Testing excitation models of rapidly oscillating Ap stars with interferometry

Rapidly oscillating Ap stars are unique objects in the potential they offer to study the interplay between a number of important physical phenomena, in particular, pulsations, magnetic fields, diffusion, and convection. Nevertheless, the simple understanding of how the observed pulsations are excited in these stars is still in progress. In this work we perform a test to what is possibly the most widely accepted excitation theory for this class of stellar pulsators. The test is based on the study of a subset of members of this class for which stringent data on the fundamental parameters are available thanks to interferometry. For three out of the four stars considered in this study, we find that linear, non-adiabatic models with envelope convection suppressed around the magnetic poles can reproduce well the frequency region where oscillations are observed. For the fourth star in our sample no agreement is found, indicating that a new excitation mechanism must be considered. For the three stars whose observed frequencies can be explained by the excitation models under discussion, we derive the minimum angular extent of the region where convection must be suppressed. Finally, we find that the frequency regions where modes are expected to be excited in these models is very sensitive to the stellar radius. This opens the interesting possibility of determining this quantity and related ones, such as the effective temperature or luminosity, from comparison between model predictions and observations, in other targets for which these parameters are not well determined.Comment: Accepted for publication in the MNRA

The prior liver cancer associated with chronic viral liver diseases

In issue the experience of treatment in 67 patients with the prior liver cancer is presented. The hepatocellular cancer was diagnosed in 62 cases (92,5%), cholangiocellular cancer in the rest 5 patients. Viral hepatitis B was evaluated in 28 cases, viral hepatitis C in 19. Surgical treatment was performed in 34, in 22 resection of liver was carried out in cases with chronical viral hepatitis and cirrhosis. 16 (47,1%) patients had complications in postoperative period, hepatocellular insufficiency developed more often in patients with viral lesions. Postoperative mortality was in 17,6%. The 5-year survival was 47±7,2%. 49,3% patients got regional chemotherapy – chemoembolization or chemoinfusion in hepatic artery. Mediana was 19,4 and 10,2 months, consequently. So, patients with viral hepatitis and cirrhosis have more complications in postoperative period after liver resections. Surgical approach needs very careful evaluation of cancer dissemination and liver dysfunction in this category of patients

Imputation of missing gas permeability data for polymer membranes using machine learning

Polymer-based membranes have the potential for use in energy efficient gas separations. The successful exploitation of new materials requires accurate knowledge of the transport properties of all gases of interest. Open-source databases of gas permeabilities are of significant potential benefit to the research community. The Membrane Society of Australasia (https://membrane-australasia.org/) hosts a database for experimentally measured and reported polymer gas permeabilities. However, the database is incomplete, limiting its potential use as a research tool. Here, missing values in the database were imputed (filled) using machine learning (ML). The ML model was validated against gas permeability measurements that were not recorded in the database. Through imputing the missing data, it is possible to re-analyse historical polymers and look for potential “missed” candidates with promising gas selectivity. In addition, for systems with limited experimental data, ML using sparse features was performed, and we suggest that once the permeability of CO2 and/or O2 for a polymer has been measured, most other gas permeabilities and selectivities, including those for CO2/CH4 and CO2/N2, can be quantitatively estimated. This early insight into the gas permeability of a new system can be used at an initial stage of experimental measurements to rapidly identify polymer membranes worth further investigation

Discovery of the longest-period rapidly oscillating Ap star HD177765

We present the discovery of a long-period, rapidly oscillating Ap star, HD177765. Using high-resolution time-series observations obtained with UVES at the ESO VLT telescope, we found radial velocity variations with amplitudes 7-150 m/s and a period of 23.6 min, exceeding that of any previously known roAp star. The largest pulsation amplitudes are observed for Eu III, Ce III and for the narrow core of Halpha. We derived the atmospheric parameters and chemical composition of HD177765, showing this star to be similar to other long-period roAp stars. Comparison with theoretical pulsational models indicates an advanced evolutionary state for HD177765. Abundance analyses of this and other roAp stars suggest a systematic variation with age of the rare-earth line anomalies seen in cool Ap stars.Comment: 5 pages, 2 figures; accepted for publication in MNRA

Mathematical modelling of thickness and temperature dependent physical aging to O2/N2 gas separation in polymeric membranes

Polymeric membranes are glassy materials at non-equilibrium state and inherently undergo a spontaneous evolution towards equilibrium known as physical aging. Volume relaxation characteristic during the course of aging is governed by the surrounding temperature in which the polymeric material is aged. Although there are studies to understand how polymeric materials evolve over time towards equilibrium at different operating temperatures, the theories have been developed merely in response to experimental observations and phenomenological theory at bulk glassy state without the implementation of sample size effects. Limited work has been done to characterize the physical aging process to thin polymeric films using reasonable physical parameters and mathematical models with incorporation of thermodynamics and film thickness consideration. The current work applies the Tait equation of states and thickness dependent glass transition temperature, integrated within a simple linear correlation, to model the temperature and thickness dependent physical aging. The mathematical model has been validated with experimental aging data, whereby a small deviation is observed that has been explained by intuitive reasoning pertaining to the thermodynamic parameters. The mathematical model has been further employed to study the gas transport properties of O(2) and N(2), which is anticipated to be applied in oxygen enriched combustion for generation of cleaner and higher efficiency fuel in future work

