UK PubMed Central (United Kingdom)

Temperature-dependent (5-42 degrees C) 13C NMR spectra of albumin complexes with 90% isotopically substituted [1-13C]decanoic acids (3 mol of fatty acid per mol of albumin) showed a single peak at greater...Full Text Available

International Nuclear Information System (INIS)

In the present study, the authors examine the interactions of pentavalent technetium ions (TcO/sup 3+/) with the basic form of the lasalocid A in pure methanol solvent and in methanol-water mixtures. There are a number of reasons for such a study. First, the interactions of technetium ions with biologically important compounds are of considerable importance owing to the widespread use of /sup 99m/Tc in diagnostic radio-imaging. Second, lasalocid A is known to transport metal ions across phospholipid bilayer membranes and between the aqueous cores of phospholipid inverse micelles. Third, lasalocid A is known to bind and solubilize metal ions in bulk organic liquid phases. Fourth, the conformation adopted by lasalocid A on interaction with TcO/sup 3+/ appears to be different than those found in most other cases and circumstances. Fifth, it may also be possible to use the competition of TcO/sup 3+/ with other, physiologically ...

Science.gov (United States)

The goal of the present study is to elucidate the effect of lipid domain formation on activities of Naja naja atra and Bungarus multicinctus phospholipase A(2) (PLA(2)) enzymes. Sphingomyelin inhibited enzymatic activity and membrane-damaging activity of PLA(2) against egg yolk phosphatidylcholine (EYPC), while cholesterol and cholesterol sulfate abrogated the inhibitory effect of sphingomyelin. The ability of cholesterol and cholesterol sulfate to abolish the inhibitory effect of sphingomyelin was closely related to their capacity to induce domain formation in EYPC/sphingomyelin vesicles. Laurdan fluorescence measurement revealed that membrane packing of EYPC/sphingomyelin vesicles was differently affected by cholesterol and cholesterol sulfate. Unlike cholesterol, cholesterol sulfate was unable to promote domain formation in dipalmitoylphosphatidylcholine (DPPC) vesicles. Cholesterol increased but cholesterol sulfate reduced PLA(2) activity against DPPC. Self-quenching studies and ...

International Science & Technology Center (ISTC)

Bilayer Lipid Membrane Supported Novel Photoelectrochemical Converter for Light Trapping

International Nuclear Information System (INIS)

The rates of spontaneous interbilayer and transbilayer exchange of ["3H]dimyristoylphosphatidylcholine (["3H]DMPC) were examined in the DMPC and DMPC/dimyristoylphosphatidylethanolamine (DMPE) large unilamellar vesicles in the liquid-crystalline-, gel-, and mixed-phase states. DMPC desorption rates from either gel or liquid-crystalline phases containing DMPE are very similar to the corresponding rates from pure DMPC gel or liquid-crystalline phases. The authors proposed that the DMPC/DSPC behavior results from packing defects in gel phases composed of both DMPC and DSPC molecules because of the four-carbon difference in the acyl chain lengths of the two species. The present results strongly support this hypothesis because no such anomalous behavior is observed in DMPC/DMPE, which is similar to DMPC/DSPC in phase behavior but does not have the chain length difference. These results are not consistent with lipid headgroup dehydration as the major energetic barrier to flip-flop but rather ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

This work showed the formation of phospholipid vesicle coating on inorganic sericite surface with characterization by combining electron microscopy of FE-SEM, TEM, AFM, and qualitatively evaluated the coated phospholipid vesicle by XPS as a function of etching time. The possibility of phospholipid vesicle mobility on the surface was restrained by the chelation effect of magnesium cation. The stabilization properties of phospholipid vesicles on sericite surface were demonstrated by the various concentration of magnesium cation. The presence of magnesium was found to have a much more pronounced influence on the lipid deposition process. The Mg cation plays an important role for attaching the phospholipids with optimum concentration of 7 mM. Totally, the phospholipid vesicles coating on inorganic powder could be useful for bio-related fields such as cosmetics and ...

UK PubMed Central (United Kingdom)

This neutron reflectometry study evaluates the structures resulting from different methods of preparing polymer-cushioned lipid bilayers. Four different techniques to deposit a dimyristoylphosphatidylcholine...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ...

