Short range nucleon correlations studied with electron and photon probes

This paper reviews experimental research into two- and three-body nucleon-nucleon interactions, carried out by the University of Glasgow Nuclear Physics research group. A key aim of these studies has been to elucidate the role of short-range nucleon-nucleon correlations (SRC). Studies of photon-induced two- and three-nucleon emission reactions from a range of light nuclei, carried out at the 840 MeV Mainz electron microtron MAMI-B, have provided detailed information on the contributing mechanisms. More recent electron scattering studies at the 6.0 GeV Jefferson Laboratory have probed SRC at high values of Q^2 and x_B and suggested a connection between SRC and the EMC effect

Factors affecting the operation of laser-triggered gas switch (LTGS) with multi-electrode spark gap

Multi-electrode spark switches can be used for switching applications at elevated voltages or for command triggering. Symmetrical field graded electrodes allow the electrical stress across individual gaps to be controlled, thus maximising the hold off voltage and reducing switch pre-fire. The paper considers some aspects of multielectrode switch design and their influence on switching behavior. Non-symmetrical, uni-directional electrode topologies can be employed with advantages over traditional symmetrical design. The choice of working gas and gas pressure can influence switching performance in terms of delay-time and jitter. Transient analysis of switch characteristics has been undertaken in order to understand multi-electrode switching

Avian community responses to the establisment of small garden allotments within a Mediterranean habitat mosaic

Estudios previos de ecología enfocados a los efectos que tienen las alteraciones de los hábitats a pequeña escala han hallado efectos positivos, nulos y negativos sobre la biodiversidad. En este trabajo describimos los efectos que tiene el establecimiento de un pequeño huerto sobre la comunidad de aves. Para ello, analizamos los valores de diversidad (i.e., riqueza de especies y abundancia) y el comportamiento (i.e., forrajeo, uso de perchas) de las comunidades de aves. Los resultados de este trabajo muestran que, aunque el cambio de uso de suelo es reciente y a pequeña escala, las comunidades de aves observadas en el huerto están dominadas por unas pocas especies, mientras que mostraron ser mayormente equitativas en las plantaciones naturalizadas de almendros (hábitat previo al establecimiento de los huertos). Cuando comparamos el comportamiento de las aves en ambos hábitats, encontramos una mayor proporción de aves en búsqueda activa de alimento en los huertos, mientras que el número de aves desarrollando otras actividades (descanso) fue mayor en las plantaciones naturalizadas. Aunque la presencia de nuevos hábitats puede elevar la riqueza regional de la avifauna en paisajes mediterráneos, nuestros resultados no muestran evidencia de un efecto positivo significativo en el aumento de la riqueza regional de aves debido al establecimiento de pequeños huertos. Proponemos que las futuras actividades agrícolas deban tener en cuenta la escala, intensidad y frecuencia de las perturbaciones generadas con la finalidad de lograr un efecto positivo sobre la biodiversidad. Palabras clave: Ecología aviar, Biodiversidad, Comunidades de aves, Transformación del uso del suelo.Estudios previos de ecología enfocados a los efectos que tienen las alteraciones de los hábitats a pequeña escala han hallado efectos positivos, nulos y negativos sobre la biodiversidad. En este trabajo describimos los efectos que tiene el establecimiento de un pequeño huerto sobre la comunidad de aves. Para ello, analizamos los valores de diversidad (i.e., riqueza de especies y abundancia) y el comportamiento (i.e., forrajeo, uso de perchas) de las comunidades de aves. Los resultados de este trabajo muestran que, aunque el cambio de uso de suelo es reciente y a pequeña escala, las comunidades de aves observadas en el huerto están dominadas por unas pocas especies, mientras que mostraron ser mayormente equitativas en las plantaciones naturalizadas de almendros (hábitat previo al establecimiento de los huertos). Cuando comparamos el comportamiento de las aves en ambos hábitats, encontramos una mayor proporción de aves en búsqueda activa de alimento en los huertos, mientras que el número de aves desarrollando otras actividades (descanso) fue mayor en las plantaciones naturalizadas. Aunque la presencia de nuevos hábitats puede elevar la riqueza regional de la avifauna en paisajes mediterráneos, nuestros resultados no muestran evidencia de un efecto positivo significativo en el aumento de la riqueza regional de aves debido al establecimiento de pequeños huertos. Proponemos que las futuras actividades agrícolas deban tener en cuenta la escala, intensidad y frecuencia de las perturbaciones generadas con la finalidad de lograr un efecto positivo sobre la biodiversidad. Palabras clave: Ecología aviar, Biodiversidad, Comunidades de aves, Transformación del uso del suelo.Ecological studies focused on small–scale habitat alterations have found positive, null, and negative effects on biodiversity. In this study, we describe the effects that establishing a relatively small area of garden allotments had on bird communities. To assess such effects, we analyzed avian community diversity (i.e., species richness and abundance) and behavioral traits (i.e., foraging, perching). Although land transformation was recent and on a small geographic–scale, our results showed that bird communities in the allotments were dominated by a few species, while in the almond plantation (former habitat) evenness was higher. When perching and foraging behavior was compared in the two study areas, we found a significantly higher proportion of foraging in the garden allotments, and a higher proportion of birds perching in the naturalized plantation. Although new habitats often enhance regional bird species richness in Mediterranean landscapes, we found no evidence of an increase in regional avian diversity related to the establishment of small garden allotments. We propose that future harvesting activities should consider the scale, intensity, and frequency of the generated perturbation in order to promote biodiversity. Key words: Avian ecology, Biodiversity, Bird communities, Land–use transformation

Surface flashover of oil-immersed dielectric materials in uniform and non-uniform fields

