124 research outputs found

    The difference of boundary effects between Bose and Fermi systems

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    In this paper, we show that there exists an essential difference of boundary effects between Bose and Fermi systems both for Dirichlet and Neumann boundary conditions: at low temperatures and high densities the influence of the boundary on the Bose system depends on the temperature but is independent of the density, but for the Fermi case the influence of the boundary is independent of the temperature but depends on the density, after omitting the negligible high-order corrections. We also show that at high temperatures and low densities the difference of the influence of the boundary between Bose and Fermi systems appears in the next-to-leading order boundary contribution, and the leading boundary contribution is independent of the density. Moreover, for calculating the boundary effects at high temperatures and low densities, since the existence of the boundary modification causes the standard virial expansion to be invalid, we introduce a modified virial expansion.Comment: 8 page

    All unitary cubic curvature gravities in D dimensions

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    We construct all the unitary cubic curvature gravity theories built on the contractions of the Riemann tensor in D -dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom, which greatly simplifies the highly complicated problem of finding the propagator of cubic curvature theories in constant curvature backgrounds. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories using different techniques and the string generated cubic curvature gravity model. We also study the scattering in critical gravity and give its cubic curvature extensions.Comment: 24 pages, 1 figure, v2: A subsection on cubic curvature extensions of critical gravity is added, v3: The part regarding critical gravity is revised. Version to appear in Class. Quant. Gra

    A Complete Classification of Higher Derivative Gravity in 3D and Criticality in 4D

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    We study the condition that the theory is unitary and stable in three-dimensional gravity with most general quadratic curvature, Lorentz-Chern-Simons and cosmological terms. We provide the complete classification of the unitary theories around flat Minkowski and (anti-)de Sitter spacetimes. The analysis is performed by examining the quadratic fluctuations around these classical vacua. We also discuss how to understand critical condition for four-dimensional theories at the Lagrangian level.Comment: 20 pages, v2: minor corrections, refs. added, v3: logic modified, v4: typos correcte

    Dramatising intelligence history on the BBC : the Camp 020 affair

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    While there is a considerable literature that considers post-1945 British intelligence historiography, little attention has been given to non-print media, such as factual depictions of intelligence affairs broadcast on television or radio. Using previously closed material from the British Broadcasting Corporation’s written archives, this article explores how factual intelligence and security issues were represented by the BBC as the 1970s drew to a close, through an examination of the Spy! television series, which approached episodes of recent intelligence history in a drama-documentary format. The second episode of the series, seen by millions of viewers, proved controversial owing to its depiction of a physical assault during interrogation at an MI5 facility, Camp 020, during the Second World War. The article explores the fallout from this episode, as numerous Camp 020 veterans made great efforts to point out that such physical violence had never taken place. For the most part, this struggle was played out in private correspondence with the BBC, while the general public was left with little reason to question what had been shown, thereby allowing the association of wartime British intelligence with physical abuse to go unchallenged

    Modulation of EEG spectral edge frequency during patterned pneumatic oral stimulation in preterm infants

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    Background—Stimulation of the nervous system plays a central role in brain development and neurodevelopmental outcome. Thalamocortical and corticocortical development is diminished in premature infants and correlated to electroencephalography (EEG) progression. The purpose of this study was to determine the effects of orocutaneous stimulation on the modulation of spectral edge frequency, fc=90% (SEF-90) derived from EEG recordings in preterm infants. Methods—Twenty two preterm infants were randomized to experimental and control conditions. Pulsed orocutaneous stimulation was presented during gavage feedings begun at around 32 weeks postmenstrual age (PMA). The SEF-90 was derived from 2-channel EEG recordings. Results—Compared to the control condition, the pulsed orocutaneous stimulation produced a significant reorganization of SEF-90 in the left (p = 0.005) and right (p \u3c 0.0001) hemispheres. Notably, the left and right hemisphere showed a reversal in the polarity of frequency shift, demonstrating hemispheric asymmetry in the frequency domain. Pulsed orocutaneous stimulation also produced a significant pattern of short term cortical adaptation and a long term neural adaptation manifest as a 0.5 Hz elevation in SEF-90 after repeated stimulation sessions. Conclusion—This is the first study to demonstrate the modulating effects of a servo-controlled oral somatosensory input on the spectral features of EEG activity in preterm infants

