Mechanical and electronic properties of monolayer and bilayer phosphorene under uniaxial and isotropic strains.

Science.gov (United States)

Hu, Ting; Han, Yang; Dong, Jinming

2014-11-14

The mechanical and electronic properties of both the monolayer and bilayer phosphorenes under either isotropic or uniaxial strain have been systematically investigated using first-principles calculations. It is interesting to find that: 1) Under a large enough isotropic tensile strain, the monolayer phosphorene would lose its pucker structure and transform into a flat hexagonal plane, while two inner sublayers of the bilayer phosphorene could be bonded due to its interlayer distance contraction. 2) Under the uniaxial tensile strain along a zigzag direction, the pucker distance of each layer in the bilayer phosphorene can exhibit a specific negative Poisson's ratio. 3) The electronic properties of both the monolayer and bilayer phosphorenes are sensitive to the magnitude and direction of the applied strains. Their band gaps decrease more rapidly under isotropic compressive strain than under uniaxial strain. Also, their direct-indirect band gap transitions happen at the larger isotropic tensile strains compared with that under uniaxial strain. 4) Under the isotropic compressive strain, the bilayer phosphorene exhibits a transition from a direct-gap semiconductor to a metal. In contrast, the monolayer phosphorene initially has the direct-indirect transition and then transitions to a metal. However, under isotropic tensile strain, both the bilayer and monolayer phosphorene show the direct-indirect transition and, finally, the transition to a metal. Our numerical results may open new potential applications of phosphorene in nanoelectronics and nanomechanical devices by external isotropic strain or uniaxial strain along different directions.

Influence of carrier density on the electronic cooling channels of bilayer graphene

NARCIS (Netherlands)

Limmer, T.; Houtepen, A.J.; Niggebaum, A.; Tautz, R.; Da Como, E.

2011-01-01

We study the electronic cooling dynamics in a single flake of bilayer graphene by femtosecond transient absorption probing the photon-energy range 0.25–1.3 eV. From the transients, we extract the carrier cooling curves for different initial temperatures and densities of the photoexcited electrons

Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

Science.gov (United States)

Kumar, Krishan; Moudgil, R K

2012-10-17

We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

Generation of valley-polarized electron beam in bilayer graphene

International Nuclear Information System (INIS)

Park, Changsoo

2015-01-01

We propose a method to produce valley-polarized electron beams using a bilayer graphene npn junction. By analyzing the transmission properties of electrons through the junction with zigzag interface in the presence of trigonal warping, we observe that there exist a range of incident energies and barrier heights in which transmitted electrons are well polarized and collimated. From this observation and by performing numerical simulations, it is demonstrated that valley-dependent electronic currents with nearly perfect polarization can be generated. We also show that the peak-to-peak separation angle between the polarized currents is tunable either by incident energy or by barrier height each of which is controlled by using top and back gate voltages. The results can be used for constructing an electron beam splitter to produce valley-polarized currents

Generation of valley-polarized electron beam in bilayer graphene

Science.gov (United States)

Park, Changsoo

2015-12-01

We propose a method to produce valley-polarized electron beams using a bilayer graphene npn junction. By analyzing the transmission properties of electrons through the junction with zigzag interface in the presence of trigonal warping, we observe that there exist a range of incident energies and barrier heights in which transmitted electrons are well polarized and collimated. From this observation and by performing numerical simulations, it is demonstrated that valley-dependent electronic currents with nearly perfect polarization can be generated. We also show that the peak-to-peak separation angle between the polarized currents is tunable either by incident energy or by barrier height each of which is controlled by using top and back gate voltages. The results can be used for constructing an electron beam splitter to produce valley-polarized currents.

Formation, Energetics, and Electronic Properties of Graphene Monolayer and Bilayer Doped with Heteroatoms

Directory of Open Access Journals (Sweden)

Yoshitaka Fujimoto

2015-01-01

Full Text Available Doping with heteroatoms is one of the most effective methods to tailor the electronic properties of carbon nanomaterials such as graphene and carbon nanotubes, and such nanomaterials doped with heteroatom dopants might therefore provide not only new physical and chemical properties but also novel nanoelectronics/optoelectronics device applications. The boron and nitrogen are neighboring elements to carbon in the periodic table, and they are considered to be good dopants for carbon nanomaterials. We here review the recent work of boron and nitrogen doping effects into graphene monolayer as well as bilayer on the basis of the first-principles electronic structure calculations in the framework of the density-functional theory. We show the energetics and the electronic properties of boron and nitrogen defects in graphene monolayer and bilayer. As for the nitrogen doping, we further discuss the stabilities, the growth processes, and the electronic properties associated with the plausible nitrogen defect formation in graphene which is suggested by experimental observations.

Transport Properties of an Electron-Hole Bilayer in Contact with a Superconductor Hybrid Junction

Science.gov (United States)

Bercioux, D.; Klapwijk, T. M.; Bergeret, F. S.

2017-08-01

We investigate the transport properties of a junction consisting of an electron-hole bilayer in contact with normal and superconducting leads. The electron-hole bilayer is considered as a semimetal with two electronic bands. We assume that in the region between the contacts the system hosts an exciton condensate described by a BCS-like model with a gap Γ in the quasiparticle density of states. We first discuss how the subgap electronic transport through the junction is mainly governed by the interplay between two kinds of reflection processes at the interfaces: the standard Andreev reflection at the interface between the superconductor and the exciton condensate, and a coherent crossed reflection at the semimetal-exciton-condensate interface that converts electrons from one layer into the other. We show that the differential conductance of the junction shows a minimum at voltages of the order of Γ /e . Such a minimum can be seen as a direct hallmark of the existence of the gapped excitonic state.

Stability of Sarma phases in density imbalanced electron-hole bilayer systems

International Nuclear Information System (INIS)

Subasi, A. L.; Tanatar, B.; Pieri, P.; Senatore, G.

2010-01-01

We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

Phase diagram of classical electronic bilayers

International Nuclear Information System (INIS)

Ranganathan, S; Johnson, R E

2006-01-01

Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength Γ and interlayer separation d to delineate its phase diagram in the Γ-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for Γ greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones

Phase diagram of classical electronic bilayers

Energy Technology Data Exchange (ETDEWEB)

Ranganathan, S [Department of Physics, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada); Johnson, R E [Department of Mathematics and Computer Science, Royal Military College of Canada, Kingston, Ontario K7K 7B4 (Canada)

2006-04-28

Extensive molecular dynamics calculations have been performed on classical, symmetric electronic bilayers at various values of the coupling strength {gamma} and interlayer separation d to delineate its phase diagram in the {gamma}-d plane. We studied the diffusion, the amplitude of the main peak of the intralayer static structure factor and the peak positions of the intralayer pair correlation function with the aim of defining equivalent signatures of freezing and constructing the resulting phase diagram. It is found that for {gamma} greater than 75, crystalline structures exist for a certain range of interlayer separations, while liquid phases are favoured at smaller and larger d. It is seen that there is good agreement between our phase diagram and previously published ones.

Phonon-induced renormalization of the electron spectrum of biased bilayer graphene

Science.gov (United States)

Kryuchkov, S. V.; Kukhar, E. I.

2018-05-01

The effect of the electron-phonon interaction on the electron subsystem of the bilayer graphene has been investigated in the case when there is a potential bias between the graphene layers. The electron-phonon interaction has been shown to lead to increasing of the curvature of the lower dispersion branch of the conduction band of the bigraphene in the vicinity of the Dirac point. The latter corresponds to the decreasing of the absolute value of the electron effective mass. The corresponding correction to the effective mass has been calculated. Dependence of this correction on the bias has been investigated. Influence of such effect on the bigraphene conductivity is discussed.

Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS 2 /WSe 2 hetero-bilayers

KAUST Repository

Zhang, Chendong

2017-01-07

By using direct growth, we create a rotationally aligned MoS2/WSe2 hetero-bilayer as a designer van der Waals heterostructure. With rotational alignment, the lattice mismatch leads to a periodic variation of atomic registry between individual van der Waals layers, exhibiting a Moiré pattern with a well-defined periodicity. By combining scanning tunneling microscopy/spectroscopy, transmission electron microscopy, and first-principles calculations, we investigate interlayer coupling as a function of atomic registry. We quantitatively determine the influence of interlayer coupling on the electronic structure of the hetero-bilayer at different critical points. We show that the direct gap semiconductor concept is retained in the bilayer although the valence and conduction band edges are located at different layers. We further show that the local bandgap is periodically modulated in the X-Y direction with an amplitude of ~0.15 eV, leading to the formation of a two-dimensional electronic superlattice.

Electronic transport of bilayer graphene with asymmetry line defects

International Nuclear Information System (INIS)

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

2016-01-01

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. (paper)

Chirality-Assisted Electronic Cloaking of Confined States in Bilayer Graphene

Science.gov (United States)

Gu, Nan; Rudner, Mark; Levitov, Leonid

2011-10-01

We show that the strong coupling of pseudospin orientation and charge carrier motion in bilayer graphene has a drastic effect on transport properties of ballistic p-n-p junctions. Electronic states with zero momentum parallel to the barrier are confined under it for one pseudospin orientation, whereas states with the opposite pseudospin tunnel through the junction totally uninfluenced by the presence of confined states. We demonstrate that the junction acts as a cloak for confined states, making them nearly invisible to electrons in the outer regions over a range of incidence angles. This behavior is manifested in the two-terminal conductance as transmission resonances with non-Lorentzian, singular peak shapes. The response of these phenomena to a weak magnetic field or electric-field-induced interlayer gap can serve as an experimental fingerprint of electronic cloaking.

Potassium-doped n-type bilayer graphene

Science.gov (United States)

Yamada, Takatoshi; Okigawa, Yuki; Hasegawa, Masataka

2018-01-01

Potassium-doped n-type bilayer graphene was obtained. Chemical vapor deposited bilayer and single layer graphene on copper (Cu) foils were used. After etching of Cu foils, graphene was dipped in potassium hydroxide aqueous solutions to dope potassium. Graphene on silicon oxide was characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Both XPS and EDX spectra indicated potassium incorporation into the bilayer graphene via intercalation between the graphene sheets. The downward shift of the 2D peak position of bilayer graphene after the potassium hydroxide (KOH) treatment was confirmed in Raman spectra, indicating that the KOH-treated bilayer graphene was doped with electrons. Electrical properties were measured using Hall bar structures. The Dirac points of bilayer graphene were shifted from positive to negative by the KOH treatment, indicating that the KOH-treated bilayer graphene was n-type conduction. For single layer graphene after the KOH treatment, although electron doping was confirmed from Raman spectra, the peak of potassium in the X-ray photoelectron spectroscopy (XPS) spectrum was not detected. The Dirac points of single layer graphene with and without the KOH treatment showed positive.

A comparison of the transport properties of bilayer graphene,monolayer graphene, and two-dimensional electron gas

Institute of Scientific and Technical Information of China (English)

Sun Li-Feng; Dong Li-Min; Wu Zhi-Fang; Fang Chao

2013-01-01

we studied and compared the transport properties of charge carriers in bilayer graphene,monolayer graphene,and the conventional semiconductors (the two-dimensional electron gas (2DEG)).It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene.However,resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene,which do not occur in the 2DEG.Furthermore,there are tunneling and forbidden regions in the transmission spectrum for each material,and the division of the two regions has been given in the work.The tunneling region covers a wide range of the incident energy for the two graphene systems,but only exists under specific conditions for the 2DEG.The counterparts of the transmission in the conductance profile are also given for the three materials,which may be used as high-performance devices based on the bilayer graphene.

Hybrid matrix method for stable numerical analysis of the propagation of Dirac electrons in gapless bilayer graphene superlattices

Science.gov (United States)

Briones-Torres, J. A.; Pernas-Salomón, R.; Pérez-Álvarez, R.; Rodríguez-Vargas, I.

2016-05-01

Gapless bilayer graphene (GBG), like monolayer graphene, is a material system with unique properties, such as anti-Klein tunneling and intrinsic Fano resonances. These properties rely on the gapless parabolic dispersion relation and the chiral nature of bilayer graphene electrons. In addition, propagating and evanescent electron states coexist inherently in this material, giving rise to these exotic properties. In this sense, bilayer graphene is unique, since in most material systems in which Fano resonance phenomena are manifested an external source that provides extended states is required. However, from a numerical standpoint, the presence of evanescent-divergent states in the eigenfunctions linear superposition representing the Dirac spinors, leads to a numerical degradation (the so called Ωd problem) in the practical applications of the standard Coefficient Transfer Matrix (K) method used to study charge transport properties in Bilayer Graphene based multi-barrier systems. We present here a straightforward procedure based in the hybrid compliance-stiffness matrix method (H) that can overcome this numerical degradation. Our results show that in contrast to standard matrix method, the proposed H method is suitable to study the transmission and transport properties of electrons in GBG superlattice since it remains numerically stable regardless the size of the superlattice and the range of values taken by the input parameters: the energy and angle of the incident electrons, the barrier height and the thickness and number of barriers. We show that the matrix determinant can be used as a test of the numerical accuracy in real calculations.

Influence of carrier density on the electronic cooling channels of bilayer graphene

Science.gov (United States)

Limmer, T.; Houtepen, A. J.; Niggebaum, A.; Tautz, R.; Da Como, E.

2011-09-01

We study the electronic cooling dynamics in a single flake of bilayer graphene by femtosecond transient absorption probing the photon-energy range 0.25-1.3 eV. From the transients, we extract the carrier cooling curves for different initial temperatures and densities of the photoexcited electrons and holes. Two regimes of carrier cooling, dominated by optical and acoustic phonons emission, are clearly identified. For increasing carrier density, the crossover between the two regimes occurs at larger carrier temperatures, since cooling via optical phonons experiences a bottleneck. Acoustic phonons, which are less sensitive to saturation, show an increasing contribution at high density.

Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayers

International Nuclear Information System (INIS)

Pieri, P.; Strinati, G. C.; Neilson, D.

2007-01-01

We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of nonoverlapping tightly bound pairs but also, by varying the electron and hole densities independently, we can analyze a number of phases that occur mainly in the crossover region. With different electron and hole effective masses, the phase diagram is asymmetric with respect to excess electron or hole densities. We propose, as the criterion for the onset of superfluidity, the jump of the electron and hole chemical potentials when their densities cross

Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO3/SrTiO3 superlattices: coexistence of Auger recombination and single-carrier trapping

Directory of Open Access Journals (Sweden)

H. J. Harsan Ma

2015-06-01

Full Text Available We report emerging photoluminescence (PL of bilayer two-dimensional electron gases (2DEG in LaAlO3/SrTiO3 (LAO/STO systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.

Highly anisotropic electronic transport properties of monolayer and bilayer phosphorene from first principles

Energy Technology Data Exchange (ETDEWEB)

Jin, Zhenghe; Mullen, Jeffrey T. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kim, Ki Wook, E-mail: kwk@ncsu.edu [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2016-08-01

The intrinsic carrier transport dynamics in phosphorene is theoretically examined. Utilizing a density functional theory treatment, the low-field mobility and the saturation velocity are characterized for both electrons and holes in the monolayer and bilayer structures. The analysis clearly elucidates the crystal orientation dependence manifested through the anisotropic band structure and the carrier-phonon scattering rates. In the monolayer, the hole mobility in the armchair direction is estimated to be approximately five times larger than in the zigzag direction at room temperature (460 cm{sup 2}/V s vs. 90 cm{sup 2}/V s). The bilayer transport, on the other hand, exhibits a more modest anisotropy with substantially higher mobilities (1610 cm{sup 2}/V s and 760 cm{sup 2}/V s, respectively). The calculations on the conduction-band electrons indicate a comparable dependence while the characteristic values are generally smaller by about a factor of two. The variation in the saturation velocity is found to be less pronounced. With the anticipated superior performance and the diminished anisotropy, few-layer phosphorene offers a promising opportunity particularly in p-type applications.

Electron-hole collision limited transport in charge-neutral bilayer graphene

Science.gov (United States)

Nam, Youngwoo; Ki, Dong-Keun; Soler-Delgado, David; Morpurgo, Alberto F.

2017-12-01

Ballistic transport occurs whenever electrons propagate without collisions deflecting their trajectory. It is normally observed in conductors with a negligible concentration of impurities, at low temperature, to avoid electron-phonon scattering. Here, we use suspended bilayer graphene devices to reveal a new regime, in which ballistic transport is not limited by scattering with phonons or impurities, but by electron-hole collisions. The phenomenon manifests itself in a negative four-terminal resistance that becomes visible when the density of holes (electrons) is suppressed by gate-shifting the Fermi level in the conduction (valence) band, above the thermal energy. For smaller densities, transport is diffusive, and the measured conductivity is reproduced quantitatively, with no fitting parameters, by including electron-hole scattering as the only process causing velocity relaxation. Experiments on a trilayer device show that the phenomenon is robust and that transport at charge neutrality is governed by the same physics. Our results provide a textbook illustration of a transport regime that had not been observed previously and clarify the nature of conduction through charge-neutral graphene under conditions in which carrier density inhomogeneity is immaterial. They also demonstrate that transport can be limited by a fully electronic mechanism, originating from the same microscopic processes that govern the physics of Dirac-like plasmas.

Tunneling Plasmonics in Bilayer Graphene.

Science.gov (United States)

Fei, Z; Iwinski, E G; Ni, G X; Zhang, L M; Bao, W; Rodin, A S; Lee, Y; Wagner, M; Liu, M K; Dai, S; Goldflam, M D; Thiemens, M; Keilmann, F; Lau, C N; Castro-Neto, A H; Fogler, M M; Basov, D N

2015-08-12

We report experimental signatures of plasmonic effects due to electron tunneling between adjacent graphene layers. At subnanometer separation, such layers can form either a strongly coupled bilayer graphene with a Bernal stacking or a weakly coupled double-layer graphene with a random stacking order. Effects due to interlayer tunneling dominate in the former case but are negligible in the latter. We found through infrared nanoimaging that bilayer graphene supports plasmons with a higher degree of confinement compared to single- and double-layer graphene, a direct consequence of interlayer tunneling. Moreover, we were able to shut off plasmons in bilayer graphene through gating within a wide voltage range. Theoretical modeling indicates that such a plasmon-off region is directly linked to a gapped insulating state of bilayer graphene, yet another implication of interlayer tunneling. Our work uncovers essential plasmonic properties in bilayer graphene and suggests a possibility to achieve novel plasmonic functionalities in graphene few-layers.

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.

Electronic and optical properties of bilayer PbI2: a first-principles study

Science.gov (United States)

Shen, Chenhai; Wang, Guangtao

2018-01-01

By employing first-principles methods, we investigate the effects of stacking patterns and interlayer coupling on the electronic structures and optical properties of bilayer (BL) PbI2. For optical properties, excitonic effects are considered. The results show that crystal-type BL PbI2 stacking pattern is the most stable bilayer structures with the equilibrium interlayer distance of 3.27 Å and a direct band structure. Moreover, for all considered patterns, the interlayer coupling can induce the band structures to transform from indirect to direct and also the band gap values to vary from 2.56 eV to 2.62 eV. In addition, our calculations show that the exciton binding energy of the most stable pattern is 0.81 eV, and excitonic effects have obvious influences on optical responses of BL PbI2. These results may be useful to future experimental studies on optoelectronic properties of two-dimensional BL PbI2 nanosheets.

Lipid Bilayer Formation on Organic Electronic Materials

KAUST Repository

Zhang, Yi; Wustoni, Shofarul; Savva, Achilleas; Giovannitti, Alexander; McCulloch, Iain; Inal, Sahika

2018-01-01

The lipid bilayer is the elemental structure of cell membrane, forming a stable barrier between the interior and exterior of the cell while hosting membrane proteins that enable selective transport of biologically important compounds and cellular

Extension of the Mott-Gurney Law for a Bilayer Gap

Science.gov (United States)

Dubinov, A. E.; Kitayev, I. N.

2018-04-01

Steady drift states of an electron flow in a planar gap filled with a bilayer dielectric have been considered. Exact mathematical formulas have been derived that describe the distributions of the electrostatic potential and space charge limited electron flow current (extended Mott-Gurney law for a bilayer diode).

Ultrafast lithium diffusion in bilayer graphene

Science.gov (United States)

Kühne, Matthias; Paolucci, Federico; Popovic, Jelena; Ostrovsky, Pavel M.; Maier, Joachim; Smet, Jurgen H.

2017-09-01

Solids that simultaneously conduct electrons and ions are key elements for the mass transfer and storage required in battery electrodes. Single-phase materials with a high electronic and high ionic conductivity at room temperature are hard to come by, and therefore multiphase systems with separate ion and electron channels have been put forward instead. Here we report on bilayer graphene as a single-phase mixed conductor that demonstrates Li diffusion faster than in graphite and even surpassing the diffusion of sodium chloride in liquid water. To measure Li diffusion, we have developed an on-chip electrochemical cell architecture in which the redox reaction that forces Li intercalation is localized only at a protrusion of the device so that the graphene bilayer remains unperturbed from the electrolyte during operation. We performed time-dependent Hall measurements across spatially displaced Hall probes to monitor the in-plane Li diffusion kinetics within the graphene bilayer and measured a diffusion coefficient as high as 7 × 10-5 cm2 s-1.

Reactions of the hydrated electron with pyrene in lipid bilayer vesicles

International Nuclear Information System (INIS)

Schnecke, W.; Graetzel, M.; Henglein, A.

1977-01-01

Pyrene and some pyrene derivatives were solubilized in bilayer vesicles of lecithin and the rates of lecithin and the rates of reaction with the hydrated electron investigated. The concentration of the vesicles was 1.3 x 10 -7 M, that of pyrene 10 -6 - 10 -4 M. The rate constant decreases with increasing pyrene concentration. The effect is explained by the highly inhomogeneous distribution of pyrene molecules in the solutions. Only those pyrene molicules are reactive that reside close to the outer surface of the vesicles. The anions of pyrene formed disappear in a second order process. It is concluded that the anions are rapidly detached from their vesicular carriers and react with each other in the aqueous phase. Fluorescence, light scattering and electron microscopic investigations were also carried out to obtain information about the properties of the vesicles used. (orig.) [de

Peierls instability and optical properties of bilayer polyacene

Energy Technology Data Exchange (ETDEWEB)

Zhang, Longlong, E-mail: zhanglonglong@tyut.edu.cn [The College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Xie, Shijie [School of Physics, Shandong University, Jinan 250100 (China)

2017-05-03

Highlights: • The Peierls instability of bilayer polyacene is discussed. • The external electric field effect on bilayer polyacene is discussed. • The pressure effect on bilayer polyacene is discussed. • The optical properties of bilayer polyacene are discussed. - Abstract: We reveal that bilayer polyacene can be the gapped state due to the intralayer Peierls instability. There are six topologically inequivalent Peierls-distorted structures and they are degenerate in energy. The external electric field can tune the Peierls gap and induce the semiconductor-to-metallic phase transitions. The optical conductivity spectra are calculated in an attempt to categorize the Peierls-distorted structures. The strength of the interlayer coupling essentially affects the electronic properties and the optical selection rules.

Dispersion of fullerenes in phospholipid bilayers and the subsequent phase changes in the host bilayers

Energy Technology Data Exchange (ETDEWEB)

Jeng, U-S. [National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China)]. E-mail: usjeng@nsrrc.org.tw; Hsu, C.-H. [National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China); Lin, T.-L. [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Wu, C.-M. [Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, H.-L. [Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Tai, L.-A. [Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Hwang, K.-C. [Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2005-02-28

We have studied the structure and phase transition characteristics of the fullerenes (C{sub 60})-embedded lipid bilayers. With small-angle neutron scattering (SANS), we have observed a degradation of bilayer ordering and a suppression effect on the phase transitions of the host vesicle bilayers of dipalmitoylphosphatidylcholine (DPPC), due to the embedment of fullerenes. The fullerene-embedded lipid system with substrate-oriented bilayers is also investigated using X-ray reflectivity and grazing incident small-angle X-ray scattering (GISAXS). In the depth direction, the multilamellar peaks observed in the X-ray reflectivity profile for the oriented DPPC/C{sub 60} bilayers reveal a larger head-to-head distance D{sub HH} of 50.6 A and a bilayer spacing D of 59.8 A, compared to the D{sub HH}=47.7 A and D=59.5 A for a pure DPPC membrane measured at the same conditions. Furthermore, the lipid head layers and water layers in the extracted electron density profile for the complex system are highly smeared, implying a fluctuating or corrugated structure in this zone. Correspondingly, GISAXS for the oriented DPPC/C{sub 60} membrane reveals stronger diffuse scatterings along the membrane plane than that for the pure DPPC system, indicating a higher in-plane correlation associated with the embedded fullerenes.

Edge states in gated bilayer-monolayer graphene ribbons and bilayer domain walls

Science.gov (United States)

Mirzakhani, M.; Zarenia, M.; Peeters, F. M.

2018-05-01

Using the effective continuum model, the electron energy spectrum of gated bilayer graphene with a step-like region of decoupled graphene layers at the edge of the sample is studied. Different types of coupled-decoupled interfaces are considered, i.e., zigzag (ZZ) and armchair junctions, which result in significant different propagating states. Two non-valley-polarized conducting edge states are observed for ZZ type, which are mainly located around the ZZ-ended graphene layers. Additionally, we investigated both BA-BA and BA-AB domain walls in the gated bilayer graphene within the continuum approximation. Unlike the BA-BA domain wall, which exhibits gapped insulating behaviour, the domain walls surrounded by different stackings of bilayer regions feature valley-polarized edge states. Our findings are consistent with other theoretical calculations, such as from the tight-binding model and first-principles calculations, and agree with experimental observations.

Chiral tunneling in a twisted graphene bilayer.

Science.gov (United States)

He, Wen-Yu; Chu, Zhao-Dong; He, Lin

2013-08-09

The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer.

Coulomb drag in electron-hole bilayer: Mass-asymmetry and exchange correlation effects

Science.gov (United States)

Arora, Priya; Singh, Gurvinder; Moudgil, R. K.

2018-04-01

Motivated by a recent experiment by Zheng et al. [App. Phys. Lett. 108, 062102 (2016)] on coulomb drag in electron-hole and hole-hole bilayers based on GaAs/AlGaAs semiconductor heterostructure, we investigate theoretically the influence of mass-asymmetry and temperature-dependence of correlations on the drag rate. The correlation effects are dealt with using the Vignale-Singwi effective inter-layer interaction model which includes correlations through local-field corrections to the bare coulomb interactions. However, in this work, we have incorporated only the intra-layer correlations using the temperature-dependent Hubbard approximation. Our results display a reasonably good agreement with the experimental data. However, it is crucial to include both the electron-hole mass-asymmetry and temperature-dependence of correlations. Mass-asymmetry and correlations are found to result in a substantial enhancement of drag resistivity.

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...

Prediction of superconductivity in Li-intercalated bilayer phosphorene

International Nuclear Information System (INIS)

Huang, G. Q.; Xing, Z. W.; Xing, D. Y.

2015-01-01

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 c can be increased up to 16.5 K, suggesting that phosphorene may be a good candidate for a nanoscale superconductor

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.

Chiral Tunnelling in Twisted Graphene Bilayer

OpenAIRE

He, Wen-Yu; Chu, Zhao-Dong; He, Lin

2013-01-01

The perfect transmission in graphene monolayer and the perfect reflection in Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in twisted graphene bilayer shows adjustable probability of chiral tunnelling for normal incidence: they can be changed fr...

Transfer matrix theory of monolayer graphene/bilayer graphene heterostructure superlattice

International Nuclear Information System (INIS)

Wang, Yu

2014-01-01

We have formulated a transfer matrix method to investigate electronic properties of graphene heterostructure consisting of monolayer graphene and bilayer counterpart. By evaluating transmission, conductance, and band dispersion, we show that, irrespective of the different carrier chiralities in monolayer graphene and bilayer graphene, superlattice consisting of biased bilayer graphene barrier and monolayer graphene well can mimic the electronic properties of conventional semiconductor superlattice, displaying the extended subbands in the quantum tunneling regime and producing anisotropic minigaps for the classically allowed transport. Due to the lateral confinement, the lowest mode has shifted away from the charge neutral point of monolayer graphene component, opening a sizeable gap in concerned structure. Following the gate-field and geometry modulation, all electronic states and gaps between them can be externally engineered in an electric-controllable strategy.

Strain-induced gap transition and anisotropic Dirac-like cones in monolayer and bilayer phosphorene

Energy Technology Data Exchange (ETDEWEB)

Wang, Can; Xia, Qinglin, E-mail: qlxia@csu.edu.cn; Nie, Yaozhuang; Guo, Guanghua, E-mail: guogh@csu.edu.cn [School of Physics and Electronics, Central South University, Changsha 410083 (China)

2015-03-28

The electronic properties of two-dimensional monolayer and bilayer phosphorene subjected to uniaxial and biaxial strains have been investigated using first-principles calculations based on density functional theory. Strain engineering has obvious influence on the electronic properties of monolayer and bilayer phosphorene. By comparison, we find that biaxial strain is more effective in tuning the band gap than uniaxial strain. Interestingly, we observe the emergence of Dirac-like cones by the application of zigzag tensile strain in the monolayer and bilayer systems. For bilayer phosphorene, we induce the anisotropic Dirac-like dispersion by the application of appropriate armchair or biaxial compressive strain. Our results present very interesting possibilities for engineering the electronic properties of phosphorene and pave a way for tuning the band gap of future electronic and optoelectronic devices.

Strain-induced recovery of electronic anisotropy in 90°-twisted bilayer phosphorene

Science.gov (United States)

Xie, Jiafeng; Luo, Qiangjun; Jia, Lei; Zhang, Z. Y.; Shi, H. G.; Yang, D. Z.; Si, M. S.

2018-01-01

It is well known that anisotropy determines the preferred transport direction of carriers. To manipulate the anisotropy is an exciting topic in two-dimensional materials, where the carriers are confined within individual layers. In this work, it is found that uniaxial strain can tune the electronic anisotropy of the 90°-twisted bilayer phosphorene. In this unique bilayer structure, the zigzag direction of one layer corresponds to the armchair one of the other layer and vice versa. Owing to this complementary structure, the directional (zigzag or armchair) deformation response to strain of one layer is opposite to that of the other layer, where the in-plane positive Poisson's ratio plays a key role. As a result, the doubly degenerate highest valence bands split, followed by a recovery of anisotropy. More interestingly, such an anisotropy, namely, the ratio of the effective mass along the Γ \\text- X direction to that along the Γ \\text- Y direction, reaches as high as 6 under a small strain of 1%, and keeps nearly unchanged up to a strain of 3%. In addition, high anisotropy only holds for hole carriers as the conduction band is insensitive to strain. These findings should shed new light on the design of semiconducting devices, where the hole acts as the transport carrier.

Robustly Engineering Thermal Conductivity of Bilayer Graphene by Interlayer Bonding

Science.gov (United States)

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

2016-01-01

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. PMID:26911859

Fabrication of Li-intercalated bilayer graphene

Directory of Open Access Journals (Sweden)

K. Sugawara

2011-06-01

Full Text Available We have succeeded in fabricating Li-intercalated bilayer graphene on silicon carbide. The low-energy electron diffraction from Li-deposited bilayer graphene shows a sharp 3×3R30° pattern in contrast to Li-deposited monolayer graphene. This indicates that Li atoms are intercalated between two adjacent graphene layers and take the same well-ordered superstructure as in bulk C6Li. The angle-resolved photoemission spectroscopy has revealed that Li atoms are fully ionized and the π bands of graphene are systematically folded by the superstructure of intercalated Li atoms, producing a snowflake-like Fermi surface centered at the Γ point. The present result suggests a high potential of Li-intercalated bilayer graphene for application to a nano-scale Li-ion battery.

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.

Tunable electric properties of bilayer InSe with different interlayer distances and external electric field

Science.gov (United States)

Shang, Jimin; Pan, Longfei; Wang, Xiaoting; Li, Jingbo; Wei, Zhongming

2018-03-01

Using density functional theory we explore the band structure of bilayer Indium selenide (InSe), and we find that the van der Waals interaction has significant effects on the electric and optical properties. We then explore the tuning electronic properties by different interlayer distances and by an external vertical electric field. Our results demonstrate that the band gaps of bilayer InSe can be continuously tuned by different interlayer coupling. With decreasing interlayer distances, the tunable band gaps of bilayer decrease linearly, owing to the enhancement of the interlayer interaction. Additionally, the band structure of bilayer InSe under external vertical fields is discussed. The presence of a small external electric field can make a new spatial distribution of electron-hole pairs. A well separation based on the electrons and holes, localized in different layers can be obtained using this easy method. These properties of bilayer InSe indicates potential applications in designing new optoelectronic devices.

Device model investigation of bilayer organic light emitting diodes

International Nuclear Information System (INIS)

Crone, B. K.; Davids, P. S.; Campbell, I. H.; Smith, D. L.

2000-01-01

Organic materials that have desirable luminescence properties, such as a favorable emission spectrum and high luminescence efficiency, are not necessarily suitable for single layer organic light-emitting diodes (LEDs) because the material may have unequal carrier mobilities or contact limited injection properties. As a result, single layer LEDs made from such organic materials are inefficient. In this article, we present device model calculations of single layer and bilayer organic LED characteristics that demonstrate the improvements in device performance that can occur in bilayer devices. We first consider an organic material where the mobilities of the electrons and holes are significantly different. The role of the bilayer structure in this case is to move the recombination away from the electrode that injects the low mobility carrier. We then consider an organic material with equal electron and hole mobilities but where it is not possible to make a good contact for one carrier type, say electrons. The role of a bilayer structure in this case is to prevent the holes from traversing the device without recombining. In both cases, single layer device limitations can be overcome by employing a two organic layer structure. The results are discussed using the calculated spatial variation of the carrier densities, electric field, and recombination rate density in the structures. (c) 2000 American Institute of Physics

Electronic Resource Management and Design

Science.gov (United States)

Abrams, Kimberly R.

2015-01-01

We have now reached a tipping point at which electronic resources comprise more than half of academic library budgets. Because of the increasing work associated with the ever-increasing number of e-resources, there is a trend to distribute work throughout the library even in the presence of an electronic resources department. In 2013, the author…

Co-sintering of CGO/NIO-CGO bilayers for solid oxide fuel cell

International Nuclear Information System (INIS)

Neto, P.P.B.; Grilo, J.P.F.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M.

2012-01-01

Reducing the operating temperature of solid oxide fuel cells (SOFC) for the range between 500 and 700°C is one of the challenges which more has aroused the interest of research in SOFC in recent years. In this context, the bilayer anode/electrolyte composed of a porous support based on Ni-doped ceria (anode) and a ceria doped gadolinia (CGO) electrolyte, presents itself as one of the half-cell configurations of the most interest towards the production of electricity in the operating logic of a SOFC. In this work, CGO films were successfully prepared on NiO-CGO substrates using the resources of the screen-printing technique. The bi-layers were co-sintered between 1350 and 1450 ° C for 4 h and then characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). The results showed good adhesion at the film/substrate interface and no cracks in the films. (author)

Cyclotron resonance in bilayer graphene.

Science.gov (United States)

Henriksen, E A; Jiang, Z; Tung, L-C; Schwartz, M E; Takita, M; Wang, Y-J; Kim, P; Stormer, H L

2008-02-29

We present the first measurements of cyclotron resonance of electrons and holes in bilayer graphene. In magnetic fields up to B=18 T, we observe four distinct intraband transitions in both the conduction and valence bands. The transition energies are roughly linear in B between the lowest Landau levels, whereas they follow square root[B] for the higher transitions. This highly unusual behavior represents a change from a parabolic to a linear energy dispersion. The density of states derived from our data generally agrees with the existing lowest order tight binding calculation for bilayer graphene. However, in comparing data to theory, a single set of fitting parameters fails to describe the experimental results.

Negative and positive magnetoresistance in bilayer graphene: Effects of weak localization and charge inhomogeneity

International Nuclear Information System (INIS)

Chen Yungfu; Bae, Myung-Ho; Chialvo, Cesar; Dirks, Travis; Bezryadin, Alexey; Mason, Nadya

2011-01-01

We report measurements of magnetoresistance in bilayer graphene as a function of gate voltage (carrier density) and temperature. We examine multiple contributions to the magnetoresistance, including those of weak localization (WL), universal conductance fluctuations (UCF), and inhomogeneous charge transport. A clear WL signal is evident at all measured gate voltages (in the hole doped regime) and temperature ranges (from 0.25 to 4.3 K), and the phase coherence length extracted from the WL data does not saturate at low temperatures. The WL data is fit to demonstrate that the electron-electron Nyquist scattering is the major source of phase decoherence. A decrease in UCF amplitude with increase in gate voltage and temperature is shown to be consistent with a corresponding decrease in the phase coherence length. In addition, a weak positive magnetoresistance at higher magnetic fields is observed, and attributed to inhomogeneous charge transport. -- Research highlights: → Weak localization theory describes low-field magnetoresistance in bilayer graphene. → Electron-electron Nyquist scattering limits phase coherence in bilayer graphene. → Positive magnetoresistance reveals charge inhomogeneity in bilayer graphene.

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.

Bi-layer structure of counterstreaming energetic electron fluxes: a diagnostic tool of the acceleration mechanism in the Earth's magnetotail

Directory of Open Access Journals (Sweden)

D. V. Sarafopoulos

2010-02-01

Full Text Available For the first time we identify a bi-layer structure of energetic electron fluxes in the Earth's magnetotail and establish (using datasets mainly obtained by the Geotail Energetic Particles and Ion Composition (EPIC/ICS instrument that it actually provides strong evidence for a purely spatial structure. Each bi-layer event is composed of two distinct layers with counterstreaming energetic electron fluxes, parallel and antiparallel to the local ambient magnetic field lines; in particular, the tailward directed fluxes always occur in a region adjacent to the lobes. Adopting the X-line as a standard reconnection model, we determine the occurrence of bi-layer events relatively to the neutral point, in the substorm frame; four (out of the shown seven events are observed earthward and three tailward, a result implying that four events probably occurred with the substorm's local recovery phase. We discuss the bi-layer events in terms of the X-line model; they add more constraints for any candidate electron acceleration mechanism. It should be stressed that until this time, none proposed electron acceleration mechanism has discussed or predicted these layered structures with all their properties. Then we discuss the bi-layer events in terms of the much promising "akis model", as introduced by Sarafopoulos (2008. The akis magnetic field topology is embedded in a thinned plasma sheet and is potentially causing charge separation. We assume that as the R_c curvature radius of the magnetic field line tends to become equal to the ion gyroradius r_g, then the ions become non-adiabatic. At the limit R_c=r_g the demagnetization process is also under way and the frozen-in magnetic field condition is violated by strong wave turbulence; hence, the ion particles in this geometry are stochastically scattered. In addition, ion diffusion probably takes place across the magnetic field, since an

Plasmon modes of bilayer molybdenum disulfide: a density functional study

Science.gov (United States)

Torbatian, Z.; Asgari, R.

2017-11-01

We explore the collective electronic excitations of bilayer molybdenum disulfide (MoS2) using density functional theory together with random phase approximation. The many-body dielectric function and electron energy-loss spectra are calculated using an ab initio based model involving material-realistic physical properties. The electron energy-loss function of the bilayer MoS2 system is found to be sensitive to either electron or hole doping and this is due to the fact that the Kohn-Sham band dispersions are not symmetric for energies above and below the zero Fermi level. Three plasmon modes are predicted, a damped high-energy mode, one optical mode (in-phase mode) for which the plasmon dispersion exhibits \\sqrt q in the long wavelength limit originating from low-energy electron scattering and finally a highly damped acoustic mode (out-of-phase mode).

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.

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

1994-12-31

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.

Anomalous conductivity noise in gapped bilayer graphene heterostructure

Science.gov (United States)

Aamir, Mohammed Ali; Karnatak, Paritosh; Sai, T. Phanindra; Ghosh, Arindam

Bilayer graphene has unique electronic properties - it has a tunable band gap and also, valley symmetry and pseudospin degree of freedom like its single layer counterpart. In this work, we present a study of conductance fluctuations in dual gated bilayer graphene heterostructures by varying the Fermi energy and the band gap independently. At a fixed band gap, we find that the conductance fluctuations obtained by Fermi energy ensemble sampling increase rapidly as the Fermi energy is tuned to charge neutrality point (CNP) whereas the time-dependent conductance fluctuations diminish rapidly. This discrepancy is completely absent at higher number densities, where the transport is expected to be through the 2D bulk of the bilayer system. This observation indicates that near the CNP, electrical transport is highly sensitive to Fermi energy, but becomes progressively immune to time-varying disorder. A possible explanation may involve transport via edge states which becomes the dominant conduction mechanism when the bilayer graphene is gapped and Fermi energy is situated close to the CNP, thereby causing a dimensional crossover from 2D to 1D transport. Our experiment outlines a possible experimental protocol to probe intrinsic topological states in gapped bilayer graphene.

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

Energy Technology Data Exchange (ETDEWEB)

Chegel, Raad, E-mail: Raad.chegel@gmail.com

2017-04-15

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-, AB{sub 1}- and AB{sub 2}- 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.

Electron transport in a bilayer graphene/layered superconductor NbSe2 junction: effect of work function difference

Science.gov (United States)

Yarimizu, Katsuhide; Tomori, Hikari; Watanabe, Kenji; Taniguchi, Takashi; Kanda, Akinobu

2018-03-01

We have experimentally studied electron transport in a bilayer graphene (BLG)/layered superconductor NbSe2 junction encapsulated with hexagonal boron nitride. The junction exhibits nonlinear current-voltage characteristics which strongly depend on the gate voltage around the charge neutrality point (CNP) of the BLG. Besides, we observe that the gate voltage dependence of electron transport in the BLG portion close to the junction interface is different from that of the BLG portion apart from the interface, indicating that the spatial variation of the Dirac point in the charge transfer region due to the difference in work function between superconductor and graphene needs to be considered in the analysis of the superconducting proximity effect.

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

KAUST Repository

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

2013-01-01

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

An electrochemical investigation on the dissolution of bilayered porous anodic alumina

International Nuclear Information System (INIS)

Liao, Jinfu; Ling, Zhiyuan; Li, Yi; Hu, Xing

2015-01-01

Highlights: • Pulse polarization was introduced to investigate the dissolution of PAA. • Electric field within the bilayers was estimated. • The formation of the barrier layer involves mainly solid-state processes. • The structure should be the determining factor in the dissolution of the bilayers. - Abstract: Anodic alumina attracts much research interest in many disciplines for its versatility. Meanwhile, some aspects regarding its growth are still not well-understood, such as the formation and properties of its bilayer structure. In this paper, along with capacitance measurement, pulse polarization is introduced to study the dissolution of bilayered porous anodic alumina (PAA). Combined with electron microscope observation, the electric field in the outer layer is estimated to be slightly higher than that in the inner layer. By comparing with (oxy-)hydroxide layers, the electric field distribution within barrier layer of PAA confirms that the bilayers are compact and are formed mainly by solid-state ionic migration. The changes of dissolution rates after annealing and application of electric pulses suggest that structure may be a determining factor for the dissolution behaviors of the bilayers.

Flexural phonon limited phonon drag thermopower in bilayer graphene

Science.gov (United States)

Ansari, Mohd Meenhaz; Ashraf, SSZ

2018-05-01

We investigate the phonon drag thermopower from flexural phonons as a function of electron temperature and carrier concentration in the Bloch-Gruneisen regime in non-strained bilayer graphene using Boltzmann transport equation approach. The flexural phonons are expected to be the major source of intrinsic scattering mechanism in unstrained bilayer graphene due to their large density. The flexural phonon modes dispersion relation is quadratic so these low energy flexural phonons abound at room temperature and as a result deform the bilayer graphene sheet in the out of plane direction and affects the transport properties. We also produce analytical result for phonon-drag thermopower from flexural phonons and find that phonon-drag thermopower depicts T2 dependence on temperature and n-1 on carrier concentration.

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Stacking change in MoS2 bilayers induced by interstitial Mo impurities.

Science.gov (United States)

Cortés, Natalia; Rosales, Luis; Orellana, Pedro A; Ayuela, Andrés; González, Jhon W

2018-02-01

We use a theoretical approach to reveal the electronic and structural properties of molybdenum impurities between MoS 2 bilayers. We find that interstitial Mo impurities are able to reverse the well-known stability order of the pristine bilayer, because the most stable form of stacking changes from AA' (undoped) into AB' (doped). The occurrence of Mo impurities in different positions shows their split electronic levels in the energy gap, following octahedral and tetrahedral crystal fields. The energy stability is related to the accommodation of Mo impurities compacted in hollow sites between layers. Other less stable configurations for Mo dopants have larger interlayer distances and band gaps than those for the most stable stacking. Our findings suggest possible applications such as exciton trapping in layers around impurities, and the control of bilayer stacking by Mo impurities in the growth process.

Metallization and superconductivity in Ca-intercalated bilayer MoS2

Science.gov (United States)

Szczȱśniak, R.; Durajski, A. P.; Jarosik, M. W.

2017-12-01

A two-dimensional molybdenum disulfide (MoS2) has attracted significant interest recently due to its outstanding physical, chemical and optoelectronic properties. In this paper, using the first-principles calculations, the dynamical stability, electronic structure and superconducting properties of Ca-intercalated bilayer MoS2 are investigated. The calculated electron-phonon coupling constant implies that the stable form of investigated system is a strong-coupling superconductor (λ = 1.05) with a low value of critical temperature (TC = 13.3 K). Moreover, results obtained within the framework of the isotropic Migdal-Eliashberg formalism proved that Ca-intercalated bilayer MoS2 exhibits behavior that goes beyond the scope of the conventional BCS theory.

Electronic Resource Management Systems

Directory of Open Access Journals (Sweden)

Mark Ellingsen

2004-10-01

Full Text Available Computer applications which deal with electronic resource management (ERM are quite a recent development. They have grown out of the need to manage the burgeoning number of electronic resources particularly electronic journals. Typically, in the early years of e-journal acquisition, library staff provided an easy means of accessing these journals by providing an alphabetical list on a web page. Some went as far as categorising the e-journals by subject and then grouping the journals either on a single web page or by using multiple pages. It didn't take long before it was recognised that it would be more efficient to dynamically generate the pages from a database rather than to continually edit the pages manually. Of course, once the descriptive metadata for an electronic journal was held within a database the next logical step was to provide administrative forms whereby that metadata could be manipulated. This in turn led to demands for incorporating more information and more functionality into the developing application.

Electron density analysis of the effects of sugars on the structure of lipid bilayers at low hydration - a preliminary study

Energy Technology Data Exchange (ETDEWEB)

Lenné, T.; Kent, B.; Koster, K.L.; Garvey, C.J.; Bryant, G. (ANSTO); (USD); (ANU); (RMIT)

2012-02-06

Small angle X-ray scattering is used to study the effects of sugars on membranes during dehydration. Previous work has shown that the bilayer and chain-chain repeat spacings of DPPC bilayers are relatively unaffected by the presence of sugars. In this work we present a preliminary analysis of the electron density profiles of DPPC in the presence of sugars at low hydration. The difficulties of determining the correct phasing are discussed. Sugars and other small solutes have been shown to have an important role in improving the tolerance of a range of species to desiccation and freezing. In particular it has been shown that sugars can stabilize membranes in the fluid membrane phase during dehydration, and in the fully dehydrated state. Equivalently, at a particular hydration, the presence of sugars lowers the transition temperature between the fluid and gel phases. There are two competing models for explaining the effects of sugars on membrane phase transition temperatures. One, designated the water replacement hypothesis (WRH) states that sugars hydrogen bond to phospholipid headgroups, thus hindering the fluid-gel phase transition. One version of this model suggests that certain sugars (such as trehalose) achieve the measured effects by inserting between the phospholipid head groups. An alternative model explains the observed effects of sugars in terms of the sugars effect on the hydration repulsion that develops between opposing membranes during dehydration. The hydration repulsion leads to a lateral compressive stress in the bilayer which squeezes adjacent lipids more closely together, resulting in a transition to the gel phase. When sugars are present, their osmotic and volumetric effects reduce the hydration repulsion, reduce the compressive stress in the membranes, and therefore tend to maintain the average lateral separation between lipids. This model is called the hydration forces explanation (HFE). We recently showed that neither mono- nor di

Controlled release from bilayer-decorated magnetoliposomes via electromagnetic heating.

Science.gov (United States)

Chen, Yanjing; Bose, Arijit; Bothun, Geoffrey D

2010-06-22

Nanoscale assemblies that can be activated and controlled through external stimuli represent a next stage in multifunctional therapeutics. We report the formation, characterization, and release properties of bilayer-decorated magnetoliposomes (dMLs) that were prepared by embedding small hydrophobic SPIO nanoparticles at different lipid molecule to nanoparticle ratios within dipalmitoylphosphatidylcholine (DPPC) bilayers. The dML structure was examined by cryogenic transmission electron microscopy and differential scanning calorimetry, and release was examined by carboxyfluorescein leakage. Nanoparticle heating using alternating current electromagnetic fields (EMFs) operating at radio frequencies provided selective release of the encapsulated molecule at low nanoparticle concentrations and under physiologically acceptable EMF conditions. Without radio frequency heating, spontaneous leakage from the dMLs decreased with increasing nanoparticle loading, consistent with greater bilayer stability and a decrease in the effective dML surface area due to aggregation. With radio frequency heating, the initial rate and extent of leakage increased significantly as a function of nanoparticle loading and electromagnetic field strength. The mechanism of release is attributed to a combination of bilayer permeabilization and partial dML rupture.

