596 research outputs found
Some minimization problems for the free analogue of the Fisher information
We consider the free non-commutative analogue Phi^*, introduced by D.
Voiculescu, of the concept of Fisher information for random variables. We
determine the minimal possible value of Phi^*(a,a^*), if a is a non-commutative
random variable subject to the constraint that the distribution of aa^* is
prescribed. More generally, we obtain the minimal possible value of
Phi^*({a_{ij},a_{ij}^*), if {a_{ij}} is a family of non-commutative random
variables such that the distribution of AA^* is prescribed, where A is the
matrix (a_{ij}). The d*d-generalization is obtained from the case d=1 via a
result of independent interest, concerning the minimal value of
Phi^*({a_{ij},a_{ij}^*), when the matrix A=(a_{ij}) and its adjoint have a
given joint distribution. We then show how the minimization results obtained
for Phi^* lead to maximization results concerning the free entropy chi^*, also
defined by Voiculescu.Comment: 31 pages, Late
Random matrix theory for CPA: Generalization of Wegner's --orbital model
We introduce a generalization of Wegner's -orbital model for the
description of randomly disordered systems by replacing his ensemble of
Gaussian random matrices by an ensemble of randomly rotated matrices. We
calculate the one- and two-particle Green's functions and the conductivity
exactly in the limit . Our solution solves the CPA-equation of the
-Anderson model for arbitrarily distributed disorder. We show how the
Lloyd model is included in our model.Comment: 3 pages, Rev-Te
Rigorous mean field model for CPA: Anderson model with free random variables
A model of a randomly disordered system with site-diagonal random energy
fluctuations is introduced. It is an extension of Wegner's -orbital model to
arbitrary eigenvalue distribution in the electronic level space. The new
feature is that the random energy values are not assumed to be independent at
different sites but free. Freeness of random variables is an analogue of the
concept of independence for non-commuting random operators. A possible
realization is the ensemble of at different lattice-sites randomly rotated
matrices. The one- and two-particle Green functions of the proposed hamiltonian
are calculated exactly. The eigenstates are extended and the conductivity is
nonvanishing everywhere inside the band. The long-range behaviour and the
zero-frequency limit of the two-particle Green function are universal with
respect to the eigenvalue distribution in the electronic level space. The
solutions solve the CPA-equation for the one- and two-particle Green function
of the corresponding Anderson model. Thus our (multi-site) model is a rigorous
mean field model for the (single-site) CPA. We show how the Llyod model is
included in our model and treat various kinds of noises.Comment: 24 pages, 2 diagrams, Rev-Tex. Diagrams are available from the
authors upon reques
Endoplasmic Reticulum PI(3)P Lipid Binding Targets Malaria Proteins to the Host Cell
SummaryHundreds of effector proteins of the human malaria parasite Plasmodium falciparum constitute a “secretome” carrying a host-targeting (HT) signal, which predicts their export from the intracellular pathogen into the surrounding erythrocyte. Cleavage of the HT signal by a parasite endoplasmic reticulum (ER) protease, plasmepsin V, is the proposed export mechanism. Here, we show that the HT signal facilitates export by recognition of the lipid phosphatidylinositol-3-phosphate (PI(3)P) in the ER, prior to and independent of protease action. Secretome HT signals, including those of major virulence determinants, bind PI(3)P with nanomolar affinity and amino acid specificities displayed by HT-mediated export. PI(3)P-enriched regions are detected within the parasite's ER and colocalize with endogenous HT signal on ER precursors, which also display high-affinity binding to PI(3)P. A related pathogenic oomycete's HT signal export is dependent on PI(3)P binding, without cleavage by plasmepsin V. Thus, PI(3)P in the ER functions in mechanisms of secretion and pathogenesis
Impact of neutron star spin on Poynting-Robertson drag during a Type I X-ray burst
External irradiation of a neutron star (NS) accretion disc induces
Poynting-Robertson (PR) drag, removing angular momentum and increasing the mass
accretion rate. Recent simulations show PR drag significantly enhancing the
mass accretion rate during Type I X-ray bursts, which could explain X-ray
spectral features such as an increase in the persistent emission and a soft
excess. However, prograde spin of the NS is expected to weaken PR drag,
challenging its importance during bursts. Here, we study the effect of spin on
PR drag during X-ray bursts. We run four simulations, with two assuming a
non-spinning NS and two using a spin parameter of , corresponding to a
rotation frequency of 500 Hz. For each scenario, we simulate the disc evolution
subject to an X-ray burst and compare it to the evolution found with no burst.
