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Sensors, Volume 8, Issue 3 (March 2008), Pages 1351-2042

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Open AccessArticle Amperometric Enzyme-based Gas Sensor for Formaldehyde: Impact of Possible Interferences
Sensors 2008, 8(3), 1351-1365; doi:10.3390/s8031351
Received: 28 December 2007 / Accepted: 25 February 2008 / Published: 27 February 2008
Cited by 13 | PDF Full-text (491 KB) | HTML Full-text | XML Full-text
Abstract
In this work, cross-sensitivities and environmental influences on the sensitivityand the functionality of an enzyme-based amperometric sensor system for the directdetection of formaldehyde from the gas phase are studied. The sensor shows a linearresponse curve for formaldehyde in the tested range (0 [...] Read more.
In this work, cross-sensitivities and environmental influences on the sensitivityand the functionality of an enzyme-based amperometric sensor system for the directdetection of formaldehyde from the gas phase are studied. The sensor shows a linearresponse curve for formaldehyde in the tested range (0 - 15 vppm) with a sensitivity of1.9 μA/ppm and a detection limit of about 130 ppb. Cross-sensitivities by environmentalgases like CO2, CO, NO, H2, and vapors of organic solvents like methanol and ethanol areevaluated as well as temperature and humidity influences on the sensor system. The sensorshowed neither significant signal to CO, H2, methanol or ethanol nor to variations in thehumidity of the test gas. As expected, temperature variations had the biggest influence onthe sensor sensitivity with variations in the sensor signal of up to 10 % of the signal for 5vppm CH2O in the range of 25 - 30 °C. Full article
Open AccessArticle Assembling Amperometric Biosensors for Clinical Diagnostics
Sensors 2008, 8(3), 1366-1399; doi:10.3390/s8031366
Received: 1 February 2008 / Accepted: 14 February 2008 / Published: 27 February 2008
Cited by 33 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
Clinical diagnosis and disease prevention routinely require the assessment ofspecies determined by chemical analysis. Biosensor technology offers several benefits overconventional diagnostic analysis. They include simplicity of use, specificity for the targetanalyte, speed to arise to a result, capability for continuous monitoring and [...] Read more.
Clinical diagnosis and disease prevention routinely require the assessment ofspecies determined by chemical analysis. Biosensor technology offers several benefits overconventional diagnostic analysis. They include simplicity of use, specificity for the targetanalyte, speed to arise to a result, capability for continuous monitoring and multiplexing,together with the potentiality of coupling to low-cost, portable instrumentation. This workfocuses on the basic lines of decisions when designing electron-transfer-based biosensorsfor clinical analysis, with emphasis on the strategies currently used to improve the deviceperformance, the present status of amperometric electrodes for biomedicine, and the trendsand challenges envisaged for the near future. Full article
Open AccessArticle Topographic Effects on the Surface Emissivity of a Mountainous Area Observed by a Spaceborne Microwave Radiometer
Sensors 2008, 8(3), 1459-1474; doi:10.3390/s8031459
Received: 23 January 2008 / Accepted: 27 February 2008 / Published: 3 March 2008
Cited by 12 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
A simulation study to understand the influence of topography on the surfaceemissivity observed by a satellite microwave radiometer is carried out. We analyze theeffects due to changes in observation angle, including the rotation of the polarization plane.A mountainous area in the Alps [...] Read more.
A simulation study to understand the influence of topography on the surfaceemissivity observed by a satellite microwave radiometer is carried out. We analyze theeffects due to changes in observation angle, including the rotation of the polarization plane.A mountainous area in the Alps (Northern Italy) is considered and the information on therelief extracted from a digital elevation model is exploited. The numerical simulation refersto a radiometric image, acquired by a conically-scanning radiometer similar to AMSR-E,i.e., flying at 705 km of altitude with an observation angle of 55°. To single out the impacton surface emissivity, scattering of the radiation due to the atmosphere or neighboringelevated surfaces is not considered. C and X bands, for which atmospheric effects arenegligible, and Ka band are analyzed. The results indicate that the changes in the localobservation angle tend to lower the apparent emissivity of a radiometric pixel with respectto the corresponding flat surface characteristics. The effect of the rotation of thepolarization plane enlarges (vertical polarization), or attenuates (horizontal polarization)this decrease. By doing some simplifying assumptions for the radiometer antenna, theconclusion is that the microwave emissivity at vertical polarization is underestimated,whilst the opposite occurs for horizontal polarization, except for Ka band, for which bothunder- and overprediction may occur. A quantification of the differences with respect to aflat soil and an approximate evaluation of their impact on soil moisture retrieval areyielded. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Three-Dimensional Transport Modeling for Proton Exchange Membrane(PEM) Fuel Cell with Micro Parallel Flow Field
Sensors 2008, 8(3), 1475-1487; doi:10.3390/s8031475
Received: 30 January 2008 / Accepted: 27 February 2008 / Published: 3 March 2008
Cited by 1 | PDF Full-text (592 KB) | HTML Full-text | XML Full-text
Abstract
Modeling and simulation for heat and mass transport in micro channel are beingused extensively in researches and industrial applications to gain better understanding of thefundamental processes and to optimize fuel cell designs before building a prototype forengineering application. In this study, we [...] Read more.
Modeling and simulation for heat and mass transport in micro channel are beingused extensively in researches and industrial applications to gain better understanding of thefundamental processes and to optimize fuel cell designs before building a prototype forengineering application. In this study, we used a single-phase, fully three dimensionalsimulation model for PEMFC that can deal with both anode and cathode flow field forexamining the micro flow channel with electrochemical reaction. The results show thathydrogen and oxygen were solely supplied to the membrane by diffusion mechanism ratherthan convection transport, and the higher pressure drop at cathode side is thought to becaused by higher flow rate of oxygen at cathode. And it is found that the amount of water incathode channel was determined by water formation due to electrochemical reaction pluselectro-osmotic mass flux directing toward the cathode side. And it is very important tomodel the back diffusion and electro-osmotic mass flux accurately since the two flux wasclosely correlated each other and greatly influenced for determination of ionic conductivityof the membrane which directly affects the performance of fuel cell. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Application of Electrostatic Extrusion – Flavour Encapsulation and Controlled Release
Sensors 2008, 8(3), 1488-1496; doi:10.3390/s8031488
Received: 10 December 2007 / Accepted: 19 February 2008 / Published: 3 March 2008
Cited by 18 | PDF Full-text (111 KB) | HTML Full-text | XML Full-text
Abstract
The subject of this study was the development of flavour alginate formulationsaimed for thermally processed foods. Ethyl vanilline was used as the model flavourcompound. Electrostatic extrusion was applied for the encapsulation of ethyl vanilline inalginate gel microbeads. The obtained microbeads with approx. [...] Read more.
