Drag De-Orbit Device: A New Standard Re-Entry Actuator for CubeSats

With the advent of CubeSats, research in Low Earth Orbit (LEO) becomes possible for universities and small research groups. Only a handful of launch sites can be used, due to geographical and political restrictions. As a result, common orbits in LEO are becoming crowded due to the additional launches made possible by low-cost access to space. CubeSat design principles require a maximum of a 25-year orbital lifetime in an effort to reduce the total number of spacecraft in orbit at any time. Additionally, since debris may survive re-entry, it is ideal to de-orbit spacecraft over unpopulated areas to prevent casualties. The Drag Deorbit Device (D3) is a self-contained targeted re-entry subsystem intended for CubeSats. By varying the cross-wind area, the atmospheric drag can be varied in such a way as to produce desired maneuvers. The D3 is intended to be used to remove spacecraft from orbit to reach a desired target interface point. Additionally, attitude stabilization is performed by the D3 prior to deployment and can replace a traditional ADACS on many missions.This paper presents the hardware used in the D3 and operation details. Four stepper-driven, repeatedly retractable booms are used to modify the cross-wind area of the D3 and attached spacecraft. Five magnetorquers (solenoids) over three axes are used to damp rotational velocity. This system is expected to be used to improve mission flexibility and allow additional launches by reducing the orbital lifetime of spacecraft.The D3 can be used to effect a re-entry to any target interface point, with the orbital inclination limiting the maximum latitude. In the chance that the main spacecraft fails, a timer will automatically deploy the booms fully, ensuring the spacecraft will at the minimum reenter the atmosphere in the minimum possible time, although not necessarily at the desired target interface point. Although this does not reduce the risk of casualties, the 25-year lifetime limit is still respected, allowing a reduction of the risk associated with a hardware failure

How do house prices respond to mortgage supply?

We examine the impact of household mortgages on house prices. Using biannual data on Italian cities in the period 2003–2015, we build an exogenous and fully data-driven indicator of mortgage supply stance and use it as instrument for actual extended mortgages. Our results indicate that mortgages have a positive and significant causal effect on house prices, with an estimated elasticity of around 0.1. The estimated effect is larger during the expansionary phase of the housing cycle. We also find evidence of significant spatial heterogeneity: mortgages push real estate values more in cities where the housing supply curve is less elastic or households are more dependent on external finance

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the Gz axis (a g) ranging from 0 to 3g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a g. In contrast, heart rate increased non-linearly with a g, whereas stroke volume decreased non-linearly: both were described by quadratic functions. Thus, the relationship between cardiac output and a g was described by a fourth power regression equation. Mean arterial pressure increased with a g non linearly, a relation that we interpolated again with a quadratic function. Thus, total peripheral resistance varied linearly with a g. These data led to predict that maximal oxygen consumption would decrease drastically as a g is increased. Maximal oxygen consumption would become equal to resting oxygen consumption when a g is around 4.5g, thus indicating the practical impossibility for humans to stay and work on the biggest Planets of the Solar Syste

Representaciones del pasado, cultura personal e identidad nacional

Memoria, Historia, Individuo, Nacion,Identidad, — asi, escritos con mayusculas — sonpalabras que se hacen presentes en el discur-so publico de cada dia. Se trata de conceptosque, en ocasiones, se convierten en armasarrojadizas en los conflictos sociales, y se agitancomo conceptos explicativos en los discursospublicos que dan cuenta de la violencia simbo-lica, y a veces de la fisica, que sufren losciudadanos de a pie; quienes, ademas de serpeones en los juegos en marcha, no dejan detener alguna responsabilidad en los resultadosque en estos se den.El proposito de este capitulo es ofrecerun conjunto de conceptos y una estructurarelacional entre ellos que facilite la conexionentre cada una de las aportaciones de queconsta el volumen en su conjunto, al mismotiempo que oferta una reflexion sobre una seriede cuestiones que, sin ser tratadas explici-tamente en cada uno de los otros capitulos,muchas veces estan presentes en forma depresuposiciones no siempre faciles de tener encuenta. Dicho en forma mas breve, lo que aquitrataremos de ofrecer es un marco general detrabajo que, al mismo tiempo, contextualice loscapitulos que siguen sobre el fondo de lapreocupacion contemporanea desde ambitosdisciplinares muy diversos sobre los temas ci-tados al principio.Las cuestiones que aqui nos van a ocu-par, como es el caso de la memoria y la iden-tidad, para ser abordadas con cierto rigor,requieren adoptar un planteamiento capaz d

