900 research outputs found
Experiment K-6-22. Growth hormone regulation, synthesis and secretion in microgravity. Part 1: Somatotroph physiology. Part 2: Immunohistochemical analysis of hypothalamic hormones. Part 3: Plasma analysis
The objectives of the 1887 mission were: (1) to determine if the results of the SL-3 pituitary gland experiment (1) were repeatable; and (2) to determine what effect a longer mission would have on the rat pituitary gland growth hormone (GH) system. In the 1887 experiment two issues were considered especially important. First, it was recognized that cells prepared from individual rat pituitary glands should be considered separately so that the data from the 5 glands could be analyzed in a statistically meaningful way. Second, results of the SL-3 flight involving the hollow fiber implant and HPLC GH-variant experiments suggested that the biological activity of the hormone had been negatively affected by flight. The results of the 1887 experiment documented the wisdom of addressing both issues in the protocol. Thus, the reduction in secretory capacity of flight cells during subsequent extended cell culture on Earth was documented statistically, and thereby established the validity of the SL-3 result. The results of both flight experiments thus support the contention that there is a secretory lesion in pituitary GH cells of flight animals. The primary objective of both missions was a clear definition of the effect of spaceflight on the GH cell system. There can no longer be any reasonable doubt that this system is affected in microgravity. One explanation for the reason(s) underlying the better known effects of spaceflight on organisms, viz. changes in bone, muscle and immune systems may very well rest with such changes in bGH. In spite of the fact that rats in the Cosmos 1887 flight were on Earth for two days after flight, the data show that the GH system had still not recovered from the effects of flight. Many questions remain. One of the more important concerns the GRF responsiveness of somatotrophs after flight. This will be tested in an upcoming experiment
Analytical Portfolio Value-at-Risk
The paper develops analytical tools used to calculate the VaR of a portfolio composed of generally distributed assets. Accordingly, the VaR of a portfolio is analytically constructed from the conditional returns of the individual assets. This analytical VaR can then be used to construct optimal portfolios of generally distributed assets for the case in which the target function and/or constraints are expressed in terms of VaR. The proposed method is applicable in a wide range of practical problems such as utility maximization under a VaR constraint. The article demonstrates this method by developing a minimal VaR rule that identifies the proportions that minimize the portfolio VaR. This rule is used to compare the minimal VaR portfolio with the minimal standard deviation portfolio in the case of the lognormal distribution. This example illustrates the importance of downside risk in optimal asset allocation even under modest deviations from the normal distribution such as in the case of the lognormal distribution
Analytical Portfolio Value-at-Risk
The paper develops analytical tools used to calculate the VaR of a portfolio composed of generally distributed assets. Accordingly, the VaR of a portfolio is analytically constructed from the conditional returns of the individual assets. This analytical VaR can then be used to construct optimal portfolios of generally distributed assets for the case in which the target function and/or constraints are expressed in terms of VaR. The proposed method is applicable in a wide range of practical problems such as utility maximization under a VaR constraint. The article demonstrates this method by developing a minimal VaR rule that identifies the proportions that minimize the portfolio VaR. This rule is used to compare the minimal VaR portfolio with the minimal standard deviation portfolio in the case of the lognormal distribution. This example illustrates the importance of downside risk in optimal asset allocation even under modest deviations from the normal distribution such as in the case of the lognormal distribution
Experiment K-6-02. Biomedical, biochemical and morphological alterations of muscle and dense, fibrous connective tissues during 14 days of spaceflight
Findings on the connective tissue response to short-term space flight (12 days) are discussed. Specifically, data regarding the biochemical, biomechanical and morphological characteristics of selected connective tissues (humerus, vertebral body, tendon and skeletal muscle) of growing rats is given. Results are given concerning the humerus cortical bone, the vertebral bone, nutritional effects on bone biomechanical properties, and soft tense fiber connective tissue response
Formation number of confined vortex rings
This paper investigates the formation number of vortex rings generated by a piston-cylinder mechanism in a confined tube. We use Direct Numerical Simulations (DNS) of axisymmetric confined vortex rings to study the influence of different parameters on the separation (or pinch-off) of the vortex ring from the trailing jet. It is shown that the structure of the vortex ring at pinch-off depends on the type of injection program (pulse dominated by either positive or negative acceleration ramps) and the confinement ratio D w /D , where D w is the inner diameter of the tube and D the diameter of the cylinder). For low confinement ratios ( D w /D ≤ 2), a vortex of opposite sign generated at the lateral wall strongly interacts with the vortex ring and the pinch-off is not clearly observed. The pinch-off is observed and analysed for confinement ratios D w /D ≥ 2 . 5. DNS data are used to estimate the value of the formation time, which is the time necessary for the vortex generator to inject the same amount of circulation as carried by the detached vortex ring. The confined vortex ring at pinch-off is described by the model suggested by Danaila, Kaplanski and Sazhin [A model for confined vortex rings with elliptical core vorticity distribution, Journal of Fluid Mechanics, 811 :67-94, 2017]. This model allows us to take into account the influence of the lateral wall and the elliptical shape of the vortex core. The value of the formation time is predicted using this model and the slug-flow model
Do Happy People Make Optimistic Investors?
