Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere     

PO Wennberg  TF Hanisco  L Jaegle  DJ Jacob  EJ Hintsa  EJ Lanzendorf  JG Anderson  R Gao  ER Keim  SG Donnelly  LAD Negro  DW Fahey  SA McKeen  RJ Salawitch  CR Webster  RD May  RL Herman  MH Proffitt  JJ Margitan  EL Atlas  SM Schauffler  F Flocke  CT McElroy  TP Bui 《Science (New York, N.Y.)》1998,279(5347):49-53

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.  相似文献   

A tunable kondo effect in quantum dots   总被引：1，自引：0，他引：1  

SM Cronenwett  TH Oosterkamp  LP Kouwenhoven 《Science (New York, N.Y.)》1998,281(5376):540-544

A tunable Kondo effect has been realized in small quantum dots. A dot can be switched from a Kondo system to a non-Kondo system as the number of electrons on the dot is changed from odd to even. The Kondo temperature can be tuned by means of a gate voltage as a single-particle energy state nears the Fermi energy. Measurements of the temperature and magnetic field dependence of a Coulomb-blockaded dot show good agreement with predictions of both equilibrium and nonequilibrium Kondo effects.  相似文献   

Effects of pimobendan on myocardial perfusion and pulmonary transit time in dogs with myxomatous mitral valve disease: a pilot study          下载免费PDF全文

SM Apple  G Menciotti  L Braz‐Ruivo  S Crosara  J Häggström  M Borgarelli 《Australian veterinary journal》2016,94(9):324-328

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Comparison of worm control strategies in grazing sheep in Denmark.     

ME Boa  SM Thamsborg  AA Kassuku  HO B?gh 《Acta veterinaria Scandinavica》2001,42(1):57-69

Control of nematode parasites with reduced reliance on the use of anthelmintics was studied in 16 ewes with suckling twin lambs on contaminated pasture in Denmark. Ewes and lambs were treated with albendazole at turn-out 3 May. Ewes were removed from the groups on 26 July, and lambs were slaughtered on 11 October. The animals were allocated to 4 groups of 8 lambs and their 4 ewes. Group TS was treated with albendazole at weeks 3, 6 and 8 after turnout and set-stocked; group TM was similarly treated but moved to clean pasture in conjunction with the last drenching; group US was untreated and set-stocked, and group UM was left untreated but moved to clean pasture week 8 after turn-out. Supplementary feed was offered in June and August due to scarcity of pasture. Strategic treatments of ewes and lambs weeks 3, 6 and 8 after turn-out, with or without a move to clean pasture, were highly effective in controlling nematode infections for most of the season. This was reflected in better weight gains and carcass characteristics in the treated compared to untreated lambs, resulting in an average increase in the value of the product by 36%. The effect of moving without treatment (UM) on faecal egg counts was limited but peak pasture infectivity was reduced to less than 10% compared to the set-stocked group and weight gains of lambs were significantly better despite poor feed availability in late season. The study showed that under set-stocked conditions repeated anthelmintic treatments of both ewes and lambs in early season may ensure sufficient nematode control whereas moving animals to clean pasture without dosing was less efficient. The latter may, however, still be a viable option in organic and other production systems where routine use of anthelmintics is banned, particularly if weaning and moving are combined or a second move is performed.  相似文献   

Identification of galegine, an isoprenyl guanidine, as the toxic principle of Schoenus asperocarpus (poison sedge)     

CR HUXTABLE  PR DORLING  SM COLEGATE 《Australian veterinary journal》1993,70(5):169-171

SUMMARY An Isoprenyl guanldine, galegine, was isolated from the Western Australian sedge Schoenus asperocarpus (Cyperaceae). Synthetic galegine was shown to reproduce the clinical and pathological features of poisoning by this plant. Preliminary results suggest that the massive thoracic effusion observed in sedge poisoning is the result of a direct effect on pulmonary vascular permeability.  相似文献   

Residues from long-acting antimicrobial preparations in injection sites in cattle   总被引：2，自引：0，他引：2  

H MAWHINNEY  SM OAKENFULL  TJ NICHOLLS 《Australian veterinary journal》1996,74(2):140-142

Objective To investigate tissue residues of two longacting oxytetracycline (OTC) preparations in cattle.
Design A randomised drug residue trial.  

