374 research outputs found

    Centennial-scale variability of the Southern Hemisphere westerly wind belt in the eastern Pacific over the past two millennia

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    We present the first high-resolution (sub-annual) dust particle data set from West Antarctica, developed from the West Antarctic Ice Sheet (WAIS) Divide deep ice core (79.468° S, 112.086° W), and use it to reconstruct changes in atmospheric circulation over the past 2400 years. We find a background dust flux of ~4 mg m−2 year−1 and a mode particle size of 5–8 μm diameter. Through comparing the WAIS Divide record with other Antarctic ice core particle records, we observe that coastal and lower-elevation sites have higher dust fluxes and coarser particle size distributions (PSDs) than sites on the East Antarctic plateau, suggesting input from local dust sources at these lower-elevation sites. In order to explore the use of the WAIS Divide dust PSD as a proxy for past atmospheric circulation, we make quantitative comparisons between both mid-latitude zonal wind speed and West Antarctic meridional wind speed and the dust size record, finding significant positive interannual relationships. We find that the dust PSD is related to mid-latitude zonal wind speed via cyclonic activity in the Amundsen Sea region. Using our PSD record, and through comparison with spatially distributed climate reconstructions from the Southern Hemisphere (SH) middle and high latitudes, we infer that the SH westerlies occupied a more southerly position from circa 1050 to 1400 CE (Common Era), coinciding with the Medieval Climate Anomaly (MCA). Subsequently, at ca. 1430 CE, the wind belt shifted equatorward, where it remained until the mid-to-late twentieth century. We find covariability between reconstructions of El Niño–Southern Oscillation (ENSO) and the mid-latitude westerly winds in the eastern Pacific, suggesting that centennial-scale circulation changes in this region are strongly influenced by the tropical Pacific. Further, we observe increased coarse particle deposition over the past 50 years, consistent with observations that the SH westerlies have been shifting southward and intensifying in recent decades

    Observation of inverse diproton photodisintegration at intermediate energies

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    The reaction pp->{pp}_s\gamma, where {pp}_s is a proton pair with an excitation energy E_{pp}<3 MeV, has been observed with the ANKE spectrometer at COSY-Juelich for proton beam energies of T_p=0.353, 0.500, and 0.550 GeV. This is equivalent to photodisintegration of a free 1S_0 diproton for photon energies E\gamma ~ T_p/2. The differential cross sections measured for c.m. angles 0 deg.<\theta_{pp}<20 deg. exhibit a steep increase with angle that is compatible with E1 and E2 multipole contributions. The ratio of the measured cross sections to those of np->d\gamma is on the 10^{-3}-10^{-2} level. The increase of the pp->{pp}_s\gamma cross section with T_p might reflect the influence of the Delta(1232) excitation.Comment: 4 pages + 4 figure

    Stimulation of spermatogenesis by combined therapy with follicle-stimulating hormone and chorionic gonadotropin for azoospermia and infertility in cases of previous ineffective monotherapy with chorionic gonadotropin and antiestrogen

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    Often there is a need of application of the methods of treatment, directed on increase in quantity of spermatozoa in an ejaculate. In the research efficiency of the combined therapy by preparation follicle-stimulating hormone was estimated and a chorionic gonadotrophin in cases of the previous inefficiency monotherapy a chorionic gonadotrophin and an anti-estrogen. The efficiency of treatment concerning an oligoteratozoospermiya made 65 %. Positive changes of morphology of spermatozoa included improvement of condensation of a chromatin and decrease of the degrading forms. At the same time this treatment was safe and didn»t lead to development of side effects

    Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure

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    The surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film system obtained by close-spaced vacuum sublimation technique under different grow conditions were investigated. Examination of surface profile and morphology was performed by scanning electron and optical microscopy. Chemical composition was studied by Rutherford back scattering method. Results of morphology studies enabled to determine dependence of the growth mechanism, roughness Ra, grain size D of ZnS layers on the growth conditions. The researches of chemical composition allowed to determine the concentration of compound elements and impurities, deviation from stoichiometry and thickness distribution of chemical elements

    Chemical Composition of Fresh Snow from Glaciar Marinelli, Tierra Del Fuego, Chile

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    A fresh-snow sampling campaign was conducted during the late austral summer of 2006 in the accumulation zone of Glaciar Marinelli, located in the Cordillera Darwin, Tierra del Fuego, Chile. Snow samples were analyzed for stable isotopes (delta(18)O, major soluble ions (Na\u27, K\u27, Ca, Mg, a NO(3)(-), SO(4)(2-), MS(-)) and major and trace elements (Na, Mg, Al, Fe, Ca, Sr, Cd, Cs, Ba, La, Ce, Pr, Dy, Ho, Er, Bi, U, As, Ti, V, Cr, Mn). The dominance of marine chemistry resembles that in studies from Patagonian glaciers. Snow chemistry was dominantly loaded by marine species (Cl(-), Na(+) and ssSO(4)(2-)), while contributions of crustal species (e.g. Al and Fe) were very low. Empirical orthogonal function analysis suggests two possible dust sources, one represented by Al and Fe and the other by La, Ce and Pr. Enrichment-factor calculations suggest the majority of elements are within average upper-crustal ratios, but major enrichments of Bi and Cd (hundreds of times) suggest possible anthropogenic sources. Linear correlation of delta(18)O and barometric pressure (r = 0.60, p \u3c 0.007) suggests a potential \u27amount effect\u27 relationship between depleted delta(18)O ratios and stronger storm conditions (e.g. greater precipitation). The snow-chemistry records from Glaciar Marinelli are the first measured in Tierra del Fuego, the southernmost glaciated region outside Antarctica

    First measurements of spin correlations in the np -> d pi^0 reaction

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    The transverse spin correlations Axx and Ayy in the np-> d pi^0 reaction have been measured for the first time in quasi-free kinematics at the COSY-ANKE facility using a polarised deuteron beam incident on a polarised hydrogen cell target. The results obtained for neutron energies close to 353 MeV and 600 MeV are in good agreement with the partial wave analysis of data on the isospin-related pp-> d pi^+ reaction, though the present results cover also the small-angle region, which was largely absent from these data
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