The applied electrical fields required to initiate surface flashover of different types of dielectric material immersed in insulating oil have been investigated, by applying impulses of increasing peak voltage until surface flashover occurred. The behavior of the materials in repeatedly over-volted gaps was also analyzed in terms of breakdown mode (some bulk sample breakdown behaviour was witnessed in this regime), time to breakdown, and breakdown voltage. Cylindrical samples of polypropylene, low-density polyethylene, ultra-high molecular weight polyethylene, and Rexolite, were held between two electrodes immersed in insulating oil, and subjected to average applied electrical fields up to 870 kV/cm. Tests were performed in both uniform- and non-uniform-fields, and with different sample topologies. In applied field measurements, polypropylene required the highest levels of average applied field to initiate flashover in all electrode configurations tested, settling at similar to 600 kV/cm in uniform fields, and similar to 325 kV/cm in non-uniform fields. In over-volted point-plane gaps, ultra-high molecular weight polyethylene exhibited the longest pre-breakdown delay times. The results will provide comparative data for system designers for the appropriate choice of dielectric materials to act as insulators for high-voltage, pulsed-power machines

Clinical studies of the high-intensity narrow-spectrum light environmental decontamination system (HINS-light EDS), for continuous disinfection in the burn unit inpatient and outpatient settings

Infections are the leading cause of morbidity and mortality in burn patients and prevention of contamination from exogenous sources including the hospital environment is becoming increasingly emphasised. The High-Intensity Narrow-Spectrum light Environmental Decontamination System (HINS-light EDS) is bactericidal yet safe for humans, allowing continuous disinfection of the environment surrounding burn patients. Environmental samples were collected from inpatient isolation rooms and the outpatient clinic in the burn unit, and comparisons were then made between the bacterial contamination levels observed with and without use of the HINS-light EDS. Over 1000 samples were taken. Inpatient studies, with sampling carried out at 0800 h, demonstrated a significant reduction in the average number of bacterial colonies following HINS-light EDS use of between 27% and 75%, (p<0.05). There was more variation when samples were taken at times of increased activity in the room. Outpatient studies during clinics demonstrated a 61% efficacy in the reduction of bacterial contamination on surfaces throughout the room during the course of a clinic (p=0.02). The results demonstrate that use of the HINS-light EDS allows efficacious bacterial reductions over and above that achieved by standard cleaning and infection control measures in both inpatient and outpatient settings in the burn unit

Micro electrostatic precipitation for air treatment

Micro-Electrostatic precipitation uses combining impulses and dc voltage in order to charge and remove fine, sub-micron particles efficiently. Short impulses are expected to increase the precipitation efficiency and to reduce power consumption

Impulse-breakdown characteristics of polymers immersed in insulating oil

Surface discharges along oil-immersed solids used as insulators and supports in high-voltage pulsed-power equipment can lead to catastrophic system failures. To achieve reliable compact pulsed-power systems, it is important to quantify the electrical fields at which surface flashover, or other types of breakdown event, will occur for different dielectric materials. This paper reports the observed behavior of samples of polypropylene, low-density polyethylene, ultrahigh-molecular-weight polyethylene, Rexolite, and Torlon, which were subjected to impulse voltages of peak amplitude of 350 kV and a rise time of 1 $muhbox{s}$. The cylindrical samples were located between pairs of electrodes immersed in insulating oil. Breakdown events were studied under both nonuniform- and uniform-field conditions, with sample lengths being chosen so that the breakdown events occurred on the rising edge of the impulse. Ultrahigh-molecular-weight polyethylene showed the highest average breakdown field, which is 645 kV/cm, in uniform fields, and the corresponding breakdown field was reduced to $sim$400 kV/cm in the nonuniform fields. Weibull plots of the various sets of results are presented, providing comparative data for system designers for the appropriate choice of dielectric materials to act as insulators for high-voltage pulsed-power machines

Excitations in the Halo Nucleus He-6 Following The Li-7(gamma,p)He-6 Reaction

A broad excited state was observed in 6-He with energy E_x = 5 +/- 1 MeV and width Gamma = 3 +/- 1 MeV, following the reaction Li-7(gamma,p)He-6. The state is consistent with a number of broad resonances predicted by recent cluster model calculations. The well-established reaction mechanism, combined with a simple and transparent analysis procedure confers considerable validity to this observation.Comment: 3 pages of LaTeX, 3 figures in PostScript, approved for publication in Phys. Rev. C, August, 200

Pulsed ultraviolet light decontamination of artificially-generated microbiological aerosols

Airborne transmission of infectious organisms is a major public health concern, particularly within healthcare and communal public environments. Methods of environmental decontamination utilising pulsed ultraviolet (UV) light are currently available, however it is important that germicidal efficacy against airborne contamination is established. In this study bacterial aerosols were generated and exposed to short duration pulses (~20 µs) of UV-rich light emitted from a xenon-filled flashlamp. The lamp was operated using a 1 kV solid–state pulsed power source, with a pulse frequency of 1 Hz, and output energy of 20 J/pulse. Post-treatment, air samples were extracted from the chamber and the surviving fraction was enumerated using standard microbiological culture methods. Results demonstrate successful aerosol inactivation, with a 92.1% reduction achieved with only 5 pulses of UV-rich light (P=<0.0002). Inactivation using continuous UV light was also investigated in order to quantify the comparative efficacy of these antimicrobial light sources. Overall, results provide evidence of the comparative efficacy of pulsed and continuous UV light for inactivation of airborne bacterial contamination. For practical application, given the safety restrictions limiting its application for decontamination of unoccupied environments, or within sealed enclosures such as air handling units, the reduced treatment times with PUV provides significant operational advantages over continuous light treatment