High efficiency electrophosphorescence from bilayer organic light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Li Minghang; Lin, Ming-Te; Shepherd, Nigel D [Department of Material Science and Engineering, University of North Texas, Denton, TX (United States); Chen, Wei-Hsuan; Oswald, Iain; Omary, Mohammad [Department of Chemeistry, University of North Texas, Denton, TX (United States)

2011-09-14

An electron mobility of 2.7 x 10{sup -5} cm{sup 2} V{sup -1} s{sup -1} was measured for the phosphorescent emitter bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II)(Pt(ptp)2), which prompted its evaluation as both the emissive layer and electron transport layer in organic light emitting diodes with a simple bilayer structure. Power and external quantum efficiencies of 54.0 {+-} 0.2 lm W{sup -1} and 15.9% were obtained, which as far as we could ascertain are amongst the highest reported values for bilayer devices. We ascribe the high device efficiency to the combination of the high electron mobility, short excited-state lifetime (117 ns) and high luminescence quantum yield (60%) of the bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II). The colour temperature of the devices was 2855 K at 5 V, which places the emission in the 'warm' light spectral region.

Electrostatically confined quantum rings in bilayer graphene.

Science.gov (United States)

Zarenia, M; Pereira, J M; Peeters, F M; Farias, G A

2009-12-01

We propose a new system where electron and hole states are electrostatically confined into a quantum ring in bilayer graphene. These structures can be created by tuning the gap of the graphene bilayer using nanostructured gates or by position-dependent doping. The energy levels have a magnetic field (B(0)) dependence that is strikingly distinct from that of usual semiconductor quantum rings. In particular, the eigenvalues are not invariant under a B(0) --> -B(0) transformation and, for a fixed total angular momentum index m, their field dependence is not parabolic, but displays two minima separated by a saddle point. The spectra also display several anticrossings, which arise due to the overlap of gate-confined and magnetically confined states.

Electronic Resources Management Project Presentation 2012

KAUST Repository

Ramli, Rindra M.

2012-11-05

This presentation describes the electronic resources management project undertaken by the KAUST library. The objectives of this project is to migrate information from MS Sharepoint to Millennium ERM module. One of the advantages of this migration is to consolidate all electronic resources into a single and centralized location. This would allow for better information sharing among library staff.

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.

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.

Lipid bilayers and interfaces

NARCIS (Netherlands)

Kik, R.A.

2007-01-01

In biological systems lipid bilayers are subject to many different interactions with other entities. These can range from proteins that are attached to the hydrophilic region of the bilayer or transmembrane proteins that interact with the hydrophobic region of the lipid bilayer. Interaction between

Novel electron gas systems

International Nuclear Information System (INIS)

Senatore, G.; Rapisarda, F.; Conti, S.

1998-01-01

We review recent progress on the physics of electrons in the bilayered electron gas, relevant to coupled quantum wells in GaAs/AIGaAs heterostructures. First we focus on the phase diagram of a symmetric bilayer at T = B = 0, obtained by diffusion Monte Carlo (DMC) simulations. It is found that inter-layer correlations stabilize crystalline structures at intermediate inter-layer separation, while favoring a liquid phase at smaller distance. Also, the available DMC evidence is in contrast with the recently (Hartree-Fock) predicted total charge transfer (TCT), whereby all the electron spontaneously jump in one layer. In fact, one can show that such a TCT state is never stable in the ideal bilayer with no tunneling. We finally comment on ongoing DMC investigations on the electron-hole bilayer, where excitonic condensation is expected to take place. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

Magnetically Assisted Bilayer Composites for Soft Bending Actuators

Directory of Open Access Journals (Sweden)

Sung-Hwan Jang

2017-06-01

Full Text Available This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.

Magnetically Assisted Bilayer Composites for Soft Bending Actuators.

Science.gov (United States)

Jang, Sung-Hwan; Na, Seon-Hong; Park, Yong-Lae

2017-06-12

This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.

PRINCIPLES OF CONTENT FORMATION EDUCATIONAL ELECTRONIC RESOURCE

Directory of Open Access Journals (Sweden)

О Ю Заславская

2017-12-01

Full Text Available The article considers modern possibilities of information and communication technologies for the design of electronic educational resources. The conceptual basis of the open educational multimedia system is based on the modular architecture of the electronic educational resource. The content of the electronic training module can be implemented in several versions of the modules: obtaining information, practical exercises, control. The regularities in the teaching process in modern pedagogical theory are considered: general and specific, and the principles for the formation of the content of instruction at different levels are defined, based on the formulated regularities. On the basis of the analysis, the principles of the formation of the electronic educational resource are determined, taking into account the general and didactic patterns of teaching.As principles of the formation of educational material for obtaining information for the electronic educational resource, the article considers: the principle of methodological orientation, the principle of general scientific orientation, the principle of systemic nature, the principle of fundamentalization, the principle of accounting intersubject communications, the principle of minimization. The principles of the formation of the electronic training module of practical studies in the article include: the principle of systematic and dose based consistency, the principle of rational use of study time, the principle of accessibility. The principles of the formation of the module for monitoring the electronic educational resource can be: the principle of the operationalization of goals, the principle of unified identification diagnosis.

Electron paramagnetic resonance (EPR spectral components of spin-labeled lipids in saturated phospholipid bilayers: effect of cholesterol

Directory of Open Access Journals (Sweden)

Heverton Silva Camargos

2013-01-01

Full Text Available Electron paramagnetic resonance (EPR spectroscopy was used to study the main structural accommodations of spin labels in bilayers of saturated phosphatidylcholines with acyl chain lengths ranging from 16 to 22 carbon atoms. EPR spectra allowed the identification of two distinct spectral components in thermodynamic equilibrium at temperatures below and above the main phase transition. An accurate analysis of EPR spectra, using two fitting programs, enabled determination of the thermodynamic profile for these major probe accommodations. Focusing the analysis on two-component EPR spectra of a spin-labeled lipid, the influence of 40 mol % cholesterol in DPPC was studied.

Electronic phase transitions under hydrostatic pressure in LaMnO3 (111) bilayers sandwiched between LaAlO3

KAUST Repository

Tahini, Hassan Ali; Cossu, Fabrizio; Singh, Nirpendra; Smith, S. C.; Schwingenschlö gl, Udo

2016-01-01

Using ab initio calculations, we investigate the effect of hydrostatic pressure on the electronic structure of LaMnO3 (111) bilayers sandwiched between LaAlO3. In the ideal heterostructure we observe Dirac cones at the Fermi energy. However, octahedral tiltings open a band gap and thus destroy the Dirac nature. We show that the effect of the tiltings can be suppressed by hydrostatic pressure from 40 GPa to 60 GPa. At higher pressure further phase transitions are encountered.

Electronic phase transitions under hydrostatic pressure in LaMnO3 (111) bilayers sandwiched between LaAlO3

KAUST Repository

Tahini, Hassan Ali

2016-01-13

Using ab initio calculations, we investigate the effect of hydrostatic pressure on the electronic structure of LaMnO3 (111) bilayers sandwiched between LaAlO3. In the ideal heterostructure we observe Dirac cones at the Fermi energy. However, octahedral tiltings open a band gap and thus destroy the Dirac nature. We show that the effect of the tiltings can be suppressed by hydrostatic pressure from 40 GPa to 60 GPa. At higher pressure further phase transitions are encountered.

Implementing CORAL: An Electronic Resource Management System

Science.gov (United States)

Whitfield, Sharon

2011-01-01

A 2010 electronic resource management survey conducted by Maria Collins of North Carolina State University and Jill E. Grogg of University of Alabama Libraries found that the top six electronic resources management priorities included workflow management, communications management, license management, statistics management, administrative…

Kohn-Luttinger superconductivity in monolayer and bilayer semimetals with the Dirac spectrum

International Nuclear Information System (INIS)

Kagan, M. Yu.; Mitskan, V. A.; Korovushkin, M. M.

2014-01-01

The effect of Coulomb interaction in an ensemble of Dirac fermions on the formation of superconducting pairing in monolayer and bilayer doped graphene is studied using the Kohn-Luttinger mechanism disregarding the Van der Waals potential of the substrate and impurities. The electronic structure of graphene is described using the Shubin-Vonsovsky model taking into account the intratomic, interatomic, and interlayer (in the case of bilayer graphene) Coulomb interactions between electrons. The Cooper instability is determined by solving the Bethe-Saltpeter integral equation. The renormalized scattering amplitude is obtained with allowance for the Kohn-Luttinger polarization contributions up to the second order of perturbation theory in the Coulomb interaction. It plays the role of effective interaction in the Bethe-Salpeter integral equation. It is shown that the allowance for the Kohn-Luttinger renormalizations as well as intersite Coulomb interaction noticeably affects the competition between the superconducting phases with the f-wave and d + id-wave symmetries of the order parameter. It is demonstrated that the superconducting transition temperature for an idealized graphene bilayer with significant interlayer Coulomb interaction between electrons is noticeably higher than in the monolayer case

Twisted Bilayer Graphene. Interlayer configuration and magnetotransport signatures

Energy Technology Data Exchange (ETDEWEB)

Rode, Johannes C.; Smirnov, Dmitri; Belke, Christopher; Schmidt, Hennrik; Haug, Rolf J. [Institut fuer Festkoerperphysik, Hannover (Germany)

2017-11-15

Twisted Bilayer Graphene may be viewed as very first representative of the now booming class of artificially layered 2D materials. Consisting of two sheets from the same structure and atomic composition, its decisive degree of freedom lies in the rotation between crystallographic axes in the individual graphene monolayers. Geometrical consideration finds angle-dependent Moire patterns as well as commensurate superlattices of opposite sublattice exchange symmetry. Beyond the approach of rigidly interposed lattices, this review takes focus on the evolving topic of lattice corrugation and distortion in response to spatially varying lattice registry. The experimental approach to twisted bilayers requires a basic control over preparation techniques; important methods are summarized and extended on in the case of bilayers folded from monolayer graphene via AFM nanomachining. Central morphological parameters to the twisted bilayer, rotational mismatch and interlayer separation are studied in a broader base of samples. Finally, experimental evidence for a number of theoretically predicted, controversial electronic scenarios are reviewed; magnetotransport signatures are discussed in terms of Fermi velocity, van Hove singularities and Berry phase and assessed with respect to the underlying experimental conditions, thereby referring back to the initially considered variations in relaxed lattice structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Managing electronic resources a LITA guide

CERN Document Server

Weir, Ryan O

2012-01-01

Informative, useful, current, Managing Electronic Resources: A LITA Guide shows how to successfully manage time, resources, and relationships with vendors and staff to ensure personal, professional, and institutional success.

Effects of co-sintering in self-standing CGO/YSZ and CGO/ ScYSZ dense bi-layers

DEFF Research Database (Denmark)

Teocoli, Francesca; Ni, De Wei; Brodersen, Karen

2014-01-01

-layers are critical due to the mismatch of thermo-mechanical and sintering properties among the materials. Despite the better sinteractivity of ScYSZ, the self-standing CGO/ScYSZ bilayer presents more challenges in terms of densification compared with the CGO/YSZ bi-layer. In particular, above 1200 C, ScYSZ and CGO......-standing bi-layered electrolyte system. The combined use of thermo-mechanical analysis, optical dilatometry, and scanning electron microscopy ensures a systematic characterization of both the individual layers and CGO/YSZ and CGO/ScYSZ bi-layered laminates. The results of the co-firing process of the bi...

Structural and electro-optical properties of bilayer graphyne like BN sheet

Science.gov (United States)

Behzad, Somayeh

2016-12-01

The structural, electronic and optical properties of bilayer graphyne like BN sheet (BNyne) with different stacking manners have been explored by the first-principles calculations. The stabilities of α-BNyne bilayers with different stacking manners are compared. The α-BNyne Bilayers have wide band gaps. Compared to the single α-BNyne, the numbers of energy bands are doubled due to the interlayer interactions and the band gap is reduced. The AB-I configuration has a direct band gap while the band gap becomes indirect for AA-II. The calculated ε2 (ω) of bilayer α-BNyne for (Eǁx) is similar to that of the monolayer α-BNyne, except for the small changes of peak positions and increasing of peak intensities. For (Eǁz), the first absorption peak occures at 3.86 eV, and the prominant peak of monolayer at 9.17 eV becomes broadened. These changes are related to the new transitions resulting from the band splitting.

Landau levels in biased graphene structures with monolayer-bilayer interfaces

Science.gov (United States)

Mirzakhani, M.; Zarenia, M.; Vasilopoulos, P.; Ketabi, S. A.; Peeters, F. M.

2017-09-01

The electron energy spectrum in monolayer-bilayer-monolayer and in bilayer-monolayer-bilayer graphene structures is investigated and the effects of a perpendicular magnetic field and electric bias are studied. Different types of monolayer-bilayer interfaces are considered as zigzag (ZZ) or armchair (AC) junctions which modify considerably the bulk Landau levels (LLs) when the spectra are plotted as a function of the center coordinate of the cyclotron orbit. Far away from the two interfaces, one obtains the well-known LLs for extended monolayer or bilayer graphene. The LL structure changes significantly at the two interfaces or junctions where the valley degeneracy is lifted for both types of junctions, especially when the distance between them is approximately equal to the magnetic length. Varying the nonuniform bias and the width of this junction-to-junction region in either structure strongly influence the resulting spectra. Significant differences exist between ZZ and AC junctions in both structures. The densities of states (DOSs) for unbiased structures are symmetric in energy whereas those for biased structures are asymmetric. An external bias creates interface LLs in the gaps between the LLs of the unbiased system in which the DOS can be quite small. Such a pattern of LLs can be probed by scanning tunneling microscopy.

Energy spectrums of bilayer triangular phosphorene quantum dots and antidots

Directory of Open Access Journals (Sweden)

Z. T. Jiang

2017-04-01

Full Text Available We theoretically investigate the confined states of the bilayer triangular phosphorene dots and antidots by means of the tight-binding approach. The dependence of the energy levels on the size, the type of the boundary edges, and the orientation of the dots and antidots, and the influences of the electric and magnetic fields on the energy levels, are all completely analyzed. It is found that the energy level numbers of the bilayer dots and antidots are determined by the energy levels in two layers. The external electric field can effectively tune the energy levels of the edge states in both layers to move in opposite directions. With the increase of the magnetic field, the magnetic energy levels can approach the Landau levels of the phosphorene monolayer, the phosphorene bilayer, or both, depending on the specific geometry of the monolayer-bilayer hybrid phosphorene quantum dots. This research should be helpful for the overall understanding of the electronic properties of the multilayer hybrid phosphorene nanostructures and designing the corresponding phosphorene devices.

Design and Analysis of CMOS-Compatible III-V Compound Electron-Hole Bilayer Tunneling Field-Effect Transistor for Ultra-Low-Power Applications.

Science.gov (United States)

Kim, Sung Yoon; Seo, Jae Hwa; Yoon, Young Jun; Lee, Ho-Young; Lee, Seong Min; Cho, Seongjae; Kang, In Man

2015-10-01

In this work, we design and analyze complementary metal-oxide-semiconductor (CMOS)-compatible III-V compound electron-hole bilayer (EHB) tunneling field-effect transistors (TFETs) by using two-dimensional (2D) technology computer-aided design (TCAD) simulations. A recently proposed EHB TFET exploits a bias-induced band-to-band tunneling (BTBT) across the electron-hole bilayer by an electric field from the top and bottom gates. This is in contrast to conventional planar p(+)-p(-)-n TFETs, which utilize BTBT across the source-to-channel junction. We applied III-V compound semiconductor materials to the EHB TFETs in order to enhance the current drivability and switching performance. Devices based on various compound semiconductor materials have been designed and analyzed in terms of their primary DC characteristics. In addition, the operational principles were validated by close examination of the electron concentrations and energy-band diagrams under various operation conditions. The simulation results of the optimally designed In0.533Ga0.47As EHB TFET show outstanding performance, with an on-state current (Ion) of 249.5 μA/μm, subthreshold swing (S) of 11.4 mV/dec, and threshold voltage (Vth) of 50 mV at VDS = 0.5 V. Based on the DC-optimized InGaAs EHB TFET, the CMOS inverter circuit was simulated in views of static and dynamic behaviors of the p-channel device with exchanges between top and bottom gates or between source and drain electrodes maintaining the device structure.

The longitudinal optical conductivity in bilayer graphene and other two-dimensional systems

Energy Technology Data Exchange (ETDEWEB)

Yang, C.H., E-mail: chyang@nuist.edu.cn [School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Ao, Z.M., E-mail: zhimin.ao@uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney ,PO Box 123, Broadway, Sydney, NSW 2007 (Australia); Wei, X.F. [West Anhui University, Luan 237012 (China); Jiang, J.J. [Department of Physics, Sanjing College, Nanjing 210012 (China)

2015-01-15

The longitudinal optical conductivity in bilayer graphene is calculated using the dielectric function by defining the density operator theoretically, while the effect of the broadening width determined by the scattering sources on the optical conductivity is also investigated. Some features, such as chirality, energy dispersion and density of state (DOS) in bilayer graphene, are similar to those in monolayer graphene and a traditional two-dimensional electron gas (2DEG). Therefore, in this paper, the bilayer graphene optical conductivity is compared with the results in these two systems. The analytical and numerical results show that the optical conductivity per graphene layer is almost a constant and close to e{sup 2}/(4ℏ), which agrees with the experimental results.

Magnetotransport of High Mobility Holes in Monolayer and Bilayer WSe2

Science.gov (United States)

Tutuc, Emanuel

Transition metal dichalcogenides have attracted significant interest because of their two-dimensional crystal structure, large band-gap, and strong spin-orbit interaction which leads to spin-valley locking. Recent advances in sample fabrication have allowed the experimental study of low temperature magneto-transport of high mobility holes in WSe2. We review here the main results of these studies which reveal clear quantum Hall states in mono- and bilayer WSe2. The data allows the extraction of an effective hole mass of m* = 0.45me (me is the bare electron mass) in both mono and bilayer WSe2. A systematic study of the carrier distribution in bilayer WSe2 determined from a Fourier analysis of the Shubnikov-de Haas oscillations indicates that the two layers are weakly coupled. The individual layer density dependence on gate bias shows negative compressibility, a signature of strong electron-electron interaction in these materials associated with the large effective mass. We discuss the interplay between cyclotron and Zeeman splitting using the dependence of the quantum Hall state sequence on carrier density, and the angle between the magnetic field and the WSe2 plane. Work done in collaboration with B. Fallahazad, H. C. P. Movva, K. Kim, S. K. Banerjee, T. Taniguchi, and K. Watanabe. This work supported by the Nanoelectronics Research Initiative SWAN center, Intel Corp., and National Science Foundation.

Condensation energy of the superconducting bilayer cuprates

Indian Academy of Sciences (India)

cuprates also depends on the number of CuO2 layers per unit cell and the extent of doping. In a bilayer or ... unit cell is smaller than the adjacent layers in a single layer system; therefore it is natural to include interlayer .... energy conservation principle, the change in the kinetic energy of the electrons in the out- of-plane ...

Transport measurements in superconductor/Heusler bilayers

Energy Technology Data Exchange (ETDEWEB)

Imort, Inga-Mareen; Fabretti, Savio; Thomas, Patrick; Reiss, Guenter; Thomas, Andy [Fakultaet fuer Physik, Universitaet Bielefeld, Bielefeld (Germany)

2012-07-01

Superconductivity and ferromagnetism are two contrary phenomena due to their electronic properties. The investigation of superconductor (S)/ferromagnet (F) heterostructures has attracted a lot of scientific interest since they allow studying the interplay between superconductivity and ferromagnetism. Additionally, applications seem possible such as F/S/F spin valves and S/F/S π-junctions. Using transport- and magnetotransport-measurements, we investigate the behavior of the superconducting transition temperature T{sub c} in NbTi/Co{sub 2}FeSi bilayers as a function of different layer thicknesses and for varying magnetic moments of the Co{sub 2}FeSi layers. Using rf-magnetron sputtering, NbTi/Co{sub 2}FeSi bilayers were grown on single-crystalline MgO(001) substrates and in-situ annealed at different temperatures. The layered character of our samples has been tested by X-ray diffraction (XRD) scans. The electronic and magnetic transport measurements have been performed between 3 and 300 K with the magnetic field up to 4 T oriented in the film plane. The dependence of T{sub c} on the NbTi- and Co{sub 2}FeSi-layer thickness enables an estimation of the interface transparency of the NbTi/Co{sub 2}FeSi barrier in the framework of recent theoretical models.

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...

Gate-Controlled Transmission of Quantum Hall Edge States in Bilayer Graphene.

Science.gov (United States)

Li, Jing; Wen, Hua; Watanabe, Kenji; Taniguchi, Takashi; Zhu, Jun

2018-02-02

The edge states of the quantum Hall and fractional quantum Hall effect of a two-dimensional electron gas carry key information of the bulk excitations. Here we demonstrate gate-controlled transmission of edge states in bilayer graphene through a potential barrier with tunable height. The backscattering rate is continuously varied from 0 to close to 1, with fractional quantized values corresponding to the sequential complete backscattering of individual modes. Our experiments demonstrate the feasibility to controllably manipulate edge states in bilayer graphene, thus opening the door to more complex experiments.

Gate-Controlled Transmission of Quantum Hall Edge States in Bilayer Graphene

Science.gov (United States)

Li, Jing; Wen, Hua; Watanabe, Kenji; Taniguchi, Takashi; Zhu, Jun

2018-02-01

The edge states of the quantum Hall and fractional quantum Hall effect of a two-dimensional electron gas carry key information of the bulk excitations. Here we demonstrate gate-controlled transmission of edge states in bilayer graphene through a potential barrier with tunable height. The backscattering rate is continuously varied from 0 to close to 1, with fractional quantized values corresponding to the sequential complete backscattering of individual modes. Our experiments demonstrate the feasibility to controllably manipulate edge states in bilayer graphene, thus opening the door to more complex experiments.

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

Effect of interlayer tunneling on the electronic structure of bilayer cuprates and quantum phase transitions in carrier concentration and high magnetic field

International Nuclear Information System (INIS)

Ovchinnikov, S. G.; Makarov, I. A.; Shneyder, E. I.

2011-01-01

We present a theoretical study of the electronic structure of bilayer HTSC cuprates and its evolution under doping and in a high magnetic field. Analysis is based on the t-t′-t″-J* model in the generalized Hartree-Fock approximation. Possibility of tunneling between CuO2 layers is taken into account in the form of a nonzero integral of hopping between the orbitals of adjacent planes and is included in the scheme of the cluster form of perturbation theory. The main effect of the coupling between two CuO 2 layers in a unit cell is the bilayer splitting manifested in the presence of antibonding and bonding bands formed by a combination of identical bands of the layers themselves. A change in the doping level induces reconstruction of the band structure and the Fermi surface, which gives rise to a number of quantum phase transitions. A high external magnetic field leads to a fundamentally different form of electronic structure. Quantum phase transitions in the field are observed not only under doping, but also upon a variation of the field magnitude. Because of tunneling between the layers, quantum transitions are also split; as a result, a more complex sequence of the Lifshitz transitions than in single-layer structures is observed.

Interlocking Friction Governs the Mechanical Fracture of Bilayer MoS2.

Science.gov (United States)

Jung, Gang Seob; Wang, Shanshan; Qin, Zhao; Martin-Martinez, Francisco J; Warner, Jamie H; Buehler, Markus J

2018-04-24

A molybdenum disulfide (MoS 2 ) layered system is a two-dimensional (2D) material, which is expected to provide the next generation of electronic devices together with graphene and other 2D materials. Due to its significance for future electronics applications, gaining a deep insight into the fundamental mechanisms upon MoS 2 fracture is crucial to prevent mechanical failure toward reliable applications. Here, we report direct experimental observation and atomic modeling of the complex failure behaviors of bilayer MoS 2 originating from highly variable interlayer frictions, elucidated with in situ transmission electron microscopy and large-scale reactive molecular dynamics simulations. Our results provide a systematic understanding of the effects that different stacking and loading conditions have on the failure mechanisms and crack-tip behaviors in the bilayer MoS 2 systems. Our findings unveil essential properties in fracture of this 2D material and provide mechanistic insight into its mechanical failure.

Spectral properties of excitons in the bilayer graphene

Science.gov (United States)

Apinyan, V.; Kopeć, T. K.

2018-01-01

In this paper, we consider the spectral properties of the bilayer graphene with the local excitonic pairing interaction between the electrons and holes. We consider the generalized Hubbard model, which includes both intralayer and interlayer Coulomb interaction parameters. The solution of the excitonic gap parameter is used to calculate the electronic band structure, single-particle spectral functions, the hybridization gap, and the excitonic coherence length in the bilayer graphene. We show that the local interlayer Coulomb interaction is responsible for the semimetal-semiconductor transition in the double layer system, and we calculate the hybridization gap in the band structure above the critical interaction value. The formation of the excitonic band gap is reported as the threshold process and the momentum distribution functions have been calculated numerically. We show that in the weak coupling limit the system is governed by the Bardeen-Cooper-Schrieffer (BCS)-like pairing state. Contrary, in the strong coupling limit the excitonic condensate states appear in the semiconducting phase, by forming the Dirac's pockets in the reciprocal space.

Strongly compressed Bi (111) bilayer films on Bi{sub 2}Se{sub 3} studied by scanning tunneling microscopy

Energy Technology Data Exchange (ETDEWEB)

Zhang, K. F.; Yang, Fang; Song, Y. R. [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Canhua; Qian, Dong; Gao, C. L.; Jia, Jin-Feng [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China)

2015-09-21

Ultra-thin Bi films show exotic electronic structure and novel quantum effects, especially the widely studied Bi (111) film. Using reflection high-energy electron diffraction and scanning tunneling microscopy, we studied the structure and morphology evolution of Bi (111) thin films grown on Bi{sub 2}Se{sub 3}. A strongly compressed, but quickly released in-plane lattice of Bi (111) is found in the first three bilayers. The first bilayer of Bi shows a fractal growth mode with flat surface, while the second and third bilayer show a periodic buckling due to the strong compression of the in-plane lattice. The lattice slowly changes to its bulk value with further deposition of Bi.

Strongly anisotropic thermal conductivity and adequate breathability of bilayered films for heat management of on-skin electronics

Science.gov (United States)

Zhou, Tianle; Wei, Hao; Tan, Huaping; Wang, Xin; Zeng, Haibo; Liu, Xiaoheng; Nagao, Shijo; Koga, Hirotaka; Nogi, Masaya; Sugahara, Tohru; Suganuma, Katsuaki

2018-07-01

Thin-film wearable electronics are required to be directly laminated on to human skin for reliable, sensitive bio-sensing but with minimal irritation to the user after long-time use. Excellent heat management films with strongly anisotropic thermal conductivity (K) and adequate breathability are increasingly desirable for shielding the skin from heating while allowing the skin to breathe properly. Here, interfacial self-assembly of a graphene oxide (GO) film covering an ambient-dried bacterial cellulose aerogel (AD-BCA) film followed by laser reduction was proposed to prepare laser-reduced GO (L-rGO)/AD-BCA bilayered films. The AD-BCA substrate provides low cross-plane K (K ⊥  ≈  0.052 W mK‑1), high breathability, and high compressive and tensile resistance by ‘partially’ inheriting the pore structure from bacterial cellulose (BC) gel. The introduction of an upper L-rGO film, which is only 0.31 wt% content, dramatically increases the in-plane K (K // ) from 0.3 W mK‑1 in AD-BCA to 10.72 W mK‑1 owing to the highly in-plane oriented, continuous, uniform assembling geometry of the GO film; while K ⊥ decreases to a lower value of 0.033 W mK‑1, mainly owing to the air pockets between L-rGO multilayers caused by the laser reduction. The bilayered films achieve a K // /K ⊥ of 325, which is substantially larger even than that of graphite and similar polymer composites. They permit high transmission rates for water vapor (416.78 g/m2/day, >204 g/m2/day of normal skin) and O2 (449.35 cm3/m2/day). The combination of strongly anisotropic thermal conductivity and adequate breathability facilitates applications in heat management in on-skin electronics.

Asymmetric intermixing in Co/Ti bilayer

International Nuclear Information System (INIS)

Suele, P.; Kotis, L.; Toth, L.; Menyhard, M.; Egelhoff, W.F.

2008-01-01

Recently we have studied the ion mixing of mass-anisotropic bilayer and found strong asymmetry depending on the succession of the layers [P. Suele, M. Menyhard, L. Kotis, J. Labar, W.F. Egelhoff Jr., J. Appl. Phys. 101 (2007) 043502]. The finding was explained by the mass difference of the constituents. To check the validity of explanation we studied the interface broadening of Co/Ti and Ti/Co bilayers due to low-energy ion bombardment. We have applied Auger electron spectroscopy depth profiling and molecular dynamics simulation to determine the intermixing. Since the Co/Ti system is nearly mass isotropic the ballistic intermixing mechanism can be ruled out and no asymmetry is expected. In contrary to the expectation both methods showed asymmetry of intermixing at bombardment of 2 keV ion energy. The asymmetry vanishes progressively with decreasing ion energy. We suggest that atomic size-anisotropy could play some role in the enhancement of interdiffusion of Co in Ti

Modeling of transient electroluminescence overshoot in bilayer organic light-emitting diodes using rate equations

Energy Technology Data Exchange (ETDEWEB)

Chandra, V.K. [Department of Electrical and Electronics Engineering, Chhatrapati Shivaji Institute of Technology, Shivaji Nagar, Kolihapuri, Durg 491001 (C.G.) (India); Chandra, B.P., E-mail: bpchandra4@yahoo.co.in [Department of Applied Physics, Ashoka Institute of Technology and Management, Rajnandgaon 491441 (C.G.) (India); Tiwari, M. [Department of Postgraduate Studies and Research in Physics and Electronics, Rani Durgavati University, Jabalpur 482001 (M.P.) (India); Baghel, R.N. [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492010 (C.G.) (India); Ramrakhiani, M. [Department of Postgraduate Studies and Research in Physics and Electronics, Rani Durgavati University, Jabalpur 482001 (M.P.) (India)

2012-06-15

When a voltage pulse is applied under forward biased condition to a spin-coated bilayer organic light-emitting diode (OLED), then initially the electroluminescence (EL) intensity appearing after a delay time, increases with time and later on it attains a saturation value. At the end of the voltage pulse, the EL intensity decreases with time, attains a minimum intensity and then it again increases with time, attains a peak value and later on it decreases with time. For the OLEDs, in which the lifetime of trapped carriers is less than the decay time of the EL occurring prior to the onset of overshoot, the EL overshoot begins just after the end of voltage pulse. The overshoot in spin-coated bilayer OLEDs is caused by the presence of an interfacial layer of finite thickness between hole and electron transporting layers in which both transport molecules coexist, whereby the interfacial energy barrier impedes both hole and electron passage. When a voltage pulse is applied to a bilayer OLED, positive and negative space charges are established at the opposite faces of the interfacial layer. Subsequently, the charge recombination occurs with the incoming flux of injected carriers of opposite polarity. When the voltage is turned off, the interfacial charges recombine under the action of their mutual electric field. Thus, after switching off the external voltage the electrons stored in the interface next to the anode cell compartment experience an electric field directed from cathode to anode, and therefore, the electrons move towards the cathode, that is, towards the positive space charge, whereby electron-hole recombination gives rise to luminescence. The EL prior to onset of overshoot is caused by the movement of electrons in the electron transporting states, however, the EL in the overshoot region is caused by the movement of detrapped electrons. On the basis of the rate equations for the detrapping and recombination of charge carriers accumulated at the interface

Gender Analysis Of Electronic Information Resource Use: The Case ...

African Journals Online (AJOL)

Based on the findings the study concluded that access and use of electronic information resources creates a “social digital divide” along gender lines. The study ... Finally, the library needs to change its marketing strategies on the availability of electronic information resources to increase awareness of these resources.

Users satisfaction with electronic information resources and services ...

African Journals Online (AJOL)

This study investigated users satisfaction on the use of electronic information resources and services in MTN Net libraries in ABU & UNIBEN. Two objectives and one null hypotheses were formulated and tested with respect to the users' satisfaction on electronic information resources and services in MTN Net libraries in ...

Modeling of transient electroluminescence overshoot in bilayer organic light-emitting diodes using rate equations

International Nuclear Information System (INIS)

Chandra, V.K.; Chandra, B.P.; Tiwari, M.; Baghel, R.N.; Ramrakhiani, M.

2012-01-01

When a voltage pulse is applied under forward biased condition to a spin-coated bilayer organic light-emitting diode (OLED), then initially the electroluminescence (EL) intensity appearing after a delay time, increases with time and later on it attains a saturation value. At the end of the voltage pulse, the EL intensity decreases with time, attains a minimum intensity and then it again increases with time, attains a peak value and later on it decreases with time. For the OLEDs, in which the lifetime of trapped carriers is less than the decay time of the EL occurring prior to the onset of overshoot, the EL overshoot begins just after the end of voltage pulse. The overshoot in spin-coated bilayer OLEDs is caused by the presence of an interfacial layer of finite thickness between hole and electron transporting layers in which both transport molecules coexist, whereby the interfacial energy barrier impedes both hole and electron passage. When a voltage pulse is applied to a bilayer OLED, positive and negative space charges are established at the opposite faces of the interfacial layer. Subsequently, the charge recombination occurs with the incoming flux of injected carriers of opposite polarity. When the voltage is turned off, the interfacial charges recombine under the action of their mutual electric field. Thus, after switching off the external voltage the electrons stored in the interface next to the anode cell compartment experience an electric field directed from cathode to anode, and therefore, the electrons move towards the cathode, that is, towards the positive space charge, whereby electron–hole recombination gives rise to luminescence. The EL prior to onset of overshoot is caused by the movement of electrons in the electron transporting states, however, the EL in the overshoot region is caused by the movement of detrapped electrons. On the basis of the rate equations for the detrapping and recombination of charge carriers accumulated at the interface

Adsorption of beryllium atoms and clusters both on graphene and in a bilayer of graphite investigated by DFT.

Science.gov (United States)

Ferro, Yves; Fernandez, Nicolas; Allouche, Alain; Linsmeier, Christian

2013-01-09

We herein investigate the interaction of beryllium with a graphene sheet and in a bilayer of graphite by means of periodic DFT calculations. In all cases, we find the beryllium atoms to be more weakly bonded on graphene than in the bilayer. Be(2) forms both magnetic and non-magnetic structures on graphene depending on the geometrical configuration of adsorption. We find that the stability of the Be/bilayer system increases with the size of the beryllium clusters inserted into the bilayer of graphite. We also find a charge transfer from beryllium to the graphite layers. All these results are analysed in terms of electronic structure.

Alcohol's Effects on Lipid Bilayer Properties

Science.gov (United States)

Ingólfsson, Helgi I.; Andersen, Olaf S.

2011-01-01

Alcohols are known modulators of lipid bilayer properties. Their biological effects have long been attributed to their bilayer-modifying effects, but alcohols can also alter protein function through direct protein interactions. This raises the question: Do alcohol's biological actions result predominantly from direct protein-alcohol interactions or from general changes in the membrane properties? The efficacy of alcohols of various chain lengths tends to exhibit a so-called cutoff effect (i.e., increasing potency with increased chain length, which that eventually levels off). The cutoff varies depending on the assay, and numerous mechanisms have been proposed such as: limited size of the alcohol-protein interaction site, limited alcohol solubility, and a chain-length-dependent lipid bilayer-alcohol interaction. To address these issues, we determined the bilayer-modifying potency of 27 aliphatic alcohols using a gramicidin-based fluorescence assay. All of the alcohols tested (with chain lengths of 1–16 carbons) alter the bilayer properties, as sensed by a bilayer-spanning channel. The bilayer-modifying potency of the short-chain alcohols scales linearly with their bilayer partitioning; the potency tapers off at higher chain lengths, and eventually changes sign for the longest-chain alcohols, demonstrating an alcohol cutoff effect in a system that has no alcohol-binding pocket. PMID:21843475

Anisotropic carrier mobility in single- and bi-layer C3N sheets

Science.gov (United States)

Wang, Xueyan; Li, Qingfang; Wang, Haifeng; Gao, Yan; Hou, Juan; Shao, Jianxin

2018-05-01

Based on the density functional theory combined with the Boltzmann transport equation with relaxation time approximation, we investigate the electronic structure and predict the carrier mobility of single- and bi-layer newly fabricated 2D carbon nitrides C3N. Although C3N sheets possess graphene-like planar hexagonal structure, the calculated carrier mobility is remarkably anisotropic, which is found mainly induced by the anisotropic effective masses and deformation potential constants. Importantly, we find that both the electron and hole mobilities are considerable high, for example, the hole mobility along the armchair direction of single-layer C3N sheets can arrive as high as 1.08 ×104 cm2 V-1 s-1, greatly larger than that of C2N-h2D and many other typical 2D materials. Owing to the high and anisotropic carrier mobility and appropriate band gap, single- and bi-layer semiconducting C3N sheets may have great potential applications in high performance electronic and optoelectronic devices.

Probing interfacial characteristics of rubrene/pentacene and pentacene/rubrene bilayers with soft X-ray spectroscopy.

Science.gov (United States)

Seo, J H; Pedersen, T M; Chang, G S; Moewes, A; Yoo, K-H; Cho, S J; Whang, C N

2007-08-16

The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.

Transient Zitterbewegung of charge carriers in mono- and bilayer graphene, and carbon nanotubes

International Nuclear Information System (INIS)

Rusin, Tomasz M.; Zawadzki, Wlodek

2007-01-01

Observable effects due to trembling motion [Zitterbewegung (ZB)] of charge carriers in bilayer graphene, monolayer graphene, and carbon nanotubes are calculated. It is shown that, when the charge carriers are prepared in the form of Gaussian wave packets, the ZB has a transient character with the decay time of femtoseconds in graphene and picoseconds in nanotubes. Analytical results for bilayer graphene allow us to investigate phenomena which accompany the trembling motion. In particular, it is shown that the transient character of ZB in graphene is due to the fact that wave subpackets related to positive and negative electron energies move in opposite directions, so their overlap diminishes with time. This behavior is analogous to that of the wave packets representing relativistic electrons in a vacuum

Tribology of implantation bilayers

International Nuclear Information System (INIS)

Pivin, J.C.

1989-01-01

The mechanical behaviour of implantation films must be analysed in terms of bilayer rheology (laws of mechanical behaviour). Tribology takes into account thermodynamical, chemical and metallurgical parameters to interpret the friction properties of a system as a whole. One can distinguish between alloying effects of ion implantation and structural modifications. Alloying affects the basic properties of the crystal: elasticity, cohesion, mobility of planar defects, and its surface electronic structure, which determines the reactivity with the atmosphere or the friction counterpart (adhesion). Radiation damage and phase changes act more particularly on the modes of gliding and climbing of dislocations, and fracture mechanisms. 105 refs.; 11 figs.; 1 table

Multifunctional stannum oxide compact bilayer modified by europium and erbium respectively doped ytterbium fluoride for high-performance dye-sensitized solar cell

International Nuclear Information System (INIS)

Yue, Jingyi; Xiao, Yaoming; Li, Yanping; Han, Gaoyi

2017-01-01

Graphical abstract: Multifunctional SnO 2 compact bilayer respectively modified by YbF 3 :Eu 3+ (SYEu) and YbF 3 :Er 3+ (SYEr) demonstrates three functions: 1) reducing the recombination rate of electron-hole pairs, 2) improving the utilization of sunlight, and 3) enhancing the long-term stability of the photovoltaic device. Display Omitted -- Highlights: •Multifunctional SYEu/SYEr compact bilayer is designed and fabricated. •The compact bilayer exhibits a reduced electron recombination rate. •The compact bilayer shows enhanced UV and IR light response via light-conversions. •The double layer has no significant influence on arising quenching effect. -- Abstract: Multifunctional stannum oxide compact bilayer modified by europium and erbium respectively doped ytterbium fluoride (SYEu/SYEr) is designed and prepared by a convenient and low-cost spin-coating approach for dye-sensitized solar cell. The most important three functions of the compact bilayer are reducing the recombination rate of electrons as a barrier layer, enlarging the utilization of sunlight as a luminescence material both with down- and up- conversions, and enhancing the long-term stability of the device as a defender of the dye. Besides, the construction of double layer with down- and up- conversion functions has no significant influence on giving rise to quenching effect. Furthermore, these findings offer potential applications for photovoltaic device with a wide range response of sunlight via the variation in rare-earth species and cell structures.

Organizational matters of competition in electronic educational resources

Directory of Open Access Journals (Sweden)

Ирина Карловна Войтович

2015-12-01

Full Text Available The article examines the experience of the Udmurt State University in conducting competitions of educational publications and electronic resources. The purpose of such competitions is to provide methodological support to educational process. The main focus is on competition of electronic educational resources. The technology of such contests is discussed through detailed analysis of the main stages of the contest. It is noted that the main task of the preparatory stage of the competition is related to the development of regulations on competition and the definition of criteria for selection of the submitted works. The paper also proposes a system of evaluation criteria of electronic educational resources developed by members of the contest organizing committee and jury members. The article emphasizes the importance of not only the preparatory stages of the competition, but also measures for its completion, aimed at training teachers create quality e-learning resources.

Superhard behaviour, low residual stress, and unique structure in diamond-like carbon films by simple bilayer approach

International Nuclear Information System (INIS)

Dwivedi, Neeraj; Kumar, Sushil; Malik, Hitendra K.

2012-01-01

Simple bilayer approach is proposed for synthesizing hard and superhard diamond-like carbon (DLC) coatings with reduced residual stress. For this, M/DLC bilayer (M = Ti and Cu) structures are grown using hybrid system involving radio frequency (RF)-sputtering and RF-plasma enhanced chemical vapor deposition techniques. Ti/DLC bilayer deposited at negative self bias of 100 V shows superhard behaviour with hardness (H) as 49 GPa. Cu/DLC bilayer grown at self bias of 100 V exhibits hard behaviour with H as 22.8 GPa. The hardness of Ti/DLC (Cu/DLC) bilayer gets changed from superhard (hard) to hard (moderate hard) regime, when the self bias is raised to 300 V. Residual stress in Ti/DLC (Cu/DLC) bilayer is found to be significantly low that varies in the range of 1 GPa-1.65 GPa (0.8 GPa-1.6 GPa). The microstructure and morphology are studied by Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). SEM and AFM pictures reveal the creation of nanostructured features in the deposited bilayers. Raman, SEM, and AFM analyses are correlated with the nano-mechanical properties. Owing to excellent nano-mechanical properties, these bilayers can find their direct industrial applications as hard and protective coatings.

Photon-Assisted Resonant Chiral Tunneling Through a Bilayer Graphene Barrier

Directory of Open Access Journals (Sweden)

Phillips A. H.

2011-01-01

Full Text Available The electronic transport property of a bilayer graphene is investigated under the effect of an electromagnetic field. We deduce an expression for the conductance by solving the Dirac equation. This conductance depends on the barrier height for graphene and the energy of the induced photons. A resonance oscillatory behavior of the conductance is observed. These oscillations are strongly depends on the barrier height for chiral tunneling through graphene. This oscillatory behavior might be due to the interference of different central band and sidebands of graphene states. The present investigation is very important for the application of bilayer graphene in photodetector devices, for example, far-infrared photodevices and ultrafast lasers.

TiO_2/WO_3 photoactive bilayers in the UV-Vis light region

International Nuclear Information System (INIS)

Vasilaki, E.; Vernardou, D.; Kenanakis, G.; Katsarakis, N.; Vamvakaki, M.

2017-01-01

In this work, photoactive bilayered films consisting of anatase TiO_2 and monoclinic WO_3 were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO_3 precursor solution, when deposited as an overlying layer on TiO_2 by two annealing steps (∝76% methylene blue decolorization in 300 min of irradiation versus ∝59% in the case of a bare TiO_2 film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO_2 films with WO_3 acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination. (orig.)

CHALLENGES OF ELECTRONIC INFORMATION RESOURCES IN ...

African Journals Online (AJOL)

This paper discusses the role of policy for proper and efficient library services in the electronic era. It points out some of the possible dangers of embarking in electronic resources without a proper focus at hand. Thus, it calls for today's librarians and policy makers to brainstorm and come up with working policies suitable to ...

Basal-plane dislocations in bilayer graphene - Peculiarities in a quasi-2D material

Science.gov (United States)

Butz, Benjamin

2015-03-01

Dislocations represent one of the most fascinating and fundamental concepts in materials science. First and foremost, they are the main carriers of plastic deformation in crystalline materials. Furthermore, they can strongly alter the local electronic or optical properties of semiconductors and ionic crystals. In layered crystals like graphite dislocation movement is restricted to the basal plane. Thus, those basal-plane dislocations cannot escape enabling their confinement in between only two atomic layers of the material. So-called bilayer graphene is the thinnest imaginable quasi-2D crystal to explore the nature and behavior of dislocations under such extreme boundary conditions. Robust graphene membranes derived from epitaxial graphene on SiC provide an ideal platform for their investigation. The presentation will give an insight in the direct observation of basal-plane partial dislocations by transmission electron microscopy and their detailed investigation by diffraction contrast analysis and atomistic simulations. The investigation reveals striking size effects. First, the absence of stacking fault energy, a unique property of bilayer graphene, leads to a characteristic dislocation pattern, which corresponds to an alternating AB BA change of the stacking order. Most importantly, our experiments in combination with atomistic simulations reveal a pronounced buckling of the bilayer graphene membrane, which directly results from accommodation of strain. In fact, the buckling completely changes the strain state of the bilayer graphene and is of key importance for its electronic/spin transport properties. Due to the high degree of disorder in our quasi-2D material it is one of the very few examples for a perfect linear magnetoresistance, i.e. the linear dependency of the in-plane electrical resistance on a magnetic field applied perpendicular to the graphene sheet up to field strengths of more than 60 T. This research is financed by the German Research Foundation

Hematite/silver nanoparticle bilayers on mica--AFM, SEM and streaming potential studies.

Science.gov (United States)

Morga, Maria; Adamczyk, Zbigniew; Oćwieja, Magdalena; Bielańska, Elżbieta

2014-06-15

Bilayers of hematite/silver nanoparticles were obtained in the self-assembly process and thoroughly characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and in situ streaming potential measurements. The hematite nanoparticles, forming a supporting layer, were 22 nm in diameter, exhibiting an isoelectric point at pH 8.9. The silver nanoparticles, used to obtain an external layer, were 29 nm in diameter, and remained negative within the pH range 3 to 11. In order to investigate the particle deposition, mica sheets were used as a model solid substrate. The coverage of the supporting layer was adjusted by changing the bulk concentration of the hematite suspension and the deposition time. Afterward, silver nanoparticle monolayers of controlled coverage were deposited under the diffusion-controlled transport. The coverage of bilayers was determined by a direct enumeration of deposited particles from SEM micrographs and AFM images. Additionally, the formation of the hematite/silver bilayers was investigated by streaming potential measurements carried out under in situ conditions. The effect of the mica substrate and the coverage of a supporting layer on the zeta potential of bilayers was systematically studied. It was established that for the coverage exceeding 0.20, the zeta potential of bilayers was independent on the substrate and the supporting layer coverage. This behavior was theoretically interpreted in terms of the 3D electrokinetic model. Beside significance for basic sciences, these measurements allowed to develop a robust method of preparing nanoparticle bilayers of controlled properties, having potential applications in catalytic processes. Copyright © 2014 Elsevier Inc. All rights reserved.

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...... between the model protein gramicidin and lipid bilayers of varying thickness. The free energy of the interaction is up to −6 kJ/mol; thus not strongly favored over lipid–lipid interactions. Incorporation of gramicidin results in increased order parameters with increased protein concentration...... 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...

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. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Use of Electronic Resources in a Private University in Nigeria ...

African Journals Online (AJOL)

The study examined awareness and constraints in the use of electronic resources by lecturers and students of Ajayi Crowther University, Oyo, Nigeria. It aimed at justifying the resources expended in the provision of electronic resources in terms of awareness, patronage and factors that may be affecting awareness and use ...

Collective chain dynamics in lipid bilayers by inelastic x-ray scattering

International Nuclear Information System (INIS)

Weiss, T.M.; Chen, P.-J.; Sinn, H.; Alp, E.E.; Chen, S.-H.; Hwang, H.W.

2003-01-01

We investigated the application of inelastic x-ray scattering (IXS) to lipid bilayers. This technique directly measures the dynamic structure factor S(q,ω) which is the space-time Fourier transform of the electron density correlation function of the measured system. For a multiatomic system, the analysis of S(q,ω) is usually complicated. But for multiple bilayers of lipid, S(q,ω) is dominated by chain-chain correlations within individual bilayers. Thus IXS provides a unique probe for the collective dynamics of lipid chains in a bilayer that cannot be obtained by any other method. IXS of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylcholine + cholesterol at two different concentrations were measured. S(q,ω) was analyzed by three-mode hydrodynamic equations, including a thermal diffusive mode and two propagating acoustic modes. We obtained the dispersion curves for the phonons that represent the collective in-plane excitations of lipid chains. The effect of cholesterol on chain dynamics was detected. Our analysis shows the importance of having a high instrument resolution as well as the requirement of sufficient signal-to-noise ratio to obtain meaningful results from such an IXS experiment. The requirement on signal-to-noise also applies to molecular dynamics simulations.

Electronic Resources Management System: Recommendation Report 2017

KAUST Repository

Ramli, Rindra M.

2017-05-01

This recommendation report provides an overview of the selection process for the new Electronic Resources Management System. The library has decided to move away from Innovative Interfaces Millennium ERM module. The library reviewed 3 system as potential replacements namely: Proquest 360 Resource Manager, Ex Libris Alma and Open Source CORAL ERMS. After comparing and trialling the systems, it was decided to go for Proquest 360 Resource Manager.

