69 research outputs found
Structural Element Testing in Support of the Design of the NASA Composite Crew Module
In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center (NESC) to design, build, and test a full-scale Composite Crew Module (CCM). For the design and manufacturing of the CCM, the team adopted the building block approach where design and manufacturing risks were mitigated through manufacturing trials and structural testing at various levels of complexity. Following NASA's Structural Design Verification Requirements, a further objective was the verification of design analysis methods and the provision of design data for critical structural features. Test articles increasing in complexity from basic material characterization coupons through structural feature elements and large structural components, to full-scale structures were evaluated. This paper discusses only four elements tests three of which include joints and one that includes a tapering honeycomb core detail. For each test series included are specimen details, instrumentation, test results, a brief analysis description, test analysis correlation and conclusions
A fully 3-dimensional thermal model of a comet nucleus
A 3-D numerical model of comet nuclei is presented. An implicit numerical
scheme was developed for the thermal evolution of a spherical nucleus composed
of a mixture of ice and dust. The model was tested against analytical
solutions, simplified numerical solutions, and 1-D thermal evolution codes. The
3-D code was applied to comet 67P/Churyumov-Gerasimenko; surface temperature
maps and the internal thermal structure was obtained as function of depth,
longitude and hour angle. The effect of the spin axis tilt on the surface
temperature distribution was studied in detail. It was found that for small
tilt angles, relatively low temperatures may prevail on near-pole areas,
despite lateral heat conduction. A high-resolution run for a comet model of
67P/Churyumov-Gerasimenko with low tilt angle, allowing for crystallization of
amorphous ice, showed that the amorphous/crystalline ice boundary varies
significantly with depth as a function of cometary latitude.Comment: 19 pages, 10 figure
Magnetic fields in star forming systems (I): Idealized synthetic signatures of dust polarization and Zeeman splitting in filaments
We use the POLARIS radiative transport code to generate predictions of the
two main observables directly sensitive to the magnetic field morphology and
strength in filaments: dust polarization and gas Zeeman line splitting. We
simulate generic gas filaments with power-law density profiles assuming two
density-field strength dependencies, six different filament inclinations, and
nine distinct magnetic field morphologies, including helical, toroidal, and
warped magnetic field geometries. We present idealized spatially resolved dust
polarization and Zeeman-derived field strengths and directions maps. Under the
assumption that dust grains are aligned by radiative torques (RATs), dust
polarization traces the projected plane-of-the-sky magnetic field morphology.
Zeeman line splitting delivers simultaneously the intensity-weighted
line-of-sight field strength and direction. We show that linear dust
polarization alone is unable to uniquely constrain the 3D field morphology. We
demonstrate that these ambiguities are ameliorated or resolved with the
addition of the Zeeman directional information. Thus, observations of both the
dust polarization and Zeeman splitting together provide the most promising
means for obtaining constraints of the 3D magnetic field configuration. We find
that the Zeeman-derived field strengths are at least a factor of a few below
the input field strengths due to line-of-sight averaging through the filament
density gradient. Future observations of both dust polarization and Zeeman
splitting are essential for gaining insights into the role of magnetic fields
in star and cluster forming filaments.Comment: 16 pages, 11 figures, 1 tabl
Learning tone and attribution for financial text mining
Attribution bias refers to the tendency of people to attribute successes to their own abilities but failures to external factors. In a business context an internal factor might be the restructuring of the firm and an external factor might be an unfavourable change in exchange or interest rates. In accounting research, the presence of an attribution bias has been demonstrated for the narrative sections of the annual financial reports. Previous studies have applied manual content analysis to this problem but in this paper we present novel work to automate the analysis of attribution bias through using machine learning algorithms. Previous studies have only applied manual content analysis on a small scale to reveal such a bias in the narrative section of annual financial reports. In our work a group of experts in accounting and finance labelled and annotated a list of 32,449 sentences from a random sample of UK Preliminary Earning Announcements (PEAs) to allow us to examine whether sentences in PEAs contain internal or external attribution and which kinds of attributions are linked to positive or negative performance. We wished to examine whether human annotators could agree on coding this difficult task and whether Machine Learning (ML) could be applied reliably to replicate the coding process on a much larger scale. Our best machine learning algorithm correctly classified performance sentences with 70% accuracy and detected tone and attribution in financial PEAs with accuracy of 79%
Disentangling magnetic hardening and molecular spin chain contributions to exchange bias in ferromagnet/molecule bilayers
We performed SQUID and FMR magnetometry experiments to clarify the
relationship between two reported magnetic exchange effects arising from
interfacial spin-polarized charge transfer within ferromagnetic metal
(FM)/molecule bilayers: the magnetic hardening effect, and
spinterface-stabilized molecular spin chains. To disentangle these effects,
both of which can affect the FM magnetization reversal, we tuned the metal
phthalocyanine molecule central site's magnetic moment to selectively enhance
or suppress the formation of spin chains within the molecular film. We find
that both effects are distinct, and additive. In the process, we 1) extended
the list of FM/molecule candidate pairs that are known to generate magnetic
exchange effects, 2) experimentally confirmed the predicted increase in
anisotropy upon molecular adsorption; and 3) showed that spin chains within the
molecular film can enhance magnetic exchange. This magnetic ordering within the
organic layer implies a structural ordering. Thus, by distengangling the
magnetic hardening and exchange bias contributions, our results confirm, as an
echo to progress regarding inorganic spintronic tunnelling, that the milestone
of spintronic tunnelling across structurally ordered organic barriers has been
reached through previous magnetotransport experiments. This paves the way for
solid-state devices studies that exploit the quantum physical properties of
spin chains, notably through external stimuli.Comment: Non
Observational and Dynamical Characterization of Main-Belt Comet P/2010 R2 (La Sagra)
We present observations of comet-like main-belt object P/2010 R2 (La Sagra)
obtained by Pan-STARRS 1 and the Faulkes Telescope-North on Haleakala in
Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on
Mauna Kea, the Danish 1.54 m telescope at La Silla, and the Isaac Newton
Telescope on La Palma. An antisolar dust tail is observed from August 2010
through February 2011, while a dust trail aligned with the object's orbit plane
is also observed from December 2010 through August 2011. Assuming typical phase
darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag
between August 2010 and December 2010, suggesting that dust production is
ongoing over this period. These results strongly suggest that the observed
activity is cometary in nature (i.e., driven by the sublimation of volatile
material), and that P/La Sagra is therefore the most recent main-belt comet to
be discovered. We find an approximate absolute magnitude for the nucleus of
H_R=17.9+/-0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an
albedo of p=0.05. Using optical spectroscopy, we find no evidence of
sublimation products (i.e., gas emission), finding an upper limit CN production
rate of Q_CN<6x10^23 mol/s, from which we infer an H2O production rate of
Q_H2O<10^26 mol/s. Numerical simulations indicate that P/La Sagra is
dynamically stable for >100 Myr, suggesting that it is likely native to its
current location and that its composition is likely representative of other
objects in the same region of the main belt, though the relatively close
proximity of the 13:6 mean-motion resonance with Jupiter and the (3,-2,-1)
three-body mean-motion resonance with Jupiter and Saturn mean that dynamical
instability on larger timescales cannot be ruled out.Comment: 23 pages, 13 figures, accepted for publication in A
Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.
Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes
Ethanolic extract of Passiflora edulis Sims leaves inhibits protein glycation and restores the oxidative burst in diabetic rat macrophages after Candida albicans exposure
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