Clay induced thermoplastic crystals in thermoset matrix: Thermal,Dynamic mechanical,and morphological analysis of clay/nylon‐6‐epoxy nanocomposites

A novel procedure to synthesize in situ clay/nylon‐6 composite suspension was explored via anionic solution polymerization. The suspension was efficiently blended with water‐based epoxy resin using mechanical stirrer at room temperature. Hence, a 3‐component coating system was obtained consisting of nano‐clay, nylon‐6 and epoxy resin. Large number of coatings and films were prepared with variation in clay and nylon‐6 loading. Concentration of clay was found to have profound effect on crystallinity of nylon‐6, thereby affecting the overall properties of clay/nylon/epoxy composite. All the films were characterized for thermal and dynamic mechanical behavior using differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA). Lower amount of clay was found to increase the crystallinity of nylon‐6 which in turn increased the plasticization of epoxy resin indicated by reduction in T_g. A multiphase morphology with distinct amorphous and crystalline zones was observed under scanning electron microscopy (SEM). A remarkable symmetrical morphology with branched dendritic crystal structure was observed for few of the clay/nylon/epoxy system. POLYM. COMPOS., 37:2206–2217, 2016. © 2015 Society of Plastics Engineers     

Integrated vaccination and non-pharmaceutical interventions based strategies in Ontario,Canada, as a case study: a mathematical modelling study

Recently, two coronavirus disease 2019 (COVID-19) vaccine products have been authorized in Canada. It is of crucial importance to model an integrated/combined package of non-pharmaceutical (physical/social distancing) and pharmaceutical (immunization) public health control measures. A modified epidemiological, compartmental SIR model was used and fit to the cumulative COVID-19 case data for the province of Ontario, Canada, from 8 September 2020 to 8 December 2020. Different vaccine roll-out strategies were simulated until 75% of the population was vaccinated, including a no-vaccination scenario. We compete these vaccination strategies with relaxation of non-pharmaceutical interventions. Non-pharmaceutical interventions were supposed to remain enforced and began to be relaxed on 31 January, 31 March or 1 May 2021. Based on projections from the data and long-term extrapolation of scenarios, relaxing the public health measures implemented by re-opening too early would cause any benefits of vaccination to be lost by increasing case numbers, increasing the effective reproduction number above 1 and thus increasing the risk of localized outbreaks. If relaxation is, instead, delayed and 75% of the Ontarian population gets vaccinated by the end of the year, re-opening can occur with very little risk. Relaxing non-pharmaceutical interventions by re-opening and vaccine deployment is a careful balancing act. Our combination of model projections from data and simulation of different strategies and scenarios, can equip local public health decision- and policy-makers with projections concerning the COVID-19 epidemiological trend, helping them in the decision-making process.     

Continuity and change in the measurement of infant attachment: Comment on Fraley and Spieker (2003).

R.C. Fraley and S.J. Spieker (2003) refocused attention on the important question of continuous versus categorical measurement of infant attachment. This commentary begins with a brief response to Fraley and Spieker's position. Next, it highlights the usefulness of the categorical approach by reviewing some of the major advances in the field that have been fostered by a categorical approach. These include the identification of the disorganized attachment group, the development of the concept of conditional behavioral strategies, the creation of systems for coding attachment beyond infancy, and a greater understanding of cross-generational associations. The author then makes several propositions for future research that are necessary for clarifying how best to measure infant attachment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design of a composite polymer plant using a simulation system

This paper describes the use of the General Purpose Simulation System (GPSS) to simulate the manufacture of a typical line of thermotropic liquid crystal polymer resins. Specifically considered were composite polymers based on parahydroxybenzoic acid with glass, graphite, or talc added as a filler or reinforcing agent. The process examined consists of a combination of batch and semicontinuous operations. Product campaigning and equipment cleaning requirements were also incorporated into the GPSS model. Different equipment configurations and manpower distributions were simulated to aid in the design of such a polymer plant. The simulation results were analyzed, and the calculated return on investment was used to select the final plant design.     

The generalization of attachment representations to new social situations: Predicting behavior during initial interactions with strangers.

