Carrier Decay and Diffusion Dynamics in Single-Crystalline CdTe as seen via Microphotoluminescence

Science.gov (United States)

Mascarenhas, Angelo; Fluegel, Brian; Alberi, Kirstin; Zhang, Yong-Hang

2015-03-01

The ability to spatially resolve the degree to which extended defects impact carrier diffusion lengths and lifetimes is important for determining upper limits for defect densities in semiconductor devices. We show that a new spatially and temporally resolved photoluminescence (PL) imaging technique can be used to accurately extract carrier lifetimes in the immediate vicinity of dark-line defects in CdTe/MgCdTe double heterostructures. A series of PL images captured during the decay process show that extended defects with a density of 1.4x10-5 cm-2 deplete photogenerated charge carriers from the surrounding semiconductor material on a nanosecond time scale. The technique makes it possible to elucidate the interplay between nonradiative carrier recombination and carrier diffusion and reveals that they both combine to degrade the PL intensity over a fractional area that is much larger than the physical size of the defects. Carrier lifetimes are correctly determined from numerical simulations of the decay behavior by taking these two effects into account. Our study demonstrates that it is crucial to measure and account for the influence of local defects in the measurement of carrier lifetime and diffusion, which are key transport parameters for the design and modeling of advanced solar-cell and light-emitting devices. We acknowledge the financial support of the Department of Energy Office of Science under Grant No. DE-AC36-08GO28308.

Minority carrier diffusion, defects, and localization in InGaAsN, with 2% nitrogen

International Nuclear Information System (INIS)

Kurtz, Steven R.; Allerman, A. A.; Seager, C. H.; Sieg, R. M.; Jones, E. D.

2000-01-01

Electron and hole transport in compensated InGaAsN (≅2% N) are examined through Hall mobility, photoconductivity, and solar cell photoresponse measurements. Short minority carrier diffusion lengths, photoconductive-response spectra, and doping dependent, thermally activated Hall mobilities reveal a broad distribution of localized states. At this stage of development, lateral carrier transport appears to be limited by large scale (>> mean free path) material inhomogeneities, not a random alloy-induced mobility edge. (c) 2000 American Institute of Physics

Diffusion length variation and proton damage coefficients for InP/In(x)Ga(1-x)As/GaAs solar cells

Science.gov (United States)

Jain, R. K.; Weinberg, I.; Flood, D. J.

1993-01-01

Indium phosphide solar cells are more radiation resistant than gallium arsenide and silicon solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of lighter, mechanically strong and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5 and 3 MeV proton irradiations are explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence is calculated by simulating the cell performance. The diffusion length damage coefficient K(L) is plotted as a function of proton fluence.

Carrier concentration effects on radiation damage in InP

International Nuclear Information System (INIS)

Yamaguchi, M.; Ando, K.; Uemura, C.

1984-01-01

Minority carrier diffusion length and carrier concentration studies have been made on room-temperature 1-MeV electron irradiated liquid-encapsulated Czochralski grown Zn-doped p-InP. The damage rate for the diffusion length and carrier removal rate due to irradiation have been found to strongly decrease with an increase in the carrier concentration in InP. These phenomena suggest that the induced defects interact with impurities in InP. A preliminary study on the annealing behavior has also been performed

Hybrid Perovskites for Photovoltaics: Charge-Carrier Recombination, Diffusion, and Radiative Efficiencies.

Science.gov (United States)

Johnston, Michael B; Herz, Laura M

2016-01-19

values extracted from OPTP measurements and their dependence on perovskite composition and morphology. The significance of the reviewed charge-carrier recombination and mobility parameters is subsequently evaluated in terms of the charge-carrier diffusion lengths and radiative efficiencies that may be obtained for such hybrid perovskites. We particularly focus on calculating such quantities in the limit of ultra-low trap-related recombination, which has not yet been demonstrated but could be reached through further advances in material processing. We find that for thin films of hybrid lead iodide perovskites with typical charge-carrier mobilities of ∼30cm(2)/(V s), charge-carrier diffusion lengths at solar (AM1.5) irradiation are unlikely to exceed ∼10 μm even if all trap-related recombination is eliminated. We further examine the radiative efficiency for hybrid lead halide perovskite films and show that if high efficiencies are to be obtained for intermediate charge-carrier densities (n ≈ 10(14) cm(-3)) trap-related recombination lifetimes will have to be enhanced well into the microsecond range.

Diffusion Length Mapping for Dye-Sensitized Solar Cells

Directory of Open Access Journals (Sweden)

Lucio Cinà

2016-08-01

Full Text Available The diffusion length (L of photogenerated carriers in the nanoporous electrode is a key parameter that summarizes the collection efficiency behavior in dye-sensitized solar cells (DSCs. At present, there are few techniques able to spatially resolve L over the active area of the device. Most of them require contact patterning and, hence, are intrinsically destructive. Here, we present the first electron diffusion length mapping system for DSCs based on steady state incident photon to collected electron (IPCE conversion efficiency ( η I P C E analysis. The measurement is conducted by acquiring complete transmittance ( T DSC and η I P C E spectra from the photo electrode (PE and counter electrode (CE for each spatial point in a raster scan manner. L ( x , y is obtained by a least square fitting of the IPCE ratio spectrum ( I P C E R = η I P C E -CE η I P C E -PE . An advanced feature is the ability to acquire η I P C E spectra using low-intensity probe illumination under weakly-absorbed background light (625 nm with the device biased close to open circuit voltage. These homogeneous conditions permit the linearization of the free electron continuity equation and, hence, to obtain the collection efficiency expressions ( η COL-PE and η COL-CE . The influence of the parameter’s uncertainty has been quantified by a sensitivity study of L. The result has been validated by quantitatively comparing the average value of L map with the value estimated from electrochemical impedance spectroscopy (EIS.

Carrier illumination measurement of dopant lateral diffusion

International Nuclear Information System (INIS)

Budiarto, E.; Segovia, M.; Borden, P.; Felch, S.

2005-01-01

This paper describes the application of the carrier illumination technique to non-destructively measure the lateral diffusion of implanted dopants after annealing. Experiments to validate the feasibility of this method employed test structures with a constant line width of 300 nm and varying undoped spaces of 100-5000 nm. The test patterns were implanted with a p-type dopant and annealed in a 3 x 3 matrix. For each implant condition, the measured lateral diffusion was found to increase with annealing temperature, as expected. More interestingly, the lateral diffusion was not observed to relate to the vertical diffusion by a fixed proportionality factor, as is usually assumed. The ratio of lateral to vertical diffusion varies with annealing temperature, with a trend that depends on the implant condition

Spin diffusion in disordered organic semiconductors

Science.gov (United States)

Li, Ling; Gao, Nan; Lu, Nianduan; Liu, Ming; Bässler, Heinz

2015-12-01

An analytical theory for spin diffusion in disordered organic semiconductors is derived. It is based on percolation theory and variable range hopping in a disordered energy landscape with a Gaussian density of states. It describes universally the dependence of the spin diffusion on temperature, carrier density, material disorder, magnetic field, and electric field at the arbitrary magnitude of the Hubbard energy of charge pairs. It is found that, compared to the spin transport carried by carriers hopping, the spin exchange will hinder the spin diffusion process at low carrier density, even under the condition of a weak electric field. Importantly, under the influence of a bias voltage, anomalous spreading of the spin packet will lead to an abnormal temperature dependence of the spin diffusion coefficient and diffusion length. This explains the recent experimental data for spin diffusion length observed in Alq3.

Determination of space charge region width and diffusion length in Cu(In,Ga)(S,Se)2 absorber from solar cell spectral characteristic

International Nuclear Information System (INIS)

Tivanov, M.; Mazanik, A.; Drozdov, N.; Zaretskaya, E.

2010-01-01

Full text : The space-charge region width and diffusion length of minority charge carriers in the base region (Cu(In,Ga)(S,Se) 2 absorber) are the most important parameters of the solar cell. These parameters determine the efficiency of a solar cell therefore the problem of their control is essential. In this work it is present simple non-destructive method of extracting the parameters of Cu(In,Ga)(S,Se) 2 -based solar cell (space-charge region width and diffusion length of minority charge carriers in Cu(In,Ga)(S,Se) 2 absorber) from the analysis of solar cell spectral photoresponse. The method is based on one-dimensional model of a solar cell and on the change of in-depth distribution of the photogenerated carriers in the solar cell and, hence, on the change of its photoresponse with the wave-length variation. The following assumptions are accepted: the reflection of charge carriers from a back contact and the ''drawing'' field in the quasi-neutral area of the absorber layers are absent, window and buffer layers are transparent in the analyzed part of photoresponse spectrum, the injection level of minority charge carriers is low, the recombination losses at the metallurgical p-n-junction interface of the studied photosensitive structure linearly depend on the photocurrent density. For the calculation it is necessary to obtain the following set of the experimental data: the spectral density of incident radiation, the spectral dependence of photocurrent or photovoltage of the studied photosensitive structure, the spectral dependences of optical absorption coefficient and reflectance.

Mathematical analysis of the Photovoltage Decay (PVD) method for minority carrier lifetime measurements

Science.gov (United States)

Vonroos, O. H.

1982-01-01

When the diffusion length of minority carriers becomes comparable with or larger than the thickness of a p-n junction solar cell, the characteristic decay of the photon-generated voltage results from a mixture of contributions with different time constants. The minority carrier recombination lifetime tau and the time constant l(2)/D, where l is essentially the thickness of the cell and D the minority carrier diffusion length, determine the signal as a function of time. It is shown that for ordinary solar cells (n(+)-p junctions), particularly when the diffusion length L of the minority carriers is larger than the cell thickness l, the excess carrier density decays according to exp (-t/tau-pi(2)Dt/4l(2)), tau being the lifetime. Therefore, tau can be readily determined by the photovoltage decay method once D and L are known.

PbCl2-tuned inorganic cubic CsPbBr3(Cl) perovskite solar cells with enhanced electron lifetime, diffusion length and photovoltaic performance

Science.gov (United States)

Li, Bo; Zhang, Yanan; Zhang, Luyuan; Yin, Longwei

2017-08-01

Inorganic CsPbBr3 perovskite is arousing great interest following after organic-inorganic hybrid halide perovskites, and is found as a good candidate for photovoltaic devices for its prominent photoelectric property and stability. Herein, we for the first time report on PbCl2-tuned inorganic Cl-doped CsPbBr3(Cl) perovskite solar cells with adjustable crystal structure and Cl doping for enhanced carrier lifetime, extraction rate and photovoltaic performance. The effect of PbCl2 on the morphologies, structures, optical, and photovoltaic performance of CsPbBr3 perovskite solar cells is investigated systemically. Compared with orthorhombic CsPbBr3, cubic CsPbBr3 demonstrates a significant improvement for electron lifetime (from 6.7 ns to 12.3 ns) and diffusion length (from 69 nm to 197 nm), as well as the enhanced electron extraction rate from CsPbBr3 to TiO2. More importantly, Cl doping benefits the further enhancement of carrier lifetime (14.3 ns) and diffusion length (208 nm). The Cl doped cubic CsPbBr3(Cl) perovskite solar cell exhibits a Jsc of 8.47 mA cm-2 and a PCE of 6.21%, superior to that of pure orthorhombic CsPbBr3 (6.22 mA cm-2 and 3.78%). The improvement of photovoltaic performance can be attributed to enhanced carrier lifetime, diffusion length and extraction rates, as well as suppressed nonradiative recombination.

Compact modeling of nanoscale triple-gate junctionless transistors covering drift-diffusion to quasi-ballistic carrier transport

Science.gov (United States)

Oproglidis, T. A.; Karatsori, T. A.; Barraud, S.; Ghibaudo, G.; Dimitriadis, C. A.

2018-04-01

In this work, we extend our analytical compact model for nanoscale junctionless triple-gate (JL TG) MOSFETs, capturing carrier transport from drift-diffusion to quasi-ballistic regime. This is based on a simple formulation of the low-field mobility extracted from experimental data using the Y-function method, taking into account the ballistic carrier motion and an increased carrier scattering in process-induced defects near the source/drain regions. The case of a Schottky junction in non-ideal ohmic contact at the drain side was also taken into account by modifying the threshold voltage and ideality factor of the JL transistor. The model is validated with experimental data for n-channel JL TG MOSFETs with channel length varying from 95 down to 25 nm. It can be easily implemented as a compact model for use in Spice circuit simulators.

Record Charge Carrier Diffusion Length in Colloidal Quantum Dot Solids via Mutual Dot-To-Dot Surface Passivation.

Science.gov (United States)

Carey, Graham H; Levina, Larissa; Comin, Riccardo; Voznyy, Oleksandr; Sargent, Edward H

2015-06-03

Through a combination of chemical and mutual dot-to-dot surface passivation, high-quality colloidal quantum dot solids are fabricated. The joint passivation techniques lead to a record diffusion length for colloidal quantum dots of 230 ± 20 nm. The technique is applied to create thick photovoltaic devices that exhibit high current density without losing fill factor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exciton diffusion length in narrow bandgap polymers

NARCIS (Netherlands)

Mikhnenko, O.V.; Azimi, H.; Morana, M.; Blom, P.W.M.; Loi, M.A.

2012-01-01

We developed a new method to accurately extract the singlet exciton diffusion length in organic semiconductors by blending them with a low concentration of methanofullerene[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The dependence of photoluminescence (PL) decay time on the fullerene

Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

KAUST Repository

Shi, Dong

2015-01-29

The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3(MA = CH3NH3 +; X = Br- or I- ) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics.We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

KAUST Repository

Shi, Dong; Adinolfi, Valerio; Comin, Riccardo; Yuan, Mingjian; Alarousu, Erkki; Buin, Andrei K.; Chen, Yin; Hoogland, Sjoerd H.; Rothenberger, Alexander; Katsiev, Khabiboulakh; Losovyj, Yaroslav B.; Zhang, Xin; Dowben, Peter A.; Mohammed, Omar F.; Sargent, E. H.; Bakr, Osman

2015-01-01

The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3(MA = CH3NH3 +; X = Br- or I- ) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics.We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

Coherent quantum transport in disordered systems: II. Temperature dependence of carrier diffusion coefficients from the time-dependent wavepacket diffusion method

International Nuclear Information System (INIS)

Zhong, Xinxin; Zhao, Yi; Cao, Jianshu

2014-01-01

The time-dependent wavepacket diffusion method for carrier quantum dynamics (Zhong and Zhao 2013 J. Chem. Phys. 138 014111), a truncated version of the stochastic Schrödinger equation/wavefunction approach that approximately satisfies the detailed balance principle and scales well with the size of the system, is applied to investigate the carrier transport in one-dimensional systems including both the static and dynamic disorders on site energies. The predicted diffusion coefficients with respect to temperature successfully bridge from band-like to hopping-type transport. As demonstrated in paper I (Moix et al 2013 New J. Phys. 15 085010), the static disorder tends to localize the carrier, whereas the dynamic disorder induces carrier dynamics. For the weak dynamic disorder, the diffusion coefficients are temperature-independent (band-like property) at low temperatures, which is consistent with the prediction from the Redfield equation, and a linear dependence of the coefficient on temperature (hopping-type property) only appears at high temperatures. In the intermediate regime of dynamic disorder, the transition from band-like to hopping-type transport can be easily observed at relatively low temperatures as the static disorder increases. When the dynamic disorder becomes strong, the carrier motion can follow the hopping-type mechanism even without static disorder. Furthermore, it is found that the memory time of dynamic disorder is an important factor in controlling the transition from the band-like to hopping-type motions. (paper)

Minority-carrier transport in InGaAsSb thermophotovoltaic diodes

International Nuclear Information System (INIS)

Charache, G.; Martinelli, R.U.; Garbuzov, D.Z.; Lee, H.; Morris, N.; Odubanjo, T.; Connolly, J.C.

1997-05-01

Uncoated InGaAsSb/GaSb thermophotovoltaic (TPV) diodes with 0.56 eV (2.2 microm) bandgaps exhibit external quantum efficiencies of 59% at 2 microm. The devices have electron diffusion lengths as long as 29 microm in 8-microm-wide p-InGaAsSb layers and hole diffusion lengths of 3 microm in 6-microm-wide n-InGaAsSb layers. The electron and hole diffusion lengths appear to increase with increasing p- and n-layer widths. At 632.8 nm the internal quantum efficiencies of diodes with 1- to 8-microm-wide p-layers are above 89% and are independent of the p-layer width, indicating long electron diffusion lengths. InGaAsSb has, therefore, excellent minority carrier transport properties that are well suited to efficient TPV diode operation. The structures were grown by molecular-beam epitaxy

Towards reaction-diffusion computing devices based on minority-carrier transport in semiconductors

International Nuclear Information System (INIS)

Asai, Tetsuya; Adamatzky, Andrew; Amemiya, Yoshihito

2004-01-01

Reaction-diffusion (RD) chemical systems are known to realize sensible computation when both data and results of the computation are encoded in concentration profiles of chemical species; the computation is implemented via spreading and interaction of either diffusive or phase waves. Thin-layer chemical systems are thought of therefore as massively-parallel locally-connected computing devices, where micro-volume of the medium is analogous to an elementary processor. Practical applications of the RD chemical systems are reduced however due to very low speed of traveling waves which makes real-time computation senseless. To overcome the speed-limitations while preserving unique features of RD computers we propose a semiconductor RD computing device where minority carriers diffuse as chemical species and reaction elements are represented by p-n-p-n diodes. We offer blue-prints of the RD semiconductor devices, and study in computer simulation propagation phenomena of the density wave of minority carriers. We then demonstrate what computational problems can be solved in RD semiconductor devices and evaluate space-time complexity of computation in the devices

Rapid diffusion of molybdenum trace contamination in silicon

International Nuclear Information System (INIS)

Tobin, S.P.; Greenwald, A.C.; Wolfson, R.G.; Meier, D.L.; Drevinsky, P.J.

1985-01-01

Molybdenum contamination has been detected in silicon epitaxial layers and substrate wafers after processing in any one of several epitaxial silicon reactors. Greatly reduced minority carrier diffusion lengths and lifetimes are consistent with Mo concentrations measured by DLTS in the 10 12 and 10 13 cm -3 ranges. Depth profiling of diffusion length and the Mo deep level show much greater penetration than expected from previous reports of Mo as a slow diffuser. The data indicate a lower limit of 10 -8 cm 2 /sec for the diffusion coefficient of Mo in silicon at 1200 0 C, consistent with high diffusivities measured for other transition metals

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

KAUST Repository

Zheng, B.; Wang, L. L.; Du, L.; Pan, Y.; Lai, Zhiping; Huang, Kuo-Wei; Du, H. L.

2016-01-01

Understanding guest diffusion in nanoporous host-guest systems is crucial in the efficient design of metal-organic frameworks (MOFs) for chemical separation and drug delivery applications. In this work, we investigated the effect of molecule length on the diffusion rate in the zeolitic imidazolate framework 8 (ZIF-8), trying to find a simple and straightforward variable to characterize the complicated guest diffusion. We found that, counter-intuitively, long guest molecules can diffuse as quickly as short molecules; the diffusion coefficient of ethyl acetate for example is of the same order of magnitude as ethane and ethanol, as excludes the existence of a simple relationship between molecule length and diffusion rate. This phenomenon is explained by a study of the contributions of intra- and inter-cage movement to overall transport. Steric confinement limits the degrees of freedom of long guest molecules, shortening their residence time and increasing the efficiency of radial diffusion. In contrast, shorter molecules meander within MOF cages, reducing transport. Furthermore, the energy barrier of inter-cage transport also does not exhibit a simple dependence on a guest molecule length, attributing to the effect of the type of functional group on diffusion. Guests over varying lengths were investigated by using theoretical methods, revealing that the guest diffusion in ZIF-8 depends on the number of contiguous carbon atoms in a molecule, rather than its overall length. Thus, we proposed simple criteria to predict arbitrary guest molecule diffusivity in ZIF-8 without time-consuming experimentation. © 2016 The Royal Society of Chemistry.

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

KAUST Repository

Zheng, B.

2016-05-11

Understanding guest diffusion in nanoporous host-guest systems is crucial in the efficient design of metal-organic frameworks (MOFs) for chemical separation and drug delivery applications. In this work, we investigated the effect of molecule length on the diffusion rate in the zeolitic imidazolate framework 8 (ZIF-8), trying to find a simple and straightforward variable to characterize the complicated guest diffusion. We found that, counter-intuitively, long guest molecules can diffuse as quickly as short molecules; the diffusion coefficient of ethyl acetate for example is of the same order of magnitude as ethane and ethanol, as excludes the existence of a simple relationship between molecule length and diffusion rate. This phenomenon is explained by a study of the contributions of intra- and inter-cage movement to overall transport. Steric confinement limits the degrees of freedom of long guest molecules, shortening their residence time and increasing the efficiency of radial diffusion. In contrast, shorter molecules meander within MOF cages, reducing transport. Furthermore, the energy barrier of inter-cage transport also does not exhibit a simple dependence on a guest molecule length, attributing to the effect of the type of functional group on diffusion. Guests over varying lengths were investigated by using theoretical methods, revealing that the guest diffusion in ZIF-8 depends on the number of contiguous carbon atoms in a molecule, rather than its overall length. Thus, we proposed simple criteria to predict arbitrary guest molecule diffusivity in ZIF-8 without time-consuming experimentation. © 2016 The Royal Society of Chemistry.

Parallel diffusion length on thermal neutrons in rod type lattices

International Nuclear Information System (INIS)

Ahmed, T.; Siddiqui, S.A.M.M.; Khan, A.M.

1981-11-01

Calculation of diffusion lengths of thermal neutrons in lead-water and aluminum water lattices in direction parallel to the rods are performed using one group diffusion equation together with Shevelev transport correction. The formalism is then applied to two practical cases, the Kawasaki (Hitachi) and the Douglas point (Candu) reactor lattices. Our results are in good agreement with the observed values. (author)

Correlation between Photoluminescence and Carrier Transport and a Simple In Situ Passivation Method for High-Bandgap Hybrid Perovskites.

Science.gov (United States)

Stoddard, Ryan J; Eickemeyer, Felix T; Katahara, John K; Hillhouse, Hugh W

2017-07-20

High-bandgap mixed-halide hybrid perovskites have higher open-circuit voltage deficits and lower carrier diffusion lengths than their lower-bandgap counterparts. We have developed a ligand-assisted crystallization (LAC) technique that introduces additives in situ during the solvent wash and developed a new method to dynamically measure the absolute intensity steady-state photoluminescence and the mean carrier diffusion length simultaneously. The measurements reveal four distinct regimes of material changes and show that photoluminescence brightening often coincides with losses in carrier transport, such as in degradation or phase segregation. Further, the measurements enabled optimization of LAC on the 1.75 eV bandgap FA 0.83 Cs 0.17 Pb(I 0.66 Br 0.34 ) 3 , resulting in an enhancement of the photoluminescence quantum yield (PLQY) of over an order of magnitude, an increase of 80 meV in the quasi-Fermi level splitting (to 1.29 eV), an increase in diffusion length by a factor of 3.5 (to over 1 μm), and enhanced open-circuit voltage and short-circuit current from photovoltaics fabricated from the LAC-treated films.

Diffusion as a Ruler: Modeling Kinesin Diffusion as a Length Sensor for Intraflagellar Transport.

Science.gov (United States)

Hendel, Nathan L; Thomson, Matthew; Marshall, Wallace F

2018-02-06

An important question in cell biology is whether cells are able to measure size, either whole cell size or organelle size. Perhaps cells have an internal chemical representation of size that can be used to precisely regulate growth, or perhaps size is just an accident that emerges due to constraint of nutrients. The eukaryotic flagellum is an ideal model for studying size sensing and control because its linear geometry makes it essentially one-dimensional, greatly simplifying mathematical modeling. The assembly of flagella is regulated by intraflagellar transport (IFT), in which kinesin motors carry cargo adaptors for flagellar proteins along the flagellum and then deposit them at the tip, lengthening the flagellum. The rate at which IFT motors are recruited to begin transport into the flagellum is anticorrelated with the flagellar length, implying some kind of communication between the base and the tip and possibly indicating that cells contain some mechanism for measuring flagellar length. Although it is possible to imagine many complex scenarios in which additional signaling molecules sense length and carry feedback signals to the cell body to control IFT, might the already-known components of the IFT system be sufficient to allow length dependence of IFT? Here we investigate a model in which the anterograde kinesin motors unbind after cargo delivery, diffuse back to the base, and are subsequently reused to power entry of new IFT trains into the flagellum. By mathematically modeling and simulating such a system, we are able to show that the diffusion time of the motors can in principle be sufficient to serve as a proxy for length measurement. We found that the diffusion model can not only achieve a stable steady-state length without the addition of any other signaling molecules or pathways, but also is able to produce the anticorrelation between length and IFT recruitment rate that has been observed in quantitative imaging studies. Copyright © 2017 Biophysical

Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films.

Science.gov (United States)

Ciesielski, Richard; Schäfer, Frank; Hartmann, Nicolai F; Giesbrecht, Nadja; Bein, Thomas; Docampo, Pablo; Hartschuh, Achim

2018-03-07

Micro- and nanocrystalline methylammonium lead iodide (MAPI)-based thin-film solar cells today reach power conversion efficiencies of over 20%. We investigate the impact of grain boundaries on charge carrier transport in large crystal MAPI thin films using time-resolved photoluminescence (PL) microscopy and numerical model calculations. Crystal sizes in the range of several tens of micrometers allow for the spatially and time resolved study of boundary effects. Whereas long-ranged diffusive charge carrier transport is observed within single crystals, no detectable diffusive transport occurs across grain boundaries. The observed PL transients are found to crucially depend on the microscopic geometry of the crystal and the point of observation. In particular, spatially restricted diffusion of charge carriers leads to slower PL decay near crystal edges as compared to the crystal center. In contrast to many reports in the literature, our experimental results show no quenching or additional loss channels due to grain boundaries for the studied material, which thus do not negatively affect the performance of the derived thin-film devices.

Exciton diffusion length in some thermocleavable polythiophenes by the surface photovoltage method

DEFF Research Database (Denmark)

Tousek, J.; Touskova, J.; Remes, Z.

2012-01-01

property is that P3MHOCT can serve as a precursor which, after thermal annealing, converts into more rigid and insoluble P3CT and further thermal treatment produces native unsubstituted PT. Ellipsometric measurement yielded data on the thickness of the spin coated layers; absorption coefficients were...... be ascribed to the increase of the crystalline fraction. The highest diffusion length was found in P3CT polymer but its large resistivity represents a disadvantage in application in solar cells. Taking into account just these parameters, relatively low resistivity together with quite high diffusion length (13...

Analysis of the photo voltage decay /PVD/ method for measuring minority carrier lifetimes in P-N junction solar cells

Science.gov (United States)

Von Roos, O.

1981-01-01

The photo voltage decay (PVD) method for the measurement of minority carrier lifetimes in P-N junction solar cells with cell thickness comparable to or even less than the minority carrier diffusion length is examined. The method involves the generation of free carriers in the quasi-neutral bulk material by flashes of light and the monitoring of the subsequent decay of the induced open-circuit voltages as the carriers recombine, which is dependent on minority carrier recombination lifetime. It is shown that the voltage versus time curve for an ordinary solar cell (N(+)-P junction) is proportional to the inverse minority carrier lifetime plus a factor expressing the ratio of diffusion length to cell thickness. In the case of an ideal back-surface-field cell (N(+)-P-P(+) junction) however, the slope is directly proportional to the inverse minority carrier lifetime. It is noted that since most BSF cells are not ideal, possessing a sizable back surface recombination velocity, the PVD measurements must be treated with caution and supplemented with other nonstationary methods.

Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)

2013-12-09

The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ∼1.2 nm at room temperature and ∼1.6 nm at 8 K.

Investigation of the extraction of short diffusion lengths from simulated electron-beam induced current

Energy Technology Data Exchange (ETDEWEB)

Wee, D.; Parish, G.; Nener, B. [Microelectronics Research Group, The University of Western Australia, 35 Stirling Highway, 6009 Crawley (Perth) (Australia)

2010-10-15

This paper reports on the investigations via 2-D simulation into the accuracy of diffusion length extraction from scanning electron-beam induced current measurements when the diffusion length, L is very short. L is extracted by using the direct method proposed by Chan et al.[1] and later refined by Kurniawan and Ong[2] to take finite junction depth into account. The 2-D simulations were undertaken using Synopsys {sup registered} Sentaurus TCAD and a realistic electron-hole pair generation volume was created using CASINO v2.42[3], a Monte Carlo Scanning Electron Microscope interaction simulation software, and imported into Sentaurus. The voltage and diameter of the electron beam and diffusion length and surface recombination velocity of the semiconductor materials were varied in the simulations to determine the errors in the diffusion length extracted from the EBIC signals as a function of these parameters. The results of the simulation show that the accuracy of the method proposed in[1] is reasonably accurate and that the beam voltage and spot size do not have significant effects on the accuracy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Investigation of the extraction of short diffusion lengths from simulated electron-beam induced current

International Nuclear Information System (INIS)

Wee, D.; Parish, G.; Nener, B.

2010-01-01

This paper reports on the investigations via 2-D simulation into the accuracy of diffusion length extraction from scanning electron-beam induced current measurements when the diffusion length, L is very short. L is extracted by using the direct method proposed by Chan et al.[1] and later refined by Kurniawan and Ong[2] to take finite junction depth into account. The 2-D simulations were undertaken using Synopsys registered Sentaurus TCAD and a realistic electron-hole pair generation volume was created using CASINO v2.42[3], a Monte Carlo Scanning Electron Microscope interaction simulation software, and imported into Sentaurus. The voltage and diameter of the electron beam and diffusion length and surface recombination velocity of the semiconductor materials were varied in the simulations to determine the errors in the diffusion length extracted from the EBIC signals as a function of these parameters. The results of the simulation show that the accuracy of the method proposed in[1] is reasonably accurate and that the beam voltage and spot size do not have significant effects on the accuracy (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Electron microscopy characterization of a molybdenum diffusion barrier in metallizations for chip carriers

International Nuclear Information System (INIS)

He Anqiang; Ivey, Douglas G.

2004-01-01

Mo layers have been studied as potential diffusion barriers for Au-Sn solder bonds in micro/optoelectronic device packaging. Solder was electroplated as alternating AuSn and Au 5 Sn multi-layers on wafers covered with Ti as an adhesion layer, followed by Mo as the diffusion barrier and Au as a capping layer. Samples were annealed at 340-420 deg. C for as long as 20 min. Scanning and transmission electron microscopy (SEM and TEM) were utilized to characterize interfacial reactions. Mo was found to be metallurgically stable, relative to the Au-Sn solder and the other metallization components, at temperatures up to at least 420 deg. C. However, the effectiveness of Mo as a barrier can be compromised by two factors. One of these is related to surface roughness associated with AlN or Al 2 O 3 carriers. Non-uniform metallization coverage can lead to breaks in the Mo barrier, resulting in contact between the carrier and molten solder during bonding applications. In addition, thermal stresses generated during heating and cooling can lead to cracking and spalling of the Mo and adhesion layers, exposing the carrier material to molten solder. Pre-annealing can help to relieve the thermal stresses and prevent spalling

Estimation and calibration of the water isotope differential diffusion length in ice core records

NARCIS (Netherlands)

van der Wel, G.; Fischer, H.; Oerter, H.; Meyer, H.; Meijer, H. A. J.

2015-01-01

Palaeoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation

Measurement of the diffusion length of thermal neutrons inside graphite

International Nuclear Information System (INIS)

Ertaud, A.; Beauge, R.; Fauquez, H.; De Laboulay, H.; Mercier, C.; Vautrey, L.

1948-11-01

The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra α → Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm ± 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)

Determination of thermal neutrons diffusion length in graphite

International Nuclear Information System (INIS)

Garcia Fite, J.

1959-01-01

The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs

Measurement of the diffusion length of thermal neutrons in the beryllium oxide

International Nuclear Information System (INIS)

Koechlin, J.C.; Martelly, J.; Duggal, V.P.

1955-01-01

The diffusion length of thermal neutrons in the beryllium oxide has been obtained while studying the spatial distribution of the neutrons in a massive parallelepiped of this matter placed before the thermal column of the reactor core of Saclay. The mean density of the beryllium oxide (BeO) is 2,95 gr/cm 3 , the mean density of the massif is 2,92 gr/cm 3 . The value of the diffusion length, deducted of the done measures, is: L = 32,7 ± 0,5 cm (likely gap). Some remarks are formulated about the influence of the spectral distribution of the neutrons flux used. (authors) [fr

MO-G-BRF-07: Anomalously Fast Diffusion of Carbon Nanotubes Carriers in 3D Tissue Model

International Nuclear Information System (INIS)

Wang, Y; Bahng, J; Kotov, N

2014-01-01

Purpose: We aim to investigate and understand diffusion process of carbon nanotubes (CNTs) and other nanoscale particles in tissue and organs. Methods: In this research, we utilized a 3D model tissue of hepatocellular carcinoma (HCC)cultured in inverted colloidal crystal (ICC) scaffolds to compare the diffusivity of CNTs with small molecules such as Rhodamine and FITC in vitro, and further investigated the transportation of CNTs with and without targeting ligand, TGFβ1. The real-time permeation profiles of CNTs in HCC tissue model with high temporal and spatial resolution was demonstrated by using standard confocal microscopy. Quantitative analysis of the diffusion process in 3D was carried out using luminescence intensity in a series of Z-stack images obtained for different time points of the diffusion process after initial addition of CNTs or small molecules to the cell culture and the image data was analyzed by software ImageJ and Mathematica. Results: CNTs display diffusion rate in model tissues substantially faster than small molecules of the similar charge such as FITC, and the diffusion rate of CNTs are significantly enhanced with targeting ligand, TGFβ1. Conclusion: In terms of the advantages of in-vitro model, we were able to have access to measuring the rate of CNT penetration at designed conditions with variable parameters. And the findings by using this model, changed our understanding about advantages of CNTs as nanoscale drug carriers and provides design principles for making new drug carriers for both treatment and diagnostics. Additionally the fast diffusion opens the discussion of the best possible drug carriers to reach deep parts of cancerous tissues, which is often a prerequisite for successful cancer treatment. This work was supported by the Center for Photonic and Multiscale Nanomaterials funded by National Science Foundation Materials Research Science and Engineering Center program DMR 1120923. The work was also partially supported by NSF

MO-G-BRF-07: Anomalously Fast Diffusion of Carbon Nanotubes Carriers in 3D Tissue Model

Energy Technology Data Exchange (ETDEWEB)

Wang, Y; Bahng, J; Kotov, N [University of Michigan, Ann Arbor, MI (United States)

2014-06-15

Purpose: We aim to investigate and understand diffusion process of carbon nanotubes (CNTs) and other nanoscale particles in tissue and organs. Methods: In this research, we utilized a 3D model tissue of hepatocellular carcinoma (HCC)cultured in inverted colloidal crystal (ICC) scaffolds to compare the diffusivity of CNTs with small molecules such as Rhodamine and FITC in vitro, and further investigated the transportation of CNTs with and without targeting ligand, TGFβ1. The real-time permeation profiles of CNTs in HCC tissue model with high temporal and spatial resolution was demonstrated by using standard confocal microscopy. Quantitative analysis of the diffusion process in 3D was carried out using luminescence intensity in a series of Z-stack images obtained for different time points of the diffusion process after initial addition of CNTs or small molecules to the cell culture and the image data was analyzed by software ImageJ and Mathematica. Results: CNTs display diffusion rate in model tissues substantially faster than small molecules of the similar charge such as FITC, and the diffusion rate of CNTs are significantly enhanced with targeting ligand, TGFβ1. Conclusion: In terms of the advantages of in-vitro model, we were able to have access to measuring the rate of CNT penetration at designed conditions with variable parameters. And the findings by using this model, changed our understanding about advantages of CNTs as nanoscale drug carriers and provides design principles for making new drug carriers for both treatment and diagnostics. Additionally the fast diffusion opens the discussion of the best possible drug carriers to reach deep parts of cancerous tissues, which is often a prerequisite for successful cancer treatment. This work was supported by the Center for Photonic and Multiscale Nanomaterials funded by National Science Foundation Materials Research Science and Engineering Center program DMR 1120923. The work was also partially supported by NSF

Measurement of neutron diffusion length in heavy concrete

International Nuclear Information System (INIS)

Krejci, D.

2007-04-01

Using an aluminium sampler filled with heavy concrete the neutron diffusion length was determined, measuring thermal and fast neutrons over the whole beam hole with various threshold detectors using gold samples. These calculations should describe the neutron distribution in the whole concrete shield of the reactor and contribute to the investigation of the activation of the concrete shield using reactor parameters like operating time, power and neutron flux. Instrumentation, activation and positioning of the samples in the beam hole of the TRIGA Mark II reactor are described. (nevyjel)

Measurement of diffusion length of thermal neutrons in concrete

International Nuclear Information System (INIS)

Moser, M.

2007-04-01

The diffusion length of neutrons with a medium energy < 0.025 eV in concrete were determined using 4π-β detector and gamma detectors. Then it was possible to determine how deep can neutrons penetrate diverse concrete construction parts in a reactor in operation, with this method the dismantling process of a reactor can be planned in terms of what parts can be removed without danger and what parts can be assumed still are activated. (nevyjel)

Two dimensional numerical simulations of carrier dynamics during time-resolved photoluminescence decays in two-photon microscopy measurements in semiconductors

International Nuclear Information System (INIS)

Kanevce, Ana; Kuciauskas, Darius; Levi, Dean H.; Johnston, Steven W.; Allende Motz, Alyssa M.

2015-01-01

We use two-dimensional numerical simulations to analyze high spatial resolution time-resolved spectroscopy data. This analysis is applied to two-photon excitation time-resolved photoluminescence (2PE-TRPL) but is broadly applicable to all microscopic time-resolved techniques. By solving time-dependent drift-diffusion equations, we gain insight into carrier dynamics and transport characteristics. Accurate understanding of measurement results establishes the limits and potential of the measurement and enhances its value as a characterization method. Diffusion of carriers outside of the collection volume can have a significant impact on the measured decay but can also provide an estimate of carrier mobility as well as lifetime. In addition to material parameters, the experimental conditions, such as spot size and injection level, can impact the measurement results. Although small spot size provides better resolution, it also increases the impact of diffusion on the decay; if the spot size is much smaller than the diffusion length, it impacts the entire decay. By reproducing experimental 2PE-TRPL decays, the simulations determine the bulk carrier lifetime from the data. The analysis is applied to single-crystal and heteroepitaxial CdTe, material important for solar cells, but it is also applicable to other semiconductors where carrier diffusion from the excitation volume could affect experimental measurements

Non-monotonic effect of growth temperature on carrier collection in SnS solar cells

International Nuclear Information System (INIS)

Chakraborty, R.; Steinmann, V.; Mangan, N. M.; Brandt, R. E.; Poindexter, J. R.; Jaramillo, R.; Mailoa, J. P.; Hartman, K.; Polizzotti, A.; Buonassisi, T.; Yang, C.; Gordon, R. G.

2015-01-01

We quantify the effects of growth temperature on material and device properties of thermally evaporated SnS thin-films and test structures. Grain size, Hall mobility, and majority-carrier concentration monotonically increase with growth temperature. However, the charge collection as measured by the long-wavelength contribution to short-circuit current exhibits a non-monotonic behavior: the collection decreases with increased growth temperature from 150 °C to 240 °C and then recovers at 285 °C. Fits to the experimental internal quantum efficiency using an opto-electronic model indicate that the non-monotonic behavior of charge-carrier collection can be explained by a transition from drift- to diffusion-assisted components of carrier collection. The results show a promising increase in the extracted minority-carrier diffusion length at the highest growth temperature of 285 °C. These findings illustrate how coupled mechanisms can affect early stage device development, highlighting the critical role of direct materials property measurements and simulation

Direct minority carrier transport characterization of InAs/InAsSb superlattice nBn photodetectors

International Nuclear Information System (INIS)

Zuo, Daniel; Liu, Runyu; Wasserman, Daniel; Mabon, James; He, Zhao-Yu; Liu, Shi; Zhang, Yong-Hang; Kadlec, Emil A.; Olson, Benjamin V.; Shaner, Eric A.

2015-01-01

We present an extensive characterization of the minority carrier transport properties in an nBn mid-wave infrared detector incorporating a Ga-free InAs/InAsSb type-II superlattice as the absorbing region. Using a modified electron beam induced current technique in conjunction with time-resolved photoluminescence, we were able to determine several important transport parameters of the absorber region in the device, which uses a barrier layer to reduce dark current. For a device at liquid He temperatures, we report a minority carrier diffusion length of 750 nm and a minority carrier lifetime of 200 ns, with a vertical diffusivity of 3 × 10 −2  cm 2 /s. We also report on the device's optical response characteristics at 78 K

No differences in brain microstructure between young KIBRA-C carriers and non-carriers.

Science.gov (United States)

Hu, Li; Xu, Qunxing; Li, Jizhen; Wang, Feifei; Xu, Xinghua; Sun, Zhiyuan; Ma, Xiangxing; Liu, Yong; Wang, Qing; Wang, Dawei

2018-01-02

KIBRA rs17070145 polymorphism is associated with variations in memory function and the microstructure of related brain areas. Diffusion kurtosis imaging (DKI) as an extension of diffusion tensor imaging that can provide more information about changes in microstructure, based on the idea that water diffusion in biological tissues is heterogeneous due to structural hindrance and restriction. We used DKI to explore the relationship between KIBRA gene polymorphism and brain microstructure in young adults. We recruited 100 healthy young volunteers, including 53 TT carriers and 47 C allele carriers. No differences were detected between the TT homozygotes and C-allele carriers for any diffusion and kurtosis parameter. These results indicate KIBRA rs17070145 polymorphism likely has little or no effect on brain microstructure in young adults.

Roles of binding energy and diffusion length of singlet and triplet excitons in organic heterojunction solar cells

International Nuclear Information System (INIS)

Narayan, Monishka Rita; Singh, Jai

2012-01-01

The influence of binding energy and diffusion length on the dissociation of excitons in organic solids is studied. The binding energy and excitonic Bohr radius of singlet and triplet excitons are calculated and compared using the dissociation energy of 0.3 eV, which is provided by the lowest unoccupied molecular orbital offset in heterojunction organic solar cells. A relation between the diffusion coefficient and diffusion length of singlet and triplet excitons is derived using the Foerster and Dexter transfer processes and are plotted as a function of the donor-acceptor separation. The diffusion length reduces nearly to a zero if the distance between donor and acceptor is increased to more than 1.5 nm. It is found that the donor-acceptor separation needs to be ≤ 1.5 nm for easy dissociation on singlet excitons leading to better conversion efficiency in heterojunction organic solar cells. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Roles of binding energy and diffusion length of singlet and triplet excitons in organic heterojunction solar cells

Energy Technology Data Exchange (ETDEWEB)

Narayan, Monishka Rita [Centre for Renewable Energy and Low Emission Technology, Charles Darwin University, Darwin, NT 0909 (Australia); Singh, Jai [School of Engineering and IT, Charles Darwin University, Darwin, NT 0909 (Australia)

2012-12-15

The influence of binding energy and diffusion length on the dissociation of excitons in organic solids is studied. The binding energy and excitonic Bohr radius of singlet and triplet excitons are calculated and compared using the dissociation energy of 0.3 eV, which is provided by the lowest unoccupied molecular orbital offset in heterojunction organic solar cells. A relation between the diffusion coefficient and diffusion length of singlet and triplet excitons is derived using the Foerster and Dexter transfer processes and are plotted as a function of the donor-acceptor separation. The diffusion length reduces nearly to a zero if the distance between donor and acceptor is increased to more than 1.5 nm. It is found that the donor-acceptor separation needs to be {<=} 1.5 nm for easy dissociation on singlet excitons leading to better conversion efficiency in heterojunction organic solar cells. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Diffusion effects on volume-selective NMR at small length scales

International Nuclear Information System (INIS)

Gaedke, Achim

2009-01-01

In this thesis, the interplay between diffusion and relaxation effects in spatially selective NMR experiments at short length scales is explored. This is especially relevant in the context of both conventional and mechanically detected MRI at (sub)micron resolution in biological specimens. Recent results on selectively excited very thin slices showed an in-slice-magnetization recovery orders of magnitude faster than the longitudinal relaxation time T1. However, those experiments were run on fully relaxed samples while MRI and especially mechanically detected NMR experiments are typically run in a periodic fashion with repetition times far below T1. The main purpose of this work therefore was to extend the study of the interplay between diffusion and longitudinal relaxation to periodic excitations. In some way, this is inverse phenomenon to the DESIRE (Diffusive Enhancement of SIgnal and REsolution) approach, proposed 1992 by Lauterbur. Experiments on periodically excited thin slices were carried out at a dedicated static field gradient cryomagnet with magnetic field gradients up to 180 T/m. In order to obtain plane slices, an appropriate isosurface of the gradient magnet had to be identified. It was found at a field of 3.8 T with a gradient of 73 T/m. In this field, slices down to a thickness of 3.2 μm could be excited. The detection of the NMR signal was done using FIDs instead of echoes as the excitation bandwidth of those thin slices is sufficiently small to observe FIDs which are usually considered to be elusive to detection in such strong static field gradients. A simulation toolbox based on the full Bloch-Torrey-equation was developed to describe the excitation and the formation of NMR signals under those unusual conditions as well as the interplay of diffusion and magnetization recovery. Both the experiments and the simulations indicate that diffusion effects lead to a strongly enhanced magnetization modulation signal also under periodic excitation

Correlation of optical emission and turbulent length scale in a coaxial jet diffusion flame

OpenAIRE

松山, 新吾; Matsuyama, Shingo

2014-01-01

This article investigates the correlation between optical emission and turbulent length scale in a coaxial jet diffusion flame. To simulate the H2O emission from an H2/O2 diffusion flame, radiative transfer is calculated on flame data obtained by numerical simulation. H2O emission characteristics are examined for a one-dimensional opposed-flow diffusion flame. The results indicate that H2O emission intensity is linearly dependent on flame thickness. The simulation of H2O emission is then exte...

Centimetre-scale electron diffusion in photoactive organic heterostructures

Science.gov (United States)

Burlingame, Quinn; Coburn, Caleb; Che, Xiaozhou; Panda, Anurag; Qu, Yue; Forrest, Stephen R.

2018-02-01

The unique properties of organic semiconductors, such as flexibility and lightness, are increasingly important for information displays, lighting and energy generation. But organics suffer from both static and dynamic disorder, and this can lead to variable-range carrier hopping, which results in notoriously poor electrical properties, with low electron and hole mobilities and correspondingly short charge-diffusion lengths of less than a micrometre. Here we demonstrate a photoactive (light-responsive) organic heterostructure comprising a thin fullerene channel sandwiched between an electron-blocking layer and a blended donor:C70 fullerene heterojunction that generates charges by dissociating excitons. Centimetre-scale diffusion of electrons is observed in the fullerene channel, and this can be fitted with a simple electron diffusion model. Our experiments enable the direct measurement of charge diffusivity in organic semiconductors, which is as high as 0.83 ± 0.07 square centimetres per second in a C60 channel at room temperature. The high diffusivity of the fullerene combined with the extraordinarily long charge-recombination time yields diffusion lengths of more than 3.5 centimetres, orders of magnitude larger than expected for an organic system.

A voxel-based morphometry and diffusion tensor imaging analysis of asymptomatic Parkinson's disease-related G2019S LRRK2 mutation carriers.

Science.gov (United States)

Thaler, Avner; Artzi, Moran; Mirelman, Anat; Jacob, Yael; Helmich, Rick C; van Nuenen, Bart F L; Gurevich, Tanya; Orr-Urtreger, Avi; Marder, Karen; Bressman, Susan; Bloem, Bastiaan R; Hendler, Talma; Giladi, Nir; Ben Bashat, Dafna

2014-05-01

Patients with Parkinson's disease have reduced gray matter volume and fractional anisotropy in both cortical and sub-cortical structures, yet changes in the pre-motor phase of the disease are unknown. A comprehensive imaging study using voxel-based morphometry and diffusion tensor imaging tract-based spatial statistics analysis was performed on 64 Ashkenazi Jewish asymptomatic first degree relatives of patients with Parkinson's disease (30 mutation carriers), who carry the G2019S mutation in the leucine-rich repeat kinase 2 (LRRK2) gene. No between-group differences in gray matter volume could be noted in either whole-brain or volume-of-interest analysis. Diffusion tensor imaging analysis did not identify group differences in white matter areas, and volume-of-interest analysis identified no differences in diffusivity parameters in Parkinson's disease-related structures. G2019S carriers do not manifest changes in gray matter volume or diffusivity parameters in Parkinson's disease-related structures prior to the appearance of motor symptoms. © 2014 International Parkinson and Movement Disorder Society.

Magnetic field dependence of the magnon spin diffusion length in the magnetic insulator yttrium iron garnet

NARCIS (Netherlands)

Cornelissen, L. J.; van Wees, B. J.

2016-01-01

We investigated the effect of an external magnetic field on the diffusive spin transport by magnons in the magnetic insulator Y3Fe5O12, using a nonlocal magnon transport measurement geometry. We observed a decrease in magnon spin diffusion length lambda(m) for increasing field strengths, where

Enhancing light absorption within the carrier transport length in quantum junction solar cells.

Science.gov (United States)

Fu, Yulan; Hara, Yukihiro; Miller, Christopher W; Lopez, Rene

2015-09-10

Colloidal quantum dot (CQD) solar cells have attracted tremendous attention because of their tunable absorption spectrum window and potentially low processing cost. Recently reported quantum junction solar cells represent a promising approach to building a rectifying photovoltaic device that employs CQD layers on each side of the p-n junction. However, the ultimate efficiency of CQD solar cells is still highly limited by their high trap state density in both p- and n-type CQDs. By modeling photonic structures to enhance the light absorption within the carrier transport length and by ensuring that the carrier generation and collection efficiencies were both augmented, our work shows that overall device current density could be improved. We utilized a two-dimensional numerical model to calculate the characteristics of patterned CQD solar cells based on a simple grating structure. Our calculation predicts a short circuit current density as high as 31  mA/cm2, a value nearly 1.5 times larger than that of the conventional flat design, showing the great potential value of patterned quantum junction solar cells.

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

Science.gov (United States)

Weizer, V. G.; Godlewski, M. P.

1984-01-01

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

Measurement of minority carrier lifetime in silicon solar cells using an a. c. light source

Energy Technology Data Exchange (ETDEWEB)

Nagpal, A.; Gupta, R.S.; Srivastava, G.P. (Delhi Univ., New Delhi (India). Dept. of Electronic Sciences); Jain, V.K. (Solid State Physics Lab., Delhi (India)); Chilana, G.S. (Delhi Univ. (India). Dept. of Physics and Astrophysics)

1990-06-01

A simple technique for the measurement of minority carriers lifetimes is proposed. It is based on the modification of the junction structure by the addition of a d.c. bias to the a.c. source. This always keeps the solar cell in the forward biased condition and also keeps it in the operating range. This method provides a direct measurement of minority carriers lifetimes. The lifetime is found to increase from 2.89 {mu}s at 30deg C to 4.55 {mu}s at 120deg C. The lifetime reduces to 1.45 {mu}s at liquid air temperature. Based on these lifetime measurements, the diffusion length of the carriers has also been calculated. (orig.).

Minority Carrier Lifetime and Photoluminescence Studies of Antimony-Based Superlattices

Science.gov (United States)

Hoglund, Linda; Soibel, Alexander; Ting, David Z.; Khoshakhlagh, Arezou; Hill, Cory J.; Gunapala, Sarath D.

2012-01-01

In this paper, we have used the OMR technique to study the minority carrier lifetimes in three InAs/GaSb-photoluminescence (PL) structures with different number of periods in the absorber: 300, 400 and 600 periods respectively. The feasibility of using a visible 643 nm laser source with short penetration depth for lifetime measurements was studied by comparing the achieved results to measurements performed on the same samples with a 1550 nm IR laser source, which penetrates much deeper into the sample. Despite the differences in excitation wavelengths and penetration depths, the results from both measurements were very similar. This indicates that the diffusion length is long enough to facilitate a homogeneous distribution of excess carriers in the material.

Strongly extended diffusion length for the nonequilibrium magnons in Y3F e5O12 by photoexcitation

Science.gov (United States)

Wang, S. H.; Li, G.; Guo, E. J.; Zhao, Y.; Wang, J. Y.; Zou, L. K.; Yan, H.; Cai, J. W.; Zhang, Z. T.; Wang, M.; Tian, Y. Y.; Zheng, X. L.; Sun, J. R.; Jin, K. X.

2018-05-01

Y3F e5O12 (YIG) is known for its long magnon diffusion length. Although it has the known lowest damping rate, an even longer diffusion distance is still highly desired since it may lead to a much more efficient information transmission and processing. While most of previous works focused on the generation and detection of magnons in YIG, here we demonstrate how to depress the damping rate during the diffusion of magnon. By selectively exciting the spin state transition of the Fe ions in YIG, we successfully increase magnon diffusion length by one order of magnitude, i.e., from the previous reported ˜10 μm up to ˜156 μm (for the sample prepared by liquid phase epitaxy) and ˜180 μm (for the sample prepared by pulsed laser deposition) at room temperature. The diffusion length, determined by nonlocal geometry, is ˜30 μm for the magnons induced by visible light and above 150 μm for the laser of 980 nm. In addition to thermal gradient, light excitation affects the electron configuration of the F e3 + ion in YIG. Long-wavelength laser is more effective since it causes a transition of the F e3 + ions in Fe O6 octahedron from a high spin to a low spin state and thus causes a magnon softening which favors a long-distance diffusion. The present work paves the way toward an efficient tuning of magnon transport which is crucially important for magnon spintronics.

