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Sensors, Volume 10, Issue 6 (June 2010), Pages 5294-6274

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Open AccessArticle Transversely Excited Multipass Photoacoustic Cell Using Electromechanical Film as Microphone
Sensors 2010, 10(6), 5294-5307; doi:10.3390/s100605294
Received: 19 April 2010 / Revised: 21 May 2010 / Accepted: 24 May 2010 / Published: 26 May 2010
Cited by 6 | PDF Full-text (262 KB) | HTML Full-text | XML Full-text
Abstract
A novel multipass photoacoustic cell with five stacked electromechanical films as a microphone has been constructed, tested and characterized. The photoacoustic cell is an open rectangular structure with two steel plates facing each other. The longitudinal acoustic resonances are excited transversely in an
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A novel multipass photoacoustic cell with five stacked electromechanical films as a microphone has been constructed, tested and characterized. The photoacoustic cell is an open rectangular structure with two steel plates facing each other. The longitudinal acoustic resonances are excited transversely in an optical multipass configuration. A detection limit of 22 ppb (10−9) was achieved for flowing NO2 in N2 at normal pressure by using the maximum of 70 laser beams between the resonator plates. The corresponding minimum detectable absorption and the normalized noise-equivalent absorption coefficients were 2:2 × 10−7 cm−1 and 3:2 × 10−9 cm−1WHz−1/2, respectively. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessArticle Electrochemical Microsensors for the Detection of Cadmium(II) and Lead(II) Ions in Plants
Sensors 2010, 10(6), 5308-5328; doi:10.3390/s100605308
Received: 13 February 2010 / Revised: 4 April 2010 / Accepted: 19 April 2010 / Published: 27 May 2010
Cited by 35 | PDF Full-text (1123 KB) | HTML Full-text | XML Full-text
Abstract
Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for
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Routine determination of trace metals in complex media is still a difficult task for many analytical instruments. The aim of this work was to compare three electro-chemical instruments [a standard potentiostat (Autolab), a commercially available miniaturized potentiostat (PalmSens) and a homemade micropotentiostat] for easy-to-use and sensitive determination of cadmium(II) and lead(II) ions. The lowest detection limits (hundreds of pM) for both metals was achieved by using of the standard potentiostat, followed by the miniaturized potentiostat (tens of nM) and the homemade instrument (hundreds of nM). Nevertheless, all potentiostats were sensitive enough to evaluate contamination of the environment, because the environmental limits for both metals are higher than detection limits of the instruments. Further, we tested all used potentiostats and working electrodes on analysis of environmental samples (rainwater, flour and plant extract) with artificially added cadmium(II) and lead(II). Based on the similar results obtained for all potentiostats we choose a homemade instrument with a carbon tip working electrode for our subsequent environmental experiments, in which we analyzed maize and sunflower seedlings and rainwater obtained from various sites in the Czech Republic. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Lazy Approaches for Interval Timing Correlation of Sensor Data Streams
Sensors 2010, 10(6), 5329-5345; doi:10.3390/s100605329
Received: 29 March 2010 / Revised: 20 May 2010 / Accepted: 21 May 2010 / Published: 27 May 2010
PDF Full-text (261 KB) | HTML Full-text | XML Full-text
Abstract
We propose novel algorithms for the timing correlation of streaming sensor data. The sensor data are assumed to have interval timestamps so that they can represent temporal uncertainties. The proposed algorithms can support efficient timing correlation for various timing predicates such as deadline,
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We propose novel algorithms for the timing correlation of streaming sensor data. The sensor data are assumed to have interval timestamps so that they can represent temporal uncertainties. The proposed algorithms can support efficient timing correlation for various timing predicates such as deadline, delay, and within. In addition to the classical techniques, lazy evaluation and result cache are utilized to improve the algorithm performance. The proposed algorithms are implemented and compared under various workloads. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Low Frequency Electromagnetic Sensor for Indirect Measurement of Glucose Concentration: In Vitro Experiments in Different Conductive Solutions
Sensors 2010, 10(6), 5346-5358; doi:10.3390/s100605346
Received: 7 January 2010 / Revised: 4 March 2010 / Accepted: 12 May 2010 / Published: 28 May 2010
Cited by 20 | PDF Full-text (215 KB) | HTML Full-text | XML Full-text
Abstract
In recent years there has been considerable interest in the study of glucose-induced dielectric property variations of human tissues as a possible approach for non-invasive glycaemia monitoring. We have developed an electromagnetic sensor, and we tested in vitro its ability to estimate variations
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In recent years there has been considerable interest in the study of glucose-induced dielectric property variations of human tissues as a possible approach for non-invasive glycaemia monitoring. We have developed an electromagnetic sensor, and we tested in vitro its ability to estimate variations in glucose concentration of different solutions with similarities to blood (sodium chloride and Ringer-lactate solutions), differing though in the lack of any cellular components. The sensor was able to detect the effect of glucose variations over a wide range of concentrations (~78–5,000 mg/dL), with a sensitivity of ~0.22 mV/(mg/dL). Our proposed system may thus be useful in a new approach for non-invasive and non-contact glucose monitoring. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessArticle Real-Time Gas Identification by Analyzing the Transient Response of Capillary-Attached Conductive Gas Sensor
Sensors 2010, 10(6), 5359-5377; doi:10.3390/s100605359
Received: 10 March 2010 / Revised: 29 April 2010 / Accepted: 30 April 2010 / Published: 28 May 2010
Cited by 6 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the ability of the Capillary-attached conductive gas sensor (CGS) in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples
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In this study, the ability of the Capillary-attached conductive gas sensor (CGS) in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples to the first 100 samples. Different feature extraction and classification methods were applied on the selected portions. Validation of methods was evaluated to study the ability of an early portion of the CGS transient response in target gas (TG) identification. Experimental results proved that applying extracted features from an early part of the CGS transient response along with a classifier can distinguish short-chain alcohols from each other perfectly. Decreasing time of exposition in the interaction between target gas and sensing element improved the reliability of the sensor. Classification rate was also improved and time of identification was decreased. Moreover, the results indicated the optimum interval of the early transient response of the CGS for selecting portions to achieve the best classification rates. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Integration of a Multi-Camera Vision System and Strapdown Inertial Navigation System (SDINS) with a Modified Kalman Filter
Sensors 2010, 10(6), 5378-5394; doi:10.3390/s100605378
Received: 1 April 2010 / Revised: 20 April 2010 / Accepted: 10 May 2010 / Published: 28 May 2010
Cited by 10 | PDF Full-text (1145 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the development of a modified Kalman filter to integrate a multi-camera vision system and strapdown inertial navigation system (SDINS) for tracking a hand-held moving device for slow or nearly static applications over extended periods of time. In this algorithm, the
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This paper describes the development of a modified Kalman filter to integrate a multi-camera vision system and strapdown inertial navigation system (SDINS) for tracking a hand-held moving device for slow or nearly static applications over extended periods of time. In this algorithm, the magnitude of the changes in position and velocity are estimated and then added to the previous estimation of the position and velocity, respectively. The experimental results of the hybrid vision/SDINS design show that the position error of the tool tip in all directions is about one millimeter RMS. The proposed Kalman filter removes the effect of the gravitational force in the state-space model. As a result, the resulting error is eliminated and the resulting position is smoother and ripple-free. Full article
Open AccessArticle Data Acquisition, Analysis and Transmission Platform for a Pay-As-You-Drive System
Sensors 2010, 10(6), 5395-5408; doi:10.3390/s100605395
Received: 30 March 2010 / Revised: 15 April 2010 / Accepted: 13 May 2010 / Published: 1 June 2010
Cited by 5 | PDF Full-text (1337 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a platform used to acquire, analyse and transmit data from a vehicle to a Control Centre as part of a Pay-As-You-Drive system. The aim is to monitor vehicle usage (how much, when, where and how) and,
