611 resultados para Randall-Sundrum
Resumo:
Recovery plans identify reasonable actions which are believed to be required to recover and/or protect endangered species. Plans are prepared by the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (FWS) and sometimes with the assistance of recovery teams, contractors, State agencies, and others. This plan was prepared by Randall R. Reeves, Phillip J. Clapham, Robert L. Brownell, Jr., and Gregory K. Silber for NMFS. Recovery plans do not necessarily represent the views nor the official positions or approvals of any individuals or agencies, other than those of NMFS, and they represent the views of NMFS only after they have been approved by the Assistant Administrator for Fisheries. Objectives will only be attained and funds expended contingent upon appropriations, priorities, and other budgetary constraints. Approved recovery plans are subject to modification as dictated by new findings, changes in species status, and the completion of recovery tasks described in the plan.
Resumo:
The seasonal distributions of humpback and blue whales (Megaptera novaeangliae and Balaenoptera musculus, respectively) in the North Atlantic Ocean are not fully understood. Although humpbacks have been studied intensively in nearshore or coastal feeding and breeding areas, their migratory movements between these areas have been largely inferred. Blue whales have only been studied intensively along the north shore of the Gulf of St. Lawrence, and their seasonal occurrence and movements elsewhere in the North Atlantic are poorly known. We investigated the historical seasonal distributions of these two species using sighting and catch data extracted from American 18th and 19th century whaling logbooks. These data suggest that humpback whales migrated seasonally from low-latitude calving/ breeding grounds over a protracted period, and that some of them traveled far offshore rather than following coastal routes. Also, at least some humpbacks apparently fed early in the summer west of the Mid-Atlantic Ridge, well south of their known present-day feeding grounds. In assessing the present status of the North Atlantic humpback population, it will be important to determine whether such offshore feeding does in fact occur. Blue whales were present across the southern half of the North Atlantic during the autumn and winter months, and farther north in spring and summer, but we had too few data points to support inferences about these whales’ migratory timing and routes.
Resumo:
Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH) is a frequent but unpredictable complication associated with poor outcome. Current vasospasm therapies are suboptimal; new therapies are needed. Clazosentan, an endothelin receptor antagonist, has shown promise in phase 2 studies, and two randomized, double-blind, placebo-controlled phase 3 trials (CONSCIOUS-2 and CONSCIOUS-3) are underway to further investigate its impact on vasospasm-related outcome after aSAH. Here, we describe the design of these studies, which was challenging with respect to defining endpoints and standardizing endpoint interpretation and patient care. Main inclusion criteria are: age 18-75 years; SAH due to ruptured saccular aneurysm secured by surgical clipping (CONSCIOUS-2) or endovascular coiling (CONSCIOUS-3); substantial subarachnoid clot; and World Federation of Neurosurgical Societies grades I-IV prior to aneurysm-securing procedure. In CONSCIOUS-2, patients are randomized 2:1 to clazosentan (5 mg/h) or placebo. In CONSCIOUS-3, patients are randomized 1:1:1 to clazosentan 5, 15 mg/h, or placebo. Treatment is initiated within 56 h of aSAH and continued until 14 days after aSAH. Primary endpoint is a composite of mortality and vasospasm-related morbidity within 6 weeks of aSAH (all-cause mortality, vasospasm-related new cerebral infarction, vasospasm-related delayed ischemic neurological deficit, neurological signs or symptoms in the presence of angiographic vasospasm leading to rescue therapy initiation). Main secondary endpoint is extended Glasgow Outcome Scale at week 12. A critical events committee assesses all data centrally to ensure consistency in interpretation, and patient management guidelines are used to standardize care. Results are expected at the end of 2010 and 2011 for CONSCIOUS-2 and CONSCIOUS-3, respectively.
