2,807 research outputs found

    Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics

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    The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution Of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature

    Entropy and Spin Susceptibility of s-wave Type-II Superconductors near Hc2H_{c2}

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    A theoretical study is performed on the entropy SsS_{\rm s} and the spin susceptibility χs\chi_{\rm s} near the upper critical field Hc2H_{c2} of s-wave type-II superconductors with arbitrary impurity concentrations. The changes of these quantities through Hc2H_{c2} may be expressed as [Ss(T,B)Ss(T,0)]/[Sn(T)Ss(T,0)]=1αS(1B/Hc2)(B/Hc2)αS[S_{\rm s}(T,B)-S_{\rm s}(T,0)]/[S_{\rm n}(T)-S_{\rm s}(T,0)]=1-\alpha_{S}(1-B/H_{c2})\approx (B/H_{c2})^{\alpha_{S}}, for example, where BB is the average flux density and SnS_{\rm n} denotes entropy in the normal state. It is found that the slopes αS\alpha_{S} and αχ\alpha_{\chi} at T=0 are identical, connected directly with the zero-energy density of states, and vary from 1.72 in the dirty limit to 0.50.60.5\sim 0.6 in the clean limit. This mean-free-path dependence of αS\alpha_{S} and αχ\alpha_{\chi} at T=0 is quantitatively the same as that of the slope αρ(T=0)\alpha_{\rho}(T=0) for the flux-flow resistivity studied previously. The result suggests that Ss(B)S_{\rm s}(B) and χs(B)\chi_{\rm s}(B) near T=0 are convex downward (upward) in the dirty (clean) limit, deviating substantially from the linear behavior B/Hc2\propto B/H_{c2}. The specific-heat jump at Hc2H_{c2} also shows fairly large mean-free-path dependence.Comment: 8 pages, 5 figure

    Properties of Nambu-Goldstone Bosons in a Single-Component Bose-Einstein Condensate

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    We theoretically study the properties of Nambu-Goldstone bosons in an interacting single-component Bose-Einstein condensate (BEC). We first point out that the proofs of Goldstone's theorem by Goldstone, et al. [Phys. Rev. {\bf 127} (1962) 965] may be relevant to distinct massless modes of the BEC: whereas the first proof deals with the poles of the single-particle Green's function G^\hat{G}, the second one concerns those of the two-particle Green's function. Thus, there may be multiple Nambu-Goldstone bosons even in the single-component BEC with broken U(1) symmetry. The second mode turns out to have an infinite lifetime in the long-wavelength limit in agreement with the conventional viewpoint. In contrast, the first mode from G^\hat{G}, i.e., the Bogoliubov mode in the weak-coupling regime, is shown to be a "bubbling" mode fluctuating temporally out of and back into the condensate. The substantial lifetime originates from an "improper" structure of the self-energy inherent in the BEC, which has been overlooked so far and will be elucidated here, and removes various infrared divergences pointed out previously.Comment: 9 pages, 6 gigure

    Reactivity difference between protolytic forms of some macrocyclic chromium(III) complexes in ligand substitution and electron transfer processes

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    The review provides insight into the mechanism of ligand substitution and electron transfer (from chromium( III) to iron(III)) by comparison of the reactivity of some tetraazamacrocyclic chromium(III) complexes in the conjugate acid-base forms. Use of two geometrical isomers made possible to estimate the influence of geometry and protolytic reactions in trans and cis position towards the leaving group on the rate enhancement. Studies on the reaction rates in different media demonstrated the role played by outer sphere interactions in a monodentate ligand substitution

    Critical light scattering in liquids

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    We compare theoretical results for the characteristic frequency of the Rayleigh peak calculated in one-loop order within the field theoretical method of the renormalization group theory with experiments and other theoretical results. Our expressions describe the non-asymptotic crossover in temperature, density and wave vector. In addition we discuss the frequency dependent shear viscosity evaluated within the same model and compare our theoretical results with recent experiments in microgravity.Comment: 17 pages, 12 figure

    Self-Consistent Approximations for Superconductivity beyond the Bardeen-Cooper-Schrieffer Theory

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    We develop a concise self-consistent perturbation expansion for superconductivity where all the pair processes are naturally incorporated without drawing "anomalous" Feynman diagrams. This simplification results from introducing an interaction vertex that is symmetric in the particle-hole indices besides the ordinary space-spin coordinates. The formalism automatically satisfies conservation laws, includes the Luttinger-Ward theory as the normal-state limit, and reproduces the Bardeen-Cooper-Schrieffer theory as the lowest-order approximation. It enables us to study the thermodynamic, single-particle, two-particle, and dynamical properties of superconductors with competing fluctuations based on a single functional Φ[G^]\Phi[\hat{G}] of Green's function G^\hat{G} in the Nambu space. Specifically, we derive closed equations in the FLEX-S approximation, i.e., the fluctuation exchange approximation for superconductivity with all the pair processes, which contains extra terms besides those in the standard FLEX approximation.Comment: 14 pages, 6 figure

    Mechanisms that influence the formation of high-ozone regions in the boundary layer downwind of the Asian continent in winter and spring

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    The seasonal variation of ozone (O3) in the boundary layer (BL) over the western Pacific is investigated using a chemistry-transport model. The model results for January and April-May 2002 were evaluated by comparison with PEACE aircraft observations. In January, strong northwesterlies efficiently transported NOx from the continent, leading to an O3 increase of approximately 5-10 ppbv over a distance of about 3000 km. In April, southwesterlies dominated due to anticyclone development over the western Pacific. Along this flow, O3 continued to be produced by NO x emitted from East Asia. This resulted in the formation of a high-O3 (> 50 ppbv) region extending along the coastal areas of East Asia. This seasonal change in O3 was driven in part by a change in the net O3 production rate due to increases in solar UV and H 2O. Its exact response depended on the NOx values in the BL. The net O3 production rate increased between winter and spring over the Asian continent and decreased over the remote western Pacific. Model simulations show that about 25% of the total O3 (of 10-20 ppbv) increase over the coastal region of Northeast Asia was due to local production from NOx emissions from China, and the rest was due to changes in background levels as well as emissions from Korea, Japan, and east Siberia. Uplift of BL air over Asia, horizontal transport in the free troposphere, and subsidence were the principal mechanisms of transporting Asian O3 to the central and eastern North Pacific Copyright 2008 by the American Geophysical Union
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