Two independent measurements of Debye lengths in doped nonpolar liquids.

Science.gov (United States)

Prieve, D C; Hoggard, J D; Fu, R; Sides, P J; Bethea, R

2008-02-19

Electric current measurements were performed between 2.5 cm x 7.5 cm parallel-plate electrodes separated by 1.2 mm of heptane doped with 0-15% w/w poly(isobutylene succinimide) (PIBS) having a molecular weight of about 1700. The rapid (microsecond) initial charging of the capacitor can be used to infer the dielectric constant of the solution. The much slower decay of current arising from the polarization of electrodes depends on the differential capacitance of the diffuse clouds of charge carriers accumulating next to each electrode and on the ohmic resistance of the fluid. Using the Gouy-Chapman model for the differential capacitance, Debye lengths of 80-600 nm were deduced that decrease with increasing concentration of PIBS. Values of the Debye lengths were confirmed by performing independent measurements of double-layer repulsion between a 6 microm polystyrene (PS) latex sphere and a PS-coated glass plate using total internal reflection microscopy in the same solutions. The charge carriers appear to be inverted PIBS micelles having apparent Stokes diameters of 20-40 nm. Dynamic light scattering reveals a broad distribution of sizes having an intensity-averaged diameter of 15 nm. This smaller size might arise (1) from overestimating the electrophoretic mobility of micelles by treating them as point charges or (2) because charged micelles are larger on average than uncharged micelles. When Faradaic reactions and zeta potentials on the electrodes can be neglected, such current versus time experiments yield values for the Debye length and ionic strength with less effort than force measurements. To obtain the concentration of charge carriers from measurements of conductivity, the mobility of the charge carriers must be known.

Turbulent jet diffusion flame length evolution with cross flows in a sub-pressure atmosphere

International Nuclear Information System (INIS)

Wang, Qiang; Hu, Longhua; Zhang, Xiaozheng; Zhang, Xiaolei; Lu, Shouxiang; Ding, Hang

2015-01-01

Highlights: • Quantifying turbulent jet diffusion flame length with cross flows. • Unique data revealed for a sub-atmospheric pressure. • Non-dimensional global correlation proposed for flame trajectory-line length. - Abstract: This paper investigates the evolution characteristics of turbulent jet diffusion flame (flame trajectory-line length, flame height in vertical jet direction) with increasing cross flows in a sub-pressure (64 kPa) atmosphere. The combined effect of cross flow and a special sub-pressure atmosphere condition is revealed, where no data is available in the literatures. Experiments are carried out with a wind tunnel built specially in Lhasa city (altitude: 3650 m; pressure: 64 kPa) and in Hefei city (altitude: 50 m; pressure: 100 kPa), using nozzles with diameter of 3 mm, 4 mm and 5 mm and propane as fuel. It is found that, as cross flow air speed increases from zero, the flame trajectory-line length firstly decreases and then becomes almost stable (for relative small nozzle, 3 mm in this study) or increases (for relative large nozzle, 4 mm and 5 mm in this study) beyond a transitional critical cross flow air speed in normal pressure, however decreases monotonically until being blown-out in the sub-pressure atmosphere. The flame height in jet direction decreases monotonically with cross air flow speed and then reaches a steady value in both pressures. For the transitional state of flame trajectory-line length with increasing cross air flow speed, the corresponding critical cross flow air speed is found to be proportional to the fuel jet velocity, meanwhile independent of nozzle diameter. Correlation models are proposed for the flame height in jet direction and the flame trajectory-line length for both ambient pressures, which are shown to be in good agreement with the experimental results.

Measurement of the diffusion length of thermal neutrons inside graphite; Mesure de la longueur de diffusion des neutrons thermiques dans le graphite

Energy Technology Data Exchange (ETDEWEB)

Ertaud, A; Beauge, R; Fauquez, H; De Laboulay, H; Mercier, C; Vautrey, L

1948-11-01

The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra {alpha} {yields} Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm {+-} 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)

Improved longitudinal length accuracy of gross tumor volume delineation with diffusion weighted magnetic resonance imaging for esophageal squamous cell carcinoma

International Nuclear Information System (INIS)

Hou, Dong-Liang; Shi, Gao-Feng; Gao, Xian-Shu; Asaumi, Junichi; Li, Xue-Ying; Liu, Hui; Yao, Chen; Chang, Joe Y

2013-01-01

To analyze the longitudinal length accuracy of gross tumor volume (GTV) delineation with diffusion weighted magnetic resonance imaging for esophageal squamous cell carcinoma (SCC). Forty-two patients from December 2011 to June 2012 with esophageal SCC who underwent radical surgery were analyzed. Routine computed tomography (CT) scan, T2-weighted MRI and diffusion weighted magnetic resonance imaging (DWI) were employed before surgery. Diffusion-sensitive gradient b-values were taken at 400, 600, and 800 s/mm 2 . Gross tumor volumes (GTV) were delineated using CT, T2-weighted MRI and DWI on different b-value images. GTV longitude length measured using the imaging modalities listed above was compared with pathologic lesion length to determine the most accurate imaging modality. CMS Xio radiotherapy planning system was used to fuse DWI scans and CT images to investigate the possibility of delineating GTV on fused images. The differences between the GTV length according to CT, T2-weighted MRI and pathology were 3.63 ± 12.06 mm and 3.46 ± 11.41 mm, respectively. When the diffusion-sensitive gradient b-value was 400, 600, and 800 s/mm 2 , the differences between the GTV length using DWI and pathology were 0.73 ± 6.09 mm, -0.54 ± 6.03 mm and −1.58 ± 5.71 mm, respectively. DWI scans and CT images were fused accurately using the radiotherapy planning system. GTV margins were depicted clearly on fused images. DWI displays esophageal SCC lengths most precisely when compared with CT or regular MRI. DWI scans fused with CT images can be used to improve accuracy to delineate GTV in esophageal SCC

Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks.

Science.gov (United States)

Hwang, Seungtaik; Gopalan, Arun; Hovestadt, Maximilian; Piepenbreier, Frank; Chmelik, Christian; Hartmann, Martin; Snurr, Randall Q; Kärger, Jörg

2018-03-15

Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n- alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n- butane was observed, followed by an increase for n- pentane, and another decrease for n- hexane. This observation was confirmed by uptake measurements with n- butane/ n -pentane mixtures, which yield faster uptake of n- pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n- pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n- alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks

Directory of Open Access Journals (Sweden)

Seungtaik Hwang

2018-03-01

Full Text Available Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.

The thermoballistic transport model a novel approach to charge carrier transport in semiconductors

CERN Document Server

Lipperheide, Reinhard

2014-01-01

The book presents a comprehensive survey of the thermoballistic approach to charge carrier transport in semiconductors. This semi-classical approach, which the authors have developed over the past decade, bridges the gap between the opposing drift-diffusion and ballistic  models of carrier transport. While incorporating basic features of the latter two models, the physical concept underlying the thermoballistic approach constitutes a novel, unifying scheme. It is based on the introduction of "ballistic configurations" arising from a random partitioning of the length of a semiconducting sample into ballistic transport intervals. Stochastic averaging of the ballistic carrier currents over the ballistic configurations results in a position-dependent thermoballistic current, which is the key element of the thermoballistic concept and forms  the point of departure for the calculation of all relevant transport properties. In the book, the thermoballistic concept and its implementation are developed in great detai...

Measurement of the diffusion length of thermal neutrons in the beryllium oxide; Mesure de la longueur de diffusion des neutrons thermiques dans l'oxyde de beryllium

Energy Technology Data Exchange (ETDEWEB)

Koechlin, J C; Martelly, J; Duggal, V P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

The diffusion length of thermal neutrons in the beryllium oxide has been obtained while studying the spatial distribution of the neutrons in a massive parallelepiped of this matter placed before the thermal column of the reactor core of Saclay. The mean density of the beryllium oxide (BeO) is 2,95 gr/cm{sup 3}, the mean density of the massif is 2,92 gr/cm{sup 3}. The value of the diffusion length, deducted of the done measures, is: L = 32,7 {+-} 0,5 cm (likely gap). Some remarks are formulated about the influence of the spectral distribution of the neutrons flux used. (authors) [French] La longueur de diffusion des neutrons thermiques dans l'oxyde de beryllium a ete obtenue en etudiant la repartition spatiale des neutrons dans un massif parallelepipedique de cette matiere placee devant la colonne thermique de la Pile de Saclay. La densite moyenne de l'oxyde de beryllium (BeO) est de 2,95 gr/cm{sup 3}, la densite moyenne du massif de 2,92 gr/cm{sup 3}. La valeur de la longueur de diffusion, deduite des mesures effectuees est: L 32,7 {+-} 0,5 cm (ecart probable). Des remarques sont formulees quant a l'influence de la repartition spectrale du flux de neutrons utilise. (auteurs)

Microscopic study on the carrier distribution in optoelectronic device structures: experiment and modeling

Science.gov (United States)

Huang, Wenchao; Xia, Hui; Wang, Shaowei; Deng, Honghai; Wei, Peng; Li, Lu; Liu, Fengqi; Li, Zhifeng; Li, Tianxin

2011-12-01

Scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) both are capable of mapping the 2-demensional carrier distribution in semiconductor device structures, which is essential in determining their electrical and optoelectronic performances. In this work, cross-sectional SCM1,2 is used to study the InGaAs/InP P-i-N junctions prepared by area-selective p-type diffusion. The diffusion lengths in the depth as well as the lateral directions are obtained for junctions under different window sizes in mask, which imply that narrow windows may result in shallow p-n junctions. The analysis is beneficial to design and fabricate focal plane array of near infrared photodetectors with high duty-cycle and quantum efficiency. On the other hand, SSRM provides unparalleled spatial resolution (demanded for studying low-dimensional structures. However, to derive the carrier density from the measured local conductance in individual quantum structures, reliable model for SSRM is necessary but still not well established. Based on the carrier concentration related transport mechanisms, i.e. thermionic emission and thermionic field emission4,5, we developed a numerical model for the tip-sample Schottky contact4. The calculation is confronted with SSRM study on the dose-calibrated quantum wells (QWs).

Bacterial Carriers for Glioblastoma Therapy

Directory of Open Access Journals (Sweden)

Nalini Mehta

2017-03-01

Full Text Available Treatment of aggressive glioblastoma brain tumors is challenging, largely due to diffusion barriers preventing efficient drug dosing to tumors. To overcome these barriers, bacterial carriers that are actively motile and programmed to migrate and localize to tumor zones were designed. These carriers can induce apoptosis via hypoxia-controlled expression of a tumor suppressor protein p53 and a pro-apoptotic drug, Azurin. In a xenograft model of human glioblastoma in rats, bacterial carrier therapy conferred a significant survival benefit with 19% overall long-term survival of >100 days in treated animals relative to a median survival of 26 days in control untreated animals. Histological and proteomic analyses were performed to elucidate the safety and efficacy of these carriers, showing an absence of systemic toxicity and a restored neural environment in treated responders. In the treated non-responders, proteomic analysis revealed competing mechanisms of pro-apoptotic and drug-resistant activity. This bacterial carrier opens a versatile avenue to overcome diffusion barriers in glioblastoma by virtue of its active motility in extracellular space and can lead to tailored therapies via tumor-specific expression of tumoricidal proteins.

MAGNETIC QUENCHING OF TURBULENT DIFFUSIVITY: RECONCILING MIXING-LENGTH THEORY ESTIMATES WITH KINEMATIC DYNAMO MODELS OF THE SOLAR CYCLE

International Nuclear Information System (INIS)

Munoz-Jaramillo, Andres; Martens, Petrus C. H.; Nandy, Dibyendu

2011-01-01

The turbulent magnetic diffusivity in the solar convection zone is one of the most poorly constrained ingredients of mean-field dynamo models. This lack of constraint has previously led to controversy regarding the most appropriate set of parameters, as different assumptions on the value of turbulent diffusivity lead to radically different solar cycle predictions. Typically, the dynamo community uses double-step diffusivity profiles characterized by low values of diffusivity in the bulk of the convection zone. However, these low diffusivity values are not consistent with theoretical estimates based on mixing-length theory, which suggest much higher values for turbulent diffusivity. To make matters worse, kinematic dynamo simulations cannot yield sustainable magnetic cycles using these theoretical estimates. In this work, we show that magnetic cycles become viable if we combine the theoretically estimated diffusivity profile with magnetic quenching of the diffusivity. Furthermore, we find that the main features of this solution can be reproduced by a dynamo simulation using a prescribed (kinematic) diffusivity profile that is based on the spatiotemporal geometric average of the dynamically quenched diffusivity. This bridges the gap between dynamically quenched and kinematic dynamo models, supporting their usage as viable tools for understanding the solar magnetic cycle.

The effects of metallicity, radiation field and dust extinction on the charge state of PAHs in diffuse clouds: implications for the DIB carrier

NARCIS (Netherlands)

Cox, N.L.J.; Spaans, M.

2006-01-01

Context.The unidentified diffuse interstellar bands (DIB) are observed throughout the Galaxy, the Local Group and beyond. Their carriers are possibly related to complex carbonaceous gas-phase molecules, such as (cationic) polycyclic aromatic hydrocarbons and fullerenes. Aims.In order to reveal the

The effects of metallicity, radiation field and dust extinction on the charge state of PAHs in diffuse clouds : implications for the DIB carrier

NARCIS (Netherlands)

Cox, NLJ; Spaans, M

Context. The unidentified diffuse interstellar bands (DIB) are observed throughout the Galaxy, the Local Group and beyond. Their carriers are possibly related to complex carbonaceous gas-phase molecules, such as (cationic) polycyclic aromatic hydrocarbons and fullerenes. Aims. In order to reveal the

Near-infrared free carrier absorption in heavily doped silicon

International Nuclear Information System (INIS)

Baker-Finch, Simeon C.; McIntosh, Keith R.; Yan, Di; Fong, Kean Chern; Kho, Teng C.

2014-01-01

Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10 18 and 3 × 10 20  cm −3 . Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis

Diffusion length of positrons and positronium investigated using a positronbeam with longitudinal geometry

Science.gov (United States)

van Petegem, S.; Dauwe, C.; van Hoecke, T.; de Baerdemaeker, J.; Segers, D.

2004-09-01

Positronium emission from single crystalline Al2O3 , MgO and vitreous a-SiO2 surfaces was studied as a function of the positron implantation energy E by means of Doppler broadening spectroscopy and Compton-to-peak ratio analysis. When the Ge-detector is in-line with the positron beam, the emission of para-positronium yields a red-shifted fly-away peak with intensity IpPse . An analysis of IpPse versus E for Al2O3 and MgO where no Ps is formed in the bulk (fPs=0) results in positron diffusion lengths L+(Al2O3)=(18±1)nm and L+(MgO)=(14±1)nm , and efficiencies for the emission of Ps by picking up of a surface electron of fpu(Al2O3)=(0.28±0.2) and fpu(MgO)=(0.24±0.2) . For a-SiO2 the bulk Ps fraction is fPs(a-SiO2)=(0.72±0.01) , fpu(a-SiO2)=(0.12±0.01) and the diffusion lengths of positrons, para-positronium and ortho-positronium are L+(SiO2)=(8±2)nm , LpPs(SiO2)=(14.5±2)nm and LoPs(SiO2)=(11±2)=nm . Depending on the specimen-detector geometry the emission of Ps at low implantation energy may cause either an increase or a decrease of the width of the annihilation line shape at low implantation energies.

Incorporating photon recycling into the analytical drift-diffusion model of high efficiency solar cells

Energy Technology Data Exchange (ETDEWEB)

Lumb, Matthew P. [The George Washington University, 2121 I Street NW, Washington, DC 20037 (United States); Naval Research Laboratory, Washington, DC 20375 (United States); Steiner, Myles A.; Geisz, John F. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Walters, Robert J. [Naval Research Laboratory, Washington, DC 20375 (United States)

2014-11-21

The analytical drift-diffusion formalism is able to accurately simulate a wide range of solar cell architectures and was recently extended to include those with back surface reflectors. However, as solar cells approach the limits of material quality, photon recycling effects become increasingly important in predicting the behavior of these cells. In particular, the minority carrier diffusion length is significantly affected by the photon recycling, with consequences for the solar cell performance. In this paper, we outline an approach to account for photon recycling in the analytical Hovel model and compare analytical model predictions to GaAs-based experimental devices operating close to the fundamental efficiency limit.

Structural vs. intrinsic carriers: contrasting effects of cation chemistry and disorder on ionic conductivity in pyrochlores

International Nuclear Information System (INIS)

Perriot, Romain; Uberuaga, Blas P.

2015-01-01

We use molecular dynamics simulations to investigate the role of cation disorder on oxygen diffusion in Gd 2 Zr 2 O 7 (GZO) and Gd 2 Ti 2 O 7 (GTO) pyrochlores, a class of complex oxides which contain a structural vacancy relative to the basic fluorite structure. The introduction of disorder has distinct effects depending on the chemistry of the material, increasing the mobility of structural carriers by up to four orders of magnitude in GZO. In contrast, in GTO, there is no mobility at zero or low disorder on the ns timescale, but higher disorder liberates the otherwise immobile carriers, allowing diffusion with rates comparable to GZO for the fully disordered material. Here, we show that the cation disorder enhances the diffusivity by both increasing the concentration of mobile structural carriers and their individual mobility. The disorder also influences the diffusion in materials containing intrinsic carriers, such as additional vacancies VO or oxygen interstitials OI. And while in ordered GZO and GTO the contribution of the intrinsic carriers dominates the overall diffusion of oxygen, OI in GZO contributes along with structural carriers, and the total diffusion rate can be calculated by assuming simple additive contributions from the two sources. Although the disorder in the materials with intrinsic defects usually enhances the diffusivity as in the defect-free case, in low concentrations, cation antisites AB or BA, where A = Gd and B = Zr or Ti, can act as traps for fast intrinsic defects. The trapping results in a lowering of the diffusivity, and causes a non-monotonic behavior of the diffusivity with disorder. Conversely, in the case of slow intrinsic defects, the main effect of the disorder is to liberate the structural carriers, resulting in an increase of the diffusivity regardless of the defect trapping.

Probing Exciton Diffusion and Dissociation in Single-Walled Carbon Nanotube-C60 Heterojunctions

Energy Technology Data Exchange (ETDEWEB)

Dowgiallo, Anne-Marie; Mistry, Kevin S.; Johnson, Justin C.; Reid, Obadiah G.; Blackburn, Jeffrey L.

2016-05-19

The efficiency of thin-film organic photovoltaic (OPV) devices relies heavily upon the transport of excitons to type-II heterojunction interfaces, where there is sufficient driving force for exciton dissociation and ultimately the formation of charge carriers. Semiconducting single-walled carbon nanotubes (SWCNTs) are strong near-infrared absorbers that form type-II heterojunctions with fullerenes such as C60. Although the efficiencies of SWCNT-fullerene OPV devices have climbed over the past few years, questions remain regarding the fundamental factors that currently limit their performance. In this study, we determine the exciton diffusion length in the C60 layer of SWCNT-C60 bilayer active layers using femtosecond transient absorption measurements. We demonstrate that hole transfer from photoexcited C60 molecules to SWCNTs can be tracked by the growth of narrow spectroscopic signatures of holes in the SWCNT 'reporter layer'. In bilayers with thick C60 layers, the SWCNT charge-related signatures display a slow rise over hundreds of picoseconds, reflecting exciton diffusion through the C60 layer to the interface. A model based on exciton diffusion with a Beer-Lambert excitation profile, as well as Monte Carlo simulations, gives the best fit to the data as a function of C60 layer thickness using an exciton diffusion length of approximately 5 nm.

INTERACTION BETWEEN THE BROAD-LINED TYPE Ic SUPERNOVA 2012ap AND CARRIERS OF DIFFUSE INTERSTELLAR BANDS

International Nuclear Information System (INIS)

Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Soderberg, Alicia M.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish; Chakraborti, Sayan; Kirshner, Robert P.; Foster, Jonathan B.; Fesen, Robert A.; Parrent, Jerod T.; Pickering, Timothy E.; Cenko, S. Bradley; Silverman, Jeffrey M.; Marion, G. H. Howie; Vinko, Jozsef; Filippenko, Alexei V.; Mazzali, Paolo; Maeda, Keiichi

2014-01-01

Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (≲ 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with time, whereas the 5780 Å feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers

INTERACTION BETWEEN THE BROAD-LINED TYPE Ic SUPERNOVA 2012ap AND CARRIERS OF DIFFUSE INTERSTELLAR BANDS

Energy Technology Data Exchange (ETDEWEB)

Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Soderberg, Alicia M.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish; Chakraborti, Sayan; Kirshner, Robert P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Foster, Jonathan B. [Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States); Fesen, Robert A.; Parrent, Jerod T. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Lab, Hanover, NH 03755 (United States); Pickering, Timothy E. [Southern African Large Telescope, P.O. Box 9, Observatory 7935, Cape Town (South Africa); Cenko, S. Bradley [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Silverman, Jeffrey M.; Marion, G. H. Howie; Vinko, Jozsef [University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Mazzali, Paolo [Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom); Maeda, Keiichi, E-mail: dmilisav@cfa.harvard.edu [Department of Astronomy, Kyoto University Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); and others

2014-02-10

Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (≲ 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with time, whereas the 5780 Å feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers.

Tracking Ultrafast Carrier Dynamics in Single Semiconductor Nanowire Heterostructures

Directory of Open Access Journals (Sweden)

Taylor A.J.

2013-03-01

Full Text Available An understanding of non-equilibrium carrier dynamics in silicon (Si nanowires (NWs and NW heterostructures is very important due to their many nanophotonic and nanoelectronics applications. Here, we describe the first measurements of ultrafast carrier dynamics and diffusion in single heterostructured Si nanowires, obtained using ultrafast optical microscopy. By isolating individual nanowires, we avoid complications resulting from the broad size and alignment distribution in nanowire ensembles, allowing us to directly probe ultrafast carrier dynamics in these quasi-one-dimensional systems. Spatially-resolved pump-probe spectroscopy demonstrates the influence of surface-mediated mechanisms on carrier dynamics in a single NW, while polarization-resolved femtosecond pump-probe spectroscopy reveals a clear anisotropy in carrier lifetimes measured parallel and perpendicular to the NW axis, due to density-dependent Auger recombination. Furthermore, separating the pump and probe spots along the NW axis enabled us to track space and time dependent carrier diffusion in radial and axial NW heterostructures. These results enable us to reveal the influence of radial and axial interfaces on carrier dynamics and charge transport in these quasi-one-dimensional nanosystems, which can then be used to tailor carrier relaxation in a single nanowire heterostructure for a given application.

Spin-diffusion lengths in metals and alloys, and spin-flipping at metal/metal interfaces: an experimentalist's critical review

International Nuclear Information System (INIS)

Bass, Jack; Pratt, William P Jr

2007-01-01

In magnetoresistance (MR) studies of magnetic multilayers composed of combinations of ferromagnetic (F) and non-magnetic (N) metals, the magnetic moment (or related 'spin') of each conduction electron plays a crucial role, supplementary to that of its charge. While initial analyses of MR in such multilayers assumed that the direction of the spin of each electron stayed fixed as the electron transited the multilayer, we now know that this is true only in a certain limit. Generally, the spins 'flip' in a distance characteristic of the metal, its purity, and the temperature. They can also flip at F/N or N1/N2 interfaces. In this review we describe how to measure the lengths over which electron moments flip in pure metals and alloys, and the probability of spin-flipping at metallic interfaces. Spin-flipping within metals is described by a spin-diffusion length, l sf M , where the metal M F or N. Spin-diffusion lengths are the characteristic lengths in the current-perpendicular-to-plane (CPP) and lateral non-local (LNL) geometries that we focus upon in this review. In certain simple cases, l sf N sets the distance over which the CPP-MR and LNL-MR decrease as the N-layer thickness (CPP-MR) or N-film length (LNL) increases, and l sf F does the same for increase of the CPP-MR with increasing F-layer thickness. Spin-flipping at M1/M2 interfaces can be described by a parameter, δ M1/M2 , which determines the spin-flipping probability, P = 1-exp(-δ). Increasing δ M1/M2 usually decreases the MR. We list measured values of these parameters and discuss the limitations on their determinations. (topical review)

Diffusion length measurements in bulk and epitaxially grown 3-5 semiconductors using charge collection microscopy

Science.gov (United States)

Leon, R. P.

1987-01-01

Diffusion lengths and surface recombination velocities were measured in GaAs diodes and InP finished solar cells. The basic techniques used was charge collection microscopy also known as electron beam induced current (EBIC). The normalized currents and distances from the pn junction were read directly from the calibrated curves obtained while using the line scan mode in an SEM. These values were then equated to integral and infinite series expressions resulting from the solution of the diffusion equation with both extended generation and point generation functions. This expands previous work by examining both thin and thick samples. The surface recombination velocity was either treated as an unknown in a system of two equations, or measured directly using low e(-) beam accelerating voltages. These techniques give accurate results by accounting for the effects of surface recombination and the finite size of the generation volume.

Preparation of Polysaccharide-Based Microspheres by a Water-in-Oil Emulsion Solvent Diffusion Method for Drug Carriers

Directory of Open Access Journals (Sweden)

Yodthong Baimark

2013-01-01

Full Text Available Polysaccharide-based microspheres of chitosan, starch, and alginate were prepared by the water-in-oil emulsion solvent diffusion method for use as drug carriers. Blue dextran was used as a water-soluble biomacromolecular drug model. Scanning electron microscopy showed sizes of the resultant microspheres that were approximately 100 μm or less. They were spherical in shape with a rough surface and good dispersibility. Microsphere matrices were shown as a sponge. Drug loading efficiencies of all the microspheres were higher than 80%, which suggested that this method has potential to prepare polysaccharide-based microspheres containing a biomacromolecular drug model for drug delivery applications.

Identification of deep trap energies and influences of oxygen plasma ashing on semiconductor carrier lifetime

International Nuclear Information System (INIS)

Koprowski, A; Humbel, O; Plappert, M; Krenn, H

2015-01-01

We have performed an analytical study of the effects of oxygen plasma ashing processes in semiconductor device fabrication and its impact on minority carrier lifetime in high voltage semiconductor devices. Our work includes a critical background study of life time killing mechanisms by deep traps imparted into the semiconductor by barrel plasma ashing. The Elymat technique provides the opportunity to measure lifetime and diffusion length of minority carriers and surface photo voltage (SPV) measurement was used to analyse influences of process parameters such as photoresist, time budget and positioning in the process chamber. It was shown that in microwave plasma processes the diffusion length changes severely with tempering at 200 °C, whereas RF-plasma processes show a significant process time-dependence. Batch tools in general suffer from a strong first wafer effect which could be correlated with the static electrical parameters of the semiconductor devices. The trap identities were detected by using deep level transient spectroscopy and the chemical species of the traps has been proven by inductive coupled plasma mass spectrometry. The deep-bandgap trap energies are reliable fingerprints of the chosen process parameters such as process time and of resist-influences. By microwave plasma processes intrinsic Fe and FeB-complex levels were identified and a good agreement with the SPV-measurement and electrical device characteristic was shown. RF-plasma processes impart levels attributed to Pt levels and an additional level, which could be identified as a trap level probably forming a complex of Pt and H. (paper)

Diffusion transport of nanoparticles at nanochannel boundaries

International Nuclear Information System (INIS)

Mahadevan, T. S.; Milosevic, M.; Kojic, M.; Hussain, F.; Kojic, N.; Serda, R.; Ferrari, M.; Ziemys, A.

2013-01-01

The manipulation of matter at the nanoscale has unleashed a great potential for engineering biomedical drug carriers, but the transport of nanoparticles (NPs) under nanoscale confinement is still poorly understood. Using colloidal physics to describe NP interactions, we have computationally studied the passive transport of NPs using experimentally relevant conditions from bulk into a nanochannel of 60–90 nm height. NP size, channel height, and the Debye length are comparable so that changes in nanoscale dimensions may induce substantial changes in NP transport kinetics. We show that subtle changes in nanochannel dimensions may alter the energy barrier by about six orders of magnitude resulting in different NP penetration depths and diffusion mechanisms: ballistic, first-order and quasi zero-order transport regimes. The analysis of NP diffusion by continuum methods reveals that apparent diffusivity is reduced by decreasing channel size. The continuum finite element (FE) numerical method reproduced the colloidal model results only when surface interactions were accounted for. These results give a new insight into NP passive transport at the boundaries of nanoconfined domains, and have implications on the design of nanoscale fluidics and NP systems for biomedical and engineering applications.

The effect of the cation alkyl chain length on density and diffusion in dialkylpyrrolidinium bis(mandelato)borate ionic liquids.

Science.gov (United States)

Filippov, Andrei; Taher, Mamoun; Shah, Faiz Ullah; Glavatskih, Sergei; Antzutkin, Oleg N

2014-12-28

The physicochemical properties of ionic liquids are strongly affected by the selective combination of the cations and anions comprising the ionic liquid. In particular, the length of the alkyl chains of ions has a clear influence on the ionic liquid's performance. In this paper, we study the self-diffusion of ions in a series of halogen-free boron-based ionic liquids (hf-BILs) containing bis(mandelato)borate anions and dialkylpyrrolidinium cations with long alkyl chains CnH2n+1 with n from 4 to 14 within a temperature range of 293-373 K. It was found that the hf-BILs with n = 4-7 have very similar diffusion coefficients, while hf-BILs with n = 10-14 exhibit two liquid sub-phases in almost the entire temperature range studied (293-353 K). Both liquid sub-phases differ in their diffusion coefficients, while values of the slower diffusion coefficients are close to those of hf-BILs with shorter alkyl chains. To explain the particular dependence of diffusion on the alkyl chain length, we examined the densities of the hf-BILs studied here. It was shown that the dependence of the density on the number of CH2 groups in long alkyl chains of cations can be accurately described using a "mosaic type" model, where regions of long alkyl chains of cations (named 'aliphatic' regions) and the residual chemical moieties in both cations and anions (named 'ionic' regions) give additive contributions. Changes in density due to an increase in temperature and the number of CH2 groups in the long alkyl chains of cations are determined predominantly by changes in the free volume of the 'ionic' regions, while 'aliphatic' regions are already highly compressed by van der Waals forces, which results in only infinitesimal changes in their free volumes with temperature.

Diffusion effects on volume-selective NMR at small length scales; Diffusionseffekte in volumenselektiver NMR auf kleinen Laengenskalen

Energy Technology Data Exchange (ETDEWEB)

Gaedke, Achim

2009-01-21

In this thesis, the interplay between diffusion and relaxation effects in spatially selective NMR experiments at short length scales is explored. This is especially relevant in the context of both conventional and mechanically detected MRI at (sub)micron resolution in biological specimens. Recent results on selectively excited very thin slices showed an in-slice-magnetization recovery orders of magnitude faster than the longitudinal relaxation time T1. However, those experiments were run on fully relaxed samples while MRI and especially mechanically detected NMR experiments are typically run in a periodic fashion with repetition times far below T1. The main purpose of this work therefore was to extend the study of the interplay between diffusion and longitudinal relaxation to periodic excitations. In some way, this is inverse phenomenon to the DESIRE (Diffusive Enhancement of SIgnal and REsolution) approach, proposed 1992 by Lauterbur. Experiments on periodically excited thin slices were carried out at a dedicated static field gradient cryomagnet with magnetic field gradients up to 180 T/m. In order to obtain plane slices, an appropriate isosurface of the gradient magnet had to be identified. It was found at a field of 3.8 T with a gradient of 73 T/m. In this field, slices down to a thickness of 3.2 {mu}m could be excited. The detection of the NMR signal was done using FIDs instead of echoes as the excitation bandwidth of those thin slices is sufficiently small to observe FIDs which are usually considered to be elusive to detection in such strong static field gradients. A simulation toolbox based on the full Bloch-Torrey-equation was developed to describe the excitation and the formation of NMR signals under those unusual conditions as well as the interplay of diffusion and magnetization recovery. Both the experiments and the simulations indicate that diffusion effects lead to a strongly enhanced magnetization modulation signal also under periodic excitation

Low-field mobility and carrier transport mechanism transition in nanoscale MOSFETs

International Nuclear Information System (INIS)

Liu Hongwei; Wang Runsheng; Huang Ru; Zhang Xing

2010-01-01

This paper extends the flux scattering method to study the carrier transport property in nanoscale MOSFETs with special emphasis on the low-field mobility and the transport mechanism transition. A unified analytical expression for the low-field mobility is proposed, which covers the entire regime from drift-diffusion transport to quasi-ballistic transport in 1-D, 2-D and 3-D MOSFETs. Two key parameters, namely the long-channel low-field mobility (μ 0 ) and the low-field mean free path (λ 0 ), are obtained from the experimental data, and the transport mechanism transition in MOSFETs is further discussed both experimentally and theoretically. Our work shows that λ 0 is available to characterize the inherent transition of the carrier transport mechanism rather than the low-field mobility. The mobility reduces in the MOSFET with the shrinking of the channel length; however, λ 0 is nearly a constant, and λ 0 can be used as the 'entry criterion' to determine whether the device begins to operate under quasi-ballistic transport to some extent. (semiconductor devices)

Performance-based standards for South African car-carriers

CSIR Research Space (South Africa)

De Saxe, C

2012-12-01

Full Text Available Until recently, car-carriers in South Africa operated under abnormal load permits allowing a finite relaxation of legal height and length limits. This practice is being phased out, and exemption will only be granted if a car-carrier complies...

Carrier transport dynamics in Mn-doped CdSe quantum dot sensitized solar cells

Science.gov (United States)

Poudyal, Uma; Maloney, Francis S.; Sapkota, Keshab; Wang, Wenyong

2017-10-01

In this work quantum dot sensitized solar cells (QDSSCs) were fabricated with CdSe and Mn-doped CdSe quantum dots (QDs) using the SILAR method. QDSSCs based on Mn-doped CdSe QDs exhibited improved incident photon-to-electron conversion efficiency. Carrier transport dynamics in the QDSSCs were studied using the intensity modulated photocurrent/photovoltage spectroscopy technique, from which transport and recombination time constants could be derived. Compared to CdSe QDSSCs, Mn-CdSe QDSSCs exhibited shorter transport time constant, longer recombination time constant, longer diffusion length, and higher charge collection efficiency. These observations suggested that Mn doping in CdSe QDs could benefit the performance of solar cells based on such nanostructures.

Carrier gas effects on aluminum-catalyzed nanowire growth

International Nuclear Information System (INIS)

Ke, Yue; Hainey, Mel Jr; Won, Dongjin; Weng, Xiaojun; Eichfeld, Sarah M; Redwing, Joan M

2016-01-01

Aluminum-catalyzed silicon nanowire growth under low-pressure chemical vapor deposition conditions requires higher reactor pressures than gold-catalyzed growth, but the reasons for this difference are not well understood. In this study, the effects of reactor pressure and hydrogen partial pressure on silicon nanowire growth using an aluminum catalyst were studied by growing nanowires in hydrogen and hydrogen/nitrogen carrier gas mixtures at different total reactor pressures. Nanowires grown in the nitrogen/hydrogen mixture have faceted catalyst droplet tips, minimal evidence of aluminum diffusion from the tip down the nanowire sidewalls, and significant vapor–solid deposition of silicon on the sidewalls. In comparison, wires grown in pure hydrogen show less well-defined tips, evidence of aluminum diffusion down the nanowire sidewalls at increasing reactor pressures and reduced vapor–solid deposition of silicon on the sidewalls. The results are explained in terms of a model wherein the hydrogen partial pressure plays a critical role in aluminum-catalyzed nanowire growth by controlling hydrogen termination of the silicon nanowire sidewalls. For a given reactor pressure, increased hydrogen partial pressures increase the extent of hydrogen termination of the sidewalls which suppresses SiH_4 adsorption thereby reducing vapor–solid deposition of silicon but increases the surface diffusion length of aluminum. Conversely, lower hydrogen partial pressures reduce the hydrogen termination and also increase the extent of SiH_4 gas phase decomposition, shifting the nanowire growth window to lower growth temperatures and silane partial pressures. (paper)

Insight into carrier lifetime impact on band-modulation devices

Science.gov (United States)

Parihar, Mukta Singh; Lee, Kyung Hwa; Park, Hyung Jin; Lacord, Joris; Martinie, Sébastien; Barbé, Jean-Charles; Xu, Yue; El Dirani, Hassan; Taur, Yuan; Cristoloveanu, Sorin; Bawedin, Maryline

2018-05-01

A systematic study to model and characterize the band-modulation Z2-FET device is developed bringing light to the relevance of the carrier lifetime influence. This work provides guidelines to optimize the Z2-FETs for sharp switching, ESD protection, and 1T-DRAM applications. Lower carrier lifetime in the Z2-FET helps in attaining the sharp switch. We provide new insights into the correlation between generation/recombination, diffusion, electrostatic barriers and carrier lifetime.

Quantitative theory of channeling particle diffusion in transverse energy in the presence of nuclear scattering and direct evaluation of dechanneling length

Energy Technology Data Exchange (ETDEWEB)

Tikhomirov, Victor V. [Belarusian State University, Institute for Nuclear Problems, Minsk (Belarus)

2017-07-15

A refined equation for channeling particle diffusion in transverse energy taking into consideration large-angle scattering by nuclei is suggested. This equation is reduced to the Sturm-Liouville problem, allowing one to reveal both the origin and the limitations of the dechanneling length notion. The values of the latter are evaluated for both positively and negatively charged particles of various energies. New features of the dechanneling dynamics of positively charged particles are also revealed. First, it is demonstrated that the dechanneling length notion is completely inapplicable for their nuclear dechanneling process. Second, the effective electron dechanneling length of positively charged particle varies more than twice converging to a constant asymptotic value only at the depth exceeding the latter. (orig.)

Duchenne muscular dystrophy carriers

International Nuclear Information System (INIS)

Matsumura, K.; Nakano, I.

1989-01-01

By means of magnetic resonance imaging (MRI), the proton spin-lattice relaxation times (T1 values) of the skeletal muscles were measured in Duchenne muscular dystrophy (DMD) carriers and normal controls. The bound water fraction (BWF) was calculated from the T1 values obtained, according to the fast proton diffusion model. In the DMD carriers, T1 values of the gluteus maximus and quadriceps femoris muscles were significantly higher, and BWFs of these muscles were significantly lower than in normal control. Degenerative muscular changes accompanied by interstitial edema were presumed responsible for this abnormality. No correlation was observed between the muscle T1 and serum creatine kinase values. The present study showed that MRI could be a useful method for studying the dynamic state of water in both normal and pathological skeletal muscles. Its possible utility for DMD carrier detection was discussed briefly. (orig.)

Diffuse charge dynamics in ionic thermoelectrochemical systems.

Science.gov (United States)

Stout, Robert F; Khair, Aditya S

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion

Diffuse charge dynamics in ionic thermoelectrochemical systems

Science.gov (United States)

Stout, Robert F.; Khair, Aditya S.

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion

Diffusion-driven and excitation-dependent recombination rate in blue InGaN/GaN quantum well structures

International Nuclear Information System (INIS)

Aleksiejūnas, R.; Gelžinytė, K.; Nargelas, S.; Jarašiūnas, K.; Vengris, M.; Armour, E. A.; Byrnes, D. P.; Arif, R. A.; Lee, S. M.; Papasouliotis, G. D.

2014-01-01

We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above ∼5 × 10 18  cm −3 , a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses

Diffusion-driven and excitation-dependent recombination rate in blue InGaN/GaN quantum well structures

Energy Technology Data Exchange (ETDEWEB)

Aleksiejūnas, R.; Gelžinytė, K.; Nargelas, S., E-mail: saulius.nargelas@ff.vu.lt; Jarašiūnas, K. [Department of Semiconductor Optoelectronics, Institute of Applied Research, Vilnius University, Saulėtekio 9–III, 10222 Vilnius (Lithuania); Vengris, M. [Laser Research Center, Vilnius University, Saulėtekio 10, 10223 Vilnius (Lithuania); Armour, E. A.; Byrnes, D. P.; Arif, R. A.; Lee, S. M.; Papasouliotis, G. D. [Veeco Instruments, Turbodisc Operations, 394 Elizabeth Avenue, Somerset, New Jersey 08873 (United States)

2014-01-13

We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above ∼5 × 10{sup 18} cm{sup −3}, a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses.

Steady state minority carrier lifetime and defect level occupation in thin film CdTe solar cells

International Nuclear Information System (INIS)

Cheng, Zimeng; Delahoy, Alan E.; Su, Zhaoqian; Chin, Ken K.

2014-01-01

A model consisting of Shockley Read Hall (SRH) recombination under steady state conditions of constant photon injection is proposed in this work to study the steady state minority carrier lifetime in CdS/CdTe thin film solar cells. The SRH recombination rate versus optical injection level is analytically approximated in the junction and neutral regions. In the neutral region, it is found that the recombination rate through certain defect levels has one constant value under lower optical injection conditions and another constant value under higher optical injection conditions with the transition occurring at a critical optical injection level. By simultaneously solving the equations of charge neutrality, charge conservation and SRH recombination in the neutral region, it is found that the compensation of doping and the reduction of minority carrier lifetime by donors in the p-type semiconductor can each be remedied by optical injection. It is also demonstrated that this optical-dependent SRH recombination is significant in large bandgap thin films. The measured minority carrier diffusion length in a CdS/CdTe solar cells, as determined from the steady-state photo-generated carrier collection efficiency, shows the predicted transition of minority carrier lifetime versus optical injection level. A numerical fitting of the indirectly-measured minority carrier lifetime by assuming the minority carrier mobility gives a non-intuitive picture of the p–n junction with a low free hole concentration but a narrow depletion region width. - Highlights: • Minority carrier lifetimes under different optical injections are solved. • Simplifications of Shockley–Read–Hall recombination equation are discussed. • The compensation of donor can be remedied with optical injection. • The recombination efficiency of donor can be remedied with optical injection. • The minority carrier lifetime transition under illumination was experimentally observed

Polycrystalline Silicon Gettered by Porous Silicon and Heavy Phosphorous Diffusion

Institute of Scientific and Technical Information of China (English)

LIU Zuming(刘祖明); Souleymane K Traore; ZHANG Zhongwen(张忠文); LUO Yi(罗毅)

2004-01-01

The biggest barrier for photovoltaic (PV) utilization is its high cost, so the key for scale PV utilization is to further decrease the cost of solar cells. One way to improve the efficiency, and therefore lower the cost, is to increase the minority carrier lifetime by controlling the material defects. The main defects in grain boundaries of polycrystalline silicon gettered by porous silicon and heavy phosphorous diffusion have been studied. The porous silicon was formed on the two surfaces of wafers by chemical etching. Phosphorous was then diffused into the wafers at high temperature (900℃). After the porous silicon and diffusion layers were removed, the minority carrier lifetime was measured by photo-conductor decay. The results show that the lifetime's minority carriers are increased greatly after such treatment.

The small FOXP1 isoform predominantly expressed in activated B cell-like diffuse large B-cell lymphoma and full-length FOXP1 exert similar oncogenic and transcriptional activity in human B cells.

Science.gov (United States)

van Keimpema, Martine; Grüneberg, Leonie J; Schilder-Tol, Esther J M; Oud, Monique E C M; Beuling, Esther A; Hensbergen, Paul J; de Jong, Johann; Pals, Steven T; Spaargaren, Marcel

2017-03-01

The forkhead transcription factor FOXP1 is generally regarded as an oncogene in activated B cell-like diffuse large B-cell lymphoma. Previous studies have suggested that a small isoform of FOXP1 rather than full-length FOXP1, may possess this oncogenic activity. Corroborating those studies, we herein show that activated B cell-like diffuse large B-cell lymphoma cell lines and primary activated B cell-like diffuse large B-cell lymphoma cells predominantly express a small FOXP1 isoform, and that the 5'-end of the Foxp1 gene is a common insertion site in murine lymphomas in leukemia virus- and transposon-mediated insertional mutagenesis screens. By combined mass spectrometry, (quantative) reverse transcription polymerase chain reaction/sequencing, and small interfering ribonucleic acid-mediated gene silencing, we determined that the small FOXP1 isoform predominantly expressed in activated B cell-like diffuse large B-cell lymphoma lacks the N-terminal 100 amino acids of full-length FOXP1. Aberrant overexpression of this FOXP1 isoform (ΔN100) in primary human B cells revealed its oncogenic capacity; it repressed apoptosis and plasma cell differentiation. However, no difference in potency was found between this small FOXP1 isoform and full-length FOXP1. Furthermore, overexpression of full-length FOXP1 or this small FOXP1 isoform in primary B cells and diffuse large B-cell lymphoma cell lines resulted in similar gene regulation. Taken together, our data indicate that this small FOXP1 isoform and full-length FOXP1 have comparable oncogenic and transcriptional activity in human B cells, suggesting that aberrant expression or overexpression of FOXP1, irrespective of the specific isoform, contributes to lymphomagenesis. These novel insights further enhance the value of FOXP1 for the diagnostics, prognostics, and treatment of diffuse large B-cell lymphoma patients. Copyright© Ferrata Storti Foundation.

Drift-Diffusion Equation

Directory of Open Access Journals (Sweden)

K. Banoo

1998-01-01

equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.

Computer assisted analysis of hand radiographs in infantile hypophosphatasia carriers

International Nuclear Information System (INIS)

Chodirker, B.N.; Greenberg, C.R.; Manitoba Univ., Winnipeg, MB; Roy, D.; Cheang, M.; Evans, J.A.; Manitoba Univ., Winnipeg, MB; Manitoba Univ., Winnipeg, MB; Reed, M.H.; Manitoba Univ., Winnipeg, MB

1991-01-01

Hand radiographs of 49 carriers of infantile hypophosphatasia and 67 non-carriers were evaluated using two Apple IIe Computer Programs and Apple Graphics Tablet. CAMPS was used to determine the bone lengths and calculate the metacarpophalangeal profiles. A newly developed program (ADAM) was used to determine bone density based on percent cortical area of the second metacarpal. Carriers of infantile hypophosphatasia had significantly less dense bones. (orig.)

Acid extraction by supported liquid membranes containing basic carriers

International Nuclear Information System (INIS)

Danesi, P.R.; Cianetti, C.; Horwitz, E.P.

1983-01-01

The extraction of HNO 3 (nitric acid) from aqueous solutions by permeation through a number of supported liquid membranes containing basic carriers dissolved in diethylbenzene has been studied. The results have shown that the best permeations are obtained with long chain aliphatic amines (TLA, Primene JM-T) followed by TOPO (trioctylphosphine oxide) and then by other monofunctional and bifunctional organophosphorous basic carriers. The influence of an aliphatic diluent on the permeability of HNO 3 through a supported liquid membrane containing TLA as carrier was also investigated. In this case the permeability to HNO 3 decreases as a result of the lower diffusion coefficient of the acid-carrier complex in the more vicous aliphatic solvent. 4 figures

Protection switching for carrier ethernet multicast

DEFF Research Database (Denmark)

Ruepp, Sarah Renée; Wessing, Henrik; Berger, Michael Stübert

2010-01-01

This paper addresses network survivability for IPTV multicast transport in Carrier Ethernet networks. The impact of link failures is investigated and suggestions for intelligent multicast resilience schemes are proposed. In particular, functions of the multicast tree are integrated with the Carri...... recovery path length, recovery time, number of branch nodes and operational complexity. The integrated approach therefore shows significant potential to increase the QoE for IPTV users in case of network failures and recovery actions.......This paper addresses network survivability for IPTV multicast transport in Carrier Ethernet networks. The impact of link failures is investigated and suggestions for intelligent multicast resilience schemes are proposed. In particular, functions of the multicast tree are integrated with the Carrier...

Probing the diffuse interstellar medium with diffuse interstellar bands

Science.gov (United States)

Theodorus van Loon, Jacco; Bailey, Mandy; Farhang, Amin; Javadi, Atefeh; Khosroshahi, Habib

2015-08-01

For a century already, a large number of absorption bands have been known at optical wavelengths, called the diffuse interstellar bands (DIBs). While their carriers remain unidentified, the relative strengths of these bands in various environments make them interesting new probes of the diffuse interstellar medium (ISM). We present the results from two large, dedicated campaigns to map the ISM using DIBs measured in the high signal-to-noise spectra of hundreds of early-type stars: [1] in and around the Local Bubble using ESO's New Technology Telescope and the Isaac Newton Telescope, and [2] across both Magellanic Clouds using the Very Large Telescope and the Anglo-Australian Telescope. We discuss the implications for the structure and dynamics of the ISM, as well as the constraints these maps place on the nature of the carriers of the DIBs. Partial results have appeared in the recent literature (van Loon et al. 2013; Farhang et al. 2015a,b; Bailey, PhD thesis 2014) with the remainder being prepared for publication now.

Diffusion of zinc into an unpassivated surface of indium phosphide

International Nuclear Information System (INIS)

Budko, T.O.; Gushchinskaya, E.V.; Emelyanenko, Yu.S.; Malyshev, S.A.

1989-01-01

Peculiarities are studied of the diffusion of Zn into an unpassivated surface of InP in an open gasflow system. In the region where the carrier concentration profile is described by an erfc (error function compliment), the diffusion coefficient and activation energy are determined. It is shown that thermal processes cause changes in the charge state of Zn in InP which result in a variation of the carrier profile in the semiconductor. (author)

Theoretical optimization of base doping concentration for radiation resistance of InGaP subcells of InGaP/GaAs/Ge based on minority-carrier lifetime

International Nuclear Information System (INIS)

Elfiky, Dalia; Yamaguchi, Masafumi; Sasaki, Takuo

2010-01-01

One of the fundamental objectives for research and development of space solar cells is to improve their radiation resistance. InGaP solar cells with low base carrier concentrations under low-energy proton irradiations have shown high radiation resistances. In this study, an analytical model for low-energy proton radiation damage to InGaP subcells based on a fundamental approach for radiative and nonradiative recombinations has been proposed. The radiation resistance of InGaP subcells as a function of base carrier concentration has been analyzed by using the radiative recombination lifetime and damage coefficient K for the minority-carrier lifetime of InGaP. Numerical analysis shows that an InGaP solar cell with a lower base carrier concentration is more radiation-resistant. Satisfactory agreements between analytical and experimental results have been obtained, and these results show the validity of the analytical procedure. The damage coefficients for minority-carrier diffusion length and carrier removal rate with low-energy proton irradiations have been observed to be dependent on carrier concentration through this study. As physical mechanisms behind the difference observed between the radiation-resistant properties of various base doping concentrations, two mechanisms, namely, the effect of a depletion layer as a carrier collection layer and generation of the impurity-related complex defects due to low-energy protons stopping within the active region, have been proposed. (author)

Diffusion-limited mixing by incompressible flows

Science.gov (United States)

Miles, Christopher J.; Doering, Charles R.

2018-05-01

Incompressible flows can be effective mixers by appropriately advecting a passive tracer to produce small filamentation length scales. In addition, diffusion is generally perceived as beneficial to mixing due to its ability to homogenize a passive tracer. However we provide numerical evidence that, in cases where advection and diffusion are both actively present, diffusion may produce negative effects by limiting the mixing effectiveness of incompressible optimal flows. This limitation appears to be due to the presence of a limiting length scale given by a generalised Batchelor length (Batchelor 1959 J. Fluid Mech. 5 113–33). This length scale limitation may in turn affect long-term mixing rates. More specifically, we consider local-in-time flow optimisation under energy and enstrophy flow constraints with the objective of maximising the mixing rate. We observe that, for enstrophy-bounded optimal flows, the strength of diffusion may not impact the long-term mixing rate. For energy-constrained optimal flows, however, an increase in the strength of diffusion can decrease the mixing rate. We provide analytical lower bounds on mixing rates and length scales achievable under related constraints (point-wise bounded speed and rate-of-strain) by extending the work of Lin et al (2011 J. Fluid Mech. 675 465–76) and Poon (1996 Commun. PDE 21 521–39).

The Effective Coherence Length in Anisotropic Superconductors

International Nuclear Information System (INIS)

Polturak, E.; Koren, G.; Nesher, O

1999-01-01

If electrons are transmitted from a normal conductor(N) into a superconductor(S), common wisdom has it that the electrons are converted into Cooper pairs within a coherence length from the interface. This is true in conventional superconductors with an isotropic order parameter. We have established experimentally that the situation is rather different in high Tc superconductors having an anisotropic order parameter. We used epitaxial thin film S/N bilayers having different interface orientations in order to inject carriers from S into N along different directions. The distance to which these carriers penetrate were determined through their effect on the Tc of the bilayers. We found that the effective coherence length is 20A only along the a or b directions, while in other directions we find a length of 250dr20A out of plane, and an even larger value for in-plane, off high symmetry directions. These observations can be explained using the Blonder-Tinkham-Klapwijk model adapted to anisotropic superconductivity. Several implications of our results on outstanding problems with high Tc junctions will be discussed

Determination of thermal neutrons diffusion length in graphite; Determinacion de la Longitud de Difusion de los Neutrones Termicos en Grafito

Energy Technology Data Exchange (ETDEWEB)

Garcia Fite, J

1959-07-01

The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs.