The idea that attachment representations are generalized to new social situations and guide behavior with unfamiliar others is central to attachment theory. However, research regarding this important theoretical postulate has been lacking in adolescence and adulthood, as most research has focused on establishing the influence of attachment representations on close relationship dynamics. Thus, the goal of this investigation was to examine the extent to which attachment representations are predictive of adolescents' initial behavior when meeting and interacting with new peers. High school adolescents (N = 135) participated with unfamiliar peers from another school in 2 social support interactions that were videotaped and coded by independent observers. Results indicated that attachment representations (assessed through interview and self-report measures) were predictive of behaviors exhibited during the discussions. Theoretical implications of the results and contributions to the existing literature are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis and characterization of crosslinked polyurethane/clay nanocomposites

A series of glycerin‐crosslinked polyurethane (XPU)‐clay nanocomposites were prepared by in situ polymerization followed by solution casting and thermal treatment. The weight percent (wt %) of clay in the nanocomposites was varied between 0.25 and 10. The structural, rheological and dynamic mechanical properties of the nanocomposites were investigated. X‐ray diffraction (XRD) analysis showed that well dispersed clay platelets were formed in nanocomposites containing up to 1 wt % of clay. Scanning electron microscopy (SEM) showed that poorly dispersed and non‐exfoliated clays were present in composites containing >2 wt % of clay and resulted in phase‐separated disparities within the matrix. Rheological studies demonstrated that processability of polyurethane was significantly improved after clay addition such that solution viscosity decreased by between 76 and 90%. Furthermore, the presence of chemical and physical crosslink networks within the matrix resulted in a remarkable enhancement in the rubbery plateau storage modulus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43346.     

Minimizing transportation cost of a joint inventory location model using modified adaptive differential evolution algorithm

Transportation is a key issue in supply chain management and is a major concern for a company. This paper considers a joint-location inventory problem involving a set of suppliers producing different products and a set of retailers where some retailers are treated as distribution centers (DCs). The problem is to determine which retailers to be assigned as DCs, which retailers to receive direct shipments, how much of the retailer’s demand to allocate to the DCs, and how much of the DC’s demand is to be met by different suppliers. The problem is formulated as a mixed integer model and it has been solved through an adaptive differential evolution algorithm known as modified J. Adaptive Differential Evolution. The solutions obtained are compared with that of simple genetic algorithm. This paper also shows that the proposed model is robust in nature and offers near-optimal results for different distributions. The sum of the cost of establishing some retailers as DCs and the total transportation cost incurred in shipping products from the suppliers to the retailers via DCs(for some retailers) or directly (for the other retailers) is also compared with the total transportation cost incurred when all the products are shipped directly from the suppliers to the retailers.     

Surface Composition and Topography of Electrodeposited Polypyrrole Coatings on Steel Substrates

Polypyrrole coatings were successfully electrodeposited on low-carbon steel substrates from aqueous oxalate solutions. The surface composition and topography of the polypyrrole coatings formed under different conditions were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results show that the surface composition of the electrodeposited polypyrrole coatings basically reflects their bulk composition. Deposition of polypyrrole coatings on steel substrates also increased the surface roughness of the steel substrates.     

Gender difference in walleye PCB concentrations persists following remedial dredging

Eleven male walleyes (Sander vitreus) and 10 female walleyes from the Saginaw Bay (Lake Huron) population were caught during the spawning run at Dow Dam (Midland, Michigan) in the Tittabawassee River during April 1996, and individual whole-fish polychlorinated biphenyl (PCB) determinations were made. Total PCB concentrations averaged 7.95 and 3.17 mg/kg for males and females, respectively. As part of the Natural Resource Damage Assessment remediation process, contaminated sediments from the Saginaw River, the main tributary to Saginaw Bay, were removed during 2000 and 2001. Total PCB concentrations of 10 male and 10 female walleyes caught at Dow Dam during April 2007 averaged 1.58 and 0.55 mg/kg, respectively. Thus, dredging of the Saginaw River appeared to be effective in reducing PCB concentrations of Saginaw Bay adult walleyes, as both males and females decreased in PCB concentration by more than 80% between 1996 and 2007. However, the ratio of male PCB concentration to female PCB concentration did not decline between 1996 and 2007. This persistent gender difference in PCB concentrations was apparently due to a gender difference in habitat utilization coupled with a persistent spatial gradient in prey fish PCB concentrations from the Saginaw River to Lake Huron.