2,385 research outputs found

    Non-isotropy in the CMB power spectrum in single field inflation

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    Contaldi et al. [1] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low multipoles. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low multipoles.Comment: 25 pages, 12 figures. In this revised version, we include the Integrated Sachs-Wolfe effect, which was missing from the original. This modifies some results in the low multipoles. The comparison with experiment is slightly better but the change is not statistically significan

    A study of the role of intervention in the final outcome of acute pancreatitis

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    Background: Acute pancreatitis is a common disease which varies in severity, from mild self-limiting pancreatic inflammation to severe pancreatic necrosis with life-threatening sequelae. As per the recent recommendations early intensive care with delayed intervention and step-up approach when indicated has definite survival advantages over the risks associated with early surgical procedures. The present study was aimed at evaluating the mortality and morbidity risk in patients undergoing procedural intervention in acute pancreatitis.Methods: This was a prospective study done in Sri Ramachandra Medical College and Hospital from April 2012- September 2014. All patients with a diagnosis of acute pancreatitis were included in this study. A total of 110 patients were analysed. Routine lab parameters, serum amylase, lipase, lipid profile, calcium, CRP, LDH, CT abdomen, CXR and 2D Echo was done for all patients. Procedural intervention was planned as per the guidelines.Results: Patients were given early intensive care as per the initial severity scores. 25 patients required intervention. Serum LDH, amylase, lipase and CT severity index were better predictors of requirement of intervention and death. Open necrosectomy was done in 15 patients (13.6%), laparoscopic necrosectomy in 3 patients (2.7%) and step up approach was tried in 7 patients (6.4%). Patients who were tried step up approach were monitored closely for any deterioration in their clinical condition to decide about surgery. 7 out of 8 patients who underwent surgery died.  Alcoholic pancreatitis that underwent intervention had a high risk of mortality.Conclusions: Intensive care monitoring with delayed intervention had a better survival benefit. Patients subjected to minimally invasive interventions had a better chance of survival.

    Sharp Raman Anomalies and Broken Adiabaticity at a Pressure Induced Transition from Band to Topological Insulator in Sb2Se3

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    The nontrivial electronic topology of a topological insulator is thus far known to display signatures in a robust metallic state at the surface. Here, we establish vibrational anomalies in Raman spectra of the bulk that signify changes in electronic topology: an E2 g phonon softens unusually and its linewidth exhibits an asymmetric peak at the pressure induced electronic topological transition (ETT) in Sb2Se3 crystal. Our first-principles calculations confirm the electronic transition from band to topological insulating state with reversal of parity of electronic bands passing through a metallic state at the ETT, but do not capture the phonon anomalies which involve breakdown of adiabatic approximation due to strongly coupled dynamics of phonons and electrons. Treating this within a four-band model of topological insulators, we elucidate how nonadiabatic renormalization of phonons constitutes readily measurable bulk signatures of an ETT, which will facilitate efforts to develop topological insulators by modifying a band insulator

    Peyer's Patches Are Precocious to the Appendix in Human Development

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    PP are first visible at ∼15.5 wk gestation after which there is a rapid spurt in the development and maturation of lymphoid follicles so that at any given point of time new foci of PP development are continuously formed at a rapid rate. Addition of rows of follicles results in the formation of a PP. Immature PP of younger fetuses have a spongy structure in contrast with the compact lymphoid follicles of mature PP of older fetuses. Immunocytochemical studies reveal that there is a subtle gradation in the expression of lymphocyte surface markers with increasing fetal age. Expression of antigenic markers occurs in an ordered sequence viz. HLA – DR, CD19 (B cell population), CD9 (pre-B cells), CD3 T lymphocytes, CD4 helper / inducer lymphocytes, the CD8 suppressor / cytotoxic cells and lastly, the CD57 Natural Killer cells. The antigens are expressed first on lymphocytes of PP and thereafter in those of the appendix. Our findings clearly demonstrate that the ∼5 wk fetal period from 17.5 wk to 22 wk represents a major growth phase in the development of surface markers of lymphocytes in the mucosal immune system of the gut

    Raman anomalies as signatures of pressure induced electronic topological and structural transitions in black phosphorus: Experiments and Theory

