Showing papers in "Sensors in 2007"
TL;DR: In this article, a review of gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers has been reviewed.
Abstract: The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.
1,333 citations
TL;DR: In this paper, the authors present an overview of the triangle method for estimating soil surface wetness and evapotranspiration fraction from satellite imagery and show how the triangle can be created from a land surface model by superimposing the model triangle over the observed one.
Abstract: Toby Carlson Professor of Meteorology, PennState University, 619 Walker Building, University Park, PA 16802 E-Mail: tnc@meteo.psu.edu; http://www.met.psu.edu/dept/faculty/carlson.htm Tel. +1 814 863 1582; Fax: +1 814 865 3663 Received: 7 August 2007 / Accepted: 21 August 2007 / Published: 24 August 2007 Abstract: An overview of the ‘triangle’ method for estimating soil surface wetness and evapotranspiration fraction from satellite imagery is presented here. The method is insensitive to initial atmospheric and surface conditions, net radiation and atmospheric correction, yet can yield accuracies comparable to other methods. We describe the method first from the standpoint of the how the triangle is observed as obtained from aircraft and satellite image data and then show how the triangle can be created from a land surface model. By superimposing the model triangle over the observed one, pixel values from the image are determined for all points within the triangle. We further show how the stretched (or ‘universal’) triangle can be used to interpret pixel configurations within the triangle, showing how the temporal trajectories of points uniquely describe patterns of land use change. Finally, we conclude the paper with a brief assessment of the method’s limitations. Keywords: Triangle Method, Evapotranspiration, Surface Wetness, Land Use Analysis 1. Background Remote sensing of surface turbulent energy fluxes and surface soil water content dates back to the 1970s. The basic technique was first attempted by geologists (Watson; 1971) to help locate mineral deposits, and later by meteorologists (Price, 1980; Soer, 1980; Carlson et al., 1981; Price, 1982; Wetzel et al., 1983; Carlson et al., 1984) to estimate surface turbulent energy fluxes and surface soil water content. Many other papers, following along on similar lines, emerged during the 1990s, of which only a few notable papers will be mentioned here: Nemani and Running, 1989; Kustas, 1990;
601 citations
TL;DR: Differences in the topographic effect on the EVI and the NDVI are theoretically analyzed based on a non-Lambertian model and two airborne-based images acquired from a mountainous area covered by high-density Japanese cypress plantation were used as a case study, indicating that the soil adjustment factor “L” in theEVI makes it more sensitive to topographic conditions than is theNDVI.
Abstract: Vegetation indices play an important role in monitoring variations in vegetation.The Enhanced Vegetation Index (EVI) proposed by the MODIS Land Discipline Groupand the Normalized Difference Vegetation Index (NDVI) are both global-based vegetationindices aimed at providing consistent spatial and temporal information regarding globalvegetation. However, many environmental factors such as atmospheric conditions and soilbackground may produce errors in these indices. The topographic effect is another veryimportant factor, especially when the indices are used in areas of rough terrain. In thispaper, we theoretically analyzed differences in the topographic effect on the EVI and theNDVI based on a non-Lambertian model and two airborne-based images acquired from amountainous area covered by high-density Japanese cypress plantation were used as a casestudy. The results indicate that the soil adjustment factor "L" in the EVI makes it moresensitive to topographic conditions than is the NDVI. Based on these results, we stronglyrecommend that the topographic effect should be removed in the reflectance data beforethe EVI was calculated-as well as from other vegetation indices that similarly include a term without a band ratio format (e.g., the PVI and SAVI)-when these indices are used in the area of rough terrain, where the topographic effect on the vegetation indices having only a band ratio format (e.g., the NDVI) can usually be ignored.
506 citations
TL;DR: The distribution of ISA in the world's primary drainage basins indicates that watersheds damaged by ISA are primarily concentrated in the USA, Europe, Japan, China and India.
