Water vapor and oxygen permeability of wax films

The water vapor (WVP) and oxygen (O₂P) permeabilities of beeswax (BW), candelilla wax (CnW), carnauba wax (CrW) and microcrystalline wax (MW), formed as freestanding films, were determined. CnW and CrW both had small values for O₂P (0.29 and 0.26 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹⁴, respectively), which are less than half the value for high-density polyethylene and about a decade greater than the value for polyethylene terephthalate. O₂P values for BW and MW were about 6−9× greater than those of CnW and CrW. WVP of CnW was 0.18 g·m⁻¹·sec⁻¹·Pa⁻¹ × 10⁻¹², which is about one-half the value for CrW and MW and about one-third the value for BW. The WVP of CnW was somewhat less than that of polypropylene and somewhat greater than that of high-density polyethylene. Differences in permeabilities among the wax films are attributed mainly to differences in chemical composition and crystal type as determined by X-ray diffraction.     

Optimal sampling strategies for validation studies.

In selection instrument validation studies the situation occasionally arises in which there are a large number of observations on the predictor but criterion data are very expensive or difficult to obtain, thus making it necessary to sample values of the predictor. Three strategies (random, rectangular, and extreme groups) for sampling predictor values were compared with respect to accuracy and statistical power in estimating the total group validity. Comparisons were made on samples drawn from 6 large N (approximately 10,000) bivariate test score distributions known to contain some departures from linearity and homoscedasticity. It was shown that in this situation selecting values of the predictor that form a rectangular distribution gave, in all instances studied, at least equal accuracy and greater statistical power in estimating the total group validity compared with random sampling. When the predictor–criterion relationship was generally linear with only modest departures from linearity, selecting values from the extremes of the predictor distribution was optimal in terms of accuracy and statistical power and clearly superior to rectangular sampling. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Study of V-Be diffusion couple by ion backscattering

Ion backscattering has been used to study the diffusion couple V-Be at annealing temperatures in the range 800 to 1100 K. Analysis of proton and helium backscattering allowed determination of the average composition versus depth following in situ isothermal anneals of thin vapor-deposited vanadium films on beryllium substrates. The results were interpreted as an initial diffusion governed by grain boundary migration of the beryllium through the vanadium to form a beryllium oxide surface layer. Vanadium was found to be excluded from the beryllium oxide surface layer and also from the native oxide on the beryllium substrate. The initial rapid diffusion along grain boundaries was followed by a slower diffusion into the vanadium grains. The amount of beryllium which diffused into the vanadium film obeyed a $\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ dependence where t is the anneal time. Complete anneal sequences were taken at two temperatures and a tentative activation energy for the diffusion of beryllium in bulk vanadium of 3.4 eV was determined. The diffusion coefficient was estimated to be 1.0 × 10^?17cm²/sec at 958 K and 0.8 × 10^?18cm²/sec at 903 K.     

A microfluidic approach for development of hybrid collagen-chitosan extracellular matrix-like membranes for on-chip cell cultures

To advance organ-on-a-chip development and other areas befitting from physiologically-relevant biomembranes,a microfluidic platform is presented for synthesis of biomembranes during gelation and investigation into their role as extracellular matrix supports.In this work,high-throughput studies of collagen,chitosan,and collagen-chitosan hybrid biomembranes were carried out to characterize and compare key properties as a function of the applied hydrodynamic conditions during gelation.Specifically,depending on the biopolymer material used,varying flow conditions during biomembrane gelation caused width,uniformity,and swelling ratio to be differently affected and controllable.Finally,cell viability studies of seeded fibroblasts were conducted,thus showing the potential for biological applications.     

Node-link mapping and the evaluation of drug abuse counseling sessions.

