An RF excited plasma cathode electron beam gun design

A plasma cathode electron beam (EB) gun is presented in this work. A radio frequency (RF) excited plasma at 84 MHz was used as the electron source to produce a beam power of up to 3.2 kW at -60 kV accelerating voltage. The pressure in the plasma chamber is approximately 1 mbar. The electrons are extracted from the plasma chamber to the vacuum chamber (at 10-5 mbar) through a diaphragm with a 0.5 mm diameter nozzle. Advantages over thermionic cathode guns were demonstrated empirically. Maintenance costs are reduced, as the cathode does not wear out as quickly during use. RF modulation can be used for controlling the beam power and thus there is no requirement for a grid cup electrode. Rapid (sub 1 microsecond) beam pulsing is achievable. Optical emission spectroscopy has been used to study the plasma parameters that affect the level of beam current

Characterisation of an RF excited argon plasma cathode electron beam gun

This work describes the experimental set up used for carrying out spectroscopic measurements in a plasma cathode electron beam (EB) gun. Advantages of plasma cathode guns over thermionic guns are described. The factors affecting electron beam power such as plasma pressure, excitation power and plasma chamber geometry are discussed. The maximum beam current extracted was 53 mA from a 0.5 mm diameter aperture in the plasma chamber. In this work, the electron source is an argon plasma excited at 84 MHz. The pressure in the plasma chamber was measured to be within 0.9 to 1.2 mbar and was controlled by varying gas flow rates. The vacuum chamber was at a pressure of 10^-5 mbar.TWI and Brunel University

Ecotypic Adaptation of Medicago Polymorpha along a Gradient in Central Chile: Growth and Seed Production

Relative growth rate, total dry weight and seed yield on 19 accessions of burr medic (Medicago polymorpha L.) from different bioclimatic conditions, were assessed at Cauquenes (35°58’;72°17’W) in the subhumid mediterranean region. The accessions were sown in microplots over raised beds during two years (1991 and 1992), and swards cut periodically at 2, 6 and 10 cm height. There were significant differences between accessions in both total dry weight and seed yield (P \u3c 0.001, Table 1), but the interaction between accessions and height of cutting was not significant (P \u3e 0.05). Total dry weight was positive correlated with days to flowering (r2 = 0.81; P \u3e 0.01)

Variaciones sedimentarias durante el Eoceno medio en la sierra de Andía (Navarra)

In this paper, tkie stratigraphical and lithological character- istics of the Middle Eocene are established, in the Sierra de Andia (Navarra, Spain). Examples of the cross-stratification are described and the directional data analyzed. A study of the basin evolution is elaborated. It is pro- posed a correlation with the youngest sediments of the Sierra de Urbasa, situated more to the West

Germplasm Collection, Evaluation and Selection of Naturalized Medicago Polymorpha in the Mediterranean Zone of Chile

An introduction and evaluation programme is described that thus far includes 53 accessions of the naturalised annual medic Medicago polymorplia L. collected along a 1000 km N-S gradient in central. Chile and subsequently grown together in a common environment· selection trial together with 5 accessions received from International Center for Agricultural Research in the Dry Areas (!CARDA). Major selection criteria include: precocious phenology, spineless pods and hardseededness, and tolerance to acid soils. Onset of flowering was 82-127 day_s, later flowering being closely correlated with higher latitudes. Soil pH was 5.3-7 .5 in collection sites, and phosphorus levels were \u3e 10 ppm in 90% of the sites. There was also a correlation between flowering precocity and spineless pods. All accessions showed 100% hard seededness immediately after seed set, but the following autumn, seed hardness varied considerably. The phenological and ecophysiological ranges of adaptation exhibited in these accessions suggests that ecological adaptation has occurred in this naturalized species and that an important genetic base exists from which to select cultivars for areas throughout the Mediterranean climate region

Inicio de una investigación de diseño sobre el desarrollo de competencias numéricas con niños de 4 años

En esta investigación de diseño sobre el desarrollo de competencias numéricas, describimos el comienzo de un taller de resolución de problemas con niños de 4 y 5 años. Aspiramos a lograr una complementariedad metodológica al incorporar, dentro de la investigación de diseño, el uso del Test de Competencia Matemática Básica (TEMA-3). Con él pretendemos evaluar el desarrollo de las competencias numéricas de los niños durante el curso. Además, dado que uno de los objetivos de la investigación es el desarrollo del currículo de Educación Infantil, a través de la elaboración del taller, deseamos valorar la idoneidad del TEMA-3 para un posible estudio posterior sobre la eficiencia de la intervención a través del taller

Effects of Whole-Body Vibration Therapy in Patients with Fibromyalgia: A Systematic Literature Review

Objective. To review the literature on the effects of whole-body vibration therapy in patients with fibromyalgia. Design. Systematic literature review. Patients. Patients with fibromyalgia. Methods. An electronic search of the literature in four medical databases was performed to identify studies on whole-body vibration therapy that were published up to the 15th of January 2015. Results. Eight articles satisfied the inclusion and exclusion criteria and were analysed. According to the Dutch CBO guidelines, all selected trials had a B level of evidence. The main outcomes that were measured were balance, fatigue, disability index, health-related quality of life, and pain.Whole-body vibration appeared to improve the outcomes, especially balance and disability index. Conclusion.Wholebody vibration could be an adequate treatment for fibromyalgia as a main therapy or added to a physical exercise programme as it could improve balance, disability index, health-related quality of life, fatigue, and pain. However, this conclusion must be treated with caution because the paucity of trials and the marked differences between existing trials in terms of protocol, intervention, and measurement tools hampered the comparison of the trials