Showing papers by "National Physical Laboratory published in 2009"
TL;DR: In this paper, high conducting polyaniline (PANI)-multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by in situ polymerization.
605 citations
TL;DR: The silver–graphene nanocomposite film shows a 109-fold increase in electrical conductivity as compared to the graphite oxide film.
Abstract: Nanospacers for graphene: A facile and scalable process for the synthesis of aqueous solutions of isolated silver-decorated graphene sheets (see image) is presented. The silver–graphene nanocomposite film shows a 109-fold increase in electrical conductivity as compared to the graphite oxide film.
505 citations
TL;DR: Methods are described to provide information on how to analyze protein concentration using UV protein spectroscopy measurements, traditional dye-based absorbance measurements; BCA, Lowry, and Bradford assays and the fluorescent dye- based assays; amine derivatization and detergent partition assays.
Abstract: The measurement of protein concentration in an aqueous sample is an important assay in biochemistry research and development labs for applications ranging from enzymatic studies to providing data for biopharmaceutical lot release. Spectrophotometric protein quantitation assays are methods that use UV and visible spectroscopy to rapidly determine the concentration of protein, relative to a standard, or using an assigned extinction coefficient. Methods are described to provide information on how to analyze protein concentration using UV protein spectroscopy measurements, traditional dye-based absorbance measurements; BCA, Lowry, and Bradford assays and the fluorescent dye-based assays; amine derivatization and detergent partition assays. The observation that no single assay dominates the market is due to specific limitations of certain methods that investigators need to consider before selecting the most appropriate assay for their sample. Many of the dye-based assays have unique chemical mechanisms that are prone to interference from chemicals prevalent in many biological buffer preparations. A discussion of which assays are prone to interference and the selection of alternative methods is included.
387 citations
TL;DR: This work focuses on recent applications of organosulphur compounds (thiols) based SAMs to biomolecular electronic devices in the last about 3 years.
209 citations
TL;DR: In this paper, Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide (ITO) coated glass plate via physical adsorption for urea detection.
Abstract: Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide (ITO) coated glass plate via physical adsorption for urea detection. The magnitude of magnetization (60.9 emu/g) of Fe3O4 nanoparticles (∼22 nm) estimated using vibrating sample magnetometer (VSM) indicates superparamagnetic behaviour. It is shown that presence of Fe3O4 nanoparticles results in increased active surface area of CH-Fe3O4 nanobiocomposite for immobilization of enzymes (Ur and GLDH), enhanced electron transfer and increased shelf-life of nanobiocomposite electrode. Differential pulse voltammetry (DPV) studies show that Ur-GLDH/CH-Fe3O4/ITO bioelectrode is found to be sensitive in the 5–100 mg/dL urea concentration range and can detect as low as 0.5 mg/dL. A relatively low value of Michaelis–Menten constant (Km, 0.56 mM) indicates high affinity of enzymes (Ur and GLDH) for urea detection.
197 citations
TL;DR: In this paper, the concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India.
Abstract: The concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM10 and PM2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) µgm−3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM2.5/PM10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM10 and PM2.5, is deemed as the contribution of the coarse fraction (PM10−2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 µgm−3, 13.07%), mineral matter (12.32 µgm−3, 10.06%) and salt particles (4.92 µgm−3, 4.02%). PM2.5 are mainly made up of undetermined fractions (39.46 µgm−3, 40.9%), secondary inorganic aerosols (26.15 µgm−3, 27.1%), salt aerosols (22.48 µgm−3, 23.3%) and mineral matter (8.41 µgm−3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) µgm−3, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM10 and PM2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl−, SO42−, K+, Na+, Ca2+, NO3− and Mg2+ with PM2.5 on one hand and Mg2+ with PM10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi.
196 citations
TL;DR: The studies show that the composite can be used as structurally strong EMI shielding material and the mechanical properties of the composites were found to be comparable or better than the pure polymer.
Abstract: Electromagnetic interference (EMI) shielding effectiveness (SE) of multi-walled carbon nanotubes–polymethyl methacrylate (MWCNT–PMMA) composites prepared by two different techniques was measured. EMI SE up to 40 dB in the frequency range 8.2–12.4 GHz (X-band) was achieved by stacking seven layers of 0.3-mm thick MWCNT–PMMA composite films compared with 30 dB achieved by stacking two layers of 1.1-mm thick MWCNT–PMMA bulk composite. The characteristic EMI SE graphs of the composites and the mechanism of shielding have been discussed. SE in this frequency range is found to be dominated by absorption. The mechanical properties (tensile, flexural strength and modulus) of the composites were found to be comparable or better than the pure polymer. The studies therefore show that the composite can be used as structurally strong EMI shielding material.
