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Sample records for bilayers stability physical

  1. Nanoporous microbead supported bilayers: stability, physical characterization, and incorporation of functional transmembrane proteins.

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Ryan W. (University of New Mexico, Albuquerque, NM); Brozik, James A. (University of New Mexico, Albuquerque, NM); Brozik, Susan Marie; Cox, Jason M. (University of New Mexico, Albuquerque, NM); Lopez, Gabriel P. (University of New Mexico, Albuquerque, NM); Barrick, Todd A. (University of New Mexico, Albuquerque, NM); Flores, Adrean (University of New Mexico, Albuquerque, NM)

    2007-03-01

    The introduction of functional transmembrane proteins into supported bilayer-based biomimetic systems presents a significant challenge for biophysics. Among the various methods for producing supported bilayers, liposomal fusion offers a versatile method for the introduction of membrane proteins into supported bilayers on a variety of substrates. In this study, the properties of protein containing unilamellar phosphocholine lipid bilayers on nanoporous silica microspheres are investigated. The effects of the silica substrate, pore structure, and the substrate curvature on the stability of the membrane and the functionality of the membrane protein are determined. Supported bilayers on porous silica microspheres show a significant increase in surface area on surfaces with structures in excess of 10 nm as well as an overall decrease in stability resulting from increasing pore size and curvature. Comparison of the liposomal and detergent-mediated introduction of purified bacteriorhodopsin (bR) and the human type 3 serotonin receptor (5HT3R) are investigated focusing on the resulting protein function, diffusion, orientation, and incorporation efficiency. In both cases, functional proteins are observed; however, the reconstitution efficiency and orientation selectivity are significantly enhanced through detergent-mediated protein reconstitution. The results of these experiments provide a basis for bulk ionic and fluorescent dye-based compartmentalization assays as well as single-molecule optical and single-channel electrochemical interrogation of transmembrane proteins in a biomimetic platform.

  2. Strain, stabilities and electronic properties of hexagonal BN bilayers

    Science.gov (United States)

    Fujimoto, Yoshitaka; Saito, Susumu

    Hexagonal boron nitride (h-BN) atomic layers have been regarded as fascinating materials both scientifically and technologically due to the sizable band gap. This sizable band-gap nature of the h-BN atomic layers would provide not only new physical properties but also novel nano- and/or opto-electronics applications. Here, we study the first-principles density-functional study that clarifies the biaxial strain effects on the energetics and the electronic properties of h-BN bilayers. We show that the band gaps of the h-BN bilayers are tunable by applying strains. Furthermore, we show that the biaxial strains can produce a transition from indirect to direct band gaps of the h-BN bilayer. We also discuss that both AA and AB stacking patterns of h-BN bilayer become feasible structures because h-BN bilayers possess two different directions in the stacking patterns. Supported by MEXT Elements Strategy Initiative to Form Core Research Center through Tokodai Institute for Element Strategy, JSPS KAKENHI Grant Numbers JP26390062 and JP25107005.

  3. 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.

  4. Amphotericin B induced interdigitation of apolipoprotein stabilized nanodisk bilayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-12-07

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

  5. Stability of monolayers and bilayers in a copolymer-homopolymer blend model

    NARCIS (Netherlands)

    Gennip, van Y.; Peletier, M.A.

    2007-01-01

    We study the stability of layered structures in a variational model for diblock copolymer- homopolymer blends. The main step consists of calculating the first and second derivative of a sharp-interface Ohta-Kawasaki energy for straight mono- and bilayers. By developing the interface perturbations in

  6. Stacking stability of MoS2 bilayer: An ab initio study

    International Nuclear Information System (INIS)

    Tao Peng; Guo Huai-Hong; Yang Teng; Zhang Zhi-Dong

    2014-01-01

    The study of the stacking stability of bilayer MoS 2 is essential since a bilayer has exhibited advantages over single layer MoS 2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS 2 , and (especially) the effect of inter-layer stress, by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band (CI-NEB) method. Among five typical stacking orders, which can be categorized into two kinds (I: AA, AB and II: AA', AB', A'B), we found that stacking orders with Mo and S superposing from both layers, such as AA' and AB, is more stable than the others. With smaller computational efforts than potential energy profile searching, we can study the effect of inter-layer stress on the stacking stability. Under isobaric condition, the sliding barrier increases by a few eV/(ucGPa) from AA' to AB', compared to 0.1 eV/(ucGPa) from AB to [AB]. Moreover, we found that interlayer compressive stress can help enhance the transport properties of AA'. This study can help understand why inter-layer stress by dielectric gating materials can be an effective means to improving MoS 2 on nanoelectronic applications. (condensed matter: structural, mechanical, and thermal properties)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-10-15

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    Highlights: • Superparamagnetic iron oxide nanoparticles were stabilized with oleic acid. • Maximum stabilization was achieved at neutral pH. • Magnetic resonance imaging and magnetic hyperthermia applications were tested. • The produced nanoparticles are viable for both biomedical applications. - Abstract: Iron oxide nanoparticles (Fe_3O_4, IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI.

  9. 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.

  10. 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

  11. 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.

  12. Stabilization of functional recombinant cannabinoid receptor CB(2 in detergent micelles and lipid bilayers.

    Directory of Open Access Journals (Sweden)

    Krishna Vukoti

    Full Text Available Elucidation of the molecular mechanisms of activation of G protein-coupled receptors (GPCRs is among the most challenging tasks for modern membrane biology. For studies by high resolution analytical methods, these integral membrane receptors have to be expressed in large quantities, solubilized from cell membranes and purified in detergent micelles, which may result in a severe destabilization and a loss of function. Here, we report insights into differential effects of detergents, lipids and cannabinoid ligands on stability of the recombinant cannabinoid receptor CB(2, and provide guidelines for preparation and handling of the fully functional receptor suitable for a wide array of downstream applications. While we previously described the expression in Escherichia coli, purification and liposome-reconstitution of multi-milligram quantities of CB(2, here we report an efficient stabilization of the recombinant receptor in micelles - crucial for functional and structural characterization. The effects of detergents, lipids and specific ligands on structural stability of CB(2 were assessed by studying activation of G proteins by the purified receptor reconstituted into liposomes. Functional structure of the ligand binding pocket of the receptor was confirmed by binding of (2H-labeled ligand measured by solid-state NMR. We demonstrate that a concerted action of an anionic cholesterol derivative, cholesteryl hemisuccinate (CHS and high affinity cannabinoid ligands CP-55,940 or SR-144,528 are required for efficient stabilization of the functional fold of CB(2 in dodecyl maltoside (DDM/CHAPS detergent solutions. Similar to CHS, the negatively charged phospholipids with the serine headgroup (PS exerted significant stabilizing effects in micelles while uncharged phospholipids were not effective. The purified CB(2 reconstituted into lipid bilayers retained functionality for up to several weeks enabling high resolution structural studies of this GPCR at

  13. Stability study of cermet-supported solid oxide fuel cells with bi-layered electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinge; Gazzarri, Javier; Robertson, Mark; Deces-Petit, Cyrille [National Research Council, Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC (Canada); Kesler, Olivera [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, ON (Canada)

    2008-12-01

    Performance and stability of five cermet-supported button-type solid oxide fuel cells featuring a bi-layered electrolyte (SSZ/SDC), an SSC cathode, and a Ni-SSZ anode, were analyzed using polarization curves, impedance spectroscopy, and post-mortem SEM observation. The cell performance degradation at 650 C in H{sub 2}/air both with and without DC bias conditions was manifested primarily as an increase in polarization resistance, approximately at a rate of 2.3 m{omega} cm{sup 2} h{sup -1} at OCV, suggesting a decrease in electrochemical kinetics as the main phenomenon responsible for the performance decay. In addition, the initial series resistance was about ten times higher than the calculated resistance corresponding to the electrolyte, reflecting a possible inter-reaction between the electrolyte layers that occurred during the sintering stage. In situ and ex situ sintered cathodes showed no obvious difference in cell performance or decay rate. The stability of the cells with and without electrical load was also investigated and no significant influence of DC bias was recorded. Based on the experimental results presented, we preliminarily attribute the performance degradation to electrochemical and microstructural degradation of the cathode. (author)

  14. Stability study of cermet-supported solid oxide fuel cells with bi-layered electrolyte

    Science.gov (United States)

    Zhang, Xinge; Gazzarri, Javier; Robertson, Mark; Decès-Petit, Cyrille; Kesler, Olivera

    Performance and stability of five cermet-supported button-type solid oxide fuel cells featuring a bi-layered electrolyte (SSZ/SDC), an SSC cathode, and a Ni-SSZ anode, were analyzed using polarization curves, impedance spectroscopy, and post-mortem SEM observation. The cell performance degradation at 650 °C in H 2/air both with and without DC bias conditions was manifested primarily as an increase in polarization resistance, approximately at a rate of 2.3 mΩ cm 2 h -1 at OCV, suggesting a decrease in electrochemical kinetics as the main phenomenon responsible for the performance decay. In addition, the initial series resistance was about ten times higher than the calculated resistance corresponding to the electrolyte, reflecting a possible inter-reaction between the electrolyte layers that occurred during the sintering stage. In situ and ex situ sintered cathodes showed no obvious difference in cell performance or decay rate. The stability of the cells with and without electrical load was also investigated and no significant influence of DC bias was recorded. Based on the experimental results presented, we preliminarily attribute the performance degradation to electrochemical and microstructural degradation of the cathode.

  15. Graphene Oxide Monolayer as a Compatibilizer at the Polymer-Polymer Interface for Stabilizing Polymer Bilayer Films against Dewetting.

    Science.gov (United States)

    Kim, Tae-Ho; Kim, Hyeri; Choi, Ki-In; Yoo, Jeseung; Seo, Young-Soo; Lee, Jeong-Soo; Koo, Jaseung

    2016-12-06

    We investigate the effect of adding graphene oxide (GO) sheets at the polymer-polymer interface on the dewetting dynamics and compatibility of immiscible polymer bilayer films. GO monolayers are deposited at the poly(methyl methacrylate) (PMMA)-polystyrene (PS) interface by the Langmuir-Schaefer technique. GO monolayers are found to significantly inhibit the dewetting behavior of both PMMA films (on PS substrates) and PS films (on PMMA substrates). This can be interpreted in terms of an interfacial interaction between the GO sheets and these polymers, which is evidenced by the reduced contact angle of the dewet droplets. The favorable interaction of GO with both PS and PMMA facilitates compatibilization of the immiscible polymer bilayer films, thereby stabilizing their bilayer films against dewetting. This compatibilization effect is verified by neutron reflectivity measurements, which reveal that the addition of GO monolayers broadens the interface between PS and the deuterated PMMA films by 2.2 times over that of the bilayer in the absence of GO.

  16. The physics of sawtooth stabilization

    International Nuclear Information System (INIS)

    Chapman, I T; Pinches, S D; Graves, J P; Akers, R J; Appel, L C; Budny, R V; Coda, S; Conway, N J; Bock, M de; Eriksson, L-G; Hastie, R J; Hender, T C; Huysmans, G T A; Johnson, T; Koslowski, H R; Kraemer-Flecken, A; Lennholm, M; Liang, Y; Saarelma, S; Sharapov, S E; Voitsekhovitch, I

    2007-01-01

    Long period sawteeth have been observed to result in low-β triggering of neo-classical tearing modes, which can significantly degrade plasma confinement. Consequently, a detailed physical understanding of sawtooth behaviour is critical, especially for ITER where fusion-born α particles are likely to lead to very long sawtooth periods. Many techniques have been developed to control, and in particular to destabilize the sawteeth. The application of counter-current neutral beam injection (NBI) in JET has resulted in shorter sawtooth periods than in Ohmic plasmas. This result has been explained because, firstly, the counter-passing fast ions give a destabilizing contribution to the n = 1 internal kink mode-which is accepted to be related to sawtooth oscillations-and secondly, the flow shear strongly influences the stabilizing trapped particles. A similar experimental result has been observed in counter-NBI heated plasmas in MAST. However, the strong toroidal flows in spherical tokamaks mean that the sawtooth behaviour is determined by the gyroscopic flow stabilization of the kink mode rather than kinetic effects. In NBI heated plasmas in smaller conventional aspect-ratio tokamaks, such as TEXTOR, the flow and kinetic effects compete to give different sawtooth behaviour. Other techniques applied to destabilize sawteeth are the application of electron cyclotron current drive (ECCD) or ion cyclotron resonance heating (ICRH). In JET, it has been observed that localized ICRH is able to destabilize sawteeth which were otherwise stabilized by a co-existing population of energetic trapped ions in the core. This is explained through the dual role of the ICRH in reducing the critical magnetic shear required to trigger a sawtooth crash, and the increase in the local magnetic shear which results from driving current near the q = 1 rational surface. Sawtooth control in ITER could be provided by a combination of ECCD and co-passing off-axis negative-NBI fast ions

  17. Full-scale magnetic, microstructural, and physical properties of bilayered CoSiB/FeSiB ribbons

    Czech Academy of Sciences Publication Activity Database

    Životský, O.; Titov, A.; Jirásková, Yvonna; Buršík, Jiří; Kalbáčová, J.; Janičkovič, D.; Švec, P.

    2013-01-01

    Roč. 581, DEC (2013), s. 685-692 ISSN 0925-8388 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Keywords : Bilayered ribbons * Soft magnetic materials * Microstructure * Surface and bulk magnetic properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.726, year: 2013

  18. Gammasphere physics far from stability

    International Nuclear Information System (INIS)

    Nazarewicz, W.; Oak Ridge National Lab., TN; Warsaw Univ.

    1995-01-01

    Exotic nuclear states and excitation modes at extreme angular momenta, extreme deformations, and extreme excitation energies have been in the center of interest of GAMMASPHERE. In this presentation, the author discusses yet another limit of nuclear structure at extreme conditions--a territory of the future GAMMASPHERE physics--namely the physics of exotic nuclei with extreme proton-to-neutron ratios

  19. Stability of zero-mode Landau levels in bilayer graphene against disorder in the presence of the trigonal warping

    International Nuclear Information System (INIS)

    Kawarabayashi, Tohru; Hasugai, Yasuhiro; Aoki, Hideo

    2013-01-01

    The stability of the zero-energy Landau levels in bilayer graphene against the chiral symmetric disorder is examined in the presence of the trigonal warping. Based on the tight-binding lattice model with a bond disorder correlated over several lattice constants, it is shown that among the four Landau levels per spin and per valley, two Landau levels exhibit the anomalous sharpness as in the absence of the trigonal warping, while the other two are broadened, yielding split peaks in the density of states. This can be attributed to the fact that the total chirality in each valley is ±2, which is protected topologically even in the presence of an intra-valley scattering due to disorder

  20. The physics of wheel-rail stability

    Science.gov (United States)

    Tan, B. T. G.

    2018-05-01

    This article discusses, at a simple level, the dynamics of the wheel-rail interface, which is fundamental to the stability of rail vehicles. The physics underlying this topic deserves to be better known by physicists and physics students, as it underpins such an important part of our technological infrastructure.

  1. The Physics of Wheel-Rail Stability

    Science.gov (United States)

    Tan, B. T. G.

    2018-01-01

    This article discusses, at a simple level, the dynamics of the wheel-rail interface, which is fundamental to the stability of rail vehicles. The physics underlying this topic deserves to be better known by physicists and physics students, as it underpins such an important part of our technological infrastructure

  2. Proton and carbon-13 nuclear magnetic resonance studies of the effects of retinal on the dynamic structure and stability of lipid bilayer

    International Nuclear Information System (INIS)

    Inoue, Yoshio; Hanafusa, Yoshito; Toda, Masakazu; Chujo, Riichiro

    1982-01-01

    The effects of retinal and vitamin A on the dynamic structure and stability of hen egg yolk lecithin bilayers have been studied by means of carbon-13 and proton NMR spectroscopies. 13 C spin-lattice relaxation and paramagnetic ion permeability studies on lecithin bilayers indicate a marked decrease in flexibility of the lipid acyl chain and a breakdown of membrane impermeableness to ion by the intercalated all-trans- and 11-cis-retinal, whereas the effect of incorporated vitamin A on the fluidity of bilayers is small and its impermeableness to ion remains effective even in the presence of higher concentration of vitamin A. The experimental results are discussed in connection with the mechanism of the permeability change in photoreceptive disk membrane. (author)

  3. On the hydrodynamics of a solvent-satured lipid bilayer. 2. Stability criteria

    International Nuclear Information System (INIS)

    Bisch, P.M.; Wendel, H.

    1983-01-01

    The semiphenomenological model introduced recently is used to investigate the role of steric forces on the dynamics of black lipid films. A linear stability analysis of hydrodynamic fluctuations for lipid films submitted to an applyed electric field is performed. By neglecting dissipation, this our analysis is concentrated on the competitive effects of electrostatic, van der Waals and steric forces. In the long wavelenght limit it is shown that the stability of the film against bending deformations is governed by the total film tension. Similarly, for periodic thickness fluctuations the stability is determined by the film elasticity. In both cases a stabilizing positive contribution is found of steric forces produced by the overlap of lipid chains at the center of the film. The stability diagram shows a region, for sufficiently small thickness, where only bending modes are unstable. (Author) [pt

  4. Nonconservative stability problems of modern physics

    CERN Document Server

    Kirillov, Oleg N

    2013-01-01

    This work gives a complete overview on the subject of nonconservative stability from the modern point of view. Relevant mathematical concepts are presented, as well as rigorous stability results and numerous classical and contemporary examples from mechanics and physics.The book shall serve to present and prospective specialists providing the current state of knowledge in this actively developing field. The understanding of this theory is vital for many areas of technology, as dissipative effects in rotor dynamics orcelestial mechanics.

  5. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature.

    Science.gov (United States)

    Barani, Hossein; Montazer, Majid; Braun, Hans-Georg; Dutschk, Victoria

    2014-12-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a simple and safe method by using lecithin as a stabilising agent and their stability was examined at various temperatures. The effect of the lecithin concentrations on the stability of the synthesised silver nanoparticles was examined from 25 to 80°C at 5°C intervals, by recording the changes in the UV-vis absorption spectra, the hydrodynamic diameter and the light scattering intensity of the silver nanoparticles. In addition, the morphology of the synthesised silver nanoparticles was investigated with the low-voltage scanning electron microscopy and transmission electron microscopy. The results indicated that increasing temperature caused different changes in the size of the stabilised and the unstabilised silver nanoparticles. The size of the stabilised silver nanoparticles reduced from 38 to 36 nm during increasing temperature, which confirmed good stability.

  6. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature

    NARCIS (Netherlands)

    Barani, H.; Montazer, M.; Braun, H.G.; Dutschk, Victoria

    2014-01-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a

  7. The effect of metal-buffer bilayer drain/source electrodes on the operational stability of the organic field effect transistors

    International Nuclear Information System (INIS)

    Karimi-Alavijeh, H.R.; Ehsani, A.

    2015-01-01

    In this paper, we have investigated experimentally the effect of different drain/source (D/S) electrodes and charge injection buffer layers on the electrical properties and operational stability of a stilbene organic field effect transistor (OFET). The results show that the organic buffer layer of copper phthalocyanine (CuPc) considerably improves the electrical properties of the transistors, but has a negligible effect on their temporal behavior. On the other hand, inorganic metal-oxide buffer layer of molybdenum oxide (MoO 3 ) drastically changes both the electrical properties and operational stability. The functionalities of this metal-oxide tightly depend on the properties of the D/S metallic electrodes. OFETs with Al/MoO 3 as the bilayer D/S electrodes have the best electrical properties: field effect mobility μ eff = 0.32 cm 2 V −1 s −1 and threshold voltage V TH = − 5 V and the transistors with Ag/MoO 3 have the longest operational stability. It was concluded that the chemical stability of the metal/metal-oxide or metal/organic interfaces of the bilayer D/S electrodes determine the operational stability of the OFETs. - Highlights: • The effect of buffer layers on the performance of the stilbene OFETs has been investigated. • Inorganic buffer layer improved the electrical and temporal behaviors simultaneously. • Organic buffer layer only changes the electrical properties. • Chemical stability of the interfaces determines the operational stability of the transistor

  8. Analysis of Al2O3—parylene C bilayer coatings and impact of microelectrode topography on long term stability of implantable neural arrays

    Science.gov (United States)

    Caldwell, Ryan; Mandal, Himadri; Sharma, Rohit; Solzbacher, Florian; Tathireddy, Prashant; Rieth, Loren

    2017-08-01

    Objective. Performance of many dielectric coatings for neural electrodes degrades over time, contributing to loss of neural signals and evoked percepts. Studies using planar test substrates have found that a novel bilayer coating of atomic-layer deposited (ALD) Al2O3 and parylene C is a promising candidate for neural electrode applications, exhibiting superior stability to parylene C alone. However, initial results from bilayer encapsulation testing on non-planar devices have been less positive. Our aim was to evaluate ALD Al2O3-parylene C coatings using novel test paradigms, to rigorously evaluate dielectric coatings for neural electrode applications by incorporating neural electrode topography into test structure design. Approach. Five test devices incorporated three distinct topographical features common to neural electrodes, derived from the utah electrode array (UEA). Devices with bilayer (52 nm Al2O3  +  6 µm parylene C) were evaluated against parylene C controls (N  ⩾  6 per device type). Devices were aged in phosphate buffered saline at 67 °C for up to 311 d, and monitored through: (1) leakage current to evaluate encapsulation lifetimes (>1 nA during 5VDC bias indicated failure), and (2) wideband (1-105 Hz) impedance. Main results. Mean-times-to-failure (MTTFs) ranged from 12 to 506 d for bilayer-coated devices, versus 10 to  >2310 d for controls. Statistical testing (log-rank test, α  =  0.05) of failure rates gave mixed results but favored the control condition. After failure, impedance loss for bilayer devices continued for months and manifested across the entire spectrum, whereas the effect was self-limiting after several days, and restricted to frequencies  physiological fluids may improve performance. Testing frameworks which take neural electrode complexities into account will be well suited to reliably evaluate such encapsulation schemes.

  9. Physical and electrical properties of bilayer CeO{sub 2}/TiO{sub 2} gate dielectric stack

    Energy Technology Data Exchange (ETDEWEB)

    Chong, M.M.V. [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore); GlobalFoundries Singapore Private Limited, 60 Woodlands Industrial Park D Street 2, Singapore 738406 (Singapore); Lee, P.S. [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore); Tok, A.I.Y., E-mail: MIYTOK@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore)

    2016-08-15

    Highlights: • A bilayer gate dielectric stack of CeO{sub 2}/TiO{sub 2} to study the dependency of film growth with varying annealing temperatures is proposed. • The study demonstrates CeO{sub 2}/TiO{sub 2} bilayer stack with comparable κ-value as that of HfO{sub 2} but with reduced leakage current density of 4 orders of magnitude. • Schottky emission is the dominant leakage conduction mechanism of annealed CeO{sub 2}/TiO{sub 2} stack due to thermionic effect of interface properties. - Abstract: This study demonstrates a bilayer gate oxide structure of cerium oxide deposited via pulsed laser deposition and titanium oxide using conventional atomic layer deposition. Samples were deposited on p-type Si (100) substrate and exhibit interesting physical and electrical properties such that 600 °C annealed CeO{sub 2}/TiO{sub 2} samples having κ-value of 18 whereas pure CeO{sub 2} deposited samples have dielectric constant of 17.1 with leakage current density of 8.94 × 10{sup −6} A/cm{sup 2} at 1 V applied voltage. The result shows promising usage of the synthesized rare earth oxides as gate dielectric where ideal κ-value and significant reduction of the leakage current by 5 orders of magnitude is achieved. Leakage current conduction mechanism for as-deposited sample is found to be dominated by Poole–Frenkel (PF) emission; the trap level is found to be at 1.29 eV whereas annealed samples (600 °C and 800 °C) exhibited Schottky emission with trap levels at 1.45 eV and 0.81 eV, respectively.

  10. Stellar Physics 2: Stellar Evolution and Stability

    CERN Document Server

    Bisnovatyi-Kogan, Gennady S

    2011-01-01

    "Stellar Physics" is a an outstanding book in the growing body of literature on star formation and evolution. Not only does the author, a leading expert in the field, very thoroughly present the current state of knowledge on stellar physics, but he handles with equal care the many problems that this field of research still faces. A bibliography with well over 1000 entries makes this book an unparalleled reference source. "Stellar Evolution and Stability" is the second of two volumes and can be read, as can the first volume "Fundamental Concepts and Stellar Equilibrium," as a largely independent work. It traces in great detail the evolution of protostars towards the main sequence and beyond this to the last stage of stellar evolution, with the corresponding vast range from white dwarfs to supernovae explosions, gamma-ray bursts and black hole formation. The book concludes with special chapters on the dynamical, thermal and pulsing stability of stars. This second edition is carefully updated in the areas of pre...

  11. Nonlinear physical systems spectral analysis, stability and bifurcations

    CERN Document Server

    Kirillov, Oleg N

    2013-01-01

    Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam

  12. Optimization of drug loading to improve physical stability of paclitaxel-loaded long-circulating liposomes.

    Science.gov (United States)

    Kannan, Vinayagam; Balabathula, Pavan; Divi, Murali K; Thoma, Laura A; Wood, George C

    2015-01-01

    The effect of formulation and process parameters on drug loading and physical stability of paclitaxel-loaded long-circulating liposomes was evaluated. The liposomes were prepared by hydration-extrusion method. The formulation parameters such as total lipid content, cholesterol content, saturated-unsaturated lipid ratio, drug-lipid ratio and process parameters such as extrusion pressure and number of extrusion cycles were studied and their impact on drug loading and physical stability was evaluated. A proportionate increase in drug loading was observed with increase in the total phospholipid content. Cholesterol content and saturated lipid content in the bilayer showed a negative influence on drug loading. The short-term stability evaluation of liposomes prepared with different drug-lipid ratios demonstrated that 1:60 as the optimum drug-lipid ratio to achieve a loading of 1-1.3 mg/mL without the risk of physical instability. The vesicle size decreased with an increase in the extrusion pressure and number of extrusion cycles, but no significant trends were observed for drug loading with changes in process pressure or number of cycles. The optimization of formulation and process parameters led to a physically stable formulation of paclitaxel-loaded long-circulating liposomes that maintain size, charge and integrity during storage.

  13. Accelerated Physical Stability Testing of Amorphous Dispersions.

    Science.gov (United States)

    Mehta, Mehak; Suryanarayanan, Raj

    2016-08-01

    The goal was to develop an accelerated physical stability testing method of amorphous dispersions. Water sorption is known to cause plasticization and may accelerate drug crystallization. In an earlier investigation, it was observed that both the increase in mobility and decrease in stability in amorphous dispersions was explained by the "plasticization" effect of water (Mehta et al. Mol. Pharmaceutics 2016, 13 (4), 1339-1346). In this work, the influence of water concentration (up to 1.8% w/w) on the correlation between mobility and crystallization in felodipine dispersions was investigated. With an increase in water content, the α-relaxation time as well as the time for 1% w/w felodipine crystallization decreased. The relaxation times of the systems, obtained with different water concentration, overlapped when the temperature was scaled (Tg/T). The temperature dependencies of the α-relaxation time as well as the crystallization time were unaffected by the water concentration. Thus, the value of the coupling coefficient, up to a water concentration of 1.8% w/w, was approximately constant. Based on these findings, the use of "water sorption" is proposed to build predictive models for crystallization in slow crystallizing dispersions.

  14. 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.

  15. 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.

  16. Density-Imbalance Stability Diagram of the νT = 1 Bilayer Electron System at Full Spin Polarization

    International Nuclear Information System (INIS)

    Takase, Keiko; Muraki, Koji

    2011-01-01

    We investigate the evolution of the total Landau level filling factor ν T = 1 bilayer quantum Hall (QH) state versus density imbalance at full spin polarization under a tilted magnetic field. When the system is well below the compressible-incompressible transition point at the balanced density, the ν T = 1 QH state extends widely versus density imbalance, continuously merging into the single-layer ν = 1 QH state. In the vicinity of the transition point, the ν T = 1 QH state is only weakly developed at small imbalance but increases in strength toward ν T = 1/3 + 2/3, where it is clearly separated from the single-layer ν = 1 QH state. These results suggest that the system at the imbalance of Δν = 1/3 undergoes a transition from the correlated ν T = 1 QH state to single-layer fractional QH states with increasing density.

  17. 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.

  18. Insertion of Neurotransmitters into a Lipid Bilayer Membrane and Its Implication on Membrane Stability: A Molecular Dynamics Study.

    Science.gov (United States)

    Shen, Chun; Xue, Minmin; Qiu, Hu; Guo, Wanlin

    2017-03-17

    The signaling molecules in neurons, called neurotransmitters, play an essential role in the transportation of neural signals, during which the neurotransmitters interact with not only specific receptors, but also cytomembranes, such as synaptic vesicle membranes and postsynaptic membranes. Through extensive molecular dynamics simulations, the atomic-scale insertion dynamics of typical neurotransmitters, including methionine enkephalin (ME), leucine enkephalin (LE), dopamine (DA), acetylcholine (ACh), and aspartic acid (ASP), into lipid bilayers is investigated. The results show that the first three neurotransmitters (ME, LE, and DA) are able to diffuse freely into both 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membranes, and are guided by the aromatic residues Tyr and Phe. Only a limited number of these neurotransmitters are allowed to penetrate into the membrane, which suggests an intrinsic mechanism by which the membrane is protected from being destroyed by excessive inserted neurotransmitters. After spontaneous insertion, the neurotransmitters disturb the surrounding phospholipids in the membrane, as indicated by the altered distribution of components in lipid leaflets and the disordered lipid tails. In contrast, the last two neurotransmitters (ACh and ASP) cannot enter the membrane, but instead always diffuse freely in solution. These findings provide an understanding at the atomic level of how neurotransmitters interact with the surrounding cytomembrane, as well as their impact on membrane behavior. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Physical inactivation and stabilization of sludges

    International Nuclear Information System (INIS)

    Alexandre, D.

    1979-07-01

    High temperature conditioning of sludge is a stabilization process that insures sterilization. Both thermal pasteurization and irradiation are inactivation processes. Viruses and parasites are inactivated at 70-80 0 C. Total bacterial destruction requires higher temperatures and/or detention time. Radio sensitivity of pathogens and pertinent treatment parameters are examined. If sludge is to be land disposed, disinfection requires irradiation doses ranging 500 Krad; if cattle feeding is considered, the required dose is 1 Mrad

  20. Atomic physics effects on dissipative toroidal drift wave stability

    International Nuclear Information System (INIS)

    Beer, M.A.; Hahm, T.S.

    1992-02-01

    The effects of atomic physics processes such as ionization, charge exchange, and radiation on the linear stability of dissipative drift waves are investigated in toroidal geometry both numerically and analytically. For typical TFTR and TEXT edge parameters, overall linear stability is determined by the competition between the destabilizing influence of ionization and the stabilizing effect due to the electron temperature gradient. An analytical expression for the linear marginal stability condition, η e crit , is derived. The instability is most likely to occur at the extreme edge of tokamaks with a significant ionization source and a steep electron density gradient

  1. Neutral insulin solutions physically stabilized by addition of Zn2+.

    Science.gov (United States)

    Brange, J; Havelund, S; Hommel, E; Sørensen, E; Kühl, C

    1986-01-01

    Commercial neutral insulin solutions, all of which contain 2-3 zinc atoms per hexameric unit of insulin, have a relatively limited physical stability when exposed to heat and movement, as for example in insulin infusion pumps. Physical stabilization of neutral insulin solutions has been obtained by addition of two extra Zn2+ per hexamer of insulin. This addition stabilizes porcine and human neutral solutions equally well and does not affect the chemical stability of the insulin. The stabilization is probably obtained by a further strengthening of the hexameric structure of insulin, so that the formation of insoluble insulin fibrils (via the dissociation into the insulin monomer or dimer) is impeded or prevented. The addition of an extra 2 Zn2+ has been shown to be without influence on the insulin immunogenicity in rabbits or on the rate of absorption after subcutaneous injection in diabetic patients. It is concluded that neutral insulin solution can be physically stabilized by addition of extra Zn2+ without affecting other qualities of the insulin preparation including chemical stability, immunogenicity, and duration of action after injection.

  2. Physical stability of API/polymer-blend amorphous solid dispersions.

    Science.gov (United States)

    Lehmkemper, Kristin; Kyeremateng, Samuel O; Bartels, Mareike; Degenhardt, Matthias; Sadowski, Gabriele

    2018-03-01

    The preparation of amorphous solid dispersions (ASDs) is a well-established strategy for formulating active pharmaceutical ingredients by embedding them in excipients, usually amorphous polymers. Different polymers can be combined for designing ASDs with desired properties like an optimized dissolution behavior. One important criterion for the development of ASD compositions is the physical stability. In this work, the physical stability of API/polymer-blend ASDs was investigated by thermodynamic modeling and stability studies. Amorphous naproxen (NAP) and acetaminophen (APAP) were embedded in blends of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and either poly(vinylpyrrolidone) (PVP) or poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA64). Parameters for modeling the API solubility in the blends and the glass-transition temperature curves of the water-free systems with Perturbed-Chain Statistical Associating Fluid Theory and Kwei equation, respectively, were correlated to experimental data. The phase behavior for standardized storage conditions (0%, 60% and 75% relative humidity (RH)) was predicted and compared to six months-long stability studies. According to modeling and experimental results, the physical stability was reduced with increasing HPMCAS content and increasing RH. This trend was observed for all investigated systems, with both APIs (NAP and APAP) and both polymer blends (PVP/HPMCAS and PVPVA64/HPMCAS). PC-SAFT and the Kwei equation turned out to be suitable tools for modeling and predicting the physical stability of the investigated API/polymer-blends ASDs. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Physical stability of R-(+)-Limonene emulsions stabilized by Ulva fasciata algae polysaccharide.

    Science.gov (United States)

    Shao, Ping; Ma, Huiling; Qiu, Qiang; Jing, Weiping

    2016-11-01

    The physical stability of R-(+)-Limonene emulsions stabilized by Ulva fasciata polysaccharide (UFP) was investigated in this study. Emulsion physical stability was evaluated under different polysaccharide concentrations (1%-5%, wt/wt) and pH values (3.0-11.0). The stability of R-(+)-Limonene emulsions was demonstrated by droplet size distribution, rheological properties, zeta potential and visual phase separation. R-(+)-Limonene emulsions displayed monomodal droplet size distributions, high absolute values of zeta potential and good storage stability when 3% (wt/wt) UFP was used. The rheological properties and stability of R-(+)-Limonene emulsions appeared to be dependent on polysaccharide concentration. The emulsion stability was impacted by pH. Higher zeta potential (-52.6mV) and smaller mean droplet diameter (2.45μm) were achieved in neutral liquid environment (pH 7.0). Extreme acidity caused the flocculation of emulsions, which was manifested as phase separation, while emulsions were quite stable in an alkaline environment. Through comparing the stabilities of emulsions stabilized by different emulsifiers (i.e. UFP, GA and Gelatin), the result suggested that UFP was the best emulsifying agent among them. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Novel β-TCP/PVA bilayered hydrogels with considerable physical and bio-functional properties for osteochondral repair.

    Science.gov (United States)

    Yao, Hang; Kang, Junpei; Li, Weichang; Liu, Jian; Xie, Renjian; Wang, Yingjun; Liu, Sa; Wang, Dong-An; Ren, Li

    2017-12-07

    Cartilage repairing grafts have been widely studied, and osteochondral replacement hydrogels have proven to be an excellent method in research and clinical fields. However, it has been difficult to simultaneously solve three main issues in osteochondral replacement preparation: surface lubrication, overall mechanical support and good simulations of cell regeneration. A novel integrated bilayered hydrogel osteochondral replacement was constructed by blending polyvinyl alcohol (PVA) and β-tricalcium phosphate (β-TCP) in this study. Separated nano-ball milling with ultrasound dispersion prepared β-TCP demonstrated suitable properties of tiny particle size, high purity and ideal distribution, improving the mechanical properties of the novel integrated hydrogel, and providing a cartilage-like lubrication effect and high biocompatibility, including cytocompatibility and osteogenesis. The reinforcement of β-TCP and integrated molding technology enabled the hydrogel to demonstrate excellent component compatibility and good bonding between the two layers, which promoted the strengthening of the compression modulus and tensile modulus up to three times by mechanical testing. The surface lubrication properties of the novel osteochondral hydrogel were similar to the natural cartilage by friction coefficient characterization. The two layers of the novel integrated graft provided a considerable bio-function by co-culturing with chondrocytes and synovium mesenchymal stem cells: chondrocytes promoted adherence achieved by the upper density layer and better osteogenesis performance of the porous lower layer. The design of the bilayered β-TCP/PVA osteochondral hydrogel is promising for use in articular cartilage repair.

  5. 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.

  6. Physical and chemical stability of pemetrexed in infusion solutions.

    Science.gov (United States)

    Zhang, Yanping; Trissel, Lawrence A

    2006-06-01

    Pemetrexed is a multitargeted, antifolate, antineoplastic agent that is indicated for single-agent use in locally advanced or metastatic non-small-cell lung cancer after prior chemotherapy and in combination with cisplatin for the treatment of malignant pleural mesothelioma not treatable by surgery. Currently, there is no information on the long-term stability of pemetrexed beyond 24 hours. To evaluate the longer-term physical and chemical stability of pemetrexed 2, 10, and 20 mg/mL in polyvinyl chloride (PVC) bags of dextrose 5% injection and NaCl 0.9% injection. Triplicate samples of pemetrexed were prepared in the concentrations and infusion solutions required. Evaluations for physical and chemical stability were performed initially and over 2 days at 23 degrees C protected from light and exposed to fluorescent light, and over 31 days of storage at 4 degrees C protected from light. Physical stability was assessed using turbidimetric and particulate measurement as well as visual observation. Chemical stability was evaluated by HPLC. All pemetrexed solutions remained chemically stable, with little or no loss of pemetrexed over 2 days at 23 degrees C, protected from light and exposed to fluorescent light, and over 31 days of storage at 4 degrees C, protected from light. The room temperature samples were physically stable throughout the 48 hour test period. However, pemetrexed admixtures developed large numbers of microparticulates during refrigerated storage exceeding 24 hours. Pemetrexed is chemically stable for 2 days at room temperature and 31 days refrigerated in dextrose 5% injection and NaCl 0.9% injection. However, substantial numbers of microparticulates may form in pemetrexed diluted in the infusion solutions in PVC bags, especially during longer periods of refrigerated storage. Limiting the refrigerated storage period to the manufacturer-recommended 24 hours will limit particulate formation.

  7. [Stability of physical state on compound hawthorn dropping pills].

    Science.gov (United States)

    Zhang, Wei; Chen, Hong-Yan; Jiang, Jian-Lan

    2008-11-01

    To evaluate the stability of physical state with accelerate test and dropping in process before and after on compound hawthorn dropping pills. Scanning electron microscope, TG-DTA, FT-IR and XRD were used. The active components presented amorphous, tiny crystal and molecular state in dropping pills, and it had no obvious reaction between PEG 4000 and active components. With time prolonging, a little of active components changed from amorphous state to tiny crystal or molecular state. Solid dispersion improved the stability and dissolution of compound hawthorn dropping pills.

  8. 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.

  9. Noise stabilization effects in models of interdisciplinary physics

    International Nuclear Information System (INIS)

    Spagnolo, B; Augello, G; Caldara, P; Fiasconaro, A; La Cognata, A; Pizzolato, N; Valenti, D; Dubkov, A A; Pankratov, A L

    2009-01-01

    Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The investigation of noise-induced phenomena in far from equilibrium systems is one of the approaches used to understand the behaviour of physical and biological complex systems. The enhancement of the lifetime of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) polymer translocation dynamics; (ii) transient regime of FitzHugh-Nagumo model; (iii) market stability in a nonlinear Heston model; (iv) dynamics of Josephson junctions; (v) metastability in a quantum bitable system.

  10. 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

  11. Physical and chemical stability of different formulations with superoxide dismutase.

    Science.gov (United States)

    Di Mambro, V M; Campos, P M B G Maia; Fonseca, M J V

    2004-10-01

    Topical formulations with superoxide dismutase (SOD), a scavenger of superoxide radicals, have proved to be effective against some skin diseases. Nevertheless, formulations with proteins are susceptible to both chemical and physical instability. Three different formulations (anionic and non-ionic gel and emulsion) were developed and supplemented with SOD in order to determine the most stable formulation that would maintain SOD activity. Physical stability was evaluated by assessing the rheological behavior of the formulations stored at room temperature, 37 and 45 degrees C. Chemical stability was evaluated by the measurement of enzymatic activity in the formulations stored at room temperature and at 45 degrees C. Formulations showed a flow index less than one, characterizing pseudoplastic behavior. There was no significant difference in initial values of flow index, tixotropy or minimum apparent viscosity. Neither gel showed significant changes in minimum apparent viscosity concerning storage time or temperature, as well, SOD presence and its activity. The emulsion showed decreased viscosity by the 28th day, but no significant changes concerning storage temperature or SOD presence, although it showed a decreased activity. The addition of SOD to the formulations studied did not affect their physical stability but gel formulations seem to be better bases for enzyme addition.

  12. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

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

    2012-01-01

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

  13. 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.

  14. Physical Stability of Freeze-Dried Isomalt Diastereomer Mixtures

    DEFF Research Database (Denmark)

    Koskinen, Anna-Kaisa; Fraser-Miller, Sara J.; Bøtker, Johan P.

    2016-01-01

    Purpose Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried. Methods Isomalt was freeze-dried in......Purpose Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried. Methods Isomalt was freeze......-dried in four different diastereomer compositions and its physical stability was investigated with differential scanning calorimetry, Fourier-transform infrared and Raman spectroscopy, X-ray powder diffraction, Karl-Fischer titration and thermogravimetric analysis in order to verify the solid state form...... of the diastereomer compositions showed signs of physical instability when stored in the highest relative humidity condition. The four different crystalline diastereomer mixtures showed specific identifiable solid state properties. Conclusions Isomalt was shown to be a suitable excipient for freeze-drying. Preferably...

  15. 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.

  16. Analysis of Physical Education Students’ Emotional Stability and Reactibility

    Directory of Open Access Journals (Sweden)

    Radka Peřinová

    2015-03-01

    Full Text Available Analysis of Physical Education Students’ Emotional Stability and Reactibility This paper will aim to show the possible association between emotional stability and reaction time variability of Physical Education students. It can be stated that our study confirmed our suppositions which were based on works that have focused on similar topics. Our research sample showed the expected characteristics: primarily lower neuroticism values and higher extraversion when compared to the non-sporting population. Emotional stability which was reflected in the neuroticism dimension in EPQ-R (Eysenck Personality Questionnaire was shown to be connected with variability of the reaction time in the test of reactability to selected visual stimulus, disregarding the reaction rate. The effect of extraversion is partly reflected by the tendency of the sanguine temperament type to react in a balanced manner (i.e. with low reaction time variability during the reactability test. Due to the relatively low number of other temperament types in our sample, it is not possible to draw any conclusions in this regard. Analýza emocionální stability a reaktibility studentů tělesné výchovy Tento příspěvek poukazuje na možnou asociaci mezi emocionální stabilitou a časovou variabilitou dob reakcí u studentů tělesné výchovy. Lze konstatovat, že studie potvrdila naše předpoklady vycházející z odborných prací na obdobná témata. Výzkumný soubor vykazoval předpokládané charakteristiky, především nižších hodnot neuroticismu a vyšší extroverze oproti nesportující populaci. Emocionální stabilita vyjádřená pomocí dimenze neuroticismu (v EPQ-R se ukázala v asociaci s časovou variabilitou dob reakcí v testu reaktibility na výběrový zrakový podnět bez ohledu na rychlost reakce. Vliv extroverze do jisté míry odráží naznačená tendence sangvinického typu temperamentu reagovat vyrovnaně (tedy s nízkou časovou variabilitou dob

  17. Global physical and numerical stability of a nuclear reactor core

    International Nuclear Information System (INIS)

    Morales-Sandoval, Jaime; Hernandez-Solis, Augusto

    2005-01-01

    Low order models are used to investigate the influence of integration methods on observed power oscillations of some nuclear reactor simulators. The zero-power point reactor kinetics with six-delayed neutron precursor groups are time discretized using explicit, implicit and Crank-Nicholson methods, and the stability limit of the time mesh spacing is exactly obtained by locating their characteristic poles in the z-transform plane. These poles are the s to z mappings of the inhour equation roots and, except for one of them, they show little or no dependence on the integration method. Conditions for stable power oscillations can be also obtained by tracking when steady state output signals resulting from reactivity oscillations in the s-Laplace plane cross the imaginary axis. The dynamics of a BWR core operating at power conditions is represented by a reduced order model obtained by adding three ordinary differential equations, which can model void and Doppler reactivity feedback effects on power, and collapsing all delayed neutron precursors in one group. Void dynamics are modeled as a second order system and fuel heat transfer as a first order system. This model shows rich characteristics in terms of indicating the relative importance of different core parameters and conditions on both numerical and physical oscillations observed by large computer code simulations. A brief discussion of the influence of actual core and coolant conditions on the reduced order model is presented

  18. Effect of the aminoacid composition of model α-helical peptides on the physical properties of lipid bilayers and peptide conformation: a molecular dynamics simulation

    Czech Academy of Sciences Publication Activity Database

    Melicherčík, Milan; Holúbeková, A.; Hianik, T.; Urban, J.

    2013-01-01

    Roč. 19, č. 11 (2013), s. 4723-4730 ISSN 1610-2940 Institutional support: RVO:67179843 Keywords : Bilayer lipid membranes * Helical peptides * Molecular dynamics simulations * Phase transitions Subject RIV: BO - Biophysics Impact factor: 1.867, year: 2013

  19. Gas adsorption, energetics and electronic properties of boron- and nitrogen-doped bilayer graphenes

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, Yoshitaka, E-mail: fujimoto@stat.phys.titech.ac.jp [Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan); Saito, Susumu [Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan); International Research Center for Nanoscience and Quantum Physics, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503 (Japan)

    2016-10-20

    We study stabilities and electronic properties of several environmental polluting or toxic gas molecules (CO, CO{sub 2}, NO, and NO{sub 2}) adsorbed on B and N atoms in bilayer graphene using first-principles electronic-structure calculations. We find that NO and NO{sub 2} molecules can be bound chemically on B-doped bilayer graphene with large adsorption energies, while CO and CO{sub 2} molecules are not adsorbed chemically on B-doped one. In the case of the N-doped graphene, all four gases do not bind with chemical bonds but adsorb rather physically with small adsorption energies at long distances between gases and graphene. The adsorptions of NO and NO{sub 2} molecules on B-doped bilayer graphene induce the acceptor states above the Fermi energy, and we also find that the charge transfer takes place when the NO and the NO{sub 2} molecules are adsorbed. Thereby, the B-doped bilayer graphene is expected to be useful for NO and NO{sub 2} gas sensor materials.

  20. 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.

  1. Cholesterol Perturbs Lipid Bilayers Nonuniversally

    International Nuclear Information System (INIS)

    Pan Jianjun; Mills, Thalia T.; Tristram-Nagle, Stephanie; Nagle, John F.

    2008-01-01

    Cholesterol is well known to modulate the physical properties of biomembranes. Using modern x-ray scattering methods, we have studied the effects of cholesterol on the bending modulus K C , the thickness D HH , and the orientational order parameter S xray of lipid bilayers. We find that the effects are different for at least three classes of phospholipids characterized by different numbers of saturated hydrocarbon chains. Most strikingly, cholesterol strongly increases K C when both chains of the phospholipid are fully saturated but not at all when there are two monounsaturated chains

  2. 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.

  3. Fluorination of Isotopically Labeled Turbostratic and Bernal Stacked Bilayer Graphene

    Czech Academy of Sciences Publication Activity Database

    Ek Weis, Johan; da Costa, Sara; Frank, Otakar; Bastl, Zdeněk; Kalbáč, Martin

    2015-01-01

    Roč. 21, č. 3 (2015), s. 1081-1087 ISSN 1521-3765 R&D Projects: GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : fluorination * graphene * bilayers Subject RIV: CF - Physical ; Theoretical Chemistry

  4. 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.

  5. Physics validation for design change of KSTAR passive stabilizer

    Science.gov (United States)

    Jeon, Y. M.; Kim, J. Y.; Oh, Y. K.; Yang, H. L.; Kim, W. C.; Kim, H. K.; Sabbagh, S. A.; Bialek, J. M.; Humphreys, D. A.; Welander, A. S.; Walker, M. L.

    2009-11-01

    Recently, the design of the passive stabilizer in KSTAR has been changed to improve controllability of the active control system and reduce the possibility of producing an additional error field. Originally the passive stabilizer in KSTAR was designed for RWM and vertical instability (or VDE) stabilizations and plasma startup efficiency, so that current bridges were designed and combined through 3D saddle-loop connections. Since the key design change is removing the current bridges, it's essential to assure satisfactory control performance for these instabilities under the design change. Control capability for n=1 RWM and achievable βN will be addressed as a primary goal of the passive stabilizer together with vertical instability control and effects on plasma startup. In addition, the changes in electro-magnetic force on conducting structures will be discussed qualitatively as a key engineering issue of the design change.

  6. 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....

  7. Physical and chemical stability of the bentonite buffer

    Energy Technology Data Exchange (ETDEWEB)

    Jinsong Liu; Neretnieks, Ivars [Chemical Engineering and Technology, Royal I nstitute of Technology, Stockholm (Sweden)

    2007-12-15

    A literature study was made on previous work on clay erosion and on the fundamental processes that govern the stability of clay gels. Mechanical erosion has been studied earlier and models devised to estimate the tendency to erode. We have used a different approach that we deem is fundamentally more correct. Chemical erosion processes have not been found to be studied previously and we have approached the problem by applying simple but fundamental mass balances and transport processes to the problem. The physical and chemical processes that govern the repulsive and cohesive forces in clay are well understood in principle but cannot yet be applied quantitatively to predict the gel/sol behaviour of the bentonite clay. It was necessary to rely directly on laboratory measurements for information on swelling and gel/sol properties. The backfill bentonite clay acts as a Bingham fluid over a wide range of clay density. To mobilise the clay a shear stress larger than the Bingham yield stress must be applied to the gel. The Bingham yield stress has been measured to be larger than 1 Pa (N/m{sup 2}) although it cannot be ruled out that lower values can be found under different experimental conditions than those reported. Shear stresses exerted by the water flowing in the fractures that intersect the deposition holes with the clay backfill have been estimated for a wide range of fracture transmissivities, apertures and hydraulic gradients that could exist under repository conditions. This includes the extremely high gradients that could exist during some periods during an ice age. For fracture transmissivities ranging from 10{sup -9} to 10{sup -6} m{sup 2}/s, fracture apertures from 0.1 to 2 mm and the hydraulic gradients from 0.01 to 1 mH{sub 2}O/m, the largest local shear stress found in this range was about 0.1 Pa. To investigate a 'what if' situation where the shear stress exceeds the yield stress simple models were devised. They were used to assess the rate of

  8. Physical and chemical stability of the bentonite buffer

    International Nuclear Information System (INIS)

    Jinsong Liu; Neretnieks, Ivars

    2007-12-01

    A literature study was made on previous work on clay erosion and on the fundamental processes that govern the stability of clay gels. Mechanical erosion has been studied earlier and models devised to estimate the tendency to erode. We have used a different approach that we deem is fundamentally more correct. Chemical erosion processes have not been found to be studied previously and we have approached the problem by applying simple but fundamental mass balances and transport processes to the problem. The physical and chemical processes that govern the repulsive and cohesive forces in clay are well understood in principle but cannot yet be applied quantitatively to predict the gel/sol behaviour of the bentonite clay. It was necessary to rely directly on laboratory measurements for information on swelling and gel/sol properties. The backfill bentonite clay acts as a Bingham fluid over a wide range of clay density. To mobilise the clay a shear stress larger than the Bingham yield stress must be applied to the gel. The Bingham yield stress has been measured to be larger than 1 Pa (N/m 2 ) although it cannot be ruled out that lower values can be found under different experimental conditions than those reported. Shear stresses exerted by the water flowing in the fractures that intersect the deposition holes with the clay backfill have been estimated for a wide range of fracture transmissivities, apertures and hydraulic gradients that could exist under repository conditions. This includes the extremely high gradients that could exist during some periods during an ice age. For fracture transmissivities ranging from 10 -9 to 10 -6 m 2 /s, fracture apertures from 0.1 to 2 mm and the hydraulic gradients from 0.01 to 1 mH 2 O/m, the largest local shear stress found in this range was about 0.1 Pa. To investigate a 'what if' situation where the shear stress exceeds the yield stress simple models were devised. They were used to assess the rate of erosion by the groundwater. In

  9. 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.

  10. Long term physical and chemical stability of polyelectrolyte multilayer membranes

    NARCIS (Netherlands)

    de Grooth, Joris; Haakmeester, Brian; Wever, Carlos; Potreck, Jens; de Vos, Wiebe Matthijs; Nijmeijer, Dorothea C.

    2015-01-01

    This work presents a detailed investigation into the long term stability of polyelectrolyte multilayer (PEM) modified membranes, a key factor for the application of these membranes in water purification processes. Although PEM modified membranes have been frequently investigated, their long term

  11. 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.

  12. Physical stability and clinical efficacy of Crocodylus niloticus oil lotion

    Directory of Open Access Journals (Sweden)

    Telanie Venter

    Full Text Available ABSTRACT The stability and the anti-ageing, skin hydrating and anti-erythema effects of a commercialized Crocodylus niloticus Laurenti, 1768, Crocodylidae, oil lotion was determined. The lotion was stored at controlled conditions over six months during which several stability tests were performed. For the clinical efficacy studies lotion was applied on volar forearm skin (female volunteers and compared to a liquid paraffin-containing reference product. Skin hydrating and anti-ageing effects were determined with a Corneometer®, Cutometer® and Visioscan®, following single (3 h and multiple applications (12 weeks. The Vapometer® and Mexameter® were utilized to determine this lotion's anti-erythema effects on sodium lauryl sulfate irritated skin. The lotion demonstrated good stability over 6 months. The reference product increased skin hydration and decreased skin wrinkles to a larger extent than the C. niloticus lotion after a single application, whereas the C. niloticus lotion decreased skin scaliness better than the reference product. During the long-term study, the reference product overall increased skin hydration more than the C. niloticus lotion, whereas C. niloticus lotion increased skin elasticity to a larger extent than the reference product. C. niloticus lotion increased skin wrinkles and decreased skin scaliness over 12 weeks. Compared to non-treated, irritated skin, C. niloticus lotion demonstrated some potential anti-inflammatory characteristics.

  13. Physical Analysis Work for Slope Stability at Shah Alam, Selangor

    Science.gov (United States)

    Ishak, M. F.; Zaini, M. S. I.

    2018-04-01

    Slope stability analysis is performed to assess the equilibrium conditions and the safe design of a human-made or natural slope to find the endangered areas. Investigation of potential failure and determination of the slope sensitivity with regard to safety, reliability and economics were parts of this study. Ground anchor is designed to support a structure in this study. Ground anchor were implemented at the Mechanically Stabilized Earth (MSE) wall along Anak Persiaran Jubli Perak to overcome the further cracking of pavement parking, concrete deck and building of the Apartments. A result from the laboratory testing of soil sample such as index test and shear strength test were applied to the Slope/W software with regard to the ground anchors that were implemented. The ground anchors were implemented to increase the value of the factor of safety (FOS) of the MSE Wall. The value of the factor of safety (FOS) before implementing the ground anchor was 0.800 and after the ground anchor was implemented the value increase to 1.555. The increase percentage of factor of safety by implementing on stability of slope was 94.38%.

  14. Physical and oxidative stability of fish oil-in-water emulsions stabilized with beta-lactoglobulin and pectin.

    Science.gov (United States)

    Katsuda, Marly S; McClements, D J; Miglioranza, Lucia H S; Decker, Eric A

    2008-07-23

    The oxidation of fatty acids can be inhibited by engineering the surface of oil-in-water emulsion droplets to decrease interactions between aqueous phase prooxidants and lipids. The objective of this research was to evaluate whether emulsions stabilized by a multilayer emulsifier systems consisting of beta-lactoglobulin and citrus or sugar beet pectin could produce fish oil-in-water emulsions that had good physical and oxidative stability. Sugar beet pectin was compared to citrus pectin because the sugar beet pectin contains the known antioxidant, ferulic acid. A primary Menhaden oil-in-water emulsion was prepared with beta-lactoglobulin upon which the pectins were electrostatically deposited at pH 3.5. Emulsions prepared with 1% oil, 0.05% beta-lactoglobulin, and 0.06% pectins were physically stable for up to 16 days. As determined by monitoring lipid hydroperoxide and headspace propanal formation, emulsions prepared with the multilayer system of beta-lactoglobulin and citrus pectin were more stable than emulsions stabilized with beta-lactoglobulin alone. Emulsions prepared with the multilayer system of beta-lactoglobulin and sugar beet pectin were less stable than emulsions stabilized with beta-lactoglobulin alone despite the presence of ferulic acid in the sugar beet pectin. The lower oxidative stability of the emulsions with the sugar beet pectin could be due to its higher iron and copper concentrations which would produce oxidative stress that would overcome the antioxidant capacity of ferulic acid. These data suggest that the oxidative stability of oil-in-water emulsions containing omega-3 fatty acids could be improved by the use of multilayer emulsion systems containing pectins with low metal concentrations.

  15. 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....

  16. Topical formulations with superoxide dismutase: influence of formulation composition on physical stability and enzymatic activity.

    Science.gov (United States)

    Di Mambro, Valéria M; Borin, Maria F; Fonseca, Maria J V

    2003-04-24

    Three different topical formulations were supplemented with superoxide dismutase (SOD) and evaluated concerning physical and chemical stabilities in order to determine the most stable formulation that would maintain SOD activity. Physical stability was evaluated by storing the formulation at room temperature, and at 37 and 45 degrees C for 28 days. Samples were collected at 7-day intervals for assessment of rheological behavior. Chemical stability was evaluated by the measurement of enzymatic activity in formulations stored at room temperature and at 45 degrees C for 75 days. The formulations showed a pseudoplastic behavior, with a flow index of less than 1. There was no significant difference in the initial values of flow index, hysteresis loop or minimum apparent viscosity. The simple emulsion and the one stabilized with hydroxyethylcellulose showed decreased viscosity by the 21st day and with higher temperature, but no significant changes concerning the presence of SOD. Although there were no significant changes concerning storage time or temperature, the formulation stabilized with hydroxyethylcellulose showed a marked loss of SOD activity. The addition of SOD to the formulations studied did not affect their physical stability. Simple emulsions or emulsions stabilized with carboxypolymethylene seem to be better bases for enzyme addition than emulsion stabilized with hydroxyethylcellulose.

  17. AFRL’s ALREST Physics-Based Combustion Stability Program

    Science.gov (United States)

    2012-11-08

    enduring challenge because of the inherent complexities in the physics of multiphase turbulent flames. The present paper provides the Air Force...Combustor F i d e l i t y URANS LES Steady RANS HLES Current SOA Capability with 2000 cores Capability at Program End in 2015 (2,000 cores+GPUs) Capability...Unlimited ALREST Validation Cases “Final Exam ” Hydrogen Stable Single Element (PSU) Stable Single Element Methane (Singla) Supercritical Non

  18. Phase behavior of supported lipid bilayers: A systematic study by coarse-grained molecular dynamics simulations

    DEFF Research Database (Denmark)

    Poursoroush, Asma; Sperotto, Maria Maddalena; Laradji, Mohamed

    2017-01-01

    Solid-supported lipid bilayers are utilized by experimental scientists as models for biological membranes because of their stability. However, compared to free standing bilayers, their close proximity to the substrate may affect their phase behavior. As this is still poorly understood, and few co...

  19. Chemical stability and physical properties of Caesium uranates

    International Nuclear Information System (INIS)

    Berton, J.P.; Baron, D.; Coquerelle, M.

    1998-01-01

    Caesium is one of the most abundant fission products in PWR nuclear fuel or in fast reactor fuel as well. A work program has been started at the TUI Karlsruhe, in collaboration with EDF Etudes et Recherches, to determine the thermal stability and conductivity, the mechanical properties and the thermal expansion coefficient of Cs 2 UO 4 . The Caesium mono-uranate was obtained by a chemical reaction between Cs 2 O 3 and U 3 O 8 powders mixed together, pressed and heated at 670 deg. C for 24 hours. The compound was found stable up to 830 deg. C. Mechanical compressive hardening tests allowed to evaluate the elastic modulus versus temperature in the range 200 to 800 deg. C. Furthermore the viscous behaviour of the compound above 400 deg. C was confirmed. The thermal expansion coefficient of Cs 2 UO 4 was found somewhat 40% higher than the thermal expansion coefficient of UO 2 . The thermal conductivity is about 1.5 to 1.8 W/m/K for temperatures ranging from 100 to 700 deg. C, a value very similar to the UO 2 fuel thermal conductivity at high burnup in the same temperature range. (author)

  20. 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.

  1. Influence of particle size and preparation methods on the physical and chemical stability of amorphous simvastatin

    DEFF Research Database (Denmark)

    Zhang, Fang; Aaltonen, Jaakko; Tian, Fang

    2009-01-01

    This study investigated the factors influencing the stability of amorphous simvastatin. Quench-cooled amorphous simvastatin in two particle size ranges, 150-180 microm (QC-big) and ... compared to the crystalline form. The rank of solubility was found to be QC-big=QC-small>CM>crystalline. For the physical stability, the highest crystallization rate was observed for CM, and the slowest rate was detected for QC-big, with an intermediate rate occurring for QC-small. QC exhibited lower...

  2. A Molecular-Level View of the Physical Stability of Amorphous Solid Dispersions

    Science.gov (United States)

    Yuan, Xiaoda

    Many pharmaceutical compounds being developed in recent years are poorly soluble in water. This has led to insufficient oral bioavailability of many compounds in vitro. The amorphous formulation is one of the promising techniques to increase the oral bioavailability of these poorly water-soluble compounds. However, an amorphous drug substance is inherently unstable because it is a high energy form. In order to increase the physical stability, the amorphous drug is often formulated with a suitable polymer to form an amorphous solid dispersion. Previous research has suggested that the formation of an intimately mixed drug-polymer mixture contributes to the stabilization of the amorphous drug compound. The goal of this research is to better understand the role of miscibility, molecular interactions and mobility on the physical stability of amorphous solid dispersions. Methods were developed to detect different degrees of miscibility on nanometer scale and to quantify the extent of hydrogen-bonding interactions between the drug and the polymer. Miscibility, hydrogen-bonding interactions and molecular mobility were correlated with physical stability during a six-month period using three model systems. Overall, this research provides molecular-level insights into many factors that govern the physical stability of amorphous solid dispersions which can lead to a more effective design of stable amorphous formulations.

  3. 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

  4. Leachability and physical stability of solidified and stabilized pyrite cinder sludge from dye effluent treatment

    Directory of Open Access Journals (Sweden)

    Kerkez Đurđa V.

    2015-01-01

    Full Text Available This work is concerned with exploring the possibilities of using solidification/stabilization (S/S treatment for toxic sludge generated in dye effluent treatment, when pyrite cinder is used as catalytic iron source in the modified heterogeneous Fenton process. S/S treatment was performed by using different clay materials (kaolin, bentonite and native clay from the territory of Vojvodina and fly ash in order to immobilize toxic metals and arsenic presented in sludge. For the evaluation of the extraction potential of toxic metals and the effectiveness of the S/S treatment applied, four single-step leaching tests were performed. Leaching test results indicated that all applied S/S treatments were effective in immobilizing toxic metals and arsenic presented in sludge. X-ray diffraction analysis confirmed the formation of pozzolanic products, and compressive strength measurement proved the treatment efficacy. It can be concluded that the S/S technique has significant potential for solving the problem of hazardous industrial waste and its safe disposal. [Projekat Ministarstva nauke Republike Srbije, br. III43005 i br. TR37004

  5. 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.

  6. Habit in the physical activity domain: integration with intention stability and action control

    NARCIS (Netherlands)

    Rhodes, R.E.; de Bruijn, G.J.; Matheson, D.

    2010-01-01

    The purpose of this study was to explore the role of habit in predicting physical activity with the theory of planned behavior (TPB). The study extended previous research by (a) including a measure of temporal intention stability in the regression equation, and (b) unpacking the intention x behavior

  7. The physical stability of the recombinant tuberculosis fusion antigens h1 and h56

    DEFF Research Database (Denmark)

    Hamborg, Mette; Kramer, Ryan; Schanté, Carole E

    2013-01-01

    a gradual loss of secondary as well as tertiary structure as a function of temperature, with no cooperative transitions observed. Preformulation studies with the Th1-inducing cationic adjuvant CAF01 showed that the antigens were almost completely surface adsorbed. Upon adsorption, the liposome size...... and it is therefore important to characterize their conformational stability in solution as well as upon interaction with adjuvants. In this study, the physical stability of the two antigens was characterized using a number of biophysical techniques. Dynamic light scattering and sodium dodecyl sulfate...... increased; however, the physical stabilities of the bound and the unbound antigens were comparable. This study provides important information about the biophysical properties of H1 and H56 and highlights the analytical challenges of characterizing complex vaccine formulations....

  8. 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

  9. Physical and chemical stability of palonosetron HCl in 4 infusion solutions.

    Science.gov (United States)

    Trissel, Lawrence A; Xu, Quanyun A

    2004-10-01

    Palonosetron HCl is a selective 5-HT(3) receptor antagonist used for the prevention of chemotherapy-induced nausea and vomiting. Palonosetron HCl may be diluted in an infusion solution for administraton. Consequently, stability information is needed for palonosetron HCl admixed in common infusion solutions. To evaluate the physical and chemical stability of palonosetron HCl in concentrations of 5 and 30 microg/mL in dextrose 5% injection, NaCl 0.9% injection, dextrose 5% in NaCl 0.45% injection, and dextrose 5% in lactated Ringer's injection. Triplicate test samples of palonosetron HCl at each concentration in each diluent were tested. Samples were stored and evaluated at appropriate intervals for up to 48 hours at room temperature ( approximately 23 degrees C) and 14 days under refrigeration (4 degrees C). Physical stability was assessed using turbidimetric and particulate measurement, as well as visual inspection. Chemical stability was assessed by HPLC. All of the admixtures were initially clear and colorless when viewed in normal fluorescent room light and with a Tyndall beam. Measured turbidity and particulate content were low initially and remained low throughout the study. The drug concentration was unchanged in any of the samples at either temperature throughout the study. Palonosetron HCl is physically and chemically stable in all 4 common infusion solutions for at least 48 hours at room temperature and 14 days under refrigeration.

  10. Derivation of the physical equations solved in the inertial confinement stability code DOC. Informal report

    International Nuclear Information System (INIS)

    Scannapieco, A.J.; Cranfill, C.W.

    1978-11-01

    There now exists an inertial confinement stability code called DOC, which runs as a postprocessor. DOC (a code that has evolved from a previous code, PANSY) is a spherical harmonic linear stability code that integrates, in time, a set of Lagrangian perturbation equations. Effects due to real equations of state, asymmetric energy deposition, thermal conduction, shock propagation, and a time-dependent zeroth-order state are handled in the code. We present here a detailed derivation of the physical equations that are solved in the code

  11. Derivation of the physical equations solved in the inertial confinement stability code DOC. Informal report

    Energy Technology Data Exchange (ETDEWEB)

    Scannapieco, A.J.; Cranfill, C.W.

    1978-11-01

    There now exists an inertial confinement stability code called DOC, which runs as a postprocessor. DOC (a code that has evolved from a previous code, PANSY) is a spherical harmonic linear stability code that integrates, in time, a set of Lagrangian perturbation equations. Effects due to real equations of state, asymmetric energy deposition, thermal conduction, shock propagation, and a time-dependent zeroth-order state are handled in the code. We present here a detailed derivation of the physical equations that are solved in the code.

  12. 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...

  13. Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

    Science.gov (United States)

    Capece, Maxx; Davé, Rajesh

    2015-06-01

    Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  14. Interplay Between Energy-Market Dynamics and Physical Stability of a Smart Power Grid

    Science.gov (United States)

    Picozzi, Sergio; Mammoli, Andrea; Sorrentino, Francesco

    2013-03-01

    A smart power grid is being envisioned for the future which, among other features, should enable users to play the dual role of consumers as well as producers and traders of energy, thanks to emerging renewable energy production and energy storage technologies. As a complex dynamical system, any power grid is subject to physical instabilities. With existing grids, such instabilities tend to be caused by natural disasters, human errors, or weather-related peaks in demand. In this work we analyze the impact, upon the stability of a smart grid, of the energy-market dynamics arising from users' ability to buy from and sell energy to other users. The stability analysis of the resulting dynamical system is performed assuming different proposed models for this market of the future, and the corresponding stability regions in parameter space are identified. We test our theoretical findings by comparing them with data collected from some existing prototype systems.

  15. Association between the physical stability of flurbiprofen suspension and the interaction of HPMC/SDS

    Directory of Open Access Journals (Sweden)

    Hongyu Wang

    2018-01-01

    Full Text Available The anionic surfactant sodium dodecylsulfate (SDS has improved the physical stability of flurbiprofen (FBP suspension, which was suspended by 0.2% (w/v hydroxypropylmethyl cellulose (HPMC, K4M. Therefore, the physical stability of FBP suspensions and the interaction of HPMC/SDS were studied, and a certain association between them was revealed. The anti-solvent precipitation method was used to prepare suspensions. The apparent drug concentration from different sites was evaluated to get the dispersion of drug actually. The process of flocculation and deflocculation with the addition of SDS was caught by analyzing the morphology of the suspended particles. The physical stability of the FBP suspensions was characterized mainly by measuring the re-dispersion time, the zeta potential and particle size. Meanwhile, conductivity measurements were carried out to obtain the characteristic concentrations of SDS in HPMC/SDS system. The viscosities, the abilities for improving the solubility and wettability of FBP in the separate and mixed HPMC/SDS solutions were also contrasted respectively. The suspensions prepared with HPMC/SDS possessed better physical stability. The suspensions were uniform when the concentration of SDS was between the critical adsorption concentration (CAC and the polymer saturation point (PSP. After PSP, the uniformity became worse and worse until the SDS was enough to form a deflocculation state. Besides, the re-dispersion time of FBP suspensions was longest when the concentration of SDS around CAC and shorter by shorter after the critical micelle concentration (CMC. The article provided a new sight on the relation between the interaction of excipient matrix and pharmaceutical preparations.

  16. 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.

  17. Physical stability, biocompatibility and potential use of hybrid iron oxide-gold nanoparticles as drug carriers

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, Christopher M. [School of Pharmacy, Keele University (United Kingdom); Gueorguieva, Mariana [Institute of Medical Science and Technology, University of Dundee (United Kingdom); Lees, Martin R. [University of Warwick, Physics Department (United Kingdom); McGarvey, David J. [School of Physical and Geographical Sciences, Keele University, Lennard-Jones Laboratories (United Kingdom); Hoskins, Clare, E-mail: c.hoskins@keele.ac.uk [Institute for Science and Technology in Medicine, Keele University (United Kingdom)

    2013-06-15

    Hybrid nanoparticles (HNPs) such as iron oxide-gold nanoparticles are currently being exploited for their potential application in image-guided therapies. However, little investigation has been carried out into their physical or chemical stability and potential cytotoxicity in biological systems. Here, we determine the HNPs physical stability over 6 months and chemical stability in physiological conditions, and estimate the biological activity of uncoated and poly(ethylene glycol) coated nanoparticles on human pancreatic adenocarcinoma (BxPC-3) and differentiated human monocyte cells (U937). The potential of these HNPs to act as drug carrier vehicles was determined using the model drug 6-Thioguanine (6-TG). The data showed that the HNPs maintained their structural integrity both physically and chemically throughout the duration of the studies. In addition, negligible cytotoxicity or free radical production was observed in the cell lines tested. The 6-TG was successfully conjugated; with a ratio of 3:1:10 Fe:Au:6-TG (wt:wt:wt). After incubation with BxPC-3 cells, enhanced cellular uptake was reported with the 6-TG-conjugated HNPs compared with free drug along with a 10-fold decrease in IC{sub 50}. This exciting data highlights the potential of HNPs for use in image-guided drug delivery.

  18. Sensitivity analysis and calibration of a dynamic physically based slope stability model

    Science.gov (United States)

    Zieher, Thomas; Rutzinger, Martin; Schneider-Muntau, Barbara; Perzl, Frank; Leidinger, David; Formayer, Herbert; Geitner, Clemens

    2017-06-01

    Physically based modelling of slope stability on a catchment scale is still a challenging task. When applying a physically based model on such a scale (1 : 10 000 to 1 : 50 000), parameters with a high impact on the model result should be calibrated to account for (i) the spatial variability of parameter values, (ii) shortcomings of the selected model, (iii) uncertainties of laboratory tests and field measurements or (iv) parameters that cannot be derived experimentally or measured in the field (e.g. calibration constants). While systematic parameter calibration is a common task in hydrological modelling, this is rarely done using physically based slope stability models. In the present study a dynamic, physically based, coupled hydrological-geomechanical slope stability model is calibrated based on a limited number of laboratory tests and a detailed multitemporal shallow landslide inventory covering two landslide-triggering rainfall events in the Laternser valley, Vorarlberg (Austria). Sensitive parameters are identified based on a local one-at-a-time sensitivity analysis. These parameters (hydraulic conductivity, specific storage, angle of internal friction for effective stress, cohesion for effective stress) are systematically sampled and calibrated for a landslide-triggering rainfall event in August 2005. The identified model ensemble, including 25 behavioural model runs with the highest portion of correctly predicted landslides and non-landslides, is then validated with another landslide-triggering rainfall event in May 1999. The identified model ensemble correctly predicts the location and the supposed triggering timing of 73.0 % of the observed landslides triggered in August 2005 and 91.5 % of the observed landslides triggered in May 1999. Results of the model ensemble driven with raised precipitation input reveal a slight increase in areas potentially affected by slope failure. At the same time, the peak run-off increases more markedly, suggesting that

  19. Impact of new physics on the EW vacuum stability in a curved spacetime background

    Science.gov (United States)

    Bentivegna, E.; Branchina, V.; Contino, F.; Zappalà, D.

    2017-12-01

    It has been recently shown that, contrary to an intuitive decoupling argument, the presence of new physics at very large energy scales (say around the Planck scale) can have a strong impact on the electroweak vacuum lifetime. In particular, the vacuum could be totally destabilized. This study was performed in a flat spacetime background, and it is important to extend the analysis to curved spacetime since these are Planckian-physics effects. It is generally expected that under these extreme conditions gravity should totally quench the formation of true vacuum bubbles, thus washing out the destabilizing effect of new physics. In this work we extend the analysis to curved spacetime and show that, although gravity pushes toward stabilization, the destabilizing effect of new physics is still (by far) the dominating one. In order to get model independent results, high energy new physics is parametrized in two different independent ways: as higher order operators in the Higgs field, or introducing new particles with very large masses. The destabilizing effect is observed in both cases, hinting at a general mechanism that does not depend on the parametrization details for new physics, thus maintaining the results obtained from the analysis performed in flat spacetime.

  20. Effect of formulation variables on the physical properties and stability of Dead Sea mud masks.

    Science.gov (United States)

    Shahin, Sawsan; Hamed, Saja; Alkhatib, Hatim S

    2015-01-01

    The physical stability of Dead Sea mud mask formulations under different conditions and their rheological properties were evaluated as a function of the type and level of thickeners, level of the humectant, incorporation of ethanol, and mode of mud treatment. Formulations were evaluated in terms of visual appearance, pH, moisture content, spreadability, extrudability, separation, rate of drying at 32 degrees C, and rheological properties. Prepared mud formulations and over-the-shelf products showed viscoplastic shear thinning behavior; satisfactory rheological behavior was observed with formulations containing a total concentration of thickeners less than 10% (w/w). Casson and Herschel-Bulkley models were found the most suitable to describe the rheological data of the prepared formulations. Thickener incorporation decreased phase separation and improved formulation stability. Bentonite incorporation in the mud prevented color changes during stability studies while glycerin improved spreadability. Addition of 5% (w/w) ethanol improved mud extrudability, slightly increased percent separation, accelerated drying at 32 degrees C, and decreased viscosity and yield stress values. Different mud treatment techniques did not cause a clear behavioral change in the final mud preparation. B10G and K5B5G were labeled as "best formulas" based on having satisfactory physical and aesthetic criteria investigated in this study, while other formulations failed in one or more of the tests we have performed.

  1. Coamorphous Loratadine-Citric Acid System with Enhanced Physical Stability and Bioavailability.

    Science.gov (United States)

    Wang, Jin; Chang, Ruimiao; Zhao, Yanan; Zhang, Jiye; Zhang, Ting; Fu, Qiang; Chang, Chun; Zeng, Aiguo

    2017-10-01

    Coamorphous systems using citric acid as a small molecular excipient were studied for improving physical stability and bioavailability of loratadine, a BCS class II drug with low water solubility and high permeability. Coamorphous loratadine-citric acid systems were prepared by solvent evaporation technique and characterized by differential scanning calorimetry, X-ray powder diffraction, and Fourier transform infrared spectroscopy. Solid-state analysis proofed that coamorphous loratadine-citric acid system (1:1) was amorphous and homogeneous, had a higher T g over amorphous loratadine, and the intermolecular hydrogen bond interactions between loratadine and citric acid exist. The solubility and dissolution of coamorphous loratadine-citric acid system (1:1) were found to be significantly greater than those of crystalline and amorphous form. The pharmacokinetic study in rats proved that coamorphous loratadine-citric acid system (1:1) could significantly improve absorption and bioavailability of loratadine. Coamorphous loratadine-citric acid system (1:1) showed excellently physical stability over a period of 3 months at 25°C under 0% RH and 25°C under 60% RH conditions. The improved stability of coamorphous loratadine-citric acid system (1:1) could be related to an elevated T g over amorphous form and the intermolecular hydrogen bond interactions between loratadine and citric acid. These studies demonstrate that the developed coamorphous loratadine-citric acid system might be a promising oral formulation for improving solubility and bioavailability of loratadine.

  2. A Pilot Chemical and Physical Stability Study of Extemporaneously Compounded Levetiracetam Intravenous Solution.

    Science.gov (United States)

    Raphael, Chenzira D; Zhao, Fang; Hughes, Susan E; Juba, Katherine M

    2015-01-01

    Levetiracetam is a commonly used antiepileptic medication for tumor-related epilepsy. However, the 100 mL intravenous (IV) infusion volume can be burdensome to imminently dying hospice patients. A reduced infusion volume would improve patient tolerability. The purpose of this study was to evaluate the stability of 1000 mg/25 mL (40 mg/mL) levetiracetam IV solution in sodium chloride 0.9%. We prepared levetiracetam 40 mg/mL IV solution and added it to polyvinyl chloride (PVC) bags, polyolefin bags, and polypropylene syringes. Triplicate samples of each product were stored at refrigeration (2-8°C) and analyzed on days 0, 1, 4, 7, and 14. Samples were subjected to visual inspection, pH measurement, and stability-indicating high-performance liquid chromatography (HPLC) analysis. Over the 2-week storage period, there was no significant change in visual appearance or pH for any of the stability samples. The HPLC results confirmed that all stability samples retained 94.2-101.3% of initial drug concentration and no degradation products or leachable material from the packaging materials were observed. We conclude that levetiracetam 1000 mg/25 mL IV solution in sodium chloride 0.9% is physically and chemically stable for up to 14 days under refrigeration in polypropylene syringes, PVC bags, and polyolefin bags.

  3. Assessment of Physical Stability and Antioxidant Activity of Polysiloxane Polyalkyl Polyether Copolymer-Based Creams

    Directory of Open Access Journals (Sweden)

    Atif Ali

    2013-01-01

    Full Text Available The purpose of the present work was to investigate the changes on physical stability (color, creaming, liquefaction, pH, conductivity, centrifugation, viscosity and rheological parameters by non-ionic surfactant polysiloxane polyalkyl polyether copolymer based creams following inclusion of plant extract containing phenolic compounds. The antioxidant activity of the plant extract alone and after addition in the cream was assessed using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH assay. Physical stability was assessed by submitting the creams to storage at 8°C, 25°C, 40°C, and at 40°C with 70% RH (relative humidity for a period of two months. Physical characteristics of polysiloxane polyalkyl polyether copolymer based creams, that is, color, creaming, liquefaction, centrifugation and pH were noted at various intervals for 2 months. The viscosities and rheological behavior of creams were determined using a rotational rheometer. Data were analyzed by using Brookfield Software Rheocalc version (2.6 with IPC Paste and Power Law (PL math models. Cream with plant extract showed pseudo plastic behaviour with decreasing on viscosity. The Acacia nilotica (AN extract alone and the cream containing this extract showed great antioxidant and free radical scavenging activities. Power Law and IPC analysis were found to fit all the rheograms.

  4. 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

  5. Physical and chemical stability of proflavine contrast agent solutions for early detection of oral cancer.

    Science.gov (United States)

    Kawedia, Jitesh D; Zhang, Yan-Ping; Myers, Alan L; Richards-Kortum, Rebecca R; Kramer, Mark A; Gillenwater, Ann M; Culotta, Kirk S

    2016-02-01

    Proflavine hemisulfate solution is a fluorescence contrast agent to visualize cell nuclei using high-resolution optical imaging devices such as the high-resolution microendoscope. These devices provide real-time imaging to distinguish between normal versus neoplastic tissue. These images could be helpful for early screening of oral cancer and its precursors and to determine accurate margins of malignant tissue for ablative surgery. Extemporaneous preparation of proflavine solution for these diagnostic procedures requires preparation in batches and long-term storage to improve compounding efficiency in the pharmacy. However, there is a paucity of long-term stability data for proflavine contrast solutions. The physical and chemical stability of 0.01% (10 mg/100 ml) proflavine hemisulfate solutions prepared in sterile water was determined following storage at refrigeration (4-8℃) and room temperature (23℃). Concentrations of proflavine were measured at predetermined time points up to 12 months using a validated stability-indicating high-performance liquid chromatography method. Proflavine solutions stored under refrigeration were physically and chemically stable for at least 12 months with concentrations ranging from 95% to 105% compared to initial concentration. However, in solutions stored at room temperature increased turbidity and particulates were observed in some of the tested vials at 9 months and 12 months with peak particle count reaching 17-fold increase compared to baseline. Solutions stored at room temperature were chemically stable up to six months (94-105%). Proflavine solutions at concentration of 0.01% were chemically and physically stable for at least 12 months under refrigeration. The solution was chemically stable for six months when stored at room temperature. We recommend long-term storage of proflavine solutions under refrigeration prior to diagnostic procedure. © The Author(s) 2014.

  6. Microstructural development in physical vapour-deposited partially stabilized zirconia thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Sohn, Y. H. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States)); Biederman, R.R. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States)); Sisson, R.D. Jr. (Center for Intelligent Processing of Materials, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609-2280 (United States))

    1994-10-01

    The effects of processing parameters of physical vapour deposition on the microstructure of partially stabilized zirconia (PSZ) thermal barrier coatings have been experimentally investigated. Emphasis has been placed on the crystallographic texture of the PSZ coatings and the microstructure of the top surface of the PSZ coatings as well as the metal-ceramic interface. The variations in the deposition chamber temperature, substrate thickness, substrate rotation and vapour incidence angle resulted in the observation of significant differences in the crystallographic texture and microstructure of the PSZ coatings. ((orig.))

  7. Coamorphous drug systems: enhanced physical stability and dissolution rate of indomethacin and naproxen

    DEFF Research Database (Denmark)

    Löbmann, Korbinian; Laitinen, Riikka; Grohganz, Holger

    2011-01-01

    . In this study, a coamorphous drug/drug combination between the two nonsteroidal anti-inflammatory drugs, naproxen and ¿-indomethacin, was prepared and investigated. At molar ratios of 2:1, 1:1 and 1:2, the drugs were quench cooled in order to obtain a coamorphous binary phase. Physical stability was examined...... at 277.15 and 298.15 K under dry conditions (phosphorus pentoxide) and analyzed with X-ray powder diffraction (XRPD). Intrinsic dissolution testing was carried out to identify dissolution advantages of the coamorphous form over its crystalline counterparts or amorphous indomethacin. Fourier transform...

  8. On the physical problem of spatial dimensions: an alternative procedure to stability arguments

    International Nuclear Information System (INIS)

    Caruso, F.; Xavier, R.M.

    1986-01-01

    The three-dimensionality of space as a physical problem is discussed. Consideration on previous works is done, in which it is showed that the n-dimensional solar system can be stable only for n=3 and, from quantum mechanics, that this is the case also for hydrogen atons. Thus the epistemological consequences of the use of the stability postulate to derive spatial dimensionality is critically reviewed. The distinguished role of Maxwell's eletromagnetic theory in the determination of space dimensionality is stressed. 'Metric versus' 'topological' 'arguments are compared and shown to apply respectively to 'matter' and 'fields'. (G.D.F.) [pt

  9. 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.

  10. The physical and chemical stability of suspensions of sustained-release diclofenac microspheres.

    Science.gov (United States)

    Lewis, L; Boni, R L; Adeyeye, C M

    1998-01-01

    The major challenge in liquid sustained-release oral suspensions is to minimize drug diffusion into the suspending medium and to retain the original properties of the microparticles during storage. Diclofenac wax microspheres prepared by the hydrophobic congealable disperse phase method were formulated as a sustained release suspension and stored at three different temperatures (25, 37 and 45 degrees C) for 3 months, to evaluate the physical and chemical stability of the suspended microspheres. Suspensions of microspheres stored at ambient temperatures were both physically and chemically stable, but at higher temperatures, up to 45 degrees C, there was a decrease in drug release due to scaling and melting on the microsphere surface as observed by scanning electron microscopy. However, on prolonged storage, up to 90 days, especially at 45 degrees C, temperature became a dominant factor causing an increase in drug release. The suspension of diclofenac microspheres was chemically stable for 3 months, while the plain drug suspension exhibited slight degradation.

  11. Processing-structure-property relationships in electron beam physical vapor deposited yttria stabilized zirconia coatings

    International Nuclear Information System (INIS)

    Rao, D. Srinivasa; Valleti, Krishna; Joshi, S. V.; Janardhan, G. Ranga

    2011-01-01

    The physical and mechanical properties of yttria stabilized zirconia (YSZ) coatings deposited by the electron beam physical vapor deposition technique have been investigated by varying the key process variables such as vapor incidence angle and sample rotation speed. The tetragonal zirconia coatings formed under varying process conditions employed were found to have widely different surface and cross-sectional morphologies. The porosity, phase composition, planar orientation, hardness, adhesion, and surface residual stresses in the coated specimens were comprehensively evaluated to develop a correlation with the process variables. Under transverse scratch test conditions, the YSZ coatings exhibited two different crack formation modes, depending on the magnitude of residual stress. The influence of processing conditions on the coating deposition rate, column orientation angle, and adhesion strength has been established. Key relationships between porosity, hardness, and adhesion are also presented.

  12. 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.

  13. 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.

  14. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  15. Physical stability of asphalt emulsion admix seal radon barrier for uranium mill tailings

    International Nuclear Information System (INIS)

    Gates, T.E.

    1983-09-01

    Pacific Northwest Laboratory, is investigating the use of an asphalt emulsion admix seal to reduce the release of radon from uranium mill tailings. A key requirement of any cover system is its long-term stability; the cover must withstand failure over very long periods of time. An important determinant of overall cover system stability is the integrity of the 6.35-cm (2.5-in.) thick asphalt admix seal. Therefore, the physical stability of this seal was examined. The investigation considered the mechanical interaction between the tailings pile and cover. The potential effect of differential settlement of the tailings pile on the integrity of the seal system was also examined. Results indicate that the minimum span length the seal could withstand without failing is 0.34 m (1.1 ft). This assumes a differential settlement of 4.92 cm (1.94 in.) at the center resulting from the application of a 0.76-m (2.5-ft) cover. At spans greater than 0.60 m (1.97 ft), no tensile strain would develop

  16. Physical and Oxidative Stability of Uncoated and Chitosan-Coated Liposomes Containing Grape Seed Extract

    Directory of Open Access Journals (Sweden)

    Jochen Weiss

    2013-08-01

    Full Text Available Polyphenol-rich grape seed extract (0.1 w/w% was incorporated in liposomes (1 w/w% soy lecithin by high pressure homogenization (22,500 psi and coated with chitosan (0.1 w/w%. Primary liposomes and chitosan-coated secondary liposomes containing grape seed extract showed good physical stability during 98 days of storage. Most of the polyphenols were incorporated in the shell of the liposomes (85.4%, whereas only 7.6% of the polyphenols of grape seed extract were located in the interior of the liposomes. Coating with chitosan did not change the polyphenol content in the liposomes (86.6%. The uncoated liposomes without grape seed extract were highly prone to lipid oxidation. The cationic chitosan coating, however, improved the oxidative stability to some extent, due to its ability to repel pro-oxidant metals. Encapsulated grape seed extract showed high antioxidant activity in both primary and secondary liposomes, which may be attributed to its polyphenol content. In conclusion, the best chemical stability of liposomes can be achieved using a combination of grape seed extract and chitosan.