UK PubMed Central (United Kingdom)

A remarkable aspect of the interaction of Cryptococcus neoformans with mammalian hosts is a consistent increase in capsule volume. Given...Full Text Available

International Nuclear Information System (INIS)

English 2008 p. 216 Poland Zalewski, K. Nitkiewicz, B. Department of

International Nuclear Information System (INIS)

Phospholipid vesicles were found to be lysed by exposure to free radicals derived from irradiated glycine and galactose. The decomposition yield increased with vesicle concentration, and attained values of 0.0006 vesicles destroyed per radical added. Ionic charge at the phospholipid end groups was found to be more important than degree of unsaturation in determining this yield. Radicals derived from irradiated serine and alanine had no detectable lytic action at the vesicle concentrations tested.

Energy Technology Data Exchange (ETDEWEB)

A widely used veterinary antibiotic, tetracycline (TC), has been incorporated in Langmuir-Blodgett (LB) films of dipalmitoylphosphatidic acid (DPPA) by means of two different procedures: co-transfer and incubation in solution. The resulting structures were characterized by means of contact angle and ellipsometric measurements. The presence of the antibiotic in the phospholipid film was evidenced by means of UV-Vis electronic absorption and infrared vibrational spectroscopy. The two sets of measurements unambiguously indicated the presence of the drug in the LB layer films obtained with both methods, although incubation led to a smaller content of immobilized tetracycline. In both cases, the drug was found to reside in the hydrophilic portion of the layers due to specific interactions of the dimethylamino group of the molecule with the polar head groups of the phospholipid.

UK PubMed Central (United Kingdom)

Sphingomyelin (SM) is an abundant phospholipid in cell membranes and in lipoproteins. In human plasma, SM is mainly found in atherogenic lipoproteins; therefore, higher levels of SM may promote atherogenesis....Full Text Available

UK PubMed Central (United Kingdom)

Mitochondria must uptake some phospholipids from the endoplasmic reticulum (ER) for the biogenesis of their membranes. They convert one of these lipids, phosphatidylserine, to phosphatidylethanolamine,...Full Text Available

UK PubMed Central (United Kingdom)

Natural abundance 13C solid-state nuclear magnetic resonance spectroscopy was used to investigate the effect of the incorporation of cholesterol on the dynamics of dimyristoylphosphatidylcholine (DMPC)...Full Text Available

UK PubMed Central (United Kingdom)

The binding of amphiphilic molecules to lipid bilayers is followed by ¹⁹F NMR using chemical shift and line shape differences between the solution and membrane-tethered states of...Full Text Available

UK PubMed Central (United Kingdom)

The interaction of β-cyclodextrin (β-CD) with mixed bilayers composed of sphingomylein and cholesterol (Chol) above and below the accepted stable complexation...Full Text Available

International Nuclear Information System (INIS)

For spintronic applications it is important to establish how efficiently spins can be injected from a magnetic material into a non-magnetic material and the distance over which those spins survive. It is thought that spin polarised transport current can be determined by using the suppression of the Andreev reflection between a superconductor and the spin polarised material (Science 282 (1998) 85). Cu/Co bilayers are potentially an ideal test system for such study. In this paper we assess the feasibility of using point contact Andreev reflection spectroscopy to address this problem using a superconducting niobium tip at 4.2 K.

British Library Electronic Table of Contents (United Kingdom)

This study describes the role of "inflammatory" oxidized (Ox) phospholipids in regulation of rahU (PA0122) expression and biofilm formation in Pseudomonas aeruginosa (383) wild type (rahU+) and rahU mutant (rahU-) strains. Functional analysis of RahU protein from P. aeruginosa in presence of Ox-phospholipids show: (a) LysoPC modulates RahU gene/and protein expression in rahU+ cells; (b) rahU promoter activity is increased by lysoPC and inhibited by PAPC, Ox-PAPC and arachidonic acid; the latter inhibitory effect can be reversed by lysoPC, which was enzymatically derived from PAPC; (c) biofilm formation increased in rahU- cells as compared to rahU+; and (d) inhibition of rahU promoter activity by PAPC and AA (but not lysoPC) showed significantly augmented biofilm formation in rahU+ but not ...

