1,085 research outputs found

    Singular normal form for the Painlev\'e equation P1

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    We show that there exists a rational change of coordinates of Painlev\'e's P1 equation y=6y2+xy''=6y^2+x and of the elliptic equation y=6y2y''=6y^2 after which these two equations become analytically equivalent in a region in the complex phase space where yy and yy' are unbounded. The region of equivalence comprises all singularities of solutions of P1 (i.e. outside the region of equivalence, solutions are analytic). The Painlev\'e property of P1 (that the only movable singularities are poles) follows as a corollary. Conversely, we argue that the Painlev\'e property is crucial in reducing P1, in a singular regime, to an equation integrable by quadratures

    Ionization in damped time-harmonic fields

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    We study the asymptotic behavior of the wave function in a simple one dimensional model of ionization by pulses, in which the time-dependent potential is of the form V(x,t)=2δ(x)(1eλtcosωt)V(x,t)=-2\delta(x)(1-e^{-\lambda t} \cos\omega t), where δ\delta is the Dirac distribution. We find the ionization probability in the limit tt\to\infty for all λ\lambda and ω\omega. The long pulse limit is very singular, and, for ω=0\omega=0, the survival probability is constλ1/3const \lambda^{1/3}, much larger than O(λ)O(\lambda), the one in the abrupt transition counterpart, V(x,t)=δ(x)1{t1/λ}V(x,t)=\delta(x)\mathbf{1}_{\{t\ge 1/\lambda\}} where 1\mathbf{1} is the Heaviside function

    Decay versus survival of a localized state subjected to harmonic forcing: exact results

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    We investigate the survival probability of a localized 1-d quantum particle subjected to a time dependent potential of the form rU(x)sinωtrU(x)\sin{\omega t} with U(x)=2δ(xa)U(x)=2\delta (x-a) or U(x)=2δ(xa)2δ(x+a)U(x)= 2\delta(x-a)-2\delta (x+a). The particle is initially in a bound state produced by the binding potential 2δ(x)-2\delta (x). We prove that this probability goes to zero as tt\to\infty for almost all values of rr, ω\omega, and aa. The decay is initially exponential followed by a t3t^{-3} law if ω\omega is not close to resonances and rr is small; otherwise the exponential disappears and Fermi's golden rule fails. For exceptional sets of parameters r,ωr,\omega and aa the survival probability never decays to zero, corresponding to the Floquet operator having a bound state. We show similar behavior even in the absence of a binding potential: permitting a free particle to be trapped by harmonically oscillating delta function potential

    Differing roles of autophagy in HIV-associated neurocognitive impairment and encephalitis with implications for morphine co-exposure

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    We investigated the role of autophagy in HIV-infected subjects with neurocognitive impairment (NCI) ± HIV encephalitis (HIVE), many of which had a history of polysubstance abuse/dependence, using post-mortem brain tissues to determine whether differences in autophagy related factors may be more associated with NCI or NCI-encephalitis. Using qRT-PCR, we detected significant differences in gene expression levels with SQSTM1, LAMP1 higher in HIV-infected subjects without NCI while ATG5, SQSTM1 were then lower in HIV infection/NCI and ATG7, SQSTM1 being higher in NCI-HIVE. Immunohistochemical labeling of these autophagy associated proteins (also including Beclin 1 and LC3B) in Iba1-positive microglial cells showed generally higher immunoreactivity in the NCI and NCI-HIVE groups with more focal vs. diffuse patterns of expression in the NCI-HIVE group. Furthermore, analysis of microarray data from these same subjects found significantly higher levels of LAMP1 in NCI-HIVE compared to uninfected subjects in the basal ganglia. Finally, we tested the effect of supernatant from HIV-1-infected microglia and HIV-1 Tat protein in combination with morphine on neurons in vitro and found opposing events with both significant inhibition of autophagic flux and reduced dendrite length for morphine and supernatant treatment while Tat and morphine exposure resulted in lower autophagic activity at an earlier time point and higher levels in the later. These results suggest autophagy genes and their corresponding proteins may be differentially regulated at the transcriptional, translational, and post-translational levels in the brain during various stages of the HIV disease and that infected individuals exposed to morphine can experience mixed signaling of autophagic activity which could lead to more severe NCI than those without opioid use

