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Sample records for bilayer hydrocarbon core

  1. Lateral diffusion of peripheral membrane proteins on supported lipid bilayers is controlled by the additive frictional drags of (1) bound lipids and (2) protein domains penetrating into the bilayer hydrocarbon core.

    Science.gov (United States)

    Ziemba, Brian P; Falke, Joseph J

    2013-01-01

    Peripheral membrane proteins bound to lipids on bilayer surfaces play central roles in a wide array of cellular processes, including many signaling pathways. These proteins diffuse in the plane of the bilayer and often undergo complex reactions involving the binding of regulatory and substrate lipids and proteins they encounter during their 2D diffusion. Some peripheral proteins, for example pleckstrin homology (PH) domains, dock to the bilayer in a relatively shallow position with little penetration into the bilayer. Other peripheral proteins exhibit more complex bilayer contacts, for example classical protein kinase C isoforms (PKCs) bind as many as six lipids in stepwise fashion, resulting in the penetration of three PKC domains (C1A, C1B, C2) into the bilayer headgroup and hydrocarbon regions. A molecular understanding of the molecular features that control the diffusion speeds of proteins bound to supported bilayers would enable key molecular information to be extracted from experimental diffusion constants, revealing protein-lipid and protein-bilayer interactions difficult to study by other methods. The present study investigates a range of 11 different peripheral protein constructs comprised by 1-3 distinct domains (PH, C1A, C1B, C2, anti-lipid antibody). By combining these constructs with various combinations of target lipids, the study measures 2D diffusion constants on supported bilayers for 17 different protein-lipid complexes. The resulting experimental diffusion constants, together with the known membrane interaction parameters of each complex, are used to analyze the molecular features correlated with diffusional slowing and bilayer friction. The findings show that both (1) individual bound lipids and (2) individual protein domains that penetrate into the hydrocarbon core make additive contributions to the friction against the bilayer, thereby defining the 2D diffusion constant. An empirical formula is developed that accurately estimates the diffusion

  2. Hydrocarbon chain conformation in an intercalated surfactant monolayer and bilayer

    Indian Academy of Sciences (India)

    N V Venkataraman; S Vasudevan

    2001-10-01

    Cetyl trimethyl ammonium (CTA) ions have been confined within galleries of layered CdPS3 at two different grafting densities. Low grafting densities are obtained on direct intercalation of CTA ions into CdPS3 to give Cd0.93PS3(CTA)0.14. Intercalation occurs with a lattice expansion of 4.8 Å with the interlamellar surfactant ion lying flat forming a monolayer. Intercalation at higher grafting densities was effected by a two-step ion-exchange process to give Cd0.83PS3(CTA)0.34, with a lattice expansion of 26.5 Å. At higher grafting densities the interlamellar surfactant ions adopt a tilted bilayer structure. 13C NMR and orientation-dependent IR vibrational spectroscopy on single crystals have been used to probe the conformation and orientation of the methylene ‘tail’ of the intercalated surfactant in the two phases. In the monolayer phase, the confined methylene chain adopts an essentially all-trans conformation with most of the trans chain aligned parallel to the gallery walls. On lowering the temperature, molecular plane aligns parallel, so that the methylene chain lies flat, rigid and aligned to the confining surface. In the bilayer phase, most bonds in the methylene chain are in trans conformation. It is possible to identify specific conformational sequences containing a gauche bond, in the interior and termini of the intercalated methylene. These high energy conformers disappear on cooling leaving all fifteen methylene units of the intercalated cetyl trimethyl ammonium ion in trans conformational registry at 40 K.

  3. High-resolution sedimentary record of hydrocarbon contaminants in a core from the major reaches of the Pearl River, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The concentrations and compositions of hydrocarbon contaminants, and molecularmarker indices in modern sediments from a core in the major reaches of the Pearl River were investigated. The sedimentary record of hydrocarbons in the core, in combination with 210pb-dating,was used to reconstruct the pollution history of hydrocarbon pollutants in the Pearl River in the past 100 years.

  4. Characterization of hydrocarbon emissions from green sand foundry core binders by analytical pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Yujue Wang; Fred S. Cannon; Magda Salama; Jeff Goudzwaard; James C. Furness [Pennsylvania State University, University Park, PA (United States). Department of Civil and Environmental Engineering

    2007-11-15

    Analytical pyrolysis was conducted to compare the hydrocarbon and greenhouse gas emissions of three foundry sand binders: (a) conventional phenolic urethane resin, (b) biodiesel phenolic urethane resin, and (c) collagen-based binder. These binders are used in the metal casting industry to create internal cavities within castings. Green sand contains silica sand, clay, carbonaceous additives (eg bituminous coal) and water. The core samples were flash pyrolyzed in a Curie-point pyrolyzer at 920{sup o}C with a heating rate of about 3000{sup o}C/sec. This simulated some key features of the fast heating conditions that the core binders would experience at the metal-core interface when molten metal is poured into green sand molds. The core samples were also pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temperature to 1000{sup o}C with a heating rate of 30{sup o}C/min, and this simulated key features of the slow heating conditions that the core binders would experience at distances that are further away from the metal-core interface during casting cooling. Hydrocarbon emissions from flash pyrolysis were analyzed with a gas chromatography-flame ionization detector, while hydrocarbon and greenhouse gas emissions from TGA pyrolysis were monitored with mass spectrometry. The prominent hazardous air pollutant emissions during pyrolysis of the three binders were phenol, cresols, benzene, and toluene for the conventional phenolic urethane resin and biodiesel resin, and benzene and toluene for the collagen-based binder. Bench-scale analytical pyrolysis techniques could be a useful screening tool for the foundries to compare the relative emissions of alternative core binders and to choose proper materials in order to comply with air-emission regulations. 20 refs., 4 figs., 1 tab.

  5. Historical Profiles of Polycyclic Aromatic Hydrocarbons (PAHs) in Marine Sediment Cores from Northwest Spain.

    Science.gov (United States)

    Pérez-Fernández, Begoña; Viñas, Lucía; Bargiela, Jesica

    2016-11-01

    The northwest coast of Spain is characterized by an irregular coastline rich in marine life and with the highest mussel production in Europe. Taking this into account, the characterization of the pollution levels and the sources involved appear necessary. Not only were parent Polycyclic Aromatic Hydrocarbons (PAHs) analysed but also their alkylated homologues. In total, 35 compounds were analyzed in 5 sediment cores. Sediments were collected using a box core dredge and extracted by (Pressurized Liquid Extraction) whilst the quantification of PAHs was performed using gas chromatography coupled to mass spectrometry (GC-MS). The total concentration detected varied from 49.6 to 2489 ng g(-1) dry weight (d.w.) of which parent PAHs ranged from 44.5 to 2254 ng g(-1) d.w. and alkylated PAHs varied from 5.04 to 317 ng g(-1) d.w. Temporal and spatial evolution were outlined and pollution sources were identified along with a possible correlation between this pollution and local history and industry. Most of the PAHs from the superficial samples have a biomass and coal combustion profile, and some specific, localized events are reflected in the total PAH concentration evolution. Moreover, the study of the deepest layers of the sampled cores provides a baseline to develop background concentration values that will help in future sediment quality assessment.

  6. Molecular Dynamics of a Water-Lipid Bilayer Interface

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

    We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

  7. SHEAR BOND STRENGTHS BETWEEN CERAMIC CORES AND VENEERING CERAMICS OF DENTAL BI-LAYERED CERAMIC SYSTEMS AND THE SENSITIVITY TO THERMOCYCLING

    Directory of Open Access Journals (Sweden)

    SUN TING, BDS, DDS

    2012-09-01

    Full Text Available The purpose of this study was to investigate the bond strength between various commercial ceramic core materials and veneering ceramics of dental bi-layered ceramic combinations and the effect of thermocycling. The shear bond strength of four dental bi-layered ceramic combinations (white Cercon, yellow Cercon, white Lava, yellow Lava, IPS E.max were tested. Metal ceramic combinations were conducted as a control group. Half of each group was subjected to thermocycling. All specimens were thereafter subjected to a shear force. The initial mean shear bond strength values in MPa ± S.D were 28.02 ± 3.04 for White Cercon Base/Cercon Ceram Kiss, 27.54 ± 2.20 for Yellow Cercon Base/Cercon Ceram Kiss, 28.43 ± 2.13for White Lava Frame/Lava Ceram, 27.36 ± 2.25 for Yellow Lava Frame/Lava Ceram, 47.10 ± 3.77 for IPS E.max Press/IPS E.max Ceram and 30.11 ± 2.15 for metal ceramic control. The highest shear strength was recorded for IPS E.max Press/IPS E.max Ceram before and after thermocycling. The mean shear bond strength values of five other combinations were not significantly different (P < 0.05. Lithium-disilicate based combinations produced the highest core-veneer bonds that overwhelmed the metal ceramic combinations. Thermocycling had no effect on the core-veneer bonds. The core-veneer bonds of zirconia based combinations were not weakened by the addition of coloring pigments.

  8. Distribution of trace metals, aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in sediment cores from the Sicily Channel and the gulf of Tunis (south-western Mediterranean Sea).

    Science.gov (United States)

    Mzoughi, Nadia; Chouba, Lassaad

    2011-01-01

    Under the framework of the IAEA's Technical Co-operation project RAF7/004, international research cruises were carried out in 2004 to assess the distribution of radionuclides and micropollutants in the south-western Mediterranean Sea. Sediments samples had variable concentrations of total aliphatic hydrocarbons and polycyclic aromatic hydrocarbons ranging from 0.2 to 1.8 microg g(-1) and 26.9 to 364.4 ng g(-1), respectively, in the Sicily Channel and from 0.7 to 2.8 microg g(-1) and 14.7 to 618.1 ng g(-1), respectively, in the open sea of the Gulf of Tunis. Hydrocarbon concentrations changed with depth and were relatively high at 3 cm and 10 cm depths. The use of 'fingerprint' ratios of certain isomeric pairs of polycyclic aromatic hydrocarbons (PAH) and the proportion of 2-3 ring and 4-5 ring PAH concentrations showed that the main origins are characteristic of petroleum sources. The ranges of trace metal concentrations, expressed in microgg(-1), in the Sicily Channel and in the Gulf of Tunis, respectively, were: Hg 0.009-0.2 and 0.02-0.1; Pb 9.9-26.1 and 21.2-32.5; Cd 0.06-0.1 and 0.07-0.33; Fe 23.7-28.1 and 29.9-36.2p; Zn 83-99.5 and 83-104; Mn 309.2-752.5 and 651-814; Cu 17.1-18.5 and 33.5-51.3. Sediment metal abundances were in the order: Mn > Zn > Fe > Cu > Pb > Cd > Hg. The results showed significant differences (p < 0.001) for trace metal and hydrocarbon mean concentrations between the two cores. These concentrations are generally similar to the background levels from the Mediterranean Sea and could be affected by physico-chemical conditions and sedimentation rate as well as biodegradation.

  9. Aliphatic hydrocarbons in sediment cores from the southern basin of Lake Michigan

    Energy Technology Data Exchange (ETDEWEB)

    Doskey, P.V. [Argonne National Lab., IL (United States). Environmental Research Division; Andren, A.W. [Univ. of Wisconsin, Madison, WI (United States). Water Chemistry Program

    1991-10-01

    Aliphatic hydrocarbons in sediments of the southern basin of Lake Michigan have planktonic, terrigenous, and petroleum residue origins. Surficial sediments collected near the eastern shore in 60-80 m of water contained more petroleum residue and planktonic hydrocarbons and exhibited less terrigenous character than sediments collected from the deepest location in the basin. Petroleum residue inputs have increased since 1900 as evidenced by a change in the flux of an unresolved complex mixture (UCM) of hydrocarbons from 6 ng/cm{sup 2}{center_dot}yr to a flux of approximately 100 ng/cm{sup 2}{center_dot}yr in 1980. Sediment profiles of the UCM exhibited subsurface concentration maxima that may be due to reduced inputs of combustion products or feeding by oligochaetes. Profiles of n-C{sub l7} and pristane indicated that planktonic n-alkanes undergo degradation in the aerobic, mixed zone of the sediments.

  10. Indole Localization in an Explicit Bilayer Revealed via Molecular Dynamics

    Science.gov (United States)

    Norman, Kristen

    2005-11-01

    It is well known that the amino-acid tryptophan is particularly stable in the interfacial region of biological membranes, and this preference is a property of the tryptophan side-chain. Analogues of this side-chain, such as indole, strongly localize in the interfacial region, especially near the glycerol moiety of the lipids in the bilayer. Using molecular dynamics calculations, we determine the potential of mean force (PMF) for indoles in the bilayer. We compare the calculated PMF for indole with that of benzene to show that exclusion from the center of the lipid bilayer does not occur in all aromatics, but is strong in indoles. We find three minima in the PMF. Indole is most stabilized near the glycerol moiety. A weaker binding location is found near the choline groups of the lipid molecules. An even weaker binding side is found near the center of the lipid hydrocarbon core. Comparisions between uncharged, weakly charged, and highly charged indoles demonstrate that the exclusion is caused by the charge distribution on the indole rather than the ``lipo-phobic'' effect. High temperature simulations are used to determine the relative contribution of enthalpy and entropy to indole localization. The orientation of indole is found to be largely charge independent and is a strong function of depth within the bilayer. We find good agreement between simulated SCD order parameters for indole and experimentally determined order parameters.

  11. Cholesterol enhances surface water diffusion of phospholipid bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chi-Yuan; Kausik, Ravinath; Han, Songi, E-mail: songi@chem.ucsb.edu [Department of Chemistry and Biochemistry and Materials Research Laboratory, University of California, Santa Barbara, California 93106 (United States); Olijve, Luuk L. C. [Laboratory of Macromolecular and Organic Chemistry and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Netherlands)

    2014-12-14

    Elucidating the physical effect of cholesterol (Chol) on biological membranes is necessary towards rationalizing their structural and functional role in cell membranes. One of the debated questions is the role of hydration water in Chol-embedding lipid membranes, for which only little direct experimental data are available. Here, we study the hydration dynamics in a series of Chol-rich and depleted bilayer systems using an approach termed {sup 1}H Overhauser dynamic nuclear polarization (ODNP) NMR relaxometry that enables the sensitive and selective determination of water diffusion within 5–10 Å of a nitroxide-based spin label, positioned off the surface of the polar headgroups or within the nonpolar core of lipid membranes. The Chol-rich membrane systems were prepared from mixtures of Chol, dipalmitoyl phosphatidylcholine and/or dioctadecyl phosphatidylcholine lipid that are known to form liquid-ordered, raft-like, domains. Our data reveal that the translational diffusion of local water on the surface and within the hydrocarbon volume of the bilayer is significantly altered, but in opposite directions: accelerated on the membrane surface and dramatically slowed in the bilayer interior with increasing Chol content. Electron paramagnetic resonance (EPR) lineshape analysis shows looser packing of lipid headgroups and concurrently tighter packing in the bilayer core with increasing Chol content, with the effects peaking at lipid compositions reported to form lipid rafts. The complementary capability of ODNP and EPR to site-specifically probe the hydration dynamics and lipid ordering in lipid membrane systems extends the current understanding of how Chol may regulate biological processes. One possible role of Chol is the facilitation of interactions between biological constituents and the lipid membrane through the weakening or disruption of strong hydrogen-bond networks of the surface hydration layers that otherwise exert stronger repulsive forces, as reflected in

  12. Quartz Capillary Cladding Anthracene and Polycyclic Aromatic Hydrocarbon(PAH)-Core Scintillating/WLS Fibers for High Rates and Radiation Damage Resistance

    CERN Document Server

    Albayrak-Yetkin, A; Corso, J; Jennings, G; Mestvirisvilli, A; Onel, Y; Schmidt, I; Sanzeni, C; Winn, D R; Yetkin, T

    2013-01-01

    Quartz capillary tube/fibers have been filled with anthracene by a melt and vacuum inbibition process to fabricate a scintillating core fiber. Other polcyclic aromatic hydrocarbons(PAH), such as p-Terphenyl (pTP), stilbene or naphthalene are also well-suited to scintillating/shifting fiber cores. The resulting scintillating core with quartz cladding capillary fibers (250-750 micron cores) had a high specific light output when tested with muons (8 p.e. per MIP). These PAH core quartz capillary cladding scintillating/shifting optical fibers have the potential of high radiation resistance, fast response, and are applicable to many energy and intensity frontier experiments.

  13. Relationship between polycyclic aromatic hydrocarbons (PAHs) and particle size in dated core sediments in Lake Lianhuan, Northeast China.

    Science.gov (United States)

    Sun, Li; Zang, Shuying

    2013-09-01

    Atmospheric particle associated with pyrogenic polycyclic aromatic hydrocarbons (PAHs) poses serious threats to human health by inhalation exposure, especially in semiarid areas. Hence, the distributions of PAHs and particle size in two core sediments collected from Lake Lianhuan, Northeast China were studied. The sediments were dated radiometrically, and particle size distribution and PAH concentration were evaluated and potential human health risk was assessed. From 1980 to 2007, the dominant PAHs in the two cores were 2- and 3-ring PAHs, and the concentrations of 3-6 ring PAHs gradually increased from the early 1990s. Diagnostic ratios indicated that pyrogenic PAHs were the main sources of PAHs which changed over time from combustions of wood and coal to liquid fossil fuel sources. Fine particles (PAHs (especially carcinogenic 5-6 ring PAHs) and 10-35 μm particulate fractions indicated that eolian particles played an important role in adsorbing pyrogenic PAHs. Petroleum source of PAHs was only identified during the 1980s in one core sediments, in which positive correlations between 2-ring PAHs and particulate fractions of >125 μm were found. Future research should focus on the seven carcinogenic pyrogenic PAHs due to a rapidly increasing trend since 1995 based on the assessment of toxic equivalency factors.

  14. Bilayer-thickness-mediated interactions between integral membrane proteins

    CERN Document Server

    Kahraman, Osman; Klug, William S; Haselwandter, Christoph A

    2016-01-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology al...

  15. Sedimentary record of polycyclic aromatic hydrocarbons in a sediment core from the Pearl River Estuary, South China.

    Science.gov (United States)

    Liu, G Q; Zhang, G; Li, X D; Li, J; Peng, X Z; Qi, S H

    2005-01-01

    Owing to the hydrodynamic and sedimentation conditions, the western shoal of the Pearl River Estuary (PRE) is known to be an important sink of terrestrial substances including particle-associated pollutants from the Pearl River Delta (PRD) region. In this study, we report the sedimentary record of polycyclic aromatic hydrocarbons (PAHs) during the 20(th) century in a sediment core from the western shoal of the PRE. The summation PAH concentration ranged from 59 ng g(-1) to 330 ng g(-1) in the core with two distinct peaks. An initial increase of summation PAH concentration was found around the 1860s. The amounts of PAHs remained relatively constant for roughly 100 years, followed by the first peak in the 1950s. Then, there was a decrease in PAH concentration and flux in the 1960s and 1970s. A sharp increase of PAH concentration was observed in the early 1980s with a maximum concentration in the 1990s. The PAH diagnostic ratios indicated that the PAHs in the sediment core were mainly of pyrolytic origin, and that atmospheric deposition and land runoff may serve as the important pathways for PAHs input to the sediment. The Gross Domestic Product (GDP) was used as an index of socioeconomic development in the PRD region, which was correlated positively with the changes of PAH concentration and flux in the sediment core. The rapid increase in vehicle numbers and energy consumption in the region in the last two decades may have contributed to the rapid PAH increase since the early 1980s. The results clearly elucidated the impact of regional economic development on the estuarine environment.

  16. Identifying the source of petroleum pollution in sediment cores of southwest of the Caspian Sea using chemical fingerprinting of aliphatic and alicyclic hydrocarbons.

    Science.gov (United States)

    Shirneshan, Golshan; Bakhtiari, Alireza Riyahi; Memariani, Mahmoud

    2017-02-15

    In this study, the concentration and sources of aliphatic and petroleum markers were investigated in 105 samples of Anzali, Rezvanshahr and Astara cores from the southwest of Caspian Sea. Petroleum importation was diagnosed as a main source in most depths of cores by the results of unresolved complex mixture, carbon preference index and hopanes and steranes. From the chemical diagnostic parameters, petroleum inputs in sediment of cores were determined to be different during years and the sources of hydrocarbons in some sections differed than Anzali and Turkmenistan and Azerbaijan oils. Diagenic ratios in most sediments of upper and middle sections in Astara core were determined to be highly similar to those of Azerbaijan oil, while the presence of Turkmenistan and Anzali oils were detected in a few sections of Anzali and Rezvanshahr cores and only five layers of downer section in Anzali core, respectively.

  17. Analyzing tree cores to detect petroleum hydrocarbon-contaminated groundwater at a former landfill site in the community of Happy Valley-Goose Bay, eastern Canadian subarctic.

    Science.gov (United States)

    Fonkwe, Merline L D; Trapp, Stefan

    2016-08-01

    This research examines the feasibility of analyzing tree cores to detect benzene, toluene, ethylbenzene, and m, p, o-xylene (BTEX) compounds and methyl tertiary-butyl ether (MTBE) in groundwater in eastern Canada subarctic environments, using a former landfill site in the remote community of Happy Valley-Goose Bay, Labrador. Petroleum hydrocarbon contamination at the landfill site is the result of environmentally unsound pre-1990s disposal of households and industrial solid wastes. Tree cores were taken from trembling aspen, black spruce, and white birch and analyzed by headspace-gas chromatography-mass spectrometry. BTEX compounds were detected in tree cores, corroborating known groundwater contamination. A zone of anomalously high concentrations of total BTEX constituents was identified and recommended for monitoring by groundwater wells. Tree cores collected outside the landfill site at a local control area suggest the migration of contaminants off-site. Tree species exhibit different concentrations of BTEX constituents, indicating selective uptake and accumulation. Toluene in wood exhibited the highest concentrations, which may also be due to endogenous production. Meanwhile, MTBE was not found in the tree cores and is considered to be absent in the groundwater. The results demonstrate that tree-core analysis can be useful for detecting anomalous concentrations of petroleum hydrocarbons, such as BTEX compounds, in subarctic sites with shallow unconfined aquifers and permeable soils. This method can therefore aid in the proper management of contamination during landfill operations and after site closures.

  18. Fluorescent molecular probes based on excited state prototropism in lipid bilayer membrane

    Science.gov (United States)

    Mohapatra, Monalisa; Mishra, Ashok K.

    2012-03-01

    Excited state prototropism (ESPT) is observed in molecules having one or more ionizable protons, whose proton transfer efficiency is different in ground and excited states. The interaction of various ESPT molecules like naphthols and intramolecular ESPT (ESIPT) molecules like hydroxyflavones etc. with different microheterogeneous media have been studied in detail and excited state prototropism as a probe concept has been gaining ground. The fluorescence of different prototropic forms of such molecules, on partitioning to an organized medium like lipid bilayer membrane, often show sensitive response to the local environment with respect to the local structure, physical properties and dynamics. Our recent work using 1-naphthol as an ESPT fluorescent molecular probe has shown that the incorporation of monomeric bile salt molecules into lipid bilayer membranes composed from dipalmitoylphosphatidylcholine (DPPC, a lung surfactant) and dimyristoylphosphatidylcholine (DMPC), in solid gel and liquid crystalline phases, induce appreciable wetting of the bilayer up to the hydrocarbon core region, even at very low (fisetin, an ESIPT molecule having antioxidant properties, in lipid bilayer membrane has been sensitively monitored from its intrinsic fluorescence behaviour.

  19. CORE

    DEFF Research Database (Denmark)

    Krigslund, Jeppe; Hansen, Jonas; Hundebøll, Martin

    2013-01-01

    different flows. Instead of maintaining these approaches separate, we propose a protocol (CORE) that brings together these coding mechanisms. Our protocol uses random linear network coding (RLNC) for intra- session coding but allows nodes in the network to setup inter- session coding regions where flows...... intersect. Routes for unicast sessions are agnostic to other sessions and setup beforehand, CORE will then discover and exploit intersecting routes. Our approach allows the inter-session regions to leverage RLNC to compensate for losses or failures in the overhearing or transmitting process. Thus, we...... increase the benefits of XORing by exploiting the underlying RLNC structure of individual flows. This goes beyond providing additional reliability to each individual session and beyond exploiting coding opportunistically. Our numerical results show that CORE outperforms both forwarding and COPE...

  20. Effects of imidazolium-based ionic surfactants on the size and dynamics of phosphatidylcholine bilayers with saturated and unsaturated chains.

    Science.gov (United States)

    Lee, Hwankyu

    2015-07-01

    Imidazolium-based ionic surfactants of different sizes were simulated with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers. Regardless of the phospholipid type, larger surfactants at higher concentrations more significantly insert into the bilayer and increase the bilayer-surface size, in agreement with experiments and previous simulations. Insertion of surfactants only slightly decreases the bilayer thickness, as also observed in experiments. Although the surfactant insertion and its effect on the bilayer size and thickness are similar in different types of bilayers, the volume fractions of surfactants in the bilayer are higher for DMPC bilayers than for POPC and DOPC bilayers. In particular, ionic surfactants with four hydrocarbons yield their volume fractions of 4.6% and 8.7%, respectively, in POPC and DMPC bilayers, in quantitative agreement with experimental values of ∼5% and ∼10%. Also, the inserted surfactants increase the lateral diffusivity of the bilayer, which depends on the bilayer type. These findings indicate that although the surfactant insertion does not depend on the bilayer type, the effects of surfactants on the volume fraction and bilayer dynamics occur more significantly in the DMPC bilayer because of the smaller area per lipid and shorter saturated tails, which helps explain the experimental observations regarding different volume fractions of surfactants in POPC and DMPC bilayers.

  1. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

    Steven P. Wrenn, Stephen M. Dicker, Eleanor F. Small, Nily R. Dan, Michał Mleczko, Georg Schmitz, Peter A. Lewin

    2012-01-01

    Full Text Available This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol (PEG - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented

  2. Rapid determination of polycyclic aromatic hydrocarbons in rainwater by liquid-liquid microextraction and LC with core-shell particles column and fluorescence detection.

    Science.gov (United States)

    Vinci, Giuliana; Antonelli, Marta L; Preti, Raffaella

    2013-02-01

    Liquid-liquid microextraction coupled to LC with fluorescence detection for the determination of Environmental Protection Agency's 16 priority pollutant polycyclic aromatic hydrocarbons in rainwater has been developed. The optimization of the extraction method has involved several parameters, including the comparison between an ultrasonic bath and a magnetic stirrer as extractant apparatus, the choice of the extractant solvent, and the optimization of the extraction time. Liquid-liquid microextraction gave good results in terms of recoveries (from 73.6 to 102.8% in rainwater) and repeatability, with a very simple procedure and low solvent consumption. The reported chromatographic method uses a Core-Shell technology column, with particle size system rather than the more expensive ultrahigh performance LC (UHPLC). An average decrease of 59% in run time and 75% in eluent consumption has been obtained, compared to classical HPLC methods, keeping good separation, sensitivity, and repeatability. The proposed conditions were successfully applied to the determinations of polycyclic aromatic hydrocarbons in genuine rainwater samples.

  3. Structural Effects of Small Molecules on Phospholipid Bilayers Investigated by Molecular Simulations

    CERN Document Server

    Lee, B W; Sum, A K; Vattulainen, I; Patra, M; Karttunen, M; Lee, Bryan W; Faller, Roland; Sum, Amadeu K; Vattulainen, Ilpo; Patra, Michael; Karttunen, Mikko

    2004-01-01

    We summarize and compare recent Molecular Dynamics simulations on the interactions of dipalmitoylphosphatidylcholine (DPPC) bilayers in the liquid crystalline phase with a number of small molecules including trehalose, a disaccharide of glucose, alcohols, and dimethylsulfoxide (DMSO). The sugar molecules tend to stabilize the structure of the bilayer as they bridge adjacent lipid headgroups. They do not strongly change the structure of the bilayer. Alcohols and DMSO destabilize the bilayer as they increase its area per molecule in the bilayer plane and decrease the order parameter. Alcohols have a stronger detrimental effect than DMSO. The observables which we compare are the area per molecule in the plane of the bilayer, the membrane thickness, and the NMR order parameter of DPPC hydrocarbon tails. The area per molecule and the order parameter are very well correlated whereas the bilayer thickness is not necessarily correlated with them.

  4. Solid-state NMR studies of a diverged microsomal amino-proximate delta12 desaturase peptide reveal causes of stability in bilayer: tyrosine anchoring and arginine snorkeling.

    Science.gov (United States)

    Gibbons, William J; Karp, Ethan S; Cellar, Nick A; Minto, Robert E; Lorigan, Gary A

    2006-02-15

    This study reports the solid-state NMR spectroscopic characterization of the amino-proximate transmembrane domain (TM-A) of a diverged microsomal delta12-desaturase (CREP-1) in a phospholipid bilayer. A series of TM-A peptides were synthesized with 2H-labeled side chains (Ala-53, -56, and -63, Leu-62, Val-50), and their dynamic properties were studied in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) bilayers at various temperatures. At 6 mol % peptide to lipid, 31P NMR spectra indicated that the peptides did not significantly disrupt the phospholipid bilayer in the L(alpha) phase. The 2H NMR spectra from Ala-53 and Ala-56 samples revealed broad Pake patterns with quadrupolar splittings of 16.9 kHz and 13.3 kHz, respectively, indicating restricted motion confined within the hydrocarbon core of the phospholipid bilayer. Conversely, the deuterated Ala-63 sample revealed a peak centered at 0 kHz with a linewidth of 1.9 kHz, indicating increased side-chain motion and solvent exposure relative to the spectra of the other Ala residues. Val-50 and Leu-62 showed Pake patterns, with quadrupolar splittings of 3.5 kHz and 3.7 kHz, respectively, intermediate to Ala-53/Ala-56 and Ala-63. This indicates partial motional averaging and supports a model with the Val and Leu residues embedded inside the lipid bilayer. Solid-state NMR spectroscopy performed on the 2H-labeled Ala-56 TM-A peptide incorporated into magnetically aligned phospholipid bilayers indicated that the peptide is tilted 8 degrees with respect to the membrane normal of the lipid bilayer. Snorkeling and anchoring interactions of Arg-44 and Tyr-60, respectively, with the polar region or polar hydrophobic interface of the lipid bilayer are suggested as control elements for insertional depth and orientation of the helix in the lipid matrix. Thus, this study defines the location of key residues in TM-A with respect to the lipid bilayer, describes the conformation of TM-A in a biomembrane mimic, presents a

  5. Hydrocarbon pneumonia

    Science.gov (United States)

    Pneumonia - hydrocarbon ... Coughing Fever Shortness of breath Smell of a hydrocarbon product on the breath Stupor (decreased level of ... Most children who drink or inhale hydrocarbon products and develop ... hydrocarbons may lead to rapid respiratory failure and death.

  6. Bilayer-thickness-mediated interactions between integral membrane proteins.

    Science.gov (United States)

    Kahraman, Osman; Koch, Peter D; Klug, William S; Haselwandter, Christoph A

    2016-04-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology allows accurate prediction of thickness-mediated protein interactions for arbitrary protein symmetries at arbitrary protein separations and relative orientations. We provide exact analytic solutions for cylindrical integral membrane proteins with constant and varying hydrophobic thickness, and develop perturbative analytic solutions for noncylindrical protein shapes. We complement these analytic solutions, and assess their accuracy, by developing both finite element and finite difference numerical solution schemes. We provide error estimates of our numerical solution schemes and systematically assess their convergence properties. Taken together, the work presented here puts into place an analytic and numerical framework which allows calculation of bilayer-mediated elastic interactions between integral membrane proteins for the complicated protein shapes suggested by structural biology and at the small protein separations most relevant for the crowded membrane

  7. Volumetric characterization of ester- and ether-linked lipid bilayers by pressure perturbation calorimetry and densitometry.

    Science.gov (United States)

    Tamai, Nobutake; Nambu, Yuko; Tanaka, Saeko; Goto, Masaki; Matsuki, Hitoshi; Kaneshina, Shoji

    2012-04-01

    We investigated the thermotropic volume behavior of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and dihexadecylphosphatidylcholine (DHPC) membranes using pressure perturbation calorimetry (PPC) and densitometry. The ln φ(2) vs temperature curves (φ(2): apparent molar volume of phospholipid) obtained from the PPC data using an analysis method that we developed agreed with the results from the density measurements for these lipids within the relative difference of about 0.62%. From those curves, the volume changes with the main transition were estimated at 18.0±0.49, 23.5±2.33 and 23.0±0.33 cm(3) mol(-1) for DMPC, DPPC and DHPC, respectively. For DPPC and DMPC, the average volume per methylene group of the hydrocarbon chains v(CH2) calculated by referring to the procedure by Nagle and Wilkinson was consistent with the previous result, which indicates that the DPPC bilayer in the gel state has denser hydrophobic bilayer core than the DMPC bilayer. For DHPC, the volume of the headgroup region v(H) was calculated to be 244 Å(3) by assuming that v(CH2) of DHPC equals that of DPPC above 45°C. This value was comparable to that of DPPC when the volume of the carbonyl groups was considered, which may signify that there is no significant conformational difference in the polar headgroups of both phospholipids. However, it was suggested from the consideration on v(H) of DHPC at 20°C that expansion of the headgroup region should occur as the interdigitated structure is formed, which means some conformational change of the headgroup region is induced by the interdigitation.

  8. Squalane is in the midplane of the lipid bilayer: implications for its function as a proton permeability barrier.

    Science.gov (United States)

    Hauss, Thomas; Dante, Silvia; Dencher, Norbert A; Haines, Thomas H

    2002-12-01

    A recently proposed model for proton leakage across biological membranes [Prog. Lipid Res. 40 (2001) 299] suggested that hydrocarbons specifically in the center of the lipid bilayer inhibit proton leaks. Since cellular membranes maintain a proton electrochemical gradient as a principal energy transducer, proton leakage unproductively consumes cellular energy. Hydrocarbons in the bilayer are widespread in membranes that sustain such gradients. The alkaliphiles are unique in that they contain up to 40 mol% isoprenes in their membranes including 10-11 mol% squalene [J. Bacteriol. 168 (1986) 334]. Squalene is a polyisoprene hydrocarbon without polar groups. Localizing hydrocarbons in lipid bilayers has not been trivial. A myriad of physical methods including fluorescence spectroscopy, electron-spin resonance, nuclear magnetic resonance as well as X-ray and neutron diffraction have been used to explore this question with various degrees of success and often contradictory results. Seeking unambiguous evidence for the localization of squalene in membranes or lipid bilayers, we employed neutron diffraction. We incorporated 10 mol% perdeuterated or protonated squalane, an isosteric analogue of squalene, into stacked bilayers of dioleoyl phosphatidyl choline (DOPC) doped with dioleoyl phosphatidyl glycerol (DOPG) to simulate the negative charges found on natural membranes. The neutron diffraction data clearly show that the squalane lies predominantly in the bilayer center, parallel to the plane of the membrane.

  9. Nanoparticle-lipid bilayer interactions studied with lipid bilayer arrays

    Science.gov (United States)

    Lu, Bin; Smith, Tyler; Schmidt, Jacob J.

    2015-04-01

    The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which can provide insight into the nature of the particle-membrane interaction through variation of membrane and solution properties not possible with cell-based assays. However, the scope of these studies can be limited because of the low throughput characteristic of lipid bilayer platforms. We have recently described an easy to use, parallel lipid bilayer platform which we have used to electrically investigate the activity of 60 nm diameter amine and carboxyl modified polystyrene nanoparticles (NH2-NP and COOH-NP) with over 1000 lipid bilayers while varying lipid composition, bilayer charge, ionic strength, pH, voltage, serum, particle concentration, and particle charge. Our results confirm recent studies finding activity of NH2-NP but not COOH-NP. Detailed analysis shows that NH2-NP formed pores 0.3-2.3 nm in radius, dependent on bilayer and solution composition. These interactions appear to be electrostatic, as they are regulated by NH2-NP surface charge, solution ionic strength, and bilayer charge. The ability to rapidly measure a large number of nanoparticle and membrane parameters indicates strong potential of this bilayer array platform for additional nanoparticle bilayer studies.The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which

  10. Molecular Dynamics of Lipid Bilayers

    Science.gov (United States)

    1989-08-09

    The aim of this work is to study, by molecular dynamics simulations, the properties of lipid bilayers. We have applied the vectorizable, order-N...fast angle-dependent force/potential algorithms to treat angle bending and torsion. Keywords: Molecular dynamics , Lipid bilayers.

  11. Pattern Formation in Dewetting Nanoparticle/Polymer Bilayers

    Science.gov (United States)

    Esker, Alan; Paul, Rituparna; Karabiyik, Ufuk; Swift, Michael; Hottle, John

    2008-03-01

    Comprised of inorganic cores and flexible organic coronae with 1 -- 2 nm diameter monodisperse sizes, polyhedral oligomeric silsesquioxanes (POSS) are ideal model nanofillers. Our discovery that one POSS derivative, trisilanolphenyl-POSS (TPP), can form Langmuir-Blodgett (LB) films on hydrophobic substrates, allows us to create thin film bilayers of precisely controlled thickness and architecture. Work with poly(t-butylacrylate) (PtBA)/TPP bilayers reveals a two-step dewetting mechanism in which the upper TPP layer dewets first, followed by the formation of isolated holes with intricate, fractal, nanofiller aggregates. Like the PtBA/TPP bilayers, polystyrene (PS)/TPP bilayers also undergo a two-step dewetting mechanism. However, the upper TPP layer initially forms cracks that may arise from mismatches in thermal expansion coefficients. These cracks then serve as nucleation sites for complete dewetting of the entire bilayer. Understanding the rich diversity of surface patterns that can be formed from relatively simple processes is a key feature of this work.

  12. Lipid bilayers on nano-templates

    Science.gov (United States)

    Noy, Aleksandr; Artyukhin, Alexander B.; Bakajin, Olgica; Stoeve, Pieter

    2009-08-04

    A lipid bilayer on a nano-template comprising a nanotube or nanowire and a lipid bilayer around the nanotube or nanowire. One embodiment provides a method of fabricating a lipid bilayer on a nano-template comprising the steps of providing a nanotube or nanowire and forming a lipid bilayer around the polymer cushion. One embodiment provides a protein pore in the lipid bilayer. In one embodiment the protein pore is sensitive to specific agents

  13. Failure modes and fracture origins of porcelain veneers on bilayer dental crowns.

    Science.gov (United States)

    Liu, Yihong; Liu, Guanghua; Wang, Yong; Shen, James Zhijian; Feng, Hailan

    2014-01-01

    The aims of this study were to determine the fracture origins and crack paths in the porcelain of clinically failed bilayer ceramic restorations and to reveal the correlation between the porcelain failures and material properties. Three clinically failed crowns of each material (bilayer zirconia crowns, galvano-ceramic crowns, and porcelain-fused-to-metal crowns) were collected and underwent failure analysis. The fractures found in porcelain veneers showed several characteristics including wear, Hertzian cone crack, chipping off, and delamination. The results indicated that the fracture origins and features of the porcelain in bilayer ceramic restorations might be affected by the rigidity of core materials and thickness of copings.

  14. Reversal of exchange bias in nanocrystalline antiferromagnetic-ferromagnetic bilayers

    CERN Document Server

    Prados, C; Hernando, A; Montone, A

    2002-01-01

    The sign of the exchange bias in field cooled nanocrystalline antiferromagnetic-ferromagnetic bilayers (Co-O and Ni-O/permalloy) is reversed at temperatures approaching the antiferromagnetic (AFM) blocking temperature. A similar phenomenon is observed after magnetic training processes at similar temperatures. These effects can be explained assuming that the boundaries of nanocrystalline grains in AFM layers exhibit lower transition temperatures than grain cores.

  15. Analyzing tree cores to detect petroleum hydrocarbon-contaminated groundwater at a former landfill site in the community of Happy Valley-Goose Bay, eastern Canadian subarctic

    DEFF Research Database (Denmark)

    Fonkwe, Merline L D; Trapp, Stefan

    2016-01-01

    This research examines the feasibility of analyzing tree cores to detect benzene, toluene, ethylbenzene, and m, p, o-xylene (BTEX) compounds and methyl tertiary-butyl ether (MTBE) in groundwater in eastern Canada subarctic environments, using a former landfill site in the remote community of Happy...... at a local control area suggest the migration of contaminants off-site. Tree species exhibit different concentrations of BTEX constituents, indicating selective uptake and accumulation. Toluene in wood exhibited the highest concentrations, which may also be due to endogenous production. Meanwhile, MTBE...

  16. The binding and insertion of imidazolium-based ionic surfactants into lipid bilayers: the effects of the surfactant size and salt concentration.

    Science.gov (United States)

    Lee, Hwankyu; Jeon, Tae-Joon

    2015-02-28

    Imidazolium-based ionic surfactants with hydrocarbon tails of different sizes were simulated with lipid bilayers at different salt concentrations. Starting with the random position of ionic surfactants outside the bilayer, surfactants with long tails mostly insert into the bilayer, while those with short tails show the insertion of fewer surfactant molecules, indicating the effect of the tail length. In particular, surfactants with a tail of two or four hydrocarbons insert and reversibly detach from the bilayer, while the inserted longer surfactants cannot be reversibly detached because of the strong hydrophobic interaction with lipid tails, in quantitative agreement with experiments. Longer surfactants insert more deeply and irreversibly into the bilayer and thus increase lateral diffusivities of the bilayer, indicating that longer surfactants more significantly disorder lipid bilayers, which also agrees with experiments regarding the effect of the tail length of ionic surfactants on membrane permeability and toxicity. Addition of NaCl ions weakens the electrostatic interactions between headgroups of surfactants and lipids, leading to the binding of fewer surfactants into the bilayer. In particular, our simulation findings indicate that insertion of ionic surfactants can be initiated by either the hydrophobic interaction between tails of surfactants and lipids or the electrostatic binding between imidazolium heads and lipid heads, and the strength of hydrophobic and electrostatic interactions depends on the tail length of surfactants.

  17. Multiple locations of peptides in the hydrocarbon core of gel-phase membranes revealed by peptide (13)C to lipid (2)H rotational-echo double-resonance solid-state nuclear magnetic resonance.

    Science.gov (United States)

    Xie, Li; Jia, Lihui; Liang, Shuang; Weliky, David P

    2015-01-27

    Membrane locations of peptides and proteins are often critical to their functions. Solid-state rotational-echo double-resonance (REDOR) nuclear magnetic resonance is applied to probe the locations of two peptides via peptide (13)CO to lipid (2)H distance measurements. The peptides are KALP, an α-helical membrane-spanning peptide, and HFP, the β-sheet N-terminal fusion peptide of the HIV gp41 fusion protein that plays an important role in HIV-host cell membrane fusion. Both peptides are shown to have at least two distinct locations within the hydrocarbon core of gel-phase membranes. The multiple locations are attributed to snorkeling of lysine side chains for KALP and to the distribution of antiparallel β-sheet registries for HFP. The relative population of each location is also quantitated. To the best of our knowledge, this is the first clear experimental support of multiple peptide locations within the membrane hydrocarbon core. These data are for gel-phase membranes, but the approach should work for liquid-ordered membranes containing cholesterol and may be applicable to liquid-disordered membranes with appropriate additional analysis to take into account protein and lipid motion. This paper also describes the methodological development of (13)CO-(2)H REDOR using the lyophilized I4 peptide that is α-helical and (13)CO-labeled at A9 and (2)Hα-labeled at A8. The I4 spins are well-approximated as an ensemble of isolated (13)CO-(2)H spin pairs each separated by 5.0 Å with a 37 Hz dipolar coupling. A pulse sequence with rectangular 100 kHz (2)H π pulses results in rapid and extensive buildup of REDOR (ΔS/S0) with a dephasing time (τ). The buildup is well-fit by a simple exponential function with a rate of 24 Hz and an extent close to 1. These parameter values reflect nonradiative transitions between the (2)H spin states during the dephasing period. Each spin pair spends approximately two-thirds of its time in the (13)CO-(2)H (m = ±1) states and

  18. Interplay between alkyl chain asymmetry and cholesterol addition in the rigid ion pair amphiphile bilayer systems

    Science.gov (United States)

    Huang, Fong-yin; Chiu, Chi-cheng

    2017-01-01

    Ion pair amphiphile (IPA), a molecular complex composed of a pair of cationic and anionic surfactants, has been proposed as a novel phospholipid substitute. Controlling the physical stability of IPA vesicles is important for its application developments such as cosmetic and drug deliveries. To investigate the effects of IPA alkyl chain combinations and the cholesterol additive on the structural and mechanical properties of IPA vesicular bilayers, we conducted a series of molecular dynamics studies on the hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS) and dodecyltrimethylammonium-hexadecylsulfate (DTMA-HS) IPA bilayers with cholesterol. We found that both IPA bilayers are in the gel phase at 298 K, consistent with experimental observations. Compared with the HTMA-DS system, the DTMA-HS bilayer has more disordered alkyl chains in the hydrophobic region. When adding cholesterol, it induces alkyl chain ordering around its rigid sterol ring. Yet, cholesterol increases the molecular areas for all species and disturbs the molecular packing near the hydrophilic region and the bilayer core. Cholesterol also promotes the alkyl chain mismatch between the IPA moieties, especially for the DTMA-HS bilayer. The combined effects lead to non-monotonically enhancement of the membrane mechanical moduli for both IPA-cholesterol systems. Furthermore, cholesterol can form H-bonds with the alkylsulfate and thus enhance the contribution of alkylsulfate to the overall mechanical moduli. Combined results provide valuable molecular insights into the roles of each IPA component and the cholesterol on modulating the IPA bilayer properties.

  19. Cholesterol effect on water permeability through DPPC and PSM lipid bilayers: a molecular dynamics study.

    Science.gov (United States)

    Saito, Hiroaki; Shinoda, Wataru

    2011-12-29

    Water permeability of two different lipid bilayers of dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) in the absence and presence of cholesterol (0-50 mol %) have been studied by molecular dynamics simulations to elucidate the molecular mechanism of the reduction in water leakage across the membranes by the addition of cholesterol. An enhanced free energy barrier was observed in these membranes with increased cholesterol concentration, and this was explained by the reduced cavity density around the cholesterol in the hydrophobic membrane core. There was an increase of trans conformers in the hydrophobic lipid chains adjacent to the cholesterol, which reduced the cavity density. The enhanced free energy barrier was found to be the main reason to reduce the water permeability with increased cholesterol concentration. At low cholesterol concentrations the PSM bilayer exhibited a higher free energy barrier than the DPPC bilayer for water permeation, while at greater than 30 mol % of cholesterol the difference became minor. This tendency for the PSM and DPPC bilayers to resemble each other at higher cholesterol concentrations was similar to commonly observed trends in several structural properties, such as order parameters, cross-sectional area per molecule, and cavity density profiles in the hydrophobic regions of bilayer membranes. These results demonstrate that DPPC and PSM bilayers with high cholesterol contents possess similar physical properties, which suggests that the solubility of cholesterol in these lipid bilayers has importance for an understanding of multicomponent lipid membranes with cholesterol.

  20. Apparatus for hydrocarbon extraction

    Science.gov (United States)

    Bohnert, George W.; Verhulst, Galen G.

    2013-03-19

    Systems and methods for hydrocarbon extraction from hydrocarbon-containing material. Such systems and methods relate to extracting hydrocarbon from hydrocarbon-containing material employing a non-aqueous extractant. Additionally, such systems and methods relate to recovering and reusing non-aqueous extractant employed for extracting hydrocarbon from hydrocarbon-containing material.

  1. Compartmentalisation Strategies for Hydrocarbon-based Biota on Titan

    Science.gov (United States)

    Norman, L.; Fortes, A. D.; Skipper, N.; Crawford, I.

    2013-05-01

    The goal of our study is to determine the nature of compartimentalisation strategies for any organisms inhabiting the hydrocarbon lakes of Titan (the largest moon of Saturn). Since receiving huge amounts of data via the Cassini-Huygens mission to the Saturnian system astrobiologists have speculated that exotic biota might currently inhabit this environment. The biota have been theorized to consume acetylene and hydrogen whilst excreting methane (1,2) leading to an anomalous hydrogen depletion near the surface; and there has been evidence to suggest this depletion exists (3). Nevertheless, many questions still remain concerning the possible physiological traits of biota in these environments, including whether cell-like structures can form in low temperature, low molecular weight hydrocarbons. The backbone of terrestrial cell membranes are vesicular structures composed primarily of a phospholipid bilayer with the hydrophilic head groups arranged around the periphery and are thought to be akin to the first protocells that terrestrial life utilised (4). It my be possible that reverse vesicles composed of a bilayer with the hydrophilic head groups arranged internally and a nonpolar core may be ideal model cell membranes for hydrocarbon-based organisms inhabiting Titan's hydrocarbon lakes (5). A variety of different surfactants have been used to create reverse vesicles in nonpolar liquids to date including; non-ionic ethers (7) and esters (6, 8); catanionic surfactant mixtures (9); zwitterionic gemini surfactants (10); coblock polymer surfactants (11); and zwitterionic phospholipid surfactants (12). In order to discover whether certain phospholipids can exhibit vesicular behaviour within hydrocarbon liquids, and to analyse their structure, we have carried out experimental studies using environmental conditions that are increasing comparable to those found on the surface of Titan. Experimental methods that have been used to determine the presence of vesicles include the

  2. Molecular dynamics of dibenz[a,h]anthracene and its metabolite interacting with lung surfactant phospholipid bilayers.

    Science.gov (United States)

    Padilla-Chavarría, Helmut I; Guizado, Teobaldo R C; Pimentel, Andre S

    2015-08-28

    The interaction of dibenz[a,h]anthracene and its ultimate carcinogenic 3,4-diol-1,2-epoxide with lung surfactant phospholipid bilayers was successfully performed using molecular dynamics. The DPPC/DPPG/cholesterol bilayer (64 : 64 : 2) was used as the lung surfactant phospholipid bilayer model and compared with the DPPC bilayer as a reference. Dibenz[a,h]anthracene and its 3,4-diol-1,2-epoxide were inserted in water and lipid phases in order to investigate their interactions with the lung surfactant phospholipid bilayers. The radial distribution function between two P atoms in polar heads shows that the 3,4-diol-1,2-epoxide affects the order between the P atoms in the DPPC/DPPG/cholesterol model more than dibenz[a,h]anthracene, which is a consequence of its preference for the polar heads and dibenz[a,h]anthracene prefers to be located in the hydrocarbon chain of the phospholipid bilayers. Dibenz[a,h]anthracene and its 3,4-diol-1,2-epoxide may form aggregates in water and lipid phases, and in the water-lipid interface. The implications for the possible effect of dibenz[a,h]anthracene and its 3,4-diol-1,2-epoxide in the lung surfactant phospholipid bilayers are discussed.

  3. Structure and dynamics of POPC bilayers in water solutions of room temperature ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Benedetto, Antonio [School of Physics, University College Dublin, Dublin 4 (Ireland); Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen (Switzerland); Bingham, Richard J. [York Centre for Complex Systems Analysis, University of York, York YO10 5GE (United Kingdom); Ballone, Pietro [Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia (IIT), 00185 Roma (Italy); Department of Physics, Università di Roma “La Sapienza,” 00185 Roma (Italy)

    2015-03-28

    Molecular dynamics simulations in the NPT ensemble have been carried out to investigate the effect of two room temperature ionic liquids (RTILs), on stacks of phospholipid bilayers in water. We consider RTIL compounds consisting of chloride ([bmim][Cl]) and hexafluorophosphate ([bmim][PF{sub 6}]) salts of the 1-buthyl-3-methylimidazolium ([bmim]{sup +}) cation, while the phospholipid bilayer is made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Our investigations focus on structural and dynamical properties of phospholipid and water molecules that could be probed by inelastic and quasi-elastic neutron scattering measurements. The results confirm the fast incorporation of [bmim]{sup +} into the lipid phase already observed in previous simulations, driven by the Coulomb attraction of the cation for the most electronegative oxygens in the POPC head group and by sizeable dispersion forces binding the neutral hydrocarbon tails of [bmim]{sup +} and of POPC. The [bmim]{sup +} absorption into the bilayer favours the penetration of water into POPC, causes a slight but systematic thinning of the bilayer, and further stabilises hydrogen bonds at the lipid/water interface that already in pure samples (no RTIL) display a lifetime much longer than in bulk water. On the other hand, the effect of RTILs on the diffusion constant of POPC (D{sub POPC}) does not reveal a clearly identifiable trend, since D{sub POPC} increases upon addition of [bmim][Cl] and decreases in the [bmim][PF{sub 6}] case. Moreover, because of screening, the electrostatic signature of each bilayer is only moderately affected by the addition of RTIL ions in solution. The analysis of long wavelength fluctuations of the bilayers shows that RTIL sorption causes a general decrease of the lipid/water interfacial tension and bending rigidity, pointing to the destabilizing effect of RTILs on lipid bilayers.

  4. Increased adhesion between neutral lipid bilayers: interbilayer bridges formed by tannic acid.

    Science.gov (United States)

    Simon, S A; Disalvo, E A; Gawrisch, K; Borovyagin, V; Toone, E; Schiffman, S S; Needham, D; McIntosh, T J

    1994-06-01

    Tannic acid (TA) is a naturally occurring polyphenolic compound that aggregates membranes and neutral phosolipid vesicles and precipitates many proteins. This study analyzes TA binding to lipid membranes and the ensuing aggregation. The optical density of dispersions of phosphatidylcholine (PC) vesicles increased upon the addition of TA and electron micrographs showed that TA caused the vesicles to aggregate and form stacks of tightly packed disks. Solution calorimetry showed that TA bound to PC bilayers with a molar binding enthalpy of -8.3 kcal/mol and zeta potential measurements revealed that TA imparted a small negative charge to PC vesicles. Monolayer studies showed that TA bound to PC with a dissociation constant of 1.5 microM and reduced the dipole potential by up to 250 mV. Both the increase in optical density and decrease in dipole potential produced by TA could be reversed by the addition of polyvinylpyrrolidone, a compound that chelates TA by providing H-bond acceptor groups. NMR, micropipette aspiration, and x-ray diffraction experiments showed that TA incorporated into liquid crystalline PC membranes, increasing the area per lipid molecule and decreasing the bilayer thickness by 2 to 4%. 2H-NMR quadrupole splitting measurements also showed that TA associated with a PC molecule for times much less than 10(-4) s. In gel phase bilayers, TA caused the hydrocarbon chains from apposing monolayers to fully interdigitate. X-ray diffraction measurements of both gel and liquid crystalline dispersions showed that TA, at a critical concentration of about 1 mM, reduced the fluid spacing between adjacent bilayers by 8-10 A. These data place severe constraints on how TA can pack between adjacent bilayers and cause vesicles to adhere. We conclude that TA promotes vesicle aggregation by reducing the fluid spacing between bilayers by the formation of transient interbilayer bridges by inserting its digallic acid residues into the interfacial regions of adjacent bilayers

  5. Bilayer Effects of Antimalarial Compounds.

    Directory of Open Access Journals (Sweden)

    Nicole B Ramsey

    Full Text Available Because of the perpetual development of resistance to current therapies for malaria, the Medicines for Malaria Venture developed the Malaria Box to facilitate the drug development process. We tested the 80 most potent compounds from the box for bilayer-mediated effects on membrane protein conformational changes (a measure of likely toxicity in a gramicidin-based stopped flow fluorescence assay. Among the Malaria Box compounds tested, four compounds altered membrane properties (p< 0.05; MMV007384 stood out as a potent bilayer-perturbing compound that is toxic in many cell-based assays, suggesting that testing for membrane perturbation could help identify toxic compounds. In any case, MMV007384 should be approached with caution, if at all.

  6. Horizontal Bilayer for Electrical and Optical Recordings

    Directory of Open Access Journals (Sweden)

    Alf Honigmann

    2012-12-01

    Full Text Available Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to investigate these model bilayer membranes and the membrane proteins therein with high resolution fluorescence techniques up to the single-molecule level. Here, we describe a bilayer microchip system in which long-term stable horizontal free-standing and hydrogel-supported bilayers can be formed and demonstrate its prospects particularly for single-molecule fluorescence spectroscopy and high resolution fluorescence microscopy in probing the physicochemical properties like phase behavior of the bilayer-forming lipids, as well as in functional studies of membrane proteins.

  7. Modulation of folding and assembly of the membrane protein bacteriorhodopsin by intermolecular forces within the lipid bilayer.

    Science.gov (United States)

    Curran, A R; Templer, R H; Booth, P J

    1999-07-20

    Three different lipid systems have been developed to investigate the effect of physicochemical forces within the lipid bilayer on the folding of the integral membrane protein bacteriorhodopsin. Each system consists of lipid vesicles containing two lipid species, one with phosphatidylcholine and the other with phosphatidylethanolamine headgroups, but the same hydrocarbon chains: either L-alpha-1, 2-dioleoyl, L-alpha-1,2-dipalmitoleoyl, or L-alpha-1,2-dimyristoyl. Increasing the mole fraction of the phosphatidylethanolamine lipid increases the desire of each monolayer leaflet in the bilayer to curve toward water. This increases the torque tension of such monolayers, when they are constrained to remain flat in the vesicle bilayer. Consequently, the lateral pressure in the hydrocarbon chain region increases, and we have used excimer fluorescence from pyrene-labeled phosphatidylcholine lipids to probe these pressure changes. We show that bacteriorhodopsin regenerates to about 95% yield in vesicles of 100% phosphatidylcholine. The regeneration yield decreases as the mole fraction of the corresponding phosphatidylethanolamine component is increased. The decrease in yield correlates with the increase in lateral pressure which the lipid chains exert on the refolding protein. We suggest that the increase in lipid chain pressure either hinders insertion of the denatured state of bacterioopsin into the bilayer or slows a folding step within the bilayer, to the extent that an intermediate involved in bacteriorhodopsin regeneration is effectively trapped.

  8. The Role of Atomic Polarization in the Thermodynamics of Chloroform Partitioning to Lipid Bilayers.

    Science.gov (United States)

    Vorobyov, Igor; Bennett, W F Drew; Tieleman, D Peter; Allen, Toby W; Noskov, Sergei

    2012-02-14

    In spite of extensive research and use in medical practice, the precise molecular mechanism of volatile anesthetic action remains unknown. The distribution of anesthetics within lipid bilayers and potential targeting to membrane proteins is thought to be central to therapeutic function. Therefore, obtaining a molecular level understanding of volatile anesthetic partitioning into lipid bilayers is of vital importance to modern pharmacology. In this study we investigate the partitioning of the prototypical anesthetic, chloroform, into lipid bilayers and different organic solvents using molecular dynamics simulations with potential models ranging from simplified coarse-grained MARTINI to additive and polarizable CHARMM all-atom force fields. Many volatile anesthetics display significant inducible dipole moments, which correlate with their potency, yet the exact role of molecular polarizability in their stabilization within lipid bilayers remains unknown. We observe that explicit treatment of atomic polarizability makes it possible to accurately reproduce solvation free energies in solvents with different polarities, allowing for quantitative studies in heterogeneous molecular distributions, such as lipid bilayers. We calculate the free energy profiles for chloroform crossing lipid bilayers to reveal a role of polarizability in modulating chloroform partitioning thermodynamics via the chloroform-induced dipole moment and highlight competitive binding to the membrane core and toward the glycerol backbone that may have significant implications for understanding anesthetic action.

  9. Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy

    Science.gov (United States)

    Nusair, Nisreen A.; Tiburu, Elvis K.; Dave, Paresh C.; Lorigan, Gary A.

    2004-06-01

    This is the first time 2H solid-state NMR spectroscopy and spin-labeled EPR spectroscopy have been utilized to probe the structural orientation and dynamics of a stearic acid incorporated into magnetically aligned phospholipid bilayers or bicelles. The data gleaned from the two different techniques provide a more complete description of the bilayer membrane system. Both methods provided similar qualitative information on the phospholipid bilayer, high order, and low motion for the hydrocarbon segment close to the carboxyl groups of the stearic acid and less order and more rapid motion at the end towards the terminal methyl groups. However, the segmental order parameters differed markedly due to the different orientations that the nitroxide and C-D bond axes transform with the various stearic acid acyl chain conformations, and because of the difference in dynamic sensitivity between NMR and EPR over the timescales examined. 5-, 7-, 12-, and 16-doxylstearic acids spin-labels were used in the EPR experiments and stearic acid-d 35 was used in the solid-state NMR experiments. The influence of the addition of cholesterol and the variation of temperature on the fatty acid hydrocarbon chain ordering in the DMPC/DHPC phospholipid bilayers was also studied. Cholesterol increased the degree of ordering of the hydrocarbon chains. Conversely, as the temperature of the magnetically aligned phospholipid bilayers increased, the order parameters decreased due to the higher random motion of the acyl chain of the stearic acid. The results indicate that magnetically aligned phospholipid bilayers are an excellent model membrane system and can be used for both NMR and EPR studies.

  10. Tailored sequential drug release from bilayered calcium sulfate composites

    Energy Technology Data Exchange (ETDEWEB)

    Orellana, Bryan R.; Puleo, David A., E-mail: puleo@uky.edu

    2014-10-01

    The current standard for treating infected bony defects, such as those caused by periodontal disease, requires multiple time-consuming steps and often multiple procedures to fight the infection and recover lost tissue. Releasing an antibiotic followed by an osteogenic agent from a synthetic bone graft substitute could allow for a streamlined treatment, reducing the need for multiple surgeries and thereby shortening recovery time. Tailorable bilayered calcium sulfate (CS) bone graft substitutes were developed with the ability to sequentially release multiple therapeutic agents. Bilayered composite samples having a shell and core geometry were fabricated with varying amounts (1 or 10 wt.%) of metronidazole-loaded poly(lactic-co-glycolic acid) (PLGA) particles embedded in the shell and simvastatin directly loaded into either the shell, core, or both. Microcomputed tomography showed the overall layered geometry as well as the uniform distribution of PLGA within the shells. Dissolution studies demonstrated that the amount of PLGA particles (i.e., 1 vs. 10 wt.%) had a small but significant effect on the erosion rate (3% vs. 3.4%/d). Mechanical testing determined that introducing a layered geometry had a significant effect on the compressive strength, with an average reduction of 35%, but properties were comparable to those of mandibular trabecular bone. Sustained release of simvastatin directly loaded into CS demonstrated that changing the shell to core volume ratio dictates the duration of drug release from each layer. When loaded together in the shell or in separate layers, sequential release of metronidazole and simvastatin was achieved. By introducing a tunable, layered geometry capable of releasing multiple drugs, CS-based bone graft substitutes could be tailored in order to help streamline the multiple steps needed to regenerate tissue in infected defects. - Highlights: • Bilayered CS composites were fabricated as potential bone graft substitutes. • The shell

  11. The hydrocarbon sphere

    Energy Technology Data Exchange (ETDEWEB)

    Mandev, P.

    1984-01-01

    The hydrocarbon sphere is understood to be the area in which hydrocarbon compounds are available. It is believed that the lower boundary on the hydrocarbon sphere is most probably located at a depth where the predominant temperatures aid in the destruction of hydrocarbons (300 to 400 degrees centigrade). The upper limit on the hydrocarbon sphere obviously occurs at the earth's surface, where hydrocarbons oxidize to H20 and CO2. Within these ranges, the occurrence of the hydrocarbon sphere may vary from the first few hundred meters to 15 kilometers or more. The hydrocarbon sphere is divided into the external (mantle) sphere in which the primary gas, oil and solid hydrocarbon fields are located, and the internal (metamorphic) sphere containing primarily noncommercial accumulations of hydrocarbon gases and solid carbon containing compounds (anthraxilite, shungite, graphite, etc.) based on the nature and scale of hydrocarbon compound concentrations (natural gas, oil, maltha, asphalt, asphaltite, etc.).

  12. Superdiffusion in supported lipid bilayers

    CERN Document Server

    Campagnola, Grace; Schroder, Bryce W; Peersen, Olve B; Krapf, Diego

    2015-01-01

    We study the diffusion of membrane-targeting C2 domains using single-molecule tracking in supported lipid bilayers. The ensemble-averaged mean square displacement (MSD) exhibits superdiffusive behavior. However, the time-averaged MSD of individual trajectories is found to be linear with respect to lag time, as in Brownian diffusion. These observations are explained in terms of bulk excursions that introduce jumps with a heavy-tail distribution. Our experimental results are shown to agree with analytical models of bulk-mediated diffusion and with numerical simulations.

  13. Pseudocritical Behavior and Unbinding of Phospholipid Bilayers

    DEFF Research Database (Denmark)

    Lemmich, Jesper; Mortensen, Kell; Ipsen, John Hjorth;

    1995-01-01

    The temperature dependence of the small-angle neutron scattering from fully hydrated multilamellar phospholipid bilayers near the main phase transition is analyzed by means of a simple geometric model which yields both the lamellar repeat distance as well as the hydrophobic thickness of the bilayer...

  14. Planar bilayer membranes from photoactivable phospholipids.

    Science.gov (United States)

    Borle, F; Sänger, M; Sigrist, H

    1991-07-22

    Planar bilayer membranes formed from photoactivable phospholipids have been characterized by low frequency voltametry. Cyclic voltametric measurements were applied for simultaneous registration of planar membrane conductivity and capacitance. The procedure has been utilized to characterize the formation and stability of planar bilayer membranes. Bilayer membranes were formed from N'-(1,2-dimyristoyl-sn-glycero-3-phosphoethyl)-N-((m-3- trifluoromethyldiazirine)phenyl)thiourea (C14-PED), a head-group photosensitive phospholipid. In situ photoactivation of C14-PED at wavelengths greater than or equal to 320 nm altered neither the mean conductivity nor the capacitance of the bilayer. Ionophore (valinomycin) and ion channel (gramicidin) activities were not impaired upon photoactivation. In contrast, bilayer membranes formed from 1,2-bis(hexadeca-2,4-dienoyl)-sn- glycero-3-phosphocholine (C16-DENPC) revealed short life times. In situ photopolymerization of the diene fatty acids significantly increased the membrane conductivity or led to membrane rupture.

  15. Multiscale Modeling of supported bilayers

    Science.gov (United States)

    Faller, Roland; Xing, Chenyue; Hoopes, Matthew I.

    2009-03-01

    Supported Lipid Bilayers are an abundant research platform for understanding the behavior of real cell membranes as they allow for additional mechanical stability. We studied systematically the changes that a support induces on a phospholipid bilayer using coarse-grained molecular modeling on different levels. We characterize the density and pressure profiles as well as the density imbalance inflicted on the membrane by the support. We also determine the diffusion coefficients and characterize the influence of different corrugations of the support. We then determine the free energy of transfer of phospholipids between the proximal and distal leaflet of a supported membrane using the coarse-grained Martini model. It turns out that there is at equilibrium about a 2-3% higher density in the proximal leaflet. These results are in favorable agreement with recent data obtained by very large scale modeling using a water free model where flip-flop can be observed directly. We compare results of the free energy of transfer obtained by pulling the lipid across the membrane in different ways. There are small quantitative differences but the overall picture is consistent. We are additionally characterizing the intermediate states which determine the barrier height and therefore the rate of translocation.

  16. Nanocrystal bilayer for tandem catalysis.

    Science.gov (United States)

    Yamada, Yusuke; Tsung, Chia-Kuang; Huang, Wenyu; Huo, Ziyang; Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Somorjai, Gabor A; Yang, Peidong

    2011-05-01

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO(2)-Pt and Pt-SiO(2), can be used to catalyse two distinct sequential reactions. The CeO(2)-Pt interface catalysed methanol decomposition to produce CO and H(2), which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO(2) interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts.

  17. "Nanocrystal bilayer for tandem catalysis"

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

    2011-01-24

    Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

  18. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Nai; TIAN ZuoJi; LENG YingYing; WANG HuiTong; SONG FuQing; MENG JianHua

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2)branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4)phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hydrocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclusions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydrocarbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram.And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion,saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  19. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2) branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4) phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hy-drocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclu-sions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydro-carbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram. And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion, saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  20. Probing the position of resveratrol in lipid bilayers

    DEFF Research Database (Denmark)

    de Ghellinck, Alexis; Shen, Chen; Fragneto, Giovanna;

    2015-01-01

    The effect of the natural antioxidant resveratrol on the structure of solid supported di-palmitoyl-phosphatidyl-choline (DPPC) bilayers in their fluid state was investigated by neutron reflectometry. Results reveal an accumulation of resveratrol (up to 25%, mol/mol) inside the headgroups...... and they exclude its presence in the hydrophobic core. The presence of resveratrol induces an increase of the average thickness and of the interfacial roughness of the headgroup layer. This may be due to a change of the tilt angle of the phosphocholine headgroups residing next to the resveratrol to a more upright...... orientation and leading to a reduction of the projected area per headgroup. This effect is propagated into the hydrophobic core, where the chain packing is modified despite the absence of resveratrol. When interacting with a DPPC/cholesterol membrane, resveratrol has a similar effect on the neighboring PC...

  1. Biotechnology Applications of Tethered Lipid Bilayer Membranes

    Directory of Open Access Journals (Sweden)

    Joshua A. Jackman

    2012-12-01

    Full Text Available The importance of cell membranes in biological systems has prompted the development of model membrane platforms that recapitulate fundamental aspects of membrane biology, especially the lipid bilayer environment. Tethered lipid bilayers represent one of the most promising classes of model membranes and are based on the immobilization of a planar lipid bilayer on a solid support that enables characterization by a wide range of surface-sensitive analytical techniques. Moreover, as the result of molecular engineering inspired by biology, tethered bilayers are increasingly able to mimic fundamental properties of natural cell membranes, including fluidity, electrical sealing and hosting transmembrane proteins. At the same time, new methods have been employed to improve the durability of tethered bilayers, with shelf-lives now reaching the order of weeks and months. Taken together, the capabilities of tethered lipid bilayers have opened the door to biotechnology applications in healthcare, environmental monitoring and energy storage. In this review, several examples of such applications are presented. Beyond the particulars of each example, the focus of this review is on the emerging design and characterization strategies that made these applications possible. By drawing connections between these strategies and promising research results, future opportunities for tethered lipid bilayers within the biotechnology field are discussed.

  2. Texture of lipid bilayer domains

    DEFF Research Database (Denmark)

    Jensen, Uffe Bernchou; Brewer, Jonathan R.; Midtiby, Henrik Skov;

    2009-01-01

    We investigate the texture of gel (g) domains in binary lipid membranes composed of the phospholipids DPPC and DOPC. Lateral organization of lipid bilayer membranes is a topic of fundamental and biological importance. Whereas questions related to size and composition of fluid membrane domain...... are well studied, the possibility of texture in gel domains has so far not been examined. When using polarized light for two-photon excitation of the fluorescent lipid probe Laurdan, the emission intensity is highly sensitive to the angle between the polarization and the tilt orientation of lipid acyl...... chains. By imaging the intensity variations as a function of the polarization angle, we map the lateral variations of the lipid tilt within domains. Results reveal that gel domains are composed of subdomains with different lipid tilt directions. We have applied a Fourier decomposition method...

  3. Spin dynamics of bilayer manganites

    Indian Academy of Sciences (India)

    Tapan Chatterji

    2004-07-01

    The results of inelastic and quasi-elastic neutron scattering investigations on the 40% hole-doped quasi-2D bilayer manganites La1.2Sr1.8Mn2O7 have been reviewed. The complete set of exchange interactions have been determined on the basis of a localized Heisenberg model. However, the spin wave dispersion in La1.2Sr1.8Mn2O7 shows softening close to the zone boundary and are also heavily damped especially close to the zone boundary and deviate from that expected for a simple Heisenberg model. A minimal double exchange model including quantum corrections can reproduce these effects qualitatively but falls short of quantitative agreement.

  4. Fragmented state of lipid bilayers in water

    DEFF Research Database (Denmark)

    Helfrich, W.; Thimmel, J.; Klösgen, Beate Maria

    1999-01-01

    The bilayers of some typical biological membrane lipids such as PC and DGDG disintegrate in a large excess of water to form an optically invisible dispersive bilayer phase. `Dark bodies' can be reversibly precipitated from it by raising the temperature. The dispersive phase probably consists...... of `knotted sticks', i.e. very thin nodular tubes of bilayer. After reviewing pertinent experimental and theoretical work we report on the discovery of a lower consolute point near room temperature in DGDG/water systems. Its existence shows that the dispersive phase and the dark bodies belong to the same...

  5. Berry phase transition in twisted bilayer graphene

    Science.gov (United States)

    Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.

    2016-09-01

    The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.

  6. Hydrophobic silver nanoparticles trapped in lipid bilayers: Size distribution, bilayer phase behavior, and optical properties

    Directory of Open Access Journals (Sweden)

    Bothun Geoffrey D

    2008-11-01

    Full Text Available Abstract Background Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assemblies (LNAs consisting of hydrophobic silver-decanethiol particles (5.7 ± 1.8 nm embedded within 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC bilayers is demonstrated as a function of the DPPC/Ag nanoparticle (AgNP ratio. The effect of nanoparticle loading on the size distribution, bilayer phase behavior, and bilayer fluidity is determined. Concomitantly, the effect of bilayer incorporation on the optical properties of the AgNPs is also examined. Results The dispersions were stable at 50°C where the bilayers existed in a liquid crystalline state, but phase separated at 25°C where the bilayers were in a gel state, consistent with vesicle aggregation below the lipid melting temperature. Formation of bilayer-embedded nanoparticles was confirmed by differential scanning calorimetry and fluorescence anisotropy, where increasing nanoparticle concentration suppressed the lipid pretransition temperature, reduced the melting temperature, and disrupted gel phase bilayers. The characteristic surface plasmon resonance (SPR wavelength of the embedded nanoparticles was independent of the bilayer phase; however, the SPR absorbance was dependent on vesicle aggregation. Conclusion These results suggest that lipid bilayers can distort to accommodate large hydrophobic nanoparticles, relative to the thickness of the bilayer, and may provide insight into nanoparticle/biomembrane interactions and the design of multifunctional liposomal carriers.

  7. Reappraisal of hydrocarbon biomarkers in Archean rocks

    Science.gov (United States)

    French, Katherine L.; Hallmann, Christian; Hope, Janet M.; Schoon, Petra L.; Zumberge, J. Alex; Hoshino, Yosuke; Peters, Carl A.; George, Simon C.; Love, Gordon D.; Brocks, Jochen J.; Buick, Roger; Summons, Roger E.

    2015-05-01

    Hopanes and steranes found in Archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes, but the syngeneity of these hydrocarbon biomarkers is controversial. To resolve this debate, we performed a multilaboratory study of new cores from the Pilbara Craton, Australia, that were drilled and sampled using unprecedented hydrocarbon-clean protocols. Hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit, but when they were detectable, they had total hopane (oxygenic photosynthesis and eukaryotes by ∼2.7 billion years ago. Although suitable Proterozoic rocks exist, no currently known Archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation, so future exploration for Archean biomarkers should screen for rocks with milder thermal histories.

  8. Dynamic Morphologies of Microscale Droplet Interface Bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Mruetusatorn, Prachya [ORNL; Boreyko, Jonathan B [ORNL; Sarles, Stephen A [ORNL; Venkatesan, Guru [The University of Tennessee; Hayes, Douglas G [ORNL; Collier, Pat [ORNL

    2014-01-01

    Droplet interface bilayers (DIBs) are a powerful platform for studying the dynamics of synthetic cellular membranes; however, very little has been done to exploit the unique dynamical features of DIBs. Here, we generate microscale droplet interface bilayers ( DIBs) by bringing together femtoliter-volume water droplets in a microfluidic oil channel, and characterize morphological changes of the DIBs as the droplets shrink due to evaporation. By varying the initial conditions of the system, we identify three distinct classes of dynamic morphology. (1) Buckling and Fission: When forming DIBs using the lipid-out method (lipids in oil phase), lipids in the shrinking monolayers continually pair together and slide into the bilayer to conserve their mass. As the bilayer continues to grow, it becomes confined, buckles, and eventually fissions one or more vesicles. (2) Uniform Shrinking: When using the lipid-in method (lipids in water phase) to form DIBs, lipids uniformly transfer from the monolayers and bilayer into vesicles contained inside the water droplets. (3) Stretching and Unzipping: Finally, when the droplets are pinned to the wall(s) of the microfluidic channel, the droplets become stretched during evaporation, culminating in the unzipping of the bilayer and droplet separation. These findings offer a better understanding of the dynamics of coupled lipid interfaces.

  9. RKKY interaction in bilayer graphene

    Science.gov (United States)

    Mohammadi, Yawar; Moradian, Rostam

    2015-12-01

    We study the RKKY interaction between two magnetic impurities located on the same layer (intralayer case) or on different layers (interlayer case) in undoped bilayer graphene (BLG) in the four-bands model, by directly calculating the Green functions in the eigenvalues and eigenvectors representation. Our results show that both intra- and interlayer RKKY interactions between two magnetic impurities located on the same (opposite) sublattice are always ferromagnetic (antiferromagnetic). Furthermore we find unusual long-distance decay of the RKKY interaction in BLG. The intralyer RKKY interactions between two magnetic impurities located on the same sublattice, J AnAn(R) and J BnBn(R), decay closely as 1 /R6 and 1 /R2 at large impurity distances respectively, but when they are located on opposite sublattices the RKKY interactions exhibit 1 /R4 decays approximately. In the interlayer case, the RKKY interactions between two magnetic impurities located on the same sublattice show a decay close to 1 /R4 at large impurity distances, but if two magnetic impurities be on opposite sublattices the RKKY interactions, J A1B2(R) and J B1A2(R), decay closely as 1 /R6 and 1 /R2 respectively. Both intra- and interlayer RKKY interactions have anisotropic oscillatory factors which for intralayer case is equal to that for single layer graphene (SLG). Our results at weak and strong interlayer coupling limits reduce to the RKKY interaction of SLG and that of BLG in the two-bands approximation respectively.

  10. Piezoelectricity in asymmetrically strained bilayer graphene

    Science.gov (United States)

    Van der Donck, M.; De Beule, C.; Partoens, B.; Peeters, F. M.; Van Duppen, B.

    2016-09-01

    We study the electronic properties of commensurate faulted bilayer graphene by diagonalizing the one-particle Hamiltonian of the bilayer system in a complete basis of Bloch states of the individual graphene layers. Our novel approach is very general and can be easily extended to any commensurate graphene-based heterostructure. Here, we consider three cases: (i) twisted bilayer graphene, (ii) bilayer graphene where triaxial stress is applied to one layer and (iii) bilayer graphene where uniaxial stress is applied to one layer. We show that the resulting superstructures can be divided into distinct classes, depending on the twist angle or the magnitude of the induced strain. The different classes are distinguished from each other by the interlayer coupling mechanism, resulting in fundamentally different low-energy physics. For the cases of triaxial and uniaxial stress, the individual graphene layers tend to decouple and we find significant charge transfer between the layers. In addition, this piezoelectric effect can be tuned by applying a perpendicular electric field. Finally, we show how our approach can be generalized to multilayer systems.

  11. Magnetoacoustic resonance in magnetoelectric bilayers

    Science.gov (United States)

    Filippov, D. A.; Bichurin, M. I.; Petrov, V. M.; Srinivasan, G.

    2004-03-01

    Layered composites of ferrite and ferroelectric single crystal thin films are of interest for studies on magnetoelectric interactions [1,2]. Such interactions result in unique and novel effects that are absent in single phase materials. For example, in a single crystal composite it is possible to control the ferromagnetic resonance (FMR) parameters for the ferrite by means of hypersonic oscillations induced in the ferroelectric phase. The absorption of acoustic oscillations by the ferrite results in variation in FMR line shape and power absorbed. One anticipates resonance absorption of elastic waves when the frequency of elastic waves coincides with the precession frequency of magnetization vector. This work is concerned with the nature of FMR under the influence of acoustic oscillations with the same frequency as FMR. Bilayers of ferrite and piezoelectric single crystals are considered. Hypersonic waves induced in the piezoelectric phase transmit acoustic power into ferrite due to mechanical connectivity between the phases. That transmission depends strongly on interface coupling [3]. We estimate the resulting variations in ferromagnetic resonance line shape. Estimates of magnetoelectric effect at magnetoacoustic resonance are also given. In addition, dependence of absorption of acoustic power on sample dimensions and compliances, electric and magnetic susceptibilities, piezoelectric and magnetostriction coefficients is discussed. The theory provided here is important for an understanding of interface coupling and the nature of magnetoelastic interactions in the composites. 1. M. I. Bichurin and V. M. Petrov, Zh. Tekh. Fiz. 58, 2277 (1988) [Sov. Phys. Tech. Phys. 33, 1389 (1988)]. 2. M.I. Bichurin, I. A. Kornev, V. M. Petrov, A. S. Tatarenko, Yu. V. Kiliba, and G. Srinivasan. Phys. Rev. B 64, 094409 (2001). 3. M. I. Bichurin, V. M. Petrov, and G. Srinivasan, J. Appl. Phys. 92, 7681 (2002). This work was supported by grants from the Russian Ministry of Education (

  12. Possible mechanism of adhesion in a mica supported phospholipid bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Pertsin, Alexander, E-mail: ig3@ix.urz.uni-heidelberg.de [Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg (Germany); Institute of Organo-Element Compounds, Russian Academy of Sciences, Vavilov Str. 28, 117991 Moscow (Russian Federation); Grunze, Michael [Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg (Germany); Institute for Functional Interfaces, Karlsruhe Institute of Technology, Hermann-von- Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2014-05-14

    Phospholipid bilayers supported on hydrophilic solids like silica and mica play a substantial role in fundamental studies and technological applications of phospholipid membranes. In both cases the molecular mechanism of adhesion between the bilayer and the support is of primary interest. Since the possibilities of experimental methods in this specific area are rather limited, the methods of computer simulation acquire great importance. In this paper we use the grand canonical Monte Carlo technique and an atomistic force field to simulate the behavior of a mica supported phospholipid bilayer in pure water as a function of the distance between the bilayer and the support. The simulation reveals a possible adhesion mechanism, where the adhesion is due to individual lipid molecules that protrude from the bilayer and form widely spaced links with the support. Simultaneously, the bilayer remains separated from the bilayer by a thin water interlayer which maintains the bilayer fluidity.

  13. Ionic motion in PEDOT and PPy conducting polymer bilayers

    DEFF Research Database (Denmark)

    Zainudeen, Umer L.; Skaarup, Steen

    2006-01-01

    Conducting polymer bilayers with poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy), each containing dodecyl benzenesulfonate (DBS) as immobile dopant species, were synthesized galvanostatically. The electrochemical behaviour of the bilayers was investigated using cyclic voltammetry...

  14. Design of Asymmetric Peptide Bilayer Membranes.

    Science.gov (United States)

    Li, Sha; Mehta, Anil K; Sidorov, Anton N; Orlando, Thomas M; Jiang, Zhigang; Anthony, Neil R; Lynn, David G

    2016-03-16

    Energetic insights emerging from the structural characterization of peptide cross-β assemblies have enabled the design and construction of robust asymmetric bilayer peptide membranes. Two peptides differing only in their N-terminal residue, phosphotyrosine vs lysine, coassemble as stacks of antiparallel β-sheets with precisely patterned charged lattices stabilizing the bilayer leaflet interface. Either homogeneous or mixed leaflet composition is possible, and both create nanotubes with dense negative external and positive internal solvent exposed surfaces. Cross-seeding peptide solutions with a preassembled peptide nanotube seed leads to domains of different leaflet architecture within single nanotubes. Architectural control over these cross-β assemblies, both across the bilayer membrane and along the nanotube length, provides access to highly ordered asymmetric membranes for the further construction of functional mesoscale assemblies.

  15. Mechanism of lipid bilayer penetration by mixed monolayer-protected gold nanoparticles

    Science.gov (United States)

    van Lehn, Reid; Atukorale, Prabhani; Carney, Randy; Stellacci, Francesco; Irvine, Darrell; Alexander-Katz, Alfredo

    2013-03-01

    Recently, gold nanoparticles (AuNPs) protected by a binary mixture of hydrophobic and hydrophilic alkanethiol ligands were observed to spontaneously penetrate cellular membranes via a non-specific mechanism. Penetration was observed even at low temperatures and in the presence of endocytotic inhibitors, implying that AuNPs crossed the membrane by a non-endocytotic process. Furthermore, penetration was shown to depend on the amphiphilicity and nanoscale morphology of the protecting monolayer. In this work, we use a variety of simulation techniques to elucidate the mechanism of lipid bilayer penetration and compare our results to experiments with lipid vesicles. We show that these AuNPs can stably embed within lipid bilayers by ``snorkeling'' charges out of the bilayer core; the stability of such a state is a function of particle size, the composition of the protecting monolayer, and other environmental conditions. We use detailed simulations to analyze structural changes in the surrounding lipids and show that the energy barrier for embedding is considerably reduced in the presence of bilayer defects. We expect that these results will enable the design of novel drug delivery carriers and biosensors.

  16. Tip-induced deformation of a phospholipid bilayer: Theoretical perspective of sum frequency generation imaging

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, Victor [Bereozovaya 2A, Konstantinovo, Moscow Region 140207 (Russian Federation)

    2014-10-21

    The paper addresses theory of Sum Frequency Generation imaging of an atomic force microscopy tip-induced deformation of a bilayer phospholipid membrane deposited over a pore: known as a nano-drum system. Image modeling employed nonlinearities of the normal modes specific to hydrocarbon terminal methyls, which are distributed about the deformed surfaces of inner and outer leaflets. The deformed profiles are according to the solutions of shape equation for Canham-Helfrich Hamiltonian accounting properties of four membranes, which differ in elasticity and adhesion. The results indicate that in continuous deformed surfaces, the difference in the curvature of the outer and inner leaflets dominates in the imaged nonlinearity. This is different comparing to the results for a perfect bilayer spherical cap system (the subject of previous study), where nonlinear image response is dominated by the mismatch of the inner and outer leaflets’ surface areas (as projected to the image plane) at the edge of perfectly spherical structure. The results of theoretical studies, here, demonstrate that Sum Frequency Generation imaging in continuous and deformed bilayer surfaces are helpful to address curvature locally and anticipate mechanical properties of membrane. The articles discuss applicability and practical limitations of the approach. Combination of Atomic Force Microscopy and Sum Frequency Generation imaging under controlled tip-induced deformation provides a good opportunity to probe and test membranes physical properties with rigor of adopted theory.

  17. Capacitance Variation of Electrolyte-Gated Bilayer Graphene Based Transistors

    OpenAIRE

    Hediyeh Karimi; Rubiyah Yusof; Mohammad Taghi Ahmadi; Mehdi Saeidmanesh; Meisam Rahmani; Elnaz Akbari; Wong King Kiat

    2013-01-01

    Quantum capacitance of electrolyte-gated bilayer graphene field-effect transistors is investigated in this paper. Bilayer graphene has received huge attention due to the fact that an energy gap could be opened by chemical doping or by applying external perpendicular electric field. So, this extraordinary property can be exploited to use bilayer graphene as a channel in electrolyte-gated field-effect transistors. The quantum capacitance of bi-layer graphene with an equivalent circuit is presen...

  18. Temperature effect on plasmons in bilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Digish K., E-mail: jdiggish@gmail.com; Sharma, A. C. [Physics Department, Faculty of Science, The M.S. University of Baroda, Vadodara-390002, Gujarat (India); Ashraf, S. S. Z. [Physics Department, Faculty of Science, Aligarh Muslim University, Aligarh-202002, Uttar Pradesh (India); Ambavale, S. K. [Vishwakarma Government Engineering College Chandkheda, Ahmedabad-382424, Gujarat (India)

    2015-06-24

    We have theoretically investigated the plasmon dispersion and damping rate of doped bilayer graphene (BLG) at finite temperatures within the random phase approximation. Our computed results on plasmon dispersion show that plasmon frequency enhances with increasing temperatures in contrast to single layer graphene where it is suppressed. This can be attributed to the fact that the dynamic response of the electron gas or screening in bilayer graphene is different from that of single layer graphene. Further the temperature effect on damping rate is also discussed.

  19. Bilayer graphene quantum dot defined by topgates

    Energy Technology Data Exchange (ETDEWEB)

    Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W., E-mail: hans.w.schumacher@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

    2014-06-21

    We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.

  20. Flexible-to-semiflexible chain crossover on the pressure-area isotherm of a lipid bilayer

    Science.gov (United States)

    Krivonos, I. N.; Mukhin, S. I.

    2008-01-01

    We find theoretically that competition between ˜ K f q 4 and ˜ Qq 2 terms in the Fourier-transformed conformational energy of a single-lipid chain, in combination with interchain entropic repulsion in the hydrophobic part of the lipid (bi)layer, may cause a crossover on the bilayer pressure-area isotherm P( A)˜( A- A 0)-α. The crossover manifests itself in the transition from α = 5/3 to α = 3. Our microscopic model represents a single-lipid molecule as a worm-like chain with a finite irreducible cross-section area A 0, a flexural rigidity K f , and a stretching modulus Q in a parabolic potential with the self-consistent curvature B( A) formed by entropic interactions between hydrocarbon chains in the lipid layer. The crossover area A* obeys the relation Q/√ K f B( A*) ≈ 2. We predict a peculiar possibility of deducing the effective elastic moduli K f and Q of an individual hydrocarbon chain from the analysis of the isotherm with such a crossover. Also calculated is the crossover-related behavior of the area compressibility modulus K A , the equilibrium area per lipid A t , and the chain order parameter S(θ).

  1. Molecular characterization of gel and liquid-crystalline structures of fully hydrated POPC and POPE bilayers.

    Science.gov (United States)

    Leekumjorn, Sukit; Sum, Amadeu K

    2007-05-31

    Molecular dynamics simulations were used for a comprehensive study of the structural properties of monounsaturated POPC and POPE bilayers in the gel and liquid-crystalline state at a number of temperatures, ranging from 250 to 330 K. Though the chemical structures of POPC and POPE are largely similar (choline versus ethanolamine headgroup), their transformation processes from a gel to a liquid-crystalline state are contrasting. In the similarities, the lipid tails for both systems are tilted below the phase transition and become more random above the phase transition temperature. The average area per lipid and bilayer thickness were found less sensitive to phase transition changes as the unsaturated tails are able to buffer reordering of the bilayer structure, as observed from hysteresis loops in annealing simulations. For POPC, changes in the structural properties such as the lipid tail order parameter, hydrocarbon trans-gauche isomerization, lipid tail tilt-angle, and level of interdigitation identified a phase transition at about 270 K. For POPE, three temperature ranges were identified, in which the lower one (270-280 K) was associated with a pre-transition state and the higher (290-300 K) with the post-transition state. In the pre-transition state, there was a significant increase in the number of gauche arrangements formed along the lipid tails. Near the main transition (280-290 K), there was a lowering of the lipid order parameters and a disappearance of the tilted lipid arrangement. In the post-transition state, the carbon atoms along the lipid tails became less hindered as their density profiles showed uniform distributions. This study also demonstrates that atomistic simulations of current lipid force fields are capable of capturing the phase transition behavior of lipid bilayers, providing a rich set of molecular and structural information at and near the main transition state.

  2. Nanostructured antireflective bilayers: Optical design and preparation

    Energy Technology Data Exchange (ETDEWEB)

    Detrich, Ádám [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary); Nagy, Norbert [Research Centre for Natural Sciences (MTA TTK), Institute for Technical Physics and Materials Science (MFA), P.O. Box 49, H-1525 Budapest (Hungary); Nyári, Mária; Albert, Emőke; Zámbó, Dániel [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary); Hórvölgyi, Zoltán, E-mail: zhorvolgyi@mail.bme.hu [Budapest University of Technology and Economics, Department of Physical Chemistry and Materials Science, Centre for Colloid Chemistry, H-1521 Budapest (Hungary)

    2014-05-01

    We show different methods for tailoring and fabrication of various cost-effective antireflective nanocoatings on transparent and non-transparent substrates. The main purpose was to prepare coatings with decreased reflectance in the full visible wavelength range using simple wet layer deposition techniques. Structure of coatings was designed by optical simulations applying simplified calculations. The refractive index of substrates was also considered for the calculations. The advantageous optical properties were achieved by bilayered structures combining compact and porous sol–gel derived oxide layers and nanoparticulate films. The bilayered structures enhance the flexibility of design by not only the selection of the layer thicknesses but also by different ways of adjusting the effective refractive index of the layers. Furthermore, chemical stability of the coatings was also investigated. The optical and structural properties of prepared films and bilayered coatings were studied by UV–vis spectroscopy and scanning electron microscopy, respectively. The transmittance of coated glass substrates was above 97.5%, while the reflectance of coated silicon substrates was below 4% between 450 nm and 900 nm. - Highlights: • Designed antireflective bilayered coatings on glass and silicon. • Simple, colloid chemical approaches to preparation. • Favorable optical properties by combining compact and porous oxide layers. • Different ways for adjusting the effective refractive index. • Strong chemical resistance against acidic effects.

  3. Reversible Polarization Rotation in Epitaxial Ferroelectric Bilayers

    DEFF Research Database (Denmark)

    Liu, Guangqing; Zhang, Qi; Huang, Hsin-Hui

    2016-01-01

    large-scale polarization rotation switching (≈60 μC cm−2) and an effective d 33 response 500% (≈250 pm V−1) larger than the PZT-R layer alone. Furthermore, this enhancement is stable for more than 107 electrical switching cycles. These bilayers present a simple and highly controllable means to design...

  4. Localized plasmons in bilayer graphene nanodisks

    DEFF Research Database (Denmark)

    Wang, Weihua; Xiao, Sanshui; Mortensen, N. Asger

    2016-01-01

    We study localized plasmonic excitations in bilayer graphene (BLG) nanodisks, comparing AA-stacked and AB-stacked BLG and contrasting the results to the case of two monolayers without electronic hybridization. The electrodynamic response of the BLG electron gas is described in terms of a spatially...

  5. Capillary wrinkling of thin bilayer polymeric sheets

    Science.gov (United States)

    Chang, Jooyoung; Menon, Narayanan; Russell, Thomas

    We have investigated capillary force induced wrinkling on a floated polymeric bilayer thin sheet. The origin of the wrinkle pattern is compressional hoop stress caused by the capillary force of a water droplet placed on the floated polymeric thin sheet afore investigated. Herein, we study the effect of the differences of surface energy arising from the hydrophobicity of Polystyrene (PS Mw: 97 K, Contact Angle: 88 º) and the hydrophilicity of Poly(methylmethacrylate) (PMMA Mw: 99K, Contact Angle: 68 º) on two sides of a bilayer film. We measure the number and the length of the wrinkles by broadly varying the range of thicknesses of top (9 nm to 550 nm) and bottom layer (25 nm to 330 nm). At the same, there is only a small contrast in mechanical properties of the two layers (PS E = 3.4 GPa, and PMMA E = 3 GPa). The number of the wrinkles is not strongly affected by the composition (PS(Top)/PMMA(Bottom) or PMMA(Top)/PS(Bottom)) and the thickness of each and overall bilayer system. However, the length of the wrinkle is governed by the contact angle of the drop on the top layer of bilayer system. We also compare this to the wrinkle pattern obtained in monolayer systems over a wide range of thickness from PS and PMMA (7 nm to 1 μm). W.M. Keck Foundation.

  6. Bilayer Tablet via Microsphere: A Review

    Directory of Open Access Journals (Sweden)

    Piyushkumar Vinubhai Gundaraniya

    2013-01-01

    Full Text Available The aim of the present work is to develop bilayer tablets containing sustained release microspheres as one layer and immediate release as another layer. The proposed dosage form is intended to decrease the dosing frequency and the combined administration of an anti-diabetic agent. Several pharmaceutical companies are currently developing bi-layer tablets, for a variety of reasons: patent extension, therapeutic, marketing to name a few. To reduce capital investment, quite often existing but modified tablet presses are used to develop and produce such tablets. One such approach is using microspheres as carriers for drugs also known as micro particles. It is the reliable means to deliver the drug to the target site with specificity, if modified, and to maintain the desired concentration at the site of interest. Microspheres received much attention not only for prolonged release, but also for targeting of anti-diabetic drugs. Bilayer tablet via microsphere is new era for the successful development of controlled release formulation along with various features to provide a way of successful drug delivery system. Especially when in addition high production output is required. An attempt has been made in this review article to introduce the society to the current technological developments in bilayer and floating drug delivery system.

  7. Confinement of charge carriers in bilayer graphene

    NARCIS (Netherlands)

    Goossens, A.M.

    2013-01-01

    In this thesis we investigate the fundamental properties of electronic transport in bilayer graphene. We do this by confining electrons to narrow constrictions and small islands. Our key result is the fabrication and measurement of nanoscale devices that permit confinement with electric fields in b

  8. Electronic properties of a biased graphene bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Eduardo V; Lopes dos Santos, J M B [CFP and Departamento de Fisica, Faculdade de Ciencias Universidade do Porto, P-4169-007 Porto (Portugal); Novoselov, K S; Morozov, S V; Geim, A K [Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Peres, N M R [Centre of Physics and Departamento de Fisica, Universidade do Minho, P-4710-057 Braga (Portugal); Nilsson, Johan; Castro Neto, A H [Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215 (United States); Guinea, F [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

    2010-05-05

    We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and {gamma}{sub 4} (inter-layer), and the on-site energy {Delta}.

  9. Electronic properties of a biased graphene bilayer.

    Science.gov (United States)

    Castro, Eduardo V; Novoselov, K S; Morozov, S V; Peres, N M R; Lopes dos Santos, J M B; Nilsson, Johan; Guinea, F; Geim, A K; Castro Neto, A H

    2010-05-01

    We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system-a biased bilayer. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its four-band and two-band continuum approximations, and the four-band model is shown to always be a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, made out of either SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point for understanding the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, such as the second-nearest-neighbour hopping energies t' (in-plane) and γ(4) (inter-layer), and the on-site energy Δ.

  10. Topological transformation of a surfactant bilayer

    DEFF Research Database (Denmark)

    Le, T.D.; Olsson, U.; Mortensen, K.

    2000-01-01

    Surfactant lamellar phases are often complicated by the formation of multilamellar (onions) under shear, which can originate simply by shaking the sample. A systematic study has been performed on the C10E3-D2O system in which different bilayer structures under a steady shear flow were investigated...

  11. Electronic properties of graphene-based bilayer systems

    Energy Technology Data Exchange (ETDEWEB)

    Rozhkov, A.V., E-mail: arozhkov@gmail.com [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141700 (Russian Federation); Sboychakov, A.O. [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Rakhmanov, A.L. [CEMS, RIKEN, Saitama 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412 Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141700 (Russian Federation); All-Russia Research Institute of Automatics, Moscow, 127055 (Russian Federation); Nori, Franco, E-mail: fnori@riken.jp [CEMS, RIKEN, Saitama 351-0198 (Japan); Physics Department, The University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2016-08-23

    This article reviews the theoretical and experimental work related to the electronic properties of bilayer graphene systems. Three types of bilayer stackings are discussed: the AA, AB, and twisted bilayer graphene. This review covers single-electron properties, effects of static electric and magnetic fields, bilayer-based mesoscopic systems, spin–orbit coupling, dc transport and optical response, as well as spontaneous symmetry violation and other interaction effects. The selection of the material aims to introduce the reader to the most commonly studied topics of theoretical and experimental research in bilayer graphene.

  12. Electronic properties of graphene-based bilayer systems

    Science.gov (United States)

    Rozhkov, A. V.; Sboychakov, A. O.; Rakhmanov, A. L.; Nori, Franco

    2016-08-01

    This article reviews the theoretical and experimental work related to the electronic properties of bilayer graphene systems. Three types of bilayer stackings are discussed: the AA, AB, and twisted bilayer graphene. This review covers single-electron properties, effects of static electric and magnetic fields, bilayer-based mesoscopic systems, spin-orbit coupling, dc transport and optical response, as well as spontaneous symmetry violation and other interaction effects. The selection of the material aims to introduce the reader to the most commonly studied topics of theoretical and experimental research in bilayer graphene.

  13. In situ atomic force microscope imaging of supported lipid bilayers

    DEFF Research Database (Denmark)

    Kaasgaard, Thomas; Leidy, Chad; Ipsen, John Hjorth

    2001-01-01

    In situ AFM images of phospholipase A/sub 2/ (PLA/sub 2/) hydrolysis of mica-supported one- and two-component lipid bilayers are presented. For one-component DPPC bilayers an enhanced enzymatic activity is observed towards preexisting defects in the bilayer. Phase separation is observed in two......-component DMPC-DSPC bilayers and a remarkable enhanced hydrolytic activity of the PLA/sub 2/-enzyme for the DMPC-rich phase is seen. Furthermore, in a supported double bilayer system a characteristic ripple structure, most likely related to the formation of the P/sub beta /-ripple phase is observed....

  14. Oxygenated Derivatives of Hydrocarbons

    Science.gov (United States)

    For the book entitled “Insect Hydrocarbons: Biology, Biochemistry and Chemical Ecology”, this chapter presents a comprehensive review of the occurrence, structure and function of oxygenated derivatives of hydrocarbons. The book chapter focuses on the occurrence, structural identification and functi...

  15. Hydrocarbon Spectral Database

    Science.gov (United States)

    SRD 115 Hydrocarbon Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.

  16. Proteomics Core

    Data.gov (United States)

    Federal Laboratory Consortium — Proteomics Core is the central resource for mass spectrometry based proteomics within the NHLBI. The Core staff help collaborators design proteomics experiments in a...

  17. Proteomics Core

    Data.gov (United States)

    Federal Laboratory Consortium — Proteomics Core is the central resource for mass spectrometry based proteomics within the NHLBI. The Core staff help collaborators design proteomics experiments in...

  18. General model of phospholipid bilayers in fluid phase within the single chain mean field theory

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yachong; Baulin, Vladimir A. [Departament d’Enginyeria Química, Universitat Rovira i Virgili, Av. dels Paisos Catalans 26, 43007 Tarragona (Spain); Pogodin, Sergey [Institute of Chemical Research of Catalonia, ICIQ, Av. Paisos Catalans 16, 43007 Tarragona (Spain)

    2014-05-07

    Coarse-grained model for saturated phospholipids: 1,2-didecanoyl-sn-glycero-3-phosphocholine (DCPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and unsaturated phospholipids: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2- dioleoyl-sn-glycero-3-phosphocholine (DOPC) is introduced within the single chain mean field theory. A single set of parameters adjusted for DMPC bilayers gives an adequate description of equilibrium and mechanical properties of a range of saturated lipid molecules that differ only in length of their hydrophobic tails and unsaturated (POPC, DOPC) phospholipids which have double bonds in the tails. A double bond is modeled with a fixed angle of 120°, while the rest of the parameters are kept the same as saturated lipids. The thickness of the bilayer and its hydrophobic core, the compressibility, and the equilibrium area per lipid correspond to experimentally measured values for each lipid, changing linearly with the length of the tail. The model for unsaturated phospholipids also fetches main thermodynamical properties of the bilayers. This model is used for an accurate estimation of the free energies of the compressed or stretched bilayers in stacks or multilayers and gives reasonable estimates for free energies. The proposed model may further be used for studies of mixtures of lipids, small molecule inclusions, interactions of bilayers with embedded proteins.

  19. Plant hydrocarbon recovery process

    Energy Technology Data Exchange (ETDEWEB)

    Dzadzic, P.M.; Price, M.C.; Shih, C.J.; Weil, T.A.

    1982-01-26

    A process for production and recovery of hydrocarbons from hydrocarbon-containing whole plants in a form suitable for use as chemical feedstocks or as hydrocarbon energy sources which process comprises: (A) pulverizing by grinding or chopping hydrocarbon-containing whole plants selected from the group consisting of euphorbiaceae, apocynaceae, asclepiadaceae, compositae, cactaceae and pinaceae families to a suitable particle size, (B) drying and preheating said particles in a reducing atmosphere under positive pressure (C) passing said particles through a thermal conversion zone containing a reducing atmosphere and with a residence time of 1 second to about 30 minutes at a temperature within the range of from about 200* C. To about 1000* C., (D) separately recovering the condensable vapors as liquids and the noncondensable gases in a condition suitable for use as chemical feedstocks or as hydrocarbon fuels.

  20. Plasma devices for hydrocarbon reformation

    KAUST Repository

    Cha, Min Suk

    2017-02-16

    Plasma devices for hydrocarbon reformation are provided. Methods of using the devices for hydrocarbon reformation are also provided. The devices can include a liquid container to receive a hydrocarbon source, and a plasma torch configured to be submerged in the liquid. The plasma plume from the plasma torch can cause reformation of the hydrocarbon. The device can use a variety of plasma torches that can be arranged in a variety of positions in the liquid container. The devices can be used for the reformation of gaseous hydrocarbons and/or liquid hydrocarbons. The reformation can produce methane, lower hydrocarbons, higher hydrocarbons, hydrogen gas, water, carbon dioxide, carbon monoxide, or a combination thereof.

  1. Hydrocarbon geochemistry of the Puget Sound region. II. Sedimentary diterpenoid, steroid and triterpenoid hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Barrick, R.C.; Hedges, J.I.

    1981-03-01

    Cyclic components of the aliphatic hydrocarbon mixtures extracted from Puget Sound sediment cores include a suite of C/sub 19/ and C/sub 20/ diterpenoid hydrocarbons of which fichtelite, sandaracopimaradiene, and isopimaradiene have been identified. Although apparently also derived from vascular plants, these diterpenoid hydrocarbons have relative abundances distinctly different from the co-existing plant wax n-alkane suite. Five C/sub 27/, C/sub 28/ and C/sub 29/ diasteranes and four C/sub 29/, C/sub 30/ and C/sub 31/ 17..cap alpha..(H), 21..beta..(H) hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage. These chromatographically resolved cycloalkanes, along with the strongly covarying unresolved complex mixture, have been introduced to Puget Sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill. Naturally-occurring triterpenoid hydrocarbons, including hop-22(29)-ene (diploptene), are also present. A new group of C/sub 30/ polyenes has been detected which contains compounds apparently structurally related to a co-existing bicyclic C/sub 25/ diene and to C/sub 20/ and C/sub 25/ acyclic multibranched hydrocarbons described in a previous paper (Barrick et al., 1980).

  2. Hydrocarbon geochemistry of the Puget Sound region - II. Sedimentary diterpenoid, steroid and triterpenoid hydrocarbons

    Science.gov (United States)

    Barrick, Robert C.; Hedges, John I.

    1981-03-01

    Cyclic components of the 'aliphatic' hydrocarbon mixtures extracted from Puget Sound sediment cores include a suite of C 19 and C 20 diterpenoid hydrocarbons of which fichtelite. sandaracopimaradiene, and isopimaradiene have been identified. Although apparently also derived from vascular plants, these diterpenoid hydrocarbons have relative abundances distinctly different from the co-existing plant wax n-alkane suite. Five C 27, C 28 and C 29 diasteranes and four C 29, C 30 and C 31 17α(H), 21β(H) hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage. These chromatographically resolved cycloalkanes. along with the strongly covarying unresolved complex mixture, have been introduced to Puget Sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill. Naturally-occurring triterpenoid hydrocarbons, including hop-22(29)-ene (diploptene), are also present. A new group of C 30 polyenes has been detected which contains compounds apparently structurally related to a co-existing bicyclic C 25 diene and to C 20 and C 25 acyclic multibranched hydrocarbons described in a previous paper ( BARRICK et al., 1980).

  3. Construction and Structural Analysis of Tethered Lipid Bilayer Containing Photosynthetic Antenna Proteins for Functional Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sumino, Ayumi; Dewa, Takehisa; Takeuchi, Toshikazu; Sugiura, Ryuta; Sasaki, Nobuaki; Misawa, Nobuo; Tero, Ryugo; Urisu, Tsuneo; Gardiner, Alastair T; Cogdell, Richard J; Hashimoto, Hideki; Nango, Mamoru

    2011-07-11

    The construction and structural analysis of a tethered planar lipid bilayer containing bacterial photosynthetic membrane proteins, light-harvesting complex 2 (LH2), and light-harvesting core complex (LH1-RC) is described and establishes this system as an experimental platform for their functional analysis. The planar lipid bilayer containing LH2 and/or LH1-RC complexes was successfully formed on an avidin-immobilized coverglass via an avidin-biotin linkage. Atomic force microscopy (AFM) showed that a smooth continuous membrane was formed there. Lateral diffusion of these membrane proteins, observed by a fluorescence recovery after photobleaching (FRAY), is discussed in terms of the membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane architecture. Energy transfer from LH2 to LH1-RC within the tethered membrane was observed by steady-state fluorescence spectroscopy, indicating that the tethered membrane can mimic the natural situation.

  4. Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications

    Science.gov (United States)

    Soares, Paula I. P.; Laia, César A. T.; Carvalho, Alexandra; Pereira, Laura C. J.; Coutinho, Joana T.; Ferreira, Isabel M. M.; Novo, Carlos M. M.; Borges, João Paulo

    2016-10-01

    Iron oxide nanoparticles (Fe3O4, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of -120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

  5. Design of a bilayer ceramic capacitor with low temperature coefficient of capacitance

    Science.gov (United States)

    Foeller, P. Y.; Dean, J. S.; Reaney, I. M.; Sinclair, D. C.

    2016-08-01

    We show how a simple bilayer system that combines a layer of undoped BaTiO3 (BT) with a second layer of Ba0.975Na0.025Ti0.975Nb0.025O3 (2.5NNBT) can be used to improve the temperature coefficient of capacitance (TCC) of BaTiO3-based materials for capacitor applications. The bilayer system emulates the volume ratio between a conventional core and shell phase microstructure allowing a simple resource efficient approach to optimise the system for low TCC. Optimisation was achieved with a volume ratio of 0.67 2.5NNBT with 0.33 BT and results in a TCC of ±6% over the temperature range ˜25 to 125 °C whilst maintaining a permittivity of ɛr ˜ 3000 and low dielectric loss.

  6. Multiscale Modeling of Supported Lipid Bilayers

    Science.gov (United States)

    Hoopes, Matthew I.; Xing, Chenyue; Faller, Roland

    Cell membranes consist of a multitude of lipid molecules that serve as a framework for the even greater variety of membrane associated proteins [1-4]. As this highly complex (nonequilibrium) system cannot easily be understood and studied in a controlled way, a wide variety of model systems have been devised to understand the dynamics, structure, and thermodynamics in biological membranes. One such model system is a supported lipid bilayer (SLB), a two-dimensional membrane suspended on a surface. SLBs have been realized to be manageable experimentally while reproducing many of the key features of real biological membranes [5,6]. One of the main advantages of supported bilayers is the physical stability due to the solid support that enables a wide range of surface characterization techniques not available to free or unsupported membranes. As SLBs maintain some of the crucial structural and dynamic properties of biological membranes, they provide an important bridge to natural systems. In order to mimic cell membranes reliably, certain structural and dynamic features have to be reliably reproduced in the artificially constructed lipid bilayers. SLBs should display lateral mobility as in living cells, because many membrane activities involve transport, recruitment, or assembly of specific components. It is also critical for membranes to exhibit the correct thermodynamic phase, namely, a fluid lipid bilayer, to respond to environmental stress such as temperature and pressure changes [7]. There are several ways to fabricate supported lipid bilayers (SLBs) on planar substrates. One can use vesicle fusion on solid substrates [5,8-10] as well as Langmuir-Blodgett deposition [11,12]. Proteoliposome adsorption and subsequent membrane formation on a mica surface was first demonstrated by Brian and McConnell [13]. Because of its simplicity and reproducibility, this is one of the most common approaches to prepare supported membranes. A diverse range of different solid substrates

  7. A New Route to Liposil Formation by an Interfacial Sol-Gel Process Confined by Lipid Bilayer.

    Science.gov (United States)

    Shen, Shukun; Yang, Lu; Lu, Yaxing; Chen, Jian-Gang; Song, Shaofei; Hu, Daodao; Parikh, Atul

    2015-11-18

    We report a new and simple approach to prepare a class of silica-reinforced liposomes with hybrid core-shell nanostructures. The amphiphilic natural structure of lipids was exploited to sequester hydrophobic molecules, namely precursor TEOS and pyrene, in the hydrophobic midplane of liposomal bilayer assemblies in the aqueous phase. Subsequent interfacial hydrolysis of TEOS at the bilayer/water interface and ensuing condensation within the hydrophobic interstices of the lipid bilayer drives silica formation in situ, producing a novel class of silica-lipid hybrid liposils. Structural characterization by scanning- and transmission electron microscopy confirm that the liposils so generated preserve closed topologies and size-monodipersity of the parent lecithin liposomes, and DSC-TGA and XRD measurements provide evidence for the silica coating. Monitoring fluorescence measurements using embedded pyrene yield detailed information on microenvironment changes, which occur during sol-gel process and shed light on the structural evolution during silica formation. We envisage that liposils formed by this simple, new approach, exploiting the hydrophobic core of the lipid bilayer to spatially localize silica-forming precursors enables preparation of stable liposils exhibiting capacity for cargo encapsulation, bicompatibility, and fluorescence monitoring, more generally opening a window for construction of stable, functional hybrid materials.

  8. Fluctuations in lipid bilayers: Are they understood?

    CERN Document Server

    Schmid, Friederike

    2013-01-01

    We review recent computer simulation studies of undulating lipid bilayers. Theoretical interpretations of such fluctuating membranes are most commonly based on generalized Helfrich-type elastic models, with additional contributions of local "protrusions" and/or density fluctuations. Such models provide an excellent basis for describing the fluctuations of tensionless bilayers in the fluid phase at a quantitative level. However, this description is found to fail for membranes in the gel phase and for membranes subject to high tensions. The fluctuations of tilted gel membranes show a signature of the modulated ripple structure, which is a nearby phase observed in the pretransition regime between the fluid and tilted gel state. This complicates a quantitative analysis on mesoscopic length scales. In the case of fluid membranes under tension, the large-wavelength fluctuation modes are found to be significantly softer than predicted by theory. In the latter context, we also address the general problem of the relat...

  9. Stokesian jellyfish: Viscous locomotion of bilayer vesicles

    CERN Document Server

    Evans, Arthur A; Lauga, Eric

    2010-01-01

    Motivated by recent advances in vesicle engineering, we consider theoretically the locomotion of shape-changing bilayer vesicles at low Reynolds number. By modulating their volume and membrane composition, the vesicles can be made to change shape quasi-statically in thermal equilibrium. When the control parameters are tuned appropriately to yield periodic shape changes which are not time-reversible, the result is a net swimming motion over one cycle of shape deformation. For two classical vesicle models (spontaneous curvature and bilayer coupling), we determine numerically the sequence of vesicle shapes through an enthalpy minimization, as well as the fluid-body interactions by solving a boundary integral formulation of the Stokes equations. For both models, net locomotion can be obtained either by continuously modulating fore-aft asymmetric vesicle shapes, or by crossing a continuous shape-transition region and alternating between fore-aft asymmetric and fore-aft symmetric shapes. The obtained hydrodynamic e...

  10. Electric Octupole Order in Bilayer Rashba System

    Science.gov (United States)

    Hitomi, Takanori; Yanase, Youichi

    2016-12-01

    The odd-parity multipole is an emergent degree of freedom, leading to spontaneous inversion symmetry breaking. The odd-parity multipole order may occur by forming staggered even-parity multipoles in a unit cell. We focus on a locally noncentrosymmetric bilayer Rashba system, and study an odd-parity electric octupole order caused by the antiferro stacking of local electric quadrupoles. Analyzing the forward scattering model, we show that the electric octupole order is stabilized by a layer-dependent Rashba spin-orbit coupling. The roles of the spin-orbit coupling are clarified on the basis of the analytic formula of multipole susceptibility. The spin texture allowed in the D2d point group symmetry and its magnetic response are revealed. Furthermore, we show that the parity-breaking quantum critical point appears in the magnetic field. The possible realization of the electric octupole order in bilayer high-Tc cuprate superconductors is discussed.

  11. Historical polycyclic aromatic and petrogenic hydrocarbon loading in Northern Central Gulf of Mexico shelf sediments

    Energy Technology Data Exchange (ETDEWEB)

    Overton, E.B.; Ashton, B.M.; Miles, M.S. [Louisiana State University, Baton Rouge, LA (United States). Dept. of Environmental Studies

    2005-10-01

    The distribution of selected hydrocarbons within ten dated sediment cores taken from the Mississippi River Bight off coastal Louisiana suggests a chronic contaminant loading from several sources including the river itself, oil and gas exploration in the central Gulf of Mexico (GOM) shelf area, and natural geologic hydrocarbon seeps. Data were grouped as either total polycyclic aromatic hydrocarbons (PAH's), which were indicative of pyrogenic PAH's; or estimated total hopanes (indicative of petrogenic hydrocarbons). The total PAH concentrations and estimated total hopanes begin increasing above background levels (approximately 200 ng g{sup -1}) after the 1950s. The distribution of these hydrocarbons and hopanes within the dated sediment cores suggests that the Mississippi River is a regional source of pyrogenic PAH's, and that the hopanes are from natural geologic hydrocarbon seeps, oil and gas exploration in the GOM, or both. (author)

  12. Structure of twisted and buckled bilayer graphene

    Science.gov (United States)

    Jain, Sandeep K.; Juričić, Vladimir; Barkema, Gerard T.

    2017-03-01

    We study the atomic structure of twisted bilayer graphene, with very small mismatch angles (θ ∼ {0.28}0), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for single-layer graphene, with a new term for out-of-plane deformations, (Jain et al 2015 J. Phys. Chem. C 119 9646) and an often-used interlayer potential (Kolmogorov et al 2005 Phys. Rev. B 71 235415). This combination of potentials is computationally cheap but accurate and precise at the same time, allowing us to study very large samples, which is necessary to reach very small mismatch angles in periodic samples. By performing large scale atomistic simulations, we show that the vortices appearing in the Moiré pattern in the twisted bilayer graphene samples converge to a constant size in the thermodynamic limit. Furthermore, the well known sinusoidal behavior of energy no longer persists once the misorientation angle becomes very small (θ \\lt {1}0). We also show that there is a significant buckling after the relaxation in the samples, with the buckling height proportional to the system size. These structural properties have direct consequences on the electronic and optical properties of bilayer graphene.

  13. Ion beam mixing isotopic metal bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Fell, C.J. [Newcastle Univ., NSW (Australia). Dept. of Physics; Kenny, M.J. [CSIRO, Lindfield, NSW (Australia). Div. of Applied Physics

    1993-12-31

    In order to obtain an insight into the mechanisms of ion-solid interactions, bilayer targets can be prepared from two different isotopes. A mixing study SIMS is to be carried out using specially grown monocrystalline bilayers of {sup 58}Ni / {sup 60}Ni. An important aspect of the work is the preparation of high quality single-crystal thin films. The Ni layers will be grown on the (110) surface of pure Ni and verified for crystallinity using Reflection High-Energy Electron Diffraction and Rutherford Backscattering channelling analysis. The Pd bilayers will be grown on a Pd (100) surface. RHEED will be used to confirm the two-dimensional crystallinity of the surface before and after deposition of each layer, and channelling used to confirm bulk film crystallinity. Single crystal substrates are currently being prepared. Analysis of the Ni (110) surface using RHEED at 9 kV shows a streak spacing which corresponds to a lattice spacing of 2.47 {+-} 0.09 Angstroms. 9 refs., 1 fig.

