPOT images were established. The multivariate model takes into consideration the wavelength-dependent combined effect of individual seawater constituents on the sea surface reflectance and is superior over the univariate model. Finally, quantitative coastal water quality mapping was accomplished by substituting the pixel-specific spectral reflectance into the multivariate water quality estimation model. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Thin Film on CMOS Active Pixel Sensor for Space Applications
Sensors 2008, 8(10), 6340-6354; doi:10.3390/s8106340
Received: 8 September 2008 / Revised: 23 September 2008 / Accepted: 8 October 2008 / Published: 13 October 2008
Cited by 4 | PDF Full-text (367 KB) | HTML Full-text | XML Full-text
Abstract
A 664 x 664 element Active Pixel image Sensor (APS) with integrated analog signal processing, full frame synchronous shutter and random access for applications in star sensors is presented and discussed. A thick vertical diode array in Thin Film on CMOS (TFC) [...] Read more.
A 664 x 664 element Active Pixel image Sensor (APS) with integrated analog signal processing, full frame synchronous shutter and random access for applications in star sensors is presented and discussed. A thick vertical diode array in Thin Film on CMOS (TFC) technology is explored to achieve radiation hardness and maximum fill factor. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
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Open AccessArticle Room Temperature Ammonia Gas Sensing Using Mixed Conductor based TEMPOS Structures
Sensors 2008, 8(10), 6355-6370; doi:10.3390/s8106355
Received: 20 August 2008 / Revised: 18 September 2008 / Accepted: 7 October 2008 / Published: 14 October 2008
Cited by 16 | PDF Full-text (112 KB) | HTML Full-text | XML Full-text
Abstract
The current/voltage characteristics of mixed (ion+electron) conductor-based ‘TEMPOS’ (Tunable Electronic Material with Pores in Oxide on Silicon) structures are reported. TEMPOS are novel electronic MOS-like structures having etched swift heavy ion tracks (i.e., nanopores) in the dielectric layer filled with some conducting [...] Read more.
The current/voltage characteristics of mixed (ion+electron) conductor-based ‘TEMPOS’ (Tunable Electronic Material with Pores in Oxide on Silicon) structures are reported. TEMPOS are novel electronic MOS-like structures having etched swift heavy ion tracks (i.e., nanopores) in the dielectric layer filled with some conducting material. The three contacts (two on top and one on the bottom), which resemble the classical bipolar or field effect transistor arrangements are, in principle, interchangeable when the overall electrical resistance along the tracks and on the surface are similar. Consequently, three configurations are obtained by interchanging the top contacts with the base contact in electronic circuits. The current/voltage characteristics show a diode like behaviour. Impedance measurements have been made for TEMPOS structures with tracks filled with ion conductors and also mixed conductors to study the ammonia sensing behaviour. The impedance has been found to be a function of frequency and magnitude of the applied signal and concentration of the ammonia solution. This is attributed to the large number of charge carriers (here protons) available for conduction on exposure to ammonia and also to the large surface to volume ratio of the polymer composites embedded in the ion tracks. The measurement of both, the real and imaginary parts of impedance allows one to enhance the detection sensitivity greatly. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Mining the Urban Sprawl Pattern: A Case Study on Sunan, China
Sensors 2008, 8(10), 6371-6395; doi:10.3390/s8106371
Received: 13 August 2008 / Revised: 9 October 2008 / Accepted: 10 October 2008 / Published: 14 October 2008
Cited by 14 | PDF Full-text (1699 KB) | HTML Full-text | XML Full-text
Abstract
China’s urbanization is going into a fast development stage. This paper focuses on the recent evolution of an urbanized area – Sunan, the southern part of Jiangsu province in the Yangtze River Delta in China – by means of complementary approaches, especially [...] Read more.
China’s urbanization is going into a fast development stage. This paper focuses on the recent evolution of an urbanized area – Sunan, the southern part of Jiangsu province in the Yangtze River Delta in China – by means of complementary approaches, especially different fractal and autocorrelation measures. The research shows that Sunan’s urban clusters are becoming more and more homogenous and compact and are growing up along the important transportation axes. The enriching discussion of the findings establishes the links between the morphology of urban sprawl and recent socio-economic changes in China. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Implantable Biosensors for Real-time Strain and Pressure Monitoring
Sensors 2008, 8(10), 6396-6406; doi:10.3390/s8106396
Received: 15 August 2008 / Revised: 7 October 2008 / Accepted: 10 October 2008 / Published: 15 October 2008
Cited by 18 | PDF Full-text (150 KB) | HTML Full-text | XML Full-text
Abstract
Implantable biosensors were developed for real-time monitoring of pressure and strain in the human body. The sensors, which are wireless and passive, consisted of a soft magnetic material and a permanent magnet. When exposed to a low frequency AC magnetic field, the [...] Read more.
