527 research outputs found

    On simultaneous limits for aggregation of stationary randomized INAR(1) processes with Poisson innovations

    Get PDF
    We investigate joint temporal and contemporaneous aggregation of N independent copies of strictly stationary INteger-valued AutoRegressive processes of order 1 (INAR(1)) with random coefficient α(0,1)\alpha\in(0,1) and with idiosyncratic Poisson innovations. Assuming that α\alpha has a density function of the form ψ(x)(1x)β\psi(x) (1 - x)^\beta, x(0,1)x \in (0,1), with β(1,)\beta\in(-1,\infty) and limx1ψ(x)=ψ1(0,)\lim_{x\uparrow 1} \psi(x) = \psi_1 \in (0,\infty), different limits of appropriately centered and scaled aggregated partial sums are shown to exist for β(1,0]\beta\in(-1,0] in the so-called simultaneous case, i.e., when both NN and the time scale nn increase to infinity at a given rate. The case β(0,)\beta\in(0,\infty) remains open. We also give a new explicit formula for the joint characteristic functions of finite dimensional distributions of the appropriately centered aggregated process in question.Comment: 38 page

    Probability equivalent level of Value at Risk and higher-order Expected Shortfalls

    Full text link
    We investigate the probability equivalent level of Value at Risk and nthn^{\mathrm{th}}-order Expected Shortfall (called PELVE_n), which can be considered as a variant of the notion of the probability equivalent level of Value at Risk and Expected Shortfall (called PELVE) due to Li and Wang (2022). We study the finiteness, uniqueness and several properties of PELVE_n, we calculate PELVE_n of some notable distributions, PELVE_2 of a random variable having generalized Pareto excess distribution, and we describe the asymptotic behaviour of PELVE_2 of regularly varying distributions as the level tends to 00. Some properties of nthn^{\mathrm{th}}-order Expected Shortfall are also investigated. Among others, it turns out that the Gini Shortfall at some level p[0,1)p\in[0,1) corresponding to a (loading) parameter λ0\lambda\geq 0 is the linear combination of the Expected Shortfall at level pp and the 2nd2^{\mathrm{nd}}-order Expected Shortfall at level pp with coefficients 12λ1-2\lambda and 2λ2\lambda, respectively.Comment: 45 page

    Assessment of Methods to Consolidate Iodine-Loaded Silver-Functionalized Silica Aerogel

    Get PDF
    The U.S. Department of Energy is currently investigating alternative sorbents for the removal and immobilization of radioiodine from the gas streams in a nuclear fuel reprocessing plant. One of these new sorbents, Ag0-functionalized silica aerogels, shows great promise as a potential replacement for Ag-bearing mordenites because of its high selectivity and sorption capacity for iodine. Moreover, a feasible consolidation of iodine-loaded Ag0-functionalized silica aerogels to a durable SiO2-based waste form makes this aerogel an attractive choice for sequestering radioiodine. This report provides a preliminary assessment of the methods that can be used to consolidate iodine-loaded Ag0-functionalized silica aerogels into a final waste form. In particular, it focuses on experimental investigation of densification of as prepared Ag0-functionalized silica aerogels powders, with or without organic moiety and with or without sintering additive (colloidal silica), with three commercially available techniques: 1) hot uniaxial pressing (HUP), 2) hot isostatic pressing (HIP), and 3) spark plasma sintering (SPS). The densified products were evaluated with helium gas pycnometer for apparent density, with the Archimedes method for apparent density and open porosity, and with high-resolution scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) for the extent of densification and distribution of individual elements. The preliminary investigation of HUP, HIP, and SPS showed that these sintering methods can effectively consolidate powders of Ag0-functionalized silica aerogel into products of near-theoretical density. Also, removal of organic moiety and adding 5.6 mass% of colloidal silica to Ag0-functionalized silica aerogel powders before processing provided denser products. Furthermore, the ram travel data for SPS indicated that rapid consolidation of powders can be performed at temperatures below 950°C

    A Review of Adult Mortality Due to 2009 Pandemic (H1N1) Influenza A in California

    Get PDF
    BACKGROUND: While children and young adults had the highest attack rates due to 2009 pandemic (H1N1) influenza A (2009 H1N1), studies of hospitalized cases noted high fatality in older adults. We analyzed California public health surveillance data to better characterize the populations at risk for dying due to 2009 H1N1. METHODS AND FINDINGS: A case was an adult ≥20 years who died with influenza-like symptoms and laboratory results indicative of 2009 H1N1. Demographic and clinical data were abstracted from medical records using a standardized case report form. From April 3, 2009-August 10, 2010, 541 fatal cases ≥20 years with 2009 H1N1 were reported. Influenza fatality rates per 100,000 population were highest in persons 50-59 years (3.5; annualized rate = 2.6) and 60-69 years (2.3; annualized rate = 1.7) compared to younger and older age groups (0.4-1.9; annualized rates = 0.3-1.4). Of 486 cases hospitalized prior to death, 441 (91%) required intensive care unit (ICU) admission. ICU admission rates per 100,000 population were highest in adults 50-59 years (8.6). ICU case-fatality ratios among adults ranged from 24-42%, with the highest ratios in persons 70-79 years. A total of 425 (80%) cases had co-morbid conditions associated with severe seasonal influenza. The prevalence of most co-morbid conditions increased with increasing age, but obesity, pregnancy and obstructive sleep apnea decreased with age. Rapid testing was positive in 97 (35%) of 276 tested. Of 482 cases with available data, 384 (80%) received antiviral treatment, including 49 (15%) of 328 within 48 hours of symptom onset. CONCLUSIONS: Adults aged 50-59 years had the highest fatality due to 2009 H1N1; older adults may have been spared due to pre-existing immunity. However, once infected and hospitalized in intensive care, case-fatality ratios were high for all adults, especially in those over 60 years. Vaccination of adults older than 50 years should be encouraged

    Human Erythrocytes Selectively Bind and Enrich Infectious HIV-1 Virions

    Get PDF
    Although CD4(+) cells represent the major target for HIV infection in blood, claims of complement-independent binding of HIV-1 to erythrocytes and the possible role of Duffy blood group antigen, have generated controversy. To examine the question of binding to erythrocytes, HIV-1 was incubated in vitro with erythrocytes from 30 healthy leukapheresis donors, and binding was determined by p24 analysis and adsorption of HIV-1 with reduction of infectivity for CD4(+) target cells. All of the cells, regardless of blood group type, bound HIV-1 p24. A typical preparation of erythrocytes bound <2.4% of the added p24, but erythrocytes selectively removed essentially all of the viral infectivity as determined by decreased infection of CD4(+) target cells; however, cell-associated HIV-1 was approximately 100-fold more efficient, via trans infection, than unadsorbed virus for infection of CD4(+) cells. All of the bound HIV-1 p24 was released by treatment of the cells with EDTA, and binding was optimized by adding Ca2+ and Mg2+ during the washing of erythrocytes containing bound HIV-1. Although the small number of contaminating leukocytes in the erythrocyte preparation also bound HIV-1 p24, there was no significant binding to CD4, and it thus appears that the binding occurred on leukocytes at non-CD4 sites. Furthermore, binding occurred to erythrocyte ghosts from which contaminating leukocytes had been previously removed. The results demonstrate that erythrocytes incubated in vitro with HIV-1 differentially adsorb all of the infectious HIV-1 virions (as opposed to non-infectious or degraded virions) in the absence of complement and independent of blood group, and binding is dependent on divalent cations. By analogy with HIV-1 bound to DC-SIGN on dendritic cells, erythrocyte-bound HIV-1 might comprise an important surface reservoir for trans infection of permissive cells

    Quantum Multibaker Maps: Extreme Quantum Regime

    Full text link
    We introduce a family of models for quantum mechanical, one-dimensional random walks, called quantum multibaker maps (QMB). These are Weyl quantizations of the classical multibaker models previously considered by Gaspard, Tasaki and others. Depending on the properties of the phases parametrizing the quantization, we consider only two classes of the QMB maps: uniform and random. Uniform QMB maps are characterized by phases which are the same in every unit cell of the multibaker chain. Random QMB maps have phases that vary randomly from unit cell to unit cell. The eigenstates in the former case are extended while in the latter they are localized. In the uniform case and for large \hbar, analytic solutions can be obtained for the time dependent quantum states for periodic chains and for open chains with absorbing boundary conditions. Steady state solutions and the properties of the relaxation to a steady state for a uniform QMB chain in contact with ``particle'' reservoirs can also be described analytically. The analytical results are consistent with, and confirmed by, results obtained from numerical methods. We report here results for the deep quantum regime (large \hbar) of the uniform QMB, as well as some results for the random QMB. We leave the moderate and small \hbar results as well as further consideration of the other versions of the QMB for further publications.Comment: 17 pages, referee's and editor's comments addresse

    Charged black holes: Wave equations for gravitational and electromagnetic perturbations

    Get PDF
    A pair of wave equations for the electromagnetic and gravitational perturbations of the charged Kerr black hole are derived. The perturbed Einstein-Maxwell equations in a new gauge are employed in the derivation. The wave equations refer to the perturbed Maxwell spinor Φ0\Phi_0 and to the shear σ\sigma of a principal null direction of the Weyl curvature. The whole construction rests on the tripod of three distinct derivatives of the first curvature κ\kappa of a principal null direction.Comment: 12 pages, to appear in Ap.
    corecore