Orientation-dependent Casimir force arising from highly anisotropic crystals: application to Bi2Sr2CaCu2O8+delta

We calculate the Casimir interaction between parallel planar crystals of Au and the anisotropic cuprate superconductor Bi2Sr2CaCu2O8+delta (BSCCO), with BSCCO's optical axis either parallel or perpendicular to the crystal surface, using suitable generalizations of the Lifshitz theory. We find that the strong anisotropy of the BSCCO permittivity gives rise to a difference in the Casimir force between the two orientations of the optical axis, which depends on distance and is of order 10-20% at the experimentally accessible separations 10 to 5000 nm.Comment: 5 pages, 3 figures. Accepted for publication in Physical Review

Second order hydrodynamic coefficients from kinetic theory

In a relativistic setting, hydrodynamic calculations which include shear viscosity (which is first order in an expansion in gradients of the flow velocity) are unstable and acausal unless they also include terms to second order in gradients. To date such terms have only been computed in supersymmetric N=4 Super-Yang-Mills theory at infinite coupling. Here we compute these second-order hydrodynamic coefficients in weakly coupled QCD, perturbatively to leading order in the QCD coupling, using kinetic theory. We also compute them in QED and scalar lambda phi^4 theory.Comment: 31 pages including 3 figures. Corrected for algebraic error which affected the coefficient lambda_1, which turns out to be positive and about twice the magnitude previously foun

Excitation spectrum and instability of a two-species Bose-Einstein condensate

We numerically calculate the density profile and excitation spectrum of a two-species Bose-Einstein condensate for the parameters of recent experiments. We find that the ground state density profile of this system becomes unstable in certain parameter regimes, which leads to a phase transition to a new stable state. This state displays spontaneously broken cylindrical symmetry. This behavior is reflected in the excitation spectrum: as we approach the phase transition point, the lowest excitation frequency goes to zero, indicating the onset of instability in the density profile. Following the phase transition, this frequency rises again.Comment: 8 pages, 5 figures, uses REVTe

Novel TNF Receptor-1 Inhibitors Identified as Potential Therapeutic Candidates for Traumatic Brain Injury

Background: Traumatic brain injury (TBI) begins with the application of mechanical force to the head or brain, which initiates systemic and cellular processes that are hallmarks of the disease. The pathological cascade of secondary injury processes, including inflammation, can exacerbate brain injury-induced morbidities and thus represents a plausible target for pharmaceutical therapies. We have pioneered research on post-traumatic sleep, identifying that injury-induced sleep lasting for 6 h in brain-injured mice coincides with increased cortical levels of inflammatory cytokines, including tumor necrosis factor (TNF). Here, we apply post-traumatic sleep as a physiological bio-indicator of inflammation. We hypothesized the efficacy of novel TNF receptor (TNF-R) inhibitors could be screened using post-traumatic sleep and that these novel compounds would improve functional recovery following diffuse TBI in the mouse. Methods: Three inhibitors of TNF-R activation were synthesized based on the structure of previously reported TNF CIAM inhibitor F002, which lodges into a defined TNFR1 cavity at the TNF-binding interface, and screened for in vitro efficacy of TNF pathway inhibition (IκB phosphorylation). Compounds were screened for in vivo efficacy in modulating post-traumatic sleep. Compounds were then tested for efficacy in improving functional recovery and verification of cellular mechanism. Results: Brain-injured mice treated with Compound 7 (C7) or SGT11 slept significantly less than those treated with vehicle, suggesting a therapeutic potential to target neuroinflammation. SGT11 restored cognitive, sensorimotor, and neurological function. C7 and SGT11 significantly decreased cortical inflammatory cytokines 3 h post-TBI. Conclusions: Using sleep as a bio-indicator of TNF-R-dependent neuroinflammation, we identified C7 and SGT11 as potential therapeutic candidates for TBI

Single Cell RNA Profiling Reveals Adipocyte to Macrophage Signaling Sufficient to Enhance Thermogenesis [preprint]

