The Crystal Structure of Tobermorite 14 Å (Plombierite), a C-S-H phase

The crystal structure of tobermorite 14 Å (plombierite) was solved by means of the application of the order-disorder (OD) theory and was refined through synchrotron radiation diffraction data. Two polytypes were detected within one very small crystal from Crestmore, together with possibly disordered sequences of layers, giving diffuse streaks along c*. Only one of the two polytypes, could be refined: it has B11b space group symmetry and cell parameters a = 6.735(2) Å, b = 7.425(2) Å, c = 27.987(5) A, γ = 123.25(1)° . The refinement converged to R = 0.152 for 1291 reflections with F 0>4σ(F 0). The characteristic reflections of the other polytype, F2dd space group, a ≈11.2 Å, b ≈ 7.3 Å, c ≈ 56 Å, were recognized but they were too weak and diffuse to be used in a structure refinement. The structure of tobermorite 14 Å is built up of complex layers, formed by sheets of sevenfold coordinated calcium cations, flanked on both sides by wollastonite-like chains. The space between two complex layers contains additional calcium cations and H 2O molecules; their distribution, as well as the system of hydrogen bonds, are presented and discussed. The crystal chemical formula indicated by the structural results is Ca 5Si 6O 16(OH) 2 ·7H 2O

Probe induced voids in a dusty plasma

An experimental study of the formation of voids (dust-free regions) around negatively biased probes in a dusty plasma is described. Stable voids are maintained by the balance of electric and ion drag forces on the dust particles. A theoretical model is proposed to explain how the size of the void scales with the probe bias potential

Anomalous dust temperature in dusty plasma experiments

Dust heating in dusty plasmas due to thermal electric field fluctuations and dust acoustic waves is examined. It is shown that dust particles acquire large random motion in fluctuating electric fields (within dust cloud) of background plasma causing dust electrostatic pressure PE [K. Avinash, Phys. Plasmas 13 (2006) 012109] and corresponding large temperature TE. Due to quadratic dependence on qd and high dust charge (∼ 103–104e), TE is much bigger than the dust kinetic temperature Td and is in the range of 10–300 eV for typical experimental numbers. Using global energy constraints dust heating due to dust acoustic waves is examined. It is shown that dust acoustic waves are potentially capable of heating dust to high temperatures in the range of a few hundreds of eV

Рентгенометрический анализ кинематики L4-L5 И L5-S1 позвоночных сегментов в III стадии дегенеративного процесса

ПОЗВОНОЧНИКА БОЛЕЗНИОСТЕОХОНДРОЗОСТЕОХОНДРИТГРЫЖА МЕЖПОЗВОНОЧНОГО ДИСКАМЕЖПОЗВОНКОВОГО ДИСКА СМЕЩЕНИЕРЕНТГЕНОГРАФИ

Screening of a Moving Parton in the Quark-Gluon Plasma

The screening potential of a parton moving through a quark-gluon plasma is calculated using the semi-classical transport theory. An anisotropic potential showing a minimum in the direction of the parton velocity is found. As consequences possible new bound states and J/psi dissociation are discussed.Comment: 4 pages, 2 figures, final, extended version, to be published in Phys.Rev.