552 research outputs found
Bi-fuel SI engine model for analysis and optimization
The natural gas as an alternative fuel has
economical and environmental benefits. Bi-fuel engines
powered by gasoline and compressed natural gas (CNG) are
an intermediate and alternative step to dedicated CNG
engines. The conversion to bi-fuel CNG engine could be a
short-term solution to air pollution problem in many
developing countries. In this paper a mathematical model of
a bi-fuel four-stroke spark ignition (SI) engine is presented
for comparative studies and analysis. It is based on the
two-zone combustion model, and it has the ability to
simulate turbulent combustion. The model is capable of
predicting the cylinder temperature and pressure, heat
transfer, brake work , brake thermal and volumetric
efficiency, brake torque, brake specific fuel consumption
(BSFC), brake mean effective pressure (BMEP),
concentration of CO2, brake specific CO (BSCO) and brake
specific NOx (BSNOx). The effect of engine speed,
equivalence ratio and performance parameters using
gasoline and CNG fuels are analysed. The model has been
validated by experimental data using the results obtained
from a bi-fuel engine. The results show the capability of the
model in terms of engine performance optimization and
minimization of the emissions. The engine used in this study
is a typical example of a modified bi-fuel engine conversion,
which could benefit the researchers in the field
How to find discrete contact symmetries
This paper describes a new algorithm for determining all discrete contact
symmetries of any differential equation whose Lie contact symmetries are known.
The method is constructive and is easy to use. It is based upon the observation
that the adjoint action of any contact symmetry is an automorphism of the Lie
algebra of generators of Lie contact symmetries. Consequently, all contact
symmetries satisfy various compatibility conditions. These conditions enable
the discrete symmetries to be found systematically, with little effort
First-principles extrapolation method for accurate CO adsorption energies on metal surfaces
We show that a simple first-principles correction based on the difference
between the singlet-triplet CO excitation energy values obtained by DFT and
high-level quantum chemistry methods yields accurate CO adsorption properties
on a variety of metal surfaces.
We demonstrate a linear relationship between the CO adsorption energy and the
CO singlet-triplet splitting, similar to the linear dependence of CO adsorption
energy on the energy of the CO 2* orbital found recently {[Kresse {\em et
al.}, Physical Review B {\bf 68}, 073401 (2003)]}. Converged DFT calculations
underestimate the CO singlet-triplet excitation energy ,
whereas coupled-cluster and CI calculations reproduce the experimental . The dependence of on is used
to extrapolate for the top, bridge and hollow sites for the
(100) and (111) surfaces of Pt, Rh, Pd and Cu to the values that correspond to
the coupled-cluster and CI value. The correction
reproduces experimental adsorption site preference for all cases and obtains
in excellent agreement with experimental results.Comment: Table sent as table1.eps. 3 figure
A numerical study of multi-soliton configurations in a doped antiferromagnetic Mott insulator
We evaluate from first principles the self-consistent Hartree-Fock energies
for multi-soliton configurations in a doped, spin-1/2, antiferromagnetic Mott
insulator on a two-dimensional square lattice. We find that nearest-neighbor
Coulomb repulsion stabilizes a regime of charged meron-antimeron vortex soliton
pairs over a region of doping from 0.05 to 0.4 holes per site for intermediate
coupling 3 < U/t <8. This stabilization is mediated through the generation of
``spin-flux'' in the mean-field antiferromagnetic (AFM) background. Holes
cloaked by a meron-vortex in the spin-flux AFM background are charged bosons.
Our static Hartree-Fock calculations provide an upper bound on the energy of a
finite density of charged vortices. This upper bound is lower than the energy
of the corresponding charged stripe configurations. A finite density of charge
carrying vortices is shown to produce a large number of unoccupied electronic
levels in the Mott-Hubbard charge transfer gap. These levels lead to
significant band tailing and a broad mid-infrared band in the optical
absorption spectrum as observed experimentally. At very low doping (below 0.05)
the doping charges create extremely tightly bound meron-antimeron pairs or even
isolated conventional spin-polarons, whereas for very high doping (above 0.4)
the spin background itself becomes unstable to formation of a conventional
Fermi liquid and the spin-flux mean-field is energetically unfavorable. Our
results point to the predominance of a quantum liquid of charged, bosonic,
vortex solitons at intermediate coupling and intermediate doping
concentrations.Comment: 12 pages, 25 figures; added references, modified/eliminated some
figure
Are Solar Active Regions with Major Flares More Fractal, Multifractal, or Turbulent than Others?