  17. Effect of okra cell wall and polysaccharide on physical properties and stability of ice cream.

    Science.gov (United States)

    Yuennan, Pilapa; Sajjaanantakul, Tanaboon; Goff, H Douglas

    2014-08-01

    Stabilizers are used in ice cream to increase mix viscosity, promote smooth texture, and improve frozen stability. In this study, the effects of varying concentrations (0.00%, 0.15%, 0.30%, and 0.45%) of okra cell wall (OKW) and its corresponding water-soluble polysaccharide (OKP) on the physical characteristics of ice cream were determined. Ice cream mix viscosity was measured as well as overrun, meltdown, and consumer acceptability. Ice recrystallization was determined after ice cream was subjected to temperature cycling in the range of -10 to -20 °C for 10 cycles. Mix viscosity increased significantly as the concentrations of OKW and OKP increased. The addition of either OKW or OKP at 0.15% to 0.45% significantly improved the melting resistance of ice cream. OKW and OKP at 0.15% did not affect sensory perception score for flavor, texture, and overall liking of the ice cream. OKW and OKP (0.15%) reduced ice crystal growth to 107% and 87%, respectively, as compared to 132% for the control (0.00%). Thus, our results suggested the potential use of OKW and OKP at 0.15% as a stabilizer to control ice cream quality and retard ice recrystallization. OKP, however, at 0.15% exhibited greater effect on viscosity increase and on ice recrystallization inhibition than OKW. © 2014 Institute of Food Technologists®

  18. Quality by Design (QbD) approach to optimize the formulation of a bilayer combination tablet (Telmiduo®) manufactured via high shear wet granulation.

    Science.gov (United States)

    Lee, Ah Ram; Kwon, Seok Young; Choi, Du Hyung; Park, Eun Seok

    2017-12-20

    A bilayer tablet, which consisted of telmisartan and amlodipine besylate, was formulated based on a Quality by Design (QbD) approach. The control and response factors were determined based on primary knowledge and the target values of the control tablet (Twynsta ® ). A D-optimal mixture design was used to obtain the optimal formulations in terms of D-mannitol, crospovidone, and MCC for the telmisartan layer, and CCM-Na, PVP K25, and Prosolv for the amlodipine layer. The quantitative effects of the different formulation factors on the response factors were accurately predicted using the equations of best fit and a strong linearity was observed between the predicted and actual values of the response factors. The optimized bilayer tablet was obtained using a numeric optimization technique and was characterized compared with a control (Twynsta ® ) by using various physical evaluations and in vivo pharmacokinetic parameters. The physical stability of Telmiduo ® was greater than that of Twynsta ® owing to the improvement of formulation factors. The in vivo pharmacokinetic parameters suggested that Telmiduo ® might have pharmaceutical equivalence and bioequivalence with Twynsta ® . Therefore, the bilayer tablet that consisted of telmisartan and amlodipine besylate could be produced using a more economical and simpler method than that used to produce Twynsta ® . Moreover, the suitability of QbD for effective product development in the pharmaceutical industry was shown. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release.

    Science.gov (United States)

    Cao, Yizheng; Teng, Jing; Selbo, Jon

    2017-11-09

    Epigallocatechin gallate (EGCG) has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity) and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus ® 50:50 ( w / w ) shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma.

  20. Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release

    Directory of Open Access Journals (Sweden)

    Yizheng Cao

    2017-11-01

    Full Text Available Epigallocatechin gallate (EGCG has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus® 50:50 (w/w shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma.

  1. Short-Range-Order Mineral Physical Protection On Black Carbon Stabilization

    Science.gov (United States)

    Liang, B.; Weng, Y. T.; Wang, C. C.; Song, Y. F.; Lehmann, J.; Wang, C. H.

    2015-12-01

    Soil organic matter is one of the largest reservoirs in global carbon cycle, and black carbon (BC) represents a chemical resistant component. Black C plays an important role in global climate change. Generally considered recalcitrant due to high aromaticity, the reactive surface and functional groups of BC are crucial for carbon sequestration in soils. Mineral sorption and physical protection is an important mechanism for BC long term stabilization and sequestration in environments. Previous studies on mineral protection of BC were limited to analysis techniques in two-dimensions, for example, by SEM, TEM, and NanoSIMS. Little is known about the scope of organo-mineral association, the in-situ distribution and forms of minerals, and the ultimate interplay of BC and minerals. The aim of this study is to investigate the three-dimensional interaction of organic C and minerals in submicron scale using synchrotron-based Transmission X-ray Microcopy (TXM) and Fourier-Transform Infrared Spectroscopy (FTIR). Abundant poorly-crystallined nano-minerals particles were observed. These short-range-order (SRO) minerals also aggregate into clusters and sheets, and form envelops-like structures on the surface of BC. On top of large surface contact area, the intimate interplay between BC and minerals reinforces the stability of both organic C and minerals, resulting from chemical bonding through cation bridging and ligand exchange. The mineral protection enhances BC stabilization and sequestration and lowers its bioavailability in environment. The results suggest that mineral physical protection for BC sequestration may be more important than previous understanding.

  2. Double-Layer Structured CO2 Adsorbent Functionalized with Modified Polyethyleneimine for High Physical and Chemical Stability.

    Science.gov (United States)

    Jeon, Sunbin; Jung, Hyunchul; Kim, Sung Hyun; Lee, Ki Bong

    2018-06-18

    CO 2 capture using polyethyleneimine (PEI)-impregnated silica adsorbents has been receiving a lot of attention. However, the absence of physical stability (evaporation and leaching of amine) and chemical stability (urea formation) of the PEI-impregnated silica adsorbent has been generally established. Therefore, in this study, a double-layer impregnated structure, developed using modified PEI, is newly proposed to enhance the physical and chemical stabilities of the adsorbent. Epoxy-modified PEI and diepoxide-cross-linked PEI were impregnated via a dry impregnation method in the first and second layers, respectively. The physical stability of the double-layer structured adsorbent was noticeably enhanced when compared to the conventional adsorbents with a single layer. In addition to the enhanced physical stability, the result of simulated temperature swing adsorption cycles revealed that the double-layer structured adsorbent presented a high potential working capacity (3.5 mmol/g) and less urea formation under CO 2 -rich regeneration conditions. The enhanced physical and chemical stabilities as well as the high CO 2 working capacity of the double-layer structured adsorbent were mainly attributed to the second layer consisting of diepoxide-cross-linked PEI.

  3. Rheological properties and physical stability of ecological emulsions stabilized by a surfactant derived from cocoa oil and high pressure homogenization

    Directory of Open Access Journals (Sweden)

    Trujillo-Cayado, L. A.

    2015-09-01

    Full Text Available The goal of this work was to investigate the influence of the emulsification method on the rheological properties, droplet size distribution and physical stability of O/W green emulsions formulated with an eco-friendly surfactant derived from cocoa oil. The methodology used can be applied to other emulsions. Polyoxyethylene glycerol esters are non-ionic surfactants obtained from a renewable source which fulfill the environmental and toxicological requirements to be used as eco-friendly emulsifying agents. In the same way, N,NDimethyloctanamide and α-Pinene (solvents used as oil phase could be considered green solvents. Emulsions with submicron mean diameters and slight shear thinning behavior were obtained regardless of the homogenizer, pressure or number of passes used. All emulsions exhibited destabilization by creaming and a further coalescence process which was applied to the coarse emulsion prepared with a rotor-stator homogenizer. The emulsion obtained with high pressure at 15000 psi and 1-pass was the most stable.El objetivo de este trabajo fue estudiar la influencia del método de emulsificación sobre las propiedades reológicas, la distribución de tamaños de gota y la estabilidad física de emulsiones verdes O/W formuladas con un tensioactivo derivado del aceite de coco respetuoso con el medioambiente. La metodología empleada puede ser aplicada a cualquier otro tipo de emulsiones. Los ésteres polietoxilados de glicerina son tensioactivos no iónicos obtenidos de fuentes renovables que cumplen requisitos medioambientales y toxicológicos para ser usados como agentes emulsionantes ecológicos. Del mismo modo, la N,N-dimetil octanamida y el α-Pineno (disolventes usados como fase oleosa pueden ser considerados como disolventes verdes. Se han obtenido emulsiones con diámetros medio submicrónicos y comportamiento ligeramente pseudoplástico independientemente del equipo, la presión o el número de pasadas empleados. Todas las

  4. New transparent metal-like bilayer composite films with highly conducting layers of {theta}-(BET-TTF){sub 2}Br.3H{sub 2}O nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Mas-Torrent, M.; Laukhina, E.; Rovira, C.; Veciana, J. [Campus Univ. de Bellaterra, Barcelona (Spain). Inst. de Ciencia de Materials; Tkacheva, V. [RAS, Chernogolovka (Russian Federation). Inst. of Problems of Chemical Physics; Zorina, L.; Khasanov, S. [RAS, Chernogolovka (Russian Federation). Inst. of Solid State Physics

    2001-08-01

    A novel conducting bilayer composite (BLC) film-a polycarbonate matrix with a conducting surface layer of a crystalline network of an organic conductor-is presented. A BLC film combines the high stability and physical properties of an organic conductor, in this case the molecular metal {theta}-(BET-TTF){sub 2}Br.3H{sub 2}O, with the flexibility, transparency, and low density of a polymer matrix. The determination of the optimal conditions for the preparation of the new film, which is extremely transparent and has metal-like transport properties down to liquid helium temperature, is described. (orig.)

  5. 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.

  6. Physical and chemical stability of reconstituted and diluted dexrazoxane infusion solutions.

    Science.gov (United States)

    Zhang, Yan-Ping; Myers, Alan L; Trinh, Van A; Kawedia, Jitesh D; Kramer, Mark A; Benjamin, Robert S; Tran, Hai T

    2014-02-01

    Dexrazoxane is used clinically to prevent anthracycline-associated cardiotoxicity. Hydrolysis of dexrazoxane prior to reaching the cardiac membranes severely hampers its mode of action; therefore, degradation during the preparation and administration of intravenous dexrazoxane admixtures demands special attention. Moreover, the ongoing national shortage of one dexrazoxane formulation in the United States has forced pharmacies to dispense other commercially available dexrazoxane products. However, the manufacturers' limited stability data restrict the flexibility of dexrazoxane usage in clinical practice. The aims of this study are to determine the physical and chemical stability of reconstituted and diluted solutions of two commercially available dexrazoxane formulations. The stability of two dexrazoxane products, brand and generic name, in reconstituted and intravenous solutions stored at room temperature without light protection in polyvinyl chloride bags was determined. The concentrations of dexrazoxane were measured at predetermined time points up to 24 h using a validated reversed phase high-performance liquid chromatography with ultraviolet detection assay. Brand (B-) and generic (G-) dexrazoxane products, reconstituted in either sterile water or 0.167 M sodium lactate (final concentration of 10 mg/mL), were found stable for at least to 8 h. Infusion solutions of B-dexrazoxane, prepared according to each manufacturer's directions, were stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. Infusion solutions of G-dexrazoxane, prepared in either 5% dextrose or 0.9% sodium chloride following the manufacturer's guidelines, were also stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. All tested solutions were found physically stable up to 24 h at room temperature. The stability of dexrazoxane infusion solutions reported herein permits advance preparation of dexrazoxane intravenous admixtures, facilitating

  7. 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.

  8. 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

  9. Valley Topological Phases in Bilayer Sonic Crystals

    Science.gov (United States)

    Lu, Jiuyang; Qiu, Chunyin; Deng, Weiyin; Huang, Xueqin; Li, Feng; Zhang, Fan; Chen, Shuqi; Liu, Zhengyou

    2018-03-01

    Recently, the topological physics in artificial crystals for classical waves has become an emerging research area. In this Letter, we propose a unique bilayer design of sonic crystals that are constructed by two layers of coupled hexagonal array of triangular scatterers. Assisted by the additional layer degree of freedom, a rich topological phase diagram is achieved by simply rotating scatterers in both layers. Under a unified theoretical framework, two kinds of valley-projected topological acoustic insulators are distinguished analytically, i.e., the layer-mixed and layer-polarized topological valley Hall phases, respectively. The theory is evidently confirmed by our numerical and experimental observations of the nontrivial edge states that propagate along the interfaces separating different topological phases. Various applications such as sound communications in integrated devices can be anticipated by the intriguing acoustic edge states enriched by the layer information.

  10. 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.

  11. Electronic transport in bilayer graphene

    International Nuclear Information System (INIS)

    Koshino, Mikito

    2009-01-01

    We present theoretical studies on the transport properties and localization effects of bilayer graphene. We calculate the conductivity by using the effective mass model with the self-consistent Born approximation, in the presence and absence of an energy gap opened by the interlayer asymmetry. We find that, in the absence of the gap, the minimum conductivity approaches the universal value by increasing the disorder potential, and the value is robust in the strong disorder regime where mixing with high-energy states is considerable. The gap-opening suppresses the conductivity over a wide energy range, even in the region away from the gap.We also study the localization effects in the vicinity of zero energy in bilayer graphene. We find that the states are all localized in the absence of the gap, while the gap-opening causes a phase transition analogous to the quantum Hall transition, which is accompanied by electron delocalization.

  12. 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.

  13. 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.

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

    Science.gov (United States)

    Saito, Hiroaki; Shinoda, Wataru

    2011-12-29

    Water permeability of two different lipid bilayers of dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) in the absence and presence of cholesterol (0-50 mol %) have been studied by molecular dynamics simulations to elucidate the molecular mechanism of the reduction in water leakage across the membranes by the addition of cholesterol. An enhanced free energy barrier was observed in these membranes with increased cholesterol concentration, and this was explained by the reduced cavity density around the cholesterol in the hydrophobic membrane core. There was an increase of trans conformers in the hydrophobic lipid chains adjacent to the cholesterol, which reduced the cavity density. The enhanced free energy barrier was found to be the main reason to reduce the water permeability with increased cholesterol concentration. At low cholesterol concentrations the PSM bilayer exhibited a higher free energy barrier than the DPPC bilayer for water permeation, while at greater than 30 mol % of cholesterol the difference became minor. This tendency for the PSM and DPPC bilayers to resemble each other at higher cholesterol concentrations was similar to commonly observed trends in several structural properties, such as order parameters, cross-sectional area per molecule, and cavity density profiles in the hydrophobic regions of bilayer membranes. These results demonstrate that DPPC and PSM bilayers with high cholesterol contents possess similar physical properties, which suggests that the solubility of cholesterol in these lipid bilayers has importance for an understanding of multicomponent lipid membranes with cholesterol. © 2011 American Chemical Society

  15. Remote operation of the vertical plasma stabilization @ the GOLEM tokamak for the plasma physics education

    Energy Technology Data Exchange (ETDEWEB)

    Svoboda, V., E-mail: svoboda@fjfi.cvut.cz [Faculty of Nuclear Sciences and Physical Engineering CTU Prague, CZ-115 19 (Czech Republic); Kocman, J.; Grover, O. [Faculty of Nuclear Sciences and Physical Engineering CTU Prague, CZ-115 19 (Czech Republic); Krbec, J.; Stöckel, J. [Faculty of Nuclear Sciences and Physical Engineering CTU Prague, CZ-115 19 (Czech Republic); Institute of Plasma Physics AS CR, CZ-182 21 Prague (Czech Republic)

    2015-10-15

    Graphical abstract: * Understandable remote operation of a vertical plasma position control system in the tokamak GOLEM for educational purposes.* Two combinable modes of real-time plasma position control: position based feedback and a pre-defined waveform.* More than 20% plasma life prolongation with plasma position control in feedback mode. - Highlights: • Understandable remote operation of a vertical plasma position control system in the tokamak GOLEM for educational purposes. • Two combinable modes of real-time plasma position control: position based feedback and a pre-defined waveform. • More than 20% plasma life prolongation with plasma position control in feedback mode. - Abstract: The GOLEM tokamak at the Czech Technical University has been established as an educational tokamak device for domestic and foreign students. Remote participation in the scope of several laboratory practices, plasma physics schools and workshops has been successfully performed from abroad. A new enhancement allowing understandable remote control of vertical plasma position in two modes (i) predefined and (ii) feedback control is presented. It allows to drive the current in the stabilization coils in any time-dependent scenario, which can include as a parameter the actual plasma position measured by magnetic diagnostics. Arbitrary movement of the plasma column in a vertical direction, stabilization of the plasma column in the center of the tokamak vessel as well as prolongation/shortening of plasma life according to the remotely defined request are demonstrated.

  16. Influence of solvent evaporation rate and formulation factors on solid dispersion physical stability.

    Science.gov (United States)

    Wu, Jian X; Yang, Mingshi; Berg, Frans van den; Pajander, Jari; Rades, Thomas; Rantanen, Jukka

    2011-12-18

    New chemical entities (NCEs) often show poor water solubility necessitating solid dispersion formulation. The aim of the current study is to employ design of experiments in investigating the influence of one critical process factor (solvent evaporation rate) and two formulation factors (PVP:piroxicam ratio (PVP:PRX) and PVP molecular weight (P(MW))) on the physical stability of PRX solid dispersion prepared by the solvent evaporation method. The results showed the rank order of an increase in factors contributing to a decrease in the extent of PRX nucleation being evaporation rate>PVP:PRX>P(MW). The same rank order was found for the decrease in the extent of PRX crystal growth in PVP matrices from day 0 up to day 12. However, after 12days the rank became PVP:PRX>evaporation rate>P(MW). The effects of an increase in evaporation rate and PVP:PRX ratio in stabilizing PRX were of the same order of magnitude, while the effect from P(MW) was much smaller. The findings were confirmed by XRPD. FT-IR showed that PRX recrystallization in the PVP matrix followed Ostwald's step rule, and an increase in the three factors all led to increased hydrogen bonding interaction between PRX and PVP. The present study showed the applicability of the Quality by Design approach in solid dispersion research, and highlights the need for multifactorial analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Variability and Stability in Daily Moderate-to-Vigorous Physical Activity among 10 Year Old Children

    Science.gov (United States)

    Pereira, Sara; Gomes, Thayse Natacha; Borges, Alessandra; Santos, Daniel; Souza, Michele; dos Santos, Fernanda K.; Chaves, Raquel N.; Katzmarzyk, Peter T.; Maia, José A. R.

    2015-01-01

    Day-to-day variability and stability of children’s physical activity levels across days of the week are not well understood. Our aims were to examine the day-to-day variability of moderate-to-vigorous physical activity (MVPA), to determine factors influencing the day-to-day variability of MVPA and to estimate stability of MVPA in children. The sample comprises 686 Portuguese children (10 years of age). MVPA was assessed with an accelerometer, and BMI was computed from measured height and weight. Daily changes in MVPA and their correlates (gender, BMI, and maturity) were modeled with a multilevel approach, and tracking was calculated using Foulkes & Davies γ. A total of 51.3% of boys and 26.2% of girls achieved 60 min/day of MVPA on average. Daily MVPA was lower during the weekend (23.6% of boys and 13.6% of girls comply with the recommended 60 min/day of MVPA) compared to weekdays (60.8% and 35.4%, boys and girls, respectively). Normal weight children were more active than obese children and no effect was found for biological maturation. Tracking is low in both boys (γ = 0.59 ± 0.01) and girls (γ = 0.56 ± 0.01). Children’s MVPA levels during a week are highly unstable. In summary, boys are more active than girls, maturation does not affect their MVPA, and obese children are less likely to meet 60 min/day of MVPA. These results highlight the importance of providing opportunities for increasing children’s daily MVPA on all days of week, especially on the weekend. PMID:26262632

  18. Effects of anticaking agents and relative humidity on the physical and chemical stability of powdered vitamin C.

    Science.gov (United States)

    Lipasek, Rebecca A; Taylor, Lynne S; Mauer, Lisa J

    2011-09-01

    Vitamin C is an essential nutrient that is widely used by the food industry in the powder form for both its nutritional and functional properties. However, vitamin C is deliquescent, and deliquescence has been linked to physical and chemical instabilities. Anticaking agents are often added to powder systems to delay or prevent caking, but little is known about their effect on the chemical stability of powders. In this study, various anticaking agents (calcium phosphate, calcium silicate, calcium stearate, corn starch, and silicon dioxide) were combined with sodium ascorbate at 2% and 50% w/w ratios and stored at various relative humidities (23%, 43%, 64%, 75%, 85%, and 98% RHs). Chemical and physical stability and moisture sorption were monitored over time. Additionally, saturated solution samples were stored at various pHs to determine the effect of surface pH and dissolution on the vitamin degradation rate. Storage RH, time, and anticaking agent type and ratio all significantly affected (P vitamin C stability. Silicon dioxide and calcium silicate (50% w/w) and calcium stearate (at both ratios) were the only anticaking agents to improve the physical stability of powdered sodium ascorbate while none of the anticaking agents improved its chemical stability. However, corn starch and calcium stearate had the least adverse effect on chemical stability. Dissolution rate and pH were also important factors affecting the chemical and physical stability of the powders. Therefore, monitoring storage environmental conditions and anticaking agent usage are important for understanding the stability of vitamin C. Anticaking agent type and ratio significantly affected the physical and chemical stability of vitamin C over time and over a range of RHs. No anticaking agent improved the chemical stability of the vitamin, and most caused an increase in chemical degradation even if physical stability was improved. It is possible that anticaking agents would greatly affect other

  19. 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.

  20. In situ evidence of mineral physical protection and carbon stabilization revealed by nanoscale 3-D tomography

    Science.gov (United States)

    Weng, Yi-Tse; Wang, Chun-Chieh; Chiang, Cheng-Cheng; Tsai, Heng; Song, Yen-Fang; Huang, Shiuh-Tsuen; Liang, Biqing

    2018-05-01

    An approach for nanoscale 3-D tomography of organic carbon (OC) and associated mineral nanoparticles was developed to illustrate their spatial distribution and boundary interplay, using synchrotron-based transmission X-ray microscopy (TXM). The proposed 3-D tomography technique was first applied to in situ observation of a laboratory-made consortium of black carbon (BC) and nanomineral (TiO2, 15 nm), and its performance was evaluated using dual-scan (absorption contrast and phase contrast) modes. This novel tool was then successfully applied to a natural OC-mineral consortium from mountain soil at a spatial resolution of 60 nm, showing the fine structure and boundary of OC, the distribution of abundant nano-sized minerals, and the 3-D organo-mineral association in situ. The stabilization of 3500-year-old natural OC was mainly attributed to the physical protection of nano-sized iron (Fe)-containing minerals (Fe oxyhydroxides including ferrihydrite, goethite, and lepidocrocite), and the strong organo-mineral complexation. In situ evidence revealed an abundance of mineral nanoparticles, in dense thin layers or nano-aggregates/clusters, instead of crystalline clay-sized minerals on or near OC surfaces. The key working minerals for C stabilization were reactive short-range-order (SRO) mineral nanoparticles and poorly crystalline submicron-sized clay minerals. Spectroscopic analyses demonstrated that the studied OC was not merely in crisscross co-localization with reactive SRO minerals; there could be a significant degree of binding between OC and the minerals. The ubiquity and abundance of mineral nanoparticles on the OC surface, and their heterogeneity in the natural environment may have been severely underestimated by traditional research approaches. Our in situ description of organo-mineral interplay at the nanoscale provides direct evidence to substantiate the importance of mineral physical protection for the long-term stabilization of OC. This high-resolution 3-D

  1. 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

  2. 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

  3. Physical exercises to improve the stability of the target sight in sport shooting

    Directory of Open Access Journals (Sweden)

    Mercedes Miló Dubé

    2017-04-01

    Full Text Available Sport shooting stands for a highly technical sport, and a competitive art. It is the target sight one of the more important technical elements because it favors the sport performance and it must be considered in the training sessions from the junior school categories. This research meets the goals of proposing a set of physical exercises to improve the stability of the target sight technique for the Shooting athletes, category 13-16, field Standard gun pistol in the Sport School “Ormani Arenado Llonch” in Pinar del Río, Cuba. To fulfill this objective it was applied scientific observation, surveys and interviews, theoretical methods were also used in this research adjusted to 11 athletes and 3 coaches as the sample of research belonging to this school under study. Based on the diagnosed weaknesses found along the training was selected a set of physical exercise to improve the target sight empowering the pedagogical implication and without breaking the planning process of the sport.

  4. 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

  5. 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.

  6. 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.

  7. On the physics of ion ring generation for the stabilization of FRX discharges. Final report

    International Nuclear Information System (INIS)

    Fleischmann, H.

    1995-01-01

    As envisioned in the respective proposals, the author's work over the final periods of this contract centered on experimental and related theoretical investigations of the physics of the generation of ion rings which might be used for a tilt stabilization of FRX rings, with experiments centering around the new MICE equipment constructed during the earlier parts of the work. In particular, the work mainly consisted of the following: (i) investigations concerning the operation of the ion beam driver constructed earlier, especially of the magnetically insulated ion diode and possible improvements of that diode; (ii) theoretical analyses on the propagation and neutralization of the ion beam during its injection into the confinement tank; and (iii) experimental investigations on the physics of ion beam injection and ring formation in the MICE device; in these latter experiments very significant discrepancies of various observed data and those predicted from single-particle orbit calculations were found. Unfortunately, the work could not be completed due to stop in funding, but a semiquantitative analysis of these discrepancies indicated insufficient space charge neutralization of the ion beam in the tank and/or charge-exchange effects in the diode are considered the most likely reasons. In contrast to claims by its authors, a similar discrepancy also was found in the published data of the earlier IREX experiment. The results of their investigations, which together with the design and construction of the equipment provided the basis for two PhD theses, will be briefly described in this report; the full details can be obtained from the two theses

  8. Impact of polymer type on bioperformance and physical stability of hot melt extruded formulations of a poorly water soluble drug.

    Science.gov (United States)

    Mitra, Amitava; Li, Li; Marsac, Patrick; Marks, Brian; Liu, Zhen; Brown, Chad

    2016-05-30

    Amorphous solid dispersion formulations have been widely used to enhance bioavailability of poorly soluble drugs. In these formulations, polymer is included to physically stabilize the amorphous drug by dispersing it in the polymeric carrier and thus forming a solid solution. The polymer can also maintain supersaturation and promote speciation during dissolution, thus enabling better absorption as compared to crystalline drug substance. In this paper, we report the use of hot melt extrusion (HME) to develop amorphous formulations of a poorly soluble compound (FaSSIF solubility=1μg/mL). The poor solubility of the compound and high dose (300mg) necessitated the use of amorphous formulation to achieve adequate bioperformance. The effect of using three different polymers (HPMCAS-HF, HPMCAS-LF and copovidone), on the dissolution, physical stability, and bioperformance of the formulations was demonstrated. In this particular case, HPMCAS-HF containing HME provided the highest bioavailability and also had better physical stability as compared to extrudates using HPMCAS-LF and copovidone. The data demonstrated that the polymer type can have significant impact on the formulation bioperformance and physical stability. Thus a thorough understanding of the polymer choice is imperative when designing an amorphous solid dispersion formulation, such that the formulation provides robust bioperformance and has adequate shelf life. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils

    Energy Technology Data Exchange (ETDEWEB)

    Diebold, J.P.

    1999-01-27

    Understanding the fundamental chemical and physical aging mechanisms is necessary to learn how to produce a bio-oil that is more stable during shipping and storage. This review provides a basis for this understanding and identifies possible future research paths to produce bio-oils with better storage stability.

  10. Goal conflict and the moderating effects of intention stability in intention-behavior relations: physical activity among Hong Kong chinese.

    Science.gov (United States)

    Li, Kin-Kit; Chan, Darius K S

    2008-02-01

    This study examined how goal conflict influences the pattern of the moderating effects of intention stability on the intention-behavior relations in the context of physical activity participation. A longitudinal study of 136 young adult students with three waves of data collection (a 2-week interval between waves) was conducted. Results showed a significant three-way interaction among intention, goal conflict,& intention stability in explaining vigorous-intensity physical activity (Beta = -.25, p goal conflict was low, the intention-behavior relations were stronger with stable intentions and weaker with unstable intentions. However, when the level of goal conflict was high, the intention-behavior relations were weaker with stable intentions and stronger with unstable intentions. Possible underlying processes of goal conflict and intention stability on the intention-behavior relations are discussed.

  11. 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).

  12. 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...

  13. 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

  14. 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.

  15. Stabilization of red fruit-based smoothies by high-pressure processing. Part A. Effects on microbial growth, enzyme activity, antioxidant capacity and physical stability.

    Science.gov (United States)

    Hurtado, Adriana; Guàrdia, Maria Dolors; Picouet, Pierre; Jofré, Anna; Ros, José María; Bañón, Sancho

    2017-02-01

    Non-thermal pasteurization by high-pressure processing (HPP) is increasingly replacing thermal processing (TP) to maintain the properties of fresh fruit products. However, most of the research on HPP-fruit products only partially addresses fruit-pressure interaction, which limits its practical interest. The objective of this study was to assess the use of a mild HPP treatment to stabilize red fruit-based smoothies (microbial, enzymatic, oxidative and physical stability). HPP (350 MPa/10 °C/5 min) was slightly less effective than TP (85 °C/7 min) in inactivating microbes (mesophilic and psychrophilic bacteria, coliforms, yeasts and moulds) in smoothies kept at 4 °C for up to 28 days. The main limitation of using HPP was its low efficacy in inactivating oxidative (polyphenol oxidase and peroxidase) and hydrolytic (pectin methyl esterase) enzymes. Data on antioxidant status, colour parameters, browning index, transmittance, turbidity and viscosity confirmed that the HPP-smoothies have a greater tendency towards oxidation and clarification, which might lead to undesirable sensory and nutritional changes (see Part B). The microbial quality of smoothies was adequately controlled by mild HPP treatment without affecting their physical-chemical characteristics; however, oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests that additional strategies should be used to stabilize smoothies. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  16. Preparation, physical characterization, and stability of Ferrous-Chitosan microcapsules using different iron sources

    Science.gov (United States)

    Handayani, Noer Abyor; Luthfansyah, M.; Krisanti, Elsa; Kartohardjono, Sutrasno; Mulia, Kamarza

    2017-11-01

    Dietary modification, supplementation and food fortification are common strategies to alleviate iron deficiencies. Fortification of food is an effective long-term approach to improve iron status of populations. Fortification by adding iron directly to food will cause sensory problems and decrease its bioavailability. The purpose of iron encapsulation is: (1) to improve iron bioavailability, by preventing oxidation and contact with inhibitors and competitors; and (2) to disguise the rancid aroma and flavor of iron. A microcapsule formulation of two suitable iron compounds (iron II fumarate and iron II gluconate) using chitosan as a biodegradable polymer will be very important. Freeze dryer was also used for completing the iron microencapsulation process. The main objective of the present study was to prepare and characterize the iron-chitosan microcapsules. Physical characterization, i.e. encapsulation efficiency, iron loading capacity, and SEM, were also discussed in this paper. The stability of microencapsulated iron under simulated gastrointestinal conditions was also investigated, as well. Both iron sources were highly encapsulated, ranging from 71.5% to 98.5%. Furthermore, the highest ferrous fumarate and ferrous gluconate loaded were 1.9% and 4.8%, respectively. About 1.04% to 9.17% and 45.17% to 75.19% of Fe II and total Fe, were released in simulated gastric fluid for two hours and in simulated intestinal fluid for six hours, respectively.

  17. Relationship of Physical Parameters in Pb-Contaminated by Stabilization/Solidification Method

    Directory of Open Access Journals (Sweden)

    Ahmad Tajudin Saiful Azhar

    2016-01-01

    Full Text Available This research was performed to investigate the relationship between compressive strength, density and water absorption of Pb-contaminated soil treated by Ordinary Portland cement (OPC incorporated with sugarcane bagasse (SCB using the Stablisation/Solidification (S/S method. The SCB and OPC varying from 5% to 15% was added to stabilize and solidify the Pb-contaminated soil. The cylindrical samples were prepared and cured at room temperature for 28 days. Unconfined compression test, density test and water absorption test were conducted on these samples. The relationship between these variables were determined using simple statistical method by Analysis of Variance (ANOVA. Results indicate that there is a strong relationship between compressive strength and density with a regression coefficient of 77.4%. There is also a significant relationship between density and water absorption of approximately 70.7%. In addition, compressive strength and water absorption produced a strong relationship which is 73.6% of variability in strength development. In a nutshell, the strong relationship between these three variables represent the actual physical characteristics in S/S application.

  18. Physical vapor deposited films of a perylene derivative: supramolecular arrangement and thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Jose Diego; Alessio, Priscila; Silva, Matheus Rodrigues Medeiros; Aroca, Ricardo Flavio; Souza, Agda Eunice de; Constantino, Carlos Jose Leopoldo, E-mail: case@fct.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Presidente Prudente, SP (Brazil). Dept. de Fisica

    2017-07-15

    The analysis of supramolecular arrangement is essential to understand the role of this key factor on the optical and electrical properties of organic thin films. In this work, thin solid films of bis(phenethylimido) perylene (PhPTCD) fabricated using physical vapor deposition (PVD) technique (thermal evaporation), deposited simultaneously onto different substrates (Ag mirror, Ge, and quartz plates) contingent on the characterization technique. The main objective is to study the PhPTCD supramolecular arrangement and the thermal stability of this arrangement in PVD films. The ultraviolet-visible absorption reveals a controlled growth of the PVD films, and the micro-Raman scattering data show that the PhPTCD molecule is not thermally degraded in the conditions of these experiments. The microscopy also shows a homogeneous morphological surface of the PVD film at macro and micro scales, with molecular aggregates at nanoscale. Besides, the PVD film roughness does not follow substrate roughness. The X-ray diffraction indicates a crystalline structure for PhPTCD powder and an amorphous form for PhPTCD PVD film. The infrared absorption spectroscopy points to a preferential flat-on organization of the molecules in the PVD films. In addition, the annealing process (200 deg C for 20 minutes) does not affect the supramolecular arrangement of the PhPTCD PVD films. (author)

  19. Physical vapor deposited films of a perylene derivative: supramolecular arrangement and thermal stability

    International Nuclear Information System (INIS)

    Fernandes, Jose Diego; Alessio, Priscila; Silva, Matheus Rodrigues Medeiros; Aroca, Ricardo Flavio; Souza, Agda Eunice de; Constantino, Carlos Jose Leopoldo

    2017-01-01

    The analysis of supramolecular arrangement is essential to understand the role of this key factor on the optical and electrical properties of organic thin films. In this work, thin solid films of bis(phenethylimido) perylene (PhPTCD) fabricated using physical vapor deposition (PVD) technique (thermal evaporation), deposited simultaneously onto different substrates (Ag mirror, Ge, and quartz plates) contingent on the characterization technique. The main objective is to study the PhPTCD supramolecular arrangement and the thermal stability of this arrangement in PVD films. The ultraviolet-visible absorption reveals a controlled growth of the PVD films, and the micro-Raman scattering data show that the PhPTCD molecule is not thermally degraded in the conditions of these experiments. The microscopy also shows a homogeneous morphological surface of the PVD film at macro and micro scales, with molecular aggregates at nanoscale. Besides, the PVD film roughness does not follow substrate roughness. The X-ray diffraction indicates a crystalline structure for PhPTCD powder and an amorphous form for PhPTCD PVD film. The infrared absorption spectroscopy points to a preferential flat-on organization of the molecules in the PVD films. In addition, the annealing process (200 deg C for 20 minutes) does not affect the supramolecular arrangement of the PhPTCD PVD films. (author)

  20. Physical stability, microstructure and micro-rheological properties of water-in-oil-in-water (W/O/W) emulsions stabilized by porcine gelatin.

    Science.gov (United States)

    Zhu, Qiaomei; Qiu, Shuang; Zhang, Hongwei; Cheng, Yongqiang; Yin, Lijun

    2018-07-01

    Water-in-oil-in-water (W/O/W) emulsions could be utilized for fat-reduced food formulation and delivery of bioactive nutrients. However, due to thermodynamic instability, it is difficult to prepare stable double emulsions. The purpose of this study was to improve the stability of W/O/W double emulsions containing 2.0 M MgCl 2 by adding porcine gelatin in the inner water phase. The impact of gelatin on the physical stability, microstructure and micro-rheological properties of W/O/W emulsions was investigated. It was found that, when the concentration of porcine gelatin exceeded 4.0 wt%, the stability of emulsions was improved, due to increased viscoelasticity of emulsion droplets. When MgCl 2 concentration increased to 2.0 M, the particle size of emulsions increased, due to the osmotic pressure gradient, and the presence of gelatin further increased the droplet size. Confocal microscopy results showed that the presence of gelatin could improve the stability of W/O/W emulsions against coalescence。. Copyright © 2018. Published by Elsevier Ltd.

  1. "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

  2. High surface stability of magnetite on bi-layer Fe3O4/Fe/MgO(0 0 1) films under 1 MeV Kr+ ion irradiation

    Czech Academy of Sciences Publication Activity Database

    Kim-Ngan, N.-T.H.; Krupska, M.; Balogh, A.G.; Malinský, Petr; Macková, Anna

    2017-01-01

    Roč. 8, č. 4 (2017), č. článku 045005. E-ISSN 2043-6262 R&D Projects: GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : nanoscience * thin film * surface and interface Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders OBOR OECD: Nuclear physics

  3. Physical and oxidative stability of high fat fish oil-in-water emulsions stabilized with combinations of sodium caseinate and sodium alginate

    DEFF Research Database (Denmark)

    Yesiltas, Betül; García Moreno, Pedro Jesús; Sørensen, Ann-Dorit Moltke

    2017-01-01

    .2 ratio NaCas:NaAlg by Box-Behnken's design, the formulae 70%-1.4%-1.2 was decided due to high fish oil content's decreasing effect on droplet size and peroxide value. Practical applications: Physically and oxidatively stable high fat (50-70%) omega-3 delivery fish oil-in-water emulsions are of high......A systematic study was carried out in order to evaluate the physical and oxidative stability of high fat omega-3 delivery fish oil-in-water emulsions stabilized with combinations of sodium caseinate (NaCas) and sodium alginate (NaAlg). The influence of 3 factors related to emulsion composition...... (fish oil content: 50, 60 and 70%; total amount of NaCas and NaAlg: 1.4, 2.1 and 2.8 %; and ratio NaCas:NaAlg: 0.4, 1.2 and 2) on physical (droplet size, viscosity and zeta potential) and oxidative (primary and secondary oxidation products) parameters was evaluated. It was possible to produce emulsions...

  4. 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.

  5. Physical and chemical stability of palonosetron hydrochloride with dacarbazine and with methylprednisolone sodium succinate during simulated y-site administration.

    Science.gov (United States)

    Trissel, Lawrence A; Zhang, Yanping; Xu, Quanyun A

    2006-01-01

    The objective of this study was to evaluate the physical and chemical stability of mixtures of undiluted palonosetron hydrochloride 50 micrograms/mL with dacarbazine 4 mg/mL and with methylprednisolone sodium succinate 5 mg/mL in 5% dextrose injection during simulated Y-site administration. Triplicate test samples were prepared by admixing 7.5 mL of palonosetron hydrochloride with 7.5 mL of dacarbazine solution and, separately, methylprednisolone sodium succinate solution. Physical stability was assessed by using a multistep evaluation procedure that included both turbidimetric and particulate measurement as well as visual inspection. Chemical stability was assessed by using stability-indicating high-performance liquid chromatographic analytical techniques that determined drug concentrations. Evaluations were performed immediately after mixing and 1 and 4 hours after mixing. The palonosetron hydrochloride-dacarbazine samples were clear and colorless when viewed in normal fluorescent room light and when viewed with a Tyndall beam. Measured turbidities remained unchanged; particulate contents were low and exhibited little change. High-performance liquid chromatography analysis revealed that palonosetron hydrochloride and dacarbazine remained stable throughout the 4-hour test with no drug loss. Palonosetron hydrochloride is, therefore, physically compatible and chemically stable with dacarbazine during Y-site administration. Within 4 hours, the mixtures of palonosetron hydrochloride and methylprednisolone sodium succinate developed a microprecipitate that became a white precipitate visible to the unaided eye. The precipitate was analyzed and identified as methylprednisolone. Palonosetron hydrochloride is incompatible with methylprednisolone sodium succinate.

  6. Correlating the Impact of Well-Defined Oligosaccharide Structures on Physical Stability Profiles of IgG1-Fc Glycoforms.

    Science.gov (United States)

    More, Apurva S; Toprani, Vishal M; Okbazghi, Solomon Z; Kim, Jae H; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

    2016-02-01

    As part of a series of articles in this special issue describing 4 well-defined IgG1-Fc glycoforms as a model system for biosimilarity analysis (high mannose-Fc, Man5-Fc, GlcNAc-Fc and N297Q-Fc aglycosylated), the focus of this work is comparisons of their physical properties. A trend of decreasing apparent solubility (thermodynamic activity) by polyethylene glycol precipitation (pH 4.5, 6.0) and lower conformational stability by differential scanning calorimetry (pH 4.5) was observed with reducing size of the N297-linked oligosaccharide structures. Using multiple high-throughput biophysical techniques, the physical stability of the Fc glycoproteins was then measured in 2 formulations (NaCl and sucrose) across a wide range of temperatures (10°C-90°C) and pH (4.0-7.5) conditions. The data sets were used to construct 3-index empirical phase diagrams and radar charts to visualize the regions of protein structural stability. Each glycoform showed improved stability in the sucrose (vs. salt) formulation. The HM-Fc and Man5-Fc displayed the highest relative stability, followed by GlcNAc-Fc, with N297Q-Fc being the least stable. Thus, the overall physical stability profiles of the 4 IgG1-Fc glycoforms also show a correlation with oligosaccharide structure. These data sets are used to develop a mathematical model for biosimilarity analysis (as described in a companion article by Kim et al. in this issue). Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  7. Physical and chemical stability of expired fixed dose combination artemether-lumefantrine in uncontrolled tropical conditions

    Directory of Open Access Journals (Sweden)

    Hess Kimberly

    2009-02-01

    Full Text Available Abstract Background New artemisinin combination therapies pose difficulties of implementation in developing and tropical settings because they have a short shelf-life (two years relative to the medicines they replace. This limits the reliability and cost of treatment, and the acceptability of this treatment to health care workers. A multi-pronged investigation was made into the chemical and physical stability of fixed dose combination artemether-lumefantrine (FDC-ALU stored under heterogeneous, uncontrolled African conditions, to probe if a shelf-life extension might be possible. Methods Seventy samples of expired FDC-ALU were collected from private pharmacies and malaria researchers in seven African countries. The samples were subjected to thin-layer chromatography (TLC, disintegration testing, and near infrared Raman spectrometry for ascertainment of active ingredients, tablet integrity, and chemical degradation of the tablet formulation including both active ingredients and excipients. Results Seventy samples of FDC-ALU were tested in July 2008, between one and 58 months post-expiry. 68 of 70 (97% samples passed TLC, disintegration and Raman spectrometry testing, including eight samples that were post-expiry by 20 months or longer. A weak linear association (R2 = 0.33 was observed between the age of samples and their state of degradation relative to brand-identical samples on Raman spectrometry. Sixty-eight samples were retested in February 2009 using Raman spectrometry, between eight and 65 months post-expiry. 66 of 68 (97% samples passed Raman spectrometry retesting. An unexpected observation about African drug logistics was made in three batches of FDC-ALU, which had been sold into the public sector at concessional pricing in accordance with a World Health Organization (WHO agreement, and which were illegally diverted to the private sector where they were sold for profit. Conclusion The data indicate that FDC-ALU is chemically and

  8. The nursing home elder microbiome stability and associations with age, frailty, nutrition and physical location.

    Science.gov (United States)

    Haran, John P; Bucci, Vanni; Dutta, Protiva; Ward, Doyle; McCormick, Beth

    2018-01-01

    The microbiome from nursing home (NH) residents is marked by a loss in diversity that is associated with increased frailty. Our objective was to explore the associations of NH environment, frailty, nutritional status and residents' age to microbiome composition and potential metabolic function. We conducted a prospective longitudinal cohort study of 23 residents, 65 years or older, from one NH that had four floors: two separate medical intensive floors and two floors with active elders. Residents were assessed using the mini nutritional assessment tool and clinical frailty scale. Bacterial composition and metabolic potential of residents' stool samples was determined by metagenomic sequencing. We performed traditional unsupervised correspondence analysis and linear mixed effect modelling regression to assess the bacteria and functional pathways significantly affected by these covariates.Results/Key findings. NH resident microbiomes demonstrated temporal stability (PERMANOVA P=0.001) and differing dysbiotic associations with increasing age, frailty and malnutrition scores. As residents aged, the abundance of microbiota-encoded genes and pathways related to essential amino acid, nitrogenous base and vitamin B production declined. With increasing frailty, residents had lower abundances of butyrate-producing organisms, which are associated with increased health and higher abundances of known dysbiotic species. As residents became malnourished, butyrate-producing organisms declined and dysbiotic bacterial species increased. Finally, the microbiome of residents living in proximity shared similar species and, as demonstrated for Escherichia coli, similar strains. These findings support the conclusion that a signature 'NH' microbiota may exist that is affected by the residents' age, frailty, nutritional status and physical location.

