Immobilization of Fungal β-Glucosidase on Silica Gel and Kaolin Carriers

β-Glucosidase is a key enzyme in the hydrolysis of cellulose for producing feedstock glucose for various industrial processes. Reuse of enzyme through immobilization can significantly improve the economic characteristics of the process. Immobilization of the fungal β-glucosidase by covalent binding and physical adsorption on silica gel and kaolin was conducted for consequent application of these procedures in large-scale industrial processes. Different immobilization parameters (incubation time, ionic strength, pH, enzyme/support ratio, glutaric aldehyde concentration, etc.) were evaluated for their effect on the thermal stability of the immobilized enzyme. It was shown that the immobilized enzyme activity is stable at 50 °C over 8 days. It has also been shown that in the case of immobilization on kaolin, approximately 95% of the initial enzyme was immobilized onto support, and loss of activity was not observed. However, covalent binding of the enzyme to silica gel brings significant loss of enzyme activity, and only 35% of activity was preserved. In the case of physical adsorption on kaolin, gradual desorption of enzyme takes place. To prevent this process, we have carried out chemical modification of the protein. As a result, after repeated washings, enzyme desorption from kaolin has been reduced from 75 to 20–25% loss.     

Potential of point charge in a semiconductor heterostructure with cylindrical symmetry

General expressions for the potential of a point charge in a coaxial semiconductor heterostructure composed by three cylindrical regions with different dielectric constants and for arbitrary location of the charged center in the heterostructure are derived.     

Static and noise characteristics of nanocomposite gas sensors

Thin film gas sensors based on nanocomposite In₂O₃·Ga₂O₃·SnO₂ (70:20:10) have been manufactured by the high-frequency magnetron sputtering method. The technological cycle of sensor fabrication processes is described. Sensitivity of the prepared sensors at the temperature of working body 250°C and low-frequency noises within the 1–300 Hz range were investigated. The response of sensors to vapors of ethanol and acetone was investigated using resistive and noise methods. It is shown that the value of the sensitivity measured by the noise method exceeds the value of sensitivity measured by the resistive method. Sensors show appreciable sensitivity to the ethanol vapors already at working body temperature 150°C. Sensors can be used for the detection of low concentrations of ethanol vapors. The monotonous increase in the sensitivity of these sensors with increase in the ethanol and acetone vapors content allows applying nanosensors also for fast determination of gases concentration in air.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Compton scattering from chiral dynamics with unitarity and causality

Proton Compton scattering is analyzed with the chiral Lagrangian. Partial-wave amplitudes are obtained by an analytic extrapolation of subthreshold reaction amplitudes computed in chiral perturbation theory, where the constraints set by electromagnetic-gauge invariance, causality and unitarity are used to stabilize the extrapolation. We present and discuss predictions for various spin observables and polarizabilities of the proton. While for the transition polarizabilities γE1M2, γM1E2 we recover the results of strict chiral perturbation theory, for the diagonal γE1E1, γM1M1 elements we find significant effects from rescattering.     

Mathematical modeling of the heating of a fast ignition target by an ion beam

We develop a BIN computer code for simulating the interaction of a monochromatic ion beam with a plasma, which takes into account changes in the spatial distribution of the heated-plasma temperature. This enables us to calculate the heating of both homogeneous and inhomogeneous plasmas with parameters corresponding to their real spatial distributions at the time of maximum compression of the inertial confinement fusion (ICF) target. We present the results of a numerical simulation using the BIN code for the heating of a homogeneous deuterium–tritium plasma by a short pulse of monochromatic ions at various ion velocity and plasma–electron thermal velocity ratios. We also present the results of calculations for the heating of an inhomogeneous plasma of a non-cryogenic target formed as a beryllium deuteride–tritide shell by beams of light, medium, and heavy ions. As the initial distributions, we use the results of numerical simulations for such a target, precompressed by a laser pulse (carried out at the M. V. Keldysh Institute of Applied Mathematics using the DIANA code). We demonstrate the possibility of forming the central ignitor with the parameters sufficient for igniting the targets by beams of ions with energies E ~ 100 ? 400 MeV/u and specific energy densities of the beam Q ～ 5?20 GJ/cm². The required specific energy density drops with increase in the ion energy; however, due to the increased path length, larger-charge ions have to be used.     

Covariogram of a parallelogram

In this paper we obtain the explicit forms of the covariogram and the orientation-dependent chord length distribution function for any parallelogram. The explicit form of the chord length distribution function for a parallelogram is also obtained.