UK PubMed Central (United Kingdom)

Most antibodies to factor VIII have recently been shown to react with discrete regions of the factor VIII light chain (within the C2 domain) and/or the factor VIII heavy chain (within the amino-terminal...Full Text Available

CERN Document Server

Small angle neutron scattering (SANS) on the unilamellar vesicle populations (diameter 500 and 1000 angstrom) was used to characterize lipid vesicles from dimyristoylphosphatidylcholine (DMPC) at three phases (gel, ripple, and liquid). Parameters of vesicle populations and internal structure of the DMPC bilayer were characterized on the basis of the Separated Form Factor (SFF) model. Parameters of the internal bilayer structure (thickness of the membrane and the hydrophobic core, hydration, and surface area of lipid molecule) were determined on the basis of the Hydrophobic-Hydrophilic (HH) approximation of neutron scattering length density across the bilayer r(x) and of the Step Function (SF) approximation of r(x). It was demonstrated in frame of HH approximation that DMPC membrane thickness in liquid phase (T=30 degrees) depends on the membrane curvature. The dependence of the DMPC membrane thickness on temperature was ...

British Library Electronic Table of Contents (United Kingdom)

The physicochemical properties of binary lipid mixtures of diether C25,25 lipids and dipalmitoyl-L-a-phosphatidylcholine (DPPC) were studied using photon correlation, fluorescence and electron paramagnetic resonance spectroscopy, and transmission electron microscopy. These two types of lipids can be mixed at all molar ratios to form unilamellar and multilamellar liposomes. Fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatrien in mixed liposomes indicates that the abrupt changes in order parameter in the hydrophobic part of bilayer membranes made of DPPC lipids disappears with increasing mol%C25,25 lipids. Electron paramagnetic resonance spectroscopy shows that at temperatures below 50^oC, the interfacial regions of membrane bilayer of mixed liposomes is more fluid than for pure DPPC lipo...

Science.gov (United States)

This study addresses the modeling of transdermal diffusion of drugs, to better understand the permeation of molecules through the skin, and especially the stratum corneum, which forms the main permeation barrier of the skin. In transdermal delivery of systemic drugs, the drugs diffuse from a patch placed on the skin through the epidermis to the underlying blood vessels. The epidermis is the outermost layer of the skin and can be further divided into the stratum corneum (SC) and the viable epidermis layers. The SC consists of keratinous cells (corneocytes) embedded in the lipid multi-bilayers of the intercellular space. It is widely accepted that the barrier properties of the skin mostly arises from the ordered structure of the lipid bilayers. The diffusion path, at least for lipophilic molecules, seems to be mainly through the lipid bilayers. Despite the advantages of transdermal drug delivery compared to other drug ...

Energy Technology Data Exchange (ETDEWEB)

A) diffuse bilayer, B) spontaneously formed multilayer, and C) vertically homogenous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Energy Technology Data Exchange (ETDEWEB)

This study was undertaken to determine if a combined treatment (marinating in natural plant extracts or vacuum) with irradiation could have a synergistic effect, in order to prevent the lipid oxidation resulting in the development of undesirable flavours. The fresh chicken legs were irradiated at 0,3 and 5 kGy. The fatty acids composition of lipids was identified using gas liquid chromatography. The effect of irradiation treatment combined with a pre-treatment on the fatty acids composition was followed. The day after irradiation, ten panallists were asked to evaluate, using the instruction scaling, the overall appearance, the odor, the flavor and the overall acceptability of the samples. The major fatty acids identified in lipids were oleic acid, palmitic acid, palmitoleic acid and stearic acid. Pre-treatments have a significant effect on linoleic acid (C18:2) and higher fatty acids. The unsaturated fatty acids derived from phospholipids appeared to be more ...

Energy Technology Data Exchange (ETDEWEB)

An open bilayer ground-crew chemical defense ensemble (CDE) was proposed to reduce the thermal burden during vapor-only exposure periods. This study compared the thermal-stress profile of the proposed ensemble to that produced by the currently employed closed CDE. Four subjects, alternating ensembles on separate days, walked on a treadmill in an environmental chamber at 5.3 km/h (3.3 mph) and 2% grade (an energy expenditure of 350 kcal/h) for alternating work/rest to achieve significant recovery. Mean total sweat production was lower (1.38 vs. 2.50 liters) and percent sweat evaporation greater (65.7% vs. 30.0%) in the prototype ensemble than in the CDE. The prototype ensemble provided greater heat dissipation and allowed more-efficient sweat evaporation which had the double benefit of reducing heat storage and limiting dehydration.

