14,707 research outputs found
Conformal anomaly and the vector coupling in dense matter
We construct an effective chiral Lagrangian for hadrons implemented by the
conformal invariance and discuss the properties of nuclear matter at high
density. The model is formulated based on two alternative assignment, "naive"
and mirror, of chirality to the nucleons. It is shown that taking the dilaton
limit, in which the mended symmetry of Weinberg is manifest, the vector-meson
Yukawa coupling becomes suppressed and the symmetry energy becomes softer as
one approaches the chiral phase transition. This leads to softer equations of
state (EoS) and could accommodate the EoS without any exotica consistent with
the recent measurement of a neutron star.Comment: v2:10 pages, 2 figures, typos corrected, a rough estimate of m0 adde
Helices at Interfaces
Helically coiled filaments are a frequent motif in nature. In situations
commonly encountered in experiments coiled helices are squeezed flat onto two
dimensional surfaces. Under such 2-D confinement helices form "squeelices" -
peculiar squeezed conformations often resembling looped waves, spirals or
circles. Using theory and Monte-Carlo simulations we illuminate here the
mechanics and the unusual statistical mechanics of confined helices and show
that their fluctuations can be understood in terms of moving and interacting
discrete particle-like entities - the "twist-kinks". We show that confined
filaments can thermally switch between discrete topological twist quantized
states, with some of the states exhibiting dramatically enhanced
circularization probability while others displaying surprising
hyperflexibility
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Nucleation and phase selection in undercooled melts: Magnetic alloys of industrial relevance (MAGNEPHAS)
Studies of phase selection and microstructure evolution in high-performance magnetic materials are an urgent need for optimization of production routes. Containerless solidification experiments by electromagnetic levitation and drop tube solidification were conducted in undercooled melts of Fe-Co, Fe-Ni soft magnetic, and Nd-Fe-B hard magnetic alloys. Melt undercooling under microgravity was achieved in the TEMPUS facility during parabolic flight campaigns. For Fe-Co and Fe-Ni alloys significant effects of microgravity on metastable phase formation were discovered. Microstructure modifications as well as metastable phase formation as function of undercooling and melt flow were elucidated in Nd-Fe-B. Modeling of solidification processes, fluid flow and heat transfer provide predictive tools for microstructure engineering from the melt. They were developed as a link between undercooling experiments under terrestrial and microgravity conditions and the production routes of magnetic materials
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 ÎŒm. 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
Ultrasound- guided fine needle aspiration cytology and cell block in the diagnosis of focal liver lesions at Khartoum Hospital, Sudan
Background: The appropriate clinical management of various hepatic lesions depends on accurate diagnosis. Fine needle aspiration and cell block have gained popularity because they are convenient, minimally invasive, quick and have good performance profiles.Objective: To investigate the cytomorphological features of distinctive non-neoplastic and neoplastic lesions of the liver and to evaluate the sensitivity, specificity and diagnostic accuracy of ultrasound- guided (USG) fine needle aspiration cytology (FNAC) and cell block in the diagnosis ofliver diseases at Khartoum Teaching Hospital.Method: A cross-sectional study was conducted at Khartoum Teaching Hospital, Sudan during the period of November 2008 to October 2011. One hundred and five cytological materials were collected from patients with focal liver lesions who referred after initial clinical and radiologicalassessment for ultrasoundâguided fine needle aspiration cytology (USG -FNAC).Results: The age of the patients ranged from 5- 60 years and 64 (61%) of these patients were males. Out of 105 investigated samples 76 (72.4%) and 41(39.0%) were malignant by cytology and cell block respectively. Out of these 105 samples, 71 were investigated by both cytology and cell blocks and were included in the final analyses of the FNAC in comparison to cell block. The sensitivity, specificity, positive predictive value and negative predictive value of the cytology were 100% (93.0 â 100%), 63.3% (45.2 â 79.0%), 78.8% (66.2 â 88.3%) and 0 (0 â 14.6%), respectively.Conclusion: Thus, USG -FNAC is a sensitive but not specific method in differentiating the benign and malignant focal liver lesions. Differentiation between primary liver malignant lesions and metastatic lesion needs adjunct techniqueKey words: neoplastic lesion, non-neoplastic lesio
Macroscopic effects of the spectral structure in turbulent flows
Two aspects of turbulent flows have been the subject of extensive, split
research efforts: macroscopic properties, such as the frictional drag
experienced by a flow past a wall, and the turbulent spectrum. The turbulent
spectrum may be said to represent the fabric of a turbulent state; in practice
it is a power law of exponent \alpha (the "spectral exponent") that gives the
revolving velocity of a turbulent fluctuation (or "eddy") of size s as a
function of s. The link, if any, between macroscopic properties and the
turbulent spectrum remains missing. Might it be found by contrasting the
frictional drag in flows with differing types of spectra? Here we perform
unprecedented measurements of the frictional drag in soap-film flows, where the
spectral exponent \alpha = 3 and compare the results with the frictional drag
in pipe flows, where the spectral exponent \alpha = 5/3. For moderate values of
the Reynolds number Re (a measure of the strength of the turbulence), we find
that in soap-film flows the frictional drag scales as Re^{-1/2}, whereas in
pipe flows the frictional drag scales as Re^{-1/4} . Each of these scalings may
be predicted from the attendant value of \alpha by using a new theory, in which
the frictional drag is explicitly linked to the turbulent spectrum. Our work
indicates that in turbulence, as in continuous phase transitions, macroscopic
properties are governed by the spectral structure of the fluctuations.Comment: 6 pages, 3 figure
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