Estacionalidad de ias precipitaciones en el territorio continental argentino

Se llevó a cabo un estudio de los regímenes estacionales de precipitación correspondientes al territorio continental argentino, efectuado con el mayor detalle posible que permitieron los registros pluviométricos más extensos y completos que se pudieron reunir con la colaboración del Servicio Meteorológico Nacional y otras fuentes. Se aplicaron los índices de estaclonalidad de Lawler y Walsh, diseñados para cuantlficar los regímenes pluviosos de Areas extensas en función de la variación estacional de la precipitación, tanto para el año promedio como respecto a su variabilidad interanual, lo que asegura un grado de confiabilidad aceptable en la definición de cada régimen. Puesto que los índices mencionados no toman en cuenta la distribución temporal de las lluvias mensuales, el estudio fue completado con el cálculo de las relaciones porcentuales entre la precipitación normal del semestre cálido y la precipitación anual, obteniendo además las distintas secuencias de importancia relativa de las precipitaciones para las cuatro estaciones del año, anotando además en cada caso, los meses de máxima y mínima. El trabajo que se ilustra con tablas y mapas tiene el objeto de establecer fehacientemente los diferentes regímenes de precipitación observables en el país para fines prácticos de interés geográfico, ecológico, agroclimático, económico, etc. y para comprender mejor las características de los procesos meteorológicos que generan precipitaciones en las distintas regiones del país.A study on the precipitation seasonal regimes corresponding to the Argentina's continental territory was undertaken with the largest possible detail permitted by the precipitation records, more extended in time and complete, which have been obtained, with the colaboration of the National Meteorological Service and other sources. The Lawler and Walsh's seasonality indexes were applied. These Indexes are designed to quantify the rainfall regimes of large areas as a function of the seasonal variation of precipitation for the average year as well as with respect of its inter-annual variation. This ensures an acceptable degree of confiability for the definition of each regime. Since these indexes do not take into consideration the temporal distribution of monthly precipitations, the study was completed with the porcentual relations between the normal precipitation of the warm semestre and the annual one, and with the different sequences of relative importance of precipitations for the four seasons, recording in each case the month of maximun and minimum precipitation. The work is illustrated with tables and maps to clearly establish the different precipitation regimes observed in the country for their use in geographic, ecological, agroclimatic, economic activities, etc. and to better understand the ccharacterlstics of the meteorological processes generating precipitations in different regions of the country.Asociación Argentina de Geofísicos y Geodesta

Frequency of Agenesis Palmaris Longus through Clinical Examination - An East African Study

INTRODUCTION: The Palmaris longus, one of the most variable muscles in the body both flexes the wrist and tenses the palmar fascia. It is used by surgeons as a source of tendon graft and racial differences in its variation have been documented. We sought to determine the frequency of the absence of the Palmaris longus in an East African population. METHODS: A prospective study was conducted using ten common clinical tests among patients and students in a large teaching hospital in East Africa to determine the presence of a Palmaris longus. RESULTS: The overall rate of absence was 4.4% with unilateral absence at 3.3% and bilateral absence at 1.1%. The overall difference between males and females was not statistically significant (p = 0.605). Participants were more likely to have absence in their non dominant hand. DISCUSSION: Our findings though in contrast to many studies worldwide, it concurs with most studies done in the African setting. These differences may be due to the higher levels of manual labour and the more use of the right hand in these activities. The frequency of the absence of Palmaris longus in East Africa has been determined. Surgeons should acquaint themselves with prevalence in their areas of practice

X-band photoinjector for a chirped-pulse FEL

The phase noise and jitter characteristics of the laser and rf systems of a high gradient X-band photoinjector have been measured experimentally. When > 100 coherently phased 5 MeV electron bunches are produced in bursts, the photoinjector should be an ideal electron source for a pulsed, pre-bunched free-electron laser (FEL) operating at 100 GHz. The laser oscillator is a self-modelocked Titanium:Sapphire system operating at the 108th subharmonic of the rf gun. The X-band signal is produced from the laser by a phase-locked dielectric resonance oscillator, and amplified by a pulsed TWT and klystron. A comparison between the klystron and TWT amplifier phase noise and the fields excited in the rf gun demonstrates the filtering effect of the high Q structure, thus indicating that the rf gun can be used as a master oscillator, and could be energized by either a rf oscillator such as a magnetron or a compact source such as a cross-field amplifier. In particular, the rf gun can play the role of a pulsed rf clock to synchronize the photocathode laser system: direct drive of a synchronously mode-locked AlGaAs quantum well laser has been achieved using the X0-band gun rf fields. This novel, GHz repetition rate, sub-picosecond laser system is being developed to replace the more conventional femtosecond Ti: Al2O3 system. Some advantages include pumping this laser with a stabilized current source instead of a costly, low efficiency pump laser. Finally, dark current measurements and initial photoelectron measurements are reported

Spectral analysis of the nonlinear relativistic Doppler shift in ultrahigh intensity Compton scattering

International audienc

Electron beam and rf characterization of a low-emittance X-band photoinjector

Detailed experimental studies of the first operation of an X-band (8.547 GHz) rf photoinjector are reported. The rf characteristics of the device are first described, as well as the tuning technique used to ensure operation of the 11/2-cell rf gun in the balanced π-mode. The characterization of the photoelectron beam produced by the rf gun includes: measurements of the bunch charge as a function of the laser injection phase, yielding information about the quantum efficiency of the Cu photocathode ( 2×10^{-5} for a surface field of 100 MV/m); measurements of the beam energy (1.5–2 MeV) and relative energy spread ( Δγ/γ_{0}=1.8±0.2%) using a magnetic spectrometer; measurements of the beam 90% normalized emittance, which is found to be ɛ_{n}=1.65π mm mrad for a charge of 25 pC; and measurements of the bunch duration ( <2 ps). Coherent synchrotron radiation experiments at Ku-band and Ka-band confirm the extremely short duration of the photoelectron bunch and a peak power scaling quadratically with the bunch charge