Enhanced structural and magnetic properties of fcc colloidal crystals of cobalt nanoparticles.

We report the elaboration of supercrystals made up of dodecanoic acid-coated 8.1 nm-Co nanocrystals with controlled supercrystallinity, morphology and magnetic properties. Supercrystal growth is controlled using a solvent-mediated ligand-ligand interaction strategy. Either face-centered cubic supercrystalline films or single colloidal crystals composed of cobalt nanocrystals are obtained. The change in supercrystal morphology is explained by Flory-type solvation theory using Hansen solubility colloidal parameters. The use of the same batch of Co nanocrystals for the fabrication of supercrystalline films and colloidal crystals enables accurate comparative structural and magnetic studies using (high-resolution) transmission electron microscopy, field emission gun scanning electron microscopy, grazing incidence small-angle X-ray scattering and vibrating sample magnetometry. The nearest neighbor distance between nanoparticles is interpreted using theoretical models proposed in the literature. We evidence the increase in both geometric anisotropy and magnetic dipolar interactions for colloidal crystals compared to supercrystalline films.

[Mechanisms and causes of death in 143 Vietnamese HIV-infected patients hospitalized for tuberculosis]. / Evolutions fatales chez les patients vietnamiens co-infectés par le virus VIH et la tuberculose BAAR (+) au cours ou au décours immédiat de leur hospitalisation.

OBJECTIVE OF THE STUDY: To know the mechanisms and causes of death in Vietnamese VIH-infected patients hospitalized for tuberculosis. METHODS: Retrospective analysis of a monocentric cohort of 143 consecutive co infected patients admitted to Pham Ngoc Thach Hospital, in Ho Chi Minh City, between January 2004 and November 2004. MAIN RESULTS: All the patients were HIV-infected and AFB smear positive. The CD4 T lymphocyte count was 55/mm3 and the body mass index was 15.8 +/- 2 kg/m2. During the first three months after hospital admission and tuberculosis diagnosis, the percentage of deaths was 28.7% (41/143). The mechanisms of deaths were: progressive cachexia, acute respiratory failure, cardiogenic or bacteremic shock, coma and unexpected cardio respiratory arrest. The causes of death were tuberculosis (particularly mechanical complications such as compressive pneumothorax, pericarditis or pleuritis), metabolic disorders (mainly hyponatrémie and dyskaliema) and associated infection. In multivariate analysis, two parameters (available at admission) were predictive of short-term death: anemia (p=0.024) and hyponatrémie (p=0.026). CONCLUSION: The short term mortality of co infected patients with AIDS and tuberculosis remains high in developing countries. However, some causes of death such as compressive pneumothorax-pleuritis-pericarditis, metabolic disorder or even associated opportunistic infection i. e. pneumocystosis may be prevented or cured. Consequently, such patients must be carefully monitored and more particularly those with severe anemia and/or hyponatrémie at admission. Similarly appropriate diagnostic algorithms must be used in case of unfavorable evolution particularly to diagnose curable complication.

A Systematic Review of Outcomes Following Percutaneous Transluminal Angioplasty and Stenting in the Treatment of Transplant Renal Artery Stenosis.

PURPOSE: To evaluate outcomes following treatment of transplant renal artery stenosis by percutaneous transluminal angioplasty and stent insertion. MATERIALS AND METHODS: A literature search was performed using Pubmed, MEDLINE, Embase, Wiley Interscience and the Cochrane Library databases. Outcome measures were glomerular filtration rate, creatinine, blood pressure and number of antihypertensive medications. Technical and clinical success, patency and complication rates were also analysed. RESULTS: Thirty-two studies met the inclusion criteria, involving a total of 884 interventions including PTA, stenting, or combinations of both. Clinical success rates were in the range 65.5-94%. The majority of studies reported technical success rates higher than 90%. Patency rates were in the range of 42-100%. However, the definition and diagnostic criteria for TRAS varied widely between studies. Also, marked heterogeneity was observed in the reporting of outcome measures with no consensus in outcome criteria or follow up schedule. CONCLUSION: Outcomes following PTA and stenting for the treatment of TRAS have been shown to be favourable. However, there is a distinct lack of well designed studies assessing outcomes following intervention. Outcome reporting may be improved by the introduction of standardised outcome measures with reporting of outcomes into a multi-centre registry.

