43 research outputs found
Legendre structure of the thermostatistics theory based on the Sharma-Taneja-Mittal entropy
The statistical proprieties of complex systems can differ deeply for those of
classical systems governed by Boltzmann-Gibbs entropy. In particular, the
probability distribution function observed in several complex systems shows a
power law behavior in the tail which disagrees with the standard exponential
behavior showed by Gibbs distribution. Recently, a two-parameter deformed
family of entropies, previously introduced by Sharma, Taneja and Mittal (STM),
has been reconsidered in the statistical mechanics framework. Any entropy
belonging to this family admits a probability distribution function with an
asymptotic power law behavior. In the present work we investigate the Legendre
structure of the thermostatistics theory based on this family of entropies. We
introduce some generalized thermodynamical potentials, study their
relationships with the entropy and discuss their main proprieties.
Specialization of the results to some one-parameter entropies belonging to the
STM family are presented.Comment: 11 pages, RevTex4; contribution to the international conference "Next
Sigma Phi" on News, EXpectations, and Trends in statistical physics, Crete
200
In-plane dipole coupling anisotropy of a square ferromagnetic Heisenberg monolayer
In this study we calculate the dipole-coupling-induced quartic in-plane
anisotropy of a square ferromagnetic Heisenberg monolayer. This anisotropy
increases with an increasing temperature, reaching its maximum value close to
the Curie temperature of the system. At T=0 the system is isotropic, besides a
small remaining anisotropy due to the zero-point motion of quantum mechanical
spins. The reason for the dipole-coupling-induced anisotropy is the disturbance
of the square spin lattice due to thermal fluctuations ('order-by-disorder'
effect). For usual ferromagnets its strength is small as compared to other
anisotropic contributions, and decreases by application of an external magnetic
field. The results are obtained from a Heisenberg Hamiltonian by application of
a mean field approach for a spin cluster, as well as from a many-body Green's
function theory within the Tyablikov-decoupling (RPA).Comment: 6 pages, 2 figures, accepted for publication in RP
Connections between Tsallis' formalisms employing the standard linear average energy and ones employing the normalized -average energy
Tsallis' thermostatistics with the standard linear average energy is
revisited by employing , which is the Tsallis entropy with
replaced by . We explore the connections among the approach and
the other different versions of Tsallis formalisms. It is shown that the
normalized -average energy and the standard linear average energy are
related to each other. The relations among the Lagrange multipliers of the
different versions are revealed. The relevant Legendre transform structures
concerning the Lagrange multipliers associated with the normalization of
probability are studied. It is shown that the generalized Massieu potential
associated with and the linear average energy is related to one
associated with the normalized Tsallis entropy and the normalized -average
energy.Comment: 16 pages, no figure, submitted to Physics Letter
Soft Photons in Hadron-Hadron Collisions: Synchrotron Radiation from the QCD Vacuum?
We discuss the production of soft photons in high energy hadron-hadron
collisions. We present a model where quarks and antiquarks in the hadrons emit
``synchrotron light'' when being deflected by the chromomagnetic fields of the
QCD vacuum, which we assume to have a nonperturbative structure. This gives a
source of prompt soft photons with frequencies in the c.m.
system of the collision in addition to hadronic bremsstrahlung. In comparing
the frequency spectrum and rate of ``synchrotron'' photons to experimental
results we find some supporting evidence for their existence. We make an
exclusive--inclusive connection argument to deduce from the ``synchrotron''
effect a behaviour of the neutron electric formfactor proportional
to for . We find this to be consistent with
available data. In our view, soft photon production in high energy
hadron-hadron and lepton-hadron collisions as well as the behaviour of
electromagnetic hadron formfactors for low are thus sensitive probes of
the nonperturbative structure of the QCD vacuum.Comment: Heidelberg preprint HD-THEP-94-36, 31 pages, LaTeX + ZJCITE.sty
(included), 12 figures appended as uuencoded compressed ps-fil
Additive and Multiplicative Noise Driven Systems in 1+1 Dimensions: Waiting Time Extraction of Nucleation Rates
We study the rate of true vacuum bubble nucleation numerically for a phi^4
field system coupled to a source of thermal noise. We compare in detail the
cases of additive and multiplicative noise. We pay special attention to the
choice of initial field configuration, showing the advantages of a version of
the quenching technique. We advocate a new method of extracting the nucleation
time scale that employs the full distribution of nucleation times. Large data
samples are needed to study the initial state configuration choice and to
extract nucleation times to good precision. The 1+1 dimensional models afford
large statistics samples in reasonable running times. We find that for both
additive and multiplicative models, nucleation time distributions are well fit
by a waiting time, or gamma, distribution for all parameters studied. The
nucleation rates are a factor three or more slower for the multiplicative
compared to the additive models with the same dimensionless parameter choices.
