646 research outputs found
Rotatable non-circular forebody flow controller
The invention is a rotatable, non-circular forebody flow controller. The apparatus comprises a small geometric device located at a nose of a forebody of an aircraft and a non-circular cross-sectional area that extends toward the apex of the aircraft. The device is symmetrical about a reference plane and preferably attaches to an axle which in turn attaches to a rotating motor. The motor rotates the device about an axis of rotation. Preferably, a control unit connected to an aircraft flight control computer signals to the rotating motor the proper rotational positioning of the geometric device
The complexities of text recycling in professional scientific discourse and implications for plagiarism prevention in higher education
Within higher education, guidelines for plagiarism almost always state that whenever a writer uses the exact words from a source, that material must be identified by quotation marks or block indentation, and the source of the reused material must be identified and attributed to the source. Nevertheless, text recycling--the unacknowledged reuse of previously published material—is common practice in STEM fields within the world of professional practice. Further complicating matters, the rise of online plagiarism detection tools by journals in recent years has spurred confusion and debate about the practice of text recycling even in the scientific community—as a quick web search for “text recycling” AND “self-plagiarism” reveals. Depending on what you happen to read, the practice is represented as unavoidable, shameful or useful. Although scholars of plagiarism have repeatedly made the case that plagiarism is a complex, contextually-situated matter, the practice of text recycling remains largely invisible--from writing textbooks to library research guides. The result is that students are left largely on their own to negotiate the complicated intersection of school and professional norms. This talk will (1) describe the conventions and debates related to text recycling, (2) explain the challenges faced by students, teachers and librarians, and (3) offer ideas for addressing text recycling in the academic setting
XC-35 Gust Research Project Characteristics of Vertical Drafts and Associated Vertical Gust Velocities Within Convective Type Clouds
XC-35 gust research project preliminary analysis of the lateral distribution of gust velocity along the span of an airplane
Mineralogy and Surface Composition of Asteroids
Methods to constrain the surface mineralogy of asteroids have seen
considerable development during the last decade with advancement in laboratory
spectral calibrations and validation of our interpretive methodologies by
spacecraft rendezvous missions. This has enabled the accurate identification of
several meteorite parent bodies in the main asteroid belt and helped constrain
the mineral chemistries and abundances in ordinary chondrites and basaltic
achondrites. With better quantification of spectral effects due to temperature,
phase angle, and grain size, systematic discrepancies due to non-compositional
factors can now be virtually eliminated for mafic silicate-bearing asteroids.
Interpretation of spectrally featureless asteroids remains a challenge. This
paper presents a review of all mineralogical interpretive tools currently in
use and outlines procedures for their application.Comment: Chapter to appear in the Space Science Series Book: Asteroids IV, 51
pages, 7 figures, 2 table
Unexpected D-type Interlopers in the Inner Main Belt
Very red featureless asteroids (spectroscopic D-types) are expected to have
formed in the outer solar system far from the sun. They comprise the majority
of asteroids in the Jupiter Trojan population, and are also commonly found in
the outer main belt and among Hildas. The first evidence for D-types in the
inner and middle parts of the main belt was seen in the Sloan Digital Sky
Survey (SDSS). Here we report follow-up observations of SDSS D-type candidates
in the near-infrared. Based on follow up observations of 13 SDSS D-type
candidates, we find a ~20% positive confirmation rate. Known inner belt D-types
range in diameter from roughly 7 to 30 kilometers. Based on these detections we
estimate there are ~100 inner belt D-types with diameters between 2.5 and 20km.
The lower and upper limits for total mass of inner belt D-types is 2x
kg to 2x kg which represents 0.01% to 0.1% of the mass of the inner
belt. The inner belt D-types have albedos at or above the upper end typical for
D-types which raises the question as to whether these inner belt bodies
represent only a subset of D-types, they have been altered by external factors
such as weathering processes, or if they are compositionally distinct from
other D-types. All D-types and candidates have diameters less than 30km, yet
there is no obvious parent body in the inner belt. Dynamical models have yet to
show how D-types originating from the outer solar system could penetrate into
the inner reaches of the Main Belt under current scenarios of planet formation
and subsequent Yarkovsky drift.Comment: 16 pages, 3 figures, 4 tables -- accepted for publication in Icaru
The effect of high pressure on the NMDA receptor: molecular dynamics simulations
Professional divers exposed to ambient pressures above 11 bar develop the high pressure neurological syndrome (HPNS), manifesting as central nervous system (CNS) hyperexcitability, motor disturbances, sensory impairment, and cognitive deficits. The glutamate-type N-methyl-D-aspartate receptor (NMDAR) has been implicated in the CNS hyperexcitability of HPNS. NMDARs containing different subunits exhibited varying degrees of increased/decreased current at high pressure. The mechanisms underlying this phenomenon remain unclear. We performed 100 ns molecular dynamics (MD) simulations of the NMDAR structure embedded in a dioleoylphosphatidylcholine (DOPC) lipid bilayer solvated in water at 1 bar, hydrostatic 25 bar, and in helium at 25 bar. MD simulations showed that in contrast to hydrostatic pressure, high pressure helium causes substantial distortion of the DOPC membrane due to its accumulation between the two monolayers: reduction of the Sn-1 and Sn-2 DOPC chains and helium-dependent dehydration of the NMDAR pore. Further analysis of important regions of the NMDAR protein such as pore surface (M2 α-helix), Mg2+ binding site, and TMD-M4 α-helix revealed significant effects of helium. In contrast with previous models, these and our earlier results suggest that high pressure helium, not hydrostatic pressure per se, alters the receptor tertiary structure via protein-lipid interactions. Helium in divers’ breathing mixtures may partially contribute to HPNS symptoms. © 2019, The Author(s).The Oak Ridge Leadership Computational Facility (OLCF) at Oak Ridge National Laboratory provided access to the Titan supercomputer. The authors wish to thank Mr. Bogdan Iaparov for calculating the DOPC order parameters, Veronika Bikova and Anastasia Bazhutina for molecular volume and RDF calculations. Y.M. was partly supported by UrFU Competitiveness Enhancement Program (agreement 02.A03.21.0006)
Rotational properties of the Haumea family members and candidates: Short-term variability
Haumea is one of the most interesting and intriguing transneptunian objects
(TNOs). It is a large, bright, fast rotator, and its spectrum indicates nearly
pure water ice on the surface. It has at least two satellites and a dynamically
related family of more than ten TNOs with very similar proper orbital
parameters and similar surface properties. The Haumean family is the only one
currently known in the transneptunian belt. Various models have been proposed
but the formation of the family remains poorly understood. In this work, we
have investigated the rotational properties of the family members and
unconfirmed family candidates with short-term variability studies, and report
the most complete review to date. We present results based on five years of
observations and report the short-term variability of five family members, and
seven candidates. The mean rotational periods, from Maxwellian fits to the
frequency distributions, are 6.27+/-1.19 h for the confirmed family members,
6.44+/-1.16 h for the candidates, and 7.65+/-0.54 h for other TNOs (without
relation to the family). According to our study, there is a suggestion that
Haumea family members rotate faster than other TNOs, however, the sample of
family member is still too limited for a secure conclusion. We also highlight
the fast rotation of 2002 GH32. This object has a 0.36+/-0.02 mag amplitude
lightcurve and a rotational period of about 3.98 h. Assuming 2002 GH32 is a
triaxial object in hydrostatic equilibrium, we derive a lower limit to the
density of 2.56 g cm^-3. This density is similar to Haumea's and much more
dense than other small TNO densities.Comment: Accepted for publication, A
The Effect of Lunar-like Satellites on the Orbital Infrared Light Curves of Earth-analog Planets
We investigate the influence of lunar-like satellites on the infrared orbital
light curves of Earth-analog extra-solar planets. Such light curves will be
obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as
a consequence of repeat observations to confirm the companion status of a
putative planet. We use an energy balance model to calculate disk-averaged
infrared (bolometric) fluxes from planet-satellite systems over a full orbital
period (one year). The satellites are assumed to lack an atmosphere, have a low
thermal inertia like that of the Moon and span a range of plausible radii. The
planets are assumed to have thermal and orbital properties that mimic those of
the Earth while their obliquities and orbital longitudes of inferior
conjunction remain free parameters. Even if the gross thermal properties of the
planet can be independently constrained (e.g. via spectroscopy or
visible-wavelength detection of specular glint from a surface ocean) only the
largest (approximately Mars-size) lunar-like satellites can be detected by
light curve data from a TPF-like instrument (i.e. one that achieves a
photometric signal-to-noise of 10-20 at infrared wavelengths). Non-detection of
a lunar-like satellite can obfuscate the interpretation of a given system's
infrared light curve so that it may resemble a single planet with high
obliquity, different orbital longitude of vernal equinox relative to inferior
conjunction and in some cases drastically different thermal characteristics. If
the thermal properties of the planet are not independently established then the
presence of a lunar-like satellite cannot be inferred from infrared data, thus
demonstrating that photometric light curves alone can only be used for
preliminary study of extra-solar Earth-like planets.Comment: 34 pages, 7 figures, accepted to Astrobiolog
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