Discussion influence of yield surface curvature on flow localization in dilatant plasticity

The results of finite element calculations for a hollow sphere micromodel are used to examine the underlying assumptions and the specific yield functions in the dilatant plasticity theories of Gurson (1977) and Mear and Hutchinson     

Using physical memorabilia as opportunities to move into collocated digital photo-sharing

The uptake of digital photos vs. print photos has altered the practice of photo-sharing. Print photos are easy to share within the home, but much harder to share outside of it. The opposite is true of digital photos. People easily share digital photos outside the home, e.g., to family and friends by e-mail gift-giving, and to social networks and the broader public by web publishing. Yet within the home, collocated digital photo-sharing is harder, primarily because digital photos are typically stored on personal accounts in desktop computers located in home offices. This leads to several consequences. (1) The invisibility of digital photos implies few opportunities for serendipitous photo-sharing. (2) Access control and navigation issues inhibit family members from retrieving photo collections. (3) Photo viewing is compromised as digital photos are displayed on small screens in an uncomfortable viewing setting.To mitigate some of these difficulties, we explore how physical memorabilia collected by family members can create opportunities that encourage social and collocated digital photo-sharing. First, we studied (via contextual interviews with 20 households) how families currently practice photo-sharing and how they keep memorabilia. We identified classes of memorabilia that can serve as memory triggers to family events, trips, and times when people took photos. Second, we designed Souvenirs, a photo-viewing system that exploits memorabilia as a social instrument. Using Souvenirs, a family member can meaningfully associate physical memorabilia with particular photo-sets. Later, any family member can begin their story-telling with others through the physical memento, and then enrich the story by displaying its associated photos simply by moving the memento close to the home's large-format television screen. Third, we re-examined our design premises by evoking household reactions to an early version of Souvenirs. Based on these interviews, we redesigned Souvenirs to better reflect the preferences and real practices of photo and memorabilia use in the home.     

The interaction between skill, postures, forces and back pain in wool handling

Wool handling is an important rural occupation where workers process 200 or more fleeces daily, separating them into various quality components. Loads and postures they experience carry substantial risk of low back pain (LBP). Although a formal skill training structure exists, interaction with loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads of 60 wool handlers representing 3 skill levels. LBP prevalence ranged from 20% for junior (lowest skill) to 45% for open class (highest skill) wool handlers. Open class wool handlers demonstrated increased lateral bend and more axially twisted postures, generating greater medio-lateral shear forces and lateral bend and axial twist moments. LBP was associated with open class wool handlers spending more time in severe axially twisted postures. These findings suggest that skill-based training needs to be reviewed to reduce the quantity of axially twisted posture which may help reduce the prevalence of LBP in this workforce.     

Three-dimensional spinal motion and risk of low back injury during sheep shearing

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.     

Isolation and characterization of the Saccharomyces cerevisiae DPP1 gene encoding diacylglycerol pyrophosphate phosphatase

Diacylglycerol pyrophosphate (DGPP) is involved in a putative novel lipid signaling pathway. DGPP phosphatase (DGPP phosphohydrolase) is a membrane-associated 34-kDa enzyme from Saccharomyces cerevisiae which catalyzes the dephosphorylation of DGPP to yield phosphatidate (PA) and then catalyzes the dephosphorylation of PA to yield diacylglycerol. Amino acid sequence information derived from DGPP phosphatase was used to identify and isolate the DPP1 (diacylglycerol pyrophosphate phosphatase) gene encoding the enzyme. Multicopy plasmids containing the DPP1 gene directed a 10-fold overexpression of DGPP phosphatase activity in S. cerevisiae. The heterologous expression of the S. cerevisiae DPP1 gene in Sf-9 insect cells resulted in a 500-fold overexpression of DGPP phosphatase activity over that expressed in wild-type S. cerevisiae. DGPP phosphatase possesses a Mg2+-independent PA phosphatase activity, and its expression correlated with the overexpression of DGPP phosphatase activity in S. cerevisiae and in insect cells. DGPP phosphatase was predicted to be an integral membrane protein with six transmembrane-spanning domains. The enzyme contains a novel phosphatase sequence motif found in a superfamily of phosphatases. A dpp1Delta mutant was constructed by deletion of the chromosomal copy of the DPP1 gene. The dpp1Delta mutant was viable and did not exhibit any obvious growth defects. The mutant was devoid of DGPP phosphatase activity and accumulated (4-fold) DGPP. Analysis of the mutant showed that the DPP1 gene was not responsible for all of the Mg2+-independent PA phosphatase activity in S. cerevisiae.     

