Design and Synthesis of Waterborne Polyurethanes

Waterborne polyurethanes (WBPUs) have attracted increasing attention in a wide range of industrial applications because of their versatile properties as well as ecofriendly nature. Although extensive research has been carried out on WBPU synthesis, the roles of some of the key synthesis components remain unclear. In this study, through systematically controlling and fine tuning the precursor compositions and reaction conditions, over 300 WBPUs are synthesized. This research enables the roles of several key components that govern WBPU physicochemical properties and ultimately the potential WBPU applications to be identified. Using hair styling as an example, it is demonstrated that only the WBPUs with an optimal range of properties (e.g., Young's modulus >150 MPa, elongation at break: 15–300%, moisture uptake <10%) can achieve strong styling performance. To further improve the natural‐feel sensory benefits in the final styling products, a number of fatty acids with different carbon chain lengths or unsaturation levels are incorporated into WBPUs. Among the ten fatty acids studied, linoleic acid is identified as the most preferred additive. Both in vitro and in vivo testing demonstrate that WBPUs with optimal properties are promising materials for developing strong, long‐lasting styling products with natural feel.     

Analysis and insights from a dynamical model of nuclear plant safety risk

In this paper, we expand upon previously reported results of a dynamical systems model for the impact of plant processes and programmatic performance on nuclear plant safety risk. We utilize both analytical techniques and numerical simulations typical of the analysis of nonlinear dynamical systems to obtain insights important for effective risk management. This includes use of bifurcation diagrams to show that period doubling bifurcations and regions of chaotic dynamics can occur. We also investigate the impact of risk mitigating functions (equipment reliability and loss prevention) on plant safety risk and demonstrate that these functions are capable of improving risk to levels that are better than those that are represented in a traditional risk assessment. Next, we analyze the system response to the presence of external noise and obtain some conclusions with respect to the allocation of resources to ensure that safety is maintained at optimal levels. In particular, we demonstrate that the model supports the importance of management and regulator attention to plants that have demonstrated poor performance by providing an external stimulus to obtain desired improvements. Equally important, the model suggests that excessive intervention, by either plant management or regulatory authorities, can have a deleterious impact on safety for plants that are operating with very effective programs and processes. Finally, we propose a modification to the model that accounts for the impact of plant risk culture on process performance and plant safety risk. We then use numerical simulations to demonstrate the important safety benefits of a strong risk culture.     

Evidence for the covalent binding of hydroxyethyl radicals to rat liver microsomal proteins

It is well known that acetaldehyde is capable of covalent binding to liver proteins. However, in experiments using liver microsomes prepared from chronically ethanol-fed rats we have observed that the addition of EDTA-iron complex to the microsomes increases by about 4-5 fold both the spin trapping of hydroxyethyl radicals and the covalent binding of 14C-ethanol to proteins, while it only doubles acetaldehyde formation. Conversely, the presence of GSH strongly decreases the trapping of hydroxyethyl radicals and completely inhibits the covalent binding, without affecting acetaldehyde production. Furthermore, the spin trapping agent 4-pyridyl-N-oxide-t-butyl nitrone (4-POBN), previously employed for the detection of hydroxyethyl radicals, decreases by about 70% the covalent binding of 14C-ethanol to microsomal proteins. 4-POBN does not affect acetaldehyde production by liver microsomes, nor does it interfere with the covalent binding of acetaldehyde produced by ADH-mediated oxidation of ethanol. The results obtained indicate that hydroxyethyl radicals generated during ethanol oxidation by cytochrome P-450 play an important role in the alkylation of microsomal proteins consequent to ethanol metabolism.     

Update on and Advances in Assessment and Cognitive-Behavioral Treatment of Anxiety Disorders in Children and Adolescents.

Most child psychologists would agree that treating anxiety disorders in children is extremely challenging at times but also rewarding. This article provides an updated look at assessment strategies and promising psychosocial treatment techniques for children with 3 common anxiety disorders: separation anxiety disorder, social phobia, and generalized anxiety disorder. The need for comprehensive diagnostic evaluations is highlighted through information on the wide range of assessment procedures and instruments available to practicing psychologists interested in treating anxious youth. In addition, a treatment approach shown to be empirically efficacious for treating anxious children, cognitive-behavioral therapy, is described. We provide practical examples of assessment and treatment techniques for clinical practice. Tables are included that can serve as useful quick references for the 3 areas covered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

