From Random Matrices to Stochastic Operators

We propose that classical random matrix models are properly viewed as finite difference schemes for stochastic differential operators. Three particular stochastic operators commonly arise, each associated with a familiar class of local eigenvalue behavior. The stochastic Airy operator displays soft edge behavior, associated with the Airy kernel. The stochastic Bessel operator displays hard edge behavior, associated with the Bessel kernel. The article concludes with suggestions for a stochastic sine operator, which would display bulk behavior, associated with the sine kernel.Comment: 41 pages, 5 figures. Submitted to Journal of Statistical Physics. Changes in this revision: recomputed Monte Carlo simulations, added reference [19], fit into margins, performed minor editin

Gamow-Teller Strength in the Region of 100^{100}Sn

New calculations are presented for Gamow-Teller beta decay of nuclei near $^{100}$Sn. Essentially all of the $^{100}$Sn Gamow-Teller decay strength is predicted to go to a single state at an excitation energy of 1.8 MeV in $^{100}$In. The first calculations are presented for the decays of neighboring odd-even and odd-odd nuclei which show, in contrast to $^{100}$Sn, surprisingly complex and broad Gamow-Teller strength distributions. The results are compared to existing experimental data and the resulting hindrance factors are discussed.Comment: 12 pages (latex) and 2 figures available on reques

Formation and structure of the three Neptune-mass planets system around HD69830

Since the discovery of the first giant planet outside the solar system in 1995 (Mayor & Queloz 1995), more than 180 extrasolar planets have been discovered. With improving detection capabilities, a new class of planets with masses 5-20 times larger than the Earth, at close distance from their parent star is rapidly emerging. Recently, the first system of three Neptune-mass planets has been discovered around the solar type star HD69830 (Lovis et al. 2006). Here, we present and discuss a possible formation scenario for this planetary system based on a consistent coupling between the extended core accretion model and evolutionary models (Alibert et al. 2005a, Baraffe et al. 2004,2006). We show that the innermost planet formed from an embryo having started inside the iceline is composed essentially of a rocky core surrounded by a tiny gaseous envelope. The two outermost planets started their formation beyond the iceline and, as a consequence, accrete a substantial amount of water ice during their formation. We calculate the present day thermodynamical conditions inside these two latter planets and show that they are made of a rocky core surrounded by a shell of fluid water and a gaseous envelope.Comment: Accepted in AA Letter

A common neural system mediating two different forms of social judgement

Background: A wide range of neuropsychiatric conditions, including schizophrenia and autistic spectrum disorder (ASD), are associated with impairments in social function. Previous studies have shown that individuals with schizophrenia and ASD have deficits in making a wide range of social judgements from faces, including decisions related to threat (such as judgements of approachability) and decisions not related to physical threat (such as judgements of intelligence). We have investigated healthy control participants to see whether there is a common neural system activated during such social decisions, on the basis that deficits in this system may contribute to the impairments seen in these disorders. Method: We investigated the neural basis of social decision making during judgements of approachability and intelligence from faces in 24 healthy participants using functional magnetic resonance imaging (fMRI). We used conjunction analysis to identify common brain regions activated during both tasks. Results: Activation of the amygdala, medial prefrontal cortex, inferior prefrontal cortex and cerebellum was seen during performance of both social tasks, compared to simple gender judgements from the same stimuli. Task-specific activations were present in the dorsolateral prefrontal cortex in the intelligence task and in the inferior and middle temporal cortex in the approachability task. Conclusions: The present study identified a common network of brain regions activated during the performance of two different forms of social judgement from faces. Dysfunction of this network is likely to contribute to the broad-ranging deficits in social function seen in psychiatric disorders such as schizophrenia and ASD

Effect of C∕Si ratio on deep levels in epitaxial 4H–SiC

Changing the ratio of carbon to silicon during the epitaxial 4H–SiC growth is expected to alter the dominant deep level trap, which has been attributed to a native defect. The C∕Si ratio was changed from one to six during epitaxialgrowth of SiC. Diodes fabricated on the epitaxial layer were then characterized using current-voltage and deep level transient spectroscopy. The single peak at 340K (Z1/Z2 peak), was deconvolved into two traps, closely spaced in energy. The concentration of one of the Z1/Z2 traps decreased with increasing C∕Si ratio. This result opposes theoretical predictions of carboninterstitial components, and supports assignment to a silicon antisite or carbonvacancy relationship. The concentration of the second component of the peak at 340K did not depend on the C∕Si ratio, which would indicate an impurity in an interstitial site

