Atomistic Simulations of Bicelle Mixtures

AbstractMixtures of long- and short-tail phosphatidylcholine lipids are known to self-assemble into a variety of aggregates combining flat bilayerlike and curved micellelike features, commonly called bicelles. Atomistic simulations of bilayer ribbons and perforated bilayers containing dimyristoylphosphatidylcholine (DMPC, di-C14 tails) and dihexanoylphosphatidylcholine (DHPC, di-C6 tails) have been carried out to investigate the partitioning of these components between flat and curved microenvironments and the stabilization of the bilayer edge by DHPC. To approach equilibrium partitioning of lipids on an achievable simulation timescale, configuration-bias Monte Carlo mutation moves were used to allow individual lipids to change tail length within a semigrand-canonical ensemble. Since acceptance probabilities for direct transitions between DMPC and DHPC were negligible, a third component with intermediate tail length (didecanoylphosphatidylcholine, di-C10 tails) was included at a low concentration to serve as an intermediate for transitions between DMPC and DHPC. Strong enrichment of DHPC is seen at ribbon and pore edges, with an excess linear density of ∼3 nm−1. The simulation model yields estimates for the onset of edge stability with increasing bilayer DHPC content between 5% and 15% DHPC at 300 K and between 7% and 17% DHPC at 323 K, higher than experimental estimates. Local structure and composition at points of close contact between pores suggest a possible mechanism for effective attractions between pores, providing a rationalization for the tendency of bicelle mixtures to aggregate into perforated vesicles and perforated sheets

Indonesian Muslim Women and the Gender Equality Movement

Throughout the history of Indonesia, the concepts of gender and power-relations between men and women have been linked to a shifting and fluctuating idea of what constitutes good women, good men, and good gender relationships within the context of Indonesia and Islam. To analyse these changing attitudes to women\u27s issues in Indonesia, we need to pay attention to several points: the character of the women\u27s organizations, whether fully independent, semi autonomous, or subsidiaries of existing male organizations; the important issues rising within the movements, as well as the strategies to deal with them; and lastly the influential factor of government intervention in the women\u27s movement. This paper tries to explore the Muslim women\u27s movement and its strategy to accommodate or resist from the domination of Islam in terms of the nation state, the constitution and the dominant cultural norms in Indonesia

Determination of the superconducting gap in near optimally doped Bi_2Sr_{2-x}La_xCuO_{6+\delta} (x ~ 0.4) from low-temperature specific heat

Low-temperature specific heat of the monolayer high-Tc superconductor Bi_2Sr_{2-x}La_xCuO_{6+\delta} has been measured close to the optimal doping point (x ~ 0.4) in different magnetic fields. The identification of both a T^2 term in zero field and a \sqrt{H} dependence of the specific heat in fields is shown to follow the theoretical prediction for d-wave pairing, which enables us to extract the slope of the superconducting gap in the vicinity of the nodes (v_{\Delta}, which is proportional to the superconducting gap \Delta_0 at the antinodes according to the standard d_{x^2-y^2} gap function). The v_{\Delta} or \Delta_0 (~ 12 meV) determined from this bulk measurement shows close agreement with that obtained from spectroscopy or tunneling measurements, which confirms the simple d-wave form of the superconducting gap.Comment: 5 pages, 4 figures, 1 tabl

Biocompatible Mesoporous Hollow Carbon Nanocapsules for High Performance Supercapacitors.

A facile and general method for the controllable synthesis of N-doped hollow mesoporous carbon nanocapsules (NHCNCs) with four different geometries has been developed. The spheres (NHCNC-1), low-concaves (NHCNC-2), semi-concaves (NHCNC-3) and wrinkles (NHCNC-4) shaped samples were prepared and systematically investigated to understand the structural effects of hollow particles on their supercapacitor performances. Compared with the other three different shaped samples (NHCNC-1, NHCNC-2, and NHCNC-4), the as-synthesized semi-concave structured NHCNC-3 demonstrated excellent performance with high gravimetric capacitance of 326 F g-1 (419 F cm-3) and ultra-stable cycling stability (96.6% after 5000 cycles). The outstanding performances achieved are attributed to the unique semi-concave structure, high specific surface area (1400 m2 g-1), hierarchical porosity, high packing density (1.41 g cm-3) and high nitrogen (N) content (up to 3.73%) of the new materials. These carbon nanocapsules with tailorable structures and properties enable them as outstanding carriers and platforms for various emerging applications, such as nanoscale chemical reactors, catalysis, batteries, solar energy harvest, gas storage and so on. In addition, these novel carbons have negligible cytotoxicity and high biocompatibility for human cells, promising a wide range of bio applications, such as biomaterials, drug delivery, biomedicine, biotherapy and bioelectronic devices