Energy Technology Data Exchange (ETDEWEB)

This project has received DOE support since July 1, 1978. During this period, 40 papers have been published dealing predominantly with chlorophyll-photosensitized electron transfer reactions in a variety of media (solutions, polymer films, lipid bilayer membranes). The overall theme of this work has been to develop mechanistic strategies f or photochemical energy storage via chlorophyll, using the green plant photosynthetic system as a paradigm for designing in vitro systems. Microheterogeneous lipid vesicle suspensions allow ready application of time-resolved optical spectroscopy to follow the course of light-induced electron transfer processes. Both the yields and the lifetimes of electron transfer products were markedly improved in the vesicle systems. In subsequent studies, this compartmentalization was favorably manipulated by controlling the electrical charge on the membrane surface, by controlling the solubility properties of the acceptors, by varying the ...

Energy Technology Data Exchange (ETDEWEB)

Samples of 100Cr6 steel were treated by different ion beams in order to study the evolution of their tribological properties. A strong correlation was found between the amount of surface carbon, whatever its origin (contamination, direct C implantation or ion-beam mixing of a deposited carbon layer), and the reduction of the friction coefficient as well as the improvement of the wear resistance. These results are discussed in the framework of a recent statistical model founded on the asperity concept and describing the tribological behaviour of bilayer systems.

CERN Document Server

Spatial Fluorescence Cross Correlation Spectroscopy is a rarely investigated version of Fluorescence Correlation Spectroscopy, in which the fluorescence signals from differ-ent observation volumes are cross-correlated. In the reported experiments, two observation volumes, typically shifted by a few $\\mu$m, are produced, with a Spatial Light Modulator and two adjustable pinholes. We illustrated the feasibility and potentiality of this technique by: i) measuring molecular flows, in the range 0.2 - 1.5 $\\mu$m/ms, of solutions seeded with fluorescent nanobeads or rhodamine molecules (simulating active transport phenomenons); ii) investigating the perme-ability of phospholipidic membrane of Giant Unilamellar Vesicles versus hydrophilic or hydrophobic molecules (in that case the laser spots were set on both sides of the mem-brane). Theoretical descriptions are proposed together with a discussion about FCS based, alternative methods.

British Library Electronic Table of Contents (United Kingdom)

Ozone has in recent years been increasingly investigated for its potential use in the control of insect pests of stored cereals. Ozone is a powerful oxidizing agent that can react directly, or via production of reactive oxygen species, with proteins, DNA and double bonds of polyunsaturated fatty acids (PUFA). The aim of the present study was to investigate the mode of action in ozone toxicity using the red flour beetle, Tribolium castaneum (Herbst), as a relevant model. Transcription of focal genes thought to be involved in protection against ozone, and repair of cellular damage caused by ozone exposure, was studied together with the composition of storage lipid fatty acids and membrane phospholipid fatty acids in order to detect lipid peroxidation. Contrary to expectations, transcription ...

International Nuclear Information System (INIS)

High quality "3"1P MR spectra (signal to noise ratio (S/N) approximately 18, 15 min acquisition for each spectrum) were consistently obtained with surface coils over a period of 6-week RT. Both transient and steady state alterations in metabolites in response to RT were found in this case. The transient changes occurred during the first 3 hr immediately after the 3rd fractionated RT, these changes include the transient elevation of the PCr resonance, a decrease in PDE and an increase in intracellular pH. The monitoring showed that the metabolites approached steady state approximately 2 hr after the fractionated radiation intervention, suggesting that in vivo MRS can be useful for studying the dynamics of tumor response to RT such as repair of potential lethal damage, growth delay, and reoxygenation etc. The steady-state MR spectra showed the net response to each intervention and can clinically be useful for predicting and measuring the result of the fractionated RT. In this case study, ...

British Library Electronic Table of Contents (United Kingdom)

We report the fabrication and characterization of glucose-tolerant Raney-platinum cathodes for oxygen reduction in potentially implantable glucose fuel. Fabricated by extraction of aluminum from 1mm thin platinum-aluminum bi-layers annealed at 300^oC, the novel cathodes show excellent resistance against hydrolytic and oxidative attack. This renders them superior over previous cathodes fabricated from hydrogel-bound catalyst particles. Annealing times of 60, 120, and 240min result in approximately 400-550nm thin porous films (roughness factors ~100-150), which contain platinum and aluminum in a ratio of ~9:1. Aluminum release during electrode operation can be expected to have no significant effect on physiological normal levels, which promises good biocompatibility. Annealing time has a dis...