The influence of a back support harness on spinal forces during sheep shearing

Previous research has classified the occupation of sheep shearing as heavy work where shearers flex their spine and hips for long periods of time, handle awkward loads and expend high amounts of energy. The aim of this research was to investigate the magnitude of spinal forces produced during the shearing phase of the work and to determine whether the use of a commercially available back support harness would reduce these forces. Following discussion on task complexity and risk of back injury with senior shearing instructors, three component tasks of the shearing phase were identified as posing high risk of injury and were prioritized for primary analysis. Although the dragging out of a sheep in preparation for shearing and an unexpected loss of animal control were also identified as being of high risk, technological and instrumentation difficulties precluded their analysis. Twelve experienced shearers were videotaped while shearing with and without the use of a back harness. Surface mounted retro-reflective markers placed on the trunk defined three linked segments: Pelvis, Lumbar and Head, Arms, and Upper Trunk (HAUT). A 3D, link segment, top down, inverse dynamics approach was used to describe the motion and to estimate forces involved during the identified tasks of shearing. The spinal force/time profiles of this sample of shearers demonstrated large compressive and shear forces for all three tasks that are close to the NIOSH and University of Waterloo action limits for compressive and shear forces respectively (McGill 1997, Yingling and McGill 1999, Marras 2000). The use of the back support harness reduced these forces by substantial and statistically significant amounts. This effect was consistent across all three tasks. The results of this study demonstrate the production of high levels of compressive and shear forces within the spine of shearers during the three shearing tasks studied and that the use of a back support harness can substantially reduce these forces. Therefore the use of a back harness may reduce the cumulative load on the spine during shearing thereby moderating damage to the articular structures. However it is not known whether the harness would protect the spine from a sudden or unexpected force.     

Alienation and drinking motivations among adolescent females.

188 female and 140 male 9th–12th graders in a small Wyoming community completed measures of alienation, drinking motivations, and positive social and personal psychological functions of drinking. Among females, problem-related drinking motivations correlated positively with alienation, whereas social-convivial motivations correlated negatively with this attribute. No comparable correlations were found among the males. It is concluded that important sex differences in the dynamics of problem drinking are worthy of additional study. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proinflammatory macrophage-activating properties of the novel phospholipid diacylglycerol pyrophosphate

We have found that the novel phospholipid diacylglycerol pyrophosphate (DGPP), identified in bacteria, yeast, and plants, but not in mammalian cells, is able to potently activate macrophages for enhanced secretion of arachidonate metabolites, a key event in the immunoinflammatory response of leukocytes. Macrophage responses to DGPP are specific and are not mediated by its conversion into other putative lipid mediators such as phosphatidic acid, lysophosphatidic acid, or diacylglycerol. The responses to DGPP are compatible with a receptor-recognition event because they are blocked by suramin. Intracellular signaling initiated by DGPP includes phosphorylation and activation of the Group IV cytosolic phospholipase A2 and of the extracellular-signal regulated p42 mitogen-activated protein kinase (MAPK) and p44 MAPK, and membrane translocation of the protein kinase C isoenzymes alpha, epsilon, delta. These results establish DGPP as a novel macrophage-activating factor and suggest a potential role for this compound in triggering homeostatic cellular responses.     

Ytterbium-doped silica fiber lasers: versatile sources for the1-1.2 μm region

Ytterbium-doped silica fibers exhibit very broad absorption and emission bands, from ~800 nm to ~1064 nm for absorption and ~970 nm to ~1200 nm for emission. The simplicity of the level structure provides freedom from unwanted processes such as excited state absorption, multiphonon nonradiative decay, and concentration quenching. These fiber lasers therefore offer a very efficient and convenient means of wavelength conversion from a wide variety of pump lasers, including AlGaAs and InGaAs diodes and Nd:YAG lasers. Efficient operation with narrow linewidth at any wavelength in the emission range can be conveniently achieved using fiber gratings. A wide range of application for these sources can be anticipated. In this paper, the capabilities of this versatile source are reviewed. Analytical procedures and numerical data are presented to enable design choices to be made for the wide range of operating conditions