Navier–Stokes and direct Monte-Carlo simulations of the circumnuclear gas coma III. Spherical, inhomogeneous sources

We pursue our program of comparative simulations of the cometary gas coma by the two most advanced techniques available: (1) numerical solution of Navier–Stokes equations coupled to the Boltzman equation in the surface boundary layer, and (2) direct Monte-Carlo simulation. Here, we consider two different spherical but compositionally inhomogeneous nuclei, at three very different levels of gas production. The results show the same excellent agreement between the two methods in a domain adjacent to the surface as found precedingly, practically down to free-molecular conditions. A wealth of coma density patterns with non-intuitive structure is obtained. Some of these structures appear even under free-molecular effusion from the surface. The physical origin of all structures is discussed, and their evolution with changing gas production is studied. The computed comae are compared to those computed by various authors precedingly. Intercomparison of the present results demonstrates that differing inhomogeneity patterns may lead to similar structures in the gas coma. Comparison between these structures and those created by homogeneous, aspherical surfaces shows that it is not possible to guess from empirical rules which one of the two processes is responsible for the creation of a given structure. The implications for the interpretation of future high resolution images, or of future in situ mass spectrometric samplings of the near-nucleus gas coma are discussed

The prediction of the gas environment of the PHILAE probe during its 2014 descent to the nucleus of the comet 67P

International audienceOne of the objectives of the ESA ”ROSETTA” mission to the comet 67P was to insert, in August 2014, an orbiter probe around the so-called nucleus of the comet, and to deposit the ”PHILAE” lander at the surface of the nucleus in November 2014. The selection of the landing site and the definition of the release point and initial descent velocity vector were made in the period August to October 2014 on the basis of simulations of the descent trajectory. This requested an assessment of the gravitational and aerodynamic forces on PHILAE. We here describe the so-called RZC model developed to predict the gas environment of 67P in November 2014 and compute the aerodynamic force. We first outline the unusual diffculties resulting from (1) the complexity of the nucleus surface on all scales, (2) the absence of direct measurements of the gas flux at the surface itself, (3) the time-dependence of the gas production induced by the fast nucleus rotation, (4) the need to perform the whole program within less than three months. Then we outline the physical approach adopted to overcome these diffculties, and describe the RZC model which included three differing tools: (1) a set of gasdynamic/gaskinetic codes to compute the vacuum outflow of a rarefied gas mixture from a highly aspherical rotating solid source; (2) an heuristic approach to deal with the solid/gas initial boundary conditions, and (3) an iterative procedure to derive the gas production parameters on the nucleus surface from the observational data acquired from the orbiter probe. The satisfactory operation of the RZC code in the weeks preceding the November 2014 PHILAE descent is shown, and the forecasted aerodynamic force during the PHILAE descent is compared to the gravitational force

Многоцентровое ретроспективное исследование клинико-лабораторных предикторов и морфологических характеристик рака околощитовидной железы

