29,234 research outputs found
Error estimation in the histogram Monte Carlo method
We examine the sources of error in the histogram reweighting method for Monte
Carlo data analysis. We demonstrate that, in addition to the standard
statistical error which has been studied elsewhere, there are two other sources
of error, one arising through correlations in the reweighted samples, and one
arising from the finite range of energies sampled by a simulation of finite
length. We demonstrate that while the former correction is usually negligible
by comparison with statistical fluctuations, the latter may not be, and give
criteria for judging the range of validity of histogram extrapolations based on
the size of this latter correction.Comment: 7 pages including 3 postscript figures, typeset in LaTeX using the
RevTeX macro packag
Analytical Investigations of Coil-System Design Parameters for a Constant-Velocity Traveling Magnetic Wave Plasma Engine
Coil-system design parameters for constant velocity traveling-magnetic-wave plasma engin
Some implications of sampling choices on comparisons between satellite and model aerosol optical depth fields
The comparison of satellite and model aerosol optical depth (AOD) fields provides useful information on the strengths and weaknesses of both. However, the sampling of satellite and models is very different and some subjective decisions about data selection and aggregation must be made in order to perform such comparisons. This work examines some implications of these decisions, using GlobAerosol AOD retrievals at 550 nm from Advanced Along-Track Scanning Radiometer (AATSR) measurements, and aerosol fields from the GEOS-Chem chemistry transport model. It is recommended to sample the model only where the satellite flies over on a particular day; neglecting this can cause regional differences in model AOD of up to 0.1 on monthly and annual timescales. The comparison is observed to depend strongly upon thresholds for sparsity of satellite retrievals in the model grid cells. Requiring at least 25% coverage of the model grid cell by satellite data decreases the observed difference between the two by approximately half over land. The impact over ocean is smaller. In both model and satellite datasets, there is an anticorrelation between the proportion <i>p</i> of a model grid cell covered by satellite retrievals and the AOD. This is attributed to small <i>p</i> typically occuring due to high cloud cover and lower AODs being found in large clear-sky regions. Daily median AATSR AODs were found to be closer to GEOS-Chem AODs than daily means (with the root mean squared difference being approximately 0.05 smaller). This is due to the decreased sensitivity of medians to outliers such as cloud-contaminated retrievals, or aerosol point sources not included in the model
Star formation and accretion in the circumnuclear disks of active galaxies
We explore the evolution of supermassive black holes (SMBH) centered in a
circumnuclear disk (CND) as a function of the mass supply from the host galaxy
and considering different star formation laws, which may give rise to a
self-regulation via the injection of supernova-driven turbulence. A system of
equations describing star formation, black hole accretion and angular momentum
transport was solved for an axisymmetric disk in which the gravitational
potential includes contributions from the black hole, the disk and the hosting
galaxy. Our model extends the framework provided by Kawakatu et al. (2008) by
separately considering the inner and outer part of the disk, and by introducing
a potentially non-linear dependence of the star formation rate on the gas
surface density and the turbulent velocity. The star formation recipes are
calibrated using observational data for NGC 1097, while the accretion model is
based on turbulent viscosity as a source of angular momentum transport in a
thin viscous accretion disk. We find that current data provide no strong
constraint on the star formation recipe, and can in particular not distinguish
between models entirely regulated by the surface density, and models including
a dependence on the turbulent velocity. The evolution of the black hole mass,
on the other hand, strongly depends on the applied star formation law, as well
as the mass supply from the host galaxy. We suggest to explore the star
formation process in local AGN with high-resolution ALMA observations to break
the degeneracy between different star formation models.Comment: 13 pages, 15 figures, 6 tables, accepted at A&
Research Notes : United States : Genetic studies with T263
We reported inheritance studies and linkage tests with T263 (Palmer, 1977), a line carrying a gene for dwarfness. We had not completed allelism tests with the other available dwarfs, df2, df3, and df4, at that time. In this report, we give the allelism test results, as well as results of linkage tests of T263 with y13, Y12, G, T, and a chromosome interchange from PI 101,404B (Glycine soja)
Challenges for South African anthropology in the 3rd Millennium
Towards the end of oneās career, thereās a powerful inclination to look backwards instead of forwards. You become more interested in histories, biographies and obituaries; you reflect on your own life and career. Itās not inevitable, and it can be resisted. Marshall McLuhan was well into his 50s ā an obscure Canadian Eng Lit academic ā when he had his vision of the nature and future of the media and anticipated a āglobal villageā that the Internet has turned into a reality since his death in 1980 (McLuhan and Powers 1989) ā but more on that in due course. Cui Bono? At first I gave into the tendency to look back. Initially, for this lecture, I thought to analyse my own career in South Africa in terms of who benefited most from it: South African anthropology and my students ā¦ or me. I would call the lecture āCui Bono?ā But then I realised, with Latin tags on the way out, younger colleagues and students in the audience might think I was referring to a traditional Australian greeting (Coo-ee) and an Irish philanthropist pop singer (Bono). The title would be totally mystifying to many until I explained that it meant āto whom the goodā ā in other words, who benefits? But there were other objections to this project besides the title. Even the most postmodern of reflexive anthropologists would balk at making such a self-assessment ā it was not for me to judge. Anyway, I already knew the answer: My career in South Africa has not been impeded by political harassments, imprisonment or conscription. I did make some small negligible contributions to the āstruggleā through writing or drawing, and I did some community service, on campus or off in the same way. At a critical stage I assisted with the process that eventually produced a national staff association, now called NTESU. The only price I have paid for these distractions from serious publishing at a critical stage of my career was deservedly slow promotion. I continue to contribute to the community mainly through membership of the older of Grahamstownās two very active Rotary clubs. Itās all I have time for, but nothing to boast about. In sum, Iāve enjoyed what my long-term colleague and Grahamstownās Citizen of the Year (another Rotary initiative) Michael Whisson likes to call āsheltered employmentā ā his typically ironic way of reminding us of how privileged we academics are, doing what we enjoy, in pleasant surroundings, among intelligent colleagues and the cream of our youth, with plenty of flexi-time and opportunities for subsidized travel. And now I have benefited again by being promoted to full professor without sufficiently earning my keep through subsidies on academic outputs. Whatever I might have given back through teaching and administration the net is in my favour, and I am grateful beyond words
Where to from here?
The author, a former politician and Prime Minister, provides a comment on the Treaty of Waitangi and the then-newly introduced Treaty Settlement process. The article is divided into two parts. The first part of the article asks what had been done since the signing of the Treaty, with Palmer arguing that the changing position of MÄori in the New Zealand constitution was the most significant constitutional change. The second part of the article asks where New Zealand was headed next, arguing that MÄori representation is (and always has been) a major issue. The author concludes that we would be better to concentrate on the very real complexities involved in getting to grips with the Treaty rather than marching off in some other direction to the beat of false drums
Guidance, Flight Mechanics and Trajectory Optimization. Volume 5 - State Determination And/or Estimation
Guidance, flight mechanics, and trajectory optimizatio
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