Liquid water breakthrough location distances on a gas diffusion layer of polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Yu, Junliang; Froning, Dieter; Reimer, Uwe; Lehnert, Werner

2018-06-01

The lattice Boltzmann method is adopted to simulate the three dimensional dynamic process of liquid water breaking through the gas diffusion layer (GDL) in the polymer electrolyte membrane fuel cell. 22 micro-structures of Toray GDL are built based on a stochastic geometry model. It is found that more than one breakthrough locations are formed randomly on the GDL surface. Breakthrough location distance (BLD) are analyzed statistically in two ways. The distribution is evaluated statistically by the Lilliefors test. It is concluded that the BLD can be described by the normal distribution with certain statistic characteristics. Information of the shortest neighbor breakthrough location distance can be the input modeling setups on the cell-scale simulations in the field of fuel cell simulation.

Novel electrospun gas diffusion layers for polymer electrolyte membrane fuel cells: Part II. In operando synchrotron imaging for microscale liquid water transport characterization

NASA Astrophysics Data System (ADS)

Chevalier, S.; Ge, N.; Lee, J.; George, M. G.; Liu, H.; Shrestha, P.; Muirhead, D.; Lavielle, N.; Hatton, B. D.; Bazylak, A.

2017-06-01

This is the second paper in a two-part series in which we investigate the impact of the gas diffusion layer structure on the liquid water distribution in an operating polymer electrolyte membrane (PEM) fuel cell through the procedures of design, fabrication, and testing of novel hydrophobic electrospun gas diffusion layers (eGDLs). In this work, fibre diameters and alignment in eGDLs are precisely controlled, and concurrent synchrotron X-ray radiography and electrochemical impedance spectroscopy (EIS) are used to evaluate the influence of the controlled eGDL parameters on the liquid water distribution and on membrane liquid water content. For eGDLs with small fibre diameters (150-200 nm) and correspondingly smaller pore sizes, reduced liquid water accumulation under the flow field ribs is observed. However, more liquid water is pinned onto the eGDL - at the interface with flow field channels. Orienting fibre alignment perpendicular to the flow field channel direction leads to improved eGDL-catalyst layer contact and prevents rib-channel membrane deformation. On the other hand, eGDLs facilitate significant membrane dry-out, even under highly humidified operating conditions at high current densities.

Water Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

NASA Astrophysics Data System (ADS)

Qin, C.; Hassanizadeh, S. M.

2015-12-01

In this work, a recently developed dynamic pore-network model is presented [1]. The model explicitly solves for both water pressure and capillary pressure. A semi-implicit scheme is used in updating water saturation in each pore body, which considerably increases the numerical stability at low capillary number values. Furthermore, a multiple-time-step algorithm is introduced to reduce the computational effort. A number of case studies of water transport in the micro porous layer (MPL) and gas diffusion layer (GDL) are conducted. We illustrate the role of MPL in reducing water flooding in the GDL. Also, the dynamic water transport through the MPL-GDL interface is explored in detail. This information is essential to the reduced continua model (RCM), which was developed for multiphase flow through thin porous layers [2, 3]. C.Z. Qin, Water transport in the gas diffusion layer of a polymer electrolyte fuel cell: dynamic pore-network modeling, J Electrochimical. Soci., 162, F1036-F1046, 2015. C.Z. Qin and S.M. Hassanizadeh, Multiphase flow through multilayers of thin porous media: general balance equations and constitutive relationships for a solid-gas-liquid three-phase system, Int. J. Heat Mass Transfer, 70, 693-708, 2014. C.Z. Qin and S.M. Hassanizadeh, A new approach to modeling water flooding in a polymer electrolyte fuel cell, Int. J. Hydrogen Energy, 40, 3348-3358, 2015.

Measurement of effective bulk and contact resistance of gas diffusion layer under inhomogeneous compression - Part I: Electrical conductivity

NASA Astrophysics Data System (ADS)

Vikram, Ajit; Chowdhury, Prabudhya Roy; Phillips, Ryan K.; Hoorfar, Mina

2016-07-01

This paper describes a measurement technique developed for the determination of the effective electrical bulk resistance of the gas diffusion layer (GDL) and the contact resistance distribution at the interface of the GDL and the bipolar plate (BPP). The novelty of this study is the measurement and separation of the bulk and contact resistance under inhomogeneous compression, occurring in an actual fuel cell assembly due to the presence of the channels and ribs on the bipolar plates. The measurement of the electrical contact resistance, contributing to nearly two-third of the ohmic losses in the fuel cell assembly, shows a non-linear distribution along the GDL/BPP interface. The effective bulk resistance of the GDL under inhomogeneous compression showed a decrease of nearly 40% compared to that estimated for homogeneous compression at different compression pressures. Such a decrease in the effective bulk resistance under inhomogeneous compression could be due to the non-uniform distribution of pressure under the ribs and the channels. This measurement technique can be used to identify optimum GDL, BPP and channel-rib structures based on minimum bulk and contact resistances measured under inhomogeneous compression.

Multi-scale structural analysis of gas diffusion layers

NASA Astrophysics Data System (ADS)

Göbel, Martin; Godehardt, Michael; Schladitz, Katja

2017-07-01

The macroscopic properties of materials are strongly determined by their micro structure. Here, transport properties of gas diffusion layers (GDL) for fuel cells are considered. In order to simulate flow and thermal properties, detailed micro structural information is essential. 3D images obtained by high-resolution computed tomography using synchrotron radiation and scanning electron microscopy (SEM) combined with focused ion beam (FIB) serial slicing were used. A recent method for reconstruction of porous structures from FIB-SEM images and sophisticated morphological image transformations were applied to segment the solid structural components. The essential algorithmic steps for segmenting the different components in the tomographic data-sets are described and discussed. In this paper, two types of GDL, based on a non-woven substrate layer and a paper substrate layer were considered, respectively. More than three components are separated within the synchrotron radiation computed tomography data. That is, fiber system, polytetrafluoroethylene (PTFE) binder/impregnation, micro porous layer (MPL), inclusions within the latter, and pore space are segmented. The usage of the thus derived 3D structure data in different simulation applications can be demonstrated. Simulations of macroscopic properties such as thermal conductivity, depending on the flooding state of the GDL are possible.

Tomographic Imaging of Water Injection and Withdrawal in PEMFC Gas Diffusion Layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGill U; Gostick, J. T.; Gunterman, H. P.

2010-06-25

X-ray computed tomography was used to visualize the water configurations inside gas diffusion layers for various applied capillary pressures, corresponding to both water invasion and withdrawal. A specialized sample holder was developed to allow capillary pressure control on the small-scale samples required. Tests were performed on GDL specimens with and without hydrophobic treatments.

Interactions between liquid-water and gas-diffusion layers in polymer-electrolyte fuel cells

DOE PAGES

Das, Prodip K.; Santamaria, Anthony D.; Weber, Adam Z.

2015-06-11

Over the past few decades, a significant amount of research on polymer-electrolyte fuel cells (PEFCs) has been conducted to improve performance and durability while reducing the cost of fuel cell systems. However, the cost associated with the platinum (Pt) catalyst remains a barrier to their commercialization and PEFC durability standards have yet to be established. An effective path toward reducing PEFC cost is making the catalyst layers (CLs) thinner thus reducing expensive Pt content. The limit of thin CLs is high gas-transport resistance and the performance of these CLs is sensitive to the operating temperature due to their inherent lowmore » water uptake capacity, which results in higher sensitivity to liquid-water flooding and reduced durability. Therefore, reducing PEFC's cost by decreasing Pt content and improving PEFC's performance and durability by managing liquid-water are still challenging and open topics of research. An overlooked aspect nowadays of PEFC water management is the gas-diffusion layer (GDL). While it is known that GDL's properties can impact performance, typically it is not seen as a critical component. In this work, we present data showing the importance of GDLs in terms of water removal and management while also exploring the interactions between liquid-water and GDL surfaces. The critical interface of GDL and gas-flow-channel in the presence of liquid-water was examined through systematic studies of adhesion forces as a function of water-injection rate for various GDLs of varying thickness. GDL properties (breakthrough pressure and adhesion force) were measured experimentally under a host of test conditions. Specifically, the effects of GDL hydrophobic (PTFE) content, thickness, and water-injection rate were examined to identify trends that may be beneficial to the design of liquid-water management strategies and next-generation GDL materials for PEFCs.« less

The effects of gas diffusion layers structure on water transportation using X-ray computed tomography based Lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Jinuntuya, Fontip; Whiteley, Michael; Chen, Rui; Fly, Ashley

2018-02-01

The Gas Diffusion Layer (GDL) of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) plays a crucial role in overall cell performance. It is responsible for the dissemination of reactant gasses from the gas supply channels to the reactant sites at the Catalyst Layer (CL), and the adequate removal of product water from reactant sites back to the gas channels. Existing research into water transport in GDLs has been simplified to 2D estimations of GDL structures or use virtual stochastic models. This work uses X-ray computed tomography (XCT) to reconstruct three types of GDL in a model. These models are then analysed via Lattice Boltzmann methods to understand the water transport behaviours under differing contact angles and pressure differences. In this study, the three GDL samples were tested over the contact angles of 60°, 80°, 90°, 100°, 120° and 140° under applied pressure differences of 5 kPa, 10 kPa and 15 kPa. By varying the contact angle and pressure difference, it was found that the transition between stable displacement and capillary fingering is not a gradual process. Hydrophilic contact angles in the region of 60°<θ < 90° showed stable displacement properties, whereas contact angles in the region of 100°<θ < 140° displayed capillary fingering characteristics.

A critical review on gas diffusion micro and macroporous layers degradations for improved membrane fuel cell durability

NASA Astrophysics Data System (ADS)

Lapicque, Francois; Belhadj, Mariem; Bonnet, Caroline; Pauchet, Joël; Thomas, Yohann

2016-12-01

Formerly considered as a secondary component of fuel cell, gas diffusion layers (GDLs) have been shown to have a key role in gas transport to the catalyst layers and in water management: in particular, the microporous layer (MPL) deposited on the diffusion substrate has an active part in water distribution in the membrane electrode assembly and in its efficient removal from the cell. In addition to its perfect design for the targeted application and in combination with the macroporous substrate (MPS), the MPL structure and physicochemical properties have to contribute to the cell durability, which is still considered as insufficient for larger, massive commercialisation of this energy conversion system. The paper is aimed at reviewing the main knowledge gained on the role of the MPL on GDL operation and durability, with investigation of degradation phenomena of both MPL and MPS, together with the role played by the MPL in mitigating the occurrence of degradation phenomena that can occur in the whole fuel cell. In addition to the reviewing purpose, original data on ex-situ degradation of GDL are presented.

Microstructural analysis of mass transport phenomena in gas diffusion media for high current density operation in PEM fuel cells

NASA Astrophysics Data System (ADS)

Kotaka, Toshikazu; Tabuchi, Yuichiro; Mukherjee, Partha P.

2015-04-01

Cost reduction is a key issue for commercialization of fuel cell electric vehicles (FCEV). High current density operation is a solution pathway. In order to realize high current density operation, it is necessary to reduce mass transport resistance in the gas diffusion media commonly consisted of gas diffusion layer (GDL) and micro porous layer (MPL). However, fundamental understanding of the underlying mass transport phenomena in the porous components is not only critical but also not fully understood yet due to the inherent microstructural complexity. In this study, a comprehensive analysis of electron and oxygen transport in the GDL and MPL is conducted experimentally and numerically with three-dimensional (3D) microstructural data to reveal the structure-transport relationship. The results reveal that the mass transport in the GDL is strongly dependent on the local microstructural variations, such as local pore/solid volume fractions and connectivity. However, especially in the case of the electrical conductivity of MPL, the contact resistance between carbon particles is the dominant factor. This suggests that reducing the contact resistance between carbon particles and/or the number of contact points along the transport pathway can improve the electrical conductivity of MPL.

An integrated simulator of structure and anisotropic flow in gas diffusion layers with hydrophobic additives

NASA Astrophysics Data System (ADS)

Burganos, Vasilis N.; Skouras, Eugene D.; Kalarakis, Alexandros N.

2017-10-01

The lattice-Boltzmann (LB) method is used in this work to reproduce the controlled addition of binder and hydrophobicity-promoting agents, like polytetrafluoroethylene (PTFE), into gas diffusion layers (GDLs) and to predict flow permeabilities in the through- and in-plane directions. The present simulator manages to reproduce spreading of binder and hydrophobic additives, sequentially, into the neat fibrous layer using a two-phase flow model. Gas flow simulation is achieved by the same code, sidestepping the need for a post-processing flow code and avoiding the usual input/output and data interface problems that arise in other techniques. Compression effects on flow anisotropy of the impregnated GDL are also studied. The permeability predictions for different compression levels and for different binder or PTFE loadings are found to compare well with experimental data for commercial GDL products and with computational fluid dynamics (CFD) predictions. Alternatively, the PTFE-impregnated structure is reproduced from Scanning Electron Microscopy (SEM) images using an independent, purely geometrical approach. A comparison of the two approaches is made regarding their adequacy to reproduce correctly the main structural features of the GDL and to predict anisotropic flow permeabilities at different volume fractions of binder and hydrophobic additives.

Thermal conductivity of a graphite bipolar plate (BPP) and its thermal contact resistance with fuel cell gas diffusion layers: Effect of compression, PTFE, micro porous layer (MPL), BPP out-of-flatness and cyclic load

NASA Astrophysics Data System (ADS)

Sadeghifar, Hamidreza; Djilali, Ned; Bahrami, Majid

2015-01-01

This paper reports on measurements of thermal conductivity of a graphite bipolar plate (BPP) as a function of temperature and its thermal contact resistance (TCR) with treated and untreated gas diffusion layers (GDLs). The thermal conductivity of the BPP decreases with temperature and its thermal contact resistance with GDLs, which has been overlooked in the literature, is found to be dominant over a relatively wide range of compression. The effects of PTFE loading, micro porous layer (MPL), compression, and BPP out-of-flatness are also investigated experimentally. It is found that high PTFE loadings, MPL and even small BPP out-of-flatness increase the BPP-GDL thermal contact resistance dramatically. The paper also presents the effect of cyclic load on the total resistance of a GDL-BPP assembly, which sheds light on the behavior of these materials under operating conditions in polymer electrolyte membrane fuel cells.

Theoretical examination of effective oxygen diffusion coefficient and electrical conductivity of polymer electrolyte fuel cell porous components

NASA Astrophysics Data System (ADS)

Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki

2016-09-01

The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.

Modeling of the anode of a liquid-feed DMFC: Inhomogeneous compression effects and two-phase transport phenomena

NASA Astrophysics Data System (ADS)

García-Salaberri, Pablo A.; Vera, Marcos; Iglesias, Immaculada

2014-01-01

An isothermal two-phase 2D/1D across-the-channel model for the anode of a liquid-feed Direct Methanol Fuel Cell (DMFC) is presented. The model takes into account the effects of the inhomogeneous assembly compression of the Gas Diffusion Layer (GDL), including the spatial variations of porosity, diffusivity, permeability, capillary pressure, and electrical conductivity. The effective anisotropic properties of the GDL are evaluated from empirical data reported in the literature corresponding to Toray carbon paper TGP-H series. Multiphase transport is modeled according to the classical theory of porous media (two-fluid model), considering the effect of non-equilibrium evaporation and condensation of methanol and water. The numerical results evidence that the hydrophobic Leverett J-function approach is physically inconsistent to describe capillary transport in the anode of a DMFC when assembly compression effects are considered. In contrast, more realistic results are obtained when GDL-specific capillary pressure curves reflecting the mixed-wettability characteristics of GDLs are taken into account. The gas coverage factor at the GDL/channel interface also exhibits a strong influence on the gas-void fraction distribution in the GDL, which in turn depends on the relative importance between the capillary resistance induced by the inhomogeneous compression, Rc(∝ ∂pc / ∂ ε) , and the capillary diffusivity, Dbarc(∝ ∂pc / ∂ s) .

Effect of through-plane polytetrafluoroethylene distribution in gas diffusion layers on performance of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Ito, Hiroshi; Iwamura, Takuya; Someya, Satoshi; Munakata, Tetsuo; Nakano, Akihiro; Heo, Yun; Ishida, Masayoshi; Nakajima, Hironori; Kitahara, Tatsumi

2016-02-01

This experimental study identifies the effect of through-plane polytetrafluoroethylene (PTFE) distribution in gas diffusion backing (GDB) on the performance of proton exchange membrane fuel cells (PEMFC). PTFE-drying under vacuum pressure created a relatively uniform PTFE distribution in GDB compared to drying under atmospheric pressure. Carbon paper samples with different PTFE distributions due to the difference in drying conditions were prepared and used for the cathode gas diffusion layer (GDL) of PEMFCs. Also investigated is the effect of MPL application on the performance for those samples. The current density (i) - voltage (V) characteristics of these PEMFCs measured under high relative humidity conditions clearly showed that, with or without MPL, the cell using the GDL with PTFE dried under vacuum condition showed better performance than that dried under atmospheric condition. It is suggested that this improved performance is caused by the efficient transport of liquid water through the GDB due to the uniform distribution of PTFE.

Microscale X-ray tomographic investigation of the interfacial morphology between the catalyst and micro porous layers in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Prass, Sebastian; Hasanpour, Sadegh; Sow, Pradeep Kumar; Phillion, André B.; Mérida, Walter

2016-07-01

The interfacial morphology between the catalyst layer (CL) and micro porous layer (MPL) influences the performance of proton exchange membrane fuel cells (PEMFCs). Here we report a direct method to investigate the CL-MPL interfacial morphology of stacked and compressed gas diffusion layer (GDL with MPL)-catalyst coated membrane (CCM) assemblies. The area, origin and dimensions of interfacial gaps are studied with high-resolution X-ray micro computed tomography (X-μCT). The projected gap area (fraction of the CL-MPL interface separated by gaps) is higher for GDL-CCM assemblies with large differences in the surface roughness between CL and MPL but reduces with increasing compression and similarity in roughness. Relatively large continuous gaps are found in proximity to cracks in the MPL. These are hypothesized to form due to the presence of large pores on the surface of the GDL. Smaller gaps are induced by the surface roughness features throughout the CL-MPL interface. By modification of the pore sizes on the GDL surface serving as substrate for the MPL, the number and dimension of MPL crack induced gaps can be manipulated. Moreover, adjusting the CL and MPL surface roughness parameters to achieve similar orders of roughness can improve the surface mating characteristics of these two components.

Validation of pore network simulations of ex-situ water distributions in a gas diffusion layer of proton exchange membrane fuel cells with X-ray tomographic images

NASA Astrophysics Data System (ADS)

Agaesse, Tristan; Lamibrac, Adrien; Büchi, Felix N.; Pauchet, Joel; Prat, Marc

2016-11-01

Understanding and modeling two-phase flows in the gas diffusion layer (GDL) of proton exchange membrane fuel cells are important in order to improve fuel cells performance. They are scientifically challenging because of the peculiarities of GDLs microstructures. In the present work, simulations on a pore network model are compared to X-ray tomographic images of water distributions during an ex-situ water invasion experiment. A method based on watershed segmentation was developed to extract a pore network from the 3D segmented image of the dry GDL. Pore network modeling and a full morphology model were then used to perform two-phase simulations and compared to the experimental data. The results show good agreement between experimental and simulated microscopic water distributions. Pore network extraction parameters were also benchmarked using the experimental data and results from full morphology simulations.

Dynamic behaviors of liquid droplets on a gas diffusion layer surface: Hybrid lattice Boltzmann investigation

NASA Astrophysics Data System (ADS)

Wu, Jie; Huang, Jun-Jie

2015-07-01

Water management is one of the key issues in proton exchange membrane fuel cells. Fundamentally, it is related to dynamic behaviors of droplets on a gas diffusion layer (GDL) surface, and consequently they are investigated in this work. A two-dimensional hybrid method is employed to implement numerical simulations, in which the flow field is solved by using the lattice Boltzmann method and the interface between droplet and gas is captured by solving the Cahn-Hilliard equation directly. One or two liquid droplets are initially placed on the GDL surface of a gas channel, which is driven by the fully developed Poiseuille flow. At a fixed channel size, the effects of viscosity ratio of droplet to gas ( μ ∗ ), Capillary number (Ca, ratio of gas viscosity to surface tension), and droplet interaction on the dynamic behaviors of droplets are systematically studied. By decreasing viscosity ratio or increasing Capillary number, the single droplet can detach from the GDL surface easily. On the other hand, when two identical droplets stay close to each other or a larger droplet is placed in front of a smaller droplet, the removal of two droplets is promoted.

Formulation, Implementation and Validation of a Two-Fluid model in a Fuel Cell CFD Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, Kunal; Cole, J. Vernon; Kumar, Sanjiv

2008-12-01

Water management is one of the main challenges in PEM Fuel Cells. While water is essential for membrane electrical conductivity, excess liquid water leads to flooding of catalyst layers. Despite the fact that accurate prediction of two-phase transport is key for optimal water management, understanding of the two-phase transport in fuel cells is relatively poor. Wang et. al. have studied the two-phase transport in the channel and diffusion layer separately using a multiphase mixture model. The model fails to accurately predict saturation values for high humidity inlet streams. Nguyen et. al. developed a two-dimensional, two-phase, isothermal, isobaric, steady state modelmore » of the catalyst and gas diffusion layers. The model neglects any liquid in the channel. Djilali et. al. developed a three-dimensional two-phase multicomponent model. The model is an improvement over previous models, but neglects drag between the liquid and the gas phases in the channel. In this work, we present a comprehensive two-fluid model relevant to fuel cells. Models for two-phase transport through Channel, Gas Diffusion Layer (GDL) and Channel-GDL interface, are discussed. In the channel, the gas and liquid pressures are assumed to be same. The surface tension effects in the channel are incorporated using the continuum surface force (CSF) model. The force at the surface is expressed as a volumetric body force and added as a source to the momentum equation. In the GDL, the gas and liquid are assumed to be at different pressures. The difference in the pressures (capillary pressure) is calculated using an empirical correlations. At the Channel-GDL interface, the wall adhesion affects need to be taken into account. SIMPLE-type methods recast the continuity equation into a pressure-correction equation, the solution of which then provides corrections for velocities and pressures. However, in the two-fluid model, the presence of two phasic continuity equations gives more freedom and more complications. A general approach would be to form a mixture continuity equation by linearly combining the phasic continuity equations using appropriate weighting factors. Analogous to mixture equation for pressure correction, a difference equation is used for the volume/phase fraction by taking the difference between the phasic continuity equations. The relative advantages of the above mentioned algorithmic variants for computing pressure correction and volume fractions are discussed and quantitatively assessed. Preliminary model validation is done for each component of the fuel cell. The two-phase transport in the channel is validated using empirical correlations. Transport in the GDL is validated against results obtained from LBM and VOF simulation techniques. The Channel-GDL interface transport will be validated against experiment and empirical correlation of droplet detachment at the interface.« less

Advanced control of liquid water region in diffusion media of polymer electrolyte fuel cells through a dimensionless number

NASA Astrophysics Data System (ADS)

Wang, Yun; Chen, Ken S.

2016-05-01

In the present work, a three-dimension (3-D) model of polymer electrolyte fuel cells (PEFCs) is employed to investigate the complex, non-isothermal, two-phase flow in the gas diffusion layer (GDL). Phase change in gas flow channels is explained, and a simplified approach accounting for phase change is incorporated into the fuel cell model. It is found that the liquid water contours in the GDL are similar along flow channels when the channels are subject to two-phase flow. Analysis is performed on a dimensionless parameter Da0 introduced in our previous paper [Y. Wang and K. S. Chen, Chemical Engineering Science 66 (2011) 3557-3567] and the parameter is further evaluated in a realistic fuel cell. We found that the GDL's liquid water (or liquid-free) region is determined by the Da0 number which lumps several parameters, including the thermal conductivity and operating temperature. By adjusting these factors, a liquid-free GDL zone can be created even though the channel stream is two-phase flow. Such a liquid-free zone is adjacent to the two-phase region, benefiting local water management, namely avoiding both severe flooding and dryness.

Advanced control of liquid water region in diffusion media of polymer electrolyte fuel cells through a dimensionless number

DOE PAGES

Wang, Yun; Chen, Ken S.

2016-03-21

In the present study, a three-dimension (3-D) model of polymer electrolyte fuel cells (PEFCs) is employed to investigate the complex, non-isothermal, two-phase flow in the gas diffusion layer (GDL). Phase change in gas flow channels is explained, and a simplified approach accounting for phase change is incorporated into the fuel cell model. It is found that the liquid water contours in the GDL are similar along flow channels when the channels are subject to two-phase flow. Here, analysis is performed on a dimensionless parameter Da 0 introduced in our previous paper and the parameter is further evaluated in a realisticmore » fuel cell. We found that the GDL's liquid water (or liquid-free) region is determined by the Da 0 number which lumps several parameters, including the thermal conductivity and operating temperature. By adjusting these factors, a liquid-free GDL zone can be created even though the channel stream is two-phase flow. Such a liquid-free zone is adjacent to the two-phase region, benefiting local water management, namely avoiding both severe flooding and dryness.« less

Multiphase transport in polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Gauthier, Eric D.

Polymer electrolyte membrane fuel cells (PEMFCs) enable efficient conversion of fuels to electricity. They have enormous potential due to the high energy density of the fuels they utilize (hydrogen or alcohols). Power density is a major limitation to wide-scale introduction of PEMFCs. Power density in hydrogen fuel cells is limited by accumulation of water in what is termed fuel cell `flooding.' Flooding may occur in either the gas diffusion layer (GDL) or within the flow channels of the bipolar plate. These components comprise the electrodes of the fuel cell and balance transport of reactants/products with electrical conductivity. This thesis explores the role of electrode materials in the fuel cell and examines the fundamental connection between material properties and multiphase transport processes. Water is generated at the cathode catalyst layer. As liquid water accumulates it will utilize the largest pores in the GDL to go from the catalyst layer to the flow channels. Water collects to large pores via lateral transport at the interface between the GDL and catalyst layer. We have shown that water may be collected in these large pores from several centimeters away, suggesting that we could engineer the GDL to control flooding with careful placement and distribution of large flow-directing pores. Once liquid water is in the flow channels it forms slugs that block gas flow. The slugs are pushed along the channel by a pressure gradient that is dependent on the material wettability. The permeable nature of the GDL also plays a major role in slug growth and allowing bypass of gas between adjacent channels. Direct methanol fuel cells (DMFCs) have analogous multiphase flow issues where carbon dioxide bubbles accumulate, `blinding' regions of the fuel cell. This problem is fundamentally similar to water management in hydrogen fuel cells but with a gas/liquid phase inversion. Gas bubbles move laterally through the porous GDL and emerge to form large bubbles within the flow channel. We have compared the role of GDL materials in liquid drop and gas bubble formation and movement within fuel cells.

Metal based gas diffusion layers for enhanced fuel cell performance at high current densities

NASA Astrophysics Data System (ADS)

Hussain, Nabeel; Van Steen, Eric; Tanaka, Shiro; Levecque, Pieter

2017-01-01

The gas diffusion layer strongly influences the performance and durability of polymer electrolyte fuel cells. A major drawback of current carbon fiber based GDLs is the non-controlled variation in porosity resulting in a random micro-structure. Moreover, when subjected to compression these materials show significant reduction in porosity and permeability leading to water management problems and mass transfer losses within the fuel cell. This study investigated the use of uniform perforated metal sheets as GDLs in conjunction with microchannel flowfields. A metal sheet design with a pitch of 110 μm and a hole diameter of 60 μm in combination with an MPL showed superior performance in the high current density region compared to a commercially available carbon paper based GDL in a single cell environment. Fuel cell testing with different oxidants (air, heliox and oxygen) indicate that the metal sheet offers both superior diffusion and reduced flooding in comparison to the carbon based GDL. The presence of the MPL has been found to be critical to the functionality of the metal sheet suggesting that the MPL design may represent an important optimisation parameter for further improvements in performance.

Water Management In PEM Fuel Cell -“ A Lattice-Boltzmann Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, Shiladitya; Cole, James Vernon; Jain, Kunal

2009-06-01

In Proton Exchange Membrane Fuel Cells (PEMFCs), water management and the effective transport of water through the gas-diffusion-layer (GDL) are key issues for improved performance at high power density and for durability during freeze-thaw cycles. The diffusion layer is a thin (~150-350{micro}m), porous material typically composed of a web of carbon fibers and particles, and is usually coated with hydrophobic Teflon to remove the excess water through capillary action. In-situ diagnostics of water movement and gas-reactant transport through this thin opaque substrate is challenging. Numerical analyses are typically based on simplified assumptions, such as Darcy's Law and Leverett functions formore » the capillary pressure. The objective of this work is to develop a high fidelity CFD modeling and analysis tool to capture the details of multiphase transport through the porous GDL. The tool can be utilized to evaluate GDL material design concepts and optimize systems based on the interactions between cell design, materials, and operating conditions. The flow modeling is based on the Lattice Boltzmann Method (LBM). LBM is a powerful modeling tool to simulate multiphase flows. Its strength is in its kinetic theory based foundation, which provides a fundamental basis for incorporating intermolecular forces that lead to liquid-gas phase separation and capillary effects without resorting to expensive or ad-hoc interface reconstruction schemes. At the heart of the solution algorithm is a discrete form of the well-known Boltzmann Transport Equation (BTE) for molecular distribution, tailored to recover the continuum Navier-Stokes flow. The solution advances by a streaming and collision type algorithm, mimicking actual molecular physics, which makes it suitable for porous media involving complex boundaries. We developed a numerical scheme to reconstruct various porous GDL microstructures including Teflon loading. Single and multiphase LBM models are implemented to compute permeability. Predicted values are in good agreement with measured data. The present modeling approach resolves the GDL microstructures and captures the influence of fiber orientation on permeability and the influence of Teflon loading on the development of preferential flow paths through the GDL. These observations can potentially guide the development of novel GDL materials designed for efficient removal of water.« less

Effect of clamping pressure on ohmic resistance and compression of gas diffusion layers for polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Mason, Thomas J.; Millichamp, Jason; Neville, Tobias P.; El-kharouf, Ahmad; Pollet, Bruno G.; Brett, Daniel J. L.

2012-12-01

This paper describes the use of an in situ analytical technique based on simultaneous displacement and resistance measurement of gas diffusion layers (GDLs) used in polymer electrolyte fuel cells (PEFCs), when exposed to varying compaction pressure. In terms of the losses within fuel cells, the ohmic loss makes up a significant portion. Of this loss, the contact resistance between the GDL and the bipolar plate (BPP) is an important constituent. By analysing the change in thickness and ohmic resistance of GDLs under compression, important mechanical and electrical properties are obtained. Derived parameters such as the 'displacement factor' are used to characterise a representative range of commercial GDLs. Increasing compaction pressure leads to a non-linear decrease in resistance for all GDLs. For Toray paper, compaction becomes more irreversible with pressure with no elastic region observed. Different GDLs have different intrinsic resistance; however, all GDLs of the same class share a common compaction profile (change in resistance with pressure). Cyclic compression of Toray GDL leads to progressive improvement in resistance and reduction in thickness that stabilises after ∼10 cycles.

Isothermal Ice Crystallization Kinetics in the Gas-Diffusion Layer of a Proton-Exchange-Membrane Fuel Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dursch, Thomas J.; Ciontea, Monica A.; Radke, Clayton J.

2011-12-01

Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are studied using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear ice-crystallization rate expression is developed using Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction timesmore » follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. Finally, a validated rate expression is now available for predicting ice-crystallization kinetics in GDLs.« less

On the effects of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions: A 2D numerical study

NASA Astrophysics Data System (ADS)

García-Salaberri, P. A.; Vera, M.

2015-07-01

The influence of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions is explored by means of a 2D/1D multiphysics across-the-channel model. The numerical formulation incorporates a comprehensive 2D description of the anode GDL, including two-phase phenomena, non-uniform anisotropic transport properties, and electrical contact resistances at the GDL/BPP interface. GDL effective properties are evaluated using empirical data corresponding to Toray® carbon paper. A simplified but physically sound 1D description, locally coupled to the 2D anode GDL model, is adopted to describe transport processes in the MPLs, membrane and cathode GDL, whereas the catalyst layers are treated as infinitely thin surfaces. Good agreement is found between the numerical results and previous experimental data. The interplay between assembly compression, bipolar plate material, and channel configuration is also investigated. The results show that there is an optimum GDL compression ratio in terms of overall power density, the optimal compression level being strongly dependent on bipolar plate material. Beyond the optimum, the detrimental effect of compression is larger in non-parallel flow fields due to the additional reduction of methanol transported by under-rib convection. The results suggest that, under certain conditions, this transport mechanism could be more important than diffusion in the anode of liquid-feed DMFCs.

Surface Properties of PEMFC Gas Diffusion Layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

WoodIII, David L; Rulison, Christopher; Borup, Rodney

2010-01-01

The wetting properties of PEMFC Gas Diffusion Layers (GDLs) were quantified by surface characterization measurements and modeling of material properties. Single-fiber contact-angle and surface energy (both Zisman and Owens-Wendt) data of a wide spectrum of GDL types is presented to delineate the effects of hydrophobic post-processing treatments. Modeling of the basic sessile-drop contact angle demonstrates that this value only gives a fraction of the total picture of interfacial wetting physics. Polar forces are shown to contribute 10-20 less than dispersive forces to the composite wetting of GDLs. Internal water contact angles obtained from Owens-Wendt analysis were measured at 13-19 highermore » than their single-fiber counterparts. An inverse relationship was found between internal contact angle and both Owens-Wendt surface energy and % polarity of the GDL. The most sophisticated PEMFC mathematical models use either experimentally measured capillary pressures or the standard Young-Laplace capillary-pressure equation. Based on the results of the Owens-Wendt analysis, an advancement to the Young-Laplace equation is proposed for use in these mathematical models, which utilizes only solid surface energies and fractional surface coverage of fluoropolymer. Capillary constants for the spectrum of analyzed GDLs are presented for the same purpose.« less

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered

PubMed Central

Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M

2017-01-01

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time. PMID:28773156

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered.

PubMed

Jayakumar, Arunkumar; Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M; Pethaiah, Sethu Sundar

2017-07-14

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time.

Investigation of GDL compression effects on the performance of a PEM fuel cell cathode by lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Molaeimanesh, G. R.; Nazemian, M.

2017-08-01

Proton exchange membrane (PEM) fuel cells with a great potential for application in vehicle propulsion systems will have a promising future. However, to overcome the exiting challenges against their wider commercialization further fundamental research is inevitable. The effects of gas diffusion layer (GDL) compression on the performance of a PEM fuel cell is not well-recognized; especially, via pore-scale simulation technique capturing the fibrous microstructure of the GDL. In the current investigation, a stochastic microstructure reconstruction method is proposed which can capture GDL microstructure changes by compression. Afterwards, lattice Boltzmann pore-scale simulation technique is adopted to simulate the reactive gas flow through 10 different cathode electrodes with dissimilar carbon paper GDLs produced from five different compression levels and two different carbon fiber diameters. The distributions of oxygen mole fraction, water vapor mole fraction and current density for the simulated cases are presented and analyzed. The results of simulations demonstrate that when the fiber diameter is 9 μm adding compression leads to lower average current density while when the fiber diameter is 7 μm the compression effect is not monotonic.

Characterization of highly hydrophobic textiles by means of X-ray microtomography, wettability analysis and drop impact

NASA Astrophysics Data System (ADS)

Santini, M.; Guilizzoni, M.; Fest-Santini, S.; Lorenzi, M.

2017-11-01

Highly hydrophobic surfaces have been intensively investigated in the last years because their properties may lead to very promising technological spillovers encompassing both everyday use and high-tech fields. Focusing on textiles, hydrophobic fabrics are of major interest for applications ranging from clothes to architecture to environment protection and energy conversion. Gas diffusion media - made by a gas diffusion layer (GDL) and a microporous layer (MPL) - for fuel cells are a good benchmark to develop techniques aimed at characterizing the wetting performances of engineered textiles. An experimental investigation was carried out about carbon-based, PTFE-treated GDLs with and without MPLs. Two samples (woven and woven-non-woven) were analysed before and after coating with a MPL. Their three-dimensional structure was reconstructed and analysed by computer-aided X-ray microtomography (µCT). Static and dynamic wettability analyses were then carried out using a modified axisymmetric drop shape analysis technique. All the surfaces exhibited very high hydrophobicity, three of them near to a super-hydrophobic behavior. Water drop impacts were performed, evidencing different bouncing, sticking and fragmentation outcomes for which critical values of the Weber number were identified. Finally, a µCT scan of a drop on a GDL was performed, confirming the Cassie-Baxter wetting state on such surface.

Investigating Phase-Change-Induced Flow in Gas Diffusion Layers in Fuel Cells with X-ray Computed Tomography

DOE PAGES

Shum, Andrew D.; Parkinson, Dilworth Y.; Xiao, Xianghui; ...

2017-10-07

The performance of polymer-electrolyte fuel cells is heavily dependent on proper management of liquid water. One particular reason is that liquid water can collect in the gas diffusion layers (GDLs) blocking the reactant flow to the catalyst layer. This results in increased mass-transport losses. At higher temperatures, evaporation of water becomes a dominant water-removal mechanism and specifically phase-change-induced (PCI) flow is present due to thermal gradients. This study used synchrotron based micro X-ray computed tomography (CT) to visualize and quantify the water distribution within gas diffusion layers subject to a thermal gradient. Plotting saturation as a function of through-plane distancemore » quantitatively shows water redistribution, where water evaporates at hotter locations and condenses in colder locations. The morphology of the 2 GDLs on the micro-scale, as well as evaporating water clusters, are resolved, indicating that the GDL voids are slightly prolate, whereas water clusters are oblate. From the mean radii of water distributions and visual inspection, it is observed that larger water clusters evaporate faster than smaller ones.« less

Ex-situ gas diffusion layer intrusion effect determination of polymer electrolyte membrane fuel cell flow fields

NASA Astrophysics Data System (ADS)

Haase, S.; Rauber, M.

2015-09-01

In automotive PEM fuel cell systems, one of the most important targets is to reduce the parasitic power of balance of plant components, e.g. the air supply. This can be achieved for example by decreasing air stoichiometry. However, this could lead to bad flow sharing in the fuel cell stack. Therefore the fluid distribution in the flow field has to be evaluated, understood and optimized. This work evaluates the effect of GDL intrusion on the pressure drop via ex-situ determination of GDL intrusion using CFD simulation. The intruded GDL geometries, evaluated by an optical microscope with 200 times enlargement, are transferred to pressure drop behaviors by a numerical CFD model. These results are compared to the results of the differential pressure method of mapping the pressure distribution, described in [43]. The intrusion of the GDL leads to homogeneous flow distribution up to clamping pressures of 2.5 MPa. The inhomogeneous intrusion, induced by cracked fibers that extend into the channel, dominates the flow at higher clamping pressures and leads to the exponential increase in pressure drop in the differential pressure method. For clamping pressures used in typical fuel cell applications, the results of both methods show homogeneous flow through the channels.

Large scale simulation of liquid water transport in a gas diffusion layer of polymer electrolyte membrane fuel cells using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Sakaida, Satoshi; Tabe, Yutaka; Chikahisa, Takemi

2017-09-01

A method for the large-scale simulation with the lattice Boltzmann method (LBM) is proposed for liquid water movement in a gas diffusion layer (GDL) of polymer electrolyte membrane fuel cells. The LBM is able to analyze two-phase flows in complex structures, however the simulation domain is limited due to heavy computational loads. This study investigates a variety means to reduce computational loads and increase the simulation areas. One is applying an LBM treating two-phases as having the same density, together with keeping numerical stability with large time steps. The applicability of this approach is confirmed by comparing the results with rigorous simulations using actual density. The second is establishing the maximum limit of the Capillary number that maintains flow patterns similar to the precise simulation; this is attempted as the computational load is inversely proportional to the Capillary number. The results show that the Capillary number can be increased to 3.0 × 10-3, where the actual operation corresponds to Ca = 10-5∼10-8. The limit is also investigated experimentally using an enlarged scale model satisfying similarity conditions for the flow. Finally, a demonstration is made of the effects of pore uniformity in GDL as an example of a large-scale simulation covering a channel.

New Method for Super Hydrophobic Treatment of Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells Using Electrochemical Reduction of Diazonium Salts.

PubMed

Thomas, Yohann R J; Benayad, Anass; Schroder, Maxime; Morin, Arnaud; Pauchet, Joël

2015-07-15

The purpose of this article is to report a new method for the surface functionalization of commercially available gas diffusion layers (GDLs) by the electrochemical reduction of diazonium salt containing hydrophobic functional groups. The method results in superhydrophobic GDLs, over a large area, without pore blocking. An X-ray photoelectron spectroscopy study based on core level spectra and chemical mapping has demonstrated the successful grafting route, resulting in a homogeneous distribution of the covalently bonded hydrophobic molecules on the surface of the GDL fibers. The result was corroborated by contact angle measurement, showing similar hydrophobicity between the grafted and PTFE-modified GDLs. The electrochemically modified GDLs were tested in proton exchange membrane fuel cells under automotive, wet, and dry conditions and demonstrated improved performance over traditional GDLs.

Investigation of water droplet dynamics in PEM fuel cell gas channels

NASA Astrophysics Data System (ADS)

Gopalan, Preethi

Water management in Proton Exchange Membrane Fuel Cell (PEMFC) has remained one of the most important issues that need to be addressed before its commercialization in automotive applications. Accumulation of water on the gas diffusion layer (GDL) surface in a PEMFC introduces a barrier for transport of reactant gases through the GDL to the catalyst layer. Despite the fact that the channel geometry is one of the key design parameters of a fluidic system, very limited research is available to study the effect of microchannel geometry on the two-phase flow structure. In this study, the droplet-wall dynamics and two-phase pressure drop across the water droplet present in a typical PEMFC channel, were examined in auto-competitive gas channel designs (0.4 x 0.7 mm channel cross section). The liquid water flow pattern inside the gas channel was analyzed for different air velocities. Experimental data was analyzed using the Concus-Finn condition to determine the wettability characteristics in the corner region. It was confirmed that the channel angle along with the air velocity and the channel material influences the water distribution and holdup within the channel. Dynamic contact angle emerged as an important parameter in controlling the droplet-wall interaction. Experiments were also performed to understand how the inlet location of the liquid droplet on the GDL surface affects the droplet dynamic behavior in the system. It was found that droplets emerging near the channel wall or under the land lead to corner filling of the channel. Improvements in the channel design has been proposed based on the artificial channel roughness created to act as capillary grooves to transport the liquid water away from the land area. For droplets emerging near the center of the channel, beside the filling and no-filling behavior reported in the literature, a new droplet jumping behavior was observed. As droplets grew and touched the sidewalls, they jumped off to the sidewall leaving the whole GDL exposed for gases to diffuse to the catalyst layer. A theoretical model was developed and a criterion was proposed to predict the droplet jumping behavior in the gas channel. A theoretical force balance model was proposed to predict the pressure force and air velocity required to remove the droplet from the channel to avoid complete channel blockage. The overall goal of this work was to identify the gas channel configuration that provides efficient water removal with a lower pressure drop in the system efficiency while meeting the US Department of Energy's specifications for a PEMFC for automotive application.

Real Time Monitoring of Temperature of a Micro Proton Exchange Membrane Fuel Cell

PubMed Central

Lee, Chi-Yuan; Lee, Shuo-Jen; Hu, Yuh-Chung; Shih, Wen-Pin; Fan, Wei-Yuan; Chuang, Chih-Wei

2009-01-01

Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature inside the fuel cell. Experimental results demonstrate that temperature was generally linearly related to resistance and that accuracy and sensitivity were within 0.5 °C and 1.68×10−3/°C, respectively. The best experimental performance was 9.37 mW/cm2 at an H2/O2 dry gas flow rate of 30/30 SCCM. Fuel cell temperature during operation was 27 °C, as measured using thermocouples in contact with the backside of the electrode. Fuel cell operating temperature measured in situ was 30.5 °C. PMID:22573963

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shum, Andrew D.; Parkinson, Dilworth Y.; Xiao, Xianghui

The performance of polymer-electrolyte fuel cells is heavily dependent on proper management of liquid water. One particular reason is that liquid water can collect in the gas diffusion layers (GDLs) blocking the reactant flow to the catalyst layer. This results in increased mass-transport losses. At higher temperatures, evaporation of water becomes a dominant water-removal mechanism and specifically phase-change-induced (PCI) flow is present due to thermal gradients. This study used synchrotron based micro X-ray computed tomography (CT) to visualize and quantify the water distribution within gas diffusion layers subject to a thermal gradient. Plotting saturation as a function of through-plane distancemore » quantitatively shows water redistribution, where water evaporates at hotter locations and condenses in colder locations. The morphology of the 2 GDLs on the micro-scale, as well as evaporating water clusters, are resolved, indicating that the GDL voids are slightly prolate, whereas water clusters are oblate. From the mean radii of water distributions and visual inspection, it is observed that larger water clusters evaporate faster than smaller ones.« less

Contact behavior modelling and its size effect on proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

2017-10-01

Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

Impact of micro-porous layer on liquid water distribution at the catalyst layer interface and cell performance in a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Tabe, Yutaka; Aoyama, Yusuke; Kadowaki, Kazumasa; Suzuki, Kengo; Chikahisa, Takemi

2015-08-01

In polymer electrolyte membrane fuel cells, a gas diffusion layer (GDL) with a micro-porous layer (MPL) gives better anti-flooding performance than GDLs without an MPL. To investigate the function and mechanism of the MPL to suppress water flooding, the liquid water distribution at the cathode catalyst layer (CL) surface are observed by a freezing method; in the method liquid water is immobilized in ice form by rapid freezing, followed by disassembling the cell for observations. The ice covered area is quantified by image processing and cells with and without an MPL are compared. The results show that the MPL suppresses water accumulation at the interface due to smaller pore size and finer contact with the CL, and this results in less water flooding. Investigation of ice formed after -10 °C cold start shutdowns and the temporary performance deterioration at ordinary temperatures also indicates a significant influence of the liquid water accumulating at the interface. The importance of the fine contact between CL and MPL, the relative absence of gaps, is demonstrated by a gas diffusion electrode (GDE) which is directly coated with catalyst ink on the surface of the MPL achieving finer contact of the layers.

Upshot of natural graphite inclusion on the performance of porous conducting carbon fiber paper in a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Kaushal, Shweta; Negi, Praveen; Sahu, A. K.; Dhakate, S. R.

2017-09-01

Porous conducting carbon fiber paper (PCCFP) is one of the vital component of the gas diffusion layer (GDL) in a fuel cell. This PCCFP serves as the most suitable substrate for the GDL due to its electrical conductivity, mechanical properties, and porosity. In this approach, carbon fiber composite papers were developed by incorporating different fractions of natural graphite (NG) in the matrix phase, i.e. Phenolic resin, and using the combined process of paper making and carbon-carbon composite formation technique. These prepared samples were then heat treated at 1800 °C in an inert atmosphere. The effect of natural graphite incorporation was ascertained by characterizing porous carbon paper by various techniques i.e. X-ray diffraction, Raman spectroscopy, Scanning electron microscopy, electrical and mechanical properties, and I-V performance in a unit fuel cell assembly. The inclusion of NG certainly enhance the properties of the carbon matrix as well as improving the conductive path of carbon fibers. In this study addition of 1 wt.% of natural graphite demonstrated a significant improvement in the electrical conductivity and performance of PCCFP and resulted in the improvement of power density from 361-563 mW cm-2. This paper reports that the uniform dispersion of NG was able to generate a maximum number of macrosize pores in the carbon paper that strengthened the flexural modulus from 4 to 12 GPa without compromising the porosity required for the GDL.

Numerical investigation of interfacial transport resistance due to water droplets in proton exchange membrane fuel cell air channels

NASA Astrophysics Data System (ADS)

Koz, Mustafa; Kandlikar, Satish G.

2013-12-01

Oxygen transport resistance at the air flow channel and gas diffusion layer (GDL) interface is needed in modelling the performance of a proton exchange membrane fuel cell (PEMFC). This resistance is expressed through the non-dimensional Sherwood number (Sh). The effect of the presence of a droplet on Sh is studied numerically in an isolated air flow channel using a commercially available package, COMSOL Multiphysics®. A droplet is represented as a solid obstruction placed on the GDL-channel interface and centred along the channel width. The effect of a single droplet is first studied for a range of superficial mean air velocities and droplet sizes. Secondly, the effect of droplet spacing on Sh is studied through simulations of two consecutive droplets. Lastly, multiple droplets in a row are studied as a more representative case of a PEMFC air flow channel. The results show that the droplets significantly increase Sh above the fully developed value in the wake region. This enhancement increases with the number of droplets, droplet size, and superficial mean air velocity. Moreover, the analogy between mass and heat transfer is investigated by comparing Sh to the equivalent Nusselt number.

High surface area synthesis, electrochemical activity, and stability of tungsten carbide supported Pt during oxygen reduction in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Chhina, H.; Campbell, S.; Kesler, O.

The oxidation of carbon catalyst supports to carbon dioxide gas leads to degradation in catalyst performance over time in proton exchange membrane fuel cells (PEMFCs). The electrochemical stability of Pt supported on tungsten carbide has been evaluated on a carbon-based gas diffusion layer (GDL) at 80 °C and compared to that of HiSpec 4000™ Pt/Vulcan XC-72R in 0.5 M H 2SO 4. Due to other electrochemical processes occurring on the GDL, detailed studies were also performed on a gold mesh substrate. The oxygen reduction reaction (ORR) activity was measured both before and after accelerated oxidation cycles between +0.6 V and +1.8 V vs. RHE. Tafel plots show that the ORR activity remained high even after accelerated oxidation tests for Pt/tungsten carbide, while the ORR activity was extremely poor after accelerated oxidation tests for HiSpec 4000™. In order to make high surface area tungsten carbide, three synthesis routes were investigated. Magnetron sputtering of tungsten on carbon was found to be the most promising route, but needs further optimization.

Application of gas diffusion biocathode in microbial electrosynthesis from carbon dioxide.

PubMed

Bajracharya, Suman; Vanbroekhoven, Karolien; Buisman, Cees J N; Pant, Deepak; Strik, David P B T B

2016-11-01

Microbial catalysis of carbon dioxide (CO 2 ) reduction to multi-carbon compounds at the cathode is a highly attractive application of microbial electrosynthesis (MES). The microbes reduce CO 2 by either taking the electrons or reducing the equivalents produced at the cathode. While using gaseous CO 2 as the carbon source, the biological reduction process depends on the dissolution and mass transfer of CO 2 in the electrolyte. In order to deal with this issue, a gas diffusion electrode (GDE) was investigated by feeding CO 2 through the GDE into the MES reactor for its reduction at the biocathode. A combination of the catalyst layer (porous activated carbon and Teflon binder) and the hydrophobic gas diffusion layer (GDL) creates a three-phase interface at the electrode. So, CO 2 and reducing equivalents will be available to the biocatalyst on the cathode surface. An enriched inoculum consisting of acetogenic bacteria, prepared from an anaerobic sludge, was used as a biocatalyst. The cathode potential was maintained at -1.1 V vs Ag/AgCl to facilitate direct and/or hydrogen-mediated CO 2 reduction. Bioelectrochemical CO 2 reduction mainly produced acetate but also extended the products to ethanol and butyrate. Average acetate production rates of 32 and 61 mg/L/day, respectively, with 20 and 80 % CO 2 gas mixture feed were achieved with 10 cm 2 of GDE. The maximum acetate production rate remained 238 mg/L/day for 20 % CO 2 gas mixture. In conclusion, a gas diffusion biocathode supported bioelectrochemical CO 2 reduction with enhanced mass transfer rate at continuous supply of gaseous CO 2 . Graphical abstract ᅟ.

PTFE effect on the electrocatalysis of the oxygen reduction reaction in membraneless microbial fuel cells.

PubMed

Guerrini, Edoardo; Grattieri, Matteo; Faggianelli, Alessio; Cristiani, Pierangela; Trasatti, Stefano

2015-12-01

Influence of PTFE in the external Gas Diffusion Layer (GDL) of open-air cathodes applied to membraneless microbial fuel cells (MFCs) is investigated in this work. Electrochemical measurements on cathodes with different PTFE contents (200%, 100%, 80% and 60%) were carried out to characterize cathodic oxygen reduction reaction, to study the reaction kinetics. It is demonstrated that ORR is not under diffusion-limiting conditions in the tested systems. Based on cyclic voltammetry, an increase of the cathodic electrochemical active area took place with the decrease of PTFE content. This was not directly related to MFC productivity, but to the cathode wettability and the biocathode development. Low electrodic interface resistances (from 1 to 1.5 Ω at the start, to near 0.1 Ω at day 61) indicated a negligible ohmic drop. A decrease of the Tafel slopes from 120 to 80 mV during productive periods of MFCs followed the biological activity in the whole MFC system. A high PTFE content in the cathode showed a detrimental effect on the MFC productivity, acting as an inhibitor of ORR electrocatalysis in the triple contact zone.

Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

NASA Astrophysics Data System (ADS)

Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

2014-09-01

In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

Performance evaluation of platinum-molybdenum carbide nanocatalysts with ultralow platinum loading on anode and cathode catalyst layers of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Saha, Shibely; Cabrera Rodas, José Andrés; Tan, Shuai; Li, Dongmei

2018-02-01

An alternative catalyst platform, consisting of a phase-pure transition carbide (TMC) support and Pt nanoparticles (NPs) in the range of subnanometer to < 2.7 nm, is established that can be used in both anode and cathode catalyst layers. While some TMCs with low Pt loadings have demonstrated similar activity as commercial Pt catalyst in idealized disk electrode screening tests, few to none have been applied in a realistic fuel cell membrane electrode assembly (MEA). We recently reported that β-Mo2C hollow nanotubes modified with Pt NPs via atomic layer deposition (ALD) possess better activity and durability than 20% Pt/C. This paper presents systematic evaluation of the Pt/Mo2C catalysts in a MEA, investigating effects of different MEA preparation techniques, gas diffusion layers (GDL) and various Pt loadings in the ultralow range (<0.04 mg/cm2) on MEA performance. Most importantly, we demonstrate, for the first time, that Pt/Mo2C catalyst on both anode and cathode, with a loading of 0.02 mg (Pt) cm-2, generated peak power density of 414 mW cm-2 that corresponds to 10.35 kWgPt-1 using hydrogen (H2) and oxygen (O2). Accelerated degradation tests (ADT) on Pt/Mo2C catalysts show 111% higher power density than commercial 20% Pt/C after the vigorous ADT.

Durability of Polymer Electrolyte Membrane Fuel Cells Operated at Subfreezing Temperatures

DOE PAGES

Macauley, Natalia; Lujan, Roger W.; Spernjak, Dusan; ...

2016-09-15

The structure, composition, and interfaces of membrane electrode assemblies (MEA) and gas-diffusion layers (GDLs) have a significant effect on the performance of single-proton-exchange-membrane (PEM) fuel cells operated isothermally at subfreezing temperatures. During isothermal constant-current operation at subfreezing temperatures, water forming at the cathode initially hydrates the membrane, then forms ice in the catalyst layer and/or GDL. This ice formation results in a gradual decay in voltage. High-frequency resistance initially decreases due to an increase in membrane water content and then increases over time as the contact resistance increases. The water/ice holding capacity of a fuel cell decreases with decreasing subfreezingmore » temperature (-10°C vs. -20°C vs. -30°C) and increasing current density (0.02 A cm -2 vs. 0.04 A cm -2). Ice formation monitored using in-situ high-resolution neutron radiography indicated that the ice was concentrated near the cathode catalyst layer at low operating temperatures (≈-20°C) and high current densities (0.04 A cm -2). Significant ice formation was also observed in the GDLs at higher subfreezing temperatures (≈-10°C) and lower current densities (0.02 A cm -2). These results are in good agreement with the long-term durability observations that show more severe degradation at lower temperatures (-20°C and -30°C).« less

Design of experiments and principal component analysis as approaches for enhancing performance of gas-diffusional air-breathing bilirubin oxidase cathode

NASA Astrophysics Data System (ADS)

Babanova, Sofia; Artyushkova, Kateryna; Ulyanova, Yevgenia; Singhal, Sameer; Atanassov, Plamen

2014-01-01

Two statistical methods, design of experiments (DOE) and principal component analysis (PCA) are employed to investigate and improve performance of air-breathing gas-diffusional enzymatic electrodes. DOE is utilized as a tool for systematic organization and evaluation of various factors affecting the performance of the composite system. Based on the results from the DOE, an improved cathode is constructed. The current density generated utilizing the improved cathode (755 ± 39 μA cm-2 at 0.3 V vs. Ag/AgCl) is 2-5 times higher than the highest current density previously achieved. Three major factors contributing to the cathode performance are identified: the amount of enzyme, the volume of phosphate buffer used to immobilize the enzyme, and the thickness of the gas-diffusion layer (GDL). PCA is applied as an independent confirmation tool to support conclusions made by DOE and to visualize the contribution of factors in individual cathode configurations.

High performance and durability of order-structured cathode catalyst layer based on TiO2@PANI core-shell nanowire arrays

NASA Astrophysics Data System (ADS)

Chen, Ming; Wang, Meng; Yang, Zhaoyi; Wang, Xindong

2017-06-01

In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO2@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO2@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm-2) than conventional PEMFC (699.30 mW cm-2). Electrochemically active surface area (ECSA) and charge transfer impedance (Rct) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO2@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order-structured membrane electrode with lower Pt loading for PEMFC in the future.

DE-FG02-08ER64658 (OASIS) - Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharman, Jonathan

Project OASIS (Operation of Advanced Structures, Interfaces and Sub-components for MEAs) was a 12 month project that ran from 1st September 2008 to 31st August 2009, and was managed by the Department of Energy Office of Science, Chicago Office, as Award No DE-FG02-08ER64658, with Johnson Matthey Fuel Cells Inc. as the sole contractor. The project was completed on schedule, with technical successes (details below) and payment of the full grant award made by DOE. The aim of the project was the development of membrane electrode assemblies (MEAs) for H2/air polymer electrolyte membrane (PEM) fuel cells that would give higher performancemore » under hot/dry and dry operating conditions, ideally with no loss of performance under wet conditions. Reducing or eliminating the need for humidifying the incoming gases will allow significant system cost and size reduction for many fuel cell applications including automotive, stationary and back-up power, and portable systems. Portable systems are also of particular interest in military markets. In previous work Johnson Matthey Fuel Cells had developed very stable, corrosion-resistant catalysts suitable for resisting degradation by carbon corrosion in particular. These materials were applied within the OASIS project as they are considered necessary for systems such as automotive where multiple start-stop events are experienced. These catalysts were contrasted with more conventional materials in the design of catalyst layers and novel microporous layers (MPLs) and gas diffusion layer (GDL) combinations were also explored. Early on in the work it was shown how much more aggressive high temperature operation is than dry operation. At the same humidity, tests at 110?C caused much more dehydration than tests at 80?C and the high temperature condition was much more revealing of improvements made to MEA design. Alloy catalysts were introduced and compared with Pt catalysts with a range of particle sizes. It was apparent that the larger particle sizes of the alloy catalysts led to a reduction in performance that offset much of their kinetic advantage. The Pt-only materials clearly showed that small particles are beneficial to good performance under hot/dry conditions, because of their higher surface area, although they are known to be less stable to cyclic operation. An ex-situ water vapour sorption technique was developed that showed a very clear correlation with in-cell performance: catalyst powders that absorbed more water gave better performance in-cell. It was shown that alloy catalysts could give a 25 mV advantage over Pt-only at 1 Acm-2. GDL design was also shown to influence performance and more permeable GDLs on the anode allowed better membrane hydration and therefore conductivity. A very impermeable GDL on the cathode caused cathode flooding even under dry conditions, but a novel cathode MPL incorporating ionomer and operating at 110?C, 33/17% RH showed a 150 mV gain at 800 mAcm-2 over the conventional MPL. This project has increased the understanding of the factors that influence performance loss under dry conditions, including the development of an insightful ex-situ characterisation technique (Dynamic Vapour Sorption). All the approaches investigated can be readily implemented in state-of the-art MEAs, although optimisation would be needed to integrate the new designs with existing MEA types and to tune to the exact range of operating conditions. The work is thus expected to benefit the public by feeding through more condition-tolerant production MEAs to a range of applications and thereby accelerate the commercialisation of fuel cell technology. In summary, a number of specific catalyst, catalyst layer, MPL and GDL improvements were made during this project. Often the best designs under dry conditions translated to some performance loss under wet conditions, but compromise situations were also found where dry performance was improved with no loss of wet performance.« less

Encapsulation of concentrated hemoglobin solution in phospholipid vesicles retards the reaction with NO, but not CO, by intracellular diffusion barrier.

PubMed

Sakai, Hiromi; Sato, Atsushi; Masuda, Kaoru; Takeoka, Shinji; Tsuchida, Eishun

2008-01-18

One physiological significance of the red blood cell (RBC) structure is that NO binding of Hb is retarded by encapsulation with the cell membrane. To clarify the mechanism, we analyzed Hb-vesicles (HbVs) with different intracellular Hb concentrations, [Hb](in), and different particle sizes using stopped-flow spectrophotometry. The apparent NO binding rate constant, k(on)('(NO)), of HbV at [Hb](in) = 1 g/dl was 2.6 x 10(7) m(-1) s(-1), which was almost equal to k(on)((NO)) of molecular Hb, indicating that the lipid membrane presents no obstacle for NO binding. With increasing [Hb](in) to 35 g/dl, k(on)('(NO)) decreased to 0.9 x 10(7) m(-1) s(-1), which was further decreased to 0.5 x 10(7) m(-1) s(-1) with enlarging particle diameter from 265 to 452 nm. For CO binding, which is intrinsically much slower than NO binding, k(on)('(CO)) did not change greatly with [Hb](in) and the particle diameter. Results obtained using diffusion simulations coupled with elementary binding reactions concur with these tendencies and clarify that NO is trapped rapidly by Hb from the interior surface region to the core of HbV at a high [Hb](in), retarding NO diffusion toward the core of HbV. In contrast, slow CO binding allows time for further CO-diffusion to the core. Simulations extrapolated to larger particles (8 mum) showing retardation even for CO binding. The obtained k(on)('(NO)) and k(on)('(NO)) yield values similar to those reported for RBCs. In summary, the intracellular, not extracellular, diffusion barrier is predominant due to the rapid NO binding that induces a rapid sink of NO from the interior surface to the core, retarding further NO diffusion and binding.

Development of membrane electrode assembly for high temperature proton exchange membrane fuel cell by catalyst coating membrane method

NASA Astrophysics Data System (ADS)

Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Pasupathi, Sivakumar

2015-08-01

Membrane electrode assembly (MEA), which contains cathode and anode catalytic layer, gas diffusion layers (GDL) and electrolyte membrane, is the key unit of a PEMFC. An attempt to develop MEA for ABPBI membrane based high temperature (HT) PEMFC is conducted in this work by catalyst coating membrane (CCM) method. The structure and performance of the MEA are examined by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and I-V curve. Effects of the CCM preparation method, Pt loading and binder type are investigated for the optimization of the single cell performance. Under 160 °C and atmospheric pressure, the peak power density of the MEA, with Pt loading of 0.5 mg cm-2 and 0.3 mg cm-2 for the cathode and the anode, can reach 277 mW cm-2, while a current density of 620 A cm-2 is delivered at the working voltage of 0.4 V. The MEA prepared by CCM method shows good stability operating in a short term durability test: the cell voltage maintained at ∼0.45 V without obvious drop when operated at a constant current density of 300 mA cm-2 and 160 °C under ambient pressure for 140 h.

Investigations of direct methanol fuel cell (DMFC) fading mechanisms

NASA Astrophysics Data System (ADS)

Sarma, Loka Subramanyam; Chen, Ching-Hsiang; Wang, Guo-Rung; Hsueh, Kan-Lin; Huang, Chiou-Ping; Sheu, Hwo-Shuenn; Liu, Ding-Goa; Lee, Jyh-Fu; Hwang, Bing-Joe

In this report, we present the microscopic investigations on various fading mechanisms of a direct methanol fuel cell (DMFC). High energy X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopic analysis were applied to a membrane-electrode-assembly (MEA) before and after fuel cell operation to figure out the various factors causing its fading. High energy XRD analysis of the fresh and faded MEA revealed that the agglomeration of the catalyst particles in the cathode layer of the faded MEA was more significant than in the anode layer of the faded MEA. The XAS analysis demonstrated that the alloying extent of Pt (J Pt) and Ru (J Ru) in the anode catalyst was increased and decreased, respectively, from the fresh to the faded MEA, indicating that the Ru environment in the anode catalyst was significantly changed after the fuel cell operation. Based on the X-ray absorption edge jump measurements at the Ru K-edge on the anode catalyst of the fresh and the faded MEA it was found that Ru was dissolved from the Pt-Ru catalyst after the fuel cell operation. Both the Ru K-edge XAS and EDX analysis on the cathode catalyst layer of the faded MEA confirms the presence of Ru environment in the cathode catalyst due to the Ru crossover from the anode to the cathode side. The changes in the membrane and the gas diffusion layer (GDL) after the fuel cell operation were observed from the Raman spectroscopy analysis.

Manipulating Water in High-Performance Hydroxide Exchange Membrane Fuel Cells through Asymmetric Humidification and Wetproofing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaspar, RB; Letterio, MP; Wittkopf, JA

Hydroxide exchange membrane fuel cells (HEMFCs) are an emerging low-cost alternative to conventional proton exchange membrane fuel cells. In addition to producing water at the anode, HEMFCs consume water at the cathode, leading to distinctive water transport behavior. We report that gas diffusion layer (GDL) wetproofing strictly lowers cell performance, but that the penalty is much higher when the anode side is wetproofed compared to the cathode side. We attribute this penalty primarily to mass transport losses from anode flooding, suggesting that cathode humidification may be more beneficial than anode humidification for this device. GDLs with little or no wetproofingmore » perform best, yielding a competitive peak power density of 737 mW cm(-2). (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, hup://creativecommons.orgilicenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.« less

μPIV measurements of two-phase flows of an operated direct methanol fuel cell

NASA Astrophysics Data System (ADS)

Burgmann, Sebastian; Blank, Mirja; Panchenko, Olha; Wartmann, Jens

2013-05-01

In direct methanol fuel cells (DMFCs), two-phase flows appear in the channels of the anode side (CO2 bubbles in a liquid water-methanol environment) as well as of the cathode side (water droplets or films in an ambient air flow). CO2 bubbles or water droplets may almost completely fill the cross-section of a channel. The instantaneous effect of the formation of two-phase flows on the cell performance has not been investigated in detail, yet. In the current project, the micro particle image velocimetry (μPIV) technique is used to elucidate the corresponding flow phenomena on the anode as well as on the cathode side of a DMFC and to correlate those phenomena with the performance of the cell. A single-channel DMFC with optical access at the anode and the cathode side is constructed and assembled that allows for μPIV measurements at both sides as well as a detailed time-resolved cell voltage recording. The appearance and evolution of CO2 bubbles on the anode side is qualitatively and quantitatively investigated. The results clearly indicate that the cell power increases when the free cross-section area of the channel is decreased by huge bubbles. Methanol is forced into the porous gas diffusion layer (GDL) between the channels and the membrane is oxidized to CO2, and hence, the fuel consumption is increased and the cell performance rises. Eventually, a bubble forms a moving slug that effectively cleans the channel from CO2 bubbles on its way downstream. The blockage effect is eliminated; the methanol flow is not forced into the GDL anymore. The remaining amount of methanol in the GDL is oxidized. The cell power decreases until enough CO2 is produced to eventually form bubbles again and the process starts again. On the other hand under the investigated conditions, water on the cathode side only forms liquid films on the channels walls rather than channel-filling droplets. Instantaneous changes of the cell power due to liquid water formation could not be observed. The timescales of the two-phase flow on the cathode side are significantly larger than on the anode side. However, the μPIV measurements at the cathode side demonstrate the ability of feeding gas flows in microchannels with liquid tracer particles and the ability to measure in two-phase flows in such a configuration.

Low cost fuel cell diffusion layer configured for optimized anode water management

DOEpatents

Owejan, Jon P; Nicotera, Paul D; Mench, Matthew M; Evans, Robert E

2013-08-27

A fuel cell comprises a cathode gas diffusion layer, a cathode catalyst layer, an anode gas diffusion layer, an anode catalyst layer and an electrolyte. The diffusion resistance of the anode gas diffusion layer when operated with anode fuel is higher than the diffusion resistance of the cathode gas diffusion layer. The anode gas diffusion layer may comprise filler particles having in-plane platelet geometries and be made of lower cost materials and manufacturing processes than currently available commercial carbon fiber substrates. The diffusion resistance difference between the anode gas diffusion layer and the cathode gas diffusion layer may allow for passive water balance control.

GNU Data Language (GDL) - a free and open-source implementation of IDL

NASA Astrophysics Data System (ADS)

Arabas, Sylwester; Schellens, Marc; Coulais, Alain; Gales, Joel; Messmer, Peter

2010-05-01

GNU Data Language (GDL) is developed with the aim of providing an open-source drop-in replacement for the ITTVIS's Interactive Data Language (IDL). It is free software developed by an international team of volunteers led by Marc Schellens - the project's founder (a list of contributors is available on the project's website). The development is hosted on SourceForge where GDL continuously ranks in the 99th percentile of most active projects. GDL with its library routines is designed as a tool for numerical data analysis and visualisation. As its proprietary counterparts (IDL and PV-WAVE), GDL is used particularly in geosciences and astronomy. GDL is dynamically-typed, vectorized and has object-oriented programming capabilities. The library routines handle numerical calculations, data visualisation, signal/image processing, interaction with host OS and data input/output. GDL supports several data formats such as netCDF, HDF4, HDF5, GRIB, PNG, TIFF, DICOM, etc. Graphical output is handled by X11, PostScript, SVG or z-buffer terminals, the last one allowing output to be saved in a variety of raster graphics formats. GDL is an incremental compiler with integrated debugging facilities. It is written in C++ using the ANTLR language-recognition framework. Most of the library routines are implemented as interfaces to open-source packages such as GNU Scientific Library, PLPlot, FFTW, ImageMagick, and others. GDL features a Python bridge (Python code can be called from GDL; GDL can be compiled as a Python module). Extensions to GDL can be written in C++, GDL, and Python. A number of open software libraries written in IDL, such as the NASA Astronomy Library, MPFIT, CMSVLIB and TeXtoIDL are fully or partially functional under GDL. Packaged versions of GDL are available for several Linux distributions and Mac OS X. The source code compiles on some other UNIX systems, including BSD and OpenSolaris. The presentation will cover the current status of the project, the key accomplishments, and the weaknesses - areas where contributions and users' feedback are welcome! While still being in beta-stage of development, GDL proved to be a useful tool for classroom work on data analysis. Its usage for teaching meteorological-data processing at the University of Warsaw will serve as an example.

Factors Associated with Haemoglobin Concentration among Timor-Leste Children Aged 6–59 Months

PubMed Central

Agho, K.E.; Dibley, M.J.; D'Este, C.; Gibberd, R.