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

Mechanical and tribological properties of a-C/a-C:Ti multilayer films with various bilayer periods

Energy Technology Data Exchange (ETDEWEB)

Bai, W.Q.; Cai, J.B.; Wang, X.L., E-mail: wangxl@zju.edu.cn; Wang, D.H.; Gu, C.D.; Tu, J.P., E-mail: tujp@zju.edu.cn

2014-05-02

Thick a-C/a-C:Ti multilayer films with bilayer periods of 12–70 nm were deposited on Ti6Al4V alloy substrate by means of closed field unbalance magnetron sputtering. The morphology and microstructure of the multilayer films were investigated by scanning electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Nanocrystalline TiC was distributed in the a-C:Ti layer and at the interface between the two adjacent layers. The mechanical and tribological properties were evaluated by Rockwell and scratch tests, a nanoindentor and a ball-on-disk tribometer. The multilayer film with a bilayer period of 12 nm showed the highest adhesion strength, hardness (26 GPa) and elastic modulus (232 GPa); it also had the lowest average coefficient of friction (0.09) and a wear rate of 8.06 × 10{sup −17} m{sup 3} N{sup −1} m{sup −1}. - Highlights: • a-C/a-C:Ti multilayers with various bilayer periods were prepared. • Nanocrystalline TiCs were confirmed in the a-C:Ti layer and at the interface. • These multilayers show fine ability to comply with substrate deformation. • The multilayer with a bilayer period of 12 nm exhibits the best properties.

use of electronic resources by graduate students of the department

African Journals Online (AJOL)

respondent's access electronic resources from the internet via Cybercafé .There is a high ... KEY WORDS: Use, Electronic Resources, Graduate Students, Cybercafé. INTRODUCTION ... Faculty of Education, University of Uyo, Uyo. Olu Olat ...

Depth profiles of pulmonary surfactant protein B in phosphatidylcholine bilayers, studied by fluorescence and electron spin resonance spectroscopy

DEFF Research Database (Denmark)

Cruz, A; Casals, C; Plasencia, I

1998-01-01

Pulmonary surfactant-associated protein B (SP-B) has been isolated from porcine lungs and reconstituted in bilayers of dipalmitoylphosphatidylcholine (DPPC) or egg yolk phosphatidylcholine (PC) to characterize the extent of insertion of the protein into phospholipid bilayers. The parameters...... for the interaction of SP-B with DPPC or PC using different reconstitution protocols have been estimated from the changes induced in the fluorescence emission spectrum of the single protein tryptophan. All the different reconstituted SP-B-phospholipid preparations studied had similar Kd values for the binding...... that there are significant differences in the extent of insertion of the protein, depending on the method of reconstitution. SP-B reconstituted from lipid/protein mixtures in organic solvents is inserted more deeply in PC or DPPC bilayers than the protein reconstituted by addition to preformed phospholipid vesicles...

Quantum Hall bilayers and the chiral sine-Gordon equation

International Nuclear Information System (INIS)

Naud, J.D.; Pryadko, Leonid P.; Sondhi, S.L.

2000-01-01

The edge state theory of a class of symmetric double-layer quantum Hall systems with interlayer electron tunneling reduces to the sum of a free field theory and a field theory of a chiral Bose field with a self-interaction of the sine-Gordon form. We argue that the perturbative renormalization group flow of this chiral sine-Gordon theory is distinct from the standard (non-chiral) sine-Gordon theory, contrary to a previous assertion by Renn, and that the theory is manifestly sensible only at a discrete set of values of the inverse period of the cosine interaction (β-circumflex). We obtain exact solutions for the spectra and correlation functions of the chiral sine-Gordon theory at the two values of β-circumflex at which electron tunneling in bilayers is not irrelevant. Of these, the marginal case (β-circumflex 2 =4) is of greatest interest: the spectrum of the interacting theory is that of two Majorana fermions with different, dynamically generated, velocities. For the experimentally observed bilayer 331 state at filling factor 1/2, this implies the trifurcation of electrons added to the edge. We also present a method for fermionizing the theory at the discrete points (β-circumflex 2 is an element of Z + ) by the introduction of auxiliary degrees of freedom that could prove useful in other problems involving quantum Hall multi-layers

Nanoscale magnetism and novel electronic properties of a bilayer bismuth(111) film with vacancies and chemical doping.

Science.gov (United States)

Sahoo, M P K; Zhang, Yajun; Wang, Jie

2016-07-27

Magnetically doped topological insulators (TIs) exhibit several exotic phenomena including the magnetoelectric effect and quantum anomalous Hall effect. However, from an experimental perspective, incorporation of spin moment into 3D TIs is still challenging. Thus, instead of 3D TIs, the 2D form of TIs may open up new opportunities to induce magnetism. Based on first principles calculations, we demonstrate a novel strategy to realize robust magnetism and exotic electronic properties in a 2D TI [bilayer Bi(111) film: abbreviated as Bi(111)]. We examine the magnetic and electronic properties of Bi(111) with defects such as bismuth monovacancies (MVs) and divacancies (DVs), and these defects decorated with 3d transition metals (TMs). It has been observed that the MV in Bi(111) can induce novel half metallicity with a net magnetic moment of 1 μB. The origin of half metallicity and magnetism in MV/Bi(111) is further explained by the passivation of the σ-dangling bonds near the defect site. Furthermore, in spite of the nonmagnetic nature of DVs, the TMs (V, Cr, Mn, and Fe) trapped at the 5/8/5 defect structure of DVs can not only yield a much higher spin moment than those trapped at the MVs but also display intriguing electronic properties such as metallic, semiconducting and spin gapless semiconducting properties. The predicted magnetic and electronic properties of TM/DV/Bi(111) systems are explained through density of states, spin density distribution and Bader charge analysis.

Numerical investigation on asymmetric bilayer system at integer filling factor

Czech Academy of Sciences Publication Activity Database

Nomura, K.; Yoshioka, D.; Jungwirth, Tomáš; MacDonald, A. H.

2004-01-01

Roč. 22, - (2004), s. 60-63 ISSN 1386-9477. [International Conference on Electronic Properties of Two-Dimensional Systems /15./. Nara, 14.07.2003-18.07.2003] Institutional research plan: CEZ:AV0Z1010914 Keywords : quantum Hall ferromagnet * asymmetric bilayer systems * anisotropy * stripe states Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.898, year: 2004

Electronic resource management practical perspectives in a new technical services model

CERN Document Server

Elguindi, Anne

2012-01-01

A significant shift is taking place in libraries, with the purchase of e-resources accounting for the bulk of materials spending. Electronic Resource Management makes the case that technical services workflows need to make a corresponding shift toward e-centric models and highlights the increasing variety of e-formats that are forcing new developments in the field.Six chapters cover key topics, including: technical services models, both past and emerging; staffing and workflow in electronic resource management; implementation and transformation of electronic resource management systems; the ro

Molecular packing and area compressibility of lipid bilayers

International Nuclear Information System (INIS)

White, S.H.; King, G.I.

1985-01-01

Knowledge of the molecular packing of lipids and water in lipid bilayers is important for understanding bilayer mechanics and thermodynamics. Information on packing is most often obtained from x-ray or neutron diffraction measurements. Given the d spacing, composition, and partial specific volumes of the lipid and water, it is a simple matter to calculate the area per lipid molecule, bilayer thickness, and bilayer mass density. The partial specific volumes are commonly assumed to be those of bulk water and of lipid in excess water regardless of the degree of bilayer hydration. The authors present evidence here that these assumptions should be seriously questioned. At low hydrations, they find the head groups of egg and dioleoyl lecithin to be much less tightly packed than previously thought and the partial specific volume of water to be considerably smaller than 1 ml/g. Because the molecular packing affects the mechanical properties of bilayers, they use the results to reevaluate published experiments concerning the elastic area compressibility modulus of egg lecithin bilayers and the repulsive hydration force between bilayers

Enhanced electrical properties in bilayered ferroelectric thin films

Science.gov (United States)

Zhang, Hao; Long, WeiJie; Chen, YaQing; Guo, DongJie

2013-03-01

Sr2Bi4Ti5O18 (SBTi) single layered and Sr2Bi4Ti5O18/Pb(Zr0.53Ti0.47)O3 (SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition (PLD). The related structural characterizations and electrical properties have been comparatively investigated. X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces. Both films show well-saturated ferroelectric hysteresis loops, however, compared with the single layered SBTi films, the SBTi/PZT bilayered films have significantly increased remnant polarization ( P r) and decreased coercive field ( E c), with the applied field of 260 kV/cm. The measured P r and E c of SBTi and SBTi/PZT films were 7.9 μC/cm2, 88.1 kV/cm and 13.0 μC/cm2, 51.2 kV/cm, respectively. In addition, both films showed good fatigue-free characteristics, the switchable polarization decreased by 9% and 11% of the initial values after 2.2×109 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films, respectively. Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.

Utilization of electronic information resources by academic staff at ...

African Journals Online (AJOL)

The study investigated the utilization of Electronic Information resources by the academic staff of Makerere University in Uganda. It examined the academic staff awareness of the resources available, the types of resources provided by the Makerere University Library, the factors affecting resource utilization. The study was ...

Mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the in-plane biaxial strain

Science.gov (United States)

Behzad, Somayeh

2017-11-01

Recently, a new two-dimensional (2D) material, the 2D BC3 crystal, has been synthesized. Here, the mechanical control of the electro-optical properties of monolayer and bilayer BC3 by applying the biaxial strain is investigated. The electronic structure calculations showed that the strain-free monolayer and bilayer BC3 are indirect band-gap semiconductors with band gap of 0.62 and 0.29 eV, respectively, where the conduction band minimum (CBM) is at the M point whereas the valence band maximum (VBM) is at the Γ point. The doubly degenerated bands in the monolayer BC3 are splitted in the bilayer BC3 due to the interlayer interactions. Both monolayer and bilayer BC3 remain indirect gap semiconductor under biaxial tensile strain and their band gaps increases with strain. On the other hand, by increasing the magnitude of tensile strain, the optical spectra shift to the lower energies and the static dielectric constant increases. These findings suggest the potential of strain-engineered 2D BC3 in electronic and optoelectronic device applications.

Dependency of {gamma}-secretase complex activity on the structural integrity of the bilayer

Energy Technology Data Exchange (ETDEWEB)

Zhou, Hua, E-mail: hzhou2@lbl.gov [Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Zhou, Shuxia; Walian, Peter J.; Jap, Bing K. [Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

2010-11-12

Research highlights: {yields} Partial solubilization of membranes with CHAPSO can increase {gamma}-secretase activity. {yields} Completely solubilized {gamma}-secretase is inactive. {yields} Purified {gamma}-secretase regains activity after reconstitution into lipid bilayers. {yields} A broad range of detergents can be used to successfully reconstitute {gamma}-secretase. -- Abstract: {gamma}-secretase is a membrane protein complex associated with the production of A{beta} peptides that are pathogenic in Alzheimer's disease. We have characterized the activity of {gamma}-secretase complexes under a variety of detergent solubilization and reconstitution conditions, and the structural state of proteoliposomes by electron microscopy. We found that {gamma}-secretase activity is highly dependent on the physical state or integrity of the membrane bilayer - partial solubilization may increase activity while complete solubilization will abolish it. The activity of well-solubilized {gamma}-secretase can be restored to near native levels when properly reconstituted into a lipid bilayer environment.

Electronic Resources Management Project Presentation 2012

KAUST Repository

Ramli, Rindra M.

2012-01-01

This presentation describes the electronic resources management project undertaken by the KAUST library. The objectives of this project is to migrate information from MS Sharepoint to Millennium ERM module. One of the advantages of this migration

Influence of ferroelectric layer on artificial multiferroic LSMO/BTO bilayers deposited by Dc and RF sputtering

Energy Technology Data Exchange (ETDEWEB)

Ordonez, J. E.; Gomez, M. E.; Lopera, W. [Universidad del Valle, Department of Physics, A. A. 25360 Cali (Colombia)

2016-11-01

La{sub 2/3}Sr{sub 1/3}MnO{sub 3} (LSMO)/BaTiO{sub 3} (BTO) bilayers were deposited on (001) SrTiO{sub 3} substrates via Dc and RF sputtering at pure oxygen atmosphere at a substrate temperature of 830 degrees Celsius. We studied the structural, electrical and magnetic properties on LSMO/BTO bilayers, when LSMO thickness is fixed at nm and BTO thickness is varied from 20 to 100 nm. Reciprocal Space Maps in LSMO show a strained growth for all samples, while BTO layers are always relaxed. Magnetization and electrical measurements indicate the influence of the ferroelectric layer, due to saturation magnetization increases from 500 to 590 emu/cm{sup 3} and coercive field decreases from 178 to 82 Oe with BTO thickness. Mean Field mechanism is identified on all samples with critical exponent β between 0.42 and 0.54. Resistivity measurements show electron-electron and magnon-magnon scattering conduction mechanisms. The influence on magnetic and electrical properties of bilayers with BTO thickness is attributed to crystallographic strains at the interface and the corresponding relaxation with increasing BTO layer thickness. The thickness of the individual layers were obtained by X-ray reflectivity measurements in the bilayers, not shown. X-ray diffraction and Reciprocal Space Maps measurements show highly textured layers with preferential growth in the c-axis direction. (Author)

Microstructures and Recording Mechanism of Mo/Si Bilayer Applied for Write-Once Blue Laser Optical Recording

Directory of Open Access Journals (Sweden)

Sin-Liang Ou

2014-01-01

Full Text Available Mo/Si bilayer thin films were grown by magnetron sputtering and applied to write-once blu-ray disc (BD-R. The microstructures and optical storage properties of Mo/Si bilayer were investigated. From the temperature dependence of reflectivity measurement, it was revealed that a phase change occurred in the range of 255–425°C. Transmission electron microscopy analysis showed that the as-deposited film possessed Mo polycrystalline phase. The hexagonal MoSi2 and cubic Mo3Si phases appeared after annealing at 300 and 450°C, respectively. By measuring the optical reflectivity at a wavelength of 405 nm, the optical contrast of Mo/Si bilayer between as-deposited and 450°C-annealed states was evaluated to 25.8%. The optimum jitter value of 6.8% was obtained at 10.65 mW for 4× recording speed. The dynamic tests show that the Mo/Si bilayer has high potential in BD-R applications.

TiO{sub 2}/WO{sub 3} photoactive bilayers in the UV-Vis light region

Energy Technology Data Exchange (ETDEWEB)

Vasilaki, E. [University of Crete, Department of Chemistry, Heraklion, Crete (Greece); Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Vernardou, D. [Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Kenanakis, G.; Katsarakis, N. [Technological Educational Institute of Crete, Center of Materials Technology and Photonics, School of Engineering, Heraklion, Crete (Greece); Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Vassilika Vouton, P.O. Box 1385, Heraklion, Crete (Greece); Vamvakaki, M. [Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Vassilika Vouton, P.O. Box 1385, Heraklion, Crete (Greece); University of Crete, Department of Materials Science and Technology, Heraklion, Crete (Greece)

2017-04-15

In this work, photoactive bilayered films consisting of anatase TiO{sub 2} and monoclinic WO{sub 3} were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO{sub 3} precursor solution, when deposited as an overlying layer on TiO{sub 2} by two annealing steps (∝76% methylene blue decolorization in 300 min of irradiation versus ∝59% in the case of a bare TiO{sub 2} film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO{sub 2} films with WO{sub 3} acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination. (orig.)

Practical guide to electronic resources in the humanities

CERN Document Server

Dubnjakovic, Ana

2010-01-01

From full-text article databases to digitized collections of primary source materials, newly emerging electronic resources have radically impacted how research in the humanities is conducted and discovered. This book, covering high-quality, up-to-date electronic resources for the humanities, is an easy-to-use annotated guide for the librarian, student, and scholar alike. It covers online databases, indexes, archives, and many other critical tools in key humanities disciplines including philosophy, religion, languages and literature, and performing and visual arts. Succinct overviews of key eme

Study on the optical and electrical properties of tetracyanoethylene doped bilayer graphene stack for transparent conducting electrodes

International Nuclear Information System (INIS)

Limbu, Tej B.; Barrionuevo, Danilo; Katiyar, Ram S.; Morell, Gerardo; Mendoza, Frank; Carpena, Jennifer; Maruyama, Benji; Weiner, Brad R.

2016-01-01

We report the optical and electrical properties of chemically-doped bilayer graphene stack by tetracyanoethylene, a strong electron acceptor. The Tetracyanoethylene doping on the bilayer graphene via charge transfer was confirmed by Raman spectroscopy and Infrared Fourier transform spectroscopy. Doped graphene shows a significant increase in the sheet carrier concentration of up to 1.520 × 10"1"3 cm"−"2 with a concomitant reduction of the sheet resistance down to 414.1 Ω/sq. The high optical transmittance (ca. 84%) in the visible region in combination with the low sheet resistance of the Tetracyanoethylene-doped bilayer graphene stack opens up the possibility of making transparent conducting electrodes for practical applications.

Utilisation of Electronic Information Resources By Lecturers in ...

African Journals Online (AJOL)

This study assesses the use of information resources, specifically, electronic databases by lecturers/teachers in Universities and Colleges of Education in South Western Nigeria. Information resources are central to teachers' education. It provides lecturers/teachers access to information that enhances research and ...

Homogeneous PCBM layers fabricated by horizontal-dip coating for efficient bilayer heterojunction organic photovoltaic cells.

Science.gov (United States)

Huh, Yoon Ho; Bae, In-Gon; Jeon, Hong Goo; Park, Byoungchoo

2016-10-31

We herein report a homogeneous [6,6]-phenyl C61 butyric acid methyl ester (PCBM) layer, produced by a solution process of horizontal-dipping (H-dipping) to improve the photovoltaic (PV) effects of bilayer heterojunction organic photovoltaic cells (OPVs) based on a bi-stacked poly(3-hexylthiophene) (P3HT) electron donor layer and a PCBM electron acceptor layer (P3HT/PCBM). It was shown that a homogeneous and uniform coating of PCBM layers in the P3HT/PCBM bilayer OPVs resulted in reliable and reproducible device performance. We recorded a power conversion efficiency (PCE) of 2.89%, which is higher than that (2.00%) of bilayer OPVs with a spin-coated PCBM layer. Moreover, introducing surfactant additives of poly(oxyethylene tridecyl ether) (PTE) into the homogeneous P3HT/PCBM PV layers resulted in the bilayer OPVs showing a PCE value of 3.95%, which is comparable to those of conventional bulk-heterojunction (BHJ) OPVs (3.57-4.13%) fabricated by conventional spin-coating. This improved device performance may be attributed to the selective collection of charge carriers at the interfaces among the active layers and electrodes due to the PTE additives as well as the homogeneous formation of the functional PCBM layer on the P3HT layer. Furthermore, H-dip-coated PCBM layers were deposited onto aligned P3HT layers by a rubbing technique, and the rubbed bilayer OPV exhibited improved in-plane anisotropic PV effects with PCE anisotropy as high as 1.81, which is also higher than that (1.54) of conventional rubbed BHJ OPVs. Our results suggest that the use of the H-dip-coating process in the fabrication of PCBM layers with the PTE interface-engineering additive could be of considerable interest to those seeking to improve PCBM-based opto-electrical organic thin-film devices.

Reactions of radicals with lecithin bilayers

International Nuclear Information System (INIS)

Barber, D.J.W.; Thomas, J.K.

1978-01-01

The kinetics of reaction of .OH and e/sub aq/ - with lecithin bilayers have been measured. The rate for .OH + lecithin is 5.1 +- 0.9 x 10 8 M -1 sec -1 while the e/sub aq/ - + lecithin rate is very slow. When a solute such as pyrene is solubilized in the bilayer, .OH and e/sub aq/ - may react with the solute; rates of 1.65 +- 0.12 x 10 9 M -1 sec -1 and 7 x 10 7 M -1 sec -1 have been measured for reaction of .OH and e/sub aq/ - , respectively, with pyrene in lecithin. These rates are lower than those observed for similar reactions in homogeneous systems. This is explained in terms of (a) the protective effect of the bilayer, this being especially true for e/sub aq/ - which does not readily leave the aqueous phase, and (b) in terms of the restricted diffusion imposed on the reactive species by the bilayer. The kinetics in these model systems are relevant to reactions of radicals with membranes. Long-term alteration in the model membrane following .OH attack is manifested in terms of damage to the head group, increasing water penetration of the bilayer, and of cross-linking with the membrane, thereby restricting motion in the interior of the bilayer. Increased rigidity and leakiness of membranes is an expected consequence of radiation damage

Development and characterization of sugar palm starch and poly(lactic acid) bilayer films.

Science.gov (United States)

Sanyang, M L; Sapuan, S M; Jawaid, M; Ishak, M R; Sahari, J

2016-08-01

The development and characterization of environmentally friendly bilayer films from sugar palm starch (SPS) and poly(lactic acid) (PLA) were conducted in this study. The SPS-PLA bilayer films and their individual components were characterized for their physical, mechanical, thermal and water barrier properties. Addition of 50% PLA layer onto 50% SPS layer (SPS50-PLA50) increased the tensile strength of neat SPS film from 7.74 to 13.65MPa but reduced their elongation at break from 46.66 to 15.53%. The incorporation of PLA layer significantly reduced the water vapor permeability as well as the water uptake and solubility of bilayer films which was attributed to the hydrophobic characteristic of the PLA layer. Furthermore, scanning electron microscopy (SEM) image of SPS50-PLA50 revealed lack of strong interfacial adhesion between the SPS and PLA. Overall, the incorporation of PLA layer onto SPS films enhances the suitability of SPS based films for food packaging. Copyright © 2016 Elsevier Ltd. All rights reserved.

Discipline, availability of electronic resources and the use of Finnish National Electronic Library - FinELib

Directory of Open Access Journals (Sweden)

Sanna Torma

2004-01-01

Full Text Available This study elaborated relations between digital library use by university faculty, users' discipline and the availability of key resources in the Finnish National Electronic Library (FinELib, Finnish national digital library, by using nationwide representative survey data. The results show that the perceived availability of key electronic resources by researchers in FinELib was a stronger predictor of the frequency and purpose of use of its services than users' discipline. Regardless of discipline a good perceived provision of central resources led to a more frequent use of FinELib. The satisfaction with the services did not vary with the discipline, but with the perceived availability of resources.

The Role of the Acquisitions Librarian in Electronic Resources Management

Science.gov (United States)

Pomerantz, Sarah B.

2010-01-01

With the ongoing shift to electronic formats for library resources, acquisitions librarians, like the rest of the profession, must adapt to the rapidly changing landscape of electronic resources by keeping up with trends and mastering new skills related to digital publishing, technology, and licensing. The author sought to know what roles…

Co-sintering of CGO/NIO-CGO bilayers for solid oxide fuel cell; Co-sinterizacao de bi-camadas anodo/eletrolito para celulas a combustivel de oxido solido

Energy Technology Data Exchange (ETDEWEB)

Neto, P.P.B.; Grilo, J.P.F.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M., E-mail: pbritoneto@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

2012-07-01

Reducing the operating temperature of solid oxide fuel cells (SOFC) for the range between 500 and 700°C is one of the challenges which more has aroused the interest of research in SOFC in recent years. In this context, the bilayer anode/electrolyte composed of a porous support based on Ni-doped ceria (anode) and a ceria doped gadolinia (CGO) electrolyte, presents itself as one of the half-cell configurations of the most interest towards the production of electricity in the operating logic of a SOFC. In this work, CGO films were successfully prepared on NiO-CGO substrates using the resources of the screen-printing technique. The bi-layers were co-sintered between 1350 and 1450 ° C for 4 h and then characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). The results showed good adhesion at the film/substrate interface and no cracks in the films. (author)

Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

Energy Technology Data Exchange (ETDEWEB)

Mohri, Maryam [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud, E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

2015-05-29

Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

Analysis of Pedagogic Potential of Electronic Educational Resources with Elements of Autodidactics

Directory of Open Access Journals (Sweden)

Igor A.

2018-03-01

Full Text Available Introduction: in recent years didactic properties of electronic educational resources undergo considerable changes, nevertheless, the question of studying of such complete phenomenon as “an electronic educational resource with autodidactics elements” remains open, despite sufficient scientific base of researches of the terms making this concept. Article purpose – determination of essence of electronic educational resources with autodidactics elements. Materials and Methods: the main method of research was the theoretical analysis of the pedagogical and psychological literature on the problem under study. We used the theoretical (analysis, synthesis, comparison and generalization methods, the method of interpretation, pedagogical modeling, and empirical methods (observation, testing, conversation, interview, analysis of students’ performance, pedagogical experiment, peer review. Results: we detected the advantages of electronic educational resources in comparison with traditional ones. The concept of autodidactics as applied to the subject of research is considered. Properties of electronic educational resources with a linear and nonlinear principle of construction are studied.The influence of the principle of construction on the development of the learners’ qualities is shown. We formulated an integral definition of electronic educational resources with elements of autodidactics, namely, the variability, adaptivity and cyclicity of training. A model of the teaching-learning process with electronic educational resources is developed. Discussion and Conclusions: further development of a problem will allow to define whether electronic educational resources with autodidactics elements pedagogical potential for realization of educational and self-educational activity of teachers have, to modify technological procedures taking into account age features of students, their specialties and features of the organization of process of training of

Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

Science.gov (United States)

Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

2016-02-01

Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Preservation and conservation of electronic information resources of ...

African Journals Online (AJOL)

The major holdings of the broadcast libraries of the Nigerian Television Authority (NTA) are electronic information resources; therefore, providing safe places for general management of these resources have aroused interest in the industry in Nigeria for sometimes. The need to study the preservation and conservation of ...

Building an electronic resource collection a practical guide

CERN Document Server

Lee, Stuart D

2004-01-01

This practical book guides information professionals step-by-step through building and managing an electronic resource collection. It outlines the range of electronic products currently available in abstracting and indexing, bibliographic, and other services and then describes how to effectively select, evaluate and purchase them.

Analysis of Human Resources Management Strategy in China Electronic Commerce Enterprises

Science.gov (United States)

Shao, Fang

The paper discussed electronic-commerce's influence on enterprise human resources management, proposed and proved the human resources management strategy which electronic commerce enterprise should adopt from recruitment strategy to training strategy, keeping talent strategy and other ways.

Bilayers of phosphatidyldiacylglycerol and phosphatidylcholesterol give 31P-NMR spectra characteristic for hexagonal and isotropic phases

NARCIS (Netherlands)

Noggle, J.H.; Marecek, J.F.; Mandal, S.B.; Venetie, R. van; Rogers, J.; Jain, M.K.; Ramirez, F.

1982-01-01

Aqueous dispersions of phosphatidyldiacylglycerol and phosphatidylcholesterol are shown to form bilayers by differential scanning calorimetry, diphenylhexatriene fluorescence polarization, and electron microscopy; however, 31P-nuclear magnetic resonance spectra of these dispersions are

Mixed Mechanism of Lubrication by Lipid Bilayer Stacks.

Science.gov (United States)

Boţan, Alexandru; Joly, Laurent; Fillot, Nicolas; Loison, Claire

2015-11-10

Although the key role of lipid bilayer stacks in biological lubrication is generally accepted, the mechanisms underlying their extreme efficiency remain elusive. In this article, we report molecular dynamics simulations of lipid bilayer stacks undergoing load and shear. When the hydration level is reduced, the velocity accommodation mechanism changes from viscous shear in hydration water to interlayer sliding in the bilayers. This enables stacks of hydrated lipid bilayers to act as efficient boundary lubricants for various hydration conditions, structures, and mechanical loads. We also propose an estimation for the friction coefficient; thanks to the strong hydration forces between lipid bilayers, the high local viscosity is not in contradiction with low friction coefficients.

Infrared spectroscopy of fluid lipid bilayers.

Science.gov (United States)

Hull, Marshall C; Cambrea, Lee R; Hovis, Jennifer S

2005-09-15

Infrared spectroscopy is a powerful technique for examining lipid bilayers; however, it says little about the fluidity of the bilayer-a key physical aspect. It is shown here that it is possible to both acquire spectroscopic data of supported lipid bilayer samples and make measurements of the membrane fluidity. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR) is used to obtain the spectroscopic information and fluorescence recovery after photobleaching (FRAP) is used to determine the fluidity of the samples. In the infrared spectra of lipid bilayers composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, the following major peaks were observed; nu(as)(CH3) 2954 cm(-1), nu(s)(CH3) 2870 cm(-1), nu(as)(CH2) 2924 cm(-1), nu(s)(CH2) 2852 cm(-1), nu(C=O) 1734 cm(-1), delta(CH2) 1463-1473 cm(-1), nu(as)(PO2-) 1226 cm(-1), nu(s)(PO2-) 1084 cm(-1), and nu(as)(N+(CH3)3) 973 cm(-1). The diffusion coefficient of the same lipid bilayer was measured to be 3.5 +/- 0.5 micom(2)/s with visual recovery also noted through use of epifluorescence microscopy. FRAP and visual data confirm the formation of a uniform, mobile supported lipid bilayer. The combination of ATR-FT-IR and FRAP provides complementary data giving a more complete picture of fully hydrated model membrane systems.

Using XML Technologies to Organize Electronic Reference Resources

OpenAIRE

Huser, Vojtech; Del Fiol, Guilherme; Rocha, Roberto A.

2005-01-01

Provision of access to reference electronic resources to clinicians is becoming increasingly important. We have created a framework for librarians to manage access to these resources at an enterprise level, rather than at the individual hospital libraries. We describe initial project requirements, implementation details, and some preliminary results.

Viscoelastic deformation of lipid bilayer vesicles.

Science.gov (United States)

Wu, Shao-Hua; Sankhagowit, Shalene; Biswas, Roshni; Wu, Shuyang; Povinelli, Michelle L; Malmstadt, Noah

2015-10-07

Lipid bilayers form the boundaries of the cell and its organelles. Many physiological processes, such as cell movement and division, involve bending and folding of the bilayer at high curvatures. Currently, bending of the bilayer is treated as an elastic deformation, such that its stress-strain response is independent of the rate at which bending strain is applied. We present here the first direct measurement of viscoelastic response in a lipid bilayer vesicle. We used a dual-beam optical trap (DBOT) to stretch 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) giant unilamellar vesicles (GUVs). Upon application of a step optical force, the vesicle membrane deforms in two regimes: a fast, instantaneous area increase, followed by a much slower stretching to an eventual plateau deformation. From measurements of dozens of GUVs, the average time constant of the slower stretching response was 0.225 ± 0.033 s (standard deviation, SD). Increasing the fluid viscosity did not affect the observed time constant. We performed a set of experiments to rule out heating by laser absorption as a cause of the transient behavior. Thus, we demonstrate here that the bending deformation of lipid bilayer membranes should be treated as viscoelastic.

Dynamics, Surface Electrostatics and Phase Properties of Nanoscale Curved Lipid Bilayers

Science.gov (United States)

Koolivand, Amir

Surface electrostatic potential of a lipid bilayer governs many vital functions of living cells. Several classes of proteins are known of exhibiting strong binding preferences to curved lipid bilayer surfaces. In this project we employed electron paramagnetic resonance (EPR) of a recently introduced phospholipid (IMTSL-PTE) bearing a pH-sensitive nitroxide covalently attached to the lipid head group to measure the surface electrostatics of the lipid membrane and nanopore-confined lipid bilayers as a function of the bilayer curvature. The pKa of the ionizable group of this lipid-based spin probe is reporting on the bilayer surface electrostatics potential by changes in the EPR spectra. Specifically, both rotational dynamics and magnetic parameters of the nitroxide are affected by the probe protonation. Effect of curvature on the surface electrostatic potential and dynamics of lipid bilayer was studied for POPG and DMPG unilamellar vesicles (ULVs). It was found that the magnitude of the negative surface electrostatic potential increased upon decrease in the vesicle diameter for the bilayers in the fluid phase; however, no significant changes were observed for DMPG ULVs in a gel phase. We speculate that biologically relevant fluid bilayer phase allows for a larger variability in the lipid packing density in the lipid polar head group region than a more ordered gel phase and it is likely that the lipid flip-flop is responsible for pH equilibration of IMTSL-PTE. The kinetic EPR study of nitroxide reduction showed that the rate of flip-flop is in the order of 10-5 s-1. The flip-flop rate constant increases when vesicle size deceases. Oxygen permeability measured by X-ban EPR decreases in higher curved vesicles---an observation that is consistent with a tighter packing in smaller vesicles. Partitioning of a small nitroxide molecule TEMPO into ULVs was measured by X-band (9 GHz) and W-band (95 GHz) EPR spectroscopy. The partitioning coefficient of this probe in the lipid

Electronic structure and optical properties of twisted bilayer graphene calculated via time evolution of states in real space

Science.gov (United States)

Le, H. Anh; Do, V. Nam

2018-03-01

We investigate the electronic and optical properties of twisted bilayer graphene with arbitrary twist angles θ . Our results are based on a method of evolving in time quantum states in lattice space. We propose an efficient scheme of sampling lattice nodes that helps to reduce significantly computational cost, particularly for tiny twist angles. We demonstrate the continuous variation of the density of states and the optical conductivity with respect to the twist angle. It indicates that the commensurability between the two graphene layers does not play an essential role in governing the electronic and optical properties. We point out that, for the twist angles roughly in the range 0 .1∘energy exhibits the typical W shape with a small peak locating at the Fermi energy. This peak is formed as the merging of two van Hove peaks and reflects the appearance of states strongly localized in the AA-like region of moiré zones. When decreasing the twist angle to zero, the W shape is gradually transformed to the U shape, which is seen as the behavior of the density of states in the limit of θ →0∘ .

Chirality effect on electron phonon relaxation, energy loss, and thermopower in single and bilayer graphene in BG regime

Science.gov (United States)

Ansari, Meenhaz; Ashraf, S. S. Z.

2017-10-01

We investigate the energy dependent electron-phonon relaxation rate, energy loss rate, and phonon drag thermopower in single layer graphene (SLG) and bilayer graphene (BLG) under the Bloch-Gruneisen (BG) regime through coupling to acoustic phonons interacting via the Deformation potential in the Boltzmann transport equation approach. We find that the consideration of the chiral nature of electrons alters the temperature dependencies in two-dimensional structures of SLG and BLG from that shown by other conventional 2DEG system. Our investigations indicate that the BG analytical results are valid for temperatures far below the BG limit (˜TBG/4) which is in conformity with a recent experimental investigation for SLG [C. B. McKitterick et al., Phys. Rev. B 93, 075410 (2016)]. For temperatures above this renewed limit (˜TBG/4), there is observed a suppression in energy loss rate and thermo power in SLG, but enhancement is observed in relaxation rate and thermopower in BLG, while a suppression in the energy loss rate is observed in BLG. This strong nonmonotonic temperature dependence in SLG has also been experimentally observed within the BG limit [Q. Ma et al., Phys. Rev. Lett. 112, 247401 (2014)].

Cholesterol Bilayer Domains in the Eye Lens Health: A Review.

Science.gov (United States)

Widomska, Justyna; Subczynski, Witold K; Mainali, Laxman; Raguz, Marija

2017-12-01

The most unique biochemical characteristic of the eye lens fiber cell plasma membrane is its extremely high cholesterol content, the need for which is still unclear. It is evident, however, that the disturbance of Chol homeostasis may result in damages associated with cataracts. Electron paramagnetic resonance methods allow discrimination of two types of lipid domains in model membranes overloaded with Chol, namely, phospholipid-cholesterol domains and pure Chol bilayer domains. These domains are also detected in human lens lipid membranes prepared from the total lipids extracted from lens cortices and nuclei of donors from different age groups. Independent of the age-related changes in phospholipid composition, the physical properties of phospholipid-Chol domains remain the same for all age groups and are practically identical for cortical and nuclear membranes. The presence of Chol bilayer domains in these membranes provides a buffering capacity for cholesterol concentration in the surrounding phospholipid-Chol domains, keeping it at a constant saturating level and thus keeping the physical properties of the membrane consistent with and independent of changes in phospholipid composition. It seems that the presence of Chol bilayer domains plays an integral role in the regulation of cholesterol-dependent processes in fiber cell plasm membranes and in the maintenance of fiber cell membrane homeostasis.

Electronic Resources and Mission Creep: Reorganizing the Library for the Twenty-First Century

Science.gov (United States)

Stachokas, George

2009-01-01

The position of electronic resources librarian was created to serve as a specialist in the negotiation of license agreements for electronic resources, but mission creep has added more functions to the routine work of electronic resources such as cataloging, gathering information for collection development, and technical support. As electronic…

Josephson tunneling in bilayer quantum Hall system

International Nuclear Information System (INIS)

Ezawa, Z.F.; Tsitsishvili, G.; Sawada, A.

2012-01-01

A Bose–Einstein condensation is formed by composite bosons in the quantum Hall state. A composite boson carries the fundamental charge (−e). We investigate Josephson tunneling of such charges in the bilayer quantum Hall system at the total filling ν=1. We show the existence of the critical current for the tunneling current to be coherent and dissipationless. Our results explain recent experiments due to [L. Tiemann, Y. Yoon, W. Dietsche, K. von Klitzing, W. Wegscheider, Phys. Rev. B 80 (2009) 165120] and due to [Y. Yoon, L. Tiemann, S. Schmult, W. Dietsche, K. von Klitzing, Phys. Rev. Lett. 104 (2010) 116802]. We predict also how the critical current changes as the sample is tilted in the magnetic field. -- Highlights: ► Composite bosons undergo Bose–Einstein condensation to form the bilayer quantum Hall state. ► A composite boson is a single electron bound to a flux quantum and carries one unit charge. ► Quantum coherence develops due to the condensation. ► Quantum coherence drives the supercurrent in each layer and the tunneling current. ► There exists the critical input current so that the tunneling current is coherent and dissipationless.

Engineering plant membranes using droplet interface bilayers.

Science.gov (United States)

Barlow, N E; Smpokou, E; Friddin, M S; Macey, R; Gould, I R; Turnbull, C; Flemming, A J; Brooks, N J; Ces, O; Barter, L M C

2017-03-01

Droplet interface bilayers (DIBs) have become widely recognised as a robust platform for constructing model membranes and are emerging as a key technology for the bottom-up assembly of synthetic cell-like and tissue-like structures. DIBs are formed when lipid-monolayer coated water droplets are brought together inside a well of oil, which is excluded from the interface as the DIB forms. The unique features of the system, compared to traditional approaches (e.g., supported lipid bilayers, black lipid membranes, and liposomes), is the ability to engineer multi-layered bilayer networks by connecting multiple droplets together in 3D, and the capability to impart bilayer asymmetry freely within these droplet architectures by supplying droplets with different lipids. Yet despite these achievements, one potential limitation of the technology is that DIBs formed from biologically relevant components have not been well studied. This could limit the reach of the platform to biological systems where bilayer composition and asymmetry are understood to play a key role. Herein, we address this issue by reporting the assembly of asymmetric DIBs designed to replicate the plasma membrane compositions of three different plant species; Arabidopsis thaliana , tobacco, and oats, by engineering vesicles with different amounts of plant phospholipids, sterols and cerebrosides for the first time. We show that vesicles made from our plant lipid formulations are stable and can be used to assemble asymmetric plant DIBs. We verify this using a bilayer permeation assay, from which we extract values for absolute effective bilayer permeation and bilayer stability. Our results confirm that stable DIBs can be assembled from our plant membrane mimics and could lead to new approaches for assembling model systems to study membrane translocation and to screen new agrochemicals in plants.

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.

Interaction of elaiophylin with model bilayer membrane

Science.gov (United States)

Genova, J.; Dencheva-Zarkova, M.

2017-01-01

Elaiophylin is a new macrodiolide antibiotic, which is produced by the Streptomyces strains [1]. It displays biological activities against Gram-positive bacteria and fungi. The mode of action of this antibiotic has been attributed to an alteration of the membrane permeability. When this antibiotic is inserted into the bilayer membranes destabilization of the membrane and formation of ion-penetrable channels is observed. The macrodiolide antibiotic forms stable cation selective ion channels in synthetic lipid bilayer membranes. The aim of this work was to study the interactions of Elaiophylin with model bilayer membranes and to get information on the mechanical properties of lipid bilayers in presence of this antibiotic. Patch-clamp technique [2] were used in the study

Pair interaction of bilayer-coated nanoscopic particles

International Nuclear Information System (INIS)

Qi-Yi, Zhang

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 placed 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 amphiphiles, 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. (condensed matter: structure, thermal and mechanical properties)

Enhanced intrinsic voltage gain in artificially stacked bilayer CVD graphene field effect transistors

Energy Technology Data Exchange (ETDEWEB)

Pandey, Himadri; Kataria, Satender [RWTH Aachen University, Chair for Electronic Devices, Aachen (Germany); University of Siegen, School of Science and Technology, Siegen (Germany); Aguirre-Morales, Jorge-Daniel; Fregonese, Sebastien; Zimmer, Thomas [IMS Laboratory, Centre National de la Recherche Scientifique, University of Bordeaux, Talence (France); Passi, Vikram [University of Siegen, School of Science and Technology, Siegen (Germany); AMO GmbH, Advanced Microelectronics Center Aachen (Germany); Iannazzo, Mario; Alarcon, Eduard [Technical University of Catalonia, Department of Electronics Engineering, UPC, Barcelona (Spain); Lemme, Max C. [RWTH Aachen University, Chair for Electronic Devices, Aachen (Germany); University of Siegen, School of Science and Technology, Siegen (Germany); AMO GmbH, Advanced Microelectronics Center Aachen (Germany)

2017-11-15

We report on electronic transport in dual-gate, artificially stacked bilayer graphene field effect transistors (BiGFETs) fabricated from large-area chemical vapor deposited (CVD) graphene. The devices show enhanced tendency to current saturation, which leads to reduced minimum output conductance values. This results in improved intrinsic voltage gain of the devices when compared to monolayer graphene FETs. We employ a physics based compact model originally developed for Bernal stacked bilayer graphene FETs (BSBGFETs) to explore the observed phenomenon. The improvement in current saturation may be attributed to increased charge carrier density in the channel and thus reduced saturation velocity due to carrier-carrier scattering. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

KAUST Repository

Brinkman, Daniel

2013-05-01

We present and discuss a mathematical model for the operation of bilayer organic photovoltaic devices. Our model couples drift-diffusion-recombination equations for the charge carriers (specifically, electrons and holes) with a reaction-diffusion equation for the excitons/polaron pairs and Poisson\\'s equation for the self-consistent electrostatic potential. The material difference (i.e. the HOMO/LUMO gap) of the two organic substrates forming the bilayer device is included as a work-function potential. Firstly, we perform an asymptotic analysis of the scaled one-dimensional stationary state system: (i) with focus on the dynamics on the interface and (ii) with the goal of simplifying the bulk dynamics away from the interface. Secondly, we present a two-dimensional hybrid discontinuous Galerkin finite element numerical scheme which is very well suited to resolve: (i) the material changes, (ii) the resulting strong variation over the interface, and (iii) the necessary upwinding in the discretization of drift-diffusion equations. Finally, we compare the numerical results with the approximating asymptotics. © 2013 World Scientific Publishing Company.

Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

Energy Technology Data Exchange (ETDEWEB)

Markov, V.V. E-mail: ise@iph.krasn.ruise@iph.krasnoyarsk.su; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V

2001-08-01

Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T{sub C}=85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it.

Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

International Nuclear Information System (INIS)

Markov, V.V.; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V.

2001-01-01

Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T C =85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it

Strongly Enhanced Tunneling at Total Charge Neutrality in Double-Bilayer Graphene-WSe_{2} Heterostructures.

Science.gov (United States)

Burg, G William; Prasad, Nitin; Kim, Kyounghwan; Taniguchi, Takashi; Watanabe, Kenji; MacDonald, Allan H; Register, Leonard F; Tutuc, Emanuel

2018-04-27

We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe_{2} barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.

Strongly Enhanced Tunneling at Total Charge Neutrality in Double-Bilayer Graphene-WSe2 Heterostructures

Science.gov (United States)

Burg, G. William; Prasad, Nitin; Kim, Kyounghwan; Taniguchi, Takashi; Watanabe, Kenji; MacDonald, Allan H.; Register, Leonard F.; Tutuc, Emanuel

2018-04-01

We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe2 barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.

Properties of POPC/POPE supported lipid bilayers modified with hydrophobic quantum dots on polyelectrolyte cushions.

Science.gov (United States)

Kolasinska-Sojka, Marta; Wlodek, Magdalena; Szuwarzynski, Michal; Kereiche, Sami; Kovacik, Lubomir; Warszynski, Piotr

2017-10-01

The formation and properties of supported lipid bilayers (SLB) containing hydrophobic nanoparticles (NP) was studied in relation to underlying cushion obtained from selected polyelectrolyte multilayers. Lipid vesicles were formed from zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in phosphate buffer (PBS). As hydrophobic nanoparticles - quantum dots (QD) with size of 3.8nm (emission wavelength of 420nm) were used. Polyelectrolyte multilayers (PEM) were constructed by the sequential, i.e., layer-by-layer (LbL) adsorption of alternately charged polyelectrolytes from their solutions. Liposomes and Liposome-QDs complexes were studied with Transmission Cryo-Electron Microscopy (Cryo-TEM) to verify the quality of vesicles and the position of QD within lipid bilayer. Deposition of liposomes and liposomes with quantum dots on polyelectrolyte films was studied in situ using quartz crystal microbalance with dissipation (QCM-D) technique. The fluorescence emission spectra were analyzed for both: suspension of liposomes with nanoparticles and for supported lipid bilayers containing QD on PEM. It was demonstrated that quantum dots are located in the hydrophobic part of lipid bilayer. Moreover, we proved that such QD-modified liposomes formed supported lipid bilayers and their final structure depended on the type of underlying cushion. Copyright © 2017 Elsevier B.V. All rights reserved.

Possible mechanism of adhesion in a mica supported phospholipid bilayer

International Nuclear Information System (INIS)

Pertsin, Alexander; Grunze, Michael

2014-01-01

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

Photon-Assisted Resonant Chiral Tunneling Through a Bilayer Graphene Barrier

OpenAIRE

Phillips A. H.; Mina A. N.

2011-01-01

The electronic transport property of a bilayer graphene is investigated under the effect of an electromagnetic field. We deduce an expression for the conductance by solving the Dirac equation. This conductance depends on the barrier height for graphene and the energy of the induced photons. A resonance oscillatory behavior of the conductance is observed. These oscillations are strongly depends on the barrier height for chiral tunneling through graphene. This oscillatory behavio...

Superluminal plasmons with resonant gain in population inverted bilayer graphene

KAUST Repository

Low, Tony

2017-12-28

AB-stacked bilayer graphene with a tunable electronic bandgap in excess of the optical phonon energy presents an interesting active medium, and we consider such theoretical possibility in this work. We argue the possibility of a highly resonant optical gain in the vicinity of the asymmetry gap. Associated with this resonant gain are strongly amplified plasmons, plasmons with negative group velocity and superluminal effects, as well as directional leaky modes.

Superluminal plasmons with resonant gain in population inverted bilayer graphene

KAUST Repository

Low, Tony; Chen, Pai-Yen; Basov, D. N.

2017-01-01

AB-stacked bilayer graphene with a tunable electronic bandgap in excess of the optical phonon energy presents an interesting active medium, and we consider such theoretical possibility in this work. We argue the possibility of a highly resonant optical gain in the vicinity of the asymmetry gap. Associated with this resonant gain are strongly amplified plasmons, plasmons with negative group velocity and superluminal effects, as well as directional leaky modes.

Study of the ion-channel behavior on glassy carbon electrode supported bilayer lipid membranes stimulated by perchlorate anion

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhiquan; Shi, Jun; Huang, Weimin, E-mail: huangwm@jlu.edu.cn

2015-10-01

In this paper, a kind of didodecyldimethylammonium bromide (DDAB) layer membranes was supported on a glassy carbon electrode (GCE). We studied the ion channel behavior of the supported bilayer lipid membrane by scanning electrochemical microscopy (SCEM) in tris(2,2′-bipyridine) ruthenium(II) solution. Perchlorate anion was used as a presence of stimulus and ruthenium(II) complex cations as the probing ions for the measurement of SECM, the lipid membrane channel was opened and exhibited the behavior of distinct SECM positive feedback curve. The channel was in a closed state in the absence of perchlorate anions while reflected the behavior of SECM negative feedback curve. The rates of electron transfer reaction in the lipid membranes surface were detected and it was dependant on the potential of SECM. - Highlights: • The rates of electron transfer reaction in the lipid membranes surface were detected. • Dynamic investigations of ion-channel behavior of supported bilayer lipid membranes by scanning electrochemical microscopy • A novel way to explore the interaction between molecules and supported bilayer lipid membranes.

Viscoelastic deformation of lipid bilayer vesicles†

Science.gov (United States)

Wu, Shao-Hua; Sankhagowit, Shalene; Biswas, Roshni; Wu, Shuyang; Povinelli, Michelle L.

2015-01-01

Lipid bilayers form the boundaries of the cell and its organelles. Many physiological processes, such as cell movement and division, involve bending and folding of the bilayer at high curvatures. Currently, bending of the bilayer is treated as an elastic deformation, such that its stress-strain response is independent of the rate at which bending strain is applied. We present here the first direct measurement of viscoelastic response in a lipid bilayer vesicle. We used a dual-beam optical trap (DBOT) to stretch 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) giant unilamellar vesicles (GUVs). Upon application of a step optical force, the vesicle membrane deforms in two regimes: a fast, instantaneous area increase, followed by a much slower stretching to an eventual plateau deformation. From measurements of dozens of GUVs, the average time constant of the slower stretching response was 0.225 ± 0.033 s (standard deviation, SD). Increasing the fluid viscosity did not affect the observed time constant. We performed a set of experiments to rule out heating by laser absorption as a cause of the transient behavior. Thus, we demonstrate here that the bending deformation of lipid bilayer membranes should be treated as viscoelastic. PMID:26268612

Electronic Resources Management System: Recommendation Report 2017

KAUST Repository

Ramli, Rindra M.

