Red-Shifted Substrates for FAST Fluorogen-Activating Protein Based on the GFP-Like Chromophores

A genetically encoded fluorescent tag for live cell microscopy is presented. This tag is composed of previously published fluorogen-activating protein FAST and a novel fluorogenic derivative of green fluorescent protein (GFP)-like chromophore with red fluorescence. The reversible binding of the novel fluorogen and FAST is accompanied by three orders of magnitude increase in red fluorescence (580–650 nm). The proposed dye instantly stains target cellular proteins fused with FAST, washes out in a minute timescale, and exhibits higher photostability of the fluorescence signal in confocal and widefield microscopy, in contrast with previously published fluorogen:FAST complexes.     

Laser excitation of long-lived oscillatory states in a dusty-plasma trap

Vertical oscillations of a single particle in a monolayer dusty-plasma sheath have been excited by a laser radiation pulse. The particle oscillates in a self-sustained regime at a characteristic frequency of about ?? = 25 Hz. It is established that phenomena related to the particle recharge and the delay of its charge variation relative to the equilibrium value cannot account for the self-sustained regime of oscillations. It is suggested that the experimentally observed vertical auto-oscillations of a single particle take place due to resonant pumping of the kinetic energy of the chaotic motion of particles in the dusty-plasma sheath to the energy of vertical oscillations.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.     

Bipolar charging of dust particles under ultraviolet radiation

The photoemission charging of dust particles under ultraviolet radiation from a xenon lamp has been investigated. The velocities of yttrium dust particles with a work function of 3.3 eV and their charges have been determined experimentally; the latter are about 400–500 and about 100 elementary charges per micron of radius for the positively and negatively charged fractions, respectively. The dust particle charging and the dust cloud evolution in a photoemission cell after exposure to an ultraviolet radiation source under the applied voltage have been simulated numerically. The photoemission charging of dust particles has been calculated on the basis of nonlocal and local charging models. Only unipolar particle charging is shown to take place in a system of polydisperse dust particles with the same photoemission efficiency. It has been established that bipolar charging is possible in the case of monodisperse particles with different quantum efficiencies. Polydispersity in this case facilitates the appearance of oppositely charged particles in a photoemission plasma.     

Volume reflection of 1-GeV protons by a bent silicon crystal

The volume reflection of 1-GeV protons by a bent crystal has been observed. The crystal is made of single crystal silicon. The (111) atomic planes are bent owing to the elastic quasimosaicity effect, which makes it possible to reduce the crystal length for a beam to 30 μm. It is found that the probability of the reflection effect is higher than the probability of the channeling effect (0.71 vs. 0.63), and the deflection angle of the protons reflected inside the crystal is equal to 1.39 ± 0.04 in terms of the critical angle for channeling under the conditions of the experiment (170 μrad). The width of the reflected peak is equal to 1.76 ± 0.04 in the same units. The protons that are not involved in channeling at the angular position of maximum channeling undergo volume reflection and are deflected in the direction opposite to the channeled beam by the angle 1.01 ± 0.05 in terms of the critical angle for channeling. The width of the reflected peak is equal to 1.94 ± 0.08 in the same units. Original Russian Text ? Yu.M. Ivanov, N.F. Bondar’, Yu.A. Gavrikov, A.S. Denisov, A.V. Zhelamkov, V.G. Ivochkin, S.V. Kos’yanenko, L.P. Lapina, A.A. Petrunin, V.V. Skorobogatov, V.M. Suvorov, A.I. Shchetkovsky, A.M. Taratin, W. Scandale, 2006, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2006, Vol. 84, No. 7, pp. 445–450.     

Catalytic homogeneous hydrogenation of compounds containing X --> O semipolar bonds (X = N, S, P) with para-hydrogen as a promising route for preparation of para-water

The quantum-chemical simulation (DFT, PBE, TZ2p basis set) of the mechanism of catalytic hydrogenation of compounds containing R(n)X --> O semipolar bonds (R(n)X = N(2), Me(2)S, C(5)H(5)N, Ph(3)P) on the Wilkinson catalyst (Ph(3)P)(3)RhCl with para-hydrogen showed that this process proceeds with retention of proton nuclear spin correlation, which enables a principal possibility to synthesize para-H(2)O, i.e. the nuclear spin isomer of water with antiparallel proton spins, using this route.     

Analysis of pair interparticle interaction in nonideal dissipative systems

A new method is proposed for determining the interaction forces between particles in nonideal dissipative systems with isotropic pair potentials. The method is based on the solution of the inverse problem describing the motion of interacting particles by a system of Langevin equations and allows one to recover the parameters of the external confining potential without referring to a priori information on the friction coefficients of the particles. This procedure was tested by a numerical simulation of the problem in a wide range of parameters typical of experimental conditions in a laboratory dusty plasma. The results of the first experimental approbation of the method as applied to the analysis of the interaction of dust particles in a laboratory high-frequency capacitive discharge plasma are presented.     

Isotopic effect in the energy dependence of the total fission cross section of lead and 209Bi nuclei for protons with energies up to 1 GeV

The results from measurements of the total fission cross sections of ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb nuclei for protons with energies from 207 to 1000 MeV and a step of ≈100 MeV. These results complemented by our data for ²⁰⁹Bi and the data of the EXFOR world base allow determination of absolute and relative contributions of the isotopic effect.     

Propagation of Plasma Bunches through a Transverse Magnetic Barrier

The injection of a plasma bunch into a multipolar trap can be applied to fill the trap with a plasma. The injection of the bunch into a tokamak-like trap can be considered an additional means for controlling the processes of plasma heating and fuel delivery to the central zone of a thermonuclear reactor. In both cases, the bunch is injected normally to the magnetic field of the trap. It has been shown theoretically, experimentally, and by numerical simulation that the depth of plasma bunch penetration into the magnetic field varies in direct proportion to the bunch energy and in inverse proportion to the magnetic pressure and the cross-sectional area of the plasma bunch. The data of this work allow researchers to estimate the values of plasma bunch parameters at which the bunch will be trapped. As a result, the process of plasma bunch trapping has been optimized.     

Natural Vibrations of a Liquid-Transporting Pipeline on an Elastic Base

Flexural free vibrations of an ideal-liquid-transporting pipeline on an elastic base are studied. A numerical-analytical method for finding the pipeline natural frequencies and vibration modes is developed, which permits one to determine the natural frequencies and modes for the case in which the tension or compression (the longitudinal force acting along the pipeline axis), the pipe diameter, and hence the velocity of the incompressible fluid being transported are arbitrary functions of the longitudinal coordinate measured along the pipeline axis. The least natural frequencies are calculated for the case in which the variable elasticity of the base is given by some test functions.