1,245 research outputs found
Endocardite infectieuse en milieu cardiologique Dakarois: étude descriptive à propos de 39 cas
L’endocardite infectieuse est une complication fréquente des cardiopathies rhumatismales. L’objectif de ce travail était de faire une étude descriptive de l’endocardite infectieuse, en milieu hospitalier Dakarois. Il s’agit d’une étude rétrospective, descriptive, réalisée à la clinique cardiologique de l’hôpital Aristide Le Dantec, durant la période allant de Janvier
2004 à Décembre 2008. Etaient inclus tous les patients hospitalisés et traités pour endocardite infectieuse certaine ou probable, selon les critères de Durack. Nous avons étudié les paramètres épidémiologiques, cliniques, biologiques et échocardiographiques. Le nombre total d’admissions dans le service durant la période d’étude était de 3746 patients, dont 870 pour valvulopathies rhumatismales. Nous avions enregistré 39 cas d’endocardite infectieuse soit une prévalence de 1,04% et 4,48% valvulopathies rhumatismales. L’âge moyen de nos
patients était de 24 plus ou moins 11,5 ans avec des extrêmes de 6 et 52 ans. Plus de la moitié des patients soit 58,9 % (23 patients) avaient moins de 25 ans. On notait une légère prédominance féminine avec un sex-ratio homes/femmes de 0,95. La porte d’entrée était essentiellement bucco-dentaire 40%. L’anémie était constante avec un taux d’hémoglobine moyen à 8,4g/dl. Les hémocultures étaient positives chez 6 patients et le Staphylococcus Aureus était le germe le plus retrouvé. L’électrocardiogramme avait montré des troubles du rythme et de la conduction respectivement dans 69,2 et 10,2% des cas. L’échographie cardiaque mettait en évidence des végétations chez tous les patients, une rupture de cordage dans 6 cas et un abcès chez trois patients. L’endocardite infectieuse constitue encore une réalité dans nos régions. Elle survient habituellement sur cardiopathie rhumatismale. Son diagnostic repose sur les hémocultures et l’échocardiographie
Hypertension artérielle pulmonaire au cours de la sclérodermie: à propos de 12 cas
Introduction: La survenue de l’hypertension artérielle pulmonaire (HTAP) est un tournant dans l’évolution de la sclérodermie. L’objectif de cette étude est de décrire les aspects épidémiologiques et évolutifs de l’HTAP au cours de la sclérodermie systémique.Méthodes: Nous avons réalisé une étude descriptive concernant des patients suivis pour sclérodermie systémique, au service de Dermatologie de l’hôpital Aristide Le Dantec entre Janvier 2000 et Août 2009. Ces patients étaient inclus dans l’étude après exploration cardio-vasculaire (ECG, échocardiographie-Doppler). Nous avons étudié les paramètres épidémiologiques, cliniques, paracliniques et évolutifs des patients. Résultats: Nous avons enregistré 12 cas d’hypertension artérielle pulmonaire parmi les 83 patients atteints de sclérodermie systémique soit une prévalence de 14,45%. L’âge moyen des patients était de 43,58 ans ± 12,5 ans et le sex-ratio (H/F) de 0,33. Sur le plan clinique, la dyspnée était quasi constante (75%) et la douleur thoracique présente dans 25% des cas. Le syndrome de Raynaud était observé chez 8 patients soit 66,67% de nos patients. L’électrocardiogramme montrait des signes de surcharge droite chez 4 malades (33,33%) et la radiographie thoracique en faveur d’une fibrose pulmonaire chez 4 patients. L’échocardiographie-Doppler notait une insuffisance tricuspide importante dans 58, 33% des cas (7 patients), une pression artérielle pulmonaire systolique (PAPs) en moyenne de 66,25 ± 29,3 mmHg, une dilatation des cavités cardiaques droites dans 5 cas et un mouvement paradoxal du septum interventriculaire chez 3 malades (33,33%). Il était également noté 3 cas (25%) d’épanchement péricardique. Nous avons déploré 4 décès (33,33%).Conclusion: L’hypertension artérielle pulmonaire est une complication fréquente et grave de la sclérodermie. Son dépistage, grâce à l’échocardiographie- Doppler systématique, constitue une étape fondamentale de la prise en charge
Spinless impurities and Kondo-like behavior in strongly correlated electron systems
We investigate magnetic properties induced by a spinless impurity in strongly
correlated electron systems, i.e. the Hubbard model in the spatial dimension
and 3. For the 1D system exploiting the Bethe ansatz exact solution we
find that the spin susceptibility and the local density of states in the
vicinity of a spinless impurity show divergent behaviors. The results imply
that the induced local moment is not completely quenched at any finite
temperatures. On the other hand, the spin lattice relaxation rate obtained by
bosonization and boundary conformal field theory satisfies a relation analogous
to the Korringa law, . In the 2D and 3D systems, the
analysis based upon the antiferromagnetically correlated Fermi liquid theory
reveals that the antiferromagnetic spin fluctuation developed in the bulk is
much suppressed in the vicinity of a spinless impurity, and thus magnetic
properties are governed by the induced local moment, which leads to the
Korringa law of .Comment: 9pages,1figure, final version accepted for publication in
Phys.Rev.B(Jan2001
Boundary contributions to specific heat and susceptibility in the spin-1/2 XXZ chain
Exact low-temperature asymptotic behavior of boundary contribution to
specific heat and susceptibility in the one-dimensional spin-1/2 XXZ model with
exchange anisotropy 1/2 < \Delta \le 1 is analytically obtained using the
Abelian bosonization method. The boundary spin susceptibility is divergent in
the low-temperature limit. This singular behavior is caused by the first-order
contribution of a bulk leading irrelevant operator to boundary free energy. The
result is confirmed by numerical simulations of finite-size systems. The
anomalous boundary contributions in the spin isotropic case are universal.Comment: 6 pages, 3 figures; corrected typo
Photonic Analogue of Two-dimensional Topological Insulators and Helical One-Way Edge Transport in Bi-Anisotropic Metamaterials
Recent progress in understanding the topological properties of condensed
matter has led to the discovery of time-reversal invariant topological
insulators. Because of limitations imposed by nature, topologically non-trivial
electronic order seems to be uncommon except in small-band-gap semiconductors
with strong spin-orbit interactions. In this Article we show that artificial
electromagnetic structures, known as metamaterials, provide an attractive
platform for designing photonic analogues of topological insulators. We
demonstrate that a judicious choice of the metamaterial parameters can create
photonic phases that support a pair of helical edge states, and that these edge
states enable one-way photonic transport that is robust against disorder.Comment: 13 pages, 3 figure
Holographic Conductivity in Disordered Systems
The main purpose of this paper is to holographically study the behavior of
conductivity in 2+1 dimensional disordered systems. We analyze probe D-brane
systems in AdS/CFT with random closed string and open string background fields.
