9,412 research outputs found
Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the hot Jupiter WASP-4b
We present the complete optical transmission spectrum of the hot Jupiter
WASP-4b from 440-940 nm at R ~ 400-1500 obtained with the Gemini Multi-Object
Spectrometers (GMOS); this is the first result from a comparative
exoplanetology survey program of close-in gas giants conducted with GMOS.
WASP-4b has an equilibrium temperature of 1700 K and is favorable to study in
transmission due to a large scale height (370 km). We derive the transmission
spectrum of WASP-4b using 4 transits observed with the MOS technique. We
demonstrate repeatable results across multiple epochs with GMOS, and derive a
combined transmission spectrum at a precision about twice above photon noise,
which is roughly equal to to one atmospheric scale height. The transmission
spectrum is well fitted with a uniform opacity as a function of wavelength. The
uniform opacity and absence of a Rayleigh slope from molecular hydrogen suggest
that the atmosphere is dominated by clouds with condensate grain size of ~1 um.
This result is consistent with previous observations of hot Jupiters since
clouds have been seen in planets with similar equilibrium temperatures to
WASP-4b. We describe a custom pipeline that we have written to reduce GMOS
time-series data of exoplanet transits, and present a thorough analysis of the
dominant noise sources in GMOS, which primarily consist of wavelength- and
time- dependent displacements of the spectra on the detector, mainly due to a
lack of atmospheric dispersion correction.Comment: 23 pages, 12 figures, accepted for publication in AJ, 2017 July
The tree cut and merge algorithm for estimation of network reliability
This article presents Monte Carlo techniques for estimating network reliability. For highly reliable networks, techniques based on graph evolution models provide very good performance. However, they are known to have significant simulation cost. An existing hybrid scheme (based on partitioning the time space) is available to speed up the simulations; however, there are difficulties with optimizing the important parameter associated with this scheme. To overcome these difficulties, a new hybrid scheme (based on partitioning the edge set) is proposed in this article. The proposed scheme shows orders of magnitude improvement of performance over the existing techniques in certain classes of network. It also provides reliability bounds with little overhead.K.P. Hui, N. Bean, M. Kraetzl and D. Kroes
Metallicities of M Dwarf Planet Hosts from Spectral Synthesis
We present the first spectroscopic metallicities of three M dwarfs with known
or candidate planetary mass companions. We have analyzed high resolution, high
signal-to-noise spectra of these stars which we obtained at McDonald
Observatory. Our analysis technique is based on spectral synthesis of atomic
and molecular features using recently revised cool-star model atmospheres and
spectrum synthesis code. The technique has been shown to yield results
consistent with the analyses of solar-type stars and allows measurements of M
dwarf [M/H] values to 0.12 dex precision. From our analysis, we find [M/H] =
-0.12, -0.32, and -0.33 for GJ 876, GJ 436, and GJ 581 respectively. These
three M dwarf planet hosts have sub-solar metallicities, a surprising departure
from the trend observed in FGK-type stars. This study is the first part of our
ongoing work to determine the metallicities of the M dwarfs included in the
McDonald Observatory planet search program.Comment: 13 pages, 2 figures, accepted for publication in ApJ
Ultrasound diagnosis of endometrial cancer by subjective pattern recognition in women with postmenopausal bleeding: a prospective inter-rater agreement and reliability study
OBJECTIVES: The objective of our study was to assess the inter-rater agreement and reliability of using subjective pattern recognition to diagnose endometrial cancer on ultrasound in women with postmenopausal bleeding. METHODS: This was a prospective cross-sectional study at a gynaecological rapid access clinic, between Oct 2016 - Dec 2017, where consecutive women with postmenopausal bleeding and endometrial thickness of â„4.5mm on transvaginal ultrasound scan were included. We excluded women on hormone replacement therapy, tamoxifen or with a history of primary gynaecological malignancy. Two raters independently performed ultrasound examinations, blinded to each other's findings, and classified women into having uniformly thickened endometrium, benign polyp or endometrial cancer, by subjective pattern recognition. Inter-rater reliability of the ultrasound diagnoses was assessed by using Cohen's kappa statistics. All women subsequently underwent either outpatient endometrial biopsy, hysteroscopy or hysterectomy. RESULTS: Forty women were included in the study with a median age of 61 (IQR 57-69) and a median endometrial thickness of 11.0mm (IQR 6.2-20.3). Final histological analysis confirmed 16 (40%) women with endometrial cancer, 16 (40%) endometrial polyps, 4 (10%) atrophic endometrium, 3 (7%) proliferative endometrium and 1 (3%) endometrial hyperplasia. Inter-rater agreement for the ultrasound diagnoses of uniformly thickened endometrium, polyp and cancer, were 14/16 (87.5%), 22/30 (73.3%) and 28/34 (82.4%), respectively; the inter-rater reliability was good (ÎșÂ =Â 0.69, 95% C.I. 0.49-0.88). When the ultrasound diagnoses were combined as either cancer or no cancer, the inter-rater agreement was 85% and the inter-rater reliability was also good (ÎșÂ =Â 0.78, 95% C.I. 0.61-0.95). Rater A correctly identified 14/16 cancers and Rater B identified 15/16. Endometrial cancers were misdiagnosed as benign polyps on ultrasound in two women by Rater A, and in one woman by Rater B. The overall accuracies of Rater A and Rater B in differentiating between benign endometrial pathologies and malignancy were 90% and 85%, respectively. CONCLUSIONS: Our results showed good inter-rater reliability of subjective pattern recognition in diagnosing uniformly thickened endometrium, polyp and cancer on ultrasound in women with postmenopausal bleeding. Our findings should facilitate wider use of subjective pattern recognition in routine clinical practice
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Psychometric properties of the Late-Life Function and Disability Instrument: a systematic review