Implantable biosensors were developed for real-time monitoring of pressure and strain in the human body. The sensors, which are wireless and passive, consisted of a soft magnetic material and a permanent magnet. When exposed to a low frequency AC magnetic field, the soft magnetic material generated secondary magnetic fields that also included the higher-order harmonic modes. Parameters of interest were determined by measuring the changes in the pattern of these higher-order harmonic fields, which was achieved by changing the intensity of a DC magnetic field generated by a permanent magnet. The DC magnetic field, or the biasing field, was altered by changing the separation distance between the soft magnetic material and the permanent magnet. For pressure monitoring, the permanent magnet was placed on the membrane of an airtight chamber. Changes in the ambient pressure deflected the membrane, altering the separation distance between the two magnetic elements and thus the higher-order harmonic fields. Similarly, the soft magnetic material and the permanent magnet were separated by a flexible substrate in the stress/strain sensor. Compressive and tensile forces flexed the substrate, changing the separation distance between the two elements and the higher-order harmonic fields. In the current study, both stress/strain and pressure sensors were fabricated and characterized. Good stability, linearity and repeatability of the sensors were demonstrated. This passive and wireless sensor technology may be useful for long term detection of physical quantities within the human body as a part of treatment assessment, disease diagnosis, or detection of biomedical implant failures. Full article
(This article belongs to the Special Issue BioMEMS)
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Open AccessArticle Effects of Gold Nanoparticles on the Response of Phenol Biosensor Containing Photocurable Membrane with Tyrosinase
Sensors 2008, 8(10), 6407-6416; doi:10.3390/s8106407
Received: 14 April 2008 / Revised: 27 September 2008 / Accepted: 13 October 2008 / Published: 16 October 2008
Cited by 10 | PDF Full-text (130 KB) | HTML Full-text | XML Full-text
Abstract
The role of incorporation of gold nanoparticles (50-130 nm in diameter) into a series of photocurable methacrylic-acrylic based biosensor membranes containing tyrosinase on the response for phenol detection was investigated. Membranes with different hydrophilicities were prepared from 2-hydroxyethyl methacrylate and n-butyl acrylate [...] Read more.
The role of incorporation of gold nanoparticles (50-130 nm in diameter) into a series of photocurable methacrylic-acrylic based biosensor membranes containing tyrosinase on the response for phenol detection was investigated. Membranes with different hydrophilicities were prepared from 2-hydroxyethyl methacrylate and n-butyl acrylate via direct photocuring. A range of gold nanoparticles concentrations from 0.01 to 0.5 % (w/w) was incorporated into these membranes during the photocuring process. The addition of gold nanoparticles to the biosensor membrane led to improvement in the response time by a reduction of approximately 5 folds to give response times of 5-10 s. The linear response range of the phenol biosensor was also extended from 24 to 90 mM of phenol. The hydrophilicities of the membrane matrices demonstrated strong influence on the biosensor response and appeared to control the effect of the gold nanoparticles. For less hydrophilic methacrylic-acrylic membranes, the addition of gold nanoparticles led to a poorer sensitivity and detection limit of the biosensor towards phenol. Therefore, for the application of gold nanoparticles in the enhancement of a phenol biosensor response, the nanoparticles should be immobilized in a hydrophilic matrix rather than a hydrophobic material. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Development of Light Powered Sensor Networks for Thermal Comfort Measurement
Sensors 2008, 8(10), 6417-6432; doi:10.3390/s8106417
Received: 2 September 2008 / Revised: 6 October 2008 / Accepted: 13 October 2008 / Published: 16 October 2008
Cited by 11 | PDF Full-text (2355 KB) | HTML Full-text | XML Full-text
Abstract
Recent technological advances in wireless communications have enabled easy installation of sensor networks with air conditioning equipment control applications. However, the sensor node power supply, through either power lines or battery power, still presents obstacles to the distribution of the sensing systems. [...] Read more.
Recent technological advances in wireless communications have enabled easy installation of sensor networks with air conditioning equipment control applications. However, the sensor node power supply, through either power lines or battery power, still presents obstacles to the distribution of the sensing systems. In this study, a novel sensor network, powered by the artificial light, was constructed to achieve wireless power transfer and wireless data communications for thermal comfort measurements. The sensing node integrates an IC-based temperature sensor, a radiation thermometer, a relative humidity sensor, a micro machined flow sensor and a microprocessor for predicting mean vote (PMV) calculation. The 935 MHz band RF module was employed for the wireless data communication with a specific protocol based on a special energy beacon enabled mode capable of achieving zero power consumption during the inactive periods of the nodes. A 5W spotlight, with a dual axis tilt platform, can power the distributed nodes over a distance of up to 5 meters. A special algorithm, the maximum entropy method, was developed to estimate the sensing quantity of climate parameters if the communication module did not receive any response from the distributed nodes within a certain time limit. The light-powered sensor networks were able to gather indoor comfort-sensing index levels in good agreement with the comfort-sensing vote (CSV) preferred by a human being and the experimental results within the environment suggested that the sensing system could be used in air conditioning systems to implement a comfort-optimal control strategy. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle Real-time Monitoring of Non-specific Toxicity Using a Saccharomyces cerevisiae Reporter System
Sensors 2008, 8(10), 6433-6447; doi:10.3390/s8106433
Received: 31 August 2008 / Revised: 27 September 2008 / Accepted: 7 October 2008 / Published: 16 October 2008
Cited by 6 | PDF Full-text (256 KB) | HTML Full-text | XML Full-text
Abstract
Baker’s yeast, Saccharomyces cerevisiae, is the simplest and most well-known representative of eukaryotic cells and thus a convenient model organism for evaluating toxic effects in human cells and tissues. Yeast cell sensors are easy to maintain with short generation times, which makes [...] Read more.