187 citations
01 Jun 2009-Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
TL;DR: The state-of-the-art in the more well-known large-scale dimensional metrology methods are described in detail in this paper, where relevant specialist review papers exist, these are cited as further reading.
Abstract: With ever-more demanding requirements for the accurate manufacture of large components, dimensional measuring techniques are becoming progressively more sophisticated. This review describes some of the more recently developed techniques and the state-of-the-art in the more well-known large-scale dimensional metrology methods. In some cases, the techniques are described in detail, or, where relevant specialist review papers exist, these are cited as further reading. The traceability of the measurement data collected is discussed with reference to new international standards that are emerging. In some cases, hybrid measurement techniques are finding specialized applications and these are referred to where appropriate. © IMechE 2009.
182 citations
TL;DR: In this paper, the advantages and roles of various matrices, different strategies for biosensor construction, analytical performance and applications are discussed, and the prospects of urea biosensors for medical applications are also discussed.
182 citations
TL;DR: Aerosol black carbon (BC) mass concentrations measured continuously during a multi-platform field experiment, Integrated Campaign for Aerosols gases and Radiation Budget (ICARB, March-May 2006), from a network of eight observatories spread over geographically distinct environments of India, (which included five mainland stations, one highland station, and two island stations (one each ill Arabian Sea and Bay of Bengal)) are examined for their spatio-temporal characteristics as mentioned in this paper.
171 citations
TL;DR: This work discusses procedures for calculating the signal-to-noise ratios and the dynamic ranges of terahertz time-domain spectrometers and offers recommendations for standardized calculations for time- domain and frequency-domain data.
Abstract: We discuss procedures for calculating the signal-to-noise ratios and the dynamic ranges of terahertz time-domain spectrometers. We also offer recommendations for standardized calculations for time-domain and frequency-domain data.
TL;DR: In this article, day-and nighttime aerosol samples were collected at an urban site in New Delhi, India, in winter 2006-2007, and they were studied for low molecular weight dicarboxylic acids and related compounds, as well as total water-soluble organic carbon (TWSOC).
Abstract: [1] Day- and nighttime aerosol samples were collected at an urban site in New Delhi, India, in winter 2006–2007. They were studied for low molecular weight dicarboxylic acids and related compounds, as well as total water-soluble organic carbon (TWSOC). High concentrations of diacids (up to 6.03 μg m−3), TWSOC, and OC were obtained, which are substantially higher than those previously observed at other urban sites in Asia. Daytime TWSOC/OC ratio (37%) was on average higher than that in nighttime (25%). In particular, more water-soluble OC (M-WSOC) to TWSOC ratio in daytime (50%) was twice higher than in nighttime (27%), suggesting that aerosols in New Delhi are photochemically more processed in daytime to result in more water-soluble organic compounds. Oxalic acid (C2) was found as the most abundant dicarboxylic acid, followed by succinic (C4) and malonic (C3) acids. Contributions of C2 to M-WSOC were greater (av. 8%) in nighttime than daytime (av. 3%). Positive correlations of C2 with malic acid (hC4), glyoxylic acid (ωC2), and relative humidity suggest that secondary production of C2 probably in aqueous phase is important in nighttime via the oxidation of both longer-chain diacids and ωC2. C2 also showed a positive correlation with potassium (K+) in nighttime, suggesting that the enhanced C2 concentrations are associated with biomass/biofuel burning. More tight, positive correlation between less water-soluble OC (L-WSOC) and K+ was found in both day- and nighttime, suggesting that L-WSOC, characterized by longer chain and/or higher molecular weight compounds, is significantly influenced by primary emissions from biomass/biofuel burning.
TL;DR: In this article, a correlation between increase in hole concentration with decrease in magnetization and Curie temperature in ZnO:Li nanorods was found to explain the observed ferromagnetism.