The subject of this study was the development of flavour alginate formulationsaimed for thermally processed foods. Ethyl vanilline was used as the model flavourcompound. Electrostatic extrusion was applied for the encapsulation of ethyl vanilline inalginate gel microbeads. The obtained microbeads with approx. 10 % w/w of ethylvanilline encapsulated in about 2 % w/w alginate were uniformly sized spheres of about450 μm. Chemical characterization by H-NMR spectroscopy revealed that the alginateused in this study had a high content (67 %) of guluronic residues and was rich in GG diadblocks (FGG = 55%) and thus presented a high-quality immobilisation matrix. The thermalbehaviour of alginate beads encapsulating ethyl vanilline was investigated bythermogravimetric (TG) and differential scanning calorimetry measurements (TG-DSC)under heating conditions which mimicked usual food processing to provide informationabout thermal decomposition of alginate matrix and kinetics of aroma release. Two wellresolved weight losses were observed. The first one was in the 50-150 °C temperaturerange with the maximum at approx. 112 °C, corresponding to the dehydration of thepolymer network. The second loss in the 220-325 °C temperature range, with a maximumat ~ 247 °C corresponded to the release of vanilline. The obtained results indicate that up to230 °C most of the vanilline remained intacta, while prolonged heating at elevatedtemperatures led to the entire loss of the aroma compound. Full article
Open AccessArticle Amperometric Low-Potential Detection of Malic Acid Using Single-Wall Carbon Nanotubes Based Electrodes
Sensors 2008, 8(3), 1497-1507; doi:10.3390/s8031497
Received: 4 February 2008 / Accepted: 21 February 2008 / Published: 3 March 2008
Cited by 13 | PDF Full-text (216 KB) | HTML Full-text | XML Full-text
Abstract
The electrocatalytical property of single-wall carbon nanotube (SWNT)modified electrode toward NADH detection was explored by cyclic voltammetry andamperometry techniques. The experimental results show that SWNT decrease theovervoltage required for oxidation of NADH (to 300 mV vs. Ag/AgCl) and this propertymake them suitable [...] Read more.
The electrocatalytical property of single-wall carbon nanotube (SWNT)modified electrode toward NADH detection was explored by cyclic voltammetry andamperometry techniques. The experimental results show that SWNT decrease theovervoltage required for oxidation of NADH (to 300 mV vs. Ag/AgCl) and this propertymake them suitable for dehydrogenases based biosensors. The behavior of the SWNTmodified biosensor for L-malic acid was studied as an example for dehydrogenasesbiosensor. The amperometric measurements indicate that malate dehydrogenase (MDH)can be strongly adsorbed on the surface of the SWNT-modified electrode to form anapproximate monolayer film. Enzyme immobilization in Nafion membrane can increasethe biosensor stability. A linear calibration curve was obtained for L-malic acidconcentrations between 0.2 and 1mM. Full article
Open AccessArticle Synthesis and Characterization of Carbon Nitride Films for Micro Humidity Sensors
Sensors 2008, 8(3), 1508-1518; doi:10.3390/s8031508
Received: 23 January 2008 / Accepted: 26 February 2008 / Published: 3 March 2008
Cited by 22 | PDF Full-text (1903 KB) | HTML Full-text | XML Full-text
Abstract
Nano-structured carbon nitride (CNx) films were synthesized by a reactive RFmagnetron sputtering system with a DC bias under various deposition conditions, and theirphysical and electrical properties were investigated with a view to using them for microhumidity sensors. The FTIR spectra [...] Read more.
Nano-structured carbon nitride (CNx) films were synthesized by a reactive RFmagnetron sputtering system with a DC bias under various deposition conditions, and theirphysical and electrical properties were investigated with a view to using them for microhumidity sensors. The FTIR spectra of the deposited films showed a C=N stretching bandin the range of 1600~1700 ㎝-1, depending on the amount of nitrogen incorporation. Thecarbon nitride films deposited on the Si substrate had a nano-structured surfacemorphology with a grain size of about 20 nm, and their deposition rate was 1.5 μm/hr. Thesynthesized films had a high electrical resistivity in the range of 108 to 109 ω·cm,depending on the deposition conditions. The micro humidity sensors showed a goodlinearity and low hysteresis between 5 ~ 95 %RH. Full article
Open AccessArticle The Application of DNA-Biosensors and Differential Scanning Calorimetry to the Study of the DNA-Binding Agent Berenil
Sensors 2008, 8(3), 1519-1538; doi:10.3390/s8031519
Received: 29 January 2008 / Accepted: 14 February 2008 / Published: 3 March 2008
Cited by 13 | PDF Full-text (241 KB) | HTML Full-text | XML Full-text
Abstract
The in situ DNA-damaging capacity of berenil (1) has been investigated usingan electrochemical approach employing double stranded (ds) DNA-modified glassy carbonelectrode biosensors. Electrochemical voltammetric sensing of damage caused by 1 todsDNA was monitored by the appearance of peaks diagnostic of the oxidation [...] Read more.
The in situ DNA-damaging capacity of berenil (1) has been investigated usingan electrochemical approach employing double stranded (ds) DNA-modified glassy carbonelectrode biosensors. Electrochemical voltammetric sensing of damage caused by 1 todsDNA was monitored by the appearance of peaks diagnostic of the oxidation of guanineand adenine. When 1 was incorporated directly onto the biosensor surface, DNA damagecould be observed at concentrations of additive as low as 10 μM. In contrast, when thedsDNA-modified biosensor was exposed to 1, in acetate buffer solution, the method wasmuch less sensitive and DNA damage could be detected only in the presence of 100 μMberenil. When mixed solutions of 1 and single stranded (ss) DNA, polyguanylic acid orpolyadenylic acid were submitted to voltammetric study, the oxidation signals of therespective bases decreased in a concentration-dependent manner and the major variation ofthe adenine current peak indicated preferential binding of 1 to adenine. The electrochemical results were in close agreement with those deriving from a differentialscanning calorimetric study of the DNA-berenil complex. Full article
Open AccessArticle Low-cost Sensors Based on the GMI Effect in Recycled Transformer Cores
Sensors 2008, 8(3), 1575-1584; doi:10.3390/s8031575
Received: 9 January 2008 / Accepted: 25 February 2008 / Published: 10 March 2008
Cited by 6 | PDF Full-text (490 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Sensors based on the giant magnetoimpedance (GMI) effect in silicon steelswere constructed. Strips of silicon steels (0.500 mm-thick, 35.0 mm-long) with widthsranging from 0.122 to 1.064 mm were cut from recycled transformer cores. Since amaximum GMI ratio of 300% and a maximum [...] Read more.
Sensors based on the giant magnetoimpedance (GMI) effect in silicon steelswere constructed. Strips of silicon steels (0.500 mm-thick, 35.0 mm-long) with widthsranging from 0.122 to 1.064 mm were cut from recycled transformer cores. Since amaximum GMI ratio of 300% and a maximum field sensitivity of 1.5%/Oe were observedin a 1.064 mm-wide sample at 200 kHz, the 1.064 mm-wide strips were chosen as sensingelements in a slot key switch, angular velocity sensor, current sensor and force sensor. Thesensing elements were integrated into electronic circuits and the changes in impedancewere monitored. Variations in voltage due to these changes were typically small and musttherefore be amplified by the electronic circuits. For the current sensor and force sensor,the variation in the voltage drop across the GMI sensing element had non-linear variationswith either current or force and a conversion formula from a computer program wastherefore needed. The performance of the systems was tested. These sensing systems werestable, highly sensitive, hysteresis-free and could be produced on a mass scale. Based ontheir GMI effect, the silicon steels are versatile alternative low-cost sensors. Full article
Open AccessArticle An Artificial Neural Network Approach for the Prediction of Absorption Measurements of an Evanescent Field Fiber Sensor
Sensors 2008, 8(3), 1585-1594; doi:10.3390/s8031585
Received: 2 November 2007 / Accepted: 29 February 2008 / Published: 10 March 2008
Cited by 18 | PDF Full-text (135 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes artificial neural network (ANN) based prediction of theresponse of a fiber optic sensor using evanescent field absorption (EFA). The sensingprobe of the sensor is made up a bundle of five PCS fibers to maximize the interaction ofevanescent field with [...] Read more.