2008-01-01

The study was conducted to assess the prevalence of and factors associated with haemoglobin (Hb) concentrations among children aged 6–59 months in Timor-Leste. The 2003 Demographic and Health Survey was a multi-stage cluster survey of 4,320 households from four different geographic regions in Timor-Leste. In total, 4,514 children aged 6–59 months were included in the analysis. The prevalence of anaemia (Hb concentration <11.0g/dL) was 38.2% (638/1,668) for children aged 6–23 months and 22.6% (644/2,846) for older children (p<0.001). Girls had a higher mean Hb concentration than boys (11.9g/dL vs 11.7g/dL, p<0.006) and children who had diarrhoea in the previous two weeks had a lower Hb concentration than children without diarrhoea (11.5g/dL vs 11.9g/dL, p<0.001). Children from the richest and middle-class households had a lower average Hb concentration than those from the poorest households (11.8g/dL, 11.7g/dL vs 12.0g/dL, p<0.001). Children of mothers with some secondary or more education had a lower mean Hb concentration than children of mothers with completed primary, some primary and no education (11.7 g/dL vs 11.9 g/dL, 11.8 g/dL, and 11.9 g/dL, p=0.002). Children from severely-anaemic mothers had a lower mean Hb concentration than children from moderately-, mild and not anaemic mothers (10.5 g/dL vs 11.1 g/dL, 11.6 g/dL, 12.0 g/dL, p<0.001). After backward stepwise hierarchical multiple regression, wasting, male sex, recent diarrhoea, household wealth index (richest and middle-class), maternal educational status (some secondary or more and some primary), and maternal anaemic status were significantly associated with a lower Hb concentration in children and increased age of child and duration of breastfeeding (6 months) with a higher Hb concentration. Anaemia-prevention programmes among children in Timor-Leste should focus on those children aged less than two years, children with recent diarrhoea, wasted children, high socioeconomic status, and anaemic mothers. PMID:18686553

Electrical enhancement of direct methanol fuel cells by metal-plasma ion implantation Pt-Ru/C multilayer catalysts.

PubMed

Weng, Ko-Wei; Chen, Yung-Lin; Chen, Ya-Chi; Lin, Tai-Nan

2009-02-01

Direct methanol fuel cells (DMFC) have been widely studied owing to their simple cell configuration, high volume energy density, short start-up time, high operational reliability and other favorable characteristics. However, major limitations include high production cost, poisoning of the catalyst and methanol crossover. This study adopts a simple technique for preparing Pt-Ru/C multilayer catalysts, including magnetron sputtering (MS) and metal-plasma ion implantation (MPII). The Pt catalysts were sputtered onto the gas diffusion layer (GDL), followed by the implantation of Ru catalysts using MPII (at an accelerating voltage of 20 kV and an implantation dose of 1 x 10(16) ions/cm2). Pt-Ru is repeatedly processed to prepare Pt-Ru/C multilayer catalysts. The catalyst film structure and microstructure were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM), respectively. The cell performance was tested using a potential stat/galvano-stat. The results reveal that the membrane electrode assembly (MEA) of four multilayer structures enhances the cell performance of DMFC. The measured power density is 2.2 mW/cm2 at a methanol concentration of 2 M, with an OCV of 0.493 V.

Management of anaemia in haemodialysis and peritoneal dialysis patients (chapter 8).

PubMed

Richardson, Donald; Hodsman, Alex; van Schalkwyk, Dirk; Tomson, Charlie; Warwick, Graham

2007-08-01

Forty-one percent of UK patients commence RRT with an Hb < 10.0 g/dl. The mean Hb at commencement of RRT is 10.3 g/dl. Eighty-five percent of patients on dialysis in the UK have an Hb > or = 10.0 g/dl by 6 months after commencement of RRT. The median Hb on haemodialysis in the UK is 11.8 g/dl with an IQR of 10.7-12.8 g/dl. Eighty-six percent of haemodialysis patients in the UK have a Hb > or = 10.0 g/dl. The median Hb on peritoneal dialysis in the UK is 12.0 g/dl with an IQR of 11.0-12.9 g/dl. Ninety percent of peritoneal dialysis patients in the UK have an Hb > or = 10.0 g/dl. In the UK, 49% of patients on PD and 48% of patients on haemodialysis have an Hb between 10.5-12.5 g/dl. The median ferritin in UK haemodialysis patients is 413 microg/l (IQR 262-623), 95% of UK haemodialysis patients have a ferritin > or =100 microg/l. The median ferritin in UK PD patients is 256 microg/l (IQR 147-421), 86% of UK peritoneal dialysis patients have a ferritin > or = 100 microg/l. A higher proportion of HD patients than PD patients receive ESA therapy (88% vs 76%). The ESA dose is higher for HD than PD patients (9204 vs 6080 IU/week).

Comparison of refractometry and biuret assay for measurement of total protein concentration in canine abdominal and pleural fluid specimens.

PubMed

Rose, Alexandra; Funk, Deborah; Neiger, Reto

2016-04-01

To compare total protein (TP) concentrations in canine pleural and abdominal fluid specimens as measured by refractometry and biuret assay. Diagnostic test evaluation. Data regarding 92 pleural and 148 abdominal fluid specimens from dogs with various diseases. TP concentrations in fluid specimens as measured by refractometry and biuret assay were recorded. Strength of association between sets of measurements was assessed by Spearman rank correlations and Bland-Altman plots. Optimal concentration cutoff for diagnostic discrimination between exudate and nonexudate was identified by construction of receiver operating characteristic curves. Median TP concentration in pleural fluid specimens was 2.7 g/dL (range, 0.3 to 4.8 g/dL) for refractometry and 2.9 g/dL (range, 0.7 to 5.8 g/dL) for biuret assay. Median TP concentration in abdominal fluid specimens was 3.5 g/dL (range, 0.1 to 6.0 g/dL) for refractometry and 3.5 g/dL (range, 0.6 to 5.7 g/dL) for biuret assay. Correlation was significant between refractometric and biuret results for pleural (ρ = 0.921) and abdominal (ρ = 0.908) fluid. Bland-Altman plots revealed bias of -0.18 g/dL for pleural fluid and -0.03 g/dL for abdominal fluid for refractometry versus biuret assay. With a TP concentration of ≥ 3 g/dL used to distinguish exudate from nonexudate, sensitivity of refractometry was 77% for pleural fluid and 80% for abdominal fluid. Specificity was 100% and 94%, respectively. Refractometry yielded acceptable results for measurement of TP concentration in canine pleural and abdominal fluid specimens, providing a more rapid and convenient method than biuret assay.

Factors associated with haemoglobin concentration among Timor-Leste children aged 6-59 months.

PubMed

Agho, K E; Dibley, M J; D'Este, C; Gibberd, R

2008-06-01

The study was conducted to assess the prevalence of and factors associated with haemoglobin (Hb) concentrations among children aged 6-59 months in Timor-Leste. The 2003 Demographic and Health Survey was a multi-stage cluster survey of 4,320 households from four different geographic regions in Timor-Leste. In total, 4,514 children aged 6-59 months were included in the analysis. The prevalence of anaemia (Hb concentration <11.0g/dL) was 38.2% (638/1,668) for children aged 6-23 months and 22.6% (644/2,846) for older children (p<0.001). Girls had a higher mean Hb concentration than boys (11.9g/dL vs 11.7g/ dL, p<0.006) and children who had diarrhoea in the previous two weeks had a lower Hb concentration than children without diarrhoea (11.5g/dL vs 11.9g/dL, p<0.001). Children from the richest and middle-class households had a lower average Hb concentration than those from the poorest households (11.8g/ dL, 11.7g/dL vs 12.0g/dL, p<0.001). Children of mothers with some secondary or more education had a lower mean Hb concentration than children of mothers with completed primary, some primary and no education (11.7 g/dL vs 11.9 g/dL, 11.8 g/dL, and 11.9 g/dL, p=0.002). Children from severely-anaemic mothers had a lower mean Hb concentration than children from moderately-, mild and not anaemic mothers (10.5 g/dL vs 11.1 g/dL, 11.6 g/dL, 12.0 g/dL, p<0.001). After backward stepwise hierarchical multiple regression, wasting, male sex, recent diarrhoea, household wealth index (richest and middle-class), maternal educational status (some secondary or more and some primary), and maternal anaemic status were significantly associated with a lower Hb concentration in children and increased age of child and duration of breastfeeding (6 months) with a higher Hb concentration. Anaemia-prevention programmes among children in Timor-Leste should focus on those children aged less than two years, children with recent diarrhoea, wasted children, high socioeconomic status, and anaemic mothers.

Behavioral Impact of Graduated Driver Licensing on Teenage Driving Risk and Exposure1

PubMed Central

Karaca-Mandic, Pinar; Ridgeway, Greg

2009-01-01

Graduated Driver Licensing (GDL) is a critical policy tool for potentially improving teenage driving while reducing teen accident exposure. While previous studies demonstrated that GDL reduces teenage involvement in fatal crashes, much remains unanswered. We explore the mechanisms through which GDL influences accident rates as well as its long term effectiveness on teen driving. In particular, we investigate; 1) whether GDL policies improve teenage driving behavior, or simply reduce teenage prevalence on the roads; 2) whether GDL exposed teens become better drivers in later years. We employ a unique data source, the State Data System, which contains all police reported accidents (fatal and non-fatal) during 1990–2005 for twelve states. We estimate a structural model that separately identifies GDL s effect on relative teenage prevalence and relative teenage riskiness. Identification of the model is driven by the relative numbers of crashes between two teenagers, two adults, or a teenager and an adult. We find that the GDL policies reduce the number of 15–17 year-old accidents by limiting the amount of teenage driving rather than by improving teenage driving. This prevalence reduction primarily occurs at night and stricter GDL policies, especially those with nighttime driving restrictions, are the most effective. Finally, we find that teen driving quality does not improve ex-post GDL exposure. PMID:19942310

A Coordination Chemistry Approach to Fine-Tune the Physicochemical Parameters of Lanthanide Complexes Relevant to Medical Applications.

PubMed

Le Fur, Mariane; Molnár, Enikő; Beyler, Maryline; Kálmán, Ferenc K; Fougère, Olivier; Esteban-Gómez, David; Rousseaux, Olivier; Tripier, Raphaël; Tircsó, Gyula; Platas-Iglesias, Carlos

2018-03-02

The geometric features of two pyclen-based ligands possessing identical donor atoms but different site organization have a profound impact in their complexation properties toward lanthanide ions. The ligand containing two acetate groups and a picolinate arm arranged in a symmetrical fashion (L1) forms a Gd 3+ complex being two orders of magnitude less stable than its dissymmetric analogue GdL2. Besides, GdL1 experiences a much faster dissociation following the acid-catalyzed mechanism than GdL2. On the contrary, GdL1 exhibits a lower exchange rate of the coordinated water molecule compared to GdL2. These very different properties are related to different strengths of the Gd-ligand bonds associated to steric effects, which hinder the coordination of a water molecule in GdL2 and the binding of acetate groups in GdL1. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Building Chronic Kidney Disease Clinical Practice Guidelines Using the openEHR Guideline Definition Language.

PubMed

Lin, Ching-Heng; Lo, Ying-Chih; Hung, Pei-Yuan; Liou, Der-Ming

2016-12-07

As a result of the disease's high prevalence, chronic kidney disease (CKD) has become a global public health problem. A clinical decision support system that integrates with computer-interpretable guidelines (CIGs) should improve clinical outcomes and help to ensure patient safety. The openEHR guideline definition language (GDL) is a formal language used to represent CIGs. This study explores the feasibility of using a GDL approach for CKD; it also attempts to identify any potential gaps between the ideal concept and reality. Using the Kidney Disease Improving Global Outcomes (KDIGO) anemia guideline as material, we designed a development workflow in order to establish a series of GDL guidelines. Focus group discussions were conducted in order to identify important issues related to GDL implementation. Ten GDL guidelines and 37 archetypes were established using the KDIGO guideline document. For the focus group discussions, 16 clinicians and 22 IT experts were recruited and their perceptions, opinions and attitudes towards the GDL approach were explored. Both groups provided positive feedback regarding the GDL approach, but raised various concerns about GDL implementation. Based on the findings of this study, we identified some potential gaps that might exist during implementation between the GDL concept and reality. Three directions remain to be investigated in the future. Two of them are related to the openEHR GDL approach. Firstly, there is a need for the editing tool to be made more sophisticated. Secondly, there needs to be integration of the present approach into non openEHR-based hospital information systems. The last direction focuses on the applicability of guidelines and involves developing a method to resolve any conflicts that occur with insurance payment regulations.

Chapter 8 Haemoglobin, ferritin and erythropoietin amongst UK adult dialysis patients in 2010: national and centre-specific analyses.

PubMed

Webb, Lynsey; Gilg, Julie; Wilkie, Martin

2012-01-01

The UK Renal Association (RA) and National Institute for Health and Clinical Excellence (NICE) have published clinical practice guidelines which include recommendations for management of anaemia in established renal failure. To determine the extent to which the guidelines for anaemia management are met in the UK. Quarterly data were obtained regarding haemoglobin (Hb) and factors that influence Hb from renal centres in England, Wales, Northern Ireland (EWNI) and the Scottish Renal Registry for the incident and prevalent renal replacement therapy (RRT) cohorts for 2010. In the UK, in 2010 53.6% of patients commenced dialysis therapy with Hb ≥ 10.0 g/dl (median Hb 10.1 g/dl). The median Hb of haemodialysis (HD) patients was 11.5 g/dl with an interquartile range (IQR) of 10.5-12.3 g/dl. Of HD patients 84.6% had Hb ≥ 10.0 g/dl. The median Hb of peritoneal dialysis (PD) patients in the UK was 11.6 g/dl (IQR 10.6-12.5 g/dl). Of UK PD patients, 87.2% had Hb ≥ 10.0 g/dl. The median ferritin in HD patients in EWNI was 444 µg/L (IQR 299-635) and 96% of HD patients had a ferritin ≥ 100 µg/L. The median ferritin in PD patients was 264 µg/L (IQR 148-426) with 86% of PD patients having a ferritin ≥ 100 µg/L. In EWNI the mean Erythropoietin Stimulating Agent (ESA) dose was higher for HD than PD patients (9,020 vs. 6,202 IU/week). Of prevalent HD patients, 52.7% had Hb ≥ 10 and ≤ 12 g/dl. Of prevalent PD patients, 54.3% had Hb 10.5-12.5 g/dl. Copyright © 2012 S. Karger AG, Basel.

PLASMA ELECTROPHORETIC PROFILES IN THE EASTERN MASSASAUGA (SISTRURUS CATENATUS) AND INFLUENCES OF AGE, SEX, YEAR, LOCATION, AND SNAKE FUNGAL DISEASE.

PubMed

Allender, Matthew C; Junge, Randall E; Baker-Wylie, Sarah; Hileman, Eric T; Faust, Lisa J; Cray, Carolyn

2015-12-01

The purpose of this study was to establish reference intervals of the protein electrophoretic fractions and the acute-phase proteins hemoglobin binding protein (as determined by the haptoglobin assay) and C-reactive protein (CRP) and assess any possible correlations between varying age class, sex, location (Illinois or Michigan), year, or presence of snake fungal disease (SFD). Banked plasma samples were assayed from 130 eastern massasaugas from 2009 to 2014 in Illinois and Michigan. Snakes from Michigan had higher total protein (mean: 5.50 g/dl), albumin/globulin ratio (0.42), albumin (1.59 g/dl), and gamma globulins (0.55 g/dl) than from snakes in Illinois (4.72 g/dl, 0.29, 1.03 g/dl, 0.38 g/dl, respectively). Snakes in Illinois (22.19 g/ml) had higher CRP than snakes in Michigan (10.89 mg/ml). Adults had higher gamma globulins (0.47 g/dl) than juveniles (0.28 g/dl). Males had higher alpha-2 globulins (0.98 g/dl) and CRP (21.4 mg/ml) than females (0.85, 11.6, respectively). There were no significant differences in absolute plasma proteins in SFD-positive snakes, but the percentage of gamma globulins was significantly higher in positive snakes. Future research in this area can now build on this data to determine changes in population health over time or due to specific environmental or disease threats.

National evaluation of graduated driver licensing programs.

DOT National Transportation Integrated Search

2006-06-01

Context. Implementation of Graduated Driver Licensing (GDL) programs is associated with lower fatal crash : rates of young drivers, but the contribution of specific components of GDL programs is not known. : Objective. To determine which types of GDL...

An evaluation of the effect of Ohio's graduated driver licensing law on motor vehicle crashes and crash outcomes involving drivers 16 to 20 years of age.

PubMed

Conner, Kristen A; Smith, Gary A

2017-05-19

Nationally, motor vehicle crashes are the leading cause of death among youth ages 16 to 20 years. Graduated driver licensing (GDL) laws have been implemented to reduce motor vehicle crashes among teen drivers. Studies have shown decreases in teen crash rates and crash-related fatality rates following enactment of GDL laws. However, GDL laws typically apply to teens only until their 18th birthday; therefore, the effect, if any, that GDL laws have on youth drivers ages 18 to 20 years and whether these programs should be extended to include these older youth warrant further study. The objective of this study was to evaluate the effects of Ohio's 2007 revised GDL law on motor vehicle crashes and crash-related injuries for crashes involving teen drivers ages 16 to 20 years, with a focus on the effects on crashes involving drivers ages 18 to 20 years. Cross-sectional analysis of motor vehicle crashes involving drivers ages 16 to 20 years in Ohio in the pre-GDL (2004-2006) and post-GDL (2008-2010) periods was performed. Descriptive statistics and population-based crash rates for drivers and occupants ages 16 to 20 years were calculated, as well as rate ratios and 95% confidence intervals (CIs) comparing crashes in the pre-GDL and post-GDL periods. Compared with the pre-GDL period, the post-GDL period was associated with lower crash rates for drivers age 16 years (relative risk [RR] = 0.94; 95% CI, 0.90-0.98), age 17 years (RR = 0.90; 95% CI, 0.88-0.93), age 18 years (RR = 0.95; 95% CI, 0.92-0.97), and ages 16-17 years combined (RR = 0.92; 95% CI, 0.90-0.95). Crash rate was higher for the post-GDL period for drivers age 19 years (RR = 1.04; 95% CI, 1.01-1.07), age 20 years (RR = 1.09; 95% CI, 1.05-1.13), and ages 18-20 years combined (RR = 1.02; 95% CI, 1.00-1.03). Unlike previous studies, this investigation used linked data to evaluate the outcomes of all occupants in crashes involving drivers ages 16-20 years. The post-GDL period was associated with lower crash, injury crash, and fatal crash involvement among drivers and occupants ages 16-17 years but higher overall crash involvement for drivers and occupants ages 19 years, 20 years, and 18-20 years combined. These findings support extending GDL restrictions to novice drivers ages 18 through 20 years to reduce crashes in that group.

[Nitrogen and protein content analysis of human milk, diurnality vs nocturnality].

PubMed

Sánchez López, C L; Hernández, A; Rodríguez, A B; Rivero, M; Barriga, C; Cubero, J

2011-01-01

Breast milk is changing with the progression of lactation and during a 24-h period. To determine the effect of diurnality or nocturnality on total nitrogen and protein content of the breast milk. We collected human milk samples from health mothers living throughout Community of Extremadura (Spain) from January 2008 to December 2008 with less than two months of lactation. We divided the samples in three groups: calostral group (1-5 days postpartum), transitional group (6-15 days postpartum) and mature group (> 15 days postpartum). All samples were stored in a freezer at -80 ºC. We considered as day period between 08:00-20:00 h and night period 20:00-08:00 h. Analysis of the human milk samples was based on the Kjeldahl method. Protein contents were calculated from total nitrogen x 6,25. The statistical analysis of the data was descriptive (mean ± standard deviation) and inferential (T-Student test). No differences (P > 0,05) were found to exist among the contents of individual human milk samples. The mean contents of each component were as follows: Total nitrogen of calostral, transitional and mature group was 0,30 ± 0,06 g/dL (night period), 0,29 ± 0,05 g/dL (day period); 0,26 ± 0,04 g/dL (night period), 0,25 ± 0,04 g/dL (day period); 0,22 ± 0,05 g/dL (night period), 0,20 ± 0,04 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Protein content of calostral, transitional and mature group was 1,88 ± 0,4 g/dL (night period), 1,81 ± 0,3 g/dL (day period); 1,62 ± 0,3 g/dL (night period), 1,59 ± 0,3 g/dL (day period); 1,35 ± 0,3 g/dL (night period), 1,26 ± 0,3 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Although we observed differences in the nitrogen and protein content during the individual stages of lactation, it is just in the population of mature lactating women, where the components analyzed varied significantly between day and night.

UK Renal Registry 15th annual report: Chapter 6 haemoglobin, ferritin and erythropoietin amongst UK adult dialysis patients in 2011: national and centre-specific analyses.

PubMed

Rao, Anirudh; Gilg, Julie; Williams, Andrew

2013-01-01

The UK Renal Association (RA) and National Institute for Health and Care Excellence (NICE) have published Clinical Practice Guidelines which include recommendations for management of anaemia in established renal failure. To determine the extent to which the guidelines for anaemia management are met in the UK. Quarterly data were obtained for haemoglobin (Hb) and factors that influence Hb from renal centres in England, Wales, Northern Ireland (E, W, NI) and the Scottish Renal Registry for the incident and prevalent renal replacement therapy (RRT) cohorts for 2011. In the UK, in 2011 51% of patients commenced dialysis therapy with Hb ≥10.0 g/dl (median Hb 10 g/dl). Of patients in the early presentation group, 55% started dialysis with Hb ≥10.0 g/dl whilst 37% of patients presenting late started dialysis with Hb ≥10.0 g/dl. The UK median Hb of haemodialysis (HD) patients was 11.2 g/dl with an inter-quartile range (IQR) of 10.3-12.1 g/dl. Of UK HD patients, 82% had Hb ≥10.0 g/dl. The median Hb of peritoneal dialysis (PD) patients in the UK was 11.4 g/dl (IQR 10.5-12.3 g/dl). Of UK PD patients, 85% had Hb ≥10.0 g/dl. The median ferritin in HD patients in the UK was 436 mg/L (IQR 292-625) and 96% of HD patients had a ferritin ≥100 mg/ L. In EW&NI the median ferritin in PD patients was 273 mg/ L (IQR 153-446) with 86% of PD patients having a ferritin ≥100 mg/L. In EW&NI the mean erythropoietin stimulating agent (ESA) dose was higher for HD than PD patients (8,740 vs. 6,624 IU/week). Prevalent HD and PD patients had 56% and 53% respectively within the Hb ≥10 and ≤12 g/dl target. Copyright © 2013 S. Karger AG, Basel.

Prognostic implications of baseline anaemia and changes in haemoglobin concentrations with amphotericin B therapy for cryptococcal meningitis.

PubMed

Tugume, L; Morawski, B M; Abassi, M; Bahr, N C; Kiggundu, R; Nabeta, H W; Hullsiek, K H; Taseera, K; Musubire, A K; Schutz, C; Muzoora, C; Williams, D A; Rolfes, M A; Meintjes, G; Rhein, J; Meya, D B; Boulware, D R

2017-01-01

Anaemia represents a common toxicity with amphotericin B-based induction therapy in HIV-infected persons with cryptococcal meningitis. We sought to examine the impact of amphotericin-related anaemia on survival. We used data from Ugandan and South African trial participants to characterize the variation of haemoglobin concentrations from diagnosis to 12 weeks post-diagnosis. Anaemia severity was classified based on the haemoglobin concentration at cryptococcal meningitis diagnosis, and nadir haemoglobin values during amphotericin induction. Cox proportional hazard models were used to estimate 2- and 10-week mortality risk. We also estimated 10-week mortality risk among participants with nadir haemoglobin < 8.5 g/dL during amphotericin induction and who survived ≥ 2 weeks post-enrolment. The median haemoglobin concentration at meningitis diagnosis was 11.5 g/dL [interquartile range (IQR) 9.7-13 g/dL; n = 311] with a mean decline of 4.2 g/dL [95% confidence interval (CI) -4.6 to -3.8; P < 0.001; n = 148] from diagnosis to nadir value among participants with baseline haemoglobin ≥ 8.5 g/dL. The median haemoglobin concentration was 8.1 g/dL (IQR 6.5-9.5 g/dL) at 2 weeks, increasing to 9.4 g/dL (IQR 8.2-10.9 g/dL) by 4 weeks and continuing to increase to 12 weeks. Among participants with haemoglobin < 8.5 g/dL at diagnosis, mortality risk was elevated at 2 weeks [hazard ratio (HR) 2.7; 95% CI 1.5-4.9; P < 0.01] and 10 weeks (HR 1.8; 95% CI 1.1-2.2; P = 0.03), relative to those with haemoglobin ≥ 8.5 g/dL. New-onset anaemia occurring with amphotericin therapy did not have a statistically significant association with 10-week mortality (HR 2.0; 95% CI 0.5-9.1; P = 0.4). Amphotericin induced significant haemoglobin declines, which were mostly transient and did not impact 10-week mortality. Individuals with moderate to life-threatening anaemia at baseline had a higher mortality risk at 2 and 10 weeks post-enrolment. © 2016 British HIV Association.

Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Kim, Jinyong; Luo, Gang; Wang, Chao-Yang

2017-10-01

3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

Low platinum loading for high temperature proton exchange membrane fuel cell developed by ultrasonic spray coating technique

NASA Astrophysics Data System (ADS)

Su, Huaneng; Jao, Ting-Chu; Barron, Olivia; Pollet, Bruno G.; Pasupathi, Sivakumar

2014-12-01

This paper reports use of an ultrasonic-spray for producing low Pt loadings membrane electrode assemblies (MEAs) with the catalyst coated substrate (CCS) fabrication technique. The main MEA sub-components (catalyst, membrane and gas diffusion layer (GDL)) are supplied from commercial manufacturers. In this study, high temperature (HT) MEAs with phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB-PBI) membrane are fabricated and tested under 160 °C, hydrogen and air feed 100 and 250 cc min-1 and ambient pressure conditions. Four different Pt loadings (from 0.138 to 1.208 mg cm-2) are investigated in this study. The experiment data are determined by in-situ electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high Pt loading MEA exhibits higher performance at high voltage operating conditions but lower performances at peak power due to the poor mass transfer. The Pt loading 0.350 mg cm-2 GDE performs the peak power density and peak cathode mass power to 0.339 W cm-2 and 0.967 W mgPt-1, respectively. This work presents impressive cathode mass power and high fuel cell performance for high temperature proton exchange membrane fuel cells (HT-PEMFCs) with low Pt loadings.

UK Renal Registry 13th Annual Report (December 2010): Chapter 9: haemoglobin, ferritin and erythropoietin amongst UK adult dialysis patients in 2009: national and centre-specific analyses.

PubMed

Gilg, Julie; Webb, Lynsey; Feest, Terry; Fogarty, Damian

2011-01-01

The UK Renal Association (RA) and National Institute for Health and Clinical Excellence (NICE) have published Clinical Practice Guidelines which include recommendations for management of anaemia in established renal failure. To determine the extent to which the guidelines for anaemia management are met in the UK. Quarterly data were obtained regarding haemoglobin (Hb) and factors that influence Hb from renal centres in England, Wales, Northern Ireland (EWNI) and the Scottish Renal Registry for the incident and prevalent renal replacement therapy (RRT) cohorts for 2009. In the UK, in 2009 55% of patients commenced dialysis therapy with Hb x10.0 g/dl (median Hb 10.2 g/dl). The median Hb of haemodialysis (HD) patients was 11.6 g/dl with an interquartile range (IQR) of 10.6 - 12.4 g/dl. Of HD patients 85% had Hb ≥ 10.0 g/dl. The median Hb of peritoneal dialysis (PD) patients in the UK was 11.7 g/dl (IQR 10.7-12.6 g/dl). Of UK PD patients, 88% had Hb ≥ 10.0 g/dl. The median ferritin in HD patients in EWNI was 441 mg/L (IQR 289-629) and 96% of HD patients had a ferritin ≥ 100 mg/L. The median ferritin in PD patients was 249 mg/L (IQR 142-412) with 86% of PD patients having a ferritin 5100 mg/L. In EWNI the mean Erythropoietin Stimulating Agent (ESA) dose was higher for HD than PD patients (9,507 vs. 6,212 IU/week). In 2009, 56% of prevalent HD patients had a Hb ≥ 10.5 and ≤ 12.5 g/dl compared with 54% in 2008 and 53% in 2007. Fifty-four percent of prevalent PD patients had a Hb ≥10.5 and ≤12.5 g/dl compared to 55% in 2008. Copyright © 2011 S. Karger AG, Basel.

Anemia and mortality in hemodialysis patients: accounting for morbidity and treatment variables updated over time.

PubMed

Robinson, Bruce M; Joffe, Marshall M; Berns, Jeffrey S; Pisoni, Ronald L; Port, Friedrich K; Feldman, Harold I

2005-11-01

The objective of this study was to gain insight into the associations of anemia with mortality among maintenance hemodialysis (HD) patients and patient subgroups by an analysis that more comprehensively represents hemoglobin (Hb) level, morbidity, and treatment characteristics over time than was possible in prior observational studies. A cohort study was conducted among 5517 subjects in the American arm of the Dialysis Outcomes and Practice Patterns Study Phase I. We used proportional hazard analysis to model all-cause mortality as a function of Hb level measured 1, 3, and 6 months previously. Forty-five potentially confounding patient-level characteristics were considered, including demographics, comorbidities, and time-updated levels of erythropoietin and parenteral iron dosing, medical events, and laboratory and dialysis measures. Compared to Hb 11 to <12 g/dL, subjects with Hb <11 g/dL had increased mortality [adjusted hazard ratios (95% confidence interval) in the 3-month-lagged model = 1.74 (1.24 to 2.43) for <9 g/dL, 1.25 (0.96 to 1.63) for 9 to <10 g/dL, and 1.22 (0.99 to 1.49) for 10 to <11 g/dL categories]. Mortality rates for subjects with Hb 12 to <13 g/dL and > or = 13 g/dL did not differ significantly from those with Hb 11 to <12 g/dL. The relationships between Hb and mortality varied modestly with changes in the time interval between Hb measurement and the time at risk for mortality, but did not vary according to ESRD vintage or health status indicators. Our findings confirm the associations of Hb levels > or =11 g/dL with longer survival among maintenance HD patients, but show no additional survival advantage for patients with Hb levels > or =12 g/dL. Further investigation of the relationships among anemia, treatment of anemia, and survival is warranted.

Improving graduated driver licensing systems: a conceptual approach and its implications.

PubMed

Foss, Robert D

2007-01-01

Graduated driver licensing (GDL) is a concept for how to transform non-drivers into reasonably safe drivers while minimizing the risks as they learn. Several state GDL programs can be improved by moving their structures closer to an adequate implementation of that concept. The learner stage of a GDL system needs to be long enough for beginners to obtain a thorough introduction to the vagaries of driving. The second or intermediate stage needs to effectively limit exposure to known high risk conditions as novices adapt to being fully in charge of the vehicle. The benefits of GDL to date are due almost entirely to the risk-reducing conditions it implements. To improve the functioning of GDL will probably require a better understanding of teen driving than we presently have. The likelihood of further gains will be enhanced by efforts to learn more about the actual causes of teen crashes, the nature and type of teen driver exposures, and what parents do with their teens during the supervised driving stage of GDL. Without a better understanding of these, and other, phenomena it will be difficult to further reduce crashes among young beginning drivers, whether through GDL enhancements or with other approaches.

Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: IV. Diffuse Layer Charge/Potential Relationships

EPA Science Inventory

Most current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson - Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain ...

Thermodynamic stability, kinetic inertness and relaxometric properties of monoamide derivatives of lanthanide(III) DOTA complexes.

PubMed

Tei, Lorenzo; Baranyai, Zsolt; Gaino, Luca; Forgács, Attila; Vágner, Adrienn; Botta, Mauro

2015-03-28

A complete thermodynamic and kinetic solution study on lanthanide(III) complexes with monoacetamide (DOTAMA, L1) and monopropionamide (DOTAMAP, L2) derivatives of DOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was undertaken with the aim to elucidate their stability and inertness in aqueous media. The stability constants of GdL1 and GdL2 are comparable, whereas a more marked difference is found in the kinetic inertness of the two complexes. The formation of the Eu(III) and Ce(III) complexes takes place via the formation of the protonated intermediates which can deprotonate and transform into the final complex through a OH(-) assisted pathway. GdL2 shows faster rates of acid catalysed decomplexation with respect to GdL1, which has a kinetic inertness comparable to GdDOTA. Nevertheless, GdL2 is one order of magnitude more inert than GdDO3A. A novel DOTAMAP-based bifunctional chelating ligand and its deoxycholic acid derivative (L5) were also synthesized. Since the coordinated water molecule in GdL2 is characterized by an exchange rate ca. two orders of magnitude greater than in GdL1, the relaxivity of the macromolecular derivatives of L5 should not be limited by the slow water exchange process. The relaxometric properties of the supramolecular adduct of GdL5 with human serum albumin (HSA) were investigated in aqueous solution by measuring the magnetic field dependence of the (1)H relaxivity which, at 20 MHz and 298 K, shows a 430% increase over that of the unbound GdL5 chelate. Thus, Gd(III) complexes with DOTAMAP macrocyclic ligands can represent good candidates for the development of stable and highly effective bioconjugate systems for molecular imaging applications.

Anomalous Diffusion of Water in Lamellar Membranes Formed by Pluronic Polymers

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Ohl, Michael; Han, Youngkyu; Smith, Gregory; Do, Changwoo; Biology; Soft-Matter Division, Oak Ridge National Laboratory Team; Julich CenterNeutron Science Team

Water diffusion is playing an important role in polymer systems. We calculated the water diffusion coefficient at different layers along z-direction which is perpendicular to the lamellar membrane formed by Pluronic block copolymers (L62: (EO6-PO34-EO6)) with the molecular dynamics simulation trajectories. Water molecules at bulk layers are following the normal diffusion, while that at hydration layers formed by polyethylene oxide (PEO) and hydrophobic layers formed by polypropylene oxide (PPO) are following anomalous diffusion. We find that although the subdiffusive regimes at PEO layers and PPO layers are the same, which is the fractional Brownian motion, however, the dynamics are different, i.e. diffusion at the PEO layers is much faster than that at the PPO layers, and meanwhile it exhibits a normal diffusive approximation within a short time period which is governed by the localized free self-diffusion, but becomes subdiffusive after t >8 ps, which is governed by the viscoelastic medium. The Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy; and Zhe Zhang gratefully acknowledges financial support from Julich Center for Neutron Science.

Optimizing diffusion in multiplexes by maximizing layer dissimilarity

NASA Astrophysics Data System (ADS)

Serrano, Alfredo B.; Gómez-Gardeñes, Jesús; Andrade, Roberto F. S.

2017-05-01

Diffusion in a multiplex depends on the specific link distribution between the nodes in each layer, but also on the set of the intralayer and interlayer diffusion coefficients. In this work we investigate, in a quantitative way, the efficiency of multiplex diffusion as a function of the topological similarity among multiplex layers. This similarity is measured by the distance between layers, taken among the pairs of layers. Results are presented for a simple two-layer multiplex, where one of the layers is held fixed, while the other one can be rewired in a controlled way in order to increase or decrease the interlayer distance. The results indicate that, for fixed values of all intra- and interlayer diffusion coefficients, a large interlayer distance generally enhances the global multiplex diffusion, providing a topological mechanism to control the global diffusive process. For some sets of networks, we develop an algorithm to identify the most sensitive nodes in the rewirable layer, so that changes in a small set of connections produce a drastic enhancement of the global diffusion of the whole multiplex system.

An Evaluation of Graduated Driver Licensing Effects on Fatal Crash Involvements of Young Drivers in the United States

PubMed Central

Fell, James C.; Jones, Kristina; Romano, Eduardo; Voas, Robert

2013-01-01

Objective Graduated driver licensing (GDL) systems are designed to reduce the high crash risk of young novice drivers. Almost all states in the United States have some form of a three-phased GDL system with various restrictions in the intermediate phase. Studies of the effects of GDL in various states show significant reductions in fatal crash involvements of 16- and 17-year-old drivers; however, only a few national studies of GDL effects have been published. The objective of this national panel study was to evaluate the effect of GDL laws on the fatal crash involvements of novice drivers while controlling for possible confounding factors not accounted for in prior studies. Methods The Fatality Analysis Reporting System (FARS) was used to examine 16- and 17-year-old driver involvement in fatal crashes (where GDL laws are applied) relative to two young driver age groups (19-20, 21-25) where GDL would not be expected to have an effect. Dates when various GDL laws were adopted in the states between 1990 and 2007 were coded from a variety of sources. Covariates in the longitudinal panel regression analyses conducted included four laws that could have an effect on 16- and 17-year-old drivers: primary enforcement seat belt laws, zero-tolerance (ZT) alcohol laws for drivers younger than age 21, lowering the blood alcohol concentration limit for driving to .08, and so-called “use and lose” laws where drivers aged 20 and younger lose their licenses for underage drinking violations. Results The adoption of a GDL law of average strength was associated with a significant decrease in fatal crash involvements of 16- and 17-year-old drivers relative to fatal crash involvements of one of the two comparison groups. GDL laws rated as “good” showed stronger relationships to fatal crash reductions, and laws rated as “less than good” showed no reductions in crash involvements relative to the older driver comparison groups. Conclusions States that adopt a basic GDL law can expect a decrease of 8 to 14% in the proportion of 16- and 17-year-old drivers involved in fatal crashes (relative to 21- to 25-year-old drivers), depending upon their other existing laws that affect novice drivers, such as those used in these analyses. This finding is consistent with recent national studies that used different outcome measures and covariates. The results of this study provide additional support for states to adopt, maintain, and upgrade GDL systems to reduce youthful traffic crash fatalities. PMID:21972851

Conductive polymer layers to limit transfer of fuel reactants to catalysts of fuel cells to reduce reactant crossover

DOEpatents

Stanis, Ronald J.; Lambert, Timothy N.

2016-12-06

An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.

EFFECT OF Mg AND TEMPERATURE ON Fe-Al ALLOY LAYER IN Fe/(Zn-6%Al-x%Mg) SOLID-LIQUID DIFFUSION COUPLES

NASA Astrophysics Data System (ADS)

Liang, Liu; Liu, Ya-Ling; Liu, Ya; Peng, Hao-Ping; Wang, Jian-Hua; Su, Xu-Ping

Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe-Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe-Al alloy layer. It was found that the Fe2Al5Znx phase layer forms close to the iron sheet and the FeAl3Znx phase layer forms near the side of the melted Zn-6%Al-3%Mg in diffusion couples. When the Fe/(Zn-6%Al-3%Mg) diffusion couple is kept at 510∘C for more than 15min, a continuous Fe-Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples, the Fe-Al alloy layer on the interface of the Fe/(Zn-6% Al-3% Mg) diffusion couple is the thinnest. The Fe-Al alloy layer forms only when the diffusion temperature is above 475∘. These results show that the Fe-Al alloy layer in Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples is composed of Fe2Al5Znx and FeAl3Znx phase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe-Al alloy layer. When the Mg content in the Fe/(Zn-6%Al-x%Mg) diffusion couples is 3%, the growth of the Fe-Al alloy layer is inhibited. These results may explain why there is no obvious Fe-Al alloy layer formed on the interface of steel with a Zn-6%Al-3%Mg coating.

Space Missions: Long Term Preservation of IDL-based Software using GDL

NASA Astrophysics Data System (ADS)

Coulais, A.; Schellens, M.; Arabas, S.; Lenoir, M.; Noreskal, L.; Erard, S.

2012-09-01

GNU Data Language (GDL) is a free software clone of IDL, an interactive language widely used in Astronomy and space missions since decades. Proprietary status, license restrictions, price, sustainability and continuity of support for particular platforms are recurrent concerns in the Astronomy community, especially concerning space missions, which require long-term support. In this paper, we describe the key features of GDL and the main achievements from recent development work. We illustrate the maturity of GDL by presenting two examples of application: reading spectral cubes in PDS format and use of the HEALPix library. These examples support the main argument of the paper: that GDL has reached a level of maturity and usability ensuring long term preservation of analysis capabilities for numerous ground experiments and spaces missions based on IDL.

Polymeric hydrogen diffusion barrier, high-pressure storage tank so equipped, method of fabricating a storage tank and method of preventing hydrogen diffusion

DOEpatents

Lessing, Paul A [Idaho Falls, ID

2008-07-22

An electrochemically active hydrogen diffusion barrier which comprises an anode layer, a cathode layer, and an intermediate electrolyte layer, which is conductive to protons and substantially impermeable to hydrogen. A catalytic metal present in or adjacent to the anode layer catalyzes an electrochemical reaction that converts any hydrogen that diffuses through the electrolyte layer to protons and electrons. The protons and electrons are transported to the cathode layer and reacted to form hydrogen. The hydrogen diffusion barrier is applied to a polymeric substrate used in a storage tank to store hydrogen under high pressure. A storage tank equipped with the electrochemically active hydrogen diffusion barrier, a method of fabricating the storage tank, and a method of preventing hydrogen from diffusing out of a storage tank are also disclosed.

Polymeric hydrogen diffusion barrier, high-pressure storage tank so equipped, method of fabricating a storage tank and method of preventing hydrogen diffusion

DOEpatents

Lessing, Paul A.

2004-09-07

An electrochemically active hydrogen diffusion barrier which comprises an anode layer, a cathode layer, and an intermediate electrolyte layer, which is conductive to protons and substantially impermeable to hydrogen. A catalytic metal present in or adjacent to the anode layer catalyzes an electrochemical reaction that converts any hydrogen that diffuses through the electrolyte layer to protons and electrons. The protons and electrons are transported to the cathode layer and reacted to form hydrogen. The hydrogen diffusion barrier is applied to a polymeric substrate used in a storage tank to store hydrogen under high pressure. A storage tank equipped with the electrochemically active hydrogen diffusion barrier, a method of fabricating the storage tank, and a method of preventing hydrogen from diffusing out of a storage tank are also disclosed.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-07-25

Embodiments of the disclosure relate to electrocatalysts. The electrocatalyst may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

General Model of Hindered Diffusion.

PubMed

Eloul, Shaltiel; Compton, Richard G

2016-11-03

The diffusion of a particle from bulk solution is slowed as it moves close to an adsorbing surface. A general model is reported that is easily applied by theoreticians and experimentalists. Specifically, it is shown here that in general and regardless of the space size, the magnitude of the effect of hindered diffusion on the flux is a property of the diffusion layer thickness. We explain and approximate the effect. Predictions of concentration profiles show that a "hindered diffusion layer" is formed near the adsorbing surface within the diffusion layer, observed even when the particle radius is just a 0.1% of the diffusion layer thickness. In particular, we focus on modern electrochemistry processes involving with impact of particles with either ultrasmall electrodes or particles in convective systems. The concept of the "hindered diffusion layer" is generally important for example in recent biophysical models of particles diffusion to small targets.

Influence of capillary barrier effect on biogas distribution at the base of passive methane oxidation biosystems: Parametric study.

PubMed

Ahoughalandari, Bahar; Cabral, Alexandre R

2017-05-01

The efficiency of methane oxidation in passive methane oxidation biosystems (PMOBs) is influenced by, among other things, the intensity and distribution of the CH 4 loading at the base of the methane oxidation layer (MOL). Both the intensity and distribution are affected by the capillary barrier that results from the superposition of the two materials constituting the PMOB, namely the MOL and the gas distribution layer (GDL). The effect of capillary barriers on the unsaturated flow of water has been well documented in the literature. However, its effect on gas flow through PMOBs is still poorly documented. In this study, sets of numerical simulations were performed to evaluate the effect of unsaturated hydraulic characteristics of the MOL material on the value and distribution of moisture and hence, the ease and uniformity in the distribution of the upward flow of biogas along the GDL-MOL interface. The unsaturated hydraulic parameters of the materials used to construct the experimental field plot at the St-Nicephore landfill (Quebec, Canada) were adopted to build the reference simulation of the parametric study. The behavior of the upward flow of biogas for this particular material was analyzed based on its gas intrinsic permeability function, which was obtained in the laboratory. The parameters that most influenced the distribution and the ease of biogas flow at the base of the MOL were the saturated hydraulic conductivity and pore size distribution of the MOL material, whose effects were intensified as the slope of the interface increased. The effect of initial dry density was also assessed herein. Selection of the MOL material must be made bearing in mind that these three parameters are key in the effort to prevent unwanted restriction in the upward flow of biogas, which may result in the redirection of biogas towards the top of the slope, leading to high CH 4 fluxes (hotspots). In a well-designed PMOB, upward flow of biogas across the GDL-MOL interface is unrestricted and moisture distribution is uniform. This paper tries to show how to obtain this. Copyright © 2016 Elsevier Ltd. All rights reserved.

Retrospective checking of compliance with practice guidelines for acute stroke care: a novel experiment using openEHR’s Guideline Definition Language

PubMed Central

2014-01-01

Background Providing scalable clinical decision support (CDS) across institutions that use different electronic health record (EHR) systems has been a challenge for medical informatics researchers. The lack of commonly shared EHR models and terminology bindings has been recognised as a major barrier to sharing CDS content among different organisations. The openEHR Guideline Definition Language (GDL) expresses CDS content based on openEHR archetypes and can support any clinical terminologies or natural languages. Our aim was to explore in an experimental setting the practicability of GDL and its underlying archetype formalism. A further aim was to report on the artefacts produced by this new technological approach in this particular experiment. We modelled and automatically executed compliance checking rules from clinical practice guidelines for acute stroke care. Methods We extracted rules from the European clinical practice guidelines as well as from treatment contraindications for acute stroke care and represented them using GDL. Then we executed the rules retrospectively on 49 mock patient cases to check the cases’ compliance with the guidelines, and manually validated the execution results. We used openEHR archetypes, GDL rules, the openEHR reference information model, reference terminologies and the Data Archetype Definition Language. We utilised the open-sourced GDL Editor for authoring GDL rules, the international archetype repository for reusing archetypes, the open-sourced Ocean Archetype Editor for authoring or modifying archetypes and the CDS Workbench for executing GDL rules on patient data. Results We successfully represented clinical rules about 14 out of 19 contraindications for thrombolysis and other aspects of acute stroke care with 80 GDL rules. These rules are based on 14 reused international archetypes (one of which was modified), 2 newly created archetypes and 51 terminology bindings (to three terminologies). Our manual compliance checks for 49 mock patients were a complete match versus the automated compliance results. Conclusions Shareable guideline knowledge for use in automated retrospective checking of guideline compliance may be achievable using GDL. Whether the same GDL rules can be used for at-the-point-of-care CDS remains unknown. PMID:24886468

Scaling GDL for Multi-cores to Process Planck HFI Beams Monte Carlo on HPC

NASA Astrophysics Data System (ADS)

Coulais, A.; Schellens, M.; Duvert, G.; Park, J.; Arabas, S.; Erard, S.; Roudier, G.; Hivon, E.; Mottet, S.; Laurent, B.; Pinter, M.; Kasradze, N.; Ayad, M.

2014-05-01

After reviewing the majors progress done in GDL -now in 0.9.4- on performance and plotting capabilities since ADASS XXI paper (Coulais et al. 2012), we detail how a large code for Planck HFI beams Monte Carlo was successfully transposed from IDL to GDL on HPC.

Understanding adolescent development: implications for driving safety.

PubMed

Keating, Daniel P

2007-01-01

The implementation of Graduated Driver Licensing (GDL) programs has significantly improved the crash and fatality rates of novice teen drivers, but these rates remain unacceptably high. A review of adolescent development research was undertaken to identify potential areas of improvement. Research support for GDL was found to be strong, particularly regarding early acquisition of expertise in driving safety (beyond driving skill), and to limitations that reduce opportunities for distraction. GDL regimes are highly variable, and no US jurisdictions have implemented optimal regimes. Expanding and improving GDL to enhance acquisition of expertise and self-regulation are indicated for implementation and for applied research. Driver training that effectively incorporates safety goals along with driving skill is another target. The insurance industry will benefit from further GDL enhancements. Benefits may accrue to improved driver training, improved simulation devices during training, and automated safety feedback instrumentation.

The Modification of Fuel Cell-Based Breath Alcohol Sensor Materials to Improve Water Retention of Sensing Performance

NASA Astrophysics Data System (ADS)

Allan, Jesse

Fuel cell based breath alcohol sensors (BrASs) are one of the most important tools used by law enforcement today. The ability to screen potentially intoxicated subjects with the ease, speed, and flexibility the BrAS can provide is unmatched by any other device of its kind. While these devices are used globally, they all suffer from a common deficiency: reliance on water. The ability of the fuel cell sensor to manage water content is one of the greatest fundamental challenges facing this technology today. In order to evaluate the fuel cell sensor device, a methodology was required that would allow in-house sensor testing to be coupled with a diagnostic testing method to not only test materials sensing performance, but also determine why a sensor behaved how it did. To do this, a next-generation fuel cell was designed specifically for sensor testing along with a test station that allowed for rapid response and sensor characteristics of a given material. The fuel cell was designed to allow in-situ testing of a membrane electrode assembly (MEA) of interest using cyclic voltammetry and electrochemical impedance spectroscopy. The in-house design was validated against a commercial cell to provide feedback on how materials in the in-house cell would behave in a commercial designed unit. The results showed that our cell with a commercial MEA behaved identically to a commercial cell with the same MEA. Following validation of our cell, common membrane materials were investigated to identify their suitability in a senor role. The materials chosen were designed for power generating devices, so they provided a benchmark to identify which properties would be important for sensor operation. It was found that while the Nafion membrane and sulfonated poly (ether ether ketone) did show performance increases over the commercial MEA, the thin characteristics of these membranes limited performance in drier conditions. From these results, it was determined that thicker membrane materials are better suited for sensor applications. The commercially used porous poly-vinyl chloride (PVC) membrane was investigated and modified to improve performance of this material. As PVC does not contain any natural hydroscopic properties, the addition of various hydrophilic groups to the PVC would aid in water management. It was found that while chemical modification could improve water retention, optimization of the modifications would be required to ensure flooding was not an issue. Composites of PVC and sulfonated silica showed performance that matched that of the commercial PVC, whilst using significantly less water to achieve those results. By reducing the water required for sensing, leaching of acid, as well as flooding could be reduced. Finally, the catalyst layer and gas diffusion layer (GDL) were investigated to understand what properties of these would impart the best performance increases for the sensor. For the catalyst layer, it was found that platinum black and 20% platinum supported on carbon achieved similar results. Platinum black has excellent catalytic activity for the ethanol oxidation reaction, while the surface area of the 20% platinum supported on carbon would allow for more ethanol to react, increasing the overall sensor capability. The choice of catalyst was less of an issue than the choice of GDL. It was found that using carbon fiber paper GDLs lead to greater retention of water in the MEA compared to carbon cloth GDLs due to the lower air permeability. This came at a cost however in that with a lower air permeability, less ethanol vapour would reach the catalytic sites, reducing sensing performance. Depending on the choice of membrane, removal of the GDL could impart performance increases, but could also cause detrimental failure in the case of Nafion based systems.

Patient blood transfusion management: discharge hemoglobin level as a surrogate marker for red blood cell utilization appropriateness.

PubMed

Edwards, Jason; Morrison, Chris; Mohiuddin, Maleeha; Tchatalbachev, Vladislav; Patel, Charmi; Schwickerath, Vicki L; Menitove, Jay E; Singh, Gurmukh

2012-11-01

Blood transfusion management strategies minimize transfusion-associated risks, enhance outcomes, and reduce costs. We explored an association of discharge hemoglobin (Hb) with pretransfusion Hb, transfusion indications, and red blood cell (RBC) transfusions. We stipulate that patients with discharge Hb concentrations greater than 10.0 g/dL, or even 9.0 g/dL, received excessive RBC transfusions. We examined aggregate data from five hospitals and for one of the hospitals, the focus hospital, we reviewed patient records for a period of 6 months. Data analyses included number of RBC units transfused and Hb values before transfusion, after transfusion, and at discharge. In aggregate, 27% to 47% patients had discharge Hb levels greater than 10.0 g/dL. At the focus hospital, 27% had a discharge Hb level greater than 10 g/dL and 50.3% had a discharge Hb level greater than 9.0 g/dL. At the focus hospital, the mean Hb trigger for transfusion was a Hb level of 7.3 g/dL; the mean posttransfusion Hb level was 9.3 g/dL and mean discharge Hb level was 9.2 g/dL. Overall, 76% of the transfusions were of an even number of RBC units. In aggregate, overutilization exceeded 20%. At the focus hospital, approximately one-quarter of patients receiving transfusions had a Hb concentration greater than 10.0 g/dL at discharge. Transfused patients' discharge Hb concentration represents an effective indicator for retrospective monitoring of transfusion appropriateness. In light of the large number of patients receiving even number transfusions, reviewing Hb levels after transfusion of each RBC unit could reduce unnecessary transfusions. Retrospective review of discharge Hb data focuses providers on transfusion outcomes and affords an educational opportunity for blood utilization management. © 2012 American Association of Blood Banks.

The accuracy of noninvasive hemoglobin monitoring using the radical-7 pulse CO-Oximeter in children undergoing neurosurgery.

PubMed

Park, Yong-Hee; Lee, Ji-Hyun; Song, Hyun-Gul; Byon, Hyo-Jin; Kim, Hee-Soo; Kim, Jin-Tae

2012-12-01

The most common method for determining the hemoglobin concentration is to draw blood from a patient. However, the Radical-7 Pulse CO-Oximeter (Masimo Corporation, Irvine, CA) can noninvasively provide continuous hemoglobin concentration (SpHb). In our study we compared noninvasive measurements of SpHb with simultaneous laboratory measurements of total hemoglobin in arterial blood samples taken from children (tHb). Arterial blood samples were analyzed using a laboratory CO-oximeter, and SpHb was simultaneously recorded in pediatric patients undergoing neurosurgery. When patients met the criteria for hypovolemia, 10 mL/kg of colloids or red blood cells were administered over 10 minutes. SpHb and tHb data were collected before and after intravascular volume resuscitation. The relationship between SpHb and tHb was assessed using a 4-quadrant plot, linear regression, mixed-effect model, and modified Bland-Altman analyses. One hundred nineteen paired samples were analyzed. The correlation coefficient between SpHb and tHb was 0.53 (P < 0.001), whereas that of change in SpHb versus change in tHb was 0.75 (P < 0.001). The average difference (bias) between tHb and SpHb was 0.90 g/dL (95% confidence interval [CI], 0.48-1.32 g/dL) and 1 standard deviation of the difference (sd) was 1.35 g/dL. The concordance rate (a measure of the number of data points that are in 1 of the 2 quadrants of agreement) determined using a 4-quadrant plot was 93%. The correlation coefficient between SpHb and tHb after intravascular volume resuscitation was 0.58 (P < 0.001), whereas that of changes in SpHb and tHb was 0.87 (P < 0.001). The bias immediately after volume resuscitation was 1.18 g/dL (95% CI, 0.81-1.55 g/dL), and sd was 1.28 g/dL with a concordance rate of 94.4%. The bias was -0.03 g/dL when tHb was ≥11 g/dL, which was significantly lower in comparison with biases when tHb <9 g/dL (1.24 g/dL) and tHb was 9-11 g/dL (1.17 g/dL) (P = 0.004). The Radical-7 Pulse CO-Oximeter can be useful as a trend monitor in children during surgery even immediately after intravascular volume expanders are administered. However, it is advisable to confirm the baseline hemoglobin level and to consider the influence of tHb level on the bias. In addition, one should be cautious with regard to using SpHb alone when making transfusion decisions.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-12-26

Embodiments of the disclosure relate to membrane electrode assemblies. The membrane electrode assembly may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Disintegration of collagen fibrils by Glucono-δ-lactone: An implied lead for disintegration of fibrosis.

PubMed

Jayamani, Jayaraman; Ravikanth Reddy, R; Madhan, Balaraman; Shanmugam, Ganesh

2018-02-01

Excess accumulation of collagen (fibrosis) undergoes self-aggregation, which leads to fibrillar collagen, on the extracellular matrix is the hallmark of a number of diseases such as keloids, hypertrophic scars, and systemic scleroderma. Direct inhibition or disintegration of collagen fibrils by small molecules offer a therapeutic approach to prevent or treat the diseases related to fibrosis. Herein, the anti-fibrotic property of Glucono-δ-lactone (GdL), known as acidifier, on the fibrillation and its disintegration of collagen was investigated. As collagen fibrillation is pH dependent, the pH modulation property of GdL is attractive to inhibit self-association of collagen. Optical density and microscopic data indicate that GdL elicits concentration-dependent fibril inhibition and also disintegrates pre-formed collagen fibrils. The simultaneous pH analysis showed that the modulation(lowering) of pH by GdL is the primary cause for its anti-fibrotic activity. The intact triple helical structure of collagen upon treatment of GdL suggests that collagen fibril disintegration can be achieved without affecting the native structure of collagen which is essential for any anti-fibrotic agents. Saturation transfer difference (STD) NMR result reveals that GdL is in proximity to collagen. The present results thus suggest that GdL provides a lead to design novel anti-fibrotic agents for the pathologies related to collagen deposition. Copyright © 2017 Elsevier B.V. All rights reserved.

Analysis of spatial variations in the effectiveness of graduated driver's licensing (GDL) program in the state of Michigan.

PubMed

Chen, Yu; Berrocal, Veronica J; Bingham, C Raymond; Song, Peter X K

2014-04-01

Injury resulting from motor vehicle crashes is the leading cause of death among teenagers in the US. Few programs or policies have been found to be effective in reducing the risk of fatal car crashes for young novice drivers. One effective policy that has been widely implemented is Graduated Driver Licensing (GDL). Published articles have mostly reported on the temporal effectiveness of GDL in the US. This article reports on the development of spatial statistical modeling approaches to evaluate and compare the effectiveness of GDL policy across eighty-three counties in the state of Michigan. Data were gathered from several publicly available databases, including the US Fatality Analysis Reporting System (FARS), US Census Bureau, US Bureau of Labor Statistics, and US Department of Agriculture. To account for spatial dependence among crash counts from adjacent counties we invoke spatial random effects, which we provide with a Conditionally AutoRegressive (CAR) prior. Our analysis confirms previous findings that GDL in Michigan is an effective policy that significantly reduces the risk of fatal car crashes among novice teenage drivers. In addition, it indicates that rurality is an important contextual variable associated with spatial differences in GDL effectiveness across the state of Michigan. Finally, our findings provide information that can be used to strengthen GDL policy and its implementation to further enhance teenage-driver safety. Copyright © 2013 Elsevier Ltd. All rights reserved.

On the meaning of the diffusion layer thickness for slow electrode reactions.

PubMed

Molina, A; González, J; Laborda, E; Compton, R G

2013-02-21

A key concept underpinning electrochemical science is that of the diffusion layer - the zone of depletion around an electrode accompanying electrolysis. The size of this zone can be found either from the simulated or measured concentration profiles (yielding the 'true' diffusion layer thickness) or, in the case of the Nernst ('linear') diffusion layer by extrapolating the concentration gradient at the electrode surface to the distance at which the concentration takes its bulk value. The latter concept is very well developed in the case of fast (so-called reversible) electrode processes, however the study of the linear diffusion layer has received scant attention in the case of slow charge transfer processes, despite its study being of great interest in the analysis of the influence of different experimental variables which determine the electrochemical response. Analytical explicit solutions for the concentration profiles, surface concentrations and real and linear diffusion layers corresponding to the application of a potential step to a slow charge transfer process are presented. From these expressions the dependence of the diffusion layer thickness on the potential, pulse time, heterogeneous rate constant and ratio of bulk concentrations of electroactive species and of diffusion coefficients is quantified. A profound influence of the reversibility degree of the charge transfer on the diffusion layer thickness is clear, showing that for non-reversible processes the real and linear diffusion layers reveal a minimum thickness which coincides with the equilibrium potential of the redox couple in the former case and with the reversible half-wave potential in the latter one.

Association of anaemia in primary care patients with chronic kidney disease: cross sectional study of quality improvement in chronic kidney disease (QICKD) trial data

PubMed Central

2013-01-01

Background Anaemia is a known risk factor for cardiovascular disease and treating anaemia in chronic kidney disease (CKD) may improve outcomes. However, little is known about the scope to improve primary care management of anaemia in CKD. Methods An observational study (N = 1,099,292) with a nationally representative sample using anonymised routine primary care data from 127 Quality Improvement in CKD trial practices (ISRCTN5631023731). We explored variables associated with anaemia in CKD: eGFR, haemoglobin (Hb), mean corpuscular volume (MCV), iron status, cardiovascular comorbidities, and use of therapy which associated with gastrointestinal bleeding, oral iron and deprivation score. We developed a linear regression model to identify variables amenable to improved primary care management. Results The prevalence of Stage 3–5 CKD was 6.76%. Hb was lower in CKD (13.2 g/dl) than without (13.7 g/dl). 22.2% of people with CKD had World Health Organization defined anaemia; 8.6% had Hb ≤ 11 g/dl; 3% Hb ≤ 10 g/dl; and 1% Hb ≤ 9 g/dl. Normocytic anaemia was present in 80.5% with Hb ≤ 11; 72.7% with Hb ≤ 10 g/dl; and 67.6% with Hb ≤ 9 g/dl; microcytic anaemia in 13.4% with Hb ≤ 11 g/dl; 20.8% with Hb ≤ 10 g/dl; and 24.9% where Hb ≤ 9 g/dl. 82.7% of people with microcytic and 58.8% with normocytic anaemia (Hb ≤ 11 g/dl) had a low ferritin (<100ug/mL). Hypertension (67.2% vs. 54%) and diabetes (30.7% vs. 15.4%) were more prevalent in CKD and anaemia; 61% had been prescribed aspirin; 73% non-steroidal anti-inflammatory drugs (NSAIDs); 14.1% warfarin 12.4% clopidogrel; and 53.1% aspirin and NSAID. 56.3% of people with CKD and anaemia had been prescribed oral iron. The main limitations of the study are that routine data are inevitably incomplete and definitions of anaemia have not been standardised. Conclusions Medication review is needed in people with CKD and anaemia prior to considering erythropoietin or parenteral iron. Iron stores may be depleted in over >60% of people with normocytic anaemia. Prescribing oral iron has not corrected anaemia. PMID:23351270

Secondary gastrointestinal amyloid A amyloidosis possibly caused by hidradenitis suppurativa.

PubMed

Kochi, Shuji; Esaki, Motohiro; Kurahara, Koichi

2018-06-22

A 54-year-old man was referred to our hospital because of 2 years' duration of extended multiple nodules with abscess and fistula with pus discharge in the gluteal and perianal regions (Fig. 1a). Laboratory data identified inflammatory reaction (WBC, 11430 /μl, and C-reactive protein, 4.5 mg/dl) and anemia (hemoglobin levels, 8.6 g/dl). Serum amyloid A protein was elevated (50.2 μg/ml). Ileocolonoscopy showed diffuse coarse mucosa with numerous diminutive nodules throughout the colorectum (Fig. 1b). This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Maternal hemoglobin concentration and adverse pregnancy outcomes at low and moderate altitudes in Peru.

PubMed

Gonzales, Gustavo F; Tapia, Vilma; Gasco, Manuel; Carrillo, Carlos E

2012-07-01

To identify associations of maternal hemoglobin (Hb) with perinatal outcomes at low and moderate altitudes in Peru. Study of records with sequential information using perinatal database system. The study included 295 651 pregnant women with their products. Using multiple logistic regression analysis, we estimated the probability of stillbirths, preterm and small for gestational age (SGA) births associated with maternal Hb levels at low (0-1999 m) and moderate altitudes (2000-2999 m). Maternal Hb decreased as pregnancy progressed from first to third trimester at both altitudes. Hb was higher at moderate than at low altitude (p < 0.001). Risks for stillbirths increased with low maternal Hb (odds ratio [OR]: 1.39 for Hb 9-9.9; OR: 1.84 for Hb 8-8.9; OR: 3.25 for Hb 7-7.9; and OR: 7.8 for Hb <7 g/dl); with Hb higher than 14.5 g/dl (OR: 1.31) and with altitudes ≥ 2000 m (OR: 1.2). High preterm rates were also observed with low Hbs (OR: 1.16 for Hb 9-9.9; OR: 1.64 for Hb 8-8.9; OR: 2.25 for Hb 7-7.9; and OR:2.87 for Hb<7 g/dl) and with Hb higher than 14.5 g/dl (OR: 1.14). High SGA rates were observed in neonates with maternal Hb of 7-7.9 (OR: 1.35) and <7 g/dl (OR:1.57), and higher than 14.5 g/dl (OR: 1.33), and with moderate altitudes (OR: 1.12). The cut-off points for lower risks of stillbirth and preterm births was 10 g/dl, and for SGA 9 g/dl of hemoglobin. Low and high maternal Hb levels and moderate altitude were independent risk factors for adverse perinatal outcomes.

Bedside hemoglobinometry in hemodialysis patients: lessons from point-of-care testing.

PubMed

Agarwal, R; Heinz, T

2001-01-01

The HemoCue B-hemoglobin test system (HemoCue, Inc., Mission Viejo, CA) is a photometric method for rapid bedside determination of hemoglobin (Hb). We compared the performance of HemoCue measured Hb against Coulter STK-S (CSTK) measured Hb in chronic hemodialysis (HD) patients in two different settings. In the first setting, Hemocue analysis was performed by multiple HD technicians (n = 132). In the second setting, a nurse trained in proper specimen handling performed the HemoCue analysis (n = 74). Simultaneous measurement of Hb by the CSTK method was performed. First setting: Hb was 11.1+/-1.66 (SD) g/dl by CSTK and 11.7+/-2.29 g/dl by HemoCue. The HemoCue method consistently overestimated Hb by an average (SD) of 0.63 (1.267) g/dl (95% CI = 0.42 to 0.85). Hb was overestimated in 25.7% and underestimated in 2.3% of the patients by 1 g/dl or more. Thus, the HemoCue system was accurate within 1 g/dl only 72% of the time. Second setting: HemoCue overestimated Hb by an average (SD) of 0.29 (0.52) g/dl (95% CI, 0.17 to 0.41). Only 4% of all patients had errors in estimation of 1 g/dl or more. Thus, HemoCue was accurate in 96% of the patients within 1 g/dl. After reviewing the two protocols, the primary difference in the two studies was the technique used to obtain the specimens. When performed properly, Hb testing using the HemoCue testing system had a high level of agreement with CSTK. Appropriate training in specimen handling, as well as test performance, will increase accuracy and reliability of bedside hemoglobinometry.

A 1-year trial of repeated high-dose intravenous iron isomaltoside 1000 to maintain stable hemoglobin levels in inflammatory bowel disease.

PubMed

Reinisch, Walter; Altorjay, Istvan; Zsigmond, Ferenc; Primas, Christian; Vogelsang, Harald; Novacek, Gottfried; Reinisch, Sieglinde; Thomsen, Lars L

2015-01-01

Iron isomaltoside 1000 (Monofer®) is a high-dose intravenous (IV) iron, which in a recent 8 weeks trial in inflammatory bowel disease (IBD) subjects with iron deficiency anemia (IDA) demonstrated good tolerability and efficacy. The present trial is an extension to this trial, which evaluates the need for additional high IV iron doses to maintain a stable hemoglobin (Hb) ≥12.0 g/dl. This was a prospective, open-label, 12 months trial of European IBD subjects willing to participate after completing the lead-in trial. Subjects were allowed re-dosing with 500-2000 mg single doses of iron isomaltoside 1000 infused over ∼15 min at 3 months intervals depending on a predefined algorithm. Outcome measures included Hb, safety parameters and need for additional iron dosing. A total of 39 subjects were enrolled of which 34 subjects required re-dosing with a median cumulative 1-year dose of 1.8 g (mean cumulative dose 2.2 g). The mean (SD) Hb was 12.3 (1.5) g/dl at baseline, 12.8 (1.6) g/dl at 3 months, 12.8 (1.6) g/dl at 6 months, 12.9 (1.4) g/dl at 9 months and 12.9 (1.6) g/dl at 12 months. Seventy-four percent of subjects who had an Hb ≥12.0 g/dl at baseline were able to maintain Hb ≥12.0 g/dl till the end of the trial at 12 months. Nonserious probably related hypersensitivity reactions without significant hypotension were reported at the beginning of the infusion in two subjects, who recovered without sequelae. Repeated treatment of iron deficiency with iron isomaltoside 1000 could avoid episodes of IDA without major safety issues.

Impact of ultra-low Pt loadings on the performance of anode/cathode in a proton-exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Billy, E.; Maillard, F.; Morin, A.; Guetaz, L.; Emieux, F.; Thurier, C.; Doppelt, P.; Donet, S.; Mailley, S.

This study focuses on the elaboration of PEMFC electrodes containing ultra-low platinum (Pt) loadings by direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD). DLI-MOCVD offers a large number of advantages for the elaboration of model PEMFC electrodes. First, by using different metal precursors or elaboration temperature, the size of the Pt nanoparticles and thus the intrinsic catalytic activity can easily be tailored in the nanometer range. In this work, Pt nanoparticles (1-5 nm) with remarkable low degree of agglomeration and uniform distribution were deposited onto the microporous side of a commercial gas-diffusion layer (GDL). Second, reduction of the Pt loading is made possible by varying the Pt deposition time and its influence of the cell performance can be extracted without variation of the thickness of the catalytic layer (in previous studies, a decrease of the catalyst utilization was observed when increasing the Pt loading, i.e. the thickness of the catalytic layer (CL)). The electrocatalytic activity of home-made Pt nanoparticles elaborated by DLI-MOCVD was measured in liquid electrolyte or in complete fuel cell operating on H 2/O 2 or H 2/air and compared vs. that of a commercially available electrode containing 500 μg Pt cm -2 (Pt Ref500). At the cathode, the performance of the electrodes containing 104-226 μg of Pt per cm 2 of electrode compares favorably with that of the Pt Ref500 in H 2/O 2 conditions. In H 2/air conditions, additional mass-transport losses are detected in the low-current density region but the high effectiveness of our electrodes improves the performance in the high-current density region. At the anode, the Pt loading can be reduced to 35 μg Pt cm -2 without any voltage loss in agreement with previous observations.

General solution for diffusion-controlled dissolution of spherical particles. 1. Theory.

PubMed

Wang, J; Flanagan, D R

1999-07-01

Three classical particle dissolution rate expressions are commonly used to interpret particle dissolution rate phenomena. Our analysis shows that an assumption used in the derivation of the traditional cube-root law may not be accurate under all conditions for diffusion-controlled particle dissolution. Mathematical analysis shows that the three classical particle dissolution rate expressions are approximate solutions to a general diffusion layer model. The cube-root law is most appropriate when particle size is much larger than the diffusion layer thickness, the two-thirds-root expression applies when the particle size is much smaller than the diffusion layer thickness. The square-root expression is intermediate between these two models. A general solution to the diffusion layer model for monodispersed spherical particles dissolution was derived for sink and nonsink conditions. Constant diffusion layer thickness was assumed in the derivation. Simulated dissolution data showed that the ratio between particle size and diffusion layer thickness (a0/h) is an important factor in controlling the shape of particle dissolution profiles. A new semiempirical general particle dissolution equation is also discussed which encompasses the three classical particle dissolution expressions. The success of the general equation in explaining limitations of traditional particle dissolution expressions demonstrates the usefulness of the general diffusion layer model.

Serum protein electrophoretic pattern in one-humped camels (Camelus dromedarius) in Tripoli, Libya.

PubMed

Abdoslam, Omran; Bayt-Almal, Mahmoud; Almghrbe, Abdullah; Algriany, Omran

2018-01-01

The aim of this study was to characterize serum protein capillary electrophoretic pattern in apparently healthy adult male (age: 3-7 years) dromedary camels and also evaluate total protein and albumin levels using automated analyzer. Blood samples were taken from 20 camels. 5ml of blood was collected from the jugular vein and serum was separated from samples by centrifugation. Capillary electrophoresis of serum proteins identified six protein fractions in adult camels, including albumin, alpha1, alpha2, beta1, beta2 and gamma globulins, serum levels of these parameters were 3.9±0.04 g/dl, 0.16±0.01 g/dl, 0.39±0.03 g/dl, 0.515±0.03 g/dl, 0.205±0.01 g/dl and 0.61±0.04 g/dl, and 65.42±0.62 g/l, respectively. The total protein concentration was 65.42±0.62 g/L, while, the albumin/globulin (A/G) ratio was 2.4±0.14. The present study indicates six peaks with minicapillary electrophoresis and the results obtained were compared and interpreted in the light of finding reported by other investigators in camels.