Background: there are no specific markers of the parathyroid carcinoma (PC) therefore, the development of algorithms for identifying high-risk patients is an urgent task. Aims: to determine the clinical and laboratory predictors of PC and to identify the factors of a poor prognosis. Materials and methods: A multicenter retrospective study included 242 patients with primary hyperparathyroidism (PHPT) who were divided into groups: 162 with adenomas, 30 with аtypical adenomas (АА) and 50 patients with PC. Data collection and analysis was carried out from 2017 to 2020. The primary goal assessment of the possibility of PС using preoperative laboratory and instrumental data. The group of PC was divided into subgroups: the patients in recurrences (n=17) and remission (n=33). The level of the total calcium, albumin, alkaline phosphatase (ALP), ionized calcium (Ca ++) in the blood were determined on the automatic biochemical analyzer; the level of parathyroid hormone (PTH) by electrochemoluminescent analyzer. The size of the PG determined by the ellipse formula: V (cm3) = (A B C) 0.49. Statistical analysis was performed with Statistica 13 and SPSS software packages. For multiple comparisons, the Bonferroni correction was applied. Results: the group of patients with increased risk of PC include persons with increased level of PTH 443 pg/ml, Ca++ 1.5 mmol/l, total calcium 3.2 mmol/l, ALP 176 IU/L, V of tumors 2.6 cm3, largest size 22.5 mm (p 0,001). Heterogeneous structure is more typical to PC compared to the АА (p = 0,004 and р = 0,011), the same applies to indefinite contour (р = 0,001 и р = 0,011). Pathological mitosis is a prognostically unfavorable factor of recurrence of PC (р=0,007). Conclusions: the patients with PC and AA are characterized with more aggressive course of PHPT compared to the group of adenomas.Обоснование: в связи с отсутствием специфичных маркеров рака околощитовидной железы (ОЩЖ) разработка алгоритмов выделения групп повышенного риска представляется актуальной задачей. Цель исследования: определить клинико-лабораторные предикторы злокачественных новообразований ОЩЖ и выделить факторы неблагоприятного прогноза. Материалы и методы: проведено многоцентровое ретроспективное исследование с включением 242 пациентов с ПГПТ, разделенных на группы карцином (n=50), атипических аденом (АА) (n=30) и аденом (n=162) ОЩЖ. Сбор и анализ данных проводился с 2017 по 2020 гг. Первичная конечная точка оценка возможности наличия рака ОЩЖ в послеоперационном гистологическом материале с помощью предоперационных лабораторных и инструментальных данных. Дополнительно выделены подгруппы больных с рецидивом (n=17) и с ремиссией заболевания (n=33). Общий кальций, альбумин, щелочная фосфатаза (ЩФ), ионизированный кальций (Са++) в крови определяли на автоматическом биохимическом анализаторе. Анализ крови с определением интактного паратгормона (иПТГ) выполнен на электрохемилюминесцентном анализаторе. Объем ОЩЖ по данным ультразвукового исследования (УЗИ) рассчитывался по формуле эллипса: V(см3) = (A B C) 0,49. Статистический анализ проводили с использованием пакетов программ STATISTICA 13 и SPSS. Для множественных сравнений применялась поправка Бонферрони. Результаты: в группу повышенного риска наличия рака ОЩЖ на предоперационном этапе следует относить лиц с ПТГ более 443,55 пг/мл, Са++ более 1,5 ммоль/л; альбумин-скорректированным кальцием более 3,2 ммоль/л, ЩФ более 176 ед/л, размером новообразования более 22,5 мм и объемом более 2,6 см3 (р 0,001). По данным УЗИ для карцином и АА по сравнению с группой аденом чаще характерна неоднородная структура (p = 0,004 и р = 0,011 соответственно) и нечеткий контур (р = 0,001 и р = 0,011 соответственно). Патологические митозы - прогностически неблагоприятный фактор в отношении рецидива рака ОЩЖ (р=0,007). Заключение: для пациентов с карциномой и АА ОЩЖ характерно более агрессивное течение ПГПТ по сравнению с группой аденом

Measurements of the Total Reaction Cross Sections for 6,8^{6,8}He and 8,9^{8,9}Li Nuclei with Energies of (25-45)A Mev on nat^{nat}Al, nat^{nat}Ta and nat^{nat}Pb

International audienceThe total nuclear reaction cross sections (σR) measurements have long been of interest since they tell us about the radii and transparency of these nuclei and give clues to understanding of their structure. For studies of unstable nuclei, in particular the physical properties of halo nuclei and the neutron skin thickness, it is valuable to know not only the root-mean-square radii (rms) but it is important to know the details of nucleusnucleus potentials. Our goal was to study total reaction cross sections (σR) by a direct measurement technique (the so-called beam attenuation or transmission method) which allows to extract model independent information. The interaction radii for 6He, 8,9Li were extracted, which are in agreement with the previous measurement at the similar energies (about a few tens of AMeV) Our results show a tendency of increasing radii as function of mass of the secondary targets