5,078 research outputs found
Renormalisation and fixed points in Hilbert Space
The energies of low-lying bound states of a microscopic quantum many-body
system of particles can be worked out in a reduced Hilbert space. We present
here and test a specific non-perturbative truncation procedure. We also show
that real exceptional points which may be present in the spectrum can be
identified as fixed points of coupling constants in the truncation procedure.Comment: 4 pages, 1 tabl
Interferons and tumor necrosis factors have similar catabolic effects on 3T3 L1 cells.
C4 olefin conversion on reduced nickel y faujasite. Evidence for C5 olefin formation via C4 olefin disproportionation
Metal-to-insulator transition and magnetic ordering in CaRu_{1-x}Cu_xO_3
CaRuO_3 is perovskite with an orthorhombic distortion and is believed to be
close to magnetic ordering. Magnetic studies of single crystal and
polycrystalline CaRu_{1-x}Cu_xO_3 (0\le x \le 15 at.%Cu) reveal that
spin-glass-like transition develops for x\le 7 at.%Cu and obtained value for
effective magnetic moment p_{eff}=3.55 mu_B for x=5 at.% Cu, single crystal,
indicates presence of Ru^{5+}. At higher Cu concentrations more complex
magnetic behaviors are observed. Electrical resistivity measured on
polycrystalline samples shows metal-to-insulator transition (MIT) at 51 K for
only 2 at.% Cu. Charge compensation, which is assumed to be present upon
Cu^{2+/3+} substitution, induces appearance of Ru^{5+} and/or creation of
oxygen vacancies in crystal structure. Since the observed changes in physical
properties are completely attributable to the charge compensation, they cannot
be related to behaviors of pure compound where no such mechanism is present.
This study provides the criterion for "good" chemical probes for studying
Ru-based perovskites.Comment: 12 pages, 7 figure
Quasi-Elastic Scattering in the Inclusive (He, t) Reaction
The triton energy spectra of the charge-exchange C(He,t) reaction
at 2 GeV beam energy are analyzed in the quasi-elastic nucleon knock-out
region. Considering that this region is mainly populated by the charge-exchange
of a proton in He with a neutron in the target nucleus and the final proton
going in the continuum, the cross-sections are written in the distorted-wave
impulse approximation. The t-matrix for the elementary exchange process is
constructed in the DWBA, using one pion- plus rho-exchange potential for the
spin-isospin nucleon- nucleon potential. This t-matrix reproduces the
experimental data on the elementary pn np process. The calculated
cross-sections for the C(He,t) reaction at to triton
emission angle are compared with the corresponding experimental data, and are
found in reasonable overall accord.Comment: 19 pages, latex, 11 postscript figures available at
[email protected], submitted to Phy.Rev.
Synthesis effects on the magnetic and superconducting properties of RuSr2GdCu2O8
A systematic study on the synthesis of the Ru-1212 compound by preparing a
series of samples that were annealed at increasing temperatures and then
quenched has been performed. It results that the optimal temperature for the
annealing lies around 1060-1065 C; a further temperature increase worsens the
phase formation. Structural order is very important and the subsequent grinding
and annealing improves it. Even if from the structural point of view the
samples appear substantially similar, the physical characterization highlight
great differences both in the electrical and magnetic properties related to
intrinsic properties of the phase as well as to the connection between the
grains as inferred from the resistive and the Curie Weiss behaviour at high
temperature as well as in the visibility of ZFC anf FC magnetic signals.Comment: 17 pages, 12 figures. Proc. Int. Workshop " Ruthenate and
rutheno-cuprate materials: theory and experiments", Vietri, October 2001. To
be published on LNP Series, Springer Verlag, Berlin, C. Noce, A. Vecchione,
M. Cuoco, A. Romano Eds, 200
Magnetoconductivity of quantum wires with elastic and inelastic scattering
We use a Boltzmann equation to determine the magnetoconductivity of quantum
wires. The presence of a confining potential in addition to the magnetic field
removes the degeneracy of the Landau levels and allows one to associate a group
velocity with each single-particle state. The distribution function describing
the occupation of these single-particle states satisfies a Boltzmann equation,
which may be solved exactly in the case of impurity scattering. In the case
where the electrons scatter against both phonons and impurities we solve
numerically - and in certain limits analytically - the integral equation for
the distribution function, and determine the conductivity as a function of
temperature and magnetic field. The magnetoconductivity exhibits a maximum at a
temperature, which depends on the relative strength of the impurity and
electron-phonon scattering, and shows oscillations when the Fermi energy or the
magnetic field is varied.Comment: 21 pages (revtex 3.0), 5 postscript figures available upon request at
[email protected] or [email protected]
Bridging the data gaps in the epidemiology of hepatitis C virus infection in Malaysia using multi-parameter evidence synthesis
BACKGROUND: Collecting adequate information on key epidemiological indicators is a prerequisite to informing a public health response to reduce the impact of hepatitis C virus (HCV) infection in Malaysia. Our goal was to overcome the acute data shortage typical of low/middle income countries using statistical modelling to estimate the national HCV prevalence and the distribution over transmission pathways as of the end of 2009. METHODS: Multi-parameter evidence synthesis methods were applied to combine all available relevant data sources - both direct and indirect - that inform the epidemiological parameters of interest. RESULTS: An estimated 454,000 (95% credible interval [CrI]: 392,000 to 535,000) HCV antibody-positive individuals were living in Malaysia in 2009; this represents 2.5% (95% CrI: 2.2-3.0%) of the population aged 15-64 years. Among males of Malay ethnicity, for 77% (95% CrI: 69-85%) the route of probable transmission was active or a previous history of injecting drugs. The corresponding proportions were smaller for male Chinese and Indian/other ethnic groups (40% and 71%, respectively). The estimated prevalence in females of all ethnicities was 1% (95% CrI: 0.6 to 1.4%); 92% (95% CrI: 88 to 95%) of infections were attributable to non-drug injecting routes of transmission. CONCLUSIONS: The prevalent number of persons living with HCV infection in Malaysia is estimated to be very high. Low/middle income countries often lack a comprehensive evidence base; however, evidence synthesis methods can assist in filling the data gaps required for the development of effective policy to address the future public health and economic burden due to HCV. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12879-014-0564-6) contains supplementary material, which is available to authorized users
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