Massive black holes in stellar systems: 'quiescent' accretion and luminosity

Only a small fraction of local galaxies harbor an accreting black hole, classified as an active galactic nucleus (AGN). However, many stellar systems are plausibly expected to host black holes, from globular clusters to nuclear star clusters, to massive galaxies. The mere presence of stars in the vicinity of a black hole provides a source of fuel via mass loss of evolved stars. In this paper we assess the expected luminosities of black holes embedded in stellar systems of different sizes and properties, spanning a large range of masses. We model the distribution of stars and derive the amount of gas available to a central black hole through a geometrical model. We estimate the luminosity of the black holes under simple, but physically grounded, assumptions on the accretion flow. Finally we discuss the detectability of 'quiescent' black holes in the local Universe.Comment: ApJ in pres

The Relationship Between Self Concept and Children\u27s Figure Drawings

The present study investigated the relationship between self concept and children\u27s figure drawings. The principle variable under consideration in each child\u27s drawing were (a) size of drawing and (b) number of colors used. The Tennessee Self Concept Scale (Fitts, 1965) was administered to 80 students selected from the seventh grade at Logan Junior High School, Logan, Utah. The subjects were then instructed to draw a picture of themselves. No further instructions were given regarding specific details of the requested picture. Ten colored pencils along with a regular pencil were made available to each student. No instructions were given as to the type or number of pencils to be used in their figure drawing. After the subjects completed their respective drawings, the experimenter rated each picture in terms of (a) number of colors used for the drawing, and (b) the height or vertical size of the drawing measured in millimeters from top to bottom of the drawing. It was hypothesized that students who obtain high scores on a measure of self concept (positive self concept) will use a greater number of colors in drawing a picture of themselves than will students who score low (negative self concept) on the same self concept measure. Students with high score on the measure of self concept will also draw a picture of themselves which is larger in size (height) than will students with low scores on the self concept measure. In addition to the two major hypotheses, it was also hypothesized that: (1) the high self concept group will have more smiles on the faces of their drawings than the low self concept group; (2) the high self concept group will draw more full figures than the low self concept group; (3) the high self concept group will use more total space on the paper than the low self concept group; and (4) the high self concept group will draw their figures more in the top two-thirds of the page and the low concept group will draw their figures more in the bottom two-thirds of the page. All of the subjects were ranked from high to low scores obtained on the Tennessee Self Concept Scale and were then divided into a high self concept group (top 20 scores) and a low self concept group (bottom 20 scores). Scores for the total sample of 80 students ranged from 193 to 394. Thus, the high self concept group was comprised of students with scores from 314 to 394. The low self concept group scores ranged from 193 to 246. The figure drawings of high and low scorers on the Self Concept Scale were then compared to determine any apparent relationship between measured self concept and (a) number of colors used in the drawing and (b) overall size of the drawing. Analysis of the figure drawings indicated no significant differences, either in number of colors used, or in size of figure between high and low scorers on the Self Concept Scale. The mean number of colors used by high scorers was 3.5 millimeters. Thus, the basic hypotheses of the study were not substantiated by the results obtained. However, subjective inspection of the pictures in terms of the four sub-hypotheses did produce two significant findings in terms of projective-type ratings of the pictures and statistical analysis by the chi square method. In brief, these particular differences were that students who scored high in self concept drew more pictures with smiling faces and utilized the top two-thirds of the drawing paper, while students with low self concept drew pictures with sadder-looking faces and more toward the bottom two thirds of the paper. The data also showed a significantly higher number of boys than girls in the high self concept group

Myosin VI contributes to synaptic transmission and development at the Drosophila neuromuscular junction

Abstract Background Myosin VI, encoded by jaguar (jar) in Drosophila melanogaster, is a unique member of the myosin superfamily of actin-based motor proteins. Myosin VI is the only myosin known to move towards the minus or pointed ends of actin filaments. Although Myosin VI has been implicated in numerous cellular processes as both an anchor and a transporter, little is known about the role of Myosin VI in the nervous system. We previously recovered jar in a screen for genes that modify neuromuscular junction (NMJ) development and here we report on the genetic analysis of Myosin VI in synaptic development and function using loss of function jar alleles. Results Our experiments on Drosophila third instar larvae revealed decreased locomotor activity, a decrease in NMJ length, a reduction in synaptic bouton number, and altered synaptic vesicle localization in jar mutants. Furthermore, our studies of synaptic transmission revealed alterations in both basal synaptic transmission and short-term plasticity at the jar mutant neuromuscular synapse. Conclusions Altogether these findings indicate that Myosin VI is important for proper synaptic function and morphology. Myosin VI may be functioning as an anchor to tether vesicles to the bouton periphery and, thereby, participating in the regulation of synaptic vesicle mobilization during synaptic transmission

