3,397 research outputs found
Array-based iterative measurements of SmKS travel times and their constraints on outermost core structure
Vigorous convection in Earth's outer core led to the suggestion that it is chemically homogeneous. However, there is increasing seismic evidence for structural complexities close to the outer core's upper and lower boundaries. Both body waves and normal mode data have been used to estimate a P wave velocity, V_p, at the top of the outer core (the Eâ layer), which is lower than that in the Preliminary Reference Earth Model. However, these low V_p models do not agree on the form of this velocity anomaly. One reason for this is the difficulty in retrieving and measuring SmKS arrival times. To address this issue, we propose a novel approach using data from seismic arrays to iteratively measure SmKS-SKKS-differential travel times. This approach extracts individual SmKS signal from mixed waveforms of the SmKS series, allowing us to reliably measure differential travel times. We successfully use this method to measure SmKS time delays from earthquakes in the FijiâTonga and Vanuatu subduction zones. SmKS time delays are measured by waveform cross correlation between SmKS and SKKS, and the crossâcorrelation coefficient allows us to access measurement quality. We also apply this iterative scheme to synthetic SmKS seismograms to investigate the 3âD mantle structure's effects. The mantle structure corrections are not negligible for our data, and neglecting them could bias the V_p estimation of uppermost outer core. After mantle structure corrections, we can still see substantial time delays of S3KS, S4KS, and S5KS, supporting a low V_p at the top of Earth's outer core
Iron testes: sperm mitochondria as a context for dissecting iron metabolism
A recent paper in BMC Developmental Biology reports that a mitochondrial iron importer is required for Drosophila male fertility and normal mitochondrial shaping in spermatids. This suggests that mitochondrial morphogenesis during insect spermatogenesis may be a useful new context in which to study iron metabolism
Slow light in molecular aggregates nanofilms
We study slow light performance of molecular aggregates arranged in nanofilms
by means of coherent population oscillations (CPO). The molecular cooperative
behavior inside the aggregate enhances the delay of input signals in the GHz
range in comparison with other CPO-based devices. Moreover, the problem of
residual absorption present in CPO processes, is removed. We also propose an
optical switch between different delays by exploiting the optical bistability
of these aggregates.Comment: 4 pages, 4 figure
Sport Mega-Events and Public Opposition: A Sociological Study of the London 2012 Olympics
This article examines the diverse forms of public opposition, protest, criticism, and complaint in the United Kingdom on the staging of the 2012 Olympic and Paralympic Games in London. Our discussion draws heavily on empirical research, primarily fieldwork and interviews in East London with local residents, opposition groups, business people, politicians, and other stakeholders. The article is separated into three main parts. First, we explore the setting and political?economic context for London 2012. The main Olympic setting?the London Borough of Newham?features very high levels of poverty and ethnic diversity. We argue that London 2012 represented a form of ?festival capitalism? that was part of a broader set of ?New Right two-step? policies in poor urban areas, involving initial Keynesian investment, followed by a deeper and far-reaching array of neo-liberal measures. Second, in the main part of the article, we identify and examine, in turn, six forms of public conflict, criticism, and complaint that centered on the Games, specifically national criticisms (e.g., on distribution of Olympic resources), local criticisms (e.g., on lack of jobs and business benefits), issue-specific campaigns (e.g., on the environment), ?glocal? protests against specific nations and sponsors (e.g., campaigns against BP, Dow, and Rio Tinto), neo-tribal transgressions and situationist spectacles (e.g., mass cycle rides near Olympic venues), and anti-Olympic forums and demonstrations (e.g., critical web sites, multi-group marches). Third, we set out briefly the importance of conducting research into critics and opponents of sport mega-events, and discuss different arguments on how the social impact of protest movements might have been intensified at London 2012. The findings in this article may be extended to examine critical public responses to the hosting of other mega-events in different settings
Omega Oracle: forecasting estuarine carbonate weather
There are serious concerns about ecological, social, and economic impacts in the Pacific Northwest due to Ocean Acidification (OA). We built a system to predict aragonite saturation state (Ω) of seawater in Netarts Bay, Oregon based on large scale forcing parameters. An artificial neural network â trained against a continuous, multiyear monitoring record of carbonate chemistry â learns a regression estimate of Ω based on seasonality, tides, and wind conditions. This approach is agnostic to the details of the underlying chemical and biological processes offering a distinct modelling perspective. The result is a conceptually simpler and more strictly empirical parameterization and a model that is flexible in application due to dependence on only easily obtainable parameters. Forecast validation by a cross validation method indicates good prediction performance, particularly for the high frequency content of the Ω time series, over periods of stable wind forecasting. Our forecast model demonstrates that the complex temporal dynamics of carbonate chemistry within an estuary can emerge from forcing operating on longer timescales. This further elucidates the management and commercial value of this model; experimental work with calcifiers suggests the details of these high frequency chemical dynamics are critical to the magnitude of stress imposed. Lastly, these forecasts, deployed as a web application, can facilitate OA mitigation strategies by providing aquaculturists with real-time predictions for consideration in operational decisions. Numerous sites, including on the Salish Sea, are poised to soon have viable training data for application of this method. Broader deployment promises to enable comparison between sites and expansion of direct aquaculture and management applications. Expansion to other sites is expected to require altered explanatory variables but this exercise may itself yield insight. Relatedly, we note the potential of this approach to help constrain timescales and sources (natural and anthropogenic) of contributions to physiological OA stress
