Implementation of mean-timing and subsequent logic functions on an FPGA

This article describes the implementation of a mean-timer and coincidence logic on a Virtex-5 FPGA for trigger purposes in a particle physics experiment. The novel feature is that the mean-timing and the coincidence logic are not synchronized with a clock which allows for a higher resolution of approximately 400 ps, not limited by a clock frequency.Comment: 15 pages, 11 figure

Making a Difference in Schools: The Big Brothers Big Sisters School-Based Mentoring Impact Study

School-based mentoring is one of the fastest growing forms of mentoring in the US today; yet, few studies have rigorously examined its impacts. This landmark random assignment impact study of Big Brothers Big Sisters School-Based Mentoring is the first national study of this program model. It involves 10 agencies, 71 schools and 1,139 9- to 16-year-old youth randomly assigned to either a treatment group of program participants or a control group of their non-mentored peers. Surveys were administered to all participating youth, their teachers and mentors in the fall of 2004, spring of 2005 and late fall of 2005.The report describes the programs and their participants and answers several key questions, including: Does school-based mentoring work? What kinds of mentoring experiences help to ensure benefits? How much do these programs cost? Our findings highlight both the strengths of this program model and its current limitations and suggest several recommendations for refining this promising model-recommendations that Big Brothers Big Sisters agencies across the country are already working to implement

Making a Difference in Schools: The Big Brothers Big Sisters School-Based Mentoring Impact Study Executive Summary

Serving almost 870,000 youth nationwide, school-based mentoring is one of the fastest growing forms of mentoring in the US today. Making a Difference in Schools presents findings from a landmark random assignment impact study of Big Brothers Big Sisters School-Based Mentoring -- the first national study of this program model. This executive summary highlights nine key findings from the full report and outlines several recommendations for policy and practice

Deriving bases for Abelian functions

We present a new method to explicitly define Abelian functions associated with algebraic curves, for the purpose of finding bases for the relevant vector spaces of such functions. We demonstrate the procedure with the functions associated with a trigonal curve of genus four. The main motivation for the construction of such bases is that it allows systematic methods for the derivation of the addition formulae and differential equations satisfied by the functions. We present a new 3-term 2-variable addition formulae and a complete set of differential equations to generalise the classic Weierstrass identities for the case of the trigonal curve of genus four.Comment: 35page

Bringing closure to microlensing mass measurement

Interferometers offer multiple methods for studying microlensing events and determining the properties of the lenses. We investigate the study of microlensing events with optical interferometers, focusing on narrow-angle astrometry, visibility, and closure phase. After introducing the basics of microlensing and interferometry, we derive expressions for the signals in each of these three channels. For various forecasts of the instrumental performance, we discuss which method provides the best means of measuring the lens angular Einstein radius theta_E, a prerequisite for determining the lens mass. If the upcoming generation of large-aperture, AO-corrected long baseline interferometers (e.g. VLTI, Keck, OHANA) perform as well as expected, theta_E may be determined with signal-to-noise greater than 10 for all bright events. We estimate that roughly a dozen events per year will be sufficiciently bright and have long enough durations to allow the measurement of the lens mass and distance from the ground. We also consider the prospects for a VLTI survey of all bright lensing events using a Fisher matrix analysis, and find that even without individual masses, interesting constraints may be placed on the bulge mass function, although large numbers of events would be required.Comment: 23 pages, aastex, submitted to Ap

Impacts of the Mount Pinatubo eruption on ENSO in the GEOS seasonal-to-subseasonal forecasting system

The eruption of Mount Pinatubo in June 1991 introduced a perturbation of the Earth's global energy budget by increasing the stratospheric aerosol loading by an order of magnitude, with effects on the global climate. In this presentation we analyze the effects of the Mt. Pinatubo eruption on the seasonal forecast performed with Goddard Earth Observing System Seasonal-to Subseasonal (GEOS-S2S) system, an Earth System Model that includes an interactive ocean and a bulk aerosol model coupled to radiation. We performed 10-member ensembles for the year after the eruption (June 1991-May 1992) at ~0.5 horizontal resolution, with and without the inclusion of the Mt. Pinatubo eruption. In GEOS-S2S, the eruption leads to ta strengthening of El Nino peaking in January 1992. The strengthening is mainly due to the weakening of the trade winds, which is caused by a attening of the temperature gradient across the Pacic due to a differential response to the volcanic forcing between the central and eastern Pacic (ocean-dynamical thermostat). This response largely depends on the assumed size for the volcanic aerosols. Indeed, we performed simulations assuming a volcanic aerosol effective radius of 0.35 m (similar to tropospheric aerosol, and the default in GEOS) and 0.6 m (closer to observations of volcanic aerosol from Pinatubo-sized eruptions). We nd that in the latter case the tropical radiative forcing is lower, since smaller aerosols scatter shortwave radiation more eciently than larger ones. Accordingly, the impact on ENSO is not statistically signicant when a larger and more realistic particle radius is assumed

