3,248 research outputs found
C1− Continuous crack propagation for mixed-mode fracture problems
In this work a C1− continuous crack propagation algorithm is proposed to improve the numerical simulation of localized deformation patterns, using higher order elements. The algorithm is applied for a standard smeared crack model and is validated by a mixed-mode fracture problem. From the results a reduction of mesh-induced directional bias is observed
Fermentation of animal components in strict carnivores: a comparative study with cheetah fecal inoculum
The natural diet of felids contains highly digestible animal tissues but also fractions resistant to small intestinal digestion, which enter the large intestine where they may be fermented by the resident microbial population. Little information exists on the microbial degradability of animal tissues in the large intestine of felids consuming a natural diet. This study aimed to rank animal substrates in their microbial degradability by means of an in vitro study using captive cheetahs fed a strict carnivorous diet as fecal donors. Fresh cheetah fecal samples were collected, pooled, and incubated with various raw animal substrates (chicken cartilage, collagen, glucosamine-chondroitin, glucosamine, rabbit bone, rabbit hair, and rabbit skin; 4 replicates per substrate) for cumulative gas production measurement in a batch culture technique. Negative (cellulose) and positive (casein and fructo-oligosaccharides; FOS) controls were incorporated in the study. Additionally, after 72 h of incubation, short-chain fatty acids (SCFA), including branched-chain fatty acids (BCFA), and ammonia concentrations were determined for each substrate. Glucosamine and glucosamine-chondroitin yielded the greatest OM cumulative gas volume (OMCV) among animal substrates (P < 0.05), whereas total SCFA production was greatest for collagen (P < 0.05). Collagen induced an acetate production comparable to FOS and a markedly high acetate-to-propionate ratio (8.41:1) compared to all other substrates (1.67:1 to 2.97:1)
Photoconductive switching of a high-voltage spark gap
We have demonstrated photoconductive switching of a gas-filled spark gap. A femtosecond Ti:sapphire laser was focused in a 1 mm spark gap biased at 4.5 kV. There is a clear transition between triggered operation, when only part of the path between the electrodes is ionized, and photoconductive switching, when the entire length of the gap is ionized directly by the laser. The measured standard deviation of the time fluctuations between the rising edge of the transmitted electrical pulse and the laser was less than 15 ps
Shop Smart, Buy Green: a consumer's guide to saving money and reducing environmental impacts
Properties of 3-manifolds for relativists
In canonical quantum gravity certain topological properties of 3-manifolds
are of interest. This article gives an account of those properties which have
so far received sufficient attention, especially those concerning the
diffeomorphism groups of 3-manifolds. We give a summary of these properties and
list some old and new results concerning them. The appendix contains a
discussion of the group of large diffeomorphisms of the -handle 3-manifold.Comment: 20 pages. Plain-TeX, no figures, 1 Table (A4 format
An Analysis of the Representations of the Mapping Class Group of a Multi-Geon Three-Manifold
It is well known that the inequivalent unitary irreducible representations
(UIR's) of the mapping class group of a 3-manifold give rise to ``theta
sectors'' in theories of quantum gravity with fixed spatial topology. In this
paper, we study several families of UIR's of and attempt to understand the
physical implications of the resulting quantum sectors. The mapping class group
of a three-manifold which is the connected sum of with a finite number
of identical irreducible primes is a semi-direct product group. Following
Mackey's theory of induced representations, we provide an analysis of the
structure of the general finite dimensional UIR of such a group. In the picture
of quantized primes as particles (topological geons), this general
group-theoretic analysis enables one to draw several interesting qualitative
conclusions about the geons' behavior in different quantum sectors, without
requiring an explicit knowledge of the UIR's corresponding to the individual
primes.Comment: 52 pages, harvmac, 2 postscript figures, epsf required. Added an
appendix proving the semi-direct product structure of the MCG, corrected an
error in the characterization of the slide subgroup, reworded extensively.
All our analysis and conclusions remain as befor
The influence of sensationalist features in television news stories on perceived news quality and perceived sensationalism of viewers in different age groups
This study investigates whether the decreased trust in news media can be explained by the increase in sensationalism in news. To this end, an experiment was conducted in which viewers (N = 288) evaluated sensationalist versus non-sensationalist television news in terms of perceived news quality and perceived sensationalism. Each participant watched four television news stories that varied in the presence of two categories of sensationalism: arousing content and tabloid packaging. Findings showed that sensationalist television news tends to be more negatively evaluated than non-sensationalist news. In addition, critical views on arousing content appeared to be particularly visible among young and middle-aged adults. These findings suggest that the rise of sensationalist news could be an explanation of the declining trust in news media that is witnessed in a number of countries
- …