Baker’s yeast, Saccharomyces cerevisiae, is the simplest and most well-known representative of eukaryotic cells and thus a convenient model organism for evaluating toxic effects in human cells and tissues. Yeast cell sensors are easy to maintain with short generation times, which makes the analytical method of assessing antifungal toxicity cheap and less-time consuming. In this work, the toxicity of test compounds was assessed in bioassays based on bioluminescence inhibition and on traditional growth inhibition on agar plates. The model organism in both tests was a modified S. cerevisiae sensor strain that produces light when provided with D-luciferin in an insect luciferase reporter gene activity assay. The bioluminescence assay showed toxic effects for yeast cell sensor of 5,6-benzo-flavone, rapamycin, nystatin and cycloheximide at concentrations of nM to µM. In addition, arsenic compounds, cadmium chloride, copper sulfate and lead acetate were shown to be potent non-specific inhibitors of the reporter organism described here. The results from a yeast agar diffusion assay correlated with the bioluminescence assay results. Full article
(This article belongs to the Special Issue Toxin Sensors)
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Open AccessCommunication Extreme Silica Optical Fibre Gratings
Sensors 2008, 8(10), 6448-6452; doi:10.3390/s8106448
Received: 2 September 2008 / Revised: 18 September 2008 / Accepted: 17 October 2008 / Published: 20 October 2008
Cited by 101 | PDF Full-text (164 KB) | HTML Full-text | XML Full-text
Abstract A regenerated optical fibre Bragg grating that survives temperature cycling up to 1,295°C is demonstrated. A model based on seeded crystallisation or amorphisation is proposed. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Detection of Staphylococcus epidermidis by a Quartz Crystal Microbalance Nucleic Acid Biosensor Array Using Au Nanoparticle Signal Amplification
Sensors 2008, 8(10), 6453-6470; doi:10.3390/s8106453
Received: 2 September 2008 / Revised: 3 October 2008 / Accepted: 17 October 2008 / Published: 21 October 2008
Cited by 18 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcus epidermidis is a critical pathogen of nosocomial blood infections, resulting in significant morbidity and mortality. A piezoelectric quartz crystal microbalance (QCM) nucleic acid biosensor array using Au nanoparticle signal amplification was developed to rapidly detect S. epidermidis in clinical samples. The [...] Read more.
Staphylococcus epidermidis is a critical pathogen of nosocomial blood infections, resulting in significant morbidity and mortality. A piezoelectric quartz crystal microbalance (QCM) nucleic acid biosensor array using Au nanoparticle signal amplification was developed to rapidly detect S. epidermidis in clinical samples. The synthesized thiolated probes specific targeting S. epidermidis 16S rRNA gene were immobilized on the surface of QCM nucleic acid biosensor arrays. Hybridization was induced by exposing the immobilized probes to the PCR amplified fragments of S. epidermidis, resulting in a mass change and a consequent frequency shift of the QCM biosensor. To further enhance frequency shift results from above described hybridizations, streptavidin coated Au nanoparticles were conjugated to the PCR amplified fragments. The results showed that the lowest detection limit of current QCM system was 1.3×103 CFU/mL. A linear correlation was found when the concentration of S. epidermidis varied from 1.3×103 to 1.3×107 CFU/mL. In addition, 55 clinical samples were detected with both current QCM biosensor system and conventional clinical microbiological method, and the sensitivity and specificity of current QCM biosensor system were 97.14% and 100%, respectively. In conclusion, the current QCM system is a rapid, low-cost and sensitive method that can be used to identify infection of S. epidermidis in clinical samples. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Effect of the Temperature-Emissivity Contrast on the Chemical Signal for Gas Plume Detection Using Thermal Image Data
Sensors 2008, 8(10), 6471-6483; doi:10.3390/s8106471
Received: 4 September 2008 / Revised: 17 October 2008 / Accepted: 20 October 2008 / Published: 21 October 2008
Cited by 2 | PDF Full-text (191 KB) | HTML Full-text | XML Full-text
Abstract
Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which [...] Read more.
Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on chemical signal are described. This analysis shows that the plume’s physical state, emission or absorption, is directly dependent on the background emissivity and plume/ground temperatures. It then describes what conditions on the background emissivity and plume/ground temperatures have inhibiting or amplifying effects on the chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the adaptive matched filter using two chemicals and three distinct background emissivities. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Two-dimensional Co-Seismic Surface Displacements Field of the Chi-Chi Earthquake Inferred from SAR Image Matching
Sensors 2008, 8(10), 6484-6495; doi:10.3390/s8106484
Received: 10 June 2008 / Revised: 14 August 2008 / Accepted: 20 October 2008 / Published: 21 October 2008
Cited by 20 | PDF Full-text (1741 KB) | HTML Full-text | XML Full-text
Abstract
The Mw=7.6 Chi-Chi earthquake in Taiwan occurred in 1999 over the Chelungpu fault and caused a great surface rupture and severe damage. Differential Synthetic Aperture Radar Interferometry (DInSAR) has been applied previously to study the co-seismic ground displacements. There have [...] Read more.
