Ellyn K. Baines, Jeremy Jones, James H. Clark
et al.
During the course of publishing angular diameters from the Navy Precision Optical Interferometer data archive, we found we had data on 17 confirmed exoplanet host stars and one exoplanet candidate (HD 20902/alpha Per). Here, we update our previously published stellar radii with more precise Gaia parallaxes when available, and use our radius and effective temperature measurements to fit each star's mass and age using MIST models. The mass changed by more than 10% for 9 of the 18 stars. Combining our updated masses, radii, and temperatures, we present refined planetary masses as well as habitable zone calculations.
Light echoes of stellar flares provide an intriguing option for exploring protoplanetary disks in young stellar systems. Previous work on light echoes of circumstellar disks made use of delta-function flares for modeling. We present a new model that incorporates echoes produced by extended, time-resolved flares. We then test this model on known disk-bearing stars with Kepler K2 data by estimating disk parameters from possible echo signals. We focus on two stars; the first appears to be a good candidate for use of this echo model, which predicts disk parameters that are consistent with known values. The second star turns out to be more problematic as a result of high brightness variability in its post-peak lightcurve. These two cases show both the promise and limitations of light echoes as a tool for exploring protoplanetary disks in the time domain
We present an efficient and accurate algorithm for solving the Poisson equation in spherical polar coordinates with a logarithmic radial grid and open boundary conditions. The method employs a divide-and-conquer strategy, decomposing the computational domain into hierarchical units with varying cell sizes. James's algorithm is used to compute the zero-boundary potentials of lower-level units, which are systematically integrated to reconstruct the zero-boundary potential over the entire domain. These calculations are performed efficiently via matrix-vector operations using various precomputed kernel matrices. The open-boundary potential is then obtained by applying a discrete Green's function to the effective screening density induced at the domain boundaries. The overall algorithm achieves a computational complexity of $\mathcal{O}(N^3 \log N)$, where $N$ denotes the number of cells in one dimension. We implement the solver in the FARGO3D magnetohydrodynamics code and demonstrate its performance and second-order accuracy through a series of test problems.
Stellar coronagraphs designed for high-contrast imaging of exoplanets inevitably introduce a small amount of instrumental polarization, called \emph{secondary polarization}. At the contrast levels required to detect and characterize terrestrial planets, these effects may become significant. Instrumentally induced polarization is often referred to as ``incoherent," yet this use of the term lacks rigor. This work uses Jones calculus and vector field simulations, including interactions with dielectric surfaces to show that the secondary polarization is fully coherent with the input field, but it does not interfere with it due to orthogonality. A key consequence of the coherence secondary polarization is that the process of creating a dark hole in the primary polarization tends to also significantly mitigate the intensity corresponding to the secondary polarization, called the \emph{secondary intensity}, in the dark hole region. This reduction of the secondary intensity may lead to relaxed polarization design requirements in future coronagraphs. Additionally, if the contrast is sufficient to make the secondary intensity non-negligible, modulation schemes to separate the planet from the instrumental light need to account for the modulation of the secondary intensity.
Sam de Regt, Siddharth Gandhi, Louis Siebenaler
et al.
In recent years, significant advances have been made in exoplanet and brown dwarf observations. By using state-of-the-art models, astronomers can determine properties of their atmospheres, such as temperatures, the presence of clouds, or the chemical abundances of molecules and atoms. Accurate and up-to-date opacities are crucial to avoid inconclusive or biased results, but it can be challenging to compute opacity cross-sections from the line lists provided by various online databases. We introduce pyROX, an easy-to-use Python package to calculate molecular and atomic cross-sections. Since pyROX works on CPUs, it can compute a small line list on a regular workstation, but it is also easily parallelised on a cluster for larger line lists. In addition to line opacities, pyROX also supports calculations of collision-induced absorption. Tutorials are provided in the online documentation which explain the configuration parameters and different functionalities of pyROX.
Spacecraft equipped with multiple propulsion modes or systems can offer enhanced performance and mission flexibility compared with traditional configurations. Despite these benefits, the trajectory optimization of spacecraft utilizing such configurations remains a complex challenge. This paper presents a sequential convex programming (SCP) approach for the optimal design of multi-mode and multi-propulsion spacecraft trajectories. The method extends the dynamical linearization within SCP using sparse automatic differentiation, enabling efficient inclusion of multiple propulsion modes or systems without complex manual reformulation while maintaining comparable computational efficiency. New constraint formulations are introduced to ensure selection of a single propulsion mode at each time step and limit the total number of modes used. The approach is demonstrated for (i) a low-thrust Earth-67P rendezvous using the SPT-140 thruster with 20 discrete modes, and (ii) an Earth-Mars transfer employing both a low-thrust engine and a solar sail. Results confirm that the proposed method can efficiently compute optimal trajectories for these scenarios.