Neural network accelerator for quantum control

Efficient quantum control is necessary for practical quantum computing implementations with current technologies. Conventional algorithms for determining optimal control parameters are computationally expensive, largely excluding them from use outside of the simulation. Existing hardware solutions structured as lookup tables are imprecise and costly. By designing a machine learning model to approximate the results of traditional tools, a more efficient method can be produced. Such a model can then be synthesized into a hardware accelerator for use in quantum systems. In this study, we demonstrate a machine learning algorithm for predicting optimal pulse parameters. This algorithm is lightweight enough to fit on a low-resource FPGA and perform inference with a latency of 175 ns and pipeline interval of 5 ns with $~>~$0.99 gate fidelity. In the long term, such an accelerator could be used near quantum computing hardware where traditional computers cannot operate, enabling quantum control at a reasonable cost at low latencies without incurring large data bandwidths outside of the cryogenic environment.Comment: 7 pages, 10 figure

Fairness Testing: Testing Software for Discrimination

This paper defines software fairness and discrimination and develops a testing-based method for measuring if and how much software discriminates, focusing on causality in discriminatory behavior. Evidence of software discrimination has been found in modern software systems that recommend criminal sentences, grant access to financial products, and determine who is allowed to participate in promotions. Our approach, Themis, generates efficient test suites to measure discrimination. Given a schema describing valid system inputs, Themis generates discrimination tests automatically and does not require an oracle. We evaluate Themis on 20 software systems, 12 of which come from prior work with explicit focus on avoiding discrimination. We find that (1) Themis is effective at discovering software discrimination, (2) state-of-the-art techniques for removing discrimination from algorithms fail in many situations, at times discriminating against as much as 98% of an input subdomain, (3) Themis optimizations are effective at producing efficient test suites for measuring discrimination, and (4) Themis is more efficient on systems that exhibit more discrimination. We thus demonstrate that fairness testing is a critical aspect of the software development cycle in domains with possible discrimination and provide initial tools for measuring software discrimination.Comment: Sainyam Galhotra, Yuriy Brun, and Alexandra Meliou. 2017. Fairness Testing: Testing Software for Discrimination. In Proceedings of 2017 11th Joint Meeting of the European Software Engineering Conference and the ACM SIGSOFT Symposium on the Foundations of Software Engineering (ESEC/FSE), Paderborn, Germany, September 4-8, 2017 (ESEC/FSE'17). https://doi.org/10.1145/3106237.3106277, ESEC/FSE, 201

A Phase Ib/II Study of WNT974 + Encorafenib + Cetuximab in Patients With BRAF V600E-Mutant KRAS Wild-Type Metastatic Colorectal Cancer

Cetuximab; Colorectal cancer; MetastaticCetuximab; Càncer de còlon; MetastàticCetuximab; Cáncer de colon; MetastásicoBackground WNT974 is a small molecule inhibitor of Wnt signaling that specifically inhibits porcupine O-acyltransferase. This phase Ib dose-­escalation study evaluated the maximum tolerated dose of WNT974 in combination with encorafenib and cetuximab in patients with BRAF V600E-mutant metastatic colorectal cancer with RNF43 mutations or RSPO fusions. Patients and Methods Patients received once-daily encorafenib and weekly cetuximab, in addition to once-daily WNT974, in sequential dosing cohorts. In the first cohort, patients received 10-mg WNT974 (COMBO10), which was reduced in subsequent cohorts to 7.5-mg (COMBO7.5) or 5-mg (COMBO5) after dose–limiting toxicities (DLTs) were observed. Primary endpoints were incidence of DLTs and exposure to WNT974 and encorafenib. Secondary endpoints were anti-tumor activity and safety. Results Twenty patients were enrolled (COMBO10, n = 4; COMBO7.5, n = 6; COMBO5, n = 10). DLTs were observed in 4 patients, including grade 3 hypercalcemia (COMBO10, n = 1; COMBO7.5, n = 1), grade 2 dysgeusia (COMBO10, n = 1), and lipase increased (COMBO10, n = 1). A high incidence of bone toxicities (n = 9) was reported, including rib fracture, spinal compression fracture, pathological fracture, foot fracture, hip fracture, and lumbar vertebral fracture. Serious adverse events were reported in 15 patients, most frequently bone fracture, hypercalcemia, and pleural effusion. The overall response rate was 10% and disease control rate 85%; most patients achieved stable disease as their best response. Conclusion Concerns surrounding the safety and lack of preliminary evidence of improved anti-tumor activity of WNT974 + encorafenib + cetuximab, compared with previous encorafenib + cetuximab data, ultimately led to study discontinuation. Phase II was not initiated. Trial registration ClinicalTrials.gov, NCT02278133This study was sponsored by Array BioPharma in collaboration with Novartis. Array BioPharma was acquired by Pfizer in July 2019. For V.K.M., this work was supported by the generous philanthropic contributions to the Khalifa Scholars Programs (from the Khalifa Bin Zayed Al Nahyan Foundation), the Advanced Scholar Program (from the CG Johnson Foundation), and the NIH/NCI (award number K12 CA088084)

