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

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$_2$

Mère

ma dyemma temmut, a wer d-yeqqim yism n tmeṭṭut« Si ma mère meurt, qu’il ne reste même plus un nom de femme ! »(Parole d’un Kabyle) Que de force affective dans l’évocation de cette mère unique, universellement partagée à travers le monde entier peuplé d’hommes et de femmes enfantés chacun par l’une d’entre elles ! Certes, les cultures partagent nombre de similitudes à travers le monde, pourtant, la place faite à la mère dans ses relations à ses enfants peut s’avérer assez complexe au sein de ..

Fluorescent oxide nanoparticles adapted to active tips for near-field optics

We present a new kind of fluorescent oxide nanoparticles with properties well suited to active-tip based near-field optics. These particles with an average diameter in the range 5-10 nm are produced by Low Energy Cluster Beam Deposition (LECBD) from a YAG:Ce3+ target. They are studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), classical photoluminescence, cathodoluminescence and near-field scanning optical microscopy (NSOM). Particles of extreme photo-stability as small as 10 nm in size are observed. These emitters are validated as building blocks of active NSOM tips by coating a standard optical tip with a 10 nm thick layer of YAG:Ce3+ particles directly in the LECBD reactor and by subsequently performing NSOM imaging of test surfaces.Comment: Changes made following Referee's comments; added references; one added figure. See story on this article at: http://nanotechweb.org/cws/article/tech/3606

Muscle recovery after ACL reconstruction with 4-strand semitendinosus graft harvested through either a posterior or anterior incision: A preliminary study

AbstractIntroductionHarvesting of a 4-strand semitendinosis (ST4) graft during anterior cruciate ligament (ACL) reconstruction can be performed through either a posterior or anterior approach. The objective of this study was to evaluate the recovery of the quadriceps and hamstring muscles as a function of the graft harvesting method. We hypothesized that posterior harvesting (PH) would lead to better recovery in hamstring strength than anterior harvesting (AH).MethodsIn this prospective study, the semitendinosus was harvested through an anterior incision in the first group of patients and through a posterior one in the second group of patients. The patients were enrolled consecutively, without randomization. Isokinetic muscle testing was performed three and six months postoperative to determine the strength deficit in the quadriceps and hamstring muscles of the operated leg relative to the uninjured contralateral leg.ResultsThirty-nine patients were included: 20 in the AH group and 19 in the PH group. The mean quadriceps strength deficit after three and six months was 42% and 26% for AH and 29% and 19% for the PH, respectively (P=0.01 after three months and P=0.16 after six months). The mean hamstring strength deficit after three and six months was 31% and 17% for AH and 23% and 15% for the PH, respectively (P=0.09 after three months and P=0.45 after six months). After three months, the PH group had recovered 12% more quadriceps muscle strength than the AH group (P=0.03).ConclusionOur hypothesis was not confirmed. Harvesting of a ST4 graft for ACL reconstruction using a posterior approach led to better muscle strength recovery in the quadriceps only after three months.Case control studyLevel 3

Autocorrelation analysis for the unbiased determination of power-law exponents in single-quantum-dot blinking

We present an unbiased and robust analysis method for power-law blinking statistics in the photoluminescence of single nano-emitters, allowing us to extract both the bright- and dark-state power-law exponents from the emitters' intensity autocorrelation functions. As opposed to the widely-used threshold method, our technique therefore does not require discriminating the emission levels of bright and dark states in the experimental intensity timetraces. We rely on the simultaneous recording of 450 emission timetraces of single CdSe/CdS core/shell quantum dots at a frame rate of 250 Hz with single photon sensitivity. Under these conditions, our approach can determine ON and OFF power-law exponents with a precision of 3% from a comparison to numerical simulations, even for shot-noise-dominated emission signals with an average intensity below 1 photon per frame and per quantum dot. These capabilities pave the way for the unbiased, threshold-free determination of blinking power-law exponents at the micro-second timescale