  9. Assessing the physical-chemical properties and stability of dapivirine-loaded polymeric nanoparticles.

    Science.gov (United States)

    das Neves, José; Amiji, Mansoor; Bahia, Maria Fernanda; Sarmento, Bruno

    2013-11-18

    Nanocarriers may provide interesting delivery platforms for microbicide drugs and their characterization should be addressed early in development. Differently surface-engineered dapivirine-loaded, poly(epsilon-caprolactone) (PCL)-based nanoparticles (NPs) were obtained by nanoprecipitation using polyethylene oxide (PEO), sodium lauryl sulfate (SLS), or cetyltrimethylammonium bromide (CTAB) as surface modifiers. Physical-chemical properties of NP aqueous dispersions were evaluated upon storage at -20-40 °C for one year. NPs presented 170-200 nm in diameter, roundish-shape, low polydispersity index (≤0.18), and high drug association efficiency (≥97%) and loading (≥12.7%). NPs differed in zeta potential, depending on surface modifier (PEO: -27.9 mV; SLS: -54.7 mV; CTAB: +42.4 mV). No interactions among formulation components were detected by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR), except for SLS-PCL NPs. Colloidal properties of NPs were lost at -20 °C storage. Negatively charged NPs were stable up to one year at 5-40°C; as for CTAB-PCL NPs, particle aggregation was observed from 30 to 90 days of storage depending on temperature. Colloidal instability affected the in vitro drug release of CTAB-PCL NPs after 360 days. In any case, no degradation of dapivirine was apparent. Overall, PEO-PCL and SLS-PCL NPs presented suitable properties as nanocarriers for dapivirine. Conversely, CTAB-PCL NPs require additional strategies in order to increase stability. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Evaluation of physical stability and leachability of Portland Pozzolona Cement (PPC) solidified chemical sludge generated from textile wastewater treatment plants

    International Nuclear Information System (INIS)

    Patel, Hema; Pandey, Suneel

    2012-01-01

    Highlights: ► Stabilization/solidification of chemical sludge from textile wastewater treatment plants using Portland Pozzolona Cement (PPC) containing fly ash. ► Physical engineering (compressive strength and block density) indicates that sludge has potential to be reused for construction purpose after stabilization/solidification. ► Leaching of heavy metals from stabilized/solidified materials were within stipulated limits. ► There is a modification of microstructural properties of PPC with sludge addition as indicated by XRD and SEM patterns. - Abstract: The chemical sludge generated from the treatment of textile dyeing wastewater is a hazardous waste as per Indian Hazardous Waste Management rules. In this paper, stabilization/solidification of chemical sludge was carried out to explore its reuse potential in the construction materials. Portland Pozzolona Cement (PPC) was selected as the binder system which is commercially available cement with 10–25% fly ash interground in it. The stabilized/solidified blocks were evaluated in terms of unconfined compressive strength, block density and leaching of heavy metals. The compressive strength (3.62–33.62 MPa) and block density (1222.17–1688.72 kg/m 3 ) values as well as the negligible leaching of heavy metals from the stabilized/solidified blocks indicate that there is a potential of its use for structural and non-structural applications.

  11. Structural Stability Monitoring of a Physical Model Test on an Underground Cavern Group during Deep Excavations Using FBG Sensors

    Directory of Open Access Journals (Sweden)

    Yong Li

    2015-08-01

    Full Text Available Fiber Bragg Grating (FBG sensors are comprehensively recognized as a structural stability monitoring device for all kinds of geo-materials by either embedding into or bonding onto the structural entities. The physical model in geotechnical engineering, which could accurately simulate the construction processes and the effects on the stability of underground caverns on the basis of satisfying the similarity principles, is an actual physical entity. Using a physical model test of underground caverns in Shuangjiangkou Hydropower Station, FBG sensors were used to determine how to model the small displacements of some key monitoring points in the large-scale physical model during excavation. In the process of building the test specimen, it is most successful to embed FBG sensors in the physical model through making an opening and adding some quick-set silicon. The experimental results show that the FBG sensor has higher measuring accuracy than other conventional sensors like electrical resistance strain gages and extensometers. The experimental results are also in good agreement with the numerical simulation results. In conclusion, FBG sensors could effectively measure small displacements of monitoring points in the whole process of the physical model test. The experimental results reveal the deformation and failure characteristics of the surrounding rock mass and make some guidance for the in situ engineering construction.

  12. 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....

  13. Discrete particle modeling and micromechanical characterization of bilayer tablet compaction.

    Science.gov (United States)

    Yohannes, B; Gonzalez, M; Abebe, A; Sprockel, O; Nikfar, F; Kiang, S; Cuitiño, A M

    2017-08-30

    A mechanistic particle scale model is proposed for bilayer tablet compaction. Making bilayer tablets involves the application of first layer compaction pressure on the first layer powder and a second layer compaction pressure on entire powder bed. The bonding formed between the first layer and the second layer particles is crucial for the mechanical strength of the bilayer tablet. The bonding and the contact forces between particles of the first layer and second layer are affected by the deformation and rearrangement of particles due to the compaction pressures. Our model takes into consideration the elastic and plastic deformations of the first layer particles due to the first layer compaction pressure, in addition to the mechanical and physical properties of the particles. Using this model, bilayer tablets with layers of the same material and different materials, which are commonly used pharmaceutical powders, are tested. The simulations show that the strength of the layer interface becomes weaker than the strength of the two layers as the first layer compaction pressure is increased. The reduction of strength at the layer interface is related to reduction of the first layer surface roughness. The reduced roughness decreases the available bonding area and hence reduces the mechanical strength at the interface. In addition, the simulations show that at higher first layer compaction pressure the bonding area is significantly less than the total contact area at the layer interface. At the interface itself, there is a non-monotonic relationship between the bonding area and first layer force. The bonding area at the interface first increases and then decreases as the first layer pressure is increased. These results are in agreement with findings of previous experimental studies. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Analysis of the hydrogen permeation properties of TiN-TiC bilayers deposited on martensitic stainless steel

    International Nuclear Information System (INIS)

    Checchetto, R.; Horino, Y.; Benamati, G.

    1996-01-01

    The efficiency of TiN-TiC bilayer coatings, deposited by ion-beam-assisted deposition on martensitic steel, as a hydrogen permeation barrier was investigated by a gas phase method; the hydrogen permeability in the TiN-TiC bilayers is very low, at least 10 4 times lower than in the steel substrate in the temperature interval 470-570 K. Possible physical mechanisms, responsible for the reduced permeability of the ceramic bilayers, are discussed. In particular, from our experimental results, it can be concluded that chemisorption and/or hydrogen jumping from surface sites to the first subsurface atomic layer represents the hydrogen permeation limiting process. (orig.)

  15. Nanobioarchitectures based on chlorophyll photopigment, artificial lipid bilayers and carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Marcela Elisabeta Barbinta-Patrascu

    2014-12-01

    Full Text Available In the last decade, building biohybrid materials has gained considerable interest in the field of nanotechnology. This paper describes an original design for bionanoarchitectures with interesting properties and potential bioapplications. Multilamellar lipid vesicles (obtained by hydration of a dipalmitoyl phosphatidylcholine thin film with and without cholesterol were labelled with a natural photopigment (chlorophyll a, which functioned as a sensor to detect modifications in the artificial lipid bilayers. These biomimetic membranes were used to build non-covalent structures with single-walled carbon nanotubes. Different biophysical methods were employed to characterize these biohybrids such as: UV–vis absorption and emission spectroscopy, zeta potential measurements, AFM and chemiluminescence techniques. The designed, carbon-based biohybrids exhibited good physical stability, good antioxidant and antimicrobial properties, and could be used as biocoating materials. As compared to the cholesterol-free samples, the cholesterol-containing hybrid structures demonstrated better stability (i.e., their zeta potential reached the value of −36.4 mV, more pronounced oxygen radical scavenging ability (affording an antioxidant activity of 73.25% and enhanced biocidal ability, offering inhibition zones of 12.4, 11.3 and 10.2 mm in diameter, against Escherichia coli, Staphylococcus aureus and Enterococcus faecalis, respectively.

  16. Texture of lipid bilayer domains

    DEFF Research Database (Denmark)

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

    2009-01-01

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

  17. Preparation and characterization of nano fluids: Influence of variables on its stability, agglomeration state and physical properties

    International Nuclear Information System (INIS)

    Mondragon, R.; Julia, J. E.; Barba, A.; Jarque, J. C.

    2014-01-01

    In recent years it has spread the use of suspensions containing nano metre sized particles, known as nano fluids, in many applications owing the good properties having nanocrystalline materials. One of the main advantages of using nano fluids is its high stability, which causes the particles do not settle over long periods of time. This stability depends on the preparation conditions such as pH, the presence of electrolytes or the solids content. Moreover, there are a number of physical properties which are influenced and altered by agglomeration of the particles. This article will analyze all the variables that affect agglomeration of the particles, nano fluids stability and properties from which it can obtain information on the state of suspension. It then lays out the different methods of dispersion of nanoparticles and their effectiveness. (Author)

  18. Physical stabilization of low-molecular-weight amorphous drugs in the solid state: a material science approach.

    Science.gov (United States)

    Qi, Sheng; McAuley, William J; Yang, Ziyi; Tipduangta, Pratchaya

    2014-07-01

    Use of the amorphous state is considered to be one of the most effective approaches for improving the dissolution and subsequent oral bioavailability of poorly water-soluble drugs. However as the amorphous state has much higher physical instability in comparison with its crystalline counterpart, stabilization of amorphous drugs in a solid-dosage form presents a major challenge to formulators. The currently used approaches for stabilizing amorphous drug are discussed in this article with respect to their preparation, mechanism of stabilization and limitations. In order to realize the potential of amorphous formulations, significant efforts are required to enable the prediction of formulation performance. This will facilitate the development of computational tools that can inform a rapid and rational formulation development process for amorphous drugs.

  19. Lipid Bilayer – mediated Regulation of Ion Channel Function by Amphiphilic Drugs

    DEFF Research Database (Denmark)

    Lundbæk, Jens August

    2008-01-01

    that are transforming it into a subject of quantitative science. It is described how the hydrophobic interactions between a membrane protein and the host lipid bilayer provide the basis for a mechanism, whereby protein function is regulated by the bilayer physical properties. The use of gramicidin channels as single-molecule......Drugs that at pico- to nanomolar concentration regulate ion channel function by high-affi nity binding to their cognate receptor often have a “ secondary pharmacology, ” in which the same molecule at low micromolar concentrations regulates a diversity of membrane proteins in an apparently...... nonspecifi c manner. It has long been suspected that this promiscuous regulation of membrane protein function could be due to changes in the physical properties of the host lipid bilayer, but the underlying mechanisms have been poorly understood. Given that pharmacological research often involves drug...

  20. Calculation of TC in a normal-superconductor bilayer using the microscopic-based Usadel theory

    International Nuclear Information System (INIS)

    Martinis, John M.; Hilton, G.C.; Irwin, K.D.; Wollman, D.A.

    2000-01-01

    The Usadel equations give a theory of superconductivity, valid in the diffusive limit, that is a generalization of the microscopic equations of the BCS theory. Because the theory is expressed in a tractable and physical form, even experimentalists can analytically and numerically calculate detailed properties of superconductors in physically relevant geometries. Here, we describe the Usadel equations and review their solution in the case of predicting the transition temperature T C of a thin normal-superconductor bilayer. We also extend this calculation for thicker bilayers to show the dependence on the resistivity of the films. These results, which show a dependence on both the interface resistance and heat capacity of the films, provide important guidance on fabricating bilayers with reproducible transition temperatures

  1. 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)

  2. Immediate physical therapy in dogs with rupture of the cranial cruciate ligament submitted to extracapsular surgical stabilization

    Directory of Open Access Journals (Sweden)

    L. Berté

    2012-02-01

    Full Text Available The study evaluated the influence of immediate physical therapy on the functional recovery of hind limbs of dogs with experimental cranial cruciate ligament rupture which underwent surgical extracapsular stabilization as well as to verify its interference in joint stability. Eight dogs were randomly divided into two groups: GI (control (n=4 and GII (physical therapy (n=4. The dogs in GII underwent the following therapeutic treatments in the postoperative period: cryotherapy, passive joint movement, massage, passive straightening, neuromuscular electrical stimulation, hydrotherapy (bath and aquatic mat and therapeutic exercises. We performed evaluations of the thigh circumference, goniometry, X-ray, and knee stability (drawer test. Results did not demonstrate a significant difference between the groups nor between different post-operative times. Regarding gait analysis, we found that the 4 dogs in GI remained in degree 3 of lameness 45 and 90 days postoperatively. However, in GII, one dog remained in degree 3 45 and 90 days after surgery; one dog changed from degree 3 to 4 90 days after surgery and the other 2 dogs changed from degree 3 to 5 90 days after surgery. It is possible to conclude that dogs with CCL rupture that undergo immediate physical therapy demonstrate better results in regards to functional gait recovery. The therapeutic modalities used in the immediate post-operative period did not cause instability of the operated knee. Further studies are needed with a larger number of dogs to indicate the immediate physical therapy in dogs with CCL ligament rupture which underwent extracapsular stabilization.

  3. Physical Stability of Oil in Water Emulsions in the Presence of Gamma Irradiated Gum Tragacanth

    DEFF Research Database (Denmark)

    Meybodi, Neda Mollakhalili; Mohammadifar, Mohammad Amin; Farhoodi, Mehdi

    2017-01-01

    Gum tragacanth (GT) exuded from an Iranian Astragalus species was γ-irradiated at 0, 0.75, 1.5, 3, 5, 7, 10 kGy and used to stabilize a model oil in water emulsion system. Stability and physicochemical properties of emulsion samples were investigated with respect to the effect of irradiation...... treatment on functional properties of gum tragacanth. Particle size distribution, interfacial tension, zeta potential, steady shear and oscillatory rheological measurements were used to characterize and evaluate the emulsion samples and obtain more information about the possible stability mechanism...

  4. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Science.gov (United States)

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Influence of flocculating agents and structural vehicles on the physical stability and rheological behavior of nitrofurantoin suspension.

    Science.gov (United States)

    Moghimipour, Eskandar; Salimi, Anayatollah; Rezaee, Saeed; Balack, Maryam; Handali, Somayeh

    2014-05-01

    Nitrofurantoin is a nitrofuran antibiotic that has been used for treatment of urinary tract against positive and negative bacteria. The aim of this study was to evaluate the effect of structural vehicles and flocculating agents on physical stability and rheological behavior of nitrofurantoin suspension. To formulate the suspensions, the effect of glycerin and polysorbate 80 as wetting agents was evaluated and their particle sizes were determined using the sieve method. Then to achieve controlled flocculation, sodium citrate and aluminum chloride were added. After choosing the suitable wetting and flocculating agents, structural vehicles such as sodium carboxyl methyl cellulose and Veegum were evaluated individually and in combination. In addition, the effect of sorbitol on density of continuous phase and some physical stability parameters such as sedimentation volume, degree of flocculation and ease of redispersion of the suspensions were evaluated. After incorporation of structural vehicles, the rheological properties of formulations were also determined to find their flow behavior. According to the results, glycerin (0.2%) and sodium citrate (0.3%) had the best effect on the suspension stability as wetting and flocculating agents, respectively. Rheological properties of formulations showed pseudoplastic behavior with some degree of thixotropy. In conclusion, the suspension containing Veegum 1%, sodium carboxy methyl cellulose 1%, glycerine 0.2%, sodium citrate 0.3% and sorbitol 20 % was chosen as the most physically stable formulation.

  6. 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

  7. 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...

  8. 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

  9. 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

  10. 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...

  11. Chemical and physical aspects of the stability of mica on heating

    International Nuclear Information System (INIS)

    Muromtsev, V.A.; Arkhangel'skii, S.V.; Egorov, S.V.

    1989-01-01

    An attempt was made in this study to comparatively determine the degree of hydration and thermal stability of micas and to analyze the possible causes of differences in interpreting the results on establishment of the degree of hydration on the example of phlogopites from the Kovdor and Aldan deposits by methods of flame photometry, γ-radiometric determination of K 2 O, thermal stability, and gravimetric methods of analysis of the moisture content and weight loss in calcination

  12. 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

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

    Science.gov (United States)

    Koolivand, Amir

    phase of the bilayer was higher in smaller vesicles likely due to a larger number of defects in smaller vesicles allowing more water soluble molecules partitioning into lipid bilayers. However, the rotational correlation time for TEMPO slows down in smaller vesicles indicating an increase in the lipid packing. Pulsed EPR techniques, HYSCORE and ESEEM spectroscopy, were used to detect local water concentration and distinguish the hydrogen bonded water to the nitroxide from the bulk one. HYSCORE was then employed to investigate the effect of bilayer curvature on the water penetration into lipid bilayer and it was found that the higher curved lipids allow more water to penetrate into lipid bilayer as a result of more defects in the highly curved lipid vesicles. Nanopore-confined lipid bilayers formed inside ordered nanochannels of anodic aluminum oxide (AAO) have found many practical applications, serving as thermodynamically stable biophysical models of cellular membranes of concave curvature and allowing for stabilization of membrane proteins in functional conformations. It was found that surface potential of POPG lipids inside the AAO pores are higher than that of vesicles---the effect that is attributed to highly ordered and packed lipids inside the AAO nanopores. At pH=7.0 the AAO zeta potential was found to be -29+/-0.64 mV. Cytochrome C and poly glutamic acid as positively and negatively charged macromolecules in physiological pH (7.4) were used to prepare multilayer protein nanotubes and cytochrome c interaction with AAO was studied by CD and UV-Vis spectroscopy. Lipid nanotube arrays containing a transmembrane WALP peptide were also formed and these macroscopically aligned lipid nanotubes were studied by CD spectroscopy. The lipid phase transition of DMPC and binding of melittin, an antibacterial peptide model, were observed from a frequency change for the QCM quartz-AAO-Lipid as a promising "biosensor".

  14. PHYSICAL AND CHEMICAL STABILITY ANALYSIS OF COSMETIC MULTI- PLE EMULSIONS LOADED WITH ASCORBYL PALMITATE AND SODIUM ASCORBYL PHOSPHATE SALTS.

    Science.gov (United States)

    Khan, Hira; Akhtar, Naveed; Ali, Atif; Khan, Haji M Shoaib; Sohail, Muhammad; Naeem, Muhammad; Nawaz, Zarqa

    2016-09-01

    Stability of hydrophilic and lipophilic vitamin C derivatives for quenching synergistic antioxidant activities and to treat oxidative related diseases is a major issue. This study was aimed to encapsulate hydrophilic and lipophilic vitamin C derivatives (ascorbyl palmitate and sodium ascorbyl phosphate) as functional ingredients in a newly formulated multiple emulsion of the W//W type to attain the synergistic antioxidant effects and the resultant system's long term physical and chemical stability. Several multiple emulsions using the same concentration of emulsifiers but different concentrations of ascorbyl palmitate and sodium ascorbyl phosphate were developed. Three finally selected multiple emulsions (ME₁, ME₂ and ME₃) were evaluated for physical stability in terms of rheology, microscopy, conductivity, pH, and organoleptic characteristics under different storage conditions for 3 months. Chemical stability was determined by HPLC on Sykam GmbH HPLC system (Germany), equipped with a variable UV detector. Results showed that at accelerated storage conditions all the three multiple emulsions had shear thinning behavior of varying shear stress with no influence of location of functional ingredients in a carrier system. Conductivity values increased and pH values remained within the skin pH range for 3 months. Microscopic analysis showed an increase in globule size with the passage of time, especially at higher temperatures while decreased at low temperatures. Centrifugation test did not cause phase separation till the 45th day, but little effects after 2 months. Chemical stability analysis by HPLC at the end of 3 months showed that ascorbyl palmitate and sodium ascorbyl phosphate were almost stable in all multiple emulsions with no influence of their location in a carrier system. Multiple emulsions were found a stable carrier for hydrophilic and lipophilic vitamin C derivatives to enhance their desired effects. Considering that many topical formulations

  15. Thermo-physical stability of fatty acid eutectic mixtures subjected to accelerated aging for thermal energy storage (TES) application

    International Nuclear Information System (INIS)

    Fauzi, Hadi; Metselaar, Hendrik S.C.; Mahlia, T.M.I.; Silakhori, Mahyar

    2014-01-01

    The thermo-physical stability of fatty acids eutectic mixtures subjected to accelerated number of melting/solidification processes has been identified using thermal cycling test in this study. Myristic acid/palmitic acid (MA/PA) (70/30, wt.%) and myristic acid/palmitic acid/sodium stearate (MA/PA/SS) (70/30/5, wt.%) were selected as eutectic phase change materials (PCMs) to evaluate their stability of phase transition temperature, latent heat of fusion, chemical structure, and volume changes after 200, 500, 1000, and 1500 thermal cycles. The thermal properties of each eutectic PCMs measured by differential scanning calorimetric (DSC) indicated the phase transition temperature and latent heat of fusion values of MA/PA/SS has a smallest changes after 1500 thermal cycles than MA/PA eutectic mixture. MA/PA/SS also has a better chemical structure stability and smaller volume change which is 1.2%, compared to MA/PA with a volume change of 1.6% after 1500 cycles. Therefore, it is concluded that the MA/PA/SS eutectic mixture is suitable for use as a phase change material in thermal energy storage (TES) such as solar water heating and solar space heating applications. - Highlights: •The prepared MA/PA and MA/PA/SS were used as eutectic phase change materials (PCM). •Thermo-physical reliability of eutectic PCMs evaluated using a thermal cycling test. •MA/PA/SS has a great thermo-physical stability than MA/PA after 1500 thermal cycles

  16. Slope Stability Analysis Based on Type, Physical And Mechanical Properties Rock in Teluk Pandan District, East Kutai Regency, East Kalimantan

    Directory of Open Access Journals (Sweden)

    Sujiman Kusnadi

    2017-12-01

    Full Text Available Research was located In Teluk Pandan District, East Kutai Regency, East Kalimantan Province.  It’s aimed to determine the lithology in the  research area and to find out how the amount of slope that will be a landslide at that location. The research conducted with the analysis of coring drilling results and then analyzed in the laboratory of rock mechanics to get the characteristic of physical and mechanical properties of the rocks. The data analysis using Hoek and Bray Method. The results showed that in the area study has a sedimentary rock lithology fine to medium detritus, such as claystone, siltstone and sandstone, as well as inserts are coal and shale. Based on the results of laboratory analysis of rock mechanics obtained density between 2,648 to 2,770. While the test results obtained value triaxial cohesion between (6.66 - 9:05 Kg / cm2, friction angle in between (37.19 - 44.08o, cohesion residual (2.72 - 3.10 Kg / cm2, residual friction angle (27.22 - 32.44o. While the direct shear test the cohesion of the summit between (6.66 - 9:05 Kg / cm2, friction angle in the cohesion peak (36.15 - 43.00o, cohesion residual (2:22 to 3:10 Kg / cm2, friction angle in the cohesion residual (37.22 - 33.85o. The simulation results stability of the slope stability Hoek and Bray using rockslide software, the result is that if the slope with a single slope stability, the stability of the slope is 60o, and if the slope with the stability of the slope overall stability of the slope is 48o.

  17. Student evaluations of physics teachers: On the stability and persistence of gender bias

    Directory of Open Access Journals (Sweden)

    Geoff Potvin

    2016-08-01

    Full Text Available [This paper is part of the Focused Collection on Gender in Physics.] There is a long history of research which confounds the simple interpretation that evaluations in an educational context are purely measures of competency. One such issue is that of gender bias in student evaluations of their teachers. In our prior work, we found that male students underrated female high school teachers in biology and chemistry while all students underrated female high school teachers in physics. In the current work, we independently checked and extended this earlier work to examine the effect of physics identity on student evaluations and gender bias. Employing multiple regression on survey data from a representative sample of 6772 college students across the U.S., attending both 2-year and 4-year post-secondary institutions (including STEM and non-STEM majors, we find the core physics effect is unchanged despite a gap between studies of nearly 10 years. Namely, both male and female students underrate their female high school physics teachers, even after controlling for physics grades and classroom experiences. Our new focus on physics identity reveals that students with a strong physics identity show a larger gender bias in favor of male teachers than those with less of a physics identity. These results may help to explain how structures that privilege certain groups and marginalize others are prevalent amongst the youngest members of a defined physics community and may serve to uphold the status quo as these young members traverse to higher levels of physics community membership. Furthermore, biased evaluative feedback structures may be one of the propagators of women’s lower competency beliefs in physics, a result that has been found by many prior studies.

  18. Student evaluations of physics teachers: On the stability and persistence of gender bias

    Science.gov (United States)

    Potvin, Geoff; Hazari, Zahra

    2016-12-01

    [This paper is part of the Focused Collection on Gender in Physics.] There is a long history of research which confounds the simple interpretation that evaluations in an educational context are purely measures of competency. One such issue is that of gender bias in student evaluations of their teachers. In our prior work, we found that male students underrated female high school teachers in biology and chemistry while all students underrated female high school teachers in physics. In the current work, we independently checked and extended this earlier work to examine the effect of physics identity on student evaluations and gender bias. Employing multiple regression on survey data from a representative sample of 6772 college students across the U.S., attending both 2-year and 4-year post-secondary institutions (including STEM and non-STEM majors), we find the core physics effect is unchanged despite a gap between studies of nearly 10 years. Namely, both male and female students underrate their female high school physics teachers, even after controlling for physics grades and classroom experiences. Our new focus on physics identity reveals that students with a strong physics identity show a larger gender bias in favor of male teachers than those with less of a physics identity. These results may help to explain how structures that privilege certain groups and marginalize others are prevalent amongst the youngest members of a defined physics community and may serve to uphold the status quo as these young members traverse to higher levels of physics community membership. Furthermore, biased evaluative feedback structures may be one of the propagators of women's lower competency beliefs in physics, a result that has been found by many prior studies.

  19. Cathodic polarization as a mean to stabilize physical parameters of underground pipelines

    International Nuclear Information System (INIS)

    Skritskij, R.R.

    1993-01-01

    Possibilities of further utilization of old gas-pipelines are determined. The investigations conducted confirm the conclusions of the previous researches on the stabilizing and improving effect of cathode polarization on the physico-mechanical properties of gas pipeline steel. Efficient and constant electrochemical protection of gas pipelines with the expired or close to expiration life time stabilizers and improves the basic physicomechanical properties of pipeline steel: ultimate strength and yield point, relative stretching. The same refers to impact strength. Degradation of physico-mechanical properties of gas pipeline steel is observed only in the zone of the welded joint

  20. 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.

  1. Addressing Raman features of individual layers in isotopically labeled Bernal stacked bilayer graphene

    Czech Academy of Sciences Publication Activity Database

    da Costa, Sara; Ek Weis, Johan; Frank, Otakar; Fridrichová, Michaela; Kalbáč, Martin

    2016-01-01

    Roč. 3, č. 2 (2016), 025022 ISSN 2053-1583 R&D Projects: GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : graphene bilayer * Raman spectroscopy * isotope labeling Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 6.937, year: 2016

  2. Statistical thermodynamics of association colloids : the equilibrium structure of micelles, vesicles, and bilayer membranes

    NARCIS (Netherlands)

    Leermakers, F.A.M.

    1988-01-01

    The aim of the present study was to unravel the general equilibrium physical properties of lipid bilayer membranes. We consider four major questions:
    1. What determines the morphology of the association colloids (micelles, membranes, vesicles) in general?
    2. Do the

  3. Supported lipid bilayer on nanocrystalline diamond: dual optical and field-effect sensor for membrane disruption

    Czech Academy of Sciences Publication Activity Database

    Ang, P.K.; Loh, K.P.; Wohland, T.; Nesládek, Miloš; Van Hove, E.

    2009-01-01

    Roč. 19, č. 1 (2009), s. 109-116 ISSN 1616-301X Institutional research plan: CEZ:AV0Z10100520 Keywords : nanocrystalline diamond * biocompatibility * supported lipid bilayers * biosensors * solution gate field effect transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.990, year: 2009

  4. Bilayer Localization of Membrane-Active Peptides Studied in Biomimetic Vesicles by Visible and Fluorescence Spectroscopies

    Czech Academy of Sciences Publication Activity Database

    Sheynis, T.; Sýkora, Jan; Benda, Aleš; Kolusheva, S.; Hof, Martin; Jelinek, R.

    2003-01-01

    Roč. 270, č. 22 (2003), s. 4478-4487 ISSN 0014-2956 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4040901 Keywords : solvent relaxation * fluorescence correlation spectroscopy * lipid bilayers Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.001, year: 2003

  5. Theory of phase equilibria and critical mixing points in binary lipid bilayers

    DEFF Research Database (Denmark)

    Risbo, Jens; Sperotto, Maria Maddalena; Mouritsen, Ole G.

    1995-01-01

    the transition is discussed in terms of the molecular properties of the lipid acyl chains. The results of the numerical model study are expected to have consequences for the interpretation of experimental measurements on lipid bilayer systems in terms of phase diagrams. (C) 1995 American Institute of Physics....

  6. Study of Charged particles transport across model and real phospholipid bilayers

    Czech Academy of Sciences Publication Activity Database

    Navrátil, Tomáš; Šestáková, Ivana; Jaklová Dytrtová, Jana; Jakl, M.; Mareček, Vladimír

    2010-01-01

    Roč. 6, č. 3 (2010), s. 208-219 ISSN 1790-5079 R&D Projects: GA AV ČR IAA400400806 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : phospholipid bilayers * voltammetry * environment Subject RIV: CF - Physical ; Theoretical Chemistry http://www.worldses.org/journals/environment/index.html

  7. Processed beetroot (Beta vulgaris L. as a natural antioxidant in mayonnaise: Effects on physical stability, texture and sensory attributes

    Directory of Open Access Journals (Sweden)

    Vassilios Raikos

    2016-12-01

    Full Text Available The oxidative and physical stability of the reformulated mayonnaise with processed beetroot was investigated and compared with a control (mayonnaise without beetroot and a commercially available product. Processing of beetroot had an impact on the structural integrity of the antioxidants present. Microwaving (960 W for 7 min was advantageous for preserving the betalain and polyphenol content of beetroot compared to roasting (180 °C for 90 min and boiling (100 °C for 30 min. The oxidative stability of mayonnaise samples was determined by Rancimat and the thiobarbituric (TBA assay. The addition of microwaved beetroot significantly enhanced the oxidative stability of mayonnaise at the end of a storage period of 4 weeks (4 °C. Although no significant differences (P > 0.05 were detected between the mayonnaise samples containing beetroot and the commercial control, the latter was less susceptible to oxidation during storage. The turbiscan stability index (TSI revealed that the commercial mayonnaise was less prone to destabilization phenomena. All the textural parameters increased with the incorporation of beetroot. The sensory evaluation revealed that, with the exception of graininess and uniformity, most of the sensory attributes are preserved if not improved with the addition of beetroot.

  8. Protein Comparability Assessments and Potential Applicability of High Throughput Biophysical Methods and Data Visualization Tools to Compare Physical Stability Profiles

    Directory of Open Access Journals (Sweden)

    Mohammad A. Alsenaidy

    2014-03-01

    Full Text Available In this review, some of the challenges and opportunities encountered during protein comparability assessments are summarized with an emphasis on developing new analytical approaches to better monitor higher-order protein structures. Several case studies are presented using high throughput biophysical methods to collect protein physical stability data as function of temperature, agitation, ionic strength and/or solution pH. These large data sets were then used to construct empirical phase diagrams (EPDs, radar charts, and comparative signature diagrams (CSDs for data visualization and structural comparisons between the different proteins. Protein samples with different sizes, post-translational modifications, and inherent stability are presented: acidic fibroblast growth factor (FGF-1 mutants, different glycoforms of an IgG1 mAb prepared by deglycosylation, as well as comparisons of different formulations of an IgG1 mAb and granulocyte colony stimulating factor (GCSF. Using this approach, differences in structural integrity and conformational stability profiles were detected under stress conditions that could not be resolved by using the same techniques under ambient conditions (i.e., no stress. Thus, an evaluation of conformational stability differences may serve as an effective surrogate to monitor differences in higher-order structure between protein samples. These case studies are discussed in the context of potential utility in protein comparability studies.

  9. Protein comparability assessments and potential applicability of high throughput biophysical methods and data visualization tools to compare physical stability profiles.

    Science.gov (United States)

    Alsenaidy, Mohammad A; Jain, Nishant K; Kim, Jae H; Middaugh, C Russell; Volkin, David B

    2014-01-01

    In this review, some of the challenges and opportunities encountered during protein comparability assessments are summarized with an emphasis on developing new analytical approaches to better monitor higher-order protein structures. Several case studies are presented using high throughput biophysical methods to collect protein physical stability data as function of temperature, agitation, ionic strength and/or solution pH. These large data sets were then used to construct empirical phase diagrams (EPDs), radar charts, and comparative signature diagrams (CSDs) for data visualization and structural comparisons between the different proteins. Protein samples with different sizes, post-translational modifications, and inherent stability are presented: acidic fibroblast growth factor (FGF-1) mutants, different glycoforms of an IgG1 mAb prepared by deglycosylation, as well as comparisons of different formulations of an IgG1 mAb and granulocyte colony stimulating factor (GCSF). Using this approach, differences in structural integrity and conformational stability profiles were detected under stress conditions that could not be resolved by using the same techniques under ambient conditions (i.e., no stress). Thus, an evaluation of conformational stability differences may serve as an effective surrogate to monitor differences in higher-order structure between protein samples. These case studies are discussed in the context of potential utility in protein comparability studies.

  10. Mixed-chain phosphatidylcholine bilayers: structure and properties

    International Nuclear Information System (INIS)

    Mattai, J.; Sripada, P.K.; Shipley, G.G.

    1987-01-01

    Calorimetric and x-ray diffraction data are reported for two series of saturated mixed-chain phosphatidylcholines (PCs), 18:0/n:0-PC and n:0/18:0-PC, where the sn-1 and sn-2 fatty acyl chains on the glycerol backbone are systematically varied by two methylene groups from 18:0 to 10:0 (n = 18, 16, 14, 12, or 10). Fully hydrated PCs were annealed at -4 0 C and their multilamellar dispersions characterized by differential scanning calorimetry and x-ray diffraction. All mixed-chain PCs form low-temperature crystalline bilayer phases following low-temperature incubation, except 18:0/10:0-PC. The subtransition temperature (T/sub s/) shifts toward the main (chain melting) transition temperature (T/sub m/) as the sn-1 or sn-2 fatty acyl chain is reduced in length. T/sub m/ decreases with acyl chain length for both series of PCs except 18:0/10:0-PC, while for the positional isomers, n:0/18:0-PC and 18:0/n:0-PC, T/sub m/ is higher for the isomer with the longer acyl chain in the sn-2 position of the glycerol backbone. The conversion from the crystalline bilayer L/sub c/phase to the liquid-crystalline L/sub α/ phase with melted hydrocarbon chains occurs through a series of phase changes which are chain length dependent. Molecular models indicate that the bilayer gel phases for the more asymmetric PC series, 18:0/n:0-PC, must undergo progressive interdigitation with chain length reduction to maintain maximum chain-chain interaction. The L/sub β/* phase of 18:0/10:p-PC is the most stable structure for this PC below T/sub m/. The formation and stability of the triple-chain structures can be rationalized from molecular models

  11. 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

  12. The Association between Physical Activity During the Day and Long-Term Memory Stability.

    Science.gov (United States)

    Pontifex, Matthew B; Gwizdala, Kathryn L; Parks, Andrew C; Pfeiffer, Karin A; Fenn, Kimberly M

    2016-12-02

    Despite positive associations between chronic physical activity and memory; we have little understanding of how best to incorporate physical activity during the day to facilitate the consolidation of information into memory, nor even how time spent physically active during the day relates to memory processes. The purpose of this investigation was to examine the relation between physical activity during the day and long-term memory. Ninety-two young adults learned a list of paired-associate items and were tested on the items after a 12-hour interval during which heart rate was recorded continuously. Although the percentage of time spent active during the day was unrelated to memory, two critical physical activity periods were identified as relating to the maintenance of long-term memory. Engaging in physical activity during the period 1 to 2-hours following the encoding of information was observed to be detrimental to the maintenance of information in long-term memory. In contrast, physical activity during the period 1-hour prior to memory retrieval was associated with superior memory performance, likely due to enhanced retrieval processing. These findings provide initial evidence to suggest that long-term memory may be enhanced by more carefully attending to the relative timing of physical activity incorporated during the day.

  13. 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.

  14. Dynamic patterns in a supported lipid bilayer driven by standing surface acoustic waves.

    Science.gov (United States)

    Hennig, Martin; Neumann, Jürgen; Wixforth, Achim; Rädler, Joachim O; Schneider, Matthias F

    2009-11-07

    In the past decades supported lipid bilayers (SLBs) have been an important tool in order to study the physical properties of biological membranes and cells. So far, controlled manipulation of SLBs is very limited. Here we present a new technology to create lateral patterns in lipid membranes controllable in both space and time. Surface acoustic waves (SAWs) are used to generate lateral standing waves on a piezoelectric substrate which create local "traps" in the lipid bilayer and lead to a lateral modulation in lipid concentration. We demonstrate that pattern formation is reversible and does not affect the integrity of the lipid bilayer as shown by extracting the diffusion constant of fluid membranes. The described method could possibly be used to design switchable interfaces for the lateral transport and organization of membrane bound macromolecules to create dynamic bioarrays and control biofilm formation.

  15. New optical method for measuring the bending elasticity of lipid bilayers

    International Nuclear Information System (INIS)

    Minetti, C; Dubois, F; Vitkova, V; Bivas, I

    2016-01-01

    The knowledge of the elasticity of lipid bilayer structures is fundamental for new developments in biophysics, pharmacology and biomedical research. Lipid vesicles are readily prepared in laboratory conditions and employed for studying the physical properties of lipid membranes. The thermal fluctuation analysis of the shape of lipid vesicles (or flicker spectroscopy) is one of the experimental methods widely used for the measurement of the bending modulus of lipid bilayers. We present direct phase measurements performed on dilute vesicular suspensions by means of a new optical method exploiting holographic microscopy. For the bending constant of phosphatidylcholine bilayers we report the value of 23k B T in agreement with values previously measured by micropipette aspiration, electrodeformation and flicker spectroscopy of giant lipid vesicles. The application of this novel approach for the evaluation of the bending elasticity of lipid membranes opens the way to future developments in the phase measurements on lipid vesicles for the evaluation of their mechanical constants. (paper)

  16. 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.

  17. 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

  18. 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.

  19. Lipid Bilayer Formation on Organic Electronic Materials

    KAUST Repository

    Zhang, Yi

    2018-04-23

    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 recognition. Monitoring the quality and function of lipid bilayers is thus essential and can be performed using electrically active substrates that allow for transduction of signals. Such a promising electronic transducer material is the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) which has provided a plethora of novel bio transducing architectures. The challenge is however in assembling a bilayer on the conducting polymer surface, which is defect-free and has high mobility. Herein, we investigate the fusion of zwitterionic vesicles on a variety of PEDOT:PSS films, but also on an electron transporting, negatively charged organic semiconductor, in order to understand the surface properties that trigger vesicle fusion. The PEDOT:PSS films are prepared from dispersions containing different concentrations of ethylene glycol included as a formulation additive, which gives a handle to modulate surface physicochemical properties without a compromise on the chemical composition. The strong correlation between the polarity of the surface, the fusion of vesicles and the mobility of the resulting bilayer aides extracting design principles for the development of future conducting polymers that will enable the formation of lipid bilayers.

  20. 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.

  1. Self-organizing Map Analysis for Understanding Comprehensive Relationships between Formulation Variables, State of Water, and the Physical Stability of Pharmaceutical Emulsions

    OpenAIRE

    Onuki, Yoshinori; Hasegawa, Naoki; Horita, Akihiro; Ueno, Naomi; Kida, Chihiro; Hayashi, Yoshihiro; Obata, Yasuko; Toshokan, Toshokan

    2015-01-01

    The physical stability of pharmaceutical emulsions is an important quality attribute to be considered. To obtain a better understanding of this issue, this study investigated the contribution of the state of water to the physical stability of pharmaceutical emulsions. The key technology to evaluate the state of water was magnetic resonance imaging (MRI). For sample preparation, model emulsions with different formulation variables (surfactant content, water content, and hydrophilic–lipophilic ...

  2. Long-Term Stability of NIST Chip-Scale Atomic Clock Physics Packages

    Science.gov (United States)

    2007-01-01

    vacuum packaging), as has been demonstrated by Lutwak et al. [3]. Nevertheless, we tried to investigate the causes for the frequency shifts of...stability,” Optics Express, 13, 1249-1253. [3] R. Lutwak , J. Deng, W. Riley, M. Varghese, J. Leblanc, G. Tepolt, M. Mescher, D. K. Serkland, K. M. Geib...the 1st Annual Multiconference on Electronics and Photonics, 7-11 November 2006, Guanajuato, Mexico, in press. [6] R. Lutwak , P. Vlitas, M

  3. A high throughput platform for understanding the influence of excipients on physical and chemical stability

    DEFF Research Database (Denmark)

    Raijada, Dhara; Cornett, Claus; Rantanen, Jukka

    2013-01-01

    The present study puts forward a miniaturized high-throughput platform to understand influence of excipient selection and processing on the stability of a given drug compound. Four model drugs (sodium naproxen, theophylline, amlodipine besylate and nitrofurantoin) and ten different excipients were...... for chemical degradation. The proposed high-throughput platform can be used during early drug development to simulate typical processing induced stress in a small scale and to understand possible phase transformation behaviour and influence of excipients on this....

  4. Remote operation of the vertical plasma stabilization @ the GOLEM tokamak for the plasma physics education

    Czech Academy of Sciences Publication Activity Database

    Svoboda, V.; Kocman, J.; Grover, O.; Krbec, Jaroslav; Stöckel, Jan

    96-97, October (2015), s. 974-979 ISSN 0920-3796. [Symposium on Fusion Technology 2014(SOFT-28)/28./. San Sebastián, 29.09.2014-03.10.2014] Institutional support: RVO:61389021 Keywords : tokamak technology * remote participation * plasma stabilization Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 1.301, year: 2015 http://dx.doi.org/10.1016/j.fusengdes.2015.06.044

  5. Effect of Maillard Conjugates on the Physical Stability of Zein Nanoparticles Prepared by Liquid Antisolvent Coprecipitation.

    Science.gov (United States)

    Davidov-Pardo, Gabriel; Joye, Iris J; Espinal-Ruiz, Mauricio; McClements, David Julian

    2015-09-30

    Protein nanoparticles are often not very stable in a complex food matrix because they are primarily stabilized by electrostatic repulsion. In this study, we envisaged the stabilization of zein nanoparticles through Maillard conjugation reactions with polysaccharides of different molecular mass. Zein nanoparticles (0.5% w/v) containing resveratrol (0.025% w/v grape skin extract) were produced by liquid antisolvent precipitation and coated with Maillard conjugates (MC) of sodium caseinate and different molecular mass carbohydrates during particle production. Zein nanoparticles coated with conjugated polysaccharides of 2.8, 37, and 150 kDa had diameters of 198 ± 5, 176 ± 6, and 180 ± 3 nm, respectively. The encapsulation efficiency (∼83%) was not affected by conjugation, but the conjugates significantly improved particle stability against changes in pH (2.0-9.0), CaCl2 addition (up to 100 mM), and heat treatment (30-90 °C, 30 min). Zein nanoparticles coated by MC may therefore be suitable delivery systems for hydrophobic bioactive molecules in a wide range of commercial products.

  6. Physical and Chemical Stability of Urapidil in 0.9% Sodium Chloride in Elastomeric Infusion Pump.

    Science.gov (United States)

    Tomasello, Cristina; Leggieri, Anna; Rabbia, Franco; Veglio, Franco; Baietto, Lorena; Fulcheri, Chiara; De Nicolò, Amedeo; De Perri, Giovanni; D'Avolio, Antonio

    2016-01-01

    Urapidil is an antihypertensive agent, usually administered through intravenous bolus injection, slow-intravenous infusion, or continuous-drug infusion by perfusor. Since to date no evidences are available on drug stability in elastomeric pumps, patients have to be hospitalized. The purpose of this study was to validate an ultra-performance liquid chromatographic method to evaluate urapidil stability in an elastomeric infusion pump, in order to allow continuous infusion as home-care treatment. Analyses were conducted by diluting urapidil in an elastomeric pump. Two concentrations were evaluated: 1.6 mg/mL and 3.3 mg/mL. For the analyses, a reverse-phase ultra-performance liquid chromatographic- photodiode array detection instrument was used. Stressed degradation, pH changes, and visual clarity were used as stability indicators up to 10 days after urapidil solution preparation. The drug showed no more than 5% degradation during the test period at room temperature. No pH changes and no evidences of incompatibility were observed. Stress tests resulted in appreciable observation of degradation products. Considering the observed mean values, urapidil hydrochloride in sodium chloride 0.9% in elastomeric infusion pumps is stable for at least 10 days. These results indicate that this treatment could be administered at home for a prolonged duration (at least 7 days) with a satisfactory response. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

  7. Stability evaluation considering the scattering of the physical properties of rock mass

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Shin, Koichi

    1988-01-01

    The objective of this research is to establish the rational design method which could be evaluated the influence of the scattering of mechanical properties on the stability of the foundation ground of Nuclear Power Plant and surrounding slope. For this purpose, investigation on the actual scattering state of mechanical properties of rock and rock masses, and the stability estimations by the probabilistic method are conducted in this report, and following results are obtained. (1) The actual distribution of scattering of mechanical properties could describe in the probabilistic models of Weibull and Gamma distribution most accurately. The Normal distribution model could also do almostly. The coefficients of variation are so large in the range of 0.4 - 0.8, the remarkable tendency of them among the kinds of mechanical Properties and among the rock classification are not recognized. (2) It is found that the stability estimation considering the scattering of mechanical properties can be sufficiently conducted by using the conventional deterministic method, and the results of deterministic method using the average value of scattering need not be reduce in proportional to the degree of scattering of mechanical properties. (3) Based on these results, new rational design method and procedure, which could be evaluated the scattering of mechanical properties of ground material, is proposed. (author)

  8. 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

  9. 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...

