The electron density profile on a plasma surface has a decisive influence on the mechanism and characteristics of the plasma high-order harmonic generation. When the pre-pulse has a similar spatial and temporal distribution as the main laser pulse, the plasma surface on the target will expand to form a convex profile of the similar size as the focal spot of the main pulse. We experimentally observed that the divergence of the harmonics generated by the relativistic laser light incident on a silica target has a saddle-shaped structure. The two-dimensional particle-in-cell simulation with convex plasma surfaces explains the experimental results very well and infers a 0.12λL plasma scale length around the center of the convex profile. Further, we qualitatively explained that the asymmetry of the saddle-shaped harmonic divergence is caused by oblique incidence.
O Sol e as estrelas apresentam atividade magnética na forma de manchas escuras em sua superfície, além de produzirem explosões e ejeções de massa de suas atmosferas. As assinaturas de manchas escuras na superfície das estrelas podem ser modeladas a fim de caraterizar seus tamanhos e temperaturas. Estrelas jovens e anãs M produzem energéticas superexplosões, as quais podem impactar os planetas em órbitas, principalmente os que estiverem bem próximos da sua estrela hospedeira. O fluxo de radiação ultravioleta destas explosões pode ser prejudicial para possíveis organismos vivos na superfície de exoplanetas orbitando na zona habitável de estrelas ativas. Entretanto, uma atmosfera com ozônio poderia protegê-los, ou então um oceano. Os ventos estelares também afetam as atmosferas planetárias, podendo ser responsáveis pela sua erosão.
A atração gravitacional mútua entre os planetas do sistema solar provocam alterações nas suas orbitas que seriam perfeitamente elípticas se os planetas estivessem sujeitos somente sob a ação gravitacional do Sol. Essas alterações nas orbitas podem ser de períodos relativamente curtos (alguns anos) ao final dos quais os planetas voltam ao seu estado anterior. Podem também ter um efeito cumulativo alterando pouco a pouco as orbitas ao longo de anos ou séculos seguidos modificando completamente a órbita original ou retornando ao estado inicial depois de vários séculos. Essas são as mais interessantes de se analisar e são chamadas de perturbações seculares. Nesse texto se analisa o caso mais aparente desse fenômeno é a interação gravitacional entre Júpiter e Saturno. Alterações significativas foram detectadas pelo astrônomo Halley em 1695, e naquela época nenhuma justificativa razoável à luz da lei da gravitação universal foi encontrada, chegando a se duvidar da validade dessa lei. O problema foi solucionado quase 100 anos depois por Laplace. Esse texto é uma analise do artigo de Laplace, Mémoire sur les inégalités séculaires des planètes et des satellites, de 1787, e seus desdobramentos posteriores.
John A. Seed, Helen R. Sharpe, Harry J. Futcher
et al.
AbstractTreatment of [Ph3EMe][I] with [Na{N(SiMe3)2}] affords the ylides [Ph3E=CH2] (E=As, 1As; P, 1P). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium‐ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P, confirming the long‐proposed hypothesis of increasing pyramidalisation of the ylide‐carbon, highlighting the increasing dominance of E+−C− dipolar resonance form (sp3‐C) over the E=C ene π‐bonded form (sp2‐C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH2CH2NSiPri3)2(CH2CH2SiPri2CH(Me)CH2)}] reacts with 1As and 1P by α‐proton abstraction to give [U(TrenTIPS)(CHEPh3)] (TrenTIPS=N(CH2CH2NSiPri3)3; E=As, 2As; P, 2P), where 2As is an unprecedented structurally characterised arsonium‐carbene complex. The short U−C distances and obtuse U‐C‐E angles suggest significant U=C double bond character. A shorter U−C distance is found for 2As than 2P, consistent with increased uranium‐ and reduced pnictonium‐stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations.
Austin Rothermich, Adam C. Schneider, Jacqueline K. Faherty
et al.
We present the discovery of CWISE J203546.35-493611.0, a peculiar M8 companion to the M4.5 star APMPM J2036-4936 discovered through the citizen science project Backyard Worlds: Planet 9. Given CWISE J203546.35-493611.0's proper motion ($μ_α$, $μ_δ$) = ($-$126$\pm$22, $-$478$\pm$23) and angular separation of 34.2$''$ from APMPM 2036-4936, we calculate a chance alignment probability of $1.15 \times 10^{-6}$. Both stars in this system appear to be underluminous, and the spectrum obtained for CWISE J203546.35-493611.0 shows a triangular H band. Further study of this system is warranted to understand these peculiarities.
L. M. Flor-Torres, R. Coziol, K. -P. Schröder
et al.
