The effect of a zirconium strength differential on cladding collapse predictions

An investigation was made into the occurrence of a strength differential in the Zircaloy cladding of LWR fuels, and into the effect such a strength differential can have on the analytical predictions of cladding creep collapse during fuel densification. The strength differential, or SD, refers to the difference in the compressive and tensile yield strengths of a material. It was concluded that an SD in Zircaloy cladding can have a significant effect on cladding collapse predictions; inclusion of SD considerations in cladding creep down analysis can increase predicted collapse times by a factor of two.     

Assessment of bone in Ehlers Danlos syndrome by ultrasound and densitometry

OBJECTIVE: Ehlers Danlos syndrome (EDS) is an inherited disorder of connective tissue characterised by hyperextensible skin, joint laxity, and easy bruising. There are phenotypic similarities with osteogenesis imperfecta, but in EDS a tendency to fracture or altered bone mass has not previously been considered to be a cardinal feature. METHOD: This case-control design study investigates whether 23 patients with EDS had differences in fracture rates, bone mass, and calcaneal ultrasound parameters compared with age and sex matched controls. RESULTS: 23 cases of EDS (mean (SD) age 38.5 (15.5)) were compared with 23 controls (mean age 37.8 (14.5)). A significant reduction in bone density measured by dual energy x ray absorptiometry was found at the neck of femur by 0.9 SD, p = 0.05, and lumbar spine by 0.74 SD, p = 0.02. At the calcaneum, broad band ultrasound attenuation and speed of sound were significantly reduced compared with controls by 0.95 SD (p = 0.004) and 0.49 SD (p = 0.004) for broad band ultrasound attenuation and speed of sound respectively. Broad band ultrasound attenuation and speed of sound remained significantly reduced after adjusting for bone mineral density (BMD). After adjusting for functional status (HAQ), age and sex, hypermobility was inversely correlated with broad band ultrasound attenuation and SOS, but not BMD at hip or spine. Previous fracture was 10 times more common in EDS (p < 0.001), with 86.9% of patients reporting a total of 47 low impact fractures, compared with 8.7% of controls. CONCLUSION: This study has identified a tendency of EDS patients to fracture, have low bone mass and abnormal bone structure. The aetiology is likely to be multifactorial, with an inherited structural element, accentuated by immobility or reduced exercise. This is one of the first clinical studies to suggest ultrasound can detect structural differences in bone, independent of dual energy x ray absorptiometry.     

Role of the cytoskeleton during early development.

Oocytes, eggs, and embryos from a diverse array of species have evolved cytoskeletal specializations which allow them to meet the needs of early embryogenesis. While each species studied possesses one or more specializations which are unique, several cytoskeletal features are widely conserved across different animal phyla. These features include highly-developed cortical cytoskeletal domains associated with developmental information, microtubule-mediated pronuclear transport, and rapid intracellular signal-regulated control of cytoskeletal organization.     

A 1D- and 2D-NMR Study of an Anionic Surfactant/Neutral Polymer Complex

NMR chemical shifts and linewidth measurements were examined for mixtures of sodium 10-phenyldecanoate (Na ω-PhDec) in deuterated aqueous solutions in the presence of varying compositions of poly(ethylene oxide) (PEO) polymers of 2000 and 4000 molecular weight. In addition, variable temperature NMR spectra and NMR spin lattice relaxation times (T ₁) were obtained for the PEO-4000/Na ω-PhDec system as a function of varying polymer concentrations. As expected, the polymer/surfactant systems exhibit the behaviour typical of that of an anionic surfactant/neutral polymer system with well defined critical aggregation concentrations (CMC) corresponding to the formation of polymer/surfactant complexes below the CMC of the free surfactant. The ¹H-NMR linewidths acquired for the Na ω-PhDec/PEO-4000 system before and after the CMC region of the surfactant indicate that the maximum in the linewidth of the PEO proton peak is reached at approximately twice the CMC of the free surfactant. 2D-NMR NOESY measurements on this system exhibit cross peaks between the PEO protons and the protons on the surfactant backbone, consistent with the location of the phenyl group in the micellar interior. All these NMR experiments are interpreted in terms of the structure of the polymer/surfactant complexes as a function of the system composition.

