250 research outputs found
Buerger's disease manifesting nodular erythema with livedo reticularis
ArticleINTERNAL MEDICINE. 46(21):1815-1819(2007)journal articl
Dissecting early regulatory relationships in the lamprey neural crest gene network
The neural crest, a multipotent embryonic cell type, originates at the border between neural and nonneural ectoderm. After neural tube closure, these cells undergo an epithelial–mesenchymal transition, migrate to precise, often distant locations, and differentiate into diverse derivatives. Analyses of expression and function of signaling and transcription factors in higher vertebrates has led to the proposal that a neural crest gene regulatory network (NC-GRN) orchestrates neural crest formation. Here, we interrogate the NC-GRN in the lamprey, taking advantage of its slow development and basal phylogenetic position to resolve early inductive events, 1 regulatory step at the time. To establish regulatory relationships at the neural plate border, we assess relative expression of 6 neural crest network genes and effects of individually perturbing each on the remaining 5. The results refine an upstream portion of the NC-GRN and reveal unexpected order and linkages therein; e.g., lamprey AP-2 appears to function early as a neural plate border rather than a neural crest specifier and in a pathway linked to MsxA but independent of ZicA. These findings provide an ancestral framework for performing comparative tests in higher vertebrates in which network linkages may be more difficult to resolve because of their rapid development
Holographic Thermodynamics at Finite Baryon Density: Some Exact Results
We use the AdS/CFT correspondence to study the thermodynamics of massive N=2
supersymmetric hypermultiplets coupled to N=4 supersymmetric SU(Nc) Yang-Mills
theory in the limits of large Nc and large 't Hooft coupling. In particular, we
study the theory at finite baryon number density. At zero temperature, we
present an exact expression for the hypermultiplets' leading-order contribution
to the free energy, and in the supergravity description we clarify which
D-brane configuration is appropriate for any given value of the chemical
potential. We find a second-order phase transition when the chemical potential
equals the mass. At finite temperature, we present an exact expression for the
hypermultiplets' leading-order contribution to the free energy at zero mass.Comment: 21 pages, 1 figure; v2 corrected typos, added comments to sections
2.2 and 2.
Criticality, Scaling and Chiral Symmetry Breaking in External Magnetic Field
We consider a D7-brane probe of in the presence of pure
gauge -field. The dual gauge theory is flavored Yang-Mills theory in
external magnetic field. We explore the dependence of the fermionic condensate
on the bare quark mass and study the discrete self-similar behavior of
the theory near the origin of the parametric space. We calculate the critical
exponents of the bare quark mass and the fermionic condensate. A study of the
meson spectrum supports the expectation based on thermodynamic considerations
that at zero bare quark mass the stable phase of the theory is a chiral
symmetry breaking one. Our study reveals the self-similar structure of the
spectrum near the critical phase of the theory, characterized by zero fermionic
condensate and we calculate the corresponding critical exponent of the meson
spectrum.Comment: 29 pages, 9 figures. Accepted in JHEP. Updated to mach the published
version. One figure added, some definitions improve
Notes on Properties of Holographic Matter
Probe branes with finite worldvolume electric flux in the background created
by a stack of Dp branes describe holographically strongly interacting
fundamental matter at finite density. We identify two quantities whose leading
low temperature behavior is independent of the dimensionality of the probe
branes: specific heat and DC conductivity. This behavior can be inferred from
the dynamics of the fundamental strings which provide a good description of the
probe branes in the regime of low temperatures and finite densities. We also
comment on the speed of sound on the branes and the temperature dependence of
DC conductivity at vanishing charge density.Comment: 18 pages, 2 figures; v2: corrected error in Section 6, conclusions
unchanged; v3: improved figures and added clarifying comment
Reconstitution into liposomes of membrane proteins involved in ribosome binding on rough endoplasmic reticulum. Ribosome-binding capacity
Cold Nuclear Matter In Holographic QCD
We study the Sakai-Sugimoto model of holographic QCD at zero temperature and
finite chemical potential. We find that as the baryon chemical potential is
increased above a critical value, there is a phase transition to a nuclear
matter phase characterized by a condensate of instantons on the probe D-branes
in the string theory dual. As a result of electrostatic interactions between
the instantons, this condensate expands towards the UV when the chemical
potential is increased, giving a holographic version of the expansion of the
Fermi surface. We argue based on properties of instantons that the nuclear
matter phase is necessarily inhomogeneous to arbitrarily high density. This
suggests an explanation of the "chiral density wave" instability of the quark
Fermi surface in large N_c QCD at asymptotically large chemical potential. We
study properties of the nuclear matter phase as a function of chemical
potential beyond the transition and argue in particular that the model can be
used to make a semi-quantitative prediction of the binding energy per nucleon
for nuclear matter in ordinary QCD.Comment: 31 pages, LaTeX, 1 figure, v2: some formulae corrected, qualitative
results unchange
Holographic phase transitions at finite baryon density
We use holographic techniques to study SU(Nc) super Yang-Mills theory coupled
to Nf << Nc flavours of fundamental matter at finite temperature and baryon
density. We focus on four dimensions, for which the dual description consists
of Nf D7-branes in the background of Nc black D3-branes, but our results apply
in other dimensions as well. A non-zero chemical potential mu or baryon number
density n is introduced via a nonvanishing worldvolume gauge field on the
D7-branes. Ref. [1] identified a first order phase transition at zero density
associated with `melting' of the mesons. This extends to a line of phase
transitions for small n, which terminates at a critical point at finite n.
Investigation of the D7-branes' thermodynamics reveals that (d mu / dn)_T <0 in
a small region of the phase diagram, indicating an instability. We comment on a
possible new phase which may appear in this region.Comment: 33 pages, 22 figure
Thermodynamic Properties of Holographic Multiquark and the Multiquark Star
We study thermodynamic properties of the multiquark nuclear matter. The
dependence of the equation of state on the colour charges is explored both
analytically and numerically in the limits where the baryon density is small
and large at fixed temperature between the gluon deconfinement and chiral
symmetry restoration. The gravitational stability of the hypothetical
multiquark stars are discussed using the Tolman-Oppenheimer-Volkoff equation.
Since the equations of state of the multiquarks can be well approximated by
different power laws for small and large density, the content of the multiquark
stars has the core and crust structure. We found that most of the mass of the
star comes from the crust region where the density is relatively small. The
mass limit of the multiquark star is determined as well as its relation to the
star radius. For typical energy density scale of ,
the converging mass and radius of the hypothetical multiquark star in the limit
of large central density are approximately solar mass and 15-27 km.
The adiabatic index and sound speed distributions of the multiquark matter in
the star are also calculated and discussed. The sound speed never exceeds the
speed of light and the multiquark matters are thus compressible even at high
density and pressure.Comment: 27 pages, 17 figures, 1 table, JHEP versio
Self-bound dense objects in holographic QCD
We study a self-bound dense object in the hard wall model. We consider a
spherically symmetric dense object which is characterized by its radial density
distribution and non-uniform but spherically symmetric chiral condensate. For
this we analytically solve the partial differential equations in the hard wall
model and read off the radial coordinate dependence of the density and chiral
condensate according to the AdS/CFT correspondence. We then attempt to describe
nucleon density profiles of a few nuclei within our framework and observe that
the confinement scale changes from a free nucleon to a nucleus. We briefly
discuss how to include the effect of higher dimensional operator into our
study. We finally comment on possible extensions of our work.Comment: 17 pages, 5 figures, figures replaced, minor revision, to appear in
JHE
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