32,519 research outputs found

    Shrinkage Estimation in Multilevel Normal Models

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    This review traces the evolution of theory that started when Charles Stein in 1955 [In Proc. 3rd Berkeley Sympos. Math. Statist. Probab. I (1956) 197--206, Univ. California Press] showed that using each separate sample mean from k3k\ge3 Normal populations to estimate its own population mean μi\mu_i can be improved upon uniformly for every possible μ=(μ1,...,μk)\mu=(\mu_1,...,\mu_k)'. The dominating estimators, referred to here as being "Model-I minimax," can be found by shrinking the sample means toward any constant vector. Admissible minimax shrinkage estimators were derived by Stein and others as posterior means based on a random effects model, "Model-II" here, wherein the μi\mu_i values have their own distributions. Section 2 centers on Figure 2, which organizes a wide class of priors on the unknown Level-II hyperparameters that have been proved to yield admissible Model-I minimax shrinkage estimators in the "equal variance case." Putting a flat prior on the Level-II variance is unique in this class for its scale-invariance and for its conjugacy, and it induces Stein's harmonic prior (SHP) on μi\mu_i.Comment: Published in at http://dx.doi.org/10.1214/11-STS363 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Cross-sectional Analysis of Sound Levels in the Neonatal Intensive Care Unit (NICU) at Thomas Jefferson University Hospital

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    Introduction . Infants in the NICU are considered at greater risk of developmental delay. It is now known that excessively loud noise can have a negative impact on parameters such as blood pressure, breathing, heart beat and oxygen saturation. Previous research has concluded that the optimal decibel (dB) level for proper growth of neonate hair cells rests around 45dB. Consequently, the American Academy of Pediatrics recommends that noise levels in the NICU be maintained to a maximum of 45dBA. However, little research has focused on designing new noise-altering products and their impact on neonatal outcomes. Methods. This was a cross sectional study. The NICU at Thomas Jefferson University Hospital was observed for room arrangements and general workflow. Additionally, decibel levels around empty neonatal incubators were measured. A decibel analyzer (REED Instruments SD-4023, Wilmington, NC) was used to record sound levels, both inside and outside of isolettes during various routine activities, including patient rounds, provider-parent conversations and vital monitoring alarms. Results. 30 discrete data points were surveyed, in addition to a 24-hour continuous decibel recording. Across all discrete data points, decibel levels had a mean of 65.6dB (SD ± 10.3). Ambient noise alone in a patient room was measured at 50dB. Noise levels in an open and closed isolette were measured at 58 and 57dB, respectively. Isolette side door opening and closing had a mean of 80.2dB (SD ± 7.60). With medical devices active in the patient room, noise levels had a mean of 62.7dB (SD ± 7.74). Conclusions. All data points were above the recommended safe noise level of 45dB. This data supports our development of a noise reduction product for use within neonatal isolettes. Our design will incorporate sterilizable, sound-absorbent materials and diffusion technologies to decrease ambient noise within neonatal incubators

    The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei -- I. The Observations

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    We present high quality (high signal-to-noise ratio and moderate spectral resolution) near-infrared (near-IR) spectroscopic observations of 23 well-known broad-emission line active galactic nuclei (AGN). Additionally, we obtained simultaneous (within two months) optical spectroscopy of similar quality. The near-IR broad emission line spectrum of AGN is dominated by permitted transitions of hydrogen, helium, oxygen, and calcium, and by the rich spectrum of singly-ionized iron. In this paper we present the spectra, line identifications and measurements, and address briefly some of the important issues regarding the physics of AGN broad emission line regions. In particular, we investigate the excitation mechanism of neutral oxygen and confront for the first time theoretical predictions of the near-IR iron emission spectrum with observations.Comment: 45 pages, 17 figures, accepted by ApJ

    The Rent-Price Ratio for the Aggregate Stock of Owner-Occupied Housing

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    We construct a time series of the rent-price ratio for the owner- occupied stock of housing, starting in 1960:1, by merging micro data from the last five Decennial Censuses of Housing with price indexes for house prices and rents.House Prices, Housing, Rents, CMHPI, Capitalization Rates

    An Exact Renormalization Group analysis of 3-d Well Developed turbulence

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    We take advantage of peculiar properties of three dimensional incompressible turbulence to introduce a nonstandard Exact Renormalization Group method. A Galilean invariance preserving regularizing procedure is utilized and a field truncation is adopted to test the method. Results are encouraging: the energy spectrum E(k) in the inertial range scales with exponent -1.666+/- 0.001 and the Kolmogorov constant C_K, computed for several (realistic) shapes of the stirring force correlator, agrees with experimental data.Comment: 12 pg, 2figures, LaTex, To be published on Physics Letters

    Effect of type of otolith and preparation technique on age estimation of larval and juvenile spot (Leiostomus xanthurus)

