We review the current status of studies on accretion and protoplanetary disks of young stars with large-scale magnetic fields. Observational data on magnetic fields of the disks are compiled and analysed. Modern analytical and numerical MHD models of protoplanetary disks are discussed. The mechanisms of angular momentum transport via turbulence, magnetic tensions and outflows are outlined. We consider the influence of Ohmic dissipation, magnetic ambipolar diffusion, magnetic buoyancy, and the Hall effect on the evolution of the magnetic flux in disks. Modern MHD models of accretion disks show that the magnetic field can influence the structure of protoplanetary disks. We argue that the available observational data on the magnetic fields in protoplanetary disks can be interpreted within the framework of fossil magnetic field theory. We summarize the problems of the modern theory of accretion and protoplanetary disks with magnetic fields and also outline the prospects for further research.
In the era of space exploration, coronal holes on the sun play a significant role due to their impact on satellites and aircraft through their open magnetic fields and increased solar wind emissions. This study employs computer vision techniques to detect coronal hole regions and estimate their sizes using imagery from the Solar Dynamics Observatory (SDO). Additionally, we utilize hybrid time series prediction model, specifically combination of Long Short-Term Memory (LSTM) networks and ARIMA, to analyze trends in the area of coronal holes and predict their areas across various solar regions over a span of seven days. By examining time series data, we aim to identify patterns in coronal hole behavior and understand their potential effects on space weather.
During its annual conference in 2024, the French Society of Astronomy & Astrophysics (SF2A) hosted a special session dedicated to discussing the environmental transition within the scope of our occupation. Since 2021, thinking on this subject has progressed significantly, both quantitatively and qualitatively. This year was an opportunity to take stock of the main areas of reflection that we need to keep in mind in order to implement a fair, collective and effective environmental transition. This proceeding summarizes the key points from the plenary session related to the environmental transition special session. The purpose of the messages disseminated here is to suggest ideas for reflection and inspiration, so as to initiate, stimulate, and foster discussions within the A&A research community, towards the implementation of concrete measures to mitigate our environmental footprint.
Geothermal energy on Flores Island is a suitable subject for a contextual approach in physics studies. Research activities, exploration, and the practical application of geothermal energy rely on fundamental physical concepts and principles. Flores Island and the surrounding archipelago are endowed with significant geothermal potential. Consequently, this research endeavor, aimed at assessing the potential and utilization of geothermal energy on Flores Island, serves as an excellent resource for contextual physics learning, particularly in the context of Flores Island. This research uses a literature study approach by reviewing related literature to obtain information about the research object. Flores Island and its neighboring island groups host 24 volcanoes. Specifically, Flores Island boasts 20 locations with geothermal potential, with resources capable of generating up to 739.5 MWe. Notably, by 2023, three Geothermal Power Plants (PLTP) will be operational on Flores Island, including Ulumbu PLTP, Mataloko PLTP, and Sokoria PLTP. These developments have positioned Flores as the first island in Indonesia to surpass the Renewable Energy mix target of 25.38%.
Ahmet Uçar, Eva González-Fernández, Matteo Staderini
et al.
Implantable electrochemical sensors that enable the real-time detection of significant biomarkers offer huge potential for the enhancement and personalisation of therapies; however, biofouling is a key challenge encountered by any implantable system. This is particularly an issue immediately after implantation, when the foreign body response and associated biofouling processes are at their most active in passivating a foreign object. Here, we present the development of a sensor protection and activation strategy against biofouling, based on coatings consisting of a pH-triggered, dissolvable polymer, that covered a functionalised electrode surface. We demonstrate that reproducible delayed sensor activation can be achieved, and that the length of this delay can be controlled by the optimisation of coating thickness, homogeneity and density through tuning of the coating method and temperature. Comparative evaluation of the polymer-coated and uncoated probe-modified electrodes in biological media revealed significant improvements in their anti-biofouling characteristics, demonstrating that this offers a promising approach to the design of enhanced sensing devices.
Uma das ideias fundadoras da física quântica, a quantização da energia, foi exposta por Max Planck em 1900, durante uma reunião da Sociedade Alemã de Física. A publicação originada daquele seminário é apresentada nessa tradução direta do alemão para o português.
