Electron-impact fragmentation of Cl 2 Collins, G. F.; Pegg, D. J.; Fritioff, K. ...
Physical review. A, Atomic, molecular, and optical physics,
10/2005, Letnik:
72, Številka:
4
Journal Article
A merged beam technique has been used to investigate the fragmentation of the Cl-2(-) ion in collisions with electrons over an energy range of 0-200 eV. We have measured absolute cross sections for ...detachment, detachment plus dissociation and dissociation processes. Over the energy range studied, the dominant breakup mechanism is dissociation. Dissociation is relatively enhanced in the e(-)+Cl-2(-) collision system due to the suppression of the normally dominant detachment process, as a result of the large difference between the equilibrium internuclear distances of the Cl-2 and Cl-2(-) ground state potential curves. A prominent structure is observed just above the threshold in the Cl-+Cl+e(-) dissociation channel. It is proposed that the structure is a resonance associated with production and rapid decay of an excited state of the doubly charged Cl-2(-) ion. A plausible mechanism for production of the di-anionic state based on an excitation plus capture process is suggested.
Environmental chamber exposure and bronchoalveolar lavage (BAL) were used to study the dose-response relationship between short-term exposure to sulfur dioxide (SO₂) and inflammatory reactions in the ...human lung as reflected in BAL fluid. Healthy subjects were exposed to 10, 13, 20, or 30 mg/m³ for 20 min. BAL was performed several weeks preexposure and 24 h postexposure. Mast cells, lymphocytes, lysozyme positive macrophages, and the total number of macrophages were significantly increased after SO₂ exposure. A dose-dependent increase in the cell response in BAL fluid was observed after exposure to 10—20 mg/m³, but no further increase was detected after 30 mg/m³. Inflammatory cell response was found in BAL fluid at SO₂ levels that occur in industrial indoor environments worldwide, and cell response to SO₂ was also seen below the short-term exposure limit of Sweden and many other countries (13 mg/m³).
We present the detection of extended (~30 kpc^2) dust emission in the tidal \hi\ arm near NGC 3077 (member of the M\,81 triplet) using SPIRE on board Herschel. Dust emission in the tidal arm is ...typically detected where the \hi\ column densities are >10^21 cm^-2. The SPIRE band ratios show that the dust in the tidal arm is significantly colder (~13 K) than in NGC 3077 itself (~31 K), consistent with the lower radiation field in the tidal arm. The total dust mass in the tidal arm is ~1.8 x 10^6 M_sun (assuming beta=2), i.e. substantially larger than the dust mass associated with NGC 3077 (~2 x 10^5 M_sun). Where dust is detected, the dust-to-gas ratio is 6+/-3 x 10^-3, consistent within the uncertainties with what is found in NGC 3077 and nearby spiral galaxies with Galactic metallicities. The faint HII regions in the tidal arm can not be responsible for the detected enriched material and are not the main source of the dust heating in the tidal arm. We conclude that the interstellar medium (atomic HI, molecules and dust) in this tidal feature was pre-enriched and stripped off NGC 3077 during its recent interaction (~3 x 10^8 yr ago) with M 82 and M 81. This implies that interaction can efficiently remove heavy elements and enriched material (dust, molecular gas) from galaxies. As interactions were more frequent at large lookback times, it is conceivable that they could substantially contribute (along with galactic outflows) to the enrichment of the intergalactic medium.
The Small Magellanic Cloud (SMC) provides a unique laboratory for the study of the lifecycle of dust given its low metallicity (~1/5 solar) and relative proximity (~60 kpc). This motivated the ...SAGE-SMC (Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low Metallicity Small Magellanic Cloud) Spitzer Legacy program with the specific goals of studying the amount and type of dust in the present interstellar medium, the sources of dust in the winds of evolved stars, and how much dust is consumed in star formation. This program mapped the full SMC (30 sq. deg.) including the Body, Wing, and Tail in 7 bands from 3.6 to 160 micron using the IRAC and MIPS instruments on the Spitzer Space Telescope. The data were reduced, mosaicked, and the point sources measured using customized routines specific for large surveys. We have made the resulting mosaics and point source catalogs available to the community. The infrared colors of the SMC are compared to those of other nearby galaxies and the 8 micron/24 micron ratio is somewhat lower and the 70 micron/160 micron ratio is somewhat higher than the average. The global infrared spectral energy distribution shows that the SMC has ~3X lower aromatic emission/PAH (polycyclic aromatic hydrocarbon) abundances compared to most nearby galaxies. Infrared color-magnitude diagrams are given illustrating the distribution of different asymptotic giant branch stars and the locations of young stellar objects. Finally, the average spectral energy distribution (SED) of HII/star formation regions is compared to the equivalent Large Magellanic Cloud average HII/star formation region SED. These preliminary results are expanded in detail in companion papers.
Astrophys.J.632:L103-L106,2005 We present infrared observations of the young, oxygen-rich supernova remnant
1E 0102.2-7219 (E0102) in the Small Magellanic Cloud, obtained with the Spitzer
Space ...Telescope. The remnant is detected at 24 um but not at 8 or 70 um and has
a filled morphology with two prominent filaments. We find evidence for the
existence of up to 8x10^-4 Msolar of hot dust (T~120 K) associated with the
remnant. Most of the hot dust is located in the central region of E0102 which
appears significantly enhanced in infrared and radio continuum emission
relative to the X--ray emission. Even if all of the hot dust was formed in the
explosion of E0102, the estimated mass of dust is at least 100 times lower that
what is predicted by some recent theoretical models.
