2,279 research outputs found
The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5
We present Hubble Space Telescope (HST) near-infrared photometry of the
coldest known brown dwarf, WISE J085510.83071442.5 (WISE 08550714). WISE
08550714 was observed with the Wide Field Camera 3 (WFC3) aboard HST using
the F105W, F125W, and F160W filters, which approximate the , , and
near-infrared bands. WISE 08550714 is undetected at F105W with a
corresponding 2 magnitude limit of 26.9. We marginally detect
WISE 08550714 in the F125W images (S/N 4), with a measured magnitude
of 26.41 0.27, more than a magnitude fainter than the band magnitude
reported by Faherty and coworkers. WISE J08550714 is clearly detected in the
F160W band, with a magnitude of 23.90 0.02, the first secure detection of
WISE 08550714 in the near-infrared. Based on these data, we find that WISE
08550714 has extremely red F105WF125W and F125WF160W colors relative
to other known Y dwarfs. We find that when compared to the models of Saumon et
al. and Morley et al., the F105WF125W and F125WF160W colors of WISE
08550714 cannot be accounted for simultaneously. These colors likely
indicate that we are seeing the collapse of flux on the Wien tail for this
extremely cold object.Comment: Accepted for publication in ApJ Letter
Investigation of aerothermodynamics and optical radiation in the AFE hypersonic flow field
Research for the radiation experiments on the Aeroassist Flight Experiment (AFE) was performed to obtain a data base for development of engineering requirements for aerobrakes. Due to funding restrictions, the necessary Aerobrake design data were obtained from ground based experiments, specifically arc-jet wind tunnels. Except for the instrument windows, final development of the AFE radiometers was completed. Window definition included several designs to be flight validated in arc-jets. This work was completed, and successful designs have evolved which will yield full scientific return from the flight experiment. The theoretical work includes final code development to describe the spacecraft environment to support instrument definition, optical radiation codes that operate at significantly improved speeds, and calculation of radiation forebody loads and effects on experiment objectives for varying AFE weights and trajectories. Furthermore, radiant flux vectors at the AFE base were predicted to be used for afterbody instrument definition. The Vacuum Ultraviolet Experiment for the Arc-Jet was completed, and arc-jet experiment conditions and experiment objectives were refined to incorporate the most current thinking. Ballistic range experiments were completed. Several shadowgraphs indicating corner turning angles and waviness structures were obtained, and the results were used to estimate the compression region location for the AFE flight. The waviness measured has helped to model the temporal variations of wake radiation for purposes of defining radiometers to measure the energy content of wake dynamics
The Development of Roman Schools and Education
Education develops as a nation progresses. Roman education paralleled the growth of the Roman state. Thus we find three stages in the development of education, corresponding to the development and expansion of Rome. In the first period of the early Republic, education was elementary and solely a preparation for life and service to the state. In the second period, when Rome is expanding, fighting the Punic war, and extending its boundaries, education is coming under the Greek influence and culture. In the third period, when Rome is an empire, a world state, education is Graeco-Roman; broadened and expanded to include that culture which the people of a world state demand. The Romans, now that they have conquered the world, have time for aesthetic development, moreover, the greatest profession is that of the orator, and the successful orator must have a well balanced cultural training
Near-Infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit Candidates
The 2MASS photometric calibration observations cover ~6 square degrees on the
sky in 35 "calibration fields" each sampled in nominal photometric conditions
between 562 and 3692 times during the four years of the 2MASS mission. We
compile a catalog of variables from the calibration observations to search for
M dwarfs transited by extra-solar planets. We present our methods for measuring
periodic and non-periodic flux variability. From 7554 sources with apparent Ks
magnitudes between 5.6 and 16.1, we identify 247 variables, including
extragalactic variables and 23 periodic variables. We have discovered three M
dwarf eclipsing systems, including two candidates for transiting extrasolar
planets.Comment: The Astrophysical Journal Supplement, in press; figures compresse
Prevalence of diabetic retinopathy in type 2 diabetes mellitus patients attending medicine out-patient department of a tertiary care hospital in Alappuzha, Kerala, India
Background: Diabetic retinopathy is a microvascular complication affecting the eyes of both Type 1 and Type 2 diabetes mellitus due to long-term hyperglycaemia. Diabetic retinopathy is the leading cause of blindness among working aged adults around the world. There are various factors leading to the development of diabetic retinopathy namely duration of diabetes, glycaemic control, age at onset of diabetes, uncontrolled hypertension. This is a hospital based cross-sectional study which aimed to study the prevalence of diabetic retinopathy in type 2 diabetes mellitus patients attending Medicine out-patient department of Government T. D. Medical College, Alappuzha, Kerala, India. The factors contributing to the development of retinopathy was also studied.Methods: 200 already diagnosed type 2 diabetic subjects were included in the study. Subjects were explained about the study and once the consent was received, data regarding age, gender, age at onset of diabetes, duration of diabetes, history of smoking, alcohol intake, and socio-economic status was documented. Height and weight was measured. Blood pressure was recorded with mercury sphygmomanometer. Then the subjects were evaluated for diabetic retinopathy by fundus examination after dilating the eyes. Findings were noted and subjects were categorized as no retinopathy, nonproliferative and proliferative diabetic retinopathy using the ETDRS classification.Results: In present study, out of 200 subjects, 63 subjects (31.5%) were affected with diabetic retinopathy (non-proliferative retinopathy=22.5%, proliferative retinopathy=9%). Prevalence of mild, moderate and severe non-proliferative retinopathy was 7.5% each. Significant association was found between diabetic retinopathy and duration of diabetes.Conclusions: Therefore, periodic screening of diabetic patients should be carried out for early detection and prevention of loss of vision
SNIFFER WFD119: Enhancement of the River Invertebrate Classification Tool (RICT)
EXECUTIVE SUMMARY
Project funders/partners: Environment Agency (EA), Northern Ireland Environment Agency (NIEA), Scotland & Northern Ireland Forum for Environmental Research (SNIFFER), Scottish Environment Protection Agency (SEPA)
Background to research
The Regulatory Agencies in the UK (the Environment Agency; Scottish Environment Protection Agency; and the Northern Ireland Environment Agency) now use the River Invertebrate Classification Tool (RICT) to classify the ecological quality of rivers for Water Framework Directive compliance monitoring. RICT incorporates RIVPACS IV predictive models and is a highly capable tool written in a modern software programming language.