The Mw=7.6 Chi-Chi earthquake in Taiwan occurred in 1999 over the Chelungpu fault and caused a great surface rupture and severe damage. Differential Synthetic Aperture Radar Interferometry (DInSAR) has been applied previously to study the co-seismic ground displacements. There have however been significant limitations in the studies. First, only one-dimensional displacements along the Line-of-Sight (LOS) direction have been measured. The large horizontal displacements along the Chelungpu fault are largely missing from the measurements as the fault is nearly perpendicular to the LOS direction. Second, due to severe signal decorrelation on the hangling wall of the fault, the displacements in that area are un-measurable by differential InSAR method. We estimate the co-seismic displacements in both the azimuth and range directions with the method of SAR amplitude image matching. GPS observations at the 10 GPS stations are used to correct for the orbital ramp in the amplitude matching and to create the two-dimensional (2D) co-seismic surface displacements field using the descending ERS-2 SAR image pair. The results show that the co-seismic displacements range from about -2.0 m to 0.7 m in the azimuth direction (with the positive direction pointing to the flight direction), with the footwall side of the fault moving mainly southwards and the hanging wall side northwards. The displacements in the LOS direction range from about -0.5 m to 1.0 m, with the largest displacement occuring in the northeastern part of the hanging wall (the positive direction points to the satellite from ground). Comparing the results from amplitude matching with those from DInSAR, we can see that while only a very small fraction of the LOS displacement has been recovered by the DInSAR mehtod, the azimuth displacements cannot be well detected with the DInSAR measurements as they are almost perpendicular to the LOS. Therefore, the amplitude matching method is obviously more advantageous than the DInSAR in studying the Chi-Chi earthquake. Another advantage of the method is that the displacement in the hanging wall of the fault that is un-measurable with DInSAR due to severe signal decorrelation can almost completely retrieved in this research. This makes the whole co-seismic displacements field clearly visible and the location of the rupture identifiable. Using displacements measured at 15 independent GPS stations for validation, we found that the RMS values of the differences between the two types of results were 6.9 cm and 5.7 cm respectively in the azimuth and the range directions. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
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Open AccessArticle Arc-Welding Spectroscopic Monitoring based on Feature Selection and Neural Networks
Sensors 2008, 8(10), 6496-6506; doi:10.3390/s8106496
Received: 9 October 2008 / Revised: 17 October 2008 / Accepted: 21 October 2008 / Published: 21 October 2008
Cited by 7 | PDF Full-text (1222 KB) | HTML Full-text | XML Full-text
Abstract
A new spectral processing technique designed for application in the on-line detection and classification of arc-welding defects is presented in this paper. A noninvasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral [...] Read more.
A new spectral processing technique designed for application in the on-line detection and classification of arc-welding defects is presented in this paper. A noninvasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral information is then processed in two consecutive stages. A compression algorithm is first applied to the data, allowing real-time analysis. The selected spectral bands are then used to feed a classification algorithm, which will be demonstrated to provide an efficient weld defect detection and classification. The results obtained with the proposed technique are compared to a similar processing scheme presented in previous works, giving rise to an improvement in the performance of the monitoring system. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
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Open AccessArticle Porous Silicon Based Resonant Mirrors for Biochemical Sensing
Sensors 2008, 8(10), 6549-6556; doi:10.3390/s8106549
Received: 6 June 2008 / Revised: 6 October 2008 / Accepted: 21 October 2008 / Published: 23 October 2008
Cited by 27 | PDF Full-text (282 KB) | HTML Full-text | XML Full-text
Abstract
We report on our preliminary results in the realization and characterization of a porous silicon (PSi) resonant mirror (RM) for optical biosensing. We have numerically and experimentally studied the coupling between the electromagnetic field, totally reflected at the base of a high [...] Read more.
We report on our preliminary results in the realization and characterization of a porous silicon (PSi) resonant mirror (RM) for optical biosensing. We have numerically and experimentally studied the coupling between the electromagnetic field, totally reflected at the base of a high refractive index prism, and the optical modes of a PSi waveguide. This configuration is very sensitive to changes in the refractive index and/or in thickness of the sensor surface. Due to the high specific area of the PSi waveguide, very low DNA concentrations can be detected confirming that the RM could be a very sensitive and labelfree optical biosensor. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor
Sensors 2008, 8(10), 6557-6565; doi:10.3390/s8106557
Received: 26 August 2008 / Revised: 25 September 2008 / Accepted: 21 October 2008 / Published: 23 October 2008
Cited by 4 | PDF Full-text (407 KB) | HTML Full-text | XML Full-text
Abstract
Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in [...] Read more.
Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds
Sensors 2008, 8(10), 6595-6604; doi:10.3390/s8106595
Received: 23 September 2008 / Revised: 16 October 2008 / Accepted: 21 October 2008 / Published: 23 October 2008
Cited by 5 | PDF Full-text (1902 KB) | HTML Full-text | XML Full-text
Abstract
Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here [...] Read more.
Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
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Open AccessArticle Surface-Modified Gold Nanoparticles with Folic Acid as Optical Probes for Cellular Imaging
Sensors 2008, 8(10), 6660-6673; doi:10.3390/s8106660
Received: 24 July 2008 / Revised: 21 September 2008 / Accepted: 21 October 2008 / Published: 24 October 2008
Cited by 25 | PDF Full-text (1143 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we demonstrate that the uptake rate of the surface-modified gold nanoparticles (GNPs) with folic acid by specific cells can be increased significantly, if the membranes of these cells have sufficient folic-acid receptors. Two human breast cancer cell lines were [...] Read more.