  14. Self-folding graphene-polymer bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Tao [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China); Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Yoon, ChangKyu [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Jin, Qianru [Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Li, Mingen [Department of Physics, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Liu, Zewen [Institute of Microelectronics, Tsinghua University, Beijing 100084 (China); Gracias, David H., E-mail: dgracias@jhu.edu [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2015-05-18

    In order to incorporate the extraordinary intrinsic thermal, electrical, mechanical, and optical properties of graphene with three dimensional (3D) flexible substrates, we introduce a solvent-driven self-folding approach using graphene-polymer bilayers. A polymer (SU-8) film was spin coated atop chemically vapor deposited graphene films on wafer substrates and graphene-polymer bilayers were patterned with or without metal electrodes using photolithography, thin film deposition, and etching. After patterning, the bilayers were released from the substrates and they self-folded to form fully integrated, curved, and folded structures. In contrast to planar graphene sensors on rigid substrates, we assembled curved and folded sensors that are flexible and they feature smaller form factors due to their 3D geometry and large surface areas due to their multiple rolled architectures. We believe that this approach could be used to assemble a range of high performance 3D electronic and optical devices of relevance to sensing, diagnostics, wearables, and energy harvesting.

  15. Self-folding graphene-polymer bilayers

    Science.gov (United States)

    Deng, Tao; Yoon, ChangKyu; Jin, Qianru; Li, Mingen; Liu, Zewen; Gracias, David H.

    2015-05-01

    In order to incorporate the extraordinary intrinsic thermal, electrical, mechanical, and optical properties of graphene with three dimensional (3D) flexible substrates, we introduce a solvent-driven self-folding approach using graphene-polymer bilayers. A polymer (SU-8) film was spin coated atop chemically vapor deposited graphene films on wafer substrates and graphene-polymer bilayers were patterned with or without metal electrodes using photolithography, thin film deposition, and etching. After patterning, the bilayers were released from the substrates and they self-folded to form fully integrated, curved, and folded structures. In contrast to planar graphene sensors on rigid substrates, we assembled curved and folded sensors that are flexible and they feature smaller form factors due to their 3D geometry and large surface areas due to their multiple rolled architectures. We believe that this approach could be used to assemble a range of high performance 3D electronic and optical devices of relevance to sensing, diagnostics, wearables, and energy harvesting.

  16. Thraustochytrid protists degrade hydrocarbons

    Digital Repository Service at National Institute of Oceanography (India)

    Raikar, M.T.; Raghukumar, S.; Vani, V.; David, J.J.; Chandramohan, D.

    Rev, 54 (1990) 305-315. 12 Fedorak P M & Westlake D W S, Microbial degradation of aromatics and saturates in Prudhoe Bay crude oil as determined by glass capillary gas chromatography, Can J Microbiol, (1981) 432-443. 13 Atlas R M, Microbial... degradation of petroleum hydrocarbons: An environmental perspective, Microbiol Rev, 45 (1981) 180-209. 14 Atlas R M, Microbial hydrocarbon degradation- Bioremediation of oil spills, J Chem Tech Biotechnol, 52 (1991) 149-156 15 Venkateswaran K, Iwabuchi T...

  17. Method of fabricating lipid bilayer membranes on solid supports

    Science.gov (United States)

    Cho, Nam-Joon (Inventor); Frank, Curtis W. (Inventor); Glenn, Jeffrey S. (Inventor); Cheong, Kwang Ho (Inventor)

    2012-01-01

    The present invention provides a method of producing a planar lipid bilayer on a solid support. With this method, a solution of lipid vesicles is first deposited on the solid support. Next, the lipid vesicles are destabilized by adding an amphipathic peptide solution to the lipid vesicle solution. This destabilization leads to production of a planar lipid bilayer on the solid support. The present invention also provides a supported planar lipid bilayer, where the planar lipid bilayer is made of naturally occurring lipids and the solid support is made of unmodified gold or titanium oxide. Preferably, the supported planar lipid bilayer is continuous. The planar lipid bilayer may be made of any naturally occurring lipid or mixture of lipids, including, but not limited to phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinsitol, cardiolipin, cholesterol, and sphingomyelin.

  18. Molecular dynamics modelling of EGCG clusters on ceramide bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Yeo, Jingjie; Cheng, Yuan; Li, Weifeng; Zhang, Yong-Wei [Institute of High Performance Computing, A*STAR, 138632 (Singapore)

    2015-12-31

    A novel method of atomistic modelling and characterization of both pure ceramide and mixed lipid bilayers is being developed, using only the General Amber ForceField. Lipid bilayers modelled as pure ceramides adopt hexagonal packing after equilibration, and the area per lipid and bilayer thickness are consistent with previously reported theoretical results. Mixed lipid bilayers are modelled as a combination of ceramides, cholesterol, and free fatty acids. This model is shown to be stable after equilibration. Green tea extract, also known as epigallocatechin-3-gallate, is introduced as a spherical cluster on the surface of the mixed lipid bilayer. It is demonstrated that the cluster is able to bind to the bilayers as a cluster without diffusing into the surrounding water.

  19. Equilibrium insertion of nanoscale objects into phospholipid bilayers

    CERN Document Server

    Pogodin, Sergey

    2011-01-01

    Certain membrane proteins, peptides, nanoparticles and nanotubes have rigid structure and fixed shape. They are often viewed as spheres and cylinders with certain surface properties. Single Chain Mean Field theory is used to model the equilibrium insertion of nanoscale spheres and rods into the phospholipid bilayer. The equilibrium structures and the resulting free energies of the nano-objects in the bilayer allow to distinguish different orientations in the bilayer and estimate the energy barrier of insertion.

  20. Pair interaction of bilayer-coated nanoscopic particles

    Institute of Scientific and Technical Information of China (English)

    Zhang Qi-Yi

    2009-01-01

    The pair interaction between bilayer membrane-coated nanosized particles has been explored by using the self-consistent field (SCF) theory. The bilayer membranes are composed of amphiphilic polymers. For different system parameters, the pair-interaction free energies are obtained. Particular emphasis is placcd on the analysis of a sequence of structural transformations of bilayers on spherical particles, which occur during their approaching processes. For different head fractions of amphiphilcs, the asymmetrical morphologies between bilayers on two particles and the inverted micellar intermediates have been found in the membrane fusion pathway. These results can benefit the fabrication of vesicles as encapsulation vectors for drug and gene delivery.

  1. Intercalation of small hydrophobic molecules in lipid bilayers containing cholesterol

    Energy Technology Data Exchange (ETDEWEB)

    Worcester, D.L.; Hamacher, K.; Kaiser, H.; Kulasekere, R.; Torbet, J. [Univ. of Missouri, Columbia, MO (United States)

    1994-12-31

    Partitioning of small hydrophobic molecules into lipid bilayers containing cholesterol has been studied using the 2XC diffractometer at the University of Missouri Research Reactor. Locations of the compounds were determined by Fourier difference methods with data from both deuterated and undeuterated compounds introduced into the bilayers from the vapor phase. Data fitting procedures were developed for determining how well the compounds were localized. The compounds were found to be localized in a narrow region at the center of the hydrophobic layer, between the two halves of the bilayer. The structures are therefore intercalated structures with the long axis of the molecules in the plane of the bilayer.

  2. Faraday rotation in bilayer graphene-based integrated microcavity.

    Science.gov (United States)

    Da, Hai-Xia; Yan, Xiao-Hong

    2016-01-01

    Bernal-stacked bilayer graphene has rich ground states with various broken symmetries, allowing the existence of magneto-optical (MO) effects even in the absence of an external magnetic field. Here we report controllable Faraday rotation (FR) of bilayer graphene induced by electrostatic gate voltage, whose value is 10 times smaller than the case of single layer graphene with a magnetic field. A proposed bilayer graphene-based microcavity configuration enables the enhanced FR angle due to the large localized electromagnetic field. Our results offer unique opportunities to apply bilayer graphene for MO devices.

  3. Ice cores

    DEFF Research Database (Denmark)

    Svensson, Anders

    2014-01-01

    Ice cores from Antarctica, from Greenland, and from a number of smaller glaciers around the world yield a wealth of information on past climates and environments. Ice cores offer unique records on past temperatures, atmospheric composition (including greenhouse gases), volcanism, solar activity......, dustiness, and biomass burning, among others. In Antarctica, ice cores extend back more than 800,000 years before present (Jouzel et al. 2007), whereas. Greenland ice cores cover the last 130,000 years...

  4. ATR-IR spectroscopic study of the structural changes in the hydrophobic region of ICPAN/DPPC bilayers

    Science.gov (United States)

    Cieślik-Boczula, Katarzyna; Czarnik-Matusewicz, Bogusława; Perevozkina, Margarita; Filarowski, Aleksander; Boens, Noël; De Borggraeve, Wim M.; Koll, Aleksander

    2008-04-01

    Structural changes in the hydrophobic region in the self-aggregates of the long hydrocarbon chain ICPAN ((( N, N-dimethyl- N-octyl-2-ammonioethyl)-3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate bromide)) homologues and their interaction with a DPPC (dipalmitoylophosphatidylcholine) bilayer were the subject of detailed investigation using ATR infrared spectroscopy. On the base of analysis of the bands assigned to CH 2 stretching, scissoring, and rocking and CH wagging vibrations it was revealed that the hydrophobic parts ICPANs adopt a gauche-rich disordering structure. Moreover, it was shown that the micellar- or lamellar-like character of these structures depends on the hydrocarbon chain length. Results obtained from the ICPAN/DPPC mixtures indicate an increase in the conformational disorder in hydrophobic part compare to pure DPPC film. This effect depends on the length of the aliphatic chain of ICPAN homologues and on the relative concentrations of DPPC and ICPAN.

  5. Ether- versus ester-linked phospholipid bilayers containing either linear or branched apolar chains.

    Science.gov (United States)

    Balleza, Daniel; Garcia-Arribas, Aritz B; Sot, Jesús; Ruiz-Mirazo, Kepa; Goñi, Félix M

    2014-09-16

    We studied the properties of bilayers formed by ether-and ester-containing phospholipids, whose hydrocarbon chains can be either linear or branched, using sn-1,2 dipalmitoyl, dihexadecyl, diphytanoyl, and diphytanyl phosphatidylcholines (DPPC, DHPC, DPhoPC, and DPhPC, respectively) either pure or in binary mixtures. Differential scanning calorimetry and confocal fluorescence microscopy of giant unilamellar vesicles concurred in showing that equimolar mixtures of linear and branched lipids gave rise to gel/fluid phase coexistence at room temperature. Mixtures containing DHPC evolved in time (0.5 h) from initial reticulated domains to extended solid ones when an equilibrium was achieved. The nanomechanical properties of supported planar bilayers formed by each of the four lipids studied by atomic force microscopy revealed average breakdown forces Fb decreasing in the order DHPC ≥ DPPC > DPhoPC > DPhPC. Moreover, except for DPPC, two different Fb values were found for each lipid. Atomic force microscopy imaging of DHPC was peculiar in showing two coexisting phases of different heights, probably corresponding to an interdigitated gel phase that gradually transformed, over a period of 0.5 h, into a regular tilted gel phase. Permeability to nonelectrolytes showed that linear-chain phospholipids allowed a higher rate of solute + water diffusion than branched-chain phospholipids, yet the former supported a smaller extent of swelling of the corresponding vesicles. Ether or ester bonds appeared to have only a minor effect on permeability.

  6. Neutron reflectivity studies of single lipid bilayers supported on planar substrates

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, S.; Orts, W.J.; Berk, N.F.; Majkrzak, C.F. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Koenig, B.W. [National Inst. of Health, Bethesda, MD (United States)

    1994-12-31

    Neutron reflectivity was used to probe the structure of single phosphatidylcholine (PC) lipid bilayers adsorbed onto a planar silicon surface in an aqueous environment. Fluctuations in the neutron scattering length density profiles perpendicular to the silicon/water interface were determined for different lipids as a function of the hydrocarbon chain length. The lipids were studied in both the gel and liquid crystalline phases by monitoring changes in the specularly-reflected neutron intensity as a function of temperature. Contrast variation of the neutron scattering length density was applied to both the lipid and the solvent. Scattering length density profiles were determined using both model-independent and model-dependent fitting methods. During the reflectivity measurements, a novel experimental set-up was implemented to decrease the incoherent background scattering due to the solvent. Thus, the reflectivity was measured to Q {approx} 0.3{Angstrom}{sup -1}, covering up to seven orders of magnitude in reflected intensity, for PC bilayers in D{sub 2}O and silicon-matched (38% D{sub 2}O/62% H{sub 2}O) water. The kinetics of lipid adsorption at the silicon/water interface were also explored by observing changes in the reflectivity at low Q values under silicon-matched water conditions.

  7. Anisotropic metal growth on phospholipid nanodiscs via lipid bilayer expansion

    Science.gov (United States)

    Oertel, Jana; Keller, Adrian; Prinz, Julia; Schreiber, Benjamin; Hübner, René; Kerbusch, Jochen; Bald, Ilko; Fahmy, Karim

    2016-05-01

    Self-assembling biomolecules provide attractive templates for the preparation of metallic nanostructures. However, the intuitive transfer of the “outer shape” of the assembled macromolecules to the final metallic particle depends on the intermolecular forces among the biomolecules which compete with interactions between template molecules and the metal during metallization. The shape of the bio-template may thus be more dynamic than generally assumed. Here, we have studied the metallization of phospholipid nanodiscs which are discoidal particles of ~10 nm diameter containing a lipid bilayer ~5 nm thick. Using negatively charged lipids, electrostatic adsorption of amine-coated Au nanoparticles was achieved and followed by electroless gold deposition. Whereas Au nanoparticle adsorption preserves the shape of the bio-template, metallization proceeds via invasion of Au into the hydrophobic core of the nanodisc. Thereby, the lipidic phase induces a lateral growth that increases the diameter but not the original thickness of the template. Infrared spectroscopy reveals lipid expansion and suggests the existence of internal gaps in the metallized nanodiscs, which is confirmed by surface-enhanced Raman scattering from the encapsulated lipids. Interference of metallic growth with non-covalent interactions can thus become itself a shape-determining factor in the metallization of particularly soft and structurally anisotropic biomaterials.

  8. Vortex dynamics in ferromagnetic/superconducting bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cieplak, M.Z.; Adamus, Z. [Polish Acad Sci, Inst Phys, PL-02668 Warsaw, (Poland); Konczykowski, M. [CEA, DSM, DRECAM, Lab Solides Irradies, Ecole Polytechnique, CNRS-UMR 7642, F-91128 Palaiseau (France); Zhu, L.Y.; Chien, C.L. [Johns Hopkins Univ, Dept Phys and Astron, Baltimore, MD 21218 (United States)

    2008-07-01

    The dependence of vortex dynamics on the geometry of magnetic domain pattern is studied in the superconducting/ferromagnetic bilayers, in which niobium is a superconductor, and Co/Pt multilayer with perpendicular magnetic anisotropy serves as a ferromagnetic layer. Magnetic domain patterns with different density of domains per surface area and different domain size, w, are obtained for Co/Pt with different thickness of Pt. The dense patterns of domains with the size comparable to the magnetic penetration depth (w {>=} {lambda}) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w {>=}{>=} {lambda}) enhance pinning less effectively and result in flux jumps during flux motion. (authors)

  9. Bilayer avalanche spin-diode logic

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Joseph S., E-mail: joseph.friedman@u-psud.fr; Querlioz, Damien [Institut d’Electronique Fondamentale, Univ. Paris-Sud, CNRS, 91405 Orsay (France); Fadel, Eric R. [Department of Materials Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wessels, Bruce W. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Materials Science & Engineering, Northwestern University, Evanston, IL 60208 (United States); Sahakian, Alan V. [Department of Electrical Engineering & Computer Science, Northwestern University, Evanston, IL 60208 (United States); Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208 (United States)

    2015-11-15

    A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing.

  10. Giant magnetoresistance in bilayer graphene nanoflakes

    Science.gov (United States)

    Farghadan, Rouhollah; Farekiyan, Marzieh

    2016-09-01

    Coherent spin transport through bilayer graphene (BLG) nanoflakes sandwiched between two electrodes made of single-layer zigzag graphene nanoribbon was investigated by means of Landauer-Buttiker formalism. Application of a magnetic field only on BLG structure as a channel produces a perfect spin polarization in a large energy region. Moreover, the conductance could be strongly modulated by magnetization of the zigzag edge of AB-stacked BLG, and the junction, entirely made of carbon, produces a giant magnetoresistance (GMR) up to 100%. Intestinally, GMR and spin polarization could be tuned by varying BLG width and length. Generally, MR in a AB-stacked BLG strongly increases (decreases) with length (width).

  11. Twisted CFT and bilayer Quantum Hall systems

    CERN Document Server

    Cristofano, G; Naddeo, A

    2003-01-01

    We identify the impurity interactions of the recently proposed CFT description of a bilayer Quantum Hall system at filling nu =m/(pm+2) in Mod. Phys. Lett. A 15 (2000) 1679. Such a CFT is obtained by m-reduction on the one layer system, with a resulting pairing symmetry and presence of quasi-holes. For the m=2 case boundary terms are shown to describe an impurity interaction which allows for a localized tunnel of the Kondo problem type. The presence of an anomalous fixed point is evidenced at finite coupling which is unstable with respect to unbalance and flows to a vacuum state with no quasi-holes.

  12. Rich Polymorphic Behavior of Wigner Bilayers

    Science.gov (United States)

    Antlanger, Moritz; Kahl, Gerhard; Mazars, Martial; Šamaj, Ladislav; Trizac, Emmanuel

    2016-09-01

    Self-assembly into target structures is an efficient material design strategy. Combining analytical calculations and computational techniques of evolutionary and Monte Carlo types, we report about a remarkable structural variability of Wigner bilayer ground states, when charges are confined between parallel charged plates. Changing the interlayer separation, or the plate charge asymmetry, a cascade of ordered patterns emerges. At variance with the symmetric case phenomenology, the competition between commensurability features and charge neutralization leads to long range attraction, appearance of macroscopic charges, exotic phases, and nonconventional phase transitions with distinct critical indices, offering the possibility of a subtle, but precise and convenient control over patterns.

  13. Quantitative Hydrocarbon Surface Analysis

    Science.gov (United States)

    Douglas, Vonnie M.

    2000-01-01

    The elimination of ozone depleting substances, such as carbon tetrachloride, has resulted in the use of new analytical techniques for cleanliness verification and contamination sampling. The last remaining application at Rocketdyne which required a replacement technique was the quantitative analysis of hydrocarbons by infrared spectrometry. This application, which previously utilized carbon tetrachloride, was successfully modified using the SOC-400, a compact portable FTIR manufactured by Surface Optics Corporation. This instrument can quantitatively measure and identify hydrocarbons from solvent flush of hardware as well as directly analyze the surface of metallic components without the use of ozone depleting chemicals. Several sampling accessories are utilized to perform analysis for various applications.

  14. The effects of globotriaosylceramide tail saturation level on bilayer phases

    DEFF Research Database (Denmark)

    Pezeshkian, Weria; Chaban, Vitaly V; Johannes, Ludger

    2015-01-01

    of the Gb3 concentration and its acyl chain saturation on the phase behaviour of a mixed bilayer of dioleoylphosphatidylcholine and Gb3. The simulation results show that: (1) the Gb3 acyl chains (longer tails) from one leaflet interdigitate into the opposing leaflet and lead to significant bilayer...

  15. Cholesterol orientation and tilt modulus in DMPC bilayers

    OpenAIRE

    Khelashvili, George; Pabst, Georg; Harries, Daniel

    2010-01-01

    We performed molecular dynamics (MD) simulations of hydrated bilayers containing mixtures of dimyristoylphosphatidylcholine (DMPC) and Cholesterol at various ratios, to study the effect of cholesterol concentration on its orientation, and to characterize the link between cholesterol tilt and overall phospholipid membrane organization. The simulations show a substantial probability for cholesterol molecules to transiently orient perpendicular to the bilayer normal, and suggest that cholesterol...

  16. Alpha-tocopherol inhibits pore formation in the oxidized bilayers

    CERN Document Server

    Boonnoy, Phansiri; Wong-ekkabut, Jirasak

    2016-01-01

    In biological membranes, alpha-tocopherols ({\\alpha}-toc; vitamin E) protect polyunsaturated lipids from free radicals. Although the interactions of {\\alpha}-toc with non-oxidized lipid bilayers have been studied, their on oxidized bilayers remain unknown. In this study, atomistic molecular dynamics (MD) simulations of oxidized lipid bilayers were performed with varying concentrations of {\\alpha}-toc. Bilayers with 1-palmitoyl-2-lauroyl-sn-glycero-3-phosphocholine (PLPC) lipids and its aldehyde derivatives at 1:1 ratio were studied. Our simulations show that oxidized lipids self-assemble into aggregates with a water pore rapidly developing across the lipid bilayer. The free energy of transporting an {\\alpha}-toc molecule in a lipid bilayer suggests that {\\alpha}-tocs can passively adsorb into the bilayer. When {\\alpha}-toc molecules were present at low concentrations in bilayers containing oxidized lipids, the formation of water pores was slowed down. At high {\\alpha}-toc concentra-tions, no pores were observ...

  17. Regulation of sodium channel function by bilayer elasticity

    DEFF Research Database (Denmark)

    Lundbaek, Jens A; Birn, Pia; Hansen, Anker J

    2004-01-01

    be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta-octyl-glucoside, Genapol X-100......, Triton X-100, and reduced Triton X-100) that make lipid bilayers less "stiff", as measured using gA channels, shift the voltage dependence of sodium channel inactivation toward more hyperpolarized potentials. At low amphiphile concentration, the magnitude of the shift is linearly correlated to the change...... in gA channel lifetime. Cholesterol-depletion, which also reduces bilayer stiffness, causes a similar shift in sodium channel inactivation. These results provide strong support for the notion that bilayer-protein hydrophobic coupling allows the bilayer elastic properties to regulate membrane protein...

  18. Thermotropic and Barotropic Phase Behavior of Phosphatidylcholine Bilayers

    Directory of Open Access Journals (Sweden)

    Nobutake Tamai

    2013-01-01

    Full Text Available Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of some major phospholipids contained in biological membranes, phosphatidylcholines (PCs, depending on temperature and pressure. Bilayers of dipalmitoylphosphatidylcholine (DPPC, which is the most representative lipid in model membrane studies, will first be explained. Then, the bilayer phase behavior of various kinds of PCs with different molecular structures is revealed from the temperature–pressure phase diagrams, and the difference in phase stability among these PC bilayers is discussed in connection with the molecular structure of the PC molecules. Furthermore, the solvent effect on the phase behavior is also described briefly.

  19. Asymmetric heat transfer from nanoparticles in lipid bilayers

    Science.gov (United States)

    Potdar, Dipti; Sammalkorpi, Maria

    2015-12-01

    Here, we use molecular dynamics simulations to characterize the heat transfer properties of lipid bilayer - gold nanoparticle systems in which the nanoparticle acts as a heat source. The focus is on dipalmitoylphosphatidylcholine (DPPC) lipid bilayers and thiolated alcohol and alkyl functionalized nanoparticles as prototype hydrophilic and hydrophobic nanoparticles. We find hydrophilic nanoparticles which are partly in contact with the surrounding water environment are more efficient in transferring heat to the system than hydrophobic ones which reside surrounded by the membrane. This is because of the hydrogen bonding capability of the hydroxy pentanethiol and the more efficient heat conductivity through water than the lipid bilayer. Additionally, we find the heat conductance is strongly asymmetric and has a discontinuity between the bilayer leaflets. In total, the findings provide understanding on heat transport from localized heat sources in lipid bilayers and could bear significance, e.g., in engineering and controlling photoactivated triggering of liposomal systems.

  20. Theoretical study on stability of hybrid bilayers

    Science.gov (United States)

    Silva, Thiago S.; de Lima Bernardo, Bertúlio; Azevedo, Sèrgio

    2015-04-01

    Motivated by the recent experimental realization of the hybrid nanostructure of graphene and boron nitride (h-BN) sheet, and studies of gap modulation by strain, we use first principles calculations based on density functional theory to investigate the effects of strain in hybrid bilayers composed of two monolayers of graphene with a nanodomain of {{B}3}{{N}3}. The calculations were made with two different approximations for the functional exchange-correlation, GGA and VDW-DF. We investigate the modification in the electronic structure and structural properties of various configurations of the hybrid bilayers. Among the configurations, those with Bernal stacking are found to be more stable when compared to the others. Studies of the compressive strain influence were made only in the structure that has been shown to be the most stable. We have found that the two approximations used in the calculations exhibit the same results for the electronic properties of all structures. The opening of the energy gap due to strain was possible in the calculations by using the GGA approximation, but the same does not happen in the calculations using the VDW-DF approximation. Our analysis shows that the VDW-DF approximation is better suited for studies involving surfaces.

  1. Theory of skyrmions in bilayer systems

    Science.gov (United States)

    Koshibae, Wataru; Nagaosa, Naoto

    2017-02-01

    Skyrmion is an emergent particle consisting of many spins in magnets, and has many nontrivial features such as (i) nano-scale size, (ii) topological stability, (iii) gyrodynamics, and (iv) highly efficient spin transfer torque, which make skyrmions the promising candidate for the magnetic devices. Earlier works were focusing on the bulk or thin film of Dzyaloshinskii-Moriya (DM) magnets, while recent advances are focusing on the skyrmions induced by the interfaces. Therefore, the superstructures naturally leads to the interacting skyrmions on different interfaces, which has unique dynamics compared with those on the same interface. Here we theoretically study the two skyrmions on bilayer systems employing micromagnetic simulations as well as the analysis based on Thiele equation, revealing the reaction between them such as the collision and bound state formation. The dynamics depends sensitively on the sign of DM interactions, i.e., helicities, and skyrmion numbers of two skyrmions, which can be well described by Thiele equation. Furthermore, we have found the colossal spin-transfer-torque effect of bound skyrmion pair on antiferromagnetically coupled bilayer systems.

  2. Optrode for sensing hydrocarbons

    Science.gov (United States)

    Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

    1987-01-01

    A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

  3. Apparatus and methods for hydrocarbon extraction

    Science.gov (United States)

    Bohnert, George W.; Verhulst, Galen G.

    2016-04-26

    Systems and methods for hydrocarbon extraction from hydrocarbon-containing material. Such systems and methods relate to extracting hydrocarbon from hydrocarbon-containing material employing a non-aqueous extractant. Additionally, such systems and methods relate to recovering and reusing non-aqueous extractant employed for extracting hydrocarbon from hydrocarbon-containing material.

  4. Modeling Yeast Organelle Membranes and How Lipid Diversity Influences Bilayer Properties.

    Science.gov (United States)

    Monje-Galvan, Viviana; Klauda, Jeffery B

    2015-11-17

    Membrane lipids are important for the health and proper function of cell membranes. We have improved computational membrane models for specific organelles in yeast Saccharomyces cerevisiae to study the effect of lipid diversity on membrane structure and dynamics. Previous molecular dynamics simulations were performed by Jo et al. [(2009) Biophys J. 97, 50-58] on yeast membrane models having six lipid types with compositions averaged between the endoplasmic reticulum (ER) and the plasma membrane (PM). We incorporated ergosterol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol lipids in our models to better describe the unique composition of the PM, ER, and trans-Golgi network (TGN) bilayers of yeast. Our results describe membrane structure based on order parameters (SCD), electron density profiles (EDPs), and lipid packing. The average surface area per lipid decreased from 63.8 ± 0.4 Å(2) in the ER to 47.1 ± 0.3 Å(2) in the PM, while the compressibility modulus (KA) varied in the opposite direction. The high SCD values for the PM lipids indicated a more ordered bilayer core, while the corresponding lipids in the ER and TGN models had lower parameters by a factor of at least 0.7. The hydrophobic core thickness (2DC) as estimated from EDPs is the thickest for PM, which is in agreement with estimates of hydrophobic regions of transmembrane proteins from the Orientation of Proteins in Membranes database. Our results show the importance of lipid diversity and composition on a bilayer's structural and mechanical properties, which in turn influences interactions with the proteins and membrane-bound molecules.

  5. Molecular aspects of electrical excitation in lipid bilayers and cell membranes.

    Science.gov (United States)

    Mueller, P

    1976-01-01

    Several compounds of fungal or bacterial origin (EIM, alamethicin, monazomycin, DJ400B) can be incorporated into planar lipid bilayers where they form molecular channels and generate voltage-dependent ion conductances. When studied by voltage clamp, the kinetic and steady-state characteristics of these conductance changes are in every respect identical to those found in excitable cell membranes, and their major aspects can be quantitatively described by the Hodgkin-Huxley equations. Thus, the steady-state conductance is an expotential function of the membrane potential, the conductance rises with a sigmoid time course and decays exponentially, and the time constants of the conductance changes go through a maximum as a function of the potential. The conductances also show inactivation as seen in the sodium channels of nerve and the potassium channels of muscle. In addition, there appear for particular pulsing sequences certain kinetic transients that cannot be accounted for by the Hodgkin-Huxley equations but are also seen in identical form in nerve. Because the kinetics are identical in all excitable cell membranes and in these bilayers, it is likely that, in spite of the diverse chemical nature of the channel-forming molecules in the bilayers and the widely differing ion selectivities in the cellular systems, the mechanism by which the membrane opens and closes for the flow of ions is essentially the same in all cases. The kinetic data imply that a cooperative process is involved in the gating action. In principle, two different concepts could account for the kinetics--one involving an intramolecular configurational change within a complex permanent channel, the other, the assembly of a channel through the voltage-dependent aggregation of monomeric channel precursors. In the bilayers the high-order dependence of the steady-state conductance and of the gating time constants on the concentration of the channel formers suggests an aggregation mechanism in which the

  6. X-ray reflectivity investigation of the foam bilayer film formed by hexaethylene glycol dodecyl ether

    Institute of Scientific and Technical Information of China (English)

    SHEN Qiang; J. J. Benattar; LI Xin; LIU Shaojie

    2003-01-01

    Structural parameters for the free-standing foam film of hexaethylene glycol monododecyl ether (C12E6) have been measured by using X-ray reflectometry. The results indicate that a "five-laminae" model corresponds to this inverted bilayer and divides it into five regions. The thicknesses of the aliphatic chainregions, the polar head-group regions, and the central aqueous core are 0.90, 1.35 and 1.31 nm, respectively; and their corresponding electron densities are 2.4 ( 10?3, 2.6 ( 10?3 and 2.3(10?3 electron/nm3, respectively; the interfacial roughness between adjacent regions is 0.34 nm. The central core of this foam film does not contain free water, its thickness decreased 0.40 nm under the irradiation of infrared rays due to the loss of structural water.

  7. Microbial degradation of petroleum hydrocarbons.

    Science.gov (United States)

    Varjani, Sunita J

    2017-01-01

    Petroleum hydrocarbon pollutants are recalcitrant compounds and are classified as priority pollutants. Cleaning up of these pollutants from environment is a real world problem. Bioremediation has become a major method employed in restoration of petroleum hydrocarbon polluted environments that makes use of natural microbial biodegradation activity. Petroleum hydrocarbons utilizing microorganisms are ubiquitously distributed in environment. They naturally biodegrade pollutants and thereby remove them from the environment. Removal of petroleum hydrocarbon pollutants from environment by applying oleophilic microorganisms (individual isolate/consortium of microorganisms) is ecofriendly and economic. Microbial biodegradation of petroleum hydrocarbon pollutants employs the enzyme catalytic activities of microorganisms to enhance the rate of pollutants degradation. This article provides an overview about bioremediation for petroleum hydrocarbon pollutants. It also includes explanation about hydrocarbon metabolism in microorganisms with a special focus on new insights obtained during past couple of years.

  8. Combinatorics of giant hexagonal bilayer hemoglobins.

    Science.gov (United States)

    Hanin, L G; Vinogradov, S N

    2000-01-01

    The paper discusses combinatorial and probabilistic models allowing to characterize various aspects of spacial symmetry and structural heterogeneity of the giant hexagonal bilayer hemoglobins (HBL Hb). Linker-dodecamer configurations of HBL are described for two and four linker types (occurring in the two most studied HBL Hb of Arenicola and Lumbricus, respectively), and the most probable configurations are found. It is shown that, for HBL with marked dodecamers, the number of 'normal-marked' pairs of dodecamers in homological position follows a binomial distribution. The group of symmetries of the dodecamer substructure of HBL is identified with the dihedral group D6. Under natural symmetry assumptions, the total dipole moment of the dodecamer substructure of HBL is shown to be zero. Biological implications of the mathematical findings are discussed.

  9. Interaction of neurotransmitters with a phospholipid bilayer

    DEFF Research Database (Denmark)

    Peters, Günther H.J.; Werge, Mikkel; Elf-Lind, Maria Northved

    2014-01-01

    We have performed a series of molecular dynamics simulations to study the interactions between the neurotransmitters (NTs) γ-aminobutyrate (GABA), glycine (GLY), acetylcholine (ACH) and glutamate (GLU) as well as the amidated/acetylated γ-aminobutyrate (GABAneu) and the osmolyte molecule glycerol...... in the vicinity of the lipid glycerol backbone. The most important interaction of NTs with the bilayer is the charged amino group of NTs with the lipid phosphate group.......We have performed a series of molecular dynamics simulations to study the interactions between the neurotransmitters (NTs) γ-aminobutyrate (GABA), glycine (GLY), acetylcholine (ACH) and glutamate (GLU) as well as the amidated/acetylated γ-aminobutyrate (GABAneu) and the osmolyte molecule glycerol...

  10. Space charge and screening in bilayer graphene

    Science.gov (United States)

    Kolomeisky, Eugene B.; Straley, Joseph P.; Abrams, Daniel L.

    2016-11-01

    Undoped bilayer graphene is a two-dimensional semimetal with a low-energy excitation spectrum that is parabolic in the momentum. As a result, the screening of an arbitrary external charge Ze is accompanied by a reconstruction of the ground state: valence band electrons (for Z  >  0) are promoted to form a space charge around the charge while the holes leave the physical picture. The outcome is a flat neutral object resembling the regular atom except that for Z\\gg 1 it is described by a strictly linear Thomas-Fermi theory. This theory also predicts that the bilayer’s static dielectric constant is the same as that of a two-dimensional electron gas in the long-wavelength limit.

  11. Oxygen diffusion in bilayer polymer films

    DEFF Research Database (Denmark)

    Poulsen, Lars; Zebger, Ingo; Tofte, Jannik Pentti;

    2004-01-01

    Experiments to quantify oxygen diffusion have been performed on polymer samples in which a film of poly(ethylene-co-norbornene) was cast onto a film of polystyrene which, in turn, was cast onto an oxygen-impermeable substrate. In the technique employed, the time evolution of oxygen transport...... through the film of poly(ethylene-co-norbornene) and into the polystyrene film was monitored using the phosphorescence of singlet oxygen as a spectroscopic probe. To analyze the data, it was necessary to solve Fick's second law of diffusion for both polymer films. Tractable analytical and numerical...... solutions were obtained for the problem. Moreover, the numerical solution is sufficiently general that it can be used to simulate oxygen concentration profiles in films consisting of more than two layers. Data obtained from the bilayer films yield a diffusion coefficient for oxygen in poly...

  12. Multiscale molecular modeling of tertiary supported lipid bilayers

    Science.gov (United States)

    Ranz, Holden T.; Faller, Roland

    2015-08-01

    Ternary lipid bilayer systems assembled from mixtures of dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), and cholesterol have been studied using coarse-grained molecular dynamics at biologically relevant temperatures (280 K to 310 K), which are between the chain melting temperatures of the pure lipid component. Free lipid bilayers were simulated using the MARTINI model (Stage I) and a variant with water-water interactions reduced to 76% (Stage II). The latter was subsequently used for preparing supported lipid bilayer simulations (Stage III). Clustering of like lipids was observed, but the simulation timescale did not yield larger phaseseparated domains.

  13. Charge detection in a bilayer graphene quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Fringes, Stefan; Norda, Caroline; Dauber, Jan; Engels, Stephan [JARA-FIT and II, Institute of Physics B, RWTH Aachen University, 52074 Aachen (Germany); Volk, Christian; Terres, Bernat; Stampfer, Christoph [JARA-FIT and II, Institute of Physics B, RWTH Aachen University, 52074 Aachen (Germany); Peter Gruenberg Institute (PGI-8/9), Forschungszentrum Juelich, 52425 Juelich (Germany); Trellenkamp, Stefan [Peter Gruenberg Institute (PGI-8/9), Forschungszentrum Juelich, 52425 Juelich (Germany)

    2011-11-15

    We show measurements on a bilayer graphene quantum dot (QD) with an integrated charge detector. The focus lies on enabling charge detection with a 30 nm wide bilayer graphene nanoribbon located approximately 35 nm next to a bilayer graphene QD with an island diameter of about 100 nm. Local resonances in the nanoribbon can be successfully used to detect individual charging events in the dot even in regimes where the QD Coulomb peaks cannot be measured by conventional techniques. False color atomic force microscope image of the investigated device. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers

    KAUST Repository

    Manchon, Aurelien

    2017-01-01

    We investigate the emergence of spin Hall magnetoresistance in a magnetic bilayer composed of a normal metal adjacent to an antiferromagnet. Based on a recently derived drift diffusion equation, we show that the resistance of the bilayer depends on the relative angle between the direction transverse to the current flow and the Néel order parameter. While this effect presents striking similarities with the spin Hall magnetoresistance recently reported in ferromagnetic bilayers, its physical origin is attributed to the anisotropic spin relaxation of itinerant spins in the antiferromagnet.

  15. Modeling liquid crystal bilayer structures with minimal surfaces.

    Science.gov (United States)

    Enlow, J D; Enlow, R L; McGrath, K M; Tate, M W

    2004-01-22

    This paper describes a new convenient and accurate method of calculating x-ray diffraction integrated intensities from detailed cubic bilayer structures. The method is employed to investigate the structure of a particular surfactant system (didodecyldimethylammonium bromide in a solution of oil and heavy water), for which single-crystal experimental data have recently been collected. The diffracted peak intensities correlate well with theoretical structures based on mathematical minimal surfaces. Optimized electron density profiles of the bilayer are presented, providing new insight into key features of the bilayer structure.

  16. Membrane separation of hydrocarbons

    Science.gov (United States)

    Chang, Y. Alice; Kulkarni, Sudhir S.; Funk, Edward W.

    1986-01-01

    Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture through a polymeric membrane. The membrane which is utilized to effect the separation comprises a polymer which is capable of maintaining its integrity in the presence of hydrocarbon compounds and which has been modified by being subjected to the action of a sulfonating agent. Sulfonating agents which may be employed will include fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, etc., the surface or bulk modified polymer will contain a degree of sulfonation ranging from about 15 to about 50%. The separation process is effected at temperatures ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psig.

  17. Direct hydrocarbon fuel cells

    Science.gov (United States)

    Barnett, Scott A.; Lai, Tammy; Liu, Jiang

    2010-05-04

    The direct electrochemical oxidation of hydrocarbons in solid oxide fuel cells, to generate greater power densities at lower temperatures without carbon deposition. The performance obtained is comparable to that of fuel cells used for hydrogen, and is achieved by using novel anode composites at low operating temperatures. Such solid oxide fuel cells, regardless of fuel source or operation, can be configured advantageously using the structural geometries of this invention.

  18. STABLE HIGH CONDUCTIVITY BILAYERED ELECTROLYTES FOR LOW TEMPERATURE SOLID OXIDE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Eric D. Wachsman

    2000-10-01

    Solid oxide fuel cells (SOFCs) are the future of energy production in America. They offer great promise as a clean and efficient process for directly converting chemical energy to electricity while providing significant environmental benefits (they produce negligible CO, HC, or NOx and, as a result of their high efficiency, produce about one-third less CO{sub 2} per kilowatt hour than internal combustion engines). Unfortunately, the current SOFC technology, based on a stabilized zirconia electrolyte, must operate in the region of 1000 C to avoid unacceptably high ohmic losses. These high temperatures demand (a) specialized (expensive) materials for the fuel cell interconnects and insulation, (b) time to heat up to the operating temperature and (c) energy input to arrive at the operating temperature. Therefore, if fuel cells could be designed to give a reasonable power output at lower temperatures tremendous benefits may be accrued, not the least of which is reduced cost. The problem is, at lower temperatures the conductivity of the conventional stabilized zirconia electrolyte decreases to the point where it cannot supply electrical current efficiently to an external load. The primary objectives of the proposed research is to develop a stable high conductivity (>0.05 S cm{sup -1} at 550 C) electrolyte for lower temperature SOFCs. This objective is specifically directed toward meeting the lowest (and most difficult) temperature criteria for the 21st Century Fuel Cell Program. Meeting this objective provides a potential for future transportation applications of SOFCs, where their ability to directly use hydrocarbon fuels could permit refueling within the existing transportation infrastructure. In order to meet this objective we are developing a functionally gradient bilayer electrolyte comprised of bismuth oxide on the air side and ceria on the fuel side. Bismuth oxide and doped ceria are among the highest ionic conducting electrolytes and in fact bismuth oxide based

  19. The use of virtual ground to control transmembrane voltages and measure bilayer currents in serial arrays of droplet interface bilayers

    Science.gov (United States)

    Sarles, Stephen A.

    2013-09-01

    The droplet interface bilayer (DIB) is a simple technique for constructing a stable lipid bilayer at the interface of two lipid-encased water droplets submerged in oil. Networks of DIBs formed by connecting more than two droplets constitute a new form of modular biomolecular smart material, where the transduction properties of a single lipid bilayer can affect the actions performed at other interface bilayers in the network via diffusion through the aqueous environments of shared droplet connections. The passive electrical properties of a lipid bilayer and the arrangement of droplets that determine the paths for transport in the network require specific electrical control to stimulate and interrogate each bilayer. Here, we explore the use of virtual ground for electrodes inserted into specific droplets in the network and employ a multichannel patch clamp amplifier to characterize bilayer formation and ion-channel activity in a serial DIB array. Analysis of serial connections of DIBs is discussed to understand how assigning electrode connections to the measurement device can be used to measure activity across all lipid membranes within a network. Serial arrays of DIBs are assembled using the regulated attachment method within a multi-compartment flexible substrate, and wire-type electrodes inserted into each droplet compartment of the substrate enable the application of voltage and measurement of current in each droplet in the array.

  20. THERMOCHEMISTRY OF HYDROCARBON RADICALS

    Energy Technology Data Exchange (ETDEWEB)

    Kent M. Ervin, Principal Investigator

    2004-08-17

    Gas phase negative ion chemistry methods are employed to determine enthalpies of formation of hydrocarbon radicals that are important in combustion processes and to investigate the dynamics of ion-molecule reactions. Using guided ion beam tandem mass spectrometry, we measure collisional threshold energies of endoergic proton transfer and hydrogen atom transfer reactions of hydrocarbon molecules with negative reagent ions. The measured reaction threshold energies for proton transfer yield the relative gas phase acidities. In an alternative methodology, competitive collision-induced dissociation of proton-bound ion-molecule complexes provides accurate gas phase acidities relative to a reference acid. Combined with the electron affinity of the R {center_dot} radical, the gas phase acidity yields the RH bond dissociation energy of the corresponding neutral molecule, or equivalently the enthalpy of formation of the R{center_dot} organic radical, using equation: D(R-H) = {Delta}{sub acid}H(RH) + EA(R) - IE(H). The threshold energy for hydrogen abstraction from a hydrocarbon molecule yields its hydrogen atom affinity relative to the reagent anion, providing the RH bond dissociation energy directly. Electronic structure calculations are used to evaluate the possibility of potential energy barriers or dynamical constrictions along the reaction path, and as input for RRKM and phase space theory calculations. In newer experiments, we have measured the product velocity distributions to obtain additional information on the energetics and dynamics of the reactions.

  1. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling

    Energy Technology Data Exchange (ETDEWEB)

    Pera, H.; Kleijn, J. M.; Leermakers, F. A. M., E-mail: Frans.leermakers@wur.nl [Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6307 HB Wageningen (Netherlands)

    2014-02-14

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus k{sub c} and k{sup ¯} and the preferred monolayer curvature J{sub 0}{sup m}, and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of k{sub c} and the area compression modulus k{sub A} are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k{sup ¯} and J{sub 0}{sup m} can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k{sup ¯} and J{sub 0}{sup m} change sign with relevant parameter changes. Although typically k{sup ¯}<0, membranes can form stable cubic phases when the Gaussian bending modulus becomes positive, which occurs with membranes composed of PC lipids with long tails. Similarly, negative monolayer curvatures appear when a small head group such as PE is combined with long lipid tails, which hints towards the stability of inverse hexagonal phases at the cost of the bilayer topology. To prevent the destabilisation of bilayers, PG lipids can be mixed into these PC or PE lipid membranes. Progressive loading of bilayers with PG lipids lead to highly charged membranes, resulting in J{sub 0}{sup m}≫0, especially at low ionic

  2. Ice Cores

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Records of past temperature, precipitation, atmospheric trace gases, and other aspects of climate and environment derived from ice cores drilled on glaciers and ice...

  3. Core BPEL

    DEFF Research Database (Denmark)

    Hallwyl, Tim; Højsgaard, Espen

    extensions. Combined with the fact that the language definition does not provide a formal semantics, it is an arduous task to work formally with the language (e.g. to give an implementation). In this paper we identify a core subset of the language, called Core BPEL, which has fewer and simpler constructs......, does not allow omissions, and does not contain ignorable elements. We do so by identifying syntactic sugar, including default values, and ignorable elements in WS-BPEL. The analysis results in a translation from the full language to the core subset. Thus, we reduce the effort needed for working...... formally with WS-BPEL, as one, without loss of generality, need only consider the much simpler Core BPEL. This report may also be viewed as an addendum to the WS-BPEL standard specification, which clarifies the WS-BPEL syntax and presents the essential elements of the language in a more concise way...

  4. Polycyclic aromatic hydrocarbons as plausible prebiotic membrane components.

    Science.gov (United States)

    Groen, Joost; Deamer, David W; Kros, Alexander; Ehrenfreund, Pascale

    2012-08-01

    Aromatic molecules delivered to the young Earth during the heavy bombardment phase in the early history of our solar system were likely to be among the most abundant and stable organic compounds available. The Aromatic World hypothesis suggests that aromatic molecules might function as container elements, energy transduction elements and templating genetic components for early life forms. To investigate the possible role of aromatic molecules as container elements, we incorporated different polycyclic aromatic hydrocarbons (PAH) in the membranes of fatty acid vesicles. The goal was to determine whether PAH could function as a stabilizing agent, similar to the role that cholesterol plays in membranes today. We studied vesicle size distribution, critical vesicle concentration and permeability of the bilayers using C(6)-C(10) fatty acids mixed with amphiphilic PAH derivatives such as 1-hydroxypyrene, 9-anthracene carboxylic acid and 1,4 chrysene quinone. Dynamic Light Scattering (DLS) spectroscopy was used to measure the size distribution of vesicles and incorporation of PAH species was established by phase-contrast and epifluorescence microscopy. We employed conductimetric titration to determine the minimal concentration at which fatty acids could form stable vesicles in the presence of PAHs. We found that oxidized PAH derivatives can be incorporated into decanoic acid (DA) vesicle bilayers in mole ratios up to 1:10 (PAH:DA). Vesicle size distribution and critical vesicle concentration were largely unaffected by PAH incorporation, but 1-hydroxypyrene and 9-anthracene carboxylic acid lowered the permeability of fatty acid bilayers to small solutes up to 4-fold. These data represent the first indication of a cholesterol-like stabilizing effect of oxidized PAH derivatives in a simulated prebiotic membrane.

  5. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function

    Directory of Open Access Journals (Sweden)

    Jakob Andersson

    2016-05-01

    Full Text Available Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties.

  6. Pairing of cholesterol with oxidized phospholipid species in lipid bilayers

    DEFF Research Database (Denmark)

    Khandelia, Himanshu; Loubet, Bastien; Olzynska, Agnieszka

    2014-01-01

    We claim that (1) cholesterol protects bilayers from disruption caused by lipid oxidation by sequestering conical shaped oxidized lipid species such as 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PZPC) away from phospholipid, because cholesterol and the oxidized lipid have complementary...... shapes and (2) mixtures of cholesterol and oxidized lipids can self-assemble into bilayers much like lysolipid–cholesterol mixtures. The evidence for bilayer protection comes from molecular dynamics (MD) simulations and dynamic light scattering (DLS) measurements. Unimodal size distributions of extruded...... vesicles (LUVETs) made up of a mixture of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and PZPC containing high amounts of PZPC are only obtained when cholesterol is present in high concentrations. In simulations, bilayers containing high amounts of PZPC become porous, unless cholesterol is also present...

  7. Lipid peroxidation and water penetration in lipid bilayers

    DEFF Research Database (Denmark)

    Conte, Elena; Megli, Francesco Maria; Khandelia, Himanshu

    2012-01-01

    changes in the acyl chain order in the sub-polar region and at the methyl-terminal induced by lipid peroxidation were detected by X-band EPR. Concomitantly, the polarity and proticity of the membrane bilayer in those regions were investigated at W band in frozen samples. Analysis of the g(xx) and A......(zz) parameters revealed that OHPLPC, but mostly HpPLPC, induced a measurable increase in polarity and H-bonding propensity in the central region of the bilayer. Molecular dynamics simulation performed on 16-DSA in the PLPC-HpPLPC bilayer revealed that water molecules are statistically favored with respect...... to the hydroperoxide groups to interact with the nitroxide at the methyl-terminal, confirming that the H-bonds experimentally observed are due to increased water penetration in the bilayer. The EPR and MD data on model membranes demonstrate that cell membrane damage by oxidative stress cause alteration of water...

  8. Electronic properties of asymmetrically doped twisted graphene bilayers

    Science.gov (United States)

    Trambly de Laissardière, Guy; Namarvar, Omid Faizy; Mayou, Didier; Magaud, Laurence

    2016-06-01

    Rotated graphene bilayers form an exotic class of nanomaterials with fascinating electronic properties governed by the rotation angle θ . For large rotation angles, the electron eigenstates are restricted to one layer and the bilayer behaves like two decoupled graphene layers. At intermediate angles, Dirac cones are preserved but with a lower velocity and van Hove singularities are induced at energies where the two Dirac cones intersect. At very small angles, eigenstates become localized in peculiar moiré zones. We analyze here the effect of an asymmetric doping for a series of commensurate rotated bilayers on the basis of tight-binding calculations of their band dispersions, density of states, participation ratio, and diffusive properties. While a small doping level preserves the θ dependence of the rotated bilayer electronic structure, larger doping induces a further reduction of the band velocity in the same way as a further reduction of the rotation angle.

  9. Sub-wavelength antenna enhanced bilayer graphene tunable photodetector

    Energy Technology Data Exchange (ETDEWEB)

    Beechem, III, Thomas Edwin; Howell, Stephen W.; Peters, David W.; Davids, Paul; Ohta, Taisuke

    2016-03-22

    The integration of bilayer graphene with an absorption enhancing sub-wavelength antenna provides an infrared photodetector capable of real-time spectral tuning without filters at nanosecond timescales.

  10. Capacitance Variation of Electrolyte-Gated Bilayer Graphene Based Transistors

    Directory of Open Access Journals (Sweden)

    Hediyeh Karimi

    2013-01-01

    Full Text Available Quantum capacitance of electrolyte-gated bilayer graphene field-effect transistors is investigated in this paper. Bilayer graphene has received huge attention due to the fact that an energy gap could be opened by chemical doping or by applying external perpendicular electric field. So, this extraordinary property can be exploited to use bilayer graphene as a channel in electrolyte-gated field-effect transistors. The quantum capacitance of bi-layer graphene with an equivalent circuit is presented, and also based on the analytical model a numerical solution is reported. We begin by modeling the DOS, followed by carrier concentration as a function V in degenerate and nondegenerate regimes. To further confirm this viewpoint, the presented analytical model is compared with experimental data, and acceptable agreement is reported.

  11. Bilayer properties of hydroxytyrosol- and tyrosol-phosphatidylcholine lipids

    Science.gov (United States)

    Tyrosol and hydroxytyrosol are the phytochemicals abundantly found in olive oil. Transphosphatidylation of tyrosol and hydroxytyrosol with dioleoylphosphocholine resulted in phospholipids with antioxidant properties. The ability of these phyto-phospholipids to form liposomes and supported bilayers w...

  12. Ion dynamics in cationic lipid bilayer systems in saline solutions

    DEFF Research Database (Denmark)

    Miettinen, Markus S; Gurtovenko, Andrey A; Vattulainen, Ilpo

    2009-01-01

    mixture of cationic dimyristoyltrimethylammoniumpropane (DMTAP) and zwitterionic (neutral) dimyristoylphosphatidylcholine (DMPC) lipids. Using atomistic molecular dynamics simulations, we address the effects of bilayer composition (cationic to zwitterionic lipid fraction) and of NaCl electrolyte...

  13. A generic model for lipid monolayers, bilayers, and membranes

    CERN Document Server

    Schmid, F; Lenz, O; West, B

    2007-01-01

    We describe a simple coarse-grained model which is suited to study lipid layers and their phase transitions. Lipids are modeled by short semiflexible chains of beads with a solvophilic head and a solvophobic tail component. They are forced to self-assemble into bilayers by a computationally cheap `phantom solvent' environment. The model reproduces the most important phases and phase transitions of monolayers and bilayers. Technical issues such as Monte Carlo parallelization schemes are briefly discussed.

  14. Gates controlled parallel-coupled bilayer graphene double quantum dot

    CERN Document Server

    Wang, Lin-Jun; Wei, Da; Cao, Gang; Tu, Tao; Xiao, Ming; Guo, Guang-Can; Chang, A M

    2011-01-01

    Here we report the fabrication and quantum transport measurements of gates controlled parallel-coupled bilayer graphene double quantum dot. It is shown that the interdot coupling strength of the parallel double dots can be effectively tuned from weak to strong regime by both the in-plane plunger gates and back gate. All the relevant energy scales and parameters of the bilayer graphene parallel-coupled double dot can be extracted from the honeycomb charge stability diagrams revealed through the transport measurements.

  15. Molecular doping and band-gap opening of bilayer graphene.

    OpenAIRE

    Samuels, AJ; Carey, JD

    2013-01-01

    The ability to induce an energy band gap in bilayer graphene is an important development in graphene science and opens up potential applications in electronics and photonics. Here we report the emergence of permanent electronic and optical band gaps in bilayer graphene upon adsorption of π electron containing molecules. Adsorption of n- or p-type dopant molecules on one layer results in an asymmetric charge distribution between the top and bottom layers and in the formation of an energy gap. ...

  16. Tunable Fermi surface topology and Lifshitz transition in bilayer graphene

    OpenAIRE

    Varlet, Anastasia; Mucha-Kruczyński, Marcin; Bischoff, Dominik; Simonet, Pauline; Taniguchi, Takashi; Watanabe, Kenji; Fal'ko, Vladimir; Ihn, Thomas; Ensslin, Klaus

    2015-01-01

    Bilayer graphene is a highly tunable material: not only can one tune the Fermi energy using standard gates, as in single-layer graphene, but the band structure can also be modified by external perturbations such as transverse electric fields or strain. We review the theoretical basics of the band structure of bilayer graphene and study the evolution of the band structure under the influence of these two external parameters. We highlight their key role concerning the ease to experimentally pro...

  17. Microbial production of aliphatic hydrocarbons. Progress report, February 1, 1979-September 30, 1979. [Optimization for commercial oily hydrocarbon production

    Energy Technology Data Exchange (ETDEWEB)

    Tornabene, T G

    1979-09-01

    The neutral lipids of nine species of methanogenic bacteria, two thermoacidophiles, two alkalinophiles and 20 algal samples were analyzed. The major components were C/sub 30/, C/sub 25/, and/or C/sub 20/ acyclic isoprenoid hydrocarbons with a continuous range of hydroisoprenoid homologues. The range or acyclic isoprenoids detected were from C/sub 14/ to C/sub 30/. The neutral lipid composition from these bacteria resembles the isoprenoid distribution isolated from ancient sediments and petroleum. Therefore, these findings may have major implications to biological and biogeochemical evolution. In this connection, samples and cores from ancient sediments and future fossil fuel source beds are being analyzed for these neutral lipids as well as the more polar isopranyl glycerol-ether lipids. The derivation of fossil fuels and the biomass accumulations are the focal points of this phase of the study. Ancient and recent sediments, future source beds, and local esturaries are being enriched for microorganisms to establish a range and capability profile for hydrocarbon production. Only a relatively small percent of the microorganisms isolated demonstrated the ability to synthesize hydrocarbons; however, one particular algal isolate demonstrated that it can synthesize hydrocarbons while in a green physiological stage. Greater production is expected in the brown phase of growth. Hydrocarbon biosynthesis studies were conducted in an attempt to better understand the conditions required to maximize hydrocarbon production. The program involved physical and chemical parameters as well as assays of specifically labelled precusors with a cell free enzyme system to measure their conversions to hydrocarbons. The results have indicated a complex one enzyme system is involved in condensation and reduction of two fatty acids into hydrocarbons.

  18. Mechanism of unassisted ion transport across membrane bilayers

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1996-01-01

    To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

  19. PI3 kinase enzymology on fluid lipid bilayers.

    Science.gov (United States)

    Dutta, Debjit; Pulsipher, Abigail; Luo, Wei; Yousaf, Muhammad N

    2014-10-21

    We report the use of fluid lipid bilayer membrane as a model platform to study the influence of the bilayer microenvironment and composition on the enzymology in membrane. As a model system we determined the enzyme kinetics on membranes for the transformation of bilayers containing phosphoinositol(4,5)-bisphosphate (PI(4,5)P2) to phosphoinositol(3,4,5)-trisphosphate (PI(3,4,5)P3) by the enzyme phosphoinositol-3-kinase (PI3K) using radiolabeled ATP. The activity of the enzyme was monitored as a function of the radioactivity incorporated within the bilayer. The transformation of PI(4,5)P2 to PI(3,4,5)P3 was determined using a mass strip assay. The fluidity of the bilayer was confirmed by Fluorescence Recovery After Photobleaching (FRAP) experiments. Kinetic simulations were performed based on Langmuir adsorption and Michaelis-Menton kinetics equations to generate the rate constants for the enzymatic reaction. The effect of cholesterol on the enzyme kinetics was studied by doping the bilayer with 1% cholesterol. This leads to significant reduction in reaction rate due to change in membrane microenvironment. This strategy provides a method to study the enzymology of various kinases and phosphatases occurring at the membrane and also how these reactions are affected by the membrane composition and surface microenvironment.

  20. Different oxidized phospholipid molecules unequally affect bilayer packing.

    Science.gov (United States)

    Megli, Francesco M; Russo, Luciana

    2008-01-01

    The aim of this study was to gain more detailed knowledge about the effect of the presence of defined oxidized phospholipid molecules in phospholipid bilayers. After chromatographic and mass spectrometry analysis, the previously used product of the Fenton reaction with unsaturated lecithins proved to consist of a plethora of oxidatively modified lecithins, useless either for the detailed study of the effects brought about in the bilayer or as the source of defined oxidized phospholipid molecules. The latter, particularly 2-(omega-carboxyacyl)- and 2-(n-hydroperoxyacyl)-lecithins, can be more conveniently prepared by chemical or enzymatic synthesis rather than by chemical or physical oxidation. The effect of those molecules and of commercially available 12-hydroxy-stearic and dodecanedioic acid was studied in planar supported phospholipid bilayers (SPBs) by use of EPR spectrometry. The SPBs also contained 2-(5-doxylstearoyl)-lecithin as the spin probe, and the EPR spectral anisotropy loss, indicative of bilayer disordering, was measured as a function of the molar percentage of oxidized lipid. Most oxidized lipid molecules examined in this study were able to induce bilayer disordering, while hydroperoxyl group-bearing acyl chains appeared to be much less effective. It is concluded that the effects of different oxidized phospholipids on phospholipid bilayer structure cannot be generalized, as happens with batch-oxidized phospholipids, and that the use of defined oxidized phospholipid molecular species for membrane oxidative stress guarantees a more reliable and detailed response.

