6,592 research outputs found
United States Practice And The Bearing Sea: Is It Consistent With A Norm Of Ecosystem Management?
The need for management of our planet\u27s oceanic environment on an ecosystem level has been an important and much discussed topic in marine science and policy circles. At least one scholar has argued that customary international law requires states to manage the earth\u27s oceans on an ecosystem level rather than by using an ad hoc or species-byspecies system. Ecosystem management provides for a more comprehensive approach toward the utilization and protection of resources in a given geographic area than does species specific management. Not only does ecosystem management consider complex interrelationships among species, but it also takes into account considerations such as habitat, human needs, and air and water quality. Such an analysis does not merely boil down to, for example, jobs versus spotted owls, or the commercial Alaskan pollock harvest versus the Steller sea lion, but requires managers to take a broader view of the consequences of their actions for the benefit of all. Marine ecosystems like the Bering ecosystem are not made up of thousands of separate species of plants and animals each acting autonomously. Rather, they are made up of species which interact with each other and with their environment and are affected directly and indirectly by human activities such as commercial fishing and oil drilling. This web of interrelationships between human activities, natural biological occurrences, marine habitats and the environment is one example of what is meant by the term ecosystem. Ecosystem management requires that a comprehensive planning method be undertaken to regulate the whole ecologic mosaic in a region. As Professor Belsky notes: In other words, the premise of the [ecosystem] model is simply a plea by scientists for holistic or comprehensive research and management [of a given geographic area]. The ecosystem model theorizes that if an integral species like the Alaska pollock in the Bering Sea ecosystem is depleted by overfishing, not only may this significantly affect the human economic interests in the region, but it will also affect the habitat and species that are dependent on those species. Thus, the current management system, which sets annual quotas on individual fish species like pollock, may not be the most effective way to preserve other important economic and ecological interests in the ecosystem. A more effective means of ensuring the health of the Bering Sea and other ecosystems may be to consider a commercially significant species like pollock as just one, albeit critical, component of a functioning system, characterized by complex interrelationships, and which must be managed as a whole. Actions taken by the United States with respect to the Bering Sea ecosystem are important because of their global significance both economically and ecologically. The behavior of the United States is important particularly because much of the Bering Sea ecosystem lies within its Exclusive Economic Zone (EEZ). In addition, the United States is seen as the final remaining superpower, and its actions are often looked to by other nations as an indication of the current standards of conduct under international law. The purpose of this Comment is to explore whether actual U.S. government practice supports the emergence of a customary international law norm requiring nations to engage in marine ecosystem management. Part II describes the theory that there exists such an emerging international law norm. As will be explained, this norm is illustrated by recent developments in international law, including provisions of the United Nations Draft Agreement on Straddling Fish Stocks and Highly Migratory Fish Stocks and the United Nations Convention on the Law of the Sea (LOS). The domestic legal tools that the United States can employ to manage the marine environment on an ecosystem level are the National Environmental Policy Act (NEPA), the Magnuson Fishery Conservation and Management Act (Magnuson Act),\u27 the Marine Mammal Protection Act (MMPA), and the Endangered Species Act (ESA). These are explored in Part III. In order to ascertain whether the United States is using these domestic tools in accordance with the emerging international duty to manage on an ecosystem level, Part IV analyzes the actions of the U.S. government with respect to a specific marine ecosystem, the Bering Sea, and a specific species, the Walleye pollock (pollock). The Bering Sea is one of the most biologically productive waters of the world. Unlike many of the United States\u27 erstwhile fishery-rich ecosystems, it supports a fishery which as recently as 1990 was described as “healthy.” The pollock is a key species both commercially and ecologically in the Bering Sea. As such, the pollock illustrates the necessity of management on an ecosystem level and presents an opportunity for the United States to engage in such management. This Comment will demonstrate that the United States is moving away from a species-by-species approach and toward a more comprehensive, ecosystem-oriented approach of management in the Bering Sea. However, this movement is in its embryonic stages and it remains to be seen whether the United States will use its domestic tools and engage in international efforts to successfully support an emerging international norm requiring ecosystem management