  10. Supported liquid membrane stability in chiral resolution by chemically and physically modified membranes

    Energy Technology Data Exchange (ETDEWEB)

    Molinari, R.; Argurio, P. [Arcavata di Rende Univ. of Calabria, Arcavata di Rende, CS (Italy). Dept. of Chemical and Materials Engineering

    2001-04-01

    In the present work some stability studies on Supported Liquid Membranes (SLMs) to be used for chiral separations were realized. In particular, primary aim was to determine how a modification of the support surface influences the SLM stability. First, the procedure for support modification was optimised, making a screening of various compounds (sulphuric acid, nitric acid, chromic acid, sodium dodecyl sulphate (SDS), glycerol, oleic alcohol, propylene glycol (PPG), bovine serum albumin (BSA)) and testing their performance by means of contact angle measurements. Next, a second screening was realized by permeation tests in a stirred cell. Finally, to compare the stability of modified with unmodified support in a process of interest for chemical and/or biochemical industries, some permeation tests for resolution of DNB-DL-Leucine were realized in a re-circulation system. Results showed a better surface hydrophilization of chemically modified support and better stability of the sulphonated support. However, in operating conditions a little high stability of the unmodified support was obtained. [Italian] Nel presente lavoro sono stati realizzati degli studi di stabilita' di Membrane Liquide Supportate (SLMs) da impiegare in separazioni chirali. In particolare, obiettivo principale e' stato quello di determinare l'influenza che una modifica della superficie del supporto ha sulla stabilita' della SLM. Cosi', in un primo momento, e' stata ottimizzata le procedura di modifica del supporto, facendo una selezione tra vari composti (acido solforico, acido nitrico, acido cromico, sodio dodecil solfato (SDS), glicerolo, alcool oleico, glicole propilenico (PPG), siero di albumina bovina (BSA)) basata su misure dell'angolo di contatto. Successivamente, e' stata realizzata una seconda selezione mediante prove di permeazione in una cella agitata. Infine, con lo scopo di confrontare la stabilita' della SLM con supporto modificato rispetto

  11. Polyhydroxy surfactants for the formulation of lipid nanoparticles (SLN and NLC): effects on size, physical stability and particle matrix structure.

    Science.gov (United States)

    Kovacevic, A; Savic, S; Vuleta, G; Müller, R H; Keck, C M

    2011-03-15

    The two polyhydroxy surfactants polyglycerol 6-distearate (Plurol(®)Stearique WL1009 - (PS)) and caprylyl/capryl glucoside (Plantacare(®) 810 - (PL)) are a class of PEG-free stabilizers, made from renewable resources. They were investigated for stabilization of aqueous solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) dispersions. Production was performed by high pressure homogenization, analysis by photon correlation spectroscopy (PCS), laser diffraction (LD), zeta potential measurements and differential scanning calorimetry (DSC). Particles were made from Cutina CP as solid lipid only (SLN) and its blends with Miglyol 812 (NLC, the blends containing increasing amounts of oil from 20% to 60%). The obtained particle sizes were identical for both surfactants, about 200 nm with polydispersity indices below 0.20 (PCS), and unimodal size distribution (LD). All dispersions with both surfactants were physically stable for 3 months at room temperature, but Plantacare (PL) showing a superior stability. The melting behaviour and crystallinity of bulk lipids/lipid blends were compared to the nanoparticles. Both were lower for the nanoparticles. The crystallinity of dispersions stabilized with PS was higher, the zeta potential decreased with storage time associated with this higher crystallinity, and leading to a few, but negligible larger particles. The lower crystallinity particles stabilized with PL remained unchanged in zeta potential (about -50 mV) and in size. These data show that surfactants have a distinct influence on the particle matrix structure (and related stability and drug loading), to which too little attention was given by now. Despite being from the same surfactant class, the differences on the structure are pronounced. They are attributed to the hydrophobic-lipophilic tail structure with one-point anchoring in the interface (PL), and the loop conformation of PS with two hydrophobic anchor points, i.e. their molecular structure and its

  12. 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...

  13. 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.

  14. 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.

  15. Highly Stable Bimetallic AuIr/TiO₂ Catalyst: Physical Origins of the Intrinsic High Stability against Sintering.

    Science.gov (United States)

    Han, Chang Wan; Majumdar, Paulami; Marinero, Ernesto E; Aguilar-Tapia, Antonio; Zanella, Rodolfo; Greeley, Jeffrey; Ortalan, Volkan

    2015-12-09

    It has been a long-lived research topic in the field of heterogeneous catalysts to find a way of stabilizing supported gold catalyst against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To reveal the physical origin of the high stability of AuIr/TiO2, we used aberration-corrected scanning transmission electron microscopy (STEM), STEM-tomography, and density functional theory (DFT) calculations. Three-dimensional structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of AuIr nanoparticles as compared to Au nanoparticles.

  16. 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.

  17. The Effect of Protein PEGylation on Physical Stability in Liquid Formulation

    DEFF Research Database (Denmark)

    Holm, Louise Stenstrup; Mcumber, Aaron; Rasmussen, Jakob Ewald

    2014-01-01

    The presence of micron aggregates in protein formulations has recently attracted increased interest from regulatory authorities, industry, and academia because of the potential undesired side effects of their presence. In this study, we characterized the micron aggregate formation of hen egg...... approximately half as many particles as Lyz, despite its lower apparent thermodynamic stability and more loose protein fold. Further characterization showed that the PEGylation led to a change from attractive to repulsive protein-protein interactions, which may partly explain the reduced particle formation...

  18. Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change

    Science.gov (United States)

    Teller, E.; Hyde, T.; Wood, L.

    2002-04-18

    We offer a case for active technical management of the radiative forcing of the temperatures of the Earth's fluid envelopes, rather than administrative management of atmospheric greenhouse gas inputs, in order to stabilize both the global- and time-averaged climate and its mesoscale features. We suggest that active management of radiative forcing entails negligible--indeed, likely strongly negative--economic costs and environmental impacts, and thus best complies with the pertinent mandate of the UN Framework Convention on Climate Change. We propose that such approaches be swiftly evaluated in sub-scale in the course of an intensive international program.

  19. Physical stability and moisture sorption of aqueous chitosan-amylose starch films plasticized with polyols

    DEFF Research Database (Denmark)

    Cervera, Mirna Fernández; Karjalainen, Milja; Airaksinen, Sari

    2004-01-01

    The short-term stability and the water sorption of films prepared from binary mixtures of chitosan and native amylose maize starch (Hylon VII) were evaluated using free films. The aqueous polymer solutions of the free films contained 2% (w/w) film formers, glycerol, or erythritol as a plasticizer...... in the crystallinity of the films are evident within a 3-month period of storage, and the changes in the solid state are dependent on the plasticizer and storage conditions. When stored at ambient conditions for 3 months, the aqueous chitosan-amylose starch films plasticized with erythritol exhibited a partly...

  20. 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...

  1. Influence of Casein-Phospholipid Combinations as Emulsifier on the Physical and Oxidative Stability of Fish Oil-in-Water Emulsions

    DEFF Research Database (Denmark)

    García Moreno, Pedro Jesús; Horn, Anna Frisenfeldt; Jacobsen, Charlotte

    2014-01-01

    The objective of this study was to investigate the influence of casein (0.3% w/w) and phospholipid (0.5% w/w) emulsifier combinations on the physical and oxidative stability of 10% fish oil-in-water emulsions at pH 7. For that purpose, three phospholipids were evaluated, namely, lecithin (LC......), phosphatidylcholine (PC), and phosphatidylethanolamine (PE). The emulsion stabilized with LC showed the best physical stability having the most negative zeta potential and the lowest mean droplet size. In addition, this emulsion was also the least oxidized in terms of peroxide value and concentration of the volatile...

  2. Physical modeling of river spanning rock structures: Evaluating interstitial flow, local hydraulics, downstream scour development, and structure stability

    Science.gov (United States)

    Collins, K.L.; Thornton, C.I.; Mefford, B.; Holmquist-Johnson, C. L.

    2009-01-01

    Rock weir and ramp structures uniquely serve a necessary role in river management: to meet water deliveries in an ecologically sound manner. Uses include functioning as low head diversion dams, permitting fish passage, creating habitat diversity, and stabilizing stream banks and profiles. Existing information on design and performance of in-stream rock structures does not provide the guidance necessary to implement repeatable and sustainable construction and retrofit techniques. As widespread use of rock structures increases, the need for reliable design methods with a broad range of applicability at individual sites grows as well. Rigorous laboratory testing programs were implemented at the U.S. Bureau of Reclamation (Reclamation) and at Colorado State University (CSU) as part of a multifaceted research project focused on expanding the current knowledge base and developing design methods to improve the success rate of river spanning rock structures in meeting project goals. Physical modeling at Reclamation is being used to measure, predict, and reduce interstitial flow through rock ramps. CSU is using physical testing to quantify and predict scour development downstream of rock weirs and its impact on the stability of rock structures. ?? 2009 ASCE.

  3. Sensory acceptability and physical stability evaluation of a prebiotic soy-based dessert developed with passion fruit juice

    Directory of Open Access Journals (Sweden)

    Daniel Granato

    2012-03-01

    Full Text Available The aim of this study was to use a factorial design approach for developing a palatable and stable soy-based dessert with the addition of Soy Protein (SP, oligofructose, and Passion Fruit Juice (PFJ. Panelists (n = 50 used a seven-point hedonic scale to assess the overall liking, degree of liking of creaminess, taste, and color of the desserts. In addition, the samples were submitted to a preference ranking test in order to evaluate the products' preference. Water Holding Capacity (WHC and backscattering (BS measures were also determined to assess the physical stability of the trials. Sample F3 (35% PFJ and 2% SP was the only one that presented a WHC index of 94.8%; moreover, none of the developed samples had synerisis after 72 hours of storage indicating adequate physical stability of the emulsion process. Samples F2 (25% PFJ, and 3.0% SP, F4 (35% PFJ, and 3.0% SP, and F5 (30% PFJ, and 2.5% SP presented mean hedonic scores above 'slightly liked' for all sensory attributes. The acceptance index of samples varied from 62.50 to 88% showing the great sensory potential of such products.

  4. Effects of core stabilization with and without conventional physical therapy for the management of non-specific low back pain

    International Nuclear Information System (INIS)

    Shoukat, F.; Ahmed, A.

    2014-01-01

    The purpose of the study was to examine the effects of core stabilization exercises with conventional physiotherapy for the management of non-specific low back pain (LBP). Methodology: This experimental comparative study was conducted at Department of Physiotherapy, PSRD hospital, Ferozpur Road Lahore. The study involved 40 subjects diagnosed with non-specific LBP with age ranges from 18 - 65 years. Patients were randomly allocated into 2 groups: treated with core stabilization exercises and conventional physiotherapy. Group - B (Control Group): In this group, patients were treated by conventional physiotherapy alone. The outcome measures were pain and physical functional outcomes. Pain was measured by using Visual Analo- gue Scale (V AS) and the physical functional outcomes of patients were measured by using Modified Oswes- tery Disability Questionnaire (MODQ). Results: By applying paired t-test in group - A, the p-values obtained for VAS and MODQ were statisti- cally significant (i.e., p = 0.000, p = 0.000 respectively) while in group - B, the p-values for VAS and MODQ were also found to be significant (p = 0.000, p = 0.000 respectively). By applying repeated measure analysis of variance (ANOVA), p-values were find to be insignificant for VAS (p = 0.09) and MODQ (p = 0.018). Conclusion: Both groups showed improvement in severity of pain and functional activity but the group- A that was given core stabilization exercises along with conventional treatment showed same improve- ment in pain and functional status as shown by group- B so any of the intervention can be used to gain better results as both are equally effective. (author)

  5. Physical stability comparisons of IgG1-Fc variants: effects of N-glycosylation site occupancy and Asp/Gln residues at site Asn 297.

    Science.gov (United States)

    Alsenaidy, Mohammad A; Okbazghi, Solomon Z; Kim, Jae Hyun; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

    2014-06-01

    The structural integrity and conformational stability of various IgG1-Fc proteins produced from the yeast Pichia pastoris with different glycosylation site occupancy (di-, mono-, and nonglycosylated) were determined. In addition, the physical stability profiles of three different forms of nonglycosylated Fc molecules (varying amino-acid residues at site 297 in the CH 2 domain due to the point mutations and enzymatic digestion of the Fc glycoforms) were also examined. The physical stability of these IgG1-Fc glycoproteins was examined as a function of pH and temperature by high-throughput biophysical analysis using multiple techniques combined with data visualization tools (three index empirical phase diagrams and radar charts). Across the pH range of 4.0-6.0, the di- and monoglycosylated forms of the IgG1-Fc showed the highest and lowest levels of physical stability, respectively, with the nonglycosylated forms showing intermediate stability depending on solution pH. In the aglycosylated Fc proteins, the introduction of Asp (D) residues at site 297 (QQ vs. DN vs. DD forms) resulted in more subtle changes in structural integrity and physical stability depending on solution pH. The utility of evaluating the conformational stability profile differences between the various IgG1-Fc glycoproteins is discussed in the context of analytical comparability studies. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  6. Chemical and physical stability of smectites and illite in electrolyte solutions: experimental study at 150 C

    International Nuclear Information System (INIS)

    Boutiche, M.

    1995-01-01

    Chemical interactions between electrolytic solutions commonly used i drilling muds and clays have been studies under P-T conditions similar to those of drillings (150 deg C) in order to determine the eventual consequences on the stability of clay rich formations. The experimental work has been carried out using several solutions (water, NaOH (pH 8, 10, 12), KCI (0,1, 1 2 mol./l), sea water, and K 2 CO 3 ) and clay minerals with low to high amounts of swelling layers (smectite (Na, Na-Ca, Ca), mixed layered illite-smectite minerals). Run products are studied by X-ray diffraction and electronic microprobe. Smectite layers show series of mineralogical changes (cation exchange in the interlayer site, formation of non-swelling layers, hydrolysis), which, however, do not yield to the formation of new minerals, except in the case of the interaction with K 2 CO 3 at 150 deg C (zeolite crystallisation). Cation exchange in the interlayer depends on the nature of the cation, cation concentration in the solution, exchange constants, and liquid/solid ratio. In dilute solutions ( 1 mol./l), because they favour the collapse of swelling layers, and dispersion. Solutions of K 2 CO 3 at 150 deg C are at the origin of the transformation of smectite to zeolites, and high pH - highly saline solutions are rather aggressive, and would probably not stabilize the argilites. (author)

  7. [Physical and chemical stability of fortified ophtalmic ready-to-use solutions: review of literature].

    Science.gov (United States)

    Sourdeau, P; Evrard, J-M; Remy, G; Hecq, J-D

    2012-03-01

    Ophtalmic infections and inflammations are often encountered during hospitalization. They require the preparation of "fortified" ophtalmic solutions, i.e. pharmaceutical ophtalmic solutions which are hyperconcentrated in active substance. The data of physicochemical stabilities are modified and it is therefore essential to gather the results of the various publications devoted to this subject. In 2006, an initial literature review was undertaken to identify the molecules mostly used in the preparation of fortified ophtalmic solutions in hospital. A second review of the literature in 2010 has enriched the knowledge about it. Two new drugs have entered the summary table: amikacin and ticarcillin disodium. Date on 12 molecules already known in 2006 were updated to improve clinical practices. A review of the literature was undertaken in order to collect the results of the molecules mostly used for the preparation of the fortified ophtalmic solutions in hospitals. A summary table, indicating the active substance, its concentration, the assay method, the storage temperature and physicochemical modifications, presents all the results. This review of literature makes it possible to match stability and validity period to these preparations. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

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

    KAUST Repository

    Gan, Liyong; Zhang, Lihong; Zhang, Qingyun; Guo, Chunsheng; Schwingenschlö gl, Udo; Zhao, Yong

    2015-01-01

    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

  9. Bioplasmonic Alloyed Nanoislands Using Dewetting of Bilayer Thin Films.

    Science.gov (United States)

    Kang, Minhee; Ahn, Myeong-Su; Lee, Youngseop; Jeong, Ki-Hun

    2017-10-25

    Unlike monometallic materials, bimetallic plasmonic materials offer extensive benefits such as broadband tuning capability or high environmental stability. Here we report a broad range tuning of plasmon resonance of alloyed nanoislands by using solid-state dewetting of gold and silver bilayer thin films. Thermal dewetting after successive thermal evaporation of thin metal double-layer films readily forms AuAg-alloyed nanoislands with a precise composition ratio. The complete miscibility of alloyed nanoislands results in programmable tuning of plasmon resonance wavelength in a broadband visible range. Such extraordinary tuning capability opens up a new direction for plasmonic enhancement in biophotonic applications such as surface-enhanced Raman scattering or plasmon-enhanced fluorescence.

  10. Comparative study of Ta, TaN and Ta/TaN bi-layer barriers for Cu-ultra low-k porous polymer integration

    International Nuclear Information System (INIS)

    Yang, L.Y.; Zhang, D.H.; Li, C.Y.; Foo, P.D.

    2004-01-01

    Tantalum (Ta), TaN and bilayer Ta/TaN barriers deposited on ultra-low-k porous polymer (ULKPP) and the thermal stability of their structures are comparatively investigated using various techniques. The Ta/ultra-low-k polymer shows the smallest sheet resistance, but the poorest thermal stability, while TaN on the ultra-low-k polymer shows the highest resistance but the best thermal stability. The bi-layer Ta/TaN barrier takes the advantage of both Ta and TaN barriers and gives reasonable resistance and thermal stability. The electrical tests indicate that the Cu lines with the TaN and bi-layer Ta/TaN barriers exhibit the smaller leakage current and higher breakdown voltage compared with the Cu lines with the Ta barrier. The better thermal stability of the TaN and the bi-layer Ta/TaN barriers is mainly due to the amorphous/nanostructure and less grain boundaries of the barriers. In addition, the texture discontinuity at the Ta/TaN interfaces in the bi-layers barrier also plays an important role in reducing mutual diffusion of Ta atoms in the Ta barrier and some atoms in the ultra-low-k porous polymer

  11. Stability of asymmetric lipid bilayers assessed by molecular dynamics simulations

    NARCIS (Netherlands)

    Esteban-Martin, Santi; Risselada, H. Jelger; Salgado, Jesus; Marrink, Siewert J.

    2009-01-01

    The asymmetric insertion of amphiphiles into biological membranes compromises the balance between the inner and outer monolayers. As a result, area expansion of the receiving leaflet and curvature strain may lead to membrane permeation, shape changes, or membrane fusion events. We have conducted

  12. Physical stability of a microcrystalline beta-sitosterol suspension in oil

    DEFF Research Database (Denmark)

    von Bonsdorff-Nikander, Anna; Karjalainen, Milja; Rantanen, Jukka

    2003-01-01

    Sterols have been shown to reduce plasma cholesterol by blocking the absorption of cholesterol from the gut. The physical properties of crystalline plant sterols limit their use in foods. A coarse-grained structure can be avoided by recrystallisation, a method that affords a reduction in the part......Sterols have been shown to reduce plasma cholesterol by blocking the absorption of cholesterol from the gut. The physical properties of crystalline plant sterols limit their use in foods. A coarse-grained structure can be avoided by recrystallisation, a method that affords a reduction......-ray diffraction. Suspensions can, in most cases, be stored for 16 weeks without any changes to the size and habit. The only evidence of crystal growth came from a suspension with a low sterol concentration at a temperature of +4 degrees C. This is due to the dissolution-diffusion process which is affected...

  13. Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film.

    Science.gov (United States)

    Lee, Ka-Yeon; Song, Kyung Bin

    2017-03-01

    Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG-PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10 -9 g·m/m 2 ·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG-PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG-PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material. © 2017 Institute of Food Technologists®.

  14. 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.

  15. 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.

  16. Electronic properties of graphene-based bilayer systems

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-08-23

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

  17. 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 ...

  18. 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...

  19. Topological transformation of a surfactant bilayer

    DEFF Research Database (Denmark)

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

    2000-01-01

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

  20. Electronic properties of a biased graphene bilayer

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  1. Nonmonotonic critical temperature in superconductor ferromagnet bilayers

    NARCIS (Netherlands)

    Fominov, Ya. V.; Fominov, I.V.; Chtchelkatchev, N.M.; Golubov, Alexandre Avraamovitch

    2002-01-01

    The critical temperature Tc of a superconductor/ferromagnet (SF) bilayer can exhibit nonmonotonic dependence on the thickness df of the F layer. SF systems have been studied for a long time; according to the experimental situation, a ¿dirty¿ limit is often considered which implies that the mean free

  2. INTERLAYER OPTICAL CONDUCTIVITY OF A SUPERCONDUCTING BILAYER

    NARCIS (Netherlands)

    GARTSTEIN, YN; RICE, MJ; VANDERMAREL, D

    1994-01-01

    We employ the Bardeen-Cooper-Schrieffer theory to calculate the frequency-dependent interlayer conductivity of a superconducting bilayer, the two layers of which are coupled by weak single-particle tunneling. The effect of the superconducting transition on the normal-state absorption band is to

  3. 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.

  4. 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.

  5. 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.

  6. Optical response of Al/Ti bilayer transition edge sensors

    International Nuclear Information System (INIS)

    Zhang Qing-Ya; Liu Jian-She; Dong Wen-Hui; He Gen-Fang; Li Tie-Fu; Chen Wei; Wang Tian-Shun; Zhou Xing-Xiang

    2014-01-01

    We report the optical response characteristics of Al/Ti bilayer transition edge sensors (TESs), which are mainly comprised of Al/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measurement was performed in a 3 He sorption refrigerator and the device's response to optical pulses was investigated using a pulsed laser source. Based on these measurements, we obtained the effective recovery time (τ eff ) of the devices at different biases and discussed the dependence of τ eff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τ eff = 3.9 μs, which indicates a high temperature sensitivity (α = T/R · dR/dT = 326). The results also showed that the TES exhibits good linearity under optical pulses of variable widths. (interdisciplinary physics and related areas of science and technology)

  7. 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.

  8. Early Life Factors and Adult Leisure Time Physical Inactivity Stability and Change.

    Science.gov (United States)

    Pinto Pereira, Snehal M; Li, Leah; Power, Chris

    2015-09-01

    Physical inactivity has a high prevalence and associated disease burden. A better understanding of influences on sustaining and changing inactive lifestyles is needed. We aimed to establish whether leisure time inactivity was stable in midadulthood and whether early life factors were associated with inactivity patterns. In the 1958 British birth cohort (n = 12,271), leisure time inactivity (frequency, less than once a week) assessed at 33 and 50 yr was categorized as "never inactive," "persistently inactive," "deteriorating," or "improving." Early life factors (birth to 16 yr) were categorized into three (physical, social, and behavioral) domains. Using multinomial logistic regression, we assessed associations with inactivity persistence and change of factors within each early life domain and the three domains combined with and without adjustment for adult factors. Inactivity prevalence was similar at 33 and 50 yr (approximately 31%), but 17% deteriorated and 18% improved with age. In models adjusted for all domains simultaneously, factors associated with inactivity persistence versus never inactive were prepubertal stature (8% lower risk/height SD), poor hand control/coordination (17% higher risk/increase on four-point scale), cognition (16% lower/SD in ability) (physical); parental divorce (25% higher), class at birth (7% higher/reduction on four-point scale), minimal parental education (16% higher), household amenities (2% higher/increase in 19-point score (high = poor)) (social); and inactivity (22% higher/reduction in activity on four-point scale), low sports aptitude (47% higher), smoking (30% higher) (behavioral). All except stature, parental education, sports aptitude, and smoking were associated also with inactivity deterioration. Poor hand control/coordination was the only factor associated with improved status (13% lower/increase on four-point scale) versus persistently inactive. Adult leisure time inactivity is moderately stable. Early life factors are

  9. 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.

  10. Physical and mechanical properties of sand stabilized by cement and natural zeolite

    Science.gov (United States)

    Salamatpoor, Sina; Jafarian, Yaser; Hajiannia, Alborz

    2018-05-01

    Loose sands are prone to lose their shear strength when being subjected to static or cyclic loads. To this end, there exist several methods to improve the mechanical properties of sands, but the most crucial and viable approach is the one with the lowest harmful environmental impact both in production and recycling processes. In this regard, zeolite as a natural pozzolanic additive offers an eco-friendly improvement in strength parameters of cemented sandy soils. Thereby, in this study, a series of unconfined compressive strength (UCS) tests are conducted to evaluate the mechanical parameters of the zeolite-cemented sand. The results demonstrate a meaningful increase in the UCS of the treated sand samples for replacement of cement by zeolite at an optimum proportion of 40% in specimens with 14 and 28 days curing time. The effectiveness of the improvement process is demonstrated by the strength improvement ratio which was up to be 128% to 209% for the samples with 14 and 28 days curing time, respectively. With regard to the above results, zeolite can be introduced as a promising cement substitute in stabilization of sandy ground including backfills, roadbed, embankments, and other structural filling systems.

  11. Improvement of the Physical and Oxidative Stability Characteristics of Ice Cream through Interesterified Moringa Oleifera Oil

    International Nuclear Information System (INIS)

    Nadeem, M.; Ullah, R.; Ullah, A.

    2016-01-01

    This study aimed to investigate the effect of high melting point interesterified M. oleifera oil (35.6 degree centigrade) with substantial amount of unsaturated fatty acids on physicochemical and oxidative stability characteristics of ice cream. Of the 10 percent fat in the ice cream, 30 percent was replaced by interesterified M. oleifera oil at three levels i.e. 10, 20 and 30 percent (T1, T2 and T3, respectively). Oleic acid increased from 26.55 percent to 31.69 percent, 36.94 percent and 42.15 percent in T1, T2 and T3 with no effect on melting time, compositional attributes and free fatty acid content of ice cream (P>0.05). Supplementation of ice cream with interesterified M. oleifera oil inhibited the autoxidation process in ice cream during 3 months storage period (P<0.05).The loss of oleic and linoleic acid in fresh and 3 months stored control and T2 was 26.55 percent, 24.15 percent, 26.39% percent and 1.93 percent, 1.24 percent and 1.79 percent, respectively. Peroxide value of three months stored control and T3 was 1.12 and 0.39 (meqO2/kg). The overall acceptability score of T2 was 80% of the total score (9). (author)

  12. Low noise charge sensitive preamplifier DC stabilized without a physical resistor

    Science.gov (United States)

    Bertuccio, Giuseppe; Rehak, Pavel; Xi, Deming

    1994-09-13

    The invention is a novel charge sensitive preamplifier (CSP) which has no resistor in parallel with the feedback capacitor. No resetting circuit is required to discharge the feedback capacitor. The DC stabilization of the preamplifier is obtained by means of a second feedback loop between the preamplifier output and the common base transistor of the input cascode. The input transistor of the preamplifier is a Junction Field Transistor (JFET) with the gate-source junction forward biased. The detector leakage current flows into this junction. This invention is concerned with a new circuit configuration for a charge sensitive preamplifier and a novel use of the input Field Effect Transistor of the CSP itself. In particular this invention, in addition to eliminating the feedback resistor, eliminates the need for external devices between the detector and the preamplifier, and it eliminates the need for external circuitry to sense the output voltage and reset the CSP. Furthermore, the noise level of the novel CSP is very low, comparable with the performance achieved with other solutions. Experimental tests prove that this configuration for the charge sensitive preamplifier permits an excellent noise performance at temperatures including room temperature. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using a commercial JFET as input device of the preamplifier.

  13. Physical and physicochemical stability evaluation of cosmetic formulations containing soybean extract fermented by Bifidobacterium animalis

    Directory of Open Access Journals (Sweden)

    Rafael Pinto Vieira

    2009-09-01

    Full Text Available Peel off facial masks, based on polyvinyl alcohol (PVA, are formulations that, after application and drying, form an occlusive film over the face. After removing, they provide cleanness, tensor and moisturizing effects, removing dead cells, residues and other materials deposited on the stratum corneous. The soybean extract fermented by Bifidobacterium animalis has sugars, amino acids, peptides, proteins and free isoflavonoids in high concentrations, when compared to the unfermented extract, providing benefits to the cosmetic formulations like anti-aging effect, moisture, tensor action and emollience. The cosmetic bases of peel off facial masks, added with 5.0% w/w of fermented soybean extract, were submitted to Preliminary and Accelerated Stability Studies. Eight (8 preparations were evaluated in several conditions of temperature (-10.0, 5.0, 22.0 and 45.0 ºC and time (maximum of 15 days, comparing the results with the initial condition (48 h after preparation. The variables observed were: organoleptic characteristics, pH and appearing viscosity value and film drying time. The preparation containing 17.0% w/w of PVA and 0.5% w/w of guar gum was selected between the eight preparations initially prepared, because it presented the best performance in the stability test, being recommended storage at low temperatures (5.0 ºC.As máscaras faciais peel off a base de álcool polivinílico (PVA são formulações que, após a aplicação e secagem, formam um filme oclusivo sobre a face e, após sua remoção, conferem limpeza, ação tensora e hidratação à pele, retirando células mortas do estrato córneo, resíduos e outros materiais depositados. O extrato de soja fermentado por Bifidobacterium animalis possui açúcares, aminoácidos, peptídeos, e alto teor de isoflavonas na forma livre, quando comparado ao leite não fermentado, propiciando benefícios às formulações cosméticas, como ação antienvelhecimento, hidratação, efeito tensor e

  14. 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.

  15. Development of Bilayer Tablets with Modified Release of Selected Incompatible Drugs.

    Science.gov (United States)

    Dhiman, Neha; Awasthi, Rajendra; Jindal, Shammy; Khatri, Smriti; Dua, Kamal

    2016-01-01

    The oral route is considered to be the most convenient and commonly-employed route for drug delivery. When two incompatible drugs need to be administered at the same time and in a single formulation, bilayer tablets are the most appropriate dosage form to administer such incompatible drugs in a single dose. The aim of the present investigation was to develop bilayered tablets of two incompatible drugs; telmisartan and simvastatin. The bilayer tablets were prepared containing telmisartan in a conventional release layer using croscarmellose sodium as a super disintegrant and simvastatin in a slow-release layer using HPMC K15M, Carbopol 934P and PVP K 30 as matrix forming polymers. The tablets were evaluated for various physical properties, drug-excipient interactions using FTIR spectroscopy and in vitro drug release using 0.1M HCl (pH 1.2) for the first hour and phosphate buffer (pH 6.8) for the remaining period of time. The release kinetics of simvastatin from the slow release layer were evaluated using the zero order, first order, Higuchi equation and Peppas equation. All the physical parameters (such as hardness, thickness, disintegration, friability and layer separation tests) were found to be satisfactory. The FTIR studies indicated the absence of interactions between the components within the individual layers, suggesting drug-excipient compatibility in all the formulations. No drug release from the slow-release layer was observed during the first hour of the dissolution study in 0.1M HCl. The release-controlling polymers had a significant effect on the release of simvastatin from the slow-release layer. Thus, the formulated bilayer tablets avoided incompatibility issues and proved the conventional release of telmisartan (85% in 45 min) and slow release of simvastatin (80% in 8 h). Stable and compatible bilayer tablets containing telmisartan and simvastatin were developed with better patient compliance as an alternative to existing conventional dosage forms.

  16. The influence of hyaluronan on the structure of a DPPC-bilayer under high pressures.

    Science.gov (United States)

    Zander, Thomas; Wieland, D C Florian; Raj, Akanksha; Wang, Min; Nowak, Benedikt; Krywka, Christina; Dėdinaitė, Andra; Claesson, Per Martin; Garamus, Vasil M; Schreyer, Andreas; Willumeit-Römer, Regine

    2016-06-01

    The superior lubrication properties of synovial joints have inspired many studies aiming at uncovering the molecular mechanisms which give rise to low friction and wear. However, the mechanisms are not fully understood yet, and, in particular, it has not been elucidated how the biolubricants present at the interface of cartilage respond to high pressures, which arise during high loads of joints. In this study we utilize a simple model system composed of two biomolecules that have been implied as being important for joint lubrication. It consists of a solid supported dipalmitoylphosphatidylcholin (DPPC) bilayer, which was formed via vesicles fusion on a flat Si wafer, and the anionic polysaccharide hyaluronan (HA). We first characterized the structure of the HA layer that adsorbed to the DPPC bilayers at ambient pressure and different temperatures using X-ray reflectivity (XRR) measurements. Next, XRR was utilized to evaluate the response of the system to high hydrostatic pressures, up to 2kbar (200MPa), at three different temperatures. By means of fluorescence microscopy images the distribution of DPPC and HA on the surface was visualized. Our data suggest that HA adsorbs to the headgroup region that is oriented towards the water side of the supported bilayer. Phase transitions of the bilayer in response to temperature and pressure changes were also observed in presence and absence of HA. Our results reveal a higher stability against high hydrostatic pressures for DPPC/HA composite layers compared to that of the DPPC bilayer in absence of HA. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Analysis of Core Stability Exercise Effect on the Physical and Psychological Function of Elderly Women Vulnerable to Falls during Obstacle Negotiation

    OpenAIRE

    Ko, Dae-Sik; Jung, Dae-In; Jeong, Mi-Ae

    2014-01-01

    [Purpose] The aim of the present study was to investigate the effects of core stability exercise (CSE) on the physical and psychological functions of elderly women while negotiating general obstacles. [Subjects and Methods] After allocating 10 elderly women each to the core stability training group and the control group, we carried out Performance-Oriented Mobility Assessment (POMA) and measured crossing velocity (CV), maximum vertical heel clearance (MVHC), and knee flexion angle for assessi...

  18. Stability of deep features across CT scanners and field of view using a physical phantom

    Science.gov (United States)

    Paul, Rahul; Shafiq-ul-Hassan, Muhammad; Moros, Eduardo G.; Gillies, Robert J.; Hall, Lawrence O.; Goldgof, Dmitry B.

    2018-02-01

    Radiomics is the process of analyzing radiological images by extracting quantitative features for monitoring and diagnosis of various cancers. Analyzing images acquired from different medical centers is confounded by many choices in acquisition, reconstruction parameters and differences among device manufacturers. Consequently, scanning the same patient or phantom using various acquisition/reconstruction parameters as well as different scanners may result in different feature values. To further evaluate this issue, in this study, CT images from a physical radiomic phantom were used. Recent studies showed that some quantitative features were dependent on voxel size and that this dependency could be reduced or removed by the appropriate normalization factor. Deep features extracted from a convolutional neural network, may also provide additional features for image analysis. Using a transfer learning approach, we obtained deep features from three convolutional neural networks pre-trained on color camera images. An we examination of the dependency of deep features on image pixel size was done. We found that some deep features were pixel size dependent, and to remove this dependency we proposed two effective normalization approaches. For analyzing the effects of normalization, a threshold has been used based on the calculated standard deviation and average distance from a best fit horizontal line among the features' underlying pixel size before and after normalization. The inter and intra scanner dependency of deep features has also been evaluated.

  19. Analysis of Core Stability Exercise Effect on the Physical and Psychological Function of Elderly Women Vulnerable to Falls during Obstacle Negotiation.

    Science.gov (United States)

    Ko, Dae-Sik; Jung, Dae-In; Jeong, Mi-Ae

    2014-11-01

    [Purpose] The aim of the present study was to investigate the effects of core stability exercise (CSE) on the physical and psychological functions of elderly women while negotiating general obstacles. [Subjects and Methods] After allocating 10 elderly women each to the core stability training group and the control group, we carried out Performance-Oriented Mobility Assessment (POMA) and measured crossing velocity (CV), maximum vertical heel clearance (MVHC), and knee flexion angle for assessing physical performances. We evaluated depression and fear of falling for assessing psychological functions. [Results] Relative to the control group, the core stability training group showed statistically significant overall changes after the training session: an increase in POMA scores, faster CV, lower MVHC, and a decrease in knee flexion angle. Furthermore, depression and fear of falling decreased significantly. [Conclusion] CSE can have a positive effect on the improvement of physical and psychological performances of older women who are vulnerable to falls as they negotiate everyday obstacles.

  20. Exchange anisotropy and micromagnetic properties of PtMn/NiFe bilayers

    International Nuclear Information System (INIS)

    Pokhil, Taras; Linville, Eric; Mao, Sining

    2001-01-01

    Magnetic microstructure, exchange induced uniaxial and unidirectional anisotropy and structural transformation have been studied in PtMn/NiFe bilayer films and small elements as a function of annealing time. The relationship between the fcc-fct ordering phase transformation in PtMn and the development of exchange induced magnetic properties in PtMn/NiFe bilayers is complicated by the fact that the transformation occurs throughout the entire volume of the PtMn film, while the exchange between the layers is predominantly an interface effect. Consequently, the development of the exchange anisotropy should depend primarily on the character of the structural transformation at the interface between PtMn and NiFe. The purpose of this article is to correlate the volume phase transformation in PtMn to the development of exchange anisotropy and micromagnetic behavior in PtMn/NiFe bilayers. The interface structure can be inferred from the anisotropy and micromagnetic measurements, leading to a model that explains the relationship between the volume and interface transformation structures in PtMn, and magnetic properties of the bilayers. The structure and magnetic properties were characterized by x-ray diffraction, vibrating sample magnetometry, and magnetic force microscopy. [copyright] 2001 American Institute of Physics

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

    Science.gov (United States)

    Mohapatra, Monalisa; Mishra, Ashok K.

    2012-03-01

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

  2. Effect of lipid viscosity and high-pressure homogenization on the physical stability of "Vitamin E" enriched emulsion.

    Science.gov (United States)

    Alayoubi, Alaadin; Abu-Fayyad, Ahmed; Rawas-Qalaji, Mutasem M; Sylvester, Paul W; Nazzal, Sami

    2015-01-01

    Recently there has been a growing interest in vitamin E for its potential use in cancer therapy. The objective of this work was therefore to formulate a physically stable parenteral lipid emulsion to deliver higher doses of vitamin E than commonly used in commercial products. Specifically, the objectives were to study the effects of homogenization pressure, number of homogenizing cycles, viscosity of the oil phase, and oil content on the physical stability of emulsions fortified with high doses of vitamin E (up to 20% by weight). This was done by the use of a 27-run, 4-factor, 3-level Box-Behnken statistical design. Viscosity, homogenization pressure, and number of cycles were found to have a significant effect on particle size, which ranged from 213 to 633 nm, and on the percentage of vitamin E remaining emulsified after storage, which ranged from 17 to 100%. Increasing oil content from 10 to 20% had insignificant effect on the responses. Based on the results it was concluded that stable vitamin E rich emulsions could be prepared by repeated homogenization at higher pressures and by lowering the viscosity of the oil phase, which could be adjusted by blending the viscous vitamin E with medium-chain triglycerides (MCT).

  3. A physical and numerical modelling investigation of the roadway stability in longwall mining, with and without narrow pillar protection

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz, H.; Fowell, R.J. [Suleyman Demirel University, Isparta (Turkey)

    2004-03-01

    The drivage of the supply gate of a development panel in the presumed low stress zone adjacent to the loader gate of an excavated panel with a very small width of intervening pillar between the two entries, known as skin-to-skin working, resulted in an extensive fall of the supply gate roof at Bilsthorpe colliery in 1993. This fall left a question over the application of skin-to-skin drivage of gate entries supported primarily by rock bolts. To investigate the possible reasons behind this fall, both physical and numerical modelling studies were carried out. Physical and numerical models were successful in demonstrating the potential danger of the working method with the rock bolt support system employed. Development of a shear failure plane from the rib edge into roof strata of the loader gate and development of the second shear failure plane at the abutment side of the supply gate exposed the supply gate to the fall of large rock blocks released by shear failure zones. Models demonstrated that the fall of the supply gate roof was not due to the inability of the rock bolts to prevent bed separation, but it was the method of working that made the bolts ineffective due to the height of the block delineated by the shear failure planes. Further physical and numerical models were undertaken to investigate the influence of 5, 7.5 and 10 in wide intervening pillars between the entries on the stability of the rock bolt supported supply gate roof. These studies showed that a 7.5 in or 10 in wide pillar would have prevented development of failure zones and fall of the roof while a 5 in pillar was found to be an undersized pillar width causing the development of extensive failure zones in the roof.

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. /SIGMA PHI/-tocopherol: modifier of the phase state of the lipid bilayer

    International Nuclear Information System (INIS)

    Skrypin, V.I.; Bratkcovskaya, L.B.; Erin, A.N.; Kagan, V.E.

    1985-01-01

    This paper determines the action of low (near-physiological) concentrations of alpha-tocopherol on the character of the gel-liquid crystal transition in a lipid bilayer containing free fatty acids. Fifty mM of K + -phosphate buffer was made up in D 2 O and kept for several hours to enable substitution of H 1 by D 2, after which the buffer was dried and redissolved in D 2 O. The graphs of temperature dependence of relative signal intensity of protons of methylene groups in liposomes of different composition are presented. It is shown that the stabilizing action of alpha-tocopherol on the phase state of the lipid bilayer of membranes is one of the mechanisms by which the recently demonstrated ability of alpha-tocopherol to protect biological membranes against the injurious action of free fatty acids, through the formation of complexes of alpha-tocopherol with fatty acides, may be effected

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. Evaluation and enhancement of physical stability of semi-solid dispersions containing piroxicam into hard gelatin capsules.

    Science.gov (United States)

    Karataş, Ayşegül; Bekmezci, Serife

    2013-01-01

    The aim of the study was to investigate the physical stability of the semi-solid dispersions into the hard gelatine capsules prepared with Gelucire 44/14, Labrasol and different additives such as microcrystalline cellulose (MCC), mannitol and lactose (alpha-monohydrate) used for enhancing the stability of the formulations. The master dispersion prepared with only Gelucire 44/14 (20% w/w) and Labrasol (80% w/w) was stored in a refrigerator (5 +/- 3 degrees C), while the modified dispersions with the additives (2% w/w) were kept in a climatic chamber (25 +/- 2 degrees C / 60 +/- 5% RH) for 12 months. Dissolution tests of the semi-solid dispersions were performed in media with different pH's immediatly after preparation and after 3, 6 and 12 months of storage. FTIR and DSC studies were also carried out at the same time points. The ideal storage condition for the master dispersion was found to be at 5 degrees C. The addition of MCC, mannitol and lactose (alpha-monohydrate) to the original dispersion afforded a solidification effect on the formulation at room temperature and showed the same dissolution behavior (not less than 85% of piroxicam within 30 min in pH 1.2, 4.5 and 6.8; and water) with the master. The dispersion including lactose was stable at 25 degrees C for 12 months. However, the ideal period of storage for the modified dispersions including MCC and mannitol was 6 months at 25 degrees C. FTIR and DSC results both confirmed the amorphous state of piroxicam in all semi-solid dispersions under storage conditions for 12 months.

  17. Physical-chemical characterization and stability study of alpha-trypsin at ph 3.0 by differential scanning calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Santos, A.M.C.; Santana, M.A.; Gomide, F.T.F.; Oliveira, J.S.; Vilas Boas, F.A.S.; Santoro, M.M.; Teixera, K.N. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Inst. de Ciencias Biologicas (ICB). Dept. de Bioquimica e Imunologia; Miranda, A.A.C.; Biondi, I. [Universidade Estadual de Feira de Santana (UEFS), BA (Brazil). Dept. de Ciencias Biologicas; Vasconcelos, A.B.; Bemquerer, M.P. [EMBRAPA Recursos Geneticos e Biotecnologia, Brasilia, DF (Brazil). Parque Estacao Biologica (PqEB)

    2008-07-01

    Full text: {alpha}-Trypsin is a serine-protease with a polypeptide chain of 223 amino acid residues and six disulfide bridges. It is a globular protein with predominance of antiparallel {beta}-sheet secondary structure and it has two domains with similar structures. In the present work, a stability study of {alpha}-trypsin in the acid pH range was performed and physical-chemical denaturation parameters were measured by using differential scanning calorimetry (DSC). The {alpha}-trypsin has a shelf-life (t{sub 95%}) of about ten months at pH 3.0 and 4 deg C and its hydrolysis into the {psi}-trypsin isoform is negligible during six months as monitored by mass spectrometry (Micromass Q-ToF). The observed {delta}H{sub cal}/{delta}H{sub vH} ratio is close to unity for {alpha}-trypsin denaturation, which suggests the occurrence of a two-state transition, devoid of molten-globule intermediates. At pH 3.0, {alpha}-trypsin unfolded with T{sub m} 325.9 K and {delta}H= 99.10 kcal mol{sup -1}, and the change in heat capacity between the native and unfolded forms of the protein was estimated to be 1.96 {+-} 0.18 kcal mol{sup -1} K{sup -1}. The stability of {alpha}-trypsin calculated at 298 K and at pH 3.0 was {delta}G{sub U} = 6.10 kcal mol{sup -1}. These values are in the range expected for a small globular protein. These results show that the thermodynamic parameters for unfolding of {beta}-trypsin do not change substantially after its conversion to {alpha}-trypsin.