In this study, we demonstrate that the uptake rate of the surface-modified gold nanoparticles (GNPs) with folic acid by specific cells can be increased significantly, if the membranes of these cells have sufficient folic-acid receptors. Two human breast cancer cell lines were studied; one is MDA-MB-435S cell, and the other T-47D cell. The expression of the folic acid receptors of the former is much higher than that of the latter. These cells were incubated with media containing bare GNPs or GNPs conjugated with folic acid individually. Due to the unique optical behavior (i.e. surface plasmon resonance) of GNPs, the uptake amount of GNPs by cells can be identified by using the laser scanning confocal microscopy. Our experiments show that the uptake amount of GNPs in MDAMB-435S cells is higher than that in T-47D cells for the same culture time, if the culture medium contains bare GNPs. Moreover, if the GNPs conjugated with folic acid are used for the culture, the uptake rate of GNPs by MDA-MB-435S cells is improved more. In contrast, the uptake rates of both GNPs are almost the same by T-47D cells. The phenomenon indicates that the uptake rate of GNPs can be improved via the ligand-receptor endocytosis, compared with the nonspecific endocytosis. Therefore, the uptake rate of GNPs conjugated with folic acid by MDA-MB-435S cells is higher than that of bare GNPs. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Impact of Link Unreliability and Asymmetry on the Quality of Connectivity in Large-scale Sensor Networks
Sensors 2008, 8(10), 6674-6691; doi:10.3390/s8106674
Received: 1 July 2008 / Revised: 12 October 2008 / Accepted: 22 October 2008 / Published: 24 October 2008
Cited by 4 | PDF Full-text (300 KB) | HTML Full-text | XML Full-text
Abstract
Connectivity is a fundamental issue in research on wireless sensor networks. However, unreliable and asymmetric links have a great impact on the global quality of connectivity (QoC). By assuming the deployment of nodes a homogeneous Poisson point process and eliminating the border [...] Read more.
Connectivity is a fundamental issue in research on wireless sensor networks. However, unreliable and asymmetric links have a great impact on the global quality of connectivity (QoC). By assuming the deployment of nodes a homogeneous Poisson point process and eliminating the border effect, this paper derives an explicit expression of node non-isolation probability as the upper bound of one-connectivity, based on an analytical link model which incorporates important parameters such as path loss exponent, shadowing variance of channel, modulation, encoding method etc. The derivation has built a bridge over the local link property and the global network connectivity, which makes it clear to see how various parameter impact the QoC. Numerical results obtained further confirm the analysis and can be used as reference for practical design and simulation of wireless ad hoc and sensor networks. Besides, we find giant component size a good relaxed measure of connectivity in some applications that do not require full connectivity. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Comparative and Combinative Study of Urban Heat island in Wuhan City with Remote Sensing and CFD Simulation
Sensors 2008, 8(10), 6692-6703; doi:10.3390/s8106692
Received: 26 March 2008 / Revised: 28 September 2008 / Accepted: 21 October 2008 / Published: 25 October 2008
Cited by 10 | PDF Full-text (541 KB) | HTML Full-text | XML Full-text
Abstract
Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment [...] Read more.
Urban heat islands are one of the most critical urban environment heat problems. Landsat ETM+ satellite data were used to investigate the land surface temperature and underlying surface indices such as NDVI and NDBI. A comparative study of the urban heat environment at different scales, times and locations was done to verify the heat island characteristics. Since remote sensing technology has limitations for dynamic flow analysis in the study of urban spaces, a CFD simulation was used to validate the improvement of the heat environment in a city by means of wind. CFD technology has its own shortcomings in parameter setting and verification, while RS technology is helpful to remedy this. The city of Wuhan and its climatological condition of being hot in summer and cold in winter were chosen to verify the comparative and combinative application of RS with CFD in studying the urban heat island. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
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Open AccessArticle Immunoglobulin G Determination in Human Serum and Milk Using an Immunosensor of New Conception Fitted with an Enzyme Probe as Transducer
Sensors 2008, 8(10), 6727-6746; doi:10.3390/s8106727
Received: 20 May 2008 / Revised: 6 September 2008 / Accepted: 17 October 2008 / Published: 28 October 2008
Cited by 7 | PDF Full-text (219 KB) | HTML Full-text | XML Full-text
Abstract
To completely overcome the problem of the presence of urea in the serum, which can be the cause (especially at low immunoglobulin G concentrations) of a small but non negligible interference in the enzyme reaction of the enzymatic marker, when the measurement [...] Read more.
