Double noding technique for mixed mode crack propagation studies

A simple dynamic finite element algorithm for analysing a propagating mixed mode crack tip is presented. A double noding technique, which can be easily incorporated into existing dynamic finite element codes, is used together with a corrected ? integral to extract modes I and II dynamic stress intensity factors of a propagating crack. The utility of the procedure is demonstrated by analysing test problems involving a mode I central crack propagating in a plate subjected to uniaxial tension, a stationary slanted central crack in a plate subjected to uniaxial inpact loading and an extending slanted-edge crack in plate subjected to uniaxial tension.     

Under microscopes the poly(styrene/butadiene) nanoparticles

There has been considerable interest, both academic and industrial, in developing synthesis processes for making polymeric nanoparticles. Our effort relied on the nanoassembly concepts of block macromolecules in solutions to prepare particles with a hard core made of crosslinked plastics and a soft shell made of low T(g) elastomer. By a suitable variation of the composition, polymer molecular weight and solute concentration, we were able to produce spherical, ellipsoidal, cylindrical, and chain-like nanoparticles. Under microscopes, the chain-like nanoparticles displayed very rich conformational features in diluted and dense states. Our observation on the conformation characters of the nanochains in 3D diluted state agreed well with the proposition of the self-avoid coil model. However, in 2D dense state, our observation on the nanochains appeared to be in contradiction with the segregated globule model proposed by de Gennes.     

Disorders of adult attachment.

This article presents an overview of J. Bowlby's framework of attachment (e.g., 1990) for conceptualizing adult psychopathology and its application to clinical practice. The theory proposes that psychological disorders reflect an internalization of adverse attachment experiences, both current and past, and in particular those that undermine self-reliance and feelings of security. Clinical syndromes indicate intensification of anxiety, depression, and/or anger to a degree which interferes with adaptive functioning and interactions with others. The secure base of therapy provides a new model of what close relationships can be like, as well as a setting for exploring and possibly modifying the meaning given to separation and loss experiences. Issues of prevention and social policy are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sydenham Chorea: magnetic resonance imaging reveals permanent basal ganglia injury

We report the case of a 26-year-old man with diffuse esophageal leiomyomatosis involving the trachea. The tumor was resected by total esophagectomy and partial resection of the trachea and the left main bronchus. The tracheobronchial defect was repaired with a free forearm skin graft with satisfactory outcome. This approach offers good long-term prospects.     

Care tracker: a new approach to nursing care in ambulatory settings

It is becoming increasingly clear that mitochondrial Ca2+ uptake from and release into the cytosol has important consequences for neuronal and glial activity. Ca2+ regulates mitochondrial metabolism, and mitochondrial Ca2+ uptake and release modulate physiological and pathophysiological cytosolic responses. In glial cells, inositol 1,4,5-trisphosphate-dependent Ca2+ responses are faithfully translated into elevations in mitochondrial Ca2+ levels, which modifies cytosolic Ca2+ wave propagation and may activate mitochondrial enzymes. The location of mitochondria within neurones may partially determine their role in Ca2+ signalling. Neuronal death due to NMDA-evoked Ca2+ entry can be delayed by an inhibitor of the mitochondrial permeability transition pore, and mitochondrial dysfunction is being increasingly implicated in a number of neurodegenerative conditions. These findings are illustrative of an emerging realization by neuroscientists of the importance of mitochondrial Ca2+ regulation as a modulator of cellular energetics, endoplasmic reticulum Ca2+ release and neurotoxicity.     

Apoptosis after traumatic human spinal cord injury

OBJECT: Apoptosis is a form of programmed cell death seen in a variety of developmental and disease states, including traumatic injuries. The main objective of this study was to determine whether apoptosis is observed after human spinal cord injury (SCI). The spatial and temporal expression of apoptotic cells as well as the nature of the cells involved in programmed cell death were also investigated. METHODS: The authors examined the spinal cords of 15 patients who died between 3 hours and 2 months after a traumatic SCI. Apoptotic cells were found at the edges of the lesion epicenter and in the adjacent white matter, particularly in the ascending tracts, by using histological (cresyl violet, hematoxylin and eosin) and nuclear staining (Hoechst 33342). The presence of apoptotic cells was supported by staining with the terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labeling technique and confirmed by immunostaining for the processed form of caspase-3 (CPP-32), a member of the interleukin-1beta-converting enzyme/Caenorhabditis elegans D 3 (ICE/CED-3) family of proteases that plays an essential role in programmed cell death. Apoptosis in this series of human SCIs was a prominent pathological finding in 14 of the 15 spinal cords examined when compared with five uninjured control spinal cords. To determine the type of cells undergoing apoptosis, the authors immunostained specimens with a variety of antibodies, including glial fibrillary acidic protein, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase), and CD45/68. Oligodendrocytes stained with CNPase and a number of apoptotic nuclei colocalized with positive staining for this antibody. CONCLUSIONS: These results support the hypothesis that apoptosis occurs in human SCIs and is accompanied by the activation of caspase-3 of the cysteine protease family. This mechanism of cell death contributes to the secondary injury processes seen after human SCI and may have important clinical implications for the further development of protease inhibitors to prevent programmed cell death.     

Contact thermal shock test of ceramics

A novel quantitative thermal shock test of ceramics is described. The technique employs contact between a metal cooling rod and hot disc-shaped specimen. In contrast with traditional techniques, the well-defined thermal boundary condition allows for accurate analyses of heat transfer, stress, and fracture. Uniform equi-biaxial tensile stresses are induced in the centre of the test specimen. Transient specimen temperature and acoustic emission are monitored continuously during the thermal stress cycle. The technique is demonstrated with soda-lime glass specimens. Experimental results are compared with theoretical predictions based on a finite element method thermal stress analysis combined with a statistical model of fracture. Material strength parameters are determined using concentric ring flexure tests. Good agreement is found between experimental results and theoretical predictions of failure probability as a function of time and initial specimen temperature.     

Attachment, detachment and borderline personality disorder.

In an attempt to expand understanding of more severe pathology, attachment theory, developed by John Bowlby, is applied to borderline personality disorder in adults. Conceptualized as a condition of profound insecure attachment, with extreme vacillations between a desire for proximity and attachment and a dread and avoidance of engagement, borderline pathology reflects traumatic attachment experiences, beginning early in life. Besides the importance of trauma, disturbances in affect regulation and cognitive distortions are emphasized. The secure base of a therapeutic bond provides consistency, reliability, and affirmation while encouraging exploration of separation and loss experiences, both current and past, in order to modify inner working models of oneself and relationships with others. Implications for prevention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)