Node-link mapping is a visual representation system that can be used in group and individual counseling sessions to illustrate clients' problems, issues, and plans. One hundred sixty-nine methadone treatment clients and their 10 counselors evaluated each of their individual and group sessions during a 2.5-month period by using the Session Evaluation Questionnaire (W. B. Stiles, 1980) and map rating items. A series of multivariate analyses of variance and correlational analyses indicated that the use of mapping (including the quantity and quality of mapping) was positively related to higher ratings of session depth by both clients and counselors. In addition, mapped group sessions were rated higher on several evaluative dimensions than were mapped individual sessions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optical properties of solvent‐cast polarizer films for liquid‐crystal displays: A viscoelastic modeling framework

Abstract— Many of the films used in polarizer assemblies in LCDs (e.g., triacetyl cellulose or TAC) are produced by a solvent‐casting process, which is known to impart optical anisotropy to the film expressed as finite out‐of‐plane birefringence. This feature of the film could have a significant impact on the optical performance of the display and it needs to be accounted for in any compensation scheme for the LC cell. This paper reviews the origin of this optical anisotropy, and it presents a viscoelastic model that links this property to the solvent‐casting process and to some key material parameters. The model results are compared with experimental data generated for polystyrene films cast from toluene, and generally good agreement is demonstrated.     

The effects of message framing on mammography utilization.

This experiment compared the effectiveness of gain- versus loss-framed messages to persuade women to obtain mammography screening. One hundred and thirty-three women 40 years and older and not adhering to current guidelines for obtaining mammography screening were assigned randomly to view either gain-framed (emphasizing the benefits of obtaining mammography) or loss-framed (emphasizing the risks of not obtaining mammography) persuasive videos that were factually equivalent. Attitudes and beliefs were measured before and immediately following the intervention. Mammography utilization was assessed 6 and 12 months later. Consistent with predictions based on prospect theory, women who viewed the loss-framed message were more likely to have obtained a mammogram within 12 months of the intervention. These findings suggest that loss-framed messages may have an advantage in the promotion of detection behaviors such as mammography. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A theory of roll coating of viscous and viscoelastic fluids

A theory for roll coating of a fluid onto a moving sheet is developed utilizing the usual “lubrication approximations.” The effects of fluid and operating parameters on coating thickness and pressure distribution are determined for a Newtonian fluid, and for a purely viscous non-Newtonian fluid obeying the Power Law. The results for these cases are obtained analytically, and are rather straightforward. A viscoelastic fluid is considered, of a type which shows typical non-Newtonian shear behavior observed in polymer melts and solutions and which also exhibits normal stress behavior. Analytical solutions are not possible, but a perturbation method, using a viscoelastic perturbation parameter related to a Deborah number, yields an approximate solution. Only terms to first order in the perturbation parameter are given. Subject to that degree of approximation, the following conclusions are drawn:

• 1 Non-Newtonian shear behavior reduces the pressure distribution, and increases the coating thickness.
• 1 Elasticity of the type usually observed in polymer solutions makes only a minor contribution to the roll-separating (load-carrying) force. The contribution is positive, but smaller than the corresponding negative contribution due to the non-Newtonian shear effects.
• 1 An increase in load-carrying capacity would require a different viscoelastic fluid than the type considered here—one that is essentially Newtonian in shear but, independently, capable of developing significant normal stresses.

     

Blade-coating of a viscoelastic fluid

A theory is presented which describes the dynamics of blade-coating of a viscoelstic fluid onto a moving sheet. The method begins with the usual “lubrication” approximation, and develops the solution as a perturbation about the Newtonian case. Viscoelasticity is described by an empirical constitutive equation which shows non-Newtonian viscosity and finite normal stress behavior consistent with typical observations of polymeric fluids. Theoretical results indicate a small increase in coating thickness due to departure from Newtonian behavior, and a significant decrease in the magnitude of the pressure developed under the blade. Consequently, the blade loading can be reduced significantly by viscoelastic effects. The results for the loading may be an artifact of the specific constitutive model, since it can be shown that some viscoelastic fluids, specifically an “elastic Newtonian” fluid, would exhibit increased loading relative to the inelastic Newtonian case.