Design and Investigation of de Vries Liquid Crystals Based on 5-Phenyl-Pyrimidine and (R,R)-2,3-Epoxyhexoxy backbone.

Calamitic liquid crystals based on 5-phenyl-pyrimidine derivatives have been designed, synthesized, and characterized. The 5-phenyl pyrimidine core was functionalized with a chiral (R,R)-2,3-epoxyhexoxy chain on one side and either siloxane or perfluoro terminated chains on the opposite side. The one involving a perfluorinated chain shows SmA^{*} phase over a wide temperature range of 82 °C, whereas the siloxane analog exhibits both SmA^{*} and SmC^{*} phases over a broad range of temperatures, and a weak first-order SmA^{*}-SmC^{*} transition is observed. For the siloxane analog, the reduction factor for the layer shrinkage R (relative to its thickness at the SmA^{*}-SmC^{*} transition temperature, T_{AC}) is ∼0.373, and layer shrinkage is 1.7% at a temperature of 13 °C below the T_{AC}. This compound is considered to have de Vries smectic characteristics with the de Vries coefficient C_{deVries} of ∼0.86 on the scale of zero (maximum-layer shrinkage) to 1 (zero-layer shrinkage). A three-parameter mean-field model is introduced for the orientational distribution function (ODF) to reproduce the electro-optic properties. This model explains the experimental results and leads to the ODF, which exhibits a crossover from the sugar-loaf to diffuse-cone ODF some 3 °C above T_{AC}

A flaring X-ray pulsar in Dorado

A study of unusual gamma-ray bursts detected on March 5 and March 6, 1979 in the KONUS experiment on the Venera 11 and Venera 12 spacecraft shows their source to be flaring X-ray pulsar in Dorado

Preliminary results of a gamma-ray burst study in the Konus experiment on the Venera-11 and Venera-12 space probes

Twenty-one gamma-ray bursts and 68 solar flares in the hard X-ray range were detected on Venera-11 and Venera-12 space probes during the initial 50-day observation period. Major characteristics of the equipment used and preliminary data on the temporal structure and energy spectra of the gamma-ray bursts are considered. The pattern of gamma-ray burst frequency distribution vs. intensity, N(S), is established

Coulomb singularity effects in tunnelling spectroscopy of individual impurities

Non-equilibrium Coulomb effects in resonant tunnelling processes through deep impurity states are analyzed. It is shown that Coulomb vertex corrections to the tunnelling transfer amplitude lead to a power-law singularity in current- voltage characteristicsComment: 7 pages, 2 figure

Energy dependence of Ti/Fe ratio in the Galactic cosmic rays measured by the ATIC-2 experiment

Titanium is a rare, secondary nucleus among Galactic cosmic rays. Using the Silicon matrix in the ATIC experiment, Titanium has been separated. The energy dependence of the Ti to Fe flux ratio in the energy region from 5 GeV per nucleon to about 500 GeV per nucleon is presented.Comment: 8 pages, 4 figures, accepted for publication in Astronomy Letter

Досвід проведення поперекової симпатичної блокади з метою мінімізації ускладнень перед симпатиколізисом

Сучасним методом лікування симпатично підтримуваного болю є проведення симпатичних блокад. З метою мінімізації ускладнень перед проведенням симпатиколізису представлено досвід проведення поперекової симпатичної блокади із застосуванням рентгенконтрасту і рентгенконтролю. Для візуалізації голки та ділянки поширення анестетику застосовували рентгенконтраст Visipaque, апарат ЕОП «Eхрoscop 8000». Матеріали та методи. Проведено 22 поперекові симпатичні блокади у 11 хворих з оклюзуючими захворюваннями артерій нижніх кінцівок 2–3 ступеня за Фонтейном і в 11 хворих із синдромом симпатично підтримуваного болю, зумовленого остеохондрозом поперекового відділу хребта. Результати. Введення контрасту і відслідковування ділянки його розповсюдження з рентгенконтролем у фронтальній і боковій проекціях дозволяє точно позиціонувати голку на передньолатеральній поверхні тіл хребців при мінімальній затраті часу і точно визначити, які структури будуть заблоковані. Це дозволяє без сумнівів уводити місцевий анестетик при терапевтично-діагностичній блокаді та проводити нейролітичну блокаду

Nematic twist-bend phase with nanoscale modulation of molecular orientation

A state of matter in which molecules show a long-range orientational order and no positional order is called a nematic liquid crystal. The best known and most widely used (for example, in modern displays) is the uniaxial nematic, with the rod-like molecules aligned along a single axis, called the director. When the molecules are chiral, the director twists in space, drawing a right-angle helicoid and remaining perpendicular to the helix axis; the structure is called a chiral nematic. Here using transmission electron and optical microscopy, we experimentally demonstrate a new nematic order, formed by achiral molecules, in which the director follows an oblique helicoid, maintaining a constant oblique angle with the helix axis and experiencing twist and bend. The oblique helicoids have a nanoscale pitch. The new twist-bend nematic represents a structural link between the uniaxial nematic (no tilt) and a chiral nematic (helicoids with right-angle tilt)

Nematic Twist-Bend Phase with Nanoscale Modulation of Molecular Orientation

Peer reviewedPublisher PD

Discontinuous Change in the Smectic Layer Thickness in Ferrielectric Liquid Crystals

The temperature dependence of the thickness of thick free-standing films is studied using a high-resolution film thickness measurement technique. A small discontinuity in the temperature dependence of the smectic layer thickness at every phase transition between ferro-, ferri-, and antiferroelectric phases is observed. We show that the major contribution to it arises from a change in the smectic tilt angle