The Water Uptake of Experimental Soft Lining Materials

PhDIn order to develop a successful soft lining material various factors have to be considered; physical strength, adhesion to the denture base ( or prosthetic) and the durability of the material's properties when in the mouth. It has been recognised that in order to fulfil these criteria the material must be stable and have a low water uptake from the aqueous environments of the mouth. In the dental field comparatively little work has focused on how soft lining materials behave in water where as water in polymers has received a considerable amount of interest, with many different types of behaviour being observed and explained. It has been realised by previous authors that the water uptake of elastomers is primarily driven by soluble impurities, these form solution droplets within the material. The nature of the growth is somewhat more debatable, with both Fickian and dual sorption kinetics being reported. Two basic types of materials were used in the study; silicone polymers and elastomer / methacrylate materials. Silicone polymers are characterised by a low water uptake and form the basis of perhaps the most successful soft lining material ('Molloplast B'). The elastomer / methacrylate materials were based on those developed by Parker (1982), Parker and Braden (1990) which showed considerable promise but suffered from an extensive protracted uptake. Water uptake at 370C in conjunction with the tensile strength were used to evaluate the materials produced as these simple tests enabled the behaviour of the material in service to estimated. Three different types of silicone polymers were used during the study classified by the curing mechanism (condensation, peroxide and hydrosilanised), various fillers and additives (such as calcium stearate) were incorporated into the materials and different uptakes observed. The condensation silicones demonstrated large weight losses (up to 20 wt%) in water which is attributed to hydrolytic instability of the siloxane bridge in the presence of an organo tin compound leading to a leaching of siloxane. The pure peroxide and hydrosilanised materials both demonstrated a low water uptake but when doped they form solution droplets in a similar way to that described in the literature. Other additives showed different behaviour with the formation of cracks within the silicone due to failure of the material around the droplets, the action of hydrophilic but insoluble fillers also promotes the uptake. The hydrosilanised silicone polymers showed considerable promise as soft lining materials with low water uptake and good tensile strength. 11 The elastomer / methacrylate materials were based initially on butadiene styrene copolymer and a higher methacrylate monomer which formed a gel this was then free radically cured. The water uptake of these materials was attributed to soluble separating agent added to the butadiene styrene (to prevent particle agglomeration) during the production of the powdered elastomer. The extent of the uptake could be controlled by improving the strength of the material but the overall uptake remained too high. When the material was placed in an osmotic solution (Na CI or glucose) the water uptake was significantly reduced and the behaviour could be described by a modified (for small strains) version of the Thomas and Muniandy (1987) theory for the growth of water droplets in a elastomer. In order to reduce the water uptake of the elastomer / methacrylate materials butadiene styrene copolymers without separating agent was used. The emulsion polymerised material contained soluble impurities from the polymerisation (i.e. soap)which acted to drive the water uptake. Solution polymerised butadiene styrene also demonstrated a high uptake but this is attributed to a clustering behaviour of carboxylic and hydroxyl groups which formed post production. Similar behaviour is also seen for a solution polymerised isoprene styrene elastomer. The role of crosslinking the material in restraining the growth of the droplets is also investigated with dramatic reductions in the uptake being observed as the crosslink density increased. The employment of a reinforcing silica filler proved more effective than simply using a dimethacrylate. Oxidation is another problem (characterised by an upturn in the absorption), although not observed in every case it was a problem for all of the unsaturated elastomers and was found to be promoted by ions present within saliva. Saturated butyl based (including chloro and bromo butyl) elastomers were used instead and did not show any tendency for oxidation but they still showed an uptake of approximately 3 to 4 wt%. Their stability however and reasonable strength makes them suitable for further development as soft lining materials. Theoretical considerations were investigated by HI NMR imaging with the formation of droplets being observed, the profiles seen indicating the absorption to be two stage rather than Fickian. The role of creep or stress relaxation is also identified as a mechanism for extending the uptake by reducing the restraining force. Further reasoning on all the data presented here concluded the role of chemical potential change associated with the water into the matrix or the droplets will determine the nature of the uptake observed

The Ethno- and Research History of the Lake Louise Field Station, Valdosta State University, Valdosta, GA

The history of the Lake Louise Field Station, from its 1951 purchase by George Leiby to its acquisition in 2009 by Valdosta State University, provides an interesting and varied look into the stewardship critical to teaching and research and the role played by the station in the development of the fields of paleoecology, paleotempestology and ethnohistory. During this 58-year period several individuals played critical roles in the development of this 76.9 hectare field station as a natural area for teaching and research. Notable among them were George and Louise Leiby who, working with Leo Lorenzo and Clyde Connell, set aside the station as a natural area for teaching and research. From the 1960s to the present, WA Watts, H Grissino-Mayer, J Tepper, D Hyatt, and J Pascarella and others have conducted research that has provided critical insight into the history and ecology of the area extending to 47,000 BP