This paper describes artificial neural network (ANN) based prediction of theresponse of a fiber optic sensor using evanescent field absorption (EFA). The sensingprobe of the sensor is made up a bundle of five PCS fibers to maximize the interaction ofevanescent field with the absorbing medium. Different backpropagation algorithms areused to train the multilayer perceptron ANN. The Levenberg-Marquardt algorithm, aswell as the other algorithms used in this work successfully predicts the sensor responses. Full article
(This article belongs to the Special Issue Intelligent Sensors)
Open AccessArticle Object-based Land Cover Classification and Change Analysis in the Baltimore Metropolitan Area Using Multitemporal High Resolution Remote Sensing Data
Sensors 2008, 8(3), 1613-1636; doi:10.3390/s8031613
Received: 29 January 2008 / Accepted: 28 February 2008 / Published: 10 March 2008
Cited by 78 | PDF Full-text (801 KB) | HTML Full-text | XML Full-text
Abstract
Accurate and timely information about land cover pattern and change in urbanareas is crucial for urban land management decision-making, ecosystem monitoring andurban planning. This paper presents the methods and results of an object-basedclassification and post-classification change detection of multitemporal high-spatialresolution Emerge aerial [...] Read more.
Accurate and timely information about land cover pattern and change in urbanareas is crucial for urban land management decision-making, ecosystem monitoring andurban planning. This paper presents the methods and results of an object-basedclassification and post-classification change detection of multitemporal high-spatialresolution Emerge aerial imagery in the Gwynns Falls watershed from 1999 to 2004. TheGwynns Falls watershed includes portions of Baltimore City and Baltimore County,Maryland, USA. An object-based approach was first applied to implement the land coverclassification separately for each of the two years. The overall accuracies of theclassification maps of 1999 and 2004 were 92.3% and 93.7%, respectively. Following theclassification, we conducted a comparison of two different land cover change detectionmethods: traditional (i.e., pixel-based) post-classification comparison and object-basedpost-classification comparison. The results from our analyses indicated that an objectbasedapproach provides a better means for change detection than a pixel based methodbecause it provides an effective way to incorporate spatial information and expertknowledge into the change detection process. The overall accuracy of the change mapproduced by the object-based method was 90.0%, with Kappa statistic of 0.854, whereasthe overall accuracy and Kappa statistic of that by the pixel-based method were 81.3% and0.712, respectively. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
Open AccessCommunication A Fluorescent Sensor for Dinitrobenzoic Acid Based on a Cyanuric Acid and Xanthene Skeleton
Sensors 2008, 8(3), 1637-1644; doi:10.3390/s8031637
Received: 12 February 2008 / Accepted: 11 March 2008 / Published: 11 March 2008
Cited by 5 | PDF Full-text (127 KB) | HTML Full-text | XML Full-text
Abstract A new fluorescent sensor based on a dimethylxanthene skeleton has beensynthesized. Because of its oxyanion hole structure, this receptor includes a suitablecavity for the association of carboxylic acids. The receptor’s fluorescence is quenchedupon addition of dinitrobenzoic acid. Full article
(This article belongs to the Special Issue Molecular Recognition and Sensors, Including Molecular Imprinting)
Open AccessArticle Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors
Sensors 2008, 8(3), 1645-1703; doi:10.3390/s8031645
Received: 31 December 2007 / Accepted: 22 February 2008 / Published: 11 March 2008
Cited by 142 | PDF Full-text (337 KB) | HTML Full-text | XML Full-text
Abstract
Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively [...] Read more.
Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast response and rational selectivity. The vital component of such plasticizedPVC members is the ionophore involved, defining the selectivity of the electrodes' complexformation. Molecular recognition causes the formation of many different supramolecules.Different types of supramolecules, like calixarenes, cyclodextrins and podands, have beenused as a sensing material in the construction of ion selective sensors. Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anioncomplexes will be described. Liquid membrane sensors based on Schiff's bases and crownethers will then be discussed. Full article
(This article belongs to the Special Issue Supramolecular Sensors)
Open AccessArticle Multiscale Unsupervised Segmentation of SAR Imagery Using the Genetic Algorithm
Sensors 2008, 8(3), 1704-1711; doi:10.3390/s8031704
Received: 17 January 2008 / Accepted: 25 February 2008 / Published: 12 March 2008
Cited by 6 | PDF Full-text (171 KB) | HTML Full-text | XML Full-text
Abstract
A valid unsupervised and multiscale segmentation of synthetic aperture radar(SAR) imagery is proposed by a combination GA-EM of the Expectation Maximization(EM) algorith with the genetic algorithm (GA). The mixture multiscale autoregressive(MMAR) model is introduced to characterize and exploit the scale-to-scale statisticalvariations and [...] Read more.
A valid unsupervised and multiscale segmentation of synthetic aperture radar(SAR) imagery is proposed by a combination GA-EM of the Expectation Maximization(EM) algorith with the genetic algorithm (GA). The mixture multiscale autoregressive(MMAR) model is introduced to characterize and exploit the scale-to-scale statisticalvariations and statistical variations in the same scale in SAR imagery due to radar speckle,and a segmentation method is given by combining the GA algorithm with the EMalgorithm. This algorithm is capable of selecting the number of components of the modelusing the minimum description length (MDL) criterion. Our approach benefits from theproperties of the Genetic and the EM algorithm by combination of both into a singleprocedure. The population-based stochastic search of the genetic algorithm (GA) exploresthe search space more thoroughly than the EM method. Therefore, our algorithm enablesescaping from local optimal solutions since the algorithm becomes less sensitive to itsinitialization. Some experiment results are given based on our proposed approach, andcompared to that of the EM algorithms. The experiments on the SAR images show that theGA-EM outperforms the EM method. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
Open AccessCommunication Carbon Nanotubes Based Glucose Needle-type Biosensor
Sensors 2008, 8(3), 1712-1718; doi:10.3390/s8031712
Received: 12 December 2007 / Accepted: 21 February 2008 / Published: 12 March 2008
Cited by 9 | PDF Full-text (66 KB) | HTML Full-text | XML Full-text
Abstract
A novel needle-type biosensor based on carbon nanotubes is reported. Thebiosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs),graphite powder and glucose oxidase (Gox) freeze-dried powder into a glass capillary of 0.5mm inner diameter. The resulting amperometric [...] Read more.
