Parity nonconservation in deuteron photoreactions

We calculate the asymmetries in parity nonconserving deuteron photodisintegration due to circularly polarized photons gamma+d to n+p with the photon laboratory energy ranging from the threshold up to 10 MeV and the radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We use the leading order electromagnetic Hamiltonian neglecting the smaller nuclear exchange currents. Comparative calculations are done by using the Reid93 and Argonne v18 potentials for the strong interaction and the DDH and FCDH "best" values for the weak couplings in a weak one-meson exchange potential. A weak NDelta transition potential is used to incorporate also the Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2

Parity nonconservation effects in the photodesintegration of polarized deuterons

P-odd correlations in the deuteron photodesintegration are considered. The $\pi$-meson exchange is not operative in the case of unpolarized deuterons. For polarized deuterons a P-odd correlation due to the $\pi$-meson exchange is about $3 \times 10^{-9}$. Short-distance P-odd contributions exceed essentially than the contribution of the $\pi$-meson exchange.Comment: 12 pages, Latex, 3 figure

Biological sources and sinks of nitrous oxide and strategies to mitigate emissions

Nitrous oxide (N 2 O) is a powerful atmospheric greenhouse gas and cause of ozone layer depletion. Global emissions continue to rise. More than two-thirds of these emissions arise from bacterial and fungal denitrification and nitrification processes in soils, largely as a result of the application of nitrogenous fertilizers. This article summarizes the outcomes of an interdisciplinary meeting, ‘Nitrous oxide (N 2 O) the forgotten greenhouse gas’, held at the Kavli Royal Society International Centre, from 23 to 24 May 2011. It provides an introduction and background to the nature of the problem, and summarizes the conclusions reached regarding the biological sources and sinks of N 2 O in oceans, soils and wastewaters, and discusses the genetic regulation and molecular details of the enzymes responsible. Techniques for providing global and local N 2 O budgets are discussed. The findings of the meeting are drawn together in a review of strategies for mitigating N 2 O emissions, under three headings, namely: (i) managing soil chemistry and microbiology, (ii) engineering crop plants to fix nitrogen, and (iii) sustainable agricultural intensification. </jats:p

Methane emission by Camelids

Methane emissions from ruminant livestock have been intensively studied in order to reduce contribution to the greenhouse effect. Ruminants were found to produce more enteric methane than other mammalian herbivores. As camelids share some features of their digestive anatomy and physiology with ruminants, it has been proposed that they produce similar amounts of methane per unit of body mass. This is of special relevance for countrywide greenhouse gas budgets of countries that harbor large populations of camelids like Australia. However, hardly any quantitative methane emission measurements have been performed in camelids. In order to fill this gap, we carried out respiration chamber measurements with three camelid species (Vicugna pacos, Lama glama, Camelus bactrianus; n = 16 in total), all kept on a diet consisting of food produced from alfalfa only. The camelids produced less methane expressed on the basis of body mass (0.3260.11 L kg21 d21) when compared to literature data on domestic ruminants fed on roughage diets (0.5860.16 L kg21 d21). However, there was no significant difference between the two suborders when methane emission was expressed on the basis of digestible neutral detergent fiber intake (92.7633.9 L kg21 in camelids vs. 86.2612.1 L kg21 in ruminants). This implies that the pathways of methanogenesis forming part of the microbial digestion of fiber in the foregut are similar between the groups, and that the lower methane emission of camelids can be explained by their generally lower relative food intake. Our results suggest that the methane emission of Australia’s feral camels corresponds only to 1 to 2% of the methane amount produced by the countries’ domestic ruminants and that calculations of greenhouse gas budgets of countries with large camelid populations based on equations developed for ruminants are generally overestimating the actual levels

The atmospheric cycling of radiomethane and the "fossil fraction" of the methane source

International audienceThe cycling of 14CH4 ("radiomethane") through the atmosphere has been strongly perturbed in the industrial era by the release of 14C-free methane from geologic reservoirs ("fossil methane" emissions), and in the nuclear era, especially since ca 1970, by the direct release of nucleogenic radiomethane from nuclear power facilities. Contemporary measurements of atmospheric radiomethane have been used to estimate the proportion of fossil methane in the global methane source (the "fossil fraction"), but such estimates carry high uncertainty due to the ill-determined nuclear-power source. Guided by a mass-balance formulation in a companion paper, we apply a contemporary time series of atmospheric radiomethane to quantify both the fossil fraction and the strength of the nuclear power source. We deduce that 30.0±2.3% (1 s.d.) of the global methane source for 1986?2000 has fossil origin, a fraction which may include some 14C-depleted refractory carbon such as from aged peat deposits. Since this estimate depends upon the validity of assumptions underlying a linear regression model, it should be seen as providing a plausible re-estimate rather than a definitive revision. Such a fossil fraction would be much larger (by 50%) than is commonly accepted, with implications for inventory compilation. The co-estimated strength of the global nuclear-power source of radiomethane is consistent with values inferred independently from local nuclear facilities

Social-demographic and reproductive characteristics of mothers delivered at the Korle-Bu Teaching Hospital, Ghana

Objectives: To measure selected socio-demographic and reproductive history characteristics of parturients at the Korle-Bu Teaching Hospital (KBTH), Accra, Ghana, and to compute the risk load. Design: A non-randomised cross-sectional survey. Setting: Korle-Bu Teaching Hospital, Accra, Ghana. Subjects: Korle-Bu Teaching Hospital, a tertiary institution delivers about 11000 women annually. From 1st November to 12th December 1994, 961 parturients were studied out of 978 delivered during the study period. Seventeen questionnaires were excluded from analysis because of errors and omissions that could not be corrected before the parturients' discharge from hospital. Methods: The data sources were the patients' antenatal and delivery records, and a structured interviewer-administered questionnaire. Results: More than three per cent of the subjects were less than 18 years, and 10.8% were over 35 years of age. Before the index delivery, 5.8% were grand multiparae. Eighteen per cent had never been to school. Seventeen per cent of parous subjects had experienced a perinatal death. The non-educated had significantly more births. The mean birth interval was less than two years in 26.4%. Fifty percent of those who had been previously pregnant had a history of at least one induced-abortion. Only 21.0% of the 961 subjects had ever-used a family planning method. The risk load was 53.0%. Conclusion: Analysis of the historical factors of parturients surveyed at the KBTH showed a high risk load related mainly to lack of education. Formal education of the female child and family health education of our women are recommended to reduce the high past abortion rate and risk load. Additionally, postpartum tubal ligation for those who have completed their families will further reduce the risk load. (East African Medical Journal: 2002 79(4): 176-180