Ablation in meteors

A comparison of theoretical calculations with the results of radar meteor observations shows that the theory of radio meteors satisfactorily represents observational data. Radar meteor observations are incompatible with the idea of low density for small meteoroids in the ablation process. The main mechanism of ablation is evaporation. During intensive evaporation, small meteoroids have a density close to that of usual stone meteorites

On the mechanism behind the fragmentation of tiny meteor bodies in the atmosphere

Fragmentation mechanism of small meteors during atmospheric entr

Meteoric phenomena in the earth's atmosphere. Investigations of meteors, no. 2

Meteoritic radiance and ionization observations in earth atmospher

The role of fragmentation in interaction of meteoroids with the Earth's atmosphere

As a rule, when analyzing the mechanism of quasi continuous fragmentation (QCF) it is assumed that fragments separated from the parent meteoroid (PM) are of equal initial mass. In reality, this may not be so. A major difficulty is the lack of observational data on the function of the fragment initial mass distribution and so one must resort to theoretical modeling. A discrete distribution is considered which excluded to a certain extent some mathematical difficulties. The calculation results are given and discussed

Mass Loss Due to Sputtering and Thermal Processes in Meteoroid Ablation

Conventional meteoroid theory assumes that the dominant mode of ablation is by evaporation following intense heating during atmospheric flight. In this paper we consider the question of whether sputtering may provide an alternative disintegration process of some importance.For meteoroids in the mass range from 10^-3 to 10^-13 kg and covering a meteor velocity range from 11 to 71 km/s, we numerically modeled both thermal ablation and sputtering ablation during atmospheric flight. We considered three meteoroid models believed to be representative of asteroidal (3300 kg m^-3 mass density), cometary (1000 kg m^-3) and porous cometary (300 kg m^-3) meteoroid structures. Atmospheric profiles which considered the molecular compositions at different heights were used in the sputtering calculations. We find that while in many cases (particularly at low velocities and for relatively large meteoroid masses) sputtering contributes only a small amount of mass loss during atmospheric flight, in some cases sputtering is very important. For example, a 10^-10 kg porous meteoroid at 40 km/s will lose nearly 51% of its mass by sputtering, while a 10^-13 kg asteroidal meteoroid at 60 km/s will lose nearly 83% of its mass by sputtering. We argue that sputtering may explain the light production observed at very great heights in some Leonid meteors. The impact of this work will be most dramatic for very small meteoroids such as those observed with large aperture radars.Comment: in pdf form, 48 pgs incl figures and table

DESIGN OF AN INFORMATION SYSTEM FOR MONITORING AND ANALYZING THE RADIATION SITUATION AT THE PHRO OF THE SVERDLOVSK BRANCH OF THE UTO BRANCH OF THE FED

A comparison of the available software and justification of the choice of structure and software for the rapid assessment of the radiation situation at PRO of the Sverdlovsk branch of the branch "Urals territorial district" of the FSUE RosRAO based on the analysis of mon-itoring results

Strong E region ionization caused by the 1767 trail during the 2002 Leonids

Intensive E region ionization extending up to 140 km altitude and lasting for several hours was observed with the European Incoherent Scatter (EISCAT) UHF radar during the 2002 Leonids meteor shower maximum. The level of global geomagnetic disturbance as well as the local geomagnetic and auroral activity in northern Scandinavia were low during the event. Thus, the ionization cannot be explained by intensive precipitation. The layer was 30–40 km thick, so it cannot be classified as a sporadic E layer which are typically just a few kilometers wide. Incoherent scatter radars have not to date reported any notable meteor shower-related increases in the average background ionization. The 2002 Leonids storm flux, however, was so high that it might have been able to induce such an event. The Chemical Ablation Model is used to estimate deposition rates of individual meteors. The resulting electron production, arising from hyperthermal collisions of ablated atoms with atmospheric molecules, is related to the predicted Leonid flux values and observed ionization on 19 November 2002. The EISCAT Svalbard Radar (ESR) located at some 1000 km north of the UHF site did not observe any excess ionization during the same period. The high-latitude electrodynamic conditions recorded by the SuperDARN radar network show that the ESR was within a strongly drifting convection cell continuously fed by fresh plasma while the UHF radar was outside the polar convection region maintaining the ionization

Эффективность и безопасность винфлунина во 2-й линии терапии у больных распространенным переходно-клеточным раком мочевых путей в клинической практике

Objective: to investigate the safety of vinflunine, the rate and duration of its treatment response, progression-free and overall survival rates in patients receiving this drug in routine clinical practice for first-line chemotherapy (CT) – resistant disseminated transitional cell carcinoma of the urinary tract.Materials and methods. This retrospective observational multicenter study included data on 25 patients with verified disseminated transitional cell carcinoma of the urinary tract who took vinflunine for tumor progression after first-line CT performed in 11 Russian clinical centers in 23 March 2013 to 26 June 2016. The median age of the patients was 60 (44‒81) years. Their baseline somatic status was rated as ECOG 0 in 1 (4.0 %) patient, ECOG 1 in 13 (52.0 %) patients, EGOG 2 in 9 (36.0 %), and ECOG 3 in 2 (8.0 %). The most common sites of tumor foci were bones (n = 14, 56.0 %), lymph nodes of different groups (n = 14; 56.0 %), and lung (n = 9; 36.0 %).Results. Adverse reactions were recorded in 24 (96.0 %) cases. The most common types of toxicity were asthenia (n = 19; 76.0 %), anemia (n = 18; 72.0 %), neutropenia (n = 13; 52 %), and nausea (n = 12; 48.0 %). Most adverse events were grades I–II and well controlled. There were no deaths due to adverse events. The best treatment response was regarded as partial in 6 (24.0 %) patients; stabilization and progression were observed in 10 (40.0 %) and 9 (36.0 %) patients, respectively. The median duration of partial response was 5.1 (95 % confidence interval (CI), 0.6–15.0) months; that of stabilization was 3.4 (95 % CI, 1.2–6.3) months. In all the 25 cases, the median progression-free and overall survival rates were 3.7 (95 % CI, 2.1‒5.3) and 6.5 (95 % CI, 5.2‒7.8) months, respectively. The somatic status was a predictor of overall survival (p < 0.0001).Conclusion. The efficacy and safety of vinflunine in second-line therapy for first-line CT-resistant disseminated transitional cell carcinoma of the urinary tract in unselected patients agree with those previously observed in Phase III randomized trial.Цель исследования – изучение безопасности, частоты и длительности ответов, беспрогрессивной и общей выживаемости у больных, получавших винфлунин в рутинной клинической практике по поводу распространенного переходно-клеточного рака мочевых путей, резистентного к 1-й линии химиотерапии (ХТ).Материалы и методы. В ретроспективное наблюдательное многоцентровое исследование включены данные 25 больных верифицированным распространенным переходно-клеточным раком мочевых путей, получавших винфлунин по поводу прогрессии опухоли после проведения ХТ 1-й линии с 23.03.2013 по 26.06.2016 в 11 клинических центрах России. Медиана возраста – 60 (44–81) лет. Исходный соматический статус по шкале ECOG был расценен как 0 у 1 (4,0 %), 1 – у 13 (52,0 %), 2 – у 9 (36,0 %), 3 – у 2 (8,0 %) больных. Наиболее распространенными локализациями опухолевых очагов были кости (n =14; 56,0 %), лимфатические узлы различных групп (n =14; 56,0 %) и легкие (n = 9; 36,0 %).Результаты. Нежелательные явления были зарегистрированы в 24 (96,0 %) случаях. Наиболее распространенными видами токсичности являлись астения (n =19; 76,0 %), анемия (n =18; 72,0 %), нейтропения (n =13; 52,0 %), тошнота (n = 12; 48,0 %). Нежелательные явления в большинстве наблюдений имели I–II степени тяжести и хорошо контролировались. Смертности, обусловленной нежелательными явлениями, не зарегистрировано. Наилучший ответ на лечение расценен как частичный у 6 (24,0 %), стабилизация – у 10 (40,0 %), прогрессирование – у 9 (36,0 %) больных. Медиана длительности частичного ответа составила 5,1 (95 % доверительный интервал (ДИ) 0,6–15,0) мес, стабилизации – 3,4 (95 % ДИ 1,2–6,3) мес. Медиана беспрогрессивной и общей выживаемости всех 25 больных составила 3,7 (95 % ДИ 2,1–5,3) и 6,5 (95 % ДИ 5,2–7,8) мес соответствен- но. Соматический статус являлся фактором прогноза общей выживаемости (p < 0,0001).Заключение. Эффективность и безопасность применения винфлунина во 2-й линии терапии распространенного переходно-клеточного рака мочевых путей, резистентного к 1-й линии ХТ, у неотобранных больных соответствуют ранее полученным результатам рандомизированного исследования III фазы.