Structure prediction based on ab initio simulated annealing for boron nitride

Possible crystalline modifications of chemical compounds at low temperatures correspond to local minima of the energy landscape. Determining these minima via simulated annealing is one method for the prediction of crystal structures, where the number of atoms per unit cell is the only information used. It is demonstrated that this method can be applied to covalent systems, at the example of boron nitride, using ab initio energies in all stages of the optimization, i.e. both during the global search and the subsequent local optimization. Ten low lying structure candidates are presented, including both layered structures and 3d-network structures such as the wurtzite and zinc blende types, as well as a structure corresponding to the beta-BeO type

Oral diabetes medication monotherapy and short-term mortality in individuals with type 2 diabetes and coronary artery disease

Objective To determine whether sulfonylurea use, compared with non-sulfonylurea oral diabetes medication use, was associated with 2-year mortality in individuals with well-controlled diabetes and coronary artery disease (CAD). Research design and methods We studied 5352 US veterans with type 2 diabetes, obstructive CAD on coronary angiography, hemoglobin A1c ≤7.5% at the time of catheterization, and taking zero or one oral diabetes medication (categorized as no medications, non-sulfonylurea medication, or sulfonylurea). We estimated the association between medication category and 2-year mortality using inverse probability of treatment-weighted (IPW) standardized mortality differences and IPW multivariable Cox proportional hazards regression. Results 49%, 35%, and 16% of the participants were on no diabetes medications, non-sulfonylurea medications, and sulfonylureas, respectively. In individuals on no medications, non-sulfonylurea medications, and sulfonylureas, the unadjusted mortality rates were 6.6%, 5.2%, and 11.9%, respectively, and the IPW-standardized mortality rates were 5.9%, 6.5%, and 9.7%, respectively. The standardized absolute 2-year mortality difference between non-sulfonylurea and sulfonylurea groups was 3.2% (95% CI 0.7 to 5.7) (p=0.01). In Cox proportional hazards models, the point estimate suggested that sulfonylurea use might be associated with greater hazard of mortality than non-sulfonylurea medication use, but this finding was not statistically significant (HR 1.38 (95% CI 1.00 to 1.93), p=0.05). We did not observe significant mortality differences between individuals on no diabetes medications and non-sulfonylurea users. Conclusions Sulfonylurea use was common (nearly one-third of those taking medications) and was associated with increased 2-year mortality in individuals with obstructive CAD. The significance of the association between sulfonylurea use and mortality was attenuated in fully adjusted survival models. Caution with sulfonylurea use may be warranted for patients with well-controlled diabetes and CAD, and metformin or newer diabetes medications with cardiovascular safety data could be considered as alternatives when individualizing therapy

Expanded Sampling Across Ontogeny in <I>Deltasuchus motherali</I> (Neosuchia, Crocodyliformes)

A revised diagnosis of this species, describing the new material and discussing incidents of apparent ontogenetic variation across the sampled population. The results of the ensuing phylogenetic analyses both situate Deltasuchus within an endemic clade of Appalachian crocodyliforms, separate and diagnosable from goniopholidids and pholidosaurs. This title is also available as Open Access on Cambridge Core

Decolonising qualitative research with respectful, reciprocal, and responsible research practice: A narrative review of the application of Yarning method in qualitative Aboriginal and Torres Strait Islander health research

Background Indigenous academics have advocated for the use and validity of Indigenous methodologies and methods to centre Indigenous ways of knowing, being and doing in research. Yarning is the most reported Indigenous method used in Aboriginal and Torres Strait Islander qualitative health research. Despite this, there has been no critical analysis of how Yarning methods are applied to research conduct and particularly how they privilege Indigenous peoples. Objective To investigate how researchers are applying Yarning method to health research and examine the role of Aboriginal and Torres Strait Islander researchers in the Yarning process as reported in health publications. Design Narrative review of qualitative studies. Data sources Lowitja Institute LitSearch January 2008 to December 2021 to access all literature reporting on Aboriginal and Torres Strait Islander health research in the PubMed database. A subset of extracted data was used for this review to focus on qualitative publications that reported using Yarning methods. Methods Thematic analysis was conducted using hybrid of inductive and deductive coding. Initial analysis involved independent coding by two authors, with checking by a third member. Once codes were developed and agreed, the remaining publications were coded and checked by a third team member. Results Forty-six publications were included for review. Yarning was considered a culturally safe data collection process that privileges Indigenous knowledge systems. Details of the Yarning processes and team positioning were vague. Some publications offered a more comprehensive description of the research team, positioning and demonstrated reflexive practice. Training and experience in both qualitative and Indigenous methods were often not reported. Only 11 publications reported being Aboriginal and/or Torres Strait Islander led. Half the publications reported Aboriginal and Torres Strait Islander involvement in data collection, and 24 reported involvement in analysis. Details regarding the role and involvement of study reference or advisory groups were limited. Conclusion Aboriginal and Torres Strait Islander people should be at the forefront of Indigenous research. While Yarning method has been identified as a legitimate research method to decolonising research practice, it must be followed and reported accurately. Researcher reflexivity and positioning, and Aboriginal and Torres Strait Islander ownership, stewardship and custodianship of data collected were significantly under detailed in the publications included in our review. Journals and other establishments should review their processes to ensure necessary details are reported in publications and engage Indigenous Editors and peer reviewers to uphold respectful, reciprocal, responsible and ethical research practice

