5,994 research outputs found
Computation of topological phase diagram of disordered PbSnTe using the kernel polynomial method
We present an algorithm to determine topological invariants of inhomogeneous
systems, such as alloys, disordered crystals, or amorphous systems. Based on
the kernel polynomial method, our algorithm allows us to study samples with
more than degrees of freedom. Our method enables the study of large
complex compounds, where disorder is inherent to the system. We use it to
analyse PbSnTe and tighten the critical concentration for the
phase transition.Comment: 4 pages + supplemental materia
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The Immunological Basis of Dry Eye Disease and Current Topical Treatment Options.
Homeostasis of the lacrimal functional unit is needed to ensure a well-regulated ocular immune response comprising innate and adaptive phases. When the ocular immune system is excessively stimulated and/or immunoregulatory mechanisms are disrupted, the balance between innate and adaptive phases is dysregulated and chronic ocular surface inflammation can result, leading to chronic dry eye disease (DED). According to the Tear Film and Ocular Surface Society Dry Eye Workshop II definition, DED is a multifactorial disorder of the ocular surface characterized by impairment and loss of tear homeostasis (hyperosmolarity), ocular discomfort or pain, and neurosensory abnormalities. Dysregulated ocular immune responses result in ocular surface damage, which is a further contributing factor to DED pathology. Several therapeutics are available to break the vicious circle of DED and prevent chronic disease and progression, including immunosuppressive agents (steroids) and immunomodulators (cyclosporine and lifitegrast). Given the chronic inflammatory nature of DED, each of these agents is commonly used in clinical practice. In this study, we review the immunopathology of DED and the molecular and cellular actions of current topical DED therapeutics to inform clinical decision making
Perspectives on Quantum Gravity Phenomenology
The idea that quantum gravity manifestations would be associated with a
violation of Lorentz invariance is very strongly bounded and faces serious
theoretical challenges. Other related ideas seem to be drowning in
interpretational quagmires. This leads us to consider alternative lines of
thought for such phenomenological search. We discuss the underlying viewpoints
and briefly mention their possible connections with other current theoretical
ideas.Comment: Latex, 23 page
The Seeds of Cosmic structure as a door to New Physics
There is something missing in our understanding of the origin of the seeds of
Cosmic Structuture.
The fact that the fluctuation spectrum can be extracted from the inflationary
scenario through an analysis that involves quantum field theory in curved
space-time, and that it coincides with the observational data has lead to a
certain complacency in the community, which prevents the critical analysis of
the obscure spots in the derivation. The point is that the inhomogeneity and
anisotropy of our universe seem to emerge from an exactly homogeneous and
isotropic initial state through processes that do not break those symmetries.
This article gives a brief recount of the problems faced by the arguments based
on established physics, which comprise the point of view held by a large
majority of researchers in the field.
The conclusion is that we need some new physics to be able to fully address
the problem. The article then exposes one avenue that has been used to address
the central issue and elaborates on the degree to which, the new approach makes
different predictions from the standard analyses.
The approach is inspired on Penrose's proposals that Quantum Gravity might
lead to a real, dynamical collapse of the wave function, a process that we
argue has the properties needed to extract us from the theoretical impasse
described above.Comment: Prepared for the proceedings of the conference NEBXII " Recent
Developments in Gravity", Napfio Grece June 2006. LateX, 15 page
Characterization of influenza virus sialic acid receptors in minor poultry species
It is commonly accepted that avian influenza viruses (AIVs) bind to terminal α2,3 sialic acid (SA) residues whereas human influenza viruses bind to α2,6 SA residues. By a series of amino acid changes on the HA surface protein, AIVs can switch receptor specificity and recognize α2,6 SA positive cells, including human respiratory epithelial cells. Animal species, like pigs and Japanese quail, that contain both α2,3 and α2,6 SA become ideal environments for receptor switching. Here, we describe the SA patterns and distributions in 6 common minor domestic poultry species: Peking duck, Toulouse geese, Chinese ring-neck pheasant, white midget turkey, bobwhite quail, and pearl guinea fowl. Lectins specific to α2,3 and α2,6 SA (Maakia amurensis agglutinin and Sambuca nigra agglutinin, respectively) were used to detect SA by an alkaline phosphotase-based method and a fluorescent-based method. Differences in SA moieties and their ability to bind influenza viruses were visualized by fluorescent labeling of 4 different H3N2 influenza viruses known to be specific for one receptor or the other. The geese and ducks showed α2,3 SA throughout the respiratory tract and marginal α2,6 SA only in the colon. The four other avian species showed both α2,3 and α2,6 SA in the respiratory tract and the intestines. Furthermore, the turkey respiratory tract showed a positive correlation between age and α2,6 SA levels. The fact that these birds have both avian and human flu receptors, combined with their common presence in backyard farms and live bird markets worldwide, mark them as potential mixing bowl species and necessitates improved surveillance and additional research about the role of these birds in influenza host switching
NuSTAR Tests of Sterile-Neutrino Dark Matter: New Galactic Bulge Observations and Combined Impact
We analyze two dedicated NuSTAR observations with exposure ks
located from the Galactic plane, one above and the other
below, to search for x-ray lines from the radiative decay of sterile-neutrino
dark matter. These fields were chosen to minimize astrophysical x-ray
backgrounds while remaining near the densest region of the dark matter halo. We
find no evidence of anomalous x-ray lines in the energy range 5--20 keV,
corresponding to sterile neutrino masses 10--40 keV. Interpreted in the context
of sterile neutrinos produced via neutrino mixing, these observations provide
the leading constraints in the mass range 10--12 keV, improving upon previous
constraints in this range by a factor . We also compare our results to
Monte Carlo simulations, showing that the fluctuations in our derived limit are
not dominated by systematic effects. An updated model of the instrumental
background, which is currently under development, will improve NuSTAR's
sensitivity to anomalous x-ray lines, particularly for energies 3--5 keV.Comment: 16 pages, 5 figures. Text updated to match published version in PRD.
Conclusions unchange
Validation of Slosh Model Parameters and Anti-Slosh Baffle Designs of Propellant Tanks by Using Lateral Slosh Testing
The slosh dynamics of propellant tanks can be represented by an equivalent mass-pendulum-dashpot mechanical model. The parameters of this equivalent model, identified as slosh mechanical model parameters, are slosh frequency, slosh mass, and pendulum hinge point location. They can be obtained by both analysis and testing for discrete fill levels. Anti-slosh baffles are usually needed in propellant tanks to control the movement of the fluid inside the tank. Lateral slosh testing, involving both random excitation testing and free-decay testing, are performed to validate the slosh mechanical model parameters and the damping added to the fluid by the anti-slosh baffles. Traditional modal analysis procedures were used to extract the parameters from the experimental data. Test setup of sub-scale tanks will be described. A comparison between experimental results and analysis will be presented
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