Laser-driven wakefield acceleration (LWFA) has attracted lots of attention in recent years. However, few writers have been able to make systematic research into the bow waves generated along with the wake waves. Research about the bow waves will help to improve the understanding about the motion of the electrons near the wake waves. In addition, the relativistic energetic electron density peaks have great potential in electron acceleration and reflecting flying mirrors. In this paper, the bow waves generated in laser-plasma interactions as well as the effects of different laser and plasma parameters are investigated. Multidimensional particle-in-cell simulations are made to present the wake waves and bow waves by showing the electron density and momentum distribution as well as the electric field along x and y directions. The evolution of the bow wave structure is investigated by measuring the open angle between the bow wave and the wake wave cavity. The angle as well as the peak electron density and transverse momentum is demonstrated with respect to different laser intensities, spot sizes, plasma densities, and preplasma lengths. The density peak emits high-order harmonics up to 150 orders and can be a new kind of “flying mirror” to generate higher order harmonics. The study on the bow waves is important for further investigation on the electron motion around the wake waves, generation of dense electron beams, generation of high-order harmonics, and other research and applications based on the bow waves.
Classical DQ stars are white dwarfs whose atmospheres contain detectable traces of carbon brought up to the surface by a convective dredge-up process. Intriguingly, unlike other white dwarf spectral classes, DQ stars virtually never show signs of external pollution by elements heavier than carbon. In this Letter, we solve this long-standing problem by showing that the absence of detectable external pollution in DQ stars is naturally explained by the impact of metal accretion on the atmospheric structure of the white dwarf. A DQ star that accretes heavy elements sees its atmospheric density decrease, which leads to a sharp drop in the molecular carbon abundance and a strong suppression of the C$_2$ Swan bands. We show that a typical DQ star that accretes heavy elements from planetary material generally transforms directly into a DZ star.
The presence of possible correlations between stellar rotation rate $Ω$ and the frequency of the activity cycle $ω_\mathrm{cyc}$ is still much debated. We implement a new Bayesian classification algorithm based on a simultaneous regression analysis of multiple scaling laws and we demonstrate the existence of two different scalings in the $\log_{10} ω_\mathrm{cyc}$ -- $\log_{10} Ω$ plane for an extended Mt.~Wilson sample of 67 stars. Thanks to metallicity measurements obtained from both ESA Gaia and high-resolution spectroscopy, we argue that the origin of this dichotomy is likely related to the chemical composition: stars whose magnetic cycle frequency increases with rotation rate are less metallic than stars whose magnetic cycle frequency decreases with stellar rotation rates. On the contrary, no clear difference in chromospheric magnetic activity indicators characterizes the two branches.
Neste trabalho, os monitores do Observatório Astronômico do Ifes Guarapari (OAIG), que são alunos do Ensino Médio, construíram um espectroscópio baseado no trabalho de Azevedo, Souza e Castro, de 2019. Como a proposta era desenvolver um instrumento de baixo custo e acessível, foram feitas algumas modificações no modelo. Essas alterações consistiram na substituição da rede de difração por um DVD e também na troca do dispositivo de captura de imagem por uma webcam. O aparato construído foi utilizado para coletar o espectro solar.Apesar das limitações impostas, devido a faixa de sensibilidade da webcam e ao poder de resolução do DVD, os resultados obtidos mostraram que algumas linhas de Fraunhofer coincidem com aquelas presentes na literatura, com destaque para o Fe I e Mg I.Apesar desta limitação, o aparato cumpre seu objetivo didático e possibilita a abordagem de temas ligados à física quântica e a óptica física. Por outro lado, o uso da CCD e de uma rede de difração comercial com mais ranhuras, melhorariam significativamente os resultados obtidos, do mesmo modo que, aumentaria o custo de construção.
Steven G. Woodward, Karan Varshney, P. Anne
et al.
