4,969 research outputs found
Health effects of gasoline exposure. I. Exposure assessment for U.S. distribution workers.
Personal exposures were estimated for a large cohort of workers in the U.S. domestic system for distributing gasoline by trucks and marine vessels. This assessment included development of a rationale and methodology for extrapolating vapor exposures prior to the availability of measurement data, analysis of existing measurement data to estimate task and job exposures during 1975-1985, and extrapolation of truck and marine job exposures before 1975. A worker's vapor exposure was extrapolated from three sets of factors: the tasks in his or her job associated with vapor sources, the characteristics of vapor sources (equipment and other facilities) at the work site, and the composition of petroleum products producing vapors. Historical data were collected on the tasks in job definitions, on work-site facilities, and on product composition. These data were used in a model to estimate the overall time-weighted-average vapor exposure for jobs based on estimates of task exposures and their duration. Task exposures were highest during tank filling in trucks and marine vessels. Measured average annual, full-shift exposures during 1975-1985 ranged from 9 to 14 ppm of total hydrocarbon vapor for truck drivers and 2 to 35 ppm for marine workers on inland waterways. Extrapolated past average exposures in truck operations were highest for truck drivers before 1965 (range 140-220 ppm). Other jobs in truck operations resulted in much lower exposures. Because there were few changes in marine operations before 1979, exposures were assumed to be the same as those measured during 1975-1985. Well-defined exposure gradients were found across jobs within time periods, which were suitable for epidemiologic analyses
Constraining melt geometries beneath the Afar Depression, Ethiopia from teleseismic receiver functions: the anisotropic H-Îș stacking technique
Understanding the nature of the crust has long been a goal for seismologists when imaging the Earth. This is particularly true in volcanic regions where imaging melt storage and migration can have important implications for the size and nature of an eruption. Receiver functions and the H-Îș stacking (HÎș) technique are often used to constrain crustal thickness (H) and the ratio of P to S wave velocities (Îș). In this paper, I show that it is essential to consider anisotropy when performing HÎș. I show that in a medium with horizontally transverse isotropy a strong variation in Îș with back azimuth is present, which characterizes the anisotropic medium. In a vertically transverse isotropic medium, no variation in Îș with back azimuth is observed, but Îș is increased across all back azimuths. Thus, estimates of Îș are more difficult to relate to composition than previously thought. I extend these models to melt-induced anisotropy and show that similar patterns are observed, but with more significant variations and increases in Îș. Based on these observations, I develop a new anisotropic H-Îș stacking technique which inverts HÎș data for melt fraction, aspect ratio, and orientation of melt inclusions. I apply this to data for the Afar Depression and show that melt is stored in interconnected stacked sills in the lower crust, which likely supply the recent volcanic eruptions and dike intrusions. This new technique can be applied to any anisotropic medium where it can provide constraints on the average crustal anisotropy
A Role for Actin, Cdc1p, and Myo2p in the Inheritance of Late Golgi Elements in \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e
In Saccharomyces cerevisiae, Golgi elements are present in the bud very early in the cell cycle. We have analyzed this Golgi inheritance process using fluorescence microscopy and genetics. In rapidly growing cells, late Golgi elements show an actin-dependent concentration at sites of polarized growth. Late Golgi elements are apparently transported into the bud along actin cables and are also retained in the bud by a mechanism that may involve actin. A visual screen for mutants defective in the inheritance of late Golgi elements yielded multiple alleles of CDC1. Mutations in CDC1 severely depolarize the actin cytoskeleton, and these mutations prevent late Golgi elements from being retained in the bud. The efficient localization of late Golgi elements to the bud requires the type V myosin Myo2p, further suggesting that actin plays a role in Golgi inheritance. Surprisingly, early and late Golgi elements are inherited by different pathways, with early Golgi elements localizing to the bud in a Cdc1p- and Myo2p-independent manner. We propose that early Golgi elements arise from ER membranes that are present in the bud. These two pathways of Golgi inheritance in S. cerevisiae resemble Golgi inheritance pathways in vertebrate cells
The Dynamic Crust of Northern Afar and Adjacent Rift Margins: New Evidence From Receiver Function Analysis in Eritrea and Ethiopia
Afar is undergoing the final stages of continental rifting and hosts the triple junction between the Red Sea, Gulf of Aden, and Main Ethiopian rifts. To better understand the nature of the crust and continental breakup in the region, we calculate teleseismic receiver functions across northeastern Afar and the Danakil microplate, using new data from a regional deployment in Eritrea. We estimate the Moho depth and bulk crustal V P /V S ratio using the HâÎș stacking method. The heterogeneity of our crustal thickness estimates (âŒ19â35 km) indicates that the Danakil microplate has undergone stretching and crustal thinning. By investigating the relationship between crustal thickness and topographic elevation, we estimate the regional crustal bulk density as Ï c â 2,850 ± 20 kg mâ3, which is higher than expected, given the crustal thickness of the region. We show that topography is 1.5 ± 0.4 km higher than would be expected due to crustal isostasy alone. We propose that this topography is supported by the same hot mantle upwelling suggested to be responsible for the onset of rifting in East Africa. Uplift is generated due to the presence of a hot thermal anomaly beneath the plate and by thinning of the lithospheric mantle. Our results are consistent with a number of independent constraints on the thermal structure of the asthenospheric and lithospheric mantle. Evidence of melt within the crust is provided by anomalously high V P /V S ratios of >1.9, demonstrating that magmaâassisted extension continues to be important in the final stages of continental breakup
Seismicity of the central Afar rift and implications for Tendaho dam hazards
Temporary broadband seismic networks deployed from 2007 to 2011 around the Afar triple junction of the East African Rift System provide insights into seismicity patterns of the actively deforming crust around the 1.86 km3 impounded lake system behind the Tendaho dam. The observed seismicity correlates well with the active magmatic centres around central Afar. The area around the dam site is characterized by a network of intersecting NNE- and NW-trending faults. Seismicity clusters observed in the specified time interval indicate that both fault sets are active and are potential sources of seismogenic hazards. The dam neighbourhood is naturally active and it is a challenge to associate the observed seismic activity to either a change in magmato-tectonic conditions or attribute it to the influence of reservoir load. It is evident that the dam region experi- ences high levels of seismic and volcano-tectonic unrest, regardless of the origin of the activity. The spatial overlap of narrow zones of crustal seismicity and upper mantle low velocity zones observed in S-wave tomography models suggests that melt production zones guide the distribution of strain during continental rupture. Given its volcanically and seismically active setting, the Tendaho dam site and the surrounding region require continuous monitoring for the safety of downstream popu- lations and development infrastructures in the Afar National Regional State of Ethiopia
A new flood risk assessment framework for evaluating the effectiveness of policies to improve urban flood resilience
This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.To better understand the impacts of flooding such that authorities can plan for adapting measures to
cope with future scenarios, we have developed a modified Drivers-Pressures-State-Impact-Response
(DPSIR) framework to allow policy makers to evaluate strategies for improving flood resilience in cities.