Resumo:
Objectives: Previous research conducted in the late 1980s suggested that vehicle impacts following an initial barrier collision increase severe occupant injury risk. Now over 25years old, the data are no longer representative of the currently installed barriers or the present US vehicle fleet. The purpose of this study is to provide a present-day assessment of secondary collisions and to determine if current full-scale barrier crash testing criteria provide an indication of secondary collision risk for real-world barrier crashes. Methods: To characterize secondary collisions, 1,363 (596,331 weighted) real-world barrier midsection impacts selected from 13years (1997-2009) of in-depth crash data available through the National Automotive Sampling System (NASS) / Crashworthiness Data System (CDS) were analyzed. Scene diagram and available scene photographs were used to determine roadside and barrier specific variables unavailable in NASS/CDS. Binary logistic regression models were developed for second event occurrence and resulting driver injury. To investigate current secondary collision crash test criteria, 24 full-scale crash test reports were obtained for common non-proprietary US barriers, and the risk of secondary collisions was determined using recommended evaluation criteria from National Cooperative Highway Research Program (NCHRP) Report 350. Results: Secondary collisions were found to occur in approximately two thirds of crashes where a barrier is the first object struck. Barrier lateral stiffness, post-impact vehicle trajectory, vehicle type, and pre-impact tracking conditions were found to be statistically significant contributors to secondary event occurrence. The presence of a second event was found to increase the likelihood of a serious driver injury by a factor of 7 compared to cases with no second event present. The NCHRP Report 350 exit angle criterion was found to underestimate the risk of secondary collisions in real-world barrier crashes. Conclusions: Consistent with previous research, collisions following a barrier impact are not an infrequent event and substantially increase driver injury risk. The results suggest that using exit-angle based crash test criteria alone to assess secondary collision risk is not sufficient to predict second collision occurrence for real-world barrier crashes.
Resumo:
Recent claims of blood vessels extracted from dinosaur fossils challenge classical views of soft-tissue preservation. Alternatively, these structures may represent postdepositional,diagenetic biofilms that grew on vascular cavity surfaces within the fossil. Similar red, hollow, tube-shaped structures were recovered from well-preserved and poorly-preserved (abraded, desiccated, exposed) Upper Cretaceous dinosaur fossils in this study. Integration of light microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy was used to compare these vessel structures to the fossils from which they are derived. Vessel structures are typically 100-400 μm long, 0.5-1.5 μm thick, 10-40 μm in diameter and take on a wide range of straight, curved, andbranching morphologies. Interior surfaces vary from smooth to globular and typically contain spheres, rods, and fibrous structures (< 2 μm in diameter) incorporated into the surface. Exterior surfaces exhibit 2-μm-tall converging ridges, spaced 1-3 μm apart, that are sub-parallel to the long axis of the vessel structure. Fossil vascular cavities are typically coated with a smooth or grainy orange layer that shows a wide range of textures including smooth, globular, rough, ropy, and combinations thereof. Coatings tend to overlay secondary mineral crystals and framboids, confirming they are not primary structures of the fossil. For some cavity coatings, the surface that had been in contact with the bone exhibits a ridged texture, similar to that of vessel structures, having formed as a mold of the intravascular bone surface. Thus, vessel structures are interpreted as intact cavity coatings isolated after the fossil is demineralized. The presence of framboids and structures consistent in size and shape with bacteria cells, the abundance of iron in cavity coatings, and the growth of biofilms directly from the fossil that resemble respective cavity coatings support the hypothesis that vessel structures result from ironconsuming bacteria that form biofilms on the intravascular bone surfaces of fossil dinosaur bone. This also accounts for microstructures resembling osteocytes as some fossil lacunae are filled with the same iron oxide that comprises vessel structures andcoatings. Results of this study show that systematic, high-resolution SEM analyses of vertebrate fossils can provide improved insight on microtaphonomic processes, including the role of bacteria in diagenesis. These results conflict with earlier claims of dinosaurblood vessels and osteocytes.
Resumo:
Clazosentan, an endothelin receptor antagonist, has been shown to reduce vasospasm after aneurysmal subarachnoid hemorrhage (aSAH). CONSCIOUS-3 assessed whether clazosentan reduced vasospasm-related morbidity and all-cause mortality postaSAH secured by endovascular coiling.
