Cold atomic hydrogen in the inner galaxy

The VLA is used to measure 21 cm absorption in directions with the absolute value of b less than 1 deg., the absolute value of 1 less than 25 deg. to probe the cool atomic gas in the inner galaxy. Abundant H I absorption is detected; typical lines are deep and narrow, sometimes blending in velocity with adjacent features. Unlike 21 cm emission not all allowed velocities are covered: large portions of the l-v diagram are optically thin. Although not similar to H I emission, the absorption shows a striking correspondence with CO emission in the inner galaxy: essentially every strong feature detected in one survey is seen in the other. The provisional conclusion is that in the inner galaxy most cool atomic gas is associated with molecular cloud complexes. There are few or no cold atomic clouds devoid of molecules in the inner galaxy, although these are common in the outer galaxy

Admissions Criteria and Academic Performance in the AFIT Graduate Cost Analysis Program

This research examined the admissions criteria used by the Air Force Institute of Technology (AFIT) to determine academic eligibility for the in-residence Graduate Cost Analysis (GCA) master\u27s degree program. Using the cumulative graduate grade point average earned at AFIT as the measure of academic performance, comparisons were made between the predictive capability of the current criteria and other potential factors. Factors considered included scores from the Graduate Record Examination (GRE) and the Graduate Management Admissions Test (GMAT), undergraduate cumulative and math grade point averages, applicant\u27s age and gender, ratings of the undergraduate school\u27s admissions competitiveness, undergraduate degree type, and various measures of the applicant\u27s time in military service. Predictive models were developed using stepwise linear regression. This research found the GMAT is more useful than the GRE as a predictor of GGPA in the AFIT GCA program. The optimal model accounted for up to 45% of the variance in GGPA, and included the GMAT Verbal score, UGPA, and a dichotomous indicator of prior service as a member of the military enlisted corps

The Search for Million Degree Gas Through The NVII Hyperfine Line

Gas in the million degree range occurs in a variety of astronomical environments, and it may be the main component of the elusive missing baryons at low redshift. The NVII ion is found in this material and it has a hyperfine spin-flip transition with a rest frequency of 53.042 GHz, which can be observed for z > 0.1, when it is shifted into a suitably transparent radio band. We used the 42-48 GHz spectrometer on the Green Bank Telescope to search for both emission and absorption from this NVII transmission. For absorption studies, 3C273, 3C 279, 3C 345, and 4C+39.25 were observed but no feature were seen above the 5 sigma level. For emission line studies, we observed Abell 1835, Abell 2390 and the star-forming galaxy PKS 1345+12, but no features were seen exceeding 5 sigma. We examine whether the strongest emission feature, in Abell 2390 (3.7 sigma), and the strongest absorption feature, toward 4C+39.25 (3.8 sigma), might be expected from theoretical models. The emission feature would require ~1E10 Msolar of 1E6 K gas, which is inconsistent with X-ray limits for the O VII Kalpha line, so it is unlikely to be real. The NVII absorption feature requires a NVII column of 6E16 cm^-2, higher than model predictions by at least an order of magnitude, which makes it inconsistent with model expectations. The individual observations were less than 1 hr in length, so for lengthy observations, we show that NVII absorption line observations can begin to be useful in in the search for hot intergalactic gas.Comment: 27 total pages; 16 figures; Accepted for publication in The Astrophysical Journa

When a 520 million-year-old Chengjiang fossil meets a modern micro-CT - a case study

The 520 million-year-old Chengjiang biota of China (UNESCO World Heritage) presents the earliest known evidence of the so-called Cambrian Explosion. Studies, however, have mainly been limited to the information exposed on the surface of the slabs. Thus far, structures preserved inside the slabs were accessed by careful removal of the matrix, in many cases with the unfortunate sacrifice of some "less important" structures, which destroys elements of exceptionally preserved specimens. Here, we show for the first time that microtomography (micro-CT) can reveal structures situated inside a Chengjiang fossil slab without causing any damage. In the present study a trilobitomorph arthropod (Xandarella spectaculum) can be reliably identified only with the application of micro-CT. We propose that this technique is an important tool for studying three-dimensionally preserved Chengjiang fossils and, most likely, also those from other biota with a comparable type of preservation, specifically similar iron concentrations

Neighborhood and community interactions determine the spatial pattern of tropical tree seedling survival

