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Resistance Measurements (resistance + measurement)
Kinds of Resistance Measurements Selected AbstractsIncorporation of Pulmonary Vascular Resistance Measurement into Standard Echocardiography: Implications for Assessment of Pulmonary HypertensionECHOCARDIOGRAPHY, Issue 10 2007Kimberly B. Ulett B.S Doppler estimation of pulmonary artery systolic pressure (PASP) from tricuspid regurgitation velocity is a simple approach to the detection of pulmonary hypertension but may be influenced by right ventricular stroke volume. We sought the clinical utility of incorporating Doppler calculation of pulmonary vascular resistance (PVR) into determination of pulmonary hypertension in 578 consecutive patients with tricuspid regurgitation. Right atrial pressure was estimated from vena caval dimensions and collapsibility. Pulmonary hypertension was classified on the basis of a) PASP >35mmHg, b) age-/gender normalized PASP, c) PVR >2 Wood units. The mean PASP was 40 ± 13 mmHg and PVR was 1.9 ± 0.8 Wood units. Standard PASP identified pulmonary hypertension in 58%, compared with 36% by age-/gender normalized PASP (P < 0.0001), and 31% by PVR (P < 0.0001). Of patients who had pulmonary hypertension by PASP, 33% were reclassified as normal on the basis of PVR and 6% were reclassified from normal to pulmonary hypertension. PVR is easy to incorporate into a standard echo exam, and identifies a small group with normal PASP as having PAH, and a larger group of apparently increased PASP as normal. [source] Large-area epitaxial silicon solar cells based on industrial screen-printing processesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2005Filip Duerinckx Abstract Thin-film epitaxial silicon solar cells are an attractive future alternative for bulk silicon solar cells incorporating many of the process advantages of the latter, but on a potentially cheap substrate. Several challenges have to be tackled before this potential can be successfully exploited on a large scale. This paper describes the points of interest and how IMEC aims to solve them. It presents a new step forward towards our final objective: the development of an industrial cell process based on screen-printing for >,15% efficient epitaxial silicon solar cells on a low-cost substrate. Included in the discussion are the substrates onto which the epitaxial deposition is done and how work is progressing in several research institutes and universities on the topic of a high-throughput epitaxial reactor. The industrial screen-printing process sequence developed at IMEC for these epitaxial silicon solar cells is presented, with emphasis on plasma texturing and improvement of the quality of the epitaxial layer. Efficiencies between 12 and 13% are presented for large-area (98,cm2) epitaxial layers on highly doped UMG-Si, off-spec and reclaim material. Finally, the need for an internal reflection scheme is explained. A realistically achievable internal reflection at the epi/substrate interface of 70% will result in a calculated increase of 3,mA/cm2 in short-circuit current. An interfacial stack of porous silicon layers (Bragg reflectors) is chosen as a promising candidate and the challenges facing its incorporation between the epitaxial layer and the substrate are presented. Experimental work on this topic is reported and concentrates on the extraction of the internal reflection at the epi/substrate interface from reflectance measurements. Initial results show an internal reflectance between 30 and 60% with a four-layer porous silicon stack. Resistance measurements for majority carrier flow through these porous silicon stacks are also included and show that no resistance increase is measurable for stacks up to four layers. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electron transport properties in InAs four-terminal ballistic junctions under weak magnetic fieldsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2009M. Koyama Abstract We report on the electron transport properties based on ballistic electrons under magnetic fields in four-terminal ballistic junctions fabricated on an InAs/AlGaSb heterostructure. The four-terminal junction structure is composed of two longitudinal stems with two narrow wires slanted with 30 degree from the perpendicular axis. The electron focusing peak was obtained with the bend resistance measurement. Then it was investigated the nonlinear electron transport property of potential difference between longitudinal stems due to ballistic electrons with applying direct current from narrow wires. Observed nonlinearity showed clear rectification effects which have negative polarity regardless of input voltage polarity. Although this nonlinearity was qualitatively changed due to the Lorentz force under magnetic fields, the degradation of ballistic effects on nonlinear properties were observed when the current increased to higher strength. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Cu3Ox glass-ceramic superconductorCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2004T. S. Kayed Abstract A glass-ceramic Bi1.7V0.3Sr2Ca2Cu3Ox superconductor was prepared by the melt-quenching method. The compound was characterized by scanning electron microscopy, x-ray diffraction, differential thermal analysis, current-voltage characteristics, transport resistance measurements, and Hall effect measurements. Two main phases (BSCCO 2212 and 2223) were observed in the x-ray data and the values of the lattice parameters quite agree with the known values for 2212 and 2223 phases. The glass transition temperature was found to be 426 °C while the activation energy for crystallization of glass has been found to be Ea = 370.5 kJ / mol. This result indicates that the substitution of vanadium increased the activation energy for the BSCCO system. An offset Tc of 80 K was measured and the onset Tc was 100 K. The Hall resistivity ,H was found to be almost field-independent at the normal state. A negative Hall coefficient was observed and no sign reversal of ,H or RH could be noticed. The mobility and carrier density at different temperatures in the range 140-300 K under different applied magnetic fields up to 1.4 T were also measured and the results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Monotonic and Cyclic Deformation Behaviour of the SiC Particle-Reinforced Aluminium Matrix Composite AMC225xe,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marek Smaga The monotonic and cyclic deformation behaviour of the aluminium matrix composite AMC225xe , i.e., the aerospace grade aluminium alloy AA 2124 reinforced with 25,vol.-% ultrafine SiC particles , is characterised in detail on the basis of mechanical stress,strain hysteresis curves as well as temperature and electrical resistance measurements. A pronounced difference in plastic strain response is observed between tension and compression under monotonic and cyclic loading. In fully reversed stress-controlled constant amplitude tests, negative plastic mean strains developed. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. The endurance limit is reliably estimated in continuous load increase tests. In particular, electrical resistance data are used as input parameters for fatigue life calculations analogous to the Basquin equation. Microstructural details are investigated by light and scanning electron microscopy. [source] Influences of the Process Chain on the Fatigue Behavior of Samples with Tension Screw Geometry,ADVANCED ENGINEERING MATERIALS, Issue 4 2010Marcus Klein To analyze the influence of the material batch, the structure of the manufacturing process chain, and the process parameters, four different material batches of the quenched and tempered steel SAE 4140 were used to manufacture samples with tension screw geometry. Five different, manufacturing process chains, consisting of the process steps heat treatment, turning, and grinding, were applied. After selected process steps, light and SEM micrographs as well as fatigue experiments were performed. The process itself as well as the process parameters influences the properties of the surface layers and the fatigue behavior in a characteristic manner. For example the variation of the feed rate and cutting speed in the hard-turning process leads to significantly different mechanical properties of the surface layers and residual stress states, which could be correlated with the fatigue behavior. The cyclic deformation behavior of the investigated components can be benchmarked equivalently with stress,strain hysteresis as well as high precision temperature and electrical resistance measurements. The temperature and electrical resistance measurements are suitable for component applications and provide an enormous advantage of information about the fatigue behavior. The temperature changes of the failed areas of the samples with tension screw geometry were significantly higher, a reliable identification of endangered areas is thereby possible. A new test procedure, developed at the Institute of Materials Science and Engineering of the University of Kaiserslautern, with inserted load-free-states during constant amplitude loading, provides the opportunity to detect proceeding fatigue damage in components during inspections. [source] "PHYBAL" a Short-Time Procedure for a Reliable Fatigue Life CalculationADVANCED ENGINEERING MATERIALS, Issue 4 2010Peter Starke Abstract The reliable calculation of the fatigue life of high-strength