Nucleation and growth of sodium colloids in NaCl under irradiation: theory and experiment

A mechanism of radiation-induced emission of Schottky defects from extended defects proposed originally for metals has recently been applied to ionic crystals, where it is based on interactions of excitons with extended defects such as dislocations and colloids. Exciton trapping and decay at colloids may result in the emission of F centers and consequent shrinkage of the colloid. In the present paper, the radiation-induced emission of F centers is taken into account in the modeling of nucleation and growth of sodium colloids and chlorine bubbles in NaCl exposed to electron or gamma irradiation. The evolution of colloid and bubble number densities and volume fractions with increasing irradiation dose is modeled in the framework of a modified rate theory and compared with experimental data. Experimental values of the colloid volume fractions and number densities have been estimated on the basis of latent heat of melting of metallic Na obtained with combined differential scanning calorimetry experiments and atomic force microscopy investigations of metallic clusters.

Homogeneous bubble nucleation limit of lead

Liquid heavy metal coolant in a fast reactor, as well as in accelerator driven systems, is exhibited to large thermal and pressure shocks which can cause cavitation in the coolant. Here we calculated the work of the critical bubble formation in the lead coolant and the nucleation rate in terms of the generalized Gibbs approach. It is demonstrated that such approach provides a more adequate description of the process of bubble nucleation as compared with the classical nucleation theory.Теплоносители на основе жидких тяжелых металлов в быстрых реакторах и реакторах, управляемых ускорителем, подвержены значительным тепловым и гидравлическим ударам, что может приводить к кавитации теплоносителя. Рассчитаны работа образования критических пузырьков в свинцовом теплоносителе и скорость их зарождения в рамках обобщенного подхода Гиббса. Показано, что такой подход обеспечивает более адекватное описание процесса зарождения пузырьков по сравнению с классической теорией нуклеации.Теплоносії на основі рідких важких металів у швидких реакторах і реакторах, керованих прискорювачем, схильні до значних теплових і гідравлічних ударів, що може призводити до кавітації теплоносія. Розраховані робота утворення критичних пухирців в свинцевому теплоносії та швидкість їх зародження в рамках узагальненого підходу Гіббса. Показано, що такий підхід забезпечує більш адекватний опис процесу зародження пухирців в порівнянні з класичною теорією нуклеації

Homogeneous bubble nucleation limit of mercury under the normal working conditions of the planned European Spallation Source

In spallation neutron sources, liquid mercury is the subject of big thermal and pressure shocks, upon adsorbing the proton beam. These changes can cause unstable bubbles in the liquid, which can damage the structural material. While there are methods to deal with the pressure shock, the local temperature shock cannot be avoided. In our paper we calculated the work of the critical cluster formation (i.e. for mercury micro-bubbles) together with the rate of their formation (nucleation rate). It is shown that the homogeneous nucleation rates are very low even after adsorbing several proton pulses, therefore the probability of temperature induced homogeneous bubble nucleation is negligible.Comment: 22 Pages, 11 figures, one of them is colour, we plan to publish it in Eur. Phys. J.

Procedure of nanodimensional amorphous-microcrystalline structure formation by radiation in single crystal silicon

Quantum structures with enhanced electric conductivity have been formed in a single-crystal silicon matrix. An array of quantum filaments improves the collection of low-mobility charge carriers in the emitter structure of the c−Si(p, n) photoconverter. Experimental results of applying radiation technologies for creation of that sort of structures are presented.Сформованi в монокристалiчнiй матрицi кремнiю квантовi структури з пiдвищеною питомою електричною провiднiстю. Масив квантових ниток покращує виведення носiїв заряду з малою рухливiстю з об’єму емiтерної структури c−Si(p, n) -фотопреобразователя. Приведено експериментальнi результати застосування радiацiйних технологiй для створення таких структур.Сформированы в монокристаллической матрице кремния квантовые структуры с повышенной удельной электрической проводимостью. Массив квантовых нитей улучшает выведение носителей заряда с малой подвижностью из объема эмиттерной структуры c − Si(p, n)-фотопреобразователя. Приведены экспериментальные результаты применения радиационных технологий для создания таких структур

