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Sample records for bilayers stability physical

  1. Thermal stability of Mo/Au bilayers for TES applications

    International Nuclear Information System (INIS)

    Mo/Au bilayers are among the most suitable materials to be used as transition-edge sensors (TES) in cryogenic microcalorimeters and bolometers, developed, among other fields, for space missions. For this purpose the thermal stability of TES at temperatures below 150 °C is a critical issue. We report on the dependence of functional properties (superconducting critical temperature, residual resistance and α) as well as on microstructure, chemical composition and interface quality for optimized high quality Mo/Au bilayers on annealing temperature and time. Data show that the functional properties of the bilayers remain stable at T C at T ≥ 200 °C are mainly due to an increase in the average Au grain size and to Au migration along the Mo grain boundaries at the Au/Mo interface. A way to stabilize the functional properties of the Mo/Au bilayers against temperature enhancements is proposed. (paper)

  2. Stability analysis of the pulmonary liquid bilayer.

    Science.gov (United States)

    Halpern, David; Grotberg, James

    2010-11-01

    The lung consists of liquid-lined compliant airways that convey air to and from the alveoli where gas exchange takes place. Because the airways are coated with a bilayer consisting of a mucus layer on top of a periciliary fluid layer, a surface tension instability can generate flows within the bilayer and induce the formation of liquid plugs that block the passage of air. This is a problem for example with premature neonates whose lungs do not produce sufficient quantities of surfactant and suffer from respiratory distress syndrome. To study this instability a system of coupled nonlinear evolution equations are derived using lubrication theory for the thicknesses of the two liquid layers which are assumed to be Newtonian. A normal mode analysis is used to investigate the initial growth of the disturbances, and reveals how the grow rate is affected by the ratio of viscosities λ, film thicknesses η and surface tensions δ of the two layers which can change by disease. Numerical solutions of the evolution equations show that there is a critical bilayer thickness ɛc above which closure occurs, and that a more viscous and thicker layer compared to the periciliary layer closes more slowly. However, ɛcis weakly dependent on λ, η and δ. We also examine the potential impact of wall shear stress and normal stress on cell damage. This work is funded by NIH HL85156.

  3. On the stability of foams made with surfactant bilayer phases.

    Science.gov (United States)

    Briceño-Ahumada, Zenaida; Maldonado, Amir; Impéror-Clerc, Marianne; Langevin, Dominique

    2016-02-01

    The stability of foams made with sponge phases (L3 phases) and lamellar phases (L(α) phases), both containing surfactant bilayers, has been investigated. The extreme stability of foams made with lamellar phases seems essentially due to the high viscosity of the foaming solution, which slows down gravity drainage. Moreover, the foams start draining only when the buoyancy stress overcomes the yield stress of the L(α) phase. The bubble growth associated with gas transfer is unusual: it follows a power law with an exponent smaller than those corresponding to Ostwald ripening (wet foams) and to coarsening (dry foams). The foams made with sponge phases are in turn very unstable, even less stable than pure surfactant foams made with glycerol solutions having the same viscosity. The fact that the surfactant bilayers in the sponge phase have a negative Gaussian curvature could facilitate bubble coalescence. PMID:26647140

  4. BI-LAYER HYBRID BIOCOMPOSITES: CHEMICAL RESISTANT AND PHYSICAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Mohammad Jawaid,

    2012-02-01

    Full Text Available Bi-layer hybrid biocomposites were fabricated by hand lay-up technique by reinforcing oil palm empty fruit bunch (EFB and jute fibre mats with epoxy matrix. Hybrid composites were prepared by varying the relative weight fraction of the two fibres. The physical (void content, density, dimensional stability, and chemical resistant properties of hybrid composites were evaluated. When the jute fibre loading increased in hybrid composites, physical and chemical resistant properties of hybrid composites were enhanced. Void content of hybrid composites decreased with an increase in jute fibre loading because jute fibres showed better fibre/matrix interface bonding, which leads to a reduction in voids. The density of hybrid composite increased as the quantity of jute fibre loading increased. The hybridization of the jute fibres with EFB composite improved the dimensional stability of the hybrid composites. The performance of hybrid composites towards chemical reagents improved with an increase in jute fibre loading as compared to the EFB composite. The combination of oil palm EFB/jute fibres with epoxy matrix produced hybrid biocomposites material that is competitive to synthetic composites.

  5. Biaxially aligned buffer layers of cerium oxide, yttria stabilized zirconia, and their bilayers

    International Nuclear Information System (INIS)

    Biaxially aligned cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55 degree to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth of CeO2 by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBAD CeO2 and YSZ films, and the CeO2/YSZ bilayers have a (111) pole in the ion beam direction. copyright 1997 American Institute of Physics

  6. Monolayer curvature stabilizes nanoscale raft domains in mixed lipid bilayers

    CERN Document Server

    Meinhardt, Sebastian; Schmid, Friederike

    2013-01-01

    According to the lipid raft hypothesis, biological lipid membranes are laterally heterogeneous and filled with nanoscale ordered "raft" domains, which are believed to play an important role for the organization of proteins in membranes. However, the mechanisms stabilizing such small rafts are not clear, and even their existence is sometimes questioned. Here we report the observation of raft-like structures in a coarse-grained molecular model for multicomponent lipid bilayers. On small scales, our membranes demix into a liquid ordered (lo) and a liquid disordered (ld) phase. On large scales, phase separation is suppressed and gives way to a microemulsion-type state that contains nanometer size lo domains in a ld environment. Furthermore, we introduce a mechanism that generates rafts of finite size by a coupling between monolayer curvature and local composition. We show that mismatch between the spontaneous curvatures of monolayers in the lo and ld phase induces elastic interactions, which reduce the line tensi...

  7. Bilayer graphene: physics and application outlook in photonics

    Directory of Open Access Journals (Sweden)

    Yan Hugen

    2015-05-01

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

  8. The Bilayer Enhances Rhodopsin Kinetic Stability in Bovine Rod Outer Segment Disk Membranes

    OpenAIRE

    Corley, Scott C.; Sprangers, Peter; Albert, Arlene D.

    2011-01-01

    Rhodopsin is a kinetically stable protein constituting >90% of rod outer segment disk membrane protein. To investigate the bilayer contribution to rhodopsin kinetic stability, disk membranes were systematically disrupted by octyl-β-D-glucopyranoside. Rhodopsin kinetic stability was examined under subsolubilizing (rhodopsin in a bilayer environment perturbed by octyl-β-D-glucopyranoside) and under fully solubilizing conditions (rhodopsin in a micelle with cosolubilized phospholipids). As deter...

  9. Regulation of channel function due to physical energetic coupling with a lipid bilayer

    International Nuclear Information System (INIS)

    Highlights: • Lipid membrane regulation of membrane protein functions has been addressed. • Energetics behind ion channel-membrane coupling phenomena has been investigated. • Charge based interactions stabilize peptide–lipid complex. • Screened Coulomb interaction model explains the energetics. • Van der Waals and electrostatic forces drive peptides and lipids to close proximity. - Abstract: Regulation of membrane protein functions due to hydrophobic coupling with a lipid bilayer has been investigated. An energy formula describing interactions between lipid bilayer and integral ion channels with different structures, which is based on the screened Coulomb interaction approximation, has been developed. Here the interaction energy is represented as being due to charge-based interactions between channel and lipid bilayer. The hydrophobic bilayer thickness channel length mismatch is found to induce channel destabilization exponentially while negative lipid curvature linearly. Experimental parameters related to channel dynamics are consistent with theoretical predictions. To measure comparable energy parameters directly in the system and to elucidate the mechanism at an atomistic level we performed molecular dynamics (MD) simulations of the ion channel forming peptide–lipid complexes. MD simulations indicate that peptides and lipids experience electrostatic and van der Waals interactions for short period of time when found within each other’s proximity. The energies from these two interactions are found to be similar to the energies derived theoretically using the screened Coulomb and the van der Waals interactions between peptides (in ion channel) and lipids (in lipid bilayer) due to mainly their charge properties. The results of in silico MD studies taken together with experimental observable parameters and theoretical energetic predictions suggest that the peptides induce ion channels inside lipid membranes due to peptide–lipid physical interactions

  10. Regulation of channel function due to physical energetic coupling with a lipid bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Ashrafuzzaman, Md., E-mail: mashrafuzzaman@ksu.edu.sa [Department of Biochemistry, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia); Tseng, C.-Y. [Department of Oncology, University of Alberta, Edmonton (Canada); Tuszynski, J.A. [Department of Oncology, University of Alberta, Edmonton (Canada); Department of Physics, University of Alberta, Edmonton (Canada)

    2014-03-07

    Highlights: • Lipid membrane regulation of membrane protein functions has been addressed. • Energetics behind ion channel-membrane coupling phenomena has been investigated. • Charge based interactions stabilize peptide–lipid complex. • Screened Coulomb interaction model explains the energetics. • Van der Waals and electrostatic forces drive peptides and lipids to close proximity. - Abstract: Regulation of membrane protein functions due to hydrophobic coupling with a lipid bilayer has been investigated. An energy formula describing interactions between lipid bilayer and integral ion channels with different structures, which is based on the screened Coulomb interaction approximation, has been developed. Here the interaction energy is represented as being due to charge-based interactions between channel and lipid bilayer. The hydrophobic bilayer thickness channel length mismatch is found to induce channel destabilization exponentially while negative lipid curvature linearly. Experimental parameters related to channel dynamics are consistent with theoretical predictions. To measure comparable energy parameters directly in the system and to elucidate the mechanism at an atomistic level we performed molecular dynamics (MD) simulations of the ion channel forming peptide–lipid complexes. MD simulations indicate that peptides and lipids experience electrostatic and van der Waals interactions for short period of time when found within each other’s proximity. The energies from these two interactions are found to be similar to the energies derived theoretically using the screened Coulomb and the van der Waals interactions between peptides (in ion channel) and lipids (in lipid bilayer) due to mainly their charge properties. The results of in silico MD studies taken together with experimental observable parameters and theoretical energetic predictions suggest that the peptides induce ion channels inside lipid membranes due to peptide–lipid physical interactions

  11. Hydrogel-Stabilized Droplet Bilayers for High Speed Solution Exchange

    Science.gov (United States)

    Acharya, Shiv A.; Portman, Alexander; Salazar, Carl S.; Schmidt, Jacob J.

    2013-11-01

    Many applications utilizing artificial lipid bilayers require the ability to exchange the bilayer's solution environment. However, because of the instability of the bilayer, the rate of solution exchange is limited, which significantly hinders the measurement rate and throughput. We have developed an artificial bilayer system that can withstand high flow speeds, up to 2.1 m/s, by supporting the bilayer with a hydrogel. We demonstrated the ability to measure during flow by measuring the conductance of gramicidin-A channels while switching between solutions of two different compositions, recording a time to measure 90% change in current of approximately 2.7 seconds at a flow rate of 0.1 m/s. We also demonstrated a potential application of this system by measuring the conductance modulation of the rat TRPM8 ion channel by an agonist and antagonist at varying concentrations, obtaining 7-point IC50 and EC50 values in approximately 7 minutes and 4-point values within 4 minutes.

  12. STABILITY AND MORPHOLOGICAL EVOLUTION IN POLYMER/NANOPARTICLE BILAYERS AND BLENDS CONFINED TO THIN FILM GEOMETRIES

    OpenAIRE

    Paul, Rituparna

    2007-01-01

    Thin film bilayers and blends composed of polymers and nanoparticles are increasingly important for technological applications that range from space survivable coatings to novel drug delivery systems. Dewetting or spontaneous hole formation in amorphous polymer films and phase separation in multicomponent polymer films can hinder the stability of these systems at elevated temperatures. Hence, fundamental understanding of dewetting and phase separation in polymer/nanoparticle bilayer and blen...

  13. The Stability and Charge Carriers in Bilayer Silicene

    OpenAIRE

    Rui, Wang; Shaofeng, Wang; Xiaozhi, Wu

    2013-01-01

    The structure optimization, phonon, and ab initio ?nite temperature molecular dynamics calculations have been performed to predict that bilayer silicene has stable structure with AB stacking geometry and is more favorable energetically to synthesize than monolayer silicene, a two-dimensional honeycomb lattice with buckled geometry. Marvellously, its electronic bands show that the charge carriers behave like relativistic Dirac fermions with linear energy dispersions near the K points. An insig...

  14. 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.

  15. Stability of a melittin pore in a lipid bilayer a molecular dynamics study

    OpenAIRE

    Lin, J -H; Baumgärtner, A

    2000-01-01

    We have investigated the configuration and the stability of a single membrane pore bound by four melittin molecules and embedded in a fully hydrated bilayer lipid membrane. We used molecular dynamics simulations up to 5.8 ns. It is found that the initial tetrameric configuration decays with increasing time into a stable trimer and one monomer. This continuous transformation is accompanied by a lateral expansion of the aqueous pore exhibiting a final size comparable to experimental findings. T...

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

    Science.gov (United States)

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

    2014-10-01

    The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, 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 MoS2 on nanoelectronic applications.

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

    International Nuclear Information System (INIS)

    The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, 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 MoS2 on nanoelectronic applications. (condensed matter: structural, mechanical, and thermal properties)

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

    CERN Document Server

    van Gennip, Yves

    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 a Fourier series we fully characterise the stability of the structures in terms of the energy parameters. In the course of our computations we also give the Green's function for the Laplacian on a periodic strip and explain the heuristic method by which we found it.

  19. Improved stability of free-standing lipid bilayers based on nanoporous alumina films

    Science.gov (United States)

    Hirano-Iwata, Ayumi; Taira, Tasuku; Oshima, Azusa; Kimura, Yasuo; Niwano, Michio

    2010-05-01

    In this study, we propose a method for improving the stability of free-standing bilayer lipid membranes (BLMs) by preparing BLMs across nanoporous alumina films. The use of porous alumina reduced individual membrane size to improve the BLM stability. The BLMs were stable under an applied voltage of ±1 V. The lifetime of the BLMs was 16-30 h with and without incorporated gramicidin channels. Electric properties of the BLMs as a platform for channel-current recordings are also discussed. Since the total area of the BLMs is still large to facilitate protein incorporation, our approach is useful for designing highly sensitive biosensors based on channel proteins.

  20. Biaxially aligned buffer layers of cerium oxide, yttria stabilized zirconia, and their bilayers

    Science.gov (United States)

    Gnanarajan, S.; Katsaros, A.; Savvides, N.

    1997-05-01

    Biaxially aligned cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55° to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth of CeO2 by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBAD CeO2 and YSZ films, and the CeO2/YSZ bilayers have a (111) pole in the ion beam direction.

  1. Physics and applications of novel structures with CVD graphene: edges, grain boundaries, twisted bilayers, and hybrids

    Science.gov (United States)

    Chen, Yong P.

    2014-03-01

    In this talk, I will discuss experimental studies (including electronic transport, optical/Raman, and STM) of physical properties of various novel synthetic graphene structures formed in CVD graphene grown on Cu, including edges of graphene single crystals, grain boundaries between such single crystals, and twisted bilayer graphene. Such synthetic graphene structures could be used as playground to explore novel physics and engineer new functionalities in graphene based electronic devices. Furthermore, I will discuss graphene based ``hybrid'' materials combining CVD graphene with semiconductor and metallic nanostructures for potential optoelectronic and plasmonics applications.

  2. Docosahexaenoic acid and eicosapentaenoic acid induce changes in the physical properties of a lipid bilayer model membrane.

    Science.gov (United States)

    Onuki, Yoshinori; Morishita, Mariko; Chiba, Yoshiyuki; Tokiwa, Shinji; Takayama, Kozo

    2006-01-01

    We investigated the effect of fatty acids such as stearic acid (SA, 18:0), oleic acid (OA, 18:1), eicosapentaenoic acid (EPA, 20:5), and docosahexaenoic acid (DHA, 22:6) on a dipalmitoylphosphatidylcholine (DPPC) bilayer by determining the phase transition temperature, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH), and detergent insolubility. Treatment with unsaturated fatty acid broadened and shifted the phase transitions of the DPPC bilayer to a lower temperature. The phase transition temperature and the value of fluorescence anisotropy of DPH at 37 degrees C decreased progressively with increasing treatment amounts of unsaturated fatty acid. A large amount of the DPPC bilayer treated with unsaturated fatty acid was dissolved in Triton X-100, obtaining a low level of detergent insolubility. These modifications of the bilayer physical properties were most pronounced with DHA and EPA treatment. These data show that unsaturated fatty acids, particularly DHA and EPA, induce a marked change in the lipid bilayer structure. The composition of fatty acids in the DPPC bilayer was similar after treatment with various unsaturated fatty acids, suggesting that the different actions of unsaturated fatty acids are attributed to change in the molecular structure (e.g., kinked conformation by double bonds). We further explored the change in physical properties induced by fatty acids dispersed in a water-in-oil-in-water multiple emulsion and found that unsaturated fatty acids acted efficiently on the DPPC bilayer, even when incorporated in emulsion form. PMID:16394552

  3. 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

  4. Biopolymer-Lipid Bilayer Interaction Modulates the Physical Properties of Liposomes: Mechanism and Structure.

    Science.gov (United States)

    Tan, Chen; Zhang, Yating; Abbas, Shabbar; Feng, Biao; Zhang, Xiaoming; Xia, Wenshui; Xia, Shuqin

    2015-08-19

    This study was conducted to elucidate the conformational dependence of the modulating ability of chitosan, a positively charged biopolymer, on a new type of liposome composed of mixed lipids including egg yolk phosphatidylcholine (EYPC) and nonionic surfactant (Tween 80). Analysis of the dynamic and structure of bilayer membrane upon interaction with chitosan by fluorescence and electron paramagnetic resonance techniques demonstrated that, in addition to providing a physical barrier for the membrane surface, the adsorption of chitosan extended and crimped chains rigidified the lipid membrane. However, the decrease in relative microviscosity and order parameter suggested that the presence of chitosan coils disturbed the membrane organization. It was also noted that the increase of fluidity in the lipid bilayer center was not pronounced, indicating the shallow penetration of coils into the hydrophobic interior of bilayer. Microscopic observations revealed that chitosan adsorption not only affected the morphology of liposomes but also modulated the particle aggregation and fusion. Especially, a number of very heterogeneous particles were visualized, which tended to confirm the role of chitosan coils as a "polymeric surfactant". In addition to particle deformation, the membrane permeability was also tuned. These findings may provide a new perspective to understand the physiological functionality of biopolymer and design biopolymer-liposome composite structures as delivery systems for bioactive components. PMID:26173584

  5. Nonconservative stability problems of modern physics

    OpenAIRE

    Kirillov, Oleg

    2013-01-01

    International audience This monograph 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.It deals with both finite- and infinite-dimensional nonconservative systems and covers the fundamentals of the theory, including such topics as Lyapunov stability and linear stability analysis, H...

  6. Theoretical study of polyiodide formation and stability on monolayer and bilayer graphene.

    Science.gov (United States)

    Tristant, Damien; Puech, Pascal; Gerber, Iann C

    2015-11-28

    The presence of polyiodide complexes have been reported several times when carbon-based materials were doped by iodine molecules, but their formation mechanism remains unclear. By using first-principles calculations that include nonlocal correlation effects by means of a van der Waals density functional approach, we propose that the formation of triiodide (I3(-)) and pentaiodide (I5(-)) is due to a large density of iodine molecules (I2) in interaction with a carbonaceous substrate. As soon as the concentration of surface iodine reaches a threshold value of 12.5% for a graphene monolayer and 6.25% for a bilayer, these complexes spontaneously appear. The corresponding structural and energetic aspects, electronic structures and vibrational frequencies support this statement. An upshift of the Dirac point from the Fermi level with values of 0.45 and 0.52 eV is observed for adsorbed complexes on graphene and intercalated complexes between two layers, respectively. For doped-graphene, it corresponds to a graphene hole density of around 1.1 × 10(13) cm(-2), in quantitative agreement with experiments. Additionally, we have studied the thermal stability at room temperature of these adsorbed ions on graphene by means of ab initio molecular dynamics, which also shows successful p-doping with polyiodide complexes. PMID:26497888

  7. The structure and stability of phospholipid bilayers by atomic force microscopy.

    Science.gov (United States)

    Hui, S W; Viswanathan, R; Zasadzinski, J A; Israelachvili, J N

    1995-01-01

    Atomic force microscopy (AFM) was used to investigate the structure, stability, and defects of the hydrophilic surfaces of Langmuir-Blodgett bilayer films of distearoylphosphatidylcholine (DSPC) and dipalmitoylphosphatidylethanolamine (DPPE) in the solid phase, and dilinoleoylphosphatidylethanolamine (DLPE) in the fluid phase. Their relative resilience to external mechanical stress by the scanning tip and by fluid exchange were also investigated. DPPE monolayers showed parallel ridges at the surface with a period of 0.49 nm, corresponding to the rows of aligned headgroups consistent with the known crystallographic structure. DSPC and DLPE monolayers did not show any periodic order. The solid DSPC and DPPE monolayers were stable to continued rastering by the AFM tip; however, the stability of DLPE monolayers depended on the pH of the aqueous environment. Structural defects in the form of monolayer gaps and holes were observed after fluid exchange, but the defects in DLPE monolayer at pH 11 were stable during consecutive scanning. At pH 9 and below, the defects induced by fluid exchange over DLPE monolayers were more extensive and were deformed easily by consecutive scanning of the AFM tip at a force of 10 nN. The pH dependence of resilience was explained by the increasing bending energy or frustration due to the high spontaneous curvature of DLPE monolayers at low pH. The tangential stress exerted by the AFM tip on the deformable monolayers eventually produced a ripple pattern, which could be described as a periodic buckling known as Shallamach waves. PMID:7711239

  8. Formation, Stability, and Mobility of One-Dimensional Lipid Bilayer on High Curvature Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J; Martinez, J; Artyukhin, A; Sirbuly, D; Wang, Y; Ju, J W; Stroeve, P; Noy, A

    2007-03-23

    Curved lipid membranes are ubiquitous in living systems and play an important role in many biological processes. To understand how curvature and lipid composition affect membrane formation and fluidity we have assembled and studied mixed 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC) and 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) supported lipid bilayers on amorphous silicon nanowires with controlled diameters ranging from 20 nm to 200 nm. Addition of cone-shaped DOPE molecules to cylindrical DOPC molecules promotes vesicle fusion and bilayer formation on smaller diameter nanowires. Our experiments demonstrate that nanowire-supported bilayers are mobile, exhibit fast recovery after photobleaching, and have low concentration of defects. Lipid diffusion coefficients in these high-curvature tubular membranes are comparable to the values reported for flat supported bilayers and increase with decreasing nanowire diameter.

  9. Protein stability and conformational rearrangements in lipid bilayers: linear gramicidin, a model system.

    OpenAIRE

    Cotten, M; Xu, F.; Cross, T A

    1997-01-01

    The replacement of four tryptophans in gramicidin A by four phenylalanines (gramicidin M) causes no change in the molecular fold of this dimeric peptide in a low dielectric isotropic organic solvent, but the molecular folds are dramatically different in a lipid bilayer environment. The indoles of gramicidin A interact with the anisotropic bilayer environment to induce a change in the molecular fold. The double-helical fold of gramicidin M, as opposed to the single-stranded structure of gramic...

  10. 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.

  11. Development and characterization of stabilized, polymerized phospholipid bilayers on silica particles for specific immobilization of His-tagged proteins

    Indian Academy of Sciences (India)

    Seid M Adem

    2015-04-01

    Stabilized phospholipid bilayer (PLB) coated silica microspheres were prepared via polymerization of lipid monomers. These lipid coated silica microspheres are stable to both extended storage in solution at 4°C and dry storage at room temperature. These stabilized lipid coated microspheres have also been functionalized with nickel-chelating lipids, a commonly used tool for immobilizing polyhistidine-tagged proteins. It is shown that 6xHis-EGFP interacts with (poly)bis-SorbPC/DOGS-NTA-Ni2+ coated silica and this interaction was interrupted by washing with imidazole indicating the reversibility of the interaction. No interaction was observed between the functionalized silica substrate and EGFP, which lacks the 6xHis-tag. Furthermore, these biocompatible (poly)bis-SorbPC coated microspheres were able to minimize non-specific protein adsorption.

  12. Stability, Higgs Boson Mass and New Physics

    CERN Document Server

    Branchina, Vincenzo

    2013-01-01

    When the particle with mass $\\sim 126$ GeV discovered at LHC is identified with the Higgs boson of the Standard Model, intriguing and challenging questions arise. Among them, the issue of the EW vacuum stability. We find that, despite claims to the contrary, the latter strongly depends on new physics interactions. In particular, if $\\tau$ is the lifetime of the EW vacuum, new physics can turn $\\tau$ from $\\tau >> T_U$ to $\\tau << T_U$, where $T_U$ is the age of the Universe.

  13. Effects of imidazolium-based ionic liquids on the stability and dynamics of gramicidin A and lipid bilayers at different salt concentrations.

    Science.gov (United States)

    Lee, Hwankyu; Kim, Sun Min; Jeon, Tae-Joon

    2015-09-01

    Gramicidin A (gA) dimers with bilayers, which consist of phospholipids and ionic liquids (ILs) at different molar ratios, were simulated at different salt concentrations of 0.15 and 1M NaCl. Bilayer thickness is larger than the length of a gA dimer, and hence lipids around the gA dimer are significantly disordered to adapt to the gA dimer, yielding membrane curvature. As the IL concentration increases, the bilayer thickness decreases and becomes closer to the gA length, leading to less membrane curvature. Also, ILs significantly increase lateral diffusivities of the gA dimer and lipids at 0.15M NaCl, but not at 1M NaCl because strong electrostatic interactions between salt ions and lipid head groups suppress an increase in the lateral mobility of the bilayer at high salt concentration. These findings help explain the conflicting experimental results that showed the increased ion permeability in electrophysiological experiments at 1M NaCl, but the reduced ion permeability in fluorescent experiments at 0.15M NaCl. ILs disorder lipids and make bilayers thinner, which yields less membrane curvature around the gA dimer and thus stabilizes the gA dimer, leading to the increased ion permeability. This IL effect predominantly occurs at 1M NaCl, where ILs only slightly increase the bilayer dynamics because of the strong electrostatic interactions between salt ions and lipids. In contrast, at 0.15M NaCl, ILs do not only stabilize the curved bilayer but also significantly increase the lateral mobility of gA dimers and lipids, which can reduce gA-induced pore formation, leading to the decreased ion permeability. PMID:26188795

  14. Quantum Hall states stabilized in semi-magnetic bilayers of topological insulators

    Science.gov (United States)

    Yoshimi, R.; Yasuda, K.; Tsukazaki, A.; Takahashi, K. S.; Nagaosa, N.; Kawasaki, M.; Tokura, Y.

    2015-10-01

    By breaking the time-reversal symmetry in three-dimensional topological insulators with the introduction of spontaneous magnetization or application of magnetic field, the surface states become gapped, leading to quantum anomalous Hall effect or quantum Hall effect, when the chemical potential locates inside the gap. Further breaking of inversion symmetry is possible by employing magnetic topological insulator heterostructures that host non-degenerate top and bottom surface states. Here we demonstrate the tailored-material approach for the realization of robust quantum Hall states in the bilayer system, in which the cooperative or cancelling combination of the anomalous and ordinary Hall responses from the respective magnetic and non-magnetic layers is exemplified. The appearance of quantum Hall states at filling factor 0 and +1 can be understood by the relationship of energy band diagrams for the two independent surface states. The designable heterostructures of magnetic topological insulator may explore a new arena for intriguing topological transport and functionality.

  15. A New Method for Measuring Edge Tensions and Stability of Lipid Bilayers: Effect of Membrane Composition

    CERN Document Server

    Portet, Thomas; 10.1016/j.bpj.2010.09.032

    2011-01-01

    We report a new and facile method for measuring edge tensions of lipid membranes. The approach is based on electroporation of giant unilamellar vesicles and analysis of the pore closure dynamics. We applied this method to evaluate the edge tension in membranes with four different compositions: egg phosphatidylcholine (EggPC), dioleoylphosphatidylcholine (DOPC), and mixtures of the latter with cholesterol and dioleoylphosphatidylethanolamine (DOPE). Our data confirm previous results for EggPC and DOPC. The addition of 17 mol % cholesterol to the DOPC membrane causes an increase in the membrane edge tension. On the contrary, when the same fraction of DOPE is added to the membrane, a decrease in the edge tension is observed, which is an unexpected result considering the inverted-cone shape geometry of the molecule. Presumably, interlipid hydrogen bonding lies in the origin of this behavior. Furthermore, cholesterol was found to lower the lysis tension of DOPC bilayers. This behavior differs from that observed on...

  16. Control of bilayer stability in Clostridium butyricum: phase behavior of the ether lipids

    International Nuclear Information System (INIS)

    In Clostridium butyricum approx. half of the phospholipid consists of phosphatidylethanolamine (PE), plasmenylethanolamine (PlaE), and the glycerol acetal of PlaE (GA). These lipids are predominantly in the outer monolayer of the cell membrane. Phosphatidylglycerol and cardiolipin appear to be predominantly in the inner monolayer. When grown on mixtures of palmitic (16:0) and oleic (18:1) acids in the absence of biotin, the 18:1 content of the phospholipid acyl chains responds strongly to the medium 18:1/16:0 ratio. At high 18:1/16:0, both the acyl and ether-linked chains are highly unsaturated, and the ratio of GA to PE plus PlaE increases from 0.7 to 2.0. 31P NMR and X-ray diffraction show that the oleate-enriched PE plus PlaE from C. butyricum grown on 100% oleate (PE/sub cb/o/) forms an H11 phase above 00 C, whereas dioleoyl GA forms bilayers at physiological temperature X-ray diffraction studies with dioleoyl PE and dioleoyl GA show that 2:1 and 1:1 (wt/wt) ratios form mixed lamellar and hexagonal phases at 460 C. A 1:3 mixture, is lamellar at 460C. With PE/sub cb/o/dioleoyl GA, 31P NMR shows that a 2:1 mixture undergoes a lamellar to non-lamellar transition between 30 and 400C, whereas a 1:1 mixture forms a lamellar phase up to 450C. Growth of this organism with highly unsaturated membranes appears to depend on its ability to regulate its ether lipid composition, primarily by increasing the proportions of bilayer-forming GA

  17. Structure and stability of phospholipid bilayers hydrated by a room-temperature ionic liquid/water solution: a neutron reflectometry study.

    Science.gov (United States)

    Benedetto, Antonio; Heinrich, Frank; Gonzalez, Miguel A; Fragneto, Giovanna; Watkins, Erik; Ballone, Pietro

    2014-10-23

    Neutron reflectometry (NR) measurements were carried out to probe the structure and stability of two model biomembranes consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) phospholipid bilayers hydrated by water solutions of two prototypical room-temperature ionic liquids (RTILs), namely, 1-butyl-3-methyl-imidazolium chloride ([bmim][Cl]) and choline chloride ([Chol][Cl]) at concentrations of 0.1 M and 0.5 M, respectively. The raw data were analyzed by fitting a distribution of scattering length densities arising from the different chemical species in the system. The results of this analysis show that (a) for all systems and concentrations that we considered, the thickness of the bilayers shrinks by ∼1 Å upon dissolving the ionic liquid into water and that (b) the RTIL ions enter the bilayer, finding their way to a preferred location in the lipid range that is nearly independent of the lipid and of the [bimim](+) or [Chol](+) choice. The volume fraction of RTIL sorbed in/on the bilayer, however, does depend on the lipid, but, again, is the same for [bmim][Cl] and for [Chol][Cl]. Thus, the RTIL occupies ∼5% of the bilayer volume in POPC, rising to ∼10% in DMPC. Repeating the measurements and data analysis after rinsing in pure water shows that the changes in the bilayer due to the RTIL sorption are irreversible and that a measurable amount of IL remains in the lipid fraction, that is, ∼2.5% of the bilayer volume in POPC and ∼8% in DMPC. PMID:25251987

  18. Radion Physics, Stability and Cosmological issues

    International Nuclear Information System (INIS)

    Moduli fields are a known ingredient of models that involve extra compact dimensions, as the Kaluza-Klein theories, String theory, and models with compact extra dimensions. They are scalar fields that emerge when the configuration of the compact space is perturbed. The radion is a particular example of this type of fields, which is associated to the variations of the total volume of compact space. Radions usually couple to all other fields, affecting the definition of coupling constants and gravity strength. They also modify gravitational potentials in a way that may be tested in table top experiments. Usually, these fields are run away modes which manifest the difficulties to stabilize the shape of the compact manifold of extra space. This is feature that can be a threat for cosmology on the early Universe. Here we provide a brief discussion of these general aspects of the radion physics.

  19. Regulation of bilayer stability in Clostridium butyricum: studies on the polymorphic phase behavior of the ether lipids

    International Nuclear Information System (INIS)

    Three of the major phospholipids of the cell membrane of Clostridium butyricum are phosphatidylethanolamine (PE), plasmenylethanolamine (PlaE), and the glycerol acetal of plasmenylethanolamine. When cultured in the absence of biotin in media supplemented with a cis-unsaturated fatty acid, the cellular lipids become highly enriched with the fed fatty acid. Under these conditions, the ratio of the glycerol acetal of PlaE to the sum of PE plus PlaE increases markedly over that seen in cells containing mixtures of saturated and unsaturated fatty acids. The authors have studied the polymorphic phase behavior of the phospholipids from C. butyricum grown on oleic acid using differential scanning calorimetry, 31P nuclear magnetic resonance, and X-ray diffraction. The mixed PE plus PlaE fraction undergoes a transition from the gel to liquid-crystalline state at -1.90C and a lamellar to reversed hexagonal (L → H) transition at or near 00C. The glycerol acetal of PlaE melts at 16.10C, and as predicted from lipid packing theory, the lamellar phase is stabilized, up to 500C. Addition of the oleate-enriched glycerol acetal of PlaE to dioleoylphosphatidylethanolamine, or the PE plus PlaE fraction from oleate-grown cells, stabilized the lamellar arrangement of the mixtures. It appears that these cells are capable of regulating the stability of the bilayer arrangement of the cell membrane by altering the ratio of the glycerol acetal of PlaE to the total PE fraction in response to changes in membrane lipid unsaturation

  20. 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, V.

    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

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

    International Nuclear Information System (INIS)

    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 (MoO3) 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/MoO3 as the bilayer D/S electrodes have the best electrical properties: field effect mobility μeff = 0.32 cm2 V−1 s−1 and threshold voltage VTH = − 5 V and the transistors with Ag/MoO3 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

  2. Stability of charged membranes

    OpenAIRE

    Bensimon, D; David, F.; Leibler, S.; Pumir, A.

    1990-01-01

    The electrostatic contribution to the bending elastic modulus of charged phospholipid bilayers in an ionic solution is computed. It is found to be the same for conducting and non-conducting membranes and is always stabilizing. This stability for free membranes is shown to be a simple consequence of the vanishing of the physical surface tension.

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

    Energy Technology Data Exchange (ETDEWEB)

    Karimi-Alavijeh, H.R., E-mail: h.karimi@eng.ui.ac.ir [Department of Electrical Engineering, University of Isfahan, Isfahan (Iran, Islamic Republic of); Ehsani, A. [Department of Electrical and Avionics Engineering, Malek-Ashtar University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-09-01

    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{sub 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{sub 3} as the bilayer D/S electrodes have the best electrical properties: field effect mobility μ{sub eff} = 0.32 cm{sup 2} V{sup −1} s{sup −1} and threshold voltage V{sub TH} = − 5 V and the transistors with Ag/MoO{sub 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.

  4. Stabilization criteria for cubic AlN in TiN/AlN and CrN/AlN bi-layer systems

    International Nuclear Information System (INIS)

    We combine the finite element (ABAQUS) and ab initio methods to study and predict the equilibrium critical thickness up to which the metastable cubic (c) AlN phase is energetically favoured to the stable wurtzite (w) variant in TiN/AlN and CrN/AlN bi-layer systems. The results show that the w-AlN phase is preferred for all thicknesses in the free-standing configuration (without a substrate) when grown on TiN, while 4 nm thick c-AlN is predicted for CrN bi-layer material systems. The substrate helps to stabilize c-AlN up to 15.8 nm, and for an incoherent interface between the substrate and the TiN or CrN interlayer, the stabilization mechanically supports the interlayer against relaxation. For a coherent interface to the substrate, a small lattice constant (as, e.g., in the case of Al substrate) helps to stabilize c-AlN, whereas a large lattice constant (as, e.g., in the case of MgO) promotes w-AlN. Finally, we predict that 〈111〉 orientated specimens allow for thicker c-AlN layers than those grown along the 〈100〉 direction.

  5. Physical inactivation and stabilization of sludges

    International Nuclear Information System (INIS)

    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 70-800C. 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

  6. Stability of the EW vacuum, Higgs boson, and new physics

    CERN Document Server

    Branchina, Vincenzo

    2014-01-01

    The possibility that the Standard Model (SM) is valid up to the Planck scale $M_P$, i.e. that new physics occurs only around $M_P$, is nowadays largely explored. For a metastable EW vacuum, we show that new physics interactions can have a great impact on its lifetime, and, differently from previous analyses, they cannot be neglected. Therefore, contrary to usual believes, the stability phase diagram of the SM depends on new physics. This has far reaching consequences. Beyond SM theories can be tested against their prediction for the stability of the EW vacuum. Moreover, despite of some recent claims, higher precision measurements of the top and Higgs masses cannot provide any definite answer on the SM stability properties. Finally, doubts on Higgs inflation scenarios, all based on results obtained neglecting new physics interactions, are also cast.

  7. On the principle of stability of invariance of physical systems

    International Nuclear Information System (INIS)

    The point of view that the invariance principles are fundamental laws of nature and that the qualitative aspects of a physical system are equally important are taken. With this in mind a physical system is studied. The concept of invariance stability is introduced analogous to structural stability. As a consequence, it is found that only those conservation laws which are due to abelian symmetries cannot be violated. For instance energy-momentum and charge conservation. All other conservation laws due to non-abelian (continuous) symmetries can always be violated by the variation of some parameter of the theory concerned

  8. Mechanical and physical properties of plasma-sprayed stabilized zirconia

    Science.gov (United States)

    Siemers, P. A.; Mehan, R. L.

    1983-01-01

    Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

  9. The Role of Physical Stabilization in Whole Blood Preservation

    Science.gov (United States)

    Wong, Keith H. K.; Sandlin, Rebecca D.; Carey, Thomas R.; Miller, Kathleen L.; Shank, Aaron T.; Oklu, Rahmi; Maheswaran, Shyamala; Haber, Daniel A.; Irimia, Daniel; Stott, Shannon L.; Toner, Mehmet

    2016-02-01

    The rapid degradation of blood ex vivo imposes logistical limitations on the utilization of blood-borne cells in medical diagnostics and scientific investigations. A fundamental but overlooked aspect in the storage of this fluid tissue is blood settling, which induces physical stress and compaction, aggregates blood cells, and causes collateral damage due to leukocyte activation. Here we show that the polymer Ficoll 70 kDa stabilized blood samples and prevented blood settling over the course of 72 hours, primarily by inhibiting depletion-mediated red blood cell aggregation. Physical stabilization decreased echinocyte formation, improved leukocyte viability, and inhibited the release of neutrophil elastase—a marker of neutrophil extracellular trap formation. In addition, Ficoll-stabilized blood was compatible with common leukocyte enrichment techniques including red blood cell lysis and immunomagnetic purification. This study showed for the first time that blood settling can be prevented using polymers and has implications in diagnostics.

  10. Analysis of the flexibility and stability of the structure of magainin in a bilayer, and in aqueous and nonaqueous solutions using molecular dynamics simulations.

    Science.gov (United States)

    Esmaili, Elham; Shahlaei, Mohsen

    2015-04-01

    The precise mode of the antimicrobial activity of Magainin (Mag)-an antimicrobial peptide (AMP)-is still unclear. In this study, the conformation of Mag was characterized in water, and in a methanol and lipid bilayer [palmitoyl-oleoylphosphatidylcholine (POPC)] using a molecular dynamics (MD) simulation technique. To describe the role conformation plays in Mag function, the global conformational differences within three systems were studied. Through analysis of the resulting configuration ensembles, the differences in the three systems, such as overall flexibility and average secondary structure, were studied. It is suggested that these differences may be important enough to influence interactions with lipid biomembranes, thereby influencing key properties such as penetration into cell membrane and stability. PMID:25750019

  11. Physical and Oxidative Stability of Fish Oil-In-Water Emulsions Stabilized with Fish Protein Hydrolysates

    DEFF Research Database (Denmark)

    García Moreno, Pedro Jesús; Guadix, Antonio; Guadix, Emilia M.;

    2016-01-01

    The emulsifying and antioxidant properties of fish protein hydrolysates (FPH) for the physical and oxidative stabilization of 5% (by weight) fish oil-in-water emulsions were investigated. Muscle proteins from sardine (Sardina pilchardus) and small-spotted catshark (Scyliorhinus canicula) were......% yielded a physically stable emulsion with low concentration of unsaturated aldehydes. These results show the potential of FPH as alternative protein emulsifiers for the production of oxidatively stable fish oil-in-water emulsions....

  12. Noise stabilization effects in models of interdisciplinary physics

    International Nuclear Information System (INIS)

    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.

  13. The temperature-dependent physical state of polar lipids and their miscibility impact the topography and mechanical properties of bilayer models of the milk fat globule membrane.

    Science.gov (United States)

    Murthy, Appala Venkata Ramana; Guyomarc'h, Fanny; Lopez, Christelle

    2016-09-01

    The polar lipid assembly and biophysical properties of the biological membrane enveloping the milk fat globules (the MFGM) are yet poorly known, especially in connection with the temperature history that milk can experience after its secretion. However, bioactive mechanisms depend on biological structure, which itself highly depend on temperature. The objectives of this study were to investigate polar lipid packing in hydrated bilayers, models of the MFGM, and to follow at intermolecular level temperature-induced changes in the range 60-6°C, using the combination of differential scanning calorimetry, X-ray diffraction, atomic force microscopy (AFM) imaging and force spectroscopy. MFGM polar lipids, especially sphingomyelin, contain long chain saturated fatty acids with high phase transition temperatures. On cooling, the liquid disordered ld to solid ordered so (gel) phase transition of MFGM polar lipids started at about 40°C, leading to phase separation and formation of so phase domains protruding by about 1nm from the ld phase. Indentation measurements using AFM revealed that the resistance of the so phase domains to rupture was significantly higher than that of the ld phase and that it increased for both the domain and fluid phases with decreasing temperature. However, packing and stability of the bilayers were adversely affected by fast cooling to 6°C or by cooling-rewarming cycle. This study showed that MFGM polar lipid bilayers are dynamic systems. Heterogeneity in the structure and mechanical properties of the membrane was induced by temperature-dependent so/ld phase immiscibility of the lipid components. This could have consequences on the MFGM technological and biological functions (e.g. immunity and milk lipid digestion). PMID:27349732

  14. HIRESSS: a physically based slope stability simulator for HPC applications

    Directory of Open Access Journals (Sweden)

    G. Rossi

    2013-01-01

    Full Text Available HIRESSS (HIgh REsolution Slope Stability Simulator is a physically based distributed slope stability simulator for analyzing shallow landslide triggering conditions in real time and on large areas using parallel computational techniques. The physical model proposed is composed of two parts: hydrological and geotechnical. The hydrological model receives the rainfall data as dynamical input and provides the pressure head as perturbation to the geotechnical stability model that computes the factor of safety (FS in probabilistic terms. The hydrological model is based on an analytical solution of an approximated form of the Richards equation under the wet condition hypothesis and it is introduced as a modeled form of hydraulic diffusivity to improve the hydrological response. The geotechnical stability model is based on an infinite slope model that takes into account the unsaturated soil condition. During the slope stability analysis the proposed model takes into account the increase in strength and cohesion due to matric suction in unsaturated soil, where the pressure head is negative. Moreover, the soil mass variation on partially saturated soil caused by water infiltration is modeled.