    Cohomological BRST aspects of the massless tensor field with the mixed symmetry (k,k)

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    The main BRST cohomological properties of a free, massless tensor field that transforms in an irreducible representation of GL(D,R), corresponding to a rectangular, two-column Young diagram with k>2 rows are studied in detail. In particular, it is shown that any non-trivial co-cycle from the local BRST cohomology group H(s|d) can be taken to stop either at antighost number (k+1) or k, its last component belonging to the cohomology of the exterior longitudinal derivative H(gamma) and containing non-trivial elements from the (invariant) characteristic cohomology H^{inv}(delta|d).Comment: Latex, 50 pages, uses amssym

    Hamiltonian BRST deformation of a class of n-dimensional BF-type theories

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    Consistent Hamiltonian interactions that can be added to an abelian free BF-type class of theories in any n greater or equal to 4 spacetime dimensions are constructed in the framework of the Hamiltonian BRST deformation based on cohomological techniques. The resulting model is an interacting field theory in higher dimensions with an open algebra of on-shell reducible first-class constraints. We argue that the Hamiltonian couplings are related to a natural structure of Poisson manifold on the target space.Comment: 27 pages, uses JHEP3.cl

    Evolution of the one-phonon 2(1,ms)(+) mixed-symmetry state in N=80 isotones as a local measure for the proton-neutron quadrupole interaction

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    An inverse kinematics Coulomb excitation experiment was performed to obtain absolute E2 and M1 transition strengths in 134Xe. The measured transition strengths indicate that the 23+ state of 134Xe is the dominant fragment of the one-phonon 21, ms+ mixed-symmetry state. Comparing the energy of the 21, ms+ mixed-symmetry state in 134Xe to that of the 21, ms+ levels in the N = 80 isotonic chain indicates that the separation in energy between the fully-symmetric 21+ state and the 21, ms+ level increases as a function of the number of proton pairs outside the Z = 50 shell closure. This behavior can be understood as resulting from the mixing of the basic components of a two-fluid quantum system. A phenomenological fit based on this concept was performed. It provides the first experimental estimate of the strength of the proton-neutron quadrupole interaction derived from nuclear collective states with symmetric and antisymmetric nature

    Histological changes in the vulva and vagina from ovariectomised rats undergoing oestrogen treatment

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    Background: The purpose of this study was to assess the histological changes occurring in the vagina and vulva in ovariectomised female rats, as well as the response to the administration of injectable oestrogens. Material and methods: We used 30 female Wistar white rats, distributed as follows: group 1 — the control group, group 2 — the operated but untreated rats, and groups 3, 4 and 5 — operated rats, to which oestrogenic treatment was administered (Estradiol, Estradurin, Sintofolin) at a dosage of 0.2 mg/rat/day. After 14 days of treatment, all animals were sacrificed and vaginal and vulvar biopsies were taken from all groups. Results: In group 2, we encountered structural changes of the vaginal mucosa, with severe atrophy and alterations in the thickness of the vagina and vulva. In groups 3, 4 and 5 we found marked hyperplasia of the vaginal and vulvar epithelium, eosinophilic and mast cell infiltration in the chorion. Conclusions: Our study proves that the histopathological changes during anoestrus after administration of oestrogens are cell hyperplasia, thickening of the superficial mucosal layer, eosinophilic and mast cells infiltrations, and chorionic congestion. Furthermore, we demonstrated that Estradiol therapy induces the most evident histological changes when compared to synthetic oestrogens such as Estradurin or Sintofolin.

    Transition probabilities in the X(5) candidate 122^{122}Ba

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    To investigate the possible X(5) character of 122Ba, suggested by the ground state band energy pattern, the lifetimes of the lowest yrast states of 122Ba have been measured, via the Recoil Distance Doppler-Shift method. The relevant levels have been populated by using the 108Cd(16O,2n)122Ba and the 112Sn(13C,3n)122Ba reactions. The B(E2) values deduced in the present work are compared to the predictions of the X(5) model and to calculations performed in the framework of the IBA-1 and IBA-2 models
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