822 research outputs found
University students and faculty have positive perceptions of open/alternative resources and their utilization in a textbook replacement initiative
This is contribution no. 16-114-J from the Kansas Agricultural Experiment Station.
The Kansas State University Open/Alternative Textbook Initiative provides grants to faculty members to replace textbooks with open/alternative educational resources (OAERs) that are available at no cost to students. Open educational resources are available for anyone to access, while alternative educational resources are not open. The objective of this study was to determine the perceptions towards OAERs and the initiative, of students enrolled in, and faculty members teaching, courses using OAERs. A survey was sent out to 2,074 students in 13 courses using the OAERs. A total of 524 (25.3%) students completed the survey and a faculty member from each of the 13 courses using OAERs was interviewed. Students rated the OAERs as good quality, preferred using them instead of buying textbooks for their courses, and agreed that they would like OAERs used in other courses. Faculty felt that student learning was somewhat better and it was somewhat easier to teach using OAERs than when they used the traditional textbooks. Nearly all faculty members preferred teaching with OAERs and planned to continue to do so after the funding period. These results, combined with the tremendous savings to students, support the continued funding of the initiative and similar approaches at other institutions
Intensive Care Usage by HIV-Positive Patients in the HAART Era
In the 1980s the outlook for patients with the acquired immunodeficiency syndrome (AIDS) and critical illness was poor. Since then several studies of outcome of HIV+ patients on ICU have shown improving prognosis, with anti-retroviral therapy playing a large part. We retrospectively examined intensive care (ICU) admissions in a large HIV unit in London. Between April 2001 and April 2006 43 patients were admitted to the ICU. The mean age of patients was 44 years and 74% were male. Fifty-six percent of admissions were receiving anti-retroviral therapy and 44% had an AIDS defining diagnosis. The median CD4 count was 128 cells/mL and the median APACHE II score was 21. The commonest diagnostic ICU admission category was respiratory disease. This group experienced higher mortality despite slightly lower APACHE II scores, though this did not achieve statistical significance. The follow up period was one year or until April 2007, when data were censored. ICU mortality was 33%, in hospital mortality was 51% and overall mortality at the end of the study period was 67%. Median survival was 1008 days. The CD4 count did not predict long-term survival, although the sample size was too small for this to be conclusive
TRIS III: the diffuse galactic radio emission at
We present values of temperature and spectral index of the galactic diffuse
radiation measured at 600 and 820 MHz along a 24 hours right ascension circle
at declination . They have been obtained from a subset of
absolute measurements of the sky temperature made with TRIS, an experiment
devoted to the measurement of the Cosmic Microwave Background temperature at
decimetric-wavelengths with an angular resolution of about .
Our analysis confirms the preexisting picture of the galactic diffuse
emission at decimetric wavelength and improves the accuracy of the measurable
quantities. In particular, the signal coming from the halo has a spectral index
in the range above 600 MHz, depending on the sky position. In the
disk, at TRIS angular resolution, the free-free emission accounts for the 11%
of the overall signal at 600 MHz and 21% at 1420 MHz. The polarized component
of the galactic emission, evaluated from the survey by Brouw and Spoelstra,
affects the observations at TRIS angular resolution by less than 3% at 820 MHz
and less than 2% at 600 MHz. Within the uncertainties, our determination of the
galactic spectral index is practically unaffected by the correction for
polarization.
Since the overall error budget of the sky temperatures measured by TRIS at
600 MHz, that is 66 mK(systematic)18 mK (statistical), is definitely smaller
than those reported in previous measurements at the same frequency, our data
have been used to discuss the zero levels of the sky maps at 150, 408, 820 and
1420 MHz in literature. Concerning the 408 MHz survey, limiting our attention
to the patch of sky corresponding to the region observed by TRIS, we suggest a
correction of the base-level of K.Comment: Accepted for publication in the Astrophysical Journa
Radio spectral properties and the magnetic field of the SNR S147
(Abridged) S147 is a large faint shell-type supernova remnant (SNR). Its
remarkable spectral break at cm-wavelengths is an important physical property
to characterize the SNR evolution. However, the spectral break is based on
radio observations with limited precision. We made new radio continuum and
polarization observations of S147 at 11cm and at 6cm with the Effelsberg 100-m
telescope and the Urumqi 25-m telescope, respectively. These new data were
combined with published lower frequency data from the Effelsberg 100-m
telescope and very high frequency data from WMAP to investigate the spectral
turnover and polarization properties of S147. S147 consists of numerous
filaments embedded in diffuse emission. We found that the integrated flux
densities of S147 are 34.8+/-4.0 Jy at 11cm and 15.4+/-3.0Jy at 6cm. These new
measurements confirm the known spectral turnover at ~1.5GHz, which can be
entirely attributed to the diffuse emission component. The spectral index above
the turnover is -1.35+/-0.20. The filamentary emission component has a constant
spectral index over the entire wavelength range up to 40.7GHz of -0.35+/-0.15.