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This paper presents a platform used to acquire, analyse and transmit data from a vehicle to a Control Centre as part of a Pay-As-You-Drive system. The aim is to monitor vehicle usage (how much, when, where and how) and, based on this information, assess the associated risk and set an appropriate insurance premium. To determine vehicle usage, the system analyses the driver's respect for speed limits, driving style (aggressive or non-aggressive), mobile telephone use and the number of vehicle passengers. An electronic system on board the vehicle acquires these data, processes them and transmits them by mobile telephone (GPRS/UMTS) to a Control Centre, at which the insurance company assesses the risk associated with vehicles monitored by the system. The system provides insurance companies and their customers with an enhanced service and could potentially increase responsible driving habits and reduce the number of road accidents. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Immunosensor Incorporating Anti-His (C-term) IgG F(ab’) Fragments Attached to Gold Nanorods for Detection of His-Tagged Proteins in Culture Medium
Sensors 2010, 10(6), 5409-5424; doi:10.3390/s100605409
Received: 1 April 2010 / Revised: 13 May 2010 / Accepted: 20 May 2010 / Published: 1 June 2010
Cited by 13 | PDF Full-text (928 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Immunosensors based on gold electrodes (electrochemical) or gold discs (optical) modified with 1,6-hexanedithiol, gold nanorods and Anti-His (C-term) monoclonal antibody F(ab’) fragment are described. The antigen detected by the sensing platform is a recombinant histidine-tagged silk proteinase inhibitor (rSPI2-His6). Electrochemical impedance spectroscopy (EIS)
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Immunosensors based on gold electrodes (electrochemical) or gold discs (optical) modified with 1,6-hexanedithiol, gold nanorods and Anti-His (C-term) monoclonal antibody F(ab’) fragment are described. The antigen detected by the sensing platform is a recombinant histidine-tagged silk proteinase inhibitor (rSPI2-His6). Electrochemical impedance spectroscopy (EIS) and surface plasmon resonance (SPR) techniques were used as methods for detection of the antigen. This approach allows to detect the antigen protein in concentration of 10 pg per mL (0.13 pM) of culture medium. The immunosensor shows good reproducibility due to covalent immobilization of F(ab’) fragments to gold nanorods layer Full article
(This article belongs to the Special Issue Bio-devices and Materials)
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Open AccessArticle A Differential Evolution-Based Routing Algorithm for Environmental Monitoring Wireless Sensor Networks
Sensors 2010, 10(6), 5425-5442; doi:10.3390/s100605425
Received: 9 April 2010 / Revised: 29 April 2010 / Accepted: 20 May 2010 / Published: 1 June 2010
Cited by 13 | PDF Full-text (362 KB) | HTML Full-text | XML Full-text
Abstract
The traditional Low Energy Adaptive Cluster Hierarchy (LEACH) routing protocol is a clustering-based protocol. The uneven selection of cluster heads results in premature death of cluster heads and premature blind nodes inside the clusters, thus reducing the overall lifetime of the network. With
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The traditional Low Energy Adaptive Cluster Hierarchy (LEACH) routing protocol is a clustering-based protocol. The uneven selection of cluster heads results in premature death of cluster heads and premature blind nodes inside the clusters, thus reducing the overall lifetime of the network. With a full consideration of information on energy and distance distribution of neighboring nodes inside the clusters, this paper proposes a new routing algorithm based on differential evolution (DE) to improve the LEACH routing protocol. To meet the requirements of monitoring applications in outdoor environments such as the meteorological, hydrological and wetland ecological environments, the proposed algorithm uses the simple and fast search features of DE to optimize the multi-objective selection of cluster heads and prevent blind nodes for improved energy efficiency and system stability. Simulation results show that the proposed new LEACH routing algorithm has better performance, effectively extends the working lifetime of the system, and improves the quality of the wireless sensor networks. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Modeling of Current Consumption in 802.15.4/ZigBee Sensor Motes
Sensors 2010, 10(6), 5443-5468; doi:10.3390/s100605443
Received: 2 February 2010 / Revised: 12 April 2010 / Accepted: 6 May 2010 / Published: 1 June 2010
Cited by 48 | PDF Full-text (592 KB) | HTML Full-text | XML Full-text
Abstract
Battery consumption is a key aspect in the performance of wireless sensor networks. One of the most promising technologies for this type of networks is 802.15.4/ZigBee. This paper presents an empirical characterization of battery consumption in commercial 802.15.4/ZigBee motes. This characterization is based
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Battery consumption is a key aspect in the performance of wireless sensor networks. One of the most promising technologies for this type of networks is 802.15.4/ZigBee. This paper presents an empirical characterization of battery consumption in commercial 802.15.4/ZigBee motes. This characterization is based on the measurement of the current that is drained from the power source under different 802.15.4 communication operations. The measurements permit the definition of an analytical model to predict the maximum, minimum and mean expected battery lifetime of a sensor networking application as a function of the sensor duty cycle and the size of the sensed data. Full article
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Open AccessArticle Studies of Scattering, Reflectivity, and Transmitivity in WBAN Channel: Feasibility of Using UWB
Sensors 2010, 10(6), 5503-5529; doi:10.3390/s100605503
Received: 9 April 2010 / Revised: 20 May 2010 / Accepted: 21 May 2010 / Published: 2 June 2010
Cited by 2 | PDF Full-text (789 KB) | HTML Full-text | XML Full-text
Abstract
The Wireless Personal Area Network (WPAN) is one of the fledging paradigms that the next generation of wireless systems is sprouting towards. Among them, a more specific category is the Wireless Body Area Network (WBAN) used for health monitoring. On the other hand,
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The Wireless Personal Area Network (WPAN) is one of the fledging paradigms that the next generation of wireless systems is sprouting towards. Among them, a more specific category is the Wireless Body Area Network (WBAN) used for health monitoring. On the other hand, Ultra-Wideband (UWB) comes with a number of desirable features at the physical layer for wireless communications. One big challenge in adoption of UWB in WBAN is the fact that signals get attenuated exponentially. Due to the intrinsic structural complexity in human body, electromagnetic waves show a profound variation during propagation through it. The reflection and transmission coefficients of human body are highly dependent upon the dielectric constants as well as upon the frequency. The difference in structural materials such as fat, muscles and blood essentially makes electromagnetic wave attenuation to be different along the way. Thus, a complete characterization of body channel is a challenging task. The connection between attenuation and frequency of the signal makes the investigation of UWB in WBAN an interesting proposition. In this paper, we study analytically the impact of body channels on electromagnetic signal propagation with reference to UWB. In the process, scattering, reflectivity and transmitivity have been addressed with analysis of approximate layer-wise modeling, and with numerical depictions. Pulses with Gaussian profile have been employed in our analysis. It shows that, under reasonable practical approximations, the human body channel can be modeled in layers so as to have the effects of total reflections or total transmissions in certain frequency bands. This could help decide such design issues as antenna characteristics of implant devices for WBAN employing UWB. Full article
Open AccessArticle Illumination-Based Synchronization of High-Speed Vision Sensors
Sensors 2010, 10(6), 5530-5547; doi:10.3390/s100605530
Received: 13 April 2010 / Revised: 5 May 2010 / Accepted: 25 May 2010 / Published: 2 June 2010
Cited by 7 | PDF Full-text (3634 KB) | HTML Full-text | XML Full-text
Abstract
To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. This paper describes an illumination-based synchronization method derived from the phase-locked loop (PLL) algorithm. Incident light to a vision sensor from an
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To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. This paper describes an illumination-based synchronization method derived from the phase-locked loop (PLL) algorithm. Incident light to a vision sensor from an intensity-modulated illumination source serves as the reference signal for synchronization. Analog and digital computation within the vision sensor forms a PLL to regulate the output signal, which corresponds to the vision frame timing, to be synchronized with the reference. Simulated and experimental results show that a 1,000 Hz frame rate vision sensor was successfully synchronized with 32 μs jitters. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle An Energy-efficient Rate Adaptive Media Access Protocol (RA-MAC) for Long-lived Sensor Networks