The Feedback-Regulated Growth of Black Holes and Bulges through Gas Accretion and Starbursts in Cluster Central Dominant Galaxies

We present an analysis of the growth of black holes through accretion and bulges through star formation in 33 galaxies at the centers of cooling flows. Most of these systems show evidence of cavities in the intracluster medium (ICM) inflated by radio jets emanating from their active galactic nuclei (AGN). We present a new and extensive analysis of X-ray cavities in these systems. We find that AGN are energetically able to balance radiative losses (cooling) from the ICM in more than half of our sample. Using a subsample of 17 systems, we examine the relationship between cooling and star formation. We find that the star formation rates are approaching or are comparable to X-ray and far UV limits on the rates of gas condensation onto the central galaxy. The remaining radiative losses could be offset by AGN feedback. The vast gulf between radiative losses and the sink of cooling material, which has been the primary objection to cooling flows, has narrowed and, in some cases, is no longer a serious issue. Using the cavity (jet) powers, we place strong lower limits on the rate of growth of supermassive black holes in central galaxies, and we find that they are growing at an average rate of ~ 0.1 solar masses per year, with some systems growing as quickly as ~ 1 solar mass per year. We find a trend between bulge growth (star formation) and black hole growth that is approximately in accordance with the slope of the local (Magorrian) relation between black hole and bulge mass. However, the large scatter in the trend suggests that bulges and black holes do not always grow in lock step. (Abridged)Comment: 17 pages, 6 figures, accepted to ApJ. Minor changes to text and figure

Early respiratory viral infections in infants with cystic fibrosis

This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Background Viral infections contribute to morbidity in cystic fibrosis (CF), but the impact of respiratory viruses on the development of airway disease is poorly understood. Methods Infants with CF identified by newborn screening were enrolled prior to 4 months of age to participate in a prospective observational study at 4 centers. Clinical data were collected at clinic visits and weekly phone calls. Multiplex PCR assays were performed on nasopharyngeal swabs to detect respiratory viruses during routine visits and when symptomatic. Participants underwent bronchoscopy with bronchoalveolar lavage (BAL) and a subset underwent pulmonary function testing. We present findings through 8.5 months of life. Results Seventy infants were enrolled, mean age 3.1 ± 0.8 months. Rhinovirus was the most prevalent virus (66%), followed by parainfluenza (19%), and coronavirus (16%). Participants had a median of 1.5 viral positive swabs (range 0–10). Past viral infection was associated with elevated neutrophil concentrations and bacterial isolates in BAL fluid, including recovery of classic CF bacterial pathogens. When antibiotics were prescribed for respiratory-related indications, viruses were identified in 52% of those instances. Conclusions Early viral infections were associated with greater neutrophilic inflammation and bacterial pathogens. Early viral infections appear to contribute to initiation of lower airway inflammation in infants with CF. Antibiotics were commonly prescribed in the setting of a viral infection. Future investigations examining longitudinal relationships between viral infections, airway microbiome, and antibiotic use will allow us to elucidate the interplay between these factors in young children with CF

The Extended Blue Continuum and Line Emission around the Central Radio Galaxy in Abell 2597

We present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling flow cluster Abell 2597, using data obtained with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). This object is one of the archetypal "blue-lobed" cooling flow radio elliptical galaxies, also displaying a luminous emission-line nebula, a compact radio source, and a significant dust lane and evidence of molecular gas in its center. We show that the radio source is surrounded by a complex network of emission-line filaments, some of which display a close spatial association with the outer boundary of the radio lobes. We present a detailed analysis of the physical properties of ionized and neutral gas associated with the radio lobes, and show that their properties are strongly suggestive of direct interactions between the radio plasma and ambient gas. We resolve the blue continuum emission into a series of knots and clumps, and present evidence that these are most likely due to regions of recent star formation. We investigate several possible triggering mechanisms for the star formation, including direct interactions with the radio source, filaments condensing from the cooling flow, or the result of an interaction with a gas-rich galaxy, which may also have been responsible for fueling the active nucleus. We propose that the properties of the source are plausibly explained in terms of accretion of gas by the cD during an interaction with a gas-rich galaxy, which combined with the fact that this object is located at the center of a dense, high-pressure ICM can account for the high rates of star formation and the strong confinement of the radio source.Comment: Astrophysical Journal, in press, 34 pages, includes 6 PostScript figures. Latex format, uses aaspp4.sty and epsf.sty file