Age-Dependence of Femoral Strength in White Women and Men

Although age-related variations in areal bone mineral density (aBMD) and the prevalence of osteoporosis have been well characterized, there is a paucity of data on femoral strength in the population. Addressing this issue, we used finite-element analysis of quantitative computed tomographic scans to assess femoral strength in an age-stratified cohort of 362 women and 317 men, aged 21 to 89 years, randomly sampled from the population of Rochester, MN, and compared femoral strength with femoral neck aBMD. Percent reductions over adulthood were much greater for femoral strength (55% in women, 39% in men) than for femoral neck aBMD (26% in women, 21% in men), an effect that was accentuated in women. Notable declines in strength started in the mid-40s for women and one decade later for men. At advanced age, most of the strength deficit for women compared with men was a result of this decade-earlier onset of strength loss for women, this factor being more important than sex-related differences in peak bone strength and annual rates of bone loss. For both sexes, the prevalence of “low femoral strength” (<3000 N) was much higher than the prevalence of osteoporosis (femoral neck aBMD T-score of −2.5 or less). We conclude that age-related declines in femoral strength are much greater than suggested by age-related declines in femoral neck aBMD. Further, far more of the elderly may be at high risk of hip fracture because of low femoral strength than previously assumed based on the traditional classification of osteoporosis. © 2010 American Society for Bone and Mineral Research

Proceedings of the Tenth Annual Beef Cattle Short Course.

91 p

The Human Phenotype Ontology project:linking molecular biology and disease through phenotype data

The Human Phenotype Ontology (HPO) project, available at http://www.human-phenotype-ontology.org, provides a structured, comprehensive and well-defined set of 10,088 classes (terms) describing human phenotypic abnormalities and 13,326 subclass relations between the HPO classes. In addition we have developed logical definitions for 46% of all HPO classes using terms from ontologies for anatomy, cell types, function, embryology, pathology and other domains. This allows interoperability with several resources, especially those containing phenotype information on model organisms such as mouse and zebrafish. Here we describe the updated HPO database, which provides annotations of 7,278 human hereditary syndromes listed in OMIM, Orphanet and DECIPHER to classes of the HPO. Various meta-attributes such as frequency, references and negations are associated with each annotation. Several large-scale projects worldwide utilize the HPO for describing phenotype information in their datasets. We have therefore generated equivalence mappings to other phenotype vocabularies such as LDDB, Orphanet, MedDRA, UMLS and phenoDB, allowing integration of existing datasets and interoperability with multiple biomedical resources. We have created various ways to access the HPO database content using flat files, a MySQL database, and Web-based tools. All data and documentation on the HPO project can be found online

Individual Attachment Style Modulates Human Amygdala and Striatum Activation during Social Appraisal

Adult attachment style refers to individual personality traits that strongly influence emotional bonds and reactions to social partners. Behavioral research has shown that adult attachment style reflects profound differences in sensitivity to social signals of support or conflict, but the neural substrates underlying such differences remain unsettled. Using functional magnetic resonance imaging (fMRI), we examined how the three classic prototypes of attachment style (secure, avoidant, anxious) modulate brain responses to facial expressions conveying either positive or negative feedback about task performance (either supportive or hostile) in a social game context. Activation of striatum and ventral tegmental area was enhanced to positive feedback signaled by a smiling face, but this was reduced in participants with avoidant attachment, indicating relative impassiveness to social reward. Conversely, a left amygdala response was evoked by angry faces associated with negative feedback, and correlated positively with anxious attachment, suggesting an increased sensitivity to social punishment. Secure attachment showed mirror effects in striatum and amygdala, but no other specific correlate. These results reveal a critical role for brain systems implicated in reward and threat processing in the biological underpinnings of adult attachment style, and provide new support to psychological models that have postulated two separate affective dimensions to explain these individual differences, centered on the ventral striatum and amygdala circuits, respectively. These findings also demonstrate that brain responses to face expressions are not driven by facial features alone but determined by the personal significance of expressions in current social context. By linking fundamental psychosocial dimensions of adult attachment with brain function, our results do not only corroborate their biological bases but also help understand their impact on behavior

Biomarkers of vitamin B-12 status in NHANES: a roundtable summary123456

A roundtable to discuss the measurement of vitamin B-12 (cobalamin) status biomarkers in NHANES took place in July 2010. NHANES stopped measuring vitamin B-12–related biomarkers after 2006. The roundtable reviewed 3 biomarkers of vitamin B-12 status used in past NHANES—serum vitamin B-12, methylmalonic acid (MMA), and total homocysteine (tHcy)—and discussed the potential utility of measuring holotranscobalamin (holoTC) for future NHANES. The roundtable focused on public health considerations and the quality of the measurement procedures and reference methods and materials that past NHANES used or that are available for future NHANES. Roundtable members supported reinstating vitamin B-12 status measures in NHANES. They noted evolving concerns and uncertainties regarding whether subclinical (mild, asymptomatic) vitamin B-12 deficiency is a public health concern. They identified the need for evidence from clinical trials to address causal relations between subclinical vitamin B-12 deficiency and adverse health outcomes as well as appropriate cutoffs for interpreting vitamin B-12–related biomarkers. They agreed that problems with sensitivity and specificity of individual biomarkers underscore the need for including at least one biomarker of circulating vitamin B-12 (serum vitamin B-12 or holoTC) and one functional biomarker (MMA or tHcy) in NHANES. The inclusion of both serum vitamin B-12 and plasma MMA, which have been associated with cognitive dysfunction and anemia in NHANES and in other population-based studies, was preferable to provide continuity with past NHANES. Reliable measurement procedures are available, and National Institute of Standards and Technology reference materials are available or in development for serum vitamin B-12 and MMA

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29