    The model is then inserted into a Monte Carlo simulation, to manage the typical uncertainty in the values of the input geotechnical and hydrological parameters, which is a common weak point of deterministic models. The Monte Carlo simulation manages a probability distribution of input parameters providing results in terms of slope failure probability. The developed software uses the computational power offered by multicore and multiprocessor hardware, from modern workstations to supercomputing facilities (HPC, to achieve the simulation in reasonable runtimes, compatible with civil protection real time monitoring.

    A first test of HIRESSS in three different areas is presented to evaluate the reliability of the results and the runtime performance on

  15. Physical and oxidative stability of fish oil-in-water emulsions stabilized with fish protein hydrolysates.

    Science.gov (United States)

    García-Moreno, Pedro J; Guadix, Antonio; Guadix, Emilia M; Jacobsen, Charlotte

    2016-07-15

    The emulsifying and antioxidant properties of fish protein hydrolysates (FPH) for the physical and oxidative stabilization of 5% (by weight) fish oil-in-water emulsions were investigated. Muscle proteins from sardine (Sardina pilchardus) and small-spotted catshark (Scyliorhinus canicula) were hydrolyzed to degrees of hydrolysis (DH) of 3-4-5-6% with subtilisin. Sardine hydrolysates with low DH, 3% and 4%, presented the most effective peptides to physically stabilize emulsions with smaller droplet size. This implied more protein adsorbed at the interface to act as physical barrier against prooxidants. This fact might also be responsible for the higher oxidative stability of these emulsions, as shown by their lowest peroxide value and concentration of volatiles such as 1-penten-3-one and 1-penten-3-ol. Among the hydrolysates prepared from small-spotted catshark only the hydrolysate with DH 3% yielded a physically stable emulsion with low concentration of unsaturated aldehydes. These results show the potential of FPH as alternative protein emulsifiers for the production of oxidatively stable fish oil-in-water emulsions. PMID:26948597

  16. Twisted Bilayer Graphene Superlattices

    OpenAIRE

    Wang, Yanan; Su, Zhihua; Wu, Wei; Nie, Shu; Xie, Nan; Gong, Huiqi; Guo, Yang; Lee, Joon Hwan; Xing, Sirui; Lu, Xiaoxiang; Wang, Haiyan; Lu, Xinghua; McCarty, Kevin; Pei, Shin- shem; Robles-Hernandez, Francisco

    2013-01-01

    Twisted bilayer graphene (tBLG) provides us with a large rotational freedom to explore new physics and novel device applications, but many of its basic properties remain unresolved. Here we report the synthesis and systematic Raman study of tBLG. Chemical vapor deposition was used to synthesize hexagon- shaped tBLG with a rotation angle that can be conveniently determined by relative edge misalignment. Superlattice structures are revealed by the observation of two distinctive Raman features: ...

  17. Cholesterol's location in lipid bilayers.

    Science.gov (United States)

    Marquardt, Drew; Kučerka, Norbert; Wassall, Stephen R; Harroun, Thad A; Katsaras, John

    2016-09-01

    It is well known that cholesterol modifies the physical properties of lipid bilayers. For example, the much studied liquid-ordered Lo phase contains rapidly diffusing lipids with their acyl chains in the all trans configuration, similar to gel phase bilayers. Moreover, the Lo phase is commonly associated with cholesterol-enriched lipid rafts, which are thought to serve as platforms for signaling proteins in the plasma membrane. Cholesterol's location in lipid bilayers has been studied extensively, and it has been shown - at least in some bilayers - to align differently from its canonical upright orientation, where its hydroxyl group is in the vicinity of the lipid-water interface. In this article we review recent works describing cholesterol's location in different model membrane systems with emphasis on results obtained from scattering, spectroscopic and molecular dynamics studies. PMID:27056099

  18. Stability of MHD shear flows: Application to space physics

    International Nuclear Information System (INIS)

    Shear slows of magnetised plasmas are routinely observed in the solar atmosphere, in planetary magnetospheres, and in interplanetary space. They are also ubiquitous elements of models of remote astrophysical objects like the interacting stellar winds in binary stellar systems. Studying stability of such flows is paramount for understanding physical processes in space. The simplest shear flow is a tangential magnetohydrodynamic (MHD) discontinuity. We start our review from considering the instability of tangential MHD discontinuity (called the Kelvin-Helmholtz (KH) instability) first in incompressible plasmas, and then taking the compressibility into account. We introduce the notion of the absolute and convective instabilities. The physical behaviour of absolutely unstable flows is qualitatively different from that of convectively unstable flows. Studying the absolute and convective instabilities is based on the analysis of asymptotic behaviour (for large time) of the solution of the initial value problem. The initial value problem for a tangential discontinuity is ill-posed: the instability increment is unbounded. This implies that the absolute and convective instabilities of tangential discontinuities cannot be studied. To obtain a well-posed problem we have either to take dissipation into account, or to consider a continuous velocity profile. In both cases we obtain a surprising result: the account of either of these two effects decreases the threshold value of the velocity jump needed for instability. This phenomenon is related to negative energy waves. We show that, in both cases, the instability is the so-called negative energy instability rather than the KH instability. Finally we consider two examples of the theory application: the heliopause stability and the stability of the Earth's magnetopause.

  19. Magnetic core–bilayer shell complex of magnetite nanoparticle stabilized with mPEG–polyester amphiphilic block copolymer

    International Nuclear Information System (INIS)

    In this article, we report the synthesis of magnetite nanoparticles (Fe3O4) coated with methoxy poly(ethylene glycol) (mPEG)–polyester amphiphilic block copolymers. The coating polymer layer contains a hydrophobic inner layer of polyester and a hydrophilic corona of mPEG. The copolymers were first prepared via a direct condensation between diacid, diol compounds and mPEG oligomer to obtain a hydrophobic polyester block and hydrophilic mPEG block and then “grafted onto” a magnetite nanoparticle surface. The copolymer composition was varied by changing the structure of the diacid, diol, and the molecular weight ( M-bar n ) of the mPEG such that particles with good dispersibility and stability in water were obtained. It was found that the copolymer prepared from 1,6-hexanediol can effectively stabilize the particles in water regardless of the types of diacid and M-bar n of mPEG used. The particle size was approximately 10 nm in diameter, and the particle dispersibility in water was quite dependent on the type and concentration of the copolymer used. Thermogravimetric analysis revealed the presence of less than 37 % Fe3O4 and about 48–53 % of the copolymer in the complexes. The percent entrapment efficiency and loading efficiency of indomethacin model drug in the copolymer-coated magnetite nanoparticles were 19 and 77 %, respectively

  20. Magnetic core–bilayer shell complex of magnetite nanoparticle stabilized with mPEG–polyester amphiphilic block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Mekkapat, Supachai; Thong-On, Bandit; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha, E-mail: methar@nu.ac.th [Naresuan University, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science (Thailand)

    2013-11-15

    In this article, we report the synthesis of magnetite nanoparticles (Fe{sub 3}O{sub 4}) coated with methoxy poly(ethylene glycol) (mPEG)–polyester amphiphilic block copolymers. The coating polymer layer contains a hydrophobic inner layer of polyester and a hydrophilic corona of mPEG. The copolymers were first prepared via a direct condensation between diacid, diol compounds and mPEG oligomer to obtain a hydrophobic polyester block and hydrophilic mPEG block and then “grafted onto” a magnetite nanoparticle surface. The copolymer composition was varied by changing the structure of the diacid, diol, and the molecular weight ( M-bar {sub n} ) of the mPEG such that particles with good dispersibility and stability in water were obtained. It was found that the copolymer prepared from 1,6-hexanediol can effectively stabilize the particles in water regardless of the types of diacid and M-bar {sub n} of mPEG used. The particle size was approximately 10 nm in diameter, and the particle dispersibility in water was quite dependent on the type and concentration of the copolymer used. Thermogravimetric analysis revealed the presence of less than 37 % Fe{sub 3}O{sub 4} and about 48–53 % of the copolymer in the complexes. The percent entrapment efficiency and loading efficiency of indomethacin model drug in the copolymer-coated magnetite nanoparticles were 19 and 77 %, respectively.

  1. Physical understanding of cryogenic implant benefits for electrical junction stability

    Energy Technology Data Exchange (ETDEWEB)

    Adeni Khaja, Fareen; Colombeau, Benjamin; Thanigaivelan, Thirumal; Ramappa, Deepak; Henry, Todd [Applied Materials-Varian Semiconductor Equipment, 35 Dory Road, Gloucester, Massachusetts 01930 (United States)

    2012-03-12

    We investigate the effect of cryogenic temperature implants on electrical junction stability for ultra shallow junction applications for sub-32 nm technology nodes and beyond. A comprehensive study was conducted to gain physical understanding of the impact of cryogenic temperature implants on dopant-defect interactions. Carborane (C{sub 2}B{sub 10}H{sub 12}) molecule, a potential alternative to monomer boron was implanted in carbon preamorphized silicon substrates at cryogenic implant temperatures. Results indicate implants at cryogenic temperatures increase dopant activation with reduced diffusion, resulting in lower sheet resistance for a lower junction depth. Further, this study emphasizes the benefits of co-implants performed at cryogenic temperatures as alternative to traditional preamorphizing implants.

  2. Physical Stability of Whippable Oil-in-Water Emulsions

    DEFF Research Database (Denmark)

    Munk, Merete Bøgelund

    despite appliance of shear and temperature changes from 5 to 20 °C. Globule aggregation induced by LACTEM was impeded when used in combination with GMS. On the contrary, GMU induced very dense fat globule networks in emulsions which transformed emulsions into very firm solid-like pastes. This effect was...... of the melting range, and possibly fatty acid composition, crystal conformation and wettability of crystals. Polymorphism of dispersed triacylglycerides was found not to be related to physical instability of emulsions. Interfacial protein displacement by LMW-emulsifiers was not prerequisite for...... layer in emulsions with GMU. Three different mechanisms of GMU, LACTEM, and GMS in emulsions were proposed based on the emulsifiers’ effect on emulsion stability and protein displacement from the interface of fat globules. A flocculated network of fat globules was formed in emulsions with LACTEM due to...

  3. Effect of antimicrobial peptide on the dynamics of phosphocholine membrane: role of cholesterol and physical state of bilayer.

    Science.gov (United States)

    Sharma, V K; Mamontov, E; Anunciado, D B; O'Neill, H; Urban, V S

    2015-09-14

    Antimicrobial peptides are universal in all forms of life and are well known for their strong interaction with the cell membrane. This makes them a popular target for investigation of peptide-lipid interactions. Here we report the effect of melittin, an important antimicrobial peptide, on the dynamics of membranes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid in both the solid gel and fluid phases. To probe the phase transition, elastic neutron intensity temperature scans have been carried out on DMPC-based unilamellar vesicles (ULV) with and without melittin. We have found that addition of a small amount (0.2 mol%) melittin eliminates the steep fall in the elastic intensity at 296 K associated with the solid gel to fluid phase transition, which is observed for pure DMPC vesicles. Quasielastic neutron scattering (QENS) experiments have been carried out on DMPC ULV in the solid gel and fluid phases with and without 0.2 mol% melittin. The data analysis invariably shows the presence of lateral and internal motions of the DMPC molecule. We found that melittin does have a profound effect on the dynamics of lipid molecules, especially on the lateral motion, and affects it in a different way, depending on the phase of the bilayers. In the solid gel phase, it acts as a plasticizer, enhancing the lateral motion of DMPC. However, in the fluid phase it acts as a stiffening agent, restricting the lateral motion of the lipid molecules. These observations are consistent with the mean squared displacements extracted from the elastic intensity temperature scans. Their importance lies in the fact that many membrane processes, including signaling and energy transduction pathways, are controlled to a great extent by the lateral diffusion of lipids in the membrane. To investigate the effect of melittin on vesicles supplemented with cholesterol, QENS experiments have also been carried out on DMPC ULV with cholesterol in the presence and absence of 0.2 mol% melittin

  4. Silica-based cationic bilayers as immunoadjuvants

    OpenAIRE

    Carmona-Ribeiro Ana M; da Costa Maria; Faquim-Mauro Eliana; Santana Mariana RA; Lincopan Nilton

    2009-01-01

    Abstract Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6...

  5. Interactional processes for stabilizing conceptual coherences in physics

    CERN Document Server

    Frank, Brian W

    2012-01-01

    Research in student knowledge and learning of science has typically focused on explaining conceptual change. Recent research, however, documents the great degree to which student thinking is dynamic and context-sensitive, implicitly calling for explanations not only of change but also of stability. In other words: When a pattern of student reasoning is sustained in specific moments and settings, what mechanisms contribute to sustaining it? We characterize student understanding and behavior in terms of multiple local coherences in that they may be variable yet still exhibit local stabilities. We attribute stability in local conceptual coherences to real-time activities that sustain these coherences. For example, particular conceptual understandings may be stabilized by the linguistic features of a worksheet question, or by feedback from the students' spatial arrangement and orientation. We document a group of university students who engage in multiple local conceptual coherences while thinking about motion dur...

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

    OpenAIRE

    Venter, Telanie; Lizelle T. Fox; Gerber, Minja; du Preez, Jan L.; Van Zyl, Sterna; Boneschans, Banie; du Plessis, Jeanetta

    2016-01-01

    The stability and the anti-ageing, skin hydrating and anti-erythema effects of a commercialized Crocodylus niloticus 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®,...

  7. Physical and Chemical Aspects of Stabilization of Compounds in Silk

    OpenAIRE

    Pritchard, Eleanor M.; Dennis, Patrick B.; Omenetto, Fiorenzo; Naik, Rajesh R.; Kaplan, David L.

    2012-01-01

    The challenge of stabilization of small molecules and proteins has received considerable interest. The biological activity of small molecules can be lost as a consequence of chemical modifications, while protein activity may be lost due to chemical or structural degradation, such as a change in macromolecular conformation or aggregation. In these cases stabilization is required to preserve therapeutic and bioactivity efficacy and safety. In addition to use in therapeutic applications, strateg...

  8. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Eric D. Wachsman; Keith L. Duncan

    2002-09-30

    A bilayer electrolyte consisting of acceptor-doped ceria (on the fuel/reducing side) and cubic-stabilized bismuth oxide (on the oxidizing side) was developed. The bilayer electrolyte that was developed showed significant improvement in open-circuit potential versus a typical ceria based SOFC. Moreover, the OCP of the bilayer cells increased as the thickness of the bismuth oxide layer increased relative to the ceria layer. Thereby, verifying the bilayer concept. Although, because of the absence of a suitable cathode (a problem we are still working assiduously to solve), we were unable to obtain power density curves, our modeling work predicts a reduction in electrolyte area specific resistance of two orders of magnitude over cubic-stabilized zirconia and projects a maximum power density of 9 W/m{sup 2} at 800 C and 0.09 W/m{sup 2} at 500 C. Towards the development of the bilayer electrolyte other significant strides were made. Among these were, first, the development of a, bismuth oxide based, oxide ion conductor with the highest conductivity (0.56 S/cm at 800 C and 0.043 S/cm at 500 C) known to date. Second, a physical model of the defect transport mechanisms and the driving forces for the ordering phenomena in bismuth oxide and other fluorite systems was developed. Third, a model for point defect transport in oxide mixed ionic-electronic conductors was developed, without the typical assumption of a uniform distribution of ions and including the effect of variable loads on the transport properties of an SOFC (with either a single or bilayer electrolyte).

  10. Interactional processes for stabilizing conceptual coherences in physics

    Science.gov (United States)

    Frank, Brian W.; Scherr, Rachel E.

    2012-12-01

    Research in student knowledge and learning of science has typically focused on explaining conceptual change. Recent research, however, documents the great degree to which student thinking is dynamic and context-sensitive, implicitly calling for explanations not only of change but also of stability. In other words, when a pattern of student reasoning is sustained in specific moments and settings, what mechanisms contribute to sustaining it? We characterize student understanding and behavior in terms of multiple local coherences in that they may be variable yet still exhibit local stabilities. We attribute stability in local conceptual coherences to real-time activities that sustain these coherences. For example, particular conceptual understandings may be stabilized by the linguistic features of a worksheet question or by feedback from the students’ spatial arrangement and orientation. We document a group of university students who engage in multiple local conceptual coherences while thinking about motion during a collaborative learning activity. As the students shift their thinking several times, we describe mechanisms that may contribute to local stability of their reasoning and behavior.

  11. Physical and chemical stability of the bentonite buffer

    International Nuclear Information System (INIS)

    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/m2) 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 m2/s, fracture apertures from 0.1 to 2 mm and the hydraulic gradients from 0.01 to 1 mH2O/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 one model

  12. Emergence, Flexibility, and Stabilization of Language in a Physics Classroom

    Science.gov (United States)

    Roth, Wolff-Michael; Duit, Reinders

    2003-01-01

    Learning physics is a complex phenomenon. In this article, we use concepts from the theory of nonlinear systems to study the development of language in classroom science in an experimental unit on chaos theory in a German 10th-grade physics classroom. In ongoing activity, the explanations students developed for phenomena emerged through…

  13. Physical and chemical stability of gum arabic-stabilized conjugated linoleic acid oil-in-water emulsions.

    Science.gov (United States)

    Yao, Xiaolin; Xu, Qiong; Tian, Dazhi; Wang, Nana; Fang, Yapeng; Deng, Zhongyang; Phillips, Glyn O; Lu, Jiang

    2013-05-15

    Oil-in-water (O/W) emulsions have been used as a delivery system to protect conjugated linoleic acid (CLA), a polyunsaturated fatty acid, from oxidation. Conventional gum arabic (GA) and two matured gum arabic samples (EM2 and EM10) were used as emulsifiers to prepare CLA-in-water emulsions. The emulsions have optimal physical and chemical stability at gum concentrations of 5% for all three gums. Emulsions with higher gum concentrations are more susceptible to lipid oxidation. This is attributed to reduced physical stability at higher gum concentrations because of the coalescence and depletion-induced flocculation of the emulsion droplets. The prooxidants iron and copper intrinsically contained in the gums could also contribute to this instability. Among the three gums, EM10 provides the most effective protection for CLA both physically and chemically, because of its superior interfacial properties over GA and EM2. PMID:23614832

  14. 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

  15. 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

    using DSC in order to link the physical and chemical stability with molecular mobility. Chemical stability was studied with high-performance liquid chromatography (HPLC). Results obtained from the current study revealed that the solubility of amorphous forms prepared by both methods was enhanced...

  16. 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

  17. Excitonic condensation in bilayer systems

    Science.gov (United States)

    Su, Jung-Jung

    Among the many examples of Bose condensation considered in physics, electron-hole-pair (exciton) condensation has maintained special interest because it has been difficult to realize experimentally, and because of controversy about condensate properties. In this thesis, we studied the various aspects of spontaneous symmetry broken state of exciton in bilayer using mean field theory. We calculated the photoluminescence of excitonic condensation created by laser. We developed a one-dimensional toy model of excitonic supercurrent using mean field theory plus non-equilibrium Green's function (NEGF) which give qualitatively consistent results with experiments. We proposed graphene bilayer as a novel system for excitonic condensation to occur and estimate it to exist even at temperature as high as room temperature.

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

    OpenAIRE

    Trujillo-Cayado, L. A.; Natera, A.; M.C. García; Muñoz, J.; Alfaro, M. C.

    2015-01-01

    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 emulsi...

  19. Fluid lipid bilayers: Intermonolayer coupling and its thermodynamic manifestations

    DEFF Research Database (Denmark)

    Hansen, Per Lyngs; Miao, Ling; Ipsen, John Hjorth

    1998-01-01

    A fluid membrane of lipid bilayer consists of two individual molecular monolayers physically opposed to each other. This unique molecular architecture naturally necessitates the need to treat a lipid-bilayer membrane as one entity of two coupled two-dimensional systems (monolayers), each of which...

  20. Dermal nanocrystals from medium soluble actives - physical stability and stability affecting parameters.

    Science.gov (United States)

    Zhai, Xuezhen; Lademann, Jürgen; Keck, Cornelia M; Müller, Rainer H

    2014-09-01

    Nanocrystals are meanwhile applied to increase the dermal penetration of drugs, but were applied by now only to poorly soluble drugs (e.g. 1-10 μg/ml). As a new concept nanocrystals from medium soluble actives were produced, using caffeine as model compound (solubility 16 mg/ml at 20 °C). Penetration should be increased by (a) further increase in solubility and (b) mainly by increased hair follicle targeting of nanocrystals compared to pure solution. Caffeine nanocrystal production in water lead to pronounced crystal growth. Therefore the stability of nanocrystals in water-ethanol (1:9) and ethanol-propylene glycol (3:7) mixtures with lower dielectric constant D was investigated, using various stabilizers. Both mixtures in combination with Carbopol 981 (non-neutralized) yielded stable nanosuspensions over 2 months at 4 °C and room temperature. Storage at 40 °C lead to crystal growth, attributed to too strong solubility increase, supersaturation and Ostwald ripening effects. Stability of caffeine nanocrystals at lower temperatures could not only be attributed to lower solubility, because the solubilities of caffeine in mixtures and in water are not that much different. Other effects such as quantified by reduced dielectric constant D, and specific interactions between dispersion medium and crystal surface seem to play a role. With the 2 mixtures and Carbopol 981, a basic formulation composition for this type of nanocrystals has been established, to be used in the in vivo proof of principle of the new concept. PMID:25016978

  1. Direct in situ measurement of specific capacitance, monolayer tension, and bilayer tension in a droplet interface bilayer.

    Science.gov (United States)

    Taylor, Graham J; Venkatesan, Guru A; Collier, C Patrick; Sarles, Stephen A

    2015-10-14

    Thickness and tension are important physical parameters of model cell membranes. However, traditional methods to measure these quantities require multiple experiments using separate equipment. This work introduces a new multi-step procedure for directly accessing in situ multiple physical properties of droplet interface bilayers (DIB), including specific capacitance (related to thickness), lipid monolayer tension in the Plateau-Gibbs border, and bilayer tension. The procedure employs a combination of mechanical manipulation of bilayer area followed by electrowetting of the capacitive interface to examine the sensitivities of bilayer capacitance to area and contact angle to voltage, respectively. These data allow for determining the specific capacitance of the membrane and surface tension of the lipid monolayer, which are then used to compute bilayer thickness and tension, respectively. The use of DIBs affords accurate optical imaging of the connected droplets in addition to electrical measurements of bilayer capacitance, and it allows for reversibly varying bilayer area. After validating the accuracy of the technique with diphytanoyl phosphatidylcholine (DPhPC) DIBs in hexadecane, the method is applied herein to quantify separately the effects on membrane thickness and tension caused by varying the solvent in which the DIB is formed and introducing cholesterol into the bilayer. Because the technique relies only on capacitance measurements and optical images to determine both thickness and tension, this approach is specifically well-suited for studying the effects of peptides, biomolecules, natural and synthetic nanoparticles, and other species that accumulate within membranes without altering bilayer conductance. PMID:26289743

  2. Effect of monoglycerides and fatty acids on a ceramide bilayer.

    Science.gov (United States)

    Akinshina, Anna; Das, Chinmay; Noro, Massimo G

    2016-07-14

    Monoglycerides and unsaturated fatty acids, naturally present in trace amounts in the stratum corneum (top layer of skin) lipid matrix, are commonly used in pharmaceutical, cosmetic and health care formulations. However, a detailed molecular understanding of how the oil additives get incorporated into the skin lipids from topical application and, once incorporated, how they affect the properties and integrity of the lipid matrix remains unexplored. Using ceramide 2 bilayers as skin lipid surrogates, we use a series of molecular dynamics simulations with six different natural oil ingredients at multiple concentrations to investigate the effect of the oils on the properties and stability of the bilayers. The six oils: monoolein, monostearin, monoelaidin, oleic acid, stearic acid and linoleic acid - all having the same length of the alkyl chain, C18, but a varying degree of saturation, allow us to systematically address the effect of unsaturation in the additives. Our results show that at low oil concentration (∼5%) the mixed bilayers containing any of the oils and ceramide 2 (CER2) become more rigid than pure CER2 bilayers due to more efficient lipid packing. Better packing also results in the formation of larger numbers of hydrogen bonds between the lipids, which occurs at the expense of the hydrogen bonds between lipids and water. The mixed bilayers with saturated or trans-unsaturated oils remain stable over the whole range of oil concentration. In contrast, the presence of the oils with at least one cis-double bond leads to bilayer instability and complete loss of bilayer structure at the oil content of about 50-65%. Two cis-double bonds in the lipid tail induce bilayer disruption at even lower concentration (∼30%). The mixed bilayers remain in the gel phase (without melting to a fluid phase) until the phase transition to a non-bilayer phase occurs. We also demonstrate that the stability of the bilayer strongly correlates with the order parameter of the lipid

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    Membrane protein function is regulated by the host lipid bilayer composition. This regulation may depend on specific chemical interactions between proteins and individual molecules in the bilayer, as well as on non-specific interactions between proteins and the bilayer behaving as a physical enti...... use of gramicidin 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....

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

    DEFF Research Database (Denmark)

    Hamborg, Mette; Kramer, Ryan; Schanté, Carole E; Agger, Else Marie; Christensen, Dennis; Jorgensen, Lene; Foged, Camilla; Middaugh, C Russell

    2013-01-01

    gel electrophoresis analyses demonstrated that both antigens exist as a distribution of multimeric states under nonstressed conditions. Their conformational stability was monitored as a function of pH and temperature and visualized in three-index empirical phase diagrams. Both antigens showed a...... 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-polyacrylamide...

  5. Compressibility of bilayer graphene

    OpenAIRE

    Borghi, Giovanni; Polini, Marco; Asgari, Reza; MacDonald, A. H.

    2010-01-01

    Bilayer graphene is a recently isolated and intriguing class of many-body systems with massive chiral quasiparticles. We present theoretical results for the electronic compressibility of bilayer graphene that are based on a four-band continuum band structure model combined with a random phase approximation treatment of electronic correlations. We find that the compressibility is strongly suppressed by electron-electron interactions at low carrier densities. Correlations do not lead to any qua...

  6. 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

  7. 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

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

    NARCIS (Netherlands)

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

    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

  9. A factorial design study on the physical stability of 3-in-1 admixtures.

    Science.gov (United States)

    Li, L C; Sampogna, T P

    1993-11-01

    The effects of dextrose concentration, the compounding method, and storage conditions, on the physical stability of 3-in-1 admixtures were investigated using a 2n factorial design. The main effect of these three variables on the weight percent of oil globules larger than 5 microns (by HIAC) was found to be statistically significant. However, the effects of interaction amongst these variables, except the two-way interaction between dextrose concentration and storage conditions, were found to be statistically insignificant. A higher dextrose concentration was shown to enhance the physical stability of the admixtures, while low-temperature storage (three days at 5 degrees C) was more favourable for maintaining the physical stability of the admixtures with a low dextrose concentration. Although sequential pumping produced admixtures with a slightly lower final weight percentage of larger oil globules (> 5 microns), the method of compounding has the least impact on the physical stability of the admixtures in comparison with the other two variables evaluated in this study. The storage of the admixtures at room temperature for one day was shown to have a greater adverse effect on admixtures with a low dextrose concentration. PMID:7908042

  10. On the Physical Problem of Spatial Dimensions: An Alternative Procedure to Stability Arguments

    CERN Document Server

    Caruso, Francisco

    2012-01-01

    Why is space 3-dimensional? The first answer to this question, entirely based on Physics, was given by Ehrenfest, in 1917, who showed that the stability requirement for $n$-dimensional two-body planetary system very strongly constrains space dimensionality, favoring 3-d. This kind of approach will be generically called "stability postulate" throughout this paper and was shown by Tangherlini, in 1963, to be still valid in the framework of general relativity as well as for quantum mechanical hydrogen atom, giving the same constraint for space-dimensionality. In the present work, before criticizing this methodology, a brief discussion has been introduced, aimed at stressing and clarifying some general physical aspects of the problem of how to determine the number of space dimensions. Then, the epistemological consequences of Ehrenfest's methodology are critically reviewed. An alternative procedure to get at the proper number of dimensions, in which the stability postulate (and the implicit singularities in three...

  11. Layer resolved capacitive probing of graphene bilayers

    Science.gov (United States)

    Zibrov, Alexander; Parmentier, François; Li, Jia; Wang, Lei; Hunt, Benjamin; Dean, Cory; Hone, James; Taniguchi, Takashi; Watanabe, Kenji; Young, Andrea

    Compared to single layer graphene, graphene bilayers have an additional ``which-layer'' degree of freedom that can be controlled by an external electric field in a dual-gated device geometry. We describe capacitance measurements capable of directly probing this degree of freedom. By performing top gate, bottom gate, and penetration field capacitance measurements, we directly extract layer polarization of both Bernal and twisted bilayers. We will present measurements of hBN encapsulated bilayers at both zero and high magnetic field, focusing on the physics of the highly degenerate zero-energy Landau level in the high magnetic field limit where spin, valley, and layer degeneracy are all lifted by electronic interactions.

  12. High carotenoid bioaccessibility through linseed oil nanoemulsions with enhanced physical and oxidative stability.

    Science.gov (United States)

    Sotomayor-Gerding, Daniela; Oomah, B Dave; Acevedo, Francisca; Morales, Eduardo; Bustamante, Mariela; Shene, Carolina; Rubilar, Mónica

    2016-05-15

    Carotenoid (astaxanthin or lycopene) emulsions obtained by high pressure homogenization were investigated for their physical, oxidative and storage stability and biological fate on an in vitro digestion model of bioaccessibility. Emulsion stability evaluated at various processing environments (20-50°C, 2-10 pH, 0-500 mM NaCl, and 0-35 days storage at 25°C) depended on carotenoid and homogenization pressures (5, 10, 100 MPa). Trolox increased the oxidative stability of nanoemulsions (100 MPa) and acted synergistically with BHT in increasing the stability of lycopene nanoemulsion. Intestinal digestibility depended on homogenization pressures with the fastest release and lower amount of free fatty acids observed at 100 MPa. Carotenoid nanoemulsions (100 MPa) were partially (66%) digested and highly bioaccessible (>70%). Therefore, nanoemulsions provide an effective and stable system for efficient astaxanthin or lycopene delivery and bioavailability in foods, beverages, nutraceuticals and/or other agriproducts. PMID:26775996

  13. Improved physical stability and injectability of non-aqueous in situ PLGA microparticle forming emulsions.

    Science.gov (United States)

    Voigt, M; Koerber, M; Bodmeier, R

    2012-09-15

    The goal of this study was to obtain physically stable non-aqueous in situ forming microparticle (ISM) emulsions capable of forming biodegradable microparticles upon injection. ISM emulsions consist of a biocompatible organic PLGA solution dispersed in a continuous oil phase prepared in a two-syringe/connector system prior to administration. A variety of parenteral approved excipients were tested for a stability-enhancing effect and possible stabilization mechanisms evaluated. Glycerol monostearate (GMS) showed superior stabilizing potential prolonging the emulsion stability from a few minutes to more than 12h. Flow behavior analysis, differential scanning calorimetry, polarized light- and Cryo-electron microscopy revealed, that the stabilization was caused by an immediate, more than 5-fold viscosity increase in the continuous phase after emulsification and by a stabilized interface through a liquid crystalline GMS layer around the polymer solution droplets. Despite the viscosity increase the injectability of the stabilized ISM emulsion was improved by about 30% compared to the corresponding highly viscous PLGA solution (in situ implant) due to a pronounced shear thinning of the GMS containing oil phase. The injectability improvement allows a faster administration or enables the use of thinner needles and hence reduced patient discomfort. PMID:22677417

  14. Tubular lipid membranes pulled from vesicles: Dependence of system equilibrium on lipid bilayer curvature

    Science.gov (United States)

    Golushko, I. Yu.; Rochal, S. B.

    2016-01-01

    Conditions of joint equilibrium and stability are derived for a spherical lipid vesicle and a tubular lipid membrane (TLM) pulled from this vesicle. The obtained equations establish relationships between the geometric and physical characteristics of the system and the external parameters, which have been found to be controllable in recent experiments. In particular, the proposed theory shows that, in addition to the pressure difference between internal and external regions of the system, the variable spontaneous average curvature of the lipid bilayer (forming the TLM) also influences the stability of the lipid tube. The conditions for stability of the cylindrical phase of TLMs after switching off the external force that initially formed the TLM from a vesicle are discussed. The loss of system stability under the action of a small axial force compressing the TLM is considered.

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

    CERN Document Server

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

    2004-01-01

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

  16. Gamma-irradiation of liposomes composed of saturated phospholipids: effect of bilayer composition, size, concentration and absorbed dose on chemical degradation and physical destabilization of liposomes.

    Science.gov (United States)

    Zuidam, N J; Versluis, C; Vernooy, E A; Crommelin, D J

    1996-04-01

    Liposomes composed of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG), or mixtures of these two phospholipids were exposed to gamma-irradiation in an air environment. Disappearance of the mother compounds was monitored by HPLC analysis. Plotting of the logarithmic values of residual DPPC or DPPG concentration versus irradiation dose resulted in straight lines. The slopes of these lines (overall degradation constants) depended on the type of phospholipids, concentration of the liposomes and the size of the liposomes. Under the chosen conditions, addition of DPPG in DPPC-liposomes did not affect the degradation rate constant of DPPC and vice versa. The presence of phosphate buffer (pH 7.4), pH or presence of sodium chloride did not affect the irradiation damage either. Minor changes were found upon analysis of total fatty acids by GLC and upon measurement of water soluble phosphate compounds. These changes were less pronounced than the changes monitored by HPLC of phospholipids, because the HPLC analysis monitored the overall degradation of the liposomal phospholipids. Thin-layer chromatography/fast atom bombardment mass spectrometry (TLC/FAB-MS) analysis of irradiated and non-irradiated DPPC or DPPG provided information on the structure of several degradation products. Degradation routes which include these degradation products are proposed. Gamma-irradiation neither affected the size of the liposomes nor the bilayer rigidity as determined by dynamic light scattering and fluorescence anisotropy of the probe 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. However, upon gamma-irradiation, changes in the melting characteristics of the liposomes were found by differential scanning calorimetry (DSC) measurements. The pre-transition melting enthalpy of the liposomal bilayer decreased or disappeared and the main-transition broadened. The changes found in DSC scans correlated qualitatively well with the changes recorded after HPLC analysis

  17. 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. PMID:25902736

  18. Single and Dual Physical Link Failures Stability Effect on Degree Three WDM Networks

    DEFF Research Database (Denmark)

    Gutierrez Lopez, Jose Manuel; Georgakilas, Konstantinos; Riaz, M. Tahir;

    2010-01-01

    This paper studies the effects of Single and Dual physical link failures to the stability of WDM networks when deployed as regular 3-degree structures. The failure impact on the source-destination pair connections is evaluated for the different topology scenarios. In this way it is possible to...... provide an overview of the failure effects and their relation to network metrics such as availability or cost. The results quantify how much the different network interconnection designs are affected by Single and Dual Physical link failures. The case study treats a realistic scenario, the interconnection...

  19. An assessment of techniques for evaluating the physical stability of parenteral emulsions.

    Science.gov (United States)

    Zhang, Xiaoguang; Kirsch, Lee E

    2003-01-01

    The physical stability of the parenteral emulsions is a key product quality issue. The purpose of this study is to develop, prepare and characterize model phospholipid emulsions and to critically evaluate various physical stability-indicating methods. Oil-in-water (O/W) emulsions were prepared using 20% (w/w) medium chain triglycerides (MCT) or soybean oil in 2.21% (w/w) aqueous glycerin solutions emulsified with 0.1 to 1.8 % (w/w) lecithin. The reproducibility of emulsion preparation was determined by measuring the volume-based mean droplet diameter using photon correlation spectroscopy (PCS) and zeta potential using electrophoretic light scattering. Evaluation of stability-indicating methods was conducted by comparing the mean droplet growth rate of a thermally-stressed emulsion using PCS, a light obscuration particle counter (HIAC, equipped with a laser diode sensor) and a droplet image analyzer interfaced with transmission electron microscopy (TEM) using osmium tetraoxide fixation. Emulsions with identical compositions and preparation properties had reproducible mean droplet diameter and initial zeta potential values with RSD HIAC, and TEM). The droplet growth rates estimated using PCS and TEM were nearly identical. PCS is a sufficiently accurate technique for measuring emulsion stability and is less time-consuming than TEM. The HIAC technique only measured the size of droplets with diameters larger than about 1 micron, which was considerably greater than the mean droplet diameter as determined by PCS and microscopic image analysis (TEM). Moreover, the growth rate obtained using HIAC was much greater than the rates estimated by PCS and TEM; therefore the HIAC technique was not an accurate measure of the physical stability of the thermally stressed emulsions. PMID:14558703

  20. 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: BL - Plasma and Gas Discharge Physics Impact factor: 1.152, year: 2014 http://dx.doi.org/10.1016/j.fusengdes.2015.06.044

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

    OpenAIRE

    Atif Ali; Naveed Akhtar; Haji Muhammad Shoaib Khan

    2013-01-01

    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 (DP...

  2. Single and Dual Physical Link Failures Stability Effect on Degree Three WDM Networks

    OpenAIRE

    Gutierrez Lopez, Jose Manuel; Georgakilas, Konstantinos; Riaz, M. Tahir; KATRINIS, Kostas; Pedersen, Jens Myrup; Tzanakaki , Anna; Madsen, Ole Brun

    2010-01-01

    This paper studies the effects of Single and Dual physical link failures to the stability of WDM networks when deployed as regular 3-degree structures. The failure impact on the source-destination pair connections is evaluated for the different topology scenarios. In this way it is possible to provide an overview of the failure effects and their relation to network metrics such as availability or cost. The results quantify how much the different network interconnection designs are affected by...

  3. Microstructure, Physical Stability, and Rheological Properties of Salad Dressing Emulsions Supplemented with Various Pulse Flours

    OpenAIRE

    Zhen Ma; Boye, Joyce I.

    2013-01-01

    Significant opportunities exist for using pulses in the development of health promoting foods as consumers increasingly look for functional foods with disease prevention qualities. Pulse ingredients could be considered for use in the development of novel, value-added products such as salad dressing. In this study, the rheological properties, color, physical stability, and microstructure of model salad dressing emulsions supplemented with various types of pulse flours (red lentil, green lentil...

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

    International Nuclear Information System (INIS)

    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 IC50. This exciting data highlights the potential of HNPs for use in image-guided drug delivery.

  5. Role of olive oil phenolics in physical properties and stability of mayonnaise-like emulsions.

    Science.gov (United States)

    Giacintucci, Veronica; Di Mattia, Carla; Sacchetti, Giampiero; Neri, Lilia; Pittia, Paola

    2016-12-15

    The effect of olive oil phenolic content and pattern on the physical properties and stability of olive oil mayonnaise-like emulsions has been investigated. Mayonnaises were formulated with either naturally phenolic-rich extra virgin olive oils or purified olive oil artificially enriched with a phenolic-rich olive extract and pure oleuropein. Mayonnaises were characterized by droplet size distribution, microstructure, textural properties and flow behaviour. The addition of phenolic extracts significantly affected the dispersion degree of the corresponding mayonnaise-like emulsions, their microstructure and physical stability especially in the systems prepared with purified olive oil treated with pure oleuropein and the highest olive phenolic extract concentration. The viscosity and back-extrusion analyses evidenced that the systems characterized by a relatively high content of phenolics, either natural or by addition, presented lower yield stress and viscosity indices and were easier to deform and to break. This study confirms the main role of olive phenolic compounds, and in particular that of oleuropein, in the dispersion state, and physical properties of emulsions with main effects on their quality and stability. PMID:27451193

  6. Modeling Physical Stability of Amorphous Solids Based on Temperature and Moisture Stresses.

    Science.gov (United States)

    Zhu, Donghua Alan; Zografi, George; Gao, Ping; Gong, Yuchuan; Zhang, Geoff G Z

    2016-09-01

    Isothermal microcalorimetry was utilized to monitor the crystallization process of amorphous ritonavir (RTV) and its hydroxypropylmethylcellulose acetate succinate-based amorphous solid dispersion under various stressed conditions. An empirical model was developed: ln(τ)=ln(A)+EaRT-b⋅wc, where τ is the crystallization induction period, A is a pre-exponential factor, Ea is the apparent activation energy, b is the moisture sensitivity parameter, and wc is water content. To minimize the propagation of errors associated with the estimates, a nonlinear approach was used to calculate mean estimates and confidence intervals. The physical stability of neat amorphous RTV and RTV in hydroxypropylmethylcellulose acetate succinate solid dispersions was found to be mainly governed by the nucleation kinetic process. The impact of polymers and moisture on the crystallization process can be quantitatively described by Ea and b in this Arrhenius-type model. The good agreement between the measured values under some less stressful test conditions and those predicted, reflected by the slope and R(2) of the correlation plot of these 2 sets of data on a natural logarithm scale, indicates its predictability of long-term physical stability of amorphous RTV in solid dispersions. To further improve the model, more understanding of the impact of temperature and moisture on the amorphous physical stability and fundamentals regarding nucleation and crystallization is needed. PMID:27185539

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

    DEFF Research Database (Denmark)

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

    2010-01-01

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

  8. General hydrophobic interaction potential for surfactant/lipid bilayers from direct force measurements between light-modulated bilayers

    OpenAIRE

    Donaldson, Stephen H., Jr.; Lee, C. Ted; Chmelka, Bradley F.; Israelachvili, Jacob N.

    2011-01-01

    We establish and quantify correlations among the molecular structures, interaction forces, and physical processes associated with light-responsive self-assembled surfactant monolayers or bilayers at interfaces. Using the surface forces apparatus (SFA), the interaction forces between adsorbed monolayers and bilayers of an azobenzene-functionalized surfactant can be drastically and controllably altered by light-induced conversion of trans and cis molecular conformations. These reversible confor...

  9. Eugenol improves physical and chemical stabilities of nanoemulsions loaded with β-carotene.

    Science.gov (United States)

    Guan, Yongguang; Wu, Jine; Zhong, Qixin

    2016-03-01

    Food-grade nanoemulsions are potential vehicles of labile lipophilic compounds such as β-carotene, but much work is needed to improve physical and chemical stabilities. The objective of this work was to study impacts of eugenol on physical and chemical stabilities of β-carotene-loaded nanoemulsions prepared with whey protein and lecithin. The combination of whey protein and lecithin resulted in stable nanoemulsions with eugenol added at 10% mass of soybean oil. Nanoemulsions, especially with eugenol, drastically reduced the degradation of β-carotene during ambient storage, heating at 60 and 80°C, and UV radiation at 254, 302, and 365nm. The droplet diameter of the nanoemulsion without eugenol increased from 153.6 to 227.3nm after 30-day ambient storage, contrasting with no significant changes of nanoemulsions with eugenol. Heating or UV radiation up to 8h did not significantly change the droplet diameter. Therefore, eugenol can be used to improve the stability of nanoemulsion delivery systems. PMID:26471619

  10. Chapter 3: MHD stability, operational limits and disruptions [Progress in the ITER Physics Basis (PIPB)

    International Nuclear Information System (INIS)

    Progress in the area of MHD stability and disruptions, since the publication of the 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137-2664), is reviewed. Recent theoretical and experimental research has made important advances in both understanding and control of MHD stability in tokamak plasmas. Sawteeth are anticipated in the ITER baseline ELMy H-mode scenario, but the tools exist to avoid or control them through localized current drive or fast ion generation. Active control of other MHD instabilities will most likely be also required in ITER. Extrapolation from existing experiments indicates that stabilization of neoclassical tearing modes by highly localized feedback-controlled current drive should be possible in ITER. Resistive wall modes are a key issue for advanced scenarios, but again, existing experiments indicate that these modes can be stabilized by a combination of plasma rotation and direct feedback control with non-axisymmetric coils. Reduction of error fields is a requirement for avoiding non-rotating magnetic island formation and for maintaining plasma rotation to help stabilize resistive wall modes. Recent experiments have shown the feasibility of reducing error fields to an acceptable level by means of non-axisymmetric coils, possibly controlled by feedback. The MHD stability limits associated with advanced scenarios are becoming well understood theoretically, and can be extended by tailoring of the pressure and current density profiles as well as by other techniques mentioned here. There have been significant advances also in the control of disruptions, most notably by injection of massive quantities of gas, leading to reduced halo current fractions and a larger fraction of the total thermal and magnetic energy dissipated by radiation. These advances in disruption control are supported by the development of means to predict impending disruption, most notably using neural networks. In addition to these advances in means to control or

  11. 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.