steels and components requires the systematic investigation of the cyclic deformation behaviour and the comprehensive evaluation of proceeding fatigue damage. Besides mechanical stress-strain hysteresis measurements, temperature and electrical resistance measurements were used for the detailed characterisation of the fatigue behaviour of the steel SAE 4140 in one quenched and tempered, one normalised, one bainitic and one martensitic condition. To guarantee optimal operation conditions the new fatigue life calculation method "PHYBAL" on the basis of generalised Morrow and Basquin equations was developed. It is a short-time procedure which requires the data of only three fatigue tests for a rapid and nevertheless precise determination of S-N (Woehler) curves. Consequently, "PHYBAL" provides the opportunity to reduce significantly experimental time and costs compared to conventional test methods. [source] Glass Fibers with Carbon Nanotube Networks as Multifunctional SensorsADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Shang-lin Gao Abstract A simple approach to deposit multiwalled carbon nanotube (MWNT) networks onto glass fiber surfaces achieving semiconductive MWNT,glass fibers is reported, along with application of fiber/polymer interphases as in-situ multifunctional sensors. This approach demonstrates for the first time that the techniques of conducting electrical resistance measurements could be applicable to glass fibers for in situ sensing of strain and damage; the techniques were previously limited to conductive and semiconductive materials. The electrical properties of the single MWNT,glass fiber and the "unidirectional" fiber/epoxy composite show linear or nonlinear stress/strain, temperature, and relative humidity dependencies, which are capable of detecting piezoresistive effects as well as the local glass transition temperature. The unidirectional composites containing MWNT,glass fibers exhibit ultrahigh anisotropic electrical properties and an ultralow electrical percolation threshold. Based on this approach, the glass fiber,the most widely used reinforcement in composites globally,along with the surface electrical conductivity of MWNTs will stimulate and realize a broad range of multifunctional applications. [source] Electrically Conductive Thin Films Prepared from Layer-by-Layer Assembly of Graphite PlateletsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Mubarak Alazemi Abstract Layer-by-layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/,, -methacryl-oxyethyl-trimethyl-ammonium copolymer as the cationic binder. Nanoparticle zeta (,,) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field-emission scanning electron microscopy and atomic-force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self-assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21,nm. Thin-film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6,m,,cm,2 at 173,nm to 3.5,m,,cm,2 at 276,nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly. [source] Thermal conductivity of wool and wool,hemp insulationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2006Z. Ye Abstract Measurements have been obtained for the thermal resistance of sheep-wool insulation and wool,hemp mixtures, both in the form of bonded insulation batts, using a calibrated guarded hot-box. The density was 9.6,25.9 kg m,3 for the wool and 9.9,18.1 kg m,3 for the wool,hemp mixtures. The measurements were made at a mean sample temperature of 13.3°C using a calibrated guarded hot-box. The estimated uncertainly in the resistance measurements was of the order of ±7%. The thermal conductivity of the samples, derived from the thermal resistance measurements on the basis of the measured thickness, was well correlated with the density, although the variation with density was larger than that obtained in previous studies. The conductivity of the wool,hemp samples was not significantly different from that of the wool samples at the same density. Moisture uptake produced an increase of less than 5% in the conductivity of the bonded wool insulation for an increase in absorbed moisture content of 20%. The thermal resistance was 1.6% lower on average for samples oriented in the horizontal plane rather than the vertical plane, but this difference is not significant. Copyright © 2005 John Wiley & Sons, Ltd. [source] Phenotypic analysis of the sensitivity of HIV-1 to inhibitors of the reverse transcriptase, protease, and integrase using a self-inactivating virus vector systemJOURNAL OF MEDICAL VIROLOGY, Issue 3 2001Gergely Jármy Abstract Conventional phenotypic analysis of resistance of the human immunodeficiency virus (HIV) to antiviral therapy is time-consuming and requires culture of infectious