Alpha scattering and capture reactions in the A = 7 system at low energies

Differential cross sections for $^3$He-$\alpha$ scattering were measured in the energy range up to 3 MeV. These data together with other available experimental results for $^3$He $+ \alpha$ and $^3$H $+ \alpha$ scattering were analyzed in the framework of the optical model using double-folded potentials. The optical potentials obtained were used to calculate the astrophysical S-factors of the capture reactions $^3$He$(\alpha,\gamma)^7$Be and $^3$H$(\alpha,\gamma)^7$Li, and the branching ratios for the transitions into the two final $^7$Be and $^7$Li bound states, respectively. For $^3$He$(\alpha,\gamma)^7$Be excellent agreement between calculated and experimental data is obtained. For $^3$H$(\alpha,\gamma)^7$Li a $S(0)$ value has been found which is a factor of about 1.5 larger than the adopted value. For both capture reactions a similar branching ratio of $R = \sigma(\gamma_1)/\sigma(\gamma_0) \approx 0.43$ has been obtained.Comment: submitted to Phys.Rev.C, 34 pages, figures available from one of the authors, LaTeX with RevTeX, IK-TUW-Preprint 930540

Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron

The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2] for the proton and neutron have been determined from measurements of polarised cross section asymmetries in deep inelastic scattering of 27.5 GeV longitudinally polarised positrons from polarised 1H and 3He internal gas targets. The data were collected in the region above the nucleon resonances in the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the proton the contribution to the generalised Gerasimov-Drell-Hearn integral was found to be substantial and must be included for an accurate determination of the full integral. Furthermore the data are consistent with a QCD next-to-leading order fit based on previous deep inelastic scattering data. Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte

Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction

Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark- antiquark fluctuations with the nuclear medium.Comment: RevTeX, 5 pages, 3 figure

Marine pelagic ecosystems: the West Antarctic Peninsula

The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 28C increase in the annual mean temperature and a 68C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.68C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in icedependent Ade´lie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients extending along theWAPand the presence of monitoring systems, field stations and long-term research programmes make the region an invaluable observatory of climate change and marine ecosystem response

Soil nutrient dynamics and biomass production in an organic and inorganic fertilized short rotation willow coppice system

Changes in soil nutrients and biomass production of two willow clones (Salix miyabeana - SX64 and S. purpurea - 9882-34) in a 150 and 200 kg available N ha-1 of urea commercial fertilizer (CF), biosolid compost (BC) and digested dairy manure (DM) and a control (CTO) were compared at Middlebury, VT (MID), Delhi, NY (DEL) and Fredonia, NY (FRE). There was no significant difference in biomass production among the fertilization treatments. First rotation biomass production of SX64 ranged from 13.2-19.0 Mg ha-1 yr-1 at DEL, 9.0-15.0 Mg ha-1 yr-1 at MID and 5.5-9.3 Mg ha-1 yr-1 at FRE. For 9882-34, biomass production ranged from 9.0-11.6 Mg ha-1 yr-1 at DEL, 3.4-8.8 Mg ha-1 yr-1 at MID and 3.5-7.7 Mg ha-1 yr-1 at FRE. This indicates that willow biomass can be produced without fertilizer additions. Application of BC significantly increased soil N, P, Mg and OM levels at the MID site. At the DEL site, BC and DM treatments increased soil N, P, Ca, Mg and OM levels. The fertilization treatments had no significant effect on any soil nutrients at the FRE site

Multi criteria analysis for bioenergy systems assessments

Sustainable bioenergy systems are, by definition, embedded in social, economic, and environmental contexts and depend on support of many stakeholders with different perspectives. The resulting complexity constitutes a major barrier to the implementation of bioenergy projects. The goal of this paper is to evaluate the potential of Multi Criteria Analysis (MCA) to facilitate the design and implementation of sustainable bioenergy projects. Four MCA tools (Super Decisions, DecideIT, Decision Lab, NAIADE) are reviewed for their suitability to assess sustainability of bioenergy systems with a special focus on multi-stakeholder inclusion. The MCA tools are applied using data from a multi-stakeholder bioenergy case study in Uganda. Although contributing to only a part of a comprehensive decision process, MCA can assist in overcoming implementation barriers by (i) structuring the problem, (ii) assisting in the identification of the least robust and/or most uncertain components in bioenergy systems and (iii) integrating stakeholders into the decision process. Applying the four MCA tools to a Ugandan case study resulted in a large variability in outcomes. However, social criteria were consistently identified by all tools as being decisive in making a bioelectricity project viable

Untapped Potential : Opportunities and Challenges for Sustainable Bioenergy Production from Marginal Lands in the Northeast USA

Over two million hectares of marginal land in the Northeast USA no longer used for agriculture may be suitable and available for production of second-generation cellulosic bioenergy crops, offering the potential for increased regional bioenergy production without competing with food production on prime farmland. Current yields of perennial bioenergy grasses and short-rotation woody crops range from 2.3 to 17.4 and 4.5 to 15.5 Mg/ha, respectively, and there is great potential for increased yields. Regional advantages for bioenergy development include abundant water resources, close proximity between production and markets, and compatibility of bioenergy cropping systems with existing agriculture. As New York and New England (a subset of the Northeast region) account for ~85 % of the nation’s heating oil consumption, production of bioheat, biopower, and combined heat and power could substantially reduce the region’s dependence on imported petroleum. While numerous grassroots efforts are underway in the region across supply chains, bioenergy development faces several challenges and unknowns in terms of environmental impact, production, yields, socioeconomics, and policy. We explore the opportunities for second-generation bioenergy production on the unused marginal lands of the Northeast USA and discuss the challenges to be addressed to promote sustainable bioenergy production on the region’s underutilized marginal land base