877 resultados para random regular graphs


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Seven obese Type 2 diabetic patients were studied for two 4-h periods after ingestion of a glucose load to determine the effects of preprandial subcutaneous injection of Insulin Lispro (5 min before the meal) or regular insulin (20 min before the meal) on glucose metabolism. Glucose production and utilisation were measured using a dual isotope method. After Lispro, the mean postprandial increase in plasma glucose was 29% lower and the increase in insulin concentration 25% higher than after regular insulin (p < 0.05). Suppression of endogenous glucose production was similar with both types of insulin. Thus, preprandial injection of Lispro reduced postprandial glucose increments in Type 2 diabetic patients as compared to regular insulin. This effect is best explained by the increased postprandial bioavailability of Lispro.

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Limited migration results in kin selective pressure on helping behaviors under a wide range of ecological, demographic and life-history situations. However, such genetically determined altruistic helping can evolve only when migration is not too strong and group size is not too large. Cultural inheritance of helping behaviors may allow altruistic helping to evolve in groups of larger size because cultural transmission has the potential to markedly decrease the variance within groups and augment the variance between groups. Here, we study the co-evolution of culturally inherited altruistic helping behaviors and two alternative cultural transmission rules for such behaviors. We find that conformist transmission, where individuals within groups tend to copy prevalent cultural variants (e.g., beliefs or values), has a strong adverse effect on the evolution of culturally inherited helping traits. This finding is at variance with the commonly held view that conformist transmission is a crucial factor favoring the evolution of altruistic helping in humans. By contrast, we find that under one-to-many transmission, where individuals within groups tend to copy a "leader" (or teacher), altruistic helping can evolve in groups of any size, although the cultural transmission rule itself hitchhikes rather weakly with a selected helping trait. Our results suggest that culturally determined helping behaviors are more likely to be driven by "leaders" than by popularity, but the emergence and stability of the cultural transmission rules themselves should be driven by some extrinsic factors.

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Background The global mortality caused by cardiovascular disease increases with weight. The Framingham study showed that obesity is a cardiovascular risk factor independent of other risks such as type 2 diabetes mellitus, dyslipidemia and smoking. Moreover, the main problem in the management of weight-loss is its maintenance, if it is achieved. We have designed a study to determine whether a group motivational intervention, together with current clinical practice, is more efficient than the latter alone in the treatment of overweight and obesity, for initial weight loss and essentially to achieve maintenance of the weight achieved; and, secondly, to know if this intervention is more effective for reducing cardiovascular risk factors associated with overweight and obesity. Methods This 26-month follow up multi-centre trial, will include 1200 overweight/obese patients. Random assignment of the intervention by Basic Health Areas (BHA): two geographically separate groups have been created, one of which receives group motivational intervention (group intervention), delivered by a nurse trained by an expert phsychologist, in 32 group sessions, 1 to 12 fortnightly, and 13 to 32, monthly, on top of their standard program of diet, exercise, and the other (control group), receiving the usual follow up, with regular visits every 3 months. Discussion By addressing currently unanswered questions regarding the maintenance in weight loss in obesity/overweight, upon the expected completion of participant follow-up in 2012, the IMOAP trial should document, for the first time, the benefits of a motivational intervention as a treatment tool of weight loss in a primary care setting.

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Treball final de carrera basat en el reconeixement de punts clau en imatges mitjançant l'algorisme Random Ferns.

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In this paper we prove that there are only two different classes of central configura- tions with convenient masses located at the vertices of two nested regular tetrahedra: either when one of the tetrahedra is a homothecy of the other one, or when one of the tetrahedra is a homothecy followed by a rotation of Euler angles = = 0 and = of the other one. We also analyze the central configurations with convenient masses located at the vertices of three nested regular tetrahedra when one them is a homothecy of the other one, and the third one is a homothecy followed by a rotation of Euler angles = = 0 and = of the other two. In all these cases we have assumed that the masses on each tetrahedron are equal but masses on different tetrahedra could be different.

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We consider 2n masses located at the vertices of two nested regular polyhedra with the same number of vertices. Assuming that the masses in each polyhedron are equal, we prove that for each ratio of the masses of the inner and the outer polyhedron there exists a unique ratio of the length of the edges of the inner and the outer polyhedron such that the configuration is central.

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Three regular polyhedra are called nested if they have the same number of vertices n, the same center and the positions of the vertices of the inner polyhedron ri, the ones of the medium polyhedron Ri and the ones of the outer polyhedron Ri satisfy the relation Ri = ri and Ri = Rri for some scale factors R > > 1 and for all i = 1, . . . , n. We consider 3n masses located at the vertices of three nested regular polyhedra. We assume that the masses of the inner polyhedron are equal to m1, the masses of the medium one are equal to m2, and the masses of the outer one are equal to m3. We prove that if the ratios of the masses m2/m1 and m3/m1 and the scale factors and R satisfy two convenient relations, then this configuration is central for the 3n–body problem. Moreover there is some numerical evidence that, first, fixed two values of the ratios m2/m1 and m3/m1, the 3n–body problem has a unique central configuration of this type; and second that the number of nested regular polyhedra with the same number of vertices forming a central configuration for convenient masses and sizes is arbitrary.

