Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma

Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma were directly measured using a heat flux microsensor (HFM). The energy flux evolution was compared with those obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W, the measured energy flux due to chemical reactions is estimated at about 7 W.cm\^{-2} against 0.4 W.cm\^{-2} for ion bombardment and other contributions. Time evolution of the HFM signal is also studied. The molar enthalpy of the reaction giving SiF4 molecules was evaluated and is consistent with values given in literature.Comment: 3 page

Long term dynamics of two populations of Prosopis caldenia Burkart

Los cambios más importantes registrados en la distribución del caldén (Prosopis caldenia Burkart) en la región semiárida central de Argentina, Incluyen el aumento de la densidad de esta especie y la invasión de pastizales naturales. Los factores causales y la dinámica de estos cambios no han sido detalladamente estudiados. En este trabajo se relaciona la dinámica de dos poblaciones de caldén con factores tales como manejo, fuego y precipitaciones. Se eligieron como áreas de estudios una planicie cuya vegetación original era un pastizal (sitio 1) y un bosque de caldén que originalmente fue una sabana (sitio 2). En cada sitio se determinaron los patrones espaciales en base a transectas y las tasas de Implantación las cuales fueron inferidas por dendroecologia. Las densidades estimadas fueron 586 y 1259 plantas/ha, para el sitio 1 y 2 respectivamente. No se encontraron evidencias de agrupamiento para la escala espacial de este estudio (p=0.52, sitio 1 y p=0.08, sitio 2 para n=112). Las edades de los individuos muestreados comprendieron un rango de 3 a 65 años en el sitio 1 y de 8 a 55 años en el sitio 2 (en este sitio 2 solo fueron muestreadas las plantas con diámetro menor de 30 cm). Primariamente los dos sitios fueron utilizados para erra de ovinos; durante ese periodo, las tasas de establecimiento fueron 0.99 plantas/ha/año (16 años) en el sitio 1, Y 10 plantas/ha/año (15 años) en el sitio 2. Posteriormente luego de diez años desde la introducción del ganado vacuno, las tasas ascendieron a 12.7 y 48.5 plantas/ha/año respectivamente. Un evento de fuego fue registrado en cada sitio (1980 en el sitio 1 y 1964 en el sitio 2) pero este factor no alteró la tendencia ascendente de la densidad. En el sitio 2 el Incendio fue contemporáneo con la introducción del ganado y coincide a su vez con un importante incremento en el establecimiento. No se encontró relación entre la dinámica de la población de caldén y las fluctuaciones en la precipitación anual o estacional. Las variaciones registradas en las tasas de establecimiento coincidieron con cambios en el manejo ganadero, confirmando la Importancia del ganado en la dispersión de las semillas de caldén.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la U.N.L.Pam.) Publicado en JOURNAL OF RANGE MANAGEMENT, 51 (6), November 199

Ignition and extinction phenomena in helium micro hollow cathode discharges

International audienceMicro hollow cathode discharges (MHCD) were produced using 250 µm thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 µm thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the measurement of He*(3S1) metastable atoms density by tunable diode laser spectroscopy. At the ignition of the microdischarges, 2 µs long current peak as high as 24 mA was observed, sometimes followed by low amplitude damped oscillations. At helium pressure above 400 Torr, an oscillatory behaviour of the discharge current was observed just before the extinction of the microdischarges. The same type of instability in the extinction period at high pressure also appeared on the density of He*(3S1) metastable atoms, but delayed by a few µs relative to the current oscillations. Metastable atoms thus cannot be at the origin of the generation of the observed instabilities

Neuropathic complications after 157 procedures of continuous popliteal nerve block for hallux valgus surgery. A retrospective study

SummaryBackgroundContinuous peripheral nerve block (CPNB), in particular at the popliteal fossa, is widely used in orthopedic surgery, allowing good postoperative analgesia. Possible neuropathic complications, however, remain poorly known.ObjectiveTo review the characteristics of peripheral neuropathy (PN) after sciatic CPNB at the popliteal fossa, estimating prevalence, severity, evolution and possible risk factors, especially those relating to the procedure.MethodsRetrospective study of PN associated with popliteal fossa CPNB for hallux valgus surgery, between November 1st, 2005 and November 1st, 2009. All procedures were analyzed (type of anesthesia, approach, nerve location technique, number of procedures by operator) with, for each case of PN, analysis of clinical and electromyographic data.ResultsOne hundred and fifty seven sciatic CPNBs were performed (92% women; mean age, 55 years). The approach was lateral (n=62), posterior (n=74) or unknown (n=21). Ultrasound guidance was combined to neurostimulation for 69 patients (44%). Three women (prevalence=1.91%), aged 19, 24 and 65 years respectively, developed associated common superficial peroneal and sural nerve injury (2), axonal on electromyography, with motor (n=1) and/or sensory (n=3) residual dysfunction.DiscussionThe higher prevalence found in the present study than in the literature (0 to 0.5%) raises questions of methodological bias or technical problems. The common peroneal and sural nerves seem to be exposed, unlike the tibial. Several mechanisms can be suggested: anesthetic neurotoxicity, direct mechanical lesion, or tourniquet-related ischemia and conduction block. Further studies are necessary to determine the ideal anesthetic procedure.ConclusionPatients should be informed of the potential risk, however rare, even during mild surgery. The best possible technique should be implemented, with reinforced surveillance.Level of evidenceLevel IV retrospective study

Comparison of two dengue NS1 rapid tests for sensitivity, specificity and relationship to viraemia and antibody responses

<p>Abstract</p> <p>Background</p> <p>Dengue is a major public health problem in tropical and subtropical countries. Rapid and easy diagnosis of dengue can assist patient triage and care-management. The detection of DENV NS1 on rapid lateral flow tests offers a fast route to a presumptive dengue diagnosis but careful evaluations are urgently needed as more and more people use them.</p> <p>Methods</p> <p>The sensitivity and specificity of the Bio-Rad NS1 Ag Strip and SD Dengue Duo (NS1/IgM/IgG) lateral flow rapid tests were evaluated in a panel of plasma samples from 245 Vietnamese patients with RT-PCR confirmed dengue and 47 with other febrile illnesses.</p> <p>Results</p> <p>The NS1 rapid tests had similar diagnostic sensitivities (respectively 61.6% and 62.4%) in confirmed dengue cases but were 100% specific. When IgM/IgG results from the SD Dengue Duo were included in the test interpretation, the sensitivity improved significantly from 62.4% with NS1 alone to 75.5% when NS1 and/or IgM was positive and 83.7% when NS1 and/or IgM and/or IgG was positive. Both NS1 assays were significantly more sensitive for primary than secondary dengue. NS1 positivity was associated with the underlying viraemia as NS1-positive samples had a significantly higher viraemia than NS1-negative samples.</p> <p>Conclusions</p> <p>These data suggest that the NS1 test component of these assays are highly specific and have similar levels of sensitivity. The IgM parameter in the SD Duo test improved overall test sensitivity without compromising specificity. The SD Dengue Duo lateral flow rapid test deserves further prospective evaluation in dengue endemic settings.</p