Abstract: We present the first global inventory of the spatial distribution and density ofconstructed impervious surface area (ISA). Examples of ISA include roads, parking lots,buildings, driveways, sidewalks and other manmade surfaces. While high spatialresolution is required to observe these features, the new product reports the estimateddensity of ISA on a one-km² grid based on two coarse resolution indicators of ISA - thebrightness of satellite observed nighttime lights and population count. The model wascalibrated using 30-meter resolution ISA of the USA from the U.S. Geological Survey.Nominally the product is for the years 2000-01 since both the nighttime lights andreference data are from those two years. We found that 1.05% of the United States landarea is impervious surface (83,337 km²) and 0.43 % of the world's land surface (579,703km²) is constructed impervious surface. China has more ISA than any other country(87,182 km²), but has only 67 m² of ISA per person, compared to 297 m² per person in theUSA. The distribution of ISA in the world's primary drainage basins indicates that watersheds damaged by ISA are primarily concentrated in the USA, Europe, Japan, China and India. The authors believe the next step for improving the product is to include reference ISA data from many more areas around the world.
407 citations
TL;DR: In this article, the authors developed a smart flexible sensor adapted to textile structures, able to measure their strain deformations, based on a thermoplastic elastomer (Evoprene)/carbon black nanoparticle composite.
Abstract: IEMN, Cite Scientifique, Avenue Poincare – BP 60069, 59652 Villeneuve d’Ascq, France; E-mail: claude.dufour@IEMN.Univ-Lille1.fr * Author to whom correspondence should be addressed. E-mail: vladan.koncar@ensait.fr Received: 13 March 2007 / Accepted: 17 April 2007 / Published: 18 April 2007 Abstract : The aim of this work is to develop a smart flexible sensor adapted to textile structures, able to measure their strain deformations. The sensors are “smart” because of their capacity to adapt to the specific mechanical properties of textile structures that are lightweight, highly flexible, stretchable, elastic, etc. Because of these properties, textile structures are continuously in movement and easily deformed, even under very low stresses. It is therefore important that the integration of a sensor does not modify their general behavior. The material used for the sensor is based on a thermoplastic elastomer (Evoprene)/carbon black nanoparticle composite, and presents general mechanical properties strongly compatible with the textile substrate. Two preparation techniques are investigated: the conventional melt-mixing process, and the solvent process which is found to be more adapted for this particular application. The preparation procedure is fully described, namely the optimization of the process in terms of filler concentration in which the percolation theory aspects have to be considered. The sensor is then integrated on a thin, lightweight Nylon fabric, and the electromechanical characterization is performed to demonstrate the adaptability and the correct functioning of the sensor as a strain gauge on the fabric. A normalized relative resistance is defined in order to characterize the electrical response of the sensor. Finally, the influence of environmental factors, such as temperature and atmospheric humidity, on the sensor performance is investigated. The results show that the sensor’s electrical resistance is particularly affected by humidity. This behavior is discussed in terms of the sensitivity of the carbon black filler particles to the presence of water.
332 citations
TL;DR: Notingher et al. as mentioned in this paper used Raman spectroscopy to detect changes in cell behavior, metabolism, or induction of cell death following exposure of live cells to toxic agents.
Abstract: Ioan Notingher University of Nottingham, School of Physics and Astronomy, University Park, Nottingham NG7 2RD, UK.; E-mail: ioan.notingher@nottingham.ac.uk Received: 29 June 2007 / Accepted: 25 July 2007 / Published: 26 July 2007 Abstract: One of the main challenges faced by biodetection systems is the ability to detect and identify a large range of toxins at low concentrations and in short times. Cell-based biosensors rely on detecting changes in cell behaviour, metabolism, or induction of cell death following exposure of live cells to toxic agents. Raman spectroscopy is a powerful technique for studying cellular biochemistry. Different toxic chemicals have different effects on living cells and induce different time-dependent biochemical changes related to cell death mechanisms. Cellular changes start with membrane receptor signalling leading to cytoplasmic shrinkage and nuclear fragmentation. The potential advantage of Raman spectroscopy cell-based systems is that they are not engineered to respond specifically to a single toxic agent but are free to react to many biologically active compounds. Raman spectroscopy biosensors can also provide additional information from the time-dependent changes of cellular biochemistry. Since no cell labelling or staining is required, the specific time dependent biochemical changes in the living cells can be used for the identification and quantification of the toxic agents. Thus, detection of biochemical changes of cells by Raman spectroscopy could overcome the limitations of other biosensor techniques, with respect to detection and discrimination of a large range of toxic agents. Further developments of this technique may also include integration of cellular microarrays for high throughput in vitro toxicological testing of pharmaceuticals and in situ monitoring of the growth of engineered tissues. Keywords: Raman spectroscopy, cell-based, biosensors, cells, toxic agents, toxicology. 1. Introduction In response to the increasing demand for detection of chemical and biological toxic agents, such as environmental pollutants and warfare agents, various optical techniques have been proposed. Much
293 citations
TL;DR: In this paper, the authors present a review of optical fiber biosensors in the last decade and discuss the trends in optical fiber sensor applications in real samples and discuss their applications in various analytical fields.
