Physicochemical and Rheological Properties of Crystallized Blends Containing <Emphasis Type="Italic">trans</Emphasis>-free and Partially Hydrogenated Soybean Oil

Three vegetable oil blends, intended for formulation of high melting temperature confectionary coatings, were prepared by mixing different proportions of coconut oil, palm stearin, and either partially hydrogenated soybean oil (PH-SBO) or native soybean oil (i.e., trans-free SBO). The blends were crystallized under the same isothermal conditions and the crystallized systems evaluated by DSC, SFC, polarized light microscopy, and rheology under low [i.e., G′ and yield stress (σ*)] and high (i.e., creep and recovery profiles) stress forces. Overall, all trans-free blends showed lower SFC and heat of crystallization than the ones obtained with PH-SBO blends. These results showed that trans-fatty acids decrease the level of structural order of the crystals, and probably also the organization of the crystal network. As a result, most of the crystallized blends with PH-SBO showed lower σ* values and higher creep profiles (i.e., softer texture) than trans-free blends, particularly in systems crystallized at high supercooling and blends with saturated medium chain TAG. Nevertheless, at particular crystallization temperatures some trans-free formulations provided crystallized systems with rheological properties that would result in softer textures than the ones obtained with PH-SBO blends. Knowledge of the rheological properties under low and high stress forces is vital when comparing the functionality of crystallized TAG systems with and without TAG with trans-fatty acids.     

Maximum density effects on natural convection in a vertical annulus filled with a non-Darcy porous medium

Summary This article numerically studies the problem of natural convection in a porous medium saturated with cold water, under density inversion, within a vertical annulus. In modeling the flow in the porous medium the non-Darcy effects, which include the Forchheimer inertia and Brinkman viscous effects are taken into account. The governing equations are solved numerically by the finite difference method using the modified strongly implicit procedure. The effects of the inversion parameter _m , radius ratioR ^*, aspect ratioAR, Forchheimer inertia parameter Fc/Pr, and Darcy number parameter Da on the heat transfer and fluid flow characteristics are discussed in detail. Results show that both the inversion parameter and radius ratio have a significant influence on the flow structure and heat transfer rate in the annulus. It is also found that the mean Nusselt number decreases as the Forchheimer inertia parameter or the Darcy number increases. Moreover, the results obtained here are also compared and favorably agree with numerical results and with experimental data.Nomenclature AR aspect ratio,H/L - d particle diameter - Da Darcy number,K/(L ²) - Fc Forchheimer number,K/L - g gravitational acceleration - H annulus height - K permeability - K transport property defined in Eq. (5) - L gap width,r _o –r _i - Nu _i , Nu _o local Nusselt number of the inner and outer cylinders, respectively - mean Nusselt number of the inner and outer cylinders, respectively - p pressure - Pr Prandtl number, / - q constant in Eq. (9) - r radial coordinate - R dimensionless radial coordinate,(r–r _i )/L - r _i radius of inner cylinder - r _o radius of outer cylinder - R ^* radius ratio,(r _o –r _i )/r _i - Ra Rayleigh number,K _m gL(T _h –T _c ) ^q / - T dimensional temperature - T _c dimensional temperature of inner cylinder - T _h dimensional temperature of outer cylinder - T _m temperature corresponding to the density maximum, 4.029325°C - u, v Darcian velocity components inr andz directions, respectively     

Ferroelectric field effect in SrCuO2 and SrRuO3 films

We report on ferroelectric field effect experiments on Pb(Zr_0.52Ti_0.48)O₃/SrCuO₂ and Pb(Zr_0.52Ti_0.48)O₃/SrRuO₃ epitaxial heterostructures with an emphasis on the material characterization. Upon reversing the polarization of the Pb(Zr_0.52Ti_0.48)O₃ ferroelectric layer, we measured a nonvolatile change in the resistivity of ultrathin layers of SrCuO₂ and SrRuO₃. In thin SrRuO₃ films (30 Å) up to a 9% resistivity change has been observed at room temperature.     

High-temperature superconducting shift registers operating at up to100 GHz

Shift registers have been demonstrated in YBaCuO operating at 77 K using from 64 to over 1000 junctions. These are some of the larger scale integrated circuits demonstrated to date using YBaCuO Josephson technology. The circuit is a modified rapid single flux quantum design in which a single trigger pulse causes a one bit shift of the entire word of 32-512 b in length. Two different junction technologies, electron-beam defined nanobridges and epitaxial edge junctions, have been used with parameter spreads ranging from 11% to 22%. Correct operation has been verified with low speed random word tests and circulating data tests while pseudo random bit sequence demonstrations are underway. A practical amount of time to shift between cells has been measured to be about 10 ps     

A comparison of cause-specific melanoma mortality and all-cause mortality in survival analyses after radiation treatment for uveal melanoma

