The Interfacial Interactions of Glycine and Short Glycine Peptides in Model Membrane Systems

The interactions of amino acids and peptides at model membrane interfaces have considerable implications for biological functions, with the ability to act as chemical messengers, hormones, neurotransmitters, and even as antibiotics and anticancer agents. In this study, glycine and the short glycine peptides diglycine, triglycine, and tetraglycine are studied with regards to their interactions at the model membrane interface of Aerosol-OT (AOT) reverse micelles via ¹H NMR spectroscopy, dynamic light scattering (DLS), and Langmuir trough measurements. It was found that with the exception of monomeric glycine, the peptides prefer to associate between the interface and bulk water pool of the reverse micelle. Monomeric glycine, however, resides with the N-terminus in the ordered interstitial water (stern layer) and the C-terminus located in the bulk water pool of the reverse micelle.     

Non-linear dissolution mechanisms of sodium calcium phosphate glasses as a function of pH in various aqueous media

Phosphate glasses for bioresorbable implants display dissolution rates that vary significantly with composition, however currently their mechanisms of dissolution are not well understood. Based on this systematic study we present new insights into these mechanisms. Two-stage dissolution was observed, with time dependence initially parabolic and later linear, and a two-stage model was developed to describe this behaviour. Dissolution was accelerated by lower Ca concentration in the glass, and lower pH in the dissolution medium. A new dissolution mechanism is proposed, involving an initial stage where diffusion-controlled formation of a conversion layer occurs. Once the conversion layer is stabilised, layer dissolution reactions become rate-limiting. Under this mechanism the transition time is sensitive to the nature of the conversion layer and solution conditions. These results reveal the dependence of P₂O₅–CaO–Na₂O glass dissolution on solution pH, and provide new insight into the dissolution mechanisms, particularly regarding the transition between the two dissolution stages.     

Functional Porous Polymers by Emulsion Templating: Recent Advances

Porous materials are currently of great scientific as well as technological interest. A strategy that is increasingly employed to prepare highly porous and well defined macroporous polymers is emulsion templating, whereby the droplets of a high internal phase emulsion are used to create pores in a solid material by curing or polymerization of the emulsion continuous phase. This Feature Article covers recent work in this area, focusing on: the preparation of such materials from new precursors and via novel approaches; the chemical modification of existing materials; and the application of the resulting porous structures in diverse areas of science and technology.     

Modulation of Mechanical Interactions by Local Piezoelectric Effects

Piezoelectricity is a well‐established property of biological materials, yet its functional role has remained unclear. Here, a mechanical effect of piezoelectric domains resulting from collagen fibril organisation is demonstrated, and its role in tissue function and application to material design is described. Using a combination of scanning probe and nonlinear optical microscopy, a hierarchical structuring of piezoelectric domains in collagen‐rich tissues is observed, and their mechanical effects are explored in silico. Local electrostatic attraction and repulsion due to shear piezoelectricity in these domains modulate fibril interactions from the tens of nanometre (single fibril interactions) to the tens of micron (fibre interactions) level, analogous to modulated friction effects. The manipulation of domain size and organisation thus provides a capacity to tune energy storage, dissipation, stiffness, and damage resistance.     

Why do dominant personalities attain influence in face-to-face groups? The competence-signaling effects of trait dominance.

Individuals high in the personality trait dominance consistently attain high levels of influence in groups. Why they do is unclear, however, because most group theories assert that people cannot attain influence simply by behaving assertively and forcefully; rather, they need to possess superior task abilities and leadership skills. In the present research, the authors proposed that individuals high in trait dominance attain influence because they behave in ways that make them appear competent--even when they actually lack competence. Two studies examined task groups using a social relations analysis of peer perceptions (D. A. Kenny & L. LaVoie, 1984). The authors found that individuals higher in trait dominance were rated as more competent by fellow group members, outside peer observers, and research staff members, even after controlling for individuals' actual abilities. Furthermore, frequency counts of discrete behaviors showed that dominance predicts the enactment of competence-signaling behaviors, which in turn predicts peer ratings of competence. These findings extend researchers' understanding of trait dominance, hierarchies in groups, and perceptions of competence and abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Photogenerated base as catalyst for imidization reactions

The photogeneration of free amines or diamines from soluble organic precursors such as photoactive 2-nitrobenzyl carbamates is useful for the imidization of polymers containing amic acid or amic ester moieties. The base-catalyzed reaction occurs at lower temperatures than the non-catalyzed thermal process and is applicable to the patterning of polymer coatings or thin films.     

The Hungry Cities Food Purchases Matrix: Household Food Sourcing and Food System Interaction

Urban food insecurity is partly the result of interactions between households and the broader food system. There is considerable discussion and debate on the most appropriate measures of household food insecurity but very little on how to quantify interactions between households and the system. One priority is to develop food security metrics that incorporate household interactions with the food retail environment. The Hungry Cities Food Purchases Matrix (HCFPM) is one such metric developed for relating household food sourcing behaviour to that environment. The matrix has been successfully used by the Hungry Cities Partnership to shed light on food sourcing and food system interactions in a number of cities in the Global South. Using Maputo as a case study, this paper discusses the objectives, structure and potential of the HCFPM for African cities and illustrates how in can provide important insights into household-food system interactions. The HCFPM therefore opens up a new way of understanding household purchasing behaviour and associated food insecurity.     

Videoendoscopic diagnosis of esophageal motility disorders

PURPOSE: Looking for a valid, reliable, and feasible method to collect data on the performances of practicing family physicians, the authors compare the measurement characteristics of a multiple-station examination (MSE) using standardized patients with those of a video assessment of regular consultations in daily practice (practice video assessment, PVA). METHOD: In a cross-sectional study, consultations of 90 family physicians were videotaped both in an MSE and in their daily practices. Peer-observers used a validated instrument (MAAS-Global) to assess the physicians' communication with patients and their medical performances. The physicians were randomly divided into two groups, comparable for demographic characteristics, and half underwent the assessments in reverse order to test for time-order effects. Content validity, criterion validity, reliability, and feasibility of the two methods were compared. RESULTS: Content validity of the PVA was superior to that of the MSE, since the domain of general family practice care was better covered. Observed participants judged the videotaped practice consultations to be "natural," whereas hardly any family physician, after reviewing the videotaped consultations of the MSE, recognized his or her usual working style. Specific criteria made it possible to standardize real practice. Concerning criterion validity, only the medical-performance components of the two methods correlated. No correlation was found for the communication components. Real-practice performance proved to be less influenced by observation than was performance during the MSE. The reliabilities of the two methods, expected to be better in the controlled MSE, were comparable. The administration of the PVA was more flexible, less costly, and better accepted by the family physicians than was that of the MSE. CONCLUSION: Assessment for quality improvement of family physicians' practices by video observation in daily practice is superior to video assessment in a simulated setting using standardized patients.     

Light backscattering polarization patterns from turbid media: theory and experiment

We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement.