Polymer design for high temperature shape memory: Low crosslink density polyimides

Shape memory in polymers is a process whereby mechanical energy is microscopically stored, and reversibly recovered within the polymer. Consideration of the viscoelastic and glassy dynamics necessary for each step of the process reveals key molecular characteristics that may improve performance, including a rigid polymer backbone with narrow molecular weight distribution between a low fraction of crosslinks. With this insight to guide high temperature polymer design, aromatic CP2 polyimide and associated single wall carbon nanotube (SWNTs) nanocomposites are shown to have excellent shape memory performance at 220 °C with rapid recovery (<10 s), excellent fixity (>98%), good cyclability and outstanding creep resistance. A narrow glass transition temperature regime (<10 °C) and high fragility (m ～ 117) affords a narrow triggering window and the ability to spatially localize recovery with a temperature gradient. The addition of up to 3 vol% of dispersed SWNTs improves the rubbery modulus and blocking force without substantially impacting these crucial characteristics. The structure-performance relationships in this material system reinforce the key molecular characteristics for the design of polymers for shape memory.     

3D extrusion of multi-biomaterial lattices using an environmentally informed workflow

The conventional building material palette has been proven limited in terms of adaptability to our current environmental challenges. Innovations in computational design and digital manufacturing have supported the broadening of biomaterial applications as an alternative. While biomaterials are characteristically responsive to stimuli such as temperature and humidity, their unpredictable behaviour is a hurdle to standardization and architectural utilisation. To examine the nexus between material formulation, computation and manufacturing, multi-biomaterial lattice structures were produced through an environmentally informed workflow. Customized biomaterial development resulted in three candidate biopolymer blends with varying levels of hydro-responsiveness and transparency. The computational strategy included a machine learning clustering algorithm to customise results and dictate material distribution outputs. To test the workflow, environmental data of solar radiation exposure and solar heat gain from a specific location was used to inform the material deposition via pneumatic extrusion for the design and digital fabrication of a deformation-controlled prototype of 350 mm × 350 mm. This led to a series of multi-biomaterial wall panel components that can be applied at architectural scale. In future, these techniques can support the incorporation of living elements to be embedded within the built environment for truly animate architecture.     

Psychological well-being of parents with early adolescent children.

This study examined whether parents' reports of midlife identity concerns and psychological well-being are related to signs of their youngster's transition to adolescence, including pubertal status, involvement in mixed-sex social relations, and persuasive reasoning skills. The sample was composed of 129 families with a firstborn child between the ages of 10 and 15. Findings indicate only very modest direct relations between parental well-being and signs of adolescent development; instead, the relations are moderated by the strength of the parent's orientation toward his or her paid work role. Among parents with a weak orientation toward work, signs of adolescent development are negatively associated with well-being; among parents with a relatively strong orientation toward work, the associations are often positive. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Water and air transmissivity of geotextiles

The in-plane flow characteristics of both water and air in needled, nonwoven geotextiles have been evaluated in this study. Transmissivity (equal to permeability times fabric thickness) versus applied normal stress on the fabric has been measured in a radial flow device for different fabrics and for different thicknesses of a given fabric. The transmissivity response in each case was seen to decrease with increasing stress until a residual value was reached. In none of the cases did the fabric compress to the point where flow was completely shut off, even though stress levels of 2500 psf were applied. In turn, the calculated geotextile permeability varied from a fine gravel to a medium sized sand.Planar air flow in geotextiles has been found to be in excess of two orders of magnitude greater than water flow under comparable conditions. Air flow through partially and fully saturated fabrics is shown to be of little practical interest since the air easily moves around the water in the fabric voids or displaces it entirely.The need for transmissivity test standardization for all types of geotextiles and geotextile composite systems is expressed.     

Abnormal carbohydrate metabolism in amyotrophic lateral sclerosis and Parkinsonism-dementia on Guam

Amyotrophic lateral sclerosis and Parkinsonism-dementia are unusually prevalent on Guam. Carbohydrate metabolism was studied in 110 patients with evidence diagnostic of or suspecious for these diseases. The combined incidence of known diabetes in 29 per cent of them plus a high percentage of glucose tolerance tests interpreted as abnormal, even when most age-related criteria were considered, was considerably higher than the incidence of abnormal carbohydrate metabolism reported elsewhere in the general population of the United States, the tropical Pacific area, or in recent surveys on Guam itself. The diabetes was generally mild in nature and noteworthy for a lack of retinopathy and other complications. Hypertension, hypercholesterolemia, and hyperuricemia, although highly prevalent, were not consistently associated with abnormal glucose metabolism. Similarly, no consistent association was demonstrated with such factors as age, muscle atrophy, or physical activity.