  1. Thermodynamic study of benzocaine insertion into different lipid bilayers

    Science.gov (United States)

    Cascales, J. J. López; Costa, S. D. Oliveira; Porasso, R. D.

    2011-10-01

    Despite the general consensus concerning the role played by sodium channels in the molecular mechanism of local anesthetics, the potency of anaesthetic drugs also seems to be related with their solubility in lipid bilayers. In this respect, this work represents a thermodynamic study of benzocaine insertion into lipid bilayers of different compositions by means of molecular dynamics simulation. Thus, the free energy profiles associated with benzocaine insertion into symmetric lipid bilayers composed of different proportions of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylserine were studied. From the simulation results, a maximum in the free energy (ΔG) profile was measured in the region of the lipid/solution interface. This free energy barrier appears to be very much dependent on the lipid composition of the membrane. On the other hand, the minimum free energy (ΔG) within the bilayer remained almost independent of the lipid composition of the bilayer. By repeating the study at different temperatures, it was seen how the spontaneity of benzocaine insertion into the lipid bilayer is due to an increase in the entropy associated with the process.

  2. Predicting proton titration in cationic micelle and bilayer environments

    Energy Technology Data Exchange (ETDEWEB)

    Morrow, Brian H.; Shen, Jana K. [Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201 (United States); Eike, David M.; Murch, Bruce P.; Koenig, Peter H. [Computational Chemistry, Modeling and Simulation GCO, Procter and Gamble, Cincinnati, Ohio 45201 (United States)

    2014-08-28

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pK{sub a}’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pK{sub a} of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pK{sub a} of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  3. Robustly Engineering Thermal Conductivity of Bilayer Graphene by Interlayer Bonding.

    Science.gov (United States)

    Zhang, Xiaoliang; Gao, Yufei; Chen, Yuli; Hu, Ming

    2016-02-25

    Graphene and its bilayer structure are the two-dimensional crystalline form of carbon, whose extraordinary electron mobility and other unique features hold great promise for nanoscale electronics and photonics. Their realistic applications in emerging nanoelectronics usually call for thermal transport manipulation in a controllable and precise manner. In this paper we systematically studied the effect of interlayer covalent bonding, in particular different interlay bonding arrangement, on the thermal conductivity of bilayer graphene using equilibrium molecular dynamics simulations. It is revealed that, the thermal conductivity of randomly bonded bilayer graphene decreases monotonically with the increase of interlayer bonding density, however, for the regularly bonded bilayer graphene structure the thermal conductivity possesses unexpectedly non-monotonic dependence on the interlayer bonding density. The results suggest that the thermal conductivity of bilayer graphene depends not only on the interlayer bonding density, but also on the detailed topological configuration of the interlayer bonding. The underlying mechanism for this abnormal phenomenon is identified by means of phonon spectral energy density, participation ratio and mode weight factor analysis. The large tunability of thermal conductivity of bilayer graphene through rational interlayer bonding arrangement paves the way to achieve other desired properties for potential nanoelectronics applications involving graphene layers.

  4. Microporous device for local electric recordings on model lipid bilayers

    Science.gov (United States)

    Kaufeld, Theresa; Steinem, Claudia; Schmidt, Christoph F.

    2015-01-01

    A powerful approach for characterizing lipid membranes and embedded proteins is the reconstitution of model lipid bilayers. The extreme fragility of 5 nm thick bilayers is a challenge for device design and requires a trade off of stability against accessibility. We here present a microporous lab-on-chip device that allows us to form stable, solvent-free lipid bilayers from giant unilamellar vesicles (GUVs) in a geometry that provides a unique set of access possibilities. The device is constructed around a micro-fabricated silicon chip with clusters of 1 µm-diameter pores and provides optical access to the lipid bilayers for high-NA epifluorescence imaging. At the same time, solvent exchange is possible on both sides of the lipid bilayer. Complete coverage can be achieved with GUVs, so that voltages can be applied across the lipid bilayer and single-channel currents can be measured using external or integrated silver/silver chloride electrodes. We describe the micro-fabrication by standard cleanroom techniques and the characterization of the device by atomic force microscopy, scanning electron microscopy and impedance spectroscopy. In proof-of-concept experiments we demonstrate that the device is capable of low-noise, single-ion-channel recordings. Electronic Supplementary Information (ESI) available: See DOI: 10.1039/b000000x/

  5. Condensation energy of the superconducting bilayer cuprates

    Indian Academy of Sciences (India)

    Govind; Ajay; S K Joshi

    2002-05-01

    In the present work, we report the interplay of single particle and Cooper pair tunnelings on the superconducting state of layered high-c cuprate superconductors. For this we have considered a model Hamiltonian incorporating the intra-planar interactions and the contributions arising due to the coupling between the planes. The interplanar interactions include the single particle tunneling as well as the Josephson tunneling of Cooper pairs between the two layers. The expression of the out-of-plane correlation parameter which describes the hopping of a particle from one layer to another layer in the superconducting state is obtained within a Bardeen–Cooper–Schriefer (BCS) formalism using the Green’s function technique. This correlation is found to be sensitive to the various parameter of the model Hamiltonian. We have calculated the out-of-plane contribution to the superconducting condensation energy. The calculated values of condensation energy are in agreement with those obtained from the specific heat and the -axis penetration depth measurements on bilayer cuprates.

  6. Raman modes in transferred bilayer CVD graphene

    Directory of Open Access Journals (Sweden)

    Niilisk Ahti

    2015-01-01

    Full Text Available A systematic experimental Raman spectroscopic study of twisted bilayer graphene (tBLG domains localized inside wide-area single layer graphene (SLG produced by low-pressure CVD on Cu foil and transferred onto SiO2/Si substrate has been performed. According to the Raman characterization the tBLG domains had a great variety of twisting angles θ between the bottom and top graphene layers (6° < θ < 25°. The twisting angle θ was estimated from the spectral position of the rotating R and R' modes in the Raman spectrum.Under G band resonance conditions the breathing mode ZO' with a frequency of 95- 97 cm−1 was detected, and a breathing mode ZO was found in the spectra between 804 cm−1 and 836 cm−1, its position depending on the twisting angle θ. An almost linear relationship was found between the frequencies ωZO and ωR. Also a few other spectral peculiarities were found, e.g. a high-energy excitation of the G band resonance, the 2G overtone appearing at 3170-3180 cm−1 by the G band resonance, revealing a linear dispersion of 80 cm−1/eV of the 2D band in tBLG

  7. Augmented cellular trafficking and endosomal escape of porous silicon nanoparticles via zwitterionic bilayer polymer surface engineering.

    Science.gov (United States)

    Shahbazi, Mohammad-Ali; Almeida, Patrick V; Mäkilä, Ermei M; Kaasalainen, Martti H; Salonen, Jarno J; Hirvonen, Jouni T; Santos, Hélder A

    2014-08-01

    The development of a stable vehicle with low toxicity, high cellular internalization, efficient endosomal escape, and optimal drug release profile is a key bottleneck in nanomedicine. To overcome all these problems, we have developed a successful layer-by-layer method to covalently conjugate polyethyleneimine (PEI) and poly(methyl vinyl ether-co-maleic acid) (PMVE-MA) copolymer on the surface of undecylenic acid functionalized thermally hydrocarbonized porous silicon nanoparticles (UnTHCPSi NPs), forming a bilayer zwitterionic nanocomposite containing free positive charge groups of hyper-branched PEI disguised by the PMVE-MA polymer. The surface smoothness, charge and hydrophilicity of the developed NPs considerably improved the colloidal and plasma stabilities via enhanced suspensibility and charge repulsion. Furthermore, despite the surface negative charge of the bilayer polymer-conjugated NPs, the cellular trafficking and endosomal escape were significantly increased in both MDA-MB-231 and MCF-7 breast cancer cells. Remarkably, we also showed that the conjugation of surface free amine groups of the highly toxic UnTHCPSi-PEI (Un-P) NPs to the carboxylic groups of PMVE-MA renders acceptable safety features to the system and preserves the endosomal escape properties via proton sponge mechanism of the free available amine groups located inside the hyper-branched PEI layer. Moreover, the double layer protection not only controlled the aggregation of the NPs and reduced the toxicity, but also sustained the drug release of an anticancer drug, methotrexate, with further improved cytotoxicity profile of the drug-loaded particles. These results provide a proof-of-concept evidence that such zwitterionic polymer-based PSi nanocomposites can be extensively used as a promising candidate for cytosolic drug delivery.

  8. Iron oxide nanoparticles stabilized with a bilayer of oleic acid for magnetic hyperthermia and MRI applications

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Paula I.P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Laia, César A.T. [Laboratório Associado para a Química Verde (LAQV), REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Carvalho, Alexandra [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Pereira, Laura C.J.; Coutinho, Joana T. [C2TN, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao km 139,7, 2695-066 Bobadela LRS (Portugal); Ferreira, Isabel M.M., E-mail: imf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Novo, Carlos M.M. [Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, IHMT/UNL, 1349-008 Lisboa (Portugal); Borges, João Paulo, E-mail: jpb@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

    2016-10-15

    Highlights: • Superparamagnetic iron oxide nanoparticles were stabilized with oleic acid. • Maximum stabilization was achieved at neutral pH. • Magnetic resonance imaging and magnetic hyperthermia applications were tested. • The produced nanoparticles are viable for both biomedical applications. - Abstract: Iron oxide nanoparticles (Fe{sub 3}O{sub 4}, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

  9. Hydrogel Micro-/Nanosphere Coated by a Lipid Bilayer: Preparation and Microscopic Probing

    Directory of Open Access Journals (Sweden)

    Sarah Rahni

    2017-02-01

    Full Text Available The result of polymeric nanogels and lipid vesicles interaction—lipobeads—can be considered as multipurpose containers for future therapeutic applications, such as targeted anticancer chemotherapy with superior tumor response and minimum side effects. In this work, micrometer sized lipobeads were synthesized by two methods: (i mixing separately prepared microgels made of poly(N-isopropylacrylamide (PNIPA and phospholipid vesicles of micrometer or nanometer size and (ii polymerization within the lipid vesicles. For the first time, a high vacuum scanning electron microscopy was shown to be suitable for a quick validation of the structural organization of wet lipobeads and their constituents without special sample preparation. In particular, the structural difference of microgels prepared by thermal and UV-polymerization in different solvents was revealed and three types of giant liposomes were recognized under high vacuum in conjunction with their size, composition, and method of preparation. Importantly, the substructure of the hydrogel core and multi- and unilamellar constructions of the peripheral lipid part were explicitly distinguished on the SEM images of lipobeads, justifying the spontaneous formation of a lipid bilayer on the surface of microgels and evidencing an energetically favorable structural organization of the hydrogel/lipid bilayer assembly. This key property can facilitate lipobeads’ preparation and decrease technological expenses on their scaled production. The comparison of the SEM imaging with the scanning confocal and atomic force microscopies data are also presented in the discussion.

  10. Thermophysical Properties of Hydrocarbon Mixtures

    Science.gov (United States)

    SRD 4 NIST Thermophysical Properties of Hydrocarbon Mixtures (PC database for purchase)   Interactive computer program for predicting thermodynamic and transport properties of pure fluids and fluid mixtures containing up to 20 components. The components are selected from a database of 196 components, mostly hydrocarbons.

  11. THE STRUCTURE, ORIGIN, AND EVOLUTION OF INTERSTELLAR HYDROCARBON GRAINS

    Energy Technology Data Exchange (ETDEWEB)

    Chiar, J. E.; Ricca, A. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Tielens, A. G. G. M. [Leiden Observatory, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Adamson, A. J., E-mail: jchiar@seti.org, E-mail: Alessandra.Ricca@1.nasa.gov, E-mail: tielens@strw.leidenuniv.nl, E-mail: aadamson@gemini.edu [Gemini Observatory, Northern Operations Center, 670 North A' ohoku Place, Hilo, HI 96729 (United States)

    2013-06-10

    Many materials have been considered for the carrier of the hydrocarbon absorption bands observed in the diffuse interstellar medium (ISM). In order to refine the model for ISM hydrocarbon grains, we analyze the observed aromatic (3.28, 6.2 {mu}m) and aliphatic (3.4 {mu}m) hydrocarbon absorption features in the diffuse ISM along the line of sight toward the Galactic center Quintuplet Cluster. Observationally, sp {sup 2} bonds can be measured in astronomical spectra using the 6.2 {mu}m CC aromatic stretch feature, whereas the 3.4 {mu}m aliphatic feature can be used to quantify the fraction of sp {sup 3} bonds. The fractional abundance of these components allows us to place the Galactic diffuse ISM hydrocarbons on a ternary phase diagram. We conclude that the Galactic hydrocarbon dust has, on average, a low H/C ratio and sp {sup 3} content and is highly aromatic. We have placed the results of our analysis within the context of the evolution of carbon dust in the ISM. We argue that interstellar carbon dust consists of a large core of aromatic carbon surrounded by a thin mantle of hydrogenated amorphous carbon (a-C:H), a structure that is a natural consequence of the processing of stardust grains in the ISM.

  12. A case study of the intrinsic bioremediation of petroleum hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Barker, G.W.; Raterman, K.T.; Fisher, J.B.; Corgan, J.M. [and others

    1995-12-31

    Condensate liquids have been found to contaminate soil and groundwater at two gas production sites in the Denver Basin operated by Amoco Production Co. These sites have been closely monitored since July 1993 to determine whether intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurs at a sufficient rate and to an adequate endpoint to support a no-intervention decision. Groundwater monitoring and analysis of soil cores suggest that intrinsic bioremediation is occurring at these sites by multiple pathways including aerobic oxidation, Fe{sup 3+} reduction, and sulfate reduction. In laboratory experiments the addition of gas condensate hydrocarbons to saturated soil from the gas production site stimulated sulfate reduction under anaerobic and oxygen-limiting conditions, and nitrate and Fe{sup 3+} reduction under oxygen-limiting conditions, compared to biotic controls that lacked hydrocarbon and sterile controls. The sulfate reduction corresponded to a reduction in the amount of toluene relative to other hydrocarbons. These results confirmed that subsurface soils at the gas production site have the potential for intrinsic bioremediation of hydrocarbons.

  13. Trace elements in a North Sea drill core

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar; Gwozdz, R.; Svendsen, N.

    1986-01-01

    , V, Sr, Dy, Mg, Ti, Ba and Eu. The major elements Ca and Al could be related to petrophysical parameters, particularly Al which shows a correlation with the silicification/argillaceous content. Na (and Cl) has a low content in the hydrocarbon-bearing section of the drill core suggesting that the pore...... space is filled mainly by hydrocarbons. A significant decrease of Mn with depth probably suggests diagenesis of chalk prior to, or with, hydrocarbon emplacement. Investigations of drilling fluids and cuttings reveal a strong contamination of the latter, mainly by Ba. Chalk data from comparable onshore...

  14. Concerning the petroleum hydrocarbons migration in the permafrost zone

    Science.gov (United States)

    Goncharov, I. V.; Panova, E.; Grinko, A.; Dudarev, O.; Semiletov, I. P.

    2015-12-01

    In order to understand the mechanisms controlling methane emissions in the Laptev Sea it is extremely important to know the distribution patterns of subsea permafrost in the coastal zone. One possible solution to this problem is to analyze the hydrocarbon fluids in the bottom sediments. The object of our study was the core sample from Ivashkinskaya lagoon (Lena Delta, Sakha Republic). Pyrolytic studies were performed for this core sample (ROCK- EVAL 6 TURBO). According to the pyrolysis results there were 5 samples from the upper section in the range 0.36-5.58m selected for the further studies. The common feature of these samples is high content level of the pelitic component. They contain more than 1.0% of TOC and are composed of volatile organic compounds. Extracts obtained from the core sample were analyzed by GC-MS («Hewlett Packard» 6890/5973). Analyzed extracts demonstrated different classes of organic compounds in their composition with saturated and unsaturated hydrocarbons and acids dominating. Here are the histograms of n-alkanes in function of the carbon atoms number in the molecule (Figure). Considering our work experience with the Black Sea sediments we suggest that the samples with a high degree of even n-alkanes are confined to zones of petroleum hydrocarbons migration coming from the deep oil deposits. Figure. Typical n-alkanes distribution in the extracts (horizontal axis - the number of carbon atoms in the molecule, vertical axis - relative abundance)

  15. Partitioning of propranolol in the phospholipid bilayer coat of anionic magnetoliposomes

    Energy Technology Data Exchange (ETDEWEB)

    Cocquyt, J; Saveyn, P; Meeren, P van der [Particle and Interfacial Technology Group, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent (Belgium); Soenen, S J H; Cuyper, M de [Interdisciplinary Research Centre, Laboratory of BioNanoColloids, Katholieke Universiteit Leuven-Campus Kortrijk, B-8500 Kortrijk (Belgium)], E-mail: Marcel.DeCuyper@kuleuven-kortrijk.be

    2008-05-21

    This work deals with the partitioning of the cationic amphiphilic drug, propranolol, in the coating of so-called magnetoliposomes (MLs), which consist of nanometre-sized, magnetizable iron oxide cores covered with a phospholipid bilayer. MLs of two types were used: either the ML coat consisted entirely of anionic dimyristoylphosphatidylglycerol, or it was mixed with zwitterionic dimyristoylphosphatidylcholine in a 5/95 molar ratio. To separate sorbed from non-sorbed propranolol, high-gradient magnetophoresis was used. The sorption profiles clearly show that electrostatic interactions play a key role in the sorption process as drug incorporation in the ML coat was favoured by increasing the anionic character of the ML envelope and by reducing the salt concentration of the medium. Also, upon drug binding some phospholipid molecules were expelled from the ML coat. The observations may be of relevance in the biomedical field, i.e. in the development of ML-based, intracellular theranostics.

  16. Partitioning of propranolol in the phospholipid bilayer coat of anionic magnetoliposomes

    Science.gov (United States)

    Cocquyt, J.; Soenen, S. J. H.; Saveyn, P.; Van der Meeren, P.; DeCuyper, M.

    2008-05-01

    This work deals with the partitioning of the cationic amphiphilic drug, propranolol, in the coating of so-called magnetoliposomes (MLs), which consist of nanometre-sized, magnetizable iron oxide cores covered with a phospholipid bilayer. MLs of two types were used: either the ML coat consisted entirely of anionic dimyristoylphosphatidylglycerol, or it was mixed with zwitterionic dimyristoylphosphatidylcholine in a 5/95 molar ratio. To separate sorbed from non-sorbed propranolol, high-gradient magnetophoresis was used. The sorption profiles clearly show that electrostatic interactions play a key role in the sorption process as drug incorporation in the ML coat was favoured by increasing the anionic character of the ML envelope and by reducing the salt concentration of the medium. Also, upon drug binding some phospholipid molecules were expelled from the ML coat. The observations may be of relevance in the biomedical field, i.e. in the development of ML-based, intracellular theranostics.

  17. Gold Nanoparticles Generated in Ethosome Bilayers, As Revealed by Cryo-Electron-Tomography

    CERN Document Server

    de la Presa, Patricia; Morales, Maria del Puerto; Chichon, F Javier; Arranz, Rocio; Valpuesta, Jose Maria; Hernando, Antonio; 10.1021/jp808650e

    2009-01-01

    Gold nanoparticles have been synthesized inside ethosomes, vesicles composed of phospholipid, ethanol and water, which could be very efficient not only in delivery probes to the skin but also as diagnostic and therapeutic multimodal agents. High efficiency encapsulation of gold nanoparticles is achieved by a simple strategy: the nanoparticles synthesis occurs simultaneously with the ethosomes formation, in the absence of any undesirable reducing agents. A three-dimensional reconstruction of a gold-embedded ethosome generated by cryoelectron tomography reveals that the gold particle is localized inside the lipid bilayer, leaving the ethosome surface and core free for further functionalization. The resulting gold nanoparticles are homogeneous in size and shape and, depending on synthesis temperature, the size ranges from 10 to 20 nm, as revealed by TEM. The ethosome-nanoparticles hybrids size has been investigated by means of dynamic light scattering and has been found to vary with temperature and gold salt con...

  18. Lipid bilayer microarray for parallel recording of transmembrane ion currents.

    Science.gov (United States)

    Le Pioufle, Bruno; Suzuki, Hiroaki; Tabata, Kazuhito V; Noji, Hiroyuki; Takeuchi, Shoji

    2008-01-01

    This paper describes a multiwell biochip for simultaneous parallel recording of ion current through transmembrane pores reconstituted in planar lipid bilayer arrays. Use of a thin poly(p-xylylene) (parylene) film having micrometer-sized apertures (phi=15-50 microm, t=20 microm) led to formation of highly stable bilayer lipid membranes (BLMs) for incorporation of transmembrane pores; thus, a large number of BLMs could be arrayed without any skillful technique. We optically confirmed the simultaneous formation of BLMs in a 5x5 matrix, and in our durability test, the BLM lasted more than 15 h. Simultaneous parallel recording of alamethicin and gramicidin transmembrane pores in multiple contiguous recording sites demonstrated the feasibility of high-throughput screening of transmembrane ion currents in artificial lipid bilayers.

  19. Manipulating interface states in monolayer-bilayer graphene planar junctions

    Science.gov (United States)

    Zhao, Fang; Xu, Lei; Zhang, Jun

    2016-05-01

    We report on transport properties of monolayer-bilayer graphene planar junctions in a magnetic field. Due to its unique geometry, the edge and interface states can be independently manipulated by either interlayer potential or Zeeman field, and the conductance exhibits interesting quantized behaviors. In the hybrid graphene junction, the quantum Hall (QH) conductance is no longer antisymmetric with respect to the charge neutrality point. When the Zeeman field is considered, a quantum spin Hall (QSH) phase is found in the monolayer region while the weak-QSH phase stays in the bilayer region. In the presence of both interlayer potential and Zeeman field, the bilayer region hosts a QSH phase, whereas the monolayer region is still in a QH phase, leading to a spin-polarized current in the interface. In particular, the QSH phase remains robust against the disorder.

  20. Laurdan fluorescence senses mechanical strain in the lipid bilayer membrane.

    Science.gov (United States)

    Zhang, Yan-Liang; Frangos, John A; Chachisvilis, Mirianas

    2006-09-01

    The precise molecular mechanisms by which cells transduce a mechanical stimulus into an intracellular biochemical response have not yet been established. Here, we show for the first time that the fluorescence emission of an environment-sensitive membrane probe Laurdan is modulated by mechanical strain of the lipid bilayer membrane. We have measured fluorescence emission of Laurdan in phospholipid vesicles of 30, 50, and 100 nm diameter to show that osmotically induced membrane tension leads to an increase in polarity (hydration depth) of the phospholipid bilayer interior. Our data indicate that the general polarization of Laurdan emission is linearly dependent on membrane tension. We also show that higher membrane curvature leads to higher hydration levels. We anticipate that the proposed method will facilitate future studies of mechanically induced changes in physical properties of lipid bilayer environment both in vitro and in vivo.

  1. Bilayer Deformation, Pores, and Micellation Induced by Oxidized Lipids.

    Science.gov (United States)

    Boonnoy, Phansiri; Jarerattanachat, Viwan; Karttunen, Mikko; Wong-Ekkabut, Jirasak

    2015-12-17

    The influence of different oxidized lipids on lipid bilayers was investigated with 16 individual 1 μs atomistic molecular dynamics (MD) simulations. Binary mixtures of lipid bilayers of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC) and its peroxide and aldehyde products were performed at different concentrations. In addition, an asymmetrical short chain lipid, 1-palmitoyl-2-decanoyl-sn-glycero-3-phosphatidylcholine (PDPC), was used to compare the effects of polar/apolar groups in the lipid tail on lipid bilayer. Although water defects occurred with both aldehyde and peroxide lipids, full pore formation was observed only for aldehyde lipids. At medium concentrations the pores were stable. At higher concentrations, however, the pores became unstable and micellation occurred. Data analysis shows that aldehyde lipids' propensity for pore formation is due to their shorter and highly mobile tail. The highly polar peroxide lipids are stabilized by strong hydrogen bonds with interfacial water.

  2. Equilibrium Configurations of Lipid Bilayer Membranes and Carbon Nanostructures

    Institute of Scientific and Technical Information of China (English)

    Iva(i)lo M.Mladenov; Peter A.Djondjorov; Mariana Ts.Hadzhilazova; Vassil M.Vassilev

    2013-01-01

    The present article concerns the continuum modelling of the mechanical behaviour and equilibrium shapes of two types of nano-scale objects:fluid lipid bilayer membranes and carbon nanostructures.A unified continuum model is used to handle four different case studies.Two of them consist in representing in analytic form cylindrical and axisymmetric equilibrium configurations of single-wall carbon nanotubes and fluid lipid bilayer membranes subjected to uniform hydrostatic pressure.The third one is concerned with determination of possible shapes of junctions between a single-wall carbon nanotube and a fiat graphene sheet or another single-wall carbon nanotube.The last one deals with the mechanical behaviour of closed fluid lipid bilayer membranes (vesicles) adhering onto a fiat homogeneous rigid substrate subjected to micro-injection and uniform hydrostatic pressure.

  3. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, J.P.; Gilchrist, P.J. [Univ. of Edinburgh (United Kingdom); Duff, K.C. [Univ. of Edinburgh Medical School (United Kingdom); Saxena, A.M. [Brookhaven National Laboratory, Upton, NY (United States)

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  4. Curvatronics with bilayer graphene in an effective $4D$ spacetime

    CERN Document Server

    Cariglia, M; Perali, A

    2016-01-01

    We show that in AB stacked bilayer graphene low energy excitations around the semimetallic points are described by massless, four dimensional Dirac fermions. There is an effective reconstruction of the 4 dimensional spacetime, including in particular the dimension perpendicular to the sheet, that arises dynamically from the physical graphene sheet and the interactions experienced by the carriers. The effective spacetime is the Eisenhart-Duval lift of the dynamics experienced by Galilei invariant L\\'evy-Leblond spin $\\frac{1}{2}$ particles near the Dirac points. We find that changing the intrinsic curvature of the bilayer sheet induces a change in the energy level of the electronic bands, switching from a conducting regime for negative curvature to an insulating one when curvature is positive. In particular, curving graphene bilayers allows opening or closing the energy gap between conduction and valence bands, a key effect for electronic devices. Thus using curvature as a tunable parameter opens the way for t...

  5. Molecular-dynamics simulation of a ceramide bilayer

    Science.gov (United States)

    Pandit, Sagar A.; Scott, H. Larry

    2006-01-01

    Ceramide is the simplest lipid in the biologically important class of glycosphingolipids. Ceramide is an important signaling molecule and a major component of the strateum corneum layer in the skin. In order to begin to understand the biophysical properties of ceramide, we have carried out a molecular-dynamics simulation of a hydrated 16:0 ceramide lipid bilayer at 368K (5° above the main phase transition). In this paper we describe the simulation and present the resulting properties of the bilayer. We compare the properties of the simulated ceramide bilayer to an earlier simulation of 18:0 sphingomyelin, and we discuss the results as they relate to experimental data for ceramide and other sphingolipids. The most significant differences arise at the lipid/water interface, where the lack of a large ceramide polar group leads to a different electron density and a different electrostatic potential but, surprisingly, not a different overall "dipole potential," when ceramide is compared to sphingomyelin.

  6. Meron-Pair Excitations in Bilayer Quantum Hall System

    Science.gov (United States)

    Moon, Kyungsun

    Bilayer two-dimensional electron gas systems can form unusual broken symmetry states with spontaneous inter-layer phase coherence at certain filling factors. At total filling factor νT = 1, the lowest energy charged excitation of the system is theoretically suggested to be a linearly-confined meron-pair, which is topologically identical to a single skyrmion. We will review how this remarkable excitation arises and can help unravel various experimental results demonstrated in bilayer quantum Hall system. In order to detect the linearly-confined meron-pair excitation directly, we propose a gated bilayer Hall bar experiment, where the magnitude and orientation of magnetic field B‖ applied parallel to the 2D plane can be controlled. We demonstrate a strong angle-dependent transport due to the anisotropic nature of linearly-confined meron-pairs and discuss how it would be manifested in experiment.

  7. Electro-absorption of silicene and bilayer graphene quantum dots

    Science.gov (United States)

    Abdelsalam, Hazem; Talaat, Mohamed H.; Lukyanchuk, Igor; Portnoi, M. E.; Saroka, V. A.

    2016-07-01

    We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

  8. Experimental and theoretical evidence for bilayer-by-bilayer surface melting of crystalline ice

    Science.gov (United States)

    Sánchez, M. Alejandra; Kling, Tanja; Ishiyama, Tatsuya; van Zadel, Marc-Jan; Mezger, Markus; Jochum, Mara N.; Cyran, Jenée D.; Smit, Wilbert J.; Bakker, Huib J.; Shultz, Mary Jane; Morita, Akihiro; Donadio, Davide; Nagata, Yuki; Bonn, Mischa; Backus, Ellen H. G.

    2017-01-01

    On the surface of water ice, a quasi-liquid layer (QLL) has been extensively reported at temperatures below its bulk melting point at 273 K. Approaching the bulk melting temperature from below, the thickness of the QLL is known to increase. To elucidate the precise temperature variation of the QLL, and its nature, we investigate the surface melting of hexagonal ice by combining noncontact, surface-specific vibrational sum frequency generation (SFG) spectroscopy and spectra calculated from molecular dynamics simulations. Using SFG, we probe the outermost water layers of distinct single crystalline ice faces at different temperatures. For the basal face, a stepwise, sudden weakening of the hydrogen-bonded structure of the outermost water layers occurs at 257 K. The spectral calculations from the molecular dynamics simulations reproduce the experimental findings; this allows us to interpret our experimental findings in terms of a stepwise change from one to two molten bilayers at the transition temperature. PMID:27956637

  9. Phospholipid bilayer formation at a bare Si surface

    DEFF Research Database (Denmark)

    Gutberlet, T.; Steitz, R.; Fragneto, G.;

    2004-01-01

    Neutron reflectivity was applied to monitor in situ the adsorption of small unilamellar phospholipid vesicles on a solid bare hydrophilic Si interface. The obtained reflectivity curves are consistent with the rupture and fusion model for the adsorption of phosphatidylcholine vesicles to solid...... interfaces. The results show details of the adsorbed bilayer system at ångström resolution and indicate the presence of a thin ∼6 Å thick water leaflet that separates the bilayer from the Si surface. The resolved structural details provide the basis for further investigation of processes such as adsorption...

  10. Prediction of superconductivity in Li-intercalated bilayer phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Huang, G. Q. [Department of Physics, Nanjing Normal University, Nanjing 210023 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xing, Z. W., E-mail: zwxing@nju.edu.cn [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xing, D. Y. [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

    2015-03-16

    It is shown that bilayer phosphorene can be transformed from a direct-gap semiconductor to a BCS superconductor by intercalating Li atoms. For the Li-intercalated bilayer phosphorene, we find that the electron occupation of Li-derived band is small and superconductivity is intrinsic. With increasing the intercalation of Li atoms, both increased metallicity and strong electron-phonon coupling are favorable for the enhancement of superconductivity. The obtained electron-phonon coupling λ can be larger than 1 and the superconducting temperature T{sub c} can be increased up to 16.5 K, suggesting that phosphorene may be a good candidate for a nanoscale superconductor.

  11. Anomalous Hall effect in Fe/Gd bilayers

    KAUST Repository

    Xu, W. J.

    2010-04-01

    Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010

  12. Bilayer polymer/oxide coating for electroluminescent organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana

    Organic materials have been given much attention due to their intriguing properties that can be tailored via synthetic chemistry for specific applications combined with their low price and fairly straight-forward large-scale synthesis. Para-hexaphenylene (p6P) nanofibers emit polarized light...... of the fibers with oxygen. We have developed a bilayer coating that does not change significantly the p6P spectrum but strongly reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on top of the organic nanofibers as a protecting layer for avoiding modifications of the p6...

  13. Bias induced modulation of electrical and thermal conductivity and heat capacity of BN and BN/graphene bilayers

    Science.gov (United States)

    Chegel, Raad

    2017-04-01

    By using the tight binding approximation and Green function method, the electronic structure, density of state, electrical conductivity, heat capacity of BN and BN/graphene bilayers are investigated. The AA-, AB1- and AB2- BN/graphene bilayers have small gap unlike to BN bilayers which are wide band gap semiconductors. Unlike to BN bilayer, the energy gap of graphene/BN bilayers increases with external field. The magnitude of the change in the band gap of BN bilayers is much higher than the graphene/BN bilayers. Near absolute zero, the σ(T) is zero for BN bilayers and it increases with temperature until reaches maximum value then decreases. The BN/graphene bilayers have larger electrical conductivity larger than BN bilayers. For both bilayers, the specific heat capacity has a Schottky anomaly.

  14. Solid hydrocarbon: a migration-of-fines problem in carbonate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Lomando, A.J.

    1986-05-01

    The most familiar example of a migration-of-fines problem is authigenic kaolinite, which can detach, migrate through a pore system, and bridge pore throats, thus reducing permeability. under certain conditions, a similar problem is caused by solid hydrocarbon, independent of a mode of origin, which has precipitated in carbonate pore systems. Cores from several reservoirs in the Lower Cretaceous of east Texas were used as the data base in this study. Three morphotypes of solid hydrocarbon have been identified from thin-section and scanning electron microscope observations: droplets, peanut brittle, and carpets. Droplets are small, individual, rounded particles scattered on pore walls. Peanut brittle ranges from a continuous to discontinuous thin coating with random rounded lumps that probably have droplet precursors. Carpets are thick, continuous coatings and, at the extreme, can effectively occlude whole pores. Initially, solid hydrocarbon reduces permeability without necessarily decreasing porosity significantly. Likewise, solid hydrocarbon cannot be detected directly from wireline logs. Acidizing to enhance communication to the well bore is a common completion procedure in limestone and calcareous sandstone reservoirs. In reservoirs containing solid hydrocarbon, acid etches the substrate and releases solid hydrocarbon, which migrates in the pore system and bridges pore throats. Differential well-bore pressure also may cause solid hydrocarbon to migrate. Therefore, wettability, which controls hydrocarbon adhesion to the pore walls, and the dominant morphotype are important factors in the extent of reservoir damage.

  15. Displacement sensor based on an amorphous bilayer including a magnetostrictive component

    Energy Technology Data Exchange (ETDEWEB)

    Mehnen, L. E-mail: mehnen@gte.tuwien.ac.at; Svec, P.; Pfuetzner, H.; Duhaj, P

    2003-01-01

    The present study concerns a novel type of bilayer material for displacement sensors based on the detection of curvature changes through the magnetoelastic effect. For increased bilayer stability, attempts were made to use a double-nozzle melt spinning technique (DNT) for direct flow-cast of bilayers. Compared to an agglutination technique, DNT yielded much lower sensitivity but improved long-term stability.

  16. Cationic Dimyristoylphosphatidylcholine and Dioleoyloxytrimethylammonium Propane Lipid Bilayers: Atomistic Insight for Structure and Dynamics

    DEFF Research Database (Denmark)

    Zhao, W.; Gurtovenko, A. A.; Vattulainen, I.

    2012-01-01

    of 0.4, that is, at lower TAP fractions compared with saturated PC/TAP bilayers. Adding unsaturated DOTAP lipids into DMPC bilayers was found to promote lipid chain interdigitation and to fluidize lipid bilayers, as seen through enhanced lateral lipid diffusion. The speed-up in lateral diffusion...

  17. Composition and depth distribution of hydrocarbons in Barataria Bay marsh sediments after the Deepwater Horizon oil spill.

    Science.gov (United States)

    Dincer Kırman, Zeynep; Sericano, José L; Wade, Terry L; Bianchi, Thomas S; Marcantonio, Franco; Kolker, Alexander S

    2016-07-01

    In 2010, an estimate 4.1 million barrels of oil were accidentally released into the Gulf of Mexico (GoM) during the Deepwater Horizon (DWH) Oil Spill. One and a half years after this incident, a set of subtidal and intertidal marsh sediment cores were collected from five stations in Barataria Bay, Louisiana, USA, and analyzed to determine the spatial and vertical distributions and source of hydrocarbon residues based on their chemical composition. An archived core, collected before the DWH oil spill from the same area, was also analyzed to assess the pre-spill hydrocarbon distribution in the area. Analyses of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and stable carbon isotope showed that the distribution of petroleum hydrocarbons in Barataria Bay was patchy and limited in areal extent. Significant TPH and ΣPAH concentrations (77,399 μg/g and 219,065 ng/g, respectively) were detected in the surface sediments of one core (i.e., core A) to a depth of 9 cm. Based on a sedimentation rate of 0.39 cm yr(-1), determined using (137)Cs, the presence of anthropogenic hydrocarbons in these sediment core deposited ca. 50 to 60 years ago. The historical background hydrocarbon concentrations increased significantly at the sediment surface and can be attributed to recent inputs. Although the oil present in the bay's sediments has undergone moderate weathering, biomarker analyses performed on core A samples likely indicated the presence of hydrocarbons from the DWH oil spill. The effects of oiling events on Barataria Bay and other marsh ecosystems in this region remain uncertain, as oil undergoes weathering changes over time.

  18. Hydrocarbon Leak Detection Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — FTT is proposing the development of a sensor to detect the presence of hydrocarbons in turbopump Inter-Propellant Seals (IPS). The purpose of the IPS is to prevent...

  19. A core alternative[Heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, R.H. [Chart Heat Exchangers, Wisconsin (United States)

    2001-09-01

    The development of the efficient Core-in-kettle heat exchangers by Chart Heat Exchangers as an alternative to shell and tube exchangers is reported, and its use as condensers and reboilers in ethylene plants and refrigerant condensers and chillers in natural gas processing and liquid natural gas (LNG) plants are discussed. The novel technology is described with details given of the replacement of the tube bundle with a Chart brazed aluminium plate-fin heat exchanger core, the operation of the exchanger, the savings achieved by installing these heat exchangers in new or existing plants, and Core-in-Kettle retrofits of existing shell and tube heat exchangers. The limitations of the use of Core-in-Kettle heat exchangers to clean fluids typical of hydrocarbon processing, and temperature and pressure limitations are noted.

  20. LIQUID HYDROCARBON FUEL CELL DEVELOPMENT.

    Science.gov (United States)

    A compound anode consists of a reforming catalyst bed in direct contact with a palladium-silver fuel cell anode. The objective of this study was to...prove the feasibility of operating a compound anode fuel cell on a liquid hydrocarbon and to define the important parameters that influence cell...performance. Both reformer and fuel cell tests were conducted with various liquid hydrocarbon fuels. Included in this report is a description of the

  1. Bioassay of polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Van Kirk, E.A.

    1980-08-01

    A positive relationship was found between the photodynamic activity of 24 polycyclic aromatic hydrocarbons versus published results on the mutagenicity, carcinogenicity, and initiation of unscheduled DNA synthesis. Metabolic activation of benzo(a)pyrene resulted in detection of increased mutagenesis in Paramecium tetraurelia as found also in the Ames Salmonella assay. The utility of P. tetraurelia as a biological detector of hazardous polycyclic aromatic hydrocarbons is discussed.

  2. Aliphatic hydrocarbons of the fungi.

    Science.gov (United States)

    Weete, J. D.

    1972-01-01

    Review of studies of aliphatic hydrocarbons which have been recently detected in the spores of phytopathogenic fungi, and are found to be structurally very similar to the alkanes of higher plants. It appears that the hydrocarbon components of the few mycelial and yeast forms reported resemble the distribution found in bacteria. The occurence and distribution of these compounds in the fungi is discussed. Suggested functional roles of fungal spore alkanes are presented.

  3. Evaluation of hydrocarbon potential

    Energy Technology Data Exchange (ETDEWEB)

    Cashman, P.H.; Trexler, J.H. Jr. [Univ. of Nevada, Reno, NV (United States)

    1992-09-30

    Task 8 is responsible for assessing the hydrocarbon potential of the Yucca Mountain vincinity. Our main focus is source rock stratigraphy in the NTS area in southern Nevada. (In addition, Trexler continues to work on a parallel study of source rock stratigraphy in the oil-producing region of east central Nevada, but this work is not funded by Task 8.) As a supplement to the stratigraphic studies, we are studying the geometry and kinematics of deformation at NTS, particularly as these pertain to reconstructing Paleozoic stratigraphy and to predicting the nature of the Late Paleozoic rocks under Yucca Mountain. Our stratigraphic studies continue to support the interpretation that rocks mapped as the {open_quotes}Eleana Formation{close_quotes} are in fact parts of two different Mississippian units. We have made significant progress in determining the basin histories of both units. These place important constraints on regional paleogeographic and tectonic reconstructions. In addition to continued work on the Eleana, we plan to look at the overlying Tippipah Limestone. Preliminary TOC and maturation data indicate that this may be another potential source rock.

  4. HYDROCARBONS RESERVES IN VENEZUELA

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Cruz, D.J.

    2007-07-01

    Venezuela is an important player in the energy world, because of its hydrocarbons reserves. The process for calculating oil and associated gas reserves is described bearing in mind that 90% of the gas reserves of Venezuela are associated to oil. Likewise, an analysis is made of the oil reserves figures from 1975 to 2003. Reference is also made to inconsistencies found by international experts and the explanations offered in this respect by the Ministry of Energy and Petroleum (MENPET) and Petroleos de Venezuela (PDVSA) regarding the changes that took place in the 1980s. In turn, Hubbert's Law is explained to determine peak production of conventional oil that a reservoir or field will reach, as well as its relationship with remaining reserves. Emphasis is placed on the interest of the United Nations on this topic. The reserves of associated gas are presented along with their relationship with the different crude oils that are produced and with injected gas, as well as with respect to the possible changes that would take place in the latter if oil reserves are revised. Some recommendations are submitted so that the MENPET starts preparing the pertinent policies ruling reserves. (auth)

  5. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Manyala, N., E-mail: ncholu.manyala@up.ac.za [Department of Physics, Institute of Applied Materials, SARCHI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Oliphant, C. J.; Jordaan, W. A. [National Metrology Institute of South Africa, Private Bag X34, Lynwood Ridge, Pretoria 0040 (South Africa); Fabiane, M. [Department of Physics, Institute of Applied Materials, SARCHI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Department of Physics, National University of Lesotho, P.O. Roma 180 (Lesotho)

    2016-01-07

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  6. Inducing morphological changes in lipid bilayer membranes with microfabricated substrates

    Science.gov (United States)

    Liu, Fangjie; Collins, Liam F.; Ashkar, Rana; Heberle, Frederick A.; Srijanto, Bernadeta R.; Collier, C. Patrick

    2016-11-01

    Lateral organization of lipids and proteins into distinct domains and anchoring to a cytoskeleton are two important strategies employed by biological membranes to carry out many cellular functions. However, these interactions are difficult to emulate with model systems. Here we use the physical architecture of substrates consisting of arrays of micropillars to systematically control the behavior of supported lipid bilayers - an important step in engineering model lipid membrane systems with well-defined functionalities. Competition between attractive interactions of supported lipid bilayers with the underlying substrate versus the energy cost associated with membrane bending at pillar edges can be systematically investigated as functions of pillar height and pitch, chemical functionalization of the microstructured substrate, and the type of unilamellar vesicles used for assembling the supported bilayer. Confocal fluorescent imaging and AFM measurements highlight correlations that exist between topological and mechanical properties of lipid bilayers and lateral lipid mobility in these confined environments. This study provides a baseline for future investigations into lipid domain reorganization on structured solid surfaces and scaffolds for cell growth.

  7. Super-Sensitive and Robust Biosensors from Supported Polymer Bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Paxton, Walter F. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Biological organisms are potentially the most sensitive and selective biological detection systems known, yet we are currently severely limited in our ability to exploit biological interactions in sensory devices, due in part to the limited stability of biological systems and derived materials. This proposal addresses an important aspect of integrating biological sensory materials in a solid state device. If successful, such technology could enable entirely new classes of robust biosensors that could be miniaturized and deployed in the field. The critical aims of the proposed work were 1) the calibration of a more versatile approach to measuring pH, 2) the use of this method to monitor pH changes caused by the light-induced pumping of protons across vesicles with bacteriorhodopsin integrated into the membranes (either polymer or lipid); 3) the preparation of bilayer assemblies on platinum surfaces; 4) the enhanced detection of lightinduced pH changes driven by bR-loaded supported bilayers. I have developed a methodology that may enable that at interfaces and developed a methodology to characterize the functionality of bilayer membranes with reconstituted membrane proteins. The integrity of the supported bilayer films however must be optimized prior to the full realization of the work originally envisioned in the original proposal. Nevertheless, the work performed on this project and the encouraging results it has produced has demonstrated that these goals are challenging yet within reach.

  8. Berry phase and pseudospin winding number in bilayer graphene

    Science.gov (United States)

    Park, Cheol-Hwan; Marzari, Nicola

    2012-02-01

    In 2006, two seminal studies on the novel quantum Hall effect of bilayer graphene [K. S. Novoselov et al., Nat. Phys. 2, 177 (2006); E. McCann and V. I. Fal'ko, Phys. Rev. Lett. 96, 086805 (2006)] appeared. Those papers claim that a non-trivial Berry phase of 2π in bilayer graphene is responsible for the novel quantum Hall effect described. Since then, it has become widely accepted by people working on the novel physics of graphene nanostructures that bilayer graphene has a non-trivial Berry phase of 2π (different from 0, as for conventional two-dimensional electron gas). In this talk, we show that (i) the relevant Berry phase for bilayer graphene is the same as that for a conventional two-dimensional electron gas and especially that (ii) what is actually obtained in the quantum Hall measurements is not the absolute value of the Berry phase of graphene multilayers but the pseudospin winding number. The results of our study ask for a re-interpretation of the numerous works related to the Berry phase in graphene multilayers.

  9. Anthrax toxin-induced rupture of artificial lipid bilayer membranes

    Science.gov (United States)

    Nablo, Brian J.; Panchal, Rekha G.; Bavari, Sina; Nguyen, Tam L.; Gussio, Rick; Ribot, Wil; Friedlander, Art; Chabot, Donald; Reiner, Joseph E.; Robertson, Joseph W. F.; Balijepalli, Arvind; Halverson, Kelly M.; Kasianowicz, John J.

    2013-08-01

    We demonstrate experimentally that anthrax toxin complexes rupture artificial lipid bilayer membranes when isolated from the blood of infected animals. When the solution pH is temporally acidified to mimic that process in endosomes, recombinant anthrax toxin forms an irreversibly bound complex, which also destabilizes membranes. The results suggest an alternative mechanism for the translocation of anthrax toxin into the cytoplasm.

  10. Forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces.

    Science.gov (United States)

    Zhang, Ying; Wang, Lei; Wang, Xuejing; Qi, Guodong; Han, Xiaojun

    2013-07-01

    A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer-by-layer technique on a silicon oxide surface modified with a 3-aminopropyltriethoxysilane (APTES) monolayer. The surface pK(a) value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer-by-layer assembly. Micropatterned polyelectrolyte films were obtained by deep-UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm(2) s(-1) in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field.

  11. Single lipid bilayer deposition on polymer surfaces using bicelles.

    Science.gov (United States)

    Saleem, Qasim; Zhang, Zhenfu; Petretic, Amy; Gradinaru, Claudiu C; Macdonald, Peter M

    2015-03-09

    A lipid bilayer was deposited on a 3 μm diameter polystyrene (PS) bead via hydrophobic anchoring of bicelles containing oxyamine-bearing cholesteric moieties reacting with the aldehyde functionalized bead surface. Discoidal bicelles were formed by mixing dimyristoylphosphatidylcholine (DMPC), dihexanoylphosphatidylcholine (DHPC), dimyristoyltrimethylammonium propane (DMTAP), and the oxyamine-terminated cholesterol derivative, cholest-5-en-3β-oxy-oct-3,6-oxa-an-8-oxyamine (CHOLOA), in the molar ratio DMPC/DHCP/DMTAP/CHOLOA (1/0.5/0.01/0.05) in water. Upon exposure to aldehyde-bearing PS beads, a stable single lipid bilayer coating rapidly formed at the bead surface. Fluorescence recovery after photobleaching demonstrated that the deposited lipids fused into an encapsulating lipid bilayer. Electrospray ionization mass spectrometry showed that the short chain lipid DHPC was entirely absent from the PS adherent lipid coating. Fluorescence quenching measurements proved that the coating was a single lipid bilayer. The bicelle coating method is thus simple and robust, can be modified to include membrane-associated species, and can be adapted to coat any number of different surfaces.

  12. Electronic transport of bilayer graphene with asymmetry line defects

    Science.gov (United States)

    Zhao, Xiao-Ming; Wu, Ya-Jie; Chen, Chan; Liang, Ying; Kou, Su-Peng

    2016-11-01

    In this paper, we study the quantum properties of a bilayer graphene with (asymmetry) line defects. The localized states are found around the line defects. Thus, the line defects on one certain layer of the bilayer graphene can lead to an electric transport channel. By adding a bias potential along the direction of the line defects, we calculate the electric conductivity of bilayer graphene with line defects using the Landauer-Büttiker theory, and show that the channel affects the electric conductivity remarkably by comparing the results with those in a perfect bilayer graphene. This one-dimensional line electric channel has the potential to be applied in nanotechnology engineering. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921803 and 2012CB921704), the National Natural Science Foundation of China (Grant Nos. 11174035, 11474025, 11504285, and 11404090), the Specialized Research Fund for the Doctoral Program of Higher Education, China, the Fundamental Research Funds for the Central Universities, China, the Scientific Research Program Fund of the Shaanxi Provincial Education Department, China (Grant No. 15JK1363), and the Young Talent Fund of University Association for Science and Technology in Shaanxi Province, China.

  13. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei;

    2015-01-01

    . Furthermore, the model is validated using densification results from sintering of bi-layered tubular ceramic oxygen membrane based on porous MgO and Ce0.9Gd0.1O1.95-d layers. Model input parameters, such as the shrinkage kinetics and viscous parameters are obtained experimentally using optical dilatometry...

  14. Plasmons in metallic monolayer and bilayer transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Andersen, Kirsten; Thygesen, Kristian S.

    2013-01-01

    We study the collective electronic excitations in metallic single-layer and bilayer transition metal dichalcogenides (TMDCs) using time dependent density functional theory in the random phase approximation. For very small momentum transfers (below q≈0.02 Å−1), the plasmon dispersion follows the √q...

  15. Electronic and optical studies of pulse laser deposited ZnO/NiO bilayer film

    Science.gov (United States)

    Baraskar, P.; Dar, T. A.; Choudhary, R. J.; Sen, P. K.; Sen, P.

    2016-10-01

    We report the structural, optical and electronic properties of polycrystalline ZnO and NiO thin films and amorphous ZnO/NiO bilayer film, prepared by pulsed laser deposition technique. Despite of the presence of both Zn and Ni in +2 state in the bilayer film, the grown bilayer shows no reflections (in XRD) corresponding to ZnO or NiO. The difference in crystal structure of ZnO and NiO leads to the strain in the grown bilayer film. An increase in the band gap has been observed in bilayer film which can be attributed to the amorphous nature of the structure.

  16. Efficient tunable generic model for self-assembling fluid bilayer membranes

    Science.gov (United States)

    Deserno, Markus

    2005-03-01

    We present a new model for the simulation of generic lipid bilayers in the mesoscopic regime (between a few nanometers and many tens of nanometers), which is very robust, versatile, and extremely efficient, since it avoids the need for an embedding solvent. Based entirely on simple pair potentials, it features a wide region of unassisted self assembly into fluid bilayers without the need for careful parameter tuning. The resulting membranes display the correct continuum elastic behavior with bending constants in the experimentally relevant range. It can be readily used to study events like bilayer fusion, bilayer melting, lipid mixtures, rafts, and protein-bilayer interactions.

  17. Polycyclic Aromatic Hydrocarbons

    Science.gov (United States)

    Salama, Farid

    2010-01-01

    Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of the carbonaceous materials. PAHs are the best-known candidates to account for the IR emission bands. They are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge is to reproduce in the laboratory the physical conditions that exist in the emission and absorption interstellar zones. The harsh physical conditions of the ISM -low temperature, collisionless, strong UV radiation fields- are simulated in the laboratory by associating a molecular beam with an ionizing discharge to generate a cold plasma expansion. PAH ions and radicals are formed from the neutral precursors in an isolated environment at low temperature and probed with high-sensitivity cavity ringdown spectroscopy in the NUV-NIR range. Carbon nanoparticles are also formed during the short residence time of the precursors in the plasma and are characterized with time-offlight mass spectrometry. These experiments provide unique information on the spectra of large carbonaceous molecules and ions in the gas phase that can now be directly compared to interstellar and circumstellar observations (IR emission bands, DIBs, extinction curve). These findings also hold great potential for understanding the formation process of interstellar carbonaceous grains. We will review recent progress in the experimental and theoretical studies of PAHs, compare the laboratory data with astronomical observations and discuss the global implications.

  18. The effects of residual stress, viscoelastic and thermodynamic parameters on apparent fracture toughness of dental bilayer ceramic composites

    Science.gov (United States)

    Taskonak, Burak

    Bilayer dental ceramic composites used for fixed partial dentures are becoming more widely used in dental practices because of their biocompatibility, aesthetic properties, and chemical durability. However, large statistical variations in the strength of ceramics are associated with the structural flaws as a result of processing and complex stress states within the surfaces of the materials because of thermal properties of each layer. In addition, partial delaminations of the veneer layer and connector fractures of bilayer ceramic fixed partial dentures (FPDs) have been observed in a clinical study which is a part of this dissertation. Analysis of fracture surfaces of failed FPDs reveals that such fractures of the veneering ceramic are most likely caused by lateral crack growth. Global residual stresses associated with the coefficient of thermal expansion differences between core and veneering ceramics can cause lateral crack initiation. Also, rapid cooling of bilayer ceramics from the sintering temperature of the glass veneer may not allow the interfacial stresses in the viscoelastic glass to relax to equilibrium values. This can further contribute to the propagation of lateral cracks. Furthermore, local residual stresses that develop in the plastic deformation zone below sharp contact areas on the occlusal surface are another contributor to lateral crack growth. Superposition of global residual stresses and a Boussinesq stress field can incrementally increase the possibility of lateral crack growth. The long-range goals of this study are to critically analyze the lateral crack growth mechanisms associated with residual stresses, to modify residual tensile stress distributions by controlled heat treatment, and to minimize the probability of veneering ceramic fractures. Four approaches were used to accomplish these goals: (1) clinical evaluation of a bilayer ceramic fixed partial denture system; (2) fracture surface analysis of clinically failed FPDs; (3

  19. Direct hydrocarbon exploration and gas reservoir development technology

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Young Hoon; Oh, Jae Ho; Jeong, Tae Jin [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)] [and others

    1995-12-01

    In order to enhance the capability of petroleum exploration and development techniques, three year project (1994 - 1997) was initiated on the research of direct hydrocarbon exploration and gas reservoir development. This project consists of four sub-projects. (1) Oil(Gas) - source rock correlation technique: The overview of bio-marker parameters which are applicable to hydrocarbon exploration has been illustrated. Experimental analysis of saturated hydrocarbon and bio-markers of the Pohang E and F core samples has been carried out. (2) Study on surface geochemistry and microbiology for hydrocarbon exploration: the test results of the experimental device for extraction of dissolved gases from water show that the device can be utilized for the gas geochemistry of water. (3) Development of gas and gas condensate reservoirs: There are two types of reservoir characterization. For the reservoir formation characterization, calculation of conditional simulation was compared with that of unconditional simulation. In the reservoir fluid characterization, phase behavior calculations revealed that the component grouping is more important than the increase of number of components. (4) Numerical modeling of seismic wave propagation and full waveform inversion: Three individual sections are presented. The first one is devoted to the inversion theory in general sense. The second and the third sections deal with the frequency domain pseudo waveform inversion of seismic reflection data and refraction data respectively. (author). 180 refs., 91 figs., 60 tabs.

  20. Evaporation-Induced Buckling and Fission of Microscale Droplet Interface Bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Boreyko, Jonathan B [ORNL; Mruetusatorn, Prachya [ORNL; Sarles, Stephen A [ORNL; Retterer, Scott T [ORNL; Collier, Pat [ORNL

    2013-01-01

    Droplet interface bilayers (DIBs) are a robust platform for studying synthetic cellular membranes; however, to date no DIBs have been produced at cellular length scales. Here, we create microscale droplet interface bilayers ( DIBs) at the interface between aqueous femtoliter-volume droplets within an oil-filled microfluidic channel. The uniquely large area-to-volume ratio of the droplets results in strong evaporation effects, causing the system to transition through three distinct regimes. First, the two adjacent droplets shrink into the shape of a single spherical droplet, where an augmented lipid bilayer partitions two hemi-spherical volumes. In the second regime, the combined effects of the shrinking monolayers and growing bilayer force the confined bilayer to buckle to conserve its mass. Finally, at a bending moment corresponding to a critical shear stress, the buckling bilayer fissions a vesicle to regulate its shape and stress. The DIBs produced here enable evaporation-induced bilayer dynamics reminiscent of endo- and exocytosis in cells.

  1. Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Collingwood, S.A.; Ingolfsson, H.I.;

    2010-01-01

    Membrane protein function is regulated by the host lipid bilayer composition. This regulation may depend on specific chemical interactions between proteins and individual molecules in the bilayer, as well as on non-specific interactions between proteins and the bilayer behaving as a physical entity...... with collective physical properties (e.g. thickness, intrinsic monolayer curvature or elastic moduli). Studies in physico-chemical model systems have demonstrated that changes in bilayer physical properties can regulate membrane protein function by altering the energetic cost of the bilayer deformation associated...... physical properties. This advance is because of the introduction of new tools for studying lipid bilayer regulation of protein function. The present review provides an introduction to the regulation of membrane protein function by the bilayer physical properties. We further describe the use of gramicidin...

  2. Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics.

    Science.gov (United States)

    Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep

    2015-06-23

    Cell-penetrating and antimicrobial peptides show a remarkable ability to translocate across physiological membranes. Along with factors such as electric-potential-induced perturbations of membrane structure and surface tension effects, experiments invoke porelike membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a nontrivial free-energy cost, thus necessitating a consideration of the factors associated with pore formation and the attendant free energies. Because of experimental and modeling challenges related to the long time scales of the translocation process, we use umbrella sampling molecular dynamics simulations with a lipid-density-based order parameter to investigate membrane-pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of headgroups, charge states, acyl chain lengths, and saturation. We probe the dependence of pore-formation barriers on the area per lipid, lipid bilayer thickness, and membrane bending rigidities in three different lipid classes. The pore-formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. The pore-formation free energy is higher in peptide-lipid systems than in peptide-free lipid systems due to penalties to maintain the solvation of charged hydrophilic solutes within the membrane environment.

  3. Porous nanoparticle-supported lipid bilayers (protocells) for targeted delivery and methods of using same

    Energy Technology Data Exchange (ETDEWEB)

    Brinker, C. Jeffrey; Carnes, Eric C.; Ashley, Carlee Erin; Willman, Cheryl L.

