Циклический характер изменения микротвердости алюминиевого сплава Д16 под действием ультразвуковой ударной обработки

Досліджено можливості більш ефективного, порівняно із традиційною термомеханічною обробкою, зміцнення поверхні легких конструкційних сплавів ультразвуковою ударною обробкою (УЗУО) на повітрі за умов квазі-гідростатичного стиснення зразка. На прикладі промислового алюмінієвого сплаву Д16 показано унікальну можливість зміцнення поверхні (до ∼600 %), зумовленого синергетичним впливом процесі низькотемпературної механічної наноструктуризації та механохімічної взаємодії алюмінію із киснем під дією УЗУО. Запропоновано якісну модель формування оксидного покриття товщиною кілька десятків мікрометрів. З використанням комплексу фізичних методів дослідження встановлено основні закономірності формування фазового і хімічного складу, структури та механічних властивостей поверхневих шарів сплаву Д16 залежно від амплітуди та тривалості обробки. Показано, що циклічний характер змін мікротвердості зумовлюється перебігом дисипативних процесів динамічного повернення та динамічної рекристалізації. За оптимальних режимів УЗУО зносостійкість поверхневих шарів зростає у 2,5 разу, рівень залишкових макронапружень стиснення дорівнює 650 МПа.The article studies possibilities of more effective surface hardening as compared with conventional thermomechanical processing. Specifically, we provide the insight into surface hardening of light structural alloys by ultrasonic impact treatment (UIT) in air under quasi-hydrostatic pressure of the sample. By example of the commercial aluminum alloy D16 we demonstrate the unique opportunity to harden the surface (up to ~600 %) using the synergistic effect of low-temperature processes of mechanical nanostructuring as well as mechanical and chemical interaction of aluminum with oxygen under the influence of UIT. We propose the qualitative model for formation of oxide coating several tens of micrometers thick. By employing a set of physical methods we establish basic laws of the phase formation and chemical composition, structure and mechanical properties of the D16 alloy surface layers depending on the amplitude and duration of UIT. We show that the development of dynamic recovery and dynamic recrystallization processes causes the cyclic nature of microhardness changes. Under optimal conditions of UIT the wear resistance of surface layers increased by ~2,5 times, and the compression residual stresses level is 650 MPa.Исследованы возможности более эффективного, по сравнению с традиционно термомеханической обработкой, упрочнения поверхности легких конструкционных сплавов ультразвуковой ударной обработкой (УЗУО) на воздухе в условиях квазигидростатического сжатия образца. На примере промышленного алюминиевого сплава Д16 показана уникальная возможность упрочнения поверхности (до ∼ 600 %), обусловленного синергетическим влиянием процессов низкотемпературной механической наноструктуризации и механохимического взаимодействия алюминия с кислородом под действием УЗУО. Предложена качественная модель формирования оксидного покрытия толщиной несколько десятков микрометров. С использованием комплекса физических методов исследования установлены основные закономерности формирования фазового и химического состава, структуры и механических свойств поверхностных слоев сплава Д16 в зависимости от амплитуды и длительности обработки. Показано, что циклический характер изменений микротвердости обусловлен развитием диссипативных процессов динамического возврата и динамической рекристаллизации. При оптимальных режимах УЗУО износостойкость поверхностных слоев возрастает в 2,5 раза, уровень остаточных макронапряжений сжатия равен 650 МПа

Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients

Background Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown. Methods Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding. Results A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55). Conclusions Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218. opens in new tab.

ЕЛЕКТРОКАТАЛІЗАТОРИ НА ОСНОВІ Ni-, Co-ШПІНЕЛЕЙ

The synthesis of Ni-, Co-spinels was performed using coprecipitation method with precursors Ni and Co nitrates under different conditions: using precipitators NaOH and NH4OH, at different pH values and different aging durations.Structural, adsorption and catalytic properties by of Ni-, Co-spinels were determined by X-ray diffraction, desiccator method of adsorption of benzene vapor and in redox reactionof hydrogen peroxide decomposition. The size of the crystallites of obtained spinels was calculated from X-ray diffraction patterns and all of the samples were nano-dispersed with developed surface area from 92 to 320 m2/g. Electrocatalytic investigations have shown thatthe most active spinels were obtained by precipitation with NH4OH at pH 9,0. The highest catalytic activity from all of the twelve spinels samples in hydrogen peroxide decomposition reaction had Ni-, Co-spinel, precipitated by NH4OH at pH 9,0 and aged for 3 days whichshown 100% decomposition degree of H2O2 after 45 seconds of contact.According to the results, the conditions of synthesis of Ni-, Co-spinels highly effect on their catalytic activity. Significantly lower catalytic activity of samples precipitated by NaOH, in our opinion, explained by the inhibitory effect of sodium, which is formed by the heat treatment of samples containing NaOH in trace amounts. Established that with decreasing pH values to neutral the activity of Ni-, Co-spinels increases and with increasing durationof aging of samples their catalytic activity is reduced due to the recrystallization process sediment, resulting in the number of active sites on the surface of Ni-, Co-spinels decreases.Досліджено структурно-адсорбційні та електрокаталітичні властивості нікол-кобальтових шпінелей, синтезованих методом співосадження Ni(NO3)2 та Co(NO3)2 за різних умов: рН, вид осаджувача (NaOH, NH4OH), тривалість старіння зразків шпінелей. Вперше встановлено функціональний вплив умов синтезу на структурно-адсорбційні та електрокаталітичні властивості одержаних зразків шпінелей

