High speed hydrogen/graphite interaction

Various aspects of a research program on high speed hydrogen/graphite interaction are presented. Major areas discussed are: (1) theoretical predictions of hydrogen/graphite erosion rates; (2) high temperature, nonequilibrium hydrogen flow in a nozzle; and (3) molecular beam studies of hydrogen/graphite erosion

The influence of acclimation on the organismal and molecular thermotolerance parameters in two Arctic teleosts

Thesis (M.S.) University of Alaska Fairbanks, 2022The nearshore Beaufort Sea is a highly dynamic thermal environment that is faced with climate change-driven increases in temperature. Analyzing the thermotolerance of important Arctic subsistence and prey fishes, such as broad whitefish Coregonus nasus and saffron cod Eleginus gracilis, will provide an understanding of the relative species specific responses to current and future temperature changes. The objectives of this study were to determine if acclimating broad whitefish and saffron cod to two different temperatures (5 and 15°C) affected their critical thermal maximum (CTmax) and their HSP70 protein and mRNA transcript concentrations in brain, muscle, and liver tissues. Following acclimation, fish were exposed to a thermal ramping rate of 3.4°C · h-¹. The CTmax temperature was recorded when the fish expressed a loss of equilibrium. Tissue samples were then collected and analyzed via western blotting and transcriptome sequencing. Broad whitefish and saffron cod acclimated to 15°C had a significantly higher mean CTmax (27.3°C and 25.9°C, respectively) than 5°C fish (23.7°C and 23.2°C, respectively). Broad whitefish had a significantly higher CTmax than saffron cod at 15°C in addition to significantly higher HSP70 protein concentrations in liver and muscle tissues at both acclimation temperatures. Brain and muscle tissues had the highest and lowest HSP70 protein concentrations, respectively, for both species and acclimation temperatures. The only significant difference in protein concentration between acclimation temperatures was in saffron cod liver tissues where 5°C samples had a significantly higher concentration than 15°C. Brain and liver tissues for broad whitefish acclimated to 15°C had significantly higher HSP70 mRNA transcript concentrations than the control group that remained in lab-acclimation conditions of 8°C. Transcript B expressed a higher quantity of transcripts than transcript A, but both transcripts followed similar expression profiles and there were no differences in transcript concentration between tissues. The molecular data from this study demonstrates the cellular mechanisms that are, in part, responsible for the observed shifts in broad whitefish and saffron cod organismal thermotolerance, and this elasticity could be used to respond to changing thermal conditions in the nearshore Beaufort Sea in the future.Hilcorp Alaska LLC, Alaska IDeA Network of Biomedical Research Excellence (INBRE) Bioinformatic Program, Alaska Established Program to Stimulate Competitive Research (EPSCoR) National Science Foundation (NSF) award #OIA-1757348, and the Undergraduate Research and Scholarly Activity (URSA) Mentor Award #M21-6General introduction. Chapter 1: The influence of acclimation on the organismal and molecular thermotolerance parameters in two Arctic teleosts. General conclusion

High resolution study of associated C IV absorption systems in NGC 5548

We present the results of a careful analysis of associated absorption systems toward NGC 5548. Most of the well resolved narrow components in the associated system, defined by the Lyman alpha, C IV and N V profiles, show velocity separation similar (to within 10~\kms) to the C IV doublet splitting. We estimate the chance probability of occurrence of such pairs with velocity separation equal to C IV doublet splitting to be $6\times10^{-3}$. Thus it is more likely that most of the narrow components are line-locked with C IV doublet splitting. This will mean that the radiative acceleration plays an important role in the kinematics of the absorbing clouds. We build grids of photoionization models and estimate the radiative acceleration due to all possible bound-bound transitions. We show that the clouds producing absorption have densities less than $10^9 cm^{-3}$, and are in the outer regions of the broad emission line region (BLR). We note that the clouds which are line-locked cannot produce appreciable optical depths of O VII and O VIII, and hence cannot be responsible for the observed ionized edges, in the soft X-ray. We discuss the implications of the presence of optically thin clouds in the outer regions of the BLR to the models of broad emission lines.Comment: 21 pages, latex (aasms4 style), incluedes 4 ps figures. To appear in Astrophysical Journa

Genetic studies of Type 2 (non-insulin-dependent) diabetes mellitus: lack of association with seven genetic markers