  12. [Studies on the stability and some other important physical properties of polysaccharides polyphase liposome (PPL)].

    Science.gov (United States)

    Zou, Y Y; Su, D S; Han, G C; Gu, X Q

    1989-01-01

    The stability and some other important physical properties of PPL were investigated by means of electron microscopy and MPV-TAS experiments. The results are rated as follows: Good integrity of liposome homogeneity of its particle size were reached, and at 100 degrees C PPL was found to undergo sterilization without causing changes of its shape and encapsulation efficiency for 1 h. Also, the distribution of PPL particle size and the regularity of the change of PPL particle in size were determined by Coulter counter. Using this method, the kinetic equation of coalescence of polyphase liposome and the activation energy for coalescence were obtained, and through these results the stability of PPL is elucidated. PMID:2508432

  13. Phospholipid bilayers are viscoelastic

    OpenAIRE

    Harland, Christopher W.; Bradley, Miranda J.; Parthasarathy, Raghuveer

    2010-01-01

    Lipid bilayers provide the structural framework for cellular membranes, and their character as two-dimensional fluids enables the mobility of membrane macromolecules. Though the existence of membrane fluidity is well established, the nature of this fluidity remains poorly characterized. Three-dimensional fluids as diverse as chocolates and cytoskeletal networks show a rich variety of Newtonian and non-Newtonian dynamics that have been illuminated by contemporary rheological techniques. Applyi...

  14. Irradiated bilayer graphene

    OpenAIRE

    Abergel, D. S. L.; Chakraborty, Tapash

    2010-01-01

    We describe the gated bilayer graphene system when it is subjected to intense terahertz frequency electromagnetic radiation. We examine the electron band structure and density of states via exact diagonalization methods within Floquet theory. We find that dynamical states are induced which lead to modification of the band structure. We first examine the situation where there is no external magnetic field. In the unbiased case, dynamical gaps appear in the spectrum which manifest as dips in th...

  15. Effects of some physical factors on the stability of collapsing stars

    Science.gov (United States)

    Sharif, M.; Bhatti, M. Zaeem Ul Haq

    2014-09-01

    This paper formulates the instability regions of a general charged spherically symmetric matter distribution with anisotropic pressure, shear viscosity, radiation density and radial heat flux. Matching conditions are found by taking Reissner-Nordström-Vaidya spacetime as an exterior geometry. The perturbed forms of Einstein-Maxwell field equations and conservation laws are constructed to formulate the collapse equation. The instability regions are identified under N and pN limits for the stability analysis. We conclude that the adiabatic index identifies the instability range which depends upon physical parameters like anisotropic pressure, energy density, shear viscosity and electromagnetic field and heat flux but radiation density has no role.

  16. Coassembly of Tobacco Mosaic Virus Coat Proteins into Nanotubes with Uniform Length and Improved Physical Stability.

    Science.gov (United States)

    Zhou, Kun; Eiben, Sabine; Wang, Qiangbin

    2016-06-01

    Using tobacco mosaic virus coat proteins (TMVcp) from both sources of the plant and bacterial expression systems as building blocks, we demonstrate here a coassembly strategy of TMV nanotubes in the presence of RNA. Specifically, plant-expressed cp (cpp) efficiently dominates the genomic RNA encapsidation to determine the length of assembled TMV nanotubes, whereas the incorporated Escherichia coli-expressed cp (cpec) improves the physical stability of TMV nanotubes by introducing disulfide bonds between the interfaces of subunits. We expect this coassembly strategy can be expanded to other virus nanomaterials to obtain desired properties based on rationally designed protein-RNA and protein-protein interfacial interactions. PMID:27188634

  17. Influence of an Acrylic Polymer Blend on the Physical Stability of Film-Coated Theophylline Pellets

    OpenAIRE

    Kucera, Shawn; Shah, Navnit H.; Malick, A. Waseem; Infeld, Martin H.; McGinity, James W.

    2009-01-01

    The purpose of this study was to investigate the physical stability of a coating system consisting of a blend of two sustained release acrylic polymers and its influence on the drug release rate of theophylline from coated pellets. The properties of both free films and theophylline pellets coated with the polymer blend were investigated, and the miscibility was determined via differential scanning calorimetry. Eudragit® RS 30 D was plasticized by the addition of Eudragit® NE 30 D, and the pre...

  18. Aerodynamic Characteristics of a Feathered Dinosaur Measured Using Physical Models. Effects of Form on Static Stability and Control Effectiveness

    OpenAIRE

    Evangelista, Dennis; Cardona, Griselda; Guenther-Gleason, Eric; Huynh, Tony; Kwong, Austin; Marks, Dylan; Ray, Neil; Tisbe, Adrian; Tse, Kyle; Koehl, Mimi

    2014-01-01

    We report the effects of posture and morphology on the static aerodynamic stability and control effectiveness of physical models based on the feathered dinosaur, Microraptor gui, from the Cretaceous of China. Postures had similar lift and drag coefficients and were broadly similar when simplified metrics of gliding were considered, but they exhibited different stability characteristics depending on the position of the legs and the presence of feathers on the legs and the tail. Both stability ...

  19. [Physical-mechanical and functional characteristics of xenograft during various methods of stabilization and treatment].

    Science.gov (United States)

    Kondratenko, Zh E; Kostava, V T; Bakuleva, N P; Tereshchenkova, I A; Antipas, D B

    1998-01-01

    The paper gives the results of experimental studies of the elastic-strength and functional characteristics of xenotissue samples (the pericardium of the calf, pig and Glisson's capsule) stabilized with glutaric aldehyde and polyepoxy compounds. The paper discusses various treatments of biological materials (including Glisson's capsule) anticalcified with additives (sodium dodecyl sulfate, complexes of copper and zinc) and shows that their use improves proteolytic and calcinotic resistance without deteriorating the mechanical parameters of xenotissues. Comparative analysis of the physical-mechanic and functional characteristics of xenotissues treated in different ways allows one to make anticalcifying treatment of biological tissues with copper and zinc complexes physical-mechanic and functional characteristics of xenotissues (Glisson's capsule) for clinical application. PMID:9791850

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

    International Nuclear Information System (INIS)

    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.

  1. Protein extraction from heat-stabilized defatted rice bran. 1. Physical processing and enzyme treatments.

    Science.gov (United States)

    Tang, Shanhu; Hettiarachchy, Navam S; Shellhammer, Thomas H

    2002-12-01

    Physical processing with or without enzyme treatments on protein extraction from heat-stabilized defatted rice bran (HDRB) was evaluated. Freeze-thaw, sonication, high-speed blending, and high-pressure methods extracted 12%, 15%, 16%, and 11% protein, respectively. Sonication (0-100%, 750 W), followed by amylase and combined amylase and protease treatments, extracted 25.6-33.9% and 54.0-57.8% protein, respectively. Blending followed by amylase and protease treatment extracted 5.0% more protein than the nonblended enzymatic treatments. High-pressure treatments, 0-800 MPa, with water or amylase-protease combinations, extracted 10.5-11.1% or 61.8-66.6% protein, respectively. These results suggest that physical processing in combination with enzyme treatments can be effective in extracting protein from HDRB. PMID:12452673

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

    International Nuclear Information System (INIS)

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

  3. 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. PMID:25040189

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

    International Nuclear Information System (INIS)

    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

  5. Physical Stability and HPLC Analysis of Indian Kudzu (Pueraria tuberosa Linn. Fortified Milk

    Directory of Open Access Journals (Sweden)

    Subha Rastogi

    2013-01-01

    Full Text Available Functional foods provide health benefit beyond basic nutrition. Functional foods fortified with plant ingredients are well known. Ayurveda (Indian System of Medicine has found several ways in which the medicinal benefits of herbs can be conveyed via certain foods as carriers. Milk is one such carrier which has been effectively used to deliver phytochemicals for targeted health benefits. Indian Kudzu or Pueraria tuberosa Linn. (Fabaceae is an important medicinal plant of Ayurveda, and experiments suggest that it enhances the health benefits of milk when taken with milk as a carrier. Different milk combinations with P. tuberosa were prepared by homogenizing pasteurized toned milk with its ethanolic and hot water extracts and their stability with reference to pH and coagulation was studied over a period of 15 days. The combinations were also analyzed for puerarin, the major isoflavone C-glucoside present in P. tuberosa, through high-performance liquid chromatography using photo diode array detector. It was observed that there was no precipitate formation and the pH also did not change during the study period indicating their physical stability under the experimental conditions. Also there was no significant change in the content of puerarin during the study period, thereby indicating the chemical stability of the samples. These studies will be useful for developing milk nutraceuticals fortified with Indian Kudzu which has the potential to be included as an ingredient in health and functional foods.

  6. Physical Ingredients Controlling Stability and Structural Selection of Empty Viral Capsids.

    Science.gov (United States)

    Aznar, María; Reguera, David

    2016-07-01

    One of the crucial steps in the viral replication cycle is the self-assembly of its protein shell. Typically, each native virus adopts a unique architecture, but the coat proteins of many viruses have the capability to self-assemble in vitro into different structures by changing the assembly conditions. However, the mechanisms determining which of the possible capsid shapes and structures is selected by a virus are still not well-known. We present a coarse-grained model to analyze and understand the physical mechanisms controlling the size and structure selection in the assembly of empty viral capsids. Using this model and Monte Carlo simulations, we have characterized the phase diagram and stability of T = 1,3,4,7 and snub cube shells. In addition, we have studied the tolerance of different shells to changes in physical parameters related to ambient conditions, identifying possible strategies to induce misassembly or failure. Finally, we discuss the factors that select the shape of a capsid as spherical, faceted, elongated, or decapsidated. Our model sheds important light on the ingredients that control the assembly and stability of viral shells. This knowledge is essential to get capsids with well-defined size and structure that could be used for promising applications in medicine or bionanotechnology. PMID:27114062

  7. Skin penetration and stabilization of formulations containing microfine titanium dioxide as physical UV filter.

    Science.gov (United States)

    Bennat, C; Müller-Goymann, C C

    2000-08-01

    Microfine titanium dioxide (TiO(2)) has become a frequently used physical UV filter in sunscreen formulations. Penetration of microfine TiO(2) into human skin seems to be possible because of the mean particle size of 20 nm. The small particle size results in a high surface activity of the primary particles and causes a formation of agglomerates in the formulation. The aim of this study was to investigate the in vivo and in vitro penetration behaviour of the physical UV filter into human skin. Furthermore, a stable sunscreen formulation with microfine TiO(2) which does not penetrate into the skin should be developed. According to our experiments, microfine TiO(2) penetrates deeper into human skin from an oily dispersion than from an aqueous one. Therefore, an o/w emulsion containing the dispersed micropigment in the aqueous phase was manufactured. Microfine TiO(2) cannot penetrate into human skin from this emulsion, but the storage stability of the formulation is very low at different temperatures. The encapsulation of the micropigment into liposomes does not result in a better stability but it causes a higher penetration depth of the particles into the skin. PMID:18503414

  8. On the physics of thermal-stability changes upon mutations of a protein

    Science.gov (United States)

    Murakami, Shota; Oshima, Hiraku; Hayashi, Tomohiko; Kinoshita, Masahiro

    2015-09-01

    It is of great interest from both scientific and practical viewpoints to theoretically predict the thermal-stability changes upon mutations of a protein. However, such a prediction is an intricate task. Up to now, significantly many approaches for the prediction have been reported in the literature. They always include parameters which are adjusted so that the prediction results can be best fitted to the experimental data for a sufficiently large set of proteins and mutations. The inclusion is necessitated to achieve satisfactorily high prediction performance. A problem is that the resulting values of the parameters are often physically meaningless, and the physicochemical factors governing the thermal-stability changes upon mutations are rather ambiguous. Here, we develop a new measure of the thermal stability. Protein folding is accompanied by a large gain of water entropy (the entropic excluded-volume (EV) effect), loss of protein conformational entropy, and increase in enthalpy. The enthalpy increase originates primarily from the following: The energy increase due to the break of protein-water hydrogen bonds (HBs) upon folding cannot completely be cancelled out by the energy decrease brought by the formation of protein intramolecular HBs. We develop the measure on the basis of only these three factors and apply it to the prediction of the thermal-stability changes upon mutations. As a consequence, an approach toward the prediction is obtained. It is distinguished from the previously reported approaches in the following respects: The parameters adjusted in the manner mentioned above are not employed at all, and the entropic EV effect, which is ascribed to the translational displacement of water molecules coexisting with the protein in the system, is fully taken into account using a molecular model for water. Our approach is compared with one of the most popular approaches, FOLD-X, in terms of the prediction performance not only for single mutations but also for

  9. Membrane interactions of ternary phospholipid/cholesterol bilayers and encapsulation efficiencies of a RIP II protein.

    Science.gov (United States)

    Manojlovic, V; Winkler, K; Bunjes, V; Neub, A; Schubert, R; Bugarski, B; Leneweit, G

    2008-07-15

    Membrane interactions of liposomes of ternary phospholipid/cholesterol bilayers are investigated. These interactions lead to discoidal deformations and regular aggregations and are strongly enhanced by the presence of mistletoe lectin (ML), a RIP II type protein. The encapsulation of ML into liposomal nanocapsules is studied with a systematic variation of the lipid composition to monitor its effect on the physical properties: entrapment, mean size, morphology, and stability. Extrusion of multilamellar vesicles through filters 80 nm pore size was used for the generation of liposomes. The mean sizes of liposomes ranged between 120 and 200 nm in diameter with narrow size distributions. The increase in flow rate with pressure for three dioleoylphosphatidylcholine (DOPC)/cholesterol (Chol)/dipalmitoylphosphatidylcholine (DPPC) lipid mixtures was linear and allowed to extrapolate to the minimum burst pressure of the liposomal bilayers. From the minimum pressures P(min), the bilayer lysis tensions gamma(l) were determined. The increase in P(min) and gamma(l) with an increasing content of a saturated phosopholipid (DPPC) indicates that DPPC increases the mechanical strength of lipid bilayers. Apparently, DPPC, like cholesterol, leads to a less compressible surface and a more cohesive membrane. After preparation, vesicle solutions were purified by gel permeation chromatography to separate encapsulated ML from free ML in the extravesicular solution. Purified liposomes were then characterized. The content of entrapped and adsorbed ML was measured using ELISA. Repetitive freezing/thawing cycles prior to extrusion significantly increased ML uptake. On the contrary, adsorption was not affected neither by lipid composition, nor concentration and preparation. Differences in experimental encapsulation efficiency only reflect the differences in the mean vesicle sizes of the different samples as is revealed by a comparison to a theoretical estimate. Cryo-transmission electron

  10. 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

  11. 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...

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

    Directory of Open Access Journals (Sweden)

    Sara Pereira

    2015-08-01

    Full Text Available 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.

  13. Electronic structure theory of weakly interacting bilayers

    Science.gov (United States)

    Fang, Shiang; Kaxiras, Efthimios

    2016-06-01

    We derive electronic structure models for weakly interacting bilayers such as graphene-graphene and graphene-hexagonal boron nitride, based on density functional theory calculations followed by Wannier transformation of electronic states. These transferable interlayer coupling models can be applied to investigate the physics of bilayers with arbitrary translations and twists. The functional form, in addition to the dependence on the distance, includes the angular dependence that results from higher angular momentum components in the Wannier pz orbitals. We demonstrate the capabilities of the method by applying it to a rotated graphene bilayer, which produces the analytically predicted renormalization of the Fermi velocity, Van Hove singularities in the density of states, and moiré pattern of the electronic localization at small twist angles. We further extend the theory to obtain the effective couplings by integrating out neighboring layers. This approach is instrumental for the design of van der Walls heterostructures with desirable electronic features and transport properties and for the derivation of low-energy theories for graphene stacks, including proximity effects from other layers.

  14. Sodium chloride's effect on self-assembly of diphenylalanine bilayer.

    Science.gov (United States)

    Kwon, Junpyo; Lee, Myeongsang; Na, Sungsoo

    2016-07-15

    Understanding self-assembling peptides becomes essential in nanotechnology, thereby providing a bottom-up method for fabrication of nanostructures. Diphenylalanine constitutes an outstanding building block that can be assembled into various nanostructures, including two-dimensional bilayers or nanotubes, exhibiting superb mechanical properties. It is known that the effect of the ions is critical in conformational and chemical interactions of bilayers or membranes. In this study, we analyzed the effect of sodium chloride on diphenylalanine bilayer using coarse-grained molecular dynamics simulations, and calculated the bending Young's modulus and the torsional modulus by applying normal modal analysis using an elastic network model. The results showed that sodium chloride dramatically increases the assembling efficiency and stability, thereby promising to allow the precise design and control of the fabrication process and properties of bio-inspired materials. © 2016 Wiley Periodicals, Inc. PMID:27241039

  15. 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.

  16. Physical stability of solid dispersions with respect to thermodynamic solubility of tadalafil in PVP-VA.

    Science.gov (United States)

    Wlodarski, K; Sawicki, W; Kozyra, A; Tajber, L

    2015-10-01

    The aim of this paper was to evaluate physical stability of solid dispersions in respect to the drug, tadalafil (Td), in vinylpyrrolidone and vinyl acetate block copolymer (PVP-VA). Nine solid dispersions of Td in PVP-VA (Td/PVP-VA) varied in terms of quantitative composition (1:9-9:1, w/w) were successfully produced by spray-drying. Their amorphous nature, supersaturated character and molecular level of mixing (a solid solution structure) were subsequently confirmed using DSC, PXRD, SEM and calculation of Hansen total solubility parameters. Due to thermal degradation of both components before the melting point of Td (302.3°C), an approach based on the drug crystallization from the supersaturated solid dispersion was selected to calculate the solubility of Td in the polymer. Annealing of the Td/PVP-VA solid dispersion (1:1, w/w) at selected temperatures above its Tg resulted in different stable solid dispersions. According to the Gordon-Taylor equation their new Tgs gave the information about the quantitative composition which corresponded to the thermodynamic solubility of Td in PVP-VA at given temperatures of annealing. The obtained relationship was fitted to the exponential function, with the calculated solubility of Td of 20.5% at 25°C. This value was in accordance with the results of hot stage polarizing light microscopy as well as stability tests carried out at 80°C and 0% RH, in which Td solid dispersions containing 10-20% of the drug were the only systems that did not crystallize within two months. A thermal analysis protocol utilizing a fast heating rate was shown to generate Td solubility data complementing the solid dispersion method. The Flory-Huggins model applied for the Td/PVP-VA system yielded the solubility value of 0.1% at 25°C, showing the lack of applicability in this case. PMID:26247119

  17. An investigation on subjective assessments of workload and postural stability under conditions of joint mental and physical demands

    OpenAIRE

    DiDomenico, Angela Terese

    2003-01-01

    Workload is defined as the cost incurred by an individual, given their capacities, while achieving a particular level of performance on a task with specific demands. Demands of a task or combination of tasks may include maintaining postural stability, executing physical actions, and/or performing cognitive tasks. While there have been attempts to establish a physiological measure of concurrent physical and mental workload, as yet there has been no work towards developing a single subjective...

  18. 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.

  19. Physical and oxidation stability of self-emulsifying krill oil-in-water emulsions.

    Science.gov (United States)

    Wu, Qian; Uluata, Sibel; Cui, Leqi; Wang, Chao; Li, Dongsheng; Mcclements, Julian; Decker, Eric A

    2016-08-10

    Krill oil is a unique source of omega-3 fatty acids since it is a mixture of phospholipids and triacylglycerols. Due to the presence of phospholipids, it can form oil-in-water emulsions without additional food additives. In this work, the physical stability of krill oil-in-water emulsions was determined at various pH values (3-7) and NaCl concentrations (50-1000 mM). The initial particle size ranged from 150 to 165 nm. The emulsions were the most stable at pH ≥ 5.0 and salt concentrations below 100 mM. Lipid oxidation was accelerated by iron and inhibited by Trolox and α-tocopherol. Trolox was a more effective antioxidant than α-tocopherol. α-Tocopherol had a better inhibitory effect when it was added after homogenization than when added to the lipid prior to homogenization. These results indicate that krill oil emulsions could represent a self-emulsifying, oxidatively stable source of omega-3 fatty acids that may be used in functional foods. PMID:27443794

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

    Science.gov (United States)

    Raijada, Dhara; Cornett, Claus; Rantanen, Jukka

    2013-08-30

    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 selected. Binary physical mixtures of drug and excipient were transferred to a 96-well plate followed by addition of water to simulate aqueous granulation environment. The plate was subjected for XRPD measurements followed by drying and subsequent XRPD and HPLC measurements of the dried samples. Excipients with different water sorbing potential were found to influence distinctly on the phase transformation behaviour of each drug. Moreover, the amount of water addition was also a critical factor affecting phase transformation behaviour. HPLC analysis revealed one of the drug:excipient pairs with a tendency 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. PMID:22944300

  1. The alteration of lipid bilayer dynamics by phloretin and 6-ketocholestanol

    Czech Academy of Sciences Publication Activity Database

    Przybylo, M.; Procek, J.; Hof, Martin; Langner, M.

    2014-01-01

    Roč. 178, FEB 2014 (2014), s. 38-44. ISSN 0009-3084 Institutional support: RVO:61388955 Keywords : lipid bilayers * dipole potential * water permeability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.422, year: 2014

  2. Dynamics and instabilities of lipid bilayer membrane shapes.

    Science.gov (United States)

    Shi, Zheng; Baumgart, Tobias

    2014-06-01

    Biological membranes undergo constant shape remodeling involving the formation of highly curved structures. The lipid bilayer represents the fundamental architecture of the cellular membrane with its shapes determined by the Helfrich curvature bending energy. However, the dynamics of bilayer shape transitions, especially their modulation by membrane proteins, and the resulting shape instabilities, are still not well understood. Here, we review in a unifying manner several theories that describe the fluctuations (i.e. undulations) of bilayer shapes as well as their local coupling with lipid or protein density variation. The coupling between local membrane curvature and lipid density gives rise to a 'slipping mode' in addition to the conventional 'bending mode' for damping the membrane fluctuation. This leads to a number of interesting experimental phenomena regarding bilayer shape dynamics. More importantly, curvature-inducing proteins can couple with membrane shape and eventually render the membrane unstable. A criterion for membrane shape instability is derived from a linear stability analysis. The instability criterion reemphasizes the importance of membrane tension in regulating the stability and dynamics of membrane geometry. Recent progresses in understanding the role of membrane tension in regulating dynamical cellular processes are also reviewed. Protein density is emphasized as a key factor in regulating membrane shape transitions: a threshold density of curvature coupling proteins is required for inducing membrane morphology transitions. PMID:24529968

  3. Structure of Carbon Nanotube Porins in Lipid Bilayers: An in Situ Small-Angle X-ray Scattering (SAXS) Study.

    Science.gov (United States)

    Tran, Ich C; Tunuguntla, Ramya H; Kim, Kyunghoon; Lee, Jonathan R I; Willey, Trevor M; Weiss, Thomas M; Noy, Aleksandr; van Buuren, Tony

    2016-07-13

    Carbon nanotube porins (CNTPs), small segments of carbon nanotubes capable of forming defined pores in lipid membranes, are important future components for bionanoelectronic devices as they could provide a robust analog of biological membrane channels. In order to control the incorporation of these CNT channels into lipid bilayers, it is important to understand the structure of the CNTPs before and after insertion into the lipid bilayer as well as the impact of such insertion on the bilayer structure. Here we employed a noninvasive in situ probe, small-angle X-ray scattering, to study the integration of CNT porins into dioleoylphosphatidylcholine bilayers. Our results show that CNTPs in solution are stabilized by a monolayer of lipid molecules wrapped around their outer surface. We also demonstrate that insertion of CNTPs into the lipid bilayer results in decreased bilayer thickness with the magnitude of this effect increasing with the concentration of CNTPs. PMID:27322135

  4. Interleaflet mixing and coupling in liquid-disordered phospholipid bilayers.

    Science.gov (United States)

    Capponi, Sara; Freites, J Alfredo; Tobias, Douglas J; White, Stephen H

    2016-02-01

    Organized as bilayers, phospholipids are the fundamental building blocks of cellular membranes and determine many of their biological functions. Interactions between the two leaflets of the bilayer (interleaflet coupling) have been implicated in the passage of information through membranes. However, physically, the meaning of interleaflet coupling is ill defined and lacks a structural basis. Using all-atom molecular dynamics simulations of fluid phospholipid bilayers of five different lipids with differing degrees of acyl-chain asymmetry, we have examined interleaflet mixing to gain insights into coupling. Reasoning that the transbilayer distribution of terminal methyl groups is an appropriate measure of interleaflet mixing, we calculated the transbilayer distributions of the acyl chain terminal methyl groups for five lipids: dioleoylphosphatidylcholine (DOPC), palmitoyloleoylphosphatidylcholine (POPC), stearoyloleoylphosphatidylcholine (SOPC), oleoylmyristoylphosphatidylcholine (OMPC), and dimyristoylphosphatidylcholine (DMPC). We observed in all cases very strong mixing across the bilayer midplane that diminished somewhat with increasing acyl-chain ordering defined by methylene order parameters. A hallmark of the interleaflet coupling idea is complementarity, which postulates that lipids with short alkyl chains in one leaflet will preferentially associate with lipids with long alkyl chains in the other leaflet. Our results suggest a much more complicated picture for thermally disordered bilayers that we call distributed complementarity, as measured by the difference in the peak positions of the sn-1 and sn-2 methyl distributions in the same leaflet. PMID:26657692

  5. Impact of glucose polymer chain length on heat and physical stability of milk protein-carbohydrate nutritional beverages.

    Science.gov (United States)

    Chen, Biye; O'Mahony, James A

    2016-11-15

    This study investigated the impact of glucose polymer chain length on heat and physical stability of milk protein isolate (MPI)-carbohydrate nutritional beverages containing 8.5% w/w total protein and 5% w/w carbohydrate. The maltodextrin and corn syrup solids glucose polymers used had dextrose equivalent (DE) values of 17 or 38, respectively. Increasing DE value of the glucose polymers resulted in a greater increase in brown colour development, ionic calcium, protein particle size, apparent viscosity and pseudoplastic rheological behaviour, and greater reduction in pH, hydration and heat stability on sterilisation at 120°C. Incorporation of glucose polymers with MPI retarded sedimentation of protein during accelerated physical stability testing, with maltodextrin DE17 causing a greater reduction in sedimentation velocity and compressibility of sediment formed than corn syrup solids DE38. The results demonstrate that chain length of the glucose polymer used strongly impacts heat and physical stability of MPI-carbohydrate nutritional beverages. PMID:27283657

  6. 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

  7. 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). PMID:26869421

  8. The effect of physical parameters of inertial stabilization platform on disturbance rejection ability and its improvement method

    Science.gov (United States)

    Mao, Yao; Deng, Chao; Gan, Xun; Tian, Jing

    2015-10-01

    The development of space optical communication requires arcsecond precision or even higher precision of the tracking performance of ATP(Acquisition, Tracking and Pointing) system under the condition of base disturbance. ATP system supported by stabilized reference beam which is provided by inertial stabilization platform with high precision and high bandwidth, can effectively restrain the influence of base angular disturbance on the line of sight. To get better disturbance rejection ability, this paper analyzes the influence of transfer characteristics and physical parameters of stabilization platform on disturbance stabilization performance, the result shows that the stabilization characteristics of inertial stabilization platform equals to the product of rejection characteristics of control loop and disturbance transfer characteristics of the platform, and improving isolation characteristics of the platform or extending control bandwidth can both achieve the result of getting a better rejection ability. Limited by factors such as mechanical characteristics of stabilization platform, bandwidth/noise of the sensor, and so on, as the control bandwidth of the LOS stabilization platform is limited, and high frequency disturbance can not be effectively rejected, so the rejection of high frequency disturbance mainly depends on the isolation characteristics of the platform itself. This paper puts forward three methods of improving the isolation characteristics of the platform itself, which includes 1) changing mechanical structure, such as reducing elastic coefficient, increasing moment of inertia of the platform, and so on; 2) changing electrical structure of the platform, such as increasing resistance, adding current loop, and so on; 3)adding a passive vibration isolator between the inertial stabilization platform and the base. The result of the experiment shows that adding current loop or adding a passive vibration isolator can effectively reject high frequency

  9. Predicting physical stability in pressurized metered dose inhalers via dwell and instantaneous force colloidal probe microscopy.

    Science.gov (United States)

    D'Sa, Dexter; Chan, Hak-Kim; Chrzanowski, Wojciech

    2014-09-01

    Colloidal probe microscopy (CPM) is a quantitative predictive tool, which can offer insight into particle behavior in suspension pressurized metered dose inhalers (pMDIs). Although CPM instantaneous force measurements, which involve immediate retraction of the probe upon sample contact, can provide information on inter-particle attractive forces, they lack the ability to appropriately imitate all critical particle pMDI interactions (e.g., particle re-dispersion after prolonged pMDI storage). In this paper, two novel dwell force techniques - indentation and deflection dwell - were employed to mimic long-term particle interactions present in pMDIs, using particles of various internal structures and a model liquid propellant (2H,3H perfluoropentane) as a model system. Dwell measurements involve particle contact for an extended period of time. In deflection dwell mode the probe is held at a specific position, while in indentation dwell mode the probe is forced into the sample with a constant force for the entirety of the contact time. To evaluate the applicability of CPM to predict actual pMDI physical stability, inter-particle force measurements were compared with qualitative and quantitative bulk pMDI measurement techniques (visual quality and light scattering). Measured instantaneous attractive (snap-in) and adhesive (max-pull) forces decreased as a function of increasing surface area, while adhesive forces measured by indentation dwell decreased as a function of dwell contact time for particles containing voids. Instantaneous force measurements provided information on the likelihood of floccule formation, which was predictive of partitioning rates, while indentation dwell force measurements were predictive of formulation re-dispersibility after prolonged storage. Dwell force measurements provide additional information on particle behavior within a pMDI not obtainable via instantaneous measurements. PMID:25058596

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

    Science.gov (United States)

    Li, Yong; Wang, Hanpeng; Zhu, Weishen; Li, Shucai; Liu, Jian

    2015-01-01

    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. PMID:26404287

  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. 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......, Pressure profile calculations in lipid bilayers: A lipid bilayer is merely $\\sim$5~nm thick, but the lateral pressure (parallel to the bilayer plane) varies several hundred bar on this short distance (normal to the bilayer). These variations in the lateral pressure are commonly referred to as the pressure...

  13. 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)

    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/m3) 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.

  14. 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.

  15. Evaluation of the Physical Stability of Zinc Oxide Suspensions Containing Sodium Poly-(acrylate) and Sodium Dodecylsulfate

    OpenAIRE

    Chabni, Malika; Bougherra, Hadda; Lounici, Hakim; Ahmed-Zaïd, Toudert; Canselier, Jean-Paul; Bertrand, Joël

    2011-01-01

    The physical stability of zinc oxide (ZnO) aqueous suspensions has been monitored during two months by different methods of investigation. The suspensions were formulated with ZnO at a fixed concentration (5 wt%), sodium poly-(acrylate), as a viscosifier, and sodium dodecylsulfate (SDS), as a wetting agent. The rheological study shows that the suspensions exhibit a non-Newtonian, most often shear-thinning behavior and their apparent viscosity increases with polymer concentration. The rheogram...

  16. Evaluation of the physical properties, bulk density and aggregate stability of potential substrates in quarry restoration.

    Science.gov (United States)

    Jordan, M.; Garcia-Orenes, F.; Mataix-Solera, J.; Garcia-Sanchez, E.

    2012-04-01

    Quarrying activity entails significant environmental impact affecting the soil, water, plants, landscape, etc. One of the most important impacts is the loss of the productive layer of the soil and its vegetation cover. However, mining activities are absolutely necessary for human development; keeping them sustainable implicates looking for viable solutions for the restoration of these areas to prevent degradation during and after the exploitation period. The aim of this study was to evaluate different substrates obtained from different mixes of sewage sludge and different mine spoils, to check how they are effective in quarry restoration, and to establish good practises in mining restoration. Also, the study tried to approach two refuses, one deriving from mining activity, as are the mine spoils that need to be reused for their valorisation, and the other, sewage sludge, obtained in the water depuration process to acquire a cheap substrate for soil rehabilitation. This preliminary work, which is included in a larger study, shows the results obtained from two physical properties studied, bulk density and aggregate stability, as key properties in the substrate structure for use in mining area restoration. Two doses of composted sewage sludge (30 and 90 Tm/Ha), both very rich in calcium carbonate, were applied to two different mine spoils under lab conditions. The first material, of poor quality, originated from the acquisition of arid particles in crushed limestone (Z). It is characterized by stable ''coarse elements'' predominance (up to 75% of its weight), and by the presence of elevated percentages of sand. The other waste material tested comes from limestone extraction (basically formed by the levels of interspersed non-limestone materials and the remains of stripped soils (D)). The results show that the high dose of sewage sludge applied to a mix of the two mine spoils significantly increased the percentage of stable aggregates by more than 50% than the control

  17. Physical-chemical and microbiological stability of biotherapy Candida albicans RC in different potencies

    Directory of Open Access Journals (Sweden)

    Sheila Garcia

    2011-09-01

    Full Text Available Introduction: Oral Candidiasis is an opportunist fungal infection, with high incidence in HIV and immunosuppressed patients and Candida albicans is the most common causing agent. In some cases, it can evolve to resistant injuries to antifungal conventional therapy. According to Brazilian Homeopathic Pharmacopeia (BHP [1], biotherapic medicines are prepared from chemically undefined biological products. Biotherapics created by Brazilian doctor Roberto Costa (RC have a different homeopathic compounding technique, as its dynamization starts from the ethiologic agent of the illness in its alive form, which present higher capability to stimulate the host immunological system [2,3]. Aim: The goal of this study was evaluate the physical-chemical and microbiological stability of Candida albicans RC potencies under different conditions of storage. Methodology: To prepare the biotherapics, one part of Candida albicans yeast suspension (109 cell/ml was diluted in 9 parts of sterile distillated water. After preparing this 1:10 dilution, the sample was undergone 100 succussions, resulting in the first decimal dilution (1x. Then, one part of this solution was diluted in 9 parts of sterile distillated water and submitted to 100 succussions, generating the 2x. This process was successively repeated following BHP, until 30x. Water 30x was prepared by the same technique, as control. All the solutions were prepared in aseptic and sterile conditions. Biotherapics 6x, 12x, 18x, 24x, 30x and water 30x were storage under refrigeration (2 to 8°C and at room temperate (25°C during 8 weeks. Every 15 days, the following parameters were analyzed: pH, electrical conductivity, UV absorbance (260 and 280 nm. Microbiological analyses were performed after 3 weeks by colony forming unit (CFU method [4]. Results: The preliminary analyses performed at times zero, 15, 30 and 45 days suggest that electrical conductivity of these solutions tend to increase

  18. Normal and Frictional Interactions between Liposome-Bearing Biomacromolecular Bilayers.

    Science.gov (United States)

    Gaisinskaya-Kipnis, Anastasia; Klein, Jacob

    2016-08-01

    Highly efficient lubricating boundary layers at biosurfaces such as cartilage have been proposed to comprise phospholipids complexed with biomacromolecules exposed at the surfaces. To gain insight into this, a systematic study on the normal and frictional forces between surfaces bearing a sequentially deposited model alginate-on-chitosan bilayer, bearing different adsorbed phosphatidylcholine (PC) liposomes, was carried out using a surface force balance. Structures of the resulting surface complexes were determined using atomic force microscopy (AFM) and cryo-scanning electron microscopy (cryo-SEM). The liposome/lipid-polymer complexes could maintain their integrity up to high pressures in terms of both normal and shear interactions between the surfaces, which were repeatable, reproducible, and revealed very low friction (coefficient of friction μ down to 10(-3)-10(-4), depending on the PC used) up to pressures of hundreds of atm. We attribute this remarkable lubrication capability ultimately to hydration lubrication acting at the hydrated phosphocholine headgroups of the PC lipids, either exposed at the liposome surfaces or through complexation with the polyelectrolyte bilayer. Values of μ, while low, were roughly an order of magnitude higher than for the same PC vesicles adsorbed on bare mica, a difference attributed to their lower density on the bilayer; the bilayer, however, stabilized the PC-vesicles far better than bare mica against rupture and shear at high compressions and sliding. PMID:27409248

  19. 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.

  20. Interaction of gramicidin with DPPC/DODAB bilayer fragments.

    Science.gov (United States)

    Carvalho, Camilla A; Olivares-Ortega, Constanza; Soto-Arriaza, Marco A; Carmona-Ribeiro, Ana M

    2012-12-01

    The interaction between the antimicrobial peptide gramicidin (Gr) and dipalmitoylphosphatidylcholine (DPPC)/dioctadecyldimethylammonium bromide (DODAB) 1:1 large unilamellar vesicles (LVs) or bilayer fragments (BFs) was evaluated by means of several techniques. The major methods were: 1) Gr intrinsic fluorescence and circular dichroism (CD) spectroscopy; 2) dynamic light scattering for sizing and zeta-potential analysis; 3) determination of the bilayer phase transition from extrinsic fluorescence of bilayer probes; 4) pictures of the dispersions for evaluation of coloidal stability over a range of time and NaCl concentration. For Gr in LVs, the Gr dimeric channel conformation is suggested from: 1) CD and intrinsic fluorescence spectra similar to those in trifluoroethanol (TFE); 2) KCl or glucose permeation through the LVs/Gr bilayer. For Gr in BFs, the intertwined dimeric, non-channel Gr conformation is evidenced by CD and intrinsic fluorescence spectra similar to those in ethanol. Both LVs and BFs shield Gr tryptophans against quenching by acrylamide but the Stern-Volmer quenching constant was slightly higher for Gr in BFs confirming that the peptide is more exposed to the water phase in BFs than in LVs. The DPPC/DODAB/Gr supramolecular assemblies may predict the behavior of other antimicrobial peptides in assemblies with lipids. PMID:22960286

  1. Electromechanical Oscillations in Bilayer Graphene

    OpenAIRE

    Benameur, Muhammed M.; Gargiulo, Fernando; Manzeli, Sajedeh; Autès, Gabriel; Tosun, Mahmut; Yazyev, Oleg V.; Kis, Andras

    2015-01-01

    Nanoelectromechanical systems constitute a class of devices lying at the interface between fundamental research and technological applications. Realizing nanoelectromechanical devices based on novel materials such as graphene allows studying their mechanical and electromechanical characteristics at the nanoscale and addressing fundamental questions such as electron–phonon interaction and bandgap engineering. In this work, we realize electromechanical devices using single and bilayer graphene ...

  2. Vapor deposition of water on graphitic surfaces: Formation of amorphous ice, bilayer ice, ice I, and liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria, E-mail: Valeria.Molinero@utah.edu [Department of Chemistry, The University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850 (United States)

    2014-11-14

    Carbonaceous surfaces are a major source of atmospheric particles and could play an important role in the formation of ice. Here we investigate through molecular simulations the stability, metastability, and molecular pathways of deposition of amorphous ice, bilayer ice, and ice I from water vapor on graphitic and atomless Lennard-Jones surfaces as a function of temperature. We find that bilayer ice is the most stable ice polymorph for small cluster sizes, nevertheless it can grow metastable well above its region of thermodynamic stability. In agreement with experiments, the simulations predict that on increasing temperature the outcome of water deposition is amorphous ice, bilayer ice, ice I, and liquid water. The deposition nucleation of bilayer ice and ice I is preceded by the formation of small liquid clusters, which have two wetting states: bilayer pancake-like (wetting) at small cluster size and droplet-like (non-wetting) at larger cluster size. The wetting state of liquid clusters determines which ice polymorph is nucleated: bilayer ice nucleates from wetting bilayer liquid clusters and ice I from non-wetting liquid clusters. The maximum temperature for nucleation of bilayer ice on flat surfaces, T{sub B}{sup max} is given by the maximum temperature for which liquid water clusters reach the equilibrium melting line of bilayer ice as wetting bilayer clusters. Increasing water-surface attraction stabilizes the pancake-like wetting state of liquid clusters leading to larger T{sub B}{sup max} for the flat non-hydrogen bonding surfaces of this study. The findings of this study should be of relevance for the understanding of ice formation by deposition mode on carbonaceous atmospheric particles, including soot.

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

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

    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 apolar tails of the lipids in the bilayer organise themselves more like matches in a box or rather like hot spaghetti in a pan?3. How does this membrane organisation depend on temperature?4. How do additives like surfactants or polym...

  5. Role of water in the physical stability of solid dosage formulations

    DEFF Research Database (Denmark)

    Airaksinen, Sari; Karjalainen, Milja; Shevchenko, Anna;

    2005-01-01

    The interaction of moisture with pharmaceutical solids is highly crucial to an understanding of water-based processes, for example, manufacturing processes or prediction of solid dosage form stability and shelf life. Both the active pharmaceutical ingredient (API) and excipients in the formulation...

  6. Physical characterization and photoluminescence properties of thioglycolic acid-stabilized lead sulfide nanocrystals

    International Nuclear Information System (INIS)

    Lead sulfide (PbS) nanocrystals (NCs) were surfactant-free synthesized and stabilized with thioglycolic acid (TGA) by an environmentally friendly and controllable chemical route. Structural, surface morphological, optical and photoluminescence properties of the samples were studied using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), low-resolution transmission electron microscopy (LR-TEM), FT-IR spectroscopy, UV–visible spectroscopy and fluorescence spectroscopy, respectively. The synthesized TGA-PbS NCs showed a well-defined cubic morphology and size monodispersity, as well as good dispersibility in aqueous solution. The optical and photoluminescence study showed that these NCs were very crystalline, size quantized and exhibited a single strong, narrow red emission band centered at λEm = 680 nm. Time evolution of the emission properties was analyzed after six, twelve and twenty four months. The results confirmed that the as-prepared product is photostable when it is kept under storage at 4 °C and has great potential for both biotechnological applications and analytical purposes. A probable chemical stabilization mechanism is proposed. - Highlights: • PbS NCs were synthesized and stabilized with TGA by a greener chemical route. • The TGA-PbS NCs exhibited a single strong, narrow red emission band at 680 nm. • The photostability property of the TGA-PbS NCs was monitored during 24 months. • A probable chemical stabilization mechanism is proposed

  7. The role of physical forces on cytotoxic T cell-target cell conjugate stability.

    Science.gov (United States)

    Hubbard, B B; Glacken, M W; Rodgers, J R; Rich, R R

    1990-06-01

    Theoretical considerations suggest that external forces play a significant role in cell-cell conjugate formation and may lead to the misinterpretation of adhesion data. To test this, the stability of conjugates formed between CTL and fibroblast target cells (TC) was examined in the controlled shear environment of a parallel plate flow chamber. Murine fibroblast targets expressing class I maternally transmitted Ag Mtaa or Mtab were grown on a glass slide that formed one wall of the flow chamber and were used in conjunction with anti-Mtaa and anti-Mtab specific mouse CTL clones to establish a panel of Ag-reciprocal targets and lymphocytes. Although cytolysis assays indicated that lymphocytes recognized and destroyed appropriate but not inappropriate targets, the stability of some CTL/TC conjugates was Ag independent. In all cases, the conjugate stability was shear dependent over a 100-fold range (0.04 to 4.0 dynes/cm2). For some clones, the ratio of the stabilities of Ag-specific CTL/TC conjugates to nonspecific conjugates was significantly enhanced with increasing shear. This implies that the role of Ag specificity in CTL/TC adhesion may be misinterpreted if the shear environment of CTL/TC conjugates is unknown or uncontrolled. Kinetic analysis revealed that conjugate stability was dependent on the exposure time to external forces and that there existed two populations of conjugates; weak associations that disengaged within the first 30 s of flow, and strong associations that remained attached even after a 5-min exposure to a steady shear stress. The stability of Ag-specific CTL/TC conjugates at 0.04 dynes/cm2 was enhanced by 50% as the temperature was increased from 25 to 37 degrees C, whereas the stability of nonspecific CTL/TC associations was not affected. This result indicates that significant Ag-specific strengthening may occur at physiologic temperatures. This work suggests the importance of attention to role of fluid mechanical shear stress in standard

  8. Comparison of thermal fluctuations in foam films and bilayer structures

    OpenAIRE

    Ivanova, N. G.; Tsekov, R.