Hydrogen-powered flight
As the Nation moves towards a hydrogen economy the shape of aviation will change dramatically. To accommodate a switch to hydrogen the aircraft designs, propulsion, and power systems will look much different than the systems of today. Hydrogen will enable a number of new aircraft capabilities from high altitude long endurance remotely operated aircraft (HALE ROA) that will fly weeks to months without refueling to clean, zero emissions transport aircraft. Design and development of new hydrogen powered aircraft have a number of challenges which must be addressed before an operational system can become a reality. While the switch to hydrogen will be most outwardly noticeable in the aircraft designs of the future, other significant changes will be occurring in the environment. A switch to hydrogen for aircraft will completely eliminate harmful greenhouse gases such as carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SOx), unburnt hydrocarbons and smoke. While these aircraft emissions are a small percentage of the amount produced on a daily basis, their placement in the upper atmosphere make them particularly harmful. Another troublesome gaseous emission from aircraft is nitrogen oxides (NOx) which contribute to ozone depletion in the upper atmosphere. Nitrogen oxide emissions are produced during the combustion process and are primarily a function of combustion temperature and residence time. The introduction of hydrogen to a gas turbine propulsion system will not eliminate NOx emissions; however the wide flammability range will make low NOx producing, lean burning systems feasible. A revolutionary approach to completely eliminating NOx would be to fly all electric aircraft powered by hydrogen air fuel cells. The fuel cells systems would only produce water, which could be captured on board or released in the lower altitudes. Currently fuel cell systems do not have sufficient energy densities for use in large aircraft, but the long term potential of eliminating greenhouse gas emissions makes it an intriguing and important field of research
Propulsion and Cryogenics Advanced Development (PCAD) Project Propulsion Technologies for the Lunar Lander
The Propulsion and Cryogenics Advanced Development (PCAD) Project in the Exploration Technology Development Program is developing technologies as risk mitigation for Orion and the Lunar Lander. An integrated main and reaction control propulsion system has been identified as a candidate for the Lunar Lander Ascent Module. The propellants used in this integrated system are Liquid Oxygen (LOX)/Liquid Methane (LCH4) propellants. A deep throttle pump fed Liquid Oxygen (LOX)/Liquid Hydrogen (LH2) engine system has been identified for the Lunar Lander Descent Vehicle. The propellant combination and architecture of these propulsion systems are novel and would require risk reduction prior to detailed design and development. The PCAD Project addresses the technology requirements to obtain relevant and necessary test data to further the technology maturity of propulsion hardware utilizing these propellants. This plan and achievements to date will be presented
Isostaticity of Constraints in Jammed Systems of Soft Frictionless Platonic Solids
The average number of constraints per particle in
mechanically stable systems of Platonic solids (except cubes) approaches the
isostatic limit at the jamming point (), though
average number of contacts are hypostatic. By introducing angular alignment
metrics to classify the degree of constraint imposed by each contact,
constraints are shown to arise as a direct result of local orientational order
reflected in edge-face and face-face alignment angle distributions. With
approximately one face-face contact per particle at jamming chain-like
face-face clusters with finite extent form in these systems.Comment: 4 pages, 3 figures, 4 tabl
Guadecitabine, in combination with Cyclophosphamide, promotes anti- cancer immunity in BALB/c mice bearing 4T1 mouse mammary carcinoma