ELECTROCATALYSTS BASED ON Ni-, Co-SPINELS

The synthesis of Ni-, Co-spinels was performed using coprecipitation method with precursors Ni and Co nitrates under different conditions: using precipitators NaOH and NH4OH, at different pH values and different aging durations. Structural, adsorption and catalytic properties by of Ni-, Co-spinels were determined by X-ray diffraction, desiccator method of adsorption of benzene vapor and in redox reaction of hydrogen peroxide decomposition. The size of the crystallites of obtained spinels was calculated from X-ray diffraction patterns and all of the samples were nano-dispersed with developed surface area from 92 to 320 m2/g. Electrocatalytic investigations have shown that the most active spinels were obtained by precipitation with NH4OH at pH 9,0. The highest catalytic activity from all of the twelve spinels samples in hydrogen peroxide decomposition reaction had Ni-, Co-spinel, precipitated by NH4OH at pH 9,0 and aged for 3 days which shown 100% decomposition degree of H2O2 after 45 seconds of contact. According to the results, the conditions of synthesis of Ni-, Co-spinels highly effect on their catalytic activity. Significantly lower catalytic activity of samples precipitated by NaOH, in our opinion, explained by the inhibitory effect of sodium, which is formed by the heat treatment of samples containing NaOH in trace amounts. Established that with decreasing pH values to neutral the activity of Ni-, Co-spinels increases and with increasing duration of aging of samples their catalytic activity is reduced due to the recrystallization process sediment, resulting in the number of active sites on the surface of Ni-, Co-spinels decreases

Phase transformations in Pt/Fe bilayers during post annealing probed by resistometry

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Comparison of fatal or irreversible events with extended-duration betrixaban versus standard dose enoxaparin in acutely Ill medical patients: An APEX trial substudy

Background-Extended-duration betrixaban showed a significant reduction in venous thromboembolism in the APEX trial (Acute Medically Ill VTE Prevention With Extended Duration Betrixaban Study). Given the variable clinical impact of different efficacy and safety events, one approach to assess net clinical outcomes is to include only those events that are either fatal or cause irreversible harm. Methods and Results-This was a post hoc analysis of the APEX trial-a multicenter, double-blind, randomized controlled trial comparing extended-duration betrixaban versus standard-of-care enoxaparin. A composite of all fatal or irreversible safety (fatal bleeding or intracranial hemorrhage) and efficacy events (cardiopulmonary death, myocardial infarction, pulmonary embolism, and ischemic stroke) was evaluated in a time-to-first event analysis. In patients with positive D-dimer results, betrixaban reduced fatal or irreversible events at 35 to 42 days (4.80% versus 3.54%; hazard ratio, 0.73; absolute risk reduction, 1.26%; number needed to treat, 79 [P=0.033]) and at study end at 77 days (6.27% versus 4.36%; hazard ratio, 0.70; absolute risk reduction, 1.91%; number needed to treat, 52 [P=0.005]) versus enoxaparin. In all patients, betrixaban reduced fatal or irreversible events at 35 to 42 days (4.08% versus 2.90%; hazard ratio, 0.71; absolute risk reduction, 1.18%; number needed to treat, 86 [P=0.006]) and 77 days (5.17% versus 3.64%; hazard ratio, 0.70; absolute risk reduction, 1.53%; number needed to treat, 65 [P=0.002]). Conclusions-Among hospitalized medically ill patients, extended-duration betrixaban demonstrated an 48 30% reduction in fatal or irreversible ischemic or bleeding events compared with standard-duration enoxaparin. A total of 65 patients would require treatment with betrixaban to prevent 1 fatal or irreversible event versus enoxaparin