A novel needle-type biosensor based on carbon nanotubes is reported. Thebiosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs),graphite powder and glucose oxidase (Gox) freeze-dried powder into a glass capillary of 0.5mm inner diameter. The resulting amperometric biosensor was characterizedelectrochemically using amperometry in the presence of hydrogen peroxide and in thepresence of glucose. The glucose biosensor sensitivity was influenced by the glucoseoxidase concentration within the MWCNTs mixture. The optimized glucose needle-typebiosensor displayed better sensitivity and stability, and a detected range of up to 20 mM.Based on its favorable stability, the needle biosensor was first time used in real-timemonitoring system as a kind of online glucose detector. The decay of current response isless than 10% after 24-hour continuous observation. Full article
Open AccessArticle Applications of the Integrated High-Performance CMOS Image Sensor to Range Finders — from Optical Triangulation to the Automotive Field
Sensors 2008, 8(3), 1719-1739; doi:10.3390/s8031719
Received: 22 December 2007 / Accepted: 10 March 2008 / Published: 13 March 2008
Cited by 7 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract
With their significant features, the applications of complementary metal-oxidesemiconductor (CMOS) image sensors covers a very extensive range, from industrialautomation to traffic applications such as aiming systems, blind guidance, active/passiverange finders, etc. In this paper CMOS image sensor-based active and passive rangefinders are [...] Read more.
With their significant features, the applications of complementary metal-oxidesemiconductor (CMOS) image sensors covers a very extensive range, from industrialautomation to traffic applications such as aiming systems, blind guidance, active/passiverange finders, etc. In this paper CMOS image sensor-based active and passive rangefinders are presented. The measurement scheme of the proposed active/passive rangefinders is based on a simple triangulation method. The designed range finders chieflyconsist of a CMOS image sensor and some light sources such as lasers or LEDs. Theimplementation cost of our range finders is quite low. Image processing software to adjustthe exposure time (ET) of the CMOS image sensor to enhance the performance oftriangulation-based range finders was also developed. An extensive series of experimentswere conducted to evaluate the performance of the designed range finders. From theexperimental results, the distance measurement resolutions achieved by the active rangefinder and the passive range finder can be better than 0.6% and 0.25% within themeasurement ranges of 1 to 8 m and 5 to 45 m, respectively. Feasibility tests onapplications of the developed CMOS image sensor-based range finders to the automotivefield were also conducted. The experimental results demonstrated that our range finders arewell-suited for distance measurements in this field. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
Open AccessArticle Assessing Steady-state Fluorescence and PRI from Hyperspectral Proximal Sensing as Early Indicators of Plant Stress: The Case of Ozone Exposure
Sensors 2008, 8(3), 1740-1754; doi:10.3390/s8031740
Received: 31 January 2008 / Accepted: 11 March 2008 / Published: 13 March 2008
Cited by 42 | PDF Full-text (246 KB) | HTML Full-text | XML Full-text
Abstract
High spectral resolution spectrometers were used to detect optical signals ofongoing plant stress in potted white clover canopies subjected to ozone fumigation. Thecase of ozone stress is used in this manuscript as a paradigm of oxidative stress. Steadystatefluorescence (Fs) and the Photochemical [...] Read more.
High spectral resolution spectrometers were used to detect optical signals ofongoing plant stress in potted white clover canopies subjected to ozone fumigation. Thecase of ozone stress is used in this manuscript as a paradigm of oxidative stress. Steadystatefluorescence (Fs) and the Photochemical Reflectance Index (PRI) were investigatedas advanced hyperspectral remote sensing techniques able to sense variations in the excessenergy dissipation pathways occurring when photosynthesis declines in plants exposed to astress agent. Fs and PRI were monitored in control and ozone fumigated canopies during a21-day experiment together with the traditional Normalized Difference Vegetation Index(NDVI) and physiological measurements commonly employed by physiologists to describestress development (i.e. net CO2 assimilation, active fluorimetry, chlorophyll concentrationand visible injuries). It is shown that remote detection of an ongoing stress through Fs andPRI can be achieved in an early phase, characterized by the decline of photosynthesis. Onthe contrary, NDVI was able to detect the stress only when damage occurred. These resultsopen up new possibilities for assessment of plant stress by means of hyperspectral remotesensing. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessCommunication An Open Distributed Architecture for Sensor Networks for Risk Management
Sensors 2008, 8(3), 1755-1773; doi:10.3390/s8031755
Received: 10 December 2007 / Accepted: 12 March 2008 / Published: 13 March 2008
Cited by 14 | PDF Full-text (187 KB) | HTML Full-text | XML Full-text
Abstract
Sensors provide some of the basic input data for risk management of natural andman-made hazards. Here the word ‘sensors’ covers everything from remote sensingsatellites, providing invaluable images of large regions, through instruments installed on theEarth’s surface to instruments situated in deep boreholes [...] Read more.
Sensors provide some of the basic input data for risk management of natural andman-made hazards. Here the word ‘sensors’ covers everything from remote sensingsatellites, providing invaluable images of large regions, through instruments installed on theEarth’s surface to instruments situated in deep boreholes and on the sea floor, providinghighly-detailed point-based information from single sites. Data from such sensors is used inall stages of risk management, from hazard, vulnerability and risk assessment in the preeventphase, information to provide on-site help during the crisis phase through to data toaid in recovery following an event. Because data from sensors play such an important part inimproving understanding of the causes of risk and consequently in its mitigation,considerable investment has been made in the construction and maintenance of highlysophisticatedsensor networks. In spite of the ubiquitous need for information from sensornetworks, the use of such data is hampered in many ways. Firstly, information about thepresence and capabilities of sensor networks operating in a region is difficult to obtain dueto a lack of easily available and usable meta-information. Secondly, once sensor networkshave been identified their data it is often difficult to access due to a lack of interoperability between dissemination and acquisition systems. Thirdly, the transfer and processing ofinformation from sensors is limited, again by incompatibilities between systems. Therefore,the current situation leads to a lack of efficiency and limited use of the available data thathas an important role to play in risk mitigation. In view of this situation, the EuropeanCommission (EC) is funding a number of Integrated Projects within the Sixth FrameworkProgramme concerned with improving the accessibility of data and services for riskmanagement. Two of these projects: ‘Open Architecture and Spatial Data Infrastructure forRisk Management’ (ORCHESTRA, http://www.eu-orchestra.org/) and ‘Sensors Anywhere’(SANY, http://sany-ip.eu/) are discussed in this article. These projects have developed anopen distributed information technology architecture and have implemented web servicesfor the accessing and using data emanating, for example, from sensor networks. Thesedevelopments are based on existing data and service standards proposed by internationalorganizations. The projects seek to develop the ideals of the EC directive INSPIRE(http://inspire.jrc.it), which was launched in 2001 and whose implementation began this year(2007), into the risk management domain. Thanks to the open nature of the architecture andservices being developed within these projects, they can be implemented by any interestedparty and can be accessed by all potential users. The architecture is based around a serviceorientedapproach that makes use of Internet-based applications (web services) whose inputsand outputs conform to standards. The benefit of this philosophy is that it is expected tofavor the emergence of an operational market for risk management services in Europe, iteliminates the need to replace or radically alter the hundreds of already operational ITsystems in Europe (drastically lowering costs for users), and it allows users and stakeholdersto achieve interoperability while using the system most adequate to their needs, budgets,culture etc. (i.e. it has flexibility). Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
Open AccessArticle Development and Demonstration of Measurement-Time Efficient Methods for Impedance Spectroscopy of Electrode and Sensor Arrays
Sensors 2008, 8(3), 1774-1796; doi:10.3390/s8031774
Received: 12 February 2008 / Accepted: 11 March 2008 / Published: 14 March 2008
Cited by 4 | PDF Full-text (225 KB) | HTML Full-text | XML Full-text
Abstract
The development of impedance-based array devices is hindered by a lack ofrobust platforms and methods upon which to evaluate and interrogate sensors. One aspectto be addressed is the development of measurement-time efficient techniques forbroadband impedance spectroscopy of large electrode arrays. The objective [...] Read more.
