627 research outputs found

    Coincident proton decay of the continuum induced by 200 MeV protons on 12C

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    Bibliography: p. 212-221.Coincident protons from the reaction ¹²C(p,2p) at an incident proton energy of 200 Me V, have been measured using conventional particle telescopes. Data were acquired at nine pairs of angles (θ₂=20°, 45°, 70°, 95°, 120° and 145° for θ₁ =-20°, and θ₂=35°, 85° and 135° for θ₁ =-45°). An improved model, based on previous theoretical and experimental work, has been proposed to describe the reaction mechanism leading to the observed coincident proton yield from the nuclear continuum. This model considers an initial quasifree nucleon-nucleon interaction - described by a distorted wave impulse approximation (DWIA) treatment - between the incident proton and a single target nucleon, followed by the rescattering of the struck nucleon, which behaves as an intranuclear projectile, from the spectator part of the target nucleus. The validity of the DWIA treatment used in the continuum study, has been tested by analysing the kinematic regions of the coincident proton energy spectra corresponding to the knockout of protons from the outer lp3/2 orbital of ¹²C which do not undergo further interactions with the residual nucleus. Good agreement in shape has been found between the calculated and measured cross sections in the kinematic region of interest to the continuum study. An average spectroscopic factor of 1.1±0.3 was extracted. Except in the -20°,20° case, the DWIA treatment was found to be insensitive to the choice of the initial or final energy prescriptions for the two-body scattering approximation. Nonlocality effects were found to be small, changing the absolute value of spectroscopic factors by a maximum of 20%. Coincident continuum cross sections were extracted from the experimental data corresponding to the detection of protons at the θ₁ angles with energies of 70±5 MeV, 100±5 MeV and 130±5 MeV. Comparisons were made with calculations which modelled the proposed reaction mechanism in terms of a convolution integral over the DWIA cross sections describing the initial quasifree knockout process and experimental inelastic scattering probabilities describing the further multiple scattering interactions undergone by the knocked out nucleons. Good agreement has been found between the normalized calculated and measured continuum cross sections (spectroscopic factors varying from 0.8 to 2.3 between sets of data, depending on the kinematic region sampled and the prescription used for the two-body scattering approximation). It has been shown that contributions from nucleons that are knocked out both in- and out-of-plane in the initial quasifree process should be considered, and that the contribution from neutron knockout in the initial interaction is significant, ranging from 0.13 to 0.62 that of the proton knockout contribution

    Charles Brewster of Fort Madison: a Profile in Enterprise, 1845-1875

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    Impact of Tylosin Phosphate and Distillers Dried Grains with Solubles on Amino Acid and Energy Digestibility of Diets Fed to Growing Pigs

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    Eighteen barrows with a T-cannula in the distal ileam were utilized in a study evaluating the impact of tylosin phosphate on amino acid and energy digestibility in cornsoybean meal and corn-soybean meal-distillers dried grains with soluble (DDGS) based diets. There were no interactions between the responses to tylosin phosphate and DDGS (P\u3e0.10). DDGS inclusion reduced the standardized ileal digestibility of most indispensible amino acids (P\u3c0.05) and the apparent ileal digestibility and apparent total tract digestibility of energy. Under the conditions of this experiment, tylosin phosphate did not affect digestibility of amino acids or energy and the inclusion of DDGS did not affect the response to TP

    Effects on transgenic thuringiensis on European corn borer natural enemies and non-target Lepidopteran pests

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    Field corn, genetically engineered to produce a protein derived from Bacillus thuringiensis, was evaluated for its effects on larvae of black cutworm, stalk borer, armyworm, and corn earworm. No Btcorn effects were observed on larval survival, pupal weight, or days to adult emergence for black cutworm or stalk borer. Armyworms reared on Bt leaf extract were lighter-weight, delayed in development, and showed diminished survival rates. Corn earworm showed reduced survival and delays in development. In field tests of Bt and non-Bt corn, there were no differences between the two varieties in damage from black cutworm. Stalk borer caused less leaf damage to Bt corn. Armyworm and corn earworm did less harm to Bt corn leaves than to non-Bt corn leaves, but corn earworm survived to cause some damage to Bt corn ears

    Lime binders for the repair of historic buildings: Considerations for CO2 abatement

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    Lime binders are utilised worldwide and are associated with a considerable scale of production and corresponding CO2 emissions. The relevance of this review is therefore international in scope, with production transcending geographical boundaries and construction practices. An holistic view of lime binders, considering their provenance, production and utilisation offers the potential for significant CO2 savings urgently required globally. Importantly, the technical aspects of lime materials production is critical, but the alteration of behaviour of both specifier and those undertaking the construction processes is also essential in achieving meaningful CO2 emission reduction. This review paper investigates the life cycle stages of lime binders in line with the features highlighted in the Scottish Building Alliance (SBA) ‘building life cycle stages model’. It attempts to determine what can be learnt from our understanding of the manufacture and use of binders from historic, current and future perspectives in the context of reconciling the production of historically authentic materials in a decarbonising environment. The production and use of such authentic historic lime binders initially appears highly carbon intensive through its utilisation of relatively inefficient kiln technologies and loss of economies of scale associated with larger operations. However, this review shows numerous benefits in the production of such binders; including their CO2 sequestration capability, lower potential processing energy, and a reduction in excessive ‘carbon miles’ associated with transportation. Importantly, we show how historic production and on-site manufacture approaches with lime-based materials also offers exciting potential for carbon savings. Importantly, hot mixed lime mortars offer the promise of higher durability materials compared to their modern cold manufactured counterparts, thereby reducing the frequency of repeat maintenance interventions, again yielding CO2 savings. We suggest hot mixing, whether in an innovative contemporary materials realm or within traditional contexts should be explored. In addition, hot mixed materials can concomitantly satisfy conservation requirements for repairs through better reflecting the aspired to building conservation requirement of like for like materials replacement reflected with historically produced binders. We suggest future paths for the industry that would simultaneously reconcile demands for authentic materials and production methods for the conservation sector with the necessity of achieving cleaner production in a decarbonizing world