The weak polarized emission of S147 is at the same level as the ambient diffuse
Galactic polarization. The rotation measure of the eastern filamentary shell is
about -70 rad/m2. The filamentary and diffuse emission components of S147 have
different physical properties, which make S147 outstanding among shell type
SNRs.The weak polarization of S147 at 11cm and at 6cm can be attributed to a
section of the S147 shell showing a tangential magnetic field direction.Comment: 11 pages, 17 figures, accepted for publication in Astronomy &
Astrophysics, the resolution of some figures have been reduced. For high
resolution version, see
ftp://ftp.mpifr-bonn.mpg.de/outgoing/p098wre/xiao-etal.pdf,revised following
the language edito
Titan Science with the James Webb Space Telescope (JWST)
The James Webb Space Telescope (JWST), scheduled for launch in 2018, is the
successor to the Hubble Space Telescope (HST) but with a significantly larger
aperture (6.5 m) and advanced instrumentation focusing on infrared science
(0.6-28.0 m ). In this paper we examine the potential for scientific
investigation of Titan using JWST, primarily with three of the four
instruments: NIRSpec, NIRCam and MIRI, noting that science with NIRISS will be
complementary. Five core scientific themes are identified: (i) surface (ii)
tropospheric clouds (iii) tropospheric gases (iv) stratospheric composition and
(v) stratospheric hazes. We discuss each theme in depth, including the
scientific purpose, capabilities and limitations of the instrument suite, and
suggested observing schemes. We pay particular attention to saturation, which
is a problem for all three instruments, but may be alleviated for NIRCam
through use of selecting small sub-arrays of the detectors - sufficient to
encompass Titan, but with significantly faster read-out times. We find that
JWST has very significant potential for advancing Titan science, with a
spectral resolution exceeding the Cassini instrument suite at near-infrared
wavelengths, and a spatial resolution exceeding HST at the same wavelengths. In
particular, JWST will be valuable for time-domain monitoring of Titan, given a
five to ten year expected lifetime for the observatory, for example monitoring
the seasonal appearance of clouds. JWST observations in the post-Cassini period
will complement those of other large facilities such as HST, ALMA, SOFIA and
next-generation ground-based telescopes (TMT, GMT, EELT).Comment: 50 pages, including 22 figures and 2 table
A model of diffuse Galactic Radio Emission from 10 MHz to 100 GHz
Understanding diffuse Galactic radio emission is interesting both in its own
right and for minimizing foreground contamination of cosmological measurements.
Cosmic Microwave Background experiments have focused on frequencies > 10 GHz,
whereas 21 cm tomography of the high redshift universe will mainly focus on <
0.2 GHz, for which less is currently known about Galactic emission. Motivated
by this, we present a global sky model derived from all publicly available
total power large-area radio surveys, digitized with optical character
recognition when necessary and compiled into a uniform format, as well as the
new Villa Elisa data extending the 1.4 GHz map to the entire sky. We quantify
statistical and systematic uncertainties in these surveys by comparing them
with various global multi-frequency model fits. We find that a principal
component based model with only three components can fit the 11 most accurate
data sets (at 10, 22, 45 & 408 MHz and 1.4, 2.3, 23, 33, 41, 61, 94 GHz) to an
accuracy around 1%-10% depending on frequency and sky region. Both our data
compilation and our software returning a predicted all-sky map at any frequency
from 10 MHz to 100 GHz are publicly available at
http://space.mit.edu/home/angelica/gsm .Comment: Accuracy improved with 5-year WMAP data. Our data, software and new
foreground-cleaned WMAP map are available at https://ascl.net/1011.01
Fourier Modeling of the Radio Torus Surrounding Supernova 1987A
We present detailed Fourier modeling of the radio remnant of Supernova 1987A,
using high-resolution 9 GHz and 18 GHz data taken with the Australia Telescope
Compact Array over the period 1992 to 2008. We develop a parameterized
three-dimensional torus model for the expanding radio shell, in which the
emission is confined to an inclined equatorial belt; our model also
incorporates both a correction for light travel-time effects and an overall
east-west gradient in the radio emissivity. By deriving an analytic expression
for the two-dimensional Fourier transform of the projected three-dimensional
brightness distribution, we can fit our spatial model directly to the
interferometric visibility data. This provides robust estimates to the radio
morphology at each epoch. The best-fit results suggest a constant remnant
expansion at 4000 +/- 400 km/s over the 16-year period covered by the
observations. The model fits also indicate substantial mid-latitude emission,
extending to 40 degree on either side of the equatorial plane. This likely
corresponds to the extra-planar structure seen in H and Ly
emission from the supernova reverse shock, and broadly supports hydrodynamic
models in which the complex circumstellar environment was produced by a
progression of interacting winds from the progenitor. Our model quantifies the
clear asymmetry seen in the radio images: we find that the eastern half of the
radio remnant is consistently ~40 brighter than the western half at all epochs,
which may result from an asymmetry in the ejecta distribution between these two
hemispheres.Comment: accepted by ApJ, 11 figures, some have been scaled down in resolutio
Cardiac-sparing radiotherapy for locally advanced non-small cell lung cancer
Background
We have carried out a study to determine the scope for reducing heart doses in photon beam radiotherapy of locally advanced non-small cell lung cancer (LA-NSCLC).
