Production And Studies Of Photocathodes For High Intensity Electron Beams

For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of lifetimes in an RF gun of the CLIC Test Facility II at field strengths greater than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the Cs-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials can be described by Spicer's 3-step model. Whereas during the use the threshold for photo-emission in Cs-Te was shifted to higher photon energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light, with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarized. New investigations on high mean current production are presented.Comment: Submission to LINAC2000 conference, Paper number MOB08, 3 pages, 6 figure

Des insecticides plus sélectifs

La découverte d\u27un gène spécifique élargit les voies de recherche pouvant permettre de réduire les "dommages collatéraux" des insecticides

Injection of insect membrane in Xenopus oocyte: An original method for the pharmacological characterization of neonicotinoid insecticides

Insect nicotinic acetylcholine receptors (nAChRs) represent a major target of insecticides, belonging to the neonicotinoid family. However, the pharmacological profile of native nAChRs is poorly documented, mainly because of a lack of knowledge of their subunit stoichiometry, their tissue distribution and the weak access to nAChR-expressing cells. In addition, the expression of insect nAChRs in heterologous systems remains hard to achieve. Therefore, the structure–activity characterization of nAChR-targeting insecticides is made difficult. The objective of the present study was to characterize insect nAChRs by an electrophysiological approach in a heterologous system naturally devoid of these receptors to allow a molecular/cellular investigation of the mode of action of neonicotinoids

Presa de Grandval

This important project is situated on the top section of the river Truyere, within the region of the French Central Massif. The dam has been constructed by the Electricité de France. The total hydroelectric development project in this zone involves six dams and six power stations, to exploit an overall hydrostatic head of 520 ms. The water accumulated by these dams has a maximum volume of 540.106 cubic metres, and will produce a yearly output of 1450 .106 kWh. The Grandval dam rests on strong microschistous rock folds. Its length is 330 ms, and its maximum height 88 ms, measured from the foundation base. Structurally it is formed by a series of vaults supported by abutments, which are spaced at 50 ms intervals. The mean thickness of the vaults at the base is 4.90 ms, and 1.50 at the crown. The vertical slope on the upstream side is 0.70. A feature of this design is that the vaults are not uniformly cylindrical up to the top, as is customary. The top part of the dam consists, in fact, of a small gravity dam, resting on the underlying vaulted structure. The dam is straight at the top, and a road runs along it, on an overhanging structure. The dam has a surface spillway, which is ski jump shaped, and runs over the two abutments on either side of the power station.Esta importante obra se halla situada en el tramo superior del río Truyère, en la región del Macizo Central francés. Las presas se han realizado por cuenta de Electricité de France. El conjunto del aprovechamiento hidroeléctrico tiene seis presas y otras tantas centrales que aprovechan un salto total de 530 m de altura, y las aguas almacenadas en un embalse cuya capacidad total se eleva a 540x106m3 que proporcionarán una producción anual de 1.450x106 kWh. La presa se apoya sobre un banco microesquistoso, que en algunas partes presenta grandes pliegues de gran potencia. El dique de cierre tiene una longitud total de 330 m y 88 m de altura máxima, a partir de la base de cimientos. Su estructura está constituida por una serie de bóvedas que se apoyan en contrafuertes. La luz entre éstos es de 50 metros

Foci of Schistosomiasis mekongi, Northern Cambodia: II. Distribution of infection and morbidity.

In the province of Kracheh, in Northern Cambodia, a baseline epidemiological survey on Schistosoma mekongi was conducted along the Mekong River between December 1994 and April 1995. The results of household surveys of highly affected villages of the East and the West bank of the river and of school surveys in 20 primary schools are presented. In household surveys 1396 people were examined. An overall prevalence of infection of 49.3% was detected by a single stool examination with the Kato-Katz technique. The overall intensity of infection was 118.2 eggs per gram of stool (epg). There was no difference between the population of the east and west shore of the Mekong for prevalence (P = 0.3) or intensity (P = 0.9) of infection. Severe morbidity was very frequent. Hepatomegaly of the left lobe was detected in 48.7% of the population. Splenomegaly was seen in 26.8% of the study participants. Visible diverted circulation was found in 7.2% of the population, and ascites in 0.1%. Significantly more hepatomegaly (P = 0.001), splenomegaly (P = 0. 001) and patients with diverted circulation (P = 0.001) were present on the west bank of the Mekong. The age group of 10-14 years was most affected. The prevalence of infection in this group was 71.8% and 71.9% in the population of the West and East of the Mekong, respectively. The intensity of infection was 172.4 and 194.2 epg on the West and the East bank, respectively. In the peak age group hepatomegaly reached a prevalence of 88.1% on the west and 82.8% on the east bank. In the 20 schools 2391 children aged 6-16 years were examined. The overall prevalence of infection was 40.0%, ranging from 7.7% to 72.9% per school. The overalls mean intensity of infection was 110.1 epg (range by school: 26.7-187.5 epg). Both prevalence (P = 0.001) and intensity of infection (P = 0.001) were significantly higher in schools on the east side of the Mekong. Hepatomegaly (55.2%), splenomegaly (23.6%), diverted circulation (4. 1%), ascites (0.5%), reported blood (26.7%) and mucus (24.3%) were very frequent. Hepatomegaly (P = 0.001), splenomegaly (P = 0.001), diverted circulation (P = 0.001) and blood in stool (P = 0.001) were significantly more frequent in schools of the east side of the Mekong. Boys suffered more frequently from splenomegaly (P = 0.05), ascites (P = 0.05) and bloody stools (P = 0.004) than girls. No difference in sex was found for the prevalence and intensity of infection and prevalence of hepatomegaly. On the school level prevalence and intensity of infection were highly associated (r = 0. 93, P = 0.0001). The intensity of infection was significantly associated only with the prevalence of hepatomegaly (r = 0.44, P = 0. 05) and blood in stool (r = 0.40, P = 0.02). This comprehensive epidemiological study documents for the first time the public health importance of schistosomiasis mekongi in the Province of Kracheh, Northern Cambodia and points at key epidemiological features of this schistosome species, in particular the high level of morbidity associated with infection

Etude clinique et épidémiologique du paludisme en zone urbaine d'Afrique soudano-sahélienne (Pikine-Sénégal)

Pour des raisons de coût et de tolérance, la chimiothérapie présomptive repose toujours essentiellement sur la chloroquine, malgré l'apparition, il y a dix ans en Afrique de l'Est, de souches de #Plasmodium falciparum$ résistantes à la chloroquine et leur extension à l'ensemble de l'Afrique intertropicale. Dans le cas des zones urbaines, plusieurs particularités épidémiologiques du paludisme suggèrent qu'à partir de certains niveaux de chimiorésistance d'autres stratégies de lutte anti paludique pourraient être développées avec un meilleur rapport coût/efficacité. Dans une première approche de cette question, une recherche a été faite à Pikine, à savoir s'il existait des paramètres cliniques ou épidémiologiques, faciles à obtenir chez un enfant consultant pour fièvre, qui permettraient de choisir entre trois attitudes possibles : abstention thérapeutique, traitement présomptif, confection d'une goutte épaiss