Both cases lead to high confidence level linear fits of ln(nucleation time) vs.
1/T plots, in agreement with semiclassical nucleation rate predictions.Comment: 38 pages, 20 figures, 6 table
AD51B in Familial Breast Cancer
Common variation on 14q24.1, close to RAD51B, has been associated with breast cancer: rs999737 and rs2588809 with the risk of female breast cancer and rs1314913 with the risk of male breast cancer. The aim of this study was to investigate the role of RAD51B variants in breast cancer predisposition, particularly in the context of familial breast cancer in Finland. We sequenced the coding region of RAD51B in 168 Finnish breast cancer patients from the Helsinki region for identification of possible recurrent founder mutations. In addition, we studied the known rs999737, rs2588809, and rs1314913 SNPs and RAD51B haplotypes in 44,791 breast cancer cases and 43,583 controls from 40 studies participating in the Breast Cancer Association Consortium (BCAC) that were genotyped on a custom chip (iCOGS). We identified one putatively pathogenic missense mutation c.541C>T among the Finnish cancer patients and subsequently genotyped the mutation in additional breast cancer cases (n = 5259) and population controls (n = 3586) from Finland and Belarus. No significant association with breast cancer risk was seen in the meta-analysis of the Finnish datasets or in the large BCAC dataset. The association with previously identified risk variants rs999737, rs2588809, and rs1314913 was replicated among all breast cancer cases and also among familial cases in the BCAC dataset. The most significant association was observed for the haplotype carrying the risk-alleles of all the three SNPs both among all cases (odds ratio (OR): 1.15, 95% confidence interval (CI): 1.11–1.19, P = 8.88 x 10−16) and among familial cases (OR: 1.24, 95% CI: 1.16–1.32, P = 6.19 x 10−11), compared to the haplotype with the respective protective alleles. Our results suggest that loss-of-function mutations in RAD51B are rare, but common variation at the RAD51B region is significantly associated with familial breast cancer risk
Comparative mutagenicity of two triarylmethane food dyes in salmonella, saccharomyces and drosophila
Construction of a high-resolution physical and transcription map of chromosome 16q24.3 - a region of frequent loss of heterozygosity in sporadic breast cancer
A breast cancer tumor suppressor gene has been localized to chromosome 16q24.3 by loss of heterozygosity (LOH) studies of breast tumor DNA. To identify candidate genes for this suppressor function, we have constructed a detailed physical map extending approximately 940 kb from the telomere of the long arm of chromosome 16 that encompasses the minimum LOH interval. This contig consists of a minimum overlapping set of 35 cosmids and a single PAC clone that were aligned by restriction enzyme site mapping. Cosmids were initially identified by screening filters with markers localized to the region by physical mapping using mouse/human somatic cell hybrids, and subsequently cosmid ends were used to complete the contig. A total of seven known genes, including PRSM1, PISSLRE, and the recently cloned Fanconi anemia A (FAA) gene, and potential transcripts from exon-trapping experiments have been located to this contig. A minimum of 14 new transcripts have been identified based on homology of trapped exons with database sequences. This contig and expressed sequence map will form the basis for the identification of the breast cancer tumor suppressor gene in this region.Scott A. Whitmore, Joanna Crawford, Sinoula Apostolou, Helen Eyre, Elizabeth Baker, Karen M. Lower, Chatri Settasatian, Sandra Goldup, Ram Seshadri, Rachel A. Gibson, Christopher G. Mathew, Anne-Marie Cleton-Jansen, Anna Savoia, Jan C. Pronk, Arleen D. Auerbach, Norman A. Doggett, Grant R. Sutherland, David F. Calle