    2013-01-01

    In the frames of the DLVO theory the root mean square amplitude and correlation length of capillary waves in thin liquid films are calculated. Their dependencies on some important physical parameters are studied. Two models are considered: films with classical interfaces and films between lipid bilayers. The performed numerical analysis demonstrates essential difference in their behavior, which is due to the different elastic properties of the film surfaces in the models.

  9. Interactions of monovalent salts with cationic lipid bilayers

    Czech Academy of Sciences Publication Activity Database

    Pokorná, Šárka; Jurkiewicz, Piotr; Cwiklik, Lukasz; Vazdar, Mario; Hof, Martin

    2013-01-01

    Roč. 160, č. 2013 (2013), s. 341-358. ISSN 1359-6640 R&D Projects: GA ČR GBP208/12/G016; GA AV ČR GEMEM/09/E006 Institutional support: RVO:61388955 ; RVO:61388963 Keywords : FLUORESCENCE SOLVENT RELAXATION * MOLECULAR-DYNAMICS SIMULATIONS * PHOSPHOLIPID-BILAYERS Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.194, year: 2013

  10. Capacitance of Graphene Bilayer as a Which-Layer Probe

    OpenAIRE

    Young, Andrea F.; Levitov, Leonid S.

    2011-01-01

    The unique capabilities of capacitance measurements in bilayer graphene enable probing of layer-specific properties that are normally out of reach in transport measurements. Furthermore, capacitance measurements in the top-gate and penetration field geometries are sensitive to different physical quantities: the penetration field capacitance probes the two layers equally, whereas the top gate capacitance preferentially samples the near layer, resulting in the "near-layer capacitance enhancemen...

  11. Phase-separation transitions in asymmetric lipid bilayers

    CERN Document Server

    Shimobayashi, Shunsuke F; Taniguchi, Takashi

    2015-01-01

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

  12. Einstein's physical strategy, energy conservation, symmetries, and stability: "But Grossmann & I believed that the conservation laws were not satisfied"

    Science.gov (United States)

    Pitts, J. Brian

    2016-05-01

    Recent work on the history of General Relativity by Renn et al. shows that Einstein found his field equations partly by a physical strategy including the Newtonian limit, the electromagnetic analogy, and energy conservation. Such themes are similar to those later used by particle physicists. How do Einstein's physical strategy and the particle physics derivations compare? What energy-momentum complex(es) did he use and why? Did Einstein tie conservation to symmetries, and if so, to which? How did his work relate to emerging knowledge (1911-1914) of the canonical energy-momentum tensor and its translation-induced conservation? After initially using energy-momentum tensors hand-crafted from the gravitational field equations, Einstein used an identity from his assumed linear coordinate covariance xμ‧ = Mνμ xν to relate it to the canonical tensor. Usually he avoided using matter Euler-Lagrange equations and so was not well positioned to use or reinvent the Herglotz-Mie-Born understanding that the canonical tensor was conserved due to translation symmetries, a result with roots in Lagrange, Hamilton and Jacobi. Whereas Mie and Born were concerned about the canonical tensor's asymmetry, Einstein did not need to worry because his Entwurf Lagrangian is modeled not so much on Maxwell's theory (which avoids negative-energies but gets an asymmetric canonical tensor as a result) as on a scalar theory (the Newtonian limit). Einstein's theory thus has a symmetric canonical energy-momentum tensor. But as a result, it also has 3 negative-energy field degrees of freedom (later called "ghosts" in particle physics). Thus the Entwurf theory fails a 1920s-1930s a priori particle physics stability test with antecedents in Lagrange's and Dirichlet's stability work; one might anticipate possible gravitational instability. This critique of the Entwurf theory can be compared with Einstein's 1915 critique of his Entwurf theory for not admitting rotating coordinates and not getting

  13. Bilayer Effects of Antimalarial Compounds.

    Directory of Open Access Journals (Sweden)

    Nicole B Ramsey

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Lundbaek, Jens August [Department of Physiology and Biophysics, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021 (United States)

    2006-07-19

    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{sub 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.

  15. High passive-stability diode-laser design for use in atomic-physics experiments

    CERN Document Server

    Cook, Eryn C; Brown-Heft, Tobias L; Garman, Jeffrey C; Steck, Daniel A

    2012-01-01

    We present the design and performance characterization of an external cavity diode-laser system optimized for high stability, low passive spectral linewidth, low cost, and ease of in-house assembly. The main cavity body is machined from a single aluminum block for robustness to temperature changes and mechanical vibrations, and features a stiff and light diffraction-grating arm to suppress low-frequency mechanical resonances. The cavity is vacuum-sealed, and a custom-molded silicone external housing further isolates the system from acoustic noise and temperature fluctuations. Beam shaping, optical isolation, and fiber coupling are integrated, and the design is easily adapted to many commonly used wavelengths. Resonance data, passive-linewidth data, and passive stability characterization of the new design demonstrate that its performance exceeds published specifications for commercial precision diode-laser systems. The design is fully documented and freely available.

  16. 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

  17. Cholesterol enhances surface water diffusion of phospholipid bilayers

    Science.gov (United States)

    Cheng, Chi-Yuan; Olijve, Luuk L. C.; Kausik, Ravinath; Han, Songi

    2014-12-01

    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 1H 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 faster

  18. Reversibly formed bilayer vesicles: Energetics and polydispersity

    DEFF Research Database (Denmark)

    Bergstöm, M.

    Model calculations based on the multiple equilibrium approach indicate that the spontaneous formation of geometrically closed bilayer vesicles is geared primarily by the bilayer tension which in turn is largely determined by the work of bending the bilayer into a spherical vesicle. and a statisti......Model calculations based on the multiple equilibrium approach indicate that the spontaneous formation of geometrically closed bilayer vesicles is geared primarily by the bilayer tension which in turn is largely determined by the work of bending the bilayer into a spherical vesicle. and a...... orders of magnitude larger than where the local free energy minima of the equilibrium vesicle actually occur. Moreover, according to our analysis, the relative width of a vesicle size distribution, sigma(R)/R-max, is generally at full equilibrium equal to 0.283, independently of the energetic vesicle...

  19. Reversibly formed bilayer vesicles: Energetics and polydispersity

    DEFF Research Database (Denmark)

    Bergstöm, M.

    1997-01-01

    statistical-mechanical factor that accounts for the fluctuations in composition, chain packing density and shape. We demonstrate that the free energy required to form a spherical vesicle is made up of two main contributions: the (size-independent) work of bending the constituent monolayers and the work of......Model calculations based on the multiple equilibrium approach indicate that the spontaneous formation of geometrically closed bilayer vesicles is geared primarily by the bilayer tension which in turn is largely determined by the work of bending the bilayer into a spherical vesicle. and a...... stretching the bilayer that is determined by the planar bilayer tension. A previously undiscovered contribution to the work of bending a vesicle bilayer, originating from geometrical packing constraints, is presented. On this basis we obtain vesicle size distributions with maxima located at radii several...

  20. Effect of rock mass structure and block size on the slope stability--Physical modeling and discrete element simulation

    Institute of Scientific and Technical Information of China (English)

    LI; Shihai; LIAN; Zhenzhong; J.; G.; Wang

    2005-01-01

    This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

  1. Fragmented state of lipid bilayers in water

    DEFF Research Database (Denmark)

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

    1999-01-01

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

  2. The Stability of Child Physical Placements following Divorce: Descriptive Evidence from Wisconsin

    Science.gov (United States)

    Berger, Lawrence M.; Brown, Patricia R.; Joung, Eunhee; Melli, Marygold S.; Wimer, Lynn

    2008-01-01

    This study uses administrative data from the Wisconsin Court Record Database, linked with survey data collected from mothers (n= 789) and fathers (n= 690), to describe the living arrangements of children with sole mother and shared child physical placement following parental divorce. Contrary to prior research, results provide little evidence that…

  3. 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...

  4. Numerical Stability and Accuracy of Temporally Coupled Multi-Physics Modules in Wind-Turbine CAE Tools

    Energy Technology Data Exchange (ETDEWEB)

    Gasmi, A.; Sprague, M. A.; Jonkman, J. M.; Jones, W. B.

    2013-02-01

    In this paper we examine the stability and accuracy of numerical algorithms for coupling time-dependent multi-physics modules relevant to computer-aided engineering (CAE) of wind turbines. This work is motivated by an in-progress major revision of FAST, the National Renewable Energy Laboratory's (NREL's) premier aero-elastic CAE simulation tool. We employ two simple examples as test systems, while algorithm descriptions are kept general. Coupled-system governing equations are framed in monolithic and partitioned representations as differential-algebraic equations. Explicit and implicit loose partition coupling is examined. In explicit coupling, partitions are advanced in time from known information. In implicit coupling, there is dependence on other-partition data at the next time step; coupling is accomplished through a predictor-corrector (PC) approach. Numerical time integration of coupled ordinary-differential equations (ODEs) is accomplished with one of three, fourth-order fixed-time-increment methods: Runge-Kutta (RK), Adams-Bashforth (AB), and Adams-Bashforth-Moulton (ABM). Through numerical experiments it is shown that explicit coupling can be dramatically less stable and less accurate than simulations performed with the monolithic system. However, PC implicit coupling restored stability and fourth-order accuracy for ABM; only second-order accuracy was achieved with RK integration. For systems without constraints, explicit time integration with AB and explicit loose coupling exhibited desired accuracy and stability.

  5. Immobilization of Yarrowia lipolytica Lipase—A Comparison of Stability of Physical Adsorption and Covalent Attachment Techniques

    Science.gov (United States)

    Cunha, Aline G.; Fernández-Lorente, Gloria; Bevilaqua, Juliana V.; Destain, Jacqueline; Paiva, Lúcia M. C.; Freire, Denise M. G.; Fernández-Lafuente, Roberto; Guisán, Jose M.

    Lipase immobilization offers unique advantages in terms of better process control, enhanced stability, predictable decay rates and improved economics. This work evaluated the immobilization of a highly active Yarrowia lipolytica lipase (YLL) by physical adsorption and covalent attachment. The enzyme was adsorbed on octyl-agarose and octadecyl-sepabeads supports by hydrophobic adsorption at low ionic strength and on MANAE-agarose support by ionic adsorption. CNBr-agarose was used as support for the covalent attachment immobilization. Immobilization yields of 71, 90 and 97% were obtained when Y. lipolytica lipase was immobilized into octyl-agarose, octadecyl-sepabeads and MANAE-agarose, respectively. However, the activity retention was lower (34% for octyl-agarose, 50% for octadecyl-sepabeads and 61% for MANAE-agarose), indicating that the immobilized lipase lost activity during immobilization procedures. Furthermore, immobilization by covalent attachment led to complete enzyme inactivation. Thermal deactivation was studied at a temperature range from 25 to 45°C and pH varying from 5.0 to 9.0 and revealed that the hydrophobic adsorption on octadecyl-sepabeads produced an appreciable stabilization of the biocatalyst. The octadecyl-sepabeads biocatalyst was almost tenfold more stable than free lipase, and its thermal deactivation profile was also modified. On the other hand, the Y. lipolytica lipase immobilized on octyl-agarose and MANAE-agarose supports presented low stability, even less than the free enzyme.

  6. 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...... 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...

  7. 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.

  8. Physical singularity in the regular spacetime, stability of theory and fundamental length

    International Nuclear Information System (INIS)

    It is shown that formally regular solutions in 5D Kaluza-Klein gravity have singularities. This phenomenon is connected with the existence of a minimal length in nature. The calculation of the derivative of the G55 metric component leads to the appearance of the Dirac's δ-function. In this case the Ricci scalar becomes singular since there is a square of this derivative. On the basis of the technique of Lie algebra stabilization the natural way of entering the fundamental length is considered and discussed. (author)

  9. 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...... with different water sorbing potential were found to influence distinctly on the phase transformation behaviour of each drug. Moreover, the amount of water addition was also a critical factor affecting phase transformation behaviour. HPLC analysis revealed one of the drug:excipient pairs with a...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. 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.

  12. 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.

  13. Advances in the use of nanoscale bilayers to study membrane protein structure and function.

    Science.gov (United States)

    Malhotra, Ketan; Alder, Nathan N

    2014-10-01

    Within the last decade, nanoscale lipid bilayers have emerged as powerful experimental systems in the analysis of membrane proteins (MPs) for both basic and applied research. These discoidal lipid lamellae are stabilized by annuli of specially engineered amphipathic polypeptides (nanodiscs) or polymers (SMALPs/Lipodisqs®). As biomembrane mimetics, they are well suited for the reconstitution of MPs within a controlled lipid environment. Moreover, because they are water-soluble, they are amenable to solution-based biochemical and biophysical experimentation. Hence, due to their solubility, size, stability, and monodispersity, nanoscale lipid bilayers offer technical advantages over more traditional MP analytic approaches such as detergent solubilization and reconstitution into lipid vesicles. In this article, we review some of the most recent advances in the synthesis of polypeptide- and polymer-bound nanoscale lipid bilayers and their application in the study of MP structure and function. PMID:25023464

  14. First-principles study on electronic and magnetic properties of MnO3 superhalogen cluster-doped bilayer graphene

    International Nuclear Information System (INIS)

    Stability and magnetism of MnO3 superhalogen clusters embedded in bilayer graphene are investigated on the basis of first-principles calculations. MnO3-doped bilayer structures exhibit negative formation energies; by comparison, MnO3 embedded in monolayer graphene shows higher negative formation energy. Compared to MnO3-doped monolayer graphene MnO3-doped bilayer structures have higher structural stability due to higher binding energies. The charge from the lower graphene layer by MnO3 clusters then transfers to the upper layer graphene. The significant p-d hybridization between C and O atoms in graphene and Mn atoms leads to the exchange interaction causing the spin polarization of bilayer graphene. The MnO3 doped structures exhibit a half-metal nature with potential applications for spin field effect transistors (spin-FETs). (paper)

  15. A nanohybrid membrane with lipid bilayer-like properties utilized as a conductimetric saccharin sensor.

    Science.gov (United States)

    Chalkias, Nikolaos G; Giannelis, Emmanuel P

    2007-10-31

    Since their introduction, artificial lipid bilayer membranes were used in a wide array of applications, such as sensors, biocompatible materials and study-models of the cell's outer boundary. Here, we present a nanohybrid membrane using an inorganic host and amphiphilic organic molecules with lipid bilayer-like properties. The stability of the presented mimetic membrane is significantly improved when compared to existing methods. The nanohybrid membrane exhibited two thermotropic phases corresponding to the L(alpha) and L(beta) phases that lipid bilayer membranes are known to adopt. Integration of cholesterol molecules into the nanohybrid membrane lead to the same qualitative effects as in lipid bilayers, including expansion of the bilayer spacing and decrease of the L(alpha) to L(beta) transition enthalpy. To further illustrate the similarities of the synthesized membrane with a lipid bilayer, the ability of the nanohybrid membrane to function as saccharin conductimetric sensor was evaluated. The lower limit of detection of the sensor was 6 microM and the linear range of response was from 20 to 400 microM. PMID:17548189

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

    International Nuclear Information System (INIS)

    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)

  17. Development of cetyl dimethicone based water-in-oil emulsion containing botanicals: Physical characteristics and stability.

    Science.gov (United States)

    Waqas, Muhammad Khurram; Akhtar, Naveed; Shah, Pervaiz Akhtar; Danish, Muhammad Zeeshan; Shah, Arshad Ali; Braga, Valdir de Andrade; Khan, Barkat Ali

    2016-01-01

    The aim of current research was to develop a water-in-oil emulsion containing grape seed extract for application in cosmeceuticals. Finally grinded dried grape seeds powder was extracted with hydro alcoholic mixture. Emulsions consisting of different concentrations of cetyl dimethicone (Abile EM90), the nonionic emulsifier, liquid paraffin as oily phase and water as aqueous phase were developed. Color, odor, pH, viscosity, liquefaction, phase separation, centrifugation and thermal stability of the formulated emulsions were observed at various storage temperatures i.e. 8±0.5°C, 25±0.5°C, 40±0.5°C and 40°C±0.5°C with 70% RH. The stable formulation consist of 16% mineral oil, 4% of ABIL EM 90(®), 4% grape seeds extract, 1% rose oil and 75% distilled water. All the results derived from this study showed good stability over the three months study period which indicates w/o emulsion can be used as carrier of 4% grape seeds extract to enhance desired effects when applied topically. PMID:26826810

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

    International Nuclear Information System (INIS)

    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 K2CO3) 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 K2CO3 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 K2CO3 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)

  19. Diamond stabilization of ice multilayers at human body temperature

    Science.gov (United States)

    Wissner-Gross, Alexander D.; Kaxiras, Efthimios

    2007-08-01

    Diamond is a promising material for wear-resistant medical coatings. Here we report a remarkable increase in the melting point of ice resting on a diamond (111) surface modified with a submonolayer of Na+ . Our molecular dynamics simulations show that the interfacial ice bilayer melts at a temperature 130K higher than in free ice, and relatively thick ice films ( 2.6nm at 298K and 2.2nm at 310K ) are stabilized by dipole interactions with the substrate. This unique physical effect may enable biocompatibility-enhancing ice overcoatings for diamond at human body temperature.

  20. Aerodynamic characteristics of a feathered dinosaur measured using physical models. Effects of form on static stability and control effectiveness.

    Science.gov (United States)

    Evangelista, Dennis; Cardona, Griselda; Guenther-Gleason, Eric; Huynh, Tony; Kwong, Austin; Marks, Dylan; Ray, Neil; Tisbe, Adrian; Tse, Kyle; Koehl, Mimi

    2014-01-01

    We report the effects of posture and morphology on the static aerodynamic stability and control effectiveness of physical models based on the feathered dinosaur, [Formula: see text]Microraptor gui, from the Cretaceous of China. Postures had similar lift and drag coefficients and were broadly similar when simplified metrics of gliding were considered, but they exhibited different stability characteristics depending on the position of the legs and the presence of feathers on the legs and the tail. Both stability and the function of appendages in generating maneuvering forces and torques changed as the glide angle or angle of attack were changed. These are significant because they represent an aerial environment that may have shifted during the evolution of directed aerial descent and other aerial behaviors. Certain movements were particularly effective (symmetric movements of the wings and tail in pitch, asymmetric wing movements, some tail movements). Other appendages altered their function from creating yaws at high angle of attack to rolls at low angle of attack, or reversed their function entirely. While [Formula: see text]M. gui lived after [Formula: see text]Archaeopteryx and likely represents a side experiment with feathered morphology, the general patterns of stability and control effectiveness suggested from the manipulations of forelimb, hindlimb and tail morphology here may help understand the evolution of flight control aerodynamics in vertebrates. Though these results rest on a single specimen, as further fossils with different morphologies are tested, the findings here could be applied in a phylogenetic context to reveal biomechanical constraints on extinct flyers arising from the need to maneuver. PMID:24454820

  1. Aerodynamic characteristics of a feathered dinosaur measured using physical models. Effects of form on static stability and control effectiveness.

    Directory of Open Access Journals (Sweden)

    Dennis Evangelista

    Full Text Available We report the effects of posture and morphology on the static aerodynamic stability and control effectiveness of physical models based on the feathered dinosaur, [Formula: see text]Microraptor gui, from the Cretaceous of China. Postures had similar lift and drag coefficients and were broadly similar when simplified metrics of gliding were considered, but they exhibited different stability characteristics depending on the position of the legs and the presence of feathers on the legs and the tail. Both stability and the function of appendages in generating maneuvering forces and torques changed as the glide angle or angle of attack were changed. These are significant because they represent an aerial environment that may have shifted during the evolution of directed aerial descent and other aerial behaviors. Certain movements were particularly effective (symmetric movements of the wings and tail in pitch, asymmetric wing movements, some tail movements. Other appendages altered their function from creating yaws at high angle of attack to rolls at low angle of attack, or reversed their function entirely. While [Formula: see text]M. gui lived after [Formula: see text]Archaeopteryx and likely represents a side experiment with feathered morphology, the general patterns of stability and control effectiveness suggested from the manipulations of forelimb, hindlimb and tail morphology here may help understand the evolution of flight control aerodynamics in vertebrates. Though these results rest on a single specimen, as further fossils with different morphologies are tested, the findings here could be applied in a phylogenetic context to reveal biomechanical constraints on extinct flyers arising from the need to maneuver.

  2. A true 3D physical model test study on the stability of an underground cavern group in Shuangjiangkou Hydropower Station

    Science.gov (United States)

    Zhu, Weishen; Zhang, Lei; Li, Yong; Zhang, Qianbing

    2010-03-01

    Taking the underground caverns of Shuangjiangkou (SJK) Hydropower Station as an engineering background, a largescale true 3D physical model test is performed to study the stability of the enclosing rock masses, including the analogous material, the steel structure frame, fabrications of rock bolts and cables, development of the measuring techniques, fabrication of the physical model, excavations and the overload test. The developed steel structure can simulate the complicated circumstances just like high in-situ stress and high overburden depth. It also can apply the true 3D loading on six surfaces of the physical model. Many combinational ball sliding blocks are installed between model surface and the structural wall to reduce the friction between the contact surfaces. During the model construction, precast blocks are used and monitoring holes are predefined before the analogous material is piled up. A unique grouting technique and prestressed cables are adopted in the model test. A digital photogrammetric technique, displacement sensing bars based on Fiber Bragg Gratings (FBG) technology, and mini extensometers are developed and adopted for measuring the deformation in the process of excavations. The overload tests are accomplished under the conditions of different overburden depths. The results of this research will make certain guiding significance to the practical engineering.

  3. Superdiffusion in supported lipid bilayers

    CERN Document Server

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

    2015-01-01

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

  4. The Targeted Delivery of Multicomponent Cargos to Cancer Cells via Nanoporous Particle-Supported Lipid Bilayers

    OpenAIRE

    Ashley, Carlee E.; CARNES, ERIC C.; Phillips, Genevieve K.; Padilla, David; Durfee, Paul N.; Brown, Page A.; Hanna, Tracey N.; Liu, Juewen; Phillips, Brandy; Carter, Mark B.; Carroll, Nick J.; Jiang, Xingmao; Dunphy, Darren R.; Willman, Cheryl L.; Petsev, Dimiter N.

    2011-01-01

    Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability, and a high capacity for disparate cargos. Here we report porous nanoparticle-supported lipid bilayers (protocells) that ...

  5. Physical Stability Studies of Semi-Solid Formulations from Natural Compounds Loaded with Chitosan Microspheres.

    Science.gov (United States)

    Acosta, Niuris; Sánchez, Elisa; Calderón, Laura; Cordoba-Diaz, Manuel; Cordoba-Diaz, Damián; Dom, Senne; Heras, Ángeles

    2015-09-01

    A chitosan-based hydrophilic system containing an olive leaf extract was designed and its antioxidant capacity was evaluated. Encapsulation of olive leaf extract in chitosan microspheres was carried out by a spray-drying process. The particles obtained with this technique were found to be spherical and had a positive surface charge, which is an indicator of mucoadhesiveness. FTIR and X-ray diffraction results showed that there are not specific interactions of polyphenolic compounds in olive leaf extract with the chitosan matrix. Stability and release studies of chitosan microspheres loaded with olive leaf extract before and after the incorporation into a moisturizer base were performed. The resulting data showed that the developed formulations were stable up to three months. The encapsulation efficiency was around 44% and the release properties of polyphenols from the microspheres were found to be pH dependent. At pH 7.4, polyphenols release was complete after 6 h; whereas the amount of polyphenols released was 40% after the same time at pH 5.5. PMID:26389926

  6. Annular bilayer magnetoelectric composites: theoretical analysis.

    Science.gov (United States)

    Guo, Mingsen; Dong, Shuxiang

    2010-01-01

    The laminated bilayer magnetoelectric (ME) composites consist of magnetostrictive and piezoelectric layers are known to have giant ME coefficient due to the high coupling efficiency in bending mode. In our previous report, the bar-shaped bilayer composite has been investigated by using a magnetoelectric-coupling equivalent circuit. Here, we propose an annular bilayer ME composite, which consists of magnetostrictive and piezoelectric rings. This composite has a much lower resonance frequency of bending mode compared with its radial mode. In addition, the annular bilayer ME composite is expected to respond to vortex magnetic field as well as unidirectional magnetic field. In this paper, we investigate the annular bilayer ME composite by using impedance-matrix method and predict the ME coefficients as a function of geometric parameters of the composites. PMID:20178914

  7. 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...

  8. Structural and elastic properties and stability characteristics of oxygenated carbon nanotubes under physical adsorption of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, R., E-mail: r_ansari@guilan.ac.ir [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Ajori, S. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Rouhi, S. [Department of Mechanical Engineering, Langroud Branch, Islamic Azad University, Langroud (Iran, Islamic Republic of)

    2015-03-30

    Highlights: • Buckling of functionalized CNTs under physical adsorption of polymer is studied. • Molecular dynamics simulations are employed for the study. • Values of the critical buckling load and critical strain are shown to increase. • Values of Young's modulus and their variations are dependent on adsorbed polymer type. - Abstract: The importance of covalent and non-covalent functionalization approaches for modification the properties of carbon nanotubes is being more widely recognized. To this end, elastic properties and buckling behavior of oxygenated CNT with atomic oxygen and hydroxyl under physical adsorption of PE (Polyethylene) and PEO (Poly (ethylene oxide)) are determined through employing the molecular dynamics (MD) simulations. The results demonstrate that non-covalent bonding of polymer on the surface of oxygenated CNT causes reductions in the variations of critical buckling load and critical strain compared to oxygenated CNTs. Critical buckling load and critical strain of oxygenated CNT/polymer are higher than those of oxygenated CNT. Also, it is demonstrated that critical buckling load and critical strain values in the case of oxygenated CNT/polymer are independent of polymer type unlike the value of Young's modulus. It is shown that variations of Young's modulus decrease as PE adsorbed on the surface of oxygenated CNT. Moreover, the presence of oxygen atom on PEO chain leads to bigger variations of Young's modulus with weight percentage of chemisorbed component, i.e. atomic oxygen and hydroxyl. It is also demonstrated that Young's modulus reduces more considerably in the presence of PEO chain compared to PE one.

  9. 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.

  10. Monitoring the chemical and physical stability for tromethamine excipient in a lipid based formulation by HPLC coupled with ELSD.

    Science.gov (United States)

    Rodríguez, Shirley A; Qiu, Fenghe; Mulcey, Michael; Weigandt, Karen; Tamblyn, Toby

    2015-11-10

    Tromethamine, a UV-transparent amine base excipient, was used in the liquid phase of a self-emulsifying drug delivery system-soft gelatin capsule (SEDDS-SGC) formulation as an emulsification agent and to improve solubilization of the active drug. The level of this excipient was found to be decreasing in aged and stressed drug product capsules. The decrease could potentially affect oral bioavailability of the drug; should the amount of solubilizer decrease enough to lead to precipitation of the active drug from the formulation. Therefore, further investigation was warranted. HPLC coupled with evaporative light scattering detection (ELSD) was used to monitor the physical and chemical stability of tromethamine in the SEDDS-SGC formulation. Confirmation of the tromethamine interaction products was done by LC-MS. PMID:26254033

  11. "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

  12. 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

  13. Stability and support issues in the construction of large span caverns for physics

    Energy Technology Data Exchange (ETDEWEB)

    Laughton, C.; /Fermilab

    2008-05-01

    New physics experiments, proposed to study neutrinos and protons, call for the use of large underground particle detectors. In the United States, such detectors would be housed in the US Deep Underground Science and Engineering Laboratory (DUSEL), sited within the footprint of the defunct Homestake Mine, South Dakota. Although the experimental proposals differ in detail, all rely heavily upon the ability of the mined and reinforced rock mass to serve as a stable host for the detector facilities. Experimental proposals, based on the use of Water Cherenkov detector technology, specify rock caverns with excavated volumes in excess of half a million cubic meters, spans of at least 50 m, sited at depths of approximately one to 1.5 kilometers. Although perhaps sited at shallower depth, proposals based on the use of Liquid Argon (LAr) detector technology are no less challenging. LAr proposals not only call for the excavation of large span caverns, but have an additional need for the safe management of large quantities (kilo-tonnes) of cryogenic liquid, including critical provisions for the fail-safe egress of underground personnel and the reliable exhaust of Argon gas in the event of a catastrophic release. These multi-year, high value physics experiments will provide the key experimental data needed to support the research of a new generation of physicists as they probe the behavior of basic particles and the fundamental laws of nature. The rock engineer must deliver caverns that will reliably meet operational requirements and remain stable for periods conservatively estimated to be in excess of twenty years. This paper provides an overview of the DUSEL site conditions and discusses key end-user requirements and design criteria likely to dominate in determining the viability of experimental options. The paper stresses the paramount importance of collecting adequate site-specific data to inform early siting, dimensioning and layout decisions. Given the large-scale of the

  14. Effect of Water on Molecular Mobility and Physical Stability of Amorphous Pharmaceuticals.

    Science.gov (United States)

    Mehta, Mehak; Kothari, Khushboo; Ragoonanan, Vishard; Suryanarayanan, Raj

    2016-04-01

    We investigated the influence of sorbed water concentration on the molecular mobility and crystallization behavior in a model amorphous drug and a solid dispersion. The temperature scaling (Tg/T) allowed us to simultaneously evaluate the effects of water content and temperature on the relaxation time. In the supercooled dispersions, once scaled, the relaxation times of the systems with different water content overlapped. Thus, the observed increase in mobility could be explained by the "plasticization" effect of water. This effect also explained the decrease in crystallization onset temperature brought about by water. That is, plasticization is the underlying mechanism governing the observed increase in mobility and physical instability in the supercooled state. Similar results were observed in the glassy drug substance. A single linear relationship was observed between crystallization time (time for 0.5% crystallization) and Tg/T in both dry and water containing systems. Since fragility is unaffected by modest amounts of water, much like crystallization time, the mobility in the glass is expected to scale with Tg. PMID:26954586

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

    International Nuclear Information System (INIS)

    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 104 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.)

  16. Viscoelastic changes measured in partially suspended single bilayer membranes.

    Science.gov (United States)

    Hasan, Imad Younus; Mechler, Adam

    2015-07-21

    For studies involving biomimetic phospholipid membrane systems, such as membrane-protein interactions, it is crucial that the supported membrane is biomimetic in its physical properties as well as in its composition. Two often overlooked aspects of biomimicry are the need for unrestrained lipid mobility, reflected in the viscoelastic properties of the membrane, and sufficient space between the membrane and the support for the insertion of transmembrane proteins. Here we show for a series of DMPC-based membranes that a partially suspended single bilayer membrane can be formed on functionalized gold surface without tethering. These membranes exhibit sufficient freedom of motion to represent the viscoelastic properties of a free lamellar bilayer membrane as demonstrated by determining the phase transition temperatures of these single bilayer membranes from the viscosity change upon chain melting using the dissipation signal of a quartz crystal microbalance (QCM-D). Atomic force microscopy imaging confirmed confluent, smooth membrane coverage of the QCM-D sensor that completely obscured the roughness of the sputtered gold surface. High-force AFM imaging was able to push membrane patches into the valleys of the gold morphology, confirming the inherently suspended nature of the MPA supported membrane. We show that the correlation between frequency and dissipation changes in the QCM-D sensograms is a sensitive indicator of the morphology of the membrane. PMID:26073288

  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. Physical and oxidative stability of functional olive oil-in-water emulsions formulated using olive mill wastewater biophenols and whey proteins.

    Science.gov (United States)

    Caporaso, Nicola; Genovese, Alessandro; Burke, Róisín; Barry-Ryan, Catherine; Sacchi, Raffaele

    2016-01-01

    The present paper reports on the use of phenolic extracts from olive mill wastewater (OMW) in model olive oil-in-water (O/W) emulsions to study their effect on their physical and chemical stability. Spray-dried OMW polyphenols were added to a model 20% olive O/W emulsion stabilized with whey protein isolate (WPI) and xanthan gum, in phosphate buffer solution at pH 7. The emulsions were characterised under accelerated storage conditions (40 °C) up to 30 days. Physical stability was evaluated by analysing the creaming rate, mean particle size distribution and mean droplet size, viscosity and rheological properties, while chemical stability was assessed through the measurement of primary and secondary oxidation products. The rheological behaviour and creaming stability of the emulsions were dramatically improved by using xanthan gum, whereas the concentration of WPI and the addition of encapsulated OMW phenolics did not result in a significant improvement of physical stability. The formation of oxidation products was higher when higher concentrations of encapsulated polyphenols were used, indicating a possible binding with the WPI added in the system as a natural emulsifier. This paper might help in solving the issue of using the olive mill wastewater from olive processing in formulating functional food products with high antioxidant activity and improved health properties. PMID:26692051

  19. Fusion and fission of fluid amphiphilic bilayers.

    Science.gov (United States)

    Gotter, Martin; Strey, Reinhard; Olsson, Ulf; Wennerström, Håkan

    2005-01-01

    The system water-oil (n-decane)-nonionic surfactant (C12E5) forms bilayer phases in a large concentration region, but, for a given oil-to-surfactant ratio, only in a narrow temperature range. In addition to the anisotropic lamellar phase (Lalpha) there is also, at slightly higher temperature, a sponge or L3-phase where the bilayers build up an isotropic structure extending macroscopically in three dimensions. In this phase the bilayer mid-surface has a mean curvature close to zero and a negative Euler characteristic. In this paper we study how the bilayers in the lamellar and the sponge phase respond dynamically to sudden temperature changes. The monolayer spontaneous curvature depends sensitively on temperature and a change of temperature thus provides a driving force for a change in bilayer topology. The equilibration therefore involves kinetic steps of fusion/fission of bilayers. Such dynamic processes have previously been monitored by temperature jump experiments using light scattering in the sponge phase. These experiments revealed an extraordinarily strong dependence of the relaxation time on the bilayer volume fraction phi. At phi magnetic resonance (2H-NMR) appear feasible. We here report on the first experiments concerned with the dynamics of the macroscopic phase transition sponge-lamellae by 2H-NMR. We find that the sponge-to-lamellae transition occurs through a nucleation process followed by domain growth involving bilayer fission at domain boundaries. In contrast, the lamellae-to-sponge transformation apparently occurs through a succession of uncorrelated bilayer fusion events. PMID:15715316

  20. A slow cooling rate of indomethacin melt spatially confined in microcontainers increases the physical stability of the amorphous drug without influencing its biorelevant dissolution behaviour

    DEFF Research Database (Denmark)

    Nielsen, Line Hagner; Keller, Stephan Sylvest; Boisen, Anja; Müllertz, A.; Rades, T.

    2013-01-01

    Amorphous indomethacin was prepared by melting the γ-form of indomethacin, spatially confined within microcontainers (inner diameter of 223 μm), followed by cooling of the melt at a rate of 14, 23 or 36 K/min. The physical stability of the amorphous indomethacin within microcontainers was....../min, whereas cracks and an uneven surface were observed when cooling at rates of 23 and 36 K/min. The uneven surface is hypothesised to be the main reason for the lower physical stability, as the cracks could act as nucleation sites for crystal growth. The rate of cooling was not seen to have any effect on the...

  1. Lipid bilayer-assisted release of an enediyne antibiotic from neocarzinostatin chromoprotein.

    Science.gov (United States)

    Hariharan, Parameswaran; Sudhahar, Christopher Gunasekaran; Chou, Shan-Ho; Chin, Der-Hang

    2010-09-01

    The nine-membered enediyne class has drawn extensive interest because of extremely high antitumor potency and intricate interactions with its carrier protein. While the drug-induced DNA cleavage reactions have been mostly elucidated, the critical release-transport process of the labile enediyne molecule in cellular environment remained obscure. Using neocarzinostatin chromoprotein as a model, we demonstrated a lipid bilayer-assisted release mechanism. The in vitro enediyne release rate under aqueous conditions was found to be too slow to account for its efficient DNA cleavage action. Via the presence of lipid bilayers, chaotropic agents, or organic solvents, we found the release was substantially enhanced. The increased rate was linearly dependent on the lipid bilayer concentration and the dielectric value of the binary organic solvent mixtures. While lipid bilayers provided a low surrounding dielectricity to assist in drug release, there were no major conformational changes in the apo and holo forms of the carrier protein. In addition, the lifespan of the released enediyne chromophore was markedly extended through partitioning of the chromophore in the hydrophobic bilayer phase, and the lipid bilayer-stabilized enediyne chromophore significantly enhanced DNA cleavage in vitro. Collectively, we depicted how a lipid bilayer membrane efficiently enhanced dissociation of the enediyne chromophore through a hydrophobic sensing release mechanism and then acted as a protector of the released enediyne molecule until its delivery to the target DNA. The proposed membrane-assisted antibiotic release-transport model might signify a new dimension to our understanding of the modus operandi of the antitumor enediyne drugs. PMID:20712297

  2. Is the combination of cellulosic polymers and anionic surfactants a good strategy for ensuring physical stability of BCS Class II drug nanosuspensions?

    Science.gov (United States)

    Bilgili, Ecevit; Li, Meng; Afolabi, Afolawemi

    2016-01-01

    Ensuring the physical stability of drug nanosuspensions prepared via wet media milling has been a challenge for pharmaceutical scientists. The aim of this study is to assess the combined use of non-ionic cellulosic polymers and anionic surfactants in stabilizing multiple drug nanosuspensions. Particle size of five drugs, i.e. azodicarbonamide (AZD), fenofibrate (FNB), griseofulvin (GF), ibuprofen (IBU) and phenylbutazone (PB) was reduced separately in an aqueous solution of hydroxypropyl cellulose (HPC) with/without sodium dodecyl sulfate (SDS) via a stirred media mill. Laser diffraction, scanning electron microscopy, thermal analysis, rheometry and electrophoresis were used to evaluate the breakage kinetics, storage stability, electrostatic repulsion and stabilizer adsorption. Without SDS, drug particles exhibited aggregation to different extents; FNB and GF particles aggregated the most due to low zeta potential and insufficient steric stabilization. Although aggregation in all milled suspensions was reduced due to HPC-SDS combination, FNB and IBU showed notable growth during 7-day storage. It is concluded that the combination of non-ionic cellulosic polymers and anionic surfactants is generally viable for ensuring the physical stability of wet-milled drug nanosuspensions, provided that the surfactant concentration is optimized to mitigate the Ostwald ripening, whereas cellulosic polymers alone may provide stability for some drug suspensions. PMID:25774989

  3. Berry phase transition in twisted bilayer graphene

    Science.gov (United States)

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

    2016-09-01

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

  4. 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...

  5. Texture of lipid bilayer domains

    DEFF Research Database (Denmark)

    Jensen, Uffe Bernchou; Brewer, Jonathan R.; Midtiby, Henrik Skov; Ipsen, John Hjort; Bagatolli, Luis; Simonsen, Adam Cohen

    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...... 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 as a...... which correlates with the phase state of the membrane. This is quantified by the generalized polarization (GP) function, and we demonstrate that a GP analysis can be performed on supported membranes. The results show that although the gel domains have heterogeneous texture, the membrane phase state does...

  6. Spin dynamics of bilayer manganites

    Indian Academy of Sciences (India)

    Tapan Chatterji

    2004-07-01

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

  7. Detection of bilayer lipid with graphene nanoribbon

    Science.gov (United States)

    Akbari, Elnaz; Buntat, Zolkafle; Afroozeh, Abdolkarim; Zeinalinezhad, Alireza; Nilashi, Mehrbakhsh

    2015-09-01

    Single-layer graphene consists of sp 2-bonded carbon atoms arranged in a two-dimensional (2D) hexagonal lattice comprising a thin layer of single carbon atoms. Owing to its special characteristics including electrical, physical, and optical properties, graphene is considered more suitable for sensor applications than other materials. Moreover, it is possible to produce biosensors using electrolyte-gated field-effect transistors based on graphene (GFETs) to identify the alterations in charged lipid membrane properties. This paper illustrates how membrane thickness and electrical charge can result in a monolayer GFET, with emphasis on conductance variation. It is proposed that the thickness and electrical charge of the lipid bilayer are functions of carrier density, and equations relating these suitable control parameters were derived. Adaptive neuro fuzzy inference system (ANFIS) has been incorporated to obtain other model for conductance characteristic. The comparison between the analytical models and ANFIS with the experimental data extracted from previous work show an acceptable agreement. [Figure not available: see fulltext.

  8. 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.

  9. 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. PMID:24147368

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

    International Nuclear Information System (INIS)

    Full text: α-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 β-sheet secondary structure and it has two domains with similar structures. In the present work, a stability study of α-trypsin in the acid pH range was performed and physical-chemical denaturation parameters were measured by using differential scanning calorimetry (DSC). The α-trypsin has a shelf-life (t95%) of about ten months at pH 3.0 and 4 deg C and its hydrolysis into the Ψ-trypsin isoform is negligible during six months as monitored by mass spectrometry (Micromass Q-ToF). The observed ΔHcal/ΔHvH ratio is close to unity for α-trypsin denaturation, which suggests the occurrence of a two-state transition, devoid of molten-globule intermediates. At pH 3.0, α-trypsin unfolded with Tm 325.9 K and ΔH= 99.10 kcal mol-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-1 K-1. The stability of α-trypsin calculated at 298 K and at pH 3.0 was ΔGU = 6.10 kcal mol-1. These values are in the range expected for a small globular protein. These results show that the thermodynamic parameters for unfolding of β-trypsin do not change substantially after its conversion to α-trypsin

  11. Changes in the physical properties, solubility, and heat stability of milk protein concentrates prepared from partially acidified milk.

    Science.gov (United States)

    Eshpari, H; Tong, P S; Corredig, M

    2014-12-01

    A limiting factor in using milk protein concentrates (MPC) as a high-quality protein source for different food applications is their poor reconstitutability. Solubilization of colloidal calcium phosphate (CCP) from casein micelles during membrane filtration (e.g., through acidification) may affect the structural organization of these protein particles and consequently the rehydration and functional properties of the resulting MPC powder. The main objective of this study was to investigate the effects of acidification of milk by glucono-δ-lactone (GDL) before ultrafiltration (UF) on the composition, physical properties, solubility, and thermal stability (after reconstitution) of MPC powders. The MPC samples were manufactured in duplicate, either by UF (65% protein, MPC65) or by UF followed by diafiltration (80% protein, MPC80), using pasteurized skim milk, at either the native milk pH (~pH 6.6) or at pH 6.0 after addition of GDL, followed by spray drying. Samples of different treatments were reconstituted at 5% (wt/wt) protein to compare their solubility and thermal stability. Powders were tested in duplicate for basic composition, calcium content, reconstitutability, particle size, particle density, and microstructure. Acidification of milk did not have any significant effect on the proximate composition, particle size, particle density, or surface morphology of the MPC powders; however, the total calcium content of MPC80 decreased significantly with acidification (from 1.84 ± 0.03 to 1.59 ± 0.03 g/100 g of powder). Calcium-depleted MPC80 powders were also more soluble than the control powders. Diafiltered dispersions were significantly less heat stable (at 120°C) than UF samples when dissolved at 5% solids. The present work contributes to a better understanding of the differences in MPC commonly observed during processing. PMID:25459904

  12. 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. PMID:26954090

  13. Importance of phospholipid bilayer integrity in the analysis of protein–lipid interactions

    Energy Technology Data Exchange (ETDEWEB)

    Drücker, Patrick [Institute of Biochemistry, University of Münster, Wilhelm-Klemm-Str. 2, D-48149 Münster (Germany); Gerke, Volker [Institute of Medical Biochemistry, ZMBE, University of Münster, Von-Esmarch-Str. 56, D-48149 Münster (Germany); Galla, Hans-Joachim, E-mail: gallah@uni-muenster.de [Institute of Biochemistry, University of Münster, Wilhelm-Klemm-Str. 2, D-48149 Münster (Germany)

    2014-10-10

    Highlights: • We show long-term mechanical stabilization of solid supported bilayers. • Bilayer integrity is essential for the investigation of protein–lipid interactions. • Protein adsorption to a bilayer containing defects causes membrane destruction. - Abstract: The integrity of supported phospholipid bilayer membranes is of crucial importance for the investigation of lipid–protein interactions. Therefore we recorded the formation of supported membranes on SiO{sub 2} and mica by quartz crystal microbalance and controlled the integrity by atomic force microscopy. This study aims to analyze how membrane defects affect protein–lipid interactions. The experiments focused on a lipid mixture of POPC/DOPC/Chol/POPS/PI(4,5)P{sub 2} (37:20:20:20:3) and the binding of the peripheral membrane associated protein annexin A2. We found that formation of a continuous undisturbed bilayer is an indispensable precondition for a reliable determination and quantification of lipid–protein-interactions. If membrane defects were present, protein adsorption causes membrane disruption and lipid detachment on a support thus leading to false determination of binding constants. Our results obtained for PI(4,5)P{sub 2} and cholesterol containing supported membranes yield new knowledge to construct functional surfaces that may cover nanoporous substrates, form free standing membranes or may be used for lab-on-a-chip applications.

