2,720 research outputs found
Instanton classical solutions of SU(3) fixed point actions on open lattices
We construct instanton-like classical solutions of the fixed point action of
a suitable renormalization group transformation for the SU(3) lattice gauge
theory. The problem of the non-existence of one-instantons on a lattice with
periodic boundary conditions is circumvented by working on open lattices. We
consider instanton solutions for values of the size (0.6-1.9 in lattice units)
which are relevant when studying the SU(3) topology on coarse lattices using
fixed point actions. We show how these instanton configurations on open
lattices can be taken into account when determining a few-couplings
parametrization of the fixed point action.Comment: 23 pages, LaTeX, 4 eps figures, epsfig.sty; some comments adde
Rapid evolution of female-biased genes among four species of Anopheles malaria mosquitoes.
Understanding how phenotypic differences between males and females arise from the sex-biased expression of nearly identical genomes can reveal important insights into the biology and evolution of a species. Among Anopheles mosquito species, these phenotypic differences include vectorial capacity, as it is only females that blood feed and thus transmit human malaria. Here, we use RNA-seq data from multiple tissues of four vector species spanning the Anopheles phylogeny to explore the genomic and evolutionary properties of sex-biased genes. We find that, in these mosquitoes, in contrast to what has been found in many other organisms, female-biased genes are more rapidly evolving in sequence, expression, and genic turnover than male-biased genes. Our results suggest that this atypical pattern may be due to the combination of sex-specific life history challenges encountered by females, such as blood feeding. Furthermore, female propensity to mate only once in nature in male swarms likely diminishes sexual selection of post-reproductive traits related to sperm competition among males. We also develop a comparative framework to systematically explore tissue- and sex-specific splicing to document its conservation throughout the genus and identify a set of candidate genes for future functional analyses of sex-specific isoform usage. Finally, our data reveal that the deficit of male-biased genes on the X Chromosomes in Anopheles is a conserved feature in this genus and can be directly attributed to chromosome-wide transcriptional regulation that de-masculinizes the X in male reproductive tissues
Electrostatics of Edge States of Quantum Hall Systems with Constrictions: Metal--Insulator Transition Tuned by External Gates
The nature of a metal--insulator transition tuned by external gates in
quantum Hall (QH) systems with point constrictions at integer bulk filling, as
reported in recent experiments of Roddaro et al. [1], is addressed. We are
particularly concerned here with the insulating behavior--the phenomena of
backscattering enhancement induced at high gate voltages. Electrostatics
calculations for QH systems with split gates performed here show that
observations are not a consequence of interedge interactions near the point
contact. We attribute the phenomena of backscattering enhancement to a
splitting of the integer edge into conducting and insulating stripes, which
enable the occurrence of the more relevant backscattering processes of
fractionally charged quasiparticles at the point contact. For the values of the
parameters used in the experiments we find that the conducting channels are
widely separated by the insulating stripes and that their presence alters
significantly the low-energy dynamics of the edges. Interchannel impurity
scattering does not influence strongly the tunneling exponents as they are
found to be irrelevant processes at low energies. Exponents of backscattering
at the point contact are unaffected by interchannel Coulomb interactions since
all channels have same chirality of propagation.Comment: 19 pages; To appear in Phys. Rev.
