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191.
Telma Castro Oscar Peralta Dara Salcedo José Santos María I. Saavedra María L. Espinoza Alejandro Salcido Ana-Teresa Celada-Murillo Susana Carreón-Sierra Harry Álvarez-Ospina Giovanni Carabali Valter Barrera Sasha Madronich 《Journal of Atmospheric Chemistry》2018,75(2):155-169
During the MILAGRO campaign, March 2006, eight-stage cut impactors were used to sample atmospheric particles at Tecámac (T1 supersite), towards the northeast edge of the Mexico City Metropolitan Area, collecting fresh local emissions and aged pollutants produced in Mexico City. Particle samples were analyzed to determine total mass concentrations of Ca2+, Mg2+, NH4 +, K+, Cl?, SO4 2?, and NO3 ?. Average concentrations were 22.1 ± 7.2 μg m?3 for PM10 and 18.3 ± 6.2 μg m?3 for PM1.8. A good correlation between PM10 and PM1.8, without influence from wind patterns, indicates that local emissions are more important than the city’s pollution transported to the site, despite the fact that Tecámac is just 40 km away from Mexico City. A lack of diurnal patterns in the PM2.5/PM1.8 ratio supports this conclusion. The inorganic composition of particles suggests that vehicles, soil resuspension, and industries are the main pollutant sources. Finally, the particles were found to be neutralized, in agreement with observations in the Mexico City Metropolitan Area. 相似文献
192.
Harry F.L. Williams 《第四纪科学杂志》2011,26(2):199-206
Hurricane Ike's storm surge deposited a concentrated shell bed in the form of a series of coalescing washover fans over backshore sand and adjoining marshland in part of southwest Louisiana's Chenier Plain. The shell bed is a tempestite and has distinctive morphological, sedimentological and biogenic characteristics that provide a modern analogue to aid interpretation of older shell bed tempestites in the geological record. The shell bed has a wedge‐shaped profile that thickens landward, is about 40 m wide, up to 27 cm thick and extends several hundred metres parallel to the shore. Shells are predominantly disarticulated valves of the common bivalve Mulinia lateralis, probably reworked and transported landward from skeletal remains offshore. The shell bed has an erosional base, is bioclast supported, normally graded and has common mud rip‐up clasts. Similarities between the modern shell bed and another concentrated shell deposit, forming part of a sandy beach ridge some 1.5 km inland, suggest that the palaeo shell deposit is also a tempestite recording hurricane washover of a former shoreline 600 a ago. These findings demonstrate that the shell bed deposited by Hurricane Ike is a valuable analogue for palaeotempestological investigations and that hurricanes have likely contributed to the construction of both modern berm ridges and palaeo beach ridges on this coastal plain. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
193.
194.
This study investigates the conditions of occurrence and petrographic characteristics of low‐Mg calcite (LMC) from cold seeps of the Gulf of Mexico at a water depth of 2340 m. Such LMC mineral phases should precipitate in calcite seas rather than today's aragonite sea. The 13C‐depleted carbonates formed as a consequence of anaerobic oxidation of hydrocarbons in shallow subsurface cold seep environments. The occurrence of LMC may result from brine fluid flows. Brines are relatively Ca2+‐enriched and Mg2+‐depleted (Mg/Ca mole ratio <0.7) relative to seawater, where the Mg/Ca mole ratio is ~5, which drives high‐Mg calcite and aragonite precipitation. The dissolution of aragonitic mollusk shells, grains and cements was observed. Aerobic oxidation of hydrocarbons and H2S is the most likely mechanism to explain carbonate dissolution. These findings have important implications for understanding the occurrence of LMC in deep water marine settings and consequently their counterparts in the geological record. 相似文献
195.
