Increase in temperature induces the Z to B transition of poly[d(G-C)] in water-ethanol solution

AbstractAn increase in temperature from 20 to 50° C results in the complete transition from the Z to B form of poly(d(G-C)], dissolved in a 55% ethanol-water solution. The transition is fully reversible and displays a slow kinetics. The transition profiles for the free polynucleotide and for that in the presence of ethidium bromide, which is known to stabilize the B form, are obtained by circular dichroism. Based on these data the enthalpy value for the B-Z transition in our conditions is estimated to be ΔHBZ = −0.7 kcalmol

The study of spectral changes in THz range in normal and pathological skin in vivo depending on the dehydration methods used

The terahertz (THz) attenuated total reflectance (ATR) imaging of normal and pathological skin under the action of various dehydration agents was carried out in vivo. Studies were conducted on animal models (the mouse), patients with diabetes, and healthy volunteers. For measurements, each animal was leaned against the ATR prism of the skin surface, and several locations in the skin of each animal were analyzed. Places on the skin for analysis were chosen so that the intensity spectra of the THz signal were practically the same for selected points. THz spectra measurements were carried out every 10 minutes within 45 minutes interval under the action of a dehydration agent. 40% glucose was shown to provide the most effective improving tissue optical clearing effect in the THz range

The δ-phase of SrTeO3 at 780 K1

As part of a structural investigation of strontium tellurate(IV) (STO), SrTeO3, with particular emphasis on the crystal chemistry and phase transitions, the structure of the δ-phase has been determined at 780 K using a single-crystal analysis. Both structural and non-linear optical measurements indicate that STO undergoes a γ→δ second-order ferroelectric phase transition at 633 K from the C2 (γ) to the C2/m (δ) modification. Systematic differences between the similar γ- and δ-phase structures were determined and it was found that this phase transformation can be described by a displacive mechanism

ЧИСЛЕННЫЙ АНАЛИЗ ПРИСОЕДИНЕННОГО ТЕЧЕНИЯ ЗА РЕБРОМ

Turbulent characteristics of a reattached flow separated from a rib in an air flat channel were numerically analyzed by RANS and LES methods. The both methods showed low pressure regions in corners formed by the rib and the channel walls that caused a vorticity tube to be formed along the rib. Nevertheless in RANS, a reattached flow was identified as two-dimensional with a velocity decreasing near the channel bottom wall. In LES, the low pressure regions caused transverse and normal motions in the separation region that resulted in redistributions between velocity components, Reynolds stresses and the velocity decrease near the channel bottom wall, i.e., the formation of three-dimensional reattached flow. Турбулентные характеристики присоединенного течения срывающегося с ребра в плоском воздушном канале численно анализируются методами RANS (осредненные уравнения Рейнольдса) и LES (метод крупных вихрей). Оба метода показали формирование симметричных зон низкого давления в углах, образованных ребром со стенками канала. Эти зоны вызывали генерацию вихревой трубки вдоль длины ребра. Тем не менее, присоединенное течение было идентифицировано в RANS как двумерное с уменьшением скорости у нижней стенки канала. Метод крупных вихрей показал возникновение в отрывной зоне течений в поперечном и нормальном направлениях. Они приводили к изменению соотношений между компонентами скорости и напряжений Рейнольдса, а также к снижению скорости присоединенного течения у нижней стенки канала, т. е. к формированию трехмерного течения.

Турбулентные характеристики развитого пограничного слоя в канале

Communicated by Academician Oleg G. PenyazkovMean velocity, fluctuations, spatial correlations and wave number spectra were calculated and analyzed by the LES method using the software OpenFOAM for solution of the task of the developed 3D turbulent boundary layer. The layer was formed in water flowing in the 50 х 125 х 850 mm flat channel (height, width and length, respectively) at a mean entrance velocity of 0.3 m/s that results in the Reynolds number based on the half channel height equal to 7500. The velocity profile at the channel entrance was set by the law 1/7. The turbulent parameters were calculated on two coordinates: y+ = 10 and 40, i. e. in the buffer and logarithmic regions of the boundary layer. The study showed that the vortex structures were generated in the buffer region; they were still identified at the beginning of the logarithmic region (y+ = 40). These structures form vortex packets whose scale in the transverse direction is much less than their length. The vortex packets weakly interact with each other in the transverse direction, which results in an almost constancy of the energy spectrum within a broad wave number range.Представлено академиком О. Г. ПенязьковымМетодом крупных вихрей (LES) с использованием пакета OpenFOAM (Open Field Operation and Manipulation) выполнен расчет и анализ средней скорости, пульсаций, пространственных корреляций пульсаций скорости и волновых спектров пульсаций компонент скорости в развитом трехмерном турбулентном пограничном слое. Пограничный слой формировался при течении воды со средней скоростью 0,3 м/с в плоском канале размерами 50 х 125 х 850 мм (высота, ширина и длина соответственно). Скорость на входе в канал задавалась по закону 1/7. Число Рейнольдса, рассчитанное по половине высоты канала, равнялось 7500. Расчеты выполнены на двух координатах y+ = 10 и 40, т. е. в буферной и логарифмической областях пограничного слоя. Исследования показали, что в буферной области формируются вихревые структуры, которые сохраняют свою идентификацию и в начале логарифмической области (y+ = 40). Эти структуры формируют пакеты из вихрей различного масштаба. Размер этих пакетов в поперечном сечении существенно меньше, чем их длина. Дискретные пакеты слабо взаимодействуют между собой поперек пограничного слоя, что проявляется в постоянстве энергетического спектра в широком интервале волновых чисел

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

Genetic Ablation of Pannexin1 Protects Retinal Neurons from Ischemic Injury

Pannexin1 (Panx1) forms large nonselective membrane channel that is implicated in paracrine and inflammatory signaling. In vitro experiments suggested that Panx1 could play a key role in ischemic death of hippocampal neurons. Since retinal ganglion cells (RGCs) express high levels of Panx1 and are susceptible to ischemic induced injury, we hypothesized that Panx1 contributes to rapid and selective loss of these neurons in ischemia. To test this hypothesis, we induced experimental retinal ischemia followed by reperfusion in live animals with the Panx1 channel genetically ablated either in the entire mouse (Panx1 KO), or only in neurons using the conditional knockout (Panx1 CKO) technology. Here we report that two distinct neurotoxic processes are induced in RGCs by ischemia in the wild type mice but are inactivated in Panx1KO and Panx1 CKO animals. First, the post-ischemic permeation of RGC plasma membranes is suppressed, as assessed by dye transfer and calcium imaging assays ex vivo and in vitro. Second, the inflammasome-mediated activation of caspase-1 and the production of interleukin-1β in the Panx1 KO retinas are inhibited. Our findings indicate that post-ischemic neurotoxicity in the retina is mediated by previously uncharacterized pathways, which involve neuronal Panx1 and are intrinsic to RGCs. Thus, our work presents the in vivo evidence for neurotoxicity elicited by neuronal Panx1, and identifies this channel as a new therapeutic target in ischemic pathologies

Martian dust storm impact on atmospheric H₂O and D/H observed by ExoMars Trace Gas Orbiter

Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere

No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally