8,933 research outputs found
Seasonal and inter-annual temperature variability in the bottom waters over the western Black Sea shelf
Long-term changes in the state of the Bottom Shelf Water (BSW) on the Western shelf of the Black Sea are assessed using analysis of intra-seasonal and inter-annual temperature variations. For the purpose of this study the BSW is defined as such shelf water mass between the seabed and the upper mixed layer (bounded by the σθ = 14.2 isopycnal) which has limited ability to mix vertically with oxygen-rich surface waters during the warm season due to formation of a seasonal pycnocline. A long-term time series of temperature anomalies in the BSW is constructed from in-situ observations taken over the 2nd half of the 20th century. The BSW is shown to occupy nearly half of the shelf area during the summer stratification period (May–November).The results reveal a warm phase in the 1960s/70s, followed by a cold phase between 1985 and 1995 and a further warming after 1995. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter convection is well preserved over the following months in the deep sea, the signal of winter cooling in the BSW significantly reduces during the warm season. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. It is shown that temperature in the BSW is stronger correlated with the temperature of Cold Intermediate Waters (CIW) in the deep sea than with the severity of the previous winters, thus indicating that the isopycnal exchanges with the deep sea are more important for inter-annual/inter-decadal variability of the BSW on the western Black Sea shelf than effects of winter convection on the shelf itself
New Vector Boson Near the Z-pole and the Puzzle in Precision Electroweak Data
We show that a Z' with suppressed couplings to the electron compared to the
Z-boson, with couplings to the b-quark, and with a mass close to the mass of
the Z-boson, provides an excellent fit to forward-backward asymmetry of the
b-quark and R_b measured on the Z-pole and GeV off the Z-pole, and to
A_e obtained from the measurement of left-right asymmetry for hadronic final
states. It also leads to a significant improvement in the total hadronic cross
section on the Z-pole and R_b measured at energies above the Z-pole. In
addition, with a proper mass, it can explain the excess of events at
LEP in the 90-105 GeV region of the invariant mass.Comment: 10 pages, 1 figur
Z' near the Z-pole
We present a fit to precision electroweak data in the standard model extended
by an additional vector boson, Z', with suppressed couplings to the electron
compared to the Z boson, with couplings to the b-quark, and with mass close to
the mass of the Z boson. This scenario provides an excellent fit to
forward-backward asymmetry of the b-quark measured on the Z-pole and \pm 2 GeV
off the Z-pole, and to lepton asymmetry, A_e, obtained from the measurement of
left-right asymmetry for hadronic final states, and thus it removes the tension
in the determination of the weak mixing angle from these two measurements. It
also leads to a significant improvement in the total hadronic cross section on
the Z-pole and R_b measured at energies above the Z-pole. We explore in detail
properties of the Z' needed to explain the data and present a model for Z' with
required couplings. The model preserves standard model Yukawa couplings, it is
anomaly free and can be embedded into grand unified theories. It allows a
choice of parameters that does not generate any flavor violating couplings of
the Z' to standard model fermions. Out of standard model couplings, it only
negligibly modifies the left-handed bottom quark coupling to the Z boson and
the 3rd column of the CKM matrix. Modifications of standard model couplings in
the charged lepton sector are also negligible. It predicts an additional down
type quark, D, with mass in a few hundred GeV range, and an extra lepton
doublet, L, possibly much heavier than the D quark. We discuss signatures of
the Z' at the Large Hadron Collider and calculate the Z'b production cross
section which is the dominant production mechanism for the Z'.Comment: 26 pages, 18 figures, minor modifications, one fig. added, results
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Diffusion-controlled anisotropic growth of stable and metastable crystal polymorphs in the phase-field crystal model
The official published version of the article can be accessed from the link below - Copyright @ 2009 APSWe use a simple density functional approach on a diffusional time scale, to address freezing to the body-centered cubic (bcc), hexagonal close-packed (hcp), and face-centered cubic (fcc) structures. We observe faceted equilibrium shapes and diffusion-controlled layerwise crystal growth consistent with two-dimensional nucleation. The predicted growth anisotropies are discussed in relation with results from experiment and atomistic simulations. We also demonstrate that varying the lattice constant of a simple cubic substrate, one can tune the epitaxially growing body-centered tetragonal structure between bcc and fcc, and observe a Mullins-Sekerka-Asaro-Tiller-Grinfeld-type instability.This work has been supported by the EU FP7
Collaborative Project ENSEMBLE under Grant
Agreement NMP4-SL-2008-213669, the Hungarian
Academy of Sciences under contract OTKA-K-62588, the Academy of Finland via its COMP CoE grant, and by Tekes via its MASIT33 project. A. J. acknowledges financial
support from the Finnish Academy of Science and Letters. T. P. acknowledges support from the Bolyai Ja´nos Grant
Analysis of Models for Decentralized and Collaborative AI on Blockchain
Machine learning has recently enabled large advances in artificial
intelligence, but these results can be highly centralized. The large datasets
required are generally proprietary; predictions are often sold on a per-query
basis; and published models can quickly become out of date without effort to
acquire more data and maintain them. Published proposals to provide models and
data for free for certain tasks include Microsoft Research's Decentralized and
Collaborative AI on Blockchain. The framework allows participants to
collaboratively build a dataset and use smart contracts to share a continuously
updated model on a public blockchain. The initial proposal gave an overview of
the framework omitting many details of the models used and the incentive
mechanisms in real world scenarios. In this work, we evaluate the use of
several models and configurations in order to propose best practices when using
the Self-Assessment incentive mechanism so that models can remain accurate and
well-intended participants that submit correct data have the chance to profit.