Theoretical treatments of fusion processes in collisions of weakly bound nuclei

We review the theoretical methods to evaluate fusion cross sections in collisions of weakly bound nuclei. We piont out that in such collisions the coupling to the breakup channel leads to the appearance of different fusion processes. The extentsion of the coupled-channel method to coupling with the continuum is the most successful treatment for these collisions. However, evaluating separate cross section for each fusion process remains a very hard task.Comment: 8 pages, 3 figures. Invited talk (LFC) at the IX International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, August 28- September 1, 2006. Nuclear Physics A, in pres

The 2013 Rim Fire: Implications for Predicting Extreme Fire Spread, Pyroconvection, and Smoke Emissions

Abstract The 2013 Rim Fire, which burned over 104,000 ha, was one of the most severe fire events in California's history, in terms of its rapid growth, intensity, overall size, and persistent smoke plume. At least two large pyrocumulonimbus (pyroCb) events were observed, allowing smoke particles to extend through the upper troposphere over a large portion of the Pacific Northwest. However, the most extreme fire spread was observed on days without pyroCb activity or significant regional convection. A diverse archive of ground, airborne, and satellite data collected during the Rim Fire provides a unique opportunity to examine the conditions required for both extreme spread events and pyroCb development. Results highlight the importance of upper-level and nocturnal meteorology, as well as the limitations of traditional fire weather indices. The Rim Fire dataset also allows for a detailed examination of conflicting hypotheses surrounding the primary source of moisture during pyroCb development. All pyroCbs were associated with conditions very similar to those that produce dry thunderstorms. The current suite of automated forecasting applications predict only general trends in fire behavior, and specifically do not predict 1) extreme fire spread events and 2) injection of smoke to high altitudes. While these two exceptions are related, analysis of the Rim Fire shows that they are not predicted by the same set of conditions and variables. The combination of numerical weather prediction data and satellite observations exhibits great potential for improving automated regional-scale forecasts of fire behavior and smoke emissions

Baryogenesis at Low Reheating Temperatures

We note that the maximum temperature during reheating can be much greater than the reheating temperature $T_r$ at which the Universe becomes radiation dominated. We show that the Standard Model anomalous $(B+L)$-violating processes can therefore be in thermal equilibrium for 1 GeV \simlt T_{r}\ll 100 GeV. Electroweak baryogenesis could work and the traditional upper bound on the Higgs mass coming from the requirement of the preservation of the baryon asymmetry may be relaxed. Alternatively, the baryon asymmetry may be reprocessed by sphaleron transitions either from a $(B-L)$ asymmetry generated by the Affleck-Dine mechanism or from a chiral asymmetry between $e_R$ and $e_L$ in a $B-L = 0$ Universe. Our findings are also relevant to the production of the baryon asymmetry in large extra dimension models.Comment: 4 pages, version to appear in PRL: references added, new titl

A Na\u3csup\u3e+\u3c/sup\u3e/K\u3csup\u3e+\u3c/sup\u3e ATPase Pump Regulates Chondrocyte Differentiation and Bone Length Variation in Mice

The genetic and developmental mechanisms involved in limb formation are relatively well documented, but how these mechanisms are modulated by changes in chondrocyte physiology to produce differences in limb bone length remains unclear. Here, we used high throughput RNA sequencing (RNAseq) to probe the developmental genetic basis of variation in limb bone length in Longshanks, a mouse model of experimental evolution. We find that increased tibia length in Longshanks is associated with altered expression of a few key endochondral ossification genes such as Npr3, Dlk1, Sox9, and Sfrp1, as well reduced expression of Fxyd2, a facultative subunit of the cell membrane-bound Na+/K+ ATPase pump (NKA). Next, using murine tibia and cell cultures, we show a dynamic role for NKA in chondrocyte differentiation and in bone length regulation. Specifically, we show that pharmacological inhibition of NKA disrupts chondrocyte differentiation, by upregulating expression of mesenchymal stem cell markers (Prrx1, Serpina3n), downregulation of chondrogenesis marker Sox9, and altered expression of extracellular matrix genes (e.g., collagens) associated with proliferative and hypertrophic chondrocytes. Together, Longshanks and in vitro data suggest a broader developmental and evolutionary role of NKA in regulating limb length diversity