Clinical experience with ferric carboxymaltose in the treatment of cancer- and chemotherapy-associated anaemia

PubMed Central

Steinmetz, T.; Tschechne, B.; Harlin, O.; Klement, B.; Franzem, M.; Wamhoff, J.; Tesch, H.; Rohrberg, R.; Marschner, N.

2013-01-01

Background Intravenous (i.v.) iron can improve anaemia of chronic disease and response to erythropoiesis-stimulating agents (ESAs), but data on its use in practice and without ESAs are limited. This study evaluated effectiveness and tolerability of ferric carboxymaltose (FCM) in routine treatment of anaemic cancer patients. Patients and methods Of 639 patients enrolled in 68 haematology/oncology practices in Germany, 619 received FCM at the oncologist's discretion, 420 had eligible baseline haemoglobin (Hb) measurements, and 364 at least one follow-up Hb measurement. Data of transfused patients were censored from analysis before transfusion. Results The median total iron dose was 1000 mg per patient (interquartile range 600–1500 mg). The median Hb increase was comparable in patients receiving FCM alone (1.4 g/dl [0.2–2.3 g/dl; N = 233]) or FCM + ESA (1.6 g/dl [0.7–2.4 g/dl; N = 46]). Patients with baseline Hb up to 11.0 g/dl and serum ferritin up to 500 ng/ml benefited from FCM treatment (stable Hb ≥11.0 g/dl). Also patients with ferritin >500 ng/ml but low transferrin saturation benefited from FCM treatment. FCM was well tolerated, 2.3% of patients reported putative drug-related adverse events. Conclusions The substantial Hb increase and stabilisation at 11–12 g/dl in FCM-treated patients suggest a role for i.v. iron alone in anaemia correction in cancer patients. PMID:23071262

An Advection-Diffusion Concept for Solute Transport in Heterogeneous Unconsolidated Geological Deposits

NASA Astrophysics Data System (ADS)

Gillham, R. W.; Sudicky, E. A.; Cherry, J. A.; Frind, E. O.

1984-03-01

In layered permeable deposits with flow predominately parallel to the bedding, advection causes rapid solute transport in the more permeable layers. As the solute advances more rapidly in these layers, solute mass is continually transferred to the less permeable layers as a result of molecular diffusion due to the concentration gradient between the layers. The interlayer solute transfer causes the concentration to decline along the permeable layers at the expense of increasing the concentration in the less permeable layers, which produces strongly dispersed concentration profiles in the direction of flow. The key parameters affecting the dispersive capability of the layered system are the diffusion coefficients for the less permeable layers, the thicknesses of the layers, and the hydraulic conductivity contrasts between the layers. Because interlayer solute transfer by transverse molecular diffusion is a time-dependent process, the advection-diffusion concept predicts a rate of longitudinal spreading during the development of the dispersion process that is inconsistent with the classical Fickian dispersion model. A second consequence of the solute-storage effect offered by transverse diffusion into low-permeability layers is a rate of migration of the frontal portion of a contaminant in the permeable layers that is less than the groundwater velocity. Although various lines of evidence are presented in support of the advection-diffusion concept, more work is required to determine the range of geological materials for which it is applicable and to develop mathematical expressions that will make it useful as a predictive tool for application to field cases of contaminant migration.

Multi-layer light-weight protective coating and method for application

NASA Technical Reports Server (NTRS)

Wiedemann, Karl E. (Inventor); Clark, Ronald K. (Inventor); Taylor, Patrick J. (Inventor)

1992-01-01

A thin, light-weight, multi-layer coating is provided for protecting metals and their alloys from environmental attack at high temperatures. A reaction barrier is applied to the metal substrate and a diffusion barrier is then applied to the reaction barrier. A sealant layer may also be applied to the diffusion barrier if desired. The reaction barrier is either non-reactive or passivating with respect to the metal substrate and the diffusion barrier. The diffusion barrier is either non-reactive or passivating with respect to the reaction barrier and the sealant layer. The sealant layer is immiscible with the diffusion barrier and has a softening point below the expected use temperature of the metal.

The impact of the 2007 graduated driver licensing law in Massachusetts on the rate of citations and licensing in teenage drivers.

PubMed

DePesa, Christopher; Raybould, Toby; Hurwitz, Shelley; Lee, Jarone; Gervasini, Alice; Velmahos, George C; Masiakos, Peter T; Kaafarani, Haytham M A

2017-06-01

We recently demonstrated that the 2007 Massachusetts Graduated Driving Licensing (GDL) law decreased the rate of motor vehicle crashes in teenage drivers. To better understand this decrease, we sought to examine the law's impact on the issuance of driving licenses and traffic citations to teenage drivers. Citation and license data were obtained from the Massachusetts Department of Transportation. Census data were obtained from the Census Data Center. Two study periods were defined: pre-GDL (2002-2006) and post-GDL (2007-2012). Two populations were defined: the study population (aged 16-17) and the control population (aged 25-29). The rates of licenses per population were compared pre- vs. post-GDL for the study group. The numbers of total, state, and local citations per population were compared pre- vs. post-GDL for both populations. A sensitivity analysis was performed for the rates of citations using licenses issued as a denominator. While licenses per population obtained by the study group decreased over the entire period, there was no change in the rate of decrease per year pre- vs. post-GDL (2.0% vs. 1.4%; p=0.6392). In the study population, total, state, and local citations decreased post-GDL (17.8% vs. 8.1%, p<0.0001; 3.7% vs. 2.2%, p<0.0001; 14.1% vs. 5.8%, p<0.0001, respectively). In the control group, total and state citations did not change (26.7% vs. 23.9%, p=0.3606; 9.2% vs. 10.2%, p=0.3404, respectively), and local citations decreased (17.5% vs. 13.7%, p=0.0389). The rates of decrease per year for total, state, and local citations were significantly greater in the study population compared with control (p<0.0001, p=0.0002, p<0.0001, respectively). The 2007 GDL law in Massachusetts was associated with fewer traffic citations without a change in the rate of licenses issued to teenagers. These findings suggest that 2007 GDL may be improving driving habits as opposed to motivating teenagers to delay the issuing of licenses. Copyright © 2017. Published by Elsevier Ltd.

Ultrasonic Fatigue Endurance of Thin Carbon Fiber Sheets

NASA Astrophysics Data System (ADS)

Domínguez Almaraz, Gonzalo M.; Ruiz Vilchez, Julio A.; Dominguez, Aymeric; Meyer, Yann

2016-04-01

Ultrasonic fatigue tests were carried out on thin carbon fiber sheets (0.3 mm of thickness) to determine the fatigue endurance under very high-frequency loading (20 kHz). This material, called the gas diffusion layer (GDL), plays a major role in the overall performances of proton exchange membrane fuel cells (PEMFCs). The study of its physical-chemical properties is an on-going subject in the literature; nevertheless, no knowledge is available concerning the high-frequency fatigue endurance. A principal difficulty in carrying out ultrasonic fatigue tests on this material was to determine the dimensions of testing specimen to fit the resonance condition. This aspect was solved by modal numerical simulation: The testing specimen has been a combination of a low-strength steel frame (to facilitate the attachment to the ultrasonic machine and to increase the mass of the specimen), and the carbon fiber hourglass-shape profile. Under resonance condition, a stationary elastic wave is generated along the specimen that induces high stress at the neck section and high displacements at the ends. Results show that fatigue life was close to 3 × 108 cycles when the high Von Misses stress at the neck section was 170 MPa, whereas fatigue life attains the 4.5 × 109 cycles when stress decreases to 117 MPa. Crack initiation and propagation were analyzed, and conclusions were drawn concerning the fatigue endurance of these fiber carbon sheets under ultrasonic fatigue testing.

The Thermal Diffusivity Measurement of the Two-layer Ceramics Using the Laser Flash Methodn

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Ogwa, Mitsue; Baba, Tetsuya; Mizuno, Mineo

Ceramics-based thermal barrier coatings are used as heat and wear shields of gas turbines. There are strong needs to evaluate thermophysical properties of coating, such as thermal conductivity, thermal diffusivity and heat capacity of them. Since the coatings are attached on substrates, it is no easy to measure these properties separately. The laser flash method is one of the most popular thermal diffusivity measurement methods above room temperature for solid materials. The surface of the plate shape specimen is heated by the pulsed laser-beam, then the time variation of the temperature of the rear surface is observed by the infrared radiometer. The laser flash method is non-contact and short time measurement. In general, the thermal diffusivity of solids that are dense, homogeneous and stable, are measured by this method. It is easy to measure thermal diffusivity of a specimen which shows heat diffusion time about 1 ms to 1 s consistent with the specimen thickness of about 1 mm to 5 mm. On the other hand, this method can be applied to measure the specific heat capacity of the solids. And it is also used to estimate the thermal diffusivity of an unknown layer in the layered materials. In order to evaluate the thermal diffusivity of the coating attached on substrate, we have developed a measurement procedure using the laser flash method. The multi-layer model based on the response function method was applied to calculate the thermal diffusivity of the coating attached on substrate from the temperature history curve observed for the two-layer sample. We have verified applicability of the laser flash measurement with the multi-layer model using the measured results and the simulation. It was found that the laser flash measurement for the layered sample using the multi-layer model was effective to estimate the thermal diffusivity of an unknown layer in the sample. We have also developed the two-layer ceramics samples as the reference materials for this procedure.

Convection-Diffusion Layer in an "Open Space" for Local Surface Treatment and Microfabrication using a Four-Aperture Microchemical Pen.

PubMed

Mao, Sifeng; Zhang, Yong; Zhang, Weifei; Zeng, Hulie; Nakajima, Hizuru; Lin, Jin-Ming; Uchiyama, Katsumi

2017-09-06

A four-aperture microchemical pen was used to produce a stable convection-diffusion layer in an "open space" for microreactions and microfabrication. The process represents a new method for microreactions and microfabrication in a convection-diffusion layer. To prove the concept of a convection-diffusion layer in an "open space", bovine serum albumin was labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole to confirm that the small convection-diffusion layer was effective for local surface treatment. To demonstrate the potential for microfabrication, silver patterns were fabricated on a glass surface with a convection-diffusion layer by using the silver-mirror reaction. The widths of each silver pattern could be easily controlled from 10 to 60 μm. Patterned silver lines with uniform widths or gradient widths were prepared. This is the first proof of concept study of a convection-diffusion layer in an "open space" used in local surface treatment and microfabrication on a surface. The microchemical pen represents a potential method for the region-selective microtreatment of tissues, cells, and other biological interfaces. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical and experimental study of the effects of the electrical resistance and diffusivity under clamping pressure on the performance of a metallic gas-diffusion layer in polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Tanaka, Shiro; Bradfield, Warwick W.; Legrand, Cloe; Malan, Arnaud G.

2016-10-01

The performance of a perforated metal-sheet gas-diffusion layer incorporated with a microporous layer in a fuel cell is evaluated with fine-pitch channel/land designs for the gas flow field on a bipolar plate. The combination of metal-sheet gas-diffusion layer and microporous layer exhibits significant performance without a large flooding effect. When comparing the performance with wider and narrower land cases, the land width affects the performance. To investigate the roles of the microporous layer, land width, etc. in the fuel cell with the metal-sheet gas-diffusion layer, a single-phase, isothermal, and multi-physics simulation is developed and coupled with electrical, mechanical, electrochemical and fluid dynamics factors. The simulated current-voltage performance is then compared to the experimentally measure performance. These are shown to be in good agreement apart for very high current-density cases i.e. greater than 1.5 A cm-2. This is due the flooding effect predominantly appearing. It is further demonstrated that the microporous layer serves as the key component in facilitating gas diffusion and for preventing flooding. Furthermore, the pressure is found to have a strong impact on the performance, affecting the gas diffusion and electric resistance around the microporous layer.

Pretreatment anemia is correlated with the reduced effectiveness of radiation and concurrent chemotherapy in advanced head and neck cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prosnitz, Robert G.; Yao, Bin M.S.; Farrell, Catherine L.

2005-03-15

Purpose: Pretreatment anemia is an adverse prognostic variable in squamous cell head-and-neck cancer (HNC) patients treated with radiotherapy (RT) alone. Tumor hypoxia is an adverse parameter for treatment with RT alone or with RT and concurrent chemotherapy (CCT). Tumor hypoxia is more prevalent in patients who present with pretreatment hemoglobin (Hgb) concentrations less than 13 g/dL. RT/CCT improves survival over RT alone in advanced HNC, and its use is becoming more widespread. This study was performed to evaluate whether pretreatment Hgb less than 13 g/dL was correlated with treatment outcome in patients with advanced HNC treated with a uniform regimenmore » of RT/CCT. Methods and materials: The study population consisted of patients with AJCC Stage III or IV, M0 HNC who were treated with 70 to 72.5 Gy accelerated hyperfractionated RT (1.25 Gy b.i.d.) and CCT consisting of 2 cycles of CDDP (12-20 mg/m{sup 2}/d x 5 days) and continuous infusion 5-FU (600 mg/m{sup 2}/d x 5 days) during Week 1 and Week 6. A planned break in RT occurred during Week 4. These patients were enrolled on the experimental arm of a prospective randomized trial that compared this regimen to hyperfractionated irradiation alone from 1990 to 1996. RT/CCT was delivered as standard therapy from 1996 to 2000. The primary endpoint was failure-free survival (FFS). Secondary endpoints included local-regional control and overall survival. Results: One hundred and fifty-nine patients were treated from 1990 to 2000. The median (25-75%) pretreatment Hgb was 13.6 (12.2-13.5) g/dL. Hgb was 13 g/dL or higher in 105 patients and less than 13 g/dL in 54 patients. Primary tumor sites included oropharynx (43%), hypopharynx/larynx (36%), oral cavity (9%), and nasopharynx (6%). Seventy-eight percent of the patients with Hgb 13 g/dL or higher and 92% of the patients with Hgb less than 13 g/dL had a primary tumor stage of T3 or T4 (p = 0.01). Node-positive disease was present in 74 of 105 (70%) of patients with Hgb 13 g/dL or higher patients and in 36/54 (67%) of patients with Hgb less than 13 g/dL patients. Median follow-up of surviving patients was 42 months (range, 4-128 months). Five-year FFS was 75% for patients with Hgb 13 g/dL or higher vs. 50% for patients with Hgb less than 13 g/dL had a (p < 0.01). A total of 49 failures occurred in both patient cohorts. The median (25-75%) decrease in Hgb during RT/CCT was 2.2 (1.3-3.1) g/dL, both in patients who failed and in those who remained disease-free. Conclusion: Pretreatment Hgb less than 13 g/dL is correlated with adverse outcomes in advanced HNC patients treated with RT/CCT. Whether anemia actually causes poor outcomes remains unknown. The therapeutic effect of anemia correction is being evaluated in prospective trials.« less

Hybrid diffusion-P3 equation in N-layered turbid media: steady-state domain.

PubMed

Shi, Zhenzhi; Zhao, Huijuan; Xu, Kexin

2011-10-01

This paper discusses light propagation in N-layered turbid media. The hybrid diffusion-P3 equation is solved for an N-layered finite or infinite turbid medium in the steady-state domain for one point source using the extrapolated boundary condition. The Fourier transform formalism is applied to derive the analytical solutions of the fluence rate in Fourier space. Two inverse Fourier transform methods are developed to calculate the fluence rate in real space. In addition, the solutions of the hybrid diffusion-P3 equation are compared to the solutions of the diffusion equation and the Monte Carlo simulation. For the case of small absorption coefficients, the solutions of the N-layered diffusion equation and hybrid diffusion-P3 equation are almost equivalent and are in agreement with the Monte Carlo simulation. For the case of large absorption coefficients, the model of the hybrid diffusion-P3 equation is more precise than that of the diffusion equation. In conclusion, the model of the hybrid diffusion-P3 equation can replace the diffusion equation for modeling light propagation in the N-layered turbid media for a wide range of absorption coefficients.

Contextual Approach with Guided Discovery Learning and Brain Based Learning in Geometry Learning

NASA Astrophysics Data System (ADS)

Kartikaningtyas, V.; Kusmayadi, T. A.; Riyadi

2017-09-01

The aim of this study was to combine the contextual approach with Guided Discovery Learning (GDL) and Brain Based Learning (BBL) in geometry learning of junior high school. Furthermore, this study analysed the effect of contextual approach with GDL and BBL in geometry learning. GDL-contextual and BBL-contextual was built from the steps of GDL and BBL that combined with the principles of contextual approach. To validate the models, it uses quasi experiment which used two experiment groups. The sample had been chosen by stratified cluster random sampling. The sample was 150 students of grade 8th in junior high school. The data were collected through the student’s mathematics achievement test that given after the treatment of each group. The data analysed by using one way ANOVA with different cell. The result shows that GDL-contextual has not different effect than BBL-contextual on mathematics achievement in geometry learning. It means both the two models could be used in mathematics learning as the innovative way in geometry learning.

Gradient boride layers formed by diffusion carburizing and laser boriding

NASA Astrophysics Data System (ADS)

Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.

2015-04-01

Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was sufficient, the diffusion borocarburized layer showed a better cohesion.

The association between graduated driver licensing laws and travel behaviors among adolescents: an analysis of US National Household Travel Surveys.

PubMed

Zhu, Motao; Cummings, Peter; Zhao, Songzhu; Rice, Thomas

2016-07-27

Young novice drivers have crash rates higher than any other age group. To address this problem, graduated driver licensing (GDL) laws have been implemented in the United States to require an extended learner permit phase, and create night time driving or passenger restrictions for adolescent drivers. GDL allows adolescents to gain experience driving under low-risk conditions with the aim of reducing crashes. The restricted driving might increase riding with parents or on buses, which might be safer, or walking or biking, which might be more dangerous. We examined whether GDL increases non-driver travels, and whether it reduces total travels combining drivers and non-drivers. We used data from the US National Household Travel Survey for the years 1995-1996, 2001-2002, and 2008-2009 to estimate the adjusted ratio for the number of trips and trip kilometers made by persons exposed to a GDL law, compared with those not exposed. Adolescents aged 16 years had fewer trips and kilometers as drivers when exposed to a GDL law: ratio 0.84 (95 % confidence interval (CI) 0.71, 1.00) for trips; 0.79 (0.63, 0.98) for kilometers. For adolescents aged 17 years, the trip ratio was 0.94 (0.83, 1.07) and the kilometers ratio 0.80 (0.63, 1.03). There was little association between GDL laws and trips or kilometers traveled by other methods: ratio 1.03 for trips and 1.00 for kilometers for age 16 years, 0.94 for trips and 1.07 for kilometers for age 17. If these associations are causal, GDL laws reduced driving kilometers by about 20 % for 16 and 17 year olds, and reduced the number of driving trips by 16 % among 16 year olds. GDL laws showed little relationship with trips by other methods.

A 1-year trial of repeated high-dose intravenous iron isomaltoside 1000 to maintain stable hemoglobin levels in inflammatory bowel disease

PubMed Central

Reinisch, Walter; Altorjay, Istvan; Zsigmond, Ferenc; Primas, Christian; Vogelsang, Harald; Novacek, Gottfried; Reinisch, Sieglinde; Thomsen, Lars L.

2015-01-01

Abstract Objective. Iron isomaltoside 1000 (Monofer®) is a high-dose intravenous (IV) iron, which in a recent 8 weeks trial in inflammatory bowel disease (IBD) subjects with iron deficiency anemia (IDA) demonstrated good tolerability and efficacy. The present trial is an extension to this trial, which evaluates the need for additional high IV iron doses to maintain a stable hemoglobin (Hb) ≥12.0 g/dl. Material and methods. This was a prospective, open-label, 12 months trial of European IBD subjects willing to participate after completing the lead-in trial. Subjects were allowed re-dosing with 500–2000 mg single doses of iron isomaltoside 1000 infused over ∼15 min at 3 months intervals depending on a predefined algorithm. Outcome measures included Hb, safety parameters and need for additional iron dosing. Results. A total of 39 subjects were enrolled of which 34 subjects required re-dosing with a median cumulative 1-year dose of 1.8 g (mean cumulative dose 2.2 g). The mean (SD) Hb was 12.3 (1.5) g/dl at baseline, 12.8 (1.6) g/dl at 3 months, 12.8 (1.6) g/dl at 6 months, 12.9 (1.4) g/dl at 9 months and 12.9 (1.6) g/dl at 12 months. Seventy-four percent of subjects who had an Hb ≥12.0 g/dl at baseline were able to maintain Hb ≥12.0 g/dl till the end of the trial at 12 months. Nonserious probably related hypersensitivity reactions without significant hypotension were reported at the beginning of the infusion in two subjects, who recovered without sequelae. Conclusion. Repeated treatment of iron deficiency with iron isomaltoside 1000 could avoid episodes of IDA without major safety issues. PMID:25900645

The silent burden of anaemia in Tanzanian children: a community-based study.

PubMed Central

Schellenberg, D.; Schellenberg, J. R. M. Armstrong; Mushi, A.; Savigny, D. de; Mgalula, L.; Mbuya, C.; Victora, C. G.

2003-01-01

OBJECTIVE: To document the prevalence, age-distribution, and risk factors for anaemia in Tanzanian children less than 5 years old, thereby assisting in the development of effective strategies for controlling anaemia. METHODS: Cluster sampling was used to identify 2417 households at random from four contiguous districts in south-eastern United Republic of Tanzania in mid-1999. Data on various social and medical parameters were collected and analysed. FINDINGS: Blood haemoglobin concentrations (Hb) were available for 1979 of the 2131 (93%) children identified and ranged from 1.7 to 18.6 g/dl. Overall, 87% (1722) of children had an Hb <11 g/dl, 39% (775) had an Hb <8 g/dl and 3% (65) had an Hb <5 g/dl. The highest prevalence of anaemia of all three levels was in children aged 6-11 months, of whom 10% (22/226) had an Hb <5 g/dl. However, the prevalence of anaemia was already high in children aged 1-5 months (85% had an Hb <11 g/dl, 42% had an Hb <8 g/dl, and 6% had an Hb <5 g/dl). Anaemia was usually asymptomatic and when symptoms arose they were nonspecific and rarely identified as a serious illness by the care provider. A recent history of treatment with antimalarials and iron was rare. Compliance with vaccinations delivered through the Expanded Programme of Immunization (EPI) was 82% and was not associated with risk of anaemia. CONCLUSION: Anaemia is extremely common in south-eastern United Republic of Tanzania, even in very young infants. Further implementation of the Integrated Management of Childhood Illness algorithm should improve the case management of anaemia. However, the asymptomatic nature of most episodes of anaemia highlights the need for preventive strategies. The EPI has good coverage of the target population and it may be an appropriate channel for delivering tools for controlling anaemia and malaria. PMID:14576890

Modeling solute clustering in the diffusion layer around a growing crystal.

PubMed

Shiau, Lie-Ding; Lu, Yung-Fang

2009-03-07

The mechanism of crystal growth from solution is often thought to consist of a mass transfer diffusion step followed by a surface reaction step. Solute molecules might form clusters in the diffusion step before incorporating into the crystal lattice. A model is proposed in this work to simulate the evolution of the cluster size distribution due to the simultaneous aggregation and breakage of solute molecules in the diffusion layer around a growing crystal in the stirred solution. The crystallization of KAl(SO(4))(2)12H(2)O from aqueous solution is studied to illustrate the effect of supersaturation and diffusion layer thickness on the number-average degree of clustering and the size distribution of solute clusters in the diffusion layer.

Chromium oxide as a metal diffusion barrier layer: An x-ray absorption fine structure spectroscopy study

NASA Astrophysics Data System (ADS)

Ahamad Mohiddon, Md.; Lakshun Naidu, K.; Ghanashyam Krishna, M.; Dalba, G.; Ahmed, S. I.; Rocca, F.

2014-01-01

The interaction at the interface between chromium and amorphous Silicon (a-Si) films in the presence of a sandwich layer of chromium oxide is investigated using X-ray absorption fine structure (XAFS) spectroscopy. The oxidized interface was created, in situ, prior to the deposition of a 400 nm tick a-Si layer over a 50 nm tick Cr layer. The entire stack of substrate/metallic Cr/Cr2O3/a-Si was then annealed at temperatures from 300 up to 700 °C. Analysis of the near edge and extended regions of each XAFS spectrum shows that only a small fraction of Cr is able to diffuse through the oxide layer up to 500 °C, while the remaining fraction is buried under the oxide layer in the form of metallic Cr. At higher temperatures, diffusion through the oxide layer is enhanced and the diffused metallic Cr reacts with a-Si to form CrSi2. At 700 °C, the film contains Cr2O3 and CrSi2 without evidence of unreacted metallic Cr. The activation energy and diffusion coefficient of Cr are quantitatively determined in the two temperature regions, one where the oxide acts as diffusion barrier and another where it is transparent to Cr diffusion. It is thus demonstrated that chromium oxide can be used as a diffusion barrier to prevent metal diffusion into a-Si.

Estimating diffusivity from the mixed layer heat and salt balances in the North Pacific

NASA Astrophysics Data System (ADS)

Cronin, M. F.; Pelland, N.; Emerson, S. R.; Crawford, W. R.

2015-12-01

Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20-m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1×10-4 m2/s during summer, increasing to ~3×10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivity are found based upon the mixed layer heat budget: ~ 3×10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification.

Estimating diffusivity from the mixed layer heat and salt balances in the North Pacific

NASA Astrophysics Data System (ADS)

Cronin, Meghan F.; Pelland, Noel A.; Emerson, Steven R.; Crawford, William R.

2015-11-01

Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20 m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1 × 10-4 m2/s during summer, increasing to ˜3 × 10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivities are found based upon the mixed layer heat budget: ˜ 3 × 10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification.

Interferometric measurements of a dendritic growth front solutal diffusion layer

NASA Technical Reports Server (NTRS)

Hopkins, John A.; Mccay, T. D.; Mccay, Mary H.

1991-01-01

An experimental study was undertaken to measure solutal distributions in the diffusion layer produced during the vertical directional solidification (VDS) of an ammonium chloride - water (NH4Cl-H2O) solution. Interferometry was used to obtain concentration measurements in the 1-2 millimeter region defining the diffusion layer. These measurements were fitted to an exponential form to extract the characteristic diffusion parameter for various times after the start of solidification. The diffusion parameters are within the limits predicted by steady state theory and suggest that the effective solutal diffusivity is increasing as solidification progresses.

How thin barrier metal can be used to prevent Co diffusion in the modern integrated circuits?

NASA Astrophysics Data System (ADS)

Dixit, Hemant; Konar, Aniruddha; Pandey, Rajan; Ethirajan, Tamilmani

2017-11-01

In modern integrated circuits (ICs), billions of transistors are connected to each other via thin metal layers (e.g. copper, cobalt, etc) known as interconnects. At elevated process temperatures, inter-diffusion of atomic species can occur among these metal layers, causing sub-optimal performance of interconnects, which may lead to the failure of an IC. Thus, typically a thin barrier metal layer is used to prevent the inter-diffusion of atomic species within interconnects. For ICs with sub-10 nm transistors (10 nm technology node), the design rule (thickness scaling) demands the thinnest possible barrier layer. Therefore, here we investigate the critical thickness of a titanium-nitride (TiN) barrier that can prevent the cobalt diffusion using multi-scale modeling and simulations. First, we compute the Co diffusion barrier in crystalline and amorphous TiN with the nudged elastic band method within first-principles density functional theory simulations. Later, using the calculated activation energy barriers, we quantify the Co diffusion length in the TiN metal layer with the help of kinetic Monte Carlo simulations. Such a multi-scale modelling approach yields an exact critical thickness of the metal layer sufficient to prevent the Co diffusion in IC interconnects. We obtain a diffusion length of a maximum of 2 nm for a typical process of thermal annealing at 400 °C for 30 min. Our study thus provides useful physical insights for the Co diffusion in the TiN layer and further quantifies the critical thickness (~2 nm) to which the metal barrier layer can be thinned down for sub-10 nm ICs.

Parameterization of large-scale turbulent diffusion in the presence of both well-mixed and weakly mixed patchy layers

NASA Astrophysics Data System (ADS)

Osman, M. K.; Hocking, W. K.; Tarasick, D. W.

2016-06-01

Vertical diffusion and mixing of tracers in the upper troposphere and lower stratosphere (UTLS) are not uniform, but primarily occur due to patches of turbulence that are intermittent in time and space. The effective diffusivity of regions of patchy turbulence is related to statistical parameters describing the morphology of turbulent events, such as lifetime, number, width, depth and local diffusivity (i.e., diffusivity within the turbulent patch) of the patches. While this has been recognized in the literature, the primary focus has been on well-mixed layers, with few exceptions. In such cases the local diffusivity is irrelevant, but this is not true for weakly and partially mixed layers. Here, we use both theory and numerical simulations to consider the impact of intermediate and weakly mixed layers, in addition to well-mixed layers. Previous approaches have considered only one dimension (vertical), and only a small number of layers (often one at each time step), and have examined mixing of constituents. We consider a two-dimensional case, with multiple layers (10 and more, up to hundreds and even thousands), having well-defined, non-infinite, lengths and depths. We then provide new formulas to describe cases involving well-mixed layers which supersede earlier expressions. In addition, we look in detail at layers that are not well mixed, and, as an interesting variation on previous models, our procedure is based on tracking the dispersion of individual particles, which is quite different to the earlier approaches which looked at mixing of constituents. We develop an expression which allows determination of the degree of mixing, and show that layers used in some previous models were in fact not well mixed and so produced erroneous results. We then develop a generalized model based on two dimensional random-walk theory employing Rayleigh distributions which allows us to develop a universal formula for diffusion rates for multiple two-dimensional layers with general degrees of mixing. We show that it is the largest, most vigorous and less common turbulent layers that make the major contribution to global diffusion. Finally, we make estimates of global-scale diffusion coefficients in the lower stratosphere and upper troposphere. For the lower stratosphere, κeff ≈ 2x10-2 m2 s-1, assuming no other processes contribute to large-scale diffusion.

TiO2 as diffusion barrier at Co/Alq3 interface studied by x-ray standing wave technique

NASA Astrophysics Data System (ADS)

Phatak Londhe, Vaishali; Gupta, A.; Ponpandian, N.; Kumar, D.; Reddy, V. R.

2018-06-01

Nano-scale diffusion at the interfaces in organic spin valve thin films plays a vital role in controlling the performance of magneto-electronic devices. In the present work, it is shown that a thin layer of titanium dioxide at the interface of Co/Alq3 can act as a good diffusion barrier. The buried interfaces of Co/Alq3/Co organic spin valve thin film has been studied using x-ray standing waves technique. A planar waveguide is formed with Alq3 layer forming the cavity and Co layers as the walls of the waveguide. Precise information about diffusion of Co into Alq3 is obtained through excitation of the waveguide modes. It is found that the top Co layer diffuses deep into the Alq3 resulting in incorporation of 3.1% Co in the Alq3 layer. Insertion of a 1.7 nm thick barrier layer of TiO2 at Co/Alq3 interface results in a drastic reduction in the diffusion of Co into Alq3 to a value of only 0.4%. This suggests a better performance of organic spin valve with diffusion barrier of TiO2.

Plasma electrophoretogram in feline immunodeficiency virus (FIV) and/or feline leukaemia virus (FeLV) infections.

PubMed

Miró, G; Doménech, A; Escolar, E; Collado, V M; Tejerizo, G; De Las Heras, A; Gómez-Lucía, E

2007-05-01

The electrophoretogram of 89 cats, including those infected by feline immunodeficiency virus (FIV+), feline leukaemia virus (FeLV+) and non-infected, showed statistically significant differences in several of the fractions. FIV+ cats had very high protein values (mean, 8.10 g/dl), mostly because of hypergammaglobulinemia (mean, 2.81 g/dl) as compared with non-infected animals and FeLV+. In addition, in these FIV+ animals, the albumin/globulins ratio (A/G) was very low (mean, 0.72). Statistically significant differences in A/G and alpha2-globulin fraction were observed in FeLV+ group (A/G mean, 0.88 +/- 0.08; alpha2-globulin, mean, 0.84 +/- 0.07 g/dl) when compared with non-infected group (A/G mean, 1.06 +/- 0.08; alpha2-globulin mean, 0.68 +/- 0.04 g/dl). The alpha1-globulin fraction was higher in double infected animals (FIV and FeLV positive, F-F) (3.55 g/dl), than in FeLV+ or FIV+ cats (3.10 and 3.07 g/dl respectively), but no statistical conclusions may be drawn from this fact because of the low number of F-F animals. This technique may help to assess the initial clinical status of retrovirus-infected cats, and the clinical course of these chronic diseases, specifically during and after suitable therapy.

Systematic review and meta-analysis of method comparison studies of Masimo pulse co-oximeters (Radical-7™ or Pronto-7™) and HemoCue® absorption spectrometers (B-Hemoglobin or 201+) with laboratory haemoglobin estimation.

PubMed

Hiscock, R; Kumar, D; Simmons, S W

2015-05-01

We assessed agreement in haemoglobin measurement between Masimo pulse co-oximeters (Rad-7™ and Pronto-7™) and HemoCue® photometers (201+ or B-Hemoglobin) with laboratory-based determination and identified 39 relevant studies (2915 patients in Masimo group and 3084 patients in HemoCue group). In the Masimo group, the overall mean difference was -0.03 g/dl (95% prediction interval -0.30 to 0.23) and 95% limits of agreement -3.0 to 2.9 g/dl compared to 0.08 g/dl (95% prediction interval -0.04 to 0.20) and 95% limits of agreement -1.3 to 1.4 g/dl in the HemoCue group. Only B-Hemoglobin exhibited bias (0.53, 95% prediction interval 0.27 to 0.78). The overall standard deviation of difference was larger (1.42 g/dl versus 0.64 g/dl) for Masimo pulse co-oximeters compared to HemoCue photometers. Masimo devices and HemoCue 201+ both provide an unbiased, pooled estimate of laboratory haemoglobin. However, Masimo devices have lower precision and wider 95% limits of agreement than HemoCue devices. Clinicians should carefully consider these limits of agreement before basing transfusion or other clinical decisions on these point-of-care measurements alone.

Effects of convergent diffusion and charge transfer kinetics on the diffusion layer thickness of spherical micro- and nanoelectrodes.

PubMed

Molina, A; Laborda, E; González, J; Compton, R G

2013-05-21

Nuances of the linear diffusion layer approximation are examined for slow charge transfer reactions at (hemi)spherical micro- and nanoelectrodes. This approximation is widely employed in Electrochemistry to evaluate the extent of electrolyte solution perturbed by the electrode process, which is essential to the understanding of the effects arising from thin-layer diffusion, convergent diffusion, convection, coupled chemical reactions and the double layer. The concept was well established for fast charge transfer processes at macroelectrodes, but remains unclear under other conditions such that a thorough assessment of its meaning was necessary. In a previous publication [A. Molina, J. González, E. Laborda and R. G. Compton, Phys. Chem. Chem. Phys., 2013, 15, 2381-2388] we shed some light on the influence of the reversibility degree. In the present work, the meaning of the diffusion layer thickness is investigated when very small electrodes are employed and so the contribution of convergent diffusion to the mass transport is very important. An analytical expression is given to calculate the linear diffusion layer thickness at (hemi)spherical electrodes and its behaviour is studied for a wide range of conditions of reversibility (from reversible to fully-irreversible processes) and electrode size (from macro- to nano-electrodes). Rigorous analytical solutions are deduced for true concentration profiles, surface concentrations, linear diffusion layer thickness and current densities when a potential pulse is applied at (hemi)spherical electrodes. The expressions for the magnitudes mentioned above are valid for electrodes of any size (including (hemi)spherical nanoelectrodes) and for any degree of reversibility, provided that mass transport occurs exclusively via diffusion. The variation of the above with the electrode size, applied potential and charge transfer kinetics is studied.

Light diffusion in N-layered turbid media: steady-state domain.

PubMed

Liemert, André; Kienle, Alwin

2010-01-01

We deal with light diffusion in N-layered turbid media. The steady-state diffusion equation is solved for N-layered turbid media having a finite or an infinitely thick N'th layer. Different refractive indices are considered in the layers. The Fourier transform formalism is applied to derive analytical solutions of the fluence rate in Fourier space. The inverse Fourier transform is calculated using four different methods to test their performance and accuracy. Further, to avoid numerical errors, approximate formulas in Fourier space are derived. Fast solutions for calculation of the spatially resolved reflectance and transmittance from the N-layered turbid media ( approximately 10 ms) with small relative differences (<10(-7)) are found. Additionally, the solutions of the diffusion equation are compared to Monte Carlo simulations for turbid media having up to 20 layers.

Effects of oxygen-inserted layers on diffusion of boron, phosphorus, and arsenic in silicon for ultra-shallow junction formation

NASA Astrophysics Data System (ADS)

Zhang, X.; Connelly, D.; Takeuchi, H.; Hytha, M.; Mears, R. J.; Rubin, L. M.; Liu, T.-J. K.

2018-03-01

The effects of oxygen-inserted (OI) layers on the diffusion of boron (B), phosphorus (P), and arsenic (As) in silicon (Si) are investigated, for ultra-shallow junction formation by high-dose ion implantation followed by rapid thermal annealing. The projected range (Rp) of the implanted dopants is shallower than the depth of the OI layers. Secondary ion mass spectrometry is used to compare the dopant profiles in silicon samples that have OI layers against the dopant profiles in control samples that do not have OI layers. Diffusion is found to be substantially retarded by the OI layers for B and P, and less for As, providing shallower junction depth. The experimental results suggest that the OI layers serve to block the diffusion of Si self-interstitials and thereby effectively reduce interstitial-aided diffusion beyond the depth of the OI layers. The OI layers also help to retain more dopants within the Si, which technology computer-aided design simulations indicate to be beneficial for achieving shallower junctions with lower sheet resistance to enable further miniaturization of planar metal-oxide-semiconductor field-effect transistors for improved integrated-circuit performance and cost per function.

Negative-Pressure Wound Therapy: A Hemostatic Adjunct for Control of Coagulopathic Hemorrhage in Large Soft Tissue Wounds

DTIC Science & Technology

2012-01-01

65.6 (2.05) 64.6 (1.7) 69.4 (2.6) 63.8 (0.8) 0.20 Hemoglobin level , g/dL 10.4 (0.12) 4.6 (0.23) 4.3 (0.18) 4.5 (0.17) 4.4 (0.13) 0.50 Hematocrit ...and level of negative pressure, wound filter, and wound contact layer. This modality creates a wound environment of subat- mospheric pressure (j50 to...inhibitory factors such as collagenases and inflammatory cytokines, (2) decreasing the level of bacteria, (3) improving blood flow in the wound bed and

Guided discovery learning in geometry learning

NASA Astrophysics Data System (ADS)

Khasanah, V. N.; Usodo, B.; Subanti, S.

2018-03-01

Geometry is a part of the mathematics that must be learned in school. The purpose of this research was to determine the effect of Guided Discovery Learning (GDL) toward geometry learning achievement. This research had conducted at junior high school in Sukoharjo on academic years 2016/2017. Data collection was done based on student’s work test and documentation. Hypothesis testing used two ways analysis of variance (ANOVA) with unequal cells. The results of this research that GDL gave positive effect towards mathematics learning achievement. GDL gave better mathematics learning achievement than direct learning. There was no difference of mathematics learning achievement between male and female. There was no an interaction between sex differences and learning models toward student’s mathematics learning achievement. GDL can be used to improve students’ mathematics learning achievement in geometry.

Double-diffusive layers in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Carniel, Sandro; Sclavo, Mauro; Kantha, Lakshmi; Prandke, Hartmut

2008-01-01

A microstructure profiler was deployed to make turbulence measurements in the upper layers of the southern Adriatic Sea in the Mediterranean during the Naval Research Laboratory (NRL) DART06A (Dynamics of the Adriatic in Real Time) winter cruise in March 2006. Measurements in the Po river plume along the Italian coast near the Gargano promontory displayed classic double-diffusive layers and staircase structures resulting from the relatively colder and fresher wintertime Po river outflow water masses overlying warmer and more saline water masses from the Adriatic Sea. We report here on the water mass and turbulence structure measurements made both in the double-diffusive interfaces and the adjoining mixed layers in the water columns undergoing double-diffusive convection (DDC). This dataset augments the relatively sparse observations available hitherto on the diffusive layer type of DDC. Measured turbulence diffusivities are consistent with those from earlier theoretical and experimental formulations, suggesting that the wintertime Po river plume is a convenient and easily accessible place to study double diffusive convective processes of importance to mixing in the interior of many regions of the global oceans.

Status of GDL - GNU Data Language

NASA Astrophysics Data System (ADS)

Coulais, A.; Schellens, M.; Gales, J.; Arabas, S.; Boquien, M.; Chanial, P.; Messmer, P.; Fillmore, D.; Poplawski, O.; Maret, S.; Marchal, G.; Galmiche, N.; Mermet, T.

2010-12-01

Gnu Data Language (GDL) is an open-source interpreted language aimed at numerical data analysis and visualisation. It is a free implementation of the Interactive Data Language (IDL) widely used in Astronomy. GDL has a full syntax compatibility with IDL, and includes a large set of library routines targeting advanced matrix manipulation, plotting, time-series and image analysis, mapping, and data input/output including numerous scientific data formats. We will present the current status of the project, the key accomplishments, and the weaknesses - areas where contributions are welcome!

Role of boundary layer diffusion in vapor deposition growth of chalcogenide nanosheets: the case of GeS.

PubMed

Li, Chun; Huang, Liang; Snigdha, Gayatri Pongur; Yu, Yifei; Cao, Linyou

2012-10-23

We report a synthesis of single-crystalline two-dimensional GeS nanosheets using vapor deposition processes and show that the growth behavior of the nanosheet is substantially different from those of other nanomaterials and thin films grown by vapor depositions. The nanosheet growth is subject to strong influences of the diffusion of source materials through the boundary layer of gas flows. This boundary layer diffusion is found to be the rate-determining step of the growth under typical experimental conditions, evidenced by a substantial dependence of the nanosheet's size on diffusion fluxes. We also find that high-quality GeS nanosheets can grow only in the diffusion-limited regime, as the crystalline quality substantially deteriorates when the rate-determining step is changed away from the boundary layer diffusion. We establish a simple model to analyze the diffusion dynamics in experiments. Our analysis uncovers an intuitive correlation of diffusion flux with the partial pressure of source materials, the flow rate of carrier gas, and the total pressure in the synthetic setup. The observed significant role of boundary layer diffusions in the growth is unique for nanosheets. It may be correlated with the high growth rate of GeS nanosheets, ~3-5 μm/min, which is 1 order of magnitude higher than other nanomaterials (such as nanowires) and thin films. This fundamental understanding of the effect of boundary layer diffusions may generally apply to other chalcogenide nanosheets that can grow rapidly. It can provide useful guidance for the development of general paradigms to control the synthesis of nanosheets.

Characteristic time scales for diffusion processes through layers and across interfaces

NASA Astrophysics Data System (ADS)

Carr, Elliot J.

2018-04-01

This paper presents a simple tool for characterizing the time scale for continuum diffusion processes through layered heterogeneous media. This mathematical problem is motivated by several practical applications such as heat transport in composite materials, flow in layered aquifers, and drug diffusion through the layers of the skin. In such processes, the physical properties of the medium vary across layers and internal boundary conditions apply at the interfaces between adjacent layers. To characterize the time scale, we use the concept of mean action time, which provides the mean time scale at each position in the medium by utilizing the fact that the transition of the transient solution of the underlying partial differential equation model, from initial state to steady state, can be represented as a cumulative distribution function of time. Using this concept, we define the characteristic time scale for a multilayer diffusion process as the maximum value of the mean action time across the layered medium. For given initial conditions and internal and external boundary conditions, this approach leads to simple algebraic expressions for characterizing the time scale that depend on the physical and geometrical properties of the medium, such as the diffusivities and lengths of the layers. Numerical examples demonstrate that these expressions provide useful insight into explaining how the parameters in the model affect the time it takes for a multilayer diffusion process to reach steady state.

Characteristic time scales for diffusion processes through layers and across interfaces.

PubMed

Carr, Elliot J

2018-04-01

This paper presents a simple tool for characterizing the time scale for continuum diffusion processes through layered heterogeneous media. This mathematical problem is motivated by several practical applications such as heat transport in composite materials, flow in layered aquifers, and drug diffusion through the layers of the skin. In such processes, the physical properties of the medium vary across layers and internal boundary conditions apply at the interfaces between adjacent layers. To characterize the time scale, we use the concept of mean action time, which provides the mean time scale at each position in the medium by utilizing the fact that the transition of the transient solution of the underlying partial differential equation model, from initial state to steady state, can be represented as a cumulative distribution function of time. Using this concept, we define the characteristic time scale for a multilayer diffusion process as the maximum value of the mean action time across the layered medium. For given initial conditions and internal and external boundary conditions, this approach leads to simple algebraic expressions for characterizing the time scale that depend on the physical and geometrical properties of the medium, such as the diffusivities and lengths of the layers. Numerical examples demonstrate that these expressions provide useful insight into explaining how the parameters in the model affect the time it takes for a multilayer diffusion process to reach steady state.

Hematologic and serum biochemical reference intervals for Florida panthers.

USGS Publications Warehouse

Dunbar, M.R.; Nol, P.; Linda, S.B.

1997-01-01

Ninety-four blood samples were collected from 48 (29 males and 19 females) free-ranging Florida panthers (Felis concolor coryi) captured in southern Florida (USA) from 1983 to 1994 for routine hematological and serum biochemical analysis. Florida panthers in the northern portion of their range had significantly higher red blood cell (mean +/- SD = 7.923 x 10(6) +/- 0.854 x 10(6)/microliter), hemoglobin (12.53 +/- 1.66 g/dl), and packed cell volume (36.97 +/- 4.27%) values compared to those of panthers localized in more southern parts of Florida (7.148 x 10(6) +/- 1.045 x 10(6)/microliter, 11.60 +/- 1.62 g/dl, and 34.82 +/- 5.99%, respectively). Adults had significantly higher mean serum total protein (7.50 +/- 0.59 g/dl) and packed cell volume (36.90 +/- 4.97%) values than juveniles (6.88 +/- 0.49 g/dl and 34.54 +/- 5.30%). However, mean serum albumin concentrations were significantly higher in juveniles (3.80 +/- 0.26 g/dl) when compared to adult values (3.58 +/- 0.26 g/dl). Mean serum calcium concentrations were significantly higher in juveniles (10.33 +/- 0.39 mg/dl) than in adults (9.66 +/- 0.45 mg/dl). Additionally, mean serum iron concentrations were significantly higher in those panthers of intergrade genetic stock compared to values in those of authentic genetic stock (105.6 +/- 72.1 micrograms/dl versus 59.3 +/- 19.7 micrograms/dl, respectively).

Transfusion-Free Cardiopulmonary Bypass in Jehovah’s Witness Patients Weighing Less Than 5 kg

PubMed Central

Boettcher, Wolfgang; Merkle, Frank; Huebler, Michael; Koster, Andreas; Schulz, Fritz; Kopitz, Michael; Kuppe, Hermann; Lange, Peter; Hetzer, Roland

2005-01-01

Abstract: Performing cardiac surgery on pediatric Jehovah’s Witness patients is a great challenge for the surgical team and especially for the perfusionist. Jehovah’s Witnesses reject blood transfusions on the grounds of their literal interpretation of passages of the Bible. In accordance with this belief, Jehovah’s Witnesses feel that it is also forbidden to retransfuse autologous blood that has been separated from their own circulatory system. We report the use of cardiopulmonary bypass (CPB) during open-heart surgery in three infants with a body weight of 4.5 kg, 3.5 kg, and 3.1 kg, respectively, without transfusion of blood components. A small-volume CPB circuit with a priming volume of 200 mL, including the arterial line filter, was designed to decrease the degree of hemodilution. A dedicated pediatric heart lung machine console with remote pump heads and intensive blood conservation efforts allowed the operation without the use of donor blood. The CPB circuits were primed with crystalloid solution only. The procedures were performed in normothermia or in moderate hypothermia. Pre-CPB hemoglobin levels were 10.8 g/dL, 10.6 g/dL, and 8.5 g/dL. The hemoglobin concentrations measured during CPB ranged from 5.9 to 6.5 g/dL, 6.4 to 6.8 g/dL, and 5.5 to 5.9 g/dL, respectively. The patients did not receive any blood or blood products during their entire hospital stay. PMID:16350381

Diffusion studies and critical current in superconducting Nb-Ti-Ta artificial pinning center wire

NASA Astrophysics Data System (ADS)

Bormio-Nunes, C.; Gomes, P. M. N.; Tirelli, M. A.; Ghivelder, L.

2005-08-01

The diffusion between Nb-20%Ta (wt %) and pure Ti is studied at temperatures of 973, 1023, and 1073K, for duration times among 25 and 121h in an artificial pinning center (APC) wire composed of a Ti core surrounded by a Nb-20%Ta layer. The produced diffusion layer is a ternary alloy with superconducting properties, such as critical field Bc2 and critical current density JC, which intrinsically depend on the layer composition. Measurements of layer morphology and composition were performed, and the results show a preferential diffusion of Nb and Ta into Ti. There is a slight diffusion of Ti into Nb through grain boundaries. The presence of Ta also slows down the diffusion of Nb in Ti if compared to the couple formed by pure Nb and Ti. Regarding the mechanical properties of the composite wire, the use of lower temperatures to form the ternary phase is desirable in order to avoid a larger portion of the diffusion layer rich in Ti that favorites α-Ti precipitations that are detrimental to the wire ductility. The best JC value was obtained for the sample heat treated at 973K. The improvement of the flux-line pinning was associated with a sharp change of the diffusion layer composition rather than pinning by normal layer interfaces, suggesting a new source of pinning in this kind of material. Nb-Ti-Ta ternary alloys have the potential to be used in superconducting magnets when fields above 12T are required.

An experimental study of the role of particle diffusive convection on the residence time of volcanic ash clouds

NASA Astrophysics Data System (ADS)

Deal, E.; Carazzo, G.; Jellinek, M.

2013-12-01

The longevity of volcanic ash clouds generated by explosive volcanic plumes is difficult to predict. Diffusive convective instabilities leading to the production of internal layering are known to affect the stability and longevity of these clouds, but the detailed mechanisms controlling particle dynamics and sedimentation are poorly understood. We present results from a series of analog experiments reproducing diffusive convection in a 2D (Hele-Shaw) geometry, which allow us to constrain conditions for layer formation, sedimentation regime and cloud residence time as a function of only the source conditions. We inject a turbulent particle-laden jet sideways into a tank containing a basal layer of salt water and an upper layer of fresh water, which ultimately spreads as a gravity current. After the injection is stopped, particles in suspension settle through the cloud to form particle boundary layers (PBL) at the cloud base. We vary the initial particle concentration of the plume and the injection velocity over a wide range of conditions to identify and characterize distinct regimes of sedimentation. Our experiments show that convective instabilities driven as a result of differing diffusivities of salt and particles lead to periodic layering over a wide range of conditions expected in nature. The flux of particles from layered clouds and the thicknesses of the layers are understood using classical theory for double diffusive convection adjusted for the hydrodynamic diffusion of particles. Although diffusive convection increases sedimentation rates for the smallest particles (<30 μm) its overall effect is to extend the cloud residence time to several hours by maintaining larger particles in suspension within the layers, which is several orders of magnitude longer than expected when considering individual settling rates.

How multiple social networks affect user awareness: The information diffusion process in multiplex networks

NASA Astrophysics Data System (ADS)

Li, Weihua; Tang, Shaoting; Fang, Wenyi; Guo, Quantong; Zhang, Xiao; Zheng, Zhiming

2015-10-01

The information diffusion process in single complex networks has been extensively studied, especially for modeling the spreading activities in online social networks. However, individuals usually use multiple social networks at the same time, and can share the information they have learned from one social network to another. This phenomenon gives rise to a new diffusion process on multiplex networks with more than one network layer. In this paper we account for this multiplex network spreading by proposing a model of information diffusion in two-layer multiplex networks. We develop a theoretical framework using bond percolation and cascading failure to describe the intralayer and interlayer diffusion. This allows us to obtain analytical solutions for the fraction of informed individuals as a function of transmissibility T and the interlayer transmission rate θ . Simulation results show that interaction between layers can greatly enhance the information diffusion process. And explosive diffusion can occur even if the transmissibility of the focal layer is under the critical threshold, due to interlayer transmission.

Analysis of Al diffusion processes in TiN barrier layers for the application in silicon solar cell metallization

NASA Astrophysics Data System (ADS)

Kumm, J.; Samadi, H.; Chacko, R. V.; Hartmann, P.; Wolf, A.

2016-07-01

An evaporated Al layer is known as an excellent rear metallization for highly efficient solar cells, but suffers from incompatibility with a common solder process. To enable solar cell-interconnection and module integration, in this work the Al layer is complemented with a solder stack of TiN/Ti/Ag or TiN/NiV/Ag, in which the TiN layer acts as an Al diffusion barrier. X-ray photoelectron spectroscopy measurements prove that diffusion of Al through the stack and the formation of an Al2O3 layer on the stack's surface are responsible for a loss of solderability after a strong post-metallization anneal, which is often mandatory to improve contact resistance and passivation quality. An optimization of the reactive TiN sputter process results in a densification of the TiN layer, which improves its barrier quality against Al diffusion. However, measurements with X-ray diffraction and scanning electron microscopy show that small grains with vertical grain boundaries persist, which still offer fast diffusion paths. Therefore, the concept of stuffing is introduced. By incorporating oxygen into the grain boundaries of the sputtered TiN layer, Al diffusion is strongly reduced as confirmed by secondary ion mass spectroscopy profiles. A quantitative analysis reveals a one order of magnitude lower Al diffusion coefficient for stuffed TiN layers. This metallization system maintains its solderability even after strong post-metallization annealing at 425 °C for 15 min. This paper thus presents an industrially feasible, conventionally solderable, and long-term stable metallization scheme for highly efficient silicon solar cells.

Precipitating Circumstances of Suicide and Alcohol Intoxication among U.S. Ethnic Groups

PubMed Central

Caetano, Raul; Kaplan, Mark S.; Huguet, Nathalie; Conner, Kenneth; McFarland, Bentson H.; Giesbrecht, Norman; Nolte, Kurt B.

2015-01-01

Background To assess the prevalence of nine different types of precipitating circumstances among suicide decedents, and examine the association between circumstances and post-mortem blood alcohol content (BAC ≥ 0.08 g/dl.) across U.S. ethnic groups. Methods Data come from the restricted 2003-2011 National Violent Death Reporting System (NVDRS), with post-mortem information on 59,384 male and female suicide decedents for 17 states of the U.S. Results Among men, precipitating circumstances statistically associated with a BAC ≥ 0.08 g/dl were physical health and job problems for Blacks, and experiencing a crisis, physical health problems and intimate partner problem for Hispanics. Among women, the only precipitating circumstance associated with a BAC ≥ 0.08 g/dl was substance abuse problems other than alcohol for Blacks. The number of precipitating circumstances present before the suicide was negatively associated with a BAC ≥ 0.08 g/dl for Whites, Blacks and Hispanics. Conclusions Selected precipitating circumstances were associated with a BAC ≥ 0.08 g/dl, and the strongest determinant of this level of alcohol intoxication prior to suicide among all ethnic groups was the presence of an alcohol problem. PMID:26173709

A National Evaluation of the Nighttime and Passenger Restriction Components of Graduated Driver Licensing

PubMed Central

Fell, James C.; Todd, Michael; Voas, Robert B.

2011-01-01

Introduction The high crash rate of youthful novice drivers has been recognized for half a century. Over the last decade, graduated driver licensing (GDL) systems, which extend the period of supervised driving and limit the novice’s exposure to higher-risk conditions (such as nighttime driving) has effectively reduced crash involvements of novice drivers. Method This study used data from the Fatality Analysis Reporting System (FARS) and the implementation dates of GDL laws in a state-by-year panel study to evaluate the effectiveness of two key elements of GDL laws: nighttime restrictions and passenger limitations. Results Nighttime restrictions were found to reduce 16- and 17-year-old driver involvements in nighttime fatal crashes by an estimated 10% and 16- and 17-year-old drinking drivers in nighttime fatal crashes by 13%. Passenger restrictions were found to reduce 16- and 17-year-old driver involvements in fatal crashes with teen passengers by an estimated 9%. Conclusions These results confirm the effectiveness of these provisions in GDL systems. Impact on Public Health The results of this study indicate that nighttime restrictions and passenger limitations are very important components of any GDL law. PMID:22017831

Geometric Design Laboratory Fact Sheet

DOT National Transportation Integrated Search

2006-08-02

This fact sheet provides concise information about the Geometric Design Laboratory (GDL) at the Turner-Fairbank Highway Research Center. The mission of the GDL is to provide technical support to the Federal Highway Administration's Office of Safety R...

Online data analysis using Web GDL

NASA Astrophysics Data System (ADS)

Jaffey, A.; Cheung, M.; Kobashi, A.

2008-12-01

The ever improving capability of modern astronomical instruments to capture data at high spatial resolution and cadence is opening up unprecedented opportunities for scientific discovery. When data sets become so large that they cannot be easily transferred over the internet, the researcher must find alternative ways to perform data analysis. One strategy is to bring the data analysis code to where the data resides. We present Web GDL, an implementation of GDL (GNU Data Language, open source incremental compiler compatible with IDL) that allows users to perform interactive data analysis within a web browser.

A Host-Dependent Prognostic Model for Elderly Patients with Diffuse Large B-Cell Lymphoma.

PubMed

Miura, Katsuhiro; Konishi, Jun; Miyake, Takaaki; Makita, Masanori; Hojo, Atsuko; Masaki, Yasufumi; Uno, Masatoshi; Ozaki, Jun; Yoshida, Chikamasa; Niiya, Daigo; Kitazume, Koichi; Maeda, Yoshinobu; Takizawa, Jun; Sakai, Rika; Yano, Tomofumi; Yamamoto, Kazuhiko; Sunami, Kazutaka; Hiramatsu, Yasushi; Aoyama, Kazutoshi; Tsujimura, Hideki; Murakami, Jun; Hatta, Yoshihiro; Kanno, Masatoshi

2017-05-01

Decision-making models for elderly patients with diffuse large B-cell lymphoma (DLBCL) treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) are in great demand. The Society of Lymphoma Treatment in Japan (SoLT-J), in collaboration with the West-Japan Hematology and Oncology Group (West-JHOG), collected and retrospectively analyzed the clinical records of ≥65-year-old patients with DLBCL treated with R-CHOP from 19 sites across Japan to build an algorithm that can stratify adherence to R-CHOP. A total of 836 patients with a median age of 74 years (range, 65-96 years) were analyzed. In the SoLT-J cohort ( n  = 555), age >75 years, serum albumin level <3.7 g/dL, and Charlson Comorbidity Index score ≥3 were independent adverse risk factors and were defined as the Age, Comorbidities, and Albumin (ACA) index. Based on their ACA index score, patients were categorized into "excellent" (0 points), "good" (1 point), "moderate" (2 points), and "poor" (3 points) groups. This grouping effectively discriminated the 3-year overall survival rates, mean relative total doses (or relative dose intensity) of anthracycline and cyclophosphamide, unanticipated R-CHOP discontinuance rates, febrile neutropenia rates, and treatment-related death rates. Additionally, the ACA index showed comparable results for these clinical parameters when it was applied to the West-JHOG cohort ( n  = 281). The ACA index has the ability to stratify the prognosis, tolerability to cytotoxic drugs, and adherence to treatment of elderly patients with DLBCL treated with R-CHOP. The Oncologist 2017;22:554-560 IMPLICATIONS FOR PRACTICE: Currently, little is known regarding how to identify elderly patients with diffuse large B-cell lymphoma who may tolerate a full dose of chemotherapy or to what extent cytotoxic drugs should be reduced in some specific conditions. The Society of Lymphoma Treatment in Japan developed a host-dependent prognostic model consisting of higher age (>75 years), hypoalbuminemia (<3.7 g/dL), and higher Charlson Comorbidity Index score (≥3) for such elderly patients. This model can stratify the prognosis, tolerability to cytotoxic drugs, and adherence to treatment of these patients and thus help clinicians in formulating personalized treatment strategies for this growing patient population. © AlphaMed Press 2017.

A Host‐Dependent Prognostic Model for Elderly Patients with Diffuse Large B‐Cell Lymphoma

PubMed Central

Konishi, Jun; Miyake, Takaaki; Makita, Masanori; Hojo, Atsuko; Masaki, Yasufumi; Uno, Masatoshi; Ozaki, Jun; Yoshida, Chikamasa; Niiya, Daigo; Kitazume, Koichi; Maeda, Yoshinobu; Takizawa, Jun; Sakai, Rika; Yano, Tomofumi; Yamamoto, Kazuhiko; Sunami, Kazutaka; Hiramatsu, Yasushi; Aoyama, Kazutoshi; Tsujimura, Hideki; Murakami, Jun; Hatta, Yoshihiro; Kanno, Masatoshi

2017-01-01

Abstract Background. Decision‐making models for elderly patients with diffuse large B‐cell lymphoma (DLBCL) treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R‐CHOP) are in great demand. Patients and Methods. The Society of Lymphoma Treatment in Japan (SoLT‐J), in collaboration with the West‐Japan Hematology and Oncology Group (West‐JHOG), collected and retrospectively analyzed the clinical records of ≥65‐year‐old patients with DLBCL treated with R‐CHOP from 19 sites across Japan to build an algorithm that can stratify adherence to R‐CHOP. Results. A total of 836 patients with a median age of 74 years (range, 65–96 years) were analyzed. In the SoLT‐J cohort (n = 555), age >75 years, serum albumin level <3.7 g/dL, and Charlson Comorbidity Index score ≥3 were independent adverse risk factors and were defined as the Age, Comorbidities, and Albumin (ACA) index. Based on their ACA index score, patients were categorized into “excellent” (0 points), “good” (1 point), “moderate” (2 points), and “poor” (3 points) groups. This grouping effectively discriminated the 3‐year overall survival rates, mean relative total doses (or relative dose intensity) of anthracycline and cyclophosphamide, unanticipated R‐CHOP discontinuance rates, febrile neutropenia rates, and treatment‐related death rates. Additionally, the ACA index showed comparable results for these clinical parameters when it was applied to the West‐JHOG cohort (n = 281). Conclusion. The ACA index has the ability to stratify the prognosis, tolerability to cytotoxic drugs, and adherence to treatment of elderly patients with DLBCL treated with R‐CHOP. The Oncologist 2017;22:554–560 Implications for Practice. Currently, little is known regarding how to identify elderly patients with diffuse large B‐cell lymphoma who may tolerate a full dose of chemotherapy or to what extent cytotoxic drugs should be reduced in some specific conditions. The Society of Lymphoma Treatment in Japan developed a host‐dependent prognostic model consisting of higher age (>75 years), hypoalbuminemia (<3.7 g/dL), and higher Charlson Comorbidity Index score (≥3) for such elderly patients. This model can stratify the prognosis, tolerability to cytotoxic drugs, and adherence to treatment of these patients and thus help clinicians in formulating personalized treatment strategies for this growing patient population. PMID:28408622

Diffusion induced atomic islands on the surface of Ni/Cu nanolayers

NASA Astrophysics Data System (ADS)

Takáts, Viktor; Csik, Attila; Hakl, József; Vad, Kálmán

2018-05-01

Surface islands formed by grain-boundary diffusion has been studied in Ni/Cu nanolayers by in-situ low energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, scanning probe microscopy and ex-situ depth profiling based on ion sputtering. In this paper a new experimental approach of measurement of grain-boundary diffusion coefficients is presented. Appearing time of copper atoms diffused through a few nanometer thick nickel layer has been detected by low energy ion scattering spectroscopy with high sensitivity. The grain-boundary diffusion coefficient can be directly calculated from this appearing time without using segregation factors in calculations. The temperature range of 423-463 K insures the pure C-type diffusion kinetic regime. The most important result is that surface coverage of Ni layer by Cu atoms reaches a maximum during annealing and stays constant if the annealing procedure is continued. Scanning probe microscopy measurements show a Volmer-Weber type layer growth of Cu layer on the Ni surface in the form of Cu atomic islands. Depth distribution of Cu in Ni layer has been determined by depth profile analysis.

Toward the existence of ultrafast diffusion paths in Cu with a gradient microstructure: Room temperature diffusion of Ni

NASA Astrophysics Data System (ADS)

Wang, Z. B.; Lu, K.; Wilde, G.; Divinski, S.

2008-09-01

Room temperature diffusion of Ni63 in Cu with a gradient microstructure prepared by surface mechanical attrition treatment (SMAT) was investigated by applying the radiotracer technique. The results reveal significant penetration of Ni into the nanostructured layer. The relevant diffusivity is higher than that along the conventional high-angle grain boundaries by about six orders of magnitude. This behavior is associated with a higher energy state of internal interfaces produced via plastic deformation. The diffusivity in the top surface layer is somewhat smaller than that in the subsurface layer. This fact is related to nanotwin formation in the former during SMAT.

CMOS-compatible method for doping of buried vertical polysilicon structures by solid phase diffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turkulets, Yury; Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer-Sheva 8410501; Silber, Amir

2016-03-28

Polysilicon receives attention nowadays as a means to incorporate 3D-structured photonic devices into silicon processes. However, doping of buried layers of a typical 3D structure has been a challenge. We present a method for doping of buried polysilicon layers by solid phase diffusion. Using an underlying silicon oxide layer as a dopant source facilitates diffusion of dopants into the bottom side of the polysilicon layer. The polysilicon is grown on top of the oxide layer, after the latter has been doped by ion implantation. Post-growth heat treatment drives in the dopant from the oxide into the polysilicon. To model themore » process, we studied the diffusion of the two most common silicon dopants, boron (B) and phosphorus (P), using secondary ion mass spectroscopy profiles. Our results show that shallow concentration profiles can be achieved in a buried polysilicon layer using the proposed technique. We present a quantitative 3D model for the diffusion of B and P in polysilicon, which turns the proposed method into an engineerable technique.« less

Cathodic electrocatalyst layer for electrochemical generation of hydrogen peroxide

NASA Technical Reports Server (NTRS)

Tennakoon, Charles L. K. (Inventor); Singh, Waheguru Pal (Inventor); Rhodes, Christopher P. (Inventor); Anderson, Kelvin C. (Inventor)

2011-01-01

A cathodic gas diffusion electrode for the electrochemical production of aqueous hydrogen peroxide solutions. The cathodic gas diffusion electrode comprises an electrically conductive gas diffusion substrate and a cathodic electrocatalyst layer supported on the gas diffusion substrate. A novel cathodic electrocatalyst layer comprises a cathodic electrocatalyst, a substantially water-insoluble quaternary ammonium compound, a fluorocarbon polymer hydrophobic agent and binder, and a perfluoronated sulphonic acid polymer. An electrochemical cell using the novel cathodic electrocatalyst layer has been shown to produce an aqueous solution having between 8 and 14 weight percent hydrogen peroxide. Furthermore, such electrochemical cells have shown stable production of hydrogen peroxide solutions over 1000 hours of operation including numerous system shutdowns.

Graduated driver licensing and motor vehicle crashes involving teenage drivers: an exploratory age-stratified meta-analysis.

PubMed

Zhu, Motao; Cummings, Peter; Chu, Haitao; Coben, Jeffrey H; Li, Guohua

2013-02-01

Graduated Driver Licensing (GDL) has been implemented in Australia, Canada, New Zealand, USA and Israel. We conducted an exploratory summary of available data to estimate whether GDL effects varied with age. We searched MEDLINE and other sources from 1991-2011. GDL evaluation studies with crashes resulting in injuries or deaths were eligible. They had to provide age-specific incidence rate ratios with CI or information for calculating these quantities. We included studies from individual states or provinces, but excluded national studies. We examined rates based on person-years, not license-years. Of 1397 papers, 144 were screened by abstract and 47 were reviewed. Twelve studies from 11 US states and one Canadian province were selected for meta-analysis for age 16, eight were selected for age 17, and four for age 18. Adjusted rate ratios were pooled using random effects models. The pooled adjusted rate ratios for the association of GDL presence with crash rates was 0.78 (95% CI 0.72 to 0.84) for age 16 years, 0.94 (95% CI 0.93 to 0.96) for 17 and 1.00 (95% CI 0.95 to 1.04) for 18. The difference between these three rate ratios was statistically significant: p<0.001. GDL policies were associated with a 22% reduction in crash rates among 16-year-old drivers, but only a 6% reduction for 17-year-old drivers. GDL showed no association with crashes among 18-year-old drivers. Because we had few studies to summarise, particularly for older adolescents, our findings should be considered exploratory.

Analysis of Al diffusion processes in TiN barrier layers for the application in silicon solar cell metallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumm, J.; Samadi, H.; Chacko, R. V.

An evaporated Al layer is known as an excellent rear metallization for highly efficient solar cells, but suffers from incompatibility with a common solder process. To enable solar cell-interconnection and module integration, in this work the Al layer is complemented with a solder stack of TiN/Ti/Ag or TiN/NiV/Ag, in which the TiN layer acts as an Al diffusion barrier. X-ray photoelectron spectroscopy measurements prove that diffusion of Al through the stack and the formation of an Al{sub 2}O{sub 3} layer on the stack's surface are responsible for a loss of solderability after a strong post-metallization anneal, which is often mandatorymore » to improve contact resistance and passivation quality. An optimization of the reactive TiN sputter process results in a densification of the TiN layer, which improves its barrier quality against Al diffusion. However, measurements with X-ray diffraction and scanning electron microscopy show that small grains with vertical grain boundaries persist, which still offer fast diffusion paths. Therefore, the concept of stuffing is introduced. By incorporating oxygen into the grain boundaries of the sputtered TiN layer, Al diffusion is strongly reduced as confirmed by secondary ion mass spectroscopy profiles. A quantitative analysis reveals a one order of magnitude lower Al diffusion coefficient for stuffed TiN layers. This metallization system maintains its solderability even after strong post-metallization annealing at 425 °C for 15 min. This paper thus presents an industrially feasible, conventionally solderable, and long-term stable metallization scheme for highly efficient silicon solar cells.« less

Preparation and Bond Properties of Thermal Barrier Coatings on Mg Alloy with Sprayed Al or Diffused Mg-Al Intermetallic Interlayer

NASA Astrophysics Data System (ADS)

Fan, Xizhi; Wang, Ying; Zou, Binglin; Gu, Lijian; Huang, Wenzhi; Cao, Xueqiang

2014-02-01

Sprayed Al or diffused Mg-Al layer was designed as interlayer between the thermal barrier coatings (TBCs) and Mg alloy substrate. The effects of the interlayer on the bond properties of the coats were investigated. Al layers were prepared by arc spraying and atmospheric plasma spraying (APS), respectively. Mg-Al diffused layer was obtained after the heat treatment of the sprayed sample (Mg alloy with APS Al coat) at 400 °C. The results show that sprayed Al interlayer does not improve the bond stability of TBCs. The failure of the TBCs on Mg alloy with Al interlayer occurs mainly due to the low strength of Al layer. Mg-Al diffused layer improves corrosion resistance of substrate and the bond interface. The TBCs on Mg alloy with Mg-Al diffused interlayer shows better bond stability than the sample of which the TBCs is directly sprayed on Mg alloy substrate by APS.

