4,558 research outputs found
Solar Carbon Monoxide, Thermal Profiling, and the Abundances of C, O, and their Isotopes
A solar photospheric "thermal profiling" analysis is presented, exploiting
the infrared rovibrational bands of carbon monoxide (CO) as observed with the
McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above
the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum
intensities and center-limb behavior constrained the temperature profile of the
deep photosphere, while CO center-limb behavior defined the thermal structure
at higher altitudes. The oxygen abundance was self consistently determined from
weak CO absorptions. Our analysis was meant to complement recent studies based
on 3-D convection models which, among other things, have revised the historical
solar oxygen (and carbon) abundance downward by a factor of nearly two;
although in fact our conclusions do not support such a revision. Based on
various considerations, an oxygen abundance of 700+/-100 ppm (parts per million
relative to hydrogen) is recommended; the large uncertainty reflects the model
sensitivity of CO. New solar isotopic ratios also are reported for 13C, 17O,
and 18O.Comment: 90 pages, 19 figures (some with parts "a", "b", etc.); to be
published in the Astrophysical Journal Supplement
The Mg 2 h and k lines in a sample of dMe and dM stars
Both Mg II h and k line fluxes are presented for a sample of 4 dMe and 3 dM stars obtained with the IUE satellite in the long wavelength, low dispersion mode. The observed fluxes are converted to stellar surface flux units and the importance of chromospheric non radiative heating in this sample of M dwarf stars is intercompared. In addition, the net chromospheric radiative losses due to the Ca II H and K lines in those stars in the sample for which calibrated Ca II H and K line data exist are compared. Active region filling factors which likely give rise to the observed optical and ultraviolet chromospheric emission are estimated. The implications of the results for homogeneous, single component stellar model chromospheres analyses are discussed
Recent atmospheric neutrino results from Soudan 2
An updated measurement of the atmospheric nu_mu/nu_e ratio-of-ratios,
0.68+-0.11+-0.06, has been obtained using a 4.6-kty exposure of the Soudan-2
iron tracking calorimeter. The L/E distributions have been analyzed for effects
of nu_mu -> nu_x oscillations, and an allowed region in the Delta m^2 vs. sin^2
2 theta plane has been determined.Comment: 3 pages, 4 figures; presented at TAUP99, the 6th Int. Workshop on
Topics in Astroparticle and Underground Physics, Sept. 6-10, 1999, College de
France, Paris, Franc
Evaluating Possible Heating Mechanisms Using the Transition Region Line Profiles of Late-Type Stars
Our analysis of high-resolution Goddard High-Resolution Spectrograph (GHRS) spectra of late-type stars shows that the Si IV and C IV lines formed near 10(exp 5) K can be decomposed into the sum of two Gaussians, a broad component and a narrow component. We find that the flux contribution of the broad components is correlated with both the C IV and X-ray surface fluxes. For main-sequence stars, the widths of the narrow components suggest subsonic nonthermal velocities, and there appears to be a tight correlation between these nonthermal velocities and stellar surface gravity [xi(sub nc) varies as g(sup (-.68 +/-.07))]. For evolved stars with lower surface gravities, the nonthermal velocities suggested by the narrow components are at or just above the sound speed. Nonthermal velocities computed from the widths of the broad components are always highly supersonic. We propose that the broad components are diagnostics for microflare heating. Turbulent dissipation and Alfven waves are both viable candidates for the narrow component heating mechanism. A solar analog for the broad components might be the 'explosive events' detected by the High-Resolution Telescope and Spectrograph (HRTS) experiment. The broad component we observe for the Si IV lambda 1394 line of alpha Cen A, a star that is nearly identical to the Sun, has a FWHM of 109 +/- 10 km/s and is blueshifted by 9 +/- 3 km/s relative to the narrow component. Both of these properties are consistent with the properties of the solar explosive events. However, the alpha Cen A broad component accounts for 25% +/- 4% of the total Si IV line flux, while solar explosive events are currently thought to account for no more than 5% of the Sun's total transition region emission. This discrepancy must be resolved before the connection between broad components and explosive events can be positively established. In addition to our analysis of the Si IV and C IV lines of many stars, we also provide a more thorough analysis of all of the available GHRS data for alpha Cen A (G2 V) and alpha Cen B (K1 V). We find that the transition region lines of both stars have redshifts almost identical to those observed on the Sun: showing an increase with line formation temperature up to about log T = 5.2 and then a rapid decrease. Using the O IV] lines as density diagnostics, we compute electron densities of log n(sub e) = 9.65 +/- 0.20 and log n(sub e) = 9.50 +/- 0.30 for alpha Cen A and alpha Cen B, respectively