Abstract: We have observed ferromagnetism in Li-doped ZnO nanorods with Curie temperature up to 554 K. Li forms shallow acceptor states in substitutional zinc sites giving rise to $p$-type conductivity. An explicit correlation emerges between increase in hole concentration with decrease in magnetization and Curie temperature in ZnO:Li. Occurrence of ferromagnetism at room temperature has been established with observed magnetic domain formation in ZnO:Li pellets in magnetic force microscopy and prominent ferromagnetic resonance signal in electron paramagnetic resonance spectrum. Magnetic ZnO:Li nanorods are luminescent, showing strong near UV emission. Substitutional Li atoms can induce local moments on neighboring oxygen atoms, which when considered in a correlated model for oxygen orbitals with random potentials introduced by dopant atom could explain the observed ferromagnetism and high Curie temperature in ZnO:Li nanorods.
TL;DR: In this paper, the dielectric properties of PANI and PANI-ZnO composite films have been investigated between frequency ranges of 8.5 and 13.0 GHz.
TL;DR: The results of photo-response studies carried out on HRP/NanoCeO(2)/ITO bioelectrode indicate reasonable agreement with those obtained using amperometric technique.
Centre national de la recherche scientifique1, Leibniz University of Hanover2, University of Florence3, National Physical Laboratory4, German National Metrology Institute5, Instituto Superior Técnico6, European Space Research and Technology Centre7, California Institute of Technology8, University of Western Australia9, University of Ulm10, University of Toulouse11, National Research Council12, University of Paris13, Stanford University14, Harvard University15, University of Erlangen-Nuremberg16, University of Birmingham17, University of Pisa18, University of Bremen19, Polytechnic University of Milan20, University of Hamburg21
TL;DR: The Search for Anomalous Gravitation using Atomic Sensors (SAGAS) project as mentioned in this paper aims at flying highly sensitive atomic sensors (optical clock, cold atom accelerometer, optical link) on a solar system escape trajectory in the 2020 to 2030 time-frame.
Abstract: We summarise the scientific and technological aspects of the Search for Anomalous Gravitation using Atomic Sensors (SAGAS) project, submitted to ESA in June 2007 in response to the Cosmic Vision 2015–2025 call for proposals. The proposed mission aims at flying highly sensitive atomic sensors (optical clock, cold atom accelerometer, optical link) on a Solar System escape trajectory in the 2020 to 2030 time-frame. SAGAS has numerous science objectives in fundamental physics and Solar System science, for example numerous tests of general relativity and the exploration of the Kuiper belt. The combination of highly sensitive atomic sensors and of the laser link well adapted for large distances will allow measurements with unprecedented accuracy and on scales never reached before. We present the proposed mission in some detail, with particular emphasis on the science goals and associated measurements and technologies.
TL;DR: In this article, the first time ZnSe nanoparticles were synthesized by a microwave heating process using high purity Zn and Se powders in equimolar ratio and the particle size distribution was in the range of ∼40 to 60 nm.
TL;DR: A ground level study was deliberated to analyze the contribution of wheat and rice crop stubble burning practices on concentration levels of aerosol, SO2 and NO2 in ambient air at five different sites in and around Patiala city covering agricultural, commercial and residential areas as discussed by the authors.
TL;DR: In this article, cholesterol esterase and cholesterol oxidase have been immobilized via glutaraldehyde as a crosslinker onto sol-gel-derived silica (SiO2)/chitosan (CHIT)/multi-walled carbon nanotubes (MWCNT)-based nanobiocomposite film deposited onto indium-tin-oxide (ITO) glass for estimation of esterified cholesterol.
Abstract: Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) have been immobilized via glutaraldehyde as a cross-linker onto sol–gel-derived silica (SiO2)/chitosan (CHIT)/multi-walled carbon nanotubes (MWCNT)-based nanobiocomposite film deposited onto indium-tin-oxide (ITO) glass for estimation of esterified cholesterol. The ChEt–ChOx/MWCNT/SiO2–CHIT/ITO bioelectrode characterized using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and electrochemical techniques and shows response time of 10 s, linearity as 10–500 mg/dL for esterified cholesterol (cholesterol oleate), sensitivity as 3.8 μA/mM and shelf-life of about 10 weeks under refrigerated conditions. The value of Michaelis–Menten constant (Km) estimated as 0.052 mM using Lineweaver–Burke plot indicates high affinity of ChEt and ChOx to cholesterol oleate. Attempts have been made to utilize this electrode for estimation of total cholesterol in blood serum samples.