Energy Technology Data Exchange (ETDEWEB)

A polarized neutron reflectometry study of the magnetization density depth profile of a Co{sub 0.1}Pt{sub 0.9}-CoPt{sub 3} bilayer film found evidence for an induced moment in the Co{sub 0.1}Pt{sup 0.9} overlayer in close proximity to the CoPt{sub 3} underlayer. If the moment of Co in these films is that of the bulk, then the {mu}{sub Pt} = 0.09(1){mu}{sub B} in the overlayer, and {mu}{sub Pt} = 0.04(1){mu}{sub B} in the underlayer. In addition, ferromagnetic order of the Co{sub 0.1}Pt{sub 0.9} overlayer was observed 8K above {Tc} for the material in the bulk.

British Library Electronic Table of Contents (United Kingdom)

Biodegradable helicoidal stent prototypes made up of layers of poly-L-lactic acid (PLLA) and poly(L-lactic-co-glycolic acid) (PLGA) polymers were fabricated by temperature conditioning the stents at different stages of fabrication. The process incorporated elastic memory, or self-expandability in the stent, which is desirable to minimize stent recoil. The collapse pressures of such stents were studied, with and without in vitro degradation. The effects of thickness and the composition of each layer on the collapse pressure were modeled using the simple series model. Results of the in vitro studies for over 3 months showed that collapse pressure of the stents depended mainly on the degradation and other side-effects brought about by the degradation of different polymer compositions. General...

DEFF Research Database (Denmark)

Interest in optics for hard X-ray broad-band application is growing. In this paper, we compare the hard X-ray (20-100 keV) reflectivity obtained with an energy-dispersive reflectometer, of a standard commercial gold thin-film with that of a 600 bilayer W/Si X-ray supermirror. The reflectivity of the multilayer is found to agree extraordinarily well with theory (assuming an interface roughness of 4.5 Angstrom), while the agreement for the gold film is less, The overall performance of the supermirror is superior to that of gold, extending the band of reflection at least a factor of 2.8 beyond that of the gold, Various other design options are discussed, and we conclude that continued interest in the X-ray supermirror for broad-band hard X-ray applications is warranted.

Energy Technology Data Exchange (ETDEWEB)

The role of intermediate products of dioxygen reduction in cytotoxic effects ascribed to oxygen molecules was studied in vivo using various yeast mutants with changed response to oxygen stress. It has been documented that superoxide radical exerts its deleterious effects on yeast cells directly and the role of other oxygen species derived from it is hardly detectable. Yeast Saccharomyces cerevisiae, however, cannot be considered as a typical eukaryotic organism due to its inability of synthesizing polyunsaturated fatty acids (pufa). These fatty acids are known as main target molecules during oxidative stress and their peroxidation leads to cytotoxic effects. As fatty acid content could be easily manipulated in yeast, this organism was used to evaluate the contribution of pufa peroxidation process to the cytotoxic effects of oxygen. Results obtained show, that yeast cells containing linolenic acid as the main constituent of phospholipids are hypersensitive to oxygen ...

Energy Technology Data Exchange (ETDEWEB)

Purified protein kinase C (C-kinase) from guinea pig pancreas and rat brain stimulated adenylate cyclase activity in purified rat adipocyte membranes. Cyclase stimulation occurred over 100 to 1000 mU/ml of C-kinase activity, required greater than 10 ..mu..M calcium, proceeded without a lag, was not readily reversible, and required no exogenous phospholipid. Moreover, C-kinase inhibitors, such as chlorpromazine and palmitoyl carnitine, inhibited selectively adenylate cyclase which was activated by C-kinase and calcium. Depending on assay conditions, 10 nM 12-0-tetradecanoylphorbol-13-acetate (TPA) either enhanced or was required for kinase action on cyclase. Also, TPA plus calcium promoted the quantitative association of C-kinase with membranes. Adenylate cyclase activation by C-kinase was seen both in the presence and absence of exogenous GTP, indicating that the kinase effect does not result from an action on the GTP-binding, inhibitory regulatory component (N/sub ...

