11,863 research outputs found
The economics of financial privacy : to opt out or to opt in?
Gramm-Leach-Bliley Act ; Financial services industry - Law and legislation
Building a Bird: Musculoskeletal Modeling and Simulation of Wing-Assisted Incline Running during Avian Ontogeny
Flapping flight is the most power-demanding mode of locomotion, associated with a suite of anatomical specializations in extant adult birds. In contrast, many developing birds use their forelimbs to negotiate environments long before acquiring “flight adaptations,” recruiting their developing wings to continuously enhance leg performance and, in some cases, fly. How does anatomical development influence these locomotor behaviors? Isolating morphological contributions to wing performance is extremely challenging using purely empirical approaches. However, musculoskeletal modeling and simulation techniques can incorporate empirical data to explicitly examine the functional consequences of changing morphology by manipulating anatomical parameters individually and estimating their effects on locomotion. To assess how ontogenetic changes in anatomy affect locomotor capacity, we combined existing empirical data on muscle morphology, skeletal kinematics, and aerodynamic force production with advanced biomechanical modeling and simulation techniques to analyze the ontogeny of pectoral limb function in a precocial ground bird (Alectoris chukar). Simulations of wing-assisted incline running (WAIR) using these newly developed musculoskeletal models collectively suggest that immature birds have excess muscle capacity and are limited more by feather morphology, possibly because feathers grow more quickly and have a different style of growth than bones and muscles. These results provide critical information about the ontogeny and evolution of avian locomotion by (i) establishing how muscular and aerodynamic forces interface with the skeletal system to generate movement in morphing juvenile birds, and (ii) providing a benchmark to inform biomechanical modeling and simulation of other locomotor behaviors, both across extant species and among extinct theropod dinosaurs
An Investigation of the Ability to Recover from Transients Following Failures for Single-Pilot Rotorcraft
A moving-base simulation was conducted to investigate a pilot's ability to recover from transients following single-axis hard-over failures of the flight-control system. The investigation was performed in conjunction with a host simulation that examined the influence of control modes on a single pilot's ability to perform various mission elements under high-workload conditions. The NASA Ames large-amplitude-motion Vertical Motion Simulator (VMS) was utilized, and the experimental variables were the failure axis, the severity of the failure, and the airspeed at which the failure occurred. Other factors, such as pilot workload and terrain and obstacle proximity at the time of failure, were kept as constant as possible within the framework of the host simulation task scenarios. No explicit failure warnings were presented to the pilot. Data from the experiment are shown, and pilot ratings are compared with the proposed handling-qualities requirements for military rotorcraft. Results indicate that the current proposed failure transient requirements may need revision
Negative 4-Probe Conductances of Mesoscopic Superconducting Wires
We analyze the longitudinal 4-probe conductance of mesoscopic normal and
superconducting wires and predict that in the superconducting case, large
negative values can arise for both the weakly disordered and localized regimes.
This contrasts sharply with the behaviour of the longitudinal 4-probe
conductance of normal wires, which in the localized limit is always
exponentially small and positive.Comment: Latex, 3 figures available on request to [email protected]
(Simon Robinson
Recommended from our members
Cousins Photometry and Temperatures for the Hyades, Coma, NGC 752, Praesepe, and M67
In this paper, new Cousins VRI data are presented for NGC 752 and Praesepe, and new and extant data are combined into an augmented database for M67. For those three clusters, catalogs containing Cousins VRI photometry, reddening-corrected values of (V -K)(J), and temperatures are produced. The same is done for Coma by using both previously published and newly derived Cousins photometry. An extant set of catalogs for the Hyades is updated to include V magnitudes and values of (R -I)(C) that were published after the original catalogs appeared. Finally, M67 V magnitudes published previously by Sandquist are corrected for an effect that depends on location on the face of the cluster. The corrected data and values of (V -I)(C) given by Sandquist are then set out in a supplementary catalog. Data files containing all of these catalogs are deposited in the CDS archives. To assess the quality of the data in the catalogs, the consistency of extant Cousins VRI databases is tested by performing analyses with the following features: (1) quantities as small as a few millimags are regarded as meaningful; (2) statistical analysis is applied; (3) no use is made of data other than VRI measurements and comparable results; (4) no inferences are drawn from color-magnitude comparisons; (5) pertinent data that have not been included previously are analyzed; and (6) results based on direct comparisons of stellar groups at the telescope are featured. In this way, it is found that our updated M67 color data and those of Sandquist are on the E region