Correlation Function of Superclusters of Galaxies

We present a study of the two-point correlation function of superclusters of galaxies. The largest catalogs are used. The results show negligible correlation less than 0.1-0.2 for separations up to 500-600 h^{-1} Mpc. Small correlations are obtained using various estimates and samples. Seemingly there are no structures of superclusters of galaxies.Comment: 19 pages, 3 figures, 4 tables. To appear in 1998 ApJ, 506, No. 2 (Oct 20

An Observational Limit on the Dwarf Galaxy Population of the Local Group

We present the results of an all-sky, deep optical survey for faint Local Group dwarf galaxies. Candidate objects were selected from the second Palomar survey (POSS-II) and ESO/SRC survey plates and follow-up observations performed to determine whether they were indeed overlooked members of the Local Group. Only two galaxies (Antlia and Cetus) were discovered this way out of 206 candidates. Based on internal and external comparisons, we estimate that our visual survey is more than 77% complete for objects larger than one arc minute in size and with a surface brightness greater than an extremely faint limit over the 72% of the sky not obstructed by the Milky Way. Our limit of sensitivity cannot be calculated exactly, but is certainly fainter than 25 magnitudes per square arc second in R, probably 25.5 and possibly approaching 26. We conclude that there are at most one or two Local Group dwarf galaxies fitting our observational criteria still undiscovered in the clear part of the sky, and a roughly a dozen hidden behind the Milky Way. Our work places the "missing satellite problem" on a firm quantitative observational basis. We present detailed data on all our candidates, including surface brightness measurements.Comment: 58 pages in AJ manuscript format; some figures at slightly reduced quality; accepted by the Astronomical Journa

Management practices and the quality of care in cardiac units

Importance:- To improve the quality of health care, many researchers have suggested that health care institutions adopt management approaches that have been successful in the manufacturing and technology sectors. However, relatively little information exists about how these practices are disseminated in hospitals and whether they are associated with better performance. Objectives:- To describe the variation in management practices among a large sample of hospital cardiac care units; assess association of these practices with processes of care, readmissions, and mortality for patients with acute myocardial infarction (AMI); and suggest specific directions for the testing and dissemination of health care management approaches. Design:- We adapted an approach used to measure management and organizational practices in manufacturing to collect management data on cardiac units. We scored performance in 18 practices using the following 4 dimensions: standardizing care, tracking of key performance indicators, setting targets, and incentivizing employees. We used multivariate analyses to assess the relationship of management practices with process-of-care measures, 30-day risk-adjusted mortality, and 30-day readmissions for acute myocardial infarction (AMI). Setting:- Cardiac units in US hospitals. Participants_ Five hundred ninety-seven cardiac units, representing 51.5% of hospitals with interventional cardiac catheterization laboratories and at least 25 annual AMI discharges. Main Outcome Measures:- Process-of-care measures, 30-day risk-adjusted mortality, and 30-day readmissions for AMI. Results:- We found a wide distribution in management practices, with fewer than 20% of hospitals scoring a 4 or a 5 (best practice) on more than 9 measures. In multivariate analyses, management practices were significantly correlated with mortality (P = .01) and 6 of 6 process measures (P < .05). No statistically significant association was found between management and 30-day readmissions. Conclusions and Relevance:- The use of management practices adopted from manufacturing sectors is associated with higher process-of-care measures and lower 30-day AMI mortality. Given the wide differences in management practices across hospitals, dissemination of these practices may be beneficial in achieving high-quality outcomes. Interest in quality improvement in health care during the past 10 years has been associated with a handful of important successes.1- 3 However, improvements in the quality of care have been slower than many would have hoped for,4- 8 and quality is still highly variable across organizations.9 Although significant effort has been focused on the use of evidence-based medicine—clinical practices that lead to better care—an interest in organizational strategies and management practices that enable and incentivize high-quality health care is emerging.10- 15 One of the most active areas of interest is in the use of management practices with origins in manufacturing, including, for example, “Lean” methodologies developed at Toyota16 or the use of balanced scorecard approaches that originated in the technology sector.17 These management approaches can be characterized as a set of formalized tools, the use of which is intended to improve quality through multiple pathways, such as eliminating inefficient and variable practices; engaging providers in a collaborative, team-based approach; and structuring mechanisms for setting targets and tracking progress. However, the evidence on the potential effectiveness of these approaches in health care is relatively weak13,18 and consists primarily of single-site studies.19- 21 To address this gap in knowledge, we present a new framework and instrument for defining key management dimensions and for measuring them on a large scale in health care organizations. We describe the variation in management practices among a large sample of hospitals; assess its association with processes of care, readmissions, and mortality for patients with acute myocardial infarction (AMI); and suggest specific directions for the testing and dissemination of health care management approaches