Values regarding built heritage have developed historically in response to both international agendas and local circumstances, and have underpinned the creation of World Heritage Sites and regeneration approaches within these. Such regeneration processes are an arena where different interests meet and often confront each other, with concepts and values of built heritage being used to different ends by the actors involved. However, the origins of conservation concepts and approaches are seldom considered. This paper examines the historical development of built heritage awareness and conservation policies from an institutionalist perspective at the international, European and Latin. American levels. It then considers conservation policies in Scotland and Brazil, particularly in the central areas in Edinburgh and Salvador from the 19th century to the 1970s, and the growing awareness of built heritage among certain sections of society and local institutions in these localities. Finally, the paper analyses the reasons behind, and types of, interventions in Edinburgh’s Old Town and Salvador’s Pelourinho and Maciel neighbourhoods, and the level of awareness of built heritage among the general population in the two cities. The paper draws conclusions on the influence of various factors on the development of approaches to built heritage and on the different ways in which these contributed to a particular awareness of built heritage in Edinburgh and Salvador. 相似文献
196.
Harry Enke Matthias Steinmetz Hans-Martin Adorf Alexander Beck-Ratzka Frank Breitling Thomas Brüsemeister Arthur Carlson Torsten Ensslin Mikael Högqvist Iliya Nickelt Thomas Radke Alexander Reinefeld Angelika Reiser Tobias Scholl Rainer Spurzem Jürgen Steinacker Wolfgang Voges Joachim Wambsganß Steve White 《New Astronomy》2011,16(2):79-93
We present status and results of AstroGrid-D, a joint effort of astrophysicists and computer scientists to employ grid technology for scientific applications. AstroGrid-D provides access to a network of distributed machines with a set of commands as well as software interfaces. It allows simple use of computer and storage facilities and to schedule or monitor compute tasks and data management. It is based on the Globus Toolkit middleware (GT4).Chapter 1 describes the context which led to the demand for advanced software solutions in Astrophysics, and we state the goals of the project.We then present characteristic astrophysical applications that have been implemented on AstroGrid-D in chapter 2. We describe simulations of different complexity, compute-intensive calculations running on multiple sites (Section 2.1), and advanced applications for specific scientific purposes (Section 2.2), such as a connection to robotic telescopes (Section 2.2.3). We can show from these examples how grid execution improves e.g. the scientific workflow.Chapter 3 explains the software tools and services that we adapted or newly developed. Section 3.1 is focused on the administrative aspects of the infrastructure, to manage users and monitor activity. Section 3.2 characterises the central components of our architecture: The AstroGrid-D information service to collect and store metadata, a file management system, the data management system, and a job manager for automatic submission of compute tasks.We summarise the successfully established infrastructure in chapter 4, concluding with our future plans to establish AstroGrid-D as a platform of modern e-Astronomy. 相似文献
197.
Chidong Zhang Min Dong Silvio Gualdi Harry H. Hendon Eric D. Maloney Andrew Marshall Kenneth R. Sperber Wanqiu Wang 《Climate Dynamics》2006,27(6):573-592
The status of the numerical reproduction of the Madden–Julian Oscillation (MJO) by current global models was assessed through
diagnoses of four pairs of coupled and uncoupled simulations. Slow eastward propagation of the MJO, especially in low-level
zonal wind, is realistic in all these simulations. However, the simulated MJO suffers from several common problems. The MJO
signal in precipitation is generally too weak and often eroded by an unrealistic split of an equatorial maximum of precipitation
into a double ITCZ structure over the western Pacific. The MJO signal in low-level zonal wind, on the other hand, is sometimes
too strong over the eastern Pacific but too weak over the Indian Ocean. The observed phase relationship between precipitation
and low-level zonal wind associated with the MJO in the western Pacific and their coherence in general are not reproduced
by the models. The seasonal migration in latitude of MJO activity is missing in most simulations. Air–sea coupling generally
strengthens the simulated eastward propagating signal, but its effects on the phase relationship and coherence between precipitation
and low-level zonal wind, and on their geographic distributions, seasonal cycles, and interannual variability are inconsistent
among the simulations. Such inconsistency cautions generalization of results from MJO simulations using a single model. In
comparison to observations, biases in the simulated MJO appear to be related to biases in the background state of mean precipitation,
low-level zonal wind, and boundary-layer moisture convergence. This study concludes that, while the realistic simulations
of the eastward propagation of the MJO are encouraging, reproducing other fundamental features of the MJO by current global
models remains an unmet challenge.
相似文献
Chidong ZhangEmail: |
198.