Implementation of a diffusion convection surface evolution model in WallDYN

NASA Astrophysics Data System (ADS)

Schmid, K.

2013-07-01

In thermonuclear fusion experiments with multiple plasma facing materials the formation of mixed materials is inevitable. The formation of these mixed material layers is a dynamic process driven the tight interaction between transport in the plasma scrape off layer and erosion/(re-) deposition at the surface. To track this global material erosion/deposition balance and the resulting formation of mixed material layers the WallDYN code has been developed which couples surface processes and plasma transport. The current surface model in WallDYN cannot fully handle the growth of layers nor does it include diffusion. However at elevated temperatures diffusion is a key process in the formation of mixed materials. To remedy this shortcoming a new surface model has been developed which, for the first time, describes both layer growth/recession and diffusion in a single continuous diffusion/convection equation. The paper will detail the derivation of the new surface model and compare it to TRIDYN calculations.

Randomized double-blind trial of darbepoetin alfa in patients with symptomatic heart failure and anemia.

PubMed

Ghali, Jalal K; Anand, Inder S; Abraham, William T; Fonarow, Gregg C; Greenberg, Barry; Krum, Henry; Massie, Barry M; Wasserman, Scott M; Trotman, Marie-Louise; Sun, Yan; Knusel, Beat; Armstrong, Paul

2008-01-29

Substantial evidence suggests that anemia is an independent risk factor for worse outcomes in patients with heart failure (HF). The Study of Anemia in Heart Failure Trial (STAMINA-HeFT) is the largest multicenter, randomized, double-blind, placebo-controlled trial to date evaluating the effect of treating anemia in HF. Patients (N=319) with symptomatic HF, left ventricular ejection fraction < or = 40%, and hemoglobin > or = 9.0 g/dL and < or = 12.5 g/dL were randomized (double-blind) to placebo (N=157) or darbepoetin alfa (N=162) subcutaneously every 2 weeks for 1 year (target hemoglobin, 14.0+/-1.0 g/dL). The primary end point was change from baseline to week 27 in treadmill exercise time. Secondary end points were change from baseline in New York Heart Association class and quality of life at week 27. An additional prespecified efficacy analysis included the time to death by any cause or first HF-related hospitalization by 1 year. At baseline, the median (interquartile range) hemoglobin was 11.4 (10.9, 12.0) g/dL. At week 27, darbepoetin alfa treatment increased median (interquartile range) hemoglobin by 1.8 (1.1, 2.5) g/dL (placebo, 0.3 [-0.2, 1.0] g/dL; P<0.001). Of the patients treated with darbepoetin alfa, 85% achieved 2 consecutive hemoglobin levels of 14.0+/-1.0 g/dL during the study and experienced a hemoglobin increase of > or = 1.0 g/dL from baseline. By intent-to-treat analysis, darbepoetin alfa treatment did not significantly improve exercise duration, New York Heart Association class, or quality of life score compared with placebo. A nonsignificant trend was observed toward a lower risk of all-cause mortality or first HF hospitalization in darbepoetin alfa-treated patients compared with placebo (hazard ratio, 0.68; 95% CI, 0.43, 1.08; P=0.10). Occurrences of adverse events were similar in both treatment groups. In this study of patients with symptomatic HF and anemia, treatment with darbepoetin alfa was not associated with significant clinical benefits. Darbepoetin alfa treatment was well tolerated and effectively raised hemoglobin. A trend of lower risk of morbidity and mortality was observed.

The role of albumin and endoplasmic reticulum in pathogenesis Preeclampsia. Changes of GRP78 and placental VEGF in preeclampsia.

PubMed

Aditiawarman

2014-07-01

Preeclampsia remains the highest causes of maternal mortality in Indonesia. This disease is known as "the disease of theories" since the etiology of this disease still obscure, but it is clearly accepted that this disease is correlated with placenta. The incidence of this disease increased in dr. Soetomo General Hospital during economic crisis in Indonesia, as nutritional problem occurred, but correlation between nutrition to preeclampsia still unclear. This study was conducted to find out the influence of hypoalbuminemia caused by alteration of amino acids and changes of GRP78 and placental VEGF in preeclampsia. It was cross-sectional study among 10 patients with preeclampsia albumin ⩽ gram/dL and 9 patients with preeclampsia albumin >3g/dL. Placenta collected was homogenized and blood was separated from the cells. Placental lysat, serum and plasma were stored -87°C until laboratory analysis for GRP78 and VEGF. Data were analyzed using student t test, Manova. Pearson correlation, simple and multiple regressions. There were alterations of amino acid's profile among albumin ⩽3g/dL compare with albumin >3g/dL. GRP78 concentration on albumin ⩽3g/dL group was higher, but were not significant. Weak negative correlation between albumins to GRP78 was found. Negative correlation were found in the groups of albumin ⩽3g/dL - GRP⩽425μg/dL, but significant result only on albumin ⩽3g/dL - GRP⩽425μg/dL. Positive correlation were found in the group of albumin >3g/dL - GRP>425μg/dL. Response of Endoplasmic Reticulum Stress appeared different depends on levels of albumin (stressor) and GRP78 (stress response protein). Placental VEGF were significantly lower in albumin ⩽3g/dL (p<0.05). Correlation between GRP78 on placental VEGF was negative with coefficient correlation was 3.8%. Placental VEGF profoundly decreased as correlation between albumin and GRP78 stronger. Alteration of amino acids profile influenced Albumin concentration. Hypoalbuminemia was a stressor that induced reticulum endoplasmic response by increasing GRP78, decreasing placental VEGF. Responses of Endoplasmic Reticulum Stress depend on levels of stressor (albumin) and stress response protein (GRP78). Copyright © 2014 International Society for the Study of Hypertension in Pregnancy.

Diffusion of Mg dopant in metal-organic vapor-phase epitaxy grown GaN and AlxGa1-xN

NASA Astrophysics Data System (ADS)

Köhler, K.; Gutt, R.; Wiegert, J.; Kirste, L.

2013-02-01

Diffusion of the p-type dopant Mg in GaN and AlxGa1-xN which is accompanied by segregation and affected by transient effects in metal-organic vapor-phase epitaxy reactors is investigated. We have grown 110 nm thick Mg doped GaN and Al0.1Ga0.9N layers on top of undoped GaN and Al0.1Ga0.9N layers, respectively, in a temperature range between 925 °C and 1050 °C where we placed special emphasis on the lower temperature limit without diffusion to allow separation of Mg transients, diffusion, and segregation. Hereby, AlxGa1-xN layers enable monitoring of the resolution limit by secondary ion mass spectrometry analyses for the respective samples; therefore, thin AlxGa1-xN marker layers are incorporated in the thick GaN layers. We found an upper limit of 1.25 × 1019 cm-3 for diffusing Mg atoms in both sample types. Owing to the marked influence of Mg segregation in Al0.1Ga0.9N, diffusion is only seen by using a GaN cap on top of the Al0.1Ga0.9N layer sequence. Diffusion in Al0.1Ga0.9N is shown to be increased by about 25%-30% compared to GaN. Post growth annealing experiments under conditions equivalent to those used for growth of the Mg doped samples showed negligible diffusion. Comparing the results to well established findings on other doped III-V compounds, diffusion is explained by an interstitial-substitutional mechanism with a diffusion coefficient, which is concentration dependent. Analysis of the temperature dependent diffusivity revealed an activation energy of 5.0 eV for GaN:Mg and 5.2 eV for Al0.1Ga0.9N:Mg.

Optimal resource diffusion for suppressing disease spreading in multiplex networks

NASA Astrophysics Data System (ADS)

Chen, Xiaolong; Wang, Wei; Cai, Shimin; Stanley, H. Eugene; Braunstein, Lidia A.

2018-05-01

Resource diffusion is a ubiquitous phenomenon, but how it impacts epidemic spreading has received little study. We propose a model that couples epidemic spreading and resource diffusion in multiplex networks. The spread of disease in a physical contact layer and the recovery of the infected nodes are both strongly dependent upon resources supplied by their counterparts in the social layer. The generation and diffusion of resources in the social layer are in turn strongly dependent upon the state of the nodes in the physical contact layer. Resources diffuse preferentially or randomly in this model. To quantify the degree of preferential diffusion, a bias parameter that controls the resource diffusion is proposed. We conduct extensive simulations and find that the preferential resource diffusion can change phase transition type of the fraction of infected nodes. When the degree of interlayer correlation is below a critical value, increasing the bias parameter changes the phase transition from double continuous to single continuous. When the degree of interlayer correlation is above a critical value, the phase transition changes from multiple continuous to first discontinuous and then to hybrid. We find hysteresis loops in the phase transition. We also find that there is an optimal resource strategy at each fixed degree of interlayer correlation under which the threshold reaches a maximum and the disease can be maximally suppressed. In addition, the optimal controlling parameter increases as the degree of inter-layer correlation increases.

Hybrid Monte Carlo-Diffusion Method For Light Propagation in Tissue With a Low-Scattering Region

NASA Astrophysics Data System (ADS)

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

Hybrid Monte Carlo-diffusion method for light propagation in tissue with a low-scattering region.

PubMed

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branko N. Popov

2009-03-03

The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst showsmore » the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable catalytic activity and selectivity for ORR as the Pt catalyst. A theoretical analysis is made of the four-electron reduction reaction of oxygen to water over the mixed anion and cation (202) surface of pentlandite structure Co9Se8, one of several selenide phases. Reversible potentials for forming adsorbed reaction intermediates in acid are predicted using adsorption energies calculated with the Vienna ab initio simulation program (VASP) and the known bulk solution values together in a linear Gibbs energy relationship. The effect of hydrophobic and structural properties of a single/dual-layer cathode gas diffusion layer on mass transport in PEM fuel cells was studied using an analytical expression. The simulations indicated that liquid water transport at the cathode is controlled by the fraction of hydrophilic surface and the average pore diameter in the cathode gas diffusion layer. The optimized hydrophobicity and pore geometry in a dual-layer cathode GDL leads to an effective water management, and enhances the oxygen diffusion kinetics.« less

DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branko N. Popov

2009-02-20

The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst showsmore » the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable catalytic activity and selectivity for ORR as the Pt catalyst. A theoretical analysis is made of the four-electron reduction reaction of oxygen to water over the mixed anion and cation (202) surface of pentlandite structure Co9Se8, one of several selenide phases. Reversible potentials for forming adsorbed reaction intermediates in acid are predicted using adsorption energies calculated with the Vienna ab initio simulation program (VASP) and the known bulk solution values together in a linear Gibbs energy relationship. The effect of hydrophobic and structural properties of a single/dual-layer cathode gas diffusion layer on mass transport in PEM fuel cells was studied using an analytical expression. The simulations indicated that liquid water transport at the cathode is controlled by the fraction of hydrophilic surface and the average pore diameter in the cathode gas diffusion layer. The optimized hydrophobicity and pore geometry in a dual-layer cathode GDL leads to an effective water management, and enhances the oxygen diffusion kinetics.« less

Diffusion at the boundary between the film and substrate upon the electrocrystallization of zinc on a copper substrate

NASA Astrophysics Data System (ADS)

Shtapenko, E. Ph.; Zabludovsky, V. A.; Dudkina, V. V.

2015-03-01

In this paper, we present the results of experimental investigations of the diffusion layer formed at the film-substrate interface upon the electrodeposition of zinc films on a copper substrate. The investigations have shown that, in the transient layer, the deposited metal is diffused into the material of the substrate. The depth of the diffusion layer and, consequently, the concentrations of the incorporated zinc atoms depend strongly on the conditions of electrocrystallization, which vary from 1.5 μm when using direct current to 4 μm when using direct current in combination with laser-stimulated deposition (LSD). The X-ray diffraction investigations of the transient layer at the film-substrate interface have shown that, upon electrocrystallization using pulsed current in rigid regimes with the application of the LSD, a CuZn2 phase is formed in the diffusion layer. This indicates that the diffusion of zinc into copper occurs via two mechanisms, i.e., grainboundary and bulk. The obtained values of the coefficient of diffusion of zinc adatoms in polycrystalline copper are equal to 1.75 × 10-15 m2/s when using direct current and 1.74 × 10-13 m2/s when using LSD.

The role of supervised driving in a graduated driver licensing program : traffic tech.

DOT National Transportation Integrated Search

2012-04-01

Traditional Graduated Driver Licensing (GDL) systems, : in place in all the States, include three licensing stages: the : initial learner stage, an intermediate or provisional phase, : and full licensure. An important component of GDL systems : is th...

Meta-analysis of graduated driver licensing laws.

DOT National Transportation Integrated Search

2015-11-01

The objective of the present study was to assess the effectiveness of GDL programs for reducing total, injury, and fatal crashes among drivers 15 to 20 years old by conducting a meta-analysis of GDL research since 2001 that evaluated the effectivenes...

Impact of graduated driver licensing restrictions on crashes involving young drivers in New Zealand

PubMed Central

Begg, D; Stephenson, S; Alsop, J; Langley, J

2001-01-01

Objective—To determine the impact on young driver crashes of the three main driving restrictions in the New Zealand graduated driver licensing (GDL) system: night-time curfew, no carrying of young passengers, and a blood alcohol limit of 30 mg/100 ml. Method—The database for this study was created by linking police crash reports to hospital inpatient records (1980–95). Multivariate logistic regression was used to compare car crashes involving a young driver licensed before GDL (n=2252) with those who held a restricted graduated licence (n=980) and with those who held a full graduated licence (n=1273), for each of the main driving restrictions. Results—Compared with the pre-GDL group, the restricted licence drivers had fewer crashes at night (p=0.003), fewer involving passengers of all ages (p=0.018), and fewer where alcohol was suspected (p=0.034), but not fewer involving young casualties (p=0.980). Compared with the pre-GDL drivers, those with the full graduated licence had fewer night crashes (p=0.042) but did not differ significantly for any of the other factors examined. Conclusion—These results suggest that some of the GDL restrictions, especially the night-time curfew, have contributed to a reduction in serious crashes involving young drivers. PMID:11770654

Impact of graduated driver licensing restrictions on crashes involving young drivers in New Zealand.

PubMed

Begg, D J; Stephenson, S; Alsop, J; Langley, J

2001-12-01

To determine the impact on young driver crashes of the three main driving restrictions in the New Zealand graduated driver licensing (GDL) system: night-time curfew, no carrying of young passengers, and a blood alcohol limit of 30 mg/100 ml. The database for this study was created by linking police crash reports to hospital inpatient records (1980-95). Multivariate logistic regression was used to compare car crashes involving a young driver licensed before GDL (n=2,252) with those who held a restricted graduated licence (n=980) and with those who held a full graduated licence (n=1,273), for each of the main driving restrictions. Compared with the pre-GDL group, the restricted licence drivers had fewer crashes at night (p=0.003), fewer involving passengers of all ages (p=0.018), and fewer where alcohol was suspected (p=0.034), but not fewer involving young casualties (p=0.980). Compared with the pre-GDL drivers, those with the full graduated licence had fewer night crashes (p=0.042) but did not differ significantly for any of the other factors examined. These results suggest that some of the GDL restrictions, especially the night-time curfew, have contributed to a reduction in serious crashes involving young drivers.

Pure silver ohmic contacts to N- and P- type gallium arsenide materials

DOEpatents

Hogan, Stephen J.

1986-01-01

Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

Molecular dynamics simulation of the diffusion of uranium species in clay pores.

PubMed

Liu, Xiao-yu; Wang, Lu-hua; Zheng, Zhong; Kang, Ming-liang; Li, Chun; Liu, Chun-li

2013-01-15

Molecular dynamics simulations were carried out to investigate the diffusive behavior of aqueous uranium species in montmorillonite pores. Three uranium species (UO(2)(2+), UO(2)CO(3), UO(2)(CO(3))(2)(2-)) were confirmed in both the adsorbed and diffuse layers. UO(2)(CO(3))(3)(4-) was neglected in the subsequent analysis due to its scare occurrence. The species-based diffusion coefficients in montmorillonite pores were then calculated, and compared with the water mobility and their diffusivity in aqueous solution/feldspar nanosized fractures. Three factors were considered that affected the diffusive behavior of the uranium species: the mobility of water, the self-diffusion coefficient of the aqueous species, and the electrostatic forces between the negatively charged surface and charged molecules. The mobility of U species in the adsorbed layer decreased in the following sequence: UO(2)(2+)>UO(2)CO(3)>UO(2)(CO(3))(2)(2-). In the diffuse layer, we obtained the highest diffusion coefficient for UO(2)(CO(3))(2)(2-) with the value of 5.48×10(-10) m(2) s(-1), which was faster than UO(2)(2+). For these two charged species, the influence of electrostatic forces on the diffusion of solutes in the diffuse layer is overwhelming, whereas the influence of self-diffusion and water mobility is minor. Our study demonstrated that the negatively charged uranyl carbonate complex must be addressed in the safety assessment of potential radioactive waste disposal systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Fick's second law transformed: one path to cloaking in mass diffusion.

PubMed

Guenneau, S; Puvirajesinghe, T M

2013-06-06

Here, we adapt the concept of transformational thermodynamics, whereby the flux of temperature is controlled via anisotropic heterogeneous diffusivity, for the diffusion and transport of mass concentration. The n-dimensional, time-dependent, anisotropic heterogeneous Fick's equation is considered, which is a parabolic partial differential equation also applicable to heat diffusion, when convection occurs, for example, in fluids. This theory is illustrated with finite-element computations for a liposome particle surrounded by a cylindrical multi-layered cloak in a water-based environment, and for a spherical multi-layered cloak consisting of layers of fluid with an isotropic homogeneous diffusivity, deduced from an effective medium approach. Initial potential applications could be sought in bioengineering.

A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

NASA Astrophysics Data System (ADS)

Baricci, Andrea; Casalegno, Andrea

2016-09-01

Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

Anomalous plasma diffusion and the magnetopause boundary layer

NASA Technical Reports Server (NTRS)

Treumann, Rudolf A.; Labelle, James; Haerendel, Gerhard; Pottelette, Raymond

1992-01-01

An overview of the current state of anomalous diffusion research at the magnetopause and its role in the formation of the magnetopause boundary layer is presented. Plasma wave measurements in the boundary layer indicate that most of the relevant unstable wave modes contribute negligibly to the diffusion process at the magnetopause under magnetically undisturbed northward IMF conditions. The most promising instability is the lower hybrid drift instability, which may yield diffusion coefficients of the right order if the highest measured wave intensities are assumed. It is concluded that global stationary diffusion due to wave-particle interactions does not take place at the magnetopause. Microscopic wave-particle interaction and anomalous diffusion may contribute to locally break the MD frozen-in conditions and help in transporting large amounts of magnetosheath plasma across the magnetospheric boundary.

Inhibition of ordinary and diffusive convection in the water condensation zone of the ice giants and implications for their thermal evolution

NASA Astrophysics Data System (ADS)

Friedson, A. James; Gonzales, Erica J.

2017-11-01

We explore the conditions under which ordinary and double-diffusive thermal convection may be inhibited by water condensation in the hydrogen atmospheres of the ice giants and examine the consequences. The saturation of vapor in the condensation layer induces a vertical gradient in the mean molecular weight that stabilizes the layer against convective instability when the abundance of vapor exceeds a critical value. In this instance, the layer temperature gradient can become superadiabatic and heat must be transported vertically by another mechanism. On Uranus and Neptune, water is inferred to be sufficiently abundant for inhibition of ordinary convection to take place in their respective condensation zones. We find that suppression of double-diffusive convection is sensitive to the ratio of the sedimentation time scale of the condensates to the buoyancy period in the condensation layer. In the limit of rapid sedimentation, the layer is found to be stable to diffusive convection. In the opposite limit, diffusive convection can occur. However, if the fluid remains saturated, then layered convection is generally suppressed and the motion is restricted in form to weak, homogeneous, oscillatory turbulence. This form of diffusive convection is a relatively inefficient mechanism for transporting heat, characterized by low Nusselt numbers. When both ordinary and layered convection are suppressed, the condensation zone acts effectively as a thermal insulator, with the heat flux transported across it only slightly greater than the small value that can be supported by radiative diffusion. This may allow a large superadiabatic temperature gradient to develop in the layer over time. Once the layer has formed, however, it is vulnerable to persistent erosion by entrainment of fluid into the overlying convective envelope of the cooling planet, potentially leading to its collapse. We discuss the implications of our results for thermal evolution models of the ice giants, for understanding Uranus' anomalously low intrinsic luminosity, and for inducing episodes of intense convection in the atmospheres of Saturn, Uranus, and Neptune.

Simulation of thermally induced processes of diffusion and phase formation in layered binary metallic systems

NASA Astrophysics Data System (ADS)

Rusakov, V. S.; Sukhorukov, I. A.; Zhankadamova, A. M.; Kadyrzhanov, K. K.

2010-05-01

Results of the simulation of thermally induced processes of diffusion and phase formation in model and experimentally investigated layered binary metallic systems are presented. The physical model is based on the Darken phenomenological theory and on the mechanism of interdiffusion of components along the continuous diffusion channels of phases in the two-phase regions of the system. The simulation of processes in the model systems showed that the thermally stabilized concentration profiles in two-layer binary metallic systems are virtually independent of the partial diffusion coefficients; for the systems with the average concentration of components that is the same over the sample depth, the time of the thermal stabilization of the structural and phase state inhomogeneous over the depth grows according to a power law with increasing thickness of the system in such a manner that the thicknesses of the surface layers grow, while the thickness of the intermediate layer approaches a constant value. The results of the simulation of the processes of diffusion and phase formation in experimentally investigated layered binary systems Fe-Ti and Cu-Be upon sequential isothermal and isochronous annealings agree well with the experimental data.

Method for Calculating the Optical Diffuse Reflection Coefficient for the Ocular Fundus

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2016-07-01

We have developed a method for calculating the optical diffuse reflection coefficient for the ocular fundus, taking into account multiple scattering of light in its layers (retina, epithelium, choroid) and multiple refl ection of light between layers. The method is based on the formulas for optical "combination" of the layers of the medium, in which the optical parameters of the layers (absorption and scattering coefficients) are replaced by some effective values, different for cases of directional and diffuse illumination of the layer. Coefficients relating the effective optical parameters of the layers and the actual values were established based on the results of a Monte Carlo numerical simulation of radiation transport in the medium. We estimate the uncertainties in retrieval of the structural and morphological parameters for the fundus from its diffuse reflectance spectrum using our method. We show that the simulated spectra correspond to the experimental data and that the estimates of the fundus parameters obtained as a result of solving the inverse problem are reasonable.

Hemoglobin-vesicle, a cellular artificial oxygen carrier that fulfils the physiological roles of the red blood cell structure.

PubMed

Sakai, Hiromi; Sou, Keitaro; Horinouchi, Hirohisa; Kobayashi, Koichi; Tsuchida, Eishun

2010-01-01

Hb-vesicles (HbV) are artificial O(2) carriers encapsulating concentrated Hb solution (35 g/dL) with a phospholipid bilayer membrane (liposome). The concentration of the HbV suspension is extremely high ([Hb] = 10 g/dL) and it has an O(2) carrying capacity that is comparable to that of blood. HbV is much smaller than RBC (250 vs. 8000 nm), but it recreates the functions of RBCs; (i) the slower rate of O(2) unloading than Hb solution; (ii) colloid osmotic pressure is zero; (iii) the viscosity of a HbV suspension is adjustable to that of blood; (iv) HbV is finally captured by and degraded in RES; (v) co-encapsulation of an allosteric effector to regulate O(2) affinity; (vi) the lipid bilayer membrane prevents direct contact of Hb and vasculature; (vii) NO-binding is retarded to some extent by an intracellular diffusion barrier, and HbV does not induce vasoconstriction. (viii) Both RBC and HbV can be a carrier of not only O(2) but also exogenous CO. However, HbV has limitations such as a shorter functional half-life when compared with RBCs. On the other hand, the advantages of HbV are that it is pathogen-free and blood-type-antigen-free; moreover, it can withstand long-term storage of a few years, none of which can be achieved by the RBC transfusion systems.

Motor vehicle injury, mortality, and hospital charges by strength of graduated driver licensing laws in 36 States.

PubMed

Pressley, Joyce C; Benedicto, Camilla B; Trieu, Lisa; Kendig, Tiffany; Barlow, Barbara

2009-07-01

To assess the relation between strength of graduated driver licensing (GDL) laws and motor vehicle (MV) injury burden, this study examined injury mortality, hospitalizations and related charges for 15 year to 17 year olds in 36 states by strength of GDL legislation. Data sources include the CDC's Web-Based Injury Statistics Query and Reporting System (WISQARS) and the 2003 Healthcare Cost and Utilization Kids' Inpatient database (KID). Hospital admissions for injuries in 15 year to 17 year olds (n = 49,520) are unweighted. Injury severity was assessed using ICDMAP-90 and International Classification of Injury Severity Scores. The Insurance Institute for Highway Safety rating system was used to categorize legislative strength: good, fair, marginal/poor, and none. Logistic regression was used to assess independent predictors of MV injury. MV injury accounted for 14.6% of all-cause injury-related hospital admissions with 47.7% classified as drivers. Total MV occupant mortality was 14.6% lower after enactment of GDL with greater improvement observed in the good law category (26.0%). In multivariate models for hospitalized injury, all GDL law categories were protective for MV driver injury in 16 year olds. Compared with whites, black and Hispanic teens were more frequently injured as passengers than drivers. The contribution of MV occupant to all-cause injury-related hospital charges was 16.0% lower in good versus no-GDL categories and 39.5% lower for MV drivers. These findings suggest that the presence of any GDL legislation is associated with a lower burden of MV-related injury and expenditures with the largest differences observed for 16-year-old drivers.

Graduated driver license nighttime compliance in U.S. teen drivers involved in fatal motor vehicle crashes.

PubMed

Carpenter, Dustin; Pressley, Joyce C

2013-07-01

Examination of teen driver compliance with graduated driver licensing (GDL) laws could be instrumental in identifying factors associated with persistently high motor vehicle mortality rates. Fatality analysis reporting system (FARS) data from the years 2006 to 2009 were used in this nation-wide cross-sectional study of drivers covered by a state nighttime GDL law (n=3492). A new definition of weekend, based on the school night in relation to the teenage social landscape, redefined Friday night as a weekend night and Sunday night as a weekday/school night and compared it to previous weekend definitions. Multiple logistic regression was used to examine independent effects of demographic, behavioral, environmental, contextual, and other factors on compliance with nighttime GDL laws. All analyses were performed in Stata version 11. Given coverage under nighttime GDL laws, drivers aged 15-17 years were non-compliant in 14.9% of the fatal MVCs in which they were involved, and nearly one-fifth (18.8%) of all fatalities aged 15-17 years were associated with non-compliance. Mortality risk was 10% higher using a revised social (school night) versus traditional (Sat-Sun) weekend definitions. In multivariable analysis, drivers non-compliant with nighttime GDL laws were more likely to be drinking (OR=4.97, 3.85-6.40), unbelted (OR=1.58, 1.25-1.99), driving on the weekend (OR=1.82, 1.47-2.24), and killed (OR=1.31, 1.04-1.65). GDL non-compliance contributes to teen motor vehicle mortality. Legislative and enforcement efforts targeting non-school night driving, seatbelt nonuse and alcohol have potential to further reduce teen driving mortality. Copyright © 2012 Elsevier Ltd. All rights reserved.

Impact of Anemia in Critically Ill Burned Casualties Evacuated From Combat Theater via US Military Critical Care Air Transport Teams.

PubMed

Hamilton, Joshua A; Mora, Alejandra G; Chung, Kevin K; Bebarta, Vikhyat S

2015-08-01

US military Critical Care Air Transport Teams (CCATT) transport critically ill burn patients out of theater. Blood transfusion may incur adverse effects, and studies report lower hemoglobin (Hgb) value may be safe for critically ill patients. There are no studies evaluating the optimal Hgb value for critically ill burn patients prior to CCATT evacuation. The aim of the study was to determine if critically ill burn casualties with an Hgb of 10 g/dL or less, transported via CCATT, have similar clinical outcomes at 30 days as compared with patients with an Hgb of greater than 10 g/dL. We conducted an institutional review board-approved retrospective cohort study involving patients transported via CCATT. We separated our study population into two cohorts based on Hgb levels at the time of theater evacuation: Hgb ≤10 g/dL or Hgb ≥10 g/dL. We compared demographics, injury description, physiologic parameters, and clinical outcomes. Of the 140 subjects enrolled, 29 were Hgb ≤10, and 111 were Hgb ≥10. Both groups were similar in age and percent total body surface area burned. Those Hgb ≤10 had a higher injury severity score (34 ± 19.8 vs. 25 ± 16.9, P = 0.02) and were more likely to have additional trauma (50% vs. 25%, P = 0.04). Modeling revealed no persistent differences in mortality, and other clinical outcomes measured. Critical Care Air Transport Teams transport of critically ill burn patients with an Hgb of 10 g/dL or less had no significant differences in complications or mortality as compared with patients with an Hgb of greater than 10 g/dL. In this study, lower hemoglobin levels did not confer greater risk for worse outcomes.

Graduated driver licensing and motor vehicle crashes involving teenage drivers: an exploratory age-stratified meta-analysis

PubMed Central

Zhu, Motao; Cummings, Peter; Chu, Haitao; Coben, Jeffrey H; Li, Guohua

2014-01-01

Objective Graduated Driver Licensing (GDL) has been implemented in Australia, Canada, New Zealand, USA and Israel. We conducted an exploratory summary of available data to estimate whether GDL effects varied with age. Methods We searched MEDLINE and other sources from 1991–2011. GDL evaluation studies with crashes resulting in injuries or deaths were eligible. They had to provide age-specific incidence rate ratios with CI or information for calculating these quantities. We included studies from individual states or provinces, but excluded national studies. We examined rates based on person-years, not license-years. Results Of 1397 papers, 144 were screened by abstract and 47 were reviewed. Twelve studies from 11 US states and one Canadian province were selected for meta-analysis for age 16, eight were selected for age 17, and four for age 18. Adjusted rate ratios were pooled using random effects models. The pooled adjusted rate ratios for the association of GDL presence with crash rates was 0.78 (95% CI 0.72 to 0.84) for age 16 years, 0.94 (95% CI 0.93 to 0.96) for 17 and 1.00 (95% CI 0.95 to 1.04) for 18. The difference between these three rate ratios was statistically significant: p<0.001. Conclusions GDL policies were associated with a 22% reduction in crash rates among 16-year-old drivers, but only a 6% reduction for 17-year-old drivers. GDL showed no association with crashes among 18-year-old drivers. Because we had few studies to summarise, particularly for older adolescents, our findings should be considered exploratory. PMID:23211352

Low Diagnostic Utility of Rechecking Hemoglobins Within 24 Hours in Hospitalized Patients.

PubMed

Rajkomar, Alvin; McCulloch, Charles E; Fang, Margaret C

2016-11-01

Clinicians often repeat hemoglobin tests within a 24 hour period to detect or monitor anemia. We sought to determine the percentage of hemoglobin tests repeated within a single hospital day that were at least 1.0 g/dL lower than the first test. We performed a retrospective cross-sectional analysis of hospitalized adults on medical or surgical services over 1 year at a single academic hospital. Using patient and laboratory data in the electronic health record, we analyzed the proportion of repeated hemoglobin test results that were at least 1 g/dL less than the initial hemoglobin value of that day, excluding days when transfusions were administered. A total of 88,722 hemoglobin tests were obtained from 12,877 unique patients, who contributed a total of 86,859 hospitalization days. In 12,230 (14.1%) of those days, 2 or more hemoglobin tests were obtained within a single day. In the 6969 days with 2 hemoglobin tests obtained and no transfusions given, 949 (13.5%) were ≥1 g/dL lower than the initial hemoglobin value of that day, and 260 (3.7%) were ≥2 g/dL lower. Repeated tests did not often reach transfusion thresholds: 482 (6.9%) of repeat hemoglobin values were <8 g/dL, and 64 (0.9%) were <7 g/dL. Hemoglobin tests were repeated in 14% of hospital days. For patients who had 2 hemoglobin tests obtained on the same day, 13.5% demonstrated a clinically significant drop. This information may be helpful to clinicians when considering whether repeat testing is appropriate. Copyright © 2016 Elsevier Inc. All rights reserved.

Relationship between the degree of perineal trauma at vaginal birth and change in haemoglobin concentration.

PubMed

Rubio-Álvarez, Ana; Molina-Alarcón, Milagros; Hernández-Martínez, Antonio

2017-10-01

Postpartum anaemia is a problem with high prevalence that significantly affects maternal recovery. Among the causal factors is perineal trauma. However, it is still not known what degree of perineal trauma produces a greater reduction of haemoglobin. To assess the relationship between the degree of perineal trauma and change in haemoglobin concentration at vaginal birth. An observational, analytical retrospective cohort study was performed at the Mancha-Centro Hospital (Spain) during the period 2010-2014. Data were collected regarding 3479 women who gave birth vaginally. The main outcome variable was the change in haemoglobin concentration. Multivariate analysis by means of multiple linear regression was performed to control possible confounding factors and to determine the net effect of each degree of perineal trauma on haemoglobin reduction. Of the total sample, 20.1% of women (699) had an intact perineum, 41.6% (1446) experienced some form of perineal trauma, but not episiotomy, and the remaining 38.3% of women (1334) underwent an episiotomy. The average reduction of haemoglobin was 1.46g/dL (Standard Deviation (SD)=1.09g/dL) for women without episiotomy with a second degree tear and 2.07g/dL (SD=1.24g/dL) for women who had an episiotomy and no perineal tear. The greatest reduction occurred among women with episiotomy and a third or fourth degree tear with a decrease of 3.10g/dL (SD=1.32g/dL). Episiotomy is related to greater reduction of haemoglobin concentration in comparison with all degrees of spontaneous perineal trauma. The use of episiotomy should be strictly limited. Copyright © 2017 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.

Transfusion-free management of gastrointestinal bleeding: the experience of a bloodless institute.

PubMed

Sharma, Prabin; Barajas, Francisco J; Krishnamoorthy, Parasuram; Campo, Lyna M; Blumenthal, Ezra; Spinnell, Mitchell

2015-03-01

The Institute for Patient Blood Management and Bloodless Medicine at the Englewood Hospital has considerable experience in managing patients with gastrointestinal bleeding who do not accept blood-derived products. We present our data and experience over the last 8 years in managing such patients. There is paucity of data on management and outcomes of gastrointestinal bleeding in patients who do not accept blood-derived products. We performed a retrospective study of patients from 2003 to 2011 presenting with gastrointestinal bleeding who do not accept blood-derived products. Inclusion criteria were either overt bleeding with a presenting hemoglobin (Hb) of <12 g/dL or a decrease in Hb of >1.5 g/dL. Ninety-six patients who met the inclusion criteria were included. Forty-one upper and 48 lower gastrointestinal bleeding sources were identified. Mean Hb was 8.8 g/dL and mean nadir was 6.9 g/dL. Among 37 patients (80.5%) with Hb ≤6.0 g/dL, 30 (81%) survived. Four of 7 patients (57%) with a Hb <3 g/dL survived. The overall mortality rate was 10.4%. In unadjusted logistic regression models, age [1.06 (1.01-1.12 y)], admission to ICU [6.37(1.27-31.9)], and anticoagulation use [6.95 (1.57-30.6)] were associated with increased mortality. Initial Hb [0.68 (0.51-0.92)] and nadir Hb [0.48 (0.29-0.78)] inversely predicted mortality. These results suggest that transfusion-free management of gastrointestinal hemorrhage can be effective with mortality comparable with the general population accepting medically indicated transfusion. Management of these patients is challenging and requires a dedicated multidisciplinary team approach knowledgeable in techniques of blood conservation.

Development and validation of a competitive enzyme-linked immunosorbent assay for the measurement of total plasma immunoglobulins in healthy loggerhead sea (Caretta caretta) and green turtles (Chelonia mydas).

PubMed

Kaplan, Amy J; Stacy, Nicole I; Jacobson, Elliott; Le-Bert, Carolina R; Nollens, Hendrik H; Origgi, Francesco C; Green, Linda G; Bootorabi, Shadi; Bolten, Alan; Hernandez, Jorge A

2016-01-01

The quantification of circulating plasma immunoglobulins represents a valuable diagnostic tool in human and veterinary immunology, although its application is very limited in reptile medicine to date. The objectives of our study were the development and standardization of a competitive enzyme-linked immunosorbent assay (cELISA) for the measurement of total plasma immunoglobulins (Igs; both IgM and IgY) in loggerhead sea turtles (LST; Caretta caretta; n = 254) and green turtles (GT; Chelonia mydas; n = 111), the establishment of reference intervals for Ig for both species, and the examination of associations between Ig and total protein (TP), condition index, and water temperature. The cELISA for Ig was successfully developed and optimized. Reference intervals for Ig were 0.38-0.94 g/dL in LST (median: 0.59 g/dL; range: 0.16-2.15 g/dL) and 0.40-0.85 g/dL in GT (median: 0.58 g/dL; range: 0.18-1.80 g/dL). In LST, there were positive linear relationships of Ig with TP, and TP with Ig and condition index, and a negative relationship of Ig with condition index. The positive linear relationships of Ig with TP, and TP with Ig were also identified in GT. These positive associations of Ig and TP were expected, as Ig represents fractions of TP, and TP reportedly increases with straight carapace length and weight. The negative association of Ig with condition index may indicate potential biological variations. The cELISA and reference intervals for total Ig of LST and GT presented herein have the potential to be useful as a diagnostic and research tool for sea turtle immunology. © 2015 The Author(s).

Frost induced damages within porous materials - from concrete technology to fuel cells technique

NASA Astrophysics Data System (ADS)

Palecki, Susanne; Gorelkov, Stanislav; Wartmann, Jens; Heinzel, Angelika

2017-12-01

Porous media like concrete or layers of membrane electrode assemblies (MEA) within fuel cells are affected by a cyclic frost exposure due to different damage mechanisms which could lead to essential degradation of the material. In general, frost damages can only occur in case of a specific material moisture content. In fuel cells, residual water is generally available after shut down inside the membrane i.e. the gas diffusion layer (GDL). During subsequent freezing, this could cause various damage phenomena such as frost heaves and delamination effects of the membrane electrode assembly, which depends on the location of pore water and on the pore structure itself. Porous materials possess a pore structure that could range over several orders of magnitudes with different properties and freezing behaviour of the pore water. Latter can be divided into macroscopic, structured and pre-structured water, influenced by surface interactions. Therefore below 0 °C different water modifications can coexist in a wide temperature range, so that during frost exposure a high amount of unfrozen and moveable water inside the pore system is still available. This induces transport mechanisms and shrinkage effects. The physical basics are similar for porous media. While the freezing behaviour of concrete has been studied over decades of years, in order to enhance the durability, the know-how about the influence of a frost attack on fuel cell systems is not fully understood to date. On the basis of frost damage models for concrete structures, an approach to describe the impact of cyclic freezing and thawing on membrane electrode assemblies has been developed within this research work. Major aim is beyond a better understanding of the frost induced mechanisms, the standardization of a suitable test procedure for the assessment of different MEA materials under such kind of attack. Within this contribution first results will be introduced.

Performance and microbial ecology of air-cathode microbial fuel cells with layered electrode assemblies.

PubMed

Butler, Caitlyn S; Nerenberg, Robert

2010-05-01

Microbial fuel cells (MFCs) can be built with layered electrode assemblies, where the anode, proton exchange membrane (PEM), and cathode are pressed into a single unit. We studied the performance and microbial community structure of MFCs with layered assemblies, addressing the effect of materials and oxygen crossover on the community structure. Four MFCs with layered assemblies were constructed using Nafion or Ultrex PEMs and a plain carbon cloth electrode or a cathode with an oxygen-resistant polytetrafluoroethylene diffusion layer. The MFC with Nafion PEM and cathode diffusion layer achieved the highest power density, 381 mW/m(2) (20 W/m(3)). The rates of oxygen diffusion from cathode to anode were three times higher in the MFCs with plain cathodes compared to those with diffusion-layer cathodes. Microsensor studies revealed little accumulation of oxygen within the anode cloth. However, the abundance of bacteria known to use oxygen as an electron acceptor, but not known to have exoelectrogenic activity, was greater in MFCs with plain cathodes. The MFCs with diffusion-layer cathodes had high abundance of exoelectrogenic bacteria within the genus Geobacter. This work suggests that cathode materials can significantly influence oxygen crossover and the relative abundance of exoelectrogenic bacteria on the anode, while PEM materials have little influence on anode community structure. Our results show that oxygen crossover can significantly decrease the performance of air-cathode MFCs with layered assemblies, and therefore limiting crossover may be of particular importance for these types of MFCs.

Process for forming pure silver ohmic contacts to N- and P-type gallium arsenide materials

DOEpatents

Hogan, S.J.

1983-03-13

Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components a n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffuse layer and the substrate layer wherein the n-type layer comprises a substantially low doping carrier concentration.

The effect of silicon on the interaction between metallic uranium and aluminum: A 50 year long diffusion experiment

NASA Astrophysics Data System (ADS)

Leenaers, A.; Detavernier, C.; Van den Berghe, S.

2008-11-01

The core of the BR1 research reactor at SCK•CEN, Mol (Belgium) has a graphite matrix loaded with fuel rods consisting of a natural uranium slug in aluminum cladding. The BR1 reactor has been in operation since 1956 and still contains its original fuel rods. After more than 50 years irradiation at low temperature, some of the fuel rods have been examined. Fabrication reports indicate that a so-called AlSi bonding layer and an U(Al,Si) 3 anti-diffusion layer on the natural uranium fuel slug were applied to limit the interaction between the uranium fuel and aluminum cladding. The microstructure of the fuel, bonding and anti-diffusion layer and cladding were analysed using optical microscopy, scanning electron microscopy and electron microprobe analysis. It was found that the AlSi bonding layer does provide a tight bond between fuel and cladding but that it is a thin USi layer that acts as effective anti-diffusion layer and not the intended U(Al,Si) 3 layer.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Capillary-scale direct measurement of hemoglobin concentration of erythrocytes using photothermal angular light scattering.

PubMed

Kim, Uihan; Song, Jaewoo; Lee, Donghak; Ryu, Suho; Kim, Soocheol; Hwang, Jaehyun; Joo, Chulmin

2015-12-15

We present a direct, rapid and chemical-free detection method for hemoglobin concentration ([Hb]), based on photothermal angular light scattering. The iron oxides contained in hemoglobin molecules exhibit high absorption of 532-nm light and generate heat under the illumination of 532-nm light, which subsequently alters the refractive index of blood. We measured this photothermal change in refractive index by employing angular light scattering spectroscopy with the goal of quantifying [Hb] in blood samples. Highly sensitive [Hb] measurement of blood samples was performed by monitoring the shifts in angularly dispersed scattering patterns from the blood-loaded microcapillary tubes. Our system measured [Hb] over the range of 0.35-17.9 g/dL with a detection limit of ~0.12 g/dL. Our sensor was characterized by excellent correlation with a reference hematology analyzer (r>0.96), and yielded a precision of 0.63 g/dL for a blood sample of 9.0 g/dL. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaluation of citric acid and GDL in the recovery at different pH levels of Clostridium sporogenes PA 3679 spores subjected to HTST treatment conditions.

PubMed

Silla Santos, M H; Torres Zarzo, J

1996-04-01

Spores of Clostridium sporogenes PA 3679 were treated at different temperatures (121, 126, 130 and 135 degrees C) in white asparagus purée (pH 5.8) and acidified with glucono-delta-lactone (GDL) and citric acid to pH levels of 5.5, 5.0 and 4.5. Afterwards, the spores were recovered in MPA3679 medium in various conditions: unacidified (pH 7.5), acidified with GDL (500 ppm) and acidified with citric acid (500 and 250 ppm) to pH levels of 6.5, 6.0 and 5.0. The results indicated that the pH levels, concentration and type of acid used act synergistically rather than independently. Citric acid has a stronger inhibiting effect than GDL on the recovery of C. sporogenes PA 3679 spores. At the higher heat treatments (130 and 135 degrees C) the major injury on the spores sensitize more than against the acids and low pH values.

Cross-diffusion-driven hydrodynamic instabilities in a double-layer system: General classification and nonlinear simulations

NASA Astrophysics Data System (ADS)

Budroni, M. A.

2015-12-01

Cross diffusion, whereby a flux of a given species entrains the diffusive transport of another species, can trigger buoyancy-driven hydrodynamic instabilities at the interface of initially stable stratifications. Starting from a simple three-component case, we introduce a theoretical framework to classify cross-diffusion-induced hydrodynamic phenomena in two-layer stratifications under the action of the gravitational field. A cross-diffusion-convection (CDC) model is derived by coupling the fickian diffusion formalism to Stokes equations. In order to isolate the effect of cross-diffusion in the convective destabilization of a double-layer system, we impose a starting concentration jump of one species in the bottom layer while the other one is homogeneously distributed over the spatial domain. This initial configuration avoids the concurrence of classic Rayleigh-Taylor or differential-diffusion convective instabilities, and it also allows us to activate selectively the cross-diffusion feedback by which the heterogeneously distributed species influences the diffusive transport of the other species. We identify two types of hydrodynamic modes [the negative cross-diffusion-driven convection (NCC) and the positive cross-diffusion-driven convection (PCC)], corresponding to the sign of this operational cross-diffusion term. By studying the space-time density profiles along the gravitational axis we obtain analytical conditions for the onset of convection in terms of two important parameters only: the operational cross-diffusivity and the buoyancy ratio, giving the relative contribution of the two species to the global density. The general classification of the NCC and PCC scenarios in such parameter space is supported by numerical simulations of the fully nonlinear CDC problem. The resulting convective patterns compare favorably with recent experimental results found in microemulsion systems.

Changing trends in blood transfusion in children and neonates admitted in Kilifi District Hospital, Kenya.

PubMed

Pedro, Rosalon; Akech, Samuel; Fegan, Greg; Maitland, Kathryn

2010-10-30

Severe anaemia is a common cause for hospitalization in children in sub-Saharan Africa. Malaria plays an important aetiological role, resulting in a substantial burden of paediatric transfusion in hospitals. A decline in malaria and paediatric admissions to the Kilifi District Hospital has been reported recently. This study aimed to investigate whether this trend affected clinical burden, clinical severity of anaemia and requirements for paediatric transfusion. Eight-year retrospective review of paediatric admissions to Kilifi District Hospital, Kenya describing the frequency of moderate and severe anaemia, blood transfusion and case fatality over time. Definitions for severe anaemia were Hb <8 g/dl for newborns and <5 g/dl for other age groups and for moderate anaemia was Hb 8 to <11 g/dl for newborns and 5 to <9.3 g/dl for other age groups. Life threatening anaemia was defined as severe anaemia (Hb <5 g/dl) complicated by either deep breathing or prostration or profound anaemia (Hb <4 g/dl) alone. Of the 35,139 admissions 13,037 (37%) had moderate anaemia and 2,265 (6%) had severe anaemia; respiratory distress complicated 35% of cases with Hb <5 g/dl. Concurrent with the decline in malaria there was a marked decline in the prevalence of severe anaemia between 2002 (8%) and 2009 (< 4%) (chi2 for trend = 134, P < 0.0001). The number and proportion of admissions transfused also declined significantly over this time (chi2 for trend = 152, P < 0.0001). Of the 2,265 children with severe anaemia 191 (8%) died. Case fatality remained unchanged during this period (P < 0.26) and was largely explained by the unchanged proportion with life-threatening anaemia, present in 58-65% of cases throughout the study period. The impact of reduced malaria transmission on child morbidity has positive public benefits on the demand and use of blood for paediatric transfusion. Despite an overall reduction in paediatric transfusion requirement, case fatality of severe anaemia remained unchanged over this decade. Further research is required to improve outcome from severe anaemia, particularly in the high-risk group with life threatening features.

Common hand sanitizer may distort readings of breathalyzer tests in the absence of acute intoxication.

PubMed

Ali, Syed S; Wilson, Michael P; Castillo, Edward M; Witucki, Peter; Simmons, Todd T; Vilke, Gary M

2013-02-01

The use of alcohol-based hand sanitizers has recently become widespread. To the authors' knowledge, no previous study has examined whether application of ethanol-based hand sanitizers by the person operating a common breathalyzer machine will affect the accuracy of the readings. This was a prospective study investigating whether the use of hand sanitizer applied according to manufacturer's recommendations (Group I), applied improperly at standard doses (Group II), or applied improperly at high doses (Group III) had an effect on breathalyzer readings of individuals who had not ingested alcohol. The participants of the prospective study were divided into three groups to assess the effect of hand sanitizer on breathalyzer readings. Group I used one pump (1.5 mL) of hand sanitizer (Purell), allowing the hands to dry per manufacturer's recommendations; Group II used one pump (1.5 mL), without allowing the hands to dry; and Group III used two pumps (3 mL), without allowing the hands to dry. Breathalyzer measures for each group are presented as medians with interquartile ranges (IQR) and ranges. Differences between each sequential group (I vs. II and II vs. III) were assessed using a Mann-Whitney U-test (p < 0.05 significant). There were 25 study participants in each group for a total of 75 participants. The initial breathalyzer readings of all study participants were 0.000 g/dL. The median breathalyzer reading was 0.004 g/dL in Group I (IQR = 0.001 to 0.008 g/dL), 0.051 g/dL in Group II (IQR = 0.043 to 0.064 g/dL), and 0.119 g/dL in Group III (IQR = 0.089 to 0.134 g/dL). Measures between each subsequent group were all statistically different (p < 0.001). The use of common alcohol-based hand sanitizer may cause false-positive readings with a standard hospital breathalyzer when the operator uses the hand sanitizer correctly. The breathalyzer readings are further elevated if more sanitizer is used or if it is not allowed to dry appropriately. © 2013 by the Society for Academic Emergency Medicine.

The Gamma Gap and All-Cause Mortality

PubMed Central

Juraschek, Stephen P.; Moliterno, Alison R.; Checkley, William; Miller, Edgar R.

2015-01-01

Background The difference between total serum protein and albumin, i.e. the gamma gap, is a frequently used clinical screening measure for both latent infection and malignancy. However, there are no studies defining a positive gamma gap. Further, whether it is an independent risk factor of mortality is unknown. Methods and Findings This study examined the association between gamma gap, all-cause mortality, and specific causes of death (cardiovascular, cancer, pulmonary, or other) in 12,260 participants of the National Health and Nutrition Examination Survey (NHANES) from 1999–2004. Participants had a comprehensive metabolic panel measured, which was linked with vital status data from the National Death Index. Cause of death was based on ICD10 codes from death certificates. Analyses were performed with Cox proportional hazards models adjusted for mortality risk factors. The mean (SE) age was 46 (0.3) years and the mean gamma gap was 3.0 (0.01) g/dl. The population was 52% women and 10% black. During a median follow-up period of 4.8 years (IQR: 3.3 to 6.2 years), there were 723 deaths. The unadjusted 5-year cumulative incidences across quartiles of the gamma gap (1.7–2.7, 2.8–3.0, 3.1–3.2, and 3.3–7.9 g/dl) were 5.7%, 4.2%, 5.5%, and 7.8%. After adjustment for risk factors, participants with a gamma gap of ≥3.1 g/dl had a 30% higher risk of death compared to participants with a gamma gap <3.1 g/dl (HR: 1.30; 95%CI: 1.08, 1.55; P = 0.006). Gamma gap (per 1.0 g/dl) was most strongly associated with death from pulmonary causes (HR 2.22; 95%CI: 1.19, 4.17; P = 0.01). Conclusions The gamma gap is an independent risk factor for all-cause mortality at values as low as 3.1 g/dl (in contrast to the traditional definition of 4.0 g/dl), and is strongly associated with death from pulmonary causes. Future studies should examine the biologic pathways underlying these associations. PMID:26629820

Driving decisions when leaving electronic music dance events: driver, passenger, and group effects.

PubMed

Johnson, Mark B; Voas, Robert B; Miller, Brenda A

2012-01-01

The goal of this article was to identify characteristics of drivers and passengers that predicted peer groups whose drivers exit dance clubs with alcohol levels indicative of impairment (blood alcohol content [BAC] ≥ 0.05 g/dL). We used the portal survey methodology to randomly sample groups of electronic music dance event (EMDE) patrons as they entered and exited a club. From May through November 2010, data were collected from 38 EMDEs hosted by 8 clubs in the San Francisco Bay area. Data included in these analyses are results from breath samples for measuring BAC and self-report data on demographics, recent drinking history drinking, drinking intentions, travel to and from the clubs, and the familiarity/experience with other group members. These data were collected from a subset of 175 drivers and 272 passengers. Although drivers drank less than passengers, one driver in 5 groups had a BAC indicative of elevated crash risk (BAC ≥ 0.05 g/dL). Groups of drivers and/or passengers with a recent history of binge drinking were more likely to have drivers with BACs ≥ 0.05 g/dL. One unanticipated finding was that drivers who knew more group members relatively well were more likely to exit the club with a BAC ≥ 0.05 g/dL. Additionally, we found that groups with all female passengers were at greater risk for having a driver whose BAC was ≥ 0.05 g/dL. Some group characteristics predicted drivers who exit clubs with BACs ≥ 0.05 g/dL. One intervention strategy to promote safety might be to encourage group members to reconsider who is sober enough to drive away from the club; for some groups, a change of drivers would be a safer choice, because a passenger may have a relatively safe BAC. Groups of females appear to have a particularly elevated risk of having a driver whose BAC exceeds 0.05 g/dL, and new intervention efforts should be particularly directed to these at-risk groups.

Haemoglobin dynamics in Papuan and non-Papuan adults in northeast Papua, Indonesia, with acute, uncomplicated vivax or falciparum malaria

PubMed Central

2013-01-01

Background Haemoglobin (Hb) recovers slowly in malaria and may be influenced by naturally acquired immunity. Hb recovery was compared in malaria immune, indigenous Papuan and non-Papuan adults with limited malaria exposure. Methods Hb concentrations were measured on Days (D) 0, 3, 7, and 28 in 57 Papuans and 105 non-Papuans treated with chloroquine, doxycycline or both drugs for acute, uncomplicated Plasmodium vivax (n?=?64) or Plasmodium falciparum (n?=?98). Results Mean (SD, range) D0 Hb was 12.7 (2.2, 7–21.3) g/dL and was similar in P. falciparum infected Papuans and non-Papuans: 12.2 vs. 12.8 g/dL (P?=?0.15) but significantly lower in: (i) P. vivax-infected Papuans vs. P. vivax-infected non-Papuans: 11.4 vs. 13.47 g/dL [∆?=?−2.07 (95% CI: –3.3 – –0.8), P?=?0.0018], (ii) all patients with splenomegaly (vs. those without splenomegaly): 12.16 vs. 13.01 g/dL [∆?=?−0.85 (−1.6– –0.085), P?=?0.029], and (iii) all females vs. all males: 10.18 vs. 13.01 g/dL [∆?=?−2.82 (−3.97 – –1.67), P?

Full-body gestures and movements recognition: user descriptive and unsupervised learning approaches in GDL classifier

NASA Astrophysics Data System (ADS)

Hachaj, Tomasz; Ogiela, Marek R.

2014-09-01

Gesture Description Language (GDL) is a classifier that enables syntactic description and real time recognition of full-body gestures and movements. Gestures are described in dedicated computer language named Gesture Description Language script (GDLs). In this paper we will introduce new GDLs formalisms that enable recognition of selected classes of movement trajectories. The second novelty is new unsupervised learning method with which it is possible to automatically generate GDLs descriptions. We have initially evaluated both proposed extensions of GDL and we have obtained very promising results. Both the novel methodology and evaluation results will be described in this paper.

Impact of molybdenum out diffusion and interface quality on the performance of sputter grown CZTS based solar cells.

PubMed

Dalapati, Goutam Kumar; Zhuk, Siarhei; Masudy-Panah, Saeid; Kushwaha, Ajay; Seng, Hwee Leng; Chellappan, Vijila; Suresh, Vignesh; Su, Zhenghua; Batabyal, Sudip Kumar; Tan, Cheng Cheh; Guchhait, Asim; Wong, Lydia Helena; Wong, Terence Kin Shun; Tripathy, Sudhiranjan

2017-05-02

We have investigated the impact of Cu 2 ZnSnS 4 -Molybdenum (Mo) interface quality on the performance of sputter-grown Cu 2 ZnSnS 4 (CZTS) solar cell. Thin film CZTS was deposited by sputter deposition technique using stoichiometry quaternary CZTS target. Formation of molybdenum sulphide (MoS x ) interfacial layer is observed in sputter grown CZTS films after sulphurization. Thickness of MoS x layer is found ~142 nm when CZTS layer (550 nm thick) is sulphurized at 600 °C. Thickness of MoS x layer significantly increased to ~240 nm in case of thicker CZTS layer (650 nm) under similar sulphurization condition. We also observe that high temperature (600 °C) annealing suppress the elemental impurities (Cu, Zn, Sn) at interfacial layer. The amount of out-diffused Mo significantly varies with the change in sulphurization temperature. The out-diffused Mo into CZTS layer and reconstructed interfacial layer remarkably decreases series resistance and increases shunt resistance of the solar cell. The overall efficiency of the solar cell is improved by nearly five times when 600 °C sulphurized CZTS layer is applied in place of 500 °C sulphurized layer. Molybdenum and sulphur diffusion reconstruct the interface layer during heat treatment and play the major role in charge carrier dynamics of a photovoltaic device.

The accuracy of noninvasive hemoglobin measurement by multiwavelength pulse oximetry after cardiac surgery.

PubMed

Nguyen, Ba-Vinh; Vincent, Jean-Louis; Nowak, Emmanuel; Coat, Michelle; Paleiron, Nicolas; Gouny, Pierre; Ould-Ahmed, Mehdi; Guillouet, Maité; Arvieux, Charles Christian; Gueret, Gildas

2011-11-01

In March 2008, a new multiwavelength pulse oximeter, the Radical 7 (Rad7; Masimo Corp., Irvine, CA), was developed that offers noninvasive measurement of hemoglobin concentration. Accuracy has been established in healthy adults and some surgical patients, but not in cardiac surgery intensive care patients, a group at high risk of postoperative bleeding events and anemia in whom early diagnosis could improve management. In this prospective, observational study conducted in a cardiovascular intensive care unit, we compared hemoglobin concentrations shown by the Rad7 with arterial hemoglobin concentrations determined by an automated hematology analyzer, XE-2100 (Roche, Neuilly sur Seine, France). Two software versions of Rad7 (V 7.3.0.1 [42 points of comparison in 14 patients] and the updated V 7.3.1.1 [61 points of comparison in 27 patients]) were studied during two 1-week periods. Bias, defined as the difference between the 2 methods (Masimo SpHb-XE-2100 laboratory hemoglobin), was calculated. A negative bias indicated that the Masimo underestimated hemoglobin compared with the laboratory analyzer. Correlation between the perfusion index given by Rad7 and the hemoglobin bias was also studied. Correlations between Rad7 and XE-2100 were weak for both software versions (R2=0.11 for V 7.3.0.1 and R2=0.27 for V 7.3.1.1). Mean bias was -1.3 g/dL for V 7.3.0.1 and -1.7 g/dL for V 7.3.1.1, with wide 95% prediction intervals for the bias (respectively, -4.6 to 2.1 g/dL and -5.7 to 2.3 g/dL). The absolute hemoglobin bias tended to increase when the perfusion index decreased. For the V 7.3.0.1 software, the average absolute bias was 1.9 g/dL for perfusion index<2 and 0.8 g/dL for perfusion index>2 (P=0.03). For V 7.3.1.1, the mean absolute bias was 2.1 g/dL when the perfusion index was <2, and 1.6 g/dL when the perfusion index was >2 (P=0.26). Our study demonstrates poor correlation between hemoglobin measured noninvasively by multiwavelength pulse oximetry and a laboratory hematology analyzer. The difference was greater when the pulse oximetry perfusion index was low, as may occur in shock, hypothermia, or vasoconstriction patients. The multiwavelength pulse oximetry is not sufficiently accurate for clinical use in a cardiovascular intensive care unit.

Additional BCAA-enriched nutrient mixture improves the nutritional condition in cirrhotic patients with hypoalbuminemia despite treatment with regular BCAA granules: A pilot study.

PubMed

Fukui, Aiko; Kawabe, Naoto; Hashimoto, Senju; Murao, Michihito; Nakano, Takuji; Shimazaki, Hiroaki; Kan, Toshiki; Nakaoka, Kazunori; Ohki, Masashi; Takagawa, Yuka; Kamei, Hiroyuki; Yoshioka, Kentaro

2015-07-01

To elucidate the effect of adding branched-chain amino acid (BCAA)-enriched nutrient mixtures in cirrhotic patients with hypoalbuminemia despite the use of BCAA granules. A BCAA-enriched nutrient mixture containing 5.6 g of BCAA and 210 kcal was additionally administered in 40 cirrhotic patients with hypoalbuminemia despite their treatment with BCAA granules containing 12 g of BCAA. Laboratory data were assessed at 6 months before beginning additional therapy, at baseline, and at 6 months after baseline. Serum albumin levels significantly decreased from 6 months before baseline (3.14±0.47 g/dL) to baseline (2.83±0.46 g/dL), despite the treatment with BCAA granules (p<0.001), and tended to increase from baseline to 6 months after baseline (2.95±0.42 g/dL) (p=0.084). In the subset of 23 patients without hepatocellular carcinoma treatments, upper gastrointestinal tract bleeding, or albumin infusion, serum albumin levels significantly increased from baseline (2.93±0.38 g/dL) to 6 months after baseline (3.15±0.34 g/dL) (p=0.014). Additional therapy with BCAA-enriched nutrient mixtures increased serum albumin levels of the cirrhotic patients with hypoalbuminemia despite the treatment with BCAA granules and without hepatocellular carcinoma treatment, upper gastrointestinal tract bleeding, or albumin infusion.

Emergence of a Stern Layer from the Incorporation of Hydration Interactions into the Gouy-Chapman Model of the Electrical Double Layer.

PubMed

Brown, Matthew A; Bossa, Guilherme Volpe; May, Sylvio

2015-10-27

In one of the most commonly used phenomenological descriptions of the electrical double layer, a charged solid surface and a diffuse region of mobile ions are separated from each other by a thin charge-depleted Stern layer. The Stern layer acts as a capacitor that improves the classical Gouy-Chapman model by increasing the magnitude of the surface potential and limiting the maximal counterion concentration. We show that very similar Stern-like properties of the diffuse double layer emerge naturally from adding a nonelectrostatic hydration repulsion to the electrostatic Coulomb potential. The interplay of electrostatic attraction and hydration repulsion of the counterions and the surface leads to the formation of a diffuse counterion layer that remains well separated from the surface. In addition, hydration repulsions between the ions limit and control the maximal ion concentration and widen the width of the diffuse double layer. Our mean-field model, which we express in terms of electrostatic and hydration potentials, is physically consistent and conceptually similar to the classical Gouy-Chapman model. It allows the incorporation of ion specificity, accounts for hydration properties of charged surfaces, and predicts Stern layer properties, which we analyze in terms of the effective size of the hydrated counterions.

Comparison of the Radiative Two-Flux and Diffusion Approximations

NASA Technical Reports Server (NTRS)

Spuckler, Charles M.

2006-01-01

Approximate solutions are sometimes used to determine the heat transfer and temperatures in a semitransparent material in which conduction and thermal radiation are acting. A comparison of the Milne-Eddington two-flux approximation and the diffusion approximation for combined conduction and radiation heat transfer in a ceramic material was preformed to determine the accuracy of the diffusion solution. A plane gray semitransparent layer without a substrate and a non-gray semitransparent plane layer on an opaque substrate were considered. For the plane gray layer the material is semitransparent for all wavelengths and the scattering and absorption coefficients do not vary with wavelength. For the non-gray plane layer the material is semitransparent with constant absorption and scattering coefficients up to a specified wavelength. At higher wavelengths the non-gray plane layer is assumed to be opaque. The layers are heated on one side and cooled on the other by diffuse radiation and convection. The scattering and absorption coefficients were varied. The error in the diffusion approximation compared to the Milne-Eddington two flux approximation was obtained as a function of scattering coefficient and absorption coefficient. The percent difference in interface temperatures and heat flux through the layer obtained using the Milne-Eddington two-flux and diffusion approximations are presented as a function of scattering coefficient and absorption coefficient. The largest errors occur for high scattering and low absorption except for the back surface temperature of the plane gray layer where the error is also larger at low scattering and low absorption. It is shown that the accuracy of the diffusion approximation can be improved for some scattering and absorption conditions if a reflectance obtained from a Kubelka-Munk type two flux theory is used instead of a reflection obtained from the Fresnel equation. The Kubelka-Munk reflectance accounts for surface reflection and radiation scattered back by internal scattering sites while the Fresnel reflection only accounts for surface reflections.

Chromium boron surfaced nickel-iron base alloys

NASA Technical Reports Server (NTRS)

Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

1984-01-01

Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

Boundary-layer exchange by bubble: A novel method for generating transient nanofluidic layers

NASA Astrophysics Data System (ADS)

Jennissen, Herbert P.

2005-10-01

Unstirred layers (i.e., Nernst boundary layers) occur on every dynamic solid-liquid interface, constituting a diffusion barrier, since the velocity of a moving liquid approaches zero at the surface (no slip). If a macromolecule-surface reaction rate is higher than the diffusion rate, the Nernst layer is solute depleted and the reaction rate becomes mass-transport limited. The thickness of a Nernst boundary layer (δN) generally lies between 5 and 50μm. In an evanescent wave rheometer, measuring fibrinogen adsorption to fused silica, we made the fundamental observation that an air bubble preceding the sample through the flow cell abolishes the mass-transport limitation of the Nernst diffusion layer. Instead exponential kinetics are found. Experimental and simulation studies strongly indicate that these results are due to the elimination of the Nernst diffusion layer and its replacement by a dynamic nanofluidic layer (δν) maximally 200-300nm thick. It is suggested that the air bubble leads to a transient boundary-layer separation into a novel nanoboundary layer on the surface and the bulk fluid velocity profile separated by a vortex sheet with an estimated lifetime of 30-60s. A bubble-induced boundary-layer exchange from the Nernst to the nanoboundary layer and back is obtained, giving sufficient time for the measurement of unbiased exponential surface kinetics. Noteworthy is that the nanolayer can exist at all and displays properties such as (i) a long persistence and resistance to dissipation by the bulk liquid (boundary-layer-exchange-hysteresis) and (ii) a lack of solute depletion in spite of boundary-layer separation. The boundary-layer-exchange by bubble (BLEB) method therefore appears ideal for enhancing the rates of all types of diffusion-limited macromolecular reactions on surfaces with contact angles between 0° and 90° and only appears limited by slippage due to nanobubbles or an air gap beneath the nanofluidic layer on very hydrophobic surfaces. The possibility of producing nanoboundary layers without any nanostructuring or nanomachining should also be useful for fundamental physical studies in nanofluidics.

Computational modeling of mediator oxidation by oxygen in an amperometric glucose biosensor.

PubMed

Simelevičius, Dainius; Petrauskas, Karolis; Baronas, Romas; Razumienė, Julija

2014-02-07

In this paper, an amperometric glucose biosensor is modeled numerically. The model is based on non-stationary reaction-diffusion type equations. The model consists of four layers. An enzyme layer lies directly on a working electrode surface. The enzyme layer is attached to an electrode by a polyvinyl alcohol (PVA) coated terylene membrane. This membrane is modeled as a PVA layer and a terylene layer, which have different diffusivities. The fourth layer of the model is the diffusion layer, which is modeled using the Nernst approach. The system of partial differential equations is solved numerically using the finite difference technique. The operation of the biosensor was analyzed computationally with special emphasis on the biosensor response sensitivity to oxygen when the experiment was carried out in aerobic conditions. Particularly, numerical experiments show that the overall biosensor response sensitivity to oxygen is insignificant. The simulation results qualitatively explain and confirm the experimentally observed biosensor behavior.

Computational Modeling of Mediator Oxidation by Oxygen in an Amperometric Glucose Biosensor

PubMed Central

Šimelevičius, Dainius; Petrauskas, Karolis; Baronas, Romas; Julija, Razumienė

2014-01-01

In this paper, an amperometric glucose biosensor is modeled numerically. The model is based on non-stationary reaction-diffusion type equations. The model consists of four layers. An enzyme layer lies directly on a working electrode surface. The enzyme layer is attached to an electrode by a polyvinyl alcohol (PVA) coated terylene membrane. This membrane is modeled as a PVA layer and a terylene layer, which have different diffusivities. The fourth layer of the model is the diffusion layer, which is modeled using the Nernst approach. The system of partial differential equations is solved numerically using the finite difference technique. The operation of the biosensor was analyzed computationally with special emphasis on the biosensor response sensitivity to oxygen when the experiment was carried out in aerobic conditions. Particularly, numerical experiments show that the overall biosensor response sensitivity to oxygen is insignificant. The simulation results qualitatively explain and confirm the experimentally observed biosensor behavior. PMID:24514882

Reaction layer formation at the graphite/copper-chromium alloy interface

NASA Technical Reports Server (NTRS)

Devincent, Sandra M.; Michal, Gary M.

1992-01-01

Sessile drop tests were used to obtain information about copper chromium alloys that suitably wet graphite. Characterization of graphite/copper-chromium alloy interfaces subjected to elevated temperatures were conducted using scanning electron micrography, energy dispersive spectroscopy, auger electron spectroscopy, and x ray diffraction analyses. These analyses indicate that during sessile drop tests conducted at 1130 C for one hour, copper alloys containing greater than 0.98 percent chromium form continuous reaction layers of approximately 10 micron thickness. The reaction layers adhere to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 degrees or less. X ray diffraction results indicate that the reaction layer is chromium carbide. The kinetics of reaction layer formation were modelled in terms of bulk diffusion mechanisms. Reaction layer thickness is controlled initially by the diffusion of Cr out of Cu alloy and later by the diffusion of C through chromium carbide.

Reaction layer formation at the graphite/copper-chromium alloy interface

NASA Technical Reports Server (NTRS)

Devincent, Sandra M.; Michal, Gary M.

1993-01-01

Sessile drop tests were used to obtain information about copper chromium alloys that suitably wet graphite. Characterization of graphite/copper-chromium alloy interfaces subjected to elevated temperatures were conducted using scanning electron micrography, energy dispersive spectroscopy, Auger electron spectroscopy, and X-ray diffraction analyses. These analyses indicate that during sessile drop tests conducted at 1130 C for one hour, copper alloys containing greater than 0.98 percent chromium form continuous reaction layers of approximately 10 micron thickness. The reaction layers adhere to the graphite surface. The copper wets the reaction layer to form a contact angle of 60 degrees or less. X-ray diffraction results indicate that the reaction layer is chromium carbide. The kinetics of reaction layer formation were modelled in terms of bulk diffusion mechanisms. Reaction layer thickness is controlled initially by the diffusion of Cr out of Cu alloy and later by the diffusion of C through chromium carbide.

Effects of Refractive Index and Diffuse or Specular Boundaries on a Radiating Isothermal Layer

NASA Technical Reports Server (NTRS)

Siegel, R.; Spuckler, C. M.

1994-01-01

Equilibrium temperatures of an absorbing-emitting layer were obtained for exposure to incident radiation and with the layer boundaries either specular or diffuse. For high refractive indices the surface condition can influence the radiative heat balance if the layer optical thickness is small. Hence for a spectrally varying absorption coefficient the layer temperature is affected if there is significant radiative energy in the spectral range with a small absorption coefficient. Similar behavior was obtained for transient radiative cooling of a layer where the results are affected by the initial temperature and hence the fraction of energy radiated in the short wavelength region where the absorption coefficient is small. The results are a layer without internal scattering. If internal scattering is significant, the radiation reaching the internal surface of a boundary is diffused and the effect of the two different surface conditions would become small.