Sensors 2010, 10(6), 5548-5568; doi:10.3390/s100605548
Received: 30 April 2010 / Revised: 18 May 2010 / Accepted: 18 May 2010 / Published: 2 June 2010
Cited by 3 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves
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We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application’s link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode) on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment. Full article
Open AccessArticle Modeling and Analysis of Energy Conservation Scheme Based on Duty Cycling in Wireless Ad Hoc Sensor Network
Sensors 2010, 10(6), 5569-5589; doi:10.3390/s100605569
Received: 5 February 2010 / Revised: 22 April 2010 / Accepted: 25 May 2010 / Published: 3 June 2010
Cited by 5 | PDF Full-text (420 KB) | HTML Full-text | XML Full-text
Abstract
In sensor network, energy conservation is one of the most critical issues since sensor nodes should perform a sensing task for a long time (e.g., lasting a few years) but the battery of them cannot be replaced in most practical situations. For this
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In sensor network, energy conservation is one of the most critical issues since sensor nodes should perform a sensing task for a long time (e.g., lasting a few years) but the battery of them cannot be replaced in most practical situations. For this purpose, numerous energy conservation schemes have been proposed and duty cycling scheme is considered the most suitable power conservation technique, where sensor nodes alternate between states having different levels of power consumption. In order to analyze the energy consumption of energy conservation scheme based on duty cycling, it is essential to obtain the probability of each state. In this paper, we analytically derive steady state probability of sensor node states, i.e., sleep, listen, and active states, based on traffic characteristics and timer values, i.e., sleep timer, listen timer, and active timer. The effect of traffic characteristics and timer values on the steady state probability and energy consumption is analyzed in detail. Our work can provide sensor network operators guideline for selecting appropriate timer values for efficient energy conservation. The analytical methodology developed in this paper can be extended to other energy conservation schemes based on duty cycling with different sensor node states, without much difficulty. Full article
Open AccessArticle Electrical Conductivity Response of Poly(Phenylene-vinylene)/ Zeolite Composites Exposed to Ammonium Nitrate
Sensors 2010, 10(6), 5590-5603; doi:10.3390/s100605590
Received: 30 January 2010 / Revised: 27 March 2010 / Accepted: 22 April 2010 / Published: 3 June 2010
Cited by 13 | PDF Full-text (2731 KB) | HTML Full-text | XML Full-text
Abstract
Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added
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Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3.The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Comparison of Several Methods for Determining the Internal Resistance of Lithium Ion Cells
Sensors 2010, 10(6), 5604-5625; doi:10.3390/s100605604
Received: 28 January 2010 / Revised: 25 March 2010 / Accepted: 18 May 2010 / Published: 3 June 2010
Cited by 36 | PDF Full-text (742 KB) | HTML Full-text | XML Full-text
Abstract
The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by current
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The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by current step methods, AC (alternating current) methods, electrochemical impedance spectroscopy and thermal loss methods. The outcomes of these measurements have been compared with each other. If charge or discharge of the cell is limited, current step methods provide the same results as energy loss methods. Full article
Open AccessArticle On the Use of Piezoelectric Sensors in Structural Mechanics: Some Novel Strategies
Sensors 2010, 10(6), 5626-5641; doi:10.3390/s100605626
Received: 30 March 2010 / Revised: 26 April 2010 / Accepted: 27 April 2010 / Published: 3 June 2010
Cited by 8 | PDF Full-text (202 KB) | HTML Full-text | XML Full-text
Abstract
In the present paper, a review on piezoelectric sensing of mechanical deformations and vibrations of so-called smart or intelligent structures is given. After a short introduction into piezoelectric sensing and actuation of such controlled structures, we pay special emphasis on the description of
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In the present paper, a review on piezoelectric sensing of mechanical deformations and vibrations of so-called smart or intelligent structures is given. After a short introduction into piezoelectric sensing and actuation of such controlled structures, we pay special emphasis on the description of some own work, which has been performed at the Institute of Technical Mechanics of the Johannes Kepler University of Linz (JKU) in the last years. Among other aspects, this work has been motivated by the fact that collocated control of smart structures requires a sensor output that is work-conjugated to the input by the actuator. This fact in turn brings into the play the more general question of how to measure mechanically meaningful structural quantities, such as displacements, slopes, or other quantities, which form the work-conjugated quantities of the actuation, by means piezoelectric sensors. At least in the range of small strains, there is confidence that distributed piezoelectric sensors or sensor patches in smart structures do measure weighted integrals over their domain. Therefore, there is a need of distributing or shaping the sensor activity in order to be able to re-interpret the sensor signals in the desired mechanical sense. We sketch a general strategy that is based on a special application of work principles, more generally on displacement virials. We also review our work in the past on bringing this concept to application in smart structures, such as beams, rods and plates. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Austria)
Open AccessArticle Gait Event Detection on Level Ground and Incline Walking Using a Rate Gyroscope
Sensors 2010, 10(6), 5683-5702; doi:10.3390/s100605683
Received: 23 March 2010 / Revised: 24 May 2010 / Accepted: 25 May 2010 / Published: 4 June 2010
Cited by 26 | PDF Full-text (371 KB) | HTML Full-text | XML Full-text
Abstract
Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper
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Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects walking outdoors on level ground, and up and down an incline. Performance was compared with a reference pressure measurement system. The mean difference between the gyroscope and the reference was less than –25 ms for IC and less than 75 ms for FO for all terrains. Detection success was over 98%. These results provide preliminary evidence supporting the use of the gyroscope for gait event detection on inclines as well as level walking. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
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Open AccessArticle Real-Time Plasma Process Condition Sensing and Abnormal Process Detection
Sensors 2010, 10(6), 5703-5723; doi:10.3390/s100605703
Received: 25 April 2010 / Revised: 15 May 2010 / Accepted: 25 May 2010 / Published: 8 June 2010
Cited by 6 | PDF Full-text (423 KB) | HTML Full-text | XML Full-text
Abstract
The plasma process is often used in the fabrication of semiconductor wafers. However, due to the lack of real-time etching control, this may result in some unacceptable process performances and thus leads to significant waste and lower wafer yield. In order to maximize
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The plasma process is often used in the fabrication of semiconductor wafers. However, due to the lack of real-time etching control, this may result in some unacceptable process performances and thus leads to significant waste and lower wafer yield. In order to maximize the product wafer yield, a timely and accurately process fault or abnormal detection in a plasma reactor is needed. Optical emission spectroscopy (OES) is one of the most frequently used metrologies in in-situ process monitoring. Even though OES has the advantage of non-invasiveness, it is required to provide a huge amount of information. As a result, the data analysis of OES becomes a big challenge. To accomplish real-time detection, this work employed the sigma matching method technique, which is the time series of OES full spectrum intensity. First, the response model of a healthy plasma spectrum was developed. Then, we defined a matching rate as an indictor for comparing the difference between the tested wafers response and the health sigma model. The experimental results showed that this proposal method can detect process faults in real-time, even in plasma etching tools. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Windows on the Human Body – in Vivo High-Field Magnetic Resonance Research and Applications in Medicine and Psychology
Sensors 2010, 10(6), 5724-5757; doi:10.3390/s100605724
Received: 3 March 2010 / Revised: 2 April 2010 / Accepted: 17 May 2010 / Published: 8 June 2010
Cited by 6 | PDF Full-text (3169 KB) | HTML Full-text | XML Full-text
Abstract
Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic
[...] Read more.
Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic information from the human body with unsurpassed quality. Recent achievements in high and ultra-high field MR (at 3 and 7 Tesla) are described, and representative research applications in Medicine and Psychology in Austria are discussed. Finally, an overview of current and prospective research in multi-modal imaging, potential clinical applications, as well as current limitations and challenges is given. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Austria)
Open AccessArticle Enzymatic Determination of Diglyceride Using an Iridium Nano-Particle Based Single Use, Disposable Biosensor
Sensors 2010, 10(6), 5758-5773; doi:10.3390/s100605758
Received: 26 April 2010 / Revised: 15 May 2010 / Accepted: 28 May 2010 / Published: 8 June 2010
PDF Full-text (1892 KB) | HTML Full-text | XML Full-text
Abstract
A single use, disposable iridium-nano particle contained biosensor had been developed for the determination of diglyceride (DG). In this study hydrogen peroxide, formed through the enzymatic breakdown of DG via lipase, glycerol kinase and glycerol 3-phosphate oxidase, was electrochemically oxidized at an applied
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A single use, disposable iridium-nano particle contained biosensor had been developed for the determination of diglyceride (DG). In this study hydrogen peroxide, formed through the enzymatic breakdown of DG via lipase, glycerol kinase and glycerol 3-phosphate oxidase, was electrochemically oxidized at an applied potential of +0.5 V versus the Ag/AgCl reference electrode. The oxidation current was then used to quantify the diglyceride concentration. Optimum enzyme concentrations and the surfactant loading used were established for successful sensor response. Good linear performance was observed over a DG concentration range of 0 to 25 µM in phosphate buffer and bovine serum media. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Label Free Detection of CD4+ and CD8+ T Cells Using the Optofluidic Ring Resonator
Sensors 2010, 10(6), 5798-5808; doi:10.3390/s100605798
Received: 3 April 2010 / Revised: 16 May 2010 / Accepted: 1 June 2010 / Published: 8 June 2010
Cited by 26 | PDF Full-text (252 KB) | HTML Full-text | XML Full-text
Abstract
We have demonstrated label free detection of CD4+ and CD8+ T-Lymphocyte whole cells and CD4+ T-Lymphocyte cell lysis using the optofluidic ring resonator (OFRR) sensor. The OFRR sensing platform incorporates microfluidics and photonics in a setup that utilizes small sample volume and achieves
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We have demonstrated label free detection of CD4+ and CD8+ T-Lymphocyte whole cells and CD4+ T-Lymphocyte cell lysis using the optofluidic ring resonator (OFRR) sensor. The OFRR sensing platform incorporates microfluidics and photonics in a setup that utilizes small sample volume and achieves a fast detection time. In this work, white blood cells were isolated from healthy blood and the concentrations were adjusted to match T-Lymphocyte levels of individuals infected with HIV. Detection was accomplished by immobilizing CD4 and CD8 antibodies on the inner surface of the OFRR. Sensing results show excellent detection of CD4+ and CD8+ T-Lymphocyte cells at medically significant concentrations with a detection time of approximately 30 minutes. This work will lead to a rapid and low-cost sensing device that can provide a CD4 and CD8 count as a measure of HIV progression. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Power Consumption Analysis of Operating Systems for Wireless Sensor Networks
Sensors 2010, 10(6), 5809-5826; doi:10.3390/s100605809
Received: 19 April 2010 / Revised: 10 May 2010 / Accepted: 25 May 2010 / Published: 8 June 2010
Cited by 19 | PDF Full-text (722 KB) | HTML Full-text | XML Full-text
Abstract
In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring
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In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring a fair evaluation, a benchmark composed of four applications has been developed, covering the most typical tasks that a Wireless Sensor Network performs. The results show the instant and average current consumption of the devices during the execution of these applications. The experimental measurements provide a good insight into the power mode in which the device components are running at every moment, and they can be used to compare the performance of different operating systems executing the same tasks. Full article
Open AccessArticle Using Automated Point Dendrometers to Analyze Tropical Treeline Stem Growth at Nevado de Colima, Mexico
Sensors 2010, 10(6), 5827-5844; doi:10.3390/s100605827
Received: 10 May 2010 / Revised: 2 June 2010 / Accepted: 4 June 2010 / Published: 9 June 2010
Cited by 19 | PDF Full-text (416 KB) | HTML Full-text | XML Full-text
Abstract
The relationship between wood growth and environmental variability at the tropical treeline of North America was investigated using automated, solar-powered sensors (a meteorological station and two dendrometer clusters) installed on Nevado de Colima, Mexico (19° 35’ N, 103° 37’ W, 3,760 m a.s.l.).
