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Abstract: We demonstrate cyclic strain hardening and frequency-dependent fatigue life in electrodeposited nanocrystalline Ni subjected to tension–tension cyclic deformation. These observations are rationalized through mechanistic arguments based on the exhaustion of dislocation sources in the early stages of cyclic loading and on the domination of diffusive processes during later stages. [Copyright &y& Elsevier]

Autoimmune bullous diseases are a heterogenous group of diseases characterized by cutaneous and mucosal vesicles and bullae. Diagnosis is based on a combination of clinical, histopathological, and immunofluorescence findings. Current treatment, including vigilant wound care, significantly reduces disease morbidity and mortality. [ABSTRACT FROM AUTHOR]

Abstract: The early stage sliding contact fatigue behavior of nanocrystalline materials, with average and total range of grain sizes well below 100nm, was studied. The evolution of friction and damage during repeated sliding contact in the nanocrystalline metals and alloys was systematically compared and contrasted with that in ultrafine-crystalline and microcrystalline materials so as to develop a broad perspective on the effects of grain size on sliding contact fatigue. Some critical experiments were performed to separate the effects of material strength and grain size on friction and damage evolution. Over the range of materials examined, strength rather than grain size appeared to dominate the steady-state friction coefficient and damage accumulation, each diminishing with substantial increases in material strength. [Copyright &y& Elsevier]

Abstract: In this work, the stress-life fatigue behavior and fatigue crack growth characteristics of pure Ni were studied as a function of grain size spanning a range of tens of nanometer to tens of micrometer. The fatigue response of electrodeposited, fully dense, nanocrystalline pure Ni, with average and total range of grain sizes well below 100nm, was compared and contrasted with that of electrodeposited ultrafine-crystalline pure Ni with an average grain size of about 300nm and conventional microcrystalline Ni with an average grain size in excess of 10μm. It was found that grain refinement to the nanocrystalline regime generally leads to an increase in total life under stress-controlled fatigue whereas a deleterious effect was seen on the resistance to fatigue crack growth at low and high tensile load ratio levels. To explore the generality of the above trends, systematic experiments were also performed in ultrafine-crystalline pure Ti produced by equal-channel angular pressing where a reduction in grain size was found to cause an increase in fatigue crack growth rates at different tensile load ratios. Grain refinement from the microcrystalline to the ultrafine-crystalline regime by cryomilling of Al alloys also showed a similar response. Possible mechanistic origins of such trends are explored, and some general conclusions are extracted on strategies for improvements in the fatigue resistance of engineering structures by recourse to grain refinement down to the nanocrystalline regime. [Copyright &y& Elsevier]

The fatigue response of electrodeposited nanocrystalline pure Ni and a cryomilled ultra-fine-crystalline Al–Mg alloy was studied. It was found that grain refinement generally leads to an increase in resistance to failure under stress-controlled fatigue whereas a generally deleterious effect was seen on the resistance to fatigue crack growth. [Copyright &y& Elsevier]

We report an x-ray diffraction study of a HgTe-CdTe superlattice (SL)/HgCdTe heterostructure grown by molecular beam epitaxy (MBE). The diffraction results are used to place an upper bound on the misfit accommodation at the lattice-mismatched SL/HgCdTe interface. The misfit accommodation at the heterointerface is at least an order of magnitude less than that predicted by equilibrium misfit theory. It appears that the low substrate temperature used in MBE HgCdTe growth imposes a kinetic barrier to misfit accommodation. [ABSTRACT FROM AUTHOR]