We showed that this framework proved an effective approach to assessing and improving urban flood
resilience, albeit with some limitations. This framework has difficulties in capturing all the important
relationships in cities, especially with regards to feedbacks. There is therefore a need to develop
improved techniques for understanding components and their relationships. While this research
showed that risk assessment is possible even at the mega-city scale, new techniques will support
advances in this field. Finally, a chain of models engenders uncertainties. However, the resilience
approach promoted in this research, is an effective manner to work with uncertainty by providing the
capacity to cope and respond to multiple scenariosResearch on the CORFU (Collaborative research on flood resilience in urban areas) project was funded
by the European Commission through Framework Programme 7, Grant Number 244047. The work in
this paper was partially funded by the PEARL (Preparing for Extreme And Rare events in coastaL
regions) project, supported by the European Union's Seventh Framework Programme under Grant
Agreement No 603663
Allocation mechanisms, incentives, and endemic institutional externalities
Whether an economic agentâs decision creates an externality often depends on the institutional context in which the decision was made. Indeed, in orthodox economics, a technological or exogenous externality occurs just in case one agentâs economic welfare or production possibilities are directly affected by the market decisions of other agents. A pecuniary externality occurs just in case one consumerâs economic welfare or producerâs profit is affected indirectly by price changes caused by changes in other agentsâ decisions. Similarly, an institutional or endogenous externality may arise whenever allocations are determined by a mechanism that is not strategy proof for some agent. Then even a resource balance constraint creates an institutional externality except in special cases such as when no individual agentâs action can affect market clearing prices â i.e., there are no pecuniary externalities
Advances in plant virus evolution: translating evolutionary insights into better disease management
[EN] Recent studies in plant virus evolution are revealing that genetic structure and behavior of virus and viroid populations can explain important pathogenic properties of these agents, such as host resistance breakdown, disease severity, and host shifting, among others. Genetic variation is essential for the survival of organisms. The exploration of how these subcellular parasites generate and maintain a certain frequency of mutations at the intra- and inter-host levels is revealing novel molecular virus plant interactions. They emphasize the role of host environment in the dynamic genetic composition of virus populations. Functional genomics has identified host factors that are transcriptionally altered after virus infections. The analyses of these data by means of systems biology approaches are uncovering critical plant genes specifically targeted by viruses during host adaptation. Also, a next-generation re-sequencing approach of a whole virus genome is opening new avenues to study virus recombination and the relationships between intra-host virus composition and pathogenesis. Altogether, the analyzed data indicate that systematic disruption of some specific parameters of evolving virus populations could lead to more efficient ways of disease prevention, eradication, or tolerable virus plant coexistence.Acosta-Leal, R.; Duffy, S.; Xiong, Z.; Hammond, R.; Elena Fito, SF. (2011). Advances in plant virus evolution: translating evolutionary insights into better disease management. Phytopathology. 101(10):1136-1148. doi:10.1094/ PHYTO-01-11-0017S113611481011
Isolation and primary cultures of human intrahepatic bile ductular epithelium
A technique for the isolation of human intrahepatic bile ductular epithelium, and the establishment of primary cultures using a serum- and growth-factor-supplemented medium combined with a connective tissue substrata is described. Initial cell isolates and monolayer cultures display phenotypic characteristics of biliary epithelial cells (low molecular weight prekeratin positive; albumin, alphafetoprotein, and Factor VIII-related antigen negative). Ultrastructural features of the cultured cells show cell polarization with surface microvilli, numerous interepithelial junctional complexes and cytoplasmic intermediate prekeratin filaments. © 1988 Tissue Culture Association, Inc
Massive Electrodynamics and Magnetic Monopoles
Including torsion in the geometric framework of the Weyl-Dirac theory we
build up an action integral, and obtain from it a gauge covariant (in the Weyl
sense) general relativistic massive electrodynamics. Photons having an
arbitrary mass, electric, and magnetic currents (Dirac's monopole) coexist
within this theory. Assuming that the space-time is torsionless, taking the
photons mass zero, and turning to the Einstein gauge we obtain Maxwell's
electrodynamics.Comment: LaTex File, 9 pages, no figure
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