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Search Results: 1 - 10 of 415651 matches for " J. E. Larkin "
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Faint Field Galaxies Around Bright Stars - A New Strategy for Imaging at the Diffraction Limit
J. E. Larkin,T. M. Glassman
Physics , 1999, DOI: 10.1086/316448
Abstract: This paper presents a new strategy for observing faint galaxies with high order natural guide star systems. We have imaged 5 high galactic latitude fields within the isoplanatic patch of bright stars (8.5 < R < 10.3 mag). The fields provide a rich set of faint field galaxies that are observable with a natural guide star adaptive optics system on a large telescope. Due to the small fields of many AO science cameras, these preliminary images are necessary to identify candidate galaxies. We present the photometry and positions for 78 objects (at least 40 galaxies) near five bright stars, appropriate for diffraction limited studies with the Keck and other AO systems on large ground-based telescopes. The K band seeing conditions in each field were excellent (0.4" - 0.7") allowing us to identify stars and estimate galaxy sizes. We also simulate AO images of field galaxies to determine the feasibility of infrared morphological studies at the diffraction limit. With new high order AO systems coming on line with 8-10 meter class telescopes, we believe these observations are invaluable in beginning to study faint galaxy populations at the diffraction limit.
Image Slicing with Infrared Fibers
J. E. Larkin,A. Quirrenbach,J. R. Graham
Physics , 1999,
Abstract: We are proposing to build a new integral field instrument (OSIRIS) for use with the Keck Adaptive Optics System. It will utilize a large (1024 element) fiber optic bundle to slice the field and feed a standard infrared spectrograph with a spectral resolution of 5000. To improve the fill factor of the fiber bundle, we plan on coupling it to a matched lenslet array. The spectrograph will have three plate scales of 0.05'', 0.10'' and 0.20'' per pixel, and full broad band spectra will fit on a single 2048x2048 infrared array. Other innovations include using some of the fibers for pseudo-slits and sky measurements and non-uniform spacing for the "linear" feed to the spectrograph.
Fournier's Gangrene - Findings on Computed Tomography
I. M. Cullen,J. O. Larkin,M. Moore,E. Fitzgerald
The Scientific World Journal , 2007, DOI: 10.1100/tsw.2007.250
Morphological Evolution of Distant Galaxies from Adaptive Optics Imaging
T. M. Glassman,J. E. Larkin,D. Lafrenière
Physics , 2002, DOI: 10.1086/344294
Abstract: We report here on a sample of resolved, infrared images of galaxies at z~0.5 taken with the 10-m Keck Telescope's Adaptive Optics (AO) system. We regularly achieve a spatial resolution of 0.05'' and are thus able to resolve both the disk and bulge components. We have extracted morphological information for ten galaxies and compared their properties to those of a local sample. The selection effects of both samples were explicitly taken into account in order to derive the unbiased result that disks at z~0.5 are ~0.6 mag arcsec^-2 brighter than, and about the same size as, local disks. The no-luminosity-evolution case is ruled out at 90% confidence. We also find, in a more qualitative analysis, that the bulges of these galaxies have undergone a smaller amount of surface brightness evolution and have also not changed significantly in size from z~0.5 to today. This is the first time this type of morphological evolution has been measured in the infrared and it points to the unique power of AO in exploring galaxy evolution.
Adaptive Optics Near-Infrared Spectroscopy of the Sgr A* Cluster
S. Gezari,A. M. Ghez,E. E. Becklin,J. Larkin,I. S. McLean,M. Morris
Physics , 2002, DOI: 10.1086/341807
Abstract: We present K-band $\lambda/\Delta\lambda$ ~ 2600 spectroscopy of five stars (K ~ 14 - 16 mag) within 0.''5 of Sgr A*, the radio source associated with the compact massive object suspected to be a 2.6 x 10$^{6}$ \msun black hole at the center of our Galaxy. High spatial resolution of ~ 0.''09, and good strehl ratios of ~ 0.2 achieved with adaptive optics on the 10-meter Keck telescope make it possible to measure moderate-resolution spectra of these stars individually for the first time. Two stars (S0-17 and S0-18) are identified as late-type stars by the detection of CO bandhead absorption in their spectra. Their absolute K magnitudes and CO bandhead absorption strengths are consistent with early K giants. Three stars (S0-1, S0-2, and S0-16), with r$_{proj}$ $<$ 0.0075 pc (~ 0.''2) from Sgr A*, lack CO bandhead absorption, confirming the results of earlier lower spectral and lower spatial resolution observations that the majority of the stars in the Sgr A* Cluster are early-type stars. The absolute K magnitudes of the early-type stars suggest that they are late O - early B main sequence stars of ages $<$ 20 Myr. The presence of young stars in the Sgr A* Cluster, so close to the central supermassive black hole, poses the intriguing problem of how these stars could have formed, or could have been brought, within its strong tidal field.