The development of impedance-based array devices is hindered by a lack ofrobust platforms and methods upon which to evaluate and interrogate sensors. One aspectto be addressed is the development of measurement-time efficient techniques forbroadband impedance spectroscopy of large electrode arrays. The objective of this workwas to substantially increase the low frequency impedance measurement throughputcapability of a large channel count array analyzer by developing true parallel measurementmethods. The goal was achieved by Fourier transform-based analysis of simultaneouslyacquiredmulti-channel time-based current and voltage data. Efficacy and quantitativeanalysis of the parallel approach at frequencies less than ca. 10 Hz as well as a combinedsequential parallel approach for efficient broadband impedance spectroscopy over 5-orders of magnitude in frequency is demonstrated through complex impedancemeasurement of arrays consisting of up to 100 elements. Full article
Open AccessArticle Localization Algorithm Based on a Spring Model (LASM) for Large Scale Wireless Sensor Networks
Sensors 2008, 8(3), 1797-1818; doi:10.3390/s8031797
Received: 6 December 2007 / Accepted: 12 March 2008 / Published: 15 March 2008
Cited by 9 | PDF Full-text (384 KB) | HTML Full-text | XML Full-text
Abstract
A navigation method for a lunar rover based on large scale wireless sensornetworks is proposed. To obtain high navigation accuracy and large exploration area, highnode localization accuracy and large network scale are required. However, thecomputational and communication complexity and time consumption are [...] Read more.
A navigation method for a lunar rover based on large scale wireless sensornetworks is proposed. To obtain high navigation accuracy and large exploration area, highnode localization accuracy and large network scale are required. However, thecomputational and communication complexity and time consumption are greatly increasedwith the increase of the network scales. A localization algorithm based on a spring model(LASM) method is proposed to reduce the computational complexity, while maintainingthe localization accuracy in large scale sensor networks. The algorithm simulates thedynamics of physical spring system to estimate the positions of nodes. The sensor nodesare set as particles with masses and connected with neighbor nodes by virtual springs. Thevirtual springs will force the particles move to the original positions, the node positionscorrespondingly, from the randomly set positions. Therefore, a blind node position can bedetermined from the LASM algorithm by calculating the related forces with the neighbornodes. The computational and communication complexity are O(1) for each node, since thenumber of the neighbor nodes does not increase proportionally with the network scale size.Three patches are proposed to avoid local optimization, kick out bad nodes and deal withnode variation. Simulation results show that the computational and communicationcomplexity are almost constant despite of the increase of the network scale size. The time consumption has also been proven to remain almost constant since the calculation steps arealmost unrelated with the network scale size. Full article
Open AccessArticle A New PC and LabVIEW Package Based System for Electrochemical Investigations
Sensors 2008, 8(3), 1819-1831; doi:10.3390/s8031819
Received: 28 February 2008 / Accepted: 12 March 2008 / Published: 15 March 2008
Cited by 20 | PDF Full-text (1111 KB) | HTML Full-text | XML Full-text
Abstract
The paper describes a new PC and LabVIEW software package based system forelectrochemical research. An overview of well known electrochemical methods, such aspotential measurements, galvanostatic and potentiostatic method, cyclic voltammetry andEIS is given. Electrochemical impedance spectroscopy has been adapted for systemscontaining large [...] Read more.
The paper describes a new PC and LabVIEW software package based system forelectrochemical research. An overview of well known electrochemical methods, such aspotential measurements, galvanostatic and potentiostatic method, cyclic voltammetry andEIS is given. Electrochemical impedance spectroscopy has been adapted for systemscontaining large capacitances. For signal generation and recording of the response ofinvestigated electrochemical cell, a measurement and control system was developed, basedon a PC P4. The rest of the hardware consists of a commercially available AD-DA converterand an external interface for analog signal processing. The interface is a result of authorsown research. The software platform for desired measurement methods is LabVIEW 8.2package, which is regarded as a high standard in the area of modern virtual instruments. Thedeveloped system was adjusted, tested and compared with commercially available systemand ORCAD simulation. Full article
Open AccessArticle Estimation of the Total Atmospheric Water Vapor Content and Land Surface Temperature Based on AATSR Thermal Data
Sensors 2008, 8(3), 1832-1845; doi:10.3390/s8031832
Received: 7 November 2007 / Accepted: 8 February 2008 / Published: 16 March 2008
Cited by 2 | PDF Full-text (354 KB) | HTML Full-text | XML Full-text
Abstract
The total atmospheric water vapor content (TAWV) and land surfacetemperature (LST) play important roles in meteorology, hydrology, ecology and some otherdisciplines. In this paper, the ENVISAT/AATSR (The Advanced Along-Track ScanningRadiometer) thermal data are used to estimate the TAWV and LST over the [...] Read more.
The total atmospheric water vapor content (TAWV) and land surfacetemperature (LST) play important roles in meteorology, hydrology, ecology and some otherdisciplines. In this paper, the ENVISAT/AATSR (The Advanced Along-Track ScanningRadiometer) thermal data are used to estimate the TAWV and LST over the Loess Plateauin China by using a practical split window algorithm. The distribution of the TAWV isaccord with that of the MODIS TAWV products, which indicates that the estimation of thetotal atmospheric water vapor content is reliable. Validations of the LST by comparingwith the ground measurements indicate that the maximum absolute derivation, themaximum relative error and the average relative error is 4.0K, 11.8% and 5.0%respectively, which shows that the retrievals are believable; this algorithm can provide anew way to estimate the LST from AATSR data. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Amperometric Determination of Sulfite by Gas Diffusion- Sequential Injection with Boron-Doped Diamond Electrode
Sensors 2008, 8(3), 1846-1857; doi:10.3390/s8031846
Received: 2 January 2008 / Accepted: 5 March 2008 / Published: 17 March 2008
Cited by 18 | PDF Full-text (92 KB) | HTML Full-text | XML Full-text
Abstract
A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU) was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid [...] Read more.
A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU) was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1 M phosphate buffer (pH 8)/0.1% sodium dodecyl sulfate in the acceptor channel of theGDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell anddetected directly by amperometry using the boron-doped diamond electrode at 0.95 V(versus Ag/AgCl). Sodium dodecyl sulfate was added to the carrier solution to preventelectrode fouling. This method was applicable in the concentration range of 0.2-20 mgSO32−/L and a detection limit (S/N = 3) of 0.05 mg SO32−/L was achieved. This method wassuccessfully applied to the determination of sulfite in wines and the analytical resultsagreed well with those obtained by iodimetric titration. The relative standard deviations forthe analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was65 h−1. Full article
Open AccessArticle An Approach for Measuring the Sorptive Behavior of Odorants Using a Multifunction Thermal Desorber Unit: Preliminary Tests on Reduced Sulfur Compounds
Sensors 2008, 8(3), 1858-1871; doi:10.3390/s8031858
Received: 2 January 2008 / Accepted: 14 March 2008 / Published: 7 March 2008
Cited by 1 | PDF Full-text (104 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the sorptive behavior of reduced sulfur compounds (RSC) was investigated using a combination of thermal desorber (TD) unit and gas chromatography (GC). To examine the sorptive properties of RSC on textile materials, two types of experiments were conducted under [...] Read more.
