Radiative interactions in laminar duct flows

Analyses and numerical procedures are presented for infrared radiative energy transfer in gases when other modes of energy transfer occur simultaneously. Two types of geometries are considered, a parallel plate duct and a circular duct. Fully developed laminar incompressible flows of absorbing-emitting species in black surfaced ducts are considered under the conditions of uniform wall heat flux. The participating species considered are OH, CO, CO2, and H2O. Nongray as well as gray formulations are developed for both geometries. Appropriate limiting solutions of the governing equations are obtained and conduction-radiation interaction parameters are evaluated. Tien and Lowder's wide band model correlation was used in nongray formulation. Numerical procedures are presented to solve the integro-differential equations for both geometries. The range of physical variables considered are 300 to 2000 K for temperature, 0.1 to 100.0 atm for pressure, and 0.1 to 100 cm spacings between plates/radius of the tube. An extensive parametric study based on nongray formulation is presented. Results obtained for different flow conditions indicate that the radiative interactions can be quite significant in fully developed incompressible flows

Antiferromagnetism and phase separation in the t-J model at low doping: a variational study

Using Gutzwiller-projected wave functions, I estimate the ground-state energy of the t-J model for several variational states relevant for high-temperature cuprate superconductors. The results indicate antiferromagnetism and phase separation at low doping both in the superconducting state and in the staggered-flux normal state proposed for the vortex cores. While phase separation in the underdoped superconducting state may be relevant for the stripe formation mechanism, the results for the normal state suggest that similar charge inhomogeneities may also appear in vortex cores up to relatively high doping values.Comment: 4 pages, 3 figures, reference adde

Axions as Quintessence in String Theory

We construct a model of quintessence in string theory based on the idea of axion monodromy as discussed by McAllister, Silverstein and Westphal arXiv:0808.0706. In the model, the quintessence field is an axion whose shift symmetry is broken by the presence of 5-branes which are placed in highly warped throats. This gives rise to a potential for the axion field which is slowly varying, even after incorporating the effects of moduli stabilization and supersymmetry breaking. We find that the resulting time dependence in the equation of state of Dark Energy is potentially detectable, depending on the initial conditions. The model has many very light extra particles which live in the highly warped throats, but these are hard to detect. A signal in the rotation of the CMB polarization can also possibly arise.Comment: 41 pages, 1 figure, v2: references adde

Particle-Hole Symmetry and the Effect of Disorder on the Mott-Hubbard Insulator

Recent experiments have emphasized that our understanding of the interplay of electron correlations and randomness in solids is still incomplete. We address this important issue and demonstrate that particle-hole (ph) symmetry plays a crucial role in determining the effects of disorder on the transport and thermodynamic properties of the half-filled Hubbard Hamiltonian. We show that the low-temperature conductivity decreases with increasing disorder when ph-symmetry is preserved, and shows the opposite behavior, i.e. conductivity increases with increasing disorder, when ph-symmetry is broken. The Mott insulating gap is insensitive to weak disorder when there is ph-symmetry, whereas in its absence the gap diminishes with increasing disorder.Comment: 4 pages, 4 figure

Mystery of Excess Low Energy States in a Disordered Superconductor in a Zeeman Field

Tunneling density of states measurements of disordered superconducting (SC) Al films in high Zeeman fields reveal a significant population of subgap states which cannot be explained by standard BCS theory. We provide a natural explanation of these excess states in terms of a novel disordered Larkin-Ovchinnikov (dLO) phase that occurs near the spin-paramagnetic transition at the Chandrasekhar-Clogston critical field. The dLO superconductor is characterized by a pairing amplitude that changes sign at domain walls. These domain walls carry magnetization and support Andreev bound states, which lead to distinct spectral signatures at low energy.Comment: 5 pages, 4 figures, plus supplementary section describing methods (2 pages

Non-Supersymmetric Attractors in String Theory

We find examples of non-supersymmetric attractors in Type II string theory compactified on a Calabi Yau three-fold. For a non-supersymmetric attractor the fixed values to which the moduli are drawn at the horizon must minimise an effective potential. For Type IIA at large volume, we consider a configuration carrying D0, D2, D4 and D6 brane charge. When the D6 brane charge is zero, we find for some range of the other charges, that a non-supersymmetric attractor solution exists. When the D6 brane charge is non-zero, we find for some range of charges, a supersymmetry breaking extremum of the effective potential. Closer examination reveals though that it is not a minimum of the effective potential and hence the corresponding black hole solution is not an attractor. Away from large volume, we consider the specific case of the quintic in CP^4. Working in the mirror IIB description we find non-supersymmetric attractors near the Gepner point.Comment: Added a few clarification

On the role of confinement on solidification in pure materials and binary alloys

We use a phase-field model to study the effect of confinement on dendritic growth, in a pure material solidifying in an undercooled melt, and in the directional solidification of a dilute binary alloy. Specifically, we observe the effect of varying the vertical domain extent ($\delta$) on tip selection, by quantifying the dendrite tip velocity and curvature as a function of $\delta$, and other process parameters. As $\delta$ decreases, we find that the operating state of the dendrite tips becomes significantly affected by the presence of finite boundaries. For particular boundary conditions, we observe a switching of the growth state from 3-D to 2-D at very small $\delta$, in both the pure material and alloy. We demonstrate that results from the alloy model compare favorably with those from an experimental study investigating this effect.Comment: 13 pages, 9 figures, 3 table

Three rare and accidental findings of hemoglobinopathies encountered in high-performance liquid chromatography: case series

Hemoglobinopathies are the leading cause of some major genetic and social health problem in India. Among all hemoglobinopathies, sickle cell disorder and thalassemia are commonly found in Gujarat state. Double heterozygous state of hemoglobin S and D, hemoglobin E trait, hemoglobin D disease are very uncommon. In present instance, one case of 25-year-old male was diagnosed with sickle cell hemoglobin D disease. The case was confirmed through slide-based sickle test and high-performance liquid chromatography (HPLC). The peripheral smear findings showed presence of microcytic hypochromic red blood cells (RBCs) and many sickled RBCs. Ultrasonography (USG) findings showed hepatomegaly. Second case of 30-year-old female was diagnosed with hemoglobin E trait. The case was confirmed by HPLC. The peripheral findings showed normocytic normochromic RBCs and occasional target cells. Presence of gross hepatomegaly on palpation. Third case of 20-year-old female was diagnosed with hemoglobin D trait. The case was confirmed by HPLC. The peripheral findings showed normocytic normochromic RBCs