Plasma diffusion at the magnetopause - The case of lower hybrid drift waves

NASA Technical Reports Server (NTRS)

Treumann, R. A.; Labelle, J.; Pottelette, R.

1991-01-01

The diffusion expected from the quasi-linear theory of the lower hybrid drift instability at the earth's magnetopause is recalculated. The resulting diffusion coefficient is marginally large enough to explain the thickness of the boundary layer under quiet conditions, based on observational upper limits for the wave intensities. Thus, one possible model for the boundary layer could involve equilibrium between the diffusion arising from lower hybrid waves and various loss processes.

Far-field analysis of coupled bulk and boundary layer diffusion toward an ion channel entrance.

PubMed Central

Schumaker, M F; Kentler, C J

1998-01-01

We present a far-field analysis of ion diffusion toward a channel embedded in a membrane with a fixed charge density. The Smoluchowski equation, which represents the 3D problem, is approximated by a system of coupled three- and two-dimensional diffusions. The 2D diffusion models the quasi-two-dimensional diffusion of ions in a boundary layer in which the electrical potential interaction with the membrane surface charge is important. The 3D diffusion models ion transport in the bulk region outside the boundary layer. Analytical expressions for concentration and flux are developed that are accurate far from the channel entrance. These provide boundary conditions for a numerical solution of the problem. Our results are used to calculate far-field ion flows corresponding to experiments of Bell and Miller (Biophys. J. 45:279, 1984). PMID:9591651

Surface recombination velocity and diffusion length of minority carriers in heavily doped silicon layers

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Watanabe, M.; Actor, G.

1977-01-01

Quantitative analysis of the electron beam-induced current and the dependence of the effective diffusion length of the minority carriers on the penetration depth of the electron beam were employed for the analysis of the carrier recombination characteristics in heavily doped silicon layers. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two dimensional mapping of the surface recombination velocity of P-diffused Si layers will be presented together with a three dimensional mapping of minority carrier lifetime in ion implanted Si. Layers heavily doped with As exhibit improved recombination characteristics as compared to those of the layers doped with P.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowgiallo, Anne-Marie; Mistry, Kevin S.; Johnson, Justin C.

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 absorptionmore » 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.« less

Probing Exciton Diffusion and Dissociation in Single-Walled Carbon Nanotube-C(60) Heterojunctions.

PubMed

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.

Viscous diffusion of vorticity in unsteady wall layers using the diffusion velocity concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strickland, J.H.; Kempka, S.N.; Wolfe, W.P.

1995-03-01

The primary purpose of this paper is to provide a careful evaluation of the diffusion velocity concept with regard to its ability to predict the diffusion of vorticity near a moving wall. A computer code BDIF has been written which simulates the evolution of the vorticity field near a wall of infinite length which is moving in an arbitrary fashion. The simulations generated by this code are found to give excellent results when compared to several exact solutions. We also outline a two-dimensional unsteady viscous boundary layer model which utilizes the diffusion velocity concept and is compatible with vortex methods.more » A primary goal of this boundary layer model is to minimize the number of vortices generated on the surface at each time step while achieving good resolution of the vorticity field near the wall. Preliminary results have been obtained for simulating a simple two-dimensional laminar boundary layer.« less

Diffusion behavior of Cu/Ta heterogeneous interface under high temperature and high strain: An atomistic investigation

NASA Astrophysics Data System (ADS)

Li, Ganglong; Wu, Houya; Luo, Honglong; Chen, Zhuo; Tay, Andrew A. O.; Zhu, Wenhui

2017-09-01

Three-dimensional (3D) integration technology using Cu interconnections has emerged as a promising solution to improve the performance of silicon microelectronic devices. However, Cu diffuses into SiO2 and requires a barrier layer such as Ta to ensure acceptable reliability. In this paper, the effects of temperature and strain normal to the interface on the inter-diffusion of Cu and Ta at annealing conditions are investigated using a molecular dynamics (MD) technique with embedded atomic method (EAM) potentials. Under thermal annealing conditions without strain, it is found that a Cu-rich diffusion region approximately 2 nm thick is formed at 1000 K after 10 ns of annealing. Ta is capable of diffusing into the interior of Cu but Cu hardly diffuses into the inner lattice of Ta. At the Cu side near the interface an amorphous structure is formed due to the process of diffusion. The diffusion activation energy of Cu and Ta are found to be 0.9769 and 0.586 eV, respectively. However, when a strain is applied, a large number of crystal defects are generated in the sample. As the strain is increased, extrinsic stacking faults (ESFs) and lots of Shockley partial dislocations appear. The density of the dislocations and the diffusion channels increase, promoting the diffusion of Cu atoms into the inner lattice of Ta. The thickness of the diffusion layer increases to 4 times the value when only a temperature load of 700 K is applied. The MD simulations demonstrated that Ta is very effective as a barrier layer under thermal loading only, and its effectiveness is impaired by tensile strain at the Cu/Ta interface. The simulations also clarified the mechanism that caused the impairment. The methodology and approach described in this paper can be followed further to study the effectiveness of barrier layers under various annealing and strain conditions, and to determine the minimum thickness of barrier layers required for a particular application.

Optical measurements of absorption changes in two-layered diffusive media

NASA Astrophysics Data System (ADS)

Fabbri, Francesco; Sassaroli, Angelo; Henry, Michael E.; Fantini, Sergio

2004-04-01

We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is ~0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of ~4% for the superficial layer and ~10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers.

Feasibility study of tungsten as a diffusion barrier between nickel-chromium-aluminum and Gamma/Gamma prime - Delta eutectic alloys

NASA Technical Reports Server (NTRS)

Young, S. G.; Zellars, G. R.

1978-01-01

Coating systems proposed for potential use on eutectic alloy components in high-temperature gas turbine engines were studied with emphasis on deterioration of such systems by diffusion. A 1-mil thick W sheet was placed between eutectic alloys and a NiCrAl layer. Layered test specimens were aged at 1100 C for as long as long as 500 hours. Without the W barrier, the delta phase of the eutectic deteriorated by diffusion of Nb into the NiCrAl. Insertion of the W barrier stopped the diffusion of Nb from delta. Chromium diffusion from the NiCrAl into the gamma/gamma prime phase of the eutectic was greatly reduced by the barrier. However, the barrier thickness decreased with time; and W diffused into both the NiCrAl and the eutectic. When the delta platelets were alined parallel to the NiCrAl layer, rather than perpendicular, diffusion into the eutectic was reduced.

Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

PubMed

Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

2014-04-22

Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800 °C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

Au/Ti resistors used for Nb/Pb-alloy Josephson junctions. II. Thermal stability

NASA Astrophysics Data System (ADS)

Murakami, Masanori; Kim, K. K.

1984-10-01

In the preceding paper bilayered Au/Ti resistors were found to have excellent electrical stability during storage at room temperature after preannealing at an elevated temperature, which is essential to design logic and memory circuits of Nb/Pb-alloy Josephson junction devices. The resistors could contact directly with the Pb-alloy control lines in which Pb and In atoms which are known to intermix easily with Au atoms are contained. Since Pb and In atoms in the control lines are separated from Au atoms of the resistors by thin Ti layers, thermal stability at the contacts is a major concern for use of the Au/Ti resistor material in the Josephson devices. In the present study, surface morphology change and diffusion mechanism at the resistor/control-line contacts were studied using x-ray diffraction and scanning electron microscopy for square-shaped Au/Ti resistors covered by Pb-In layers. The samples were isothermally annealed at temperatures ranging from 353 to 423 K. The diffusion did not occur immediately after annealing at these temperatures. After the incubation period, the interdiffusion was observed to initiate at the edges of the resistors facing to the center of the cathode. Significant amounts of the In atoms in the Pb-In layers were observed to diffuse into the Au layers of the resistors, forming AuIn2 compounds under the Ti layers. By measuring growth rates of the AuIn2 layers, the diffusion coefficients and the activation energy for the layer growth were determined. Also, by analyzing changes in the In concentration in the Pb-In layers during annealing, interdiffusion coefficients of In atoms in the Pb-In layers were determined using a computer simulation technique. The activation energy was about 1.1 eV. Since these diffusion coefficients were found to be very close to those determined previously in bulk materials, the diffusion kinetics is believed to be controlled by the lattice diffusion. Based on the present results, several methods to reduce the interdiffusion between Pb-alloy and Au/Ti resistors were proposed.

Reflectance spectroscopy can quantify cutaneous haemoglobin oxygenation by oxygen uptake from the atmosphere after epidermal barrier disruption.

PubMed

Heise, H M; Lampen, P; Stücker, M

2003-11-01

The supply of oxygen to the viable skin tissue within the upper layers is not only secured by the cutaneous blood vascular system, but to a significant part also by oxygen diffusion from the atmosphere through the horny layer. The aim of this study was to examine whether changes in haemoglobin oxygenation can be observed within the isolated perfused bovine udder skin used as a skin model by removing the upper horny layer by adhesive tape stripping. Diffuse reflectance spectroscopy in the visible spectral range was used for non-invasive characterisation of haemoglobin oxygenation in skin under in vitro conditions. Mid-infrared attenuated total reflectance spectroscopy was employed for analysing the surface layer of the stratum corneum with respect to keratin, water and lipid components. Skin barrier disruption was achieved by repeated stripping of superficial corneocyte layers by adhesive tape. Significant changes in skin haemoglobin oxygenation were observed for skin areas with reduced lipid concentration and a reduced stratum corneum layer, as determined from the quantitative evaluation of the diffuse reflectance skin spectra. The result can be interpreted as an increase of oxygen diffusion after the removal of the upper horny layer.

Investigation of water mobility and diffusivity in hydrating micronized low-substituted hydroxypropyl cellulose, hydroxypropylmethyl cellulose, and hydroxypropyl cellulose matrix tablets by magnetic resonance imaging (MRI).

PubMed

Kojima, Masazumi; Nakagami, Hiroaki

2002-12-01

The water mobility and diffusivity in the gel-layer of hydrating low-substituted hydroxypropyl cellulose (LH41) tablets with or without a drug were investigated by magnetic resonance imaging (MRI) and compared with those properties in the gel-layer of hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) tablets. For this purpose, a localized image-analysis method was newly developed, and the spin-spin relaxation time (T(2)) and apparent self-diffusion coefficient (ADC) of water in the gel-layer were visualized in one-dimensional maps. Those maps showed that the extent of gel-layer growth in the tablets was in the order of HPC>HPMC>LH41, and there was a water mobility gradient across the gel-layers of all three tablet formulations. The T(2) and ADC in the outer parts of the gel-layers were close to those of free water. In contrast, these values in the inner parts of the gel-layer decreased progressively; suggesting that the water mobility and diffusivity around the core interface were highly restricted. Furthermore, the correlation between the T(2) of (1)H proton in the gel-layer of the tablets and the drug release rate from the tablets was observed.

High mobility, dual layer, c-axis aligned crystalline/amorphous IGZO thin film transistor

NASA Astrophysics Data System (ADS)

Chung, Chen-Yang; Zhu, Bin; Greene, Raymond G.; Thompson, Michael O.; Ast, Dieter G.

2015-11-01

We demonstrate a dual layer IGZO thin film transistor (TFT) consisting of a 310 °C deposited c-axis aligned crystal (CAAC) 20 nm thick channel layer capped by a second, 30 nm thick, 260 °C deposited amorphous IGZO layer. The TFT exhibits a saturation field-effect mobility of ˜20 cm2/V s, exceeding the mobility of 50 nm thick single layer reference TFTs fabricated with either material. The deposition temperature of the second layer influences the mobility of the underlying transport layer. When the cap layer is deposited at room temperature (RT), the mobility in the 310 °C deposited CAAC layer is initially low (6.7 cm2/V s), but rises continuously with time over 58 days to 20.5 cm2/V s, i.e., to the same value as when the second layer is deposited at 260 °C. This observation indicates that the two layers equilibrate at RT with a time constant on the order of 5 × 106 s. An analysis based on diffusive transport indicates that the room temperature diffusivity must be of the order of 1 × 10-18 cm2 s-1 with an activation enthalpy EA < 0.2 eV for the mobility limiting species. The findings are consistent with a hypothesis that the amorphous layer deposited on top of the CAAC has a higher solubility for impurities and/or structural defects than the underlying nanocrystalline transport layer, and that the equilibration of the mobility limiting species is rate limited by hydrogen diffusion, whose known diffusivity fits these estimates.

Molecular dynamics simulation of diffusion and electrical conductivity in montmorillonite interlayers

DOE PAGES

Greathouse, Jeffery A.; Cygan, Randall T.; Fredrich, Joanne T.; ...

2016-01-20

In this study, the diffusion of water and ions in the interlayer region of smectite clay minerals represents a direct probe of the type and strength of clay–fluid interactions. Interlayer diffusion also represents an important link between molecular simulation and macroscopic experiments. Here we use molecular dynamics simulation to investigate trends in cation and water diffusion in montmorillonite interlayers, looking specifically at the effects of layer charge, interlayer cation and cation charge (sodium or calcium), water content, and temperature. For Na-montmorillonite, the largest increase in ion and water diffusion coefficients occurs between the one-layer and two-layer hydrates, corresponding to themore » transition from inner-sphere to outer-sphere surface complexes. Calculated activation energies for ion and water diffusion in Na-montmorillonite are similar to each other and to the water hydrogen bond energy, suggesting the breaking of water–water and water–clay hydrogen bonds as a likely mechanism for interlayer diffusion. A comparison of interlayer diffusion with that of bulk electrolyte solutions reveals a clear trend of decreasing diffusion coefficient with increasing electrolyte concentration, and in most cases the interlayer diffusion results are nearly coincident with the corresponding bulk solutions. Trends in electrical conductivities computed from the ion diffusion coefficients are also compared.« less

Fuel cell assembly unit for promoting fluid service and electrical conductivity

DOEpatents

Jones, Daniel O.

1999-01-01

Fluid service and/or electrical conductivity for a fuel cell assembly is promoted. Open-faced flow channel(s) are formed in a flow field plate face, and extend in the flow field plate face between entry and exit fluid manifolds. A resilient gas diffusion layer is located between the flow field plate face and a membrane electrode assembly, fluidly serviced with the open-faced flow channel(s). The resilient gas diffusion layer is restrained against entering the open-faced flow channel(s) under a compressive force applied to the fuel cell assembly. In particular, a first side of a support member abuts the flow field plate face, and a second side of the support member abuts the resilient gas diffusion layer. The support member is formed with a plurality of openings extending between the first and second sides of the support member. In addition, a clamping pressure is maintained for an interface between the resilient gas diffusion layer and a portion of the membrane electrode assembly. Preferably, the support member is spikeless and/or substantially flat. Further, the support member is formed with an electrical path for conducting current between the resilient gas diffusion layer and position(s) on the flow field plate face.

Augmenting ejector endwall effects. [V/STOL aircraft

NASA Technical Reports Server (NTRS)

Porter, J. L.; Squyers, R. A.

1979-01-01

Rectangular inlet ejectors which had multiple hypermixing nozzles for their primary jets were investigated for the effects of endwall blowing on thrust augmentation performance. The ejector configurations tested had both straight wall and active boundary layer control type diffusers. Endwall flows were energized and controlled by simple blowing jets suitably located in the ejector. Both the endwall and boundary layer control diffuser blowing rates were varied to determine optimum performance. High area ratio diffusers with insufficient endwall blowing showed endwall separation and rapid degradation of thrust performance. Optimized values of diffuser boundary layer control and endwall nozzle blowing rates in an ejector augmenter were shown to achieve high levels of augmentation performance for maximum compactness.

Experimental investigation of the excess charge and time constant of minority carriers in the thin diffused layer of 0.1 ohm-cm silicon solar cells

NASA Technical Reports Server (NTRS)

Godlewski, M. P.; Brandhorst, H. W., Jr.; Lindholm, F. A.; Sah, C. T.

1976-01-01

An experimental method is presented that can be used to interpret the relative roles of bandgap narrowing and recombination processes in the diffused layer. This method involves measuring the device time constant by open-circuit voltage decay and the base region diffusion length by X-ray excitation. A unique illuminated diode method is used to obtain the diode saturation current. These data are interpreted using a simple model to determine individually the minority carrier lifetime and the excess charge. These parameters are then used to infer the relative importance of bandgap narrowing and recombination processes in the diffused layer.

Graduated Driver Licensing in the United States: Evaluation Results from the Early Programs.

ERIC Educational Resources Information Center

Shope, Jean T.; Molnar, Lisa J.

2003-01-01

Review of graduated driver-licensing (GDL) programs in six states. Concludes that GDL programs are effective in reducing the crash risk of teenage drivers and that the impact of these studies and others to come will guide future research, practice, and policy. (Contains 2 tables and 19 references.) (AUTHOR/WFA)

Glutathione and 2,3-diphosphoglycerate in the blood of hypoxic ruminants.

PubMed

O'Dea, J D; Agar, N S

1980-09-01

Two merino sheep and two angora goats were subjected to simulated altitudes of up to 5500 m for about 10 h per day for 38 days. Packed cell volume (PCV), haemoglobin (Hb) concentration and red blood cell (RBC) levels of reduced glutathione (GSH) and 2,3-diphosphoglycerate (2,3-DPG) were measured at regular intervals. Mean PCV increased from 33 per cent to 60 per cent in the sheep and from 33 per cent to 45 per cent in the goats. Mean Hb concentration rose from 11.7 g/dl to 23.1 g/dl in the sheep, and from 11.4 g/dl to 16.0 g/dl in the goats. The level of GSH began to rise in the sheep only after the animals were no longer being subjected to the hypoxic stress, increasing by about 20 mg/dl RBC. In the goats, the levels of GSH rose during, as well as after, the period of hypoxic stress, also by about 20 mg/dl RBC. No change in 2,3-DPG levels was found in either species.

Ultrafast demagnetization by hot electrons: Diffusion or super-diffusion?

PubMed

Salvatella, G; Gort, R; Bühlmann, K; Däster, S; Vaterlaus, A; Acremann, Y

2016-09-01

Ultrafast demagnetization of ferromagnetic metals can be achieved by a heat pulse propagating in the electron gas of a non-magnetic metal layer, which absorbs a pump laser pulse. Demagnetization by electronic heating is investigated on samples with different thicknesses of the absorber layer on nickel. This allows us to separate the contribution of thermalized hot electrons compared to non-thermal electrons. An analytical model describes the demagnetization amplitude as a function of the absorber thickness. The observed change of demagnetization time can be reproduced by diffusive heat transport through the absorber layer.

A study of interdiffusion in beta + gamma/gamma + gamma prime Ni-Cr-Al. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Carol, L. A.

1985-01-01

Ternary diffusion in the NiCrAl system at 1200 C was studied with beta + gamma/gamma + gamma prime infinite diffusion couples. Interdiffusion resulted in the formation of complex, multiphase diffusion zones. Concentration/distance profiles for Cr and Al in the phases present in the diffusion zone were measured after 200 hr. The Ni-rich portion of the NiCrAl phase diagram (1200 C) was also determined. From these data, bulk Cr and Al profiles were calculated and translated to diffusion paths on the ternary isotherm. Growth layer kinetics of the layers present in the diffusion zone were also measured.

Effects of Mg pre-flow, memory, and diffusion on the growth of p-GaN with MOCVD (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tu, Charng-Gan; Chen, Hao-Tsung; Chen, Sheng-Hung; Chao, Chen-Yao; Kiang, Yean-Woei; Yang, Chih-Chung

2017-02-01

In MOCVD growth, two key factors for growing a p-type structure, when the modulation growth or delta-doping technique is used, include Mg memory and diffusion. With high-temperature growth (>900 degree C), doped Mg can diffuse into the under-layer. Also, due to the high-pressure growth and growth chamber coating in MOCVD, plenty Mg atoms exist in the growth chamber for a duration after Mg supply is ended. In this situation, Mg doping continues in the following designated un-doped layers. In this paper, we demonstrate the study results of Mg preflow, memory, and diffusion. The results show that pre-flow of Mg into the growth chamber can lead to a significantly higher Mg doping concentration in growing a p-GaN layer. In other words, a duration for Mg buildup is required for high Mg incorporation. Based on SIMS study, we find that with the pre-flow growth, a high- and a low-doping p-GaN layer are formed. The doping concentration difference between the two layers is about 10 times. The thickness of the high- (low-) doping layer is about 40 (65) nm. The growth of the high-doping layer starts 10-15 min after Mg supply starts (Mg buildup time). The diffusion length of Mg into the AlGaN layer beneath (Mg content reduced to <5%) is about 10 nm. The memory time of Mg in the growth chamber is about 60 min, after which the Mg doping concentration is reduced to <1%.

Measurement of Small Molecular Dopant F4TCNQ and C 60F 36 Diffusion in Organic Bilayer Architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jun; Rochester, Chris W.; Jacobs, Ian E.

2015-12-03

The diffusion of molecules through and between organic layers is a serious stability concern in organic electronic devices. In this paper, the temperature-dependent diffusion of molecular dopants through small molecule hole transport layers is observed. Specifically we investigate bilayer stacks of small molecules used for hole transport (MeO-TPD) and p-type dopants (F4TCNQ and C 60F 36) used in hole injection layers for organic light emitting diodes and hole collection electrodes for organic photovoltaics. With the use of absorbance spectroscopy, photoluminescence spectroscopy, neutron reflectometry, and near-edge X-ray absorption fine structure spectroscopy, we are able to obtain a comprehensive picture of themore » diffusion of fluorinated small molecules through MeO-TPD layers. F4TCNQ spontaneously diffuses into the MeO-TPD material even at room temperature, while C 60F 36, a much bulkier molecule, is shown to have a substantially higher morphological stability. Finally, this study highlights that the differences in size/geometry and thermal properties of small molecular dopants can have a significant impact on their diffusion in organic device architectures.« less

The influence of radiation-induced vacancy on the formation of thin-film of compound layer during a reactive diffusion process

NASA Astrophysics Data System (ADS)

Akintunde, S. O.; Selyshchev, P. A.

2016-05-01

A theoretical approach is developed that describes the formation of a thin-film of AB-compound layer under the influence of radiation-induced vacancy. The AB-compound layer is formed as a result of a chemical reaction between the atomic species of A and B immiscible layers. The two layers are irradiated with a beam of energetic particles and this process leads to several vacant lattice sites creation in both layers due to the displacement of lattice atoms by irradiating particles. A- and B-atoms diffuse via these lattice sites by means of a vacancy mechanism in considerable amount to reaction interfaces A/AB and AB/B. The reaction interfaces increase in thickness as a result of chemical transformation between the diffusing species and surface atoms (near both layers). The compound layer formation occurs in two stages. The first stage begins as an interfacial reaction controlled process, and the second as a diffusion controlled process. The critical thickness and time are determined at a transition point between the two stages. The influence of radiation-induced vacancy on layer thickness, speed of growth, and reaction rate is investigated under irradiation within the framework of the model presented here. The result obtained shows that the layer thickness, speed of growth, and reaction rate increase strongly as the defect generation rate rises in the irradiated layers. It also shows the feasibility of producing a compound layer (especially in near-noble metal silicide considered in this study) at a temperature below their normal formation temperature under the influence of radiation.

Permission to park: A statewide study of high school parking permits to determine compliance with graduated driver licensing law.

PubMed

Apanovitch, Audrey; Champany, Victoria; Wilson, Meghan; Emam, Hadeer; Ruiz, Kelly; Borrup, Kevin; Lapidus, Garry

2015-09-01

Motor vehicle crashes are the leading cause of fatality among teens in the United States. Beginning in the 1990s, many states enacted graduated driver licensing (GDL) systems to delay full licensure while allowing beginners to obtain experience under lower-risk conditions. Many high schools require parent and guardians of newly licensed teen drivers to complete a student parking pass application (PPA) for their son/daughter to drive, park, and transport themselves to and from school activities. The objective of this study was to describe the content of these PPAs for compliance with Connecticut's GDL law. PPAs were requested via e-mail, fax, or telephone from all Connecticut's high schools (n = 233). PPA variables included school demographics, parking rules, prohibitions and sanctions for violations, as well as reference to GDL law. Seventy-four schools were excluded because students were not allowed to park and schools did not require PPAs or declined to send us a copy of their PPAs. Of the remaining 159 schools, 122 (76.7%) sent us their PPAs. Responding schools were more likely to be suburban or rural. Most PPAs included a section on prohibitions and sanctions for driving misbehavior. Forty-three percent prohibited students from going to car during school hours, and 34% prohibited driving off campus/parking lot. Seventy percent warned of consequences for dangerous driving in parking lot, and 88% included the possibility of revocation for infractions. Only 14% had any reference to Connecticut's GDL law on their PPAs. A small percentage of Connecticut high schools include information about GDL laws on their PPAs. All states should examine their PPA content and adopt a uniform high school PPA that includes key provisions of their state's GDL laws in an effort to promote teen driving safety. Therapeutic study, level V.

Iodine deficiency in Saudi Arabia.

PubMed

Al-Nuaim, A R; Al-Mazrou, Y; Kamel, M; Al-Attas, O; Al-Daghari, N; Sulimani, R

1997-05-01

Data on the status of iodine deficiency in the Arabian peninsula is scarce. We have conducted a cross-sectional national epidemiological survey in Saudi Arabia to study the iodine status of Saudi schoolchildren, between eight and ten years, who were randomly selected, after taking into consideration the gender, provincial population and area distribution. Casual urine samples were collected and sent to the central laboratory for analysis. Clinical assessment for the presence of goiter was conducted in four areas with different geographical natures. The survey included 4638 subjects, and their median and mean (SD) of urinary iodine concentration was 18 and 17 m g/dL, respectively. We found provincial differences with respect to urinary iodine concentration and the percentage of subjects with urinary iodine concentration <10 m g/dL. The Southern province had the lowest median (11 m g/dL) and the highest percentage (45%) of subjects with urinary iodine concentration <10 m g/dL. On the other hand, subjects of the Western province had the highest median (24 m g/dL) and the lowest percentage (8%) of subjects with urinary iodine concentration <10 m g/dL. The clinical assessment revealed that the highest prevalence and more advanced grade of goiter (22%, 95% CI 19-25, grade 1; 8%, 95% CI 6-10, grade 2) was found in the Asir region, a high-altitude area in the Southern province. The lowest prevalence of goiter (4%, 95% CI 0.8-7.2, grade 1) was found in Gizan, an urban coastal community. There was a significant relationship between the prevalence of goiter and the urinary iodine concentration. The survey for iodine deficiency disorder (IDD) in Saudi Arabia has shown a mild degree of iodine deficiency in the Southern province. Odds ratio (OR) was used to study the statistical relationship between the prevalence of goiter and the urinary iodine concentration. There is a need to launch a control program to ensure the exclusive availability of iodized salt in Saudi Arabia, especially in the Southern province.

Hemoglobin levels above anemia thresholds are maximally predictive for long-term survival in COPD with chronic respiratory failure.

PubMed

Kollert, Florian; Tippelt, Andrea; Müller, Carolin; Jörres, Rudolf A; Porzelius, Christine; Pfeifer, Michael; Budweiser, Stephan

2013-07-01

In patients with COPD, chronic anemia is known as an unfavorable prognostic factor. Whether the association between hemoglobin (Hb) levels and long-term survival is restricted to anemia or extends to higher Hb levels has not yet been systematically assessed. We determined Hb levels in 309 subjects with COPD and chronic respiratory failure prior to initiation of noninvasive ventilation, accounting for confounders that might affect Hb. Subjects were categorized as anemic (Hb < 12 g/dL in females, Hb < 13 g/dL in males), polycythemic (Hb ≥ 15 g/dL in females, Hb ≥ 17 g/dL in males), or normocythemic. In addition, percentiles of Hb values were analyzed with regard to mortality from any cause. Two-hundred seven subjects (67.0%) showed normal Hb levels, 46 (14.9%) had anemia, and 56 (18.1%) had polycythemia. Polycythemic subjects showed a higher survival rate than anemic (P = .01) and normocythemic subjects (P = .043). In a univariate Cox hazards model, Hb was associated with long-term survival (hazard ratio 0.855; 95% CI 0.783-0.934, P < .001). The 58th percentiles of Hb (14.3 g/dL in females, 15.1 g/dL in males) yielded the highest discriminative value for predicting survival (hazard ratio 0.463, 95% CI 0.324-0.660, P < .001). In the multivariate analysis this cutoff was an independent predictor for survival (hazard ratio 0.627, 95% CI 0.414-0.949, P = .03), in addition to age and body mass index. In subjects with COPD and chronic respiratory failure undergoing treatment with noninvasive ventilation and LTOT, high Hb levels are associated with better long-term survival. The optimal cutoff level for prediction was above the established threshold defining anemia. Thus, predicting survival only on the basis of anemia does not fully utilize the prognostic potential of Hb values in COPD.

Driver licensing and reasons for delaying licensure among young adults ages 18-20, United States, 2012.

PubMed

Tefft, Brian C; Williams, Allan F; Grabowski, Jurek G

2014-12-01

Motor vehicle crashes are the leading cause of death for teens and young adults in the United States. Graduated driver licensing (GDL) systems were designed to protect young novice drivers by limiting their exposure to specific risks while they gain experience driving. In the United States, most states' GDL systems only apply to new drivers younger than 18. Some experts suggest that GDL might encourage young people to wait until age 18 to obtain a license, to avoid GDL requirements, resulting in older teenagers having less driving experience and higher crash risk than they might have had without GDL. This study examined the prevalence and timing of licensure among young adults, and explored factors associated with delaying licensure among those not licensed before age 18. An online questionnaire was completed by 1,039 persons aged 18-20 years, recruited from a representative panel of United States households. Main outcome measures were acquisition of driver's license (a) within 12 months of the state minimum age for licensure, (b) before age 18. Associations of timing of licensure with demographic characteristics were assessed using multivariable logistic regression. Respondents not licensed before age 18 were asked to rate the importance of various possible reasons for delaying licensure. 54% of respondents were licensed before age 18. Blacks (37%; adjusted Prevalence Ratio 0.67, 95% Confidence Interval 0.48-0.93) and Hispanics (29%; adjusted Prevalence Ratio 0.60, 95% Confidence Interval 0.45-0.81) were less likely than non-Hispanic whites (67%) to be licensed before age 18. Lower household income was independently associated with delayed licensure (P < .001). The most common self-reported reasons for not becoming licensed sooner were not having a car, being able to get around without driving, and costs associated with driving. There was little evidence that GDL is a major contributor to delayed licensure; however, a substantial minority of young people do not obtain a driver's license until age 18 or older and thus begin driving outside of the GDL system, which in most states only applies to new drivers younger than 18. More research is needed to investigate the safety of older novice drivers.

Frictional and structural characterization of ion-nitrided low and high chromium steels

NASA Technical Reports Server (NTRS)

Spalvins, T.

1985-01-01

Low Cr steels AISI 41410, AISI 4340, and high Cr austenitic stainless steels AISI 304, AISI 316 were ion nitrided in a dc glow discharge plasma consisting of a 75 percent H2 - 25 percent N2 mixture. Surface compound layer phases were identified, and compound layer microhardness and diffusion zone microhardness profiles were established. Distinct differences in surface compound layer hardness and diffusion zone profiles were determined between the low and high Cr alloy steels. The high Cr stainless steels after ion nitriding displayed a hard compound layer and an abrupt diffusion zone. The compound layers of the high Cr stainless steels had a columnar structure which accounts for brittleness when layers are exposed to contact stresses. The ion nitrided surfaces of high and low Cr steels displayed a low coefficient of friction with respect to the untreated surfaces when examined in a pin and disk tribotester.

Graduated driver licensing for reducing motor vehicle crashes among young drivers.

PubMed

Russell, Kelly F; Vandermeer, Ben; Hartling, Lisa

2011-10-05

Graduated driver licensing (GDL) has been proposed as a means of reducing crash rates among novice drivers by gradually introducing them to higher risk driving situations. To examine the effectiveness of GDL in reducing crash rates among young drivers. Studies were identified through searching MEDLINE, EMBASE, CINAHL, Healthstar, Web of Science, NTIS Bibliographic Database, TRIS Online, SIGLE, the World Wide Web, conference proceedings, consultation with experts and reference lists in relevant published literature. The searches were conducted from the time of inception to May 2009, and the Cochrane Injuries Group conducted an updated search of the TRANSPORT database in September 2009. Studies were included if: 1) they compared outcomes pre- and post-implementation of a GDL program within the same jurisdiction, 2) comparisons were made between jurisdictions with and without GDL, or 3) both. Studies had to report at least one objective, quantified outcome. Results were not pooled due to substantial heterogeneity. Percentage change was calculated for each year after the intervention, using one year prior to the intervention as baseline. Results were adjusted by internal controls. Analyses were stratified by denominators (population, licensed drivers). Results were calculated for the different crash types and presented for 16 year-olds alone as well as all teenage drivers. We included 34 studies evaluating 21 GDL programs and 2 analyses of >40 US states. GDL programs were implemented in the US (n=16), Canada (n=3), New Zealand (n=1), and Australia (n=1) and varied in their restrictions during the intermediate stage. Based on the Insurance Institute for Highway Safety (IIHS) classification, eleven programs were good, four were fair, five were marginal, one was poor and two could not be assessed. Reductions in crash rates were seen in all jurisdictions and for all crash types. Among 16 year-old drivers, the median decrease in per population adjusted overall crash rates during the first year was 15.5% (range -27 to -8%, five studies). There was a decrease in per population adjusted injury crash rates (median -21%, range -46 to -2%, five studies). Results for all teenage drivers, rates per licensed driver, and rates adjusting for internal controls were generally reduced when comparing within jurisdictions. GDL is effective in reducing crash rates among young drivers, although the magnitude of the effect varies. The conclusions are supported by consistent findings, temporal relationship, and plausibility of the association. Stronger GDL programs (i.e. more restrictions or higher quality based on IIHS classification) appear to result in greater fatality reduction. Future studies should focus on which components and combination of components yield the greatest reductions.

Experiments on tandem diffusers with boundary-layer suction applied in between

NASA Technical Reports Server (NTRS)

Barna, P. S.

1979-01-01

Experiments were performed on conical diffusers of various configurations with the same, but rather unusually large, 16:1 area ratio. Because available performance data on diffusers fall short of very large area ratio configurations, an unconventional design, consisting of two diffusers following each other in tandem, was proposed. Both diffusers had the same area ratio of 4:1, but had different taper angles. While for the first diffuser (called leading) the angle remained constant, for the second (called follower), the taper angle was stepped up to higher values. Boundary layer control, by way of suction, was applied between the diffusers, and a single slot suction ring was inserted between them. The leading diffuser had an enclosed nominal divergence angle 2 theta = 5 degrees, while the follower diffusers had either 10, 20, 30, or 40 degrees, respectively, giving 4 combinations. The experiments were performed at four different Reynolds numbers with various suction rates. The rates indicate a general improvement in the performance of all diffusers with boundary layer suction. It appears that the improvement of the pressure recovery depends on both the Reynolds number and the suction rate, and the largest increase, 0.075, was found at the lowest R sub e when the follower divergence was 2 theta = 40 degrees.

Limiting diffusion current at rotating disk electrode with dense particle layer.

PubMed

Weroński, P; Nosek, M; Batys, P

2013-09-28

Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

Investigation of Perforated Convergent-divergent Diffusers with Initial Boundary Layer

NASA Technical Reports Server (NTRS)

Weinstein, Maynard I

1950-01-01

An experimental investigation was made at Mach number 1.90 of the performance of a series of perforated convergent-divergent supersonic diffusers operating with initial boundary layer, which was induced and controlled by lengths of cylindrical inlets affixed to the diffusers. Supercritical mass-flow and peak total-pressure recoveries were decreased slightly by use of the longest inlets (4 inlet diameters in length). Combinations of cylindrical inlets, perforated diffusers, and subsonic diffuser were evaluated as simulated wind tunnels having second throats. Comparisons with noncontracted configurations of similar scale indicated conservatively computed power reductions of 25 percent.

Diffusion and surface alloying of gradient nanostructured metals

PubMed Central

Lu, Ke

2017-01-01

Gradient nanostructures (GNSs) have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed. PMID:28382244

A direct numerical method for predicting concentration profiles in a turbulent boundary layer over a flat plate. M.S. Thesis

NASA Technical Reports Server (NTRS)

Dow, J. W.

1972-01-01

A numerical solution of the turbulent mass transport equation utilizing the concept of eddy diffusivity is presented as an efficient method of investigating turbulent mass transport in boundary layer type flows. A FORTRAN computer program is used to study the two-dimensional diffusion of ammonia, from a line source on the surface, into a turbulent boundary layer over a flat plate. The results of the numerical solution are compared with experimental data to verify the results of the solution. Several other solutions to diffusion problems are presented to illustrate the versatility of the computer program and to provide some insight into the problem of mass diffusion as a whole.

Impact of a boron rich layer on minority carrier lifetime degradation in boron spin-on dopant diffused n-type crystalline silicon solar cells

NASA Astrophysics Data System (ADS)

Singha, Bandana; Singh Solanki, Chetan

2016-03-01

In the production of n-type crystalline silicon solar cells with boron diffused emitters, the formation of a boron rich layer (BRL) is a common phenomenon and is largely responsible for bulk lifetime degradation. The phenomenon of BRL formation during diffusion of boron spin-on dopant and its impact on bulk lifetime degradation are investigated in this work. The BRL formed beneath the borosilicate glass layer has thicknesses varying from 10 nm-150 nm depending on the diffusion conditions. The effective and bulk minority carrier lifetimes, measured with Al2O3 deposited layers and a quinhydron-methanol solution, show that carrier lifetime degradation is proportional to the BRL thicknesses and their surface recombination velocities. The controlled diffusion processes and different oxidation techniques used in this work can partially reduce the BRL thickness and improve carrier lifetime by more than 10%. But for BRL thicknesses higher than 50 nm, different etching techniques further lower the carrier lifetime and the degradation in the device cannot be recovered.

Molecular Diagnostics of Diffusive Boundary Layers

NASA Astrophysics Data System (ADS)

Rawlings, J. M. C.; Hartquist, T. W.

1997-10-01

We have examined the chemistry in thin (<~0.01 pc) boundary layers between dark star-forming cores and warm, shocked T Tauri winds on the assumption that turbulence-driven diffusion occurs within them. The results indicate that emissions from C+, CH, OH, H2O and the J = 6 --> 5 transition of CO, among others, may serve as diagnostics of the boundary layers.

DIFFUSION IN THE VICINITY OF STANDARD-DESIGN NUCLEAR POWER PLANTS-I. WIND-TUNNEL EVALUATION OF DIFFUSIVE CHARACTERISTICS OF A SIMULATED SUBURBAN NEUTRAL ATMOSPHERIC BOUNDARY LAYER

EPA Science Inventory

A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated ...

Modification of the Near Surface Region Metastable Phases and Ion Induced Reactions

DTIC Science & Technology

1984-02-03

cell Si Dave Lilienfeld - amorphous Si layer thickness Au diffusion in metallic glasses Dave Lilienfeld & - low temperature Cu diffusion in Si Tim...Sullivan Fritz Stafford - defect characterization in implanted & annealed silicon-on-sapphire Peter Zielinski - Composition of CuZr metallic glass...ribbons 5. Prof. Johnson Dave Kuhn - measurement of Pd layer thickness Alexandra Elve - hydrogen profiles in metals Lauren Heitner - hydrogen diffusion in

Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO-Based Cathode Buffer Layers.

PubMed

Kang, Jia-Jhen; Yang, Tsung-Yu; Lan, Yi-Kang; Wu, Wei-Ru; Su, Chun-Jen; Weng, Shih-Chang; Yamada, Norifumi L; Su, An-Chung; Jeng, U-Ser

2018-04-01

Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X-ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO-based CBL, is developed. Uniquely revealed for a high-performance model PSC are the often overlooked porosity distributions of the ZnO-based CBL and the differential diffusions of the polymer PTB7-Th and fullerene derivative PC 71 BM of the active layer into the CBL. Interface modification of the ZnO-based CBL with fullerene derivative PCBEOH for size-selective nanochannels can selectively improve the diffusion of PC 71 BM more than that of the polymer. The deeper penetration of PC 71 BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE-OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold diffusion in mercury cadmium telluride grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Selamet, Yusuf; Singh, Rasdip; Zhao, Jun; Zhou, Yong D.; Sivananthan, Sivalingam; Dhar, Nibir K.

2003-12-01

The growth and characterization of Au-doped HgCdTe layers on (211)B CdTe/Si substrates grown by molecular beam epitaxy reported. The electrical properties of these layers studied for diffusion are presented. For ex-situ experiments, thin Au layers were deposited by evaporation and annealed at various temperatures and times to investigate the p-type doping properties and diffusion of Au in HgCdTe. The atomic distribution of the diffused Au was determined by secondary ion mass spectroscopy. We found clear evidence for p-type doping of HgCdTe:Au by in-situ and ex-situ methods. For in-situ doped layers, we found that, the Au cell temperature needs to be around 900°C to get p-type behavior. The diffusion coefficient of Au in HgCdTe was calculated by fitting SIMS profiles after annealing. Both complementary error functions and gaussian fittings were used, and were in full agreement. Diffusion coefficient as low as 8x10-14cm2/s observed for a sample annealed at 250°C and slow component of a diffusion coefficient as low as 2x10-15 cm2/s observed for a sample annealed at 300°C. Our preliminary results indicate no appreciable diffusion of Au in HgCdTe under the conditions used in these studies. Further work is in progress to confirm these results and to quantify our SIMS profiles.

Complete suppression of boron transient-enhanced diffusion and oxidation-enhanced diffusion in silicon using localized substitutional carbon incorporation

NASA Astrophysics Data System (ADS)

Carroll, M. S.; Chang, C.-L.; Sturm, J. C.; Büyüklimanli, T.

1998-12-01

In this letter, we show the ability, through introduction of a thin Si1-x-yGexCy layer, to eliminate the enhancement of enhanced boron diffusion in silicon due to an oxidizing surface or ion implant damage. This reduction of diffusion is accomplished through a low-temperature-grown thin epitaxial Si1-x-yGexCy layer which completely filters out excess interstitials introduced by oxidation or ion implant damage. We also quantify the oxidation-enhanced diffusion (OED) and transient-enhanced diffusion (TED) dependence on substitutional carbon level, and further report both the observation of carbon TED and OED, and its dependence on carbon levels.

Protective coatings for sensitive materials

DOEpatents

Egert, Charles M.

1997-01-01

An enhanced protective coating to prevent interaction between constituents of the environment and devices that can be damaged by those constituents. This coating is provided by applying a synergistic combination of diffusion barrier and physical barrier materials. These materials can be, for example, in the form of a plurality of layers of a diffusion barrier and a physical barrier, with these barrier layers being alternated. Further protection in certain instances is provided by including at least one layer of a getter material to actually react with one or more of the deleterious constituents. The coating is illustrated by using alternating layers of an organic coating (such as Parylene-C.TM.) as the diffusion barrier, and a metal coating (such as aluminum) as the physical barrier. For best results there needs to be more than one of at least one of the constituent layers.

Interfacial layers in high-temperature-oxidized NiCrAl

NASA Technical Reports Server (NTRS)

Larson, L. A.; Browning, R.; Poppa, H.; Smialek, J.

1983-01-01

The utility of Auger electron spectroscopy combined with ball cratering for depth analysis of oxide and diffusion layers produced in a Ni-14Cr-24Al alloy by oxidation in air at 1180 C for 25 hr is demonstrated. During postoxidation cooling, the oxide layers formed by this alloy spalled profusely. The remaining very thin oxide was primarily Cr2O3 with a trace of Ni. The underlying metal substrate exhibited gamma/gamma-prime and beta phases with a metallic interfacial layer which was similar to the bulk gamma/gamma-prime phase but slightly enriched in Cr and Al. These data are compared to electron microprobe results from a nominally identical alloy. The diffusion layer thickness is modelled with a simple mass balance equation and compared to recent results on the diffusion process in NiCrAl alloys.

Low temperature Zn diffusion for GaSb solar cell structures fabrication

NASA Technical Reports Server (NTRS)

Sulima, Oleg V.; Faleev, Nikolai N.; Kazantsev, Andrej B.; Mintairov, Alexander M.; Namazov, Ali

1995-01-01

Low temperature Zn diffusion in GaSb, where the minimum temperature was 450 C, was studied. The pseudo-closed box (PCB) method was used for Zn diffusion into GaAs, AlGaAs, InP, InGaAs and InGaAsP. The PCB method avoids the inconvenience of sealed ampoules and proved to be simple and reproducible. The special design of the boat for Zn diffusion ensured the uniformality of Zn vapor pressure across the wafer surface, and thus the uniformity of the p-GaSb layer depth. The p-GaSb layers were studied using Raman scattering spectroscopy and the x-ray rocking curve method. As for the postdiffusion processing, an anodic oxidation was used for a precise thinning of the diffused GaSb layers. The results show the applicability of the PCB method for the large-scale production of the GaSb structures for solar cells.

Dynamics behavior of lithium in graphite lattice: MD calculation approach

NASA Astrophysics Data System (ADS)

Shimizu, A.; Tachikawa, H.

2000-12-01

In order to investigate the diffusion process of Li atom in graphite, molecular dynamics simulation was achieved on the basis of molecular mechanics 2 (MM2) method using four layers cluster model one of which is composed of C150H30 with terminating hydrogen atoms. According to the simulations at 500 K, Li atom stabilizes initially around the center of mass, gets out of the graphite layers after 3.0 ps through diffusion, which is different from the movement of Li+ ion captured by the dangling bonds of the edge carbon atoms. The diffusion process of Li atom is found to be composed of following four steps in series: (1) vibration around the stabilization point; (2) bulk diffusion; (3) vibration under influence of the dangling bonds of edge carbon atoms; and (4) escape from the graphite layers. The diffusivity for step (3) is smaller than that for step (2).

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

NASA Astrophysics Data System (ADS)

Chen, Guifeng; Wang, Mengxue; Yang, Wenxian; Tan, Ming; Wu, Yuanyuan; Dai, Pan; Huang, Yuyang; Lu, Shulong

2017-12-01

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace. The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements. The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission, which indicates that Zn was commendably diffused into InP layer as the acceptor. High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 °C for 10 min. Furthermore, more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process. Based on the above Zn-diffusion technique, a 50 μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of -5 V and a high breakdown voltage of larger than 41 V (I < 10 μA). In addition, a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector. Project supported by the Key R&D Program of Jiangsu Province (No. BE2016085) , the National Natural Science Foundation of China (Nos. 61674051), and the External Cooperation Program of BIC, Chinese Academy of Sciences (No. 121E32KYSB20160071).

Effects of nitrogen and biochar amendment on soil methane concentration profiles and diffusion in a rice-wheat annual rotation system

NASA Astrophysics Data System (ADS)

Xu, Xin; Wu, Zhen; Dong, Yubing; Zhou, Ziqiang; Xiong, Zhengqin

2016-12-01

The CH4 emissions from soil were influenced by the changeable CH4 concentrations and diffusions in soil profiles, but that have been subjected to nitrogen (N) and biochar amendment over seasonal and annual time frames. Accordingly, a two-year field experiment was conducted in southeastern China to determine the amendment effects on CH4 concentrations and diffusive effluxes as measured by a multilevel sampling probe in paddy soil during two cycles of rice-wheat rotations. The results showed that the top 7-cm soil layers were the primary CH4 production sites during the rice-growing seasons. This layer acted as the source of CH4 generation and diffusion, and the deeper soil layers and the wheat season soil acted as the sink. N fertilization significantly increased the CH4 concentration and diffusive effluxes in the top 7-cm layers during the 2013 and 2014 rice seasons. Following biochar amendment, the soil CH4 concentrations significantly decreased during the rice season in 2014, relative to the single N treatment. Moreover, 40 t ha-1 biochar significantly decreased the diffusive effluxes during the rice seasons in both years. Therefore, our results showed that biochar amendment is a good strategy for reducing the soil profile CH4 concentrations and diffusive effluxes induced by N in paddy fields.

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells

PubMed Central

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n+ emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion. PMID:25520602

Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

PubMed

Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

2014-01-01

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

Effects of nitrogen and biochar amendment on soil methane concentration profiles and diffusion in a rice-wheat annual rotation system.

PubMed

Xu, Xin; Wu, Zhen; Dong, Yubing; Zhou, Ziqiang; Xiong, Zhengqin

2016-12-08

The CH 4 emissions from soil were influenced by the changeable CH 4 concentrations and diffusions in soil profiles, but that have been subjected to nitrogen (N) and biochar amendment over seasonal and annual time frames. Accordingly, a two-year field experiment was conducted in southeastern China to determine the amendment effects on CH 4 concentrations and diffusive effluxes as measured by a multilevel sampling probe in paddy soil during two cycles of rice-wheat rotations. The results showed that the top 7-cm soil layers were the primary CH 4 production sites during the rice-growing seasons. This layer acted as the source of CH 4 generation and diffusion, and the deeper soil layers and the wheat season soil acted as the sink. N fertilization significantly increased the CH 4 concentration and diffusive effluxes in the top 7-cm layers during the 2013 and 2014 rice seasons. Following biochar amendment, the soil CH 4 concentrations significantly decreased during the rice season in 2014, relative to the single N treatment. Moreover, 40 t ha -1 biochar significantly decreased the diffusive effluxes during the rice seasons in both years. Therefore, our results showed that biochar amendment is a good strategy for reducing the soil profile CH 4 concentrations and diffusive effluxes induced by N in paddy fields.

Diffusion-Based Design of Multi-Layered Ophthalmic Lenses for Controlled Drug Release

PubMed Central

Pimenta, Andreia F. R.; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde

2016-01-01

The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses. PMID:27936138

An Experimental Investigation of Forced Mixing of a Turbulent Boundary Layer in an Annular Diffuser. Ph.D. Thesis - Ohio State Univ.; [for boundary layer control

NASA Technical Reports Server (NTRS)

Shaw, R. J.

1979-01-01

The forced mixing process of a turbulent boundary layer in an axisymmetric annular diffuser using conventional wing-like vortex generators was studied. Flow field measurements were made at four axial locations downstream of the vortex generators. At each axial location, a total of 25 equally spaced profiles were measured behind three consecutive vortex generators which formed two pairs of vortex generators. Hot film anemometry probes measured the boundary layer turbulence structure at the same locations where pressure measurements were made. Both single and cross film probes were used. The diffuser turbulence data was teken only for a nominal inlet Mach number of 0.3. Three vortex generator configurations were tested. The differences between configurations involved changes in size and relative vortex generator positions. All three vortex generator configurations tested provided increases in diffuser performance. Distinct differences in the boundary layer integral properties and skin friction levels were noted between configurations. The axial turbulence intensity and Reynolds stress profiles measured displayed similarities in trends but differences in levels for the three configurations.

Reliable recovery of the optical properties of multi-layer turbid media by iteratively using a layered diffusion model at multiple source-detector separations

PubMed Central

Liao, Yu-Kai; Tseng, Sheng-Hao

2014-01-01

Accurately determining the optical properties of multi-layer turbid media using a layered diffusion model is often a difficult task and could be an ill-posed problem. In this study, an iterative algorithm was proposed for solving such problems. This algorithm employed a layered diffusion model to calculate the optical properties of a layered sample at several source-detector separations (SDSs). The optical properties determined at various SDSs were mutually referenced to complete one round of iteration and the optical properties were gradually revised in further iterations until a set of stable optical properties was obtained. We evaluated the performance of the proposed method using frequency domain Monte Carlo simulations and found that the method could robustly recover the layered sample properties with various layer thickness and optical property settings. It is expected that this algorithm can work with photon transport models in frequency and time domain for various applications, such as determination of subcutaneous fat or muscle optical properties and monitoring the hemodynamics of muscle. PMID:24688828

Graduated driver license compliant teens involved in fatal motor vehicle crashes.

PubMed

Pressley, Joyce C; Addison, Diane; Dawson, Patrick; Nelson, Sharifa S

2015-09-01

Significant reductions in motor vehicle injury mortality have been reported for teen drivers after passage of graduated driver licensing (GDL), seat belt, and no tolerance alcohol and drug laws. Despite this, teen drivers remain a vulnerable population with elevated fatal crash involvement. This study examines driver, vehicle, and crash characteristics of GDL-compliant, belted, and unimpaired teen drivers with the goal of identifying areas where further improvements might be realized. The Fatality Analysis Reporting System (FARS) for 2007 to 2009 was used to examine and classify driver violations/errors in compliant teen drivers (n = 1,571) of passenger vehicles involved in a fatal collision. Teens driving unbelted, non-GDL compliant, or impaired by alcohol or drugs were excluded. Statistical analysis used χ, Fisher's exact and multivariable logistic regression. Odds ratios are reported with 95% confidence intervals. Significance was defined as p < 0.05. Nearly one third (n = 1,571) of teen drivers involved in a fatal motor vehicle crash were GDL compliant, unimpaired, and belted. The majority held an intermediate GDL license (90.6%). Crash-related factors were identified for 63.1% of fatal crashes. Age- and sex-adjusted odds identified overcorrecting, speeding, lane errors, school morning crashes, distractions, and driving on slippery surfaces as having increased odds of fatality for the teen driver as well as newer vehicle models and heavier vehicle weight as protective. Among compliant drivers, weekday crashes before and after school and committing a driving violation at the time of crash were associated with increased risk of driver death and higher incidence of incapacitating injury in surviving drivers. Therapeutic study, level V.

Epoetin alfa improves survival after chemoradiation for Stage III esophageal cancer: Final results of a prospective observational study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rades, Dirk; Tribius, Silke; Yekebas, Emre F.

Purpose: This prospective, nonrandomized study evaluates the effectiveness of epoetin alfa to maintain the hemoglobin levels at 12 to14 g/dL (optimal range for tumor oxygenation) during chemoradiation for Stage III esophageal cancer and its impact on overall survival (OS), metastatic-free survival (MFS), and locoregional control (LC). Methods and Materials: Ninety-six patients were included. Forty-two patients received epoetin alfa (150 IU/kg, 3 times a week) during radiotherapy, which was started at hemoglobin less than 13 g/dL and stopped at 14 g/dL or higher. Hemoglobin levels were measured weekly during RT. Results: Both groups were balanced for age, sex, performance status, tumormore » length/location, histology, grading, T-stage/N-stage, chemotherapy, treatment schedule, and hemoglobin before RT. Median change of hemoglobin was +0.3 g/dL/wk with epoetin alfa and -0.5 g/dL/wk without epoetin alfa. At least 60% of hemoglobin levels were 12 to 14 g/dL in 64% and 17% of the patients, respectively (p < 0.001). Patients who received epoetin alfa had better OS (32% vs. 8% at 2 years, p = 0.009) and LC (67% vs. 15% at 2 years, p = 0.001). MFS was not significantly different (42% vs. 18% at 2 years, p = 0.09). Conclusions: The findings suggest that epoetin alfa when used to maintain the hemoglobin levels at 12 to 14 g/dL can improve OS and LC of Stage III esophageal cancer patients.« less

Imaging laminar structures in the gray matter with diffusion MRI.

PubMed

Assaf, Yaniv

2018-01-05

The cortical layers define the architecture of the gray matter and its neuroanatomical regions and are essential for brain function. Abnormalities in cortical layer development, growth patterns, organization, or size can affect brain physiology and cognition. Unfortunately, while large population studies are underway that will greatly increase our knowledge about these processes, current non-invasive techniques for characterizing the cortical layers remain inadequate. For decades, high-resolution T1 and T2 Weighted Magnetic Resonance Imaging (MRI) have been the method-of-choice for gray matter and layer characterization. In the past few years, however, diffusion MRI has shown increasing promise for its unique insights into the fine structure of the cortex. Several different methods, including surface analysis, connectivity exploration, and sub-voxel component modeling, are now capable of exploring the diffusion characteristics of the cortex. In this review, we will discuss current advances in the application of diffusion imaging for cortical characterization and its unique features, with a particular emphasis on its spatial resolution, arguably its greatest limitation. In addition, we will explore the relationship between the diffusion MRI signal and the cellular components of the cortex, as visualized by histology. While the obstacles facing the widespread application of cortical diffusion imaging remain daunting, the information it can reveal may prove invaluable. Within the next few years, we predict a surge in the application of this technique and a concomitant expansion of our knowledge of cortical layers. Copyright © 2018 Elsevier Inc. All rights reserved.

Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone

USGS Publications Warehouse

Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Robert G.; Stonestrom, David A.

2015-01-01

Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.

Passive Rocket Diffuser Testing: Reacting Flow Performance of Four Second-Throat Geometries

NASA Technical Reports Server (NTRS)

Jones, Daniel R.; Allgood, Daniel C.; Saunders, Grady P.

2016-01-01

Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure. As one of the nation's largest rocket testing facilities, the performance and design limitations of diffusers are of great interest to NASA's Stennis Space Center. This paper describes a series of tests conducted on four diffuser configurations to better understand the effects of inlet geometry and throat area on starting behavior and boundary layer separation. The diffusers were tested for a duration of five seconds with a 1455-pound thrust, LO2/GH2 thruster to ensure they each reached aerodynamic steady state. The effects of a water spray ring at the diffuser exits and a water-cooled deflector plate were also evaluated. Static pressure and temperature measurements were taken at multiple axial locations along the diffusers, and Computational Fluid Dynamics (CFD) simulations were used as a tool to aid in the interpretation of data. The hot combustion products were confirmed to enable the diffuser start condition with tighter second throats than predicted by historical cold-flow data or the theoretical normal shock method. Both aerodynamic performance and heat transfer were found to increase with smaller diffuser throats. Spray ring and deflector cooling water had negligible impacts on diffuser boundary layer separation. CFD was found to accurately capture diffuser shock structures and full-flowing diffuser wall pressures, and the qualitative behavior of heat transfer. However, the ability to predict boundary layer separated flows was not consistent.

Corrosion resistant coatings suitable for elevated temperature application

DOEpatents

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Layer Structure of a Refractory Multilayer Ti/Al Composite After Pressure Diffusion Welding

NASA Astrophysics Data System (ADS)

Karpov, M. I.; Korzhov, V. P.; Zheltyakova, I. S.

2016-05-01

A composite refractory material with layer structure obtained by the method of pressure diffusion welding of multilayer Ti/Al packets composed of Ti- and Al-foils is studied. The welding temperature of the packets does not exceed 1200 - 1250°C. A layer structure forms in the process of interdiffusion of titanium and aluminum during welding of the packets.

Ion Layer Separation and Equilibrium Zonal Winds in Midlatitude Sporadic E

NASA Technical Reports Server (NTRS)

Earle, G. D.; Kane, T. J.; Pfaff, R. F.; Bounds, S. R.

2000-01-01

In-situ observations of a moderately strong mid-latitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe(+), Mg(+), and NO(+). From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 meters per second, and the vertical wavelength is less than 10 km.

Solution of the nonlinear Poisson-Boltzmann equation: Application to ionic diffusion in cementitious materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnold, J.; Kosson, D.S., E-mail: david.s.kosson@vanderbilt.edu; Garrabrants, A.

2013-02-15

A robust numerical solution of the nonlinear Poisson-Boltzmann equation for asymmetric polyelectrolyte solutions in discrete pore geometries is presented. Comparisons to the linearized approximation of the Poisson-Boltzmann equation reveal that the assumptions leading to linearization may not be appropriate for the electrochemical regime in many cementitious materials. Implications of the electric double layer on both partitioning of species and on diffusive release are discussed. The influence of the electric double layer on anion diffusion relative to cation diffusion is examined.

Association between New Jersey's Graduated Driver Licensing decal provision and crash rates of young drivers with learners' permits.

PubMed

Curry, Allison E; Pfeiffer, Melissa R; Elliott, Michael R; Durbin, Dennis R

2015-12-01

New Jersey (NJ) implemented the first-in-the-US Graduated Driver Licensing (GDL) decal provision in May 2010 for young drivers with learner's permits or intermediate licenses. Previous analyses found an association between the provision and crash reduction among intermediate drivers. The aim of this study is to examine the association between NJ's provision and GDL citation and crash rates among drivers aged <21 years with learner's permits. We estimated monthly per-driver rates from January 2006 through June 2012. Negative binomial modeling compared pre and post decal crash rates adjusted for gender, age, calendar month, and gas price. The monthly GDL citation rate was two per 10,000 drivers in the predecal and postdecal periods. Crashes were rare and rates declined similarly pre and post decal (adjusted rate ratio of postdecal vs predecal slope: 1.04 (0.97 to 1.12)). NJ's GDL decal provision was not associated with a change in citation or crash rates among young NJ drivers with learner's permits. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

[Effect of freezing on the "creamatocrit" measurement of the lipid content of human donor milk].

PubMed

Vázquez-Román, S; Alonso-Díaz, C; García-Lara, N R; Escuder-Vieco, D; Pallás-Alonso, C R

2014-09-01

To determine, by the creamatocrit measurement, the effect on the fat content of raw and pasteurized donor milk of freezing during 3 months at -20 °C. The evolution of the creamatocrit measurement (following Lucas technique) on frozen (-20 °C), raw and pasteurized human milk, was analyzed during 3 months. The fat content of raw milk (n=44) was 3.19 g/dl at the beginning and 2.86 g/dl after 3 months frozen (p=0.02). In pasteurized milk (n=36) fat content at the first determination was 2.59 g/dl and 2.20 g/dl after 1 month frozen (p=0.01). Afterwards there were no significant changes up to 3 months frozen. Variability was observed in the intermediate values. A reduction on the fat content measurement of raw and pasteurized donor human milk after freezing was observed. Freezing does not inactivate the milk lipase but does destroy the fat globule. Creamatocrit measurement may not be the best method to determine the fat content of processed human milk. Copyright © 2013 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.

The adaptation of GDL motion recognition system to sport and rehabilitation techniques analysis.

PubMed

Hachaj, Tomasz; Ogiela, Marek R

2016-06-01

The main novelty of this paper is presenting the adaptation of Gesture Description Language (GDL) methodology to sport and rehabilitation data analysis and classification. In this paper we showed that Lua language can be successfully used for adaptation of the GDL classifier to those tasks. The newly applied scripting language allows easily extension and integration of classifier with other software technologies and applications. The obtained execution speed allows using the methodology in the real-time motion capture data processing where capturing frequency differs from 100 Hz to even 500 Hz depending on number of features or classes to be calculated and recognized. Due to this fact the proposed methodology can be used to the high-end motion capture system. We anticipate that using novel, efficient and effective method will highly help both sport trainers and physiotherapist in they practice. The proposed approach can be directly applied to motion capture data kinematics analysis (evaluation of motion without regard to the forces that cause that motion). The ability to apply pattern recognition methods for GDL description can be utilized in virtual reality environment and used for sport training or rehabilitation treatment.

Effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Astrophysics Data System (ADS)

Saunders, B. V.; Murray, B. T.; McFadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1991-10-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress free boundaries is studied using Floquet theory for the linear stability analysis. Situations are considered for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double diffusive convection. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency.

A Fast Hyperspectral Vector Radiative Transfer Model in UV to IR spectral bands

NASA Astrophysics Data System (ADS)

Ding, J.; Yang, P.; Sun, B.; Kattawar, G. W.; Platnick, S. E.; Meyer, K.; Wang, C.

2016-12-01

We develop a fast hyperspectral vector radiative transfer model with a spectral range from UV to IR with 5 nm resolutions. This model can simulate top of the atmosphere (TOA) diffuse radiance and polarized reflectance by considering gas absorption, Rayleigh scattering, and aerosol and cloud scattering. The absorption component considers several major atmospheric absorbers such as water vapor, CO2, O3, and O2 including both line and continuum absorptions. A regression-based method is used to parameterize the layer effective optical thickness for each gas, which substantially increases the computation efficiency for absorption while maintaining high accuracy. This method is over 500 times faster than the existing line-by-line method. The scattering component uses the successive order of scattering (SOS) method. For Rayleigh scattering, convergence is fast due to the small optical thickness of atmospheric gases. For cloud and aerosol layers, a small-angle approximation method is used in SOS calculations. The scattering process is divided into two parts, a forward part and a diffuse part. The scattering in the small-angle range in the forward direction is approximated as forward scattering. A cloud or aerosol layer is divided into thin layers. As the ray propagates through each thin layer, a portion diverges as diffuse radiation, while the remainder continues propagating in forward direction. The computed diffuse radiance is the sum of all of the diffuse parts. The small-angle approximation makes the SOS calculation converge rapidly even in a thick cloud layer.

Resistance switching mode transformation in SrRuO3/Cr-doped SrZrO3/Pt frameworks via a thermally activated Ti out-diffusion process

PubMed Central

Jo, Yongcheol; Jung, Kyooho; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Hong, Jinpyo; Lee, Jeon-Kook; Im, Hyunsik

2014-01-01

This work reports on a mechanism for irreversible resistive switching (RS) transformation from bipolar to unipolar RS behavior in SrRuO3 (SRO)/Cr-doped SrZrO3 (SZO:Cr)/Pt capacitor structures prepared on a Ti/SiO2/Si substrate. Counter-clockwise bipolar RS memory current-voltage (I–V) characteristics are observed within the RS voltage window of −2.5 to +1.9 V, with good endurance and retention properties. As the bias voltage increases further beyond 4 V under a forward bias, a forming process occurs resulting in irreversible RS mode transformation from bipolar to unipolar mode. This switching mode transformation is a direct consequence of thermally activated Ti out-diffusion from a Ti adhesion layer. Transition metal Ti effectively out-diffuses through the loose Pt electrode layer at high substrate temperatures, leading to the unintended formation of a thin titanium oxide (TiOx where x < 2) layer between the Pt electrode and the SZO:Cr layer as well as additional Ti atoms in the SZO:Cr layer. Cross-sectional scanning electron microscopy, transmission electron microscopy and Auger electron spectroscopy depth-profile measurements provided apparent evidence of the Ti out-diffusion phenomenon. We propose that the out-diffusion-induced additional Ti atoms in the SZO:Cr layer contributes to the creation of the metallic filamentary channels. PMID:25483325

High Temperature Oxidation of Hot-Dip Aluminized T92 Steels

NASA Astrophysics Data System (ADS)

Abro, Muhammad Ali; Hahn, Junhee; Lee, Dong Bok

2018-03-01

The T92 steel plate was hot-dip aluminized, and oxidized in order to characterize the high-temperature oxidation behavior of hot-dip aluminized T92 steel. The coating consisted of Al-rich topcoat with scattered Al3Fe grains, Al3Fe-rich upper alloy layer with scattered (Al, Al5Fe2, AlFe)-grains, and Al5Fe2-rich lower alloy layer with scattered (Al5Fe2, AlFe)-grains. Oxidation at 800 °C for 20 h formed (α-Al2O3 scale)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer), while oxidation at 900 °C for 20 h formed (α-Al2O3 scale plus some Fe2O3)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer) from the surface. During oxidation, outward migration of all substrate elements, inward diffusion of oxygen, and back and forth diffusion of Al occurred according to concentration gradients. Also, diffusion transformed and broadened AlFe and AlFe3 layers dissolved with some oxygen and substrate alloying elements. Hot-dip aluminizing improved the high-temperature oxidation resistance of T92 steel through preferential oxidation of Al at the surface.

High Temperature Oxidation of Hot-Dip Aluminized T92 Steels

NASA Astrophysics Data System (ADS)

Abro, Muhammad Ali; Hahn, Junhee; Lee, Dong Bok

2018-05-01

The T92 steel plate was hot-dip aluminized, and oxidized in order to characterize the high-temperature oxidation behavior of hot-dip aluminized T92 steel. The coating consisted of Al-rich topcoat with scattered Al3Fe grains, Al3Fe-rich upper alloy layer with scattered (Al, Al5Fe2, AlFe)-grains, and Al5Fe2-rich lower alloy layer with scattered (Al5Fe2, AlFe)-grains. Oxidation at 800 °C for 20 h formed (α-Al2O3 scale)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer), while oxidation at 900 °C for 20 h formed (α-Al2O3 scale plus some Fe2O3)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer) from the surface. During oxidation, outward migration of all substrate elements, inward diffusion of oxygen, and back and forth diffusion of Al occurred according to concentration gradients. Also, diffusion transformed and broadened AlFe and AlFe3 layers dissolved with some oxygen and substrate alloying elements. Hot-dip aluminizing improved the high-temperature oxidation resistance of T92 steel through preferential oxidation of Al at the surface.

Testing conceptual and physically based soil hydrology schemes against observations for the Amazon Basin

NASA Astrophysics Data System (ADS)

Guimberteau, M.; Ducharne, A.; Ciais, P.; Boisier, J. P.; Peng, S.; De Weirdt, M.; Verbeeck, H.

2014-06-01

This study analyzes the performance of the two soil hydrology schemes of the land surface model ORCHIDEE in estimating Amazonian hydrology and phenology for five major sub-basins (Xingu, Tapajós, Madeira, Solimões and Negro), during the 29-year period 1980-2008. A simple 2-layer scheme with a bucket topped by an evaporative layer is compared to an 11-layer diffusion scheme. The soil schemes are coupled with a river routing module and a process model of plant physiology, phenology and carbon dynamics. The simulated water budget and vegetation functioning components are compared with several data sets at sub-basin scale. The use of the 11-layer soil diffusion scheme does not significantly change the Amazonian water budget simulation when compared to the 2-layer soil scheme (+3.1 and -3.0% in evapotranspiration and river discharge, respectively). However, the higher water-holding capacity of the soil and the physically based representation of runoff and drainage in the 11-layer soil diffusion scheme result in more dynamic soil water storage variation and improved simulation of the total terrestrial water storage when compared to GRACE satellite estimates. The greater soil water storage within the 11-layer scheme also results in increased dry-season evapotranspiration (+0.5 mm d-1, +17%) and improves river discharge simulation in the southeastern sub-basins such as the Xingu. Evapotranspiration over this sub-basin is sustained during the whole dry season with the 11-layer soil diffusion scheme, whereas the 2-layer scheme limits it after only 2 dry months. Lower plant drought stress simulated by the 11-layer soil diffusion scheme leads to better simulation of the seasonal cycle of photosynthesis (GPP) when compared to a GPP data-driven model based on eddy covariance and satellite greenness measurements. A dry-season length between 4 and 7 months over the entire Amazon Basin is found to be critical in distinguishing differences in hydrological feedbacks between the soil and the vegetation cover simulated by the two soil schemes. On average, the multilayer soil diffusion scheme provides little improvement in simulated hydrology over the wet tropical Amazonian sub-basins, but a more significant improvement is found over the drier sub-basins. The use of a multilayer soil diffusion scheme might become critical for assessments of future hydrological changes, especially in southern regions of the Amazon Basin where longer dry seasons and more severe droughts are expected in the next century.

[Macronutrients and energy in milk from mothers of premature infants].

