The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Alexander F Goncharov - One of the best experts on this subject based on the ideXlab platform.
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pressure stress and strain distribution in the double stage diamond Anvil cell
Journal of Applied Physics, 2015Co-Authors: Sergey S Lobanov, Vitali B Prakapenka, Clemens Prescher, Zuzana Konopkova, Hannspeter Liermann, K L Crispin, Chi Zhang, Alexander F GoncharovAbstract:Double stage diamond Anvil cells (DACs) of two designs have been assembled and tested. We used a standard symmetric DAC with flat or beveled culets as a primary stage and CVD microAnvils machined by a focused ion beam as a second. We evaluated pressure, stress, and strain distributions in gold and a mixture of gold and iron as well as in secondary Anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage Anvil culet size. We found that the stress field generated by the second stage Anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary Anvil and by cupping of the first stage diamond Anvil in the presented experimental designs. Also, our experiments show that pressures of several megabars may be reached without sacrificing the first stage diamond Anvils.
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pressure stress and strain distribution in the double stage diamond Anvil cell
arXiv: Materials Science, 2015Co-Authors: Sergey S Lobanov, Vitali B Prakapenka, Clemens Prescher, Zuzana Konopkova, Hannspeter Liermann, K L Crispin, Chi Zhang, Alexander F GoncharovAbstract:Double stage diamond Anvil cells (DAC) of two designs have been assembled and tested. We used a standard symmetric DAC as a primary stage and CVD microAnvils machined by a focused ion beam - as a second. We evaluated pressure, stress, and strain distributions in Au and Fe-Au samples as well as in secondary Anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage Anvil culet size. We found that the stress field generated by the second stage Anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary Anvil and by cupping of the first stage diamond Anvil in the presented experimental designs. Also, our experiments show that pressures of several megabars may be reached without sacrificing the first stage diamond Anvils.
Andrew J. Heymsfield - One of the best experts on this subject based on the ideXlab platform.
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vertical structures of Anvil clouds of tropical mesoscale convective systems observed by cloudsat
Journal of the Atmospheric Sciences, 2011Co-Authors: Jian Yuan, Robert A Houze, Andrew J. HeymsfieldAbstract:AbstractA global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6–8 and 1–3 km. High-topped clouds extend outward from raining cores of MCSs to form Anvil clouds. Closest to the raining cores, the Anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of Anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS Anvil clouds vary little across the tropics, except that (i) in continental MCS Anvils...
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Evolution of a Florida Cirrus Anvil
Journal of the Atmospheric Sciences, 2005Co-Authors: Timothy J. Garrett, Andrew J. Heymsfield, Eric J. Jensen, Darrel Baumgardner, B. C. Navarro, Cynthia H. Twohy, P. T. Bui, H. Gerber, Robert L. Herman, Paul LawsonAbstract:Abstract This paper presents a detailed study of a single thunderstorm Anvil cirrus cloud measured on 21 July 2002 near southern Florida during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE). NASA WB-57F and University of North Dakota Citation aircraft tracked the microphysical and radiative development of the Anvil for 3 h. Measurements showed that the cloud mass that was advected downwind from the thunderstorm was separated vertically into two layers: a cirrus Anvil with cloud-top temperatures of −45°C lay below a second, thin tropopause cirrus (TTC) layer with the same horizontal dimensions as the Anvil and temperatures near −70°C. In both cloud layers, ice crystals smaller than 50 μm across dominated the size distributions and cloud radiative properties. In the Anvil, ice crystals larger than 50 μm aggregated and precipitated while small ice crystals increasingly dominated the size distributions; as a consequence, measured ice water content...
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Evidence for the Predominance of Mid-Tropospheric Aerosols as Subtropical Anvil Cloud Nuclei
Science (New York N.Y.), 2004Co-Authors: Ann M. Fridlind, Andrew J. Heymsfield, Andrew S. Ackerman, Eric J. Jensen, Michael R. Poellot, David E. Stevens, Donghai Wang, Larry M. Miloshevich, Darrel Baumgardner, R. Paul LawsonAbstract:NASA's recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment focused on Anvil cirrus clouds, an important but poorly understood element of our climate system. The data obtained included the first comprehensive measurements of aerosols and cloud particles throughout the atmospheric column during the evolution of multiple deep convective storm systems. Coupling these new measurements with detailed cloud simulations that resolve the size distributions of aerosols and cloud particles, we found several lines of evidence indicating that most Anvil crystals form on mid-tropospheric rather than boundary-layer aerosols. This result defies conventional wisdom and suggests that distant pollution sources may have a greater effect on Anvil clouds than do local sources.
