Comparison of microwave and thermal cure of an epoxy/amine matrix

An investigation was carried out into the effect ofa microwave cure on an epoxy prepolymer with a cycloaliphatic diamine mixture, as compared to a standard thermal cure. The microwave waveguide and process (propagation mode TE₀₁) were adjusted to obtain large homogeneous samples. The extent of reaction, x, was measured during the microwave processing by size exclusion chromatography and differential scanning calorimetry. A good estimate of x was found using a modified DiBenedetto equation correlating x and the glass transition temperature T_g. The homogeneity of the samples was checked during the last steps of cure, showing the efficiency of the microwave processing and waveguide. The influence of the nature of the mold (metallic or dielectric) on the reaction kinetic was also investigated. Samples cured by both thermal and microwave processing were characterized by dynamic and static mechanical properties and then compared with those of fully crosslinked networks, i.e., postcured at a high temperature.     

A postsynaptic interaction between dopamine D1 and NMDA receptors promotes presynaptic inhibition in the rat nucleus accumbens via adenosine release

The mechanism underlying dopamine D1 receptor-mediated attenuation of glutamatergic synaptic input to nucleus accumbens (NAcc) neurons was investigated in slices of rat forebrain, using whole-cell patch-clamp recording. The depression by dopamine of EPSCs evoked by single-shock cortical stimulation was stimulus-dependent. Synaptic activation of NMDA-type glutamate receptors was critical for this effect, because dopamine-induced EPSC depressions were blocked by the competitive NMDA receptor antagonist D/L-2-amino-5-phosphonopentanoate (AP5). Application of NMDA also depressed the EPSC, and both this effect and the dopamine depressions were blocked by the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), implicating adenosine release in the EPSC depression. A1 receptor agonists also depressed EPSCs by a presynaptic action, causing increased paired-pulse facilitation, but this was insensitive to AP5. Activation of D1 receptors enhanced both postsynaptic inward currents evoked by NMDA application and the isolated NMDA receptor-mediated component of synaptic transmission. The biochemical processes underlying the dopamine-induced EPSC depression did not involve either protein kinase A or the production of cAMP and its metabolites, because this effect was resistant to the protein kinase inhibitors H89 and H7 and the cAMP-specific phosphodiesterase inhibitor rolipram. We conclude that activation of postsynaptic D1 receptors enhances the synaptic activation of NMDA receptors in nucleus accumbens neurons, thereby promoting a transsynaptic feedback inhibition of glutamatergic synaptic transmission via release of adenosine. Unusually for D1 receptors, this phenomenon occurs independently of adenylyl cyclase stimulation. This process may contribute to the locomotor stimulant action of dopaminergic agents in the NAcc.     

The reconstructed evolutionary process

Phylogenies reconstructed from contemporary taxa do not contain information about lineages that have gone extinct. We derive probability models for such phylogenies, allowing real data to be compared with specified null models of evolution, and lineage birth and death rates to be estimated.     

Electrical basis of peristalsis in the mammalian upper urinary tract

1. Peristalsis in the mammalian upper urinary tract (UUT) is mostly myogenic in origin, originating predominately in the proximal pelvicalyceal regions of the renal pelvis, an area that is enriched with specialized smooth muscle cells termed 'atypical' smooth muscle cells. Propagating peristaltic contractions are little affected by blockers of either autonomic nerve function or nerve impulse propagation; however, blockers of sensory nerve function or prostaglandin synthesis reduce both the frequency and the strength of the spontaneous contractions underlying peristalsis. 2. The electrical drive for these peristaltic contractions has long been considered to involve mechanisms analogous to the heart, such that 'atypical' smooth muscle cells generate spontaneous 'pacemaker' action potentials. These pacemaker potentials trigger the firing of action potentials and contraction in the muscular regions of the renal pelvis, which propagate distally to the ureter, propelling urine towards the bladder. 3. Recent intracellular microelectrode and single cell/channel patch-clamp studies have revealed that the ionic conductances underlying the action potentials recorded in the UUT are likely to involve the opening and slow closure of voltage-activated 'L-type' Ca2+ channels, offset by the time-dependent opening and closure of both voltage- and Ca(2+)-activated K+ channels. 4. In the present review we summarize the current knowledge of the ionic mechanisms underlying action potential discharge in the UUT, as well as present our view on how this electrical activity supports the initiation and conduction of UUT peristalsis.     