PubMed

He, Bi-Zi; Sun, Xiu-Jing; Quan, Mei-Ying; Wang, Dan-Hua

2014-07-01

To study the dynamic changes in macronutrients and energy in human milk from mothers of premature infants. A total of 339 human milk samples were collected from 170 women who delivered preterm or full-term infants in the Department of Obstetrics and Gynecology, Peking Union Medical College Hospital between November 2012 and January 2014. Macronutrients (proteins, fats and carbohydrates and energy were measured using a MIRIS human milk analyzer and compared between groups. In milk samples from premature infants' mothers, the protein levels were the highest in colostrum (2.22±0.49 g/dL), less in transitional milk (1.83±0.39 g/dL), and the least in mature milk (1.40±0.28 g/dL) (P<0.01), and the levels of fats (2.4±1.3 g/dL vs 3.1±1.1 g/dL; P<0.01), carbohydrates (6.4±0.9 g/dL vs 6.6±0.4 g/dL; P<0.05) and energy (55±9 kcal/dL vs 62±8 kcal/dL; P<0.01) were significantly lower in colostrum than in transitional milk. The protein levels in colostrum from premature infants' mothers were significantly higher than those in colostrum from term infants' mothers (2.22±0.49 g/dL vs 2.07±0.34 g/dL; P<0.05). The colostrum from mothers of premature infants with a gestational age of ≤30 weeks had significantly higher protein levels than those from mothers of premature infants with gestational ages of 30(+1)-33(+6) weeks and ≥34 weeks (2.48±0.68 g/dL vs 2.11±0.25 g/dL and 2.22±0.39 g/dL respectively, P<0.05); the energy levels in colostrum from mothers of premature infants with a gestational age of ≤30 weeks group (51±6 kcal/dL) were significantly lower than those in colostrum from mothers of premature infants with a gestational age of 30(+1)-33(+6) weeks (58±8 kcal/d; P<0.05). The carbohydrate levels in transitional milk from mothers of premature infants with a gestational age of ≤30 weeks were significantly higher than those in transitional milk from mothers of premature infants with gestational ages of 30(+1)-33(+6) weeks and ≥34 weeks (P<0.05). The protein levels in mature milk from mothers of premature infants with a gestational age of 30(+1)-33(+6) weeks were significantly higher than those in mature milk from mothers of premature infants with gestational ages of ≤30 weeks and ≥34 weeks (P<0.05). The levels of macronutrients and energy in milk from mothers of premature infants vary significantly between colostrum, transitional milk, and mature milk. Protein levels are significantly higher in colostrum from premature infants' mothers than in colostrum from term infants' mothers, but the significant difference is not seen for mature milk. Macronutrient and energy levels show significant differences between milk samples from mothers of premature infants with different gestational ages, so as to meet different needs of premature infants.

Protective coatings for sensitive materials

DOEpatents

Egert, C.M.

1997-08-05

An enhanced protective coating is disclosed to prevent interaction between constituents of the environment and devices that can be damaged by those constituents. This coating is provided by applying a synergistic combination of diffusion barrier and physical barrier materials. These materials can be, for example, in the form of a plurality of layers of a diffusion barrier and a physical barrier, with these barrier layers being alternated. Further protection in certain instances is provided by including at least one layer of a getter material to actually react with one or more of the deleterious constituents. The coating is illustrated by using alternating layers of an organic coating (such as Parylene-C{trademark}) as the diffusion barrier, and a metal coating (such as aluminum) as the physical barrier. For best results there needs to be more than one of at least one of the constituent layers. 4 figs.

Distributed modeling of diffusive solute transport in peritoneal dialysis.

PubMed

Waniewski, Jacek

2002-01-01

The diffusive transport between blood and an ex-tissue medium (dialysis fluid) is evaluated using a mathematical model that takes into account the (quasicontinuous) distribution of capillaries within the tissue at various distances from the tissue surface, and includes diffusive-convective transport through the capillary wall and lymphatic absorption from the tissue. General formulas for solute penetration depth, lambda, and for the diffusive mass transport coefficient for the transport between blood and dialysis fluid, K(BD), are provided in terms of local transport coefficients for capillary wall, tissue, and lymphatic absorption. For pure diffusive transport between blood and dialysis fluid and thick tissue layers (i.e., if the solute penetration depth is much lower than the tissue thickness) these formulas yield previously known expressions. It is shown that apparent tissue layers, with widths lambdaTBL and lambdaT, respectively, may be defined according to the values of local transport parameters in such a way that K(BD) is equal to the solute clearance K(TBL) from the tissue by blood and lymph for a layer with width lambdaTBL or to the solute clearance K(T) from blood to dialysate by diffusion through the tissue layer with width lambdaT. For tissue layers with width much higher than the penetration depth: lambdaT approximately = lambdaTBL approximately = lambda. These characteristic width lengths depend on the transport parameters (and thus on the size) of solutes. Effective blood flow, which may be related to the exchange of the solute between blood and dialysate, is defined using an analogy to the extraction/absorption coefficients for blood-tissue exchange. Various approximations for the distributed model formula for diffusive mass transport coefficient (K(BD)) are possible. The appropriate range for their application is obtained from the general formula.

Analytical and numerical solutions for mass diffusion in a composite cylindrical body

NASA Astrophysics Data System (ADS)

Kumar, A.

1980-12-01

The analytical and numerical solution techniques were investigated to study moisture diffusion problems in cylindrical bodies that are assumed to be composed of a finite number of layers of different materials. A generalized diffusion model for an n-layer cylindrical body with discontinuous moisture content at the interfaces was developed and the formal solutions were obtained. The model is to be used for describing mass transfer rates of any composite body, such as an ear of corn which could be assumed of consisting two different layers: the inner core represents the woody cob and the outer cylinder represents the kernel layer. Data describing the fully exposed drying characteristics of ear corn at high air velocity were obtained under different drying conditions. Ear corns were modeled as homogeneous bodies since composite model did not improve the fit substantially. A computer program using multidimensional optimization technique showed that diffusivity was an exponential function of moisture content and an arrhenius function of temperature of drying air.

Progress on Fabrication of Planar Diffusion Couples with Representative TRISO PyC/SiC Microstructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunn, John D.; Jolly, Brian C.; Gerczak, Tyler J.

Release of fission products from tristructural-isotropic (TRISO) coated particle fuel limits the fuel’s operational lifetime and creates potential safety and maintenance concerns. A need for diffusion analysis in representative TRISO layers exists to provide fuel performance models with high fidelity data to improve fuel performance and efficiency. An effort has been initiated to better understand fission product transport in, and release from, quality TRISO fuel by investigating diffusion couples with representative pyrocarbon (PyC) and silicon carbide (SiC). Here planar PyC/SiC diffusion couples are being developed with representative PyC/SiC layers using a fluidized bed chemical vapor deposition (FBCVD) system identical tomore » those used to produce laboratory-scale TRISO fuel for the Advanced Gas Reactor Fuel Qualification and Development Program’s (AGR) first fuel irradiation. The diffusivity of silver, the silver and palladium system, europium, and strontium in the PyC/SiC will be studied at elevated temperatures and under high temperature neutron irradiation. The study also includes a comparative study of PyC/SiC diffusion couples with varying TRISO layer properties to understand the influence of SiC microstructure (grain size) and the PyC/SiC interface on fission product transport. The first step in accomplishing these goals is the development of the planar diffusion couples. The diffusion couple construction consists of multiple steps which includes fabrication of the primary PyC/SiC structures with targeted layer properties, introduction of fission product species and seal coating to create an isolated system. Coating development has shown planar PyC/SiC diffusion couples with similar properties to AGR TRISO fuel can be produced. A summary of the coating development process, characterization methods, and status are presented.« less

Determination of carrier diffusion length in GaN

NASA Astrophysics Data System (ADS)

Hafiz, Shopan; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit; Metzner, Sebastian; Bertram, Frank; Christen, Jürgen; Gil, Bernard

2015-01-01

Diffusion lengths of photo-excited carriers along the c-direction were determined from photoluminescence (PL) and cross-sectional cathodoluminescence (CL) measurements in p- and n-type GaN epitaxial layers grown on c-plane sapphire by metal-organic chemical vapor deposition. The investigated samples incorporate a 6 nm thick In0.15Ga0.85N active layer capped with either 500 nm p-GaN or 1500 nm n-GaN. The top GaN layers were etched in steps and PL from the InGaN active region and the underlying layers was monitored as a function of the top GaN thickness upon photo-generation near the surface region by above bandgap excitation. Taking into consideration the absorption in the top GaN layer as well as active and underlying layers, the diffusion lengths at 295 K and at 15 K were measured to be 93 ± 7 nm and 70 ± 7 nm for Mg-doped p-type GaN and 432 ± 30 nm and 316 ± 30 nm for unintentionally doped n-type GaN, respectively, at photogenerated carrier densities of 4.2 × 1018 cm-3 using PL spectroscopy. CL measurements of the unintentionally doped n-type GaN layer at much lower carrier densities of 1017 cm-3 revealed a longer diffusion length of 525 ± 11 nm at 6 K.

Manipulation of heat-diffusion channel in laser thermal lithography.

PubMed

Wei, Jingsong; Wang, Yang; Wu, Yiqun

2014-12-29

Laser thermal lithography is a good alternative method for forming small pattern feature size by taking advantage of the structural-change threshold effect of thermal lithography materials. In this work, the heat-diffusion channels of laser thermal lithography are first analyzed, and then we propose to manipulate the heat-diffusion channels by inserting thermal conduction layers in between channels. Heat-flow direction can be changed from the in-plane to the out-of-plane of the thermal lithography layer, which causes the size of the structural-change threshold region to become much smaller than the focused laser spot itself; thus, nanoscale marks can be obtained. Samples designated as "glass substrate/thermal conduction layer/thermal lithography layer (100 nm)/thermal conduction layer" are designed and prepared. Chalcogenide phase-change materials are used as thermal lithography layer, and Si is used as thermal conduction layer to manipulate heat-diffusion channels. Laser thermal lithography experiments are conducted on a home-made high-speed rotation direct laser writing setup with 488 nm laser wavelength and 0.90 numerical aperture of converging lens. The writing marks with 50-60 nm size are successfully obtained. The mark size is only about 1/13 of the focused laser spot, which is far smaller than that of the light diffraction limit spot of the direct laser writing setup. This work is useful for nanoscale fabrication and lithography by exploiting the far-field focusing light system.

Chemistry and Formation of the Beilby Layer During Polishing of Fused Silica Glass

DOE PAGES

Suratwala, Tayyab; Steele, William; Wong, Lana; ...

2015-05-19

The chemical characteristics and the proposed formation mechanisms of the modified surface layer (called the Beilby layer) on polished fused silica glasses are described. Fused silica glass samples were polished using different slurries, polyurethane pads, and at different rotation rates. The concentration profiles of several key contaminants, such as Ce, K, and H, were measured in the near surface layer of the polished samples using Secondary Ion Mass Spectroscopy (SIMS). The penetration of K, originating from KOH used for pH control during polishing, decreased with increase in polishing material removal rate. In contrast, penetration of the Ce and H increasedmore » with increase in polishing removal rate. In addition, Ce penetration was largely independent of the other polishing parameters (e.g., particle size distribution and the properties of the polishing pad). The resulting K concentration depth profiles are described using a two-step diffusion process: (1) steady-state moving boundary diffusion (due to material removal during polishing) followed by (2) simple diffusion during ambient postpolishing storage. Using known alkali metal diffusion coefficients in fused silica glass, this diffusion model predicts concentration profiles that are consistent with the measured data at various polishing material removal rates. On the other hand, the observed Ce profiles are inconsistent with diffusion based transport. Rather we propose that Ce penetration is governed by the ratio of Ce–O–Si and Si–O–Si hydrolysis rates; where this ratio increases with interface temperature (which increases with polishing material removal rate) resulting in greater Ce penetration into the Beilby layer. Calculated Ce surface concentrations using this mechanism are in good agreement to the observed change in measured Ce surface concentrations with polishing material removal rate. In conclusion, these new insights into the chemistry of the Beilby layer, combined together with details of the single particle removal function during polishing, are used to develop a more detailed and quantitative picture of the polishing process and the formation of the Beilby layer.« less

Equilibrium and NMR studies on GdIII, YIII, CuII and ZnII complexes of various DTPA-N,N''-bis(amide) ligands. Kinetic stabilities of the gadolinium(III) complexes.

PubMed

Jászberényi, Zoltán; Bányai, István; Brücher, Ernö; Király, Róbert; Hideg, Kálmán; Kálai, Tamás

2006-02-28

Three DTPA-derivative ligands, the non-substituted DTPA-bis(amide) (L(0)), the mono-substituted DTPA-bis(n-butylamide) (L(1)) and the di-substituted DTPA-bis[bis(n-butylamide)] (L(2)) were synthesized. The stability constants of their Gd3+ complexes (GdL) have been determined by pH-potentiometry with the use of EDTA or DTPA as competing ligands. The endogenous Cu2+ and Zn2+ ions form ML, MHL and M(2)L species. For the complexes CuL(0) and CuL(1) the dissociation of the amide hydrogens (CuLH(-1)) has also been detected. The stability constants of complexes formed with Gd3+, Cu2+ and Zn2+ increase with an increase in the number of butyl substituents in the order ML(0) < ML(1) < ML(2). NMR studies of the diamagnetic YL(0) show the presence of four diastereomers formed by changing the chirality of the terminal nitrogens of their enantiomers. At 323 K, the enantiomerization process, involving the racemization of central nitrogen, falls into the fast exchange range. By the assignment and interpretation of 1H and 13C NMR spectra, the fractions of the diastereomers were found to be equal at pH = 5.8 for YL(0). The kinetic stabilities of GdL(0), GdL(1) and GdL(2) have been characterized by the rates of the exchange reactions occurring between the complexes and Eu3+, Cu2+ or Zn2+. The rates of reaction with Eu3+ are independent of the [Eu3+] and increase with increasing [H+], indicating the rate determining role of the proton assisted dissociation of complexes. The rates of reaction with Cu2+ and Zn2+ increase with rising metal ion concentration, which shows that the exchange can take place with direct attack of Cu2+ or Zn2+ on the complex, via the formation of a dinuclear intermediate. The rates of the proton, Cu2+ and Zn2+ assisted dissociation of Gd3+ complexes decrease with increasing number of the n-butyl substituents, which is presumably the result of steric hindrance hampering the formation or dissociation of the intermediates. The kinetic stabilities of GdL(0) and GdL(1) at pH = 7.4, [Cu2+] = 1 x 10(-6) M and [Zn(2+)] = 1 x 10(-5) M are similar to that of Gd(DTPA)2-, while the complex GdL2 possesses a much higher kinetic stability.

Fatal Traffic Crashes Involving Drinking Drivers: What have we Learned?

PubMed Central

Fell, James C.; Tippetts, A. Scott; Voas, Robert B.

2009-01-01

Alcohol involvement in fatal crashes (any driver with a blood alcohol concentration [BAC] = .01g/dL or greater) in 2007 was more than three times higher at night (6 p.m.–6 a.m.) than during the day (6 a.m.–6 p.m.) (62% versus 19%). Alcohol involvement was 35% during weekdays compared to 54% on weekends. Nearly one in four drivers (23%) of personal vehicles (e.g., passenger cars or light trucks) and more than one in four motorcyclists (27%) in fatal crashes were intoxicated (i.e., had a BAC equal to or greater than the .08 g/dL illegal limit in the United States). In contrast, only 1% of the commercial drivers of heavy trucks had BACs equal to .08 g/dL or higher. More than a quarter (26%) of the drivers with high BACs (≥.15 g/dL) did not have valid licenses. The 21- to 24-age group had the highest proportion (35%) of drivers with BACs≥.08 g/dL, followed by the 25- to 34-age group (29%). The oldest and the youngest drivers had the lowest percentages of BACs≥ .08 g/dL: those aged 75 or older were at 4%, and those aged 16 to 20 were at 17%. Utah had the lowest rate of intoxicated drivers in fatal crashes at one in every eight drivers (12%), followed by Kentucky, Indiana, Iowa, New Hampshire, and Kansas, all at 17%. Montana (31%), South Carolina (31%), and North Dakota (39%) all had more than 3 in 10 drivers in fatal crashes who were intoxicated in 2007. The United States enjoyed a remarkable downward trend in alcohol-related crashes between 1982 and 1995, which has since leveled off. That trend coincided with a period during which per capita national alcohol consumption declined, the number of young drivers decreased, and the proportion of female drivers increased. Those factors alone, however, did not appear to account for the overall reduction. This provides further evidence that impaired-driving laws and safety program activity may have been responsible for at least some of the decline. However, there was a general worldwide decline in alcohol-related crashes during the same period, and other socioeconomic factors may have played a role. Proven effective strategies that could reduce impaired driving further in the United States include more frequent highly publicized enforcement efforts, such as sobriety checkpoints; lowering the illegal BAC limit for driving to .05g/dL; and mandating alcohol ignition interlocks for all convicted impaired drivers. PMID:20184833

Accuracy of noninvasive and continuous hemoglobin measurement by pulse co-oximetry during preoperative phlebotomy.

PubMed

Dewhirst, Elisabeth; Naguib, Aymen; Winch, Peter; Rice, Julie; Galantowicz, Mark; McConnell, Patrick; Tobias, Joseph D

2014-01-01

In recent years, the continuous noninvasive hemoglobin measurement has been offered by devices using advanced pulse oximetry technology. Accuracy has been established in healthy adults as well as in surgical and intensive care unit patients but not in the setting of acute hemorrhage. In this study, we evaluated the accuracy of such a device in the clinical setting of preoperative phlebotomy thereby mimicking a scenario of acute blood loss. This prospective study included patients undergoing surgical repair of congenital heart disease (CHD) for whom preoperative phlebotomy was planned. Blood was removed after the induction of anesthesia and prior to the start of the surgical procedure. Replacement with crystalloid was guided by hemodynamic variables and cerebral oxygenation measured by near-infrared spectroscopy. Hemoglobin was measured by bedside whole blood analysis (total hemoglobin [tHb]) before and after phlebotomy, and concurrent measurements from the pulse co-oximeter (noninvasive, continuous, or spot-check testing of total hemoglobin [SpHb]) were recorded. The study cohort included 45 patients ranging in age from 3 months to 50 years. Preoperative phlebotomy removed an average of 9.2 mL/kg of blood that was replaced with an average of 7.2 mL/kg of crystalloid. The pre- and postphlebotomy tHb values were 13.0 ± 1.9 and 12.4 ± 1.8 g/dL, respectively. The absolute difference between the tHb and SpHb (▵Hb) was 1.2 ± 0.1 g/dL. Bland-Altman analysis revealed a bias of 0.1 g/dL, a precision of 1.5 g/dL, and 95% limits of agreement of -2.8 to 3.1 g/dL. In 52.2% of the sample sets, the SpHb was within 1 g/dL of the actual hemoglobin value (tHb), and in 80% of the sample sets, the SpHb was within 2 g/dL. No variation in the accuracy of the deviation was noted based on the patient's age, weight, or type of CHD (cyanotic versus acyanotic). The current study demonstrates that the accuracy of continuous, noninvasive hemoglobin measurement was not affected by acute blood loss simulated by preoperative phlebotomy. Although the device provided a clinically acceptable correlation with the actual hemoglobin value and offers the value of a continuous trend monitor, given the precision of the device, it does not appear that actual transfusion decisions can be based on the device alone. © The Author(s) 2013.

An Unusual Complication of EVAR, Spontaneous Rectus Sheath Hematoma: A Case Report

PubMed Central

Sirivanichai, Chusak

2009-01-01

Objective: To report a successful conservative management in a case of spontaneous rectus sheath hematoma (SRSH) after Endovascular Aneurysmal Repair (EVAR) of infrarenal Abdominal Aortic Aneurysm (AAA). Case Presentation: An 84-year-old woman with a 6 cm in diameter infrarenal AAA underwent EVAR at our hospital. During the procedure, intravenous heparin was administered to keep the activated clotting time around 300 seconds. One hour after the procedure, the patient complained of pain on her right side abdomen. Physical examination revealed a tender mass in the right lower abdominal wall. Laboratory studies showed a fall in hemoglobin from 12.7 g/dl to 9.3 g/dl. Ultrasound (US) examination demonstrated an 8 × 5 cm hematoma within the right rectus muscle. Follow-up US examination revealed that the hematoma had enlarged and a computed tomography (CT) examination of the lower abdomen was performed. CT scan showed a smooth-shaped mass within the layers of the anterolateral abdominal wall leading to enlargement of the right rectus abdominis muscle without signs of active bleeding. A conservative management was considered. Result: The clinical course was uneventful with a stable hemodynamic state. The patient was discharged 12 days later and was doing well at the 2 week follow-up. Conclusion: Spontaneous rectus sheath hematoma is an unusual complication of a patient on anticoagulant therapy during EVAR. A prompt radiological investigation may prevent unnecessary surgical procedures in this unusual complication. PMID:23555371

Enhanced Atom Mobility on the Surface of a Metastable Film

NASA Astrophysics Data System (ADS)

Picone, A.; Riva, M.; Fratesi, G.; Brambilla, A.; Bussetti, G.; Finazzi, M.; Duò, L.; Ciccacci, F.

2014-07-01

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization.

Enhanced atom mobility on the surface of a metastable film.

PubMed

Picone, A; Riva, M; Fratesi, G; Brambilla, A; Bussetti, G; Finazzi, M; Duò, L; Ciccacci, F

2014-07-25

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization.

Bifunctional catalytic electrode

NASA Technical Reports Server (NTRS)

Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

2005-01-01

The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

Control of the Structure of Diffusion Layer in Carbon Steels Under Nitriding with Preliminary Deposition of Copper Oxide Catalytic Films

NASA Astrophysics Data System (ADS)

Petrova, L. G.; Aleksandrov, V. A.; Malakhov, A. Yu.

2017-07-01

The effect of thin films of copper oxide deposited before nitriding on the phase composition and the kinetics of growth of diffusion layers in carbon steels is considered. The process of formation of an oxide film involves chemical reduction of pure copper on the surface of steel specimens from a salt solution and subsequent oxidation under air heating. The oxide film exerts a catalytic action in nitriding of low- and medium-carbon steels, which consists in accelerated growth of the diffusion layer, the nitride zone in the first turn. The kinetics of the nitriding process and the phase composition of the layer are controlled by the thickness of the copper oxide precursor, i.e., the deposited copper film.

Separation of the Stern and diffuse layer in coarse-grained models: the cases of phosphatidyl serine, phosphatidic acid, and PIP2 monolayers.

PubMed

Vangaveti, S; Travesset, A

2014-12-28

We present here a method to separate the Stern and diffuse layer in general systems into two regions that can be analyzed separately. The Stern layer can be described in terms of Bjerrum pairing and the diffuse layer in terms of Poisson-Boltzmann theory (monovalent) or strong coupling theory plus a slowly decaying tail (divalent). We consider three anionic phospholipids: phosphatidyl serine, phosphatidic acid, and phosphatidylinositol(4,5)bisphosphate (PIP2), which we describe within a minimal coarse-grained model as a function of ionic concentration. The case of mixed lipid systems is also considered, which shows a high level of binding cooperativity as a function of PIP2 localization. Implications for existing experimental systems of lipid heterogeneities are also discussed.

Separation of the Stern and diffuse layer in coarse-grained models: The cases of phosphatidyl serine, phosphatidic acid, and PIP2 monolayers

NASA Astrophysics Data System (ADS)

Vangaveti, S.; Travesset, A.

2014-12-01

We present here a method to separate the Stern and diffuse layer in general systems into two regions that can be analyzed separately. The Stern layer can be described in terms of Bjerrum pairing and the diffuse layer in terms of Poisson-Boltzmann theory (monovalent) or strong coupling theory plus a slowly decaying tail (divalent). We consider three anionic phospholipids: phosphatidyl serine, phosphatidic acid, and phosphatidylinositol(4,5)bisphosphate (PIP2), which we describe within a minimal coarse-grained model as a function of ionic concentration. The case of mixed lipid systems is also considered, which shows a high level of binding cooperativity as a function of PIP2 localization. Implications for existing experimental systems of lipid heterogeneities are also discussed.

Fluorescence Correlation Spectroscopy to Study Diffusion of Polymer Chains within Layered Hydrogen-Bonded Polymer Films

NASA Astrophysics Data System (ADS)

Pristinski, Denis; Kharlampieva, Evguenia; Sukhishvili, Svetlana

2002-03-01

Fluorescence Correlation Spectroscopy (FCS) has been used to probe molecular motions within polymer multilayers formed by hydrogen-bonding sequential self-assembly. Polyethylene glycol (PEG) molecules were end-labeled with the fluorescent tags, and self-assembled with polymethacrylic acid (PMAA) using layer-by-layer deposition. We have found that molecules included in the top adsorbed layer have significant mobility at the millisecond time scale, probably due to translational diffusion. However, their dynamics deviate from classical Brownian motion with a single diffusion time. Possible reasons for the deviation are discussed. We found that motions were significantly slowed with increasing depth within the PEG/PMAA multilayer. This phenomena occured in a narrow pH range around 4.0 in which intermolecular interactions were relatively weak.

Effect of dual-dielectric hydrogen-diffusion barrier layers on the performance of low-temperature processed transparent InGaZnO thin-film transistors

NASA Astrophysics Data System (ADS)

Tari, Alireza; Wong, William S.

2018-02-01

Dual-dielectric SiOx/SiNx thin-film layers were used as back-channel and gate-dielectric barrier layers for bottom-gate InGaZnO (IGZO) thin-film transistors (TFTs). The concentration profiles of hydrogen, indium, gallium, and zinc oxide were analyzed using secondary-ion mass spectroscopy characterization. By implementing an effective H-diffusion barrier, the hydrogen concentration and the creation of H-induced oxygen deficiency (H-Vo complex) defects during the processing of passivated flexible IGZO TFTs were minimized. A bilayer back-channel passivation layer, consisting of electron-beam deposited SiOx on plasma-enhanced chemical vapor-deposition (PECVD) SiNx films, effectively protected the TFT active region from plasma damage and minimized changes in the chemical composition of the semiconductor layer. A dual-dielectric PECVD SiOx/PECVD SiNx gate-dielectric, using SiOx as a barrier layer, also effectively prevented out-diffusion of hydrogen atoms from the PECVD SiNx-gate dielectric to the IGZO channel layer during the device fabrication.

Tunneling Injection and Exciton Diffusion of White Organic Light-Emitting Diodes with Composed Buffer Layers

NASA Astrophysics Data System (ADS)

Yang, Su-Hua; Wu, Jian-Ping; Huang, Tao-Liang; Chung, Bin-Fong

2018-02-01

Four configurations of buffer layers were inserted into the structure of a white organic light emitting diode, and their impacts on the hole tunneling-injection and exciton diffusion processes were investigated. The insertion of a single buffer layer of 4,4'-bis(carbazol-9-yl)biphenyl (CBP) resulted in a balanced carrier concentration and excellent color stability with insignificant chromaticity coordinate variations of Δ x < 0.023 and Δ y < 0.023. A device with a 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) buffer layer was beneficial for hole tunneling to the emission layer, resulting in a 1.45-fold increase in current density. The tunneling of holes and the diffusion of excitons were confirmed by the preparation of a dual buffer layer of CBP:tris-(phenylpyridine)-iridine (Ir(ppy)3)/BCP. A maximum current efficiency of 12.61 cd/A with a luminance of 13,850 cd/m2 was obtained at 8 V when a device with a dual-buffer layer of CBP:6 wt.% Ir(ppy)3/BCP was prepared.

Reaction products and oxide thickness formed by Ti out-diffusion and oxidization in poly-Pt/Ti/SiO 2/Si with oxide films deposited

NASA Astrophysics Data System (ADS)

Chen, Changhong; Huang, Dexiu; Zhu, Weiguang; Feng, Yi; Wu, Xigang

2006-08-01

In the paper, we present experimental results to enhance the understanding of Ti out-diffusion and oxidization in commercial poly-Pt/Ti/SiO 2/Si wafers with perovskite oxide films deposited when heat-treated in flowing oxygen ambient. It indicates that when heat-treated at 550 and 600 °C, PtTi 3+PtTi and PtTi are the reaction products from interfacial interaction, respectively; while heat-treated at 650 °C and above, the products become three layers of titanium oxides instead of the alloys. Confirmed to be rutile TiO 2, the first two layers spaced by 65 nm encapsulate the Pt surface by the first layer with 60 nm thick forming at its surface and by the next layer with 35 nm thick inserting its original layer. In addition, the next layer is formed as a barrier to block up continuous diffusion paths of Ti, and thus results in the last layer of TiO 2- x formed by the residual Ti oxidizing.

Diffuser for augmenting a wind turbine

DOEpatents

Foreman, Kenneth M.; Gilbert, Barry L.

1984-01-01

A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.

New Layer Thickness Parameterization of Diffusive Convection

NASA Astrophysics Data System (ADS)

Zhou, Sheng-Qi; Lu, Yuan-Zheng; Guo, Shuang-Xi; Song, Xue-Long; Qu, Ling; Cen, Xian-Rong; Fer, Ilker

2017-11-01

Double-diffusion convection is one of the most important non-mechanically driven mixing processes. Its importance has been particular recognized in oceanography, material science, geology, and planetary physics. Double-diffusion occurs in a fluid in which there are gradients of two (or more) properties with different molecular diffusivities and of opposing effects on the vertical density distribution. It has two primary modes: salt finger and diffusive convection. Recently, the importance of diffusive convection has aroused more interest due to its impact to the diapycnal mixing in the interior ocean and the ice and the ice-melting in the Arctic and Antarctic Oceans. In our recent work, we constructed a length scale of energy-containing eddy and proposed a new layer thickness parameterization of diffusive convection by using the laboratory experiment and in situ observations in the lakes and oceans. The new parameterization can well describe the laboratory convecting layer thicknesses (0.01 0.1 m) and those observed in oceans and lakes (0.1 1000 m). This work was supported by China NSF Grants (41476167,41406035 and 41176027), NSF of Guangdong Province, China (2016A030311042) and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA11030302).

Diffuse sorption modeling.

PubMed

Pivovarov, Sergey

2009-04-01

This work presents a simple solution for the diffuse double layer model, applicable to calculation of surface speciation as well as to simulation of ionic adsorption within the diffuse layer of solution in arbitrary salt media. Based on Poisson-Boltzmann equation, the Gaines-Thomas selectivity coefficient for uni-bivalent exchange on clay, K(GT)(Me(2+)/M(+))=(Q(Me)(0.5)/Q(M)){M(+)}/{Me(2+)}(0.5), (Q is the equivalent fraction of cation in the exchange capacity, and {M(+)} and {Me(2+)} are the ionic activities in solution) may be calculated as [surface charge, mueq/m(2)]/0.61. The obtained solution of the Poisson-Boltzmann equation was applied to calculation of ionic exchange on clays and to simulation of the surface charge of ferrihydrite in 0.01-6 M NaCl solutions. In addition, a new model of acid-base properties was developed. This model is based on assumption that the net proton charge is not located on the mathematical surface plane but diffusely distributed within the subsurface layer of the lattice. It is shown that the obtained solution of the Poisson-Boltzmann equation makes such calculations possible, and that this approach is more efficient than the original diffuse double layer model.

Ag out-surface diffusion in crystalline SiC with an effective SiO 2 diffusion barrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, H.; Xiao, H. Y.; Zhu, Z.

2015-05-07

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope ( 110mAg) through the SiC coating layer is a safety concern. In order to understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. Our results suggestmore » little migration of buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO 2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

NASA Astrophysics Data System (ADS)

Lo, Wei-Yang; Yang, Yong

2014-08-01

Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

Ag Out-surface Diffusion In Crystalline SiC With An Effective SiO2 Diffusion Barrier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, H.; Xiao, Haiyan Y.; Zhu, Zihua

2015-09-01

For applications of tristructural isotropic (TRISO) fuel particles in high temperature reactors, release of radioactive Ag isotope (110mAg) through the SiC coating layer is a safety concern. To understand the diffusion mechanism, Ag ion implantations near the surface and in the bulk were performed by utilizing different ion energies and energy-degrader foils. High temperature annealing was carried out on the as-irradiated samples to study the possible out-surface diffusion. Before and after annealing, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) measurements were employed to obtain the elemental profiles of the implanted samples. The results suggest little migration ofmore » buried Ag in the bulk, and an out-diffusion of the implanted Ag in the near-surface region of single crystal SiC. It is also found that a SiO2 layer, which was formed during annealing, may serve as an effective barrier to reduce or prevent Ag out diffusion through the SiC coating layer.« less

Plasma diffusion at the magnetopause? The case of lower hybrid drift waves

NASA Technical Reports Server (NTRS)

Treumann, R. A.; Labelle, J.; Pottelette, R.; Gary, S. P.

1990-01-01

The diffusion expected from the quasilinear theory of the lower hybrid drift instability at the Earth's magnetopause is recalculated. The resulting diffusion coefficient is in principle just marginally large enough to explain the thickness of the boundary layer under quiet conditions, based on observational upper limits for the wave intensities. Thus, one possible model for the boundary layer could involve equilibrium between the diffusion arising from lower hybrid waves and various low processes. However, some recent data and simulations seems to indicate that the magnetopause is not consistent with such a soft diffusive equilibrium model. Furthermore, investigation of the nonlinear equations for the lower hybrid waves for magnetopause parameters indicates that the quasilinear state may never arise because coalescence to large wavelengths, followed by collapse once a critical wavelengths is reached, occur on a time scale faster than the quasilinear diffusion. In this case, an inhomogeneous boundary layer is to be expected. More simulations are required over longer time periods to explore whether this nonlinear evolution really takes place at the magnetopause.

Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients

EPA Science Inventory

Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

Investigation of nitrogen transport in active screen plasma nitriding processes - Uphill diffusion effect

NASA Astrophysics Data System (ADS)

Jasinski, J. J.; Fraczek, T.; Kurpaska, L.; Lubas, M.; Sitarz, M.

2018-07-01

The paper presents a structure of a nitrided layer formed with active screen plasma nitriding (ASPN) technique, which is a modification of plasma nitriding. The model investigated material was Fe Armco. The nitriding processes were carried out at 773 K for 6 h and 150 Pa. The main objective of this study was to confirm nitrogen migration effect and its influence on the nitride layer formation in different area of the layer interfaces (ε/ε+γ‧/γ‧). The results of the tests were evaluated using scanning electron microscopy (SEM, SEM/EBSD), transmission electron microscopy - electron energy loss spectroscopy (TEM-EFTEM), secondary ion mass spectroscopy (SIMS) and Wavelength Dispersive X-Ray Spectrometry (WDS). The analysis of the results suggests that the structures of the nitrided layers and nitrides morphology differ for various parameters and are dependent on the surface layer saturation mechanism for each of the temperatures and process parameters. New approaches in diffusion of nitrogen and carbon atoms and optimizing process were also analyzed. Nitrogen and also carbon transport in the sublayer was observed by several effects i.e. uphill diffusion effect which confirmed migration of the atoms in diffusive layer towards top surface (ε/ε+γ‧ interface) and stress change effect in the nitrogen saturation area of the (Fe(C,N)+γ‧) layer. Results showed in the paper might be used both for optimization of ASPN processes, modeling of nitrided layers formation mechanism and for controlling the nitrided layers morphology when nitriding different Fe based materials.

Obtaining the porewater composition of a clay rock by modeling the in- and out-diffusion of anions and cations from an in-situ experiment.

PubMed

Appelo, C A J; Vinsot, A; Mettler, S; Wechner, S

2008-10-23

A borehole in the Callovo-Oxfordian clay rock in ANDRA's underground research facility was sampled during 1 year and chemically analyzed. Diffusion between porewater and the borehole solution resulted in concentration changes which were modeled with PHREEQC's multicomponent diffusion module. In the model, the clay rock's pore space is divided in free porewater (electrically neutral) and diffuse double layer water (devoid of anions). Diffusion is calculated separately for the two domains, and individually for all the solute species while a zero-charge flux is maintained. We explain how the finite difference formulas for radial diffusion can be translated into mixing factors for solutions. Operator splitting is used to calculate advective flow and chemical reactions such as ion exchange and calcite dissolution and precipitation. The ion exchange reaction is formulated in the form of surface complexation, which allows distributing charge over the fixed sites and the diffuse double layer. The charge distribution affects pH when calcite dissolves, and modeling of the experimental data shows that about 7% of the cation exchange capacity resides in the diffuse double layer. The model calculates the observed concentration changes very well and provides an estimate of the pristine porewater composition in the clay rock.

Leaf Concentrate Fortification of Antenatal Protein-Calorie Snacks Improves Pregnancy Outcomes

PubMed Central

Magon, Anjna; Joshi, Pallavi; Davys (Late), Glyn; Attlee, Amita; Mathur, Beena

2014-01-01

ABSTRACT Ready-to-eat (RTE) snacks are routinely distributed to pregnant women in India. These provide protein and calories but are low in micronutrients. We investigated whether RTE snacks fortified with leaf concentrate (LC) could improve pregnancy outcomes, including maternal haemoglobin (Hb) concentrations and infants’ birthweight. This randomized controlled two-arm trial was conducted over 18 months: control (sRTE) group received standard 120 g RTE snack (102 g wheat flour, 18 g soya flour); intervention (lcRTE) group received the same snack fortified with 7 g LC. The study was conducted in Jaipur, Rajasthan, India. One hundred and five pregnant women aged 18-35 years were studied. Among the 105 women randomized to the two arms of the trial, 2 (1.9%) were severely anaemic (Hb ≤6.0 g/dL); 55 (53.4%) were moderately anaemic (Hb 6.0-8.0 g/dL); 34 (33.0%) were mildly anaemic (Hb 8.6-10.9 g/dL); and 12 (11.7%) were not anaemic (Hb ≥11.0 g/dL). In the final month of pregnancy, 83.0% (39/47) of women in the sRTE group had Hb ≤8.5 g/dL compared to 37.8% (17/45) in the lcRTE group (p<0.001). After adjustment for age and baseline Hb concentration, the difference in Hb concentrations due to LC fortification was 0.94 g/dL (95% CI 6.8-12.0; p<0.001). Mean live birthweight in the lcRTE group was 2,695 g (SD 325 g) compared to 2,545 g (297 g) in the sRTE group (p=0.02). The lcRTE snacks increased infants’ birthweight by 133.7 g (95% CI 7.3-260.2; p=0.04) compared to sRTE snacks. Leaf concentrate fortification of antenatal protein-calorie snacks in a low-income setting in India protected against declining maternal haemoglobin concentrations and increased infants’ birthweight when compared with unfortified snacks. These findings require replication in a larger trial. PMID:25395906

Impact of a graduated driver's license law on crashes involving young drivers in New York State.

PubMed

Cheng, Julius D; Schubmehl, Heidi; Kahn, Steven A; Gestring, Mark L; Sangosanya, Ayodele; Stassen, Nicole A; Bankey, Paul E

2012-08-01

Motor vehicle crashes constitute the greatest risk of injury for young adults. Graduated driver licensing (GDL) laws have been used to reduce the number of injuries and deaths in the young driver population. The New York State GDL law increased supervision of young driver and limited both time-of-day driven and number of passengers. This review examines the impact of a GDL enacted in New York in September 2003. A retrospective review of New York State administrative databases from 2001 to 2009 was performed. During this period, a state-wide GDL requirement was implemented. Database review included all reported crashes to the New York State Department of Motor Vehicles by cause and driver age as well as motor fuel tax receipts by the New York State Comptroller's Office. Motor fuel tax receipts and consumption information were used as a proxy for overall miles driven. Before 2003, drivers younger than 18 years were involved in 90 fatal crashes and 10,406 personal-injury (PI) crashes, constituting 4.49% and 3.38% of all fatal and PI crashes in New York State, respectively. By 2009, the number of fatal and PI crashes involving drivers who are younger than 18 years decreased to 44 (2.87%) and 5,246 (2.24%), respectively. Of note, the number of crashes experienced by the age group 18 years to 20 years during this period also declined, from 192 (9.59% of all fatal crashes) and 25,407 (8.24% of all PI crashes) to 135 (8.81%) and 18,114 (7.73%), respectively. Overall numbers of crashes reported remained relatively stable, between 549,000 in 2001 and 520,000 in 2009. Motor fuel use during this period also declined, but to a lesser degree ($552 million to $516 million or 6.6%). The use of a GDL law in New York State has shown a large decrease in the number of fatalities and PI crashes involving young drivers. The delay in full driver privileges from the GDL did not result in an increase in fatal or PI crashes in the next older age group.

The relation between platelet reactivity and glycemic control in diabetic patients with cardiovascular disease on maintenance aspirin and clopidogrel therapy.

PubMed

Singla, Anand; Antonino, Mark J; Bliden, Kevin P; Tantry, Udaya S; Gurbel, Paul A

2009-11-01

High platelet reactivity (HPR) during aspirin and clopidogrel therapy in patients with diabetes has been reported and may affect outcomes. However, the relation of platelet reactivity to glycemic control is less studied in patients on dual antiplatelet therapy. Platelet aggregation (PA) in response to 5 and 20 micromol/L adenosine diphosphate (ADP) was compared in type 2 diabetic (n = 36) and nondiabetic patients (n = 35) undergoing elective stenting on aspirin and clopidogrel maintenance therapy. The relation of glycosylated hemoglobin (HbA(1c)) <7 g/dL (n = 16) and HbA(1c) > or =7 g/dL (n = 20) on PA was examined. High platelet reactivity was defined as >46% for 5 micromol/L ADP-induced and >59% for 20 micromol/L ADP-induced PA. Diabetic patients had higher 5 and 20 micromol/L ADP-induced PA than nondiabetic patients (45 +/- 17 vs 33 +/- 12, P = .009 and 52 +/- 19 vs 40 +/- 12, P = .004, respectively). Diabetic patients with HbA(1c) > or =7.0 g/dL had significantly higher 5 and 20 micromol/L ADP-induced PA versus patients with diabetes with HbA(1c) <7.0 g/dL (54 +/- 15 vs 34 +/- 14, P < .001 and 62 +/- 14 vs 40 +/- 17, P < .001, respectively). Among diabetic patients with HbA(1c) > or =7 g/dL, the prevalence of HPR was 65% and 60%; and among diabetic patients with HbA(1c) <7 g/dL, the prevalence of HPR was 19% and 13% as measured by 5 and 20 micromol/L ADP-induced PA, respectively. A correlation was present between 5 and 20 micromol/L ADP-induced PA and HbA(1c) (r = 0.60 and 0.62, P = .0001, respectively). An important relation exists between glycemic control and platelet reactivity in patients with type 2 diabetes mellitus treated with dual antiplatelet therapy. Poorly controlled patients with diabetes have the greatest platelet reactivity and may require alternative antiplatelet strategies, and further clinical investigations are warranted.

Anaemia during pregnancy in Burkina Faso, west Africa, 1995-96: prevalence and associated factors. DITRAME Study Group.

PubMed Central

Meda, N.; Mandelbrot, L.; Cartoux, M.; Dao, B.; Ouangré, A.; Dabis, F.

1999-01-01

We report the results of a cross-sectional study carried out in 1995-96 on anaemia in pregnant women who were attending two antenatal clinics in Bobo-Dioulasso, Burkina Faso, as part of a research programme including a clinical trial of zidovudine (ZDV) in pregnancy (ANRS 049 Clinical Trial). For women infected with human immunodeficiency virus (HIV) in Africa, anaemia is of particular concern when considering the use of ZDV to decrease mother-to-child transmission of HIV. The objectives were to determine the prevalence of and risk factors for maternal anaemia in the study population, and the effect of HIV infection on the severity of maternal anaemia. HIV counselling and testing were offered to all women, and haemograms were determined for those women who consented to serological testing. Haemoglobin (Hb) levels were available for 2308 of the 2667 women who accepted HIV testing. The prevalence of HIV infection was 9.7% (95% confidence interval (CI): 8.6-10.8%). The overall prevalence of anaemia during pregnancy (Hb level < 11 g/dl) was 66% (95% CI: 64-68%). The prevalence of mild (10 g/dl < or = Hb < 11 g/dl), moderate (7 g/dl < or = Hb < 10 g/dl) and severe (Hb < 7 g/dl) anaemia was 30.8%, 33.5% and 1.7%, respectively. The prevalence of anaemia was 78.4% in HIV-infected women versus 64.7% in HIV-seronegative women (P < 0.001). Although the relative risk of HIV-seropositivity increased with the severity of anaemia, no significant association was found between degree of anaemia and HIV serostatus among the study women with anaemia. Logistic regression analysis showed that anaemia was significantly and independently related to HIV infection, advanced gestational age, and low socioeconomic status. This study confirms the high prevalence of anaemia during pregnancy in Burkina Faso. Antenatal care in this population must include iron supplementation. Although HIV-infected women had a higher prevalence of anaemia, severe anaemia was infrequent, possibly because few women were in the advanced stage of HIV disease. A short course regimen of ZDV should be well tolerated in this population. PMID:10612887

Leaf concentrate fortification of antenatal protein-calorie snacks improves pregnancy outcomes.

PubMed

Magon, Anjna; Collin, Simon M; Joshi, Pallavi; Davys Late, Glyn; Attlee, Amita; Mathur, Beena

2014-09-01

Ready-to-eat (RTE) snacks are routinely distributed to pregnant women in India. These provide protein and calories but are low in micronutrients. We investigated whether RTE snacks fortified with leaf concentrate (LC) could improve pregnancy outcomes, including maternal haemoglobin (Hb) concentrations and infants' birthweight. This randomized controlled two-arm trial was conducted over 18 months: control (sRTE) group received standard 120 g RTE snack (102 g wheat flour, 18 g soya flour); intervention (lcRTE) group received the same snack fortified with 7 g LC. The study was conducted in Jaipur, Rajasthan, India. One hundred and five pregnant women aged 18-35 years were studied. Among the 105 women randomized to the two arms of the trial, 2 (1.9%) were severely anaemic (Hb ≤ 6.0 g/dL); 55 (53.4%) were moderately anaemic (Hb 6.0-8.0 g/dL); 34 (33.0%) were mildly anaemic (Hb 8.6-10.9 g/dL); and 12 (11.7%) were not anaemic (Hb ≥ 11.0 g/dL). In the final month of pregnancy, 83.0% (39/47) of women in the sRTE group had Hb ≤ 8.5 g/dL compared to 37.8% (17/45) in the lcRTE group (p<0.001). After adjustment for age and baseline Hb concentration, the difference in Hb concentrations due to LC fortification was 0.94 g/dL (95% CI 6.8-12.0; p<0.001). Mean live birthweight in the lcRTE group was 2,695 g (SD 325 g) compared to 2,545 g (297 g) in the sRTE group (p=0.02). The lcRTE snacks increased infants' birthweight by 133.7 g (95% CI 7.3-260.2; p=0.04) compared to sRTE snacks. Leaf concentrate fortification of antenatal protein-calorie snacks in a low-income setting in India protected against declining maternal haemoglobin concentrations and increased infants' birthweight when compared with unfortified snacks. These findings require replication in a larger trial.

Markers of nutritional status and mortality in older adults: The role of anemia and hypoalbuminemia.

PubMed

Corona, Ligiana Pires; de Oliveira Duarte, Yeda Aparecida; Lebrão, Maria Lúcia

2018-01-01

The aim of the present study was to analyze the impact of anemia and hypoalbuminemia on mortality in a 5-year period. This was longitudinal population-based observational survey part of the Saúde, Bem-Estar e Envelhecimento study (Health, Well-being and Aging), carried out with 1256 older adults from the third wave of the cohort, followed for 5 years, when they were contacted for the fourth wave, in Sao Paulo, Brazil. Anemia was defined when hemoglobin was <12 g/dL for women and <13 g/dL for men, and hypoalbuminemia when serum albumin was <3.5 g/dL. Survival functions were estimated according to nutritional status in four groups: (i) without nutritional alteration; (ii) anemia only; (iii) hypoalbuminemia only; and (iv) anemia and hypoalbuminemia. Hazard ratios were calculated, following the Cox proportional hazards model, controlling for baseline covariates. All analyses considered sample weights, and were carried out using the Stata 12. After the 5-year period, 12.3% of the participants died, and 8.2% were lost to follow up. Those who died had lower hemoglobin and albumin concentrations (13.4 g/dL and 3.7 g/dL) compared with survivors (14.3d/dL and 3.9 g/dL; P < 0.001). The crude death rate was 27.6/1000 person-years for participants in group i, 124.3 in group ii, 116.0 in group iii and 222.8 in group iv (P < 0.001). In the final Cox models, group 2 and 3 had a similar effect (hazard ratio 2.23, P = 0.020; 2.53, P = 0.005; respectively) and group 4 had a higher risk (hazard ratio 3.36; P = 0.004). Anemia and hypoalbuminemia are important markers for death in older adults, and have an additive effect on mortality. Because they are common and cost-effective biomarkers, their use should be encouraged in geriatric evaluation for all health professionals and in population settings, such as primary care. Geriatr Gerontol Int 2018; 18: 177-182. © 2017 Japan Geriatrics Society.

Determination of carrier diffusion length in p- and n-type GaN

NASA Astrophysics Data System (ADS)

Hafiz, Shopan; Metzner, Sebastian; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Karbaum, Christopher; Bertram, Frank; Christen, Jürgen; Gil, Bernard; Özgür, Ümit

2014-03-01

Diffusion lengths of photo-excited carriers along the c-direction were determined from photoluminescence (PL) measurements in p- and n-type GaN epitaxial layers grown on c-plane sapphire by metal-organic chemical vapor deposition. The investigated samples incorporate a 6 nm thick In0.15Ga0.85N active layer capped with either 500 nm p- GaN or 1300 nm n-GaN. The top GaN layers were etched in steps and PL from the InGaN active region and the underlying layers was monitored as a function of the top GaN thickness upon photogeneration near the surface region by above bandgap excitation. Taking into consideration the absorption in the active and underlying layers, the diffusion lengths at 295 K and at 15 K were measured to be about 92 ± 7 nm and 68 ± 7 nm for Mg-doped p-type GaN and 432 ± 30 nm and 316 ± 30 nm for unintentionally doped n-type GaN, respectively. Cross-sectional cathodoluminescence line-scan measurement was performed on a separate sample and the diffusion length in n-type GaN was measured to be 280 nm.

Combining diffusion magnetic resonance tractography with stereology highlights increased cross-cortical integration in primates.

PubMed

Charvet, Christine J; Hof, Patrick R; Raghanti, Mary Ann; Van Der Kouwe, Andre J; Sherwood, Chet C; Takahashi, Emi

2017-04-01

The isocortex of primates is disproportionately expanded relative to many other mammals, yet little is known about what the expansion of the isocortex entails for differences in cellular composition and connectivity patterns in primates. Across the depth of the isocortex, neurons exhibit stereotypical patterns of projections. Upper-layer neurons (i.e., layers II-IV) project within and across cortical areas, whereas many lower-layer pyramidal neurons (i.e., layers V-VI) favor connections to subcortical regions. To identify evolutionary changes in connectivity patterns, we quantified upper (i.e., layers II-IV)- and lower (i.e., layers V-VI)-layer neuron numbers in primates and other mammals such as rodents and carnivores. We also used MR tractography based on high-angular resolution diffusion imaging and diffusion spectrum imaging to compare anterior-to-posterior corticocortical tracts between primates and other mammals. We found that primates possess disproportionately more upper-layer neurons as well as an expansion of anterior-to-posterior corticocortical tracts compared with other mammals. Taken together, these findings demonstrate that primates deviate from other mammals in exhibiting increased cross-cortical connectivity. J. Comp. Neurol. 525:1075-1093, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

The Turbulent Flow in Diffusers of Small Divergence Angle

NASA Technical Reports Server (NTRS)

Gourzhienko, G. A.

1947-01-01

The turbulent flow in a conical diffuser represents the type of turbulent boundary layer with positive longitudinal pressure gradient. In contrast to the boundary layer problem, however, it is not necessary that the pressure distribution along the limits of the boundary layer(along the axis of the diffuser) be given, since this distribution can be obtained from the computation. This circumstance, together with the greater simplicity of the problem as a whole, provides a useful basis for the study of the extension of the results of semiempirical theories to the case of motion with a positive pressure gradient. In the first part of the paper,formulas are derived for the computation of the velocity and.pressure distributions in the turbulent flow along, and at right angles to, the axis of a diffuser of small cone angle. The problem is solved.

Improved diffuser for augmenting a wind turbine

DOEpatents

Foreman, K.M.; Gilbert, B.L.

A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.

Association of hemoglobin values at booking with adverse maternal outcomes among Peruvian populations living at different altitudes.

PubMed

Gonzales, Gustavo F; Tapia, Vilma; Gasco, Manuel; Carrillo, Carlos E; Fort, Alfredo L

2012-05-01

To determine hemoglobin values associated with adverse maternal outcomes among Peruvian populations at different altitudes. A retrospective cohort study was conducted using data from the Perinatal Information System. Adverse maternal outcomes were assessed. Risk of pre-eclampsia increased at maternal hemoglobin levels above 14.5 g/dL (OR 1.27; 95% CI, 1.18-1.36) or below 7.0 g/dL (OR 1.52; CI 95%, 1.08-2.14). Altitude above 2000 m reduced risk (OR 0.65; 95% CI 0.62-0.68). Risk of postpartum hemorrhage (PPH) increased with moderate/severe anemia (OR 6.15; 95% CI, 3.86-9.78) and at moderate altitudes (OR 1.26; 95% CI, 1.12-1.43). Mild anemia at any altitude was associated with reduced risk of pre-eclampsia (OR 0.85, 95% CI, 0.81-0.89) and PPH (OR 1.01; 95% CI, 0.88-1.15). Risk of premature rupture of membranes was reduced at high hemoglobin values. Maternal mortality increased at hemoglobin levels below 9.0 g/dL (OR 5.68; 95% CI, 2.97-10.80) and above 14.5 g/dL (OR 2.18; 95% CI, 1.22-3.91). Maternal mortality increased at moderate altitudes (OR 29.2; 95% CI, 2.62-324.60) and high altitudes (OR 66.4; 95% CI, 6.65-780.30) when hemoglobin levels were below 9.0 g/dL. Elevated altitude and hemoglobin levels influence maternal outcomes. Copyright © 2012 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

The effect of golimumab on haemoglobin levels in patients with rheumatoid arthritis, psoriatic arthritis or ankylosing spondylitis.

PubMed

Furst, Daniel E; Kay, Jonathan; Wasko, Mary Chester; Keystone, Edward; Kavanaugh, Arthur; Deodhar, Atul; Murphy, Frederick T; Magnus, Jeanette H; Hsia, Elizabeth C; Hsu, Benjamin; Xu, Stephen; Rahman, Mahboob U; Doyle, Mittie K

2013-10-01

To evaluate the effect of golimumab on haemoglobin levels in patients with RA, PsA or AS. Secondary analysis was performed on integrated data from five randomized controlled studies: three RA, one PsA and one AS (2303 patients total). Golimumab 50 or 100 mg was injected s.c. every 4 weeks with or without MTX. Control groups received placebo injections plus MTX or background therapy. Patients with haemoglobin levels below the age- and sex-specific normal ranges were considered to have anaemia. Ferritin levels were used to distinguish anaemia of mixed aetiology (≥ 15 and <60 ng/ml) and anaemia of inflammation (≥ 60 ng/ml). Changes from baseline to weeks 14 and 24 in haemoglobin level were compared between treatment groups using an analysis of variance on the van der Waerden normal scores. At baseline, 21% of RA patients, 9% of PsA patients and 15% of AS patients had anaemia. Of these, 24%, 57% and 25%, respectively, had anaemia of inflammation. The median increase from baseline to week 14 in the haemoglobin level of anaemic patients was 0.3 g/dl in the control group and 0.9 g/dl in the golimumab group (P < 0.001). Haemoglobin levels improved within the subgroups of patients with anaemia of mixed aetiology (control, 0.4 g/dl vs golimumab, 0.7 g/dl) (P = 0.305) and with anaemia of inflammation (0.2 vs 1.4 g/dl, respectively) (P < 0.001). Compared with the control group, patients receiving golimumab treatment had significantly improved haemoglobin levels, particularly among patients with anaemia of inflammation.

Effect of infusion of equine plasma or 6% hydroxyethyl starch (600/0.75) solution on plasma colloid osmotic pressure in healthy horses.

PubMed

McKenzie, Erica C; Esser, Melissa M; McNitt, Sarah E; Payton, Mark E

2016-07-01

OBJECTIVE To compare the effects of equivalent volumes of equine plasma and 6% hydroxyethyl starch (600/0.75) solution (hetastarch) administered IV on plasma colloid osmotic pressure (pCOP) and commonly monitored clinicopathologic variables in horses. ANIMALS 6 healthy mares. PROCEDURES In a randomized, crossover study, horses were administered hetastarch or plasma (both 10 mL/kg, IV) 18 months apart. The pCOP and variables of interest were measured before (baseline), immediately after, and at intervals up to 96 or 120 hours after infusion. Prothrombin and activated partial thromboplastin times were measured before and at 2 and 8 hours after each infusion. RESULTS Prior to hetastarch and plasma infusions, mean ± SEM pCOP was 19.4 ± 0.5 mm Hg and 19.4 ± 0.8 mm Hg, respectively. In general, hetastarch and plasma infusions comparably increased pCOP from baseline for 48 hours, with maximum increases of 2.0 and 2.3 mm Hg, respectively. Mean Hct and hemoglobin, total protein, and albumin concentrations were decreased for a period of 72, 96, or 120 hours after hetastarch infusion with maximum decrements of 8.8%, 3.2 g/dL, 1.2 g/dL, and 0.6 g/dL, respectively. Plasma infusion decreased (albeit not always significantly) hemoglobin concentration and Hct for 20 and 24 hours (maximum changes of 1.5 g/dL and 6.6%, respectively) and increased total solids concentration (maximum change of 0.6 g/dL) for 48 hours. Platelet count and coagulation times were minimally affected. CONCLUSIONS AND CLINICAL RELEVANCE Overall, the hetastarch and plasma infusions comparably increased pCOP in healthy horses for up to 48 hours. Hetastarch induced greater, more persistent perturbations in clinicopathologic variables.

Intravenous iron isomaltoside 1000 (Monofer®) reduces postoperative anaemia in preoperatively non-anaemic patients undergoing elective or subacute coronary artery bypass graft, valve replacement or a combination thereof: a randomized double-blind placebo-controlled clinical trial (the PROTECT trial).

PubMed

Johansson, P I; Rasmussen, A S; Thomsen, L L

2015-10-01

This trial explores whether intravenous iron isomaltoside 1000 (Monofer®) results in a better regeneration of haemoglobin levels and prevents anaemia compared to placebo in preoperative non-anaemic patients undergoing cardiac surgery. The trial is a prospective, double-blind, comparative, placebo-controlled trial of 60 non-anaemic patients undergoing cardiac surgery. The patients were randomized 1:1 to either 1000 mg intravenous iron isomaltoside 1000 administered perioperatively by infusion or placebo. Mean preoperative haemoglobin in the active treatment group was 14·3 g/dl vs. 14·0 g/dl in the placebo group. At discharge 5 days after surgery, haemoglobin levels were reduced to 10·7 and 10·5 g/dl, respectively. One month after surgery, haemoglobin concentration had increased to an average of 12·6 g/dl vs. 11·8 g/dl (p = 0·012) and significantly more patients were non-anaemic in the intravenous iron isomaltoside 1000-treated group compared to the placebo group (38·5% vs. 8·0%; p = 0·019). There were no differences in side-effects between the groups. A single perioperative 1000 mg dose of intravenous iron isomaltoside 1000 significantly increased the haemoglobin level and prevented anaemia 4 weeks after surgery, with a short-term safety profile similar to placebo. Future trials on potential clinical benefits of preoperative treatment with intravenous iron in non-anaemic patients are needed. © 2015 The Authors ISBT Science Series published by John Wiley & Sons Ltd on behalf of International Society of Blood Transfusion.

Association between oral nutritional supplementation and clinical outcomes among patients with ESRD.

PubMed

Cheu, Christine; Pearson, Jeffrey; Dahlerus, Claudia; Lantz, Brett; Chowdhury, Tania; Sauer, Peter F; Farrell, Robert E; Port, Friedrich K; Ramirez, Sylvia P B

2013-01-01

Oral nutritional supplementation (ONS) was provided to ESRD patients with hypoalbuminemia as part of Fresenius Medical Care Health Plan's (FMCHP) disease management. This study evaluated the association between FMCHP's ONS program and clinical outcomes. Analyses included FMCHP patients with ONS indication (n=470) defined as 2-month mean albumin <3.8 g/dl until reaching a 3-month mean ≥3.8 g/dl from February 1, 2006 to December 31, 2008. Patients did not receive ONS if deemed inappropriate or refused. Patients on ONS were compared with patients who were not, despite meeting ONS indication. Patients with ONS indication regardless of use were compared with Medicare patients with similar serum albumin levels from the 2007 Centers for Medicare and Medicaid Services Clinical Performance Measures Project (CPM). Cox models calculated adjusted hospitalization and mortality risks at 1 year. Among patients with indication for ONS, 276 received supplements and 194 did not. ONS use was associated with 0.058 g/dl higher serum albumin overall (P=0.02); this difference decreased by 0.001 g/dl each month (P=0.05) such that the difference was 0.052 g/dl (P=0.04) in month 6 and the difference was no longer significant in month 12 . In analyses based on ONS use, ONS patients had lower hospitalization at 1 year (68.4%; P<0.01) versus patients without ONS (88.7%), but there was no significant reduction in mortality risk (P=0.29). In analyses based on ONS indication, patients with indication had lower mortality at 1 year (16.2%) compared with CPM patients (23.4%; P<0.01). These findings suggest that ONS use was associated with significantly lower hospitalization rates but had no significant effect on mortality in a disease management setting.

Japanese haemodialysis anaemia management practices and outcomes (1999–2006): results from the DOPPS

PubMed Central

Akizawa, Tadao; Pisoni, Ronald L.; Akiba, Takashi; Saito, Akira; Fukuhara, Shunichi; Asano, Yasushi; Hasegawa, Takeshi; Port, Friedrich K.; Kurokawa, Kiyoshi

2008-01-01

Background. Japanese haemodialysis (HD) patients not only have a very low mortality and hospitalization risk but also low haemoglobin (Hb) levels. Internationally, anaemia is associated with mortality, hospitalization and health-related quality of life (QoL) measures of HD patients. Methods. Longitudinal data collected from 1999 to 2006 from 60 to 64 representative Japanese dialysis units participating in the Dialysis Outcomes and Practice Patterns Study (DOPPS) were used to describe anaemia management practices and outcomes for Japanese HD patients. Results. From 1999 to 2006, patient mean Hb increased from 9.7 g/dl to 10.4 g/dl, and the percentage of facilities with median Hb ≥10 g/dl increased from 27% to 75%. Hb was measured in the supine position for 90% of patients, resulting in substantially lower reported Hb values than those seen in other countries. As of 2006, erythropoietin (Epo) was prescribed to 83% of HD patients; mean Epo dose was 5231 units/week; intravenous (IV) iron use was 33% and median IV iron dose was 160 mg/month. Many patient- and facility-level factors were significantly related to higher Hb. A consistent overall pattern of lower mortality risk with higher baseline Hb levels was seen (RR = 0.89 per 1 g/dl higher Hb, P = 0.003). Facilities with median Hb ≥10.4 displayed a lower mortality risk (RR = 0.77, P = 0.03) versus facility median Hb <10.4 g/dl. Lower Hb levels were not significantly related to hospitalization risk, but were associated with lower QoL scores. Conclusions. These results provide detailed information on anaemia management practices in Japan and the relationships of anaemia control with outcomes, with implications of anaemia management worldwide. PMID:18577535

A new multi-wavelength optical-plethysmograph for quantitative determination of pulpal hemoglobin content and oxygen level using green and near-infrared LEDs

NASA Astrophysics Data System (ADS)

Kakino, S.; Miwa, Z.; Kirimoto, A.; Ohuchi, K.; Takatani, S.; Takagi, Y.

2007-02-01

A new multi-wavelength optical-plethysmograph has been designed to study the relation between the transmitted optical density (OD) of the tooth vs. hemoglobin (Hb) content and oxygen saturation (SO II) of the pulpal blood using the 467, 506, 522 and 810 nm light emitting diodes (LEDs). The experimental model utilized the extracted human upper incisor where the pulp cavity was filled with the blood having various values of Hb and SO II. A resin cap was made to fit the tooth crown and optical fibers for transmission measurement. The LEDs were pulsed sequentially at 520 Hz with the pulse duration of 240 μs. The OD as a function of Hb for the isosbestic wavelengths of 506 and 522 nm increased almost linearly from 8.0 to 11.0 for Hb changing from 0.0 (saline control) to 2.5 g/dL, but beyond 2.5 g/dL no change was observed. At 810 nm, the OD increased linearly till Hb of 13.4 g/dL, but its change was much smaller with 1.0 OD per 13.4 g/dL. As for SO II, the OD at 467 nm with Hb of 1.0 g/dL that simulated the mean pulpal Hb content in vivo varied by about 1.0 for SO II changing from 100 to 40%. The OD change with respect to Hb change at 506 and 522 nm showed better sensitivity than that at 810 nm. The combination of 467 and 506 or 522 nm wavelengths can provide a noninvasive measurement of both pulpal Hb content and SO II to diagnose pulp vitality of teeth in vivo.

Association between anemia and subclinical infection in children in Paraíba State, Brazil

PubMed Central

Sales, Márcia Cristina; de Queiroz, Everton Oliveira; Paiva, Adriana de Azevedo

2011-01-01

Background With subclinical infection, serum iron concentrations are reduced, altering the synthesis of hemoglobin, the main indicator of anemia. Objective To evaluate the association between subclinical infection and anemia in children of Paraíba State. Methods This is a cross-sectional study involving 1116 children aged 6 to 59 months from nine municipalities of Paraíba State. Demographic and socioeconomic data were collected by means of a specific questionnaire. The C-reactive protein and hemoglobin levels were determined by the latex agglutination technique and automated counter, respectively. C-reactive protein values ≥ 6 mg/L were used as indicative of subclinical infection, while the presence of anemia was determined by hemoglobin values < 11.0 g/dL. The data were analyzed using the Epi Info computer program, with significance being set at 5%. Results Data from this research showed that 80.1% of the children belonged to families that were below the bread line, with per capita income < ½ of the minimum wage at that time (R$ 350.00 approximately US$ 175.00). The prevalences of subclinical infection and anemia were 11.3% and 36.3%, respectively. Subclinical infection was significantly associated with anemia (p-value < 0.05). There were lower levels of hemoglobin in children with C-reactive protein ≥ 6 mg/L, with a mean hemoglobin level in children with subclinical infection of 10.93 g/dL (standard deviation - SD = 1.21 g/dL) and without infection of 11.26 g/dL (SD = 1.18 g/dL) (p-value < 0.05). Conclusion Anemia is associated with subclinical infection in this population, indicating that this is an important variable to be considered in studies of the prevalence of anemia in children. PMID:23284254

The effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Astrophysics Data System (ADS)

Saunders, B. V.; Murray, B. T.; McFadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1992-06-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress-free boundaries is investigated using Floquet theory for the linear stability analysis. Situations for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double-diffusive convection are considered. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency. The response to modulation of the fundamental instability of the unmodulated system is described both analytically and numerically; in the double-diffusive system this mode persists under subcritical conditions as a high-frequency lobe.

The effect of gravity modulation on thermosolutal convection in an infinite layer of fluid

NASA Technical Reports Server (NTRS)

Saunders, B. V.; Murray, B. T.; Mcfadden, G. B.; Coriell, S. R.; Wheeler, A. A.

1992-01-01

The effect of time-periodic vertical gravity modulation on the onset of thermosolutal convection in an infinite horizontal layer with stress-free boundaries is investigated using Floquet theory for the linear stability analysis. Situations for which the fluid layer is stably stratified in either the fingering or diffusive regimes of double-diffusive convection are considered. Results are presented both with and without steady background acceleration. Modulation may stabilize an unstable base solution or destabilize a stable base solution. In addition to synchronous and subharmonic response to the modulation frequency, instability in the double diffusive system can occur via a complex conjugate mode. In the diffusive regime, where oscillatory onset occurs in the unmodulated system, regions of resonant instability occur and exhibit strong coupling with the unmodulated oscillatory frequency. The response to modulation of the fundamental instability of the unmodulated system is described both analytically and numerically; in the double-diffusive system this mode persists under subcritical conditions as a high-frequency lobe.

Anisotropic diffusion of oxygen on a few layers of black phosphorous

NASA Astrophysics Data System (ADS)

Fernández-Escamilla, Hector Noe; González-Chávez, Víctor Hugo; Martínez-Guerra, Eduardo; Garay-Tapia, Andrés; Martínez-Guerra, Edgar

Recently, phosporene has also been scored well as a functional material for two-dimensional electronic and optoelectronic devices. That is, because in contrast to graphene, black phosphorous has an inherent, direct and appreciable band gap that can be modulated with the numbers of layes. However, the presence of exposed lone pairs at the surface makes phosphorous very reactive to air and humidity and consequently, degradation of its properties. No such fundamental explanation have been made, thus corresponding first principle predictions to evaluate diffusion of O over and along a mono- and a few layers are indispensable. Energy barriers and the mechanisms of oxygen diffusion on mono- and a few layer of black phosphorous were calculated using the NEB(Nudge Elastic band) method as implemented in Quantum Espresso. The electronic states are expanded in plane waves with kinetic-energy cutoffs of 25 and 200 Ry for the wave function and charge density, respectively. Also, as the H2O and O2 are polar molecules, spin-polarized calculations have been carried out. We evaluated the diffusion barriers for O2 and H2O on phosphorene along zigzag, armchair and intermediated directions. Our calculations show that diffusion of O is preferred on zigzag directions and dissociation of O2 is favored as a result of energy gains of about 2 eV. Also, apparently diffusion pathways are blocked along layers.

The value of routine haemoglobin concentration measurement before caesarean section.

PubMed

Vashisht, A; Yentis, S

2005-02-01

Women undergoing caesarean section routinely have a haemoglobin concentration check before delivery. We compared the haemoglobin concentration of 311 women taken at their 32-?34 week antenatal visit with their preoperative level. A significant rise from 11.04 g/dL to 11.51 g/dL was seen (mean (95% CI) 0.47 (0.37-0.57 g/dL)). This increase was most marked in the 201 women having emergency procedures, and there was a significant negative correlation between the 32 and 34 weeks level and the net change in haemoglobin concentration (r=-0.366 (P<0.001)). From our results we suggest that in women with an otherwise uncomplicated pregnancy, and a satisfactory haemoglobin concentration at 32-34 weeks, a repeat estimation of the blood count is unnecessary before operative delivery.

488-1D Ash Basin closure cap help modeling- Microdrain® liner option

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyer, J. A.

At the request of Area Completion Engineering and in support of the 488-1D Ash Basin closure, the Savannah River National Laboratory (SRNL) performed hydrologic simulations of the revised 488-1D Ash Basin closure cap design using the Hydrologic Evaluation of Landfill Performance (HELP) model. The revised design substitutes a MicroDrain Liner®—60-mil low-density polyethylene geomembrane structurally integrated with 130-mil drainage layer—for the previously planned drainage/barrier system—300-mil geosynthetic drainage layer (GDL), 300-mil geosynthetic clay liner (GCL), and 6-inch common fill soil layer. For a 25-year, 24-hour storm event, HELP model v3.07 was employed to (1) predict the peak maximum daily hydraulic head formore » the geomembrane layer, and (2) ensure that South Carolina Department of Health and Environmental Control (SCDHEC) requirements for the barrier layer (i.e., ≤ 12 inches hydraulic head on top of a barrier having a saturated hydraulic conductivity ≤ 1.0E-05 cm/s) will not be exceeded. A 25-year, 24-hour storm event at the Savannah River Site (SRS) is 6.1 inches rainfall (Weber 1998). HELP model v3.07 results based upon the new planned cap design suggest that the peak maximum daily hydraulic head on the geomembrane barrier layer will be 0.15 inches for a minimum slope equal to 3%, which is two orders of magnitude below the SCDHEC upper limit of 12 inches.« less

488-1D Ash basin closure cap help modeling-Microdrain® liner option

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyer, J.