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The objective of this work was to compare the relative efficiency of initial selection and genetic parameter estimation, using augmented blocks design (ABD), augmented blocks twice replicated design (DABD) and group of randomised block design experiments with common treatments (ERBCT), by simulations, considering fixed effect model and mixed model with regular treatment effects as random. For the simulations, eight different conditions (scenarios) were considered. From the 600 simulations in each scenario, the mean percentage selection coincidence, the Pearsons´s correlation estimates between adjusted means for the fixed effects model, and the heritability estimates for the mixed model were evaluated. DABD and ERBCT were very similar in their comparisons and slightly superior to ABD. Considering the initial stages of selection in a plant breeding program, ABD is a good alternative for selecting superior genotypes, although none of the designs had been effective to estimate heritability in all the different scenarios evaluated.

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1. The effect of a haematophageous ectoparasite, the hen flea, on quality an number of offspring was experimentally investigated in the great tit. The experiment consisted of a controlled infestation of a random sample of nests with the parasitic flea and of a regular treatment of control nests with Microwaves in order to eliminate the naturally occurring fleas. 2. To assess the effects of fleas on variables related to offspring number, we considered the number of hatchlings and fledglings, the mortality between hatching and fledging, and the hatching and fledging success. For assessment of offspring quality, we measured body mass, tarsus and wing length, and calculated the nutritional condition of, nestlings as the ratio of body mass to tarsus length. A physiological variable, the haematocrit level, was also measured. 3. Hatching success and hatchling numbers did not differ between the two experimental groups. Offspring mortality between hatching and fledging was significantly higher in the infested broods (xBAR = 0.22 chicks dead per day) than in the parasite-free broods (xBAR = 0.07 dead per day). Fledging success was 83% in the parasite-free broods, but only 53% in the infested ones. The number of fledglings in infested broods (xBAR = 3.7 fledglings +/-2.1 SD) was significantly lower than in the parasite-free (xBAR = 4.9 +/- 1.1 SD) broods. 4. Body mass of chicks in the infested broods was significantly smaller than in the parasite-free broods both 14 days and 17 days after hatching. The chicks in the infested broods reached a significantly smaller tarsus length than the ones in the parasite-free broods. Close to fledging, the nutritional condition of chicks was significantly lower in infested broods. Haematocrit levels were significantly lower in the infested broods. 5. Brood size correlated differently with body mass and condition of chicks in infested and parasite-free nests. In parasite-free broods both body mass and condition of chicks at age 17 days, i.e. close to fledging, were significantly higher in small broods than in large ones. However, in the infested broods chicks were of the same body mass and condition in large as in small broods. Therefore, in parasite-free broods fitness can potentially be gained through offspring quality or number or both, whereas in infested broods it can be gained through offspring quantity only. In other words, a trade-off between quality and number of offspring is feasible only in the absence of the parasitic hen flea. 6. These results emphasize the need to study the effects of ectoparasites on ecological, behavioural and evolutionary traits of their bird hosts. A knowledge of these effects is essential for the understanding of population dynamics, behaviour and life-history traits of the hosts.

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We uncover the global organization of clustering in real complex networks. To this end, we ask whether triangles in real networks organize as in maximally random graphs with given degree and clustering distributions, or as in maximally ordered graph models where triangles are forced into modules. The answer comes by way of exploring m-core landscapes, where the m-core is defined, akin to the k-core, as the maximal subgraph with edges participating in at least m triangles. This property defines a set of nested subgraphs that, contrarily to k-cores, is able to distinguish between hierarchical and modular architectures. We find that the clustering organization in real networks is neither completely random nor ordered although, surprisingly, it is more random than modular. This supports the idea that the structure of real networks may in fact be the outcome of self-organized processes based on local optimization rules, in contrast to global optimization principles.

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We present a model in which particles (or individuals of a biological population) disperse with a rest time between consecutive motions (or migrations) which may take several possible values from a discrete set. Particles (or individuals) may also react (or reproduce). We derive a new equation for the effective rest time T˜ of the random walk. Application to the neolithic transition in Europe makes it possible to derive more realistic theoretical values for its wavefront speed than those following from the single-delayed framework presented previously [J. Fort and V. Méndez, Phys. Rev. Lett. 82, 867 (1999)]. The new results are consistent with the archaeological observations of this important historical process