A sample of 46 stars, host of exoplanets, is used to search for a connection between their formation process and the formation of the planets rotating around them. Separating our sample in two, stars hosting high-mass exoplanets (HMEs) and low-mass exoplanets (LMEs), we found the former to be more massive and to rotate faster than the latter. We also found the HMEs to have higher orbital angular momentum than the LMEs and to have lost more angular momentum through migration. These results are consistent with the view that the more massive the star and higher its rotation, the more massive was its protoplanetarys disk and rotation, and the more efficient the extraction of angular momentum from the planets.
Neste artigo são revistos os principais eventos que teriam ocorrido nas primeiras fases de evolução do universo, quando o plasma cósmico é opaco à radiação eletromagnética. Neste caso, a informação sobre tais eventos não pode provir de fótons mas somente de ondas gravitacionais, detetadas pela primeira vez em 2015. Serão revisitados os espectros do fundo de ondas gravitacionais gerados durante o período inflacionário e as transições de fase eletrofraca e quark-hádron. Além disso, são examinados os espectros do fundo de ondas gravitacionais gerados em cenários alternativos ao \textit{big bang}, sugeridos por teorias efetivas de campo.
R. B. Astro, Yulius Saprianus Dala Ngapa, S. Toda
et al.
Pulau Flores yang terletak di Provinsi Nusa Tenggara Timur memiliki potensi EBT yang cukup beragam, antara lain panas bumi, air, angin, matahari, hingga arus laut. Penelitian ini bertujuan untuk menjabarkan potensi air di Flores serta sistem kerja pembangkit listrik ramah lingkungan yang memanfaatkan air sebagai sumber energi. Hasil penelitian ini dapat dimanfaatkan sebagai sumber belajar terkait potensi energi air di pulau Flores dan pemanfaatannya sebagai sumber energi listrik bersih (green energy). Penelitian ini dilaksanakan dengan metode studi literatur. Pulau Flores termasuk daerah beriklim kering dengan curah hujan yang minim dengan potensi air tergolong kecil, sehingga potensi energi air lebih tepat digunakan sebagai sumber energi listrik dengan daya menengah (PLTM) dan kecil (PLTMH). Potensi air yang tersedia juga mampu ditingkatkan dengan sistem cascade. Pada PLTM/MH energi potensial air diubah menjadi energi kinetik di dalam pipa pesat, selajutnya energi kinetik diubah menjadi energi mekanik berupa putaran poros turbin, dan terakhir energi mekanik dikonversi menjadi energi listrik oleh generator. Beberapa pembangkit listrik yang ada di pulau Flores antara lain PLTM Ndungga, PLTMH Ogi, dan PLTMH Wae Roa, PLTMH Waigarit, dan PLTMH Sita. Selain itu terdapat pula penelitian lain terkait potensi energi air di Flores yang masih dalam tahap penelitian awal dan lanjutan. Pada pengoperasiannya PLTM/MH terbukti menekan laju konsumsi bahan bakar fosil. PLTMH juga sangat memungkinkan untuk diterapkan pada daerah-daerah di Flores dan NTT umumnya yang terpencil dan jauh dari jaringan listrik PLN.
AbstractAdoptive T‐cell therapy (ACT) has emerged as a promising new way to treat systemic cancers such as acute lymphoblastic leukemia. However, the robustness and reproducibility of the manufacturing process remains a challenge. Here, a single‐use 24‐well microbioreactor (micro‐Matrix) was assessed for its use as a high‐throughput screening tool to investigate the effect and the interaction of different shaking speeds, dissolved oxygen (DO), and pH levels on the growth and differentiation of primary T cells in a perfusion‐mimic process. The full factorial design allowed for the generation of predictive models, which were used to find optimal culture conditions. Agitation was shown to play a fundamental role in the proliferation of T cells. A shaking speed of 200 rpm drastically improved the final viable cell concentration (VCC), while the viability was maintained above 90% throughout the cultivation. VCCs reached a maximum of 9.22 × 106 cells/ml. The distribution of CD8+ central memory T cells (TCM), was found to be largely unaffected by the shaking speed. A clear interaction between pH and DO (p < .001) was established for the cell growth and the optimal culture conditions were identified for a combination of 200 rpm, 25% DO, and pH of 7.4. The combination of microbioreactor technology and Design of Experiment methodology provides a powerful tool to rapidly gain an understanding of the design space of the T‐cell manufacturing process.
In this study we identify 11 Kepler systems (KIC 5255552, 5653126, 5731312, 7670617, 7821010, 8023317, 10268809, 10296163, 11519226, 11558882 and 12356914) with a "flip-flop" effect in the eclipse timing variations O-C diagrams of the systems, report on what these systems have in common and whether these systems are dynamically stable. These systems have previously reported high eccentric binary stars with highly eccentric third bodies/outer companions. We find that all of the additional bodies in the system are dynamically stable for the configurations previously reported and are therefore likely to exist as described. We also provide additional evidence of KIC5255552 being a quadruple star system comprised of an eclipsing binary pair and non-eclipsing binary pair with the possibility of a fifth body in the system. With the advent of the NASA TESS exoplanet survey, its precision photometric monitoring offers an opportunity to help confirm more local eclipsing binary star companions, including planets.