  14. Importance of phospholipid bilayer integrity in the analysis of protein–lipid interactions

    International Nuclear Information System (INIS)

    Highlights: • We show long-term mechanical stabilization of solid supported bilayers. • Bilayer integrity is essential for the investigation of protein–lipid interactions. • Protein adsorption to a bilayer containing defects causes membrane destruction. - Abstract: The integrity of supported phospholipid bilayer membranes is of crucial importance for the investigation of lipid–protein interactions. Therefore we recorded the formation of supported membranes on SiO2 and mica by quartz crystal microbalance and controlled the integrity by atomic force microscopy. This study aims to analyze how membrane defects affect protein–lipid interactions. The experiments focused on a lipid mixture of POPC/DOPC/Chol/POPS/PI(4,5)P2 (37:20:20:20:3) and the binding of the peripheral membrane associated protein annexin A2. We found that formation of a continuous undisturbed bilayer is an indispensable precondition for a reliable determination and quantification of lipid–protein-interactions. If membrane defects were present, protein adsorption causes membrane disruption and lipid detachment on a support thus leading to false determination of binding constants. Our results obtained for PI(4,5)P2 and cholesterol containing supported membranes yield new knowledge to construct functional surfaces that may cover nanoporous substrates, form free standing membranes or may be used for lab-on-a-chip applications

  15. Passive manipulation of free-surface instability by deformable solid bilayers.

    Science.gov (United States)

    Sahu, Shivam; Shankar, V

    2016-07-01

    This study deals with the elastohydrodynamic coupling that occurs in the flow of a liquid layer down an inclined plane lined with a deformable solid bilayer and its consequences on the stability of the free surface of the liquid layer. The fluid is Newtonian and incompressible, while the linear elastic constitutive relation has been considered for the deformable solid bilayer, and the densities of the fluid and the two solids are kept equal. A temporal linear stability analysis is carried out for this coupled solid-fluid system. A long-wave asymptotic analysis is employed to obtain an analytical expression for the complex wavespeed in the low wave-number regime, and a numerical shooting method is used to solve the coupled set of governing differential equations in order to obtain the stability criterion for arbitrary values of the wave number. In a previous work on plane Couette flow past an elastic bilayer, Neelmegam et al. [Phys. Rev. E 90, 043004 (2014)PLEEE81539-375510.1103/PhysRevE.90.043004] showed that the instability of the flow can be significantly influenced by the nature of the solid layer, which is adjacent to the liquid layer. In stark contrast, for free-surface flow past a bilayer, our long-wave asymptotic analysis demonstrates that the stability of the free-surface mode is insensitive to the nature of the solid adjacent to the liquid layer. Instead, it is the effective shear modulus of the bilayer G_{eff} (given by H/G_{eff}=H_{1}/G_{1}+H_{2}/G_{2}, where H=H_{1}+H_{2} is the total thickness of the solid bilayer, H_{1} and H_{2} are the thicknesses of the two solid layers, and G_{1} and G_{2} are the shear moduli of the two solid layers) that determines the stability of the free surface in the long-wave limit. We show that for a given Reynolds number, the free-surface instability is stabilized when G_{eff} decreases below a critical value. At finite wave numbers, our numerical solution indicates that additional instabilities at the free surface and

  16. Self healing nature of bilayer graphene

    Science.gov (United States)

    Debroy, Sanghamitra; Pavan Kumar Miriyala, V.; Vijaya Sekhar, K.; Acharyya, Swati Ghosh; Acharyya, Amit

    2016-08-01

    The phenomenon of self healing of cracks in bilayer graphene sheet has been studied using molecular dynamics simulations. The bilayer graphene sheet was subjected to uniaxial tensile load resulting in initiation and propagation of cracks on exceeding the ultimate tensile strength. Subsequently, all forces acting on the sheet were removed and sheet was relaxed. The cracks formed in the graphene sheet healed without any external aid within 0.4 ps The phenomenon of self healing of the cracks in graphene sheet was found to be independent of the length of the crack, but occurred for critical crack opening distance less than 5 Å for AA stacked sheet and 13 Å for AB stacked bilayer graphene sheet. Self healing was observed for both AB (mixed stacking of armchair and zigzag graphene sheet) and AA (both sheets of similar orientation i.e. either armchair-armchair or zigzag-zigzag) stacking of bilayer graphene sheet.

  17. Proximity induced superconductivity in bilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Bordaz, Julien; Wu, Fan [Institute of Nanotechnology, Karlsruhe Institute of Technology (Germany); Wolf, Michael; Beckmann, Detlef [Institute of Nanotechnology, Karlsruhe Institute of Technology (Germany); DFG Center for Functional Nanostructures, Karlsruhe Institute of Technology (Germany); Loehneysen, Hilbert von [Institute of Nanotechnology, Karlsruhe Institute of Technology (Germany); DFG Center for Functional Nanostructures, Karlsruhe Institute of Technology (Germany); Institute of Physics, Karlsruhe Institute of Technology (Germany); Institute for Solid-State Physics, Karlsruhe Institute of Technology (Germany); Watanabe, Kenji; Taniguchi, Takashi [Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba (Japan); Danneau, Romain [Institute of Nanotechnology, Karlsruhe Institute of Technology (Germany); Institute of Physics, Karlsruhe Institute of Technology (Germany)

    2013-07-01

    Proximity induced superconductivity effect occurs when graphene is connected with close enough superconducting electrodes. Observations of Andreev reflection and induced supercurrents flowing through graphene sheets have already been reported in graphene. However, these effects have not been explored in bilayer graphene so far. By applying a perpendicular electric field, it is possible to open a gap in a bilayer graphene. This can be achieved in practice by designing a top gate in addition to the usual back gate. Our devices are produced on top of sapphire wafers by using transfer techniques and standard electron-beam lithography. The bilayers are sandwiched between two atomically flat hexagonal boron nitride multilayers which are both used as gate dielectric. By inducing a band gap into a bilayer graphene connected by two superconducting leads, the supercurrent could be switched off inducing a superconductor-insulator transition.

  18. Proximity induced superconductivity in bilayer graphene

    International Nuclear Information System (INIS)

    Proximity induced superconductivity effect occurs when graphene is connected with close enough superconducting electrodes. Observations of Andreev reflection and induced supercurrents flowing through graphene sheets have already been reported in graphene. However, these effects have not been explored in bilayer graphene so far. By applying a perpendicular electric field, it is possible to open a gap in a bilayer graphene. This can be achieved in practice by designing a top gate in addition to the usual back gate. Our devices are produced on top of sapphire wafers by using transfer techniques and standard electron-beam lithography. The bilayers are sandwiched between two atomically flat hexagonal boron nitride multilayers which are both used as gate dielectric. By inducing a band gap into a bilayer graphene connected by two superconducting leads, the supercurrent could be switched off inducing a superconductor-insulator transition.

  19. The magnetic ratchet effect in bilayer graphene

    Science.gov (United States)

    McCann, Edward; Kheirabadi, Narjes; Fal'Ko, Vladimir

    Experiments have measured a magnetic ratchet effect for electrons in hydrogenated monolayer graphene, an effect in which a d.c. electric current is generated from an a.c. electric field in the presence of an in-plane magnetic field and spatial asymmetry. Here, we describe the theory of the magnetic ratchet effect in bilayer graphene. The Boltzmann kinetic equation is used to relate the d.c. current to the scattering probability of electrons in bilayer graphene. Taking into account details of the low-energy band structure of bilayer graphene, including interlayer hopping parameters, we compare contributions arising from gate- and disorder-induced spatial asymmetry, illustrating that bilayer and multilayer graphenes are natural candidates for the study of non-linear transport effects.

  20. PHYSICS

    CERN Document Server

    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 ...

  1. Lipid bilayers decorated with photosensitive ruthenium complexes

    OpenAIRE

    Bahreman, Azadeh

    2013-01-01

    In this thesis the thermal- and photo-substitution behavior of polypyridyl ruthenium complexes is described at the surface of lipid bilayers and in homogeneous solutions. It is shown that the successive thermal binding and light-induced unbinding of the cationic ruthenium complex at the surface of the lipid bilayer requires negatively charged liposomes and ruthenium complexes containing moderately hindered N-N bidentate ligands. Our results in homogeneous solution show that changing the steri...

  2. Twisted bi-layer graphene: microscopic rainbows

    OpenAIRE

    Campos-Delgado, J.; Algara-Siller, G.; Santos, C. N.; Kaiser, U.; Raskin, J.-P.

    2013-01-01

    Twisted bi-layer graphene (tBLG) has recently attracted interest due to the peculiar electrical properties that arise from its random rotational configurations. Our experiments on CVD-grown graphene from Cu foil and transferred onto Si substrates, with an oxide layer of 100 nm, reveal naturally-produced bi-layer graphene patches which present different colorations when shined with white light. In particular yellow-, pink- and blue- colored areas are evidenced. Combining optical microscopy, Ra...

  3. Bilayers merge even when exocytosis is transient

    OpenAIRE

    Taraska, Justin W; Almers, Wolfhard

    2004-01-01

    During exocytosis, the lumen of secretory vesicles connects with the extracellular space. In some vesicles, this connection closes again, causing the vesicle to be recaptured mostly intact. The degree to which the bilayers of such vesicles mix with the plasma membrane is unknown. Work supporting the kiss-and-run model of transient exocytosis implies that synaptic vesicles allow neither lipid nor protein to escape into the plasma membrane, suggesting that the two bilayers never merge. Here, we...

  4. 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...

  5. 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...

  6. 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

  7. Oxygen-driven Magnetization Reorientation in Fe(001) Bilayer: A Tight-binding Study

    Czech Academy of Sciences Publication Activity Database

    Pick, Štěpán; Dreyssé, H.

    2001-01-01

    Roč. 63, č. 20 (2001), s. 205427.1-205427.4. ISSN 0163-1829 R&D Projects: GA MŠk OC P3.140 Institutional research plan: CEZ:AV0Z4040901 Keywords : oxygen adsorption * iron bilayer * magnetic anisotropy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.070, year: 2001

  8. On the Oxygen-driven Magnetization Reorientation in Fe(OO1) Bilayer

    Czech Academy of Sciences Publication Activity Database

    Pick, Štěpán; Dreyssé, H.

    2002-01-01

    Roč. 121, 2/3 (2002), s. 123-126. ISSN 0038-1098 R&D Projects: GA MŠk OC P3.140 Institutional research plan: CEZ:AV0Z4040901 Keywords : oxygen adsorption * iron bilayer * magnetic anisotropy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.671, year: 2002

  9. 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

  10. Impact of the chemical and physical stability of ketoprofen compounded in various pharmaceutical bases on its topical and transdermal delivery.

    Science.gov (United States)

    Nornoo, Adwoa O; Wulz, Jordan; Yoon, Haena; Nan, Yu; Lese, Michele

    2016-03-01

    Increasing demands for individualized drug treatment has led to an increase in the practice of compounded medications. In this study, we determined the impact of the chemical and physical stability of ketoprofen (10%w/w) cream on its topical/transdermal delivery over a 6-month period. The shelf life of ketoprofen at 25 °C in the pharmaceutical bases LipoDerm and LipoBase (109.94 and 85.9 days) was significantly longer than that in Pluronic Lecithin Organogel (PLO; 44.81 days), justifying extending its beyond use date (BUD) from 30 (USP37/NF32) to at least 60 days in LipoDerm and LipoBase. All the creams evaluated exhibited shear-thinning flow behavior with moderate thixotropy, while the flow properties for LipoBase and PLO creams were altered at storage times greater than 90 days. The percentage of ketoprofen permeated through porcine ear skin was 13.7, 19.1 and 12.7% of the dose from LipoDerm, LipoBase and PLO, respectively and decreased 2- to 3-fold after 28 days of storage. Flux ranging from 85.3 to 446.7 µg/cm(2)/h and topical delivery, on the other hand, were not influenced by storage duration past 28 days. In conclusion, this study justifies extending the BUD of ketoprofen in LipoDerm and LipoBase to 60 days if used for topical delivery only. PMID:25431959

  11. Effect of four different size reduction methods on the particle size, solubility enhancement and physical stability of nicergoline nanocrystals.

    Science.gov (United States)

    Martena, Valentina; Shegokar, Ranjita; Di Martino, Piera; Müller, Rainer H

    2014-09-01

    Nicergoline, a poorly soluble active pharmaceutical ingredient, possesses vaso-active properties which causes peripheral and central vasodilatation. In this study, nanocrystals of nicergoline were prepared in an aqueous solution of polysorbate 80 (nanosuspension) by using four different laboratory scale size reduction techniques: high pressure homogenization (HPH), bead milling (BM) and combination techniques (high pressure homogenization followed by bead milling HPH + BM, and bead milling followed by high pressure homogenization BM + HPH). Nanocrystals were investigated regarding to their mean particles size, zeta potential and particle dissolution. A short term physical stability study on nanocrystals stored at three different temperatures (4, 20 and 40 °C) was performed to evaluate the tendency to change in particle size, aggregation and zeta potential. The size reduction technique and the process parameters like milling time, number of homogenization cycles and pressure greatly affected the size of nanocrystals. Among the techniques used, the combination techniques showed superior and consistent particle size reduction compared to the other two methods, HPH + BM and BM + HPH giving nanocrystals of a mean particle size of 260 and 353 nm, respectively. The particle dissolution was increased for any nanocrystals samples, but it was particularly increased by HPH and combination techniques. Independently to the production method, nicergoline nanocrystals showed slight increase in particle size over the time, but remained below 500 nm at 20 °C and refrigeration conditions. PMID:23815299

  12. Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube

    OpenAIRE

    Voinova Marina; Kurczy Michael; Cans Ann-Sofie; Adams Kelly; Grzhibovskis Richards; Karlsson Roger; Ewing Andrew

    2011-01-01

    Abstract In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT) that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only) or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle). For the tube-only configuration (TOC), a micropipette is used to pull a LNT into the interior of a surfa...

  13. Bilayer Photoresist Insulator for High Performance Organic Thin-Film Transistors on Plastic Films

    International Nuclear Information System (INIS)

    A novel bilayer photoresist insulator is applied in flexible vanadyl-phthalocyanine (VOPc) organic thin-film transistors (OTFTs). The micron-size patterns of this photoresisit insulator can be directly defined only by photolithography without the etching process. Furthermore, these OTFTs exhibit high field-effect mobility (about 0.8 cm2/Vs) and current on/off ratio (about 106). In particular, they show rather low hysteresis (< 1 V). The results demonstrate that this bilayer photoresist insulator can be applied in large-area electronics and in the facilitation of patterning insulators. (cross-disciplinary physics and related areas of science and technology)

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

    Science.gov (United States)

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

    2016-02-01

    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 23kBT 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.

  16. Experimental observation of surface states and Landau levels bending in bilayer graphene

    Science.gov (United States)

    Yin, Long-Jing; Zhang, Yu; Qiao, Jia-Bin; Li, Si-Yu; He, Lin

    2016-03-01

    We report on microscopic measurements of the low-energy electronic structures both at the zigzag and armchair edges of bilayer graphene using scanning tunneling microscopy and spectroscopy (STM and STS). We have found that, both in the absence and in the presence of a magnetic field, an almost zero-energy peak in the density of states was localized at the zigzag edges, as expected for the surface states at the zigzag edges of bilayer graphene. In the quantum Hall regime, we have clearly observed Landau levels bending away from the charge neutrality point near both the zigzag and armchair edges. Such a result is direct evidence for the evolution of Landau levels into quantum Hall edge states in graphene bilayers. Our experiment indicates that it is possible to explore rich quantum Hall physics in graphene systems using STM and STS.

  17. Unusual Charge Transport and Spin Response of Doped Bilayer Triangular Antiferromagnets

    Institute of Scientific and Technical Information of China (English)

    LIANG Ying; MA Tian-Xing; FENG Shi-Ping

    2003-01-01

    Within the t-J model, the charge transport and spin response of the doped bilayer triangular antiferromagnetare studied by considering the bilayer interaction. Although the bilayer interaction leads to the band splitting in theelectronic structure, the qualitative behaviors of the physical properties are the same as in the single layer case. Theconductivity spectrum shows the low-energy peak and unusual midinfrared band, the temperature-dependent resistivityis characterized by the nonlinearity metallic-like behavior in the higher temperature range and the deviation from themetallic-like behavior in the lower temperature range and the commensurate neutron scattering peak near the half-fillingis split into six incommensurate peaks in the underdoped regime, with the incommensurability increasing with the holeconcentration at lower dopings, and saturating at higher dopings.

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

    Directory of Open Access Journals (Sweden)

    Meisam Rahmani

    2013-01-01

    Full Text Available Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking and metal (AA stacking layers. To this end, an analytical model joint with numerical solution of carrier concentration for bilayer graphene nanoribbon in the degenerate and nondegenerate regimes is presented. Moreover, to determine the proposed diode performance, the carrier concentration model is adopted to derive the current-voltage characteristic of the device. The simulated results indicate a strong bilayer graphene nanoribbon geometry and temperature dependence of current-voltage characteristic showing that the forward current of the diode rises by increasing of width. In addition, the lower value of turn-on voltage appears as the more temperature increases. Finally, comparative study indicates that the proposed diode has a better performance compared to the silicon schottky diode, graphene nanoribbon homo-junction contact, and graphene-silicon schottky diode in terms of electrical parameters such as turn-on voltage and forward current.

  19. Chemically enhanced double-gate bilayer graphene field-effect transistor with neutral channel for logic applications

    International Nuclear Information System (INIS)

    In this article, we present the simulation, fabrication, and characterization of a novel bilayer graphene field-effect transistor exhibiting electron mobility up to ∼1600 cm2 V−1 s−1, a room temperature I on/I off ≈ 60, and the lowest total charge (∼1011 cm−2) reported to date. This is achieved by combined electrostatic and chemical doping of bilayer graphene, which enables one to switch off the device at zero top-gate voltage. Using density functional theory and atomistic simulations, we obtain physical insight into the impact of chemical and electrostatic doping on bandgap opening of bilayer graphene and the effect of metal contacts on the operation of the device. Our results represent a step forward in the use of bilayer graphene for high-performance logic devices in the beyond-complementary metal−oxide−semiconductor (CMOS) technology paradigm. (paper)

  20. Chemically enhanced double-gate bilayer graphene field-effect transistor with neutral channel for logic applications

    Science.gov (United States)

    Nourbakhsh, Amirhasan; Agarwal, Tarun K.; Klekachev, Alexander; Asselberghs, Inge; Cantoro, Mirco; Huyghebaert, Cedric; Heyns, Marc; Verhelst, Marian; Thean, Aaron; De Gendt, Stefan

    2014-08-01

    In this article, we present the simulation, fabrication, and characterization of a novel bilayer graphene field-effect transistor exhibiting electron mobility up to ˜1600 cm2 V-1 s-1, a room temperature I on/I off ≈ 60, and the lowest total charge (˜1011 cm-2) reported to date. This is achieved by combined electrostatic and chemical doping of bilayer graphene, which enables one to switch off the device at zero top-gate voltage. Using density functional theory and atomistic simulations, we obtain physical insight into the impact of chemical and electrostatic doping on bandgap opening of bilayer graphene and the effect of metal contacts on the operation of the device. Our results represent a step forward in the use of bilayer graphene for high-performance logic devices in the beyond-complementary metal-oxide-semiconductor (CMOS) technology paradigm.

  1. RKKY interaction in bilayer graphene

    Science.gov (United States)

    Mohammadi, Yawar; Moradian, Rostam

    2015-12-01

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

  2. 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...

  3. 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...

  4. Strength of integration of transmembrane alpha-helical peptides in lipid bilayers as determined by atomic force spectroscopy.

    Science.gov (United States)

    Ganchev, Dragomir N; Rijkers, Dirk T S; Snel, Margot M E; Killian, J Antoinette; de Kruijff, Ben

    2004-11-30

    In this study we address the stability of integration of proteins in membranes. Using dynamic atomic force spectroscopy, we measured the strength of incorporation of peptides in lipid bilayers. The peptides model the transmembrane parts of alpha-helical proteins and were studied in both ordered peptide-rich and unordered peptide-poor bilayers. Using gold-coated AFM tips and thiolated peptides, we were able to observe force events which are related to the removal of single peptide molecules out of the bilayer. The data demonstrate that the peptides are very stably integrated into the bilayer and that single barriers within the investigated region of loading rates resist their removal. The distance between the ground state and the barrier for peptide removal was found to be 0.75 +/- 0.15 nm in different systems. This distance falls within the thickness of the interfacial layer of the bilayer. We conclude that the bilayer interface region plays an important role in stably anchoring transmembrane proteins into membranes. PMID:15554706

  5. 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)

    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 UO2-PuO2 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)

  6. Time-resolved fluorescence correlation spectroscopy combined with lifetime tuning: New perspectives in supported phospholipid bilayers´ research

    Czech Academy of Sciences Publication Activity Database

    Benda, Aleš; Fagulová, Veronika; Deineka, Alexander; Enderlein, J.; Hof, Martin

    Berlin : Max Delbrück Center for Molecular Medicine, 2006 - (Cardoso, M.). s. 46 [International Symposium Optical Analysis of Biomolecular Machines. 13.07.2006-16.07.2006, Berlin] Institutional research plan: CEZ:AV0Z40400503 Keywords : fluorescence-correlation spectroscopy * phospholipid bilayers research * physical chemistry Subject RIV: CF - Physical ; Theoretical Chemistry

  7. PHYSICS

    CERN Document Server

    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...

  8. 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...

  9. Embedding Ba Monolayers and Bilayers in Boron Carbide Nanowires

    Science.gov (United States)

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

    2015-11-01

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

  10. Magneto-oscillation phase anomalies in bilayer graphene with broken inversion symmetry

    Czech Academy of Sciences Publication Activity Database

    Goncharuk, Natalya; Smrčka, Ludvík

    Melville: AIP, 2011 - (Ihm, J.; Cheong, H.), s. 821-822. (AIP Conference Proceedings. 1399). ISBN 978-0-7354-1002-2. [International Conference on the Physics of Semiconductors/30/ (ICPS-30). Seoul (KR), 25.07.2010-30.07.2010] R&D Projects: GA MŠk LC510; GA AV ČR KAN400100652 Institutional research plan: CEZ:AV0Z10100521 Keywords : biased bilayer graphene * Landau plot * magneto -oscillation phase Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. 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.

  12. Electromagnetic coupling of spins and pseudospins in bilayer graphene

    Science.gov (United States)

    Winkler, R.; Zülicke, U.

    2015-05-01

    We present a detailed theoretical study of bilayer-graphene's electronic properties in the presence of electric and magnetic fields. Using group-theoretical methods, we derive an invariant expansion of the Hamiltonian for electron states near the K point of the Brillouin zone. In contrast to known materials, including single-layer graphene, any possible coupling of physical quantities to components of the external electric (magnetic) field has a counterpart where the analogous component of the magnetic (electric) field couples to exactly the same combination of quantities. For example, a purely electric spin splitting appears as the magnetoelectric analog of the familiar 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. Our findings thus reveal unconventional behavior of spin and pseudospin degrees of freedom in their coupling to external fields. We explain how these counterintuitive couplings 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 degree of freedom characterizing the intravalley orbital motion in bilayer graphene. These rules enforced by symmetry for the matter-field interactions clarify the nature of spins versus pseudospins. We also provide numerical values of prefactors for relevant coupling terms. While our theoretical arguments use bilayer graphene as an example, they are generally valid for any material with similar symmetries. The unusual equivalence of magnetic and electric fields discussed here can provide the basis for designing more versatile device architectures for creating polarizations

  13. Energy Gaps and Layer Polarization of Integer and Fractional Quantum Hall States in Bilayer Graphene.

    Science.gov (United States)

    Shi, Yanmeng; Lee, Yongjin; Che, Shi; Pi, Ziqi; Espiritu, Timothy; Stepanov, Petr; Smirnov, Dmitry; Lau, Chun Ning; Zhang, Fan

    2016-02-01

    Owing to the spin, valley, and orbital symmetries, the lowest Landau level in bilayer graphene exhibits multicomponent quantum Hall ferromagnetism. Using transport spectroscopy, we investigate the energy gaps of integer and fractional quantum Hall (QH) states in bilayer graphene with controlled layer polarization. The state at filling factor ν=1 has two distinct phases: a layer polarized state that has a larger energy gap and is stabilized by high electric field, and a hitherto unobserved interlayer coherent state with a smaller gap that is stabilized by large magnetic field. In contrast, the ν=2/3 quantum Hall state and a feature at ν=1/2 are only resolved at finite electric field and large magnetic field. These results underscore the importance of controlling layer polarization in understanding the competing symmetries in the unusual QH system of BLG. PMID:26894724

  14. 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...

  15. 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. ...

  16. 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...

  17. Effects of types and amounts of stabilizers on physical and sensory characteristics of cloudy ready-to-drink mulberry fruit juice.

    Science.gov (United States)

    Akkarachaneeyakorn, Suthida; Tinrat, Sirikhwan

    2015-05-01

    In this study, the pH of mulberry juice was optimized for high anthocyanin content and an attractive red color. Mulberry juice pH values of 2.5, 4.0, 6.0, and 8.0 were evaluated. A pH of 2.5 gave an anthocyanin content of 541.39 ± 106.43 mg of cyanidin-3-glucoside per liter, and the a* value was 14 ± 1.00. The effects of stabilizers (CMC and xanthan gum) on the physical characteristics of cloudy ready-to-drink mulberry fruit juice (via the addition of mulberry fruit pulp at a mass fraction of 5%) during storage (4°C for 1 week) were also determined using different mass fractions of the stabilizers (0.1%, 0.3%, and 0.5%). Increasing the stabilizer mass fraction increased the viscosity, turbidity, stability of turbidity, and h* value. Using xanthan gum as the stabilizer produced better results for these parameters than CMC. The type of stabilizer and its mass fraction had no effect on most sensory characteristics, including appearance, color, taste, texture, and overall acceptability (P ≥ 0.05), but did affect the odor (P ≥ 0.05). Xanthan gum stabilizer gave the juice a better odor than CMC. Cloudy mulberry juice containing 0.5% xanthan gum as the stabilizer had the highest acceptance rate among panelists (average acceptance was 6.90 ± 1.37 points) and produced no precipitate during storage. PMID:25987996

  18. Molecular friction and epitactic coupling between monolayers in supported bilayers

    OpenAIRE

    Merkel, R.; Sackmann, E.; Evans, E

    1989-01-01

    Microfluorescence methods were used to examine monolayer-monolayer and bilayer-substrate coupling in bilayers deposited on glass substrates. In the first part, lateral diffusion of lipid probes in individual lipid layers was measured by the fluorescence recovery after photobleach technique. The aim was to evaluate viscous molecular friction (i) between monolayers that form a single bilayer and (ii) between a bilayer and an adjacent substrate based on a recent phenomenological theory for parti...

  19. Nanodiscs for immobilization of lipid bilayers and membrane receptors: kinetic analysis of cholera toxin binding to a glycolipid receptor

    DEFF Research Database (Denmark)

    Borch, Jonas; Torta, Federico; Sligar, Stephen G; Roepstorff, Peter

    2008-01-01

    Nanodiscs are self-assembled soluble discoidal phospholipids bilayers encirculated by an amphipathic protein that together provide a functional stabilized membrane disk for the incorporation of membrane-bound and membrane-associated molecules. The scope of the present work is to investigate how n...

  20. A stable, reusable, and highly active photosynthetic bioreactor by bio-interfacing an individual cyanobacterium with a mesoporous bilayer nanoshell.

    Science.gov (United States)

    Jiang, Nan; Yang, Xiao-Yu; Deng, Zhao; Wang, Li; Hu, Zhi-Yi; Tian, Ge; Ying, Guo-Liang; Shen, Ling; Zhang, Ming-Xi; Su, Bao-Lian

    2015-05-01

    An individual cyanobacterium cell is interfaced with a nanoporous biohybrid layer within a mesoporous silica layer. The bio-interface acts as an egg membrane for cell protection and growth of outer shell. The resulting bilayer shell provides efficient functions to create a single cell photosynthetic bioreactor with high stability, reusability, and activity. PMID:25641812

  1. Characterization of Lipid Bilayer Formation in Aligned Nanoporous Aluminum Oxide Nanotube Arrays

    OpenAIRE

    Karp, Ethan S.; Newstadt, Justin P.; Chu, Shidong; Lorigan, Gary A.

    2007-01-01

    Aligning lipid bilayers in nanoporous anodized aluminum oxide (AAO) is a new method to help study membrane proteins by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (NMR) spectroscopic methods. The ability to maintain hydration, sample stability, and compartmentalization over long periods of time, and to easily change solvent composition are major advantages of this new method. To date, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) has been the onl...

  2. Hierarchically designed SiOx/SiOy bilayer nanomembranes as stable anodes for lithium ion batteries.

    Science.gov (United States)

    Zhang, Lin; Deng, Junwen; Liu, Lifeng; Si, Wenping; Oswald, Steffen; Xi, Lixia; Kundu, Manab; Ma, Guozhi; Gemming, Thomas; Baunack, Stefan; Ding, Fei; Yan, Chenglin; Schmidt, Oliver G

    2014-07-01

    Hierarchically designed SiOx /SiOy rolled-up bilayer nanomembranes are used as anodes for lithium-ion batteries. The functionalities of the SiO(x,y) layers can be engineered by simply controlling the oxygen content, resulting in anodes that exhibit a reversible capacity of about 1300 mA h g(-1) with an excellent stability of over 100 cycles, as well as a good rate capability. PMID:24788116

  3. Thermally activated conductivity in gapped bilayer graphene

    Science.gov (United States)

    Trushin, Maxim

    2012-05-01

    This is a theoretical study of electron transport in gated bilayer graphene —a novel semiconducting material with a tunable band gap. It is shown that the which-layer pseudospin coherence enhances the subgap conductivity and facilitates the thermally activated transport. The mechanism proposed can also lead to the non-monotonic conductivity vs. temperature dependence at a band gap size of the order of 10 meV. The effect can be observed in gapped bilayer graphene sandwiched in boron nitride where the electron-hole puddles and flexural phonons are strongly suppressed.

  4. 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.

  5. 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...

  6. PHYSICS

    CERN Multimedia

    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...

  7. PHYSICS

    CERN Document Server

    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...

  8. 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 ...

  9. 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 ...

  10. 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 ...

  11. Specific DNA duplex formation at an artificial lipid bilayer: fluorescence microscopy after Sybr Green I staining

    Directory of Open Access Journals (Sweden)

    Emma Werz

    2014-10-01

    Full Text Available The article describes the immobilization of different probe oligonucleotides (4, 7, 10 carrying each a racemic mixture of 2,3-bis(hexadecyloxypropan-1-ol (1a at the 5’-terminus on a stable artificial lipid bilayer composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC. The bilayer separates two compartments (cis/trans channel of an optical transparent microfluidic sample carrier with perfusion capabilities. Injection of unlabeled target DNA sequences (6, 8, or 9, differing in sequence and length, leads in the case of complementarity to the formation of stable DNA duplexes at the bilayer surface. This could be verified by Sybr Green I double strand staining, followed by incubation periods and thorough perfusions, and was visualized by single molecule fluorescence spectroscopy and microscopy. The different bilayer-immobilized complexes consisting of various DNA duplexes and the fluorescent dye were studied with respect to the kinetics of their formation as well as to their stability against perfusion.

  12. Melittin-induced cholesterol reorganization in lipid bilayer membranes.

    Science.gov (United States)

    Qian, Shuo; Heller, William T

    2015-10-01

    The peptide melittin, a 26 amino acid, cationic peptide from honey bee (Apis mellifera) venom, disrupts lipid bilayer membranes in a concentration-dependent manner. Rather than interacting with a specific receptor, the peptide interacts directly with the lipid matrix of the membrane in a manner dependent on the lipid composition. Here, a small-angle neutron scattering study of the interaction of melittin with lipid bilayers made of mixtures of dimyristoylphosphatidylcholine (DMPC) and cholesterol (Chol) is presented. Through the use of deuterium-labeled DMPC, changes in the distribution of the lipid and cholesterol in unilamellar vesicles were observed for peptide concentrations below those that cause pores to form. In addition to disrupting the in-plane organization of Chol, melittin produces vesicles having inner and outer leaflet compositions that depend on the lipid-Chol molar ratio and on the peptide concentration. The changes seen at high cholesterol and low peptide concentration are similar to those produced by alamethicin (Qian, S. et al., J. Phys. Chem. B 2014, 118, 11200-11208), which points to an underlying physical mechanism driving the redistribution of Chol, but melittin displays an additional effect not seen with alamethicin. A model for how the peptide drives the redistribution of Chol is proposed. The results suggest that redistribution of the lipids in a target cell membrane by membrane active peptides takes places as a prelude to the lysis of the cell. PMID:26074009

  13. Multiscale modeling of droplet interface bilayer membrane networks.

    Science.gov (United States)

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

    2015-11-01

    Droplet interface bilayer (DIB) networks are considered for the development of stimuli-responsive membrane-based materials inspired by cellular mechanics. These DIB networks are often modeled as combinations of electrical circuit analogues, creating complex networks of capacitors and resistors that mimic the biomolecular structures. These empirical models are capable of replicating data from electrophysiology experiments, but these models do not accurately capture the underlying physical phenomena and consequently do not allow for simulations of material functionalities beyond the voltage-clamp or current-clamp conditions. The work presented here provides a more robust description of DIB network behavior through the development of a hierarchical multiscale model, recognizing that the macroscopic network properties are functions of their underlying molecular structure. The result of this research is a modeling methodology based on controlled exchanges across the interfaces of neighboring droplets. This methodology is validated against experimental data, and an extension case is provided to demonstrate possible future applications of droplet interface bilayer networks. PMID:26594262

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

    International Nuclear Information System (INIS)

    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 3He 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 (τeff) of the devices at different biases and discussed the dependence of τeff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τeff = 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)

  15. 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.

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

    DEFF Research Database (Denmark)

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

    2001-01-01

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

  17. Electronic properties of graphene-based bilayer systems

    Science.gov (United States)

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

    2016-08-01

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

  18. 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...

  19. PHYSICS

    CERN Document Server

    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...

  20. 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...

  1. 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...

  2. Lipid bilayers decorated with photosensitive ruthenium complexes

    NARCIS (Netherlands)

    Bahreman, Azadeh

    2013-01-01

    In this thesis the thermal- and photo-substitution behavior of polypyridyl ruthenium complexes is described at the surface of lipid bilayers and in homogeneous solutions. It is shown that the successive thermal binding and light-induced unbinding of the cationic ruthenium complex at the surface of t

  3. 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...

  4. Chiral electron transport in CVD bilayer graphene

    Science.gov (United States)

    Lee, Kyunghoon; Eo, Yun Suk; Kurdak, Cagliyan; Zhong, Zhaohui

    2014-03-01

    Charge carriers in bilayer graphene have a parabolic energy spectrum. Due to this band structure they are massive quasiparticles having a finite density of state at zero energy like other non-relativistic charge carriers in conventional two dimensional materials. However, they are massive Dirac fermions which have a chiral nature similar to the case of massless Dirac fermions in single layer graphene. Coupling of pseudospin and motion of charge carrier via chirality can result in dramatic consequence for transport in bipolar regime like Klein tunneling, Fabry-Perot interference, collimation of charge carrier, Veslago lens, etc. However, little attention has been paid to chiral dependent electron transport in bilayer graphene. Here we study these properties by probing phase coherent transport behavior in CVD bilayer graphene devices with sub-200nm channel length. Complex Fabry-Perot interference patterns are observed in resonant cavities defined by local gating. By applying Fourier analysis technique, we successfully analyze and identify the origin of each individual interference pattern in bipolar and monopolar regime. Our initial results also hint at the observation of cloaking of electronic states against chiral electrons in bilayer graphene.

  5. Superconducting Calcium-Intercalated Bilayer Graphene.

    Science.gov (United States)

    Ichinokura, Satoru; Sugawara, Katsuaki; Takayama, Akari; Takahashi, Takashi; Hasegawa, Shuji

    2016-02-23

    We report the direct evidence for superconductivity in Ca-intercalated bilayer graphene C6CaC6, which is regarded as the thinnest limit of Ca-intercalated graphite. We performed the electrical transport measurements with the in situ 4-point-probe method in ultrahigh vacuum under zero- or nonzero-magnetic field for pristine bilayer graphene, Li-intercalated bilayer graphene (C6LiC6) and C6CaC6 fabricated on SiC substrate. We observed that the zero-resistance state occurs in C6CaC6 with the onset temperature (Tc(onset)) of 4 K, while the Tc(onset) is gradually decreased upon applying the magnetic field. This directly proves the superconductivity origin of the zero resistance in C6CaC6. On the other hand, both pristine bilayer graphene and C6LiC6 exhibit nonsuperconducting behavior, suggesting the importance of intercalated atoms and its species to drive the superconductivity. PMID:26815333

  6. 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...

  7. Bilayer Tablet via Microsphere: A Review

    Directory of Open Access Journals (Sweden)

    Piyushkumar Vinubhai Gundaraniya

    2013-01-01

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

  8. Einstein's Physical Strategy, Energy Conservation, Symmetries, and Stability: "but Grossmann & I believed that the conservation laws were not satisfied"

    OpenAIRE

    Pitts, J. Brian

    2016-01-01

    Recent work on the history of General Relativity by Renn, Sauer, Janssen et al. shows that Einstein found his field equations partly by a physical strategy including the Newtonian limit, the electromagnetic analogy, and energy conservation. Such themes are similar to those later used by particle physicists. How do Einstein's physical strategy and the particle physics derivations compare? What energy-momentum complex(es) did he use and why? Did Einstein tie conservation to symmetries, and if s...

  9. Repetitive formation of optically-observable planar lipid bilayers by rotating chambers on a microaperture.

    Science.gov (United States)

    Tomoike, Fumiaki; Tonooka, Taishi; Osaki, Toshihisa; Takeuchi, Shoji

    2016-07-01

    Optical observation of a planar lipid bilayer is an effective method of lipid bilayer characterization. However, previous methods for optically observable lipid bilayer formation are unsuitable for repetitive formation of lipid bilayers. In this paper, we propose a system that facilitates repetitive formation of horizontal lipid bilayers via mechanical rotation of the rotating part. We show that multiple bilayers can be observed within a short period, and that the electrical and optical characteristics of a bilayer can be analyzed simultaneously. PMID:27256329

  10. Synthesis of mono- and bi-layer MFI zeolite films on macroporous alumina tubular supports: Application to nanofiltration

    Science.gov (United States)

    Said, Ali; Limousy, Lionel; Nouali, Habiba; Michelin, Laure; Halawani, Jalal; Toufaily, Joumana; Hamieh, Tayssir; Dutournié, Patrick; Daou, T. Jean

    2015-10-01

    This work is dedicated to the development of MFI-type structure zeolite films (single-layer or bilayer) on the internal layer of a specific macroporous alumina tubular support for nanofiltration applications. The bottom MFI layer was obtained by direct hydrothermal synthesis while a secondary growth method was used for the top MFI layer. A complete characterization of the obtained MFI membranes (single-layer or bilayer) is proposed using various techniques, such as X-ray diffraction, scanning electron microscopy, mercury porosimetry and nitrogen sorption measurements. Dense and highly crystallized films of MFI-type structure zeolite were obtained for both single-layer and bilayer MFI films. The total film thickness were around 7.1±0.5 μm and 14.5±1 μm for single-layer and bilayer MFI films respectively. The Si/Al molar ratio of the MFI films varied between 185 and 305 for single-layer and bilayer MFI films respectively. The hydraulic permeability of the tubular MFI membrane was achieved by the filtration of pure water. The hydraulic permeability of the single-layer and bilayer MFI membranes decreased rapidly at the beginning of the conditioning process, and stabilized at 1.08×10-14 m3 m-2 and 1.02×10-15 m3 m-2 after 15 h and the rejection rates of neutral solute (Vb 12) are 10% and 50% for the single-layer and bilayer MFI films respectively.

  11. Bilayer Approaches for Nanoparticle Phase Transfer

    Science.gov (United States)

    Kini, Gautam Chandrakanth

    Nanoparticles (NPs) are often synthesized in organic solvents due to advantages of superior size and shape control obtainable in a non-polar environment. However, many applications featuring NPs require them to be in aqueous media. To transfer NPs from oil to water, surfactants with amphiphilic (hydrophobic and hydrophilic) groups have been widely used. A popular phase-transfer approach involves formation of oil-in-water emulsions upon which the oil storing the NPs is boiled off. In the process, surfactants form bilayers with hydrophobic groups on the NPs rendering them water-dispersible. This transfer route however is limited in that NPs aggregate to form clusters which results in poor colloidal stability and for the specific case of quantum dots (QDs), adversely impacts optical properties. It has ever since remained a challenge to devise approaches that transfer NPs from oil to water as single particles without compromising NP stability and properties. We have discovered that by simple addition of salt to water during the step of emulsion formation, NP transfer efficiency can be greatly enhanced in "salty-micelles" of surfactants. The strength of this approach lies in its simplicity and generic nature in that the transfer scheme is valid for different NP, surfactant and salt types. Using a model system with cadmium selenide (CdSe) QDs as NPs, Aerosol-OT (AOT) as the surfactant and NaCl as the salt in water, we found >90% of CdSe QDs transferred in salty-micelles of AOT which was significantly higher than the 45-55% QDs that transferred in deionized-water (DI-water) micelles of AOT. In the salty-micelle environment, QDs were found to exist predominantly as single NPs with narrow size distribution, as established by light scattering, analytical ultracentrifugation and electron microscopy. The effects of salt were in lowering aqueous solubility of AOT through "salting-out" action and in screening repulsions between like-charged head groups of AOT molecules

  12. Stability and maturity of biowaste composts derived by small municipalities: Correlation among physical, chemical and biological indices.

    Science.gov (United States)

    Oviedo-Ocaña, E R; Torres-Lozada, P; Marmolejo-Rebellon, L F; Hoyos, L V; Gonzales, S; Barrena, R; Komilis, D; Sanchez, A

    2015-10-01

    Stability and maturity are important criteria to guarantee the quality of a compost that is applied to agriculture or used as amendment in degraded soils. Although different techniques exist to evaluate stability and maturity, the application of laboratory tests in municipalities in developing countries can be limited due to cost and application complexities. In the composting facilities of such places, some classical low cost on-site tests to monitor the composting process are usually implemented; however, such tests do not necessarily clearly identify conditions of stability and maturity. In this article, we have applied and compared results of stability and maturity tests that can be easily employed on site (i.e. temperature, pH, moisture, electrical conductivity [EC], odor and color), and of tests that require more complex laboratory techniques (volatile solids, C/N ratio, self-heating, respirometric index, germination index [GI]). The evaluation of the above was performed in the field scale using 2 piles of biowaste applied compost. The monitoring period was from day 70 to day 190 of the process. Results showed that the low-cost tests traditionally employed to monitor the composting process on-site, such as temperature, color and moisture, do not provide consistent determinations with the more complex laboratory tests used to assess stability (e.g. respiration index, self-heating, volatile solids). In the case of maturity tests (GI, pH, EC), both the on-site tests (pH, EC) and the laboratory test (GI) provided consistent results. Although, stability was indicated for most of the samples, the maturity tests indicated that products were consistently immature. Thus, a stable product is not necessarily mature. Conclusively, the decision on the quality of the compost in the installations located in developing countries requires the simultaneous use of a combination of tests that are performed both in the laboratory and on-site. PMID:26216503

  13. Physical stability of nanosuspensions:research advances%纳米混悬剂的物理稳定性研究进展

    Institute of Scientific and Technical Information of China (English)

    谢向阳; 陈晨; 廖祥茹; 韩亮

    2011-01-01

    纳米混悬剂具有增加药物溶解度,提高生物利用度,降低毒副作用等特点,有关这方面的研究是目前纳米制剂研究的一个热点,美国FDA至今已批准多个相关产品上市.物理稳定性问题在纳米药物混悬液中比较突出,是制约纳米混悬液研发的重要因素之一.本文就纳米混悬剂物理稳定性所面临的问题、理论机制及其应对策略进行综述.%Nanosuspensions have characteristics of increasing solubility, improving bioavailability, reducing toxicity of drugs, and have become a hotspot in the research area of nanodrugs recently. A few related drugs of nanosuspensions were approved by the FDA of USA up to date. Physical stability is a key issue that limits the research and development of naosuspen-sions. This article reviews the physical stability of nanosuspensions, including their mechanisms and corresponding strategies to overcome the stability problems.