Materials and methods
Baseline VMAT plans were created for 20 LA-NSCLC patients following the IDEAL-CRT isotoxic protocol, and were re-optimized after adding an objective limiting heart mean dose (MDHeart). Reductions in MDHeart achievable without breaching limits on target coverage or normal tissue irradiation were determined. The process was repeated for objectives limiting the heart volume receiving ≥ 50 Gy (VHeart-50-Gy) and left atrial wall volume receiving ≥ 63 Gy (VLAwall-63-Gy).
Results
Following re-optimization, mean MDHeart, VHeart-50-Gy and VLAwall-63-Gy values fell by 4.8 Gy and 2.2% and 2.4% absolute respectively. On the basis of associations observed between survival and cardiac irradiation in an independent dataset, the purposefully-achieved reduction in MDHeart is expected to lead to the largest improvement in overall survival. It also led to useful knock-on reductions in many measures of cardiac irradiation including VHeart-50-Gy and VLAwall-63-Gy, providing some insurance against survival being more strongly related to these measures than to MDHeart. The predicted hazard ratio (HR) for death corresponding to the purposefully-achieved mean reduction in MDHeart was 0.806, according to which a randomized trial would require 1140 patients to test improved survival with 0.05 significance and 80% power. In patients whose baseline MDHeart values exceeded the median value in a published series, the average MDHeart reduction was particularly large, 8.8 Gy. The corresponding predicted HR is potentially testable in trials recruiting 359 patients enriched for greater MDHeart values.
Conclusions
Cardiac irradiation in RT of LA-NSCLC can be reduced substantially. Of the measures studied, reduction of MDHeart led to the greatest predicted increase in survival, and to useful knock-on reductions in other cardiac irradiation measures reported to be associated with survival. Potential improvements in survival can be trialled more efficiently in a population enriched for patients with greater baseline MDHeart levels, for whom larger reductions in heart doses can be achieved
Outcomes of COVID-19 related hospitalization among people with HIV in the ISARIC WHO Clinical Characterization Protocol (UK): a prospective observational study
BACKGROUND: Evidence is conflicting about how HIV modulates COVID-19. We compared the presentation characteristics and outcomes of adults with and without HIV who were hospitalized with COVID-19 at 207 centers across the United Kingdom and whose data were prospectively captured by the ISARIC WHO CCP study. METHODS: We used Kaplan-Meier methods and Cox regression to describe the association between HIV status and day-28 mortality, after separate adjustment for sex, ethnicity, age, hospital acquisition of COVID-19 (definite hospital acquisition excluded), presentation date, ten individual comorbidities, and disease severity at presentation (as defined by hypoxia or oxygen therapy). RESULTS: Among 47,592 patients, 122 (0.26%) had confirmed HIV infection and 112/122 (91.8%) had a record of antiretroviral therapy. At presentation, HIV-positive people were younger (median 56 versus 74 years; p<0.001) and had fewer comorbidities, more systemic symptoms and higher lymphocyte counts and C-reactive protein levels. The cumulative day-28 mortality was similar in the HIV-positive vs. HIV-negative groups (26.7% vs. 32.1%; p=0.16), but in those under 60 years of age HIV-positive status was associated with increased mortality (21.3% vs. 9.6%; p<0.001 [log-rank test]). Mortality was higher among people with HIV after adjusting for age (adjusted hazard ratio [aHR] 1.47, 95% confidence interval [CI] 1.01-2.14; p=0.05), and the association persisted after adjusting for the other variables (aHR 1.69; 95% CI 1.15-2.48; p=0.008) and when restricting the analysis to people aged <60 years (aHR 2.87; 95% CI 1.70-4.84; p<0.001). CONCLUSIONS: HIV-positive status was associated with an increased risk of day-28 mortality among patients hospitalized for COVID-19
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