Abstract: Remarkable developments can be seen in the field of optical fibre biosensors in the last decade. More sensors for specific analytes have been reported, novel sensing chemistries or transduction principles have been introduced, and applications in various analytical fields have been realised. This review consists of papers mainly reported in the last decade and presents about applications of optical fiber biosensors. Discussions on the trends in optical fiber biosensor applications in real samples are enumerated.
277 citations
TL;DR: In this paper, the authors developed and implemented a simplified surface energy balance (SSEB) model to monitor and assess the performance of irrigated agriculture in Afghanistan using a combination of 1-km thermal data and 250-m Normalized Difference Vegetation Index (NDVI) data, both from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor.
Abstract: Accurate crop performance monitoring and production estimation are critical fortimely assessment of the food balance of several countries in the world. Since 2001, theFamine Early Warning Systems Network (FEWS NET) has been monitoring cropperformance and relative production using satellite-derived data and simulation models inAfrica, Central America, and Afghanistan where ground-based monitoring is limitedbecause of a scarcity of weather stations. The commonly used crop monitoring models arebased on a crop water-balance algorithm with inputs from satellite-derived rainfallestimates. These models are useful to monitor rainfed agriculture, but they are ineffectivefor irrigated areas. This study focused on Afghanistan, where over 80 percent ofagricultural production comes from irrigated lands. We developed and implemented aSimplified Surface Energy Balance (SSEB) model to monitor and assess the performanceof irrigated agriculture in Afghanistan using a combination of 1-km thermal data and 250-m Normalized Difference Vegetation Index (NDVI) data, both from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. We estimated seasonal actual evapotranspiration (ETa) over a period of six years (2000-2005) for two major irrigated river basins in Afghanistan, the Kabul and the Helmand, by analyzing up to 19 cloud-free thermal and NDVI images from each year. These seasonal ETa estimates were used as relative indicators of year-to-year production magnitude differences. The temporal water- use pattern of the two irrigated basins was indicative of the cropping patterns specific to each region. Our results were comparable to field reports and to estimates based on watershed-wide crop water-balance model results. For example, both methods found that the 2003 seasonal ETa was the highest of all six years. The method also captured water management scenarios where a unique year-to-year variability was identified in addition to water-use differences between upstream and downstream basins. A major advantage of the energy-balance approach is that it can be used to quantify spatial extent of irrigated fields and their water-use dynamics without reference to source of water as opposed to a water- balance model which requires knowledge of both the magnitude and temporal distribution of rainfall and irrigation applied to fields.
260 citations
TL;DR: The history of remote sensing and development of different sensors for environmental and natural resources mapping and data acquisition, and application examples in urban studies, hydrological modeling, and micro-topography correlation studies are reviewed.
Abstract: The history of remote sensing and development of different sensors for environmental and natural resources mapping and data acquisition is reviewed and reported. Application examples in urban studies, hydrological modeling such as land-cover and floodplain mapping, fractional vegetation cover and impervious surface area mapping, surface energy flux and micro-topography correlation studies is discussed. The review also discusses the use of remotely sensed-based rainfall and potential evapotranspiration for estimating crop water requirement satisfaction index and hence provides early warning information for growers. The review is not an exhaustive application of the remote sensing techniques rather a summary of some important applications in environmental studies and modeling.
225 citations
TL;DR: The demonstrated modified spectrophotometric method makes use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and its specific absorbance properties to determination of the microalgae's methanolic extracts antioxidative potentials which was independent to the employed DPPH concentrations.
