Molecular Hydrogen in Orion as Observed by the Far Ultraviolet Spectroscopic Explorer

Diffuse far-ultraviolet stellar emission scattered by dust grains has been observed in a region near the Orion Nebula. In addition to the scattered stellar continuum, emission and absorption features produced by molecular hydrogen have been identified. In this Letter, we present an analysis of this absorption and fluorescent emission from molecular hydrogen in Orion. We model the spectra obtained with the Far Ultraviolet Spectroscopic Explorer using optical depth templates and a fluorescent emission code. These results are surprising because previous studies have found little ultraviolet absorption from H_2 in this region, and the emission is coming from a seemingly empty part of the nebula. We find that the emission fills in the observed absorption lines where the two overlap. These data support the claim that fluorescent excitation by ultraviolet photons is the primary mechanism producing the near-infrared emission spectrum observed in the outer regions of the Orion Nebula.Comment: 4 pages, 2 figures, uses emulate apj. ApJL - accepte

Characteristics Symptoms of Imminent Eclampsia: A case Referent Study from a Tertiary Hospital in Tanzania

\ud \ud Maternal mortality in developing coun- tries is unacceptably high with eclampsia being con- sistently among the top causes. As yet, primary pre- vention of this complication is not possible since causes of pre-eclampsia are largely unknown and bio- chemical, hematological and radiological markers have proved unsuitable for routine prediction of eclamptic fits. Although headache, visual disturbance, abdominal pain, nausea, and vomiting are routinely elicited when managing pre-eclampsia and have been reported to predict eclamptic fits, the literature at- tempting to characterize them is scanty. We sought to establish characteristics of the prodromal symptoms of eclampsia and compare them with similar symp- toms as experienced by normotensive pregnant women at Muhimbili National Hospital (MNH) in Tanzania. Methods: This study was conducted at MNH in 2010 by enrolling 123 eclamptic and 123 normotensive women. Women in the two groups were interviewed about their experiences and characteristics of head-ache, visual disturbances, abdominal pain, nausea and vomiting using a semi structured questionnaire. The severity, nature and other characteristics of the symptoms were assessed using standard scale/meth- ods and data compared among the two groups. Re- sults: Prodromal symptoms of eclampsia were pre- sent in 90% of eclamptic women. Headache was more frequent among eclamptic women (88%) than the normotensive (43%), p < 0.001). The symptom was also more perceived as severe among eclamptic (46.3%) than the normotensive (5.7%), p < 0.001. The most frequent location for headache was frontal in 65.7% of eclamptic women compared to frontal (41.5%) or generalized (39.6%) for the normotensive. Likewise, visual problems were significantly more frequent among eclamptic women (39%) compared to the normotensive (3%), p < 0.001. Upper abdominal pain was significantly more reported by eclamptic (36%) than normotensive women (0.9%), p = 0.001. The general occurrence of abdominal pain, nausea and vomiting was not significantly different in the two groups. The time lag from development of a sym- ptom to eclamptic fit was up to seven days for most symptoms except visual disturbances of which 98% developed fits within 12 hours. Conclusion: Whereas the prodromal symptoms of eclampsia and similar symptoms in normotensive women were common, the characteristics of headache and visual disturbance differ significantly in the two groups. The knowledge of these differences could be utilized to improve the quality of management of pre-eclamptic women in order to prevent eclampsia.\u

Spitzer Mapping of PAHs and H2 in Photodissociation Regions

The mid-infrared (MIR) spectra of dense photodissociation regions (PDRs) are typically dominated by emission from polycyclic aromatic hydrocarbons (PAHs) and the lowest pure rotational states of molecular hydrogen (H2); two species which are probes of the physical properties of gas and dust in intense UV radiation fields. We utilize the high angular resolution of the Infrared Spectrograph on the Spitzer Space Telescope to construct spectral maps of the PAH and H2 features for three of the best studied PDRs in the galaxy, NGC 7023, NGC 2023 and IC 63. We present spatially resolved maps of the physical properties, including the H2 ortho-to-para ratio, temperature, and G_o/n_H. We also present evidence for PAH dehydrogenation, which may support theories of H2 formation on PAH surfaces, and a detection of preferential self-shielding of ortho-H2. All PDRs studied exhibit average temperatures of ~500 - 800K, warm H2 column densities of ~10^20 cm^-2, G_o/n_H ~ 0.1 - 0.8, and ortho-to-para ratios of ~ 1.8. We find that while the average of each of these properties is consistent with previous single value measurements of these PDRs, when available, the addition of spatial resolution yields a diversity of values with gas temperatures as high as 1500 K, column densities spanning ~ 2 orders of magnitude, and extreme ortho-to-para ratios of 3.Comment: 14 figure

