Celebration of the Periodic Table of the Elements at the Academy of Sciences of Lisbon. A Chemistry Symposium Sublime Generalization: Discovery of The Periodic Law

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HIGH RIGIDITY AND VIBRATION ENDURANCE BAR FOR DEEP HOLES

Different constructions of bars are analyzed in the article, all of which are based on the idea of creating prestressed state in material. Improved construction of bar is proposed for equable spreading of elasticity zone along axis of boring bar

Numerical Study of Free-Surface Electrohydrodynamic Wave Turbulence

Direct numerical simulation of threedimensional chaotic motion of a dielectric liquid with a free surface under the action of external horizontal electric field is carried out. The numerical model takes into account the effects of surface tension, viscosity, and external isotropic random forcing acting at large scales. A transition from dispersive capillary wave turbulence to quasi-isotropic nondispersive EHD surface turbulence with increase of the external electric field strength is numerically observed for the first time. At the regime of developed EHD wave turbulence, the total electrical energy is found to be much greater than the energy of capillary waves, i.e., electrohydrodynamic effects play a dominant role. At the same time, anisotropic effects are detected that lead to the generation of capillary wave packets traveling perpendicular to the external field direction. Despite the revealed anisotropy, the calculated spectrum of EHD wave turbulence is in very good agreement with the analytical spectrum obtained on the basis of dimensional analysis of weak turbulence spectra.Comment: 7 pages,7 figure

Inactivation of DNA-Binding Response Regulator Sak189 Abrogates β-Antigen Expression and Affects Virulence of Streptococcus agalactiae

BACKGROUND: Streptococcus agalactiae is able to colonize numerous tissues employing different mechanisms of gene regulation, particularly via two-component regulatory systems. These systems sense the environmental stimuli and regulate expression of the genes including virulence genes. Recently, the novel two-component regulatory system Sak188/Sak189 was identified. In S. agalactiae genome, it was adjacent to the bac gene encoding for beta-antigen, an important virulence factor. METHODOLOGY/PRINCIPAL FINDINGS: In this study, the sak188 and sak189 genes were inactivated, and the functional role of Sak188/Sak189 two-component system in regulation of the beta-antigen expression was investigated. It was demonstrated that both transcription of bac gene and expression of encoded beta-antigen were controlled by Sak189 response regulator, but not Sak188 histidine kinase. It was also found that the regulation occurred at transcriptional level. Finally, insertional inactivation of sak189 gene, but not sak188 gene, significantly affected virulent properties of S. agalactiae. CONCLUSIONS/SIGNIFICANCE: Sak189 response regulator is necessary for activation of bac gene transcription. It also controls the virulent properties of S. agalactiae. Given that the primary functional role of Sak188/Sak189 two-component systems is a control of bac gene transcription, this system can be annotated as BgrR/S (bacgene regulatory system)

CARBON NANOTUBE UNDER PULSED PRESSURE

The radial dynamics of a single-walled zigzag carbon nanotube under pulsed pressure is studied. Uniform external pressure is applied instantly, then remains constant for a certain time, and then is instantly released. This loading scheme allows one to consider a carbon nanotube under plane strain conditions and replace it with a circular ring formed by one zigzag row of carbon atoms. The bending deformation of the ring in its plane is described by an equation based on the Kirchhoffs hypothesis. An effective parameter is used, including the bending stiffness of the ring and areal density. The regimes of oscillatory motion and exponential growth of radial displacements are investigated depending on the magnitude and duration of the applied pressure. Alternatively, the ring is analyzed in terms of a molecular dynamics model with a reduced number of degrees of freedom, taking into account the plane strain conditions. With the help of molecular dynamics, the limits of the thin shell theory are established. For (n, 0) CNTs with n > 15, in the regime of small-amplitude vibrations, the discrepancy between the continuum model and molecular dynamics calculations does not exceed 5% and decreases with increasing n

A gorilla adenovirus-based vaccine against Zika virus induces durable immunity and confers protection in pregnancy

The teratogenic potential of Zika virus (ZIKV) has made the development of an effective vaccine a global health priority. Here, we generate two gorilla adenovirus-based ZIKV vaccines that encode for pre-membrane (prM) and envelope (E) proteins (GAd-Zvp) or prM and the ectodomain of E protein (GAd-Eecto). Both vaccines induce humoral and cell-mediated immune responses and prevent lethality after ZIKV challenge in mice. Protection is antibody dependent, CD

Photochemical Organocatalytic Functionalization of Pyridines via Pyridinyl Radicals

We report a photochemical method for the functionalization of pyridines with radicals derived from allylic C–H bonds. Overall, two substrates undergo C–H functionalization to form a new C(sp2)–C(sp3) bond. The chemistry harnesses the unique reactivity of pyridinyl radicals, generated upon single-electron reduction of pyridinium ions, which undergo effective coupling with allylic radicals. This novel mechanism enables distinct positional selectivity for pyridine functionalization that diverges from classical Minisci chemistry. Crucial was the identification of a dithiophosphoric acid that masters three catalytic tasks, sequentially acting as a Brønsted acid for pyridine protonation, a single electron transfer (SET) reductant for pyridinium ion reduction, and a hydrogen atom abstractor for the activation of allylic C(sp3)–H bonds. The resulting pyridinyl and allylic radicals then couple with high regioselectivit

The integrated method to select drilling muds for well construction in difficult geological conditions

The article is concerned with the integrated approach to choose drilling mud composition for pay horizons penetration. An optimal choice of drilling mud composition would not only mean ensuring basic fluid properties, but also should minimize the impact on the pay zones when penetrating the pay horizons for the first time. To carry out better assessment of drilling mud impact on pay horizons, it is reasonable to study both technological parameters and filtration analyses, which would allow us to estimate the level of drilling mud impact on the pay horizon

The integrated method to select drilling muds for abnormally high pressure formations

The article describes the method for choosing a drilling mud for drilling abnormally high pressure formations. A carefully selected drilling mud formulation would not only enhance an array of interrelated fluid properties, but also minimize the impact on the pay zones when the drill bit first penetrates the pay. To ensure a better assessment of drilling mud impact on the pay zone, it is reasonable to carry out the study focused on the analysis of technological parameters, involving filtration, acid and drilling mud tests, as well as formation damage analysis. This would enable evaluating the degree of mudding off, reservoirs acid fracturing effect and the risks of pipe sticking at significant depth. The article presents the results of the above-described study with regard to the currently used drilling mud and new experimental formulations developed at National Research Tomsk Polytechnic University (Drilling Mud and Cement Slurry Laboratory)