Abstract: The demonstrated modified spectrophotometric method makes use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and its specific absorbance properties Theabsorbance decreases when the radical is reduced by antioxidants In contrast to otherinvestigations, the absorbance was measured at a wavelength of 550 nm This wavelengthenabled the measurements of the stable free DPPH radical without interference frommicroalgal pigments This approach was applied to methanolic microalgae extracts for twodifferent DPPH concentrations The changes in absorbance measured vs the concentrationof the methanolic extract resulted in curves with a linear decrease ending in a saturationregion Linear regression analysis of the linear part of DPPH reduction versus extractconcentration enabled the determination of the microalgae's methanolic extractsantioxidative potentials which was independent to the employed DPPH concentrations Theresulting slopes showed significant differences (6 - 34 μmol DPPH g-1 extractconcentration) between the single different species of microalgae (Anabaena sp,Isochrysis galbana, Phaeodactylum tricornutum, Porphyridium purpureum, Synechocystissp PCC6803) in their ability to reduce the DPPH radical The independency of the signal on the DPPH concentration is a valuable advantage over the determination of the EC50 value
218 citations
TL;DR: A micro-scale air flow sensor based on a free-standing cantilever structure that has a high sensitivity, a high velocity measurement limit, and a rapid response time is presented.
Abstract: This paper presents a micro-scale air flow sensor based on a free-standingcantilever structure. In the fabrication process, MEMS techniques are used to deposit asilicon nitride layer on a silicon wafer. A platinum layer is deposited on the silicon nitridelayer to form a piezoresistor, and the resulting structure is then etched to create afreestanding micro-cantilever. When an air flow passes over the surface of the cantileverbeam, the beam deflects in the downward direction, resulting in a small variation in theresistance of the piezoelectric layer. The air flow velocity is determined by measuring thechange in resistance using an external LCR meter. The experimental results indicate that theflow sensor has a high sensitivity (0.0284 ω/ms-1), a high velocity measurement limit (45ms-1) and a rapid response time (0.53 s).
TL;DR: An application-level design methodology for WSANs in mobile control applications with emphasis on the reliability issue is presented and a simple yet efficient method is proposed to deal with unpredictable packet loss on actuator nodes.
Abstract: Wireless sensor/actuator networks (WSANs) are emerging as a new generationof sensor networks. Serving as the backbone of control applications, WSANs will enablean unprecedented degree of distributed and mobile control. However, the unreliability ofwireless communications and the real-time requirements of control applications raise greatchallenges for WSAN design. With emphasis on the reliability issue, this paper presents anapplication-level design methodology for WSANs in mobile control applications. Thesolution is generic in that it is independent of the underlying platforms, environment,control system models, and controller design. To capture the link quality characteristics interms of packet loss rate, experiments are conducted on a real WSAN system. From theexperimental observations, a simple yet efficient method is proposed to deal withunpredictable packet loss on actuator nodes. Trace-based simulations give promisingresults, which demonstrate the effectiveness of the proposed approach.
TL;DR: A review of state-of-the-art methods of measuring pH levels that are based on polymer materials can be found in this paper, which includes polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring.
Abstract: This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring.
TL;DR: The novelty of this sensor technology is its wireless and passive nature, which allows in situ determination of food quality, and the simple fabrication process and inexpensive sensor material ensure a low sensor cost, thus making this technology economically viable.
Abstract: Norinse Technologies LLC, Hancock, MI 49930, USA. * Author to whom correspondence should be addressed. E-mail: kgong@mtu.edu Received: 23 August 2007 / Accepted: 28 August 2007 / Published: 5 September 2007 Abstract: This paper describes the fabrication of a wireless, passive sensor based on an inductive-capacitive resonant circuit, and its application for in situ monitoring of the quality of dry, packaged food such as cereals, and fried and baked snacks. The sensor is made of a planar inductor and capacitor printed on a paper substrate. To monitor food quality, the sensor is embedded inside the food package by adhering it to the package’s inner wall; its response is remotely detected through a coil connected to a sensor reader. As food quality degrades due to increasing humidity inside the package, the paper substrate absorbs water vapor, changing the capacitor’s capacitance and the sensor’s resonant frequency. Therefore, the taste quality of the packaged food can be indirectly determined by measuring the change in the sensor’s resonant frequency. The novelty of this sensor technology is its wireless and passive nature, which allows in situ determination of food quality. In addition, the simple fabrication process and inexpensive sensor material ensure a low sensor cost, thus making this technology economically viable. Keywords: Resonant circuit sensor, food quality monitoring, wireless, passive. 1. Introduction Dry, packaged food usually requires an airtight package to maintain its quality and ensure food safety. For example, hermitically sealed bags are essential for dry snacks such as potato chips, corn
TL;DR: This review discusses the label-free electrochemical detection of proteins, paying particular emphasis to those that exploit intrinsic redox-active amino acids.
