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Search Results: 1 - 10 of 191429 matches for " D. Geisler "
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Standard Giant Branches in the Washington Photometric System
D. Geisler,A. Sarajedini
Physics , 1998, DOI: 10.1086/300668
Abstract: We have obtained CCD photometry in the Washington system C,T1 filters for some 850,000 objects associated with 10 Galactic globular clusters and 2 old open clusters. These clusters have well-known metal abundances, spanning a metallicity range of 2.5 dex from [Fe/H]~-2.25 to +0.25 at a spacing of ~0.2 dex. Analogous to the method employed by Da Costa and Armandroff (1990, AJ, 100, 162) for V,I photometry, we then proceed to construct standard giant branches for these clusters. The Washington system technique is found to have three times the metallicity sensitivity of the V,I technique. Thus, for a given photometric accuracy, metallicities can be determined three times more precisely with the Washington technique. We find a linear relationship between (C-T1)o (at M(T1)=-2) and metallicity (on the Zinn 1985, ApJ, 293, 424 scale) exists over the full metallicity range, with an rms of only 0.04 dex. We also derive methods to determine distance, reddening and metallicity simultaneously, and note that the Washington system holds great potential for deriving accurate ages as well.
Asymmetry in Resting Alpha Activity: Effects of Handedness  [PDF]
Ruth E. Propper, Jenna Pierce, Mark W. Geisler, Stephen D. Christman, Nathan Bellorado
Open Journal of Medical Psychology (OJMP) , 2012, DOI: 10.4236/ojmp.2012.14014
Abstract: Study Aim: Frontal electroencephalographic (EEG) alpha band power during rest shows increased right, and/or de-creased left, hemisphere activity under conditions of state or trait withdrawal-associated affect. Non-right-handers (NRH) are more likely to have mental illnesses and dispositions that involve such withdrawal-related affect. The aim of the study was to examine whether NRH might be characterized by increased right, relative to left, hemisphere activity during rest. Methods: The present research investigated that hypothesis by examining resting EEG alpha power in consistently-right-handed (CRH) and NRH individuals. Results: In support of the hypothesis, NRH demonstrated de-creased right hemisphere alpha power, and therefore increased right hemisphere activity, during rest, compared to CRH. Conclusions: The study demonstrates further support for an association between increased right hemisphere activity and negative affect via an association between such EEG activity and NRH.
Identification of children who may benefit from self-hypnosis at a pediatric pulmonary center
Ran D Anbar, Susan C Geisler
BMC Pediatrics , 2005, DOI: 10.1186/1471-2431-5-6
Abstract: A retrospective chart review was conducted for all newly referred patients to the SUNY Upstate Medical University Pediatric Pulmonary Center during an 18 month period beginning January 1, 2000. Patients were offered hypnosis if they presented with symptoms or signs suggestive of psychological difficulties. Hypnosis was taught in one or two 15–45 minute sessions by a pediatric pulmonologist.Of 725 new referrals, 424 were 0–5 years old, 193 were 6–11 years old, and 108 were 12–18 years old. Diagnoses of anxiety, habit cough, or vocal cord dysfunction accounted for 1% of the 0–5 year olds, 20% of the 6–11 year olds, and 31% of the 12–18 year olds. Hypnotherapy was offered to 1% of 0–5 year olds, 36% of 6–11 year olds, and 55% of 12–18 year olds. Of 81 patients who received instruction in self-hypnosis for anxiety, cough, chest pain, dyspnea, or inspiratory difficulties, 75% returned for follow-up, and among the returning patients 95% reported improvement or resolution of their symptoms.A large number of patients referred to a Pediatric Pulmonary Center appeared to benefit from instruction in self-hypnosis, which can be taught easily as a psychological intervention.Emotional difficulties can trigger respiratory symptoms such as dyspnea [1]. Further, psychological issues can arise as a result of patients' reactions to pulmonary disease, e.g., depression with end-stage cystic fibrosis [2]. In some patients, a vicious cycle ensues as pulmonary disease leads to psychological difficulties, which in turn trigger further symptoms that can be misinterpreted as arising from the pulmonary disease [3]. Thus, a patient with severe asthma can develop anxiety as a result of the life-threatening nature of the disease. Such stress can cause dyspnea, which might be treated inappropriately with therapy for asthma rather than anxiety [4]. In a study by Ortega et al. [5], 49% of children with asthma from cohorts in New Haven, Atlanta, NewYork, and Puerto Rico were identified through the Di
The Origin and Chemical Evolution of the Exotic Globular Cluster NGC3201
C. Mu?oz,D. Geisler,S. Villanova
Physics , 2013, DOI: 10.1093/mnras/stt868
Abstract: NGC3201 is a globular cluster (GC) which shows very peculiar kinematic characteristics including an extreme radial velocity and a highly retrograde orbit, strongly suggesting an extraGalactic origin. Our aims are to study NGC3201 in the context of multiple populations (MPs), hoping to constrain possible candidates for the self-enrichment by studying the chemical abundance pattern, as well as adding insight into the origin of this intriguing cluster. We present a detailed chemical abundance analysis of eight red giant branch (RGB) stars using high resolution spectroscopy. We measured 29 elements and found [Fe/H]=-1.53+/-0.01, we cannot rule out a metallicity spread of ~0.12 dex, and an alpha-enhancement typical of halo GCs. However significant spreads are observed in the abundances of all light elements except for Mg. We confirm the presence of an extended Na-O anticorrelation. n-capture elements generally are dominated by the r-process, in good agreement with the bulk of Galactic GCs. The total (C+N+O) abundance is slightly supersolar and requires a small downward correction to the isochrone age, yielding 11.4 Gyr. Kinematically, NGC3201 appears likely to have had an extraGalactic origin but its chemical evolution is similar to most other, presumably native, Galactic GCs.