Telomere length and advanced diffusion MRI as biomarkers for repetitive mild traumatic brain injury in adolescent rats

Directory of Open Access Journals (Sweden)

David K. Wright

Full Text Available Mild traumatic brain injuries (mTBI are of worldwide concern in adolescents of both sexes, and repeated mTBI (RmTBI may have serious long-term neurological consequences. As such, the study of RmTBI and discovery of objective biomarkers that can help guide medical decisions is an important undertaking. Diffusion-weighted MRI (DWI, which provides markers of axonal injury, and telomere length (TL are two clinically relevant biomarkers that have been implicated in a number of neurological conditions, and may also be affected by RmTBI. Therefore, this study utilized the lateral impact injury model of RmTBI to investigate changes in diffusion MRI and TL, and how these changes relate to each other. Adolescent male and female rats received either three mTBIs or three sham injuries. The first injury was given on postnatal day 30 (P30, with the repeated injuries separated by four days each. Seven days after the final injury, a sample of ear tissue was collected for TL analysis. Rats were then euthanized and whole brains were collected and fixated for MRI analyses that included diffusion and high-resolution structural sequences. Compared to the sham-injured group, RmTBI rats had significantly shorter TL at seven days post-injury. Analysis of advanced DWI measures found that RmTBI rats had abnormalities in the corpus callosum and cortex at seven days post-injury. Notably, many of the DWI changes were correlated with TL. These findings demonstrate that TL and DWI measurements are changed by RmTBI and may represent clinically applicable biomarkers for this. Keywords: Biomarker, Concussion, Track weighted imaging, Animal model, Diffusion tensor imaging, MRI

A performance-based standards regime to regulate car-carriers in South Africa

CSIR Research Space (South Africa)

De Saxe, CC

2013-07-01

Full Text Available Until recently, South African car-carriers operated under the abnormal load permit system allowing an additional 300 mm height and 500 mm length. Because car-carrier payloads are divisible and abnormal load permits are usually granted...

Modeling of carrier dynamics in quantum-well electroabsorption modulators

DEFF Research Database (Denmark)

Højfeldt, Sune; Mørk, Jesper

2002-01-01

We present a comprehensive drift-diffusion-type electroabsorption modulator (EAM) model. The model allows us to investigate both steady-state properties and to follow the sweep-out of carriers after pulsed optical excitation. Furthermore, it allows for the investigation of the influence that vari...... in the field near each well affect the escape of carriers from that well. Finally, we look at the influence that the separate-confinement heterostructure barriers have on the carrier sweep-out....... that various design parameters have on the device properties, in particular how they affect the carrier dynamics and the corresponding field dynamics. A number of different types of results are presented. We calculate absorption spectra and steady-state field screening due to carrier pile-up at the separate......-confinement heterobarriers. We then move on to look at carrier sweep-out upon short-pulse optical excitation. For a structure with one well, we analyze how the well position affects the carrier sweep-out and the absorption recovery. We calculate the field dynamics in a multiquantum-well structure and discuss how the changes...

Three dimensional simulated modelling of diffusion capacitance of ...

African Journals Online (AJOL)

A three dimensional (3-D) simulated modelling was developed to analyse the excess minority carrier density in the base of a polycrystalline bifacial silicon solar cell. The concept of junction recombination velocity was ado-pted to quantify carrier flow through the junction, and to examine the solar cell diffusion capacitance for ...

Charge Carrier Dynamics at Silver Nanocluster-Molecular Acceptor Interfaces

KAUST Repository

Almansaf, Abdulkhaleq

2017-07-01

A fundamental understanding of interfacial charge transfer at donor-acceptor interfaces is very crucial as it is considered among the most important dynamical processes for optimizing performance in many light harvesting systems, including photovoltaics and photo-catalysis. In general, the photo-generated singlet excitons in photoactive materials exhibit very short lifetimes because of their dipole-allowed spin radiative decay and short diffusion lengths. In contrast, the radiative decay of triplet excitons is dipole forbidden; therefore, their lifetimes are considerably longer. The discussion in this thesis primarily focuses on the relevant parameters that are involved in charge separation (CS), charge transfer (CT), intersystem crossing (ISC) rate, triplet state lifetime, and carrier recombination (CR) at silver nanocluster (NCs) molecular-acceptors interfaces. A combination of steady-state and femto- and nanosecond broadband transient absorption spectroscopies were used to investigate the charge carrier dynamics in various donor-acceptor systems. Additionally, this thesis was prolonged to investigate some important factors that influence the charge carrier dynamics in Ag29 silver NCs donor-acceptor systems, such as the metal doping and chemical structure of the nanocluster and molecular acceptors. Interestingly, clear correlations between the steady-state measurements and timeresolved spectroscopy results are found. In the first study, we have investigated the interfacial charge transfer dynamics in positively charged meso units of 5, 10, 15, 20-tetra (1- methyl-4-pyridino)-porphyrin tetra (p-toluene sulfonate) (TMPyP) and neutral charged 5, 10, 15, 20-tetra (4-pyridyl)-porphyrin (TPyP), with negatively charged undoped and gold (Au)- doped silver Ag29 NCs. Moreover, this study showed the impact of Au doping on the charge carrier dynamics of the system. In the second study, we have investigated the interfacial charge transfer dynamics in [Pt2 Ag23 Cl7 (PPh3

Fossil rocks of slow earthquake detected by thermal diffusion length

Science.gov (United States)

Hashimoto, Yoshitaka; Morita, Kiyohiko; Okubo, Makoto; Hamada, Yohei; Lin, Weiren; Hirose, Takehiro; Kitamura, Manami

2016-04-01

Fault motion has been estimated by diffusion pattern of frictional heating recorded in geology (e.g., Fulton et al., 2012). The same record in deeper subduction plate interface can be observed from micro-faults in an exhumed accretionary complex. In this study, we focused on a micro-fault within the Cretaceous Shimanto Belt, SW Japan to estimate fault motion from the frictional heating diffusion pattern. A carbonaceous material concentrated layer (CMCL) with ~2m of thickness is observed in study area. Some micro-faults cut the CMCL. Thickness of a fault is about 3.7mm. Injection veins and dilatant fractures were observed in thin sections, suggesting that the high fluid pressure was existed. Samples with 10cm long were collected to measure distribution of vitrinite reflectance (Ro) as a function of distance from the center of micro-fault. Ro of host rock was ~1.0%. Diffusion pattern was detected decreasing in Ro from ~1.2%-~1.1%. Characteristic diffusion distance is ~4-~9cm. We conducted grid search to find the optimal frictional heat generation per unit area per second (Q (J/m^2/s), the product of friction coefficient, normal stress and slip velocity) and slip duration (t(s)) to fit the diffusion pattern. Thermal diffusivity (0.98*10^8m^2/s) and thermal conductivity (2.0 w/mK) were measured. In the result, 2000-2500J/m^2/s of Q and 63000-126000s of t were estimated. Moment magnitudes (M0) of slow earthquakes (slow EQs) follow a scaling law with slip duration and its dimension is different from that for normal earthquakes (normal EQ) (Ide et al., 2007). The slip duration estimated in this study (~10^4-~10^5s) consistent with 4-5 of M0, never fit to the scaling law for normal EQ. Heat generation can be inverted from 4-5 of M0, corresponding with ~10^8-~10^11J, which is consistent with rupture area of 10^5-10^8m2 in this study. The comparisons in heat generation and slip duration between geological measurements and geophysical remote observations give us the

Diffusion length variation in photovoltaic cells with Bridgman-grown CuInSe2 substrates

International Nuclear Information System (INIS)

Champness, C.H.

2007-01-01

In a group of CuInSe 2 -CdS-ZnO photovoltaic cells, where the absorber was a layer cut from Bridgman-grown p-type CuInSe 2 ingots, electron diffusion lengths at room temperature (L n ) were estimated by the photocurrent-capacitance method. Dark capacitance measurements were also made on the same cells against reverse bias and from Mott-Schottky plots, slope concentrations p MS were determined at a reverse bias of 1.5 V. In a plot of L n against p MS , it was found that, despite much scatter in the experimental points, there was an apparent trend of L n decreasing by about an order of magnitude with increase of p MS from 10 16 to 10 17 cm -3 . Detailed proposals were then made to explain this trend. These were reduction of lifetime via Shockley-Read trapping with mobility decrease by impurity scattering, shunt resistance lowering by light and optical penetration depth reduction at shorter illumination wavelengths

Electrical characterization of fluorinated benzothiadiazole based conjugated copolymer – a promising material for high-performance solar cells

DEFF Research Database (Denmark)

Toušek, J.; Toušková, J.; Remeš, Z.

2015-01-01

Measurements of electrical conductivity, electron work function, carrier mobility ofholes and the diffusion length of excitons were performed on samples of conjugatedpolymers relevant to polymer solar cells. A state of the art fluorinated benzothiadiazolebased conjugated copolymer (PBDTTHD − DTBTff......) was studied and benchmarkedagainst the reference polymer poly-3-hexylthiophene (P3HT).We employed,respectively, four electrode conductivity measurements, Kelvin probe work functionmeasurements, carrier mobility using charge extraction by linearly increasing voltage(CELIV) measurements and diffusion length...

Carrier mode selective working point and side band imbalance in LIGO I

International Nuclear Information System (INIS)

D'Ambrosio, Erika; Kells, William

2006-01-01

In gravitational wave interferometers, the input laser beam is phase modulated to generate radio-frequency side bands that are used to lock the cavities. The mechanism is the following: the frequency of the side bands and the carrier is chosen in such a way that their response to small changes of the longitudinal degrees of freedom is different. This difference is therefore monitored and it serves as an error signal for controlling the optical cavity lengths, as they are linearly related to the set of observed phases between carrier and side bands. Among the others, one longitudinal degree of freedom is optimally sensitive to the space-time distortions propagating through the cosmos, as predicted by the general theory of relativity. The observation of the astrophysical signal relies on the measurement of that specific degree of freedom. The entire problem is more complex when the transverse degrees of freedom are taken into account, because the relative phase between the fields also depends on their overlap. In order to establish an unambiguous relation between length changes and phase measurements, there must be one circulating optical mode and the only difference between carrier and side bands must be their amplitude. We will show that the variability of the transverse degrees of freedom and their different actions on carrier and side band fields puts a severe limit on this assumption. Unless the system is made of perfect and perfectly matched optical cavities, it is never governed by one unique coherent state and any adjustment of the optical lengths results from a compromise between the lengths that are optimal for the carrier field and the side band ones. Such a compromise alters the correspondence between error signals and cavity lengths, calculated in the one-dimensional treatment. We assess the strength of this effect and relate it to the sensitivity of the instrument (which relies on the reconstruction of that correspondence) in realistic circumstances

Diffusion and transport coefficients in synthetic opals

International Nuclear Information System (INIS)

Sofo, J. O.; Mahan, G. D.

2000-01-01

Opals are structures composed of close-packed spheres in the size range of nano to micrometers. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the thermal and electrical conductivity is used to estimate the transport coefficients of opal structures as a function of the neck size and the mean free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures. (c) 2000 The American Physical Society

Evaluation of carrier-mediated siRNA delivery

DEFF Research Database (Denmark)

Colombo, Stefano; Nielsen, Hanne Mørck; Foged, Camilla

2013-01-01

RNA delivery. An in vitro cell culture model system expressing enhanced green fluorescent protein (EGFP) was used to develop the assay, which was based on the intracellular quantification of a full-length double-stranded Dicer substrate siRNA by stem-loop RT qPCR. The result is a well-documented protocol......RNA delivered by use of carriers remains an analytical challenge. The purpose of the present study was to optimize and validate an analytical protocol based on stem-loop reverse transcription quantitative polymerase chain reaction (RT qPCR) to quantitatively monitor the carrier-mediated intracellular si...

In-depth characterization of silicon solar cells

International Nuclear Information System (INIS)

Verhoef, L.A.; Bisschop, F.J.; Stroom, J.C.; Sinke, W.C.

1990-01-01

The authors present an extension of the photo-current decay (PCD) method to enable determination of the minority-carrier diffusion length in Si solar cells in a depth-resolved fashion. From a single decay curve three observables (quantum efficiency, fundamental decay time, and intercept of the extrapolated decay curve with the time-zero axis) are determined. It is demonstrated how three transport parameters (back-surface recombination velocity, the average minority-carrier diffusion length, and a third parameter which describes the depth-dependence of the diffusion length) are extracted from these observables. Computer simulations of the time-dependent minority-carrier transport problem are performed to unravel the relations between the recombination parameters of the solar cell base and the three observables. With the authors' experimental set-up, comprising a Ti:Sapphire laser, light pulses of wavelength 1010 nm are used to perform PCD measurements. Measurements on a set of polycrystalline Si cells were performed showing that gettering treatments during cell production result in depth-dependent lifetimes

Doping dependence and anisotropy of minority electron mobility in molecular beam epitaxy-grown p type GaInP

Energy Technology Data Exchange (ETDEWEB)

Haegel, N. M.; Christian, T.; Norman, A. G.; Mascarenhas, A. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Scandrett, C. [Naval Postgraduate School, Monterey, California 93943 (United States); Misra, Pranob; Liu, Ting; Sukiasyan, Arsen; Pickett, Evan; Yuen, Homan [Solar Junction, Inc., San Jose, California 95131 (United States)

2014-11-17

Direct imaging of minority electron transport via the spatially resolved recombination luminescence signature has been used to determine carrier diffusion lengths in GaInP as a function of doping. Minority electron mobility values are determined by performing time resolved photoluminescence measurements of carrier lifetime on the same samples. Values at 300 K vary from ∼2000 to 400 cm{sup 2}/V s and decrease with increasing doping. Anisotropic diffusion lengths and strongly polarized photoluminescence are observed, resulting from lateral composition modulation along the [110] direction. We report anisotropic mobility values associated with carrier transport parallel and perpendicular to the modulation direction.

Selective laser-induced photochemical dry etching of semiconductors controlled by ion-bombardment-induced damage

International Nuclear Information System (INIS)

Ashby, C.I.H.; Myers, D.R.; Vook, F.L.

1987-01-01

When a photochemical dry etching process requires direct participation of photogenerated carriers in the chemical reaction, it is sensitive to the electronic properties of the semiconductor. For such solid-excitation-based dry etching processes, the balance between reaction and carrier recombination rates determines the practical utility of a particular reaction for device fabrication. The distance from the surface at which the photocarriers are generated by light adsorption is determined by the absorption coefficient. In the absence of an external bias potential, only those carriers formed within a diffusion length of the surface space-charge region will have an opportunity to drive the dry etching reaction. When the absorption coefficient is high, most of the photons generate carriers within a diffusion length from the surface space-charge region, and the etching rate is largely determined by the balance between the rate of the carrier-driven reaction and the surface recombination velocity. When the recombination rate of free carriers in the bulk of the semiconductor is high, the effective diffusion length is reduced and fewer of the carriers generated in the subsurface region ever reach the surface. An important effect of ion bombardment is the creation of many lattice defects that increase the rate of recombination of electrons and holes. When a sufficient number of defects, which act as recombination sites, are formed during ion implantation, the recombination of photogenerated carriers at these defects in the subsurface region can greatly reduce the number of carriers which can reach the surface and drive a photochemical etching reaction

Analysis of a multicomponent gas absorption system with carrier gas coabsorption

International Nuclear Information System (INIS)

Merriman, J.R.

1975-03-01

Conventional integrated versions of the packed gas absorber design equations do not account for significant coabsorption of the carrier gas along with the dilute transferring species. These equations, as a result, also neglect the relationship between dilute component transfer and carrier gas coabsorption. In the absorption of Kr and Xe from various carrier gases, using CCl 2 F 2 as the process solvent, carrier coabsorption is substantial. Consequently, a design package was developed to deal with multicomponent gas absorption in systems characterized by carrier gas coabsorption. Developed within the general film theory framework, the basic feature of this design approach is a view of dilute component mass-transfer as a conventional diffusive transfer superimposed on a net flux caused by carrier absorption. Other supporting elements of the design package include predictive techniques for various fluid properties, estimating procedures for carrier gas equilibrium constants, and correlations for carrier gas and dilute gas mass-transfer coefficients. When applied to systems using CCl 2 F 2 as the solvent; He, N 2 , air, or Ar as the carrier gas; and Kr or Xe as the dilute gas; the design approach gave good results, even when extended to conditions well beyond those of its development. (U.S.)

How to measure atomic diffusion processes in the sub-nanometer range

International Nuclear Information System (INIS)

Schmidt, H.; Gupta, M.; Gutberlet, T.; Stahn, J.; Bruns, M.

2008-01-01

Self-diffusion of the atomic constituents in the solid state is a fundamental transport process that controls various materials properties. With established methods of diffusivity determination it is only possible to measure diffusion processes on a length scale down to 10 nm at corresponding diffusivities of 10 -23 m 2 s -1 . However, for complex materials like amorphous or nano-structured solids the given values are often not sufficient for a proper characterization. Consequently, it is necessary to detect diffusion length well below 1 nm. Here, we present the method of neutron reflectometry on isotope multilayers. For two model systems, an amorphous semiconductor and an amorphous metallic alloy, the efficiency of this method is demonstrated to detect minimum diffusion lengths of only 0.6-0.7 nm. It is further shown that diffusivities can be derived which are more than two orders of magnitude lower than those obtainable with conventional methods. Prospects of this method in order to solve actual kinetic problems in materials science are given

Electrical characterization of fluorinated benzothiadiazole based conjugated copolymer – a promising material for high-performance solar cells

Directory of Open Access Journals (Sweden)

J. Toušek

2015-12-01

Full Text Available Measurements of electrical conductivity, electron work function, carrier mobility of holes and the diffusion length of excitons were performed on samples of conjugated polymers relevant to polymer solar cells. A state of the art fluorinated benzothiadiazole based conjugated copolymer (PBDTTHD − DTBTff was studied and benchmarked against the reference polymer poly-3-hexylthiophene (P3HT. We employed, respectively, four electrode conductivity measurements, Kelvin probe work function measurements, carrier mobility using charge extraction by linearly increasing voltage (CELIV measurements and diffusion length determinaton using surface photovoltage measurements.

Spin drift and spin diffusion currents in semiconductors

Energy Technology Data Exchange (ETDEWEB)

Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

2008-09-15

On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Spin drift and spin diffusion currents in semiconductors

Directory of Open Access Journals (Sweden)

M Idrish Miah

2008-01-01

Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Spin drift and spin diffusion currents in semiconductors

International Nuclear Information System (INIS)

Idrish Miah, M

2008-01-01

On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Disorder-induced transition from grain boundary to bulk dominated ionic diffusion in pyrochlores

International Nuclear Information System (INIS)

Perriot, Romain; Dholabhai, Pratik P.; Uberuaga, Blas P.

2017-01-01

In this paper, we use molecular dynamics simulations to investigate the role of grain boundaries (GBs) on ionic diffusion in pyrochlores, as a function of the GB type, chemistry of the compound, and level of cation disorder. We observe that the presence of GBs promotes oxygen transport in ordered and low-disordered systems, as the GBs are found to have a higher concentration of mobile carriers with higher mobilities than in the bulk. Thus, in ordered samples, the ionic diffusion is 2D, localized along the grain boundary. When cation disorder is introduced, bulk carriers begin to contribute to the overall diffusion, while the GB contribution is only slightly enhanced. In highly disordered samples, the diffusive behavior at the GBs is bulk-like, and the two contributions (bulk vs. GB) can no longer be distinguished. There is thus a transition from 2D/GB dominated oxygen diffusivity to 3D/bulk dominated diffusivity versus disorder in pyrochlores. Finally, these results provide new insights into the possibility of using internal interfaces to enhance ionic conductivity in nanostructured complex oxides.

Self-scaling minority carrier lifetime imaging using periodically modulated electroluminescence

Science.gov (United States)

Kropp, Timo; Berner, Marcel; Werner, Jürgen H.

2017-11-01

We present a straightforward self-scaling imaging technique to extract the effective minority carrier lifetime image of silicon solar cells using periodically modulated electroluminescence. This novel modulation technique overcomes main limiting factors linked to camera integration time. Our approach is based on comparing three luminescence images taken during current modulation. One image is taken while periodically injecting excess charge carriers with a pulsed current stimulation followed by an open-circuit luminescence decay. A second image with the same injection profile is taken while additionally extracting excess charge carriers at the falling edge, accelerating the luminescence decay. Both images are normalized to a steady-state image. The camera integration time is several orders of magnitude longer than the modulation period length, and no synchronization of image acquisition is needed. The intensity difference between both modulated images is used for determining a calibration factor to convert the steady-state image into the effective minority carrier lifetime image: Our modulation method enables carrier lifetime images completely independent of the image integration time. First carrier lifetime images show good agreement with data from time resolved electroluminescence.

Determination of ion diffusion coefficients by the electromigration method

International Nuclear Information System (INIS)

Bonchev, G.D.; Milanov, M.V.; Bozhikov, G.A.; Ivanov, P.I.; Priemyshev, A.N.; Maslov, O.D.; Dmitriev, S.N.

2003-01-01

An electrophoretic method for measuring ion diffusion coefficients in aqueous solutions is developed. The value of the diffusion coefficient can be determined from the linear relationship between the square standard deviation of the electrophoretic zone and the time from the start of the diffusion process. Using the device for horizontal zone electrophoresis in a free electrolyte, a series of diffusion experiments are performed with no-carrier-added radionuclides in microconcentrations (10 -9 - 10 -10 M). Diffusion coefficients of 111 In(III), 175 Hf(IV) and 237 Pu(VI) ions at 25 0 C are determined in nitric acid media. Simultaneous determination of the diffusion coefficient and electrophoretic mobility allows one to calculate the effective charge of the investigated ions in accordance with the Nernst-Einstein law

Influence of injected charge carriers on photocurrents in polymer solar cells

NARCIS (Netherlands)

Wehenkel, D.J.; Koster, L.J.A.; Wienk, M.M.; Janssen, R.A.J.

2012-01-01

We determine and analyze the photocurrent Jph in polymer solar cells under conditions where, no, one, or two different charge carriers can be injected by choosing appropriate electrodes and compare the experimental results to simulations based on a drift-diffusion device model that accounts for

Mechanisms limiting the performance of large grain polycrystalline silicon solar cells

Science.gov (United States)

Culik, J. S.; Alexander, P.; Dumas, K. A.; Wohlgemuth, J. W.

1984-01-01

The open-circuit voltage and short-circuit current of large-grain (1 to 10 mm grain diameter) polycrystalline silicon solar cells is determined by the minority-carrier diffusion length within the bulk of the grains. This was demonstrated by irradiating polycrystalline and single-crystal (Czochralski) silicon solar cells with 1 MeV electrons to reduce their bulk lifetime. The variation of short-circuit current with minority-carrier diffusion length for the polycrystalline solar cells is identical to that of the single-crystal solar cells. The open-circuit voltage versus short-circuit current characteristic of the polycrystalline solar cells for reduced diffusion lengths is also identical to that of the single-crystal solar cells. The open-circuit voltage of the polycrystalline solar cells is a strong function of quasi-neutral (bulk) recombination, and is reduced only slightly, if at all, by grain-boundary recombination.

Theory of quantum diffusion in biased semiconductors

CERN Document Server

Bryksin, V V

2003-01-01

A general theory is developed to describe diffusion phenomena in biased semiconductors and semiconductor superlattices. It is shown that the Einstein relation is not applicable for all field strengths so that the calculation of the field-mediated diffusion coefficient represents a separate task. Two quite different diffusion contributions are identified. The first one disappears when the dipole operator commutes with the Hamiltonian. It plays an essential role in the theory of small polarons. The second contribution is obtained from a quantity that is the solution of a kinetic equation but that cannot be identified with the carrier distribution function. This is in contrast to the drift velocity, which is closely related to the distribution function. A general expression is derived for the quantum diffusion regime, which allows a clear physical interpretation within the hopping picture.

Label-free monitoring of diffusion in microfluidics

DEFF Research Database (Denmark)

Sørensen, Kristian Tølbøl; Kristensen, Anders

2017-01-01

Label-free, real-time detection of concentration gradients is demonstrated in a microfluidic H-filter, using an integrated photonic crystal slab sensor to monitor sample refractive index with spatial resolution. The recorded diffusion profiles reveal root-mean-square diffusion lengths for non...

Nonlinear optical susceptibilities in the diffusion modified AlxGa1-xN/GaN single quantum well

Science.gov (United States)

Das, T.; Panda, S.; Panda, B. K.

2018-05-01

Under thermal treatment of the post growth AlGaN/GaN single quantum well, the diffusion of Al and Ga atoms across the interface is expected to form the diffusion modified quantum well with diffusion length as a quantitative parameter for diffusion. The modification of confining potential and position-dependent effective mass in the quantum well due to diffusion is calculated taking the Fick's law. The built-in electric field which arises from spontaneous and piezoelectric polarizations in the wurtzite structure is included in the effective mass equation. The electronic states are calculated from the effective mass equation using the finite difference method for several diffusion lengths. Since the effective well width decreases with increasing diffusion length, the energy levels increase with it. The intersubband energy spacing in the conduction band decreases with diffusion length due to built-in electric field and reduction of effective well width. The linear susceptibility for first-order and the nonlinear second-order and third-order susceptibilities are calculated using the compact density matrix approach taking only two levels. The calculated susceptibilities are red shifted with increase in diffusion lengths due to decrease in intersubband energy spacing.

Ambipolar diffusion regulated collapse of filaments threaded by perpendicular magnetic fields

Science.gov (United States)

Burge, C. A.; Van Loo, S.; Falle, S. A. E. G.; Hartquist, T. W.

2016-11-01

Context. In giant molecular clouds (GMCs), the fractional ionisation is low enough that the neutral and charged particles are weakly coupled. A consequence of this is that the magnetic flux redistributes within the cloud, allowing an initially magnetically supported region to collapse. Aims: We aim to elucidate the effects of ambipolar diffusion on the evolution of infinitely long filaments and the effect of decaying turbulence on that evolution. Methods: First, in ideal magnetohydrodynamics (MHD), a two-dimensional cylinder of an isothermal magnetised plasma with initially uniform density was allowed to evolve to an equilibrium state. Then, the response of the filament to ambipolar diffusion was followed using an adaptive mesh refinement multifluid MHD code. Various ambipolar resistivities were chosen to reflect different ratios of Jeans length to ambipolar diffusion length scale. To study the effect of turbulence on the ambipolar diffusion rate, we perturbed the equilibrium filament with a turbulent velocity field quantified by a rms sonic Mach number, Mrms, of 10, 3 or 1. Results: We numerically reproduce the density profiles for filaments that are in magnetohydrostatic and pressure equilibrium with their surroundings obtained in a published model and show that these equilibria are dynamically stable. If the effect of ambipolar diffusion is considered, these filaments lose magnetic support initiating cloud collapse. The filaments do not lose magnetic flux. Rather the magnetic flux is redistributed within the filament from the dense centre towards the diffuse envelope. The rate of the collapse is inversely proportional to the fractional ionisation and two gravitationally-driven ambipolar diffusion regimes for the collapse are observed as predicted in a published model. For high values of the ionisation coefficient, that is X ≥ 10-7, the gas is strongly coupled to the magnetic field and the Jeans length is larger than the ambipolar diffusion length scale. Then

Electrostatic turbulence with finite parallel correlation length and radial electric field generation

International Nuclear Information System (INIS)

Vlad, M.; Spineanu, F.; Misguich, J.H.; Balescu, R.

2001-01-01

Particle diffusion in a given electrostatic turbulence with a finite correlation length along the confining magnetic field is studied in the test particle approach. An anomalous diffusion regime of amplified diffusion coefficients is found in the conditions when particle trapping in the structure of the stochastic potential is effective. The auto-generated radial electric field is calculated. (author)

Research of Innovation Diffusion on Industrial Networks

Directory of Open Access Journals (Sweden)

Yongtai Chen

2014-01-01

Full Text Available The real value of innovation consists in its diffusion on industrial network. The factors which affect the diffusion of innovation on industrial network are the topology of industrial network and rules of diffusion. Industrial network is a complex network which has scale-free and small-world characters; its structure has some affection on threshold, length of path, enterprise’s status, and information share of innovation diffusion. Based on the cost and attitude to risk of technical innovation, we present the “avalanche” diffusing model of technical innovation on industrial network.

Exciton diffusion coefficient measurement in ZnO nanowires under electron beam irradiation

Science.gov (United States)

Donatini, Fabrice; Pernot, Julien

2018-03-01

In semiconductor nanowires (NWs) the exciton diffusion coefficient can be determined using a scanning electron microscope fitted with a cathodoluminescence system. High spatial and temporal resolution cathodoluminescence experiments are needed to measure independently the exciton diffusion length and lifetime in single NWs. However, both diffusion length and lifetime can be affected by the electron beam bombardment during observation and measurement. Thus, in this work the exciton lifetime in a ZnO NW is measured versus the electron beam dose (EBD) via a time-resolved cathodoluminescence experiment with a temporal resolution of 50 ps. The behavior of the measured exciton lifetime is consistent with our recent work on the EBD dependence of the exciton diffusion length in similar NWs investigated under comparable SEM conditions. Combining the two results, the exciton diffusion coefficient in ZnO is determined at room temperature and is found constant over the full span of EBD.

Design and simulation of betavoltaic battery using large-grain polysilicon

International Nuclear Information System (INIS)

Yao, Shulin; Song, Zijun; Wang, Xiang; San, Haisheng; Yu, Yuxi

2012-01-01

In this paper, we present the design and simulation of a p–n junction betavoltaic battery based on large-grain polysilicon. By the Monte Carlo simulation, the average penetration depth were obtained, according to which the optimal depletion region width was designed. The carriers transport model of large-grain polysilicon is used to determine the diffusion length of minority carrier. By optimizing the doping concentration, the maximum power conversion efficiency can be achieved to be 0.90% with a 10 mCi/cm 2 Ni-63 source radiation. - Highlights: ► Ni 63 is employed as the pure beta radioisotope source. ► The planar p–n junction betavoltaic battery is based on large-grain polysilicon. ► The carriers transport model of large-grain polysilicon is used to determine the diffusion length of minority carrier. ► The average penetration depth was obtained by using the Monte Carlo Method.

Labeling of indocyanine green with carrier-free iodine-123

International Nuclear Information System (INIS)

Ansari, A.N.; Lambrecht, R.M.; Redvanly, C.S.; Wolf, A.P.

1976-01-01

The method is described for labeling indocyanine green (ICG) with carrier-free iodine-123 by condensing xenon-123 on crystals of ICG followed by permitting decay of the 123 Xe a sufficient length of time to produce 123 I-electronically excited ions and atoms which subsequently label ICG. 4 claims, no drawings

Durability of switchable QR code carriers under hydrolytic and photolytic conditions

International Nuclear Information System (INIS)

Ecker, Melanie; Pretsch, Thorsten

2013-01-01

Following a guest diffusion approach, the surface of a shape memory poly(ester urethane) (PEU) was either black or blue colored. Bowtie-shaped quick response (QR) code carriers were then obtained from laser engraving and cutting, before thermo-mechanical functionalization (programming) was applied to stabilize the PEU in a thermo-responsive (switchable) state. The stability of the dye within the polymer surface and long-term functionality of the polymer were investigated against UVA and hydrolytic ageing. Spectrophotometric investigations verified UVA ageing-related color shifts from black to yellow-brownish and blue to petrol-greenish whereas hydrolytically aged samples changed from black to greenish and blue to light blue. In the case of UVA ageing, color changes were accompanied by dye decolorization, whereas hydrolytic ageing led to contrast declines due to dye diffusion. The Michelson contrast could be identified as an effective tool to follow ageing-related contrast changes between surface-dyed and laser-ablated (undyed) polymer regions. As soon as the Michelson contrast fell below a crucial value of 0.1 due to ageing, the QR code was no longer decipherable with a scanning device. Remarkably, the PEU information carrier base material could even then be adequately fixed and recovered. Hence, the surface contrast turned out to be the decisive parameter for QR code carrier applicability. (paper)

Durability of switchable QR code carriers under hydrolytic and photolytic conditions

Science.gov (United States)

Ecker, Melanie; Pretsch, Thorsten

2013-09-01

Following a guest diffusion approach, the surface of a shape memory poly(ester urethane) (PEU) was either black or blue colored. Bowtie-shaped quick response (QR) code carriers were then obtained from laser engraving and cutting, before thermo-mechanical functionalization (programming) was applied to stabilize the PEU in a thermo-responsive (switchable) state. The stability of the dye within the polymer surface and long-term functionality of the polymer were investigated against UVA and hydrolytic ageing. Spectrophotometric investigations verified UVA ageing-related color shifts from black to yellow-brownish and blue to petrol-greenish whereas hydrolytically aged samples changed from black to greenish and blue to light blue. In the case of UVA ageing, color changes were accompanied by dye decolorization, whereas hydrolytic ageing led to contrast declines due to dye diffusion. The Michelson contrast could be identified as an effective tool to follow ageing-related contrast changes between surface-dyed and laser-ablated (undyed) polymer regions. As soon as the Michelson contrast fell below a crucial value of 0.1 due to ageing, the QR code was no longer decipherable with a scanning device. Remarkably, the PEU information carrier base material could even then be adequately fixed and recovered. Hence, the surface contrast turned out to be the decisive parameter for QR code carrier applicability.

Nonthermal Effects of Photon Illumination on Surface Diffusion

International Nuclear Information System (INIS)

Ditchfield, R.; Llera-Rodriguez, D.; Seebauer, E.G.

1998-01-01

Nonthermal influences of photon illumination on surface diffusion at high temperatures have been measured experimentally for the first time. Activation energies and preexponential factors for diffusion of germanium and indium on silicon change substantially in response to illumination by photons having energies greater than the substrate band gap. Results depend on doping type. Ionization of surface vacancies by photogenerated charge carriers seems to play a key role. The results have significant implications for aspects of microelectronics fabrication governed by surface mobility. copyright 1998 The American Physical Society

A nonlinear equation for ionic diffusion in a strong binary electrolyte

Science.gov (United States)

Ghosal, Sandip; Chen, Zhen

2010-01-01

The problem of the one-dimensional electro-diffusion of ions in a strong binary electrolyte is considered. The mathematical description, known as the Poisson–Nernst–Planck (PNP) system, consists of a diffusion equation for each species augmented by transport owing to a self-consistent electrostatic field determined by the Poisson equation. This description is also relevant to other important problems in physics, such as electron and hole diffusion across semiconductor junctions and the diffusion of ions in plasmas. If concentrations do not vary appreciably over distances of the order of the Debye length, the Poisson equation can be replaced by the condition of local charge neutrality first introduced by Planck. It can then be shown that both species diffuse at the same rate with a common diffusivity that is intermediate between that of the slow and fast species (ambipolar diffusion). Here, we derive a more general theory by exploiting the ratio of the Debye length to a characteristic length scale as a small asymptotic parameter. It is shown that the concentration of either species may be described by a nonlinear partial differential equation that provides a better approximation than the classical linear equation for ambipolar diffusion, but reduces to it in the appropriate limit. PMID:21818176

Surface/Interface Carrier-Transport Modulation for Constructing Photon-Alternative Ultraviolet Detectors Based on Self-Bending-Assembled ZnO Nanowires.

Science.gov (United States)

Guo, Zhen; Zhou, Lianqun; Tang, Yuguo; Li, Lin; Zhang, Zhiqi; Yang, Hongbo; Ma, Hanbin; Nathan, Arokia; Zhao, Dongxu

2017-09-13

Surface/interface charge-carrier generation, diffusion, and recombination/transport modulation are especially important in the construction of photodetectors with high efficiency in the field of nanoscience. In the paper, a kind of ultraviolet (UV) detector is designed based on ZnO nanostructures considering photon-trapping, surface plasmonic resonance (SPR), piezophototronic effects, interface carrier-trapping/transport control, and collection. Through carefully optimized surface/interface carrier-transport modulation, a designed device with detectivity as high as 1.69 × 10 16 /1.71 × 10 16 cm·Hz 1/2 /W irradiating with 380 nm photons under ultralow bias of 0.2 V is realized by alternating nanoparticle/nanowire active layers, respectively, and the designed UV photodetectors show fast and slow recovery processes of 0.27 and 4.52 ms, respectively, which well-satisfy practical needs. Further, it is observed that UV photodetection could be performed within an alternative response by varying correlated key parameters, through efficient surface/interface carrier-transport modulation, spectrally resolved photoresponse of the detector revealing controlled detection in the UV region based on the ZnO nanomaterial, photodetection allowed or limited by varying the active layers, irradiation distance from one of the electrodes, standing states, or electric field. The detailed carrier generation, diffusion, and recombination/transport processes are well illustrated to explain charge-carrier dynamics contributing to the photoresponse behavior.

HTLV-I carrier with unusual brain MR imaging findings

Energy Technology Data Exchange (ETDEWEB)

Yata, Shinsaku; Ogawa, Toshihide; Sugihara, Shuji; Matsusue, Eiji; Fujii, Shinya; Kinoshita, Toshibumi [Tottori University, Department of Pathophysiological and Therapeutic Science, Yonago (Japan); Faculty of Medicine, Tottori University, Yonago (Japan)

2004-09-01

We describe unusual brain MR imaging findings in a patient who is an HTLV-I carrier without myelopathy. T2-weighted MR images showed hyperintense signal abnormalities in the pyramidal tract, superior and middle cerebellar peduncles, and decussation of the superior cerebellar peduncles, in addition to subcortical white matter involvement. Diffusion-weighted images also showed hyperintense signal abnormalities in the same regions by T2 shine-through effect. (orig.)

Fibreoptic diffuse-light irradiators of biological tissues

International Nuclear Information System (INIS)

Volkov, Vladimir V; Loshchenov, V B; Konov, Vitalii I; Kononenko, Vitalii V

2010-01-01

We report techniques for the fabrication of laser radiation diffusers for interstitial photodynamic therapy. Using chemical etching of the distal end of silica fibre with a core diameter of 200 - 600 μm, we have obtained long (up to 40 mm) diffusers with good scattering uniformity. Laser ablation has been used to produce cylindrical diffusers with high emission contrast and a scattering uniformity no worse than ∼10 % in their middle part. The maximum length of the diffusers produced by this method is 20 - 25 mm. (laser applications and other topics in quantum electronics)

Quantifying brain microstructure with diffusion MRI

DEFF Research Database (Denmark)

Novikov, Dmitry S.; Jespersen, Sune N.; Kiselev, Valerij G.

2016-01-01

the potential to quantify the relevant length scales for neuronal tissue, such as the packing correlation length for neuronal fibers, the degree of neuronal beading, and compartment sizes. The second avenue corresponds to the long-time limit, when the observed signal can be approximated as a sum of multiple non......-exchanging anisotropic Gaussian components. Here the challenge lies in parameter estimation and in resolving its hidden degeneracies. The third avenue employs multiple diffusion encoding techniques, able to access information not contained in the conventional diffusion propagator. We conclude with our outlook...... on the future research directions which can open exciting possibilities for developing markers of pathology and development based on methods of studying mesoscopic transport in disordered systems....

Trace diffusion of different nuclear reactions products in polycrystalline tantalum

International Nuclear Information System (INIS)

Beyer, G.J.; Fromm, W.D.; Novgorodov, A.F.

1976-07-01

Measurements of the lattice diffusion coefficients for carrier free isotopes of Hf, Lu, Yb, Tm, Tb, Gd, Eu, Ba, Cs, Y, Sr, Rb and As in polycrystalline tantalum were made over the temperature range 1700 Fsub(As)>Fsub(lanthanides)>Fsub(Sr)>Fsub(Ba)>Fsub(Hf)>Fsub(Rb)>Fsub(Cs). The data indicate, that the Arrhenius relation was obeyed over the entire temperature range. Within the lanthanide-group no differences in the diffusion velocities could be detected, this fact points to a diffusion mechanism of Me 3+ -ions of lanthanides, Me 2+ -ions of earth alkaline elements and Me + -ions of alkaline elements. (author)

Radon diffusion studies in air, gravel, sand, soil and water

International Nuclear Information System (INIS)

Singh, B.; Singh, S.; Virk, H.S.

1993-01-01

Radon isotopes are practically inert and have properties of gases under conditions of geological interest. During their brief lives their atoms are capable of moving from sites of their generation. Radon diffusion studies were carried out in air, gravel, sand, soil and water using silicon diffused junction electronic detector, Alphameter-400. Diffusion constant and diffusion length is calculated for all these materials. (author)

The relative efficiency of zinc carriers on growth and zinc nutrition of corn

International Nuclear Information System (INIS)

Prasad, B.; Sinha, K.

1981-01-01

A comparison of different zinc carriers showed that application of Zn-DTPA, Zn-EDTA, Zn-fulvate and ZnSO 4 significantly increased the dry matter yield and zinc uptake by corn over the control treatment where no zinc was applied. The chelates in particular enhanced to a greater extent the uptake of both native and applied sources than that observed with ZnSO 4 as the zinc carrier. Both the dry matter yield and zinc uptake by corn showed a positive and significant relationship with self-diffusion coefficient of zinc showing thereby that diffusion contributed mainly the supply of Zn from the ambient soil matrix to plant roots. The effectiveness of the chelates varied depending on their capacity to retain Zn in a soluble form in the soil solution. It is evident that zinc nutrition of plants in alkaline and calcareous soils can be more effectively regulated by both synthetic and natural chelates or organic manures which contain substantial amount of complexed zinc. (orig.)

Electrical and optical characterization of surface passivation in GaAs nanowires.

Science.gov (United States)

Chang, Chia-Chi; Chi, Chun-Yung; Yao, Maoqing; Huang, Ningfeng; Chen, Chun-Chung; Theiss, Jesse; Bushmaker, Adam W; Lalumondiere, Stephen; Yeh, Ting-Wei; Povinelli, Michelle L; Zhou, Chongwu; Dapkus, P Daniel; Cronin, Stephen B

2012-09-12

We report a systematic study of carrier dynamics in Al(x)Ga(1-x)As-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (L(diff)) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and the photoluminescence (PL) lifetime increases from sub-60 ps to 1.3 ns. A 48-fold enhancement in the continuous-wave PL intensity is observed on the same individual nanowire with and without the Al(x)Ga(1-x)As passivation layer, indicating a significant reduction in surface recombination. These results indicate that, in passivated nanowires, the minority carrier lifetime is not limited by twin stacking faults. From the PL lifetime and minority carrier diffusion length, we estimate the surface recombination velocity (SRV) to range from 1.7 × 10(3) to 1.1 × 10(4) cm·s(-1), and the minority carrier mobility μ is estimated to lie in the range from 10.3 to 67.5 cm(2) V(-1) s(-1) for the passivated nanowires.

Photoluminescence and Photoconductivity to Assess Maximum Open-Circuit Voltage and Carrier Transport in Hybrid Perovskites and Other Photovoltaic Materials.

Science.gov (United States)

Braly, Ian L; Stoddard, Ryan J; Rajagopal, Adharsh; Jen, Alex K-Y; Hillhouse, Hugh W

2018-06-06

Photovoltaic (PV) device development is much more expensive and time consuming than the development of the absorber layer alone. This perspective focuses on two methods that can be used to rapidly assess and develop PV absorber materials independent of device development. The absorber material properties of quasi-Fermi level splitting and carrier diffusion length under steady effective one-Sun illumination are indicators of a material's ability to achieve high VOC and JSC. These two material properties can be rapidly and simultaneously assessed with steady-state absolute intensity photoluminescence and photoconductivity measurements. As a result, these methods are extremely useful for predicting the quality and stability of PV materials prior to PV device development. Here, we summarize the methods, discuss their strengths and weaknesses, and compare photoluminescence and photoconductivity results with device performance for four hybrid perovskite compositions of various bandgaps (1.35 to 1.82 eV), CISe, CIGSe, and CZTSe.

Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators

Science.gov (United States)

Nagarjun, K. P.; Selvaraja, Shankar Kumar; Supradeepa, V. R.

2016-03-01

High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

[Enterotoxin genes occurance among S. aureus strains isolated from inpatients and carriers].

Science.gov (United States)

Lawrynowicz-Paciorek, Maja; Kochman, Maria; Piekarska, Katarzyna; Wyrebiak, Agata; Potracka, Ewa; Leniak-Chmiel, Urszula; Magdziak, Agnieszka

2006-01-01

We examined 44 inpatients and 66 carriers Staphylococcus aureus strains, isolated in years 2002-2005, for the presence of 18 enterotoxin genes (se/sel) (by PCR), the ability for A-D enterotoxin production (by SET-RPLA) and antibiotic resistance distribution (by disc diffusion method). se/sel genes were detected in 90,9% of all strains, sea (70,5%) and selk and selq (52,3%) - among inpatients strains and egc (65,2%) - among carriers strains were the most frequently se/sel genes found. Positive results of SET-RPLA were consistent with PCR results. There was no correlation observed between antibiotic resistance and se/sel genes distribution among tested S. aureus strains.

The structure of horizontal hydrogen-steam diffusion flames

International Nuclear Information System (INIS)

Chan, C.K.; Guerrero, A.

1997-01-01

This paper summarizes a systematic study on the stability, peak temperature and flame length of various horizontal hydrogen-steam diffusion flames in air. Results from this study are discussed in terms of their impact on hydrogen management in a nuclear containment building after a nuclear reactor accident. They show that, for a certain range of emerging hydrogen-steam compositions, a stable diffusion flame can anchor itself at the break in the primary heat transport system. The length of this flame can be up to 100 times the break diameter. This implies that creation of a stable diffusion flame at the break is a possible outcome of the deliberate ignition mitigation scheme. The high temperature and heat flux from a diffusion flame can threaten nearby equipment. However, due to the presence of steam and turbulent mixing with surrounding air, the peak temperatures of these diffusion flames are much lower than the adiabatic constant pressure combustion temperature of a stoichiometric hydrogen-air mixture. These results suggest that the threat of a diffusion flame anchored at the break may be less severe than conservative analysis would indicate. Furthermore, such a flame can remove hydrogen at the source and minimize the possibility of a global gas explosion. (author)

Studies of matrix diffusion in gas phase

International Nuclear Information System (INIS)

Hartikainen, K.; Timonen, J.; Vaeaetaeinen, K.; Pietarila, H.

1994-03-01

The diffusion of solutes from fractures into rock matrix is an important factor in the safety analysis of disposal of radioactive waste. Laboratory measurements are needed to complement field investigations for a reliable determination of the necessary transport parameters. Measurements of diffusion coefficients in tight rock samples are usually time consuming because the diffusion processes are slow. On the other hand it is well known that diffusion coefficients in the gas phase are roughly four orders of magnitude larger than those in the liquid phase. Therefore, for samples whose structures do not change much upon drying, it is possible to estimate the diffusion properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements. In the measurements nitrogen was used as the carrier gas and helium as the tracer gas, and standard techniques have been used for helium detection. Techniques have been developed for both channel flow and through-diffusion measurements. The breakthrough curves have been measured in every experiment and all measurements have been modelled by using appropriate analytical models. As a result matrix porosities and effective diffusion coefficients in the gas phase have been determined. (12 refs., 21 figs., 6 tabs.)

Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites.

Science.gov (United States)

Marsh, Lorraine

2015-01-01

Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorable ΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorable ΔG because of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total binding ΔG arising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where "nonspecific" interactions contribute to biological function.

Molecular diffusion of stable water isotopes in polar firn as a proxy for past temperatures

Science.gov (United States)

Holme, Christian; Gkinis, Vasileios; Vinther, Bo M.

2018-03-01

Polar precipitation archived in ice caps contains information on past temperature conditions. Such information can be retrieved by measuring the water isotopic signals of δ18O and δD in ice cores. These signals have been attenuated during densification due to molecular diffusion in the firn column, where the magnitude of the diffusion is isotopologue specific and temperature dependent. By utilizing the differential diffusion signal, dual isotope measurements of δ18O and δD enable multiple temperature reconstruction techniques. This study assesses how well six different methods can be used to reconstruct past surface temperatures from the diffusion-based temperature proxies. Two of the methods are based on the single diffusion lengths of δ18O and δD , three of the methods employ the differential diffusion signal, while the last uses the ratio between the single diffusion lengths. All techniques are tested on synthetic data in order to evaluate their accuracy and precision. We perform a benchmark test to thirteen high resolution Holocene data sets from Greenland and Antarctica, which represent a broad range of mean annual surface temperatures and accumulation rates. Based on the benchmark test, we comment on the accuracy and precision of the methods. Both the benchmark test and the synthetic data test demonstrate that the most precise reconstructions are obtained when using the single isotope diffusion lengths, with precisions of approximately 1.0 °C . In the benchmark test, the single isotope diffusion lengths are also found to reconstruct consistent temperatures with a root-mean-square-deviation of 0.7 °C . The techniques employing the differential diffusion signals are more uncertain, where the most precise method has a precision of 1.9 °C . The diffusion length ratio method is the least precise with a precision of 13.7 °C . The absolute temperature estimates from this method are also shown to be highly sensitive to the choice of fractionation factor

Diffusion coefficient for anomalous transport

International Nuclear Information System (INIS)

1986-01-01

A report on the progress towards the goal of estimating the diffusion coefficient for anomalous transport is given. The gyrokinetic theory is used to identify different time and length scale inherent to the characteristics of plasmas which exhibit anomalous transport

Exciton delocalization incorporated drift-diffusion model for bulk-heterojunction organic solar cells

Science.gov (United States)

Wang, Zi Shuai; Sha, Wei E. I.; Choy, Wallace C. H.

2016-12-01

Modeling the charge-generation process is highly important to understand device physics and optimize power conversion efficiency of bulk-heterojunction organic solar cells (OSCs). Free carriers are generated by both ultrafast exciton delocalization and slow exciton diffusion and dissociation at the heterojunction interface. In this work, we developed a systematic numerical simulation to describe the charge-generation process by a modified drift-diffusion model. The transport, recombination, and collection of free carriers are incorporated to fully capture the device response. The theoretical results match well with the state-of-the-art high-performance organic solar cells. It is demonstrated that the increase of exciton delocalization ratio reduces the energy loss in the exciton diffusion-dissociation process, and thus, significantly improves the device efficiency, especially for the short-circuit current. By changing the exciton delocalization ratio, OSC performances are comprehensively investigated under the conditions of short-circuit and open-circuit. Particularly, bulk recombination dependent fill factor saturation is unveiled and understood. As a fundamental electrical analysis of the delocalization mechanism, our work is important to understand and optimize the high-performance OSCs.

Diffusion of hydrous species in model basaltic melt

Science.gov (United States)

Zhang, Li; Guo, Xuan; Wang, Qinxia; Ding, Jiale; Ni, Huaiwei

2017-10-01

Water diffusion in Fe-free model basaltic melt with up to 2 wt% H2O was investigated at 1658-1846 K and 1 GPa in piston-cylinder apparatus using both hydration and diffusion couple techniques. Diffusion profiles measured by FTIR are consistent with a model in which both molecular H2O (H2Om) and hydroxyl (OH) contribute to water diffusion. OH diffusivity is roughly 13% of H2Om diffusivity, showing little dependence on temperature or water concentration. Water diffusion is dominated by the motion of OH until total H2O (H2Ot) concentration reaches 1 wt%. The dependence of apparent H2Ot diffusivity on H2Ot concentration appears to be overestimated by a previous study on MORB melt, but H2Ot diffusivity at 1 wt% H2Ot in basaltic melt is still greater than those in rhyolitic to andesitic melts. The appreciable contribution of OH to water diffusion in basaltic melt can be explained by enhanced mobility of OH, probably associated with the development of free hydroxyl bonded with network-modifying cations, as well as higher OH concentration. Calculation based on the Nernst-Einstein equation demonstrates that OH may serve as an effective charge carrier in hydrous basaltic melt, which could partly account for the previously observed strong influence of water on electrical conductivity of basaltic melt.

Model-Independent Characterization of Charge Diffusion in Thick Fully Depleted CCDs

International Nuclear Information System (INIS)

O'Connor, P.; Takacs, P.; Lawrence, D.; Frank, J.

2011-01-01

We present a new method to measure charge diffusion in charge-coupled devices (CCDs). The method is based on a statistical characterization of the shapes of charge clouds produced by low-energy X-rays using known properties of the two-dimensional Gaussian point-spread function (PSF). The algorithm produces reliable upper and lower bounds on the size of the PSF for photons converting near the entrance window of a device. It is optimally suited to the case of thick back-illuminated CCDs where the X-ray absorption length is smaller than the silicon thickness and the diffusion scale is of the same order as the pixel size. The only assumptions are that the charge cloud width is a monotonically increasing function of distance from the conversion point to the buried channel, and that the conversion probability is peaked at the surface. Otherwise, no physical models of carrier transport or knowledge of the electric field profile in the CCD are needed. In suboptimal conditions, the upper bound increases and the lower bound is unaffected, so confidence in the correctness of results is retained. The new method has been benchmarked against Monte Carlo simulations and tested on X-ray images measured on thick high-resistivity prototype CCDs for the Large Synoptic Survey Telescope. In Monte Carlo simulations of noiseless images having the optimal diffusion scale, the upper bound approximated the true PSF within 5%, increasing to 10% in simulations with added noise. Even with severely undersampled or truncated PSFs, the method brackets the true value to within 25%. Our method is accurate and computationally efficient and offers a fast and simple experimental setup.