To completely overcome the problem of the presence of urea in the serum, which can be the cause (especially at low immunoglobulin G concentrations) of a small but non negligible interference in the enzyme reaction of the enzymatic marker, when the measurement was performed by a potentiometric immunosensor that we constructed and characterized in previous work, and which used urease as marker, we have now constructed an entirely different and highly innovative immunosensor. This new device uses the enzyme alkaline phosphatase as marker, sodium phenylphosphate as substrate but above all, a tyrosinase biosensor obtained by coupling a Clark type gas diffusion amperometric electrode and the tyrosinase enzyme, immobilized in a cellulose triacetate membrane, as transducer. After optimizing the ‘competitive’ measurement procedures, the new immunosensor was used to determine both HIgG and the anti-HIgG, with a limit of detection (LOD) of the order of 3x10-11 M. Clearly this highly innovative construction geometry makes the immunosensor extremely selective. This makes it possible to determine immunoglobulin G both in human serum and milk without the slightest interference by any urea present in these biological matrixes. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Optimization of Single-Sensor Two-State Hot-Wire Anemometer Transmission Bandwidth
Sensors 2008, 8(10), 6747-6760; doi:10.3390/s8106747
Received: 1 September 2008 / Revised: 10 October 2008 / Accepted: 24 October 2008 / Published: 28 October 2008
Cited by 6 | PDF Full-text (315 KB) | HTML Full-text | XML Full-text
Abstract
Hot-wire anemometric measurements of non-isothermal flows require the use of thermal compensation or correction circuitry. One possible solution is a two-state hot-wire anemometer that uses the cyclically changing heating level of a single sensor. The area in which flow velocity and fluid [...] Read more.
Hot-wire anemometric measurements of non-isothermal flows require the use of thermal compensation or correction circuitry. One possible solution is a two-state hot-wire anemometer that uses the cyclically changing heating level of a single sensor. The area in which flow velocity and fluid temperature can be measured is limited by the dimensions of the sensor’s active element. The system is designed to measure flows characterized by high velocity and temperature gradients, although its transmission bandwidth is very limited. In this study, we propose a method to optimize the two-state hot-wire anemometer transmission bandwidth. The method is based on the use of a specialized constanttemperature system together with variable dynamic parameters. It is also based on a suitable measurement cycle paradigm. Analysis of the method was undertaken using model testing. Our results reveal a possible significant broadening of the two-state hot-wire anemometer's transmission bandwidth. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle Modeling of an Optical Sensor Based on Whispering Gallery Modes (WGMs) on the Surface Guiding Layer of Glass Filaments
Sensors 2008, 8(10), 6761-6768; doi:10.3390/s8106761
Received: 22 September 2008 / Revised: 10 October 2008 / Accepted: 24 October 2008 / Published: 28 October 2008
Cited by 9 | PDF Full-text (251 KB) | HTML Full-text | XML Full-text
Abstract
A ring-resonator-based refractive index sensor is proposed in this paper. Glass filaments with surface guiding layers created by ion exchange are crossed with a fiber taper to act as a ring resonator sensor. Theoretical simulation of the sensor response is proposed, and [...] Read more.
A ring-resonator-based refractive index sensor is proposed in this paper. Glass filaments with surface guiding layers created by ion exchange are crossed with a fiber taper to act as a ring resonator sensor. Theoretical simulation of the sensor response is proposed, and optimization of structural parameters including thickness and refractive index of the surface guiding layer and the diameter of the ring resonator for higher sensitivity is investigated. Results show that a detection limit of a variation of ~10-5RIU can be reached. Due to its simple fabrication and easy manipulation as well as good sensing performance, we believe such a micro-cavity sensor will find potential applications in high sensitivity optical sensing. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Linear FBG Temperature Sensor Interrogation with Fabry-Perot ITU Multi-wavelength Reference
Sensors 2008, 8(10), 6769-6776; doi:10.3390/s8106769
Received: 9 October 2008 / Revised: 20 October 2008 / Accepted: 28 October 2008 / Published: 29 October 2008
Cited by 21 | PDF Full-text (350 KB) | HTML Full-text | XML Full-text
Abstract
The equidistantly spaced multi-passbands of a Fabry-Perot ITU filter are used as an efficient multi-wavelength reference for fiber Bragg grating sensor demodulation. To compensate for the nonlinear wavelength tuning effect in the FBG sensor demodulator, a polynomial fitting algorithm was applied to [...] Read more.
The equidistantly spaced multi-passbands of a Fabry-Perot ITU filter are used as an efficient multi-wavelength reference for fiber Bragg grating sensor demodulation. To compensate for the nonlinear wavelength tuning effect in the FBG sensor demodulator, a polynomial fitting algorithm was applied to the temporal peaks of the wavelength-scanned ITU filter. The fitted wavelength values are assigned to the peak locations of the FBG sensor reflections, obtaining constant accuracy, regardless of the wavelength scan range and frequency. A linearity error of about 0.18% against a reference thermocouple thermometer was obtained with the suggested method. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Interfacial Recognition of Acetylcholine by an Amphiphilic p-Sulfonatocalix[8]arene Derivative Incorporated into Dimyristoyl Phosphatidylcholine Vesicles
Sensors 2008, 8(10), 6777-6790; doi:10.3390/s8106777
Received: 23 August 2008 / Revised: 17 October 2008 / Accepted: 23 October 2008 / Published: 29 October 2008
Cited by 9 | PDF Full-text (580 KB) | HTML Full-text | XML Full-text
Abstract
Dodecyl ether derivatives 1-3 of p-sulfonatocalix[n]arene were incorporated into dimyristoyl phosphatidylcholine (DMPC) vesicles, and their binding abilities for acetylcholine (ACh) were examined by using steady-state fluorescence/fluorescence anisotropy and fluorescence correlation spectroscopy (FCS). For the detection of ACh binding to the DMPC vesicles [...] Read more.
