No description available.

No description available.

The crossing number of a graph is the minimum number of pairwise crossings of edges among all planar drawings of the graph. A graph G is k-crossing critical if it has crossing number k and any proper subgraph of G has a crossing number less than k. The set of 1-crossing critical graphs is is determined by Kuratowski’s Theorem to be {K5, K3,3}. Work has been done to approach the problem of classifying all 2-crossing critical graphs. The graph V2n is a cycle on 2n vertices with n intersecting chords. The only remaining graphs to find in the classification of 2-crossing critical graphs are those that are 3-connected with a V8 minor but no V10 minor. This paper seeks to fill some of this gap by defining and completely describing a class of graphs called fully covered. In addition, we examine other ways in which graphs may be 2-crossing critical. This discussion classifies all known examples of 3-connected, 2-crossing critical graphs with a V8 minor but no V10 minor.

Falls are the leading cause of injuries among Canadians who are aged at 65 years and over. The assessment of dynamic stability has been proved as an effective method to identify fall-prone elderly individuals, which is essential to fall prevention. Tai Chi has been recommended as an effective exercise to prevent falls by the American Geriatric Society and British Geriatric Society. It is important to examine dynamic stability among Tai Chi practitioners and to explore the mechanisms of the effects of Tai Chi practice on fall prevention. This study examined the dynamic postural stability which is assessed by center of mass (COM) range of motion, COM - center of pressure (COP) separation, and temporospacial measures of gait during obstacle-walking in two groups: Tai Chi group and healthy controls. Fifteen participants in each group were asked to complete two walking conditions, level walking and 20cm-obstacle walking. Results showed that when compared with Tai Chi group, control group adopted a conservative crossing strategy with a significantly smaller crossing stride, higher heel clearance, and smaller pre horizontal distance to make obstacle crossing as safe as possible. This conservative strategy indicates the inability to cross obstacle casually and it may be associated with the decline in muscle strength and proprioception. It also showed that Tai Chi practitioners displayed a significantly larger COM range of motion in both anteroposterior (AP) and mediolateral (ML) direction (p<0.05) and a significantly larger COM-COP separation in ML direction (p <0.01), as compared with control group. The larger range of motion of COM and distance between COM and COP indicates that Tai Chi practitioners have a better ability to tolerate unsteadiness, which means if perturbation occurs, Tai Chi practitioners have a larger range to shift COM in the boundary of base of support.

It has been suggested (Suzuki, 1965a) that the extrinsic and intrinsic factors which increase crossing over in the centromere regions of Drosophila do so by inactivating these regions at the time of crossing over; the inactivation resulting in altered chromosome structure which permits the intimate synapsis necessary for crossing over. This hypothesis predicts that the 3L heterochromatic marker w⁺ carried in Dp(wm)264.58a, which exhibits position effect variegation, would tend to be inactivated by chromosome aberrations, known to increase crossing over. The reversed acrocentric (RA) compound X chromosome, the X chromosome inversions sc⁴sc⁸ and sc⁸, the autosomal inversions Cy, Sb, and Ubx, and the Minute mutants M(2) and M(3) were tested for their effects on the expression of w⁺ in various coisogenic stocks. The amount of pigment in each eye was visually scored into twelve classes. Crossover analyses of the centromere regions of chromosomes 2 and 3 were performed to confirm the effects of sc⁴sc⁸, Cy, Ubx, and Sb on crossing over. The RA, sc⁴sc⁸, Cy, and Ubx all increase crossing over and significantly depress the activity of w⁺. The degree of pigment reduction is correlated with the amount of increase in crossing over. Combination of these aberrations produces an effect on pigmentation and crossing over greater than that produced by either considered singly. Sb has a slight effect in increasing crossing over and decreasing pigmentation. M(3), known to increase crossing over, significantly decreases pigmentation whereas M(2) does not. The effect of the X chromosome inversion sc⁸ is doubtful. Expression of w⁺ is affected similarly in males and females, an observation suggesting that the chromosome physiology of both sexes is similar although the actual factor(s) mediating crossing over are absent in the males. These results lend support to the proposed hypothesis but, with fluctuating parental source effects and variations found within a stock testifying to the general lability of the system, further tests under stringently controlled conditions are necessary before such experiments can be considered critical. / Science, Faculty of / Zoology, Department of / Graduate

Redfield's theory and the theory of master equations have been reviewed and their applications to muonium spin dynamics discussed. It was found that both theories are equivalent in the Markov limit. In some cases, analytical expressions for relaxation rates are found. In addition, Redfield's theory was applied to describe spin relaxation of muonium-substituted free radicals near level-crossing resonances. Theoretical predictions were compared with experimental data for the C₆F₆-Mu radical and the results suggest there are several relaxation mechanisms involved. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

I think of a library in a small town as a social center rather than a closed institution. It should be seen as part of the public space of the city, an open place with a cultural - educational and social life. Apart from the possibility of concentrated individual study, it should also provide space for group work and social gathering of residents. Authors' readings, lectures and workshops are held in such a library. The library environment should be pleasant and suitable for a long stay with plenty of natural light and contact with the exterior. It includes a literary café, a buffet and an open-air reading room. The library in Hranice is designed as a terraced "house" with walking roofs. The building creates a link between the park and the street of 1. Máje. You can walk through the library from the street to park and vice versa, both through the interior of the library and outside on its roof.

No description available.

Roads are prominent, contiguous features covering approximately 1% of the United States land mass and have been built for decades with little consideration for ecological effects. Increasingly, the impacts of roads are being recognized and the science of road ecology is emerging as an important area of study for conservation biologists. For wildlife, the impacts of roads are disproportionate to the area of land they occupy. Direct impacts on wildlife include mortality via vehicle collision and restriction or alteration of movement. Road kill exceeds hunting as the leading direct human cause of vertebrate mortality, with approximately one million vertebrates a day killed on roads in the United States. Roadways also affect wildlife through habitat loss and fragmentation, isolation of wildlife populations, disruption of gene flow and metapopulation dynamics. A variety of strategies have been used with mixed success to mitigate the impacts of roads on wildlife. Commonly, underpasses are used to facilitate movement of wildlife across roadways in Europe, Australia, Canada and the U.S.. However, the effectiveness of these underpasses to facilitate wildlife movement depends on a number of variables, including: size, proximity to natural wildlife corridors, noise levels, substrate, vegetative cover, moisture, temperature, light, and human disturbance. Further, different species typically have different requirements. Thus if crossing structures are designed for use by a singles species, they may constitute an absolute barrier for other species that have different requirements. Most attempts to evaluate wildlife crossing structures focus exclusively on documenting wildlife use of structures. While tracking beds, cameras, and counters document the species using structures, they provide little information on those species or individuals that fail to use a structure. In contrast, telemetry, trapping and tracking studies are more useful for determining the extent to which roadways inhibit wildlife movements and the degree to which crossing structures mitigate these effects. Thus, to fully assess the effectiveness of wildlife passageways, a combination of monitoring techniques across a variety of taxa is needed to evaluate structure use impacts of transportation systems on animal movements. The goal of this study was to assess the effectiveness of wildlife crossing structures constructed as part of the Bennington Bypass (Highway 279) in southern Vermont. The bypass was completed in October 2004 and includes three wildlife crossing structures, including two extended bridges and a large culvert. This study monitored the effectiveness of these crossing structures and compared rates of wildlife movement across the highway in mitigated and unmitigated sections.

No description available.