    2017-02-28

    The present invention is directed to protocells for specific targeting of hepatocellular and other cancer cells which comprise a nanoporous silica core with a supported lipid bilayer; at least one agent which facilitates cancer cell death (such as a traditional small molecule, a macromolecular cargo (e.g. siRNA or a protein toxin such as ricin toxin A-chain or diphtheria toxin A-chain) and/or a histone-packaged plasmid DNA disposed within the nanoporous silica core (preferably supercoiled in order to more efficiently package the DNA into protocells) which is optionally modified with a nuclear localization sequence to assist in localizing protocells within the nucleus of the cancer cell and the ability to express peptides involved in therapy (apoptosis/cell death) of the cancer cell or as a reporter, a targeting peptide which targets cancer cells in tissue to be treated such that binding of the protocell to the targeted cells is specific and enhanced and a fusogenic peptide that promotes endosomal escape of protocells and encapsulated DNA. Protocells according to the present invention may be used to treat cancer, especially including hepatocellular (liver) cancer using novel binding peptides (c-MET peptides) which selectively bind to hepatocellular tissue or to function in diagnosis of cancer, including cancer treatment and drug discovery.

  4. Enrichment of light hydrocarbon mixture

    Science.gov (United States)

    Yang; Dali; Devlin, David; Barbero, Robert S.; Carrera, Martin E.; Colling, Craig W.

    2010-08-10

    Light hydrocarbon enrichment is accomplished using a vertically oriented distillation column having a plurality of vertically oriented, nonselective micro/mesoporous hollow fibers. Vapor having, for example, both propylene and propane is sent upward through the distillation column in between the hollow fibers. Vapor exits neat the top of the column and is condensed to form a liquid phase that is directed back downward through the lumen of the hollow fibers. As vapor continues to ascend and liquid continues to countercurrently descend, the liquid at the bottom of the column becomes enriched in a higher boiling point, light hydrocarbon (propane, for example) and the vapor at the top becomes enriched in a lower boiling point light hydrocarbon (propylene, for example). The hollow fiber becomes wetted with liquid during the process.

  5. Aqueous solutions at the interface with phospholipid bilayers.

    Science.gov (United States)

    Berkowitz, Max L; Vácha, Robert

    2012-01-17

    In a sense, life is defined by membranes, because they delineate the barrier between the living cell and its surroundings. Membranes are also essential for regulating the machinery of life throughout many interfaces within the cell's interior. A large number of experimental, computational, and theoretical studies have demonstrated how the properties of water and ionic aqueous solutions change due to the vicinity of membranes and, in turn, how the properties of membranes depend on the presence of aqueous solutions. Consequently, understanding the character of aqueous solutions at their interface with biological membranes is critical to research progress on many fronts. The importance of incorporating a molecular-level description of water into the study of biomembrane surfaces was demonstrated by an examination of the interaction between phospholipid bilayers that can serve as model biological membranes. The results showed that, in addition to well-known forces, such as van der Waals and screened Coulomb, one has to consider a repulsion force due to the removal of water between surfaces. It was also known that physicochemical properties of biological membranes are strongly influenced by the specific character of the ions in the surrounding aqueous solutions because of the observation that different anions produce different effects on muscle twitch tension. In this Account, we describe the interaction of pure water, and also of aqueous ionic solutions, with model membranes. We show that a symbiosis of experimental and computational work over the past few years has resulted in substantial progress in the field. We now better understand the origin of the hydration force, the structural properties of water at the interface with phospholipid bilayers, and the influence of phospholipid headgroups on the dynamics of water. We also improved our knowledge of the ion-specific effect, which is observed at the interface of the phospholipid bilayer and aqueous solution, and its

  6. Sources and deposition of polycyclic aromatic hydrocarbons to western US national parks

    Science.gov (United States)

    Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) to determine their current and historical deposition, as well as to identify thei...

  7. High Pressure Preignition Chemistry of Hydrocarbons and Hydrocarbon Mixtures

    Science.gov (United States)

    2007-11-02

    and hydrocarbon blends in our various combustion systems, with emphasis on the effects of elevated pressure using our pressurized flow reactor ( PFR ...facility. Detailed experimental data were generated from the PFR for use in associated kinetic modeling work. We continued to develop and extend both

  8. Amphiphile regulation of ion channel function by changes in the bilayer spring constant

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Koeppe, R.E.; Andersen, Oluf Sten

    2010-01-01

    Many drugs are amphiphiles that, in addition to binding to a particular target protein, adsorb to cell membrane lipid bilayers and alter intrinsic bilayer physical properties (e. g., bilayer thickness, monolayer curvature, and elastic moduli). Such changes can modulate membrane protein function b......-dependent sodium channels in living cells. The use of gA channels as molecular force probes provides a tool for quantitative, predictive studies of bilayer-mediated regulation of membrane protein function by amphiphiles....... by altering the energetic cost (Delta G(bilayer)) of bilayer deformations associated with protein conformational changes that involve the protein-bilayer interface. But amphiphiles have complex effects on the physical properties of lipid bilayers, meaning that the net change in Delta G(bilayer) cannot...... be predicted from measurements of isolated changes in such properties. Thus, the bilayer contribution to the promiscuous regulation of membrane proteins by drugs and other amphiphiles remains unknown. To overcome this problem, we use gramicidin A (gA) channels as molecular force probes to measure the net...

  9. High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene

    Science.gov (United States)

    Liu, Lixin; Zhou, Hailong; Cheng, Rui; Yu, Woo Jong; Liu, Yuan; Chen, Yu; Shaw, Jonathan; Zhong, Xing; Huang, Yu; Duan, Xiangfeng

    2012-01-01

    Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene. PMID:22906199

  10. The Mechanical Aspects of Formation and Application of PDMS Bilayers Rolled into a Cylindrical Structure

    Directory of Open Access Journals (Sweden)

    Dongwon Kang

    2015-01-01

    Full Text Available A polydimethylsiloxane (PDMS film with its surface being oxidized by a plasma treatment or a UV-ozone (UVO treatment, that is, a bilayer made of PDMS and its oxidized surface layer, is known to roll into a cylindrical structure upon exposure to the chloroform vapor due to the mismatch in the swelling ratio between PDMS and the oxidized layer by the chloroform vapor. Here we analyzed the formation of the rolled bilayer with the mechanical aspects: how the mismatch in the swelling ratio of the bilayer induces rolling of the bilayer, why any form of trigger that breaks the symmetry in the in-plane stress level is needed to roll the bilayer uniaxially, why the rolled bilayer does not unroll in the dry state when there is no more mismatch in the swelling ratio, and how the measured curvature of rolled bilayer matches well with the prediction by the theory. Moreover, for the use of the rolled bilayer as the channel of the microfluidic device, we examined whether the rolled bilayer deforms or unrolls by the flow of the aqueous solution that exerts the circumferential stress on the rolled bilayer.

  11. A Molecular Dynamics Study of the Structural and Dynamical Properties of Putative Arsenic Substituted Lipid Bilayers

    Directory of Open Access Journals (Sweden)

    Ratna Juwita

    2013-04-01

    Full Text Available Cell membranes are composed mainly of phospholipids which are in turn, composed of five major chemical elements: carbon, hydrogen, nitrogen, oxygen, and phosphorus. Recent studies have suggested the possibility of sustaining life if the phosphorus is substituted by arsenic. Although this issue is still controversial, it is of interest to investigate the properties of arsenated-lipid bilayers to evaluate this possibility. In this study, we simulated arsenated-lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-arsenocholine (POAC, lipid bilayers using all-atom molecular dynamics to understand basic structural and dynamical properties, in particular, the differences from analogous 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, (POPC lipid bilayers. Our simulations showed that POAC lipid bilayers have distinct structural and dynamical properties from those of native POPC lipid bilayers. Relative to POPC lipid bilayers, POAC lipid bilayers have a more compact structure with smaller lateral areas and greater order. The compact structure of POAC lipid bilayers is due to the fact that more inter-lipid salt bridges are formed with arsenate-choline compared to the phosphate-choline of POPC lipid bilayers. These inter-lipid salt bridges bind POAC lipids together and also slow down the head group rotation and lateral diffusion of POAC lipids. Thus, it would be anticipated that POAC and POPC lipid bilayers would have different biological implications.

  12. Dynamics and stability of lipid bilayers modulated by thermosensitive polypeptides, cholesterols, and PEGylated lipids.

    Science.gov (United States)

    Lee, Hwankyu; Kim, Hyun Ryoung; Park, Jae Chan

    2014-02-28

    Lipid bilayers, which consist of dipalmitoylglycerophosphocholines (DPPCs), PEGylated lipids, cholesterols, and elastin-like polypeptides (ELPs; [VPGVG]3) at different molar ratios, were simulated. Simulations were carried out for 2 μs using the coarse-grained (CG) model that had captured the experimentally observed phase behavior of PEGylated lipids and lateral diffusivity of DPPC bilayers. Starting with the initial position of ELPs on the bilayer surface, ELPs insert into the hydrophobic region of the bilayer because of their interaction with lipid tails, consistent with previous all-atom simulations. Lateral diffusion coefficients of DPPCs significantly increase in the bilayer composed of more ELPs and less cholesterols, showing their opposite effects on the bilayer dynamics. In particular, ELPs modulate the dynamics and phase for the disordered liquid bilayer, but not for the ordered gel bilayer, indicating that ELPs can destabilize only the disordered bilayer. In the ordered bilayer, ELP chains tend to have a spherical shape and slowly diffuse, while they are extended and diffuse faster in the disordered bilayer, indicating the effect of the bilayer phase on the conformation and diffusivity of ELPs. These findings explain the experimental observation that the ELP-conjugated liposomes are stable at 310 K (ordered phase) but become unstable and release the encapsulated drugs at 315 K (disordered phase), which suggests the effects of ELPs and cholesterols. Since the cholesterol-stabilized bilayer can be destabilized by the extended shaped ELPs only in the disordered phase (not in the ordered phase), the inclusion of cholesterols is required to safely shield drugs at 310 K as well as allow ELPs to disrupt lipids and destabilize the liposomes at 315 K.

  13. Total Petroleum Hydrocarbons (TPH): ToxFAQs

    Science.gov (United States)

    ... state: This map displays locations where Total Petroleum Hydrocarbons (TPH) is known to be present. On This ... get more information? ToxFAQs TM for Total Petroleum Hydrocarbons (TPH) ( Hidrocarburos Totales de Petróleo (TPH) ) August 1999 ...

  14. Prediction of Hydrocarbon Reservoirs Permeability Using Support Vector Machine

    Directory of Open Access Journals (Sweden)

    R. Gholami

    2012-01-01

    Full Text Available Permeability is a key parameter associated with the characterization of any hydrocarbon reservoir. In fact, it is not possible to have accurate solutions to many petroleum engineering problems without having accurate permeability value. The conventional methods for permeability determination are core analysis and well test techniques. These methods are very expensive and time consuming. Therefore, attempts have usually been carried out to use artificial neural network for identification of the relationship between the well log data and core permeability. In this way, recent works on artificial intelligence techniques have led to introduce a robust machine learning methodology called support vector machine. This paper aims to utilize the SVM for predicting the permeability of three gas wells in the Southern Pars field. Obtained results of SVM showed that the correlation coefficient between core and predicted permeability is 0.97 for testing dataset. Comparing the result of SVM with that of a general regression neural network (GRNN revealed that the SVM approach is faster and more accurate than the GRNN in prediction of hydrocarbon reservoirs permeability.

  15. Recent advances in the synthesis of Fe3O4@AU core/shell nanoparticles

    Science.gov (United States)

    Salihov, Sergei V.; Ivanenkov, Yan A.; Krechetov, Sergei P.; Veselov, Mark S.; Sviridenkova, Natalia V.; Savchenko, Alexander G.; Klyachko, Natalya L.; Golovin, Yury I.; Chufarova, Nina V.; Beloglazkina, Elena K.; Majouga, Alexander G.

    2015-11-01

    Fe3O4@Au core/shell nanoparticles have unique magnetic and optical properties. These nanoparticles are used for biomedical applications, such as magnetic resonance imaging, photothermal therapy, controlled drug delivery, protein separation, biosensors, DNA detection, and immunosensors. In this review, recent methods for the synthesis of core/shell nanoparticles are discussed. We divided all of the synthetic methods in two groups: methods of synthesis of bi-layer structures and methods of synthesis of multilayer composite structures. The latter methods have a layer of "glue" material between the core and the shell.

  16. A large scale molecular dynamics calculation of a lipid bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Okazaki, Susumu [Tokyo Inst. of Tech. (Japan)

    1998-03-01

    Long time molecular dynamics simulations for the dipalmitoylphosphatidylcholine lipid bilayer in the liquid crystal phase could successfully be performed in the isothermal-isobaric ensemble using the Nose-Parrinello-Rahman extended system method. Three independent 2 ns calculations show excellent convergence to the same equilibrium state of the system in about 0.5 ns. Various structural properties such a atomic distribution, order parameter, gauche fraction in the alkyl chains, and bent structure of the head group and sn-2 chain were satisfactorily reproduced. Dynamic quantities such as trans-gauche transition were qualitatively in good correspondence the experiment. The calculations presented a microscopic picture of the whole molecular conformations, including the finding that there is not a collective tilt in bilayer. Some interesting dynamical observations concerning large structural fluctuations and pendulum motion of the alkyl chains were also made. (author)

  17. Bilayer thickness mismatch controls domain size in biomimetic membranes

    Science.gov (United States)

    Heberle, Frederick A.; Petruzielo, Robin S.; Pan, Jianjun; Drazba, Paul; Kučerka, Norbert; Standaert, Robert F.; Feigenson, Gerald W.; Katsara, John

    2013-03-01

    In order to promote functionality, cells may alter the spatial organization of membrane lipids and proteins, including separation of liquid phases into distinct domains. In model membranes, domain size and morphology depend strongly on composition and temperature, but the physicochemical mechanisms controlling them are poorly understood. Theoretical work suggests a role for interfacial energy at domain boundaries, which may be driven in part by thickness mismatch between a domain and its surrounding bilayer. However, no direct evidence linking thickness mismatch to domain size in free-standing bilayers has been reported. We describe the use of Small Angle Neutron Scattering (SANS) to detect domains in simplified lipid-only models that mimic the composition of plasma membrane. We find that domain size is controlled by the degree of acyl chain unsaturation of low-melting temperature lipids, and that this size transition is correlated to changes in the thickness mismatch between coexisting liquid phases.

  18. Elliptical structure of phospholipid bilayer nanodiscs encapsulated by scaffold proteins

    DEFF Research Database (Denmark)

    Skar-Gislinge, Nicholas; Simonsen, Jens Bæk; Mortensen, Kell

    2010-01-01

    -angle neutron scattering in combination with variable-temperature studies of synchrotron small-angle X-ray scattering on nanodiscs in solution, we show that the fundamental nanodisc unit, consisting of a lipid bilayer surrounded by amphiphilic scaffold proteins, possesses intrinsically an elliptical shape....... The temperature dependence of the curvature of the nanodiscs prepared with two different phospholipid types (DLPC and POPC) shows that it is the scaffold protein that determines the overall elliptical shape and that the nanodiscs become more circular with increasing temperature. Our data also show...... that the hydrophobic bilayer thickness is, to a large extent, dictated by the scaffolding protein and adjusted to minimize the hydrophobic mismatch between protein and phospholipid. Our conclusions result from a new comprehensive and molecular-based model of the nanodisc structure and the use of this to analyze...

  19. First-principles modeling hydrogenation of bilayered boron nitride

    Science.gov (United States)

    Jing, Wang; Peng, Zhang; Xiang-Mei, Duan

    2016-05-01

    We have investigated the structural and electronic characteristics of hydrogenated boron-nitride bilayer (H-BNBN-H) using first-principles calculations. The results show that hydrogenation can significantly reduce the energy gap of the BN-BN into the visible-light region. Interestingly, the electric field induced by the interface dipoles helps to promote the formation of well-separated electron-hole pairs, as demonstrated by the charge distribution of the VBM and CBM. Moreover, the applied bias voltage on the vertical direction of the bilayer could modulate the band gap, resulting in transition from semiconductor to metal. We conclude that H-BNBN-H could improve the solar energy conversion efficiency, which may provide a new way for tuning the electronic devices to meet different environments and demands. Project supported by the National Natural Science Foundation of China (Grant No. 11574167).

  20. Polyglutamine expansion in huntingtin increases its insertion into lipid bilayers.

    Science.gov (United States)

    Kegel, Kimberly B; Schewkunow, Vitali; Sapp, Ellen; Masso, Nicholas; Wanker, Erich E; DiFiglia, Marian; Goldmann, Wolfgang H

    2009-09-25

    An expanded polyglutamine (Q) tract (>37Q) in huntingtin (htt) causes Huntington disease. Htt associates with membranes and polyglutamine expansion in htt may alter membrane function in Huntington disease through a mechanism that is not known. Here we used differential scanning calorimetry to examine the effects of polyQ expansion in htt on its insertion into lipid bilayers. We prepared synthetic lipid vesicles composed of phosphatidylcholine and phosphatidylethanolamine and tested interactions of htt amino acids 1-89 with 20Q, 32Q or 53Q with the vesicles. GST-htt1-89 with 53Q inserted into synthetic lipid vesicles significantly more than GST-htt1-89 with 20Q or 32Q. We speculate that by inserting more into cell membranes, mutant huntingtin could increase disorder within the lipid bilayer and thereby disturb cellular membrane function.

  1. Phase-separation transitions in asymmetric lipid bilayers

    CERN Document Server

    Shimobayashi, Shunsuke F; Taniguchi, Takashi

    2015-01-01

    Morphological transitions of phase separation associated with the asymmetry of lipid composition were investigated using micrometer-sized vesicles of lipid bilayers made from a lipid mixture. The complete macro-phase-separated morphology undergoes a transition to a micro-phase-separation-like morphology via a lorate morphology as a metastable state. The transition leads to the emergence of monodisperse nanosized domains through repeated domain scission events. Moreover, we have numerically confirmed the transitions using the time-dependent Ginzburg-Landau model describing phase separation and the bending elastic membrane, which is quantitatively consistent with experimental results by fixing one free parameter. Our findings suggest that the local spontaneous curvature due to the asymmetric composition plays an essential role in the thermodynamic stabilization of micro-phase separation in lipid bilayers.

  2. Formation of droplet interface bilayers in a Teflon tube.

    Science.gov (United States)

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R

    2016-09-29

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications.

  3. Formation of droplet interface bilayers in a Teflon tube

    Science.gov (United States)

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R.

    2016-01-01

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications. PMID:27681313

  4. Model for magnetostrictive performance in soft/hard coupled bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Jianjun, Li, E-mail: ljj8081@gmail.com [National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin 150080 (China); Laboratoire de Magnétisme de Bretagne, Université de Bretagne Occidentale, 29238 Brest Cedex 3 (France); Beibei, Duan; Minglun, Li [National Key Laboratory of Science and Technology on Advanced Composites in Special Environments, Harbin Institute of Technology, Harbin 150080 (China)

    2015-11-01

    A model is set up to investigate the magnetostrictive performance and spin response in soft/hard magnetostrictive coupled bilayers. Direct coupling between soft ferromagnet and hard TbFe{sub 2} at the interface is assumed. The magnetostriction results from the rotation of ferromagnetic vector and TbFe{sub 2} vectors from the easy axis driven by applied magnetic field. Dependence of magnetostriction on TbFe{sub 2} layer thickness and interfacial exchange interaction is studied. The simulated results reveal the compromise between interfacial exchange interaction and anisotropy of TbFe{sub 2} hard layer. - Highlights: • A model for magnetostrictive performance in soft/hard coupled bilayers. • Simulated magnetostriction loop and corresponding spin response. • Competition and compromise between interfacial interaction and TbFe{sub 2} anisotropy. • Dependence of saturated magnetostriction on different parameters.

  5. Dipolar bilayer with antiparallel polarization: A self-bound liquid

    Science.gov (United States)

    Hebenstreit, Martin; Rader, Michael; Zillich, Robert E.

    2016-01-01

    Dipolar bilayers with antiparallel polarization, i.e., opposite polarization in the two layers, exhibit liquidlike rather than gaslike behavior. In particular, even without external pressure, a self-bound liquid droplet of constant density will form. We investigate the symmetric case of two identical layers, corresponding to a two-component Bose system with equal partial densities. The zero-temperature equation of state E (ρ )/N , where ρ is the total density, has a minimum, with an equilibrium density that can be adjusted by the distance d between the layers (decreasing with increasing d ). The attraction necessary for a self-bound liquid comes from the interlayer dipole-dipole interaction that leads to a mediated intralayer attraction. We investigate the regime of negative pressure towards the spinodal instability, where the bilayer is unstable against infinitesimal fluctuations of the total density, confirmed by calculations of the speed of sound of total density fluctuations.

  6. Asymmetric bilayer graphene nanoribbon MOSFETs for analog and digital electronics

    Science.gov (United States)

    Dinarvand, A.; Ahmadi, V.; Darvish, Gh.

    2016-05-01

    In this paper, a new structure was proposed for bilayer graphene nanoribbon field-effect transistor (BGNFET) mainly to enhance the electrical characteristics in analog and digital applications. The proposed device uses two metallic gates on the top and bottom of a bilayer graphene nanoribbon, which is surrounded by SiO2 and connected to heavily doped source/drain contacts. Electrical properties of the proposed device were explored using fully self-consistent solution of Poisson and Schrödinger equations based on the nonequilibrium Green's function (NEGF) formalism. Significant improvements in the electrical behavior was seen in the simulation results for gates asymmetrically biased. The comparison with graphene nanoribbon FET showed that the proposed structure benefited from higher intrinsic voltage gain and cut-off frequency and improved switching characteristics such as delay and Ion/Ioff ratio.

  7. Bilayer graphene: physics and application outlook in photonics

    Directory of Open Access Journals (Sweden)

    Yan Hugen

    2015-05-01

    Full Text Available Layered materials, such as graphene, transition metal dichacogenides and black phosphorus have attracted lots of attention recently. They are emerging novel materials in electronics and photonics, with tremendous potential in revolutionizing the traditional electronics and photonics industry. Marrying layered material to the nanophotonics is being proved fruitful. With the recent emphasis and development of metasurfaces in nanophotonics, atomically thin materials can find their unique position and strength in this field. In this article, I will focus on one specific two dimensional material: bilayer graphene. Basic physics will be reviewed, such as band-gap opening, electron-phonon interaction, phonon-plasmon interaction and Fano resonances in the optical response. Moreover, I will review the application of bilayer graphene as a sensitive and fast photodetector. An outlook will be given in the final part of the paper.

  8. Formation of droplet interface bilayers in a Teflon tube

    Science.gov (United States)

    Walsh, Edmond; Feuerborn, Alexander; Cook, Peter R.

    2016-09-01

    Droplet-interface bilayers (DIBs) have applications in disciplines ranging from biology to computing. We present a method for forming them manually using a Teflon tube attached to a syringe pump; this method is simple enough it should be accessible to those without expertise in microfluidics. It exploits the properties of interfaces between three immiscible liquids, and uses fluid flow through the tube to pack together drops coated with lipid monolayers to create bilayers at points of contact. It is used to create functional nanopores in DIBs composed of phosphocholine using the protein α-hemolysin (αHL), to demonstrate osmotically-driven mass transfer of fluid across surfactant-based DIBs, and to create arrays of DIBs. The approach is scalable, and thousands of DIBs can be prepared using a robot in one hour; therefore, it is feasible to use it for high throughput applications.

  9. Dual-core antiresonant hollow core fibers.

    Science.gov (United States)

    Liu, Xuesong; Fan, Zhongwei; Shi, Zhaohui; Ma, Yunfeng; Yu, Jin; Zhang, Jing

    2016-07-25

    In this work, dual-core antiresonant hollow core fibers (AR-HCFs) are numerically demonstrated, based on our knowledge, for the first time. Two fiber structures are proposed. One is a composite of two single-core nested nodeless AR-HCFs, exhibiting low confinement loss and a circular mode profile in each core. The other has a relatively simple structure, with a whole elliptical outer jacket, presenting a uniform and wide transmission band. The modal couplings of the dual-core AR-HCFs rely on a unique mechanism that transfers power through the air. The core separation and the gap between the two cores influence the modal coupling strength. With proper designs, both of the dual-core fibers can have low phase birefringence and short modal coupling lengths of several centimeters.

  10. Coherence and Optical Emission from Bilayer Exciton Condensates

    Directory of Open Access Journals (Sweden)

    D. W. Snoke

    2011-01-01

    Full Text Available Experiments aimed at demonstrating Bose-Einstein condensation of excitons in two types of experiments with bilayer structures (coupled quantum wells are reviewed, with an emphasis on the basic effects. Bose-Einstein condensation implies the existence of a macroscopic coherence, also known as off-diagonal long-range order, and proposed tests and past claims for coherence in these excitonic systems are discussed.

  11. Molecular doping and band-gap opening of bilayer graphene.

    Science.gov (United States)

    Samuels, Alexander J; Carey, J David

    2013-03-26

    The ability to induce an energy band gap in bilayer graphene is an important development in graphene science and opens up potential applications in electronics and photonics. Here we report the emergence of permanent electronic and optical band gaps in bilayer graphene upon adsorption of π electron containing molecules. Adsorption of n- or p-type dopant molecules on one layer results in an asymmetric charge distribution between the top and bottom layers and in the formation of an energy gap. The resultant band gap scales linearly with induced carrier density though a slight asymmetry is found between n-type dopants, where the band gap varies as 47 meV/10(13) cm(-2), and p-type dopants where it varies as 40 meV/10(13) cm(-2). Decamethylcobaltocene (DMC, n-type) and 3,6-difluoro-2,5,7,7,8,8-hexacyano-quinodimethane (F2-HCNQ, p-type) are found to be the best molecules at inducing the largest electronic band gaps up to 0.15 eV. Optical adsorption transitions in the 2.8-4 μm region of the spectrum can result between states that are not Pauli blocked. Comparison is made between the band gaps calculated from adsorbate-induced electric fields and from average displacement fields found in dual gate bilayer graphene devices. A key advantage of using molecular adsorption with π electron containing molecules is that the high binding energy can induce a permanent band gap and open up possible uses of bilayer graphene in mid-infrared photonic or electronic device applications.

  12. A defect mediated lamellar to isotropic transition of amphiphile bilayers

    OpenAIRE

    Pal, Antara; Pabst, Georg; Raghunathan, V. A.

    2011-01-01

    We report the observation of a novel isotropic phase of amphiphile bilayers in a mixed system consisting of the ionic surfactant, sodium docecylsulphate (SDS), and the organic salt p-toludine hydrochloride (PTHC). This system forms a collapsed lamellar ($L_\\alpha$) phase over a wide range of water content, which transforms into an isotropic phase on heating. This transition is not observed in samples without excess water, where the $L_\\alpha$ phase is stable at higher temperatures. Our observ...

  13. Optimizing non-Pb radiation shielding materials using bilayers

    Energy Technology Data Exchange (ETDEWEB)

    McCaffrey, J. P.; Mainegra-Hing, E.; Shen, H. [Institute for National Measurement Standards, National Research Council of Canada, Building M-35, 1200 Montreal Road, Ottawa K1A 0R6 (Canada)

    2009-12-15

    Purpose: The objective of this study was to demonstrate that the weight of non-Pb radiation shielding materials can be minimized by structuring the material as a bilayer composed of different metal-powder-embedded elastomer layers. Methods: Measurements and Monte Carlo (MC) calculations were performed to study the attenuation properties of several non-Pb metal bilayers over the x-ray energy range 30-150 keV. Metals for the layers were chosen on the basis of low cost, nontoxicity, and complementary photoelectric absorption characteristics. The EGSnrc user code cavity.cpp was used to calculate the resultant x-ray fluence spectra after attenuation by these metal layers. Air kerma attenuation was measured using commercially manufactured metal/elastomer test layers. These layers were irradiated using the primary standard calibration beams at the Institute for National Measurement Standards in Ottawa, Canada utilizing the six x-ray beam qualities recommended in the German Standard DIN 6857. Both the measurements and the calculations were designed to approximate surface irradiation as well as penetrating radiation at 10 mm depth in soft tissue. The MC modeling point and the position of the measurement detector for surface irradiation were both directly against the downstream face of the attenuating material, as recommended in DIN 6857. Results: The low-Z upstream/high-Z downstream ordering of the metal bilayers provided substantially more attenuation than the reverse order. Optimal percentages of each metal in each bilayer were determined for each x-ray radiation beam quality. Conclusions: Depending on the x-ray quality, appropriate choices of two complementary metal-embedded elastomer layers can decrease the weight of radiation shielding garments by up to 25% compared to Pb-based elastomer garments while providing equivalent attenuation.

  14. Bending elastic moduli of lipid bilayers : modulation by solutes

    OpenAIRE

    Duwe, H.P.; Kaes, J.; Sackmann, E.

    1990-01-01

    We present high precision measurements of the bending elastic moduli for bilayers of a variety of different lipids and of modifications of the flexural rigidity by solutes. The measurements are based on the Fourier analysis of thermally excited membrane undulations (vesicle shape fluctuations) using a recently developed dynamic image processing method. Measurements of the bending modulus as a function of the undulation wave vector provide information on the limitation of the excitations by th...

  15. Bilayer Thickness Mismatch Controls Domain Size in Model Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Heberle, Frederick A [ORNL; Petruzielo, Robin S [ORNL; Pan, Jianjun [ORNL; Drazba, Paul [ORNL; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Feigenson, Gerald [Cornell University; Katsaras, John [ORNL

    2013-01-01

    The observation of lateral phase separation in lipid bilayers has received considerable attention, especially in connection to lipid raft phenomena in cells. It is widely accepted that rafts play a central role in cellular processes, notably signal transduction. While micrometer-sized domains are observed with some model membrane mixtures, rafts much smaller than 100 nm beyond the reach of optical microscopy are now thought to exist, both in vitro and in vivo. We have used small-angle neutron scattering, a probe free technique, to measure the size of nanoscopic membrane domains in unilamellar vesicles with unprecedented accuracy. These experiments were performed using a four-component model system containing fixed proportions of cholesterol and the saturated phospholipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), mixed with varying amounts of the unsaturated phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoylsn- glycero-3-phosphocholine (DOPC). We find that liquid domain size increases with the extent of acyl chain unsaturation (DOPC:POPC ratio). Furthermore, we find a direct correlation between domain size and the mismatch in bilayer thickness of the coexisting liquid-ordered and liquid-disordered phases, suggesting a dominant role for line tension in controlling domain size. While this result is expected from line tension theories, we provide the first experimental verification in free-floating bilayers. Importantly, we also find that changes in bilayer thickness, which accompany changes in the degree of lipid chain unsaturation, are entirely confined to the disordered phase. Together, these results suggest how the size of functional domains in homeothermic cells may be regulated through changes in lipid composition.

  16. Pedot and PPy Conducting Polymer Bilayer and Trilayer Actuators

    DEFF Research Database (Denmark)

    Zainudeen, Umer Lebbe; Careem, Mohamed Abdul; Skaarup, Steen

    2008-01-01

    Actuators based on conducting polymers are attracting increasing interest due to their desirable features such as large mechanical stress generated, sufficient maximum strain values, high reversibility, good safety properties and the possibility of precise control using small voltages. Many...... attempts have been made to improve the actuator performance. We report electromechanical measurements on actuators of bilayer and trilayer free standing films prepared with polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymers. Both types of conducting polymer are pre...

  17. Self-assembling bilayers of palladiumthiolates in organic media

    Indian Academy of Sciences (India)

    P John Thomas; A Lavanya; V Sabareesh; G U Kulkarni

    2001-10-01

    Alkylthiolates of palladium forming a homologous series (butyl to octadecyl) have been prepared and characterized using X-ray diffraction and STM. The thiolates adopt an unusual bilayered lamellar structure, whose thickness is governed by the length of the alkyl chain. These mesophases melt in the temperature range, 60° to 100°C, with the melting point increasing linearly with the thiol chain length. There is evidence to suggest that the alkyl chains are orientationally disordered especially prior to melting.

  18. Comment on "Raman spectra of misoriented bilayer graphene"

    OpenAIRE

    Ni, Zhenhua; Wang, Yingying; Yu, Ting; You, Yumeng; Shen, Zexiang

    2009-01-01

    In a recent paper [Phys. Rev. B 78, 113407 (2008)], Poncharal et al. studied the Raman spectra of misoriented bilayer graphene. They found that the blueshift of 2D band of misoriented graphene relative to that of single layer graphene shows a strong dependence on the excitation laser energy. The blueshift increases with decreasing excitation energy. This finding contradicts our explanation of reduction of Fermi velocity of folded/misoriented graphene [Ni et al. Phys. Rev. B 77, 235403 (2008)]...

  19. 33 CFR 157.166 - Hydrocarbon emissions.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Hydrocarbon emissions. 157.166... Crude Oil Washing (COW) System on Tank Vessels Cow Operations § 157.166 Hydrocarbon emissions. If the... ballasted in that port the hydrocarbon vapors in each tank are contained by a means under § 157.132....

  20. Compositions and methods for hydrocarbon functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Gunnoe, Thomas Brent; Fortman, George; Boaz, Nicholas C.; Groves, John T.

    2017-03-28

    Embodiments of the present disclosure provide for methods of hydrocarbon functionalization, methods and systems for converting a hydrocarbon into a compound including at least one group ((e.g., hydroxyl group) (e.g., methane to methanol)), functionalized hydrocarbons, and the like.

  1. Hydrophobic encapsulation of hydrocarbon gases.

    Science.gov (United States)

    Leontiev, Alexander V; Saleh, Anas W; Rudkevich, Dmitry M

    2007-04-26

    [reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.

  2. Effective viscosity of confined hydrocarbons

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, V.N.; Persson, B.N.J.

    2012-01-01

    We present molecular dynamics friction calculations for confined hydrocarbon films with molecular lengths from 20 to 1400 carbon atoms. We find that the logarithm of the effective viscosity ηeff for nanometer-thin films depends linearly on the logarithm of the shear rate: log ηeff=C-nlog γ̇, where...

  3. Fire-safe hydrocarbon fuels

    Energy Technology Data Exchange (ETDEWEB)

    Fodor, G.E.; Weatherford, W.D. Jr.; Wright, B.R.

    1979-11-06

    A stabilized, fire-safe, aqueous hydrocarbon fuel emulsion prepared by mixing: a diesel fuel; an emulsifier (consisting of oleyl diethanolamide, diethanolamine, and diethanolamine soap of oleic acid) which has been treated with about 0 to 7 1/2 of oleic acid. A modified version of this fuel also contains 0 to 0.5% of an antimisting agent, and water.

  4. Influence of silybin on biophysical properties of phospholipid bilayers

    Institute of Scientific and Technical Information of China (English)

    Olga WESO(L)OWSKA; Krystyna MICHALAK; Barbara (L)ANIA-PIETRZAK; Micha(l) KU(Z)D(Z)A(L); Kamila STA(N)CZAK; Daniela MOSI(A)DZ; Piotr DOBRYSZYCKI; Andrzej O(Z)YHAR; Ma(l)gorzata KOMOROWSKA; Andrzej B HENDRICH

    2007-01-01

    Aim: Silybin (silibinin)is major biologically active flavonolignan extracted from milk thistle (Sylibum marianum). Its biological activities include hepato-protection, anticancer properties, and antioxidant- and membrane-stabilizing functions. Al-though membranes are postulated to be one of the cellular targets for silybin, little is known about its interaction with phospholipid bilayers. Methods: In the present work, the interactions of silybin with phosphatidylcholine bilayers were studied in detail using fluorescence spectroscopy, microcalorimetry and electron spin resonance techniques. Results: The results showed that silybin interacted with the surface of lipid bilayers. It affected the generalized polarization of the fluores-cent probe Prodan, while not influencing the more deeplylocated Laurdan. Silybin lowered the main phospholipid phase transition temperature as judged by microcalorimetry, and caused the immobilization of spin probe Tempo-palmitate located on the surface of membranes. The mobility of spin probes 5-and 16-doxylstearic acid was not affected by silybin. Silybin-induced quenching of 1,6-diphe-nyl-1,3,5-hexatriene fluorescence indicated that some flavonoid molecules parti-tioned into the hydrophobic region of membranes, which did not change signifi-cantly the biophysical properties of the deeper membrane regions. Conclusion: Such a behavior of silybin in membranes is in accordance with its postulated biological functions and neglectable side effects of therapies using silybin.

  5. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating.

    Science.gov (United States)

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-01-01

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (-1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices.

  6. Photon-assisted transport in bilayer graphene flakes

    Science.gov (United States)

    Zambrano, D.; Rosales, L.; Latgé, A.; Pacheco, M.; Orellana, P. A.

    2017-01-01

    The electronic conductance of graphene-based bilayer flake systems reveals different quantum interference effects, such as Fabry-Pérot resonances and sharp Fano antiresonances on account of competing electronic paths through the device. These properties may be exploited to obtain spin-polarized currents when the same nanostructure is deposited above a ferromagnetic insulator. Here, we study how the spin-dependent conductance is affected when a time-dependent gate potential is applied to the bilayer flake. Following a Tien-Gordon formalism, we explore how to modulate the transport properties of such systems via appropriate choices of the ac-field gate parameters. The presence of an oscillating field opens the possibility of tuning the original antiresonances for a large set of field parameters. We show that interference patterns can be partially or fully removed by the time-dependent gate voltage. The results are reflected in the corresponding weighted spin polarization, which can reach maximum values for a given spin component. We found that differential conductance maps as functions of bias and gate potentials show interference patterns for different ac-field parameter configurations. The proposed bilayer graphene flake systems may be used as a frequency detector in the THz range.

  7. Optical rectification at visible frequency in biased bilayer graphene

    Science.gov (United States)

    Hipolito, F.; Pereira, Vitor M.

    2015-03-01

    The second order response of the electrical current to an electromagnetic field is analyzed within the framework of non-equilibrium many-body perturbation theory for the case of a two-dimensional electronic system such as graphene and its bilayer. The absence of inversion symmetry in a biased graphene bilayer allows a finite DC response in second order to an AC electromagnetic wave. The induced DC current is evaluated for biased bilayer at finite temperature, and its tunability is analyzed as a function of electron density, which can be experimentally varied by means of a global gate voltage applied to the sample. Both intrinsic and photon drag microscopic processes are considered, as they contribute on similar footing to the photocurrent in general. However, the dependencies of these two contributions on the polarization state of the incident light are different, which allows the manipulation of the relative contribution of intrinsic versus photon drag contributions by tuning the experimental parameters. For example, the photocurrent emerging from circularly polarized light stems entirely from photon drag, as the circular photogalvanic effect is forbidden by the C3 rotation symmetry of the honeycomb lattice.

  8. Amphotericin B induced interdigitation of apolipoprotein stabilized nanodisk bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, T; Weers, P M; Sulchek, T; Hoeprich, P D; Ryan, R O

    2006-12-07

    Amphotericin B nanodisks (AMB-ND) are ternary complexes of AMB, phospholipid (PL) and apolipoprotein organized as discrete nanometer scale disk-shaped bilayers. In gel filtration chromatography experiments, empty ND lacking AMB elute as a single population of particles with a molecular weight in the range of 200 kDa. AMB-ND formulated at a 4:1 PL:AMB weight ratio, separated into two peaks. Peak 1 eluted at the position of control ND lacking AMB while the second peak, containing all of the AMB present in the original sample, eluted in the void volume. When ND prepared with increased AMB (1:1 phospholipid:AMB molar ratio) were subjected to gel filtration chromatography, an increased proportion of phospholipid and apolipoprotein were recovered in the void volume with the AMB. Prior to gel filtration the AMB-ND sample could be passed through a 0.22 {micro}m filter without loss of AMB while the voided material was lost. Native gel electrophoresis studies corroborated the gel permeation chromatography data. Far UV circular dichroism analyses revealed that apoA-I associated with AMB-ND denatures at a lower guanidine HCl concentration than apoA-I associated with ND lacking AMB. Atomic force microscopy revealed that AMB induces compression of the ND bilayer thickness consistent with bilayer interdigitation, a phenomenon that is likely related to the ability of AMB to induce pore formation in susceptible membranes.

  9. Isolation and characterization of ancient hydrocarbon biomarkers from crystalline minerals

    Science.gov (United States)

    Summons, R. E.; Carrasquillo, A.; Hallmann, C.; Sherman, L. S.; Waldbauer, J. R.

    2008-12-01

    Hydrocarbon biomarker analysis is conventionally conducted on bitumen (soluble fossilized organic matter) extracted from sedimentary rocks using organic solvents. Biomarkers can also be generated by pyrolysis of kerogen (insoluble organic matter) in the same rocks. These approaches have met with much success where the organic matter has not seen significant levels of thermal metamorphism but more limited success when applied to thermally mature Archean rocks. Biomarkers have also been isolated from fluid inclusions of crystalline minerals and this approach has found wide application in petroleum exploration because of the capability of minerals that form crystals in reservoir rocks to trap organics from different episodes of fluid migration. Lastly, biogenic crystalline minerals are well known to trap organics including amino acids, fatty acids or hydrocarbons from those organisms that laid down the minerals. In fact, recent observations suggest that hydrocarbon biomarkers can be abundantly preserved in crystalline minerals where they may be protected over long periods of time and also distinguished from more recent generations of organics from endolithic organisms (modern) or anthropogenic (fossil hydrocarbon) contaminants. Here we report analyses of biomarker lipids trapped in fluid inclusions or otherwise having a "tight association" with the minerals in sedimentary rocks from Neoarchean and Paleoproterozoic successions in Australia and Southern Africa. In particular, cores recovered from the Agouron Griqualand Drilling Project contain over 2500m of well-preserved late Archean Transvaal Supergroup sediments, dating from ca. 2.67 to 2.46Ga. Bitumen extracts of samples from these strata were obtained using clean drilling, sampling and handling protocols and without overprinting with contaminant hydrocarbons. Dissolution of the mineral matrix of extracted sediments, followed by another solvent extraction, yielded a second bitumen that comprised hydrocarbons that

  10. Performance projection of bilayer graphene nanoribbon FET through quantum mechanical simulation

    Science.gov (United States)

    Rawat, Brajesh; Paily, Roy

    2016-12-01

    A quantum transport simulator based on a self-consistent solution of the Schrödinger equation within non-equilibrium Green’s function formalism and 2D Poisson equation for a bilayer graphene nanoribbon (bilayer GNR) field-effect transistor (FET) has been developed to examine the ballistic performance of a device. It is found that the lateral confinement employed in bilayer graphene to form the bilayer GNR largely increases the ON/OFF current ({I}{{ON}}/{I}{{OFF}}) ratios of FET without significantly degrading its ON current ({I}{{ON}}). On the other hand, the interlayer coupling considerably decreases the confinement-induced energy gap of the bilayer GNR and largely increases the {I}{{ON}} of the narrow bilayer GNR FET at the cost of lower {I}{{ON}}/{I}{{OFF}} ratios in comparison with the GNR FET.

  11. Time-resolved photoresponse of nanometer-thick Nb/NiCu bilayers

    Science.gov (United States)

    Parlato, L.; Pepe, G. P.; Latempa, R.; De Lisio, C.; Altucci, C.; D'Acunto, P.; Peluso, G.; Barone, A.; Taneda, T.; Sobolewski, R.

    2005-07-01

    We present femtosecond optical time-resolved pump-probe investigations of superconducting hybrids structures consisting of Nb/NiCu bilayers with various thickness. Measurements performed on pure Nb and NiCu films are also given. The photoresponse experiments provide the quasiparticle relaxation times in bilayers of different thickness ratios. The study of the photoresponse as a function of the temperature reveals the spatial evolution of the superconductor order parameter across the bilayers.

  12. Study of annealing effects in Al–Sb bilayer thin films

    Indian Academy of Sciences (India)

    R K Mangal; B Tripathi; M Singh; Y K Vijay

    2007-02-01

    In this paper, we present preparation and characterization of Al–Sb bilayer thin films. Thin films of thicknesses, 3000/1000 Å and 3000/1500 Å, were obtained by the thermal evaporation (resistive heating) method. Vacuum annealing and rapid thermal annealing methods were used to mix bilayer thin film structure. Results obtained from optical band gap data and Rutherford back scattering spectrometry showed mixing of Al–Sb bilayer system.

  13. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    OpenAIRE

    Meisam Rahmani; Razali Ismail; Mohammad Taghi Ahmadi; Mohammad Javad Kiani; Mehdi Saeidmanesh; F. A. Hediyeh Karimi; Elnaz Akbari; Komeil Rahmani

    2013-01-01

    Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking) and metal (AA ...

  14. Biodegradation of petroleum hydrocarbons in hypersaline environments

    Directory of Open Access Journals (Sweden)

    Luiz Fernando Martins

    2012-09-01

    Full Text Available Literature on hydrocarbon degradation in extreme hypersaline media presents studies that point to a negative effect of salinity increase on hydrocarbonoclastic activity, while several others report an opposite tendency. Based on information available in the literature, we present a discussion on the reasons that justify these contrary results. Despite the fact that microbial ability to metabolize hydrocarbons is found in extreme hypersaline media, indeed some factors are critical for the occurrence of hydrocarbon degradation in such environments. How these factors affect hydrocarbon degradation and their implications for the assessment of hydrocarbon biodegradation in hypersaline environments are presented in this review.

  15. Syngas Upgrading to Hydrocarbon Fuels Technology Pathway

    Energy Technology Data Exchange (ETDEWEB)

    Talmadge, M.; Biddy, M.; Dutta, A.; Jones, S.; Meyer, A.

    2013-03-01

    This technology pathway case investigates the upgrading of woody biomass derived synthesis gas (syngas) to hydrocarbon biofuels. While this specific discussion focuses on the conversion of syngas via a methanol intermediate to hydrocarbon blendstocks, there are a number of alternative conversion routes for production of hydrocarbons through a wide array of intermediates from syngas. Future work will also consider the variations to this pathway to determine the most economically viable and lowest risk conversion route. Technical barriers and key research needs have been identified that should be pursued for the syngas-to-hydrocarbon pathway to be competitive with petroleum-derived gasoline-, diesel- and jet-range hydrocarbon blendstocks.

  16. Biodegradation of petroleum hydrocarbons in hypersaline environments

    Science.gov (United States)

    Martins, Luiz Fernando; Peixoto, Raquel Silva

    2012-01-01

    Literature on hydrocarbon degradation in extreme hypersaline media presents studies that point to a negative effect of salinity increase on hydrocarbonoclastic activity, while several others report an opposite tendency. Based on information available in the literature, we present a discussion on the reasons that justify these contrary results. Despite the fact that microbial ability to metabolize hydrocarbons is found in extreme hypersaline media, indeed some factors are critical for the occurrence of hydrocarbon degradation in such environments. How these factors affect hydrocarbon degradation and their implications for the assessment of hydrocarbon biodegradation in hypersaline environments are presented in this review. PMID:24031900

  17. Animal MRI Core

    Data.gov (United States)

    Federal Laboratory Consortium — The Animal Magnetic Resonance Imaging (MRI) Core develops and optimizes MRI methods for cardiovascular imaging of mice and rats. The Core provides imaging expertise,...

  18. Permeation of halide anions through phospholipid bilayers occurs by the solubility-diffusion mechanism

    Science.gov (United States)

    Paula, S.; Volkov, A. G.; Deamer, D. W.

    1998-01-01

    Two alternative mechanisms are frequently used to describe ionic permeation of lipid bilayers. In the first, ions partition into the hydrophobic phase and then diffuse across (the solubility-diffusion mechanism). The second mechanism assumes that ions traverse the bilayer through transient hydrophilic defects caused by thermal fluctuations (the pore mechanism). The theoretical predictions made by both models were tested for halide anions by measuring the permeability coefficients for chloride, bromide, and iodide as a function of bilayer thickness, ionic radius, and sign of charge. To vary the bilayer thickness systematically, liposomes were prepared from monounsaturated phosphatidylcholines (PC) with chain lengths between 16 and 24 carbon atoms. The fluorescent dye MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) served as an indicator for halide concentration inside the liposomes and was used to follow the kinetics of halide flux across the bilayer membranes. The observed permeability coefficients ranged from 10(-9) to 10(-7) cm/s and increased as the bilayer thickness was reduced. Bromide was found to permeate approximately six times faster than chloride through bilayers of identical thickness, and iodide permeated three to four times faster than bromide. The dependence of the halide permeability coefficients on bilayer thickness and on ionic size were consistent with permeation of hydrated ions by a solubility-diffusion mechanism rather than through transient pores. Halide permeation therefore differs from that of a monovalent cation such as potassium, which has been accounted for by a combination of the two mechanisms depending on bilayer thickness.

  19. The effect of calcium on the properties of charged phospholipid bilayers

    DEFF Research Database (Denmark)

    Pedersen, U.R.; Leidy, Chad; Westh, P.

    2006-01-01

    We have performed molecular dynamics simulations to investigate the structure and dynamics of charged bilayers as well as the distribution of counterions at the bilayer interface. For this, we have considered the negatively charged di-myristoyl-phosphatidyl-glycerol (DMPG) and di-myristoyl-phosph......We have performed molecular dynamics simulations to investigate the structure and dynamics of charged bilayers as well as the distribution of counterions at the bilayer interface. For this, we have considered the negatively charged di-myristoyl-phosphatidyl-glycerol (DMPG) and di...

  20. Aqueous reactions of chlorine dioxide with hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Rav-Acha, C.; Choshen, E.

    1987-11-01

    In contrast to mechanisms proposed earlier in the literature, according to which chlorine dioxide (ClO/sub 2/) reacts with various hydrocarbons in aqueous media by abstracting allylic or benzylic hydrogens, it is shown that ClO/sub 2/ reacts with olefins through initial electron transfer. Hydrocarbons that can undergo facile oxidation, such as polycyclic aromatic hydrocarbons (PAH) and some olefins, react with ClO/sub 2/ quite rapidly, while saturated aliphatic hydrocarbons, some aromatic hydrocarbons, and olefins substituted with electron-withdrawing groups remain unreactive. This was substantiated by comparing the reactivities toward ClO/sub 2/ of a variety of hydrocarbons, including aliphatic and aromatic hydrocarbons, saturated and unsaturated acids, PAH, or cyclic and acyclic olefins. The results were supported by a detailed kinetic and product study of the reaction between ClO/sub 2/ and some model compounds.

  1. Hydrocarbons in surface sediments from a Guaymas Basin hydrothermal vent site. Technical report

    Energy Technology Data Exchange (ETDEWEB)

    Bazylinski, D.A.; Farrington, J.W.; Jannasch, H.W.

    1988-01-01

    Petroleum-like materials found at the Guaymas Basin hydrothermal vent site (Gulf of California) are derived from pyrolysis of organic matter. Two characteristics surface sediment cores differing in temperature profiles and other parameters were collected by DSV ALVIN, sectioned, and analyzed for hydrocarbons. The quantitative and qualitative composition of alkanes, steranes, diasteranes, and triterpanes differed between these cores as well as within sections of the same core. These differences, apparent for scales of tens of centimeters, are related to interactive physical, chemical, and microbial processes as well as the influence of multiple sources for the petroleum.

  2. Hydrocarbons in surface sediments from a Guaymas Basin hydrothermal vent site

    Energy Technology Data Exchange (ETDEWEB)

    Bazylinski, D.A.; Farrington, J.W.; Jannasch, H.W. (Woods Hole Oceanographic Institution, Woods Hole, MA (USA))

    1988-01-01

    Petroleum-like materials found at the Guaymas Basin hydrothermal vent site (Gulf of California) are derived from pyrolysis of organic matter. Two characteristic surface sediment cores differing in temperature profiles and other parameters were collected by DSV ALVIN, sectioned and analyzed for hydrocarbons. The quantitative and qualitative composition of alkanes, steranes, diasteranes, and triterpanes differed between these cores as well as within sections of the same core. These differences, apparent for scales of tens of centimeters, are related to interactive physical, chemical, and microbial processes as well as the influence of multiple sources for the petroleum.

  3. STABLE HIGH CONDUCTIVITY BILAYERED ELECTROLYTES FOR LOW TEMPERATURE SOLID OXIDE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Eric D. Wachsman; Keith L. Duncan

    2001-09-30

    temperature SOFCs. This objective is specifically directed toward meeting the lowest (and most difficult) temperature criteria for the 21st Century Fuel Cell Program. Meeting this objective provides a potential for future transportation applications of SOFCs, where their ability to directly use hydrocarbon fuels could permit refueling within the existing transportation infrastructure. In order to meet this objective we are developing a functionally gradient bilayer electrolyte comprised of bismuth oxide on the air side and ceria on the fuel side. Bismuth oxide and doped ceria are among the highest ionic conducting electrolytes and in fact bismuth oxide based electrolytes are the only known solid oxide electrolytes to have an ionic conductivity that meets the program conductivity goal.

  4. Thin metal bilayer for surface plasmon resonance sensors in a multimode plastic optical fiber: the case of palladium and gold metal films

    Science.gov (United States)

    Cennamo, Nunzio; Zuppella, Paola; Bacco, Davide; Corso, Alain J.; Pelizzo, Maria G.; Pesavento, Maria; Zeni, Luigi

    2016-05-01

    A novel sensing platform based on thin metal bilayer for surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) has been designed, implemented and tested. The experimental results are congruent with the numerical studies. This platform has been properly optimized to work in the 1.38 -1.42 refractive index range and it exhibits excellent sensitivity. This refractive index range is very interesting for bio-chemical applications, where the polymer layer are used as receptors (e.g. molecularly imprinted polymer) or to immobilize the bio-receptor on the metal surface. The proposed metallic bilayer is based on palladium and gold films and replaces the traditional gold by exhibiting higher performances. Furthermore, the deposition of the thin bilayer is a single process and no further manufacturing step is required. In fact, in this case the photoresist buffer layer between the POF core and the metal layer, usually required to increase the refractive index range, is no longer necessary.

  5. Hydrocarbon Rocket Technology Impact Forecasting

    Science.gov (United States)

    Stuber, Eric; Prasadh, Nishant; Edwards, Stephen; Mavris, Dimitri N.

    2012-01-01

    Ever since the Apollo program ended, the development of launch propulsion systems in the US has fallen drastically, with only two new booster engine developments, the SSME and the RS-68, occurring in the past few decades.1 In recent years, however, there has been an increased interest in pursuing more effective launch propulsion technologies in the U.S., exemplified by the NASA Office of the Chief Technologist s inclusion of Launch Propulsion Systems as the first technological area in the Space Technology Roadmaps2. One area of particular interest to both government agencies and commercial entities has been the development of hydrocarbon engines; NASA and the Air Force Research Lab3 have expressed interest in the use of hydrocarbon fuels for their respective SLS Booster and Reusable Booster System concepts, and two major commercially-developed launch vehicles SpaceX s Falcon 9 and Orbital Sciences Antares feature engines that use RP-1 kerosene fuel. Compared to engines powered by liquid hydrogen, hydrocarbon-fueled engines have a greater propellant density (usually resulting in a lighter overall engine), produce greater propulsive force, possess easier fuel handling and loading, and for reusable vehicle concepts can provide a shorter turnaround time between launches. These benefits suggest that a hydrocarbon-fueled launch vehicle would allow for a cheap and frequent means of access to space.1 However, the time and money required for the development of a new engine still presents a major challenge. Long and costly design, development, testing and evaluation (DDT&E) programs underscore the importance of identifying critical technologies and prioritizing investment efforts. Trade studies must be performed on engine concepts examining the affordability, operability, and reliability of each concept, and quantifying the impacts of proposed technologies. These studies can be performed through use of the Technology Impact Forecasting (TIF) method. The Technology Impact

  6. Microbial production of gaseous hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Hideo

    1987-10-20

    Microbial production of ethylene, isobutane and a saturated gaseous hydrocarbon mixture was described. Microbial ethylene production was studied with Penicillium digitatum IFO 9372 and a novel pathway of the ethylene biosynthesis through alpha-ketoglutarate was proposed. Rhodotorula minuta IFO 1102 was selected for the microbial production of isobutane and the interesting actions of L-leucine and L-phenylalanine for the isobutane production were found. It was finally presented about the microbial production of a saturated gaseous hydrocarbon mixture with Rhizopus japonicus IFO 4758 was described. A gas mixture was produced through a chemical reaction of SH compounds and some cellular component such as squalene under aerobic conditions. (4 figs, 7 tabs, 41 refs)

  7. Method for analyzing solvent extracted sponge core

    Energy Technology Data Exchange (ETDEWEB)

    Ellington, W.E.; Calkin, C.L.

    1988-11-22

    For use in solvent extracted sponge core measurements of the oil saturation of earth formations, a method is described for quantifying the volume of oil in the fluids resulting from such extraction. The method consists of: (a) separating the solvent/oil mixture from the water in the extracted fluids, (b) distilling at least a portion of the solvent from the solvent/oil mixture substantially without co-distillation or loss of the light hydrocarbons in the mixture, (c) determining the volume contribution of the solvent remaining in the mixture, and (d) determining the volume of oil removed from the sponge by substracting the determined remaining solvent volume.

  8. Deep desulfurization of hydrocarbon fuels

    Science.gov (United States)

    Song, Chunshan [State College, PA; Ma, Xiaoliang [State College, PA; Sprague, Michael J [Calgary, CA; Subramani, Velu [State College, PA

    2012-04-17

    The invention relates to processes for reducing the sulfur content in hydrocarbon fuels such as gasoline, diesel fuel and jet fuel. The invention provides a method and materials for producing ultra low sulfur content transportation fuels for motor vehicles as well as for applications such as fuel cells. The materials and method of the invention may be used at ambient or elevated temperatures and at ambient or elevated pressures without the need for hydrogen.

  9. Study of hydrocarbon--shale interaction. Progress report No. 1, July 1, 1976--October 1, 1976

    Energy Technology Data Exchange (ETDEWEB)

    Schettler, P.D. Jr.

    1976-01-01

    Work on Hydrocarbon-Shale Interaction at Juniata College from June 1, 1976 through September 30, 1976 is summarized. Work was accomplished in the following areas: constrictive and geometric effects associated with gas production from shale wells, diffusion constants, hydrocarbon gas analysis, adsorption isotherms and powder x-ray diffraction. A bibliography on adsorption and diffusion in shale was prepared and is included. A detailed description of the procedures used in construction and calibration of the apparatus used for sorption measurements is included. All experimental work was done on cores from Well No. 20403 in Lincoln County, West Virginia.

  10. Abnormal pressure in hydrocarbon environments

    Science.gov (United States)

    Law, B.E.; Spencer, C.W.

    1998-01-01

    Abnormal pressures, pressures above or below hydrostatic pressures, occur on all continents in a wide range of geological conditions. According to a survey of published literature on abnormal pressures, compaction disequilibrium and hydrocarbon generation are the two most commonly cited causes of abnormally high pressure in petroleum provinces. In young (Tertiary) deltaic sequences, compaction disequilibrium is the dominant cause of abnormal pressure. In older (pre-Tertiary) lithified rocks, hydrocarbon generation, aquathermal expansion, and tectonics are most often cited as the causes of abnormal pressure. The association of abnormal pressures with hydrocarbon accumulations is statistically significant. Within abnormally pressured reservoirs, empirical evidence indicates that the bulk of economically recoverable oil and gas occurs in reservoirs with pressure gradients less than 0.75 psi/ft (17.4 kPa/m) and there is very little production potential from reservoirs that exceed 0.85 psi/ft (19.6 kPa/m). Abnormally pressured rocks are also commonly associated with unconventional gas accumulations where the pressuring phase is gas of either a thermal or microbial origin. In underpressured, thermally mature rocks, the affected reservoirs have most often experienced a significant cooling history and probably evolved from an originally overpressured system.

