10,330 research outputs found
Response to tilted magnetic fields in Bi2Sr2CaCu2O8 with columnar defects: Evidence for transverse Meissner effect
The transverse Meissner effect (TME) in the highly layered superconductor
Bi2Sr2CaCu2O(8+y) with columnar defects is investigated by transport
measurements. We present detailed evidence for the persistence of the
Bose-glass phase when H is tilted at an angle theta < theta_c (T) away from the
column direction: (i) the variable-range vortex hopping process for low
currents crosses over to the half-loops regime for high currents; (ii) in both
regimes near theta_c(T) the energy barriers vanish linearly with tan(theta) ;
(iii) the transition temperature is governed by T_{BG}(0) -T_{BG}(theta) sim
|tan(theta)|^{1/\nu_{\perp}} with \nu_{\perp}=1.0 +/- 0.1. Furthermore, above
the transition as theta->\theta_c+, moving kink chains consistent with a
commensurate-incommensurate transition scenario are observed. These results
thereby clearly show the existence of the TME for theta < theta_c(T).Comment: 4 pages, RevTeX, 5 EPS figure
A statistical model for epigenetic control of miRNAs
microRNAs are small, non-coding RNAs involved in post-transcriptional gene regulation. Since the dysregulation of only a few miRNAs can affect many biological pathways, miRNAs are thought to play a key role in cancer development and can be used as biomarkers for cancer diagnosis and prognosis. In order to understand how miRNA dysregulation leads to a cancer phenotype it is important to determine the basic regulatory mechanisms that drive miRNA expression. Although much is known about miRNA-mediated post-transcriptional regulation, little is known about the epigenetic control of miRNAs. Here, we performed cell-line specific miRNA promoter predictions and built a classification model for expressed and non-expressed miRNAs based on several epigenetic features, e.g. histone marks and DNA methylation at both, miRNA promoters and around miRNA hairpins. We were able to classify intragenic and intergenic miRNAs with an accuracy of 79% and 85%, respectively, and identified the most important features for classification via feature selection. Surprisingly, we found that DNA methylation seems to have a dual role in regulating miRNA expression at transcriptional level: at promoters, high levels of DNA methylation correlate with transcriptional repression, while around miRNA hairpins high levels of DNA methylation have a positive impact on the expression level of the mature miRNA
Effect of field tilting on the vortices in irradiated Bi-2212
We report on transport measurements in a Bi-2212 single crystal with columnar
defects parallel to the c-axis. The tilt of the magnetic field away from the
direction of the tracks is studied for filling factors f=B_z/B_phi<1. Near the
Bose Glass transition temperature T_BG, the angular scaling laws are verified
and we find the field independent critical exponents nu'=1.1 and z'=5.30.
Finally, above H_perpC we evidence the signature of a smectic-A like vortex
phase. These experimental results provide support for the Bose Glass theory.Comment: 2 pages LaTeX, 2 EPS figures, uses fleqn and espcrc2 style macros.
Submitted to Proceedings of M2S-HTSC-V
Influência de diferentes embalagens e temperaturas de armazenamento na aparência de camu-camu (myrciaria dubia).
Effective restoration of the U_A(1) symmetry with temperature and density
We investigate the full U(3)U(3) chiral symmetry restoration, at
finite temperature and density, on the basis of a quark model which
incorporates the most relevant properties of QCD in this context: explicit and
spontaneous breaking of chiral symmetry and axial U(1) symmetry breaking. A
specific lattice-inspired behavior of the topological susceptibility, combined
with the convergence of chiral partners, signals the onset of an effective
chiral symmetry restoration. The results suggest that the axial part of the
symmetry is restored before the possible restoration of the full
U(3)U(3) chiral symmetry can occur. This conclusion is valid in the
context of both finite temperature and density.Comment: 5 pages, 2 figures; PRD versio
Chaos and Synchronized Chaos in an Earthquake Model
We show that chaos is present in the symmetric two-block Burridge-Knopoff
model for earthquakes. This is in contrast with previous numerical studies, but
in agreement with experimental results. In this system, we have found a rich
dynamical behavior with an unusual route to chaos. In the three-block system,
we see the appearance of synchronized chaos, showing that this concept can have
potential applications in the field of seismology.Comment: To appear in Physical Review Letters (13 pages, 6 figures
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