TL;DR: The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.
TL;DR: In this paper, electron backscattering diffraction (EBSD) was used to improve the characterisation of both the WC and Co phase size, and contiguity between them, and a good correlation was shown between the EBSD and optical techniques.
Abstract: Accurate measurements of grain size are required to underpin development of models to predict properties, particularly of hybrid and multiphase materials. The conventional method for WC grain size determination in WC/Co is to use linear intercept measurements from light microscope or scanning electron microscopic images, usually requiring lengthy manual measurements, and subjective interpretation of grain boundary positions according to the level of etching and change in contrast. The possibilities offered by electron backscattering diffraction (EBSD) for improving the characterisation of both the WC and Co phase size, and contiguity between them, has been investigated. Samples covering a range of grain sizes have been examined by both EBSD and conventional methods to determine mean values and size distributions, with a special emphasis on the measurement of small grains. Diameters determined by both area (to give a circle equivalent diameter) and linear intercept from EBSD data are compared with the SEM image linear intercept method. It is shown that although the EBSD method is automated, great care must be taken in data analysis to identify and handle consistently small size values. If care is taken in the data handling then a good correlation can be shown between the EBSD and optical techniques.
University of Düsseldorf1, University of Florence2, National Physical Laboratory3, École Normale Supérieure4, German National Metrology Institute5, Technische Universität München6, Leibniz University of Hanover7, University of Bremen8, Delft University of Technology9, University of New South Wales10, Chinese Academy of Sciences11, Peking University12, European Space Research and Technology Centre13, Max Planck Society14
TL;DR: The Einstein Gravity Explorer mission (EGE) as mentioned in this paper is devoted to a precise measurement of the properties of space-time using atomic clocks, and is based on a satellite carrying cold atom-based clocks, including a cesium microwave clock, an optical clock, a femtosecond frequency comb, as well as precise microwave time transfer systems between space and ground.
Abstract: The Einstein Gravity Explorer mission (EGE) is devoted to a precise measurement of the properties of space-time using atomic clocks. It tests one of the most fundamental predictions of Einstein’s Theory of General Relativity, the gravitational redshift, and thereby searches for hints of quantum effects in gravity, exploring one of the most important and challenging frontiers in fundamental physics. The primary mission goal is the measurement of the gravitational redshift with an accuracy up to a factor 104 higher than the best current result. The mission is based on a satellite carrying cold atom-based clocks. The payload includes a cesium microwave clock (PHARAO), an optical clock, a femtosecond frequency comb, as well as precise microwave time transfer systems between space and ground. The tick rates of the clocks are continuously compared with each other, and nearly continuously with clocks on earth, during the course of the 3-year mission. The highly elliptic orbit of the satellite is optimized for the scientific goals, providing a large variation in the gravitational potential between perigee and apogee. Besides the fundamental physics results, as secondary goals EGE will establish a global reference frame for the Earth’s gravitational potential and will allow a new approach to mapping Earth’s gravity field with very high spatial resolution. The mission was proposed as a class-M mission to ESA’s Cosmic Vision Program 2015–2025.
TL;DR: Experiments in which pork meat was thermally ablated indicate that contiguous lesions several cm(3) in volume can be produced using the patterns of multiple foci, in good agreement with linear theoretical predictions.
Abstract: Randomized phased arrays can offer electronic steering of a single focus and simultaneous multiple foci concomitant with low levels of secondary maxima and are potentially useful as sources of high intensity focused ultrasound (HIFU). This work describes laboratory testing of a 1 MHz random phased array consisting of 254 elements on a spherical shell of radius of curvature 130 mm and diameter 170 mm. Acoustic output power and efficiency are measured for a range of input electrical powers, and field distributions for various single- and multiple-focus conditions are evaluated by a novel technique using an infrared camera to provide rapid imaging of temperature changes on the surface of an absorbing target. Experimental results show that the array can steer a single focus laterally to at least ±15 mm off axis and axially to more than ±15 mm from the centre of curvature of the array and patterns of four and five simultaneous foci ±10 mm laterally and axially whilst maintaining low intensity levels in secondary maxima away from the targeted area in good agreement with linear theoretical predictions. Experiments in which pork meat was thermally ablated indicate that contiguous lesions several cm3 in volume can be produced using the patterns of multiple foci.
