Особенности формирования структуры сплавов системы Al–Ni–Zr, полученных при восстановлении оксидных соединений алюмотермией с применением СВС-металлургии

This work is focused on establishing the regularity of the effect of zirconium (2.21; 3.29; 3.69 and 6.92 wt.% Zr) on structure formation, the nature of distribution of elements and the microhardness of structural components in the Al–Ni–Zr system alloys obtained by aluminothermy using the SHS metallurgy. Regularities of the formation of structural components and their microhardness depending on the content of zirconium in Al–Ni alloys (50 wt.%) have been identified and scientifically substantiated. Structural components were identified by the methods of electromicroscopic studies and X-ray microanalysis of elements. The structure of the initial alloy consists of Al3Ni2 (β′-phase) and Al3Ni nickel aluminides. Zirconium doping of the alloy in the amount of 2.21 wt.% leads to crystallization of zirconium nickel aluminide Al2(Ni,Zr). With further increase in the content of zirconium (more than 2.21 wt.% Zr), complex alloyed intermetallic compounds crystallize – Zr, W, Si aluminides and Ni zirconides. A regularity was established in the decrease of the solubility of nickel in nickel aluminides Al3Ni2 and Al3Ni and their microhardness as the zirconium content increases in the Al–Ni–Zr alloys from 2.21 to 6.92 wt.%. In nickel aluminide with zirconium Al2(Ni,Zr), this contributes to a decrease in the solubility of Ni, Al and increase in the concentration of Si and Zr. Zirconium doping of the Al–Ni alloy in the amount over 2.21 wt.% contributes to an increase in hardness (HRA), despite a decrease in the microhardness of the metal base (Al3Ni2, Al3Ni and Al2(Ni,Zr)). The main reason for increasing the hardness of the Al–Ni–Zr alloys is the crystallization of complex-alloyed intermetallides – Zr, W, Si aluminides and nickel zirconide, which probably have an increased microhardness. Thus, zirconium doping of the Al–Ni alloy makes it possible to obtain a plastic metal base from nickel aluminides Al3Ni2, Al3Ni and Al2(Ni,Zr) and complex-alloyed intermetallides with high hardness.Настоящая работа посвящена установлению закономерности влияния добавки циркония в количестве 2,21, 3,29, 3,69 и 6,92 мас.% на структурообразование, характер распределения элементов и микротвердость структурных составляющих в сплавах системы Al–Ni–Zr, полученных алюмотермией с применением СВС-металлургии. Установлены и научно обоснованы закономерности формирования структурных составляющих и их микротвердости от содержания циркония в сплавах Al–Ni (50 мас.% Ni). Методами электронной микроскопии и микрорентгеноспектрального анализа элементов идентифицированы структурные составляющие. Структура исходного сплава состоит из алюминидов никеля Al3Ni2 (β′-фаза) и Al3Ni. Легирование сплава цирконием в количестве 2,21 мас.% приводит к кристаллизации циркониевого алюминида никеля Al2(Ni,Zr). При дальнейшем увеличении содержания циркония (более 2,21 мас.%) кристаллизуются комплексно-легированные интерметаллидные соединения – алюминиды Zr, W, Si и циркониды Ni. Установлена закономерность снижения растворимости Ni в алюминидах никеля Al3Ni2 и Al3Ni и их микротвердости по мере увеличения содержания циркония от 2,21 до 6,92 мас.% в сплавах Al–Ni–Zr. В алюминиде никеля с цирконием Al2(Ni,Zr) это способствует уменьшению растворимости Ni, Al и повышению концентраций Si и Zr. Легирование сплава Al–Ni цирконием в количестве более 2,21 мас.% способствует повышению твердости (HRA), несмотря на снижение микротвердости металлической основы (Al3Ni2, Al3Ni и Al2(Ni,Zr)). Основной причиной повышения твердости сплавов Al–Ni–Zr является кристаллизация комплексно-легированных интерметаллидов – алюминидов Zr, W, Si и цирконида никеля, обладающих, вероятно, повышенной микротвердостью. Таким образом, легирование сплава Al–Ni цирконием позволяет получить пластичную металлическую основу из алюминидов никеля Al3Ni2, Al3Ni и Al2(Ni,Zr) и высокотвердые комплексно-легированные интерметаллиды

