Effects of Zr content on microstructure and corrosion resistance of Ti–30Nb–Zr casting alloys for biomedical applications

Titanium alloys show attractive properties for biomedical applications where the most important factors are biocompatibility, corrosion resistance, low modulus of elasticity, very good strength-to-weight ratio, reasonable formability and osseointegration. The aim of this study was to investigate the effects of Zr content (7.5 and 15 wt%) on microstructure and corrosion resistance of Ti–30Nb–Zr as-cast alloy samples. The corrosion tests were carried out in a 0.9% NaCl (0.15 mol L^?1) solution at 25 °C and neutral pH range. A horizontal centrifuged solidification set-up was used to obtain as-cast samples with a fine dendritic arrangement. In order to evaluate the corrosion behavior, electrochemical impedance spectroscopy (EIS), polarization curves and an equivalent circuit analysis were used. It was found that the as-cast microstructure tends to have the dendrite arm spacings reduced with increasing Zr content. The results have shown that the addition of Zr to a Ti–30Nb alloy has been efficient to stabilize the beta phase. The resulting impedance parameters and passive current densities have shown that the Ti–30Nb alloys sample without Zr addition presents a higher surface reactivity which can induce a better osseointegration than those containing Zr.     

New Enantioselective Synthesis of Monofluorinated Pyridines Designed for the Preparation of Chemical Libraries

Chiral pyridines with a fluorine atom in the benzylic position are easily accessible from optically active propargylic fluorides by using the Bohlmann–Rahtz reaction. Such pyridines, possessing four points of molecular diversity, are useful scaffolds for the preparation of chemical libraries.     

Chemical Defenses Against Fish Predation in Three Brazilian Octocorals: 11β,12β-Epoxypukalide as a Feeding Deterrent in Phyllogorgia dilatata

The feeding-deterrence properties of crude extracts of three Brazilian octocoral species, Neospongodes atlantica Kükenthal (Alcyonacea, Nephtheidae), Plexaurella regia Castro (Gorgonacea, Plexauridae), and Phyllogorgia dilatata Esper (Gorgonacea, Gorgoniidae), were investigated. All the extracts were incorporated into food strips at the concentrations occurring in the living organisms. Crude extract and its ethyl acetate fraction obtained from P. dilatata collected in Armação dos Búzios (Rio de Janeiro State), when incorporated into artificial diets and tested in the habitat of origin, reduced consumption of food strips by fishes, relative to controls. Crude extracts from two octocoral species collected at the National Marine Park of Abrolhos (Bahia State), N. atlantica and P. regia, had no apparent feeding-deterrence properties; in fact, they seemed to stimulate feeding. Bioassay-guided fractionation of the bioactive P. dilatata crude extract revealed that the deterrent property was restricted to a medium polarity fraction. Field palatability experiments with two pure compounds isolated from this fraction revealed that the furanocembranolide 11,12-epoxypukalide is a potent feeding deterrent produced by P. dilatata against fish. Apparently, furanocembranolides are a particular class of compounds with feeding deterrent properties, protecting some octocorals from potential fish predator species in both tropical and temperate environments.     

Electron‐beam processing of destructurized allylurea–starch blends: Immobilization of plasticizer by grafting

Allylurea (AU) was used as a reactive additive with poor aptitude to homopolymerization for obtaining grafted plasticized starch films with stabilized physical properties. Potato starch was mixed with AU (30–50 parts per hundred/pph) in a mixer operating at 125°C. Upon storage in well‐defined hygrothermal conditions, the resulting thermoplastic material shows strong plasticizer migration revealed by AU crystals blooming at the samples surface and exhibits strong opacity assigned to phase separation of the organic additive inside the material. Freshly prepared thermoplastic films of appropriate thickness were exposed to a 175‐kV electron beam (EB) radiation for inducing covalent grafting of AU by a free radical process. FTIR monitoring of the resulting chemical changes in thin films of AU–starch blends indicates unambiguously the transformation of AU allylic bond. High irradiation doses are required for achieving complete conversion of AU in the blend. However, no detectable AU migration was observed for intermediate AU conversion, probably as a consequence of higher plasticizer solubility in the grafted polysaccharide. Examination of the viscoelastic properties by dynamic mechanical thermal analysis shows that artificial aging by placing the films alternatively in high and low relative humidity (RH) atmosphere does not significantly alter the thermomechanical spectrum of the material reconditioned in a cell at 58% RH. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 409–417, 1999     

