588 research outputs found
Improved AdS/QCD Model with Matter
We study an improved AdS/QCD model at finite temperature and chemical
potential. An Ansatz for the beta-function for the boundary theory allows for
the derivation of a charged dilatonic black hole in bulk. The solution is
asymptotically RN-AdS in the UV and AdS2 * R3 in the IR. We discuss the
thermodynamical aspects of the solution. The fermionic susceptibilities are
shown to deviate from the free fermionic limits at asymptotic temperatures
despite the asymptotically free nature of the gauge coupling at the boundary.
The Polyakov line, the temporal and spatial string tensions dependence on both
temperature and chemical potential are also discussed
Holographic Pomeron: Saturation and DIS
We briefly review the approach to dipole-dipole scattering in holographic QCD
developed in ARXIV:1202.0831. The Pomeron is modeled by exchanging closed
strings between the dipoles and yields Regge behavior for the elastic
amplitude. We calculate curvature corrections to this amplitude in both a
conformal and confining background, identifying the holographic direction with
the virtuality of the dipoles. The it wee-dipole density is related to the
string tachyon diffusion in both virtuality and the transverse directions. We
give an explicit derivation of the dipole saturation momentum both in the
conformal and confining metric. Our holographic result for the dipole-dipole
cross section and the it wee-dipole density in the conformal limit are shown to
be identical in form to the BFKL pomeron result when the non-critical string
transverse dimension is . The total dipole-dipole cross section is
compared to DIS data from HERA
Jet quenching in shock waves
We study the propagation of an ultrarelativistic light quark jet inside a
shock wave using the holographic principle. The maximum stopping distance and
its dependency on the energy of the jet is obtained
Algorithmic Complexity for Short Binary Strings Applied to Psychology: A Primer
Since human randomness production has been studied and widely used to assess
executive functions (especially inhibition), many measures have been suggested
to assess the degree to which a sequence is random-like. However, each of them
focuses on one feature of randomness, leading authors to have to use multiple
measures. Here we describe and advocate for the use of the accepted universal
measure for randomness based on algorithmic complexity, by means of a novel
previously presented technique using the the definition of algorithmic
probability. A re-analysis of the classical Radio Zenith data in the light of
the proposed measure and methodology is provided as a study case of an
application.Comment: To appear in Behavior Research Method
Parallel Retention of Pdx2 Genes in Cartilaginous Fish and Coelacanths
The Pdx1 or Ipf1 gene encodes an important homeodomain-containing protein with key roles in pancreas development and function. Mutations in human PDX1 are implicated in developmental defects and disease of the pancreas. Extensive research, including genome sequencing, has indicated that Pdx1 is the only member of its gene family in mammals, birds, amphibians, and ray-finned fish, and with the exception of teleost fish, this gene forms part of the ParaHox gene cluster along with Gsx1 and Cdx2. The ParaHox cluster, however, is a remnant of a 4-fold genome duplication; the three other ParaHox paralogues lack a Pdx-like gene in all vertebrate genomes examined to date. We have used bacterial artificial chromosome cloning and synteny analysis to show that the ancestor of living jawed vertebrates in fact had more ParaHox genes, including two Pdx genes (Pdx1 and Pdx2). Surprisingly, the two Pdx genes have been retained in parallel in two quite distantly related lineages, the cartilaginous fish (sharks, skates, and chimeras) and the Indonesian coelacanth, Latimeria menadoensis. The Pdx2 gene has been lost independently in ray-finned fish and in tetrapods
Sox9-Haploinsufficiency Causes Glucose Intolerance in Mice
The HMG box transcription factor Sox9 plays a critical role in progenitor cell expansion during pancreas organogenesis and is required for proper endocrine cell development in the embryo. Based on in vitro studies it has been suggested that Sox9 controls expression of a network of important developmental regulators, including Tcf2/MODY5, Hnf6, and Foxa2, in pancreatic progenitor cells. Here, we sought to: 1) determine whether Sox9 regulates this transcriptional network in vivo and 2) investigate whether reduced Sox9 gene dosage leads to impaired glucose homeostasis in adult mice. Employing two genetic models of temporally-controlled Sox9 inactivation in pancreatic progenitor cells, we demonstrate that contrary to in vitro findings, Sox9 is not required for Tcf2, Hnf6, or Foxa2 expression in vivo. Moreover, our analysis revealed a novel role for Sox9 in maintaining the expression of Pdx1/MODY4, which is an important transcriptional regulator of beta-cell development. We further show that reduced beta-cell mass in Sox9-haploinsufficient mice leads to glucose intolerance during adulthood. Sox9-haploinsufficient mice displayed 50% reduced beta-cell mass at birth, which recovered partially via a compensatory increase in beta-cell proliferation early postnatally. Endocrine islets from mice with reduced Sox9 gene dosage exhibited normal glucose stimulated insulin secretion. Our findings show Sox9 plays an important role in endocrine development by maintaining Ngn3 and Pdx1 expression. Glucose intolerance in Sox9-haploinsufficient mice suggests that mutations in Sox9 could play a role in diabetes in humans
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