  11. Hydrocarbon prospectivity in Western Greece

    Energy Technology Data Exchange (ETDEWEB)

    Maravelis, Angelos; Makrodimitras, George; Zelilidis, Avraam [Patras Univ. (Greece). Lab. of Sedimentology

    2012-06-15

    The geology of Western Greece is dominated by the most external zones of the Hellenide fold-and-thrust belt, namely the Pre-Apulian (or Paxoi) and Ionian zones. With Western Greece and Albania having undergone, in broad terms, similar geological histories, also the hydrocarbon potentials of both areas may be compared. Likewise, the hydrocarbon potential of Italy's Apulian Platform, adjoining in the westerly offshore, may serve as an analogue. Three basin types within Western Greece that deserve hydrocarbon exploration have been examined and are grouped, correlated to major tectonic features, namely foreland (Ionian thrusts' foreland basin), piggy-back (Ionian thrusts' back-arc basin) and strike-slip basins. Additionally, strike-slip basins are further subdivided into the basin north of the Borsh-Khardhiqit strike-slip fault and the Preveza basin, north of Cephalonia transfer fault. Their filling histories suggest the occurrence of Mesozoic carbonate plays and Oligocene/Miocene sandstone plays both for oil and gas.

  12. Interaction of curcumin with lipid monolayers and liposomal bilayers.

    Science.gov (United States)

    Karewicz, Anna; Bielska, Dorota; Gzyl-Malcher, Barbara; Kepczynski, Mariusz; Lach, Radosław; Nowakowska, Maria

    2011-11-01

    Curcumin shows huge potential as an anticancer and anti-inflammatory agent. However, to achieve a satisfactory bioavailability and stability of this compound, its liposomal form is preferable. Our detailed studies on the curcumin interaction with lipid membranes are aimed to obtain better understanding of the mechanism and eventually to improve the efficiency of curcumin delivery to cells. Egg yolk phosphatidylcholine (EYPC) one-component monolayers and bilayers, as well as mixed systems containing additionally dihexadecyl phosphate (DHP) and cholesterol, were studied. Curcumin binding constant to EYPC liposomes was determined based on two different methods: UV/Vis absorption and fluorescence measurements to be 4.26×10(4)M(-1) and 3.79×10(4)M(-1), respectively. The fluorescence quenching experiment revealed that curcumin locates in the hydrophobic region of EYPC liposomal bilayer. It was shown that curcumin impacts the size and stability of the liposomal carriers significantly. Loaded into the EYPC/DPH/cholesterol liposomal bilayer curcumin stabilizes the system proportionally to its content, while the EYPC/DPH system is destabilized upon drug loading. The three-component lipid composition of the liposome seems to be the most promising system for curcumin delivery. An interaction of free and liposomal curcumin with EYPC and mixed monolayers was also studied using Langmuir balance measurements. Monolayer systems were treated as a simple model of cell membrane. Condensing effect of curcumin on EYPC and EYPC/DHP monolayers and loosening influence on EYPC/DHP/chol ones were observed. It was also demonstrated that curcumin-loaded EYPC liposomes are more stable upon interaction with the model lipid membrane than the unloaded ones.

  13. AIREBO-M: A reactive model for hydrocarbons at extreme pressures

    Energy Technology Data Exchange (ETDEWEB)

    O’Connor, Thomas C., E-mail: toconnor@jhu.edu; Robbins, Mark O., E-mail: Mark.O.Robbins@jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Andzelm, Jan, E-mail: jan.w.andzelm.civ@mail.mil [Macromolecular Science and Technology Branch, U.S. Army Research Laboratory, Aberdeen, Maryland 21005 (United States)

    2015-01-14

    The Adaptive Intermolecular Reactive Empirical Bond Order potential (AIREBO) for hydrocarbons has been widely used to study dynamic bonding processes under ambient conditions. However, its intermolecular interactions are modeled by a Lennard-Jones (LJ) potential whose unphysically divergent power-law repulsion causes AIREBO to fail when applied to systems at high pressure. We present a modified potential, AIREBO-M, where we have replaced the singular Lennard-Jones potential with a Morse potential. We optimize the new functional form to improve intermolecular steric repulsions, while preserving the ambient thermodynamics of the original potentials as much as possible. The potential is fit to experimental measurements of the layer spacing of graphite up to 14 GPa and first principles calculations of steric interactions between small alkanes. To validate AIREBO-M’s accuracy and transferability, we apply it to a graphite bilayer and orthorhombic polyethylene. AIREBO-M gives bilayer compression consistent with quantum calculations, and it accurately reproduces the quasistatic and shock compression of orthorhombic polyethlyene up to at least 40 GPa.

  14. d-d excitations in bilayer manganites probed by resonant inelastic x-ray scattering.

    Energy Technology Data Exchange (ETDEWEB)

    Weber, F.; Rosenkranz, S.; Castellan, J.-P.; Osborn, R.; Mitchell, J. F.; Zheng, H.; Case, D.; Kim, J. H.; Gog, T.

    2010-01-01

    We report a high-resolution resonant inelastic x-ray scattering investigation of the bilayer manganites La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} with x=0.36 and 0.5. The momentum dependence along the crystallographic (110) direction for energy losses 1 eV {le} {Delta}E {le} 15 eV has been measured in detail with the data analysis focusing on the energy-loss region 1 eV {le} {Delta}E {le} 5 eV, which includes a strong peak located at {Delta}E {approx} 2 eV. We observe a clear dispersion of up to 0.5 eV in the measured q range, which is direct evidence of the nonlocal character of this excitation. Further, we found that the intensity in this low-energy region strongly depends on both the reduced wave vector q=(h,h,0), h=0.1-0.5, and temperature, i.e., different ordered phases. Results can be explained via an intersite d-d charge-transfer excitation, proposed for pseudocubic manganites, where the hopping rate is strongly increased (decreased) by ferromagnetic (antiferromagnetic) alignment of neighboring in-plane Mn ion core spins.

  15. Modification of thermal and electronic properties of bilayer graphene by using slow Na+ ions

    Science.gov (United States)

    Ryu, Mintae; Lee, Paengro; Kim, Jingul; Park, Heemin; Chung, Jinwook

    2016-12-01

    Bilayer graphene (BLG) has an extensive list of industrial applications in graphene-based nanodevices such as energy storage devices, flexible displays, and thermoelectric devices. By doping slow Na+ ions on Li-intercalated BLG, we find significantly improved thermal and electronic properties of BLG by using angle-resolved photoemission and high-resolution core level spectroscopy (HRCLS) with synchrotron photons. Our HRCLS data reveal that the adsorbed Na+ ions on a BLG produced by Li-intercalation through single layer graphene (SLG) spontaneously intercalate below the BLG, and substitute Li atoms to form Na-Si bonds at the SiC interface while preserving the same phase of BLG. This is in sharp contrast with no intercalation of Na+ ions on SLG though neutral Na atoms intercalate. The Na+-induced BLG is found to be stable upon heating up to T = 400 °C, but returns to SLG when heated at T d = 500 °C. The evolution of the π-bands upon doping the Na+ ions followed by thermal annealing shows that the carrier concentration of the π-band may be artificially controlled without damaging the Dirac nature of the π-electrons. The doubled desorption temperature from that (T d = 250 °C) of the Na-intercalated SLG together with the electronic stability of the Na+-intercalated BLG may find more practical and effective applications in advancing graphene-based thermoelectric devices and anode materials for rechargeable batteries.

  16. Molecular organization, localization and orientation of antifungal antibiotic amphotericin B in a single lipid bilayer

    Science.gov (United States)

    Grudzinski, Wojciech; Sagan, Joanna; Welc, Renata; Luchowski, Rafal; Gruszecki, Wieslaw I.

    2016-01-01

    Amphotericin B is a popular antifungal antibiotic, a gold standard in treatment of systemic mycotic infections, due to its high effectiveness. On the other hand, applicability of the drug is limited by its considerable toxicity to patients. Biomembranes are a primary target of physiological activity of amphotericin B and both the pharmacologically desired and toxic side effects of the drug relay on its molecular organization in the lipid phase. In the present work, molecular organization, localization and orientation of amphotericin B, in a single lipid bilayer system, was analysed simultaneously, thanks to application of a confocal fluorescence lifetime imaging microscopy of giant unilamellar vesicles. The results show that the presence of sterols, in the lipid phase, promotes formation of supramolecular structures of amphotericin B and their penetration into the membrane hydrophobic core. The fact that such an effect is substantially less pronounced in the case of cholesterol than ergosterol, the sterol of fungal membranes, provides molecular insight into the selectivity of the drug. PMID:27620838

  17. Gold nanoparticles generated in ethosome bilayers, as revealed by cryo-electron-tomography.

    Science.gov (United States)

    de la Presa, Patricia; Rueda, Tatiana; del Puerto Morales, María; Javier Chichón, F; Arranz, Rocío; Valpuesta, José María; Hernando, Antonio

    2009-03-12

    Gold nanoparticles have been synthesized inside ethosomes, vesicles composed of phospholipid, ethanol, and water, which could be very efficient not only in delivery probes to the skin but also as diagnostic and therapeutic multimodal agents. High efficiency encapsulation of gold nanoparticles is achieved by a simple strategy: the nanoparticles synthesis occurs simultaneously with the ethosomes formation in the absence of any undesirable reducing agents. A three-dimensional reconstruction of a gold-embedded ethosome generated by cryoelectron tomography reveals that the gold particle is localized inside the lipid bilayer, leaving the ethosome surface and core free for further functionalization. The resulting gold nanoparticles are homogeneous in size and shape and, depending on synthesis temperature, the size ranges from 10 to 20 nm, as revealed by TEM. The ethosome-nanoparticles hybrids' size has been investigated by means of dynamic light scattering and has been found to vary with temperature and gold salt concentration from 700 to 400 nm. Gold nanoparticles-encapsulated ethosomes offer a versatile platform for the enhancement of pharmacological efficacy in transdermal and dermal delivery systems.

  18. Band Structure Asymmetry of Bilayer Graphene Revealed by Infrared Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z.Q.; Henriksen, E.A.; Jiang, Z.; Hao, Zhao; Martin, Michael C.; Kim, P.; Stormer, H.L.; Basov, Dimitri N.

    2008-12-10

    We report on infrared spectroscopy of bilayer graphene integrated in gated structures. We observe a significant asymmetry in the optical conductivity upon electrostatic doping of electrons and holes. We show that this finding arises from a marked asymmetry between the valence and conduction bands, which is mainly due to the inequivalence of the two sublattices within the graphene layer and the next-nearest-neighbor interlayer coupling. From the conductivity data, the energy difference of the two sublattices and the interlayer coupling energy are directly determined.

  19. Photoinduced electron transfer of chlorophyll in lipid bilayer system

    Indian Academy of Sciences (India)

    D K Lee; K W Seo; Y S Kang

    2002-12-01

    Photoinduced electron transfer from chlorophyll- through the interface of dipalmitoylphosphatidylcholine (DPPC) headgroup of the lipid bilayers was studied with electron magnetic resonance (EMR). The photoproduced radicals were identified with electron spin resonance (ESR) and radical yields of chlorophyll- were determined by double integration ESR spectra. The formation of vesicles was identified by changes in measured max values from diethyl ether solutions to vesicles solutions indirectly, and observed directly with SEM and TEM images. The efficiency of photosynthesis in model system was determined by measuring the amount of chlorophyll-a radical yields which were obtained from integration of ESR spectra.

  20. Inverse Proximity Effect in Superconductor-ferromagnet Bilayer Structures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Jing

    2010-04-05

    Measurements of the polar Kerr effect using a zero-area-loop Sagnac magnetometer on Pb/Ni and Al/(Co-Pd) proximity-effect bilayers show unambiguous evidence for the 'inverse proximity effect,' in which the ferromagnet (F) induces a finite magnetization in the superconducting (S) layer. To avoid probing the magnetic effects in the ferromagnet, the superconducting layer was prepared much thicker than the light's optical penetration depth. The sign and size of the effect, as well as its temperature dependence agree with recent predictions by Bergeret et al.[1].

  1. Electronic Bloch oscillation in bilayer graphene gradient superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Hemeng; Li, Changan; Song, Yun [Department of Physics, Beijing Normal University, Beijing 100875 (China); Ma, Tianxing, E-mail: txma@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Wang, Li-Gang, E-mail: sxwlg@yahoo.com [Department of Physics, Zhejiang University, Hangzhou 310027 (China); Lin, Hai-Qing [Beijing Computational Science Research Center, Beijing 100084 (China)

    2014-08-18

    We investigate the electronic Bloch oscillation in bilayer graphene gradient superlattices using transfer matrix method. By introducing two kinds of gradient potentials of square barriers along electrons propagation direction, we find that Bloch oscillations up to terahertz can occur. Wannier-Stark ladders, as the counterpart of Bloch oscillation, are obtained as a series of equidistant transmission peaks, and the localization of the electronic wave function is also signature of Bloch oscillation. Furthermore, the period of Bloch oscillation decreases linearly with increasing gradient of barrier potentials.

  2. Affinity of four polar neurotransmitters for lipid bilayer membranes

    DEFF Research Database (Denmark)

    Wang, Chunhua; Ye, Fengbin; Valardez, Gustavo F.

    2011-01-01

    interacts unfavorably with DMPC and is thus preferentially excluded from the membrane's hydration layer. Conversely, the zwitterionic neurotransmitters are attracted to membranes with 10% anionic lipid and their local concentration at the interface is 5-10 times larger than in the aqueous bulk....... The simulations suggest that this attraction mainly relies on electrostatic interactions of the amino group of the neurotransmitter and the lipid phosphate. We conclude that moderate attraction to lipid membranes occurs for some polar neurotransmitters and hence that one premise for a theory of bilayer...

  3. Phase Diagram of Antiferromagnetically Exchange-Coupled Bilayer

    Institute of Scientific and Technical Information of China (English)

    GUO Guang-Hua; ZHANG Guang-Fu; SUN Li-Yuan; Peter A. J. de Groot

    2008-01-01

    Magnetic hysteresis properties of antiferromagnetically exchange-coupled bilayer structures, in which the two magnetic layers have different magnetic parameters and thicknesses, are studied within the framework of the Stoner-Wohifarth model. Analytical expressions for the switching fields corresponding to the linear magnetic states are obtained. By adjusting the magnetic parameters or thicknesses of layers, nine different types of easyaxis hysteresis loops may exist. The phase diagram of easy-axis hysteresis loops is mapped in the k,1 and k,2 plane, where k,1 and k,2 are the ratios of magnetic anisotropy to the interlayer exchange coupling of the two magnetic layers, respectively.

  4. Giant Frictional Drag in Double Bilayer Graphene Heterostructures

    Science.gov (United States)

    Lee, Kayoung; Xue, Jiamin; Dillen, David C.; Watanabe, Kenji; Taniguchi, Takashi; Tutuc, Emanuel

    2016-07-01

    We study the frictional drag between carriers in two bilayer graphene flakes separated by a 2-5 nm thick hexagonal boron nitride dielectric. At temperatures (T ) lower than ˜10 K , we observe a large anomalous negative drag emerging predominantly near the drag layer charge neutrality. The anomalous drag resistivity increases dramatically with reducing T , and becomes comparable to the layer resistivity at the lowest T =1.5 K . At low T the drag resistivity exhibits a breakdown of layer reciprocity. A comparison of the drag resistivity and the drag layer Peltier coefficient suggests a thermoelectric origin of this anomalous drag.

  5. Multicritical point in a diluted bilayer Heisenberg quantum antiferromagnet.

    Science.gov (United States)

    Sandvik, Anders W

    2002-10-21

    The S=1/2 Heisenberg bilayer antiferromagnet with randomly removed interlayer dimers is studied using quantum Monte Carlo simulations. A zero-temperature multicritical point (p(*),g(*)) at the classical percolation density p=p(*) and interlayer coupling g(*) approximately equal 0.16 is demonstrated. The quantum critical exponents of the percolating cluster are determined using finite-size scaling. It is argued that the associated finite-temperature quantum critical regime extends to zero interlayer coupling and could be relevant for antiferromagnetic cuprates doped with nonmagnetic impurities.

  6. Ultraviolet-induced erasable photochromism in bilayer metal oxide films

    Science.gov (United States)

    Terakado, Nobuaki; Tanaka, Keiji; Nakazawa, Akira

    2011-09-01

    We demonstrate that the optical transmittance of bilayer samples consisting of pyrolytically coated amorphous Mg-Sn-O and metal oxide films such as In 2O 3 and SnO 2 decreases upon ultraviolet illumination, but can be recovered by annealing in air at ˜300 ∘C. Spectral, structural, and compositional studies suggest that this photochromic phenomenon is induced by photoelectronic excitation in the Mg-Sn-O film, electron injection into the metal oxide, which becomes negatively charged, and subsequent formation of metallic particles, which absorb and/or scatter visible light.

  7. Negative terahertz conductivity in remotely doped graphene bilayer heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhii, V. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Institute of Ultra High Frequency Semiconductor Electronics of RAS, and Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 111005 (Russian Federation); Ryzhii, M. [Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580 (Japan); Mitin, V. [Department of Electrical Engineering, University at Buffalo, SUNY, Buffalo, New York 1460-1920 (United States); Shur, M. S. [Departments of Electrical, Electronics, and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Otsuji, T. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan)

    2015-11-14

    Injection or optical generation of electrons and holes in graphene bilayers (GBLs) can result in the interband population inversion enabling the terahertz (THz) radiation lasing. The intraband radiative processes compete with the interband transitions. We demonstrate that remote doping enhances the indirect interband generation of photons in the proposed GBL heterostructures. Therefore, such remote doping helps to surpass the intraband (Drude) absorption, and results in large absolute values of the negative dynamic THz conductivity in a wide range of frequencies at elevated (including room) temperatures. The remotely doped GBL heterostructure THz lasers are expected to achieve higher THz gain compared with previously proposed GBL-based THz lasers.

  8. Interaction of S-methyl methanethiosulfonate with DPPC bilayer

    Science.gov (United States)

    Defonsi Lestard, María E.; Díaz, Sonia B.; Tuttolomondo, María E.; Sánchez Cortez, Santiago; Puiatti, Marcelo; Pierini, Adriana B.; Ben Altabef, Aida

    2012-11-01

    The present study is a first step towards the investigation of S-methyl methanethiosulfonate (MMTS) interaction with membrane model systems like liposomes. In this paper, the interaction of MMTS with dipalmitoylphosphatidylcholine (DPPC) bilayers was studied by FTIR and SERS spectroscopy. Lysolipid effect on vesicle stability was studied. The results show that MMTS interacts to different extents with the phosphate and carbonyl groups of membranes in the gel and the liquid crystalline states. To gain a deeper insight into MMTS properties that may be potentially helpful in the design of new drugs with therapeutic effects, we performed theoretical studies that may be the basis for the design of their mode of action.

  9. Monte Carlo simulation of charge mediated magnetoelectricity in multiferroic bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Álvarez, H.H. [Universidad de Caldas, Manizales (Colombia); Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia); Bedoya-Hincapié, C.M. [Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia); Universidad Santo Tomás, Bogotá (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia)

    2014-12-01

    Simulations of a bilayer ferroelectric/ferromagnetic multiferroic system were carried out, based on the Monte Carlo method and Metropolis dynamics. A generic model was implemented with a Janssen-like Hamiltonian, taking into account magnetoelectric interactions due to charge accumulation at the interface. Two different magnetic exchange constants were considered for accumulation and depletion states. Several screening lengths were also included. Simulations exhibit considerable magnetoelectric effects not only at low temperature, but also at temperature near to the transition point of the ferromagnetic layer. The results match experimental observations for this kind of structure and mechanism.

  10. Hydrocarbon Reserves: Abundance or Scarcity

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    IFP and the OAPEC jointly organize a regular international seminar dealing with world oil-related problems appearing in the news. For the first time, this seminar has been opened to oil and gas company specialists, service companies, research centers and independents. This year's theme concerns oil and gas reserves: are they abundant or are we headed towards the shortages announced by some experts? This theme is especially topical in that: oil and gas currently meet two thirds of world energy needs and almost completely dominate the transport sector; the reserves declared by the OAPEC countries account for nearly half of world reserves; the price of a barrel of oil went through the roof in 2004; world energy demand is growing fast and alternative sources of energy are far from ready to take over from oil and gas in the next few decades. Since the reserves correspond to the volume it is technically and economically viable to produce, the seminar has, of course, dealt with the technical and economic questions that arise in connection with exploration and production, but it has also considered changes in the geopolitical context. Presentations by the leading companies of the OAPEC countries and by the IFP group were completed by presentation from the International Energy Agency (IEA), the United States Geological Survey (USGS), the IHS Energy Group, Total and Gaz de France. This document gathers the transparencies of the following presentations: Hydrocarbon reserves in OAPEC members countries: current and future (M. Al-Lababidi); Non OAPEC liquid reserves and production forecasts (Y. Mathieu); World oil and gas resources and production outlook (K. Chew); Global investments in the upstream (F. Birol); Total's policy in the oil and gas sector (C. de Margerie); Gaz de France's policy in the oil and gas sector (J. Abiteboul); NOC/IOC's opportunities in OPEC countries (I. Sandrea); Relationships between companies, countries and investors: How they may

  11. Regulation of membrane protein function by lipid bilayer elasticity—a single molecule technology to measure the bilayer properties experienced by an embedded protein

    DEFF Research Database (Denmark)

    Lundbæk, Jens August

    2008-01-01

    , in the general regulation of membrane protein function, is unclear. This is to a large extent due to lack of a generally accepted framework in which to understand the many observations. The present review summarizes studies which have demonstrated that the hydrophobic interactions between a membrane protein...... and the host lipid bilayer provide an energetic coupling, whereby protein function can be regulated by the bilayer elasticity. The feasibility of this ‘hydrophobic coupling mechanism’ has been demonstrated using the gramicidin channel, a model membrane protein, in planar lipid bilayers. Using voltage...... properties experienced by an embedded protein has been developed. A theoretical and technological framework, to study the regulation of membrane protein function by lipid bilayer elasticity, has been established....

  12. Molecular dynamics simulations and free energy profile of Paracetamol in DPPC and DMPC lipid bilayers

    Indian Academy of Sciences (India)

    Yousef Nademi; Sepideh Amjad Iranagh; Abbas Yousefpour; Seyedeh Zahra Mousavi; Hamid Modarress

    2014-05-01

    Molecular dynamics (MD) simulations and biased MD simulation were carried out for the neutral form of Paracetamol inserted in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) lipid bilayers. For comparison, fully hydrated DMPC and DPPC lipid bilayers were also simulated separately without Paracetamol. The simulation time for each system was 50 ns. At two concentrations of Paracetamol, various properties of the lipid bilayer such as area per lipid, order parameter, diffusion coefficient, radial distribution function, electrostatic potential, mass density and hydrogen bonds have been calculated. Also, the convergence in time of the free energy profile of the Paracetamol along a DPPC bilayer normal was calculated by umbrella sampling method. From the obtained results, it can be concluded that neutral form of Paracetamol shows a generally similar behaviour in DPPC and DMPC lipid bilayers. It was shown that the addition of Paracetamol causes a decrease in tail order parameter of both DPPC and DMPC lipid bilayers and the tail of Paracetamol adopts an inward orientation in the lipid bilayers. Also from the free energy profile, the high penetration barrier in the bilayer centre was determined.

  13. Alginate based bilayer hydrocolloid films as potential slow-release modern wound dressing.

    Science.gov (United States)

    Thu, Hnin-Ei; Zulfakar, Mohd Hanif; Ng, Shiow-Fern

    2012-09-15

    The aims of this research were to develop a novel bilayer hydrocolloid film based on alginate and to investigate its potential as slow-release wound healing vehicle. The bilayer is composed of an upper layer impregnated with model drug (ibuprofen) and a drug-free lower layer, which acted as a rate-controlling membrane. The thickness uniformity, solvent loss, moisture vapour transmission rate (MVTR), hydration rate, morphology, rheology, mechanical properties, in vitro drug release and in vivo wound healing profiles were investigated. A smooth bilayer film with two homogenous distinct layers was produced. The characterisation results showed that bilayer has superior mechanical and rheological properties than the single layer films. The bilayers also showed low MVTR, slower hydration rate and lower drug flux in vitro compared to single layer inferring that bilayer may be useful for treating low suppurating wounds and suitable for slow release application on wound surfaces. The bilayers also provided a significant higher healing rate in vivo, with well-formed epidermis with faster granulation tissue formation when compared to the controls. In conclusions, a novel alginate-based bilayer hydrocolloid film was developed and results suggested that they can be exploited as slow-release wound dressings.

  14. Lindane Suppresses the Lipid-bilayer Permeability in Main Transition Region

    DEFF Research Database (Denmark)

    Sabra, Mads Christian; Jørgensen, Kent; Mouritsen, Ole G.

    1996-01-01

    %) of lindane. Fluorescence spectroscopy was used to measure the passive permeability of unilamellar DMPC bilayers to Co2+ ions. The data show that lindane seals the bilayer for Co2+ penetration and that this effect increases with increasing lindane concentration. The results are discussed in relation...... to the effects on the permeability of other small molecules, e.g., anesthetics....

  15. Sign reversal of drag in bilayer systems with in-plane periodic potential modulation

    DEFF Research Database (Denmark)

    Alkauskas, A.; Flensberg, Karsten; Hu, Ben Yu-Kuang;

    2002-01-01

    We develop a theory for describing frictional drag in bilayer systems with in-plane periodic potential modulations, and use it to investigate the drag between bilayer systems in which one of the layers is modulated in one direction. At low temperatures, as the density of carriers in the modulated...

  16. k-core covers and the core

    NARCIS (Netherlands)

    Sanchez-Rodriguez, E.; Borm, Peter; Estevez-Fernandez, A.; Fiestras-Janeiro, G.; Mosquera, M.A.

    2015-01-01

    This paper extends the notion of individual minimal rights for a transferable utility game (TU-game) to coalitional minimal rights using minimal balanced families of a specific type, thus defining a corresponding minimal rights game. It is shown that the core of a TU-game coincides with the core of

  17. Academic Rigor: The Core of the Core

    Science.gov (United States)

    Brunner, Judy

    2013-01-01

    Some educators see the Common Core State Standards as reason for stress, most recognize the positive possibilities associated with them and are willing to make the professional commitment to implementing them so that academic rigor for all students will increase. But business leaders, parents, and the authors of the Common Core are not the only…

  18. Correlation between hydrocarbon distribution and water-hydrocarbon ratio in Fischer-Tropsch synthesis

    Institute of Scientific and Technical Information of China (English)

    Xiaofeng Zhou; Qingling Chen; Yuewu Tao; Huixin Weng

    2011-01-01

    In order to shorten the evaluation cycle of cobalt catalyst before the optimized catalyst is fixed on,a mathematical method is proposed to calculate weight percentage of C5+ hydrocarbons.Based on the carbide polymerization mechanism and the main hydrocarbons being linear alkanes and α-olefins,the correlation between hydrocarbon distribution and the molecular mass ratio of water to hydrocarbons is discussed.The result shows the ratio was within the range of 1.125-1.286 and the lower the ratio,the more gaseous hydrocarbons were obtained.Moreover,a linear equation between the weight percentage of C5+ hydrocarbons and the weight ratio of C5+ hydrocarbons to the total water is established.These results are validated by corresponding experiments.The weight percentage of C5+ hydrocarbons could be immediately calculated by this linear equation without detailed gas chromatography (GC) analysis of them.

  19. HYDROCARBON AND SULFUR SENSORS FOR SOFC SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    A.M. Azad; Chris Holt; Todd Lesousky; Scott Swartz

    2003-11-01

    The following report summarizes work conducted during the Phase I program Hydrocarbon and Sulfur Sensors for SOFC Systems under contract No. DE-FC26-02NT41576. For the SOFC application, sensors are required to monitor hydrocarbons and sulfur in order to increase the operation life of SOFC components. This report discusses the development of two such sensors, one based on thick film approach for sulfur monitoring and the second galvanic based for hydrocarbon monitoring.

  20. Filament networks attached to membranes: cytoskeletal pressure and local bilayer deformation

    Energy Technology Data Exchange (ETDEWEB)

    Auth, Thorsten [Department of Materials and Interfaces, Weizmann Institute of Science, PO Box 26, Rehovot 76100 (Israel); Safran, S A [Department of Materials and Interfaces, Weizmann Institute of Science, PO Box 26, Rehovot 76100 (Israel); Gov, Nir S [Department of Chemical Physics, Weizmann Institute of Science, PO Box 26, Rehovot 76100 (Israel)

    2007-11-15

    Several cell types, among them red blood cells, have a cortical, two-dimensional (2D) network of filaments sparsely attached to their lipid bilayer. In many mammalian cells, this 2D polymer network is connected to an underlying 3D, more rigid cytoskeleton. In this paper, we consider the pressure exerted by the thermally fluctuating, cortical network of filaments on the bilayer and predict the bilayer deformations that are induced by this pressure. We treat the filaments as flexible polymers and calculate the pressure that a network of such linear chains exerts on the bilayer; we then minimize the bilayer shape in order to predict the resulting local deformations. We compare our predictions with membrane deformations observed in electron micrographs of red blood cells. The polymer pressure along with the resulting membrane deformation can lead to compartmentalization, regulate in-plane diffusion and may influence protein sorting as well as transmit signals to the polymerization of the underlying 3D cytoskeleton.

  1. Removal of the mechanoprotective influence of the cytoskeleton reveals PIEZO1 is gated by bilayer tension

    Science.gov (United States)

    Cox, Charles D.; Bae, Chilman; Ziegler, Lynn; Hartley, Silas; Nikolova-Krstevski, Vesna; Rohde, Paul R.; Ng, Chai-Ann; Sachs, Frederick; Gottlieb, Philip A.; Martinac, Boris

    2016-01-01

    Mechanosensitive ion channels are force-transducing enzymes that couple mechanical stimuli to ion flux. Understanding the gating mechanism of mechanosensitive channels is challenging because the stimulus seen by the channel reflects forces shared between the membrane, cytoskeleton and extracellular matrix. Here we examine whether the mechanosensitive channel PIEZO1 is activated by force-transmission through the bilayer. To achieve this, we generate HEK293 cell membrane blebs largely free of cytoskeleton. Using the bacterial channel MscL, we calibrate the bilayer tension demonstrating that activation of MscL in blebs is identical to that in reconstituted bilayers. Utilizing a novel PIEZO1-GFP fusion, we then show PIEZO1 is activated by bilayer tension in bleb membranes, gating at lower pressures indicative of removal of the cortical cytoskeleton and the mechanoprotection it provides. Thus, PIEZO1 channels must sense force directly transmitted through the bilayer.

  2. X-Ray Kinematography of Temperature-Jump Relaxation Probes the Elastic Properties of Fluid Bilayers

    CERN Document Server

    Pabst, G; Amenitsch, H; Bernstorff, S; Laggner, P; Pabst, Georg; Rappolt, Michael; Amenitsch, Heinz; Bernstorff, Sigrid; Laggner, Peter

    2000-01-01

    The response kinetics of liquid crystalline phosphatidylcholine bilayerstacks to rapid, IR-laser induced temperature jumps has been studied bymillisecond time-resolved x-ray diffraction. The system reacts on the fasttemperature change by a discrete bilayer compression normal to its surface anda lateral bilayer expansion. Since water cannot diffuse from the excess phaseinto the interbilayer water region within the 2 ms duration of the laser pulse,the water layer has to follow the bilayer expansion, by an anomalous thinning.Structural analysis of a 20 ms diffraction pattern from the intermediate phaseindicates that the bilayer thickness remains within the limits of isothermalequilibrium values. Both, the intermediate structure and its relaxation intothe original equilibrium L_(alpha)-phase, depend on the visco-elasticproperties of the bilayer/water system. We present an analysis of therelaxation process by an overdamped one-dimensional oscillation model revealingthe concepts of Hooke's law for phospholipid bila...

  3. Intrinsic magnetism and spontaneous band gap opening in bilayer silicene and germanene.

    Science.gov (United States)

    Wang, Xinquan; Wu, Zhigang

    2017-01-18

    It has been long sought to create magnetism out of simple non-magnetic materials, such as silicon and germanium. Here we show that intrinsic magnetism exists in bilayer silicene and germanene with no need to cut, etch, or dope. Unlike bilayer graphene, strong covalent interlayer bonding formed in bilayer silicene and germanene breaks the original π-bonding network of each layer, leaving the unbonded electrons unpaired and localized to carry magnetic moments. These magnetic moments then couple ferromagnetically within each layer while antiferromagnetically across two layers, giving rise to an infinite magnetic sheet with structural integrity and magnetic homogeneity. Furthermore, this unique magnetic ordering results in fundamental band gaps of 0.55 eV and 0.32 eV for bilayer silicene and germanene, respectively. The integration of intrinsic magnetism and spontaneous band gap opening makes bilayer silicene and germanene attractive for future nanoelectronics as well as spin-based computation and data storage.

  4. Filament networks attached to membranes: cytoskeletal pressure and local bilayer deformation

    Science.gov (United States)

    Auth, Thorsten; Safran, S. A.; Gov, Nir S.

    2007-11-01

    Several cell types, among them red blood cells, have a cortical, two-dimensional (2D) network of filaments sparsely attached to their lipid bilayer. In many mammalian cells, this 2D polymer network is connected to an underlying 3D, more rigid cytoskeleton. In this paper, we consider the pressure exerted by the thermally fluctuating, cortical network of filaments on the bilayer and predict the bilayer deformations that are induced by this pressure. We treat the filaments as flexible polymers and calculate the pressure that a network of such linear chains exerts on the bilayer; we then minimize the bilayer shape in order to predict the resulting local deformations. We compare our predictions with membrane deformations observed in electron micrographs of red blood cells. The polymer pressure along with the resulting membrane deformation can lead to compartmentalization, regulate in-plane diffusion and may influence protein sorting as well as transmit signals to the polymerization of the underlying 3D cytoskeleton.

  5. Ground states of bilayered and extended t-J-U models

    Energy Technology Data Exchange (ETDEWEB)

    Voo, Khee-Kyun, E-mail: kkvoo@mail.oit.edu.tw

    2015-09-04

    The ground states of bilayered and extended t-J-U models are investigated with renormalized mean field theory. The trial wave functions are Gutzwiller projected Hartree–Fock states, and the site double occupancies are variational parameters. It is found that a spontaneous interlayer phase separation (PS) may arise in bilayers. In electron–hole doping asymmetric systems, the propensity for PS is stronger in electron doped bands. Via a PS, superconductivity can survive to lower doping densities, and antiferromagnetism in electron doped systems may survive to higher doping densities. The result is related to the superconducting cuprates. - Highlights: • Ground states in doped bilayered t-J-U models are studied. • Variational wave functions are Gutzwiller projected wave functions. • Site double occupancies are variational parameters. • Spontaneous interlayer phase separation may occur in bilayers. • Stronger tendency toward phase separation in electron doped bilayers.

  6. Specific heat of twisted bilayer graphene: Engineering phonons by atomic plane rotations

    Energy Technology Data Exchange (ETDEWEB)

    Nika, Denis L. [E. Pokatilov Laboratory of Physics and Engineering of Nanomaterials, Department of Physics and Engineering, Moldova State University, Chisinau MD-2009, Republic of Moldova (Moldova, Republic of); Nano-Device Laboratory, Department of Electrical Engineering and Materials Science and Engineering Program, Bourns College of Engineering, University of California—Riverside, Riverside, California, 92521 (United States); Cocemasov, Alexandr I. [E. Pokatilov Laboratory of Physics and Engineering of Nanomaterials, Department of Physics and Engineering, Moldova State University, Chisinau MD-2009, Republic of Moldova (Moldova, Republic of); Balandin, Alexander A., E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory, Department of Electrical Engineering and Materials Science and Engineering Program, Bourns College of Engineering, University of California—Riverside, Riverside, California, 92521 (United States)

    2014-07-21

    We have studied the phonon specific heat in single-layer, bilayer, and twisted bilayer graphene. The calculations were performed using the Born-von Karman model of lattice dynamics for intralayer atomic interactions and spherically symmetric interatomic potential for interlayer interactions. We found that at temperature T < 15 K, specific heat varies with temperature as T{sup n}, where n = 1 for graphene, n = 1.6 for bilayer graphene, and n = 1.3 for the twisted bilayer graphene. The phonon specific heat reveals an intriguing dependence on the twist angle in bilayer graphene, which is particularly pronounced at low temperature. The results suggest a possibility of phonon engineering of thermal properties of layered materials by twisting the atomic planes.

  7. CONTEMPORARY APPROACHES FOR BI-LAYER TECHNOLOGY OF DRUGS THROUGH ORAL ROUTE: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    Rishikesh*, M. A. Bhuiyan, S. M. Ashraful Islam, I. Dewan, Md. A. Islam and Md. S.- Ul H. Miah

    2013-04-01

    Full Text Available ABSTRACT: Bi-layer tablet technology for bimodal release of drug and co-administration of drugs via oral route has been engaged a significant place in the field of drug delivery technology. At present, several pharmaceutical companies are developing bilayer tablet for co-administration of drugs to improve the therapeutic efficacy as well as to reduce the chances of drug-drug interaction. This review indicates the different aspects of drug release mechanism, different strategies of drug release, various techniques for bilayer tablet, and the influence of different process and formulation parameters must be considered during the development of bilayer tablet. Bi-layer tablet is suitable for sequential release of two drugs in combination, separate two incompatible substances, and also for sustained release tablet in which one layer is immediate release as initial dose and second layer is maintenance dose.

  8. Growth and characterization of the ZnO/ZnS bilayer obtained by chemical spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, M.C. [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Dptos Fisica Aplicada and Dpto Ingenieria Quimica, Facultad de Ciencias, Universidad de Malaga, E29071 Malaga (Spain); Espinos, J.P. [Instituto de Ciencias de Materiales de Sevilla (CSIC), Avda. Americo Vespucio s/n, E41092 Sevilla (Spain); Leinen, D.; Martin, F. [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Dptos Fisica Aplicada and Dpto Ingenieria Quimica, Facultad de Ciencias, Universidad de Malaga, E29071 Malaga (Spain); Centeno, S.P. [Departamento de Quimica-Fisica, Facultad de Ciencias, Universidad de Malaga, E29071 Malaga (Spain); Romero, R. [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Dptos Fisica Aplicada and Dpto Ingenieria Quimica, Facultad de Ciencias, Universidad de Malaga, E29071 Malaga (Spain); Ramos-Barrado, J.R. [Laboratorio de Materiales y Superficie (Unidad Asociada al CSIC), Dptos Fisica Aplicada and Dpto Ingenieria Quimica, Facultad de Ciencias, Universidad de Malaga, E29071 Malaga (Spain)], E-mail: barrado@uma.es

    2008-12-30

    ZnO/ZnS bilayer antireflection coatings have been prepared by spray pyrolysis using aqueous solutions of zinc acetate and thiourea or zinc chloride and thiourea. The structure, surface morphology, chemical composition and optical transmittance of the bilayer have been examined as a function of the composition of the initial solution. X-ray photoelectron spectroscopy analysis and Ar ion-beam sputter etching was carried out to obtain a depth profile of bilayer. Neither carbon nor other by-products, which could alter the optical transmittance of the bilayer were found in either the interface or bulk. The differences between the bilayers arise from the annealing of the ZnS underlayer, as well as the precursor used to prepare it.

  9. 40 CFR 90.316 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 90... Equipment Provisions § 90.316 Hydrocarbon analyzer calibration. (a) Calibrate the FID and HFID hydrocarbon... thereafter, adjust the FID and HFID hydrocarbon analyzer for optimum hydrocarbon response as specified...

  10. 40 CFR 86.121-90 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 86... Complete Heavy-Duty Vehicles; Test Procedures § 86.121-90 Hydrocarbon analyzer calibration. The hydrocarbon... FID and HFID hydrocarbon analyzers shall be adjusted for optimum hydrocarbon response....

  11. 40 CFR 91.316 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 91....316 Hydrocarbon analyzer calibration. (a) Calibrate the FID and HFID hydrocarbon analyzer as described... thereafter, adjust the FID and HFID hydrocarbon analyzer for optimum hydrocarbon response as specified...

  12. 40 CFR 89.319 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 89... Equipment Provisions § 89.319 Hydrocarbon analyzer calibration. (a) The FID hydrocarbon analyzer shall... and at least annually thereafter, adjust the FID hydrocarbon analyzer for optimum hydrocarbon...

  13. Detection of hydrocarbons in irradiated foods

    Energy Technology Data Exchange (ETDEWEB)

    Miyahara, Makoto; Maitani, Tamio [National Inst. of Health Sciences, Tokyo (Japan); Saito, Akiko; Kamimura, Tomomi; Nagasawa, Taeko [Kitasato Univ., Sagamihara, Kanagawa (Japan). School of Allied Health Sciences; Kobayashi, Yasuo; Ito, Hitoshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Establishment

    2003-06-01

    The hydrocarbon method for the detection of irradiated foods is now recognized as the international technique. This method is based on radiolysis of fatty acids in food to give hydrocarbons. In order to expand this technique's application, ten foods (butter, cheese, chicken, pork, beef, tuna, dry shrimp, avocado, papaya, and mango) were irradiated in the range from 0.5 to 10 kGy and the hydrocarbons in them were detected. Recoveries of the hydrocarbons from most foods were acceptable (38-128%). Some hydrocarbons were found in non-irradiated foods, particularly, in butter, cheese, tuna, and shrimp. Seven irradiated foods, butter, cheese, chicken, beef, pork, tuna, dry shrimp, and avocado were detectable at their practical doses by measuring the appropriate marker hydrocarbons. In most case, marker hydrocarbon will be 1,7-hexadecadiene. However, the marker hydrocarbons produced only in irradiated foods varied from food to food; therefore, it is necessary to check a specific irradiated food for marker hydrocarbons. On the other hand, two irradiated foods (papaya and mango which were irradiated at their practical doses) were difficult to distinguish from non-irradiated foods using this method. (author)

  14. One-dimensional Topological Edge States of Bismuth Bilayers

    Science.gov (United States)

    Drozdov, Ilya; Alexandradinata, Aris; Jeon, Sangjun; Nadj-Perge, Stevan; Ji, Huiwen; Cava, Robert; Bernevig, B. Andrei; Yazdani, Ali

    2014-03-01

    The hallmark of a time-reversal symmetry protected topologically insulating state of matter in two-dimensions (2D) is the existence of chiral edge modes propagating along the perimeter of the sample. Bilayers of bismuth (Bi), an elemental system theoretically predicted to be a Quantum Spin Hall (QSH) insulator1, has been studied with Scanning Tunneling Microscopy (STM) and the electronic structure of its bulk and edge modes has been experimentally investigated. Spectroscopic mapping with STM reveals the presence of the state bound to the edges of the Bi-bilayer. By visualizing quantum interference of the edge state quasi-particles in confined geometries we characterize their dispersion and demonstrate that their properties are consistent with the absence of backscattering. Hybridization of the edge modes to the underlying substrate will be discussed. [1] Shuichi Murakami, Phys. Rev. Lett. 97, 236805 (2006). The work at Princeton and the Princeton Nanoscale Microscopy Laboratory was supported by ARO MURI program W911NF-12-1-0461, DARPA-SPWAR Meso program N6601-11-1-4110, NSF-DMR1104612, and NSF-MRSEC programs through the Princeton Center for Complex Materials (DMR-0819860)

  15. Interlayer thermal conductance within a phosphorene and graphene bilayer.

    Science.gov (United States)

    Hong, Yang; Zhang, Jingchao; Zeng, Xiao Cheng

    2016-11-24

    Monolayer graphene possesses unusual thermal properties, and is often considered as a prototype system for the study of thermal physics of low-dimensional electronic/thermal materials, despite the absence of a direct bandgap. Another two-dimensional (2D) atomic layered material, phosphorene, is a natural p-type semiconductor and it has attracted growing interest in recent years. When a graphene monolayer is overlaid on phosphorene, the hybrid van der Waals (vdW) bilayer becomes a potential candidate for high-performance thermal/electronic applications, owing to the combination of the direct-bandgap properties of phosphorene with the exceptional thermal properties of graphene. In this work, the interlayer thermal conductance at the phosphorene/graphene interface is systematically investigated using classical molecular dynamics (MD) simulation. The transient pump-probe heating method is employed to compute the interfacial thermal resistance (R) of the bilayer. The predicted R value at the phosphorene/graphene interface is 8.41 × 10(-8) K m(2) W(-1) at room temperature. Different external and internal conditions, i.e., temperature, contact pressure, vacancy defect, and chemical functionalization, can all effectively reduce R at the interface. Numerical results of R reduction as a function of temperature, interfacial coupling strength, defect ratio, or hydrogen coverage are reported with the most R reduction amounting to 56.5%, 70.4%, 34.8% and 84.5%, respectively.

  16. Unexpected bilayer formation in Langmuir films of nucleolipids.

    Science.gov (United States)

    Desbat, Bernard; Arazam, Nessim; Khiati, Salim; Tonelli, Giovanni; Neri, Wilfrid; Barthélémy, Philippe; Navailles, Laurence

    2012-05-01

    Langmuir monolayers have been extensively investigated by various experimental techniques. These studies allowed an in-depth understanding of the molecular conformation in the layer, phase transitions, and the structure of the multilayer. As the monolayer is compressed and the surface pressure is increased beyond a critical value, usually occurring in the minimal closely packed molecular area, the monolayer fractures and/or folds, forming multilayers in a process referred to as collapse. Various mechanisms for monolayer collapse and the resulting reorganization of the film have been proposed, and only a few studies have demonstrated the formation of a bilayer after collapse and with the use of a Ca(2+) solution. In this work, Langmuir isotherms coupled with imaging ellipsometry and polarization modulation infrared reflection absorption spectroscopy were recorded to investigate the air-water interface properties of Langmuir films of anionic nucleolipids. We report for these new molecules the formation of a quasi-hexagonal packing of bilayer domains at a low compression rate, a singular behavior for lipids at the air-water interface that has not yet been documented.

  17. Fibonacci anyons from Abelian bilayer quantum Hall states.

    Science.gov (United States)

    Vaezi, Abolhassan; Barkeshli, Maissam

    2014-12-05

    The possibility of realizing non-Abelian statistics and utilizing it for topological quantum computation (TQC) has generated widespread interest. However, the non-Abelian statistics that can be realized in most accessible proposals is not powerful enough for universal TQC. In this Letter, we consider a simple bilayer fractional quantum Hall system with the 1/3 Laughlin state in each layer. We show that interlayer tunneling can drive a transition to an exotic non-Abelian state that contains the famous "Fibonacci" anyon, whose non-Abelian statistics is powerful enough for universal TQC. Our analysis rests on startling agreements from a variety of distinct methods, including thin torus limits, effective field theories, and coupled wire constructions. We provide evidence that the transition can be continuous, at which point the charge gap remains open while the neutral gap closes. This raises the question of whether these exotic phases may have already been realized at ν=2/3 in bilayers, as past experiments may not have definitively ruled them out.

  18. Bi-layer functionally gradient thick film semiconducting methane sensors

    Indian Academy of Sciences (India)

    A Banerjee; A K Haldar; J Mondal; A Sen; H S Maiti

    2002-11-01

    Gas sensors based on metal oxide semiconductors like tin dioxide are widely used for the detection of toxic and combustible gases like carbon monoxide, methane and LPG. One of the problems of such sensors is their lack of sensitivity, which to some extent, can be circumvented by using different catalysts. However, highly reactive volatile organic compounds (VOC) coming from different industrial and domestic products (e.g. paints, lacquers, varnishes etc) can play havoc on such sensors and can give rise to false alarms. Any attempt to adsorb such VOCs (e.g. by using activated charcoal) results in sorption of the detecting gases (e.g. methane) too. To get round the problem, bi-layer sensors have been developed. Such tin oxide based functionally gradient bi-layer sensors have different compositions at the top and bottom layers. Here, instead of adsorbing the VOCs, they are allowed to interact and are consumed on the top layer of the sensors and a combustible gas like methane being less reactive, penetrates the top layer and interacts with the bottom layer. By modifying the chemical compositions of the top and bottom layers and by designing the electrode-lead wire arrangement properly, the top layer can be kept electrically shunted from the bottom layer and the electrical signal generated at the bottom layer from the combustible gas is collected. Such functionally gradient sensors, being very reliable, can find applications in domestic, industrial and strategic sectors.

  19. Nonlocal Drag of Magnons in a Ferromagnetic Bilayer

    Science.gov (United States)

    Liu, Tianyu; Vignale, G.; Flatté, Michael E.

    2016-06-01

    Quantized spin waves, or magnons, in a magnetic insulator are assumed to interact weakly with the surroundings, and to flow with little dissipation or drag, producing exceptionally long diffusion lengths and relaxation times. In analogy to Coulomb drag in bilayer two-dimensional electron gases, in which the contribution of the Coulomb interaction to the electric resistivity is studied by measuring the interlayer resistivity (transresistivity), we predict a nonlocal drag of magnons in a ferromagnetic bilayer structure based on semiclassical Boltzmann equations. Nonlocal magnon drag depends on magnetic dipolar interactions between the layers and manifests in the magnon current transresistivity and the magnon thermal transresistivity, whereby a magnon current in one layer induces a chemical potential gradient and/or a temperature gradient in the other layer. The largest drag effect occurs when the magnon current flows parallel to the magnetization; however, for oblique magnon currents a large transverse current of magnons emerges. We examine the effect for practical parameters, and find that the predicted induced temperature gradient is readily observable.

  20. Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers

    Science.gov (United States)

    Avci, Can Onur; Garello, Kevin; Ghosh, Abhijit; Gabureac, Mihai; Alvarado, Santos F.; Gambardella, Pietro

    2015-07-01

    Magnetoresistive effects are usually invariant on inversion of the magnetization direction. In non-centrosymmetric conductors, however, nonlinear resistive terms can give rise to a current dependence that is quadratic in the applied voltage and linear in the magnetization. Here we demonstrate that such conditions are realized in simple bilayer metal films where the spin-orbit interaction and spin-dependent scattering couple the current-induced spin accumulation to the electrical conductivity. We show that the longitudinal resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of the current or the sign of the magnetization. This unidirectional magnetoresistance scales linearly with current density and has opposite sign in Ta and Pt, which we associate with the modification of the interface scattering potential induced by the spin Hall effect in these materials. Our results suggest a route to control the resistance and detect magnetization switching in spintronic devices using a two-terminal geometry, which applies also to heterostructures including topological insulators.

  1. Embedding Ba Monolayers and Bilayers in Boron Carbide Nanowires

    Science.gov (United States)

    Yu, Zhiyang; Luo, Jian; Shi, Baiou; Zhao, Jiong; Harmer, Martin P.; Zhu, Jing

    2015-11-01

    Aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) was employed to study the distribution of barium atoms on the surfaces and in the interiors of boron carbide based nanowires. Barium based dopants, which were used to control the crystal growth, adsorbed to the surfaces of the boron-rich crystals in the form of nanometer-thick surficial films (a type of surface complexion). During the crystal growth, these dopant-based surface complexions became embedded inside the single crystalline segments of fivefold boron-rich nanowires collectively, where they were converted to more ordered monolayer and bilayer modified complexions. Another form of bilayer complexion stabilized at stacking faults has also been identified. Numerous previous works suggested that dopants/impurities tended to segregate at the stacking faults or twinned boundaries. In contrast, our study revealed the previously-unrecognized possibility of incorporating dopants and impurities inside an otherwise perfect crystal without the association to any twin boundary or stacking fault. Moreover, we revealed the amount of barium dopants incorporated was non-equilibrium and far beyond the bulk solubility, which might lead to unique properties.

  2. Multiscale modeling of droplet interface bilayer membrane networks.

    Science.gov (United States)

    Freeman, Eric C; Farimani, Amir B; Aluru, Narayana R; Philen, Michael K

    2015-11-01

    Droplet interface bilayer (DIB) networks are considered for the development of stimuli-responsive membrane-based materials inspired by cellular mechanics. These DIB networks are often modeled as combinations of electrical circuit analogues, creating complex networks of capacitors and resistors that mimic the biomolecular structures. These empirical models are capable of replicating data from electrophysiology experiments, but these models do not accurately capture the underlying physical phenomena and consequently do not allow for simulations of material functionalities beyond the voltage-clamp or current-clamp conditions. The work presented here provides a more robust description of DIB network behavior through the development of a hierarchical multiscale model, recognizing that the macroscopic network properties are functions of their underlying molecular structure. The result of this research is a modeling methodology based on controlled exchanges across the interfaces of neighboring droplets. This methodology is validated against experimental data, and an extension case is provided to demonstrate possible future applications of droplet interface bilayer networks.

  3. Modeling the Elastic Properties of Lipid Bilayer Membranes

    Science.gov (United States)

    Barry, Edward; Gibaud, Thomas; Zakhary, Mark; Dogic, Zvonimir

    2011-03-01

    Model membranes such as lipid bilayers have been indispensable tools for our understanding of the elastic properties of biological membranes. In this talk, I will introduce a colloidal model for membranes and demonstrate that the physical properties of these colloidal membranes are identical to lipid bilayers. The model system is unique in that the constituent molecules are homogenous and non-amphiphilic, yet their self-assembly into membranes and other hierarchical assemblages, such as a lamellar type phases and chiral ribbons, proceeds spontaneously in solution. Owing to the large size of the constituent molecules, individual molecules can be directly visualized and simultaneous observations at the continuum and molecular lengthscales are used to characterize the behavior of model membranes with unprecedented detail. Moreover, once assembled in solution, molecular interactions can be controlled in situ. In particular, the strength of chiral interactions can be varied, leading to fascinating transitions in behavior that resembles the formation of starfish vesicles. These observations point towards the important role of line tension, and have potential implications for phase separated lipid mixtures or lipid rafts.

  4. Surface and interfacial creases in a bilayer tubular soft tissue

    Science.gov (United States)

    Razavi, Mir Jalil; Pidaparti, Ramana; Wang, Xianqiao

    2016-08-01

    Surface and interfacial creases induced by biological growth are common types of instability in soft biological tissues. This study focuses on the criteria for the onset of surface and interfacial creases as well as their morphological evolution in a growing bilayer soft tube within a confined environment. Critical growth ratios for triggering surface and interfacial creases are investigated both analytically and numerically. Analytical interpretations provide preliminary insights into critical stretches and growth ratios for the onset of instability and formation of both surface and interfacial creases. However, the analytical approach cannot predict the evolution pattern of the model after instability; therefore nonlinear finite element simulations are carried out to replicate the poststability morphological patterns of the structure. Analytical and computational simulation results demonstrate that the initial geometry, growth ratio, and shear modulus ratio of the layers are the most influential factors to control surface and interfacial crease formation in this soft tubular bilayer. The competition between the stretch ratios in the free and interfacial surfaces is one of the key driving factors to determine the location of the first crease initiation. These findings may provide some fundamental understanding in the growth modeling of tubular biological tissues such as esophagi and airways as well as offering useful clues into normal and pathological functions of these tissues.

  5. Entrenched metal lift-off using a novel bilayer process

    Science.gov (United States)

    Dubois, Thomas D.; Tranjan, Farid M.; Jones, Susan K.; Bobbio, Stephen M.; Kellam, Mark D.; Frieser, Rudolph G.; Jones, A. D.

    1990-01-01

    This paper will discuss the preparation and characterization of a modified photoresist and describe its use in a novel bilayer process. The modified photoresist solutions are prepared by dissolving enough cyclic phosphonitrilic chloride trimer, PNCT, in commercially available photoresist solutions to achieve phosphorus concentrations of 10 to 12 weight percent in the resulting films. FTNMR and FTIR data will be presented which demonstrate that the cyclic phosphonitrilic chloride trimer does not undergo chemical reaction with the components of the photoresist in the photoresist solutions or photoresist films. The exposure threshold of the PNCT modified photoresist films is 1.5 times greater than that of the unmodified films. Experimental data will be discussed which suggests the decrease in exposure threshold is the result of a relatively lower concentration of photoactive compound in the PNCT modified films. The PNCT modified films will be shown to provide resolution comparable to that of the unmodified photoresist films and yield a process window of better than 20%. A mechanism for the formation of the 02/N2 plasma resistant etch barrier formed during 02/N2 plasma etching will be discussed. Finally, a bilayer process which uses the PNCT modified photoresist in generating metal features entrenched in polyimide will be presented.

  6. Embedding Ba Monolayers and Bilayers in Boron Carbide Nanowires.

    Science.gov (United States)

    Yu, Zhiyang; Luo, Jian; Shi, Baiou; Zhao, Jiong; Harmer, Martin P; Zhu, Jing

    2015-11-26

    Aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) was employed to study the distribution of barium atoms on the surfaces and in the interiors of boron carbide based nanowires. Barium based dopants, which were used to control the crystal growth, adsorbed to the surfaces of the boron-rich crystals in the form of nanometer-thick surficial films (a type of surface complexion). During the crystal growth, these dopant-based surface complexions became embedded inside the single crystalline segments of fivefold boron-rich nanowires collectively, where they were converted to more ordered monolayer and bilayer modified complexions. Another form of bilayer complexion stabilized at stacking faults has also been identified. Numerous previous works suggested that dopants/impurities tended to segregate at the stacking faults or twinned boundaries. In contrast, our study revealed the previously-unrecognized possibility of incorporating dopants and impurities inside an otherwise perfect crystal without the association to any twin boundary or stacking fault. Moreover, we revealed the amount of barium dopants incorporated was non-equilibrium and far beyond the bulk solubility, which might lead to unique properties.

  7. Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    李纯泉; 陈红汉; 李思田; 张希明; 陈汉林

    2004-01-01

    The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was characterized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematic analysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions under UV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoir indicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings occurred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

  8. Hydrocarbon charging histories of the Ordovician reservoir in the Tahe oil field, Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    李纯泉; 陈红汉; 李思田; 张希明; 陈汉林

    2004-01-01

    The Ordovician reservoir of the Tahe oil field went through many tectonic reconstructions, and was charac-terized by multiple hydrocarbon chargings. The aim of this study was to unravel the complex charging histories. Systematicanalysis of fluid inclusions was employed to complete the investigation. Fluorescence observation of oil inclusions underUV light, and microthermometry of both oil and aqueous inclusions in 105 core samples taken from the Ordovician reservoirindicated that the Ordovician reservoir underwent four oil chargings and a gas charging. The hydrocarbon chargings oc-curred at the late Hercynian, the Indo-Sinian and Yanshan, the early Himalaya, the middle Himalaya, and the late Himalaya,respectively. The critical hydrocarbon charging time was at the late Hercynian.

  9. Applied bioremediation of petroleum hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Hinchee, R.E.; Kittel, J.A. [eds.] [Battelle Memorial Inst., Columbus, OH (United States); Reisinger, H.J. [ed.] [Integrated Science and Technology, Inc., Marietta, GA (United States)

    1995-12-31

    This volume is part of a ten volume set of papers derived from the Third International In Situ and On-Site Bioreclamation Symposium which was held in San Diego, California, in April 1995. The purpose of the conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on bioremediation. The papers in this volume focus on petroleum hydrocarbon bioremediation, with an emphasis on pilot-scale and field-scale applications. Individual papers have been processed separately for inclusion in the appropriate data bases.

