Accelerated procedures for the solution of discrete Markov control problems Final report

Accelerated procedures for solution of discrete Markov control problem

Mathematical programming and the control of Markov chains

Linear and dynamic programming and Markov chain optimal contro

SDSS White Dwarf mass distribution at low effective temperatures

The DA white dwarfs in the Sloan Digital Sky Survey, as analyzed in the papers for Data Releases 1 and 4, show an increase in surface gravity towards lower effective temperatures below 11500 K. We study the various possible explanations of this effect, from a real increase of the masses to uncertainties or deficiencies of the atmospheric models. No definite answer is found but the tentative conclusion is that it is most likely the current description of convection in the framework of the mixing-length approximation, which leads to this effect.Comment: to appear in the proceedings of the 16th European Workshop on White Dwarfs, Barcelona, 200

Thermoregulation in a Cold Environment: Effects of Body Weight

The present experiment, then, was conducted to ascertain the role of body weight in the physiological and behavioral adjustment to cold. Specifically, it was hypothesized that animals which gained weight after periodic exposure to cold would show a decreased temperature loss as well as less lever-pressing behavior for infra-red heat reinforcement than animals which were maintained at their pre-experimental weight level

The development of voluntary cardiovascular control

Several lines of evidence have suggested that the normally involuntary status of the autonomic nervous system is due to a lack of discriminable afferent information to the central nervous system. This proposition has been implicitly supported by many behavioral studies all of which provided extrinsic feedback of cardiovascular performance in an attempt to produce learned cardiovascular control. In order to explicitly determine whether discrimination of afferent information from the heart facilitates subsequent learned heart rate control, therefore, the first experiment of this dissertation was performed. During the first phase of this experiment, human subjects were trained to discriminate their pulses, and during the second phase; these same subjects were required to increase and decrease their heart rates under conditions of augmented sensory feedback of heart rate, and under conditions when no extrinsic feedback was provided. The results of this experiment demonstrated that a significant improvement in heart rate control during the second phase developed as a function of previous pulse discrimination training. In addition, pulse discrimination training facilitated the development of learned heart rate control under conditions of augmented sensory feedback. These findings were taken to support the original hypothesis that training designed to facilitate discrimination of the internal afferent information associated with a visceral response would also facilitate the development-learned control over that response. The results of this experiment together with other reports indicating that vo1untary visceral control is more effective under conditions of extrinsic response contingent feedback of visceral responding suggested the possibility that voluntary control might be developed over other aspects of cardiovascular functioning following the implementation of procedures which utilized augmented sensory feedback of the relevant response process. The second experiment in this dissertation investigated the possibility of producing voluntary control over changes in systolic blood pressure. During two training sessions, two groups of subjects were instructed to increase or decrease their systolic blood pressure while receiving virtually continuous extrinsic information of blood pressure changes. Heart rate was continuously monitored in all subjects to determine the relationship between changes in this cardiac response and systolic blood pressure. The results of this study demonstrated that following the implementation of a simple operant procedure, reliable increases and decreases in systolic blood pressure may be obtained, Moreover, such changes developed according to an instructional requirement and not as a function of habituation to the experimental environment, or as a result of unconditioned stimulus effects. Although these blood pressure changes were produced in the absence of any systematic changes in heart rate, it was found that increases and decreases in blood pressure ware associated with greater heart rate differences during certain periods in the development of learned blood pressure control than during other periods. The implications of these findings were discussed with respect to the use of visceral response discrimination and operant training procedures in the therapeutic control of emotional and psychosomatic behavior patterns

New Pulsating DB White Dwarf Stars from the Sloan Digital Sky Survey

We are searching for new He atmosphere white dwarf pulsators (DBVs) based on the newly found white dwarf stars from the spectra obtained by the Sloan Digital Sky Survey. DBVs pulsate at hotter temperature ranges than their better known cousins, the H atmosphere white dwarf pulsators (DAVs or ZZ Ceti stars). Since the evolution of white dwarf stars is characterized by cooling, asteroseismological studies of DBVs give us opportunities to study white dwarf structure at a different evolutionary stage than the DAVs. The hottest DBVs are thought to have neutrino luminosities exceeding their photon luminosities (Winget et al. 2004), a quantity measurable through asteroseismology. Therefore, they can also be used to study neutrino physics in the stellar interior. So far we have discovered nine new DBVs, doubling the number of previously known DBVs. Here we report the new pulsators' lightcurves and power spectra.Comment: 15 pages, 2 figures, 3 tables, ApJ accepte

Development's 'downside': social and psychological pathology in countries undergoing social change

Emphasis on the decline in mortality related to infectious disease, the improvement in child survival and the extension in longevity creates an optimistic view of the effects on health of social change. In contrast, attention to behavioural and social problems apparently stemming from current global social transformations leads to a more negative assessment. Specific historical processes shape local worlds of experience so as to yield complex patterns of social change with multiple outcomes. Study should be directed at the specific mediating social and moral processes that yield negative mental-health outcomes in order to develop international mental-health policy to guide prevention, and to control the dangerously destructive effects of specific social transformations, planned as well as unplanned

Revisiting the theoretical DBV (V777 Her) instability strip: the MLT theory of convection

We reexamine the theoretical instability domain of pulsating DB white dwarfs (DBV or V777 Her variables). We performed an extensive $g$-mode nonadiabatic pulsation analysis of DB evolutionary models considering a wide range of stellar masses, for which the complete evolutionary stages of their progenitors from the ZAMS, through the thermally pulsing AGB and born-again phases, the domain of the PG1159 stars, the hot phase of DO white dwarfs, and then the DB white dwarf stage have been considered. We explicitly account for the evolution of the chemical abundance distribution due to time-dependent chemical diffusion processes. We examine the impact of the different prescriptions of the MLT theory of convection and the effects of small amounts of H in the almost He-pure atmospheres of DB stars on the precise location of the theoretical blue edge of the DBV instability strip.Comment: Proceedings, 16th European White Dwarf Workshop, Barcelona, 200

Intrinsic and Rashba Spin-orbit Interactions in Graphene Sheets

Starting from a microscopic tight-binding model and using second order perturbation theory, we derive explicit expressions for the intrinsic and Rashba spin-orbit interaction induced gaps in the Dirac-like low-energy band structure of an isolated graphene sheet. The Rashba interaction parameter is first order in the atomic carbon spin-orbit coupling strength $\xi$ and first order in the external electric field $E$ perpendicular to the graphene plane, whereas the intrinsic spin-orbit interaction which survives at E=0 is second order in $\xi$. The spin-orbit terms in the low-energy effective Hamiltonian have the form proposed recently by Kane and Mele. \textit{Ab initio} electronic structure calculations were performed as a partial check on the validity of the tight-binding model.Comment: 5 pages, 2 figures; typos corrected, references update