Passive Evolution: Are the Faint Blue Galaxy Counts Produced by a Population of Eternally Young Galaxies?

A constant age population of blue galaxies, postulated in the model of Gronwall & Koo (1995), seems to provide an attractive explanation of the excess of very blue galaxies in the deep galaxy counts. Such a population may be generated by a set of galaxies with cycling star formation rates, or at the other extreme, be maintained by the continual formation of new galaxies which fade after they reach the age specified in the Gronwall and Koo model. For both of these hypotheses, we have calculated the luminosity functions including the respective selection criteria, the redshift distributions, and the number counts in the B_J and K bands. We find a substantial excess in the number of galaxies at low redshift (0 < z < 0.05) over that observed in the CFH redshift survey (Lilly et al. 1995) and at the faint end of the Las Campanas luminosity function (Lin et al. 1996). Passive or mild evolution fails to account for the deep galaxy counts because of the implications for low redshift determinations of the I-selected redshift distribution and the r-selected luminosity function in samples where the faded counterparts of the star-forming galaxies would be detectable.Comment: 11 pages, LaTeX type (aaspp4.sty), 3 Postscript figures, submitted to ApJ Letter

Intrinsic Axis Ratio Distribution of Early-type Galaxies From Sloan Digital Sky Survey

Using Sloan Digital Sky Survey Data Release 5, we have investigated the intrinsic axis ratio distribution (ARD) for early-type galaxies. We have constructed a volume-limited sample of 3,922 visually-inspected early-type galaxies at $0.05 \leq z \leq 0.06$ carefully considering sampling biases caused by the galaxy isophotal size and luminosity. We attempt to de-project the observed ARD into three-dimensional types (oblate, prolate, and triaxial), which are classified in terms of triaxiality. We confirm that no linear combination of $randomly$-distributed axis ratios of the three types can reproduce the observed ARD. However, using Gaussian intrinsic distributions, we have found reasonable fits to the data with preferred mean axis ratios for oblate, prolate, and triaxial (triaxials in two axis ratios), $\mu_o=0.44, \mu_p=0.72, \mu_{t,\beta}=0.92, \mu_{t,\gamma}=0.78$ where the fractions of oblate, prolate and triaxial types are \textrm{O:P:T}=0.29^{\pm0.09}:0.26^{\pm0.11}:0.45^{\pm0.13}$. We have also found that the luminous sample ($-23.3 < M_r \leq -21.2$) tends to have more triaxials than the less luminous ($-21.2 < M_r <-19.3$) sample does. Oblate is relatively more abundant among the less luminous galaxies. Interestingly, the preferences of axis ratios for triaxial types in the two luminosity classes are remarkably similar. We have not found any significant influence of the local galaxy number density on ARD. We show that the results can be seriously affected by the details in the data selection and type classification scheme. Caveats and implications on galaxy formation are discussed.Comment: 9 pages, 11 figures, Accepted for publication in Ap

Stellar and Gas properties of High HI Mass-to-Light Ratio Galaxies in the Local Universe

We present a multi-wavelength study (BVRI band photometry and HI line interferometry) of nine late-type galaxies selected from the HIPASS Bright Galaxy Catalog on the basis of apparently high HI mass-to-light ratios (3 M_sun/L_sun < M_HI/L_B < 27 M_sun/L_sun). We found that most of the original estimates for M_HI/L_B based on available photographic magnitudes in the literature were too high, and conclude that genuine high HI mass-to-light ratio (>5 M_sun/L_sun) galaxies are rare in the Local Universe. Extreme high M_HI/L_B galaxies like ESO215-G?009 appear to have formed only the minimum number of stars necessary to maintain the stability of their HI disks, and could possibly be used to constrain galaxy formation models. They may to have been forming stars at a low, constant rate over their lifetimes. The best examples all have highly extended HI disks, are spatially isolated, and have normal baryonic content for their total masses but are deficent in stars. This suggests that high M_HI/L_B galaxies are not lacking the baryons to create stars, but are underluminous as they lack either the internal or external stimulation for more extensive star formation.Comment: 29 Pages, 59 Figures. Accepted for publication in AJ (to be published ~April 2006