Enhancements in laser-generated hot-electron production via focusing cone targets at short pulse and high contrast.

We report on the increase in the accelerated electron number and energy using compound parabolic concentrator (CPC) targets from a short-pulse (∼150 fs), high-intensity (>10^{18} W/cm^{2}), and high-contrast (∼10^{8}) laser-solid interaction. We report on experimental measurements using CPC targets where the hot-electron temperature is enhanced up to ∼9 times when compared to planar targets. The temperature measured from the CPC target is 〈T_{e}〉=4.4±1.3 MeV. Using hydrodynamic and particle in cell simulations, we identify the primary source of this temperature enhancement is the intensity increase caused by the CPC geometry that focuses the laser, reducing the focal spot and therefore increasing the intensity of the laser-solid interaction, which is also consistent with analytic expectations for the geometrical focusing.

Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging.

Radiographic imaging with x-rays and protons is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. The information contained in both modalities can often be valuable in principle, but difficult to access simultaneously. Laser-driven solid-density plasma-sources deliver both kinds of radiation, but mostly single modalities have been explored for applications. Their potential for bi-modal radiographic imaging has never been fully realized, due to problems in generating appropriate sources and separating image modalities. Here, we report on the generation of proton and x-ray micro-sources in laser-plasma interactions of the focused Texas Petawatt laser with solid-density, micrometer-sized tungsten needles. We apply them for bi-modal radiographic imaging of biological and technological objects in a single laser shot. Thereby, advantages of laser-driven sources could be enriched beyond their small footprint by embracing their additional unique properties, including the spectral bandwidth, small source size and multi-mode emission.

The response function of Fujifilm BAS-TR imaging plates to laser-accelerated titanium ions.

Calibrated diagnostics for energetic particle detection allow for the systematic study of charged particle sources. The Fujifilm BAS-TR imaging plate (IP) is a reusable phosphorescent detector for radiation applications such as x-ray and particle beam detection. The BAS-TR IP has been absolutely calibrated to many low-Z (low proton number) ions, and extending these calibrations to the mid-Z regime is beneficial for the study of laser-driven ion sources. The Texas Petawatt Laser was used to generate energetic ions from a 100 nm titanium foil, and charge states Ti10+ through Ti12+, ranging from 6 to 27 MeV, were analyzed for calibration. A plastic detector of CR-39 with evenly placed slots was mounted in front of the IP to count the number of ions that correspond with the IP levels of photo-stimulated luminescence (PSL). A response curve was fitted to the data, yielding a model of the PSL signal vs ion energy. Comparisons to other published response curves are also presented, illustrating the trend of PSL/nucleon decreasing with increasing ion mass.

Proton acceleration by irradiation of isolated spheres with an intense laser pulse.

We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2-3×10^{20}Wcm^{-2}. With a laser focal spot size of 10 µm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 µm. Maximum proton energies of ∼25 MeV are achieved for targets matching the focal spot size of 10 µm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.

Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV.

Laser-plasma accelerators of only a centimetre's length have produced nearly monoenergetic electron bunches with energy as high as 1 GeV. Scaling these compact accelerators to multi-gigaelectronvolt energy would open the prospect of building X-ray free-electron lasers and linear colliders hundreds of times smaller than conventional facilities, but the 1 GeV barrier has so far proven insurmountable. Here, by applying new petawatt laser technology, we produce electron bunches with a spectrum prominently peaked at 2 GeV with only a few per cent energy spread and unprecedented sub-milliradian divergence. Petawatt pulses inject ambient plasma electrons into the laser-driven accelerator at much lower density than was previously possible, thereby overcoming the principal physical barriers to multi-gigaelectronvolt acceleration: dephasing between laser-driven wake and accelerating electrons and laser pulse erosion. Simulations indicate that with improvements in the laser-pulse focus quality, acceleration to nearly 10 GeV should be possible with the available pulse energy.

Breast carcinoma survival analysis for African American and white women in an equal-access health care system.

BACKGROUND: This retrospective review of breast carcinoma cases in the Department of Defense (DoD) Central Tumor Registry evaluated differences in survival patterns between African American and white women treated in U.S. military health care facilities. The study examined the effects of age, stage of cancer, tumor size, grade, lymph node involvement, waiting time between diagnosis and first treatment, marital status, military dependent status, alcohol usage, tobacco usage, and family history of cancer. METHODS: Researchers reviewed the tumor registry records of 6577 women (5879 whites and 698 African Americans) diagnosed with breast carcinoma. The patients, ages 19-97 years, were diagnosed between 1975 and 1994. A hazard ratio (relative risk of mortality) model compared African American and white patients, adjusting for various combinations of covariates; impact of independent variables on the risk of death; prognostic factors significantly associated with survival; disease free and overall survival times; effects of ethnicity, stage, and age on survival; and trends in stage at diagnosis. A P value (2-sided) of less than 0.05 was considered statistically significant. RESULTS: After adjustment for age, the risk of death was 1.45 (95% confidence interval [CI], 1.20-1.76) times greater for African American women than for white women. Adjustment for stage reduced the risk to 1.41 (95% CI, 1.16-1.70); further adjustment for demographic variables and most clinical variables had no effect. Still, African American women treated in the military health care facilities had a better survival rate than African American women represented in the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. In our study, the 5-year risk of death, from any cause, was 1.37 for African American women with breast carcinoma; in other words, the mortality rate for African American women was 24.77% compared with 18.08% for white women. In the latest SEER data, the 5-year relative risk of death for African American women compared with white women is 1.86. The mortality rate in SEER is 34.2% for African American women and 18.4% for white women. The survival rate for white DoD beneficiaries is comparable to that for white women in SEER. CONCLUSIONS: These observations suggest that ready access to medical facilities and the full complement of treatment options that are standard for all DoD patients improve survival rates for African American women. However, a significant unexplained difference in survival still exists between African American and white military beneficiaries.

