252 research outputs found
Overcoming the critical slowing down of flat-histogram Monte Carlo simulations: Cluster updates and optimized broad-histogram ensembles
We study the performance of Monte Carlo simulations that sample a broad
histogram in energy by determining the mean first-passage time to span the
entire energy space of d-dimensional ferromagnetic Ising/Potts models. We first
show that flat-histogram Monte Carlo methods with single-spin flip updates such
as the Wang-Landau algorithm or the multicanonical method perform sub-optimally
in comparison to an unbiased Markovian random walk in energy space. For the
d=1,2,3 Ising model, the mean first-passage time \tau scales with the number of
spins N=L^d as \tau \propto N^2L^z. The critical exponent z is found to
decrease as the dimensionality d is increased. In the mean-field limit of
infinite dimensions we find that z vanishes up to logarithmic corrections. We
then demonstrate how the slowdown characterized by z>0 for finite d can be
overcome by two complementary approaches - cluster dynamics in connection with
Wang-Landau sampling and the recently developed ensemble optimization
technique. Both approaches are found to improve the random walk in energy space
so that \tau \propto N^2 up to logarithmic corrections for the d=1 and d=2
Ising model
Solving the large discrepancy between inclusive and exclusive measurements of the reaction cross section at astrophysical energies
A solution of the large discrepancy existing between inclusive and exclusive
measurements of the reaction
cross section at MeV is evaluated. This problem has profound
astrophysical relevance for this reaction is of great interest in Big-Bang and
r-process nucleosynthesis. By means of a novel technique, a comprehensive study
of all existing cross section
data is carried out, setting up a consistent picture in which all the inclusive
measurements provide the reliable value of the cross section. New unambiguous
signatures of the strong branch pattern non-uniformities, near the threshold of
higher excited levels, are presented and their possible
origin, in terms of the cluster structure of the involved excited states of
and nuclei, is discussed.Comment: 5 pages, 4 figures, 1 tabl
Systemic Immune Responses in Alzheimer’s Disease: In Vitro Mononuclear Cell Activation and Cytokine Production
To investigate the systemic signs of immune-inflammatory responses in Alzheimer’s disease (AD), in the present study
we have analyzed blood lymphocyte subsets and the expression of activation markers on peripheral blood mononuclear cells
(PBMCs) fromADpatients and age-matched healthy controls (HC) activated in vitro by recombinant amyloid-β peptide (rAβ42).
Our study of AD lymphocyte subpopulations confirms the already described decrease of the absolute number and percentage of
B cells when compared to HC lymphocytes, whereas the other subsets are not significantly different in patients and controls.
We report the increased expression of the activation marker CD69 and of the chemokine receptors CCR2 and CCR5 on T cells
but no changes of CD25 after activation. B cells are also activated by rAβ42 as demonstrated by the enhanced expression of
CCR5. Moreover, rAβ42 induces an increased expression of the scavenger receptor CD36 on monocytes. Some activation
markers and chemokine receptors are overexpressed in unstimulated AD cells when compared to controls. This is evidence of
the pro-inflammatory status of AD. Stimulation by rAβ42 also induces the production of the pro-inflammatory cytokines IL-1β,
IL-6, IFN-γ, and TNF-α, and of the anti-inflammatory cytokines IL-10 and IL-1Ra. The chemokines RANTES, MIP-1β, and
eotaxin as well as some growth factors (GM-CSF, G-CSF) are also overproduced by AD-derived PBMC activated by rAβ42.
These results support the involvement of systemic immunity in AD patients. However, our study is an observational one so we
cannot draw a conclusion about its contribution to the pathophysiology of the disease
The CMS RPC gas gain monitoring system: an overview and preliminary results
The status of the CMS RPC Gas Gain Monitoring (GGM) system developed at the
Frascati Laboratory of INFN (Istituto Nazionale di Fisica Nucleare) is reported
on. The GGM system is a cosmic ray telescope based on small RPC detectors
operated with the same gas mixture used by the CMS RPC system. The GGM gain and
efficiency are continuously monitored on-line, thus providing a fast and
accurate determination of any shift in working point conditions. The
construction details and the first result of GGM commissioning are described.Comment: 8 pages, 9 figures, uses lnfprepCMS.sty, presented by L. Benussi at
RPC07, Mumbai, INDIA 200
Gas Analysis and Monitoring Systems for the RPC Detector of CMS at LHC
The Resistive Plate Chambers (RPC) detector of the CMS experiment at the LHC
proton collider (CERN, Switzerland) will employ an online gas analysis and
monitoring system of the freon-based gas mixture used. We give an overview of
the CMS RPC gas system, describe the project parameters and first results on
gas-chromatograph analysis. Finally, we report on preliminary results for a set
of monitor RPC.Comment: 9 pages, 8 figures. Presented by Stefano Bianco (Laboratori Nazionali
di Frascati dell'INFN) at the IEEE NSS, San Diego (USA), October 200
On the magnitude of the 8Li + 4He → 11B + n reaction cross section at the Big-Bang temperature
n/
Cytolytic T-cell response against Epstein-Barr virus in lung cancer patients and healthy subjects
<p>Abstract</p> <p>Background</p> <p>This study aimed to examine whether EBV seropositive patients with lung cancer have an altered virus-specific CTL response, as compared to age-matched healthy controls and whether any variation in this response could be attributed to senescence.</p> <p>Methods</p> <p>Peripheral blood mononuclear cells from lung cancer patients, age-matched and younger healthy individuals were used to measure EBV-specific CTLs after in vitro amplification with the GLCTLVAML and RYSIFFDYM peptides followed by HLA-multimer staining.</p> <p>Results</p> <p>Lung cancer patients and aged-matched controls had significantly lesser EBV-specific CTL than younger healthy individuals. Multimer positive populations from either group did not differ with respect to the percentage of multimer positive CTLs and the intensity of multimer binding.</p> <p>Conclusions</p> <p>This study provides evidence that patients with lung cancer exhibit an EBV-specific CTL response equivalent to that of age-matched healthy counterparts. These data warrant the examination of whether young individuals have a more robust anti-tumor response, as is the case with the anti-EBV response.</p
Gas analysis and monitoring systems for the RPC detector of CMS at LHC
1-9, arXiv:physics/0701014. Publisher: Los AlamosNational Laboratoty, CODEN: LNPHF9
available at
http://arxiv.org/PS_cache/physics/pdf/0701/0701014v1.pd
Proposal for a systematic study of the CERN Closed Loop gas system used by the RPC muon detectors in CMS
http://www.lnf.infn.it/sis/preprint/pdf/getfile.php?filename=LNF-06-27(IR).pd
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