2,793 research outputs found
Transport models for numerical forecast
The explosive growth of computing power, coupled with scientific and technological emphasis on a national scale, has led to significant major advances in operational numerical weather prediction (NWP) during the last two decades. There are about half a dozen major centers around the world running global NWP models operationally. Many more countries have operational hemispheric or limited-area models which provide weather forecasts. The global models typically have several hundred kilometer resolution, while the limited-area models usually have horizontal spacing of 50 to 100 km. Given the pace of burgeoning growth in this area, it seems warranted to occasionally take an overview of aspects of the field common to all modelers. Here, a brief look is taken at the nature of subgrid scale turbulence transport parameterization, and some of the difficulties pertaining thereto, with particular emphasis on operational NWP models
Received optical power calculations for optical communications link performance analysis
The factors affecting optical communication link performance differ substantially from those at microwave frequencies, due to the drastically differing technologies, modulation formats, and effects of quantum noise in optical communications. In addition detailed design control table calculations for optical systems are less well developed than corresponding microwave system techniques, reflecting the relatively less mature state of development of optical communications. Described below are detailed calculations of received optical signal and background power in optical communication systems, with emphasis on analytic models for accurately predicting transmitter and receiver system losses
An automatic system for determining solar absorptance and thermal emittance of surfaces from spectral normal reflectance measurements
Spectrophotometers, digitizer, and computer system to determine solar absorptance and thermal emittance of surfaces from spectral reflectance measurement
Evaluation of an on-site sewage disposal system at the Lake of the Ozarks
An aeration device - conventional soil disposal field system was monitored for one year in the Lake of the Ozarks area to assess its treatment efficiency and effect on the water quality of the immediate area. The aeration unit consistently produced a well oxidized effluent (soluble COD=44 mg/L; N03-N=22 mg/L; P04=6. 3 mg /L; SS=l 4 mg /L). Soi1-water samples taken from the tile line and 2 and 5 m down slope indicate that considerable denitrification was occurring but may be decreasing. Little coliform movement was detected. The practice of excavating tile lines into the bedrock was discouraged due to a lack of treatment occurring.Project # G-1235-06 Agreement # 14-08-0001-G-1235-0
Understanding Student Computational Thinking with Computational Modeling
Recently, the National Research Council's framework for next generation
science standards highlighted "computational thinking" as one of its
"fundamental practices". 9th Grade students taking a physics course that
employed the Modeling Instruction curriculum were taught to construct
computational models of physical systems. Student computational thinking was
assessed using a proctored programming assignment, written essay, and a series
of think-aloud interviews, where the students produced and discussed a
computational model of a baseball in motion via a high-level programming
environment (VPython). Roughly a third of the students in the study were
successful in completing the programming assignment. Student success on this
assessment was tied to how students synthesized their knowledge of physics and
computation. On the essay and interview assessments, students displayed unique
views of the relationship between force and motion; those who spoke of this
relationship in causal (rather than observational) terms tended to have more
success in the programming exercise.Comment: preprint to submit to PERC proceedings 201
The Labour Government, the Treasury and the £6 pay policy of July 1975
The 1974-79 Labour Government was elected in a climate of opinion that was fiercely opposed to government intervention in the wage determination process, and was committed to the principles of free collective bargaining in its manifestoes. However, by December 1974 the Treasury was advocating a formal incomes policy, and by July 1975 the government had introduced a £6 flat rate pay norm. With reference to archival sources, the paper demonstrates that TUC and Labour Party opposition to incomes policy was reconciled with the Treasury's advocacy by limiting the Bank of England‟s intervention in the foreign exchange market when sterling came under pressure. This both helped to achieve the Treasury's objective of improving the competitiveness of British industry, and acted as a catalyst for the introduction of incomes policy because the slide could be attributed to a lack of market confidence in British counter-inflation policy
Visual, Optical and Replica Inspections: Surface Preparation of 650 MHz NB Cavity for PIP-II Linac
Surface preparation of niobium superconducting RF cavities is a critical step
for achieving good RF performance under the superconducting state. Surface
defect, roughness, and contamination affect the accelerating gradient and
quality factor of the cavities. We report surface inspection methods used to
control the surface processing of 650 MHz cavities designated for the
pre-production and prototype cryomodules for PIP-II linac. The cavity surface
was routinely inspected visually, with an optical camera, and by microscopic
scanning of surface replicas. This article covers details on the surface
inspection methods and surface polishing process used to repair the surface
Oxidation chemistry of d^0 organometallic complexes
Electron-transfer processes can play an important role in organometallic chemistry. Herein, we demonstrate that even d^0 organometallic complexes exhibit a rich redox chemistry and present electrochemical, kinetics, and stereochemical studies that establish a general outer-sphere oxidation process for d^0 group 4 metallocene complexes. This oxidation chemistry closely parallels the reported LMCT photochemistry of these complexes
HIF-2α downregulation in the absence of functional VHL is not sufficient for renal cell differentiation
<p>Abstract</p> <p>Background</p> <p>Mutational inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene has been linked to hereditary as well as sporadic clear cell renal carcinomas. The product of the VHL gene, pVHL, acts to target hypoxia-inducible factor alpha (HIF-α) subunits for ubiquitination and subsequent degradation. Using an RNA interference approach to lower levels of HIF-2α in two different renal cell lines that lack functional pVHL, we have tested the contribution of HIF-2α toward cellular pVHL activities.</p> <p>Results</p> <p>Knockdown of HIF-2α resulted in cell cycle arrest of renal cells that were grown on collagen I, indicating that this pVHL function is dependent on HIF-2α regulation. However, cellular morphological changes and downregulation of integrins α5 and β1, which were seen upon pVHL replacement, were not faithfully phenocopied by HIF-2α reduction. Moreover, fibronectin deposition and expression of renal cell differentiation markers were observed in cells containing replaced pVHL, but not in HIF-2α knockdown cells, indicating that these pVHL functions may occur independently of HIF-2α downregulation.</p> <p>Conclusion</p> <p>These results indicate that HIF-2α regulation is not sufficient for pVHL-induced renal cell differentiation. We hypothesize that in addition to HIF-2α dysregulation, abrogation of additional pVHL functions is required for the initiation of renal carcinogenesis.</p
Coupling to haloform molecules in intercalated C60?
For field-effect-doped fullerenes it was reported that the superconducting
transition temperature Tc is markedly larger for C60.2CHX_3 (X=Cl, Br)
crystals, than for pure C60. Initially this was explained by the expansion of
the volume per C60-molecule and the corresponding increase in the density of
states at the Fermi level in the intercalated crystals. On closer examination
it has, however, turned out to be unlikely that this is the mechanism behind
the increase in Tc. An alternative explanation of the enhanced transition
temperatures assumes that the conduction electrons not only couple to the
vibrational modes of the C60-molecule, but also to the modes of the
intercalated molecules. We investigate the possibility of such a coupling. We
find that, assuming the ideal bulk structure of the intercalated crystal, both
a coupling due to hybridization of the molecular levels, and a coupling via
dipole moments should be very small. This suggests that the presence of the
gate-oxide in the field-effect-devices strongly affects the structure of the
fullerene crystal at the interface.Comment: 4 pages, 1 figure, to be published in PRB (rapid communication
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