Pressure dependence of the superconducting state parameters of metallic glass superconductor Mg70Zn30

Explicit expressions have been derived for the volume dependence of electron-phonon coupling strength (λ) and the Coulomb pseudopotential (μ^*) considering the variation of Fermi momentum (κ _F) and Debye temperature (θ _D) with volume. Ashcroft’s model pseudopotential and RPA form of dielectric screening have been used for obtaining pressure dependence of transition temperature (T _C) and the logarithmic volume derivative (Φ) of the effective interaction strength (N ₀ V) for metallic glass superconductor Mg₇₀Zn₃₀. It has been observed that T _C of the metallic glass Mg₇₀Zn₃₀ decreases rapidly with increase of pressure and the superconducting phase disappears at about 30% decrease of volume, for which the μ^* curve shows a minimum and an elbow is formed in the Φ graph.     

Long-pulse and CW tests of a 110-GHz gyrotron with an internal,quasi-optical converter

A high-power gyrotron, employing an internal converter that produces a Gaussian-like output mode, has been designed and tested. The tube employed a TE_22.6.1-mode interaction cavity that was designed for operation at a frequency of 110 GHz. An internal converter, consisting of an advanced launcher design and four mirrors, produced a Gaussian mode that had a relatively uniform profile at the tube output window to minimize the peak power density. Tests on the tube resulted in output power levels of 680, 530, and 350 kW for pulse durations of 0.5, 2.0, and 10.0 s, respectively. Measurements of the temperature of the output window were made during the long-pulse tests. Output power levels of 1 MW were achieved under short-pulse (1 ms) operation and the tube was operated at CW power levels in excess of 100 kW     

A front-tracking method with Catmull–Clark subdivision surfaces for studying liquid capsules enclosed by thin shells in shear flow

This paper presents a front-tracking method for studying the large deformation of a liquid capsule enclosed by a thin shell in a shear flow. The interaction between the fluid and the shell body is accomplished through an implicit immersed boundary method. An improved thin-shell model for computing the forces acting on the shell middle surface during the deformation is described in surface curvilinear coordinates and within the framework of the principle of virtual displacements. This thin-shell model takes full account of in-plane tensions and bending moments developing due to the shell thickness and a preferred three-dimensional membrane structure. The approximation of the shell middle surface is performed through the use of the Catmull–Clark subdivision surfaces. The resulting limit surface is C²-continuous everywhere except at a small number of extraordinary nodes where it retains C¹ continuity. The smoothness of the limit surface significantly improves the ability of our method in simulating capsules enclosed by hyperelastic thin shells with different shapes and physical properties. The present numerical technique has been validated by several examples including an inflation of a spherical shell and deformations of spherical, ellipsoidal and biconcave capsules in the shear flow. In addition, different types of motion such as tank-treading, swinging, tumbling and transition from tumbling to swinging have been studied over a range of shear rates, viscosity ratios and bending modulus.     

A second-order Cauchy problem in a scale of Banach spaces and application to Kirchhoff equations

In a scale of Banach spaces we study the Cauchy problem for the equation u^′′=A(Bu(t),u), where A is a bilinear operator and B is a completely continuous operator. Obtained results are applied to prove existence of solutions in the Gevrey class for Kirchhoff equations.     

Photoproduction of eta mesons off protons for 0.75 GeV<E(gamma)<3 GeV

Total and differential cross sections for the reaction p(gamma,eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into peta. At medium energies we find evidence for a new resonance N(2070)D15 with (M,Gamma)=(2068+/-22, 295+/-40) MeV. At gamma energies above 1.5 GeV, a strong peak in the forward direction develops, signaling the exchange of vector mesons in the t channel.     

Molecular dynamics study of the properties of capsaicin in an 1-octanol/water system

Molecular dynamics simulations were performed to study the behavior of capsaicin in an 1-octanol/water system at 298 K and 1 bar. Capsaicin is the pungent chemical found in chili pepper that stimulates our sensory system resulting in a burning, pain sensation. In the first step toward investigating the activity of capsaicin, we have used two molecular representations for capsaicin based on the OPLS force field: all-atom and united-atom models. The octanol/water mixture was selected as a model system to determine the hydrophobic and hydrophilic properties of capsaicin by analyzing equilibrium, structural, and dynamic properties from the simulations. Our simulations showed that capsaicin preferentially partitions to the octanol phase, with its hydrocarbon segment oriented with that in octanol, while the polar part remains exposed to the aqueous phase. The simulations with the all-atom and united-atom models yielded similar results.     

A Reversible DNA Logic Gate Platform Operated by One‐ and Two‐Photon Excitations

We demonstrate the use of two different wavelength ranges of excitation light as inputs to remotely trigger the responses of the self‐assembled DNA devices (D‐OR). As an important feature of this device, the dependence of the readout fluorescent signals on the two external inputs, UV excitation for 1 min and/or near infrared irradiation (NIR) at 800 nm fs laser pulses, can mimic function of signal communication in OR logic gates. Their operations could be reset easily to its initial state. Furthermore, these DNA devices exhibit efficient cellular uptake, low cytotoxicity, and high bio‐stability in different cell lines. They are considered as the first example of a photo‐responsive DNA logic gate system, as well as a biocompatible, multi‐wavelength excited system in response to UV and NIR. This is an important step to explore the concept of photo‐responsive DNA‐based systems as versatile tools in DNA computing, display devices, optical communication, and biology.     

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

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