Changes in glycemic control from 1996 to 2006 among adults with type 2 diabetes: a longitudinal cohort study
Karen J Blumenthal, Mary E Larkin, Gail Winning, David M Nathan, Richard W Grant
BMC Health Services Research , 2010, DOI: 10.1186/1472-6963-10-158
Abstract: We identified all adults within our hospital network with T2DM who had HbA1c's measured in both 1996 and 2006 (longitudinal cohort). For patients with no data in 2006, we used hospital and social security records to distinguish patients lost to follow-up from those who died after 1996. We compared characteristics of the 3 baseline cohorts (longitudinal, lost to f/u, died) and examined metabolic trends in the longitudinal cohort.Of the 4944 patients with HbA1c measured in 1996, 1772 (36%) had an HbA1c measured in 2006, 1296 (26%) were lost to follow-up, and 1876 (38%) had died by 2006. In the longitudinal cohort, mean HbA1c decreased by 0.4 ± 1.8% over the ten-year span (from 8.2% ± 1.7% to 7.8% ± 1.4%) and mean total cholesterol decreased by 49.3 (± 46.5) mg/dL. In a multivariate model, independent predictors of HbA1c decline included older age (OR 1.41 per decade, 95% CI: 1.3-1.6, p < 0.001), baseline HbA1c (OR 2.9 per 1% increment, 2.6 - 3.2, p < 0.001), and speaking English (OR 2.1, 1.4-3.1, p < 0.001).Despite having had diabetes for an additional 10 years, patients in our longitudinal cohort had better glycemic and cholesterol control in 2006 than 1996. Greatest improvements occurred in patients with the highest levels in the baseline year.As the incidence of diabetes continues to increase in the United States, it has become increasingly important to understand trends in progression of the disease over time [1]. Type 2 diabetes (T2D) is seen as an inexorably progressive disease, with beta cell failure and increasing peripheral insulin resistance leading to worsening glycemic control, microvascular complications such as retinopathy and peripheral neuropathy, and significant macrovascular morbidity [2-4]. Medical therapy, when applied effectively, can prevent or delay the development of long-term complications, mediated largely through improved control of blood pressure, glycemia, and lipids [3,5,6].Several cross-sectional US national surveys have provided importa
Empowerment Theory in Action: The Wisdom of Collaborative Governance
Mary E. Larkin,Chelby L. Cierpial,Joan M. Stack,Victoria J. Morrison
Online Journal of Issues in Nursing , 2008,
Abstract: The purpose of this article is to demonstrate how active participation on a Collaborative Governance committee can promote empowerment, along with enthusiasm and confidence, while implementing the committee’s mission. This article will begin by delineating the concepts of empowerment theory and describing our institution’s Collaborative Governance structure and the structure of the Nursing Research Committee. Then the mechanisms that have fostered empowerment among committee members will be discussed, and evidence of empowerment among committee members will be presented. This article is offered to encourage more nurses to seek the rewards inherent in committee participation, and to demonstrate the link between committee work, empowerment, and professional development experienced by members of the Nursing Research Committee at our institution.