Dodecyl ether derivatives 1-3 of p-sulfonatocalix[n]arene were incorporated into dimyristoyl phosphatidylcholine (DMPC) vesicles, and their binding abilities for acetylcholine (ACh) were examined by using steady-state fluorescence/fluorescence anisotropy and fluorescence correlation spectroscopy (FCS). For the detection of ACh binding to the DMPC vesicles containing 5 mol % of 1-3, competitive fluorophore displacement experiments were performed, where rhodamine 6G (Rh6G) was used as a fluorescent guest. The addition of Rh6G to the DMPC vesicles containing 3 resulted in a decrease in the fluorescence intensity of Rh6G with an increase of its fluorescence anisotropy, indicating that Rh6G binds to the DMPC-3 vesicles. In the case of DMPC-1 and DMPC-2 vesicles, significant changes in the fluorescence spectra of Rh6G were not observed. When ACh was added to the DMPC-3 vesicles in the presence of Rh6G ([3]/[Rh6G]=100), the fluorescence intensity of Rh6G increased with a decrease in its fluorescence anisotropy. From the analysis of fluorescence titration data, the association constants were determined to be 7.1×105 M-1 for Rh6G-3 complex and 1.1×102 M-1 for ACh-3 complex at the DMPC-3 vesicles. To get a direct evidence for the binding of Rh6G and its displacement by ACh at the DMPC-3 vesicles, diffusion times of the Rh6G were measured by using FCS. Binding selectivity of the DMPC-3 vesicles for ACh, choline, GABA, L-aspartic acid, L-glutamic acid, L-arginine, L-lysine, L-histamine and ammonium chloride was also evaluated using FCS. Full article
(This article belongs to the Special Issue Molecular Recognition and Sensors, Including Molecular Imprinting)
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Review

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Open AccessReview First Contact to Odors: Our Current Knowledge about Odorant Receptor
Sensors 2008, 8(10), 6303-6320; doi:10.3390/s8106303
Received: 11 September 2008 / Revised: 7 October 2008 / Accepted: 8 October 2008 / Published: 9 October 2008
Cited by 5 | PDF Full-text (522 KB) | HTML Full-text | XML Full-text
Abstract
Chemical senses – especially smell – are known to be important for the fundamental life events such as sensing predators, selecting mates, as well as finding food. The chemical senses are decoded in the olfactory system which is able to detect and [...] Read more.
Chemical senses – especially smell – are known to be important for the fundamental life events such as sensing predators, selecting mates, as well as finding food. The chemical senses are decoded in the olfactory system which is able to detect and differentiate thousands of odorous substances comprised of chemically divergent structures (i.e. odorants). The high selectivity of the olfactory system is heavily dependent on the receptors for each odorants (i.e. odorant receptors). Thus, studying odorant receptors may not only facilitate our understanding the initial events of olfaction but provide crucial knowledge for developing a novel, odorant receptor-based biosensor for chemical screening. Here we provide a review of recent advances in our understanding of odorant receptors. Full article
(This article belongs to the Special Issue Monitoring of Odorous Compounds in the Environment)
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Open AccessReview Characterization of Laser Cleaning of Artworks
Sensors 2008, 8(10), 6507-6548; doi:10.3390/s8106507
Received: 7 July 2008 / Revised: 15 August 2008 / Accepted: 21 October 2008 / Published: 23 October 2008
Cited by 12 | PDF Full-text (5433 KB) | HTML Full-text | XML Full-text
Abstract
The main tasks of conservators of artworks and monuments are the estimation and analysis of damages (present condition), object conservation (cleaning process), and the protection of an object against further degradation. One of the physical methods that is becoming more and more [...] Read more.
The main tasks of conservators of artworks and monuments are the estimation and analysis of damages (present condition), object conservation (cleaning process), and the protection of an object against further degradation. One of the physical methods that is becoming more and more popular for dirt removal is the laser cleaning method. This method is non-contact, selective, local, controlled, self-limiting, gives immediate feedback and preserves even the gentlest of relief - the trace of a paintbrush. Paper presents application of different, selected physical sensing methods to characterize condition of works of art as well as laser cleaning process itself. It includes, tested in our laboratories, optical surface measurements (e.g. colorimetry, scatterometry, interferometry), infrared thermography, optical coherent tomography and acoustic measurements for “on-line” evaluation of cleaning progress. Results of laser spectrometry analyses (LIBS, Raman) will illustrate identification and dating of objects superficial layers. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview A Review of the CMOS Buried Double Junction (BDJ) Photodetector and its Applications
Sensors 2008, 8(10), 6566-6594; doi:10.3390/s8106566
Received: 8 July 2008 / Revised: 4 September 2008 / Accepted: 17 October 2008 / Published: 23 October 2008
Cited by 14 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text
Abstract
A CMOS Buried Double Junction PN (BDJ) photodetector consists of two vertically-stacked photodiodes. It can be operated as a photodiode with improved performance and wavelength-sensitive response. This paper presents a review of this device and its applications. The CMOS implementation and operating [...] Read more.