Resumo:
Previous research conducted in the late 1980’s suggested that vehicle impacts following an initial barrier collision increase severe occupant injury risk. Now over twenty-five years old, the data used in the previous research is no longer representative of the currently installed barriers or US vehicle fleet. The purpose of this study is to provide a present-day assessment of secondary collisions and to determine if full-scale barrier crash testing criteria provide an indication of secondary collision risk for real-world barrier crashes. The analysis included 1,383 (596,331 weighted) real-world barrier midsection impacts selected from thirteen years (1997-2009) of in-depth crash data available through the National Automotive Sampling System (NASS) / Crashworthiness Data System (CDS). For each suitable case, the scene diagram and available scene photographs were used to determine roadside and barrier specific variables not available in NASS/CDS. Binary logistic regression models were developed for second event occurrence and resulting driver injury. Barrier lateral stiffness, post-impact vehicle trajectory, vehicle type, and pre-impact tracking conditions were found to be statistically significant contributors toward secondary event occurrence. The presence of a second event was found to increase the likelihood of a serious driver injury by a factor of seven compared to cases with no second event present. Twenty-four full-scale crash test reports were obtained for common non-proprietary US barriers, and the risk of secondary collisions was determined using recommended evaluation criteria from NCHRP Report 350. It was found that the NCHRP Report 350 exit angle criterion alone was not sufficient to predict second collision occurrence for real-world barrier crashes.
Resumo:
This project addresses the potential impacts of changing climate on dry-season water storage and discharge from a small, mountain catchment in Tanzania. Villagers and water managers around the catchment have experienced worsening water scarcity and attribute it to increasing population and demand, but very little has been done to understand the physical characteristics and hydrological behavior of the spring catchment. The physical nature of the aquifer was characterized and water balance models were calibrated to discharge observations so as to be able to explore relative changes in aquifer storage resulting from climate changes. To characterize the shallow aquifer supplying water to the Jandu spring, water quality and geochemistry data were analyzed, discharge recession analysis was performed, and two water balance models were developed and tested. Jandu geochemistry suggests a shallow, meteorically-recharged aquifer system with short circulation times. Baseflow recession analysis showed that the catchment behavior could be represented by a linear storage model with an average recession constant of 0.151/month from 2004-2010. Two modified Thornthwaite-Mather Water Balance (TMWB) models were calibrated using historic rainfall and discharge data and shown to reproduce dry-season flows with Nash-Sutcliffe efficiencies between 0.86 and 0.91. The modified TMWB models were then used to examine the impacts of nineteen, perturbed climate scenarios to test the potential impacts of regional climate change on catchment storage during the dry season. Forcing the models with realistic scenarios for average monthly temperature, annual precipitation, and seasonal rainfall distribution demonstrated that even small climate changes might adversely impact aquifer storage conditions at the onset of the dry season. The scale of the change was dependent on the direction (increasing vs. decreasing) and magnitude of climate change (temperature and precipitation). This study demonstrates that small, mountain aquifer characterization is possible using simple water quality parameters, recession analysis can be integrated into modeling aquifer storage parameters, and water balance models can accurately reproduce dry-season discharges and might be useful tools to assess climate change impacts. However, uncertainty in current climate projections and lack of data for testing the predictive capabilities of the model beyond the present data set, make the forecasts of changes in discharge also uncertain. The hydrologic tools used herein offer promise for future research in understanding small, shallow, mountainous aquifers and could potentially be developed and used by water resource professionals to assess climatic influences on local hydrologic systems.
Resumo:
This report is a dissertation proposal that focuses on the energy balance within an internal combustion engine with a unique coolant-based waste heat recovery system. It has been predicted by the U.S. Energy Information Administration that the transportation sector in the United States will consume approximately 15 million barrels per day in liquid fuels by the year 2025. The proposed coolant-based waste heat recovery technique has the potential to reduce the yearly usage of those liquid fuels by nearly 50 million barrels by only recovering even a modest 1% of the wasted energy within the coolant system. The proposed waste heat recovery technique implements thermoelectric generators on the outside cylinder walls of an internal combustion engine. For this research, one outside cylinder wall of a twin cylinder 26 horsepower water-cooled gasoline engine will be implemented with a thermoelectric generator surrogate material. The vertical location of these TEG surrogates along the water jacket will be varied along with the TEG surrogate thermal conductivity. The aim of this proposed dissertation is to attain empirical evidence of the impact, including energy distribution and cylinder wall temperatures, of installing TEGs in the water jacket area. The results can be used for future research on larger engines and will also assist with proper TEG selection to maximize energy recovery efficiencies.
Resumo:
Age hardening occurs in alloys of the solid solution type containing a hardening constituent, be it metal or metallic compound, which is more soluble in the solvent phase at higher temperatures than at lower ones.