International Nuclear Information System (INIS)

Austenitic stainless steels have been implanted with molybdenum ions (Mo"+, 100 keV, 2.5 x 10"1"6 atoms cm"-"2). The implanted material has been characterized by XPS and RBS. The implanted region has a thickness of #approx# 1000 A with a maximum molybdenum concentration of #approx# 9 at.% Mo located at #approx# 210 A from the surface. The effects of implanted molybdenum on the passivation of the alloy in 0.5 M H_2SO_4 have been investigated by electrochemistry and XPS. After XPS analysis the samples were transferred without exposure to air into a glove-box with an inert atmosphere. The electrochemical behaviour of the alloy is significantly modified by the implanted molybdenum. The major effect is that the activation peak disappears. A bilayer structure (outer hydroxide/inner oxide) of the passive film is observed for both the implanted and non-implanted alloys and the thicknesses of the films are similar. On the implanted alloy the outer hydroxide layer contains ...

Scientific Electronic Library Online (English)

Abstract in english The tegument surface of the adult schistosome, bounded by a normal plasma membrane overlain by a secreted membranocalyx, holds the key to understanding how schistosomes evade host immune responses. Recent advances in mass spectrometry (MS), and the sequencing of the Schistosoma mansoni transcriptome/genome, have facilitated schistosome proteomics. We detached the tegument from the worm body and enriched its surface membranes by differential extraction, before subjecting t (more) he preparation to liquid chromatography-based proteomics to identify its constituents. The most exposed proteins on live worms were labelled with impearmeant biotinylation reagents, and we also developed methods to isolate the membranocalyx for analysis. We identified transporters for sugars, amino acids, inorganic ions and water, which confirm the importance of the tegument plasma membrane in nutrient acquisition and solute balance. Enzymes, including phosphohydrolases, esterases and ...

Energy Technology Data Exchange (ETDEWEB)

Thin Fe and Ta layers of 30-45 nm thickness, deposited via magnetron sputtering on Si (1 0 0) substrates, were bombarded at room temperature with 100 keV Ar{sup 1+} or Ar{sup 8+} or with 250 keV Xe{sup 1+} or Xe{sup 19+} ions in order to test the influence of the ion charge state on the surface sputtering and interface mixing. The samples were characterized by means of Rutherford backscattering at 0.9-3.0 MeV {alpha}-particle energy, time-of-flight elastic recoil detection analysis with a 53 MeV {sup 127}I{sup 10+} beam and atomic force microscopy. No influence of the charge state on the sputtering and athermal mixing rate was observed in the case of the Ta/Si system. However, in the case of the Fe/Si system, the ion charge was observed to have an influence on the mixing rate.

Energy Technology Data Exchange (ETDEWEB)

The sequence of nitride formation during the early stages of plasma nitriding of pure iron was studied by optical microscopy, SEM, TEM and x-ray diffraction. Plasma nitriding at {approximately}490 C in a 25 vol.%H{sub 2} + 75 vol.%N{sub 2} mixture starts with the formation of {gamma}{prime}-Fe{sub 4}N after 40s. Once {gamma}{prime} nucleates, it mainly spreads laterally due to diffusion shortcuts in the discontinuous surface nitride layer. Before {gamma}{prime} is continuous on the surface, {epsilon} nucleates on top of it shortly after 40S. Epsilon is then observed to grow, both inwardly and laterally along with {gamma}{prime}. A compact {gamma}{prime}/{epsilon} bilayer forms on the surface at around 100s. The kinetics of nucleation, growth and compactation of the nitrides observed in the present work was significantly more rapid than in any of the nitriding process reported in the literature, including plasma nitriding. The acceleration of the nitriding kinetics ...

International Nuclear Information System (INIS)

The electrochemical behaviour of passive films formed on one austenitic stainless steel (AISI 304) and one ferritic stainless steel (AISI 446) in solutions with pH between 0.6 and 8.4 was studied by capacitance measurements and photocurrent spectroscopy. Compositional characterization of the passive films was done by X-ray photoelectron spectroscopy. The capacitance increases with decreasing pH. Doping densities evaluated from Mott-Schottky plots are in the range 2-6 x 10"2"0 cm"-"3 and increased with the pH in the neutral/alkaline range while in pH 0.6, values above 10"2"1 cm"-"3 were found. The bandgap energy indicates two transitions, at 2.5-2.8 and 3.2 eV. The analytical data reveal that, as the pH increased, the films become enriched in Fe(II) and Fe(III), whereas the Cr(III) gradually decreases. The films formed at very low pH had a behaviour that contrasts with that of the films formed in the neutral/alkaline media. The films are described by a bilayer ...

