A phenomenological model of macrocrack initiation and growth in cyclically deformed material

Role of the process zone in fatigue macrocrack initiation and propagation is considered. An examples of the assessment of the fatigue macrocrack initiation period, Ni, and the failure period, Nf, of a notched specimens on the base of unified model using fatigue macrocrack growth rates only are shown. Some backgrounds and well-known fatigue phenomena (Kitagawa's and Smith's diagrams, etc) are discussed

Опит ассиметричного сосуществования Канады и США и возможности его проекции на украинско-российские отношения

У статті проаналізовано основні критерії, показники та ознаки асиметрії канадсько-американських відносин; визначено стратегії та фактори, що сприяють мінімізації асиметрії між державами, а також запропоновано можливі шляхи використання позитивного досвіду Канади для зовнішньої політики України.This article analyses main criteria and features of the asymmetry of Canada-U.S. relations. It defines strategies and factors that contribute to the minimization of the asymmetry between these two countries. It also proposes possible ways of adaptation of the positive Canadian experience to the foreign policy of Ukraine.Данная статья содержит анализ основных критериев, показателей и признаков асимметрии канадско-американских отношений. В статье также определены стратегии и факторы, способствующие минимизации асимметрии между странами, а также предложены возможные пути использования позитивного опыта Канады для проведения внешнеполитического курса Украины

Канадско-американские отношения в сферах безопасности и обороны

У статті проаналізовано характер і ключові аспекти співробітництва Канади та США у сферах безпеки і оборони на дво- та багатосторонньому рівнях, а також визначено особливості та шляхи мінімізації асиметрії канадсько-американських відносин у згаданих галузях.The given article provides the analysis of the character and key features of the Canada-U.S. cooperation in the defense and security spheres both on bilateral and multilateral levels. The article also defines peculiarities of the asymmetry of such cooperation and ways of its minimization.Данная статья содержит анализ характера и ключевых аспектов сотрудничества Канады и США в сферах безопасности и обороны на двустороннем и многостороннем уровнях. В статье также определены особенности и пути минимизации асимметрии канадско-американских отношений в данных сферах

Electrochemical diagnostics of the structural-phase state of pipelanes steels at durable operation

Показано, що внаслідок неоднорідного напружено-деформованого стану згинів парогонів зі сталей 12Х1МФ та 15Х1М1Ф у різних зонах (розтягнута, середня, стиснена) процеси трансформації структури і накопичення пошкоджуваності в процесі експлуатації проходить з різною інтенсивністю. Встановлено, що стандартні механічні характеристики, передбачені діючими нормативними документами, виявляють слабку чутливість (знижуються в 1.03-1.24 раза) до процесів зміни мікроструктури та накопичення пошкоджень за умови повзучості сталей 12Х1МФ і 15Х1М1Ф. З іншого боку, зміни фазового складу та мікроструктури парогінних сталей суттєво впливають на їх електрохімічну поведінку, зокрема, на швидкість репасивації свіжоутвореної поверхні Vr.It is shown that the processes of structure transformation and damage evolution under service conditions passes with different intensity as a result of nonuniform stress-strain state in different zones (tensile, middle, compressed) of the bends of 12Х1МФ or 15Х1М1Ф steel pipelines. It is established that standard mechanical properties, provided by current normative documents, exhibit weak sensitivity (decrease in 1.03–1.24 times) to the processes of the microstructure change and damage accumulation under creep conditions of 12Х1МФ and 15Х1М1Ф steels. On the other hand, phase composition and microstructure change of pipeline steels has a significant influence on their electrochemical behaviour, in particular, on the fresh surface repassivation rate Vr

Role of GntR family regulatory gene SCO1678 in gluconate metabolism in streptomyces coelicolor M145

Here we report functional characterization of the Streptomyces coelicolor M145 gene SCO1678, which encodes a GntR-like regulator of the FadR subfamily. Bioinformatic analysis suggested that SCO1678 is part of putative operon (gnt) involved in gluconate metabolism. Combining the results of SCO1678 knockout, transcriptional analysis of gnt operon, and Sco1678 protein-DNA electromobility shift assays, we established that Sco1678 protein controls the gluconate operon. It does so via repression of its transcription from a single promoter located between genes SCO1678 and SCO1679. The knockout also influenced, in a medium-dependent manner, the production of secondary metabolites by S. coelicolor. In comparison to the wild type, on gluconate-containing minimal medium, the SCO1678 mutant produced much less actinorhodin and accumulated a yellow-colored pigment, likely to be the cryptic polyketide coelimycin. Possible links between gluconate metabolism and antibiotic production are discussed

Pleiotropic regulatory genes bldA, adpA and absB are implicated in production of phosphoglycolipid antibiotic moenomycin