Abstract: Electrochemical-based protein sensors offer sensitivity, selectivity and reliabilityat a low cost, making them very attractive tools for protein detection. Although the sensorsuse a broad range of different chemistries, they all depend on the solid electrode surface,interactions with the target protein and the molecular recognition layer. Traditionally, redoxenzymes have provided the molecular recognition elements from which target proteins haveinteracted with. This necessitates that the redox-active enzymes couple with electrodesurfaces and usually requires the participation of added diffusional components, or assemblyof the enzymes in functional chemical matrices. These complications, among many others,have seen a trend towards non-enzymatic-based electrochemical protein sensors. Severalelectrochemical detection approaches have been exploited. Basically, these have fallen intotwo categories: labeled and label-free detection systems. The former rely on a redox-activesignal from a reporter molecule or a label, which changes upon the interaction of the targetprotein. In this review, we discuss the label-free electrochemical detection of proteins,paying particular emphasis to those that exploit intrinsic redox-active amino acids.
TL;DR: Simulation results demonstrate that the proposed VFCPSO is competent for dynamic deployment in WSNs and has better performance with respect to computation time and effectiveness than the VF, PSO and VFPSO algorithms.
Abstract: The effectiveness of wireless sensor networks (WSNs) depends on the coverage and target detection probability provided by dynamic deployment, which is usually supported by the virtual force (VF) algorithm. However, in the VF algorithm, the virtual force exerted by stationary sensor nodes will hinder the movement of mobile sensor nodes. Particle swarm optimization (PSO) is introduced as another dynamic deployment algorithm, but in this case the computation time required is the big bottleneck. This paper proposes a dynamic deployment algorithm which is named “virtual force directed co-evolutionary particle swarm optimization” (VFCPSO), since this algorithm combines the co-evolutionary particle swarm optimization (CPSO) with the VF algorithm, whereby the CPSO uses multiple swarms to optimize different components of the solution vectors for dynamic deployment cooperatively and the velocity of each particle is updated according to not only the historical local and global optimal solutions, but also the virtual forces of sensor nodes. Simulation results demonstrate that the proposed VFCPSO is competent for dynamic deployment in WSNs and has better performance with respect to computation time and effectiveness than the VF, PSO and VFPSO algorithms.
TL;DR: This approach does not provide maps as detailed as those produced by manually interpreting aerial photographs, but it can still extract ecologically significant classes and is an efficient way to generate accurate and detailed maps in significantly shorter time.
Abstract: Effective assessment of biodiversity in cities requires detailed vegetation maps.To date, most remote sensing of urban vegetation has focused on thematically coarse landcover products. Detailed habitat maps are created by manual interpretation of aerialphotographs, but this is time consuming and costly at large scale. To address this issue, wetested the effectiveness of object-based classifications that use automated imagesegmentation to extract meaningful ground features from imagery. We applied thesetechniques to very high resolution multispectral Ikonos images to produce vegetationcommunity maps in Dunedin City, New Zealand. An Ikonos image was orthorectified and amulti-scale segmentation algorithm used to produce a hierarchical network of image objects.The upper level included four coarse strata: industrial/commercial (commercial buildings),residential (houses and backyard private gardens), vegetation (vegetation patches larger than0.8/1ha), and water. We focused on the vegetation stratum that was segmented at moredetailed level to extract and classify fifteen classes of vegetation communities. The firstclassification yielded a moderate overall classification accuracy (64%, κ = 0.52), which ledus to consider a simplified classification with ten vegetation classes. The overallclassification accuracy from the simplified classification was 77% with a κ value close tothe excellent range (κ = 0.74). These results compared favourably with similar studies inother environments. We conclude that this approach does not provide maps as detailed as those produced by manually interpreting aerial photographs, but it can still extract ecologically significant classes. It is an efficient way to generate accurate and detailed maps in significantly shorter time. The final map accuracy could be improved by integrating segmentation, automated and manual classification in the mapping process, especially when considering important vegetation classes with limited spectral contrast.
TL;DR: Wang et al. as mentioned in this paper employed two Landsat TM/ETM+ images in the dry season to detect LULC patterns in 1998 and 2003, and to examine LULC changes during the period from 1998 to 2003.
