Two-dimensional gases of generalized statistics in a uniform magnetic field

We study the low temperature properties of two-dimensional ideal gases of generalized statistics in a uniform magnetic field. The generalized statistics considered here are the parafermion statistics and the exclusion statistics. Similarity in the behaviours of the parafermion gas of finite order $p$ and the gas with exclusion coefficient $g=1/p$ at very low temperatures is noted. These two systems become exactly equivalent at $T=0$. Qumtum Hall effect with these particles as charge carriers is briefly discussed.Comment: Latex file, 14 pages, 5 figures available on reques

Models for the integer quantum Hall effect: the network model, the Dirac equation, and a tight-binding Hamiltonian

We consider models for the plateau transition in the integer quantum Hall effect. Starting from the network model, we construct a mapping to the Dirac Hamiltonian in two dimensions. In the general case, the Dirac Hamiltonian has randomness in the mass, the scalar potential, and the vector potential. Separately, we show that the network model can also be associated with a nearest neighbour, tight-binding Hamiltonian.Comment: Revtex, 15 pages, 7 figures; submitted to Phys. Rev.

Seismology of adolescent neutron stars: Accounting for thermal effects and crust elasticity

We study the oscillations of relativistic stars, incorporating key physics associated with internal composition, thermal gradients and crust elasticity. Our aim is to develop a formalism which is able to account for the state-of-the-art understanding of the complex physics associated with these systems. As a first step, we build models using a modern equation of state including composition gradients and density discontinuities associated with internal phase-transitions (like the crust-core transition and the point where muons first appear in the core). In order to understand the nature of the oscillation spectrum, we carry out cooling simulations to provide realistic snapshots of the temperature distribution in the interior as the star evolves through adolescence. The associated thermal pressure is incorporated in the perturbation analysis, and we discuss the presence of $g$-modes arising as a result of thermal effects. We also consider interface modes due to phase-transitions and the gradual formation of the star's crust and the emergence of a set of shear modes.Comment: 27 pages, 14 figure

Biodegradable Polylactic Acid (PLA) Microstructures for Scaffold Applications

In this research, we present a simple and cost effective soft lithographic process to fabricate PLA scaffolds for tissue engineering. In which, the negative photoresist JSR THB-120N was spun on a glass subtract followed by conventional UV lithographic processes to fabricate the master to cast the PDMS elastomeric mold. A thin poly(vinyl alcohol) (PVA) layer was used as a mode release such that the PLA scaffold can be easily peeled off. The PLA precursor solution was then cast onto the PDMS mold to form the PLA microstructures. After evaporating the solvent, the PLA microstructures can be easily peeled off from the PDMS mold. Experimental results show that the desired microvessels scaffold can be successfully transferred to the biodegradable polymer PLA.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Intermediate-mass Black Holes in Galactic Nuclei

We present the first homogeneous sample of intermediate-mass black hole candidates in active galactic nuclei. Starting with broad-line active nuclei from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling relation to select a sample of 19 galaxies in the mass range M_BH ~ 8 x 10^4 - 10^6 solar masses. In contrast to the local active galaxy population, the host galaxies are ~1 mag fainter than M* and thus are probably late-type systems. The active nuclei are also faint, with M_g ~ -15 to -18 mag, while the bolometric luminosities are close to the Eddington limit. The spectral properties of the sample are compared to the related class of objects known as narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as observational analogues of primordial black holes, contributors to the integrated signal for future gravitational wave experiments, and as a valuable tool in the calibration of the M-sigma relation.Comment: 4 pages, 4 figures. To appear in "The Interplay among Black Holes, Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado, Brazil), eds Th. Storchi Bergmann, L.C. Ho, H.R. Schmit

Bose Gases Near Unitarity

We study the properties of strongly interacting Bose gases at the density and temperature regime when the three-body recombination rate is substantially reduced. In this regime, one can have a Bose gas with all particles in scattering states (i.e. the "upper branch") with little loss even at unitarity over the duration of the experiment. We show that because of bosonic enhancement, pair formation is shifted to the atomic side of the original resonance (where scattering length $a_s<0$), opposite to the fermionic case. In a trap, a repulsive Bose gas remains mechanically stable when brought across resonance to the atomic side until it reaches a critical scattering length $a_{s}^{\ast}<0$. For $a_s<a_{s}^{\ast}$, the density consists of a core of upper branch bosons surrounded by an outer layer of equilibrium phase. The conditions of low three-body recombination requires that the particle number $N<\alpha (T/\omega)^{5/2}$ in a harmonic trap with frequency $\omega$, where $\alpha$ is a constant.Comment: 4 pages, 4 figure

Analysis and design of integration formulas for a random integrand

Analysis of integration formulas and procedure for designing optimal integration formul

Self-shadowing Effects of Slim Accretion Disks in Active Galactic Nuclei: Diverse Appearance of the Broad-line Region

Supermassive black holes in active galactic nuclei (AGNs) undergo a wide range of accretion rates, which lead to diversity of appearance. We consider the effects of anisotropic radiation from accretion disks on the broad-line region (BLR), from the Shakura-Sunyaev regime to slim disks with super-Eddington accretion rates. The geometrically thick funnel of the inner region of slim disks produces strong self-shadowing effects that lead to very strong anisotropy of the radiation field. We demonstrate that the degree of anisotropy of the radiation fields grows with increasing accretion rate. As a result of this anisotropy, BLR clouds receive different spectral energy distributions depending on their location relative to the disk, resulting in diverse observational appearance of the BLR. We show that the self-shadowing of the inner parts of the disk naturally produces two dynamically distinct regions of the BLR, depending on accretion rate. These two regions manifest themselves as kinematically distinct components of the broad H$\beta$ line profile with different line widths and fluxes, which jointly account for the Lorentzian profile generally observed in narrow-line Seyfert 1 galaxies. In the time domain, these two components are expected reverberate with different time lags with respect to the varying ionizing continuum, depending on the accretion rate and the viewing angle of the observer. The diverse appearance of the BLR due to the anisotropic ionizing energy source can be tested by reverberation mapping of H$\beta$ and other broad emission lines (e.g., \feii), providing a new tool to diagnose the structure and dynamics of the BLR. Other observational consequences of our model are also explored.Comment: emulatapj style, 15 pages, 6 figures, in pres

Micro heat exchanger by using MEMS impinging jets

A micro impinging-jet heat exchanger is presented here. Heat transfer is studied for single jet, slot arrays and jet arrays. In order to facilitate micro heat transfer measurements with these devices, a MEMS sensor chip, which has an 8 x 8 temperature-sensor array on one side, and an integrated heater on the other side has been designed and fabricated. This sensor chip allows 2-D surface temperature measurement with various jets impinging on it. It is found that micro impinging jets can be highly efficient when compared to existing macro impinging-jet microelectronics packages such as IBM 4381. For example, using a single nozzle jet (500-μm diameter driven by 5 psig pressure), the sensor chip (2 x 2 cm^2) temperature can be cooled down from 70 to 33°C. The cooling becomes more efficient when nozzle arrays (4x5 over 1 cm^2 area) are used under the same driving pressure. Interestingly, although higher driving pressure gives better cooling (lower surface temperature), the cooling efficiency, defined as h/0.5pv^2, is actually higher for lower driving pressure