Counseling psychology and clinical psychology: Some preliminary comparative data.

Comments on L. F. Fitzgerald and S. H. Osipow's (see record 1986-25640-001) occupational analysis and statements regarding the lack of empirical bases to distinguish counseling psychologists from clinical psychologists by presenting findings from the present authors' own comparison of survey data from 716 counseling psychologists and 479 clinical psychologists. These data reveal several similarities and differences regarding counseling and clinical psychologists' theoretical orientations, occupational environments, amount of time devoted to specific professional and psychotherapeutic activities, and identification with a practitioner role. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of guar gum on microbial activity in the human colon

On feeding a human volunteer a control diet for 21 days, followed by one containing 13·9 g guar/day for a further 21 days, the major changes seen were an increase in faecal output and water content and a decrease in faecal pH and transit time. Faecal output remained high for at least 10 days after return to the control diet. Short chain fatty acid (SCFA) levels/g wet weight of faeces were unchanged during the guar diet but total excretion of SCFA increased because of increased faecal output. Bacterial output was increased although the proportion of guar fermenters remained approximately 20%. Utilization of guar was complete from the beginning of the guar diet, with no period of adaptation. Flatus production substantially increased during the first 10 days of the guar diet but was less noticeable thereafter, suggesting that changes in the pattern of metabolism were taking place in response to continued feeding of guar. Addition of guar to the diet increased α-galactosidase, mannanase and β-mannosidase activity in faeces and most of the activity was associated with the bacterial fraction. In vitro incubation of faecal slurries from the control and guar diets with guar, galactose or mannose showed that SCFA production was lowest and gas production highest when guar was substrate. No effect of diet was seen on utilization of carbohydrate, SCFA and gas production or enzyme activity. Enzyme activity was only induced by guar and was mainly cell-associated.     

Immediate usability: a case study of public access design for a community photo library

This paper describes a novel instantiation of a digital photo library in a public access system. It demonstrates how designers can utilize characteristics of a target user community (social constraints, trust, and a lack of anonymity) to provide capabilities, such as unrestricted annotation and uploading of photos, which would be impractical in other types of public access systems. It also presents a compact set of design principles and guidelines for ensuring the immediate usability of public access information systems. These principles and guidelines were derived from our experience developing PhotoFinder Kiosk, a community photo library. Attendees of a major HCI conference (CHI 2001 Conference on Human Factors in Computing Systems) successfully used the tool to browse and annotate collections of photographs spanning 20 years of HCI-related conferences, producing a richly annotated photo history of the field of human–computer interaction. Observations and usage log data were used to evaluate the tool and develop the guidelines. They provide specific guidance for practitioners, as well as a useful framework for additional research in public access interfaces.     

Developing narrative structure in parent–child reminiscing across the preschool years.

This study is a longitudinal exploration of relations between parents' and children's provision of narrative structure in joint retellings of the past and children's developing personal narrative skills. 15 White, middle-class families participated when children were 40 and 70 mo old. At both ages, mothers and fathers talked separately with children about shared past events and uninformed experimenters elicited children's personal narratives. Whereas mothers and fathers did not differ in how they structured past narratives, children narrated differently with fathers than with mothers. Further, even at 40 mo, girls' narratives were more contexted and evaluative than boys', but parents' provision of narrative structure increased similarly with daughters and sons over time. Children's early abilities to provide evaluative narratives was a strong predictor of their later abilities to provide evaluative narratives; maternal emphasis on evaluations also predicted children's later narrative structure. Parental and child influences on personal narrative skill development are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)