1,050 research outputs found
Abradable compressor and turbine seals, volume 2
The applications and advantages of abradable coatings as gas path seals in a general aviation turbofan engine were investigated. Abradable materials were evaluated for the high pressure radial compressor and the axial high and low pressure turbine shrouds
Abradable compressor and turbine seals, volume 1
The application and advantages of abradable coatings as gas-path seals in a general aviation turbine engine were evaluated for use on the high-pressure compressor, the high-pressure turbine, and the low-pressure turbine shrouds. Topics covered include: (1) the initial selection of candidate materials for interim full-scale engine testing; (2) interim engine testing of the initially selected materials and additional candidate materials; (3) the design of the component required to adapt the hardware to permit full-scale engine testing of the most promising materials; (4) finalization of the fabrication methods used in the manufacture of engine test hardware; and (5) the manufacture of the hardware necessary to support the final full-scale engine tests
Active current sheets and hot flow anomalies in Mercury's bow shock
Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities
interacting with collisionless bow shocks. They are typically formed when the
normal component of motional (convective) electric field points toward the
embedded current sheet on at least one of its sides. The core region of an HFA
contains hot and highly deflected ion flows and rather low and turbulent
magnetic field. In this paper, we report first observations of HFA-like events
at Mercury identified over a course of two planetary years. Using data from the
orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and
Ranging (MESSENGER) mission, we identify a representative ensemble of active
current sheets magnetically connected to Mercury's bow shock. We show that some
of these events exhibit unambiguous magnetic and particle signatures of HFAs
similar to those observed earlier at other planets, and present their key
physical characteristics. Our analysis suggests that Mercury's bow shock does
not only mediate the flow of supersonic solar wind plasma but also provides
conditions for local particle acceleration and heating as predicted by previous
numerical simulations. Together with earlier observations of HFA activity at
Earth, Venus and Saturn, our results confirm that hot flow anomalies are a
common property of planetary bow shocks, and show that the characteristic size
of these events is of the order of one planetary radius.Comment: 39 pages, 15 figures, 2 table
Statistically determined dispersion relations of magnetic field fluctuations in the terrestrial foreshock
We obtain dispersion relations of magnetic field fluctuations for two crossings of the terrestrial foreshock by Cluster spacecraft. These crossings cover plasma conditions that differ significantly in their plasma β and in the density of the reflected ion beam, but not in the properties of the encountered ion population, both showing shell-like distribution function. Dispersion relations are reconstructed using two-point instantaneous wave number estimations from pairs of Cluster spacecraft. The accessible range of wave vectors, limited by the available spacecraft separations, extends to ≈2 × 104 km. Results show multiple branches of dispersion relations, associated with different powers of magnetic field fluctuations. We find that sunward propagating fast magnetosonic waves and beam resonant modes are dominant for the high plasma β interval with a dense beam, while the dispersions of the interval with low beam density include Alfvén and fast magnetosonic modes propagating sunward and anti-sunward
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Spring School on Language, Music, and Cognition: Organizing Events in Time
The interdisciplinary spring school “Language, music, and cognition: Organizing events in time” was held from February 26 to March 2, 2018 at the Institute of Musicology of the University of Cologne. Language, speech, and music as events in time were explored from different perspectives including evolutionary biology, social cognition, developmental psychology, cognitive neuroscience of speech, language, and communication, as well as computational and biological approaches to language and music. There were 10 lectures, 4 workshops, and 1 student poster session.