Planetary engulfment events involve the chemical assimilation of a planet into a star's external layer. This can cause a change in the chemical pattern of the stellar atmosphere in a way that mirrors the composition of the rocky object engulfed, with the refractory elements being more abundant than the volatiles. Due to these stellar chemical changes, planetary engulfment events can render the process of chemical tagging potentially inaccurate. A line-by-line differential analysis of twin stars in wide binary systems allows us to test the chemical homogeneity of these associations with typical individual stellar Fe I uncertainties of 0.01 dex and eventually unveil chemical anomalies that could be attributed to planetary engulfment events. Out of the 14 systems analysed here, we report the discovery of the most chemically inhomogeneous system to date (HIP34407/HIP34426). The median difference in abundances of refractory elements within the pair is 0.19 dex and the trend between the differential abundances and condensation temperature suggests that the anomaly is likely due to a planetary engulfment event. Within our sample, five other chemically anomalous systems are found.
Daniella Bardalez Gagliuffi, Kimberly Ward-Duong, Jacqueline Faherty
et al.
Substellar multiplicity is a key outcome of the formation process. The biggest challenge for the next decade will be to distinguish between the formation history, environmental conditions, and dynamical evolution leading to the least massive brown dwarfs and the most massive planets at the tail ends of their mass functions. In this white paper, we advocate for a comprehensive characterization of both the statistical distributions of the population of ultracool dwarf multiple systems and the fundamental properties of their individual components as a function of age. A space-based precision astrometry mission in near-infrared wavelengths would provide the necessary measurements to identify and characterize age-calibrated populations of multiple systems.
Planetary bodies such as asteroids, comets, and planetary moons are high-value science targets as they hold important information about the formation and evolution of our solar system. However, due to their low-gravity, variable sizes and shapes, dedicated orbiting spacecraft missions around these target bodies is difficult. Therefore, many planetary bodies are observed during flyby encounters, and consequently, the mapping coverage of the target body is limited. In this work, we propose the use of a spacecraft swarm to provide complete surface maps of a planetary body during a close encounter flyby. With the advancement of low-cost spacecraft technology, such a swarm can be realized by using multiple miniature spacecraft. The design of a swarm mission is a complex multi-disciplinary problem. To get started, we propose the Integrated Design Engineering & Automation of Swarms (IDEAS) software. In this work, we will introduce the development of the Automated Swarm Designer module of the software and apply it to total surface mapping of asteroid 433 Eros through flybys.
Gravito-inertial waves can be excited at the interface of convective and radiative regions and by the Reynolds stresses in the bulk of the convection zone. The magnitude of their energy flux will therefore vary with the properties of the convection. To assess how convection changes with rotation, a simplified local monomodal model for rotating convection is presented that provides the magnitude of the rms velocity, degree of superadiabaticity, and characteristic length scale as a function of the convective Rossby number as well as with thermal and viscous diffusivities. In the context of this convection model, two models for assessing the gravito-inertial wave flux are considered: an interfacial model and a full treatment of the Reynolds stress impact on the waves. It is found that there are regimes where the sub-inertial waves may carry a significant energy flux relative to pure gravity waves that depend upon the convective Rossby number, the ratio of the buoyancy time-scale in the stable region to the convective overturning time, and the wave frequency.
Barrett M. Frank, Brandon Piotrzkowski, Brett Bolen
et al.
One source of noise for the Laser Interferometer Space Antenna (LISA) will be time-varying changes of the space environment in the form of solar wind particles and photon pressure from fluctuating solar irradiance. The approximate magnitude of these effects can be estimated from the average properties of the solar wind and the solar irradiance. We use data taken by the ACE (Advanced Compton Explorer) satellite and the VIRGO (Variability of solar IRradiance and Gravity Oscillations) instrument on the SOHO satellite over an entire solar cycle to calculate the forces due to solar wind and photon pressure irradiance on the LISA spacecraft. We produce a realistic model of the effects of these environmental noise sources and their variation over the expected course of the LISA mission.
Binary stars are places of complex stellar interactions. While all binaries are in principle converging towards a state of circularization, many eccentric systems are found even in advanced stellar phases. In this work we discuss the sample of binaries with a red-giant component, discovered from observations of the NASA Kepler space mission. We first discuss which effects and features of tidal interactions are detectable in photometry, spectroscopy and the seismic analysis. In a second step, the sample of binary systems observed with Kepler, is compared to the well studied sample of Verbunt & Phinney (1995, hereafter VP95). We find that this study of circularization of systems hosting evolving red-giant stars with deep convective envelopes is also well applicable to the red-giant binaries in the sample of Kepler stars.