Energy Technology Data Exchange (ETDEWEB)

Orientational constraints obtained from solid state NMR experiments on anisotropic samples are used here in molecular dynamics (MD) simulations for determining the structure and dynamics of several different membrane-bound molecules. The new MD technique is based on the inclusion of orientation dependent pseudo-forces in the COSMOS-NMR force field. These forces drive molecular rotations and re-orientations in the simulation, such that the motional time-averages of the tensorial NMR properties approach the experimentally measured parameters. The orientational-constraint-driven MD simulations are universally applicable to all NMR interaction tensors, such as chemical shifts, dipolar couplings and quadrupolar interactions. The strategy does not depend on the initial choice of coordinates, and is in principle suitable for any flexible molecule. To test the method on three systems of increasing complexity, we used as constraints some deuterium quadrupolar couplings from the literature on ...

Energy Technology Data Exchange (ETDEWEB)

Small unilamellar vesicles which form when gel-state long-chain phosphatidylcholines are mixed with micellar short-chain lecithins undergo an increase in size as the long-chain species melts to its liquid-crystalline form. Analysis of the vesicle population with quasi-elastic light scattering shows that the particle size increases from 90-A radius to greater than 5000-A radius. Resonance energy transfer experiments show total mixing of lipid probes with unlabeled vesicles only when the Tm of the long-chain phosphatidylcholine is exceeded. This implies that the large size change represents a fusion process. Aqueous compartments are also mixed during this transition. 31P NMR analysis of the vesicle mixtures above the phase transition shows a great degree of heterogeneity with large unilamellar particles coexisting with oligo- and multilamellar structures. Upon cooling the vesicles below the Tm, the original size distribution (e.g., small unilamellar vesicles) is obtained, as monitored by ...

International Nuclear Information System (INIS)

Many hormones elicit effects on target cells by stimulating the enzyme phospholipase-C, which catalyzes the hydrolysis of phosphoinositides to the intracellular second messengers diacylglycerol and inositol phosphates. The present study examined the roles of FSH and guanine nucleotide-binding proteins (G-proteins) in regulating the hydrolysis of phosphoinositides in Sertoli cells. Sertoli cell cultures prepared from 16- to 18-day-old rats were incubated for 24 h with myo-[2-3H] inositol to label endogenous phospholipids. Treatment of cells from 0.5-20 min with preparations of ovine FSH ranging in potency from 1-60 times that of NIH FSH S1 did not affect accumulation of inositol phosphates. Levels of total [3H]inositol phosphates [[3H]inositol mono-, di-, and triphosphates (IP, IP2, and IP3)] in FSH-treated cultures was 75-120% the levels in control cultures over the various time intervals studied. Addition of testosterone and the combination of testosterone plus ...

Energy Technology Data Exchange (ETDEWEB)

Microorganisms associated with fractured basalt core were compared to those suspended in groundwater pumped from the same well in the eastern Snake River Plain Aquifer (Idaho, USA). Two wells influenced to different degrees by a mixed-waste plume in the fractured basalt aquifer were examined. In one well, an array of dialysis cells filled with either deionized water or crushed basalt was equilibrated to compare the microorganisms collected in this fashion with those from core and groundwater samples collected in a traditional manner from the same well. Analyses were performed to characterize these samples and to provide a basis for comparison. These included total cell counts by microscopy; total biomass by phospholipid fatty acid analysis; enumerations of viable aerobic heterotrophs, groups of putative aerobic co-metabolic TCE-degraders and aerobic H2-oxidizing bacteria; mineralization of 14C- labeled acetate; and enrichments for dissimilatory iron-reducing ...

