Resolving the structure of TiBe12_{12}

There has been considerable controversy regarding the structure of TiBe$_{12}$, which is variously reported as hexagonal and tetragonal. Lattice dynamics simulations based on density functional theory show the tetragonal phase space group $I4/mmm$ to be more stable over all temperatures, while the hexagonal phase exhibits an imaginary phonon mode, which, if followed, would lead to the cell adopting the tetragonal structure. We then report the predicted ground state elastic constants and temperature dependence of the bulk modulus and thermal expansion for the tetragonal phase.Comment: In press at Acta Crystallographica B. Supplementary material appende

Effect of Static Strains on Diffusion

A theory is developed that gives the diffusion coefficient in strained systems as an exponential function of the strain. This theory starts with the statistical theory of the atomic jump frequency as developed by Vineyard. The parameter determining the effect of strain on diffusion is related to the changes in the inter-atomic forces with strain. Comparison of the theory with published experimental results for the effect of pressure on diffusion shows that the experiments agree with the form of the theoretical equation in all cases within experimental error

Snowpack augmentation by cloud seeding in Colorado and Utah

August 1979.Submitted to the Water Resources Planning Fellowship Steering Committee, Colorado State University, in fulfillment of requirements for AE 795 AV Special Study in Planning.Bibliography: pages [80]-83

From solid solution to cluster formation of Fe and Cr in α\alpha-Zr

To understand the mechanisms by which Fe and Cr additions increase the corrosion rate of irradiated Zr alloys, a combination of experimental (atom probe tomography, x-ray diffraction and thermoelectric power measurements) and modelling (density functional theory) techniques are employed to investigate the non-equilibrium solubility and clustering of Fe and Cr in binary Zr alloys. Cr occupies both interstitial and substitutional sites in the {\alpha}-Zr lattice, Fe favours interstitial sites, and a low-symmetry site that was not previously modelled is found to be the most favourable for Fe. Lattice expansion as a function of alloying concentration (in the dilute regime) is strongly anisotropic for Fe additions, expanding the $c$-axis while contracting the $a$-axis. Defect clusters are observed at higher solution concentrations, which induce a smaller amount of lattice strain compared to the dilute defects. In the presence of a Zr vacancy, all two-atom clusters are more soluble than individual point defects and as many as four Fe or three Cr atoms could be accommodated in a single Zr vacancy. The Zr vacancy is critical for the increased solubility of defect clusters, the implications for irradiation induced microstructure changes in Zr alloys are discussed.Comment: 15 pages including figure, 9 figures, 2 tables. Submitted for publication in Acta Mater, Journal of Nuclear Materials (2015

A study to determine the incidence and prevalence of newly discovered human immunodeficiency virus infection during the prenatal care period.

OBJECTIVES: This study asked the following questions: 1) Does HIV testing in pregnancy identify women who previously were not known to be HIV positive? 2) When in pregnancy are women identified as HIV infected? 3) Does HIV seroconversion occur during the prenatal care period? METHODS: Medical records of 97 women from two primarily indigent care hospitals in Houston, TX who were found to be HIV positive at delivery were reviewed to determine if they had tested positive during the prenatal care period. Demographics and time of gestation of the prenatal testing also were recorded. The outcome measures were: 1) number of women found positive during prenatal care; 2) week of gestation at discovery of HIV positivity; and 3) number of women seroconverting between the initiation of prenatal care and delivery. RESULTS: Thirty women were known to be HIV positive prior to pregnancy. Fifty-six women were found to be positive during prenatal care and the seropositivity of 44 was discovered before the 34th week of pregnancy. Ten women were found to be positive at their first prenatal visit, which occurred after the 34th week. Date of testing was unknown for two women. Eleven women who received no prenatal care were found to be HIV positive at delivery. There were no seroconversions while women were under prenatal care. CONCLUSIONS: HIV testing at delivery did not find any HIV-positive women who had tested negative during prenatal care. Testing is very important for women who do not receive prenatal care. Making certain that high-risk women get into prenatal care also is very important

Genetic Improvement Made Through DNA Testing and Artificial Insemination to High- Growth, High Carcass Value Angus Sires

The beef industry has improved the recording of pedigrees and performance data through the use of breed associations and herd health databases. Constant evaluation of genetics and performance has allowed producers to make more informed breeding decisions that help improve herd productivity. As a result of recent droughts and elevated feed and grain prices, however, the American beef cowherd is at a record-low 29 million head. For the United States to continue to be the leading producer of beef in the world, the industry must adopt technologies that improve efficiency of the cowherd and the quality of beef being produced. There are two sizable pools of relatively low-grading, low-value carcass genetics in the U.S. beef industry: (1) southern cattle with significant Bos indicus influence, and (2) cattle with a relatively high percentage of Continental breeding. The objective of this research project was to demonstrate the improvement in marbling and grid premium potential that can be made in a cow base with average to below-average genetic potential in just one generation through the use of genomics and artificial insemination

Parent-child interaction in Nigerian families: conversation analysis, context and culture

This paper uses a conversation analysis (CA) approach to explore parent child interaction (PCI) within Nigerian families. We illustrate how speech and language therapists (SLTs), by using CA, can tailor recommendations according to the interactional style of each individual family that are consonant with the family’s cultural beliefs. Three parent-child dyads were videoed playing and talking together in their home environments. The analysis uncovered a preference for instructional talk similar to that used in the classroom. Closer examination revealed that this was not inappropriate when considering the context of the activities and their perceived discourse role. Furthermore, this was not necessarily at the expense of responsivity or semantic contingency. The preference for instructional talk appeared to reflect deeply held cultural beliefs about the role of adults and children within the family and it is argued that the cultural paradigm is vitally important to consider when evaluating PCI. Given a potential risk that such young children may be vulnerable in terms of language difficulties, we offer an example of how PCI can be enhanced to encourage language development without disrupting the naturally occurring talk or the underlying purpose of the interaction

Ariel - Volume 8 Number 3

Executive Editor James W. Lockard, Jr. Business Manager Neeraj K. Kanwal University News Richard J . Perry World News Doug Hiller Opinions Elizabeth A. McGuire Features Patrick P. Sokas Sports Desk Shahab S. Minassian Managing Editor Edward H. Jasper Managing Associate Brenda Peterson Photography Editor Robert D. Lehman. Jr. Graphics Christine M. Kuhnl