The Predicted Properties of Helium-Enriched Globular Cluster Progenitors at High Redshift

Globular cluster progenitors may have been detected by \textit{HST}, and are predicted to be observable with \textit{JWST} and ground-based extremely-large telescopes with adaptive optics. This has the potential to elucidate the issue of globular cluster formation and the origins of significantly helium-enriched subpopulations, a problem in Galactic astronomy with no satisfactory theoretical solution. Given this context, we use model stellar tracks and isochrones to investigate the predicted observational properties of helium-enriched stellar populations in globular cluster progenitors. We find that, relative to helium-normal populations, helium-enriched (${\Delta}Y=+0.12$) stellar populations similar to those inferred in the most massive globular clusters, are expected, modulo some rapid fluctuations in the first $\sim$30 Myr, to be brighter and redder in the rest frame. At fixed age, stellar mass, and metallicity, a helium-enriched population is predicted to converge to being $\sim$0.40 mag brighter at $\lambda \approx 2.0\, {\mu}m$, and to be 0.30 mag redder in the \textit{JWST}-NIRCam colour $(F070W-F200W)$, and to actually be fainter for $\lambda \lesssim 0.50 \, {\mu}m$. Separately, we find that the time-integrated shift in ionizing radiation is a negligible $\sim 5\%$, though we show that the Lyman-$\alpha$ escape fraction could end up higher for helium-enriched stars.Comment: Accepted for publication in MNRAS on 13 May, 2020 Replaced to update some bibliographic informatio

Migration- and exercise-induced changes to flight muscle size in migratory birds and association with \u3cem\u3eIGF1\u3c/em\u3e and \u3cem\u3emyostatin\u3c/em\u3e mRNA expression

Seasonal adjustments to muscle size in migratory birds may result from preparatory physiological changes or responses to changed workloads. The mechanisms controlling these changes in size are poorly understood. We investigated some potential mediators of flight muscle size (myostatin and insulin-like growth factor, IGF1) in pectoralis muscles of wild wintering or migrating white-throated sparrows (Zonotrichia albicollis), captive white-throated sparrows that were photoperiod manipulated to be in a `wintering\u27 or `migratory\u27 (Zugunruhe) state, and captive European starlings (Sturnus vulgaris) that were either exercised for 2 weeks in a wind tunnel or untrained. Flight muscle size increased in photo-stimulated `migrants\u27 and in exercised starlings. Acute exercise but not long-term training caused increased expression of IGF1, but neither caused a change in expression of myostatin or its metalloprotease activator TLL1. Photo-stimulated `migrant\u27 sparrows demonstrated increased expression of both myostatin and IGF1, but wild sparrows exhibited no significant seasonal changes in expression of either myostatin or IGF1. Additionally, in both study species we describe several splice variants of myostatin that are shared with distantly related bird species. We demonstrate that their expression patterns are not different from those of the typical myostatin, suggesting that they have no functional importance and may be mistakes of the splicing machinery. We conclude that IGF1 is likely to be an important mediator of muscle phenotypic flexibility during acute exercise and during endogenous, seasonal preparation for migration. The role of myostatin is less clear, but its paradoxical increase in photo-stimulated `migrants\u27 may indicate a role in seasonal adjustments of protein turnover