Animals

Two hundred and forty beef cattle in 24 groups of ten.
Procedure Two blind-coded 200 mg/mL OTC preparations were used in five treatment regimens of various combinations of injection sites (from one to five) and administrations (one or two). Five cattle from each group were slaughtered at 21, 30 and 60 days after injection and the injection site, urine, kidney and diaphragm muscle analysed for residues.
Results The OTC concentration exceeded the maximum residue limit in kidney in animals slaughtered 21 days after treatment, which is the prescribed withholding period. Concentration at the injection site was much greater than the maximum residue limit 30 days post-treatment, but not 45 days post-treatment. The residue was smaller when OTC had been injected in multiple sites. There was no difference between the two OTC preparations.
Conclusion A review of the maximum injection volume, site of injection and the withholding period is needed for long-acting OTC formulations.  相似文献   

Endocrine Disruptors and Other Food-contaminating Environmental Pollutants as Risk Factors in Animal Reproduction     

SM Rhind 《Reproduction in domestic animals》2008,43(S2):15-22

Pollutants of many chemical classes, derived primarily from anthropogenic activities, are ubiquitous in the environment, persistent, biologically available and can exert adverse effects on the reproductive and other, indirectly related, physiological systems. Food is generally considered to be the major route of animal exposure in vertebrate species but the relative contributions of other routes of exposure such as through lungs, gills or skin are not well studied and may be of importance for certain animal groups, depending on their immediate environment. Animals are particularly sensitive to exposure during developmental stages but the pattern of exposure to chemicals is likely to be different to that of adults. Quantification of the risk posed by the ingestion of pollutants in food is complex and depends on many factors including species, diet composition, duration of exposure to the food, efficiency of pollutant absorption, subsequent metabolism, sensitivity of target organs and stage of development. While the effects of high doses of single chemicals are proven, dietary exposure to pollutants generally involves prolonged, low-level exposure to a large number of compounds, each of which has different chemical characteristics, exerts different biological effects and is present at varying concentrations. Thus, while exposure to pollutants through feed is undoubtedly a significant risk factor for many species and may be the most important one for many terrestrial vertebrates, other routes of exposure may be more important in other groups.  相似文献   

Studies on the nitrogen and water relations of wheat     

K. V. M. Parameswaran  R. D. Graham  D. Aspinall 《Irrigation Science》1981,3(1):29-44

Summary The interrelations between nitrogen and water supply on the growth and yield of wheat (Triticum aestivum L.) were studied with particular attention to water use and grain yield in relation to the time of application of nitrogen to the plants. Nitrogen was applied at seeding or deferred until the double ridge-stage of development. Effects of both soil-applied and foliar-applied nitrogen were investigated under deficient or adequate water supply. The supply of water to the crop controlled the level of yield obtained and the response of the crop to applied N was markedly greater in drought-free conditions. Application of N resulted in increases in both crop leaf area duration and water use. Greater responses to N were obtained when the fertilizer was applied to the soil, rather than as a foliar spray.  相似文献   

Studies on the nitrogen and water relations of wheat II. Effects of varying nitrogen and water supply on growth and grain yield     

K. V. M. Parameswaran  R. D. Graham  D. Aspinall 《Irrigation Science》1984,5(2):105-121

Summary Wheat was grown in field and glasshouse experiments to assess the effect of nitrogen fertilizer on yield when water stress occurred in the later half of the growth. N application was deferred until the main culm apex of the plant was at the double-ridge stage of development. In the glasshouse water stress was imposed by altering the watering regime; in the field it was anticipated as naturally occurring and compared to an irrigated control. The response to deferred N was much stronger at adequate water supply giving rise to a significant positive N X W interaction effect. This positive N X W interaction was shown by number of ears, leaf area index, green area duration, water use and root growth, as well as grain yield. In both the glasshouse and field, N increased post-anthesis green area duration (PGD) which was highly correlated with grain yield, but since the components of grain yield determining the response to N were largely established by anthesis (number of ears), PGD does not appear to increase grain yield, which was rather caused by increased survival of tillers. In concert with its effect on PGD, deferred N resulted in greater root survival and/or growth at deeper layers late in the season. Water stress as measured in these experiments was insufficient to cause decreases in yield from use of N at low water supply. However, in the field nitrogen application did lower plant water potential late in the growing season.  相似文献   

Nearly singular magnetic fluctuations in the normal state of a high-Tc cuprate superconductor     

G Aeppli  TE Mason  SM Hayden  HA Mook  J Kulda 《Science (New York, N.Y.)》1997,278(5342):1432-1435

Polarized and unpolarized neutron scattering was used to measure the wave vector- and frequency-dependent magnetic fluctuations in the normal state (from the superconducting transition temperature, Tc = 35 kelvin, up to 350 kelvin) of single crystals of La1.86Sr0.14CuO4. The peaks that dominate the fluctuations have amplitudes that decrease as T-2 and widths that increase in proportion to the thermal energy, kBT (where kB is Boltzmann's constant), and energy transfer added in quadrature. The nearly singular fluctuations are consistent with a nearby quantum critical point.  相似文献