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The relationship between wood growth and environmental variability at the tropical treeline of North America was investigated using automated, solar-powered sensors (a meteorological station and two dendrometer clusters) installed on Nevado de Colima, Mexico (19° 35’ N, 103° 37’ W, 3,760 m a.s.l.). Pure stands of Pinus hartwegii Lindl. (Mexican mountain pine) were targeted because of their suitability for tree-ring analysis in low-latitude, high-elevation, North American Monsoon environments. Stem size and hydroclimatic variables recorded at half-hour intervals were summarized on a daily timescale. Power outages, insect outbreaks, and sensor failures limited the analysis to non-consecutive months during 2001–2003 at one dendrometer site, and during 2002–2005 at the other. Combined data from the two sites showed that maximum radial growth rates occur in late spring (May), as soil temperature increases, and incoming short-wave radiation reaches its highest values. Early season (April–May) radial increment correlated directly with temperature, especially of the soil, and with solar radiation. Stem expansion at the start of the summer monsoon (June–July) was mostly influenced by moisture, and revealed a drought signal, while late season relationships were more varied. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements
Sensors 2010, 10(6), 5845-5858; doi:10.3390/s100605847
Received: 30 April 2010 / Revised: 26 May 2010 / Accepted: 1 June 2010 / Published: 9 June 2010
Cited by 5 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
Abstract
Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were
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Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (~3 μm) and sand (~300 μm) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 MΩ, 4 MΩ, and 0.5 MΩ for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Development of a Quartz Crystal Microbalance Biosensor with Aptamers as Bio-recognition Element
Sensors 2010, 10(6), 5859-5871; doi:10.3390/s100605859
Received: 30 March 2010 / Revised: 20 April 2010 / Accepted: 15 May 2010 / Published: 9 June 2010
Cited by 40 | PDF Full-text (295 KB) | HTML Full-text | XML Full-text
Abstract
The ultimate goal in any biosensor development project is its use for actual sample detection. Recently, there has been an interest in biosensors with aptamers as bio-recognition elements, but reported examples all deal with standards, not human serum. In order to verify the
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The ultimate goal in any biosensor development project is its use for actual sample detection. Recently, there has been an interest in biosensors with aptamers as bio-recognition elements, but reported examples all deal with standards, not human serum. In order to verify the differences of aptamer-based biosensor and antibody-based biosensor in clinical detection, a comparison of the performance of aptamer-based and antibody-based quartz crystal microbalance (QCM) biosensors for the detection of immunoglobulin E (IgE) in human serum was carried out. Aptamers (or antibodies) specific to IgE were immobilized on the gold surface of a quartz crystal. The frequency shifts of the QCM were measured. The linear range with the antibody (10–240 μg/L) compared to that of the aptamer (2.5–200 μg/L), but a lower detection limit could be observed in the aptamer-based biosensor. The reproducibility of the two biosensors was comparable. The aptamers were equivalent or superior to antibodies in terms of specificity and sensitivity. In addition, the aptamer receptors could tolerate repeated affine layer regeneration after ligand binding and recycling of the biosensor with little loss of sensitivity. When stored for three weeks, the frequency shifts of the aptamer-coated crystals were all greater than 90% of those on the response at the first day. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle An RFID-Based Intelligent Vehicle Speed Controller Using Active Traffic Signals
Sensors 2010, 10(6), 5872-5887; doi:10.3390/s100605872
Received: 23 April 2010 / Revised: 25 May 2010 / Accepted: 28 May 2010 / Published: 9 June 2010
Cited by 36 | PDF Full-text (943 KB) | HTML Full-text | XML Full-text
Abstract
These days, mass-produced vehicles benefit from research on Intelligent Transportation System (ITS). One prime example of ITS is vehicle Cruise Control (CC), which allows it to maintain a pre-defined reference speed, to economize on fuel or energy consumption, to avoid speeding fines, or
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These days, mass-produced vehicles benefit from research on Intelligent Transportation System (ITS). One prime example of ITS is vehicle Cruise Control (CC), which allows it to maintain a pre-defined reference speed, to economize on fuel or energy consumption, to avoid speeding fines, or to focus all of the driver’s attention on the steering of the vehicle. However, achieving efficient Cruise Control is not easy in roads or urban streets where sudden changes of the speed limit can happen, due to the presence of unexpected obstacles or maintenance work, causing, in inattentive drivers, traffic accidents. In this communication we present a new Infrastructure to Vehicles (I2V) communication and control system for intelligent speed control, which is based upon Radio Frequency Identification (RFID) technology for identification of traffic signals on the road, and high accuracy vehicle speed measurement with a Hall effect-based sensor. A fuzzy logic controller, based on sensor fusion of the information provided by the I2V infrastructure, allows the efficient adaptation of the speed of the vehicle to the circumstances of the road. The performance of the system is checked empirically, with promising results. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Liquid-Phase Packaging of a Glucose Oxidase Solution with Parylene Direct Encapsulation and an Ultraviolet Curing Adhesive Cover for Glucose Sensors
Sensors 2010, 10(6), 5888-5898; doi:10.3390/s100605888
Received: 20 April 2010 / Revised: 15 May 2010 / Accepted: 30 May 2010 / Published: 9 June 2010
Cited by 5 | PDF Full-text (789 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 μL)
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We have developed a package for disposable glucose sensor chips using Parylene encapsulation of a glucose oxidase solution in the liquid phase and a cover structure made of an ultraviolet (UV) curable adhesive. Parylene was directly deposited onto a small volume (1 μL) of glucose oxidase solution through chemical vapor deposition. The cover and reaction chamber were constructed on Parylene film using a UV-curable adhesive and photolithography. The package was processed at room temperature to avoid denaturation of the glucose oxidase. The glucose oxidase solution was encapsulated and unsealed. Glucose sensing was demonstrated using standard amperometric detection at glucose concentrations between 0.1 and 100 mM, which covers the glucose concentration range of diabetic patients. Our proposed Parylene encapsulation and UV-adhesive cover form a liquid phase glucose-oxidase package that has the advantages of room temperature processing and direct liquid encapsulation of a small volume solution without use of conventional solidifying chemicals. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessArticle GPS-Free Localization Algorithm for Wireless Sensor Networks
Sensors 2010, 10(6), 5899-5926; doi:10.3390/s100605899
Received: 29 January 2010 / Revised: 26 April 2010 / Accepted: 20 May 2010 / Published: 9 June 2010
Cited by 12 | PDF Full-text (568 KB) | HTML Full-text | XML Full-text
Abstract
Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper.
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Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper. First, we develop a standardized clustering-based approach for the local coordinate system formation wherein a multiplication factor is introduced to regulate the number of master and slave nodes and the degree of connectivity among master nodes. Second, using homogeneous coordinates, we derive a transformation matrix between two Cartesian coordinate systems to efficiently merge them into a global coordinate system and effectively overcome the flip ambiguity problem. The algorithm operates asynchronously without a centralized controller; and does not require that the location of the sensors be known a priori. A set of parameter-setting guidelines for the proposed algorithm is derived based on a probability model and the energy requirements are also investigated. A simulation analysis on a specific numerical example is conducted to validate the mathematical analytical results. We also compare the performance of the proposed algorithm under a variety multiplication factor, node density and node communication radius scenario. Experiments show that our algorithm outperforms existing mechanisms in terms of accuracy and convergence time. Full article
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Open AccessArticle Application of a Hybrid 3D-2D Laser Scanning System to the Characterization of Slate Slabs
Sensors 2010, 10(6), 5949-5961; doi:10.3390/s100605949
Received: 19 April 2010 / Revised: 21 April 2010 / Accepted: 11 May 2010 / Published: 14 June 2010
Cited by 3 | PDF Full-text (872 KB) | HTML Full-text | XML Full-text
Abstract
Dimensional control based on 3D laser scanning techniques is widely used in practice. We describe the application of a hybrid 3D-2D laser scanning system to the characterization of slate slabs with structural defects that are difficult for the human eye to characterize objectively.
