1,710 research outputs found
Factors influencing the sustained participation of farmers in participatory forestry: a case study in central Sal forests in Bangladesh
ArticleJournal of Environmental Management. 74(1): 43-51 (2005)journal articl
The progress on the study of land surface heat fluxes over heterogeneous landscape of the Tibetan Plateau
Collinear Factorization for Single Transverse-Spin Asymmetry in Drell-Yan Processes
We study the scattering of a single parton state with a multi-parton state to
derive the complete results of perturbative coefficient functions at leading
order, which appear in the collinear factorization for Single transverse-Spin
Asymmetry(SSA) in Drell-Yan processes with a transversely polarized hadron in
the initial state. We find that the factorization formula of SSA contains
hard-pole-, soft-quark-pole- and soft-gluon-pole contributions. It is
interesting to note that the leading order perturbative coefficient functions
of soft-quark-pole- and soft-gluon-pole contributions are extracted from parton
scattering amplitudes at one-loop, while the functions of hard-pole
contributions are extracted from the tree level amplitudes at tree-level. Our
method to derive the factorization of SSA is different than the existing one in
literature. A comparison of our results with those obtained by other method is
made.Comment: 27 pages, 14 figures, text improved, to appear in Phys. Rev.
Single Spin Asymmetry in Lepton Angular Distribution of Drell-Yan Processes
We study the single spin asymmetry in the lepton angular distribution of
Drell-Yan processes in the frame work of collinear factorization. The asymmetry
has been studied in the past and different results have been obtained. In our
study we take an approach different than that used in the existing study. We
explicitly calculate the transverse-spin dependent part of the differential
cross-section with suitable parton states. Because the spin is transverse, one
has to take multi-parton states for the purpose. Our result agrees with one of
the existing results. A possible reason for the disagreement with others is
discussed.Comment: Typos corrected. Conclusions unchange
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Contribution of particulate nitrate to airborne measurements of total reactive nitrogen
Simultaneous measurements of speciated, total reactive nitrogen (NOy) and particulate NO3 (particle diameter <1.3 μm) were made on board the NASA P-3B aircraft over the western Pacific in February-April 2001 during the Transport and Chemical Evolution over the Pacific (TRACE-P) experiment. Gas-phase and particulate NOy was measured using a gold tube catalytic converter. For the interpretation of particulate NOy, conversion efficiencies of particulate NH4NO3, KNO3, NaNO3, and Ca(NO3)2 were measured in the laboratory. Only NH4NO3 showed quantitative conversion, and its conversion efficiency was as high as that for HNO3. NOy measured on board the aircraft was found to be systematically higher by 10-30% than the sum of the individual NOy gas components (Σ(NOy)i) at 0-4 km. Particulate NO3- concentrations measured by a particle-into-liquid sampler (PILS) were nearly equal to NOy - Σ(NOy)i under low-dust-loading conditions. The PILS data showed that the majority of the particulate NO3- was in the form of NH4NO3 under these conditions, suggesting that NH4NO3 particles were quantitatively converted to detectable NO by the NOy converter, consistent with the laboratory experiments. The contribution of particulate NO3- to NOy was most important at 0-2 km, where NO3- constituted 10-30% of NOy during TRACE-P. On average, the amounts of particulate NO3- and gas-phase HNO3 were comparable in this region. Copyright 2005 by the American Geophysical Union
Double spin asymmetry A_{LT} in direct photon production
We study the longitudinal-transverse double spin asymmetry for
direct photon production in nucleon-nucleon scattering by using the collinear
twist-3 approach. This asymmetry, which, for instance, could be measured at
RHIC, contains a complete set of collinear twist-3 correlation functions in a
transversely polarized nucleon.Comment: 9 pages, 1 figur
Further characterization of ferric—phytosiderophore transporters ZmYS1 and HvYS1 in maize and barley