Temperature-dependent electrical resistance of conductive polylactic acid filament for fused deposition modeling

This study characterizes the microstructure and temperature dependence of resistance of two commercially available electrically conductive polylactic acid (PLA) composites for fused deposition modeling (FDM): PLA-carbon black and PLA-graphene. No microstructural changes were observed between the filament and the printed parts; however, the resistivity of the filament was found to drop by four to six times upon FDM. Also, compared to the resistivity of individual extruded wire, the resistivity of the printed parts was found to be up to 1500 times higher for PLA-graphene and up to 300 times higher for PLA-carbon black. The raw PLA-carbon black filament and printed wire showed a positive temperature coefficient of resistance (α) value between ~?0.03 and 0.01 °C^?1, which makes them more suitable for sensor development. The raw PLA-graphene filament and printed wire did not exhibit a significant α, which makes them more suitable for printing wires. However, the parts made with multilayer FDM exhibited a negative or a negligible α up to a certain temperature prior to exhibiting a positive α; further, these α values were significantly lower than those obtained for the filaments before or after extrusion. These findings enable proper selection of commercial conductive FDM filaments for enabling quicker prototyping of electronics and sensors.     

Microwave absorption measurements of the electrical conductivity of small particles

A microwave absorption technique based on cavity perturbation theory is shown to be applicable for electrical conductivity measurements of both a small, single-crystal particle and finely divided powder samples when values fall in either the low (<0.1 ^–1 cm^–1) or the intermediate (0.1 100 ^–1 cm^–1) conductivity region. The results here pertain to semiconductors in the latter region. If the skin depth of the material becomes significantly smaller than the sample dimension parallel to theE-field, an appreciable error can be introduced into the calculated conductivity values; however, this discrepancy is eliminated by correcting for the field attenuation associated with the penetration depth of the microwaves. A modification of this approach utilizing the skin depth allows a first-order correction to be applied to powder samples which results in the accurate measurement of absolute values, and results with doped Si powders are compared to values obtained from one small single particle using this microwave technique as well as reported DC values determined with single crystals. The use of this microwave absorption technique with small particles having high surface/volume ratios, such as catalyst supports and oxide catalysts, under controlled environments can provide fundamental information about adsorption and catalytic processes on such semiconductor surfaces. An application to a ZnO powder demonstrates this capability.     

Transformation of the amphibian oocyte into the egg: Structural and biochemical events

Amphibian oocytes, arrested in prophase I, are stimulated to progress to metaphase II by progesterone. This process is referred to as meiotic maturation and transforms the oocyte, which cannot support the early events of embryogenesis, into the egg, which can. Meiotic maturation entails global reorganization of cell ultrastructure: In the cell cortex, the plasma membrane flattens and the cortical granules undergo redistribution. In the cell periphery, the annulate lamellae disassemble and the mitochondria become dispersed. In the cell interior, the germinal vesicle becomes disassembled and the meiotic spindles form. Marked changes in the cytoskeleton and mRNA distribution also occur throughout the cell. All of these events are temporally correlated with intracellular signalling events: Fluctuations in cAMP levels, changes in pH, phosphorylation and dephosphorylation, and ion flux changes. Evidence suggests that specific intracellular signals are responsible for specific reorganizations of ultrastructure and mRNA distribution.     

Women as authors and editors of psychological journals: A 10-year perspective.

Conducted a 1982 follow-up of the studies of M. Teghtsoonian (1974) and R. Over (see record 1982-08416-001) to construct a 10-yr basis for comparison based on the 14 journals used by Over. Percentages of women on editorial boards were compared with percentages of women who were senior authors and percentages of women in associated divisions of the American Psychological Association. Results show that board representation increased markedly in the 1st half of the decade but regressed in the last half. Findings do not confirm the suggestion by Over that the underrepresentation of women on editorial boards had been remedied by 1981. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)