In this study, the sorptive behavior of reduced sulfur compounds (RSC) was investigated using a combination of thermal desorber (TD) unit and gas chromatography (GC). To examine the sorptive properties of RSC on textile materials, two types of experiments were conducted under experimental conditions favorable for sorptive processes. In all the experiments, gaseous standards of hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide were supplied to initiate the adsorption processes on textile pieces. The textile pieces were then forced to release those adsorbed RSC under a fixed condition. It was found that the extent of adsorption, if evaluated quantitatively, occurred at approximately 1/1000 to 1/100 of the level of RSC standards supplied originally to induce adsorption. It also indicated that RSC adsorption was affected very sensitively by the initial exposure durations to induce RSC adsorption with an exponential decrease in relative recovery (RR) values with increasing exposure time. The relative sorptive patterns, when compared between different RSCs, were affected most sensitively by such factors as molecular weight and/or physical contact conditions. Full article
Open AccessArticle High Sensitive Temperature Sensor Using a Liquid-core Optical Fiber with Small Refractive Index Difference Between Core and Cladding Materials
Sensors 2008, 8(3), 1872-1878; doi:10.3390/s8031872
Received: 29 November 2007 / Accepted: 21 February 2008 / Published: 17 March 2008
Cited by 7 | PDF Full-text (136 KB) | HTML Full-text | XML Full-text
Abstract
An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of [...] Read more.
An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the liquid-core and the cladding of the fiber close. The experiment shows that a temperature sensitivity of about 5 dB/K and a tunable temperature range (from 20 oC to 60 oC) can be achieved. Based on the dielectric-clad liquid core fiber model, a simulation was carried out and the calculated results were in good accord with the experimental measurement. Full article
(This article belongs to the Special Issue Optical Biosensors)
Open AccessArticle Electrochemical Determination of Trace Sudan I Contamination in Chili Powder at Carbon Nanotube Modified Electrodes
Sensors 2008, 8(3), 1890-1900; doi:10.3390/s8031890
Received: 23 January 2008 / Accepted: 20 February 2008 / Published: 17 March 2008
Cited by 15 | PDF Full-text (370 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical [...] Read more.
We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical performance in terms of linearity (over the concentration range 6.0×10–7 to 7.5×10–5 M, r = 0.9967), detection limit (2.0×10–7 M) and reproducibility (RSD = 4.6%, n=10, for 2.0×10–5 M Sudan I). Full article
Open AccessArticle Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing
Sensors 2008, 8(3), 1901-1914; doi:10.3390/s8031901
Received: 30 January 2008 / Accepted: 17 March 2008 / Published: 18 March 2008
Cited by 8 | PDF Full-text (2378 KB) | HTML Full-text | XML Full-text
Abstract
This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral [...] Read more.
This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (Δτλaer ) and compared to the available measuring sensitivity of the sensor (NE ΔLλsensor). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle A Dynamic Range Expansion Technique for CMOS Image Sensors with Dual Charge Storage in a Pixel and Multiple Sampling
Sensors 2008, 8(3), 1915-1926; doi:10.3390/s8031915
Received: 25 December 2007 / Accepted: 12 March 2008 / Published: 18 March 2008
Cited by 5 | PDF Full-text (346 KB) | HTML Full-text | XML Full-text
Abstract
A dynamic range expansion technique for CMOS image sensors with dual charge storage in a pixel and multiple sampling technique is presented. Each pixel contains a photodiode and a storage diode which is connected to the photodiode via a separation gate. The [...] Read more.
A dynamic range expansion technique for CMOS image sensors with dual charge storage in a pixel and multiple sampling technique is presented. Each pixel contains a photodiode and a storage diode which is connected to the photodiode via a separation gate. The sensitivity of the signal charge in the storage diode can be controlled either by a separation gate which limits the charge to flow into the storage diode or by controlling the accumulation time in the storage diode. The operation of the sensitivity control with separation gate techniques is simulated and it is found that a blocking layer to the storage diode plays an important role for high controllability of sensitivity of the storage diode. A prototype chip for testing multiple short time accumulations is fabricated and measured. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
Open AccessArticle Assessment and Analysis of QuikSCAT Vector Wind Products for the Gulf of Mexico: A Long-Term and Hurricane Analysis
Sensors 2008, 8(3), 1927-1949; doi:10.3390/s8031927
Received: 9 November 2007 / Accepted: 15 March 2008 / Published: 18 March 2008
Cited by 19 | PDF Full-text (3054 KB) | HTML Full-text | XML Full-text
Abstract
The northern Gulf of Mexico is a region that has been frequently impacted in recent years by natural disasters such as hurricanes. The use of remote sensing data such as winds from NASA’s QuikSCAT satellite sensor would be useful for emergency preparedness [...] Read more.
The northern Gulf of Mexico is a region that has been frequently impacted in recent years by natural disasters such as hurricanes. The use of remote sensing data such as winds from NASA’s QuikSCAT satellite sensor would be useful for emergency preparedness during such events. In this study, the performance of QuikSCAT products, including JPL’s latest Level 2B (L2B) 12.5 km swath winds, were evaluated with respect to buoy-measured winds in the Gulf of Mexico for the period January 2005 to February 2007. Regression analyses indicated better accuracy of QuikSCAT’s L2B DIRTH, 12.5 km than the Level 3 (L3), 25 km wind product. QuikSCAT wind data were compared directly with buoy data keeping a maximum time interval of 20 min and spatial interval of 0.1° (≈10 km). R2 values for moderate wind speeds were 0.88 and 0.93 for L2B, and 0.75 and 0.89 for L3 for speed and direction, respectively. QuikSCAT wind comparisons for buoys located offshore were better than those located near the coast. Hurricanes that took place during 2002-06 were studied individually to obtain regressions of QuikSCAT versus buoys for those events. Results show QuikSCAT’s L2B DIRTH wind product compared well with buoys during hurricanes up to the limit of buoy measurements. Comparisons with the National Hurricane Center (NHC) best track analyses indicated QuikSCAT winds to be lower than those obtained by NHC, possibly due to rain contamination, while buoy measurements appeared to be constrained at high wind speeds. This study has confirmed good agreement of the new QuikSCAT L2B product with buoy measurements and further suggests its potential use during extreme weather conditions in the Gulf of Mexico. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Electrooxidation and Determination of Dopamine Using a Nafion®-Cobalt Hexacyanoferrate Film Modified Electrode
Sensors 2008, 8(3), 1950-1959; doi:10.3390/s8031950
Received: 29 May 2007 / Accepted: 17 March 2008 / Published: 19 March 2008
Cited by 25 | PDF Full-text (113 KB) | HTML Full-text | XML Full-text
Abstract
The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at [...] Read more.
The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%. Full article
Open AccessArticle A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures
Sensors 2008, 8(3), 1960-1976; doi:10.3390/s8031960
Received: 29 January 2008 / Accepted: 17 March 2008 / Published: 20 March 2008
Cited by 17 | PDF Full-text (178 KB) | HTML Full-text | XML Full-text
Abstract
Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a [...] Read more.
Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments. Full article
Open AccessArticle Hardware and Software of a Bipolar Current Source Controlled by PC
Sensors 2008, 8(3), 1977-1983; doi:10.3390/s8031977
Received: 10 March 2008 / Accepted: 20 March 2008 / Published: 22 March 2008
PDF Full-text (438 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a realization of a bipolar current source developed by the paper's authors. The source is intended for use in galvanic and other industrial plants, where a pulse-reverse current supply (with the desired shape in time) is required. A prototype [...] Read more.
This paper describes a realization of a bipolar current source developed by the paper's authors. The source is intended for use in galvanic and other industrial plants, where a pulse-reverse current supply (with the desired shape in time) is required. A prototype of the device, which provides the outcome current intensity up to ± 50 A, has been constructed. The hardware of the source consists of a Pentium IV PC, a commercial ADDA converter, an interface of authors’ original construction as well as a current regulator. The application software is developed using a commercial packet LabView as the basis. Full article
Open AccessArticle Role of Satellite Sensors in Groundwater Exploration
Sensors 2008, 8(3), 2006-2016; doi:10.3390/s8032006
Received: 1 November 2007 / Accepted: 7 February 2008 / Published: 24 March 2008
Cited by 8 | PDF Full-text (2415 KB) | HTML Full-text | XML Full-text
Abstract
Spatial as well as spectral resolution has a very important role to play in water resource management. It was a challenge to explore the groundwater and rainwater harvesting sites in the Aravalli Quartzite-Granite-Pegmatite Precambrian terrain of Delhi, India. Use of only panchromatic [...] Read more.
Spatial as well as spectral resolution has a very important role to play in water resource management. It was a challenge to explore the groundwater and rainwater harvesting sites in the Aravalli Quartzite-Granite-Pegmatite Precambrian terrain of Delhi, India. Use of only panchromatic sensor data of IRS-1D satellite with 5.8-meter spatial resolution has the potential to infer lineaments and faults in this hard rock area. It is essential to identify the location of interconnected lineaments below buried pediment plains in the hard rock area for targeting sub-surface water resources. Linear Image Self Scanning sensor data of the same satellite with 23.5-meter resolution when merged with the panchromatic data has produced very good results in delineation of interconnected lineaments over buried pediment plains as vegetation anomaly. These specific locations of vegetation anomaly were detected as dark red patches in various hard rock areas of Delhi. Field investigation was carried out on these patches by resistivity and magnetic survey in parts of Jawaharlal Nehru University (JNU), Indira Gandhi national Open University, Research and Referral Hospital and Humayuns Tomb areas. Drilling was carried out in four locations of JNU that proved to be the most potential site with ground water discharge ranging from 20,000 to 30,000 liters per hour with 2 to 4 meters draw down. Further the impact of urbanization on groundwater recharging in the terrain was studied by generating Normalized difference Vegetation Index (NDVI) map which was possible to generate by using the LISS-III sensor of IRS-1D satellite. Selection of suitable sensors has definitely a cutting edge on natural resource exploration and management including groundwater. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Monitoring the Effects of Forest Restoration Treatments on Post-Fire Vegetation Recovery with MODIS Multitemporal Data
Sensors 2008, 8(3), 2017-2042; doi:10.3390/s8032017
Received: 29 January 2008 / Accepted: 21 March 2008 / Published: 25 March 2008
Cited by 44 | PDF Full-text (3208 KB) | HTML Full-text | XML Full-text
Abstract
This study examines how satellite based time-series vegetation greenness data and phenological measurements can be used to monitor and quantify vegetation recovery after wildfire disturbances and examine how pre-fire fuel reduction restoration treatments impact fire severity and impact vegetation recovery trajectories. Pairs [...] Read more.
This study examines how satellite based time-series vegetation greenness data and phenological measurements can be used to monitor and quantify vegetation recovery after wildfire disturbances and examine how pre-fire fuel reduction restoration treatments impact fire severity and impact vegetation recovery trajectories. Pairs of wildfire affected sites and a nearby unburned reference site were chosen to measure the post-disturbance recovery in relation to climate variation. All site pairs were chosen in forested uplands in Arizona and were restricted to the area of the Rodeo-Chediski fire that occurred in 2002. Fuel reduction treatments were performed in 1999 and 2001. The inter-annual and seasonal vegetation dynamics before, during, and after wildfire events can be monitored using a time series of biweekly composited MODIS NDVI (Moderate Resolution Imaging Spectroradiometer - Normalized Difference Vegetation Index) data. Time series analysis methods included difference metrics, smoothing filters, and fitting functions that were applied to extract seasonal and inter-annual change and phenological metrics from the NDVI time series data from 2000 to 2007. Pre- and post-fire Landsat data were used to compute the Normalized Burn Ratio (NBR) and examine burn severity at the selected sites. The phenological metrics (pheno-metrics) included the timing and greenness (i.e. NDVI) for the start, peak and end of the growing season as well as proxy measures for the rate of green-up and senescence and the annual vegetation productivity. Pre-fire fuel reduction treatments resulted in lower fire severity, which reduced annual productivity much less than untreated areas within the Rodeo-Chediski fire perimeter. The seasonal metrics were shown to be useful for estimating the rate of post-fire disturbance recovery and the timing of phenological greenness phases. The use of satellite time series NDVI data and derived pheno-metrics show potential for tracking vegetation cover dynamics and successional changes in response to drought, wildfire disturbances, and forest restoration treatments in fire-suppressed forests. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)

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Open AccessReview Electrochemical Biosensors - Sensor Principles and Architectures
Sensors 2008, 8(3), 1400-1458; doi:10.3390/s80314000
Received: 23 January 2008 / Accepted: 28 January 2008 / Published: 7 March 2008
Cited by 359 | PDF Full-text (5931 KB) | HTML Full-text | XML Full-text
Abstract
Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological [...] Read more.
Quantification of biological or biochemical processes are of utmost importance for medical, biological and biotechnological applications. However, converting the biological information to an easily processed electronic signal is challenging due to the complexity of connecting an electronic device directly to a biological environment. Electrochemical biosensors provide an attractive means to analyze the content of a biological sample due to the direct conversion of a biological event to an electronic signal. Over the past decades several sensing concepts and related devices have been developed. In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing. Additional measurement techniques, which have been shown useful in combination with electrochemical detection, are also summarized, such as the electrochemical versions of surface plasmon resonance, optical waveguide lightmode spectroscopy, ellipsometry, quartz crystal microbalance, and scanning probe microscopy. The signal transduction and the general performance of electrochemical sensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. New nanotechnology-based approaches, such as the use of engineered ion-channels in lipid bilayers, the encapsulation of enzymes into vesicles, polymersomes, or polyelectrolyte capsules provide additional possibilities for signal amplification. In particular, this review highlights the importance of the precise control over the delicate interplay between surface nano-architectures, surface functionalization and the chosen sensor transducer principle, as well as the usefulness of complementary characterization tools to interpret and to optimize the sensor response. Full article
Open AccessReview Transgenic Plants as Sensors of Environmental Pollution Genotoxicity
Sensors 2008, 8(3), 1539-1558; doi:10.3390/s8031539
Received: 21 January 2008 / Accepted: 7 March 2008 / Published: 10 March 2008
Cited by 10 | PDF Full-text (353 KB) | HTML Full-text | XML Full-text
Abstract
Rapid technological development is inevitably associated with manyenvironmental problems which primarily include pollution of soil, water and air. In manycases, the presence of contamination is difficult to assess. It is even more difficult toevaluate its potential danger to the environment and humans. [...] Read more.
