Self-diffusion and viscosity coefficient of fluids in nanochannels

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Fluid viscosity and molecular diffusion in nanochannels were studied by molecular dynamics simulation. Transport processes in a plane channel, a channel of rectangular cross-section, and in porous media were investigated. The channel height was varied from 2 to 50 nm. The interaction between molecules was simulated using the hard sphere (HS) and the Lennard-Jones (LJ) intermolecular potentials. The porous matrix was modeled by cubic packing of spheres of the same radius, and the packing density and the grain size were varied. The dependence of the transport coefficients on the fluid density and channel characteristics (channel height, channel aspect ratio, porosity of the porous medium, accommodation coefficients, etc.) was investigated.Russian Foundation for Basic Research (Grant No. 10-01-00074) and the Federal Special Program “Scientific and scientific-pedagogical personnel of innovative Russia in 2009-2013” (projects No. P230 and No. 14.740.11.0579, No. 14.740.11.0103)

Obscured clusters. II. GLIMPSE-C02 - A new metal rich globular cluster in the Milky Way

The estimated total number of Milky Way globulars is 160+-20. The question of whether there are any more undiscovered globular clusters in the Milky Way is particularly relevant with advances in near and mid-IR instrumentation. This investigation is a part of a long-term project to search the inner Milky Way for hidden star clusters and to study them in detail. GLIMPSE-C02 (G02) is one of these objects, situated near the Galactic plane (l=14.129deg, b=-0.644deg). Our analysis is based on SOFI/NTT JHKs imaging and low resolution (R~1400) spectroscopy of three bright cluster red giants in the K atmospheric window. We derived the metal abundance by analysis of these spectra and from the slope of the RGB. The cluster is deeply embedded in dust and undergoes a mean reddening of Av~24.8+-3 mag. The distance to the object is D=4.6+-0.7kpc. The metal abundance of G02 is [Fe/H](H96)=-0.33+-0.14 and [Fe/H](CG)=-0.16+-0.12 using different scales. The best fit to the radial surface brightness profile with a single-mass King's model yields a core radius rc=0.70 arcmin (0.9pc), tidal radius rt=15 arcmin (20pc), and central oncentration c=1.33. We demonstrate that G02 is new Milky Way globular cluster, among the most metal rich globular clusters in the Galaxy. The object is physically located at the inner edge of the thin disk and the transition region with the bulge, and also falls in the zone of the "missing" globulars toward the central region of the Milky Way.Comment: 5 pages, 6 figures, accepted for publication in Astronomy and Astrophysic

Molecular dynamics simulation of plane poiseuille flow in nanochannels

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.This paper presents new techniques and results of simulating microflows in plane channels by the molecular dynamics (MD) method. Mass forces and thermostat are not used in these techniques. The flows are simulated by both hard-sphere molecules and molecules with the Lennard-Jones intermolecular potential. Flow at a given fluid flow rate is implemented. In this case, the initial shock profile is transformed to a parabolic type profile. However, unlike in ordinary Poiseuille flows, a slip effect is recorded on the channel walls. It is shown that, in a nanochannel, a linear pressure gradient occurs. Fluid structuring is studied. The effects of fluid density, accommodation coefficients, and channel dimensions on flow properties are investigated.This work was supported in part by the Russian Foundation for Basic Researches (grant No. 07-08-00164) and by the grant of the President of the Russian Federation for Support of Leading Scientific Schools (project no. NSh-454.2008.1)

Spontaneous breaking of superconformal invariance in (2+1)D supersymmetric Chern-Simons-matter theories in the large N limit

In this work it is studied the spontaneous breaking of superconformal and gauge invariances in the Abelian N=1,2 three-dimensional supersymmetric Chern-Simons-matter theories in a large N limit. It is computed the K\"ahlerian effective superpotential at subleading order and shown that the Coleman-Weinberg mechanism is the responsible for the dynamical generation of a mass scale in the N=1 model. This effect appears due to two-loop diagrams that are logarithmic divergent. In particular, the Coleman-Weinberg mechanism fails when we lift the N=1 to N=2 Supersymmetric Chern-Simons-Matter model, like what happens in a perturbative expansion in the coupling constants.Comment: 10 pages, 2 figures, PLB versio

Variance fluctuations in nonstationary time series: a comparative study of music genres