2017-01-01

This recommendation report provides an overview of the selection process for the new Electronic Resources Management System. The library has decided to move away from Innovative Interfaces Millennium ERM module. The library reviewed 3 system

Finite-size effects on electronic structure and local properties in passivated AA -stacked bilayer armchair-edge graphene nanoribbons

International Nuclear Information System (INIS)

Chen, Xiongwen; Shi, Zhengang; Xiang, Shaohua; Song, Kehui; Zhou, Guanghui

2017-01-01

Based on the tight-binding model and dual-probe scanning tunneling microscopy technology, we theoretically investigate the electronic structure and local property in the passivated AA -stacked bilayer armchair-edge graphene nanoribbons (AABLAGNRs). We show that they are highly sensitive to the size of the ribbons, which is evidently different from the single-layer armchair-edge graphene nanoribbons. The ‘3 p ’ rule only applies to the narrow AABLGNRs. Namely, in the passivated 3 p - and (3 p   +  1)-AABLGNRs, the narrow ribbons are semiconducting while the medium and wide ribbons are metallic. Although the passivated (3 p   +  2)-AABLGNRs are metallic, the ‘3 j ’ rule only applies to the narrow and medium ribbons. Namely, electrons are in the semiconducting states at sites of line 3 j while they are in the metallic states at other sites. This induces a series of parallel and discrete metallic channels, consisting of lines 3 j   −  1 and 3 j   −  2, for the low-energy electronic transports. In the passivated wide (3 p   +  2)-AABLGNRs, all electrons are in the metallic states. Additionally, the ‘3 p ’ and ‘3 j ’ rules are controllable to disappear and reappear by applying an external perpendicular electric field. Resultantly, an electric filed-driven current switch can be realized in the passivated narrow and medium (3 p   +  2)-AABLGNRs. (paper)

Bilayers at High pH in the Fatty Acid Soap Systems and the Applications for the Formation of Foams and Emulsions.

Science.gov (United States)

Xu, Wenlong; Zhang, Heng; Zhong, Yingping; Jiang, Liwen; Xu, Mengxin; Zhu, Xionglu; Hao, Jingcheng

2015-08-20

In our previous work, we reported bilayers at high pH in the stearic acid/CsOH/H2O system, which was against the traditional viewpoint that fatty acid (FA) bilayers must be formed at the pKa of the fatty acid. Herein, the microstructures at high pH of several fatty acid soap systems were investigated systematically. We found that palmitic acid/KOH/H2O, palmitic acid/CsOH/H2O, stearic acid/KOH/H2O, and stearic acid/CsOH/H2O systems can form bilayers at high pH. The bilayer structure was demonstrated by cryogenic transmission electron microscopy (cryo-TEM) and deuterium nuclear magnetic resonance ((2)H NMR), and molecular dynamics simulation was used to confirm the formation of bilayers. The influence of fatty acids with different chain lengths (n = 10, 12, 14, 16, and 18) and different counterions including Li(+), Na(+), K(+), Cs(+), (CH3)4N(+), (C2H5)4N(+), (C3H7)4N(+), and (C4H9)4N(+) on the formation of bilayers was discussed. The stability of foam and emulsification properties were compared between bilayers and micelles, drawing the conclusion that bilayer structures possess a much stronger ability to foam and stronger emulsification properties than micelles do.

Driven spin transitions in fluorinated single- and bilayer-graphene quantum dots

Science.gov (United States)

Żebrowski, D. P.; Peeters, F. M.; Szafran, B.

2017-06-01

Spin transitions driven by a periodically varying electric potential in dilute fluorinated graphene quantum dots are investigated. Flakes of monolayer graphene as well as electrostatic electron traps induced in bilayer graphene are considered. The stationary states obtained within the tight-binding approach are used as the basis for description of the system dynamics. The dilute fluorination of the top layer lifts the valley degeneracy of the confined states and attenuates the orbital magnetic dipole moments due to current circulation within the flake. The spin-orbit coupling introduced by the surface deformation of the top layer induced by the adatoms allows the spin flips to be driven by the AC electric field. For the bilayer quantum dots the spin flip times is substantially shorter than the spin relaxation. Dynamical effects including many-photon and multilevel transitions are also discussed.

Cholesterol Protects the Oxidized Lipid Bilayer from Water Injury

DEFF Research Database (Denmark)

Owen, Michael C; Kulig, Waldemar; Rog, Tomasz

2018-01-01

In an effort to delineate how cholesterol protects membrane structure under oxidative stress conditions, we monitored the changes to the structure of lipid bilayers comprising 30 mol% cholesterol and an increasing concentration of Class B oxidized 1-palmitoyl-2-oleoylphosphatidylcholine (POPC...... in a characteristic reduction in bilayer thickness and increase in area per lipid, thereby increasing the exposure of the membrane hydrophobic region to water. However, cholesterol was observed to help reduce water injury by moving into the bilayer core and forming more hydrogen bonds with the oxPLs. Cholesterol also...... resists altering its tilt angle, helping to maintain membrane integrity. Water that enters the 1-nm-thick core region remains part of the bulk water on either side of the bilayer, with relatively few water molecules able to traverse through the bilayer. In cholesterol-rich membranes, the bilayer does...

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.

Modification of photosensing property of CdS–Bi{sub 2}S{sub 3} bi-layer by thermal annealing and swift heavy ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Shaikh, Shaheed U.; Siddiqui, Farha Y. [Thin Film and Nanotechnology Laboratory, Department of Physics (India); Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India); Singh, Fouran; Kulriya, Pawan K. [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Phase, D.M. [UGC DAE Consortium for Scientific Research, Khandwa Road, Indore 452017 (India); Sharma, Ramphal, E-mail: ramphalsharma@yahoo.com [Thin Film and Nanotechnology Laboratory, Department of Physics (India); Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India)

2016-02-01

The CdS–Bi{sub 2}S{sub 3} bi-layer thin films have been deposited on Indium Tin Oxide (ITO) glass substrates at room temperature by Chemical Bath Deposition Technique (CBD) and bi-layer thin films were annealed in air atmosphere for 1 h at 250 {sup °}C. The air annealed sample was irradiated using Au{sup 9+} ions at the fluence 5 × 10{sup 11} ion/cm{sup 2} with 120 MeV energy. Effects of Swift Heavy Ion (SHI) irradiation on CdS–Bi{sub 2}S{sub 3} bi-layer thin films were studied. The results are explained on the basis annealing and high electronic excitation, using X-ray diffraction (XRD), Selective Electron Area Diffraction (SEAD), Atomic Force Microscopy (AFM), Raman Spectroscopy, UV spectroscopy and I–V characteristics. The photosensing property after illumination of visible light over the samples is studied. These as-deposited, annealed and irradiated bi-layer thin films are used to sense visible light at room temperature. - Graphical abstract: Schematic illustration of CdS–Bi{sub 2}S{sub 3} bi-layer thin film (a) As-deposited (b) Annealed (c) irradiated sample respectively (d) Model of bi-layer photosensor device (e) Graph of illumination intensity verses photosensitivity. - Highlights: • CdS–Bi{sub 2}S{sub 3} bi-layer thin film prepared at room temperature. • Irradiated using Au{sup 9+} ions at the fluence of 5 × 10{sup 11} ion/cm{sup 2} with 120 MeV energy. • Study of modification induced by irradiations. • Study of Photosensitivity after annealing and irradiation.

The Internet School of Medicine: use of electronic resources by medical trainees and the reliability of those resources.

Science.gov (United States)

Egle, Jonathan P; Smeenge, David M; Kassem, Kamal M; Mittal, Vijay K

2015-01-01

Electronic sources of medical information are plentiful, and numerous studies have demonstrated the use of the Internet by patients and the variable reliability of these sources. Studies have investigated neither the use of web-based resources by residents, nor the reliability of the information available on these websites. A web-based survey was distributed to surgical residents in Michigan and third- and fourth-year medical students at an American allopathic and osteopathic medical school and a Caribbean allopathic school regarding their preferred sources of medical information in various situations. A set of 254 queries simulating those faced by medical trainees on rounds, on a written examination, or during patient care was developed. The top 5 electronic resources cited by the trainees were evaluated for their ability to answer these questions accurately, using standard textbooks as the point of reference. The respondents reported a wide variety of overall preferred resources. Most of the 73 responding medical trainees favored textbooks or board review books for prolonged studying, but electronic resources are frequently used for quick studying, clinical decision-making questions, and medication queries. The most commonly used electronic resources were UpToDate, Google, Medscape, Wikipedia, and Epocrates. UpToDate and Epocrates had the highest percentage of correct answers (47%) and Wikipedia had the lowest (26%). Epocrates also had the highest percentage of wrong answers (30%), whereas Google had the lowest percentage (18%). All resources had a significant number of questions that they were unable to answer. Though hardcopy books have not been completely replaced by electronic resources, more than half of medical students and nearly half of residents prefer web-based sources of information. For quick questions and studying, both groups prefer Internet sources. However, the most commonly used electronic resources fail to answer clinical queries more than half

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.

Impact of amphiphilic molecules on the structure and stability of homogeneous sphingomyelin bilayer: Insights from atomistic simulations

Science.gov (United States)

Kumari, Pratibha; Kaur, Supreet; Sharma, Shobha; Kashyap, Hemant K.

2018-04-01

Modulation of lipid membrane properties due to the permeation of amphiphiles is an important biological process pertaining to many applications in the field of pharmaceutics, toxicology, and biotechnology. Sphingolipids are both structural and functional lipids that constitute an important component of mechanically stable and chemically resistant outer leaflets of plasma membranes. Here, we present an atomistic molecular dynamics simulation study to appreciate the concentration-dependent effects of small amphiphilic molecules, such as ethanol, acetone, and dimethyl sulfoxide (DMSO), on the structure and stability of a fully hydrated homogeneous N-palmitoyl-sphingomyelin (PSM) bilayer. The study reveals an increase in the lateral expansion of the bilayer along with disordering of the hydrophobic lipid tails on increasing the concentration of ethanol. At higher concentrations of ethanol, rupturing of the bilayer is quite evident through the analysis of partial electron density profiles and lipid tail order parameters. For ethanol containing systems, permeation of water molecules in the hydrophobic part of the bilayer is allowed through local defects made due to the entry of ethanol molecules via ethanol-ethanol and ethanol-PSM hydrogen bonds. Moreover, the extent of PSM-PSM hydrogen bonding decreases with increasing ethanol concentration. On the other hand, acetone and DMSO exhibit minimal effects on the stability of the PSM bilayer at their lower concentrations, but at higher concentrations they tend to enhance the stability of the bilayer. The simulated potential of mean force (PMF) profiles for the translocation of the three solutes studied reveal that the free-energy of transfer of an ethanol molecule across the PSM lipid head region is lower than that for acetone and DMSO molecules. However, highest free-energy rise in the core hydrophobic part of the bilayer is observed for the DMSO molecule, whereas the ethanol and acetone PMF profiles show a lower barrier in

Topological induced valley polarization in bilayer graphene/Boron Nitride

Science.gov (United States)

Basile, Leonardo; Idrobo, Juan C.

2015-03-01

Novel electronic devices relay in our ability to control internal quantum degrees of freedom of the electron e.g., its spin. The valley number degree of freedom is a pseudospin that labels degenerate eigenstates at local maximum/minimum on the valence/conduction band. Valley polarization, that is, selective electronic localization in a momentum valley and its manipulation can be achieved by means of circular polarized light (CPL) in a system with strong spin-orbit coupling (SOC). In this talk, we will show theoretically that despite the fact that neither graphene or BN have a strong SOC, a bilayer of graphene on BN oriented at a twist angle has different absorption for right- and left- CPL. This induced polarization occurs due to band folding of the electronic bands, i.e., it has a topological origin. This research was supported EPN multidisciplinary grant and by DOE SUFD MSED.

Highly sensitive and selective room-temperature NO_2 gas sensor based on bilayer transferred chemical vapor deposited graphene

International Nuclear Information System (INIS)

Seekaew, Yotsarayuth; Phokharatkul, Ditsayut; Wisitsoraat, Anurat; Wongchoosuk, Chatchawal

2017-01-01

Highlights: • Simple and low-cost fabrication of bilayer graphene gas sensor was presented. • Layer effects of graphene on NO_2 gas-sensing properties were investigated. • Bilayer graphene sensor exhibited a high linear NO_2 sensitivity of 1.409 ppm"−"1. • The NO_2-sensing mechanisms based on band diagram were highlighted. - Abstract: This work presents a highly sensitive room-temperature gas sensor based on bilayer graphene fabricated by an interfacial transfer of chemical vapor deposited graphene onto nickel interdigitated electrodes. Scanning electron microscopic and Raman spectroscopic characterizations confirm the presence of graphene on interdigitated nickel electrodes with varying numbers of graphene layers. The NO_2 detection performances of bilayer graphene gas sensor have been investigated in comparison with those of monolayer and multilayer graphene gas sensors at room temperature. From results, the bilayer graphene gas sensor exhibits higher response, sensitivity and selectivity to NO_2 than monolayer and multilayer graphene. The sensitivity of bilayer graphene gas sensor is 1.409 ppm"−"1 towards NO_2 over a concentration range of 1–25 ppm, which is more than twice higher than that of monolayer graphene. The NO_2-sensing mechanism of graphene sensing film has been explained based on the direct charge transfer process due to the adsorption of NO_2 molecules.

Annealing-Induced Bi Bilayer on Bi2Te3 Investigated via Quasi-Particle-Interference Mapping.

Science.gov (United States)

Schouteden, Koen; Govaerts, Kirsten; Debehets, Jolien; Thupakula, Umamahesh; Chen, Taishi; Li, Zhe; Netsou, Asteriona; Song, Fengqi; Lamoen, Dirk; Van Haesendonck, Chris; Partoens, Bart; Park, Kyungwha

2016-09-27

Topological insulators (TIs) are renowned for their exotic topological surface states (TSSs) that reside in the top atomic layers, and hence, detailed knowledge of the surface top atomic layers is of utmost importance. Here we present the remarkable morphology changes of Bi2Te3 surfaces, which have been freshly cleaved in air, upon subsequent systematic annealing in ultrahigh vacuum and the resulting effects on the local and area-averaging electronic properties of the surface states, which are investigated by combining scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and Auger electron spectroscopy (AES) experiments with density functional theory (DFT) calculations. Our findings demonstrate that the annealing induces the formation of a Bi bilayer atop the Bi2Te3 surface. The adlayer results in n-type doping, and the atomic defects act as scattering centers of the TSS electrons. We also investigated the annealing-induced Bi bilayer surface on Bi2Te3 via voltage-dependent quasi-particle-interference (QPI) mapping of the surface local density of states and via comparison with the calculated constant-energy contours and QPI patterns. We observed closed hexagonal patterns in the Fourier transform of real-space QPI maps with secondary outer spikes. DFT calculations attribute these complex QPI patterns to the appearance of a "second" cone due to the surface charge transfer between the Bi bilayer and the Bi2Te3. Annealing in ultrahigh vacuum offers a facile route for tuning of the topological properties and may yield similar results for other topological materials.

Interface-mediation of lipid bilayer organization and dynamics.

Science.gov (United States)

Mize, Hannah E; Blanchard, G J

2016-06-22

We report on the morphology and dynamics of planar supported lipid bilayer structures as a function of pH and ionic strength of the aqueous overlayer. Supported lipid bilayers composed of three components (phosphocholine, sphingomyelin and cholesterol) are known to exhibit phase segregation, with the characteristic domain sizes dependent on the amount and identity of each constituent, and the composition of the aqueous overlayer in contact with the bilayer. We report on fluorescence anisotropy decay imaging measurements of a rhodamine chromophore tethered to the headgroup of a phosphoethanolamine, where anisotropy decay images were acquired as a function of solution overlayer pH and ionic strength. The data reveal a two-component anisotropy decay under all conditions, with the faster time constant being largely independent of pH and ionic strength and the slower component depending on pH and ionic strength in different manners. For liposomes of the same composition, a single exponential anisotropy decay was seen. We interpret this difference in terms of bilayer curvature and support surface-bilayer interactions, and the pH and ionic strength dependencies in terms of ionic screening and protonation in the bilayer headgroup region.

Ions irradiation on bi-layer coatings

Science.gov (United States)

Tessarolo, Enrico; Corso, Alain Jody; Böttger, Roman; Martucci, Alessandro; Pelizzo, Maria G.

2017-09-01

Future space missions will operate in very harsh and extreme environments. Optical and electronics components need to be optimized and qualified in view of such operational challenges. This work focuses on the effect of low alpha particles irradiation on coatings. Low energy He+ (4 keV and 16 keV) ions have been considered in order to simulate in laboratory the irradiation of solar wind (slow and fast components) alpha particles. Mono- and proper bi-layers coatings have been investigated. The experimental tests have been carried out changing doses as well as fluxes during the irradiation sessions. Optical characterization in the UV-VIS spectral range and superficial morphological analysis have performed prior and after irradiation.

Controllable spin filter composed of ferromagnetic AB-stacking bilayer graphenes

International Nuclear Information System (INIS)

Yu, Yong; Liang, Qifeng; Dong, Jinming

2011-01-01

The electron's tunneling and spin transport in the normal/ferromagnetic/normal (N/FM/N) AB-stacking bilayer graphene (BLG) junction have been studied using Landauer-Buettiker formula. It is found that the resonant conductance peaks could be split well into spin-up and down ones by the exchange field in its FM barrier, leading to a very large spin polarization. More importantly, if a perpendicular electric field is also applied on the FM barrier, a completely spin-polarized flow can be realized by changing its barrier height, making the N/FM/N AB-stacking BLG junction act as a controllable spin filter. -- Highlights: → A study of spin transport in the ferromagnetic bilayer graphene junctions. → A serious of resonant conductance peaks could appear by tuning the barrier height. → The exchange splitting in FM barrier leads to a large spin polarization P. → P=±1 can be realized if a perpendicular electric field is applied to the FM barrier.

ANALYTICAL REVIEW OF ELECTRONIC RESOURCES FOR THE STUDY OF LATIN

Directory of Open Access Journals (Sweden)

Olena Yu. Balalaieva

2014-04-01

Full Text Available The article investigates the current state of development of e-learning content in the Latin language. It is noted that the introduction of ICT in the educational space has expanded the possibility of studying Latin, opened access to digital libraries resources, made it possible to use scientific and educational potential and teaching Latin best practices of world's leading universities. A review of foreign and Ukrainian information resources and electronic editions for the study of Latin is given. Much attention was paid to the didactic potential of local and online multimedia courses of Latin, electronic textbooks, workbooks of interactive tests and exercises, various dictionaries and software translators, databases and digital libraries. Based on analysis of the world market of educational services and products the main trends in the development of information resources and electronic books are examined. It was found that multimedia courses with interactive exercises or workbooks with interactive tests, online dictionaries and translators are the most widely represented and demanded. The noticeable lagging of Ukrainian education and computer linguistics in quantitative and qualitative measures in this industry is established. The obvious drawback of existing Ukrainian resources and electronic editions for the study of Latin is their noninteractive nature. The prospects of e-learning content in Latin in Ukraine are outlined.

Elektronik Bilgi Kaynaklarının Seçimi / Selection of Electronic Information Resources

Directory of Open Access Journals (Sweden)

Pınar Al

2003-04-01

Full Text Available For many years, library users have used only from the printed media in order to get the information that they have needed. Today with the widespread use of the Web and the addition of electronic information resources to library collections, the use of information in the electronic environment as well as in printed media is started to be used. In time, such types of information resources as, electronic journals, electronic books, electronic encyclopedias, electronic dictionaries and electronic theses have been added to library collections. In this study, selection criteria that can be used for electronic information resources are discussed and suggestions are provided for libraries that try to select electronic information resources for their collections.

Probing Lipid Bilayers under Ionic Imbalance.

Science.gov (United States)

Lin, Jiaqi; Alexander-Katz, Alfredo

2016-12-06

Biological membranes are normally under a resting transmembrane potential (TMP), which originates from the ionic imbalance between extracellular fluids and cytosols, and serves as electric power storage for cells. In cell electroporation, the ionic imbalance builds up a high TMP, resulting in the poration of cell membranes. However, the relationship between ionic imbalance and TMP is not clearly understood, and little is known about the effect of ionic imbalance on the structure and dynamics of biological membranes. In this study, we used coarse-grained molecular dynamics to characterize a dipalmitoylphosphatidylcholine bilayer system under ionic imbalances ranging from 0 to ∼0.06 e charges per lipid (e/Lip). We found that the TMP displayed three distinct regimes: 1) a linear regime between 0 and 0.045 e/Lip, where the TMP increased linearly with ionic imbalance; 2) a yielding regime between ∼0.045 and 0.060 e/Lip, where the TMP displayed a plateau; and 3) a poration regime above ∼0.060 e/Lip, where we observed pore formation within the sampling time (80 ns). We found no structural changes in the linear regime, apart from a nonlinear increase in the area per lipid, whereas in the yielding regime the bilayer exhibited substantial thinning, leading to an excess of water and Na + within the bilayer, as well as significant misalignment of the lipid tails. In the poration regime, lipid molecules diffused slightly faster. We also found that the fluid-to-gel phase transition temperature of the bilayer dropped below the normal value with increased ionic imbalances. Our results show that a high ionic imbalance can substantially alter the essential properties of the bilayer, making the bilayer more fluid like, or conversely, depolarization of a cell could in principle lead to membrane stiffening. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Bilayer graphene: gap tunability and edge properties

International Nuclear Information System (INIS)

Castro, Eduardo V; Santos, J M B Lopes dos; Peres, N M R; Guinea, F; Castro Neto, A H

2008-01-01

Bilayer graphene - two coupled single graphene layers stacked as in graphite - provides the only known semiconductor with a gap that can be tuned externally through electric field effect. Here we use a tight binding approach to study how the gap changes with the applied electric field. Within a parallel plate capacitor model and taking into account screening of the external field, we describe real back gated and/or chemically doped bilayer devices. We show that a gap between zero and midinfrared energies can be induced and externally tuned in these devices, making bilayer graphene very appealing from the point of view of applications. However, applications to nanotechnology require careful treatment of the effect of sample boundaries. This being particularly true in graphene, where the presence of edge states at zero energy - the Fermi level of the undoped system - has been extensively reported. Here we show that also bilayer graphene supports surface states localized at zigzag edges. The presence of two layers, however, allows for a new type of edge state which shows an enhanced penetration into the bulk and gives rise to band crossing phenomenon inside the gap of the biased bilayer system.

Effects of carotenoids on lipid bilayers.

Science.gov (United States)

Johnson, Quentin R; Mostofian, Barmak; Fuente Gomez, Gabriel; Smith, Jeremy C; Cheng, Xiaolin

2018-01-31

Carotenoids have been found to be important in improving the integrity of biomembranes in eukaryotes. However, the molecular details of how carotenoids modulate the physical properties of biomembranes are unknown. To this end, we have conducted a series of molecular dynamics simulations of different biologically-relevant membranes in the presence of carotenoids. The carotenoid effect on the membrane was found to be specific to the identity of the carotenoid and the composition of the membrane itself. Therefore, different classes of carotenoids produce a different effect on the membrane, and different membrane phases are affected differently by carotenoids. It is apparent from our data that carotenoids do trigger the bilayer to become thinner. The mechanism by which this occurs depends on two competing factors, the ability of the lipid tails of opposing monolayers to either (1) compress or (2) interdigitate as the bilayer condenses. Indeed, carotenoids directly influence the physical properties via these two mechanisms, thus compacting the bilayer. However, the degree to which these competing mechanisms are utilized depends on the bilayer phase and the carotenoid identity.

Computer Simulations of Lipid Bilayers and Proteins

DEFF Research Database (Denmark)

Sonne, Jacob

2006-01-01

The importance of computer simulations in lipid bilayer research has become more prominent for the last couple of decades and as computers get even faster, simulations will play an increasingly important part of understanding the processes that take place in and across cell membranes. This thesis...... entitled Computer simulations of lipid bilayers and proteins describes two molecular dynamics (MD) simulation studies of pure lipid bilayers as well as a study of a transmembrane protein embedded in a lipid bilayer matrix. Below follows a brief overview of the thesis. Chapter 1. This chapter is a short...... in the succeeding chapters is presented. Details on system setups, simulation parameters and other technicalities can be found in the relevant chapters. Chapter 3, DPPC lipid parameters: The quality of MD simulations is intimately dependent on the empirical potential energy function and its parameters, i...

Quasi-free-standing bilayer graphene nanoribbons probed by electronic transport

Science.gov (United States)

Miccoli, Ilio; Aprojanz, Johannes; Baringhaus, Jens; Lichtenstein, Timo; Galves, Lauren A.; Lopes, Joao Marcelo J.; Tegenkamp, Christoph

2017-01-01

Direct growth of graphene nanostructures by using concepts of self-assembly and intercalation without further lithography and transfer processes is beneficial for their integration into device applications. In this letter, we report on bilayer graphene nanoribbons, typically 100 nm in width, grown along step edges of SiC(0001) substrates. The ribbons are electrically decoupled from the substrate by an oxygen treatment. By means of a 4-tip STM system, the microscopic structure and transport properties were comprehensively studied. The ribbons reveal a robust hole concentration of around 1 × 1013 cm-2 and mobilities up to 700 cm2/Vs at room temperature. The comparably high mobilities are a consequence of interlayer hopping of the charge carriers. The transport is not limited by the step roughness; thus, this scalable process can be easily extended to arbitrarily shaped structures.

Access to electronic resources by visually impaired people

Directory of Open Access Journals (Sweden)

Jenny Craven

2003-01-01

Full Text Available Research into access to electronic resources by visually impaired people undertaken by the Centre for Research in Library and Information Management has not only explored the accessibility of websites and levels of awareness in providing websites that adhere to design for all principles, but has sought to enhance understanding of information seeking behaviour of blind and visually impaired people when using digital resources.

Electrochemical synthesis of bilayer coatings of poly(N-methylaniline) and polypyrrole on mild steel and their corrosion protection performances

Energy Technology Data Exchange (ETDEWEB)

Zeybek, Buelent [Ankara University, Faculty of Science, Department of Chemistry, Ankara (Turkey); Dumlupinar University, Faculty of Arts and Sciences, Department of Chemistry, Kuetahya (Turkey); Ozcicek Pekmez, Nuran, E-mail: npekmez@hacettepe.edu.t [Hacettepe University, Faculty of Science, Department of Chemistry, Ankara (Turkey); Kilic, Esma [Ankara University, Faculty of Science, Department of Chemistry, Ankara (Turkey)

2011-10-30

Highlights: > The bilayers of poly(N-methylaniline) and polypyrrole-dodecylsulfate were synthesized. > These films on mild steel were characterized by cyclic voltammetry, FTIR and FESEM. > DS dopant allows permeation to cations and decreases the ingress of chloride ions. > The PNMA/PPy-DS bilayer coating exhibited the best corrosion resistance in 0.5 M HCl. > The protective properties of polymers was developed by preparing their bilayer coatings. - Abstract: Homopolymer and bilayer coatings of poly(N-methylaniline) (PNMA) and polypyrrole-dodecylsulfate (PPy-DS) have been electropolymerized on a mild steel (MS) surface by the potentiodynamic method in aqueous oxalic acid solutions. In order to include dodecylsulfate ion as dopant in the polypyrrole, sodium dodecylsulfate was also added to the polymerization solution of pyrrole. Characterization of coatings was carried out by the cyclic voltammetry, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). Corrosion behavior of the polymer coated MS electrodes was investigated in highly aggressive 0.5 M HCl solution by the Tafel test and electrochemical impedance spectroscopy (EIS) techniques. Corrosion test revealed that among the protective coatings obtained, the PNMA/PPy-DS bilayer exhibited the best corrosion resistance at all immersion times.

DSC and EPR investigations on effects of cholesterol component on molecular interactions between paclitaxel and phospholipid within lipid bilayer membrane.

Science.gov (United States)

Zhao, Lingyun; Feng, Si-Shen; Kocherginsky, Nikolai; Kostetski, Iouri

2007-06-29

Differential scanning calorimetry (DSC) and electron paramagnetic resonance spectroscopy (EPR) were applied to investigate effects of cholesterol component on molecular interactions between paclitaxel, which is one of the best antineoplastic agents found from nature, and dipalmitoylphosphatidylcholine (DPPC) within lipid bilayer vesicles (liposomes), which could also be used as a model cell membrane. DSC analysis showed that incorporation of paclitaxel into the DPPC bilayer causes a reduction in the cooperativity of bilayer phase transition, leading to a looser and more flexible bilayer structure. Including cholesterol component in the DPPC/paclitaxel mixed bilayer can facilitate the molecular interaction between paclitaxel and lipid and make the tertiary system more stable. EPR analysis demonstrated that both of paclitaxel and cholesterol have fluidization effect on the DPPC bilayer membranes although cholesterol has more significant effect than paclitaxel does. The reduction kinetics of nitroxides by ascorbic acid showed that paclitaxel can inhibit the reaction by blocking the diffusion of either the ascorbic acid or nitroxide molecules since the reaction is tested to be a first order one. Cholesterol can remarkably increase the reduction reaction speed. This research may provide useful information for optimizing liposomal formulation of the drug as well as for understanding the pharmacology of paclitaxel.

Revival of cloaking effect in a driven bilayer graphene vector barrier

Science.gov (United States)

Maiti, S.; Panigrahi, A.; Biswas, R.; Sinha, C.

2018-05-01

Transmission profiles in bilayer graphene are studied theoretically through a rectangular vector potential (magnetic) barrier with and without the presence of an oscillatory potential. Unlike the electrostatic barrier, the Fano resonances (FR) are noted in the transmission spectra both for normal and glancing incidences due to non-conservation of chirality for a static vector barrier. The results for normal incidence indicate that the cloaking effect is a manifestation of the chirality conservation in charge transport through bilayer graphene scalar barriers. It is also noted that the aforesaid FR for a static vector barrier might disappear (photon induced electronic cloaking effect) due to the predominant photon exchange processes in presence of an external oscillating potential. The study of Fano resonances in transmission spectrum is in high demand in respect of localization of charge carriers in graphene nano structures for its potential applications in digital device fabrications.

Observation of undulation motion of lipid bilayers by neutron spin echo

International Nuclear Information System (INIS)

Yamada, Norifumi L.; Seto, Hideki; Hishida, Mafumi

2010-01-01

Aqueous solutions of synthesized phospholipids have been well investigated as model biomembranes. These lipids usually self-assemble into regular stacks of bilayers with a characteristic repeat distance on the order of nm, whereas real biomembrane exist as single bilayers. The key phenomenon in understanding the formation of single isolated bilayers in 'unbinding' of lipid bilayers, in which the inter-bilayer distance of lipid bilayers diverges by the steric interaction due to the membrane undulation. In this paper, we show some results of neutron spin-echo (NSE) experiments to investigate the effect of the steric interaction on unbinding and related phenomena. (author)

Tunable metal-insulator transitions in bilayer graphene by thermal annealing

OpenAIRE

Kalon, Gopinadhan; Shin, Young Jun; Yang, Hyunsoo

2012-01-01

Tunable and highly reproducible metal-insulator transitions have been observed in bilayer graphene upon thermal annealing at 400 K under high vacuum conditions. Before annealing, the sample is metallic in the whole temperature regime of study. Upon annealing, the conductivity changes from metallic to that of an insulator and the transition temperature is a function of annealing time. The pristine metallic state can be reinstated by exposing to air thereby inducing changes in the electronic pr...

Library training to promote electronic resource usage

DEFF Research Database (Denmark)

Frandsen, Tove Faber; Tibyampansha, Dativa; Ibrahim, Glory

2017-01-01

Purpose: Increasing the usage of electronic resources is an issue of concern for many libraries all over the world. Several studies stress the importance of information literacy and instruction in order to increase the usage. Design/methodology/approach: The present article presents the results...

Why and How to Measure the Use of Electronic Resources

Directory of Open Access Journals (Sweden)

Jean Bernon

2008-11-01

Full Text Available A complete overview of library activity implies a complete and reliable measurement of the use of both electronic resources and printed materials. This measurement is based on three sets of definitions: document types, use types and user types. There is a common model of definitions for printed materials, but a lot of questions and technical issues remain for electronic resources. In 2006 a French national working group studied these questions. It relied on the COUNTER standard, but found it insufficient and pointed out the need for local tools such as web markers and deep analysis of proxy logs. Within the French national consortium COUPERIN, a new working group is testing ERMS, SUSHI standards, Shibboleth authentication, along with COUNTER standards, to improve the counting of the electronic resources use. At this stage this counting is insufficient and its improvement will be a European challenge for the future.

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

membranes. Here we present a mesoscopic model for lipid bilayers with embedded proteins, which we have studied with the help of the dissipative particle dynamics simulation technique. Because hydrophobic matching is believed to be one of the main physical mechanisms regulating lipid-protein interactions......-induced protein tilt, with the hydrophobic mismatch ( positive and negative) between the protein hydrophobic length and the pure lipid bilayer hydrophobic thickness. The protein-induced bilayer perturbation was quantified in terms of a coherence length, xi(P), of the lipid bilayer hydrophobic thickness pro. le...... 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...

Incorporating isolated molybdenum (Mo) atoms into Bilayer Epitaxial Graphene on 4H-SiC(0001)

Science.gov (United States)

Huang, Han; Wan, Wen; Li, Hui; Wong, Swee Liang; Lv, Lu; Gao, Yongli; Wee, Andrew T. S.

2014-03-01

The atomic structures and electronic properties of isolated Mo atoms in bilayer epitaxial graphene (BLEG) on 4H-SiC(0001) are investigated by low temperature scanning tunneling microscopy (LT-STM). LT-STM results reveal that isolated Mo dopants prefer to substitute C atoms at α-sites, and preferentially locate between the graphene bilayers. First-principles calculations confirm that the embedding of single Mo dopants within BLEG is energetically favorable as compared to monolayer graphene. The calculated bandstructures show that Mo-doped BLEG is n-doped, and each Mo atom introduces a local magnetic moment of 1.81 μB. Our findings demonstrate a simple and stable method to incorporate single transition metal dopants into the graphene lattice to tune its electronic and magnetic properties for possible use in graphene spin devices. NRF-CRP (Singapore) grants R-143-000-360-281and R-144-000-295-281. ``Shenghua Professorship'' startup funding from CSU and the support from the NSF of China (Grant No.11304398).

Highly sensitive and selective room-temperature NO{sub 2} gas sensor based on bilayer transferred chemical vapor deposited graphene

Energy Technology Data Exchange (ETDEWEB)

Seekaew, Yotsarayuth [Department of Physics, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900 (Thailand); Phokharatkul, Ditsayut; Wisitsoraat, Anurat [Nanoelectronics and MEMS Laboratory, National Electronics and Computer Technology Center, Klong Luang, Pathumthani 12120 (Thailand); Wongchoosuk, Chatchawal, E-mail: chatchawal.w@ku.ac.th [Department of Physics, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900 (Thailand)

2017-05-15

Highlights: • Simple and low-cost fabrication of bilayer graphene gas sensor was presented. • Layer effects of graphene on NO{sub 2} gas-sensing properties were investigated. • Bilayer graphene sensor exhibited a high linear NO{sub 2} sensitivity of 1.409 ppm{sup −1}. • The NO{sub 2}-sensing mechanisms based on band diagram were highlighted. - Abstract: This work presents a highly sensitive room-temperature gas sensor based on bilayer graphene fabricated by an interfacial transfer of chemical vapor deposited graphene onto nickel interdigitated electrodes. Scanning electron microscopic and Raman spectroscopic characterizations confirm the presence of graphene on interdigitated nickel electrodes with varying numbers of graphene layers. The NO{sub 2} detection performances of bilayer graphene gas sensor have been investigated in comparison with those of monolayer and multilayer graphene gas sensors at room temperature. From results, the bilayer graphene gas sensor exhibits higher response, sensitivity and selectivity to NO{sub 2} than monolayer and multilayer graphene. The sensitivity of bilayer graphene gas sensor is 1.409 ppm{sup −1} towards NO{sub 2} over a concentration range of 1–25 ppm, which is more than twice higher than that of monolayer graphene. The NO{sub 2}-sensing mechanism of graphene sensing film has been explained based on the direct charge transfer process due to the adsorption of NO{sub 2} molecules.

Growth, structure and magnetic properties of single crystalline Fe/CoO/Ag(001) bilayers

Energy Technology Data Exchange (ETDEWEB)

Abrudan, R.M.

2007-07-16

The structural and magnetic properties of epitaxially deposited single-crystalline CoO layers and Fe/CoO bilayers on Ag(001) were investigated. CoO films on Ag(001) exhibit (1 x 1) Low Energy Electron Diffraction (LEED) patterns similar to the clean Ag(001) substrate. The vertical interlayer spacing of the CoO films, deduced from a kinematic analysis of LEED I(E) curves, is a {sub perpendicular} {sub to} /2=2.17 Aa, slightly expanded along the film normal. Scanning Tunneling Microscopy (STM) show a big improvement in the surface roughness after annealing the CoO films at 750 K in oxygen atmosphere. Magnetic measurements using the magneto-optical Kerr effect (MOKE) show a characteristic increase of the coercive field when the Fe/CoO bilayer system is cooled down from room temperature to 150 K. The ordering temperature for the antiferromagnetic layer is in the same range as the Neel temperature for bulk CoO (T{sub N}=290 K). X-ray absorption spectroscopy was employed to probe magnetic and electronic properties with elemental selectivity. Absorption spectra taken from bilayers with different amounts of deposited Fe show only a weak indication for the formation of Fe oxide at the Fe/CoO interface (0.3 ML Fe). From the spectral shape it is concluded that an FeO type of oxide is formed. X-ray Magnetic Circular Dichroism (XMCD) measurements exhibit a sizeable induced ferromagnetic signal at the Co L{sub 2,3} absorption edge, corresponding to an interface layer of 1.1 ML in which the magnetic spins couple with the Fe layer. The angular dependence of the X-ray Magnetic Linear Dichroism (XMLD) and X-ray Magnetic Circular Dichroism XMCD at both the Co and Fe L{sub 2,3} edges shows the orientation of the Co and Fe moments in the bilayers with respect to the crystallographic direction. PhotoElectron Emission Microscope (PEEM) is used to image each ferromagnetic and antiferromagnetic layer separately. Magnetic contrast due to the induced magnetic spins at the interface is also

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...

Cluster Formation of Polyphilic Molecules Solvated in a DPPC Bilayer

Directory of Open Access Journals (Sweden)

Xiang-Yang Guo

2017-10-01

Full Text Available We analyse the initial stages of cluster formation of polyphilic additive molecules which are solvated in a dipalmitoylphosphatidylcholine (DPPC lipid bilayer. Our polyphilic molecules comprise an aromatic (trans-bilayer core domain with (out-of-bilayer glycerol terminations, complemented with a fluorophilic and an alkyl side chain, both of which are confined within the aliphatic segment of the bilayer. Large-scale molecular dynamics simulations (1 μ s total duration of a set of six of such polyphilic additives reveal the initial steps towards supramolecular aggregation induced by the specific philicity properties of the molecules. For our intermediate system size of six polyphiles, the transient but recurrent formation of a trimer is observed on a characteristic timescale of about 100 ns. The alkane/perfluoroalkane side chains show a very distinct conformational distribution inside the bilayer thanks to their different philicity, despite their identical anchoring in the trans-bilayer segment of the polyphile. The diffusive mobility of the polyphilic additives is about the same as that of the surrounding lipids, although it crosses both bilayer leaflets and tends to self-associate.

Strain Tuning of the Charge Density Wave in Monolayer and Bilayer 1T-TaS2

KAUST Repository

Gan, Liyong

2015-12-07

By first-principles calculations, we investigate the strain effects on the charge density wave states of monolayer and bilayer 1T-TaS2. The modified stability of the charge density wave in the monolayer is understood in terms of the strain dependent electron localization, which determines the distortion amplitude. On the other hand, in the bilayer the effect of strain on the interlayer interaction is also crucial. The rich phase diagram under strain opens new venues for applications of 1T-TaS2. We interpret the experimentally observed insulating state of bulk 1T-TaS2 as inherited from the monolayer by effective interlayer decoupling.

Universal quantum computation with temporal-mode bilayer square lattices

Science.gov (United States)

Alexander, Rafael N.; Yokoyama, Shota; Furusawa, Akira; Menicucci, Nicolas C.

2018-03-01

We propose an experimental design for universal continuous-variable quantum computation that incorporates recent innovations in linear-optics-based continuous-variable cluster state generation and cubic-phase gate teleportation. The first ingredient is a protocol for generating the bilayer-square-lattice cluster state (a universal resource state) with temporal modes of light. With this state, measurement-based implementation of Gaussian unitary gates requires only homodyne detection. Second, we describe a measurement device that implements an adaptive cubic-phase gate, up to a random phase-space displacement. It requires a two-step sequence of homodyne measurements and consumes a (non-Gaussian) cubic-phase state.

Modulating the electronic and magnetic properties of bilayer borophene via transition metal atoms intercalation: from metal to half metal and semiconductor.

Science.gov (United States)

Zhang, Xiuyun; Sun, Yi; Ma, Liang; Zhao, Xinli; Yao, Xiaojing

2018-07-27

Borophene, a two-dimensional monolayer made of boron atoms, has attracted wide attention due to its appealing properties. Great efforts have been devoted to fine tuning its electronic and magnetic properties for desired applications. Herein, we theoretically investigate the versatile electronic and magnetic properties of bilayer borophene (BLB) intercalated by 3d transition metal (TM) atoms, TM@BLBs (TM = Ti-Fe), using ab initio calculations. Four allotropes of AA-stacking (α 1 -, β-, β 12 - and χ 3 -) BLBs with different intercalation concentrations of TM atoms are considered. Our results show that the TM atoms are strongly bonded to the borophene layers with fairly large binding energies, around 6.31 ∼ 15.44 eV per TM atom. The BLBs with Cr and Mn intercalation have robust ferromagnetism, while for the systems decorated with Fe atoms, fruitful magnetic properties, such as nonmagnetic, ferromagnetic or antiferromagnetic, are identified. In particular, the α 1 - and β-BLBs intercalated by Mn or Fe atom can be transformed into a semiconductor, half metal or graphene-like semimetal. Moreover, some heavily doped TM@BLBs expose high Curie temperatures above room temperature. The attractive properties of TM@BLBs entail an efficient way to modulate the electronic and magnetic properties of borophene sheets for advanced applications.

Characterization of the transverse relaxation rates in lipid bilayers

International Nuclear Information System (INIS)

Watnick, P.I.; Dea, P.; Chan, S.I.

1990-01-01

The 2H NMR transverse relaxation rates of a deuterated phospholipid bilayer reflect slow motions in the bilayer membrane. A study of dimyristoyl lecithin specifically deuterated at several positions of the hydrocarbon chains indicates that these motions are cooperative and are confined to the hydrocarbon chains of the lipid bilayer. However, lipid head group interactions do play an important role in modulating the properties of the cooperative fluctuations of the hydrocarbon chains (director fluctuations), as evidenced by the effects of various lipid additives on the 2H NMR transverse relaxation rates of the dimyristoyl lecithin bilayer

DNA nanotechnology: Bringing lipid bilayers into shape

Science.gov (United States)

Howorka, Stefan

2017-07-01

Lipid bilayers form the thin and floppy membranes that define the boundary of compartments such as cells. Now, a method to control the shape and size of bilayers using DNA nanoscaffolds has been developed. Such designer materials advance synthetic biology and could find use in membrane research.

Euler European Libraries and Electronic Resources in Mathematical Sciences

CERN Document Server

The Euler Project. Karlsruhe

The European Libraries and Electronic Resources (EULER) Project in Mathematical Sciences provides the EulerService site for searching out "mathematical resources such as books, pre-prints, web-pages, abstracts, proceedings, serials, technical reports preprints) and NetLab (for Internet resources), this outstanding engine is capable of simple, full, and refined searches. It also offers a browse option, which responds to entries in the author, keyword, and title fields. Further information about the Project is provided at the EULER homepage.

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

International Nuclear Information System (INIS)

Lundbaek, Jens August

2006-01-01

Membrane protein function is generally regulated by the molecular composition of the host lipid bilayer. The underlying mechanisms have long remained enigmatic. Some cases involve specific molecular interactions, but very often lipids and other amphiphiles, which are adsorbed to lipid bilayers, regulate a number of structurally unrelated proteins in an apparently non-specific manner. It is well known that changes in the physical properties of a lipid bilayer (e.g., thickness or monolayer spontaneous curvature) can affect the function of an embedded protein. However, the role of such changes, 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-dependent sodium channels, N-type calcium channels and GABA A receptors, it has been shown that membrane protein function in living cells can be regulated by amphiphile induced changes in bilayer elasticity. Using the gramicidin channel as a molecular force transducer, a nanotechnology to measure the elastic 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

Reliable Piezoelectricity in Bilayer WSe2 for Piezoelectric Nanogenerators.

Science.gov (United States)

Lee, Ju-Hyuck; Park, Jae Young; Cho, Eun Bi; Kim, Tae Yun; Han, Sang A; Kim, Tae-Ho; Liu, Yanan; Kim, Sung Kyun; Roh, Chang Jae; Yoon, Hong-Joon; Ryu, Hanjun; Seung, Wanchul; Lee, Jong Seok; Lee, Jaichan; Kim, Sang-Woo

2017-08-01

Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal-boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS 2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal-stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe 2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe 2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)-grown WSe 2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD-grown WSe 2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe 2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe 2 for which the device performance becomes degraded above a strain of 0.63%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bilayered construct for simultaneous regeneration of alveolar bone and periodontal ligament.

Science.gov (United States)

Nivedhitha Sundaram, M; Sowmya, S; Deepthi, S; Bumgardener, Joel D; Jayakumar, R

2016-05-01

Periodontitis is an inflammatory disease that causes destruction of tooth-supporting tissues and if left untreated leads to tooth loss. Current treatments have shown limited potential for simultaneous regeneration of the tooth-supporting tissues. To recreate the complex architecture of the periodontium, we developed a bilayered construct consisting of poly(caprolactone) (PCL) multiscale electrospun membrane (to mimic and regenerate periodontal ligament, PDL) and a chitosan/2wt % CaSO4 scaffold (to mimic and regenerate alveolar bone). Scanning electron microscopy results showed the porous nature of the scaffold and formation of beadless electrospun multiscale fibers. The fiber diameter of microfiber and nanofibers was in the range of 10 ± 3 µm and 377 ± 3 nm, respectively. The bilayered construct showed better protein adsorption compared to the control. Osteoblastic differentiation of human dental follicle stem cells (hDFCs) on chitosan/2wt % CaSO4 scaffold showed maximum alkaline phosphatase at seventh day followed by a decline thereafter when compared to chitosan control scaffold. Fibroblastic differentiation of hDFCs was confirmed by the expression of PLAP-1 and COL-1 proteins which were more prominent on PCL multiscale membrane in comparison to control membranes. Overall these results show that the developed bilayered construct might serve as a good candidate for the simultaneous regeneration of the alveolar bone and PDL. © 2015 Wiley Periodicals, Inc.

Effects of Electronic Information Resources Skills Training for Lecturers on Pedagogical Practices and Research Productivity

Science.gov (United States)

Bhukuvhani, Crispen; Chiparausha, Blessing; Zuvalinyenga, Dorcas

2012-01-01

Lecturers use various electronic resources at different frequencies. The university library's information literacy skills workshops and seminars are the main sources of knowledge of accessing electronic resources. The use of electronic resources can be said to have positively affected lecturers' pedagogical practices and their work in general. The…

Improvement of pentathiophene/fullerene planar heterojunction photovoltaic cells by improving the organic films morphology through the anode buffer bilayer

Science.gov (United States)

El Jouad, Zouhair; Cattin, Linda; Martinez, Francisco; Neculqueo, Gloria; Louarn, Guy; Addou, Mohammed; Predeep, Padmanabhan; Manuvel, Jayan; Bernède, Jean-Christian

2016-05-01

Organic photovoltaic cells (OPVCs) are based on a heterojunction electron donor (ED)/electron acceptor (EA). In the present work, the electron donor which is also the absorber of light is pentathiophene. The typical cells were ITO/HTL/pentathiophene/fullerene/Alq3/Al with HTL (hole transport layer) = MoO3, CuI, MoO3/CuI. After optimisation of the pentathiophene thickness, 70 nm, the highest efficiency, 0.81%, is obtained with the bilayer MoO3/CuI as HTL. In order to understand these results the pentathiophene films deposited onto the different HTLs were characterized by scanning electron microscopy, atomic force microscopy, X-rays diffraction, optical absorption and electrical characterization. It is shown that CuI improves the conductivity of the pentathiophene layer through the modification of the film structure, while MoO3 decreases the leakage current. Using the bilayer MoO3/CuI allows cumulating the advantages of each layer. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

Possible role of non-bilayer lipids in the structure of mitochondria. A freeze-fracture electron microscopy study

NARCIS (Netherlands)

Venetie, R. van; Verkleij, A.J.

1982-01-01

The possible role of non-bilayer phospholipids on the structure of isolated rat liver mitochondria has been morphologically studied. Freshly isolated freeze-fractured mitochondria show smooth fracture faces with particles, representing the limiting membranes. The frequency and size of the particles

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-co...

Bifurcation of self-folded polygonal bilayers

Science.gov (United States)

Abdullah, Arif M.; Braun, Paul V.; Hsia, K. Jimmy

2017-09-01

Motivated by the self-assembly of natural systems, researchers have investigated the stimulus-responsive curving of thin-shell structures, which is also known as self-folding. Self-folding strategies not only offer possibilities to realize complicated shapes but also promise actuation at small length scales. Biaxial mismatch strain driven self-folding bilayers demonstrate bifurcation of equilibrium shapes (from quasi-axisymmetric doubly curved to approximately singly curved) during their stimulus-responsive morphing behavior. Being a structurally instable, bifurcation could be used to tune the self-folding behavior, and hence, a detailed understanding of this phenomenon is appealing from both fundamental and practical perspectives. In this work, we investigated the bifurcation behavior of self-folding bilayer polygons. For the mechanistic understanding, we developed finite element models of planar bilayers (consisting of a stimulus-responsive and a passive layer of material) that transform into 3D curved configurations. Our experiments with cross-linked Polydimethylsiloxane samples that change shapes in organic solvents confirmed our model predictions. Finally, we explored a design scheme to generate gripper-like architectures by avoiding the bifurcation of stimulus-responsive bilayers. Our research contributes to the broad field of self-assembly as the findings could motivate functional devices across multiple disciplines such as robotics, artificial muscles, therapeutic cargos, and reconfigurable biomedical devices.