Background: The choice of measure for use as a primary outcome in geriatric research is contingent upon the construct of interest and evidence for its psychometric properties. The Late-Life Function and Disability Instrument (LLFDI) has been widely used to assess functional limitations and disability in studies with older adults. The primary aim of this systematic review was to evaluate the current available evidence for the psychometric properties of the LLFDI. Methods: Published studies of any design reporting results based on administration of the original version of the LLFDI in community-dwelling older adults were identified after searches of 9 electronic databases. Data related to construct validity (convergent/divergent and known-groups validity), test-retest reliability and sensitivity to change were extracted. Effect sizes were calculated for within-group changes and summarized graphically. Results: Seventy-one studies including 17,301 older adults met inclusion criteria. Data supporting the convergent/divergent and known-groups validity for both the Function and Disability components were extracted from 30 and 18 studies, respectively. High test-retest reliability was found for the Function component, while results for the Disability component were more variable. Sensitivity to change of the LLFDI was confirmed based on findings from 25 studies. The basic lower extremity subscale and overall summary score of the Function component and limitation dimension of the Disability component were associated with the strongest relative effect sizes. Conclusions: There is extensive evidence to support the construct validity and sensitivity to change of the LLFDI among various clinical populations of community-dwelling older adults. Further work is needed on predictive validity and values for clinically important change. Findings from this review can be used to guide the selection of the most appropriate LLFDI subscale for use an outcome measure in geriatric research and practice
On the sample size dependence of the critical current density in MgB superconductors
Sample size dependent critical current density has been observed in magnesium
diboride superconductors. At high fields, larger samples provide higher
critical current densities, while at low fields, larger samples give rise to
lower critical current densities. The explanation for this surprising result is
proposed in this study based on the electric field generated in the
superconductors. The dependence of the current density on the sample size has
been derived as a power law ( is the factor
characterizing curve ). This dependence provides one with
a new method to derive the factor and can also be used to determine the
dependence of the activation energy on the current density.Comment: Revtex, 4 pages, 5 figure
Autonomous clustering using rough set theory
This paper proposes a clustering technique that minimises the need for subjective
human intervention and is based on elements of rough set theory. The proposed algorithm is
unified in its approach to clustering and makes use of both local and global data properties to
obtain clustering solutions. It handles single-type and mixed attribute data sets with ease and
results from three data sets of single and mixed attribute types are used to illustrate the
technique and establish its efficiency
Large Predicted Self-Field Critical Current Enhancements In Superconducting Strips Using Magnetic Screens
A transport current distribution over a wide superconducting sheet is shown
to strongly change in a presence of bulk magnetic screens of a soft magnet with
a high permeability. Depending on the geometry, the effect may drastically
suppress or protect the Meissner state of the sheet through the enhancement or
suppression of the edge barrier critical current. The total transport current
in the magnetically screened Meissner state is expected to compete with the
critical current of the flux-filled sheet only for samples whose critical
current is initially essentially controlled by the edge barrier effect.Comment: 6 figure
Evaluation of the Single Kernel Characterization System (SKCS) for Measurement of Sorghum Grain Attributes
The single kernel characterization system (SKCS) has been widely used in the wheat industry, and SKCS parameters have been linked to end-use quality in wheat. The SKCS has promise as a tool for evaluating sorghum grain quality. However, the SKCS was designed to analyze wheat, which has a different kernel structure from sorghum. To gain a better understanding of the meaning of SKCS predictions for grain sorghum, individual sorghum grains were measured for length, width, thickness (diameter), and weight by laboratory methods and by the SKCS. SKCS predictions for kernel weight and thickness were highly correlated to laboratory measurements. However, SKCS predictions for kernel thickness were underestimated by â20%. The SKCS moisture prediction for sorghum was evaluated by tempering seven samples with varying hardness values to four moisture levels. The moisture contents predicted by SKCS were compared with a standard oven method and, while correlated, SKCS moisture predictions were less than moisture measured by air oven, especially at low moisture content. Finally, SKCS hardness values were compared with hardness measured by abrasive decortication. A moderate (r = 0.67, P \u3c 0.001) correlation was observed between the hardness measurements. The SKCS predictions of kernel weight and diameter were highly correlated with laboratory measurement. Moisture prediction, however, was substantially lower by the SKCS than as measured by an air oven method. The SKCS should be suitable for measuring sorghum grain attributes. Further research is needed to determine how SKCS hardness predictions are correlated to milling properties of sorghum grain
Hysteresis in mesoscopic superconducting disks: the Bean-Livingston barrier
The magnetization behavior of mesoscopic superconducting disks can show
hysteretic behavior which we explain by using the Ginzburg-Landau (GL) theory
and properly taking into account the de-magnetization effects due to
geometrical form factors. In large disks the Bean-Livingston surface barrier is
responsible for the hysteresis. While in small disks a volume barrier is
responsible for this hysteresis. It is shown that although the sample
magnetization is diamagnetic (negative), the measured magnetization can be
positive at certain fields as observed experimentally, which is a consequence
of the de-magnetization effects and the experimental set up.Comment: Latex file, 4 ps file
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