Several recent studies have shown that amphibian populations may exhibit high genetic subdivision in areas with recent fragmentation and urban development. Less is known about the potential for genetic differentiation in continuous habitats. We studied genetic differentiation of red-backed salamanders (Plethodon cinereus) across a 2-km transect through continuous forest in Virginia, USA. Mark-recapture studies suggest very little dispersal for this species, whereas homing experiments and post-Pleistocene range expansion both suggest greater dispersal abilities. We used six microsatellite loci to examine genetic population structure and differentiation between eight subpopulations of red-backed salamanders at distances from 200 m to 2 km. We also used several methods to extrapolate dispersal frequencies and test for sex-biased dispersal. We found small, but detectable differentiation among populations, even at distances as small as 200 m. Differentiation was closely correlated with distance and both Mantel tests and assignment tests were consistent with an isolation-by-distance model for the population. Extrapolations of intergenerational variance in spatial position (σ2<15 m2) and pair-wise dispersal frequencies (4Nm<25 for plots separated by 300 m) both suggest limited gene flow. Additionally, tests for sex-biased dispersal imply that dispersal frequency is similarly low for both sexes. We suggest that these low levels of gene flow and the infrequent dispersal observed in mark-recapture studies may be reconciled with homing ability and range expansion if dispersing animals rarely succeed in breeding in saturated habitats, if dispersal is flexible depending on the availability of habitat, or if dispersal frequency varies across the geographic range of red-backed salamanders.Heredity (2007) 98, 53–60. doi:10.1038/sj.hdy.6800905; published online 27 September 2006 [ABSTRACT FROM AUTHOR]

In this paper, the local compositional and structural changes occurring in association with stacking faults in a Ni-base superalloy are characterized and related to the possible rate-controlling processes during creep deformation at intermediate temperatures. These rate-controlling processes are not presently understood. In order to promote stacking fault shearing, compression creep tests on specially prepared single crystals of an exploratory Ni-base superalloy were conducted at 760 °C in the [0 0 1] orientation. Scanning transmission electron microscopy (STEM) imaging was coupled with state-of-the-art energy dispersive X-ray (EDX) spectroscopy to reveal for the first time an ordered compositional variation along the extrinsic faults inside the γ′ precipitates, and a distinct solute atmosphere surrounding the leading partial dislocations. The local structure and chemistry at the extrinsic fault is consistent with the η phase, a D0 24 hexagonal structure. Density Functional Theory (DFT) and high angle annular dark field (HAADF)-STEM image simulations are consistent with local η phase formation and indicate that a displacive–diffusive transformation occurs dynamically during deformation. [ABSTRACT FROM AUTHOR]

This descriptive study examines the self-reported behaviors of 285 male and female adolescent children (ages 12-17) of narcotic addicts participating in methadone maintenance programs. These children responded to an extensive 2.5-hour interview questionnaire focusing on current and past activities, including criminal activities prior to age 12. The findings revealed that early deviance, assessed by self-report measures of both severity and variety, is related to current adolescent drug and alcohol use, association with deviant peers, a negative view of home atmosphere, and psychological symptomatology. These results are contrasted with the retrospective reports of adolescent behavior obtained from adult male narcotic addicts in a prior study of vulnerability to addiction. The comparability of study results is discussed in the context of developmental risk factors, prevention and treatment strategies, and other considerations specifically related to the development of children of narcotic addicts. [ABSTRACT FROM AUTHOR]

This survey study of male and female narcotic addicts participating in methadone maintenance programs examined self-reported retrospective data on parental behavior experienced by addicts during their adolescent years. These findings were contrasted with the addicts' self-report of their current parenting practices with their own adolescent children. Results showed addicts as perceiving their mothers as significantly more functional in their parenting practices than their fathers on indices of parental involvement, attachment, and responsibility. Significant parenting differences between addicts and their parents were reported for the three indices mentioned, as well as for parent discipline and punitive actions, with the addicts rating their current parenting practices as more effective than those of their parents. Reported parenting practices were further analyzed in the context of how the ratings of parental functioning were related to problems of drug and alcohol abuse exhibited in the home. Findings are discussed in terms of the implications for prevention and treatment approaches for addicts and their children. [ABSTRACT FROM AUTHOR]

Although the mechanical behavior of carbon nanotubes has been studied extensively in recent years, very few experimental results exist on the shell buckling of nanotubes, despite its fundamental importance in nanotube mechanics and applications. Here we report an experimental technique in which individual multiwalled carbon nanotubes were axially compressed using a nanoindenter and the critical shell-buckling load was measured. The results are compared with predictions of existing continuum theories, which model multiwalled carbon nanotubes as a collection of single-walled shells, interacting through van der Waals forces. The theoretical models significantly underpredict the experimental buckling load. [ABSTRACT FROM AUTHOR]