Measuring Synchronisation and Convergence of Business Cycles

This paper investigates business cycle relations among different economies in theEuro area. Cyclical dynamics are explicitly modelled as part of a time series model. Weintroduce mechanisms that allow for increasing or diminishing phase shifts and for time-varyingassociation patterns in different cycles. Standard Kalman filter techniques are used toestimate the parameters simultaneously by maximum likelihood. The empirical illustrationsare based on gross domestic product (GDP) series of seven European countries which are comparedwith the GDP series of the Euro Area and that of the United States. The original integratedtime series are band-pass filtered. We find that there is an increasing resemblance between thebusiness cycle fluctuations of the European countries analysed and those of the Euro area,although with varying patterns

ИССЛЕДОВАНИЕ СТРОЕНИЯ ЖИДКОЙ ФАЗЫ, ПРОЦЕССОВ КРИСТАЛЛИЗАЦИИ И СТРУКТУРООБРАЗОВАНИЯ МЕДНЫХ СПЛАВОВ

The effect of alloying elements (Sn, Al, Si, Mn, Zn, Ni, As) on the morphology of the liquid phase, crystallization and structure formation processes of copper alloys (Cu + alloying elements) has been investigated. All the investigated alloying elements other than nickel are revealed to rise the degree of compaction (shrinkage) of the melt (ΔJliq) and the coefficient of thermal contraction (αliq) of liquid copper alloy because of the weakening of the binding forces between the atoms of copper and alloying elements (FCu-Cu > FCu-X). Nickel reduces the liquid state parameters due to increased binding forces between Cu and X atoms (FCu-X > > FCu-Cu), as evidenced by increase in crystallization temperature of α-solid solution. All the above alloying elements, other than Ni, lower the temperature of α-solid solution crystallization start (tliq) and end (ts) and extend the temperature range of α-solid solution crystallization tliq–ts. Copper alloys have a high degree of melt compaction during crystallization (ΔJcr): the denser the alloying element (higher density), the greater the degree of compaction ΔJcr. It is most valid for Ni and least valid for Al and Si. Up to the certain content, all the alloying elements reduce the structural components to small size (α-solid solution and eutectoid).Изучено влияние легирующих элементов (ЛЭ) – Sn, Al, Si, Mn, Zn, Ni, As – на строение жидкой фазы, процессы кристаллизации и структурообразования медных сплавов (Cu + ЛЭ). Выявлено, что все исследованные ЛЭ (кроме Ni) увеличивают степень уплотнения (усадки) расплава (ΔJж) и коэффициент термического сжатия (αж) жидкого медного сплава вследствие ослабления сил связи между атомами меди и легирующих элементов (FCu–Cu > FCu–ЛЭ). Никель же уменьшает параметры жидкого состояния из-за усиления сил связи между атомами Cu и ЛЭ (FCu–ЛЭ > FCu–Cu), о чем свидетельствует повышение температуры начала кристаллизации α-твердого раствора. Все рассмотренные легирующие элементы (кроме Ni) понижают температуры начала (tл) и конца (tс) кристаллизации α-твердого раствора и расширяют его температурный интервал tл–tс. Полученные сплавы меди обладают высокой степенью уплотнения расплава при кристаллизации (ΔJкр): чем плотнее ЛЭ (больше плотность), тем выше величина ΔJкр. В наибольшей степени это относится к Ni, а в наименьшей – к Al и Si. Установлено, что все легирующие элементы до определенного их содержания измельчают структурные составляющие (α-твердый раствор и эвтектоид)

Модифицирование литейных алюминиевых сплавов системы Al–Mg–Si обработкой жидкой фазы наносекундными электромагнитными импульсами