At the request of Area Completion Engineering and in support of the 488-1D Ash Basin closure, the Savannah River National Laboratory (SRNL) performed hydrologic simulations of the revised 488-1D Ash Basin closure cap design using the Hydrologic Evaluation of Landfill Performance (HELP) model. The revised design substitutes a MicroDrain Liner®—50-mil linear low-density polyethylene geomembrane structurally integrated with 130-mil drainage layer—for the previously planned drainage/barrier system—300-mil geosynthetic drainage layer (GDL), 300-mil geosynthetic clay liner (GCL), and 6-inch common fill soil layer. For a 25-year, 24-hour storm event, HELP model v3.07 was employed to (1) predict the peak maximum daily hydraulic headmore » for the geomembrane layer, and (2) ensure that South Carolina Department of Health and Environmental Control (SCDHEC) requirements for the barrier layer (i.e., ≤ 12 inches hydraulic head on top of a barrier having a saturated hydraulic conductivity ≤ 1.0E-05 cm/s) will not be exceeded. A 25-year, 24-hour storm event at the Savannah River Site (SRS) is 6.1 inches rainfall (Weber 1998). HELP model v3.07 results based upon the new planned cap design suggest that the peak maximum daily hydraulic head on the geomembrane barrier layer will be 0.179 inches for a minimum slope equal to 3%, which is approximately two orders of magnitude below the SCDHEC upper limit of 12 inches.« less

Groundwater discharge to lakes (GDL) - the disregarded component of lake nutrient budgets

NASA Astrophysics Data System (ADS)

Lewandowski, J.; Meinikmann, K.; Pöschke, F.; Nützmann, G.

2012-04-01

Eutrophication is a major threat to lakes in temperate climatic zones. It is necessary to determine the relevance of different nutrient sources to conduct effective management measures, to understand in-lake processes and to model future scenarios. A prerequisite for such nutrient budgets are water budgets. While most components of the water budget can be determined quite accurate the quantification of groundwater discharge to lakes (GDL) and surface water infiltration into the aquifer are much more difficult. For example, it is quite common to determine the groundwater component as residual in the water and nutrient budget which is extremely problematic since in that case all errors of the budget terms are summed up in the groundwater term. In total, we identified 10 different reasons for disregarding the groundwater path in nutrient budgets. We investigated the fate of the nutrients nitrogen and phosphorus on their pathway from the catchment through the reactive aquifer-lake interface into the lake. We reviewed the international literature and summarized numbers reported for GDL of nutrients. Since literature is quite sparse we also had a look at numbers reported for submarine groundwater discharge (SGD) of nutrients for which much more literature exists and which is despite some fundamental differences in principal comparable to GDL.

Boundary-layer electron profiles for entry of a blunts slender body at high altitude

NASA Technical Reports Server (NTRS)

Evans, J. S.; Schexnayder, C. J., Jr.; Huber, P. W.

1973-01-01

New calculations of boundary-layer electron concentration profiles for entry of a blunt-nosed slender body into the earth's atmosphere are compared with previous calculations in which ambipolar diffusion was neglected. The old and new results agree in those flight regimes where ambipolar diffusion is unimportant, but large differences are noted in both peak electron concentration and profile shape at the higher altitudes, where diffusion effects are greatest. The new results are also compared with flight-measured profiles and with calculated profiles for a viscous-shock-layer theory which was recently reported in the literature. The boundary-layer results and the data agree in most respects. Differences which occur between predicted results and the data in the outer parts of the profile are discussed in terms of the effects of aerodynamic heating of the probes.

Hemoglobin encapsulation in vesicles retards NO and CO binding and O2 release when perfused through narrow gas-permeable tubes.

PubMed

Sakai, Hiromi; Okuda, Naoto; Sato, Atsushi; Yamaue, Tatsuya; Takeoka, Shinji; Tsuchida, Eishun

2010-03-01

Intravenous administration of cell-free Hb induces vasoconstriction and circulatory disorders, presumably because of the intrinsic affinities to endogenous nitric oxide (NO) and carbon monoxide (CO) as vasorelaxation factors and because of the facilitated O(2) release that might induce autoregulatory vasoconstriction. We examined these gas reactions when Hb-containing solutions of four kinds were perfused through artificial narrow tubes at a practical Hb concentration (10 g/dl). Purified Hb solution, polymerized bovine Hb (Poly(B)Hb), encapsulated Hb [Hb-vesicles (HbV), 279 nm], and red blood cells (RBCs) were perfused through a gas-permeable narrow tube (25 microm inner diameter) at 1 mm/s centerline velocity. The level of reactions was determined microscopically based on the visible-light absorption spectrum of Hb. When the tube was immersed in NO and CO atmospheres, both NO binding and CO binding of deoxygenated Hb (deoxy-Hb) and Poly(B)Hb in the tube was faster than those of HbV and RBCs, and HbV and RBCs showed almost identical binding rates. When the tube was immersed in a N(2) atmosphere, oxygenated Hb and Poly(B)Hb showed much faster O(2) release than did HbV and RBCs. Poly(B)Hb showed a faster reaction than Hb because of the lower O(2) affinity of Poly(B)Hb than Hb. The diffusion process of the particles was simulated using Navier-Stokes and Maxwell-Stefan equations. Results clarified that small Hb (6 nm) diffuses laterally and mixes rapidly. However, the large-dimension HbV shows no such rapid diffusion. The purely physicochemical differences in diffusivity of the particles and the resulting reactivity with gas molecules are one factor inducing biological vasoconstriction of Hb-based oxygen carriers.

The layer boundary effect on multi-layer mesoporous TiO 2 film based dye sensitized solar cells

DOE PAGES

Xu, Feng; Zhu, Kai; Zhao, Yixin

2016-10-10

Multi-layer mesoporous TiO 2 prepared by screen printing is widely used for fabrication of high-efficiency dye-sensitized solar cells (DSSCs). Here, we compare the three types of ~10 um thick mesoporous TiO 2 films, which were screen printed as 1-, 2- and 4-layers using the same TiO 2 nanocrystal paste. The layer boundary of the multi-layer mesoporous TiO 2 films was observed in the cross-section SEM. The existence of a layer boundary could reduce the photoelectron diffusion length with the increase of layer number. However, the photoelectron diffusion lengths of the Z907 dye sensitized solar cells based on these different layeredmore » mesoporous TiO 2 films are all longer than the film thickness. Consequently, the photovoltaic performance seems to have little dependence on the layer number of the multi-layer TiO 2 based DSSCs.« less

The layer boundary effect on multi-layer mesoporous TiO 2 film based dye sensitized solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Feng; Zhu, Kai; Zhao, Yixin

Multi-layer mesoporous TiO 2 prepared by screen printing is widely used for fabrication of high-efficiency dye-sensitized solar cells (DSSCs). Here, we compare the three types of ~10 um thick mesoporous TiO 2 films, which were screen printed as 1-, 2- and 4-layers using the same TiO 2 nanocrystal paste. The layer boundary of the multi-layer mesoporous TiO 2 films was observed in the cross-section SEM. The existence of a layer boundary could reduce the photoelectron diffusion length with the increase of layer number. However, the photoelectron diffusion lengths of the Z907 dye sensitized solar cells based on these different layeredmore » mesoporous TiO 2 films are all longer than the film thickness. Consequently, the photovoltaic performance seems to have little dependence on the layer number of the multi-layer TiO 2 based DSSCs.« less

Interpretation of scanning electron microscope measurements of minority carrier diffusion lengths in semiconductors

NASA Technical Reports Server (NTRS)

Flat, A.; Milnes, A. G.

1978-01-01

In scanning electron microscope (SEM) injection measurements of minority carrier diffusion lengths some uncertainties of interpretation exist when the response current is nonlinear with distance. This is significant in epitaxial layers where the layer thickness is not large in relation to the diffusion length, and where there are large surface recombination velocities on the incident and contact surfaces. An image method of analysis is presented for such specimens. A method of using the results to correct the observed response in a simple convenient way is presented. The technique is illustrated with reference to measurements in epitaxial layers of GaAs. Average beam penetration depth may also be estimated from the curve shape.

Silver photo-diffusion and photo-induced macroscopic surface deformation of Ge{sub 33}S{sub 67}/Ag/Si substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakaguchi, Y., E-mail: y-sakaguchi@cross.or.jp; Asaoka, H.; Uozumi, Y.

2016-08-07

Ge-chalcogenide films show various photo-induced changes, and silver photo-diffusion is one of them which attracts lots of interest. In this paper, we report how silver and Ge-chalcogenide layers in Ge{sub 33}S{sub 67}/Ag/Si substrate stacks change under light exposure in the depth by measuring time-resolved neutron reflectivity. It was found from the measurement that Ag ions diffuse all over the matrix Ge{sub 33}S{sub 67} layer once Ag dissolves into the layer. We also found that the surface was macroscopically deformed by the extended light exposure. Its structural origin was investigated by a scanning electron microscopy.

Modeling the Impact of Cracking in Low Permeability Layers in a Groundwater Contamination Source Zone on Dissolved Contaminant Fate and Transport

NASA Astrophysics Data System (ADS)

Sievers, K. W.; Goltz, M. N.; Huang, J.; Demond, A. H.

2011-12-01

Dense Non-Aqueous Phase Liquids (DNAPLs), which are chemicals and chemical mixtures that are heavier than and only slightly soluble in water, are a significant source of groundwater contamination. Even with the removal or destruction of most DNAPL mass, small amounts of remaining DNAPL can dissolve into flowing groundwater and continue as a contamination source for decades. One category of DNAPLs is the chlorinated aliphatic hydrocarbons (CAHs). CAHs, such as trichloroethylene and carbon tetrachloride, are found to contaminate groundwater at numerous DoD and industrial sites. DNAPLs move through soils and groundwater leaving behind residual separate phase contamination as well as pools sitting atop low permeability layers. Recently developed models are based on the assumption that dissolved CAHs diffuse slowly from pooled DNAPL into the low permeability layers. Subsequently, when the DNAPL pools and residual DNAPL are depleted, perhaps as a result of a remediation effort, the dissolved CAHs in these low permeability layers still remain to serve as long-term sources of contamination, due to so-called "back diffusion." These recently developed models assume that transport in the low permeability zones is strictly diffusive; however field observations suggest that more DNAPL and/or dissolved CAH is stored in the low permeability zones than can be explained on the basis of diffusion alone. One explanation for these field observations is that there is enhanced transport of dissolved CAHs and/or DNAPL into the low permeability layers due to cracking. Cracks may allow for advective flow of water contaminated with dissolved CAHs into the layer as well as possible movement of pure phase DNAPL into the layer. In this study, a multiphase numerical flow and transport model is employed in a dual domain (high and low permeability layers) to investigate the impact of cracking on DNAPL and CAH movement. Using literature values, the crack geometry and spacing was varied to model and compare four scenarios: (1) CAH diffusion only into cracks, (2) CAH advection-dispersion into cracks, (3) separate phase DNAPL movement into the cracks, and (4) CAH diffusion into an uncracked low permeability clay layer. For each scenario, model simulations are used to show the evolution and persistence of groundwater contamination downgradient of the DNAPL source.

Gas diffusion in and out of super-hydrophobic surface in transitional and turbulent boundary layers

NASA Astrophysics Data System (ADS)

Ling, Hangjian; Fu, Matthew; Hultmark, Marcus; Katz, Joseph

2017-11-01

The rate of gas diffusion in and out of a super-hydrophobic surface (SHS) located in boundary layers is investigated at varying Reynolds numbers and ambient pressures. The hierarchical SHS consists of nano-textured, 100 μm wide spanwise grooves. The boundary layers over the SHS under the Cassie-Baxter and Wenzel states as well as a smooth wall at same conditions are characterized by particle image velocimetry. The Reynolds number based on momentum thickness of the smooth wall, ReΘ0, ranges from 518 to 2088, covering transitional and turbulent boundary layer regimes. The mass diffusion rate is estimated by using microscopy to measure the time-evolution of plastron shape and volume. The data is used for calculating the Sherwood number based on smooth wall momentum thickness, ShΘ0. As expected, the diffusion rate increases linearly with the under- or super-saturation level, i.e., ShΘ0 is independent of ambient pressure. For the turbulent boundary layers, the data collapses onto ShΘ0 = 0.47ReΘ00.77 . For the transitional boundary layer, ShΘ0 is lower than the turbulent power law. When ShΘ0 is plotted against the friction Reynolds number (Reτ0) , both the transitional and turbulent boundary layer data collapse onto a single power law, ShΘ0 = 0.34Reτ00.913 . Results scaled based on Wenzel state momentum thickness show very similar trends. Sponsored by ONR.

Interface structure in nanoscale multilayers near continuous-to-discontinuous regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradhan, P. C.; Majhi, A.; Nayak, M., E-mail: mnayak@rrcat.gov.in

2016-07-28

Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B{sub 4}C multilayer (ML) system as functions of thickness in ultrathin limit. Hard x-ray reflectivity (XRR) and x-ray diffuse scattering in conjunction with x-ray absorption near edge spectroscopy (XANES) in soft x-ray and hard x-ray regimes and depth profiling x-ray photoelectron spectroscopy (XPS) have been used to precisely evaluate detailed interfacial structure by systematically varying the individual layer thickness from continuous-to-discontinuous regime. It is observed that the interfacial morphology undergoes an unexpected significant modification as the layer thickness varies from continuous-to-discontinuous regime. The interfacial atomic diffusionmore » increases, the physical density of W layer decreases and that of B{sub 4}C layer increases, and further more interestingly the in-plane correlation length decreases substantially as the layer thickness varies from continuous-to-discontinuous regime. This is corroborated using combined XRR and x-ray diffused scattering analysis. XANES and XPS results show formation of more and more tungsten compounds at the interfaces as the layer thickness decreases below the percolation threshold due to increase in the contact area between the elements. The formation of compound enhances to minimize certain degree of disorder at the interfaces in the discontinuous region that enables to maintain the periodic structure in ML. The degree of interfacial atomic diffusion, interlayer interaction, and microstructure is correlated as a function of layer thickness during early stage of film growth.« less

Numerical Evaluation of Lateral Diffusion Inside Diffusive Gradients in Thin Films Samplers

PubMed Central

2015-01-01

Using numerical simulation of diffusion inside diffusive gradients in thin films (DGT) samplers, we show that the effect of lateral diffusion inside the sampler on the solute flux into the sampler is a nonlinear function of the diffusion layer thickness and the physical sampling window size. In contrast, earlier work concluded that this effect was constant irrespective of parameters of the sampler geometry. The flux increase caused by lateral diffusion inside the sampler was determined to be ∼8.8% for standard samplers, which is considerably lower than the previous estimate of ∼20%. Lateral diffusion is also propagated to the diffusive boundary layer (DBL), where it leads to a slightly stronger decrease in the mass uptake than suggested by the common 1D diffusion model that is applied for evaluating DGT results. We introduce a simple correction procedure for lateral diffusion and demonstrate how the effect of lateral diffusion on diffusion in the DBL can be accounted for. These corrections often result in better estimates of the DBL thickness (δ) and the DGT-measured concentration than earlier approaches and will contribute to more accurate concentration measurements in solute monitoring in waters. PMID:25877251

Investigating fuel-cell transport limitations using hydrogen limiting current

DOE PAGES

Spingler, Franz B.; Phillips, Adam; Schuler, Tobias; ...

2017-03-09

Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. Here, we use a hydrogen-pump limiting-current setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. Additionally, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measuredmore » transport resistance. This is especially true for low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and mass-dependent and independent ones, where the data suggests that a large part of the transport resistance in catalyst layers cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs.« less

Experimental analysis of two-layered dissimilar metals by roll bonding

NASA Astrophysics Data System (ADS)

Zhao, Guanghui; Li, Yugui; Li, Juan; Huang, Qingxue; Ma, Lifeng

2018-02-01

Rolling reduction and base layers thickness have important implications for rolling compounding. A two-layered 304 stainless steel/Q345R low alloyed steel was roll bonded. The roll bonding was performed at the three thickness reductions of 25%, 40% and 55% with base layers of various thicknesses (Q345R). The microstructures of the composite were investigated by the ultra-deep microscope (OM) and scanning electron microscope (SEM) and Transmission electron microscope (TEM). Simultaneously, the mechanical properties of the composite were experimentally measured and the tensile fracture surfaces were observed by SEM. The interfaces were successfully bonded without any cracking or voids, which indicated a good fabrication of the 304/Q345R composite. The rolling reduction rate and thinning increase of the substrate contributed to the bonding effects appearance of the roll bonded sheet. The Cr and Ni enriched diffusion layer was formed by the interface elements diffusion. The Cr and Ni diffusion led to the formation of ˜10 μm wide Cr and Ni layers on the carbon steel side.

Analysis of Double Layer and Adsorption Effects at the Alkaline Polymer Electrolyte-Electrode Interface

DTIC Science & Technology

2011-10-05

anion exchange mem - branes (AEM) are an attractive alternative to proton exchange mem - brane (PEM) fuel cells.1, 2 From electrocatalysts standpoint...gener- ally broken down into three distinct regions: the inner Helmholtz plane (IHP), the outer Helmholtz plane ( OHP ), and the diffuse layer. Figure 11...closest approach and is defined as OHP at a distance, x2. Nonspecifically adsorbed ions are distributed in a three dimensional region, called diffuse layer

Large-Scale Integration of Solid-State Microfluidic Valves With No Moving Parts

DTIC Science & Technology

2005-01-01

compact and diffuse layer is called outer Helmholtz plane ( OHP ). Potential drop across the diffusion layer is called the zeta potential, ζ. As the...Gouy-Chapman model. This is shown in Fig. 3. The plane at x2 is called the outer Helmholtz plane ( OHP ). Then the total double layer capacitance Cd...Enhanced Electro-Osmotic Pumping With Liquid Bridge and Field Effect Flow Rectification, ” Presented in IEEE MEMS 2004 Conference, Maastricht, The

Discrete multi-physics simulations of diffusive and convective mass transfer in boundary layers containing motile cilia in lungs.

PubMed

Ariane, Mostapha; Kassinos, Stavros; Velaga, Sitaram; Alexiadis, Alessio

2018-04-01

In this paper, the mass transfer coefficient (permeability) of boundary layers containing motile cilia is investigated by means of discrete multi-physics. The idea is to understand the main mechanisms of mass transport occurring in a ciliated-layer; one specific application being inhaled drugs in the respiratory epithelium. The effect of drug diffusivity, cilia beat frequency and cilia flexibility is studied. Our results show the existence of three mass transfer regimes. A low frequency regime, which we called shielding regime, where the presence of the cilia hinders mass transport; an intermediate frequency regime, which we have called diffusive regime, where diffusion is the controlling mechanism; and a high frequency regime, which we have called convective regime, where the degree of bending of the cilia seems to be the most important factor controlling mass transfer in the ciliated-layer. Since the flexibility of the cilia and the frequency of the beat changes with age and health conditions, the knowledge of these three regimes allows prediction of how mass transfer varies with these factors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Reduction in number of crystal defects in a p+Si diffusion layer by germanium and boron cryogenic implantation combined with sub-melt laser spike annealing

NASA Astrophysics Data System (ADS)

Murakoshi, Atsushi; Harada, Tsubasa; Miyano, Kiyotaka; Harakawa, Hideaki; Aoyama, Tomonori; Yamashita, Hirofumi; Kohyama, Yusuke

2017-09-01

To reduce the number of crystal defects in a p+Si diffusion layer by a low-thermal-budget annealing process, we have examined crystal recovery in the amorphous layer formed by the cryogenic implantation of germanium and boron combined with sub-melt laser spike annealing (LSA). The cryogenic implantation at -150 °C is very effective in suppressing vacancy clustering, which is advantageous for rapid crystal recovery during annealing. The crystallinity after LSA is shown to be very high and comparable to that after rapid thermal annealing (RTA) owing to the cryogenic implantation, although LSA is a low-thermal-budget annealing process that can suppress boron diffusion effectively. It is also shown that in the p+Si diffusion layer, there is high contact resistance due to the incomplete formation of a metal silicide contact, which originates from insufficient outdiffusion of surface contaminants such as fluorine. To widely utilize the marked reduction in the number of crystal defects, sufficient removal of surface contaminants will be required in the low-thermal-budget process.

Effect of diffusion annealing regimes on the structure of Nb3Sn layers in ITER-type bronze-processed wires

NASA Astrophysics Data System (ADS)

Valova-Zaharevskaya, E. G.; Popova, E. N.; Deryagina, I. L.; Abdyukhanov, I. M.; Tsapleva, A. S.

2018-03-01

The goal of the present study is to characterize the growth kinetics and structural parameters of the Nb3Sn layers formed under various regimes of the diffusion annealing of bronze-processed Nb/Cu-Sn composites. The structure of the superconducting layers is characterized by their thickness, average size of equiaxed grains and by the ratio of fractions of columnar and equiaxed grains. It was found that at higher diffusion annealing temperatures (above 650°C) thicker superconducting layers are obtained, but the average sizes of equiaxed Nb3Sn grains even under short exposures (10 h) are much larger than after the long low-temperature annealing. At the low-temperature (575 °C) annealing the relative fraction of columnar grains increases with increasing annealing time. Based on the data obtained, optimal regimes of the diffusion annealing can be chosen, which would on the one hand ensure complete transformation of Nb into Nb3Sn of close to the stoichiometric composition, and on the other hand prevent the formation of coarse and columnar grains.

Superplastic Forming/Diffusion Bonding Without Interlayer of 5A90 Al-Li Alloy Hollow Double-Layer Structure

NASA Astrophysics Data System (ADS)

Jiang, Shaosong; Jia, Yong; Lu, Zhen; Shi, Chengcheng; Zhang, Kaifeng

2017-09-01

The hollow double-layer structure of 5A90 Al-Li alloy was fabricated by SPF/DB process in this study. The characteristics and mechanism of 5A90 Al-Li alloy with respect to superplasticity and diffusion bonding were investigated. Tensile tests showed that the optimal elongation of tensile specimens was 243.97% at the temperature of 400 °C and the strain rate of 0.001 s-1. Effect of the surface roughness, bonding temperature and bonding time to determine the microstructure and mechanical properties of diffusion bonding joints was investigated, and the optimum bonding parameters were 540 °C/2.5 h/Ra18. Through the finite element simulation, it could be found that the SPF/DB process of hollow double-layer structure was feasible. The hollow double-layer structure of 5A90 Al-Li alloy was manufactured, showing that the thickness distribution of the bonding area was uniform and the thinnest part was the round corner. The SEM images of diffusion bonding joints showed that sound bonding interfaces were obtained in which no discontinuity existed.

Kinetics of Isothermal Reactive Diffusion Between Solid Cu and Liquid Sn

NASA Astrophysics Data System (ADS)

O, M.; Suzuki, T.; Kajihara, M.

2018-01-01

The Cu/Sn system is one of the most fundamental and important metallic systems for solder joints in electric devices. To realize reliable solder joints, information on reactive diffusion at the solder joint is very important. In the present study, we experimentally investigated the kinetics of the reactive diffusion between solid Cu and liquid Sn using semi-infinite Cu/Sn diffusion couples prepared by an isothermal bonding technique. Isothermal annealing of the diffusion couple was conducted in the temperature range of 533-603 K for various times up to 172.8 ks (48 h). Using annealing, an intermetallic layer composed of Cu6Sn5 with scallop morphology and Cu3Sn with rather uniform thickness is formed at the original Cu/Sn interface in the diffusion couple. The growth of the Cu6Sn5 scallop occurs much more quickly than that of the Cu3Sn layer and thus predominates in the overall growth of the intermetallic layer. This tendency becomes more remarkable at lower annealing temperatures. The total thickness of the intermetallic layer is proportional to a power function of the annealing time, and the exponent of the power function is close to unity at all the annealing temperatures. This means that volume diffusion controls the intermetallic growth and the morphology of the Cu6Sn5/Sn interface influences the rate-controlling process. Adopting a mean value of 0.99 for the exponent, we obtain a value of 26 kJ/mol for the activation enthalpy of the intermetallic growth.

A Physical Mechanism for the Asymmetry in Top-Down and Bottom-Up Diffusion.

NASA Astrophysics Data System (ADS)

Wyngaard, J. C.

1987-04-01

Recent large-eddy simulations of the vertical diffusion of a passive, conservative scalar through the convective boundary layer (CBL) show strikingly different eddy diffusivity profiles in the `top-down' and `bottom-up' cases. These results indicate that for a given turbulent velocity field and associated scalar flux, the mean change in scalar mixing ratio across the CBL is several times larger if the flux originates at the top of the boundary layer (i.e., in top-down diffusion) rather than at the bottom. The large-eddy simulation (LES) data show that this asymmetry is due to a breakdown of the eddy-diffusion concept.A simple updraft-downdraft model of the CBL reveals a physical mechanism that could cause this unexpected behavior. The large, positive skewness of the convectively driven vertical velocity gives an appreciably higher probability of downdrafts than updrafts; this excess probability of downdrafts, interacting with the time changes of the mean mixing ratio caused by the nonstationarity of the bottom-up and top-down diffusion processes, decreases the equilibrium value of mean mixing-ratio jump across the mixed layer in the bottom-up case and increases it in the top-down case. The resulting diffusion asymmetry agrees qualitatively with that found through LES.

Formation of Cr2O3 Diffusion Barrier Between Cr-Contained Stainless Steel and Cold-Sprayed Ni Coatings at High Temperature

NASA Astrophysics Data System (ADS)

Xu, Ya-Xin; Luo, Xiao-Tao; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

2016-02-01

A novel approach to prepare a coating system containing an in situ grown Cr2O3 diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr2O3 layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr2O3 layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr2O3 oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively.

Interface morphology of Mo/Si multilayer systems with varying Mo layer thickness studied by EUV diffuse scattering.

PubMed

Haase, Anton; Soltwisch, Victor; Braun, Stefan; Laubis, Christian; Scholze, Frank

2017-06-26

We investigate the influence of the Mo-layer thickness on the EUV reflectance of Mo/Si mirrors with a set of unpolished and interface-polished Mo/Si/C multilayer mirrors. The Mo-layer thickness is varied in the range from 1.7 nm to 3.05 nm. We use a novel combination of specular and diffuse intensity measurements to determine the interface roughness throughout the multilayer stack and do not rely on scanning probe measurements at the surface only. The combination of EUV and X-ray reflectivity measurements and near-normal incidence EUV diffuse scattering allows to reconstruct the Mo layer thicknesses and to determine the interface roughness power spectral density. The data analysis is conducted by applying a matrix method for the specular reflection and the distorted-wave Born approximation for diffuse scattering. We introduce the Markov-chain Monte Carlo method into the field in order to determine the respective confidence intervals for all reconstructed parameters. We unambiguously detect a threshold thickness for Mo in both sample sets where the specular reflectance goes through a local minimum correlated with a distinct increase in diffuse scatter. We attribute that to the known appearance of an amorphous-to-crystallization transition at a certain thickness threshold which is altered in our sample system by the polishing.

The formation of thermohaline staircases for large salt concentration differences in double diffusive convection

NASA Astrophysics Data System (ADS)

Yang, Yantao; Verzicco, Roberto; Lohse, Detlef

2016-11-01

In the upper layers of the tropical and subtropical ocean, step-like mean profiles for both temperature and salinity are often observed, a phenomenon referred to as thermohaline staircase. It consists of alternatively stacked mixing layers, and finger layers with sharp gradients in both mean temperature and salinity. It is believed that thermohaline staircases are caused by double diffusive convection (DDC), i.e. the convection flow with fluid density affected by two different scalars. Here we conducted direct numerical simulations of DDC bounded by two parallel plates and aimed to realise the multi-layer state similar to the oceanic thermohaline staircase. We applied an unstable salinity difference and a stable temperature difference across the two plates. We gradually increased the salinity Rayleigh number RaS , i.e. the strength of salinity difference, and fixed the relative strength of temperature difference. When RaS is high enough the flow undergoes a transition from a single finger layer to a triple layer state, where one mixing layer emerges between two finger layers. Such triple layer state is stable up to the turbulent diffusive time scale. The finger-layer height is larger for higher RaS . The dependences of the scalar fluxes on RaS were also investigated. Supported by Dutch FOM Foundation and NWO rpogramme MCEC; Computing resources from SURFSara and PRACE project 2015133124.

Diffusion profile of macromolecules within and between human skin layers for (trans)dermal drug delivery.

PubMed

Römgens, Anne M; Bader, Dan L; Bouwstra, Joke A; Baaijens, Frank P T; Oomens, Cees W J

2015-10-01

Delivering a drug into and through the skin is of interest as the skin can act as an alternative drug administration route for oral delivery. The development of new delivery methods, such as microneedles, makes it possible to not only deliver small molecules into the skin, which are able to pass the outer layer of the skin in therapeutic amounts, but also macromolecules. To provide insight into the administration of these molecules into the skin, the aim of this study was to assess the transport of macromolecules within and between its various layers. The diffusion coefficients in the epidermis and several locations in the papillary and reticular dermis were determined for fluorescein dextran of 40 and 500 kDa using a combination of fluorescent recovery after photobleaching experiments and finite element analysis. The diffusion coefficient was significantly higher for 40 kDa than 500 kDa dextran, with median values of 23 and 9 µm(2)/s in the dermis, respectively. The values only marginally varied within and between papillary and reticular dermis. For the 40 kDa dextran, the diffusion coefficient in the epidermis was twice as low as in the dermis layers. The adopted method may be used for other macromolecules, which are of interest for dermal and transdermal drug delivery. The knowledge about diffusion in the skin is useful to optimize (trans)dermal drug delivery systems to target specific layers or cells in the human skin. Copyright © 2015 Elsevier Ltd. All rights reserved.

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nole, Michael; Daigle, Hugh; Cook, Ann E.

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems: DIFFUSION-DRIVEN HYDRATE GROWTH IN SANDS

DOE PAGES

Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

2017-02-01

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1 to 20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two- dimensional and basin-scalemore » three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. As a result, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial.« less

String-like collective motion and diffusion in the interfacial region of ice

NASA Astrophysics Data System (ADS)

Wang, Xinyi; Tong, Xuhang; Zhang, Hao; Douglas, Jack F.

2017-11-01

We investigate collective molecular motion and the self-diffusion coefficient Ds of water molecules in the mobile interfacial layer of the secondary prismatic plane (11 2 ¯ 0 ) of hexagonal ice by molecular dynamics simulation based on the TIP4P/2005 water potential and a metrology of collective motion drawn from the field of glass-forming liquids. The width ξ of the mobile interfacial layer varies from a monolayer to a few nm as the temperature is increased towards the melting temperature Tm, in accordance with recent simulations and many experimental studies, although different experimental methods have differed in their precise estimates of the thickness of this layer. We also find that the dynamics within this mobile interfacial ice layer is "dynamically heterogeneous" in a fashion that has many features in common with glass-forming liquids and the interfacial dynamics of crystalline Ni over the same reduced temperature range, 2/3 < T/Tm < 1. In addition to exhibiting non-Gaussian diffusive transport, decoupling between mass diffusion and the structural relaxation time, and stretched exponential relaxation, we find string-like collective molecular exchange motion in the interfacial zone within the ice interfacial layer and colored noise fluctuations in the mean square molecular atomic displacement 〈u2〉 after a "caging time" of 1 ps, i.e., the Debye-Waller factor. However, while the heterogeneous dynamics of ice is clearly similar in many ways to molecular and colloidal glass-forming materials, we find distinct trends between the diffusion coefficient activation energy Ea for diffusion Ds and the interfacial width ξ from the scale of collective string-like motion L than those found in glass-forming liquids.

The role of halide ions on the electrochemical behaviour of iron in alkali solutions

NASA Astrophysics Data System (ADS)

Begum, S. Nathira; Muralidharan, V. S.; Basha, C. Ahmed

2008-02-01

Active dissolution and passivation of transition metals in alkali solutions is of technological importance in batteries. The performance of alkaline batteries is decided by the presence of halides as they influence passivation. Cyclic voltammetric studies were carried out on iron in different sodium hydroxide solutions in presence of halides. In alkali solutions iron formed hydroxo complexes and their polymers in the interfacial diffusion layer. With progress of time they formed a cation selective layer. The diffusion layer turned into bipolar ion selective layer consisted of halides, a selective inner sublayer to the metal side and cation selective outer layer to the solution side. At very high anodic potentials, dehydration and deprotonation led to the conversion of salt layer into an oxide.

Insights into Interactions of Water Ice with Regolith under Simulated Martian Conditions.

NASA Astrophysics Data System (ADS)

Chittenden, Julie; Chevrier, V.; Sears, D. W.; Roe, L. A.; Bryson, K.; Billingsly, L.; Hanley, J.

2006-09-01

In order to understand the diffusion process of water vapor through regolith, we have investigated the sublimation process of subsurface ice under varying depths of JSC Mars-1 soil simulant under martian conditions. Measurements were made at 0oC and 5.25 Torr in a CO2 atmosphere. We corrected for variations in temperature of the ice and the difference in gravity of Mars in relation to the Earth. Our results show that for depths up to 40 mm the process is mainly diffusion controlled and that for thicker regolith layers, desorption becomes the main process. After correction for the effect of desorption, we observed a decrease in sublimation rate from 0.625 ± 0.073 mm.h-1 at 5 mm of soil to 0.187 ± 0.093 mm.h-1 for 200 mm of soil. To characterize the diffusion process, we use the Farmer model (1976), which hypothesizes that the sublimation rate is equal to the diffusion coefficient divided by the soil depth. The derived diffusion coefficient from this data is 2.52 ± 0.55 mm2.h-1, or 7.0 ± 1.5 x 10-10 m2.s-1. Knowing the diffusion coefficient in the regolith, we can calculate the survival time, κ, of a layer of ice under a regolith layer which is given by τ = liceL/D, where lice is the thickness of the ice layer. Using this equation, we find that a 10 cm-thick layer of ice buried under 1 m of regolith would last for more than 4 years at 0oC. Therefore, our study indicates that the transport of water through a regolith layer is a complex multi-faceted process that is readily quantified by laboratory investigations. This is especially important in interpreting previous theoretical models and in understanding in situ observations to be performed by martian landers such as Phoenix. The W.M. Keck Foundation funded this research.

Predicting First Traversal Times for Virions and Nanoparticles in Mucus with Slowed Diffusion

PubMed Central

Erickson, Austen M.; Henry, Bruce I.; Murray, John M.; Klasse, Per Johan; Angstmann, Christopher N.

2015-01-01

Particle-tracking experiments focusing on virions or nanoparticles in mucus have measured mean-square displacements and reported diffusion coefficients that are orders of magnitude smaller than the diffusion coefficients of such particles in water. Accurate description of this subdiffusion is important to properly estimate the likelihood of virions traversing the mucus boundary layer and infecting cells in the epithelium. However, there are several candidate models for diffusion that can fit experimental measurements of mean-square displacements. We show that these models yield very different estimates for the time taken for subdiffusive virions to traverse through a mucus layer. We explain why fits of subdiffusive mean-square displacements to standard diffusion models may be misleading. Relevant to human immunodeficiency virus infection, using computational methods for fractional subdiffusion, we show that subdiffusion in normal acidic mucus provides a more effective barrier against infection than previously thought. By contrast, the neutralization of the mucus by alkaline semen, after sexual intercourse, allows virions to cross the mucus layer and reach the epithelium in a short timeframe. The computed barrier protection from fractional subdiffusion is some orders of magnitude greater than that derived by fitting standard models of diffusion to subdiffusive data. PMID:26153713

Exploiting Temporal Constraints of Clinical Guidelines by Applying OpenEHR Archetypes.

PubMed

Cintho, Lilian Mie Mukai; Garcia, Diego; da Silva Santos, Bruno Henrique; Sacchi, Lucia; Quaglini, Silvana; Moro, Claudia Maria Cabral

2017-01-01

Studies describing Computer-Interpretable Clinical Guidelines (CIG) with temporal constrains (TC) generally have not addressed issues related to their integration into Electronic Health Record (EHR) systems. This study aimed to represent TCs contained in clinical guidelines by applying archetypes and Guideline Definition Language (GDL) to incorporate decision support into EHRs. An example of each TC class in the clinical guideline for management of Atrial Fibrillation was represented using archetypes and GDL.

Determination of the crystalline structure of scale solids from the 16H evaporator gravity drain line to tank 38H

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oji, L. N.

2015-10-01

August 2015, scale solids from the 16H Evaporator Gravity Drain Line (GDL) to the Tank 38H were delivered to SRNL for analysis. The desired analytical goal was to identify and confirm the crystalline structure of the scale material and determine if the form of the aluminosilicate mineral was consistent with previous analysis of the scale material from the GDL.

Clinical and hematological response to hydroxyurea in a patient with Hb Lepore/beta-thalassemia.

PubMed

Rigano, P; Manfré, L; La Galla, R; Renda, D; Renda, M C; Calabrese, A; Calzolari, R; Maggio, A

1997-05-01

The possibility of increasing Hb F in vivo using drugs like 5-azacytidine, hydroxyurea, and butyrate has been established. However, in many cases this does not entail an increase in total hemoglobin. We report on a patient with Hb Lepore/beta-thalassemia being treated with hydroxyurea (30 mg/Kg/day) because of the presence of erythroid extramedullary masses with severe neurological abnormalities. During therapy the patient showed a remarkable improvement in neurological signs due to the reduction in extra-medullary masses, a significant increase in both total hemoglobin (from 5.8 to 9.7 g/dl) and Hb F (from 4.9 g/dl to 9.1 g/dl). The marked improvement in hemoglobin level in our patient with Hb Lepore/beta-thalassemia suggests gamma-globin gene activation due to the DNA structure determined by the crossover event.

Haemoglobin concentrations and infection by Giardia intestinalis in children: effect of treatment with secnidazole.

PubMed

Jiménez, J C; Rodríguez, N; Di Prisco, M C; Lynch, N R; Costa, V

1999-12-01

The blood concentrations of haemoglobin were investigated in 82 children aged 2-9 years. Fifty-seven (31 boys and 26 girls) were stool-positive for Giardia intestinalis but the other 25, used as controls, were negative. The mean (S.D.) haemoglobin concentration among the infected children was significantly lower pre-treatment than that for the control group [11.6 (1.2) v. 12.6 (1.5) g/dl; P < 0.05]. Treatment of the infected children with a single oral dose of secnidazole (30 mg/kg) led to a significant increase in their mean haemoglobin level 15 days later, from 11.6 (1.2) g/dl pre-treatment to 12.4 (1.2) g/dl post-treatment (P < 0.05). The results indicate that the therapeutic control of giardiasis could be important in programmes to combat anaemia in children living in endemic areas.

Blood indicators of seasonal metabolic patterns in captive adult gray wolves

USGS Publications Warehouse

Seal, U.S.; Mech, L.D.

1983-01-01

Blood samples and physical data were collected weekly from a colony of gray wolves (Canis lupus) maintained under natural weather arid light conditions. Sampling over 33 continuous months indicated that hemoglobin, hematocrit, red blood cells, mean corpuscular hemoglobin concentration (MCHC), and thyroxine exhibited consistent circannual patterns of variation in both males and females. Hemoglobin levels peaked at 15-16 g/dl in January in females and at 16-17 g/dl in February in males, and were lowest in August at 10.5-11.5 g/dl (P < 0.00001). The cyclic patterns of hematocrit, red blood cells, and MCHC were similarly timed. Females also had a cyclic pattern of white blood cell counts and body weight; their weight peaked in early February and was lowest in August (P < 0.001). Body temperature, urea nitrogen, mean corpuscular volume (MCV), serum glucose, and cortisol did not follow a consistent seasonal pattern.

Diffusion in coronas around clinopyroxene: modelling with local equilibrium and steady state, and a non-steady-state modification to account for zoned actinolite-hornblende

NASA Astrophysics Data System (ADS)

Ashworth, J. R.; Birdi, J. J.; Emmett, T. F.

1992-01-01

Retrograde coronas of Caledonian age, between clinopyroxene and plagioclase in the Jotun Nappe Complex, Norway, illustrate the effects of diffusion kinetics on mineral distributions among layers and on the compositions of hornblende-actinolite. One corona type comprises a symplectite of epidote + quartz adjacent to plagioclase, and a less well-organized intergrowth of amphibole + quartz replacing clinopyroxene. The observed mineral proportions imply an open-system reaction, but the similarity of Al/Si ratios in reactant plagioclase and product symplectite indicates approximate conservation of Al2O3 and SiO2. The largest inferred open-system flux is a loss of CaO, mostly derived from consumption of clinopyroxene. The approximate layer structure, Pl|Ep + Qtz|Hbl + Qtz|Act±Hbl + Qtz|Cpx, is modelled using the theory of steady-state diffusion-controlled growth with local equilibrium. To obtain a solution, it is necessary to use a reactant plagioclase composition which takes into account aluminous (epidote) inclusions. The results indicate that, in terms of Onsager diffusion coefficients L ii , Ca is more mobile than AL ( L CaCa/ L AlAl≳3.) (where ≳ means greater than or approximately equal to). This behaviour of Ca is comparable with that of Mg in previously studied coronas around olivine. Si is non-diffusing in the present modelling, because of silica saturation. Oxidation of some Fe2+ to Fe3+ occurs within the corona. Mg diffuses towards its source (clinopyroxene) to maintain local equilibrium. Other coronas consist of two layers, hornblende adjacent to plagioclase and zoned amphibole + quartz adjacent to clinopyroxene. In the zoned layer, actinolitic hornblende forms relict patches, separated from quartz blebs by more aluminous hornblende. A preliminary steady-state, local-equilibrium model of grain-boundary diffusion explains the formation of low-Al and high-Al layers as due to Al immobility. Zoning and replacement are qualitatively explained in terms of evolution of actinolite to more stable aluminous compositions. This is modelled by a non-steady-state modification of the theory, retaining local equilibrium in grain boundaries while relatively steep zoning profiles develop in grain interiors through slow intracrystalline diffusion. Replacement of actinolite by hornblende does not require a change in P- T conditions if actinolite is a kinetically determined, non-equilibrium product. The common preservation of a sharp contact between hornblende and actionolite layers may be explained by ineffectiveness of intracrystalline diffusion: according to the theory, given sufficient grain-boundary Al flux, a metastable actinolite + quartz layer in contact with hornblende may be diffusionally stable and may continue to grow in a steady state.

A Basin-Wide Examination of the Arctic Ocean's Double-Diffusive Staircase

NASA Astrophysics Data System (ADS)

Shibley, N.; Timmermans, M. L.; Carpenter, J. R.; Toole, J. M.

2016-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure above the Atlantic Water Layer consisting of multiple mixed layers of order 1-m in height separated by sharp interfaces. This double-diffusive staircase structure is characterized across the entire Arctic Ocean through a detailed analysis of Ice-Tethered Profiler measurements acquired between 2004 and 2013. Staircase properties (mixed layer thicknesses and temperature-salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio for 50-m spanning the staircase stratification. It is shown that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (on the Eurasian side) and higher density ratio (on the Canadian side). We find that the diffusive staircase in the Eurasian Basin is characterized by fewer, thinner mixed layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin staircase mixed layers. Using a double-diffusive 4/3 flux law parameterization, the distribution of vertical heat fluxes through the staircase is estimated across the Arctic; it is found that heat fluxes in the Eurasian Basin [O(1) W/m^2] are generally an order of magnitude larger than those in the Canadian Basin [O(0.1) W/m^2].

Direct measurement of concentration distribution within the boundary layer of an ion-exchange membrane.

PubMed

Choi, Jae-Hwan; Park, Jin-Soo; Moon, Seung-Hyeon

2002-07-15

In this study the concentration distributions within the diffusion boundary layer were obtained by directly measuring the potential drops while the currents (under- and overlimiting) passed through the Neosepta CMX cation-exchange membrane (Tokuyama Corp., Japan). Potential drops according to the distance from the membrane surface on the depleted side were measured using a microelectrode to obtain the concentration profile. From the concentration profiles obtained, it was observed that the diffusion boundary layers existed in the range of 300-350 microm, which reasonably coincide with the theoretical diffusion boundary layer thickness calculated from the limiting current density. Although there were some deviations between the concentrations determined from the Nernst model and those from experiments, it was confirmed that the Nernst model effectively depicts the transport phenomena in the ion-exchange membrane system. In addition it was found that the salt concentration at the membrane surface increased when the currents applied exceeded the limiting current. It is thought that the concentration polarization formed in the diffusion boundary layer at currents near or lower than the limiting current was disturbed by a turbulent convection when the current was greater than the limiting current. As a consequence, the concentration at the membrane surface increased to a sufficient level for generation of the overlimiting current.

Performance of a passive direct ethanol fuel cell

NASA Astrophysics Data System (ADS)

Pereira, J. P.; Falcão, D. S.; Oliveira, V. B.; Pinto, A. M. F. R.

2014-06-01

Ethanol emerges as an attractive fuel since it is less toxic and has higher energy density than methanol and can be produced from biomass. Direct ethanol fuel cells (DEFCs) appear as a good choice for producing sustainable energy for portable applications. However, they are still far from attaining acceptable levels of power output, since their performance is affected by the slow electrochemical ethanol oxidation and water and ethanol crossover. In the present work, an experimental study on the performance of a passive DEFC is described. Tailored MEAs (membrane electrode assembly) with different catalyst loadings, anode diffusion layers and membranes were tested in order to select optimal working conditions at high ethanol concentrations and low ethanol crossover. The performance increased with an increase of membrane and anode diffusion layer thicknesses and anode catalyst loading. A maximum power density of 1.33 mW cm-2, was obtained using a Nafion 117 membrane, 4 mg cm-2 of Pt-Ru and 2 mg cm-2 of Pt on the anode and cathode catalyst layers, ELAT as anode diffusion layer, carbon cloth as cathode diffusion layer and an ethanol concentration of 2 M. As far as the authors are aware this is the first work reporting an experimental optimization of passive DEFCs.

On the use of (3-trimethoxysilylpropyl)diethylenetriamine self-assembled monolayers as seed layers for the growth of Mn based copper diffusion barrier layers

NASA Astrophysics Data System (ADS)

Brady-Boyd, A.; O'Connor, R.; Armini, S.; Selvaraju, V.; Hughes, G.; Bogan, J.

2018-01-01

In this work x-ray photoelectron spectroscopy is used to investigate in-vacuo, the interaction of metallic manganese with a (3-trimethoxysilylpropyl)diethylenetriamine (DETA) self-assembled monolayer (SAM) on SiO2 and non-porous low-k dielectric materials. Subsequent deposition of a ∼0.5 nm thick Mn, followed by a 200 °C anneal results in the Mn diffusing through the SAM to interact with the underlying SiO2 layer to form a Mn-silicate layer. Furthermore, there is evidence that the Mn interacts with the carbon and nitrogen within the SAM to form Mn-carbide and Mn-nitride, respectively. When deposited on low-k materials the Mn is found to diffuse through to the SAM on deposition and interact both with the SAM and the underlying substrate in a similar fashion.

In-situ observation of impurity diffusion boundary layer in silicon Czochralski growth

NASA Astrophysics Data System (ADS)

Kakimoto, Koichi; Eguchi, Minoru; Watanabe, Hisao; Hibiya, Taketoshi

1990-01-01

In-situ observation of the impurity diffusion boundary layer during single crystal growth of indium-doped silicon was carried out by X-ray radiography. The difference in the transmitted X-ray image compared with molten silicon just beneath the crystal-melt interface was attributed to the concentration of indium impurities having a larger absorption coefficient. The intensity profile of the transmitted X-ray can be reproduced by a transmittance calculation that considers the meniscus shape and impurity distribution. The impurity distribution profile near the crystal-melt interface was estimated using the Burton-Prim-Slichter (BPS) equation. The observed impurity diffusion boundary layer thickness was about 0.5 mm. It was found that the boundary layer thickness was not constant in the radial direction, which cannot be explained by the BPS theory, since it is based on a one-dimensional calculation.

Fuel cell with interdigitated porous flow-field

DOEpatents

Wilson, Mahlon S.

1997-01-01

A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers.

Fuel cell with interdigitated porous flow-field

DOEpatents

Wilson, M.S.

1997-06-24

A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers. 9 figs.

Comparison and analysis of theoretical models for diffusion-controlled dissolution.

PubMed

Wang, Yanxing; Abrahamsson, Bertil; Lindfors, Lennart; Brasseur, James G

2012-05-07

Dissolution models require, at their core, an accurate diffusion model. The accuracy of the model for diffusion-dominated dissolution is particularly important with the trend toward micro- and nanoscale drug particles. Often such models are based on the concept of a "diffusion layer." Here a framework is developed for diffusion-dominated dissolution models, and we discuss the inadequacy of classical models that are based on an unphysical constant diffusion layer thickness assumption, or do not correctly modify dissolution rate due to "confinement effects": (1) the increase in bulk concentration from confinement of the dissolution process, (2) the modification of the flux model (the Sherwood number) by confinement. We derive the exact mathematical solution for a spherical particle in a confined fluid with impermeable boundaries. Using this solution, we analyze the accuracy of a time-dependent "infinite domain model" (IDM) and "quasi steady-state model" (QSM), both formally derived for infinite domains but which can be applied in approximate fashion to confined dissolution with proper adjustment of a concentration parameter. We show that dissolution rate is sensitive to the degree of confinement or, equivalently, to the total concentration C(tot). The most practical model, the QSM, is shown to be very accurate for most applications and, consequently, can be used with confidence in design-level dissolution models so long as confinement is accurately treated. The QSM predicts the ratio of diffusion layer thickness to particle radius (the Sherwood number) as a constant plus a correction that depends on the degree of confinement. The QSM also predicts that the time required for complete saturation or dissolution in diffusion-controlled dissolution experiments is singular (i.e., infinite) when total concentration equals the solubility. Using the QSM, we show that measured differences in dissolution rate in a diffusion-controlled dissolution experiment are a result of differences in the degree of confinement on the increase in bulk concentration independent of container geometry and polydisperse vs single particle dissolution. We conclude that the constant diffusion-layer thickness assumption is incorrect in principle and should be replaced by the QSM with accurate treatment of confinement in models of diffusion-controlled dissolution.

[Plasma exchange and continuous hemodiafiltration as an initial treatment for diffuse large B-cell lymphoma-associated hemophagocytic syndrome].

PubMed

Yanagiya, Norimitsu; Takahashi, Naoto; Nakae, Hajime; Kume, Masaaki; Chubachi, Akihiko; Miura, Ikuo

2002-01-01

A 68-year-old man was admitted to our hospital because of fever, jaundice and hepatosplenomegaly. A diagnosis of diffuse large cell, B-cell type malignant lymphoma, associated with hemophagocytic syndrome (LAHS), was made. CT scan revealed lymphadenopathy in the abdominal cavity and multiple tumors in the spleen. Performance status and hepatic coma grade were 4 and II, respectively. Laboratory findings showed bicytopenia (Hb 9.9 g/dl, platelet 35 x 10(3)/microliter), severe liver dysfunction (ALP 1,115 U/l, gamma-GTP 437 U/l, T.Bil 15.4 mg/dl, D.Bil 12.8 mg/dl) and elevated levels of beta 2 microglobulin (12.9 mg/dl), ferritin (2,300 ng/ml) and sIL-2 receptor (36,900 U/ml). Plasma exchange (PE) and continuous hemodiafiltration (CHDF) enabled the patient to undergo diagnostic procedures, irradiation (total 34 Gy) and chemotherapy. Biopsy specimens revealed infiltration of lymphoma cells into the liver and bone marrow. We measured the blood concentrations of TNF-alpha, IL-6, and IL-8 before and after PE and CHDF by the ELISA method, and found normalization of hypercytokinemia after the procedure. It was suggested that initial treatment with PE and CHDF was effective for control of HPS, enabling us to perform chemotherapy for the lymphoma.

Sintered wire cesium dispenser photocathode

DOEpatents

Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

2014-03-04

A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

Quantitative, depth-resolved determination of particle motion using multi-exposure, spatial frequency domain laser speckle imaging.

PubMed

Rice, Tyler B; Kwan, Elliott; Hayakawa, Carole K; Durkin, Anthony J; Choi, Bernard; Tromberg, Bruce J

2013-01-01

Laser Speckle Imaging (LSI) is a simple, noninvasive technique for rapid imaging of particle motion in scattering media such as biological tissue. LSI is generally used to derive a qualitative index of relative blood flow due to unknown impact from several variables that affect speckle contrast. These variables may include optical absorption and scattering coefficients, multi-layer dynamics including static, non-ergodic regions, and systematic effects such as laser coherence length. In order to account for these effects and move toward quantitative, depth-resolved LSI, we have developed a method that combines Monte Carlo modeling, multi-exposure speckle imaging (MESI), spatial frequency domain imaging (SFDI), and careful instrument calibration. Monte Carlo models were used to generate total and layer-specific fractional momentum transfer distributions. This information was used to predict speckle contrast as a function of exposure time, spatial frequency, layer thickness, and layer dynamics. To verify with experimental data, controlled phantom experiments with characteristic tissue optical properties were performed using a structured light speckle imaging system. Three main geometries were explored: 1) diffusive dynamic layer beneath a static layer, 2) static layer beneath a diffuse dynamic layer, and 3) directed flow (tube) submerged in a dynamic scattering layer. Data fits were performed using the Monte Carlo model, which accurately reconstructed the type of particle flow (diffusive or directed) in each layer, the layer thickness, and absolute flow speeds to within 15% or better.

Molecular Dynamics Simulation of the Structure and Ion Transport in the Ce1 - x Gd x O2 - δ|YSZ Heterosystem

NASA Astrophysics Data System (ADS)

Galin, M. Z.; Ivanov-Schitz, A. K.; Mazo, G. N.

2018-01-01

Molecular dynamics simulation has been used to develop a realistic atomistic model of two-layer Ce1 - x Gd x O2 - δ|YSZ heterosystem. It is shown that Ce1 - x Gd x O2 - δ and YSZ layers (about 15 and 16 Å thick, respectively) retain their crystal structure on the whole. The main structural distortions are found to occur near the Ce1 - x Gd x O2 - δ|YSZ geometric interface, within a narrow interfacial region of few angstroms thick. Both the generalized diffusion characteristics of the system as a whole and the oxygen diffusion coefficients in the layers are calculated, and the diffusion activation energies are determined.

Glass diffusion source for constraining BSF region of a solar cell

DOEpatents

Lesk, I.A.; Pryor, R.A.; Coleman, M.G.

1982-08-27

The present invention is directed to a method of fabricating a solar cell comprising simultaneous diffusion of the p and n dopant materials into the solar cell substrate. The simultaneous diffusion process is preceded by deposition of a capping layer impervious to doping by thermal diffusion processes.

Morphology, topography, and hardness of diffusion bonded sialon to AISI 420 at different bonding time

NASA Astrophysics Data System (ADS)

Ibrahim, Nor Nurulhuda Md.; Hussain, Patthi; Awang, Mokhtar

2015-07-01

Sialon and AISI 420 martensitic stainless steel were diffusion bonded in order to study the effect of bonding time on reaction layer's growth. Joining of these materials was conducted at 1200°C under a uniaxial pressure of 17 MPa in a vacuum ranging from 5.0 to 8.0×10-6 Torr with bonding time varied for 0.5, 2, and 3 h. Thicker reaction layer was formed in longer bonded sample since the elements from sialon could diffuse further into the steel. Sialon retained its microstructure but it was affected at the initial contact with the steel to form the new interface layer. Diffusion layer grew toward the steel and it was segregated with the parent steel as a result of the difference in properties between these regions. The segregation formed a stream-like structure and its depth decreased when the bonding time was increased. The microstructure of the steel transformed into large grain size with precipitates. Prolonging the bonding time produced more precipitates in the steel and reduced the steel thickness as well. Interdiffusions of elements occurred between the joined materials and the concentrations were decreasing toward the steel and vice versa. Silicon easily diffused into the steel because it possessed lower ionization potential compared to nitrogen. Formation of silicide and other compounds such as carbides were detected in the interface layer and steel grain boundary, respectively. These compounds were harmful due to silicide brittleness and precipitation of carbides in the grain boundary might cause intergranular corrosion cracking. Sialon retained its hardness but it dropped very low at the interface layer. The absence of crack at the joint in all samples could be contributed from the ductility characteristic of the reaction layer which compensated the residual stress that was formed upon the cooling process.

[Anemia in public school first graders in the city of Maceió, Alagoas, Brazil].

PubMed

Santos, Célia Dias dos; Santos, Leonor Maria Pacheco; Figueiroa, José Natal; Marroquim, Pajuçara Maria Guimarães; Oliveira, Maria Alice Araújo

2002-01-01

A cross-sectional study was conducted in a representative sample of 426 randomly selected first graders (ages 6 to 10 years) from public schools in Maceió, State of Alagoas, Brazil. The aim was to determine the prevalence of anemia, as well as its association with growth retardation. Data were collected from May to July 2000, and determination of hemoglobin (HGB) employed an STKS Coulter counter. Two cut-off points were used to classify anemia, both established by the World Health Organization: HGB < 11.5g/dl and HGB < 12.0g/dl. The indicators height/age (H/A), weight/age (W/A), and weight/height (W/H) below -2.0 standard deviations from the NCHS reference were diagnosed as growth retardation. Prevalence of anemia was 9.9% when HGB < 11.5g/dl was used, and 25.4% when the cut-off point was HGB < 12.0g/dl. Growth retardation was detected in 6.2% of children according to H/A, 4.0% for W/A, and 3.0% for W/H. There was no statistically significant association between the variables in the study. These findings confirm results of previous surveys where prevalence of anemia was much higher than that of growth retardation. The severe consequences of anemia in this age group justify the implementation of broad public policies to overcome this nutritional deficiency.

Cycad Palm Toxicosis in 14 Dogs from Texas.

PubMed

Clarke, Carolyn; Burney, Derek

The goal of this study is to report clinical information, diagnostic findings, and treatment modalities; assess variables that may help distinguish survivors from nonsurvivors; and review the outcome of cycad palm toxicosis in dogs. Fourteen client-owned dogs with confirmed cycad palm ingestion were identified by reviewing the medical record database at Gulf Coast Veterinary Specialists. Information on signalment, time of ingestion to presentation, clinical signs, physical examination findings, initial and peak/nadir laboratory abnormalities, radiographic and ultrasonographic findings, treatment modalities, liver histopathology, and clinical outcome was retrieved. Of the 14 dogs, nine (64%) died as a direct result of cycad palm intoxication, and three survivors had persistently elevated liver enzymes, signifying residual liver damage. Despite decontamination, patients continued to display evidence of illness, indicating rapid absorption of toxins. When evaluating initial and peak/nadir laboratory values, nadir serum albumin levels and nadir platelet counts were significantly lower in nonsurvivors compared to survivors (1.25 g/dL [0.4-2.1 g/dL] versus 2.6 g/dL [1.7-3.4 g/dL] and 21 × 10 3 [0-64 × 10 3 ] versus 62 × 10 3 [6-144 × 10 3 ], respectively). In this cohort of dogs, the case fatality rate was higher than previously reported. Nadir serum albumin levels and nadir platelet counts may help distinguish potential survivors from nonsurvivors.

Barometric response functions from borehole water level records and quantification of aquifer vulnerability

NASA Astrophysics Data System (ADS)

Odling, N. E.; Serrano, R. P.; Hussein, M.; Guadagnini, A.; Riva, M.

2013-12-01

In confined and semi-confined aquifers, borehole water levels respond to fluctuations in barometric pressure and this response can be used to estimate the properties of aquifer confining layers. We use this response as indicator of groundwater vulnerability for the semi-confined Chalk aquifer in East Yorkshire, UK. Time series data of borehole water levels are corrected for Earth tides and recharge, and barometric response functions (BRFs) estimated using cross-spectral deconvolution-averaging techniques. The resulting BRFs are fitted using a theoretical model of the BRF gain and phase for a semi-confined aquifer (Rojstaczer, 1988) to obtain confining layer properties. For all of the boreholes, non-zero hydraulic diffusivities for the confining layer were found indicating that the aquifer is semi-confined. A ';characteristic time scale' based on the hydraulic and pneumatic diffusivities of the confining layer is introduced as a measure of the degree of aquifer confinement and therefore groundwater vulnerability. The analytical model assumes that the confining layer and aquifer are homogeneous. However, in nature, confining layers are heterogeneous and groundwater vulnerability dominated by the presence of high diffusivity, high flow pathways through the confining layer to the aquifer. A transient numerical model (MODFLOW) was constructed to test the impact of such heterogeneities on the BRF. In the model, an observed barometric pressure time series is used as a boundary condition applied to the upper surface of the top unit of the model (representing the confining layer) and BRFs determined from the time series of model heads in the bottom unit (representing the aquifer). The results from a numerical model with a homogeneous confining layer were found to accurately reproduce the BRFs from a modified version of the analytical model. The introduction of a localized, high diffusive block in the confining layer was found to modify the BRF, reducing the gain amplitude while having limited impact on the phase. It was found that the BRF reflects the presence of a fully penetrating, high diffusivity heterogeneity up to several hundred meters distant from the observation borehole, and shows little sensitivity to the heterogeneity's horizontal dimension. Heterogeneities that are 50% partially penetrating do not significantly impact on the BRF and 90% penetrating heterogeneities can only be detected when large and close to the observation borehole. These results show that BRF gain may be particularly useful in detecting the presence of fully penetrating heterogeneities of high diffusivity within confining layers that potentially enhance groundwater vulnerability. This research has been funded in part through the EU ITN ';IMVUL' (PITN-GA-2008-212298). Reference: Rojstaczer, S. (1988) Determination of fluid-flow properties from the response of water levels in wells to atmospheric loading, Water Resources Research, 24(11), 1927-1938.

In vivo soft tissue differentiation by diffuse reflectance spectroscopy: preliminary results

NASA Astrophysics Data System (ADS)

Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael; Douplik, Alexandre

Remote laser surgery does not provide haptic feedback to operate layer by layer and preserve vulnerable anatomical structures like nerve tissue or blood vessels. The aim of this study is identification of soft tissue in vivo by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Various soft tissues can be identified by diffuse reflectance spectroscopy in vivo. The results may set the base for a feedback system to prevent nerve damage during oral and maxillofacial laser surgery.

Method for improving the performance of oxidizable ceramic materials in oxidizing environments

NASA Technical Reports Server (NTRS)

Nagaraj, Bangalore A. (Inventor)

2002-01-01

Improved adhesion of thermal barrier coatings to nonmetallic substrates using a dense layer of ceramic on an underlying nonmetallic substrate that includes at least one oxidizable component. The improved adhesion occurs because the application of the dense ceramic layer forms a diffusion barrier for oxygen. This diffusion barrier prevents the oxidizable component of the substrate from decomposing. The present invention applies ceramic by a process that deposits a relatively thick and dense ceramic layer on the underlying substrate. The formation of the dense layer of ceramic avoids the problem of void formation associated with ceramic formation by most prior art thermal decomposition processes. The formation of voids has been associated with premature spalling of thermal barrier layers and other protective layers applied to substrates.

Laboratory layered latte.

PubMed

Xue, Nan; Khodaparast, Sepideh; Zhu, Lailai; Nunes, Janine K; Kim, Hyoungsoo; Stone, Howard A

2017-12-12

Inducing thermal gradients in fluid systems with initial, well-defined density gradients results in the formation of distinct layered patterns, such as those observed in the ocean due to double-diffusive convection. In contrast, layered composite fluids are sometimes observed in confined systems of rather chaotic initial states, for example, lattes formed by pouring espresso into a glass of warm milk. Here, we report controlled experiments injecting a fluid into a miscible phase and show that, above a critical injection velocity, layering emerges over a time scale of minutes. We identify critical conditions to produce the layering, and relate the results quantitatively to double-diffusive convection. Based on this understanding, we show how to employ this single-step process to produce layered structures in soft materials, where the local elastic properties vary step-wise along the length of the material.

Characterization and diffusion model for the titanium boride layers formed on the Ti6Al4V alloy by plasma paste boriding

NASA Astrophysics Data System (ADS)

Keddam, Mourad; Taktak, Sukru

2017-03-01

The present study is focused on the estimation of activation energy of boron in the plasma paste borided Ti6Al4V alloy, which is extensively used in technological applications, using an analytical diffusion model. Titanium boride layers were successfully produced by plasma paste boriding method on the Ti6Al4V alloy in the temperature range of 973-1073 K for a treatment time ranging from 3 to 7 h. The presence of both TiB2 top-layer and TiB whiskers sub-layer was confirmed by the XRD analysis and SEM observations. The surface hardness of the borided alloy was evaluated using Micro-Knoop indenter. The formation rates of the TiB2 and TiB layers were found to have a parabolic character at all applied process temperatures. A diffusion model was suggested to estimate the boron diffusivities in TiB2 and TiB layers under certain assumptions, by considering the effect of boride incubation times. Basing on own experimental data on boriding kinetics, the activation energies of boron in TiB2 and TiB phases were estimated as 136.24 ± 0.5 and 63.76 ± 0.5 kJ mol-1, respectively. Finally, the obtained values of boron activation energies for Ti6Al4V alloy were compared with the data available in the literature.

Spatial variability of the Arctic Ocean's double-diffusive staircase

NASA Astrophysics Data System (ADS)

Shibley, N. C.; Timmermans, M.-L.; Carpenter, J. R.; Toole, J. M.

2017-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure overlying the Atlantic Water Layer that can be attributed to the diffusive form of double-diffusive convection. The staircase consists of multiple layers of O(1) m in thickness separated by sharp interfaces, across which temperature and salinity change abruptly. Through a detailed analysis of Ice-Tethered Profiler measurements from 2004 to 2013, the double-diffusive staircase structure is characterized across the entire Arctic Ocean. We demonstrate how the large-scale Arctic Ocean circulation influences the small-scale staircase properties. These staircase properties (layer thicknesses and temperature and salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio spanning the staircase stratification. We show that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (approximately 3-4) on the Eurasian side and higher density ratio (approximately 6-7) on the Canadian side. We find that the Eurasian Basin staircase is characterized by fewer, thinner layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin layers and the absence of a well-defined staircase. A double-diffusive 4/3 flux law parametrization is used to estimate vertical heat fluxes in the Canadian Basin to be O(0.1) W m-2. It is shown that the 4/3 flux law may not be an appropriate representation of heat fluxes through the Eurasian Basin staircase. Here molecular heat fluxes are estimated to be between O(0.01) and O(0.1) W m-2. However, many uncertainties remain about the exact nature of these fluxes.

Visual tracing of diffusion and biodistribution for amphiphilic cationic nanoparticles using photoacoustic imaging after ex vivo intravitreal injections

PubMed Central

Xu, Xu; Xu, Zhaokang; Liu, Junyi; Zhang, Zhaoliang; Chen, Hao; Li, Xingyi; Shi, Shuai

2016-01-01

To visually trace the diffusion and biodistribution of amphiphilic cation micelles after vitreous injection, various triblock copolymers of monomethoxy poly(ethylene glycol)–poly(ε-caprolactone)–polyethylenimine were synthesized with different structures of hydrophilic and hydrophobic segments, followed by labeling with near-infrared fluorescent dye Cyanine5 or Cyanine7. The micellar size, polydispersity index, and surface charge were measured by dynamic light scattering. The diffusion was monitored using photoacoustic imaging in real time after intravitreal injections. Moreover, the labeled nanoparticle distribution in the posterior segment of the eye was imaged histologically by confocal microscopy. The results showed that the hydrophilic segment increased vitreous diffusion, while a positive charge on the particle surface hindered diffusion. In addition, the particles diffused through the retinal layers and were enriched in the retinal pigment epithelial layer. This work tried to study the diffusion rate via a simple method by using visible images, and then provided basic data for the development of intraocular drug carriers. PMID:27785015

A comparison of Fick and Maxwell-Stefan diffusion formulations in PEMFC gas diffusion layers

NASA Astrophysics Data System (ADS)

Lindstrom, Michael; Wetton, Brian

2017-01-01

This paper explores the mathematical formulations of Fick and Maxwell-Stefan diffusion in the context of polymer electrolyte membrane fuel cell cathode gas diffusion layers. The simple Fick law with a diagonal diffusion matrix is an approximation of Maxwell-Stefan. Formulations of diffusion combined with mass-averaged Darcy flow are considered for three component gases. For this application, the formulations can be compared computationally in a simple, one dimensional setting. Despite the models' seemingly different structure, it is observed that the predictions of the formulations are very similar on the cathode when air is used as oxidant. The two formulations give quite different results when the Nitrogen in the air oxidant is replaced by helium (this is often done as a diagnostic for fuel cells designs). The two formulations also give quite different results for the anode with a dilute Hydrogen stream. These results give direction to when Maxwell-Stefan diffusion, which is more complicated to implement computationally in many codes, should be used in fuel cell simulations.

Visual tracing of diffusion and biodistribution for amphiphilic cationic nanoparticles using photoacoustic imaging after ex vivo intravitreal injections.

PubMed

Xu, Xu; Xu, Zhaokang; Liu, Junyi; Zhang, Zhaoliang; Chen, Hao; Li, Xingyi; Shi, Shuai

To visually trace the diffusion and biodistribution of amphiphilic cation micelles after vitreous injection, various triblock copolymers of monomethoxy poly(ethylene glycol)-poly(ε-caprolactone)-polyethylenimine were synthesized with different structures of hydrophilic and hydrophobic segments, followed by labeling with near-infrared fluorescent dye Cyanine5 or Cyanine7. The micellar size, polydispersity index, and surface charge were measured by dynamic light scattering. The diffusion was monitored using photoacoustic imaging in real time after intravitreal injections. Moreover, the labeled nanoparticle distribution in the posterior segment of the eye was imaged histologically by confocal microscopy. The results showed that the hydrophilic segment increased vitreous diffusion, while a positive charge on the particle surface hindered diffusion. In addition, the particles diffused through the retinal layers and were enriched in the retinal pigment epithelial layer. This work tried to study the diffusion rate via a simple method by using visible images, and then provided basic data for the development of intraocular drug carriers.

Layered materials with improved magnesium intercalation for rechargeable magnesium ion cells

DOEpatents

Doe, Robert Ellis; Downie, Craig Michael; Fischer, Christopher; Lane, George Hamilton; Morgan, Dane; Nevin, Josh; Ceder, Gerbrand; Persson, Kristin Aslaug; Eaglesham, David

2015-10-27

Electrochemical devices which incorporate cathode materials that include layered crystalline compounds for which a structural modification has been achieved which increases the diffusion rate of multi-valent ions into and out of the cathode materials. Examples in which the layer spacing of the layered electrode materials is modified to have a specific spacing range such that the spacing is optimal for diffusion of magnesium ions are presented. An electrochemical cell comprised of a positive intercalation electrode, a negative metal electrode, and a separator impregnated with a nonaqeuous electrolyte solution containing multi-valent ions and arranged between the positive electrode and the negative electrode active material is described.

Space-time modeling of the photon diffusion in a three-layered model: application to the study of muscular oxygenation

NASA Astrophysics Data System (ADS)

Mansouri, C.; L'Huillier, J. P.; Piron, V.

2007-07-01

This work presents results on the modeling of the photon diffusion in a three-layered model, (skin, fat and muscle). The Finite Element method was performed in order to calculate the temporal response of the above-mentioned structure. The thickness of the fat layer was varied from 1 to 15 mm to investigate the effects of increasing fat thickness on the muscle layer absorption coefficient measurements for a source-detector spacing of 30 mm. The simulated time-resolved reflectance data, at different wavelengths, were fitted to the diffusion model to yield the scattering and absorption coefficients of muscle. The errors in estimating muscle absorption coefficients μ α depend on the thickness of the fat layer and its optical properties. In addition, it was shown that it is possible to recover with a good precision (~2.6 % of error) the absorption coefficient of muscle and this up to a thickness of the fat layer not exceeding 4mm. Beyond this limit a correction is proposed in order to make measurements coherent. The muscle-corrected absorption coefficient can be then used to calculate hemoglobin oxygenation.

TEM/STEM study of Zircaloy-2 with protective FeAl(Cr) layers under simulated BWR environment and high-temperature steam exposure

NASA Astrophysics Data System (ADS)

Park, Donghee; Mouche, Peter A.; Zhong, Weicheng; Mandapaka, Kiran K.; Was, Gary S.; Heuser, Brent J.

