12,131 research outputs found
The computation of the cohomology rings of all groups of order 128
We describe the computation of the mod-2 cohomology rings of all 2328 groups
of order 128. One consequence is that all groups of order less than 256 satisfy
the strong form of Benson's Regularity Conjecture.Comment: 15 pages; revised versio
An Instrument of Mass Calculation made by Nastūlus in Baghdad ca. 900
This remarkable astronomical instrument was made by the Muslim astronomer known as NasÐūlus, who was active in Baghdad between 890 and 930. Its rediscovery brings our knowledge of the activities in that flourishing scientific centre a substantial step further. This type of instrument was previously not known to exist, although sundials based on the same principle are described in Arabic treatises datable to ca. 950 and ca. 1280. It is essentially a mathematical device providing a graphic solution to a problem that was of interest to Muslim astronomers, namely, the determination of the time of day as a function of the solar altitude throughout the year, here specifically for the latitude of Baghdad. The instrument reveals a level of mathematical competence and sophistication that is at first sight astounding. However, with a deeper understanding of the scientific milieu from which it came, it can be seen to be fully within the theoretical competence of the scientists of that environment. Nevertheless, the spectacular accuracy of the engraving of the principal curves on the instrument is completely unexpected. The instrument also features the earliest known solar and calendrical scales from the Islamic East; the origin of these was previously thought to be in the Islamic West
Two Newly-discovered Astrolabes from ‘Abbasid Baghdad
This is the first description of two complete astrolabes from ‘Abbāsid Baghdad. One is by the enigmatic but prolific NasÐýlus and datable ca. 900-930, and the other is the first known instrument of A¬mad al-Muhandis, datable ca. 875. Both instruments and two additional incomplete ones also described
here, are fully in the tradition of Abbasid astrolabes, of which close to two dozen, not all complete, are now known and published
Science Information and the Public - A Review of Literature
Informing the public about science: Is it an awful bore, or is it of critical importance to the survival of the world? This article is a review of literature that addresses this question. Most of the major research articles are reviewed and a bibliography is provided
Dynamics of wire frame glasses in two dimensions
The dynamics of wire frame particles in concentrated suspension are studied
by means of a 2D model and compared to those of rod-like particles. The wire
frames have bent or branched structures constructed from infinitely thin rigid
rods. In the model, a particle is surrounded by diffusing points that it cannot
cross. We derive a formal expression for the mean squared displacement (MSD)
and, by using a self-consistent approximation, we find markedly different
dynamics for wire frames and rods. For wire frames, there exists a critical
concentration of points above which they become frozen with the long time MSD
reaching a plateau. Rods, on the other hand, always diffuse by reptation. We
also study the rheology through the elastic stress, and more striking
differences are found; the initial magnitude of the stress for wire frames is
much larger than for rods, scaling like the square of the point concentration,
and above the critical concentration, the stress for wire frames appears to
persist indefinitely while for rods it always decays.Comment: 25 pages, 4 figure
Merton\u27s New Novices: The Seven Storey Mountain and Monasticism in a Freshman Seminar
Offers observation on Thomas Merton\u27s book The Seven Storey Mountain. Experience in teaching an introductory literature course to sophomore students at Kennesaw State University in Georgia; Reflections on monastic life; Description of Merton on Trappist monasteries
THE FINAL DEMISE OF EAST TENNESSEE TECHNOLOGY PARK BUILDING K-33 Health Physics Society Annual Meeting West Palm Beach, Florida June 27, 2011
Building K-33 was constructed in 1954 as the final section of the five-stage uranium enrichment cascade at the Oak Ridge Gaseous Diffusion Plant (ORGDP). The two original building (K-25 and K-27) were used to produce weapons grade highly enriched uranium (HEU). Building K-29, K-31, and K-33 were added to produce low enriched uranium (LEU) for nuclear power plant fuel. During ORGDP operations K-33 produced a peak enrichment of 2.5%. Thousands of tons of reactor tails fed into gaseous diffusion plants in the 1950s and early 1960s introducing some fission products and transuranics. Building K-33 was a two-story, 25-meters (82-feet) tall structure with approximately 30 hectare (64 acres) of floor space. The Operations (first) Floor contained offices, change houses, feed vaporization rooms, and auxiliary equipment to support enrichment operations. The Cell (second) Floor contained the enrichment process equipment and was divided into eight process units (designated K-902-1 through K-902-8). Each unit contained ten cells, and each cell contained eight process stages (diffusers) for a total of 640 enrichment stages. 1985: LEU buildings were taken off-line after the anticipated demand for uranium enrichment failed to materialize. 1987: LEU buildings were placed in permanent shutdown. Process equipment were maintained in a shutdown state. 1997: DOE signed an Action Memorandum for equipment removal and decontamination of Buildings K-29, K-31, K-33; BNFL awarded contract to reindustrialize the buildings under the Three Buildings D&D and Recycle Project. 2002: Equipment removal complete and effort shifts to vacuuming, chemical cleaning, scabbling, etc. 2005: Decontamination efforts in K-33 cease. Building left with significant {sup 99}Tc contamination on metal structures and PCB contamination in concrete. Uranium, transuranics, and fission products also present on building shell. 2009: DOE targets Building K-33 for demolition. 2010: ORAU contracted to characterize Building K-33 for final disposition at the Environmental Management Waste Management Facility (EMWMF) in Oak Ridge. ORAU collected 439 samples from May and June. LATA Sharp started removing transite panels in September. 2011: LATA Sharp began demolition in January and expects the last waste shipment to EMWMF in September. Approximately 237,000 m{sup 3} (310,000 yd{sup 3}, bulked) of waste taken to EMWMF in 23,000 truckloads expected by project completion
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