A neglected disease of humans: a new focus of visceral leishmaniasis in Bakool, Somalia.

Visceral leishmaniasis (VL) was observed in children in Bakool region, Somalia, an area where VL has not been reported before. We describe the extent of the problem in this war- and famine-stricken area. A retrospective analysis was done of all cases admitted to a VL treatment centre between July 2000 and August 2001. Patients with longstanding fever, splenomegaly and a positive direct agglutination test (DAT; titre > 1:3200) were treated as suspected VL cases. A rapid epidemiological and entomological assessment was performed in the area. Species identification was attempted from blood samples by polymerase chain reaction-restriction fragment length polymorphism analysis of cysteine proteinase B genes. In 1 year, 230 serologically-positive cases were diagnosed as VL, and response to therapy was good in 91.6% of the 225 treated with sodium stibogluconate. Parasitological confirmation was attempted and obtained in 2 cases. Parasites were found to be most similar to Sudanese and Ethiopian reference strains of the Leishmania donovani complex. In a serological survey of 161 healthy displaced persons, 15% were positive by the leishmanin skin test and 3 (2%) were positive by the DAT. The sandfly captures showed Phlebotomus martini and P. vansomerenae. VL seems to be a longstanding and serious health problem in Bakool region. Food insecurity might have contributed to the emergence and detection of VL in this area

Circular dichroism of magneto-phonon resonance in doped graphene

Polarization resolved, Raman scattering response due to E$_{2g}$ phonon in monolayer graphene has been investigated in magnetic fields up to 29 T. The hybridization of the E$_{2g}$ phonon with only the fundamental inter Landau level excitation (involving the n=0 Landau level) is observed and only in one of the two configurations of the circularly crossed polarized excitation and scattered light. This polarization anisotropy of the magneto-phonon resonance is shown to be inherent to relatively strongly doped graphene samples, with carrier concentration typical for graphene deposited on SiO$_2$

Modulational instability in dispersion-kicked optical fibers

We study, both theoretically and experimentally, modulational instability in optical fibers that have a longitudinal evolution of their dispersion in the form of a Dirac delta comb. By means of Floquet theory, we obtain an exact expression for the position of the gain bands, and we provide simple analytical estimates of the gain and of the bandwidths of those sidebands. An experimental validation of those results has been realized in several microstructured fibers specifically manufactured for that purpose. The dispersion landscape of those fibers is a comb of Gaussian pulses having widths much shorter than the period, which therefore approximate the ideal Dirac comb. Experimental spontaneous MI spectra recorded under quasi continuous wave excitation are in good agreement with the theory and with numerical simulations based on the generalized nonlinear Schr\"odinger equation

Few layer graphene on SiC, pyrolitic graphite and graphene: a Raman scattering study

The results of micro-Raman scattering measurements performed on three different ``graphitic'' materials: micro-structured disks of highly oriented pyrolytic graphite, graphene multi-layers thermally decomposed from carbon terminated surface of 4H-SiC and an exfoliated graphene monolayer are presented. Despite its multi-layer character, most parts of the surface of the graphitized SiC substrates shows a single-component, Lorentzian shape, double resonance Raman feature in striking similarity to the case of a single graphene monolayer. Our observation suggests a very weak electronic coupling between graphitic layers on the SiC surface, which therefore can be considered to be graphene multi-layers with a simple (Dirac-like) band structure.Comment: 4 pages, 3 Figures Structure of the paper strongly modified, small changes in Fig 2 and 3. Same interpretation and same result

Heteroclinic structure of parametric resonance in the nonlinear Schr\"odinger equation

We show that the nonlinear stage of modulational instability induced by parametric driving in the {\em defocusing} nonlinear Schr\"odinger equation can be accurately described by combining mode truncation and averaging methods, valid in the strong driving regime. The resulting integrable oscillator reveals a complex hidden heteroclinic structure of the instability. A remarkable consequence, validated by the numerical integration of the original model, is the existence of breather solutions separating different Fermi-Pasta-Ulam recurrent regimes. Our theory also shows that optimal parametric amplification unexpectedly occurs outside the bandwidth of the resonance (or Arnold tongues) arising from the linearised Floquet analysis