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Dimensional control based on 3D laser scanning techniques is widely used in practice. We describe the application of a hybrid 3D-2D laser scanning system to the characterization of slate slabs with structural defects that are difficult for the human eye to characterize objectively. Our study is based on automating the process using a 3D laser scanner and a 2D camera. Our results demonstrate that the application of this hybrid system optimally characterizes slate slabs in terms of the defects described by the Spanish UNE-EN 12326-1 standard. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessArticle Exploring Infrared Sensoring for Real Time Welding Defects Monitoring in GTAW
Sensors 2010, 10(6), 5962-5974; doi:10.3390/s100605962
Received: 25 April 2010 / Revised: 15 May 2010 / Accepted: 30 May 2010 / Published: 14 June 2010
Cited by 6 | PDF Full-text (918 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding
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This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding pool temperature is related to the weld penetration depth; therefore, by monitoring the temperature, the arc pool temperature and penetration depth are also monitored. Various experiments were performed; in some of them the current was varied and the temperature changes were registered, in others, defects were induced throughout the path of the weld bead for a fixed current. These simulated defects resulted in abrupt changes in the average temperature values, thus providing an indication of the presence of a defect. The data has been registered with an acquisition card. To identify defects in the samples under infrared emissions, the timing series were analyzed through graphics and statistic methods. The selection of this technique demonstrates the potential for infrared emission as a welding monitoring parameter sensor. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Fiber Optic Doppler Sensor and Its Application in Debonding Detection for Composite Structures
Sensors 2010, 10(6), 5975-5993; doi:10.3390/s100605975
Received: 30 April 2010 / Revised: 20 May 2010 / Accepted: 29 May 2010 / Published: 14 June 2010
Cited by 5 | PDF Full-text (769 KB) | HTML Full-text | XML Full-text
Abstract
Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by
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Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Wavelet Analysis for Wind Fields Estimation
Sensors 2010, 10(6), 5994-6016; doi:10.3390/s100605994
Received: 11 May 2010 / Revised: 30 May 2010 / Accepted: 5 June 2010 / Published: 14 June 2010
Cited by 12 | PDF Full-text (5580 KB) | HTML Full-text | XML Full-text
Abstract
Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing
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Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing undecimated wavelet transform approaches, by including à trous with B3 spline scaling function, in addition to other wavelet bases as Gabor and Mexican-hat. The purpose is to extract more reliable directional information, when wind speed values range from 5 to 10 ms−1. Using C-band empirical models, associated with the estimated directional information, we calculate local wind speed values and compare our results with QuikSCAT scatterometer data. The proposed approach has potential application in the evaluation of oil spills and wind farms. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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Open AccessArticle Fast Scene Recognition and Camera Relocalisation for Wide Area Augmented Reality Systems
Sensors 2010, 10(6), 6017-6043; doi:10.3390/s100606017
Received: 29 April 2010 / Revised: 29 May 2010 / Accepted: 2 June 2010 / Published: 14 June 2010
PDF Full-text (3672 KB) | HTML Full-text | XML Full-text
Abstract
This paper focuses on online scene learning and fast camera relocalisation which are two key problems currently limiting the performance of wide area augmented reality systems. Firstly, we propose to use adaptive random trees to deal with the online scene learning problem. The
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This paper focuses on online scene learning and fast camera relocalisation which are two key problems currently limiting the performance of wide area augmented reality systems. Firstly, we propose to use adaptive random trees to deal with the online scene learning problem. The algorithm can provide more accurate recognition rates than traditional methods, especially with large scale workspaces. Secondly, we use the enhanced PROSAC algorithm to obtain a fast camera relocalisation method. Compared with traditional algorithms, our method can significantly reduce the computation complexity, which facilitates to a large degree the process of online camera relocalisation. Finally, we implement our algorithms in a multithreaded manner by using a parallel-computing scheme. Camera tracking, scene mapping, scene learning and relocalisation are separated into four threads by using multi-CPU hardware architecture. While providing real-time tracking performance, the resulting system also possesses the ability to track multiple maps simultaneously. Some experiments have been conducted to demonstrate the validity of our methods. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle A New Collaborative Knowledge-Based Approach for Wireless Sensor Networks
Sensors 2010, 10(6), 6044-6062; doi:10.3390/s100606044
Received: 28 April 2010 / Revised: 15 May 2010 / Accepted: 5 June 2010 / Published: 17 June 2010
Cited by 7 | PDF Full-text (259 KB) | HTML Full-text | XML Full-text
Abstract
This work presents a new approach for collaboration among sensors in Wireless Sensor Networks. These networks are composed of a large number of sensor nodes with constrained resources: limited computational capability, memory, power sources, etc. Nowadays, there is a growing interest in the
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This work presents a new approach for collaboration among sensors in Wireless Sensor Networks. These networks are composed of a large number of sensor nodes with constrained resources: limited computational capability, memory, power sources, etc. Nowadays, there is a growing interest in the integration of Soft Computing technologies into Wireless Sensor Networks. However, little attention has been paid to integrating Fuzzy Rule-Based Systems into collaborative Wireless Sensor Networks. The objective of this work is to design a collaborative knowledge-based network, in which each sensor executes an adapted Fuzzy Rule-Based System, which presents significant advantages such as: experts can define interpretable knowledge with uncertainty and imprecision, collaborative knowledge can be separated from control or modeling knowledge and the collaborative approach may support neighbor sensor failures and communication errors. As a real-world application of this approach, we demonstrate a collaborative modeling system for pests, in which an alarm about the development of olive tree fly is inferred. The results show that knowledge-based sensors are suitable for a wide range of applications and that the behavior of a knowledge-based sensor may be modified by inferences and knowledge of neighbor sensors in order to obtain a more accurate and reliable output. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Arrhythmia ECG Noise Reduction by Ensemble Empirical Mode Decomposition
Sensors 2010, 10(6), 6063-6080; doi:10.3390/s100606063
Received: 29 April 2010 / Revised: 20 May 2010 / Accepted: 10 June 2010 / Published: 17 June 2010
Cited by 50 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
A novel noise filtering algorithm based on ensemble empirical mode decomposition (EEMD) is proposed to remove artifacts in electrocardiogram (ECG) traces. Three noise patterns with different power—50 Hz, EMG, and base line wander – were embedded into simulated and real ECG signals. Traditional
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A novel noise filtering algorithm based on ensemble empirical mode decomposition (EEMD) is proposed to remove artifacts in electrocardiogram (ECG) traces. Three noise patterns with different power—50 Hz, EMG, and base line wander – were embedded into simulated and real ECG signals. Traditional IIR filter, Wiener filter, empirical mode decomposition (EMD) and EEMD were used to compare filtering performance. Mean square error between clean and filtered ECGs was used as filtering performance indexes. Results showed that high noise reduction is the major advantage of the EEMD based filter, especially on arrhythmia ECGs. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle A Compact Tunable Diode Laser Absorption Spectrometer to Monitor CO2 at 2.7 µm Wavelength in Hypersonic Flows