Well-defined block copolymers for gene delivery to dendritic cells: probing the effect of polycation chain-length.

Science.gov (United States)

Tang, Rupei; Palumbo, R Noelle; Nagarajan, Lakshmi; Krogstad, Emily; Wang, Chun

2010-03-03

The development of safe and efficient polymer carriers for DNA vaccine delivery requires mechanistic understanding of structure-function relationship of the polymer carriers and their interaction with antigen-presenting cells. Here we have synthesized a series of diblock copolymers with well-defined chain-length using atom transfer radical polymerization and characterized the influence of polycation chain-length on the physico-chemical properties of the polymer/DNA complexes as well as the interaction with dendritic cells. The copolymers consist of a hydrophilic poly(ethylene glycol) block and a cationic poly(aminoethyl methacrylate) (PAEM) block. The average degree of polymerization (DP) of the PAEM block was varied among 19, 39, and 75, with nearly uniform distribution. With increasing PAEM chain-length, polyplexes formed by the diblock copolymers and plasmid DNA had smaller average particle size and showed higher stability against electrostatic destabilization by salt and heparin. The polymers were not toxic to mouse dendritic cells (DCs) and only displayed chain-length-dependent toxicity at a high concentration (1mg/mL). In vitro gene transfection efficiency and polyplex uptake in DCs were also found to correlate with chain-length of the PAEM block with the longer polymer chain favoring transfection and cellular uptake. The polyplexes induced a modest up-regulation of surface markers for DC maturation that was not significantly dependent on PAEM chain-length. Finally, the polyplex prepared from the longest PAEM block (DP of 75) achieved an average of 20% enhancement over non-condensed anionic dextran in terms of uptake by DCs in the draining lymph nodes 24h after subcutaneous injection into mice. Insights gained from studying such structurally well-defined polymer carriers and their interaction with dendritic cells may contribute to improved design of practically useful DNA vaccine delivery systems. Copyright 2009 Elsevier B.V. All rights reserved.

Radon diffusion studies in some building materials using solid state nuclear track detectors

CERN Document Server

Singh, S; Singh, B; Singh, J

1999-01-01

LR-115 plastic track detector has been used to study radon diffusion through some building materials, viz. cement, soil, marble chips, sand and lime as well as air. Diffusion constant and diffusion length is calculated for all these materials.

MULTIMODAL IMAGING OF MOSAIC RETINOPATHY IN CARRIERS OF HEREDITARY X-LINKED RECESSIVE DISEASES.

Science.gov (United States)

Wu, An-Lun; Wang, Jung-Pan; Tseng, Yun-Ju; Liu, Laura; Kang, Yu-Chuan; Chen, Kuan-Jen; Chao, An-Ning; Yeh, Lung-Kun; Chen, Tun-Lu; Hwang, Yih-Shiou; Wu, Wei-Chi; Lai, Chi-Chun; Wang, Nan-Kai

2018-05-01

To investigate the clinical features in carriers of X-linked retinitis pigmentosa, X-linked ocular albinism, and choroideremia (CHM) using multimodal imaging and to assess their diagnostic value in these three mosaic retinopathies. We prospectively examined 14 carriers of 3 X-linked recessive disorders (X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM). Details of abnormalities of retinal morphology were evaluated using fundus photography, fundus autofluorescence (FAF) imaging, and spectral domain optical coherence tomography. In six X-linked retinitis pigmentosa carriers, fundus appearance varied from unremarkable to the presence of tapetal-like reflex and pigmentary changes. On FAF imaging, all carriers exhibited a bright radial reflex against a dark background. By spectral domain optical coherence tomography, loss of the ellipsoid zone in the macula was observed in 3 carriers (50%). Regarding the retinal laminar architecture, 4 carriers (66.7%) showed thinning of the outer nuclear layer and a dentate appearance of the outer plexiform layer. All five X-linked ocular albinism carriers showed a characteristic mud-splatter patterned fundus, dark radial streaks against a bright background on FAF imaging, and a normal-appearing retinal structure by spectral domain optical coherence tomography imaging. Two of the 3 CHM carriers (66.7%) showed a diffuse moth-eaten appearance of the fundus, and all 3 showed irregular hyper-FAF and hypo-FAF spots throughout the affected area. In the CHM carriers, the structural changes observed by spectral domain optical coherence tomography imaging were variable. Our findings in an Asian cohort suggest that FAF imaging is a practical diagnostic test for differentiating X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM carriers. Wide-field FAF is an easy and helpful adjunct to testing for the correct diagnosis and identification of lyonization in carriers of these three mosaic retinopathies.

Formulation of a Novel Oxybenzone-Loaded Nanostructured Lipid Carriers (NLCs)

OpenAIRE

Sanad, Rania A.; AbdelMalak, Nevine Shawky; elBayoomy, Tahany S.; Badawi, Alia A.

2010-01-01

The objective of the current study was to formulate oxybenzone into nanostructured lipid carriers (NLCs) to enhance its sunscreening efficacy and safety. NLCs of oxybenzone were prepared by the solvent diffusion method. A complete 23 factorial design was used for the evaluation of the prepared oxybenzone NLCs. The study design involves the investigation of the effect of three independent variables namely liquid lipid type (Miglyol 812 and oleic acid), liquid lipid concentration (15% and 30%),...

Non-Gaussian diffusion in static disordered media

Science.gov (United States)

Luo, Liang; Yi, Ming

2018-04-01

Non-Gaussian diffusion is commonly considered as a result of fluctuating diffusivity, which is correlated in time or in space or both. In this work, we investigate the non-Gaussian diffusion in static disordered media via a quenched trap model, where the diffusivity is spatially correlated. Several unique effects due to quenched disorder are reported. We analytically estimate the diffusion coefficient Ddis and its fluctuation over samples of finite size. We show a mechanism of population splitting in the non-Gaussian diffusion. It results in a sharp peak in the distribution of displacement P (x ,t ) around x =0 , that has frequently been observed in experiments. We examine the fidelity of the coarse-grained diffusion map, which is reconstructed from particle trajectories. Finally, we propose a procedure to estimate the correlation length in static disordered environments, where the information stored in the sample-to-sample fluctuation has been utilized.

Photon and carrier management design for nonplanar thin-film copper indium gallium diselenide photovoltaics

Science.gov (United States)

Atwater, Harry A.; Callahan, Dennis; Bukowsky, Colton

2017-11-21

Photovoltaic structures are disclosed. The structures can comprise randomly or periodically structured layers, a dielectric layer to reduce back diffusion of charge carriers, and a metallic layer to reflect photons back towards the absorbing semiconductor layers. This design can increase efficiency of photovoltaic structures. The structures can be fabricated by nanoimprint.

Development of self-healing polymers via amine–epoxy chemistry: I. Properties of healing agent carriers and the modelling of a two-part self-healing system

International Nuclear Information System (INIS)

Zhang, He; Yang, Jinglei

2014-01-01

Two types of healing agent carriers (microcapsules containing epoxy solution, referred to as EP-capsules, and etched hollow glass bubbles (HGBs) loaded with amine solution, referred to as AM-HGBs) used in self-healing epoxy systems were prepared and characterized in this study. The core percentages were measured at about 80 wt% and 33 wt% for EP-capsules and AM-HGBs, respectively. The loaded amine in AM-HGB, after incorporation into the epoxy matrix, showed high stability at ambient temperature, but diffused out gradually during heat treatment at 80 °C. The amount and the mass ratio of the two released healants at the crack plane were correlated with the size, concentration, and core percentage of the healing agent carriers. A simplified cubic array model for randomly distributed healing agent carriers was adopted to depict the longest diffusion distance of the released healants, which is inversely proportional to the cubic root of the carrier concentration. (papers)

Concentration dependent carriers dynamics in CsPbBr3 perovskite nanocrystals film with transient grating

Science.gov (United States)

Wang, Yinghui; Wang, Yanting; Dev Verma, Sachin; Tan, Mingrui; Liu, Qinghui; Yuan, Qilin; Sui, Ning; Kang, Zhihui; Zhou, Qiang; Zhang, Han-Zhuang

2017-05-01

The concentration dependence of the carrier dynamics is a key parameter to describe the photo-physical properties of semiconductor films. Here, we investigate the carrier dynamics in the CsPbBr3 perovskite nanocrystal film by employing the transient grating (TG) technique with continuous bias light. The concentration of initial carriers is determined by the average number of photons per nanocrystals induced by pump light (⟨N⟩). The multi-body interaction would appear and accelerate the TG dynamics with ⟨N⟩. When ⟨N⟩ is more than 3.0, the TG dynamics slightly changes, which implies that the Auger recombination would be the highest order multi-body interaction in carrier recombination dynamics. The concentration of non-equilibrium carriers in the film is controlled by the average number of photons per nanocrystals excited by continuous bias light (⟨nne⟩). Increasing ⟨nne⟩ would improve the trapping-detrapping process by filling the trapping state, which would accelerate the carrier diffusion and add the complexity of the mono-molecular recombination mechanism. The results should be useful to further understand the mechanism of carrier dynamics in the CsPbBr3 perovskite nanocrystal film and of great importance for the operation of the corresponding optoelectronic devices.

Penetration length-dependent hot electrons in the field emission from ZnO nanowires

Science.gov (United States)

Chen, Yicong; Song, Xiaomeng; Li, Zhibing; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

2018-01-01

In the framework of field emission, whether or not hot electrons can form in the semiconductor emitters under a surface penetration field is of great concern, which will provide not only a comprehensive physical picture of field emission from semiconductor but also guidance on how to improve device performance. However, apart from some theoretical work, its experimental evidence has not been reported yet. In this article, the field penetration length-dependent hot electrons were observed in the field emission of ZnO nanowires through the in-situ study of its electrical and field emission characteristic before and after NH3 plasma treatment in an ultrahigh vacuum system. After the treatment, most of the nanowires have an increased carrier density but reduced field emission current. The raised carrier density was caused by the increased content of oxygen vacancies, while the degraded field emission current was attributed to the lower kinetic energy of hot electrons caused by the shorter penetration length. All of these results suggest that the field emission properties of ZnO nanowires can be optimized by modifying their carrier density to balance both the kinetic energy of field induced hot electrons and the limitation of saturated current under a given field.

Enhanced separation of diffusing particles by chaotic advection

International Nuclear Information System (INIS)

Aref, H.; Jones, S.W.

1989-01-01

Combining the reversibility of advection by a Stokes flow with the irreversibility of diffusion leads to a separation strategy for diffusing substances. This basic idea goes back to Taylor and Heller. It is shown here that the sensitivity of the method can be greatly enhanced by making the advection chaotic. The separation is particularly efficient when the thinnest structures resulting from advection are made comparable in size to a diffusion length. Simple heuristic estimates based on an understanding of chaotic motion and diffusion lead to a certain scaling that is seen in numerical experiments on this separation method

Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

KAUST Repository

Marcinkevičius, S.

2014-09-15

© 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

Nuclear primary energy carriers. Short version

Energy Technology Data Exchange (ETDEWEB)

Jaeck, W

1978-04-01

Basing on our present knowledge the following energy sources for energy supply must be taken into consideration in the long term: regenerative energy sources, fission energy gained by breeder reactors, nuclear fusion. While regenerative energy sources were treated at full length in the study 'Energy Sources for Tomorrow' the present study specifies the other two energy options. The availability and the reliability of nuclear primary energy carrier supply is described in detail and the conversion systems available or still being developed are investigated with regard to their specific consumption of primary energy. Topical questions concerning the proliferation stability of the fuel cycles and techniques are subject to the INFCE program. With reference to the nuclear energy documentation activities of the Federal Government this study is supposed to supply further fundamental material on nuclear primary energy carriers, consumption and readiness for application. Thus it will contribute to the question: 'Is nuclear energy an option which guarantees energy supply in the long term for the Federal Republic of Germany'. (orig.) 891 UA 892 ARA.

Nuclear primary energy carriers. Pt. 1

International Nuclear Information System (INIS)

1978-04-01

Basing on our present knowledge the following energy sources for energy supply must be taken into consideration in the long term: regenerative energy sources, fission energy gained by breeder reactors, nuclear fusion. While regenerative energy sources were treated at full length in the study 'Energy Sources for tomorrow' the present study specifies the other two energy options. The availability and the reliability of nuclear primary energy carrier supply is described in detail and the conversion systems available or still being developed are investigated with regard to their specific consumption of primary energy. Topical questions concerning the proliferation stability of the fuel cycles and techniques are subject to the INFCE programme. With reference to the nuclear energy documentation activities of the Federal Govenment this study is supposed to supply further fundamental material on nuclear primary energy carriers, consumption and readiness for application. Thus it will contribute to the question: 'Is nuclear energy an option which guarantees energy supply in the long term for the Federal Republic of Germany'. (orig.) [de

On the correct interpretation of the low voltage regime in intrinsic single-carrier devices.

Science.gov (United States)

Röhr, Jason A; Kirchartz, Thomas; Nelson, Jenny

2017-05-24

We discuss the approach of determining the charge-carrier density of a single-carrier device by combining Ohm's law and the Mott-Gurney law. We show that this approach is seldom valid, due to the fact that whenever Ohm's law is applicable the Mott-Gurney law is usually not, and vice versa. We do this using a numerical drift-diffusion solver to calculate the current density-voltage curves and the charge-carrier density, with increasing doping concentration. As this doping concentration is increased to very large values, using Ohm's law becomes a sensible way of measuring the product of mobility and doping density in the sample. However, in the high-doping limit, the current is no longer governed by space-charge and it will no longer be possible to determine the charge-carrier mobility using the Mott-Gurney law. This leaves the value for the mobility as an unknown in the mobility-doping density product in Ohm's law. We also show that, when the charge-carrier mobility for an intrinsic semiconductor is known in advance, the carrier density is underestimated up to many orders of magnitude if Ohm's law is used. We finally seek to establish a window of conditions where the two methods can be combined to yield reasonable results.

23 CFR Appendix D to Part 658 - Devices That Are Excluded From Measurement of the Length or Width of a Commercial Motor Vehicle

Science.gov (United States)

2010-04-01

...; (v) Tarp basket; (w) Tire carrier; and (x) Uppercoupler. 2. Devices excluded from length measurement... measurement are side rails running the length of the vehicle and rear doors, provided the only function of the...

Time Resolved Studies of Carrier Dynamics in III -v Heterojunction Semiconductors.

Science.gov (United States)

Westland, Duncan James

Available from UMI in association with The British Library. Requires signed TDF. Picosecond time-resolution photoluminescence spectroscopy has been used to study transient processes in Ga _{.47}In_{.53 }As/InP multiple quantum wells (MQWs), and in bulk Ga_{.47}In _{.53}As and GaSb. To facilitate the experimental studies, apparatus was constructed to allow the detection of transient luminescence with 3ps time resolution. A frequency upconversion technique was employed. Relaxation of energetic carriers in bulk Ga _{.47}In_{.53 }As by optic phonons has been investigated, and, at carrier densities ~3 times 10^{18}cm ^{-3} is found to be a considerably slower process than simple theory predicts. The discrepancy is resolved by the inclusion of a non-equilibrium population of longitudinal optic phonons in the theoretical description. Slow energy loss is also observed in a 154A MQW under similar conditions, but carriers are found to relax more quickly in a 14A MQW with a comparable repeat period. The theory of non-equilibrium mode occupation is modified to describe the case of a MQW and is found to agree with experiment. Carrier relaxation in GaSb is studied and the importance of occupation of the L _6 conduction band valley in this material is demonstrated. The ambipolar diffusion of a photoexcited carrier plasma through an InP capping layer was investigated using an optical time-of-flight technique. This experiment also enables the efficiency of carrier capture by a Ga _{.47}In_{.53 }As quantum well to be determined. A capture time of 4ps was found.

Carrier collection losses in interface passivated amorphous silicon thin-film solar cells

International Nuclear Information System (INIS)

Neumüller, A.; Sergeev, O.; Vehse, M.; Agert, C.; Bereznev, S.; Volobujeva, O.; Ewert, M.; Falta, J.

2016-01-01

In silicon thin-film solar cells the interface between the i- and p-layer is the most critical. In the case of back diffusion of photogenerated minority carriers to the i/p-interface, recombination occurs mainly on the defect states at the interface. To suppress this effect and to reduce recombination losses, hydrogen plasma treatment (HPT) is usually applied. As an alternative to using state of the art HPT we apply an argon plasma treatment (APT) before the p-layer deposition in n-i-p solar cells. To study the effect of APT, several investigations were applied to compare the results with HPT and no plasma treatment at the interface. Carrier collection losses in resulting solar cells were examined with spectral response measurements with and without bias voltage. To investigate single layers, surface photovoltage and X-ray photoelectron spectroscopy (XPS) measurements were conducted. The results with APT at the i/p-interface show a beneficial contribution to the carrier collection compared with HPT and no plasma treatment. Therefore, it can be concluded that APT reduces the recombination centers at the interface. Further, we demonstrate that carrier collection losses of thin-film solar cells are significantly lower with APT.

Carrier collection losses in interface passivated amorphous silicon thin-film solar cells

Energy Technology Data Exchange (ETDEWEB)

Neumüller, A., E-mail: alex.neumueller@next-energy.de; Sergeev, O.; Vehse, M.; Agert, C. [NEXT ENERGY EWE Research Centre for Energy Technology at the University of Oldenburg, Carl-von-Ossietzky-Straße 15, 26129 Oldenburg (Germany); Bereznev, S.; Volobujeva, O. [Department of Materials Science, Tallinn University of Technology, Ehitajate Tee 5, Tallinn 19086 (Estonia); Ewert, M.; Falta, J. [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen (Germany)

2016-07-25

In silicon thin-film solar cells the interface between the i- and p-layer is the most critical. In the case of back diffusion of photogenerated minority carriers to the i/p-interface, recombination occurs mainly on the defect states at the interface. To suppress this effect and to reduce recombination losses, hydrogen plasma treatment (HPT) is usually applied. As an alternative to using state of the art HPT we apply an argon plasma treatment (APT) before the p-layer deposition in n-i-p solar cells. To study the effect of APT, several investigations were applied to compare the results with HPT and no plasma treatment at the interface. Carrier collection losses in resulting solar cells were examined with spectral response measurements with and without bias voltage. To investigate single layers, surface photovoltage and X-ray photoelectron spectroscopy (XPS) measurements were conducted. The results with APT at the i/p-interface show a beneficial contribution to the carrier collection compared with HPT and no plasma treatment. Therefore, it can be concluded that APT reduces the recombination centers at the interface. Further, we demonstrate that carrier collection losses of thin-film solar cells are significantly lower with APT.

Nonlinear dynamic modeling of a helicopter planetary gear train for carrier plate crack fault diagnosis

Directory of Open Access Journals (Sweden)

Fan Lei

2016-06-01

Full Text Available Planetary gear train plays a significant role in a helicopter operation and its health is of great importance for the flight safety of the helicopter. This paper investigates the effects of a planet carrier plate crack on the dynamic characteristics of a planetary gear train, and thus finds an effective method to diagnose crack fault. A dynamic model is developed to analyze the torsional vibration of a planetary gear train with a cracked planet carrier plate. The model takes into consideration nonlinear factors such as the time-varying meshing stiffness, gear backlash and viscous damping. Investigation of the deformation of the cracked carrier plate under static stress is performed in order to simulate the dynamic effects of the planet carrier crack on the angular displacement of carrier posts. Validation shows good accuracy of the developed dynamic model in predicting dynamic characteristics of a planetary gear train. Fault features extracted from predictions of the model reveal the correspondence between vibration characteristic and the conditions (length and position of a planet carrier crack clearly.

A tracer diffusion model derived from microstructure

International Nuclear Information System (INIS)

Lehikoinen, Jarmo; Muurinen, Arto; Olin, Markus

2012-01-01

Document available in extended abstract form only. Full text of publication follows: Numerous attempts have been made to explain the tracer diffusion of various solutes in compacted clays. These attempts have commonly suffered from an inability to describe the diffusion of uncharged and charged solutes with a single unified model. Here, an internally consistent approach to describing the diffusion of solutes in a heterogeneous porous medium, such as compacted bentonite, in terms of its microstructure is presented. The microstructure is taken to be represented by a succession of unit cells, which consist of two consecutive regions (Do, 1996). In the first region, the diffusion is viewed to occur in two parallel paths: one through microcrystalline units (micropores) and the other through meso-pores between the microcrystalline units. Solutes exiting these two paths are then joined together to continue diffusing through the second, disordered, region, connecting the two adjacent microcrystalline units. Adsorption (incl. co-ion exclusion) is thought to occur in the micropores, whereas meso-pores and the disordered region accommodate free species alone. Co-ions are also assumed to experience transfer resistance into and out of the micropores, which is characterized in the model by a transmission coefficient. Although the model is not new per se, its application to compacted clays has never been attempted before. It is shown that in the limit of strong adsorption, the effective diffusivity is limited from above only by the microstructural parameters of the model porous medium. As intuitive and logical as this result may appear, it has not been proven before. In the limit of vanishing disordered region, the effective diffusivity is no longer explicitly constrained by any of the model parameters. The tortuosity of the diffusion path, i.e. the quotient of the actual diffusion path length in the porous-medium coordinates and the characteristic length of the laboratory frame

A complete multifluid model for bipolar semiconductors, with interacting carriers, phonons, and photons

Science.gov (United States)

Rossani, A.

2017-12-01

If electrons (e) and holes (h) in metals or semiconductors are heated to the temperatures T_e and T_h greater than the lattice temperature, the electron-phonon interaction causes energy relaxation. In the non-uniform case a momentum relaxation occurs as well. In view of such an application, a new model, based on an asymptotic procedure for solving the kinetic equations of carriers, phonons, and photons, is proposed, which gives naturally the displaced Maxwellian at the leading order. Several generation-recombination (GR) events occur in bipolar semiconductors. In the presence of photons the most important ones are the radiative GR events, direct, indirect, and exciton-catalyzed. Phonons and photons are treated here as a participating species, with their own equation. All the phonon-photon interactions are accounted for. Moreover, carrier-photon (Compton) interactions are introduced, which make complete the model. After that, balance equations for the electron number, hole number, energy densities, and momentum densities are constructed, which constitute now a system of macroscopic equations for the chemical potentials (carriers), the temperatures (carriers and bosons), and the drift velocities (carriers and bosons). In the drift-diffusion approximation the constitutive laws are derived and the Onsager relations recovered, even in the presence of an external magnetic field.

Airflow Pattern Genereated by Three Air Diffusers

DEFF Research Database (Denmark)

Olmedo, Inés; Nielsen, Peter V.; de Adana, Manuel Ruiz

The correct description of air diffusers plays a crucial role in the CFD predictions of the airflow pattern into a room. The numerical simulation of air distribution in an indoor space is challenging because of the complicated airflow pattern generated. An experimental study has been carried out...... in a full scale test room, 4.10 m (length), 3.20 m (width), and 2.70 m (height), in order to take velocity measurements of the airflow pattern generated by three different air diffusers: displacement, mixing and a low impulse diffuser. Smoke visualization has been developed to determine the direction...

Exciton diffusion in WSe2 monolayers embedded in a van der Waals heterostructure

Science.gov (United States)

Cadiz, F.; Robert, C.; Courtade, E.; Manca, M.; Martinelli, L.; Taniguchi, T.; Watanabe, K.; Amand, T.; Rowe, A. C. H.; Paget, D.; Urbaszek, B.; Marie, X.

2018-04-01

We have combined spatially resolved steady-state micro-photoluminescence with time-resolved photoluminescence to investigate the exciton diffusion in a WSe2 monolayer encapsulated with hexagonal boron nitride. At 300 K, we extract an exciton diffusion length of LX = 0.36 ± 0.02 μm and an exciton diffusion coefficient of DX = 14.5 ± 2 cm2/s. This represents a nearly 10-fold increase in the effective mobility of excitons with respect to several previously reported values on nonencapsulated samples. At cryogenic temperatures, the high optical quality of these samples has allowed us to discriminate the diffusion of the different exciton species: bright and dark neutral excitons, as well as charged excitons. The longer lifetime of dark neutral excitons yields a larger diffusion length of LXD=1.5 ±0.02 μ m.

Diffusion welding of ZrO2 solid electrolyte cells

International Nuclear Information System (INIS)

Schaefer, W.; Schmidberger, R.

1980-01-01

Zirconia based solid-electrolyte-cells can be applied as electrolysis-cells or fuel cells at high temperatures. Scaling up to technical aggregates must be realized by a gastight electrical series-connection of many tubular single cells. A suitable process for connecting single cells is diffusion welding. Starting materials were sintered zirconia-tubes (16 mm diameter, 10 mm length) and gastight interconnecting rings (16 mm diameter, 0.5-2mm length) from gold, platinum or electrically conducting mixed oxides. ZrO 2 -tubes and interconnecting rings were mounted in alternating sequence and diffusion welded under axial pressure at high temperatures. From economic reasons noble metals cannot be used for technical aggregates. The developments were therefore concentrated on the connection with mixed oxides. Optimized welding parameters are: 1400-1500 0 C welding temperature, 2 hours welding time and an axial pressure of approximately 1 Nmm 2 . Up to now gastight tubes consisting of 20 single cells were preparated by diffusion-welding in one step. The process will be further developed for the production of 50-cell-tubes with a total length of about 60 cm. (orig.) [de

Electron beam and optical depth profiling of quasibulk GaN

International Nuclear Information System (INIS)

Chernyak, L.; Osinsky, A.; Nootz, G.; Schulte, A.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Look, D. C.; Molnar, R. J.

2000-01-01

Electron beam and optical depth profiling of thick (5.5--64 μm) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 μm, at a distance of about 5 μm from the GaN/sapphire interface, to 0.63 μm at the GaN surface, for a 36-μm-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute the latter changes in PL intensity and minority carrier diffusion length to a reduced carrier mobility and lifetime at the interface, due to scattering at threading dislocations. The results of EBIC and PL measurements are in good agreement with the values for dislocation density obtained using TEM

Carrier mediated transport through supported liquid membranes; determination of transport parameters from a single transport experiment

NARCIS (Netherlands)

Chrisstoffels, L.A.J.; Struijk, Wilhelmina; de Jong, Feike; Reinhoudt, David

1996-01-01

This paper describes a time-dependent transport model for carrier assisted cation transport through supported liquid membranes. The model describes the flux of salt as a function of time and two parameters viz. the diffusion coefficient of the cation complex (D), and the extraction constant (Kex).

Minority carrier lifetime and dark current measurements in mid-wavelength infrared InAs0.91Sb0.09 alloy nBn photodetectors

Science.gov (United States)

Olson, B. V.; Kim, J. K.; Kadlec, E. A.; Klem, J. F.; Hawkins, S. D.; Leonhardt, D.; Coon, W. T.; Fortune, T. R.; Cavaliere, M. A.; Tauke-Pedretti, A.; Shaner, E. A.

2015-11-01

Carrier lifetime and dark current measurements are reported for a mid-wavelength infrared InAs0.91Sb0.09 alloy nBn photodetector. Minority carrier lifetimes are measured using a non-contact time-resolved microwave technique on unprocessed portions of the nBn wafer and the Auger recombination Bloch function parameter is determined to be |F1F2|=0.292 . The measured lifetimes are also used to calculate the expected diffusion dark current of the nBn devices and are compared with the experimental dark current measured in processed photodetector pixels from the same wafer. Excellent agreement is found between the two, highlighting the important relationship between lifetimes and diffusion currents in nBn photodetectors.

Influence of annealing temperature on the Dy diffusion process in NdFeB magnets

Energy Technology Data Exchange (ETDEWEB)

Hu, Sheng-qing, E-mail: joy_hsq@126.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Peng, Kun, E-mail: kpeng@hnu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Chen, Hong [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China)

2017-03-15

Sintered NdFeB magnets were coated with a layer of Dy metal using electron beam evaporation method and then annealed at various temperatures to investigate the temperature dependence of Dy diffusion process in NdFeB magnets. A Dy-rich phase was observed along the grain boundaries after the grain boundary diffusion process, the diffusion coefficients of various temperatures were obtained, the diffusion coefficients of Dy along the grain boundaries at 800 °C and 900 °C were determined to be 9.8×10{sup −8} cm{sup 2} s{sup −1} and 2.4×10{sup −7} cm{sup 2} s{sup −1}, respectively. The diffusion length depended on the annealing temperature and the maximum diffusion length of approximately 1.8 mm and 3.0 mm can be obtained after annealing at 800 °C and 900 °C for 8 h. Higher diffusion temperature results in the diffusion not only along the grain boundaries but also into grains and then decrease in magnetic properties. The optimum annealing conditions can be determined as 900 °C for 8 h. The coercivity was improved from 1040 kA/m to 1450 kA/m and its magnetization has no significant reduction after the grain boundary diffusion process at the optimum annealing conditions. - Highlights: • The optimum annealing conditions can be determined as 900 °C for 8 h. • The diffusion coefficient of Dy at 900 °Care determined to be 2.4×10{sup −7} cm{sup 2} s{sup −1}. • A maximum diffusion length of about 3 mm can be obtained.

Effect of Turbulence Internal Structure on Diffusion of Heavy Inertial Particles

Directory of Open Access Journals (Sweden)

I. V. Derevich

2015-01-01

Full Text Available Based on the spectral expansion of Euler correlation of the carrier medium the a closed system of functional equations for the Lagrange spectra of heavy inertial particles and the velocity fluctuations of the carrier medium on the particle trajectory have been obtained. To split the fourth moments the approximation of quasinormality and velocity fluctuations of particles is performed by a random Gaussian process. The approximate self-consistent method is proposed for solving the resulting system of functional equations. The influence of the particle inertia, the velocity of the averaged slip and microstructure of velocity fluctuations of the medium on the parameters of the chaotic motion of an impurity has been studied. It is shown that the difference in integral time scales of Eulerian and Lagrangian correlations is associated with the spatial microstructure of velocity fluctuations of the medium. It is established that in the absence of mass forces, the coefficient of the stationary diffusion of inertial particles is always greater than the diffusion coefficient of inertialess impurity. The dependence of the turbulent diffusion coefficient of particles impurity on the structural parameter of turbulence has been illustrated. The spectrum of Euler correlations of medium velocity fluctuations is modeled by Karman distributions. The influence of the particle inertia, the velocity of the averaged slip and microstructure of velocity fluctuations of the medium on the parameters of the chaotic motion of an impurity has been studied. It is shown that the difference in integral time scales of Eulerian and Lagrangian correlations is associated with the spatial microstructure of velocity fluctuations of the medium. It is established that in the absence of mass forces, the coefficient of the stationary diffusion of inertial particles is always larger than the diffusion coefficient of inertialess impurity. The dependence of the turbulent diffusion

ESTIMATION OF TURBULENT DIFFUSIVITY WITH DIRECT NUMERICAL SIMULATION OF STELLAR CONVECTION

Energy Technology Data Exchange (ETDEWEB)

Hotta, H.; Iida, Y.; Yokoyama, T., E-mail: hotta.h@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2012-05-20

We investigate the value of horizontal turbulent diffusivity {eta} by numerical calculation of thermal convection. In this study, we introduce a new method whereby the turbulent diffusivity is estimated by monitoring the time development of the passive scalar, which is initially distributed in a given Gaussian function with a spatial scale d{sub 0}. Our conclusions are as follows: (1) assuming the relation {eta} = L{sub c} v{sub rms}/3, where v{sub rms} is the root-mean-square (rms) velocity, the characteristic length L{sub c} is restricted by the shortest one among the pressure (density) scale height and the region depth. (2) The value of turbulent diffusivity becomes greater with the larger initial distribution scale d{sub 0}. (3) The approximation of turbulent diffusion holds better when the ratio of the initial distribution scale d{sub 0} to the characteristic length L{sub c} is larger.

Differential carrier lifetime and transport effects in electrically injected III-nitride light-emitting diodes

Science.gov (United States)

Rashidi, A.; Nami, M.; Monavarian, M.; Aragon, A.; DaVico, K.; Ayoub, F.; Mishkat-Ul-Masabih, S.; Rishinaramangalam, A.; Feezell, D.

2017-07-01

This work describes a small-signal microwave method for determining the differential carrier lifetime and transport effects in electrically injected InGaN/GaN light-emitting diodes (LEDs). By considering the carrier diffusion, capture, thermionic escape, and recombination, the rate equations are used to derive an equivalent small-signal electrical circuit for the LEDs, from which expressions for the input impedance and modulation response are obtained. The expressions are simultaneously fit to the experimental data for the input impedance and modulation response for nonpolar InGaN/GaN micro-LEDs on free-standing GaN substrates. The fittings are used to extract the transport related circuit parameters and differential carrier lifetimes. The dependence of the parameters on the device diameter and current density is reported. We also derive approximations for the modulation response under low and high injection levels and show that the transport of carriers affects the modulation response of the device, especially at low injection levels. The methods presented are relevant to the design of high-speed LEDs for visible-light communication.

Performance, Defect Behavior and Carrier Enhancement in Low Energy, Proton Irradiated p(+)nn(+) InP Solar Cells

Science.gov (United States)

Weinberg, I.; Rybicki, G. C.; Vargas-Aburto, C.; Jain, R. K.; Scheiman, D.

1994-01-01

InP p(+)nn(+) cells, processed by MOCVD, were irradiated by 0.2 MeV protons and their performance and defect behavior observed to a maximum fluence of 10(exp 13)/sq cm. Their radiation induced degradation, over this fluence range, was considerably+less than observed for similarly irradiated, diffused junction n p InP cells. Significant degradation occurred in both the cell's emitter and base regions the least degradation occurring in the depletion region. A significant increase in series resistance occurs at the highest fluenc.e. Two majority carrier defect levels, E7 and E10, are observed by DLTS with activation energies at (E(sub C) - 0.39)eV and (E(sub C) - 0.74)eV respectively. The relative concentration of these defects differs considerably from that observed after 1 MeV electron irradiation. An increased carrier concentration in the cell's n-region was observed at the highest proton fluence, the change in carrier concentration being insignificant at the lower fluences. In agreement with previous results, for 1 and 1.5 MeV electron irradiated InP p(+)n junctions, the defect level E10 is attributed to a complex between zinc, diffused into the n-region from the zinc doped emitter, and a radiation induced defect. The latter is assumed to be either a phosphorus vacancy or interstitial. The increased, or enhanced carrier concentration is attributed to this complex acting as a donor.

Interaction dynamics of two diffusing particles: contact times and influence of nearby surfaces.

Science.gov (United States)

Tränkle, B; Ruh, D; Rohrbach, A

2016-03-14

Interactions of diffusing particles are governed by hydrodynamics on different length and timescales. The local hydrodynamics can be influenced substantially by simple interfaces. Here, we investigate the interaction dynamics of two micron-sized spheres close to plane interfaces to mimic more complex biological systems or microfluidic environments. Using scanned line optical tweezers and fast 3D interferometric particle tracking, we are able to track the motion of each bead with precisions of a few nanometers and at a rate of 10 kilohertz. From the recorded trajectories, all spatial and temporal information is accessible. This way, we measure diffusion coefficients for two coupling particles at varying distances h to one or two glass interfaces. We analyze their coupling strength and length by cross-correlation analysis relative to h and find a significant decrease in the coupling length when a second particle diffuses nearby. By analysing the times the particles are in close contact, we find that the influence of nearby surfaces and interaction potentials reduce the diffusivity strongly, although we found that the diffusivity hardly affects the contact times and the binding probability between the particles. All experimental results are compared to a theoretical model, which is based on the number of possible diffusion paths following the Catalan numbers and a diffusion probability, which is biased by the spheres' surface potential. The theoretical and experimental results agree very well and therefore enable a better understanding of hydrodynamically coupled interaction processes.

Systematic homogenization and self-consistent flux and pin power reconstruction for nodal diffusion methods. 1: Diffusion equation-based theory

International Nuclear Information System (INIS)

Zhang, H.; Rizwan-uddin; Dorning, J.J.

1995-01-01

A diffusion equation-based systematic homogenization theory and a self-consistent dehomogenization theory for fuel assemblies have been developed for use with coarse-mesh nodal diffusion calculations of light water reactors. The theoretical development is based on a multiple-scales asymptotic expansion carried out through second order in a small parameter, the ratio of the average diffusion length to the reactor characteristic dimension. By starting from the neutron diffusion equation for a three-dimensional heterogeneous medium and introducing two spatial scales, the development systematically yields an assembly-homogenized global diffusion equation with self-consistent expressions for the assembly-homogenized diffusion tensor elements and cross sections and assembly-surface-flux discontinuity factors. The rector eigenvalue 1/k eff is shown to be obtained to the second order in the small parameter, and the heterogeneous diffusion theory flux is shown to be obtained to leading order in that parameter. The latter of these two results provides a natural procedure for the reconstruction of the local fluxes and the determination of pin powers, even though homogenized assemblies are used in the global nodal diffusion calculation

SNAP - a three dimensional neutron diffusion code

International Nuclear Information System (INIS)

McCallien, C.W.J.

1993-02-01

This report describes a one- two- three-dimensional multi-group diffusion code, SNAP, which is primarily intended for neutron diffusion calculations but can also carry out gamma calculations if the diffusion approximation is accurate enough. It is suitable for fast and thermal reactor core calculations and for shield calculations. SNAP can solve the multi-group neutron diffusion equations using finite difference methods. The one-dimensional slab, cylindrical and spherical geometries and the two-dimensional case are all treated as simple special cases of three-dimensional geometries. Numerous reflective and periodic symmetry options are available and may be used to reduce the number of mesh points necessary to represent the system. Extrapolation lengths can be specified at internal and external boundaries. (Author)

Genome-wide assessment of the carriers involved in the cellular uptake of drugs: a model system in yeast.

Science.gov (United States)

Lanthaler, Karin; Bilsland, Elizabeth; Dobson, Paul D; Moss, Harry J; Pir, Pınar; Kell, Douglas B; Oliver, Stephen G

2011-10-24

The uptake of drugs into cells has traditionally been considered to be predominantly via passive diffusion through the bilayer portion of the cell membrane. The recent recognition that drug uptake is mostly carrier-mediated raises the question of which drugs use which carriers. To answer this, we have constructed a chemical genomics platform built upon the yeast gene deletion collection, using competition experiments in batch fermenters and robotic automation of cytotoxicity screens, including protection by 'natural' substrates. Using these, we tested 26 different drugs and identified the carriers required for 18 of the drugs to gain entry into yeast cells. As well as providing a useful platform technology, these results further substantiate the notion that the cellular uptake of pharmaceutical drugs normally occurs via carrier-mediated transport and indicates that establishing the identity and tissue distribution of such carriers should be a major consideration in the design of safe and effective drugs.

Transient current changes induced in pin-diodes by nanosecond electron pulses

International Nuclear Information System (INIS)

Leonhardt, J.W.; Goldner, R.; Bos, J.; Mehnert, R.

1984-01-01

The electron pulse technique can be applied as a diagnostic method to measure charge carrier lifetimes, diffusion length or junction width in semiconductor p + -i-n + diodes. The described effect of the pulse length dependence on the electron energy might be of importance as an energy monitor for pulsed electron accelerators. (author)

Single Crystal Diffuse Neutron Scattering

Directory of Open Access Journals (Sweden)

Richard Welberry

2018-01-01

Full Text Available Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.

Theoretical and computational studies of entangled rod-coil block copolymer diffusion

Science.gov (United States)

Wang, Muzhou; Alexander-Katz, Alfredo; Olsen, B. D.

2012-02-01

Despite continued interest in the thermodynamics of rod-coil block copolymers for functional nanostructured materials in organic electronics and biomaterials, relatively few studies have investigated the dynamics of these systems which are important for understanding diffusion, mechanics, and self-assembly kinetics. Here, the diffusion of coil-rod-coil block copolymers through entangled melts is simulated using the Kremer-Grest molecular dynamics model, demonstrating that the mismatch between the curvature of the rod and coil blocks results in dramatically slower reptation through the entanglement tube. For rod lengths near the tube diameter, this hindered diffusion is explained by a local curvature-dependent free energy penalty produced by the curvature mismatch, resulting in a rough energy surface as the rod moves along the tube contour. Compared to coil homopolymers which reptate freely along the tube, rod-coil block copolymers undergo an activated diffusion process which is considerably slower as the rod length increases. For large rods, diffusion of the rod through the tube only occurs when the coil blocks occupy straight entanglement tubes, which requires ``arm retraction'' as the dominant relaxation mechanism.

On the correct interpretation of the low voltage regime in intrinsic single-carrier devices

International Nuclear Information System (INIS)

Röhr, Jason A; Nelson, Jenny; Kirchartz, Thomas

2017-01-01

We discuss the approach of determining the charge-carrier density of a single-carrier device by combining Ohm’s law and the Mott–Gurney law. We show that this approach is seldom valid, due to the fact that whenever Ohm’s law is applicable the Mott–Gurney law is usually not, and vice versa. We do this using a numerical drift-diffusion solver to calculate the current density–voltage curves and the charge-carrier density, with increasing doping concentration. As this doping concentration is increased to very large values, using Ohm’s law becomes a sensible way of measuring the product of mobility and doping density in the sample. However, in the high-doping limit, the current is no longer governed by space-charge and it will no longer be possible to determine the charge-carrier mobility using the Mott–Gurney law. This leaves the value for the mobility as an unknown in the mobility-doping density product in Ohm’s law. We also show that, when the charge-carrier mobility for an intrinsic semiconductor is known in advance, the carrier density is underestimated up to many orders of magnitude if Ohm’s law is used. We finally seek to establish a window of conditions where the two methods can be combined to yield reasonable results. (paper)

Carrier dynamics and surface vibration-assisted Auger recombination in porous silicon

Science.gov (United States)

Zakar, Ammar; Wu, Rihan; Chekulaev, Dimitri; Zerova, Vera; He, Wei; Canham, Leigh; Kaplan, Andrey

2018-04-01

Excitation and recombination dynamics of the photoexcited charge carriers in porous silicon membranes were studied using a femtosecond pump-probe technique. Near-infrared pulses (800 nm, 60 fs) were used for the pump while, for the probe, we employed different wavelengths in the range between 3.4 and 5 μ m covering the medium wavelength infrared range. The data acquired in these experiments consist of simultaneous measurements of the transmittance and reflectance as a function of the delay time between the pump and probe for different pump fluences and probe wavelengths. To evaluate the results, we developed an optical model based on the two-dimensional Maxwell-Garnett formula, incorporating the free-carrier Drude contribution and nonuniformity of the excitation by the Wentzel-Kramers-Brillouin model. This model allowed the retrieval of information about the carrier density as a function of the pump fluence, time, and wavelength. The carrier density data were analyzed to reveal that the recombination dynamics is governed by Shockley-Read-Hall and Auger processes, whereas the diffusion has an insignificant contribution. We show that, in porous silicon samples, the Auger recombination process is greatly enhanced at the wavelength corresponding to the infrared-active vibrational modes of the molecular impurities on the surface of the pores. This observation of surface-vibration-assisted Auger recombination is not only for porous silicon in particular, but for low-dimension and bulk semiconductors in general. We estimate the time constants of Shockley-Read-Hall and Auger processes, and demonstrate their wavelength dependence for the excited carrier density in the range of 1018-10191 /cm3 . We demonstrate that both processes are enhanced by up to three orders of magnitude with respect to the bulk counterpart. In addition, we provide a plethora of the physical parameters evaluated from the experimental data, such as the dielectric function and its dependence on the

Modeling charge collection efficiency degradation in partially depleted GaAs photodiodes using the 1- and 2-carrier Hecht equations

International Nuclear Information System (INIS)

Auden, E.C.; Vizkelethy, G.; Serkland, D.K.; Bossert, D.J.; Doyle, B.L.

2017-01-01

The Hecht equation can be used to model the nonlinear degradation of charge collection efficiency (CCE) in response to radiation-induced displacement damage in both fully and partially depleted GaAs photodiodes. CCE degradation is measured for laser-generated photocurrent as a function of fluence and bias in Al_0_._3Ga_0_._7As/GaAs/Al_0_._2_5Ga_0_._7_5As p-i-n photodiodes which have been irradiated with 12 MeV C and 7.5 MeV Si ions. CCE is observed to degrade more rapidly with fluence in partially depleted photodiodes than in fully depleted photodiodes. When the intrinsic GaAs layer is fully depleted, the 2-carrier Hecht equation describes CCE degradation as photogenerated electrons and holes recombine at defect sites created by radiation damage in the depletion region. If the GaAs layer is partially depleted, CCE degradation is more appropriately modeled as the sum of the 2-carrier Hecht equation applied to electrons and holes generated within the depletion region and the 1-carrier Hecht equation applied to minority carriers that diffuse from the field-free (non-depleted) region into the depletion region. Enhanced CCE degradation is attributed to holes that recombine within the field-free region of the partially depleted intrinsic GaAs layer before they can diffuse into the depletion region.

Modeling charge collection efficiency degradation in partially depleted GaAs photodiodes using the 1- and 2-carrier Hecht equations

Energy Technology Data Exchange (ETDEWEB)

Auden, E.C., E-mail: eauden@sandia.gov; Vizkelethy, G.; Serkland, D.K.; Bossert, D.J.; Doyle, B.L.

2017-05-15

The Hecht equation can be used to model the nonlinear degradation of charge collection efficiency (CCE) in response to radiation-induced displacement damage in both fully and partially depleted GaAs photodiodes. CCE degradation is measured for laser-generated photocurrent as a function of fluence and bias in Al{sub 0.3}Ga{sub 0.7}As/GaAs/Al{sub 0.25}Ga{sub 0.75}As p-i-n photodiodes which have been irradiated with 12 MeV C and 7.5 MeV Si ions. CCE is observed to degrade more rapidly with fluence in partially depleted photodiodes than in fully depleted photodiodes. When the intrinsic GaAs layer is fully depleted, the 2-carrier Hecht equation describes CCE degradation as photogenerated electrons and holes recombine at defect sites created by radiation damage in the depletion region. If the GaAs layer is partially depleted, CCE degradation is more appropriately modeled as the sum of the 2-carrier Hecht equation applied to electrons and holes generated within the depletion region and the 1-carrier Hecht equation applied to minority carriers that diffuse from the field-free (non-depleted) region into the depletion region. Enhanced CCE degradation is attributed to holes that recombine within the field-free region of the partially depleted intrinsic GaAs layer before they can diffuse into the depletion region.

Molecular exchange of n-hexane in zeolite sieves studied by diffusion-diffusion and T{sub 1}-diffusion nuclear magnetic resonance exchange spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Neudert, Oliver; Stapf, Siegfried; Mattea, Carlos, E-mail: carlos.mattea@tu-ilmenau.de [Fachgebiet Technische Physik II/Polymerphysik, Institute of Physics, Technische Universitaet Ilmenau, PO Box 100 565, 98684 Ilmenau (Germany)

2011-03-15

Molecular exchange properties and diffusion of n-hexane embedded in a bimodal pore structure with characteristic length scales in the order of nano and micrometres, respectively, formed by packing of zeolite particles, are studied. Two-dimensional (2D) nuclear magnetic resonance (NMR) diffusion correlation experiments together with relaxation-diffusion correlation experiments are performed at low magnetic field using a single-sided NMR scanner. The exchange time covers a range from 10{sup -3} to 10{sup -1} s. The molecular exchange properties are modulated by transport inside the zeolite particles. Different exchange regimes are observed for molecules starting from different positions inside the porous sample. The influence of the spin-lattice relaxation properties of the fluid molecules inside the zeolite particles on the signal intensity is also studied. A Monte Carlo simulation of the exchange process is performed and is used to support the analysis of the experimental data.

Nitrogen diffusion in hafnia and the impact of nitridation on oxygen and hydrogen diffusion: A first-principles study

Energy Technology Data Exchange (ETDEWEB)

Sathiyanarayanan, Rajesh, E-mail: rajessat@in.ibm.com, E-mail: rajesh.sathiyanarayanan@gmail.com; Pandey, R. K.; Murali, K. V. R. M. [IBM Semiconductor Research and Development Center, Bangalore 560045 (India)

2015-01-21

Using first-principles simulations, we have computed incorporation energies and diffusion barriers of ammonia, the nitrogen molecule and atomic nitrogen in monoclinic hafnia (m-HfO{sub 2}). Our calculations show that ammonia is likely to dissociate into an NH{sub 2} molecular unit, whereas the nitrogen molecule remains as a molecule either in the interstitial space or at an oxygen lattice site. The lowest energy pathway for the diffusion of atomic nitrogen interstitials consists of the hopping of the nitrogen interstitial between neighboring three-coordinated lattice oxygen atoms that share a single Hf atom, and the barrier for such hops is determined by a switching mechanism. The substitutional nitrogen atom shows a preference for diffusion through the doubly positive oxygen vacancy-mediated mechanism. Furthermore, we have investigated the impact of nitrogen atoms on the diffusion barriers of oxygen and hydrogen interstitials in m-HfO{sub 2}. Our results show that nitrogen incorporation has a significant impact on the barriers for oxygen and hydrogen diffusion: nitrogen atoms attract oxygen and hydrogen interstitials diffusing in the vicinity, thereby slowing down (reducing) their diffusion (diffusion length)

The Electrical and Optical Properties of Organometal Halide Perovskites Relevant to Optoelectronic Performance

KAUST Repository

Adinolfi, Valerio; Peng, Wei; Walters, Grant; Bakr, Osman; Sargent, Edward H.

2017-01-01

ultimately affect device performance. Material attributes and techniques used to estimate them are analyzed for different perovskite materials, with a particular focus on the bandgap, mobility, diffusion length, carrier lifetime, and trap-state density.

Assessment of two carrier materials for phosphate solubilizing biofertilizers and their effect on growth of wheat (Triticum aestivum L.).

Science.gov (United States)

Mukhtar, Salma; Shahid, Izzah; Mehnaz, Samina; Malik, Kauser A

2017-12-01

Biofertilizers are usually carrier-based inoculants containing beneficial microorganisms. Incorporation of microorganisms in carrier material enables easy-handling, long-term storage and high effectiveness of biofertilizers. Objective of the present study was to assess enriched biogas sludge and soil as biofertilizer carriers on growth and yield of wheat. Six phosphate solubilizing strains were used in this study. Three phosphate solubilizing strains, 77-NS2 (Bacillus endophyticus), 77-CS-S1 (Bacillus sphaericus) and 77-NS5 (Enterobacter aerogenes) were isolated from the rhizosphere of sugarcane, two strains, PSB5 (Bacillus safensis) and PSB12 (Bacillus megaterium) from the rhizosphere of wheat and one halophilic phosphate solubilizing strain AT2RP3 (Virgibacillus sp.) from the rhizosphere of Atriplex amnicola, were used as bioinoculants. Phosphate solubilization ability of these strains was checked in vitro in Pikovskaya medium, containing rock phosphate (RP) as insoluble P source, individually supplemented with three different carbon sources, i.e., glucose, sucrose and maltose. Maximum phosphate solubilization; 305.6μg/ml, 217.2μg/ml and 148.1μg/ml was observed in Bacillus strain PSB12 in Pikovskaya medium containing sucrose, maltose and glucose respectively. A field experiment and pot experiments in climate control room were conducted to study the effects of biogas sludge and enriched soil based phosphorous biofertilizers on growth of wheat. Bacillus strain PSB12 significantly increased root and shoot dry weights and lengths using biogas sludge as carrier material in climate control room experiments. While in field conditions, significant increase in root and shoot dry weights, lengths and seed weights was seen by PSB12 and PSB5 (Bacillus) and Enterobacter strain 77-NS5 using biogas sludge as carrier. PSB12 also significantly increased both root and shoot dry weights and lengths in field conditions when used as enriched soil based inoculum. These results

Functionalized bimodal mesoporous silicas as carriers for controlled aspirin delivery

Science.gov (United States)

Gao, Lin; Sun, Jihong; Li, Yuzhen

2011-08-01

The bimodal mesoporous silica modified with 3-aminopropyltriethoxysilane was performed as the aspirin carrier. The samples' structure, drug loading and release profiles were characterized with X-ray diffraction, scanning electron microscopy, N 2 adsorption and desorption, Fourier transform infrared spectroscopy, TG analysis, elemental analysis and UV-spectrophotometer. For further exploring the effects of the bimodal mesopores on the drug delivery behavior, the unimodal mesoporous material MCM-41 was also modified as the aspirin carrier. Meantime, Korsmeyer-Peppas equation ft= ktn was employed to analyze the dissolution data in details. It is indicated that the bimodal mesopores are beneficial for unrestricted drug molecules diffusing and therefore lead to a higher loading and faster releasing than that of MCM-41. The results show that the aspirin delivery properties are influenced considerably by the mesoporous matrix, whereas the large pore of bimodal mesoporous silica is the key point for the improved controlled-release properties.

Effects of absorption on coherence domain path length resolved dynamic light scattering in the diffuse regime

NARCIS (Netherlands)

Petoukhova, A. L.; Steenbergen, W.; van Leeuwen, T. G.; de Mul, F. F. M.