Mark D. Blumenthal, Declan Mahony, Salahuddeen Ahmad
et al.
AbstractThe need to pump single electrons with a high degree of accuracy and fidelity has led to the development of a range of different pump and turnstile designs. Previous pumping mechanisms have all demonstrated that pumping more than one electron per cycle degrades the quantisation of the measured current. This unreliable delivery of multiple electrons per cycle has limited the use of on-demand single electron sources in electron quantum optic experiments. We present highly quantised current with multiple electrons pumped per cycle. We experimentally demonstrate that in our pumps an increase in electron throughput per cycle does not lead to an appreciable degradation in the accuracy of the produced current.Our pump is realised in an aluminium gallium arsenide two-dimensional electron gas, where electrons are pumped through a one-dimensional split-gate confinement potential under the influence of an applied source-drain voltage $V_{\text{SD}}$ V SD , and where the pump is driven by a trapezoidal arbitrary waveform. This combination of a split-gate potential, $V_{\text{SD}}$ V SD bias and trapezoidal wave form has led to the observation of robust quantised plateaus where not just a single electron, but a multiple integer number of electrons are pumped per cycle with a high degree of robustness and without the need of a magnetic field. For seven electrons per cycle, we report an increase of over two orders of magnitude in pumping accuracy from $2.72 \times 10^{-2}$ 2.72 × 10 − 2 in devices operating in the conventional pumping regime, to $1.64 \times 10^{-4}$ 1.64 × 10 − 4 in pumps operating in what we call the long plateau regime, a regime accessed under a change in a split-gate pumps applied $V_{\text{SD}}$ V SD voltage. This pump will find direct use in quantum transport measurements where the metrological accuracy of single electrons pumped per cycle is not required and the low throughput per cycle of electrons is limiting.
A nucleossíntese primordial é o tema central deste artigo que descreve a evolução do universo desde a sua origem até os 3 primeiros minutos após o big bang. O universo é caracterizado como um caldeirão de partículas. À medida em que o universo se expande e a temperatura diminui, ocorre uma competição entre a criação e a aniquilação das partículas, levando à formação dos primeiros núcleos leves, como hidrogênio, deutério, trítio, lítio, berílio e boro. A formação destes núcleos de massas leves é apresentada sob o ponto de vista da Física Nuclear.
The Galileo Project is the first systematic scientific research program in search for potential astro-archaeological artifacts or remnants of extraterrestrial technological civilizations (ETCs) or potentially active equipment near Earth. Taking a path not taken, it conceivably may pick some low-hanging fruit, and without asserting probabilities - make discoveries of ETC-related objects, which would have far-reaching implications for science and our worldview.
Purpose/Objective We present our single-institution experience in the management of invasive breast cancer with targeted intraoperative radiotherapy (TARGIT-IORT), focusing on patient suitability for IORT determined by the American Society for Radiation Oncology (ASTRO) Accelerated Partial Breast Irradiation (APBI) consensus guidelines. Materials/Methods We identified 237 patients treated for biopsy-proven early-stage invasive breast cancer using low energy x-ray TARGIT-IORT at the time of lumpectomy between September 2013 and April 2020 who were prospectively enrolled in an institutional review board (IRB) approved database. We retrospectively reviewed preoperative and postoperative clinicopathologic factors to determine each patient’s ASTRO APBI suitability (suitable, cautionary or unsuitable) according to the 2017 consensus guidelines (CG). Change in suitability group was determined based on final pathology. Kaplan-Meier methods were used to estimate the survival probability and recurrence probability across time. Results 237 patients were included in this analysis, based on preoperative clinicopathologic characteristics, 191 (80.6%) patients were suitable, 46 (19.4%) were cautionary and none were deemed unsuitable. Suitability classification changed in 95 (40%) patients based on final pathology from lumpectomy. Increasing preoperative lesion size or a body mass index (BMI) ≥ 30 kg/m2 were significant predictors for suitability group change. Forty-one (17.3%) patients received additional adjuvant whole breast radiotherapy after TARGIT-IORT. At a median follow up of 38.2 months (range 0.4 – 74.5), five (2.1%) patients had ipsilateral breast tumor recurrences (IBTR), including two (0.8%) true local recurrences defined as a recurrence in the same quadrant as the initial lumpectomy bed with the same histology as the initial tumor. IBTR occurred in 1/103 (0.09%) patient in the post-op suitable group, 4/98 (4.08%) patients in the post-op cautionary group, and no patients in the post-op unsuitable group. At 3-years, the overall survival rate was 98.4% and the local recurrence free survival rate was 97.1%. Conclusion There is a low rate of IBTR after TARGIT-IORT when used in appropriately selected patients. Change in suitability classification pre to postoperatively is common, highlighting a need for further investigation to optimize preoperative patient risk stratification in this setting. Patients who become cautionary or unsuitable based on final pathology should be considered for additional adjuvant therapy.
