The Effect of Mixing on the Mechanical Properties of Hyaluronan‐Based Injectable Hydrogels

A method for determining the correlation between the mixing of two reactive polymers and the structural and mechanical properties of the formed hydrogels is presented. Rheological measurements show that insufficient mixing gives rise to soft and not fully crosslinked hydrogels while excessive mixing beyond gel point results in weaker hydrogels due to potential breakage of their 3D network. Furthermore, the hydrogels swell significantly more in cell culture medium than in phosphate‐buffered saline, attributed to interactions with additional molecules such as proteins. Thus, moderate mixing gives rise to the most homogenous and mechanically stable hydrogels and the choice of medium e.g., for release experiments, should be consistent in order to avoid unnecessary variations in the data caused by different swelling profiles.

     

Home Foreclosures as Early Warning Indicator of Neighborhood Decline

Problem, research strategy, and findings: Ideally, planners would intervene in neighborhood processes before substantial forces of decline have gained momentum. Unfortunately, currently there is no guidance about which neighborhood indicators forecast future neighborhood changes. This study seeks a neighborhood early warning indicator that is readily available, frequently updated, and that predicts with substantial foresight and accuracy future changes in key aspects of neighborhood market processes and quality of life. We search over a range of neighborhood indicators for one or more that clearly lead others in a temporal sense, instead of lagging behind them. We employ Granger causality tests with indicators related to public safety, housing market, and economic activity that are based on data from Chicago neighborhoods between 1998 and 2009. Our key finding is that only one indicator analyzed, completed home foreclosures, systematically precedes other neighborhood indicators but does not systematically follow after them. All other indicators are enmeshed in complicated, often mutually causal temporal patterns, which render them inappropriate for forecasting. We conclude that completed home foreclosures is an appropriate early warning indicator of neighborhood decline in several dimensions.

Takeaway for practice: Planners interested in identifying imminently emerging problems in their constituents’ neighborhoods should regularly acquire and map data on home foreclosures as soon as they become available, and then undertake compensatory actions as quickly as feasible.     

Auditory registration without learning.

In 3 studies, the authors explore how repeated exposure to a spoken word affects memory for perceptual attributes associated with the word (such as a talker's voice or a word's plurality). Subjects heard a list of words; particular words were repeated differing numbers of times. At test, subjects estimated the frequency of each word, with instructions to give frequency judgments of "zero" to words with changed attributes. The experiments demonstrate that memory for perceptual attributes improves very little after the first few repetitions, although word memory continues to improve. The experiments extend the registration without learning effect (D. L. Hintzman, T. Curran, and B. Oppy, 1992) to auditory words, to complex attributes (voice), and to conditions of low and high stimulus variability (two or many voices). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The genetic aspects of developmental dyslexia.

Discusses evidence concerning genetic influences on developmental dyslexia, a disorder characterized by difficulty in learning to read despite adequate opportunity and intelligence. Research on familial incidence, concordance in twins, the influence of parental age at the child's birth, and the subtyping of dyslexics is summarized. It is concluded that there is strong evidence for the heritability of a subtype based on verbal/language deficiency, perhaps reflecting reversed cerebral asymmetry, for which a genetic marker has been found. It is uncertain whether this subtype is caused by left hemispheric impairment or immaturity. There is somewhat weaker evidence for the heritability of a subtype based on visual/spatial deficiencies and a mixed subtype. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shape-preserving knot removal

Starting with a shape-preserving C¹ quadratic spline, we show how knots can be removed to produce a new spline which is within a specified tolerance of the original one, and which has the same shape properties. We give specific algorithms and some numerical examples, and also show how the method can be used to compute approximate best free-knot splines. Finally, we discuss how to handle noisy data, and develop an analogous knot removal algorithm for a monotonicity preserving surface method.     

Capillary electrophoresis frontal analysis for characterization of alphavbeta3 integrin binding interactions

The specific binding characteristics of alphavbeta3 integrins with an arginine-glycine-aspartic-acid (RGD) containing fluorescently labeled cyclic peptide is investigated with capillary electrophoresis-frontal analysis method. The new algorithm used to calculate the binding constants and binding stoichiometry was derived without the assumptions made in the commonly used Scatchard Plot method, thus enabling the determination of specific binding parameters in the presence of nonspecific binding. The alphavbeta3 integrin, a membrane protein, was studied in solution, without the need of immobilization or any other kind of modification. An RGD containing fluorescently labeled cyclic pentapeptide is used as the ligand with both specific and nonspecific binding characteristics, and an arginine-alanine-aspartic-acid (RAD) containing peptide is used as the control for nonspecific binding. While a typical specific binding isotherm has a shape of a rectangular hyperbola, a nonspecific binding isotherm is linear in the same ligand concentration region. A 1:2 specific binding stoichiometry was revealed with the second binding having a similar affinity compared to the first binding event.     