2002-01-01

A low coherence Mach-Zehnder interferometer is developed for path length resolved dynamic light scattering in highly turbid media. The path length distribution of multiply scattered photons in Intralipid is changed by the addition of absorbing dyes. Path length distributions obtained for various

Effects of absorption on coherence domain path length resolved dynamic light scattering in the diffuse regime

NARCIS (Netherlands)

Petoukhova, Anna; Steenbergen, Wiendelt; van Leeuwen, Ton; de Mul, F.F.M.

2002-01-01

A low coherence Mach–Zehnder interferometer is developed for path length resolved dynamic light scattering in highly turbid media. The path length distribution of multiply scatteredphotons in Intralipid is changed by the addition of absorbing dyes. Path length distributions obtained for various

Tritium diffusion in polycrystalline lithium tungstate

International Nuclear Information System (INIS)

Krutyakov, A.N.; Shadrin, A.A.; Saunin, E.I.; Gromov, V.V.; Shafiev, A.I.

1984-01-01

Using radiometric method the investigation of tritium separation from neutron irradiated (neutron flux density 1.2x10 13 n/cm 2 xs) polycrystalline Li 2 WO 4 in the temperature range 200-680 deg C has been carried out. It is established that the use of helium as gas-carrier of flow-type gas-discharge counter permits to conduct continuous stable measurements of concentrations of tritium extracted depending on its chemical state. It is shown that volume diffusion is the process, limiting tritiated particle separation rate from Li 2 WO 4 . It is found that the process of tritium volume diffusion in Li 2 WO 4 corresponds to two different mechanisms respectively in low- (200-300 deg C) and high-temperature (350-680 deg C) ranges. A supposition is made that in the low-temperature range the process of diffusion is conditioned by the dissociation of the radiation defect-tritiated particle complex, which is confirmed by the data on radiation defect annealing in Li 2 WO 4 . The value of activation energy of tritium separation process in the range 350-680 deg C, proved to be equal to 13.3 kJ/mol. Possible role of crystal structure peculiarities of Li 2 WO 4 for diffusion process is pointed out

Metal Halide Perovskite Single Crystals: From Growth Process to Application

Directory of Open Access Journals (Sweden)

Shuigen Li

2018-05-01

Full Text Available As a strong competitor in the field of optoelectronic applications, organic-inorganic metal hybrid perovskites have been paid much attention because of their superior characteristics, which include broad absorption from visible to near-infrared region, tunable optical and electronic properties, high charge mobility, long exciton diffusion length and carrier recombination lifetime, etc. It is noted that perovskite single crystals show remarkably low trap-state densities and long carrier diffusion lengths, which are even comparable with the best photovoltaic-quality silicon, and thus are expected to provide better optoelectronic performance. This paper reviews the recent development of crystal growth in single-, mixed-organic-cation and fully inorganic halide perovskite single crystals, in particular the solution approach. Furthermore, the application of metal hybrid perovskite single crystals and future perspectives are also highlighted.

Upper-limit on the Advanced Virgo output mode cleaner cavity length noise

Science.gov (United States)

Bonnand, R.; Ducrot, M.; Gouaty, R.; Marion, F.; Masserot, A.; Mours, B.; Pacaud, E.; Rolland, L.; Was, M.

2017-09-01

The Advanced Virgo detector uses two monolithic optical cavities at its output port to suppress higher order modes and radio frequency sidebands from the carrier light used for gravitational wave detection. These two cavities in series form the output mode cleaner. We present a measured upper limit on the length noise of these cavities that is consistent with the thermo-refractive noise prediction of 8×10-16~m~Hz-1/2 at 15 Hz. The cavity length is controlled using Peltier cells and piezo-electric actuators to maintain resonance on the incoming light. A length lock precision of 3.5×10-13 m is achieved. These two results are combined to demonstrate that the broadband length noise of the output mode cleaner in the 10-60 Hz band is at least a factor 10 below other expected noise sources in the Advanced Virgo detector design configuration.

Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime

DEFF Research Database (Denmark)

Mics, Zoltán; D’Angio, Andrea; Jensen, Søren A.

2013-01-01

In a series of systematic optical pump–terahertz probe experiments, we study the density-dependent electron scattering rate in photoexcited GaAs in the regime of strong carrier diffusion. The terahertz frequency-resolved transient sheet conductivity spectra are perfectly described by the Drude...... model, directly yielding the electron scattering rates. A diffusion model is applied to determine the spatial extent of the photoexcited electron-hole gas at each moment after photoexcitation, yielding the time-dependent electron density, and hence the density-dependent electron scattering time. We find...

Overview of phosphorus diffusion and gettering in multicrystalline silicon

International Nuclear Information System (INIS)

Bentzen, A.; Holt, A.

2009-01-01

This paper gives an overview of phosphorus emitter diffusion and gettering as experienced in multicrystalline silicon solar cell processing. The paper gives a brief summary of the diffusion properties of phosphorus in silicon, explaining the nature behind the characteristic kink-and-tail profiles often encountered in silicon solar cells. Then, phosphorus diffusion gettering is discussed with particular focus to the inhomogeneous nature of multicrystalline silicon, and it is discussed how the abundant presence of dislocations in the areas of the material having a low recombination lifetime can cause only minor lifetime enhancements in such areas upon phosphorus diffusion. Attributed to dissociation of precipitated impurities in combination with longer effective diffusion lengths of the impurities, it is then seen that even poor areas of multicrystalline can exhibit a noticeable improvement by phosphorus diffusion gettering when applying a lower diffusion temperature for a longer duration.

The effect of radionuclides and their carriers on diffusion coefficient of radionuclides in local rocks

International Nuclear Information System (INIS)

Othman, I.; Takriti, S.

1995-07-01

The diffusion coefficient of sup 9 sup 0 Sr and sup 1 sup 3 sup 7 Cs has been calculated for different local rocks in stationary and dynamic state. The effect of pH radioisotope solution dependence in shown by diffusion coefficient in some rocks. The results show that the cement and dolomite have the best quality of radioisotope retention which do not allow them to pollute the environment. (author). 6 refs., 2 tabs., 13 figs

Numerical method for a 2D drift diffusion model arising in strained n ...

Indian Academy of Sciences (India)

Abstract. This paper reports the calculation of electron transport in metal oxide semiconductor field effects transistors (MOSFETs) with biaxially tensile strained silicon channel. The calculation is formulated based on two-dimensional drift diffusion model (DDM) including strain effects. The carrier mobility dependence on the ...

Flame structure of methane inverse diffusion flame

KAUST Repository

Elbaz, Ayman M.; Roberts, William L.

2014-01-01

This paper presents high speed images of OH-PLIF at 10. kHz simultaneously with 2D PIV (particle image velocimetry) measurements collected along the entire length of an inverse diffusion flame with circumferentially arranged methane fuel jets. For a

Diffusion of radioactively tagged penetrants through rubbery polymers. II. Dependence on molecular length of penetrant

International Nuclear Information System (INIS)

Rhee, C.K.; Ferry, J.D.; Fetters, L.J.

1977-01-01

The diffusion of radioactively tagged n-hexadecane, n-dotriacontane, and a polybutadiene oligomer with molecular weight 1600 has been studied in 12 rubbery polymers. Diffusion coefficients were obtained from the theory for the thin smear method: for n-hexadecane and for n-dotriacontane (with one exception), in the form appropriate for a completely miscible polymer-penetrant pair, and for the oligomer in the form appropriate for slow entry of the pentrant across the penetrant-polymer interface. For the four flexible linear penetrants, n-dodecane, n-hexadecane, n-dotriacontane, and oligomer, the ratios of diffusion coefficients (or translational friction coefficients) are nearly the same in every polymer. It is concluded that these penetrants travel with similar segmentwise motions, although that is not the case with bulkier, more rigid penetrants. For the three normal paraffins, the friction coefficient is approximately proportional to molecular weight, but that for the oligomer is smaller than would be predicted on this basis

Quantum efficiency investigations of type-II InAs/GaSb midwave infrared superlattice photodetectors

Energy Technology Data Exchange (ETDEWEB)

Giard, E., E-mail: edouard.giard@onera.fr; Ribet-Mohamed, I.; Jaeck, J.; Viale, T.; Haïdar, R. [ONERA, DOTA, Chemin de la Hunière, 91761 Palaiseau Cedex (France); Taalat, R.; Delmas, M.; Rodriguez, J.-B.; Christol, P. [Institut d' Electronique du Sud, UMR-CNRS 5214, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier Cedex 5 (France); Steveler, E.; Bardou, N. [Laboratoire de Photonique et de Nanostructures (LPN-CNRS), Route de Nozay, 91460 Marcoussis (France); Boulard, F. [CEA, LETI, MINATEC Campus, 17 Avenue des martyrs, 38054 Grenoble (France)

2014-07-28

We present in this paper a comparison between different type-II InAs/GaSb superlattice (T2SL) photodiodes and focal plane array (FPA) in the mid-wavelength infrared domain to understand which phenomenon drives the performances of the T2SL structure in terms of quantum efficiency (QE). Our measurements on test photodiodes suggest low minority carrier diffusion length in the “InAs-rich” design, which penalizes carriers' collection in this structure for low bias voltage and front side illumination. This analysis is completed by a comparison of the experimental data with a fully analytic model, which allows to infer a hole diffusion length shorter than 100 nm. In addition, measurements on a FPA with backside illumination are finally presented. Results show an average QE in the 3–4.7 μm window equal to 42% for U{sub bias} = −0.1 V, 77 K operating temperature and no anti-reflection coating. These measurements, completed by modulation transfer function and noise measurements, reveal that the InAs-rich design, despite a low hole diffusion length, is promising for high performance infrared imaging applications.

Diffusion of hydrogen from plasma source by grain boundaries in EFG silicon

International Nuclear Information System (INIS)

Fedotov, A.; Saad, Anis M.H.; Drozdov, N.; Mazanik, A.; Ulyashin, A.; Fahrner, W.R.; Stognii, A.

2001-01-01

Diffusion of atomized hydrogen along grain boundaries (GBs) studied by transformation of their electrical activity in p-type silicon bi crystalline samples cut from EFG silicon crystals was investigated. The changes in electrical activity of GBs was estimated relative to both minority (MiC) and majority (MaC) carriers and demonstrated the correlation between the type, structure and thermal pre-history of GBs. It was shown on the base of this study that diffusion along GBs depends essentially on three factors: type of GBs, state of ribbons (as-grown or annealed) and concurrence of grain boundary dangling bonds and boron passivation effects. The model of the longitudinal hydrogen diffusion that explains these results is proposed

Diffusive charge transport in graphene

Science.gov (United States)

Chen, Jianhao

The physical mechanisms limiting the mobility of graphene on SiO 2 are studied and printed graphene devices on a flexible substrate are realized. Intentional addition of charged scattering impurities is used to study the effects of charged impurities. Atomic-scale defects are created by noble-gas ions irradiation to study the effect of unitary scatterers. The results show that charged impurities and atomic-scale defects both lead to conductivity linear in density in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates. While charged impurities cause intravalley scattering and induce a small change in the minimum conductivity, defects in graphene scatter electrons between the valleys and suppress the minimum conductivity below the metallic limit. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a small resistivity which is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO2 substrate give rise to an activated, carrier density-dependent resistivity. Graphene is also made into high mobility transparent and flexible field effect device via the transfer-printing method. Together the results paint a complete picture of charge carrier transport in graphene on SiO2 in the diffusive regime, and show the promise of graphene as a novel electronic material that have potential applications not only on conventional inorganic substrates, but also on flexible substrates.

Influence of microemulsion-mucin interaction on the fate of microemulsions diffusing through pig gastric mucin solutions.

Science.gov (United States)

Zhang, Jianbin; Lv, Yan; Wang, Bing; Zhao, Shan; Tan, Mingqian; Lv, Guojun; Ma, Xiaojun

2015-03-02

Mucus layer, a selective diffusion barrier, has an important effect on the fate of drug delivery systems in the gastrointestinal tract. To study the fate of microemulsions in the mucus layer, four microemulsion formulations with different particle sizes and lipid compositions were prepared. The microemulsion-mucin interaction was demonstrated by the fluorescence resonance energy transfer (FRET) method. Moreover, the microemulsions were observed aggregated into micron-sized emulsions by laser confocal microscopy. We concluded the microemulsion-mucin interaction not only led to microemulsions closely adhered to mucins but also destroyed the structure of microemulsions. At last, the diffusion of blank microemulsions and microemulsion-carried drugs (resveratrol and hymecromone) through mucin solutions was determined by the fluorescence recovery after photobleaching (FRAP) method and the Franz diffusion cell method. The results demonstrated the diffusion of microemulsions was significantly hindered by mucin solutions. The particle size of microemulsions had a negligible effect on the diffusion coefficients. However, the type of lipid played an important role, which could form hydrophobic interactions with mucins. Interestingly, microemulsion-carried drugs with different core/shell locations seemed to suffer different fates in the mucin solutions. The drug incorporated in the oil core of microemulsions, resveratrol, was transported through the mucus layer by the carriers, while the drug incorporated in the surfactant shell of microemulsions, hymecromone, was separated from the carriers and diffused toward the epithelium in the form of free molecules.

Parametric inference for discretely observed non-ergodic diffusions

OpenAIRE

Jacod, Jean

2006-01-01

We consider a multidimensional diffusion process [math] whose drift and diffusion coefficients depend respectively on a parameter [math] and [math] . This process is observed at [math] equally spaced times [math] , and [math] denotes the length of the `observation window'. We are interested in estimating [math] and/or [math] . Under suitable smoothness and identifiability conditions, we exhibit estimators [math] and [math] , such that the variables [math] and [math] are tight for [math] and [...

Diffusivities and Viscosities of Poly(ethylene oxide) Oligomers †

KAUST Repository

Hong, Bingbing

2010-10-14

Diffusivities and viscosities of poly(ethylene oxide) (PEO) oligomer melts with 1 to 12 repeat units have been obtained from equilibrium molecular dynamics simulations using the TraPPE-UA force field. The simulations generated diffusion coefficients with high accuracy for all of the molar masses studied, but the statistical uncertainties in the viscosity calculations were significantly larger for longer chains. There is good agreement of the calculated viscosities and densities with available experimental data, and thus, the simulations can be used to bridge gaps in the data and for extrapolations with respect to chain length, temperature, and pressure. We explored the convergence characteristics of the Green-Kubo formulas for different chain lengths and propose minimal production times required for convergence of the transport properties. The chain-length dependence of the transport properties suggests that neither Rouse nor reptation models are applicable in the short-chain regime investigated. © 2010 American Chemical Society.

Correlation of normal-range FMR1 repeat length or genotypes and reproductive parameters.

Science.gov (United States)

Maslow, Bat-Sheva L; Davis, Stephanie; Engmann, Lawrence; Nulsen, John C; Benadiva, Claudio A

2016-09-01

This study aims to ascertain whether the length of normal-ranged CGG repeats on the FMR1 gene correlates with abnormal reproductive parameters. We performed a retrospective, cross-sectional study of all FMR1 carrier screening performed as part of routine care at a large university-based fertility center from January 2011 to March 2014. Correlations were performed between normal-range FMR1 length and baseline serum anti-Müllerian hormone (AMH), cycle day 3 follicle stimulating hormone (FSH), ovarian volumes (OV), antral follicle counts (AFC), and incidence of diminished ovarian reserve (DOR), while controlling for the effect of age. Six hundred three FMR1 screening results were collected. One subject was found to be a pre-mutation carrier and was excluded from the study. Baseline serum AMH, cycle day 3 FSH, OV, and AFC data were collected for the 602 subjects with normal-ranged CGG repeats. No significant difference in median age was noted amongst any of the FMR1 repeat genotypes. No significant correlation or association was found between any allele length or genotype, with any of the reproductive parameters or with incidence of DOR at any age (p > 0.05). However, subjects who were less than 35 years old with low/low genotype were significantly more likely to have below average AMH levels compared to those with normal/normal genotype (RR 3.82; 95 % CI 1.38-10.56). This large study did not demonstrate any substantial association between normal-range FMR1 repeat lengths and reproductive parameters.

Direct observation of short-circuit diffusion during the formation of a single cupric oxide nanowire

International Nuclear Information System (INIS)

Cheng, C-L; Ma, Y-R; Chou, M H; Huang, C Y; Yeh, V; Wu, S Y

2007-01-01

Short-circuit diffusion was observed in a single CuO nanowire synthesized using a thermal oxidation method. The confocal Raman spectra of a single CuO nanowire permit direct observation of the nature of an individual CuO nanowire. The parameter order obtained from the inverse Raman B g 2 peak linewidth results in the length dependence of the linewidth and a short-circuit diffusion length of 3.3 μm. The observed structural information is also consistent with the energy dispersive x-ray spectroscopic mapping. The results confirm that the growth of CuO nanowires occurs through the short-circuit diffusion mechanism

Prevalence of precore-defective mutant of hepatitis B virus in HBV carriers.

Science.gov (United States)

Niitsuma, H; Ishii, M; Saito, Y; Miura, M; Kobayashi, K; Ohori, H; Toyota, T

1995-08-01

Two hundred and seventy-three serum specimens from hepatitis B virus (HBV) carriers were examined for the presence of a characteristic one point mutation at nucleotide (nt) 1896 from the EcoRI site of the HBV genome in the precore region (the preC mutant) using restriction fragment length polymorphism (RFLP) analysis. This assay approach could detect preC mutants or wild-type sequences when either form constituted more than 10% of the total sample. Overall, 65.5% (76/116) of HBeAg-positive carriers had only the preC wild-type. All HBeAg-positive asymptomatic carriers (n = 14) had only the preC wild-type. In patients with chronic hepatitis B and in anti-HBe-positive asymptomatic carriers, increased prevalence of the preC mutant was associated with the development of anti-HBe antibodies and normalization of the serum alanine aminotransferase concentration. Furthermore, 27 (29.0%) of 93 HBeAg-negative carriers had unexpectedly preC wild-type sequences only. Direct sequencing of the HBV precore region of HBV specimens from 24 patients revealed no mutation at nt 1896, supporting the specificity of the RFLP analysis. These results suggest that RFLP analysis was accurate for the detection of the preC mutation and that the absence of serum HBeAg cannot be explained solely by the dominance of the preC mutant.

Polymer diffusion in the interphase between surface and solution.

Science.gov (United States)

Weger, Lukas; Weidmann, Monika; Ali, Wael; Hildebrandt, Marcus; Gutmann, Jochen Stefan; Hoffmann-Jacobsen, Kerstin

2018-05-22

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of polyethylene glycol solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in solution is assigned to long range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling (D~N -1 ) indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale.

Charged Particle Diffusion in Isotropic Random Magnetic Fields

Energy Technology Data Exchange (ETDEWEB)

Subedi, P.; Matthaeus, W. H.; Chuychai, P.; Parashar, T. N.; Chhiber, R. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Sonsrettee, W. [Faculty of Engineering and Technology, Panyapiwat Institute of Management, Nonthaburi 11120 (Thailand); Blasi, P. [INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5—I-50125 Firenze (Italy); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Montgomery, D. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Dmitruk, P. [Departamento de Física Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Ciudad Universitaria, 1428 Buenos Aires (Argentina); Wan, M. [Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055 (China)

2017-03-10

The investigation of the diffusive transport of charged particles in a turbulent magnetic field remains a subject of considerable interest. Research has most frequently concentrated on determining the diffusion coefficient in the presence of a mean magnetic field. Here we consider the diffusion of charged particles in fully three-dimensional isotropic turbulent magnetic fields with no mean field, which may be pertinent to many astrophysical situations. We identify different ranges of particle energy depending upon the ratio of Larmor radius to the characteristic outer length scale of turbulence. Two different theoretical models are proposed to calculate the diffusion coefficient, each applicable to a distinct range of particle energies. The theoretical results are compared to those from computer simulations, showing good agreement.

Numerical method for a 2D drift diffusion model arising in strained n ...

Indian Academy of Sciences (India)

This paper reports the calculation of electron transport in metal oxide semiconductor field effects transistors (MOSFETs) with biaxially tensile strained silicon channel. The calculation is formulated based on two-dimensional drift diffusion model (DDM) including strain effects. The carrier mobility dependence on the lateral and ...

Development of a primary diffusion source of organic vapors for gas analyzer calibration

Science.gov (United States)

Lecuna, M.; Demichelis, A.; Sassi, G.; Sassi, M. P.

2018-03-01

The generation of reference mixtures of volatile organic compounds (VOCs) at trace levels (10 ppt-10 ppb) is a challenge for both environmental and clinical measurements. The calibration of gas analyzers for trace VOC measurements requires a stable and accurate source of the compound of interest. The dynamic preparation of gas mixtures by diffusion is a suitable method for fulfilling these requirements. The estimation of the uncertainty of the molar fraction of the VOC in the mixture is a key step in the metrological characterization of a dynamic generator. The performance of a dynamic generator was monitored over a wide range of operating conditions. The generation system was simulated by a model developed with computational fluid dynamics and validated against experimental data. The vapor pressure of the VOC was found to be one of the main contributors to the uncertainty of the diffusion rate and its influence at 10-70 kPa was analyzed and discussed. The air buoyancy effect and perturbations due to the weighing duration were studied. The gas carrier flow rate and the amount of liquid in the vial were found to play a role in limiting the diffusion rate. The results of sensitivity analyses were reported through an uncertainty budget for the diffusion rate. The roles of each influence quantity were discussed. A set of criteria to minimize the uncertainty contribution to the primary diffusion source (25 µg min-1) were estimated: carrier gas flow rate higher than 37.7 sml min-1, a maximum VOC liquid mass decrease in the vial of 4.8 g, a minimum residual mass of 1 g and vial weighing times of 1-3 min. With this procedure a limit uncertainty of 0.5% in the diffusion rate can be obtained for VOC mixtures at trace levels (10 ppt-10 ppb), making the developed diffusion vials a primary diffusion source with potential to become a new reference material for trace VOC analysis.

Hot carrier degradation and a new lifetime prediction model in ultra-deep sub-micron pMOSFET

International Nuclear Information System (INIS)

Lei Xiao-Yi; Liu Hong-Xia; Zhang Kai; Zhang Yue; Zheng Xue-Feng; Ma Xiao-Hua; Hao Yue

2013-01-01

The hot carrier effect (HCE) of an ultra-deep sub-micron p-channel metal—oxide semiconductor field-effect transistor (pMOSFET) is investigated in this paper. Experiments indicate that the generation of positively charged interface states is the predominant mechanism in the case of the ultra-deep sub-micron pMOSFET. The relation of the pMOSFET hot carrier degradation to stress time (t), channel width (W), channel length (L), and stress voltage (V d ) is then discussed. Based on the relation, a lifetime prediction model is proposed, which can predict the lifetime of the ultra-deep sub-micron pMOSFET accurately and reflect the influence of the factors on hot carrier degradation directly. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Study of excess carrier dynamics in polar, semi-polar, and non-polar (In,Ga)N epilayers and QWs

Energy Technology Data Exchange (ETDEWEB)

Aleksiejunas, R. [Institute of Applied Research, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania); Laser Research Center, Vilnius University, Sauletekio Ave. 10, 10222 Vilnius (Lithuania); Lubys, L.; Jarasiunas, K. [Institute of Applied Research, Vilnius University, Sauletekio Ave. 9-III, 10222 Vilnius (Lithuania); Vengris, M. [Laser Research Center, Vilnius University, Sauletekio Ave. 10, 10222 Vilnius (Lithuania); Wernicke, T.; Hoffmann, V.; Netzel, C.; Knauer, A.; Weyers, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12498 Berlin (Germany); Kneissl, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12498 Berlin (Germany); Institute of Solid State Physics, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

2011-07-15

We studied carrier recombination and diffusion in GaN/sapphire templates, (In,Ga)N layers, and (In,Ga)N quantum well structures oriented along the polar [0001], semi-polar [11-22], and non-polar [11-20] orientations by means of light induced transient grating, differential transmission, and photoluminescence optical techniques. We show that the lifetime of excess carriers drops by orders of magnitude when changing the orientation from polar to non-polar, both in GaN templates and (In,Ga)N layers. We attribute the shorter lifetime to carrier trapping by extended structural defects that are more abundant in non-polar grown samples. In addition, we observe pronounced carrier localization effects in the semi- and non-polar layers. We show that thick (In,Ga)N layers inherit the properties of the GaN templates. However, the thin quantum well structures show a lower carrier trapping activity. So, a better electrical quality can be assumed as compared to the thick (In,Ga)N layers. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

High-temperature resistant, thermally sprayed diffusion barrier coatings on CFC lightweight materials; Hochtemperaturbestaendige, thermisch gespritzte Diffusionsbarriereschichten auf CFC-Leichtbauchargiergestellen

Energy Technology Data Exchange (ETDEWEB)

Drehmann, Rico; Rupprecht, Christian; Wielage, Bernhard; Lampke, Thomas [Technische Univ. Chemnitz (Germany). Inst. fuer Werkstoffwissenschaft und Werkstofftechnik (IWW); Gilbert, Maria; Uhlig, Volker; Trimis, Dimosthenis [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Waermetechnik und Thermodynamik (IWTT); Heuer, Volker [ALD Vacuum Technologies GmbH, Hanau (Germany)

2013-03-15

In heat treating processes as well as in high temperature brazing processes, charge carriers enable the positioning and transport of work pieces. Recently, charge carriers consisting of graphite or carbon fibre reinforced carbon (CFC) are used. The main disadvantage of charge carriers based on CFC is the undesirable carburization of the overlying components due to diffusion processes. Under this aspect, thermally sprayed coatings are applied on CFC and tested with respect to their suitability as a high-temperature diffusion barrier. The ceramic powders aluminium oxide, aluminium oxide/chromium oxide, aluminium oxide/titanium oxide and zirconium oxide/yttrium oxide are used as a coating material which is processed by means of the powder flame spraying as well as atmospheric plasma spraying. Molybdenum and silicon carbide are used as an adhesive layer. The coating materials aluminium oxide and aluminium oxide/chromium oxide on siliconized CFC presented excellent results. This supplies a large potential of application for thermally sprayed ceramic coatings on carbon-based lightweight materials.

Influence of annealing temperature on the Dy diffusion process in NdFeB magnets

Science.gov (United States)

Hu, Sheng-qing; Peng, Kun; Chen, Hong

2017-03-01

Sintered NdFeB magnets were coated with a layer of Dy metal using electron beam evaporation method and then annealed at various temperatures to investigate the temperature dependence of Dy diffusion process in NdFeB magnets. A Dy-rich phase was observed along the grain boundaries after the grain boundary diffusion process, the diffusion coefficients of various temperatures were obtained, the diffusion coefficients of Dy along the grain boundaries at 800 °C and 900 °C were determined to be 9.8×10-8 cm2 s-1 and 2.4×10-7 cm2 s-1, respectively. The diffusion length depended on the annealing temperature and the maximum diffusion length of approximately 1.8 mm and 3.0 mm can be obtained after annealing at 800 °C and 900 °C for 8 h. Higher diffusion temperature results in the diffusion not only along the grain boundaries but also into grains and then decrease in magnetic properties. The optimum annealing conditions can be determined as 900 °C for 8 h. The coercivity was improved from 1040 kA/m to 1450 kA/m and its magnetization has no significant reduction after the grain boundary diffusion process at the optimum annealing conditions.

Diffusion of antimony in silicon in the presence of point defects

International Nuclear Information System (INIS)

Yu Xiangkun; Ma, K.B.; Chen, Q.Y.; Wang Xuemei; Liu Jiarui; Chu, W.-K.; Shao Lin; Thompson, Phillip E.

2007-01-01

We have investigated the diffusion of Sb in Si in the presence of defects injected by high-energy implantation of Si ions at room temperature. MeV ion implantation increases the concentrations of vacancies, which induce transient-enhanced diffusion of Sb deposited in Si. We observed a significant enhancement of Sb diffusion. Secondary ions mass spectroscopy has been performed on the implanted samples before and after annealing. Rutherford-backscattering spectrometry has been used to characterize the high-energy implantation damage. By fitting diffusion profiles to a linear diffusive model, information about atomic scale diffusion of Sb, i.e. the generation rate of mobile state Sb and its mean migration length were extracted

Preparation and characterization of etoricoxib solid dispersions using lipid carriers by spray drying technique

OpenAIRE

Chauhan, Bhaskar; Shimpi, Shyam; Paradkar, Anant

2005-01-01

The basic objectives of this study were to prepare and characterize solid dispersions of poorly water-soluble drug etoricoxib using lipid carriers by spray drying technique. The properties of solid dispersions were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), differential scanning calorimetry (DSC), hotstage microscopy (HSM), radiograph powder diffraction (XRPD), and dissolution studies. The absence of etoricoxib peaks in XRPD profiles of solid dispersions ...

Genetic and epigenetic alterations of the reduced folate carrier in untreated diffuse large B-cell lymphoma

DEFF Research Database (Denmark)

Kastrup, Ingelise Bjerring; Worm, Jesper; Ralfkiaer, Elisabeth

2007-01-01

The reduced folate carrier (RFC) is a transmembrane protein that mediates cellular uptake of reduced folates and antifolate drugs, including methotrexate (MTX). Acquired alterations of the RFC gene have been associated with resistance to MTX in cancer cell lines and primary osteosarcomas. Here, we...

Low-complexity Joint Sub-carrier Phase Noise Compensation for Digital Multi-carrier Systems

DEFF Research Database (Denmark)

Yankov, Metodi Plamenov; Barletta, Luca; Zibar, Darko

2017-01-01

Joint sub-carrier phase noise processing is proposed which recovers the SNR penalty related to decreased sub-carrier baudrate w.r.t. single carrier systems. The method enables digital sub-banding to be safely employed for nonlinear mitigation for modulation formats of up to 256-QAM.......Joint sub-carrier phase noise processing is proposed which recovers the SNR penalty related to decreased sub-carrier baudrate w.r.t. single carrier systems. The method enables digital sub-banding to be safely employed for nonlinear mitigation for modulation formats of up to 256-QAM....

Carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool

International Nuclear Information System (INIS)

Cai, Yu; Sha, Shuang

2016-01-01

This paper proposes a new carrier-interleaved orthogonal multi-electrode multi-carrier resistivity-measurement tool used in a cylindrical borehole environment during oil-based mud drilling processes. The new tool is an orthogonal frequency division multiplexing access-based contactless multi-measurand detection tool. The tool can measure formation resistivity in different azimuthal angles and elevational depths. It can measure many more measurands simultaneously in a specified bandwidth than the legacy frequency division multiplexing multi-measurand tool without a channel-select filter while avoiding inter-carrier interference. The paper also shows that formation resistivity is not sensitive to frequency in certain frequency bands. The average resistivity collected from N subcarriers can increase the measurement of the signal-to-noise ratio (SNR) by N times given no amplitude clipping in the current-injection electrode. If the clipping limit is taken into account, with the phase rotation of each single carrier, the amplitude peak-to-average ratio can be reduced by 3 times, and the SNR can achieve a 9/ N times gain over the single-carrier system. The carrier-interleaving technique is also introduced to counter the carrier frequency offset (CFO) effect, where the CFO will cause inter-pad interference. A qualitative analysis and simulations demonstrate that block-interleaving performs better than tone-interleaving when coping with a large CFO. The theoretical analysis also suggests that increasing the subcarrier number can increase the measurement speed or enhance elevational resolution without sacrificing receiver performance. The complex orthogonal multi-pad multi-carrier resistivity logging tool, in which all subcarriers are complex signals, can provide a larger available subcarrier pool than other types of transceivers. (paper)

Collective scattering of electromagnetic waves and cross-B plasma diffusion

International Nuclear Information System (INIS)

Gresillon, D.; Cabrit, B.; Truc, A.

1992-01-01

Magnetized plasmas occuring in nature as well as in fusion laboratories are oftenly irregularly shaked by magnetic field fluctuations. The so-called ''coherent scattering'' of electromagnetic wave from nonuniform, irregularly moving plasmas is investigated in the case where the scattering wavelength is large compared to the Debye length, but of the order of the irregularities correlation length. The scattered signal frequency spectrum is shown to be a transform of the plasma motion statistical characteristics. When the scattering wavelength is larger than the plasma motion correlation length, the frequency spectrum is shown to be of a lorentzian shape, with a frequency width that provides a direct measurement of the cross-B particle diffusion coefficient. This is illustrated by two series of recently obtained experimental results: radar coherent backscattering observations of the auroral plasma, and far infrared scattering from tokamak fusion plasma. Radar coherent backscattering shows the transition from Gauss to Lorentz scattered frequency spectra. In infrared Laser coherent scattering experiments from the Tore-Supra tokamak, a particular frequency line is observed to present a Lorentzian shape, that directly provides an electron cross-field diffusion coefficient. This diffusion coefficient agrees with the electron heat conductivity coefficient that is obtained from the observation of temperature profiles and energy balance. (Author)

NMR-CT in muscular disorders. Muscle T/sub 1/ values in Duchenne muscular dystrophy carriers

Energy Technology Data Exchange (ETDEWEB)

Matsumura, Kiichiro; Nakano, Imaharu; Fukuda, Nobuo; Ikehira, Hiroo; Tateno, Yukio

1987-02-01

Proton NMR-CT (magnetic field strength 0.1 Tesla, resonant frequency 4.5 MHz) was performed in 10 normal females and 19 Duchenne muscular dystrophy (DMD) carriers. The mean age was 39 +- 12 years for the normal females and 42 +- 6 years for the DMD carriers. In DMD carriers, there were 4 definite, 4 probable, and 11 possible carriers. T/sub 1/ (spin-lattice relaxation time) image was obtained for a slice at the buttock, mid-thigh and calf levels respectively. T/sub 1/ values were measured for the medial portion of the gluteus maximus, the vastus lateralis of the quadriceps femoris, and the gastrocnemius. The bound water fraction (BWF) was calculated from Fullerton's equation based on the fast proton diffusion model. The following results were obtained: (1) In normal females, muscle T/sub 1/ value was highest in the gastrocnemius and lowest in the gluteus maximus. (2) In DMD carriers, T/sub 1/ values of the gluteus maximus and quadriceps femoris were significantly higher than those of the normal females. There was, however, no significant difference in T/sub 1/ value of the gastrocnemius between DMD carriers and normal females. (3) In DMD carriers, BWFs of the gluteus maximus and quadriceps femoris were significantly lower than those of the normal females. (4) In DMD carriers, no significant correlation was observed between the muscle T/sub 1/ values and the serum creatine phosphokinase values. Increased tissue water content in the lower parts of the body due to gravity is considered to be the primary cause of the high T/sub 1/ value in the gastrocnemius of normal females. The presence of the degenerating muscle fibers are presumed responsible for the high T/sub 1/ value and low BWF in the proximal muscles of DMD carriers.

NMR-CT in muscular disorders. Muscle T/sub 1/ values in Duchenne muscular dystrophy carriers

Energy Technology Data Exchange (ETDEWEB)

Matsumura, Kiichiro; Nakano, Imaharu; Fukuda, Nobuo; Ikehira, Hiroo; Tateno, Yukio

1987-02-01

Proton NMR-CT (magnetic field strength 0.1 Tesla, resonant frequency 4.5 MHz) was performed in 10 normal females and 19 Duchenne muscular dystrophy (DMD) carriers. The mean age was 39 +- 12 years for the normal females and 42 +- 6 years for the DMD carriers. In DMD carriers, there were 4 definite, 4 probable, and 11 possible carriers. T/sub 1/ (spin-lattice relaxation time) image was obtained for a slice at the buttock, mid-thigh and calf levels respectively. T/sub 1/ values were measured for the medial portion of the gluteus maximus, the vastus lateralis of the quadriceps femoris, and the gastrocnemius. The bound water fraction (BWF) was calculated from Fullerton's equation based on the fast proton diffusion model. The following results were obtained: (1) In normal females, muscle T/sub 1/ value was highest in the gastrocnemius and lowest in the gluteus maximus. (2) In DMD carriers, T/sub 1/ values of the gluteus maximus and quadriceps femoris were significantly higher than those of the normal females. There was, however, no significant difference in T/sub 1/ value of the gastrocnemius between DMD carriers and normal females. (3) In DMD carriers, BWFs of the gluteus maximus and quadriceps femoris were significantly lower than those of the normal females. (4) In DMD carriers, no significant correlation was observed between the muscle T/sub 1/ values and the serum creatine phosphokinase values. Increased tissue water content in the lower parts of the body due to gravity is considered to be the primary cause of the high T/sub 1/ value in the gastrocnemius of normal females. The presence of the degenerating muscle fibers are presumed responsible for the high T/sub 1/ value and low BWF in the proximal muscles of DMD carriers.

Cycle length maximization in PWRs using empirical core models

International Nuclear Information System (INIS)

Okafor, K.C.; Aldemir, T.

1987-01-01

The problem of maximizing cycle length in nuclear reactors through optimal fuel and poison management has been addressed by many investigators. An often-used neutronic modeling technique is to find correlations between the state and control variables to describe the response of the core to changes in the control variables. In this study, a set of linear correlations, generated by two-dimensional diffusion-depletion calculations, is used to find the enrichment distribution that maximizes cycle length for the initial core of a pressurized water reactor (PWR). These correlations (a) incorporate the effect of composition changes in all the control zones on a given fuel assembly and (b) are valid for a given range of control variables. The advantage of using such correlations is that the cycle length maximization problem can be reduced to a linear programming problem

General working principles of CH3NH3PbX3 perovskite solar cells.

Science.gov (United States)

Gonzalez-Pedro, Victoria; Juarez-Perez, Emilio J; Arsyad, Waode-Sukmawati; Barea, Eva M; Fabregat-Santiago, Francisco; Mora-Sero, Ivan; Bisquert, Juan

2014-02-12

Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin films of CH3NH3PbI(3-x)Clx and CH3NH3PbI3 infiltrated on nanostructured TiO2. The results show nearly identical spectral characteristics indicating a unique photovoltaic operating mechanism that provides long diffusion lengths (1 μm). Carrier conductivity in both devices is closely matched, so that the most significant differences in performance are attributed to recombination rates. These results highlight the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and provide a new tool for improved optimization of perovskite solar cells. We report for the first time a measurement of the diffusion length in a nanostructured perovskite solar cell.

Effect of silicon nitride layers on the minority carrier diffusion length in c-Si wafers

Czech Academy of Sciences Publication Activity Database

Toušek, J.; Toušková, J.; Poruba, A.; Hlídek, P.; Lorinčík, Jan

2006-01-01

Roč. 100, č. 11 (2006), s. 113716.1-113716.6 ISSN 0021-8979 Institutional research plan: CEZ:AV0Z20670512 Keywords : solar cells * hydrogen * plasma Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.316, year: 2006

Research on an uplink carrier sense multiple access algorithm of large indoor visible light communication networks based on an optical hard core point process.

Science.gov (United States)

Nan, Zhufen; Chi, Xuefen

2016-12-20

The IEEE 802.15.7 protocol suggests that it could coordinate the channel access process based on the competitive method of carrier sensing. However, the directionality of light and randomness of diffuse reflection would give rise to a serious imperfect carrier sense (ICS) problem [e.g., hidden node (HN) problem and exposed node (EN) problem], which brings great challenges in realizing the optical carrier sense multiple access (CSMA) mechanism. In this paper, the carrier sense process implemented by diffuse reflection light is modeled as the choice of independent sets. We establish an ICS model with the presence of ENs and HNs for the multi-point to multi-point visible light communication (VLC) uplink communications system. Considering the severe optical ICS problem, an optical hard core point process (OHCPP) is developed, which characterizes the optical CSMA for the indoor VLC uplink communications system. Due to the limited coverage of the transmitted optical signal, in our OHCPP, the ENs within the transmitters' carrier sense region could be retained provided that they could not corrupt the ongoing communications. Moreover, because of the directionality of both light emitting diode (LED) transmitters and receivers, theoretical analysis of the HN problem becomes difficult. In this paper, we derive the closed-form expression for approximating the outage probability and transmission capacity of VLC networks with the presence of HNs and ENs. Simulation results validate the analysis and also show the existence of an optimal physical carrier-sensing threshold that maximizes the transmission capacity for a given emission angle of LED.

Electrochemical Impedance Imaging via the Distribution of Diffusion Times

Science.gov (United States)

Song, Juhyun; Bazant, Martin Z.

2018-03-01

We develop a mathematical framework to analyze electrochemical impedance spectra in terms of a distribution of diffusion times (DDT) for a parallel array of random finite-length Warburg (diffusion) or Gerischer (reaction-diffusion) circuit elements. A robust DDT inversion method is presented based on complex nonlinear least squares regression with Tikhonov regularization and illustrated for three cases of nanostructured electrodes for energy conversion: (i) a carbon nanotube supercapacitor, (ii) a silicon nanowire Li-ion battery, and (iii) a porous-carbon vanadium flow battery. The results demonstrate the feasibility of nondestructive "impedance imaging" to infer microstructural statistics of random, heterogeneous materials.

Comparison of the electron work function, hole concentration and exciton diffusion length for P3HT and PT prepared by thermal or acid cleavage

DEFF Research Database (Denmark)

Tousek, J.; Touskova, J.; Ludvík, J.

2016-01-01

samples were prepared from 2 different precursors by thermal or chemical treatment at room temperature. Cyclic voltammetry and work function measurements were used for estimating the concentration of holes. The measured data were evaluated assuming the validity of band theory based on the tight......-binding model. Published data on the valence bandwidth were used for calculating the value of the overlap integral which is related to the hole effective mass. Energy band diagrams were constructed for all 3 materials. Finally, the exciton diffusion length, which is a critical parameter for the application....... It is stated that a native polythiophene prepared by treatment with acids is a prospective material for solar cells and shows a similar quality as that produced by a thermal process. © 2015 Elsevier Ltd. All rights reserved....

Do methicillin resistant staphylococcus (MRSA) carrier patients influence MRSA infection more than MRSA-carrier medical officers and MRSA-carrier family?

Science.gov (United States)

Dilogo, Ismail H; Arya, Abikara; Phedy; Loho, Tony

2013-07-01

to determine the rate of MRSA-carrier among patients, family members and health care providers, and the association between MRSA-carrier family members and health care providers on MRSA infection patient after orthopaedic surgery. this is a cross-sectional analytical study. Samples were taken consecutively during December 2010 to December 2011, consisting of postoperative patients infected with MRSA, attending family members, and the medical officers with history of contact with the patient. Swab culture were taken from nasal and axilla of all subjects. The incidence of MRSA infection, and MRSA-carrier on the patient, family members and medical officers were presented descriptively, while their association with MRSA infection was statistically tested using Fischer exact test. during the study period, there were 759 surgeries, with 4 (0.5%) patients were identified to have MRSA infection. Of these four cases, 48 subjects were enrolled. The rate of MRSA-carrier among patients, family and health care providers were 50%, 25% and 0% respectively. There were no significant association between MRSA and the rates of MRSA-carrier on the family member or health care providers. the incidence of MRSA infection, MRSA-carrier patient, MRSA-carrier health care providers, and family member carrier were 0.5%, 50%, 0%, and 25% respectively. No significant association found between MRSA-carrier on the family member or health care providers and MRSA infection patient. There were no MRSA infection found on the health care provider.

Duchenne muscular dystrophy carriers. Proton spin-lattice relaxation times of skeletal muscles on magnetic resonance imaging

Energy Technology Data Exchange (ETDEWEB)

Matsumura, K.; Nakano, I. (Shimoshizu National Hospital, Chiba (Japan). Dept. of Neurology); Fukuda, N.; Ikehira, H.; Tateno, Y. (National Inst. of Radiological Sciences, Chiba (Japan). Div. of Clinical Research); Aoki, Y. (National Inst. of Radiological Sciences, Chiba (Japan))

1989-11-01

By means of magnetic resonance imaging (MRI), the proton spin-lattice relaxation times (T1 values) of the skeletal muscles were measured in Duchenne muscular dystrophy (DMD) carriers and normal controls. The bound water fraction (BWF) was calculated from the T1 values obtained, according to the fast proton diffusion model. In the DMD carriers, T1 values of the gluteus maximus and quadriceps femoris muscles were significantly higher, and BWFs of these muscles were significantly lower than in normal control. Degenerative muscular changes accompanied by interstitial edema were presumed responsible for this abnormality. No correlation was observed between the muscle T1 and serum creatine kinase values. The present study showed that MRI could be a useful method for studying the dynamic state of water in both normal and pathological skeletal muscles. Its possible utility for DMD carrier detection was discussed briefly. (orig.).

Characterization of thermal, optical and carrier transport properties of porous silicon using the photoacoustic technique

International Nuclear Information System (INIS)

Sheng, Chan Kok; Mahmood Mat Yunus, W.; Yunus, Wan Md. Zin Wan; Abidin Talib, Zainal; Kassim, Anuar

2008-01-01

In this work, the porous silicon layer was prepared by the electrochemical anodization etching process on n-type and p-type silicon wafers. The formation of the porous layer has been identified by photoluminescence and SEM measurements. The optical absorption, energy gap, carrier transport and thermal properties of n-type and p-type porous silicon layers were investigated by analyzing the experimental data from photoacoustic measurements. The values of thermal diffusivity, energy gap and carrier transport properties have been found to be porosity-dependent. The energy band gap of n-type and p-type porous silicon layers was higher than the energy band gap obtained for silicon substrate (1.11 eV). In the range of porosity (50-76%) of the studies, our results found that the optical band-gap energy of p-type porous silicon (1.80-2.00 eV) was higher than that of the n-type porous silicon layer (1.70-1.86 eV). The thermal diffusivity value of the n-type porous layer was found to be higher than that of the p-type and both were observed to increase linearly with increasing layer porosity

Model for transport and reaction of defects and carriers within displacement cascades in gallium arsenide

International Nuclear Information System (INIS)

Wampler, William R.; Myers, Samuel M.

2015-01-01

A model is presented for recombination of charge carriers at evolving displacement damage in gallium arsenide, which includes clustering of the defects in atomic displacement cascades produced by neutron or ion irradiation. The carrier recombination model is based on an atomistic description of capture and emission of carriers by the defects with time evolution resulting from the migration and reaction of the defects. The physics and equations on which the model is based are presented, along with the details of the numerical methods used for their solution. The model uses a continuum description of diffusion, field-drift and reaction of carriers, and defects within a representative spherically symmetric cluster of defects. The initial radial defect profiles within the cluster were determined through pair-correlation-function analysis of the spatial distribution of defects obtained from the binary-collision code MARLOWE, using recoil energies for fission neutrons. Properties of the defects are discussed and values for their parameters are given, many of which were obtained from density functional theory. The model provides a basis for predicting the transient response of III-V heterojunction bipolar transistors to displacement damage from energetic particle irradiation

'LTE-diffusion approximation' for arc calculations

International Nuclear Information System (INIS)

Lowke, J J; Tanaka, M

2006-01-01

This paper proposes the use of the 'LTE-diffusion approximation' for predicting the properties of electric arcs. Under this approximation, local thermodynamic equilibrium (LTE) is assumed, with a particular mesh size near the electrodes chosen to be equal to the 'diffusion length', based on D e /W, where D e is the electron diffusion coefficient and W is the electron drift velocity. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Use of the LTE-diffusion approximation for a 200 A arc with a thermionic cathode gives predictions of total arc voltage, electrode temperatures, arc temperatures and radial profiles of heat flux density and current density at the anode that are in approximate agreement with more accurate calculations which include an account of the diffusion of electric charges to the electrodes, and also with experimental results. Calculations, which include diffusion of charges, agree with experimental results of current and heat flux density as a function of radius if the Milne boundary condition is used at the anode surface rather than imposing zero charge density at the anode

Ergodicity breaking, ageing, and confinement in generalized diffusion processes with position and time dependent diffusivity

International Nuclear Information System (INIS)

Cherstvy, Andrey G; Metzler, Ralf

2015-01-01

We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) ∼ D 0 |x| α t β depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements. (paper)

Analytic 1D pn junction diode photocurrent solutions following ionizing radiation and including time-dependent changes in the carrier lifetime.

Energy Technology Data Exchange (ETDEWEB)

Axness, Carl L.; Keiter, Eric Richard; Kerr, Bert (New Mexico Tech, Socorro, NM)

2011-04-01

Circuit simulation tools (e.g., SPICE) have become invaluable in the development and design of electronic circuits in radiation environments. These codes are often employed to study the effect of many thousands of devices under transient current conditions. Device-scale simulation tools (e.g., MEDICI) are commonly used in the design of individual semiconductor components, but require computing resources that make their incorporation into a circuit code impossible for large-scale circuits. Analytic solutions to the ambipolar diffusion equation, an approximation to the carrier transport equations, may be used to characterize the transient currents at nodes within a circuit simulator. We present new transient 1D excess carrier density and photocurrent density solutions to the ambipolar diffusion equation for low-level radiation pulses that take into account a finite device geometry, ohmic fields outside the depleted region, and an arbitrary change in the carrier lifetime due to neutron irradiation or other effects. The solutions are specifically evaluated for the case of an abrupt change in the carrier lifetime during or after, a step, square, or piecewise linear radiation pulse. Noting slow convergence of the raw Fourier series for certain parameter sets, we use closed-form formulas for some of the infinite sums to produce 'partial closed-form' solutions for the above three cases. These 'partial closed-form' solutions converge with only a few tens of terms, which enables efficient large-scale circuit simulations.

Determination of diffusible and total hydrogen concentration in coated and uncoated steel

Energy Technology Data Exchange (ETDEWEB)

Mabho, Nonhlangabezo

2010-09-23

The new trend in the steel industry demands thin, flexible, high strength steels with low internal embrittlement. It is a well known fact that the atomic hydrogen which is picked up during production, fabrication and service embrittles the steel. This has led to an extensive research towards the improvement of the quality of metallic materials by focusing on total and diffusible hydrogen concentrations which are responsible for hydrogen embrittlement. Since the internal embrittlement cannot be foreseen, the concentrations of diffusible hydrogen work as indicators while the total hydrogen characterizes the absorbed quantities and quality of that particular product. To meet these requirements, the analytical chemistry methods which include the already existing carrier gas melt (fusion) extraction methods that use infrared and thermal conductivity for total hydrogen detection were applied. The newly constructed carrier gas thermal desorption mass spectroscopy was applied to monitor the diffusible concentration at specific temperatures and desorption rates of hydrogen which will contribute towards the quality of materials during service. The TDMS method also involved the characterization of the energy quantity (activation energy) required by hydrogen to be removed from traps of which irreversible traps are preferred because they enhance the stability of the product by inhibiting the mobility of hydrogen which is detrimental to the metallic structures. The instrumentation for TDMS is quite simple, compact, costs less and applicable to routine analysis. To determine total and diffusible hydrogen, the influence of the following processes: chemical and mechanical zinc coating removal, sample cleaning with organic solvents, conditions for hydrogen absorption by electrolytic hydrogen charging, conditions of hydrogen desorption by storing the sample at room temperature, solid CO{sub 2} and at temperatures of the drier was analysed. The contribution of steel alloys towards

14 CFR 399.82 - Passing off of carrier identity by affiliation between carriers.

Science.gov (United States)

2010-01-01

... forth in paragraph (c) of this section. In such cases the Board may determine in an adjudicatory... carrier shall not engage in joint public relations activities at points served by both carriers which tend... either carrier are performed in common with the other carrier or as part of a single system. In cases...

Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence

Directory of Open Access Journals (Sweden)

Saiful Islam

2008-01-01

Full Text Available This paper presents the design, construction, and testing of grounded frequency selective surface (FSS array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter. The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT, fabricated by etching technique, and characterized the S-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.

Crack diffusion coefficient - A candidate fracture toughness parameter for short fiber composites

Science.gov (United States)

Mull, M. A.; Chudnovsky, A.; Moet, A.

1987-01-01

In brittle matrix composites, crack propagation occurs along random trajectories reflecting the heterogeneous nature of the strength field. Considering the crack trajectory as a diffusive process, the 'crack diffusion coefficient' is introduced. From fatigue crack propagation experiments on a set of identical SEN polyester composite specimens, the variance of the crack tip position along the loading axis is found to be a linear function of the effective 'time'. The latter is taken as the effective crack length. The coefficient of proportionality between variance of the crack trajectory and the effective crack length defines the crack diffusion coefficient D which is found in the present study to be 0.165 mm. This parameter reflects the ability of the composite to deviate the crack from the energetically most efficient path and thus links fracture toughness to the microstructure.

Effect of potassium chloride on diffusion of theophylline at T = 298.15 K

Energy Technology Data Exchange (ETDEWEB)

Santos, Cecilia I.A.V., E-mail: cecilia.alves@uah.e [Departamento de Quimica Fisica, Facultad de Farmacia, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain); Lobo, Victor M.M., E-mail: vlobo@ci.uc.p [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Esteso, Miguel A., E-mail: miguel.esteso@uah.e [Departamento de Quimica Fisica, Facultad de Farmacia, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain); Ribeiro, Ana C.F., E-mail: anacfrib@ci.uc.p [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal)

2011-06-15

Research highlights: {yields} Mutual diffusion coefficients of theophylline in aqueous dilute solutions. {yields} Influence of the presence of potassium chloride in the aqueous media. {yields} Estimation of the association constant, K, between THP and KCl. - Abstract: Ternary mutual diffusion coefficients measured by Taylor dispersion method (D{sub 11}, D{sub 22}, D{sub 12}, and D{sub 21}) are reported for aqueous solutions of KCl + theophylline (THP) at T = 298.15 K at carrier concentrations from (0.000 to 0.010) mol {center_dot} dm{sup -3}, for each solute. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and the thermodynamic behavior of potassium chloride and theophylline in solution. For example, from these data it will be possible to make conclusions about the influence of this electrolyte in diffusion of THP and to estimate some parameters, such as the diffusion coefficient of the aggregate between KCl and THP.

