37,752 research outputs found
The Formation of Thin Continuous Films from Isolated Nuclei
Formation of thin continuous films from isolated nuclei and effect of electron beam, residual gases, and surface conditions on film growt
Erythropoietin production by fetal mouse liver cells in response to hypoxia and adenylate cyclase stimulation
This study was done to investigate aspects of control of extrarenal erythropoietin (Ep) production. To this end we studied the effects of three stimuli of renal Ep production in the adult, i.e. hypoxia, cobalt, and activation of adenylate cyclase on Ep generation by cultured fetal mouse liver cells. The fetal liver was taken as a model for extrarenal Ep production because this organ is considered the predominant site of extrarenal Ep production. We found that Ep production by the cells increased as the oxygen concentration was decreased in the incubation atmosphere from 20% to 1%. Cobalt (10(-4)-10(-5) M) had no effect on Ep production. Activation of adenylate cyclase by forskolin (10(-5) M) or isoproterenol (10(-5) M) greatly enhanced Ep production. These findings indicate that the Ep-stimulating effect of cobalt is specific for the kidney. However, oxygen depletion and activation of adenylate cyclase seem to be more general stimuli in Ep-producing cells. Furthermore we found that Ep production in hypoxia correlated with lactate formation in the cultured liver cells. This finding suggests that Ep production in fetal livers under hypoxic conditions parallels the shift from aerobic to anaerobic cellular energy metabolism
Future capacity growth of energy technologies: are scenarios consistent with historical evidence?
Future scenarios of the energy system under greenhouse gas emission constraints depict dramatic growth in a range of energy technologies. Technological growth dynamics observed historically provide a useful comparator for these future trajectories. We find that historical time series data reveal a consistent relationship between how much a technology’s cumulative installed capacity grows, and how long this growth takes. This relationship between extent (how much) and duration (for how long) is consistent across both energy supply and end-use technologies, and both established and emerging technologies. We then develop and test an approach for using this historical relationship to assess technological trajectories in future scenarios. Our approach for “learning from the past” contributes to the assessment and verification of integrated assessment and energy-economic models used to generate quantitative scenarios. Using data on power generation technologies from two such models, we also find a consistent extent - duration relationship across both technologies and scenarios. This relationship describes future low carbon technological growth in the power sector which appears to be conservative relative to what has been evidenced historically. Specifically, future extents of capacity growth are comparatively low given the lengthy time duration of that growth. We treat this finding with caution due to the low number of data points. Yet it remains counter-intuitive given the extremely rapid growth rates of certain low carbon technologies under stringent emission constraints. We explore possible reasons for the apparent scenario conservatism, and find parametric or structural conservatism in the underlying models to be one possible explanation
Spin transfer torque on magnetic insulators
Recent experimental and theoretical studies focus on spin-mediated heat
currents at interfaces between normal metals and magnetic insulators. We
resolve conflicting estimates for the order of magnitude of the spin transfer
torque by first-principles calculations. The spin mixing conductance
G^\uparrow\downarrow of the interface between silver and the insulating
ferrimagnet Yttrium Iron Garnet (YIG) is dominated by its real part and of the
order of 10^14 \Omega^-1m^-2, i.e. close to the value for intermetallic
interface, which can be explained by a local spin model.Comment: 4 pages, 4 figures, 2 table
Characterization of Active Main Belt Object P/2012 F5 (Gibbs): A Possible Impacted Asteroid
In this work we characterize the recently discovered active main belt object
P/2012 F5 (Gibbs), which was discovered with a dust trail > 7' in length in the
outer main belt, 7 months prior to aphelion. We use optical imaging obtained on
UT 2012 March 27 to analyze the central condensation and the long trail. We
find nuclear B-band and R-band apparent magnitudes of 20.96 and 19.93 mag,
respectively, which give an upper limit on the radius of the nucleus of 2.1 km.
The geometric cross-section of material in the trail was ~ 4 x 10^8 m^2,
corresponding to a dust mass of ~ 5 x 10^7 kg. Analysis of infrared images
taken by the Wide-Field Infrared Survey Explorer in September 2010 reveals that
the object was below the detection limit, suggesting that it was less active
than it was during 2012, or possibly inactive, just 6 months after it passed
through perihelion. We set a 1-sigma upper limit on its radius during this time
of 2.9 km. P/2012 F5 (Gibbs) is dynamically stable in the outer main belt on
timescales of ~ 1 Gyr, pointing towards an asteroidal origin. We find that the
morphology of the ejected dust is consistent with it being produced by a single
event that occurred on UT 2011 July 7 20 days, possibly as the result of
a collision with a small impactor.Comment: 29 pages, 5 figures. Accepted for publication in Ap
A Comparative Analysis of the Nativity Wealth Gap
This paper investigates the source of the gap in the relative wealth position of immigrant households residing in Australia, Germany and the United States. Our results indicate that in German and the United States wealth differentials are largely the result of disparity in the educational attainment and demographic composition of the native and immigrant populations, while income differentials are relatively unimportant in understanding the nativity wealth gap. In contrast, the relatively small wealth gap between Australian and foreign-born households, exists because immigrants to Australia do not translate their relative educational and demographic advantage into a wealth advantage. On balance, our results point to substantial cross-nationality disparity in the economic well-being of immigrant and native families, which is largely consistent with domestic labor markets and the selection policies used to shape the nature of immigration flow.International migration, wealth accumulation
From infinite to two dimensions through the functional renormalization group
We present a novel scheme for an unbiased and non-perturbative treatment of
strongly correlated fermions. The proposed approach combines two of the most
successful many-body methods, i.e., the dynamical mean field theory (DMFT) and
the functional renormalization group (fRG). Physically, this allows for a
systematic inclusion of non-local correlations via the flow equations of the
fRG, after the local correlations are taken into account non-perturbatively by
the DMFT. To demonstrate the feasibility of the approach, we present numerical
results for the two-dimensional Hubbard model at half-filling.Comment: 5 pages, 4 figure
A Comparative Analysis of the Nativity Wealth Gap
This paper investigates the source of the gap in the relative wealth position of immigrant households residing in Australia, Germany and the United States. Our results indicate that in Germany and the United States wealth differentials are largely the result of disparity in the educational attainment and demographic composition of the native and immigrant populations, while income differentials are relatively unimportant in understanding the nativity wealth gap. In contrast, the relatively small wealth gap between Australian- and foreign-born households exists because immigrants to Australia do not translate their relative educational and demographic advantage into a wealth advantage. On balance, our results point to substantial cross-national disparity in the economic well-being of immigrant and native families, which is largely consistent with domestic labor markets and the selection policies used to shape the nature of the immigration flow.international migration, wealth accumulation
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