725 research outputs found
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
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 . 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 , 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
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