A CMOS Buried Double Junction PN (BDJ) photodetector consists of two vertically-stacked photodiodes. It can be operated as a photodiode with improved performance and wavelength-sensitive response. This paper presents a review of this device and its applications. The CMOS implementation and operating principle are firstly described. This includes the description of several key aspects directly related to the device performances, such as surface reflection, photon absorption and electron-hole pair generation, photocurrent and dark current generation, etc. SPICE modelling of the detector is then presented. Next, design and process considerations are proposed in order to improve the BDJ performance. Finally, several BDJ-detector-based image sensors provide a survey of their applications. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
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Open AccessReview Molecular Recognition and Specific Interactions for Biosensing Applications
Sensors 2008, 8(10), 6605-6641; doi:10.3390/s8106605
Received: 25 September 2008 / Revised: 16 October 2008 / Accepted: 20 October 2008 / Published: 23 October 2008
Cited by 35 | PDF Full-text (1361 KB) | HTML Full-text | XML Full-text
Abstract
Molecular recognition and specific interactions are reliable and versatile routes for site-specific and well-oriented immobilization of functional biomolecules on surfaces. The control of surface properties via the molecular recognition and specific interactions at the nanoscale is a key element for the nanofabrication [...] Read more.
Molecular recognition and specific interactions are reliable and versatile routes for site-specific and well-oriented immobilization of functional biomolecules on surfaces. The control of surface properties via the molecular recognition and specific interactions at the nanoscale is a key element for the nanofabrication of biosensors with high sensitivity and specificity. This review intends to provide a comprehensive understanding of the molecular recognition- and specific interaction-mediated biosensor fabrication routes that leads to biosensors with well-ordered and controlled structures on both nanopatterned surfaces and nanomaterials. Herein self-assembly of the biomolecules via the molecular recognition and specific interactions on nanoscaled surfaces as well as nanofabrication techniques of the biomolecules for biosensor architecture are discussed. We also describe the detection of molecular recognition- and specific interaction-mediated molecular binding as well as advantages of nanoscale detection. Full article
(This article belongs to the Special Issue Molecular Recognition and Sensors, Including Molecular Imprinting)
Open AccessReview Oil Spill Detection by SAR Images: Dark Formation Detection, Feature Extraction and Classification Algorithms
Sensors 2008, 8(10), 6642-6659; doi:10.3390/s8106642
Received: 10 June 2008 / Revised: 24 August 2008 / Accepted: 21 October 2008 / Published: 23 October 2008
Cited by 64 | PDF Full-text (278 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides a comprehensive review of the use of Synthetic Aperture Radar images (SAR) for detection of illegal discharges from ships. It summarizes the current state of the art, covering operational and research aspects of the application. Oil spills are seriously [...] Read more.
This paper provides a comprehensive review of the use of Synthetic Aperture Radar images (SAR) for detection of illegal discharges from ships. It summarizes the current state of the art, covering operational and research aspects of the application. Oil spills are seriously affecting the marine ecosystem and cause political and scientific concern since they seriously effect fragile marine and coastal ecosystem. The amount of pollutant discharges and associated effects on the marine environment are important parameters in evaluating sea water quality. Satellite images can improve the possibilities for the detection of oil spills as they cover large areas and offer an economical and easier way of continuous coast areas patrolling. SAR images have been widely used for oil spill detection. The present paper gives an overview of the methodologies used to detect oil spills on the radar images. In particular we concentrate on the use of the manual and automatic approaches to distinguish oil spills from other natural phenomena. We discuss the most common techniques to detect dark formations on the SAR images, the features which are extracted from the detected dark formations and the most used classifiers. Finally we conclude with discussion of suggestions for further research. The references throughout the review can serve as starting point for more intensive studies on the subject. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
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Open AccessReview NeuroMEMS: Neural Probe Microtechnologies
Sensors 2008, 8(10), 6704-6726; doi:10.3390/s8106704
Received: 2 July 2008 / Revised: 27 September 2008 / Accepted: 21 October 2008 / Published: 25 October 2008
Cited by 71 | PDF Full-text (2316 KB) | HTML Full-text | XML Full-text
Abstract
Neural probe technologies have already had a significant positive effect on our understanding of the brain by revealing the functioning of networks of biological neurons. Probes are implanted in different areas of the brain to record and/or stimulate specific sites in the [...] Read more.
Neural probe technologies have already had a significant positive effect on our understanding of the brain by revealing the functioning of networks of biological neurons. Probes are implanted in different areas of the brain to record and/or stimulate specific sites in the brain. Neural probes are currently used in many clinical settings for diagnosis of brain diseases such as seizers, epilepsy, migraine, Alzheimer’s, and dementia. We find these devices assisting paralyzed patients by allowing them to operate computers or robots using their neural activity. In recent years, probe technologies were assisted by rapid advancements in microfabrication and microelectronic technologies and thus are enabling highly functional and robust neural probes which are opening new and exciting avenues in neural sciences and brain machine interfaces. With a wide variety of probes that have been designed, fabricated, and tested to date, this review aims to provide an overview of the advances and recent progress in the microfabrication techniques of neural probes. In addition, we aim to highlight the challenges faced in developing and implementing ultralong multi-site recording probes that are needed to monitor neural activity from deeper regions in the brain. Finally, we review techniques that can improve the biocompatibility of the neural probes to minimize the immune response and encourage neural growth around the electrodes for long term implantation studies. Full article
(This article belongs to the Special Issue BioMEMS)
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