Stabilization of nano-sized structures in the volume of single-crystalline silicon for photoconverters

The paper considers the possibilities of stabilization of microstructures created in the latent tracks in single-crystalline silicon by multicharged ions from the nuclear fragments formed as a result of heavy element photofission in the process of hydrogenating. The presence of hydrogen in the amorphous silicon structures leads to the clustering of vacancies, intrinsic interstitial and impurity atoms. For quantum structures, passivated with hydrogen atoms, the annihilation process is slowed down. In the process of annealing the silicon structures the strong (Si − H)n-bonds prevent the defect annihilation and thus stimulate the processes of precipitation and clusterization. Hydrogen, filling the irradiation-broken bonds, neutralizes their electrical activity. Optimal conditions for stabilisation of such structures are determined: irradiation doses, methods of hydrogenation and dissociation of H2, annealing parameters.Розглядаються можливостi стабiлiзацiї мiкроструктур, створюваних в прихованих треках в монокристалiчному кремнiї багатозарядними iонами з осколкiв ядер важких елементiв при їх фотодiленнi, в процесi гiдрування. Присутнiсть водню в аморфних структурах кремнiю приводить до кластеризацiї вакансiй, власних мiжвузельних i домiшкових атомiв. Для квантових структур, пасивованих атомами водню, процес анiгiляцiї загальмований. При вiдпалi кремнiєвих структур мiцнi (Si − H)n-зв’язки перешкоджають анiгiляцiї дефектiв i тим самим стимулюють процеси преципiтацiї i кластеризацiї. Водень, заповнюючи обiрванi в результатi опромiнювання зв’язки, нейтралiзує їх електричну активнiсть. Визначено оптимальнi умови створення таких структур: дози опромiнювання, методи гiдрування та дисоцiацiї H2, режими вiдпалу.Рассматриваются возможности стабилизации микроструктур, создаваемых в скрытых треках в моно-кристаллическом кремнии многозарядными ионами из осколков ядер тяжелых элементов при их фото- делении, в процессе гидрирования. Присутствие водорода в аморфных структурах кремния приводит к кластеризации вакансий, собственных межузельных и примесных атомов. Для квантовых структур, пассивированных атомами водорода, процесс аннигиляции заторможен. При отжиге кремниевых структур прочные (Si − H)n-связи препятствуют аннигиляции дефектов и тем самым стимулируют процессы преципитации и кластеризации. Водород, заполняя оборванные в результате облучения связи, нейтрализует их электрическую активность. Определены оптимальные условия создания таких структур: дозы облучения, методы гидрирования и диссоциации H2, режимы отжига

Hot deformation behavior and processing maps of diamond/Cu composites

The hot deformation behaviors of 50 vol pct uncoated and Cr-coated diamond/Cu composites were investigated using hot isothermal compression tests under the temperature and strain rate ranging from 1073 K to 1273 K (800 C to 1000 C) and from 0.001 to 5 s1, respectively. Dynamic recrystallization was determined to be the primary restoration mechanism during deformation. The Cr3C2 coating enhanced the interfacial bonding and resulted in a larger flow stress for the Cr-coated diamond/Cu composites. Moreover, the enhanced interfacial affinity led to a higher activation energy for the Cr-coated diamond/Cu composites (238 kJ/mol) than for their uncoated counterparts (205 kJ/mol). The strain-rate-dependent constitutive equations of the diamond/Cu composites were derived based on the Arrhenius model, and a high correlation (R = 0.99) was observed between the calculated flow stresses and experimental data. With the help of processing maps, hot extrusions were realized at 1123 K/0.01 s1 and 1153 K/0.01 s1 (850 C/0.01 s1 and 880 C/0.01 s1) for the uncoated and coated diamond/Cu composites, respectively. The combination of interface optimization and hot extrusion led to increases of the density and thermal conductivity, thereby providing a promising route for the fabrication of diamond/Cu composites