Sensors 2010, 10(6), 6081-6091; doi:10.3390/s100606081
Received: 21 May 2010 / Revised: 4 June 2010 / Accepted: 8 June 2010 / Published: 17 June 2010
Cited by 5 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based
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Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Background Subtraction Approach Based on Independent Component Analysis
Sensors 2010, 10(6), 6092-6114; doi:10.3390/s100606092
Received: 26 April 2010 / Revised: 16 May 2010 / Accepted: 28 May 2010 / Published: 18 June 2010
Cited by 13 | PDF Full-text (7971 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a new approach to background subtraction based on independent component analysis is presented. This approach assumes that background and foreground information are mixed in a given sequence of images. Then, foreground and background components are identified, if their probability density
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In this work, a new approach to background subtraction based on independent component analysis is presented. This approach assumes that background and foreground information are mixed in a given sequence of images. Then, foreground and background components are identified, if their probability density functions are separable from a mixed space. Afterwards, the components estimation process consists in calculating an unmixed matrix. The estimation of an unmixed matrix is based on a fast ICA algorithm, which is estimated as a Newton-Raphson maximization approach. Next, the motion components are represented by the mid-significant eigenvalues from the unmixed matrix. Finally, the results show the approach capabilities to detect efficiently motion in outdoors and indoors scenarios. The results show that the approach is robust to luminance conditions changes at scene. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Development of an Ion Sensitive Field Effect Transistor Based Urea Biosensor with Solid State Reference Systems
Sensors 2010, 10(6), 6115-6127; doi:10.3390/s100606115
Received: 14 April 2010 / Revised: 25 May 2010 / Accepted: 1 June 2010 / Published: 21 June 2010
Cited by 5 | PDF Full-text (521 KB) | HTML Full-text | XML Full-text
Abstract
Ion sensitive field-effect transistor (ISFET) based urease biosensors with solid state reference systems for single-ended and two-ended differential readout electronics were investigated. The sensing membranes of the biosensors were fabricated with urease immobilized in a conducting polymer-based matrix. The responses of 12.9~198.1 mV
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Ion sensitive field-effect transistor (ISFET) based urease biosensors with solid state reference systems for single-ended and two-ended differential readout electronics were investigated. The sensing membranes of the biosensors were fabricated with urease immobilized in a conducting polymer-based matrix. The responses of 12.9~198.1 mV for the urea concentrations of 8~240 mg/dL reveal that the activity of the enzyme was not significantly decreased. Biosensors combined with solid state reference systems were fabricated, and the evaluation results demonstrated the feasibility of miniaturization. For the differential system, the optimal transconductance match for biosensor and reference field-effect transistors (REFET) pair was determined through the modification of the membranes of the REFETs and enzyme field-effect transistors (EnFETs). The results show that the transconductance curve of polymer based REFET can match with that of the EnFET by adjusting the photoresist/NafionTM ratio. The match of the transconductance curves for the differential pairs provides a wide dynamic operating measurement range. Accordingly, the miniaturized quasi-reference electrode (QRE)/REFET/EnFET combination with differential arrangement achieved similar urea response curves as those measured by a conventional large sized discrete sensor. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle An Emergency-Adaptive Routing Scheme for Wireless Sensor Networks for Building Fire Hazard Monitoring
Sensors 2010, 10(6), 6128-6148; doi:10.3390/s100606128
Received: 8 May 2010 / Revised: 4 June 2010 / Accepted: 7 June 2010 / Published: 21 June 2010
Cited by 3 | PDF Full-text (487 KB) | HTML Full-text | XML Full-textRetraction
Abstract This paper has been retracted on 4 March 2011. The paper is republished with the authorship and acknowledgements fully disclosed as Sensors 2011, 11, 2899-2919; doi:10.3390/s110302899. Available at http://www.mdpi.com/1424-8220/11/3/2899/. Full article
Open AccessArticle SirT1—A Sensor for Monitoring Self-Renewal and Aging Process in Retinal Stem Cells
Sensors 2010, 10(6), 6172-6194; doi:10.3390/s100606172
Received: 8 January 2010 / Revised: 28 February 2010 / Accepted: 3 May 2010 / Published: 21 June 2010
Cited by 11 | PDF Full-text (763 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Retinal stem cells bear potency of proliferation, self-renewal, and differentiation into many retinal cells. Utilizing appropriate sensors one can effectively detect the self-renewal and aging process abilities. Silencing information regulator (SirT1), a member of the sirtuin family, is a NAD-dependent histone deacetylase and
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Retinal stem cells bear potency of proliferation, self-renewal, and differentiation into many retinal cells. Utilizing appropriate sensors one can effectively detect the self-renewal and aging process abilities. Silencing information regulator (SirT1), a member of the sirtuin family, is a NAD-dependent histone deacetylase and an essential mediator for longevity in normal cells by calorie restriction. We firstly investigate the SirT1 mRNA expression in retinal stem cells from rats and 19 human eyes of different ages. Results revealed that SirT1 expression was significantly decreased in in vivo aged eyes, associated with poor self-renewal abilities. Additionally, SirT1 mRNA levels were dose-dependently increased in resveratrol- treated retinal stem cells. The expression of SirT1 on oxidative stress-induced damage was significantly decreased, negatively correlated with the level of intracellular reactive oxygen species production. Treatment with resveratrol could effectively further reduce oxidative stress induced by H2O2 treatment in retinal stem cells. Importantly, the anti-oxidant effects of resveratrol in H2O2-treated retinal stem cells were significantly abolished by knockdown of SirT1 expression (sh-SirT1). SirT1 expression provides a feasible sensor in assessing self-renewal and aging process in retinal stem cells. Resveratrol can prevent reactive oxygen species-induced damages via increased retinal SirT1 expression. Full article
(This article belongs to the Special Issue Delft Workshop 2008-2009—Sensors and Imagers: a VLSI Perspective)
Open AccessArticle A Nitrite Biosensor Based on Co-immobilization of Nitrite Reductase and Viologen-modified Chitosan on a Glassy Carbon Electrode
Sensors 2010, 10(6), 6241-6256; doi:10.3390/s100606241
Received: 18 May 2010 / Revised: 8 June 2010 / Accepted: 14 June 2010 / Published: 22 June 2010
Cited by 10 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
An electrochemical nitrite biosensor based on co-immobilization of copper- containing nitrite reductase (Cu-NiR, from Rhodopseudomonas sphaeroides forma sp. denitrificans) and viologen-modified chitosan (CHIT-V) on a glassy carbon electrode (GCE) is presented. Electron transfer (ET) between a conventional GCE and immobilized Cu-NiR was
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An electrochemical nitrite biosensor based on co-immobilization of copper- containing nitrite reductase (Cu-NiR, from Rhodopseudomonas sphaeroides forma sp. denitrificans) and viologen-modified chitosan (CHIT-V) on a glassy carbon electrode (GCE) is presented. Electron transfer (ET) between a conventional GCE and immobilized Cu-NiR was mediated by the co-immobilized CHIT-V. Redox-active viologen was covalently linked to a chitosan backbone, and the thus produced CHIT-V was co-immobilized with Cu-NiR on the GCE surface by drop-coating of hydrophilic polyurethane (HPU). The electrode responded to nitrite with a limit of detection (LOD) of 40 nM (S/N = 3). The sensitivity, linear response range, and response time (t90%) were 14.9 nA/mM, 0.04−11 mM (r2 = 0.999) and 15 s, respectively. The corresponding Lineweaver-Burk plot showed that the apparent Michaelis-Menten constant (KMapp) was 65 mM. Storage stability of the biosensor (retaining 80% of initial activity) was 65 days under ambient air and room temperature storage conditions. Reproducibility of the sensor showed a relative standard deviation (RSD) of 2.8% (n = 5) for detection of 1 mM of nitrite. An interference study showed that anions commonlyfound in water samples such as chlorate, chloride, sulfate and sulfite did not interfere with the nitrite detection. However, nitrate interfered with a relative sensitivity of 64% and this interference effect was due to the intrinsic character of the NiR employed in this study. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Response to Specific Interactions
