Deactivation of Li by vacancy clusters in ion-implanted and flash-annealed ZnO

Li is present in hydrothermally grown ZnO at high concentrations and is known to compensate both n- and p-type doping due to its amphoteric nature. However, Li can be manipulated by annealing and ion implantation in ZnO. Fast, 20 ms flash anneals in the 900–1400°C range result in vacancy cluster formation and, simultaneously, a low-resistive layer in the implanted part of the He- and Li-implanted ZnO. The vacancy clusters, involving 3-4 Zn vacancies, trap and deactivate Li, leaving other in-grown donors to determine the electrical properties. Such clusters are not present in sufficient concentrations after longer (1h) anneals because of a relatively low dissociation barrier ∼2.6 ± 0.3 eV, so ZnO remains compensated until Li diffuses out after 1250°C anneals.Peer reviewe

Identification of substitutional Li in n-type ZnO and its role as an acceptor

Monocrystalline n-type zinc oxide (ZnO) samples prepared by different techniques and containing various amounts of lithium (Li) have been studied by positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry. A distinct PAS signature of negatively charged Li atoms occupying a Zn-site (Li−Zn), so-called substitutional Li, is identified and thus enables a quantitative determination of the content of LiZn. In hydrothermally grown samples with a total Li concentration of ~2×10 exp 17 cm exp −3,LiZn is found to prevail strongly, with only minor influence, by other possible configurations of Li. Also in melt grown samples doped with Li to a total concentration as high as 1.5×10 exp 19 cm exp −3, a considerable fraction of the Li atoms (at least 20%) is shown to reside on the Zn-site, but despite the corresponding absolute acceptor concentration of ⩾(2–3)×10 exp 18 cm exp −3, the samples did not exhibit any detectable p-type conductivity. The presence of LiZn is demonstrated to account for the systematic difference in positron lifetime of 10–15 ps between Li-rich and Li-lean ZnO materials as found in the literature, but further work is needed to fully elucidate the role of residual hydrogen impurities and intrinsic open volume defects.Peer reviewe

Minority and mode conversion heating in (3He)-H JET plasma

Radio frequency (RF) heating experiments have recently been conducted in JET (He-3)-H plasmas. This type of plasmas will be used in ITER's non-activated operation phase. Whereas a companion paper in this same PPCF issue will discuss the RF heating scenario's at half the nominal magnetic field, this paper documents the heating performance in (He-3)-H plasmas at full field, with fundamental cyclotron heating of He-3 as the only possible ion heating scheme in view of the foreseen ITER antenna frequency bandwidth. Dominant electron heating with global heating efficiencies between 30% and 70% depending on the He-3 concentration were observed and mode conversion (MC) heating proved to be as efficient as He-3 minority heating. The unwanted presence of both He-4 and D in the discharges gave rise to 2 MC layers rather than a single one. This together with the fact that the location of the high-field side fast wave (FW) cutoff is a sensitive function of the parallel wave number and that one of the locations of the wave confluences critically depends on the He-3 concentration made the interpretation of the results, although more complex, very interesting: three regimes could be distinguished as a function of X[He-3]: (i) a regime at low concentration (X[He-3] < 1.8%) at which ion cyclotron resonance frequency (ICRF) heating is efficient, (ii) a regime at intermediate concentrations (1.8 < X[He-3] < 5%) in which the RF performance is degrading and ultimately becoming very poor, and finally (iii) a good heating regime at He-3 concentrations beyond 6%. In this latter regime, the heating efficiency did not critically depend on the actual concentration while at lower concentrations (X[He-3] < 4%) a bigger excursion in heating efficiency is observed and the estimates differ somewhat from shot to shot, also depending on whether local or global signals are chosen for the analysis. The different dynamics at the various concentrations can be traced back to the presence of 2 MC layers and their associated FW cutoffs residing inside the plasma at low He-3 concentration. One of these layers is approaching and crossing the low-field side plasma edge when 1.8 < X[He-3] < 5%. Adopting a minimization procedure to correlate the MC positions with the plasma composition reveals that the different behaviors observed are due to contamination of the plasma. Wave modeling not only supports this interpretation but also shows that moderate concentrations of D-like species significantly alter the overall wave behavior in He-3-H plasmas. Whereas numerical modeling yields quantitative information on the heating efficiency, analytical work gives a good description of the dominant underlying wave interaction physics

Лечение стриктур билиодигестивного анастомоза после трансплантации левого латерального сектора печени