ПЕРВИЧНЫЙ РАК ПЕЧЕНИ, АССОЦИИРОВАННЫЙ С ХРОНИЧЕСКИМИ ВИРУСНЫМИ ЗАБОЛЕВАНИЯМИ ПЕЧЕНИ

In issue the experience of treatment in 67 patients with the prior liver cancer is presented. The hepatocellular cancer was diagnosed in 62 cases (92,5%), cholangiocellular cancer in the rest 5 patients. Viral hepatitis B was evaluated in 28 cases, viral hepatitis C in 19. Surgical treatment was performed in 34, in 22 resection of liver was carried out in cases with chronical viral hepatitis and cirrhosis. 16 (47,1%) patients had complications in postoperative period, hepatocellular insufficiency developed more often in patients with viral lesions. Postoperative mortality was in 17,6%. The 5-year survival was 47±7,2%. 49,3% patients got regional chemotherapy – chemoembolization or chemoinfusion in hepatic artery. Mediana was 19,4 and 10,2 months, consequently. So, patients with viral hepatitis and cirrhosis have more complications in postoperative period after liver resections. Surgical approach needs very careful evaluation of cancer dissemination and liver dysfunction in this category of patients.Представлен опыт лечения 67 больных первичным раком печени. Гепатоцеллюлярный рак диагностирован у 62 (92,5%) пациентов, холангиоцеллюлярный рак у 5. Вирусный гепатит В имел место у 28 больных, вирусный гепатит С – 19. Оперативное лечение злокачественного новообразования печени предпринято у 34 пациентов, из них в 22 наблюдениях резекция органа выполнялась на фоне сопутствующего хронического гепатита или цирроза печени. Осложненный послеоперационный период имел место у 16 (47,1%) больных. У пациентов с хроническим вирусным заболеванием печени гораздо чаще в послеоперационном периоде встречалось прогрессирование гепатоцеллюлярной недостаточности. Послеоперационная летальность составила 17,6%. Пятилетняя выживаемость составила 47,±7,2%. У 49,3% с нерезектабельным гепатоцеллюлярным раком выполнена лечебная регионарная химиотерапия – масляная химиоэмболизация или химиоинфузия печеночной артерии. Медиана выживаемости составила 19,4 и 10,2 месяцев соответственно. Выполнение резекции печени у пациентов на фоне сопутствующего хронического вирусного заболевания сопровождается более тяжелым послеоперационным течением. Хирургическая тактика у больных первичным раком печени и хроническим гепатитом или циррозом печени требует детальной оценки распространенности опухолевого поражения и выраженности гепатоцеллюлярной дисфункции

Карциносаркома предстательной железы: клинический случай

Carcinosarcoma is an exceedingly rare and highly aggressive malignant tumor. Some patients with carcinosarcoma have normal levels of prostate specific antigen; therefore, digital rectal examination is the only method of early diagnosis in them. In this article, we report a case of prostate carcinosarcoma and describe its diagnosis and treatment.Карциносаркома — крайне редкая высокоагрессивная злокачественная опухоль. У части пациентов с карциносаркомой уровень простатического специфического антигена может находиться в пределах нормальных значений, что делает пальцевое ректальное исследование единственным методом ранней диагностики этой патологии. В настоящей статье представлен клинический случай диагностики и лечения карциносаркомы предстательной железы

Fundamental properties of a selected sample of Ap stars: Inferences from interferometric and asteroseismic constraints

Magnetic fields influence the formation and evolution of stars and impact the observed stellar properties. Ap stars (magnetic A-type stars) are a prime example of this. Access to precise and accurate determinations of their stellar fundamental properties, such as masses and ages, is crucial to understand the origin and evolution of fossil magnetic fields. We propose using the radii and luminosities determined from interferometric measurements, in addition to seismic constraints when available, to infer fundamental properties of 14 Ap stars préviously characterised. We used a grid-based modelling approach, employing stellar models computed with the \textsc{cestam} stellar evolution code, and the parameter search performed with the \textsc{aims} optimisation method. The stellar model grid was built using a wide range of initial helium abundances and metallicities in order to avoid any bias originating from the initial chemical composition. The large frequency separations ( Δν ) of HR\,1217 (HD\,24712) and α~Cir (HD\,128898), two rapidly oscillating Ap stars of the sample, were used as seismic constraints. We inferred the fundamental properties of the 14 stars in the sample. The overall results are consistent within 1σ with previous studies, however, the stellar masses inferred in this study are higher. This trend likely originates from the broader range of chemical compositions considered in this work. We show that the use of Δν in the modelling significantly improves our inferences, allowing us to set reasonable constraints on the initial metallicity which is, otherwise, unconstrained. This gives an indication of the efficiency of atomic diffusion in the atmospheres of roAp stars and opens the possibility of characterising the transport of chemical elements in their interiors