Thermodynamics of the Mg-B system: Implications for the deposition of MgB2 thin films

We have studied thermodynamics of the Mg-B system with the modeling technique CALPHAD using a computerized optimization procedure. Temperature-composition, pressure-composition, and pressure-temperature phase diagrams under different conditions are obtained. The results provide helpful insights into appropriate processing conditions for thin films of the superconducting phase, MgB2, including the identification of the pressure/temperature region for adsorption-controlled growth. Due to the high volatility of Mg, MgB2 is thermodynamically stable only under fairly high Mg overpressures for likely growth temperatures. This constraint places severe temperature constraints on deposition techniques employing high vacuum conditions

Examining geomorphic effects of flow diversions on low-gradient mountain streams in the Routt National Forest, Colorado

2012 Fall.Includes bibliographical references.The western United States is faced with an increasing human demand for water, coupled with a decreasing supply. Resource managers are looking for ways to meet the demands of both anthropogenic use and the needs of instream flows to maintain channel characteristics for water quality as well as riparian and aquatic ecosystems. In the Routt National Forest in northern Colorado, ditches typically divert flows from headwater streams to supply the land below the mountains for agricultural purposes. Many studies have focused on the biotic response to streamflow diversions, but relatively little research has been done to quantify the physical effects of ditch diversions. The purpose of this study was to contribute to the understanding of geomorphic effects of flow diversions in the Routt National Forest, and to inform management decisions related to water on the Routt by supplying localized data. Thirteen streams were surveyed during the summer of 2011, yielding 11 control reaches, located upstream of a diversion point, and 11 diverted reaches, which were downstream of a diversion point. Reach lengths were spaced approximately 20 times bankfull width. Four cross sections per reach were surveyed to collect width and depth information using reference discharge indicators approximating bankfull flow. Pebble counts of 100 clasts per reach were evenly spaced between riffles, and pools were avoided. Riparian vegetation, lithology, and valley characteristics were qualitatively and quantitatively assessed at the reach sites and using US Forest Service geospatial data. Statistical analyses conducted using the collected data included both t-tests and non-parametric Wilcoxon tests, as the small sample size limited the ability to reject assumptions of normality and conduct multivariate analyses. Univariate mixed-effects models were developed to compare reach response variables between diverted and control reaches while including the effects of unevenly-paired reaches, valley characteristics, lithology, and riparian vegetation. T-tests and Wilcoxon tests found only sinuosity to be significant, with the possibility of riparian vegetation types (willow or grass/sedge) having an effect on variables related to bank stability (width, depth). The mixed effects models found width, width-to-depth ratio, sinuosity, and cross-sectional area to be significant. Because the mixed models included the effects of valley characteristics, riparian vegetation types, lithology, and drainage basin size, these are considered to be more representative of the downstream response to flow diversions than the t-tests and Wilcoxon tests. This study provides some evidence for the downstream alteration of channels due to diversions. Two channels were noted to have been completely dewatered at the time of surveying in late July-to-August, and several variables were significantly different in statistical tests. For management purposes, it is recommended that high flows periodically enter diverted reaches to help offset the morphology and water quality effects of diversions during dry years. This study stresses the importance of further research to more accurately constrain and quantify physical effects of diversions

Vaccines against Human Carcinomas: Strategies to Improve Antitumor Immune Responses

Multiple observations in preclinical and clinical studies support a role for the immune system in controlling tumor growth and progression. Various components of the innate and adaptive immune response are able to mediate tumor cell destruction; however, certain immune cell populations can also induce a protumor environment that favors tumor growth and the development of metastasis. Moreover, tumor cells themselves are equipped with various mechanisms that allow them to evade surveillance by the immune system. The goal of cancer vaccines is to induce a tumor-specific immune response that ultimately will reduce tumor burden by tipping the balance from a protumor to an antitumor immune environment. This review discusses common mechanisms that govern immune cell activation and tumor immune escape, and some of the current strategies employed in the field of cancer vaccines aimed at enhancing activation of tumor-specific T-cells with concurrent reduction of immunosuppression

Isolation of host-range variants of mouse mammary tumor viruses that efficiently infect cells in vitro

Host-range variants of mouse mammary tumor virus (MMTV) have been isolated that have the ability to productively infect cells in vitro with high efficiency (at multiplicities of infection ≤1) and with extremely short latent periods to the production of de novo virus (as short as 4 days after infection). These variants of the highly oncogenic MMTV of RIII, C3H, and GR mice were obtained by serial virus passage in feline cells. The resultant variant stocks react in group-specific radioimmunoassays for the MMTV major external glycoprotein (gp52) and major internal protein (p28), possess a protein profile similar to that of wild-type MMTV, and contain a virion-associated DNA polymerase with a magnesium cation preference. Addition of dexamethasone and insulin to culture media enhances the titer of de novo MMTV to levels of approximately 10(10) particles per 75-cm(2) flask (containing 5 × 10(6) cells) per 24 hr. Variant stocks exhibit no evidence of contamination with either murine or feline type C retroviruses, as assayed by various techniques. The variants of MMTV derived from C3H and RIII mice exhibit differential host ranges that include the ability to productively infect feline, canine, bat, mink, murine, and human cells. Use of these MMTV host-range variants now facilitates the study of the complete replicative cycle of MMTV as well as an elucidation of the interaction of MMTV with various hormones, physical or chemical carcinogens, and tumor promoters in the initiation and promotion of mammary neoplasia

Si-compatible candidates for high-K dielectrics with the Pbnm perovskite structure

We analyze both experimentally (where possible) and theoretically from first-principles the dielectric tensor components and crystal structure of five classes of Pbnm perovskites. All of these materials are believed to be stable on silicon and are therefore promising candidates for high-K dielectrics. We also analyze the structure of these materials with various simple models, decompose the lattice contribution to the dielectric tensor into force constant matrix eigenmode contributions, explore a peculiar correlation between structural and dielectric anisotropies in these compounds and give phonon frequencies and infrared activities of those modes that are infrared-active. We find that CaZrO_3, SrZrO_3, LaHoO_3, and LaYO_3 are among the most promising candidates for high-K dielectrics among the compounds we considered.Comment: 17 pages, 9 figures, 4 tables. Supplementary information: http://link.aps.org/supplemental/10.1103/PhysRevB.82.064101 or http://www.physics.rutgers.edu/~sinisa/highk/supp.pd