While RICT classifies waters for general degradation and organic pollution stress, producing assessments of status class and uncertainty, WFD compliance monitoring also requires the UK Agencies to assess the impacts of a wide range of pressures including hydromorphological and acidification stresses. Some of these pressures alter the predictor variables that current RIVPACS models use to derive predicted biotic indices. This project has sought to broaden the scope of RICT by developing one or more RIVPACS model(s) that do not use predictor variables that are affected by these stressors, but instead use alternative GIS based variables that are wholly independent of these pressures.
This project has also included a review of the wide range of biotic indices now available in RICT, identifying published sources, examining index performance, and where necessary making recommendations on further needs for index testing and development.
Objectives of research
•To remove and derive alternative predictive variables that are not affected by stressors, with particular emphasis on hydrological/acidification metric predictors.
•To construct one or more new RIVPACS model(s) using stressor independent variables.
•Review WFD reporting indices notably AWIC(species), LIFE (species), PSI & WHPT.
Key findings and recommendations :
Predictor variables and intellectual property rights :
An extensive suite of new variables have been derived by GIS for the RIVPACS reference sites that have been shown to act as stressor-independent predictor variables. These include measures of stream order, solid and drift geology, and a range of upstream catchment characteristics (e.g. catchment area, mean altitude of upstream catchment, and catchment aspect).
It is recommended that decisions are reached on which of the newly derived model(s) are implemented in RICT so that IPR issues for the relevant datasets can be quickly resolved and the datasets licensed. It is also recommended that licensing is sought for a point and click system (where the dataset cannot be reverse engineered) that is capable of calculating any of the time-invariant RIVPACS environmental predictor variables used by any of the newly derived (and existing) RIVPACS models, and for any potential users.
New stressor-independent RIVPACS models :
Using the existing predictor variables, together with new ones derived for their properties of stressor-independence, initial step-wise forward selection discriminant models suggested a range of 36 possible models that merited further testing. Following further testing, the following models are recommended for assessing watercourses affected by flow/hydromorphological and/or acidity stress:
• For flow/hydromorphological stressors that may have modified width, depth and/or substrate in GB, it is suggested that a new ‘RIVPACS IV – Hydromorphology Independent’ model (Model 24) is used (this does not use the predictor variables width, depth and substratum, but includes a suite of new stressor-independent variables).
• For acidity related stressors in GB, it is suggested that a new ‘RIVPACS IV – Alkalinity Independent’ model (Model 35) is used (this does not use the predictor variable alkalinity, but includes new stressor-independent variables).
• For flow/hydromorphological stressors and acidity related stressors in GB, it is suggested that a new ‘RIVPACS IV – Hydromorphology & Alkalinity Independent’ model (Model 13) is used (this does not use the predictor variables width, depth, substratum and alkalinity, but includes a suite of new stressor-independent variables).
• Reduced availability of appropriate GIS tools at this time has meant that no new models have been developed for Northern Ireland.
Discriminant functions and end group means have now been calculated to enable any of these models to be easily implemented in the RICT software.
Biotic indices :
The RIVPACS models in RICT can now produce expected values for a wide range of biotic indices addressing a variety of stressors. These indices will support the use of RICT as a primary tool for WFD classification and reporting of the quality of UK streams and rivers. There are however a number of outstanding issues with indices that need to be addressed:
• There is a need to develop a biotic index for assessing metal pollution.
• WFD EQR banding schemes are required for many of the indices to report what is considered an acceptable degree of stress (High-Good) and what is not (Moderate, Poor or Bad).
