HAT-P-42b and HAT-P-43b Boisse, I; Hartman, J D; Bakos, G A ...
Astronomy and astrophysics (Berlin),
10/2013, Letnik:
558
Journal Article
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Aims. We announce the discovery of two new transiting planets, and provide their accurate initial characterization. Methods. First identified from the HATNet wide-field photometric survey, these ...candidate transiting planets were then followed-up with a variety of photometric observations. Determining the planetary nature of the objects and characterizing the parameters of the systems were mainly done with the SOPHIE spectrograph at the 1.93 m telescope at OHP and the TRES spectrograph at the 1.5 m telescope at FLWO. Results. HAT-P-42b and HAT-P-43b are typical hot Jupiters on circular orbits around early-G/late-F main sequence host stars, with periods of 4.641878 + or - 0.000032 and 3.332687 + or - 0.000015 days, masses of 1.044 + or - 0.083 and 0.662 + or - 0.060 My, and radii of 1.280 + or - 0.153 and 1.28 super(+0.062) sub(-0.033RJ), respectively. These discoveries increase the sample of planets with measured mean densities, which are needed to constrain theories of planetary interiors and atmospheres. Moreover, their hosts are relatively bright (V < 13.5), which facilitates further follow-up studies.
Step-by-step (SBS) stair navigation is used by those with movement limitations or lower-limb prosthetics and by humanoid robots. Knowledge of biomechanical parameters for SBS gait, however, is ...limited. Inverted pendulum (IP) models used to assess dynamic stability have not been applied to SBS gait. This study examined the ability of the linear inverted pendulum (LIP) model and a closed-form, variable-height inverted pendulum (VHIP) model to predict capture-point (CP) stability in healthy adults executing a single stair climb. A second goal was to provide baseline kinematic and kinetic data for SBS gait. Twenty young adults executed a single step onto stairs of two heights, while attached marker positions and ground reaction forces were recorded. opensim software determined body kinematics and joint kinetics. Trials were analyzed with LIP and VHIP models, and the predicted CP compared to the actual center-of-pressure (CoP) on the stair. Lower-limb joint moments were larger than those reported for step-over-step (SOS) stair gait. Leading knee rather than trailing ankle was dominant. Center-of-mass (CoM) velocity peaked at push-off. The VHIP model accounted for only slightly more than half of the forward progression of the vertical projection of the CoM and was not better than LIP predictions. This suggests that IP models are limited in modeling SBS gait, likely due to large hip and knee moments. The results from this study may also provide target values and strategies to aid design of lower-limb prostheses and powered exoskeletons.
HAT-P-55b: A Hot Jupiter Transiting a Sun-Like Star Juncher, D; Buchhave, L A; Hartman, J D ...
Publications of the Astronomical Society of the Pacific,
09/2015, Letnik:
127, Številka:
955
Journal Article
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We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The planet orbits a V = 13.207 + or - 0.039 sun-like star with a mass of 1.013 + or - 0.037 Mmiddot in circle, a radius of ...1.011 + or - 0.036 Rmiddot in circle, and a metallicity of -0.03 + or - 0.08. The planet itself is a typical hot Jupiter with a period of 3.5852467 + or - 0.0000064 days, a mass of 0.582 + or - 0.056 MJ and a radius of 1.182 + or - 0.055 RJ. This discovery adds to the increasing sample of transiting planets with measured bulk densities, which is needed to put constraints on models of planetary structure and formation theories.
Contribution: This article measures the impact of a service-learning project in a first-year introduction to computing course on students' understanding of engineers' roles and responsibilities and ...their attitudes toward plastic pollution. Background: Service learning has been integrated into classrooms for many years, but its utilization in engineering courses is lacking. Furthermore, plastic pollution is a complex and multidisciplinary problem that requires social, political, environmental, and engineering solutions. This work provides a quantitative assessment on whether service learning through a litter pickup project impacts students' views of the role of engineers in solving complex sociotechnical problems. Research Questions: 1) How does service learning change students' perception of an engineer's role in solving sociotechnical problems? and 2) how can service learning be used to increase students' environmental awareness and action? Methodology: Surveys were administered to students before and after their participation in a service-learning project. The study was conducted across five sections of an introduction to a computer programming course that is required of first-year civil, electrical, and mechanical engineering students. Findings: After the service-learning project, students were more likely to agree that engineers have the skills, knowledge, and responsibility to solve societal problems. Students also demonstrated a more holistic understanding of plastic pollution and reported changes in their waste reduction behaviors.
Abstract Following a balance perturbation, a stepping response is commonly used to regain support, and the distance of the recovery step can vary. To date, no other studies have examined joint ...kinetics in young and old adults during increasing step distances, when participants are required to bring their rear foot forward. Therefore, the purpose of this study was to examine age-related differences in joint kinetics with increasing step distance. Twenty young and 20 old adults completed the study. Participants completed a step starting from double support, at an initial distance equal to the individual's average step length. The distance was increased by 10% body height until an unsuccessful attempt. A one-way, repeated measures ANOVA was used to determine the effects of age on joint kinetics during the maximum step distance. A two-way, repeated measures, mixed model ANOVA was used to determine the effects of age, step distance, and their interaction on joint kinetics during the first three step distances for all participants. Young adults completed a significantly longer step than old adults. During the maximum step, in general, kinetic measures were greater in the young than in the old. As step distance increased, all but one kinetic measure increased for both young and old adults. This study has shown the ability to discriminate between young and old adults, and could potentially be used in the future to distinguish between fallers and non-fallers.
The orbital distribution of Kuiper Belt objects (KBOs) provides important tests of solar system evolution models. However, our understanding of this orbital distribution can be affected by many ...observational biases. An important but difficult to quantify bias results from tracking selection effects; KBOs are recovered or lost depending on assumptions made about their orbital elements when fitting the initial (short) observational arc. Quantitatively studying the effects and significance of this bias is generally difficult, because only the objects where the assumptions were correct are recovered and thus available to study 'the problem,' and because different observers use different assumptions and methods. We have used a sample of 38 KBOs that were discovered and tracked, bias-free, as part of the Canada-France Ecliptic Plane Survey to evaluate the potential for losing objects based on the two most common orbit and ephemeris prediction sources: the Minor Planet Center (MPC) and the Bernstein and Khushalani (BK) orbit fitting code. In both cases, we use early discovery and recovery astrometric measurements of the objects to generate ephemeris predictions that we then compare to later positional measurements; objects that have large differences between the predicted and actual positions would be unlikely to be recovered and are thus considered 'lost.' We find systematic differences in the orbit distributions which would result from using the two orbit-fitting procedures. In our sample, the MPC-derived orbit solutions lost slightly fewer objects (five out of 38) due to large ephemeris errors at one year recovery, but the objects which were lost belonged to more 'unusual' orbits such as scattering disk objects or objects with semimajor axes interior to the 3:2 resonance. Using the BK code, more objects (seven out of 38) would have been lost due to ephemeris errors, but the lost objects came from a range of orbital regions, primarily the classical belt region. We also compare the accuracy of orbits calculated from one year arcs against orbits calculated from multiple years of observations and find that two-opposition orbits without additional observations acquired at least two months from opposition are unreliable for dynamical modeling.
A Search for Satellites around Ceres Bieryla, A; Parker, J. Wm; Young, E. F ...
The Astronomical journal,
06/2011, Letnik:
141, Številka:
6
Journal Article
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We conducted a satellite search around the dwarf planet 1 Ceres using Hubble Space Telescope and ground-based Palomar data. No candidate objects were found orbiting Ceres in its entire stability ...region down to ~500 km from the surface of Ceres. Assuming a satellite would have the same albedo as Ceres, which has a visual geometric albedo of 0.07-0.10, our detection limit is sensitive to satellites larger than 1-2 km in diameter.
Abstract The goal of this study was to determine if practicing recovery from a simulated trip improved the ability of older adults to recover from an actual trip. Twelve healthy older adults ranging ...in age from 63 to 83 years were randomly assigned to either a control or an experimental group. Each group performed one trip before and one trip after an intervention. The experimental group received trip recovery training on a modified treadmill while the control group walked on a treadmill for 15 min. Compared to the control group, the experimental group showed greater reduction in maximum trunk angle ( p = 0.027) and time to maximum trunk angle ( p = 0.043), as well as increased minimum hip height ( p = 0.020). Although the results showed beneficial effects of trip recovery training on actual trip recovery, future studies should explore the ability to retain improvements over extended periods.
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