Unlike the majority of actinomycete secondary metabolic pathways, the biosynthesis of peptidoglycan glycosyltransferase inhibitor moenomycin in Streptomyces ghanaensis does not involve any cluster-situated regulators (CSRs). This raises questions about the regulatory signals that initiate and sustain moenomycin production. We now show that three pleiotropic regulatory genes for Streptomyces morphogenesis and antibiotic production—bldA, adpA and absB—exert multi-layered control over moenomycin biosynthesis in native and heterologous producers. The bldA gene for tRNALeuUAA is required for the translation of rare UUA codons within two key moenomycin biosynthetic genes (moe), moeO5 and moeE5. It also indirectly influences moenomycin production by controlling the translation of the UUA-containing adpA and, probably, other as-yet-unknown repressor gene(s). AdpA binds key moe promoters and activates them. Furthermore, AdpA interacts with the bldA promoter, thus impacting translation of bldA-dependent mRNAs—that of adpA and several moe genes. Both adpA expression and moenomycin production are increased in an absB-deficient background, most probably because AbsB normally limits adpA mRNA abundance through ribonucleolytic cleavage. Our work highlights an underappreciated strategy for secondary metabolism regulation, in which the interaction between structural genes and pleiotropic regulators is not mediated by CSRs. This strategy might be relevant for a growing number of CSR-free gene clusters unearthed during actinomycete genome mining

Model and exploitation degradation of aircraft aluminium alloys

Представлено результати дослідження деградації матеріалів верхньої (В95Т1) та нижньої (Д16АТНВ) обшивок крила літака АН-12 після 40 років експлуатації неруйнівним вихрострумовим методом. Показано можливість оцінювання рівня навантаженості локальних зон обшивки крила літака за величиною зміни питомої електропровідності матеріалу. Отримані дані можна розглядати як базу для створення системи моніторингу оцінювання технічного стану авіаційних конструкцій під час тривалої експлуатації.A study results of aluminium type Д16 and В95Т1 alloys degradation after 40 years exploitation in wing skin of the АН – 12 airplane are presented. It has been shown that loading level of local zones on wing skin can be evaluated by change in specific conductivity of the material. The obtained data can be considered as a basis for creation of monitoring system allowing to evaluation of aircraft structures technical condition during long-term operation

Effect of Water Vapor Amount in a Hydrogenous Atmosphere on Structure and Properties of Nickel-Zirconia Anode Materials for Solid Oxide Fuel Cells

Nickel-zirconia anode ceramics of YSZ-NiO system for solid oxide fuel cells (SOFCs) has been investigated. A series of specimens were singly reduced in hydrogenous atmosphere (the Ar-5 vol%H2 mixture) at 600°C under the pressure of 0.15 MPa or subjected to reduction-oxidation (redox) cyclic treatment at 600°C. Influence of water vapor concentration in hydrogenous atmosphere on structure and properties of the materials was studied. Based on structural changes in the as-received material it was revealed that a small amount of water vapor in Ar-5 vol% H2 mixture (water vapor pressure below 0.03 MPa) accelerates a reduction of the nickel phase at 600°C with formation of nanopores on tiny Ni particles. A higher concentration of water vapor (the pressure above 0.03-0.05 MPa) causes a converse change in the reduction kinetics. For as-received material, such an amount of water vapor in the mixture is an obstacle for its reduction. For the material treated by redox cycling, better physical and mechanical properties were revealed after dwelling at 600°C in a water depleted gas mixture. Based on the SEM microscopy and the data on the conductivity and strength, the dual effect of water vapor on durability of a nickel-zirconia anode is discussed

Rational design of glycomimetic compounds targeting the Saccharomyces cerevisiae transglycosylase Gas2

The transglycosylase Saccharomyces cerevisiae Gas2 (ScGas2) belongs to a large family of enzymes that are key players in yeast cell wall remodeling. Despite its biological importance, no studies on the synthesis of substrate-based compounds as potential inhibitors have been reported. We have synthesized a series of docking-guided glycomimetics that were evaluated by fluorescence spectroscopy and saturation-transfer difference (STD) NMR experiments, revealing that a minimum of three glucose units linked via a β-(1,3) linkage are required for achieving molecular recognition at the binding donor site. The binding mode of our compounds is further supported by STD-NMR experiments using the active site-mutants Y107Q and Y244Q. Our results are important for both understanding of ScGas2-substrate interactions and setting up the basis for future design of glycomimetics as new antifungal agents.This study was supported by the Ministerio de Economía y Competitividad (MINECO) and FEDER Program (Madrid, Spain, projects CTQ2013-44367-C2-1-P and CTQ2013-44367-C2-2-P), and the Gobierno de Aragón (Zaragoza, Spain. E. M. and J. V.G. thank MEC for FPU and FPI predoctoral grants, respectively. The ARAID Foundation (Gobierno de Aragón, Spain) is also acknowledged for financial support.Peer reviewe

The membrane anchor of penicillin-binding protein PBP2a from Streptococcus pneumoniae influences peptidoglycan chain length.

The pneumococcus is an important Gram-positive pathogen, which shows increasing resistance to antibiotics, including β-lactams that target peptidoglycan assembly. Understanding cell-wall synthesis, at the molecular and cellular level, is essential for the prospect of combating drug resistance. As a first step towards reconstituting pneumococcal cell-wall assembly in vitro, we present the characterization of the glycosyltransferase activity of penicillin-binding protein (PBP)2a from Streptococcus pneumoniae. Recombinant full-length membrane-anchored PBP2a was purified by ion-exchange chromatography. The glycosyltransferase activity of this enzyme was found to differ from that of a truncated periplasmic form. The full-length protein with its cytoplasmic and transmembrane segment synthesizes longer glycan chains than the shorter form. The transpeptidase active site was functional, as shown by its reactivity towards bocillin and the catalysis of the hydrolysis of a thiol-ester substrate analogue. However, PBP2a did not cross-link the peptide stems of glycan chains in vitro. The absence of transpeptidase activity indicates that an essential component is missing from the in vitro system