Scanning spreading resistance microscopy (SSRM) 2d carrier profiling for ultra-shallow junction characterization in deep-submicron technologies

International Nuclear Information System (INIS)

Eyben, P.; Janssens, T.; Vandervorst, W.

2005-01-01

This work presents the recent progress in SSRM capabilities highlighting simultaneous performances in terms of sensitivity (<10%), spatial resolution (1-3 nm), dopant gradient resolution (1-2 nm/decade) and quantification accuracy (20-30%). The latter is illustrated through the analysis of different carrier profiling applications, i.e. the calibration of process simulations for a 90 nm n-MOS technology, the determination of the impact of nitridation on the lateral diffusion in a 40 nm n-MOS technology, the study of activation and diffusion problems in SPER-anneals of shallow implants, the observation of stress-induced diffusion mechanisms in the vicinity of shallow trench isolations (STI) and the study of diffusion and mobility mechanisms in SiGe MOS structures. Favorable comparisons with SCM and STM are also presented and do illustrate the unique capability of the SSRM technique

An improved procedure for determining grain boundary diffusion coefficients from averaged concentration profiles

Science.gov (United States)

Gryaznov, D.; Fleig, J.; Maier, J.

2008-03-01

Whipple's solution of the problem of grain boundary diffusion and Le Claire's relation, which is often used to determine grain boundary diffusion coefficients, are examined for a broad range of ratios of grain boundary to bulk diffusivities Δ and diffusion times t. Different reasons leading to errors in determining the grain boundary diffusivity (DGB) when using Le Claire's relation are discussed. It is shown that nonlinearities of the diffusion profiles in lnCav-y6/5 plots and deviations from "Le Claire's constant" (-0.78) are the major error sources (Cav=averaged concentration, y =coordinate in diffusion direction). An improved relation (replacing Le Claire's constant) is suggested for analyzing diffusion profiles particularly suited for small diffusion lengths (short times) as often required in diffusion experiments on nanocrystalline materials.

Post-processing interstitialcy diffusion from molecular dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Bhardwaj, U., E-mail: haptork@gmail.com [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Bukkuru, S. [Nuclear Physics Dept., Andhra University, Visakhapatnam, 530003 (India); Warrier, M. [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India)

2016-01-15

An algorithm to rigorously trace the interstitialcy diffusion trajectory in crystals is developed. The algorithm incorporates unsupervised learning and graph optimization which obviate the need to input extra domain specific information depending on crystal or temperature of the simulation. The algorithm is implemented in a flexible framework as a post-processor to molecular dynamics (MD) simulations. We describe in detail the reduction of interstitialcy diffusion into known computational problems of unsupervised clustering and graph optimization. We also discuss the steps, computational efficiency and key components of the algorithm. Using the algorithm, thermal interstitialcy diffusion from low to near-melting point temperatures is studied. We encapsulate the algorithms in a modular framework with functionality to calculate diffusion coefficients, migration energies and other trajectory properties. The study validates the algorithm by establishing the conformity of output parameters with experimental values and provides detailed insights for the interstitialcy diffusion mechanism. The algorithm along with the help of supporting visualizations and analysis gives convincing details and a new approach to quantifying diffusion jumps, jump-lengths, time between jumps and to identify interstitials from lattice atoms. -- Graphical abstract:.

Post-processing interstitialcy diffusion from molecular dynamics simulations

International Nuclear Information System (INIS)

Bhardwaj, U.; Bukkuru, S.; Warrier, M.

2016-01-01

An algorithm to rigorously trace the interstitialcy diffusion trajectory in crystals is developed. The algorithm incorporates unsupervised learning and graph optimization which obviate the need to input extra domain specific information depending on crystal or temperature of the simulation. The algorithm is implemented in a flexible framework as a post-processor to molecular dynamics (MD) simulations. We describe in detail the reduction of interstitialcy diffusion into known computational problems of unsupervised clustering and graph optimization. We also discuss the steps, computational efficiency and key components of the algorithm. Using the algorithm, thermal interstitialcy diffusion from low to near-melting point temperatures is studied. We encapsulate the algorithms in a modular framework with functionality to calculate diffusion coefficients, migration energies and other trajectory properties. The study validates the algorithm by establishing the conformity of output parameters with experimental values and provides detailed insights for the interstitialcy diffusion mechanism. The algorithm along with the help of supporting visualizations and analysis gives convincing details and a new approach to quantifying diffusion jumps, jump-lengths, time between jumps and to identify interstitials from lattice atoms. -- Graphical abstract:

Carbapenem-resistant Enterobacteriaceae colonization and infection in critically ill patients: a retrospective matched cohort comparison with non-carriers.

Science.gov (United States)

Dickstein, Y; Edelman, R; Dror, T; Hussein, K; Bar-Lavie, Y; Paul, M

2016-09-01

To examine whether carbapenem-resistant Enterobacteriaceae (CRE) carriage is associated with incidence of clinical infection as a means of assessing whether the morbidity and mortality associated with these bacteria are mediated by underlying conditions or intrinsic properties of CRE. This retrospective matched cohort study compared the incidence of invasive infections in CRE-colonized patients and matched non-carriers in the intensive care unit (ICU). The primary outcome was infection caused by CRE of the same species as the colonizing strain among CRE carriers, and infections caused by carbapenem-sensitive strains of the same organism in non-carriers. Hospital discharge and death were considered as competing events. Competing-risks hazard analysis was performed for the entire cohort and for a nested cohort matched by Acute Physiology and Chronic Health Evaluation (APACHE) II scores, stratified by matching. In total, 146 CRE carriers were compared with 292 non-carriers. Patients were well matched for most risk factors for Enterobacteriaceae infection, including age, renal failure, previous invasive infection, previous hospitalization, APACHE II score, length of mechanical ventilation, length of hospitalization and CRE carriage. On regression analysis, colonization with CRE was independently associated with Enterobacteriaceae infection {cause-specific hazard ratio (CSHR) 2.06 [95% confidence interval (CI) 1.03-4.09]}. On regression analysis of the APACHE-II-matched cohort (N=284), colonization with CRE remained significantly associated with Enterobacteriaceae infection [CSHR 3.32 (95% CI 1.31-8.43)]. Colonization with CRE was associated with at least a two-fold increased risk of infection by the colonizing strain amongst ICU patients. Copyright © 2016 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Both Hemophilia Health Care Providers and Hemophilia A Carriers Report that Carriers have Excessive Bleeding

Science.gov (United States)

Paroskie, Allison; Oso, Olatunde; DeBaun, Michael R.; Sidonio, Robert F

2014-01-01

Introduction Hemophilia A, the result of reduced factor VIII (FVIII) activity, is an X-linked recessive bleeding disorder. Previous reports of Hemophilia A carriers suggest an increased bleeding tendency. Our objective was to determine the attitudes and understanding of the Hemophilia A carrier bleeding phenotype, and opinions regarding timing of carrier testing from the perspective of both medical providers and affected patients. Data from this survey was used as preliminary data for an ongoing prospective study. Material and Methods An electronic survey was distributed to physicians and nurses employed at Hemophilia Treatment Centers (HTC), and Hemophilia A carriers who were members of Hemophilia Federation of America. Questions focused on the clinical understanding of bleeding symptoms and management of Hemophilia A carriers, and the timing and intensity of carrier testing. Results Our survey indicates that 51% (36/51) of providers compared to 78% (36/46) of carriers believe that Hemophilia A carriers with normal FVIII activity have an increased bleeding tendency (pHemophilia A carriers report a high frequency of bleeding symptoms. Regarding carrier testing, 72% (50/69) of medical providers recommend testing after 14 years of age, conversely 65% (29/45) of Hemophilia A carriers prefer testing to be done prior to this age (pHemophilia A carriers self-report a higher frequency of bleeding than previously acknowledged, and have a preference for earlier testing to confirm carrier status. PMID:24309601

The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) . I. Project description, survey sample, and quality assessment

Science.gov (United States)

Cox, Nick L. J.; Cami, Jan; Farhang, Amin; Smoker, Jonathan; Monreal-Ibero, Ana; Lallement, Rosine; Sarre, Peter J.; Marshall, Charlotte C. M.; Smith, Keith T.; Evans, Christopher J.; Royer, Pierre; Linnartz, Harold; Cordiner, Martin A.; Joblin, Christine; van Loon, Jacco Th.; Foing, Bernard H.; Bhatt, Neil H.; Bron, Emeric; Elyajouri, Meriem; de Koter, Alex; Ehrenfreund, Pascale; Javadi, Atefeh; Kaper, Lex; Khosroshadi, Habib G.; Laverick, Mike; Le Petit, Franck; Mulas, Giacomo; Roueff, Evelyne; Salama, Farid; Spaans, Marco

2017-10-01

The carriers of the diffuse interstellar bands (DIBs) are largely unidentified molecules ubiquitously present in the interstellar medium (ISM). After decades of study, two strong and possibly three weak near-infrared DIBs have recently been attributed to the C60^+ fullerene based on observational and laboratory measurements. There is great promise for the identification of the over 400 other known DIBs, as this result could provide chemical hints towards other possible carriers. In an effort tosystematically study the properties of the DIB carriers, we have initiated a new large-scale observational survey: the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES). The main objective is to build on and extend existing DIB surveys to make a major step forward in characterising the physical and chemical conditions for a statistically significant sample of interstellar lines-of-sight, with the goal to reverse-engineer key molecular properties of the DIB carriers. EDIBLES is a filler Large Programme using the Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope at Paranal, Chile. It is designed to provide an observationally unbiased view of the presence and behaviour of the DIBs towards early-spectral-type stars whose lines-of-sight probe the diffuse-to-translucent ISM. Such a complete dataset will provide a deep census of the atomic and molecular content, physical conditions, chemical abundances and elemental depletion levels for each sightline. Achieving these goals requires a homogeneous set of high-quality data in terms of resolution (R 70 000-100 000), sensitivity (S/N up to 1000 per resolution element), and spectral coverage (305-1042 nm), as well as a large sample size (100+ sightlines). In this first paper the goals, objectives and methodology of the EDIBLES programme are described and an initial assessment of the data is provided.

Bond-length fluctuations in the copper oxide superconductors

Energy Technology Data Exchange (ETDEWEB)

Goodenough, John B [Texas Materials Institute, ETC 9.102, University of Texas at Austin, Austin, TX 78712 (United States)

2003-02-26

Superconductivity in the copper oxides occurs at a crossover from localized to itinerant electronic behaviour, a transition that is first order. A spinodal phase segregation is normally accomplished by atomic diffusion; but where it occurs at too low a temperature for atomic diffusion, it may be realized by cooperative atomic displacements. Locally cooperative, fluctuating atomic displacements may stabilize a distinguishable phase lying between a localized-electron phase and a Fermi-liquid phase; this intermediate phase exhibits quantum-critical-point behaviour with strong electron-lattice interactions making charge transport vibronic. Ordering of the bond-length fluctuations at lower temperatures would normally stabilize a charge-density wave (CDW), which suppresses superconductivity. It is argued that in the copper oxide superconductors, crossover occurs at an optimal doping concentration for the formation of ordered two-electron/two-hole bosonic bags of spin S = 0 in a matrix of localized spins; the correlation bags contain two holes in a linear cluster of four copper centres ordered within alternate Cu-O-Cu rows of a CuO{sub 2} sheet. This ordering is optimal at a hole concentration per Cu atom of p {approx} 1/6, but it is not static. Hybridization of the vibronic electrons with the phonons that define long-range order of the fluctuating (Cu-O) bond lengths creates barely itinerant, vibronic quasiparticles of heavy mass. The heavy itinerant vibrons form Cooper pairs having a coherence length of the dimension of the bosonic bags. It is the hybridization of electrons and phonons that, it is suggested, stabilizes the superconductive state relative to a CDW state. (topical review)

Heteroduplex analysis of the dystrophin gene: Application to point mutation and carrier detection

Energy Technology Data Exchange (ETDEWEB)

Prior, T.W.; Papp, A.C.; Snyder, P.J.; Sedra, M.S.; Western, L.M.; Bartolo, C.; Mendell, J.R. [Ohio State Univ., Columbus, OH (United States); Moxley, R.T. [Univ. of Rochester Medical Center, NY (United States)

1994-03-01

Approximately one-third of Duchenne muscular dystrophy patients have undefined mutations in the dystrophin gene. For carrier and prenatal studies in families without detectable mutations, the indirect restriction fragment length polymorphism linkage approach is used. Using a multiplex amplification and heteroduplex analysis of dystrophin exons, the authors identified nonsense mutations in two DMD patients. Although the nonsense mutations are predicted to severely truncate the dystrophin protein, both patients presented with mild clinical courses of the disease. As a result of identifying the mutation in the affected boys, direct carrier studies by heteroduplex analysis were extended to other relatives. The authors conclude that the technique is not only ideal for mutation detection but is also useful for diagnostic testing. 29 refs., 4 figs.

Microstructure, length, and connection of limbic tracts in normal human brain development

Directory of Open Access Journals (Sweden)

Qiaowen eYu

2014-08-01

Full Text Available The cingulum and fornix play an important role in memory, attention, spatial orientation and feeling functions. Both microstructure and length of these limbic tracts can be affected by mental disorders such as Alzheimer’s disease, depression, autism, anxiety, and schizophrenia. To date, there has been little systematic characterization of their microstructure, length and functional connectivity in normally developing brains. In this study, diffusion tensor imaging (DTI and resting state functional MRI (rs-fMRI data from 65 normally developing right-handed subjects from birth to young adulthood was acquired. After cingulate gyrus part of the cingulum (cgc, hippocampal part of the cingulum (cgh and fornix (fx were traced with DTI tractography, absolute and normalized tract lengths and DTI-derived metrics including fractional anisotropy, mean, axial and radial diffusivity were measured for traced limbic tracts. Free water elimination (FWE algorithm was adopted to improve accuracy of the measurements of DTI-derived metrics. The role of these limbic tracts in the functional network at birth and adulthood was explored. We found a logarithmic age-dependent trajectory for FWE-corrected DTI metric changes with fast increase of microstructural integrity from birth to 2-year-old followed by a slow increase to 25-year-old. Normalized tract length of cgc increases with age, while no significant relationship with age was found for normalized tract lengths of cgh and fx. Stronger microstructural integrity on the left side compared to that of right side was found. With integrated DTI and rs-fMRI, the key connectional role of cgc and cgh in the default mode network (DMN was confirmed as early as birth. Systematic characterization of length and DTI metrics after FWE correction of limbic tracts offers insight into their morphological and microstructural developmental trajectories. These trajectories may serve as a normal reference for pediatric patients with

A multi-resolution analysis of lidar-DTMs to identify geomorphic processes from characteristic topographic length scales

Science.gov (United States)

Sangireddy, H.; Passalacqua, P.; Stark, C. P.

2013-12-01

Characteristic length scales are often present in topography, and they reflect the driving geomorphic processes. The wide availability of high resolution lidar Digital Terrain Models (DTMs) allows us to measure such characteristic scales, but new methods of topographic analysis are needed in order to do so. Here, we explore how transitions in probability distributions (pdfs) of topographic variables such as (log(area/slope)), defined as topoindex by Beven and Kirkby[1979], can be measured by Multi-Resolution Analysis (MRA) of lidar DTMs [Stark and Stark, 2001; Sangireddy et al.,2012] and used to infer dominant geomorphic processes such as non-linear diffusion and critical shear. We show this correlation between dominant geomorphic processes to characteristic length scales by comparing results from a landscape evolution model to natural landscapes. The landscape evolution model MARSSIM Howard[1994] includes components for modeling rock weathering, mass wasting by non-linear creep, detachment-limited channel erosion, and bedload sediment transport. We use MARSSIM to simulate steady state landscapes for a range of hillslope diffusivity and critical shear stresses. Using the MRA approach, we estimate modal values and inter-quartile ranges of slope, curvature, and topoindex as a function of resolution. We also construct pdfs at each resolution and identify and extract characteristic scale breaks. Following the approach of Tucker et al.,[2001], we measure the average length to channel from ridges, within the GeoNet framework developed by Passalacqua et al.,[2010] and compute pdfs for hillslope lengths at each scale defined in the MRA. We compare the hillslope diffusivity used in MARSSIM against inter-quartile ranges of topoindex and hillslope length scales, and observe power law relationships between the compared variables for simulated landscapes at steady state. We plot similar measures for natural landscapes and are able to qualitatively infer the dominant geomorphic

A microscopic model of ballistic-diffusive crossover

International Nuclear Information System (INIS)

Bagchi, Debarshee; Mohanty, P K

2014-01-01

Several low-dimensional systems show a crossover from diffusive to ballistic heat transport when system size is decreased. Although there is some phenomenological understanding of this crossover phenomenon at the coarse-grained level, a microscopic picture that consistently describes both the ballistic and the diffusive transport regimes has been lacking. In this work we derive a scaling form for the thermal current in a class of one dimensional systems attached to heat baths at boundaries and rigorously show that the crossover occurs when the characteristic length scale of the system competes with the system size. (paper)

Network degeneration and dysfunction in presymptomatic C9ORF72 expansion carriers

Directory of Open Access Journals (Sweden)

Suzee E. Lee

2017-01-01

Full Text Available Hexanucleotide repeat expansions in C9ORF72 are the most common known genetic cause of familial and sporadic frontotemporal dementia and amyotrophic lateral sclerosis. Previous work has shown that patients with behavioral variant frontotemporal dementia due to C9ORF72 show salience and sensorimotor network disruptions comparable to those seen in sporadic behavioral variant frontotemporal dementia, but it remains unknown how early in the lifespan these and other changes in brain structure and function arise. To gain insights into this question, we compared 15 presymptomatic carriers (age 43.7 ± 10.2 years, nine females to matched healthy controls. We used voxel-based morphometry to assess gray matter, diffusion tensor imaging to interrogate white matter tracts, and task-free functional MRI to probe the salience, sensorimotor, default mode, and medial pulvinar thalamus-seeded networks. We further used a retrospective chart review to ascertain psychiatric histories in carriers and their non-carrier family members. Carriers showed normal cognition and behavior despite gray matter volume and brain connectivity deficits that were apparent as early as the fourth decade of life. Gray matter volume deficits were topographically similar though less severe than those in patients with behavioral variant frontotemporal dementia due to C9ORF72, with major foci in cingulate, insula, thalamus, and striatum. Reduced white matter integrity was found in the corpus callosum, cingulum bundles, corticospinal tracts, uncinate fasciculi and inferior longitudinal fasciculi. Intrinsic connectivity deficits were detected in all four networks but most prominent in salience and medial pulvinar thalamus-seeded networks. Carrier and control groups showed comparable relationships between imaging metrics and age, suggesting that deficits emerge during early adulthood. Carriers and non-carrier family members had comparable lifetime histories of psychiatric symptoms. Taken

Soot emissions from turbulent diffusion flames burning simple alkane fuels

Energy Technology Data Exchange (ETDEWEB)

Canteenwalla, P.M.; Johnson, M.R. [Carleton Univ., Ottawa, ON (Canada). Dept. of Mechanical and Aerospace Engineering; Thomson, K.A.; Smallwood, G.J. [National Research Council of Canada, Ottawa, ON (Canada). Inst. for Chemical Process and Environmental Technology

2007-07-01

A classic problem in combustion involves measurement and prediction of soot emissions from turbulent diffusion flames. Very high-sensitivity measurements of particulate matter (PM) from very low-sooting diffusion flames burning methane and other simple alkane fuels have been enabled from recent advances in laser-induced incandescence (LII). In order to quantify soot emissions from a lab-scale turbulent diffusion flame burner, this paper presented a study that used LII to develop a sampling protocol. The purpose of the study was to develop an experimentally based model to predict PM emissions from flares used in industry using soot emissions from lab-scale flares. Quantitative results of mass of soot emitted per mass of fuel burned were presented across a range of flow conditions and fuels. The experiment used digital imaging to measure flame lengths and estimate flame residence times. Comparisons were also made between current measurements and results of previous researchers for soot in the overfire region. The study also considered the validity applicability of buoyancy based models for predicting and scaling soot emissions. The paper described the experimental setup including sampling system and flame length imaging. Background information on soot yield and a comparison of flame residence time definitions were provided. The results and discussion of results were also presented. It was concluded that the results highlighted the subjective nature of flame length measurements. 10 refs., 4 figs.

Past surface temperatures at the NorthGRIP drill site from the difference in firn diffusion of water isotopes

DEFF Research Database (Denmark)

Simonsen, Sebastian Bjerregaard; Johnsen, S. J.; Popp, T. J.

2011-01-01

A new ice core paleothermometer is introduced based on the temperature dependent diffusion of the stable water isotopes in the firn. A new parameter called differential diffusion length is defined as the difference between the diffusion length of the two stable water isotopologues 2H1H16O and 1H218......O. A model treatment of the diffusion process of the firn and the ice is presented along with a method of retrieving the diffusion signal from the ice core record of water isotopes using spectral methods. The model shows how the diffusion process is highly dependent on the inter-annual variations...... warmer than observed in other ice core based temperature reconstructions. The mechanisms behind this behaviour are not fully understood. The method shows the need of an expansion of high resolution stable water isotope datasets from ice cores. However, the new ice core paleothermometer presented here...

A numerical model for charge transport and energy conversion of perovskite solar cells.

Science.gov (United States)

Zhou, Yecheng; Gray-Weale, Angus

2016-02-14

Based on the continuity equations and Poisson's equation, we developed a numerical model for perovskite solar cells. Due to different working mechanisms, the model for perovskite solar cells differs from that of silicon solar cells and Dye Sensitized Solar Cells. The output voltage and current are calculated differently, and in a manner suited in particular to perovskite organohalides. We report a test of our equations against experiment with good agreement. Using this numerical model, it was found that performances of solar cells increase with charge carrier's lifetimes, mobilities and diffusion lengths. The open circuit voltage (Voc) of a solar cell is dependent on light intensities, and charge carrier lifetimes. Diffusion length and light intensity determine the saturated current (Jsc). Additionally, three possible guidelines for the design and fabrication of perovskite solar cells are suggested by our calculations. Lastly, we argue that concentrator perovskite solar cells are promising.

Universal diffusion-limited injection and the hook effect in organic thin-film transistors

Science.gov (United States)

Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

2016-01-01

The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials. PMID:27440253

Improvement in deuterium recovery from water–isotope mixture by thermal diffusion in the device of branch columns

International Nuclear Information System (INIS)

Hsu, Ching-Chun; Yeh, Ho-Ming

2014-01-01

Highlights: • Recovery of deuterium by thermal diffusion from water–isotope mixture has been investigated. • The undesirable remixing effect can be reduced by employing the device of branch columns. • Deuterium recoveries were compared with that in a single column of the same total column length. • Considerable recovery improvement is obtainable in the device of branch columns, instead of in a single-column device. - Abstract: Deuterium recovery from water–isotopes mixture using thermal diffusion can be improved by employing the branch column device, instead of single column devices, with the same total column length. The remixing effect due to convection currents in a thermal diffusion column for heavy water enrichment is thus reduced and separation improvement increases when the flow rate or the total column length increases. The improvement in separation can reach about 50% for the numerical example given

Diffuse mode and diffuse-to-filamentary transition in a high pressure nanosecond scale corona discharge under high voltage

International Nuclear Information System (INIS)

Tardiveau, P; Moreau, N; Bentaleb, S; Postel, C; Pasquiers, S

2009-01-01

The dynamics of a point-to-plane corona discharge induced in high pressure air under nanosecond scale high overvoltage is investigated. The electrical and optical properties of the discharge can be described in space and time with fast and precise current measurements coupled to gated and intensified imaging. Under atmospheric pressure, the discharge exhibits a diffuse pattern like a multielectron avalanche propagating through a direct field ionization mechanism. The diffuse regime can exist since the voltage rise time is much shorter than the characteristic time of the field screening effects, and as long as the local field is higher than the critical ionization field in air. As one of these conditions is not fulfilled, the discharge turns into a multi-channel regime and the diffuse-to-filamentary transition strongly depends on the overvoltage, the point-to-plane gap length and the pressure. When pressure is increased above atmospheric pressure, the diffuse stage and its transition to streamers seem to satisfy similarity rules as the key parameter is the reduced critical ionization field only. However, above 3 bar, neither diffuse avalanche nor streamer filaments are observed but a kind of streamer-leader regime, due to the fact that mechanisms such as photoionization and heat diffusion are not similar to pressure.

Molecular dynamics simulations of the penetration lengths: application within the fluctuation theory for diffusion coefficients

DEFF Research Database (Denmark)

Galliero, Guillaume; Medvedev, Oleg; Shapiro, Alexander

2005-01-01

A 322 (2004) 151). In the current study, a fast molecular dynamics scheme has been developed to determine the values of the penetration lengths in Lennard-Jones binary systems. Results deduced from computations provide a new insight into the concept of penetration lengths. It is shown for four different...... fluctuation theory and molecular dynamics scheme exhibit consistent trends and average deviations from experimental data around 10-20%. (c) 2004 Elsevier B.V. All rights reserved....

Diffuse-charge dynamics of ionic liquids in electrochemical systems.

Science.gov (United States)

Zhao, Hui

2011-11-01

We employ a continuum theory of solvent-free ionic liquids accounting for both short-range electrostatic correlations and steric effects (finite ion size) [Bazant et al., Phys. Rev. Lett. 106, 046102 (2011)] to study the response of a model microelectrochemical cell to a step voltage. The model problem consists of a 1-1 symmetric ionic liquid between two parallel blocking electrodes, neglecting any transverse transport phenomena. Matched asymptotic expansions in the limit of thin double layers are applied to analyze the resulting one-dimensional equations and study the overall charge-time relation in the weakly nonlinear regime. One important conclusion is that our simple scaling analysis suggests that the length scale √(λ*(D)l*(c)) accurately characterizes the double-layer structure of ionic liquids with strong electrostatic correlations where l*(c) is the electrostatic correlation length (in contrast, the Debye screening length λ*(D) is the primary double-layer length for electrolytes) and the response time of λ(D)(*3/2)L*/(D*l(c)(1/2)) (not λ*(D)L*/D* that is the primary charging time of electrolytes) is the correct charging time scale of ionic liquids with strong electrostatic correlations where D* is the diffusivity and L* is the separation length of the cell. With these two new scales, data of both electric potential versus distance from the electrode and the total diffuse charge versus time collapse onto each individual master curve in the presence of strong electrostatic correlations. In addition, the dependance of the total diffuse charge on steric effects, short-range correlations, and driving voltages is thoroughly examined. The results from the asymptotic analysis are compared favorably with those from full numerical simulations. Finally, the absorption of excess salt by the double layer creates a depletion region outside the double layer. Such salt depletion may bring a correction to the leading order terms and break down the weakly nonlinear

Deposition and characterization of ZnS/Si heterojunctions produced by vacuum evaporation

Science.gov (United States)

Landis, Geoffrey A.; Loferski, Joseph J.; Beaulieu, Roland

1988-01-01

Isotype heterojunctions of ZnS (lattice constant 5.41 A) were grown on silicon (lattice constant 5.43 A) p-n junctions to form a minority-carrier mirror. The deposition process was vacuum evaporation from a ZnS powder source onto a heated (450 C) substrate. Both planar (100) and textured (111) surfaces were used. A reduction of the minority-carrier recombination at the surface was seen from increased short-wavelength quantum response and increased illuminated open-circuit voltage. The minority-carrier diffusion length was not degraded by the process.

Semiconductor surface diffusion: Nonthermal effects of photon illumination

International Nuclear Information System (INIS)

Ditchfield, R.; Llera-Rodriguez, D.; Seebauer, E. G.

2000-01-01

Nonthermal influences of photon illumination on surface diffusion at high temperatures have been measured experimentally. Activation energies and pre-exponential factors for diffusion of germanium, indium, and antimony on silicon change by up to 0.3 eV and two orders of magnitude, respectively, in response to illumination by photons having energies greater than the substrate band gap. The parameters decrease for n-type material and increase for p-type material. Aided by results from photoreflectance spectroscopy, we suggest that motion of the surface quasi-Fermi-level for minority carriers accounts for much of the effect by changing the charge states of surface vacancies. An additional adatom-vacancy complexation mechanism appears to operate on p-type substrates. The results have significant implications for aspects of microelectronics fabrication by rapid thermal processing that are governed by surface mobility. (c) 2000 The American Physical Society

Electroluminescence of a-Si/c-Si heterojunction solar cells after high energy irradiation

Energy Technology Data Exchange (ETDEWEB)

Ferrara, Manuela

2009-11-24

The crystalline silicon as absorber material will certainly continue to dominate the market for space applications of solar cells. In the contribution under consideration the applicability of a-Si:H/c-Si heterojunction solar cells in space has been tested by the investigation of the cell modification by high energy protons and comparing the results to the degradation of homojunction crystalline silicon reference cells. The investigated solar cells have been irradiated with protons of different energies and doses. For all investigated solar cells the maximum damage happens for an energy of about 1.7 MeV and is mainly due to the decrease of the effective minority carrier diffusion length in the crystalline silicon absorber. Simulations carried out by AFORS-HET, a heterojunction simulation program, also confirmed this result. The main degradation mechanism for all types of devices is the monotonically decreasing charge carrier diffusion length in the p-type monocrystalline silicon absorber layer. For the heterojunction solar cell an enhancement of the photocurrent in the blue wavelength region has been observed but only in the case of heterojunction solar cell with intrinsic a-Si:H buffer layer. Additionally to the traditional characterization techniques the electroluminescence technique used for monitoring the modifications of the heteroluminescence technique used for monitoring the modifications of the heterointerface between amorphous silicon and crystalline silicon in solar cells after proton irradiation. A direct relation between minority carrier diffusion length and electroluminescence quantum efficiency has been observed but also details of the interface modification could be monitored by this technique.

Visualizing Carrier Transport in Metal Halide Perovskite Nanoplates via Electric Field Modulated Photoluminescence Imaging.

Science.gov (United States)

Hu, Xuelu; Wang, Xiao; Fan, Peng; Li, Yunyun; Zhang, Xuehong; Liu, Qingbo; Zheng, Weihao; Xu, Gengzhao; Wang, Xiaoxia; Zhu, Xiaoli; Pan, Anlian

2018-05-09

Metal halide perovskite nanostructures have recently been the focus of intense research due to their exceptional optoelectronic properties and potential applications in integrated photonics devices. Charge transport in perovskite nanostructure is a crucial process that defines efficiency of optoelectronic devices but still requires a deep understanding. Herein, we report the study of the charge transport, particularly the drift of minority carrier in both all-inorganic CsPbBr 3 and organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoplates by electric field modulated photoluminescence (PL) imaging. Bias voltage dependent elongated PL emission patterns were observed due to the carrier drift at external electric fields. By fitting the drift length as a function of electric field, we obtained the carrier mobility of about 28 cm 2 V -1 S -1 in the CsPbBr 3 perovskite nanoplate. The result is consistent with the spatially resolved PL dynamics measurement, confirming the feasibility of the method. Furthermore, the electric field modulated PL imaging is successfully applied to the study of temperature-dependent carrier mobility in CsPbBr 3 nanoplates. This work not only offers insights for the mobile carrier in metal halide perovskite nanostructures, which is essential for optimizing device design and performance prediction, but also provides a novel and simple method to investigate charge transport in many other optoelectronic materials.

Double diffusivity model under stochastic forcing

Science.gov (United States)

Chattopadhyay, Amit K.; Aifantis, Elias C.

2017-05-01

The "double diffusivity" model was proposed in the late 1970s, and reworked in the early 1980s, as a continuum counterpart to existing discrete models of diffusion corresponding to high diffusivity paths, such as grain boundaries and dislocation lines. It was later rejuvenated in the 1990s to interpret experimental results on diffusion in polycrystalline and nanocrystalline specimens where grain boundaries and triple grain boundary junctions act as high diffusivity paths. Technically, the model pans out as a system of coupled Fick-type diffusion equations to represent "regular" and "high" diffusivity paths with "source terms" accounting for the mass exchange between the two paths. The model remit was extended by analogy to describe flow in porous media with double porosity, as well as to model heat conduction in media with two nonequilibrium local temperature baths, e.g., ion and electron baths. Uncoupling of the two partial differential equations leads to a higher-ordered diffusion equation, solutions of which could be obtained in terms of classical diffusion equation solutions. Similar equations could also be derived within an "internal length" gradient (ILG) mechanics formulation applied to diffusion problems, i.e., by introducing nonlocal effects, together with inertia and viscosity, in a mechanics based formulation of diffusion theory. While being remarkably successful in studies related to various aspects of transport in inhomogeneous media with deterministic microstructures and nanostructures, its implications in the presence of stochasticity have not yet been considered. This issue becomes particularly important in the case of diffusion in nanopolycrystals whose deterministic ILG-based theoretical calculations predict a relaxation time that is only about one-tenth of the actual experimentally verified time scale. This article provides the "missing link" in this estimation by adding a vital element in the ILG structure, that of stochasticity, that takes into

Time-dependent mobility and recombination of the photoinduced charge carriers in conjugated polymer/fullerene bulk heterojunction solar cells

Science.gov (United States)

Mozer, A. J.; Dennler, G.; Sariciftci, N. S.; Westerling, M.; Pivrikas, A.; Österbacka, R.; Juška, G.

2005-07-01

Time-dependent mobility and recombination in the blend of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)- C61 (PCBM) is studied simultaneously using the photoinduced charge carrier extraction by linearly increasing voltage technique. The charge carriers are photogenerated by a strongly absorbed, 3 ns laser flash, and extracted by the application of a reverse bias voltage pulse after an adjustable delay time (tdel) . It is found that the mobility of the extracted charge carriers decreases with increasing delay time, especially shortly after photoexcitation. The time-dependent mobility μ(t) is attributed to the energy relaxation of the charge carriers towards the tail states of the density of states distribution. A model based on a dispersive bimolecular recombination is formulated, which properly describes the concentration decay of the extracted charge carriers at all measured temperatures and concentrations. The calculated bimolecular recombination coefficient β(t) is also found to be time-dependent exhibiting a power law dependence as β(t)=β0t-(1-γ) with increasing slope (1-γ) with decreasing temperatures. The temperature dependence study reveals that both the mobility and recombination of the photogenerated charge carriers are thermally activated processes with activation energy in the range of 0.1 eV. Finally, the direct comparison of μ(t) and β(t) shows that the recombination of the long-lived charge carriers is controlled by diffusion.

Impact of Nanostructuring on the Phase Behavior of Insertion Materials: The Hydrogenation Kinetics of a Magnesium Thin Film

NARCIS (Netherlands)

Bannenberg, L.J.; Schreuders, H.; van Eijck, L.; Heringa, J.R.; Steinke, N.J.; Dalgliesh, RM; Dam, B.; Mulder, F.M.; van Well, A.A.

2016-01-01

Nanostructuring is widely applied in both battery and hydrogen materials to improve the performance of these materials as energy carriers. Nanostructuring changes the diffusion length as well as the thermodynamics of materials. We studied the impact of nanostructuring on the hydrogenation in a model

Hybrid solar cells : Perovskites under the Sun

NARCIS (Netherlands)

Loi, Maria Antonietta; Hummelen, Jan C.

2013-01-01

Mixed-halide organic–inorganic hybrid perovskites are reported to display electron–hole diffusion lengths over 1 μm. This observation provides important insight into the charge-carrier dynamics of this class of semiconductors and increases the expectations for highly efficient and cheap solar cells.

Sealed substrate carrier for electroplating

Science.gov (United States)

Ganti, Kalyana Bhargava [Fremont, CA

2012-07-17

One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The substrate carrier includes a non-conductive carrier body on which the substrates are held, and conductive lines are embedded within the carrier body. A conductive bus bar is embedded into a top side of the carrier body and is conductively coupled to the conductive lines. A thermoplastic overmold covers a portion of the bus bar, and there is a plastic-to-plastic bond between the thermoplastic overmold and the non-conductive carrier body. Other embodiments, aspects and features are also disclosed.

Multi-Gigahertz radar range processing of baseband and RF carrier modulated signals in Tm:YAG

International Nuclear Information System (INIS)

Merkel, K.D.; Krishna Mohan, R.; Cole, Z.; Chang, T.; Olson, A.; Babbitt, W.R.

2004-01-01

An optical device is described and demonstrated that uses a spatial-spectral holographic material to perform coherent signal processing operations on analog, high-bandwidth optical signals with large time-bandwidth-products. Signal processing is performed as the material records the coherent spectral interference (or cross-power spectrum) of modulated optical signals as a spatial-spectral population grating between electronic transition states. Multiple exposures of processing pulse sequences are integrated with increasing grating strength. The device, coined as the Spatial-Spectral Coherent Holographic Integrating Processor (or S 2 -CHIP), is described as currently envisioned for a broadband, mid-to-high pulse repetition frequency range-Doppler radar signal processing system. Experiments were performed in Tm:YAG (0.1 at% at 5 K) to demonstrate time delay variation, integration dynamics, and effects of coding as applied to a radar range processor. These demonstrations used baseband modulation with a 1 gigabit per second (GPBS) bit rate and code length of 512 bits (512 ns), where delays up to 1.0 μs were resolved with greater than a 40 dB peak to RMS sidelobe ratio after 800 processing shots. Multi-GHz processing was demonstrated using a bit rate of 2.5 GBPS (baseband modulation) and code length of 2048 bits (819.2 ns). Processing of double-sideband modulated signals on a radio frequency (RF) carrier was demonstrated, where 512 bit, 1.0 GBPS codes were modulated on a 1.75 GHz carrier and then modulated on the optical carrier

Carrier-carrier relaxation kinetics in quantum well semiconductor structures with nonparabolic energy bands

DEFF Research Database (Denmark)

Dery, H.; Tromborg, Bjarne; Eisenstein, G.

2003-01-01

We describe carrier-carrier scattering dynamics in an inverted quantum well structure including the nonparabolic nature of the valance band. A solution of the semiconductor Bloch equations yields strong evidence to a large change in the temporal evolution of the carrier distributions compared to ...

29 CFR 1201.1 - Carrier.

Science.gov (United States)

2010-07-01

... 29 Labor 4 2010-07-01 2010-07-01 false Carrier. 1201.1 Section 1201.1 Labor Regulations Relating to Labor (Continued) NATIONAL MEDIATION BOARD DEFINITIONS § 1201.1 Carrier. The term carrier includes any express company, sleeping car company, carrier by railroad, subject to the Interstate Commerce Act...

RAPID COMMUNICATION: Diffusion thermopower in graphene

Science.gov (United States)

Vaidya, R. G.; Kamatagi, M. D.; Sankeshwar, N. S.; Mulimani, B. G.

2010-09-01

The diffusion thermopower of graphene, Sd, is studied for 30 < T < 300 K, considering the electrons to be scattered by impurities, vacancies, surface roughness and acoustic and optical phonons via deformation potential couplings. Sd is found to increase almost linearly with temperature, determined mainly by vacancy and impurity scatterings. A departure from linear behaviour due to optical phonons is noticed. As a function of carrier concentration, a change in the sign of |Sd| is observed. Our analysis of recent thermopower data obtains a good fit. The limitations of Mott formula are discussed. Detailed analysis of data will enable a better understanding of the scattering mechanisms operative in graphene.

H2 as a Possible Carrier of the DIBs?

Science.gov (United States)

Ubachs, W.

2014-02-01

In the 1990s the hydrogen molecule, by far the most abundant molecular species in the interstellar medium, has been proposed as a possible carrier of the diffuse interstellar bands. While some remarkable coincidences were found in the rich spectrum of inter-Rydberg transitions of this molecule with DIB-features, both in frequency position as in linewidth, some open issues remained on a required non-linear optical pumping scheme that should explain the population of certain intermediate levels and act as a selection mechanism. Recently a similar scheme has been proposed relating the occurrence of the UV-bump (the ubiquitous 2170 Å extinction feature) to the spectrum of H2, therewith reviving the H2 hypothesis.

The diffusion of some radionuclides in local rocks collected from potential repository in Syria

International Nuclear Information System (INIS)

Othman, Ibrahim; Abou Jamous, Jamal

1992-07-01

Diffusion factor was estimated for 137 Cs in local rocks marl, limestone, and basalt. Slab activity measuring was constructed. Factors affecting the 137 Cs diffusion has been studied. These are dynamic state of water, length of contacting time and the concentration of radioisotope. (author). 9 refs., 12 figs., 6 tabs

Ultrafast Carrier Dynamics Measured by the Transient Change in the Reflectance of InP and GaAs Film

Energy Technology Data Exchange (ETDEWEB)

Klopf, John [Helmholtz Association of German Research Centers, Dresden (Germany)

2005-10-31

Advancements in microfabrication techniques and thin film growth have led to complex integrated photonic devices, also known as optoelectronics. The performance of these devices relies upon precise control of the band gap and optical characteristics of the thin film structures, as well as a fundamental understanding of the photoexcited carrier thermalization, relaxation, and recombination processes. An optical pump-probe technique has been developed to measure the transient behavior of these processes on a sub-picosecond timescale. This method relies upon the generation of hot carriers by theabsorption of an intense ultrashort laser pulse (~ 135 fs). The transient changes in reflectance due to the pump pulse excitation are monitored using a weaker probe pulse. Control of the relative time delay between the pump and probe pulses allows for temporal measurements with resolution limited only by the pulse width. The transient change in reflectance is the result of a transient change in the carrier distribution. Observation of the reflectance response of indium phosphide (InP) and gallium arsenide (GaAs) films on a sub-picosecond timescale allows for detailed examination of thermalization and relaxation processes of the excited carriers. Longer timescales (> 100 ps) are useful for correlating the transient reflectance response to slower processes such as the diffusion and recombination of the photoexcited carriers. This research investigates the transient hot carrier processes in several InP and GaAs based films similar to those commonly used in optoelectronics. This technique is especially important as it provides a non-destructive means of evaluating these materials; whereas much of the research performed in this field has relied upon the measurement of transient changes in the transmission of transparent films. The process of preparing films that are transparent renders them unusable in functioning devices. This research should not only extend the understanding of

Entanglement of conjugated polymer chains influences molecular self-assembly and carrier transport

KAUST Repository

Zhao, Kui; Khan, Hadayat Ullah; Li, Ruipeng; Su, Yisong; Amassian, Aram

2013-01-01

The influence of polymer entanglement on the self-assembly, molecular packing structure, and microstructure of low-Mw (lightly entangled) and high-Mw (highly entangled) poly (3-hexylthiophene) (P3HT), and the carrier transport in thin-film transistors, are investigated. The polymer chains are gradually disentangled in a marginal solvent via ultrasonication of the polymer solution, and demonstrate improved diffusivity of precursor species (coils, aggregates, and microcrystallites), enhanced nucleation and crystallization of P3HT in solution, and self-assembly of well-ordered and highly textured fibrils at the solid-liquid interface. In low-Mw P3HT, reducing chain entanglement enhances interchain and intrachain ordering, but reduces the interconnectivity of ordered domains (tie molecules) due to the presence of short chains, thus deteriorating carrier transport even in the face of improving crystallinity. Reducing chain entanglement in high-Mw P3HT solutions increases carrier mobility up to ≈20-fold, by enhancing interchain and intrachain ordering while maintaining a sufficiently large number of tie molecules between ordered domains. These results indicate that charge carrier mobility is strongly governed by the balancing of intrachain and interchain ordering, on the one hand, and interconnectivity of ordered domains, on the other hand. In high-Mw P3HT, intrachain and interchain ordering appear to be the key bottlenecks to charge transport, whereas in low-Mw P3HT, the limited interconnectivity of the ordered domains acts as the primary bottleneck to charge transport. Conjugated polymer chains of poly(3-hexylthiophene) (P3HT) are gradually disentangled in solution and trends in carrier transport mechanisms in organic thin film transistors for low- and high-molecular weight P3HT are investigated. While intrachain and interchain ordering within ordered domains are the key bottlenecks to charge transport in high-Mw P3HT films, the limited interconnectivity of ordered

Entanglement of conjugated polymer chains influences molecular self-assembly and carrier transport

KAUST Repository

Zhao, Kui

2013-06-26

The influence of polymer entanglement on the self-assembly, molecular packing structure, and microstructure of low-Mw (lightly entangled) and high-Mw (highly entangled) poly (3-hexylthiophene) (P3HT), and the carrier transport in thin-film transistors, are investigated. The polymer chains are gradually disentangled in a marginal solvent via ultrasonication of the polymer solution, and demonstrate improved diffusivity of precursor species (coils, aggregates, and microcrystallites), enhanced nucleation and crystallization of P3HT in solution, and self-assembly of well-ordered and highly textured fibrils at the solid-liquid interface. In low-Mw P3HT, reducing chain entanglement enhances interchain and intrachain ordering, but reduces the interconnectivity of ordered domains (tie molecules) due to the presence of short chains, thus deteriorating carrier transport even in the face of improving crystallinity. Reducing chain entanglement in high-Mw P3HT solutions increases carrier mobility up to ≈20-fold, by enhancing interchain and intrachain ordering while maintaining a sufficiently large number of tie molecules between ordered domains. These results indicate that charge carrier mobility is strongly governed by the balancing of intrachain and interchain ordering, on the one hand, and interconnectivity of ordered domains, on the other hand. In high-Mw P3HT, intrachain and interchain ordering appear to be the key bottlenecks to charge transport, whereas in low-Mw P3HT, the limited interconnectivity of the ordered domains acts as the primary bottleneck to charge transport. Conjugated polymer chains of poly(3-hexylthiophene) (P3HT) are gradually disentangled in solution and trends in carrier transport mechanisms in organic thin film transistors for low- and high-molecular weight P3HT are investigated. While intrachain and interchain ordering within ordered domains are the key bottlenecks to charge transport in high-Mw P3HT films, the limited interconnectivity of ordered

Differential Analysis of the Nasal Microbiome of Pig Carriers or Non-Carriers of Staphylococcus aureus

DEFF Research Database (Denmark)

Espinosa-Gongora, Carmen; Larsen, Niels; Schonning, Kristian

2016-01-01

pathogen in animal carriers. The aim of this study was to determine whether the nasal microbiome of pig S. aureus carriers differs from that of non-carriers. The V3-V5 region of the 16S rRNA gene was sequenced from nasal swabs of 44 S. aureus carriers and 56 non-carriers using the 454 GS FLX titanium...... microbiome of pigs that are not colonized with S. aureus harbours several species/taxa that are significantly less abundant in pig carriers, suggesting that the nasal microbiota may play a role in the individual predisposition to S. aureus nasal carriage in pigs. Further research is warranted to isolate...

Personality traits in Huntington's disease: An exploratory study of gene expansion carriers and non-carriers.

Science.gov (United States)

Larsen, Ida Unmack; Mortensen, Erik Lykke; Vinther-Jensen, Tua; Nielsen, Jørgen Erik; Knudsen, Gitte Moos; Vogel, Asmus

2016-12-01

Huntington's disease (HD) is associated with risk for developing psychiatric symptoms. Vulnerability or resilience to psychiatric symptoms may be associated with personality traits. This exploratory study, aimed to investigate personality traits in a large cohort of HD carriers and at risk gene-expansion negative individuals (HD non-carriers), exploring whether carrying the HD gene or growing up in an HD family influences personality traits. Forty-seven HD carriers, Thirty-nine HD non-carriers, and 121 healthy controls answered the Danish version of the revised NEO personality inventory. Comparisons between HD carriers and HD non-carriers were mostly non-significant but the combined group of HD carriers and non-carriers showed significantly higher scores on the facets: "hostility," "assertiveness," and "activity" and on the trait "Conscientiousness" relative to controls, "Conscientiousness" have been associated with resilience to psychiatric symptoms. Twelve HD carriers and non-carriers were classified as depressed and showed significantly lower scores on "Extraversion" and "Conscientiousness" and significantly higher scores on "Neuroticism," which are associated with vulnerability to psychiatric symptoms. Our findings suggest that, there is no direct effect of the HD gene on personality traits, but that personality assessment may be relevant to use when identifying individuals from HD families who are vulnerable to develop psychiatric symptoms. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Ionic Diffusion in a Ternary Superionic Conductor: An {ital Ab Initio} Molecular Dynamics Study

Energy Technology Data Exchange (ETDEWEB)

Wengert, S.; Nesper, R.; Andreoni, W.; Parrinello, M. [Laboratorium fuer Anorganische Chemie, ETH Zuerich, 8092 Zuerich (Switzerland)]|[IBM Research Division, Zurich Research Laboratory, 8803 Rueschlikon (Switzerland)]|[Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart (Germany)

1996-12-01

We present Car-Parrinello molecular dynamics simulations of a novel superionic conductor, Li{sub 2{minus}2{ital x}}Mg{sub 1+{ital x}}Si ({ital x}{approximately}0.06), at different temperatures. The calculations clarify the nature of the ionic conduction and lead to the prediction of the first inorganic magnesium superionic conductor. In fact, both lithium and magnesium are found to act as charge carriers. The diffusion is fast and can be described as vacancy migration through directed jumps. The calculated diffusion constants for lithium are consistent with recent electrochemical measurements. {copyright} {ital 1996 The American Physical Society.}

Direct measurement of time dependent diffusion for Ag and Au under ambient conditions

Energy Technology Data Exchange (ETDEWEB)

Yoo, Pil Sun; Jo, Han Yeol; Kim, Tae Kyeong [Hankuk University of Foreign Studies, Yongin (Korea, Republic of)

2014-12-15

Time-dependent diffusion for Ag and Au metal atoms was measured using the scanning tunneling microscope break-junction technique in ambient conditions. We observed that Ag contacts do not form long single-atomic chains compared to Au contacts during the elongation of each metal electrode, and Ag atoms diffuse more quickly than Au atoms after metal contact rupture. This is consistent with previous results of molecular dynamic simulations. Further, we found a correlation between diffusion length and the evolution time on an atomic scale to reveal the time-dependent diffusion for Ag and Au metal atoms.

Peptide-Carrier Conjugation

DEFF Research Database (Denmark)

Hansen, Paul Robert

2015-01-01

To produce antibodies against synthetic peptides it is necessary to couple them to a protein carrier. This chapter provides a nonspecialist overview of peptide-carrier conjugation. Furthermore, a protocol for coupling cysteine-containing peptides to bovine serum albumin is outlined....

Simple structure diffusion cloud chamber for educational purpose

International Nuclear Information System (INIS)

Hrehuss, Gy.; Molnar, B.

1982-01-01

A simple structure diffusion cloud chamber was designed and built with educational aim. The source of alpha particles is Am-241 radioisotope smeared on steel foil, the source of vapor is a felt disc saturated with methanol. Five minutes after covering the chamber the system achieves the thermodynamic equilibrium and alpha particle tracks of 5 cm length become visible in the centre of the chamber. Life-time of a track is about 0.5-1 second, the frequency is 2-3 tracks/s. The presented diffusion chamber can be built simply and easily, using cheap common materials and components. (D.Gy.)

Carrier-free, functionalized pure drug nanorods as a novel cancer-targeted drug delivery platform

International Nuclear Information System (INIS)

Li Yanan; An Feifei; Zhang Xiaohong; Yang Yinlong; Liu Zhuang; Zhang Xiujuan

2013-01-01

A one-dimensional drug delivery system (1D DDS) is highly attractive since it has distinct advantages such as enhanced drug efficiency and better pharmacokinetics. However, drugs in 1D DDSs are all encapsulated in inert carriers, and problems such as low drug loading content and possible undesirable side effects caused by the carriers remain a serious challenge. In this paper, a novel, carrier-free, pure drug nanorod-based, tumor-targeted 1D DDS has been developed. Drugs are first prepared as nanorods and then surface functionalized to achieve excellent water dispersity and stability. The resulting drug nanorods show enhanced internalization rates mainly through energy-dependent endocytosis, with the shape-mediated nanorod (NR) diffusion process as a secondary pathway. The multiple endocytotic mechanisms lead to significantly improved drug efficiency of functionalized NRs with nearly ten times higher cytotoxicity than those of free molecules and unfunctionalized NRs. A targeted drug delivery system can be readily achieved through surface functionalization with targeting group linked amphipathic surfactant, which exhibits significantly enhanced drug efficacy and discriminates between cell lines with high selectivity. These results clearly show that this tumor-targeting DDS demonstrates high potential toward specific cancer cell lines. (paper)

Studies on dissolution enhancement and mathematical modeling of drug release of a poorly water-soluble drug using water-soluble carriers.