Electronic Properties of Graphene-PtSe2 Contacts.

Science.gov (United States)

Sattar, Shahid; Schwingenschlögl, Udo

2017-05-10

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe 2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe 2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe 2 and a p-type Schottky contact with bilayer PtSe 2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

Electronic Properties of Graphene–PtSe2 Contacts

KAUST Repository

Sattar, Shahid

2017-04-26

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

Electronic Properties of Graphene–PtSe2 Contacts

KAUST Repository

Sattar, Shahid; Schwingenschlö gl, Udo

2017-01-01

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

Magnetic flux distributions in chiral helimagnet/superconductor bilayers

Energy Technology Data Exchange (ETDEWEB)

Kato, Masaru, E-mail: kato@ms.osakafu-u.ac.jp [Department of Mathematical Sciences, Osaka Prefecture University, 1-1, Gakuencho, Nakaku, Sakai, Osaka 599-8531 (Japan); Fukui, Saoto [Department of Mathematical Sciences, Osaka Prefecture University, 1-1, Gakuencho, Nakaku, Sakai, Osaka 599-8531 (Japan); Sato, Osamu [Osaka Prefecture University College of Technology, 26-12, Saiwaicho, Neyagawa, Osaka 572-8572 (Japan); Togawa, Yoshihiko [Department of Physics and Electronics, Osaka Prefecture University, 1-1, Gakuencho, Nakaku, Sakai, Osaka 599-8531 (Japan)

2017-02-15

Highlights: • Vortex states in a chiral helimagnet/superconductor bilayer are investigated. • Vortex and anti-vortex appears depending on strength of helimagnet. • Vortex is elongated under a gradient field. • Vortices form a undulated triangular lattice. - Abstarct: Vortex states in a chiral helimagnet/superconductor bilayer are investigated numerically, using the Ginzburg–Landau equations with the finite element method. In this bilayer, effect of the chiral helimagnet on the superconductor is taken as an external field. Magnetic field distribution can be controlled by an applied field to the bilayer. It is shown that a single vortex in a gradient field is elongated along the field gradient. In zero applied field, there are up- and down vortices which are parallel or antiparallel to the z-axis, respectively. But increasing the applied field, down-vortices disappear and up-vortices form undulated triangular lattices.

Interfacial exciplex formation in bilayers of conjugated polymers

Science.gov (United States)

Nobuyasu, R. S.; Araujo, K. A. S.; Cury, L. A.; Jarrosson, T.; Serein-Spirau, F.; Lère-Porte, J.-P.; Dias, F. B.; Monkman, A. P.

2013-10-01

The donor-acceptor interactions in sequential bilayer and blend films are investigated. Steady-state and time-resolved photoluminescence (PL) were measured to characterize the samples at different geometries of photoluminescence collection. At standard excitation, with the laser incidence at 45° of the normal direction of the sample surface, a band related to the aggregate states of donor molecules appears for both blend and bilayer at around 540 nm. For the PL spectra acquired from the edge of the bilayer, with the laser incidence made at normal direction of the sample surface (90° geometry), a new featureless band emission, red-shifted from donor and acceptor emission regions was observed and assigned as the emission from interfacial exciplex states. The conformational complexity coming from donor/acceptor interactions at the heterojunction interface of the bilayer is at the origin of this interfacial exciplex emission.

Transport properties in monolayer-bilayer-monolayer graphene planar junctions

Institute of Scientific and Technical Information of China (English)

Kai-Long Chu; Zi-Bo Wang; Jiao-Jiao Zhou; Hua Jiang

2017-01-01

The transport study of graphene based junctions has become one of the focuses in graphene research.There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions.One is the two monolayer graphene contacting the same side of the bilayer graphene,and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene.In this paper,according to the Landauer-Büttiker formula,we study the transport properties of these two configurations.The influences of the local gate potential in each part,the bias potential in bilayer graphene,the disorder and external magnetic field on conductance are obtained.We find the conductances of the two configurations can be manipulated by all of these effects.Especially,one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene.The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.

Asymptotic and numerical prediction of current-voltage curves for an organic bilayer solar cell under varying illumination and comparison to the Shockley equivalent circuit

KAUST Repository

Foster, J. M.; Kirkpatrick, J.; Richardson, G.

2013-01-01

In this study, a drift-diffusion model is used to derive the current-voltage curves of an organic bilayer solar cell consisting of slabs of electron acceptor and electron donor materials sandwiched together between current collectors. A simplified

Electromagnetic coupling of spins and pseudospins in bilayer graphene

Science.gov (United States)

Winkler, R.; Zülicke, U.

2015-03-01

We present a theoretical study of bilayer-graphene's electronic properties in the presence of electric and magnetic fields. In contrast to known materials, including single-layer graphene, any possible coupling of physical quantities to components of the electric field has a counterpart where the analogous component of the magnetic field couples to exactly the same quantities. For example, a purely electric spin splitting appears as the magneto-electric analogue of the magnetic Zeeman spin splitting. The measurable thermodynamic response induced by magnetic and electric fields is thus completely symmetric. The Pauli magnetization induced by a magnetic field takes exactly the same functional form as the polarization induced by an electric field. Although they seem counterintuitive, our findings are consistent with fundamental principles such as time reversal symmetry. For example, only a magnetic field can give rise to a macroscopic spin polarization, whereas only a perpendicular electric field can induce a macroscopic polarization of the sublattice-related pseudospin in bilayer graphene. These rules enforced by symmetry for the matter-field interactions clarify the nature of spins versus pseudospins. We have obtained numerical values of prefactors for relevant terms. NSF Grant DMR-1310199 and Marsden Fund Contract No. VUW0719.

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.

Electrostatic double-layer interaction between stacked charged bilayers

Science.gov (United States)

Hishida, Mafumi; Nomura, Yoko; Akiyama, Ryo; Yamamura, Yasuhisa; Saito, Kazuya

2017-10-01

The inapplicability of the DLVO theory to multilayered anionic bilayers is found in terms of the co-ion-valence dependence of the lamellar repeat distance. Most of the added salt is expelled from the interlamellar space to the bulk due to the Gibbs-Donnan effect on multiple bilayers with the bulk. The electrostatic double-layer interaction is well expressed by the formula recently proposed by Trefalt. The osmotic pressure due to the expelled ions, rather than the van der Waals interaction, is the main origin of the attractive force between the bilayers.

Fabrication of bi-layer graphene and theoretical simulation for its possible application in thin film solar cell.

Science.gov (United States)

Behura, Sanjay K; Mahala, Pramila; Nayak, Sasmita; Yang, Qiaoqin; Mukhopadhyay, Indrajit; Janil, Omkar

2014-04-01

High quality graphene film is fabricated using mechanical exfoliation of highly-oriented pyrolytic graphite. The graphene films on glass substrates are characterized using field-emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, UV-vis spectroscopy and Fourier transform infrared spectroscopy. A very high intensity ratio of 2D to G-band (to approximately 1.67) and narrow 2D-band full-width at half maximum (to approximately 40 cm(-1)) correspond to the bi-layer graphene formation. The bi-layer graphene/p-GaN/n-InGaN/n-GaN/GaN/sAl2O3 system is studied theoretically using TCAD Silvaco software, in which the properties of exfoliated bi-layer graphene are used as transparent and conductive film, and the device exhibits an efficiency of 15.24% compared to 13.63% for ITO/p-GaN/n-InGaN/n-GaN/GaN/Al2O3 system.

Lipid bilayer-coated mesoporous silica nanoparticles carrying bovine hemoglobin towards an erythrocyte mimic.

Science.gov (United States)

Tu, Jing; Bussmann, Jeroen; Du, Guangsheng; Gao, Yue; Bouwstra, Joke A; Kros, Alexander

2018-05-30

Hemoglobin (Hb)-loaded mesoporous silica nanoparticles (MSNs) coated with a lipid bilayer (LB-MSNs) were investigated as an erythrocyte mimic. MSNs with a large average pore size (10 nm) act as a rigid core and provide a protective environment for Hb encapsulated inside the pores. The colloidal stability of Hb-loaded MSNs was enhanced upon the application of a lipid bilayer, through fusion of PEGylated liposomes onto the exterior surface of Hb-loaded MSNs. The morphology and mesostructure of the MSNs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and surface area analysis. The Hb loading capacity (mg/g) in MSNs was studied by thermogravimetric analysis (TGA). UV-Vis absorption spectroscopy revealed that Hb inside MSNs had an identical, but slightly broadened peak in the Soret region compared to free Hb. Furthermore the encapsulated Hb exhibits similar peroxidase-like activity in catalyzing the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) with hydrogen peroxide. The introduction of a supported lipid bilayer (LB) demonstrated the potential to prevent premature Hb release (the burst release decreased from 25.50 ± 0.33% to 6.73 ± 0.83%) and increased the colloidal stability of the Hb-loaded MSNs (hydrodynamic diameter remained ∼250 nm for at least one week). The in vivo systemic circulation and biodistribution of LB-MSNs were studied in optically transparent zebrafish embryos, revealing that LB-MSNs have the potential to act as an erythrocyte mimic in transfusion therapy. Copyright © 2018 Elsevier B.V. All rights reserved.

Electronic Commerce Resource Centers. An Industry--University Partnership.

Science.gov (United States)

Gulledge, Thomas R.; Sommer, Rainer; Tarimcilar, M. Murat

1999-01-01

Electronic Commerce Resource Centers focus on transferring emerging technologies to small businesses through university/industry partnerships. Successful implementation hinges on a strategic operating plan, creation of measurable value for customers, investment in customer-targeted training, and measurement of performance outputs. (SK)

Growth feature of ionic nitrogen doped CN_x bilayer films with Ti and TiN interlayer by pulse cathode arc discharge

International Nuclear Information System (INIS)

Zhou, Bing; Liu, Zhubo; Piliptsou, D.G.; Rogachev, A.V.; Yu, Shengwang; Wu, Yanxia; Tang, Bin; Rudenkov, A.S.

2016-01-01

Graphical abstract: - Highlights: • Ti/ and TiN/CN_x (N"+) bilayers are prepared at various frequencies by pulse cathode arc. • Ti interlayer facilitates the introduction of N atoms into the CN_x (N"+) films. • The most N-sp"2C bonds (mainly graphite-like N) present in the TiN/CN_x (N"+, 3 Hz) film. • Ti/CN_x (N"+, 3 Hz) bilayer possesses small size and disordering of Csp"2 clusters. • The higher hardness and the lower stress presents in the TiN/CN_x (N"+, 10 Hz) bilayer. - Abstract: Using nano-scaled Ti and TiN as interlayer, ionic nitrogen doped carbon (CN_x (N"+)) bilayer films were prepared at various pulse frequencies by cathode arc technique. Elemental distribution at the interface, bonding compositions, microstructure, and mechanical properties of CN_x (N"+) bilayer films were investigated in dependence of interlayer and pulse frequency by Auger electron spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, nanoindentation, and surface profilometer. The results showed that the diffusion extent of C atoms at the interface of CN_x (N"+) bilayers is higher than for the α-C and CN_x (N_2) bilayers with the same interlayer. Nitrogen atoms could diffuse throughout the pre-deposited Ti and TiN layers into the Si substrate for all CN_x (N"+) bilayers. Ti interlayer facilitates the introduction of N atoms into the CN_x (N"+) films and exhibits a certain catalytic effect on the coordination of N atoms with sp"2- and sp"3-C binding. More nitrogenated and intense CN bonding configurations (mainly graphite-like N) form in the TiN/CN_x (N"+) bilayer. Ti/CN_x (N"+) bilayer prepared at low frequency possesses small size and disordering of Csp"2 clusters but TiN interlayer weakens the formation of Csp"2 bonding and increases the disordering of Csp"2 clusters in the films. The residual stress in the bilayer is lower than for CN_x (N"+) monolayer. The higher hardness and the lower residual stress are present in the TiN/CN_x (N"+, 10 Hz) bilayer.

Magnetically assisted bilayer composites for soft bending actuators

NARCIS (Netherlands)

Jang, S.H.; Na, Seon Hong; Park, Yong Lae

2017-01-01

This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically

Direct measurement of discrete valley and orbital quantum numbers in bilayer graphene.

Science.gov (United States)

Hunt, B M; Li, J I A; Zibrov, A A; Wang, L; Taniguchi, T; Watanabe, K; Hone, J; Dean, C R; Zaletel, M; Ashoori, R C; Young, A F

2017-10-16

The high magnetic field electronic structure of bilayer graphene is enhanced by the spin, valley isospin, and an accidental orbital degeneracy, leading to a complex phase diagram of broken symmetry states. Here, we present a technique for measuring the layer-resolved charge density, from which we directly determine the valley and orbital polarization within the zero energy Landau level. Layer polarization evolves in discrete steps across 32 electric field-tuned phase transitions between states of different valley, spin, and orbital order, including previously unobserved orbitally polarized states stabilized by skew interlayer hopping. We fit our data to a model that captures both single-particle and interaction-induced anisotropies, providing a complete picture of this correlated electron system. The resulting roadmap to symmetry breaking paves the way for deterministic engineering of fractional quantum Hall states, while our layer-resolved technique is readily extendable to other two-dimensional materials where layer polarization maps to the valley or spin quantum numbers.The phase diagram of bilayer graphene at high magnetic fields has been an outstanding question, with orders possibly between multiple internal quantum degrees of freedom. Here, Hunt et al. report the measurement of the valley and orbital order, allowing them to directly reconstruct the phase diagram.

Collective excitations of strongly coupled bilayer charged Bose liquids in the third-frequency-moment sum rule

International Nuclear Information System (INIS)

Tas, Murat; Tanatar, B.

2008-01-01

We calculate the collective excitation modes of strongly coupled bilayer charged Bose systems. We employ the dielectric matrix formulation to study the correlation effects within the random-phase approximation (RPA), the self consistent field approximation Singwi, Tosi, Land, and Sjoelander (STLS), and the quasilocalized charge approximation (QLCA), which satisfies the third-frequency-moment ( 3 >) sum rule. We find that the QLCA predicts a long-wavelength correlation-induced energy gap in the out-of-phase plasmon mode, similar to the situation in electronic bilayer systems. The energy gap and the plasmon density of states are studied as a function of interlayer separation and coupling parameter r s . The results should be helpful for experimental investigations

Predicting proton titration in cationic micelle and bilayer environments

Science.gov (United States)

Morrow, Brian H.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.; Shen, Jana K.

2014-08-01

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 pKa'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 pKa 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 pKa 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.

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.

Phase diagram of a symmetric electron-hole bilayer system: a variational Monte Carlo study.

Science.gov (United States)

Sharma, Rajesh O; Saini, L K; Bahuguna, Bhagwati Prasad

2018-05-10

We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

Poly(amidoamine) dendrimers on lipid bilayers II: Effects of bilayer phase and dendrimer termination.

Science.gov (United States)

Kelly, Christopher V; Leroueil, Pascale R; Orr, Bradford G; Banaszak Holl, Mark M; Andricioaei, Ioan

2008-08-07

The molecular structures and enthalpy release of poly(amidoamine) (PAMAM) dendrimers binding to 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) bilayers were explored through atomistic molecular dynamics. Three PAMAM dendrimer terminations were examined: protonated primary amine, neutral acetamide, and deprotonated carboxylic acid. Fluid and gel lipid phases were examined to extract the effects of lipid tail mobility on the binding of generation-3 dendrimers, which are directly relevant to the nanoparticle interactions involving lipid rafts, endocytosis, lipid removal, and/or membrane pores. Upon binding to gel phase lipids, dendrimers remained spherical, had a constant radius of gyration, and approximately one-quarter of the terminal groups were in close proximity to the lipids. In contrast, upon binding to fluid phase bilayers, dendrimers flattened out with a large increase in their asphericity and radii of gyration. Although over twice as many dendrimer-lipid contacts were formed on fluid versus gel phase lipids, the dendrimer-lipid interaction energy was only 20% stronger. The greatest enthalpy release upon binding was between the charged dendrimers and the lipid bilayer. However, the stronger binding to fluid versus gel phase lipids was driven by the hydrophobic interactions between the inner dendrimer and lipid tails.

SFG studies on interactions between antimicrobial peptides and supported lipid bilayers.

Science.gov (United States)

Chen, Xiaoyun; Chen, Zhan

2006-09-01

The mode of action of antimicrobial peptides (AMPs) in disrupting cell membrane bilayers is of fundamental importance in understanding the efficiency of different AMPs, which is crucial to design antibiotics with improved properties. Recent developments in the field of sum frequency generation (SFG) vibrational spectroscopy have made it a powerful and unique biophysical technique in investigating the interactions between AMPs and a single substrate supported planar lipid bilayer. We will review some of the recent progress in applying SFG to study membrane lipid bilayers and discuss how SFG can provide novel information such as real-time bilayer structure change and AMP orientation during AMP-lipid bilayer interactions in a very biologically relevant manner. Several examples of applying SFG to monitor such interactions between AMPs and a dipalmitoyl phosphatidylglycerol (DPPG) bilayer are presented. Different modes of actions are observed for melittin, tachyplesin I, d-magainin 2, MSI-843, and a synthetic antibacterial oligomer, demonstrating that SFG is very effective in the study of AMPs and AMP-lipid bilayer interactions.

Alpha-tocopherol inhibits pore formation in oxidized bilayers

NARCIS (Netherlands)

Boonnoy, P.; Karttunen, M.; Wong-Ekkabut, J.

2017-01-01

In biological membranes, alpha-tocopherols (α-toc; vitamin E) protect polyunsaturated lipids from free radicals. Although the interactions of α-toc with non-oxidized lipid bilayers have been studied, their effects on oxidized bilayers remain unknown. In this study, atomistic molecular dynamics (MD)

Slaved diffusion in phospholipid bilayers

Science.gov (United States)

Zhang, Liangfang; Granick, Steve

2005-01-01

The translational diffusion of phospholipids in supported fluid bilayers splits into two populations when polyelectrolytes adsorb at incomplete surface coverage. Spatially resolved measurements using fluorescence correlation spectroscopy show that a slow mode, whose magnitude scales inversely with the degree of polymerization of the adsorbate, coexists with a fast mode characteristic of naked lipid diffusion. Inner and outer leaflets of the bilayer are affected nearly equally. Mobility may vary from spot to spot on the membrane surface, despite the lipid composition being the same. This work offers a mechanism to explain how nanosized domains with reduced mobility arise in lipid membranes. PMID:15967988

GABA_A receptor function is regulated by lipid bilayer elasticity

DEFF Research Database (Denmark)

Søgaard, Rikke; Werge, Thomas; Berthelsen, Camilla

2006-01-01

( s) underlying these effects are poorly understood. DHA and Triton X-100, at concentrations that affect GABAA receptor function, increase the elasticity of lipid bilayers measured as decreased bilayer stiffness using gramicidin channels as molecular force transducers. We have previously shown...... reduced the peak amplitude of the GABA-induced currents and increased the rate of receptor desensitization. The effects of the amphiphiles did not correlate with the expected changes in monolayer spontaneous curvature. We conclude that GABAA receptor function is regulated by lipid bilayer elasticity....... PUFAs may generally regulate membrane protein function by affecting the elasticity of the host lipid bilayer....

Selfenergy effect on the magnetic ordering transition in the mono- and bilayer honeycomb Hubbard model

Energy Technology Data Exchange (ETDEWEB)

Honerkamp, Carsten [Institute for Theoretical Solid State Physics, RWTH Aachen University (Germany); JARA - Fundamentals of Future Information Technology, Aachen (Germany)

2017-11-15

We investigate the impact of electron self-energy corrections on potential antiferromagnetic ordering instabilities in mono- and bilayer graphene, modeled by a Hubbard-type lattice model with onsite interactions among the electrons, using a self-consistent random phase approximation (RPA). In qualitative agreement with earlier studies we find that the electronic interactions cause non-Fermi liquid behavior at low energies. In self-consistent RPA, the transition scales for antiferromagnetic ordering are renormalized significantly by these self-energy effects, both for interaction-driven and temperature-driven cases. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Wetting - Dewetting Transitions of Au/Ni Bilayer Films

Science.gov (United States)

Cen, Xi

Thin films deposited at low temperatures are often kinetically constrained and will dewet the underlying substrate when annealed. Solid state dewetting is driven by the minimization of the total free energy of thin film-substrate interface and free surface, and mostly occurs through surface diffusion. Dewetting is a serious concern in microelectronics reliability. However, it can also be utilized for the self-assembly of nanostructures with potentials in storage, catalysis, or transistors. Therefore, a fundamental understanding of the dewetting behavior of thin metal films is critical for improving the thermal stability of microelectronics and controlling the order of self-assembled nanostructures. Mechanisms for dewetting of single layer films have been studied extensively. However little work has been reported on multilayer or alloyed thin films. In the thesis, the solid state dewetting of Au/Ni bilayer films deposited on SiO2/Si substrates was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and aberration corrected scanning TEM (STEM). Ex-situ SEM and TEM studies were performed with in-situ TEM heating characterization to identify the mechanisms during the dewetting process of Au/Ni bilayer films. The solid state dewetting of Au/Ni bilayer films from SiO2/Si substrates exhibits both homogeneous and localized dewetting of Ni and long-edge retraction for Au under isothermal annealing condition. The top Au layer retracts up to 1 mm from the edge of the substrate wafer to reduce the energetically unfavored Au/Ni interface. In contrast, Ni dewets and agglomerates locally due to its limited diffusivity compared to Au. Film morphology and local chemical composition varies significantly across hundreds of microns along the direction normal to the retracting edge. Besides long range edge receding, localized dewetting shows significant changes in film morphology and chemical distribution. Both Au and Ni shows texturing. Despite

Lipid peroxidation and water penetration in lipid bilayers

DEFF Research Database (Denmark)

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

2012-01-01

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......(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...

Characteristics of TiO_2/ZnO bilayer film towards pH sensitivity prepared by different spin coating deposition process

International Nuclear Information System (INIS)

Rahman, Rohanieza Abdul; Zulkefle, Muhammad Al Hadi; Abdullah, Wan Fazlida Hanim; Rusop, M.; Herman, Sukreen Hana

2016-01-01

In this study, titanium dioxide (TiO_2) and zinc oxide (ZnO) bilayer film for pH sensing application will be presented. TiO_2/ZnO bilayer film with different speed of spin-coating process was deposited on Indium Tin Oxide (ITO), prepared by sol-gel method. This fabricated bilayer film was used as sensing membrane for Extended Gate Field-Effect Transistor (EGFET) for pH sensing application. Experimental results indicated that the sensor is able to detect the sensitivity towards pH buffer solution. In order to obtained the result, sensitivity measurement was done by using the EGFET setup equipment with constant-current (100 µA) and constant-voltage (0.3 V) biasing interfacing circuit. TiO_2/ZnO bilayer film which the working electrode, act as the pH-sensitive membrane was connected to a commercial metal-oxide semiconductor FET (MOSFET). This MOSFET then was connected to the interfacing circuit. The sensitivity of the TiO2 thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. These thin films were characterized by using Field Emission Scanning Electron Microscope (FESEM) to obtain the surface morphology of the composite bilayer films. In addition, I-V measurement was done in order to determine the electrical properties of the bilayer films. According to the result obtained in this experiment, bilayer film that spin at 4000 rpm, gave highest sensitivity which is 52.1 mV/pH. Relating the I-V characteristic of the thin films and sensitivity, the sensing membrane with higher conductivity gave better sensitivity.

Adsorption and magnetism of bilayer graphene on the MnO polar surface with oxygen vacancies in the interface: First principles study

Science.gov (United States)

Ilyasov, Victor V.; Ershov, Igor V.; Popova, Inna G.; Pham, Khang D.; Nguyen, Chuong V.

2018-05-01

In this paper, we investigate systematically the structural, electronic, magnetic and adsorption properties of Bernal-stacked bilayer graphene on MnO(111) surface terminated by an oxygen atom, as a function of nonstoichiometric composition of the BLG/MnOx(111) interface. For additional functionalization of the BLG/MnOx(111) system, we also studied the adsorption properties of oxygen adsorbed on the BLG/MnOx(111) interface. Our results showed that the BLG is bound to the MnOx(111) substrate by the weak interaction for both spin-up and spin-down. Furthermore, we found that BLG adsorbed on the MnOx(111) substrate with a reduced oxygen symmetry in the interface is accompanied with a downshift of the Fermi level, which identifies the band structure of BLG as a p-type semiconductor. Upon interaction between BLG and MnOx(111) substrate, a forbidden gap of about 350 meV was opened between its bonding and antibonding π bands. A forbidden gap and the local magnetic moments in bilayer graphene can be controlled by changing the oxygen nonstoichometry or by oxygen adsorption. Additionally, magnetism has been predicted in the bilayer graphene adsorbed on the polar MnOx(111) surface with oxygen vacancies in the BLG/MnOx(111) interface, and its nature has also been discussed in this work. These results showed that the adsorption of bilayer graphene on the MnO(111) substrate can be used for developing novel generation of electronic and spintronic devices.

Multilayered gold/silica nanoparticulate bilayer devices using layer-by-layer self organisation for flexible bending and pressure sensing applications

Energy Technology Data Exchange (ETDEWEB)

Shah Alam, Md. [Department of Electrical and Electronic Engineering, Rajshahi University of Engineering and Technology, Rajshahi 6204 (Bangladesh); Center of Excellence in Nanotechnology, Asian Institute of Technology, 12120 Pathumthani (Thailand); Mohammed, Waleed S., E-mail: waleed.m@bu.ac.th [Center of Research in Optoelectronics, Communication and Control System (BU-CROCCS), School of Engineering, Bangkok University, Pathumthani 12120 (Thailand); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Center of Excellence in Nanotechnology, Asian Institute of Technology, 12120 Pathumthani (Thailand); Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al Khoud 123 (Oman)

2014-02-17

A pressure and bending sensor was fabricated using multilayer thin films fabricated on a flexible substrate based on layer-by-layer self-organization of 18 nm gold nanoparticles separated by a dielectric layer of 30 nm silica nanoparticles. 50, 75, and 100 gold-silica bi-layered films were deposited and the device characteristics were studied. A threshold voltage was required for electron conduction which increases from 2.4 V for 50 bi-layers to 3.3 V for 100 bi-layers. Upon bending of the device up to about 52°, the threshold voltage and slope of the I-V curves change linearly. Electrical characterization of the multilayer films was carried out under ambient conditions with different pressures and bending angles in the direct current mode. This study demonstrates that the developed multilayer thin films can be used as pressure as well as bending sensing applications.

Interface properties of bilayer structure Alq{sub 3}/Fe{sub 65}Co{sub 35}

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhen, E-mail: wangzhen@chd.edu.cn [Department of Applied Physics, Chang’an University, Xi’an 710064 (China); Xu, Chunlong; Wang, Jinguo; Chang, Qiaoli [Department of Applied Physics, Chang’an University, Xi’an 710064 (China); Zuo, Yalu; Xi, Li [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2015-04-01

Highlights: • Bilayer structure of Alq{sub 3}/FeCo was fabricated in a dual ultra high vacuum chamber. • Organic layer reacts partially with the FeCo film. • Electronic injection barrier is 0.76 eV in the interface. • The induced uniaxial anisotropy appears in Alq{sub 3}/FeCo. - Abstract: The interface between the organic and magnetic electrodes is a fundamental problem in organic spintronics devices. Therefore, bilayer structure of Alq{sub 3}/FeCo was fabricated in a dual ultra high vacuum chamber. The electronic structure of Alq{sub 3}–FeCo interface has been studied by X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy with Argon ion etching technique. It was found that organic layer reacts partially with the FeCo film, forming complex binding of metallic carbide and/or oxidation state in the interfacial region. Electronic injection barrier is 0.76 eV in the interface. The structural variation of the contact region is proposed to be one of the possible factors resulting in spin-injection failure. The magnetic properties of FeCo film with different thicknesses on glass substrate and Alq{sub 3} layer are also investigated. The induced uniaxial anisotropy only presents in 3 nm FeCo thickness for glass/FeCo, while it appears in 3–5 nm FeCo for Alq{sub 3}/FeCo.

Pt and PtRu catalyst bilayers increase efficiencies for ethanol oxidation in proton exchange membrane electrolysis and fuel cells

Science.gov (United States)

Altarawneh, Rakan M.; Pickup, Peter G.

2017-10-01

Polarization curves, product distributions, and reaction stoichiometries have been measured for the oxidation of ethanol at anodes consisting of Pt and PtRu bilayers and a homogeneous mixture of the two catalysts. These anode structures all show synergies between the two catalysts that can be attributed to the oxidation of acetaldehyde produced at the PtRu catalyst by the Pt catalyst. The use of a PtRu layer over a Pt layer produces the strongest effect, with higher currents than a Pt on PtRu bilayer, mixed layer, or either catalyst alone, except for Pt at high potentials. Reaction stoichiometries (average number of electrons transferred per ethanol molecule) were closer to the values for Pt alone for both of the bilayer configurations but much lower for PtRu and mixed anodes. Although Pt alone would provide the highest overall fuel cell efficiency at low power densities, the PtRu on Pt bilayer would provide higher power densities without a significant loss of efficiency. The origin of the synergy between the Pt and PtRu catalysts was elucidated by separation of the total current into the individual components for generation of carbon dioxide and the acetaldehyde and acetic acid byproducts.

The intriguing electronic and optical properties modulation of hydrogen and fluorine codecorated silicene layers

International Nuclear Information System (INIS)

Yang, Qun; Tan, Chunjian; Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Sun, Xiang; Yang, Daoguo; Chen, Xianping

2017-01-01

Highlights: • The HSiF bilayer is very stable due to the high binding energy even larger than the ones of bilayer graphene. • The HSiF bilayer exhibits a moderate direct band gap of 0.296 eV much lower than that of HSiF monolayer. • All the HSiF layers have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS 2 layers. Besides, it is advantageous to the application of HSiF layers in the field of optical devices. • The external electric field can effectively tune the band gaps of HSiF layers. Especially, even a semiconductor–metal transition occurs. • After the formation of HSiF bilayer, the complete electron-hole separation enhances the photocatalytic efficiency of HSiF bilayer and it exhibits a significantly improved visible light adsorption peak. - Abstract: First-principles calculations based on density-functional theory reveal some superior physical properties of hydrogen and fluorine co-decorated silicene (HSiF) monolayer and bilayer. Our simulated results reveal that the HSiF monolayer is a large direct band gap semiconductor greatly differing from the gapless semi-metallic silicene. There exists strong interlayer coupling in HSiF bilayer, leading to the good stabilities of HSiF bilayer even beyond bilayer graphene. The proposed HSiF bilayer exhibits a moderate direct band gap of 0.296 eV which is much lower than that of HSiF monolayer. Encouragingly, HSiF layers all have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS 2 layers. Furthermore, an out-of-plane electric field has an evident impact on the band structures of the HSiF monolayer and bilayer. Especially, the band gap of HSiF bilayer can be effectively tuned by external electric field, even a semiconductor–metal transition occurs. More importantly, the HSiF bilayer exhibits a significant improved visible light adsorption peak with

Electroplex emission from bi-layer blue emitting organic materials

Science.gov (United States)

Zhang, Fujun; Zhao, Suling; Zhao, Dewei; Jiang, Weiwei; Li, Yuan; Yuan, Guangcai; Zhu, Haina; Xu, Zheng

2007-04-01

Electroluminescence (EL) and photoluminescence (PL) spectra of an electron donor, an (poly(N-vinylcarbazole) (PVK))/electron acceptor, and a (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD)) bi-layer solid film are analysed. The EL emission peak has an apparent red-shift with the increase of driving voltage. There maybe exist an electroplex emission between the PVK and PBD interface under high electric field strength. According to their energy level, the electroplex emission peak should locate at 460 nm. There are great spectra overlapping between PVK emission and electroplex emission, and the ratio of electroplex emission intensity to exciton emission intensity (Ielectroplex/Iexciton) increases from 0.38 at 10 to 0.81 at 16 V. Therefore the measured emission peaks continuously shift from 410 nm at 10 V to 445 nm at 16 V.

Electroplex emission from bi-layer blue emitting organic materials

International Nuclear Information System (INIS)

Zhang Fujun; Zhao Suling; Zhao Dewei; Jiang Weiwei; Li Yuan; Yuan Guangcai; Zhu Haina; Xu Zheng

2007-01-01

Electroluminescence (EL) and photoluminescence (PL) spectra of an electron donor, an (poly(N-vinylcarbazole) (PVK))/electron acceptor, and a (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD)) bi-layer solid film are analysed. The EL emission peak has an apparent red-shift with the increase of driving voltage. There maybe exist an electroplex emission between the PVK and PBD interface under high electric field strength. According to their energy level, the electroplex emission peak should locate at 460 nm. There are great spectra overlapping between PVK emission and electroplex emission, and the ratio of electroplex emission intensity to exciton emission intensity (I electroplex /I exciton ) increases from 0.38 at 10 to 0.81 at 16 V. Therefore the measured emission peaks continuously shift from 410 nm at 10 V to 445 nm at 16 V

Electroplex emission from bi-layer blue emitting organic materials

Energy Technology Data Exchange (ETDEWEB)

Zhang Fujun; Zhao Suling; Zhao Dewei; Jiang Weiwei; Li Yuan; Yuan Guangcai; Zhu Haina; Xu Zheng [Key Laboratory for Information Storage, Display and Materials, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

2007-04-15

Electroluminescence (EL) and photoluminescence (PL) spectra of an electron donor, an (poly(N-vinylcarbazole) (PVK))/electron acceptor, and a (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD)) bi-layer solid film are analysed. The EL emission peak has an apparent red-shift with the increase of driving voltage. There maybe exist an electroplex emission between the PVK and PBD interface under high electric field strength. According to their energy level, the electroplex emission peak should locate at 460 nm. There are great spectra overlapping between PVK emission and electroplex emission, and the ratio of electroplex emission intensity to exciton emission intensity (I{sub electroplex}/I{sub exciton}) increases from 0.38 at 10 to 0.81 at 16 V. Therefore the measured emission peaks continuously shift from 410 nm at 10 V to 445 nm at 16 V.

Interaction between U/UO2 bilayers and hydrogen studied by in-situ X-ray diffraction

Science.gov (United States)

Darnbrough, J. E.; Harker, R. M.; Griffiths, I.; Wermeille, D.; Lander, G. H.; Springell, R.

2018-04-01

This paper reports experiments investigating the reaction of H2 with uranium metal-oxide bilayers. The bilayers consist of ≤ 100 nm of epitaxial α-U (grown on a Nb buffer deposited on sapphire) with a UO2 overlayer of thicknesses of between 20 and 80 nm. The oxides were made either by depositing via reactive magnetron sputtering, or allowing the uranium metal to oxidise in air at room temperature. The bilayers were exposed to hydrogen, with sample temperatures between 80 and 200 C, and monitored via in-situ x-ray diffraction and complimentary experiments conducted using Scanning Transmission Electron Microscopy - Electron Energy Loss Spectroscopy (STEM-EELS). Small partial pressures of H2 caused rapid consumption of the U metal and lead to changes in the intensity and position of the diffraction peaks from both the UO2 overlayers and the U metal. There is an orientational dependence in the rate of U consumption. From changes in the lattice parameter we deduce that hydrogen enters both the oxide and metal layers, contracting the oxide and expanding the metal. The air-grown oxide overlayers appear to hinder the H2-reaction up to a threshold dose, but then on heating from 80 to 140 C the consumption is more rapid than for the as-deposited overlayers. STEM-EELS establishes that the U-hydride layer lies at the oxide-metal interface, and that the initial formation is at defects or grain boundaries, and involves the formation of amorphous and/or nanocrystalline UH3. This explains why no diffraction peaks from UH3 are observed.

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.

Intercalation of small hydrophobic molecules in lipid bilayers containing cholesterol

International Nuclear Information System (INIS)

Worcester, D.L.; Hamacher, K.; Kaiser, H.; Kulasekere, R.; Torbet, J.

1994-01-01

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

Ionic motion in PEDOT and PPy conducting polymer bilayers

DEFF Research Database (Denmark)

Zainudeen, Umer L.; Careem, M.A.; 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...

Controlling the layer localization of gapless states in bilayer graphene with a gate voltage

Science.gov (United States)

Jaskólski, W.; Pelc, M.; Bryant, Garnett W.; Chico, Leonor; Ayuela, A.

2018-04-01

Experiments in gated bilayer graphene with stacking domain walls present topological gapless states protected by no-valley mixing. Here we research these states under gate voltages using atomistic models, which allow us to elucidate their origin. We find that the gate potential controls the layer localization of the two states, which switches non-trivially between layers depending on the applied gate voltage magnitude. We also show how these bilayer gapless states arise from bands of single-layer graphene by analyzing the formation of carbon bonds between layers. Based on this analysis we provide a model Hamiltonian with analytical solutions, which explains the layer localization as a function of the ratio between the applied potential and interlayer hopping. Our results open a route for the manipulation of gapless states in electronic devices, analogous to the proposed writing and reading memories in topological insulators.

Stacking order dependent mechanical properties of graphene/MoS{sub 2} bilayer and trilayer heterostructures

Energy Technology Data Exchange (ETDEWEB)

Elder, Robert M., E-mail: robert.elder26.ctr@mail.mil, E-mail: mahesh.neupane.ctr@mail.mil; Neupane, Mahesh R., E-mail: robert.elder26.ctr@mail.mil, E-mail: mahesh.neupane.ctr@mail.mil; Chantawansri, Tanya L. [U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

2015-08-17

Transition metal dichalcogenides (TMDC) such as molybdenum disulfide (MoS{sub 2}) are two-dimensional materials that show promise for flexible electronics and piezoelectric applications, but their weak mechanical strength is a barrier to practical use. In this work, we perform nanoindentation simulations using atomistic molecular dynamics to study the mechanical properties of heterostructures formed by combining MoS{sub 2} with graphene. We consider both bi- and tri-layer heterostructures formed with MoS{sub 2} either supported or encapsulated by graphene. Mechanical properties, such as Young's modulus, bending modulus, ultimate tensile strength, and fracture strain, are extracted from nanoindentation simulations and compared to the monolayer and homogeneous bilayer systems. We observed that the heterostructures, regardless of the stacking order, are mechanically more robust than the mono- and bi-layer MoS{sub 2}, mainly due to the mechanical reinforcement provided by the graphene layer. The magnitudes of ultimate strength and fracture strain are similar for both the bi- and tri-layer heterostructures, but substantially larger than either the mono- and bi-layer MoS{sub 2}. Our results demonstrate the potential of graphene-based heterostructures to improve the mechanical properties of TMDC materials.

Biomimetic Cationic Nanoparticles Based on Silica: Optimizing Bilayer Deposition from Lipid Films

Directory of Open Access Journals (Sweden)

Rodrigo T. Ribeiro

2017-10-01

Full Text Available The optimization of bilayer coverage on particles is important for a variety of biomedical applications, such as drug, vaccine, and genetic material delivery. This work aims at optimizing the deposition of cationic bilayers on silica over a range of experimental conditions for the intervening medium and two different assemblies for the cationic lipid, namely, lipid films or pre-formed lipid bilayer fragments. The lipid adsorption on silica in situ over a range of added lipid concentrations was determined from elemental analysis of carbon, hydrogen, and nitrogen and related to the colloidal stability, sizing, zeta potential, and polydispersity of the silica/lipid nanoparticles. Superior bilayer deposition took place from lipid films, whereas adsorption from pre-formed bilayer fragments yielded limiting adsorption below the levels expected for bilayer adsorption.

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.

High transition temperature superconductor/insulator bilayers for the development of ultra-fast electronics

International Nuclear Information System (INIS)

Sirena, M.; Félix, L. Avilés; Haberkorn, N.

2013-01-01

High transition temperature superconductor (HTc)/SrTiO 3 (STO) bilayers were fabricated by sputtering deposition on (100) STO substrates. Their transport and morphological properties were characterized using conductive atomic force microscopy. The STO barriers present good insulating properties, with long attenuation lengths (λ ∼ 1 nm) which reduce the junction resistance and increase the operating critical current. The samples present roughness values smaller than 1 nm, with an extremely low density of surface defects (∼5 × 10 −5 defects/μm 2 ). The high control of the barrier quality over large defect free surfaces is encouraging for the development of microelectronics devices based in HTc Josephson junctions

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.

Periodontal regeneration using a bilayered PLGA/calcium phosphate construct.

Science.gov (United States)

Carlo Reis, Emily C; Borges, Andréa P B; Araújo, Michel V F; Mendes, Vanessa C; Guan, Limin; Davies, John E

2011-12-01

The regeneration of tissues affected by periodontal disease is a complex process; it encompasses the formation of bone, cementum and periodontal ligament. We developed a semi-rigid PLGA (polylactide-co-glycolide acid)/CaP (calcium phosphate) bilayered biomaterial construct to promote periodontal regeneration, which has a continuous outer barrier membrane and an inner topographically complex component. Our experimental model compared periodontal prophylaxis alone with prophylaxis and biomaterial implantation in the treatment of class II furcation defects in dogs. Clinical evaluation, micro-computed tomography, histology and backscattered electron imaging were used for data analysis. Healing occurred uneventfully and bone volumetric values, trabecular number and trabecular thickness were all significantly greater in the treated group; while trabecular separation was significantly greater in the control group. New cementum, bone, and periodontal ligament with Sharpey fibre insertions were only seen in the treated group. Although periodontal regeneration has been reported elsewhere, the advantages of employing our bilayered PLGA + CaP construct are twofold: 1)it did not collapse into the defect; and, 2) its inner side was able to retain the blood clot throughout the buccal defect. The result was greater periodontal regeneration than has previously been reported with traditional flexible membranes. Copyright © 2011 Elsevier Ltd. All rights reserved.

Voltage tunable plasmon propagation in dual gated bilayer graphene

Science.gov (United States)

Farzaneh, Seyed M.; Rakheja, Shaloo

2017-10-01

In this paper, we theoretically investigate plasmon propagation characteristics in AB and AA stacked bilayer graphene (BLG) in the presence of energy asymmetry due to an electrostatic field oriented perpendicularly to the plane of the graphene sheet. We first derive the optical conductivity of BLG using the Kubo formalism incorporating energy asymmetry and finite electron scattering. All results are obtained for room temperature (300 K) operation. By solving Maxwell's equations in a dual gate device setup, we obtain the wavevector of propagating plasmon modes in the transverse electric (TE) and transverse magnetic (TM) directions at terahertz frequencies. The plasmon wavevector allows us to compare the compression factor, propagation length, and the mode confinement of TE and TM plasmon modes in bilayer and monolayer graphene sheets and also to study the impact of material parameters on plasmon characteristics. Our results show that the energy asymmetry can be harnessed to increase the propagation length of TM plasmons in BLG. AA stacked BLG shows a larger increase in the propagation length than AB stacked BLG; conversely, it is very insensitive to the Fermi level variations. Additionally, the dual gate structure allows independent modulation of the energy asymmetry and the Fermi level in BLG, which is advantageous for reconfiguring plasmon characteristics post device fabrication.

Characteristics of TiO{sub 2}/ZnO bilayer film towards pH sensitivity prepared by different spin coating deposition process

Energy Technology Data Exchange (ETDEWEB)

Rahman, Rohanieza Abdul, E-mail: rohanieza.abdrahman@gmail.com; Zulkefle, Muhammad Al Hadi, E-mail: alhadizulkefle@gmail.com [NANO-Electronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Abdullah, Wan Fazlida Hanim, E-mail: wanfaz@salam.uitm.edu.my [Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM) Shah Alam, 40450 Shah Alam, Selangor (Malaysia); Rusop, M., E-mail: rusop@salam.uitm.com [NANO-Electronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-Science Technology Centre (NST), Institute of Science (IOS), Faculty of Applied Science, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Herman, Sukreen Hana, E-mail: hana1617@salam.uitm.edu.my [NANO-Electronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); CoRe of Frontier Materials & Industry Applications, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia)

2016-07-06

In this study, titanium dioxide (TiO{sub 2}) and zinc oxide (ZnO) bilayer film for pH sensing application will be presented. TiO{sub 2}/ZnO bilayer film with different speed of spin-coating process was deposited on Indium Tin Oxide (ITO), prepared by sol-gel method. This fabricated bilayer film was used as sensing membrane for Extended Gate Field-Effect Transistor (EGFET) for pH sensing application. Experimental results indicated that the sensor is able to detect the sensitivity towards pH buffer solution. In order to obtained the result, sensitivity measurement was done by using the EGFET setup equipment with constant-current (100 µA) and constant-voltage (0.3 V) biasing interfacing circuit. TiO{sub 2}/ZnO bilayer film which the working electrode, act as the pH-sensitive membrane was connected to a commercial metal-oxide semiconductor FET (MOSFET). This MOSFET then was connected to the interfacing circuit. The sensitivity of the TiO2 thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. These thin films were characterized by using Field Emission Scanning Electron Microscope (FESEM) to obtain the surface morphology of the composite bilayer films. In addition, I-V measurement was done in order to determine the electrical properties of the bilayer films. According to the result obtained in this experiment, bilayer film that spin at 4000 rpm, gave highest sensitivity which is 52.1 mV/pH. Relating the I-V characteristic of the thin films and sensitivity, the sensing membrane with higher conductivity gave better sensitivity.

Electric field-triggered metal-insulator transition resistive switching of bilayered multiphasic VOx

Science.gov (United States)

Won, Seokjae; Lee, Sang Yeon; Hwang, Jungyeon; Park, Jucheol; Seo, Hyungtak

2018-01-01

Electric field-triggered Mott transition of VO2 for next-generation memory devices with sharp and fast resistance-switching response is considered to be ideal but the formation of single-phase VO2 by common deposition techniques is very challenging. Here, VOx films with a VO2-dominant phase for a Mott transition-based metal-insulator transition (MIT) switching device were successfully fabricated by the combined process of RF magnetron sputtering of V metal and subsequent O2 annealing to form. By performing various material characterizations, including scanning transmission electron microscopy-electron energy loss spectroscopy, the film is determined to have a bilayer structure consisting of a VO2-rich bottom layer acting as the Mott transition switching layer and a V2O5/V2O3 mixed top layer acting as a control layer that suppresses any stray leakage current and improves cyclic performance. This bilayer structure enables excellent electric field-triggered Mott transition-based resistive switching of Pt-VOx-Pt metal-insulator-metal devices with a set/reset current ratio reaching 200, set/reset voltage of less than 2.5 V, and very stable DC cyclic switching upto 120 cycles with a great set/reset current and voltage distribution less than 5% of standard deviation at room temperature, which are specifications applicable for neuromorphic or memory device applications. [Figure not available: see fulltext.

USE OF ELECTRONIC EDUCATIONAL RESOURCES WHEN TRAINING IN WORK WITH SPREADSHEETS

Directory of Open Access Journals (Sweden)

Х А Гербеков

2017-12-01

Full Text Available Today the tools for maintaining training courses based on opportunities of information and communication technologies are developed. Practically in all directions of preparation and on all subject matters electronic textbook and self-instruction manuals are created. Nevertheless the industry of computer educational and methodical materials actively develops and gets more and more areas of development and introduction. In this regard more and more urgent is a problem of development of the electronic educational resources adequate to modern educational requirements. Creation and the organization of training courses with use of electronic educational resources in particular on the basis of Internet technologies remains a difficult methodical task.In article the questions connected with development of electronic educational resources for use when studying the substantial line “Information technologies” of a school course of informatics in particular for studying of spreadsheets are considered. Also the analysis of maintenance of a school course and the unified state examination from the point of view of representation of task in him corresponding to the substantial line of studying “Information technologies” on mastering technology of information processing in spreadsheets and the methods of visualization given by means of charts and schedules is carried out.

Proton permeation of lipid bilayers.

Science.gov (United States)

Deamer, D W

1987-10-01

Proton permeation of the lipid bilayer barrier has two unique features. First, permeability coefficients measured at neutral pH ranges are six to seven orders of magnitude greater than expected from knowledge of other monovalent cations. Second, proton conductance across planar lipid bilayers varies at most by a factor of 10 when pH is varied from near 1 to near 11. Two mechanisms have been proposed to account for this anomalous behavior: proton conductance related to contaminants of lipid bilayers, and proton translocation along transient hydrogen-bonded chains (tHBC) of associated water molecules in the membrane. The weight of evidence suggests that trace contaminants may contribute to proton conductance across planar lipid membranes at certain pH ranges, but cannot account for the anomalous proton flux in liposome systems. Two new results will be reported here which were designed to test the tHBC model. These include measurements of relative proton/potassium permeability in the gramicidin channel, and plots of proton flux against the magnitude of pH gradients. (1) The relative permeabilities of protons and potassium through the gramicidin channel, which contains a single strand of hydrogen-bonded water molecules, were found to differ by at least four orders of magnitude when measured at neutral pH ranges. This result demonstrates that a hydrogen-bonded chain of water molecules can provide substantial discrimination between protons and other cations. It was also possible to calculate that if approximately 7% of bilayer water was present in a transient configuration similar to that of the gramicidin channel, it could account for the measured proton flux. (2) The plot of proton conductance against pH gradient across liposome membranes was superlinear, a result that is consistent with one of three alternative tHBC models for proton conductance described by Nagle elsewhere in this volume.

P3HT-graphene bilayer electrode for Schottky junction photodetectors

Science.gov (United States)

Aydın, H.; Kalkan, S. B.; Varlikli, C.; Çelebi, C.