Do happy people predict future risk and return differently from unhappy people, or do individuals rely only on economic facts? We survey investors on their subjective sentiment-creating factors, return and risk expectations, and investment plans. We find that non-economic factors systematically affect return and risk expectations, where the return effect is more profound. Investment plans are also affected by non-economic factors. Sports results and general feelings significantly affect predictions. Sufferers from seasonal affective disorder have lower return expectations in the autumn than in other seasons, supporting the Winter Blues hypothesis
VaR Risk Measures versus Traditional Risk Measures: an Analysis and Survey
The article presents an analysis and survey regarding the validity of VaR risk measures in comparison to traditional risk measures. Individuals are assumed to either maximize their expected utility or possess a lexicographic utility function. The analysis is carried out for generally distributed functions and for the normal and lognormal
distributions. The main conclusion is that although VaR is an inadequate measure within the expected utility framework, it is at least as good as other traditional risk measures. Moreover, it can be improved by modified versions such as
the Accumulated-VaR (Mean-Shortfall) Assuming a lexicographic expected utility strengthens the argument for using AVaR as a legitimate risk measure especially in
the case of a regulated firm
VaR Risk Measures versus Traditional Risk Measures: an Analysis and Survey
The article presents an analysis and survey regarding the validity of VaR risk measures in comparison to traditional risk measures. Individuals are assumed to either maximize their expected utility or possess a lexicographic utility function. The analysis is carried out for generally distributed functions and for the normal and lognormal
distributions. The main conclusion is that although VaR is an inadequate measure within the expected utility framework, it is at least as good as other traditional risk measures. Moreover, it can be improved by modified versions such as
the Accumulated-VaR (Mean-Shortfall) Assuming a lexicographic expected utility strengthens the argument for using AVaR as a legitimate risk measure especially in
the case of a regulated firm
El Patrimonio arbóreo de Capilla del Señor, Provincia de Buenos Aires, Argentina
[ES] Capilla del Señor es una de las Ciudades principales del Partido de Exaltación
de la Cruz, ubicado en la Provincia de Buenos Aires, República Argentina,
a 83 Km de la Ciudad Autónoma de Buenos Aires. Fue creada en 1735
y actualmente posee una superficie de 5 km² y una población de 9.500 habitantes,
en su mayorÃa trabajadores rurales y una pequeña proporción urbana.
En 1994 el Poder Ejecutivo Nacional la declaró Bien de Interés Histórico
Nacional, por su Patrimonio arquitectónico, de tradiciones y leyendas, siendo
uno de los pueblos más antiguos de la Provincia de Buenos Aires.
Con la finalidad de contribuir a la preservación del Patrimonio histórico,
cultural, paisajÃstico, turÃstico, ambiental y social de Capilla, se propuso
efectuar el relevamiento del arbolado urbano, en principio del Casco histórico
que abarca alrededor de nueve manzanas, siendo la intención de continuar
con la totalidad de la Ciudad.
El objetivo es realizar un diagnóstico de la situación actual del arbolado urbano.
Para dicha tarea se utilizó como MetodologÃa, la resolución de una Planilla
censal, en la que se establecieron caracterÃsticas morfológicas, estructurales
y afectaciones sanitarias de cada árbol, situación del entorno y del sitio de
implantación, descripción de daños, entre otras.
El resultado aportará información sobre el estado general de cada una de
las especies, y con ello se podrán implementar las propuestas de trabajo e intervenciones
requeridas de manejo, logrando de este modo conservar los
beneficios ambientales y sociales del arbolado.
Como conclusión general, se pretende concientizar a la población y a los estamentos
gubernamentales, de la antigüedad del arbolado y su necesidad de
preservación, para la población actual y que sea sostenible en el tiempo, en
especial aquellas especies de amplia tradición en la Ciudad, como son los
Citrus aurantium (naranjo amargo).Kaplanski, M.; Vernier, J. (2014). El Patrimonio arbóreo de Capilla del Señor, Provincia de Buenos Aires, Argentina. En XVI CONGRESO NACIONAL DE ARBORICULTURA. Editorial Universitat Politècnica de València. 56-64. http://hdl.handle.net/10251/91336OCS566
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