Overall, the spring school investigated language and music as neurocognitive systems and focused on a mechanistic approach exploring the neural substrates underlying musical, linguistic, social, and emotional processes and behaviors. In particular, researchers approached questions concerning cognitive processes, computational procedures, and neural mechanisms underlying the temporal organization of language and music, mainly from two perspectives: one was concerned with syntax or structural representations of language and music as neurocognitive systems (i.e., an intrapersonal perspective), while the other emphasized social interaction and emotions in their communicative function (i.e., an interpersonal perspective). The spring school not only acted as a platform for knowledge transfer and exchange but also generated a number of important research questions as challenges for future investigations
ION ACCELERATION AT THE QUASI-PARALLEL BOW SHOCK: DECODING THE SIGNATURE OF INJECTION
Collisionless shocks are efficient particle accelerators. At Earth, ions with
energies exceeding 100 keV are seen upstream of the bow shock when the magnetic
geometry is quasi-parallel, and large-scale supernova remnant shocks can
accelerate ions into cosmic rays energies. This energization is attributed to
diffusive shock acceleration, however, for this process to become active the
ions must first be sufficiently energized. How and where this initial
acceleration takes place has been one of the key unresolved issues in shock
acceleration theory. Using Cluster spacecraft observations, we study the
signatures of ion reflection events in the turbulent transition layer upstream
of the terrestrial bow shock, and with the support of a hybrid simulation of
the shock, we show that these reflection signatures are characteristic of the
first step in the ion injection process. These reflection events develop in
particular in the region where the trailing edge of large-amplitude upstream
waves intercept the local shock ramp and the upstream magnetic field changes
from quasi-perpendicular to quasi-parallel. The dispersed ion velocity
signature observed can be attributed to a rapid succession of ion reflections
at this wave boundary. After the ions' initial interaction with the shock, they
flow upstream along the quasi-parallel magnetic field. Each subsequent wave
front in the upstream region will sweep the ions back toward the shock, where
they gain energy with each transition between the upstream and the shock wave
frames. Within three to five gyroperiods, some ions have gained enough parallel
velocity to escape upstream, thus completing the injection process.Comment: 30 pages, 10 figures. Accepted for publication in The Astrophysical
Journa
Frozen steady states in active systems
Even simple active systems can show a plethora of intriguing phenomena and
often we find complexity were we would have expected simplicity. One striking
example is the occurrence of a quiescent or absorbing state with frozen
fluctuations that at first sight seems to be impossible for active matter
driven by the incessant input of energy. While such states were reported for
externally driven systems through macroscopic shear or agitation, the
investigation of frozen active states in inherently active systems like
cytoskeletal suspensions or active gels is still at large. Using high density
motility assay experiments, we demonstrate that frozen steady states can arise
in active systems if active transport is coupled to growth processes. The
experiments are complemented by agent-based simulations which identify the
coupling between self-organization, growth and mechanical properties to be
responsible for the pattern formation process
The incidence of liver injury in Uyghur patients treated for TB in Xinjiang Uyghur autonomous region, China, and its association with hepatic enzyme polymorphisms nat2, cyp2e1, gstm1 and gstt1.
BACKGROUND AND OBJECTIVE: Of three first-line anti-tuberculosis (anti-TB) drugs, isoniazid is most commonly associated with hepatotoxicity. Differences in INH-induced toxicity have been attributed to genetic variability at several loci, NAT2, CYP2E1, GSTM1and GSTT1, that code for drug-metabolizing enzymes. This study evaluated whether the polymorphisms in these enzymes were associated with an increased risk of anti-TB drug-induced hepatitis in patients and could potentially be used to identify patients at risk of liver injury. METHODS AND DESIGN: In a cross-sectional study, 2244 tuberculosis patients were assessed two months after the start of treatment. Anti-TB drug-induced liver injury (ATLI) was defined as an ALT, AST or bilirubin value more than twice the upper limit of normal. NAT2, CYP2E1, GSTM1 and GSTT1 genotypes were determined using the PCR/ligase detection reaction assays. RESULTS: 2244 patients were evaluated, there were 89 cases of ATLI, a prevalence of 4% 9 patients (0.4%) had ALT levels more than 5 times the upper limit of normal. The prevalence of ATLI was greater among men than women, and there was a weak association with NAT2*5 genotypes, with ATLI more common among patients with the NAT2*5*CT genotype. The sensitivity of the CT genotype for identifying patients with ATLI was 42% and the positive predictive value 5.9%. CT ATLI was more common among slow acetylators (prevalence ratio 2.0 (95% CI 0.95,4.20) )compared to rapid acetylators. There was no evidence that ATLI was associated with CYP2E1 RsaIc1/c1genotype, CYP2E1 RsaIc1/c2 or c2/c2 genotypes, or GSTM1/GSTT1 null genotypes. CONCLUSIONS: In Xinjiang Uyghur TB patients, liver injury was associated with the genetic variant NAT2*5, however the genetic markers studied are unlikely to be useful for screening patients due to the low sensitivity and low positive predictive values for identifying persons at risk of liver injury
A Comparison of Stimulus Set Size on Tact Training for Children with Autism Spectrum Disorder
Previous studies on skill acquisition have taught targets in stimulus sets composed of different numbers of stimuli. Although the rationale for selection of a stimulus set size is not clear, the number of target stimuli trained within a set is a treatment decision for which there is limited empirical support. The current investigation compared the efficiency of tact training in 4 stimulus set sizes, each of which included 12 stimuli grouped into (a) 4 sets of 3 stimuli, (b) 3 sets of 4 stimuli, (c) 2 sets of 6 stimuli, and (d) 1 set of 12 stimuli. Results of all 4 participants with autism spectrum disorder show tact training with larger (i.e., 6 and 12) stimulus set sizes was more efficient than training with smaller (i.e., 3 and 4) stimulus set sizes
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