2,784 research outputs found
Fracture Mechanics of Joints
Almost every engineering design requires that component members be connected. A disadvantage of mechanical connections such as bolts, screws or rivets is that they do not uniformly distribute the load; hence large local stresses result. This problem can often be reduced ~ joining the members adhesively. Major problems with adhesives that have tended to limit their wider us age include: (1) how the strength of an adhesive and the joint in which it is used can reliably be predicted, and (2) what factors tend to limit the strength of an adhesive joint and how they might be eliminated . It is the intent of the authors to show how fracture mechanics might be used to develop a rational philosophy and methodology that will aid in overcoming these problems
Trading interactions for topology in scale-free networks
Scale-free networks with topology-dependent interactions are studied. It is
shown that the universality classes of critical behavior, which conventionally
depend only on topology, can also be explored by tuning the interactions. A
mapping, , describes how a shift of the
standard exponent of the degree distribution can absorb the
effect of degree-dependent pair interactions .
Replica technique, cavity method and Monte Carlo simulation support the
physical picture suggested by Landau theory for the critical exponents and by
the Bethe-Peierls approximation for the critical temperature. The equivalence
of topology and interaction holds for equilibrium and non-equilibrium systems,
and is illustrated with interdisciplinary applications.Comment: 4 pages, 5 figure
Phylogenetic analysis and review of Panacea and Batesia butterflies (Nymphalidae)
Phylogenetic analysis of 53 morphological characte rs for five species of Panacea and Batesia hypochlora supports the separation of the two genera and showed that the monotypic genus Batesia is basal to Panacea. Male genitalia were Ilniform within Panacea and characters inir)f)llative for phylogeny reconstruction were restricted to wing coloration. Illustrations of adults and genitalia, a brief diagnosis, and distributions are provided le)r each species
Testosterone Might Not Be Necessary To Support Female Aggression In Incubating Northern Cardinals
Testosterone\u27s (T) influence on male aggression has been well established in many vertebrate species, but the impact of T on female aggressive behaviour is poorly understood. Among birds, a link between T and female aggression is plausible, as females of many species exhibit a seasonal peak in T concentrations at the onset of breeding when social instability is greatest and they may have circulating T through much of the breeding season. However, investigations examining the relationship between T and female aggression are few and have yielded conflicting results, with experimentally or endogenously elevated T supporting aggressive behaviour in females of some species but not others, and T elevating with aggression at some points of the reproductive cycle but not others. We examined the relationship between endogenous levels of T and female aggression in the northern cardinal, Cardinalis cardinalis, a resident temperate species in which pairs exhibit prolonged territoriality and females have measurable levels of T year-round, including all stages of reproduction (incubation, nestling feeding, etc.). Using simulated nest intrusions, we assessed aggressive responses of incubating females to intrasexual \u27intruders\u27 at the nest and quantified T levels after each aggressive encounter. Displays of aggression towards \u27intruders\u27 varied among females; yet, individuals showing greater levels of aggression did not demonstrate higher levels of T. These results imply that T might not support maternal aggression in this species
Escape Behavior of Quantum Two-Particle Systems with Coulomb Interactions
Quantum escapes of two particles with Coulomb interactions from a confined
one-dimensional region to a semi-infinite lead are discussed by the probability
of particles remaining in the confined region, i.e. the survival probability,
in comparison with one or two free particles. For free-particle systems the
survival probability decays asymptotically in power as a function of time. On
the other hand, for two-particle systems with Coulomb interactions it shows an
exponential decay in time. A difference of escape behaviors between Bosons and
Fermions is considered as quantum effects of identical two particles such as
the Pauli exclusion principle. The exponential decay in the survival
probability of interacting two particles is also discussed in a viewpoint of
quantum chaos based on a distribution of energy level spacings.Comment: 10 pages, 7 figure
A new approximation scheme in quantum mechanics
An approximation method which combines the perturbation theory with the
variational calculation is constructed for quantum mechanical problems. Using
the anharmonic oscillator and the He atom as examples, we show that the present
method provides an efficient scheme in estimating both the ground and the
excited states. We also discuss the limitations of the present method.Comment: 14pages, to be published in Eur. J. Phy
Molecular cloning and expression of a prostaglandin E2 receptor of the EP3β subtype from rat hepatocytes
AbstractRat hepatocytes have previously been reported to possess prostaglandin E2 receptors of the EP3-type (EP3-receptors) that inhibit glucagon-stimulated glycogenolysis by decreasing cAMP. Here, the isolation of a functional EP3β receptor cDNA clone from a rat hepatocyte cDNA library is reported. This clone can be translated into a 362-amino-acid protein, that displays over 95% homology to the EP3β receptor from mouse mastocytoma. The amino- and carboxy-terminal region of the protein are least conserved. Transiently transfected HEK 293 cells expressed a single binding site for PGE2 with an apparent Kd of 15 nM. PGE2 > PGF2α > PGD2 competed for [3H]PGE2 binding sites as did the EP3 receptor agonists M&B 28767 = sulprostone > misoprostol but not the EP1 receptor antagonist SC 19220. In stably transfected CHO cells M&B 28767 > sulprostone = PGE2 > misoprostol > PGF2α inhibited the forskolin-elicited cAMP formation. Thus, the characteristics of the EP3β receptor of rat hepatocytes closely resemble those of the EP3β receptor of mouse mastocytoma
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