Este trabalho apresenta uma visão da Geofísica no que diz respeito à algumas manifestações físicas que trazem informações sobre a estrutura interna da Terra. Desta forma, são abordados alguns conceitos básicos sobre sismologia, o estudo das ondas elásticas liberadas por terremotos, geomagnetismo, o estudo do campo magnético gerado no interior da Terra, e gravimetria, a interpretação das anomalias gravimétricas produzidas pelas heterogeneidades nas estruturas internas da Terra.
Social companion robots are getting more attention to assist elderly people to stay independent at home and to decrease their social isolation. When developing solutions, one remaining challenge is to design the right applications that are usable by elderly people. For this purpose, co-creation methodologies involving multiple stakeholders and a multidisciplinary researcher team (e.g., elderly people, medical professionals, and computer scientists such as roboticists or IoT engineers) are designed within the ACCRA (Agile Co-Creation of Robots for Ageing) project. This paper will address this research question: How can Internet of Robotic Things (IoRT) technology and co-creation methodologies help to design emotional-based robotic applications? This is supported by the ACCRA project that develops advanced social robots to support active and healthy ageing, co-created by various stakeholders such as ageing people and physicians. We demonstra this with three robots, Buddy, ASTRO, and RoboHon, used for daily life, mobility, and conversation. The three robots understand and convey emotions in real-time using the Internet of Things and Artificial Intelligence technologies (e.g., knowledge-based reasoning).
Background: Although chest radiographs have not been utilised well for classifying stroke subtypes, they could provide a plethora of information on cardioembolic stroke. This study aimed to develop a deep convolutional neural network that could diagnose cardioembolic stroke based on chest radiographs. Methods: Overall, 4,064 chest radiographs of consecutive patients with acute ischaemic stroke were collected from a prospectively maintained stroke registry. Chest radiographs were randomly partitioned into training/validation (n = 3,255) and internal test (n = 809) datasets in an 8:2 ratio. A densely connected convolutional network (ASTRO-X) was trained to diagnose cardioembolic stroke based on chest radiographs. The performance of ASTRO-X was evaluated using the area under the receiver operating characteristic curve. Gradient-weighted class activation mapping was used to evaluate the region of focus of ASTRO-X. External testing was performed with 750 chest radiographs of patients with acute ischaemic stroke from 7 hospitals. Findings: The areas under the receiver operating characteristic curve of ASTRO-X were 0.86 (95% confidence interval [CI], 0.83–0.89) and 0.82 (95% CI, 0.79–0.85) during the internal and multicentre external testing, respectively. The gradient-weighted class activation map demonstrated that ASTRO-X was focused on the area where the left atrium was located. Compared with cases predicted as non-cardioembolism by ASTRO-X, cases predicted as cardioembolism by ASTRO-X had higher left atrial volume index and lower left ventricular ejection fraction in echocardiography. Interpretation: ASTRO-X, a deep neural network developed to diagnose cardioembolic stroke based on chest radiographs, demonstrated good classification performance and biological plausibility.
Importance The 2014 publication of the Society of Surgical Oncology-American Society for Radiation Oncology (SSO-ASTRO) Consensus Guideline on Margins for Breast-Conserving Surgery recommended a negative margin definition of no ink on tumor. Adoption of this guideline would represent a major change in surgical practice that could lower the rates of reoperation. Objective To assess changes in reoperation rates after publication of the SSO-ASTRO guideline. Data Sources A systematic search of Embase, PREMEDLINE, Evidence-Based Medicine Reviews, Scopus, and Web of Science for biomedical literature published from January 2014 to July 2019 was performed. This search was supplemented by web searches and manual searching of conference abstracts. Study Selection Included studies compared the reoperation rates in preguideline vs postguideline cohorts (actual change), retrospectively applied the SSO-ASTRO guideline to a preguideline cohort (projected change), or described the economic outcomes of the guideline. Data Extraction and Synthesis Study characteristics and reoperation rates were extracted independently by 2 reviewers. Odds ratios (ORs) were pooled by random effects meta-analysis. Analyses were stratified by study setting (institutional or population) and preguideline accepted margins. The economic outcomes of the guideline were summarized narratively. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Main Outcomes and Measures Odds ratios for postguideline vs preguideline reoperation rates. Results From 1114 citations, 30 studies (with 599 016 participants) reported changes in reoperation rates. Studies included a median (range) of 487 (100-521 578) participants, and 20 studies were undertaken in the US, 6 in the UK, 3 in Canada, and 1 in Australia. Among 21 studies of actual changes, pooled ORs showed a statistically significant reduction in reoperation, with an OR lower in institution-based studies than in population-based studies (OR, 0.62 [95% CI, 0.52-0.74] vs 0.76 [95% CI, 0.72-0.80]; P = .04 for subgroup differences). Among 9 studies of projected changes, the pooled OR was lower for preguideline margin thresholds of 2 mm or more compared with 1 mm (OR, 0.47 [95% CI, 0.40-0.56] vs 0.85 [95% CI, 0.79-0.91; P < .001 for subgroup differences). Projected changes were likely to overestimate actual changes. Six studies that estimated the postguideline economic outcome found the guideline to be potentially cost saving, with a median (range) saving of US $3540 ($1800-$25 650) per woman avoiding reoperation. Conclusions and Relevance This study found a decrease in reoperation rates after the publication of the SSO-ASTRO guideline; this reduction was greater at an institutional level than a population level, the latter reflecting the differences in guideline adoption between centers. These early outcomes may be conservative estimates of longer-term implications.
