430 research outputs found
Discussion of "Statistical Modeling of Spatial Extremes" by A. C. Davison, S. A. Padoan and M. Ribatet
Discussion of "Statistical Modeling of Spatial Extremes" by A. C. Davison, S.
A. Padoan and M. Ribatet [arXiv:1208.3378].Comment: Published in at http://dx.doi.org/10.1214/12-STS376A the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Approximate Birkhoff-James orthogonality and smoothness in the space of bounded linear operators
We study approximate Birkhoff-James orthogonality of bounded linear operators
defined between normed linear spaces and As an
application of the results obtained, we characterize smoothness of a bounded
linear operator under the condition that
the space of compact linear operators is
an ideal in the space of bounded
linear operators
Inertial- and Dissipation-Range Asymptotics in Fluid Turbulence
We propose and verify a wave-vector-space version of generalized extended
self similarity and broaden its applicability to uncover intriguing, universal
scaling in the far dissipation range by computing high-order (\leq 20\/)
structure functions numerically for: (1) the three-dimensional, incompressible
Navier Stokes equation (with and without hyperviscosity); and (2) the GOY shell
model for turbulence. Also, in case (2), with Taylor-microscale Reynolds
numbers 4 \times 10^{4} \leq Re_{\lambda} \leq 3 \times 10^{6}\/, we find
that the inertial-range exponents (\zeta_{p}\/) of the order - p\/
structure functions do not approach their Kolmogorov value p/3\/ as
Re_{\lambda}\/ increases.Comment: RevTeX file, with six postscript figures. epsf.tex macro is used for
figure insertion. Packaged using the 'uufiles' utilit
Turbulence and Multiscaling in the Randomly Forced Navier Stokes Equation
We present an extensive pseudospectral study of the randomly forced
Navier-Stokes equation (RFNSE) stirred by a stochastic force with zero mean and
a variance , where is the wavevector and the dimension . We present the first evidence for multiscaling of velocity structure
functions in this model for . We extract the multiscaling exponent
ratios by using extended self similarity (ESS), examine their
dependence on , and show that, if , they are in agreement with those
obtained for the deterministically forced Navier-Stokes equation (NSE). We
also show that well-defined vortex filaments, which appear clearly in studies
of the NSE, are absent in the RFNSE.Comment: 4 pages (revtex), 6 figures (postscript
Hexagonal patterns in a model for rotating convection
We study a model equation that mimics convection under rotation in a fluid with temperature- dependent properties (non-Boussinesq (NB)), high Prandtl number and idealized boundary conditions. It is based on a model equation proposed by Segel [1965] by adding rotation terms that lead to a Kuppers-Lortz instability [Kuppers & Lortz, 1969] and can develop into oscillating hexagons. We perform a weakly nonlinear analysis to find out explicitly the coefficients in the amplitude equation as functions of the rotation rate. These equations describe hexagons and os- cillating hexagons quite well, and include the Busse?Heikes (BH) model [Busse & Heikes, 1980] as a particular case. The sideband instabilities as well as short wavelength instabilities of such hexagonal patterns are discussed and the threshold for oscillating hexagons is determined
Cytotoxic polyfunctionality maturation of cytomegalovirus-pp65-specific CD4 + and CD8 + T-cell responses in older adults positively correlates with response size
Cytomegalovirus (CMV) infection is one of the most common persistent viral infections in humans worldwide and is epidemiologically associated with many adverse health consequences during aging. Previous studies yielded conflicting results regarding whether large, CMV-specific T-cell expansions maintain their function during human aging. In the current study, we examined the in vitro CMV-pp65-reactive T-cell response by comprehensively studying five effector functions (i.e., interleukin-2, tumor necrosis factor-α, interferon-γ, perforin, and CD107a expression) in 76 seropositive individuals aged 70 years or older. Two data-driven, polyfunctionality panels (IL-2-associated and cytotoxicity-associated) derived from effector function co-expression patterns were used to analyze the results. We found that, CMV-pp65-reactive CD8 + and CD4 + T cells contained similar polyfunctional subsets, and the level of polyfunctionality was related to the size of antigen-specific response. In both CD8 + and CD4 + cells, polyfunctional cells with high cytotoxic potential accounted for a larger proportion of the total response as the total response size increased. Notably, a higher serum CMV-IgG level was positively associated with a larger T-cell response size and a higher level of cytotoxic polyfunctionality. These findings indicate that CMV-pp65-specific CD4 + and CD8 + T cell undergo simultaneous cytotoxic polyfunctionality maturation during aging