Sensors 2010, 10(6), 6257-6274; doi:10.3390/s100606257
Received: 8 January 2010 / Revised: 12 March 2010 / Accepted: 9 June 2010 / Published: 22 June 2010
Cited by 23 | PDF Full-text (935 KB) | HTML Full-text | XML Full-text
Abstract
Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis
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Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis of the observed shifts in the WGM wavelength positions are applied and used to quantify the adsorbed mass densities, which are then compared with the results of a comparative surface plasmon resonance (SPR) study. Full article
(This article belongs to the Section Biosensors)
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Review

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Open AccessReview Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring
Sensors 2010, 10(6), 5469-5502; doi:10.3390/s100605469
Received: 30 March 2010 / Revised: 10 May 2010 / Accepted: 20 May 2010 / Published: 1 June 2010
Cited by 273 | PDF Full-text (1815 KB) | HTML Full-text | XML Full-text
Abstract
Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively
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Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
Open AccessReview Methodology of Pulsed Photoacoustics and Its Application to Probe Photosystems and Receptors
Sensors 2010, 10(6), 5642-5667; doi:10.3390/s100605642
Received: 23 February 2010 / Revised: 27 May 2010 / Accepted: 27 May 2010 / Published: 3 June 2010
Cited by 7 | PDF Full-text (802 KB) | HTML Full-text | XML Full-text
Abstract
We review recent advances in the methodology of pulsed time-resolved photoacoustics and its application to studies of photosynthetic reaction centers and membrane receptors such as the G protein-coupled receptor rhodopsin. The experimental parameters accessible to photoacoustics include molecular volume change and photoreaction enthalpy
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We review recent advances in the methodology of pulsed time-resolved photoacoustics and its application to studies of photosynthetic reaction centers and membrane receptors such as the G protein-coupled receptor rhodopsin. The experimental parameters accessible to photoacoustics include molecular volume change and photoreaction enthalpy change. Light-driven volume change secondary to protein conformational changes or electrostriction is directly related to the photoreaction and thus can be a useful measurement of activity and function. The enthalpy changes of the photochemical reactions observed can be measured directly by photoacoustics. With the measurement of enthalpy change, the reaction entropy can also be calculated when free energy is known. Dissecting the free energy of a photoreaction into enthalpic and entropic components may provide critical information about photoactivation mechanisms of photosystems and photoreceptors. The potential limitations and future applications of time-resolved photoacoustics are also discussed. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessReview The Role of PAS Kinase in PASsing the Glucose Signal
Sensors 2010, 10(6), 5668-5682; doi:10.3390/s100605668
Received: 4 February 2010 / Revised: 20 March 2010 / Accepted: 12 May 2010 / Published: 4 June 2010
Cited by 8 | PDF Full-text (4234 KB) | HTML Full-text | XML Full-text
Abstract
PAS kinase is an evolutionarily conserved nutrient responsive protein kinase that regulates glucose homeostasis. Mammalian PAS kinase is activated by glucose in pancreatic beta cells, and knockout mice are protected from obesity, liver triglyceride accumulation, and insulin resistance when fed a high-fat diet.
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PAS kinase is an evolutionarily conserved nutrient responsive protein kinase that regulates glucose homeostasis. Mammalian PAS kinase is activated by glucose in pancreatic beta cells, and knockout mice are protected from obesity, liver triglyceride accumulation, and insulin resistance when fed a high-fat diet. Yeast PAS kinase is regulated by both carbon source and cell integrity stress and stimulates the partitioning of glucose toward structural carbohydrate biosynthesis. In our current model for PAS kinase regulation, a small molecule metabolite binds the sensory PAS domain and activates the enzyme. Although bona fide PAS kinase substrates are scarce, in vitro substrate searches provide putative targets for exploration. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessReview Sensor Systems for Prognostics and Health Management
Sensors 2010, 10(6), 5774-5797; doi:10.3390/s100605774
Received: 20 April 2010 / Revised: 27 May 2010 / Accepted: 28 May 2010 / Published: 8 June 2010
Cited by 85 | PDF Full-text (298 KB) | HTML Full-text | XML Full-text
Abstract
Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM
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Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM to monitor environmental, operational, and performance-related characteristics. The gathered data can be analyzed to assess product health and predict remaining life. In this paper, the considerations for sensor system selection for PHM applications, including the parameters to be measured, the performance needs, the electrical and physical attributes, reliability, and cost of the sensor system, are discussed. The state-of-the-art sensor systems for PHM and the emerging trends in technologies of sensor systems for PHM are presented. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Recent Applications of Fluorescence Recovery after Photobleaching (FRAP) to Membrane Bio-Macromolecules
Sensors 2010, 10(6), 5927-5948; doi:10.3390/s100605927
Received: 20 April 2010 / Revised: 10 May 2010 / Accepted: 28 May 2010 / Published: 10 June 2010
Cited by 20 | PDF Full-text (425 KB) | HTML Full-text | XML Full-text
Abstract
This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies. Initially, we discuss the lateral diffusion of membrane proteins, as measured by FRAP. Then, we talk about the use of FRAP to
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This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies. Initially, we discuss the lateral diffusion of membrane proteins, as measured by FRAP. Then, we talk about the use of FRAP to probe interactions between membrane proteins by obtaining fundamental information such as geometry and stoichiometry of the interacting complex. Afterwards, we discuss some applications of FRAP at the cellular level as well as the level of organisms. We conclude by comparing diffusion coefficients obtained by FRAP and several other alternative methods. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessReview Review on the Modeling of Electrostatic MEMS
Sensors 2010, 10(6), 6149-6171; doi:10.3390/s100606149
Received: 9 March 2010 / Revised: 18 May 2010 / Accepted: 24 May 2010 / Published: 21 June 2010
Cited by 41 | PDF Full-text (660 KB) | HTML Full-text | XML Full-text
Abstract
Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis,
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Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering - 2009)
Open AccessReview Glucose Signaling-Mediated Coordination of Cell Growth and Cell Cycle in Saccharomyces Cerevisiae
Sensors 2010, 10(6), 6195-6240; doi:10.3390/s100606195
Received: 7 May 2010 / Revised: 26 May 2010 / Accepted: 27 May 2010 / Published: 21 June 2010
Cited by 45 | PDF Full-text (790 KB) | HTML Full-text | XML Full-text
Abstract
Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their
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Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes. Full article
(This article belongs to the Special Issue Glucose Sensors)

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