The AA 511 alloy of the Al–Mg–Si system was used as an example to demonstrate that aluminum melt irradiation with nanosecond electromagnetic pulses (NEPs) leads to a significant change in the nature of structure formation during crystallization. It was found that an increase in the frequency of melt irradiation with NEPs is accompanied by the refinement of the alloy structural components, while the greatest grain size reduction of the α-solid solution and intergranular inclusions of the eutectic Mg2Si phase is observed at a NEPs frequency f = 1000 Hz. An increase in the NEPs frequency leads to a significant increase in the concentration of magnesium in the α-solid solution and the fragmentation of Mg2Si phase intergranular inclusions, which is released in the form of compact isolated inclusions when the melt is irradiated at a frequency of 1000 Hz. It was shown that melt processing with NEPs leads to an increase in the Brinell hardness of as-cast specimens, as well as to a significant increase in the microhardness of α-solid solution grains (from 38.21 HV in the initial state to 61.85 HV after irradiation with a frequency of 1000 Hz). It was assumed that the effect of a pulsed electromagnetic field leads to a decrease in the critical values of the Gibbs free energy required to initiate nucleation processes, and to a decrease in the surface tension at the «growing crystal – molten metal» interface, which causes a modifying effect on the alloy structure due to a decrease in the critical size of crystal nuclei.На примере сплава АА 511 системы Al–Mg–Si показано, что облучение алюминиевых расплавов наносекундными электромагнитными импульсами (НЭМИ) приводит к существенному изменению характера структурообразования при кристаллизации. Установлено, что повышение частоты облучения расплавов НЭМИ сопровождается измельчением структурных составляющих сплава и перераспределением в них легирующих элементов. При этом наибольшая степень уменьшения размеров зерен α-твердого раствора и межзеренных включений эвтектической фазы Mg2Si наблюдается при частоте НЭМИ f = 1000 Гц. Повышение частоты НЭМИ приводит к значительному увеличению концентрации магния в α-твердом растворе и фрагментации межзеренных включений фазы Mg2Si, которая при облучении расплава с f = 1000 Гц выделяется в форме компактных изолированных включений. Показано, что обработка расплавов НЭМИ приводит к повышению твердости (по Бринеллю) образцов в литом состоянии, а также к увеличению микротвердости зерен α-твердого раствора (с 38,21 HV в исходном состоянии до 61,85 HV после облучения с частотой 1000 Гц). Было сделано предположение, что воздействие импульсного электромагнитного поля приводит к понижению критических значений свободной энергии Гиббса, необходимых для инициации процессов зародышеобразования, и снижению поверхностного натяжения на границах раздела «растущий кристалл – металлический расплав», что обусловливает модифицирующее воздействие на структуру сплава за счет уменьшения критического размера зародышей кристаллизации

The Role of Dicer Protein Partners in the Processing of MicroRNA Precursors

One of the cellular functions of the ribonuclease Dicer is to process microRNA precursors (pre-miRNAs) into mature microRNAs (miRNAs). Human Dicer performs this function in cooperation with its protein partners, AGO2, PACT and TRBP. The exact role of these accessory proteins in Dicer activity is still poorly understood. In this study, we used the northern blotting technique to investigate pre-miRNA cleavage efficiency and specificity after depletion of AGO2, PACT and TRBP by RNAi. The results showed that the inhibition of either Dicer protein partner substantially affected not only miRNA levels but also pre-miRNA levels, and it had a rather minor effect on the specificity of Dicer cleavage. The analysis of the Dicer cleavage products generated in vitro revealed the presence of a cleavage intermediate when pre-miRNA was processed by recombinant Dicer alone. This intermediate was not observed during pre-miRNA cleavage by endogenous Dicer. We demonstrate that AGO2, PACT and TRBP were required for the efficient functioning of Dicer in cells, and we suggest that one of the roles of these proteins is to assure better synchronization of cleavages triggered by two RNase III domains of Dicer

