660 research outputs found
Transverse-longitudinal HBT correlations in proton-antiproton collisions at root(s) = 630 GeV
Correlations of like-sign pion pairs emerging from proton-antiproton
collisions are analysed in the two-dimensional (q_L,q_T) decomposition of the
three-momentum difference q. While the data cannot be adequately represented by
gaussian, exponential, power-law or Edgeworth parametrisations, more elaborate
ones such as Levy and an exponential with a cross term do better. A two-scale
model using a hard cut to separate small and large scales may indicate a core
that is more prolate than the halo. Consideration not only of the interference
peak at small (q_L,q_T), but also of the shape of the correlation distribution
at intermediate momentum differences is crucial to understanding the data.Comment: 12 pages, 5 figures, uses elsart.cl
Face-Centered-Cubic B Metal: Density functional theory calculations
By means of ab initio calculations within the density functional theory, we
have found that B80 fullerenes can condense to form stable face-centered-cubic
fcc solids. It is shown that when forming a crystal, B80 cages are
geometrically distorted, the Ih symmetry is lowered to Th, and four boron-boron
chemical bonds are formed between every two nearest neighbor B80 cages. The
cohesive energy of B80 fcc solid is 0.23 eV/atom with respect to the isolated
B80 fullerene. The calculated electronic structure reveals that the fcc B80
solid is a metal. The predicted solid phase would constitute a form of pure
boron and might have diverse implications. In addition, a simple electron
counting rule is proposed, which could explain the stability of B80 fullerene
and the recently predicted stable boron sheet.Comment: 5 pages, 4 figure
Adaptive modulations of martensites
Modulated phases occur in numerous functional materials like giant
ferroelectrics and magnetic shape memory alloys. To understand the origin of
these phases, we review and generalize the concept of adaptive martensite. As a
starting point, we investigate the coexistence of austenite, adaptive 14M phase
and tetragonal martensite in Ni-Mn-Ga magnetic shape memory alloy epitaxial
films. The modulated martensite can be constructed from nanotwinned variants of
a tetragonal martensite phase. By combining the concept of adaptive martensite
with branching of twin variants, we can explain key features of modulated
phases from a microscopic view. This includes phase stability, the sequence of
6M-10M-NM intermartensitic transitions, and magnetocrystalline anisotropy.Comment: 4 pages manuscript, 8 pages supplemen
Enhanced Event-by-Event Fluctuations in Pion Multiplicity as a Signal of Disoriented Chiral Condensates at RHIC
The factorial moments of the pion multiplicity distributions are calculated
with HIJING and UrQMD and found to be independent of the pT range included, in
contrast to recent simulations with the linear sigma model which leads to large
enhancements for pions with transverse kinetic energies below 200 MeV. This
supports the use of the ratio of the factorial moments of low and high pT pions
as a signal of ``new'' physics at low momentum scales, such as the formation of
disoriented chiral condensates.Comment: 4 pages total, incl 4 eps figures ([email protected]
Tuning of crystal structure and magnetic properties by exceptionally large epitaxial strains
Huge deformations of the crystal lattice can be achieved in materials with
inherent structural instability by epitaxial straining. By coherent growth on
seven different substrates the in-plane lattice constants of 50 nm thick
Fe70Pd30 films are continuously varied. The maximum epitaxial strain reaches
8,3 % relative to the fcc lattice. The in-plane lattice strain results in a
remarkable tetragonal distortion ranging from c/abct = 1.09 to 1.39, covering
most of the Bain transformation path from fcc to bcc crystal structure. This
has dramatic consequences for the magnetic key properties. Magnetometry and
X-ray circular dichroism (XMCD) measurements show that Curie temperature,
orbital magnetic moment, and magnetocrystalline anisotropy are tuned over broad
ranges.Comment: manuscript, 3 figures, auxiliary materia
Integral correlation measures for multiparticle physics
We report on a considerable improvement in the technique of measuring
multiparticle correlations via integrals over correlation functions. A
modification of measures used in the characterization of chaotic dynamical
sytems permits fast and flexible calculation of factorial moments and cumulants
as well as their differential versions. Higher order correlation integral
measurements even of large multiplicity events such as encountered in heavy ion
collisons are now feasible. The change from ``ordinary'' to ``factorial''
powers may have important consequences in other fields such as the study of
galaxy correlations and Bose-Einstein interferometry.Comment: 23 pages, 6 tar-compressed uuencoded PostScript figures appended,
preprint TPR-92-4
Intermittency in Branching Processes
We study the intermittency properties of two branching processes, one with a
uniform and another with a singular splitting kernel. The asymptotic
intermittency indices, as well as the leading corrections to the asymptotic
linear regime are explicitly computed in an analytic framework. Both models are
found to possess a monofractal spectrum with . Relations with
previous results are discussed.Comment: 20 pages, UCLA93/TEP/2
Histone variant MacroH2A1 is downregulated in prostate cancer and influences malignant cell phenotype
Background: Prostate cancer (PCa), a major cause of cancer-related morbidity and mortality worldwide and mostly asymptomatic at earliest stages, is characterized by disruption of genetic and epigenetic balance. A better understanding of how those mechanisms orchestrate disease might improve diagnostic and prognostic tools, allowing for improvements in treatment efficacy. Replacement of canonical histones, an epigenetic mechanism, is highly conserved among species and altered expression of histones variants (e.g., MacroH2A1) has been associated with tumorigenesis. H2AFY gene encodes two isoforms of H2A histone variant MacroH2A1: MacroH2A1.1 and MacroH2A1.2. Specifically, MacroH2A1.1 isoform inhibits cell proliferation and promotes cellular differentiation. Because the contribution of this histone variant to carcinogenesis has been reported in several cancer types, but not for PCa, we aimed to investigate the contribution of MacroH2A1 for prostate carcinogenesis. Methods: MacroH2A1, MacroH2A1.1 and MacroH2A1.2 isoforms and the corresponding splicing regulators transcript levels were evaluated by RT-qPCR, in a tissue cohort composed by PCa, prostatic intraepithelial neoplasia (PIN) and normal prostate cases. Knockdown for MacroH2A1 and MacroH2A1.1 was performed through lentiviral transduction in DU145 cells, and MacroH2A1.1 overexpression was achieved in LNCaP cells by plasmid transfection, followed by functional assays. Biological and/or experimental replicates were performed when necessary, and specific statistical tests were applied to perform data analysis. Results: MacroH2A1.1 transcript levels were downregulated in PIN and primary PCa compared to normal prostate tissues. The same was found for QKI, a MacroH2A1.1's splicing regulator. Moreover, lower MacroH2A1.1 and QKI expression levels associated with less differentiated tumors (Gleason score ≥ 7). Interestingly, MacroH2A1.1, but more impressively DDX17 (AUC = 0.93; p < 0.0001) and QKI (AUC = 0.94; p < 0.0001), accurately discriminated cancerous from noncancerous prostate tissues. Furthermore, in PCa cell lines, total MacroH2A1 knockdown augmented malignant features, whereas MacroH2A1.1 overexpression impressively attenuated the malignant phenotype. Conclusions: Overall, our data, derived from primary PCa tissues and cell lines, anticipate a tumor suppressive role for MacroH2A1, particularly for the MacroH2A1.1 isoform, in prostate carcinogenesis
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