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Sensing
Kinds of Sensing Terms modified by Sensing Selected AbstractsHealth Monitoring of Rehabilitated Concrete Bridges Using Distributed Optical Fiber SensingCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2006Wei Zhang As newly developed techniques, distributed optical fiber sensing (DOFS) have gradually played a prominent role in structural health monitoring for the last decade. This article focuses on the employment of two types of DOFS, namely fiber Bragg grating (FBG) and Brillouin optical time domain reflectometry (BOTDR), into an integrated HMS for rehabilitated RC girder bridges by means of a series of static and dynamic loading tests to a simply supported RC T-beam strengthened by externally post-tensioned aramid fiber reinforced polymer (AFRP) tendons. Before the loading tests, a calibration test for FBG and another one for BOTDR were implemented to, respectively, obtain good linearity for both of them. Monitoring data were collected in real time during the process of external strengthening, static loading, and dynamic loading, respectively, all of which well identified the relevant structural state. The beam was finally vibrated for 2 million cycles and then loaded monotonously to failure. Based on the bending strength of externally prestressed members, ultimate values for the test specimen were numerically computed via a newly developed simplified model, which satisfactorily predicted the ultimate structural state of the beam. And then the alert values were adopted to compare with the monitoring results for safety alarm. The investigation results show a great deal of applicability for the integrated SHM by using both DOFS in rehabilitated concrete bridges strengthened by external prestressing. [source] Characteristics of Important Stopover Locations for Migrating Birds: Remote Sensing with Radar in the Great Lakes BasinCONSERVATION BIOLOGY, Issue 2 2009DAVID N. BONTER ave terrestre migratoria; migración; radar; sitios de escala temporal; WSR-88D Abstract:,A preliminary stage in developing comprehensive conservation plans involves identifying areas used by the organisms of interest. The areas used by migratory land birds during temporal breaks in migration (stopover periods) have received relatively little research and conservation attention. Methodologies for identifying stopover sites across large geographic areas have been, until recently, unavailable. Advances in weather-radar technology now allow for evaluation of bird migration patterns at large spatial scales. We analyzed radar data (WSR-88D) recorded during spring migration in 2000 and 2001 at 6 sites in the Great Lakes basin (U.S.A.). Our goal was to link areas of high migrant activity with the land-cover types and landscape contexts corresponding to those areas. To characterize the landscapes surrounding stopover locations, we integrated radar and land-cover data within a geographic information system. We compared landscape metrics within 5 km of areas that consistently hosted large numbers of migrants with landscapes surrounding randomly selected areas that were used by relatively few birds during migration. Concentration areas were characterized by 1.2 times more forest cover and 9.3 times more water cover than areas with little migrant activity. We detected a strong negative relationship between activity of migratory birds and agricultural land uses. Examination of individual migration events confirmed the importance of fragments of forested habitat in highly altered landscapes and highlighted large concentrations of birds departing from near-shore terrestrial areas in the Great Lakes basin. We conclude that conservation efforts can be more effectively targeted through intensive analysis of radar imagery. Resumen:,Una etapa preliminar en el desarrollo de planes de conservación integrales implica la identificación de áreas utilizadas por los organismos de interés. Las áreas utilizadas por aves terrestres migratorias durante escalas temporales en la migración (períodos de parada) han recibido relativamente poca atención de investigación y conservación. Hasta hace poco, las metodologías para la identificación de sitios de parada en áreas geográficas extensas han sido escasas. Ahora, los avances en la tecnología de radar meteorológico permiten la evaluación de patrones de migración de aves en escalas espaciales grandes. Analizamos datos de radar (WSR-88D) registrados en seis sitios en la cuenca de los Grandes Lagos (E.U.A.) durante la migración en las primaveras de 2000 y 2001. Nuestra meta fue relacionar áreas con gran actividad migratoria con los tipos de cobertura de suelo y los contextos del paisaje correspondientes a esas áreas. Para caracterizar los paisajes circundantes a las localidades de parada, integramos los datos de radar y de cobertura de suelo a un sistema de información geográfica. Comparamos las medidas del paisaje en un radio de 5 km en las áreas que consistentemente albergaron a grandes números de migrantes con los paisajes circundantes a áreas seleccionadas aleatoriamente y que eran utilizadas por relativamente pocas aves durante la migración. Las áreas de concentración se caracterizaron por tener 1.3 veces más cobertura forestal y 9.3 veces más cobertura de agua que las áreas con poca actividad migratoria. Detectamos una fuerte relación negativa entre la actividad de las aves migratorias y los usos de suelo agrícolas. El examen de eventos migratorios individuales confirmó la importancia de los fragmentos de hábitat boscoso en paisajes muy alterados y resaltó las grandes concentraciones de aves partiendo de áreas terrestres cercanas a la costa en la cuenca de los Grandes Lagos. Concluimos que los esfuerzos de conservación pueden ser abordados más efectivamente mediante el análisis intensivo de imágenes de radar. [source] Delivering a Global, Terrestrial, Biodiversity Observation System through Remote SensingCONSERVATION BIOLOGY, Issue 2 2009GRAEME M. BUCHANAN First page of article [source] Glucose-induced inhibition: how many ionic mechanisms?ACTA PHYSIOLOGICA, Issue 3 2010D. Burdakov Abstract Sensing of sugar by specialized ,glucose-inhibited' cells helps organisms to counteract swings in their internal energy levels. Evidence from several cell types in both vertebrates and invertebrates suggests that this process involves sugar-induced stimulation of plasma membrane K+ currents. However, the molecular composition and the mechanism of activation of the underlying channel(s) remain controversial. In mouse hypothalamic neurones and neurosecretory cells of the crab Cancer borealis, glucose stimulates K+ currents displaying leak-like properties. Yet knockout of some of the candidate ,leak' channel subunits encoded by the KCNK gene family so far failed to abolish glucose inhibition of hypothalamic cells. Moreover, in other tissues, such as the carotid body, glucose-stimulated K+ channels appear to be not leak-like but voltage-gated, suggesting that glucose-induced inhibition may engage multiple types of K+ channels. Other mechanisms of glucose-induced inhibition, such as hyperpolarization mediated by opening of Cl, channels and depolarization block caused by closure of KATP channels have also been proposed. Here we review known ionic and pharmacological features of glucose-induced inhibition in different cell types, which may help to identify its molecular correlates. [source] Satellite Remote Sensing as a Tool in Lahar Disaster ManagementDISASTERS, Issue 2 2002Norman Kerle At least 40,000 deaths have been attributed to historic lahars (volcanic mudflows). The most recent lahar disaster occurred in 1998 at Casita volcano, Nicaragua, claiming over 2,500 lives. Lahars can cover large areas and be highly destructive, and constitute a challenge for disaster management. With infrastructure affected and access frequently impeded, disaster management can benefit from the synoptic coverage provided by satellite imagery. This potential has been recognised for other types of natural disasters, but limitations are also known. Dedicated satellite constellations for disaster response and management have been proposed as one solution. Here we investigate the utility of currently available and forthcoming optical and radar sensors as tools in lahar disaster management. Applied to the Casita case, we find that imagery available at the time could not have significantly improved disaster response. However, forthcoming satellites, especially radar, will improve the situation, reducing the benefit of dedicated constellations. [source] Electrochemical Sensing of Thiocyanate Using Gold Electrodes Modified with an Underpotentially Deposited Silver MonolayerELECTROANALYSIS, Issue 2 2010Christopher Abstract Gold electrodes modified by underpotential deposition to expose a layer of silver atoms on their surfaces were used to measure thiocyanate concentrations in aqueous solutions. When exposed to thiocyanate, the ion adsorbs onto the modified electrode and causes changes in the electrochemical properties of the silver adlayer. Coulometric measurement of the fraction of the silver adlayer that remains in its original state provides a means for determining thiocyanate concentrations. The adsorption of thiocyanate onto the electrode follows a first-order process with a rate constant of ca. 440,L/mol s that defines its concentration/time response. [source] Electrodeposited Silver Nanoparticles on Carbon Ionic Liquid Electrode for Electrocatalytic Sensing of Hydrogen PeroxideELECTROANALYSIS, Issue 13 2009Afsaneh Safavi Abstract Silver nanoparticles (narrowly dispersed in diameter) were electrodeposited on carbon ionic liquid electrode (CILE) surface using a two-step potentiostatic method. Potentiostatic double pulse technique was used as a suitable and simple method for controlling the size and morphologies of silver nanoparticles electrodeposited on CILE. The obtained silver nanoparticles deposited on CILE surface showed excellent electrocatalytic activity (low overpotential of ,0.35,V vs. Ag/AgCl) towards reduction of hydrogen peroxide. A linear dynamic range of 2,200,,M with an experimental detection limit of 0.7,,M (S/N=3) and reproducibility of 4.1% (n=5) make the constructed sensor suitable for peroxide determination in aqueous solutions. [source] Dendritic Silver/Silicon Dioxide Nanocomposite Modified Electrodes for Electrochemical Sensing of Hydrogen PeroxideELECTROANALYSIS, Issue 17 2008Peixi Yuan Abstract A novel biosensor for hydrogen peroxide was prepared by immobilizing horseradish peroxidase (HPR) on newly synthesized dendritic silver/silicon dioxide nanocomposites, which were coated on a glassy carbon electrode. The modified electrode was characterized with XPS, SEM, and electrochemical methods. This biosensor showed a very fast amperometric response to hydrogen peroxide with a linear range from 0.7 to 120,,M, a limit of detection of 0.05,,M and a sensitivity of 1.02,mA mM,1 cm,2. The Michaelis-Menten constant of the immobilized HRP was estimated to be 0.21,mM, indicating a high affinity of the HRP to H2O2 without loss of enzymatic activity. The preparation of the proposed biosensor was convenient, and it showed high sensitivity and good stability. [source] Direct Electrochemical Sensing and Detection of Natural Antioxidants and Antioxidant Capacity in Vitro SystemsELECTROANALYSIS, Issue 22 2007Antonio, Javier Blasco Abstract This review highlights the role of electrochemical approaches in the sensing of antioxidants and their antioxidant capacity with especial attention to the analytical possibilities of electrochemistry in the direct evaluation of antioxidant capacity exhibited by food and biological samples due to the termed dietary, natural or biological antioxidants (mainly polyphenols, and vitamins C and E). The analytical potency of the electrochemistry is comprehensively stated and the selected results found in the literature are summarized and discussed critically. The main electrochemical approaches used have been cyclic voltammetry (CV) and flow injection analysis with amperometric detection (FIA-ED). In addition, miniaturization is going to break new frontiers in the evaluation of antioxidant activity. [source] Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device.ELECTROANALYSIS, Issue 5 2007Abstract Quaternized poly(4-vinylpyridine) (QPVP) has been incorporated as an anion exchanger into sol-gel derived silica films for use in a spectroelectrochemical sensor. The preparation, characteristics and performance of these films are described. The films, which are spin-coated onto the surface of a planar optically transparent electrode, are optically transparent and uniform. Scanning electron microscopy and spectroscopic ellipsometry have been used to examine film structure, thickness and optical properties. These films have been shown both spectroscopically and electrochemically to preconcentrate ferrocyanide, a model analyte for the sensor. The films can be regenerated for multiple measurements by exposure to 1,M KNO3. The effects of polymer molecular weight and storage conditions on film performance are described. The overall response of this film is comparable to the poly(dimethyldiallylammonium chloride)-silica films previously used for this sensor. [source] Electrochemical Sensing of ExplosivesELECTROANALYSIS, Issue 4 2007Joseph Wang Abstract This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field-deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low-cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low-cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (,Lab-on-Chip') devices for on-site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems. [source] Copper Oxide , Graphite Composite Electrodes: Application to Nitrite SensingELECTROANALYSIS, Issue 1 2007Biljana, ljuki Abstract A simple method for the modification of carbon powder with copper oxides is presented. Carbon powder is impregnated with copper(II) nitrate by stirring carbon powder in copper(II) nitrate solution for 1 hour and subsequently thermally treated at 823,K. The modified carbon powder was characterized using electrochemical and spectroscopic techniques. The existence of both copper(I) and copper(II) oxides have been established. The copper oxide modified carbon powder was used for preparation of composite electrodes, and the electrochemical and electrocatalytic behavior of the resulting composite electrodes was studied. The copper oxide modified carbon powder , epoxy composite electrodes showed a high electrocatalytic activity for the nitrite detection in aqueous media, with the detection limit comparable or lower than detection limits obtained with other electrochemical sensors. [source] Palladium Sub-Nanoparticle Decorated ,Bamboo' Multi-Walled Carbon Nanotubes Exhibit Electrochemical Metastability: Voltammetric Sensing in Otherwise Inaccessible pH RangesELECTROANALYSIS, Issue 24 2006Xiaobo Ji Abstract A generic approach for the detection of electroactive species in potential ranges that would normally be inhibited due to the stripping of the electrocatalytic material is presented. We demonstrate, via the example of the electrochemical oxidation of hydrazine, that palladium nanoparticle (< 1,nm) decorated bamboo multi-walled carbon nanotubes exhibit a metastability such that they allow the sensing of hydrazine in the pH range where palladium metal would normally be voltammetrically stripped (oxidized) from the surface of convectional electrodes. [source] A Tubulin-Based Quantitative Assay for Taxol (Paclitaxel) with Enzyme Channeling SensingELECTROANALYSIS, Issue 8 2004Shin-ichiro Suye Abstract We report the development and characterization of a biosensor for sensitive and rapid determination of the anticancer agent Taxol (paclitaxel). The sensor is based on the interaction of Taxol with its receptor protein tubulin in conjunction with the separation-free immunosensor technique of enzyme channeling. The sensor system consisted of a three electrode electrochemical cell containing a graphite carbon electrode modified with glucose oxidase and tubulin as working electrode poised at +40,mV (vs. Ag/AgCl). Addition of Taxol, horseradish peroxidase labeled Taxol, glucose and potassium iodide to the cell generated a cathodic current response that was proportional to the concentration of Taxol in the range of 10 to 1,000,pM. [source] Sensing with Nafion Coated Carbon Nanotube Field-Effect TransistorsELECTROANALYSIS, Issue 1-2 2004Alexander Star Abstract Sequential CVD and CMOS processes were used to make a FET that has single walled carbon nanotubes to serve as the conducting source to drain channel. This structure can be decorated to provide gas and liquid responses and herein is evaluated as a humdity sensor. The Na+, K+, and Ca2+ ion-exchanged Nafion polymer acts as the chemically sensitive layer in this electrochemical sensor. The effect of gate voltage on the charge-sensitive NT structure was found to be RH dependent over the range of 12,93% RH with msec response time. [source] Novel RuII Complexes with Bispidine-Based Bridging Ligands: Luminescence Sensing and Photocatalytic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2010Christoph Busche Abstract New ligands with a bidentate bipyridyl (bpy) and a tetradentate bispidine (bisp) subunit (bipyridyl = 2,2,-bipyridine derivative, bispidine = 3,7-diazabicyclo[3.3.1]nonane derivative) and their heterodinuclear {[Ru(bpy)3]2+ -[M(bisp)]2+} complexes (M = Cu2+, Fe2+) were prepared and characterized. The luminescence of the mononuclear RuII complexes (metal-free bisp subunit) is efficiently quenched in presence of CuII. An EPR spectroscopic study reveals thatvisible light irradiation does not alter the oxidation states of the two metal ions in {[Ru(bpy)3]2+ -[Cu(bisp)]2+}, i.e. there is energy rather than electron transfer. The heterodinuclear {[Ru(bpy)3]2+ -[Cu(bisp)]2+} complex shows a significantphotocatalytic activity in the aziridination of styrene. [source] Ratiometric Fluorescence Sensing of Fluoride Ions by an Asymmetric Bidentate Receptor Containing a Boronic Acid and Imidazolium GroupEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2009Zhaochao Xu Abstract The synthesis of the first examples of anion receptors that utilize boron,fluoride interactions and (C,H)+···F, -type ionic hydrogen-bond interactions in the binding of F ions is reported herein. o -, m -, and p -Phenylboronic acids were linked to naphthoimidazolium through a methylene group. On the basis of fluorescence and 19F NMR studies, we have confirmed that the addition of fluoride to a boron center occurs prior to the formation of (C,H)+···F, -type ionic hydrogen bond with the imidazolium moiety. More importantly, these investigations have demonstrated that only the receptor bearing the ortho -directed boron and imidazolium exhibits enhanced fluoride binding. The increased binding ability of the asymmetric bidentate receptor of ortho -boronic acid and imidazolium towards F, enables it to sense fluoride ions in a 95:5 CH3CN/HEPES aqueous solution. The fluorescence responses to different anions were also explored; the ortho -boron-imidazolium receptor displayed ratiometric fluorescence changes and a high selectivity towards fluoride ions over other anions (Cl,, Br,, CH3CO2,, HSO4,, and H2PO4,).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Porous Silicon-Based Optical Microsensors for Volatile Organic Analytes: Effect of Surface Chemistry on Stability and SpecificityADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Anne M. Ruminski Abstract Sensing of the volatile organic compounds (VOCs) isopropyl alcohol (IPA) and heptane in air using sub-millimeter porous silicon-based sensor elements is demonstrated in the concentration range 50,800 ppm. The sensor elements are prepared as one-dimensional photonic crystals (rugate filters) by programmed electrochemical etch of p++ silicon, and analyte sensing is achieved by measurement of the wavelength shift of the photonic resonance. The sensors are studied as a function of surface chemistry: ozone oxidation, thermal oxidation, hydrosilylation (1-dodecene), electrochemical methylation, reaction with dicholorodimethylsilane and thermal carbonization with acetylene. The thermally oxidized and the dichlorodimethylsilane-modified materials show the greatest stability under atmospheric conditions. Optical microsensors are prepared by attachment of the porous Si layer to the distal end of optical fibers. The acetylated porous Si microsensor displays a greater response to heptane than to IPA, whereas the other chemical modifications display a greater response to IPA than to heptane. The thermal oxide sensor displays a strong response to water vapor, while the acetylated material shows a relatively weak response. The results suggest that a combination of optical fiber sensors with different surface chemistries can be used to classify VOC analytes. Application of the miniature sensors to the detection of VOC breakthrough in a full-scale activated carbon respirator cartridge simulator is demonstrated. [source] pH-Activated Near-Infrared Fluorescence Nanoprobe Imaging Tumors by Sensing the Acidic MicroenvironmentADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Cong Li Abstract Imaging tumors in their early stages is crucial to increase the surviving rate of cancer patients. Currently most fluorescence probes visualize the neoplasia by targeting the tumor-associated receptor over-expressed on the cancer cell membrane. However, the expression level of these receptors in vivo is hard to predict, which limits their clinical translation. Furthermore, the signal output of these receptor-targeting probes usually stays at a high level, which leads to a strong background signal in normal tissue due to non-specific binding. In contrast to receptors, characteristics of the tumor microenvironment , such as acidosis , are pervasive in almost all solid tumors and can be easily accessed. In this work, a novel biodegradable nanoprobe InNP1 that demonstrates pH-activated near-infrared (NIR) fluorescence in both human glioblastoma U87MG cancer cells in vitro and the subcutaneous U87MG tumor xenografts in vivo is developed. Bio-distribution, in vivo optical imaging, and autoradiography studies demonstrate that the pH-activated NIR fluorescence is the dominant factor responsible for the high tumor/normal tissue (T/N) ratio of InNP1 in vivo. Overall, the work provides a nanoprobe prototype to visualize the solid tumor in vivo with high sensitivity and minimal systemic toxicity by sensing the tumor acidic microenvironment. [source] Synthesis of Poly(4-vinylpyridine) Thin Films by Initiated Chemical Vapor Deposition (iCVD) for Selective Nanotrench-Based Sensing of NitroaromaticsADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Wyatt E. Tenhaeff Abstract A new nanoscale sensing concept for the detection of nitroaromatic explosives is described. The design consists of nitroaromatic-selective polymeric layers deposited inside microfabricated trenches. As the layers are exposed to nitroaromatic vapors, they swell and contact each other to close an electrical circuit. The nitroaromatic selective polymer, poly(4-vinylpyridine) (P4VP), is deposited in the trenches using initiated chemical vapor deposition (iCVD). P4VP is characterized for the first time as a selective layer for the absorption of nitroaromatic vapors. The Flory,Huggins equation is used to model the swelling response to nitroaromatic vapors. The Flory,Huggins interaction parameter for the P4VP,nitrobenzene system at 40,°C is 0.71 and 0.25 for P4VP,4-nitrotoluene at 60,°C. Sensing of nitrobenzene vapors is demonstrated in a prototype device, while techniques to improve the performance of the design in terms of response time and sensitivities are described. Modeling shows that concentration and mass limits of detection of 0.95,ppb and 3 fg, respectively, can be achieved. [source] Sensing of Alkylating Agents Using Organic Field-Effect TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Yair Gannot Abstract Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields, such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical warfare agents. The detection and identification of alkylating agent is not a trivial issue because of their high reactivity and simple structure. Here, a novel polythiophene derivative that is capable of reacting with alkylating agents is reported, along with its application in direct electrical sensing of alkylators using an organic field-effect transistor, OFET, device. Upon reacting with alkylators, the OFET containing the new polythiophene analogue as its channel becomes conductive, and the gate effect is lost; this is in marked contrast to the response of the OFET to "innocent" vapors, such as alcohols and acetone. By following the drain,source current under gate bias, one can easily follow the processes of absorption of the analyte to the polythiophene channel and their subsequent reaction. [source] Bioinspired Material Approaches to SensingADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Michael E. McConney Abstract Bioinspired design is an engineering approach that involves working to understand the design principles and strategies employed by biology in order to benefit the development of engineered systems. From a materials perspective, biology offers an almost limitless source of novel approaches capable of arousing innovation in every aspect of materials, including fabrication, design, and functionality. Here, recent and ongoing work on the study of bioinspired materials for sensing applications is presented. Work presented includes the study of fish flow receptor structures and the subsequent development of similar structures to improve flow sensor performance. The study of spider air-flow receptors and the development of a spider-inspired flexible hair is also discussed. Lastly, the development of flexible membrane based infrared sensors, highly influenced by the fire beetle, is presented, where a pneumatic mechanism and a thermal-expansion stress-mediated buckling-based mechanism are investigated. Other areas that are discussed include novel biological signal filtering mechanisms and reciprocal benefits offered through applying the biology lessons to engineered systems. [source] Large-Scale Synthesis of Long Crystalline Cu2-xSe Nanowire Bundles by Water-Evaporation-Induced Self-Assembly and Their Application in Gas SensingADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Jun Xu Abstract By a facile water evaporation process without adding any directing agent, Cu2-xSe nanowire bundles with diameters of 100,300,nm and lengths up to hundreds of micrometers, which comprise crystalline nanowires with diameters of 5,8,nm, are obtained. Experiments reveal the initial formation/stacking of CuSe nanoplates and the subsequent transformation to the Cu2-xSe nanowire bundles. A water-evaporation-induced self-assembly (WEISA) mechanism is proposed, which highlights the driving force of evaporation in promoting the nanoplate stacking, CuSe-to-Cu2-xSe transformation and the growth/bundling of the Cu2-xSe nanowires. The simplicity, benignancy, scalability, and high-yield of the synthesis of this important nanowire material herald its numerous applications. As one example, the use of the Cu2-xSe nanowire bundles as a photoluminescence-type sensor of humidity is demonstrated, which shows good sensitivity, ideal linearity, quick response/recovery and long lifetime in a very wide humidity range at room temperature. [source] Hyperspectral Remote Sensing of VegetationGEOGRAPHY COMPASS (ELECTRONIC), Issue 6 2008Jungho Im Hyperspectral analysis of vegetation involves obtaining spectral reflectance measurements in hundreds of bands in the electromagnetic spectrum. These measurements may be obtained using hand-held spectroradiometers or hyperspectral remote sensing instruments placed onboard aircraft or satellites. Hyperspectral remote sensing provides valuable information about vegetation type, leaf area index, biomass, chlorophyll, and leaf nutrient concentration which are used to understand ecosystem functions, vegetation growth, and nutrient cycling. This article first reviews hyperspectral remote sensing and then describes current modeling and classification techniques used to estimate and predict vegetation type and biophysical characteristics. [source] Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub-Micrometer FibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jeremy M. Rathfon Abstract The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro-Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub-micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices. [source] Debating the greening vs. browning of the North American boreal forest: differences between satellite datasetsGLOBAL CHANGE BIOLOGY, Issue 2 2010DOMINGO ALCARAZ-SEGURA Abstract A number of remote sensing studies have evaluated the temporal trends of the normalized difference vegetation index (NDVI or vegetation greenness) in the North American boreal forest during the last two decades, often getting quite different results. To examine the effect that the use of different datasets might be having on the estimated trends, we compared the temporal trends of recently burned and unburned sites of boreal forest in central Canada calculated from two datasets: the Global Inventory, Monitoring, and Modeling Studies (GIMMS), which is the most commonly used 8 km dataset, and a new 1 km dataset developed by the Canadian Centre for Remote Sensing (CCRS). We compared the NDVI trends of both datasets along a fire severity gradient in order to evaluate the variance in regeneration rates. Temporal trends were calculated using the seasonal Mann,Kendall trend test, a rank-based, nonparametric test, which is robust against seasonality, nonnormality, heteroscedasticity, missing values, and serial dependence. The results showed contrasting NDVI trends between the CCRS and the GIMMS datasets. The CCRS dataset showed NDVI increases in all recently burned sites and in 50% of the unburned sites. Surprisingly, the GIMMS dataset did not capture the NDVI recovery in most burned sites and even showed NDVI declines in some burned sites one decade after fire. Between 50% and 75% of GIMMS pixels showed NDVI decreases in the unburned forest compared with <1% of CCRS pixels. Being the most broadly used dataset for monitoring ecosystem and carbon balance changes, the bias towards negative trends in the GIMMS dataset in the North American boreal forest has broad implications for the evaluation of vegetation and carbon dynamics in this region and globally. [source] Selective Zinc(II)-Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Krishanu Sarkar Abstract A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+ -bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87,×,104M,1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy. [source] Conjugated Polyelectrolytes as Light-Up Macromolecular Probes for Heparin SensingADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Kan-Yi Pu Abstract Two cationic poly(fluorene- alt -benzothiadiazole)s with different side chains are designed and synthesized. Both polymers show low fluorescence in aqueous solution due to the charge-transfer character of the polymer's excited states. Fluorescence turn-on biosensors for heparin detection and quantification are developed, taking advantage of complexation-induced aggregation, which increases the polymer fluorescence in aqueous solution. It is found that good polymer water-solubility is beneficial to the sensitivity and fluorescence contrast of the heparin turn-on sensor as a result of the low fluorescence background. Moreover, stronger complexation between the polymer/heparin leads to a substantially larger fluorescence increase in the presence of heparin relative to that in the presence of its analog, hyaluronic acid (HA), allowing discrimination of heparin from HA. Heparin quantification with a practical calibration range covering the whole therapeutic dosing levels (0.2,8 U mL,1) is realized based on the polymer with good water-solubility. This investigation provides a new insight for designing conjugated polymers with a light-up signature for biomolecular sensing. [source] Sensing of Damage Mechanisms in Fiber-Reinforced Composites under Cyclic Loading using Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Limin Gao Abstract The expanded use of advanced fiber-reinforced composites in structural applications has brought attention to the need to monitor the health of these structures. It has been established that adding carbon nanotubes to fiber-reinforced composites is a promising way to detect the formation of microscale damage. Because carbon nanotubes are three orders of magnitude smaller than traditional advanced fibers, it is possible for nanotubes to form an electrically conductive network in the polymer matrix surrounding the fibers. In this work, multi-walled carbon nanotubes are dispersed into epoxy and infused into a glass-fiber preform to form a network of in situ sensors. The resistance of the cross-ply composite is measured in real-time during incremental cyclic tensile loading tests to evaluate the damage evolution and failure mechanisms in the composite. Edge replication is conducted to evaluate the crack density after each cycle, and optical microscopy is utilized to study the crack mode and growth. The evolution of damage can be clearly identified through the damaged resistance parameter. Through analyzing the damaged resistance response curves with measurements of transverse crack density and strain, the transition between different failure modes can be identified. It is demonstrated that the integration of an electrically conducting network of carbon nanotubes in a glass fiber composite adds unique damage-sensing functionality that can be utilized to track the nature and extent of microstructural damage in fiber composites. [source] Potential for Satellite Remote Sensing of Ground WaterGROUND WATER, Issue 2 2006Matthew W. Becker Predicting hydrologic behavior at regional scales requires heterogeneous data that are often prohibitively expensive to acquire on the ground. As a result, satellite-based remote sensing has become a powerful tool for surface hydrology. Subsurface hydrology has yet to realize the benefits of remote sensing, even though surface expressions of ground water can be monitored from space. Remotely sensed indicators of ground water may provide important data where practical alternatives are not available. The potential for remote sensing of ground water is explored here in the context of active and planned satellite-based sensors. Satellite technology is reviewed with respect to its ability to measure ground water potential, storage, and fluxes. It is argued here that satellite data can be used if ancillary analysis is used to infer ground water behavior from surface expressions. Remotely sensed data are most useful where they are combined with numerical modeling, geographic information systems, and ground-based information. [source] | ||||||||||||||||||||||||||||||||||