  10. Predicting solute partitioning in lipid bilayers: Free energies and partition coefficients from molecular dynamics simulations and COSMOmic

    Energy Technology Data Exchange (ETDEWEB)

    Jakobtorweihen, S., E-mail: jakobtorweihen@tuhh.de; Ingram, T.; Gerlach, T.; Smirnova, I. [Institute of Thermal Separation Processes, Hamburg University of Technology, Eissendorfer Str. 38, 21073 Hamburg (Germany); Zuniga, A. Chaides; Keil, F. J. [Institute of Chemical Reaction Engineering, Hamburg University of Technology, Eissendorfer Str. 38, 21073 Hamburg (Germany)

    2014-07-28

    Quantitative predictions of biomembrane/water partition coefficients are important, as they are a key property in pharmaceutical applications and toxicological studies. Molecular dynamics (MD) simulations are used to calculate free energy profiles for different solutes in lipid bilayers. How to calculate partition coefficients from these profiles is discussed in detail and different definitions of partition coefficients are compared. Importantly, it is shown that the calculated coefficients are in quantitative agreement with experimental results. Furthermore, we compare free energy profiles from MD simulations to profiles obtained by the recent method COSMOmic, which is an extension of the conductor-like screening model for realistic solvation to micelles and biomembranes. The free energy profiles from these molecular methods are in good agreement. Additionally, solute orientations calculated with MD and COSMOmic are compared and again a good agreement is found. Four different solutes are investigated in detail: 4-ethylphenol, propanol, 5-phenylvaleric acid, and dibenz[a,h]anthracene, whereby the latter belongs to the class of polycyclic aromatic hydrocarbons. The convergence of the free energy profiles from biased MD simulations is discussed and the results are shown to be comparable to equilibrium MD simulations. For 5-phenylvaleric acid the influence of the carboxyl group dihedral angle on free energy profiles is analyzed with MD simulations.

  11. Similar Energetic Contributions of Packing in the Core of Membrane and Water-Soluble Proteins

    Energy Technology Data Exchange (ETDEWEB)

    Joh, Nathan H.; Oberai, Amit; Yang, Duan; Whitelegge, Julian P.; Bowie, James U.; (UCLA)

    2009-09-15

    A major driving force for water-soluble protein folding is the hydrophobic effect, but membrane proteins cannot make use of this stabilizing contribution in the apolar core of the bilayer. It has been proposed that membrane proteins compensate by packing more efficiently. We therefore investigated packing contributions experimentally by observing the energetic and structural consequences of cavity creating mutations in the core of a membrane protein. We observed little difference in the packing energetics of water and membrane soluble proteins. Our results imply that other mechanisms are employed to stabilize the structure of membrane proteins.

  12. RECENT DECLINES IN PAH, PCB, AND TOXAPHENE LEVELS IN THE NORTHERN GREAT LAKES AS DETERMINED FROM HIGH RESOLUTION SEDIMENT CORES. (R825151)

    Science.gov (United States)

    Sediment cores were collected from two sites in Grand Traverse Bay, Lake Michigan in May 1998, dated using 210Pb geochronology, and analyzed for polychlorinated biphenyl (PCB) congeners, polycyclic aromatic hydrocarbons (PAHs), and toxaphene. The extraor...

  13. Characterization and analysis of Devonian shales as related to release of gaseous hydrocarbons. Well K-4 Johnson County, Kentucky

    Energy Technology Data Exchange (ETDEWEB)

    Kalyoncu, R.S.; Snyder, M.J.

    1979-08-15

    Various characterization tasks were performed on 54 cored shale samples from Johnson County, Kentucky. Core samples were obtained from depths of 967 to 1510 feet. A total of 126 samples were canned for several DOE contractors, including Battelle Columbus. Free gas analyses indicate the presence of significant quantities of higher chain hydrocarbon gases in the K-4 shales. Hydrocarbon gas release rates and kinetic studies indicate that diffusion coefficients are inversely proportional to the square root of the molecular weight of diffusing species. Although wide scatter is observed in the chemical and physical characterization data, good correlations exist between the hydrocarbon gas contents and various laboratory characterization values (physical and chemical). A number of one-to-one relationships are pointed out and discussed. Lithologically, inorganic portions of K-4 shales are composed predominantly of quartz and illite with small quantities of pyrite and various carbonate minerals.

  14. 40 CFR 52.1877 - Control strategy: Photochemical oxidants (hydrocarbons).

    Science.gov (United States)

    2010-07-01

    ... oxidants (hydrocarbons). 52.1877 Section 52.1877 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY....1877 Control strategy: Photochemical oxidants (hydrocarbons). (a) The requirements of Subpart G of this... national standard for photochemical oxidants (hydrocarbons) in the Metropolitan Cincinnati...

  15. A DSC and FTIR spectroscopic study of the effects of the epimeric coprostan-3-ols and coprostan-3-one on the thermotropic phase behaviour and organization of dipalmitoylphosphatidylcholine bilayer membranes: Comparison with their 5-cholesten analogues.

    Science.gov (United States)

    Benesch, Matthew G K; Lewis, Ruthven N A H; Mannock, David A; McElhaney, Ronald N

    2015-05-01

    We present the results of a comparative differential calorimetric and Fourier transform infrared spectroscopic study of the effect of cholesterol and five analogues on the thermotropic phase behaviour and organization of dipalmitoylphosphatidylcholine bilayer membranes. These sterols/steroids differ in both the nature and stereochemistry of the polar head group at C3 (β-OH, α-OH or CO) and in the presence or absence of a double bond in ring B and in the orientation of rings A and B. The Δ(5) sterols/steroid have a trans rather than a cis ring A/B junction, and the concentration of these compounds required to abolish the DPPC pretransition, inversely related to their relative ability to disorder gel state DPPC bilayers, decreases in the order β-OH > α-OH > CO. However, in the saturated ring junction-inverted (cis) series, these concentrations are much more similar, regardless of polar head group chemical structure. Similarly, the residual enthalpy of the DPPC main phase transition at 50 mol% sterol/steroid, which is inversely related to the miscibility of these compounds in fluid DPPC bilayers, also increases in the order β-OH > α-OH > CO, but this effect is attenuated in the saturated series with an inverted ring A/B orientation. Moreover, replacement of the double bond at C5-C6 with a saturated linkage and inversion of the ring A/B junction reduces both sterol/steroid solubility and the ability to order the hydrocarbon chains of fluid DPPC molecules all cases. Thus, the characteristic effects of sterols/steroids on fluid lipid bilayers are generally optimal when an OH group rather than CO group is present at C3, and when this OH group is in the equatorial (β) orientation, and when the orientation of the ring A/B fusion is trans rather than cis. Overall, these results demonstrate that variations in the saturation and stereochemistry of the steroid ring system influence the effect of variations in the nature and stereochemistry of the polar headgroup at C3

  16. Cool Sooting Flames of Hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    Z.A. MANSUROV

    2001-01-01

    This paper presents the study of polycyclic aromatic hydrocarbons (PAH) and paramagnetism of soot particles sampled from cool sooting flames of methane and propane in a separately-heated two-sectional reactor under atmospheric pressure at the reactor temperatures of 670-1170 K. The temperature profiles of the flames were studied. The sampling was carried out with a quartz sampler and the samples were frozen with liquid nitrogen. A number of polyaromatic hydrocarbons such as pyrene, fluoranthene, coronene, anthanthrene, 1,12-benzperylene,were identified by spectroscopic methods in the extract of soot. The processes of soot formation at methaneoxygen mixture combustion in the electric field with applied potential changed from 0 to 2,2 kV at different polarity of electrodes have been investigated. It has been stated that at the electrical field application, an increase in soot particle sizes and soot yield occurs; besides, at the application of the field, speeding up the positively charged particles, the interplanar distance decreases. On the basis of investigation of soot particles paramagnetism, it was shown that initially soot particles have high carcinogetic activity and pollute the environment owing to a rapid decrease of the number of these radical centers. The reduction of the radical concentration is connected with radical recombination on soot.

  17. Hydrocarbon degradation by antarctic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cavanagh, J.A.E.; Nichols, P.D.; McMeekin, T.A.; Franzmann, P.D. [Univ. of Tasmania (Australia)] [and others

    1996-12-31

    Bacterial cultures obtained from sediment samples collected during a trial oil spill experiment conducted at Airport beach, Eastern Antarctica were selectively enriched for n-alkane-degrading and phenanthrenedegrading bacteria. Samples were collected from a control site and sites treated with different hydrocarbon mixtures - Special Antarctic blend (SAB), BP-Visco and orange roughy oils. One set of replicate sites was also treated with water from Organic Lake which had previously been shown to contain hydrocarbon-degrading bacteria. No viable bacteria were obtained from samples collected from sites treated with orange roughy oil. Extensive degradation of n-alkanes by enrichment cultures obtained from sites treated with SAB and BP-Visco occurred at both 25{degrees}C and 10{degrees}C. Extensive degradation of phenanthrene also occurred in enrichment cultures from these sites grown at 25{degrees}C. Concurrent increases of polar lipid in these cultures were also observed. The presence of 1,4-naphthaquinone and 1-naphthol during the growth of the cultures on phenanthrene is unusual and warrants further investigation of the mechanism of phenanthrene-degradation by these Antarctic bacteria.

  18. Comodules over semiperfect corings

    CERN Document Server

    Caenepeel, S

    2011-01-01

    We discuss when the Rat functor associated to a coring satisfying the left $\\alpha$-condition is exact. We study the category of comodules over a semiperfect coring. We characterize semiperfect corings over artinian rings and over qF-rings.

  19. Coring Sample Acquisition Tool

    Science.gov (United States)

    Haddad, Nicolas E.; Murray, Saben D.; Walkemeyer, Phillip E.; Badescu, Mircea; Sherrit, Stewart; Bao, Xiaoqi; Kriechbaum, Kristopher L.; Richardson, Megan; Klein, Kerry J.

    2012-01-01

    A sample acquisition tool (SAT) has been developed that can be used autonomously to sample drill and capture rock cores. The tool is designed to accommodate core transfer using a sample tube to the IMSAH (integrated Mars sample acquisition and handling) SHEC (sample handling, encapsulation, and containerization) without ever touching the pristine core sample in the transfer process.

  20. Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations

    Science.gov (United States)

    Ameen, Nawrass

    2013-04-01

    This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hradčany, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified

  1. Comparative Genomics of the Ubiquitous, Hydrocarbon-degrading Genus Marinobacter

    Science.gov (United States)

    Singer, E.; Webb, E.; Edwards, K. J.

    2012-12-01

    The genus Marinobacter is amongst the most ubiquitous in the global oceans and strains have been isolated from a wide variety of marine environments, including offshore oil-well heads, coastal thermal springs, Antarctic sea water, saline soils and associations with diatoms and dinoflagellates. Many strains have been recognized to be important hydrocarbon degraders in various marine habitats presenting sometimes extreme pH or salinity conditions. Analysis of the genome of M. aquaeolei revealed enormous adaptation versatility with an assortment of strategies for carbon and energy acquisition, sensation, and defense. In an effort to elucidate the ecological and biogeochemical significance of the Marinobacters, seven Marinobacter strains from diverse environments were included in a comparative genomics study. Genomes were screened for metabolic and adaptation potential to elucidate the strategies responsible for the omnipresence of the Marinobacter genus and their remedial action potential in hydrocarbon-polluted waters. The core genome predominantly encodes for key genes involved in hydrocarbon degradation, biofilm-relevant processes, including utilization of external DNA, halotolerance, as well as defense mechanisms against heavy metals, antibiotics, and toxins. All Marinobacter strains were observed to degrade a wide spectrum of hydrocarbon species, including aliphatic, polycyclic aromatic as well as acyclic isoprenoid compounds. Various genes predicted to facilitate hydrocarbon degradation, e.g. alkane 1-monooxygenase, appear to have originated from lateral gene transfer as they are located on gene clusters of 10-20% lower GC-content compared to genome averages and are flanked by transposases. Top ortholog hits are found in other hydrocarbon degrading organisms, e.g. Alcanivorax borkumensis. Strategies for hydrocarbon uptake encoded by various Marinobacter strains include cell surface hydrophobicity adaptation via capsular polysaccharide biosynthesis and attachment

  2. Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico.

    Directory of Open Access Journals (Sweden)

    Isabel C Romero

    Full Text Available The Deepwater Horizon (DWH spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000-1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC, aliphatic, polycyclic aromatic hydrocarbon (PAHs, and biomarker (hopanes, steranes, diasteranes compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1 sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material, and 2 advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related variability in the DeSoto Canyon, NE of the DWH wellhead.

  3. Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico

    Science.gov (United States)

    Romero, Isabel C.; Schwing, Patrick T.; Brooks, Gregg R.; Larson, Rebekka A.; Hastings, David W.; Ellis, Greg; Goddard, Ethan A.; Hollander, David J.

    2015-01-01

    The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000 – 1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead. PMID:26020923

  4. Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico.

    Science.gov (United States)

    Romero, Isabel C; Schwing, Patrick T; Brooks, Gregg R; Larson, Rebekka A; Hastings, David W; Ellis, Greg; Goddard, Ethan A; Hollander, David J

    2015-01-01

    The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000-1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead.

  5. Equilibrium passive sampling as a tool to study polycyclic aromatic hydrocarbons in Baltic Sea sediment pore-water systems

    DEFF Research Database (Denmark)

    Lang, Susann-Cathrin; Hursthouse, Andrew; Mayer, Philipp

    2015-01-01

    Solid Phase Microextraction (SPME) was applied to provide the first large scale dataset of freely dissolved concentrations for 9 polycyclic aromatic hydrocarbons (PAHs) in Baltic Sea sediment cores. Polydimethylsiloxane (PDMS) coated glass fibers were used for ex-situ equilibrium sampling followed...

  6. Evaluation of hydrocarbon potential, Task 8

    Energy Technology Data Exchange (ETDEWEB)

    Cashman, P.H.; Trexler, J.H. Jr. [Univ. of Nevada, Reno (United States)

    1993-09-30

    Task 8 is responsible for assessing the hydrocarbon potential of the Yucca Mountain vicinity. Our main focus is source rock stratigraphy in the Nevada Test Site (NTS) area in southern Nevada. In order to reconstruct the Paleozoic stratigraphy, we are also studying the geometry and kinematics of deformation at NTS. A thorough understanding of the structure will also be essential to predicting the nature of the Late Paleozoic rocks under Yucca Mountain. Our stratigraphic studies continue to support the interpretation that rocks mapped as the {open_quotes}Eleana Formation{close_quotes} are in fact parts of two different Mississippian units. We are now provisionally limiting the name {open_quotes}Eleana Formation{close_quotes} to the rocks that make up the Eleana Range - i.e., the rocks that we have been calling {open_quotes}western Eleana{close_quotes}. The mudstone section (which we have until now called {open_quotes}eastern Eleana{close_quotes}) we are provisionally calling the {open_quotes}Chainman Shale{close_quotes}, in keeping with regional lithostratigraphic nomenclature. We continue to work out the internal stratigraphies and basin histories of both units; XRD (r-ray diffraction) determinations of clay mineralogy are an addition to our understanding of the Chainman. The basin histories place important constraints on regional paleogeographic and tectonic reconstructions. This year we have hired a consulting petroleum geologist for two jobs: (1) to review drillhole data from southern Nevada on file at NBMG and make recommendations about more detailed study of any interesting drillholes; and (2) to log the UE17e core (in the Chainman) and evaluate source rock potential. The results of these studies have been incorporated into this report, and the consultant`s reports.

  7. Primary biodegradation of petroleum hydrocarbons in seawater

    Energy Technology Data Exchange (ETDEWEB)

    Comber, M.I.H.; Den Haan, K.H.; Djemel, N.; Eadsforth, C.V.; King, D.; Paumen, M.L.; Parkerton, T.; Dmytrasz, B.

    2012-12-15

    This report describes primary biodegradation experiments performed to determine the persistence of higher molecular weight petroleum hydrocarbons in seawater. Results from the biodegradation experiments show that the majority of tested petroleum hydrocarbons have half-lives in seawater less than 60 days.

  8. Versatility of hydrocarbon production in cyanobacteria.

    Science.gov (United States)

    Xie, Min; Wang, Weihua; Zhang, Weiwen; Chen, Lei; Lu, Xuefeng

    2017-02-01

    Cyanobacteria are photosynthetic microorganisms using solar energy, H2O, and CO2 as the primary inputs. Compared to plants and eukaryotic microalgae, cyanobacteria are easier to be genetically engineered and possess higher growth rate. Extensive genomic information and well-established genetic platform make cyanobacteria good candidates to build efficient biosynthetic pathways for biofuels and chemicals by genetic engineering. Hydrocarbons are a family of compounds consisting entirely of hydrogen and carbon. Structural diversity of the hydrocarbon family is enabled by variation in chain length, degree of saturation, and rearrangements of the carbon skeleton. The diversified hydrocarbons can be used as valuable chemicals in the field of food, fuels, pharmaceuticals, nutrition, and cosmetics. Hydrocarbon biosynthesis is ubiquitous in bacteria, yeasts, fungi, plants, and insects. A wide variety of pathways for the hydrocarbon biosynthesis have been identified in recent years. Cyanobacteria may be superior chassis for hydrocabon production in a photosynthetic manner. A diversity of hydrocarbons including ethylene, alkanes, alkenes, and terpenes can be produced by cyanobacteria. Metabolic engineering and synthetic biology strategies can be employed to improve hydrocarbon production in cyanobacteria. This review mainly summarizes versatility and perspectives of hydrocarbon production in cyanobacteria.

  9. Chain elongation of diacylphosphatidylcholine induces fully bilayer interdigitation under atmospheric pressure.

    Science.gov (United States)

    Goto, Masaki; Wilk, Agnieszka; Kazama, Akira; Chodankar, Shirish; Kohlbrecher, Joachim; Matsuki, Hitoshi

    2011-05-01

    The phase transitions of dibehenoylphosphatidylcholine (C22PC) bilayer membrane were observed by differential scanning calorimetry under atmospheric pressure and light-transmittance measurements under high pressure. The constructed temperature-pressure phase diagram suggests that the gel phase at low temperatures is the interdigitated gel phase. To confirm the phase state, we performed small-angle neutron scattering and fluorescence measurements using a polarity-sensitive probe Prodan for the C22PC bilayer membrane under atmospheric pressure. The peaks obtained in both measurements clearly showed the characteristic patterns of the fully interdigitated gel phase. Taking into account of previous studies on the gel phase for long-chain PC bilayers under atmospheric pressure and our studies on the pressure-induced bilayer interdigitaion of diacyl-PCs, it turned out that the interdigitation of diacyl-PC bilayer membranes occurs when the carbon number of acyl chain reaches at least 22. The present study revealed that the interdigitation of PC bilayer membranes occurs not only by weakening the attractive force of polar head groups but also by strengthening the cohesive force of acyl chains. When dominating the force of acyl chains, the interdigitation can be induced even in a diacyl-PC bilayer membrane by only hydration under atmospheric pressure.

  10. Lepromatous leprosy patients produce antibodies that recognise non-bilayer lipid arrangements containing mycolic acids

    Directory of Open Access Journals (Sweden)

    Isabel Baeza

    2012-12-01

    Full Text Available Non-bilayer phospholipid arrangements are three-dimensional structures that form when anionic phospholipids with an intermediate structure of the tubular hexagonal phase II are present in a bilayer of lipids. Antibodies that recognise these arrangements have been described in patients with antiphospholipid syndrome and/or systemic lupus erythematosus and in those with preeclampsia; these antibodies have also been documented in an experimental murine model of lupus, in which they are associated with immunopathology. Here, we demonstrate the presence of antibodies against non-bilayer phospholipid arrangements containing mycolic acids in the sera of lepromatous leprosy (LL patients, but not those of healthy volunteers. The presence of antibodies that recognise these non-bilayer lipid arrangements may contribute to the hypergammaglobulinaemia observed in LL patients. We also found IgM and IgG anti-cardiolipin antibodies in 77% of the patients. This positive correlation between the anti-mycolic-non-bilayer arrangements and anti-cardiolipin antibodies suggests that both types of antibodies are produced by a common mechanism, as was demonstrated in the experimental murine model of lupus, in which there was a correlation between the anti-non-bilayer phospholipid arrangements and anti-cardiolipin antibodies. Antibodies to non-bilayer lipid arrangements may represent a previously unrecognised pathogenic mechanism in LL and the detection of these antibodies may be a tool for the early diagnosis of LL patients.

  11. Corrugation of Phase-Separated Lipid Bilayers Supported by Nanoporous Silica Xerogel Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Goksu, E I; Nellis, B A; Lin, W; Satcher Jr., J H; Groves, J T; Risbud, S H; Longo, M L

    2008-10-30

    Lipid bilayers supported by substrates with nanometer-scale surface corrugations holds interest in understanding both nanoparticle-membrane interactions and the challenges of constructing models of cell membranes on surfaces with desirable properties, e.g. porosity. Here, we successfully form a two-phase (gel-fluid) lipid bilayer supported by nanoporous silica xerogel. Surface topology, diffusion, and lipid density in comparison to mica-supported lipid bilayers were characterized by AFM, FRAP, FCS, and quantitative fluorescence microscopy, respectively. We found that the two-phase lipid bilayer follows the xerogel surface contours. The corrugation imparted on the lipid bilayer results in a lipid density that is twice that on a flat mica surface. In direct agreement with the doubling of actual bilayer area in a projected area, we find that the lateral diffusion coefficient (D) of lipids on xerogel ({approx}1.7 {micro}m{sup 2}/s) is predictably lower than on mica ({approx}4.1 {micro}m{sup 2}/s) by both FRAP and FCS techniques. Furthermore, the gel-phase domains on xerogel compared to mica were larger and less numerous. Overall, our results suggest the presence of a relatively defect-free continuous two-phase bilayer that penetrates approximately midway into the first layer of {approx}50 nm xerogel beads.

  12. Multi-Stacked Supported Lipid Bilayer Micropatterning through Polymer Stencil Lift-Off

    Directory of Open Access Journals (Sweden)

    Yujie Zhu

    2015-08-01

    Full Text Available Complex multi-lamellar structures play a critical role in biological systems, where they are present as lamellar bodies, and as part of biological assemblies that control energy transduction processes. Multi-lamellar lipid layers not only provide interesting systems for fundamental research on membrane structure and bilayer-associated polypeptides, but can also serve as components in bioinspired materials or devices. Although the ability to pattern stacked lipid bilayers at the micron scale is of importance for these purposes, limited work has been done in developing such patterning techniques. Here, we present a simple and direct approach to pattern stacked supported lipid bilayers (SLBs using polymer stencil lift-off and the electrostatic interactions between cationic and anionic lipids. Both homogeneous and phase-segregated stacked SLB patterns were produced, demonstrating that the stacked lipid bilayers retain lateral diffusivity. We demonstrate patterned SLB stacks of up to four bilayers, where fluorescence resonance energy transfer (FRET and quenching was used to probe the interactions between lipid bilayers. Furthermore, the study of lipid phase behaviour showed that gel phase domains align between adjacent layers. The proposed stacked SLB pattern platform provides a robust model for studying lipid behaviour with a controlled number of bilayers, and an attractive means towards building functional bioinspired materials or devices.

  13. Molecular dynamics simulation of the partitioning of benzocaine and phenytoin into a lipid bilayer.

    Science.gov (United States)

    Martin, Lewis J; Chao, Rebecca; Corry, Ben

    2014-01-01

    Molecular dynamics simulations were used to examine the partitioning behaviour of the local anaesthetic benzocaine and the anti-epileptic phenytoin into lipid bilayers, a factor that is critical to their mode of action. Free energy methods are used to quantify the thermodynamics of drug movement between water and octanol as well as for permeation across a POPC membrane. Both drugs are shown to favourably partition into the lipid bilayer from water and are likely to accumulate just inside the lipid headgroups where they may alter bilayer properties or interact with target proteins. Phenytoin experiences a large barrier to cross the centre of the bilayer due to less favourable energetic interactions in this less dense region of the bilayer. Remarkably, in our simulations both drugs are able to pull water into the bilayer, creating water chains that extend back to bulk, and which may modify the local bilayer properties. We find that the choice of atomic partial charges can have a significant impact on the quantitative results, meaning that careful validation of parameters for new drugs, such as performed here, should be performed prior to their use in biomolecular simulations.

  14. The effect of temperature on supported dipalmitoylphosphatidylcholine (DPPC) bilayers: structure and lubrication performance.

    Science.gov (United States)

    Wang, Min; Zander, Thomas; Liu, Xiaoyan; Liu, Chao; Raj, Akanksha; Wieland, D C Florian; Garamus, Vasil M; Willumeit-Römer, Regine; Claesson, Per Martin; Dėdinaitė, Andra

    2015-05-01

    Phospholipids fulfill an important role in joint lubrication. They, together with hyaluronan and glycoproteins, are the biolubricants that sustain low friction between cartilage surfaces bathed in synovial fluid. In this work we have investigated how the friction force and load bearing capacity of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers on silica surfaces are affected by temperature, covering the temperature range 25-52°C. Friction forces have been determined utilizing the AFM colloidal probe technique, which showed that DPPC bilayers are able to provide low friction forces over the whole temperature interval. However, the load bearing capacity is improved at higher temperatures. We interpret this finding as being a consequence of lower rigidity and higher self-healing capacity of the DPPC bilayer in the liquid disordered state compared to the gel state. The corresponding structure of solid supported DPPC bilayers at the silica-liquid interface has been followed using X-ray reflectivity measurements, which suggests that the DPPC bilayer is in the gel phase at 25°C and 39°C and in the liquid disordered state at 55°C. Well-defined bilayer structures were observed for both phases. The deposited DPPC bilayers were also imaged using AFM PeakForce Tapping mode, and these measurements indicated a less homogeneous layer at temperatures below 37°C.

  15. Role of substrate induced electron-phonon interactions in biased graphitic bilayers

    Science.gov (United States)

    Davenport, A. R.; Hague, J. P.

    2016-08-01

    Bilayers of graphitic materials have potential applications in field effect transistors (FETs). A potential difference applied between certain ionic bilayers made from insulating graphitic materials such as BN, ZnO and AlN could reduce gap sizes, turning them into useful semiconductors. On the other hand, opening of a small semiconducting gap occurs in graphene bilayers under applied field. The aim here is to investigate to what extent substrate induced electron-phonon interactions (EPIs) modify this gap change. We examine EPIs in several lattice configurations of graphitic bilayers, using a perturbative approach. The typical effect of EPIs on the ionic bilayers is an undesirable gap widening. The size of this gap change varies considerably with lattice structure and the magnitude of the bias. When bias is larger than the non-interacting gap size, EPIs have the smallest effect on the bandgap, especially in configurations with A{{A}\\prime} and AB structures. Thus careful selection of substrate, lattice configuration and bias strength to minimise the effects of EPIs could be important for optimising the properties of electronic devices. We use parameters related to BN in this article. In practice, the results presented here are broadly applicable to other graphitic bilayers, and are likely to be qualitatively similar in metal dichalcogenide bilayers such as MoS2, which are already of high interest for their use in FETs.

  16. Effect of monoglyceride structure and cholesterol content on water permeability of the droplet bilayer.

    Science.gov (United States)

    Michalak, Zuzanna; Muzzio, Michelle; Milianta, Peter J; Giacomini, Rosario; Lee, Sunghee

    2013-12-23

    The process of water permeation across lipid membranes has significant implications for cellular physiology and homeostasis, and its study may lead to a greater understanding of the relationship between the structure of lipid bilayer and the role that lipid structure plays in water permeation. In this study, we formed a droplet interface bilayer (DIB) by contacting two aqueous droplets together in an immiscible solvent (squalane) containing bilayer-forming surfactant (monoglycerides). Using the DIB model, we present our results on osmotic water permeabilities and activation energy for water permeation of an associated series of unsaturated monoglycerides as the principal component of droplet bilayers, each having the same chain length but differing in the position and number of double bonds, in the absence and presence of a varying concentration of cholesterol. Our findings suggest that the tailgroup structure in a series of monoglyceride bilayers is seen to affect the permeability and activation energy for the water permeation process. Moreover, we have also established the insertion of cholesterol into the droplet bilayer, and have detected its presence via its effect on water permeability. The effect of cholesterol differs depending on the type of monoglyceride. We demonstrate that the DIB can be employed as a convenient model membrane to rapidly explore subtle structural effects on bilayer water permeability.

  17. Studying the lateral chain packing in a ceramide bilayer with molecular dynamics simulations

    Science.gov (United States)

    Papadimitriou, N. I.; Karozis, S. N.; Kainourgiakis, M. E.; Charalambopoulou, G. Ch

    2015-01-01

    In this work, we present a novel technique, based on molecular dynamics simulations, that allows the study of the lateral chain packing in a lipid bilayer. It utilizes the radial distribution function of the alkyl chains to determine the arrangement of the chains along the bilayer plane. The positions of the mass centres of the chains are projected onto the bilayer plane and a 2D radial distribution function is calculated for these projections. The proposed technique can be particularly useful for lipid bilayers in the gel (solid) phase where the chains present a limited degree of mobility. As a case study, we have examined a bilayer that consists of ceramide NS 24:0. Ceramide bilayers can be found in the lipid domain of the skin where they have a significant role in its barrier function. The specific bilayer was found (at 300 K) to adopt a strictly hexagonal chain packing with a separation distance between the chains of 0.466 nm, in good agreement with the available experimental data.

  18. Fluorescence of Supported Phospholipid Bilayers Recorded in a Conventional Horizontal-Beam Spectrofluorometer.

    Science.gov (United States)

    Kovrigina, Elizaveta A; Kovrigin, Evgenii L

    2016-03-01

    Supported phospholipid bilayers are a convenient model of cellular membranes in studies of membrane biophysics and protein-lipid interactions. Traditionally, supported lipid bilayers are formed on a flat surface of a glass slide to be observed through fluorescence microscopes. This paper describes a method to enable fluorescence detection from the supported lipid bilayers using standard horizontal-beam spectrofluorometers instead of the microscopes. In the proposed approach, the supported lipid bilayers are formed on the inner optical surfaces of the standard fluorescence microcell. To enable observation of the bilayer absorbed on the cell wall, the microcell is placed in a standard fluorometer cell holder and specifically oriented to expose the inner cell walls to both excitation and emission channels with a help of the custom cell adaptor. The signal intensity from supported bilayers doped with 1 % (mol) of rhodamine-labeled lipid in the standard 3-mm optical microcell was equivalent to fluorescence of the 70-80 nM reference solution of rhodamine recorded in a commercial microcell adaptor. Because no modifications to the instruments are required in this method, a variety of steady-state and time-domain fluorescence measurements of the supported phospholipid bilayers may be performed with the spectral resolution using standard horizontal-beam spectrofluorometers.

  19. Phospholipid and Hydrocarbon Interactions with a Charged Electrode Interface.

    Science.gov (United States)

    Levine, Zachary A; DeNardis, Nadica Ivošević; Vernier, P Thomas

    2016-03-22

    Using a combination of molecular dynamics simulations and experiments we examined the interactions of alkanes and phospholipids at charged interfaces in order to understand how interfacial charge densities affect the association of these two representative molecules with electrodes. Consistent with theory and experiment, these model systems reveal interfacial associations mediated through a combination of Coulombic and van der Waals forces. van der Waals forces, in particular, mediate rapid binding of decane to neutral electrodes. No decane binding was observed at high surface charge densities because of interfacial water polarization, which screens hydrophobic attractions. The positively charged choline moiety of the phospholipid palmitoyloleoylphosphatidylcholine (POPC) is primarily responsible for POPC attraction by a moderately negatively charged electrode. The hydrocarbon tails of POPC interact with the hydrophobic electrode interface similarly to decane. Previously reported electrochemical results confirm these findings by demonstrating bipolar displacement currents from PC vesicles adhering to moderately negatively charged interfaces, originating from the choline interactions observed in simulations. At more negatively charged interfaces, choline-to-surface binding was stronger. In both simulations and experiments the maximal interaction of anionic PS occurs with a positively charged interface, provided that the electrostatic forces outweigh local Lennard-Jones interactions. Direct comparisons between the binding affinities measured in experiments and those obtained in simulations reveal previously unobserved atomic interactions that facilitate lipid vesicle adhesion to charged interfaces. Moreover, the implementation of a charged interface in molecular dynamics simulations provides an alternative method for the generation of large electric fields across phospholipid bilayers, especially for systems with periodic boundary conditions, and may be useful for

  20. Comparative Study of Monolayer and Bilayer Epitaxial Graphene Field-Effect Transistors on SiC Substrates

    Institute of Scientific and Technical Information of China (English)

    Ze-Zhao He; Ke-Wu Yang; Cui Yu; Qing-Bin Liu; Jing-Jing Wang; Xu-Bo Song; Ting-Ting Han

    2016-01-01

    Monolayer and bilayer graphenes have generated tremendous excitement as the potentially useful electronic materials due to their unique features.We report on monolayer and bilayer epitaxial graphene field-effect transistors (GFETs) fabricated on SiC substrates.Compared with monolayer GFETs,the bilayer GFETs exhibit a significant improvement in dc characteristics,including increasing current density IDS,improved transconductance gm,reduced sheet resistance Ron,and current saturation.The improved electrical properties and tunable bandgap in the bilayer graphene lead to the excellent dc performance of the bilayer GFETs.Furthermore,the improved dc characteristics enhance a better rf performance for bilayer graphene devices,demonstrating that the quasifree-standing bilayer graphene on SiC substrates has a great application potential for the future graphene-based electronics.

  1. Ultra-high vacuum surface analysis study of rhodopsin incorporation into supported lipid bilayers.

    Science.gov (United States)

    Michel, Roger; Subramaniam, Varuni; McArthur, Sally L; Bondurant, Bruce; D'Ambruoso, Gemma D; Hall, Henry K; Brown, Michael F; Ross, Eric E; Saavedra, S Scott; Castner, David G

    2008-05-06

    Planar supported lipid bilayers that are stable under ambient atmospheric and ultra-high-vacuum conditions were prepared by cross-linking polymerization of bis-sorbylphosphatidylcholine (bis-SorbPC). X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed to investigate bilayers that were cross-linked using either redox-initiated radical polymerization or ultraviolet photopolymerization. The redox method yields a more structurally intact bilayer; however, the UV method is more compatible with incorporation of transmembrane proteins. UV polymerization was therefore used to prepare cross-linked bilayers with incorporated bovine rhodopsin, a light-activated, G-protein-coupled receptor (GPCR). A previous study (Subramaniam, V.; Alves, I. D.; Salgado, G. F. J.; Lau, P. W.; Wysocki, R. J.; Salamon, Z.; Tollin, G.; Hruby, V. J.; Brown, M. F.; Saavedra, S. S. J. Am. Chem. Soc. 2005, 127, 5320-5321) showed that rhodopsin retains photoactivity after incorporation into UV-polymerized bis-SorbPC, but did not address how the protein is associated with the bilayer. In this study, we show that rhodopsin is retained in supported bilayers of poly(bis-SorbPC) under ultra-high-vacuum conditions, on the basis of the increase in the XPS nitrogen concentration and the presence of characteristic amino acid peaks in the ToF-SIMS data. Angle-resolved XPS data show that the protein is inserted into the bilayer, rather than adsorbed on the bilayer surface. This is the first study to demonstrate the use of ultra-high-vacuum techniques for structural studies of supported proteolipid bilayers.

  2. Ghost Fano Resonance of Excitons in Twisted Bilayer Graphene

    Science.gov (United States)

    Liang, Yufeng

    2014-03-01

    Metallic systems are generally considered to be unable to harbor tightly bound excitons because of the strong screening effect as well as the absence of a finite band gap. Previously, exception has only been found in one-dimensional metallic carbon nanotubes due to the depressed screening effects and the symmetry gap. We explore the exciton spectra of twisted bilayer graphene (tBLG) and predict the existence of even more strongly bound exciton (with binding energy as large as 0.5eV) in this system despite of its higher dimensionality. Based on our results from first-principles simulations and effective model calculations, a mechanism known as the ghost Fano resonance is proposed for the bound exciton formation in metallic systems beyond the dimensonality-related argument. Our results shed light on engineering the e-h excitations in the few-layer van der Waals heterojunction. NSF Grant No. DMR-1207141.

  3. Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers

    Science.gov (United States)

    Saidaoui, Hamed Ben Mohamed; Manchon, A.

    2016-07-01

    Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ . While the spin Hall effect dominates in the diffusive limit (d ≫λ ), spin swapping dominates in the Knudsen regime (d ≲λ ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.

  4. Effects of butanol isomers on dipalmitoylphosphatidylcholine bilayer membranes.

    Science.gov (United States)

    Reeves, Megan D; Schawel, Adam K; Wang, Weidong; Dea, Phoebe

    2007-06-01

    Differential scanning calorimetry and (31)P-NMR were used to study the effects of butanol isomers on the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers. The threshold concentration for the onset of interdigitation for each isomer was determined by the disappearance of the pretransition and the onset of a large hysteresis between the heating and cooling scans of the gel-to-liquid main transition. The threshold concentration was found to correlate with increased solubility of the isomers in the aqueous phase, led by tert-butanol. However, as the solution concentration of tert-butanol increased, there was an abrupt shrinking of the hysteresis, initially with well-resolved shoulder peaks indicating mixed phases. The eventual disappearance of the shoulder peaks was correlated with a breakdown of the multilamellar structure identified using (31)P-NMR.

  5. Stacking transition in bilayer graphene caused by thermally activated rotation

    Science.gov (United States)

    Zhu, Mengjian; Ghazaryan, Davit; Son, Seok-Kyun; Woods, Colin R.; Misra, Abhishek; He, Lin; Taniguchi, Takashi; Watanabe, Kenji; Novoselov, Kostya S.; Cao, Yang; Mishchenko, Artem

    2017-03-01

    Crystallographic alignment between two-dimensional crystals in van der Waals heterostructures brought a number of profound physical phenomena, including observation of Hofstadter butterfly and topological currents, and promising novel applications, such as resonant tunnelling transistors. Here, by probing the electronic density of states in graphene using graphene-hexagonal boron nitride-graphene tunnelling transistors, we demonstrate a structural transition of bilayer graphene from incommensurate twisted stacking state into a commensurate AB stacking due to a macroscopic graphene self-rotation. This structural transition is accompanied by a topological transition in the reciprocal space and by pseudospin texturing. The stacking transition is driven by van der Waals interaction energy of the two graphene layers and is thermally activated by unpinning the microscopic chemical adsorbents which are then removed by the self-cleaning of graphene.

  6. Lipid Bilayer Composition Affects Transmembrane Protein Orientation and Function

    Directory of Open Access Journals (Sweden)

    Katie D. Hickey

    2011-01-01

    Full Text Available Sperm membranes change in structure and composition upon ejaculation to undergo capacitation, a molecular transformation which enables spermatozoa to undergo the acrosome reaction and be capable of fertilization. Changes to the membrane environment including lipid composition, specifically lipid microdomains, may be responsible for enabling capacitation. To study the effect of lipid environment on proteins, liposomes were created using lipids extracted from bull sperm membranes, with or without a protein (Na+ K+-ATPase or -amylase. Protein incorporation, function, and orientation were determined. Fluorescence resonance energy transfer (FRET confirmed protein inclusion in the lipid bilayer, and protein function was confirmed using a colourometric assay of phosphate production from ATP cleavage. In the native lipid liposomes, ATPase was oriented with the subunit facing the outer leaflet, while changing the lipid composition to 50% native lipids and 50% exogenous lipids significantly altered this orientation of Na+ K+-ATPase within the membranes.

  7. A Bilayer Resource Model for Cloud Manufacturing Services

    Directory of Open Access Journals (Sweden)

    Linan Zhu

    2013-01-01

    Full Text Available Cloud Manufacturing and Cloud Service is currently one of the main directions of development in the manufacturing industry. Under the Cloud Manufacturing environment, the characteristics of publishing, updating, searching, and accessing manufacturing resources are massive, complex, heterogeneous, and so forth. A bilayer manufacturing resource model with separation of Cloud End and Cloud Manufacturing Platform is proposed in this paper. In Cloud End, manufacturing resources are divided into single resource and complex resource, and a basic data model of manufacturing resources oriented to enterprise interior is established to store the physical characteristics. In Cloud Manufacturing Platform, a resource service attribute model oriented to actual users is established to store the service characteristics. This model is described in detail and realized with stateful Web Service Description Language (WSDL document. An example is provided for illustrating the implementation of the concept.

  8. Magnetic bilayer-skyrmions without skyrmion Hall effect

    Science.gov (United States)

    Zhang, Xichao; Zhou, Yan; Ezawa, Motohiko

    2016-01-01

    Magnetic skyrmions might be used as information carriers in future advanced memories, logic gates and computing devices. However, there exists an obstacle known as the skyrmion Hall effect (SkHE), that is, the skyrmion trajectories bend away from the driving current direction due to the Magnus force. Consequently, the skyrmions in constricted geometries may be destroyed by touching the sample edges. Here we theoretically propose that the SkHE can be suppressed in the antiferromagnetically exchange-coupled bilayer system, since the Magnus forces in the top and bottom layers are exactly cancelled. We show that such a pair of SkHE-free magnetic skyrmions can be nucleated and be driven by the current-induced torque. Our proposal provides a promising means to move magnetic skyrmions in a perfectly straight trajectory in ultra-dense devices with ultra-fast processing speed.

  9. Supported lipid bilayers as templates to design manganese oxide nanoparticles

    Indian Academy of Sciences (India)

    J Maheshkumar; B Sreedhar; B U Nair; A Dhathathreyan

    2012-09-01

    This work reports on the preparation of nanoclusters of manganese oxide using biotemplating techniques. Supported lipid bilayers (SLBs) on quartz using cationic lipid [Dioctadecyldimethylammonium bromide (DOMA)] and mixed systems with neutral phospholipids dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) have been used as templates to synthesize these nanoparticles in a waterbased medium at room temperature. The Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) show manganese oxide nanostructures that are composed of crystals or small clusters in the size range of 20-50 nm in diameter. Small angle XRD showed that template removal through calcining process results in nanostructures of the manganese oxide in sizes from 30 to 50 nm. Using these organized assemblies it is possible to control the nano and mesoscopic morphologies of particles and both rod-like and spherical particles can be synthesized.

  10. The enhancement of vortex pinning in ferromagnet/superconductor bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cieplak, Marta Z.; Adamus, Z.; Abal' oshev, A.; Abal' osheva, I.; Berkowski, M. [Polish Academy of Sciences, Al. Lotnikw 32/46, 02668 Warsaw (Poland); Cheng, X.M.; Sang, Hai; Chien, C.L. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Md 21218 (United States)

    2005-03-01

    The magnetic-domain induced vortex pinning is studied in the ferromagnet/superconductor bilayers (FSB's), in which the F layers are Co/Pt multilayers with perpendicular magnetic anisotropy, and the S layers are either niobium or high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO). The magnetization measurements reveal the enhancement of the flux pinning in both types of FSB's during the reversal of the magnetization of the F layer, but the details of the behavior depend on the type of the S layer. In the case of niobium FSB the maximum of pinning appears when the F layer is in the final stage of the magnetic reversal process, while the FSB with YBCO shows the maximum when the F layer is saturated. The possible origins of these differences are discussed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Theoretical studies of lipid bilayer electroporation using molecular dynamics simulations

    Science.gov (United States)

    Levine, Zachary Alan

    Computer simulations of physical, chemical, and biological systems have improved tremendously over the past five decades. From simple studies of liquid argon in the 1960s to fully atomistic simulations of entire viruses in the past few years, recent advances in high-performance computing have continuously enabled simulations to bridge the gap between scientific theory and experiment. Molecular dynamics simulations in particular have allowed for the direct observation of spatial and temporal events which are at present inaccessible to experiments. For this dissertation I employ all-atom molecular dynamics simulations to study the transient, electric field-induced poration (or electroporation) of phospholipid bilayers at MV/m electric fields. Phospholipid bilayers are the dominant constituents of cell membranes and act as both a barrier and gatekeeper to the cell interior. This makes their structural integrity and susceptibility to external perturbations an important topic for study, especially as the density of electromagnetic radiation in our environment is increasing steadily. The primary goal of this dissertation is to understand the specific physical and biological mechanisms which facilitate electroporation, and to connect our simulated observations to experiments with live cells and to continuum models which seek to describe the underlying biological processes of electroporation. In Chapter 1 I begin with a brief introduction to phospholipids and phospholipid bilayers, followed by an extensive overview of electroporation and atomistic molecular dynamics simulations. The following chapters will then focus on peer-reviewed and published work we performed, or on existing projects which are currently being prepared for submission. Chapter 2 looks at how external electric fields affect both oxidized and unoxidized lipid bilayers as a function of oxidation concentration and oxidized lipid type. Oxidative damage to cell membranes represents a physiologically relevant

  12. Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed

    2016-07-12

    Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ. While the spin Hall effect dominates in the diffusive limit (d≫λ), spin swapping dominates in the Knudsen regime (d≲λ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.

  13. Monolayer curvature stabilizes nanoscale raft domains in mixed lipid bilayers

    CERN Document Server

    Meinhardt, Sebastian; Schmid, Friederike

    2013-01-01

    According to the lipid raft hypothesis, biological lipid membranes are laterally heterogeneous and filled with nanoscale ordered "raft" domains, which are believed to play an important role for the organization of proteins in membranes. However, the mechanisms stabilizing such small rafts are not clear, and even their existence is sometimes questioned. Here we report the observation of raft-like structures in a coarse-grained molecular model for multicomponent lipid bilayers. On small scales, our membranes demix into a liquid ordered (lo) and a liquid disordered (ld) phase. On large scales, phase separation is suppressed and gives way to a microemulsion-type state that contains nanometer size lo domains in a ld environment. Furthermore, we introduce a mechanism that generates rafts of finite size by a coupling between monolayer curvature and local composition. We show that mismatch between the spontaneous curvatures of monolayers in the lo and ld phase induces elastic interactions, which reduce the line tensi...

  14. Topological states in two-dimensional hexagon lattice bilayers

    Science.gov (United States)

    Zhang, Ming-Ming; Xu, Lei; Zhang, Jun

    2016-10-01

    We investigate the topological states of the two-dimensional hexagon lattice bilayer. The system exhibits a quantum valley Hall (QVH) state when the interlayer interaction t⊥ is smaller than the nearest neighbor hopping energy t, and then translates to a trivial band insulator state when t⊥ / t > 1. Interestingly, the system is found to be a single-edge QVH state with t⊥ / t = 1. The topological phase transition also can be presented via changing bias voltage and sublattice potential in the system. The QVH states have different edge modes carrying valley current but no net charge current. The bias voltage and external electric field can be tuned easily in experiments, so the present results will provide potential application in valleytronics based on the two-dimensional hexagon lattice.

  15. Butterfly micro bilayer thermal energy harvester geometry with improved performances

    Science.gov (United States)

    Trioux, E.; Monfray, S.; Basrour, S.

    2016-11-01

    This paper reports the recent progress of a new technology to scavenge thermal energy, implying a double-step transduction through thermal buckling of a bilayer aluminum nitride / aluminum bridge and piezoelectric transduction. A completely new scavenger design is presented, improving greatly its final performance. The butterfly shape reduces the overall device mechanical rigidity, which leads to a decrease of buckling temperatures compared to previously studied rectangular plates. In a first time we compared performances of rectangular and butterfly plates with an equal thickness of Al and AlN. In a second time, with a thicker Al layer than AlN layer, we will study only butterfly structure in terms of output power and buckling temperatures, and compare it to the previous stack.

  16. Modeling Kinetics of Distortion in Porous Bi-layered Structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Bjørk, Rasmus;

    2013-01-01

    Shape distortions during constrained sintering experiment of bi-layer porous and dense cerium gadolinium oxide (CGO) structures have been modeled. Technologies like solid oxide fuel cells require co-firing thin layers with different green densities, which often exhibit differential shrinkage...... because of different sintering rates of the materials resulting in undesired distortions of the component. An analytical model based on the continuum theory of sintering has been developed to describe the kinetics of densification and distortion in the sintering processes. A new approach is used...... to extract the material parameters controlling shape distortion through optimizing the model to experimental data of free shrinkage strains. The significant influence of weight of the sample (gravity) on the kinetics of distortion is taken in to consideration. The modeling predictions indicate good agreement...

  17. Superconducting properties of lithium-decorated bilayer graphene

    Science.gov (United States)

    Szczȩśniak, Dominik

    2015-07-01

    The present study provides a comprehensive theoretical analysis of the superconducting phase in selected lithium-decorated bilayer graphene nanostructures. The numerical calculations, conducted within the Eliashberg formalism, give quantitative estimations of the most important thermodynamic properties such as the critical temperature, specific heat, critical field and others. It is shown that discussed lithium-graphene systems present enhancement of their thermodynamic properties comparing to the monolayer case, e.g., the critical temperature can be raised to ∼15 \\text{K} . Furthermore, estimated characteristic thermodynamic ratios exceed predictions of the Bardeen-Cooper-Schrieffer theory suggesting that the considered lithium-graphene systems can be properly analyzed only within the strong-coupling regime.

  18. Resonant tunnelling in a Fibonacci bilayer graphene superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, S.; Sinha, C. [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, West Bengal (India); Biswas, R. [Department of Physics, PK College, Contai, Purba Medinipur, West Bengal (India)

    2010-02-15

    The transmission coefficients (TCs) and angularly averaged conductance for quasi-particle transport are studied for a bilayer graphene superlattice arranged according to the Fibonacci sequence. The transmission is found to be symmetric around the superlattice growth direction and highly sensitive to the direction of the quasi-particle incidence. The transmission spectra are fragmented and appear in groups due to the quasi-periodicity of the system. The average conductance shows interesting structures sharply dependent on the height of the potential barriers between two graphene strips. The low-energy conductance due to Klein transmission is substantially modified by the inclusion of quasi-periodicity in the system. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  19. Protein-induced bilayer Perturbations: Lipid ordering and hydrophobic coupling

    DEFF Research Database (Denmark)

    Petersen, Frederic Nicolas Rønne; Laursen, Ib; Bohr, Henrik;

    2009-01-01

    The host lipid bilayer is increasingly being recognized as an important non-specific regulator of membrane protein function. Despite considerable progress the interplay between hydrophobic coupling and lipid ordering is still elusive. We use electron spin resonance (ESR) to study the interaction...... and hydrophobic mismatch. Our findings also show that at high protein:lipid ratios the lipids are motionally restricted but not completely immobilized. Both exchange on and off rate values for the lipid ↔ gramicidin interaction are lowest at optimal hydrophobic matching. Hydrophobic mismatch of few Å results...... in up to 10-fold increased exchange rates as compared to the ‘optimal’ match situation pointing to the regulatory role of hydrophobic coupling in lipid–protein interactions....

  20. Phosphatidyl-hydroxytyrosol and phosphatidyl-tyrosol bilayer properties.

    Science.gov (United States)

    Evans, Kervin O; Compton, David L

    2017-01-01

    Hydroxytyrosol and tyrosol phospholipids were enzymatically synthesized and investigated for their bilayer properties. Dynamic light scattering demonstrated that hand extrusion at 100nm consistently resulted in liposomes of nearly 85nm diameter for both phosphatidyl-hydroxytyrosol (DOPHT) and phosphatidyl-tyrosol (DOPT). Transmission electron microscopy showed DOPT and DOPHT liposomes extruded at 100-nm to be spherical and non-distinctive from one another. Zeta potential measurements resulted in surface charges<-25mV, demonstrating both DOPT and DOPHT form highly stable liposomes. Quartz crystal microbalance with dissipation monitoring measurements demonstrated that liposomal adsorption was dependent on a combination of DOPT (or DOPHT) mole-percent and calcium ions concentration. Fluorescence anisotropy measurements indicated that melting temperatures of DOPT and DOPHT were below 4°C, suggesting that adsorption behavior and liposome formation was limited by electrostatic interactions and not gel-state formation.

  1. Thickness dependence of the exchange bias in epitaxial manganite bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kobrinskii, A. L. [University of Minnesota; Goldman, A. M. [University of Minnesota; Varela del Arco, Maria [ORNL

    2009-01-01

    Exchange bias has been studied in a series of La{sub 2/3}Ca{sub 1/3}MnO{sub 3}/La{sub 1/3}Ca{sub 2/3}MnO{sub 3} bilayers grown on (001) SrTiO{sub 3} substrates by ozone-assisted molecular-beam epitaxy. The high crystalline quality of the samples and interfaces has been verified using high-resolution x-ray diffractometry and Z-contrast scanning transmission electron microscopy with electron-energy-loss spectroscopy. The dependence of exchange bias on the thickness of the antiferromagnetic layer has been investigated. A critical value for the onset of the hysteresis loop shift has been determined. An antiferromagnetic anisotropy constant has been obtained by fitting the results to the generalized Meiklejohn-Bean model.

  2. Thickness dependence of the exchange bias in epitaxial manganite bilayers

    Science.gov (United States)

    Kobrinskii, A. L.; Goldman, A. M.; Varela, Maria; Pennycook, S. J.

    2009-03-01

    Exchange bias has been studied in a series of La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 bilayers grown on (001) SrTiO3 substrates by ozone-assisted molecular-beam epitaxy. The high crystalline quality of the samples and interfaces has been verified using high-resolution x-ray diffractometry and Z -contrast scanning transmission electron microscopy with electron-energy-loss spectroscopy. The dependence of exchange bias on the thickness of the antiferromagnetic layer has been investigated. A critical value for the onset of the hysteresis loop shift has been determined. An antiferromagnetic anisotropy constant has been obtained by fitting the results to the generalized Meiklejohn-Bean model.

  3. Bilayer fractal structure with multiband left-handed characteristics.

    Science.gov (United States)

    Du, Qiujiao; Liu, Jinsong; Yang, Hongwu; Yi, Xunong

    2011-08-20

    We present a bilayer fractal structure for the realization of multiband left-handed metamaterial at terahertz frequencies. The structure is composed of metallic H-fractal pairs separated by a dielectric layer. The electromagnetic properties of periodic H-fractal pairs have been investigated by numerical simulation. The period in the propagation direction is extremely small as compared to the wavelength at the operational frequency. Under the electromagnetic wave normal incidence, the material exhibits negative refraction simultaneously around the frequencies of 0.10 and 0.15 THz for parallel polarization, and around the frequencies of 0.19 and 0.38 THz for perpendicular polarization. The design provides a left-handed metamaterial suitable for multiband and compact devices at terahertz frequencies.

  4. Early events following radiolytic and photogeneration of radical cations in hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Werst, D.W.; Trifunac, A.D.

    1992-11-01

    Real-time studies in hydrocarbons have revealed a richness of chemistry involving the initial ionic species produced in radiolysis and photoionization. A modified radical cation mechanism patterned after the core mechanism for alkane radiolysis-formation of radical cations and their disappearance via ion-molecule reactions - is capable of explaining a wide range of observations in high-energy photochemistry, and thus unifies two high-energy regimes. Fundamental studies of radical cations suggest strategies for mitigating radiation effects in materials.

  5. Early events following radiolytic and photogeneration of radical cations in hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Werst, D.W.; Trifunac, A.D.

    1992-01-01

    Real-time studies in hydrocarbons have revealed a richness of chemistry involving the initial ionic species produced in radiolysis and photoionization. A modified radical cation mechanism patterned after the core mechanism for alkane radiolysis-formation of radical cations and their disappearance via ion-molecule reactions - is capable of explaining a wide range of observations in high-energy photochemistry, and thus unifies two high-energy regimes. Fundamental studies of radical cations suggest strategies for mitigating radiation effects in materials.

  6. Phase Transition of MoS2 Bilayer Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Bothra, Pallavi; Pati, Swapan K.

    2016-01-01

    In the present study, using density functional calculations we have investigated a possible mechanism for the structural phase transition of the semiconducting bilayer 2H-MoS2 via lithiation. The results indicate that the addition of lithium to the bilayer 2H-MoS2 transforms the bilayer to a hete...... microscopic mechanism of the phase transition in MoS2 and enriches the atomic scale understanding of the interaction of MoS2 with the alkali ions and other transition metal dichalcogenides manifesting a similar phase transition....

  7. The interaction of new piroxicam analogues with lipid bilayers--a calorimetric and fluorescence spectroscopic study.

    Science.gov (United States)

    Maniewska, Jadwiga; Szczęśniak-Sięga, Berenika; Poła, Andrzej; Sroda-Pomianek, Kamila; Malinka, Wiesław; Michalak, Krystyna

    2014-01-01

    The purpose of the present paper was to assess the ability of new piroxicam analogues to interact with the lipid bilayers. The results of calorimetric and fluorescence spectroscopic experiments of two new synthesized analogues of piroxicam, named PR17 and PR18 on the phase behavior of phospholipid bilayers and fluorescence quenching of fluorescent probes (Laurdan and Prodan), which molecular location within membranes is known with certainty, are shown in present work. The presented results revealed that, depending on the details of chemical structure, the studied compounds penetrated the lipid bilayers.

  8. Finite element modeling of camber evolution during sintering of bi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Ni, De Wei; Bulatova, Regina;

    2014-01-01

    The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber...... and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence...... making use of the effect of gravity and friction to minimize the shape distortions during sintering of bilayers....

  9. Addressing Raman features of individual layers in isotopically labeled Bernal stacked bilayer graphene

    Science.gov (United States)

    Costa, Sara D.; Weis, Johan Ek; Frank, Otakar; Fridrichová, Michaela; Kalbac, Martin

    2016-06-01

    In this report important Raman modes for the evaluation of strain in graphene (the 2D and 2D‧) are analyzed. The isotope labeling is used to disentangle contribution of individual graphene layers of graphene bilayer to the studied Raman modes. It is shown that for Bernal-stacked bilayers, the 2D and the 2D‧ Raman modes have three distinct components that can be assigned to processes originating solely from the top graphene layer, bottom graphene layer, and from a combination of processes originating both from the top and bottom layers. The reported results thus enable addressing the properties of individual graphene layers in graphene bilayer by Raman spectroscopy.

  10. Hydroxytyrosol and tyrosol esters partitioning into, location within, and effect on DOPC liposome bilayer behavior.

    Science.gov (United States)

    Evans, Kervin O; Laszlo, Joseph A; Compton, David L

    2015-05-01

    The phenols hydroxytyrosol and tyrosol made abundantly available through olive oil processing were enzymatically transesterified into effective lipophilic antioxidants with cuphea oil. The hydroxytyrosyl and tyrosyl esters made from cuphea oil were assessed for their ability to partition into, locate within and effect the bilayer behavior of 1,2-dioloeoylphosphatidylcholine liposomes and compared to their counterparts made from decanoic acid. Partitioning into liposomes was on the same scale for both hydroxytyrosyl derivatives and both tyrosyl derivatives. All were found to locate nearly at the same depth within the bilayer. Each was found to affect bilayer behavior in a distinct manner.

  11. Hexagonal-shaped monolayer-bilayer quantum disks in graphene: A tight-binding approach

    Science.gov (United States)

    da Costa, D. R.; Zarenia, M.; Chaves, Andrey; Pereira, J. M.; Farias, G. A.; Peeters, F. M.

    2016-07-01

    Using the tight-binding approach, we investigate confined states in two different hybrid monolayer-bilayer systems: (i) a hexagonal monolayer area surrounded by bilayer graphene in the presence of a perpendicularly applied electric field and (ii) a hexagonal bilayer graphene dot surrounded by monolayer graphene. The dependence of the energy levels on dot size and external magnetic field is calculated. We find that the energy spectrum for quantum dots with zigzag edges consists of states inside the gap which range from dot-localized states, edge states, to mixed states coexisting together, whereas for dots with armchair edges, only dot-localized states are observed.

  12. Boundary potential of lipid bilayers: methods and interpretations

    Science.gov (United States)

    Ermakov, Yu A.; Nesterenko, A. M.