Never Resting Brain: Simultaneous Representation of Two Alpha Related Processes in Humans

Brain activity is continuously modulated, even at “rest”. The alpha rhythm (8–12 Hz) has been known as the hallmark of the brain's idle-state. However, it is still debated if the alpha rhythm reflects synchronization in a distributed network or focal generator and whether it occurs spontaneously or is driven by a stimulus. This EEG/fMRI study aimed to explore the source of alpha modulations and their distribution in the resting brain. By serendipity, while computing the individually defined power modulations of the alpha-band, two simultaneously occurring components of these modulations were found. An ‘induced alpha’ that was correlated with the paradigm (eyes open/ eyes closed), and a ‘spontaneous alpha’ that was on-going and unrelated to the paradigm. These alpha components when used as regressors for BOLD activation revealed two segregated activation maps: the ‘induced map’ included left lateral temporal cortical regions and the hippocampus; the ‘spontaneous map’ included prefrontal cortical regions and the thalamus. Our combined fMRI/EEG approach allowed to computationally untangle two parallel patterns of alpha modulations and underpin their anatomical basis in the human brain. These findings suggest that the human alpha rhythm represents at least two simultaneously occurring processes which characterize the ‘resting brain’; one is related to expected change in sensory information, while the other is endogenous and independent of stimulus change

Clarifying mammalian RISC assembly in vitro

<p>Abstract</p> <p>Background</p> <p>Argonaute, the core component of the RNA induced silencing complex (RISC), binds to mature miRNAs and regulates gene expression at transcriptional or post-transcriptional level. We recently reported that Argonaute 2 (Ago2) also assembles into complexes with miRNA precursors (pre-miRNAs). These Ago2:pre-miRNA complexes are catalytically active <it>in vitro </it>and constitute non-canonical RISCs.</p> <p>Results</p> <p>The use of pre-miRNAs as guides by Ago2 bypasses Dicer activity and complicates <it>in vitro </it>RISC reconstitution. In this work, we characterized Ago2:pre-miRNA complexes and identified RNAs that are targeted by miRNAs but not their corresponding pre-miRNAs. Using these target RNAs we were able to recapitulate <it>in vitro </it>pre-miRNA processing and canonical RISC loading, and define the minimal factors required for these processes.</p> <p>Conclusions</p> <p>Our results indicate that Ago2 and Dicer are sufficient for processing and loading of miRNAs into RISC. Furthermore, our studies suggest that Ago2 binds primarily to the 5'- and alternatively, to the 3'-end of select pre-miRNAs.</p

Resveratrol Suppresses Constitutive Activation of AKT via Generation of ROS and Induces Apoptosis in Diffuse Large B Cell Lymphoma Cell Lines

BACKGROUND: We have recently shown that deregulation PI3-kinase/AKT survival pathway plays an important role in pathogenesis of diffuse large B cell lymphoma (DLBCL). In an attempt to identify newer therapeutic agents, we investigated the role of Resveratrol (trans-3,4', 5-trihydroxystilbene), a naturally occurring polyphenolic compound on a panel of diffuse large B-cell lymphoma (DLBCL) cells in causing inhibition of cell viability and inducing apoptosis. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the action of Resveratrol on DLBCL cells and found that Resveratrol inhibited cell viability and induced apoptosis by inhibition of constitutively activated AKT and its downstream targets via generation of reactive oxygen species (ROS). Simultaneously, Resveratrol treatment of DLBCL cell lines also caused ROS dependent upregulation of DR5; and interestingly, co-treatment of DLBCL with sub-toxic doses of TRAIL and Resveratrol synergistically induced apoptosis via utilizing DR5, on the other hand, gene silencing of DR5 abolished this effect. CONCLUSION/SIGNIFICANCE: Altogether, these data suggest that Resveratrol acts as a suppressor of AKT/PKB pathway leading to apoptosis via generation of ROS and at the same time primes DLBCL cells via up-regulation of DR5 to TRAIL-mediated apoptosis. These data raise the possibility that Resveratrol may have a future therapeutic role in DLBCL and possibly other malignancies with constitutive activation of the AKT/PKB pathway