Multiple recent investigations of solar magnetic field measurements have
raised claims that the scale-free (fractal) or multiscale (multifractal)
parameters inferred from the studied magnetograms may help assess the eruptive
potential of solar active regions, or may even help predict major flaring
activity stemming from these regions. We investigate these claims here, by
testing three widely used scale-free and multiscale parameters, namely, the
fractal dimension, the multifractal structure function and its inertial-range
exponent, and the turbulent power spectrum and its power-law index, on a
comprehensive data set of 370 timeseries of active-region magnetograms (17,733
magnetograms in total) observed by SOHO's Michelson Doppler Imager (MDI) over
the entire Solar Cycle 23. We find that both flaring and non-flaring active
regions exhibit significant fractality, multifractality, and non-Kolmogorov
turbulence but none of the three tested parameters manages to distinguish
active regions with major flares from flare-quiet ones. We also find that the
multiscale parameters, but not the scale-free fractal dimension, depend
sensitively on the spatial resolution and perhaps the observational
characteristics of the studied magnetograms. Extending previous works, we
attribute the flare-forecasting inability of fractal and multifractal
parameters to i) a widespread multiscale complexity caused by a possible
underlying self-organization in turbulent solar magnetic structures, flaring
and non-flaring alike, and ii) a lack of correlation between the fractal
properties of the photosphere and overlying layers, where solar eruptions
occur. However useful for understanding solar magnetism, therefore, scale-free
and multiscale measures may not be optimal tools for active-region
characterization in terms of eruptive ability or, ultimately,for major
solar-flare prediction.Comment: 25 pages, 7 figures, 2 tables, Solar Phys., in pres
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"Older Adults with ASD: The Consequences of Aging." Insights from a series of special interest group meetings held at the International Society for Autism Research 2016-2017
A special interest group (SIG) entitled "Older Adults with ASD: The Consequences of Aging" was held at the International Society for Autism Research (INSAR) annual meetings in 2016 and 2017. The SIG and subsequent meetings brought together, for the first time, international delegates who were members of the autistic community, researchers, practitioners and service providers. Based on aging autism research that is already underway in UK, Europe, Australia and North America, discussions focussed on conceptualising the parameters of aging when referring to autism, and the measures that are appropriate to use with older adults when considering diagnostic assessment, cognitive factors and quality of life in older age. Thus, the aim of this SIG was to progress the research agenda on current and future directions for autism research in the context of aging. A global issue on how to define 'aging' when referring to ASD was at the forefront of discussions. The âagingâ concept can in principle refer to all developmental transitions. However, in this paper we focus on the cognitive and physical changes that take place from mid-life onwards. Accordingly, it was agreed that aging and ASD research should focus on adults over the age of 50 years, given the high rates of co-occurring physical and mental health concerns and increased risk of premature death in some individuals. Moreover, very little is known about the cognitive change, care needs and outcomes of autistic adults beyond this age. Discussions on the topics of diagnostic and cognitive assessments, and of quality of life and well-being were explored through shared knowledge about which measures are currently being used and which background questions should be asked to obtain comprehensive and informative developmental and medical histories. Accordingly, a survey was completed by SIG delegates who were representatives of international research groups across four continents, and who are currently conducting studies with older autistic adults. Considerable overlap was identified across different research groups in measures of both autism and quality of life, which pointed to combining data and shared learnings as the logical next step. Regarding the background questions that were asked, the different research groups covered similar topics but the groups differed in the way these questions were formulated when working with autistic adults across a range of cognitive abilities. It became clear that continued input from individuals on the autism spectrum is important to ensure that questionnaires used in ongoing and future are accessible and understandable for people across the whole autistic spectrum, including those with limited verbal abilities
Risk of major cardiovascular events in patients with psoriasis receiving biologic therapies: a prospective cohort study
Background:
The cardiovascular safety profile of biologic therapies used for psoriasis is unclear.
Objectives:
To compare the risk of major cardiovascular events (CVEs; acute coronary syndrome, unstable angina, myocardial infarction and stroke) in patients with chronic plaque psoriasis treated with adalimumab, etanercept or ustekinumab in a large prospective cohort.
