Describing the sorption characteristics of a ternary system of benzene (1) and alcohol (2) in a nonporous polymer membrane (3) by the Flory–Huggins model

The Flory–Huggins equation was used to describe results of total and preferential sorption measurements for the binary liquid mixture of benzene (1) and alcohol (2) in one of two nonporous polymer membranes (3), low‐density polyethylene (LDPE) and Nafion membrane. The concentration dependence of binary and ternary interaction parameters was determined. The interaction parameters for the benzene – methanol binary mixture were obtained from binary vapor‐liquid equilibrium data in the literature to decrease the number of adjusted parameters. The results show that use of a ternary interaction parameter is necessary. Data treatment was performed assuming either no crystallinity or an average crystallinity typical for the studied membranes. Subsequently, the limiting activity coefficients of solutes in LDPE were calculated from the values of the interaction parameters and their values compared to values of the limiting activity coefficients of benzene and methanol in hypothetical liquid alkane with the same density as LDPE obtained by the UNIFAC method. POLYM. ENG. SCI., 55:1187–1195, 2015. © 2014 Society of Plastics Engineers     

Leg stiffness of sprinters using running-specific prostheses

Running-specific prostheses (RSF) are designed to replicate the spring-like nature of biological legs (bioL) during running. However, it is not clear how these devices affect whole leg stiffness characteristics or running dynamics over a range of speeds. We used a simple spring–mass model to examine running mechanics across a range of speeds, in unilateral and bilateral transtibial amputees and performance-matched controls. We found significant differences between the affected leg (AL) of unilateral amputees and both ALs of bilateral amputees compared with the bioL of non-amputees for nearly every variable measured. Leg stiffness remained constant or increased with speed in bioL, but decreased with speed in legs with RSPs. The decrease in leg stiffness in legs with RSPs was mainly owing to a combination of lower peak ground reaction forces and increased leg compression with increasing speeds. Leg stiffness is an important parameter affecting contact time and the force exerted on the ground. It is likely that the fixed stiffness of the prosthesis coupled with differences in the limb posture required to run with the prosthesis limits the ability to modulate whole leg stiffness and the ability to apply high vertical ground reaction forces during sprinting.     

Tocols of selected spring wheat (Triticum aestivum L.), einkorn wheat (Triticum monococcum L.) and wild emmer (Triticum dicoccum Schuebl [Schrank]) varieties

Wheat contributes significantly worldwide to antioxidant income with beneficial healthy effects. Two varieties of einkorn wheat (Triticum monococcum L. – Escana and Schwedisches Einkorn), two varieties of wild emmer [Triticum dicoccum Schuebl (Schrank)] (Rudico and Kahler Emmer) and three varieties of spring wheat (Triticum aestivum L. – Granny, Kärtner Früher and SW Kadrilj) were evaluated for tocols – tocopherols and tocotrienols by high performance liquid chromatography – electrospray ionisation tandem mass spectrometry (HPLC–ESI/MS/MS). Investigated emmer and einkorn wheat varieties have shown minor lower total tocols content in comparison with spring varieties, however significant typical levels of tocopherols and tocotrienols were found in these groups. In einkorn wheat varieties the major abundance of total tocols is represented by tocotrienols (Schwedisches Einkorn 65.0%, Escana 54.9%), in emmer wheat varieties the abundance of tocotrienols and tocopherols were similar (Rudico 48.9% of tocotrienols, Kahler Emmer 47.6%), whereas in spring bread wheat higher tocopherols (SW Kadrilj 54.5%, Kärtner Früher 60.2%, Granny 55.0%) were recorded.     

Surface properties of poly(ethylene terephthalate) foils of different thicknesses

Surface properties of commercially available poly(ethylene terephthalate) (PET) foils of different thicknesses (3, 13, 23, 50, and 100 μm) were characterized using different analytical methods. Surface roughness and morphology were determined by atomic force microscopy, goniometry was used for determination of contact angle (wettability of surface) and electrokinetical analysis (zeta potential) for characterization of surface polarity and conductivity. X-ray photoelectron spectroscopy was used for characterization of PET surface chemistry. Infrared spectroscopy and differential scanning calorimetry (DSC) were used for determination of crystallinity portion. By DSC analysis, it was confirmed that the crystallinity portion depends on the foil thickness. Most important result of this study is that the surface properties of PET foils depend not only on the foil thickness but also on the foil side under study. This finding may be of importance for future experiments performed on PET foils and for their application in tissue engineering or microelectronics.     

Photoelectrochemical and photocatalytic properties of titanium (IV) oxide nanoparticulate layers

Titania nanostructured particles were produced by the sol-gel method in the reverse micelle environment treated thermally and by various extraction steps including supercritical carbon dioxide, subcritical water and their combinations. Thin films comprised of the organized nanoparticles were tested in photoelectrochemical and photocatalytic experiments. The former were configured for the open circuit potential measurements and evaluation of polarization curves and the corresponding photocurrents. Photocatalytic activities of the layered films were assessed by following decomposition of the methyl ester of stearic acid. Attention was also paid to evaluation of the extent of the surface wettability of the layers. The effect of content of residual surface carbon, extent of hydrophilic properties and presence of anatase structure were identified as essential parameters responsible for the enhanced photoactivity of the tested layers. On the other hand also layers treated without any thermal steps revealed certain level of photoactivity that might be of special importance in some specific applications.     

Necessary and sufficient conditions for reachability on a simplex

In this paper we solve the general problem of designing a feedback controller to reach a set of facets of an n-dimensional simplex in finite time, for a system evolving with linear affine dynamics. Necessary and sufficient conditions are presented in the form of bilinear inequalities on the vertices of the simplex. By exploiting the structure of the problem, the bilinear inequalities are converted to a series of linear programming problems.     

Non-Newtonian effects of blood flow in complete coronary and femoral bypasses

A numerical investigation of non-Newtonian steady blood flow in a complete idealized 3D bypass model with occluded native artery is presented in order to study the non-Newtonian effects for two different sets of physiological parameters (artery diameter and inlet Reynolds number), which correspond to average coronary and femoral native arteries. Considering the blood to be a generalized Newtonian fluid, the shear-dependent viscosity is evaluated using the Carreau–Yasuda model. All numerical simulations are performed by an incompressible Navier–Stokes solver developed by the authors, which is based on the pseudo-compressibility approach and the cell-centred finite volume method defined on unstructured hexahedral computational grid. For the time integration, the fourth-stage Runge–Kutta algorithm is used. The analysis of numerical results obtained for the non-Newtonian and Newtonian flows through the coronary and femoral bypasses is focused on the distribution of velocity and wall shear stress in the entire length of the computational model, which consists of the proximal and distal native artery and the connected end-to-side bypass graft.     

Single- and two-photon spectral imaging of intrinsic fluorescence of transformed human hepatocytes

Autofluorescence (AF) originating from the cytoplasmic region of mammalian cells has been thoroughly investigated; however, AF from plasma membranes of viable intact cells is less well known, and has been mentioned only in a few older publications. Herein, we report results describing single- and two-photon spectral properties of a strong yellowish-green AF confined to the plasma-membrane region of transformed human hepatocytes (HepG2) grown in vitro as small three-dimensional aggregates or as monolayers. The excitation-emission characteristics of the membrane AF indicate that it may originate from a flavin derivative. Furthermore, the AF was closely associated with the plasma membranes of HepG2 cells, and its presence and intensity were dependent on cell metabolic state, membrane integrity and presence of reducing agents. This AF could be detected both in live intact cells and in formaldehyde-fixed cells.