2,380 research outputs found
Polarization and energy dynamics in ultrafocused optical Kerr propagation
Developing a complete vectorial description of optical nonparaxial propagation of highly focused beams in Kerr media, we disclose a family of new phenomena. These phenomena appear to emerge as a consequence of the mutual coupling of all three components of the optical field. This circumstance, which is intrinsic to the very nature of Kerr propagation, was previously discarded on the basis of the conjecture that a reduced system is possible in which only one transverse field component interacts with the longitudinal component
The Adiabatic Piston and the Second Law of Thermodynamics
A detailed analysis of the adiabatic-piston problem reveals peculiar
dynamical features that challenge the general belief that isolated systems
necessarily reach a static equilibrium state. In particular, the fact that the
piston behaves like a perpetuum mobile, i.e., it never stops but keeps
wandering, undergoing sizable oscillations, around the position corresponding
to maximum entropy, has remarkable implications on the entropy variations of
the system and on the validity of the second law when dealing with systems of
mesoscopic dimensions.Comment: 6 pages, 4 figures, First International Conference on Quantum Limits
to the Second La
Absorption Effects due to Spin in the Worldline Approach to Black Hole Dynamics
We generalize the effective point particle approach to black hole dynamics to
include spin. In this approach dissipative effects are captured by degrees of
freedom localized on the wordline. The absorptive properties of the black hole
are determined by correlation functions which can be matched with the graviton
absorption cross section in the long wavelength approximation. For rotating
black holes, superradiance is responsible for the leading contribution. The
effective theory is then used to predict the power loss due to spin in the
dynamics of non-relativistic binary systems. An enhancement of three powers of
the relative velocity is found with respect to the non-rotating case. Then we
generalize the results to other type of constituents in the binary system, such
as rotating neutron stars. Finally we compute the power loss absorbed by a test
spinning black hole in a given spacetime background.Comment: 17 pages, 2 figures. v2 Typos and misprints fixe
Accumulation and thermalization of cold atoms in a finite-depth magnetic trap
We experimentally and theoretically study the continuous accumulation of cold
atoms from a magneto-optical trap (MOT) into a finite depth trap, consisting in
a magnetic quadrupole trap dressed by a radiofrequency (RF) field. Chromium
atoms (52 isotope) in a MOT are continuously optically pumped by the MOT lasers
to metastable dark states. In presence of a RF field, the temperature of the
metastable atoms that remain magnetically trapped can be as low as 25 microK,
with a density of 10^17 atoms.m-3, resulting in an increase of the phase-space
density, still limited to 7.10^-6 by inelastic collisions. To investigate the
thermalization issues in the truncated trap, we measure the free evaporation
rate in the RF-truncated magnetic trap, and deduce the average elastic cross
section for atoms in the 5D4 metastable states, equal to 7.0 10^-16m2.Comment: 9 pages, 10 Figure
Growth hormone (GH)‐induced reconstitution of CD8+ CD28+ T lymphocytes in a rare case of severe lymphopenia associated with Juvenile Haemochromatosis and Turner's syndrome.
Clin Endocrinol (Oxf). 2004 Oct;61(4):437-40.
Growth hormone (GH)-induced reconstitution of CD8+ CD28+ T lymphocytes in a rare case of severe lymphopenia associated with Juvenile Haemochromatosis and Turner's syndrome.
Porto G, Cruz E, Miranda HP, Porto B, Vasconcelos JC, Lacerda R, Roetto A, Daraio F, Bacelar C.
Santo António General Hospital, Porto, Portugal. [email protected]
Abstract
This paper describes a rare case of Turner's syndrome associated with Juvenile Haemochromatosis and severe lymphopenia, followed-up for a period of 5 years. Because of the indication for treatment with growth hormone (GH), this case was observed as a model to analyse the effects of GH on growth, iron mobilization and lymphocyte reconstitution. For this purpose, a serial study of the T lymphocyte subpopulations CD4+, CD8+, CD8+ CD28+ and CD8+ CD28- was performed by immunophenotyping during the follow-up period. Besides the impact of both phlebotomy treatment and GH on the rapid growth and mobilization of 20.8 g of iron in 136 weeks, the most relevant observation was the finding of a significant expansion of CD8+ T lymphocytes expressing the costimulatory marker CD28 in the setting of the severe lymphopenia. These findings constitute new clinical evidence supporting the notion that the GH/IGF-1 system has an important role on the maintenance of T cell homeostasis in vivo, and that GH may be regarded as a putative therapeutic agent in T lymphocyte reconstitution.
PMID: 15473875 [PubMed - indexed for MEDLINE
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