Detecting the Rise and Fall of 21 cm Fluctuations with the Murchison Widefield Array
We forecast the sensitivity with which the Murchison Widefield Array (MWA)
can measure the 21 cm power spectrum of cosmic hydrogen, using radiative
transfer simulations to model reionization and the 21 cm signal. The MWA is
sensitive to roughly a decade in scale (wavenumbers of k ~ 0.1 - 1 h Mpc^{-1}),
with foreground contamination precluding measurements on larger scales, and
thermal detector noise limiting the small scale sensitivity. This amounts
primarily to constraints on two numbers: the amplitude and slope of the 21 cm
power spectrum on the scales probed. We find, however, that the redshift
evolution in these quantities can yield important information about
reionization. Although the power spectrum differs substantially across
plausible models, a generic prediction is that the amplitude of the 21 cm power
spectrum on MWA scales peaks near the epoch when the intergalactic medium (IGM)
is ~ 50% ionized. Moreover, the slope of the 21 cm power spectrum on MWA scales
flattens as the ionization fraction increases and the sizes of the HII regions
grow. Considering detection sensitivity, we show that the optimal MWA antenna
configuration for power spectrum measurements would pack all 500 antenna tiles
as close as possible in a compact core. The MWA is sensitive enough in its
optimal configuration to measure redshift evolution in the slope and amplitude
of the 21 cm power spectrum. Detecting the characteristic redshift evolution of
our models will confirm that observed 21 cm fluctuations originate from the
IGM, and not from foregrounds, and provide an indirect constraint on the
volume-filling factor of HII regions during reionization. After two years of
observations under favorable conditions, the MWA can constrain the filling
factor at an epoch when ~ 0.5 to within roughly +/- 0.1 at 2-sigma.Comment: 14 pages, 9 figures, submitted to Ap
Elements of paradoxes in supply chain management literature: A systematic literature review
This study reports the results of a systematic literature review investigating paradoxes in supply chain management. This issue is important because supply chain practitioners frequently face paradoxes in industry with little direction provided in supply chain literature. Investigating the years 1997 through 2019, we identified 64 articles as the basis of our research containing a total of 68 unique paradoxes. In identifying the paradox elements (PEs), we adopted paradox theory (PT) as the base theoretical approach, which was utilized in only 7 of the articles. We employed contingency theory, institutional complexity theory, and complexity theory to support our findings. For each paradox, we also extracted and summarized managerial insights for practitioners. This study addresses the emergent needs of investigating paradoxes in the supply chain management domain to extend the use of PT and complementary theories that can aid practitioners in how to efficiently manage the paradoxes they encounter in industry
Dust masses of disks around 8 Brown Dwarfs and Very Low-Mass Stars in Upper Sco OB1 and Ophiuchus
We present the results of ALMA band 7 observations of dust and CO gas in the
disks around 7 objects with spectral types ranging between M5.5 and M7.5 in
Upper Scorpius OB1, and one M3 star in Ophiuchus. We detect unresolved
continuum emission in all but one source, and the CO J=3-2 line in two
sources. We constrain the dust and gas content of these systems using a grid of
models calculated with the radiative transfer code MCFOST, and find disk dust
masses between 0.1 and 1 M, suggesting that the stellar mass / disk
mass correlation can be extrapolated for brown dwarfs with masses as low as
0.05 M. The one disk in Upper Sco in which we detect CO emission, 2MASS
J15555600, is also the disk with warmest inner disk as traced by its H - [4.5]
photometric color. Using our radiative transfer grid, we extend the correlation
between stellar luminosity and mass-averaged disk dust temperature originally
derived for stellar mass objects to the brown dwarf regime to , applicable to spectral types
of M5 and later. This is slightly shallower than the relation for earlier
spectral type objects and yields warmer low-mass disks. The two prescriptions
cross at 0.27 L, corresponding to masses between 0.1 and 0.2 M
depending on age.Comment: 9 pages,6 figures, accepted to ApJ on 26/01/201
Formal Verification of a Geometry Algorithm: A Quest for Abstract Views and Symmetry in Coq Proofs
This extended abstract is about an effort to build a formal description of a
triangulation algorithm starting with a naive description of the algorithm
where triangles, edges, and triangulations are simply given as sets and the
most complex notions are those of boundary and separating edges. When
performing proofs about this algorithm, questions of symmetry appear and this
exposition attempts to give an account of how these symmetries can be handled.
All this work relies on formal developments made with Coq and the mathematical
components library
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