Science.gov (United States)

Ahuja, Naveen; Katare, Om Prakash; Singh, Bhupinder

2007-01-01

Role of various water-soluble carriers was studied for dissolution enhancement of a poorly soluble model drug, rofecoxib, using solid dispersion approach. Diverse carriers viz. polyethylene glycols (PEG 4000 and 6000), polyglycolized fatty acid ester (Gelucire 44/14), polyvinylpyrollidone K25 (PVP), poloxamers (Lutrol F127 and F68), polyols (mannitol, sorbitol), organic acid (citric acid) and hydrotropes (urea, nicotinamide) were investigated for the purpose. Phase-solubility studies revealed AL type of curves for each carrier, indicating linear increase in drug solubility with carrier concentration. The sign and magnitude of the thermodynamic parameter, Gibbs free energy of transfer, indicated spontaneity of solubilization process. All the solid dispersions showed dissolution improvement vis-à-vis pure drug to varying degrees, with citric acid, PVP and poloxamers as the most promising carriers. Mathematical modeling of in vitro dissolution data indicated the best fitting with Korsemeyer-Peppas model and the drug release kinetics primarily as Fickian diffusion. Solid state characterization of the drug-poloxamer binary system using XRD, FTIR, DSC and SEM techniques revealed distinct loss of drug crystallinity in the formulation, ostensibly accounting for enhancement in dissolution rate.

A drift-diffusion-reaction model for excitonic photovoltaic bilayers: Photovoltaic bilayers: Asymptotic analysis and a 2D hdg finite element scheme

KAUST Repository

Brinkman, Daniel; Fellner, Klemens J.; Markowich, Peter A.; Wolfram, Marie Therese

2013-01-01

We present and discuss a mathematical model for the operation of bilayer organic photovoltaic devices. Our model couples drift-diffusion-recombination equations for the charge carriers (specifically, electrons and holes) with a reaction

Measurements of ultrafast spin-profiles and spin-diffusion properties in the domain wall area at a metal/ferromagnetic film interface.

Science.gov (United States)

Sant, T; Ksenzov, D; Capotondi, F; Pedersoli, E; Manfredda, M; Kiskinova, M; Zabel, H; Kläui, M; Lüning, J; Pietsch, U; Gutt, C

2017-11-08

Exciting a ferromagnetic material with an ultrashort IR laser pulse is known to induce spin dynamics by heating the spin system and by ultrafast spin diffusion processes. Here, we report on measurements of spin-profiles and spin diffusion properties in the vicinity of domain walls in the interface region between a metallic Al layer and a ferromagnetic Co/Pd thin film upon IR excitation. We followed the ultrafast temporal evolution by means of an ultrafast resonant magnetic scattering experiment in surface scattering geometry, which enables us to exploit the evolution of the domain network within a 1/e distance of 3 nm to 5 nm from the Al/FM film interface. We observe a magnetization-reversal close to the domain wall boundaries that becomes more pronounced closer to the Al/FM film interface. This magnetization-reversal is driven by the different transport properties of majority and minority carriers through a magnetically disordered domain network. Its finite lateral extension has allowed us to measure the ultrafast spin-diffusion coefficients and ultrafast spin velocities for majority and minority carriers upon IR excitation.

Design optimization of GaAs betavoltaic batteries

International Nuclear Information System (INIS)

Chen Haiyanag; Jiang Lan; Chen Xuyuan

2011-01-01

GaAs junctions are designed and fabricated for betavoltaic batteries. The design is optimized according to the characteristics of GaAs interface states and the diffusion length in the depletion region of GaAs carriers. Under an illumination of 10 mCi cm -2 63 Ni, the open circuit voltage of the optimized batteries is about ∼0.3 V. It is found that the GaAs interface states induce depletion layers on P-type GaAs surfaces. The depletion layer along the P + PN + junction edge isolates the perimeter surface from the bulk junction, which tends to significantly reduce the battery dark current and leads to a high open circuit voltage. The short circuit current density of the optimized junction is about 28 nA cm -2 , which indicates a carrier diffusion length of less than 1 μm. The overall results show that multi-layer P + PN + junctions are the preferred structures for GaAs betavoltaic battery design.

Effect of alkyl chain length on the rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imides.

Science.gov (United States)

Gangamallaiah, V; Dutt, G B

2013-10-10

Rotational diffusion of a nonpolar solute 9-phenylanthracene (9-PA) and a cationic solute rhodamine 110 (R110) has been examined in a series of 1-alkyl-3-methylimidazolium (alkyl = octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bis(trifluoromethylsulfonyl)imides to understand the influence of alkyl chain length on solute rotation. In this study, reorientation times (τr) have been measured as a function of viscosity (η) by varying the temperature (T) of the solvents. These results have been analyzed using the Stokes-Einstein-Debye (SED) hydrodynamic theory along with the ones obtained for the same solutes in 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides (Gangamallaiah and Dutt, J. Phys. Chem. B 2012, 116, 12819-12825). It has been noticed that the data for 9-PA and R110 follows the relation τr = A(η/T)(n) with A being the ratio of hydrodynamic volume of the solute to the Boltzmann constant and n = 1 as envisaged by the SED theory. However, upon increasing the alkyl chain length from methyl to octadecyl significant deviations from the SED theory have been observed especially from the octyl derivative onward. From methyl to octadecyl derivatives, the value of A decreases by a factor of 3 for both the solutes and n by a factor of 1.4 and 1.6 for 9-PA and R110, respectively. These observations have been rationalized by taking into consideration the organized structure of the ionic liquids, whose influence appears to be pronounced when the number of carbon atoms in the alkyl chain attached to the imidazolium cation exceeds eight.

7 CFR 35.4 - Carrier.

Science.gov (United States)

2010-01-01

... AND PLUMS Definitions § 35.4 Carrier. Carrier means any common or private carrier, including, but not being limited to, trucks, rail, airplanes, vessels, tramp or chartered steamers, whether carrying for...

A longitudinal study of visual function in carriers of X-linked recessive retinitis pigmentosa.

Science.gov (United States)

Grover, S; Fishman, G A; Anderson, R J; Lindeman, M

2000-02-01

This study was carried out to evaluate the progression of visual function impairment in carriers of X-linked recessive retinitis pigmentosa. We also assessed the relationship between the retinal findings at presentation and the extent of deterioration. Observational, retrospective, case series. Twenty-seven carriers of X-linked recessive retinitis pigmentosa. Each carrier was clinically categorized into one of four grades (grades 0 through 3) depending on the presence or absence of a tapetal-like retinal reflex and the extent of peripheral pigmentary degeneration. A complete ophthalmologic examination was performed and data for visual acuity, visual field area, and electroretinographic measurements were collected on the most recent visit in both eyes. These were then compared with similar data obtained on their initial visits. A comparison of visual function was carried out between the initial visit and the most recent visit on each carrier. The visual acuity was measured with Snellen's acuity charts. The visual fields to targets V-4-e and II-4-e were planimeterized and used for the analysis. The electroretinographic (ERG) measures used were light-adapted single-flash b-wave amplitudes and 30-Hz red flicker for cone function, dark-adapted maximal b-wave amplitudes, and response to a low intensity blue-flash for rod function. None of the 11 carriers with a tapetal-like reflex only (grade 1) showed any significant change in visual acuity or fields as compared with 3 of 7 (43%) carriers with diffuse peripheral pigmentary findings (grade 3) who showed significant deterioration in visual acuity in at least one eye, and 6 of 7 (86%) who showed a significant decrease in visual field area with at least one target size in at least one eye. By comparison, only 1 of 10 carriers with a grade 1 fundus finding demonstrated a significant decrease in maximal dark-adapted ERG function as compared with 5 of 6 (83%) carriers with grade 3 in response to a single-flash stimulus and

Diffusion of nanoparticles in solution through elastomeric membrane

International Nuclear Information System (INIS)

Zemzem, Mohamed; Vinches, Ludwig; Hallé, Stéphane

2017-01-01

Diffusion phenomena encountered in mass transfer of liquids play an important role in many technological processes of polymer manufacturing and use. In addition and alongside the notable growth of nanoparticles use, particularly when in suspension in liquid solutions, it has become important to pay some attention to their interactions with polymeric structures. The aim of this work is to evaluate some diffusion parameters of gold nanoparticle solutions as well as of their liquid carrier (water) through elastomeric membranes. Gravimetric method was chosen as the main technique to quantify swelling phenomena and to assess kinetic properties. The dynamic liquid uptake measurements were conducted on gold nanoparticles (5 nm and 50 nm in diameter) in aqueous solutions when brought into contact with two types of nitrile material samples. Results showed that diffusion mechanism of the liquids lies between Fickian and sub-Fickian modes. Slight deviations were noticed with the gold nanoparticle solutions. A growth in liquid interaction with the rubbery structure in presence of the nanoparticles was also observed from comparison of K factor (characteristic of the elastomer-liquid interaction). Difference between the characteristics of the two membranes was also reported using this parameter. Besides, diffusion coefficients testified the impact of the membrane thickness on the penetration process, while no significant effect of the nature of the nanoparticle solution can be seen on this coefficient. (paper)

Diffusion of nanoparticles in solution through elastomeric membrane

Science.gov (United States)

Zemzem, Mohamed; Vinches, Ludwig; Hallé, Stéphane

2017-04-01

Diffusion phenomena encountered in mass transfer of liquids play an important role in many technological processes of polymer manufacturing and use. In addition and alongside the notable growth of nanoparticles use, particularly when in suspension in liquid solutions, it has become important to pay some attention to their interactions with polymeric structures. The aim of this work is to evaluate some diffusion parameters of gold nanoparticle solutions as well as of their liquid carrier (water) through elastomeric membranes. Gravimetric method was chosen as the main technique to quantify swelling phenomena and to assess kinetic properties. The dynamic liquid uptake measurements were conducted on gold nanoparticles (5 nm and 50 nm in diameter) in aqueous solutions when brought into contact with two types of nitrile material samples. Results showed that diffusion mechanism of the liquids lies between Fickian and sub-Fickian modes. Slight deviations were noticed with the gold nanoparticle solutions. A growth in liquid interaction with the rubbery structure in presence of the nanoparticles was also observed from comparison of K factor (characteristic of the elastomer-liquid interaction). Difference between the characteristics of the two membranes was also reported using this parameter. Besides, diffusion coefficients testified the impact of the membrane thickness on the penetration process, while no significant effect of the nature of the nanoparticle solution can be seen on this coefficient.

The influence of grain boundary diffusion on the electro-optical properties of CdTe/CdS solar cells

Energy Technology Data Exchange (ETDEWEB)

Levi, D.H.; Albin, D.S.; Gessert, T.A.; Reedy, R.C.; Ahrenkiel, R.K. [National Renewable Energy Lab., Golden, CO (United States); Woods, L.M. [Colorado State Univ., Fort Collins, CO (United States)

1998-09-01

The authors report on a study of the effects of diffusion of metals through polycrystalline CdTe thin films. The metals Ni, Pd, Cu, Cr, and Te are deposited onto the back surface of 10-{micro}m thick CdTe/CdS device structures using room-temperature evaporation. The authors found that four out of the five metals produce significant changes in the photoluminescence (PL) of the near-junction CdTe material. These changes are explained in terms of spatial variations of the photoexcited carrier distribution and spatial variations in the sulfur composition of the CdTeS alloy material near the CdTeS interface. The changes in carrier distribution appear to be associated with band bending and electric fields induced by diffusion of the metals to the CdTe/CdS interface. In addition to PL measurements, the authors have also utilized a technique for detaching the CdTe film from the CdS/TCO/glass superstrate to directly access the front surface of the CdTe absorber layer. The authors have used secondary ion mass spectroscopy to measure the metal diffusion profiles from this interface.

Nanostructured Lipid Carriers (NLC) as Vehicles for Topical Administration of Sesamol: In Vitro Percutaneous Absorption Study and Evaluation of Antioxidant Activity.

Science.gov (United States)

Puglia, Carmelo; Lauro, Maria Rosaria; Offerta, Alessia; Crascì, Lucia; Micicchè, Lucia; Panico, Anna Maria; Bonina, Francesco; Puglisi, Giovanni

2017-03-01

Sesamol is a natural phenolic compound extracted from Sesamum indicum seed oil. Sesamol is endowed with several beneficial effects, but its use as a topical agent is strongly compromised by unfavorable chemical-physical properties. Therefore, to improve its characteristics, the aim of the present work was the formulation of nanostructured lipid carriers as drug delivery systems for topical administration of sesamol.Two different nanostructured lipid carrier systems have been produced based on the same solid lipid (Compritol® 888 ATO) but in a mixture with two different kinds of oil phase such as Miglyol® 812 (nanostructured lipid carrier-M) and sesame oil (nanostructured lipid carrier-PLUS). Morphology and dimensional distribution of nanostructured lipid carriers have been characterized by differential scanning calorimetry and photon correlation spectroscopy, respectively. The release pattern of sesamol from nanostructured lipid carriers was evaluated in vitro determining drug percutaneous absorption through excised human skin. Furthermore, an oxygen radical absorbance capacity assay was used to determine their antioxidant activity.From the results obtained, the method used to formulate nanostructured lipid carriers led to a homogeneous dispersion of particles in a nanometric range. Sesamol has been encapsulated efficiently in both nanostructured lipid carriers, with higher encapsulation efficiency values (> 90 %) when sesame oil was used as the oil phase (nanostructured lipid carrier-PLUS). In vitro evidences show that nanostructured lipid carrier dispersions were able to control the rate of sesamol diffusion through the skin, with respect to the reference formulations.Furthermore, the oxygen radical absorbance capacity assay pointed out an interesting and prolonged antioxidant activity of sesamol, especially when vehiculated by nanostructured lipid carrier-PLUS. Georg Thieme Verlag KG Stuttgart · New York.

Ultrafast carrier dynamics in a p-type GaN wafer under different carrier distributions

Science.gov (United States)

Fang, Yu; Yang, Junyi; Yang, Yong; Wu, Xingzhi; Xiao, Zhengguo; Zhou, Feng; Song, Yinglin

2016-02-01

The dependence of the carrier distribution on photoexcited carrier dynamics in a p-type Mg-doped GaN (GaN:Mg) wafer were systematically measured by femtosecond transient absorption (TA) spectroscopy. The homogeneity of the carrier distribution was modified by tuning the wavelength of the UV pulse excitation around the band gap of GaN:Mg. The TA kinetics appeared to be biexponential for all carrier distributions, and only the slower component decayed faster as the inhomogeneity of the carrier distribution increased. It was concluded that the faster component (50-70 ps) corresponded to the trap process of holes by the Mg acceptors, and the slower component (150-600 ps) corresponded to the combination of non-radiative surface recombination and intrinsic carrier recombination via dislocations. Moreover, the slower component increased gradually with the incident fluence due to the saturation of surface states.

Scaling of the critical free length for progressive unfolding of self-bonded graphene

Energy Technology Data Exchange (ETDEWEB)

Kwan, Kenny; Cranford, Steven W., E-mail: s.cranford@neu.edu [Laboratory of Nanotechnology in Civil Engineering (NICE), Department of Civil and Environmental Engineering, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, Massachusetts 02115 (United States)

2014-05-19

Like filled pasta, rolled or folded graphene can form a large nanocapsule surrounding a hollow interior. Use as a molecular carrier, however, requires understanding of the opening of such vessels. Here, we investigate a monolayer sheet of graphene as a theoretical trial platform for such a nanocapsule. The graphene is bonded to itself via aligned disulfide (S-S) bonds. Through theoretical analysis and atomistic modeling, we probe the critical nonbonded length (free length, L{sub crit}) that induces fracture-like progressive unfolding as a function of folding radius (R{sub i}). We show a clear linear scaling relationship between the length and radius, which can be used to determine the necessary bond density to predict mechanical opening/closing. However, stochastic dissipated energy limits any exact elastic formulation, and the required energy far exceeds the dissociation energy of the S-S bond. We account for the necessary dissipated kinetic energy through a simple scaling factor (Ω), which agrees well with computational results.

Hot carrier degradation in semiconductor devices

CERN Document Server

2015-01-01

This book provides readers with a variety of tools to address the challenges posed by hot carrier degradation, one of today’s most complicated reliability issues in semiconductor devices.  Coverage includes an explanation of carrier transport within devices and book-keeping of how they acquire energy (“become hot”), interaction of an ensemble of colder and hotter carriers with defect precursors, which eventually leads to the creation of a defect, and a description of how these defects interact with the device, degrading its performance. • Describes the intricacies of hot carrier degradation in modern semiconductor technologies; • Covers the entire hot carrier degradation phenomenon, including topics such as characterization, carrier transport, carrier-defect interaction, technological impact, circuit impact, etc.; • Enables detailed understanding of carrier transport, interaction of the carrier ensemble with the defect precursors, and an accurate assessment of how the newly created defects imp...

Diffusion-driven growth of nanowires by low-temperature molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Rueda-Fonseca, P.; Orrù, M. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Institut NEEL, F-38000 Grenoble (France); CEA, INAC, F-38000 Grenoble (France); Bellet-Amalric, E.; Robin, E. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, INAC, F-38000 Grenoble (France); Den Hertog, M.; Genuist, Y.; André, R.; Tatarenko, S.; Cibert, J., E-mail: joel.cibert@neel.cnrs.fr [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Institut NEEL, F-38000 Grenoble (France)

2016-04-28

With ZnTe as an example, we use two different methods to unravel the characteristics of the growth of nanowires (NWs) by gold-catalyzed molecular beam epitaxy at low temperature. In the first approach, CdTe insertions have been used as markers, and the nanowires have been characterized by scanning transmission electron microscopy, including geometrical phase analysis and energy dispersive electron spectrometry; the second approach uses scanning electron microscopy and the statistics of the relationship between the length of the tapered nanowires and their base diameter. Axial and radial growth are quantified using a diffusion-limited model adapted to the growth conditions; analytical expressions describe well the relationship between the NW length and the total molecular flux (taking into account the orientation of the effusion cells), and the catalyst-nanowire contact area. A long incubation time is observed. This analysis allows us to assess the evolution of the diffusion lengths on the substrate and along the nanowire sidewalls, as a function of temperature and deviation from stoichiometric flux.

Maintainable substrate carrier for electroplating

Science.gov (United States)

Chen, Chen-An [Milpitas, CA; Abas, Emmanuel Chua [Laguna, PH; Divino, Edmundo Anida [Cavite, PH; Ermita, Jake Randal G [Laguna, PH; Capulong, Jose Francisco S [Laguna, PH; Castillo, Arnold Villamor [Batangas, PH; Ma,; Xiaobing, Diana [Saratoga, CA

2012-07-17

One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The carrier includes a non-conductive carrier body on which the substrates are placed and conductive lines embedded within the carrier body. A plurality of conductive clip attachment parts are attached in a permanent manner to the conductive lines embedded within the carrier body. A plurality of contact clips are attached in a removable manner to the clip attachment parts. The contact clips hold the substrates in place and conductively connecting the substrates with the conductive lines. Other embodiments, aspects and features are also disclosed.

Charge-carrier transport and recombination in heteroepitaxial CdTe

International Nuclear Information System (INIS)

Kuciauskas, Darius; Farrell, Stuart; Dippo, Pat; Moseley, John; Moutinho, Helio; Li, Jian V.; Allende Motz, A. M.; Kanevce, Ana; Zaunbrecher, Katherine; Gessert, Timothy A.; Levi, Dean H.; Metzger, Wyatt K.; Colegrove, Eric; Sivananthan, S.

2014-01-01

We analyze charge-carrier dynamics using time-resolved spectroscopy and varying epitaxial CdTe thickness in undoped heteroepitaxial CdTe/ZnTe/Si. By employing one-photon and nonlinear two-photon excitation, we assess surface, interface, and bulk recombination. Two-photon excitation with a focused laser beam enables characterization of recombination velocity at the buried epilayer/substrate interface, 17.5 μm from the sample surface. Measurements with a focused two-photon excitation beam also indicate a fast diffusion component, from which we estimate an electron mobility of 650 cm 2 (Vs) −1 and diffusion coefficient D of 17 cm 2  s −1 . We find limiting recombination at the epitaxial film surface (surface recombination velocity S surface  = (2.8 ± 0.3) × 10 5  cm s −1 ) and at the heteroepitaxial interface (interface recombination velocity S interface  = (4.8 ± 0.5) × 10 5  cm s −1 ). The results demonstrate that reducing surface and interface recombination velocity is critical for photovoltaic solar cells and electronic devices that employ epitaxial CdTe.

Non-permeable substrate carrier for electroplating

Science.gov (United States)

Abas, Emmanuel Chua; Chen, Chen-An; Ma, Diana Xiaobing; Ganti, Kalyana Bhargava

2012-11-27

One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The substrate carrier comprises a non-conductive carrier body on which the substrates are to be held. Electrically-conductive lines are embedded within the carrier body, and a plurality of contact clips are coupled to the electrically-conductive lines embedded within the carrier body. The contact clips hold the substrates in place and electrically couple the substrates to the electrically-conductive lines. The non-conductive carrier body is continuous so as to be impermeable to flow of electroplating solution through the non-conductive carrier body. Other embodiments, aspects and features are also disclosed.

Estimation of Kubo number and correlation length of fluctuating magnetic fields and pressure in BOUT + + edge pedestal collapse simulation

Science.gov (United States)

Kim, Jaewook; Lee, W.-J.; Jhang, Hogun; Kaang, H. H.; Ghim, Y.-C.

2017-10-01

Stochastic magnetic fields are thought to be as one of the possible mechanisms for anomalous transport of density, momentum and heat across the magnetic field lines. Kubo number and Chirikov parameter are quantifications of the stochasticity, and previous studies show that perpendicular transport strongly depends on the magnetic Kubo number (MKN). If MKN is smaller than one, diffusion process will follow Rechester-Rosenbluth model; whereas if it is larger than one, percolation theory dominates the diffusion process. Thus, estimation of Kubo number plays an important role to understand diffusion process caused by stochastic magnetic fields. However, spatially localized experimental measurement of fluctuating magnetic fields in a tokamak is difficult, and we attempt to estimate MKNs using BOUT + + simulation data with pedestal collapse. In addition, we calculate correlation length of fluctuating pressures and Chirikov parameters to investigate variation correlation lengths in the simulation. We, then, discuss how one may experimentally estimate MKNs.

EVIDENCE FOR DIACETYLENE CATION AS THE CARRIER OF A DIFFUSE INTERSTELLAR BAND

International Nuclear Information System (INIS)

Krelowski, J.; Beletsky, Y.; LoCurto, G.; Galazutdinov, G. A.; Kolos, R.; Gronowski, M.

2010-01-01

High-quality spectra acquired at three different observatories point to the presence of a new diffuse interstellar band (DIB) at 5069 A. The spectral profile of this DIB matches published laboratory measurements of the diacetylene cation A 2 Π u -X 2 Π g (0-0) low-temperature gas-phase optical absorption. HC 4 H + is approximately 60-80 times less abundant than CH along the analyzed lines of sight. Only an upper limit could presently be inferred from the search for an analogous band of the triacetylene cation HC 6 H + , expected at 6001.1 A, which implies the HC 6 H + to HC 4 H + ratio of less than ∼1/3.

Carrier of Wingless (Cow), a Secreted Heparan Sulfate Proteoglycan, Promotes Extracellular Transport of Wingless

Science.gov (United States)

Chang, Yung-Heng; Sun, Yi Henry

2014-01-01

Morphogens are signaling molecules that regulate growth and patterning during development by forming a gradient and activating different target genes at different concentrations. The extracellular distribution of morphogens is tightly regulated, with the Drosophila morphogen Wingless (Wg) relying on Dally-like (Dlp) and transcytosis for its distribution. However, in the absence of Dlp or endocytic activity, Wg can still move across cells along the apical (Ap) surface. We identified a novel secreted heparan sulfate proteoglycan (HSPG) that binds to Wg and promotes its extracellular distribution by increasing Wg mobility, which was thus named Carrier of Wg (Cow). Cow promotes the Ap transport of Wg, independent of Dlp and endocytosis, and this function addresses a previous gap in the understanding of Wg movement. This is the first example of a diffusible HSPG acting as a carrier to promote the extracellular movement of a morphogen. PMID:25360738

Facilitated transport of HNO3 through a supported liquid membrane containing a tertiary amine as carrier

International Nuclear Information System (INIS)

Cianetti, C.; Danesi, P.R.

1983-01-01

The facilitated transport of HNO 3 through a supported liquid membrane consisting of a porous polypropylene film containing a solution of trilaurylamine in diethylbenzene as carrier was studied as a function of the stirring speed of the aqueous solutions and the membrane composition. A physico-chemical model which takes into account diffusion through an aqueous boundary layer, a fast interfacial chemical reaction leading to the formation of a membrane soluble alkylammonium salt and diffusion through the membrane was proposed. In this way, equations were derived which describe how composition changes, occurring in the course of the permeation process, influence the membrane permeability. The experimental data were quantitatively explained by the derived equations. The results indicate that the monomeric form of the trilaurylammonium nitrate salt is the species which is mainly responsible for the acid transport through the membrane. The diffusion coefficient of the permeating species and the order of magnitude of the thickness of the aqueous boundary layer were evaluated. 8 figures

Hydroxyl and molecular H2O diffusivity in a haploandesitic melt

Science.gov (United States)

Ni, Huaiwei; Xu, Zhengjiu; Zhang, Youxue

2013-02-01

H2O diffusion in a haploandesitic melt (a high-silica and Fe-free andesitic melt, NBO/T = 0.173) has been investigated at 1 GPa in a piston-cylinder apparatus. We adopted a double diffusion couple technique, in which one couple was composed of a nominally anhydrous glass with 0.01 wt.% H2O and a hydrous glass with 5.7 wt.% H2O, and the other contained the same nominally anhydrous glass and a hydrous glass with 3.3 wt.% H2O. Both couples were annealed in a single experimental run and hence experienced exactly the same P-T history, which is crucial for constraining the dependence of H2O diffusivity on water content. H2O concentration profiles were measured by both Fourier transform infrared (FTIR) microspectroscopy and confocal Raman microspectroscopy. Nearly identical profiles were obtained from Raman and FTIR methods for profile length >1 mm (produced at 1619-1842 K). By contrast, for profile lengths <100 μm (produced at 668-768 K), FTIR profiles show marked convolution effects compared to Raman profiles. A comparison between the short FTIR and Raman profiles indicates that the real spatial resolution (FWHM) of FTIR analyses is about 28 μm for a 7 μm wide aperture on ˜200 μm thick glasses. While the short profiles are not reliable for quantitative modeling, the long diffusion profiles at superliquidus temperatures can be fit reasonably well by a diffusivity model previously developed for felsic melts, in which molecular H2O (H2Om) is the only diffusive species and its diffusivity (D) increases exponentially with the content of total water (H2Ot). However, there is noticeable misfit of the data at low H2Ot concentrations, suggesting that OH diffusivity (DOH) cannot be neglected in this andesitic melt at high temperatures and low water contents. We hence develop a new fitting procedure that simultaneously fits both diffusion profiles from a single experimental run and accounts for the roles of both OH and H2Om diffusion. With this procedure, DOH/D is constrained

The rate-limiting mechanism of transition metal gettering in multicrystalline silicon

International Nuclear Information System (INIS)

McHugo, S.A.; Thompson, A.C.; Imaizumi, M.

1997-01-01

Multicrystalline silicon is a very interesting material for terrestrial solar cells. Its low cost and respectable energy conversion efficiency (12-15%) makes it arguably the most cost competitive material for large-volume solar power generation. However, the solar cell efficiency of this material is severely degraded by regions of high minority carrier recombination which have been shown to possess both dislocations and microdefects. These structural defects are known to increase in recombination activity with transition metal decoration. Therefore, gettering of metal impurities from the material would be expected to greatly enhance solar cell performance. Contrary to this rationale, experiments using frontside phosphorus and/or backside aluminum treatments have been found to improve regions with low recombination activity while having little or no effect on the high recombination regions and in turn only slightly improving the overall cell performance. The goal of this research is to determine the mechanism by which gettering is ineffectual on these high recombination regions. The authors have performed studies on integrated circuit (IC) quality single crystal and multicrystalline solar cell silicon (mc-silicon) in the as-grown state and after a variety of processing/gettering steps. With Surface Photovoltage measurements of the minority carrier diffusion length which is inversely proportional to carrier recombination, they have seen that aluminum gettering is effective for improving IC quality material but ineffective for improving the regions of initially low diffusion lengths (high recombination rates) in mc-silicon. Of particular interest is the great increase in diffusion length for IC material as compared to the mc-silicon. Clearly the IC material has benefited to a greater extent from the gettering procedure than the mc-silicon

Photon assisted Lévy flights of minority carriers in n-InP

International Nuclear Information System (INIS)

Semyonov, Oleg; Subashiev, Arsen V.; Chen Zhichao; Luryi, Serge

2012-01-01

We study the photoluminescence spectra of n-doped InP bulk wafers, both in the reflection and the transmission geometries relative to the excitation beam. From the observed spectra we estimate the spatial distribution of minority carriers allowing for the spectral filtering due to reabsorption of luminescence in the wafer. This distribution unambiguously demonstrates a non-exponential drop-off with distance from the excitation region. Such a behavior evidences an anomalous photon-assisted transport of minority carriers enhanced owing to the high quantum efficiency of emission. It is shown that the transport conforms very well to the so-called Lévy-flights process corresponding to a peculiar random walk that does not reduce to diffusion. The index γ of the Lévy flights distribution is found to be in the range γ=0.64–0.79, depending on the doping. Thus, we propose the high-efficiency direct-gap semiconductors as a remarkable laboratory system for studying the anomalous transport. - Highlights: ► Spatial distribution of minority carriers is found from photoluminescence spectra. ► The distribution shows a power-law drop-off with distance from the excitation plane. ► The photon-assisted transport is a random walk well described by the Lévy flight. ► Emission quantum efficiency of n-InP is independently determined. ► Results are in excellent agreement with earlier luminescence kinetics experiments.

Diffusive charge transport in graphene on SiO 2

Science.gov (United States)

Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

2009-07-01

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

The Green’s functions for peridynamic non-local diffusion

Science.gov (United States)

Wang, L. J.; Xu, J. F.

2016-01-01

In this work, we develop the Green’s function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green’s functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green’s functions by the Fourier transform method for unsteady and steady diffusions in infinite domains. We also demonstrate that the peridynamic non-local solutions converge to the classical differential solutions when the non-local length approaches zero. Finally, the peridynamic analytical solutions are applied to an infinite plate heated by a Gauss source, and the predicted variations of temperature are compared with the classical local solutions. The peridynamic non-local diffusion model predicts a lower rate of variation of the field quantities than that of the classical theory, which is consistent with experimental observations. The developed method is applicable to general diffusion-type problems. PMID:27713658

Diffusive Dynamics of Nanoparticles in Arrays of Nanoposts

KAUST Repository

He, Kai; Babaye Khorasani, Firoozeh; Retterer, Scott T.; Thomas, Darrell K.; Conrad, Jacinta C.; Krishnamoorti, Ramanan

2013-01-01

The diffusive dynamics of dilute dispersions of nanoparticles of diameter 200-400 nm were studied in microfabricated arrays of nanoposts using differential dynamic microscopy and single particle tracking. Posts of diameter 500 nm and height 10 μm were spaced by 1.2-10 μm on a square lattice. As the spacing between posts was decreased, the dynamics of the nanoparticles slowed. Moreover, the dynamics at all length scales were best represented by a stretched exponential rather than a simple exponential. Both the relative diffusivity and the stretching exponent decreased linearly with increased confinement and, equivalently, with decreased void volume. The slowing of the overall diffusive dynamics and the broadening distribution of nanoparticle displacements with increased confinement are consistent with the onset of dynamic heterogeneity and the approach to vitrification. © 2013 American Chemical Society.

Diffusive Dynamics of Nanoparticles in Arrays of Nanoposts

KAUST Repository

He, Kai

2013-06-25

The diffusive dynamics of dilute dispersions of nanoparticles of diameter 200-400 nm were studied in microfabricated arrays of nanoposts using differential dynamic microscopy and single particle tracking. Posts of diameter 500 nm and height 10 μm were spaced by 1.2-10 μm on a square lattice. As the spacing between posts was decreased, the dynamics of the nanoparticles slowed. Moreover, the dynamics at all length scales were best represented by a stretched exponential rather than a simple exponential. Both the relative diffusivity and the stretching exponent decreased linearly with increased confinement and, equivalently, with decreased void volume. The slowing of the overall diffusive dynamics and the broadening distribution of nanoparticle displacements with increased confinement are consistent with the onset of dynamic heterogeneity and the approach to vitrification. © 2013 American Chemical Society.

Efficacy observation on multiple wave length laser for diabetic retinopathy and central retinal vein occlusion

Directory of Open Access Journals (Sweden)

Tao Tian

2014-07-01

Full Text Available AIM:To observe the efficacy of the multiple wave length laser in treating diabetic retinopathy combined with central retinal vein occlusion. METHODS:Totally 95 cases(100 eyeswith diabetic retinopathy combined with central retinal vein occlusion were treated by multiple wave length laser. Krypton yellow laser was used for macular edema in focal photocoagulation and diffuse photocoagulation. For peripheral retina, krypton green or krypton red laser were used. Visual acuity, slit-lamp biomicroscopy, ophthalmoscopy and fundus fluorescein angiography were performed preoperatively and postoperatively. The patients were followed up for 12 to 48wk. In this study, change in visual acuity and macular edema were observed in both groups, and statistical analysis was performed. RESULTS:The effective rate was 61.2% in diffuse macular edema group and 86.3% in focal macular edema group. The general effective rate of later was higher than the former, while the treatment effect had significant statistical difference(PCONCLUSION: Multiple wave length laser is an effective and safe way to treat diabetic macular edema of diabetic retinopathy combined with central retinal vein occlusion,which is worth widely applying in clinical practice.

Diffusion Capillary Phantom vs. Human Data: Outcomes for Reconstruction Methods Depend on Evaluation Medium

Directory of Open Access Journals (Sweden)

Sarah D. Lichenstein

2016-09-01

Full Text Available Purpose: Diffusion MRI provides a non-invasive way of estimating structural connectivity in the brain. Many studies have used diffusion phantoms as benchmarks to assess the performance of different tractography reconstruction algorithms and assumed that the results can be applied to in vivo studies. Here we examined whether quality metrics derived from a common, publically available, diffusion phantom can reliably predict tractography performance in human white matter tissue. Material and Methods: We compared estimates of fiber length and fiber crossing among a simple tensor model (diffusion tensor imaging, a more complicated model (ball-and-sticks and model-free (diffusion spectrum imaging, generalized q-sampling imaging reconstruction methods using a capillary phantom and in vivo human data (N=14. Results: Our analysis showed that evaluation outcomes differ depending on whether they were obtained from phantom or human data. Specifically, the diffusion phantom favored a more complicated model over a simple tensor model or model-free methods for resolving crossing fibers. On the other hand, the human studies showed the opposite pattern of results, with the model-free methods being more advantageous than model-based methods or simple tensor models. This performance difference was consistent across several metrics, including estimating fiber length and resolving fiber crossings in established white matter pathways. Conclusions: These findings indicate that the construction of current capillary diffusion phantoms tends to favor complicated reconstruction models over a simple tensor model or model-free methods, whereas the in vivo data tends to produce opposite results. This brings into question the previous phantom-based evaluation approaches and suggests that a more realistic phantom or simulation is necessary to accurately predict the relative performance of different tractography reconstruction methods. Acronyms: BSM: ball-and-sticks model; d

Tunneling Characteristics Depending on Schottky Barriers and Diffusion Current in SiOC.

Science.gov (United States)

Oh, Teresa; Kim, Chy Hyung

2016-02-01

To obtain a diffusion current in SiOC, the aluminum doped zinc oxide films were deposited on SiOC/Si wafer by a RF magnetron sputtering. All the X-ray patterns of the SiOC films showed amorphous phases. The level of binding energy of Si atoms will lead to an additional potential modulation by long range Coulombic and covalent interactions with oxygen ions. The growth of the AZO film was affected by the characteristics of SiOC, resulting in similar trends in XPS spectra and a shift to higher AZO lattice d values than the original AZO d values in XRD analyses. The charges trapped by the defects at the interlayer between AZO and SiOC films induced the decreased mobility of carriers. In the absence of trap charges, AZO grown on SiOC film such as the sample prepared at O2 = 25 or 30 sccm, which has low charge carrier concentration and high mobility, showed high mobility in an ambipolar characteristic of oxide semiconductor due to the tunneling effect and diffusion current. The structural matching of an interface between AZO and amorphous SiOC enhanced the height of Schottky Barrier (SB), and then the mobility was increased by the tunneling effect from band to band through the high SB.

Diffusion near buildings as determined from atmospheric tracer experiments. Technical report

Energy Technology Data Exchange (ETDEWEB)

Sagendorf, J.F.; Ricks, N.R.; Start, G.E.; Dickson, C.R.

1980-09-01

Data from the innermost arcs and roof top samplers of the Rancho Seco and EOCR field studies were used to examine diffusion close to a building. The minimum length plume paths were determined from each release location to each sampler position at these two test sites. Measured concentrations, normalized by source strength (C/Q), were plotted versus plume path length and an envelope containing 95% of the measured values of C/Q was determined. The curves from the two sites were similar in shape and implied three zones of diffusion. Comparisons were also made with current NRC methods for predicting maximum expected concentrations close to a building. The NRC model overestimated concentrations in all but one case. The model was generally within an order of magnitude at EOCR, and within two orders of magnitude at Rancho Seco.

Genetic and epigenetic alterations of the reduced folate carrier in untreated diffuse large B-cell lymphoma

DEFF Research Database (Denmark)

Kastrup, I.B.; Worm, J.; Ralfkiaer, E.

2008-01-01

The reduced folate carrier (RFC) is a transmembrane protein that mediates cellular uptake of reduced folates and antifolate drugs, including methotrexate (MTX). Acquired alterations of the RFC gene have been associated with resistance to MTX in cancer cell lines and primary osteosarcomas. Here, w...... with adverse outcome. In DLBCL, genetic and epigenetic alterations of RFC were detected at diagnosis in the absence of a selective MTX pressure, suggesting that these alterations may possibly contribute to the development of lymphoma Udgivelsesdato: 2008/1...

Mass transfer rate through liquid membranes: interfacial chemical reactions and diffusion as simultaneous permeability controlling factors

International Nuclear Information System (INIS)

Danesi, P.R.; Horwitz, E.P.; Vandegrift, G.F.; Chiarizia, R.

1981-01-01

Equations describing the permeability of a liquid membrane to metal cations have been derived taking into account aqueous diffusion, membrane diffusion, and interfacial chemical reactions as simultaneous permeability controlling factors. Diffusion and chemical reactions have been coupled by a simple model analogous to the one previously described by us to represent liquid-liquid extraction kinetics. The derived equations, which make use of experimentally determined interfacial reaction mechanisms, qualitatively fit unexplained literature data regarding Cu 2+ transfer through liquid membranes. Their use to predict and optimize membrane permeability in practical separation processes by setting the appropriate concentration of the membrane carrier [LIX 64 (General Mills), a commercial β-hydroxy-oxime] and the pH of the aqueous copper feed solution is briefly discussed. 4 figures

7 CFR 33.4 - Carrier.

Science.gov (United States)

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Carrier. 33.4 Section 33.4 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... ISSUED UNDER AUTHORITY OF THE EXPORT APPLE ACT Definitions § 33.4 Carrier. Carrier means any common or...

Use of x-ray absorption imaging to evaluate the effects of heterogeneity on matrix diffusion

International Nuclear Information System (INIS)

Altman, S.J.; Tidwell, V.C.; McKenna, S.A.; Meigs, L.C.

1998-01-01

An understanding of matrix diffusion is important in assessing potential nuclear waste repositories in geologic media, as it is a potentially significant process in retarding the transport of contaminant species. Recent work done in evaluating the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico has brought up two issues that complicate the incorporation of diffusion in Performance Assessment calculations. First, interpretations of single-well tracer test data suggest that the tracer was diffusing at multiple rates. Second, the estimated relevant rate(s) of diffusion are dependent on the time and length scales of the problem. To match the observed tracer test data, a model with a distribution of diffusion coefficients was required. This has led to the proposal of applying a model with multiple rates of diffusion, the multirate model, to Performance Assessment calculations for the WIPP. A series of laboratory- scale experiments have been designed for the purpose of evaluating heterogeneity and scaling properties of diffusion rates and to test the multirate model. X-ray absorption imaging was used to visualize and quantify the effects of matrix heterogeneity on the diffusion characteristics for four different centimeter-scale samples of dolomite. The samples were obtained from the Culebra dolomite at the WIPP site. Significant variations in diffusion rates were observed over relatively small length and time (months) scales for the preliminary laboratory experiments. A strong correlation between diffusion rate and porosity was also observed in each of the samples. Two sets of experiments are planned for 1998. The first set of experiments is similar to those described above. For these experiments, fourteen samples exhibiting a broader range of physical characteristics are being tested. The second set of experiments will visualize the combined effect of advection in a fracture and diffusion into adjacent matrix materials. Tracer solution will flow through

Low-cost carriers fare competition effect

NARCIS (Netherlands)

Carmona Benitez, R.B.; Lodewijks, G.

2010-01-01

This paper examines the effects that low-cost carriers (LCC’s) produce when entering new routes operated only by full-service carriers (FSC’s) and routes operated by low-cost carriers in competition with full-service carriers. A mathematical model has been developed to determine what routes should

Relationships among hepatitis C virus, hepatocellular carcinoma, and diffuse large B cell lymphoma: A case report

Energy Technology Data Exchange (ETDEWEB)

Byun, Hyuk Jun; Kim, Seong Hoon [Dept. of Radiology, Daegu Fatima Hospital, Daegu (Korea, Republic of)

2015-07-15

Hepatitis C virus (HCV) is one of the main causes of hepatocellular carcinoma (HCC). Recent studies have reported various associations between HCV and the incidence of non-Hodgkin's lymphoma. We report the radiologic findings in a rare case of simultaneous occurrence of HCC and diffuse large B cell lymphoma in a HCV carrier.

Estimating Motor Carrier Management Information System Crash File Underreporting from Carrier Records.

Science.gov (United States)

2017-08-01

This FMCSA-sponsored research investigated the claim that motor carriers have a substantial number of crashes in their own records that are not contained in the Motor Carrier Management Information System (MCMIS) crash file. Based on the results of t...

NEAR INFRARED DIFFUSE INTERSTELLAR BANDS TOWARD THE CYGNUS OB2 ASSOCIATION

Energy Technology Data Exchange (ETDEWEB)

Hamano, Satoshi; Kondo, Sohei; Sameshima, Hiroaki; Nakanishi, Kenshi; Kawakita, Hideyo [Laboratory of Infrared High-resolution Spectroscopy, Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan); Kobayashi, Naoto [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Ikeda, Yuji [Photocoding, 460-102 Iwakura-Nakamachi, Sakyo-ku, Kyoto, 606-0025 (Japan); Yasui, Chikako; Mizumoto, Misaki; Matsunaga, Noriyuki; Fukue, Kei; Yamamoto, Ryo; Izumi, Natsuko [Department of Astronomy, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Mito, Hiroyuki [Kiso Observatory, Institute of Astronomy, School of Science, The University of Tokyo, 10762-30 Mitake, Kiso-machi, Kiso-gun, Nagano, 397-0101 (Japan); Nakaoka, Tetsuya; Kawanishi, Takafumi; Kitano, Ayaka; Otsubo, Shogo [Department of Physics, Faculty of Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan); Kinoshita, Masaomi, E-mail: hamano@cc.kyoto-su.ac.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601 (Japan)

2016-04-10

We obtained the near-infrared (NIR) high-resolution (R ≡ λ/Δλ ∼ 20,000) spectra of the seven brightest early-type stars in the Cygnus OB2 association for investigating the environmental dependence of diffuse interstellar bands (DIBs). The WINERED spectrograph mounted on the Araki 1.3 m telescope in Japan was used to collect data. All 20 of the known DIBs within the wavelength coverage of WINERED (0.91 < λ < 1.36 μm) were clearly detected along all lines of sight because of their high flux density in the NIR wavelength range and the large extinction. The equivalent widths (EWs) of DIBs were not correlated with the column densities of C{sub 2} molecules, which trace the patchy dense component, suggesting that the NIR DIB carriers are distributed mainly in the diffuse component. On the basis of the correlations among the NIR DIBs both for stars in Cyg OB2 and stars observed previously, λλ10780, 10792, 11797, 12623, and 13175 are found to constitute a “family,” in which the DIBs are correlated well over the wide EW range. In contrast, the EW of λ10504 is found to remain almost constant over the stars in Cyg OB2. The extinction estimated from the average EW of λ10504 (A{sub V} ∼ 3.6 mag) roughly corresponds to the lower limit of the extinction distribution of OB stars in Cyg OB2. This suggests that λ10504 is absorbed only by the foreground clouds, implying that the carrier of λ10504 is completely destroyed in Cyg OB2, probably by the strong UV radiation field. The different behaviors of the DIBs may be caused by different properties of the DIB carriers.

[Retrospective analysis of pulp revascularization in immature permanent teeth with diffuse pulpitis].

Science.gov (United States)

Peng, C F; Zhao, Y M; Yang, Y; Liu, H; Qin, M

2017-01-09

Objective: To evaluate the treatment effectiveness of revascularization in immature permanent teeth with diffuse pulpitis and to provide an alternative approach for the treatment of these teeth. Methods: Clinical and radiographic data were collected from 17 immature permanent teeth which were diagnosed as diffuse pulpitis and with their pulp extirpated at Emergency Department of Peking University School and Hospital of Stomatology. All these teeth were treated using pulp revascularization at Department of Pediatric Dentistry. Clinical success rate was then evaluated based on the clinical and radiographic findings. The increase of root length and dentin wall thickness of the revascularized teeth and the contralateral control teeth were measured and compared according to the preoperative and recall periapical radiographs. Results: The average follow-uptime is (25.8±9.9) months (12-46 months). Totally 13 out of the 17 teeth showed normal clinical and radiographic manifestation and achieved the increasein root length and dentin wall thickness. They met criteria for success treatment. The rest 4 out of the 17 teeth also showed root length and dentin wall thickness increaseand apical foramen closure. However, periapical inflammations were observed during 12 to 36 monthfollow-ups. These cases were recognized as failed. In all the17 teeth, the increase of root length and dentin wall thickness was not significantly different between the revascularized teeth and the contralateral control teeth ( P> 0.05). Conclusions: Pulp revascularization in young permanent teeth with diffuse pulpitis resulted in similar clinical outcomes in root development and root canal wall formation compared with the contralateral control teeth. However, reinfection might occur during long-term follow-up.

[Length of stay in patients admitted for acute heart failure].

Science.gov (United States)

Martín-Sánchez, Francisco Javier; Carbajosa, Virginia; Llorens, Pere; Herrero, Pablo; Jacob, Javier; Miró, Òscar; Fernández, Cristina; Bueno, Héctor; Calvo, Elpidio; Ribera Casado, José Manuel

2016-01-01

To identify the factors associated with prolonged length of hospital stay in patients admitted for acute heart failure. Multipurpose observational cohort study including patients from the EAHFE registry admitted for acute heart failure in 25 Spanish hospitals. Data were collected on demographic and clinical variables and on the day and place of admission. The primary outcome was length of hospital stay longer than the median. We included 2,400 patients with a mean age of 79.5 (9.9) years; of these, 1,334 (55.6%) were women. Five hundred and ninety (24.6%) were admitted to the short stay unit (SSU), 606 (25.2%) to cardiology, and 1,204 (50.2%) to internal medicine or gerontology. The mean length of hospital stay was 7.0 (RIC 4-11) days. Fifty-eight (2.4%) patients died and 562 (23.9%) were readmitted within 30 days after discharge. The factors associated with prolonged length of hospital stay were chronic pulmonary disease; being a device carrier; having an unknown or uncommon triggering factor; the presence of renal insufficiency, hyponatremia and anaemia in the emergency department; not being admitted to an SSU or the lack of this facility in the hospital; and being admitted on Monday, Tuesday or Wednesday. The factors associated with length of hospital stay≤7days were hypertension, having a hypertensive episode, or a lack of treatment adherence. The area under the curve of the mixed model adjusted to the center was 0.78 (95% CI: 0.76-0.80; p<0.001). A series of factors is associated with prolonged length of hospital stay and should be taken into account in the management of acute heart failure. Copyright © 2016 SESPAS. Published by Elsevier Espana. All rights reserved.

Further characterization of cadmium uptake by rat liver sinusoidal plasma membrane vesicles as a carrier mediated process

International Nuclear Information System (INIS)

Eastman, H.B.; Frazier, J.M.

1990-01-01

Previously we have reported that cadmium (Cd) transport by rat hepatic sinusoidal plasma membrane vesicles (SPMV's) occurs by both carrier mediated process and simple diffusion. This study was undertaken in order to further characterize the carrier mediated component of Cd transport as a carrier mediated process. Efflux of Cd from SPMV's was measured by first loading the vesicles with 1 μM Cd, containing 109 Cd (Amersham, 0.25 mCi/ml, carrier free) as a tracer, and then diluting the vesicles 1 to 5 into efflux buffer containing 0.25 M sucrose, 150 mM NaCl and 50 mM Tris/HCl (pH 7.4). Under standard conditions, no efflux of Cd from the vesicles was observed. However, the presence of 4mM CdCl 2 or 4.0% BSA in the efflux buffer was able to release 109 Cd from the vesicles. When the vesicles were lysed with 0.1% Triton X-100, approximately 75% of the internalized Cd could be released from the vesicles. Efflux of Cd from the vesicles was also determined to be a temperature dependent process. At 0 C the efflux of Cd from the vesicles, in the presence of a 4 mM CdCl 2 or 4.0% BSA chase, was blocked. The specificity of the carrier mediated component of Cd transport for Cd was investigated by determining whether other metals could compete for Cd uptake. Zinc was a competitive inhibitor of the carrier mediated component of Cd uptake while calcium had no effect on Cd uptake. Using this system, we have demonstrated that one component of Cd transport exhibits the basic characteristics of a carrier mediated process: saturation, reversibility, specificity and temperature dependence

Carrier transport uphill. I. General

DEFF Research Database (Denmark)

Rosenberg, T; Wilbrandt, W

1963-01-01

A quantitative treatment of a carrier pump operating with two carrier forms C and Z is presented. Asymmetric metabolic reactions are assumed to transform Z into C on one and C into Z on the other side of the membrane, establishing a carrier cycle. The kinetical consequences of this mechanism...

Inert carriers for column extraction chromatography

International Nuclear Information System (INIS)

Katykhin, G.S.

1978-01-01

Inert carriers used in column extraction chromatography are reviewed. Such carriers are devided into two large groups: hydrophilic carriers which possess high surface energy and are well wetted only with strongly polar liquids (kieselguhrs, silica gels, glasses, cellulose, Al 2 O 3 ) and water-repellent carriers which possess low surface energy and are well wetted with various organic solvents (polyethylene, polytetrafluorethylene polytrifluorochlorethylene). Properties of various carriers are presented: structure, chemical and radiation stability, adsorption properties, extracting agent capacity. The effect of structure and sizes of particles on the efficiency of chromatography columns is considered. Ways of immovable phase deposition on the carrier and the latter's regeneration. Peculiarities of column packing for preparative and continuous chromatography are discussed

Biosynthesis of medium chain length alkanes for bio-aviation fuel by metabolic engineered Escherichia coli.

Science.gov (United States)

Wang, Meng; Nie, Kaili; Cao, Hao; Xu, Haijun; Fang, Yunming; Tan, Tianwei; Baeyens, Jan; Liu, Luo

2017-09-01

The aim of this work was to study the synthesis of medium-chain length alkanes (MCLA), as bio-aviation product. To control the chain length of alkanes and increase the production of MCLA, Escherichia coli cells were engineered by incorporating (i) a chain length specific thioesterase from Umbellularia californica (UC), (ii) a plant origin acyl carrier protein (ACP) gene and (iii) the whole fatty acid synthesis system (FASs) from Jatropha curcas (JC). The genetic combination was designed to control the product spectrum towards optimum MCLA. Decanoic, lauric and myristic acid were produced at concentrations of 0.011, 0.093 and 1.657mg/g, respectively. The concentration of final products nonane, undecane and tridecane were 0.00062mg/g, 0.0052mg/g, and 0.249mg/g respectively. Thioesterase from UC controlled the fatty acid chain length in a range of 10-14 carbons and the ACP gene with whole FASs from JC significantly increased the production of MCLA. Copyright © 2017 Elsevier Ltd. All rights reserved.

Purified reconstituted lac carrier protein from Escherichia coli is fully functional.

Science.gov (United States)

Viitanen, P; Garcia, M L; Kaback, H R

1984-03-01

Proteoliposomes reconstituted with lac carrier protein purified from the plasma membrane of Escherichia coli catalyze each of the translocation reactions typical of the beta-galactoside transport system (i.e., active transport, counterflow, facilitated influx and efflux) with turnover numbers and apparent Km values comparable to those observed in right-side-out membrane vesicles. Furthermore, detailed kinetic studies show that the reconstituted system exhibits properties analogous to those observed in membrane vesicles. Imposition of a membrane potential (delta psi, interior negative) causes a marked decrease in apparent Km (by a factor of 7 to 10) with a smaller increase in Vmax (approximately equal to 3-fold). At submaximal values of delta psi, the reconstituted carrier exhibits biphasic kinetics, with one component manifesting the kinetic parameters of active transport and the other exhibiting the characteristics of facilitated diffusion. Finally, at low lactose concentrations, the initial velocity of influx varies linearly with the square of the proton electro-chemical gradient. The results provide quantitative support for the contention that a single polypeptide species, the product of the lac y gene, is responsible for each of the transport reactions typical of the beta-galactoside transport system.