PURPOSE Utilization of hypofractionated radiation (HR) as a component of breast conserving treatment (BCT) in breast cancer is relatively low in the U.S. despite studies demonstrating its efficacy and guidelines supporting its use from the American Society for Radiation Oncology (ASTRO) in 2011 and 2018. Little is known regarding national trends in uptake and factors associated with uptake of HR in the U.S. since the 2011 ASTRO guidelines. METHODS We performed a retrospective review of the National Cancer Database (2012-2016) on patients undergoing BCT. Logistic regression modeling was used to identify relationships between patient, hospital, and tumor factors with the use of HR or traditional radiation (TR). RESULTS A total of 259,342 cases of BCT were identified with 60% (n=155,447) undergoing TR and 40% (n=103,895) undergoing HR. There was an increase in use among patients meeting 2011 ASTRO criteria from 26.2% in 2012 to 67.0% in 2016. The odds of utilization of HR increased with year of diagnosis, patient age, higher median income, private insurance, treatment at an academic center, travel distance to treatment >20 miles, smaller tumors, lymph node negative disease, and without use of chemotherapy (p-values <0.0001, Table 1). CONCLUSION Guidelines supporting the use of HR in BCT have been associated with a dramatic increase in utilization of HR in the U.S. However, there are substantial, identifiable disparities in the uptake of HR at patient and facility levels. By understanding which patient populations are at risk of not receiving the benefit of this therapy, we can improve our utilization of HR in the U.S., potentially leading to reduced healthcare costs and increased patient satisfaction.
In this paper, we first investigate the quality of aerial air pollution measurements and characterize the main error sources of drone-mounted gas sensors. To that end, we build ASTRO+, an aerial-ground pollution monitoring platform, and use it to collect a comprehensive dataset of both aerial and reference air pollution measurements. We show that the dynamic airflow caused by drones affects temperature and humidity levels of the ambient air, which then affect the measurement quality of gas sensors. Then, in the second part of this paper, we leverage the effects of weather conditions on pollution measurements' quality in order to design a UAV mission planning algorithm that adapts the trajectory of the drones while taking into account the quality of aerial measurements. We evaluate our mission planning approach based on a VOC pollution dataset and show a high performance improvement that is due to the fine characterization of the measurement errors.
Abstract In this chapter, we give a brief explanation of the concept of deep learning. Afterwards, we introduce four of the most prominent deep learning approaches, namely, convolutional neural networks, recurrent neural networks, variational autoencoders, and generative adversarial networks. For the main part of this chapter, we highlight use cases throughout astro- and geophysics.
This paper presents CAMP, a new static performance analysis framework for message-passing concurrent and distributed systems, based on the theory of multiparty session types (MPST). Understanding the run-time performance of concurrent and distributed systems is of great importance for the identification of bottlenecks and optimisation opportunities. In the message-passing setting, these bottlenecks are generally communication overheads and synchronisation times. Despite its importance, reasoning about these intensional properties of software, such as performance, has received little attention, compared to verifying extensional properties, such as correctness. Behavioural protocol specifications based on sessions types capture not only extensional, but also intensional properties of concurrent and distributed systems. CAMP augments MPST with annotations of communication latency and local computation cost, defined as estimated execution times, that we use to extract cost equations from protocol descriptions. CAMP is also extendable to analyse asynchronous communication optimisation built on a recent advance of session type theories. We apply our tool to different existing benchmarks and use cases in the literature with a wide range of communication protocols, implemented in C, MPI-C, Scala, Go, and OCaml. Our benchmarks show that, in most of the cases, we predict an upper-bound on the real execution costs with < 15% error.
The characterization and treatment of oligometastatic disease (OMD) are rapidly growing areas of research. Consensus statements have recently been developed by European Society for Radiotherapy and Oncology (ESTRO)/American Society for Radiation Oncology (ASTRO) and ESTRO/European Organization for Research and Treatment of Cancer (EORTC) in an effort to harmonize terminology describing OMD. The purpose of this study was to assess patient populations eligible for ongoing clinical trials evaluating stereotactic ablative radiotherapy (SABR) in OMD in the context of key definitions from both statements. Using the clinicaltrials.gov database, a search of ongoing OMD clinical trials evaluating the use of SABR was performed from inception to January 2020, using the keywords "oligometastasis", "stereotactic radiotherapy", and related terms. Results were independently reviewed by two investigators, with discrepancies settled by a third. Information from these trials including study design, population criteria, and primary endpoints were extracted. OMD was defined in general as a limited number of metastases that could be safely treated with metastasis-directed therapy. States of OMD were broadly categorized into de novo, repeat, and induced, with synchronous and metachronous being subsets of de novo. The initial search strategy identified 293 trials, of which 85 met our eligibility criteria. Phase II trials were by far the most common (n=46, 52%). Most trials had a single treatment arm (n=43, 51%), and 31 (36%) were randomized. The majority of trials (n=65, 76%) had populations that included all three subsets of OMD. Notably, 70 trials (82%) also included oligoprogressive disease, which is debatably a distinct entity from OMD. Progressionfree survival was the most common primary endpoint (n=31, 36%), followed by local control (n=17, 20%), toxicity (n=14, 16%) and overall survival (n=7, 8%). Although the use of SABR for OMD is an active area of prospective clinical trial research, ongoing studies include mixed populations as defined by new consensus statements. Therefore, the applicability of results from these trials should be considered within relevant OMD scenarios.