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    Otoliths of larval and juvenile fish provide a record of age, size, growth, and development (Campana and Neilson, 1985; Thorrold and Hare, 2002). However, determining the time of first increment formation in otoliths (Campana, 2001) and assessing the accuracy (deviation from real age) and precision (repeatability of increment counts from the same otolith) of increment counts are prerequisites for using otoliths to study the life history of fish (Campana and Moksness, 1991). For most fish species, first increment deposition occurs either at hatching, a day after hatching, or after first feeding and yolksac absorption (Jones, 1986; Thorrold and Hare, 2002). Increment deposition before hatching also occurs (Barkmann and Beck, 1976; Radtke and Dean, 1982). If first increment deposition does not occur at hatching, the standard procedure is to add a predetermined number to increment counts to estimate fish age (Campana and Neilson, 1985)

    The largest oxigen bearing organic molecule repository

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    We present the first detection of complex aldehydes and isomers in three typical molecular clouds located within 200pc of the center of our Galaxy. We find very large abundances of these complex organic molecules (COMs) in the central molecular zone (CMZ), which we attribute to the ejection of COMs from grain mantles by shocks. The relative abundances of the different COMs with respect to that of CH3OH are strikingly similar for the three sources, located in very different environments in the CMZ. The similar relative abundances point toward a unique grain mantle composition in the CMZ. Studying the Galactic center clouds and objects in the Galactic disk having large abundances of COMs, we find that more saturated molecules are more abundant than the non-saturated ones. We also find differences between the relative abundance between COMs in the CMZ and the Galactic disk, suggesting different chemical histories of the grain mantles between the two regions in the Galaxy for the complex aldehydes. Different possibilities for the grain chemistry on the icy mantles in the GC clouds are briefly discussed. Cosmic rays can play an important role in the grain chemistry. With these new detections, the molecular clouds in the Galactic center appear to be one of the best laboratories for studying the formation of COMs in the Galaxy.Comment: 20 pages, 4 figures, accepted in Ap

    Vertex corrections in localized and extended systems

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    Within many-body perturbation theory we apply vertex corrections to various closed-shell atoms and to jellium, using a local approximation for the vertex consistent with starting the many-body perturbation theory from a DFT-LDA Green's function. The vertex appears in two places -- in the screened Coulomb interaction, W, and in the self-energy, \Sigma -- and we obtain a systematic discrimination of these two effects by turning the vertex in \Sigma on and off. We also make comparisons to standard GW results within the usual random-phase approximation (RPA), which omits the vertex from both. When a vertex is included for closed-shell atoms, both ground-state and excited-state properties demonstrate only limited improvements over standard GW. For jellium we observe marked improvement in the quasiparticle band width when the vertex is included only in W, whereas turning on the vertex in \Sigma leads to an unphysical quasiparticle dispersion and work function. A simple analysis suggests why implementation of the vertex only in W is a valid way to improve quasiparticle energy calculations, while the vertex in \Sigma is unphysical, and points the way to development of improved vertices for ab initio electronic structure calculations.Comment: 8 Pages, 6 Figures. Updated with quasiparticle neon results, extended conclusions and references section. Minor changes: Updated references, minor improvement

    Exercise and progressive supranuclear palsy : the need for explicit exercise reporting

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    Background Progressive Supranuclear Palsy (PSP) is the most frequent form of atypical Parkinsonism. Although there is preliminary evidence for the benefits of gait rehabilitation, balance training and oculomotor exercises in PSP, the quality of reporting of exercise therapies appears mixed. The current investigation aims to evaluate the comprehensiveness of reporting of exercise and physical activity interventions in the PSP literature. Methods Two independent reviewers used the Consensus on Exercise Reporting Template (CERT) to extract all exercise intervention data from 11 studies included in a systematic review. CERT items covered: ‘what’ (materials), ‘who’ (instructor qualifications), ‘how’ (delivery), ‘where’ (location), ‘when’, ‘how much’ (dosage), ‘tailoring’ (what, how), and ‘how well’ (fidelity) exercise delivery complied with the protocol. Each exercise item was scored ‘1’ (adequately reported) or ‘0’ (not adequately reported or unclear). The CERT score was calculated, as well as the percentage of studies that reported each CERT item. Results The CERT scores ranged from 3 to 12 out of 19. No PSP studies adequately described exercise elements that would allow exact replication of the interventions. Well-described items included exercise equipment, exercise settings, exercise therapy scheduling, frequency and duration. Poorly described items included decision rules for exercise progression, instructor qualifications, exercise adherence, motivation strategies, safety and adverse events associated with exercise therapies. Discussion The results revealed variability in the reporting of physical therapies for people living with PSP. Future exercise trials need to more comprehensively describe equipment, instructor qualifications, exercise and physical activity type, dosage, setting, individual tailoring of exercises, supervision, adherence, motivation strategies, progression decisions, safety and adverse events. Conclusion Although beneficial for people living with PSP, exercise and physical therapy interventions have been inadequately reported. It is recommended that evidence-based reporting templates be utilised to comprehensively document therapeutic exercise design, delivery and evaluation
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