Relationship between X-ray and ultraviolet emission of flares from dMe stars observed by XMM-Newton
We present simultaneous ultraviolet and X-ray observations of the dMe-type
flaring stars AT Mic, AU Mic, EV Lac, UV Cet and YZ CMi obtained with the
XMM-Newton observatory. During 40 hours of simultaneous observation we identify
13 flares which occurred in both wave bands. For the first time, a correlation
between X-ray and ultraviolet flux for stellar flares has been observed. We
find power-law relationships between these two wavelength bands for the flare
luminosity increase, as well as for flare energies, with power-law exponents
between 1 and 2. We also observe a correlation between the ultraviolet flare
energy and the X-ray luminosity increase, which is in agreement with the
Neupert effect and demonstrates that chromospheric evaporation is taking place.Comment: 8 pages, 4 figures, 3 tables, accepted by A&A (30 Sept. 2004
Informal ActionâAdjudicationâRule Making: Some Recent Developments in Federal Administrative Law
Direct energy consumption of ICT hardware is only âhalf the story.â In order to get the âwhole story,â energy consumption during the entire life cycle has to be taken into account. This chapter is a first step toward a more comprehensive picture, showing the âgrey energyâ (i.e., the overall energy requirements) as well as the releases (into air, water, and soil) during the entire life cycle of exemplary ICT hardware devices by applying the life cycle assessment method. The examples calculated show that a focus on direct energy consumption alone fails to take account of relevant parts of the total energy consumption of ICT hardware as well as the relevance of the production phase. As a general tendency, the production phase is more and more important the smaller (and the more energy-efficient) the devices are. When in use, a tablet computer is much more energy-efficient than a desktop computer system with its various components, so its production phase has a much greater relative importance. Accordingly, the impacts due to data transfer when using Internet services are also increasingly relevant the smaller the end-user device is, reaching up to more than 90Â % of the overall impact when using a tablet computer.QC 20140825</p
Animal Defenses against Infectious Agents: Is Damage Control More Important Than Pathogen Control?
The ability of hosts to withstand a given number of pathogens is a critical component of health. Now playing catch-up with plant biologists, animal biologists are starting to formally separate this form of defense from classical resistance
Evaluation of White Clover Breeding Lines in the Australasian Region
The accuracy of predicting breeding line performance across target environments is a significant criterion in the development of cultivars with broad or specific adaptation. This paper characterises the type and magnitude of genotype-by-environment (GE) interactions estimated from a multi-site white clover (Trifolium repens L.) breeding line evaluation trial conducted across sites in New Zealand and Australia
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Red cell differential width (RDW) as a predictor of survival outcomes with palliative and adjuvant chemotherapy for metastatic penile cancer.
PURPOSE: Red cell distribution width (RDW) measures red cells' size variability. Metastatic penile cancer displays poor chemotherapy response. As no validated prognostic predictor exists, we investigated whether RDW correlates independently with survival outcomes in metastatic penile cancer treated by chemotherapy. METHODS: Electronic chemotherapy files of patients with metastatic penile cancer (M1 or N3) from a large academic supra-regional centre were retrospectively analysed between 2005 and 2018. Patients were stratified into RDWâ>â13.9% andâ<â13.9%, as per published data on RDW in renal cell carcinoma. Survival time was calculated from the date of chemotherapy initiation until the date of death. RESULTS: 58 patients were analysed. The RDW-high group (nâ=â31) had a poorer survival than the RDW-low group (nâ=â27). Median overall survival (mOS) in all patients was 19.0Â months (95% CI 13.1-24.9). mOS for RDW-high was 15.0Â months (95% CI 10.1-19.9) and 37.0Â months (95% CI 32.3-43.1) for RDW-low. Kaplan-Meier curves showed a clear disparity in survival (log rank pâ=â0.025). Cox proportional hazard ratio for death, corrected for T-stage, grade, age and deprivation score was 0.43 (pâ=â0.04). Sub-analysis of the M1 patients showed mOS in RDW-high of 17Â m (95% CI 11.6-22.4) vs. NR; HR for death of 0.42. N3 patients' mOS in RDW-high cohort was 30Â months (95% CI 4.5-55.9) vs. 13Â months (95% CI 1.8-24.2) in RDW-low; HR for death was 0.30. CONCLUSION: RDW correlates independently with survival outcomes in metastatic penile cancer and may act as a potential predictor of survival outcomes for patients with metastatic penile cancer receiving chemotherapy
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