PR drag drains the inner disc region during a burst, moving the inner disc
radius outward by km in the and by km in the
simulation. The burst enhances the mass accretion rate across the
innermost stable circular orbit times when the NS is not spinning
and times when it is spinning. The explanation for this seemingly
contradictory result is that the disc is closer to the NS when , and
the resulting stronger irradiating flux offsets the weakening effect of spin on
the PR drag. Hence, PR drag remains a viable explanation for the increased
persistent emission and soft excess observed during X-ray bursts in spinning NS
systems.Comment: 9 pages, 8 figures, accepted for publication in MNRA
The Free Quon Gas Suffers Gibbs' Paradox
We consider the Statistical Mechanics of systems of particles satisfying the
-commutation relations recently proposed by Greenberg and others. We show
that although the commutation relations approach Bose (resp.\ Fermi) relations
for (resp.\ ), the partition functions of free gases are
independent of in the range . The partition functions exhibit
Gibbs' Paradox in the same way as a classical gas without a correction factor
for the statistical weight of the -particle phase space, i.e.\ the
Statistical Mechanics does not describe a material for which entropy, free
energy, and particle number are extensive thermodynamical quantities.Comment: number-of-pages, LaTeX with REVTE
Metaphase and Interphase Cytogenetics with Alu-PCR-amplified Yeast Artificial Chromosome Clones Containing the BCR Gene and the Protooncogenes c-raf-1, c-fms, and c-erbB-21
A human yeast artificial chromosome (YAC) library was screened by polymerase chain reaction with oligonucleotide primers defined for DNA sequences of the BCR gene and the protooncogenes c-raf-1, c-fms, and c-erB-2. Alu-PCR-generated human DNA sequences were obtained from the respective YAC clones and used for fluorescence in situ hybridization experiments under suppression conditions. After chromosomal in situ suppression hybridization to GTG-banded human prometaphase chromosomes, seven of nine initially isolated YAC clones yielded strong signals exclusively in the chromosome bands containing the respective genes. Two clones yielded additional signals on other chromosomes and were excluded from further tests. The band-specific YACs were successfully applied to visualize specific structural chromosome aberrations in peripheral blood cells from patients with myelodysplasia exhibiting del(5)(q13q34), chronic myeloid leukemia and acute lymphocytic leukemia with t(9;22)(q34;q11), acute promyelocytic leukemia (M3) with t(15;17)(q22;q21), and in a cell line established from a proband with the constitutional translocation t(3;8)(p14.2;q24). In addition to the analysis of metaphase spreads, we demonstrate the particular usefulness of these YAC clones in combination with whole chromosome painting to analyze specific chromosome aberrations directly in the interphase nucleus
Superheavy nuclei in relativistic effective Lagrangian model
Isotopic and isotonic chains of superheavy nuclei are analyzed to search for
spherical double shell closures beyond Z=82 and N=126 within the new effective
field theory model of Furnstahl, Serot, and Tang for the relativistic nuclear
many-body problem. We take into account several indicators to identify the
occurrence of possible shell closures, such as two-nucleon separation energies,
two-nucleon shell gaps, average pairing gaps, and the shell correction energy.
The effective Lagrangian model predicts N=172 and Z=120 and N=258 and Z=120 as
spherical doubly magic superheavy nuclei, whereas N=184 and Z=114 show some
magic character depending on the parameter set. The magicity of a particular
neutron (proton) number in the analyzed mass region is found to depend on the
number of protons (neutrons) present in the nucleus.Comment: 26 pages, REVTeX, 10 ps figures; changed conten
Superheavy nuclei in relativistic effective Lagrangian model
Isotopic and isotonic chains of superheavy nuclei are analyzed to search for
spherical double shell closures beyond Z=82 and N=126 within the new effective
field theory model of Furnstahl, Serot, and Tang for the relativistic nuclear
many-body problem. We take into account several indicators to identify the
occurrence of possible shell closures, such as two-nucleon separation energies,
two-nucleon shell gaps, average pairing gaps, and the shell correction energy.
The effective Lagrangian model predicts N=172 and Z=120 and N=258 and Z=120 as
spherical doubly magic superheavy nuclei, whereas N=184 and Z=114 show some
magic character depending on the parameter set. The magicity of a particular
neutron (proton) number in the analyzed mass region is found to depend on the
number of protons (neutrons) present in the nucleus.Comment: 26 pages, REVTeX, 10 ps figures; changed conten
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