The Origin of Fe II Emission in AGN

We used a very large set of models of broad emission line (BEL) clouds in AGN to investigate the formation of the observed Fe II emission lines. We show that photoionized BEL clouds cannot produce both the observed shape and observed equivalent width of the 2200-2800A Fe II UV bump unless there is considerable velocity structure corresponding to a microturbulent velocity parameter v_turb > 100 km/s for the LOC models used here. This could be either microturbulence in gas that is confined by some phenomenon such as MHD waves, or a velocity shear such as in the various models of winds flowing off the surfaces of accretion disks. The alternative way that we can find to simultaneously match both the observed shape and equivalent width of the Fe II UV bump is for the Fe II emission to be the result of collisional excitation in a warm, dense gas. Such gas would emit very few lines other than Fe II. However, since the collisionally excited gas would constitute yet another component in an already complicated picture of the BELR, we prefer the model involving turbulence. In either model, the strength of Fe II emission relative to the emission lines of other ions such as Mg II depends as much on other parameters (either v_turb or the surface area of the collisionally excited gas) as it does on the iron abundance. Therefore, the measurement of the iron abundance from the FeII emission in quasars becomes a more difficult problem.Comment: 23 pages. Accepted by Ap

The Lopsidedness of Present-Day Galaxies: Results from the Sloan Digital Sky Survey

Large-scale asymmetries in the stellar mass distribution in galaxies are believed to trace non-equilibrium situations in the luminous and/or dark matter component. These may arise in the aftermath of events like mergers, accretion, and tidal interactions. These events are key in the evolution of galaxies. In this paper we quantify the large-scale lopsidedness of light distributions in 25155 galaxies at z < 0.06 from the Sloan Digital Sky Survey Data Release 4 using the m = 1 azimuthal Fourier mode. We show that the lopsided distribution of light is primarily due to a corresponding lopsidedness in the stellar mass distribution. Observational effects, such as seeing, Poisson noise, and inclination, introduce only small errors in lopsidedness for the majority of this sample. We find that lopsidedness correlates strongly with other basic galaxy structural parameters: galaxies with low concentration, stellar mass, and stellar surface mass density tend to be lopsided, while galaxies with high concentration, mass, and density are not. We find that the strongest and most fundamental relationship between lopsidedness and the other structural parameters is with the surface mass density. We also find, in agreement with previous studies, that lopsidedness tends to increase with radius. Both these results may be understood as a consequence of several factors. The outer regions of galaxies and low-density galaxies are more susceptible to tidal perturbations, and they also have longer dynamical times (so lopsidedness will last longer). They are also more likely to be affected by any underlying asymmetries in the dark matter halo.Comment: 42 pages, 13 figures, 3 tables, accepted to Ap

Quality of life and persisting symptoms in intensive care unit survivors: implications for care after discharge

<p>Abstract</p> <p>Background</p> <p>We assessed the quality of life of ICU survivors using SF-36 at 4 months after ICU discharge and investigated any correlation of PCS and MCS with age, illness severity and hospital or ICU length of stay. We examined the relationship between these variables, persisting physical and psychological symptoms and the perceived benefit of individual patients of follow-up.</p> <p>Findings</p> <p>For one year, adult patients admitted for multiple organ or advanced respiratory support for greater than 48 hours to a 16-bedded teaching hospital general intensive care unit were identified. Those surviving to discharge were sent a questionnaire at 4 months following ICU discharge assessing quality of life and persisting symptoms. Demographic, length of stay and illness severity data were recorded. Higher or lower scores were divided at the median value. A two-tailed Students t-test assuming equal variances was used for normally-distributed data and Mann-Whitney tests for non-parametric data.</p> <p>87 of 175 questionnaires were returned (50%), but only 65 had sufficient data giving a final response rate of 37%. Elderly patients had increased MCS as compared with younger patients. The PCS was inversely related to hospital LOS. There was a significant correlation between the presence of psychological and physical symptoms and desire for follow-up.</p> <p>Conclusion</p> <p>Younger age and prolonged hospital stay are associated with lower mental or physical quality of life and may be targets for rehabilitation. Patients with persisting symptoms at 4 months view follow-up as beneficial and a simple screening questionnaire may identify those likely to attend outpatient services.</p