The first interstellar object observed in our solar system, 1I/2017 U1 (`Oumuamua), exhibited a number of peculiar properties, including extreme elongation and acceleration excess. Recently, \cite{Seligman:2020vb} proposed that the object was made out of molecular hydrogen (H$_{2}$) ice. The question is whether H$_2$ objects could survive their travel from the birth sites to the solar system. Here we study destruction processes of icy H$_2$ objects through their journey from giant molecular clouds (GMCs) to the interstellar medium (ISM) and the solar system, owing to interstellar radiation, gas and dust, and cosmic rays. We find that thermal sublimation due to heating by starlight can destroy `Oumuamua-size objects in less than 10 Myr. Thermal sublimation by collisional heating in GMCs could destroy H$_2$ objects of `Oumuamua-size before their escape into the ISM. Most importantly, the formation of icy grains rich in H$_2$ is unlikely to occur in dense environments because collisional heating raises the temperature of the icy grains, so that thermal sublimation rapidly destroys the H$_2$ mantle before grain growth.
This is our reply to the comment of T. Metcalfe and J. van Saders on the Science report "The Sun is less active than other solar-like stars" by T. Reinhold, A. I. Shapiro, S. K. Solanki, B. T. Montet, N. A. Krivova, R. H. Cameron, E. M. Amazo-Gomez. We hope that both the comment and our reply lead to fruitful discussions which of the two presented scenarios is more likely.
Considere ao pé-da-letra a expressão "imagem de um buraco negro", atribuindo a cada palavra o significado usual. Verá que ela não faz muito sentido e, se faz, soa estranha. É que a expressão é científica. Cada palavra adquiriu significado num vasto contexto de conceitos articulados numa teoria; esses conceitos, por sua vez, muitas vezes têm referências empíricas laboratoriais ou observacionais (astronômicas); o desenrolar histórico, normalmente imprevisível de descobertas observacionais ou de criações intelectuais, também adiciona às palavras, não explicações causais, mas meras referências casuais. Considerando a importância da popularização da ciência, como meio de promover a necessária alfabetização e letramento científico do público em geral, resolvi tirar vantagem da empolgação científica já suscitada pela grande mídia, quando anunciou a primeira imagem de um buraco negro. Não era mais preciso interessar as pessoas, pois elas já estavam interessadas no tema. Porém, notas quase telegráficas de jornais e noticiários atingem apenas superficialmente o público. Como teste de uma estratégia de divulgação científica e, também, como experimento de comunicação científica, decidi preparar e oferecer ao público um texto, antes de tudo elucidador do conteúdo científico e da complexa técnica de obtenção da imagem, mas também crítico do modo científico de investigar a natureza e incitador da aplicação da ciência, na medida em que ela possa tornar o mundo melhor e mais humano.
Abstract Precision measurements of charged cosmic rays have recently been carried out by space-born (e.g. AMS-02), or ground experiments (e.g. HESS). These measured data are important for the studies of astro-physical phenomena, including supernova remnants, cosmic ray propagation, solar physics and dark matter. Those scenarios usually contain a number of free parameters that need to be adjusted by observed data. Some techniques, such as Markov Chain Monte Carlo and MultiNest, are developed in order to solve the above problem. However, it is usually required a computing farm to apply those tools. In this paper, a genetic algorithm for finding the optimum parameters for cosmic ray injection and propagation is presented. We find that this algorithm gives us the same best fit results as the Markov Chain Monte Carlo but consuming less computing power by nearly 2 orders of magnitudes. Program summary Operating system: Linux Programming Language: C Software Package: ROOT Libraries: cmath, cstdio, cstdlib, ctime Optional Software Package: DRAGON