Type 2 (non-insulin-dependent) diabetes mellitus, a disease of complex aetiology, has been reported to be nonrandomly associated with several polymorphic markers in human populations. These data, plus evidence of a high prevalence of Type 2 diabetes mellitus in American Indians and mixed populations, such as Mexican-Americans, which is only partially attributable to the prevalence of obesity in these populations, makes it imperative that the nature of such associations be clarified in relation to genetic susceptibility to Type 2 diabetes mellitus. The present paper reports the results of tests of association between Type 2 diabetes mellitus and seven polymorphic markers: the blood groups - ABO, Rhesus, Duffy and Kell (K and KP) - haptoglobin and group specific component; among Anglo and Hispanic populations in the San Luis Valley of Colorado, USA. The sample population consisted of 788 individuals of which 398 were Anglo subjects (97 Type 2 diabetes mellitus patients and 301 normal individuals) and 390 Hispanic subjects (191 Type 2 diabetes mellitus patients and 199 normal individuals). Association between Type 2 diabetes mellitus and genetic markers in patients was tested using the G2 statistic within each ethnic class using normal frequencies as a comparison. Results of the tests indicated that only the Kell blood group was significantly associated with Type 2 diabetes mellitus at a 5% level among the Anglo subjects (G2=5.16, 1df). This significant value can be explained by chance alone, if multiple comparisons are taken into account. Our tests have not shown the previously reported haptoglobin or Rhesus blood group associations seen in Mexican-Americans in San Antonio, Texas

Dipolar ordering in Fe8?

We show that the low-temperature physics of molecular nanomagnets, contrary to the prevailing one-molecule picture, must be determined by the long-range magnetic ordering due to many-body dipolar interactions. The calculations here performed, using Ewald's summation, suggest a ferromagnetic ground state with a Curie temperature of about 130 mK. The energy of this state is quite close to those of an antiferromagnetic state and to a glass of frozen spin chains. The latter may be realized at finite temperature due to its high entropy.Comment: 7 pages, no figures, submitted to EP

Trends in High-Risk HLA Susceptibility Genes Among Colorado Youth With Type 1 Diabetes

OBJECTIVE—Type 1 diabetes is associated with a wide spectrum of susceptibility and protective genotypes within the HLA class II system. It has been reported that adults diagnosed with youth-onset type 1 diabetes more recently have been found to have fewer classical high-risk HLA class II genotypes than those diagnosed several decades ago. We hypothesized that such temporal trends in the distribution of HLA-DR, DQ genotypes would be evident, and perhaps even stronger, among 5- to 17-year-old Hispanic and non-Hispanic white (NHW) youth diagnosed with type 1 diabetes in Colorado between 1978 and 2004

The Recycling and Transcytotic Pathways for IgG Transport by FcRn are Distinct and Display an Inherent Polarity

The Fc receptor FcRn traffics immunoglobulin G (IgG) in both directions across polarized epithelial cells that line mucosal surfaces, contributing to host defense. We show that FcRn traffics IgG from either apical or basolateral membranes into the recycling endosome (RE), after which the actin motor myosin Vb and the GTPase Rab25 regulate a sorting step that specifies transcytosis without affecting recycling. Another regulatory component of the RE, Rab11a, is dispensable for transcytosis, but regulates recycling to the basolateral membrane only. None of these proteins affect FcRn trafficking away from lysosomes. Thus, FcRn transcytotic and recycling sorting steps are distinct. These results are consistent with a single structurally and functionally heterogeneous RE compartment that traffics FcRn to both cell surfaces while discriminating between recycling and transcytosis pathways polarized in their direction of transport

Static chaos and scaling behaviour in the spin-glass phase

We discuss the problem of static chaos in spin glasses. In the case of magnetic field perturbations, we propose a scaling theory for the spin-glass phase. Using the mean-field approach we argue that some pure states are suppressed by the magnetic field and their free energy cost is determined by the finite-temperature fixed point exponents. In this framework, numerical results suggest that mean-field chaos exponents are probably exact in finite dimensions. If we use the droplet approach, numerical results suggest that the zero-temperature fixed point exponent $\theta$ is very close to $\frac{d-3}{2}$. In both approaches $d=3$ is the lower critical dimension in agreement with recent numerical simulations.Comment: 28 pages + 6 figures, LateX, figures uuencoded at the end of fil