2018-04-01

We have investigated the effect of a poly (3-hexylthiophene-2.5-diyl)(P3HT)-graphene bilayer electrode on the photoresponsivity characteristics of Si-based Schottky photodetectors. P3HT, which is known to be an electron donor and absorb light in the visible spectrum, was placed on CVD grown graphene by dip-coating method. The results of the UV-vis and Raman spectroscopy measurements have been evaluated to confirm the optical and electronic modification of graphene by the P3HT thin film. Current-voltage measurements of graphene/Si and P3HT-graphene/Si revealed rectification behavior confirming a Schottky junction formation at the graphene/Si interface. Time-resolved photocurrent spectroscopy measurements showed the devices had excellent durability and a fast response speed. We found that the maximum spectral photoresponsivity of the P3HT-graphene/Si photodetector increased more than three orders of magnitude compared to that of the bare graphene/Si photodetector. The observed increment in the photoresponsivity of the P3HT-graphene/Si samples was attributed to the charge transfer doping from P3HT to graphene within the spectral range between near-ultraviolet and near-infrared. Furthermore, the P3HT-graphene electrode was found to improve the specific detectivity and noise equivalent power of graphene/Si photodetectors. The obtained results showed that the P3HT-graphene bilayer electrodes significantly improved the photoresponsivity characteristics of our samples and thus can be used as a functional component in Si-based optoelectronic device applications.

The Integrin Receptor in Biologically Relevant Bilayers

DEFF Research Database (Denmark)

Kalli, Antreas C.; Róg, Tomasz; Vattulainen, Ilpo

2017-01-01

/talin complex was inserted in biologically relevant bilayers that resemble the cell plasma membrane containing zwitterionic and charged phospholipids, cholesterol and sphingolipids to study the dynamics of the integrin receptor and its effect on bilayer structure and dynamics. The results of this study...... demonstrate the dynamic nature of the integrin receptor and suggest that the presence of the integrin receptor alters the lipid organization between the two leaflets of the bilayer. In particular, our results suggest elevated density of cholesterol and of phosphatidylserine lipids around the integrin....../talin complex and a slowing down of lipids in an annulus of ~30 Å around the protein due to interactions between the lipids and the integrin/talin F2–F3 complex. This may in part regulate the interactions of integrins with other related proteins or integrin clustering thus facilitating signal transduction...

Reconstruction of living bilayer human skin equivalent utilizing human fibrin as a scaffold.

Science.gov (United States)

Mazlyzam, A L; Aminuddin, B S; Fuzina, N H; Norhayati, M M; Fauziah, O; Isa, M R; Saim, L; Ruszymah, B H I

2007-05-01

Our aim of this study was to develop a new methodology for constructing a bilayer human skin equivalent to create a more clinical compliance skin graft composite for the treatment of various skin defects. We utilized human plasma derived fibrin as the scaffold for the development of a living bilayer human skin equivalent: fibrin-fibroblast and fibrin-keratinocyte (B-FF/FK SE). Skin cells from six consented patients were culture-expanded to passage 1. For B-FF/FK SE formation, human fibroblasts were embedded in human fibrin matrix and subsequently another layer of human keratinocytes in human fibrin matrix was stacked on top. The B-FF/FK SE was then transplanted to athymic mice model for 4 weeks to evaluate its regeneration and clinical performance. The in vivo B-FF/FK SE has similar properties as native human skin by histological analysis and expression of basal Keratin 14 gene in the epidermal layer and Collagen type I gene in the dermal layer. Electron microscopy analysis of in vivo B-FF/FK SE showed well-formed and continuous epidermal-dermal junction. We have successfully developed a technique to engineer living bilayer human skin equivalent using human fibrin matrix. The utilization of culture-expanded human skin cells and fibrin matrix from human blood will allow a fully autologous human skin equivalent construction.

Changes in work function due to NO2 adsorption on monolayer and bilayer epitaxial graphene on SiC(0001)

Science.gov (United States)

Caffrey, Nuala M.; Armiento, Rickard; Yakimova, Rositsa; Abrikosov, Igor A.

2016-11-01

The electronic properties of monolayer graphene grown epitaxially on SiC(0001) are known to be highly sensitive to the presence of NO2 molecules. The presence of small areas of bilayer graphene, on the other hand, considerably reduces the overall sensitivity of the surface. We investigate how NO2 molecules interact with monolayer and bilayer graphene, both free-standing and on a SiC(0001) substrate. We show that it is necessary to explicitly include the effect of the substrate in order to reproduce the experimental results. When monolayer graphene is present on SiC, there is a large charge transfer from the interface between the buffer layer and the SiC substrate to the molecule. As a result, the surface work function increases by 0.9 eV after molecular adsorption. A graphene bilayer is more effective at screening this interfacial charge, and so the charge transfer and change in work function after NO2 adsorption is much smaller.

Cu2O/CuO Bilayered Composite as a High-Efficiency Photocathode for Photoelectrochemical Hydrogen Evolution Reaction

Science.gov (United States)

Yang, Yang; Xu, Di; Wu, Qingyong; Diao, Peng

2016-10-01

Solar powered hydrogen evolution reaction (HER) is one of the key reactions in solar-to-chemical energy conversion. It is desirable to develop photocathodic materials that exhibit high activity toward photoelectrochemical (PEC) HER at more positive potentials because a higher potential means a lower overpotential for HER. In this work, the Cu2O/CuO bilayered composites were prepared by a facile method that involved an electrodeposition and a subsequent thermal oxidation. The resulting Cu2O/CuO bilayered composites exhibited a surprisingly high activity and good stability toward PEC HER, expecially at high potentials in alkaline solution. The photocurrent density for HER was 3.15 mA·cm-2 at the potential of 0.40 V vs. RHE, which was one of the two highest reported at the same potential on copper-oxide-based photocathode. The high photoactivity of the bilayered composite was ascribed to the following three advantages of the Cu2O/CuO heterojunction: (1) the broadened light absorption band that made more efficient use of solar energy, (2) the large space-charge-region potential that enabled a high efficiency for electron-hole separation, and (3) the high majority carrier density that ensured a faster charge transportation rate. This work reveals the potential of the Cu2O/CuO bilayered composite as a promising photocathodic material for solar water splitting.

ZnO/CdS bi-layer nanostructures photoelectrode for dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Dalal, Paresh V., E-mail: paresh10dalal@gmail.com [Physics Research Lab, Shri V. S. Naik Arts, Commerce and Science College, Raver-425508 (M. S.) (India); Deshpande, Milind P., E-mail: vishwadeshpande@yahoo.co.in [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120 (Gujarat) (India); Solanki, Bharat G., E-mail: bhrt.solanki17@gmail.com; Soni, Saurabh S., E-mail: soni-b21@yahoo.co.in [Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar-388120 (Gujarat) (India)

2016-05-06

Simple chemical deposition method for the synthesis of ZnO/CdS bilayer photoelectrode on fluorine doped tin oxide (FTO) coated glass substrate in aqueous medium at low temperature (< 373K) is described. The different preparative parameters such as deposition time, bath temperature, concentration of precursor solution and, pH of the bath etc. were optimized. Nanograined ZnO was deposited on FTO coated glass substrates by dip-coating method, whereas CdS nanorods were successfully synthesized on pre-deposited ZnO film by Chemical Bath Deposition (CBD) method. The Photovoltaic properties of FTO/ZnO/CdS bilayer photo electrodes were also studied. A maximum short circuit current density of 9.1 mA cm-2 and conversion efficiency 1.05% are observed for ZnO/CdS-10min. Layer, which supports fast electron injection kinetics due to hetero structured nanorod, while minimum values of 0.53mA cm-2 and 0.01% respectively are observed for only ZnO deposited layer.

A simple method to tune graphene growth between monolayer and bilayer

Directory of Open Access Journals (Sweden)

Xiaozhi Xu

2016-02-01

Full Text Available Selective growth of either monolayer or bilayer graphene is of great importance. We developed a method to readily tune large area graphene growth from complete monolayer to complete bilayer. In an ambient pressure chemical vapor deposition process, we used the sample temperature at which to start the H2 flow as the control parameter and realized the change from monolayer to bilayer growth of graphene on Cu foil. When the H2 starting temperature was above 700°C, continuous monolayer graphene films were obtained. When the H2 starting temperature was below 350°C, continuous bilayer films were obtained. Detailed characterization of the samples treated under various conditions revealed that heating without the H2 flow caused Cu oxidation. The more the Cu substrate oxidized, the less graphene bilayer could form.

Influence of ester-modified lipids on bilayer structure.

Science.gov (United States)

Villanueva, Diana Y; Lim, Joseph B; Klauda, Jeffery B

2013-11-19

Lipid membranes function as barriers for cells to prevent unwanted chemicals from entering the cell and wanted chemicals from leaving. Because of their hydrophobic interior, membranes do not allow water to penetrate beyond the headgroup region. We performed molecular simulations to examine the effects of ester-modified lipids, which contain ester groups along their hydrocarbon chains, on bilayer structure. We chose two lipids from those presented in Menger et al. [J. Am. Chem. Soc. 2006, 128, 14034] with ester groups in (1) the upper half of the lipid chain (MEPC) and (2) the middle and end of the lipid chain (MGPC). MGPC (30%)/POPC bilayers formed stable water pores of diameter 5-7 Å, but MGPC (22%)/POPC and MEPC (30%)/POPC bilayers did not form these defects. These pores were similar to those formed during electroporation; i.e., the head groups lined the pore and allowed water and ions to transport across the bilayer. However, we found that lateral organization of the MGPC lipids into clusters, instead of an electric field or charge disparity as in electroporation, was essential for pore formation. On the basis of this, we propose an overall mechanism for pore formation. The similarities between the ester-modified lipids and byproducts of lipid peroxidation with multiple hydrophilic groups in the middle of the chain suggest that free radical reactions with unsaturated lipids and sterols result in fundamental changes that may be similar to what is seen in bilayers with ester-modified lipids.

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.

The intriguing electronic and optical properties modulation of hydrogen and fluorine codecorated silicene layers

Energy Technology Data Exchange (ETDEWEB)

Yang, Qun; Tan, Chunjian [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China); Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Sun, Xiang [Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China); Yang, Daoguo [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Chen, Xianping, E-mail: xianpingchen@cqu.edu.cn [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Opto-Electronic Engineering, Chongqing University, 400044 Chongqing (China)

2017-03-15

Highlights: • The HSiF bilayer is very stable due to the high binding energy even larger than the ones of bilayer graphene. • The HSiF bilayer exhibits a moderate direct band gap of 0.296 eV much lower than that of HSiF monolayer. • All the HSiF layers have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS{sub 2} layers. Besides, it is advantageous to the application of HSiF layers in the field of optical devices. • The external electric field can effectively tune the band gaps of HSiF layers. Especially, even a semiconductor–metal transition occurs. • After the formation of HSiF bilayer, the complete electron-hole separation enhances the photocatalytic efficiency of HSiF bilayer and it exhibits a significantly improved visible light adsorption peak. - Abstract: First-principles calculations based on density-functional theory reveal some superior physical properties of hydrogen and fluorine co-decorated silicene (HSiF) monolayer and bilayer. Our simulated results reveal that the HSiF monolayer is a large direct band gap semiconductor greatly differing from the gapless semi-metallic silicene. There exists strong interlayer coupling in HSiF bilayer, leading to the good stabilities of HSiF bilayer even beyond bilayer graphene. The proposed HSiF bilayer exhibits a moderate direct band gap of 0.296 eV which is much lower than that of HSiF monolayer. Encouragingly, HSiF layers all have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS{sub 2} layers. Furthermore, an out-of-plane electric field has an evident impact on the band structures of the HSiF monolayer and bilayer. Especially, the band gap of HSiF bilayer can be effectively tuned by external electric field, even a semiconductor–metal transition occurs. More importantly, the HSiF bilayer exhibits a significant improved visible light adsorption

Evaluation of the performance characteristics of bilayer tablets: Part II. Impact of environmental conditions on the strength of bilayer tablets.

Science.gov (United States)

Kottala, Niranjan; Abebe, Admassu; Sprockel, Omar; Bergum, James; Nikfar, Faranak; Cuitiño, Alberto M

2012-12-01

Ambient air humidity and temperature are known to influence the mechanical strength of tablets. The objective of this work is to understand the influence of processing parameters and environmental conditions (humidity and temperature) on the strength of bilayer tablets. As part of this study, bilayer tablets were compressed with different layer ratios, dwell times, layer sequences, material properties (plastic and brittle), first and second layer forces, and lubricant concentrations. Compressed tablets were stored in stability chambers controlled at predetermined conditions (40C/45%RH, 40C/75%RH) for 1, 3, and 5 days. The axial strength of the stored tablets was measured and a statistical model was developed to determine the effects of the aforementioned factors on the strength of bilayer tablets. As part of this endeavor, a full 3 × 2(4) factorial design was executed. Responses of the experiments were analyzed using PROC GLM of SAS (SAS Institute Inc, Cary, North Carolina, USA). A model was fit using all the responses to determine the significant interactions (p < 0.05). Results of this study indicated that storage conditions and storage time have significant impact on the strength of bilayer tablets. For Avicel-lactose and lactose-Avicel tablets, tablet strength decreased with the increasing humidity and storage time. But for lactose-lactose tablets, due to the formation of solid bridges upon storage, an increase in tablet strength was observed. Significant interactions were observed between processing parameters and storage conditions on the strength of bilayer tablets.

High transition temperature superconductor/insulator bilayers for the development of ultra-fast electronics

Energy Technology Data Exchange (ETDEWEB)

Sirena, M.; Félix, L. Avilés [Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Atómico Bariloche, CNEA, Bustillo 9500, 8400 Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo and CNEA, 8400 Bariloche (Argentina); Haberkorn, N. [Consejo Nacional de Investigaciones Científicas y Técnicas, Centro Atómico Bariloche, CNEA, Bustillo 9500, 8400 Bariloche (Argentina)

2013-07-29

High transition temperature superconductor (HTc)/SrTiO{sub 3} (STO) bilayers were fabricated by sputtering deposition on (100) STO substrates. Their transport and morphological properties were characterized using conductive atomic force microscopy. The STO barriers present good insulating properties, with long attenuation lengths (λ ∼ 1 nm) which reduce the junction resistance and increase the operating critical current. The samples present roughness values smaller than 1 nm, with an extremely low density of surface defects (∼5 × 10{sup −5} defects/μm{sup 2}). The high control of the barrier quality over large defect free surfaces is encouraging for the development of microelectronics devices based in HTc Josephson junctions.

Double trigonal warping and the anomalous quantum Hall step in bilayer graphene with Rashba spin-orbit coupling

International Nuclear Information System (INIS)

Wang Bo; Ma Zhongshui; Zhang, C

2012-01-01

We demonstrate that the trigonal warping observed in bilayer graphene is doubled in the presence of Rashba spin-orbit (RSO) coupling, i.e. the Dirac points along the three-fold symmetry axis are doubled. There are now seven Dirac points. Furthermore, the RSO interaction breaks the electron-hole symmetry of the magnetic band structure. The most intriguing feature is that the step of the quantum Hall plateau at zero energy is four times that at finite energy. The number of Dirac points and the zero energy Hall step are only determined by the existence of RSO coupling, but are independent of the strength of the coupling. The robustness of these phenomena suggests equivalence between the RSO coupling and the topological effect in bilayer coupling.

Lipids, lipid bilayers and vesicles as seen by neutrons

International Nuclear Information System (INIS)

Seto, Hideki

2011-01-01

Lipid molecules self-assemble into bilayers in water with their hydrocarbon chains facing inward due to their amphiphilic nature. The structural and dynamical properties of lipids and lipid bilayers have been studied by neutron scattering intensively. In this article, 3 topics are shown as typical examples. 1) a time-resolved small-angle neutron scattering on uni-lamellar vesicles composed of deuterated and protonated lipids to determine lipid kinetics, 2) small-angle neutron scattering to investigate spontaneous formation of nanopores on uni-lamellar vesicles, and 3) neutron spin echo study to determine bending modulus of lipid bilayers. (author)

Bi-layer plate-type acoustic metamaterials with Willis coupling

Science.gov (United States)

Ma, Fuyin; Huang, Meng; Xu, Yicai; Wu, Jiu Hui

2018-01-01

Dynamic effective negative parameters are principal to the representation of the physical properties of metamaterials. In this paper, a bi-layer plate-type unit was proposed with both a negative mass density and a negative bulk modulus; moreover, through analysis of these bi-layer structures, some important problems about acoustic metamaterials were studied. First, dynamic effective mass densities and the bulk modulus of the bi-layer plate-type acoustic structure were clarified through both the direct and the retrieval methods, and, in addition, the intrinsic relationship between the sound transmission (absorption) characteristics and the effective parameters was analyzed. Furthermore, the properties of dynamic effective parameters for an asymmetric bi-layer acoustic structure were further considered through an analysis of experimental data, and the modified effective parameters were then obtained through consideration of the Willis coupling in the asymmetric passive system. In addition, by taking both the clamped and the periodic boundary conditions into consideration in the bi-layer plate-type acoustic system, new perspectives were presented for study on the effective parameters and sound insulation properties in the range below the cut-off frequency. The special acoustic properties established by these effective parameters could enrich our knowledge and provide guidance for the design and installation of acoustic metamaterial structures in future sound engineering practice.

Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference.

Science.gov (United States)

Jolie, Wouter; Lux, Jonathan; Pörtner, Mathias; Dombrowski, Daniela; Herbig, Charlotte; Knispel, Timo; Simon, Sabina; Michely, Thomas; Rosch, Achim; Busse, Carsten

2018-03-09

We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n-band material.

Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference

Science.gov (United States)

Jolie, Wouter; Lux, Jonathan; Pörtner, Mathias; Dombrowski, Daniela; Herbig, Charlotte; Knispel, Timo; Simon, Sabina; Michely, Thomas; Rosch, Achim; Busse, Carsten

2018-03-01

We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n -band material.

Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

Science.gov (United States)

Taleatu, B A; Arbab, E A A; Omotoso, E; Mola, G T

2014-10-01

Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Optical and Structural Characterization of ZnO/TiO2 Bilayer Thin Films Grown by Sol-Gel Spin Coating

Science.gov (United States)

Gareso, P. L.; Musfitasari; Juarlin, Eko

2018-03-01

Structural and optical properties of ZnO/TiO2 bilayers thin films have been investigated using x-ray diffraction (X-RD), scanning electron microscopy (SEM), and optical transmittance UV-Vis measurements. ZnO thin films were prepared by dissolving zinc acetate dehydrated into a solvent of ethanol and then added triethanolamin. In the case of TiO2 layers, tetraisoproxide was dissolved into ethanol and then added an acetate acid. The layer of ZnO was deposited first followed by TiO2 layer on a glass substrate using a spin coating technique. The ZnO/TiO2 bilayers were annealed at various temperatures from 300°C until 600°C for 60 minutes. The X-ray diffraction results show that there was an enhancement of the x-ray spectra as annealed temperature increased to 600°C in comparison to the samples that were annealed at 300°C. Based on the optical measurement of UV-Vis, the band gap energy of ZnO/TiO2 bilayer is around 3.2 eV at temperature of 300°C. This value is similar to the band gap energy of ZnO. SEM results show that there is no cluster in the surface of ZnO/TiO2 bilayer.

Analytical Study of Usage of Electronic Information Resources at Pharmacopoeial Libraries in India

Directory of Open Access Journals (Sweden)

Sunil Tyagi

2014-02-01

Full Text Available The objective of this study is to know the rate and purpose of the use of e-resource by the scientists at pharmacopoeial libraries in India. Among other things, this study examined the preferences of the scientists toward printed books and journals, electronic information resources, and pattern of using e-resources. Non-probability sampling specially accidental and purposive technique was applied in the collection of primary data through administration of user questionnaire. The sample respondents chosen for the study consists of principle scientific officer, senior scientific officer, scientific officer, and scientific assistant of different division of the laboratories, namely, research and development, pharmaceutical chemistry, pharmacovigilance, pharmacology, pharmacogonosy, and microbiology. The findings of the study reveal the personal experiences and perceptions they have had on practice and research activity using e-resource. The major findings indicate that of the total anticipated participants, 78% indicated that they perceived the ability to use computer for electronic information resources. The data analysis shows that all the scientists belonging to the pharmacopoeial libraries used electronic information resources to address issues relating to drug indexes and compendia, monographs, drugs obtained through online databases, e-journals, and the Internet sources—especially polices by regulatory agencies, contacts, drug promotional literature, and standards.

The radiation effects on lipid bilayers

International Nuclear Information System (INIS)

Ikigai, Hajime; Matsuura, Tomio; Narita, Noboru; Ozawa, Atsushi.

1980-01-01

The Radiation effects on lipid bilayers are studied by the electron spin resonance. Egg lecithin liposomes and human erythrocytes are labeled with spin probes (5 SAL, 12 SAL). Effects of membrane fluidity by X-Ray (or ultraviolet) irradiation are measured by change of the order parameter S. The results obtained are as follows: 1) A similar tendency is observed on the order parameter S between X-Ray irradiated egg lecithin liposomes and human erythrocytes. 2) The rapid changes of the membrane fluidity are observed below 1 krad. The fluctuation of membrane fluidity decreases above 1 krad, consequently the membrane has a tendency changing to a rigid state at low dose area. 3) It is suggested that the more effective radicals are hydroxyl radicals and superoxide radicals. 4) The effects of ultraviolet irradiation with hydrogen peroxide show that hydroxyl radicals lead to changes of membrane fluidity. (author)

Densification rate and interfacial adhesion of bilayer cemented tungsten carbide and steel

Energy Technology Data Exchange (ETDEWEB)

Ojo-kupoluyi, Oluwatosin Job; Tahir, Suraya Mohd; Ariff, Azmah Hanim Mohamed; Baharudin, B.T. Hang Tuah [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Mechanical and Manufacturing Engineering; Matori, Khamirul Amin [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Physics; Univ. Putra Malaysia, Selangor (Malaysia). Inst. of Advanced Technology (ITMA); Shamsul Anuar, Mohd [Univ. Putra Malaysia, Selangor (Malaysia). Dept. of Process and Food Engineering

2017-12-15

Manufacturing tailored materials is commonly faced with the challenge of shrinkage mismatch between layers resulting in delamination. The effects of sintering temperature and carbon variation on the densification and interfacial bond strength of bilayer cemented tungsten carbide and steel processed through powder metallurgy are analyzed. It is revealed through field-emission scanning electron microscopy images that inter-layer diffusion induced by liquid-phase sintering plays a major role in the densification and bonding of layers. Through dimensional analysis of sintered bilayer specimens, the strain rate of cemented tungsten carbide is observed to surpass that of steel. An enhanced densification rate of 6.1 % and M{sub 6}C (eta carbide) reduction with increased carbon level results in strong interfacial bonding in specimens sintered at 1 280 C. At 1 295 C, diffusion accelerates and the axial and radial shrinkage increase by 14.05 % and 13.35 %, respectively, in 93.8 wt.% WC - 6 wt.% Fe - 0.2 wt.% C and 93.2 wt.% Fe - 6 wt.% WC - 0.8 wt.% C, thereby increasing the tendency for complete delamination.

Densification rate and interfacial adhesion of bilayer cemented tungsten carbide and steel

International Nuclear Information System (INIS)

Ojo-kupoluyi, Oluwatosin Job; Tahir, Suraya Mohd; Ariff, Azmah Hanim Mohamed; Baharudin, B.T. Hang Tuah; Shamsul Anuar, Mohd

2017-01-01

Manufacturing tailored materials is commonly faced with the challenge of shrinkage mismatch between layers resulting in delamination. The effects of sintering temperature and carbon variation on the densification and interfacial bond strength of bilayer cemented tungsten carbide and steel processed through powder metallurgy are analyzed. It is revealed through field-emission scanning electron microscopy images that inter-layer diffusion induced by liquid-phase sintering plays a major role in the densification and bonding of layers. Through dimensional analysis of sintered bilayer specimens, the strain rate of cemented tungsten carbide is observed to surpass that of steel. An enhanced densification rate of 6.1 % and M 6 C (eta carbide) reduction with increased carbon level results in strong interfacial bonding in specimens sintered at 1 280 C. At 1 295 C, diffusion accelerates and the axial and radial shrinkage increase by 14.05 % and 13.35 %, respectively, in 93.8 wt.% WC - 6 wt.% Fe - 0.2 wt.% C and 93.2 wt.% Fe - 6 wt.% WC - 0.8 wt.% C, thereby increasing the tendency for complete delamination.

Band-gap tunability and dynamical instability in strained monolayer and bilayer phosphorenes

International Nuclear Information System (INIS)

Huang, G Q; Xing, Z W

2015-01-01

Very recently, field-effect transistors based on few-layer phosphorene crystals with a thickness of down to a few nanometres were successfully fabricated, triggering interest in this new functional two-dimensional material. In this work, we apply first-principles calculations to studying the evolution of electronic and phononic structures with out-of-plane strain for monolayer and bilayer phosphorenes. It is found that the vertical stress can be used to tune the band gap of a semiconducting phosphorene in a wide range. On the other hand, the vertical stress can make the phosphorene lattice become dynamically unstable and surface reconstruction or structural phase transition may occur. Due to the interlayer van der Waals coupling, the dynamically stable range of bilayer phosphorene under vertical stress is wider than that of monolayer phosphorene. It is proposed whether or not a semiconductor-semimetal transition occurring in a strained phosphorene is determined not only by its band gap closing, but also by its lattice stability against strain. This information is essential for the strain engineering of phosphorene and future device fabrication. (paper)

Page 170 Use of Electronic Resources by Undergraduates in Two ...

African Journals Online (AJOL)

undergraduate students use electronic resources such as NUC virtual library, HINARI, ... web pages articles from magazines, encyclopedias, pamphlets and other .... of Nigerian university libraries have Internet connectivity, some of the system.

Quantitative Raman microspectroscopy for water permeability parameters at a droplet interface bilayer.

Science.gov (United States)

Braziel, S; Sullivan, K; Lee, S

2018-01-29

Using confocal Raman microspectroscopy, we derive parameters for bilayer water transport across an isolated nanoliter aqueous droplet pair. For a bilayer formed with two osmotically imbalanced and adherent nanoliter aqueous droplets in a surrounding oil solvent, a droplet interface bilayer (DIB), the water permeability coefficient across the lipid bilayer was determined from monitoring the Raman scattering from the C[triple bond, length as m-dash]N stretching mode of K 3 Fe(CN) 6 as a measure of water uptake into the swelling droplet of a DIB pair. We also derive passive diffusional permeability coefficient for D 2 O transport across a droplet bilayer using O-D Raman signal. This method provides a significant methodological advance in determining water permeability coefficients in a convenient and reliable way.

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...

Cross-sectional characterization of the dewetting of a Au/Ni bilayer film

Energy Technology Data Exchange (ETDEWEB)

Cen, Xi; Thron, Andrew M.; Zhang, Xinming; Benthem, Klaus van

2017-07-15

The solid state dewetting of Au/Ni bilayer films was investigated by cross-sectional transmission electron microscopy techniques, including energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy and precession electron diffraction. After annealing under high vacuum conditions the early stage of film agglomeration revealed significant changes in film morphology and chemical distribution. Both Au and Ni showed texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO{sub 2}/Si interface structure, the majority of the metal/SiO{sub 2} interface was Au/SiO{sub 2} after annealing at 675 °C for 1 h. Void nucleation was predominantly observed at Au/Ni/SiO{sub 2} triple junctions, rather than grain boundary grooving at free surface of the metal film. Detailed cross-sectional characterization reveals that the Au/Ni interface in addition to small amounts of metal alloying strongly affects film break-up and agglomeration kinetics. The formation of Au/SiO{sub 2} interface sections is found to be energetically preferred over Ni/SiO{sub 2} due to compressive stress in the as-deposited Ni layer. Void nucleation is observed at the film/substrate interface, while the formation of voids at Ni/Au phase boundaries inside the metal film is caused by the Kirkendall effect. - Highlights: • The dewetting of Au/Ni bilayer films was studied by cross-sectional TEM techniques. • The majority of the metal/SiO{sub 2} interface was comprised of Au/SiO{sub 2} after annealing. • Void formation was dominant for hole nucleation at early dewetting stage. • The Kirkendall effect was also observed to cause the formation of voids.

A systematic investigation and insight into the formation mechanism of bilayers of fatty acid/soap mixtures in aqueous solutions.

Science.gov (United States)

Xu, Wenlong; Song, Aixin; Dong, Shuli; Chen, Jingfei; Hao, Jingcheng

2013-10-08

Vesicles are the most common form of bilayer structures in fatty acid/soap mixtures in aqueous solutions; however, a peculiar bilayer structure called a "planar sheet" was found for the first time in the mixtures. In the past few decades, considerable research has focused on the formation theory of bilayers in fatty acid/soap mixtures. The hydrogen bond theory has been widely accepted by scientists to explain the formation of bilayers. However, except for the hydrogen bond, no other driving forces were proposed systematically. In this work, three kinds of weak interactions were investigated in detail, which could perfectly demonstrate the formation mechanism of bilayer structures in the fatty acid/soap mixtures in aqueous solutions. (i) The influence of hydrophobic interaction was detected by changing the chain length of fatty acid (C(n)H(2n+1)COOH), in which n = 10 to 18, the phase behavior was investigated, and the phase region was presented. With the help of cryogenic transmission electron microscopy (cryo-TEM) observations, deuterium nuclear magnetic resonance ((2)H NMR), and X-ray diffraction (XRD) measurements, the vesicles and planar sheets were determined. The chain length of C(n)H(2n+1)COOH has an important effect on the physical state of the hydrophobic chain, resulting in an obvious difference in the viscoelasticity of the solution samples. (ii) The existence of hydrogen bonds between fatty acids and their soaps in aqueous solutions was demonstrated by Fourier transform infrared (FT-IR) spectroscopy and molecule dynamical simulation. From the pH measurements, the pH ranges of the bilayer formation were at the pKa values of fatty acids, respectively. (iii) Counterions can be embedded in the stern layer of the bilayers and screen the electrostatic repulsion between the COO(-) anionic headgroups. FT-IR characterization demonstrated a bidentate bridging coordination mode between counterions and carboxylates. The conductivity measurements provided the degree

Layer configurations comparison of bilayer-films for EGFET pH sensor application

Science.gov (United States)

Rahman, R. A.; Zulkefle, M. A.; Yusof, K. A.; Abdullah, W. F. H.; Rusop, M.; Herman, S. H.

2018-05-01

The comparison between bilayer configurations were presented in this paper. TiO2 and ZnO layer configurations were manipulated in order to investigate which configuration produce highest sensing performance to be applied as EGFET pH sensor. Both of the materials were deposited together as the bilayer film. The configurations were manipulated between TiO2/ZnO and ZnO/TiO2. ITO was used as the substrate in this study and both of the materials were deposited by using sol-gel spin coating technique. After deposition process, these bilayer film then undergone for EGFET pH sensor measurement and physical characterization. The EGFET pH sensor measurement was done by dipping the fabricated bilayer film into three different pH values, which is pH4, pH7 and pH10. Bilayer film act as the pH-sensitive membrane, which connected to the commercial metal-oxide semiconductor FET (MOSFET). This MOSFET was connected to the interfacing circuit. Voltage output obtained were recorded and the graph was plotted by using the data recorded. Based on the EGFET pH sensor measurement, TiO2/ZnO bilayer film exhibit higher sensing performance, compared with ZnO/TiO2. TiO2/ZnO bilayer film produced 53.10 mV/pH with the linearity value of 0.9913. Afterwards, fabricated bilayer films then were characterized with AFM to explore their surface roughness and surface topography behavior.

Realization of free-standing silicene using bilayer graphene

Energy Technology Data Exchange (ETDEWEB)

Neek-Amal, M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Department of Physics, Shahid Rajaee Teacher Training University, Lavizan, Tehran 16785-136 (Iran, Islamic Republic of); Sadeghi, A. [Department of Physics, Basel University, Klingelbergestrasse 82, CH-4056 Basel (Switzerland); Berdiyorov, G. R.; Peeters, F. M. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

2013-12-23

The available synthesized silicene-like structures have been only realized on metallic substrates which are very different from the standalone buckled silicene, e.g., the Dirac cone of silicene is destroyed due to lattice distortion and the interaction with the substrate. Using graphene bilayer as a scaffold, a route is proposed to synthesize silicene with electronic properties decoupled from the substrate. The buckled hexagonal arrangement of silicene between the graphene layers is found to be very similar to the theoretically predicted standalone buckled silicene which is only very weakly van der Waals coupled to the graphene layers with a graphite-like interlayer distance of 3.42 Å and without any lattice distortion. We found that these stacked layers are stable well above room temperature.

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.

Model of e-learning with electronic educational resources of new generation

Directory of Open Access Journals (Sweden)

A. V. Loban

2017-01-01

Full Text Available Purpose of the article: improving of scientific and methodical base of the theory of the е-learning of variability. Methods used: conceptual and logical modeling of the е-learning of variability process with electronic educational resource of new generation and system analysis of the interconnection of the studied subject area, methods, didactics approaches and information and communication technologies means. Results: the formalization complex model of the е-learning of variability with electronic educational resource of new generation is developed, conditionally decomposed into three basic components: the formalization model of the course in the form of the thesaurusclassifier (“Author of e-resource”, the model of learning as management (“Coordination. Consultation. Control”, the learning model with the thesaurus-classifier (“Student”. Model “Author of e-resource” allows the student to achieve completeness, high degree of didactic elaboration and structuring of the studied material in triples of variants: modules of education information, practical task and control tasks; the result of the student’s (author’s of e-resource activity is the thesaurus-classifier. Model of learning as management is based on the principle of personal orientation of learning in computer environment and determines the logic of interaction between the lecturer and the student when determining the triple of variants individually for each student; organization of a dialogue between the lecturer and the student for consulting purposes; personal control of the student’s success (report generation and iterative search for the concept of the class assignment in the thesaurus-classifier before acquiring the required level of training. Model “Student” makes it possible to concretize the learning tasks in relation to the personality of the student and to the training level achieved; the assumption of the lecturer about the level of training of a

A survey of the use of electronic scientific information resources among medical and dental students

Directory of Open Access Journals (Sweden)

Aarnio Matti

2006-05-01

Full Text Available Abstract Background To evaluate medical and dental students' utilization of electronic information resources. Methods A web survey sent to 837 students (49.9% responded. Results Twenty-four per cent of medical students and ninteen per cent of dental students searched MEDLINE 2+ times/month for study purposes, and thiry-two per cent and twenty-four per cent respectively for research. Full-text articles were used 2+ times/month by thirty-three per cent of medical and ten per cent of dental students. Twelve per cent of respondents never utilized either MEDLINE or full-text articles. In multivariate models, the information-searching skills among students were significantly associated with use of MEDLINE and full-text articles. Conclusion Use of electronic resources differs among students. Forty percent were non-users of full-text articles. Information-searching skills are correlated with the use of electronic resources, but the level of basic PC skills plays not a major role in using these resources. The student data shows that adequate training in information-searching skills will increase the use of electronic information resources.

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.

Porous Materials to Support Bilayer Lipid Membranes for Ion Channel Biosensors

Directory of Open Access Journals (Sweden)

Thai Phung

2011-01-01

Full Text Available To identify materials suitable as membrane supports for ion channel biosensors, six filter materials of varying hydrophobicity, tortuosity, and thickness were examined for their ability to support bilayer lipid membranes as determined by electrical impedance spectroscopy. Bilayers supported by hydrophobic materials (PTFE, polycarbonate, nylon, and silanised silver had optimal resistance (14–19 GΩ and capacitance (0.8–1.6 μF values whereas those with low hydrophobicity did not form BLMs (PVDF or were short-lived (unsilanised silver. The ability of ion channels to function in BLMs was assessed using a method recently reported to improve the efficiency of proteoliposome incorporation into PTFE-supported bilayers. Voltage-gated sodium channel activation by veratridine and inhibition by saxitoxin showed activity for PTFE, nylon, and silanised silver, but not polycarbonate. Bilayers on thicker, more tortuous, and hydrophobic materials produced higher current levels. Bilayers that self-assembled on PTFE filters were the longest lived and produced the most channel activity using this method.

Assessment of bilayer silicene to probe as quantum spin and valley Hall effect

Science.gov (United States)

Rehman, Majeed Ur; Qiao, Zhenhua

2018-02-01

Silicene takes precedence over graphene due to its buckling type structure and strong spin orbit coupling. Motivated by these properties, we study the silicene bilayer in the presence of applied perpendicular electric field and intrinsic spin orbit coupling to probe as quantum spin/valley Hall effect. Using analytical approach, we calculate the spin Chern-number of bilayer silicene and then compare it with monolayer silicene. We reveal that bilayer silicene hosts double spin Chern-number as compared to single layer silicene and therefore accordingly has twice as many edge states in contrast to single layer silicene. In addition, we investigate the combined effect of intrinsic spin orbit coupling and the external electric field, we find that bilayer silicene, likewise single layer silicene, goes through a phase transitions from a quantum spin Hall state to a quantum valley Hall state when the strength of the applied electric field exceeds the intrinsic spin orbit coupling strength. We believe that the results and outcomes obtained for bilayer silicene are experimentally more accessible as compared to bilayer graphene, because of strong SO coupling in bilayer silicene.

Degradation of Bilayer Organic Light-Emitting Diodes Studied by Impedance Spectroscopy.

Science.gov (United States)

Sato, Shuri; Takata, Masashi; Takada, Makoto; Naito, Hiroyoshi

2016-04-01

The degradation of bilayer organic light-emitting diodes (OLEDs) with a device structure of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) (hole transport layer) and tris-(8-hydroxyquinolate)aluminum (Alq3) (emissive layer and electron transport layer) has been studied by impedance spectroscopy and device simulation. Two modulus peaks are found in the modulus spectra of the OLEDs below the electroluminescence threshold. After aging of the OLEDs, the intensity of electroluminescence is degraded and the modulus peak due to the Alq3 layer is shifted to lower frequency, indicating that the resistance of the Alq3 layer is increased. Device simulation reveals that the increase in the resistance of the Alq3 layer is due to the decrease in the electron mobility in the Alq3 layer.

Step-wise potential development across the lipid bilayer under external electric fields

Science.gov (United States)

Majhi, Amit Kumar

2018-04-01

Pore formation across the bilayers under external electric field is an important phenomenon, which has numerous applications in biology and bio-engineering fields. However, it is not a ubiquitous event under all field applications. To initiate a pore in the bilayer a particular threshold electric field is required. The electric field alters the intrinsic potential distribution across the bilayer as we as it enhances total potential drop across the bilayer, which causes the pore formation. The intrinsic potential profile has a maximum peak value, which is 0.8 V and it gets enhanced under application of external field, 0.43 V/nm. The peak value becomes 1.4 V when a pore appears in the bilayer and it continues to evolve as along as the external electric field remains switched on.

Non-bilayer structures in mitochondrial membranes regulate ATP synthase activity.

Science.gov (United States)

Gasanov, Sardar E; Kim, Aleksandr A; Yaguzhinsky, Lev S; Dagda, Ruben K

2018-02-01

Cardiolipin (CL) is an anionic phospholipid at the inner mitochondrial membrane (IMM) that facilitates the formation of transient non-bilayer (non-lamellar) structures to maintain mitochondrial integrity. CL modulates mitochondrial functions including ATP synthesis. However, the biophysical mechanisms by which CL generates non-lamellar structures and the extent to which these structures contribute to ATP synthesis remain unknown. We hypothesized that CL and ATP synthase facilitate the formation of non-bilayer structures at the IMM to stimulate ATP synthesis. By using 1 H NMR and 31 P NMR techniques, we observed that increasing the temperature (8°C to 37°C), lowering the pH (3.0), or incubating intact mitochondria with CTII - an IMM-targeted toxin that increases the formation of immobilized non-bilayer structures - elevated the formation of non-bilayer structures to stimulate ATP synthesis. The F 0 sector of the ATP synthase complex can facilitate the formation of non-bilayer structures as incubating model membranes enriched with IMM-specific phospholipids with exogenous DCCD-binding protein of the F 0 sector (DCCD-BPF) elevated the formation of immobilized non-bilayer structures to a similar manner as CTII. Native PAGE assays revealed that CL, but not other anionic phospholipids, specifically binds to DCCD-BPF to promote the formation of stable lipid-protein complexes. Mechanistically, molecular docking studies identified two lipid binding sites for CL in DCCD-BPF. We propose a new model of ATP synthase regulation in which CL mediates the formation of non-bilayer structures that serve to cluster protons and ATP synthase complexes as a mechanism to enhance proton translocation to the F 0 sector, and thereby increase ATP synthesis. Copyright © 2017 Elsevier B.V. All rights reserved.

Computational Design of Multi-component Bio-Inspired Bilayer Membranes

Directory of Open Access Journals (Sweden)

Evan Koufos

2014-04-01

Full Text Available Our investigation is motivated by the need to design bilayer membranes with tunable interfacial and mechanical properties for use in a range of applications, such as targeted drug delivery, sensing and imaging. We draw inspiration from biological cell membranes and focus on their principal constituents. In this paper, we present our results on the role of molecular architecture on the interfacial, structural and dynamical properties of bio-inspired membranes. We focus on four lipid architectures with variations in the head group shape and the hydrocarbon tail length. Each lipid species is composed of a hydrophilic head group and two hydrophobic tails. In addition, we study a model of the Cholesterol molecule to understand the interfacial properties of a bilayer membrane composed of rigid, single-tail molecular species. We demonstrate the properties of the bilayer membranes to be determined by the molecular architecture and rigidity of the constituent species. Finally, we demonstrate the formation of a stable mixed bilayer membrane composed of Cholesterol and one of the phospholipid species. Our approach can be adopted to design multi-component bilayer membranes with tunable interfacial and mechanical properties. We use a Molecular Dynamics-based mesoscopic simulation technique called Dissipative Particle Dynamics that resolves the molecular details of the components through soft-sphere coarse-grained models and reproduces the hydrodynamic behavior of the system over extended time scales.

Access to electronic information resources by students of federal ...

African Journals Online (AJOL)

The paper discusses access to electronic information resources by students of Federal Colleges of Education in Eha-Amufu and Umunze. Descriptive survey design was used to investigate sample of 526 students. Sampling technique used was a Multi sampling technique. Data for the study were generated using ...

Adoption and use of electronic information resources by medical ...

African Journals Online (AJOL)

This study investigated the adoption and use of electronic information resources by medical science students of the University of Benin. The descriptive survey research design was adopted for the study and 390 students provided the data. Data collected were analysed with descriptive Statistics(Simple percentage and ...

Prevention of intra-abdominal adhesion by bi-layer electrospun membrane.

Science.gov (United States)

Jiang, Shichao; Wang, Wei; Yan, Hede; Fan, Cunyi

2013-06-04

The aim of this study was to compare the anti-adhesion efficacy of a bi-layer electrospun fibrous membrane consisting of hyaluronic acid-loaded poly(ε-caprolactone) (PCL) fibrous membrane as the inner layer and PCL fibrous membrane as the outer layer with a single-layer PCL electrospun fibrous membrane in a rat cecum abrasion model. The rat model utilized a cecal abrasion and abdominal wall insult surgical protocol. The bi-layer and PCL membranes were applied between the cecum and the abdominal wall, respectively. Control animals did not receive any treatment. After postoperative day 14, a visual semiquantitative grading scale was used to grade the extent of adhesion. Histological analysis was performed to reveal the features of adhesion tissues. Bi-layer membrane treated animals showed significantly lower adhesion scores than control animals (p compared with the PCL membrane. Histological analysis of the bi-layer membrane treated rat rarely demonstrated tissue adhesion while that of the PCL membrane treated rat and control rat showed loose and dense adhesion tissues, respectively. Bi-layer membrane can efficiently prevent adhesion formation in abdominal cavity and showed a significantly decreased adhesion tissue formation compared with the control.

Tensile and shear methods for measuring strength of bilayer tablets.

Science.gov (United States)

Chang, Shao-Yu; Li, Jian-Xin; Sun, Changquan Calvin

2017-05-15

Both shear and tensile measurement methods have been used to quantify interfacial bonding strength of bilayer tablets. The shear method is more convenient to perform, but reproducible strength data requires careful control of the placement of tablet and contact point for shear force application. Moreover, data obtained from the shear method depend on the orientation of the bilayer tablet. Although more time-consuming to perform, the tensile method yields data that are straightforward to interpret. Thus, the tensile method is preferred in fundamental bilayer tableting research to minimize ambiguity in data interpretation. Using both shear and tensile methods, we measured the mechanical strength of bilayer tablets made of several different layer combinations of lactose and microcrystalline cellulose. We observed a good correlation between strength obtained by the tensile method and carefully conducted shear method. This suggests that the shear method may be used for routine quality test of bilayer tablets during manufacturing because of its speed and convenience, provided a protocol for careful control of the placement of the tablet interface, tablet orientation, and blade is implemented. Copyright © 2017 Elsevier B.V. All rights reserved.

Buckling-dependent switching behaviours in shifted bilayer germanene nanoribbons: A computational study

Science.gov (United States)

Arjmand, T.; Tagani, M. Bagheri; Soleimani, H. Rahimpour

2018-01-01

Bilayer germanene nanoribbons are investigated in different stacks like buckled and flat armchair and buckled zigzag germanene nanoribbons by performing theoretical calculations using the nonequilibrium Greens function method combined with density functional theory. In these bilayer types, the current oscillates with change of interlayer distances or intra-layer overlaps and is dependent on the type of the bilayer. Band gap of AA-stacked of shifted flat bilayer armchair germanene nanoribbon oscillates by change of interlayer distance which is in contrast to buckled bilayer armchair germanene nanoribbon. So, results show the buckling makes system tend to be a semiconductor with wide band gap. Therefore, AA-stacked of shifted flat bilayer armchair germanene nanoribbon has properties between zigzag and armchair edges, the higher current under bias voltages similar to zigzag edge and also oscillations in current like buckled armchair edges. Also, it is found that HOMO-LUMO band gap strongly affects oscillation in currents and their I-V characteristic. This kind of junction improves the switching properties at low voltages around the band gap.

Quantum mechanical rippling of a MoS2 monolayer controlled by interlayer bilayer coupling.

Science.gov (United States)

Zheng, Yi; Chen, Jianyi; Ng, M-F; Xu, Hai; Liu, Yan Peng; Li, Ang; O'Shea, Sean J; Dumitrică, T; Loh, Kian Ping

2015-02-13

Nanoscale corrugations are of great importance in determining the physical properties of two-dimensional crystals. However, the mechanical behavior of atomically thin films under strain is not fully understood. In this Letter, we show a layer-dependent mechanical response of molybdenum disulfide (MoS(2)) subject to atomistic-precision strain induced by 2H-bilayer island epitaxy. Dimensional crossover in the mechanical properties is evidenced by the formation of star-shaped nanoripple arrays in the first monolayer, while rippling instability is completely suppressed in the bilayer. Microscopic-level quantum mechanical simulations reveal that the nanoscale rippling is realized by the twisting of neighboring Mo-S bonds without modifying the chemical bond length, and thus invalidates the classical continuum mechanics. The formation of nanoripple arrays significantly changes the electronic and nanotribological properties of monolayer MoS(2). Our results suggest that quantum mechanical behavior is not unique for sp(2) bonding but general for atomic membranes under strain.

Effect of free cholesterol on incorporation of triolein in phospholipid bilayers

International Nuclear Information System (INIS)

Spooner, P.J.R.; Small, D.M.

1987-01-01

Triacylglycerols are the major substrates for lipolytic enzymes that act at the surface of emulsion-like particles such as triglyceride-rich lipoproteins, chylomicrons, and intracellular lipid droplets. This study examines the effect of cholesterol on the solubility of a triacylglycerol, triolein, in phospholipid surfaces. Solubilities of [carbonyl- 13 C] triolein in phospholipid bilayer vesicles containing between 0 and 50 mol % free cholesterol, prepared by cosonication, were measured by 13 C NMR. The carbonyl resonances from bilayer-incorporated triglyceride were shifted downfield in the 13 C NMR spectra from those corresponding to excess, nonincorporated material. This enabled solubilities to be determined directly from carbonyl peak intensities at most cholesterol concentration. The bilayer solubility of triolein was inversely proportional to the cholesterol/phospholipid mole ratio. In pure phospholipid vesicles the triolein solubility was 2.2 mol %. The triglyceride incorporation decreased to 1.1 mol % at a cholesterol/phospholipid mole ratio of 0.5, and at a mole ratio of 1.0 for the bilayer lipids, the triolein solubility was reduced to just 0.15 mol %. The effects of free cholesterol were more pronounced and progressive than observed previously on the bilayer solubility of cholestery oleate. As with cholesteryl oleate, they suggest that cholesterol also displaces solubilized triglyceride to deeper regions of the bilayer

Composition Dependence of Water Permeation Across Multicomponent Gel-Phase Bilayers

NARCIS (Netherlands)

Hartkamp, R.M.; Moore, Timothy C.; Iacovella, Christopher R.; Thompson, Michael A.; Bulsara, Pallav A.; Moore, David J.; McCabe, Clare

2018-01-01

The permeability of multicomponent phospholipid bilayers in the gel phase is investigated via molecular dynamics simulation. The physical role of the different molecules is probed by comparing multiple mixed-component bilayers containing distearylphosphatidylcholine (DSPC) with varying amounts of

Where Do Electronic Books Fit in the College Research Arsenal of Resources?

Science.gov (United States)

Barbier, Patricia

2007-01-01

Student use of electronic books has become an accepted supplement to traditional resources. Student use and satisfaction was monitored through an online course discussion board. Increased use of electronic books indicate this service is an accepted supplement to the print book collection.

Modeling constrained sintering of bi-layered tubular structures

DEFF Research Database (Denmark)

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

2015-01-01

Constrained sintering of tubular bi-layered structures is being used in the development of various technologies. Densification mismatch between the layers making the tubular bi-layer can generate stresses, which may create processing defects. An analytical model is presented to describe the densi...... and thermo-mechanical analysis. Results from the analytical model are found to agree well with finite element simulations as well as measurements from sintering experiment....