    In Vivo Quantitative Study of Sized-Dependent Transport and Toxicity of Single Silver Nanoparticles Using Zebrafish Embryos

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    Nanomaterials possess distinctive physicochemical properties (e.g., small sizes and high surface area-to-volume ratios) and promise a wide variety of applications, ranging from the design of high quality consumer products to effective disease diagnosis and therapy. These properties can lead to toxic effects, potentially hindering advances in nanotechnology. In this study, we have synthesized and characterized purified and stable (nonaggregation) silver nanoparticles (Ag NPs, 41.6 ± 9.1 nm in average diameter) and utilized early developing (cleavage-stage) zebrafish embryos (critical aquatic and eco- species) as in vivo model organisms to probe the diffusion and toxicity of Ag NPs. We found that single Ag NPs (30-72 nm diameters) passively diffused into the embryos through chorionic pores via random Brownian motion and stayed inside the embryos throughout their entire development (120 hours-post-fertilization, hpf). Dose-and size-dependent toxic effects of the NPs on embryonic development were observed, showing the possibility of tuning biocompatibility and toxicity of the NPs. At lower concentrations of the NPs (≤0.02 nM), 75-91% of embryos developed into normal zebrafish. At the higher concentrations of NPs (≥0.20 nM), 100% of embryos became dead. At the concentrations in between (0.02-0.2 nM), embryos developed into various deformed zebrafish. Number and sizes of individual Ag NPs embedded in tissues of normal and deformed zebrafish at 120 hpf were quantitatively analyzed, showing deformed zebrafish with higher number of larger NPs than normal zebrafish and size-dependent nanotoxicity. By comparing with our previous studies of smaller Ag NPs (11.6 ± 3.5 nm), we found striking size-dependent nanotoxicity that, at the same molar concentration, the larger Ag NPs (41.6 ± 9.1 nm) are more toxic than the smaller Ag NPs (11.6 ± 3.5 nm)

    Type 1 Autoimmune Pancreatitis in Europe: Clinical Profile and Response to Treatment.

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    Background and aimsAutoimmune pancreatitis (AIP) is an immune-mediated disease of the pancreas with distinct pathophysiology and manifestations. Our aims were to characterize type 1 AIP in a large pan-European cohort and study the effectiveness of current treatment regimens.MethodsWe retrospectively analyzed adults diagnosed since 2005 with type 1 or not-otherwise-specified AIP in 42 European university hospitals. Type 1 AIP was uniformly diagnosed using specific diagnostic criteria. Patients with type 2 AIP and those who had undergone pancreatic surgery were excluded. The primary endpoint was complete remission, defined as the absence of clinical symptoms and resolution of the index radiological pancreatic abnormalities attributed to AIP.ResultsWe included 735 individuals with AIP (69% male; median age 57 years; 85% White). Steroid treatment was started in 634 patients, of whom 9 (1%) were lost to follow-up. The remaining 625 had a 79% (496/625) complete, 18% (111/625) partial, and 97% (607/625) cumulative remission rate, while 3% (18/625) did not achieve remission. No treatment was given in 95 patients, who had a 61% complete (58/95), 19% partial (18/95), and 80% cumulative (76/95) spontaneous remission rate. Higher (≥0.4 mg/kg/day) corticosteroid doses were no more effective than lower ( 2 weeks (OR 0.908; 95%CI 0.818-1.009). Elevated IgG4 levels were independently associated with a decreased chance of complete remission (OR 0.639; 95%CI 0.427-0.955). Relapse occurred in 30% of patients. Relapses within 6 months of remission induction were independent of the steroid tapering duration, induction treatment duration, and total cumulative dose.ConclusionPatients with type 1 AIP and elevated IgG4 level may need closer monitoring. For remission induction, a starting dose of 0.4 mg/kg/day for 2 weeks followed by a short taper period seems effective. This study provides no evidence to support more aggressive regimens
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