Diffusion Driven Combustion Waves in Porous Media

Science.gov (United States)

Aldushin, A. P.; Matkowsky, B. J.

2000-01-01

Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases

Contribution to the determination of the mixing length in a channel; Contribution a la determination de la longueur de bon melange dans un canal

Energy Technology Data Exchange (ETDEWEB)

Spitalnik, J [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1967-04-15

A formula giving the mixing length in a rectangular channel is established. The value of that mixing length depends on the geometrical dimensions of the channel, the longitudinal, lateral and vertical diffusion coefficients, and the water average velocity in the channel. (author) [French] On etablit une formule permettant de calculer la longueur de bon melange dans un canal rectangulaire. La valeur de cette longueur depend des donnees geometriques du canal, des coefficients de diffusion longitudinal, transversal et vertical, et de la vitesse moyenne de l'eau dans le canal. (auteur)

Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurments of diffuse light

NARCIS (Netherlands)

Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton; Steenbergen, Wiendelt

2007-01-01

The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a

Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light

NARCIS (Netherlands)

Varghese, Babu; Rajan, Vinayakrishnan; van Leeuwen, Ton G.; Steenbergen, Wiendelt

2007-01-01

The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a

Diffusion of oxygen in cork.

Science.gov (United States)

Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Simon, Jean-Marc; Paulin, Christian; Bellat, Jean-Pierre

2012-04-04

This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.

Joint Iterative Carrier Synchronization and Signal Detection for Dual Carrier 448 Gb/s PDM 16-QAM

DEFF Research Database (Denmark)

Zibar, Darko; Carvalho, Luis; Estaran Tolosa, Jose Manuel

2013-01-01

Soft decision driven joint carrier synchronization and signal detection, employing expectation maximization, is experimentally demonstrated. Employing soft decisions offers an improvement of 0.5 dB compared to hard decision digital PLL based carrier synchronization and demodulation.......Soft decision driven joint carrier synchronization and signal detection, employing expectation maximization, is experimentally demonstrated. Employing soft decisions offers an improvement of 0.5 dB compared to hard decision digital PLL based carrier synchronization and demodulation....

EFFECT OF FORCED ROTATING VANELESS DIFFUSERS ON CENTRIFUGAL COMPRESSOR STAGE PERFORMANCE

Directory of Open Access Journals (Sweden)

S. SERALATHAN

2011-10-01

Full Text Available Non-uniform flow at the exit of the centrifugal impeller mixes in the vaneless space of the diffuser causing a rise in static pressure as well as significant loss of total pressure. These mixing losses are usually an important source of inefficiency. Forced rotating vaneless diffusers is one such concept which reduces the energy losses associated with diffusion. Forced rotating vaneless diffuser involves the concept of blade cutback and shroud extension. In the present computational investigations, the effects of blade cutback of 5%, 10% and 20% of vane length, shroud extension of 10%, 20%, 30% and 40% of impeller tip diameter and impeller without shroud extension on flow diffusion and performance are analyzed, while all the other dimensions remaining same. The performance characteristics of various blade cutback configurations are less in terms of efficiency, energy coefficient as well as static pressure rise. The objective of obtaining higher static pressure rise with wide operating range and reduced losses over stationary vaned diffuser is achieved by shroud extension of 30%, followed by shroud extension of 20%.

Fundamental length and relativistic length

International Nuclear Information System (INIS)

Strel'tsov, V.N.

1988-01-01

It si noted that the introduction of fundamental length contradicts the conventional representations concerning the contraction of the longitudinal size of fast-moving objects. The use of the concept of relativistic length and the following ''elongation formula'' permits one to solve this problem

Time-optimized high-resolution readout-segmented diffusion tensor imaging.

Directory of Open Access Journals (Sweden)

Gernot Reishofer

Full Text Available Readout-segmented echo planar imaging with 2D navigator-based reacquisition is an uprising technique enabling the sampling of high-resolution diffusion images with reduced susceptibility artifacts. However, low signal from the small voxels and long scan times hamper the clinical applicability. Therefore, we introduce a regularization algorithm based on total variation that is applied directly on the entire diffusion tensor. The spatially varying regularization parameter is determined automatically dependent on spatial variations in signal-to-noise ratio thus, avoiding over- or under-regularization. Information about the noise distribution in the diffusion tensor is extracted from the diffusion weighted images by means of complex independent component analysis. Moreover, the combination of those features enables processing of the diffusion data absolutely user independent. Tractography from in vivo data and from a software phantom demonstrate the advantage of the spatially varying regularization compared to un-regularized data with respect to parameters relevant for fiber-tracking such as Mean Fiber Length, Track Count, Volume and Voxel Count. Specifically, for in vivo data findings suggest that tractography results from the regularized diffusion tensor based on one measurement (16 min generates results comparable to the un-regularized data with three averages (48 min. This significant reduction in scan time renders high resolution (1 × 1 × 2.5 mm(3 diffusion tensor imaging of the entire brain applicable in a clinical context.

Antibiotic-containing hyaluronic acid gel as an antibacterial carrier: Usefulness of sponge and film-formed HA gel in deep infection.

Science.gov (United States)

Matsuno, Hiroaki; Yudoh, Kazuo; Hashimoto, Masamichi; Himeda, Yasukazu; Miyoshi, Teruzo; Yoshida, Kaoru; Kano, Syogo

2006-03-01

We have developed a novel bioabsorbable antibacterial carrier using hyaluronic acid (HA) gel for prevention and treatment of orthopedic infections. In this study, we investigated the in vivo antibacterial effects of two forms of this new material, an HA gel sponge and an HA gel film. A titanium cylinder was inserted into the intramedullary cavity of each rabbit femur, along with an HA gel sponge or HA gel film containing antibiotics. The HA gel sponge contained gentamycin, vancomycin, tobramycin, or minomycin. The HA gel film contained gentamycin or vancomycin. After 0, 7, and 14 days, the rabbit bone marrow was collected, and the antibacterial activity of the HA gel was determined by agar diffusion test. As a control, we used Septocoll, a commercially available antibacterial carrier. Both the HA gel sponge and HA gel film exhibited antibacterial activity. The present results indicate that HA gel containing antibiotics is a clinically useful bioabsorbable antibacterial carrier. Copyright 2006 Orthopaedic Research Society.

Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier

Energy Technology Data Exchange (ETDEWEB)

Li, Jing; Xu, Lu, E-mail: xl2013109@163.com; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming, E-mail: li_sanming2013@163.com

2015-10-01

This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. - Highlights: • Chiral mesoporous silica was synthesized using biomimetic method. • pH influenced energetics of self-assembly process of chiral mesoporous silica. • Stirring rate determined the particle length of chiral mesoporous silica. • Controlled release behaviors of chiral mesoporous silica varied based on structures.

Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier

International Nuclear Information System (INIS)

Li, Jing; Xu, Lu; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming

2015-01-01

This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. - Highlights: • Chiral mesoporous silica was synthesized using biomimetic method. • pH influenced energetics of self-assembly process of chiral mesoporous silica. • Stirring rate determined the particle length of chiral mesoporous silica. • Controlled release behaviors of chiral mesoporous silica varied based on structures

LIQUIFIED NATURAL GAS (LNG CARRIERS

Directory of Open Access Journals (Sweden)

Daniel Posavec

2010-12-01

Full Text Available Modern liquefied natural gas carriers are double-bottom ships classified according to the type of LNG tank. The tanks are specially designed to store natural gas cooled to -161°C, the boiling point of methane. Since LNG is highly flammable, special care must be taken when designing and operating the ship. The development of LNG carriers has begun in the middle of the twentieth century. LNG carrier storage space has gradually grown to the current maximum of 260000 m3. There are more than 300 LNG carriers currently in operation (the paper is published in Croatian.

Quantitation of chemical exchange rates using pulsed-field-gradient diffusion measurements

International Nuclear Information System (INIS)

Andrec, Michael; Prestegard, James H.

1997-01-01

A new approach to the quantitation of chemical exchange rates is presented, and its utility is illustrated with application to the exchange of protein amide protons with bulk water. The approach consists of a selective-inversion exchange HMQC experiment in which a short spin echo diffusion filter has been inserted into the exchange period. In this way, the kinetics of exchange are encoded directly in an apparent diffusion coefficient which is a function of the position of the diffusion filter in the pulse sequence. A detailed theoretical analysis of this experiment indicates that, in addition to the measurement of simple exchange rates, the experiment is capable of measuring the effect of mediated exchange, e.g. the transfer of magnetization from bulk water to an amide site mediated by an internal bound water molecule or a labile protein side-chain proton in fast exchange with bulk water. Experimental results for rapid water/amide exchange in acyl carrier protein are shown to be quantitatively consistent with the exchange rates measured using a selective-inversion exchange experiment

CGG repeat length and AGG interruptions as indicators of fragile X-associated diminished ovarian reserve.

Science.gov (United States)

Lekovich, Jovana; Man, Limor; Xu, Kangpu; Canon, Chelsea; Lilienthal, Debra; Stewart, Joshua D; Pereira, Nigel; Rosenwaks, Zev; Gerhardt, Jeannine

2017-12-21

PurposeFragile X premutation (PM) carriers may experience difficulties conceiving a child probably due to fragile X-associated diminished ovarian reserve (FXDOR). We investigated which subgroups of carriers with a PM are at higher risk of FXDOR, and whether the number of AGG interruptions within the repeat sequence further ameliorates the risk.MethodsWe compared markers of ovarian reserve, including anti-Müllerian hormone, antral follicle count, and number of oocytes retrieved between different subgroups of patients with a PM.ResultsWe found that carriers with midrange repeats size (70-90 CGG) demonstrate significantly lower ovarian reserve. Additionally, the number of AGG interruptions directly correlated with parameters of ovarian reserve. Patients with longer uninterrupted CGG repeats post-AGG interruptions had the lowest ovarian reserve.ConclusionThis study connects AGG interruptions and certain CGG repeat length to reduced ovarian reserve in carriers with a PM. A possible explanation for our findings is the proposed gonadotoxicity of the FMR1 transcripts. Reduction of AGG interruptions could increase the likelihood that secondary RNA structures in the FMR1 messenger RNA are formed, which could cause cell dysfunction within the ovaries. These findings may provide women with guidance regarding their fertility potential and accordingly assist with their family planning.GENETICS in MEDICINE advance online publication, 21 December 2017; doi:10.1038/gim.2017.220.

Air Carrier Traffic Statistics.

Science.gov (United States)

2013-11-01

This report contains airline operating statistics for large certificated air carriers based on data reported to U.S. Department of Transportation (DOT) by carriers that hold a certificate issued under Section 401 of the Federal Aviation Act of 1958 a...

Air Carrier Traffic Statistics.

Science.gov (United States)

2012-07-01

This report contains airline operating statistics for large certificated air carriers based on data reported to U.S. Department of Transportation (DOT) by carriers that hold a certificate issued under Section 401 of the Federal Aviation Act of 1958 a...

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES)

Science.gov (United States)

Cami, J.; Cox, N. L.; Farhang, A.; Smoker, J.; Elyajouri, M.; Lallement, R.; Bacalla, X.; Bhatt, N. H.; Bron, E.; Cordiner, M. A.; de Koter, A..; Ehrenfreund, P.; Evans, C.; Foing, B. H.; Javadi, A.; Joblin, C.; Kaper, L.; Khosroshahi, H. G.; Laverick, M.; Le Petit, F..; Linnartz, H.; Marshall, C. C.; Monreal-Ibero, A.; Mulas, G.; Roueff, E.; Royer, P.; Salama, F.; Sarre, P. J.; Smith, K. T.; Spaans, M.; van Loon, J. T..; Wade, G.

2018-03-01

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES) is a Large Programme that is collecting high-signal-to-noise (S/N) spectra with UVES of a large sample of O and B-type stars covering a large spectral range. The goal of the programme is to extract a unique sample of high-quality interstellar spectra from these data, representing different physical and chemical environments, and to characterise these environments in great detail. An important component of interstellar spectra is the diffuse interstellar bands (DIBs), a set of hundreds of unidentified interstellar absorption lines. With the detailed line-of-sight information and the high-quality spectra, EDIBLES will derive strong constraints on the potential DIB carrier molecules. EDIBLES will thus guide the laboratory experiments necessary to identify these interstellar “mystery molecules”, and turn DIBs into powerful diagnostics of their environments in our Milky Way Galaxy and beyond. We present some preliminary results showing the unique capabilities of the EDIBLES programme.

Diffusive processes in a stochastic magnetic field

International Nuclear Information System (INIS)

Wang, H.; Vlad, M.; Vanden Eijnden, E.; Spineanu, F.; Misguich, J.H.; Balescu, R.

1995-01-01

The statistical representation of a fluctuating (stochastic) magnetic field configuration is studied in detail. The Eulerian correlation functions of the magnetic field are determined, taking into account all geometrical constraints: these objects form a nondiagonal matrix. The Lagrangian correlations, within the reasonable Corrsin approximation, are reduced to a single scalar function, determined by an integral equation. The mean square perpendicular deviation of a geometrical point moving along a perturbed field line is determined by a nonlinear second-order differential equation. The separation of neighboring field lines in a stochastic magnetic field is studied. We find exponentiation lengths of both signs describing, in particular, a decay (on the average) of any initial anisotropy. The vanishing sum of these exponentiation lengths ensures the existence of an invariant which was overlooked in previous works. Next, the separation of a particle's trajectory from the magnetic field line to which it was initially attached is studied by a similar method. Here too an initial phase of exponential separation appears. Assuming the existence of a final diffusive phase, anomalous diffusion coefficients are found for both weakly and strongly collisional limits. The latter is identical to the well known Rechester-Rosenbluth coefficient, which is obtained here by a more quantitative (though not entirely deductive) treatment than in earlier works

Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

International Nuclear Information System (INIS)

Feng, Shih-Wei; Liao, Po-Hsun; Leung, Benjamin; Han, Jung; Yang, Fann-Wei; Wang, Hsiang-Chen

2015-01-01

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED

Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Feng, Shih-Wei, E-mail: swfeng@nuk.edu.tw; Liao, Po-Hsun [Department of Applied Physics, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan Tzu Dist., 811 Kaohsiung, Taiwan (China); Leung, Benjamin; Han, Jung [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Yang, Fann-Wei [Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Wang, Hsiang-Chen [Graduate Institute of Opto-Mechatronics and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chia-Yi, Taiwan (China)

2015-07-28

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED.

Modified electron beam induced current technique for in(Ga)As/InAsSb superlattice infrared detectors

Science.gov (United States)

Yoon, N.; Reyner, C. J.; Ariyawansa, G.; Duran, J. M.; Scheihing, J. E.; Mabon, J.; Wasserman, D.

2017-08-01

Electron beam induced current (EBIC) measurements provide a powerful tool for characterizing semiconductor based materials and devices. By measuring the current generated by the electron beam of a scanning electron microscope (SEM), EBIC allows us to extract the minority carrier diffusion length (L) and the surface recombination velocity to diffusivity ratio (S/D) of a material. When combined with information on minority carrier lifetime (τ), for instance from time-resolved photoluminescence measurements, the minority carrier mobility of the material can be extracted. However, the EBIC technique relies heavily on the accurate modeling of the carrier generation and collection process. Traditionally, this was achieved using a combination of empirical analytical expressions (and later Monte Carlo simulations) for carrier generation and analytical diffusion/recombination expressions for carrier collection. This approach introduces significant uncertainties into the extracted material parameters. Here, we present a numerical approach to EBIC modeling which improves the spatial resolution of our model, while also retaining information regarding the relative EBIC signal as a function of incident beam energies and currents. We apply this technique to investigate the temperature dependent minority carrier mobility of InAs/InAsSb and InGaAs/InAsSb strained layer superlattice infrared detectors and compare our results to the values obtained using external quantum efficiency measurements of the same samples. Our approach not only allows for an improvement in the uncertainty of the extracted material parameters, but also offers insight into the material and device behavior as a function of nonequilibrium carrier concentration. The technique presented here offers potentially improved characterization of not only infrared detectors, but a range of semiconductor-based devices.

Ternary mutual diffusion of isoniazid in aqueous sodium chloride, sodium hydroxide, and hydrochloric acid at T = 298.15 K

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, Ana C.F., E-mail: anacfrib@ci.uc.p [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Santos, Ana C.G., E-mail: anacatarinasantos123@gmail.co [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Lobo, Victor M.M., E-mail: vlobo@ci.uc.p [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Sobral, Abilio J.F.N., E-mail: asobral@ci.uc.p [Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal); Cabral, Ana M.T.D.P.V., E-mail: acabral@ff.uc.p [Faculty of Pharmacy, University of Coimbra, 3000-295 Coimbra (Portugal); Esteso, Miguel A., E-mail: miguel.esteso@uah.e [Departamento de Quimica Fisica, Facultad de Farmacia, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain)

2010-07-15

Ternary mutual diffusion coefficients measured by Taylor dispersion method (D{sub 11}, D{sub 22}, D{sub 12}, and D{sub 21}) are reported for aqueous solutions containing isoniazid and different electrolytes (NaCl, NaOH, or HCl) at T = 298.15 K at different carrier concentrations. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and the thermodynamic behaviour of isoniazid in different media. For example, it is possible to make conclusions about the influence of these electrolytes in diffusion of isoniazid, and to obtain information concerning the number of moles of each component transported per mole of the other component driven by its own concentration gradient.

Optical techniques for probing the excited state dynamics of quantum dot solids

Energy Technology Data Exchange (ETDEWEB)

Moroz, P.; Kholmicheva, N.; Razgoniaeva, N. [Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43402 (United States); Department of Physics, Bowling Green State University, Bowling Green, OH 43402 (United States); Burchfield, D. [Department of Chemistry, Bowling Green State University, Bowling Green, OH 43402 (United States); Sharma, N.; Acharya, A. [Department of Physics, Bowling Green State University, Bowling Green, OH 43402 (United States); Zamkov, M., E-mail: zamkovm@bgsu.edu [Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43402 (United States); Department of Physics, Bowling Green State University, Bowling Green, OH 43402 (United States)

2016-06-01

Highlights: • Optical techniques represent a powerful tool for probing exciton diffusion in QD solids. • Exciton dissociation in QD solids is caused by charge tunneling to traps and other dots. • Exciton and free-carrier lifetimes are given by fast and slow components of PL decay. • Surface PL offers valuable information on the type and density of traps in QD solids. - Abstract: Quantum dot (QD) solids represent an important class of functional materials that holds strong promise for future applications in technology. Their optoelectronic properties are determined by energy diffusion processes, which character can often be inferred from the temporal and spectral analysis of the film’s photoluminescence (PL). Here, optical techniques based on PL lifetime, bulk quenching, and temperature-dependent PL will be discussed. These techniques complement the electrical conductivity measurements by mapping the flow of optically induced excitons through undepleted, contact-free films with an unprecedented temporal and spatial resolution. By correlating the QD solid morphology with the ensuing photoluminescence (PL) dynamics, these methods allow estimating important transport characteristics, including exciton and charge carrier diffusion lengths, the rate of interparticle energy transfer, carrier mobility, and the exciton diffusivity. The review will cover most popular PL-based strategies and summarize the key experimental findings resulting from these works.

Determination of Diffusion Coefficients and Activation Energy of Selected Organic Liquids using Reversed-Flow Gas Chromatographic Technique

International Nuclear Information System (INIS)

Khalisanni Khalid; Rashid Atta Khan; Sharifuddin Mohd Zain

2012-01-01

Evaporation of vaporize organic liquid has ecological consequences when the compounds are introduced into both freshwater and marine environments through industrial effluents, or introduced directly into the air from industrial unit processes such as bioreactors and cooling towers. In such cases, a rapid and simple method are needed to measure physicochemical properties of the organic liquids. The Reversed-Flow Gas Chromatography (RF-GC) sampling technique is an easy, fast and accurate procedure. It was used to measure the diffusion coefficients of vapors from liquid into a carrier gas and at the same time to determine the rate coefficients for the evaporation of the respective liquid. The mathematical expression describing the elution curves of the samples peaks was derived and used to calculate the respective parameters for the selected liquid pollutants selected such as methanol, ethanol, 1-propanol, 1-butanol, n-pentane, n-hexane, n-heptane and n-hexadecane, evaporating into the carrier gas of nitrogen. The values of diffusion coefficients found were compared with those calculated theoretically or reported in the literature. The values of evaporation rate were used to determine the activation energy of respective samples using Arrhenius equation. An interesting finding of this work is by using an alternative mathematical analysis based on equilibrium at the liquid-gas interphase, the comparison leads to profound agreement between theoretical values of diffusion coefficients and experimental evidence. (author)

Response of GaAs charge storage devices to transient ionizing radiation

Science.gov (United States)

Hetherington, D. L.; Klem, J. F.; Hughes, R. C.; Weaver, H. T.

Charge storage devices in which non-equilibrium depletion regions represent stored charge are sensitive to ionizing radiation. This results since the radiation generates electron-hole pairs that neutralize excess ionized dopant charge. Silicon structures, such as dynamic RAM or CCD cells are particularly sensitive to radiation since carrier diffusion lengths in this material are often much longer than the depletion width, allowing collection of significant quantities of charge from quasi-neutral sections of the device. For GaAs the situation is somewhat different in that minority carrier diffusion lengths are shorter than in silicon, and although mobilities are higher, we expect a reduction of radiation sensitivity as suggested by observations of reduced quantum efficiency in GaAs solar cells. Dynamic memory cells in GaAs have potential increased retention times. In this paper, we report the response of a novel GaAs dynamic memory element to transient ionizing radiation. The charge readout technique is nondestructive over a reasonable applied voltage range and is more sensitive to stored charge than a simple capacitor.

Transcellular movement of hydroxyurea is mediated by specific solute carrier transporters

Science.gov (United States)

Walker, Aisha L.; Franke, Ryan M.; Sparreboom, Alex; Ware, Russell E.

2015-01-01

Objective Hydroxyurea has proven laboratory and clinical therapeutic benefits for sickle cell anemia (SCA) and other diseases, yet many questions remain regarding its in vivo pharmacokinetic and pharmacodynamic profiles. Previous reports suggest that hydroxyurea passively diffuses across cells, but its observed rapid absorption and distribution are more consistent with facilitated or active transport. We investigated the potential role of solute carrier (SLC) transporters in cellular uptake and accumulation of hydroxyurea. Materials and Methods Passive diffusion of hydroxyurea across cell membranes was determined using the parallel artificial membrane permeability assay. SLC transporter screens were conducted using in vitro intracellular drug accumulation and transcellular transport assays in cell lines and oocytes overexpressing SLC transporters. Gene expression of SLC transporters was measured by real-time PCR in human tissues and cell lines. Results Hydroxyurea had minimal diffusion across a lipid bilayer but was a substrate for 5 different SLC transporters belonging to the OCTN and OATP families of transporters and urea transporters A and B. Further characterization of hydroxyurea transport revealed that cellular uptake by OATP1B3 is time and temperature dependent and inhibited by known substrates of OATP1B3. Urea transporters A and B are expressed differentially in human tissues and erythroid cells, and transport hydroxyurea bidirectionally via facilitated diffusion. Conclusions These studies provide new insight into drug transport proteins that may be involved in the in vivo absorption, cellular distribution, and elimination of hydroxyurea. Elucidation of hydroxyurea transcellular movement should improve our understanding of its pharmacokinetics and pharmacodynamics, and may help explain some of the inter-patient drug variability observed in patients with SCA. PMID:21256917

Identification of Human T-lymphotropic Virus Type I (HTLV-I Subtypes Using Restrited Fragment Length Polymorphism in a Cohort of Asymptomatic Carriers and Patients with HTLV-I-associated Myelopathy/tropical Spastic Paraparesis from São Paulo, Brazil

Directory of Open Access Journals (Sweden)

Segurado Aluisio AC

2002-01-01

Full Text Available Although human T-lymphotropic virus type I (HTLV-I exhibits high genetic stability, as compared to other RNA viruses and particularly to human immunodeficiency virus (HIV, genotypic subtypes of this human retrovirus have been characterized in isolates from diverse geographical areas. These are currently believed not to be associated with different pathogenetic outcomes of infection. The present study aimed at characterizing genotypic subtypes of viral isolates from 70 HTLV-I-infected individuals from São Paulo, Brazil, including 42 asymptomatic carriers and 28 patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP, using restricted fragment length polymorphism (RFLP analysis of long terminal repeat (LTR HTLV-I proviral DNA sequences. Peripheral blood mononuclear cell lysates were amplified by nested polymerase chain reaction (PCR and amplicons submitted to enzymatic digestion using a panel of endonucleases. Among HTLV-I asymptomatic carriers, viral cosmopolitan subtypes A, B, C and E were identified in 73.8%, 7.1%, 7.1% and 12% of tested samples, respectively, whereas among HAM/TSP patients, cosmopolitan A (89.3%, cosmopolitan C (7.1% and cosmopolitan E (3.6% subtypes were detected. HTLV-I subtypes were not statistically significant associated with patients' clinical status. We also conclude that RFLP analysis is a suitable tool for descriptive studies on the molecular epidemiology of HTLV-I infections in our environment.

Fractional Diffusion Equations and Anomalous Diffusion

Science.gov (United States)

Evangelista, Luiz Roberto; Kaminski Lenzi, Ervin

2018-01-01

Preface; 1. Mathematical preliminaries; 2. A survey of the fractional calculus; 3. From normal to anomalous diffusion; 4. Fractional diffusion equations: elementary applications; 5. Fractional diffusion equations: surface effects; 6. Fractional nonlinear diffusion equation; 7. Anomalous diffusion: anisotropic case; 8. Fractional Schrödinger equations; 9. Anomalous diffusion and impedance spectroscopy; 10. The Poisson–Nernst–Planck anomalous (PNPA) models; References; Index.

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

Energy Technology Data Exchange (ETDEWEB)

Sundqvist, Kyle Michael [Univ. of California, Berkeley, CA (United States)

2012-01-01

dipoles, and capture forming "anion" (D^-/A⁺) states. We also generate predictions for impact ionization of shallow impurities and of impact "neutralization" of D^-/A⁺ states. We use measurements of carrier capture performed on CDMS detectors to validate a plausible model for electron and hole capture due to neutral shallow impurities and their charged D^-/A⁺ states. This model, along with carrier drift and diffusion parameters from Monte Carlo simulation, can be used as the foundation for simulations of space charge evolution in CDMS detectors, simultaneously solving continuity equations with Poisson's equation.

Positron diffusion in zinc-blende-type semiconductors

International Nuclear Information System (INIS)

Singh, R.P.; Singh, M.

1992-01-01

A theory of positron diffusion in the presence of positron scattering with acoustic, piezoelectric-acoustic, and optical phonons in zinc-blende-type semiconductors is developed. The velocity-velocity correlation function is used to calculate the diffusion coefficient and the Green's function is used to calculate the correlation function. In this formulation the relaxation time automatically appears through the imaginary part of the self-energy. The effect of screening is included within the Thomas-Fermi approximation. The theory is used to calculate the energy relaxation time and diffusion length of positrons in GaAs. It is shown that the transverse and longitudinal phonons contribute almost the same amount towards the relaxation time in the piezoelectric-acoustic-phonon scattering of positrons. It is also found that the contribution of piezoelectric-acoustic-phonon scattering is about 10% to that of acoustic-phonon scattering at low temperatures. We obtained a fairly good agreement between our theory and experimental results available to us. It is found that optical-phonon scattering plays an important role in getting good agreement between theory and experiment at high temperatures

Accurate numerical simulation of reaction-diffusion processes for heavy oil recovery

Energy Technology Data Exchange (ETDEWEB)

Govind, P.A.; Srinivasan, S. [Society of Petroleum Engineers, Richardson, TX (United States)]|[Texas Univ., Austin, TX (United States)

2008-10-15

This study evaluated a reaction-diffusion simulation tool designed to analyze the displacement of carbon dioxide (CO{sub 2}) in a simultaneous injection of carbon dioxide and elemental sodium in a heavy oil reservoir. Sodium was used due to the exothermic reaction of sodium with in situ that occurs when heat is used to reduce oil viscosity. The process also results in the formation of sodium hydroxide that reduces interfacial tension at the bitumen interface. A commercial simulation tool was used to model the sodium transport mechanism to the reaction interface through diffusion as well as the reaction zone's subsequent displacement. The aim of the study was to verify if the in situ reaction was able to generate sufficient heat to reduce oil viscosity and improve the displacement of the heavy oil. The study also assessed the accuracy of the reaction front simulation tool, in which an alternate method was used to model the propagation front as a moving heat source. The sensitivity of the simulation results were then evaluated in relation to the diffusion coefficient in order to understand the scaling characteristics of the reaction-diffusion zone. A pore-scale simulation was then up-scaled to grid blocks. Results of the study showed that when sodium suspended in liquid CO{sub 2} is injected into reservoirs, it diffuses through the carrier phase and interacts with water. A random walk diffusion algorithm with reactive dissipation was implemented to more accurately characterize reaction and diffusion processes. It was concluded that the algorithm modelled physical dispersion while neglecting the effect of numerical dispersion. 10 refs., 3 tabs., 24 figs.

Impact of carriers in oral absorption

DEFF Research Database (Denmark)

Gram, Luise Kvisgaard; Rist, Gerda Marie; Lennernäs, Hans

2009-01-01

Carriers may mediate the permeation across enterocytes for drug substances being organic anions. Carrier mediated permeation for the organic anions estrone-3-sulfate (ES) and glipizide across Caco-2 cells were investigated kinetically, and interactions on involved carriers evaluated. Initial...

Carrier-added and no-carrier-added syntheses of [18F]spiroperidol and [18F]haloperidol

International Nuclear Information System (INIS)

Kilbourn, M.R.; Welch, M.J.; Dence, C.S.; Tewson, T.J.; Saji, H.; Maeda, M.

1984-01-01

Syntheses of [ 18 F]haloperidol and [ 18 F]spiroperidol in both no-carrier-added and carrier-added forms have been accomplished. The no-carrier-added [ 18 F]butyrophenone neuroleptics were prepared in low ( 18 F-neuroleptics were prepared in better (5-17%) yields by 18 F-for- 19 F nucleophilic aromatic substitution. The preparation of all synthetic precursors, and procedures for radiolabeling are fully described. (author)

14 CFR 271.4 - Carrier costs.

Science.gov (United States)

2010-01-01

... Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS GUIDELINES FOR SUBSIDIZING AIR CARRIERS PROVIDING ESSENTIAL AIR TRANSPORTATION § 271.4 Carrier costs. (a) The reasonable costs projected for a carrier providing essential air service at an eligible...

14 CFR 271.5 - Carrier revenues.

Science.gov (United States)

2010-01-01

... Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS GUIDELINES FOR SUBSIDIZING AIR CARRIERS PROVIDING ESSENTIAL AIR TRANSPORTATION § 271.5 Carrier revenues. (a) The projected passenger revenue for a carrier providing essential air service at an eligible...

Charge carrier dynamics investigation of CuInS{sub 2} quantum dots films using injected charge extraction by linearly increasing voltage (i-CELIV): the role of ZnS Shell

Energy Technology Data Exchange (ETDEWEB)

Bi, Ke; Sui, Ning; Zhang, Liquan; Wang, Yinghui, E-mail: yinghui-wang@outlook.com; Liu, Qinghui, E-mail: liuqinghui@jlu.edu.cn; Tan, Mingrui [Jilin University, Femtosecond Laser Laboratory, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics (China); Zhou, Qiang [Jilin University, Key Laboratory of Superhard Materials, College of Physics (China); Zhang, Hanzhuang, E-mail: zhanghz@jlu.edu.cn [Jilin University, Femtosecond Laser Laboratory, Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics (China)

2016-12-15

The role of ZnS shell on the photo-physical properties within CuInS{sub 2}/ZnS quantum dots (QDs) is carefully studied in optoelectronic devices. Linearly increasing voltage technique has been employed to investigate the charge carrier dynamics of both CuInS{sub 2} and CuInS{sub 2}/ZnS QDs films. This study shows that charge carriers follow a similar behavior of monomolecular recombination in this film, with their charge transfer rate correlates to the increase of applied voltage. It turns out that the ZnS shell could affect the carrier diffusion process through depressing the trapping states and would build up a potential barrier.

Facilitated transport of hydrophilic salts by mixtures of anion and cation carriers and by ditopic carriers

NARCIS (Netherlands)

Chrisstoffels, L.A.J.; de Jong, Feike; Reinhoudt, David; Sivelli, Stefano; Gazzola, Licia; Casnati, Alessandro; Ungaro, Rocco

1999-01-01

Anion transfer to the membrane phase affects the extraction efficiency of salt transport by cation carriers 1 and 3. Addition of anion receptors 5 or 6 to cation carriers 1, 3, or 4 in the membrane phase enhances the transport of salts under conditions in which the cation carriers alone do not

Diffusion of Sites versus Polymers in Polyelectrolyte Complexes and Multilayers.

Science.gov (United States)

Fares, Hadi M; Schlenoff, Joseph B

2017-10-18

It has long been assumed that the spontaneous formation of materials such as complexes and multilayers from charged polymers depends on (inter)diffusion of these polyelectrolytes. Here, we separately examine the mass transport of polymer molecules and extrinsic sites-charged polyelectrolyte repeat units balanced by counterions-within thin films of polyelectrolyte complex, PEC, using sensitive isotopic labeling techniques. The apparent diffusion coefficients of these sites within PEC films of poly(diallyldimethylammonium), PDADMA, and poly(styrenesulfonate), PSS, are at least 2 orders of magnitude faster than the diffusion of polyelectrolytes themselves. This is because site diffusion requires only local rearrangements of polyelectrolyte repeat units, placing far fewer kinetic limitations on the assembly of polyelectrolyte complexes in all of their forms. Site diffusion strongly depends on the salt concentration (ionic strength) of the environment, and diffusion of PDADMA sites is faster than that of PSS sites, accounting for the asymmetric nature of multilayer growth. Site diffusion is responsible for multilayer growth in the linear and into the exponential regimes, which explains how PDADMA can mysteriously "pass through" layers of PSS. Using quantitative relationships between site diffusion coefficient and salt concentration, conditions were identified that allowed the diffusion length to always exceed the film thickness, leading to full exponential growth over 3 orders of magnitude thickness. Both site and polymer diffusion were independent of molecular weight, suggesting that ion pairing density is a limiting factor. Polyelectrolyte complexes are examples of a broader class of dynamic bulk polymeric materials that (self-) assemble via the transport of cross-links or defects rather than actual molecules.

Development of solar cells with back surface field made by aluminum paste and belt furnace diffusion; Desenvolvimento de celulas solares com campo retrodifusor formado por pasta de aluminio e difusao em forno de esteira

Energy Technology Data Exchange (ETDEWEB)

Marcolino, Juliane Bernardes

2011-01-15

Photovoltaics is based on the direct conversion of solar energy into electricity and is a promising alternative to diversify the world's energy matrix. This work aims to develop and analyse the deposition of Al paste by screen printing and firing/diffusion in a belt furnace to produce a BSF region in monocrystalline Si wafers. The diffusion of Al into the substrate was implemented by two different processes. In the first process the diffusion/firing of the Al paste and the firing of the Ag paste was carried out in independent steps. In this case, solar cells with an average efficiency ({eta}{sub average}) of 11.5 % and a maximum of 12.0 % were produced, but with the formation Al clusters in the back surface of the devices. In the second process firing/diffusion of such pastes was done on the same step. In this case, the best results were obtained for a firing/diffusion temperature of 860 deg C and belt furnace speed (V{sub E}) of 150 cm/min and also for 890 deg C and 180 cm/min. For the former parameters, {eta}{sub average} was 12.4 % and the maximum was 12.8 %. For the later, {eta}{sub average} was 12.5 % and the maximum was 12.6 %. Considering a temperature of 900 deg C and V{sub E} of 190 cm/min, {eta}{sub average} was 12.4 %. It was observed that minority carriers diffusion lengths were smaller than the thickness of silicon wafers. Open circuit voltages were 30 mV lower than that from similar cells fabricated at NT-Solar by using high purity Al deposited by e-beam evaporation indicating that the developed process produced low quality BSF. (author)

The Effect of the Chain Length on MMA Free Radicl Polymerization

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

In the polymerization process of methyl methacrylate (MMA), the Arrhenius parameters (activation energy and frequency factor) of propagating reaction monotonically decrease with increasing monomer conversion. At the beginning and middle stage of the propagating reaction, the increase of radical chain length is the main reason of above mentioned change. And at the end stage, the sharp decrease of kp indicates that the activation energy is approximately incline to zero and the propagating reaction is controlled by molecular diffusion motion.

Carrier-mediated system for transport of biotin in rat intestine in vitro

International Nuclear Information System (INIS)

Said, H.M.; Redha, R.

1987-01-01

Transport of biotin was examined in rat intestine using the everted sac technique. Transport of 0.1 μM biotin was linear with time for at least 30 min of incubation and occurred at a rate 3.7 pmol g initial tissue wet wt -1 min -1 . Transport of biotin was higher in the jejunum than the ileum and was minimum in the colon (85 +/- 6, 36 +/- 6, and 2.8 +/- 0.6 pmol x g initial tissue wet wt -1 x 25 min -1 , respectively). In the jejunum, transport of biotin was saturable at low concentrations but linear at higher concentrations. The transport of low concentrations of biotin was 1) inhibited by structural analogues (desthiobiotin, biotin methyl ester, diaminobiotin, and biocytin), 2) Na + dependent, 3) energy dependent, 4) temperature dependent, and 5) proceeded against a concentration gradient in the serosal compartment. No metabolic alteration occurs to the biotin molecule during transport. This study demonstrates that biotin transport in rat intestine occurs by a carrier-mediated process at low concentrations and by simple diffusion at high concentrations. Furthermore, the carrier-mediated process is Na + , energy, and temperature dependent

Analytical approximate solutions of the time-domain diffusion equation in layered slabs.

Science.gov (United States)

Martelli, Fabrizio; Sassaroli, Angelo; Yamada, Yukio; Zaccanti, Giovanni

2002-01-01

Time-domain analytical solutions of the diffusion equation for photon migration through highly scattering two- and three-layered slabs have been obtained. The effect of the refractive-index mismatch with the external medium is taken into account, and approximate boundary conditions at the interface between the diffusive layers have been considered. A Monte Carlo code for photon migration through a layered slab has also been developed. Comparisons with the results of Monte Carlo simulations showed that the analytical solutions correctly describe the mean path length followed by photons inside each diffusive layer and the shape of the temporal profile of received photons, while discrepancies are observed for the continuous-wave reflectance or transmittance.

Single-molecule diffusion and conformational dynamics by spatial integration of temporal fluctuations

KAUST Repository

Serag, Maged F.

2014-10-06

Single-molecule localization and tracking has been used to translate spatiotemporal information of individual molecules to map their diffusion behaviours. However, accurate analysis of diffusion behaviours and including other parameters, such as the conformation and size of molecules, remain as limitations to the method. Here, we report a method that addresses the limitations of existing single-molecular localization methods. The method is based on temporal tracking of the cumulative area occupied by molecules. These temporal fluctuations are tied to molecular size, rates of diffusion and conformational changes. By analysing fluorescent nanospheres and double-stranded DNA molecules of different lengths and topological forms, we demonstrate that our cumulative-area method surpasses the conventional single-molecule localization method in terms of the accuracy of determined diffusion coefficients. Furthermore, the cumulative-area method provides conformational relaxation times of structurally flexible chains along with diffusion coefficients, which together are relevant to work in a wide spectrum of scientific fields.

Single-molecule diffusion and conformational dynamics by spatial integration of temporal fluctuations

KAUST Repository

Serag, Maged F.; Abadi, Maram; Habuchi, Satoshi

2014-01-01

Single-molecule localization and tracking has been used to translate spatiotemporal information of individual molecules to map their diffusion behaviours. However, accurate analysis of diffusion behaviours and including other parameters, such as the conformation and size of molecules, remain as limitations to the method. Here, we report a method that addresses the limitations of existing single-molecular localization methods. The method is based on temporal tracking of the cumulative area occupied by molecules. These temporal fluctuations are tied to molecular size, rates of diffusion and conformational changes. By analysing fluorescent nanospheres and double-stranded DNA molecules of different lengths and topological forms, we demonstrate that our cumulative-area method surpasses the conventional single-molecule localization method in terms of the accuracy of determined diffusion coefficients. Furthermore, the cumulative-area method provides conformational relaxation times of structurally flexible chains along with diffusion coefficients, which together are relevant to work in a wide spectrum of scientific fields.

Incoherent neutron scattering functions for random jump diffusion in bounded and infinite media

International Nuclear Information System (INIS)

Hall, P.L.; Ross, D.K.

1981-01-01

The incoherent neutron scattering function for unbounded jump diffusion is calculated from random walk theory assuming a gaussian distribution of jump lengths. The method is then applied to calculate the scattering function for spatially bounded random jumps in one dimension. The dependence on momentum transfer of the quasi-elastic energy broadenings predicted by this model and a previous model for bounded one-dimensional continuous diffusion are calculated and compared with the predictions of models for diffusion in unbounded media. The one-dimensional solutions can readily be generalized to three dimensions to provide a description of quasi-elastic scattering of neutrons by molecules undergoing localized random motions. (author)

Numerical Study of Operating Pressure Effect on Carbon Nanotube Growth Rate and Length Uniformity

Directory of Open Access Journals (Sweden)

B. Zahed

2014-01-01

Full Text Available Chemical Vapor Deposition (CVD is one of the most popular methods for producing Carbon Nanotubes (CNTs. The growth rate of CNTs based on CVD technique is investigated by using a numerical model based on finite volume method. Inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at atmospheric pressure. In this article the operating pressure variations are studied as the effective parameter on CNT growth rate and length uniformity.

Diffusion of charged particles in a stochastic magnetic field

International Nuclear Information System (INIS)

Balescu, R.; Misguich, J.H.; Nakach, R.

1992-07-01

The diffusive motion of charged particles in a stochastic magnetic field is investigated systematically in a model in which the statistics of both the collisions and the magnetic field are described by coloured noises characterized, respectively, by a finite correlation time and finite correlation lengths. An analytic solution is obtained for the basic nonlinear differential equation of the model..It describes asymptotically a pure diffusion process, in which the mean square displacement in the perpendicular direction, Γ(t), grows proportionally to time (after a sufficiently long time). The corresponding diffusion coefficient scales like the fourth power of the magnetic fluctuation intensity. The values obtained are in very good agreement with experimental data in reverse-field pinch experiments. The present result contradicts earlier results predicting subdiffusive behaviour: Γ(t) ∼ t 1/2 or Γ(t) ∼ t 1/4 . The relation of these results to ours is discussed in detail

Perpendicular Diffusion Coefficient of Comic Rays: The Presence of Weak Adiabatic Focusing

Energy Technology Data Exchange (ETDEWEB)

Wang, J. F.; Ma, Q. M.; Song, T.; Yuan, S. B. [Research Department of Biomedical Engineering, Institute of Electrical Engineering, Chinese Academy of Science, Beijing 100190 (China); Qin, G., E-mail: wangjunfang@mail.iee.ac.cn, E-mail: qingang@hit.edu.cn [School of Science, Harbin Institute of Technology, Shenzhen 518055 (China)

2017-08-20

The influence of adiabatic focusing on particle diffusion is an important topic in astrophysics and plasma physics. In the past, several authors have explored the influence of along-field adiabatic focusing on the parallel diffusion of charged energetic particles. In this paper, using the unified nonlinear transport theory developed by Shalchi and the method of He and Schlickeiser, we derive a new nonlinear perpendicular diffusion coefficient for a non-uniform background magnetic field. This formula demonstrates that the particle perpendicular diffusion coefficient is modified by along-field adiabatic focusing. For isotropic pitch-angle scattering and the weak adiabatic focusing limit, the derived perpendicular diffusion coefficient is independent of the sign of adiabatic focusing characteristic length. For the two-component model, we simplify the perpendicular diffusion coefficient up to the second order of the power series of the adiabatic focusing characteristic quantity. We find that the first-order modifying factor is equal to zero and that the sign of the second order is determined by the energy of the particles.

Perpendicular Diffusion Coefficient of Comic Rays: The Presence of Weak Adiabatic Focusing

Science.gov (United States)

Wang, J. F.; Qin, G.; Ma, Q. M.; Song, T.; Yuan, S. B.

2017-08-01

The influence of adiabatic focusing on particle diffusion is an important topic in astrophysics and plasma physics. In the past, several authors have explored the influence of along-field adiabatic focusing on the parallel diffusion of charged energetic particles. In this paper, using the unified nonlinear transport theory developed by Shalchi and the method of He and Schlickeiser, we derive a new nonlinear perpendicular diffusion coefficient for a non-uniform background magnetic field. This formula demonstrates that the particle perpendicular diffusion coefficient is modified by along-field adiabatic focusing. For isotropic pitch-angle scattering and the weak adiabatic focusing limit, the derived perpendicular diffusion coefficient is independent of the sign of adiabatic focusing characteristic length. For the two-component model, we simplify the perpendicular diffusion coefficient up to the second order of the power series of the adiabatic focusing characteristic quantity. We find that the first-order modifying factor is equal to zero and that the sign of the second order is determined by the energy of the particles.

Perpendicular Diffusion Coefficient of Comic Rays: The Presence of Weak Adiabatic Focusing

International Nuclear Information System (INIS)

Wang, J. F.; Ma, Q. M.; Song, T.; Yuan, S. B.; Qin, G.

2017-01-01

The influence of adiabatic focusing on particle diffusion is an important topic in astrophysics and plasma physics. In the past, several authors have explored the influence of along-field adiabatic focusing on the parallel diffusion of charged energetic particles. In this paper, using the unified nonlinear transport theory developed by Shalchi and the method of He and Schlickeiser, we derive a new nonlinear perpendicular diffusion coefficient for a non-uniform background magnetic field. This formula demonstrates that the particle perpendicular diffusion coefficient is modified by along-field adiabatic focusing. For isotropic pitch-angle scattering and the weak adiabatic focusing limit, the derived perpendicular diffusion coefficient is independent of the sign of adiabatic focusing characteristic length. For the two-component model, we simplify the perpendicular diffusion coefficient up to the second order of the power series of the adiabatic focusing characteristic quantity. We find that the first-order modifying factor is equal to zero and that the sign of the second order is determined by the energy of the particles.

Orientational diffusion of n-alkyl cyanides

International Nuclear Information System (INIS)

Zhu Xiang; Farrer, Richard A; Zhong Qin; Fourkas, John T

2005-01-01

Ultrafast optical Kerr effect spectroscopy has been used to study the temperature-dependent orientational dynamics of a series of nitriles with n-alkyl chains ranging from one to 11 carbons in length. In all cases the orientational diffusion is found to be described by a single-exponential decay. Analysis of the orientational correlation times using the Debye-Stokes-Einstein equation suggests that the molecules adopt extended configurations and reorient as rigid rods. The liquids with shorter alkyl chains undergo an apparent ordering transition as they are cooled

Radiation resistance of InP-related materials

International Nuclear Information System (INIS)

Yamaguchi, Masafumi; Takamoto, Tatsuya; Ikeda, Eiji; Kurita, Hiroshi; Ohmori, Masamichi; Ando, Koshi; Vargas-Aburto, C.

1995-01-01

Irradiation effects of 1-MeV electrons on InP-related materials such as InP, InGaP and InGaAsP have been examined in comparison with those of GaAs. Superior radiation-resistance of InP-related materials and their devices compared to GaAs has been found in terms of minority-carrier diffusion length and properties of devices such as solar cells and light-emitting devices. Moreover, minority-carrier injection-enhanced annealing of radiation-induced defects in InP-related materials has also been observed. (author)

Emptiness formation probability of XX-chain in diffusion process

International Nuclear Information System (INIS)

Ogata, Yoshiko

2004-01-01

We study the distribution of emptiness formation probability of XX-model in the diffusion process. There exits a Gaussian decay as well as an exponential decay. The Gaussian decay is caused by the existence of zero point in the Fermi distribution function. The correlation length for each point of scaling factor varies up to the initial condition, monotonically or non-monotonically

Carrier-added and no-carrier-added syntheses of (/sup 18/F)spiroperidol and (/sub 18/F)haloperidol

Energy Technology Data Exchange (ETDEWEB)

Kilbourn, M R; Welch, M J; Dence, C S; Tewson, T J; Saji, H; Maeda, M

1984-07-01

Syntheses of (18F)haloperidol and (18F)spiroperidol in both no-carrier-added and carrier-added forms have been accomplished. The no-carrier-added (18F)butyrophenone neuroleptics were prepared in low (less than 2%) yield by acid decomposition of aryl piperidine triazenes. Carrier-added 18F-neuroleptics were prepared in better (5-17%) yields by 18F-for-19F nucleophilic aromatic substitution. The preparation of all synthetic precursors, and procedures for radiolabeling are fully described.

Process Research on Polycrystalline Silicon Material (PROPSM)

Science.gov (United States)

Culik, J. S.; Wrigley, C. Y.

1985-01-01

Results of hydrogen-passivated polycrysalline silicon solar cell research are summarized. The short-circuit current of solar cells fabricated from large-grain cast polycrystalline silicon is nearly equivalent to that of single-crystal cells, which indicates long bulk minority-carrier diffusion length. Treatments with molecular hydrogen showed no effect on large-grain cast polycrystalline silicon solar cells.

Rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides: is solute rotation always influenced by the length of the alkyl chain on the imidazolium cation?

Science.gov (United States)

Gangamallaiah, V; Dutt, G B

2012-10-25

In an attempt to find out whether the length of the alkyl chain on the imidazolium cation has a bearing on solute rotation, temperature-dependent fluorescence anisotropies of three structurally similar solutes have been measured in a series of 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides. Solute-solvent coupling constants obtained from the experimentally measured reorientation times with the aid of Stokes-Einstein-Debye hydrodynamic theory indicate that there is no influence of the length of the alkyl chain on the rotation of nonpolar, anionic, and cationic solutes 9-phenylanthracene (9-PA), fluorescein (FL), and rhodamine 110 (R110), respectively. It has also been noticed that the rotational diffusion of 9-PA is closer to the predictions of slip hydrodynamics, whereas the rotation of negatively charged FL and positively charged R110 is almost identical and follows stick hydrodynamics in these ionic liquids. Despite having similar shape and size, ionic solutes rotate slower by a factor of 3-4 compared to the nonpolar solute. Interplay of specific and electrostatic interactions between FL and the imidazolium cation of the ionic liquids, and between R110 and the bis(trifluoromethylsulfonyl)imide anion, appear to be responsible for the observed behavior. These results are an indication that the length of the alkyl chain on the imidazolium cation does not alter their physical properties in a manner that has an effect on solute rotation.

Altered structural brain connectome in young adult fragile X premutation carriers.

Science.gov (United States)

Leow, Alex; Harvey, Danielle; Goodrich-Hunsaker, Naomi J; Gadelkarim, Johnson; Kumar, Anand; Zhan, Liang; Rivera, Susan M; Simon, Tony J

2014-09-01

Fragile X premutation carriers (fXPC) are characterized by 55-200 CGG trinucleotide repeats in the 5' untranslated region on the Xq27.3 site of the X chromosome. Clinically, they are associated with the fragile X-Associated Tremor/Ataxia Syndrome, a late-onset neurodegenerative disorder with diffuse white matter neuropathology. Here, we conducted first-ever graph theoretical network analyses in fXPCs using 30-direction diffusion-weighted magnetic resonance images acquired from 42 healthy controls aged 18-44 years (HC; 22 male and 20 female) and 46 fXPCs (16 male and 30 female). Globally, we found no differences between the fXPCs and HCs within each gender for all global graph theoretical measures. In male fXPCs, global efficiency was significantly negatively associated with the number of CGG repeats. For nodal measures, significant group differences were found between male fXPCs and male HCs in the right fusiform and the right ventral diencephalon (for nodal efficiency), and in the left hippocampus [for nodal clustering coefficient (CC)]. In female fXPCs, CC in the left superior parietal cortex correlated with counting performance in an enumeration task. Copyright © 2014 Wiley Periodicals, Inc.

Shear-limited test particle diffusion in 2-dimensional plasmas

International Nuclear Information System (INIS)

Anderegg, Francois; Driscoll, C. Fred; Dubin, Daniel H.E.

2002-01-01

Measurements of test-particle diffusion in pure ion plasmas show 2D enhancements over the 3D rates, limited by shear in the plasma rotation ω E (r). The diffusion is due to 'long-range' ion-ion collisions in the quiescent, steady-state Mg + plasma. For short plasma length L p and low shear S≡r∂ω E /∂r, thermal ions bounce axially many times before shear separates them in θ, so the ions move in (r,θ) as bounce averaged 'rods' of charge (i.e. 2D point vortices). Experimentally, we vary the number of bounces over the range 0.2≤N b ≤10,000. For long plasmas with N b ≤1, we observe diffusion in quantitative agreement with the 3D theory of long-range ExB drift collisions. For shorter plasmas or lower shear, with N b >1, we measure diffusion rates enhanced by up to 100x. For exceedingly small she0ar, i.e. N b ≥1000, we observe diffusion rates consistent with the Taylor-McNamara estimates for a shear-free thermal plasma. Overall, the data shows fair agreement with Dubin's new theory of 2D diffusion in shear, which predicts an enhancement of D 2D /D 3D ≅N b up to the Taylor-McNamara limit