  18. Phase Transition of MoS2 Bilayer Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Bothra, Pallavi; Pati, Swapan K.

    2016-01-01

    to a heterostructure of the 2H and 1T structures instead of a complete conversion to the 1T bilayer structure. Therefore, we propose that the desired synthesis of the 1T-MoS2 from the bulk 2H-MoS2 takes place through the hybrid 2H-1T structure. Our finding gives physical insight into the experimentally described...

  19. 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.

  20. Rapid Identification of Stacking Orientation in Isotopically Labeled Chemical-Vapor Grown Bilayer Graphene by Raman Spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Fang, W.; Hsu, A. L.; Caudillo, R.; Song, Y.; Birdwell, A. G.; Zakar, E.; Kalbáč, Martin; Dubey, M.; Palacios, T.; Dresselhaus, M. S.; Araujo, P. T.; Kong, J.

    2013-01-01

    Roč. 13, č. 4 (2013), s. 1541-1548 ISSN 1530-6984 R&D Projects: GA ČR(CZ) GAP208/12/1062; GA MŠk LH13022 Institutional support: RVO:61388955 Keywords : AB-stacked bilayer graphene * carbon isotope * fluorination Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 12.940, year: 2013

  1. Lack of a synergistic effect of arginine-glutamic acid on the physical stability of spray-dried bovine serum albumin.

    Science.gov (United States)

    Reslan, Mouhamad; Demir, Yusuf K; Trout, Bernhardt L; Chan, Hak-Kim; Kayser, Veysel

    2017-09-01

    Improving the physical stability of spray-dried proteins is essential for enabling pulmonary delivery of biotherapeutics as a noninvasive alternative to injections. Recently, a novel combination of two amino acids - l-arginine (l-Arg) and l-glutamic acid (l-Glu), has been reported to have synergistic protein-stabilizing effects on various protein solutions. Using spray-dried bovine serum albumin (BSA) reconstituted in solution as a model protein, we investigated the synergistic effect of these amino acids on the physical stability of proteins. Five BSA solutions were prepared: (1) BSA with no amino acids (control); (2) with 50 mM l-Arg; (3) with 200 mM l-Arg, (4) with 50 mM l-Glu and (5) with 25:25 mM of Arg:Glu. All solutions were spray-dried and accelerated studies at high temperatures were performed. Following accelerated studies, monomer BSA loss was measured using SE-HPLC. We found that l-Arg significantly improved the physical stability of spray-dried BSA even at low concentrations, however, when combined with l-Glu, was ineffective at reducing monomer BSA loss. Our findings demonstrate the limitations in using Arg-Glu for the stabilization of spray-dried BSA. Furthermore, we found that a low concentration of l-Glu enhanced monomer BSA loss. These findings may have significant implications on the design of future biotherapeutic formulations.

  2. 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.

  3. 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

  4. 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)

  5. 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

  6. Fine tuning of optical transition energy of twisted bilayer graphene via interlayer distance modulation

    Czech Academy of Sciences Publication Activity Database

    del Corro, Elena; Peňa-Álvarez, Miriam; Sato, K.; Morales-García, A.; Bouša, Milan; Mračko, Michal; Kolman, Radek; Pacáková, Barbara; Kavan, Ladislav; Kalbáč, Martin; Frank, Otakar

    2017-01-01

    Roč. 95, č. 8 (2017), č. článku 085138. ISSN 2469-9950 R&D Projects: GA ČR GA14-15357S; GA MŠk LL1301; GA ČR GA16-03823S Institutional support: RVO:61388955 ; RVO:61388998 ; RVO:68378271 Keywords : twisted bilayer graphene * tuning * silicon Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  7. The stability of children's weight status over time, and the role of television, physical activity, and diet.

    Science.gov (United States)

    Jackson, Sandra L; Cunningham, Solveig A

    2017-07-01

    Weight-related behaviors such as sedentary activity, physical activity, and diet have been the focus of efforts to prevent and reduce the occurrence of obesity and overweight in children, but few longitudinal studies have examined the effects of weight-related behaviors on changes in weight status over time in children. This study examines the effects of weight-related behaviors on subsequent changes in weight during childhood. We used the Early Childhood Longitudinal Study Kindergarten Cohort (ECLS-K), a nationally representative prospective cohort of children in the United States. Data, including anthropometric measures, were collected six times across 1998-2007 (analytic sample=4938). We employed an autoregressive cross-lagged model in a structural equation model framework to assess the effects of behavioral factors -intake of fruit, vegetables, fast food and sugar-sweetened beverages, television viewing, and physical activity - on weight stability over time. BMI z-scores were highly stable throughout childhood: the standardized parameter estimates of BMI z-scores on subsequent-period BMI z-scores ranged from 0.79 to 0.86. BMI z-scores were least stable between Kindergarten and 1st grade but became highly stable between 3rd and 5th grades. After accounting for prior weight, behavioral factors had little effect on subsequent weight. The most important behavioral factor was TV viewing in the 1st and 3rd grades: an additional hour of daily TV viewing was associated with 0.04 higher BMI z-score. It is important to prevent excessive weight gain early in childhood, as weight patterns are long-lasting; the most important behavioral factor may be limiting children's screen time. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Influence of solvent composition on the miscibility and physical stability of naproxen/PVP K 25 solid dispersions prepared by cosolvent spray-drying.

    Science.gov (United States)

    Paudel, Amrit; Van den Mooter, Guy

    2012-01-01

    To investigate the influence of solvent properties on the phase behavior and physical stability of spray-dried solid dispersions containing naproxen and PVP K 25 prepared from binary cosolvent systems containing methanol, acetone and dichloromethane. The viscosity, polymer globular size and evaporation rate of the spray-drying feed solutions were characterized. The solid dispersions were prepared by spray-drying drug-polymer solutions in binary solvent blends containing different proportions of each solvent. The phase behavior was investigated with mDSC, pXRD, FT-IR and TGA. Further, physical stability of solid dispersions was assessed by analyzing after storage at 75% RH. The solid dispersions prepared from solvent/anti-solvent mixture showed better miscibility and physical stability over those prepared from the mixtures of good solvents. Thus, solid dispersions prepared from dichloromethane-acetone exhibited the best physicochemical attributes followed by those prepared from methanol-acetone. FT-IR analysis revealed differential drug-polymer interaction in solid dispersions prepared from various solvent blends, upon the exposure to elevated humidity. Spray-drying from a cocktail of good solvent and anti-solvent with narrower volatility difference produces solid dispersions with better miscibility and physical stability resulting from the simultaneous effect on the polymer conformation and better dispersivity of drug.

  9. Physical and oxidative stability of fish oil-in-water emulsions fortified with enzymatic hydrolysates from common carp (Cyprinus carpio) roe

    DEFF Research Database (Denmark)

    Ghelichi, Sakhi; Sørensen, Ann-Dorit Moltke; García Moreno, Pedro Jesús

    2017-01-01

    Physical and oxidative stability of 5% (by weight) cod liver oil-in-water emulsions fortified with common carp (C. carpio) roe protein hydrolysate (CRPH) were examined. CRPH was obtained by enzymatic hydrolysis of discarded roe by using Alcalase 2.4 L for 30, 60, 90, and 120 min to yield different...

  10. Adhesion Improvement and Characterization of Magnetron Sputter Deposited Bilayer Molybdenum Thin Films for Rear Contact Application in CIGS Solar Cells

    Directory of Open Access Journals (Sweden)

    Weimin Li

    2016-01-01

    Full Text Available Molybdenum (Mo thin films are widely used as rear electrodes in copper indium gallium diselenide (CIGS solar cells. The challenge in Mo deposition by magnetron sputtering lies in simultaneously achieving good adhesion to the substrates while retaining the electrical and optical properties. Bilayer Mo films, comprising five different thickness ratios of a high pressure (HP deposited bottom layer and a low pressure (LP deposited top layer, were deposited on 40 cm × 30 cm soda-lime glass substrates by DC magnetron sputtering. We focus on understanding the effects of the individual layer properties on the resulting bilayer Mo films, such as microstructure, surface morphology, and surface oxidation. We show that the thickness of the bottom HP Mo layer plays a major role in determining the micromechanical and physical properties of the bilayer Mo stack. Our studies reveal that a thicker HP Mo bottom layer not only improves the adhesion of the bilayer Mo, but also helps to improve the film crystallinity along the preferred [110] direction. However, the surface roughness and the porosity of the bilayer Mo films are found to increase with increasing bottom layer thickness, which leads to lower optical reflectance and a higher probability for oxidation at the Mo surface.

  11. Formation of 3D cholesterol crystals from 2D nucleation sites in lipid bilayer membranes: implications for atherosclerosis.

    Science.gov (United States)

    Varsano, Neta; Fargion, Iael; Wolf, Sharon G; Leiserowitz, Leslie; Addadi, Lia

    2015-02-04

    Atherosclerosis is the major precursor of cardiovascular disease. The formation of cholesterol crystals in atherosclerotic plaques is associated with the onset of acute pathology. The cholesterol crystals induce physical injury in the plaque core, promoting cell apoptosis and triggering an increased inflammatory response. Herein we address the question of how cholesterol crystal formation occurs in atherosclerosis. We demonstrate that three-dimensional (3D) cholesterol crystals can undergo directed nucleation from bilayer membranes containing two-dimensional (2D) cholesterol crystalline domains. We studied crystal formation on supported lipid bilayers loaded with exogenous cholesterol and labeled using a monoclonal antibody that specifically recognizes ordered cholesterol arrays. Our findings show that 3D crystals are formed exclusively on the bilayer regions where there are segregated 2D cholesterol crystalline domains and that they form on the domains. This study has potentially significant implications for our understanding of the crucial step in the mechanism by which atherosclerotic lesions form.

  12. Physical Stability of Octenyl Succinate-Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems.

    Science.gov (United States)

    Puerta-Gomez, Alex F; Castell-Perez, M Elena

    2015-06-01

    The high cost and potential toxicity of biodegradable polymers like poly(lactic-co-glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate-modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α-lactalbumin (α-L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim-Andersen-de Boer model indicated that native waxy corn had significantly (P whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%-OSA modification had a "melted" appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA-modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications. © 2015 Institute of Food Technologists®

  13. 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

  14. Study on the enhanced and stable field emission behavior of a novel electrosprayed Al-doped ZnO bilayer film

    KAUST Repository

    Mahmood, Khalid; Munir, Rahim; Swain, Bhabani Sankar; Han, Gill Sang; Kim, Byeong Jo; Jung, Hyun Suk

    2014-01-01

    A novel electrosprayed bilayer film composed of an over-layer (L 2) of aluminium-doped ZnO (AZO) nanoflakes (NF-AZO) and a under-layer (L1) of AZO nanocrystallites structure (NC-AZO) named BL:NF/NC-AZO is studied as an excellent field-emitter. The XRD pattern demonstrated that the doped bilayer film has preferential growth along the c-axis with hexagonal wurtzite structure and the (0 0 2) peak shifted toward the larger angle side after doping. The lowest turn-on field of ∼2.8 V μm-1, highest emission current density of 1.95 mA cm-2 is obtained for BL:NF/NC-AZO under the field of 6.8 V μm-1 and as well as the highest field enhancement factor (β) is estimated to be 4370 ± 3, compared to pure ZnO bilayer film (BL:NF/NC-ZnO) and also better than NC-AZO film and possesses the excellent long term stability of emission current. The PL intensity of doped ZnO bilayer film is very much stronger than pure ZnO bilayer structure. The superior field emission properties are attributed to the better morphologies, Al-doping and better crystallinity of bilayer AZO films. © 2014 The Royal Society of Chemistry.

  15. EDITORIAL: Stability and nonlinear dynamics of plasmas: A symposium celebrating Professor Robert Dewar's accomplishments in plasma physics Stability and nonlinear dynamics of plasmas: A symposium celebrating Professor Robert Dewar's accomplishments in plasma physics

    Science.gov (United States)

    Bhattacharjee, Amitava

    2012-01-01

    covered in the talks at the Symposium. The paper by David Barmaz and coworkers published in this issue discusses the problem diamagnetic stabilization of ballooning instabilities in stellarators. It is not surprising that Bob's work on ballooning modes shows an accomplished master of WKB theory at work, for it is the culmination of a process that began many years earlier. His involvement in applications of WKB theory to problems involving instability and turbulence began in 1970, when he was a graduate student. At this time he wrote a very influential paper, discussed at the Symposium, on the interaction between hydromagnetic waves and a timedependent inhomogeneous medium. This paper is widely cited, especially in the astrophysical and space plasma literature, for it gives a rigorous method of evaluating the effects of lowfrequency hydromagnetic fluctuations on a slowly varying background medium. The method has found use in problems as diverse as the self-sustainment of molecular clouds, the heating and acceleration of the solar wind, and the effect of cosmic rays on the interplanetary medium. Attentive readers will note that Bob has been drafted as a co-author and participant in about half of the publications in this issue. This is a reflection of Bob's continued and tireless involvement in a wide spectrum of research problems that have their genesis in his fundamental contributions to plasma physics, as well as the eagerness with which we all welcome his involvement in our own projects. We hope to have this continue for many years to come.

  16. Physical stability of 20% lipid injectable emulsions via simulated syringe infusion: effects of glass vs plastic product packaging.

    Science.gov (United States)

    Driscoll, David F; Ling, Pei-Ra; Bistrian, Bruce R

    2007-01-01

    The United States Pharmacopeia (USP) has proposed large-globule-size limits to ensure the physical stability of lipid injectable emulsions, expressed as the percent fat >5 microm, or PFAT(5), not exceeding 0.05%. Visibly obvious phase separation as free oil has been shown to occur in some samples if PFAT(5) is >0.4%. We recently found that lipids, newly packaged in plastic (P), exceed the proposed USP limits and seem to produce less stable total nutrient admixtures compared with those made from conventional glass (G), which do meet proposed USP standards. We tested the possible stability differences between 20% lipid injectable emulsions in either P or G in a simulated neonatal syringe infusion study. Eighteen individual syringes were prepared from each 20% lipid injectable emulsion product (n = 36) and attached to a syringe pump set at an infusion rate of 0.5 mL/hour. The starting PFAT(5) levels were measured at time 0 and after 24 hours of infusion, using a laser-based light obscuration technique as described by the USP Chapter . The data were assessed by a 2-way analysis of variance (ANOVA) with Container (G vs P) and Time as the independent variables and PFAT as the dependent variable. At time 0, the starting PFAT(5) level for lipids packaged in G was 0.006% +/- 0.001% vs 0.162% +/- 0.026% for P, whereas at the end of the infusion they were 0.013% +/- 0.003% and 0.328% +/- 0.046%, respectively. Significant differences were noted overall between groups for Container, Time, and Container-Time interaction (all p emulsions packaged in newly introduced plastic containers exceed the proposed USP PFAT(5) limits and subsequently become significantly less stable during a simulated syringe-based infusion. Although modest growth (p = NS) in large-diameter fat globules was observed for the glass-based lipids, they remained within proposed USP globule size limits throughout the study. Glass-based lipids seem to be a more stable dosage form and potentially a safer way to

  17. Aharonov-Bohm effect in bilayer graphene

    Science.gov (United States)

    Park, Chang-Soo

    2017-06-01

    We investigate Aharonov-Bohm effect in bilayer graphene. We consider a setup of n- p (n‧)-n junction with Aharonov-Bohm loop connected in the transmission region. In the presence of trigonal warping we show that, due to the anisotropic dispersion of eigenspectrum, the Aharonov-Bohm interference depends on the geometry of junction: it exists for armchair interface but vanishes for zigzag interface. For the armchair interface, it is demonstrated that the period of Aharonov-Bohm oscillation is Φ0 = h / e and the amplitude of oscillation can be varied with incident energy and the barrier height of the junction.

  18. Fano resonances in bilayer phosphorene nanoring

    Science.gov (United States)

    Zhang, Rui; Wu, Zhenhua; Li, X. J.; Li, L. L.; Chen, Qiao; Li, Yun-Mei; Peeters, F. M.

    2018-05-01

    Tunable transport properties and Fano resonances are predicted in a circular bilayer phosphorene nanoring. The conductance exhibits Fano resonances with varying incident energy and applied perpendicular magnetic field. These Fano resonance peaks can be accurately fitted with the well known Fano curves. When a magnetic field is applied to the nanoring, the conductance oscillates periodically with magnetic field which is reminiscent of the Aharonov–Bohm effect. Fano resonances are tightly related to the discrete states in the central nanoring, some of which are tunable by the magnetic field.

  19. Vortex dynamics in ferromagnetic/superconducting bilayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-01

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

  20. Evaluation of Maltose-Induced Chemical Degradation at the Interface of Bilayer Tablets.

    Science.gov (United States)

    Matsuzaki, Naoya; Yamamoto, Yousuke; Murayama, Daisuke; Katakawa, Yoshifumi; Mimura, Hisashi; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

    2017-01-01

    Fixed dose combination tablets consisting of mirabegron (MB) and solifenacin succinate (SS) were developed and formulated into bilayer tablets in the current study. The results of a chemical stability study showed that the original formulation for the tablets led to a significant increase of unknown degradants in the SS layer. Two compatibility studies were conducted to simulate the interface between the MB and SS layers, and the results revealed that the degradants only formed in the presence of both active pharmaceutical ingredients (APIs), and that the presence of maltose in the SS layer was critical to inducing degradation. High resolution mass spectroscopy coupled with high performance liquid chromatography was used to determine the chemical structures of the degradants, which were identified to MB derivatives bearing one or two sugar units. These findings therefore suggested that the degradation of the API could be attributed to the addition of sugar units from maltose to MB under the acidic conditions caused by SS. With this in mind, we developed a new formulation by replacing maltose with hydroxypropyl cellulose as a polymer-type binder. The results showed that this formulation suppressed the formation of the degradants. The results of this study have shown that chemical degradation can occur at the interface of bilayer tablets and that an alternative strategy is available to formulate more stable MB/SS bilayer tablets.

  1. Formation of supported lipid bilayers of charged E. coli lipids on modified gold by vesicle fusion

    Directory of Open Access Journals (Sweden)

    Ileana F. Márquez

    2017-01-01

    Full Text Available We describe a simple way of fusing E. coli lipid vesicles onto a gold surface. Supported lipid bilayers on metal surfaces are interesting for several reasons: transducing a biological signal to an electric readout, using surface analytical tools such as Surface Plasmon Resonance (SPR, Infrared Reflection Absorption Spectroscopy, Neutron Reflectivity or Electrochemistry. The most widely used method to prepare supported lipid membranes is fusion of preexisting liposomes. It is quite efficient on hydrophilic surfaces such as glass, mica or SiO2, but vesicle fusion on metals and metal oxide surfaces (as gold, titanium oxide or indium tin oxide, remains a challenge, particularly for vesicles containing charged lipids, as is the case of bacterial lipids. We describe a simple method based on modifying the gold surface with a charged mercaptopropionic acid self-assembled monolayer and liposomes partially solubilized with detergent. The formed bilayers were characterized using a Quartz Crystal Microbalance with dissipation (QCM-D and Atomic Force Microscopy (AFM. Some advantages of this protocol are that the stability of the self-assembled monolayer allows for repeated use of the substrate after detergent removal of the bilayer and that the amount of detergent required for optimal fusion can be determined previously using the lipid-detergent solubility curve.

  2. 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)

  3. 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

  4. 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

  5. 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)

  6. Fast neutron breeder reactor Rapsodie - situation of physics, hydraulic, thermal and dynamics studies and studies of stability early in 1963

    International Nuclear Information System (INIS)

    1964-01-01

    Early in 1963, it was necessary to make a choice among the two fuels examined for Rapsodie: the UPuMo alloy with double cladding, Nb and stainless steel, and the UO 2 -PuO 2 mix oxide. This report presents the results of the studies effected with the two types of fuel. We reconsider at first the different models which have been studied and we give a detailed description of the alloy and oxide cores as they are envisaged early in 1963. We give then the most important physics performances of the two cores: neutron flux and spectrum, reactivity of the compensation find safety rods, neutrons balance, specific power, effective fraction of delayed neutrons, lifetime of the prompt neutrons, reactivity coefficient. We describe the hydraulic studies and experiments which have been done concerning the two cores. We discuss the criteria adopted as basis for the flow calculations. We give the results of pressure drop and sub-assembly lifting, force measurements, and vibration and pin flow distribution experiments. We discuss the constants utilized for the thermal calculations and we give the temperatures of sodium and alloy or oxide fuel, the temperature increases due to the hot points, and the limitation of the oxide fuel burn-up, originated by the pressure of the fission gases. We treat the hypotheses having been utilized for the dynamics calculations and we describe the different accidents which have been studied. We give the results of the calculations for every accident and each fuel, and we show fuel melting or sodium boiling can be avoided, even in case of the most pessimistic hypotheses, by modifying reactor characteristics (shim-rod reactivity or power of the reactor with only one cooling circuit). The reactor stability has been evaluated with the hypotheses utilized for the dynamics calculations, except of the Doppler coefficient which was intentionally increased. We show that the alloy and oxide cores are stable for every envisaged reactor power. (authors) [fr

  7. 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.

  8. Do neighborhood economic characteristics, racial composition, and residential stability predict perceptions of stress associated with the physical and social environment? Findings from a multilevel analysis in Detroit.

    Science.gov (United States)

    Schulz, Amy J; Zenk, Shannon N; Israel, Barbara A; Mentz, Graciela; Stokes, Carmen; Galea, Sandro

    2008-09-01

    As the body of evidence linking disparities in the health of urban residents to disparate social, economic and environmental contexts grows, efforts to delineate the pathways through which broader social and economic inequalities influence health have burgeoned. One hypothesized pathway connects economic and racial and ethnic inequalities to differentials in stress associated with social and physical environments, with subsequent implications for health. Drawing on data from Detroit, Michigan, we examined contributions of neighborhood-level characteristics (e.g., poverty rate, racial and ethnic composition, residential stability) and individual-level characteristics (e.g., age, gender) to perceived social and physical environmental stress. We found that neighborhood percent African American was positively associated with perceptions of both social and physical environmental stress; neighborhood percent poverty and percent Latino were positively associated with perceived physical environmental stress; and neighborhood residential stability was negatively associated with perceived social environmental stress. At the individual level, whites perceived higher levels of both social and physical environmental stress compared to African American residents of the same block groups, after accounting for other variables included in the models. Our findings suggest the importance of understanding and addressing contributions of neighborhood structural characteristics to perceptions of neighborhood stress. The consistency of the finding that neighborhood racial composition and individual-level race influence perceptions of both social and physical environments suggests the continuing importance of understanding the role played by structural conditions and by personal and collective histories that vary systematically by race and ethnicity within the United States.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Modeling the Effects of Lipid Composition on Stratum Corneum Bilayers Using Molecular Dynamics Simulations

    Science.gov (United States)

    Huzil, J. Torin; Sivaloganathan, Siv; Kohandel, Mohammad; Foldvari, Marianna

    2011-11-01

    The advancement of dermal and transdermal drug delivery requires the development of delivery systems that are suitable for large protein and nucleic acid-based therapeutic agents. However, a complete mechanistic understanding of the physical barrier properties associated with the epidermis, specifically the membrane structures within the stratum corneum, has yet to be developed. Here, we describe the assembly and computational modeling of stratum corneum lipid bilayers constructed from varying ratios of their constituent lipids (ceramide, free fatty acids and cholesterol) to determine if there is a difference in the physical properties of stratum corneum compositions.

  14. Bilayered Oxide thin films for transparent electrode application

    Science.gov (United States)

    Dutta, Titas; Narayan, Jagdish

    2008-10-01

    Ga doped ZnO films with electrical and optical properties comparable to indium tin oxide (ITO) is a promising candidate for transparent conducting oxides (TCOs) because of its superior stability in hydrogen environment, benign nature and relatively inexpensive supply. However, ZnO based TCO films suffer from low work function, which is a critical parameter for device applications. We report here the growth of a novel bilayered structure consisting of very thin (few monolayers) ITO, MoOx layer on Zn0.95Ga0.05O film for transparent electrode applications by using pulsed laser deposition technique at different temperatures and oxygen partial pressure. The characteristics of the ITO film and the heterostructure have been investigated in detail using XRD, TEM, XPS, and electrical and optical property measurements. It is envisaged that the overall transmittance and the resistivity are dictated by the thicker layer of ZnGa0.05O beneath the ITO layer. Hence, this study is aimed to improve the surface characteristics without affecting the overall transmittance and sheet resistance. This will enhance the transport of the carriers across the heterojunction in the device, thus, resulting in the increase in device efficiency.

  15. Physical and Oxidative Stability of Flaxseed Oil-in-Water Emulsions Fabricated from Sunflower Lecithins: Impact of Blending Lecithins with Different Phospholipid Profiles.

    Science.gov (United States)

    Liang, Li; Chen, Fang; Wang, Xingguo; Jin, Qingzhe; Decker, Eric Andrew; McClements, David Julian

    2017-06-14

    There is great interest in the formulation of plant-based foods enriched with nutrients that promote health, such as polyunsaturated fatty acids. This study evaluated the impact of sunflower phospholipid type on the formation and stability of flaxseed oil-in-water emulsions. Two sunflower lecithins (Sunlipon 50 and 90) with different phosphatidylcholine (PC) levels (59 and 90%, respectively) were used in varying ratios to form emulsions. Emulsion droplet size, charge, appearance, microstructure, and oxidation were measured during storage at 55 °C in the dark. The physical and chemical stability increased as the PC content of the lecithin blends decreased. The oxidative stability of emulsions formulated using Sunlipon 50 was better than emulsions formulated using synthetic surfactants (SDS or Tween 20). The results are interpreted in terms of the impact of emulsifier type on the colloidal interactions between oil droplets and on the molecular interactions between pro-oxidants and oil droplet surfaces.

  16. 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.

  17. Nanoemulsions produced with varied type of emulsifier and oil content: An influence of formulation and process parameters on the characteristics and physical stability

    Directory of Open Access Journals (Sweden)

    Đorđević Sanela M.

    2013-01-01

    Full Text Available The aim of the present study was to prepare oil-in-water nanoemulsions stabilized with a novel natural alkyl polyglucoside surfactant and to compare them with corresponding lecithin/polysorbate 80 - based nanoemulsions in terms of physicochemical properties and physical stability. Nanoemulsions were prepared by high pressure homogenization, using 20, 30 and 40% (w/w medium chain triglyceride as oil phase, and 4, 6 and 8% (w/w lecithin/polysorbate 80 mixture (1/1 or caprylyl/capryl glucoside as emulsifiers. The influence of emulsifier type, emulsifier concentration and oil content was investigated with respect to changes in particle size, particle size distribution, surface charge and physical stability. The influence of production parameters (number of homogenization cycles, type of homogenization process, homogenization pressure on particle size was also investigated. Analysis was performed by photon correlation spectroscopy, laser diffraction, zeta potential, pH and electrical conductivity measurements. All formulations produced revealed a small droplet size ranging from 147 to 228 nm and a very narrow size distribution (polydispersity index range 0,072-0,124. Zeta potentials were about -20 mV and -50 mV for nanoemulsions stabilized with lecithin/polysorbate 80 and caprylyl/capryl glucoside, respectively. The results obtained during the stability studies (6 months at 25°C and 1 month at 40°C indicated that nanoemulsion stability was influenced by their composition. Acquired results also suggested the most appropriate production parameters: 9 homogenization cycles, homogenization pressure of 500 bar and discontinuous process of homogenization.

  18. PHYSICS

    CERN Multimedia

    P. Sphicas

    There have been three physics meetings since the last CMS week: “physics days” on March 27-29, the Physics/ Trigger week on April 23-27 and the most recent physics days on May 22-24. The main purpose of the March physics days was to finalize the list of “2007 analyses”, i.e. the few topics that the physics groups will concentrate on for the rest of this calendar year. The idea is to carry out a full physics exercise, with CMSSW, for select physics channels which test key features of the physics objects, or represent potential “day 1” physics topics that need to be addressed in advance. The list of these analyses was indeed completed and presented in the plenary meetings. As always, a significant amount of time was also spent in reviewing the status of the physics objects (reconstruction) as well as their usage in the High-Level Trigger (HLT). The major event of the past three months was the first “Physics/Trigger week” in Apri...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Topological Quantum Phase Transitions in Two-Dimensional Hexagonal Lattice Bilayers

    Science.gov (United States)

    Zhai, Xuechao; Jin, Guojun

    2013-09-01

    Since the successful fabrication of graphene, two-dimensional hexagonal lattice structures have become a research hotspot in condensed matter physics. In this short review, we theoretically focus on discussing the possible realization of a topological insulator (TI) phase in systems of graphene bilayer (GBL) and boron nitride bilayer (BNBL), whose band structures can be experimentally modulated by an interlayer bias voltage. Under the bias, a band gap can be opened in AB-stacked GBL but is still closed in AA-stacked GBL and significantly reduced in AA- or AB-stacked BNBL. In the presence of spin-orbit couplings (SOCs), further demonstrations indicate whether the topological quantum phase transition can be realized strongly depends on the stacking orders and symmetries of structures. It is observed that a bulk band gap can be first closed and then reopened when the Rashba SOC increases for gated AB-stacked GBL or when the intrinsic SOC increases for gated AA-stacked BNBL. This gives a distinct signal for a topological quantum phase transition, which is further characterized by a jump of the ℤ2 topological invariant. At fixed SOCs, the TI phase can be well switched by the interlayer bias and the phase boundaries are precisely determined. For AA-stacked GBL and AB-stacked BNBL, no strong TI phase exists, regardless of the strength of the intrinsic or Rashba SOCs. At last, a brief overview is given on other two-dimensional hexagonal materials including silicene and molybdenum disulfide bilayers.

  4. 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.

  5. Superhydrophobic Bilayer Coating Based on Annealed Electrospun Ultrathin Poly(ε-caprolactone Fibers and Electrosprayed Nanostructured Silica Microparticles for Easy Emptying Packaging Applications

    Directory of Open Access Journals (Sweden)

    Juliana Lasprilla-Botero

    2018-05-01

    Full Text Available A coating rendering superhydrophobic properties to low-density polyethylene (LDPE films used in packaging applications was herein generated by means of the electrohydrodynamic processing (EHDP technique. To this end, electrospun ultrathin poly(ε-caprolactone (PCL fibers, followed by electrosprayed nanostructured silica (SiO2 microparticles, were deposited on top of the LDPE film. Various electrospinning and electrospraying times were tested and optimized followed by a thermal post-treatment to provide physical adhesion between the bilayer coating and the LDPE substrate. The morphology, hydrophobicity, permeance to limonene, and thermal stability of the resultant nanostructured coatings were characterized. It was observed that by controlling both the deposition time of the electrospun ultrathin PCL fibers and the electrosprayed SiO2 microparticles, as well as the conditions of the thermal post-treatment, effective superhydrophobic coatings were developed onto the LDPE films. The resultant multilayer presented a hierarchical micro/nanostructured surface with an apparent contact angle of 157° and a sliding angle of 8°. The addition of silica reduced, to some extent, the limonene (aroma barrier, likely due to the increased surface-to-volume ratio, which allowed permeant sorption to occur but improved the thermal stability of the LDPE/PCL film. As a result, the developed multilayer system of LDPE/PCL/SiO2 has significant potential for use in easy-to-empty packaging applications of high water activity products.

  6. 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

  7. 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...

  8. 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.

  9. 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)

  10. 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.

  11. 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

  12. 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.

  13. Electrostatic and magnetic fields in bilayer graphene

    Science.gov (United States)

    Jellal, Ahmed; Redouani, Ilham; Bahlouli, Hocine

    2015-08-01

    We compute the transmission probability through rectangular potential barriers and p-n junctions in the presence of a magnetic and electric fields in bilayer graphene taking into account contributions from the full four bands of the energy spectrum. For energy E higher than the interlayer coupling γ1 (E >γ1) two propagation modes are available for transport giving rise to four possible ways for transmission and reflection coefficients. However, when the energy is less than the height of the barrier the Dirac fermions exhibit transmission resonances and only one mode of propagation is available for transport. We study the effect of the interlayer electrostatic potential denoted by δ and variations of different barrier geometry parameters on the transmission probability.

  14. The impact of resveratrol in lipid bilayers

    DEFF Research Database (Denmark)

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

    The natural antioxidant resveratrol, contained in the skin of grape and accordingly in red wine, has significant health effects such as cardiovascular protection and anti-oxidation. Clinical trials of resveratrol as prophylactic or even therapeutic drug are ongoing. Most probably, the working...... mechanism is unspecific. However, there are only few biophysical studies regarding the impact of resveratrol on lipid membranes. Here, results from a neutron reflectometry investigation on solid supported di-palmitoyl-phosphatidyl-choline (DPPC) bilayers with incorporated resveratrol are presented. The data...... show an accumulation of resveratrol in between the headgroups and evidence its absence in the hydrophobic core. Without a removal mechanism, the headgroup region hosts up to ~25 mol% of resveratrol. The presence of resveratrol induces a change of the tilt angle of the PC headgroups to a more upright...

  15. 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)

  16. Energy gap of ferromagnet-superconductor bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Halterman, Klaus; Valls, Oriol T

    2003-10-15

    The excitation spectrum of clean ferromagnet-superconductor bilayers is calculated within the framework of the self-consistent Bogoliubov-de Gennes theory. Because of the proximity effect, the superconductor induces a gap in the ferromagnet spectrum, for thin ferromagnetic layers. The effect depends strongly on the exchange field in the ferromagnet. We find that as the thickness of the ferromagnetic layer increases, the gap disappears, and that its destruction arises from those quasiparticle excitations with wave vectors mainly along the interface. We discuss the influence that the interface quality and Fermi energy mismatch between the ferromagnet and superconductor have on the calculated energy gap. We also evaluate the density of states in the ferromagnet, and we find it in all cases consistent with the gap results.

  17. 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.

  18. Reversible Polarization Rotation in Epitaxial Ferroelectric Bilayers

    DEFF Research Database (Denmark)

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

    2016-01-01

    Polarization rotation engineering is a promising path to giant dielectric and electromechanical responses in ferroelectric materials and devices. This work demonstrates robust and reversible in- to out-of-plane polarization rotation in ultrathin (nanoscale) epitaxial (001) tetragonal PbZr0.3Ti0.7O3...... large-scale polarization rotation switching (≈60 μC cm−2) and an effective d 33 response 500% (≈250 pm V−1) larger than the PZT-R layer alone. Furthermore, this enhancement is stable for more than 107 electrical switching cycles. These bilayers present a simple and highly controllable means to design...... and optimize rotational polar systems as an alternate to traditional composition-based approaches. The precise control of the subtle interface-driven interactions between the lattice and the external factors that control polarization opens a new door to enhanced—or completely new—functional properties....

  19. Nanoporous hydroxyapatite/sodium titanate bilayer on titanium implants for improved osteointegration.

    Science.gov (United States)

    Carradò, A; Perrin-Schmitt, F; Le, Q V; Giraudel, M; Fischer, C; Koenig, G; Jacomine, L; Behr, L; Chalom, A; Fiette, L; Morlet, A; Pourroy, G

    2017-03-01

    The aim of this study was to improve the strength and quality of the titanium-hydroxyapatite interface in order to prevent long-term failure of the implanted devices originating from coating delamination and to test it in an in-vivo model. Ti disks and dental commercial implants were etched in Kroll solution. Thermochemical treatments of the acid-etched titanium were combined with sol-gel hydroxyapatite (HA) coating processes to obtain a nanoporous hydroxyapatite/sodium titanate bilayer. The sodium titanate layer was created by incorporating sodium ions onto the Ti surface during a NaOH alkaline treatment and stabilized using a heat treatment. HA layer was added by dip-coating in a sol-gel solution. The bioactivity was assessed in vitro with murine MC3T3-E1 and human SaOs-2 cells. Functional and histopathological evaluations of the coated Ti implants were performed at 22, 34 and 60days of implantation in a dog lower mandible model. Nanoporous hydroxyapatite/sodium titanate bilayer on titanium implants was sensitive neither to crack propagation nor to layer delamination. The in vitro results on murine MC3T3-E1 and human SaOs-2 cells confirm the advantage of this coating regarding the capacity of cell growth and differentiation. Signs of progressive bone incorporation, such as cancellous bone formed in contact with the implant over the existing compact bone, were notable as early as day 22. Overall, osteoconduction and osteointegration mean scores were higher for test implants compared to the controls at 22 and 34 days. Nanoporous hydroxyapatite/sodium titanate bilayer improves the in-vivo osteoconduction and osteointegration. It prevents the delamination during the screwing and it could increase HA-coated dental implant stability without adhesive failures. The combination of thermochemical treatments with dip coating is a low-cost strategy. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. 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.

  1. PHYSICS

    CERN Multimedia

    D. Acosta

    2010-01-01

    A remarkable amount of progress has been made in Physics since the last CMS Week in June given the exponential growth in the delivered LHC luminosity. The first major milestone was the delivery of a variety of results to the ICHEP international conference held in Paris this July. For this conference, CMS prepared 15 Physics Analysis Summaries on physics objects and 22 Summaries on new and interesting physics measurements that exploited the luminosity recorded by the CMS detector. The challenge was incorporating the largest batch of luminosity that was delivered only days before the conference (300 nb-1 total). The physics covered from this initial running period spanned hadron production measurements, jet production and properties, electroweak vector boson production, and even glimpses of the top quark. Since then, the accumulated integrated luminosity has increased by a factor of more than 100, and all groups have been working tremendously hard on analysing this dataset. The September Physics Week was held ...

  2. PHYSICS

    CERN Multimedia

    J. Incandela

    There have been numerous developments in the physics area since the September CMS week. The biggest single event was the Physics/Trigger week in the end of Octo¬ber, whereas in terms of ongoing activities the “2007 analyses” went into high gear. This was in parallel with participation in CSA07 by the physics groups. On the or¬ganizational side, the new conveners of the physics groups have been selected, and a new database for man¬aging physics analyses has been deployed. Physics/Trigger week The second Physics-Trigger week of 2007 took place during the week of October 22-26. The first half of the week was dedicated to working group meetings. The ple¬nary Joint Physics-Trigger meeting took place on Wednesday afternoon and focused on the activities of the new Trigger Studies Group (TSG) and trigger monitoring. Both the Physics and Trigger organizations are now focused on readiness for early data-taking. Thus, early trigger tables and preparations for calibr...

  3. PHYSICS

    CERN Multimedia

    P. Sphicas

    The CPT project came to an end in December 2006 and its original scope is now shared among three new areas, namely Computing, Offline and Physics. In the physics area the basic change with respect to the previous system (where the PRS groups were charged with detector and physics object reconstruction and physics analysis) was the split of the detector PRS groups (the old ECAL-egamma, HCAL-jetMET, Tracker-btau and Muons) into two groups each: a Detector Performance Group (DPG) and a Physics Object Group. The DPGs are now led by the Commissioning and Run Coordinator deputy (Darin Acosta) and will appear in the correspond¬ing column in CMS bulletins. On the physics side, the physics object groups are charged with the reconstruction of physics objects, the tuning of the simulation (in collaboration with the DPGs) to reproduce the data, the provision of code for the High-Level Trigger, the optimization of the algorithms involved for the different physics analyses (in collaboration with the analysis gr...

  4. Supported Lipid Bilayers with Phosphatidylethanolamine as the Major Component.

    Science.gov (United States)

    Sendecki, Anne M; Poyton, Matthew F; Baxter, Alexis J; Yang, Tinglu; Cremer, Paul S

    2017-11-21

    Phosphatidylethanolamine (PE) is notoriously difficult to incorporate into model membrane systems, such as fluid supported lipid bilayers (SLBs), at high concentrations because of its intrinsic negative curvature. Using fluorescence-based techniques, we demonstrate that having fewer sites of unsaturation in the lipid tails leads to high-quality SLBs because these lipids help to minimize the curvature. Moreover, shorter saturated chains can help maintain the membranes in the fluid phase. Using these two guidelines, we find that up to 70 mol % PE can be incorporated into SLBs at room temperature and up to 90 mol % PE can be incorporated at 37 °C. Curiously, conditions under which three-dimensional tubules project outward from the planar surface as well as conditions under which domain formation occurs can be found. We have employed these model membrane systems to explore the ability of Ni 2+ to bind to PE. It was found that this transition metal ion binds 1000-fold tighter to PE than to phosphatidylcholine lipids. In the future, this platform could be exploited to monitor the binding of other transition metal ions or the binding of antimicrobial peptides. It could also be employed to explore the physical properties of PE-containing membranes, such as phase domain behavior and intermolecular hydrogen bonding.

  5. Microfluidic passive permeability assay using nanoliter droplet interface lipid bilayers.

    Science.gov (United States)

    Nisisako, Takasi; Portonovo, Shiva A; Schmidt, Jacob J

    2013-11-21

    Membrane permeability assays play an important role in assessing drug transport activities across biological membranes. However, in conventional parallel artificial membrane permeability assays (PAMPA), the membrane model used is dissimilar to biological membranes physically and chemically. Here, we describe a microfluidic passive permeability assay using droplet interface bilayers (DIBs). In a microfluidic network, nanoliter-sized donor and acceptor aqueous droplets are alternately formed in cross-flowing oil containing phospholipids. Subsequently, selective removal of oil through hydrophobic pseudo-porous sidewalls induces the contact of the lipid monolayers, creating arrayed planar DIBs between the donor and acceptor droplets. Permeation of fluorescein from the donor to the acceptor droplets was fluorometrically measured. From the measured data and a simple diffusion model we calculated the effective permeabilities of 5.1 × 10(-6) cm s(-1), 60.0 × 10(-6) cm s(-1), and 87.6 × 10(-6) cm s(-1) with donor droplets at pH values of 7.5, 6.4 and 5.4, respectively. The intrinsic permeabilities of specific monoanionic and neutral fluorescein species were obtained similarly. We also measured the permeation of caffeine in 10 min using UV microspectroscopy, obtaining a permeability of 20.8 × 10(-6) cm s(-1). With the small solution volumes, short measurement time, and ability to measure a wide range of compounds, this device has considerable potential as a platform for high-throughput drug permeability assays.

  6. Desktop 3D printing of controlled release pharmaceutical bilayer tablets.

    Science.gov (United States)

    Khaled, Shaban A; Burley, Jonathan C; Alexander, Morgan R; Roberts, Clive J

    2014-01-30

    Three dimensional (3D) printing was used as a novel medicine formulation technique for production of viable tablets capable of satisfying regulatory tests and matching the release of standard commercial tablets. Hydroxypropyl methylcellulose (HPMC 2208) (Methocel™ K100M Premium) and poly(acrylic acid) (PAA) (Carbopol(®) 974P NF) were used as a hydrophilic matrix for a sustained release (SR) layer. Hypromellose(®) (HPMC 2910) was used as a binder while microcrystalline cellulose (MCC) (Pharmacel(®) 102) and sodium starch glycolate (SSG) (Primojel(®)) were used as disintegrants for an immediate release (IR) layer. Commercial guaifenesin bi-layer tablets (GBT) were used as a model drug (Mucinex(®)) for this study. There was a favourable comparison of release of the active guaifenesin from the printed hydrophilic matrix compared with the commercially available GBT. The printed formulations were also evaluated for physical and mechanical properties such as weight variation, friability, hardness and thickness as a comparison to the commercial tablet and were within acceptable range as defined by the international standards stated in the United States Pharmacopoeia (USP). All formulations (standard tablets and 3D printed tablets) showed Korsmeyer-Peppas n values between 0.27 and 0.44 which indicates Fickian diffusion drug release through a hydrated HPMC gel layer. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Localization and Orientation of Xanthophylls in a Lipid Bilayer.

