694 research outputs found
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Impacts of aerosols and clouds on photolysis frequencies and photochemistry during TRACE-P: 2. Three-dimensional study using a regional chemical transport model
Evaluating regional emission estimates using the TRACE-P observations
Measurements obtained during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) experiment are used in conjunction with regional modeling analysis to evaluate emission estimates for Asia. A comparison between the modeled values and the observations is one method to evaluate emissions. Based on such analysis it is concluded that the inventory performs well for the light alkanes, CO, ethyne, SO2, and NOₓ. Furthermore, based on model skill in predicting important photochemical species such as O₃, HCHO, OH, HO₂, and HNO₃, it is found that the emissions inventories are of sufficient quality to support preliminary studies of ozone production. These are important finding in light of the fact that emission estimates for many species (such as speciated NMHCs and BC) for this region have only recently been estimated and are highly uncertain. Using a classification of the measurements built upon trajectory analysis, we compare observed species distributions and ratios of species to those modeled and to ratios estimated from the emissions inventory. It is shown that this technique can reconstruct a spatial distribution of propane/benzene that looks remarkably similar to that calculated from the emissions inventory. A major discrepancy between modeled and observed behavior is found in the Yellow Sea, where modeled values are systematically underpredicted. The integrated analysis suggests that this may be related to an underestimation of emissions from the domestic sector. The emission is further tested by comparing observed and measured species ratios in identified megacity plumes. Many of the model derived ratios (e.g., BC/CO, SOₓ/C₂H₂) fall within ∼25% of those observed and all fall outside of a factor of 2.5. (See Article file for details of the abstract.)Department of Civil and Environmental EngineeringAuthor name used in this publication: Wang, T
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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
Analytical and numerical analyses of the micromechanics of soft fibrous connective tissues
State of the art research and treatment of biological tissues require
accurate and efficient methods for describing their mechanical properties.
Indeed, micromechanics motivated approaches provide a systematic method for
elevating relevant data from the microscopic level to the macroscopic one. In
this work the mechanical responses of hyperelastic tissues with one and two
families of collagen fibers are analyzed by application of a new variational
estimate accounting for their histology and the behaviors of their
constituents. The resulting, close form expressions, are used to determine the
overall response of the wall of a healthy human coronary artery. To demonstrate
the accuracy of the proposed method these predictions are compared with
corresponding 3-D finite element simulations of a periodic unit cell of the
tissue with two families of fibers. Throughout, the analytical predictions for
the highly nonlinear and anisotropic tissue are in agreement with the numerical
simulations
Uniform electron gases
We show that the traditional concept of the uniform electron gas (UEG) --- a
homogeneous system of finite density, consisting of an infinite number of
electrons in an infinite volume --- is inadequate to model the UEGs that arise
in finite systems. We argue that, in general, a UEG is characterized by at
least two parameters, \textit{viz.} the usual one-electron density parameter
and a new two-electron parameter . We outline a systematic
strategy to determine a new density functional across the
spectrum of possible and values.Comment: 8 pages, 2 figures, 5 table
Choroidal melanoma metastasizing to maxillofacial bones
BACKGROUND: Melanomas are malignant neoplasm of melanocytic origin, commonly seen on skin and various mucous membranes. Melanomas are the commonest intraocular malignant tumour in the adults. CASE PRESENTATION: A 50-year-old female presented with complains of painless progressive swelling in right cheek region of two months duration. Examination revealed a 6 × 4 cm bony hard swelling in right zygomatic region near and below lateral canthus of right eye with loss of vision. Investigations revealed it to be a choroidal melanoma metastatising to the zygomatic bone. Patient was successfully treated by surgery. CONCLUSION: Choroidal melanoma, which commonly metastasizes to liver and lungs, never involves the lymph nodes and metastasis to facial bones is rare. Here we report a case of choroidal melanoma metastasizing to maxillofacial bones
Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers
The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devicesopen4
Observation of the Charmed Baryon at CLEO
The CLEO experiment at the CESR collider has used 13.7 fb of data to
search for the production of the (css-ground state) in
collisions at {\rm GeV}. The modes used to
study the are ,
, , , and
. We observe a signal of 40.49.0(stat) events
at a mass of 2694.62.6(stat)1.9(syst) {\rm MeV/}, for all modes
combined.Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Evidence of New States Decaying into
Using 13.7 of data recorded by the CLEO detector at CESR, we report
evidence for two new charmed baryons: one decaying into
with the subsequent decay , and its
isospin partner decaying into followed by
. We measure the following mass differences
for the two states: =318.2+-1.3+-2.9 MeV,
and =324.0+-1.3+-3.0 MeV. We interpret
these new states as the particles, the charmed-strange
analogs of the .Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
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