Ultrafast sodium channel block by dietary fish oil prevents dofetilide-induced ventricular arrhythmias in rabbit hearts

9 pages, 4 figures, 1 table.-- et al.Several epidemiologic and clinical studies show that following myocardial infarction, dietary supplements of omega-3 polyunsaturated fatty acids (omega3FA) reduce sudden death. Animal data show that omega3FA have antiarrhythmic properties, but their mechanisms of action require further elucidation. The effects of omega3FA supplementation were studied in female rabbits to analyze whether their antiarrhythmic effects are due to a reduction of triangulation, reverse use-dependence, instability, and dispersion (TRIaD) of the cardiac action potential (TRIaD as a measure of proarrhythmic effects). In Langendorff-perfused hearts challenged by a selective rapidly activating delayed rectifier potassium current inhibitor that has been shown to exhibit proarrhythmic effects (dofetilide; 1 to 100 nM), omega3FA pretreatment (30 days; n=6) prolonged the plateau phase of the monophasic action potential; did not slow the terminal fast repolarization; reduced the dofetilide-induced prolongation of the action potential duration; reduced dofetilide-induced triangulation; and reduced dofetilide-induced reverse use-dependence, instability of repolarization, and dispersion. Dofetilide reduced excitability in omega3FA-pretreated hearts but not in control hearts. Whereas torsades de pointes (TdP) were observed in five out of six in control hearts, none were observed in omega3FA-pretreated hearts. Docosahexaenoic acid (DHA) inhibited the sodium current with ultrafast kinetics. Dietary omega3FA supplementation markedly reduced dofetilide-induced TRIaD and abolished dofetilide-induced TdP. Ultrafast sodium channel block by DHA may account for the antiarrhythmic protection of the dietary supplements of omega3FA against dofetilide-induced proarrhythmia observed in this animal model.This work was funded by Solvay Pharma, Novartis, Grants CICYT SAF2004-06856 and SAF2007-65868 and Red Temática de Investigación Cooperativa Grant FIS RD06/0014/0006.Peer reviewe

Fotonima stimulirana desorpcija vodikovih iona iz poluvodičkih površina: dokazi izravnih i posrednih procesa

Photon-stimulated desorption of positive hydrogen ions from hydrogenated diamond and GaAs surfaces have been studied for incident photon energies around core-level binding energies of substrate atoms. In the case of diamond surfaces, the comparison between the H+ yield and the near edge X-ray absorption fine structure (NEXAFS) for electrons of selected kinetic energies reveals two different processes leading to photodesorption: an indirect process involving secondary electrons from the bulk and a direct process involving core-level excitations of surface carbon atoms bonded to hydrogen. The comparison of H+ photodesorption and electron photoemission as the function of photon energy from polar and non-polar GaAs surfaces provides clear evidence for direct desorption processes initiated by ionisation of corresponding core levels of bonding atoms.Proučavali smo fotonima stimuliranu desorpciju pozitivnih iona vodika iz hidrogeniziranih površina dijamanta i GaAs, za fotone energije oko energija vezanja unutarnjih elektrona atoma podloge. U slučaju površine dijamanta, usporedba prinosa H+ i fine strukture blizu-rubne apsorpcije X-zračenja (NEXAFS) za elektrone odabranih kinetičkih energija otkriva dva različita procesa koji uzrokuju fotodesorpciju: posredan proces uz sudjelovanje sekundarnih elektrona iz osnovnog materijala, i izravan proces uzrokovan uzbudom unutarnjih elektrona površinskih atoma ugljika vezanih na vodik. Usporedba fotodesorpcije H+ i emisije elektrona u ovisnosti o energiji fotona iz polarnih i nepolarnih površina GaAs daje jasne dokaze za izravne procese desorpcije uzrokovane ionizacijom odgovarajućih unutarnjih stanja veznih atoma