    Science.gov (United States)

    Grudzinski, Wojciech; Nierzwicki, Lukasz; Welc, Renata; Reszczynska, Emilia; Luchowski, Rafal; Czub, Jacek; Gruszecki, Wieslaw I

    2017-08-29

    Xanthophylls (polar carotenoids) play diverse biological roles, among which are modulation of the physical properties of lipid membranes and protection of biomembranes against oxidative damage. Molecular mechanisms underlying these functions are intimately related to the localization and orientation of xanthophyll molecules in lipid membranes. In the present work, we address the problem of localization and orientation of two xanthophylls present in the photosynthetic apparatus of plants and in the retina of the human eye, zeaxanthin and lutein, in a single lipid bilayer membrane formed with dimyristoylphosphatidylcholine. By using fluorescence microscopic analysis and Raman imaging of giant unilamellar vesicles, as well as molecular dynamics simulations, we show that lutein and zeaxanthin adopt a very similar transmembrane orientation within a lipid membrane. In experimental and computational approach, the average tilt angle of xanthophylls relative to the membrane normal is independently found to be ~40 deg, and results from hydrophobic mismatch between the membrane thickness and the distance between the terminal hydroxyl groups of the xanthophylls. Consequences of such a localization and orientation for biological activity of xanthophylls are discussed.

  8. Power losses in bilayer inverted small molecule organic solar cells

    KAUST Repository

    Trinh, Cong

    2012-01-01

    Inverted bilayer organic solar cells using copper phthalocyanine (CuPc) as a donor and C60 as an acceptor with the structure: glass/indium tin oxide (ITO)/ZnO/C60/CuPc/MoO3/Al, in which the zinc oxide (ZnO) was deposited by atomic layer deposition, are compared with a conventional device: glass/ITO/CuPc/C60/bathocuproine/Al. These inverted and conventional devices give short circuit currents of 3.7 and 4.8 mA/cm 2, respectively. However, the inverted device gives a reduced photoresponse from the CuPc donor compared to that of the conventional device. Optical field models show that the arrangement of organic layers in the inverted devices leads to lower absorption of long wavelengths by the CuPc donor; the low energy portion of the spectrum is concentrated near the metal oxide electrode in both devices. © 2012 American Institute of Physics.

  9. 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...

  10. 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.

  11. 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)

  12. 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.

  13. 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.

  14. PHYSICS

    CERN Multimedia

    Submitted by

    Physics Week: plenary meeting on physics groups plans for startup (14–15 May 2008) The Physics Objects (POG) and Physics Analysis (PAG) Groups presented their latest developments at the plenary meeting during the Physics Week. In the presentations particular attention was given to startup plans and readiness for data-taking. Many results based on the recent cosmic run were shown. A special Workshop on SUSY, described in a separate section, took place the day before the plenary. At the meeting, we had also two special DPG presentations on “Tracker and Muon alignment with CRAFT” (Ernesto Migliore) and “Calorimeter studies with CRAFT” (Chiara Rovelli). We had also a report from Offline (Andrea Rizzi) and Computing (Markus Klute) on the San Diego Workshop, described elsewhere in this bulletin. Tracking group (Boris Mangano). The level of sophistication of the tracking software increased significantly over the last few months: V0 (K0 and Λ) reconstr...

  15. Influence of chemical and physical characteristics of cement kiln dusts (CKDs) on their hydration behavior and potential suitability for soil stabilization

    International Nuclear Information System (INIS)

    Peethamparan, Sulapha; Olek, Jan; Lovell, Janet

    2008-01-01

    The interaction of CKDs with a given soil depends on the chemical and physical characteristics of the CKDs. Hence, the characterization of CKDs and their hydration products may lead to better understanding of their suitability as soil stabilizers. In the present article, four different CKD powders are characterized and their hydration products are evaluated. A detailed chemical (X-ray diffraction), thermogravimetric and morphological (scanning electron microscope) analyses of both the CKD powders and the hydrated CKD pastes are presented. In general, high free-lime content (∼ 14-29%) CKDs, when reacted with water produced significant amounts of calcium hydroxide, ettringite and syngenite. These CKDs also developed higher unconfined compressive strength and higher temperature of hydration compared to CKDs with lower amounts of free-lime. An attempt was made to qualitatively correlate the performance of CKD pastes with the chemical and physical characteristics of the original CKD powders and to determine their potential suitability as soil stabilizers. To that effect a limited unconfined compressive strength testing of CKD-treated kaolinite clays was performed. The results of this study suggest that both the compressive strength and the temperature of hydration of the CKD paste can give early indications of the suitability of particular CKD for soil stabilization

  16. 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...

  17. 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....

  18. 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...

  19. 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.

  20. 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)

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. PHYSICS

    CERN Multimedia

    D. Futyan

    A lot has transpired on the “Physics” front since the last CMS Bulletin. The summer was filled with preparations of new Monte Carlo samples based on CMSSW_3, the finalization of all the 10 TeV physics analyses [in total 50 analyses were approved] and the preparations for the Physics Week in Bologna. A couple weeks later, the “October Exercise” commenced and ran through an intense two-week period. The Physics Days in October were packed with a number of topics that are relevant to data taking, in a number of “mini-workshops”: the luminosity measurement, the determination of the beam spot and the measurement of the missing transverse energy (MET) were the three main topics.  Physics Week in Bologna The second physics week in 2009 took place in Bologna, Italy, on the week of Sep 7-11. The aim of the week was to review and establish how ready we are to do physics with the early collisions at the LHC. The agenda of the week was thus pac...

  6. PHYSICS

    CERN Multimedia

    D. Futyan

    A lot has transpired on the “Physics” front since the last CMS Bulletin. The summer was filled with preparations of new Monte Carlo samples based on CMSSW_3, the finalization of all the 10 TeV physics analyses [in total 50 analyses were approved] and the preparations for the Physics Week in Bologna. A couple weeks later, the “October Exercise” commenced and ran through an intense two-week period. The Physics Days in October were packed with a number of topics that are relevant to data taking, in a number of “mini-workshops”: the luminosity measurement, the determination of the beam spot and the measurement of the missing transverse energy (MET) were the three main topics.   Physics Week in Bologna The second physics week in 2009 took place in Bologna, Italy, on the week of Sep 7-11. The aim of the week was to review and establish (we hoped) the readiness of CMS to do physics with the early collisions at the LHC. The agenda of the...

  7. Stability of physical fitness and functional capacity in physically active women aged 50 to 89 years. DOI: 10.5007/1980-0037.2011v13n1p8

    Directory of Open Access Journals (Sweden)

    João Pedro Silva Júnior

    2011-12-01

    Full Text Available The objective of this study was to evaluate the effect of a physical activity program and the stability of physical fitness and functional capacity in physically active adult women. Thirty-four adult women aged 50-89 years, who participated in a physical activity group at Camilo Castelo Branco University, were studied. Criteria for inclusion were attendance of at least 75% of the classes (3x/week and undergoing at least one assessment per year between 2005 and 2007. All evaluations were conducted in June. Anthropometric (body weight, height, waist-hip ratio, neuromotor (rising from a chair in seconds, rising from a chair in 30 seconds, elbow flexion, shuttle-run, static and dynamic balance, and metabolic parameters (2-min step in place test according to the CELAFISCS standard were evaluated. One-way ANOVA followed by the post hoc Scheffe test, delta percentage and Spearman’s rho correlation were used for data analysis, with the level of significance set at p<0.05. In the three evaluations, body weight, body mass index and waist-hip ratio indicated overweight. Analysis of functional capacity showed a significant increase in upper (42% and lower (5.2% limb strength and in balance (14.1% when comparing the results from 2005 to 2007. The same was not observed for agility (2.1%. For body mass index, waist-hip ratio, strength and static balance, stability ranged from 0.26 to 0.91 (p<0.05. The physical activity program contributed to the maintenance of physical fitness and functional capacity in adult women.

  8. Stability of physical fitness and functional capacity in physically active women aged 50 to 89 years. DOI: 10.5007/1980-0037.2011v13n1p8

    Directory of Open Access Journals (Sweden)

    Mauricio dos Santos

    2011-01-01

    Full Text Available The objective of this study was to evaluate the effect of a physical activity program and the stability of physical fitness and functional capacity in physically active adult women. Thirty-four adult women aged 50-89 years, who participated in a physical activity group at Camilo Castelo Branco University, were studied. Criteria for inclusion were attendance of at least 75% of the classes (3x/week and undergoing at least one assessment per year between 2005 and 2007. All evaluations were conducted in June. Anthropometric (body weight, height, waist-hip ratio, neuromotor (rising from a chair in seconds, rising from a chair in 30 seconds, elbow flexion, shuttle-run, static and dynamic balance, and metabolic parameters (2-min step in place test according to the CELAFISCS standard were evaluated. One-way ANOVA followed by the post hoc Scheffe test, delta percentage and Spearman’s rho correlation were used for data analysis, with the level of significance set at p<0.05. In the three evaluations, body weight, body mass index and waist-hip ratio indicated overweight. Analysis of functional capacity showed a significant increase in upper (42% and lower (5.2% limb strength and in balance (14.1% when comparing the results from 2005 to 2007. The same was not observed for agility (2.1%. For body mass index, waist-hip ratio, strength and static balance, stability ranged from 0.26 to 0.91 (p<0.05. The physical activity program contributed to the maintenance of physical fitness and functional capacity in adult women.

  9. Physical reason for quantum behaviour of the electron and stability of the main state of the hydrogen atom

    International Nuclear Information System (INIS)

    Rangelov, J.M.

    1986-01-01

    An electron model is proposed explaining the physical reasons for its nonrelativistic quantum-mechanical behaviour, the origin of its own mechanical and magnetic momentum and field energy. As an example the main electron state in hydrogen atom is obtained

  10. Physical characteristics of the coastal waters between Navapur and Umbharat, West coast of India. Part 3. Stability and dispersion

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.; Vijayakumar, C.V.

    and current. Considering the physical behaviour, the coastal waters of this highly industrialised region were found to possess high instantaneous dilution capacity. However the spatial and temporal variability of the parameters calls for better understanding...

  11. 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.

  12. Structural refinement of vitreous silica bilayers

    Science.gov (United States)

    Sadjadi, Mahdi; Wilson, Mark; Thorpe, M. F.

    The importance of glasses resides not only in their applications but in fundamental questions that they put forth. The continuous random network model can successfully describe the glass structure, but determining details, like ring statistics, has always been difficult using only diffraction data. But recent atomic images of 2D vitreous silica bilayers can offer valuable new insights which are hard to be observed directly in 3D silica models/experiments (for references see). However, the experimental results are prone to uncertainty in atomic positions, systematic errors, and being finite. We employ special boundary conditions developed for such networks to refine the experimental structures. We show the best structure can be found by using various potentials to maximize information gained from the experimental samples. We find a range of densities, the so-called flexibility window, in which tetrahedra are perfect. We compare results from simulations using harmonic potentials, MD with atomic polarizabilities included and DFT. We should thank David Drabold and Bishal Bhattarai for useful discussions. Support through NSF Grant # DMS 1564468 is gratefully acknowledged.

  13. Giant proximity effect in ferromagnetic bilayers

    Science.gov (United States)

    Ramos, Silvia; Charlton, Tim; Quintanilla, Jorge; Suter, Andreas; Moodera, Jagadeesh; Prokscha, Thomas; Salman, Zaher; Forgan, Ted

    2013-03-01

    The proximity effect is a phenomenon where an ordered state leaks from a material into an adjacent one over some finite distance, ξ. For superconductors, this distance is ~ the coherence length. Nevertheless much longer-range, ``giant'' proximity effects have been observed in cuprate junctions. This surprising effect can be understood as a consequence of critical opalescence. Since this occurs near all second order phase transitions, giant proximity effects should be very general and, in particular, they should be present in magnetic systems. The ferromagnetic proximity effect has the advantage that its order parameter (magnetization) can be observed directly. We investigate the above phenomenon in Co/EuS bilayer films, where both materials undergo ferromagnetic transitions but at rather different temperatures (bulk TC of 1400K for Co and 16.6K for EuS). A dramatic increase in the range of the proximity effect is expected near the TC of EuS. We present the results of our measurements of the magnetization profiles as a function of temperature, carried out using the complementary techniques of low energy muon rotation and polarized neutron reflectivity. Work supported by EPSRC, STFC and ONR grant N00014-09-1-0177 and NSF grant DMR 0504158.

  14. PHYSICS

    CERN Multimedia

    J. Incandela

    The all-plenary format of the CMS week in Cyprus gave the opportunity to the conveners of the physics groups to present the plans of each physics analysis group for tackling early physics analyses. The presentations were complete, so all are encouraged to browse through them on the Web. There is a wealth of information on what is going on, by whom and on what basis and priority. The CMS week was followed by two CMS “physics events”, the ICHEP08 days and the physics days in July. These were two weeks dedicated to either the approval of all the results that would be presented at ICHEP08, or to the review of all the other Monte-Carlo based analyses that were carried out in the context of our preparations for analysis with the early LHC data (the so-called “2008 analyses”). All this was planned in the context of the beginning of a ramp down of these Monte Carlo efforts, in anticipation of data.  The ICHEP days are described below (agenda and talks at: http://indic...

  15. PHYSICS

    CERN Multimedia

    Joe Incandela

    There have been two plenary physics meetings since the December CMS week. The year started with two workshops, one on the measurements of the Standard Model necessary for “discovery physics” as well as one on the Physics Analysis Toolkit (PAT). Meanwhile the tail of the “2007 analyses” is going through the last steps of approval. It is expected that by the end of January all analyses will have converted to using the data from CSA07 – which include the effects of miscalibration and misalignment. January Physics Days The first Physics Days of 2008 took place on January 22-24. The first two days were devoted to comprehensive re¬ports from the Detector Performance Groups (DPG) and Physics Objects Groups (POG) on their planning and readiness for early data-taking followed by approvals of several recent studies. Highlights of POG presentations are included below while the activities of the DPGs are covered elsewhere in this bulletin. January 24th was devo...

  16. Formulating food protein-stabilized indomethacin nanosuspensions into pellets by fluid-bed coating technology: physical characterization, redispersibility, and dissolution.

    Science.gov (United States)

    He, Wei; Lu, Yi; Qi, Jianping; Chen, Lingyun; Yin, Lifang; Wu, Wei

    2013-01-01

    Drug nanosuspensions are very promising for enhancing the dissolution and bioavailability of drugs that are poorly soluble in water. However, the poor stability of nanosuspensions, reflected in particle growth, aggregation/agglomeration, and change in crystallinity state greatly limits their applications. Solidification of nanosuspensions is an ideal strategy for addressing this problem. Hence, the present work aimed to convert drug nanosuspensions into pellets using fluid-bed coating technology. Indomethacin nanosuspensions were prepared by the precipitation-ultrasonication method using food proteins (soybean protein isolate, whey protein isolate, β-lactoglobulin) as stabilizers. Dried nanosuspensions were prepared by coating the nanosuspensions onto pellets. The redispersibility, drug dissolution, solid-state forms, and morphology of the dried nanosuspensions were evaluated. The mean particle size for the nanosuspensions stabilized using soybean protein isolate, whey protein isolate, and β-lactoglobulin was 588 nm, 320 nm, and 243 nm, respectively. The nanosuspensions could be successfully layered onto pellets with high coating efficiency. Both the dried nanosuspensions and nanosuspensions in their original amorphous state and not influenced by the fluid-bed coating drying process could be redispersed in water, maintaining their original particle size and size distribution. Both the dried nanosuspensions and the original drug nanosuspensions showed similar dissolution profiles, which were both much faster than that of the raw crystals. Fluid-bed coating technology has potential for use in the solidification of drug nanosuspensions.

  17. 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

  18. New cytotoxic butyltin complexes with 2-sulfobenzoic acid: Molecular interaction with lipid bilayers and DNA as well as in vitro anticancer activity

    Czech Academy of Sciences Publication Activity Database

    Pruchnik, H.; Kral, Teresa; Poradowski, D.; Drynda, A.; Obmińska-Mrukowicz, B.; Hof, Martin

    2016-01-01

    Roč. 243, JAN 2016 (2016), s. 107-118 ISSN 0009-2797 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : Butyltin 2-sulfobenzoates * Antitumor activity * Lipid bilayer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.143, year: 2016

  19. 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)

  20. Physics

    CERN Document Server

    Cullen, Katherine

    2005-01-01

    Defined as the scientific study of matter and energy, physics explains how all matter behaves. Separated into modern and classical physics, the study attracts both experimental and theoretical physicists. From the discovery of the process of nuclear fission to an explanation of the nature of light, from the theory of special relativity to advancements made in particle physics, this volume profiles 10 pioneers who overcame tremendous odds to make significant breakthroughs in this heavily studied branch of science. Each chapter contains relevant information on the scientist''s childhood, research, discoveries, and lasting contributions to the field and concludes with a chronology and a list of print and Internet references specific to that individual.

  1. Storage stability study for margarines produced by enzymatically interesterified fats compared to the margarines by the conventional methods I. Physical properties

    DEFF Research Database (Denmark)

    Zhang, Hong; Jacobsen, Charlotte; Adler-Nissen, Jens

    2005-01-01

    was more similar to that of the physically mixed fat than that of the margarine from the chemically randomized fat, which had less color. Crystal transformation was accelerated at high storage temperature. Crystal size was not only related to the types of crystals, but also to the driving force......In this study, margarine hardstocks were produced from two enzymatically interesterified fats at conversion degrees of 80 and 100%, a chemically randomized fat and a physically mixed fat, respectively. These four hardstocks blended with 50% of sunflower oil were mainly used for the production...... of table margarines in a pilot plant. Storage stability studies were carried out at storage temperatures of 5 and 25 7C during 12 wk. Margarines from the enzymatically interesterified fats were compared to the margarines produced by conventional methods and to selected commercial products. The changes...

  2. PHYSICS

    CERN Multimedia

    Guenther Dissertori

    The time period between the last CMS week and this June was one of intense activity with numerous get-together targeted at addressing specific issues on the road to data-taking. The two series of workshops, namely the “En route to discoveries” series and the “Vertical Integration” meetings continued.   The first meeting of the “En route to discoveries” sequence (end 2007) had covered the measurements of the Standard Model signals as necessary prerequisite to any claim of signals beyond the Standard Model. The second meeting took place during the Feb CMS week and concentrated on the commissioning of the Physics Objects, whereas the third occurred during the April Physics Week – and this time the theme was the strategy for key new physics signatures. Both of these workshops are summarized below. The vertical integration meetings also continued, with two DPG-physics get-togethers on jets and missing ET and on electrons and photons. ...

  3. PHYSICS

    CERN Multimedia

    Chris Hill

    2012-01-01

    The months that have passed since the last CMS Bulletin have been a very busy and exciting time for CMS physics. We have gone from observing the very first 8TeV collisions produced by the LHC to collecting a dataset of the collisions that already exceeds that recorded in all of 2011. All in just a few months! Meanwhile, the analysis of the 2011 dataset and publication of the subsequent results has continued. These results come from all the PAGs in CMS, including searches for the Higgs boson and other new phenomena, that have set the most stringent limits on an ever increasing number of models of physics beyond the Standard Model including dark matter, Supersymmetry, and TeV-scale gravity scenarios, top-quark physics where CMS has overtaken the Tevatron in the precision of some measurements, and bottom-quark physics where CMS made its first discovery of a new particle, the Ξ*0b baryon (candidate event pictured below). Image 2:  A Ξ*0b candidate event At the same time POGs and PAGs...

  4. PHYSICS

    CERN Multimedia

    D. Acosta

    2011-01-01

    Since the last CMS Week, all physics groups have been extremely active on analyses based on the full 2010 dataset, with most aiming for a preliminary measurement in time for the winter conferences. Nearly 50 analyses were approved in a “marathon” of approval meetings during the first two weeks of March, and the total number of approved analyses reached 90. The diversity of topics is very broad, including precision QCD, Top, and electroweak measurements, the first observation of single Top production at the LHC, the first limits on Higgs production at the LHC including the di-tau final state, and comprehensive searches for new physics in a wide range of topologies (so far all with null results unfortunately). Most of the results are based on the full 2010 pp data sample, which corresponds to 36 pb-1 at √s = 7 TeV. This report can only give a few of the highlights of a very rich physics program, which is listed below by physics group...

  5. Contribution to the study of the physical stability of the suspensions of zinc oxide, titanium dioxide and precipitated sulphur employing emulsified solid greases like vehicle

    International Nuclear Information System (INIS)

    Porras Navarro, Martha

    2001-01-01

    This research evaluated the physical stability of the suspensions of zinc oxide, precipitated sulphur and titanium dioxide. By using emulsified vehicles of three solid greases: stearilic alcohol, stearic acid and beeswax. That varies the concentration of solid grease (2%, 4%, 6 %) and the velocity of agitation for the emulsified vehicle's preparation (250, 500, 750 revolutions by minutes). That got 81 suspensions, 27 for every grease employed. The following effects there were evaluated like indicators of the physical stability of the suspensions: volume of sediment, apparent viscosity, facility of resuspension. There was effected an analysis of the varying of two controlled factors to establish the importance since the statistical viewpoint of the variants of the process over the volume of the sediment. This study indicates that the selection of solid grease is an parameter which influence is significant, what supports the got data through the research. By giving as a result that the stearilic alcohol is the most competent vehicle for the preparation of these suspensions. (Author) [es

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. The effect of GlycoPEGylation on the physical stability of human rFVIIa with increasing calcium chloride concentration

    DEFF Research Database (Denmark)

    Plesner, Bitten; Westh, Peter; Hvidt, Søren

    2011-01-01

    The effects of calcium chloride on the structural, kinetic and thermal stability of recombinant human factor VIIa (rFVIIa) were investigated using rFVIIa and two GlycoPEGylated recombinant human FVIIa derivatives, a linear 10 kDa PEG and a branched 40 kDa PEG, respectively. Three different CaCl(2......) concentrations were used: 10mM, 35 mM and 100mM. The secondary structure and tertiary structure of rFVIIa at 25C, measured by circular dichroism (CD), were maintained upon GlycoPEGylation as well as CaCl(2) content. In contrast, the thermal stability of the three rFVIIa compounds, measured by differential......FVIIa, whereas the concentration of CaCl(2) has to be raised to 100mM in order to see the same effect on the GlycoPEGylated rFVIIa compounds. The temperature of aggregation of rFVIIa, T(agg), increased as the CaCl(2) concentration increased from 35 mM to 100 mM, while T(agg) for the GlycoPEGylated r...

  13. Prestresses in bilayered all-ceramic restorations.

    Science.gov (United States)

    Aboushelib, Moustafa N; Feilzer, Albert J; de Jager, Niek; Kleverlaan, Cornelis J

    2008-10-01

    A general trend in all ceramic systems is to use veneering ceramics of slightly lower thermal expansion coefficients compared with that of the framework resulting in a positive mismatch in thermal expansion coefficient (+DeltaTEC). The concept behind this TEC mismatch is to generate compressive stresses in the weaker veneering ceramic and thus enhance the overall strength of the restoration. This technique had excellent results with porcelain fused to metal restorations (PFM). However, there are concerns to apply this concept to all-ceramic restorations. The aim of this research was to determine the stresses in bilayered all-ceramic restorations due to the mismatch in TEC. Two commercial veneering ceramics with a TEC lower than that of zirconia (+DeltaTEC); NobelRondo zirconiatrade mark and Lava Ceramtrade mark, plus one experimental veneering ceramic with an identical TEC that matches that of zirconia (DeltaTEC = 0) were used to veneer zirconia discs. The specimens were loaded in biaxial flexure test setup with the veneer ceramic in tension. The stresses due to load application and TEC mismatch were calculated using fractography, engineering mathematics, and finite element analysis (FEA). In this study, the highest load at failure (64 N) was obtained with the experimental veneer where the thermal mismatch between zirconia and veneering ceramic was minimal. For the two commercial veneer ceramics the magnitude of the thermal mismatch localized at the zirconia veneer interface (42 MPa) exceeded the bond strength between the two materials and resulted in delamination failure during testing (ca. 50 MPa). For all-ceramic zirconia veneered restorations it is recommended to minimize the thermal mismatch as much as possible. (c) 2008 Wiley Periodicals, Inc.

  14. Schottky Barriers in Bilayer Phosphorene Transistors.

    Science.gov (United States)

    Pan, Yuanyuan; Dan, Yang; Wang, Yangyang; Ye, Meng; Zhang, Han; Quhe, Ruge; Zhang, Xiuying; Li, Jingzhen; Guo, Wanlin; Yang, Li; Lu, Jing

    2017-04-12

    It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the Fermi-level pinning. Here, we report the first systematical study of bilayer (BL) phosphorene FETs in contact with a series of metals with a wide work function range (Al, Ag, Cu, Au, Cr, Ti, Ni, and Pd) by using both ab initio electronic band calculations and quantum transport simulation (QTS). Different from only one type of Schottky barrier (SB) identified in the ML phosphorene FETs, two types of SBs are identified in BL phosphorene FETs: the vertical SB between the metallized and the intact phosphorene layer, whose height is determined from the energy band analysis (EBA); the lateral SB between the metallized and the channel BL phosphorene, whose height is determined from the QTS. The vertical SBHs show a better consistency with the lateral SBHs of the ML phosphorene FETs from the QTS compared than that of the popular WFA. Therefore, we develop a better and more general method than the WFA to estimate the lateral SBHs of ML semiconductor transistors with strongly interacted electrodes based on the EBA for its BL counterpart. In terms of the QTS, n-type lateral Schottky contacts are formed between BL phosphorene and Cr, Al, and Cu electrodes with electron SBH of 0.27, 0.31, and 0.32 eV, respectively, while p-type lateral Schottky contacts are formed between BL phosphorene and Pd, Ti, Ni, Ag, and Au electrodes with hole SBH of 0.11, 0.18, 0.19, 0.20, and 0.21 eV, respectively. The theoretical polarity and SBHs are in good agreement with available experiments. Our study provides an insight into the BL phosphorene-metal interfaces that are crucial for designing the BL phosphorene device.

  15. PHYSICS

    CERN Multimedia

    Darin Acosta

    2010-01-01

    The collisions last year at 900 GeV and 2.36 TeV provided the long anticipated collider data to the CMS physics groups. Quite a lot has been accomplished in a very short time. Although the delivered luminosity was small, CMS was able to publish its first physics paper (with several more in preparation), and commence the commissioning of physics objects for future analyses. Many new performance results have been approved in advance of this CMS Week. One remarkable outcome has been the amazing agreement between out-of-the-box data with simulation at these low energies so early in the commissioning of the experiment. All of this is testament to the hard work and preparation conducted beforehand by many people in CMS. These analyses could not have happened without the dedicated work of the full collaboration on building and commissioning the detector, computing, and software systems combined with the tireless work of many to collect, calibrate and understand the data and our detector. To facilitate the efficien...

  16. PHYSICS

    CERN Multimedia

    D. Acosta

    2010-01-01

    The Physics Groups are actively engaged on analyses of the first data from the LHC at 7 TeV, targeting many results for the ICHEP conference taking place in Paris this summer. The first large batch of physics approvals is scheduled for this CMS Week, to be followed by four more weeks of approvals and analysis updates leading to the start of the conference in July. Several high priority analysis areas were organized into task forces to ensure sufficient coverage from the relevant detector, object, and analysis groups in the preparation of these analyses. Already some results on charged particle correlations and multiplicities in 7 TeV minimum bias collisions have been approved. Only one small detail remains before ICHEP: further integrated luminosity delivered by the LHC! Beyond the Standard Model measurements that can be done with these data, the focus changes to the search for new physics at the TeV scale and for the Higgs boson in the period after ICHEP. Particle Flow The PFT group is focusing on the ...

  17. PHYSICS

    CERN Multimedia

    the PAG conveners

    2011-01-01

    The delivered LHC integrated luminosity of more than 1 inverse femtobarn by summer and more than 5 by the end of 2011 has been a gold mine for the physics groups. With 2011 data, we have submitted or published 14 papers, 7 others are in collaboration-wide review, and 75 Physics Analysis Summaries have been approved already. They add to the 73 papers already published based on the 2010 and 2009 datasets. Highlights from each physics analysis group are described below. Heavy ions Many important results have been obtained from the first lead-ion collision run in 2010. The published measurements include the first ever indications of Υ excited state suppression (PRL synopsis), long-range correlation in PbPb, and track multiplicity over a wide η range. Preliminary results include the first ever measurement of isolated photons (showing no modification), J/ψ suppression including the separation of the non-prompt component, further study of jet fragmentation, nuclear modification factor...

  18. PHYSICS

    CERN Multimedia

    L. Demortier

    Physics-wise, the CMS week in December was dominated by discussions of the analyses that will be carried out in the “next six months”, i.e. while waiting for the first LHC collisions.  As presented in December, analysis approvals based on Monte Carlo simulation were re-opened, with the caveat that for this work to be helpful to the goals of CMS, it should be carried out using the new software (CMSSW_2_X) and associated samples.  By the end of the week, the goal for the physics groups was set to be the porting of our physics commissioning methods and plans, as well as the early analyses (based an integrated luminosity in the range 10-100pb-1) into this new software. Since December, the large data samples from CMSSW_2_1 were completed. A big effort by the production group gave a significant number of events over the end-of-year break – but also gave out the first samples with the fast simulation. Meanwhile, as mentioned in December, the arrival of 2_2 meant that ...

  19. PHYSICS

    CERN Multimedia

    C. Hill

    2012-01-01

      2012 has started off as a very busy year for the CMS Physics Groups. Planning for the upcoming higher luminosity/higher energy (8 TeV) operation of the LHC and relatively early Rencontres de Moriond are the high-priority activities for the group at the moment. To be ready for the coming 8-TeV data, CMS has made a concerted effort to perform and publish analyses on the 5 fb−1 dataset recorded in 2011. This has resulted in the submission of 16 papers already, including nine on the search for the Higgs boson. In addition, a number of preliminary results on the 2011 dataset have been released to the public. The Exotica and SUSY groups approved several searches for new physics in January, such as searches for W′ and exotic highly ionising particles. These were highlighted at a CERN seminar given on 24th  January. Many more analyses, from all the PAGs, including the newly formed SMP (Standard Model Physics) and FSQ (Forward and Small-x QCD), were approved in February. The ...

  20. PHYSICS

    CERN Document Server

    C. Hill

    2012-01-01

      The period since the last CMS Bulletin has been historic for CMS Physics. The pinnacle of our physics programme was an observation of a new particle – a strong candidate for a Higgs boson – which has captured worldwide interest and made a profound impact on the very field of particle physics. At the time of the discovery announcement on 4 July, 2012, prominent signals were observed in the high-resolution H→γγ and H→ZZ(4l) modes. Corroborating excess was observed in the H→W+W– mode as well. The fermionic channel analyses (H→bb, H→ττ), however, yielded less than the Standard Model (SM) expectation. Collectively, the five channels established the signal with a significance of five standard deviations. With the exception of the diphoton channel, these analyses have all been updated in the last months and several new channels have been added. With improved analyses and more than twice the i...

  1. Effect of surface bilayer charges on the magnetic field around ionic channels

    Energy Technology Data Exchange (ETDEWEB)

    Gomes Soares, Marília Amável [Post-graduation in Computational Sciences, Rio de Janeiro State University (Brazil); Cortez, Celia Martins, E-mail: ccortezs@ime.uerj.br [Post-graduation in Computational Sciences, Rio de Janeiro State University (Brazil); Department of Applied Mathematics, Rio de Janeiro State University (Brazil); Oliveira Cruz, Frederico Alan de [Post-graduation in Computational Sciences, Rio de Janeiro State University (Brazil); Department of Physics, Rural Federal University of Rio de Janeiro (Brazil); Silva, Dilson [Post-graduation in Computational Sciences, Rio de Janeiro State University (Brazil); Department of Applied Mathematics, Rio de Janeiro State University (Brazil)

    2017-01-01

    In this work, we present a physic-mathematical model for representing the ion transport through membrane channels, in special Na{sup +} and K{sup +}-channels, and discuss the influence of surface bilayer charges on the magnetic field behavior around the ionic current. The model was composed of a set of equations, including: a nonlinear differential Poisson-Boltzmann equation which usually allows to estimate the surface potentials and electric potential profile across membrane; equations for the ionic flux through channel and the ionic current density based on Armstrong's model for Na{sup +} and K{sup +} permeability and other Physics concepts; and a magnetic field expression derived from the classical Ampère equation. Results from computational simulations using the finite element method suggest that the ionic permeability is strongly dependent of surface bilayer charges, the current density through a K{sup +}-channel is very less sensible to temperature changes than the current density through a Na{sup +}- channel, active Na{sup +}-channels do not directly interfere with the K{sup +}-channels around, and vice-versa, since the magnetic perturbation generated by an active channel is of short-range.

  2. 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.

  3. Constitutive dimerization of the G-protein coupled receptor, neurotensin receptor 1, reconstituted into phospholipid bilayers.

    Science.gov (United States)

    Harding, Peter J; Attrill, Helen; Boehringer, Jonas; Ross, Simon; Wadhams, George H; Smith, Eleanor; Armitage, Judith P; Watts, Anthony

    2009-02-01

    Neurotensin receptor 1 (NTS1), a Family A G-protein coupled receptor (GPCR), was expressed in Escherichia coli as a fusion with the fluorescent proteins eCFP or eYFP. A fluorophore-tagged receptor was used to study the multimerization of NTS1 in detergent solution and in brain polar lipid bilayers, using fluorescence resonance energy transfer (FRET). A detergent-solubilized receptor was unable to form FRET-competent complexes at concentrations of up to 200 nM, suggesting that the receptor is monomeric in this environment. When reconstituted into a model membrane system at low receptor density, the observed FRET was independent of agonist binding, suggesting constitutive multimer formation. In competition studies, decreased FRET in the presence of untagged NTS1 excludes the possibility of fluorescent protein-induced interactions. A simulation of the experimental data indicates that NTS1 exists predominantly as a homodimer, rather than as higher-order multimers. These observations suggest that, in common with several other Family A GPCRs, NTS1 forms a constitutive dimer in lipid bilayers, stabilized through receptor-receptor interactions in the absence of other cellular signaling components. Therefore, this work demonstrates that well-characterized model membrane systems are useful tools for the study of GPCR multimerization, allowing fine control over system composition and complexity, provided that rigorous control experiments are performed.

  4. Formulation, evaluation, and comparison of bilayered and multilayered mucoadhesive buccal devices of propranolol hydrochloride.

    Science.gov (United States)

    Patel, Vishnu M; Prajapati, Bhupendra G; Patel, Madhabhai M

    2007-03-16

    The purpose of this research work was to establish mucoadhesive buccal devices of propranolol hydrochloride (PRH) in the forms of bilayered and multilayered tablets. The tablets were prepared using sodium carboxymethylcellulose (SCMC) and Carbopol-934 (CP) as bioadhesive polymers to impart mucoadhesion and ethyl cellulose (EC) to act as an impermeable backing layer. Buccal devices were evaluated by different parameters such as weight uniformity, content uniformity, thickness, hardness, surface pH, swelling index, ex vivo mucoadhesive strength, ex vivo mucoadhesion time, in vitro drug release, and in vitro drug permeation. As compared with bilayered tablets, multilayered tablets showed slow release rate of drug with improved ex vivo bioadhesive strength and enhanced ex vivo mucoadhesion time. The mechanism of drug release was found to be non-Fickian diffusion (value of n between 0.5 and 1.0) for both the buccal devices. The stability of drug in both the optimized buccal devices was tested for 6 hours in natural human saliva; both the buccal devices were found to be stable in natural human saliva. The present study concludes that mucoadhesive buccal devices of PRH can be a good way to bypass the extensive hepatic first-pass metabolism and to improve the bioavailability of PRH.

  5. 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.

  6. 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)

  7. Active Bilayer PE/PCL Films for Food Packaging Modified with Zinc Oxide and Casein

    Directory of Open Access Journals (Sweden)

    Ana Rešček

    2015-12-01

    Full Text Available This paper studies the properties of active polymer food packaging bilayer polyethylene/polycaprolactone (PE/PCL films. Such packaging material consists of primary PE layer coated with thin film of PCL coating modified with active component (zinc oxide or zinc oxide/casein complex with intention to extend the shelf life of food and to maintain the quality and health safety. The influence of additives as active components on barrier, mechanical, thermal and antimicrobial properties of such materials was studied. The results show that, in comparison to the neat PE and PE/PCL films, some of PE/PCL bilayer films with additives exhibit improved barrier properties i.e. decreased water vapour permeability. Higher thermal stability of modified PE/PCL material is obtained due to a modified mechanism of thermal degradation. The samples with the additive nanoparticles homogeneously dispersed in the polymer matrix showed good mechanical properties. Addition of higher ZnO content contributes to the enhanced antibacterial activity of a material.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-14

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

  9. Physically-based slope stability modelling and parameter sensitivity: a case study in the Quitite and Papagaio catchments, Rio de Janeiro, Brazil

    Science.gov (United States)

    de Lima Neves Seefelder, Carolina; Mergili, Martin

    2016-04-01

    conservative than those yielded with the infinite slope stability model. The sensitivity of AUCROC to variations in the geohydraulic parameters remains small as long as the calculated degree of saturation of the soils is sufficient to result in the prediction of a significant amount of landslide release pixels. Due to the poor sensitivity of AUCROC to variations of the geotechnical and geohydraulic parameters it is hard to optimize the parameters by means of statistics. Instead, the results produced with many different combinations of parameters correspond reasonably well with the distribution of the observed landslide release areas, even though they vary considerably in terms of their conservativeness. Considering the uncertainty inherent in all geotechnical and geohydraulic data, and the impossibility to capture the spatial distribution of the parameters by means of laboratory tests in sufficient detail, we conclude that landslide susceptibility maps yielded by catchment-scale physically-based models should not be interpreted in absolute terms. Building on the assumption that our findings are generally valid, we suggest that efforts to develop better strategies for dealing with the uncertainties in the spatial variation of the key parameters should be given priority in future slope stability modelling efforts.

  10. Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

    International Nuclear Information System (INIS)

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

    2015-01-01

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I ON levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures

  11. Assessment of pseudo-bilayer structures in the 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); Medina-Bailón, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

    2015-06-29

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I{sub ON} levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. Lecithin-based microemulsion of a peptide for oral administration: preparation, characterization, and physical stability of the formulation.

    Science.gov (United States)

    Cilek, Ayşe; Celebi, Nevin; Tirnaksiz, Figen

    2006-01-01

    The objective of our study was to prepare and characterize a stable microemulsion formulation for oral administration of a peptide, e.g., rh-insulin. The microemulsions were prepared using Labrafil M 1944 CS, Phospholipon 90G (lecithin), absolute alcohol, and bidistilled water. Commercially available soybean lecithins (namely, Phospholipon 80, phosphatidylcholine purity 76 +/- 3%, and Phospholipon 90G, phosphatidylcholine purity 93 +/- 3%) were used in the study. The results showed that the phase diagram obtained using a low purity lecithin was not similar to that obtained with a high purity lecithin. We observed that the microemulsion area was wider at the phase diagram obtained with the higher purity lecithin. We found that the extent of the microemulsion region depended upon both the purity of the lecithin and the surfactant/co-surfactant (s/co-s) mixing ratios (K(m)). The rheological studies showed that microemulsions followed a Newtonian behavior. Such physical characteristics as viscosity, turbidity, density, conductivity, refractive index, droplet size, physical appearance, and phase separation of the microemulsion were measured at different temperatures (4 degrees C, 25 degrees C, and 40 degrees C) during 6 months. The results indicated that the physical characteristics of the developed microemulsions did not change under different storage temperatures (p > 0.05).

  2. Physical limit of stability in supercooled D2O and D2O+H2O mixtures

    Science.gov (United States)

    Kiselev, S. B.; Ely, J. F.

    2003-01-01

    The fluctuation theory of homogeneous nucleation was applied for calculating the physical boundary of metastable states, the kinetic spinodal, in supercooled D2O and D2O+H2O mixtures. The kinetic spinodal in our approach is completely determined by the surface tension and equation of state of the supercooled liquid. We developed a crossover equation of state for supercooled D2O, which predicts a second critical point of low density water-high density water equilibrium, CP2, and represents all available experimental data in supercooled D2O within experimental accuracy. Using Turnbull's expression for the surface tension we calculated with the crossover equation of state for supercooled D2O the kinetic spinodal, TKS, which lies below the homogeneous nucleation temperature, TH. We show that CP2 always lies inside in the so-called "nonthermodynamic habitat" and physically does not exist. However, the concept of a second "virtual" critical point is physical and very useful. Using this concept we have extended this approach to supercooled D2O+H2O mixtures. As an example, we consider here an equimolar D2O+H2O mixture in normal and supercooled states at atmospheric pressure, P=0.1 MPa.

  3. PHYSICS

    CERN Multimedia

    J. D'Hondt

    The Electroweak and Top Quark Workshop (16-17th of July) A Workshop on Electroweak and Top Quark Physics, dedicated on early measurements, took place on 16th-17th July. We had more than 40 presentations at the Workshop, which was an important milestone for 2007 physics analyses in the EWK and TOP areas. The Standard Model has been tested empirically by many previous experiments. Observables which are nowadays known with high precision will play a major role for data-based CMS calibrations. A typical example is the use of the Z to monitor electron and muon reconstruction in di-lepton inclusive samples. Another example is the use of the W mass as a constraint for di-jets in the kinematic fitting of top-quark events, providing information on the jet energy scale. The predictions of the Standard Model, for what concerns proton collisions at the LHC, are accurate to a level that the production of W/Z and top-quark events can be used as a powerful tool to commission our experiment. On the other hand the measure...

  4. PHYSICS

    CERN Multimedia

    Christopher Hill

    2013-01-01

    Since the last CMS Bulletin, the CMS Physics Analysis Groups have completed more than 70 new analyses, many of which are based on the complete Run 1 dataset. In parallel the Snowmass whitepaper on projected discovery potential of CMS for HL-LHC has been completed, while the ECFA HL-LHC future physics studies has been summarised in a report and nine published benchmark analyses. Run 1 summary studies on b-tag and jet identification, quark-gluon discrimination and boosted topologies have been documented in BTV-13-001 and JME-13-002/005/006, respectively. The new tracking alignment and performance papers are being prepared for submission as well. The Higgs analysis group produced several new results including the search for ttH with H decaying to ZZ, WW, ττ+bb (HIG-13-019/020) where an excess of ~2.5σ is observed in the like-sign di-muon channel, and new searches for high-mass Higgs bosons (HIG-13-022). Search for invisible Higgs decays have also been performed both using the associ...

  5. PHYSICS

    CERN Multimedia

    C. Hill

    2013-01-01

    In the period since the last CMS Bulletin, the LHC – and CMS – have entered LS1. During this time, CMS Physics Analysis Groups have performed more than 40 new analyses, many of which are based on the complete 8 TeV dataset delivered by the LHC in 2012 (and in some cases on the full Run 1 dataset). These results were shown at, and well received by, several high-profile conferences in the spring of 2013, including the inaugural meeting of the Large Hadron Collider    Physics Conference (LHCP) in Barcelona, and the 26th International Symposium on Lepton Photon Interactions at High Energies (LP) in San Francisco. In parallel, there have been significant developments in preparations for Run 2 of the LHC and on “future physics” studies for both Phase 1 and Phase 2 upgrades of the CMS detector. The Higgs analysis group produced five new results for LHCP including a new H-to-bb search in VBF production (HIG-13-011), ttH with H to γ&ga...

  6. PHYSICS

    CERN Multimedia

    C. Hill

    2013-01-01

    The period since the last CMS bulletin has seen the end of proton collisions at a centre-of-mass energy 8 TeV, a successful proton-lead collision run at 5 TeV/nucleon, as well as a “reference” proton run at 2.76 TeV. With these final LHC Run 1 datasets in hand, CMS Physics Analysis Groups have been busy analysing these data in preparation for the winter conferences. Moreover, despite the fact that the pp run only concluded in mid-December (and there was consequently less time to complete data analyses), CMS again made a strong showing at the Rencontres de Moriond in La Thuile (EW and QCD) where nearly 40 new results were presented. The highlight of these preliminary results was the eagerly anticipated updated studies of the properties of the Higgs boson discovered in July of last year. Meanwhile, preparations for Run 2 and physics performance studies for Phase 1 and Phase 2 upgrade scenarios are ongoing. The Higgs analysis group produced updated analyses on the full Run 1 dataset (~25 f...

  7. 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.

  8. 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.

  9. Electronic band structure of magnetic bilayer graphene superlattices

    International Nuclear Information System (INIS)

    Pham, C. Huy; Nguyen, T. Thuong; Nguyen, V. Lien

    2014-01-01

    Electronic band structure of the bilayer graphene superlattices with δ-function magnetic barriers and zero average magnetic flux is studied within the four-band continuum model, using the transfer matrix method. The periodic magnetic potential effects on the zero-energy touching point between the lowest conduction and the highest valence minibands of pristine bilayer graphene are exactly analyzed. Magnetic potential is shown also to generate the finite-energy touching points between higher minibands at the edges of Brillouin zone. The positions of these points and the related dispersions are determined in the case of symmetric potentials.

