Constraining the extra heating of the Diffuse Ionized Gas in the Milky Way

The detailed observations of the diffuse ionized gas through the emission lines H$\alpha$, [NII], and [SII] in the Perseus Arm of our Galaxy by the Wisconsin H$\alpha$ Mapper (WHAM)--survey challenge photoionization models. They have to explain the observed rise in the line ratios [NII]/H$\alpha$ and [SII]/H$\alpha$. The models described here consider for the first time the detailed observational geometry toward the Perseus Arm. The models address the vertical variation of the line ratios up to height of 2 kpc above the midplane. The rising trends of the line ratios are matched. The increase in the line ratios is reflected in a rise of the temperature of the gas layer. This is due to the progressive hardening of the radiation going through the gas. However an extra heating above photoionization is needed to explain the absolute values. Two different extra heating rates are investigated which are proportional to $n^0$ and $n^1$. The models show that a combination of both are best to explain the data, where the extra heating independent of density is dominant for z $>$ 0.8 kpc.Comment: accepted for publication in Ap

Sensitivity of PDR Calculations to Microphysical Details

Our understanding of physical processes in Photodissociation regions or Photon Dominated Regions (PDRs) largely depends on the ability of spectral synthesis codes to reproduce the observed infrared emission-line spectrum. In this paper, we explore the sensitivity of a single PDR model to microphysical details. Our calculations use the Cloudy spectral synthesis code, recently modified to include a wealth of PDR physical processes. We show how the chemical/thermal structure of a PDR, along with the calculated spectrum, changes when the treatment of physical processes such as grain physics and atomic/molecular rates are varied. We find a significant variation in the intensities of PDR emission lines, depending on different treatments of the grain physics. We also show how different combinations of the cosmic-ray ionization rate, inclusion of grain-atom/ion charge transfer, and the grain size distribution can lead to very similar results for the chemical structure. Additionally, our results show the utility of Cloudy for the spectral modeling of molecular environments.Comment: 36 pages, 17 figures, accepted for publication in Ap

X-Ray Polarization of Solar Flares Measured with Rhessi

The degree of linear polarization in solar flares has not yet been precisely determined despite multiple attempts to measure it with different missions. The high energy range in particular has very rarely been explored, due to its greater instrumental difficulties. We approached the subject using the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite to study 6 X-class and 1 M-class flares in the energy range between 100 keV and 350 keV. Using RHESSI as a polarimeter requires the application of strict cuts to the event list in order to extract those photons that are Compton scattered between two detectors. Our measurements show polarization values between 2% and 54%, with errors ranging from 10% to 26% in 1 sigma level. In view of the large uncertainties in both the magnitude and direction of the polarization vector, the results can only reject source models with extreme properties.Comment: 26 pages, 11 figures, accepted for publication by Solar Physic

Adaptive model-driven user interface development systems

Adaptive user interfaces (UIs) were introduced to address some of the usability problems that plague many software applications. Model-driven engineering formed the basis for most of the systems targeting the development of such UIs. An overview of these systems is presented and a set of criteria is established to evaluate the strengths and shortcomings of the state-of-the-art, which is categorized under architectures, techniques, and tools. A summary of the evaluation is presented in tables that visually illustrate the fulfillment of each criterion by each system. The evaluation identified several gaps in the existing art and highlighted the areas of promising improvement

Assessing survival in widowers, and controls -A nationwide, six- to nine-year follow-up

To access full text version of this article. Please click on the hyperlink "View/open" at the bottom of this pageThe aim of this study was to assess if widowers had an increased mortality rate during the first 6 to 9 years after the death of their wife, compared initially to an age-matched control group and also compared to the general population of Iceland. The study base was comprised of all 371 men born in 1924-1969 who were widowed in Iceland in 1999-2001 and 357 controls, married men, who were matched by age and residence.The widowers and controls were followed through the years 2002-2007 using information from Statistics Iceland. Mortality rates were compared between the groups and also with the general population. The mortality rate comparisons were: study group vs. control group, on the one hand, and study group vs. general population on the other. Causes of death were also compared between widowers and their wives. A statistically significant increase in mortality in the widowers' group, compared to controls, was observed.Lifestyle-related factors could not be excluded as contributing to cause of death in these cases. Being a widower was related to an increased risk of death for at least 9 years after the death of their wife.Landspitali - National University Hospital in Reykjavik Iceland, Rannis, the Icelandic Centre for Research (provides assistance to Icelandic science & technology, Reykjavik, Iceland), Utfararstofa Islands (a funeral home, Reykjavik, Iceland), Swedish Cancer Society (Cancerfonden), Styrktarsjodur Lifsins samtaka um liknarmedferd (Palliative Care Association, Iceland), Utfarastofa Kirkjugardanna (a funeral home, Reykjavik, Iceland

Solar soft X-rays and solar activity

Soft solar X-rays (8 ⩽ gl ⩽ 12 Å) were observed from OSO-III. An analysis of the X-ray enhancements associated with 165 solar flares revealed that there is a tendency for a weak soft X-ray enhancement to precede the cm- λ burst and H α flare. The peak soft X-ray flux follows the cm- λ peak by about 4 min, on the average. Additionally, it was found that flare-rich active centers tend to produce flares which are stronger X-ray and cm- λ emitters than are flares which take place in flare-poor active centers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43754/1/11207_2004_Article_BF00155382.pd