Science.gov (United States)

Cardiac contractile function is dependent on the integrity and function of the sarcolemmal membrane. Swimming exercise training is known to increase cardiac contractile performance. The purpose of the present study was to examine whether a swimming exercise program would alter sarcolemmal enzyme activity, ion flux, and composition in rat hearts. After approximately 11 wk of exercise training, cardiac myosin and actomyosin Ca2+-adenosinetriphosphatase (ATPase) activity was significantly higher in exercised rat hearts than in sedentary control rat hearts. Glycogen content was increased in plantaris and gastrocnemius muscles from exercised animals as was succinic dehydrogenase activity in gastrocnemius muscle of exercised rats in comparison to sedentary rat preparations. Sarcolemmal vesicles were isolated from hearts of exercise-trained and control rats. Sarcolemmal Na+-K+-ATPase and K+-p-nitrophenylphosphatase activities, Na+-Ca2+ exchange, and passive Ca2+ binding did not differ between ...

International Nuclear Information System (INIS)

Austenitic stainless steels (304-type) have been implanted with nitrogen ions in order to investigate the effects of implanted nitrogen on their electrochemical behaviour and on the nature of the passive film formed on the steels in acid (0.5M H_2SO_4). Alloys with two nitrogen doses have been prepared (2.5x10"1"6 and 2x10"1"7 N atoms/cm"2). The implanted alloys have been characterized by "1"5N-NRA (nuclear reaction analysis) and XPS (X-ray photoelectron spectroscopy). Alloy surfaces with well-defined N concentrations were prepared, prior to the electrochemical measurements, by argon-ion sputtering of the implanted material for a fixed time in order to reach a well-defined point on the nitrogen depth profile. The samples were then transferred without exposure to air to an electrochemical cell mounted in an inert gas glove box. The implanted nitrogen modifies the electrochemical behaviour of the alloy. The anodic dissolution in the active state is enhanced, and the current density in ...

Energy Technology Data Exchange (ETDEWEB)

A mesoscopically ordered lamellar gel phase of a polymer-grafted, lipid-based complex fluid is used as a scaffolding to spatially organize inorganic nanoparticles. The complex fluid provides both a highly anisotropic environment and a segregated aqueous and organic domains in which inorganic nanoparticles can be selectively placed by tailoring their size and surface characteristics. Three types of silver nanoparticles -- underivatized, surfactant-stabilized, and dodecanthiol-derivatized -- were evaluated. Comparison of the surface plasmon resonance of the various silver particles dispersed in conventional solvents to those contained within the complex fluid was used to determine the region of spatial localization in the lamellar gel phase. Silver particles rendered hydrophobic by capping with an alkane thiol insert into the hydrocarbon bilayer region. Surfactant-stabilized and underivatized silver nanoparticles reside in the aqueous channels, with the latter ...

International Nuclear Information System (INIS)

The potentiodynamic polarization measurement of 254SMO stainless steel (UNS 31254) was conducted in 3.5% NaCl solutions with pH ranging from 0.1 to 5. The results indicated that this stainless steel offered excellent pitting corrosion resistance in corrosive environments. Further, it also exhibited various features on the polarization curves in different pH solutions. The electrochemical constant-potential passivation treatment performed at different pH followed by XPS analysis revealed that the primary constituents of the outermost layer of the passive films formed in the weak (pH 5) and strong (pH 0.8) acid solutions are iron oxides and Cr_2O_3 and Cr(OH)_3, respectively. Molybdenum oxides, primarily in the six-valence state, existed in the outermost layer of the passive film. Only very weak signals corresponding to that of nickel oxides were detected in the film formed in the weak acid (pH 5) solution. The ICP-MS analyses indicated selective dissolution of a significant amount of Fe ...

Energy Technology Data Exchange (ETDEWEB)

Passive films were formed on chromium by polarization at +400 mV/SHE in 0.5 M H{sub 2}SO{sub 4} for different times (30 minutes, 2 hours and 20 hours) without and with chlorides. The effect of chlorides was studied by adding NaCl to the solution before or after passivation. The chloride concentrations were 0.05, 0.3 and 1 M. The (i-E) curves recorded for Cr without and with Cl{sup -} are similar and the addition of chlorides after passivation has no significant effect on the current recorded in the passive state. The passive films were analyzed by angle-resolved XPS (AR-XPS). The measurements performed at different take-off angles of the photoelectrons show that the films have a bilayer structure constituted of an outer hydroxide layer, Cr(OH){sub 3}, and an inner oxide layer, Cr{sub 2}O{sub 3}. The thicknesses of the oxide and hydroxide layers are 3 A and 9 A, 6 A and 7 A and 6 A and 6 A for the films formed in 0.5 M H{sub 2}SO{sub 4} after 30 minutes, 2 hours and ...