We give a prescription of calculating the DC conductivity holographically in
disordered systems. In particular, we find an analytical formula of the
conductivity in the presence of codimension one randomness. We also
systematically study the AC conductivity in various probe brane setups without
disorder and find analogues of Mott insulators.Comment: 43 pages, 28 figures, latex, references added, minor correction
Hydrodynamics of R-charged D1-branes
We study the hydrodynamic properties of strongly coupled Yang-Mills
theory of the D1-brane at finite temperature and at a non-zero density of
R-charge in the framework of gauge/gravity duality. The gravity dual
description involves a charged black hole solution of an
Einstein-Maxwell-dilaton system in 3 dimensions which is obtained by a
consistent truncation of the spinning D1-brane in 10 dimensions. We evaluate
thermal and electrical conductivity as well as the bulk viscosity as a function
of the chemical potential conjugate to the R-charges of the D1-brane. We show
that the ratio of bulk viscosity to entropy density is independent of the
chemical potential and is equal to . The thermal conductivity and bulk
viscosity obey a relationship similar to the Wiedemann-Franz law. We show that
at the boundary of thermodynamic stability, the charge diffusion mode becomes
unstable and the transport coefficients exhibit critical behaviour. Our method
for evaluating the transport coefficients relies on expressing the second order
differential equations in terms of a first order equation which dictates the
radial evolution of the transport coefficient. The radial evolution equations
can be solved exactly for the transport coefficients of our interest. We
observe that transport coefficients of the D1-brane theory are related to that
of the M2-brane by an overall proportionality constant which sets the
dimensions.Comment: 57 pages, 12 figure
Topological Surface States Protected From Backscattering by Chiral Spin Texture
Topological insulators are a new class of insulators in which a bulk gap for
electronic excitations is generated by strong spin orbit coupling. These novel
materials are distinguished from ordinary insulators by the presence of gapless
metallic boundary states, akin to the chiral edge modes in quantum Hall
systems, but with unconventional spin textures. Recently, experiments and
theoretical efforts have provided strong evidence for both two- and
three-dimensional topological insulators and their novel edge and surface
states in semiconductor quantum well structures and several Bi-based compounds.
A key characteristic of these spin-textured boundary states is their
insensitivity to spin-independent scattering, which protects them from
backscattering and localization. These chiral states are potentially useful for
spin-based electronics, in which long spin coherence is critical, and also for
quantum computing applications, where topological protection can enable
fault-tolerant information processing. Here we use a scanning tunneling
microscope (STM) to visualize the gapless surface states of the
three-dimensional topological insulator BiSb and to examine their scattering
behavior from disorder caused by random alloying in this compound. Combining
STM and angle-resolved photoemission spectroscopy, we show that despite strong
atomic scale disorder, backscattering between states of opposite momentum and
opposite spin is absent. Our observation of spin-selective scattering
demonstrates that the chiral nature of these states protects the spin of the
carriers; they therefore have the potential to be used for coherent spin
transport in spintronic devices.Comment: to be appear in Nature on August 9, 200
Observation of Dirac plasmons in a topological insulator
Plasmons are the quantized collective oscillations of electrons in metals and
doped semiconductors. The plasmons of ordinary, massive electrons are since a
long time basic ingredients of research in plasmonics and in optical
metamaterials. Plasmons of massless Dirac electrons were instead recently
observed in a purely two-dimensional electron system (2DEG)like graphene, and
their properties are promising for new tunable plasmonic metamaterials in the
terahertz and the mid-infrared frequency range. Dirac quasi-particles are known
to exist also in the two-dimensional electron gas which forms at the surface of
topological insulators due to a strong spin-orbit interaction. Therefore,one
may look for their collective excitations by using infrared spectroscopy. Here
we first report evidence of plasmonic excitations in a topological insulator
(Bi2Se3), that was engineered in thin micro-ribbon arrays of different width W
and period 2W to select suitable values of the plasmon wavevector k. Their
lineshape was found to be extremely robust vs. temperature between 6 and 300 K,
as one may expect for the excitations of topological carriers. Moreover, by
changing W and measuring in the terahertz range the plasmonic frequency vP vs.
k we could show, without using any fitting parameter, that the dispersion curve
is in quantitative agreement with that predicted for Dirac plasmons.Comment: 11 pages, 3 figures, published in Nature Nanotechnology (2013
Complete mitochondrial genomes and nuclear ribosomal RNA operons of two species of Diplostomum (Platyhelminthes: Trematoda): a molecular resource for taxonomy and molecular epidemiology of important fish pathogens
© 2015 Brabec et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article
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