We have analyzed simulations for each of three models: Perceptron, Na\"ive
Bayes, and a Nearest Centroid Classifier, with three different datasets:
predicting a sport with user activity from Endomondo, sentiment analysis on
movie reviews from IMDB, and determining if a news article is fake. We compare
several factors for each dataset when models are hosted in smart contracts on a
public blockchain: their accuracy over time, balances of a good and bad user,
and transaction costs (or gas) for deploying, updating, collecting refunds, and
collecting rewards. A free and open source implementation for the Ethereum
blockchain and simulations written in Python is provided at
https://github.com/microsoft/0xDeCA10B. This version has updated gas costs
using newer optimizations written after the original publication.Comment: Accepted to ICBC 202
A new Al-Zr-Ti master alloy for ultrasonic grain refinement of wrought and foundry aluminum alloys
A new grain refiner master alloy based on the Al-Zr-Ti system was prepared by salt assisted synthesis. 90% of Al3Zr particles in the master alloy were ranged between 1 and 13 μm. 80% reduction of grain size was observed with the addition of 0.2wt% Zr equivalent master alloy combined with ultrasonic treatment in an Al alloy. The new master alloy demonstrated 30% improvement in grain refinement efficiency compared to the one prepared by a conventional alloy route.The authors wish to acknowledge financial support from the ExoMet Project, which is co-funded by the European Commission in the 7th Framework Programme (contract FP7-NMP3-LA-2012-280421), by the European Space Agency and by the individual partner organisations
Tidally induced lateral dispersion of the Storfjorden overflow plume
We investigate the flow of brine-enriched shelf water from Storfjorden (Svalbard) into Fram Strait and onto the western Svalbard Shelf using a regional set-up of NEMO-SHELF, a 3-D numerical ocean circulation model. The model is set up with realistic bathymetry, atmospheric forcing, open boundary conditions and tides. The model has 3 km horizontal resolution and 50 vertical levels in the sh-coordinate system which is specially designed to resolve bottom boundary layer processes. In a series of modelling experiments we focus on the influence of tides on the propagation of the dense water plume by comparing results from tidal and non-tidal model runs. Comparisons of non-tidal to tidal simulations reveal a hotspot of tidally induced horizontal diffusion leading to the lateral dispersion of the plume at the southernmost headland of Spitsbergen which is in close proximity to the plume path. As a result the lighter fractions in the diluted upper layer of the plume are drawn into the shallow coastal current that carries Storfjorden water onto the western Svalbard Shelf, while the dense bottom layer continues to sink down the slope. This bifurcation of the plume into a diluted shelf branch and a dense downslope branch is enhanced by tidally induced shear dispersion at the headland. Tidal effects at the headland are shown to cause a net reduction in the downslope flux of Storfjorden water into the deep Fram Strait. This finding contrasts previous results from observations of a dense plume on a different shelf without abrupt topography
Effect of natural spices on the progression of microbial food spoilage in the steamed beans pudding, moin-moin
Using a completely randomized block design, the progression of microbial food spoilage and the microbiological and sensory qualities of steamed cowpea paste (moin-moin) seasoned with onion, garlic, nutmeg and cinnamon was investigated. The total plate count was enumerated at approximately four hour intervals using Mueller-Hinton and Sabroaud dextrose agar for bacteria and fungal spoilage organisms respectively. Sensory evaluation was carried out using a 9-point hedonic scale. Results revealed no statistically significant difference in the progression of microbial spoilage. Eight bacterial species were isolated from the treatment samples as follows: Bacillus nealsoni, B. megaterium, B. pumilus, B marinus, Salimicrobium halophilum and Micrococcus varians. While 7 (seven) isolated fungi from the treatment samples are Gonatobotrys spp, Alternaria spp, Gymnoascus spp, Acremonium spp, Geotrichum spp, Oidiodendrum spp and Cladosporium spp. Untreated control and samples treated with nutmeg were preserved for the longest period of 23 hours. The present results show that moin-moin would spoil within 24 hours if kept at ambient temperature. The widely accepted reports of in-vitro anti-microbial effect of the spices was not observed in-vivo. Furtherwork is needed on increasing the shelf-life of moin-moin and other similar foods.Keywords: Antimicrobial activity, in-vivo, flow diagram
The QCD equation of state at finite T and mu
We calculate the pressure (p), the energy density (epsilon) and the baryon density (n(B)) of QCD at finite temperatures (T) and chemical potentials (mu). The recently proposed overlap improving multi-parameter reweighting technique is used to determine observables at nonvanishing chemical potentials. Our results are obtained by studying n(f) =2+1 dynamical staggered quarks with semi-realistic masses on N-t = 4 lattices
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