Abstract: Land use and land cover change is a major issue in global environment change, and is especially significant in rapidly developing regions in the world. With its economic development, population growth, and urbanization, Guangzhou, a major metropolitan in South China, have experienced a dramatic land use and land cover (LULC) change over the past 30 years. Fast LULC change have resulted in degradation of its ecosystems and affected adversely the environment. It is urgently needed to monitor its LULC changes and to analyses the consequences of these changes in order to provide information for policymakers to support sustainable development. This study employed two Landsat TM/ETM+ images in the dry season to detect LULC patterns in 1998 and 2003, and to examine LULC changes during the period from 1998 to 2003. The type, rate, and pattern of the changes among five counties of Guangzhou Municipality were analyzed in details by post-classification method. LULC conversion matrix was produced for each county in order to explore and explain the urban expansion and cropland loss, the most significant types of LULC change. Land use conversion matrixes of five counties were discussed respectively in order to explore and explain the inherence of land use change. The results showed that urban expansion in these five counties kept an even rate of increase, while substantial amount of cropland vanished during the period. It is also noted that the conversion between cropland and orchard land was intensive. Forest land became the main source of new croplands.
TL;DR: Starch-capped gold nanoparticles with hexagon and boot shapes were prepared through using a nontoxic and biologically benign aqueous-phase synthetic route, and it was found that different-shaped gold nanoparticle possess different SERS properties.
Abstract: Specially shaped gold nanoparticles have intrigued considerable attention because they usually possess high-sensitivity surface-enhanced Raman scattering (SERS) and thus result in large advantages in trace biodetermination. In this article, starch-capped gold nanoparticles with hexagon and boot shapes were prepared through using a nontoxic and biologically benign aqueous-phase synthetic route. Shape effects of gold nanoparticles on SERS properties were mainly investigated, and found that different-shaped gold nanoparticles possess different SERS properties. Especially, the boot-shaped nanoparticles could induce more 100-fold SERS enhancements in sensitivity as compared with those from gold nanospheres. The extremely strong SERS properties of gold nanoboots have been successfully applied to the detection of avidin. The unique nanoboots with high-sensitivity SERS properties are also expected to find use in many other fields such as biolabel, bioassay, biodiagnosis, and even clinical diagnosis and therapy.
TL;DR: In this article, the authors present a network of ULF monitoring in the Tokyo area by describing their ULF magnetic sensors and finally present a few, latest results on seismogenic electromagnetic emissions for recent large earthquakes with the use of sophisticated signal processing.
Abstract: ULF (ultra-low-frequency) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before a few large earthquakes. Then, we present our network of ULF monitoring in the Tokyo area by describing our ULF magnetic sensors and we finally present a few, latest results on seismogenic electromagnetic emissions for recent large earthquakes with the use of sophisticated signal processings.
TL;DR: In this paper, the authors proposed a possible use of VLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding of the seismo-ionospheric perturbations.
Abstract: It is recently recognized that the ionosphere is very sensitive to seismic effects, and the detection of ionospheric perturbations associated with earthquakes, seems to be very promising for short-term earthquake prediction. We have proposed a possible use of VLF/LF (very low frequency (3-30 kHz) /low frequency (30-300 kHz)) radio sounding of the seismo-ionospheric perturbations. A brief history of the use of subionospheric VLF/LF propagation for the short-term earthquake prediction is given, followed by a significant finding of ionospheric perturbation for the Kobe earthquake in 1995. After showing previous VLF/LF results, we present the latest VLF/LF findings; One is the statistical correlation of the ionospheric perturbation with earthquakes and the second is a case study for the Sumatra earthquake in December, 2004, indicating the spatical scale and dynamics of ionospheric perturbation for this earthquake.
TL;DR: Guided-wave optical biosensors are reviewed in this paper, where the possibility to use Mach-Zehnder and Young interferometers, microdisk and microring resonators, surface plasmon resonance, hollow and antiresonant waveguides, and Bragg gratings is discussed.
Abstract: Guided-wave optical biosensors are reviewed in this paper. Advantages related to optical technologies are presented and integrated architectures are investigated in detail. Main classes of bio receptors and the most attractive optical transduction mechanisms are discussed. The possibility to use Mach-Zehnder and Young interferometers, microdisk and microring resonators, surface plasmon resonance, hollow and antiresonant waveguides, and Bragg gratings to realize very sensitive and selective, ultra-compact and fast biosensors is discussed. Finally, CMOS-compatible technologies are proved to be the most attractive for fabrication of guided-wave photonic biosensors.
TL;DR: The paper analyses and compares different types of high-birefringence fiber loop mirror sensors using conventional and microstructured optical fibers, for simultaneous measurement of physical parameters when combined with others optical devices.
Abstract: Recent advances in devices and applications of high-birefringence fiber loopmirror sensors are addressed. In optical sensing, these devices may be used as strain andtemperature sensors, in a separate or in a simultaneous measurement. Other describedapplications include: refractive index measurement, optical filters for interrogate gratingsstructures and chemical etching control. The paper analyses and compares different types ofhigh-birefringence fiber loop mirror sensors using conventional and microstructured opticalfibers. Some configurations are presented for simultaneous measurement of physicalparameters when combined with others optical devices, for example with a long periodgrating.
TL;DR: Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed and special focus will be given to configurations where the sensing dots are incorporated in solid membranes and immobilized in optical fibers or planar waveguide platforms.
Abstract: Recent advances in the application of semiconductor nanocrystals, or quantumdots, as biochemical sensors are reviewed. Quantum dots have unique optical properties thatmake them promising alternatives to traditional dyes in many luminescence basedbioanalytical techniques. An overview of the more relevant progresses in the application ofquantum dots as biochemical probes is addressed. Special focus will be given toconfigurations where the sensing dots are incorporated in solid membranes and immobilizedin optical fibers or planar waveguide platforms.
TL;DR: In this article, the transferability of this approach to a 128 km2 large mountainous region in Vorarlberg, Austria, was evaluated, where inventory data as operationally collected by Austrian foresters were used.
Abstract: Airborne laser scanning (ALS) is an active remote sensing technique that uses the time-of-flight measurement principle to capture the three-dimensional structure of the earth's surface with pulsed lasers that transmit nanosecond-long laser pulses with a high pulse repetition frequency. Over forested areas most of the laser pulses are reflected by the leaves and branches of the trees, but a certain fraction of the laser pulses reaches the forest floor through small gaps in the canopy. Thus it is possible to reconstruct both the three-dimensional structure of the forest canopy and the terrain surface. For the retrieval of quantitative forest parameters such as stem volume or biomass it is necessary to use models that combine ALS with inventory data. One approach is to use multiplicative regression models that are trained with local inventory data. This method has been widely applied over boreal forest regions, but so far little experience exists with applying this method for mapping alpine forest. In this study the transferability of this approach to a 128 km2 large mountainous region in Vorarlberg, Austria, was evaluated. For the calibration of the model, inventory data as operationally collected by Austrian foresters were used. Despite these inventory data are based on variable sample plot sizes, they could be used for mapping stem volume for the entire alpine study area. The coefficient of determination R2 was 0.85 and the root mean square error (RMSE) 90.9 m3ha−1 (relative error of 21.4%) which is comparable to results of ALS studies conducted over topographically less complex environments. Due to the increasing availability, ALS data could become an operational part of Austrian's forest inventories.
TL;DR: Improved VFA is improved to overcome the factors of the convergence, the boundary in Region Of Interest, effective distance of acting force and useless moving, etc, and an expression of exponential function for the relationship of virtual force is proposed to converge rapidly.
Abstract: Virtual Force Algorithm (VFA) is becoming a main solution to area coverage forhomogeneous wireless sensor networks with random distribution of mobile sensor nodes.Consider the factors of the convergence, the boundary in Region Of Interest (ROI), effec-tive distance of acting force and useless moving, etc, VFA is improved to overcome the aboveproblems. Furthermore, an expression of exponential function for the relationship of vir-tual force is proposed to converge rapidly. Extensive simulation results indicate that theseimproved VFA get better performance in coverage rate, moving energy consumption, conver-gence etc. than original VFA.
TL;DR: The applications of magnetic microbeads in biosensors and bio-bar code assays allow the detection at very low concentration of biological molecules, similar to PCR sensitivity.