  14. PHYSICS

    CERN Document Server

    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...

  15. Strain-modulated excitonic gaps in mono- and bi-layer MoSe2

    Science.gov (United States)

    Jianting, Ji; Anmin, Zhang; Tianlong, Xia; Po, Gao; Yinghao, Jie; Qian, Zhang; Qingming, Zhang

    2016-07-01

    Photoluminescence (PL) and Raman spectra under uniaxial strain were measured in mono- and bi-layer MoSe2 to comparatively investigate the evolution of excitonic gaps and Raman phonons with strain. We observed that the strain dependence of excitonic gaps shows a nearly linear behavior in both flakes. One percent of strain increase gives a reduction of ∼ 42 meV (∼ 35 meV) in A-exciton gap in monolayer (bilayer) MoSe2. The PL width remains little changed in monolayer MoSe2 while it increases rapidly with strain in the bilayer case. We have made detailed discussions on the observed strain-modulated results and compared the difference between monolayer and bilayer cases. The hybridization between 4d orbits of Mo and 4p orbits of Se, which is controlled by the Se–Mo–Se bond angle under strain, can be employed to consistently explain the observations. The study may shed light into exciton physics in few-layer MoSe2 and provides a basis for their applications. Project supported by the National Basic Research Program of China (Grant No. 2012CB921701) and the National Natural Science Foundation of China (Grant Nos. 11474357 and 11004245). Qingming Zhang and Tianlong Xia were supported by the Fundamental Research Funds for the Central Universities of China and the Research Funds of Renmin University of China.

  16. Experimental evidence for non-Abelian gauge potentials in twisted graphene bilayers

    Science.gov (United States)

    Yin, Long-Jing; Qiao, Jia-Bin; Zuo, Wei-Jie; Li, Wen-Tian; He, Lin

    2015-08-01

    Non-Abelian gauge potentials are quite relevant in subatomic physics, but they are relatively rare in a condensed matter context. Here we report the experimental evidence for non-Abelian gauge potentials in twisted graphene bilayers by scanning tunneling microscopy and spectroscopy. At a magic twisted angle, θ ≈(1.11±0.05 ) ∘ , a pronounced sharp peak, which arises from the nondispersive flat bands at the charge neutrality point, is observed in the tunneling density of states due to the action of the non-Abelian gauge fields. Moreover, we observe confined electronic states in the twisted bilayer, as manifested by regularly spaced tunneling peaks with energy spacing δ E ≈vF/D ≈70 meV (here vF is the Fermi velocity of graphene and D is the period of the moiré patterns). This indicates that the non-Abelian gauge potentials in twisted graphene bilayers confine low-energy electrons into a triangular array of quantum dots following the modulation of the moiré patterns. Our results also directly demonstrate that the Fermi velocity in twisted bilayers can be tuned from about 106m /s to zero by simply reducing the twisted angle of about 2∘.

  17. Formulation, Evaluation and Optimization of Bilayer Floating Tablet of Repaglinide and Glipizide

    Directory of Open Access Journals (Sweden)

    SOLANKI PRIYANKA DHARMENDRASINH

    2012-09-01

    Full Text Available Objective: The aim of the present research was to develop a bilayer floating drug delivery system. That contains two layers immediate release layer and sustain release layer. First immediate release layer quickly releases drugs and attains onset of action, subsequently floating sustained release layer floats over gastric fluid and releases the drug in sustained or controlled manner. Experimental Work: In bilayer tablet formulation, the floating sustained release layer was compressed and immediate release layer was added over it, then both layers were compressed. Tablets were characterized using the official methods. Immediate release layer contained Repaglinide, Sodium starch glycolate & Microcrystalline cellulose. In this study floating sustain release layer tablets were prepared using HPMC K4M alone, Na CMC alone & combination of HPMC K4M & Na CMC. Sodium bicarbonate & Citric acid were used as an effervescent agent. All formulations were prepared by using factorial design (32 & 23. All the above formulations were evaluated for in vitro drug release, buoyancy lag time (BLT, swelling ability, floating behavior.Results and Discussion: All formulations showed anomalous transport mechanism. This means diffusion as well as swelling controlled had played an essential role in drug release. Finally bilayer floating sustained release tablets was formulated by using optimized immediate release layer and optimized floating sustained release layer & evaluated as earlier. The optimized bilayer tablet formulation was subjected to stability study 40°C±2°C/75%RH±5%RH for 1 month according to ICH guidelines & evaluated. Conclusions: From the study it is concluded that the developed formulation has good appearance with good handling condition, therapeutically efficacious, stable. The developed Bilayer formulation is viable alternative to conventional Repaglinide and Glipizide tablet.

  18. Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

    Directory of Open Access Journals (Sweden)

    Emma Werz

    2015-06-01

    Full Text Available A series of six cyanine-5-labeled oligonucleotides (LONs 10–15, each terminally lipophilized with different nucleolipid head groups, were synthesized using the recently prepared phosphoramidites 4b–9b. The insertion of the LONs within an artificial lipid bilayer, composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE, was studied by single molecule fluorescence spectroscopy and microscopy with the help of an optically transparent microfluidic sample carrier with perfusion capabilities. The incorporation of the lipo-oligonucleotides into the bilayer was studied with respect to efficiency (maximal bilayer brightness as well as stability against perfusion (final stable bilayer brightness. Attempts to correlate these parameters with the log P values of the corresponding nucleolipid head groups failed, a result which clearly demonstrates that not only the lipophilicity but mainly the chemical structure and topology of the head group is of decisive importance for the optimal interaction of a lipo-oligonucleotide with an artificial lipid bilayer. Moreover, fluorescence half-live and diffusion time values were measured to determine the diffusion coefficients of the lipo-oligonucleotides.

  19. Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties.

    Science.gov (United States)

    Werz, Emma; Rosemeyer, Helmut

    2015-01-01

    A series of six cyanine-5-labeled oligonucleotides (LONs 10-15), each terminally lipophilized with different nucleolipid head groups, were synthesized using the recently prepared phosphoramidites 4b-9b. The insertion of the LONs within an artificial lipid bilayer, composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), was studied by single molecule fluorescence spectroscopy and microscopy with the help of an optically transparent microfluidic sample carrier with perfusion capabilities. The incorporation of the lipo-oligonucleotides into the bilayer was studied with respect to efficiency (maximal bilayer brightness) as well as stability against perfusion (final stable bilayer brightness). Attempts to correlate these parameters with the log P values of the corresponding nucleolipid head groups failed, a result which clearly demonstrates that not only the lipophilicity but mainly the chemical structure and topology of the head group is of decisive importance for the optimal interaction of a lipo-oligonucleotide with an artificial lipid bilayer. Moreover, fluorescence half-live and diffusion time values were measured to determine the diffusion coefficients of the lipo-oligonucleotides. PMID:26124894

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

    International Nuclear Information System (INIS)

    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

  1. Modification of the PTCDA-Ag bond by forming a heteromolecular bilayer film

    OpenAIRE

    Stadtmüller, Benjamin; Willenbockel, Martin; Schröder, Sonja; Kleimann, Christoph; Reinisch, Eva M.; Ules, Thomas; Soubatch, Sergey; Ramsey, Michael G.; Tautz, F. Stefan; Kumpf, Christian

    2015-01-01

    The understanding of the fundamental physical properties of metal-organic and organic-organic interfaces is crucial for improving the performance of organic electronic devices. This is particularly true for (multilayer) systems containing several molecular species due to their relevance for donor-acceptor systems. A prototypical heteromolecular bilayer system is copper-II-phthalocyanine (CuPc) on 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) on Ag(111). In an earlier work we have rep...

  2. Gate-induced magneto-oscillation phase anomalies in graphene bilayers

    Czech Academy of Sciences Publication Activity Database

    Goncharuk, Natalya; Smrčka, Ludvík

    2010-01-01

    Roč. 12, č. 8 (2010), 083048/1-083048/15. ISSN 1367-2630 R&D Projects: GA MŠk LC510; GA AV ČR KAN400100652; GA MŠk MEB020928 Institutional research plan: CEZ:AV0Z10100521 Keywords : biased bilayer graphene * magneto -oscillation phase * Landau plot * Landau Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.849, year: 2010

  3. Theory of long-wavelength spin waves in exchange biased bilayers

    International Nuclear Information System (INIS)

    Long-wavelength spin waves are examined in an exchange biased ferromagnet/antiferromagnet bilayer. The frequencies of the excitations are calculated as a function of external field strength and orientation. It is suggested that the angular dependence of the frequencies can lead to linewidth enhancements, in agreement with recent experimental results. It is also shown that the study of the spin wave frequencies can yield the strengths of the antiferromagnet anisotropy and interlayer coupling. [copyright] 2001 American Institute of Physics

  4. High temperature characteristics of bilayer epitaxial graphene field-effect transistors on SiC Substrate

    Science.gov (United States)

    Ze-Zhao, He; Ke-Wu, Yang; Cui, Yu; Qing-Bin, Liu; Jing-Jing, Wang; Jia, Li; Wei-Li, Lu; Zhi-Hong, Feng; Shu-Jun, Cai

    2016-06-01

    In this paper, high temperature direct current (DC) performance of bilayer epitaxial graphene device on SiC substrate is studied in a temperature range from 25 °C to 200 °C. At a gate voltage of ‑8 V (far from Dirac point), the drain-source current decreases obviously with increasing temperature, but it has little change at a gate bias of +8 V (near Dirac point). The competing interactions between scattering and thermal activation are responsible for the different reduction tendencies. Four different kinds of scatterings are taken into account to qualitatively analyze the carrier mobility under different temperatures. The devices exhibit almost unchanged DC performances after high temperature measurements at 200 °C for 5 hours in air ambience, demonstrating the high thermal stabilities of the bilayer epitaxial graphene devices. Project supported by the National Natural Science Foundation of China (Grant No. 61306006).

  5. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels.

    Science.gov (United States)

    Balleza, Daniel

    2012-01-01

    Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed. PMID:22790280

  6. Ultrathin Mo/MoN bilayer nanostructure for diffusion barrier application of advanced Cu metallization

    International Nuclear Information System (INIS)

    Ultrathin Mo (5 nm)/MoN (5 nm) bilayer nanostructure has been studied as a diffusion barrier for Cu metallization. The Mo/MoN bilayer was prepared by magnetron sputtering and the thermal stability of this barrier is investigated after annealing the Cu/barrier/Si film stack at different temperatures in vacuum for 10 min. The failure of barrier structure is indicated by the abrupt increase in sheet resistance and the formation of Cu3Si phase proved by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). High resolution transmission electron microscopy (HRTEM) examination suggested that the ultrathin Mo/MoN barrier is stable and can prevent the diffusion of Cu at least up to 600 deg. C.

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

    International Nuclear Information System (INIS)

    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 D2O and kept for several hours to enable substitution of H 1 by D 2, after which the buffer was dried and redissolved in D2O. 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

  8. 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

  9. Electrophoretic bilayer deposition of zirconia and reinforced bioglass system on Ti6Al4V for implant applications: an in vitro investigation.

    Science.gov (United States)

    Ananth, K Prem; Suganya, S; Mangalaraj, D; Ferreira, J M F; Balamurugan, A

    2013-10-01

    The physical, chemical and biological properties of the bioglass reinforced yttria-stabilized composite layer on Ti6Al4V titanium substrates were investigated. The Ti6Al4V substrate was deposited with yttria stabilized zirconia - YSZ as the base layer of thickness ≈4-5 μm, to inhibit metal ion leach out from the substrate and bioglass zirconia reinforced composite as the second layer of thickness ≈15 μm, which would react with surrounding bone tissue to enhance bone formation and implant fixation. The deposition of these two layers on the substrate was carried out using the most viable electrophoretic deposition (EPD) technique. Biocompatible yttria-stabilized zirconia (YSZ) in the form of nano-particles and sol gel derived bioglass in the form of micro-particles were chosen as precursors for coating. The coatings were vacuum sintered at 900 °C for 3h. The biocompatibility and corrosion resistance property were studied in osteoblast cell culture and in simulated body fluid (SBF) respectively. Analysis showed that the zirconia reinforced bioglass bilayer system promoted significant bioactivity, and it exhibited a better corrosion resistance property and elevated mechanical strength under load bearing conditions in comparison with the monolayer YSZ coating on Ti6Al4V implant surface. PMID:23910328

  10. Polymer bilayer structure via inkjet printing

    Science.gov (United States)

    Xia, Yajun; Friend, Richard H.

    2006-04-01

    We report the formation of a polymer bilayer structure by inkjet printing poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) from p-xylene solution onto a poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine (TFB) thin film. Despite the compatibility of both polymers with the same organic solvent, a TFB layer under the later-deposited F8BT was directly observed through fluorescence microscopy. Micro-Raman spectroscopy reveals that this bottom layer is ˜10nm thick for a film made by inkjet printing F8BT onto a TFB film of ˜20nm thickness. The bilayer structure leads to enhanced efficiency for light-emitting diodes in comparison with devices made from spin-coated TFB:F8BT blend films.

  11. The surface layer of cleaved bilayer manganites

    International Nuclear Information System (INIS)

    Recently, several informative reports have been published on spectroscopy experiments performed on cleaved surfaces of the bilayered colossal magnetoresistive manganite La2-2xSr1+2xMn2O7 (Konoto et al 2004 Phys. Rev. Lett. 93 107201, Freeland et al 2005 Nat. Mater. 4 62, Mannella et al 2005 Nature 438 474, Roennow et al 2006 Nature 440 1025). For the detailed interpretation of these results, it is of importance to know exactly which layer within the crystal structure is exposed to the surface upon cleavage. Here we combine crystal structure arguments, scanning tunnelling microscopy and x-ray photoelectron spectroscopy measurements to demonstrate that the crystals cleave between the rare-earth rock-salt oxide layers, leaving one outermost rare-earth oxide layer before the first electronically active MnO bilayer

  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...... thermally induced aggregation of the GlycoPEGylated rFVIIa compounds is unaffected by an increasing calcium chloride concentration....

  13. Negative differential resistance in bilayer graphene nanoribbons

    OpenAIRE

    Zahid, F.; Habib, KMM; Lake, RK

    2011-01-01

    Lack of a bandgap is one of the significant challenges for application of graphene as the active element of an electronic device. A bandgap can be induced in bilayer graphene by application of a potential difference between the two layers. The simplest geometry for creating such a potential difference is two overlayed graphene nanoribbons independently contacted. Calculations, based on density functional theory and the nonequilibrium Green's function formalism, show that transmission through ...

  14. Lipid Bilayers: Clusters, Domains and Phases

    OpenAIRE

    Ackerman, David G.; Feigenson, Gerald W.

    2015-01-01

    In this chapter we discuss the complex mixing behavior of plasma membrane lipids. To do so, we first introduce the plasma membrane and membrane mixtures often used to model its complexity. We then discuss the nature of lipid phase behavior in bilayers and the distinction between these phases and other manifestations of nonrandom mixing found in one-phase mixtures, such as clusters, micelles, and microemulsions. Finally, we demonstrate the applicability of Gibbs phase diagrams to the study of ...

  15. Interaction of small peptides with lipid bilayers.

    OpenAIRE

    Damodaran, K. V.; Merz, K M; Gaber, B P

    1995-01-01

    Molecular dynamics simulations of the tripeptide Ala-Phe-Ala-O-tert-butyl interacting with dimyristoylphosphatidylcholine lipid bilayers have been carried out. The lipid and aqueous environments of the peptide, the alkyl chain order, and the lipid and peptide dynamics have been investigated with use of density profiles, radial distribution functions, alkyl chain order parameter profiles, and time correlation functions. It appears that the alkyl chain region accommodates the peptides in the bi...

  16. Edge states of zigzag bilayer graphite nanoribbons

    OpenAIRE

    Rhim, Jun-Won; Moon, Kyungsun

    2008-01-01

    Electronic structures of the zigzag bilayer graphite nanoribbons(Z-BGNR) with various ribbon width $N$ are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude $\\gamma_4$, which is an order of magnitude smaller than the other inter-layer hopping parameters $\\gamma_1$ and $\\gamma_3$, there exist two fixed Fermi points $\\pm k^*$ independent of the ribbon width with the peculiar energy dispersion near $k^*$ as $\\ve (k) \\sim \\pm (k-k^*)^N$. By investigating...

  17. Sub-diffraction imaging with compensating bilayers

    International Nuclear Information System (INIS)

    We derive a general expression for the material properties of a compensating bilayer, which is a pair of material layers which transfer the field distribution from one side of the bilayer to the other with resolution limited only by the deviation of the material properties from specified values. One of the layers can be free space, a special case of which is the perfect lens, but the layers need not have equal thickness. Compensating a thick layer of free space with a thin layer creates a focusing device with increased working distance, and employs an anisotropic material. It is also possible to achieve compensation of materials with property tensors that are neither positive nor negative definite. In this case, we refer to such media as indefinite, and we analyse, in detail, bilayers of these media which support coupling of internal propagating waves to incident waves of any transverse wave vector. In this case, we find that the enhanced spatial resolution provided by large transverse wave vectors is far less sensitive to loss than that of the perfect lens

  18. 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.

  19. Self-folding graphene-polymer bilayers

    Science.gov (United States)

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

    2015-05-01

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

  20. Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films

    International Nuclear Information System (INIS)

    Thin film CoPt/Co bilayers have been prepared as a model system to investigate the relationship between microstructure and exchange coupling in two-phase nanocomposite permanent magnets. The bilayers were prepared by magnetron sputter deposition of near-equiatomic CoPt with a thickness of 25 nm onto oxidized Si wafers. In the as-deposited state, CoPt had the A1 (fcc) structure and was magnetically soft. Before reinsertion into the sputtering chamber for the deposition of 2.8-16.7 nm thick Co layers, the CoPt films were annealed at 700 degree sign C for 120 min to produce the magnetically hard, fully ordered L10 phase. The presence of exchange coupling in the bilayers was verified by magnetic hysteresis and recoil measurements and showed that only for Co thicknesses below 6.3 nm was this layer (in its as-deposited state) coupled through its full thickness to the CoPt layer. Annealing the bilayer samples at 300 and 550 degree sign C for 20 min resulted in improvement of the interlayer magnetic coupling and produced clear differences in the magnetic reversal coherency and the recoil curves. However, for some samples, the improved coupling resulted in a decrease in coercivity, indicating that there is an optimum in the coupling strength for the attainment of high coercivity. Transmission electron microscopy studies of the bilayers in plan view showed that the increased interlayer coupling with annealing was a result of improved granular epitaxy of Co to CoPt. (c) 2000 American Institute of Physics

  1. Automatable lipid bilayer formation for ion channel studies

    Science.gov (United States)

    Poulos, Jason L.; Bang, Hyunwoo; Jeon, Tae-Joon; Schmidt, Jacob J.

    2008-08-01

    Transmembrane proteins and ion channels are important drug targets and have been explored as single molecule sensors. For these proteins to function normally they must be integrated within lipid bilayers; however, the labor and skill required to create artificial lipid bilayers have the limited the possible applications utilizing these proteins. In order to reduce the complexity and cost of lipid bilayer formation and measurement, we have modified a previously published lipid bilayer formation technique using mechanically contacted monolayers so that the process is automatable, requiring minimal operator input. Measurement electronics are integrated with the fluid handling system, greatly reducing the time and operator feedback characteristically required of traditional bilayer experiments. To demonstrate the biological functionality of the resultant bilayers and the system's capabilities as a membrane platform, the ion channel gramicidin A was incorporated and measured with this system.

  2. 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.

  3. Detergent Stabilized Nanopore Formation Kinetics of an Anthrax Protein

    Science.gov (United States)

    Peterson, Kelby

    2015-03-01

    This summer research project funded through the Society of Physics Students Internship Program and The National Institute of Standards and Technology focused on optimization of pore formation of Protective Antigen protein secreted by Bacillus Anthraces. This experiment analyzes the use of N-tetradecylphosphocholine (FOS-14 Detergent) to stabilize the water soluble protein, protective antigen protein (PA63) to regulate the kinetics of pore formation in a model bilayer lipid membrane. The FOS-14 Detergent was tested under various conditions to understand its impact on the protein pore formation. The optimization of this channel insertion is critical in preparing samples of oriented for neutron reflectometry that provide new data to increase the understanding of the protein's structure.

  4. Supercurrent reversal in Josephson junctions based on bilayer graphene flakes

    OpenAIRE

    Rameshti, Babak Zare; Zareyan, Malek; Moghaddam, Ali G.

    2015-01-01

    We investigate the Josephson effect in a bilayer graphene flake contacted by two monolayer sheet deposited by superconducting electrodes. It is found that when the electrodes are attached to the different layers of the bilayer, the Josephson current is in a $\\pi$ state when the bilayer region is undoped and in the absence of vertical bias. Applying doping or bias to the junction reveals $\\pi-0$ transitions which can be controlled by varying the temperature and the junction length. The supercu...

  5. 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......, optical absorption spectroscopy and electrochemical quartz crystal microbalance (EQCM) techniques. Two important conclusions of relevance for actuator performance were reached: It is possible to make a bilayer film that does not delaminate – the two polymers are compatible; and both polymers are active in...

  6. Forster Resonance Energy Transfer and Conformational Stability of Proteins: An Advanced Biophysical Module for Physical Chemistry Students

    Science.gov (United States)

    Sanchez, Katheryn M.; Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

    2008-01-01

    Protein folding is an exploding area of research in biophysics and physical chemistry. Here, we describe the integration of several techniques, including absorption spectroscopy, fluorescence spectroscopy, and Forster resonance energy transfer (FRET) measurements, to probe important topics in protein folding. Cytochrome c is used as a model…

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

    Directory of Open Access Journals (Sweden)

    He W

    2013-08-01

    Full Text Available Wei He,1,2 Yi Lu,1 Jianping Qi,1 Lingyun Chen,3 Lifang Yin,2 Wei Wu1 1School of Pharmacy, Fudan University, Key Laboratory of Smart Drug Delivery of Ministry of Education and PLA, Shanghai, 2Department of Pharmaceutics, School of Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu, People's Republic of China; 3Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, AB, Canada Background: 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. Methods: Indomethacin nanosuspensions were prepared by the precipitation-ultrasonication method using food proteins (soybean protein isolate, whey protein isolate, ß-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. Results: 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

  8. DESIGN, DEVELOPMENT AND EVALUATION OF BILAYER TABLET USING NATEGLINIDE FOR THE MANAGEMENT OF DIABETES

    Directory of Open Access Journals (Sweden)

    M. D. Bhadange

    2015-08-01

    Full Text Available The aim of present study is to formulate Nateglinide sustained release (SR and immediate release (IR bilayer tablet by different concentration of Hydroxypropyl methylcellulose (HPMC and HPMC K 100 M to control the release pattern. The sustained release layer of Nateglinide was prepared by using different grades of HPMC like, HPMC K-100, HPMC along with other excipients by direct compression technique. The immediate release layer of Nateglinide was prepared by Cross carmellose sodium and Sodium starch glycolate by direct compression technique. The powders were evaluated for their flow properties and the finished tablets were evaluated for their physical parameters. The both immediate release and sustained release layers of Nateglinide were characterized by FT-IR and in vitro dissolution studies. The drug release study of Nateglinide was evaluated using USP-II paddle type dissolution apparatus. The release rate of Nateglinide in immediate release layer was studied for 1h in 0.1 N HCL media and that of Nateglinide in sustained release layer was studied for 12 h in pH 6.8 phosphate buffer media. From the nine batches S5 batch showed good release behaviour 94.92% of drug is released over 12 hours. Nateglinide is a poorly water soluble (BCS class 2 ant diabetic drug. Due to the poor water solubility of this drug, its bioavailability is dissolution rate-limited. Total four trial batches of each drug have been manufactured to optimize and develop a robust and stable formulation, the stability studies of the products also comply with ICH guideline.

  9. The physical and chemical stability of cisplatin (Teva) in concentrate and diluted in sodium chloride 0.9%

    OpenAIRE

    Karbownik, Agnieszka; Szałek, Edyta; Urjasz, Hanna; Głęboka, Aleksandra; Mierzwa, Emilia; Grześkowiak, Edmund

    2012-01-01

    Aim of the study The subject of study was the stability of cisplatin in concentrate in glass vials and diluted in polyethylene (PE) bags stored at 15–25°C for up to 30 days. Material and methods Original vials of cisplatin injection (1 mg/ml, Teva) were stored at room temperature and subjected to re-piercing after 1, 2, 3, 7, 14, 21, 28 and 30 days following the initial piercing. Cisplatin infusions at nominal concentrations of 0.1 mg/ml were prepared in 0.9% sodium chloride (1000 ml) in PE b...

  10. 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)

    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)

  11. 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.

  12. Synthesis and sensing application of large scale bilayer graphene

    Science.gov (United States)

    Hong, Sung Ju; Yoo, Jung Hoon; Baek, Seung Jae; Park, Yung Woo

    2012-02-01

    We have synthesized large scale bilayer graphene by using Chemical Vapor Deposition (CVD) in atmospheric pressure. Bilayer graphene was grown by using CH4, H2 and Ar gases. The growth temperature was 1050^o. Conventional FET measurement shows ambipolar transfer characteristics. Results of Raman spectroscopy, Atomic Force microscope (AFM) and Transmission Electron Microscope (TEM) indicate the film is bilayer graphene. Especially, adlayer structure which interrupt uniformity was reduced in low methane flow condition. Furthermore, large size CVD bilayer graphene film can be investigated to apply sensor devices. By using conventional photolithography process, we have fabricated device array structure and studied sensing behavior.

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

    International Nuclear Information System (INIS)

    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

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

    KAUST Repository

    Mahmood, Khalid

    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. Einstein's Physical Strategy, Energy Conservation, Symmetries, and Stability: "but Grossmann & I believed that the conservation laws were not satisfied"

    CERN Document Server

    Pitts, J Brian

    2016-01-01

    Recent work on the history of General Relativity by Renn, Sauer, Janssen et al. shows that Einstein found his field equations partly by a physical strategy including the Newtonian limit, the electromagnetic analogy, and energy conservation. Such themes are similar to those later used by particle physicists. How do Einstein's physical strategy and the particle physics derivations compare? What energy-momentum complex(es) did he use and why? Did Einstein tie conservation to symmetries, and if so, to which? Einstein used an identity from his assumed linear coordinate covariance x'= Mx to relate it to the canonical tensor. Usually he avoided using matter Euler-Lagrange equations and so was not well positioned to use or reinvent the Herglotz-Mie-Born understanding that the canonical tensor was conserved due to translation symmetries, a result with roots in Lagrange, Hamilton and Jacobi. Whereas Mie and Born were concerned about the canonical tensor's asymmetry, Einstein did not need to worry because his Entwurf La...

  16. 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

    To celebrate Professor Robert Dewar's 65th birthday, a Symposium was held on 31 October 2009 in Atlanta, Georgia, just before the 51st Annual Meeting of the Division of Plasma Physics of the American Physical Society. The Symposium was attended by many of Bob's colleagues, friends, postdoctoral colleagues and students (present and former). Boyd Blackwell, Anthony Cooper, Chris Hegna, Stuart Hudson, John Krommes, Alexander Pletzer, Ellen Zweibel, and I gave talks that covered various aspects of Bob's wide-ranging scholarship, and his leadership in the Australian and the US fusion program. At the Symposium, Bob gave an insightful talk, published in this issue as a paper with D Leykam. This paper makes available for the first time unpublished results from Bob's M Sc Thesis on a general method for calculating the potential around a `dressed' test particle in an isotropic and collisionless plasma. The paper is interesting not only because it provides a glimpse of the type of elegant applied mathematics that we have come to associate with Bob, but also because he discusses some leitmotifs in his intellectual evolution since the time he was a graduate student at the University of Melbourne and Princeton University. Through his early encounter with quantum field theory, Bob appreciated the power of Lagrangian and Hamiltonian formalisms, which he used with great effectiveness in nonlinear dynamics and plasma physics. A question that animates much of his work is one that underlies the `dressed' particle problem: if one is given a Hamiltonian with an unperturbed (or `bare') part and an interaction part, how is one to obtain a canonical transformation to `the oscillation centre' thatwould reduce the interaction part to an irreducible residual part while incorporating the rest in a renormalized zeroth-order Hamiltonian? One summer in Princeton, I worked with Bob on a possible variational formulation for this problem, and failed. I was daunted enough by my failure that I turned

  17. Crystal chemistry of three-component white dwarfs and neutron star crusts: phase stability, phase stratification, and physical properties

    CERN Document Server

    Engstrom, T A; Crespi, V H

    2015-01-01

    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 before 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-gravit...

  18. Stearic acid spin labels in lipid bilayers: insight through atomistic simulations.

    Science.gov (United States)

    Stimson, Lorna; Dong, Lei; Karttunen, Mikko; Wisniewska, Anna; Dutka, Małgorzata; Róg, Tomasz

    2007-11-01

    Spin-labeled stearic acid species are commonly used for electron paramagnetic resonance (EPR) studies of cell membranes to investigate phase transitions, fluidity, and other physical properties. In this paper, we use large-scale molecular dynamics simulations to investigate the position and behavior of nitroxide spin labels attached to stearic acid molecules in dipalmitoylphosphatidylcholine (DPPC) bilayers. The results of these studies are potentially very important for the interpretation of EPR spectra, which rely on assumptions about the position of the label in the membrane. Additionally, we investigate the effect of chirality and ionization of the carboxyl group of the label. For a non-ionized species, we observe that spin-label molecules are even able to make flip-flop transitions between the leaflets of the bilayer. Such transitions have been previously observed only in very rare cases in molecular simulations. PMID:17929861

  19. Polarization-dependent fluorescence of proteins bound to nanopore-confined lipid bilayers

    Science.gov (United States)

    Li, R.-Q.; Marek, A.; Smirnov, Alex I.; Grebel, H.

    2008-09-01

    Lipid bilayers are essential structural component of biological membranes of all the living species: from viruses and bacteria to plants and humans. Biophysical and biochemical properties of such membranes are important for understanding physical mechanisms responsible for drug targeting. Binding events between proteins and the membrane may be ascertained by introducing fluorescence markers (chromophores) to the proteins. Here we describe a novel biosensing platform designed to enhance signals of these fluorescence markers. Nanoporous aluminum oxide membranes with and without gold (Au) surface coating have been employed for optical detection of bound conjugated streptavidin to biotinylated lipid bilayers-a model system that mimics protein docking to the membrane surface. Unexpectedly, it was found that fluorescence signals from such structures vary when pumped with E-polarized and H-polarized incident optical beams. The origin of the observed polarization-dependent effects and the implications for enhanced fluorescence detection in a biochip format are being discussed.

  20. Perfect Spin-filtering in graphene monolayer-bilayer superlattice with zigzag boundaries.

    Science.gov (United States)

    Yu, Hang; Liu, Jun-Feng

    2016-01-01

    We show that the spontaneous magnetization is formed at the zigzag boundary between monolayer and bilayer graphene by the self-consistent calculation based on Hubbard model. In a monolayer- bilayer graphene superlattice with zigzag boundaries, it is surprising that nearly 100% spin polarization is achieved in the energy window around the Dirac point, no matter the magnetization configuration at two boundaries is parallel or antiparallel. The reason is that the low-energy transport is only influenced by the magnetization at one edge, but not by that at the other. The underlying physics is unveiled by the spin-split band structure and the distribution of the wave-function pertaining to the lowest (highest) subband of electron (hole). PMID:27140666

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

    Science.gov (United States)

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

    2016-04-01

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

  2. Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity.

    Science.gov (United States)

    Maher, Sean; Basit, Hajra; Forster, Robert J; Keyes, Tia E

    2016-12-01

    Microcavity supported lipid bilayers, MSLBs, were applied to an electrochemical investigation of ionophore mediated ion transport. The arrays comprise of a 1cm(2) gold electrode imprinted with an ordered array of uniform spherical-cap pores of 2.8μm diameter prepared by gold electrodeposition through polystyrene templating spheres. The pores were pre-filled with aqueous buffer prior to Langmuir-Blodgett assembly of a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer. Fluorescence lifetime correlation spectroscopy enabled by the micron dimensions of the pores permitted study of lipid diffusion across single apertures, yielding a diffusion coefficient of 12.58±1.28μm(2)s(-1) and anomalous exponent of 1.03±0.02, consistent with Brownian motion. From FLCS, the MSLBs were stable over 3days and electrochemical impedance spectroscopy of the membrane with and without ionic gradient over experimental windows of 6h showed excellent stability. Two ionophores were studied at the MSLBs; Valinomycin, a K(+) uniporter and Nigericin, a K(+)/H(+) antiporter. Ionophore reconstituted into the DOPC bilayer resulted in a decrease and increase in membrane resistance and capacitance respectively. Significant increases in Valinomycin and Nigericin activity were observed, reflected in large decreases in membrane resistance when K(+) was present in the contacting buffer and in the presence of H(+) ionic gradient across the membrane respectively. PMID:27420132

  3. Protocells: Modular Mesoporous Silica Nanoparticle-Supported Lipid Bilayers for Drug Delivery.

    Science.gov (United States)

    Butler, Kimberly S; Durfee, Paul N; Theron, Christophe; Ashley, Carlee E; Carnes, Eric C; Brinker, C Jeffrey

    2016-04-01

    Mesoporous silica nanoparticle-supported lipid bilayers, termed 'protocells,' represent a potentially transformative class of therapeutic and theranostic delivery vehicle. The field of targeted drug delivery poses considerable challenges that cannot be addressed with a single 'magic bullet'. Consequently, the protocell has been designed as a modular platform composed of interchangeable biocompatible components. The mesoporous silica core has variable size and shape to direct biodistribution and a controlled pore size and surface chemistry to accommodate diverse cargo. The encapsulating supported lipid bilayer can be modified with targeting and trafficking ligands as well as polyethylene glycol (PEG) to effect selective binding, endosomal escape of cargo, drug efflux prevention, and potent therapeutic delivery, while maintaining in vivo colloidal stability. This review describes the individual components of the platform, including the mesoporous silica nanoparticle core and supported lipid bilayer, their assembly (by multiple techniques) into a protocell, and the combined, often synergistic, performance of the protocell based on in vitro and in vivo studies, including the assessment of biocompatibility and toxicity. In closing, the many emerging variations of the protocell theme and the future directions for protocell research are commented on. PMID:26780591

  4. Distribution and dynamics of quinones in the lipid bilayer mimicking the inner membrane of mitochondria.

    Science.gov (United States)

    Kaurola, Petri; Sharma, Vivek; Vonk, Amanda; Vattulainen, Ilpo; Róg, Tomasz

    2016-09-01

    Quinone and its analogues (Q) constitute an important class of compounds that perform key electron transfer reactions in oxidative- and photo-phosphorylation. In the inner membrane of mitochondria, ubiquinone molecules undergo continuous redox transitions enabling electron transfer between the respiratory complexes. In such a dynamic system undergoing continuous turnover for ATP synthesis, an uninterrupted supply of substrate molecules is absolutely necessary. In the current work, we have performed atomistic molecular dynamics simulations and free energy calculations to assess the structure, dynamics, and localization of quinone and its analogues in a lipid bilayer, whose composition mimics the one in the inner mitochondrial membrane. The results show that there is a strong tendency of both quinone and quinol molecules to localize in the vicinity of the lipids' acyl groups, right under the lipid head group region. Additionally, we observe a second location in the middle of the bilayer where quinone molecules tend to stabilize. Translocation of quinone through a lipid bilayer is very fast and occurs in 10-100ns time scale, whereas the translocation of quinol is at least an order of magnitude slower. We suggest that this has important mechanistic implications given that the localization of Q ensures maximal occupancy of the Q-binding sites or Q-entry points in electron transport chain complexes, thereby maintaining an optimal turnover rate for ATP synthesis. PMID:27342376

  5. Switchable magnetic moment in cobalt-doped graphene bilayer on Cu(111): An ab initio study

    Science.gov (United States)

    Souza, Everson S.; Scopel, Wanderlã L.; Miwa, R. H.

    2016-06-01

    In this work, we have performed an ab initio theoretical investigation of substitutional cobalt atoms in the graphene bilayer supported on the Cu(111) surface (Co/GBL/Cu). Initially, we examined the separated systems, namely, graphene bilayer adsorbed on Cu(111) (GBL/Cu) and a free standing Co-doped GBL (Co/GBL). In the former system, the GBL becomes n -type doped, where we map the net electronic charge density distribution along the GBL-Cu(111) interface. The substitutional Co atom in Co/GBL lies between the graphene layers, and present a net magnetic moment mostly due to the unpaired Co-3 dz2 electrons. In Co/GBL/Cu, we found that the Cu(111) substrate rules (i) the energetic stability, and (ii) the magnetic properties of substitutional Co atoms in the graphene bilayer. In (i), the substitutional Co atom becomes energetically more stable lying on the GBL surface, and in (ii), the magnetic moment of Co/GBL has been quenched due to the Cu(111) → Co/GBL electronic charge transfer. We verify that such a charge transfer can be tuned upon the application of an external electric field, and thus mediated by a suitable change on the electronic occupation of the Co-dz2 orbitals, we found a way to switch-on and -off the magnetization of the Co-doped GBL adsorbed on the Cu(111) surface.

  6. Bilayer avalanche spin-diode logic

    International Nuclear Information System (INIS)

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

  7. Giant magnetoresistance in bilayer graphene nanoflakes

    Science.gov (United States)

    Farghadan, Rouhollah; Farekiyan, Marzieh

    2016-09-01

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

  8. Vortex dynamics in ferromagnetic/superconducting bilayers

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-07-01

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

  9. Bilayer avalanche spin-diode logic

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-15

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

  10. Computer Simulations of Lipid Bilayers and Proteins

    OpenAIRE

    Sonne, Jacob

    2006-01-01

    Molekyldynamiske (MD) computersimuleringer benyttes i dag i stor ud\\-str{\\ae}k\\-ning til at studere forskellige typer systemer p{\\aa} submikroskopiske l{\\ae}ng\\-de\\-ska\\-laer. I denne afhandling med titlen {\\it Computer simulations of lipid bilayers and proteins} beskrives MD simuleringer af biologiske membraner og proteiner. I en MD simulering l{\\o}\\-ses Newtons be\\-v{\\ae}gel\\-ses\\-lig\\-ning numerisk for en samling af op til nogle hundrede tusinde atomer. Hovedresultatet af en s{\\aa}dan simu...

  11. DNA nanostructures interacting with lipid bilayer membranes.

    Science.gov (United States)

    Langecker, Martin; Arnaut, Vera; List, Jonathan; Simmel, Friedrich C

    2014-06-17

    CONSPECTUS: DNA has been previously shown to be useful as a material for the fabrication of static nanoscale objects, and also for the realization of dynamic molecular devices and machines. In many cases, nucleic acid assemblies directly mimic biological structures, for example, cytoskeletal filaments, enzyme scaffolds, or molecular motors, and many of the applications envisioned for such structures involve the study or imitation of biological processes, and even the interaction with living cells and organisms. An essential feature of biological systems is their elaborate structural organization and compartmentalization, and this most often involves membranous structures that are formed by dynamic assemblies of lipid molecules. Imitation of or interaction with biological systems using the tools of DNA nanotechnology thus ultimately and necessarily also involves interactions with lipid membrane structures, and thus the creation of DNA-lipid hybrid assemblies. Due to their differing chemical nature, however, highly charged nucleic acids and amphiphilic lipids do not seem the best match for the construction of such systems, and in fact they are rarely found in nature. In recent years, however, a large variety of lipid-interacting DNA conjugates were developed, which are now increasingly being applied also for the realization of DNA nanostructures interacting with lipid bilayer membranes. In this Account, we will present the current state of this emerging class of nanosystems. After a brief overview of the basic biophysical and biochemical properties of lipids and lipid bilayer membranes, we will discuss how DNA molecules can interact with lipid membranes through electrostatic interactions or via covalent modification with hydrophobic moieties. We will then show how such DNA-lipid interactions have been utilized for the realization of DNA nanostructures attached to or embedded within lipid bilayer membranes. Under certain conditions, DNA nanostructures remain mobile on

  12. Bilayer avalanche spin-diode logic

    Directory of Open Access Journals (Sweden)

    Joseph S. Friedman

    2015-11-01

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

  13. 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. PMID:25331189

  14. Deformation of giant lipid bilayer vesicles in shear flow

    NARCIS (Netherlands)

    Haas, de K.H.; Blom, C.; Ende, van den D.; Duits, M.H.G.; Mellema, J.

    1997-01-01

    We describe experimental studies of the deformation of giant lipid bilayer vesicles in shear flow. The experiments are carried out with a counterrotating Couette apparatus. The deformation depends on the mechanical properties of the lipid bilayer, the vesicle radius, and the viscosity of the surroun

  15. Tetracycline diffusion through phospholipid bilayers and binding to phospholipids.

    OpenAIRE

    Argast, M; Beck, C.F.

    1984-01-01

    The ability of tetracycline to pass through phospholipid bilayers by diffusion was investigated. Liposomes did not retain enclosed tetracycline. Accumulation of tetracycline was observed with liposomes containing entrapped Tet repressor protein. These results indicate that the drug can pass through lipid bilayers. The antibiotic was also shown to bind to liposomes and isolated phospholipids.

  16. A NOVEL APPROACH OF BILAYER TABLET TECHNOLOGY: A REVIEW

    Directory of Open Access Journals (Sweden)

    Panchal Hiten Ashok

    2012-05-01

    Full Text Available Over the past 30 years as the expense and complications involved in marketing new drug entities have increased, with concomitant recognition of the therapeutic advantages of controlled drug delivery, greater attention has been focused on development of sustained or controlled release drug delivery systems. Bilayer tablet is new era for the successful development of controlled release formulation along with various features to provide a way of successful drug delivery system. . So use of bilayer tablet is a very different aspect for anti-inflammatory and analgesic. Bi-layer tablet is suitable for sequential release of two drugs in combination, separate two incompatible substances and also for sustained release tablet in which one Layer is immediate release as initial dose and second layer is maintenance dose. Bilayer tablet is improved beneficial technology to overcome the shortcoming of the single layered tablet. Several pharmaceutical companies are currently developing bi-layer tablets. For a variety of reasons: patent extension, therapeutic, marketing to name a few. To reduce capital investment, quite often existing but modified tablet presses are used to develop and produce such tablets. This article explains about different techniques of bilayer tablet and why the development and production of quality bi-layer tablets needs to be carried out on purpose-built tablet presses to overcome common bi-layer problems, such as layer-separation, insufficient hardness, Inaccurate individual layer weight control, cross-contamination between the layers, reduced yield etc.

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

    International Nuclear Information System (INIS)

    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)

  18. 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

  19. Effects of types and amounts of stabilizers on physical and sensory characteristics of cloudy ready-to-drink mulberry fruit juice

    OpenAIRE

    Akkarachaneeyakorn, Suthida; Tinrat, Sirikhwan

    2015-01-01

    In this study, the pH of mulberry juice was optimized for high anthocyanin content and an attractive red color. Mulberry juice pH values of 2.5, 4.0, 6.0, and 8.0 were evaluated. A pH of 2.5 gave an anthocyanin content of 541.39 ± 106.43 mg of cyanidin-3-glucoside per liter, and the a* value was 14 ± 1.00. The effects of stabilizers (CMC and xanthan gum) on the physical characteristics of cloudy ready-to-drink mulberry fruit juice (via the addition of mulberry fruit pulp at a mass fraction of...