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LIRAD Observations of Tropical Cirrus Clouds in MCTEX. Part II: Optical Properties and Base Cooling in Dissipating Storm Anvil Clouds*
Journal of the Atmospheric Sciences, 2002Co-Authors: C. M. R. Platt, Richard T. Austin, Stuart A. Young, Andrew J. HeymsfieldAbstract:Abstract During the Maritime Continent Thunderstorm Experiment (MCTEX), several decaying storm Anvils were observed. The Anvil clouds exhibited typical patterns of fallout and decay over a number of hours of observation. The Anvil bases were initially very attenuating to lidar pulses, and continued that way until Anvil breakup commenced. During that time, the Anvil base reached some characteristic altitude (∼7 km) below which the cloud particles had evaporated fully. Some typical “tongues” of fallout below such levels also occurred. Millimeter radar showed the storm Anvil cloud tops to be much higher than detected by lidar until the Anvil was well dissipated. The infrared properties of the Anvils were calculated. In three of the four Anvils studied, the calculated emittance never exceeded 0.8–0.85. In the remaining case, the cloud emittance approached unity only in the period before the Anvil had descended appreciably. Radiative transfer calculations showed that the infrared emission originated mostly fro...
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cloud particle measurements in thunderstorm Anvils and possible weather threat to aviation
Journal of Aircraft, 1998Co-Authors: Paul R Lawson, Leigh J Angus, Andrew J. HeymsfieldAbstract:Since 1990, there have been at least 10 known incidents where jet aircraft have experienced loss of thrust in one or more turbofan engines while maneuvering in the Anvil region near the central core of a thunderstorm. The exact cause of the uncommanded thrust reduction, commonly called engine rollback, is still under investigation. It appears that the rollback incidents may be associated with ingestion of high mass concentrations of ice particles, snow, and possibly small concentrations of supercooled liquid water in the Anvil region. The characteristics of cloud particles in thunderstorm Anvils have not been extensively studied. Results from analysis of aircraft observations in the Anvils of midlatitude and tropical thunderstorms are discussed. Aircraft and limited radar observations show that most Anvils associated with small, garden-variety thunderstorms contain low ( < ∼ 0.4 g m -3 ) mass concentrations of ice particles. In larger, more intense midlatitude storms, Anvils may contain ice water contents from 1 to 3 g m -3 . The mean of the maximum particle dimension in the Anvil region of the more intense storms showed a strong modal size of about 2 mm. The particles themselves appear to be ice crystals and aggregates of ice crystals, i.e., snowflakes
Sergey S Lobanov - One of the best experts on this subject based on the ideXlab platform.
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pressure stress and strain distribution in the double stage diamond Anvil cell
Journal of Applied Physics, 2015Co-Authors: Sergey S Lobanov, Vitali B Prakapenka, Clemens Prescher, Zuzana Konopkova, Hannspeter Liermann, K L Crispin, Chi Zhang, Alexander F GoncharovAbstract:Double stage diamond Anvil cells (DACs) of two designs have been assembled and tested. We used a standard symmetric DAC with flat or beveled culets as a primary stage and CVD microAnvils machined by a focused ion beam as a second. We evaluated pressure, stress, and strain distributions in gold and a mixture of gold and iron as well as in secondary Anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage Anvil culet size. We found that the stress field generated by the second stage Anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary Anvil and by cupping of the first stage diamond Anvil in the presented experimental designs. Also, our experiments show that pressures of several megabars may be reached without sacrificing the first stage diamond Anvils.
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pressure stress and strain distribution in the double stage diamond Anvil cell
arXiv: Materials Science, 2015Co-Authors: Sergey S Lobanov, Vitali B Prakapenka, Clemens Prescher, Zuzana Konopkova, Hannspeter Liermann, K L Crispin, Chi Zhang, Alexander F GoncharovAbstract:Double stage diamond Anvil cells (DAC) of two designs have been assembled and tested. We used a standard symmetric DAC as a primary stage and CVD microAnvils machined by a focused ion beam - as a second. We evaluated pressure, stress, and strain distributions in Au and Fe-Au samples as well as in secondary Anvils using synchrotron x-ray diffraction with a micro-focused beam. A maximum pressure of 240 GPa was reached independent of the first stage Anvil culet size. We found that the stress field generated by the second stage Anvils is typical of conventional DAC experiments. The maximum pressures reached are limited by strains developing in the secondary Anvil and by cupping of the first stage diamond Anvil in the presented experimental designs. Also, our experiments show that pressures of several megabars may be reached without sacrificing the first stage diamond Anvils.