Thermal degradation of high‐temperature fluorinated polyimide and its carbon fiber composite

High‐temperature polymers are being used for a broad range of applications, such as composite matrices for structural applications (e.g., high speed aircraft). Polyimides are a special class of polymers that meet the thermal and oxidative stability requirements for high temperature composite aerospace applications. A weight loss study was performed on a fluorinated polyimide resin and its carbon fiber composite in an effort to determine its thermal stability and degradation mechanisms. Experiments were conducted using a preheated oven and thermogravimetric analysis to obtain the weight loss. Regardless of the method used, the resin and composite exhibited excellent thermal stability (less than 1% weight loss) below 430°C, regardless of 2–20 min of exposure. After 20 min of exposure at 510°C, the composite remained relatively stable with only 5.3% weight loss using the oven technique, whereas the neat polyimide sustained 12.6%. When degradation occurred, it was found to be the result of thermolysis and oxidation (to a lesser extent). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A review of the effects of water transfers in the La Grande Hydroelectric Complex (Québec,Canada)

Construction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m³ s^?1, and the transfer of water from two adjoining watersheds (1586m³ s^?1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m³ s^?1), Opinaca (from 260 to 35m³ s^?1), and Caniapiscau (from 1708 to 960m³ s^?1) and the waterways with increased flows, Boyd-Sakami (from 1 to 811m³ s^?1) and La Grande Rivière (from 1760 to 3400m³ s^?1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operation of the reservoirs.     

Spatial genetic structure and recruitment dynamics of burbot (Lota lota) in Eastern Lake Michigan and Michigan tributaries

Burbot (Lota lota) are the only freshwater member of the Cod like (Lotidae) family that have a circumpolar distribution and occupy the widest geographic distribution of all Laurentian Great Lakes fish species. Information regarding burbot spatial genetic structure and recruitment dynamics is critical for the development of effective management strategies. Although burbot are a species of conservation concern throughout their range, little demographic or behavioral information exists. We estimated levels of genetic diversity within, and the degree of spatial population structure between samples collected from Lake Michigan and tributaries of the Manistee River, MI. Measures of genetic diversity across 10 microsatellite loci were moderately high. Disparities between adult groups sampled in Lake Michigan and the Manistee River were notable for observed heterozygosity (0.662 vs 0.488) and allelic richness (11.7 vs 6.6). Significant levels of inter-population variance in microsatellite allele frequencies (F_ST 0.154 to 0.208) were detected between Lake Michigan and the Manistee River samples. Results indicate reproductive isolation between what plausibly may be riverine and lacustrine spawning life history types. Pedigree analyses for three cohorts sampled in the Manistee River revealed that a sizeable number of adults contributed reproductively to multiple cohorts, indicating spawning philopatry. While data were collected from restricted areas in lacustrine and river habitats, analyses revealing microgeographic genetic structuring, potentially attributed to life history polymorphisms, have significant implications for burbot management in the Great Lakes.     

Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.     

Processes and outcomes of psychotherapists' personal therapy: Replication and extension 20 years later.

In this replication and extension of a national survey of psychotherapists conducted in 1987, American psychologists (n = 219), counselors (n = 191), and social workers (n = 192) reported in 2007 on the processes and outcomes of their personal therapy experiences. Of the 85% who sought therapy at least once, women, men, and members of all three professions were equally as likely to have received personal treatment. Their top reasons for seeking therapy were marital–couple distress (20%), depression (13%), need for self-understanding (12%), and anxiety–stress (10%). Approximately 24% used psychotropic medication in combination with personal therapy. More than 90% of therapists reported positive outcomes across multiple domains. The modal lasting lessons from personal treatment related to therapist reliability, skill, and empathy. The results are tentatively compared with those obtained in 1987, thus chronicling the evolution of personal therapy among psychologists and social workers during the past 20 years. (PsycINFO Database Record (c) 2010 APA, all rights reserved)