zero point. In contrast, values of (V -I)(C) from Montgomery and collaborators are found to be too red by 27 +/- 3 mmag, with an even larger offset being likely for unpublished data from Richer and his collaborators. Zero-point tests of our Cousins VRI colors for Coma, Praesepe, and NGC 752 are also satisfactory. Scale factor tests of the M67 colors are performed, and a likely scale factor error in the Montgomery et al. colors is found. However, it appears at present that the scale factors of our M67 colors and those of Sandquist are satisfactory. For the most part, zero-point tests of the assembled V magnitudes are also satisfactory, although it is found that further work on the V magnitudes for Praesepe and M67 would be useful. To put these results in perspective, it is pointed out that photometric tests that are satisfactory at the few-millimag level have been published for some two decades and so are not appearing for the first time in this paper.Astronom
Supernova Resonance-Scattering Profiles in the Presence of External Illumination
We discuss a simple model for the formation of a supernova spectral line by
resonance scattering in the presence of external illumination of the
line-forming region by light from circumstellar interaction (toplighting). The
simple model provides a clear understanding of the most conspicuous toplighting
effect: a rescaling or, as we prefer, a ``muting'' of the line profile relative
to the continuum. This effect would be present in more realistic models, but
would be harder to isolate. An analytic expression for a muting factor for a
P-Cygni line is derived that depends on the ratio E of the toplighting specific
intensity to the specific intensity from the supernova photosphere. If E<1, the
line profile is reduced in scale or ``muted''. If E=1, the line profile
vanishes altogether. If E>1, the line profile flips vertically: then having an
absorption component near the observer-frame line center wavelength and a
blueshifted emission component.Comment: accepted for publication in PAS
African American Students\u27 Perceptions of Influential Factors for Attendance in Doctoral Psychology
This study explores African American undergraduate students’ perceptions of factors influencing their decision to attend doctoral programs in psychology. There is a scarcity of literature examining perceptions held by specific minority groups in regard to influential factors used to make a significant step toward their career development. Eight undergraduate students interested in pursuing a doctoral degree in psychology were interviewed. A semi-structured interview and two paper-pencil measures were used. Interviews were analyzed utilizing the consensual qualitative research (CQR) method. The following themes emerged: reasons for pursuing a doctoral degree, navigating the application process, factors influencing interest in psychology, perception of a program’s commitment to diversity, importance of ethnic minority representation in a program, financial concerns, family view of psychology, most important factor for attendance, and prior school experiences outside of psychology. The study found that issues related to African American representation and research, as well as the presence of financial aid, are highly relevant in students’ evaluation of which doctoral programs they prefer to attend. This information will pave the way for further studies focusing on how to increase the number of African American students in doctoral programs around the country
Variability in the extreme helium star LSS 5121
We report a photometric and spectroscopic study of the hot extreme helium
star LSS 5121. We found photometric variability, but no period was evident in
its periodogram. This is consistent with the previous proposal, based on
spectral line variations, that LSS 5121 is a non-radial pulsator similar to
other hot extreme helium stars.Comment: 5 pages, 6 figure
Medical Implications of Space Radiation Exposure Due to Low Altitude Polar Orbits
Space radiation research has progressed rapidly in recent years, but there
remain large uncertainties in predicting and extrapolating biological responses
to humans. Exposure to cosmic radiation and Solar Particle Events may pose a
critical health risk to future spaceflight crews and can have a serious impact
to all biomedical aspects of space exploration. The relatively minimal
shielding of the cancelled 1960's Manned Orbiting Laboratory program's space
vehicle and the high inclination polar orbits would have left the crew
susceptible to high exposures of cosmic radiation and high dose-rate SPEs that
are mostly unpredictable in frequency and intensity. In this study, we have
modeled the nominal and off-nominal radiation environment that a MOL-like
spacecraft vehicle would be exposed to during a 30-day mission using high
performance, multi-core computers. Projected doses from a historically large
SPE (e.g. the August 1972 solar event) have been analyzed in the context of the
MOL orbit profile, providing an opportunity to study its impact to crew health
and subsequent contingencies.It is reasonable to presume that future
commercial, government, and military spaceflight missions in low-Earth orbit
will have vehicles with similar shielding and orbital profiles. Studying the
impact of cosmic radiation to the mission's operational integrity and the
health of MOL crewmembers provides an excellent surrogate and case-study for
future commercial and military spaceflight missions.Comment: 6 pages, 4 figures, 2 table
- …