Robert A Houze - One of the best experts on this subject based on the ideXlab platform.
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vertical structures of Anvil clouds of tropical mesoscale convective systems observed by cloudsat
Journal of the Atmospheric Sciences, 2011Co-Authors: Jian Yuan, Robert A Houze, Andrew J. HeymsfieldAbstract:AbstractA global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6–8 and 1–3 km. High-topped clouds extend outward from raining cores of MCSs to form Anvil clouds. Closest to the raining cores, the Anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of Anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS Anvil clouds vary little across the tropics, except that (i) in continental MCS Anvils...
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leading and trailing Anvil clouds of west african squall lines
Journal of the Atmospheric Sciences, 2011Co-Authors: Jasmine Cetrone, Robert A HouzeAbstract:AbstractThe Anvil clouds of tropical squall-line systems over West Africa have been examined using cloud radar data and divided into those that appear ahead of the leading convective line and those on the trailing side of the system. The leading Anvils are generally higher in altitude than the trailing Anvil, likely because the hydrometeors in the leading Anvil are directly connected to the convective updraft, while the trailing Anvil generally extends out of the lower-topped stratiform precipitation region. When the Anvils are subdivided into thick, medium, and thin portions, the thick leading Anvil is seen to have systematically higher reflectivity than the thick trailing Anvil, suggesting that the leading Anvil contains numerous larger ice particles owing to its direct connection to the convective region. As the leading Anvil ages and thins, it retains its top. The leading Anvil appears to add hydrometeors at the highest altitudes, while the trailing Anvil is able to moisten a deep layer of the atmosphere.
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global variability of mesoscale convective system Anvil structure from a train satellite data
Journal of Climate, 2010Co-Authors: Jian Yuan, Robert A HouzeAbstract:Abstract Mesoscale convective systems (MCSs) in the tropics produce extensive Anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their Anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of Anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the Anvil from the raining regions of ...
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Global Variability of Mesoscale Convective System
2010Co-Authors: Jian Yuan, Robert A HouzeAbstract:Mesoscale convective systems (MCSs) in the tropics produce extensive Anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their Anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of Anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the Anvil from the raining regions of MCSs, this study leads to quantitative global maps of Anvil coverage. These maps are consistent with the MCS analysis, and they lay the foundation for estimating the global radiative effects of Anvil clouds. CloudSat radar data show that the modal thickness of MCS Anvils is about 4--5 km. Anvils are mostly confined to within 1.5--2 times the equivalent radii of the primary rain areas of the MCSs. Over the warm pool, they may extend out to about 5 times the rain area radii. The warm ocean MCSs tend to have thicker non-raining and lightly raining Anvils near the edges of their actively raining regions, indicating that Anvils are generated in and spread out from the primary raining regions of the MCSs. Thicker Anvils are nearly absent over continental regions.
Dorothy M Fragaszy - One of the best experts on this subject based on the ideXlab platform.
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use of stone hammer tools and Anvils by bearded capuchin monkeys over time and space construction of an archeological record of tool use
Journal of Archaeological Science, 2013Co-Authors: Visalberghi Elisabetta, Michael Haslam, Noemi Spagnoletti, Dorothy M FragaszyAbstract:Abstract Wild bearded capuchins (Sapajus libidinosus) in the cerrado (seasonally dry savannah-like region) of Brazil routinely crack open several species of palm nuts and other hard encased fruits and seeds on level surfaces (Anvils) using stones as hammers. At our field site, their nut cracking activity leaves enduring diagnostic physical remains: distinctive shallow depressions (pits) on the surface of the Anvil, and cracked shells and stone hammer(s) on or next to the Anvil. A monthly survey of the physical remains of percussive tool use at 58 Anvils in our study site over a 36-month period revealed repeated use, seasonal consistency, temporal variation, landscape-scale patterning, appearance of new hammers and transport of existing hammers to new Anvil sites. Artefactual evidence of the temporal and spatial pattern of tool use collected in the survey is in correspondence with concurrent direct observation of monkeys using and transporting tools at this site. Shell fragments endure for years above ground, suggesting that they may also endure in the strata around Anvil sites. The bearded capuchins provide an opportunity to study the construction of percussive tool sites suitable for archeological investigation concurrently with the behavior responsible for the construction of these sites. We suggest several lines of inquiry into tool sites created by capuchin monkeys that may be useful to interpret the archeological evidence of percussive tool use in early humans. Archeologists should be aware that transported stone materials and artificial durable landscape features may be the result of activity by non-human animals.
