864 research outputs found
Regular 3-charge 4D black holes and their microscopic description
The perturbative corrections to Type-IIA String Theory
compactified on a Calabi-Yau three-fold allow the construction of regular
three-charge supersymmetric black holes in four dimensions, whose entropy
scales with the charges as .
We construct an M-theory uplift of these quantum black holes and show that they
can be interpreted as arising from three stacks of M2 branes on a conical
singularity. This in turns allow us relate them via a series of dualities to a
system of D3 branes carrying momentum and thus to give a microscopic
interpretation of their entropy.Comment: 20 pages, LaTe
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Leptin and Its Emerging Role in Children and Adolescents
Leptin is an adipocyte-secreted hormone which plays a key role in energy homeostasis. Recent “proof of concept” studies involving leptin administration to humans support its critical role in regulating energy homeostasis, neuroendocrine and immune function as well as insulin resistance in states of energy/ caloric deprivation. Moreover, interventional studies in leptin deficient children and observational studies in normal girls and boys support a role for leptin as a permissive factor for the initiation of puberty in children. The potential clinical usefulness of leptin in several disease states in children and adolescents, including hypothalamic amenorrhea, eating disorders and syndromes of insulin resistance is still under investigation
Interface properties of the NiMnSb/InP and NiMnSb/GaAs contacts
We study the electronic and magnetic properties of the interfaces between the
half-metallic Heusler alloy NiMnSb and the binary semiconductors InP and GaAs
using two different state-of-the-art full-potential \textit{ab-initio}
electronic structure methods. Although in the case of most NiMnSb/InP(001)
contacts the half-metallicity is lost, it is possible to keep a high degree of
spin-polarization when the interface is made up by Ni and P layers. In the case
of the GaAs semiconductor the larger hybridization between the Ni- and
As- orbitals with respect to the hybridization between the Ni- and P-
orbitals destroys this polarization. The (111) interfaces present strong
interface states but also in this case there are few interfaces presenting a
high spin-polarization at the Fermi level which can reach values up to 74%.Comment: 9 pages, 9 figure
Propagators for p-forms in AdS_{2p+1} and correlation functions in the AdS_7/(2,0) CFT correspondence
In AdS_{2p+1} we construct propagators for p-forms whose lagrangians contain
terms of the form A / d A. In particular we explore the case of forms
satisfying ``self duality in odd dimensions'', and the case of forms with a
topological mass term. We point out that the ``complete'' set of maximally
symmetric bitensors previously used in all the other propagator papers is
incomplete - there exists another bitensor which can and does appear in the
formulas for the propagators in this particular case. Nevertheless, its
presence does not affect the other propagators computed so far.
On the AdS side of the correspondence we compute the 2 and 3 point functions
involving the self-dual tensor of the maximal 7d gauged supergravity (sugra),
S_{\mu\nu\rho}. Since the 7 dimensional antisymmetric self-dual tensor obeys
first order field equations (S + * d S=0), to get a nonvanishing 2 point
function we add a certain boundary term (to satisfy the variational principle
on a manifold with boundary) to the 7d action. The 3 point functions we compute
are of the type SSB and SBB, describing vertex interactions with the gauge
fields B_{\mu}.Comment: 21 pages, Latex file, one reference adde
Exotic polarizations of D2 branes and oblique vacua of (S)YM
We investigate the oblique vacua in the perturbed 2+1 dimensional gauge
theory living on D2 branes. The string theory dual of these vacua is expected
to correspond to polarizations of the D2 branes into NS5 branes with D4 brane
charge. We perturb the gauge theory by adding fermions masses. In the
nonsupersymmetric case, we also consider the effect of slight variations of the
masses of the scalars. For certain ranges of scalar masses we find oblique
vacua.
We show that D4 charge is an essential ingredient in understanding D2 -> NS5
polarizations. We find that some of the polarization states which appear as
metastable vacua when D4 charge is not considered are in fact unstable. They
decay by acquiring D4 charge, tilting and shrinking to zero size.Comment: 15 pages, 3 figures, LaTe
Important differences in nitric oxide synthase activity and predominant isoform in reproductive tissues from human and rat
For the extrapolation of data obtained from experimental animals to the human situation, it is important to know the similarities and differences between human and animal species. Some important characteristics of nitric oxide synthase (NOS) in myometrium and vagina from human and rat were compared. NOS-activity was measured by the formation of (14)C-citrulline from (14)C-arginine and the expression of NOS isoforms was examined by Western blotting. NOS activity in human uterus and vagina was significantly lower than in the tissues from rat. In contrast to the rat where NOS activity was predominantly found in the cytosolic fractions, NOS activity in particulate and cytosolic fractions from both human myometrium and vagina was similar. Data from Western blots confirmed that eNOS and nNOS isoforms were concentrated in the particulate and cytosolic fractions, respectively. Estrogen treatment of rats resulted in a down regulation of uterine cytosolic NOS activity. A down regulation of NOS in the cytosolic fraction was also seen in the human pregnant myometrium as compared with the nonpregnant myometrium. The vaginal NOS activity was considerably higher than the uterus in both species. In spite of some clear-cut qualitative and other differences between human and rat tissues, there are some interesting similarities. Downregulation in pregnancy of human uterine NOS is probably due to, at least in part, the influence of estrogen and progesterone
Isospectral domains with mixed boundary conditions
We construct a series of examples of planar isospectral domains with mixed
Dirichlet-Neumann boundary conditions. This is a modification of a classical
problem proposed by M. Kac.Comment: 9 figures. Statement of Theorem 5.1 correcte
Career Management in the Artistic Field
Career management is a concept of interest at present for organizations that aim to maintain staff employment in the long term, with the expected performance. This study looks at aspects of artistic career management within a musical theatre. The empirical research approach includes an analysis of how the artistic career is managed, starting with the studies followed by the activities that employees carry out today and projections for the future. The results of the study show that the studies completed by respondents are compatible with the current job, and the general perception of career is related to the exercise of passion
Extreme plasma states in laser-governed vacuum breakdown
Triggering vacuum breakdown at the upcoming laser facilities can provide
rapid electron-positron pair production for studies in laboratory astrophysics
and fundamental physics. However, the density of the emerging plasma should
seemingly stop rising at the relativistic critical density, when the plasma
becomes opaque. Here we identify the opportunity of breaking this limit using
optimal beam configuration of petawatt-class lasers. Tightly focused laser
fields allow plasma generation in a small focal volume much less than
, and creating extreme plasma states in terms of density and
produced currents. These states can be regarded as a new object of nonlinear
plasma physics. Using 3D QED-PIC simulations we demonstrate the possibility of
reaching densities of more than cm, which is an order of
magnitude higher than previously expected. Controlling the process via the
initial target parameters gives the opportunity to reach the discovered plasma
states at the upcoming laser facilities
A Note on (Meta)stable Brane Configurations in MQCD
We examine the M-theory version of SQCD which is known as MQCD. In the IIA
limit, this theory appears to have a supersymmetry-breaking brane configuration
which corresponds to the meta-stable state of N=1 SU(Nc) SQCD. However, the
behavior at infinity of this non-supersymmetric brane construction differs from
that of the supersymmetric ground state of MQCD. We interpret this to mean that
it is not a meta-stable state in MQCD, but rather a state in another theory.
This provides a concrete example of the fact that, while MQCD accurately
describes the supersymmetric features of SCQD, it fails to reproduce its
non-supersymmetric features (such as meta-stable states) not only
quantitatively but also qualitatively.Comment: 30 pages, 7 figures, harvmac. v2 typo correcte
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