Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser

The kinetic energy of hot (multi-keV) ions from the laser-driven Coulomb explosion of deuterium clusters and the resulting fusion yield in plasmas formed from these exploding clusters has been investigated under a variety of conditions using the Texas Petawatt laser. An optimum laser intensity was found for producing neutrons in these cluster fusion plasmas with corresponding average ion energies of 14 keV. The substantial volume (1-10 mm(3)) of the laser-cluster interaction produced by the petawatt peak power laser pulse led to a fusion yield of 1.6x10(7) neutrons in a single shot with a 120 J, 170 fs laser pulse. Possible effects of prepulses are discussed. DOI: 10.1103/PhysRevE.87.023106Glenn Focht Memorial FellowshipNNSA DE-FC52-08NA28512DOE Office of Basic Energy SciencesPhysic

The Texas Petawatt Laser And Current Experiments

The Texas Petawatt Laser is operational with experimental campaigns executed in both F/40 and F3 target chambers. Recent improvements have resulted in intensities of >2x10(21) W/cm(2) on target. Experimental highlights include, accelerated electron energies of >2 GeV, DD fusion ion temperatures >25 keV and isochorically heated solids to 10-50 eV.Physic

How Dry Are Red Mergers?

The focus of current research in galaxy evolution has increasingly turned to understanding the effect that mergers have on the evolution of systems on the red sequence. For those interactions purported to occur dissipationlessly (so called "dry mergers"), it would appear that the role of gas is minimal. However, if these mergers are not completely dry, then even low levels of gas may be detectable. The purpose of our study is to test whether early type galaxies with HI in or around them, or "wet" ellipticals, would have been selected as dry mergers by the criteria in van Dokkum (2005, AJ, 130, 2647). To that end, we examine a sample of 20 early types from the HI Rogues Gallery with neutral hydrogen in their immediate environs. Of these, the 15 brightest and reddest galaxies match the optical dry merger criteria, but in each case, the presence of HI means that they are not truly dry.Comment: 8 pages plus 1 table and 5 figures; accepted for publication in A

Correlation between X-ray Lightcurve Shape and Radio Arrival Time in the Vela Pulsar

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray emission and radio arrival times on a pulse by pulse basis. At a confidence level of 99.8% we have found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. Our results suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption of radio emission in the outer magnetosphere as a cause of the X-ray emission are explored as a possible explanation for the correlation.Comment: 6 pages, 5 figures, accepted by Ap

Exploring the gap between policy and action in Disaster Risk Reduction: A case study from India

The transition from a response-based paradigm to an anticipative, prevention-based approach remains a stubborn challenge in Disaster Risk Reduction (DRR). Whilst the United Nations Office for Disaster Risk Reduction (UNDRR) has advocated the latter since the International Decade for Natural Disaster Reduction in the 1990s, many countries have been slow to move from a response-focused approach to a preventative one. International policy guidelines have successfully informed the national DRR policies in various countries; however, their further translation down to the regional and local level is full of complex political challenges, exacerbated in many areas by an increased frequency of disasters. In this paper we explore the case of India, using the example of landslide risk management. Through an analysis of the evolution of landslide risk governance during the last two decades in two hilly regions – Darjeeling in the Himalayas and the Nilgiris in the Western Ghats – we demonstrate that while the national government appears to have made considerable efforts to move in line with the UNDRR approaches, the eventual outcome of these efforts at the regional and local level is largely an incremental improvement on the existing DRR approach and not a paradigm shift in understanding and addressing disaster risk. We argue that overcoming these issues requires attentiveness to a situated understanding of disasters and institutions at the local level, and not treating apparent gaps between policy and action as functional challenges to be overcome with new science from national level

Grassland Songbirds In A Dynamic Management Landscape: Behavioral Responses And Management Strategies

In recent decades, earlier and more frequent harvests of agricultural grasslands have been implicated as a major cause of population declines in grassland songbirds. From 2002 to 2005, in the Champlain Valley of Vermont and New York, USA, we studied the reproductive success of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. Both the number of fledglings per female per year and nest success (logistic-exposure method) varied among treatments and between species. Although birds initiated nests earlier on early-hayed fields compared to others, haying caused 99% of active Savannah Sparrow and 100% of active Bobolink nests to fail. Both the initial cutting date and time between cuttings influenced renesting behavior. After haying, Savannah Sparrows generally remained on early-hayed fields and immediately renested (clutch completion 15.6 ± 1.28 days post-haying; all values are reported as mean 6 SE), while Bobolinks abandoned the fields for at least two weeks (mean clutch completion 33 ± 0.82 days post-haying). While female Savannah Sparrows fledged more offspring per year (1.28 ± 0.16) than female Bobolinks (0.05 6 0.05), reproductive success on early-hayed fields was low. The number of fledglings per female per year was greater on middle-hayed fields (Savannah Sparrows, 3.47 ± 0.42; Bobolinks, 2.22 ± 0.26), and late-hayed fields (Savannah Sparrows, 3.29 ± 0.30; Bobolinks, 2.79 ± 0.18). Reproductive success was moderate on rotationally grazed pastures, where female Savannah Sparrows and female Bobolinks produced 2.32 ± 0.25 and 1.79 ± 0.33 fledgling per year, respectively. We simultaneously conducted cutting surveys throughout the Champlain Valley and found that 3–8% of hayfield habitat was cut by 1–4 June, 25–40% by 12–16 June, and 32–60% by 28 June–2 July. Thus, the majority of grassland habitat was cut during the breeding season; however, late-hayed fields served as high-quality reserves for late-nesting female Bobolinks that were displaced from previously hayed fields. For fields first cut in May, a 65-day interval between cuts could provide enough time for both species to successfully fledge young

Grassland Songbird Survival And Recruitment In Agricultural Landscapes: Implications For Source-Sink Demography

Population growth and decline are particularly sensitive to changes in three key life-history parameters: annual productivity, juvenile survival, and adult survival. However, for many species these parameters remain unknown. For example, although grassland songbirds are imperiled throughout North America, for this guild, only a small number of studies have assessed these parameters. From 2002 to 2006, in the agricultural landscape of the Champlain Valley of Vermont and New York, USA, we studied Savannah Sparrow (Passerculus sandwichensis) and Bobolink (Dolichonyx oryzivorus) demography on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. We assessed whether these treatments affected adult apparent survival (φ) and recruitment (ƒ ), how sensitive these parameters were to the presence of nonbreeders and local dispersal, and the populations’ ability to persist in these four habitats. On average, birds using late-hayed fields had \u3e25% higher apparent survival than those on the more intensively managed early-hayed, middle-hayed, and grazed fields. Overall male φ was 35% higher than female φ, and Savannah Sparrow φ was 44% higher than Bobolink φ. Across all analyses and treatments, apparent survival estimates were 0.58–0.85 for male and 0.48–0.71 for female Savannah Sparrows, and 0.52–0.70 for male and 0.19–0.55 for female Bobolinks. For males of both species, potential nonbreeders decreased the precision of and lowered apparent survival estimates by 25%; female estimates showed little variation with the inclusion of nonbreeders. Inclusion of local dispersal observations increased apparent survival estimates and, in many cases, increased precision, though the effect was stronger for Savannah Sparrows than for Bobolinks, and also stronger for males than for females. High Savannah Sparrow apparent survival rates resulted in stable or near stable populations (λ ≈ 1), particularly in late-hayed and grazed fields, while low Bobolink apparent survival rates resulted in strongly declining populations (λ \u3c 1) in all treatments