740 research outputs found
Spatial birth-and-death processes in random environment
We consider birth-and-death processes of objects (animals) defined in having unit death rates and random birth rates. For animals with
uniformly bounded diameter we establish conditions on the rate distribution
under which the following holds for almost all realizations of the birth rates:
(i) the process is ergodic with at worst power-law time mixing; (ii) the unique
invariant measure has exponential decay of (spatial) correlations; (iii) there
exists a perfect-simulation algorithm for the invariant measure. The results
are obtained by first dominating the process by a backwards oriented
percolation model, and then using a multiscale analysis due to Klein to
establish conditions for the absence of percolation.Comment: 48 page
The Infrared spectrum of very large (periodic) systems: global versus fragment strategies—the case of three defects in diamond
International audienc
rates of latent tuberculosis infection using different diagnostica test
Background.The interferonâgârelease assays (IGRA) are emerging as an attractive alternative to the tuberculin skin test (TST)
for the diagnosis of latent tuberculosis infection (LTBI).The absence of a gold standard for LTBI hampers the assessment of any
diagnostic test.
Methods.In a prospective study,229 patients (mean age 35.5±24.6 y) from different ward of the Hospital (Respiratory
Diseases,Dermatology, Rheumatology, Pediatrics, Infectious Diseases, Hematology and Transplant Unit) were simultaneously
tested for a suspect of either LTBI or active tuberculosis using all commercially available diagnostics: TST,QuantiFERONâTB
Gold (QFTâ2G), QuantiFERONâTB Gold InâTube(QFTâ3G) and TâSPOT.TB(TS.TB).
Results. 42(18.3%),37(16.2%),59(25.8%) and 79(34.5%) patients were positive with TST,QFTâ2G,QFTâ3G and TS.TB,
respectively.TS.TB(p<0.001) and QFTâ3G(p=0.016) provided more positive results than TST, while no difference was found for
TST and QFTâ2G(p=0.53).All IGRA showed a good overall agreement (TS.TB vs QFTâ2G,k=0.55; TS.TB vs
QFTâ3G,k=0.72;QFTâ2G vs QFTâ3G, k=0.62). In 22 subjects (9.6%) QFTâ3G was positive and QFTâ2G negative.
Indeterminate results were more frequent with QFTâ2G(18.3%) and QFTâ3G (12.7%) than with TS.TB(1.3%,p<0.0001).
Conclusion. Rates of LTBI as detected by different diagnostic tests may have significant variations. Performances of various
IGRA formats were variable in this population
Graphene growth on h-BN by Molecular Beam Epitaxy
The growth of single layer graphene nanometer size domains by solid carbon
source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is
demonstrated. Formation of single-layer graphene is clearly apparent in Raman
spectra which display sharp optical phonon bands. Atomic-force microscope
images and Raman maps reveal that the graphene grown depends on the surface
morphology of the h-BN substrates. The growth is governed by the high mobility
of the carbon atoms on the h-BN surface, in a manner that is consistent with
van der Waals epitaxy. The successful growth of graphene layers depends on the
substrate temperature, but is independent of the incident flux of carbon atoms.Comment: Solid State Communications, 201
Phases and geometry of the N=1 A_2 quiver gauge theory and matrix models
We study the phases and geometry of the N=1 A_2 quiver gauge theory using
matrix models and a generalized Konishi anomaly. We consider the theory both in
the Coulomb and Higgs phases. Solving the anomaly equations, we find that a
meromorphic one-form sigma(z)dz is naturally defined on the curve Sigma
associated to the theory. Using the Dijkgraaf-Vafa conjecture, we evaluate the
effective low-energy superpotential and demonstrate that its equations of
motion can be translated into a geometric property of Sigma: sigma(z)dz has
integer periods around all compact cycles. This ensures that there exists on
Sigma a meromorphic function whose logarithm sigma(z)dz is the differential. We
argue that the surface determined by this function is the N=2 Seiberg-Witten
curve of the theory.Comment: 41 pages, 2 figures, JHEP style. v2: references adde
Matrix metalloprotease activity is enhanced in the compensated but not in the decompensated phase of pressure overload hypertrophy
BACKGROUND: During the transition of pressure overload hypertrophy (POH) to heart failure (HF) there is intense interstitial cardiac remodeling, characterized by a complex balance between collagen deposition and degradation by matrix metalloproteases (MMPs). This study was aimed at investigating the process of cardiac remodeling during the different phases of the transition of POH to HF. METHODS: Guinea pigs underwent thoracic descending aortic banding or sham operation. Twelve weeks after surgery, left-ventricular (LV) end-diastolic internal dimension and ventricular systolic pressure were measured by combined M-mode echocardiography and micromanometer cathetherization. The MMP activity, tissue-specific MMP inhibitors (TIMPs), and collagen fraction were evaluated in LV tissue samples by zymography, ELISA, and computer-aided analysis, respectively. RESULTS: Banded animals were divided by lung weight values into either compensated left-ventricular hypertrophy (LVH) or HF groups, as compared with sham-operated controls. All HF animals exhibited a restrictive pattern of Doppler transmitral inflow, indicative of diastolic dysfunction, and developed lung congestion. Compensated LVH was associated with increased MMP-2 activity, which was blunted after transition to HF, at a time when TIMP-2 levels and collagen deposition were increased. CONCLUSIONS: The cardiac remodeling process that accompanies the development of POH is a phase-dependent process associated with progressive deterioration of cardiac function
Relation between energy metabolism, glycolysis, noradrenaline release and duration of ischemia
We studied the effect of 12-36 min of global ischemia followed by 36 min of reperfusion in Langendorff perfused rabbit hearts (n = 26). Metabolism was determined in terms of peak and total release of purines (adenosine, inosine, hypoxanthine), lactate and noradrenaline during reperfusion; and myocardial content of nucleotides (ATP, ADP, AMP), glycogen and noradrenaline at the end of reperfusion. An inverse relationship (r = -0.79) existed between duration of ischemia and developed pressure post-ischemia. Early during reperfusion, after 12 min of ischemia, the purine concentration (peak release) increased 100x (p < 0.01), that of lactate and noradrenaline 10x (p < 0.05). Total purine release rose with progression of the ischemic period (30x after 36 min of ischemia; p < 0.01), concomitant with a reduction in nucleotide content. Lactate release was independent from the duration of ischemia, although glycogen had declined by 30\% (p < 0.01) after 36 min of ischemia. The acid insoluble glycogen fraction, which presumably contains proglycogen, increased substantially during short-term ischemia. Peak noradrenaline increased 100x, and 200x, (p < 0.05) after 24 and 36 min of ischemia, respectively. Total noradrenaline release due to various periods of ischemia mirrored its peak release. Function recovery was inversely related to total purine and noradrenaline efflux (both r = -0.81); it correlated with tissue nucleotide content (r = 0.84). In conclusion, larger amounts of noradrenaline are released only after a substantial drop in myocardial ATP. During severe ischemia ATP consumption more than limited ATP production by anaerobic glycolysis, is a key factor affecting recovery on subsequent reperfusion. In contrast to lactate efflux, purine and noradrenaline release are useful markers of ischemic and reperfusion damage
Safer in the Clouds (Extended Abstract)
We outline the design of a framework for modelling cloud computing
systems.The approach is based on a declarative programming model which takes
the form of a lambda-calculus enriched with suitable mechanisms to express and
enforce application-level security policies governing usages of resources
available in the clouds. We will focus on the server side of cloud systems, by
adopting a pro-active approach, where explicit security policies regulate
server's behaviour.Comment: In Proceedings ICE 2010, arXiv:1010.530
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