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.
Raphael Gobat, Sungwook E. Hong, Owain Snaith
et al.
We study the process of panspermia in Milky Way-like galaxies by modeling the probability of successful travel of organic compounds between stars harboring potentially habitable planets. To this end, we apply the modified habitability recipe of Gobat & Hong (2016) to a model galaxy from the MUGS suite of zoom-in cosmological simulations. We find that, unlike habitability, which only occupies narrow dynamic range over the entire galaxy, the panspermia probability can vary be orders of magnitude between the inner ($R, b = 1-4 {\rm kpc}$) and outer disk. However, only a small fraction of star particles have very large values of panspermia probability and, consequently, the fraction of star particles where the panspermia process is more effective than prebiotic evolution is much lower than from naïve expectations based on the ratio between panspermia probability and natural habitability.
Abstract The X-ray Imaging and Spectroscopy Mission (XRISM) is a recovery mission of ASTRO-H (Hitomi) launched in 2016. The Resolve instrument on the XRISM is an 6 × 6 array of silicon-thermistor microcalorimeters cooled down to 50 mK combined with a 5.6 m focal length X-ray telescope. Its design inherits that of the Soft X-ray Spectrometer (SXS) onboard ASTRO-H that demonstrated high resolution spectroscopy of the X-ray microcalorimeters by observing astronomical objects and providing superb resolution spectra. The cooling chain of the Resolve consists of a 3-stage adiabatic demagnetization refrigerator (ADR), a Joule-Thomson cooler, ~ 30 L superfluid helium, four Stirling coolers and a vacuum vessel or a dewar. Design of the Resolve cooling system is basically the same as that in the SXS but several changes are adopted based on lessons learned. This paper describes mainly the cooling system from room temperature to about 1 K providing the ADR heat sink. Major changes include an aperture baffle for micrometeoroid and orbital debris protection and optical light reduction, an eddy current damper to slow a gate valve opening, a new vibration isolation system with launch-locks.
We perform a statistical inference of the astrophysical population of binary black hole (BBH) mergers observed during the first two observing runs of Advanced LIGO and Advanced Virgo, including events reported in the GWTC-1 and IAS catalogs. We derive a novel formalism to fully and consistently account for events of arbitrary significance. We carry out a software injection campaign to obtain a set of mock astrophysical events subject to our selection effects, and use the search background to compute the astrophysical probabilities $p_{\rm astro}$ of candidate events for several phenomenological models of the BBH population. Finally, we combine the information from individual events to infer the rate, spin, mass, mass-ratio and redshift distributions of the mergers. The existing population does not discriminate between random spins with a spread in the effective spin parameter, and a small but nonzero fraction of events from tidally-torqued stellar progenitors. The mass distribution is consistent with one having a cutoff at $m_{\rm max} = 41^{+10}_{-5}\,\rm M_\odot$, while the mass ratio favors equal masses; the mean mass ratio $\bar q> 0.67$. The rate shows no significant evolution with redshift. We show that the merger rate restricted to BBHs with a primary mass between 20 and $30\, \rm M_\odot$, and a mass ratio $q > 0.5$, and at $z \sim 0.2$, is 1.5 to $5.3\,{\rm Gpc^{-3} yr^{-1}}$ (90\% c.l.); these bounds are model independent and a factor of $\sim 3$ tighter than that on the local rate of all BBH mergers, and hence are a robust constraint on all progenitor models. Including the events in our catalog increases the Fisher information about the BBH population by $\sim 47\%$, and tightens the constraints on population parameters.