Factors affecting survival and recruitment of 3531 individually mapped seedlings of Myristicaceae were examined over three years in a highly diverse neotropical rain forest, at spatial scales of 1–9 m and 25 ha. We found convincing evidence of a community compensatory trend (CCT) in seedling survival (i.e., more abundant species had higher seedling mortality at the 25-ha scale), which suggests that density-dependent mortality may contribute to the spatial dynamics of seedling recruitment. Unlike previous studies, we demonstrate that the CCT was not caused by differences in microhabitat preferences or life history strategy among the study species. In local neighborhood analyses, the spatial autocorrelation of seedling survival was important at small spatial scales (1–5 m) but decayed rapidly with increasing distance. Relative seedling height had the greatest effect on seedling survival. Conspecific seedling density had a more negative effect on survival than heterospecific seedling density and was stronger and extended farther in rare species than in common species. Taken together, the CCT and neighborhood analyses suggest that seedling mortality is coupled more strongly to the landscape-scale abundance of conspecific large trees in common species and the local density of conspecific seedlings in rare species. We conclude that negative density dependence could promote species coexistence in this rain forest community but that the scale dependence of interactions differs between rare and common species

The CO-H2 conversion factor of diffuse ISM: Bright 12CO emission also traces diffuse gas

We show that the XCO factor, which converts the CO luminosity into the column density of molecular hydrogen has similar values for dense, fully molecular gas and for diffuse, partially molecular gas. We discuss the reasons of this coincidence and the consequences for the understanding of the interstellar medium.Comment: 5 pages, 1 PostScript figure. To be published in the proceedings of the Zermatt 2010 conference: "Conditions and impact of star formation: New results with Herschel and beyond". Uses EAS LaTeX macro

Platinum-group element remobilisation and concentration in the Cliff chromitites of the Shetland Ophiolite Complex, Scotland

ABSTRACTThe ~492 Ma Shetland Ophiolite Complex contains an extensive mantle section, within which numerous podiform chromitite bodies formed during melt percolation in a supra-subduction zone setting. One of the Shetland ophiolite chromitite localities has an unusual style of platinum-group element (PGE) mineralization. Specifically, the Cliff chromitite suite has relatively high (&gt;250 ppm) Pt plus Pd, compared to other chromitites in the Shetland Ophiolite Complex. In this study, we apply petrographic observation, mineral chemistry and novel X-ray microtomography data to elucidate the petrogenesis of PGE-bearing phases at Cliff. The combined datasets reveal that the PGE at Cliff have probably been fractionated by an As-rich fluid, concentrating Pt and Ir into visible (0.1–1 µm) platinum-group minerals (PGM) such as sperrylite and irarsite, respectively. The high (&gt;1 ppm) bulk-rock concentrations of the other PGE (e.g. Os) in the Cliff chromitites suggests the presence of abundant fine-grained unidentified PGM in the serpentinized groundmass. The spatial association of arsenide phases and PGM with alteration rims on Cr-spinel grains suggests that the high Pt and Pd abundances at Cliff result from a late-stage low-temperature (e.g. 200–300°C) hydrothermal event. This conclusion highlights the potential effects that secondary alteration processes can have on modifying and upgrading the tenor of PGE deposits.</jats:p

The Inter-Rater Consistency of Clinician Ratings of Posttraumatic Stress Disorder (PTSD) Therapy Content.

Effective communication between clinicians is essential for the success of mental health interventions in multidisciplinary contexts. This relies on a shared understanding of concepts, diagnoses and treatments. A major assumption of clinicians when discussing psychological treatments with each other is that both parties have a shared understanding of the theory, rationale and application of the respective technique. We aimed to determine to what extent there is inter-rater agreement between clinicians in describing the content of group therapy sessions. Pairs of clinicians, drawn from a large multidisciplinary team (13), were asked to provide ratings of the therapeutic content and emphasis of N = 154 group therapy sessions conducted during an intensive residential treatment program for post-traumatic stress disorder (PTSD). In most therapeutic content domains there was a moderate level of agreement between clinicians regarding session content (Cohen's Kappa 0.4 to 0.6), suggesting that clinicians have a broad shared understanding of therapeutic content, but that there are also frequent discordant understandings. The implications of these findings on multidisciplinary team communication, patient care and clinical handovers are discussed and directions for further research are outlined