[Penicilliosis in Vietnam: a series of 94 patients]. / La pénicilliose au Vietnam: une série de 94 cas.

PURPOSE: Haiphong is the second city of Vietnam most affected by HIV infection. Penicilliosis represents the third leading cause of opportunistic infection. However, this systemic fungal infection remains poorly knew by practitioners. This study aimed to clarify the clinical, diagnostic and therapeutic aspects of penicilliosis. METHODS: It is a descriptive study, prospective and retrospective, conducted over a 3-year period in Viet Tiep hospital, Haiphong. RESULTS: With 94 cases, penicilliosis represented 11% of opportunistic infections. The patients were young (mean: 33 years) and male (87%). The main symptoms were persistent fever (99%), weight loss (88%), skin lesions (86%), hepatomegaly (69%) and lymphadenopathy (68%). Anemia was noted in 77% of cases. The average CD4 count was 29/µL. The culture of skin biopsies and blood culture were positive for Penicillium marneffei in 94% and 90% of cases, respectively. Despite antiretroviral and antifungal therapy, the mortality rate was 18%. Itraconazole monotherapy, administered in 53 patients due to the unavailability of amphotericin B, did not significantly affect the survival compared to the recommended treatment received by the 41 other patients. CONCLUSION: In Haiphong, penicilliosis is one of the most frequent and severe opportunistic infections of AIDS. The diagnosis should be considered in all febrile and immunocompromised patients having spent time in Vietnam. The prognosis can be improved by early diagnosis through the blood culture and a good adherence to an appropriate antifungal therapy.

Assemblies of aligned magnetotactic bacteria and extracted magnetosomes: what is the main factor responsible for the magnetic anisotropy?

The origin of the magnetic anisotropy is explained in an assembly of aligned magnetic nanoparticles. For that, nanoparticles synthesized biologically by Magnetospirillum magneticum AMB-1 magnetotactic bacteria are used. For the first time, it is possible to differentiate between the two contributions arising from the alignment of the magnetosome easy axes and the strength of the magnetosome dipolar interactions. The magnetic anisotropy is shown to arise mainly from the dipolar interactions between the magnetosomes.

All-electric quantum point contact spin-polarizer.

The controlled creation, manipulation and detection of spin-polarized currents by purely electrical means remains a central challenge of spintronics. Efforts to meet this challenge by exploiting the coupling of the electron orbital motion to its spin, in particular Rashba spin-orbit coupling, have so far been unsuccessful. Recently, it has been shown theoretically that the confining potential of a small current-carrying wire with high intrinsic spin-orbit coupling leads to the accumulation of opposite spins at opposite edges of the wire, though not to a spin-polarized current. Here, we present experimental evidence that a quantum point contact -- a short wire -- made from a semiconductor with high intrinsic spin-orbit coupling can generate a completely spin-polarized current when its lateral confinement is made highly asymmetric. By avoiding the use of ferromagnetic contacts or external magnetic fields, such quantum point contacts may make feasible the development of a variety of semiconductor spintronic devices.

Mesoscopic solid structures of 11-nm maghemite, gamma-Fe2O3, nanocrystals: experiment and theory.

Solid structures made of collapsed cylinders organized in hexagonal, stripes and wavy line-like structures are fabricated by slow evaporation of maghemite nanocrystals dispersed in hexane and subjected to an applied field perpendicular to the substrate. The sizes of the experimental structures are well described by a theory based on the minimization of the total free energy. Comparison between experiment and theory shows that the structures are explained by a labyrinthine instability enabled by a colloidal liquid-gas phase transition during the evaporation process. From the theoretical model and experimental data, it is concluded that the height determines the radius of the cylinders, whereas the phase ratio of the magnetic to the total volume and the field strength have little influence under the conditions studied here.