Daily outflow frequencies and recession curves were used to identify differences in storage–outflow relationships between two different drainage systems, conventional and controlled drainage. A three‐year (1996–1999) field drainage experiment was carried out on a loamy sand soil in southern Sweden. Plots with an area of 0·2 hectares were drained by conventional subsurface drainage (CD) or by controlled drainage (CWT1 and CWT2). The controlled drainage system allowed the groundwater level in the soil to be varied during the year. It was kept at least 70 cm below the soil surface during the growing season but allowed to rise to a maximum of 20 cm below the soil surface during the rest of the year. Measurements were performed to record precipitation, drain outflow and groundwater levels. Daily values of outflow were divided into 10 categories, based on the size of outflow. Recession curves of hourly measurement of outflow were selected. They behaved like single reservoirs and a linear storage–outflow model was applied. Least squares estimates of the parameters initial outflow, initial storage volume and retention constant were calculated. Controlled drainage had a significant effect on total drain outflow and outflow pattern during the three years of measurement. The total drain outflow was 70% to 90% smaller in CWT than in CD. The analysis revealed that the initial outflows were higher, the retention constant and the temporary storage lower in CWT. The hydrological impacts of the reduction in temporary storage were higher peak flow, shorter lag time and shorter recession time and these effects increased with an increased groundwater level. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
199.
Harry Y. McSween Jr. Theodore C. Labotka Christina E. Viviano‐Beck 《Meteoritics & planetary science》2015,50(4):590-603
Compositions of basaltic and ultramafic rocks analyzed by Mars rovers and occurring as Martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions. Key minerals identified by remote sensing roughly constrain temperatures and pressures in the Martian crust. We use a traditional metamorphic approach (phase diagrams) to assess low‐grade/hydrothermal equilibrium assemblages. Basaltic rocks should produce chlorite + actinolite + albite + silica, accompanied by laumontite, pumpellyite, prehnite, or serpentine/talc. Only prehnite‐bearing assemblages have been spectrally identified on Mars, although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates. Ultramafic rocks are predicted to produce serpentine, talc, and magnesite, all of which have been detected spectrally on Mars. Mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be H2O‐rich and CO2‐poor. We confirm the hypothesis that low‐grade/hydrothermal metamorphism affected the Noachian crust on Mars, which has been excavated in large craters. We estimate the geothermal gradient (>20 °C km?1) required to produce the observed assemblages. This gradient is higher than that estimated from radiogenic heat‐producing elements in the crust, suggesting extra heating by regional hydrothermal activity. 相似文献
200.
Amy J.V. Riches Yang Liu James M.D. Day Igor S. Puchtel Douglas Rumble III Harry Y. McSween Jr. Richard J. Walker Lawrence A. Taylor 《Polar Science》2011,4(4):497-514
We report the petrography, mineral and whole-rock chemistry (major-, trace-, and highly-siderophile element abundances, and osmium and oxygen isotope compositions) of a newly recognized lherzolitic shergottite, Yamato (Y) 984028. Oxygen isotopes (Δ17O = 0.218‰) confirm a martian origin for this meteorite. Three texturally distinctive internal zones and a partially devitrified fusion crust occur in the polished section of Y 984028 studied here. The zones include: 1) a poikilitic region with pyroxene enclosing olivine and chromite (Zone A); 2) a non-poikilitic zone with cumulate olivine, interstitial pyroxene, maskelynite and Ti-rich chromite (Zone B) and; 3) a monomict breccia (Zone C). The pyroxene oikocryst in Zone A is chemically zoned from Wo3–7En76–71 in the core region to Wo33–36En52–49 at the rim, and encloses more Mg-rich olivine (Fo74–70) in the core, as compared with olivines (Fo69–68) located at the oikocryst rim. Constraints from Fe–Mg partitioning between crystals and melt indicate that constituent minerals are not in equilibrium with the corresponding bulk-rock composition, implying that Y 984028 represents a cumulate. The whole-rock major- and trace-element compositions, and initial 187Os/188Os value (0.1281 ± 0.0002) of Y 984028 are similar to other lherzolitic shergottites and this sample is probably launch-paired with Y 793602, Y 000027, Y 000047, and Y 000097. The Os isotopic composition and highly-siderophile element (HSE) abundances of Y 984028 and other lherzolitic shergottites are consistent with derivation from a martian mantle source that evolved with chondritic Re/Os. 相似文献