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characteristics of hammer stones and Anvils used by wild bearded capuchin monkeys cebus libidinosus to crack open palm nuts
American Journal of Physical Anthropology, 2007Co-Authors: Elisabetta Visalberghi, Dorothy M Fragaszy, Patricia Izar, Eduardo B Ottoni, Marino Gomes De Oliveira, Fabio Ramos Dias De AndradeAbstract:Capuchins living in Boa Vista (Piaui, Brazil) crack open hard palm nuts on hard, level surfaces (Anvils) using stones (hammers) as percussive tools. This activity leaves diagnostic physical remains: distinctive shallow depressions (pits) on the surface of the Anvil, cracked shells, and stone hammers on the Anvil. To initiate comparison of percussive stone tool use and interpretation of the artifacts it produces across capuchins, chimpanzees, and hominins, we describe a sample of the Anvils and hammer stones used by capuchin monkeys at our site. Anvils (boulders and logs) were located predominantly in the transition zone between the flat open woodland and ridges, in locations that offered some overhead coverage, and with a tree nearby, but not necessarily near palm trees. Anvils contained shallow, hemispherical pits with smooth interiors. Hammers represent a diverse assemblage of ancient rocks that are much harder than the prevailing sedimentary rock out of which they eroded. Hard stones large enough to serve as hammers were more abundant on the Anvils than in the surrounding area, indicating that capuchins transport them to the Anvils. Capuchins use hammers weighing on average more than 1 kg, a weight that is equivalent to 25–40% of the average body weight for adult males and females. Our findings indicate that capuchins select stones to use as hammers and transport stones and nuts to Anvil sites. Wild capuchins provide a new reference point for interpreting early percussive stone tool use in hominins, and a point of comparison with chimpanzees cracking nuts. Am J Phys Anthropol, 2007. © 2006 Wiley-Liss, Inc.
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wild capuchin monkeys cebus libidinosus use Anvils and stone pounding tools
American Journal of Primatology, 2004Co-Authors: Dorothy M Fragaszy, Patricia Izar, Elisabetta Visalberghi, Eduardo B Ottoni, Marino Gomes De OliveiraAbstract:We conducted an exploratory investigation in an area where nut-cracking by wild capuchin monkeys is common knowledge among local residents. In addition to observing male and female capuchin monkeys using stones to pound open nuts on stone “Anvils,” we surveyed the surrounding area and found physical evidence that monkeys cracked nuts on rock outcrops, boulders, and logs (collectively termed Anvils). Anvils, which were identified by numerous shallow depressions on the upper surface, the presence of palm shells and debris, and the presence of loose stones of an appropriate size to pound nuts, were present even on the tops of mesas. The stones used to crack nuts can weigh >1 kg, and are remarkably heavy for monkeys that weigh <4 kg. The abundance of shell remains and depressions in the Anvil surface at numerous Anvil sites indicate that nut-cracking activity is common and long-enduring. Many of the stones found on Anvils (presumably used to pound nuts) are river pebbles that are not present in the local area we surveyed (except on or near the Anvils); therefore, we surmise that they were transported to the Anvil sites. Ecologically and behaviorally, nut-cracking by capuchins appears to have strong parallels to nut-cracking by wild chimpanzees. The presence of abundant Anvil sites, limited alternative food resources, abundance of palms, and the habit of the palms in this region to produce fruit at ground level all likely contribute to the monkeys' routine exploitation of palm nuts via cracking them with stones. This discovery provides a new reference point for discussions regarding the evolution of tool use and material culture in primates. Routine tool use to exploit keystone food resources is not restricted to living great apes and ancestral hominids. Am. J. Primatol. 64:359–366, 2004. © 2004 Wiley-Liss, Inc.