Restricted proteolysis of legumin of broad beans: Effect on thermodynamic properties of aqueous solutions and interaction with ficoll

Thermodynamic properties of aqueous solutions of both native and modified legumin of broad beans (Vicia faba L.) have been examined. A restricted trypsin-induced proteolysis was used to modify protein structure. Evaluation of protein affinity to ficoll in aqueous solutions showed that modified protein possessed higher hydrophilicity. Thermodynamic properties of diluted solutions were used to predict the phase behaviour in concentrated systems containing protein and ficoll. At specific concentrations of native legumin, the system can separate in two phases, whereas in the case of modified protein the single-phase behaviour of the system was predicted for any concentrations of both components. The experimental data obtained in concentrated systems confirmed predictions of thermodynamic analysis of diluted solutions.     

Spectroscopic and SEM studies of SWNTs: Polymer solutions and films

Raman spectra of SWNTs suspended in aqueous solutions containing fragmented single-stranded DNA (SWNT:DNA), and films obtained from this suspension have been obtained. SEM study of the dried films indicated that the nanotubes tend to aggregate into bundles which results in the enhancement of the Raman intensity of the G⁻ tangential band, and an upshift and broadening of the G⁺ band. The intensity of radial breathing modes of metallic SWNTs is higher in the SWNT:DNA films as compared to that of the SWNT:DNA solution. The Raman spectra of SWNT:PVP and SWNT:agaroza samples exhibit similar changes as the SWNT:DNA samples when films are cast from the corresponding solutions. Both films and the solution forms of SWNT:DNA yield luminescence spectra which indicates the presence of individual tubes or small bundles in the films. The luminescence bands of SWNT:DNA films are relatively wider and is attributed to the interaction of DNA with the nanotube surface in the solid state.     

An optimization approach for unconfined seepage problem with semipermeable conditions

In this paper we study the unconfined potential steady flow through a porous media with semipermeable bottom. We propose a model that leads to a free boundary-value-problem with complementarities conditions on the bottom. The shape of a part of the domain boundary, called free boundary, is one of the unknown of the problem. The pressure of the flow as well as the flow velocity on the another part of the boundary, that is a one way permeable bottom, are also unknowns and satisfy a complementarity condition. We present the numerical implementation of the model based on an optimization approach. Performing a boundary-element discretization we get a nonlinear mathematical programming problem with complementarities conditions. To solve it we use Herskovits’s interior point algorithm. Numerical examples are presented.     

Modification of Iron with Degradable Silver Phases Processed via Laser Beam Melting for Implants with Adapted Degradation Rate

In medical technology, implants are used to improve the quality of patients’ lives. The development of materials with adapted properties can further increase the benefit of implants. If implants are only needed temporarily, biodegradable materials are beneficial. In this context, iron-based materials are promising due to their biocompatibility and mechanical properties, but the degradation rate needs to be accelerated. Apart from alloying, the creation of noble phases to cause anodic dissolution of the iron-based matrix is promising. Due to its high electrochemical potential, immiscibility with iron, biocompatibility, and antibacterial properties, silver is suited for the creation of such phases. A suitable technology for processing immiscible material combinations is powder-bed-based procedure like laser beam melting. This procedure offers short exposure times to high temperatures and therefore a limited time for diffusion of alloying elements. As the silver phases remain after the dissolution of the iron matrix, a modification is needed to ensure their degradability. Following this strategy, pure iron with 5 wt% of a degradable silver–calcium–lanthanum alloy is processed via laser beam melting. Investigation of the microstructure yields achievement of the intended microstructure and long-term degradation tests indicates an impact on the degradation, but no increased degradation rate.     

The recovery factor in a supersonic flow of gas with a low Prandtl number

A three-parameter differential model of turbulence supplemented with a transport equation for turbulent heat flux is used to perform calculations of the boundary layer on a heat-insulated wall in a supersonic gas flow with a value of Prandtl number Pr ≤ 0.7. The dependences on the values of Prandtl, Reynolds, and Mach numbers and of intensity of injection are obtained for the recovery factor.     

National primary standard of the unit of pressure – the pascal

The primary standard for the unit of pressure, the pascal, its constituent parts, ranges of application, and the results of key comparisons are described.     

Gd-Bi-M-Ce-O (M = Cu,Zr, Ni,Co, Mn) ceria-based solid solutions for low temperature CO oxidation

Ceria based solid solutions doped by Gd, Bi, and the third dopant were synthesized by the co-precipitation method with ultrasonic treatment, followed by calcination at the temperature of 500°С. Characterization of the synthesized nanosystems by XRD, TEM, TG, Raman spectroscopy, FTIR, XPS was carried out. It is shown that all obtained powders of solid solutions crystallized into a cubic structure of the fluorite type, with an average particle size of 5–15 nm. The samples had a mesoporous structure of the pore diameter of 2–5 nm. The catalytic activity of Gd-Bi-M-Ce-O (M = Cu, Zr, Ni, Co, Mn) solid solutions was carried out. The catalyst Gd_0.05Bi_0.15Mn_0.20Ce_0.60O₂ has the lowest oxidation temperature.     

Diffusion welding of aluminium alloy strengthened by Al2O3 particles through an Al/Cu multilayer foil

In the diffusion welding (DW) of difficult-to-deform materials (such as composites and intermetallics), the application of intermediate multilayer foils (MF), which have alternating layers of elements that form intermetallics, allows for production of a permanent joint under milder conditions. In this paper, the processes occurring in the joint zone (JZ) during DW of Al–5 wt.%Mg+27 wt.%Al₂O₃ composite material through the Al/Cu interlayer were studied. It was shown that, while heating of such a foil, phase transformations that are due to the reaction diffusion of elements, run in it. At MF heating under a continuously applied external load, the materials are plastically deformed. It is established that the intensity of foil plastic deformation at a specified load non-monotonically depends on temperature. It is shown that welding temperature is determined by the temperature at which MF can undergo superplastic flow under the impact of applied pressure. A mechanism of formation for a solid-phase joint of high-strength materials through interlayers based on the MF of intermetallic-forming elements is proposed.     

Broadband Ge/SiGe quantum dot photodetector on pseudosubstrate

We report the fabrication and characterization of a ten-period Ge quantum dot photodetector grown on SiGe pseudosubstrate. The detector exhibits tunable photoresponse in both 3- to 5- μm and 8- to 12- μm spectral regions with responsivity values up to about 1 mA/W at a bias of −3 V and operates under normal incidence radiation with background limited performance at 100 K. The relative response in the mid- and long-wave atmospheric windows could be controlled through the applied voltage.     

An interior point technique for solving bilevel programming problems

This paper deals with bilevel programs with strictly convex lower level problems. We present the theoretical basis of a kind of necessary and sufficient optimality conditions that involve a single-level mathematical program satisfying the linear independence constraint qualification. These conditions are obtained by replacing the inner problem by their optimality conditions and relaxing their inequality constraints. An algorithm for the bilevel program, based on a well known technique for classical smooth constrained optimization, is also studied. The algorithm obtains a solution of this problem with an effort similar to that required by a classical well-behaved nonlinear constrained optimization problem. Several illustrative problems which include linear, quadratic and general nonlinear functions and constraints are solved, and very good results are obtained for all cases.