Growth and dissolution of crystal nuclei in poly(l-lactic acid) (PLLA) in Tammann's development method

© 2020 Elsevier Ltd By fast scanning calorimetry (FSC), the influence of the transfer of nuclei from the nucleation stage at low temperature to the growth stage at higher temperature was systematically studied. Heating rates above 1000 K s−1 are sufficient to prevent growth of crystal nuclei at the transfer from 60 °C to 125 °C in Poly(L-lactic acid) (PLLA). The critical heating rate for preventing nuclei growth is about 1000 times higher than the critical heating rate to prevent crystal growth in a nucleated sample on heating. In a second experiment, the cluster size distribution after isothermal nucleation of PLLA at 60 °C for 1000 s was estimated. In the temperature interval from 125 °C to 145 °C, the density of critical nuclei decreases from the initial value ∼4 × 1024 m−3 to zero, as nuclei with R > 2 nm, the critical radius for 145 °C, were not formed at the nucleation temperature

Patient-reported (EORTC QLQ-CIPN20) versus physician-reported (CTCAE) quantification of oxaliplatin- and paclitaxel/carboplatin-induced peripheral neuropathy in NCCTG/Alliance clinical trials

PURPOSE: Clinical practice guidelines on chemotherapy-induced peripheral neuropathy (CIPN) use the NCI Common Terminology Criteria for Adverse Events (CTCAE), while recent clinical trials employ a potentially superior measure, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-CIPN twenty-item scale (QLQ-CIPN20), a patient-reported outcome (PRO). Practitioners and researchers lack guidance, regarding how QLQ-CIPN20 results relate to the traditional CTCAE during the serial assessment of patients undergoing chemotherapy. METHODS: Two large CIPN clinical trial datasets (538 patients) pairing QLQ-CIPN20 and CTCAE outcomes were analyzed using a multivariable linear mixed model with QLQ-CIPN20 score as the outcome variable, CTCAE grade as the main effect, and patient as random effect (accounting for internal correlation of serial measures). RESULTS: The association between QLQ-CIPN20 scores and CTCAE grades was strong (p < 0.0001), whereby patients with higher CTCAE grade had worse QLQ-CIPN20 scores. Some variation of QLQ-CIPN20 scores was observed based on drug, treatment, and cycle. While there was a marked difference in the mean QLQ-CIPN20 scores between CTCAE grades, the ranges of QLQ-CIPN20 scores within each CTCAE grade were large, leading to large overlap in CIPN20 scores across CTCAE grades. CONCLUSIONS: A strong positive association of QLQ-CIPN20 scores and CTCAE grade provides evidence of convergent validity as well as practical guidance, as to how to quantitatively interpret QLQ-CIPN20 scores at the study level in terms of the traditional CTCAE. The present results also highlight an important clinical caveat, specifically, that conversion of a specific QLQ-CIPN20 score to a specific CTCAE score may not be reliable at the level of an individual patient

The Outer Tracker Detector of the HERA-B Experiment. Part III: Operation and Performance.

In this paper we describe the operation and performance of the HERA-B Outer Tracker, a 112674 channel system of planar drift tube layers. The performance of the HERA-B Outer Tracker system fullfilled all requirements for stable and efficient operation in a hadronic environment, thus confirming the adequacy of the honeycomb drift tube technology and of the front-end readout system. The detector was stably operated with a gas gain of 30000 in an Ar/CF4/CO2 (65:30:5) gas mixture, yielding a good efficiency for triggering and track reconstruction, larger than 95 % for tracks with momenta above 5 GeV/c. The hit resolution of the drift cells was 300 to 320 micrometers and the relative momentum resolution can be described as: sigma(p)/p (in %) = (1.61 +- 0.02) + (0.0051 +- 0.0006) p. At the end of the HERA-B running no aging effects in the Outer Tracker cells were observed.Comment: 38 pages, 20 figures. v2: Added clarifications about trigger efficiency, momentum resolution and alignment precision. Corrected typos. Improved figure qualit