Band engineering in twisted molybdenum disulfide bilayers

Science.gov (United States)

Zhao, Yipeng; Liao, Chengwei; Ouyang, Gang

2018-05-01

In order to explore the theoretical relationship between interlayer spacing, interaction and band offset at the atomic level in vertically stacked two-dimensional (2D) van der Waals (vdW) structures, we propose an analytical model to address the evolution of interlayer vdW coupling with random stacking configurations in MoS2 bilayers based on the atomic-bond-relaxation correlation mechanism. We found that interlayer spacing changes substantially with respect to the orientations, and the bandgap increases from 1.53 eV (AB stacking) to 1.68 eV (AA stacking). Our results reveal that the evolution of interlayer vdW coupling originates from the interlayer interaction, leading to interlayer separations and electronic properties changing with stacking configurations. Our predictions constitute a demonstration of twist engineering the band shift in the emergent class of 2D crystals, transition-metal dichalcogenides.

Long-Lived Charge Separation at Heterojunctions between Semiconducting Single-Walled Carbon Nanotubes and Perylene Diimide Electron Acceptors

Energy Technology Data Exchange (ETDEWEB)

Kang, Hyun Suk [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Arias, Dylan H [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Blackburn, Jeffrey L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sisto, Thomas J. [Columbia University; Peurifoy, Samuel [Columbia University; Zhang, Boyuan [Columbia University; Nuckolls, Colin [Columbia University

2018-04-13

Nonfullerene electron acceptors have facilitated a recent surge in the efficiencies of organic solar cells, although fundamental studies of the nature of exciton dissociation at interfaces with nonfullerene electron acceptors are still relatively sparse. Semiconducting single-walled carbon nanotubes (s-SWCNTs), unique one-dimensional electron donors with molecule-like absorption and highly mobile charges, provide a model system for studying interfacial exciton dissociation. Here, we investigate excited-state photodynamics at the heterojunction between (6,5) s-SWCNTs and two perylene diimide (PDI)-based electron acceptors. Each of the PDI-based acceptors, hPDI2-pyr-hPDI2 and Trip-hPDI2, is deposited onto (6,5) s-SWCNT films to form a heterojunction bilayer. Transient absorption measurements demonstrate that photoinduced hole/electron transfer occurs at the photoexcited bilayer interfaces, producing long-lived separated charges with lifetimes exceeding 1.0 us. Both exciton dissociation and charge recombination occur more slowly for the hPDI2-pyr-hPDI2 bilayer than for the Trip-hPDI2 bilayer. To explain such differences, we discuss the potential roles of the thermodynamic charge transfer driving force available at each interface and the different molecular structure and intermolecular interactions of PDI-based acceptors. Detailed photophysical analysis of these model systems can develop the fundamental understanding of exciton dissociation between organic electron donors and nonfullerene acceptors, which has not been systematically studied.

Fabrication of oriented wrinkles on polydopamine/polystyrene bilayer films.

Science.gov (United States)

Wang, Rong; Long, Yuhua; Zhu, Tang; Guo, Jing; Cai, Chao; Zhao, Ning; Xu, Jian

2017-07-15

Wrinkles exist widely in nature and our life. In this paper, wrinkles on polydopamine (PDA)/polystyrene (PS) bilayer films were formed by thermal annealing due to the different thermal coefficients of expansion of each layer. The factors that influenced the dimensions of wrinkles were studied. We found that oriented wrinkles could be formed if the bilayer films were patterned with micro-grooves, and the degree of the orientation depended on the thickness of the PDA and the dimensions of the grooves. Combined with the strong adhesion, biocompatibility and reactivity of PDA, the oriented wrinkles on PDA/PS patterned bilayers may find potential application in diffraction gratings, optical sensors and microfluidic devices. Copyright © 2017 Elsevier Inc. All rights reserved.

Modulated phases of phospholipid bilayers induced by tocopherols.

Science.gov (United States)

Kamal, Md Arif; Raghunathan, V A

2012-11-01

The influence of α-, γ- and δ-tocopherols on the structure and phase behavior of dipalmitoyl phosphatidylcholine (DPPC) bilayers has been determined from X-ray diffraction studies on oriented multilayers. In all the three cases the main-transition temperature (T(m)) of DPPC was found to decrease with increasing tocopherol concentration up to around 25 mol%. Beyond this the main transition is suppressed in the case of γ-tocopherol, whereas T(m) becomes insensitive to composition in the other two cases. The pre-transition is found to be suppressed over a narrow tocopherol concentration range between 7.5 and 10 mol% in DPPC-γ-tocopherol and DPPC-δ-tocopherol bilayers, and the ripple phase occurs down to the lowest temperature studied. In all the three cases a modulated phase is observed above a tocopherol concentration of about 10 mol%, which is similar to the P(β) phase reported in DPPC-cholesterol bilayers. This phase is found to occur even in excess water conditions at lower tocopherol concentrations, and consists of bilayers with periodic height modulation. These results indicate the ability of tocopherols to induce local curvature in membranes, which could be important for some of their biological functions. Copyright © 2012 Elsevier B.V. All rights reserved.

Examining the origins of the hydration force between lipid bilayers using all-atom simulations.

Science.gov (United States)

Gentilcore, Anastasia N; Michaud-Agrawal, Naveen; Crozier, Paul S; Stevens, Mark J; Woolf, Thomas B

2010-05-01

Using 237 all-atom double bilayer simulations, we examined the thermodynamic and structural changes that occur as a phosphatidylcholine lipid bilayer stack is dehydrated. The simulated system represents a micropatch of lipid multilayer systems that are studied experimentally using surface force apparatus, atomic force microscopy and osmotic pressure studies. In these experiments, the hydration level of the system is varied, changing the separation between the bilayers, in order to understand the forces that the bilayers feel as they are brought together. These studies have found a curious, strongly repulsive force when the bilayers are very close to each other, which has been termed the "hydration force," though the origins of this force are not clearly understood. We computationally reproduce this repulsive, relatively free energy change as bilayers come together and make qualitative conclusions as to the enthalpic and entropic origins of the free energy change. This analysis is supported by data showing structural changes in the waters, lipids and salts that have also been seen in experimental work. Increases in solvent ordering as the bilayers are dehydrated are found to be essential in causing the repulsion as the bilayers come together.

Performance Enhancement of Small Molecular Solar Cells by Bilayer Cathode Buffer.

Science.gov (United States)

Sun, Qinjun; Zhao, Huanbin; Zhou, Miao; Gao, Liyan; Hao, Yuying

2016-04-01

An effective composite bilayer cathode buffer structure is proposed for use in small molecular solar cells. CsF was doped in Alq3 to form the first cathode buffer, leading to small serial resistances. BCP was used as the second cathode buffer to block the holes to the electrode. The optimized bilayer cathode buffer significantly increased the short circuit and fill factor of devices. By integrating this bilayer cathode buffer, the CuPc/C60 small molecular heterojunction cell exhibited a power conversion efficiency of up to 0.8%, which was an improvement of 56% compared to a device with only the Alq3 cathode buffer. Meanwhile, the bilayer cathode buffer still has a good protective effect on the performance of the device.

Wavepacket revivals in monolayer and bilayer graphene rings.

Science.gov (United States)

García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

2013-06-12

We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking.

Magnetically Assisted Bilayer Composites for Soft Bending Actuators

OpenAIRE

Jang, Sung-Hwan; Na, Seon-Hong; Park, Yong-Lae

2017-01-01

This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward o...

Gas Separation through Bilayer Silica, the Thinnest Possible Silica Membrane.

Science.gov (United States)

Yao, Bowen; Mandrà, Salvatore; Curry, John O; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Schrier, Joshua

2017-12-13

Membrane-based gas separation processes can address key challenges in energy and environment, but for many applications the permeance and selectivity of bulk membranes is insufficient for economical use. Theory and experiment indicate that permeance and selectivity can be increased by using two-dimensional materials with subnanometer pores as membranes. Motivated by experiments showing selective permeation of H 2 /CO mixtures through amorphous silica bilayers, here we perform a theoretical study of gas separation through silica bilayers. Using density functional theory calculations, we obtain geometries of crystalline free-standing silica bilayers (comprised of six-membered rings), as well as the seven-, eight-, and nine-membered rings that are observed in glassy silica bilayers, which arise due to Stone-Wales defects and vacancies. We then compute the potential energy barriers for gas passage through these various pore types for He, Ne, Ar, Kr, H 2 , N 2 , CO, and CO 2 gases, and use the data to assess their capability for selective gas separation. Our calculations indicate that crystalline bilayer silica, which is less than a nanometer thick, can be a high-selectivity and high-permeance membrane material for 3 He/ 4 He, He/natural gas, and H 2 /CO separations.

Calculations of the electrostatic potential adjacent to model phospholipid bilayers.

Science.gov (United States)

Peitzsch, R M; Eisenberg, M; Sharp, K A; McLaughlin, S

1995-03-01

We used the nonlinear Poisson-Boltzmann equation to calculate electrostatic potentials in the aqueous phase adjacent to model phospholipid bilayers containing mixtures of zwitterionic lipids (phosphatidylcholine) and acidic lipids (phosphatidylserine or phosphatidylglycerol). The aqueous phase (relative permittivity, epsilon r = 80) contains 0.1 M monovalent salt. When the bilayers contain equipotential surfaces are discrete domes centered over the negatively charged lipids and are approximately twice the value calculated using Debye-Hückel theory. When the bilayers contain > 25% acidic lipid, the -25 mV equipotential profiles are essentially flat and agree well with the values calculated using Gouy-Chapman theory. When the bilayers contain 100% acidic lipid, all of the equipotential surfaces are flat and agree with Gouy-Chapman predictions (including the -100 mV surface, which is located only 1 A from the outermost atoms). Even our model bilayers are not simple systems: the charge on each lipid is distributed over several atoms, these partial charges are non-coplanar, there is a 2 A ion-exclusion region (epsilon r = 80) adjacent to the polar headgroups, and the molecular surface is rough. We investigated the effect of these four factors using smooth (or bumpy) epsilon r = 2 slabs with embedded point charges: these factors had only minor effects on the potential in the aqueous phase.

Strategic Planning for Electronic Resources Management: A Case Study at Gustavus Adolphus College

Science.gov (United States)

Hulseberg, Anna; Monson, Sarah

2009-01-01

Electronic resources, the tools we use to manage them, and the needs and expectations of our users are constantly evolving; at the same time, the roles, responsibilities, and workflow of the library staff who manage e-resources are also in flux. Recognizing a need to be more intentional and proactive about how we manage e-resources, the…

REVIEW OF MOODLE PLUGINS FOR DESIGNING MULTIMEDIA ELECTRONIC EDUCATIONAL RESOURCES FROM LANGUAGE DISCIPLINES

Directory of Open Access Journals (Sweden)

Anton M. Avramchuk

2015-09-01

Full Text Available Today the problem of designing multimedia electronic educational resources from language disciplines in Moodle is very important. This system has a lot of different, powerful resources, plugins to facilitate the learning of students with language disciplines. This article presents an overview and comparative analysis of the five Moodle plugins for designing multimedia electronic educational resources from language disciplines. There have been considered their key features and functionality in order to choose the best for studying language disciplines in the Moodle. Plugins are compared by a group of experts according to the criteria: efficiency, functionality and easy use. For a comparative analysis of the plugins it is used the analytic hierarchy process.

Phase separation in lipid bilayers triggered by low pH

International Nuclear Information System (INIS)

Suresh, Swetha; Edwardson, J. Michael

2010-01-01

Research highlights: → Lipid bilayers have been imaged by atomic force microscopy (AFM). → At pH 5 phase separation occurs in lipid bilayers containing mixed acyl chains. → Phase separation does not occur when lipids have only unsaturated chains. → Phase separation might drive protein clustering during endocytosis. -- Abstract: Endocytosis involves the capture of membrane from the cell surface in the form of vesicles, which become rapidly acidified to about pH 5. Here we show using atomic force microscopy (AFM) imaging that this degree of acidification triggers phase separation in lipid bilayers containing mixed acyl chains (e.g. palmitoyl/oleoyl) or complex mixtures (e.g. total brain extract) but not in bilayers containing only lipids with unsaturated chains (e.g. dioleoyl). Since mixed-chain lipids are major constituents of the outer leaflet of the plasma membrane, the type of phase separation reported here might support protein clustering and signaling during endocytosis.

Tunneling Spectroscopy of Quantum Hall States in Bilayer Graphene

Science.gov (United States)

Wang, Ke; Harzheim, Achim; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip

In the quantum Hall (QH) regime, ballistic conducting paths along the physical edges of a sample appear, leading to quantized Hall conductance and vanishing longitudinal magnetoconductance. These QH edge states are often described as ballistic compressible strips separated by insulating incompressible strips, the spatial profiles of which can be crucial in understanding the stability and emergence of interaction driven QH states. In this work, we present tunneling transport between two QH edge states in bilayer graphene. Employing locally gated device structure, we guide and control the separation between the QH edge states in bilayer graphene. Using resonant Landau level tunneling as a spectroscopy tool, we measure the energy gap in bilayer graphene as a function of displacement field and probe the emergence and evolution of incompressible strips.

Wavepacket revivals in monolayer and bilayer graphene rings

International Nuclear Information System (INIS)

García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

2013-01-01

We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking. (paper)

Numerical study of the light output intensity of the bilayer organic light-emitting diodes

Science.gov (United States)

Lu, Feiping

2017-02-01

The structure of organic light-emitting diodes (OLEDs) is one of most important issues that influence the light output intensity (LOI) of OLEDs. In this paper, based on a simple but accurate optical model, the influences of hole and electron transport layer thickness on the LOI of bilayer OLEDs, which with N,N0- bis(naphthalen-1-yl)-N,N0- bis(phenyl)- benzidine (NPB) or N,N'- diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4-diamine (TPD) as hole transport layer, with tris(8-hydroxyquinoline) aluminum (Alq3) as electron transport and light emitting layers, were investigated. The laws of LOI for OLEDs under different organic layer thickness values were obtained. The results show that the LOI of devices varies in accordance with damped cosine or sine function as the increasing of organic layer thickness, and the results show that the bilayer OLEDs with the structure of Glass/ITO/NPB (55 nm)/Alq3 (75 nm)/Al and Glass/ITO/TPB (60 nm)/Alq3 (75 nm)/Al have most largest LOI. When the thickness of Alq3 is less than 105 nm, the OLEDs with TPD as hole transport layer have larger LOI than that with NPB as hole transport layer. The results obtained in this paper can present an in-depth understanding of the working mechanism of OLEDs and help ones fabricate high efficiency OLEDs.

Model for the structure of the lipid bilayer

International Nuclear Information System (INIS)

Pastor, R.W.; Venable, R.M.; Karplus, M.

1991-01-01

A detailed model for the structure and dynamics of the interior of the lipid bilayer in the liquid crystal phase is presented. The model includes two classes of motion: (i) the internal dynamics of the chains, determined from Brownian dynamics simulations with a continuous version of the Marcelja mean-field potential, and (ii) noncollective reorientation (axial rotation and wobble) of the entire molecule, introduced by a cone model. The basic unit of the model is a single lipid chain with field parameters adjusted to fit the 2H order parameters and the frequency-dependent 13C NMR T1 relaxation times of dipalmitoyl phosphatidylcholine bilayers. The chain configurations obtained from the trajectory are used to construct a representation of the bilayer. The resulting lipid assembly is consistent with NMR, neutron diffraction, surface area, and density data. It indicates that a high degree of chain disorder and entanglement exists in biological membranes

Diffusion quantum Monte Carlo and density functional calculations of the structural stability of bilayer arsenene

Science.gov (United States)

Kadioglu, Yelda; Santana, Juan A.; Özaydin, H. Duygu; Ersan, Fatih; Aktürk, O. Üzengi; Aktürk, Ethem; Reboredo, Fernando A.

2018-06-01

We have studied the structural stability of monolayer and bilayer arsenene (As) in the buckled (b) and washboard (w) phases with diffusion quantum Monte Carlo (DMC) and density functional theory (DFT) calculations. DMC yields cohesive energies of 2.826(2) eV/atom for monolayer b-As and 2.792(3) eV/atom for w-As. In the case of bilayer As, DMC and DFT predict that AA-stacking is the more stable form of b-As, while AB is the most stable form of w-As. The DMC layer-layer binding energies for b-As-AA and w-As-AB are 30(1) and 53(1) meV/atom, respectively. The interlayer separations were estimated with DMC at 3.521(1) Å for b-As-AA and 3.145(1) Å for w-As-AB. A comparison of DMC and DFT results shows that the van der Waals density functional method yields energetic properties of arsenene close to DMC, while the DFT + D3 method closely reproduced the geometric properties from DMC. The electronic properties of monolayer and bilayer arsenene were explored with various DFT methods. The bandgap values vary significantly with the DFT method, but the results are generally qualitatively consistent. We expect the present work to be useful for future experiments attempting to prepare multilayer arsenene and for further development of DFT methods for weakly bonded systems.

Modern ICT Tools: Online Electronic Resources Sharing Using Web ...

African Journals Online (AJOL)

Modern ICT Tools: Online Electronic Resources Sharing Using Web 2.0 and Its Implications For Library And Information Practice In Nigeria. ... The PDF file you selected should load here if your Web browser has a PDF reader plug-in installed (for example, a recent version of Adobe Acrobat Reader). If you would like more ...

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

, regulate a number of structurally unrelated proteins in an apparently non-specific manner. It is well known that changes in the physical properties of a lipid bilayer (e.g., thickness or monolayer spontaneous curvature) can affect the function of an embedded protein. However, the role of such changes......-dependent sodium channels, N-type calcium channels and GABAA receptors, it has been shown that membrane protein function in living cells can be regulated by amphiphile induced changes in bilayer elasticity. Using the gramicidin channel as a molecular force transducer, a nanotechnology to measure the elastic...... 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....

Anomalous Hall effect in Fe/Gd bilayers

KAUST Repository

Xu, W. J.; Zhang, Bei; Liu, Z. X.; Wang, Z.; Li, W.; Wu, Z. B.; Yu, R. H.; Zhang, Xixiang

2010-01-01

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

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

Unconventional fractional quantum Hall effect in monolayer and bilayer graphene

Science.gov (United States)

Jacak, Janusz; Jacak, Lucjan

2016-01-01

The commensurability condition is applied to determine the hierarchy of fractional fillings of Landau levels in monolayer and in bilayer graphene. The filling rates for fractional quantum Hall effect (FQHE) in graphene are found in the first three Landau levels in one-to-one agreement with the experimental data. The presence of even denominator filling fractions in the hierarchy for FQHE in bilayer graphene is explained. Experimentally observed hierarchy of FQHE in the first and second Landau levels in monolayer graphene and in the zeroth Landau level in bilayer graphene is beyond the conventional composite fermion interpretation but fits to the presented nonlocal topology commensurability condition. PMID:27877866

THE MODEL OF LINGUISTIC TEACHERS’ COMPETENCY DEVELOPMENT ON DESIGNING MULTIMEDIA ELECTRONIC EDUCATIONAL RESOURCES IN THE MOODLE SYSTEM

Directory of Open Access Journals (Sweden)

Anton M. Avramchuk

2017-10-01

Full Text Available The article is devoted to the problem of developing the competency of teachers of language disciplines on designing multimedia electronic educational resources in the Moodle system. The concept of "the competence of teachers of language disciplines on designing multimedia electronic educational resources in the Moodle system" is justified and defined. Identified and characterized the components by which the levels of the competency development of teachers of language disciplines on designing multimedia electronic educational resources in the Moodle system should be assessed. Developed a model for the development of the competency of teachers of language disciplines on designing multimedia electronic educational resources in the Moodle system, which is based on the main scientific approaches, used in adult education, and consists of five blocks: target, informative, technological, diagnostic and effective.

Interfacial reaction pathways and kinetics during annealing of 111-textured Al/TiN bilayers: A synchrotron x-ray diffraction and transmission electron microscopy study

International Nuclear Information System (INIS)

Chun, J.-S.; Desjardins, P.; Lavoie, C.; Petrov, I.; Cabral, C. Jr.; Greene, J. E.

2001-01-01

Growth of TiN layers in most diffusion-barrier applications is limited to deposition temperatures T s s =450 deg. C on SiO 2 by ultrahigh vacuum reactive magnetron sputter deposition in pure N 2 . Al overlayers, 160 nm thick with inherited 111 preferred orientation, were then deposited at T s =100 deg. C without breaking vacuum. The as-deposited TiN layer is underdense due to the low deposition temperature (T s /T m ≅0.23 in which T m is the melting point) resulting in kinetically limited adatom mobilities leading to atomic shadowing which, in turn, results in a columnar microstructure with both inter- and intracolumnar voids. The Al overlayer is fully dense. Synchrotron x-ray diffraction was used to follow interfacial reaction kinetics during postdeposition annealing of the 111-textured Al/TiN bilayers as a function of time (t a =12-1200 s) and temperature (T a =440-550 deg. C). Changes in bilayer microstructure and microchemistry were investigated using transmission electron microscopy (TEM) and scanning TEM to obtain compositional maps of plan-view and cross-sectional specimens. Interfacial reaction during annealing is initiated at the Al/TiN interface. Al diffuses rapidly into TiN voids during anneals at temperatures ∼ 3 Ti at the interface. Al 3 Ti exhibits a relatively planar growth front extending toward the Al free surface. Analyses of time-dependent x-ray diffraction peak intensities during isothermal annealing as a function of temperature show that Al 3 Ti growth kinetics are, for the entire temperature range investigated, diffusion limited with an activation energy of 1.5±0.2 eV

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

We performed atomistic molecular dynamics simulations of lipid bilayers consisting of a mixture of cationic dioleoyloxytrimethylammonium propane (DOTAP) and zwitterionic dimyristoylphosphatidylcholine (DMPC) lipids at different DOTAP fractions. Our primary focus was the specific effects...... of unsaturated lipid chains on structural and dynamic properties of mixed cationic bilayers. The bilayer area, as well as the ordering of lipid tails, shows a pronounced nonmonotonic behavior when TAP lipid fraction increases. The minimum in area (maximum in ordering) was observed for a bilayer with TAP fraction...... lipids, which were found to form PC-PC and PC-TAP pairs, and the formation of lipid clusters....

Developing Humanities Collections in the Digital Age: Exploring Humanities Faculty Engagement with Electronic and Print Resources

Science.gov (United States)

Kachaluba, Sarah Buck; Brady, Jessica Evans; Critten, Jessica

2014-01-01

This article is based on quantitative and qualitative research examining humanities scholars' understandings of the advantages and disadvantages of print versus electronic information resources. It explores how humanities' faculty members at Florida State University (FSU) use print and electronic resources, as well as how they perceive these…

Influence of electron transport on the efficiency of polymer-based solar cells

Energy Technology Data Exchange (ETDEWEB)

Kuxhaus, Viktor; Jaiser, Frank; Neher, Dieter [Institute of Physics and Astronomy, University Potsdam (Germany); Voges, Frank [Merck KGaA, Darmstadt (Germany)

2010-07-01

Recently, we showed that the mobility of electrons in polymer-based solar cells has a large influence on the overall performance of such devices. Here, we investigate the correlation between electron mobility and charge generation efficiency in organic bilayer solar cells for a series of electron transporting materials (ETMs) with comparable HOMO and LUMO levels. The electron mobility was measured by transient electroluminescence. Here, a thin M3EH-PPV was used as a sensing layer. The interface between M3EH-PPV and ETM acted as a recombination zone of electrons transported through the ETM layer and holes that are blocked at the interface. Therefore, the electron mobility can easily be determined from the onset of M3EH-PPV emission which is spectrally well separated from the ETM emission. To determine the charge generation efficiency, the different ETMs were combined in bilayer solar cell with PFB as donator.

A Neutron View of Proteins in Lipid Bilayers

Science.gov (United States)

White, Stephen

2012-02-01

Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly-charged S1-S4 voltage- sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated potassium channels. We have used neutron diffraction, solid-state nuclear magnetic resonance spectroscopy, and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1-S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations, cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings reveal that voltage sensors have evolved to interact with the lipid membrane while keeping the energetic and structural perturbations to a minimum, and that water penetrates into the membrane to hydrate charged residues and shape the transmembrane electric field.

Valley-filtered edge states and quantum valley Hall effect in gated bilayer graphene.

Science.gov (United States)

Zhang, Xu-Long; Xu, Lei; Zhang, Jun

2017-05-10

Electron edge states in gated bilayer graphene in the quantum valley Hall (QVH) effect regime can carry both charge and valley currents. We show that an interlayer potential splits the zero-energy level and opens a bulk gap, yielding counter-propagating edge modes with different valleys. A rich variety of valley current states can be obtained by tuning the applied boundary potential and lead to the QVH effect, as well as to the unbalanced QVH effect. A method to individually manipulate the edge states by the boundary potentials is proposed.

The self-consistent calculation of the edge states in bilayer quantum Hall bar

International Nuclear Information System (INIS)

Kavruk, A E; Orzturk, T; Orzturk, A; Atav, U; Yuksel, H

2011-01-01

In this study, we present the spatial distributions of the edge channels for each layer in bilayer quantum Hall bar geometry for a wide range of applied magnetic fields. For this purpose, we employ a self-consistent Thomas-Fermi-Poisson approach to obtain the electron density distributions and related screened potential distributions. In order to have a more realistic description of the system we solve three dimensional Poisson equation numerically in each iteration step to obtain self consistency in the Thomas-Fermi-Poisson approach instead of employing a 'frozen gate' approximation.

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.

High power density thin film SOFCs with YSZ/GDC bilayer electrolyte

International Nuclear Information System (INIS)

Cho, Sungmee; Kim, YoungNam; Kim, Jung-Hyun; Manthiram, Arumugam; Wang Haiyan

2011-01-01

Graphical abstract: . A: Cross-sectional TEM images show a GDC single layer and YSZ/GDC bilayer electrolyte structures. As clearly observed from TEM images, the YSZ interlayer thickness varies from ∼330 nm to ∼1 μm. B: The cell with the bilayer electrolyte (YSZ ∼330 nm) doubles the overall power output at 750 deg. C compared to that achieved in the GDC single layer cell. Display Omitted Highlights: → YSZ/ GDC bilayer thin film electrolytes were deposited by a pulsed laser deposition (PLD) technique. → Thin YSZ film as a blocking layer effectively suppresses the cell voltage drop without reducing the ionic conductivity of the electrolyte layer. → The YSZ/ GDC bilayer structure presents a feasible architecture for enhancing the overall power density and enabling chemical, mechanical, and structural stability in the cells. - Abstract: Bilayer electrolytes composed of a gadolinium-doped CeO 2 (GDC) layer (∼6 μm thickness) and an yttria-stabilized ZrO 2 (YSZ) layer with various thicknesses (∼330 nm, ∼440 nm, and ∼1 μm) were deposited by a pulsed laser deposition (PLD) technique for thin film solid oxide fuel cells (TFSOFCs). The bilayer electrolytes were prepared between a NiO-YSZ (60:40 wt.% with 7.5 wt.% carbon) anode and La 0.5 Sr 0.5 CoO 3 -Ce 0.9 Gd 0.1 O 1.95 (50:50 wt.%) composite cathode for anode-supported single cells. Significantly enhanced maximum power density was achieved, i.e., a maximum power density of 188, 430, and 587 mW cm -2 was measured in a bilayer electrolyte single cell with ∼330 nm thin YSZ at 650, 700, and 750 deg. C, respectively. The cell with the bilayer electrolyte (YSZ ∼330 nm) doubles the overall power output at 750 deg. C compared to that achieved in the GDC single layer cell. This signifies that the YSZ thin film serves as a blocking layer for preventing electrical current leakage in the GDC layer and also provides chemical, mechanical, and structural integrity in the cell, which leads to the overall enhanced

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.

Development of a highly efficient conversion electron Moessbauer spectroscopy (CEMS) detector for low temperature (xPb1-x)Te bilayers

International Nuclear Information System (INIS)

Pombo, Carlos Jose da Silva Matos

2006-01-01

The 57 Fe Moessbauer spectroscopy is a nuclear, non-destructive technique used for the investigation of structural, magnetic and hyperfine properties of several materials. It is a powerful tool in characterizing materials in physics, metallurgy, geology and biology field areas, especially magnetic materials, alloys and minerals containing Fe. Lately, the Conversion Electron Moessbauer Spectroscopy (CEMS) is widely used in making studies on ultra-thin magnetic films, as well as other nanostructured materials. In case of magnetic nanostructures, low temperature (LT) studies are especially important due to the possibility of dealing with superparamagnetic effects. In this work it was developed a CEMS measurement system for low temperatures ( R ) and an optical cryostat (Model SVT-400, Janis Research Co, USA), from which the project was originally conceived at the Applied Physics / Moessbauer spectroscopy Department from University of Duisburg-Essen, Germany. The LT-CEMS system was fully built, tested and successfully applied in a preliminary characterization of Fe/(Eu x Pb 1-x )Te(111) bilayers with use of a 15 angstrom, 57 Fe probe layer, with reasonable results at sample temperatures as low as 8 K. (author)

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...

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.

Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

International Nuclear Information System (INIS)

Semuk, E.Yu.; Berzhansky, V.N.; Prokopov, A.R.; Shaposhnikov, A.N.; Karavainikov, A.V.; Salyuk, O.Yu.; Golub, V.O.

2015-01-01

Magnetic properties of Bi 1.5 Gd 1.5 Fe 4.5 Al 0.5 O 12 (84 nm) and Bi 2.8 Y 0.2 Fe 5 O 12 (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi 1.5 Gd 1.5 Fe 4.5 Al 0.5 O 12 /Bi 2.8 Y 0.2 Fe 5 O 12 bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction. - Highlights: • Magnetic parameters of epitaxial Bi-YIG films and bilayers on GGG substrate. • Adaptive layers affect on high order magnetic anisotropy. • Magnetic properties of bilayers are result of strong exchange interaction

Electrical resistivity of monolayers and bilayers of alkanethiols in tunnel junction with gate electrode

International Nuclear Information System (INIS)

York, Roger L.; Nacionales, David; Slowinski, Krzysztof

2005-01-01

The tunneling resistances of monolayers and bilayers of n-alkanethiols in macroscopic Hg-Hg junctions with an electrochemical gate are reported. The resistances near zero bias calculated per 1 hydrocarbon chain vary from (5 ± 4) x 10 12 Ω for n-nonanethiol to (4 ± 2) x 10 16 Ω for n-octadecanethiol. These values indicate that monolayers of hydrocarbons in Hg-Hg junctions are substantially more resistive as compared to measurements employing microscopic tunnel junctions. The tunneling resistances of monolayer junctions are approximately 1 order of magnitude larger than those of bilayer junctions containing the same number of atoms indicating inefficient electronic coupling across the non-bonded -CH 3 |Hg interface. The symmetric current-voltage curves observed for the asymmetric junctions of Hg-S-(CH 2 ) n -CH 3 |Hg type suggest that these junctions do not behave as molecular diodes. Additional experimental evidence for the nature of the -CH 3 |Hg interface in the Hg-S-(CH 2 ) n -CH 3 |Hg junction is also presented

Direct transfer and Raman characterization of twisted graphene bilayer

International Nuclear Information System (INIS)

Othmen, R.; Arezki, H.; Boutchich, M.; Ajlani, H.; Oueslati, M.; Cavanna, A.; Madouri, A.

2015-01-01

Twisted bilayer graphene (tBLG) is constituted of a two-graphene layer with a mismatch angle θ between the two hexagonal structures. It has recently attracted much attention—thanks to its diverse electronic and optical properties. Here, we study the tBLG fabricated by the direct transfer of graphene monolayer prepared by chemical vapor deposition (CVD) onto another CVD graphene layer remaining attached to the copper foil. We show that high quality and homogeneous tBLG can be obtained by the direct transfer which prevents interface contamination. In this situation, the top graphene layer plays a supporting mechanical role to the bottom graphene layer as confirmed by optical microscopy, scanning electron microscopy, and Raman spectroscopy measurements. The effect of annealing tBLG was also investigated using micro-Raman spectroscopy. The Raman spectra exhibit a splitting of the G peak as well as a change in the 2D band shape indicating a possible decoupling of the two monolayers. We attribute these changes to the different interactions of the top and bottom layers with the substrate

Bilayer lift-off process for aluminum metallization

Science.gov (United States)

Wilson, Thomas E.; Korolev, Konstantin A.; Crow, Nathaniel A.

2015-01-01

Recently published reports in the literature for bilayer lift-off processes have described recipes for the patterning of metals that have recommended metal-ion-free developers, which do etch aluminum. We report the first measurement of the dissolution rate of a commercial lift-off resist (LOR) in a sodium-based buffered commercial developer that does not etch aluminum. We describe a reliable lift-off recipe that is safe for multiple process steps in patterning thin (recipe consists of an acid cleaning of the substrate, the bilayer (positive photoresist/LOR) deposition and development, the sputtering of the aluminum film along with a palladium capping layer and finally, the lift-off of the metal film by immersion in the LOR solvent. The insertion into the recipe of postexposure and sequential develop-bake-develop process steps are necessary for an acceptable undercut. Our recipe also eliminates any need for accompanying sonication during lift-off that could lead to delamination of the metal pattern from the substrate. Fine patterns were achieved for both 100-nm-thick granular aluminum/palladium bilayer bolometers and 500-nm-thick aluminum gratings with 6-μm lines and 4-μm spaces.

Lipid bilayers suspended on microfabricated supports

Science.gov (United States)

Ogier, Simon D.; Bushby, Richard J.; Cheng, Yaling; Cox, Tim I.; Evans, Stephen D.; Knowles, Peter F.; Miles, Robert E.; Pattison, Ian

2001-03-01

The plasma membrane, that exists as part of many animal and plant cells, is a regulator for the transport of ions and small molecules across cell boundaries. Two main components involved are the phospholipid bilayer and the transport proteins. This paper details the construction of a micromachined support for bilayers (MSB) as a first step towards the development of highly selective and highly sensitive ion-channel based biosensors. The device consists of a ~100 micrometer hole in a polymeric support above a cavity that can hold ~25 nL of electrolyte. Electrodes attached to the structure allow the resistance of the membranes to be measured using d.c. conductivity. The MSB is made in two halves, using SU8 ultra-thick resist, which are subsequently bonded together to make the final structure. A layer of gold, surrounding the aperture, enables self-assembled monolayers of alkanethiols to be used to make the polymeric structure biocompatible. Lipid membranes have been formed over these holes with resistances comparable with those of natural membranes >10 MOhmcm^2. The ion-channel gramicidin has successfully been incorporated into the bilayer and its activity monitored. It is proposed that this type of device could be used not only for studying membrane transport phenomena but also as part of an ion-channel based biosensor.

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

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...... with a protein conformational change. This type of regulation is well characterized, and its mechanistic elucidation is an interdisciplinary field bordering on physics, chemistry and biology. Changes in lipid composition that alter bilayer physical properties (including cholesterol, polyunsaturated fatty acids...... channels as molecular force probes for studying this mechanism, with a unique ability to discriminate between consequences of changes in monolayer curvature and bilayer elastic moduli....

Scattering Studies of Hydrophobic Monomers in Liposomal Bilayers: An Expanding Shell Model of Monomer Distribution

International Nuclear Information System (INIS)

Richter, Andrew; Dergunov, Sergey; Ganus, Bill; Thomas, Zachary; Pingali, Sai Venkatesh; Urban, Volker S.; Liu, Yun; Porcar, Lionel; Pinkhassik, Eugene

2011-01-01

Hydrophobic monomers partially phase separate from saturated lipids when loaded into lipid bilayers in amounts exceeding a 1:1 monomer/lipid molar ratio. This conclusion is based on the agreement between two independent methods of examining the structure of monomer-loaded bilayers. Complete phase separation of monomers from lipids would result in an increase in bilayer thickness and a slight increase in the diameter of liposomes. A homogeneous distribution of monomers within the bilayer would not change the bilayer thickness and would lead to an increase in the liposome diameter. The increase in bilayer thickness, measured by the combination of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS), was approximately half of what was predicted for complete phase separation. The increase in liposome diameter, measured by dynamic light scattering (DLS), was intermediate between values predicted for a homogeneous distribution and complete phase separation. Combined SANS, SAXS, and DLS data suggest that at a 1.2 monomer/lipid ratio approximately half of the monomers are located in an interstitial layer sandwiched between lipid sheets. These results expand our understanding of using self-assembled bilayers as scaffolds for the directed covalent assembly of organic nanomaterials. In particular, the partial phase separation of monomers from lipids corroborates the successful creation of nanothin polymer materials with uniform imprinted nanopores. Pore-forming templates do not need to span the lipid bilayer to create a pore in the bilayer-templated films.

Vacuum-assisted bilayer PEDOT:PSS/cellulose nanofiber composite film for self-standing, flexible, conductive electrodes.

Science.gov (United States)

Ko, Youngsang; Kim, Dabum; Kim, Ung-Jin; You, Jungmok

2017-10-01

Sustainable cellulose nanofiber (CNF)-based composites as functional conductive materials have garnered considerable attention recently for their use in soft electronic devices. In this work, self-standing, highly flexible, and conductive PEDOT:PSS-CNF composite films were developed using a simple vacuum-assisted filtration method. Two different composite films were successfully fabricated and then tested: 1) a single-layer composite composed of a mixture of PEDOT:PSS and CNF phases and 2) a bilayer composite composed of an upper PEDOT:PSS membrane layer and a CNF matrix sub-layer. The latter composite was constructed by electrostatic/hydrogen bonding interactions between PEDOT:PSS and CNFs coupled with sequential vacuum-assisted filtration. Our results demonstrated that the resultant bilayer composite film exhibited a competitive electrical conductivity (ca. 22.6Scm -1 ) compared to those of previously reported cellulose-based composites. Furthermore, decreases in the electrical properties were not observed in the composite films when they were bent up to 100 times at an angle of 180° and bent multiple times at an angle of 90°, clearly demonstrating their excellent mechanical flexibility. This study provides a straightforward method of fabricating highly flexible, lightweight, and conductive films, which have the potential to be used in high-performance soft electronic systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electronic resource management systems a workflow approach

CERN Document Server

Anderson, Elsa K

2014-01-01

To get to the bottom of a successful approach to Electronic Resource Management (ERM), Anderson interviewed staff at 11 institutions about their ERM implementations. Among her conclusions, presented in this issue of Library Technology Reports, is that grasping the intricacies of your workflow-analyzing each step to reveal the gaps and problems-at the beginning is crucial to selecting and implementing an ERM. Whether the system will be used to fill a gap, aggregate critical data, or replace a tedious manual process, the best solution for your library depends on factors such as your current soft

Assessment of field-induced quantum confinement in heterogate germanium electron–hole bilayer tunnel field-effect transistor

International Nuclear Information System (INIS)

Padilla, J. L.; Alper, C.; Ionescu, A. M.; Gámiz, F.

2014-01-01

The analysis of quantum mechanical confinement in recent germanium electron–hole bilayer tunnel field-effect transistors has been shown to substantially affect the band-to-band tunneling (BTBT) mechanism between electron and hole inversion layers that constitutes the operating principle of these devices. The vertical electric field that appears across the intrinsic semiconductor to give rise to the bilayer configuration makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, therefore increasing the effective bandgap close to the gates and reducing the BTBT probabilities. In this letter, we present a simulation approach that shows how the inclusion of quantum confinement and the subsequent modification of the band profile results in the appearance of lateral tunneling to the underlap regions that greatly degrades the subthreshold swing of these devices. To overcome this drawback imposed by confinement, we propose an heterogate configuration that proves to suppress this parasitic tunneling and enhances the device performance.

Assessment of field-induced quantum confinement in heterogate germanium electron–hole bilayer tunnel field-effect transistor

Energy Technology Data Exchange (ETDEWEB)

Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M. [Nanoelectronic Devices Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015 (Switzerland); Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

2014-08-25

The analysis of quantum mechanical confinement in recent germanium electron–hole bilayer tunnel field-effect transistors has been shown to substantially affect the band-to-band tunneling (BTBT) mechanism between electron and hole inversion layers that constitutes the operating principle of these devices. The vertical electric field that appears across the intrinsic semiconductor to give rise to the bilayer configuration makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, therefore increasing the effective bandgap close to the gates and reducing the BTBT probabilities. In this letter, we present a simulation approach that shows how the inclusion of quantum confinement and the subsequent modification of the band profile results in the appearance of lateral tunneling to the underlap regions that greatly degrades the subthreshold swing of these devices. To overcome this drawback imposed by confinement, we propose an heterogate configuration that proves to suppress this parasitic tunneling and enhances the device performance.

Electronic Resource Management System. Vernetzung von Lizenzinformationen

Directory of Open Access Journals (Sweden)

Michaela Selbach

2014-12-01

Full Text Available In den letzten zehn Jahren spielen elektronische Ressourcen im Bereich der Erwerbung eine zunehmend wichtige Rolle: Eindeutig lässt sich hier ein Wandel in den Bibliotheken (fort vom reinen Printbestand zu immer größeren E-Only-Beständen feststellen. Die stetig wachsende Menge an E-Ressourcen und deren Heterogenität stellt Bibliotheken vor die Herausforderung, die E-Ressourcen effizient zu verwalten. Nicht nur Bibliotheken, sondern auch verhandlungsführende Institutionen von Konsortial- und Allianzlizenzen benötigen ein geeignetes Instrument zur Verwaltung von Lizenzinformationen, welches den komplexen Anforderungen moderner E-Ressourcen gerecht wird. Die Deutsche Forschungsgemeinschaft (DFG unterstützt ein Projekt des Hochschulbibliothekszentrums des Landes Nordrhein-Westfalen (hbz, der Universitätsbibliothek Freiburg, der Verbundzentrale des Gemeinsamen Bibliotheksverbundes (GBV und der Universitätsbibliothek Frankfurt, in dem ein bundesweit verfügbares Electronic Ressource Managementsystem (ERMS aufgebaut werden soll. Ein solches ERMS soll auf Basis einer zentralen Knowledge Base eine einheitliche Nutzung von Daten zur Lizenzverwaltung elektronischer Ressourcen auf lokaler, regionaler und nationaler Ebene ermöglichen. Statistische Auswertungen, Rechteverwaltung für alle angeschlossenen Bibliotheken, kooperative Datenpflege sowie ein über standardisierte Schnittstellen geführter Datenaustausch stehen bei der Erarbeitung der Anforderungen ebenso im Fokus wie die Entwicklung eines Daten- und Funktionsmodells. In the last few years the importance of electronic resources in library acquisitions has increased significantly. There has been a shift from mere print holdings to both e- and print combinations and even e-only subscriptions. This shift poses a double challenge for libraries: On the one hand they have to provide their e-resource collections to library users in an appealing way, on the other hand they have to manage these

Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene

Directory of Open Access Journals (Sweden)

Bing Huang

2014-05-01

Full Text Available Silicon is arguably the best electronic material, but it is not a good optoelectronic material. By employing first-principles calculations and the cluster-expansion approach, we discover that hydrogenated bilayer silicene (BS shows promising potential as a new kind of optoelectronic material. Most significantly, hydrogenation converts the intrinsic BS, a strongly indirect semiconductor, into a direct-gap semiconductor with a widely tunable band gap. At low hydrogen concentrations, four ground states of single- and double-sided hydrogenated BS are characterized by dipole-allowed direct (or quasidirect band gaps in the desirable range from 1 to 1.5 eV, suitable for solar applications. At high hydrogen concentrations, three well-ordered double-sided hydrogenated BS structures exhibit direct (or quasidirect band gaps in the color range of red, green, and blue, affording white light-emitting diodes. Our findings open opportunities to search for new silicon-based light-absorption and light-emitting materials for earth-abundant, high-efficiency, optoelectronic applications.

The Electron Microscopy Outreach Program: A Web-based resource for research and education.

Science.gov (United States)

Sosinsky, G E; Baker, T S; Hand, G; Ellisman, M H

1999-01-01

We have developed a centralized World Wide Web (WWW)-based environment that serves as a resource of software tools and expertise for biological electron microscopy. A major focus is molecular electron microscopy, but the site also includes information and links on structural biology at all levels of resolution. This site serves to help integrate or link structural biology techniques in accordance with user needs. The WWW site, called the Electron Microscopy (EM) Outreach Program (URL: http://emoutreach.sdsc.edu), provides scientists with computational and educational tools for their research and edification. In particular, we have set up a centralized resource containing course notes, references, and links to image analysis and three-dimensional reconstruction software for investigators wanting to learn about EM techniques either within or outside of their fields of expertise. Copyright 1999 Academic Press.

Surface electron structure of short-period semiconductor superlattice

International Nuclear Information System (INIS)

Bartos, I.; Czech Academy Science, Prague,; Strasser, T.; Schattke, W.

2004-01-01

Full text: Semiconductor superlattices represent man-made crystals with unique physical properties. By means of the directed layer-by-layer molecular epitaxy growth their electric properties can be tailored (band structure engineering). Longer translational periodicity in the growth direction is responsible for opening of new electron energy gaps (minigaps) with surface states and resonances localized at superlattice surfaces. Similarly as for the electron structure of the bulk, a procedure enabling to modify the surface electron structure of superlattices is desirable. Short-period superlattice (GaAs) 2 (AlAs) 2 with unreconstructed (100) surface is investigated in detail. Theoretical description in terms of full eigenfunctions of individual components has to be used. The changes of electron surface state energies governed by the termination of a periodic crystalline potential, predicted on simple models, are confirmed for this system. Large surface state shifts are found in the lowest minigap of the superlattice when this is terminated in four different topmost layer configurations. The changes should be observable in angle resolved photoelectron spectroscopy as demonstrated in calculations based on the one step model of photoemission. Surface state in the center of the two dimensional Brillouin zone moves from the bottom of the minigap (for the superlattice terminated by two bilayers of GaAs) to its top (for the superlattice terminated by two bilayers of AlAs) where it becomes a resonance. No surface state/resonance is found for a termination with one bilayer of AlAs. The surface state bands behave similarly in the corresponding gaps of the k-resolved section of the electron band structure. The molecular beam epitaxy, which enables to terminate the superlattice growth with atomic layer precision, provides a way of tuning the superlattice surface electron structure by purely geometrical means. The work was supported by the Grant Agency of the Academy of Sciences

Technical Communicator: A New Model for the Electronic Resources Librarian?

Science.gov (United States)

Hulseberg, Anna

2016-01-01

This article explores whether technical communicator is a useful model for electronic resources (ER) librarians. The fields of ER librarianship and technical communication (TC) originated and continue to develop in relation to evolving technologies. A review of the literature reveals four common themes for ER librarianship and TC. While the…

Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers

DEFF Research Database (Denmark)

Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.

2003-01-01

Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...... ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating...

Small-angle neutron scattering from multilamellar lipid bilayers: Theory, model, and experiment

DEFF Research Database (Denmark)

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

1996-01-01

Small-angle neutron scattering data obtained from fully hydrated, multilamellar phospholipid bilayers with deuterated acyl chains of different length are presented and analyzed within a paracrystalline theory and a geometric model that permit the bilayer structure to be determined under conditions...... of temperature for the lamellar repeat distance, the hydrophobic bilayer thickness, as well as the thickness of the aqueous and polar head group region. In addition to these geometric parameters the analysis permits determination of molecular cross-sectional area, number of interlamellar water molecules, as well...

Interaction of Melittin with Negatively Charged Lipid Bilayers Supported on Gold Electrodes

International Nuclear Information System (INIS)

Juhaniewicz, Joanna; Sek, Slawomir

2016-01-01

ABSTRACT: The interactions of melittin, a cationic antimicrobial peptide, with model lipid membranes consisting of negatively charged phospholipids: 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) or 1,2-dimyristoyl-sn-glycero-3-phosphoserine (DMPS) were investigated using electrochemical techniques and atomic force microscopy. Lipid bilayers were deposited on gold electrodes using a combination of Langmuir-Blodgett and Langmuir-Schaefer methods and the resulting membranes established a barrier for electron transfer between the electrode and the redox probe in the solution. After exposure to melittin, the blocking properties of the membranes were monitored using cyclic voltammetry and electrochemical impedance spectroscopy. It was observed that after treatment with peptide, the charge transfer through lipid bilayer is initially strongly inhibited. However, after longer exposure to melittin, the structure of the lipid film becomes less compact and the electrode reactions are facilitated due to the presence of numerous defect sites exposing bare substrate. We have assumed that such behavior reflects initial adsorption of melittin on top of the membrane and its further insertion which leads to formation of the pores or partial micellization of the lipid film. AFM imaging revealed that the exposure to 10 μM melittin solution induces significant structural changes in DMPG and DMPS membranes. However, melittin seems to affect their organization in a different manner. DMPG film appears to be more susceptible to peptide action compared with DMPS bilayer. In the latter case, long-time exposure to melittin does not result in the rupture of the membrane but rather leads to formation of pore-like defects. This observation is explained in terms of different nanomechanical properties of DMPG and DMPS films and different barrier for the reorientation and insertion of the peptide molecules into the membranes.

Morphological evolution in dewetting polystyrene/polyhedral oligomeric silsesquioxane thin film bilayers.

Science.gov (United States)

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

2008-05-06

Morphological evolution in dewetting thin film bilayers of polystyrene (PS) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP), was studied as a function of annealing temperature and annealing time. The results demonstrate unique dewetting morphologies in PS/TPP bilayers at elevated temperatures that are significantly different from those typically observed in dewetting polymer/polymer bilayers. During temperature ramp studies by optical microscopy (OM) in the reflection mode, PS/TPP bilayers form cracks with a weak optical contrast at approximately 130 degrees C. The crack formation is attributed to tensile stresses within the upper TPP layer. The weak optical contrast of the cracks observed in the bilayers for annealing temperatures below approximately 160 degrees C is consistent with the cracking and dewetting of only the upper TPP layer from the underlying PS layer. The optical contrast of the morphological features is significantly enhanced at annealing temperatures of >160 degrees C. This observation suggests dewetting of both the upper TPP and the lower PS layers that results in the exposure of the silicon substrate. Upon annealing the PS/TPP bilayers at 200 degrees C in a temperature jump experiment, the upper TPP layer undergoes instantaneous cracking as observed by OM. These cracks in the upper TPP layer serve as nucleation sites for rapid dewetting and aggregation of the TPP layer, as revealed by OM and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) results indicated that dewetting of the lower PS layer ensued for annealing times >5 min and progressed up to 90 min. For annealing times >90 min, OM, AFM, and XPS results revealed complete dewetting of both the layers with the formation of TPP encapsulated PS droplets.