Astrophys.J.655:212-232,2007 We present the initial results from the Spitzer Survey of the Small
Magellanic Cloud (S3MC), which imaged the star-forming body of the Small
Magellanic Cloud (SMC) in all ...seven MIPS and IRAC wavebands. We find that the
F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and
takes a wide range of values that are unrelated to metallicity but
anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that
photodestruction is primarily responsible for the low abundance of PAHs
observed in star-forming low-metallicity galaxies. We use the S3MC images to
compile a photometric catalog of ~400,000 mid- and far-infrared point sources
in the SMC. The sources detected at the longest wavelengths fall into four main
categories: 1) bright 5.8 um sources with very faint optical counterparts and
very red mid-infrared colors (5.8-8.0>1.2), which we identify as YSOs. 2)
Bright mid-infrared sources with mildly red colors (0.16<5.8-8.0<0.6),
identified as carbon stars. 3) Bright mid-infrared sources with neutral colors
and bright optical counterparts, corresponding to oxygen-rich evolved stars.
And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This
excess is reminiscent of debris disks, and is detected in only a small fraction
of these stars (<5%). The majority of the brightest infrared point sources in
the SMC fall into groups one to three. We use this photometric information to
produce a catalog of 282 bright YSOs in the SMC with a very low level of
contamination (~7%).
On 2 earlier occasions, in 2002 and 2003, the Swedish Medical Products Agency (MPA) and the Swedish Reference Group for Antiviral Therapy (RAV) have jointly publicized recommendations for the ...treatment of HIV infection. A working group from the same expert team that produced the 2002 report has now revised the text again. Since the publication of the last treatment recommendations, 4 new medicines have become available: emtricitabine, atazanavir, fosamprenavir, and enfuvirtid. The last-mentioned belongs to a new class of HIV medications called fusion inhibitors (Box 1). It is likely that tipranavir will also be on the market soon. Simultaneously, the drug zalcitabin has been deregistered. The following updated recommendations parallel the earlier ones, but increased knowledge allows us to be more specific in our recommendations. Thus, it is now suggested that the initial treatment for HIV infection consist of 2 nucleoside reverse transcriptase inhibitors (NRTIs) and 1 non-nucleoside reverse transcriptase inhibitor (NNRTI); or 2 NRTIs and 1 protease inhibitor (PI). In the group of the NRTIs, stavudine is no longer recommended for this purpose. In the NNRTI group, efavirenz should be preferred to nevirapine, except under special circumstances. Finally, PIs ought to be boosted with ritonavir (PI/r). Also new are recommendations regarding treatment choices for patients co-infected with hepatitis B virus (HBV) or tuberculosis (TB). As in the case of the previous publication, recommendations are evidence-graded in accordance with the Oxford Centre for Evidence Based Medicine, 2001 (see http://www.cebm.net/levels_of_evidence.asp#levels), and have been supplemented with references to newly-added sections and data not referred to in earlier background documentation.
We present infrared observations of the young, oxygen-rich supernova remnant 1E 0102.2-7219 (E0102) in the Small Magellanic Cloud, obtained with the Spitzer Space Telescope. The remnant is detected ...at 24 um but not at 8 or 70 um and has a filled morphology with two prominent filaments. We find evidence for the existence of up to 8x10^-4 Msolar of hot dust (T~120 K) associated with the remnant. Most of the hot dust is located in the central region of E0102 which appears significantly enhanced in infrared and radio continuum emission relative to the X--ray emission. Even if all of the hot dust was formed in the explosion of E0102, the estimated mass of dust is at least 100 times lower that what is predicted by some recent theoretical models.
We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S3MC), which imaged the star-forming body of the Small Magellanic Cloud (SMC) in all seven MIPS and IRAC ...wavebands. We find that the F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and takes a wide range of values that are unrelated to metallicity but anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that photodestruction is primarily responsible for the low abundance of PAHs observed in star-forming low-metallicity galaxies. We use the S3MC images to compile a photometric catalog of ~400,000 mid- and far-infrared point sources in the SMC. The sources detected at the longest wavelengths fall into four main categories: 1) bright 5.8 um sources with very faint optical counterparts and very red mid-infrared colors (5.8-8.0>1.2), which we identify as YSOs. 2) Bright mid-infrared sources with mildly red colors (0.16<5.8-8.0<0.6), identified as carbon stars. 3) Bright mid-infrared sources with neutral colors and bright optical counterparts, corresponding to oxygen-rich evolved stars. And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This excess is reminiscent of debris disks, and is detected in only a small fraction of these stars (<5%). The majority of the brightest infrared point sources in the SMC fall into groups one to three. We use this photometric information to produce a catalog of 282 bright YSOs in the SMC with a very low level of contamination (~7%).
Francisella tularensis is the etiological agent of tularemia, a serious disease in several Northern hemisphere countries. The organism has fastidious growth requirements and is very poorly understood ...at the genetic and molecular levels. Given the lack of data on this organism, we undertook the sample sequencing of its genome. A random library of DNA fragments from a highly virulent strain (Schu 4) of F. tularensis was constructed and the nucleotide sequences of 13,904 cloned fragments were determined and assembled into 353 contigs. A total of 1.83 Mb of nucleotide sequence was obtained that had a G+C content of 33.2%. Genes located on plasmids pOM1 and pNFL10, which had been previously isolated from low virulence strains of F. tularensis, were absent but all of the other known F. tularensis genes were represented in the assembled data. F. tularensis Schu4 was able to grow in the absence of aromatic amino acids and orthologues of genes which could encode enzymes in the shikimate pathway in other bacteria were identified in the assembled data. Genes that could encode all of the enzymes in the purine biosynthetic and most of the en- zymes in the purine salvage pathways were also identified. This data will be used to develop defined rationally attenuated mutants of F. tularensis, which could be used as replacements for the existing genetically undefined live vaccine strain.
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