Abstract: This review paper reports the applications of magnetic microbeads in biosensors and bio-bar code assays. Affinity biosensors are presented through different types of transducing systems: electrochemical, piezo electric or magnetic ones, applied to immunodetection and genodetection. Enzymatic biosensors are based on biofunctionalization through magnetic microbeads of a transducer, more often amperometric, potentiometric or conductimetric. The bio-bar code assays relie on a sandwich structure based on specific biological interaction of a magnetic microbead and a nanoparticle with a defined biological molecule. The magnetic particle allows the separation of the reacted target molecules from unreacted ones. The nanoparticles aim at the amplification and the detection of the target molecule. The bio-bar code assays allow the detection at very low concentration of biological molecules, similar to PCR sensitivity.
TL;DR: A reversible photo-driven sensor for aluminum ions based on photochromic spiropyran was reported with rapid response time and metal chelation complex (Al3+-MC) can be converted into the original SP form by irradiation with visible light.
Abstract: Jiaqiang Ren and He Tian * Key Laboratory for Advanced Materials & Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, P. R. China; E-mails: Jiaqiang Ren: renjq1978@yahoo.com; He Tian: tianhe@ecust.edu.cn Author to whom correspondence should be addressed. Fax: +86-21-64252288; Email: tianhe@ecust.edu.cn Received: 30 October 2007 / Accepted: 3 December 2007 / Published: 6 December 2007 Abstract: A reversible photo-driven sensor for aluminum ions based on photochromic spiropyran was reported with rapid response time. The detection of aluminum was performed via the chelation of aluminum ions with the merocyanine form (MC) of photochromic spiropyran.
TL;DR: A very compact (device area around 40 μm2) optical ammonia sensor based on a microring resonator is presented in this work and exhibits a very good linearity and a minimum detectable refractive index shift of sensing material as low as 8×10-5.
Abstract: A very compact (device area around 40 μm2) optical ammonia sensor based on amicroring resonator is presented in this work. Silicon-on-insulator technology is used insensor design and a dye doped polymer is adopted as sensing material. The sensor exhibitsa very good linearity and a minimum detectable refractive index shift of sensing materialas low as 8x10-5, with a detection limit around 4 ‰.
TL;DR: A simulation study was carried out to describe effects of climate change on crop growth and irrigation water demand for a wheat-maize cropping sequence in a Mediterranean environment of Turkey.
Abstract: A simulation study was carried out to describe effects of climate change on cropgrowth and irrigation water demand for a wheat-maize cropping sequence in aMediterranean environment of Turkey. Climate change scenarios were projected using dataof the three general circulation models-GCMs (CGCM2, ECHAM4 and MRI)-for theperiod of 1990 to 2100 and one regional climate model-RCM-for the period of 2070 to2079. Potential impacts of climate change based on GCMs data were estimated for the A2scenario in the Special Report on Emission Scenarios (SRES). The forcing data for theboundary condition of the RCM were given by the MRI model. Daily CGCM2 and RCMdata were used for computations of water balance and crop development. Predictionsderived from the models about changes in irrigation and crop growth in this study coveredthe period of 2070 to 2079 relative to the baseline period of 1994 to 2003. The effects ofclimate change on water demand and on wheat and maize yields were predicted using thedetailed crop growth subroutine of the SWAP (Soil-Water-Atmosphere-Plant) model. Precipitation was projected to decrease by about 163, 163 and 105 mm during the periodof 1990 to 2100 under the A2 scenario of the CGCM2, ECHAM4 and MRI models,respectively. The CGCM2, ECHAM4 and MRI models projected a temperature rise of 4.3,5.3 and 3.1 oC, respectively by 2100. An increase in temperature may result in a higherevaporative demand of the atmosphere. However, actual evapotranspiration (ETa) fromwheat cropland under a doubling CO₂ concentration for the period of 2070 to 2079 wasSensors 2007, 7 2298 predicted to decrease by about 28 and 8% relative to the baseline period based on the CGCM2 and RCM data, respectively. According to these models, irrigation demand by wheat would be higher for the same period due to a decrease in precipitation. Both ETa and irrigation water for maize cropland were projected to decrease by 24 and 15% according to the CGCM2, and 28 and 22% according to the RCM, respectively. The temperature rise accelerated crop development but shortened the growing period by 24 days for wheat and 9 days for maize according to the CGCM2 data. The shortened growth duration with a higher temperature reduced the biomass accumulation of both crops regardless of CO₂-fertilization effect. With the combined effect of CO₂-fertilization and increased temperature, the CGCM2 and RCM projections resulted in an increase by 16 and 36% in grain yield of wheat and a decrease by about 25% and an increase by 3% in maize yield, respectively.