Modelling the lactation curve of dairy cows using the differentials of growth functions

Descriptions of entire lactations were investigated using six mathematical equations. comprising the differentials of four growth functions (logistic. Gompertz, Schumacher and Morgan) and two other equations (Wood and Dijkstra). The data contained monthly milk yield records from 70 first, 70 second and 75 third parity Iranian Holstein cows. Indicators of fit were model behavior, statistical evaluation and biologically meaningful parameter estimates and lactation features. Analysis of variance with equation, parity and their interaction as factors and with cows as replicates was performed to compare goodness of fit of the equations. The interaction of equation and parity was not significant for any statistics, which showed that there vas no tendency For one equation to fit a given parity better than other equations. Although model behaviour analysis showed better performance of growth functions than the Wood and Dijkstra equations in filling the individual lactation curves, statistical evaluation revealed that there was no significant difference between file goodness of fit of the different equations. Evaluation of lactation features showed that the Dijkstra equation was able to estimate the initial milk yield and peak yield more accurately than the other equations. Overall evaluation of the different equations demonstrated the potential of the differentials of simple empirical growth functions used in file Current study as equations for fitting monthly milk records of Holstein dairy cattle

Time-resolved Ultraviolet Spectroscopy of the M-dwarf GJ 876 Exoplanetary System

Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (M4V). Using the COS and STIS spectrographs aboard the Hubble Space Telescope, we have measured the 1150-3140A spectrum of GJ 876. We have reconstructed the stellar HI LyA emission line profile, and find that the integrated LyA flux is roughly equal to the rest of the integrated flux (1150-1210A + 1220-3140A) in the entire ultraviolet bandpass (F(LyA)/F(FUV+NUV) ~0.7). This ratio is ~ 2500x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) > 2000 K). We show the light-curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/quiescent flux ratios >= 10. The strong FUV radiation field of an M-star (and specifically LyA) is important for determining the abundance of O2 -- and the formation of biomarkers -- in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.Comment: 6 pages, 4 figures. ApJL accepte

Far-Ultraviolet Dust Albedo Measurements in the Upper Scorpius Cloud Using the SPINR Sounding Rocket Experiment

The Spectrograph for Photometric Imaging with Numeric Reconstruction (SPINR) sounding rocket experiment was launched on 2000 August 4 to record far-ultraviolet (912-1450 A) spectral and spatial information for the giant reflection nebula in the Upper Scorpius region. The data were divided into three arbitrary bandpasses (912-1029 A, 1030-1200 A, and 1235-1450 A) for which stellar and nebular flux levels were derived. These flux measurements were used to constrain a radiative transfer model and to determine the dust albedo for the Upper Scorpius region. The resulting albedos were 0.28+/-0.07 for the 912-1029 A bandpass, 0.33+/-0.07 for the 1030-1200 A bandpass, and 0.77+/-0.13 for the 1235-1450 A bandpass

Alkali Line Profiles in Degenerate Dwarfs

Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as those of T dwarfs, Na I and K I broadened by molecular hydrogen and helium can come to dominate the entire optical spectrum. Their profiles have been successfully modelled with accurate interaction potentials in the adiabatic theory, computing line profiles from the first few orders of a density expansion of the autocorrelation function. The line shapes in the emergent spectrum also depend on the distribution of absorbers as a function of depth, which can be modelled with improved accuracy by new models of dust condensation and settling. The far red K I wings of the latest T dwarfs still show missing opacity in these models, a phenomenon similar to what has been found for the Na I line profiles observed in extremely cool, metal-rich white dwarfs. We show that the line profile in both cases is strongly determined by multiple-perturber interactions at short distances and can no longer be reproduced by a density expansion, but requires calculation of the full profile in a unified theory. Including such line profiles in stellar atmosphere codes will further improve models for the coolest and densest dwarfs as well as for the deeper atmosphere layers of substellar objects in general.Comment: VI Serbian Conference on Spectral Line Shapes in Astrophysics; to be published by the American Institute of Physics, eds. Milan S. Dimitrijevic and Luka C. Popovic; 6 pages, 6 figure