Rapid technological development is inevitably associated with manyenvironmental problems which primarily include pollution of soil, water and air. In manycases, the presence of contamination is difficult to assess. It is even more difficult toevaluate its potential danger to the environment and humans. Despite the existence ofseveral whole organism-based and cell-based models of sensing pollution and evaluationof toxicity and mutagenicity, there is no ideal system that allows one to make a quick andcheap assessment. In this respect, transgenic organisms that can be intentionally altered tobe more sensitive to particular pollutants are especially promising. Transgenic plantsrepresent an ideal system, since they can be grown at the site of pollution or potentiallydangerous sites. Plants are ethically more acceptable and esthetically more appealing thananimals as sensors of environmental pollution. In this review, we will discuss varioustransgenic plant-based models that have been successfully used for biomonitoringgenotoxic pollutants. We will also discuss the benefits and potential drawbacks of thesesystems and describe some novel ideas for the future generation of efficient transgenicphytosensors. Full article
(This article belongs to the Special Issue Phytosensors: Environmental Sensing with Plants and Plant Cells)
Open AccessReview Ground Based Ultraviolet Remote Sensing of Volcanic Gas Plumes
Sensors 2008, 8(3), 1559-1574; doi:10.3390/s8031559
Received: 19 February 2008 / Accepted: 6 March 2008 / Published: 10 March 2008
Cited by 4 | PDF Full-text (805 KB) | HTML Full-text | XML Full-text
Abstract
Ultraviolet spectroscopy has been implemented for over thirty years to monitorvolcanic SO2 emissions. These data have provided valuable information concerningunderground magmatic conditions, which have been of utility in eruption forecastingefforts. During the last decade the traditionally used correlation spectrometers have beenupgraded [...] Read more.
Ultraviolet spectroscopy has been implemented for over thirty years to monitorvolcanic SO2 emissions. These data have provided valuable information concerningunderground magmatic conditions, which have been of utility in eruption forecastingefforts. During the last decade the traditionally used correlation spectrometers have beenupgraded with miniature USB coupled UV spectrometers, opening a series of exciting newempirical possibilities for understanding volcanoes and their impacts upon the atmosphere.Here we review these technological developments, in addition to the scientific insightsthey have precipitated, covering the strengths and current limitations of this approach. Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
Open AccessReview SU-8 Cantilevers for Bio/chemical Sensing; Fabrication, Characterisation and Development of Novel Read-out Methods
Sensors 2008, 8(3), 1595-1612; doi:10.3390/s8031595
Received: 2 November 2007 / Accepted: 3 March 2008 / Published: 10 March 2008
Cited by 71 | PDF Full-text (659 KB) | HTML Full-text | XML Full-text
Abstract
Here, we present the activities within our research group over the last five yearswith cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interestingpolymer for fabrication of cantilevers for bio/chemical sensing due to its simple processingand low Young’s modulus. [...] Read more.
Here, we present the activities within our research group over the last five yearswith cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interestingpolymer for fabrication of cantilevers for bio/chemical sensing due to its simple processingand low Young’s modulus. We show examples of different integrated read-out methodsand their characterisation. We also show that SU-8 cantilevers have a reduced sensitivity tochanges in the environmental temperature and pH of the buffer solution. Moreover, weshow that the SU-8 cantilever surface can be functionalised directly with receptormolecules for analyte detection, thereby avoiding gold-thiol chemistry. Full article
Open AccessReview Sensitive Detection of Haloperidol and Hydroxyzine at Multi-Walled Carbon Nanotubes-Modified Glassy Carbon Electrodes
Sensors 2008, 8(3), 1879-1889; doi:10.3390/s8031879
Received: 1 February 2008 / Accepted: 14 March 2008 / Published: 17 March 2008
Cited by 11 | PDF Full-text (88 KB) | HTML Full-text | XML Full-text
Abstract
Haloperidol (i.e. HPD) and hydroxyzine (i.e. HXY), two effective and important tranquilizers with low redox activity, were found to generate an irreversible anodic peak at about +0.86 V (vs. SCE) or two anodic peaks at about +0.83 and +0.91 V in 0.05 [...] Read more.
Haloperidol (i.e. HPD) and hydroxyzine (i.e. HXY), two effective and important tranquilizers with low redox activity, were found to generate an irreversible anodic peak at about +0.86 V (vs. SCE) or two anodic peaks at about +0.83 and +0.91 V in 0.05 M NaH2PO4-Na2HPO4 (pH=7.0) buffer solution with a multi-walled carbon nanotubes-modified glassy carbon electrode (i.e. MWNTs/GC), respectively. Their sensitive and quantitative measurement based on the first two anodic peaks was established under the optimum conditions. The anodic peak current was linear to HPD and HXY concentration from 1×10-7 to 2.5 ×10-5 M and 5×10-8 to 2.5 ×10-5 M, the detection limits obtained were 8×10-9 and 5×10-9 M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the detection of HPD and HXY in drug tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods. Full article
Open AccessReview Innovative Sensors for Environmental Monitoring in Museums
Sensors 2008, 8(3), 1984-2005; doi:10.3390/s8031984
Received: 29 January 2008 / Accepted: 18 March 2008 / Published: 22 March 2008
Cited by 14 | PDF Full-text (368 KB) | HTML Full-text | XML Full-text
Abstract
Different physical and chemical factors, such as light, temperature, relative humidity, pollutants and so on, can affect works of art on display. Each factor does not act individually, but its effect can be enhanced or accelerated by the presence of other factors. [...] Read more.
Different physical and chemical factors, such as light, temperature, relative humidity, pollutants and so on, can affect works of art on display. Each factor does not act individually, but its effect can be enhanced or accelerated by the presence of other factors. Accordingly, an evaluation of the impact of the whole environment on art objects is recognized as an essential requirement for conservation purposes. To meet the most up-todate guidelines on preventive conservation, in recent years several scientific projects supported by the EC were aimed at developing innovative tools that could complement the standard methods for environmental monitoring in museums. These research projects produced a new generation of passive sensors that are capable of taking into account the overall environmental effects by mimicking in some way the behaviour of real works of art. The main goal of the present paper is to provide a survey of these sensors, which represent a new frontier in the environmental control in museums. Furthermore, the use of optical fibres, as both intrinsic sensors and devices for interrogating sensors, will also be illustrated, and examples of their use in the cultural heritage field will be reported. Full article

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