In-Situ Cleaning of Metal Photo-Cathodes in rf Guns

Metal cathodes installed in rf guns typically exhibit much lower quantum efficiency than the theoretical limit. Experimenters often use some sort of in situ technique to ''clean'' the cathode to improve the QE. The most common technique is laser cleaning where the laser is focused to a small spot and scanned across the cathode surface. However, since the laser is operated near the damage threshold, it can also damage the cathode and increase the dark current. The QE also degrades over days and must be cleaned regularly. We are searching for a more robust cleaning technique that cleans the entire cathode surface simultaneously. In this paper we describe initial results using multiple techniques such as several keV ion beams, glow discharge cleaning and back bombarding electrons. Results are quantified in terms of the change in QE and dark current

Buffalo, Bush Meat, and the Zoonotic Threat of Brucellosis in Botswana

Brucellosis is a zoonotic disease of global importance infecting humans, domestic animals, and wildlife. Little is known about the epidemiology and persistence of brucellosis in wildlife in Southern Africa, particularly in Botswana.Archived wildlife samples from Botswana (1995-2000) were screened with the Rose Bengal Test (RBT) and fluorescence polarization assay (FPA) and included the African buffalo (247), bushbuck (1), eland (5), elephant (25), gemsbok (1), giraffe (9), hartebeest (12), impala (171), kudu (27), red lechwe (10), reedbuck (1), rhino (2), springbok (5), steenbok (2), warthog (24), waterbuck (1), wildebeest (33), honey badger (1), lion (43), and zebra (21). Human case data were extracted from government annual health reports (1974-2006).Only buffalo (6%, 95% CI 3.04%-8.96%) and giraffe (11%, 95% CI 0-38.43%) were confirmed seropositive on both tests. Seropositive buffalo were widely distributed across the buffalo range where cattle density was low. Human infections were reported in low numbers with most infections (46%) occurring in children (<14 years old) and no cases were reported among people working in the agricultural sector.Low seroprevalence of brucellosis in Botswana buffalo in a previous study in 1974 and again in this survey suggests an endemic status of the disease in this species. Buffalo, a preferred source of bush meat, is utilized both legally and illegally in Botswana. Household meat processing practices can provide widespread pathogen exposure risk to family members and the community, identifying an important source of zoonotic pathogen transmission potential. Although brucellosis may be controlled in livestock populations, public health officials need to be alert to the possibility of human infections arising from the use of bush meat. This study illustrates the need for a unified approach in infectious disease research that includes consideration of both domestic and wildlife sources of infection in determining public health risks from zoonotic disease invasions

An experimentally validated model of a solar-cooling system based on an ammonia-water diffusion-absorption cycle

An experimentally validated thermodynamic model of a domestic-scale solar-cooling system based on an ammonia-water diffusion-absorption refrigeration (DAR) cycle is presented. The model combines sub-component descriptions of a DAR unit and a suitably sized (matched) solar-collector array, which are validated separately; outdoor tests are performed on an evacuated-tube (ET) collector over a range of solar-irradiance conditions, while a 150-W (nominal rating) DAR unit is tested in the laboratory with a thermal input provided by controlled electrical heaters. A COP of 0.2 is reported for the DAR unit when operating with a generator temperature of 155 °C and a system charge pressure of 20.7 bar. Using the experimentally validated solar-cooling system model, it is found that the area of the collector array required to power the system depends strongly on the type of collector. Annual simulations are also performed in various geographical regions order to predict the system’s cooling output. It is found that a single DAR unit with a 3-m2 ET array has the potential to provide 150-200 kWh per year of cooling in a southern European climate, which amounts approximately to the per capita demand for space cooling in residential dwellings in the same region

Factors affecting speech perception in children cochlear 22-channel cochlear prosthesis [Abstract]

Since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne in 1985, there have been rapid expansion world-wide in the number of children using this implant system. Longer-term experience with implanted children has led to improvements in paediatric assessment and management. Speech processing strategies have also been improved, resulting in a series of increases in speech perception benefits.3-5 Apri