Background: The extremely high mortality rate of patients diagnosed with triple negative breast cancer makes it one of the deadliest forms of cancer. Due to the heterogenous nature of tumors, complete clearance is not achieved and clonal selection occurs resulting in tumor cells evading the immune system. I aim to design a therapeutic intervention that is able to elicit an effective immune response against the tumor and instill immunological memory to eradicate primary and metastatic lesions. I hypothesize that the combination of Guad and Cyp will synergize and promote anticancer immunity via increased expression of neo-tumor antigens and depletion of MDSCs and T-regs. Methods: Guadecitabine (Guad), is a second-generation DNA methyltransferase inhibitor (DMNTi) that has been reported to increase antigenicity and deplete myeloid-derived suppressor cells (MDSC’s). Cyclophosphamide (Cyp) is a chemotherapy that has been shown to deplete regulatory T-cells (T-regs). Both MDSD’s and T-regs suppress antitumor immunity. BALB/c mice were challenged with 4T1 tumor cells subcutaneously in the mammary fat pad region. 4T1-bearing mice were administered low-dose Guad and Cyp for ten consecutive days. Tumor growth curves, tumor-infiltrating lymphocytes (TILs) were measured and MDSC’s and T- regs levels were assessed by flow cytometry. Results: Results from this experiment showed significant synergy between Guad and Cyp with both drugs reducing the tumor size over monotherapy. Conclusions: Further analysis of the data along with future experiments will elucidate if this synergy is driven by the depletion of MDSC’s and T-regs alone or the increase in tumor antigenicity inducing increased numbers of TILs.https://scholarscompass.vcu.edu/gradposters/1078/thumbnail.jp
Propulsion Risk Reduction Activities for Non-Toxic Cryogenic Propulsion
The Propulsion and Cryogenics Advanced Development (PCAD) Project s primary objective is to develop propulsion system technologies for non-toxic or "green" propellants. The PCAD project focuses on the development of non-toxic propulsion technologies needed to provide necessary data and relevant experience to support informed decisions on implementation of non-toxic propellants for space missions. Implementation of non-toxic propellants in high performance propulsion systems offers NASA an opportunity to consider other options than current hypergolic propellants. The PCAD Project is emphasizing technology efforts in reaction control system (RCS) thruster designs, ascent main engines (AME), and descent main engines (DME). PCAD has a series of tasks and contracts to conduct risk reduction and/or retirement activities to demonstrate that non-toxic cryogenic propellants can be a feasible option for space missions. Work has focused on 1) reducing the risk of liquid oxygen/liquid methane ignition, demonstrating the key enabling technologies, and validating performance levels for reaction control engines for use on descent and ascent stages; 2) demonstrating the key enabling technologies and validating performance levels for liquid oxygen/liquid methane ascent engines; and 3) demonstrating the key enabling technologies and validating performance levels for deep throttling liquid oxygen/liquid hydrogen descent engines. The progress of these risk reduction and/or retirement activities will be presented
Novel Endophyte Varities: What\u27s the Difference?
Over the past few decades forage producers have seen several major changes in varieties of tall fescue. From the days of Kentucky 31 being the predominant variety, the first change was the development of endophyte-free tall fescue varieties. For many growers, these have been useful additions, especially when coupled with rotational grazing to reduce the risks of overgrazing, and practices that eradicate existing stands of KY-31 and preventing the reintroduction of endophyte infected KY-31. However, these endophyte-free varieties often lacked the persistence of Kentucky 31 and disappointed many early adopters. In the 30 years since the first generation of endophyte-free varieties, plant breeders have made incredible progress in developing additional tall fescue varieties with the latest breakthrough the development and release of novel endophyte varieties
Harvester Guidance Control System
A guidance control system for a harvester or like machinery includes a steering linkage operatively connected to at least one ground engaging wheel. Harvester steering is controlled through the linkage by either an operator controlled steering wheel or a sensor responsive self-steering mechanism. The sensor responsive self-steering mechanism includes a guide assembly pivotally mounted to the harvester. The guide assembly includes a pair of laterally spaced, cooperating tines that define a path therebetween for plants being harvested. A sensor positioned on each tine senses the position of plants as they are harvested. A control circuit is responsive to the sensors to selectively impart movement to the steering linkage to self-steer the harvester. The control circuit includes a main valve controlled by the operator controlled steering wheel and a secondary valve controlled by the sensors. An auxiliary feed line leads from the main valve to the secondary valve. When the operator utilizes the steering wheel control, an interrupter blocks hydraulic flow through the auxiliary line from the main valve to the secondary valve. Thus, operator controlled steering input overrides the sensor responsive self-steering for maximum safety. The guidance control system also eliminates harvester wander back and forth across a row by substantially preventing overcompensation by the sensor responsive self-steering
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