Pharmaceuticals, hormones and bisphenol A in untreated source and finished drinking water in Ontario, Canada--occurrence and treatment efficiency

The Ontario Ministry of the Environment (MOE) conducted a survey in 2006 on emerging organic contaminants (EOCs) which included pharmaceuticals, hormones and bisphenol A (BPA). The survey collected 258 samples over a 16 month period from selected source waters and 17 drinking water systems (DWSs), and analyzed them for 48 EOCs using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and isotope dilution mass spectrometry (IDMS) for the highest precision and accuracy of analytical data possible. 27 of the 48 target EOCs were detected in source water, finished drinking water, or both. DWSs using river and lake source water accounted for > 90% detections. Of the 27 EOCs found, we also reported the first detection of two antibiotics roxithromycin and enrofloxacin in environmental samples. The most frequently detected compounds (≥ 10%) in finished drinking water were carbamazepine (CBZ), gemfibrozil (GFB), ibuprofen (IBU), and BPA; with their concentrations accurately determined by using IDMS and calculated to be 4 to 10 times lower than those measured in the source water. Comparison of plant specific data allowed us to determine removal efficiency (RE) of these four most frequently detected compounds in Ontario DWSs. The RE of CBZ was determined to be from 71 to 93% for DWSs using granulated activated carbon (GAC); and was 75% for DWSs using GAC followed by ultraviolet irradiation (UV). The observed RE of GFB was between 44 and 55% in DWSs using GAC and increased to 82% when GAC was followed by UV. The use of GAC or GAC followed by UV provided an RE improvement of BPA from 80 to 99%. These detected concentration levels are well below the predicted no effect concentration or total allowable concentration reported in the literature. Additional targeted, site specific comparative research is required to fully assess the effectiveness of Ontario DWSs to remove particular compounds of concern.     

Good self-control moderates the effect of mass media on adolescent tobacco and alcohol use: Tests with studies of children and adolescents.

Objective: To investigate whether self-control moderates the effect of media influences on tobacco and alcohol use among youth and if so how this effect occurs. Design: In Study 1, a regional sample of 10-year olds (N = 290) was interviewed in households; attention to tobacco/alcohol advertising was assessed. In Study 2, a national sample of youth ages 10–14 years (N = 6,522) was surveyed by telephone; exposure to tobacco/alcohol use in movies was assessed. Good self-control was measured in both studies. Main Outcome Measures: Willingness to use substances and affiliation with peer substance users (Study 1); involvement in smoking or drinking (Study 2). Results: In Study 1, the effect of tobacco/alcohol advertising on predisposition for substance use was lower among persons scoring higher on good self-control. In Study 2, the effect of movie smoking/alcohol exposure on adolescent tobacco/alcohol use was lower, concurrently and prospectively, among persons scoring higher on good self-control. Moderation occurred primarily through reducing the effect of movie exposure on positive smoking/alcohol expectancies and the effect of expectancies on adolescent use; some evidence for moderation of social processes was also noted. Covariates in the analyses included demographics, sensation seeking, and IQ. Conclusion: Good self-control reduces the effect of adverse media influences on adolescent tobacco and alcohol use. Findings on the processes underlying this effect may be useful for media literacy and primary prevention programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

pH-mediated synthesis of monodisperse gold nanorods with quantitative yield and molecular level insight

Although gold nanorods(GNRs)have been produced with different dimensions and aspect ratios,the current synthesis methods through seed-mediated growth are far from ideal,for instance,the quality(rod yield)and the quantity(gold conversion)cannot be simultaneously satisfied.More critically,there is no molecular level understanding of the growth mechanism.Here,we solved the problem by employing the stoichiometric ratio of reactants and tuning the reactivity of the reductant through adjusting the initial pH value of the growth solution to achieve both good quality and high quantity simultaneously.We also extended our strategy to other enols besides ascorbic acid,such as phenolic compounds,and found that the optimal pH for GNRs synthesis depends on the structure of the individual compound.The mechanistic insight greatly enriches the toolbox of reductants for GNRs growth and makes it possible to synthesize GNRs at both acidic and basic conditions.An interesting phenomenon is that for most of the phenolic compounds we tested,the morphology of the final products follows the same sphere-rod-sphere trend as the initial pH value of the reaction increases,whether it is under acidic or basic conditions,which cannot be explained by any previously proposed mechanism.The effect of pH is mainly attributed to the regulation of the reduction potential of the reductants,and thus the reaction rate.A model has been proposed to explain the dependence of anisotropic growth of GNRs on the concentration gradient of reactants around the seeds,which is decided by both the reaction rate and diffusion rate.     

Ageing of polyethylene filled with a mineral filler

The thermo-oxidation resistance and weatherability of LDPE and HDPE compositions, containing up to 45 wt.% calcium carbonate, are investigated. The thermo-oxidation resistance is investigated by dynamic DTA and natural ageing is carried out in an exposure station in a seaside climate. The change in strength and colour after ageing is determined. The behaviours of filled and unfilled polymers are compared. Empirical equations are given, describing the change in the investigated parameters during natural ageing.