Solar sailing - mission opportunities and innovative technology demonstration

Solar sailing is a unique and elegant form of propulsion that transcends reliance on reaction mass. Rather than carrying propellant, solar sails acquire momentum from photons, the quantum packets of energy from which sunlight is composed. In addition, since solar sails are not limited by reaction mass, they can provide continual acceleration, limited only by the lifetime of the sail film in the space environment. Therefore, solar sails can expand the envelope of possible missions, enabling new high-energy mission concepts that are essentially impossible with conventional reaction propulsion, and enhancing current mission concepts by lowering launch mass and reducing trip times

Collecting cometary soil samples? Development of the ROSETTA sample acquisition system

In the reference scenario of the ROSETTA CNRS mission, the Sample Acquisition System is mounted on the Comet Lander. Its tasks are to acquire three kinds of cometary samples and to transfer them to the Earth Return Capsule. Operations are to be performed in vacuum and microgravity, on a probably rough and dusty surface, in a largely unknown material, at temperatures in the order of 100 K. The concept and operation of the Sample Acquisition System are presented. The design of the prototype corer and surface sampling tool, and of the equipment for testing them at cryogenic temperatures in ambient conditions and in vacuum in various materials representing cometary soil, are described. Results of recent preliminary tests performed in low temperature thermal vacuum in a cometary analog ice-dust mixture are provided

Morphology control of zinc oxide films via polysaccharide-mediated, low temperature, chemical bath deposition

In this study we present a three-step process for the low-temperature chemical bath deposition of crystalline ZnO films on glass substrates. The process consists of a seeding step followed by two chemical bath deposition steps. In the second step (the first of the two bath deposition steps), a natural polysaccharide, namely hyaluronic acid, is used to manipulate the morphology of the films. Previous experiments revealed a strong influence of this polysaccharide on the formation of zinc oxide crystallites. The present work aims to transfer this gained knowledge to the formation of zinc oxide films. The influence of hyaluronic acid and the time of its addition on the morphology of the resulting ZnO film were investigated. By meticulous adjustment of the parameters in this step, the film morphology can be tailored to provide an optimal growth platform for the third step (a subsequent chemical bath deposition step). In this step, the film is covered by a dense layer of ZnO. This optimized procedure leads to ZnO films with a very high electrical conductivity, opening up interesting possibilities for applications of such films. The films were characterized by means of electron microscopy, X-ray diffraction and measurements of the electrical conductivity.BMB

Dynamics of Laterally Propagating Flames in X-Ray Bursts. I. Burning Front Structure

We investigate the structure of laterally propagating flames through the highly stratified burning layer in an X-ray burst. Two-dimensional hydrodynamics simulations of flame propagation are performed through a rotating plane-parallel atmosphere, exploring the structure of the flame. We discuss the approximations needed to capture the length and timescales at play in an X-ray burst and describe the flame acceleration observed. Our studies complement other multidimensional studies of burning in X-ray bursts

Nonlinear dynamic analysis of heavy timber frame structures including passive damping devices

Engineering analysis of heavy timber structures under dynamic loads is generally lacking. Some literature suggests that heavy timber structures are stiffer than expected, but popular engineering opinion is to the contrary. In addition, prior research has shown that passive friction dampers can be used in timber structures for the intended purpose of increasing energy dissipation under seismic loadings. This study was conducted based on the hypothesis that heavy timber structures require bracing for seismic design and further that heavy timber performance under seismic loads will benefit from the addition of passive dampers. A computational study was designed to assess the performance of a two-dimensional model heavy timber structure when it is subjected to a seismic ground motion. Five building systems were included in the investigation; all were two story, single bay timber frames with 1-percent inherent material damping. The frames were differentiated by connection characteristics, the presence or absence of bracing, and the presence or absence of friction damper devices. The five building systems were: (1) moment-resisting frame (rigid connections, no bracing); (2) semi-rigid frame (semi-rigid connections, no bracing); (3) pinned braced-frame (pinned connections, concentric braces); (4) braced damped pinned-frame (pinned connections, cross braces with dampers); (5) semi-rigid damped frame (semi-rigid connections, concentric bracing with dampers). By subjecting these five structural configurations to the same ground motion, the effects of the connection rigidity, bracing, and dampers can be resolved as measured by story drift and member forces. The ground motion used was a corrected, unscaled, USGS Loma Prieta record with maximum acceleration of 1.05 g. The study frame was designed with access floor loading with computer use for a geographic location near San Francisco following the Uniform Building Code and the National Design Specification for Wood Construction. Beams and columns were glulam. The semi-rigid connections were designed as a dowel circle connection following DIN 1052, which is widely used in Europe. The software used for the investigation was DRAIN-2DX. Semi-rigid connection behavior was implemented using the Florence Model. The DRAIN-2DX software does not have a dedicated damper element. A damper element would produce a rectangular displacement-force hysteresis when subjected to a fully reversed cyclic load; the key features of this hysteresis behavior are brace stiffness followed by nearly zero stiffness at a defined force. A brace-damper superelement was created by using two compression/tension link elements in parallel with an inelastic bar element. This combination of elements produced the necessary behaviors, and the performance was verified in a single story, single bay frame subjected to a piecewise forcing function and demonstrated in a two story, one bay timber structure. The results of the analyses for the five building systems are specific to the Loma Prieta seismic ground motions. The semi-rigid moment-resisting frame remained within allowable drift limits, which suggests that the dowel circle connection produces satisfactory moment resistance. The braced pinned-frame and the braced-damped, pinned and semi-rigid frames responded similarly to each other because the large cross-section timber brace in the low rise, low mass system results in an extremely stiff structure. These structures are so stiff that the damper does not function. Evidence suggests that a rotational damper may be functional in semi-rigid connections of unbraced timber frames, but computational development of the rotational damper is needed

Additive drug-specific and sex-specific risks associated with co-use of marijuana and tobacco during pregnancy: Evidence from 3 recent developmental cohorts (2003-2015).

BACKGROUND: Methodologic challenges related to the concomitant use (co-use) of substances and changes in policy and potency of marijuana contribute to ongoing uncertainty about risks to fetal neurodevelopment associated with prenatal marijuana use. In this study, we examined two biomarkers of fetal neurodevelopmental risk-birth weight and length of gestation-associated with prenatal marijuana use, independent of tobacco (TOB), alcohol (ALC), other drug use (OTH), and socioeconomic risk (SES), in a pooled sample (N = 1191) derived from 3 recent developmental cohorts (2003-2015) with state-of-the-art substance use measures. We examined differential associations by infant sex, and multiplicative effects associated with co-use of MJ and TOB. METHODS: Participants were mother-infant dyads with complete data on all study variables derived from Growing Up Healthy (n = 251), Behavior and Mood in Babies and Mothers (Cohorts 1 and 2; n = 315), and the Early Growth and Development Study (N = 625). We estimated direct effects on birth weight and length of gestation associated with MJ, TOB, and co-use (MJ x TOB), using linear regression analysis in the full sample, and in male (n = 654) and female (n = 537) infants, separately. RESULTS: Mean birth weight and length of gestation were 3277 g (SD = 543) and 37.8 weeks (SD = 2.0), respectively. Rates of prenatal use were as follows: any use, n = 748 (62.8%); MJ use, n = 273 (22.9%); TOB use, n = 608 (51.0%); co-use of MJ and TOB, n = 230 (19.3%); ALC use, n = 464 (39.0%); and OTH use n = 115 (9.7%.) For all infants, unique effects on birth weight were observed for any MJ use [B(SE) = -84.367(38.271), 95% C.I. -159.453 to -9.281, p = .028], any TOB use [B(SE) = -0.99.416(34.418), 95% C.I. -166.942 to -31.889, p = .004], and each cigarette/day in mean TOB use [B(SE) = -12.233(3.427), 95% C.I. -18.995 to -5.510, p \u3c .001]. Additional effects of co-use on birth weight, beyond these drug-specific effects, were not supported. In analyses stratified by sex, while TOB use was associated with lower birth weight in both sexes, MJ use during pregnancy was associated with lower birth weight of male infants [B(SE) = -153.1 (54.20); 95% C.I. -259.5 to -46.7, p = .005], but not female infants [B(SE) = 8.3(53.1), 95% C.I. -96.024 to 112.551, p = .876]. TOB, MJ, and their co-use were not associated with length of gestation. CONCLUSIONS: In this sample, intrauterine co-exposure to MJ and TOB was associated with an estimated 18% reduction in birth weight not attributable to earlier delivery, exposure to ALC or OTH drugs, nor to maternal SES. We found evidence for greater susceptibility of male fetuses to any prenatal MJ exposure. Examination of dose-dependence in relationships found in this study, using continuous measures of exposure, is an important next step. Finally, we underscore the need to consider (a) the potential moderating influence of fetal sex on exposure-related neurodevelopmental risks; and (b) the importance of quantifying expressions of risk through subtle alterations, rather than dichotomous outcomes