Many studies have shown that biliary complications after transplantation of the left lateral segment (LLS) of the liver reduce graft and recipient survival. Thus, timely correction of biliary complications, and strictures in particular, improves long-term outcomes in transplantation. Objective: to analyze our own experience in correcting biliary strictures in LLS graft transplantation. Materials and methods. From February 2014 to April 2020, 425 LLS grafts were transplanted in children. 19 (4.5%) patients were diagnosed with biliary strictures at different times after transplantation (from 0.2 to 97 months). Results. Biliary strictures were more often formed a year after transplantation (17.8 ± 23.9 months). In 14 out of the 19 patients, internal-external biliary drainage was successfully performed with phased replacement of the catheter with one that was larger in diameter (from 8.5 Fr to 14 Fr). The catheters were removed in 8 patients after completion of the treatment cycle. Restenosis was not observed during follow-up (13 ± 8.7 months) after the internal-external biliary drainage catheter had been removed. In 5 cases, antegrade passage of a guide wire through the stricture was unsuccessful. As a result, biliary reconstruction was performed in 4 (21.1%) patients and retransplantation was required in 1 (5.3%) patient. Conclusion. An antegrade minimally invasive approach can successfully eliminate biliary strictures in most children after liver LLS graft transplantation. The proposed technique is effective and safe.Введение. Билиарные осложнения после трансплантации левого латерального сектора (ЛЛС) печени, согласно многим исследованиям, негативно влияют на выживаемость трансплантатов и реципиентов. Таким образом, своевременная коррекция билиарных осложнений, и в частности стриктур, позволяет улучшить отдаленные результаты трансплантации. Цель. Проанализировать собственный опыт лечения билиарных стриктур при трансплантации ЛЛС печени. Материалы и методы. С февраля 2014-го по апрель 2020 года проведено 425 трансплантаций ЛЛС печени детям. У 19 (4,5%) пациентов диагностированы стриктуры желчных протоков в разные сроки после трансплантации (от 0,2 до 97 мес.). Результаты. Билиарные стриктуры чаще формировались через год после трансплантации (17,8 ± 23,9 мес.). У 14 из 19 было успешно проведено наружно-внутреннее дренирование желчных протоков с этапной заменой дренажа на больший диаметр (с 8,5 до 14 Fr). Дренажи удалены у 8 пациентов после завершения цикла лечения. За период наблюдения (13 ± 8,7 мес.) после удаления дренажа рестенозов не отмечалось. В 5 случаях антеградное прохождение стриктуры не удалось, в связи с чем в 4 (21,1%) случаях выполнена билиарная реконструкция и в 1 (5,3%) случае потребовалась ретрансплантация. Выводы. Антеградный мини-инвазивный подход позволяет успешно устранить билиарные стриктуры у большинства детей после трансплантации ЛЛС печени. Предложенный алгоритм лечения является эффективным и безопасным

Hydrogen minority ion cyclotron resonance heating in presence of the iter-like wall in jet

The most recent JET campaign has focused on characterizing operation with the "ITER-like" wall. One of the questions that needed to be answered is whether the auxiliary heating methods do not lead to unacceptably high levels of impurity influx, preventing fusion-relevant operation. In view of its high single pass absorption, hydrogen minority fundamental cyclotron heating in a deuterium plasma was chosen as the reference wave heating scheme in the ion cyclotron domain of frequencies. The present paper discusses the plasma behavior as a function of the minority concentration X[H] in L-mode with up to 4MW of RF power. It was found that the tungsten concentration decreases by a factor of 4 when the minority concentration is increased from X[H] ≈ 5% to X[H] % 20% and that it remains at a similar level when X[H] is further increased to 30%; a monotonic decrease in Beryllium emission is simultaneously observed. The radiated power drops by a factor of 2 and reaches a minimum at X[H] ≈ 20%. It is discussed that poor single pass absorption at too high minority concentrations ultimately tailors the avoidance of the RF induced impurity influx. The edge density being different for different minority concentrations, it is argued that the impact ICRH has on the fate of heavy ions is not only a result of core (wave and transport) physics but also of edge dynamics and fueling

Answers and Solutions

Answers and solutions to the puzzles in this issue

Исследование качества жизни родственных доноров фрагмента печени в отдаленном послеоперационном периоде

Introduction. Quality of life (QoL) is a new promising area of clinical medicine that provides the opportunity to assess the state of health of the patient and to have a notion of the surgery effects based on the parameters which are lying at the intersection of scientific approach of the surgeons and subjective point of view of the patient.Materials and methods. The study included 52 living-related liver fragment donors operated between 2009 and 2014. Donors were surveyed after 2–5 years from the surgery. Comparison group was formed by healthy volunteers, students of the Medical University. The Russian version of the non-specific SF-36 questionnaire was used to assess QoL.Results. Donors in the postoperative period have demonstrated a high level of physical parameter (57.65 ± 3.8). Parameter of psychological health in the postoperative period was (52.01 ± 5.2). These figures are comparable with the results in the comparison group (p &gt; 0.05). All donors have returned to normal life.Conclusions. Overall results of this study were similar to those of the foreign colleagues which confirm the high safety of liver resection surgery and the efficacy of SF-36 questionnaire in the assessment of quality of life of the living-related liver fragment donors.Введение. Оценка качества жизни (КЖ) – новое перспективное направление клинической медицины, предоставляющее возможность оценить состояние здоровья пациента и составить представление о последствиях оперативного вмешательства по параметрам, которые находятся на стыке научного подхода хирургов и субъективной точки зрения пациента.Материалы и методы. В исследование были включены 52 родственных донора фрагмента печени, оперированных в период с 2009-го по 2014 год. Доноры опрашивались спустя 2–5 лет после оперативного вмешательства. В качестве группы сравнения выступили здоровые добровольцы – студенты медицинского университета. Для оценки качества жизни применялась русскоязычная версия неспецифического опросника SF-36.Результаты. Доноры в послеоперационном периоде продемонстрировали высокий уровень физического параметра (57,65 ± 3,8). Психологический параметр здоровья в послеоперационном периоде составил 52,01 ± 5,2. Данные показатели сопоставимы с результатами в группе сравнения (р &gt; 0,05). Все доноры вернулись к нормальной жизнедеятельности.Выводы. Результаты настоящего исследования схожи с данными зарубежных коллег, что подтверждает безопасность операции эксплантации фрагментов печени и эффективность опросника SF-36 в оценке качества жизни родственных доноров фрагмента печени