  20. Regulation of sodium channel function by bilayer elasticity

    DEFF Research Database (Denmark)

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

    2004-01-01

    kinetics of the protein conformational changes therefore will be regulated by the bilayer elasticity, which is determined by the lipid composition. This hydrophobic coupling mechanism has been studied extensively in gramicidin channels, where the channel-bilayer hydrophobic interactions link a...... "conformational" change (the monomerdimer transition) to an elastic bilayer deformation. Gramicidin channels thus are regulated by the lipid bilayer elastic properties (thickness, monolayer equilibrium curvature, and compression and bending moduli). To investigate whether this hydrophobic coupling mechanism could...... be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta...

  1. Kinetics of solubilization with Triton X-100 of egg-yolk lecithin bilayers containing cholesterol

    CERN Document Server

    Hobai, S

    2001-01-01

    The titration solubilization of multilamellar egg-yolk lecithin liposomes (MLV-EYL) with Triton X-100 was studied by rectangular optical diffusimetric measurements as a function of cholesterol (Chol) concentration. It was determinated the variation of optic percentage diffu-sion (per mmol surfactant), DDif%/mmol TX-100, in the course of solubilization of MLV-EYL-Chol system with TX-100 10mM. The statistical analysis of the titration curves can reveal the contribution of cholesterol to the stability of phospholipid bilayer membranes. The solubilization of the lecithin-cholesterol mixtures, with a high cholesterol content, much more bile salt requires.

  2. Crystal Chemistry of Three-component White Dwarfs and Neutron Star Crusts: Phase Stability, Phase Stratification, and Physical Properties

    Science.gov (United States)

    Engstrom, T. A.; Yoder, N. C.; Crespi, V. H.

    2016-02-01

    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. Millimeter-area, free standing, phospholipid bilayers.

    Science.gov (United States)

    Beltramo, Peter J; Van Hooghten, Rob; Vermant, Jan

    2016-05-11

    Minimal model biomembrane studies have the potential to unlock the fundamental mechanisms of cellular function that govern the processes upon which life relies. However, existing methods to fabricate free-standing model membranes currently have significant limitations. Bilayer sizes are often tens of micrometers, decoupling curvature or substrate effects, orthogonal control over tension, and solvent exchange combined with microscopy techniques is not possible, which restricts the studies that can be performed. Here, we describe a versatile platform to generate free standing, planar, phospholipid bilayers with millimeter scale areas. The technique relies on an adapted thin-film balance apparatus allowing for the dynamic control of the nucleation and growth of a planar black lipid membrane in the center of an orifice surrounded by microfluidic channels. Success is demonstrated using several different lipid types, including mixtures that show the same temperature dependent phase separation as existing protocols, moreover, membranes are highly stable. Two advantages unique to the proposed method are the dynamic control of the membrane tension and the possibility to make extremely large area membranes. We demonstrate this by showing how a block polymer, F68, used in drug delivery increases the membrane compliance. Together, the results demonstrate a new paradigm for studying the mechanics, structure, and function of model membranes. PMID:27050618

  4. Edge states of zigzag bilayer graphite nanoribbons

    Science.gov (United States)

    Rhim, Jun-Won; Moon, Kyungsun

    2008-09-01

    The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude γ4, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points ± k* independent of the ribbon width with a peculiar energy dispersion near k* as ɛ(k)~ ± (k-k*)N. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of γ4, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.

  5. Edge states of zigzag bilayer graphite nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Jun-Won; Moon, Kyungsun [Department of Physics and Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of)], E-mail: kmoon@yonsei.ac.kr

    2008-09-10

    The electronic structures of zigzag bilayer graphite nanoribbons (Z-BGNRs) with various ribbon widths N are studied within the tight binding approximation. Neglecting the inter-layer hopping amplitude {gamma}{sub 4}, which is an order of magnitude smaller than the other inter-layer hopping parameters, there exist two fixed Fermi points {+-} k{sup *} independent of the ribbon width with a peculiar energy dispersion near k{sup *} as {epsilon}(k){approx} {+-} (k-k{sup *}){sup N}. By investigating the edge states of Z-BGNRs, we notice that the trigonal warping of the bilayer graphene sheets is reflected in the edge state structure. With the inclusion of {gamma}{sub 4}, the above two Fermi points are not fixed but drift toward the vicinity of the Dirac point with increasing width N, as shown by the finite scaling method, and the peculiar dispersions change to parabolic ones. The edge magnetism of Z-BGNRs is also examined by solving the half-filled Hubbard Hamiltonian for the ribbon using the Hartree-Fock approximation. We have shown that within the same side of the edges, the edge spins are aligned ferromagnetically for the experimentally relevant set of parameters.

  6. Utilization of interfacial engineering to improve physicochemical stability of β-carotene emulsions: Multilayer coatings formed using protein and protein-polyphenol conjugates.

    Science.gov (United States)

    Liu, Fuguo; Wang, Di; Sun, Cuixia; McClements, David Julian; Gao, Yanxiang

    2016-08-15

    The impact of lactoferrin (LF)-chlorogenic acid (CA) and (-)-Epigallocatechin-3-gallate (EGCG) conjugates on the physicochemical properties of β-carotene emulsions was investigated. Formation of lactoferrin-polyphenol conjugates, which was confirmed by SDS-PAGE, caused changes in the structure and nature of lactoferrin. Based on layer-by-layer electrostatic deposition, β-carotene bilayer emulsions were prepared by lactoferrin and lactoferrin-polyphenol conjugates at pH 7.0. The physicochemical properties of primary and secondary emulsions were evaluated and the results suggested that LF-polyphenol conjugates-stabilized primary and secondary emulsions exhibited better emulsifying properties and improved physical stability of β-carotene bilayer emulsions under freeze-thaw, ionic strength and thermal treatments. In addition, the lactoferrin-polyphenol conjugates could effectively enhance chemical stability of β-carotene in oil-in-water emulsions against heat treatment and ultraviolet light exposure, and the least degradation of β-carotene occurred in LF-EGCG conjugate-stabilized primary emulsion. The interfacial engineering technology utilized in this study may lead to the formation of emulsions with improved physicochemical and functional performance. PMID:27006223

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

    International Nuclear Information System (INIS)

    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

  8. Characterizing the Superconducting-to-Normal Transition in Mo/Au Transition-Edge Sensor Bilayers

    Science.gov (United States)

    Smith, Stephen J.; Bandler, Simon R.; Brown, Ari. -D.; Chervenak, Jay A.; Finkbeiner, Fred M.; Iyomoto, Naoko; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.

    2007-01-01

    We are developing arrays of Mo/Au bilayer transition-edge sensors (TES's) for applications in future X-ray astronomy missions such as NASA's Constellation-X. The physical properties of the superconducting-to-normal transition in our TES bilayers, while often reproducible and characterized, are not well understood. The addition of normal metal features on top of the bilayer are found to change the shape and temperature of the transition, and they typically reduce the unexplained 'excess' noise. In order to understand and potentially optimize the properties of the transition, we have been studying the temperature, widths and current dependence of these transitions. We report on the characterization of devices both deposited on silicon substrates and suspended on thin silicon nitride membranes. This includes key device parameters such as the logarithmic resistance sensitivity with temperature alpha, and the logarithmic resistance sensitivity with current beta, of the phase-transition. We investigate alpha and beta as a function of current, both at fixed and varying bias points in the transition. Using Ginzburg-Landau theory for the current dependence of the superconducting transition temperature, we investigate the relationship between alpha and beta and compare our measured and theoretical estimates.

  9. 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. PMID:27112848

  10. Vortex structures and magnetic domain patterns in the superconductor/ferromagnet hybrid bilayer

    International Nuclear Information System (INIS)

    Superconducting vortices and magnetic domain patterns’ evolution in the superconductor-ferromagnet (SC/FM) hybrid bilayer are investigated within the Ginzburg—Landau (GL) theory of superconductivity, in combination with the Landau—Lifshitz—Gilbert (LLG) equation of ferromagnetism. Magnetic domain patterns in the ferromagnetic thin film and the vortices’ nucleation in the superconducting layer for the hybrid bilayer, subjected to perpendicular magnetic fields, are obtained by numerical simulations. A dynamical evolution picture of the magnetic domain patterns and the associated superconducting vortices’ nucleation are clearly shown. The effect of geometry parameters and physical parameters on the magnetic domain and superconducting vortex evolution are discussed. The magnetization curve of the SC film has also been illustrated. We found that the vortex dynamic behavior of the superconducting film changes substantially, and the correlated magnetic hysteresis loss is significantly reduced due to the presence of the ferromagnetic thin layer. In addition, the spontaneous vortex-antivortex (V-AV) pairs’ nucleation in the hybrid bilayer are investigated. (paper)

  11. Extension of the GLYCAM06 Biomolecular Force Field to Lipids, Lipid Bilayers and Glycolipids.

    Science.gov (United States)

    Tessier, Matthew B; Demarco, Mari L; Yongye, Austin B; Woods, Robert J

    2008-01-01

    GLYCAM06 is a generalisable biomolecular force field that is extendible to diverse molecular classes in the spirit of a small-molecule force field. Here we report parameters for lipids, lipid bilayers and glycolipids for use with GLYCAM06. Only three lipid-specific atom types have been introduced, in keeping with the general philosophy of transferable parameter development. Bond stretching, angle bending, and torsional force constants were derived by fitting to quantum mechanical data for a collection of minimal molecular fragments and related small molecules. Partial atomic charges were computed by fitting to ensemble-averaged quantum-computed molecular electrostatic potentials.In addition to reproducing quantum mechanical internal rotational energies and experimental valence geometries for an array of small molecules, condensed-phase simulations employing the new parameters are shown to reproduce the bulk physical properties of a DMPC lipid bilayer. The new parameters allow for molecular dynamics simulations of complex systems containing lipids, lipid bilayers, glycolipids, and carbohydrates, using an internally consistent force field. By combining the AMBER parameters for proteins with the GLYCAM06 parameters, it is also possible to simulate protein-lipid complexes and proteins in biologically relevant membrane-like environments. PMID:22247593

  12. Preparation and magnetic performance of the magnetic fluid stabilized by bi-surfactant

    Science.gov (United States)

    Bateer, Buhe; Qu, Yang; Meng, Xiangying; Tian, Chungui; Du, Shichao; Wang, Ruihong; Pan, Kai; Fu, Honggang

    2013-04-01

    A stable poly-alpha olefin oil based magnetic fluid of bilayer surfactant coated (oleic acid and succinimide) Fe3O4 nanoparticles was prepared by a using phase transfer method. The bilayer surfactant-coated magnetic particles are characterized by Fourier-transform infrared spectroscopy, the result shows that the Fe3O4 nanoparticles are coated by oleic acid, and the bilayer surfactant succinimide wraps the oleic acid coated Fe3O4 nanoparticles. Transmission electron microscopy images indicate that the dispersibility of the bilayer coated Fe3O4 nanoparticles is better than that of the uncoated ones. Vibrating sample magnetometer measurement confirms that both the coated and uncoated Fe3O4 nanoparticles are super-paramagnetic. Stability measurements show the magnetic fluids prepared by bilayer coated Fe3O4 nanoparticles is nearly constant for 360 days at room temperature.

  13. Fabrication of Supported Lipid Bilayer on Graphene Oxide

    International Nuclear Information System (INIS)

    Planar lipid bilayers of dioleoylphosphatidylcholine was prepared on graphene oxide (GO), as a fundamental platform for biosensing in plasma membrane model using graphene. The GO flakes were prepared according to modified Hummer's method, and deposited on thermally oxidized SiO2/Si surfaces. We found that planar lipid bilayers were reproducibility formed on the GO/SiO2/Si surface in the presence of Ca2+ ions, while unruptured vesicles remained on the GO surface without Ca2+ ion. The results of atomic force microscope observation and fluorescence recovery after photobleaching experiment revealed that double lipid bilayers were spontaneously formed on the GO surfaces.

  14. Shape Changes of Self-Assembled Actin Bilayer Composite Membranes

    CERN Document Server

    Hackl, W; Sackmann, E

    1997-01-01

    We report the self-assembly of thin actin shells beneath the membranes of giant vesicles. Ion-carrier mediated influx of Mg2+ induces actin polymerization in the initially spherical vesicles. Buckling of the vesicles and the formation of blisters after thermally induced bilayer expansion is demonstrated. Bilayer flickering is dominated by tension generated by its coupling to the actin cortex. Quantitative flicker analysis suggests the bilayer and the actin cortex are separated by 0.4 \\mum to 0.5 \\mum due to undulation forces.

  15. A circuit model for defective bilayer graphene transistors

    Science.gov (United States)

    Umoh, Ime J.; Moktadir, Zakaria; Hang, Shuojin; Kazmierski, Tom J.; Mizuta, Hiroshi

    2016-05-01

    This paper investigates the behaviour of a defective single-gate bilayer graphene transistor. Point defects were introduced into pristine graphene crystal structure using a tightly focused helium ion beam. The transfer characteristics of the exposed transistors were measured ex-situ for different defect concentrations. The channel peak resistance increased with increasing defect concentration whilst the on-off ratio showed a decreasing trend for both electrons and holes. To understand the electrical behaviour of the transistors, a circuit model for bilayer graphene is developed which shows a very good agreement when validated against experimental data. The model allowed parameter extraction of bilayer transistor and can be implemented in circuit level simulators.

  16. Fractional quantum Hall states in charge-imbalanced bilayer systems

    OpenAIRE

    Thiebaut, N.; Regnault, N.; Goerbig, M. O.

    2013-01-01

    We study the fractional quantum Hall effect in a bilayer with charge-distribution imbalance induced, for instance, by a bias gate voltage. The bilayer can either be intrinsic or it can be formed spontaneously in wide quantum wells, due to the Coulomb repulsion between electrons. We focus on fractional quantum Hall effect in asymmetric bilayer systems at filling factor nu=4/11 and show that an asymmetric Halperin-like trial wavefunction gives a valid description of the ground state of the system.

  17. Oxygen diffusion in bilayer polymer films

    DEFF Research Database (Denmark)

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

    2004-01-01

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

  18. Vortex dynamics in ferromagnetic/superconducting bilayers

    International Nuclear Information System (INIS)

    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 ≥ λ) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w ≥≥ λ) enhance pinning less effectively and result in flux jumps during flux motion. (authors)

  19. Vortex Dynamics in Ferromagnetic/Superconducting Bilayers

    Science.gov (United States)

    Cieplak, M. Z.; Adamus, Z.; Kończykowski, M.; Zhu, L. Y.; Chien, C. L.

    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 ferrromagnetic 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 ≥ qλ) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w ≫ λ) enhance pinning less effectively and result in flux jumps during flux motion.

  20. Experimental demonstration of a bilayer thermal cloak.

    Science.gov (United States)

    Han, Tiancheng; Bai, Xue; Gao, Dongliang; Thong, John T L; Li, Baowen; Qiu, Cheng-Wei

    2014-02-01

    Invisibility has attracted intensive research in various communities, e.g., optics, electromagnetics, acoustics, thermodynamics, dc, etc. However, many experimental demonstrations have only been achieved by virtue of simplified approaches due to the inhomogeneous and extreme parameters imposed by the transformation-optic method, and usually require a challenging realization with metamaterials. In this Letter, we demonstrate a bilayer thermal cloak made of bulk isotropic materials, and it has been validated as an exact cloak. We experimentally verified its ability to maintain the heat front and its heat protection capabilities in a 2D proof-of-concept experiment. The robustness of this scheme is validated in both 2D (including oblique heat front incidence) and 3D configurations. The proposed scheme may open a new avenue to control the diffusive heat flow in ways inconceivable with phonons, and also inspire new alternatives to the functionalities promised by transformation optics. PMID:24580600

  1. Population inversion in monolayer and bilayer graphene

    International Nuclear Information System (INIS)

    The recent demonstration of saturable absorption and negative optical conductivity in the Terahertz range in graphene has opened up new opportunities for optoelectronic applications based on this and other low dimensional materials. Recently, population inversion across the Dirac point has been observed directly by time- and angle-resolved photoemission spectroscopy (tr-ARPES), revealing a relaxation time of only ∼130 femtoseconds. This severely limits the applicability of single layer graphene to, for example, Terahertz light amplification. Here we use tr-ARPES to demonstrate long-lived population inversion in bilayer graphene. The effect is attributed to the small band gap found in this compound. We propose a microscopic model for these observations and speculate that an enhancement of both the pump photon energy and the pump fluence may further increase this lifetime. (paper)

  2. Charge order and phase segregation in overdoped bilayer manganites

    Energy Technology Data Exchange (ETDEWEB)

    Maitra, T [Institut fuer Theoretische Physik, J W Goethe Universitaet, Max-von-Laue-Strasse 1, 60438 Frankfurt (Germany); Taraphder, A [Department of Physics and Meteorology and Centre for Theoretical Studies, Indian Institute of Technology, Kharagpur 721302 (India); Beck, H [Institute of Physics, University of Neuchatel, rue de Breguet 1, CH-2000 (Switzerland)

    2005-07-13

    There have been recent reports of charge ordering around x = 0.5 in the bilayer manganites like La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}. At x = 0.5, there appears to be a coexistence region of layered A-type antiferromagnetic order and charge order. There are also reports of orbital order in this region without any Jahn-Teller effect. Based on physical grounds, this region is investigated from a model that incorporates the two e{sub g} orbitals at each Mn site and a near-neighbour Coulomb repulsion. It is shown that there indeed both charge and orbital order close to the half-doped region coincident with a layered magnetic structure. Although the orbital order is known to drive the magnetic order, the layered magnetic structure is also favoured in this system by the lack of coherent transport across the planes and the reduced dimensionality of the lattice. The anisotropic hopping across the e{sub g} orbitals and the underlying layered structure largely determine the orbital arrangements in this region, while the charge order is primarily due to the long-range interactions.

  3. 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. PMID:24280018

  4. Pressure effects on the equilibrium configurations of bilayer lipid membranes

    Science.gov (United States)

    DeVita, Raffaella; Stewart, Iain W.; Leo, Donald J.

    2007-10-01

    Planar bilayer lipid membranes (BLMs) are currently employed to construct many bio-inspired material systems and structures. In order to characterize the pressure effects on the equilibrium configurations of these biological membranes, a novel continuum model is proposed. The BLM is assumed to be a two-layer smectic A liquid crystal. The mean orientation of the amphiphilic molecules comprising the membrane is postulated to be perpendicular to the layers and each layer is idealized as a two-dimensional liquid. Moreover, the BLM is modeled as a simply supported plate undergoing small deformations. It is subjected to a pressure load that acts perpendicularly to the layers. The equilibrium equations and boundary conditions are derived from the bulk elastic energy for smectic A liquid crystals as described by de Gennes and Prost (1993 The Physics of Liquid Crystals 2nd edn (Oxford Science Publications)) by using variational methods. The resulting fourth-order linear partial differential equation is solved by employing cylindrical functions and the series solution is proved to be convergent. The solution is numerically computed for values of the model parameters that are reported in the literature. This paper is dedicated to the memory of our colleagues, Professors Kevin P Granata and Liviu Librescv, who lost their lives during the sensless tragedy on 16 April, 2007 at Virginia Tech.

  5. 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.

  6. Fibrillation of β amyloid peptides in the presence of phospholipid bilayers and the consequent membrane disruption.

    Science.gov (United States)

    Qiang, Wei; Yau, Wai-Ming; Schulte, Jürgen

    2015-01-01

    Fibrillation of β amyloid (Aβ) peptides and the accumulation of amyloid plaques are considered as an important clinical hallmark to identify Alzheimer's disease (AD). The physiological connection between Aβ plaques and the disruption of neuronal cells has not been clearly understood. One hypothesis to explain the Aβ neurotoxicity is that the fibrillation process induces disruption to the cellular membrane. We studied the Aβ fibrillation process in two biologically relevant conditions with the peptide either pre-incorporated into or externally added to the synthetic phospholipid bilayers. These two sample preparation conditions mimic the physiological membrane proximities of Aβ peptides before and after the enzymatic cleavage of amyloid precursor protein (APP). Using thioflavin T (ThT) fluorescence and transmission electron microscopy (TEM), we were able to monitor the kinetics and morphological evolution of fibril formation, which was highly sensitive to the two sample preparation protocols. While the external addition protocol generates long and mature fibrils through normal fibrillation process, the pre-incubation protocol was found to stabilize the immature protofibrils. Fluorescence spectroscopy studies with doubly-labeled phospholipids indicated that there may be a lipid uptake process associated with the fibril formation. Solid state nuclear magnetic resonance (NMR) spectroscopy provided evidence for high resolution structural variations in fibrils formed with different protocols, and in particular the stabilization of long-range contact between N- and C-terminal β strands. In addition, disruption of phospholipid bilayers was supported by measurements with ³¹P chemical shifts and relaxation time constants. PMID:24769158

  7. 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)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Eric D. Wachsman

    2000-10-01

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

  9. 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

    Tenerife: WSEAS Press, 2009 - (Bulucea, C.; Mladenov, V.; Pop, E.; Leba, M.; Mastorakis, N.), s. 212-217 ISBN 978-960-474-142-7. [International Conference on Environment, Ecosystems and Development (EED ´09) /7./. Tenerife (ES), 14.12.2009-16.12.2009] R&D Projects: GA AV ČR IAA400400806 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40550506 Keywords : phospholipid bilayers * environment * trace elements * charged particles Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Electronic properties of asymmetrically doped twisted graphene bilayers

    Science.gov (United States)

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

    2016-06-01

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

  11. 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.

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

    Directory of Open Access Journals (Sweden)

    Hediyeh Karimi

    2013-01-01

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

  13. Sub-wavelength antenna enhanced bilayer graphene tunable photodetector

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-22

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

  14. 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...

  15. Energy levels of hybrid monolayer-bilayer graphene quantum dots

    Science.gov (United States)

    Mirzakhani, M.; Zarenia, M.; Ketabi, S. A.; da Costa, D. R.; Peeters, F. M.

    2016-04-01

    Often real samples of graphene consist of islands of both monolayer and bilayer graphene. Bound states in such hybrid quantum dots are investigated for (i) a circular single-layer graphene quantum dot surrounded by an infinite bilayer graphene sheet and (ii) a circular bilayer graphene quantum dot surrounded by an infinite single-layer graphene. Using the continuum model and applying zigzag boundary conditions at the single-layer-bilayer graphene interface, we obtain analytical results for the energy levels and the corresponding wave spinors. Their dependence on perpendicular magnetic and electric fields are studied for both types of quantum dots. The energy levels exhibit characteristics of interface states, and we find anticrossings and closing of the energy gap in the presence of a bias potential.

  16. Effect of impurity doping in gapped bilayer graphene

    International Nuclear Information System (INIS)

    Impurity doping plays a pivotal role in semiconductor electronics. We study the doping effect in a two-dimensional semiconductor, gapped bilayer graphene. By employing in situ deposition of calcium on the bilayer graphene, dopants are controllably introduced. Low temperature transport results show a variable range hopping conduction near the charge neutrality point persisting up to 50 K, providing evidence for the impurity levels inside the gap. Our experiment confirms a predicted peculiar effect in the gapped bilayer graphene, i.e., formation of in-gap states even if the bare impurity level lies in the conduction band. The result provides perspective on the effect of doping and impurity levels in semiconducting bilayer graphene

  17. Influence of trigonal warping on interference effects in bilayer graphene

    OpenAIRE

    Kechedzhi, K.; Falko, Vladimir I; McCann, E.; Altshuler, B.L.

    2007-01-01

    Bilayer graphene (two coupled graphitic monolayers arranged according to Bernal stacking) is a two-dimensional gapless semiconductor with a peculiar electronic spectrum different from the Dirac spectrum in the monolayer material. In particular, the electronic Fermi line in each of its valleys has a strong p -> -p asymmetry due to a trigonal warping, which suppresses the weak localization effect. We show that weak localisation in bilayer graphene may be present only in devices with pronounced ...

  18. Deformation of giant lipid bilayer vesicles in shear flow

    OpenAIRE

    Haas,; Blom, C.; Ende, van den, D.; Duits, M. H. G.; Mellema, J.

    1997-01-01

    We describe experimental studies of the deformation of giant lipid bilayer vesicles in shear flow. The experiments are carried out with a counterrotating Couette apparatus. The deformation depends on the mechanical properties of the lipid bilayer, the vesicle radius, and the viscosity of the surrounding Newtonian liquid. We show that the relevant mechanical parameter is the bending rigidity. A simple model has been developed that describes the deformation of a vesicle. This model takes therma...

  19. Atomistic Simulations of Pore Formation and Closure in Lipid Bilayers

    OpenAIRE

    Bennett, W. F. Drew; Sapay, Nicolas; Tieleman, D. Peter

    2014-01-01

    Cellular membranes separate distinct aqueous compartments, but can be breached by transient hydrophilic pores. A large energetic cost prevents pore formation, which is largely dependent on the composition and structure of the lipid bilayer. The softness of bilayers and the disordered structure of pores make their characterization difficult. We use molecular-dynamics simulations with atomistic detail to study the thermodynamics, kinetics, and mechanism of pore formation and closure in DLPC, DM...

  20. Constant helical pitch of the gramicidin channel in phospholipid bilayers.

    OpenAIRE

    Katsaras, J.; Prosser, R S; Stinson, R H; Davis, J H

    1992-01-01

    X-ray diffraction has been applied in measuring the helical pitch of the gramicidin channel in oriented bilayers of dilauroylphosphatidylcholine (DLPC) and dimyristoylphosphatidylcholine (DMPC) at a polypeptide concentration of 9.1 mol %. The diffraction data show the helical pitch of gramicidin to be 4.7 +/- 0.2 A in both gel and liquid-crystalline phase bilayers, with and without monovalent cations. In addition, the width of the reflection due to the pitch of the helical gramicidin channel ...

  1. Polysaccharide-supported planar bilayer lipid model membranes

    OpenAIRE

    Baumgart, T.; Offenhäusser, A.

    2003-01-01

    Bilayer lipid membranes were deposited onto two different thin water swellable polymer cushions predominantly by Langmuir-Blodgett trough methods. Membranes consisting of zwitterionic lipids supported by agarose films were shown to be unstable, as observed by fluorescence microscopy, reflection interference contrast microscopy, and the impossibility of bilayer spreading (Radler, J.; Strey, H.; Sackmann, E. Langmuir 1995, 11, 4539-4548) on the agarose surface. Chitosan, formerly observed to pe...

  2. Dynamics and instabilities of lipid bilayer membrane shapes

    OpenAIRE

    Shi, Zheng; Baumgart, Tobias

    2014-01-01

    Biological membranes undergo constant shape remodeling involving the formation of highly curved structures. The lipid bilayer represents the fundamental architecture of the cellular membrane with its shapes determined by the Helfrich curvature bending energy. However, the dynamics of bilayer shape transitions, especially their modulation by membrane proteins, and the resulting shape instabilities, are still not well understood. Here, we review in a unifying manner several theories that descri...

  3. Molecular Dynamics of a Water-Lipid Bilayer Interface

    Science.gov (United States)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

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

  4. Edge State and Intrinsic Hole Doping in Bilayer Phosphorene

    OpenAIRE

    Osada, Toshihito

    2014-01-01

    Using a simple LCAO model by Harrison, we have qualitatively studied the edge state of bilayer phosphorene, which is a unit structure of the layered crystal of black phosphorus. This model successfully reproduces the isolated edge state in the bulk gap in monolayer phosphorene. In bilayer phosphorene, however, it shows that edge states are almost buried in the valence band and there is no isolated midgap edge state at the zigzag edge. Since the buried edge state works as acceptor, holes are d...

  5. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei; Esposito, Vincenzo; Teocoli, Francesca; Olevsky, Eugene A.; Bjørk, Rasmus; Pryds, Nini; Kaiser, Andreas; Frandsen, Henrik Lund

    2015-01-01

    densification and stress developments during sintering of tubular bi-layered samples. The correspondence between linear elastic and linear viscous theories is used as a basis for derivation of the model. The developed model is first verified by finite element simulation for sintering of tubular bi-layer system...... thermo-mechanical analysis. Results from the analytical model are found to agree well with finite element simulations as well as measurements from sintering experiment....

  6. The edge engineering of topological Bi(111) bilayer

    OpenAIRE

    Li, Xiao; Liu, Hai-Wen; Jiang, Hua; Wang, Fa; Feng, Ji

    2014-01-01

    A topological insulator is a novel quantum state, characterized by symmetry-protected non-trivial edge/surface states. Our first-principle simulations show the significant effects of the chemical decoration on edge states of topological Bi(111) bilayer nanoribbon, which remove the trivial edge state and recover the Dirac linear dispersion of topological edge state. By comparing the edge states with and without chemical decoration, the Bi(111) bilayer nanoribbon offers a simple system for asse...

  7. The role of MscL amphipathic N terminus indicates a blueprint for bilayer-mediated gating of mechanosensitive channels.

    Science.gov (United States)

    Bavi, Navid; Cortes, D Marien; Cox, Charles D; Rohde, Paul R; Liu, Weihong; Deitmer, Joachim W; Bavi, Omid; Strop, Pavel; Hill, Adam P; Rees, Douglas; Corry, Ben; Perozo, Eduardo; Martinac, Boris

    2016-01-01

    The bacterial mechanosensitive channel MscL gates in response to membrane tension as a result of mechanical force transmitted directly to the channel from the lipid bilayer. MscL represents an excellent model system to study the basic biophysical principles of mechanosensory transduction. However, understanding of the essential structural components that transduce bilayer tension into channel gating remains incomplete. Here using multiple experimental and computational approaches, we demonstrate that the amphipathic N-terminal helix of MscL acts as a crucial structural element during tension-induced gating, both stabilizing the closed state and coupling the channel to the membrane. We propose that this may also represent a common principle in the gating cycle of unrelated mechanosensitive ion channels, allowing the coupling of channel conformation to membrane dynamics. PMID:27329693

  8. 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: 2.577, year: 2014

  9. Chemotherapy Drugs Thiocolchicoside and Taxol Permeabilize Lipid Bilayer Membranes by Forming Ion Pores

    Science.gov (United States)

    Ashrafuzzaman, Md; Duszyk, M.; Tuszynski, J. A.

    2011-12-01

    We report ion channel formation by chemotherapy drugs: thiocolchicoside (TCC) and taxol (TXL) which primarily target tubulin but not only. For example, TCC has been shown to interact with GABAA, nuclear envelope and strychnine-sensitive glycine receptors. TXL interferes with the normal breakdown of microtubules inducing mitotic block and apoptosis. It also interacts with mitochondria and found significant chemotherapeutic applications for breast, ovarian and lung cancer. In order to better understand the mechanisms of TCC and TXL actions, we examined their effects on phospholipid bilayer membranes. Our electrophysiological recordings across membranes constructed in NaCl aqueous phases consisting of TCC or TXL under the influence of an applied transmembrane potential (V) indicate that both molecules induce stable ion flowing pores/channels in membranes. Their discrete current versus time plots exhibit triangular shapes which is consistent with a spontaneous time-dependent change of the pore conductance in contrast to rectangular conductance events usually induced by ion channels. These events exhibit conductance (~0.01-0.1 pA/mV) and lifetimes (~5-30 ms) within the ranges observed in e.g., gramicidin A and alamethicin channels. The channel formation probability increases linearly with TCC/TXL concentration and V and is not affected by pH (5.7 - 8.4). A theoretical explanation on the causes of chemotherapy drug induced ion pore formation and the pore stability has also been found using our recently discovered binding energy between lipid bilayer and the bilayer embedded ion channels using gramicidin A channels as tools. This picture of energetics suggests that as the channel forming agents approach to the lipids on bilayer the localized charge properties in the constituents of both channel forming agents (e.g., chemotherapy drugs in this study) and the lipids determine the electrostatic drug-lipid coupling energy through screened Coulomb interactions between the drug

  10. Chemotherapy Drugs Thiocolchicoside and Taxol Permeabilize Lipid Bilayer Membranes by Forming Ion Pores

    International Nuclear Information System (INIS)

    We report ion channel formation by chemotherapy drugs: thiocolchicoside (TCC) and taxol (TXL) which primarily target tubulin but not only. For example, TCC has been shown to interact with GABAA, nuclear envelope and strychnine-sensitive glycine receptors. TXL interferes with the normal breakdown of microtubules inducing mitotic block and apoptosis. It also interacts with mitochondria and found significant chemotherapeutic applications for breast, ovarian and lung cancer. In order to better understand the mechanisms of TCC and TXL actions, we examined their effects on phospholipid bilayer membranes. Our electrophysiological recordings across membranes constructed in NaCl aqueous phases consisting of TCC or TXL under the influence of an applied transmembrane potential (V) indicate that both molecules induce stable ion flowing pores/channels in membranes. Their discrete current versus time plots exhibit triangular shapes which is consistent with a spontaneous time-dependent change of the pore conductance in contrast to rectangular conductance events usually induced by ion channels. These events exhibit conductance (∼0.01-0.1 pA/mV) and lifetimes (∼5-30 ms) within the ranges observed in e.g., gramicidin A and alamethicin channels. The channel formation probability increases linearly with TCC/TXL concentration and V and is not affected by pH (5.7 - 8.4). A theoretical explanation on the causes of chemotherapy drug induced ion pore formation and the pore stability has also been found using our recently discovered binding energy between lipid bilayer and the bilayer embedded ion channels using gramicidin A channels as tools. This picture of energetics suggests that as the channel forming agents approach to the lipids on bilayer the localized charge properties in the constituents of both channel forming agents (e.g., chemotherapy drugs in this study) and the lipids determine the electrostatic drug-lipid coupling energy through screened Coulomb interactions between the

  11. 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

  12. 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.

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

    Science.gov (United States)

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

    2016-02-01

    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.

  14. Mechanism of unassisted ion transport across membrane bilayers

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1996-01-01

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

  15. Predicting proton titration in cationic micelle and bilayer environments

    International Nuclear Information System (INIS)

    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

  16. Formation of supported lipid bilayers by vesicle fusion

    DEFF Research Database (Denmark)

    Lind, Tania Kjellerup; Cardenas Gomez, Marite; Wacklin, Hanna

    2014-01-01

    We have investigated the effect of deposition temperature on supported lipid bilayer formation via vesicle fusion. By using several complementary surface-sensitive techniques, we demonstrate that despite contradicting literature on the subject, high-quality bilayers can be formed below the main p...... observed during the deposition process by QCM-D correspond to vesicles absorbed on top of a continuous bilayer and not to a surface-supported vesicular layer as previously reported. © 2014 American Chemical Society.......We have investigated the effect of deposition temperature on supported lipid bilayer formation via vesicle fusion. By using several complementary surface-sensitive techniques, we demonstrate that despite contradicting literature on the subject, high-quality bilayers can be formed below the main...... phase-transition temperature of the lipid. We have carefully studied the formation mechanism of supported DPPC bilayers below and above the lipid melting temperature (Tm) by quartz crystal microbalance and atomic force microscopy under continuous flow conditions. We also measured the structure of lipid...

  17. Critical phenomena in bilayer excitonic condensates

    OpenAIRE

    Huang, Xuting

    2012-01-01

    The revolution of physics from the classical to quantum mechanical view angle, ignited by a number of discoveries from the past century such as the photoelectric effect by Heinrich Hertz as well as the quantumhypothesis by Max Planck, has continued to flourish in the second half of the 20th century. One of the most intensively studied topics is the phenomenon of spontaneous symmetry breaking, which is present in both particle physics and condensed matter physics. In particle physics, the most...

  18. Magnetic Irreversibility in VO2/Ni Bilayers

    Science.gov (United States)

    de La Venta, Jose; Lauzier, Josh; Sutton, Logan

    The temperature dependence of the coercivity and magnetization of VO2/Ni bilayers was studied. VO2 exhibits a well-known Structural Phase Transition (SPT) at 330-340 K, from a low temperature monoclinic (M) to a high temperature rutile (R) structure. The SPT of VO2 induces an inverse magnetoelastic effect that strongly modifies the coercivity and magnetization of the Ni films. In addition, the growth conditions allow tuning of the magnetic properties. Ni films deposited on top of VO2 (M) show an irreversible change in the coercivity after the first cycle through the high temperature phase, with a corresponding change in the surface morphology of VO2. On the other hand, the Ni films grown on top of VO2 (R) do not show this irreversibility. These results indicate that properties of magnetic films are strongly affected by the strain induced by materials that undergo SPT and that it is possible to control the magnetic properties by tuning the growth conditions.

  19. Properties of bilayer contacts to porous silicon

    Science.gov (United States)

    Gallach, D.; Torres-Costa, V.; García-Pelayo, L.; Climent-Font, A.; Martín-Palma, R. J.; Barreiros-das-Santos, M.; Sporer, C.; Samitier, J.; Manso, M.

    2012-05-01

    The aim of the present work is the growth by PVD techniques and ulterior characterization of electrical contacts to columnar porous silicon (PSi) as an approach to reliable PSi sensor devices. Contacts consist of a NiCr (40:60) and Au bilayer on the PSi surface deposited by magnetron sputtering. These structures show a good adhesion to the rough surface of columnar PSi. The morphology of these electrical contacts is characterized by electron microscopy and their crystalline structure by X-ray diffraction. Compositional profiles are determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy, which demonstrate that the infiltration of NiCr into the PSi is at the origin of the metallic thin film adhesion improvement. I- V characteristics and impedance spectroscopy measurements show that this configuration provides rectifying electrical contacts to PSi, for which a simple equivalent circuit based on one resistor and two capacitors can be modeled. These results further support the use of PSi electrical structures for sensing purposes.

  20. Properties of bilayer contacts to porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Gallach, D.; Torres-Costa, V.; Garcia-Pelayo, L.; Climent-Font, A.; Martin-Palma, R.J.; Manso, M. [Universidad Autonoma de Madrid, Departamento de Fisica Aplicada, Madrid (Spain); Barreiros-das-Santos, M.; Sporer, C.; Samitier, J. [Institute for Bioengineering of Catalonia (IBEC), Nanobioengineering Group, Barcelona (Spain)

    2012-05-15

    The aim of the present work is the growth by PVD techniques and ulterior characterization of electrical contacts to columnar porous silicon (PSi) as an approach to reliable PSi sensor devices. Contacts consist of a NiCr (40:60) and Au bilayer on the PSi surface deposited by magnetron sputtering. These structures show a good adhesion to the rough surface of columnar PSi. The morphology of these electrical contacts is characterized by electron microscopy and their crystalline structure by X-ray diffraction. Compositional profiles are determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy, which demonstrate that the infiltration of NiCr into the PSi is at the origin of the metallic thin film adhesion improvement. I-V characteristics and impedance spectroscopy measurements show that this configuration provides rectifying electrical contacts to PSi, for which a simple equivalent circuit based on one resistor and two capacitors can be modeled. These results further support the use of PSi electrical structures for sensing purposes. (orig.)

  1. Condensation energy of the superconducting bilayer cuprates

    Indian Academy of Sciences (India)

    Govind; Ajay; S K Joshi

    2002-05-01

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

  2. Raman modes in transferred bilayer CVD graphene

    Directory of Open Access Journals (Sweden)

    Niilisk Ahti

    2015-01-01

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

  3. Localized plasmons in bilayer graphene nanodisks

    Science.gov (United States)

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

    2016-04-01

    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 homogeneous surface conductivity, and an efficient alternative two-dimensional electrostatic approach is employed to carry out all the numerical calculations of plasmon resonances. Due to unique electronic band structures, the resonance frequency of the traditional dipolar plasmonic mode in the AA-stacked BLG nanodisk is roughly doping independent in the low-doping regime, while the mode is highly damped as the Fermi level approaches the interlayer hopping energy γ associated with tunneling of electrons between the two layers. In addition to the traditional dipolar mode, we find that the AB-stacked BLG nanodisk also hosts a new plasmonic mode with energy larger than γ . This mode can be tuned by either the doping level or structural size, and, furthermore, this mode can dominate the plasmonic response for realistic structural conditions.

  4. Thermoelectric power in a bilayer graphene device

    Science.gov (United States)

    Yung-Yu, Chien; Hongtao, Yuan; Chang-Ran, Wang; Chun-Hsuan, Lin; Wei-Li, Lee; Geballe LaboratoryAdvanced Materials Collaboration; Institute of Physics, Academia Sinica, Taipei, Taiwan Team

    2014-03-01

    There have been great interests on band gap engineering in a bilayer graphene (BLG) device, where inversion symmetry breaking by a perpendicular electric field can give rise to a sizable band gap. In our previous works, we have demonstrated a large enhancement in the thermoelectric power (TEP) associated with the band gap opening in a dual-gated BLG device. It is, therefore, an interesting question to ask whether even larger TEP can be achieved with a larger perpendicular electric field applied. We explored such possibility by utilizing the ionic liquid gating technique in BLG devices. By controlling the side gate voltage of ionic liquid and the bottom gate voltage via SiO2/Si substrate, large increase of the sheet resistance at charge neutral point was observed suggesting the opening of a band gap. At T = 120 K, TEP increases by more than 44% with a side gate voltage of ~ 1V. The influence of charge puddles to TEP using ionic liquid gating will be discussed.

  5. Performance test of Ti/Au bilayer TES microcalorimeter in combination with continuous ADR

    International Nuclear Information System (INIS)

    Performance test of a Ti/Au bilayer TES microcalorimeter has been made in combination with a continuous adiabatic demagnetization refrigerator (CADR). The CADR has four stages of ADR to produce continuous cooling by recycling them in dedicated order, and is cryogen-free utilizing a 4K-GM refrigerator. We installed a Ti/Au bilayer TES microcalorimeter and 420-series SQUID array to readout the X-ray signal on the 1st (coldest) stage of the CADR. We successfully operated the CADR at temperature of 120 mK in continuous mode more than 27 hr, however, FWHM energy resolution of the TES microcalorimeter was degraded to 45 eV at 6 keV, as compared to 10 eV when measured in a dilution refrigerator. This is mainly because the temperature stability was not good enough (about 0.6 mK) and the operation temperature was not sufficiently lower than the transition temperature Tc = 135mK of the TES. We operated the TES microcalorimeter at the operation temperature of 105 mK in one-shot mode and the resolution was improved to 30 eV. We also found that the operating point of the TES was affected by the magnetic field of the 3rd and 4th ADR recycle. More complete shielding of the magnetic field is essential for further improvement of the performance of the TES microcalorimeter.

  6. Characterization of lipid bilayer formation in aligned nanoporous aluminum oxide nanotube arrays.

    Science.gov (United States)

    Karp, Ethan S; Newstadt, Justin P; Chu, Shidong; Lorigan, Gary A

    2007-07-01

    Aligning lipid bilayers in nanoporous anodized aluminum oxide (AAO) is a new method to help study membrane proteins by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (NMR) spectroscopic methods. The ability to maintain hydration, sample stability, and compartmentalization over long periods of time, and to easily change solvent composition are major advantages of this new method. To date, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) has been the only phospholipid used for membrane protein studies with AAO substrates. The different properties of lipids with varying chain lengths require modified sample preparation procedures to achieve well formed bilayers within the lining of the AAO substrates. For the first time, the current study presents a simple methodology to incorporate large quantities of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC), DMPC, and 1,2-dipalmitoyl-3-sn-phosphatidylcholine (DPPC) phospholipids inside AAO substrate nanopores of varying sizes. (2)H and (31)P solid-state NMR were used to confirm the alignment of each lipid and compare the efficiency of alignment. This study is the first step in standardizing the use of AAO substrates as a tool in NMR and EPR and will be useful for future structural studies of membrane proteins. Additionally, the solid-state NMR data suggest possible applications of nanoporous aluminum oxide in future vesicle fusion studies. PMID:17482492

  7. The targeted delivery of multicomponent cargos to cancer cells by nanoporous particle-supported lipid bilayers

    Science.gov (United States)

    Ashley, Carlee E.; Carnes, Eric C.; Phillips, Genevieve K.; Padilla, David; Durfee, Paul N.; Brown, Page A.; Hanna, Tracey N.; Liu, Juewen; Phillips, Brandy; Carter, Mark B.; Carroll, Nick J.; Jiang, Xingmao; Dunphy, Darren R.; Willman, Cheryl L.; Petsev, Dimiter N.; Evans, Deborah G.; Parikh, Atul N.; Chackerian, Bryce; Wharton, Walker; Peabody, David S.; Brinker, C. Jeffrey

    2011-05-01

    Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability and a high capacity for disparate cargos. Here we report porous nanoparticle-supported lipid bilayers (protocells) that synergistically combine properties of liposomes and nanoporous particles. Protocells modified with a targeting peptide that binds to human hepatocellular carcinoma exhibit a 10,000-fold greater affinity for human hepatocellular carcinoma than for hepatocytes, endothelial cells or immune cells. Furthermore, protocells can be loaded with combinations of therapeutic (drugs, small interfering RNA and toxins) and diagnostic (quantum dots) agents and modified to promote endosomal escape and nuclear accumulation of selected cargos. The enormous capacity of the high-surface-area nanoporous core combined with the enhanced targeting efficacy enabled by the fluid supported lipid bilayer enable a single protocell loaded with a drug cocktail to kill a drug-resistant human hepatocellular carcinoma cell, representing a 106-fold improvement over comparable liposomes.