Properties of the Fixed Point Lattice Dirac Operator in the Schwinger Model
We present a numerical study of the properties of the Fixed Point lattice
Dirac operator in the Schwinger model. We verify the theoretical bounds on the
spectrum, the existence of exact zero modes with definite chirality, and the
Index Theorem. We show by explicit computation that it is possible to find an
accurate approximation to the Fixed Point Dirac operator containing only very
local couplings.Comment: 38 pages, LaTeX, 3 figures, uses style [epsfig], a few comments and
relevant references adde
Optical conductivity of one-dimensional doped Hubbard-Mott insulator
We study the optical response of a strongly correlated electron system near
the metal-insulator transition using a mapping to the sine-Gordon model. With
semiclassical quantization, the spectral weight is distributed between a Drude
peak and absorption lines due to breathers. We calculate the Drude weight, the
optical gap, and the lineshape of breather absorption.Comment: 4 pages, 2 EPS figures, REVTEX 4, a final versio
Tails of probability density for sums of random independent variables
The exact expression for the probability density for sums of a
finite number of random independent terms is obtained. It is shown that the
very tail of has a Gaussian form if and only if all the random
terms are distributed according to the Gauss Law. In all other cases the tail
for differs from the Gaussian. If the variances of random terms
diverge the non-Gaussian tail is related to a Levy distribution for
. However, the tail is not Gaussian even if the variances are
finite. In the latter case has two different asymptotics. At small
and moderate values of the distribution is Gaussian. At large the
non-Gaussian tail arises. The crossover between the two asymptotics occurs at
proportional to . For this reason the non-Gaussian tail exists at finite
only. In the limit tends to infinity the origin of the tail is shifted
to infinity, i. e., the tail vanishes. Depending on the particular type of the
distribution of the random terms the non-Gaussian tail may decay either slower
than the Gaussian, or faster than it. A number of particular examples is
discussed in detail.Comment: 6 pages, 4 figure
muCool: A novel low-energy muon beam for future precision experiments
Experiments with muons () and muonium atoms () offer
several promising possibilities for testing fundamental symmetries. Examples of
such experiments include search for muon electric dipole moment, measurement of
muon and experiments with muonium from laser spectroscopy to gravity
experiments. These experiments require high quality muon beams with small
transverse size and high intensity at low energy.
At the Paul Scherrer Institute, Switzerland, we are developing a novel device
that reduces the phase space of a standard beam by a factor of
with efficiency. The phase space compression is achieved by
stopping a standard beam in a cryogenic helium gas. The stopped
are manipulated into a small spot with complex electric and magnetic
fields in combination with gas density gradients. From here, the muons are
extracted into the vacuum and into a field-free region. Various aspects of this
compression scheme have been demonstrated. In this article the current status
will be reported.Comment: 8 pages, 5 figures, TCP 2018 conference proceeding
Poly(ADP-ribose) polymerase family member 14 (PARP14) is a novel effector of the JNK2-dependent pro-survival signal in multiple myeloma
Copyright @ 2013 Macmillan Publishers Limited. This is the author's accepted manuscript. The final published article is available from the link below.Regulation of cell survival is a key part of the pathogenesis of multiple myeloma (MM). Jun N-terminal kinase (JNK) signaling has been implicated in MM pathogenesis, but its function is unclear. To elucidate the role of JNK in MM, we evaluated the specific functions of the two major JNK proteins, JNK1 and JNK2. We show here that JNK2 is constitutively activated in a panel of MM cell lines and primary tumors. Using loss-of-function studies, we demonstrate that JNK2 is required for the survival of myeloma cells and constitutively suppresses JNK1-mediated apoptosis by affecting expression of poly(ADP-ribose) polymerase (PARP)14, a key regulator of B-cell survival. Strikingly, we found that PARP14 is highly expressed in myeloma plasma cells and associated with disease progression and poor survival. Overexpression of PARP14 completely rescued myeloma cells from apoptosis induced by JNK2 knockdown, indicating that PARP14 is critically involved in JNK2-dependent survival. Mechanistically, PARP14 was found to promote the survival of myeloma cells by binding and inhibiting JNK1. Moreover, inhibition of PARP14 enhances the sensitization of MM cells to anti-myeloma agents. Our findings reveal a novel regulatory pathway in myeloma cells through which JNK2 signals cell survival via PARP14, and identify PARP14 as a potential therapeutic target in myeloma.Kay Kendall Leukemia Fund, NIH, Cancer Research UK, Italian Association for Cancer Research and the Foundation for Liver Research
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