Evaluation of Caribbean strains of Macrocyclops and Mesocyclops (Cyclopoida:Cyclopidae) as biological control tools for the dengue vector Aedes aegypti.

Fifteen Caribbean strains of copepods were assessed for their predation ability against mosquito larvae. Macrocyclops albidus from Nariva. Mesocyclops aspericornis from Oropouche, and Mesocyclops longisetus from E1 Socorro, Trinidad, were most effective against Aedes aegypti but not against Culex quinquefasciatus. Mesocyclops longisetus and Me. aspericornis prevented any mosquito survival over 25 wk of observation despite weekly challenges with Ae. aegypti. The copepods were tolerant to dosages of the insecticide temephos that are usually toxic to mosquito larvae. This indicated that copepods could be incorporated into an integrated control system. To determine whether pathogenic microbes might be introduced with copepods into drinking water, microbial studies were done on the copepods. These showed the presence of only Aeromonas sobria, Pseudomonas sp., Alcalignes sp., and gram-positive bacilli. Although none of these are highly pathogenic to humans, the application of these copepods has not yet been recommended for use in drinking water.

Risk assessment--is there a risk?

Mary Spinks is a health service consultant, retired regional nurse and former National Chairman of NATN. She was a member of the NATN Working Party which developed the Risk Assessment Guide (RAG), launched last year at the NATN Congress and now widely used in operating theatres in the UK. She has written this article to give guidance to those who are developing risk management principles in their own practice.

Caribbean morality: 10 years 1980-1990

A review of underlying causes of death, as gleaned from the death certificate data of CAREC's member countries, revealed interesting insights into the changes in the mortality experience of Caribbean people during the past decade. Notwithstanding the ageing of the sub-regional population, crude mortality rates have declined from 765.0 per 100 000 population in 1980 to 674.0 in 1990. Specifically, infant mortality rates declined from 28.6 per 1 000 livebirths to 18.8 in 1990. Improved living conditions, better sanitation and effective programmes of immunization, oral rehydration and maternal and child health have all influenced mortality due to communicable diseases, especially diarrhoeal disease, and perinatal conditions. The appearance of nutrition-related mortality in children aged under 5-years is cause for concern, as Governments implement economic policies. Of concern also is the fact that in 1990 AIDS became one of the ten leading causes of death in males aged 25-44 years. Chronic diseases continued to play a major role in the health of the Caribbean people, with little change in mortality due to cerebrovascular and ischaemic heart disease and significant increase in rates due to diabetes in persons aged 54-64 years, from 79.6 deaths per 100 000 population in 1980 to 153.5 in 1990. Also increasing significantly were mortality rates due to injuries. While fatal motor vehicle injury rates fell from 17.9 in 1980 to 10.0 in 1990, homicide and suicide rates quadrupled in 25-44-year-old males, from 8.6 and 9.6 to 29.7 and 31.9, respectively. Mortality from neoplasm, especially of the prostate, breast and cervix, was also notable (AU)

Evaluation of Caribbean strain of macrocyclops and mesocyclops (cyclopoida: cycopoidae) as a biological tool for the dengue vector, aedes aegypti

When 15 Caribbean strains of copepods (Cyclopoida: Cyclopidae) were assessed for their predation ability against mosquito larvae, Macrocyclops albidus from Nariva, Mesocyclops aspericornis from Oropouche and Me.longisetus from El Socorro, Trinidad, were most effective against Aedes aegypti but not against the nuisance mosquito, Culex quinquefasciatus. Me.longisetus and Me.aspericornis prevented any mosquito survival over 25 weeks of observation despite weekly challenges with Aedes aegypti. The copepods were tolerant to dosages of the insecticide temephos which are usually toxic to mosquito larvae. This indicated their ability to be incorporated into an integrated control system of biological and chemical components. Microbial studies done on the copepods showed the presence of only Aeromonas sobria, Pseudomonas sp., Alcaligenes and gram-positive bacilli. The application of these copepods has not yet been recommended for use in drinking water (AU)