EVALUATION OF A COMPOSITE BASED ON HIGH-DENSITY POLYETHYLENE FILLED WITH SURFACE-TREATED HYDROXYAPATITE

Summary  Composites properties are directly related to the degree of interaction between the plastic matrix and the inorganic filler. In the present work, the improvement of the composite’s properties by means of the addition of surface-treated and untreated hydroxyapatite (STHA and HA, respectively) was studied. An ethylene-acrylic acid copolymer was melt blended with high-density polyethylene and HA (HDPE/HA/EA). A surface treatment was performed using an ethylene-acrylic acid (EA) copolymer for STHA₁ and acrylic acid (AA) for STHA₂. High-density polyethylene (HDPE) was also tested. STHA₁ and STHA₂ composites exhibited Young’s modulus values (556 and 558 MPa, respectively) 22 % higher than that of HDPE/HA (455 MPa) and 8 % higher than that of HDPE/HA/EA (520 MPa). Additionally, STHA composites showed both yield stress and strain (σ_STHA1= 23 MPa; ε_STHA1= 9 %; σ_STHA2= 22 MPa; ε_STHA2= 10 %) having a remarkably different behavior from that of the HA composites, which showed no yielding at all. TEM micrographs showed better filler dispersion when surface treatment was applied to HA. Yet, the presence of EA copolymer exhibited a poorer thermal stability. The crystallinity degree as well as the crystallization and melting temperatures showed no significant variation. Regarding in vitro evaluation, composites with HA and EA copolymer proved to have better cell adhesion at early stages. The results of the STHA composites could be attributed to the electrostatic interactions taking place between the ethylene-acrylic acid copolymer and the polar groups of the HA.     

Microbial contamination of main contact surfaces of Automated Teller Machines from Metropolitan Area of Porto

ABSTRACT

Automated Teller Machines (ATM) are likely to be contaminated with various microorganisms because of their contact with the hands of many users daily. The main objective of this study was to investigate ATMs as a potential source of bacterial contamination. This study was conducted in the Metropolitan Area of Porto, in which 50 swab samples were cultured on selective media. Some isolates were identified based on colonial, morphological and biochemical characteristics. Susceptibility to several antibiotics was also evaluated for each isolated organism. Most contaminated ATMs had high numbers of Enterobacteriaceae and Enterococci. Staphylococci and Enterobacteriaceae were the most prevalent bacteria found. The recovered bacterial isolates varied in their antibiotic resistance pattern; Staphylococcus spp. demonstrated the most resistant profiles. With this pioneering study in Portugal, it was demonstrated that although ATMs in metropolitan area of Porto were not highly contaminated, some potentially pathogenic bacteria were present and resistant to some commonly used antibiotics.     

Mullite/SiAlON/Alumina Composites by Infiltration Processing

The formation of mullite/SiAlON/alumina composites was studied by infiltrating a SiAlON/alumina-base composite with two different solutions, followed by thermal treatment. The base composite was prepared from a mixture of tabular Al₂O₃ grains, fume SiO₂, and aluminum powders. The mixture was pressed into test bars and nitrided in a nitrogen-gas (N₂) atmosphere at 1480°C. The infiltrants were prehydrolyzed ethyl polysilicate solution and ethyl polysilicatealuminum nitrate solution. The composites were infiltrated under vacuum, cured at 100°C, and precalcined in air at 700°C. This infiltration process was repeated several times to produce bars that had been subjected to multiple infiltrations, then the bars were calcined in a N₂ atmosphere at 1480°C to obtain mullite/SiAlON/alumina composites. The infiltration process increased the percentage of nitrogenous crystalline and mullite phases in the matrix; therefore, a decrease of the composite microporosity was observed. The infiltration increased the mechanical strength of the composites. Of the two composites, the one produced using prehydrolyzed ethyl polysilicate as the infiltrant had a higher mechanical strength, before and after being subjected to a severe thermal shock.     

Study of the mechanical,thermal, and thermodegradative properties of virgin PP with recycled and non-recycled HDPE

In order to show the significance of plastic recycling, a study of the properties of blends of PP with non-recycled and recycled high density polyethylene (HDPE) is made. The results of the Young's modulus for polypropylene (PP)/non-recycled and recycled HDPE blends present a slight synergism, although no significant dependence of this property on the compound was observed. The values of elongation at break and impact strength reflect the incompatibility of the blends. In thermal studies of the blends, the values of fusion enthalpy are below the values of the components. The results of the thermodegradative studies show that activation energies (E_a) obtained are lower, in the case of the blends, than the E_a corresponding to pure polymers. In PP/recycled HDPE blends, activation energy, at 5% to 20% concentration, is maintained and falls abruptly with an increase in the concentration of the recycled material. Based upon the facts previously exposed, it is possible to recycle the recycled HDPE up to 20% concentration, in PP blends. The addition of the compatibilizer at 5% represents the optimal concentration for improving the final properties of the finished product.