The “browning” of inguinal white adipose tissue (iWAT) through increased abundance of thermogenic beige/brite adipocytes is induced by cold exposure and many other perturbations in association with beneficial systemic metabolic effects. Adipose browning is reported to require activation of sympathetic nerve fibers (SNF), aided by alternately activated macrophages within iWAT. Here we demonstrate the first example of a non-cell autonomous pathway for iWAT browning that is fully independent of SNF activity. Thus, the strong induction of thermogenic adipocytes prompted by deletion of adipocyte fatty acid synthase (iAdFASNKO mice) was unaffected by denervation or the deletion of SNF modulator Neuregulin-4. However, browning of iWAT in iAdFASNKO mice does require adipocyte cAMP/protein kinase A signaling, as it was blocked in adipocyte- selective Fasn/Gsα double KO mice. Single-cell transcriptomic analysis of iAdFASNKO mouse adipose stromal cells revealed increased macrophages displaying gene expression signatures of the alternately activated type. Mechanistically, depletion of such phagocytic immune cells in iAdFASNKO mice fully abrogated appearance of thermogenic adipocytes in iWAT. Altogether, these findings reveal an unexpected pathway of cAMP/PKA-dependent iWAT browning that is initiated by adipocyte signals and caused by macrophage-like cells independent of sympathetic neuron involvement

Scaling in Late Stage Spinodal Decomposition with Quenched Disorder

We study the late stages of spinodal decomposition in a Ginzburg-Landau mean field model with quenched disorder. Random spatial dependence in the coupling constants is introduced to model the quenched disorder. The effect of the disorder on the scaling of the structure factor and on the domain growth is investigated in both the zero temperature limit and at finite temperature. In particular, we find that at zero temperature the domain size, $R(t)$, scales with the amplitude, $A$, of the quenched disorder as $R(t) = A^{-\beta} f(t/A^{-\gamma})$ with $\beta \simeq 1.0$ and $\gamma \simeq 3.0$ in two dimensions. We show that $\beta/\gamma = \alpha$, where $\alpha$ is the Lifshitz-Slyosov exponent. At finite temperature, this simple scaling is not observed and we suggest that the scaling also depends on temperature and $A$. We discuss these results in the context of Monte Carlo and cell dynamical models for phase separation in systems with quenched disorder, and propose that in a Monte Carlo simulation the concentration of impurities, $c$, is related to $A$ by $A \sim c^{1/d}$.Comment: RevTex manuscript 5 pages and 5 figures (obtained upon request via email [email protected]

Bogoliubov approach to superfluidity of atoms in an optical lattice

We use the Bogoliubov theory of atoms in an optical lattice to study the approach to the Mott-insulator transition. We derive an explicit expression for the superfluid density based on the rigidity of the system under phase variations. This enables us to explore the connection between the quantum depletion of the condensate and the quasi-momentum distribution on the one hand and the superfluid fraction on the other. The approach to the insulator phase may be characterized through the filling of the band by quantum depletion, which should be directly observable via the matter wave interference patterns. We complement these findings by self-consistent Hartree-Fock-Bogoliubov-Popov calculations for one-dimensional lattices including the effects of a parabolic trapping potential.Comment: 25 pages, 8 figure

Grain-size distribution in the mantle wedge of subduction zones

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B10203, doi:10.1029/2011JB008294.Mineral grain size plays an important role in controlling many processes in the mantle wedge of subduction zones, including mantle flow and fluid migration. To investigate the grain-size distribution in the mantle wedge, we coupled a two-dimensional (2-D) steady state finite element thermal and mantle-flow model with a laboratory-derived grain-size evolution model. In our coupled model, the mantle wedge has a composite olivine rheology that incorporates grain-size-dependent diffusion creep and grain-size-independent dislocation creep. Our results show that all subduction settings lead to a characteristic grain-size distribution, in which grain size increases from 10 to 100 μm at the most trenchward part of the creeping region to a few centimeters in the subarc mantle. Despite the large variation in grain size, its effect on the mantle rheology and flow is very small, as >90% of the deformation in the flowing part of the creeping region is accommodated by grain-size-independent dislocation creep. The predicted grain-size distribution leads to a downdip increase in permeability by ∼5 orders of magnitude. This increase is likely to promote greater upward migration of aqueous fluids and melts where the slab reaches ∼100 km depth compared with shallower depths, potentially providing an explanation for the relatively uniform subarc slab depth. Seismic attenuation derived from the predicted grain-size distribution and thermal field is consistent with the observed seismic structure in the mantle wedge at many subduction zones, without requiring a significant contribution by the presence of melt.Funding for this research was provided by the National Science Foundation through a MARGINS Postdoctoral Fellowship (NSF OCE‐0840800) and NSF grant EAR‐0854673