5,020 research outputs found
The Generation of Fullerenes
We describe an efficient new algorithm for the generation of fullerenes. Our
implementation of this algorithm is more than 3.5 times faster than the
previously fastest generator for fullerenes -- fullgen -- and the first program
since fullgen to be useful for more than 100 vertices. We also note a
programming error in fullgen that caused problems for 136 or more vertices. We
tabulate the numbers of fullerenes and IPR fullerenes up to 400 vertices. We
also check up to 316 vertices a conjecture of Barnette that cubic planar graphs
with maximum face size 6 are hamiltonian and verify that the smallest
counterexample to the spiral conjecture has 380 vertices.Comment: 21 pages; added a not
Cross border Classical Swine Fever control: Improving Dutch and German crisis management systems by an integrated public-private approach
The objective of this research approach is to analyse in which ways crisis management measures against Classical Swine Fever (CSF) can be improved by a public private cross border model. A core activity contains the analysis of information and communication systems: In a case study it has been empirically analysed if a sufficient supply of public and private information enables crisis managers at both sides of the Dutch-German border area to take decisions about CSF control more efficient. At the end of this approach a new crisis management model had been developed. One of the most important aspects thereby is the assessment of data: (1) within private quality management systems in normal times according to the benefit for public management tasks in times of crisis and (2) within public crisis management systems according to the benefit for cross-border CSF-control activities. To this effect two different methodological approaches have been combined within the model: (1) a method to identify and illustrate public actors and their options in crisis management decision making and (2) a system of communication and information exchange between public and private as well as Dutch and German actors (engage& exchange model) which permit to collect and to evaluate data in addition for a predefined time period are activated
Development and Testing of Water-Filled Tube Systems for Flood Protection Measures
This paper provides information on mobile flood protection systems in general and on water-filled tube systems for flood control in particular. Results of field tests and laboratory tests of prototypes developed in the research project HWS-MOBILE are described and recommendations for the use of water-filled tube systems are given
Long-term monitoring of Molonglo calibrators
Before and after every 12 hour synthesis observation, the Molonglo
Observatory Synthesis Telescope (MOST) measures the flux densities of ~5
compact extragalactic radio sources, chosen from a list of 55 calibrators. From
1984 to 1996, the MOST made some 58 000 such measurements. We have developed an
algorithm to process this dataset to produce a light curve for each source
spanning this thirteen year period. We find that 18 of the 55 calibrators are
variable, on time scales between one and ten years. There is the tendency for
sources closer to the Galactic Plane to be more likely to vary, which suggests
that the variability is a result of refractive scintillation in the Galactic
interstellar medium. The sources with the flattest radio spectra show the
highest levels of variability, an effect possibly resulting from differing
orientations of the radio axes to the line of sight.Comment: 18 pages, 9 embedded EPS files. To appear in Publications of the
Astronomical Society of Australia. Data available electronically at
http://www.physics.usyd.edu.au/astrop/scan
Topological Designs
We give an exponential upper and a quadratic lower bound on the number of
pairwise non-isotopic simple closed curves can be placed on a closed surface of
genus g such that any two of the curves intersects at most once. Although the
gap is large, both bounds are the best known for large genus. In genus one and
two, we solve the problem exactly.
Our methods generalize to variants in which the allowed number of pairwise
intersections is odd, even, or bounded, and to surfaces with boundary
components.Comment: 14 p., 4 Figures. To appear in Geometriae Dedicat
X-ray properties of the Parkes sample of flat-spectrum radio sources: dust in radio-loud quasars?
We investigate the X-ray properties of the Parkes sample of flat-spectrum
radio sources using data from the ROSAT All-Sky Survey and archival pointed
PSPC observations. In total, 163 of the 323 sources are detected. For the
remaining 160 sources 2 sigma upper limits to the X-ray flux are derived. We
present power-law photon indices for 115 sources, which were either determined
with a hardness ratio technique or from direct fits to pointed PSPC data. For
quasars, the soft X-ray photon index is correlated with redshift and with radio
spectral index. Webster et al. (1995) discovered many sources with unusually
red optical continua among the quasars of this sample and interpreted this
result in terms of extinction by dust. Although the X-ray spectra in general do
not show excess absorption, we find that low-redshift optically red quasars
have significantly lower soft X-ray luminosities on average than objects with
blue optical continua. The difference disappears for higher redshifts, as is
expected for intrinsic absorption by cold gas associated with the dust.
Alternative explanations are briefly discussed. We conclude, however, that dust
does play an important role in some of the radio-loud quasars with red optical
continua.Comment: 21 pages, 13 figures, to appear in MNRA
Zur Frage der strangulationsbedingten kraniokaudalen Konzentrationsdifferenz biochemischer Parameter am Beispiel der Katecholamine
- …