    2017-01-01

    The electric field distribution at the boundaries of cell membrane consists of diffuse part of the electrical double layer and the potential drop over polar area inside the membrane itself. The latter is generally attributed to the dipole effect, which depends on the lipid hydration and phase state. This report focuses on the experimental approaches developed to detect the relation between dipole effects and the bilayer structure, and to study their molecular nature. The total boundary potential (BP) of planar bilayer lipid membranes (BLM) can be controlled by Intramembranous Field Compensation (IFC) method developed in our laboratory. When combined with electrokinetic measurements in liposome suspension it allows detecting the changes of the dipole potential due to adsorption of inorganic cations and charged molecules. Multivalent inorganic cations increase the dipole potential up to 100-150 mV and make the membrane rigid. Most of these observations were simulated by Molecular Dynamics (MD) in order to visualize the relationship of electric field with the different structural factors (lipid structure, water orientation, ion adsorption etc.) responsible for its dipole component. Two principal contributors to BP – water and lipid molecules – create the opposite effects. The negative contribution with respect to the bulk is due to lipid itself and the inorganic cation penetration into the polar area of membrane. The positive contribution is caused by water orientation. Particularly, in the case of lysine adsorption, the contribution of water includes the rearrangement of H-bonds with the lipid phosphate group. This fact explains well the unusual kinetic phenomena registered by IFC in the case of polylysine adsorption at the BLM surface.

  13. A modified microbial adhesion to hydrocarbons assay to account for the presence of hydrocarbon droplets.

    Science.gov (United States)

    Zoueki, Caroline Warne; Tufenkji, Nathalie; Ghoshal, Subhasis

    2010-04-15

    The microbial adhesion to hydrocarbons (MATH) assay has been used widely to characterize microbial cell hydrophobicity and/or the extent of cell adhesion to hydrophobic liquids. The classical MATH assay involves spectrophotometric absorbance measurements of the initial and final cell concentrations in an aqueous cell suspension that has been contacted with a hydrocarbon liquid. In this study, microscopic examination of the aqueous cell suspension after contact with hexadecane or a hexadecane/toluene mixture revealed the presence of hydrocarbon droplets. The hydrocarbon droplets contributed to the absorbance values during spectrophotometric measurements and caused erroneous estimates of cell concentrations and extents of microbial adhesion. A modified MATH assay that avoids such artefacts is proposed here. In this modified assay, microscopic examination of the aqueous suspension and direct cell counts provides cell concentrations that are free of interference from hydrocarbon droplets. The presence of hydrocarbon droplets was noted in MATH assays performed with three bacterial strains, and two different hydrocarbons, at ionic strengths of 0.2 mM and 20 mM and pH 6. In these experiments, the formation of quasi-stable hydrocarbon droplets cannot be attributed to the presence of biosurfactants, or stabilization by biocolloids. The presence of surface potential at the hydrocarbon-water interface that was characterized by electrophoretic mobility of up to -1 and -2 microm cm/Vs, likely caused the formation of the quasi-stable hydrocarbon droplets that provided erroneous results using the classical MATH assay.

  14. Evolution and hydrocarbon potential of Queen Charlotte basin, Canada

    Energy Technology Data Exchange (ETDEWEB)

    McWhae, J.R.

    1988-02-01

    The structural and depositional history of the Queen Charlotte basin, a complex Tertiary rift basin with extensive coeval volcanics, involves regional geology from the Pacific plate west of the Queen Charlotte transform fault to east of the Alexander-Wrangellia terrane, based on geophysics (including newly released seismic lines), revised stratigraphy, and well data. Eight offshore wells were drilled prior to 1970 and nine shallow onshore wells were drilled in or beyond the northwestern margin of the basin. The wells provide data on porosity, seal, maturation (geothermal and vitrinite reflectance data), and oil stains in sidewall cores of the Sockeye B-10 well in the Skonun formation, here 4500 m thick. The Skonun ranges from early Miocene (17 Ma) to latest Pliocene (2 Ma) in age and the lower part is regarded as the primary hydrocarbon objective, especially in the more southern part of the basin where more favorable depositional porosities occur in paralic and shelf sandstones. Higher-than-average geothermal temperatures, locally in the southwest corner of the basin related to oblique subduction of very young oceanic crust, may reach the hydrocarbon-generating threshold in the lower Skonun marine shales. The middle Cretaceous Haida subarkose appears to be a secondary reservoir - the thickest and cleanest of the post-collision volcaniclastics. Highly organic Lower Jurassic shales provide a second, probably oil-prone, source.

  15. Electrostatic interactions at the microscale modulate dynamics and distribution of lipids in bilayers.

    Science.gov (United States)

    Mangiarotti, Agustín; Wilke, Natalia

    2017-01-18

    For decades, it has been assumed that electrostatic long-range (micron distances) repulsions in lipid bilayers are negligible due to screening from the aqueous milieu. This concept, mostly derived from theoretical calculations, is broadly accepted in the biophysical community. Here we present experimental evidence showing that domain-domain electrostatic repulsions in charged and also in neutral lipid bilayers regulate the diffusion, in-plane structuring and merging of lipid domains in the micron range. All the experiments were performed on both, lipid monolayers and bilayers, and the remarkable similarity in the results found in bilayers compared to monolayers led us to propose that inter-domain repulsions occur mainly within the plane of the membrane. Finally, our results indicate that electrostatic interactions between the species inserted in a cell membrane are not negligible, not only at nanometric but also at larger distances, suggesting another manner for regulating the membrane properties.

  16. Quantifying the Relationship Between Curvature and Electric Potential in Lipid Bilayers

    DEFF Research Database (Denmark)

    Bruhn, Dennis Skjøth; Lomholt, Michael Andersen; Khandelia, Himanshu

    2016-01-01

    Cellular membranes mediate vital cellular processes by being subject to curvature and transmembrane electrical potentials. Here we build upon the existing theory for flexoelectricity in liquid crystals to quantify the coupling between lipid bilayer curvature and membrane potentials. Using molecular...

  17. Formation, Stability, and Mobility of One-Dimensional Lipid Bilayer on High Curvature Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J; Martinez, J; Artyukhin, A; Sirbuly, D; Wang, Y; Ju, J W; Stroeve, P; Noy, A

    2007-03-23

    Curved lipid membranes are ubiquitous in living systems and play an important role in many biological processes. To understand how curvature and lipid composition affect membrane formation and fluidity we have assembled and studied mixed 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC) and 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) supported lipid bilayers on amorphous silicon nanowires with controlled diameters ranging from 20 nm to 200 nm. Addition of cone-shaped DOPE molecules to cylindrical DOPC molecules promotes vesicle fusion and bilayer formation on smaller diameter nanowires. Our experiments demonstrate that nanowire-supported bilayers are mobile, exhibit fast recovery after photobleaching, and have low concentration of defects. Lipid diffusion coefficients in these high-curvature tubular membranes are comparable to the values reported for flat supported bilayers and increase with decreasing nanowire diameter.

  18. Camber Evolution and Stress Development of Porous Ceramic Bilayers During Co-Firing

    DEFF Research Database (Denmark)

    Ni, De Wei; Esposito, Vincenzo; Schmidt, Cristine Grings;

    2013-01-01

    Camber evolution and stress development during co-firing of asymmetric bilayer laminates, consisting of porous Ce0.9Gd0.1O1.95 gadolinium-doped cerium oxide (CGO) and La0.85Sr0.15MnO3 lanthanum strontium manganate (LSM)-CGO were investigated. Individual layer shrinkage was measured by optical...... dilatometer, and the uniaxial viscosities were determined as a function of layer density using a vertical sintering approach. The camber evolution in the bilayer laminates was recorded in situ during co-firing and it was found to correspond well with the one predicted by the theoretical model. The estimated...... sintering mismatch stress in co-fired CGO-LSM/CGO bilayer laminates was significantly lower than general sintering stresses expected for free sintering conditions. As a result, no co-firing defects were observed in the bilayer laminates, illustrating an acceptable sintering compatibility of the ceramic...

  19. Enhanced sensitivity of a microfabricated resonator using a graphene-polystyrene bilayer membrane

    Science.gov (United States)

    Yun, Minhyuk; Lee, Eunho; Cho, Kilwon; Jeon, Sangmin

    2014-08-01

    A graphene layer was synthesized using chemical vapor deposition methods and a polystyrene solution was spin-cast onto the graphene film. The graphene-polystyrene bilayer membrane was attached between the two tines of a microfabricated quartz tuning fork (QTF). The modulus of the graphene-polystyrene bilayer was measured to be twice that of a pristine polystyrene membrane. Exposure of the membrane-coated QTF to ethanol vapor decreased the resonance frequency of the microresonator. The bilayer membrane-coated QTF produced a frequency change that was three times the change obtained using a polystyrene membrane-coated QTF, with a lower degree of degradation in the Q factor. The limit of detection of the bilayer membrane-coated QTF to ethanol vapor was determined to be 20 ppm.

  20. Enhanced sensitivity of a microfabricated resonator using a graphene-polystyrene bilayer membrane

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Minhyuk; Lee, Eunho; Cho, Kilwon; Jeon, Sangmin, E-mail: jeons@postech.ac.kr [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of)

    2014-08-18

    A graphene layer was synthesized using chemical vapor deposition methods and a polystyrene solution was spin-cast onto the graphene film. The graphene-polystyrene bilayer membrane was attached between the two tines of a microfabricated quartz tuning fork (QTF). The modulus of the graphene-polystyrene bilayer was measured to be twice that of a pristine polystyrene membrane. Exposure of the membrane-coated QTF to ethanol vapor decreased the resonance frequency of the microresonator. The bilayer membrane-coated QTF produced a frequency change that was three times the change obtained using a polystyrene membrane-coated QTF, with a lower degree of degradation in the Q factor. The limit of detection of the bilayer membrane-coated QTF to ethanol vapor was determined to be 20 ppm.

  1. Lipid-Bilayer Dynamics Probed by a Carbon Dot-Phospholipid Conjugate.

    Science.gov (United States)

    Nandi, Sukhendu; Malishev, Ravit; Bhunia, Susanta Kumar; Kolusheva, Sofiya; Jopp, Jürgen; Jelinek, Raz

    2016-05-10

    Elucidating the dynamic properties of membranes is important for understanding fundamental cellular processes and for shedding light on the interactions of proteins, drugs, and viruses with the cell surface. Dynamic studies of lipid bilayers have been constrained, however, by the relatively small number of pertinent molecular probes and the limited physicochemical properties of the probes. We show that a lipid conjugate comprised of a fluorescent carbon dot (C-dot) covalently attached to a phospholipid constitutes a versatile and effective vehicle for studying bilayer dynamics. The C-dot-modified phospholipids readily incorporated within biomimetic membranes, including solid-supported bilayers and small and giant vesicles, and inserted into actual cellular membranes. We employed the C-dot-phospholipid probe to elucidate the effects of polymyxin-B (a cytolytic peptide), valproic acid (a lipophilic drug), and amyloid-β (a peptide associated with Alzheimer's disease) upon bilayer fluidity and lipid dynamics through the application of various biophysical techniques.

  2. Correlation effects in (111) bilayers of perovskite transition-metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Satoshi [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhu, Wenguang [Univ. of Science and Technology of China, Hefei (China); Nomura, Yusuke [Univ. of Tokyo (Japan); Arita, R. [Univ. of Tokyo (Japan); Xiao, Di [Carnegie Mellon Univ., Pittsburgh, PA (United States); Nagaosa, Naoto [Univ. of Tokyo (Japan); RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan)

    2014-05-15

    We investigate the correlation-induced Mott, magnetic, and topological phase transitions in artificial (111) bilayers of perovskite transition-metal oxides LaAuO3 and SrIrO3 for which the previous density-functional theory calculations predicted topological insulating states. Using the dynamical-mean-field theory with realistic band structures and Coulomb interactions, LaAuO3 bilayer is shown to be far away from a Mott insulating regime, and a topological-insulating state is robust. On the other hand, SrIrO3 bilayer is on the verge of an orbital-selective topological Mott transition and turns to a trivial insulator by an antiferromagnetic ordering. Oxide bilayers thus provide a novel class of topological materials for which the interplay between the spin-orbit coupling and electron-electron interactions is a fundamental ingredient.

  3. Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

    Science.gov (United States)

    Vu, Thanh-Tra; Tran, Van-Truong

    2016-08-01

    We theoretically investigate the effect of a transverse electric field generated by side gates and a vertical electric field generated by top/back gates on energy bands and transport properties of zigzag bilayer graphene ribbons (Bernal stacking). Using atomistic tight binding calculations and Green’s function formalism we demonstrate that a bandgap is opened when either field is applied and even enlarged under simultaneous influence of the two fields. Interestingly, although vertical electric fields are widely used to control the bandgap in bilayer graphene, here we show that transverse fields exhibit a more positive effect in terms of modulating a larger range of bandgap and retaining good electrical conductance. The Seebeck effect is also demonstrated to be enhanced strongly—by about 13 times for a zigzag bilayer graphene ribbon with 16 chain lines. These results may motivate new designs of devices made of bilayer graphene ribbons using electric gates.

  4. Role of interlayer spacing in electrical transport of bilayer graphene nanoribbon: Perpendicular and armchair direction

    Science.gov (United States)

    Jamaati, Maryam; Namiranian, Afshin

    2017-01-01

    The electrical conductance of bilayer zigzag graphene nanoribbon is numerically investigated taking advantage of Green's function. The calculations are performed within the tight binding model, which describes the interaction between carbon atoms within a layer via nearest neighbor and carbon atoms of different layers using continuum model. Our findings reveal sensitivity of the bilayer graphene conductance to changes in its relative displacement of two layers in perpendicular and armchair directions. We find that the conductance oscillates as a function of system width, and finally reduces rapidly as the relative distance of two layers becomes larger than half the system width. The results show that the conductance of the bilayer graphene could be tuned via displacement of two layers. Moreover, we obtain different results for conductance of narrow and wide bilayer nanoribbon.

  5. Using supercritical fluids to refine hydrocarbons

    Science.gov (United States)

    Yarbro, Stephen Lee

    2015-06-09

    A system and method for reactively refining hydrocarbons, such as heavy oils with API gravities of less than 20 degrees and bitumen-like hydrocarbons with viscosities greater than 1000 cp at standard temperature and pressure, using a selected fluid at supercritical conditions. A reaction portion of the system and method delivers lightweight, volatile hydrocarbons to an associated contacting unit which operates in mixed subcritical/supercritical or supercritical modes. Using thermal diffusion, multiphase contact, or a momentum generating pressure gradient, the contacting unit separates the reaction products into portions that are viable for use or sale without further conventional refining and hydro-processing techniques.

  6. Plasma Assisted Combustion Mechanism for Small Hydrocarbons

    Science.gov (United States)

    2015-01-01

    Andrey Starikovskiy Nickolay Aleksandrov PRINCETON University Plasma Assisted Combustion  Mechanism for Small  Hydrocarbons Report Documentation Page...COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Plasma Assisted Combustion Mechanism for Small Hydrocarbons 5a. CONTRACT NUMBER 5b...Kinetics of ignition of saturated  hydrocarbons  by nonequilibrium plasma: C2H6‐ to C5H12‐containing mixtures. Combustion and Flame 156  (2009) 221–233

  7. Waste Plastic Converting into Hydrocarbon Fuel Materials

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, Moinuddin; Mamunor Rashid, Mohammad; Molla, Mohammad

    2010-09-15

    The increased demand and high prices for energy sources are driving efforts to convert organic compounds into useful hydrocarbon fuels. Although much of this work has focused on biomass, there are strong benefits to deriving fuels from waste plastic material. Natural State Research Inc. (NSR) has invented a simple and economically viable process to decompose the hydrocarbon polymers of waste plastic into the shorter chain hydrocarbon of liquid fuel (patent pending). The method and principle of the production / process will be discussed. Initial tests with several widely used polymers indicate a high potential for commercialization.

  8. High-yield chemical vapor deposition growth of high-quality large-area AB-stacked bilayer graphene.

    Science.gov (United States)

    Liu, Lixin; Zhou, Hailong; Cheng, Rui; Yu, Woo Jong; Liu, Yuan; Chen, Yu; Shaw, Jonathan; Zhong, Xing; Huang, Yu; Duan, Xiangfeng

    2012-09-25

    Bernal-stacked (AB-stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electric field. Mechanical exfoliation can be used to produce AB-stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB- and randomly stacked structures. Herein we report a rational approach to produce large-area high-quality AB-stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H(2)/CH(4) ratio in a low-pressure CVD process to enable the continued growth of bilayer graphene. A high-temperature and low-pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90%) and high coverage (up to 99%). The electrical transport studies demonstrate that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB-stacked bilayer graphene with the highest carrier mobility exceeding 4000 cm(2)/V · s at room temperature, comparable to that of the exfoliated bilayer graphene.

  9. Sediment Core Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides instrumentation and expertise for physical and geoacoustic characterization of marine sediments.DESCRIPTION: The multisensor core logger measures...

  10. Sediment Core Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Provides instrumentation and expertise for physical and geoacoustic characterization of marine sediments. DESCRIPTION: The multisensor core logger measures...

  11. Dynamic Response of Metal-Polymer Bilayers - Viscoelasticity, Adhesion and Failure

    Science.gov (United States)

    2013-11-25

    stretch of two at a strain rate of 103 s_1 a pulse duration of 2 ms is required! Recently, Youssef and Gupta [8] have developed a laser ablation based...Dynamic Response of Metal -Polymer Bilayers and Failure Viscoelasticity, Adhesion Sa. CONTRACT NUMBER 5b. GRANT NUMBER N00014-09-1-0541 5c...Contract Number N00014-09-1-0541 Title of Research Dynamic Response of Metal -Polymer Bilayers - Viscoelasticity, Adhesion and Failure Principal

  12. Bimodal Distribution and Fluorescence Response of Environment-Sensitive Probes in Lipid Bilayers

    OpenAIRE

    Klymchenko, Andrey S; Duportail, Guy; Demchenko, Alexander P.; Mély, Yves

    2004-01-01

    A remarkable heterogeneity is often observed in the spectroscopic properties of environment-sensitive fluorescence probes in phospholipid bilayers. To explain its origin, we provided a detailed investigation of the fluorescence excitation and emission spectra of 4′-dimethylamino-3-hydroxyflavone (probe F) in bilayer vesicles with the variations of fatty acid composition, polar heads, temperature, and cholesterol content. Probe F, due to excited-state intramolecular proton transfer, exhibits t...

  13. Quantum transport in bilayer graphene. Fabry-Perot interferences and proximity-induced superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Du, Renjun

    2015-10-30

    Bilayer graphene (BLG) p-n junctions made of hBN-BLG-hBN (hexagonal boron nitride) heterostructures enable ballistic transport over long distances. We investigate Fabry-Perot interferences, and detect that the bilayer-like anti-Klein tunneling transits into single-layer-like Klein tunneling when tuning the Fermi level towards the band edges. Furthermore, the proximity-induced superconductivity has been studied in these devices with Al leads.

  14. Imaging and Analysis of OT1 T Cell Activation on Lipid Bilayers

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Peter Beemiller, Jordan Jacobelli & Matthew Krummel ### Abstract Supported lipid bilayers are frequently used to study cell membrane protein dynamics during immune synapse formation by T cells. Here we describe methods for the imaging and analysis of OT1+ T cell activation and T-cell receptor (TCR) dynamics on lipid bilayers. ### Introduction T cells are activated at immune synapses when TCRs bind agonist ligands on antigen presenting cells (APCs). Glass cover...

  15. Structure and Dynamics in Amphiphilic Bilayers: NMR and MD simulation Studies

    OpenAIRE

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations were employed to study molecular structure and dynamics in amphiphilic bilayers. This thesis reports on method development and practical applications to two types of bilayer systems: simple cell membrane models composed of phosphatidylcholine lipids and cholesterol; and liquid crystals composed of ethyleneoxide-based surfactants often used in technological applications and in fundamental studies ...

  16. Origin of the hysteresis in bilayer 2D systems in the quantum Hall regime

    OpenAIRE

    Ho, L. H.; Taskinen, L. J.; Micolich, A.P.; Hamilton, A. R.; Atkinson, P.; Ritchie, D. A.

    2010-01-01

    The hysteresis observed in the magnetoresistance of bilayer 2D systems in the quantum Hall regime is generally attributed to the long time constant for charge transfer between the 2D systems due to the very low conductivity of the quantum Hall bulk states. We report electrometry measurements of a bilayer 2D system that demonstrate that the hysteresis is instead due to non-equilibrium induced current. This finding is consistent with magnetometry and electrometry measurements of single 2D syste...

  17. Micromachined glass apertures for artificial lipid bilayer formation in a microfluidic system

    OpenAIRE

    Sandison, M.E.; Zagnoni, M.; Abu-Hantash, M.; Morgan, H

    2007-01-01

    The use of spark assisted chemical engraving (SACE) to produce glass apertures that are suitable for the formation of artificial bilayer lipid membranes is described. Prior to use, the glass apertures were rendered hydrophobic by a silanization process and were then incorporated into a simple microfluidic device. Successful bilayer lipid membrane (BLM) formation and the subsequent acquisition of single-channel recordings are demonstrated. Due to the simplicity and rapidity of the SACE process...

  18. 21 CFR 178.3530 - Isoparaffinic petroleum hydrocarbons, synthetic.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Isoparaffinic petroleum hydrocarbons, synthetic... hydrocarbons, synthetic. Isoparaffinic petroleum hydrocarbons, synthetic, may be safely used in the production... isoparaffinic petroleum hydrocarbons, produced by synthesis from petroleum gases consist of a mixture of...

  19. 21 CFR 172.882 - Synthetic isoparaffinic petroleum hydrocarbons.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Synthetic isoparaffinic petroleum hydrocarbons. 172... hydrocarbons. Synthetic isoparaffinic petroleum hydrocarbons may be safely used in food, in accordance with the... liquid hydrocarbons meeting the following specifications: Boiling point 93-260 °C as determined by...

  20. 40 CFR 86.317-79 - Hydrocarbon analyzer specifications.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Hydrocarbon analyzer specifications....317-79 Hydrocarbon analyzer specifications. (a) Hydrocarbon measurements are to be made with a heated... measures hydrocarbon emissions on a dry basis is permitted for gasoline-fueled testing; Provided,...

  1. 40 CFR 92.119 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 92... Hydrocarbon analyzer calibration. The HFID hydrocarbon analyzer shall receive the following initial and... into service and at least annually thereafter, the HFID hydrocarbon analyzer shall be adjusted...

  2. 40 CFR 86.1321-94 - Hydrocarbon analyzer calibration.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Hydrocarbon analyzer calibration. 86... Procedures § 86.1321-94 Hydrocarbon analyzer calibration. The FID hydrocarbon analyzer shall receive the... into service and at least annually thereafter, the FID hydrocarbon analyzer shall be adjusted...

  3. Simulation studies of protein-induced bilayer deformations, and lipid-induced protein tilting, on a mesoscopic model for lipid bilayers with embedded proteins

    DEFF Research Database (Denmark)

    Venturoli, M.; Smit, B.; Sperotto, Maria Maddalena

    2005-01-01

    for positive values of mismatch; a dependence on the protein size appears as well. In the case of large model proteins experiencing extreme mismatch conditions, in the region next to the so-called lipid annulus, there appears an undershooting ( or overshooting) region where the bilayer hydrophobic thickness...... a small size, the main mechanism to compensate for a large hydrophobic mismatch is the tilt, whereas large proteins react to negative mismatch by causing an increase of the hydrophobic thickness of the nearby bilayer. Furthermore, for the case of small, peptidelike proteins, we found the same type...

  4. Formation of individual protein channels in lipid bilayers suspended in nanopores.

    Science.gov (United States)

    Studer, André; Han, Xiaojun; Winkler, Fritz K; Tiefenauer, Louis X

    2009-10-15

    Free-standing lipid bilayers are formed in regularly arranged nanopores of 200, 400 and 800 nm in a 300 nm thin hydrophobic silicon nitride membrane separating two fluid compartments. The extraordinary stability of the lipid bilayers allows us to monitor channel formation of the model peptide melittin and alpha-hemolysin from Staphylococcus aureus using electrochemical impedance spectroscopy and chronoamperometry. We observed that melittin channel formation is voltage-dependent and transient, whereas transmembrane heptameric alpha-hemolysin channels in nano-BLMs persist for hours. The onset of alpha-hemolysin-mediated conduction depends on the applied protein concentration and strongly on the diameter of the nanopores. Heptameric channel formation from adsorbed alpha-hemolysin monomers needs more time in bilayers suspended in 200 nm pores compared to bilayers in pores of 400 and 800 nm diameters. Diffusion of sodium ions across alpha-hemolysin channels present in a sufficiently high number in the bilayers was quantitatively and specifically determined using ion selective electrodes. The results demonstrate that relatively small variations of nano-dimensions have a tremendous effect on observable dynamic biomolecular processes. Such nanopore chips are potentially useful as supports for stable lipid bilayers to establish functional assays of membrane proteins needed in basic research and drug discovery.

  5. Topological phase transition in hexagonal boron-nitride bilayers modulated by gate voltage

    Science.gov (United States)

    Jin, Guojun; Zhai, Xuechao

    2013-03-01

    We study the gate-voltage modulated electronic properties of hexagonal boron-nitride bilayers with two different stacking structures in the presence of intrinsic and Rashba spin-orbit interactions. Our analytical results show that there are striking cooperation effects arising from the spin-orbit interactions and the interlayer bias voltage. For realizing topological phase transition, in contrast to a gated graphene bilayer for increasing its energy gap, the energy gap of a boron-nitride bilayer is significantly reduced by an applied gate voltage. For the AA stacking-bilayer which has the inversion symmetry, a strong topological phase is found, and there is an interesting reentrant behavior from a normal phase to a topological phase and then to a normal phase again, characterized by the topological index. Therefore, the gate voltage modulated AA-boron nitride bilayer can be taken as a newcomer of the topological insulator family. For the AB stacking-bilayer which is lack of the inversion symmetry, it is always topologically trivial, but exhibits an unusual quantum Hall phase with four degenerate low-energy states localized at a single edge. It is suggested that these theoretical findings could be verified experimentally in the transport properties of boron-nitride bylayers. This research was supported by the NSFC (Nos. 60876065, 11074108), PAPD, and NBRPC (Nos. 2009CB929504, 2011CB922102).

  6. Influence of membrane surface charge on adsorption of complement proteins onto supported lipid bilayers.

    Science.gov (United States)

    Yorulmaz, Saziye; Jackman, Joshua A; Hunziker, Walter; Cho, Nam-Joon

    2016-12-01

    The complement system is an important part of the innate immune response, and there is great interest in understanding how complement proteins interact with lipid membrane interfaces, especially in the context of recognizing foreign particulates (e.g., liposomal nanomedicines). Herein, a supported lipid bilayer platform was employed in order to investigate the effect of membrane surface charge (positive, negative, or neutral) on the adsorption of three complement proteins. Quartz crystal microbalance-dissipation (QCM-D) experiments measured the real-time kinetics and total uptake of protein adsorption onto supported lipid bilayers. The results demonstrate that all three proteins exhibit preferential, mainly irreversible adsorption onto negatively charged lipid bilayers, yet there was also significant variation in total uptake and the relative degree of adsorption onto negatively charged bilayers versus neutral and positively charged bilayers. The total uptake was also observed to strongly depend on the bulk protein concentration. Taken together, our findings contribute to a broader understanding of the factors which influence adsorption of complement proteins onto lipid membranes and offer guidance towards the design of synthetic lipid bilayers with immunocompetent features.

  7. Self-assembly of Asymmetric Dimer Particles in Supported Copolymer Bilayer

    Institute of Scientific and Technical Information of China (English)

    Xiao-chun Qin; Chun-lai Ren

    2011-01-01

    Using self-consistent field and density functional theories, we investigate the self-assembly behavior of asymmetric dimer particles in a supported AB block copolymer bilayer. Asymmetric dimer particles are amphiphilic molecules composed by two different spheres. One prefers to A block of copolymers and the other likes B block when they are introduced into the copolymer bilayer. The two layer structure of the dimer particles is formed within the bilayer.Due to the presence of the substrate surface, the symmetry of the two leaflets of the bilayer is broken, which may lead to two different layer structures of dimer particles within each leaflet of the bilayer. With the increasing concentration of the asymmetric dimer particles,in-plane structure of the dimer particles undergoes sparse square, hexagonal, dense square, and cylindrical structures. In a further condensed packing, a bending cylindrical structure comes into being. Here we verify that the entropic effect of copolymers, the enthalpy of the system and the steric repulsion of the dimer particles are three important factors determing the self-assembly of dimer particles within the supported copolymer bilayer.

  8. The induced nontrivial Z 2 topological phase in graphene sandwiched by pnictogen bilayers.

    Science.gov (United States)

    Shu, Cheng; Qu, Jinfeng; Peng, Xiangyang; Yang, Hong; Liu, Wenliang; Wei, Xiaolin; Zhang, Kaiwang; Zhong, Jianxin

    2016-06-15

    By performing first-principles calculations, we find that graphene with nearly zero spin orbit coupling can be turned into a topological insulator after being sandwiched between pnictogen bilayers. It is found that a dipole field is induced between graphene and pnictogen bilayers, which will significantly pull down the Dirac point of graphene. Depending on the initial position of the Dirac point of graphene with respect to the energy gap of the pnictogen bilayers, Bi/graphene/Bi is found to be a metallic system while Sb/graphene/Sb a topological insulator. In Sb/graphene/Sb, a sizable gap is opened at the Dirac point of graphene. The strong spin-orbit coupling in Sb bilayers leads to a band inversion in the gapped Dirac cones of graphene via the proximity effect and the calculated Z 2 topological index further confirms that a nontrivial topological phase is induced in graphene. By applying longitudinal or lateral strains to Sb/graphene/Sb, topological phase transition occurs based on the change of the thickness of the Sb bilayer instead of the change of the separation between graphene and Sb bilayers.

  9. Kinetics and Thermodynamics of Peptide (pHLIP) insertion and folding in a lipid bilayer

    Science.gov (United States)

    Andreev, Oleg; Karabadzhak, Alexander; Weerakkody, Dhammika; Markin, Vladislav; Engelman, Donald; Reshetnyak, Yana

    2009-03-01

    We study spontaneous insertion and folding across a lipid bilayer of moderately polar membrane peptide pHLIP - pH Low Insertion Peptide. pHLIP has three major states: soluble in water or bound to the surface of a lipid bilayer as an unstructured monomer, and inserted across the bilayer as a monomeric α-helix. We used fluorescence spectroscopy and isothermal titration calorimetry to calculate the transition energies between states. The free energy of binding to a surface of lipid bilayer is about -7 kcal/mol and the free energy of insertion and folding across a lipid bilayer at low pH is nearly -2 kcal/mol. We performed stopped-flow fluorescence and CD measurements to elucidate molecular mechanism of pHLIP insertion and folding within a lipid bilayer and to calculate the activation energy of formation of transmembrane helix. pHLIP also has utility as an agent to target diseased tissues and translocate molecules through the membrane into the cytoplasm of cells in environments with elevated levels of extracellular acidity, as in cancer and inflammation. We plan to discuss a number of related kinetics and thermodynamic parameters from our measurements.

  10. Mechanical properties of electrospun bilayer fibrous membranes as potential scaffolds for tissue engineering.

    Science.gov (United States)

    Pu, Juan; Komvopoulos, Kyriakos

    2014-06-01

    Bilayer fibrous membranes of poly(l-lactic acid) (PLLA) were fabricated by electrospinning, using a parallel-disk mandrel configuration that resulted in the sequential deposition of a layer with fibers aligned across the two parallel disks and a layer with randomly oriented fibers, both layers deposited in a single process step. Membrane structure and fiber alignment were characterized by scanning electron microscopy and two-dimensional fast Fourier transform. Because of the intricacies of the generated electric field, bilayer membranes exhibited higher porosity than single-layer membranes consisting of randomly oriented fibers fabricated with a solid-drum collector. However, despite their higher porosity, bilayer membranes demonstrated generally higher elastic modulus, yield strength and toughness than single-layer membranes with random fibers. Bilayer membrane deformation at relatively high strain rates comprised multiple abrupt microfracture events characterized by discontinuous fiber breakage. Bilayer membrane elongation yielded excessive necking of the layer with random fibers and remarkable fiber stretching (on the order of 400%) in the layer with fibers aligned in the stress direction. In addition, fibers in both layers exhibited multiple localized necking, attributed to the nonuniform distribution of crystalline phases in the fibrillar structure. The high membrane porosity, good mechanical properties, and good biocompatibility and biodegradability of PLLA (demonstrated in previous studies) make the present bilayer membranes good scaffold candidates for a wide range of tissue engineering applications.

  11. Dissipative particle dynamics simulation study of the bilayer-vesicle transition

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A bilayer structure is an important immediate for the vesicle formation. However,the mechanism for the bilayer-vesicle transition remains unclear. In this work,a dissipative particle dynamics(DPD) simulation method was employed to study the mechanism of the bilayer-vesicle transition. A coarse-grained model was built based on a lipid molecule termed dimyristoylphosphatidylcholine(DMPC). Simulations were performed from two different initial configurations:a random dispersed solution and a tensionless bilayer. It was found that the bilayer-vesicle transition was driven by the minimization of the water-tail hydrophobic interaction energy,and was accompanied with the increase of the position entropy due to the redistribution of water molecules. The bulk pressure was reduced during the bilayer-vesicle transition,suggesting the evolved vesicle morphology was at the relatively low free energy state. The membrane in the product vesicle was a two-dimensional fluid. It can be concluded that the membrane of a vesicle is not interdigitated and most of the bonds in lipid chains are inclined to orient along the radical axis of the vesicle.

  12. Evaluation and biological characterization of bilayer gelatin/chondroitin-6-sulphate/hyaluronic acid membrane.

    Science.gov (United States)

    Wang, Tzu-Wei; Sun, Jui-Sheng; Wu, Hsi-Chin; Huang, Yi-Chau; Lin, Feng-Huei

    2007-08-01

    A biodegradable polymer scaffold was developed using gelatin, chondroitin-6-sulphate, and hyaluronic acid in the form of bilayer network. The bilayer porous structure of gelatin-chondroitin-6-sulphate-hyaluronic acid (G-C6S-HA) membrane was fabricated using different freezing temperatures followed by lyophilization. 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide was used as crosslinking agent to improve the biological stability of the scaffold. The morphology, physical-chemical properties, and biocompatibility of bilayer G-C6S-HA membrane were evaluated in this study. The functional groups change in crosslinked G-C6S-HA scaffold was characterized by fourier transform infrared spectroscopy. The retention of glycosaminoglycan contents and matrix degradation rate were also examined by p-dimethylamino benzaldehyde and 2,4,6-trinitrobenzene sulphonic acid, respectively. Water absorption capacity was carried out to study G-C6S-HA membrane water containing characteristics. The morphology of the bilayer G-C6S-HA membrane was investigated under scanning electron microscope and light microscopy. In vitro biocompatibility was conducted with MTT test, LDH assay, as well as histological analysis. The results showed that the morphology of bilayer G-C6S-HA membrane was well reserved. The physical-chemical properties were also adequate. With good biocompatibility, this bilayer G-C6S-HA membrane would be suitable as a matrix in the application of tissue engineering.

  13. Design and evaluation of lornoxicam bilayered tablets for biphasic release

    Directory of Open Access Journals (Sweden)

    Songa Ambedkar Sunil

    2012-12-01

    Full Text Available The objective of the present investigation was to develop bilayered tablets of lornoxicam to achieve biphasic release pattern. A bilayered tablet, consisting of an immediate and controlled release layer, was prepared by direct compression technique. The controlled release effect was achieved by using various hydrophilic natural, semi synthetic and synthetic controlled release polymers such as xanthan gum, hydroxypropyl methylcellulose (HPMC and polyethylene oxide (PEO to modulate the release of the drug. The in vitro drug release profiles showed the biphasic release behavior in which the immediate release (IR layer containing the lornoxicam was released within 15 minutes, whereas the controlled release (CR layer controlled the drug release for up to 24 h. All the bilayered tablets formulated have followed the zero order release with non-Fickian diffusion controlled release mechanism after the initial burst release. FTIR studies revealed that there was no interaction between the drug and polymers used in the study. Statistical analysis (ANOVA showed no significant difference in the cumulative amount of drug release after 15 min, but significant difference (p O objetivo do presente trabalho foi desenvolver comprimidos bicamada de lornoxicam para atingir padrão de liberação bifásica. Preparou-se, por compressão direta, comprimido bicamada, consistindo de uma camada de liberação imediata e uma de liberação controlada. A liberação controlada foi obtida pelo uso de vários polímeros naturais hidrofílicos, semi-sintéticos e sintéticos, tais como goma xantana, hidroxipropilmetil celulose (HPMC e óxido de polietileno (PEO para modular a liberação do fármaco. Os perfis de liberação in vitro mostraram comportamento bifásico em que a camada de liberação imediata (IR contendo lornoxicam foi liberada em 15 minutos, enquanto a camada de liberação controlada (CR liberou o fármaco em mais de 24 horas, Todos os comprimidos bicamada

  14. Simulated microgravity impacts the plant plasmalemma lipid bilayer

    Science.gov (United States)

    Nedukha, Olena; Berkovich, Yuliy A.; Vorobyeva, Tamara; Grakhov, Volodimir; Klimenko, Elena; Zhupanov, Ivan; Jadko, Sergiy

    Biological membranes, especially the plasmalemma, and their properties and functions can be considered one of the most sensitive indicators of gravity interaction or alteration of gravity, respectively. Studies on the molecular basis of cellular signal perception and transduction are very important in order to understand signal responses at the cellular and organism level. The plasmalemma lipid bilayer is the boundary between the cell internal and external environment and mediates communication between them. Therefore, we studied the content and composition of lipids, saturated and unsaturated fatty acids, sterols, and microviscosity in the plasmalemma isolated from pea seedling roots and epicotyls grown in the stationary conditions and under slow horizontal clinorotation. In addition, lipid peroxidation intensity of intact roots was also identified. The plasmalemma fraction was isolated by the two-phase aquatic-polymer system optimized for pea using a centrifuge Optima L-90K. Lipid bilayer components were determined by using highly effective liquid chromatography with a system Angilent 1100 (Germany). Spontaneous chemiluminescence intensity was measured with a chemiluminometer ChLMTS-01. The obtained data showed that plasmalemma investigated parameters are sensitive to clinorotation, namely: increasing or decreasing the different lipids content, among which, phospho- and glycolipids were dominated, as well as changes in the content of saturated and unsaturated fatty acids and sterols. A degree of plasmalemma sensitivity to clinorotation was higher for the root plasmalemma than epicocotyl ones. This distinguish may be naturally explained by the differences in the structure, cell types, growth, and specific functions of a root and an epicotyl, those are the most complicated in roots. An index of unsaturation under clinorotation was similar to that in the stationary conditions as a result of the certain balance between changes in the content of saturated and

  15. Biodegradation of polycyclic hydrocarbons by Phanerochaete chrysosporium

    Science.gov (United States)

    The ability of the white rot fungus Phanerochaete chrysosporium to degrade polycyclic aromatic hydrocarbons (PAHs) that are present in anthracene oil (a distillation product obtained from coal tar) was demonstrated. Analysis by capillary gas chromatography and high-performance li...

  16. Volatilisation of aromatic hydrocarbons from soil

    DEFF Research Database (Denmark)

    Lindhardt, B.; Christensen, T.H.

    1996-01-01

    The non-steady-state fluxes of aromatic hydrocarbons were measured in the laboratory from the surface of soils contaminated with coal tar Four soil samples from a former gasworks site were used for the experiments. The fluxes were quantified for 11 selected compounds, 4 mono- and 7 polycyclic...... aromatic hydrocarbons, for a period of up to 8 or 16 days. The concentrations of the selected compounds in the soils were between 0.2 and 3,100 mu g/g. The study included the experimental determination of the distribution coefficient of the aromatic hydrocarbons between the sorbed phase and the water under...... saturated conditions. The determined distribution coefficients showed that the aromatic hydrocarbons were more strongly sorbed to the total organic carbon including the coal tar pitch - by a factor of 8 to 25 - than expected for natural organic matter. The fluxes were also estimated using an analytical...

  17. Informative document halogenated hydrocarbon-containing waste

    NARCIS (Netherlands)

    Verhagen H

    1992-01-01

    This "Informative document halogenated hydrocarbon-containing waste" forms part of a series of "Informative documents waste materials". These documents are conducted by RIVM on the instructions of the Directorate General for the Environment, Waste Materials Directorate, in behal

  18. Infrared Spectra of Polycyclic Aromatic Hydrocarbons (PAHs)

    Science.gov (United States)

    Bauschlicher, Charles W., Jr.; Bakes, E. L. O.

    2000-01-01

    We have computed the synthetic infrared spectra of some polycyclic aromatic hydrocarbons containing up to 54 carbon atoms. The species studied include ovalene, circumcoronene, dicoronylene, and hexabenzocoronene. We report spectra for anions, neutrals, cations, and multiply charged cations.

  19. Nitrocarburizing in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2011-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammonia-propene-hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...

  20. Nitrocarburising in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammoniapropene- hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...

  1. Evidence that bilayer bending rigidity affects membrane protein folding.

    Science.gov (United States)

    Booth, P J; Riley, M L; Flitsch, S L; Templer, R H; Farooq, A; Curran, A R; Chadborn, N; Wright, P

    1997-01-07

    The regeneration kinetics of the integral membrane protein bacteriorhodopsin have been investigated in a lipid-based refolding system. Previous studies on bacteriorhodopsin regeneration have involved detergent-based systems, and in particular mixed dimyristoylphosphatidylcholine (DMPC)/CHAPS micelles. Here, we show that the short chain lipid dihexanoylphosphatidylcholine (DHPC) can be substituted for the detergent CHAPS and that bacteriorhodopsin can be regenerated to high yield in mixed DMPC/DHPC micelles. Bacteriorhodopsin refolding kinetics are measured in the mixed DMPC/DHPC micelles. Rapid, stopped flow mixing is employed to initiate refolding of denatured bacterioopsin in SDS micelles with mixed DMPC/DHPC micelles and time-resolved fluorescence spectroscopy to follow changes in protein fluorescence during folding. Essentially identical refolding kinetics are observed for mixed DMPC/CHAPS and mixed DMPC/DHPC micelles. Only one second-order retinal/apoprotein reaction is identified, in which retinal binds to a partially folded apoprotein intermediate, and the free energy of this retinal binding reaction is found to be the same in both types of mixed micelles. Formation of the partially folded apoprotein intermediate is a rate-limiting step in protein folding and appears to be biexponential. Both apparent rate constants are found to be dependent on the relative proportion of DMPC present in the mixed DMPC/DHPC micelles as well as on the pH of the aqueous phase. Increasing the DMPC concentration should increase the bending rigidity of the amphiphilic bilayer, and this is found to slow the rate of formation of the partially folded apoprotein intermediate. Increasing the mole fraction of DMPC from 0.3 to 0.6 slows the two apparent rate constants associated with formation of this intermediate from 0.29 and 0.031 to 0.11 and 0.013 s-1, respectively. Formation of the intermediate also slows with increasing pH, from 0.11 and 0.013 s-1 at pH 6 to 0.033 and 0.0053 s-1 at

  2. Macroporous polymer foams by hydrocarbon templating

    OpenAIRE

    Shastri, Venkatram Prasad; Martin, Ivan; Langer, Robert

    2000-01-01

    Porous polymeric media (polymer foams) are utilized in a wide range of applications, such as thermal and mechanical insulators, solid supports for catalysis, and medical devices. A process for the production of polymer foams has been developed. This process, which is applicable to a wide range of polymers, uses a hydrocarbon particulate phase as a template for the precipitation of the polymer phase and subsequent pore formation. The use of a hydrocarbon template allows for enhanced control ov...

  3. Pyrolysis of hydrocarbons from lignite semicoking tar

    Energy Technology Data Exchange (ETDEWEB)

    Platonov, V.V.; Ryl' tsova, S.V.; Proskuryakov, V.A.; Rozental, D.A.; Polovetskaya, O.S.

    2000-07-01

    Pyrolysis of hydrocarbons from lignite semicoking tar in the range 750-900{degree}C at a contact time within 0.5-6.0 s was studied. The yields of pyrocarbons, pyrolysis gas, and liquid products and the group and component compositions of the liquid and gaseous products were determined. The optimal pyrolysis parameters from the viewpoint of obtaining the maximal yield of particular 'secondary' hydrocarbons were recommended.

  4. The future of oil and hydrocarbon man

    CERN Document Server

    Campbell, Colin

    1999-01-01

    Man appeared on the planet about four million years ago, and by 1850 numbered about one billion Ten came Hydrocarbon man. World population has since increased six-fold. After the oil price shocks of the 1970s, people asked "when will production peak?". It is not easy to answer this question because of the very poor database. Reserves and the many different hydrocarbon categories are poorly defined, reporting practices are ambiguous, revisions are not backdated...

  5. Zeolitic catalytic conversion of alochols to hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Narula, Chaitanya K.; Davison, Brian H.; Keller, Martin

    2017-01-03

    A method for converting an alcohol to a hydrocarbon, the method comprising contacting said alcohol with a metal-loaded zeolite catalyst at a temperature of at least 100.degree. C. and up to 550.degree. C., wherein said alcohol can be produced by a fermentation process, said metal is a positively-charged metal ion, and said metal-loaded zeolite catalyst is catalytically active for converting said alcohol to said hydrocarbon.

  6. Making an Ice Core.

    Science.gov (United States)

    Kopaska-Merkel, David C.

    1995-01-01

    Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

  7. Ice Core Investigations

    Science.gov (United States)

    Krim, Jessica; Brody, Michael

    2008-01-01

    What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

  8. Iowa Core Annual Report

    Science.gov (United States)

    Iowa Department of Education, 2015

    2015-01-01

    One central component of a great school system is a clear set of expectations, or standards, that educators help all students reach. In Iowa, that effort is known as the Iowa Core. The Iowa Core represents the statewide academic standards, which describe what students should know and be able to do in math, science, English language arts, and…

  9. Mercury's core evolution

    Science.gov (United States)

    Deproost, Marie-Hélène; Rivoldini, Attilio; Van Hoolst, Tim

    2016-10-01

    Remote sensing data of Mercury's surface by MESSENGER indicate that Mercury formed under reducing conditions. As a consequence, silicon is likely the main light element in the core together with a possible small fraction of sulfur. Compared to sulfur, which does almost not partition into solid iron at Mercury's core conditions and strongly decreases the melting temperature, silicon partitions almost equally well between solid and liquid iron and is not very effective at reducing the melting temperature of iron. Silicon as the major light element constituent instead of sulfur therefore implies a significantly higher core liquidus temperature and a decrease in the vigor of compositional convection generated by the release of light elements upon inner core formation.Due to the immiscibility in liquid Fe-Si-S at low pressure (below 15 GPa), the core might also not be homogeneous and consist of an inner S-poor Fe-Si core below a thinner Si-poor Fe-S layer. Here, we study the consequences of a silicon-rich core and the effect of the blanketing Fe-S layer on the thermal evolution of Mercury's core and on the generation of a magnetic field.

  10. Microbial biodegradation of polyaromatic hydrocarbons.

    Science.gov (United States)

    Peng, Ri-He; Xiong, Ai-Sheng; Xue, Yong; Fu, Xiao-Yan; Gao, Feng; Zhao, Wei; Tian, Yong-Sheng; Yao, Quan-Hong

    2008-11-01

    Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenicity and carcinogenicity. Because of their hydrophobic nature, most PAHs bind to particulates in soil and sediments, rendering them less available for biological uptake. Microbial degradation represents the major mechanism responsible for the ecological recovery of PAH-contaminated sites. The goal of this review is to provide an outline of the current knowledge of microbial PAH catabolism. In the past decade, the genetic regulation of the pathway involved in naphthalene degradation by different gram-negative and gram-positive bacteria was studied in great detail. Based on both genomic and proteomic data, a deeper understanding of some high-molecular-weight PAH degradation pathways in bacteria was provided. The ability of nonligninolytic and ligninolytic fungi to transform or metabolize PAH pollutants has received considerable attention, and the biochemical principles underlying the degradation of PAHs were examined. In addition, this review summarizes the information known about the biochemical processes that determine the fate of the individual components of PAH mixtures in polluted ecosystems. A deeper understanding of the microorganism-mediated mechanisms of catalysis of PAHs will facilitate the development of new methods to enhance the bioremediation of PAH-contaminated sites.

  11. Birds and polycyclic aromatic hydrocarbons

    Science.gov (United States)

    Albers, P.H.

    2006-01-01

    Polycyclic aromatic hydrocarbons (PAH) are present throughout the global environment and are produced naturally and by activities of humans. Effects of PAH on birds have been determined by studies employing egg injection, egg immersion, egg shell application, single and multiple oral doses, subcutaneous injection, and chemical analysis of field-collected eggs and tissue. The four-to six-ring aromatic compounds are the most toxic to embryos, young birds, and adult birds. For embryos, effects include death, developmental abnormalities, and a variety of cellular and biochemical responses. For adult and young birds, effects include reduced egg production and hatching, increased clutch or brood abandonment, reduced growth, increased organweights, and a variety of biochemical responses. Trophic level accumulation is unlikely. Environmental exposure to PAH in areas of high human population or habitats affected by recent petroleum spills might be sufficient to adversely affect reproduction. Evidence of long-term effects of elevated concentrations of environmental PAH on bird populations is very limited and the mechanisms of effect are unclear.

  12. Deuterated polycyclic aromatic hydrocarbons: Revisited

    CERN Document Server

    Doney, Kirstin D; Mori, Tamami; Onaka, Takashi; Tielens, A G G M

    2016-01-01

    The amount of deuterium locked up in polycyclic aromatic hydrocarbons (PAHs) has to date been an uncertain value. We present a near-infrared (NIR) spectroscopic survey of HII regions in the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC) obtained with AKARI, which aims to search for features indicative of deuterated PAHs (PAD or Dn-PAH) to better constrain the D/H ratio of PAHs. Fifty-three HII regions were observed in the NIR (2.5-5 {\\mu}m), using the Infrared Camera (IRC) on board the AKARI satellite. Through comparison of the observed spectra with a theoretical model of deuterated PAH vibrational modes, the aromatic and (a)symmetric aliphatic C-D stretch modes were identified. We see emission features between 4.4-4.8 {\\mu}m, which could be unambiguously attributed to deuterated PAHs in only six of the observed sources, all of which are located in the Milky Way. In all cases, the aromatic C-D stretching feature is weaker than the aliphatic C-D stretching feature, and, in the case o...

  13. Mars' core and magnetism.

    Science.gov (United States)

    Stevenson, D J

    2001-07-12

    The detection of strongly magnetized ancient crust on Mars is one of the most surprising outcomes of recent Mars exploration, and provides important insight about the history and nature of the martian core. The iron-rich core probably formed during the hot accretion of Mars approximately 4.5 billion years ago and subsequently cooled at a rate dictated by the overlying mantle. A core dynamo operated much like Earth's current dynamo, but was probably limited in duration to several hundred million years. The early demise of the dynamo could have arisen through a change in the cooling rate of the mantle, or even a switch in convective style that led to mantle heating. Presently, Mars probably has a liquid, conductive outer core and might have a solid inner core like Earth.

  14. Hydrocarbon degradation by Antarctic coastal bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cavanagh, J.E. [University of Tasmania, Hobart (Australia). Antarctic Cooperative Research Centre; CSIRO Div of Marine Research, Hobart (Australia); University of Tasmania, Hobart (Australia). Dept. of Agricultural Science; Nichols, P.D. [University of Tasmania, Hobart (Australia). Antarctic Cooperative Research Centre; CSIRO Div. of Marine Research, Hobart (Australia); Franzmann, P.D. [CSIRO Land and Water, Wembley (Australia); McMeekin, T.A. [University of Tasmania, Hobart (Australia). Antarctic Cooperative Research Centre

    1999-07-01

    Bacterial cultures obtained through selective enrichment of beach sand collected 60 days and one year after treatment of sites in a pilot oil spill trial conducted at Airport Beach, Vestfold Hills, East Antarctica, were examined for the ability to degrade n-alkanes and phenanthrene. The effects of different hydrocarbon mixtures (Special Antarctic Blend [SAB] and BP-Visco), (fish oil [orange roughy]) and inoculation of replicate sites with water from Organic Lake, (previously shown to contain hydrocarbon-degrading bacteria) on the indigenous microbial population, were examined. Of the cultures obtained, those from sites treated with SAB and BP-Visco degraded n-alkanes most consistently and typically to the greatest extent. Two mixed cultures obtained from samples collected at 60 days and two isolates obtained from these cultures extensively degraded phenanthrene. 1-Hydroxy-naphthoic acid formed the major phenanthrene metabolite. Lower levels of salicyclic acid, 1-naphthol, 1,4-naphthaquinone and phenanthrene 9-10 dihydrodiol were detected in extracts of phenanthrene grown cultures. This study shows that under laboratory conditions indigenous Antarctica bacteria can degrade n-alkanes and the more recalcitrant polycyclic aromatic hydrocarbon, phenanthrene. The enrichment of hydrocarbon degrading microorganisms in Antarctic ecosystems exposed to hydrocarbons, is relevant for the long term fate of hydrocarbon spills in this environment. (author)

  15. Effect of ionic strength on dynamics of supported phosphatidylcholine lipid bilayer revealed by FRAPP and Langmuir-Blodgett transfer ratios.

    Science.gov (United States)

    Harb, Frédéric F; Tinland, Bernard

    2013-05-07

    To determine how lipid bilayer/support interactions are affected by ionic strength, we carried out lipid diffusion coefficient measurements by fluorescence recovery after patterned photobleaching (FRAPP) and transfer ratio measurements using a Langmuir balance on supported bilayers of phosphatidylcholine lipids. The main effect of increasing ionic strength is shown to be enhanced diffusion of the lipids due to a decrease in the electrostatic interaction between the bilayer and the support. We experimentally confirm that the two main parameters governing bilayer behavior are electrostatic interaction and bilayer/support distance. Both these parameters can therefore be used to vary the potential that acts on the bilayer. Additionally, our findings show that FRAPP is an extremely sensitive tool to study interaction effects: here, variations in diffusion coefficient as well as the presence or absence of leaflet decoupling.

  16. The t-core of an s-core

    OpenAIRE

    Fayers, Matthew

    2010-01-01

    We consider the $t$-core of an $s$-core partition, when $s$ and $t$ are coprime positive integers. Olsson has shown that the $t$-core of an $s$-core is again an $s$-core, and we examine certain actions of the affine symmetric group on $s$-cores which preserve the $t$-core of an $s$-core. Along the way, we give a new proof of Olsson's result. We also give a new proof of a result of Vandehey, showing that there is a simultaneous $s$- and $t$-core which contains all others.

  17. Thermal response of domains in cardiolipin content bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Domenech, Oscar [Departament de Quimica-Fisica, Facultat de Quimica, U.B. 08028 (Spain); Morros, Antoni [Unitat de Biofisica, Departament de Bioquimica i Biologia Molecular, Facultat de Medicina (Spain); Servei de Ressonancia Magnetica Nuclear (SeRMN), U.A.B., 08193 Bellaterra, Barcelona (Spain); Cabanas, Miquel E. [Servei de Ressonancia Magnetica Nuclear (SeRMN), U.A.B., 08193 Bellaterra, Barcelona (Spain); Montero, M. Teresa [Departament de Fisicoquimica, Facultat de Farmacia, U.B. 08028 (Spain); Hernandez-Borrell, Jordi [Departament de Fisicoquimica, Facultat de Farmacia, U.B. 08028 (Spain)], E-mail: jordihernandezborrell@ub.edu

    2007-10-15

    In the study described here, supported planar bilayers (SPBs) of 1-palmitoy-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE):cardiolipin (CL) (0.8:0.2, mol/mol) were examined using atomic force microscopy (AFM). SPBs were formed from suspensions of POPE:CL (0.8:0.2, mol/mol) in inverted hexagonal (H{sub II}) phases (buffer containing Ca{sup 2+}). Three laterally segregated domains which differ in height were observed at 24 degC. Based on the area accounted for each domain and the nominal composition of the mixture, we interpret that the higher domain is formed by CL, while the intermediate and lower domains (LDs) are formed by POPE. The three domains respond to temperature increase with relative changes in their area. At 37 degC, we observed that the increase in the area of the intermediate domain occurs at the expense of the LD. {sup 31}P-nuclear magnetic resonance ({sup 31}P-NMR) and Differential scanning calorimetry (DSC) were used in combination with AFM to characterize the phase behavior of the suspensions and to elucidate the nature of the structures observed.

  18. Unassisted translocation of large polypeptide domains across phospholipid bilayers.

    Science.gov (United States)

    Brambillasca, Silvia; Yabal, Monica; Makarow, Marja; Borgese, Nica

    2006-12-01

    Although transmembrane proteins generally require membrane-embedded machinery for integration, a few can insert spontaneously into liposomes. Previously, we established that the tail-anchored (TA) protein cytochrome b(5) (b5) can posttranslationally translocate 28 residues downstream to its transmembrane domain (TMD) across protein-free bilayers (Brambillasca, S., M. Yabal, P. Soffientini, S. Stefanovic, M. Makarow, R.S. Hegde, and N. Borgese. 2005. EMBO J. 24:2533-2542). In the present study, we investigated the limits of this unassisted translocation and report that surprisingly long (85 residues) domains of different sequence and charge placed downstream of b5's TMD can posttranslationally translocate into mammalian microsomes and liposomes at nanomolar nucleotide concentrations. Furthermore, integration of these constructs occurred in vivo in translocon-defective yeast strains. Unassisted translocation was not unique to b5 but was also observed for another TA protein (protein tyrosine phosphatase 1B) whose TMD, like the one of b5, is only moderately hydrophobic. In contrast, more hydrophobic TMDs, like synaptobrevin's, were incapable of supporting unassisted integration, possibly because of their tendency to aggregate in aqueous solution. Our data resolve long-standing discrepancies on TA protein insertion and are relevant to membrane evolution, biogenesis, and physiology.

  19. Power losses in bilayer inverted small molecule organic solar cells

    KAUST Repository

    Trinh, Cong

    2012-01-01

    Inverted bilayer organic solar cells using copper phthalocyanine (CuPc) as a donor and C60 as an acceptor with the structure: glass/indium tin oxide (ITO)/ZnO/C60/CuPc/MoO3/Al, in which the zinc oxide (ZnO) was deposited by atomic layer deposition, are compared with a conventional device: glass/ITO/CuPc/C60/bathocuproine/Al. These inverted and conventional devices give short circuit currents of 3.7 and 4.8 mA/cm 2, respectively. However, the inverted device gives a reduced photoresponse from the CuPc donor compared to that of the conventional device. Optical field models show that the arrangement of organic layers in the inverted devices leads to lower absorption of long wavelengths by the CuPc donor; the low energy portion of the spectrum is concentrated near the metal oxide electrode in both devices. © 2012 American Institute of Physics.

  20. Bilayer Beams and Relay Sharing based OFDMA Cellular Architecture

    Directory of Open Access Journals (Sweden)

    Yanxiong Pan

    2011-08-01

    Full Text Available Over the past decade, researchers have been putting a lot of energy on co-channel interference suppression in the forthcoming fourth generation (4G wireless networks. Existing approaches to interference suppression are mainly based on signal processing, cooperative communication or coordination techniques. Though good performance has been attained already, a more complex receiver is needed, and there is still room for improvement through other ways.Considering spatial frequency reuse, which provides an easier way to cope with the co-channel interference, this paper proposed a bilayer beams and relay sharing based (BBRS OFDMA cellular architecture and corresponding frequency planning scheme. The main features of the novel architecture are as follows. Firstly, the base station (BS uses two beams, one composed of six wide beams providing coverage to mobile stations (MSs that access to the BS, and the other composed of six narrow beams communicating with fixed relay stations (FRSs. Secondly, in the corresponding frequency planning scheme, soft frequency reuse is considered on all FRSs further. System-level simulation results demonstrate that better coverage performance is obtained and the mean data rate of MSs near the cell edge is improved significantly. The BBRS cellular architecture provides a practical method to interference suppression in 4G networks since a better tradeoff between performance and complexity is achieved.