  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. Functional reconstitution of ICln in lipid bilayers.

    Science.gov (United States)

    Fürst, J; Bazzini, C; Jakab, M; Meyer, G; König, M; Gschwentner, M; Ritter, M; Schmarda, A; Bottà, G; Benz, R; Deetjen, P; Paulmichl, M

    2000-05-01

    Reconstitution of purified ICln in lipid bilayer leads to functional ion channels showing varying rectification. The reconstituted single channels have a conductance of approximately equal to 3 pS and their open probability is sensitive to nucleoside analogues. Mutation of a putative nucleotide binding site identified at the predicted extracellular mouth of the ICln channel protein leads to the reduction of the nucleoside-analogue sensitivity. Reconstituted ICln channels can be permeated both by cations and anions. The relative permeability of cations over anions depends on the presence of calcium. In the presence of calcium reconstituted ICln channels are more permeable to bromide than chloride, and more permeable to potassium than sodium. Similarly in NIH3T3 fibroblasts, the relative permeability of cations over anions of swelling-dependent chloride channels depends on extracellular calcium. Site-directed mutagenesis revealed the calcium-binding site responsible for the shift of the selectivity from cations towards anions of reconstituted ICln channels. Additional indirect structural information has been obtained by mutating a histidine in the predicted pore region of ICln. This histidine seems to have access to the ion-conducting tunnel of the pore. Our experiments show that ICln can act as an ionic channel, which does not exclude additional functions of the protein in regulatory mechanisms of the cell. Since knocking down the ICln protein in fibroblasts and epithelial cells leads to an impaired regulatory volume decrease (RVD) after cytoplasmic swelling and reconstituted ICln channels show several biophysical features of ion channels activated after swelling, ICln is a molecular candidate for these channels. PMID:10864003

  10. Modification of the PTCDA-Ag bond by forming a heteromolecular bilayer film

    Science.gov (United States)

    Stadtmüller, Benjamin; Willenbockel, Martin; Schröder, Sonja; Kleimann, Christoph; Reinisch, Eva M.; Ules, Thomas; Soubatch, Sergey; Ramsey, Michael G.; Tautz, F. Stefan; Kumpf, Christian

    2015-04-01

    The understanding of the fundamental physical properties of metal-organic and organic-organic interfaces is crucial for improving the performance of organic electronic devices. This is particularly true for (multilayer) systems containing several molecular species due to their relevance for donor-acceptor systems. A prototypical heteromolecular bilayer system is copper-II-phthalocyanine (CuPc) on 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) on Ag(111). In an earlier work we have reported a commensurate registry between both organic layers and an enhanced charge transfer from the Ag substrate into the organic bilayer film [Phys. Rev. Lett. 108, 106103 (2012), 10.1103/PhysRevLett.108.106103], which both indicate an unexpectedly strong intermolecular interaction across the organic-organic interface. Here we present new details regarding electronic and geometric structure for the same system. In particular, we provide evidence that the enhanced charge transfer from the substrate into the organic bilayer does not involve CuPc electronic states, hence, there is no significant charge transfer into the second organic layer. Furthermore, we report vertical bonding distances revealing a shortening of the PTCDA-Ag(111) distance upon CuPc adsorption. Thus, electronic and geometric properties (charge transfer and bonding distance, respectively) both indicate a strengthening of the PTCDA-Ag(111) bond upon CuPc adsorption. We explain these findings—in particular the correlation between CuPc adsorption and increased charge transfer into PTCDA—in a model involving an intermolecular screening mechanism.

  11. Preparation and characterization of nano fluids: Influence of variables on its stability, agglomeration state and physical properties; Preparacion y caracterizacion de nanofluidos: Influencia de variables sobre su estabilidad, estado de aglomeracion y propiedades fisicas

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-01

    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)

  12. Gramicidin tryptophans mediate formamidinium-induced channel stabilization.

    OpenAIRE

    Seoh, S A; Busath, D

    1995-01-01

    Compared with alkali metal cations, formamidinium ions stabilize the gramicidin A channel molecule in monoolein bilayers (Seoh and Busath, 1993a). A similar effect is observed with N-acetyl gramicidin channel molecules in spite of the modified forces at the dimeric junction (Seoh and Busath, 1993b). Here we use electrophysiological measurements with tryptophan-to-phenylalanine-substituted gramicidin analogs to show that the formamidinium-induced channel molecule stabilization is eliminated wh...

  13. 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.

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

    International Nuclear Information System (INIS)

    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 ION levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures

  15. Preisach analysis of epitaxial hard/soft bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cornejo, D.R.; Rhen, F.M.; Missell, F.P. E-mail: fmissell@macbeth.if.usp.br; Fullerton, E.E

    2001-05-01

    We used the moving Preisach model to study the magnetization-reversal process in epitaxial SmCo (1 1 =macron 0 0)/Fe bilayers prepared by magnetron sputtering. The SmCo(20 nm)/Fe(t nm) (t=0, 5, 10, 20) bilayers were grown onto single-crystal (1 1 0)MgO substrates with an epitaxial 20 nm Cr(2 1 1) buffer layer. The second-quadrant magnetization curves were strictly reversible up to a field H{sub 0}, close to the field H{sub c} at which the magnetization switched irreversibly. Henkel plots for these bilayers indicated very strong magnetizing interactions for all films. Magnetization reversal in these films reflects their epitaxial structure.

  16. Bilayer polymer/oxide coating for electroluminescent organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana

    of the fibers with oxygen. We have developed a bilayer coating that does not change significantly the p6P spectrum but strongly reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on top of the organic nanofibers as a protecting layer for avoiding...... modifications of the p6P luminescence spectrum and as a second layer SiOx for blocking the oxyg en penetration. In this work, we show the applicability of this bilayer coating of PMMA/SiOx in prolonging the operational lifetime of field-effect transistor (FET) devices based on p6P nanofibers. The coating...... prevents strong degradation of transferred nanofibers on FET platforms during electrical biasing as is observed for uncoated devices. We are currently investigating the effect of the coating during electrically stimulated light emission experiments from transferred fibers on transistor platforms....

  17. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    International Nuclear Information System (INIS)

    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. The organization of n-alkanes in lipid bilayers.

    Science.gov (United States)

    McIntosh, T J; Simon, S A; MacDonald, R C

    1980-04-24

    The interaction of n-alkanes (C6--C16) with phosphatidylcholine has been studied by the combined use of differential scanning calorimetry, X-ray diffraction and monolayer techniques. It has been found that the thermal properties and ultrastructure of lipid-alkane vesicles are strongly dependent on the length of the n-alkanes. Long alkanes, such as tetradecane and hexadecane, increase the transition temperature of dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine, while the X-ray data indicate that these long alkanes align parallel to the lipid acyl chains. In contrast, shorter alkanes, such as hexane and octane, decrease and broaden the thermal transition and electron density profiles show that these alkanes increase bilayer width by partitioning between the apposing monolayers of the bilayer. For lipids in the gel and liquid crystalline states, the short alkanes form an alkane region in the geometric center of the bilayer. PMID:6892885

  19. 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.

  20. Interaction driven quantum Hall effect in artificially stacked graphene bilayers

    Science.gov (United States)

    Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa

    2016-04-01

    The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers.

  1. Interaction driven quantum Hall effect in artificially stacked graphene bilayers

    Science.gov (United States)

    Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa

    2016-01-01

    The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387

  2. Equilibrium Configurations of Lipid Bilayer Membranes and Carbon Nanostructures

    Institute of Scientific and Technical Information of China (English)

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

    2013-01-01

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

  3. Lipid peroxidation and water penetration in lipid bilayers

    DEFF Research Database (Denmark)

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

    2012-01-01

    Lipid peroxidation plays a key role in the alteration of cell membrane's properties. Here we used as model systems multilamellar vesicles (MLVs) made of the first two products in the oxidative cascade of linoleoyl lecithin, namely 1-palmitoyl-2-(13-hydroperoxy-9,11-octadecanedienoyl)-lecithin (Hp......(zz) parameters revealed that OHPLPC, but mostly HpPLPC, induced a measurable increase in polarity and H-bonding propensity in the central region of the bilayer. Molecular dynamics simulation performed on 16-DSA in the PLPC-HpPLPC bilayer revealed that water molecules are statistically favored with respect to the...... hydroperoxide groups to interact with the nitroxide at the methyl-terminal, confirming that the H-bonds experimentally observed are due to increased water penetration in the bilayer. The EPR and MD data on model membranes demonstrate that cell membrane damage by oxidative stress cause alteration of water...

  4. Edge State and Intrinsic Hole Doping in Bilayer Phosphorene

    Science.gov (United States)

    Osada, Toshihito

    2015-01-01

    Using a simple LCAO model by Harrison, we have qualitatively studied the edge state of bilayer phosphorene, which is a unit structure of the layered crystal of black phosphorus. This model successfully reproduces the isolated edge state in the bulk gap in monolayer phosphorene. In bilayer phosphorene, however, it shows that edge states are almost buried in the valence band and there is no isolated midgap edge state at the zigzag edge. Since the buried edge state works as acceptor, holes are doped from the edge state into the bulk. This gives a possible explanation for p-type conduction in undoped black phosphorus. Under the vertical electric field, the intrinsic hole doping is reduced because a part of edge states move into the gap. These features of bilayer phosphorene might be better suited for device application.

  5. Electronic transport in B-N substituted bilayer graphene nanojunctions

    Science.gov (United States)

    Giofré, Daniele; Ceresoli, Davide; Fratesi, Guido; Trioni, Mario I.

    2016-05-01

    We investigated a suspended bilayer graphene where the bottom/top layer is doped by boron/nitrogen substitutional atoms. By using density functional theory calculations, we found that at high dopant concentration (one B-N pair every 32 C atoms), the electronic structure of the bilayer does not depend on the B-N distance but on the relative occupation of the bilayer graphene sublattices by B and N. The presence of the dopants and the consequent charge transfer establish a built-in electric field between the layers, giving rise to an energy gap. We further investigated the electronic transport properties and found that intralayer current is weakly influenced by the presence of these dopants while the interlayer one is enhanced for biases, allowing an easy tunneling between layers. This effect leads to current rectification in asymmetric junctions.

  6. Manipulating interface states in monolayer–bilayer graphene planar junctions

    Science.gov (United States)

    Zhao, Fang; Xu, Lei; Zhang, Jun

    2016-05-01

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

  7. Efficient Organic Photovoltaics Utilizing Nanoscale Heterojunctions in Sequentially Deposited Polymer/fullerene Bilayer

    OpenAIRE

    Seok, Jeesoo; Shin, Tae Joo; Park, Sungmin; Cho, Changsoon; Lee, Jung-Yong; Yeol Ryu, Du; Kim, Myung Hwa; Kim, Kyungkon

    2015-01-01

    A highly efficient sequentially deposited bilayer (SD-bilayer) of polymer/fullerene organic photovoltaic (OPV) device is developed via the solution process. Herein, we resolve two essential problems regarding the construction of an efficient SD-bilayer OPV. First, the solution process fabrication of the SD-bilayer is resolved by incorporating an ordering agent (OA) to the polymer solution, which improves the ordering of the polymer chain and prevents the bottom-layer from dissolving into the ...

  8. Optical and electrical properties of Mg/Co bilayer thin film metal hydrides

    OpenAIRE

    M. K. JANGID,; S.P. Nehra; M Singh

    2010-01-01

    Bilayer Mg/Co thin films have been prepared using thermal evaporation method at pressure 10-5 torr. Annealing of bilayer thin films have been performed for 1 hour at different temperature. Hydrogenation of pristine and annealed bilayer structure has been performed at different hydrogen pressure for half an hour. The optical transmission increased with hydrogen pressure and also the band gap of thin films found to be increase with hydrogen pressure. Pristine Mg/Co bilayers show ohmic behavior ...

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

    OpenAIRE

    Pabst, Georg; Rappolt, Michael; Amenitsch, Heinz; Bernstorff, Sigrid; Laggner, Peter

    2000-01-01

    The response kinetics of liquid crystalline phosphatidylcholine bilayer stacks to rapid, IR-laser induced temperature jumps has been studied by millisecond time-resolved x-ray diffraction. The system reacts on the fast temperature change by a discrete bilayer compression normal to its surface and a lateral bilayer expansion. Since water cannot diffuse from the excess phase into the interbilayer water region within the 2 ms duration of the laser pulse, the water layer has to follow the bilayer...

  10. Transport methods for probing the barrier domain of lipid bilayer membranes.

    OpenAIRE

    Xiang, T X; Chen, X.; Anderson, B. D.

    1992-01-01

    Two experimental techniques have been utilized to explore the barrier properties of lecithin/decane bilayer membranes with the aim of determining the contributions of various domains within the bilayer to the overall barrier. The thickness of lecithin/decane bilayers was systematically varied by modulating the chemical potential of decane in the annulus surrounding the bilayer using different mole fractions of squalene in decane. The dependence of permeability of a model permeant (acetamide) ...

  11. Calorimetric study on pH-responsive block copolymer grafted lipid bilayers: rational design and development of liposomes.

    Science.gov (United States)

    Pippa, Natassa; Chountoulesi, Maria; Kyrili, Aimilia; Meristoudi, Anastasia; Pispas, Stergios; Demetzos, Costas

    2016-09-01

    This study is focused on chimeric advanced drug delivery nanosystems and specifically on pH-sensitive liposomes, combining lipids and pH-responsive amphiphilic block copolymers. Chimeric liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and two different forms of block copolymers, i.e. poly(n-butylacrylate)-b-poly(acrylic acid) (PnBA-b-PAA) at 70 and 85% content of PAA at six different molar ratios, each form respectively. PAA block exhibits pH-responsiveness, because of the regulative group of -COOH. -COOH is protonated under acidic pH (pKa ca. 4.2), while remains ionized under basic or neutral pH, leading to liposomes repulse and eventually stability. Lipid bilayers were prepared composed of DPPC and PnBA-b-PAA. Experiments were carried out using differential scanning calorimetry (DSC) in order to investigate their thermotropic properties. DSC indicated disappearance of pre-transition at all chimeric lipid bilayers and slight thermotropic changes of the main transition temperature. Chimeric liposomes have been prepared and their physicochemical characteristics have been explored by measuring the size, size distribution and ζ-potential, owned to the presence of pH-responsive polymer. At percentages containing medium to high amounts of the polymer, chimeric liposomes were found to retain their size during the stability studies. These results were well correlated with those indicated in the DSC measurements of lipid bilayers incorporating polymers in order to explain their physicochemical behavior. The incorporation of the appropriate amount of these novel pH-responsive block copolymers affects thus the cooperativity, the liposomal stabilization and imparts pH-responsiveness. PMID:26364717

  12. Manipulating lipid bilayer material properties using biologically active amphipathic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Ashrafuzzaman, Md [Department of Physiology and Biophysics, Weill Medical College of University of Cornell, New York, NY 10021 (United States); Lampson, M A [Department of Physiology and Biophysics, Weill Medical College of University of Cornell, New York, NY 10021 (United States); Greathouse, D V [Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701 (United States); II, R E Koeppe [Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701 (United States); Andersen, O S [Department of Physiology and Biophysics, Weill Medical College of University of Cornell, New York, NY 10021 (United States)

    2006-07-19

    Lipid bilayers are elastic bodies with properties that can be manipulated/controlled by the adsorption of amphipathic molecules. The resulting changes in bilayer elasticity have been shown to regulate integral membrane protein function. To further understand the amphiphile-induced modulation of bilayer material properties (thickness, intrinsic monolayer curvature and elastic moduli), we examined how an enantiomeric pair of viral anti-fusion peptides (AFPs)-Z-Gly-D-Phe and Z-Gly-Phe, where Z denotes a benzyloxycarbonyl group, as well as Z-Phe-Tyr and Z-D-Phe-Phe-Gly-alters the function of enantiomeric pairs of gramicidin channels of different lengths in planar bilayers. For both short and long channels, the channel lifetimes and appearance frequencies increase as linear functions of the aqueous AFP concentration, with no apparent effect on the single-channel conductance. These changes in channel function do not depend on the chirality of the channels or the AFPs. At pH 7.0, the relative changes in channel lifetimes do not vary when the channel length is varied, indicating that these compounds exert their effects primarily by causing a positive-going change in the intrinsic monolayer curvature. At pH 4.0, the AFPs are more potent than at pH 7.0 and have greater effects on the shorter channels, indicating that these compounds now change the bilayer elastic moduli. When AFPs of different anti-fusion potencies are compared, the rank order of the anti-fusion activity and the channel-modifying activity is similar, but the relative changes in anti-fusion potency are larger than the changes in channel-modifying activity. We conclude that gramicidin channels are useful as molecular force transducers to probe the influence of small amphiphiles upon lipid bilayer material properties.

  13. Formation and structure of stably dispersed particles composed of retinal with dipalmitoylphosphatidylcholine: coexistence of emulsion particles with bilayer vesicles.

    Science.gov (United States)

    Asai, Y; Watanabe, S

    1999-07-01

    In order to develop an intravenous formulation of all-trans-retinal (vitamin A aldehyde, VAA) for the treatment of night blindness, VAA and dipalmitoylphosphatidylcholine (DPPC) were sonicated and the dispersions in the VAA mole fraction range of 0.1-0.7 were stable at room temperature for 3 days. In order to clarify the dispersal mechanism, the dispersed particles were characterized and the interaction between VAA and DPPC was investigated using several physicochemical techniques. Dynamic light scattering measurements showed that the diameter of the dispersed particles was 50-70 nm. A limited amount of VAA is incorporated into DPPC bilayer membranes (approximately 5 mole%). The trapped aqueous volume inside the particles was determined fluorometrically using the aqueous space marker calcein and the volume in the VAA/DPPC particles was decreased remarkably with the addition of VAA into small unilamellar vesicles of DPPC. The decline in the fraction of vesicular particles was also confirmed by fluorescence quenching of N-dansylhexadecylamine in the DPPC membrane by the addition of the quencher CuSO(4). These results indicate that the excess VAA separated from the DPPC bilayers is stabilized as emulsion particles by the DPPC surface monolayer. The monolayer-bilayer equilibrium of VAA/DPPC mixtures was estimated by measurement of spreading and collapse pressures. The results showed that the coexistence of emulsion particles (surface monolayer of DPPC+core of VAA) with vesicular particles (bilayer) was critically important for the formation of the stably dispersed particles of the lipid mixture. PMID:10477332

  14. A SnOx-brookite TiO2 bilayer electron collector for hysteresis-less high efficiency plastic perovskite solar cells fabricated at low process temperature.

    Science.gov (United States)

    Kogo, Atsushi; Ikegami, Masashi; Miyasaka, Tsutomu

    2016-06-21

    Thin plastic film-based CH3NH3PbI3-xClx perovskite solar cells were fabricated at low process temperature using a bilayer comprising an amorphous SnOx and mesoporous brookite TiO2 as electron collectors. Void-less high quality heterojunction structures achieve hysteresis-less photovoltaic performance with a power conversion efficiency as high as 13.4% and mechanical stability against cyclic bending. PMID:27270998

  15. Diffraction studies on natural and model lipid bilayers

    Science.gov (United States)

    Sebastiani, F.; Harvey, R.; Khanniche, S.; Artero, J.-B.; Haertlein, M.; Fragneto, G.

    2012-11-01

    In this study we have used neutron diffraction to examine the swelling behaviour and bilayer parameters of membranes reconstituted from polar lipids extracted from B. subtilis and model systems composed of synthetic phospholipids. Evidence for phase separation in the model system (lacking in Lysyl-PG, L-PG) is discussed in relation to its possible contribution to membrane domain formation through lipid-lipid interactions. Comparing these results with those obtained from the bilayers composed of lipids extracted from bacterial cells gives us some indication of the role of L-PG in the B. subtilis plasma membrane.

  16. Enhanced Configurational Entropy in High-Density Nanoconfined Bilayer Ice

    Science.gov (United States)

    Corsetti, Fabiano; Zubeltzu, Jon; Artacho, Emilio

    2016-02-01

    A novel kind of crystal order in high-density nanoconfined bilayer ice is proposed from molecular dynamics and density-functional theory simulations. A first-order transition is observed between a low-temperature proton-ordered solid and a high-temperature proton-disordered solid. The latter is shown to possess crystalline order for the oxygen positions, arranged on a close-packed triangular lattice with A A stacking. Uniquely among the ice phases, the triangular bilayer is characterized by two levels of disorder (for the bonding network and for the protons) which results in a configurational entropy twice that of bulk ice.

  17. Bilayer graphene Hall bar with a pn-junction

    OpenAIRE

    Milovanovic, S. P.; Masir, M. Ramezani; Peeters, F. M.

    2013-01-01

    We investigate the magnetic field dependence of the Hall and the bend resistances for a ballistic Hall bar structure containing a pn-junction sculptured from a bilayer of graphene. The electric response is obtained using the billiard model and we investigate the cases of bilayer graphene with and without a band gap. Two different conduction regimes are possible: $i$) both sides of the junction have the same carrier type, and $ii$) one side of the junction is n-type while the other one is p-ty...

  18. Structure and metastability of N-lignocerylgalactosylsphingosine (cerebroside) bilayers.

    Science.gov (United States)

    Reed, R A; Shipley, G G

    1987-01-26

    Differential scanning calorimetry (DSC) and X-ray diffraction have been used to study hydrated N-lignocerylgalactosylsphingosine (NLGS) bilayers. DSC of fully hydrated NLGS shows an endothermic transition at 69-70 degrees C, immediately followed by an exothermic transition at 72-73 degrees C; further heating shows a high-temperature (Tc = 82 degrees C), high-enthalpy (delta H = 15.3 kcal/mol NLGS) transition. Heating to 75 degrees C, cooling to 20 degrees C and subsequent reheating shows no transitions at 69-73 degrees C; only the high-temperature (82 degrees C), high-enthalpy (15.3 kcal/mol) transition. Two exothermic transitions are observed on cooling; for the upper transition its temperature (about 65 degrees C) and enthalpy (about 6 kcal/mol NLGS) are essentially independent of cooling rate, whereas the lower transition exhibits marked changes in both temperature (30----60 degrees C) and enthalpy (2.2----9.5 kcal/mol NLGS) as the cooling rate decreases from 40 to 0.625 Cdeg/min. On reheating, the enthalpy of the 69-70 degrees C transition is dependent on the previous cooling rate. The DSC data provide clear evidence of conversions between metastable and stable forms. X-ray diffraction data recorded at 26, 75 and 93 degrees C show clearly that NLGS bilayer phases are present at all temperatures. The X-ray diffraction pattern at 75 degrees C shows a bilayer periodicity d = 65.4 A, and a number of sharp reflections in the wide-angle region indicative of a crystalline chain packing mode. This stable bilayer form converts to a liquid-crystal bilayer phase; at 93 degrees C, the bilayer periodicity d = 59.1 A, and a diffuse reflection at 1/4.6 A-1 is observed. The diffraction pattern at 22 degrees C represents a combination of the stable and metastable low-temperature bilayer forms. NLGS exhibits a complex pattern of thermotropic changes related to conversions between metastable (gel), stable (crystalline) and liquid-crystalline bilayer phases. The structure and

  19. 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

  20. Gramicidin-based fluorescence assay; for determining small molecules potential for modifying lipid bilayer properties

    NARCIS (Netherlands)

    Ingólfsson, Helgi I; Sanford, R Lea; Kapoor, Ruchi; Andersen, Olaf S

    2010-01-01

    Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions.

  1. Screening for small molecules' bilayer-modifying potential using a gramicidin-based fluorescence assay

    NARCIS (Netherlands)

    Ingólfsson, Helgi I; Andersen, Olaf S

    2010-01-01

    Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions.

  2. Phase Transition of MoS2 Bilayer Structures

    DEFF Research Database (Denmark)

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

    2016-01-01

    In the present study, using density functional calculations we have investigated a possible mechanism for the structural phase transition of the semiconducting bilayer 2H-MoS2 via lithiation. The results indicate that the addition of lithium to the bilayer 2H-MoS2 transforms the bilayer to a hete...

  3. Physical soil stability under different management of extensive pasture in haplumbrept soils /Estabilidade física de solo sob diferentes manejos de pastagem extensiva em cambissolo

    Directory of Open Access Journals (Sweden)

    Ricardo Ralisch

    2010-09-01

    Full Text Available In the dairy cattle production of the small region of São João Del Rei (MG - Brazil it is common to manage extensive native pastures with annual fires on low natural fertility Haplumbrept soils. The objective of this work was to evaluate the physical stability by measuring the degree of clay flocculation of a Haplumbrept soil under different management systems of extensive pastures. The evaluations were done using three types of managements: native pasture without fire; native pasture with fire, and recovered pasture. For each treatment it was selected one “sub area” of 1 hectare, located at the middle hillside with declivity between 10 and 12%, where, in the month of June 2007, 50 randomized deformed soil samples were collected/studied, in the layer of 0-10 cm to evaluate the degree of clay flocculation, pH, DpHH2O, pHKCl (1N, zero point charge (PCZ. The systems of soil management did influence the degree of clay flocculation, with the lowest values found in pasture with annual burning and recovered pasture. The recovery of pasture in this fragile soil requires care with physical and chemical soil management.Na pecuária leiteira da Microrregião de São João Del Rei (MG é comum o manejo de pastagem nativa extensiva com utilização de queimadas anuais em Cambissolo, considerados de baixa fertilidade natural. O objetivo deste trabalho foi avaliar a estabilidade física a partir da determinação do grau de floculação da argila de Cambissolo sob diferentes manejos de pastagem extensiva. As avaliações foram realizadas em três tipos de manejos: pastagem nativa manejada sem queimada; passagem nativa manejada com queimada e pastagem recuperada. Em cada manejo selecionou-se uma “sub área” de 1 hectare, situada em meia encosta com declive entre 10 – 12%. Em junho / 2007, foram coletadas 50 amostras deformadas de solo de forma inteiramente casualizada, na camada de 0-10 cm, para determinação do grau de floculação da argila, pHH2

  4. Bipolar resistive switching and its temperature dependence in the composite structure of BiFeO3 bilayer

    Science.gov (United States)

    Ma, W. J.; Xiong, W. M.; Zhang, X. Y.; Wang, Ying; Zhang, H. Y.; Wang, C. Q.; Wang, Biao; Zheng, Yue

    2016-04-01

    In order to demonstrate the control of BiFeO3 thin film on the resistive switching effect and achieve the high-performance resistive switching device, the single layers and bilayer have been fabricated by chemical solution deposition method, respectively. In comparison with the single films, the composite film exhibits great performance of the resistive switching in endurance and repeatability, high stability and resistance ratio of high resistance state to low resistance state. Resistive switching effect in the BiFeO3 composite structure demonstrates an effective way to improve the endurance and repeatability of the resistive switching characteristics by designing the relative devices.

  5. Defining the Free-Energy Landscape of Curvature-Inducing Proteins on Membrane Bilayers

    CERN Document Server

    Tourdot, Richard W; Radhakrishnan, Ravi

    2015-01-01

    Curvature-sensing and curvature-remodeling proteins are known to reshape cell membranes, and this remodeling event is essential for key biophysical processes such as tubulation, exocytosis, and endocytosis. Curvature-inducing proteins can act as curvature sensors as well as induce curvature in cell membranes to stabilize emergent high curvature, non-spherical, structures such as tubules, discs, and caveolae. A definitive understanding of the interplay between protein recruitment and migration, the evolution of membrane curvature, and membrane morphological transitions is emerging but remains incomplete. Here, within a continuum framework and using the machinery of Monte Carlo simulations, we introduce and compare three free-energy methods to delineate the free-energy landscape of curvature-inducing proteins on bilayer membranes. We demonstrate the utility of the Widom test-particle/field insertion methodology in computing the excess chemical potentials associated with curvature-inducing proteins on the membra...

  6. Polymeric bilayer modified microelectrodes for in-vivo determi nation of neurotransmitter dopamine

    Institute of Scientific and Technical Information of China (English)

    YANG, Li-Jua; PENG, Tu-Zhi; YANG, F. Catherine

    2000-01-01

    A composite polymer carbon fiber electrode modified with Nafion and cellulose acetate is described. The modified elec trode discriminates agninst both anionic reactants and big molecular organic compounds. The bilayer configuration is prepared in two steps, First, the carbon fiber electrode is coated with Nafion, then followed by air evaporation of the solvent, the electrode is dipped in a cellulose acetate solution and hydrolyzed for a selected time. The permeability of the film is explored by use of rotating disk electrode measure ments. Parameters affecting the fihm electrochemistry are in vestigated. The resulting electrodes show high selectivity and stability in body fluids. For in-vivo voltammetry, the com posite polymer modified electrode has been used for detection of the oxidative current of neurotransmitter dopamine in rat brain, while it inhabits the oxidation of anionic neurotransmit ter metabolites and some electroactive compounds.

  7. Thermodynamic Free Energy Methods to Investigate Shape Transitions In Bilayer Membranes

    CERN Document Server

    Ramakrishnan, N; Radhakrishnan, Ravi

    2015-01-01

    The conformational free energy landscape of a system is a fundamental thermodynamic quantity of importance particularly in the study of soft matter and biological systems, in which the entropic contributions play a dominant role. While computational methods to delineate the free energy landscape are routinely used to analyze the relative stability of conformational states, to determine phase boundaries, and to compute ligand-receptor binding energies its use in problems involving the cell membrane is limited. Here, we present an overview of four different free energy methods to study morphological transitions in bilayer membranes, induced either by the action of curvature remodeling proteins or due to the application of external forces. Using a triangulated surface as a model for the cell membrane and using the framework of dynamical triangulation Monte Carlo, we have focused on the methods of Widom insertion, thermodynamic integration, Bennett acceptance scheme, and umbrella sampling and weighted histogram a...

  8. Stability of a liquid thread and stability and nonlinear evolution of multi-layer fluid flow

    OpenAIRE

    Thompson, Julian

    2016-01-01

    This thesis is concerned with stability and existence of waves in interfacial and free surface problems. Considered is the curtain coating problem, with specific emphasis on trilayer and bilayer flows, and the breakup of a viscous thread with a solid core. Experiments on curtain coating and sheet breakup are mostly conducted by industry and as such are hidden in patents or kept secret by companies trying to gain an edge in a competitive market. Experiments on curtain breakup concentrating ...

  9. Ground state of bilayer hα-silica: mechanical and electronic properties.

    Science.gov (United States)

    Han, Yang; Hu, Ming

    2015-12-18

    The family of two-dimensional (2D) crystals was recently joined by silica, one of the most abundant resources on earth. So far two different polymorphs of this material, namely a tetrahedra-shaped monolayer and a fully saturated bilayer structure, have been synthesized on various metal substrates and their fascinating properties enable 2D silica to hold promise in nanoelectronic device applications. In this paper a new ground state of bilayer-AAr-stacking hα-silica-has been discovered by first principles calculations. The new structure is featured with a formation of Si-Si bonds between all sp(3) hybridized SiO3 triangular pyramids, lying respectively in different silica layers, with an intrinsic rotational angle of about 12.5° along the out-of-plane Si-Si bond. Due to the doubled number of Si-Si bonds in the new structure, the system energy is lowered by nearly three times more than that reported recently in literature (0.8 eV) (Özçelik et al 2014 Phys. Rev. Lett. 112 246803), when compared with the single layer hα-silica. A mechanical property investigation shows that the AAr-stacking bilayer hα-silica possesses high in-plane stiffness and a negative Poisson's ratio, which stems from the intrinsic rotational angle of the SiO3 triangular pyramids. Strikingly, the negative Poisson's ratio evolves into positive at a critical tensile strain ϵ ≈ 1.2%. Such negative-to-positive evolvement is associated with the adaptation of the rotational angle to the applied strain and the structure transition into the nearby valley of the energy landscape. The detailed transition process has been thoroughly analyzed. The electronic properties of the new ground state are also calculated, along with their response to the external strain. Our new ground state structure introduces a new member to the family of 2D bilayer silica materials and is expected to facilitate experimental studies identifying the related structures and exploring further physical and chemical properties

  10. Physical chemistry evaluation of stability, spreadability, in vitro antioxidant, and photo-protective capacities of topical formulations containing Calendula officinalis L. leaf extract

    OpenAIRE

    Viviane Cecília Kessler Nunes Deuschle; Regis Augusto Norbert Deuschle; Mariana Rocha Bortoluzzi; Margareth Linde Athayde

    2015-01-01

    Calendula is used widely in cosmetic formulations that present phenolic compounds in their chemical constitution. The objective of our research was to develop and evaluate the stability of topical formulations containing 5% hydro-ethanolic extract of calendula leaves, including spreadability, and in vitro photo-protective, and antioxidant capacity. To evaluate the stability, we used organoleptic characteristics, pH, and viscosity parameters. Antioxidant capacity was measured by the DPPH (2,2-...

  11. Formulation and Evaluation of Mucoadhesive Buccal Bilayered Tablets of Salbutamol

    Directory of Open Access Journals (Sweden)

    Dr. N.G Raghavendra Rao

    2012-12-01

    Full Text Available Salbutamol is a short-acting 2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. The salbutamol buccal mucoadhesive tablets were fabricated with objective of avoiding first pass metabolism and prolonging duration of action. Salbutamol mucoadhesive bilayered tablets were prepared by direct compression method using the bioadhesive polymers such as xanthan gum, sodium alginate and carbopol 937P along with ethyl cellulose as an impermeable backing layer. The prepared tablets evaluated for post-compressional parameter like weight variation, thickness, hardness, and friability, surface pH, mucoadhesive strength, in vitro drug release and Ex-vivo permeation study. The compatibility of drug with other ingredients was checked by FTIR studies. FTIR results revealed that there was no interaction between dug and other excipients. All the post-compressional parameter are evaluated were prescribed limits and results were within acceptable limits. The in vitro release study was carried out by using pH 6.8 buffer. The invitro drug release was in the range of 69.74% to 98.52% in eight hrs from the formulations of F1 to F6. The formulation F4 and F5 % shows the drug release 74 % and 69.74 % respectively. The results were revealed that the release of salbutamol buccal tablets was slower in formulation F4 and F5, may be due to the high concentration of xanthan gum, in comparison to other formulations. Xanthan gun, carbopol and Na-alginate were selected as the bioadhesive polymers because of their excellent bioadhesive properties. Among the all formulations studied F4 and F5 were found to be the best formulations. All the formulations showed the first order release. The stability study conducted as per the ICH guidelines and the formulations were found to be stable. The present study concludes that mucoadhesive buccal tablets of salbutamol can be a good way to bypass the extensive

  12. Enhanced resistive switching and multilevel behavior in bilayered HfAlO/HfAlOx structures for non-volatile memory applications

    International Nuclear Information System (INIS)

    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 HfAlOx layer deposited in oxygen deficient environment is evidenced from the photoluminescence spectra. Furthermore, HfAlO(oxygen rich)/HfAlOx(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/HfAlOx 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 ≈102 and ≈5 × 105, 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

  13. On the dynamics of molecular self-assembly and the structural analysis of bilayer membranes using coarse-grained molecular dynamics simulations.

    Science.gov (United States)

    Schindler, Tanja; Kröner, Dietmar; Steinhauser, Martin O

    2016-09-01

    We present a molecular dynamics simulation study of the self-assembly of coarse-grained lipid molecules from unbiased random initial configurations. Our lipid model is based on a well-tried CG polymer model with an additional potential that mimics the hydrophobic properties of lipid tails. We find that several stages of self-organization of lipid clusters are involved in the dynamics of bilayer formation and that the resulting equilibrium structures sensitively depend on the strength of hydrophobic interactions hc of the lipid tails and on temperature T. The obtained stable lipid membranes are quantitatively analyzed with respect to their local structure and their degree of order. At equilibrium, we obtain self-stabilizing bilayer membrane structures that exhibit a bending stiffness κB and compression modulus KC comparable to experimental measurements under physiological conditions. We present a phase diagram of our lipid model which covers a sol-gel transition, a liquid (or gel-like) phase including stable bilayer structures and vesicle formation, as well as a quasi-crystalline phase. We also determine the exact conditions for temperature T and degree of hydrophobicity hc for stable bilayer formation including closed vesicles. PMID:27216316

  14. 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.

  15. Large-Scale Synthesis of a Uniform Film of Bilayer MoS2 on Graphene for 2D Heterostructure Phototransistors.

    Science.gov (United States)

    Chen, Chuanmeng; Feng, Zhihong; Feng, Yiyu; Yue, Yuchen; Qin, Chengqun; Zhang, Daihua; Feng, Wei

    2016-07-27

    The large-scale synthesis of atomically thin, layered MoS2/graphene heterostructures is of great interest in optoelectronic devices because of their unique properties. Herein, we present a scalable synthesis method to prepare centimeter-scale, continuous, and uniform films of bilayer MoS2 using low-pressure chemical vapor deposition. This growth process was utilized to assemble a heterostructure by growing large-scale uniform films of bilayer MoS2 on graphene (G-MoS2/graphene). Atomic force microscopy, Raman spectra, and transmission electron microscopy characterization demonstrated that the large-scale bilayer MoS2 film on graphene exhibited good thickness uniformity and a polycrystalline nature. A centimeter-scale phototransistor prepared using the G-MoS2/graphene heterostructure exhibited a high responsivity of 32 mA/W with good cycling stability; this value is 1 order of magnitude higher than that of transferred MoS2 on graphene (2.5 mA/W). This feature results from efficient charge transfer at the interface enabled by intimate contact between the grown bilayer MoS2 (G-MoS2) and graphene. The ability to integrate multilayer materials into atomically thin heterostructures paves the way for fabricating multifunctional devices by controlling their layer structure. PMID:27381011

  16. On the optimal design of molecular sensing interfaces with lipid bilayer assemblies - A knowledge based approach

    Science.gov (United States)

    Siontorou, Christina G.

    2012-12-01

    Biosensors are analytic devices that incorporate a biochemical recognition system (biological, biologicalderived or biomimic: enzyme, antibody, DNA, receptor, etc.) in close contact with a physicochemical transducer (electrochemical, optical, piezoelectric, conductimetric, etc.) that converts the biochemical information, produced by the specific biological recognition reaction (analyte-biomolecule binding), into a chemical or physical output signal, related to the concentration of the analyte in the measuring sample. The biosensing concept is based on natural chemoreception mechanisms, which are feasible over/within/by means of a biological membrane, i.e., a structured lipid bilayer, incorporating or attached to proteinaceous moieties that regulate molecular recognition events which trigger ion flux changes (facilitated or passive) through the bilayer. The creation of functional structures that are similar to natural signal transduction systems, correlating and interrelating compatibly and successfully the physicochemical transducer with the lipid film that is self-assembled on its surface while embedding the reconstituted biological recognition system, and at the same time manage to satisfy the basic conditions for measuring device development (simplicity, easy handling, ease of fabrication) is far from trivial. The aim of the present work is to present a methodological framework for designing such molecular sensing interfaces, functioning within a knowledge-based system built on an ontological platform for supplying sub-systems options, compatibilities, and optimization parameters.

  17. Continuous and reversible tuning of the disorder-driven superconductor-insulator transition in bilayer graphene

    Science.gov (United States)

    Lee, Gil-Ho; Jeong, Dongchan; Park, Kee-Su; Meir, Yigal; Cha, Min-Chul; Lee, Hu-Jong

    2015-08-01

    The influence of static disorder on a quantum phase transition (QPT) is a fundamental issue in condensed matter physics. As a prototypical example of a disorder-tuned QPT, the superconductor-insulator transition (SIT) has been investigated intensively over the past three decades, but as yet without a general consensus on its nature. A key element is good control of disorder. Here, we present an experimental study of the SIT based on precise in-situ tuning of disorder in dual-gated bilayer graphene proximity-coupled to two superconducting electrodes through electrical and reversible control of the band gap and the charge carrier density. In the presence of a static disorder potential, Andreev-paired carriers formed close to the Fermi level in bilayer graphene constitute a randomly distributed network of proximity-induced superconducting puddles. The landscape of the network was easily tuned by electrical gating to induce percolative clusters at the onset of superconductivity. This is evidenced by scaling behavior consistent with the classical percolation in transport measurements. At lower temperatures, the solely electrical tuning of the disorder-induced landscape enables us to observe, for the first time, a crossover from classical to quantum percolation in a single device, which elucidates how thermal dephasing engages in separating the two regimes.

  18. Continuous and reversible tuning of the disorder-driven superconductor-insulator transition in bilayer graphene.

    Science.gov (United States)

    Lee, Gil-Ho; Jeong, Dongchan; Park, Kee-Su; Meir, Yigal; Cha, Min-Chul; Lee, Hu-Jong

    2015-01-01

    The influence of static disorder on a quantum phase transition (QPT) is a fundamental issue in condensed matter physics. As a prototypical example of a disorder-tuned QPT, the superconductor-insulator transition (SIT) has been investigated intensively over the past three decades, but as yet without a general consensus on its nature. A key element is good control of disorder. Here, we present an experimental study of the SIT based on precise in-situ tuning of disorder in dual-gated bilayer graphene proximity-coupled to two superconducting electrodes through electrical and reversible control of the band gap and the charge carrier density. In the presence of a static disorder potential, Andreev-paired carriers formed close to the Fermi level in bilayer graphene constitute a randomly distributed network of proximity-induced superconducting puddles. The landscape of the network was easily tuned by electrical gating to induce percolative clusters at the onset of superconductivity. This is evidenced by scaling behavior consistent with the classical percolation in transport measurements. At lower temperatures, the solely electrical tuning of the disorder-induced landscape enables us to observe, for the first time, a crossover from classical to quantum percolation in a single device, which elucidates how thermal dephasing engages in separating the two regimes. PMID:26310774

  19. Continuous and reversible tuning of the disorder-driven superconductor–insulator transition in bilayer graphene

    Science.gov (United States)

    Lee, Gil-Ho; Jeong, Dongchan; Park, Kee-Su; Meir, Yigal; Cha, Min-Chul; Lee, Hu-Jong

    2015-01-01

    The influence of static disorder on a quantum phase transition (QPT) is a fundamental issue in condensed matter physics. As a prototypical example of a disorder-tuned QPT, the superconductor–insulator transition (SIT) has been investigated intensively over the past three decades, but as yet without a general consensus on its nature. A key element is good control of disorder. Here, we present an experimental study of the SIT based on precise in-situ tuning of disorder in dual-gated bilayer graphene proximity-coupled to two superconducting electrodes through electrical and reversible control of the band gap and the charge carrier density. In the presence of a static disorder potential, Andreev-paired carriers formed close to the Fermi level in bilayer graphene constitute a randomly distributed network of proximity-induced superconducting puddles. The landscape of the network was easily tuned by electrical gating to induce percolative clusters at the onset of superconductivity. This is evidenced by scaling behavior consistent with the classical percolation in transport measurements. At lower temperatures, the solely electrical tuning of the disorder-induced landscape enables us to observe, for the first time, a crossover from classical to quantum percolation in a single device, which elucidates how thermal dephasing engages in separating the two regimes. PMID:26310774

  20. 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)