Methods:
Prospective cohort study examining the comparative risk of major CVEs was conducted using the British Association of Dermatologists Biologics and Immunomodulators Register. The main analysis compared adults with chronic plaque psoriasis receiving ustekinumab with tumour necrosisâα inhibitors (TNFi: etanercept and adalimumab), whilst the secondary analyses compared ustekinumab, etanercept or methotrexate against adalimumab. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated using overlap weights by propensity score to balance baseline covariates among comparison groups.
Results:
We included 5468 biologicânaĂŻve patients subsequently exposed (951 ustekinumab; 1313 etanercept; and 3204 adalimumab) in the main analysis. The secondary analyses also included 2189 patients receiving methotrexate. The median (p25âp75) followâup times for patients using ustekinumab, TNFi, adalimumab, etanercept and methotrexate were as follows: 2.01 (1.16â3.21), 1.93 (1.05â3.34), 1.94 (1.09â3.32), 1.92 (0.93â3.45) and 1.43 (0.84â2.53) years, respectively. Ustekinumab, TNFi, adalimumab, etanercept and methotrexate groups had 7, 29, 23, 6 and 9 patients experiencing major CVEs, respectively. No differences in the risk of major CVEs were observed between biologic therapies [adjusted HR for ustekinumab vs. TNFi: 0.96 (95% CI 0.41â2.22); ustekinumab vs. adalimumab: 0.81 (0.30â2.17); etanercept vs. adalimumab: 0.81 (0.28â2.30)] and methotrexate against adalimumab [1.05 (0.34â3.28)].
Conclusions:
In this large prospective cohort study, we found no significant differences in the risk of major CVEs between three different biologic therapies and methotrexate. Additional studies, with longer term followâup, are needed to investigate the potential effects of biologic therapies on incidence of major CVEs
Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I
We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4 Ă 10â12e at 90% confidence level assuming all three species of neutrino have common millicharge. We also set flavor-dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, 7.3 Ă 10â12e for Îœe , 1.1 Ă 10â11e for ΜΌ, and 1.1 Ă 10â11e for ÎœÏ . These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8 Ă 10â10 Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the U(1)BâL model of 1.3 Ă 10â6 if the dark photon mass is 1 Ă 10â3 MeV/c2, and 8.8 Ă 10â5 if it is 10 MeV/c2
An integrated map of structural variation in 2,504 human genomes
Structural variants are implicated in numerous diseases and make up the majority of varying nucleotides among human genomes. Here we describe an integrated set of eight structural variant classes comprising both balanced and unbalanced variants, which we constructed using short-read DNA sequencing data and statistically phased onto haplotype blocks in 26 human populations. Analysing this set, we identify numerous gene-intersecting structural variants exhibiting population stratification and describe naturally occurring homozygous gene knockouts that suggest the dispensability of a variety of human genes. We demonstrate that structural variants are enriched on haplotypes identified by genome-wide association studies and exhibit enrichment for expression quantitative trait loci. Additionally, we uncover appreciable levels of structural variant complexity at different scales, including genic loci subject to clusters of repeated rearrangement and complex structural variants with multiple breakpoints likely to have formed through individual mutational events. Our catalogue will enhance future studies into structural variant demography, functional impact and disease association. © 2015 Macmillan Publishers Limited. All rights reserved
Playing with the Rules of the Game: Social Innovation for Urban Transformation
Innovation is perhaps the buzzword in local economic development policy. Associated narrowly with neoliberal ideas, conventional notions of innovationâlike its capitalocentric counterparts, enterprise and entrepreneurialismâmay promise higher productivity, global competitiveness and technological progress but do not fundamentally change the ârules of the gameâ. In contrast, an emerging field reimagines social innovation as disruptive change in social relations and institutional configurations. This article explores the conceptual and political differences within this preâparadigmatic field, and argues for a more transformative understanding of social innovation. Building on the work of David Graeber, I mobilize the novel constructs of âplayâ and âgamesâ to advance our understanding of the contradictory process of institutionalizing social innovation for urban transformation. This is illustrated through a case study of Liverpool, where diverse approaches to innovation are employed in attempts to resolve longstanding socioâeconomic problems. Dominant marketâ and stateâled economic development policiesâlikened to a âregeneration gameââare contrasted with more experimental, creative, democratic and potentially more effective forms of social innovation, seeking urban change through playing with the rules of the game. I conclude by considering how the playâgame dialectic illuminates and reframes the way transformative social innovation might be cultivated by urban policy, the contradictions this entails, and possible ways forward
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