An electrochemical approach for the detection of HIV-1 protease

An electrochemical biosensor with a new bioorganometallic approach for the detection of human immunodeficiency virus (HIV) type 1 protease (HIV-1 PR) using surface-bound ferrocenoyl (Fc)-pepstatin conjugates is presented.     

Peak in the magnetic-field dependence of diffusion-induced thermopower for n-Bi-Sb semiconducting alloys

A peak is detected on the dependence of the diffusion-induced thermopower on transverse magnetic field in degenerate semiconducting alloys n-Bi_1?x Sb_x (0.07≤x≤0.15) doped with tellurium donor impurity. The temperature gradient is directed along the bisector axis C ₁ of the monocrystalline sample and the magnetic field is along the triad axis C ₃. The electron spectrum of the Bi-Sb alloys under investigation consists of three equivalent ellipsoids with distinctly different effective masses along the axes of the ellipsoid (m _∥/m _⊥). A simple kinetic theory shows that the presence of the peak on the diffusion thermopower is a manifestation of this strong anisotropy in the electron spectrum and of the additive contribution of all three ellipsoids to electron transport. The nonmonotonic dependence of thermopower on the transverse magnetic field makes it possible to determine the electron relaxation time, while the temperature dependence of this relaxation time can be used to separate the relaxation time for electrons scattered from ionized impurities and from acoustic phonons.     

Resonant acceptor states and terahertz stimulated emission of uniaxially strained germanium

The stimulated emission spectrum of uniaxially strained p-Ge is presented. The energy spectrum of the states of a shallow acceptor in Ge under uniaxial compression is calculated. The threshold pressure at which the acceptor state split off from the ground state becomes resonant is found. The pressure dependence of the width of this resonant level is calculated. The stimulated emission lines are identified. In particular, it is shown that the principal emission peak corresponds to the transition of holes from the resonant 1s (1s _r) state to the local p _±1 state. The probabilities of optical transitions are calculated. A mechanism of population inversion due to the intense resonant scattering of hot holes with an energy corresponding to the position of the 1s _r level is proposed. Zh. éksp. Teor. Fiz. 115, 89–100 (January 1999)     

Theory of coherent phenomena and fundamentals in nuclear resonant scattering

Muonic X-ray cascades in B, C, N, O and Ne following muonic atom formation in B₂H₆, CH₄, C₂H₆, C₄H₁₀, N₂, O₂ and Ne were investigated. The densities of the different target gases were low enough to prevent any contact of the atom or molecule on which the formation takes place with surrounding atoms or molecules during the cascade. Molecular effects of the capturing molecule are clearly seen. The observed transition yields could be reproduced by variation of only two parameters in a cascade calculation: the number of initially available electrons and the muon angular momentum distribution at the starting point of the calculation. By varying the number of electrons, the molecular effects could be described. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low-temperature thermal conductivity of tellurium-doped bismuth

Phonon thermal conductivities κ₂₂ (?T ‖ C1) and κ₃₃ (? T ‖ C₃) of tellurium-doped bismuth with an electron concentration in the range 1.8 × 10¹⁹ ≤ n_L ≤ 1.4 × 10²⁰ cm^?3 were studied in the temperature interval 2 < T < 300 K. The temperature dependence of the phonon thermal conductivity obtained on doped bismuth samples of both orientations exhibits two maxima, one at a low temperature and the other at a high temperature. The effect of various phonon relaxation mechanisms on the dependence of both phonon thermal conductivity maxima on temperature, impurity concentration, and electron density is studied.     

THE PHOTOTOXICITY OF 2,5-DIPHENYLOXAZOLE (POP) AND 1,4-BIS(5-PHENYLOXAZOL-2-YL)BENZENE (POPOP)

Abstract 2,5-Diphenyloxazole (POP) is widely used for the determination of radioactivity by scintillation counting. It has been found to be phototoxic to the yeasts Saccharomyces cerevisiae and Candida utilis , to the first instar larvae of the mosquito Aedes aegypti , to the crustaceans Daphnia magna and Artemia salida , as well as to the eggs of Drosophila melanogaster . The related molecule 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) is also phototoxic, but to a lesser degree. Both POP and POPOP can sensitize the formation of singlet oxygen.