  10. 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

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. Influences of the Structure of Lipids on Thermal Stability of Lipid Membranes

    International Nuclear Information System (INIS)

    Hai Nan-Nan; Zhou Xin; Li Ming

    2015-01-01

    The binding free energy (BFE) of lipid to lipid bilayer is a critical factor to determine the thermal or mechanical stability of the bilayer. Although the molecular structure of lipids has significant impacts on BFE of the lipid, there lacks a systematic study on this issue. In this paper we use coarse-grained molecular dynamics simulation to investigate this problem for several typical phospholipids. We find that both the tail length and tail unsaturation can significantly affect the BFE of lipids but in opposite way, namely, BFE decreases linearly with increasing length, but increases linearly with addition of unsaturated bonds. Inspired by the specific structure of cholesterol which is a crucial component of biomembrane, we also find that introduction of carbo-ring-like structures to the lipid tail or to the bilayer may greatly enhance the stability of the bilayer. Our simulation also shows that temperature can influence the bilayer stability and this effect can be significant when the bilayer undergoes phase transition. These results may be helpful to the design of liposome or other self-assembled lipid systems. (paper)

  16. The effect of formulative parameters on the size and physical stability of SLN based on "green" components.

    Science.gov (United States)

    Soddu, Elena; Rassu, Giovanna; Cossu, Massimo; Giunchedi, Paolo; Cerri, Guido; Gavini, Elisabetta

    2016-01-01

    Cocoa butter (CB) is a largely used excipient in pharmaceutical field. Aim of this work was to set formulative parameters for the preparation of SLN based on "green" lipid matrix for drug delivery as natural, both human and environmental safe systems. Double emulsion technique (w1/o/w2) was selected for SLN preparation. The effect on the dimensional properties of different surfactants (Tween 80 and PEG 40 monostearate) and co-surfactants (PEG400 monostearate, Emulium® Kappa2 and Plurol®Stearique) at different concentrations was evaluated. Stability tests were performed. SLN dispersions were exsiccated and the effect of the dried process on SLN size was evaluated. The influence of temperature on SLN dimensions was investigated at 37 °C. MTT test was performed on raw materials and formulations. The w1/o/w2 is suitable, rapid and economic technique for the preparation of CB SLN. Tween 80-Plurol Stearique combination gives the best results: particles size less than 400 nm and PI of about 0.4 are obtained when PS 2% is used. Both raw materials and formulations are safe. The importance to evaluate the effect of different surfactant and/or co-surfactant on the dimensional properties of SLN is evident by selecting substances with preferable safety profiles, and favorable environmental properties to develop stable "green" SLN.

  17. Natalizumab stabilizes physical, cognitive, MRI, and OCT markers of disease activity: A prospective, non-randomized pilot study.

    Directory of Open Access Journals (Sweden)

    Garrick D Talmage

    Full Text Available Natalizumab is an effective therapy for multiple sclerosis (MS. Its effectiveness has been demonstrated in several clinical and imaging studies. The objective of this study was to further demonstrate the efficacy of natalizumab using a comprehensive battery of clinical and imaging markers in the same cohort of patients followed longitudinally, hence capturing the multi-faceted nature of the MS disease process. A prospective, open-label, pilot study of 20 MS patients treated with natalizumab was conducted. High resolution MRI, Symbol-Digit Modalities Test (SDMT, and Optical Coherence Tomography (OCT scans were obtained at baseline, 48, and 96 weeks. 15 patients completed the study. Natalizumab treatment decreased Expanded Disability Status Scale score (EDSS and no change in SDMT, Brain Parenchymal Fraction (BPF, or any of the OCT markers of retinal degeneration was observed. Thalamic and whole brain volume as assessed by Percentage Brain Volume Change (PBVC showed continuous deterioration. Higher baseline T2 lesion load correlated with increased rate of PBVC at 96-weeks (r = 0.566, R2 = 0.320, p = 0.035 and thalamic volume loss (r = -0.586, R2 = 0.344, p = 0.027. Most patients, 93%, achieved no evidence of disease activity (NEDA at 2 years, likely due to early disease duration and lower initial baseline lesion load. This study further demonstrates stabilization of clinical and imaging markers of disease activity during natalizumab treatment.

  18. Developing eco-friendly biofungicide for the management of major seed borne diseases of rice and assessing their physical stability and storage life.

    Science.gov (United States)

    Naveenkumar, Ramasamy; Muthukumar, Arjunan; Sangeetha, Ganesan; Mohanapriya, Ramanathan

    2017-04-01

    Three plant oils (Cymbopogon citratus, Cymbopogon martini, and Pelargonium graveolens) were developed as EC formulations and tested for their physical stabilities. EC formulations (10EC, 20EC and 30EC) of C. citratus, C. martini and P. graveolens had emulsion stability, spontaneity property, heat and cold stability. EC formulated plant oils were screened against the major seed borne fungi of rice such as Curvularia lunata, Fusarium moniliforme, Bipolaris oryzae, and Sarocladium oryzae. The level of inhibition varied among the concentrations of EC formulations. Among the three EC formulations, that of C. citratus oil 30EC recorded 100% inhibition on the mycelial growth of test pathogens. In the blotter paper method, rice seeds treated with a formulation of C. citratus oil 30EC controlled the infection of C. lunata, F. moniliforme, B. oryzae and S. oryzae in rice seed to the tune of 66.0%, 60.4%, 66.0% and 69.1%, respectively. Seed soaking with formulation of C. citratus oil 30EC showed the highest percentage of normal seedlings, the lowest number of abnormal seedling and fresh ungerminated seeds when tested with the roll-towel method. Seed soaking with 30EC formulation of C. citratus oil increased seed germination, shoot length, root length and vigour of rice seedlings when tested with the plastic tray method. Transmission of pathogens from seed to seedling was reduced significantly by the 30EC formulation of C. citratus oil when tested with the plastic pot method. The effect of the storage life of the 30EC formulation of C. citratus oil showed that it had retained their antifungal effect till the end of the incubation period (120 days), and is able to inhibit the mycelial growth of all test pathogens to the 100% level. Copyright © 2017 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

  19. Final report of the Buffer Mass Test - Volume 3: Chemical and physical stability of the buffer materials

    International Nuclear Information System (INIS)

    Pusch, R.

    1985-11-01

    The Buffer Mass Test offered a possibility to investigate whether chemical changes took place in the smectite component at heating to 125 degrees C for about one year. The alterations that could possibly take place were a slight charge change in the crystal lattice with an associated precipitation of silica compounds, and a tendency of illite formation. The analysis showed that there were indications of both but to such a slight extent that the processes could not have affected the physical properties, which was also demonstrated by determining the swelling pressure and the hydraulic conductivity. The BMT also showed that the erodibility of bentonite-based buffer materials is less than or about equal to what can be expected on theoretical grounds. (author)

  20. Active packaged lamb with oxygen scavenger/carbon dioxide emitter sachet: physical-chemical and microbiological stability during refrigerated storage

    Directory of Open Access Journals (Sweden)

    Marco Antonio Trindade

    2013-09-01

    Full Text Available Lamb meat has been commercialized in Brazil almost exclusively as a frozen product due to the longer shelf life provided by freezing when compared to refrigeration. However, as a result of the current trend of increased demand for convenience products, a need has emerged for further studies to facilitate the marketing of refrigerated lamb cuts. The aim of the present study was to evaluate the contribution of active packaging technology in extending the shelf life of lamb loins (Longissimus lumborum stored under refrigeration (1±1 ° C when compared to the traditional vacuum packaging. For this purpose, two kinds of sachets were employed: oxygen scavenger sachet and oxygen scavenger/carbon dioxide emitter sachet. Experiments were conducted in three treatments: 1 Vacuum (Control, 2 Vacuum + oxygen scavenger sachet and 3 Vacuum + oxygen scavenger/carbon dioxide emitter sachet. Microbiological (counts of anaerobic psychrotrophs, coliform at 45 ° C, coagulase-positive staphylococci, Salmonella and lactic acid bacteria and physical-chemical (thiobarbituric acid reactive substances, objective color, pH value, water loss from cooking and shear force analyses were carried out weekly for a total storage period of 28 days. The experiment was performed three times for all treatments. Results showed that the lamb meat remained stable with respect to the majority of the evaluated physical and chemical indexes and remained within the standards established by Brazilian legislation for pathogenic microorganisms throughout the storage period in all three packaging systems. However, all treatments presented elevated counts of anaerobic psychrotrophic microorganisms and lactic acid bacteria, reaching values above 10(7 CFU/g at 28 days of storage. Thus, under the conditions tested, neither the oxygen scavenger sachet nor the dual function sachet (oxygen scavenger/carbon dioxide emitter were able to extend the shelf life of refrigerated lamb loin when added to this

  1. Características físicas de dietas para peixes confeccionadas com diferentes aglutinantes Influence of agglutinants on physical stability of fish diets

    Directory of Open Access Journals (Sweden)

    Margarida Maria Barros

    2002-04-01

    Full Text Available Este experimento teve por objetivo avaliar a eficiência de diferentes aglutinantes, a seco e na água, por meio da estabilidade física do pélete. Foram avaliadas duas técnicas de processamento (com ou sem vapor e seis aglutinantes (carboximetilcelulose, polimetilcarbamida, amido de mandioca, alginato de sódio, polivinilpirrolidona, goma guar, através da análise de variância no esquema fatorial (2x6, além de um controle, ao qual não foi acrescido aglutinante. Concluiu-se que o aglutinante melhora significativamente a resistência física do grânulo, independente da técnica de processamento; que o vapor determina grânulos mais estáveis quando em contato com a água e, que o alginato de sódio proporciona grânulos fisicamente mais estáveis, em ambas as técnicas de processamento, enquanto a goma guar a pior.The aim of this paper was to determine the influence of different dry and water agglutinants, through physical stability of pellets. The agglutinants were sodium alginate, guar gum, polymetylcarbamide, polyvinylpirrolidone, carboxymetilcellulose, and cassava starch. The manufacturing processes were two: with and without steam and extrusion. These treatments were evaluated through the variance analysis technique with the factorial scheme 2 x 6 (two processes and six agglutinants, and one control where no extra agglutinants was added. Results showed that, independently of processing technique, the presence the agglutinants improves the physical resistance of the pellets significantly, giving the whole pellets more stability while in contact with water, and that the sodium alginate gives pellets the highest aggregated characteristic, in both processes, while that guar gum gives the lowest.

  2. CRYSTAL CHEMISTRY OF THREE-COMPONENT WHITE DWARFS AND NEUTRON STAR CRUSTS: PHASE STABILITY, PHASE STRATIFICATION, AND PHYSICAL PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Engstrom, T. A.; Yoder, N. C.; Crespi, V. H., E-mail: tae146@psu.edu, E-mail: ncy5007@psu.edu, E-mail: vhc2@psu.edu [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2016-02-20

    A systematic search for multicomponent crystal structures is carried out for five different ternary systems of nuclei in a polarizable background of electrons, representative of accreted neutron star crusts and some white dwarfs. Candidate structures are “bred” by a genetic algorithm and optimized at constant pressure under the assumption of linear response (Thomas–Fermi) charge screening. Subsequent phase equilibria calculations reveal eight distinct crystal structures in the T = 0 bulk phase diagrams, five of which are complicated multinary structures not previously predicted in the context of compact object astrophysics. Frequent instances of geometrically similar but compositionally distinct phases give insight into structural preferences of systems with pairwise Yukawa interactions, including and extending to the regime of low-density colloidal suspensions made in a laboratory. As an application of these main results, we self-consistently couple the phase stability problem to the equations for a self-gravitating, hydrostatically stable white dwarf, with fixed overall composition. To our knowledge, this is the first attempt to incorporate complex multinary phases into the equilibrium phase-layering diagram and mass–radius-composition dependence, both of which are reported for He–C–O and C–O–Ne white dwarfs. Finite thickness interfacial phases (“interphases”) show up at the boundaries between single-component body-centered cubic (bcc) crystalline regions, some of which have lower lattice symmetry than cubic. A second application—quasi-static settling of heavy nuclei in white dwarfs—builds on our equilibrium phase-layering method. Tests of this nonequilibrium method reveal extra phases that play the role of transient host phases for the settling species.

  3. Enhanced resistive switching and multilevel behavior in bilayered HfAlO/HfAlO{sub x} structures for non-volatile memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Faita, F. L., E-mail: fabriciofaita@gmail.com [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Departamento de Física, Universidade Federal de Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Silva, J. P. B., E-mail: josesilva@fisica.uminho.pt [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, 4169-007 Porto (Portugal); Pereira, M.; Gomes, M. J. M. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2015-12-14

    In this work, hafnium aluminum oxide (HfAlO) thin films were deposited by ion beam sputtering deposition technique on Si substrate. The presence of oxygen vacancies in the HfAlO{sub x} layer deposited in oxygen deficient environment is evidenced from the photoluminescence spectra. Furthermore, HfAlO(oxygen rich)/HfAlO{sub x}(oxygen poor) bilayer structures exhibit multilevel resistive switching (RS), and the switching ratio becomes more prominent with increasing the HfAlO layer thickness. The bilayer structure with HfAlO/HfAlO{sub x} thickness of 30/40 nm displays the enhanced multilevel resistive switching characteristics, where the high resistance state/intermediate resistance state (IRS) and IRS/low resistance state resistance ratios are ≈10{sup 2} and ≈5 × 10{sup 5}, respectively. The switching mechanisms in the bilayer structures were investigated by the temperature dependence of the three resistance states. This study revealed that the multilevel RS is attributed to the coupling of ionic conduction and the metallic conduction, being the first associated to the formation and rupture of conductive filaments related to oxygen vacancies and the second with the formation of a metallic filament. Moreover, the bilayer structures exhibit good endurance and stability in time.

  4. PHYSICS

    CERN Multimedia

    V.Ciulli

    2011-01-01

    The main programme of the Physics Week held between 16th and 20th May was a series of topology-oriented workshops on di-leptons, di-photons, inclusive W, and all-hadronic final states. The goal of these workshops was to reach a common understanding for the set of objects (ID, cleaning...), the handling of pile-up, calibration, efficiency and purity determination, as well as to revisit critical common issues such as the trigger. Di-lepton workshop Most analysis groups use a di-lepton trigger or a combination of single and di-lepton triggers in 2011. Some groups need to collect leptons with as low PT as possible with strong isolation and identification requirements as for Higgs into WW at low mass, others with intermediate PT values as in Drell-Yan studies, or high PT as in the Exotica group. Electron and muon reconstruction, identification and isolation, was extensively described in the workshop. For electrons, VBTF selection cuts for low PT and HEEP cuts for high PT were discussed, as well as more complex d...

  5. Ni-YSZ cermet substrate supported thin SDC and YSZ+SDC bi-layer SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.; Robertson, M.; Deces-Petit, C.; Xie, Y.; Hui, R.; Yick, S.; Styles, E.; Roller, J.; Kesler, O.; Qu, W.; Jankovic, J.; Tang, Z.; Perednis, D.; Maric, R.; Ghosh, D. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2005-07-01

    One of the disadvantages of a ceria-based electrolyte is that it becomes a mixed conductor at anode conditions, which causes cell voltage loss and fuel efficiency loss due to internal shorting. Chemical and mechanical stability is another concern for long-term service. To lower manufacturing costs, efforts have been made to bring proven semiconductor manufacturing technology to Solid Oxide Fuel Cells (SOFCs). This study employed Tape casting of cermet substrates, Screen-printing of functional layers and Co-firing of cell components (TSC) to fabricate nickel (Ni)-cermet supported cells with mainly ceria-based thin electrolytes. Ni-Yttria-Stabilized Zirconia (YSZ) cermet supported cell with Samaria Doped Ceria (SDC) single layer electrolytes and YSZ+SDC bi-layer electrolytes were successfully developed for low-temperature performance characterization. The elemental distribution at the cell interface was mapped and the electrochemical performance of the cells was recorded. Many high-Zr-content micro-islands were found on the thin SDC surface. The influence of co-firing temperature and thin-film preparation methods on the Zr-islands' appearance was also investigated. Using in-situ sintered cathodes, high performance of the SDC cells was obtained. It was concluded that the bi-layer cells did show higher Open Circuit Voltage (OCV) values, with 1180 mW/cm{sup 2} at 650 degrees C, as well as good performance at 700-800 degrees C, with near OCV value. However, their performance was much lower than those of the SDC cells at low operating temperature. Zr-micro-islands formation on the SDC electrolyte was observed and investigated. 6 refs., 5 tabs., 7 figs.

  6. Dynamic combinatorial chemistry at the phospholipid bilayer interface

    NARCIS (Netherlands)

    Mansfeld, Friederike M.; Au-Yeung, Ho Yu; Sanders, Jeremy K.M.; Otto, Sijbren

    2010-01-01

    Background: Molecular recognition at the environment provided by the phospholipid bilayer interface plays an important role in biology and is subject of intense investigation. Dynamic combinatorial chemistry is a powerful approach for exploring molecular recognition, but has thus far not been

  7. Coherent nonlinear electromagnetic response in twisted bilayer and ...

    Indian Academy of Sciences (India)

    The phenomenon of Rabi oscillations far from resonance is described in bilayer and few-layer graphene. These oscillations in the population and polarization at the Dirac point in -layer graphene are seen in the nth harmonic termin the external driving frequency. The underlying reason behind these oscillations is ...

  8. 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.

  9. 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...

  10. Molecular Dynamics Simulations of Hydrophilic Pores in Lipid Bilayers

    NARCIS (Netherlands)

    Leontiadou, Hari; Mark, Alan E.; Marrink, Siewert J.

    Hydrophilic pores are formed in peptide free lipid bilayers under mechanical stress. It has been proposed that the transport of ionic species across such membranes is largely determined by the existence of such meta-stable hydrophilic pores. To study the properties of these structures and understand

  11. Determinants of sodium and calcium adsorption onto neutral lipid bilayers

    Czech Academy of Sciences Publication Activity Database

    Javanainen, M.; Melcrová, Adéla; Magarkar, Aniket; Jurkiewicz, Piotr; Hof, Martin; Jungwirth, Pavel; Martinez-Seara, Hector

    2017-01-01

    Roč. 46, Suppl 1 (2017), S121 ISSN 0175-7571. [IUPAB congress /19./ and EBSA congress /11./. 16.07.2017-20.07.2017, Edinburgh] Institutional support: RVO:61388963 ; RVO:61388955 Keywords : sodium * calcium * lipid bilayer Subject RIV: BO - Biophysics

  12. 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)

  13. Power losses in bilayer inverted small molecule organic solar cells

    KAUST Repository

    Trinh, Cong; Bakke, Jonathan R.; Brennan, Thomas P.; Bent, Stacey F.; Navarro, Francisco; Bartynski, Andrew; Thompson, Mark E.

    2012-01-01

    Inverted bilayer organic solar cells using copper phthalocyanine (CuPc) as a donor and C60 as an acceptor with the structure: glass/indium tin oxide (ITO)/ZnO/C60/CuPc/MoO3/Al, in which the zinc oxide (ZnO) was deposited by atomic layer deposition

  14. Pedot and PPy Conducting Polymer Bilayer and Trilayer Actuators

    DEFF Research Database (Denmark)

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

    2008-01-01

    attempts have been made to improve the actuator performance. We report electromechanical measurements on actuators of bilayer and trilayer free standing films prepared with polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymers. Both types of conducting polymer are pre...

  15. Molecular dynamics study on the relaxation properties of bilayered ...

    Indian Academy of Sciences (India)

    2017-08-31

    Aug 31, 2017 ... Abstract. The influence of defects on the relaxation properties of bilayered graphene (BLG) has been studied by molecular dynamics simulation in nanometre sizes. Type and position of defects were taken into account in the calculated model. The results show that great changes begin to occur in the ...

  16. Semiconductor particle mediated photoelectron transfers in bilayer lipid membranes

    International Nuclear Information System (INIS)

    Fendler, J.H.; Baral, S.

    1989-01-01

    This paper discusses semiconductor particles in situ generated on the cis surface of glyceryl monooleate (GMO) bilayer lipid membranes (BLMs), that have been used to mediate photoelectric effects. The presence of semiconductors on the BLM surface is addressed. The observed photoelectric effects are rationalized and presented

  17. 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.

  18. Supported lipid bilayers with controlled curvature via colloidal lithography

    DEFF Research Database (Denmark)

    Sundh, Maria; Manandhar, Michal; Svedhem, Sofia

    2011-01-01

    Supported lipid bilayers (SLBs) at surfaces provide a route to quantitatively study molecular interactions with and at lipid membranes via different surface-based analytical techniques. Here, a method to fabricate SLBs with controlled curvatures, in the nanometer regime over large areas, is prese...

  19. 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.

  20. Gate-controlled tunneling of quantum Hall edge states in bilayer graphene

    Science.gov (United States)

    Zhu, Jun; Li, Jing; Wen, Hua

    Controlled tunneling of integer and fractional quantum Hall edge states provides a powerful tool to probe the physics of 1D systems and exotic particle statistics. Experiments in GaAs 2DEGs employ either a quantum point contact or a line junction tunnel barrier. It is generally difficult to independently control the filling factors νL and νR on the two sides of the barrier. Here we show that in bilayer graphene both νL and νR as well as their Landau level structures can be independently controlled using a dual-split-gate structure. In addition, the height of the line-junction tunnel barrier implemented in our experiments is tunable via a 5th gate. By measuring the tunneling resistance across the junction RT we examine the equilibration of the edge states in a variety of νL/νR scenarios and under different barrier heights. Edge states from both sides are fully mixed in the case of a low barrier. As the barrier height increases, we observe plateaus in RT that correspond to sequential complete backscattering of edge states. Gate-controlled manipulation of edge states offers a new angle to the exploration of quantum Hall magnetism and fractional quantum Hall effect in bilayer graphene.

  1. 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.

  2. Interaction of ionizing radiation with other physical and chemical factors in improving the safety and storage stability of foods

    International Nuclear Information System (INIS)

    Farkas, J.; Adrassy, E.; Nanati, D.; Horti, K.; Meszaros, L.; Reichart, O.

    1998-01-01

    Experiments on the preservation of a vacuum packed, ready to fry, chilled meat product (tenderloin rolls), using the combination of a 2 kGy radiation dose with a reduction in pH and/or a reduction in water activity, and on the fate of Listeria monocytogenes in this product were carried out. Irradiation caused a 1-2 decimal reduction in the aerobic viable cell counts, and a 4 decimal reduction in the Enterobacteriaceae counts. Lactic acid bacteria appeared to be more resistant, and were the dominant component of the microflora during chilled storage. Combination treatments prevented growth of Enterobacteriaceae, even at 10 deg. C refrigeration. The microbial stability of the chilled product at 2 deg. C was extended for at least 5 weeks by the triple combination of a dose of 2 kGy, pH reduction to approximately 5.6 and water activity reduction to about 0.960. The combined preserved product proved to be acceptable, both sensorially and from the point of view of the thiobarbituric acid values. The ascorbic acid (as the acidulant) and Na lactate (as the humectant) additives considerably reduced the radiolytic loss of thiamine. The Listeria inoculum survived well in the chilled, non-irradiated product, but diminished by 2 log cycles as a result of irradiation; it tended to decrease even further during post-irradiation storage. In model studies, the radiation survivors of L. monocytogenes showed significantly increased salt and pH sensitivities and an increased minimum temperature for growth in tryptic phosphate broth media, but were less sensitized when recovering in brain heat infusion broth media. A reduction in pH resulted in an increase in not only the apparent lag phase of growth of this test organism but also in the lag phase ratios between the irradiated and non-irradiated populations. The predictive mathematical equations that describe the combined effect of hydrogen ion and salt concentrations on the growth parameters at 30 deg. C were constructed for

  3. Electronic and Optical Properties of Twisted Bilayer Graphene

    Science.gov (United States)

    Huang, Shengqiang

    The ability to isolate single atomic layers of van der Waals materials has led to renewed interest in the electronic and optical properties of these materials as they can be fundamentally different at the monolayer limit. Moreover, these 2D crystals can be assembled together layer by layer, with controllable sequence and orientation, to form artificial materials that exhibit new features that are not found in monolayers nor bulk. Twisted bilayer graphene is one such prototype system formed by two monolayer graphene layers placed on top of each other with a twist angle between their lattices, whose electronic band structure depends on the twist angle. This thesis presents the efforts to explore the electronic and optical properties of twisted bilayer graphene by Raman spectroscopy and scanning tunneling microscopy measurements. We first synthesize twisted bilayer graphene with various twist angles via chemical vapor deposition. Using a combination of scanning tunneling microscopy and Raman spectroscopy, the twist angles are determined. The strength of the Raman G peak is sensitive to the electronic band structure of twisted bilayer graphene and therefore we use this peak to monitor changes upon doping. Our results demonstrate the ability to modify the electronic and optical properties of twisted bilayer graphene with doping. We also fabricate twisted bilayer graphene by controllable stacking of two graphene monolayers with a dry transfer technique. For twist angles smaller than one degree, many body interactions play an important role. It requires eight electrons per moire unit cell to fill up each band instead of four electrons in the case of a larger twist angle. For twist angles smaller than 0.4 degree, a network of domain walls separating AB and BA stacking regions forms, which are predicted to host topologically protected helical states. Using scanning tunneling microscopy and spectroscopy, these states are confirmed to appear on the domain walls when inversion

  4. Feedback stabilization of MHD instabilities. Report on the Workshop held at Princeton Plasma Physics Lab., Princeton Univ., Princeton, New Jersey, United States of America, 11-13 December 1996

    International Nuclear Information System (INIS)

    McGuire, K.M.; Kugel, H.W.; La Haye, R.J.; Mauel, M.E.; Nevins, W.M.; Prager, S.C.

    1997-01-01

    The transient operating performance of magnetic confinement devices is often limited by one or two unstable MHD modes. The feedback stabilization of MHD instabilities is an area of research that is critical for improving the steady state performance and economic attractiveness of magnetic confinement devices. This growing realization motivated a Workshop dedicated to feedback stabilization of MHD instabilities, which was held from 11 to 13 December 1996 at Princeton Plasma Physics Laboratory. The resulting presentations, conclusions and recommendations are summarized. (author)

  5. Complex boron redistribution kinetics in strongly doped polycrystalline-silicon/nitrogen-doped-silicon thin bi-layers

    Energy Technology Data Exchange (ETDEWEB)

    Abadli, S. [Department of Electrical Engineering, University Aout 1955, Skikda, 21000 (Algeria); LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Mansour, F. [LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Pereira, E. Bedel [CNRS-LAAS, 7 avenue du colonel Roche, 31077 Toulouse (France)

    2012-10-15

    We have investigated the complex behaviour of boron (B) redistribution process via silicon thin bi-layers interface. It concerns the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method at 480 C, by using in-situ nitrogen-doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P{sup +}) layer. To avoid long-range B redistributions, thermal annealing was carried out at relatively low-temperatures (600 C and 700 C) for various times ranging between 30 min and 2 h. To investigate the experimental secondary ion mass spectroscopy (SIMS) doping profiles, a redistribution model well adapted to the particular structure of two thin layers and to the effects of strong-concentrations has been established. The good adjustment of the simulated profiles with the experimental SIMS profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders. The increasing kinetics of the B peak concentration near the bi-layers interface is well reproduced by the established model. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Formulation of bi-layer matrix tablets of tramadol hydrochloride: Comparison of rate retarding ability of the incorporated hydrophilic polymers.

    Science.gov (United States)

    Arif, Hasanul; Al-Masum, Abdullah; Sharmin, Florida; Reza, Selim; Sm Islam, Sm Ashraful

    2015-05-01

    Bi-layer tablets of tramadol hydrochloride were prepared by direct compression technique. Each tablet contains an instant release layer with a sustained release layer. The instant release layer was found to release the initial dose immediately within minutes. The instant release layer was combined with sustained release matrix made of varying quantity of Methocel K4M, Methocel K15MCR and Carbomer 974P. Bi-layer tablets were evaluated for various physical tests including weight variation, thickness and diameter, hardness and percent friability. Drug release from bi-layer tablet was studied in acidic medium and buffer medium for two and six hours respectively. Sustained release of tramadol hydrochloride was observed with a controlled fashion that was characteristic to the type and extent of polymer used. % Drug release from eight-hour dissolution study was fitted with several kinetic models. Mean dissolution time (MDT) and fractional dissolution values (T25%, T50% and T80%) were also calculated as well, to compare the retarding ability of the polymers. Methocel K15MCR was found to be the most effective in rate retardation of freely water-soluble tramadol hydrochloride compared to Methocel K4M and Capbomer 974P, when incorporated at equal ratio in the formulation.

  7. Phonon stiffen and soften at zigzag- and armchair-dominated edges of exfoliated bilayer graphene ribbon presented by Raman spectra

    Science.gov (United States)

    Xia, Minggang; Zhou, Xiaohua; Xin, Duqiang; Xu, Qiang

    2018-01-01

    The Raman spectra at the edge of the exfoliated bilayer graphene ribbon (GR) were investigated in detail. Results show that both G and 2D phonons stiffen (wave number increases) at zigzag-dominated edge, while they soften at armchair-dominated edge compared with those at the middle position in the GR. Furthermore, the full widths at half maximum intensity of both G and 2D Raman peaks narrow at the zigzag-dominated edge, while they broaden at the armchair-dominated edge. The stiffness and softness are attributed to the C-C bonds at the edge. For zigzag-dominated edge, the stiffness may originate in the increase of the force constant induced by the shrinking of C-C bond. For armchair-dominated edge, the softness may be due to the decrease of the force constant induced by the unsaturated hanging bonds at edge, which is different from Kohn anomaly and charge doping. The analysis is in agreement well with others calculation results about C-C bonds and the edge energy. These results may be useful to understand physical properties at the bilayer graphene edge and for applications in the device by taking advantage of the edge states in bilayer graphene.

  8. Fabrication and characterization of an integrated ionic device from suspended polypyrrole and alamethicin-reconstituted lipid bilayer membranes

    International Nuclear Information System (INIS)

    Northcutt, Robert; Sundaresan, Vishnu-Baba

    2012-01-01

    Conducting polymers are electroactive materials that undergo conformal relaxation of the polymer backbone in the presence of an electrical field through ion exchange with solid or aqueous electrolytes. This conformal relaxation and the associated morphological changes make conducting polymers highly suitable for actuation and sensing applications. Among smart materials, bioderived active materials also use ion transport for sensing and actuation functions via selective ion transport. The transporter proteins extracted from biological cell membranes and reconstituted into a bilayer lipid membrane in bioderived active materials regulate ion transport for engineering functions. The protein transporter reconstituted in the bilayer lipid membrane is referred to as the bioderived membrane and serves as the active component in bioderived active materials. Inspired by the similarities in the physics of transduction in conducting polymers and bioderived active materials, an integrated ionic device is formed from the bioderived membrane and the conducting polymer membrane. This ionic device is fabricated into a laminated thin-film membrane and a common ion that can be processed by the bioderived and the conducting polymer membranes couple the ionic function of these two membranes. An integrated ionic device, fabricated from polypyrrole (PPy) doped with sodium dodecylbenzenesulfonate (NaDBS) and an alamethicin-reconstituted DPhPC bilayer lipid membrane, is presented in this paper. A voltage-gated sodium current regulates the electrochemical response in the PPy(DBS) layer. The integrated device is fabricated on silicon-based substrates through microfabrication, electropolymerization, and vesicle fusion, and ionic activity is characterized through electrochemical measurements. (paper)

  9. COMPARISON OF PHYSICAL STABILITY PROPERTIES OF POMEGRANATE SEED OIL NANOEMULSION DOSAGE FORMS WITH LONG-CHAIN TRIGLYCERIDE AND MEDIUM-CHAIN TRIGLYCERIDE AS THE OIL PHASE

    Directory of Open Access Journals (Sweden)

    Sri Hartanti Yuliani

    2016-08-01

    Full Text Available Pomegranate seed oil has antioxidant, anti-inflammatory, and chemo preventive activities. Pomegranate seed oil is lipophilic substance suitable to be prepared in emulsion dosage forms. Long-chain triglyceride (LCT and medium-chain triglyceride (MCT are commonly used as oil phase in emulsion dosage forms. This research aimed to compare the use of LCT and MCT in the Nano emulsion formula of pomegranate seed oil dosage forms. Formulation of pomegranate seed oil Nano emulsion was conducted using high energy emulsification. Parameters observed were pH, Nano emulsion type, percent transmittance, viscosity, turbidity, and droplet size before and after 3 cycles of freeze-thaw. The result showed that there was no significant difference between physical properties of pomegranate oil Nano emulsion with LCT as oil phase and pomegranate oil Nano emulsion with MCT as oil phase. Moreover, physical stability of pomegranate oil Nano emulsion with LCT as oil phase was better than pomegranate oil Nano emulsion with MCT as oil phase.

  10. Deuterium and phosphorus-31 nuclear magnetic resonance study of the interaction of melittin with dimyristoylphosphatidylcholine bilayers and the effects of contaminating phospholipase A2

    International Nuclear Information System (INIS)

    Dempsey, C.E.; Watts, A.

    1987-01-01

    The interaction of bee venom melittin with dimyristoylphosphatidylcholine (DMPC) selectively deuteriated in the choline head group has been studied by deuterium and phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. The action of residual phospholipase A 2 in melittin samples resulted in mixtures of DMPC and its hydrolytic products that underwent reversible transitions at temperatures between 30 and 35 0 C from extended bilayers to micellar particles which gave narrow single-line deuterium and phosphorus-31 NMR spectra. Similar transitions were observed in DMPC-myristoyllysophosphatidylcholine (lysoPC)-myristic acid mixtures containing melittin but not in melittin-free mixtures, indicating that melittin is able to stabilize extended bilayers containing DMPC and its hydrolytic products in the liquid-crystalline phase. Melittin, free of phospholipase A 2 activity, and at 3-5 mol % relative to DMPC, induced reversible transitions between extended bilayers and micellar particles on passing through the liquid-crystalline to gel phase transition temperature of the lipid, effects similar to those observed in melittin-acyl chain deuteriated dipalmitoylphosphatidylcholine (DPPC) mixtures. LysoPC at concentrations of 20 mol % or greater relative to DMPC induced transitions between extended bilayers and micellar particles with characteristics similar to those induced by melittin. It is proposed that these melittin- and lysoPC-induced transitions share similar mechanisms. The effects of melittin on the quadrupole splittings and T 1 relaxation times of head-group-deuteriated DMPC in the liquid-crystalline phase share features similar to the effects of metal ions on DPPC head groups, indicating that the conformational properties of the choline head group in PC bilayers may be affected by melittin and by metal ions in a similar manner

  11. Deuterium and phosphorus-31 nuclear magnetic resonance study of the interaction of melittin with dimyristoylphosphatidylcholine bilayers and the effects of contaminating phospholipase A/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Dempsey, C.E.; Watts, A.

    1987-09-08

    The interaction of bee venom melittin with dimyristoylphosphatidylcholine (DMPC) selectively deuteriated in the choline head group has been studied by deuterium and phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. The action of residual phospholipase A/sub 2/ in melittin samples resulted in mixtures of DMPC and its hydrolytic products that underwent reversible transitions at temperatures between 30 and 35/sup 0/C from extended bilayers to micellar particles which gave narrow single-line deuterium and phosphorus-31 NMR spectra. Similar transitions were observed in DMPC-myristoyllysophosphatidylcholine (lysoPC)-myristic acid mixtures containing melittin but not in melittin-free mixtures, indicating that melittin is able to stabilize extended bilayers containing DMPC and its hydrolytic products in the liquid-crystalline phase. Melittin, free of phospholipase A/sub 2/ activity, and at 3-5 mol % relative to DMPC, induced reversible transitions between extended bilayers and micellar particles on passing through the liquid-crystalline to gel phase transition temperature of the lipid, effects similar to those observed in melittin-acyl chain deuteriated dipalmitoylphosphatidylcholine (DPPC) mixtures. LysoPC at concentrations of 20 mol % or greater relative to DMPC induced transitions between extended bilayers and micellar particles with characteristics similar to those induced by melittin. It is proposed that these melittin- and lysoPC-induced transitions share similar mechanisms. The effects of melittin on the quadrupole splittings and T/sub 1/ relaxation times of head-group-deuteriated DMPC in the liquid-crystalline phase share features similar to the effects of metal ions on DPPC head groups, indicating that the conformational properties of the choline head group in PC bilayers may be affected by melittin and by metal ions in a similar manner.

  12. Physical stability, centrifugation tests, and entrapment efficiency studies of carnauba wax-decyl oleate nanoparticles used for the dispersion of inorganic sunscreens in aqueous media.

    Science.gov (United States)

    Villalobos-Hernández, J R; Müller-Goymann, C C

    2006-06-01

    Aqueous nanoscale lipid dispersions consisting of carnauba wax-decyl oleate mixtures acting as carriers or accompanying vehicles for inorganic sunscreens such as barium sulfate, strontium carbonate, and titanium dioxide were prepared by high pressure homogenization. For the manufacture of these nanosuspensions, three pigment concentrations (%wt), namely 2, 4, and 6, and two carnauba wax-decyl oleate ratios, 1:1 and 2:1, were used, being some of these combinations chosen for stability studies. Six-month physical stability tests at 4, 20, and 40 degrees C selecting the mean particle size and the polydispersity index of the nanosuspensions as reference parameters were performed. Centrifugation tests of the nanosuspensions assessed by transmission electron microscopy and by the determination of the content of pigments and carnauba wax in the separated fractions were done. The mean particle sizes and the polydispersity indices of the nanosuspensions were not altered after six-month storages at 20 and at 40 degrees C. However, the storage of those at 4 degrees C considerably increased the particle size and polydispersity of the systems, particularly when wax-oil ratios (2:1) were used for the entrapment of the pigments. Transmission electron micrographs of centrifuged samples denoted the presence of three major fractions showing the different types of particles integrated into the nanosuspensions. Furthermore, it was observed that not all the carnauba wax participated in the entrapment of the pigment. Regarding the amount of pigment being encapsulated or bonded by the wax-oil matrices, entrapment efficiencies higher than 85.52% were reported.

  13. Heat treatment and gamma radiation effects on the physical-chemical, microbiological and sensory stability of pure sugarcane juice or added with fruit juices, stored under refrigeration

    International Nuclear Information System (INIS)

    Oliveira, Aline Cristine Garcia de

    2007-01-01

    Sugarcane juice is a taste drink, energetic, no alcoholic that conserves all the nutrients in cane sugar. It was very appreciated by the Brazilian population and its production has been shown to be a highly lucrative business. This research had the following objectives: evaluate the acceptance of the consuming market and the stability of pure sugarcane juice or added with natural fruit juices, submitted of heat treatment (70 deg C/ 25 min) and/ or gamma radiation (2,5 kGy) and stored in high density polyethylene bottles, under refrigeration (5 +- 1 deg C). Sugarcane juice market test was evaluated through the application of 350 questionnaires on six Sao Paulo cities. Sugarcane juice stability was evaluated through microbiological (psychotropic count, lactic bacteria and yeasts and molds count), physical-chemical (pH, color, titratable acidity, soluble solids, ratio and polyphenoloxidase activity) and sensory (hedonic test) parameters. Centesimal composition was determined analyzing: humidity, caloric value, total carbohydrates, total and reducing sugars, lipids, proteins, ascorbic acid, ash and minerals. Sugarcane juice shelf life period was determinate ever 7 days over a period of 42 days stored under refrigeration. The data were submitted to the variance analysis and compared by Tukey's test (p<0,05). Among the 350 interviewed people, more of the half one is interested about its habitual food safe and care about street foods. Sandwiches had been cited foods as routinely consumed, followed for the sugarcane juice and 'pastel'. Among the interviewed ones, 80% had mentioned to appreciate sugarcane juice. It had not correlation between age and school age and the preference for the consumption form was with lemon juice addition. About 55% of the interviewed ones had mentioned that would more frequently consume sugarcane juice processed and packed. Sugarcane juice processing did not modify the flavor and taste of the drink. It was concluded from the sensory analyses

  14. 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

  15. 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.

  16. Unidirectional Spin-Wave-Propagation-Induced Seebeck Voltage in a PEDOT:PSS/YIG Bilayer

    Science.gov (United States)

    Wang, P.; Zhou, L. F.; Jiang, S. W.; Luan, Z. Z.; Shu, D. J.; Ding, H. F.; Wu, D.

    2018-01-01

    We clarify the physical origin of the dc voltage generation in a bilayer of a conducting polymer film and a micrometer-thick magnetic insulator Y3Fe5O12 (YIG) film under ferromagnetic resonance and/or spin wave excitation conditions. The previous attributed mechanism, the inverse spin Hall effect in the polymer [Nat. Mater. 12, 622 (2013), 10.1038/nmat3634], is excluded by two control experiments. We find an in-plane temperature gradient in YIG which has the same angular dependence with the generated voltage. Both vanish when the YIG thickness is reduced to a few nanometers. Thus, we argue that the dc voltage is governed by the Seebeck effect in the polymer, where the temperature gradient is created by the nonreciprocal magnetostatic surface spin wave propagation in YIG.

  17. Lab on a Biomembrane: Rapid prototyping and manipulation of 2D fluidic lipid bilayers circuits

    Science.gov (United States)

    Ainla, Alar; Gözen, Irep; Hakonen, Bodil; Jesorka, Aldo

    2013-01-01

    Lipid bilayer membranes are among the most ubiquitous structures in the living world, with intricate structural features and a multitude of biological functions. It is attractive to recreate these structures in the laboratory, as this allows mimicking and studying the properties of biomembranes and their constituents, and to specifically exploit the intrinsic two-dimensional fluidity. Even though diverse strategies for membrane fabrication have been reported, the development of related applications and technologies has been hindered by the unavailability of both versatile and simple methods. Here we report a rapid prototyping technology for two-dimensional fluidic devices, based on in-situ generated circuits of phospholipid films. In this “lab on a molecularly thin membrane”, various chemical and physical operations, such as writing, erasing, functionalization, and molecular transport, can be applied to user-defined regions of a membrane circuit. This concept is an enabling technology for research on molecular membranes and their technological use. PMID:24067786

  18. Analog of electromagnetically induced transparency at terahertz frequency based on a bilayer-double-H-metamaterial

    Science.gov (United States)

    Wang, Yue'e.; Li, Zhi; Hu, Fangrong

    2018-01-01

    We designed a bilayer-double-H-metamaterials (BDHM) composed of two layers of metal and two layers of dielectric to analog a spectral response of electromagnetically induced transparency (EIT) at terahertz frequency. By changing the incident angle, the BDHM exhibits an EIT-like spectral response. The tunable spectral performances and modulation mechanism of the transparent peak are theoretically investigated using full-wave electromagnetic simulation software. The physical mechanism of the EIT-like effect is based on the constructive and destructive interference between the induced electrical dipoles. Our work provides a new way to realize the EIT-like effect only by changing the incident angles of the metamaterials. The potential applications include tunable filters, sensors, attenuators, switches, and so on.

  19. The statistical stability phenomenon

    CERN Document Server

    Gorban, Igor I

    2017-01-01

    This monograph investigates violations of statistical stability of physical events, variables, and processes and develops a new physical-mathematical theory taking into consideration such violations – the theory of hyper-random phenomena. There are five parts. The first describes the phenomenon of statistical stability and its features, and develops methods for detecting violations of statistical stability, in particular when data is limited. The second part presents several examples of real processes of different physical nature and demonstrates the violation of statistical stability over broad observation intervals. The third part outlines the mathematical foundations of the theory of hyper-random phenomena, while the fourth develops the foundations of the mathematical analysis of divergent and many-valued functions. The fifth part contains theoretical and experimental studies of statistical laws where there is violation of statistical stability. The monograph should be of particular interest to engineers...

  20. Conformal bi-layered perovskite/spinel coating on a metallic wire network for solid oxide fuel cells via an electrodeposition-based route

    Science.gov (United States)

    Park, Beom-Kyeong; Song, Rak-Hyun; Lee, Seung-Bok; Lim, Tak-Hyoung; Park, Seok-Joo; Jung, WooChul; Lee, Jong-Won

    2017-04-01

    Solid oxide fuel cells (SOFCs) require low-cost metallic components for current collection from electrodes as well as electrical connection between unit cells; however, the degradation of their electrical properties and surface stability associated with high-temperature oxidation is of great concern. It is thus important to develop protective conducting oxide coatings capable of mitigating the degradation of metallic components under SOFC operating conditions. Here, we report a conformal bi-layered coating composed of perovskite and spinel oxides on a metallic wire network fabricated by a facile electrodeposition-based route. A highly dense, crack-free, and adhesive bi-layered LaMnO3/Co3O4 coating of ∼1.2 μm thickness is conformally formed on the surfaces of wires with ∼100 μm diameter. We demonstrate that the bi-layered LaMnO3/Co3O4 coating plays a key role in improving the power density and durability of a tubular SOFC by stabilizing the surface of the metallic wire network used as a cathode current collector. The electrodeposition-based technique presented in this study offers a low-cost and scalable process to fabricate conformal multi-layered coatings on various metallic structures.