A prospective study of decline in fat free mass and skeletal muscle strength in chronic obstructive pulmonary disease

BACKGROUND: Skeletal muscle depletion is an important complication of chronic obstructive pulmonary disease (COPD) but little prospective data exists about the rate at which it occurs and the factors that promote its development. We therefore prospectively investigated the impact of disease severity, exacerbation frequency and treatment with corticosteroids on change in body composition and maximum isometric quadriceps strength (QMVC) over one year. METHODS: 64 patients with stable COPD (FEV(1 )mean (SD) 35.8(18.4) %predicted) were recruited from clinic and studied on two occasions one year apart. Fat free mass was determined using bioelectrical impedance analysis and a disease specific regression equation. RESULTS: QMVC fell from 34.8(1.5) kg to 33.3(1.5) kg (p = 0.04). The decline in quadriceps strength was greatest in those with the highest strength at baseline (R -0.28 p = 0.02) and was not correlated with lung function, exacerbation frequency or steroid treatment. Decline in fat free mass was similarly higher in those with largest FFM at baseline (R = -0.31 p = 0.01) but was more strongly correlated with greater gas trapping (R = -0.4 p = 0.001). Patients with frequent exacerbations (>1 per year) (n = 36) experienced a greater decline in fat free mass compared to infrequent exacerbators (n = 28) -1.3(3.7)kg vs. +1.2(3.1)kg (p = 0.005), as did patients on maintenance oral steroids (n = 8) -2.8(3.3) kg vs. +0.2(3.5) kg (p = 0.024) whereas in those who stopped smoking (n = 7) fat free mass increased; +2.7(3.1) kg vs. -0.51(3.5) kg (p = 0.026). CONCLUSION: Decline in fat free mass in COPD is associated with worse lung function, continued cigarette consumption and frequent exacerbations. Factors predicting progression of quadriceps weakness could not be identified from the present cohort

Metabolically active microbial communities in marine sediment under high-CO2 and low-pH extremes

Sediment-hosting hydrothermal systems in the Okinawa Trough maintain a large amount of liquid, supercritical and hydrate phases of CO2 in the seabed. The emission of CO2 may critically impact the geochemical, geophysical and ecological characteristics of the deep-sea sedimentary environment. So far it remains unclear whether microbial communities that have been detected in such high-CO2 and low-pH habitats are metabolically active, and if so, what the biogeochemical and ecological consequences for the environment are. In this study, RNA-based molecular approaches and radioactive tracer-based respiration rate assays were combined to study the density, diversity and metabolic activity of microbial communities in CO2-seep sediment at the Yonaguni Knoll IV hydrothermal field of the southern Okinawa Trough. In general, the number of microbes decreased sharply with increasing sediment depth and CO2 concentration. Phylogenetic analyses of community structure using reverse-transcribed 16S ribosomal RNA showed that the active microbial community became less diverse with increasing sediment depth and CO2 concentration, indicating that microbial activity and community structure are sensitive to CO2 venting. Analyses of RNA-based pyrosequences and catalyzed reporter deposition-fluorescence in situ hybridization data revealed that members of the SEEP-SRB2 group within the Deltaproteobacteria and anaerobic methanotrophic archaea (ANME-2a and -2c) were confined to the top seafloor, and active archaea were not detected in deeper sediments (13–30 cm in depth) characterized by high CO2. Measurement of the potential sulfate reduction rate at pH conditions of 3–9 with and without methane in the headspace indicated that acidophilic sulfate reduction possibly occurs in the presence of methane, even at very low pH of 3. These results suggest that some members of the anaerobic methanotrophs and sulfate reducers can adapt to the CO2-seep sedimentary environment; however, CO2 and pH in the deep-sea sediment were found to severely impact the activity and structure of the microbial community