Climate change projections of the North American Regional Climate Change Assessment Program (NARCCAP)
We investigate major results of the NARCCAP multiple regional climate model (RCM) experiments driven by multiple global climate models (GCMs) regarding climate change for seasonal temperature and precipitation over North America. We focus on two major questions: How do the RCM simulated climate changes differ from those of the parent GCMs and thus affect our perception of climate change over North America, and how important are the relative contributions of RCMs and GCMs to the uncertainty (variance explained) for different seasons and variables? The RCMs tend to produce stronger climate changes for precipitation: larger increases in the northern part of the domain in winter and greater decreases across a swath of the central part in summer, compared to the four GCMs driving the regional models as well as to the full set of CMIP3 GCM results. We pose some possible process-level mechanisms for the difference in intensity of change, particularly for summer. Detailed process-level studies will be necessary to establish mechanisms and credibility of these results. The GCMs explain more variance for winter temperature and the RCMs for summer temperature. The same is true for precipitation patterns. Thus, we recommend that future RCM-GCM experiments over this region include a balanced number of GCMs and RCMs
Расчёт напряженно-деформированного состояния виброизоляторов сложной формы
Розглянуто пружно-деформований стан гумових віброізоляторів з урахуванням контактної взаємодії з деталями конструкції.Stress-strain state of rubber vibroinsulators is considered, taking into account contact interaction with construction parts
Cross-correlation of the 2XMMi catalogue with Data Release 7 of the Sloan Digital Sky Survey
The Survey Science Centre of the XMM-Newton satellite released the first
incremental version of the 2XMM catalogue in August 2008 . With more than
220,000 X-ray sources, the 2XMMi was at that time the largest catalogue of
X-ray sources ever published and thus constitutes an unprecedented resource for
studying the high-energy properties of various classes of X-ray emitters such
as AGN and stars. The advent of the 7th release of the Sloan Digital Sky Survey
offers the opportunity to cross-match two major surveys and extend the spectral
energy distribution of many 2XMMi sources towards the optical bands. We here
present a cross-matching algorithm based on the classical likelihood ratio
estimator. The method developed has the advantage of providing true
probabilities of identifications without resorting to Monte-Carlo simulations.
Over 30,000 2XMMi sources have SDSS counterparts with individual probabilities
of identification higher than 90%. Using spectroscopic identifications from the
SDSS DR7 catalogue supplemented by extraction from other catalogues, we build
an identified sample from which the way the various classes of X-ray emitters
gather in the multi dimensional parameter space can be analysed. We investigate
two scientific use cases. In the first example we show how these
multi-wavelength data can be used to search for new QSO2s. Although no specific
range of observed properties allows us to identify Compton Thick QSO2s, we show
that the prospects are much better for Compton Thin AGN2 and discuss several
possible multi-parameter selection strategies. In a second example, we confirm
the hardening of the mean X-ray spectrum with increasing X-ray luminosity on a
sample of over 500 X-ray active stars and reveal that on average X-ray active M
stars display bluer colour indexes than less active ones (abridged).Comment: Accepted for publication in A&A. The corresponding fits file can be
downloaded from the XCat-DB home page (http://xcatdb.u-strasbg.fr/) (tools
and data). The file also contains line information for all SDSS spectroscopic
entries matching a 2XMM source. Results from the cross-correlation with the
2XMM DR3 are also available at the same location. 22 pages and 14 figure
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