OBJECTIVE: To determine the causes and patterns of mortality after uveal melanoma radiation. DESIGN: A cohort study from a single institution was performed. Mortality was modeled using semiparametric survival techniques. All cause and cause-specific mortality analyses were performed. Mortality was compared with expected mortality from the U.S. census data. PARTICIPANTS: A total of 731 patients were studied, and 710 (97%) of these had medium or large melanomas. The mean tumor diameter was 11.3 mm, and the mean tumor thickness was 5.8 mm. Ciliary body was involved in 122 (17%) of patients. Complete follow-up was available on 99.6% (728 of 731) of patients. MAIN OUTCOME MEASURES: The authors analyzed the distribution and causes of post-treatment mortality. RESULTS: The 5- and 10-year all-cause Kaplan-Meier survival rates were 75.6% and 62.3%, respectively. Both melanoma risk factors (older age, ciliary body involvement, and larger tumor diameter) and nonmelanoma risk factors (older age and medical condition) were significant prognostic factors of all-cause mortality. Deaths from nonmelanoma causes accounted for 91 (42.3%) of 215 deaths. The 5-year and 10-year estimates of nonmelanoma deaths were 8.3% and 15.9%, respectively. Nonmelanoma mortality was similar to that observed in the general U.S. population (91 observed, 98.1 expected). Melanoma metastases accounted for 124 (57.7%) of 215 deaths. The 5- and 10-year estimates for probability of metastatic death were 16.1% and 21.8%, respectively. The largest tumor diameter was the best predictor for melanoma mortality; ciliary body involvement, older age, and distance from the fovea also were significant in multivariate analyses. CONCLUSION: A significant proportion of patients with uveal melanoma die of nonmelanoma causes after radiation. In analyzing prognostic factors, considerable information may be lost if analyses are based on all-cause mortality rather than cause-specific mortality.     

Effects of nonuniform temperature gradients on the onset of oscillatory Marangoni convection in a magnetic field

Summary.  This article theoretically studies the onset of oscillatory Marangoni convection in a horizontal layer of an electrically conducting fluid, to which a nonuniform thermal gradient and a uniform magnetic field are applied. The top surface of a fluid layer is deformably free and the bottom is rigid. By means of the linear stability theory and a normal mode analysis, the eigenvalue equations of the perturbed state are solved by using the fourth-order Runge-Kutta-Gill's method with the shooting technique. The computational results are compared with those known from the literature, and the agreement is found out to be generally good. The results indicate that the critical Marangoni number −Ma _c increases with increasing the Chandrasekhar number Q, the Prandtl number Pr, or the Biot number Bi of the upper free surface, but decreases with increasing the Crispation number Cr. As compared with the linear temperature profile, the inverted parabolic temperature profile shows higher −Ma _c values, while the parabolic temperature profile shows lower −Ma _c values. In addition, for the piecewise linear temperature profiles, the influences of thermal depth on the critical Marangoni number are also obtained. Received June 20, 2002; revised September 27, 2002 Published online: March 20, 2003     

Reactive surface coatings based on polysilsesquioxanes: universal method toward light-responsive surfaces

Reactive surface coatings were used as an ideal precursor coating for the fabrication of three different photoswitchable surface coatings in parallel. Different light-responsive moieties, such as azobenzene, salicylideneaniline, and spiropyran, were immobilized on glass, polycarbonate, and steel surfaces. Independent from the underlying substrate, wettability could be switched reversibly by UV irradiation. The maximum switching range was obtained after functionalization of the reactive coating with spiropyran, resulting in a contact angle difference between the two isomeric states of almost 30°.     

Carbon-based layer-by-layer nanostructures: from films to hollow capsules

Over the past years, the layer-by-layer (LbL) assembly has been widely developed as one of the most powerful techniques to prepare multifunctional films with desired functions, structures and morphologies because of its versatility in the process steps in both material and substrate choices. Among various functional nanoscale objects, carbon-based nanomaterials, such as carbon nanotubes and graphene sheets, are promising candidates for emerging science and technology with their unique physical, chemical, and mechanical properties. In particular, carbon-based functional multilayer coatings based on the LbL assembly are currently being actively pursued as conducting electrodes, batteries, solar cells, supercapacitors, fuel cells and sensor applications. In this article, we give an overview on the use of carbon materials in nanostructured films and capsules prepared by the LbL assembly with the aim of unraveling the unique features and their applications of carbon multilayers prepared by the LbL assembly.     

An ablation problem in a finite medium with time‐dependent heat flux

Abstract

The objective of this work is to develop an approximate analytical solution for the transient ablation problem in a finite medium. The medium is subjected to time‐dependent boundary heat flux, i. e., q₀=at^P , and with this refined integral technique, the complicated nonlinear problem is reduced to an initial value problem, which is then solved by the Runge‐Kutta method. Results are more accurate than with the classical heat balance integral method and also indicate that the dependence of the solution on the assumed temperature profile is much weaker than is the case with the classical integral method.     

An efficient access control scheme for files protection

Abstract

A dynamic access control mechanism suitable for hardware implementation is proposed. Each file is safeguarded by q lock values, where q is number of the possible access classes. The access right of a user to some file can be revealed very efficiently. In addition, dynamic operations such as changing a privilege value, insertion or deletion of a user, and insertion or deletion of a file can be done easily. Compared to Wu and Hwangs’ and Chang's methods, the computation of lock values is simple and the verification of an access request is quite efficient. The storage required is proportional to m?n which is less than that of the above‐mentioned methods, where m is the number of users and n is the number of files.