1,785 research outputs found
Ethological Causes and Consequences of the Stress Response
Stress involves real or perceived changes within an organism or in the environment that activate an organism’s attempts to cope by means of evolutionarily ancient neural and endocrine mechanisms. Responses to acute stressors involve catecholamines released in varying proportion at different sites in the sympathetic and central nervous systems. These responses may interact with and be complemented by intrinsic rhythms and responses to chronic or intermittent stressors involving the hypothalamic-pituitary-adrenal axis. Varying patterns of responses to stressors are also affected by an animal=s assessment of their prospects for successful coping. Subsequent central and systemic consequences of the stress response include apparent changes in affect, motivation, and cognition that can result in an altered relationship to environmental and social stimuli. This review will summarize recent developments in our understanding of the causes and consequences of stress. Special problems that need to be explored involve the manner in which ensembles of adaptive responses are assembled, how autonomic and neurohormonal reflexes of the stress response come under the influence of environmental stimuli, and how some specific aspects of the stress response may be integrated into the life history of a species
Exact Dynamics of Multicomponent Bose-Einstein Condensates in Optical Lattices in One, Two and Three Dimensions
Numerous exact solutions to the nonlinear mean-field equations of motion are
constructed for multicomponent Bose-Einstein condensates on one, two, and three
dimensional optical lattices. We find both stationary and nonstationary
solutions, which are given in closed form. Among these solutions are a
vortex-anti-vortex array on the square optical lattice and modes in which two
or more components slosh back and forth between neighboring potential wells. We
obtain a variety of solutions for multicomponent condensates on the simple
cubic lattice, including a solution in which one condensate is at rest and the
other flows in a complex three-dimensional array of intersecting vortex lines.
A number of physically important solutions are stable for a range of parameter
values, as we show by direct numerical integration of the equations of motion.Comment: 22 pages, 9 figure
A review of the ecological effectiveness of subtidal marine reserves in Central California, Part I: Synopsis of scientific investigations
Marine reserves, often referred to as no-take MPAs, are defined as areas within which human activities that can result in the removal or alteration of biotic and abiotic components of an ecosystem are prohibited or greatly restricted (NRC 2001). Activities typically curtailed
within a marine reserve are extraction of organisms (e.g., commercial and recreational fishing, kelp harvesting, commercial collecting), mariculture, and those activities that can alter oceanographic or geologic attributes of the habitat (e.g., mining, shore-based industrial-related
intake and discharges of seawater and effluent). Usually, marine reserves are established to conserve biodiversity or enhance nearby fishery resources. Thus, goals and objectives of marine reserves can be inferred, even if they are not specifically articulated at the time of reserve
formation.
In this report, we review information about the effectiveness of the three marine reserves in the Monterey Bay National Marine Sanctuary (Hopkins Marine Life Refuge, Point Lobos Ecological Reserve, Big Creek Ecological Reserve), and the one in the Channel Islands National
Marine Sanctuary (the natural area on the north side of East Anacapa Island). Our efforts to objectively evaluate reserves in Central California relative to reserve theory were greatly hampered for four primary reasons; (1) few of the existing marine reserves were created with clearly articulated goals or objectives, (2) relatively few studies of the ecological consequences of existing reserves have been conducted, (3) no studies to date encompass the spatial and temporal scope needed to identify ecosystem-wide effects of reserve protection, and (4) there are
almost no studies that describe the social and economic consequences of existing reserves.
To overcome these obstacles, we used several methods to evaluate the effectiveness of subtidal marine reserves in Central California. We first conducted a literature review to find out what research has been conducted in all marine reserves in Central California (Appendix 1). We then reviewed the scientific literature that relates to marine reserve theory to help define criteria to use as benchmarks for evaluation. A recent National Research Council (2001) report summarized expected reserve benefits and provided the criteria we used for evaluation of effectiveness. The next step was to identify the research projects in this region that collected information in a way that enabled us to evaluate reserve theory relative to marine reserves in
Central California. Chapters 1-4 in this report provide summaries of those research projects. Contained within these chapters are evaluations of reserve effectiveness for meeting specific objectives. As few studies exist that pertain to reserve theory in Central California, we reviewed
studies of marine reserves in other temperate and tropical ecosystems to determine if there were lessons to be learned from other parts of the world (Chapter 5). We also included a discussion of social and economic considerations germane to the public policy decision-making processes associated with marine reserves (Chapter 6). After reviewing all of these resources, we provided a summary of the ecological benefits that could be expected from existing reserves in Central California. The summary is presented in Part II of this report. (PDF contains 133 pages.
Workshop on Mars Sample Return Science
Martian magnetic history; quarantine issues; surface modifying processes; climate and atmosphere; sampling sites and strategies; and life sciences were among the topics discussed
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Trace Elements Memorandum Report 436
A report regarding the distribution of the Leached Zone of the Bone Valley Formation, Land-Pebble Phosphate Field, Florida
Genetic Susceptibility of Cultured Shrimp (\u3ci\u3ePenaeus vannamei\u3c/i\u3e) to Infectious Hypodermal and Hematopoietic Necrosis Virus and \u3ci\u3eBaculovirus penaei\u3c/i\u3e: Possible Relationship with Growth Status and Metabolic Gene Expression
Offspring of four crosses (I, II, III, and IV) of Penaeus vannamei from known high- and low-growth families were challenged with infectious hypodermal and hematopoietic necrosis virus (IHHNV) and Baculovirus penaei (BP) to compare their susceptibility to these viral agents and examine the genetic component involved in disease resistance or susceptibility. Family crosses were made using broodstock from five families developed by the U.S. Marine Shrimp Farming Program. The prevalence of IHHNV infection was highest in cross I and lowest in cross III. Cross I was developed using male and female broodstock from the low-growth family 1.6, and cross III was developed using a female from the high-growth family 1.3 and a male from the low-growth family 1.6. The prevalence of BP infection at Day 4 was highest (100%) in cross IV, which was developed using a female from the low-growth family 1.4 and a male from the high-growth family 1.5. The reciprocal cross, cross III, had the lowest (68%) prevalence at Day 4 postexposure. Both crosses I and II had 88% prevalence of infection at Day 4. Despite 100% prevalence of BP infection in cross IV at 4 days, animals from this cross and cross II exhibited high survival by Day 18 (85 and 77%). On the other hand, crosses I and III (with 88 and 68% prevalence at Day 4, respectively) showed low survival at Day 18 (19 and 24%). On the basis of prevalence of infection and mortality rates, it was concluded that the susceptibility to BP in penaeid shrimp is governed by the genetic background of the parental crosses. The random amplified polymorphic DNA polymorphisms for crosses I, II, III, and IV, were 43, 45, 53, and 51%, respectively, showing no clear relationship between IHHNV and BP prevalence of infection and levels of nuclear genetic diversity. Though the mtDNA haplotypes in offspring from the different crosses were the same, major differences were observed in both steady-state levels and patterns of expression of the mitochondrial 12s rRNA in offspring obtained at various early developmental stages from each of the four crosses. The possible relationship among disease susceptibility, growth status, and expression of mitochondrial 12s rRNA is discussed in the context of a complex nuclear-cytoplasmic genetic system involved in the regulation of gene expression
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