virus. Although phenotypic analyses may be desirable, rapid generation of test results and decentralized availability of the test system will be important to achieve utility in the clinical practice. This study describes the design of an alternative phenotypic resistance test using replication incompetent viral vectors. Chimeric HIV vectors containing a marker gene were generated. The env and most of the regulatory and accessory genes of HIV were removed. In addition, the 3,U3 region was deleted to obtain a self-inactivating construct. Cotransfection of the plasmid with a plasmid that provided the vesicular stomatitis virus glycoprotein resulted in the production of replication-incompetent virus vectors. Infection of susceptible cells with the vectors led to marker gene expression. Vector production in the presence of protease (PR) inhibitors, or infection in the presence of reverse transcriptase (RT) or integrase (IN) inhibitors reduced marker gene expression in a dose-dependent manner. Marker gene activity was preserved at higher drug levels if vectors contained RT and PR genes from resistant virus isolates. Sensitivity to nucleoside and non-nucleoside RT inhibitors, protease and integrase inhibitors could be determined in 10 working days. The phenotypic drug resistance test using replication-incompetent HIV vectors significantly speeds up drug resistance measurements and allows testing at reduced biosafety levels. This will make clinical use of phenotypic assessment of antiviral resistance more feasible. J. Med. Virol. 64:223,231, 2001. © 2001 Wiley-Liss, Inc. [source] Improved Aging Characteristics of NTC Thermistor Thin Films Fabricated by a Hybrid Sol,Gel,MOD ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006Dmitry A. Kukuruznyak Negative temperature coefficient thermistor oxide thin films with improved aging characteristics are described. Better thermal stability has been achieved by incorporating sol,gel techniques with metallo-organic decomposition methods. A compositional range was identified whereby borosilicate may incorporate into the thermistor oxides, forming nanocomposites showing thermistor electrical characteristics. Thermistor thin films, with composition Ni0.48Co0.24Cu0.6Mn1.68O4·0.22SiO2·0.15B2O3 were deposited onto glass substrates from a solution containing organic transition metal salts, tetraethyl orthosilicate and triethyl borate. Electrical resistance measurements verified characteristic thermistor behavior. Nanocomposite thin films exhibited a factor of four improvement as compared with pure oxides after aging at 150°C for 500 h. [source] Determination of the Thermal Resistance of the Polymer,Ceramic Interface of Alumina-Filled Polymer CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2004Richard F. Hill To model the thermal conductivity of polymer composites that are filled with ceramic powders, the conductivity of each component as well as the interfacial resistance at each ceramic,polymer boundary must be known. An indirect method to determine this interfacial boundary resistance is proposed by preparing large-scale "macromodel" simulations of the polymer,ceramic interface. Macromodels, prepared by spin-coating a polymer layer onto sapphire wafers, were formed in a sapphire,polymer,sapphire sandwich type structure. The interfacial boundary thermal resistance was calculated from thermal resistance measurements made on the macromodels. [source] Optical microscopy imaging method for detection of electromigration: Theory and experimentPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007L. H. Li Abstract Electromigration is a microscopic phenomenon involving electric field-induced diffusion, which is very relevant to damage in interconnects. A common method to monitor interconnect degradation is through electrical resistance measurements, which requires direct electrical contacts. It is desirable to develop non-contact methods to monitor electromigration damage formation. Recently, we have proposed a novel Optical Microscopy Imaging Method (OMIM). Here we provide theoretical proof and additional experimental results. OMIM provides a new method for studying electromigration-induced damage. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004K. Wang Abstract The influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5 alloys has been investigated using four-point-probe electrical resistance measurements, grazing incidence X-ray diffraction (XRD), X-ray reflectometry (XRR) and variable incident angle spectroscopic ellipsometry (VASE), a static tester and atomic force microscopy (AFM). For a Ge2Sb2Te5 alloy doped with 4% Sn, two transition temperatures are observed in the temperature dependent sheet resistance measurements at 125 °C and 250 °C, respectively. The evolution of structures upon annealing, investigated by XRD, reveals that the first transition is caused by the crystallization of the amorphous film to a NaCl-type structure, while the second transition is related to the transition to a hexagonal structure. The density values of 6.02 ± 0.05 g cm,3, 6.38 ± 0.05 gcm,3 and 6.42 ± 0.05 gcm,3 are measured by XRR for the film in the amorphous, NaCl-type and hexagonal structure, respectively. Ultra-fast crystallization, which is correlated with a single NaCl-structure phase and the reduced activation barrier, is demonstrated. Sufficient optical contrast is exhibited and can be correlated with the density change upon crystallization. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Identification of degradation mechanisms in field-tested CdTe modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2006Thomas Carlsson Abstract Field tests and accelerated ageing tests were conducted on CdTe photovoltaic modules with Sb-based back contacts. Significant performance degradation was observed during one and a half years of outdoor exposure. Small-area samples were prepared from field tested modules and characterized with current,voltage, capacitance,voltage and resistance measurements. Results show that module performance degradation in the field can be partly attributed to a decrease in doping concentration close to the CdS/CdTe junction and an increased resistance in the transparent front contact. A comparison with results in the literature indicates that bias voltage may play a role in the degradation process. Copyright © 2005 John Wiley & Sons, Ltd. [source] Plethysmography and impulse oscillometry assessment of tiotropium and ipratropium bromide; a randomized, double-blind, placebo-controlled, cross-over study in healthy subjectsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 4 2006D. Singh Aims Spirometry, plethysmography and impulse oscillometry (IOS) measure different aspects of lung function. These methods have not been compared for their ability to assess long- and short-acting anticholinergic agents. We therefore performed a double-blind, placebo-controlled, four-way cross-over study in 30 healthy subjects. Methods Single doses of tiotropium bromide (Tio) 54 and 18 mcg, ipratropium bromide (IB) 40 mcg and placebo were administered. Specific conductance (sGaw), total lung capacity (TLC), inspiratory capacity (IC) and residual volume (RV) were measured using plethysmography, while IOS measured resistance (R5,25) and reactance (RF and X5). Pulmonary function was measured for 26 h post dose. Results Tio caused significant improvements in sGaw, forced expiratory voume in 1 s (FEV1), maximum mid-expiratory flow (MMEF) and R5,R25 at time points up to 26 h, with no clear differences between doses. IB improved the same parameters, but only up to 8 h. The weighted mean change (0,24 h) caused by Tio 54 mcg compared with placebo for FEV1 was 240 ml (95% confidence interval 180, 300), while for sGaw the ratio of geometric means (Tio compared with placebo) was 1.35 (1.28, 1.41). Neither drug caused consistent statistically significant changes in RF, forced vital capacity, TLC or IC over 26 h. RV was significantly improved from 8 to 24 h by Tio 54 mcg only. Conclusions In addition to spirometry, IOS resistance measurements and sGaw can distinguish between the effects of long- and shortacting anticholinergic effects in healthy subjects. [source] Single-point mutations at the surface of MB-1Trp lead to important changes in its conformational propertiesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2004M. Sasseville Abstract:, Protein design is currently used for the creation of new proteins with desirable traits. In our lab we focus on the synthesis of proteins with high essential amino acid content having potential applications in animal nutrition. One of the limitations we face in this endeavour is achieving stable proteins despite a highly biased amino acid content. We report here the synthesis and the characterization of three variants of MB-1Trp in which two solvent-exposed Leu have been replaced by Glu allowing for the formation of new salt bridges at the surface of the protein. Although both mutations were expected to be similar (i.e. same mutation in a comparable local environment), they appear to have different effects on MB-1Trp as shown by far-UV circular dichroism, thermal denaturation, fluorescence and proteolytic resistance measurements. For the mutation Leu68Glu, an increase in the protein melting temperature of 6 °C was observed. Surprisingly, the mutation in position Leu19Glu led to a decrease in melting temperature and a modification of tertiary structure. [source] | ||||||||||||||||||||||