• A comprehensive objective testing process needs to be undertaken on the indices in RICT using UK-wide, large-scale, independent test datasets to quantify their index-stressor relationships and their associated uncertainty, for example following the approach to acidity index testing in Murphy et al., (in review) or organic/general degradation indices in Banks & McFarland (2010).
• Following objective testing, the UK Agencies should make efforts to address any index under-performance issues that have been identified, and where necessary new work should be commissioned to modify existing indices, or develop new ones where required so that indices for all stress types meet certain minimum performance criteria.
• Testing needs to be done to examine index-stressor relationships with both observed index scores and RIVPACS observed/expected ratios. Work should also be done to compare the existing RIVPACS IV and the new stressor-independent models (developed in this project) as alternative sources of the expected index values for these tests.
• Consideration should be given to assessing the extent to which chemical and biological monitoring points co-occur. Site-matched (rather than reach-matched) chemical and biological monitoring points would i) generate the substantial training datasets needed to refine or develop new indices and ii) generate the independent datasets for testing
The equivalent translational stiffness of steel studs
The effect of the resilience of the steel studs on the sound insulation of steel stud cavity walls can be modelled as an equivalent translational stiffness in simple models for predicting the sound insulation of walls. Numerical calculations (Poblet-Puig et al., 2009) have shown that this equivalent translational stiffness varies with frequency. Vigran (2010a) has derived a best-fit third order polynomial approximation to the logarithm of these numerical values as a function of the logarithm of the frequency for the most common type of steel stud. This paper uses an inverse experimental technique. It determines the values of the equivalent translational stiffness of steel studs which make Davy’s (2010) sound insulation theory agree best with experimental sound insulation data from the National Research Council of Canada (NRCC) (Halliwell et al., 1998) for 126 steel stud cavity walls with gypsum plasterboard on each side of the steel studs and sound absorbing material in the wall cavity. These values are approximately constant as a function of frequency up to 400 Hz. Above 400 Hz they increase approximately as a non-integer power of the frequency. The equivalent translational stiffness also depends on the mass per unit surface area of the cladding on each side of the steel studs and on the width of the steel studs. Above 400 Hz, this stiffness also depends on the stud spacing. The equivalent translational stiffness of steel studs determined in this paper and the best-fit approximation to that data are compared with that determined numerically by Poblet-Puig et al. (2009) and with Vigran’s (2010a) best-fit approximation as a function of frequency. The best-fit approximation to the inversely experimentally determined values of equivalent translational stiffness are used with Davy’s (2010) sound insulation prediction model to predict the sound insulation of steel stud cavity walls whose sound insulation has been determined experimentally by NRCC (Halliwell et al., 1998) or CSTB (Guigou-Carter and Villot, 2006)
Three New Cool Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer (WISE) and an Improved Spectrum of the Y0 Dwarf WISE J041022.71+150248.4
As part of a larger search of Wide-field Infrared Survey Explorer (WISE) data
for cool brown dwarfs with effective temperatures less than 1000 K, we present
the discovery of three new cool brown dwarfs with spectral types later than T7.
Using low-resolution, near-infrared spectra obtained with the NASA Infrared
Telescope Facility and the Hubble Space Telescope we derive spectral types of
T9.5 for WISE J094305.98+360723.5, T8 for WISE J200050.19+362950.1, and Y0: for
WISE J220905.73+271143.9. The identification of WISE J220905.73+271143.9 as a Y
dwarf brings the total number of spectroscopically confirmed Y dwarfs to
seventeen. In addition, we present an improved spectrum (i.e. higher
signal-to-noise ratio) of the Y0 dwarf WISE J041022.71+150248.4 that confirms
the Cushing et al. classification of Y0. Spectrophotometric distance estimates
place all three new brown dwarfs at distances less than 12 pc, with WISE
J200050.19+362950.1 lying at a distance of only 3.9-8.0 pc. Finally, we note
that brown dwarfs like WISE J200050.19+362950.1 that lie in or near the
Galactic plane offer an exciting opportunity to measure their mass via
astrometric microlensing.Comment: Accepted for publication in the Astronomical Journa
Discovery of an M9.5 Candidate Brown Dwarf in the TW Hydrae Association - DENIS J124514.1-442907
We report the discovery of a fifth candidate substellar system in the ~5-10
Myr TW Hydrae Association - DENIS J124514.1-442907. This object has a NIR
spectrum remarkably similar to that of 2MASS J1139511-315921, a known TW Hydrae
brown dwarf, with low surface gravity features such as a triangular-shaped
H-band, deep H2O absorption, weak alkali lines, and weak hydride bands. We find
an optical spectral type of M9.5 and estimate a mass of <24 M_Jup, assuming an
age of ~5-10 Myr. While the measured proper motion for DENIS J124514.1-442907
is inconclusive as a test for membership, its position in the sky is coincident
with the TW Hydrae Association. A more accurate proper motion measurement,
higher resolution spectroscopy for radial velocity, and a parallax measurement
are needed to derive the true space motion and to confirm its membership.Comment: 8 pages - emulateapj style, 2 figures, 3 tables. Accepted to ApJL.
Fixed typos, added reference, added footnot
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