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

International Nuclear Information System (INIS)

Lopez, M.C.; Espinos, J.P.; Leinen, D.; Martin, F.; Centeno, S.P.; Romero, R.; Ramos-Barrado, J.R.

2008-01-01

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.

Effect of Membrane Tension on the Electric Field and Dipole Potential of Lipid Bilayer Membrane

Science.gov (United States)

Warshaviak, Dora Toledo; Muellner, Michael J.; Chachisvilis, Mirianas

2011-01-01

The dipole potential of lipid bilayer membrane controls the difference in permeability of the membrane to oppositely charged ions. We have combined molecular dynamics (MD) simulations and experimental studies to determine changes in electric field and electrostatic potential of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid bilayer in response to applied membrane tension. MD simulations based on CHARMM36 force field showed that electrostatic potential of DOPC bilayer decreases by ~45 mV in the physiologically relevant range of membrane tension values (0 to 15 dyn/cm). The electrostatic field exhibits a peak (~0.8×109 V/m) near the water/lipid interface which shifts by 0.9 Å towards the bilayer center at 15 dyn/cm. Maximum membrane tension of 15 dyn/cm caused 6.4% increase in area per lipid, 4.7% decrease in bilayer thickness and 1.4% increase in the volume of the bilayer. Dipole-potential sensitive fluorescent probes were used to detect membrane tension induced changes in DOPC vesicles exposed to osmotic stress. Experiments confirmed that dipole potential of DOPC bilayer decreases at higher membrane tensions. These results are suggestive of a potentially new mechanosensing mechanism by which mechanically induced structural changes in the lipid bilayer membrane could modulate the function of membrane proteins by altering electrostatic interactions and energetics of protein conformational states. PMID:21722624

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.

Neutron diffraction studies of amphipathic helices in phospholipid bilayers

International Nuclear Information System (INIS)

Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

1994-01-01

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

Supramolecular protein immobilization on lipid bilayers

NARCIS (Netherlands)

Bosmans, R.P.G.; Hendriksen, W.E.; Verheijden, Mark Lloyd; Eelkema, R.; Jonkheijm, Pascal; van Esch, J.H.; Brunsveld, Luc

2015-01-01

Protein immobilization on surfaces, and on lipid bilayers specifically, has great potential in biomolecular and biotechnological research. Of current special interest is the immobilization of proteins using supramolecular noncovalent interactions. This allows for a reversible immobilization and

Transport in bilayer and trilayer graphene: band gap engineering and band structure tuning

Science.gov (United States)

Zhu, Jun

2014-03-01

Controlling the stacking order of atomically thin 2D materials offers a powerful tool to control their properties. Linearly dispersed bands become hyperbolic in Bernal (AB) stacked bilayer graphene (BLG). Both Bernal (ABA) and rhombohedral (ABC) stacking occur in trilayer graphene (TLG), producing distinct band structures and electronic properties. A symmetry-breaking electric field perpendicular to the sample plane can further modify the band structures of BLG and TLG. In this talk, I will describe our experimental effort in these directions using dual-gated devices. Using thin HfO2 film deposited by ALD as gate dielectric, we are able to apply large displacement fields D > 6 V/nm and observe the opening and saturation of the field-induced band gap Eg in bilayer and ABC-stacked trilayer graphene, where the conduction in the mid gap changes by more than six decades. Its field and temperature dependence highlights the crucial role played by Coulomb disorder in facilitating hopping conduction and suppressing the effect of Eg in the tens of meV regime. In contrast, mid-gap conduction decreases with increasing D much more rapidly in clean h-BN dual-gated devices. Our studies also show the evolution of the band structure in ABA-stacked TLG, in particular the splitting of the Dirac-like bands in large D field and the signatures of two-band transport at high carrier densities. Comparison to theory reveals the need for more sophisticated treatment of electronic screening beyond self-consistent Hartree calculations to accurately predict the band structures of trilayer graphene and graphenic materials in general.

Tunable resistive switching behaviour in ferroelectric–ZnO bilayer films

International Nuclear Information System (INIS)

Zhou Mingxiu; Li Ziwei; Chen Bo; Wan Jianguo; Liu Junming

2013-01-01

Pb(Zr 0.52 Ti 0.48 )O 3 /ZnO bilayer films with various ZnO-layer thicknesses were prepared by a sol–gel process, and their phase structures, electric conduction and polarization behaviour were measured. The results showed that the preferential crystal orientation of the ZnO layer changed with a change in its thickness. The strong dependence of both asymmetric current–voltage and polarization–voltage characteristics on the ZnO-layer thickness was observed. The resistance ratio of the high-resistance state (HRS) to the low-resistance state (LRS) increased with increasing ZnO-layer thickness, and a high rectification ratio was obtained in the bilayer film with an optimized ZnO-layer thickness. The combined effects of interface polarization coupling and energy band structure on the resistive switching behaviour of the bilayer films were revealed, and the electric conduction mechanisms of the bilayer films at both HRS and LRS were analysed in detail. This work presents an effective method to modulate the resistive switching behaviour of ferroelectric–ZnO heterostructures, which is significant in designing high-performance ferroelectric–semiconductor heterostructures for actual applications. (paper)

Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

Energy Technology Data Exchange (ETDEWEB)

Semuk, E.Yu.; Berzhansky, V.N.; Prokopov, A.R.; Shaposhnikov, A.N.; Karavainikov, A.V. [Taurida National V.I. Vernadsky University, Vernadsky Avenue, 4, 95007 Simferopol (Ukraine); Salyuk, O.Yu. [Institute of Magnetism NASU and MESU, 36-B Vernadsky Blvd., 03142 Kiev (Ukraine); Golub, V.O., E-mail: golub@imag.kiev.ua [Institute of Magnetism NASU and MESU, 36-B Vernadsky Blvd., 03142 Kiev (Ukraine)

2015-11-15

Magnetic properties of Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12} (84 nm) and Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12}/Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction. - Highlights: • Magnetic parameters of epitaxial Bi-YIG films and bilayers on GGG substrate. • Adaptive layers affect on high order magnetic anisotropy. • Magnetic properties of bilayers are result of strong exchange interaction.

Bilayer expurgated LDPC codes with uncoded relaying

Directory of Open Access Journals (Sweden)

Md. Noor-A-Rahim

2017-08-01

Full Text Available Bilayer low-density parity-check (LDPC codes are an effective coding technique for decode-and-forward relaying, where the relay forwards extra parity bits to help the destination to decode the source bits correctly. In the existing bilayer coding scheme, these parity bits are protected by an error correcting code and assumed reliably available at the receiver. We propose an uncoded relaying scheme, where the extra parity bits are forwarded to the destination without any protection. Through density evolution analysis and simulation results, we show that our proposed scheme achieves better performance in terms of bit erasure probability than the existing relaying scheme. In addition, our proposed scheme results in lower complexity at the relay.

Exchange bias in diluted-antiferromagnet/antiferromagnet bilayers

International Nuclear Information System (INIS)

Mao, Zhongquan; Zhan, Xiaozhi; Chen, Xi

2015-01-01

The hysteresis-loop properties of a diluted-antiferromagnetic (DAF) layer exchange coupling to an antiferromagnetic (AF) layer are investigated by means of numerical simulations. Remarkable loop shift and coercivity enhancement are observed in such DAF/AF bilayers, while they are absent in the uncoupled DAF single layer. The influences of pinned domains, dilution, cooling field and DAF layer thickness on the loop shift are investigated systematically. The result unambiguously confirms an exchange bias (EB) effect in the DAF/AF bilayers. It also reveals that the EB effect originates from the pinned AF domains within the DAF layer. In contrast to conventional EB systems, frozen uncompensated spins are not found at the interface of the AF pinning layer. (paper)

Doping efficiency of single and randomly stacked bilayer graphene by iodine adsorption

Energy Technology Data Exchange (ETDEWEB)

Kim, HoKwon; Renault, Olivier; Rouchon, Denis; Mariolle, Denis; Chevalier, Nicolas [Univ. Grenoble Alpes, F-38000 Grenoble, France and CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Tyurnina, Anastasia; Simonato, Jean-Pierre; Dijon, Jean [Univ. Grenoble Alpes, F-38000 Grenoble, France and CEA, LITEN, Minatec Campus, F-38054 Grenoble (France)

2014-07-07

We report on the efficiency and thermal stability of p-doping by iodine on single and randomly stacked, weakly coupled bilayer polycrystalline graphene, as directly measured by photoelectron emission microscopy. The doping results in work function value increase of 0.4–0.5 eV, with a higher degree of iodine uptake by the bilayer (2%) as compared to the single layer (1%) suggesting iodine intercalation in the bilayer. The chemistry of iodine is identified accordingly as I{sub 3}{sup −} and I{sub 5}{sup −} poly iodide anionic complexes with slightly higher concentration of I{sub 5}{sup −} in bilayer than monolayer graphene, likely attributed to differences in doping mechanisms. Temperature dependent in-situ annealing of the doped films demonstrated that the doping remains efficient up to 200 °C.

Coexistence of a two-states organization for a cell-penetrating peptide in lipid bilayer.

Science.gov (United States)

Plénat, Thomas; Boichot, Sylvie; Dosset, Patrice; Milhiet, Pierre-Emmanuel; Le Grimellec, Christian

2005-12-01

Primary amphipathic cell-penetrating peptides transport cargoes across cell membranes with high efficiency and low lytic activity. These primary amphipathic peptides were previously shown to form aggregates or supramolecular structures in mixed lipid-peptide monolayers, but their behavior in lipid bilayers remains to be characterized. Using atomic force microscopy, we have examined the interactions of P(alpha), a primary amphipathic cell-penetrating peptide which remains alpha-helical whatever the environment, with dipalmitoylphosphatidylcholine (DPPC) bilayers. Addition of P(alpha) at concentrations up to 5 mol % markedly modified the supported bilayers topography. Long and thin filaments lying flat at the membrane surface coexisted with deeply embedded peptides which induced a local thinning of the bilayer. On the other hand, addition of P(alpha) only exerted very limited effects on the corresponding liposome's bilayer physical state, as estimated from differential scanning calorimetry and diphenylhexatriene fluorescence anisotropy experiments. The use of a gel-fluid phase separated supported bilayers made of a dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine mixture confirmed both the existence of long filaments, which at low peptide concentration were preferentially localized in the fluid phase domains and the membrane disorganizing effects of 5 mol % P(alpha). The simultaneous two-states organization of P(alpha), at the membrane surface and deeply embedded in the bilayer, may be involved in the transmembrane carrier function of this primary amphipathic peptide.

Subterahertz Longitudinal Phonon Modes Propagating in a Lipid Bilayer Immersed in an Aqueous Medium

Science.gov (United States)

Zakhvataev, V. E.

2018-04-01

The properties of subterahertz longitudinal acoustic phonon modes in the hydrophobic region of a lipid bilayer immersed in a compressible viscous aqueous medium are investigated theoretically. An approximate expression is obtained for the Mandelstam-Brillouin components of the dynamic structure factor of a bilayer. The analysis is based on a generalized hydrodynamic model of the "two-dimensional lipid bilayer + three-dimensional fluid medium" system, as well as on known sharp estimates for the frequencies and lifetimes of long-wavelength longitudinal acoustic phonons in a free hydrated lipid bilayer and in water, obtained from inelastic X-ray scattering experiments and molecular dynamics simulations. It is shown that, for characteristic values of the parameters of the membrane system, subterahertz longitudinal phonon-like excitations in the hydrophobic part of the bilayer are underdamped. In this case, the contribution of the viscous flow of the aqueous medium to the damping of a longitudinal membrane mode is small compared with the contribution of the lipid bilayer. Quantitative estimates of the damping ratio agree well with the experimental results for the vibration mode of the enzyme lysozyme in aqueous solution [1]. It is also shown that a coupling between longitudinal phonon modes of the bilayer and relaxation processes in its fluid environment gives rise to an additional peak in the scattering spectrum, which corresponds to a non-propagating mode.

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.

Surface and grain boundary interdiffusion in nanometer-scale LSMO/BFO bilayer

Energy Technology Data Exchange (ETDEWEB)

Kumar, Virendra [Department of Physics, National Institute of Technology, Kurukshetra 136119 (India); Gaur, Anurag, E-mail: anuragdph@gmail.com [Department of Physics, National Institute of Technology, Kurukshetra 136119 (India); Choudhary, R.J.; Gupta, Mukul [UGC-DAE Consortium for Scientific Research, Indore 452 001 (India)

2016-05-01

Epitaxial 150 nm thick LSMO/BFO bilayer is deposited on STO (100) substrate by pulsed laser deposition, to study magnetoelectric effect. Unexpected low value of room temperature magnetization in bilayer indicates towards the possibility of interdiffusion. Further, sharp fall in the value of T{sub C} (53 K) also added our anxiety towards possible interdiffusion in BFO/LSMO system. Low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena, and the temperature-dependent interdiffusivity is obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. It has been found that the diffusivity at different temperatures follows Arrhenius-type behavior. X-ray reflection (XRR) pattern obtained for the bilayer could not be fitted in the Parratt’s formalism, which confirms the interdiffusion in it. Depth profiles of {sup 209}Bi, {sup 56}Fe ions measured by secondary ion mass spectroscope (SIMS) further substantiate the diffusion of these ions from upper BFO layer into lower LSMO layer. - Highlights: • The LSMO/BFO bilayer is deposited by PLD method. • Structural, magnetic and interfacial properties of deposited films were studied. • In this article, we have raised the problem of interdiffusion in this bilayer, which can hinder its application in devices. Therefore, we feel that our article presents important finding in the area of ceramics research.

Controlling the alloy composition of PtNi nanocrystals using solid-state dewetting of bilayer films

Energy Technology Data Exchange (ETDEWEB)

Seo, Okkyun; Oh, Se An; Lee, Ji Yeon; Ha, Sung Soo; Kim, Jae Myung; Choi, Jung Won; Kim, Jin-Woo [Department of Physics and Photon Science & School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005 (Korea, Republic of); Kang, Hyon Chol [Department of Materials and Science Engineering, Chosun University, Gwangju 61542 (Korea, Republic of); Noh, Do Young, E-mail: dynoh@gist.ac.kr [Department of Physics and Photon Science & School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005 (Korea, Republic of)

2016-05-15

We demonstrate that solid-state dewetting of bilayer films is an effective way for obtaining bimetallic alloy nanocrystals of controlled composition. When a Pt–Ni bilayer film were annealed near 700 °C, Pt and Ni atoms inter-diffused to form a PtNi bimetallic alloy film. Upon annealing at higher temperatures, the bilayer films transformed into <111> oriented PtNi alloy nanocrystals in small-rhombicuboctahedron shape through solid-state dewetting process. The Pt content of the nanocrystals and the alloy films, estimated by applying the Vegard's law to the relaxed lattice constant, was closely related to the thickness of each layer in the as-grown bilayer films which can be readily controlled during bilayer deposition. - Highlights: • Composition control of PtNi nanoparticles using solid state dewetting is proposed. • PtNi alloy composition was controlled by thickness ratio of Pt–Ni bilayer films. • PtNi alloy nanocrystals were obtained in small-rhombicuboctahedron shape.

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.

Atomic Force Microscope Image Contrast Mechanisms on Supported Lipid Bilayers

OpenAIRE

Schneider, James; Dufrêne, Yves F.; Barger Jr., William R.; Lee, Gil U.

2000-01-01

This work presents a methodology to measure and quantitatively interpret force curves on supported lipid bilayers in water. We then use this method to correlate topographic imaging contrast in atomic force microscopy (AFM) images of phase-separated Langmuir-Blodgett bilayers with imaging load. Force curves collected on pure monolayers of both distearoylphosphatidylethanolamine (DSPE) and monogalactosylethanolamine (MGDG) and dioleoylethanolamine (DOPE) deposited at similar surface pressures o...

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

Positively charged lipid bilayer systems are a promising class of nonviral vectors for safe and efficient gene and drug delivery. Detailed understanding of these systems is therefore not only of fundamental but also of practical biomedical interest. Here, we study bilayers comprising a binary...... are concluded to be interesting for the physics of the whole membrane, especially considering its interaction dynamics with charged macromolecular surfaces....

Nanoscale Cross-Point Resistive Switching Memory Comprising p-Type SnO Bilayers

KAUST Repository

Hota, Mrinal Kanti; Hedhili, Mohamed N.; Wang, Qingxiao; Melnikov, Vasily; Mohammed, Omar F.; Alshareef, Husam N.

2015-01-01

Reproducible low-voltage bipolar resistive switching is reported in bilayer structures of p-type SnO films. Specifically, a bilayer homojunction comprising SnOx (oxygen-rich) and SnOy (oxygen-deficient) in nanoscale cross-point (300 × 300 nm2

Bi-layer non-doped small-molecular white organic light-emitting diodes with high colour stability

International Nuclear Information System (INIS)

Chen Shuming; Kwok, Hoi-Sing; Zhao Zujin; Tang Benzhong; Wang Zhiming; Lu Ping; Gao Zhao; Ma Yuguang

2011-01-01

Bi-layer non-doped white organic light-emitting diodes (WOLEDs) with hole-transporting layer 4-(4-(1,2,2-triphenylvinyl)phenyl)-7-(5-(4-(1,2,2-triphenylvinyl)phenyl) thiophen-2yl)benzo[c][1,2,5]thiadiazole (BTPETTD) as a red emitter and electron-transporting layer 4,4'-bis(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)biphenyl (DDPi) as a blue emitter are demonstrated. The blue emission is due to direct recombination of excitons in DPPi, while the red emission originates not only from the direct recombination of excitons in BTPETTD but also from a colour down-conversion process by absorbing blue emission and re-emitting red photons. The combination of blue emission and red emission yields an efficient and extremely stable white colour, regardless of driving voltages. In our demonstration, a bi-layer WOLED with an efficiency of 4.2 cd A -1 at 1000 cd m -2 , 1931 Commision International de L'Eclairage coordinates of (0.31, 0.31) and a high colour rendering index of 92 over a wide range of driving voltages is obtained.

Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties

International Nuclear Information System (INIS)

Burn, D M; Atkinson, D; Hase, T P A

2014-01-01

Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga + ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe. (paper)

Magnetic properties of a doped graphene-like bilayer

Energy Technology Data Exchange (ETDEWEB)

Guo, An-Bang [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Jiang, Wei, E-mail: weijiang.sut.edu@gmail.com [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Zhang, Na [Shenyang Normal University, Shenyang 110034 (China)

2017-05-15

A doped graphene-like bilayer is described using a four-sublattice Heisenberg model both ferromagnetic and antiferrimagnetic couplings. The magnetic properties of the bilayer system are studied using the Heisenberg model, retarded Green's function and the linear spin-wave approximation. The spin-wave spectra, energy gap, and the magnetization and quantum fluctuation of the system at the ground state are calculated with various intra- and interlayer couplings. The results indicate that the effect of antiferromagnetic exchange coupling on the magnetic properties of the system is significant. Magnetizations at low temperature show intersection points due to the quantum effects.

Theory of passive proton conductance in lipid bilayers.

Science.gov (United States)

Nagle, J F

1987-10-01

The large permeability of lipid bilayers to protons compared to other small ions calls for a special proton transport mechanism. At the present time, only mechanisms involving transient hydrogen-bonded chains of water can account for the experimental result that the conductance is nearly independent of pH. Three models involving transient hydrogen-bonded chains are discussed, including an outline of the kinetic calculations that lead to predictions of current versus voltage drop and current versus pH differences. These calculations can be compared to experiment to determine which, if any, of these models pertains to lipid bilayers.

MODEL OF AN ELECTRONIC EDUCATIONAL RESOURCE OF NEW GENERATION

Directory of Open Access Journals (Sweden)

Anatoliy V. Loban

2016-01-01

Full Text Available The mathematical structure of the modular architecture of an electronic educational resource (EER of new generation, which allows to decompose the process of studying the subjects of the course at a hierarchically ordered set of data (knowledge and procedures for manipulating them, to determine the roles of participants of process of training of and technology the development and use of EOR in the study procrate.

Lamellar-lamellar phase separation of phospholipid bilayers induced by salting-in/-out effects

Energy Technology Data Exchange (ETDEWEB)

Hishida, Mafumi [Institute for Integrated Cell-Material Sciences, Kyoto University, Kyoto 606-8501 (Japan); Seto, Hideki, E-mail: hideki.seto@kek.jp [KENS and CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan)

2011-01-01

The multilamellar structure of phospholipid bilayers is stabilized by the interactions between bilayers. Although the lamellar repeat distance is uniquely determined at the balance point of interactions between bilayers, a lamellar-lamellar phase separation, where the two phases with different lamellar repeat distance coexist, has been reported in a case of adding a salt to the aqueous solution of lipids. In order to understand the physical mechanism of the lamellar-lamellar phase separation, the effects of adding monovalent salt on the lamellar structure are studied by visual observation and by small-angle X-ray scattering. Further, a theoretical model based on the mean field theory is introduced and it is concluded that the salting-in and -out effects of lipid bilayers trigger the lamellar-lamellar phase separation.

Neutron scattering investigations of the lipid bilayer structure pressure dependence

International Nuclear Information System (INIS)

Solovjov, D.V.; Gordelyij, V.Yi.; Gorshkova, Yu.Je.; Yivan'kov, O.Yi.; Koval'ov, Yu.S.; Kuklyin, A.Yi.; Solovjov, D.V.; Bulavyin, L.A.; Yivan'kov, O.Yi.; Nyikolajenko, T.Yu.; Kuklyin, A.Yi.; Gordelyij, V.Yi.; Gordelyij, V.Yi.

2012-01-01

Lipid bilayer structure investigation results obtained with small angle neutron scattering method at the Joint Institute for Nuclear Research IBR-2M nuclear reactor (Dubna, Russia) are presented. Experiment has been performed with small angle neutron scattering spectrometer YuMO, upgraded with the apparatus for performing PV-T measurements on the substance under investigation. D 2 O-1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liquid system, presenting the model of natural live membrane, has been taken as the sample for investigations. The lipid bilayer spatial period was measured in experiment along with isothermal compressibility simultaneously at different pressures. It has been shown, that the bilayer structural transition from ripple (wavelike gel-phase) phase to liquid-crystal phase is accompanied with anomalous rise of isothermal compressibility, indicating occurrence of the phase transition.

Fabrication of Poly(o/m-Toluidine–SiC/Zinc Bilayer Coatings and Evaluation of Their Corrosion Resistances

Directory of Open Access Journals (Sweden)

Chuanbo Hu

2018-05-01

Full Text Available The purpose of this research was to study the structure and corrosion resistance of poly(o/m-toluidine-SiC/zinc (Zn bilayer coatings. Poly(o/m-toluidine films, such as poly(o-toluidine (POT and poly(m-toluidine (PMT, were chemically deposited on the surface of composite SiC/Zn coating using the solution evaporation method. The structures of poly(o/m-toluidine were characterized by various optic techniques and the electrochemical behavior was studied by cyclic voltammetry (CV. The structures and morphologies of the SiC/Zn coating were detected by Fourier transformation infrared spectroscopy (FTIR, X-ray diffraction (XRD, energy dispersive spectrometer (EDS, and scanning electron microscopy (SEM. Thereafter, the corrosion resistances of electrodeposited and bilayer coatings were investigated in 3.5% NaCl solution by electrochemical corrosion techniques and an accelerated immersion test. The results showed that the outer POT film exhibits a lower corrosion behavior with respect to PMT, which significantly reduces the corrosion rate of SiC/Zn coating and prolongs the service life of the zinc matrix. The conclusion demontrates that the stronger adsorptive POT film ensures the formed POT–SiC/Zn bilayer coatings possess a compact and low-defect surface, which facilitates POT film to develop its excellent barrier and passivation properties against corrosion.

Microfabrication of SrRuO3 thin films on various oxide substrates using LaAlO3/BaOx sacrificial bilayers

Science.gov (United States)

Harada, Takayuki; Tsukazaki, Atsushi

2018-02-01

Oxides provide various fascinating physical properties that could find use in future device applications. However, the physical properties of oxides are often affected by formation of oxygen vacancies during device fabrication processes. In this study, to develop a damage-free patterning process for oxides, we focus on a lift-off process using a sacrificial template layer, by which we can pattern oxide thin films without severe chemical treatment or plasma bombardment. As oxides need high thin-film growth temperature, a sacrificial template needs to be made of thermally stable and easily etchable materials. To meet these requirements, we develop a sacrificial template with a carefully designed bilayer structure. Combining a thermally and chemically stable LaAlO3 and a water-soluble BaOx, we fabricated a LaAlO3/BaOx sacrificial bilayer. The patterned LaAlO3/BaOx sacrificial bilayers were prepared on oxide substrates by room-temperature pulsed laser deposition and standard photolithography process. The structure of the sacrificial bilayer can be maintained even in rather tough conditions needed for oxide thin film growth: several hundred degrees Celsius under high oxygen pressure. Indeed, the LaAlO3/BaOx bilayer is easily removable by sonication in water. We applied the lift-off method using the LaAlO3/BaOx sacrificial bilayer to a representative oxide conductor SrRuO3 and fabricated micron-scale Hall-bar devices. The SrRuO3 channels with the narrowest line width of 5 μm exhibit an almost identical transport property to that of the pristine film, evidencing that the developed process is beneficial for patterning oxides. We show that the LaAlO3/BaOx lift-off process is applicable to various oxide substrates: SrTiO3, MgO, and Al2O3. The new versatile patterning process will expand the range of application of oxide thin films in electronic and photonic devices.

CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Pair interaction of bilayer-coated nanoscopic particles

Science.gov (United States)

Zhang, Qi-Yi

2009-02-01

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 placed 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 amphiphiles, 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.

Improvement of Metal-Graphene Ohmic Contact Resistance in Bilayer Epitaxial Graphene Devices

International Nuclear Information System (INIS)

He Ze-Zhao; Yang Ke-Wu; Yu Cui; Li Jia; Liu Qing-Bin; Lu Wei-Li; Feng Zhi-Hong; Cai Shu-Jun

2015-01-01

We report on an improved metal-graphene ohmic contact in bilayer epitaxial graphene on a SiC substrate with contact resistance below 0.1 ω·mm. Monolayer and bilayer epitaxial graphenes are prepared on a 4H-SiC substrate in this work. Their contact resistances are measured by a transfer length method. An improved photoresist-free device fabrication method is used and is compared with the conventional device fabrication method. Compared with the monolayer graphene, the contact resistance R c of bilayer graphene improves from an average of 0.24 ω·mm to 0.1 ω·mm. Ohmic contact formation mechanism analysis by Landauer's approach reveals that the obtained low ohmic contact resistance in bilayer epitaxial graphene is due to their high carrier density, high carrier transmission probability, and p-type doping introduced by contact metal Au. (paper)

Spin-1 and -2 bilayer Bethe lattice: A Monte Carlo study

International Nuclear Information System (INIS)

Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.

2016-01-01

The magnetic behaviors of bilayer with spin-1 and 2 Ising model on the Bethe lattice are investigated using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperature of the bilayer spin-1 and 2 on the Bethe lattice are studied for different values of crystal field and intralayer coupling constants of the two layers and interlayer coupling constant between the layers. The thermal and magnetic hysteresis cycles are given for different values of the crystal field, for different temperatures and for different exchange interactions. - Highlights: • The magnetic properties of bilayer on the Bethe lattice have been investigated. • The transition temperature has been deduced. • The magnetic coercive filed has been established.

Spin-1 and -2 bilayer Bethe lattice: A Monte Carlo study

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

2016-03-01

The magnetic behaviors of bilayer with spin-1 and 2 Ising model on the Bethe lattice are investigated using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperature of the bilayer spin-1 and 2 on the Bethe lattice are studied for different values of crystal field and intralayer coupling constants of the two layers and interlayer coupling constant between the layers. The thermal and magnetic hysteresis cycles are given for different values of the crystal field, for different temperatures and for different exchange interactions. - Highlights: • The magnetic properties of bilayer on the Bethe lattice have been investigated. • The transition temperature has been deduced. • The magnetic coercive filed has been established.

Vesicle fusion observed by content transfer across a tethered lipid bilayer.

Science.gov (United States)

Rawle, Robert J; van Lengerich, Bettina; Chung, Minsub; Bendix, Poul Martin; Boxer, Steven G

2011-10-19

Synaptic transmission is achieved by exocytosis of small, synaptic vesicles containing neurotransmitters across the plasma membrane. Here, we use a DNA-tethered freestanding bilayer as a target architecture that allows observation of content transfer of individual vesicles across the tethered planar bilayer. Tethering and fusion are mediated by hybridization of complementary DNA-lipid conjugates inserted into the two membranes, and content transfer is monitored by the dequenching of an aqueous content dye. By analyzing the diffusion profile of the aqueous dye after vesicle fusion, we are able to distinguish content transfer across the tethered bilayer patch from vesicle leakage above the patch. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Theory for electric dipole superconductivity with an application for bilayer excitons.

Science.gov (United States)

Jiang, Qing-Dong; Bao, Zhi-qiang; Sun, Qing-Feng; Xie, X C

2015-07-08

Exciton superfluid is a macroscopic quantum phenomenon in which large quantities of excitons undergo the Bose-Einstein condensation. Recently, exciton superfluid has been widely studied in various bilayer systems. However, experimental measurements only provide indirect evidence for the existence of exciton superfluid. In this article, by viewing the exciton in a bilayer system as an electric dipole, we derive the London-type and Ginzburg-Landau-type equations for the electric dipole superconductors. By using these equations, we discover the Meissner-type effect and the electric dipole current Josephson effect. These effects can provide direct evidence for the formation of the exciton superfluid state in bilayer systems and pave new ways to drive an electric dipole current.

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

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...

Surface functionalization of a polymeric lipid bilayer for coupling a model biological membrane with molecules, cells, and microstructures.

Science.gov (United States)

Morigaki, Kenichi; Mizutani, Kazuyuki; Saito, Makoto; Okazaki, Takashi; Nakajima, Yoshihiro; Tatsu, Yoshiro; Imaishi, Hiromasa

2013-02-26

We describe a stable and functional model biological membrane based on a polymerized lipid bilayer with a chemically modified surface. A polymerized lipid bilayer was formed from a mixture of two diacetylene-containing phospholipids, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC) and 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine (DiynePE). DiynePC formed a stable bilayer structure, whereas the ethanolamine headgroup of DiynePE enabled functional molecules to be grafted onto the membrane surface. Copolymerization of DiynePC and DiynePE resulted in a robust bilayer. Functionalization of the polymeric bilayer provided a route to a robust and biomimetic surface that can be linked with biomolecules, cells, and three-dimensional (3D) microstructures. Biotin and peptides were grafted onto the polymeric bilayer for attaching streptavidin and cultured mammalian cells by molecular recognition, respectively. Nonspecific adsorption of proteins and cells on polymeric bilayers was minimum. DiynePE was also used to attach a microstructure made of an elastomer (polydimethylsiloxan: PDMS) onto the membrane, forming a confined aqueous solution between the two surfaces. The microcompartment enabled us to assay the activity of a membrane-bound enzyme (cyochrome P450). Natural (fluid) lipid bilayers were incorporated together with membrane-bound proteins by lithographically polymerizing DiynePC/DiynePE bilayers. The hybrid membrane of functionalized polymeric bilayers and fluid bilayers offers a novel platform for a wide range of biomedical applications including biosensor, bioassay, cell culture, and cell-based assay.

"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

Effect of electrolyte composition and deposition current for Fe/Fe-P electroformed bilayers for biodegradable metallic medical applications

Energy Technology Data Exchange (ETDEWEB)

Mostavan, Afghany [Laboratory for Biomaterials and Bioengineering, Canada Research Chair Tier I, Department of Mining, Metallurgy and Materials Engineering, the CHU de Québec Research Centre, Québec City, QC G1V 0A6 (Canada); Department of Mining, Metallurgy and Materials Engineering, Laval University, Québec City, QC G1V 0A6 (Canada); Paternoster, Carlo; Tolouei, Ranna [Laboratory for Biomaterials and Bioengineering, Canada Research Chair Tier I, Department of Mining, Metallurgy and Materials Engineering, the CHU de Québec Research Centre, Québec City, QC G1V 0A6 (Canada); Ghali, Edward; Dubé, Dominique [Department of Mining, Metallurgy and Materials Engineering, Laval University, Québec City, QC G1V 0A6 (Canada); Mantovani, Diego, E-mail: Diego.Mantovani@gmn.ulaval.ca [Laboratory for Biomaterials and Bioengineering, Canada Research Chair Tier I, Department of Mining, Metallurgy and Materials Engineering, the CHU de Québec Research Centre, Québec City, QC G1V 0A6 (Canada); Department of Mining, Metallurgy and Materials Engineering, Laval University, Québec City, QC G1V 0A6 (Canada)

2017-01-01

With its proven biocompatibility and excellent mechanical properties, iron is an excellent source material for clinical cardiac and vascular applications. However, its relatively low degradation rate limits its use for the healing and remodeling of diseased blood vessels. To address these issues, a multi-purpose fabrication process to develop a bilayer alloy composed of electroformed iron (E-Fe) and iron-phosphorus (Fe-P) was employed. Bilayers of Fe/Fe-P were produced in an electrolytic bath. The effects of electrolyte chemical composition and deposition current density (i{sub dep}) on layer structure and chemical composition were assessed by scanning electron microscopy, electron probe microanalysis, X-ray diffraction and X-ray photoelectron spectroscopy. The corrosion rate was determined by potentiodynamic polarization tests. The bilayers showed an increasing amount of P with increasing NaH{sub 2}PO{sub 4}·H{sub 2}O in the electrolyte. Fe-P structure became finer for higher P amounts. Potentiodynamic polarization tests revealed that the corrosion rate was strongly influenced by deposition conditions. For a P amount of ~ 2 wt. %, the corrosion rate was 1.46 mm/year, which confirms the potential of this material to demonstrate high mechanical properties and a suitable corrosion rate for biomedical applications. - Highlights: • A phosphates and Fe chloride electrolyte was used for the fabrication of a multilayer of Fe/FeP. • Up to ~ 14% at. P was deposited by co-deposition of Fe and P. • The corrosion rate for the layer with a ~ 3% at. P was the highest one and equal to 1.46 mm/year. • For a 14% at. P, the FeP alloy shows a texture change, with only (110) reflection visible.

Plasma-assisted atomic layer deposition of Al(2)O(3) and parylene C bi-layer encapsulation for chronic implantable electronics.

Science.gov (United States)

Xie, Xianzong; Rieth, Loren; Merugu, Srinivas; Tathireddy, Prashant; Solzbacher, Florian

2012-08-27

Encapsulation of biomedical implants with complex three dimensional geometries is one of the greatest challenges achieving long-term functionality and stability. This report presents an encapsulation scheme that combines Al(2)O(3) by atomic layer deposition with parylene C for implantable electronic systems. The Al(2)O(3)-parylene C bi-layer was used to encapsulate interdigitated electrodes, which were tested invitro by soak testing in phosphate buffered saline solution at body temperature (37 °C) and elevated temperatures (57 °C and 67 °C) for accelerated lifetime testing up to 5 months. Leakage current and electrochemical impedance spectroscopy were measured for evaluating the integrity and insulation performance of the coating. Leakage current was stably about 15 pA at 5 V dc, and impedance was constantly about 3.5 MΩ at 1 kHz by using electrochemical impedance spectroscopy for samples under 67 °C about 5 months (approximately equivalent to 40 months at 37 °C). Alumina and parylene coating lasted at least 3 times longer than parylene coated samples tested at 80 °C. The excellent insulation performance of the encapsulation shows its potential usefulness for chronic implants.

Self-assembled PCBM bilayers on graphene and HOPG examined by AFM and STM

Science.gov (United States)

Li, Yanlong; Chen, Chuanhui; Burton, John; Park, Kyungwha; Heflin, James R.; Tao, Chenggang

2018-05-01

In this work we report fabrication and characterization of phenyl-C61-butyric acid methyl ester (PCBM) bilayer structures on graphene and highly oriented pyrolytic graphite (HOPG). Through careful control of the PCBM solution concentration (from 0.1 to 2 mg ml-1) and the deposition conditions, we demonstrate that PCBM molecules self-assemble into bilayer structures on graphene and HOPG substrates. Interestingly, the PCBM bilayers are formed with two distinct heights on HOPG, but only one unique representative height on graphene. At elevated annealing temperatures, edge diffusion allows neighboring vacancies to merge into a more ordered structure. This is, to the best of our knowledge, the first experimental realization of PCBM bilayer structures on graphene. This work could provide valuable insight into fabrication of new hybrid, ordered structures for applications to organic solar cells.

Agar/gelatin bilayer gel matrix fabricated by simple thermo-responsive sol-gel transition method.

Science.gov (United States)

Wang, Yifeng; Dong, Meng; Guo, Mengmeng; Wang, Xia; Zhou, Jing; Lei, Jian; Guo, Chuanhang; Qin, Chaoran

2017-08-01

We present a simple and environmentally-friendly method to generate an agar/gelatin bilayer gel matrix for further biomedical applications. In this method, the thermally responsive sol-gel transitions of agar and gelatin combined with the different transition temperatures are exquisitely employed to fabricate the agar/gelatin bilayer gel matrix and achieve separate loading for various materials (e.g., drugs, fluorescent materials, and nanoparticles). Importantly, the resulting bilayer gel matrix provides two different biopolymer environments (a polysaccharide environment vs a protein environment) with a well-defined border, which allows the loaded materials in different layers to retain their original properties (e.g., magnetism and fluorescence) and reduce mutual interference. In addition, the loaded materials in the bilayer gel matrix exhibit an interesting release behavior under the control of thermal stimuli. Consequently, the resulting agar/gelatin bilayer gel matrix is a promising candidate for biomedical applications in drug delivery, controlled release, fluorescence labeling, and bio-imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Neutron scattering investigations of the lipid bilayer structure pressure dependence

Directory of Open Access Journals (Sweden)

D. V. Soloviov

2012-03-01

Full Text Available Lipid bilayer structure investigation results obtained with small angle neutron scattering method at the Joint Institute for Nuclear Research IBR-2M nuclear reactor (Dubna, Russia are presented. Experiment has been per-formed with small angle neutron scattering spectrometer YuMO, upgraded with the apparatus for performing P-V-T measurements on the substance under investigation. D2O-1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC liquid system, presenting the model of natural live membrane, has been taken as the sample for investiga-tions. The lipid bilayer spatial period was measured in experiment along with isothermal compressibility simulta-neously at different pressures. It has been shown, that the bilayer structural transition from ripple (wavelike gel-phase phase to liquid-crystal phase is accompanied with anomalous rise of isothermal compressibility, indicat-ing occurrence of the phase transition.

The possibility of superconductivity in twisted bilayer graphene

International Nuclear Information System (INIS)

Manaf, Muhamad Nasruddin; Santoso, Iman; Hermanto, Arief

2015-01-01

We discuss the possibility of superconductivity in Twisted Bilayer Graphene (TBG). In this study we use TBG model with commensurate rotation θ=1.16° in which the van-Hove singularities (VHS) arise at 6 meV from the Fermi level. We use BCS standard formula that include Density of States (DOS) to calculate the critical temperature (T C ). Based on our calculation we predict that superconductivity will not arise in Pristine TBG because pairing potential has infinity value. In this situation, Dirac Fermions do not interact with each other since they do not form the bound states. Superconductvity may arise when the Fermi level is shifted towards the VHS. Based on this calculation, we predict that T C has value between 0.04 K and 0.12 K. The low value of T C is due to highly energetic of in plane phonon vibration which reduce the effective electron-phonon coupling. We conclude that doped TBG is candidate for Dirac Fermion superconductor

Non-leaky modes and bandgaps of surface acoustic waves in wrinkled stiff-film/compliant-substrate bilayers

Science.gov (United States)

Li, Guo-Yang; Xu, Guoqiang; Zheng, Yang; Cao, Yanping

2018-03-01

Surface acoustic wave (SAW) devices have found a wide variety of technical applications, including SAW filters, SAW resonators, microfluidic actuators, biosensors, flow measurement devices, and seismic wave shields. Stretchable/flexible electronic devices, such as sensory skins for robotics, structural health monitors, and wearable communication devices, have received considerable attention across different disciplines. Flexible SAW devices are essential building blocks for these applications, wherein piezoelectric films may need to be integrated with the compliant substrates. When piezoelectric films are much stiffer than soft substrates, SAWs are usually leaky and the devices incorporating them suffer from acoustic losses. In this study, the propagation of SAWs in a wrinkled bilayer system is investigated, and our analysis shows that non-leaky modes can be achieved by engineering stress patterns through surface wrinkles in the system. Our analysis also uncovers intriguing bandgaps (BGs) related to the SAWs in a wrinkled bilayer system; these are caused by periodic deformation patterns, which indicate that diverse wrinkling patterns could be used as metasurfaces for controlling the propagation of SAWs.

Low-dose chemotherapy of hepatocellular carcinoma through triggered-release from bilayer-decorated magnetoliposomes.

Science.gov (United States)

Chen, Yanjing; Chen, Yuan; Xiao, Da; Bose, Arijit; Deng, Ruitang; Bothun, Geoffrey D

2014-04-01

Low-dose (LD) chemotherapy is a promising treatment strategy that may be improved by controlled delivery. Polyethylene glycol-stabilized bilayer-decorated magnetoliposomes (dMLs) have been designed as a stimuli-responsive LD chemotherapy drug delivery system and tested in vitro using Huh-7 hepatocellular carcinoma cell line. The dMLs contained hydrophobic superparamagnetic iron oxide nanoparticles within the lipid bilayer and doxorubicin hydrochloride (DOX, 2 μM) within the aqueous core. Structural analysis by cryogenic transmission electron microscopy and dynamic light scattering showed that the assemblies were approximately 120 nm in diameter. Furthermore, the samples consisted of a mixture of dMLs and bare liposomes (no nanoparticles), which provided dual burst and spontaneous DOX release profiles, respectively. Cell viability results show that the cytotoxicity of DOX-loaded dMLs was similar to that of bare dMLs (∼10%), which indicates that spontaneous DOX leakage had little cytotoxic effect. However, when subjected to a physiologically acceptable radiofrequency (RF) electromagnetic field, cell viability was reduced up to 40% after 8h and significant cell death (>90%) was observed after 24h. The therapeutic mechanism was intracellular RF-triggered DOX release from the dMLs and not intracellular hyperthermia due to nanoparticle heating via magnetic losses. Copyright © 2014 Elsevier B.V. All rights reserved.

Molybdenum-gold proximity bilayers as transition edge sensors for microcalorimeters and bolometers

International Nuclear Information System (INIS)

Chen, T.C.; Bier, A.; DiCamillo, B.; Finkbeiner, F. M.

1999-01-01

Mo/Au proximity bilayers as transition edge sensors (TESs) are promising candidates for low-temperature thermometry. The transition temperature of the bilayers can be easily tuned between 50 and 600 mK, yielding sensors which can be used in a variety of calorimetric and bolometric applications. With phase transition widths of less than 1 mK, Mo/Au TESs show very high temperature sensitivity (d(logR)/d(logT)∼2500). Also, Mo/Au TESs show improved thermal and chemical stability compared to most other bilayer configurations. Fabrication issues and detector performance of Mo/Au TESs on Si 3 N 4 membranes are discussed. (author)

A criterion to identify the equilibration time in lipid bilayer simulations

Directory of Open Access Journals (Sweden)

Rodolfo D. Porasso

2012-11-01

Full Text Available With the aim of establishing a criterion for identifying when a lipid bilayer has reached steady state using the molecular dynamics simulation technique, lipid bilayers of different composition in their liquid crystalline phase were simulated in aqueous solution in presence of CaCl_2 as electrolyte, at different concentration levels. In this regard, we used two different lipid bilayer systems: one composed by 288 DPPC (DiPalmitoylPhosphatidylCholine and another constituted by 288 DPPS (DiPalmitoylPhosphatidylSerine. In this sense, for both type of lipid bilayers, we have studied the temporal evolution of some lipids properties, such as the surface area per lipid, the deuterium order parameter, the lipid hydration and the lipid-calcium coordination. From their analysis, it became evident how each property has a different time to achieve equilibrium. The following order was found, from faster property to slower property: coordination of ions $approx$ deuterium order parameter > area per lipid $approx$ hydration. Consequently, when the hydration of lipids or the mean area per lipid are stable, we can ensure that the lipid membrane has reached the steady state.

The impact of resveratrol in lipid bilayers

DEFF Research Database (Denmark)

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

The natural antioxidant resveratrol, contained in the skin of red grape and accordingly in their wines, is hold liable for health impacts such as cardiovascular protection and anti-oxidative effect. Clinical trials of resveratrol as prophylactic or even therapeutic drug are ongoing. However, basic...... knowledge on its probable working mechanism is rare. In this biophysical study, neutron reflectometry was used to investigate the direct impact of resveratrol on lipid membranes with solid supported bilayers. When interacting with di- palmitoyl-phosphatidyl-choline (DPPC) bilayers, resveratrol accumulates...... in between the headgroups but is absent in the hydrophobic core. Without a biogenic removal mechanism, the headgroup region may host up to ~25 mol% of resveratrol. The average thickness and the interfacial roughness of the headgroup layer are increased. From the structural results, the average tilting...

Electrically Controllable Magnetism in Twisted Bilayer Graphene.

Science.gov (United States)

Gonzalez-Arraga, Luis A; Lado, J L; Guinea, Francisco; San-Jose, Pablo

2017-09-08

Twisted graphene bilayers develop highly localized states around AA-stacked regions for small twist angles. We show that interaction effects may induce either an antiferromagnetic or a ferromagnetic (FM) polarization of said regions, depending on the electrical bias between layers. Remarkably, FM-polarized AA regions under bias develop spiral magnetic ordering, with a relative 120° misalignment between neighboring regions due to a frustrated antiferromagnetic exchange. This remarkable spiral magnetism emerges naturally without the need of spin-orbit coupling, and competes with the more conventional lattice-antiferromagnetic instability, which interestingly develops at smaller bias under weaker interactions than in monolayer graphene, due to Fermi velocity suppression. This rich and electrically controllable magnetism could turn twisted bilayer graphene into an ideal system to study frustrated magnetism in two dimensions.

Two-Phase Contiguous Supported Lipid Bilayer Model for Membrane Rafts via Polymer Blotting and Stenciling.

Science.gov (United States)

Richards, Mark J; Daniel, Susan

2017-02-07

The supported lipid bilayer has been portrayed as a useful model of the cell membrane compatible with many biophysical tools and techniques that demonstrate its appeal in learning about the basic features of the plasma membrane. However, some of its potential has yet to be realized, particularly in the area of bilayer patterning and phase/composition heterogeneity. In this work, we generate contiguous bilayer patterns as a model system that captures the general features of membrane domains and lipid rafts. Micropatterned polymer templates of two types are investigated for generating patterned bilayer formation: polymer blotting and polymer lift-off stenciling. While these approaches have been used previously to create bilayer arrays by corralling bilayers patches with various types of boundaries impenetrable to bilayer diffusion, unique to the methods presented here, there are no physical barriers to diffusion. In this work, interfaces between contiguous lipid phases define the pattern shapes, with continuity between them allowing transfer of membrane-bound biomolecules between the phases. We examine effectors of membrane domain stability including temperature and cholesterol content to investigate domain dynamics. Contiguous patterning of supported bilayers as a model of lipid rafts expands the application of the SLB to an area with current appeal and brings with it a useful toolset for characterization and analysis. These combined tools should be helpful to researchers investigating lipid raft dynamics and function and biomolecule partitioning studies. Additionally, this patterning technique may be useful for applications such as bioseparations that exploit differences in lipid phase partitioning or creation of membranes that bind species like viruses preferentially at lipid phase boundaries, to name a few.

Analysis of x-ray reflectivity data from low-contrast polymer bilayer systems using a Fourier method

International Nuclear Information System (INIS)

Seeck, O. H.; Kaendler, I. D.; Tolan, M.; Shin, K.; Rafailovich, M. H.; Sokolov, J.; Kolb, R.

2000-01-01

X-ray reflectivity data of polymer bilayer systems have been analyzed using a Fourier method which takes into account different limits of integration in q-space. It is demonstrated that the interfacial parameters can be determined with high accuracy although the difference in the electron density (the contrast) of the two polymers is extremely small. This method is not restricted to soft-matter thin films. It can be applied to any reflectivity data from low-contrast layer systems. (c) 2000 American Institute of Physics

Spontaneous bending of pre-stretched bilayers.

Science.gov (United States)

DeSimone, Antonio

2018-01-01

We discuss spontaneously bent configurations of pre-stretched bilayer sheets that can be obtained by tuning the pre-stretches in the two layers. The two-dimensional nonlinear plate model we use for this purpose is an adaptation of the one recently obtained for thin sheets of nematic elastomers, by means of a rigorous dimensional reduction argument based on the theory of Gamma-convergence (Agostiniani and DeSimone in Meccanica. doi:10.1007/s11012-017-0630-4, 2017, Math Mech Solids. doi:10.1177/1081286517699991, arXiv:1509.07003, 2017). We argue that pre-stretched bilayer sheets provide us with an interesting model system to study shape programming and morphing of surfaces in other, more complex systems, where spontaneous deformations are induced by swelling due to the absorption of a liquid, phase transformations, thermal or electro-magnetic stimuli. These include bio-mimetic structures inspired by biological systems from both the plant and the animal kingdoms.

Effects of cholesterol or gramicidin on slow and fast motions of phospholipids in oriented bilayers

International Nuclear Information System (INIS)