A Near Infrared Spectroscopic Survey of LINER Galaxies
J. E. Larkin,L. Armus,R. A. Knop,B. T. Soifer,K. Matthews
Physics , 1997, DOI: 10.1086/313063
Abstract: This paper reports the results of a near infrared spectroscopic survey of LINER galaxies undertaken with a new infrared spectrograph at the 5 m Hale telescope. The galaxy sample includes 11 LINERs with spectra covering the [FeII] (1.2567 microns), PaBeta (1.2818 microns), H2 (1-0 S(1), 2.1218 microns) and BrGamma (2.1655 microns) near infrared emission lines, and one additional galaxy with only [FeII] and Pa$\beta$ line coverage. All of the LINERs with infrared line detections have strong [FeII] and/or H2 emission, with about half (4 out of 9) having extremely high ratios (>2) of [FeII] to PaBeta. The strength of the H2 and [FeII] lines is well correlated with the optical [OI] line, with many LINERs having higher ratios of [FeII]/PaBeta, H2/BrGamma and [OI]/H-Alpha than other galaxy types. The LINERs with the highest [FeII]/PaBeta ratios (termed ``strong'' [FeII] LINERs) show evidence for recent star formation. Shocks from compact supernova remnants may enhance the [FeII] emission in these ``strong'' [FeII] LINERs. The LINERs with lower [FeII]/PaBeta ratios (termed ``weak'' [FeII] LINERs) are more consistent with Seyfert-like activity, including higher ionization states, some strong x-ray sources and some broad H-Alpha detections. The [FeII] luminosity and the [FeII]/PaBeta ratio in these objects are more easily explained by hard x-ray excitation than in the ``strong'' [FeII] LINERs. These ``weak'' [FeII] LINERs are considered prime candidates for being low luminosity Seyfert nuclei.
Phase transition in a chain of quantum vortices
C. Bruder,L. I. Glazman,A. I. Larkin,J. E. Mooij,A. van Oudenaarden
Physics , 1998, DOI: 10.1103/PhysRevB.59.1383
Abstract: We consider interacting vortices in a quasi-one-dimensional array of Josephson junctions with small capacitance. If the charging energy of a junction is of the order of the Josephson energy, the fluctuations of the superconducting order parameter in the system are considerable, and the vortices behave as quantum particles. Their density may be tuned by an external magnetic field, and therefore one can control the commensurability of the one-dimensional vortex lattice with the lattice of Josephson junctions. We show that the interplay between the quantum nature of a vortex, and the long-range interaction between the vortices leads to the existence of a specific commensurate-incommensurate transition in a one-dimensional vortex lattice. In the commensurate phase an elementary excitation is a soliton, with energy separated from the ground state by a finite gap. This gap vanishes in the incommensurate phase. Each soliton carries a fraction of a flux quantum; the propagation of solitons leads to a finite resistance of the array. We find the dependence of the resistance activation energy on the magnetic field and parameters of the Josephson array. This energy consists of the above-mentioned gap, and also of a boundary pinning term, which is different in the commensurate and incommensurate phases. The developed theory allows us to explain quantitatively the available experimental data.
Vemurafenib: a new treatment for BRAF-V600 mutated advanced melanoma
Fisher R, Larkin J
Cancer Management and Research , 2012, DOI: http://dx.doi.org/10.2147/CMAR.S25284
Abstract: rafenib: a new treatment for BRAF-V600 mutated advanced melanoma Review (2488) Total Article Views Authors: Fisher R, Larkin J Published Date August 2012 Volume 2012:4 Pages 243 - 252 DOI: http://dx.doi.org/10.2147/CMAR.S25284 Received: 06 May 2012 Accepted: 20 June 2012 Published: 08 August 2012 Rosalie Fisher, James Larkin Department of Medical Oncology, Royal Marsden Hospital, London, United Kingdom Abstract: The BRAF inhibitor, vemurafenib, has demonstrated improved progression-free and overall survival compared with chemotherapy in a randomized trial, and represents a new standard of care in patients with advanced melanoma harboring a BRAF-V600 mutation. A BRAF-V600 mutation is identified in approximately half of patients with cutaneous melanoma, and is unequivocally a biomarker predictive of profound clinical benefit for these patients. However, acquired vemurafenib resistance is a major clinical challenge and therapy is not yet curative. A substantial body of translational research has been performed alongside clinical trials of vemurafenib, providing key insights into the molecular basis of response and resistance. This review summarizes the development of vemurafenib for the treatment of BRAF-V600 mutant melanoma and discusses how knowledge of critical signaling pathways will be applied for its optimal clinical use in future.
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