TL;DR: In this article, the thermal, electrical, and spectral properties of polyaniline-graphite composites were characterized using in situ emulsion pathway, using different weight ratios of aniline to graphite.
Abstract: Polyaniline–graphite composites were prepared via in situ emulsion pathway, using different weight ratios of aniline to graphite. These composites were characterized for thermal, electrical, and spectral attributes. The thermal stability (∼ 230°C) and electrical conductivity (67.9 S/cm) were improved significantly as compared with polyaniline doped with conventional inorganic dopants such as HCl (140°C and 10 S/cm). Scanning electron micrographs indicated a systematic change in morphology from globular to flaky with increasing amounts of graphite. The relative shifting of UV–visible bands indicates that some interactions exist between doped polyaniline and graphite. Absorption-dominated total electromagnetic interference shielding effectiveness of the order of −33.6 dB suggests that these materials can be used as futuristic microwave shielding materials. The good electrical conductivity and thermal stability make them ideal candidates for preparing conducting composites by melt blending with conventional thermoplastics such as polyethylene, polypropylene, and polystyrene, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
TL;DR: In this paper, nanostructured zinc oxide (Nano-ZnO) film has been electrochemically deposited onto indium-tin-oxide (ITO) coated glass plate to co-immobilized urease (Urs) and glutamate dehydrogenase (GLDH) for urea detection.
TL;DR: Electrochemical studies reveal that nanoCeO(2) particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r- IgGs and electrode, and the high value of the association constant indicates the high affinity of the BSA/r-IGGs/nano CeO( 2)/ITO immunoelectrode to OTA.
Abstract: Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol–gel-derived nanostructured cerium oxide (nanoCeO2) film fabricated onto an indium–tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO2 nanostructures. Electrochemical studies reveal that nanoCeO2 particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO2/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5–6 ng dl−1), low detection limit (0.25 ng dl−1), fast response time (30 s) and high sensitivity (1.27 µA ng−1 dl−1 cm−2). The high value of the association constant (Ka, 0.9 × 1011 l mol−1) indicates the high affinity of the BSA/r-IgGs/nanoCeO2/ITO immunoelectrode to OTA.
TL;DR: In this article, the state-of-the-art of the electrochemical and physical properties of polymer electrolytes are reviewed. But the authors mainly focused on the properties of different salts, solvents, and polymer hosts, which are encaged in liquid electrolytes.
Abstract: Polymer electrolytes are an important component of many electrochemical devices This paper reviews state-of-the-art of the electrochemical and physical properties of polymer electrolytes This review mainly encompasses the properties of different salts, solvents, and polymer hosts, which are encaged in liquid electrolytes The additions of filler in polymer electrolytes result in composite polymer electrolytes, having high mechanical integrity and ionic conductivity, that are ideal electrolyte for these applications The next generation state-of-the-art room-temperature ionic liquids based electrolytes, which are far superior to corresponding nonionic solvent-based electrolytes, are also discussed
TL;DR: In this article, a chitosan (CS)-tin oxide (SnO2) nanobiocomposite film has been deposited onto an indium-tinoxide glass plate to immobilize cholesterol oxidase (ChOx) for cholesterol detection.
Abstract: A chitosan (CS)-tin oxide (SnO2) nanobiocomposite film has been deposited onto an indium-tin-oxide glass plate to immobilize cholesterol oxidase (ChOx) for cholesterol detection. The value of the Michaelis–Menten constant (Km) obtained as 3.8 mM for ChOx/CS-SnO2/ITO is lower (8 mM) than that of a ChOx/CS/ITO bioelectrode revealing enhancement in affinity and/or activity of ChOx towards cholesterol and also revealing strong binding of ChOx onto CS-SnO2/ITO electrode. This ChOx/CS-SnO2/ITO cholesterol sensor retains 95% of enzyme activity after 4–6 weeks at 4 °C with response time of 5 s, sensitivity of 34.7 μA/mg dL−1 cm2 and detection limit of 5 mg/dL.
TL;DR: In this paper, the authors measured CH4 and N2O fluxes from a sub-humid tropical rice field of Cuttack, eastern India, as affected by integrated rice-fish farming under rainfed lowland conditions.
TL;DR: In this paper, the doping of Fe (0.5, 2, and 50 mol%) in ZnO was performed using sol-gel process, which led to noteworthy alterations in the microstructure, phase formations and optical properties.