2018-04-01

FeAl(Cr) thin-film depositions on Zircaloy-2 were studied using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) with respect to oxidation behavior under simulated boiling water reactor (BWR) conditions and high-temperature steam. Columnar grains of FeAl with Cr in solid solution were formed on Zircaloy-2 coupons using magnetron sputtering. NiFe2O4 precipitates on the surface of the FeAl(Cr) coatings were observed after the sample was exposed to the simulated BWR environment. High-temperature steam exposure resulted in grain growth and consumption of the FeAl(Cr) layer, but no delamination at the interface. Outward Al diffusion from the FeAl(Cr) layer occurred during high-temperature steam exposure (700 °C for 3.6 h) to form a 100-nm-thick alumina oxide layer, which was effective in mitigating oxidation of the Zircaloy-2 coupons. Zr intermetallic precipitates formed near the FeAl(Cr) layer due to the inward diffusion of Fe and Al. The counterflow of vacancies in response to the Al and Fe diffusion led to porosity within the FeAl(Cr) layer.

Hydrodynamics of Bacterial Cooperation

NASA Astrophysics Data System (ADS)

Petroff, A.; Libchaber, A.

2012-12-01

Over the course of the last several decades, the study of microbial communities has identified countless examples of cooperation between microorganisms. Generally—as in the case of quorum sensing—cooperation is coordinated by a chemical signal that diffuses through the community. Less well understood is a second class of cooperation that is mediated through physical interactions between individuals. To better understand how the bacteria use hydrodynamics to manipulate their environment and coordinate their actions, we study the sulfur-oxidizing bacterium Thiovulum majus. These bacteria live in the diffusive boundary layer just above the muddy bottoms of ponds. As buried organic material decays, sulfide diffuses out of the mud. Oxygen from the pond diffuses into the boundary layer from above. These bacteria form communities—called veils— which are able to transport nutrients through the boundary layer faster than diffusion, thereby increasing their metabolic rate. In these communities, bacteria attach to surfaces and swim in place. As millions of bacteria beat their flagella, the community induces a macroscopic fluid flow, which mix the boundary layer. Here we present experimental observations and mathematical models that elucidate the hydrodynamics linking the behavior of an individual bacterium to the collective dynamics of the community. We begin by characterizing the flow of water around an individual bacterium swimming in place. We then discuss the flow of water and nutrients around a small number of individuals. Finally, we present observations and models detailing the macroscopic dynamics of a Thiovulum veil.

Deposition on disordered substrates with precursor layer diffusion

NASA Astrophysics Data System (ADS)

Filipe, J. A. N.; Rodgers, G. J.; Tavassoli, Z.

1998-09-01

Recently we introduced a one-dimensional accelerated random sequential adsorption process as a model for chemisorption with precursor layer diffusion. In this paper we consider this deposition process on disordered or impure substrates. The problem is solved exactly on both the lattice and continuum and for various impurity distributions. The results are compared with those from the standard random sequential adsorption model.

Diffusion of cations in chromia layers grown on iron-base alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobnig, R.E.; Hennesen, K.; Grabke, H.J.

Diffusion of the cations Cr, Fe, Mn, and Ni in Cr{sub 2}O{sub 3} has been investigated at 1,173 K. The diffusion measurements were performed on chromia layers grown on the model alloys Fe-20Cr and Fe-20Cr-12Ni in order to consider effects of small amounts of dissolved alien cations in Cr{sub 2}O{sub 3}. The samples were diffusion annealed in H{sub 2}-H{sub 2}O at an oxygen partial pressure close to the Cr{sub 2}O{sub 3}/Cr equilibrium. For all tracers the lattice-diffusion coefficients are 3-5 orders of magnitude smaller than the grain-boundary diffusion coefficients. The lattice diffusivity of Mn is about two orders of magnitudemore » greater than the other lattice-diffusion coefficients, especially in Cr{sub 2}O{sub 3} grown on Fe-20Cr-12Ni. The values of the diffusion coefficients for Cr, Fe, and Ni are in the same range. Diffusion of the tracers in Cr{sub 2}O{sub 3} grown on different alloys did not show significant differences with the exception of Mn.« less

Information transfer in community structured multiplex networks

NASA Astrophysics Data System (ADS)

Solé Ribalta, Albert; Granell, Clara; Gómez, Sergio; Arenas, Alex

2015-08-01

The study of complex networks that account for different types of interactions has become a subject of interest in the last few years, specially because its representational power in the description of users interactions in diverse online social platforms (Facebook, Twitter, Instagram, etc.). The mathematical description of these interacting networks has been coined under the name of multilayer networks, where each layer accounts for a type of interaction. It has been shown that diffusive processes on top of these networks present a phenomenology that cannot be explained by the naive superposition of single layer diffusive phenomena but require the whole structure of interconnected layers. Nevertheless, the description of diffusive phenomena on multilayer networks has obviated the fact that social networks have strong mesoscopic structure represented by different communities of individuals driven by common interests, or any other social aspect. In this work, we study the transfer of information in multilayer networks with community structure. The final goal is to understand and quantify, if the existence of well-defined community structure at the level of individual layers, together with the multilayer structure of the whole network, enhances or deteriorates the diffusion of packets of information.

Uneven-Layered Coding Metamaterial Tile for Ultra-wideband RCS Reduction and Diffuse Scattering.

PubMed

Su, Jianxun; He, Huan; Li, Zengrui; Yang, Yaoqing Lamar; Yin, Hongcheng; Wang, Junhong

2018-05-25

In this paper, a novel uneven-layered coding metamaterial tile is proposed for ultra-wideband radar cross section (RCS) reduction and diffuse scattering. The metamaterial tile is composed of two kinds of square ring unit cells with different layer thickness. The reflection phase difference of 180° (±37°) between two unit cells covers an ultra-wide frequency range. Due to the phase cancellation between two unit cells, the metamaterial tile has the scattering pattern of four strong lobes deviating from normal direction. The metamaterial tile and its 90-degree rotation can be encoded as the '0' and '1' elements to cover an object, and diffuse scattering pattern can be realized by optimizing phase distribution, leading to reductions of the monostatic and bi-static RCSs simultaneously. The metamaterial tile can achieve -10 dB RCS reduction from 6.2 GHz to 25.7 GHz with the ratio bandwidth of 4.15:1 at normal incidence. The measured and simulated results are in good agreement and validate the proposed uneven-layered coding metamaterial tile can greatly expanding the bandwidth for RCS reduction and diffuse scattering.

High Oxygen Partial Pressure Decreases Anemia-Induced Heart Rate Increase Equivalent to Transfusion

PubMed Central

Feiner, John R.; Finlay-Morreale, Heather E.; Toy, Pearl; Lieberman, Jeremy A.; Viele, Maurene K.; Hopf, Harriet W.; Weiskopf, Richard B.

2011-01-01

Background Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. We sought to compare directly the effect of high inspired oxygen fraction vs. transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia. Methods We combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by our group. We examined HR changes associated with breathing 100% oxygen by non-rebreathing face mask vs. transfusion of erythrocytes at their nadir hemoglobin (Hb) concentration of 5 g/dL. Data were analyzed using a mixed-effects model. Results HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per minute per gram of Hb (beats/min/g Hb) decrease (95% confidence interval [CI], 3.7 – 4.1 beats/min/g Hb), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g Hb (95% CI, 3.8 – 6.8 beats/min/g Hb) increase, P < 0.0001. HR at nadir Hb of 5.6 g/dL (95% CI, 5.5 – 5.7 g/dL) when breathing air (91.4 beats/min; 95% CI, 87.6 – 95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0 -87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dL when breathing oxygen was equivalent to the HR at Hb 8.9 g/dL when breathing air. Conclusions High arterial oxygen partial pressure reverses the heart rate response to anemia, probably owing to its usability, rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials. PMID:21768873

A single dose of erythropoietin reduces perioperative transfusions in cardiac surgery: results of a prospective single-blind randomized controlled trial.

PubMed

Weltert, Luca; Rondinelli, Beatrice; Bello, Ricardo; Falco, Mauro; Bellisario, Alessandro; Maselli, Daniele; Turani, Franco; De Paulis, Ruggero; Pierelli, Luca

2015-07-01

We conducted a prospective single-blind randomized study to assess whether a single 80,000 IU dose of human recombinant erythropoietin (HRE), given just 2 days before cardiac surgery, could be effective in reducing perioperative allogeneic red blood cell transfusion (aRBCt). Six-hundred patients presenting with preoperative hemoglobin (Hb) level of not more than 14.5 g/dL were randomly assigned to either HRE or control. The primary endpoint was the incidence of perioperative aRBCt. The secondary endpoints were mortality and the incidence of adverse events in the first 45 days after surgery, Hb level on Postoperative Day 4, and number of units of RBC transfusions in the first 4 days after surgery. A total of 17% (HRE) versus 39% (control) required transfusion (relative risk, 0.436; p<0.0005). After baseline Hb was controlled for, there was no difference in the incidence of aRBCt between HRE (0%) and control (3.5%) among the patients with baseline Hb of 13.0 g/dL or more, which included the nonanemic fraction of the study population. The mean (range) Hb level on Postoperative Day 4 was 10.2 (9.9-10.6) g/dL (HRE) versus 8.7 (8.5-9.2) g/dL (control; p<0.0005). The distribution of number of units transfused was shifted toward fewer units in HRE (p<0.0005). The all-cause mortality at 45 days was 3.00% (HRE) versus 3.33% (control). The 45-day adverse event rate was 4.33% (HRE) versus 5.67% (control; both p=NS). In anemic patients (Hb<13 g/dL), a single high dose of HRE administered 2 days before cardiac surgery is effective in reducing the incidence of aRBCt without increasing adverse events. © 2015 AABB.

Ferric maltol is effective in correcting iron deficiency anemia in patients with inflammatory bowel disease: results from a phase-3 clinical trial program.

PubMed

Gasche, Christoph; Ahmad, Tariq; Tulassay, Zsolt; Baumgart, Daniel C; Bokemeyer, Bernd; Büning, Carsten; Howaldt, Stefanie; Stallmach, Andreas

2015-03-01

Iron deficiency anemia (IDA) is frequently seen in inflammatory bowel disease. Traditionally, oral iron supplementation is linked to extensive gastrointestinal side effects and possible disease exacerbation. This multicenter phase-3 study tested the efficacy and safety of ferric maltol, a complex of ferric (Fe) iron with maltol (3-hydroxy-2-methyl-4-pyrone), as a novel oral iron therapy for IDA. Adult patients with quiescent or mild-to-moderate ulcerative colitis or Crohn's disease, mild-to-moderate IDA (9.5-12.0 g/dL and 9.5-13.0 g/dL in females and males, respectively), and documented failure on previous oral ferrous products received oral ferric maltol capsules (30 mg twice a day) or identical placebo for 12 weeks according to a randomized, double-blind, placebo-controlled study design. The primary efficacy endpoint was change in hemoglobin (Hb) from baseline to week 12. Safety and tolerability were assessed. Of 329 patients screened, 128 received randomized therapy (64 ferric maltol-treated and 64 placebo-treated patients) and comprised the intent-to-treat efficacy analysis: 55 ferric maltol patients (86%) and 53 placebo patients (83%) completed the trial. Significant improvements in Hb were observed with ferric maltol versus placebo at weeks 4, 8, and 12: mean (SE) 1.04 (0.11) g/dL, 1.76 (0.15) g/dL, and 2.25 (0.19) g/dL, respectively (P < 0.0001 at all time-points; analysis of covariance). Hb was normalized in two-thirds of patients by week 12. The safety profile of ferric maltol was comparable with placebo, with no impact on inflammatory bowel disease severity. Ferric maltol provided rapid clinically meaningful improvements in Hb and showed a favorable safety profile, suggesting its possible use as an alternative to intravenous iron in IDA inflammatory bowel disease.

Association between Oral Nutritional Supplementation and Clinical Outcomes among Patients with ESRD

PubMed Central

Cheu, Christine; Pearson, Jeffrey; Dahlerus, Claudia; Lantz, Brett; Chowdhury, Tania; Sauer, Peter F.; Farrell, Robert E.; Port, Friedrich K.

2013-01-01

Summary Background and objectives Oral nutritional supplementation (ONS) was provided to ESRD patients with hypoalbuminemia as part of Fresenius Medical Care Health Plan’s (FMCHP) disease management. This study evaluated the association between FMCHP’s ONS program and clinical outcomes. Design, setting, participants, & measurements Analyses included FMCHP patients with ONS indication (n=470) defined as 2-month mean albumin <3.8 g/dl until reaching a 3-month mean ≥3.8 g/dl from February 1, 2006 to December 31, 2008. Patients did not receive ONS if deemed inappropriate or refused. Patients on ONS were compared with patients who were not, despite meeting ONS indication. Patients with ONS indication regardless of use were compared with Medicare patients with similar serum albumin levels from the 2007 Centers for Medicare and Medicaid Services Clinical Performance Measures Project (CPM). Cox models calculated adjusted hospitalization and mortality risks at 1 year. Results Among patients with indication for ONS, 276 received supplements and 194 did not. ONS use was associated with 0.058 g/dl higher serum albumin overall (P=0.02); this difference decreased by 0.001 g/dl each month (P=0.05) such that the difference was 0.052 g/dl (P=0.04) in month 6 and the difference was no longer significant in month 12 . In analyses based on ONS use, ONS patients had lower hospitalization at 1 year (68.4%; P<0.01) versus patients without ONS (88.7%), but there was no significant reduction in mortality risk (P=0.29). In analyses based on ONS indication, patients with indication had lower mortality at 1 year (16.2%) compared with CPM patients (23.4%; P<0.01). Conclusions These findings suggest that ONS use was associated with significantly lower hospitalization rates but had no significant effect on mortality in a disease management setting. PMID:23085729

The association of graduated driver licensing with miles driven and fatal crash rates per miles driven among adolescents

PubMed Central

Zhu, Motao; Cummings, Peter; Zhao, Songzhu; Coben, Jeffrey H.; Smith, Gordon S.

2014-01-01

Background Graduated driver licensing (GDL) laws are associated with reduced crash rates per person-year among adolescents. It is unknown whether adolescents crash less per miles driven or drive less under GDL policies. Methods We used data from the US National Household Travel Survey and Fatality Analysis Reporting System for 1995–1996, 2001–2002, and 2008–2009. We compared adolescents subject to GDL laws with those not, by estimating adjusted incidence rate ratios for being a driver in a crash with a death per person-year (aIRRpy) and per miles driven (aIRRm), and adjusted miles driven ratios (aMR) controlling for changes in rates over time. Results Comparing persons subject to GDL policies with those not, 16-year-olds had fewer fatal crashes per person-year (aIRRpy 0.63, 95% confidence interval [CI] 0.47, 0.91), drove fewer miles (aMR 0.79, 95% CI 0.63, 0.98), and had lower crash rates per miles driven (aIRRm 0.83, 95% CI 0.65, 1.06). For age 17, the aIRRpy was 0.83 (95% CI 0.60, 1.17), the aMR 0.80 (95% CI 0.63, 1.03), and the aIRRm 1.03 (95% CI 0.80, 1.35). For age 18, the aIRRpy was 0.93 (95% CI 0.72, 1.19), the aMR 0.92 (95% CI 0.77, 1.09), and the aIRRm 1.01 (95% CI 0.84, 1.23). Conclusions If these associations are causal, GDL laws reduced crashes per person-year by about one-third among 16-year-olds; half the reduction was due to fewer crashes per miles driven and half to less driving. For ages 17 and 18, there was no evidence of reduced crash rates per miles driven. PMID:24525908

Macronutrient composition of human milk from Korean mothers of full term infants born at 37-42 gestational weeks

PubMed Central

Jung, Ji A; Kim, Hyesook; Jo, Ara; Kang, Sujeong; Lee, Si-Won; Yi, Hyunju; Kim, Jihee; Yim, Jong-Gap; Jung, Byung-Moon

2015-01-01

BACKGROUND/OBJECTIVES Breast milk is the best available food for optimum growth and development of infants and the breastfeeding rate is increasing in Korea. The purpose of this study is to measure the concentrations of macronutrients and to evaluate their changes according to lactation period in breast milk from lactating Korean women. SUBJECTS/METHODS Milk samples were obtained from 2,632 healthy lactating women (mean age; 32.0 ± 3.3 years), where the lactating period was up to a period of 8 months, who also volunteered to participate in the Human Milk Macronutrient Analysis Research. Lactose, protein, fat and water content in the breast milk samples were analyzed with infrared spectrometry using MilkoScan FT-2. RESULTS The mean macronutrient composition per 100 mL of mature breast milk was 7.1 g for lactose, 1.4 g for protein and 3.0 g for fat, and energy content was 61.1 kcal. The protein concentration was significantly lower in milk samples at 1-2 weeks (2.0 g/dL) to 2-3 months (1.4 g/dL) than those at 0-1 week (2.2 g/dL), but it was similar among samples from 3-4 months to 7-8 months (1.3 g/dL). Mean lipid levels varied among different lactational period groups (2.7-3.2 g/dL), but presented no significant difference. Lactose concentration in the milk samples did not differ with lactation period. Maternal body mass index was positively related to protein and lipid breast milk contents, but was negatively related to lactose content. General linear models examining the associations between maternal variables and milk macronutrient content revealed that lactation period had a major impact on protein and lipid, but not on lactose content in breast milk. CONCLUSIONS These results warrant future studies to explore factors that may be associated with changes in macronutrient content in human milk. PMID:26244084

Anti-Jk3 in a Filipino man.

PubMed

McCaskill, Shaina; Wise, Scott; Tinsley, Sheila

2015-01-01

A 62-year-old Filipino man with a history of chronic obstructive pulmonary disease, hypertension, and hyperlipidemia was admitted to the emergency department at Hospital A with recurrent fevers, weakness, and jaundice. The patient was evaluated and eventually discharged with a diagnosis of possible drug-induced hepatitis. One month later, the patient was admitted to Hospital B for recurrent fevers and weakness. The patient's hemoglobin was 3.8 g/dL. Six units of packed red blood cells (RBCs) were ordered for transfusion. The patient's sample typed as group B, D+, and the antibody screen was negative. All six units of packed RBCs appeared compatible (at immediate spin) and were transfused to the patient. His hemoglobin level 4 days post-transfusion was 9.3 g/dL, and the patient was discharged. The patient returned after a week for follow-up and his hemoglobin was found to have dropped to 8.5 g/dL, which continued to fall until it reached 7.0 g/dL. Additional packed RBCs were ordered for transfusion. during subsequent pre-transfusion compatibility testing, the antibody screen was found to be positive (all screening cells reactive at the antihuman globulin phase). An antibody identification panel was performed.The patient's serum was found to react with all panel cells tested, including the autocontrol tube. A direct antiglobulin test revealed the presence of both anti-IgG and anti-C3 coating the patient's RBCs. The specimen was then sent to a reference laboratory for further testing. Results from the reference lab testing revealed the presence of anti-Jk3 in the patient's serum. the patient was placed on steroids, and his reticulocyte count increased with no further signs of extravascular hemolysis. No additional transfusions were necessary. he was eventually discharged with a hemoglobin of 13.6 g/dL. the purpose of this case study is to report the findings of an extremely rare but clinically significant antibody, anti-Jk3.

Persistent mobility edges and anomalous quantum diffusion in order-disorder separated quantum films

NASA Astrophysics Data System (ADS)

Zhong, Jianxin; Stocks, G. Malcolm

2007-01-01

A concept of order-disorder separated quantum films is proposed for the design of ultrathin quantum films of a few atomic layers thick with unconventional transport properties. The concept is demonstrated through studying an atomic bilayer comprised of an ordered layer and a disordered layer. Without the disordered layer or the ordered layer, the system is a conducting two-dimensional (2D) crystal or an insulating disordered 2D electron system. Without the order-disorder phase separation, a disordered bilayer is insulating under large disorder. In an order-disorder separated atomic bilayer, however, we show that the system behaves remarkably different from conventional ordered or disordered electron systems, exhibiting metal-insulator transitions with persistent mobility edges and superdiffusive anomalous quantum diffusion.

Modelling mass diffusion for a multi-layer sphere immersed in a semi-infinite medium: application to drug delivery.

PubMed

Carr, Elliot J; Pontrelli, Giuseppe

2018-04-12

We present a general mechanistic model of mass diffusion for a composite sphere placed in a large ambient medium. The multi-layer problem is described by a system of diffusion equations coupled via interlayer boundary conditions such as those imposing a finite mass resistance at the external surface of the sphere. While the work is applicable to the generic problem of heat or mass transfer in a multi-layer sphere, the analysis and results are presented in the context of drug kinetics for desorbing and absorbing spherical microcapsules. We derive an analytical solution for the concentration in the sphere and in the surrounding medium that avoids any artificial truncation at a finite distance. The closed-form solution in each concentric layer is expressed in terms of a suitably-defined inverse Laplace transform that can be evaluated numerically. Concentration profiles and drug mass curves in the spherical layers and in the external environment are presented and the dependency of the solution on the mass transfer coefficient at the surface of the sphere analyzed. Copyright © 2018 Elsevier Inc. All rights reserved.

Proton exchange membrane micro fuel cells on 3D porous silicon gas diffusion layers

NASA Astrophysics Data System (ADS)

Kouassi, S.; Gautier, G.; Thery, J.; Desplobain, S.; Borella, M.; Ventura, L.; Laurent, J.-Y.

2012-10-01

Since the 90's, porous silicon has been studied and implemented in many devices, especially in MEMS technology. In this article, we present a new approach to build miniaturized proton exchange membrane micro-fuel cells using porous silicon as a hydrogen diffusion layer. In particular, we propose an innovative process to build micro fuel cells from a “corrugated iron like” 3D structured porous silicon substrates. This structure is able to increase up to 40% the cell area keeping a constant footprint on the silicon wafer. We propose here a process route to perform electrochemically 3D porous gas diffusion layers and to deposit fuel cell active layers on such substrates. The prototype peak power performance was measured to be 90 mW cm-2 in a “breathing configuration” at room temperature. These performances are less than expected if we compare with a reference 2D micro fuel cell. Actually, the active layer deposition processes are not fully optimized but this prototype demonstrates the feasibility of these 3D devices.

Sb lattice diffusion in Si1-xGex/Si(001) heterostructures: Chemical and stress effects

NASA Astrophysics Data System (ADS)

Portavoce, A.; Gas, P.; Berbezier, I.; Ronda, A.; Christensen, J. S.; Kuznetsov, A. Yu.; Svensson, B. G.

2004-04-01

The Sb diffusion coefficient in Si1-xGex/Si1-yGey(001) heterostructures grown by molecular beam epitaxy (MBE) was measured for temperatures ranging from 700 to 850 °C, Ge composition from 0 to 20 % and biaxial pressure from -0.8 (tension) to 1.4 GPa (compression). A quantitative separation of composition and biaxial stress effects is made. We show that the Sb lattice diffusion coefficient: (i) increases with Ge concentration in relaxed layers or at constant biaxial pressure and (ii) increases with compressive biaxial stress and decreases with tensile biaxial stress at constant Ge composition. The enhancement of Sb lattice diffusion in Si1-xGex layers in epitaxy on Si(001) is thus due to the cooperative effect of Ge composition and induced compressive biaxial stress. However, the first effect (composition) is predominant. The activation volume of Sb diffusion in Si1-xGex layers is deduced from the variation of the Sb diffusion coefficients with biaxial pressure. This volume is negative. The sign of the activation volume, its absolute value and its variation with temperature confirm the prediction of the thermodynamic model proposed by Aziz, namely, that under a biaxial stress the activation volume is reduced to the relaxation volume.

Phototransformation Rate Constants of PAHs Associated with Soot Particles

PubMed Central

Kim, Daekyun; Young, Thomas M.; Anastasio, Cort

2013-01-01

Photodegradation is a key process governing the residence time and fate of polycyclic aromatic hydrocarbons (PAHs) in particles, both in the atmosphere and after deposition. We have measured photodegradation rate constants of PAHs in bulk deposits of soot particles illuminated with simulated sunlight. The photodegradation rate constants at the surface (k0p), the effective diffusion coefficients (Deff), and the light penetration depths (z0.5) for PAHs on soot layers of variable thickness were determined by fitting experimental data with a model of coupled photolysis and diffusion. The overall disappearance rates of irradiated low molecular weight PAHs (with 2-3 rings) on soot particles were influenced by fast photodegradation and fast diffusion kinetics, while those of high molecular weight PAHs (with 4 or more rings) were apparently controlled by either the combination of slow photodegradation and slow diffusion kinetics or by very slow diffusion kinetics alone. The value of z0.5 is more sensitive to the soot layer thickness than the k0p value. As the thickness of the soot layer increases, the z0.5 values increase, but the k0p values are almost constant. The effective diffusion coefficients calculated from dark experiments are generally higher than those from the model fitting method for illumination experiments. Due to the correlation between k0p and z0.5 in thinner layers, Deff should be estimated by an independent method for better accuracy. Despite some limitations of the model used in this study, the fitted parameters were useful for describing empirical results of photodegradation of soot-associated PAHs. PMID:23247292

Evidence of a reduction reaction of oxidized iron/cobalt by boron atoms diffused toward naturally oxidized surface of CoFeB layer during annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Soshi, E-mail: sato.soshi@cies.tohoku.ac.jp; Honjo, Hiroaki; Niwa, Masaaki

2015-04-06

We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer.more » The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.« less

A Novel Strategy for Controlling the Metastatic Phenotype: Targeting the SNAG Repression Domain in the SNAIL Zinc-Finger Protein

DTIC Science & Technology

2007-07-01

interacts with nuclear receptors and can inhibit betaFTZ-F1-dependent transcription. Mol. Cell, 7, 753–765. 29. Dupont , S., Zacchigna, L., Cordenonsi, M...Washington University/ Pfizer Biomedical Research Program to GDL. GDL was an Established Investigator of the American Heart Association. 26...Cell 11, 1043-1054. Hecker, C. M., Rabiller, M., Haglund, K., Bayer , P., and Dikic, I. (2006). Specification of SUMO1- and SUMO2-interacting motifs. J

Measurement of the oxygen mass transfer through the air-water interface.

PubMed

Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas

2005-01-01

Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple technique for measuring oxygen diffusion parameters through the air-water solution surface has been developed. Derived equations enable the calculation of diffusion parameters of the surface layer at current conditions. These values of the parameters permit one to compare the resistances of the gas-liquid interface to oxygen mass transfer in the case of adsorption of different substances on the surface layer. This simple technique may be used for a determination of oxygen permeability of different water-solution surface layers. It enables one to measure the resistance to the oxygen permeability of all inflowing wastewater surface layers in the wastewater treatment plant, and to initiate a preliminary cleaning of this wastewater if required. Similarly, we can measure oxygen permeability of natural waterbodies. Especially in the case of pollution, it is important to know to what extent the oxygen permeability of the water surface layer has been decreased. Based on the tehnique presented in this research, fieldwork equipment will be developed.

Numerical investigation of metal-semiconductor-insulator-semiconductor passivated hole contacts based on atomic layer deposited AlO x

NASA Astrophysics Data System (ADS)

Ke, Cangming; Xin, Zheng; Ling, Zhi Peng; Aberle, Armin G.; Stangl, Rolf

2017-08-01

Excellent c-Si tunnel layer surface passivation has been obtained recently in our lab, using atomic layer deposited aluminium oxide (ALD AlO x ) in the tunnel layer regime of 0.9 to 1.5 nm, investigated to be applied for contact passivation. Using the correspondingly measured interface properties, this paper compares the theoretical collection efficiency of a conventional metal-semiconductor (MS) contact on diffused p+ Si to a metal-semiconductor-insulator-semiconductor (MSIS) contact on diffused p+ Si or on undoped n-type c-Si. The influences of (1) the tunnel layer passivation quality at the tunnel oxide interface (Q f and D it), (2) the tunnel layer thickness and the electron and hole tunnelling mass, (3) the tunnel oxide material, and (4) the semiconductor capping layer material properties are investigated numerically by evaluation of solar cell efficiency, open-circuit voltage, and fill factor.

Effect of concentration boundary layers on passive solute flows in a system of two polymeric membranes positioned in vertical planes.

PubMed

Slezak, Andrzej; Jasik-Slezak, Jolanta; Dworecki, Kazimierz

2003-01-01

The results of studies of influence of concentration boundary layers on passive diffusive transport in a double-membrane osmo-diffusive cell, containing a series of two (Ml and M(r)) vertically positioned, flat, microporous and symmetric polymer membranes (Nephrophane and Cellulose IMP-1) are presented in this paper. The membranes separated three compartments (l, m, r) containing binary, heterogeneous and non-ionic solutions (aqueous solutions of glucose or ethanol) or ternary non-electrolyte solutions (glucose solutions in 0.75 mol.l-1 solution of ethanol or ethanol solutions in 0.1 mol.l-1 aqueous solution of glucose). Solution concentrations fulfilled the condition C(k)l > C(k)m > C(k)r. The intermembrane compartment (m) was an infinitesimal solution layer. The volume of the m compartment and the volumes of the external (l and r) compartments fulfilled the condition Vl = Vr approximately 170 Vm. The tests were performed for configurations A and B of a double-membrane osmo-diffusive cell. In configuration A, the solution was located behind the M(r) membrane, and water was placed behind the Ml membrane, while in configuration B this sequence was reversed. The results obtained during experiment were interpreted in the categories of convective instability, which increased the value of diffusive permeability coefficient of the system: concentration boundary layer/membrane/concentration boundary layer.

Improve oxidation resistance at high temperature by nanocrystalline surface layer

NASA Astrophysics Data System (ADS)

Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

2015-08-01

An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures

NASA Technical Reports Server (NTRS)

Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.

2009-01-01

Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.

Prediction of Laminar and Turbulent Boundary Layer Flow Separation in V/STOL Engine Inlets

NASA Technical Reports Server (NTRS)

Chou, D. C.; Luidens, R. W.; Stockman, N. O.

1977-01-01

A description is presented of the development of the boundary layer on the lip and diffuser surface of a subsonic inlet at arbitrary operating conditions of mass flow rate, free stream velocity and incidence angle. Both laminar separation on the lip and turbulent separation in the diffuser are discussed. The agreement of the theoretical results with model experimental data illustrates the capability of the theory to predict separation. The effects of throat Mach number, inlet size, and surface roughness on boundary layer development and separation are illustrated.

Limits to Maximum Absorption Length in Waveguide Photodiodes

DTIC Science & Technology

2011-04-13

InGaAsP to InGaAs graded layer (35 nm), a very thin undoped InGaAs absorber layer (20 nm), a p- InP cla~din~ layer (1 J.Lm, Zn = 1x1018 em·\\ a p- InP ...expected excess opticall_oss results from non-ideal coupling, excess waveguide scattering, Zn diffusion from the p-doped InP , larger than...waveguide scattering, Zn diffusion from the p-doped InP , n-doped region absorption, or a combination of the above. The SCOWPD has demonst:r:ated an

Doped LZO buffer layers for laminated conductors

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T [Oxford, MA; Rupich, Martin W [Framingham, MA

2010-03-23

A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.

Clinical Practice Guidelines From the AABB: Red Blood Cell Transfusion Thresholds and Storage.

PubMed

Carson, Jeffrey L; Guyatt, Gordon; Heddle, Nancy M; Grossman, Brenda J; Cohn, Claudia S; Fung, Mark K; Gernsheimer, Terry; Holcomb, John B; Kaplan, Lewis J; Katz, Louis M; Peterson, Nikki; Ramsey, Glenn; Rao, Sunil V; Roback, John D; Shander, Aryeh; Tobian, Aaron A R

2016-11-15

More than 100 million units of blood are collected worldwide each year, yet the indication for red blood cell (RBC) transfusion and the optimal length of RBC storage prior to transfusion are uncertain. To provide recommendations for the target hemoglobin level for RBC transfusion among hospitalized adult patients who are hemodynamically stable and the length of time RBCs should be stored prior to transfusion. Reference librarians conducted a literature search for randomized clinical trials (RCTs) evaluating hemoglobin thresholds for RBC transfusion (1950-May 2016) and RBC storage duration (1948-May 2016) without language restrictions. The results were summarized using the Grading of Recommendations Assessment, Development and Evaluation method. For RBC transfusion thresholds, 31 RCTs included 12 587 participants and compared restrictive thresholds (transfusion not indicated until the hemoglobin level is 7-8 g/dL) with liberal thresholds (transfusion not indicated until the hemoglobin level is 9-10 g/dL). The summary estimates across trials demonstrated that restrictive RBC transfusion thresholds were not associated with higher rates of adverse clinical outcomes, including 30-day mortality, myocardial infarction, cerebrovascular accident, rebleeding, pneumonia, or thromboembolism. For RBC storage duration, 13 RCTs included 5515 participants randomly allocated to receive fresher blood or standard-issue blood. These RCTs demonstrated that fresher blood did not improve clinical outcomes. It is good practice to consider the hemoglobin level, the overall clinical context, patient preferences, and alternative therapies when making transfusion decisions regarding an individual patient. Recommendation 1: a restrictive RBC transfusion threshold in which the transfusion is not indicated until the hemoglobin level is 7 g/dL is recommended for hospitalized adult patients who are hemodynamically stable, including critically ill patients, rather than when the hemoglobin level is 10 g/dL (strong recommendation, moderate quality evidence). A restrictive RBC transfusion threshold of 8 g/dL is recommended for patients undergoing orthopedic surgery, cardiac surgery, and those with preexisting cardiovascular disease (strong recommendation, moderate quality evidence). The restrictive transfusion threshold of 7 g/dL is likely comparable with 8 g/dL, but RCT evidence is not available for all patient categories. These recommendations do not apply to patients with acute coronary syndrome, severe thrombocytopenia (patients treated for hematological or oncological reasons who are at risk of bleeding), and chronic transfusion-dependent anemia (not recommended due to insufficient evidence). Recommendation 2: patients, including neonates, should receive RBC units selected at any point within their licensed dating period (standard issue) rather than limiting patients to transfusion of only fresh (storage length: <10 days) RBC units (strong recommendation, moderate quality evidence). Research in RBC transfusion medicine has significantly advanced the science in recent years and provides high-quality evidence to inform guidelines. A restrictive transfusion threshold is safe in most clinical settings and the current blood banking practices of using standard-issue blood should be continued.

Graduated driver licensing for reducing motor vehicle crashes among young drivers.

PubMed

Hartling, L; Wiebe, N; Russell, K; Petruk, J; Spinola, C; Klassen, T P

2004-01-01

Graduated driver licensing (GDL) has been proposed as a means of reducing crash rates among novice drivers by gradually introducing them to higher risk driving situations. To examine the effectiveness of GDL systems in reducing crash rates of young drivers. Studies were identified through searches of MEDLINE, EMBASE, CINAHL, Healthstar, Web of Science, NTIS Bibliographic Database, TRIS Online, SIGLE, the World Wide Web, relevant conference proceedings, consultation with experts and authors, and reference lists. The search was not restricted by language or publication status. Studies were included if: 1) they compared outcomes pre- and post-implementation of a GDL program within the same jurisdiction, 2) comparisons were made between jurisdictions with and without GDL, or 3) both. Studies had to report at least one objective, quantified outcome. Two reviewers independently screened searches and assessed the full text of potentially relevant studies for inclusion using a standard form. Data were extracted by one reviewer and checked by a second. Additional data were requested from authors. Results were not pooled due to substantial heterogeneity between studies. Percentage change was calculated for each year after the intervention, using one year prior to the intervention as the baseline rate. Results were adjusted by internal controls. Analyses were stratified by different denominators (population, licensed drivers). Results were calculated for the different crash types (overall, injury, fatal, night-time, alcohol, and those resulting in hospitalization). Results were presented for 16 year-olds alone and all teenage drivers combined. We included 13 studies evaluating 12 GDL programs that were implemented between 1979 and 1998 in the US (n=7), Canada (3), New Zealand (1), and Australia (1). Programs varied in their restrictions during the intermediate stage: e.g. night curfews (8); limitations of extra passengers (2); roadway restrictions (1). Based on the Insurance Institute for Highway Safety classification scheme, no programs were good, six were acceptable, five were marginal, and one was poor. Reductions in crash rates were seen in all jurisdictions and for all crash types. Among 16 year-old drivers, the median decrease in per population overall crash rates during the first year was 31% (range 26-41%). Per population injury crash rates were similar (median 28%, range 4-43%). Results for all teenage drivers, rates per licensed driver, and rates adjusting for internal controls were generally reduced when comparing within jurisdictions. The existing evidence shows that GDL is effective in reducing the crash rates of young drivers, although the magnitude of the effect is unclear. The conclusions are supported by consistent direction of the findings, and the temporal relationship and plausibility of the association. The reviewers have made recommendations for primary research on GDL (e.g. study methods, standardized reporting of outcomes and results, long-term follow-up). The project has also shown what is needed to carry out systematic reviews of observational studies (e.g. quality assessment instruments).

Controlling mechanisms of metals release form cement-based waste form in acetic acid solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Kuang Ye.

1991-01-01

The purpose of this dissertation is to identify the individual leaching mechanisms of metals by knowing the pH profile within the leached specimen and the physical and chemical properties of the leached material. Leaching of cement-based waste form in acetic acid solutions with different acidic strengths has been investigated in this work. The pH profile along the acid penetration route in the cement-based waste form was identified by various pH color indicators. The pH in the surface altered layer varies from 5.0 to 6.0, which is very close to the pH in the bulk leachate. A reacting zone, where themore » pH abruptly changes from 6 to 12, sharply divides the altered surface layer from the remaining unleached waste form or kernel. Leaching of metals is controlled by the acidity available in the leachant. Dissolution of alkaline materials leaves a silica-rich layer on the surface of the cement-based waste form. This surface layer exhibits different properties than those of the unleached material. The surface layer has a higher water content, is lighter weight, and is soft and friable. Furthermore, the abundant silicate content on the solid surface detains portion of the leached metals, while they are moving through the leached layer into bulk solution. The leaching of metals is a consequence of acid penetration. The distance from the solid/solution interface to the front of the leaching boundary can be regarded as the depth of leaching zone, where the metals dissolve and diffuse out of the waste form. The metal ions diffuse through the leached layer may be retarded on the solid surface by the pH-dependent adsorption reactions. It is found that the leaching process through the leached layer is diffusion-controlled for calcium and cadmium, whereas diffusion and adsorption occur simultaneously in the leached layer for lead and arsenic.« less

Effect of permeable flow on cyclic layering in solidifying magma bodies: Insights from an analog experiment of diffusion-precipitation systems

NASA Astrophysics Data System (ADS)

Toramaru, A.; Yamauchi, S.

2012-04-01

Characteristic structures such as rhythmic layering, cress cumulate, cross bedding, perpendicular feldspar rock etc, are commonly observed in layered intrusion or shallow magmatic intrusions. These structures result from complex processes including thermal and compositional diffusions, crystallization, crystal settling, convection and interaction among three phases (crystals, bubble, melt). In order to understand how the differentiation proceeds in solidifying magma bodies from each characteristic structure together with chemical signatures, it is necessary to evaluate the relative importance among these elemental processes on structures. As an attempt to evaluate the effect of advection on a diffusion-related structure, we carried out an analog experiment of Liesegang system using lead-iodide (PbI2) crystallization in agar media which have been normally used to prohibit convection. In the ordinary Liesegang band formation experiments including only diffusion and crystallization kinetics without any advection and convection, the precipitation bands develop with regular spacing following a geometric progression due to two-component diffusion and reaction with supersaturation. This type of banding structure has been advocated as the same type of cyclic layering or vesicle layering (a sort of rhythmic layering) in dykes or sills. In order to see the effect of one-directional advection on Liesegang band, we apply the electric field (5 V to 25 V for a distance 15 cm) along the concentration gradient in agar media, thereby counteracting flows of lead anion Pb2+ and iodide ion I- are driven at constant velocities. The flows of anions and ions are equivalent to the permeable flows in porous media of crystal mush. The resultant precipitation structures exhibit very curious banding structure in which band spacings do not change with distance, are nearly constant and quite narrow, depending on the voltage, unlike those in ordinary Liesegang bands in which band spacings increase with distance following geometric progression. Further interestingly each band consists of a lot of very tiny irregular-shaped crystal aggregates. From experimental results and scaling arguments, with regard to the effect of one directional permeable flow on band spacing of cyclic layering, we propose a hypothesis of constant Peclet number that Peclet number (ratio of flow velocity to diffusive velocity) is nearly unity. By applying the hypothesis to natural examples, we can estimate a value of permeable flow velocity of interstitial melts in differentiating magma bodies from values of a band spacing and diffusivity data.

Combustion Diagnostics and Flow Visualization of Hypergolic Combustion and Gelled Mixing Behavior

DTIC Science & Technology

1997-12-19

difference. Also, Exciplex Flourescence imaging has been implented to visualize diffusion layers which form at the contact interface of mixing...have been implemented and developed as a result of this effort. Among these techniques the most noteworthy involves a unique application of Exciplex ...fluorescence for visualization of diffusion layers formed between mixing liquids. Time resolved images of Exciplex fluorescence have been obtained

Automated array assembly task, phase 1

NASA Technical Reports Server (NTRS)

Carbajal, B. G.

1977-01-01

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE PAGES

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu; ...

2017-09-01

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

A study on atomic diffusion behaviours in an Al-Mg compound casting process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yongning; Chen, Yiqing; Yang, Chunhui, E-mail: r.yang@uws.edu.au

Al and Mg alloys are main lightweight alloys of research interest and they both have superb material properties, i.e., low density and high specific strength, etc. Being different from Al alloys, the corrosion of Mg alloys is much more difficult to control. Therefore to combine merits of these two lightweight alloys as a composite-like structure is an ideal solution through using Al alloys as a protective layer for Mg alloys. Compound casting is a realistic technique to manufacture such a bi-metal structure. In this study, a compound casting technique is employed to fabricate bi-layered samples using Al and Mg andmore » then the samples are analysed using electron probe micro-analyzer (EPMA) to determine diffusion behaviours between Al and Mg. The diffusion mechanism and behaviours between Al and Mg are studied numerically at atomic scale using molecular dynamics (MD) and parametric studies are conducted to find out influences of ambient temperature and pressure on the diffusion behaviours between Al and Mg. The results obtained clearly show the effectiveness of the compound casting process to increase the diffusion between Al and Mg and thus create the Al-base protection layer for Mg.« less

Electron-stimulated reactions in layered CO/H2O films: Hydrogen atom diffusion and the sequential hydrogenation of CO to methanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrik, Nikolay G.; Monckton, Rhiannon J.; Koehler, Sven

Low-energy (100 eV) electron-stimulated reactions in layered H2O/CO/H2O ices are investigated. For CO trapped within approximately 50 ML of the vacuum interface in the amorphous solid water (ASW) films, both oxidation and reduction reactions are observed. However for CO buried more deeply in the film, only the reduction of CO to methanol is observed. Experiments with layered films of H2O and D2O show that the hydrogen atoms participating in the reduction of the buried CO originate in region from ~10 – 40 ML below the surface of the ASW films and subsequently diffuse through the film. For deeply buried COmore » layers, the CO reduction reactions quickly increase with temperature above ~60 K. We present a simple chemical kinetic model that treats the diffusion of hydrogen atoms in the ASW and sequential hydrogenation of the CO to methanol that accounts for the observations.« less

Approximate Solution Methods for Spectral Radiative Transfer in High Refractive Index Layers

NASA Technical Reports Server (NTRS)

Siegel, R.; Spuckler, C. M.

1994-01-01

Some ceramic materials for high temperature applications are partially transparent for radiative transfer. The refractive indices of these materials can be substantially greater than one which influences internal radiative emission and reflections. Heat transfer behavior of single and laminated layers has been obtained in the literature by numerical solutions of the radiative transfer equations coupled with heat conduction and heating at the boundaries by convection and radiation. Two-flux and diffusion methods are investigated here to obtain approximate solutions using a simpler formulation than required for exact numerical solutions. Isotropic scattering is included. The two-flux method for a single layer yields excellent results for gray and two band spectral calculations. The diffusion method yields a good approximation for spectral behavior in laminated multiple layers if the overall optical thickness is larger than about ten. A hybrid spectral model is developed using the two-flux method in the optically thin bands, and radiative diffusion in bands that are optically thick.

Understanding of interface structures and reaction mechanisms induced by Ge or GeO diffusion in Al{sub 2}O{sub 3}/Ge structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shibayama, Shigehisa; JSPS, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083; Kato, Kimihiko

2013-08-19

The reaction mechanisms at Al{sub 2}O{sub 3}/Ge interfaces with thermal oxidation through the Al{sub 2}O{sub 3} layer have been investigated. X-ray photoelectron spectroscopy reveals that an Al{sub 6}Ge{sub 2}O{sub 13} layer is formed near the interface, and a GeO{sub 2} layer is formed on the Al{sub 2}O{sub 3} surface, suggesting Ge or GeO diffusion from the Ge surface. It is also clarified that the Al{sub 6}Ge{sub 2}O{sub 13} layer is formed by the different mechanism with a small activation energy of 0.2 eV, compared with the GeO{sub 2} formation limited by oxygen diffusion. Formation of Al-O-Ge bonds due to themore » AlGeO formation could lead appropriate interface structures with high interface qualities.« less

Study of Diffusion Barrier for Solder/ n-Type Bi2Te3 and Bonding Strength for p- and n-Type Thermoelectric Modules

NASA Astrophysics Data System (ADS)

Lin, Wen-Chih; Li, Ying-Sih; Wu, Albert T.

2018-01-01

This paper investigates the interfacial reaction between Sn and Sn3Ag0.5Cu (SAC305) solder on n-type Bi2Te3 thermoelectric material. An electroless Ni-P layer successfully suppressed the formation of porous SnTe intermetallic compound at the interface. The formation of the layers between Bi2Te3 and Ni-P indicates that Te is the dominant diffusing species. Shear tests were conducted on both Sn and SAC305 solder on n- and p-type Bi2Te3 with and without a Ni-P barrier layer. Without a Ni-P layer, porous SnTe would result in a more brittle fracture. A comparison of joint strength for n- and p-type thermoelectric modules is evaluated by the shear test. Adding a diffusion barrier increases the mechanical strength by 19.4% in n-type and 74.0% in p-type thermoelectric modules.

Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

NASA Astrophysics Data System (ADS)

Zagula-Yavorska, Maryana; Gancarczyk, Kamil; Sieniawski, Jan

2017-03-01

CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 μm thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 ˚C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 μm platinum thick before heat treatment) consisted of two phases: γ-Ni(Al, Cr) and (Al0.25Pt0.75)Ni3. The diffusion zone obtained on Inconel 625 superalloy (3 μm platinum thick before heat treatment) consisted of the α-Pt(Ni, Cr, Al) phase. Moreover, γ-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 μm platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.

Graduated Driver Licensing

PubMed Central

Bates, Lyndel J.; Allen, Siobhan; Armstrong, Kerry; Watson, Barry; King, Mark J.; Davey, Jeremy

2014-01-01

Graduated driver licensing (GDL) aims to gradually increase the exposure of new drivers to more complex driving situations and typically consists of learner, provisional and open licence phases. The first phase, the learner licence, is designed to allow novice drivers to obtain practical driving experience in lower risk situations. The learner licence can delay licensure, encourage novice drivers to learn under supervision, mandate the number of hours of practice required to progress to the next phase and encourage parental involvement. The second phase, the provisional licence, establishes various driving restrictions and thereby reduces exposure to situations of higher risk, such as driving at night, with passengers or after drinking alcohol. Parental involvement with a GDL system appears essential in helping novices obtain sufficient practice and in enforcing compliance with restrictions once the new driver obtains a provisional licence. Given the significant number of young drivers involved in crashes within Oman, GDL is one countermeasure that may be beneficial in reducing crash risk and involvement for this group. PMID:25364543

Appraisal on the prevalence of malaria and anaemia in pregnancy and factors influencing uptake of intermittent preventive therapy with sulfadoxine-pyrimethamine in Kibaha district, Tanzania.

PubMed

Tarimo, S Donath

2007-10-01

To appraise the prevalence of malaria and anaemia in antenatal mothers; and explore the factors influencing coverage of intermittent preventive treatment (IPT) with sulfadoxine-pyrimethamine (SP) under operational conditions in the national programme for malaria control in pregnancy. Descriptive cross-sectional survey. The reproductive and child health clinic in Kibaha district hospital, Tanzania SUBECTS: Pregnant mothers on routine antenatal visits Prevalence of malaria (peripheral parasitaemia) and anaemia, coverage of IPT with SP and the factors influencing coverage. A total of 395 mothers were recruited; 27.3% had malaria. Moderate anaemia i.e. haemoglobin (Hb) level 8. -10.9 g/dl was detected in 56.7% of mothers; 34.2% had severe anaemia (Hb < 8.0 g/dl). Hb > 8.0 g/dl was strongly associated with negative parasitaemia while Hb < 8.0 gidl was strongly associated with positive parasitaemia. About a third (40.0%) of the mothers did not receive SP for IPT

Multiple relaxations of the cluster surface diffusion in a homoepitaxial SrTiO3 layer

NASA Astrophysics Data System (ADS)

Woo, Chang-Su; Chu, Kanghyun; Song, Jong-Hyun; Yang, Chan-Ho

2018-03-01

We examine the surface diffusion process of adatomic clusters on a (001)-oriented SrTiO3 single crystal using reflection high energy electron diffraction (RHEED). We find that the recovery curve of the RHEED intensity acquired after a homoepitaxial half-layer growth can be accurately fit into a double exponential function, indicating the existence of two dominant relaxation mechanisms. The characteristic relaxation times at selected growth temperatures are investigated to determine the diffusion activation barriers of 0.67 eV and 0.91 eV, respectively. The Monte Carlo simulation of the cluster hopping model suggests that the decrease in the number of dimeric and trimeric clusters during surface diffusion is the origin of the observed relaxation phenomena.

Particle Transport through Scattering Regions with Clear Layers and Inclusions

NASA Astrophysics Data System (ADS)

Bal, Guillaume

2002-08-01

This paper introduces generalized diffusion models for the transport of particles in scattering media with nonscattering inclusions. Classical diffusion is known as a good approximation of transport only in scattering media. Based on asymptotic expansions and the coupling of transport and diffusion models, generalized diffusion equations with nonlocal interface conditions are proposed which offer a computationally cheap, yet accurate, alternative to solving the full phase-space transport equations. The paper shows which computational model should be used depending on the size and shape of the nonscattering inclusions in the simplified setting of two space dimensions. An important application is the treatment of clear layers in near-infrared (NIR) spectroscopy, an imaging technique based on the propagation of NIR photons in human tissues.

Diffusion of Magnesium in Led Structures with InGaN/GaN Quantum Wells at True Growth Temperatures 860-980°C of p-GaN

NASA Astrophysics Data System (ADS)

Romanov, I. S.; Prudaev, I. A.; Brudnyi, V. N.

2018-05-01

The results of an investigation of Mg diffusion in blue LED structures with InGaN/GaN quantum wells are presented for various growth temperatures of the p-GaN layer. The values of the diffusion coefficient estimated for true growth temperatures of 860, 910, and 980°C were 7.5·10-17, 2.8·10-16, and 1.2·10-15 cm2/s, respectively. The temperature values given in the work were measured on the surface of the growing layer in situ using a pyrometer. The calculated activation energy for the temperature dependence of the diffusion coefficient was 2.8 eV.

Thermal and solutal conditions at the tips of a directional dendritic growth front

NASA Technical Reports Server (NTRS)

Mccay, T. D.; Mccay, Mary H.; Hopkins, John A.

1991-01-01

The line-of-sight averaged, time-dependent dendrite tip concentrations for the diffusion dominated vertical directional solidification of a metal model (ammonium chloride and water) were obtained by extrapolating exponentially fit diffusion layer profiles measured using a laser interferometer. The tip concentrations were shown to increase linearly with time throughout the diffusion dominated growth process for an initially stagnant dendritic array. The process was terminated for the cases chosen by convective breakdown suffered when the conditionally stable diffusion layer exceeded the critical Rayleigh criteria. The transient tip concentrations were determined to significantly exceed the values predicted for steady state, thus producing much larger constitutional undercoolings. This has ramifications for growth speeds, arm spacings and the dendritic structure itself.

Diffusion modelling of metamorphic layered coronas with stability criterion and consideration of affinity

NASA Astrophysics Data System (ADS)

Ashworth, J. R.; Sheplev, V. S.

1997-09-01

Layered coronas between two reactant minerals can, in many cases, be attributed to diffusion-controlled growth with local equilibrium. This paper clarifies and unifies the previous approaches of various authors to the simplest form of modelling, which uses no assumed values for thermochemical quantities. A realistic overall reaction must be estimated from measured overall proportions of minerals and their major element compositions. Modelling is not restricted to a particular number of components S, relative to the number of phases Φ. IfΦ > S + 1, the overall reaction is a combination of simultaneous reactions. The stepwise method, solving for the local reaction at each boundary in turn, is extended to allow for recurrence of a mineral (its presence in two parts of the layer structure separated by a gap). The equations are also given in matrix form. A thermodynamic stability criterion is derived, determining which layer sequence is truly stable if several are computable from the same inputs. A layer structure satisfying the stability criterion has greater growth rate (and greater rate of entropy production) than the other computable layer sequences. This criterion of greatest entropy production is distinct from Prigogine's theorem of minimum entropy production, which distinguishes the stationary or quasi-stationary state from other states of the same layer sequence. The criterion leads to modification of previous results for coronas comprising hornblende, spinel, and orthopyroxene between olivine (Ol) and plagioclase (Pl). The outcome supports the previous inference that Si, and particularly Al, commonly behave as immobile relative to other cation-forming major elements. The affinity (-ΔG) of a corona-forming reaction is estimated, using previous estimates of diffusion coefficient and the duration t of reaction, together with a new model quantity (-ΔG) *. For an example of the Ol + Pl reaction, a rough calculation gives (-ΔG) > 1.7RT (per mole of P1 consumed, based on a 24-oxygen formula for Pl). At 600-700°C, this represents (-ΔG) > 10kJ mol -1 and departure from equilibrium temperature by at least ˜ 100°C. The lower end of this range is petrologically reasonable and, for t < 100Ma, corresponds to a Fick's-law diffusion coefficient for Al, DAl > 10 -25m 2s -1, larger than expected for lattice diffusion but consistent with fluid-absent grain-boundary diffusion and small concentration gradients.

Maternal anaemia as an indicator for monitoring malaria control in pregnancy in sub-Saharan Africa.

PubMed

Savage, E J; Msyamboza, K; Gies, S; D'Alessandro, U; Brabin, B J

2007-10-01

Malarial anaemia is a major problem in many developing countries and often occurs more frequently in first pregnancies, as primigravidae are more susceptible to Plasmodium falciparum malaria and are at excess risk of malarial anaemia. To analyse the excess risk of anaemia in primigravidae as a potential indicator of malaria control and exposure in pregnant women living in sub-Saharan Africa. The sensitivity, specificity and predictive values for anaemia in first compared with later pregnancies are calculated for 27 studies from malarious and 7 studies from nonmalarious areas. Surveys of pregnancy anaemia reported for highly malarious and nonmalarious areas. In malarious areas, the weighted odds ratio for excess anaemia (haemoglobin [Hb] <11 g/dl) in primigravidae compared with multigravidae for all studies was 1.34 (95% CI 1.14-1.58). At an Hb cutoff below 8 g/dl, the weighted odds ratio was 1.79 (95% CI 1.52-2.10). In nonmalarious areas, there was no increased risk of anaemia in primigravidae with Hb below 11 g/dl (OR 0.80; 95% CI 0.63-1.90) or below 8 g/dl (OR 0.82, 95% CI 0.51-1.28). In view of the consistency of results across highly malarious areas compared with nonmalarious areas, maternal anaemia has the potential to be used for surveillance of malaria control in pregnancy. Based on the analysis, an anaemia nomogram is developed for use as a surveillance indicator in malarious areas in sub-Saharan Africa.

Health care utilization and charges following the enactment of the 2007 Graduated Drivers Licensing Law in Massachusetts.

PubMed

Sangji, Naveen F; Ramly, Elie P; Kaafarani, Haytham M A; Seethala, Raghu; Raybould, Toby; Camargo, Carlos A; Velmahos, George; Masiakos, Peter T; Lee, Jarone

2015-10-01

Graduated Drivers Licensing (GDL) programs phase in driving privileges for teenagers. In 2007, Massachusetts implemented a stricter version of the 1998 GDL law, with increased fines and education. This study evaluated the impact of the law on motor vehicle crash (MVC)-related health care utilization and charges. Massachusetts government and US Census Bureau data were analyzed to compare the rates of MVC-related emergency department (ED) visits and hospital charges before (2002-2006) and after (2007-2011) the 2007 GDL law. Three driver age groups were studied: 16-17 (evaluating the law effect), 18-20 (evaluating the sustainability of the effect), and 25-29 years old (control group). MVC-related ED visits per population decreased after the law for all three age groups (16-17: 2326 to 713; 18-20: 2110 to 1304; 25-29: 1694 to 1228; per 100,000, p<0.001), but the decrease was greater amongst teenagers (16-17: -69%; 18-20: -38%) compared to the control group (-27%); p<0.001. MVC-related hospital charges per population also decreased for teenagers but increased for the control group (16-17: $2.70 m to $1.45 m; 18-20: $3.52 m to $2.26 m; 25-29: $1.86 m to $1.92 m; per 100,000, p<0.001). The 2007 GDL law in Massachusetts was associated with significant decreases in MVC-related health care utilization and hospital charges among teenage drivers. Copyright © 2015 Elsevier Inc. All rights reserved.

Layered materials with improved magnesium intercalation for rechargeable magnesium ion cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doe, Robert E.; Downie, Craig M.; Fischer, Christopher

2016-01-19

Electrochemical devices which incorporate cathode materials that include layered crystalline compounds for which a structural modification has been achieved which increases the diffusion rate of multi-valent ions into and out of the cathode materials. Examples in which the layer spacing of the layered electrode materials is modified to have a specific spacing range such that the spacing is optimal for diffusion of magnesium ions are presented. An electrochemical cell comprised of a positive intercalation electrode, a negative metal electrode, and a separator impregnated with a nonaqueous electrolyte solution containing multi-valent ions and arranged between the positive electrode and the negativemore » electrode active material is described.« less

Layered materials with improved magnesium intercalation for rechargeable magnesium ion cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doe, Robert Ellis; Downie, Craig Michael; Fischer, Christopher

2016-07-26

Electrochemical devices which incorporate cathode materials that include layered crystalline compounds for which a structural modification has been achieved which increases the diffusion rate of multi-valent ions into and out of the cathode materials. Examples in which the layer spacing of the layered electrode materials is modified to have a specific spacing range such that the spacing is optimal for diffusion of magnesium ions are presented. An electrochemical cell comprised of a positive intercalation electrode, a negative metal electrode, and a separator impregnated with a nonaqueous electrolyte solution containing multi-valent ions and arranged between the positive electrode and the negativemore » electrode active material is described.« less

Effects of Formation Heterogeneity in Semi-Confining Shale Layers in Enhancing Mixing and Storage of Dissolved CO2

NASA Astrophysics Data System (ADS)

Illangasekare, T. H.; Agartan Karacaer, E.; Vargas-Johnson, J.; Cihan, A.; Birkholzer, J. T.

2017-12-01

It is expected that heterogeneity of the deep geologic formation to play a key role in both trapping of supercritical CO2 and its mixing in the formation brine. In previously reported research by the authors, a set of laboratory experiments and field-scale simulations were used to show that convective mixing and diffusion controlled trapping are two important mechanisms that contribute to the dissolution trapping in multilayered systems with homogeneous low-permeability zones such as shale. However, these low-permeability layers (e.g. shale) are not always homogeneous due to their composition and texture variations in addition to the presence of faults, fractures and fissures. In this study, we investigated the potential outcomes of heterogeneity present within these semi-confining low-permeability layers in regards to mixing and storage of dissolved CO2. An intermediate-scale laboratory experiment was designed to investigate the contribution of convective mixing, diffusion controlled trapping and back diffusion to long-term storage of dissolved CO2 in multilayered formations with heterogeneous low-permeability layers. The experiment was performed using a surrogate fluid combination to represent dissolved CO2 and brine under ambient pressure and temperature conditions. After verifying the numerical model with the experimental results, different distributions of the same low-permeability materials having similar volume ratios with the experimentally studied scenario were tested numerically. The experiment and modeling results showed that connectivity of higher permeability material within the semi-confining low-permeability layers contributes to mixing through brine leakage between upper and lower aquifers, storage through diffusion, and in the long term, back diffusion of stored mass due to reversed concentration gradient.

Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si

PubMed Central

Hsieh, Shu-Huei; Chen, Wen Jauh; Chien, Chu-Mo

2015-01-01

Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu3Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. PMID:28347099

Intra-retinal layer segmentation of 3D optical coherence tomography using coarse grained diffusion map

PubMed Central

Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D.; Sonka, Milan

2013-01-01

Optical coherence tomography (OCT) is a powerful and noninvasive method for retinal imaging. In this paper, we introduce a fast segmentation method based on a new variant of spectral graph theory named diffusion maps. The research is performed on spectral domain (SD) OCT images depicting macular and optic nerve head appearance. The presented approach does not require edge-based image information in localizing most of boundaries and relies on regional image texture. Consequently, the proposed method demonstrates robustness in situations of low image contrast or poor layer-to-layer image gradients. Diffusion mapping applied to 2D and 3D OCT datasets is composed of two steps, one for partitioning the data into important and less important sections, and another one for localization of internal layers. In the first step, the pixels/voxels are grouped in rectangular/cubic sets to form a graph node. The weights of the graph are calculated based on geometric distances between pixels/voxels and differences of their mean intensity. The first diffusion map clusters the data into three parts, the second of which is the area of interest. The other two sections are eliminated from the remaining calculations. In the second step, the remaining area is subjected to another diffusion map assessment and the internal layers are localized based on their textural similarities. The proposed method was tested on 23 datasets from two patient groups (glaucoma and normals). The mean unsigned border positioning errors (mean ± SD) was 8.52 ± 3.13 and 7.56 ± 2.95 μm for the 2D and 3D methods, respectively. PMID:23837966

Stuffed MO layer as a diffusion barrier in metallizations for high temperature electronics

NASA Technical Reports Server (NTRS)

Boah, J. K.; Russell, V.; Smith, D. P.

1981-01-01

Auger electron spectroscopy was employed to characterize the diffusion barrier properties of molybdenum in the CrSi2/Mo/Au metallization system. The barrier action of Mo was demonstrated to persist even after 2000 hours annealing time at 300 C in a nitrogen ambient. At 340 C annealing temperature, however, rapid interdiffusion was observed to have occurred between the various metal layers after only 261 hours. The presence of controlled amounts of oxygen in the Mo layer is believed to be responsible for suppressing the short circuit interdiffusion between the thin film layers. Above 340 C, its is believed that the increase in the oxygen mobility led to deterioration of its stuffing action, resulting in the rapid interdiffusion of the thin film layers along grain boundaries.

Method For Improving The Oxidation Resistance Of Metal Substrates Coated With Thermal Barrier Coatings

DOEpatents

Thompson, Anthony Mark; Gray, Dennis Michael; Jackson, Melvin Robert

2003-05-13

A method for providing a protective coating on a metal-based substrate is disclosed. The method involves the application of an aluminum-rich mixture to the substrate to form a discontinuous layer of aluminum-rich particles, followed by the application of a second coating over the discontinuous layer of aluminum-rich particles. Aluminum diffuses from the aluminum-rich layer into the substrate, and into any bond coat layer which is subsequently applied. Related articles are also described. A method for providing a protective coating on a metal-based substrate is disclosed. The method involves the application of an aluminum-rich mixture to the substrate to form a discontinuous layer of aluminum-rich particles, followed by the application of a second coating over the discontinuous layer of aluminum-rich particles. Aluminum diffuses from the aluminum-rich layer into the substrate, and into any bond coat layer which is subsequently applied. Related articles are also described.

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

PubMed

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.

Diffusion barrier properties of single- and multilayered quasi-amorphous tantalum nitride thin films against copper penetration

NASA Astrophysics Data System (ADS)

Chen, G. S.; Chen, S. T.

2000-06-01

Tantalum-related thin films containing different amounts of nitrogen are sputter deposited at different argon-to-nitrogen flow rate ratios on (100) silicon substrates. Using x-ray diffractometry, transmission electron microscopy, composition and resistivity analyses, and bending-beam stress measurement technique, this work examines the impact of varying the nitrogen flow rate, particularly on the crystal structure, composition, resistivity, and residual intrinsic stress of the deposited Ta2N thin films. With an adequate amount of controlled, reactive nitrogen in the sputtering gas, thin films of the tantalum nitride of nominal formula Ta2N are predominantly amorphous and can exist over a range of nitrogen concentrations slightly deviated from stoichiometry. The single-layered quasi-amorphous Ta2N (a-Ta2N) thin films yield intrinsic compressive stresses in the range 3-5 GPa. In addition, the use of the 40-nm-thick a-Ta2N thin films with different nitrogen atomic concentrations (33% and 36%) and layering designs as diffusion barriers between silicon and copper are also evaluated. When subjected to high-temperature annealing, the single-layered a-Ta2N barrier layers degrade primarily by an amorphous-to-crystalline transition of the barrier layers. Crystallization of the single-layered stoichiometric a-Ta2N (Ta67N33) diffusion barriers occurs at temperatures as low as 450 °C. Doing so allows copper to preferentially penetrate through the grain boundaries or thermal-induced microcracks of the crystallized barriers and react with silicon, sequentially forming {111}-facetted pyramidal Cu3Si precipitates and TaSi2 Overdoping nitrogen into the amorphous matrix can dramatically increase the crystallization temperature to 600 °C. This temperature increase slows down the inward diffusion of copper and delays the formation of both silicides. The nitrogen overdoped Ta2N (Ta64N36) diffusion barriers can thus be significantly enhanced so as to yield a failure temperature 100 °C greater than that of the Ta67N33 diffusion barriers. Moreover, multilayered films, formed by alternately stacking the Ta67N33 and Ta64N36 layers with an optimized bilayer thickness (λ) of 10 nm, can dramatically reduce the intrinsic compressive stress to only 0.7 GPa and undergo high-temperature annealing without crystallization. Therefore, the Ta67N33/Ta64N36 multilayered films exhibit a much better barrier performance than the highly crystallization-resistant Ta64N36 single-layered films.

Systematic Review and Meta-Analysis of Diagnostic Accuracy of Serum Refractometry and Brix Refractometry for the Diagnosis of Inadequate Transfer of Passive Immunity in Calves.

PubMed

Buczinski, S; Gicquel, E; Fecteau, G; Takwoingi, Y; Chigerwe, M; Vandeweerd, J M

2018-01-01

Transfer of passive immunity in calves can be assessed by direct measurement of immunoglobulin G (IgG) by methods such as radial immunodiffusion (RID) or turbidimetric immunoassay (TIA). IgG can also be measured indirectly by methods such as serum refractometry (REF) or Brix refractometry (BRIX). To determine the accuracy of REF and BRIX for assessment of inadequate transfer of passive immunity (ITPI) in calves. Systematic review and meta-analysis of diagnostic accuracy studies. Databases (PubMed and CAB Abstract, Searchable Proceedings of Animal Science) and Google Scholar were searched for relevant studies. Studies were eligible if the accuracy (sensitivity and specificity) of REF or BRIX was determined using direct measurement of IgG by RID or turbidimetry as the reference standard. The study population included calves <14 days old that were fed with natural colostrum (colostrum replacement products were excluded). Quality assessment was performed by the QUADAS-2 tool. Hierarchical models were used for meta-analysis. From 1,291 references identified, 13 studies of 3,788 calves were included. Of these, 11 studies evaluated REF and 5 studies evaluated BRIX. The median (range) prevalence of ITPI (defined as calves with IgG <10 g/L by RID or TIA) was 21% (1.3-56%). Risk of bias and applicability concerns were generally low or unclear. For REF, summary estimates were obtained for 2 different cutoffs: 5.2 g/dL (6 studies) and 5.5 g/dL (5 studies). For the 5.2 g/dL cutoff, the summary sensitivity (95% CI) and specificity (95% CI) were 76.1% (63.8-85.2%) and 89.3% (82.3-93.7%), and 88.2% (80.2-93.3%) and 77.9% (74.5-81.0%) for the 5.5 g/dL cutoff. Due to the low number of studies using the same cutoffs, summary estimates could not be obtained for BRIX. Despite their widespread use on dairy farms, evidence about the optimal strategy for using refractometry, including the optimal cutoff, are sparse (especially for BRIX). When using REF to rule out ITPI in herds, the 5.5 g/dL cutoff may be used whereas for ruling in ITPI, the 5.2 g/dL cutoff may be used. Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

NASA Astrophysics Data System (ADS)

Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

2017-06-01

Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

NASA Astrophysics Data System (ADS)

Chaia, N.; Portebois, L.; Mathieu, S.; David, N.; Vilasi, M.

2017-02-01

To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF2 as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V3Si, V5Si3, V6Si5 and VSi2) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10-9 to 10-13 cm2 s-1. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi2 layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum.

The specific diffusion behaviour in paper and migration modelling from recycled board into dry foodstuffs.

PubMed

Hauder, J; Benz, H; Rüter, M; Piringer, O-G

2013-01-01

Recycled board plays an important role in food packaging, but the great variety of organic impurities must be considered as potential food contaminants. The diffusion behaviour of the impurities is significantly different from that in plastic materials. The two-layer concept for paper and board introduced recently is now treated in more detail. In the rate-determining surface region the diffusion coefficients of the n-alkanes in the homologous series with 15-35 carbon atoms decrease proportionally as their vapour pressures. This leads to a different equation of the diffusion coefficients in comparison with that for the core layer. Different polarities of the migrants have additional influences on the diffusion due to their interactions with the fibre matrix. A new analytical method for the quantification of aromatic impurities has previously been developed. Based on this method and on the described diffusion behaviour, a migration model for specific and global mass transfer of impurities from recycled board into dry food and food simulants is given.

Wind-Tunnel Modeling of Flow Diffusion over an Urban Complex.

DTIC Science & Technology

URBAN AREAS, *ATMOSPHERIC MOTION, *AIR POLLUTION, ATMOSPHERIC MOTION, WIND TUNNEL MODELS, HEAT, DIFFUSION , TURBULENT BOUNDARY LAYER, WIND, SKIN FRICTION, MATHEMATICAL MODELS, URBAN PLANNING, INDIANA.

Scaling oxygen microprofiles at the sediment interface of deep stratified waters

NASA Astrophysics Data System (ADS)

Schwefel, Robert; Hondzo, Miki; Wüest, Alfred; Bouffard, Damien

2017-02-01

Dissolved oxygen microprofiles at the sediment-water interface of Lake Geneva were measured concurrently with velocities 0.25 to 2 m above the sediment. The measurements and scaling analyses indicate dissolved oxygen fluctuations and turbulent fluxes in exceedance of molecular diffusion in the proximity of the sediment-water interface. The measurements allowed the parameterization of the turbulent diffusion as a function of the dimensionless height above the sediment and the turbulence above the sediment-water interface. Turbulent diffusion depended strongly on the friction velocity and differed from formulations reported in the literature that are based on concepts of turbulent and developed wall-bounded flows. The dissolved oxygen microprofiles and proposed parameterization of turbulent diffusion enable a foundation for the similarity scaling of oxygen microprofiles in proximity to the sediment. The proposed scaling allows the estimation of diffusive boundary layer thickness, oxygen flux, and oxygen microprofile distribution in the near-sediment boundary layer.