    A low-cost solution for documenting distribution and abundance of endangered marine fauna and impacts from fisheries

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    Fisheries bycatch is a widespread and serious issue that leads to declines of many important and threatened marine species. However, documenting the distribution, abundance, population trends and threats to sparse populations of marine species is often beyond the capacity of developing countries because such work is complex, time consuming and often extremely expensive. We have developed a flexible tool to document spatial distribution and population trends for dugongs and other marine species in the form of an interview questionnaire supported by a structured data upload sheet and a comprehensive project manual. Recognising the effort invested in getting interviewers to remote locations, the questionnaire is comprehensive, but low cost. The questionnaire has already been deployed in 18 countries across the Indo-Pacific region. Project teams spent an average of USD 5,000 per country and obtained large data sets on dugong distribution, trends, catch and bycatch, and threat overlaps. Findings indicated that >50% of respondents had never seen dugongs and that 20% had seen a single dugong in their lifetimes despite living and fishing in areas of known or suspected dugong habitat, suggesting that dugongs occurred in low numbers. Only 3% of respondents had seen mother and calf pairs, indicative of low reproductive output. Dugong hunting was still common in several countries. Gillnets and hook and line were the most common fishing gears, with the greatest mortality caused by gillnets. The questionnaire has also been used to study manatees in the Caribbean, coastal cetaceans along the eastern Gulf of Thailand and western Peninsular Malaysia, and river dolphins in Peru. This questionnaire is a powerful tool for studying distribution and relative abundance for marine species and fishery pressures, and determining potential conservation hotspot areas. We provide the questionnaire and supporting documents for open-access use by the scientific and conservation communities

    Biotechnology and the European Corn Borer: Measuring Historical Farmer Perceptions and Adoption of Transgenic Bt Corn as a Pest Management Strategy

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    A 3-yr, multi-state survey of farmers who had planted transgenic Bacillus thuringiensis (Bt) corn was conducted to evaluate perceptions of Bt corn performance and its utility as a management option for European corn borer, Ostrinia nubilalis (Hu¨ bner). A questionnaire was sent to farmers in Illinois, Iowa, Kansas, Minnesota, Nebraska, and Pennsylvania who had grown Bt corn during the growing seasons of 1996, 1997, or 1998. There were 7,427 usable questionnaires returned with the following response percentages: 1996 (42.1%), 1997 (35.0%), and 1998 (22.6%). Adoption rates, based on percentage of acreage planted to Bt corn, increased dramatically from 1996 (10.5%) to 1998 (40.7%). The states growing the highest percentage of Bt corn were Minnesota, Iowa, and then Nebraska. However, Illinois, was adopting Bt corn at the fastest rate. Historical use of insecticides did not inßuence the adoption of Bt corn. In addition, of those farmers who used insecticides to control European corn borer, the percentage that decreased their use of insecticides nearly doubled from 13.2% (1996) to 26.0% (1998) over this 3-yr period. The primary reason farmers planted Bt corn was to eliminate the yield loss caused by European corn borer. Scouting for European corn borers decreased from 91% (scouting 2.2 times a year) in 1996 to 75% (scouting 1.8 times a year) in 1998. The percentage of farmers not scouting for European corn borers increased from 9.6% (1996) to 25% (1998). Most farmers believed yields of Bt hybrids were either similar to or greater than the yields of non-Bt hybrids. Minnesota farmers perceived the greatest yield advantages. Farmers are becoming more aware of insect resistance management guidelines; however, they also clearly show preferences for having the ßexibility to use different spatial plantings of Bt and non-Bt corn. Finally, after having planted Bt corn and obtained excellent control of European corn borer, most farmers believed that this insect had been causing more yield loss than they previously had suspected in their non-Bt corn. The data represented here provide an historical foundation for how transgenic Bt corn was used by farmers during the Þrst 3 yr of commercial availability, their initial perceptions on the performance of this technology, and their attitudes regarding management of the European corn borer

    Implications of a charged-current anomaly at HERA

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    We demonstrate that in the presence of mixing between different scalar leptoquark multiplets it is possible to simultaneously account for the HERA high-Q2Q^2 neutral current anomaly, and produce a charged current anomaly of comparable magnitude. The reduced branching ratio to electrons and jets of the lightest leptoquark state results in a significant weakening of the CDF/D0 limits on scalar leptoquarks; masses consistent with the HERA neutral current excess are comfortably within the allowed range. We show that the possibilities for such a successful mixed leptoquark scenario are quite limited, and we investigate some aspects of their phenomenology.Comment: 10 pages Latex. Corrected 3-body decay width
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