Roots of some gramineous plants secrete phytosiderophores in response to iron deficiency and take up Fe as a ferric–phytosiderophore complex through the transporter YS1 (Yellow Stripe 1). Here, this transporter in maize (ZmYS1) and barley (HvYS1) was further characterized and compared in terms of expression pattern, diurnal change, and tissue-type specificity of localization. The expression of HvYS1 was specifically induced by Fe deficiency only in barley roots, and increased with the progress of Fe deficiency, whereas ZmYS1 was expressed in maize in the leaf blades and sheaths, crown, and seminal roots, but not in the hypocotyl. HvYS1 expression was not induced by any other metal deficiency. Furthermore, in maize leaf blades, the expression was higher in the young leaf blades showing severe chlorosis than in the old leaf blades showing no chlorosis. The expression of HvYS1 showed a distinct diurnal rhythm, reaching a maximum before the onset of phytosiderophore secretion. In contrast, ZmYS1 did not show such a rhythm in expression. Immunostaining showed that ZmYS1 was localized in the epidermal cells of both crown and lateral roots, with a polar localization at the distal side of the epidermal cells. In maize leaves, ZmYS1 was localized in mesophyll cells, but not epidermal cells. These differences in gene expression pattern and tissue-type specificity of localization suggest that HvYS1 is only involved in primary Fe acquisition by barley roots, whereas ZmYS1 is involved in both primary Fe acquisition and intracellular transport of iron and other metals in maize
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Synoptic-scale transport of reactive nitrogen over the western Pacific in spring
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Impacts of biomass burning in Southeast Asia on ozone and reactive nitrogen over the western Pacific in spring
Aircraft measurements of ozone (O3) and its precursors (reactive nitrogen, CO, nonmethane hydrocarbons) were made over the western Pacific during the Transport and Chemical Evolution Over the Pacific (TRACE-P) campaign, which was conducted during February-April 2001. Biomass burning activity was high over Southeast Asia (SEA) during this period (dry season), and convective activity over SEA frequently transported air from the boundary layer to the free troposphere, followed by eastward transport to the sampling region over the western Pacific south of 30°N. This data set allows for systematic investigations of the chemical and physical processes in the outflow from SEA. Methyl chloride (CH3Cl) and CO are chosen as primary and secondary tracers, respectively, to gauge the degree of the impact of emissions of trace species from biomass burning. Biomass burning is found to be a major source of reactive nitrogen (NO x, PAN, HNO3, and nitrate) and O3 in this region from correlations of these species with the tracers. Changes in the abundance of reactive nitrogen during upward transport are quantified from the altitude change of the slopes of the correlations of these species with CO. NOx decreased with altitude due to its oxidation to HNO3. On the other hand, PAN was conserved during transport from the lower to the middle troposphere, consistent with its low water solubility and chemical stability at low temperatures. Large losses of HNO3 and nitrate, which are highly water soluble, occurred in the free troposphere, most likely due to wet removal by precipitation. This has been shown to be the major pathway of NOy loss in the middle troposphere. Increases in the mixing ratios of O3 and its precursors due to biomass burning in SEA are estimated using the tracers. Enhancements of CO and total reactive nitrogen (NOy), which are directly emitted from biomass burning, were largest at 2-4 km. At this altitude the increases in NOy and O3 were 810 parts per trillion by volume (pptv) and 26 parts per billion by volume (ppbv) above their background values of 240 pptv and 31 ppbv, respectively. The slope of the O3-CO correlation in biomass burning plumes was similar to those observed in fire plumes in northern Australia, Africa, and Canada. The O3 production efficiency (OPE) derived from the O3-CO slope and NOx/CO emission ratio (ER) is shown to be positively correlated with the C2H4 /NOx ER, indicating that the C2H4/NO x ER is a critical parameter in determining the OPE. Comparison of the net O3 flux across the western Pacific region and total O3 production due to biomass burning in SEA suggests that about 70% of O3 produced was transported to the western Pacific. Copyright 2004 by the American Geophysical Union
Sivers vs. Collins effect in azimuthal single spin asymmetries in pion production in SIDIS
Recently it has been argued that the transverse momentum dependent twist-2
Sivers distribution function does not vanish in QCD. Therefore both, the
Collins and Sivers effects, should be considered in order to explain the
azimuthal single spin asymmetries A(UL) in pion production in semi-inclusive
deeply inelastic lepton scattering of a longitudinally polarized target. On the
basis of presently available phenomenological information on the Sivers
function we estimate that for those asymmetries A(UL) in the kinematic region
of the HERMES experiments the Sivers effect can be neglected with respect to
the Collins effect. It is argued that the same feature holds also for the
COMPASS and CLAS experiments. This justifies theoretical approaches to
understand the HERMES data on the basis of the Collins effect only.Comment: 8 pages, 4 figures. References added, small changes in text, Appendix
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