An important problem in physics concerns the analysis of audio time series generated by transduced acoustic phenomena. Here, we develop a new method to quantify the scaling properties of the local variance of nonstationary time series. We apply this technique to analyze audio signals obtained from selected genres of music. We find quantitative differences in the correlation properties of high art music, popular music, and dance music. We discuss the relevance of these objective findings in relation to the subjective experience of music.Comment: 13 pages, 4 fig

Electron wave functions on T2T^2 in a static magnetic field of arbitrary direction

A basis set expansion is performed to find the eigenvalues and wave functions for an electron on a toroidal surface $T^2$ subject to a constant magnetic field in an arbitrary direction. The evolution of several low-lying states as a function of field strength and field orientation is reported, and a procedure to extend the results to include two-body Coulomb matrix elements on $T^2$ is presented.Comment: 18 pages, 6 figure

Spontaneous time reversal symmetry breaking in the pseudogap state of high-Tc superconductors

When matter undergoes a phase transition from one state to another, usually a change in symmetry is observed, as some of the symmetries exhibited are said to be spontaneously broken. The superconducting phase transition in the underdoped high-Tc superconductors is rather unusual, in that it is not a mean-field transition as other superconducting transitions are. Instead, it is observed that a pseudo-gap in the electronic excitation spectrum appears at temperatures T* higher than Tc, while phase coherence, and superconductivity, are established at Tc (Refs. 1, 2). One would then wish to understand if T* is just a crossover, controlled by fluctuations in order which will set in at the lower Tc (Refs. 3, 4), or whether some symmetry is spontaneously broken at T* (Refs. 5-10). Here, using angle-resolved photoemission with circularly polarized light, we find that, in the pseudogap state, left-circularly polarized photons give a different photocurrent than right-circularly polarized photons, and therefore the state below T* is rather unusual, in that it breaks time reversal symmetry11. This observation of a phase transition at T* provides the answer to a major mystery of the phase diagram of the cuprates. The appearance of the anomalies below T* must be related to the order parameter that sets in at this characteristic temperature .Comment: 11 pages, 4 figure

On rigidly rotating perfect fluid cylinders

The gravitational field of a rigidly rotating perfect fluid cylinder with gamma- law equation of state is found analytically. The solution has two parameters and is physically realistic for gamma in the interval (1.41,2]. Closed timelike curves always appear at large distances.Comment: 10 pages, Revtex (galley

Non-Abelian statistics and topological quantum information processing in 1D wire networks

Topological quantum computation provides an elegant way around decoherence, as one encodes quantum information in a non-local fashion that the environment finds difficult to corrupt. Here we establish that one of the key operations---braiding of non-Abelian anyons---can be implemented in one-dimensional semiconductor wire networks. Previous work [Lutchyn et al., arXiv:1002.4033 and Oreg et al., arXiv:1003.1145] provided a recipe for driving semiconducting wires into a topological phase supporting long-sought particles known as Majorana fermions that can store topologically protected quantum information. Majorana fermions in this setting can be transported, created, and fused by applying locally tunable gates to the wire. More importantly, we show that networks of such wires allow braiding of Majorana fermions and that they exhibit non-Abelian statistics like vortices in a p+ip superconductor. We propose experimental setups that enable the Majorana fusion rules to be probed, along with networks that allow for efficient exchange of arbitrary numbers of Majorana fermions. This work paves a new path forward in topological quantum computation that benefits from physical transparency and experimental realism.Comment: 6 pages + 17 pages of Supp. Mat.; 10 figures. Supp. Mat. has doubled in size to establish results more rigorously; many other improvements as wel

High-throughput spheroid screens using volume, resazurin reduction and acid phosphatase activity

Mainstream adoption of physiologically-relevant three-dimensional models has been slow in the last 50 years due to long, manual protocols with poor reproducibility, high price and closed commercial platforms. This chapter describes high-throughput, low-cost, open methods for spheroid viability assessment which use readily-available reagents and open-source software to analyse spheroid volume, metabolism and enzymatic activity. We provide two ImageJ macros for automated spheroid size determination - for both single images and for images in stacks. We also share an Excel template spreadsheet allowing users to rapidly process spheroid size data, analyse plate uniformity (such as edge effects and systematic seeding errors), detect outliers and calculate dose-response. The methods would be useful to researchers in preclinical and translational research planning to move away from simplistic monolayer studies and explore 3D spheroid screens for drug safety and efficacy without substantial investment in money or time