Neutrino oscillations in de Sitter space-time

We try to understand flavor oscillations and to develop the formulae for describing neutrino oscillations in de Sitter space-time. First, the covariant Dirac equation is investigated under the conformally flat coordinates of de Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and indicate the explicit form of the phase of wave function. Next, the concise formulae for calculating the neutrino oscillation probabilities in de Sitter space-time are given. Finally, The difference between our formulae and the standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure

Prediction research on cavitation performance for centrifugal pumps

The present situation about cavitation performance prediction of centrifugal pump is introduced. The primary methods of cavitation performance prediction for centrifugal pumps are summarized, including numerical simulation method and artificial neural network method. Based on the neutral network toolbox of MATLAB7.0, topological structures of artificial neural networks are determined and network models for predicting cavitation performance of centrifugal pumps are established by analyzing the relations between geometric parameters of centrifugal pumps and net positive suction head at designed flow rate, The BP and RBF neural networks are trained by 60 example data, which are obtained from engineering practice and normalized by using neural network toolbox function. The cavitation flow in centrifugal pumps is simulated by using the commercial CFD code FLUENT6.2 A moving reference frame technique is applied to take into account the impeller-volute interaction. The standard k-? turbulence model, mixture multiphase model and SIMPLEC algorithm are used. Velocity inlet and pressure-outlet are set as boundary conditions.The cavitation performance curves at design condition are predicted by calculating the head under different net positive suction head. The cavitation performances of 3 pumps with the different specific speeds are predicted by using numerical simulation method and neural network method respectively. The predicted values are compared with the tested values, the results show that the predictions by two methods are satisfied, the relative declination of BP and RBF for 3 pumps are 2.87?, 2.55?, 5? and 3.71?, 3.27?, 4.62? respectively. The absolute declinations of numerical simulation method are 0.17m, 0.08m and 0.16m. The advantage and disadvantage of those two methods are compared, The numerical simulation method will take a lot of time to modeling and calculating, but the law of cavitation flow in the centrifugal pumps can be obtained, which are helpful to disclosing the mechanism of cavitation characteristic; The artificial neural networks method needs a great deal of training examples, which are necessary and important to the prediction accuracy, but the math relation between input variables and output variables can be set up by using artificial neural network method, which is useful to optimize the structure of pumps.http://deepblue.lib.umich.edu/bitstream/2027.42/84212/1/CAV2009-final161.pd

Correlation between 3:2 QPO pairs and Jets in Black Hole X-ray Binaries

We argue, following our earlier works (the "CEBZMC model"), that the phenomenon of twin peak high frequency quasi-periodic oscillations (QPOs) observed in black hole X-ray binaries is caused by magnetic coupling (MC) between accretion disk and black hole (BH). Due to MC, two bright spots occur at two separate radial locations r_{in} and r_{out} at the disk surface, energized by a kind of the Blandford-Znajek mechanism (BZ). We assume, following the Kluzniak-Abramowicz QPO resonance model, that Keplerian frequencies at these two locations are in the 3:2 ratio. With this assumption, we estimate the BH spins in several sources, including GRO J1655-40, GRS 1915+105, XTE J1550-564, H1743-322 and Sgr A*. We give an interpretation of the "jet line" in the hardness-intensity plane discussing the parameter space consisting of the BH spin and the power-law index for the variation of the large-scale magnetic field in the disk. Furthermore, we propose a new scenario for the spectral state transitions in BH X-ray binaries based on fluctuation in densities of accreting plasma from a companion star.Comment: 17 pages, 6 figures, accepted by AP