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    We report high pressure Raman experiments of Black phosphorus up to 24 GPa. The line widths of first order Raman modes Ag1^1_g, B2g_{2g} and Ag2^2_g of the orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density functional analysis reveals that this is associated with the anomalies in electron-phonon coupling at the semiconductor to topological insulator transition through inversion of valence and conduction bands marking a change from trivial to nontrivial electronic topology. The frequencies of B2g_{2g} and Ag2^2_g modes become anomalous in the rhombohedral phase at 7.4 GPa, and new modes appearing in the rhombohedral phase show anomalous softening with pressure. This is shown to originate from unusual structural evolution of black phosphorous with pressure, based on first-principles theoretical analysis.Comment: 13pages, 12figure

    Observational Constraints on Axion(s) with a Cosmological Constant

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    The present work deals with a dark energy model that has an oscillating scalar field potential along with a cosmological constant (CC). The oscillating part of the potential represents the contribution of a light axion field in the dark energy that has its origin in the String-Axiverse scenario. The model has been confronted with the latest cosmological observations. The results show that a sub-Planckian value of the axion field decay constant is consistent at 1σ\sigma confidence level. The oscillating feature in the scalar field evolution and in the equation of state for the dark energy can be observed at 2σ\sigma confidence interval. It is also observed that cluster number counts in this axion model are suppressed compared to the Λ\LambdaCDM and this suppression is enhanced for the sub-Planckian values for the axion decay constant.Comment: 18 pages, LateX style. Comments welcom

    On the spectrum of Random Simplicial Complexes in Thermodynamic Regime

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    Linial-Meshulam complex is a random simplicial complex on nn vertices with a complete (d1)(d-1)-dimensional skeleton and dd-simplices occurring independently with probability p. Linial-Meshulam complex is one of the most studied generalizations of the Erd\H{o}s-R{\'e}nyi random graph in higher dimensions. In this paper, we discuss the spectrum of adjacency matrices of the Linial-Meshulam complex when npλnp \rightarrow \lambda. We prove the existence of a non-random limiting spectral distribution(LSD) and show that the LSD of signed and unsigned adjacency matrices of Linial-Meshulam complex are reflections of each other. We also show that the LSD is unsymmetric around zero, unbounded and under the normalization 1/λd1/\sqrt{\lambda d}, converges to standard semicircle law as λ\lambda \rightarrow \infty. In the later part of the paper, we derive the local weak limit of the line graph of the Linial-Meshulam complex and study its consequence on the continuous part of the LSD.Comment: 32 Pages, 7 Figures, 1 Tabl

    Strings, Junctions and Stability

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    Identification of string junction states of pure SU(2) Seiberg-Witten theory as B-branes wrapped on a Calabi-Yau manifold in the geometric engineering limit is discussed. The wrapped branes are known to correspond to objects in the bounded derived category of coherent sheaves on the projective line \cp{1} in this limit. We identify the pronged strings with triangles in the underlying triangulated category using Pi-stability. The spiral strings in the weak coupling region are interpreted as certain projective resolutions of the invertible sheaves. We discuss transitions between the spiral strings and junctions using the grade introduced for Pi-stability through the central charges of the corresponding objects.Comment: 15 pages, LaTeX; references added. typos correcte

    Localization of Phosphatidylinositol 4,5-Bisphosphate to Lipid Rafts and Uroids in the Human Protozoan Parasite Entamoeba histolytica

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    Entamoeba histolytica is an intestinal protozoan parasite and is the causative agent of amoebiasis. During invasive infection, highly motile amoebae destroy the colonic epithelium, enter the blood circulation, and disseminate to other organs such as liver, causing liver abscess. Motility is a key factor in E. histolytica pathogenesis, and this process relies on a dynamic actomyosin cytoskeleton. In other systems, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is known to regulate a wide variety of cellular functions, including signal transduction, actin remodeling, and cell motility. Little is known about the role of PI(4,5)P2 in E. histolytica pathogenicity. In this study, we demonstrate that PI(4,5)P2 is localized to cholesterol-rich microdomains, lipid rafts, and the actin-rich fractions of the E. histolytica membrane. Microscopy revealed that the trailing edge of polarized trophozoites, uroids, are highly enriched in lipid rafts and their constituent lipid, PI(4,5)P2. Polarization and enrichment of uroids and rafts with PI(4,5)P2 were enhanced upon treatment of E. histolytica cells with cholesterol. Exposure to cholesterol also increased intracellular calcium, which is a downstream effector of PI(4,5)P2, with a concomitant increase in motility. Together, our data suggest that in E. histolytica, PI(4,5)P2 may signal from lipid rafts and cholesterol may play a role in triggering PI(4,5)P2-mediated signaling to enhance the motility of this pathogen
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