Photometric study of Galactic star clusters in the VVV survey
F. Mauro,C. Moni Bidin,D. Geisler
Physics , 2012,
Abstract: We show the preliminary analysis of some Galactic stellar clusters (GSCls) candidates and the results of the analysis of two new interesting GSCls found in the "VISTA Variables in the Via Lactea" (VVV) Survey. The VVV photometric data are being used also to improve the knowledge of the Galactic structure. The photometric data are obtained with the new automatic photometric pipeline VVV-SkZ_pipeline.
Uncovering Multiple Populations with Washington Photometry: I. The Globular Cluster NGC 1851
Jeffrey D. Cummings,D. Geisler,S. Villanova,G. Carraro
Physics , 2014, DOI: 10.1088/0004-6256/148/2/27
Abstract: The analysis of multiple populations (MPs) in globular clusters (GCs) has become a forefront area of research in astronomy. Multiple red giant branches (RGBs), subgiant branches (SGBs), and even main sequences (MSs) have now been observed photometrically in many GCs. UV photometry has been crucial in discovering and analyzing these MPs, but the Johnson U and the Stromgren and Sloan u filters that have generally been used are relatively inefficient and very sensitive to reddening and atmospheric extinction. In contrast, the Washington C filter is much broader and redder than these competing UV filters. Here we investigate the use of the Washington system to uncover MPs using only a 1-meter telescope. Our analysis of the well-studied GC NGC 1851 finds that the C filter is both very efficient and effective at detecting its previously discovered MPs in the RGB and SGB. Remarkably, we have also detected an intrinsically broad MS best characterized by two distinct but heavily overlapping populations that cannot be explained by binaries, field stars, or photometric errors. The MS distribution is in very good agreement with that seen on the RGB, with ~30% of the stars belonging to the second population. There is also evidence for two sequences in the red horizontal branch, but this appears to be unrelated to the MPs in this cluster. Neither of these latter phenomena have been observed previously in this cluster. The redder MS stars are also more centrally concentrated than the blue MS. This is the first time MPs in a MS have been discovered from the ground, and using only a 1-meter telescope. The Washington system thus proves to be a very powerful tool for investigating MPs, and holds particular promise for extragalactic objects where photons are limited.
Estimates of Electronic Medical Records in U.S. Emergency Departments
Benjamin P. Geisler,Jeremiah D. Schuur,Daniel J. Pallin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009274
Abstract: Policymakers advocate universal electronic medical records (EMRs) and propose incentives for “meaningful use” of EMRs. Though emergency departments (EDs) are particularly sensitive to the benefits and unintended consequences of EMR adoption, surveillance has been limited. We analyze data from a nationally representative sample of US EDs to ascertain the adoption of various EMR functionalities.
The star formation history of M33′s outer regions
M. K. Barker,A. Sarajedini,D. Geisler,P. Harding
Revista mexicana de astronomía y astrofísica , 2007,
Abstract: The stellar populations of a galaxy are a fossil record of its formation and evolution and the various physical processes involved.
The Richness of the Globular Cluster System of NGC 3923: Clues to Elliptical Galaxy Formation
S. E. Zepf,D. Geisler,K. M. Ashman
Physics , 1994, DOI: 10.1086/187608
Abstract: We present new data on the globular cluster system of the elliptical galaxy NGC 3923 which show that it has the most globular clusters per unit luminosity of any non-cluster elliptical yet observed, with $S_N=6.4 \pm1.4$. NGC 3923 is also among the brightest ellipticals outside of a galaxy cluster for which the number of globular clusters has been determined. Our observation of a large number of clusters per unit luminosity (high $S_N$ value) for a bright elliptical in a sparse environment is consistent with the suggestion of Djorgovski \& Santiago that the number of globular clusters is a power law function of the luminosity with an exponent greater than one. We relate this higher specific frequency of globular clusters in more luminous galaxies to other observations which indicate that the physical conditions within elliptical galaxies at the time of their formation were dependent on galaxy mass.
Photometric Metallicities in Bootes I
J. Hughes,G. Wallerstein,A. Dotter,D. Geisler
Physics , 2014, DOI: 10.1093/mnras/stt2500
Abstract: We present new Stromgren and Washington data sets for the Bootes I dwarf galaxy, and combine them with the available SDSS photometry. The goal of this project is to refine a ground-based, practical, accurate method to determine age and metallicity for individual stars in Bootes I that can be selected in an unbiased imaging survey, without having to take spectra. We produce photometric metallicities from Stromgren and Washington photometry, for stellar systems with a range of $-1.0>[Fe/H]>-3.5$. To avoid the decrease in sensitivity of the Stromgren metallicity index on the lower red-giant branch, we replace the Stromgren v-filter with the broader Washington C-filter; we find that $CT_1by$ is the most successful filter combination, for individual stars with $[Fe/H]<-2.0$, to maintain ~0.2 dex $[Fe/H]$-resolution over the whole red-giant branch. We demonstrate that we can break the isochrones' age-metallicity degeneracy with these filters, using stars with log g=2.5-3.0, which have less than a 2% change in their $(C-T_1)$-colour due to age, over a range of 11-14 Gyr.
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