92,371 research outputs found
Charging Ultra-nanoporous Electrodes with Size-asymmetric Ions Assisted by Apolar Solvent
We develop a statistical theory of charging quasi single-file pores with cations and anions of different sizes as well as solvent molecules or voids. This is done by mapping the charging onto a one-dimensional Blume–Emery–Griffith model with variable coupling constants. The results are supported by three-dimensional Monte Carlo simulations in which many limitations of the theory are lifted. We explore the different ways of enhancing the energy storage which depend on the competitive adsorption of ions and solvent molecules into pores, the degree of ionophilicity and the voltage regimes accessed. We identify new solvent-related charging mechanisms and show that the solvent can play the role of an “ionophobic agent”, effectively controlling the pore ionophobicity. In addition, we demonstrate that the ion-size asymmetry can significantly enhance the energy stored in a nanopore
The production of a non-homogeneous classical pion field and the distribution of the neutral and charged pions
The probability distribution as a function of the ratio
of the neutral to total multiplicities is calculated for the
classical pion fields quickly varying in space and time.Comment: 6 pages, 1 .eps figure, using epsfig, submitted to Phys.Let
The effects of numerical resolution on hydrodynamical surface convection simulations and spectral line formation
The computationally demanding nature of radiative-hydrodynamical simulations
of stellar surface convection warrants an investigation of the sensitivity of
the convective structure and spectral synthesis to the numerical resolution and
dimension of the simulations, which is presented here. With too coarse a
resolution the predicted spectral lines tend to be too narrow, reflecting
insufficient Doppler broadening from the convective motions, while at the
currently highest affordable resolution the line shapes have converged
essentially perfectly to the observed profiles. Similar conclusions are drawn
from the line asymmetries and shifts. In terms of abundances, weak FeI and FeII
lines show a very small dependence (~0.02 dex) while for intermediate strong
lines with significant non-thermal broadening the sensitivity increases (~0.10
dex). Problems arise when using 2D convection simulations to describe an
inherent 3D phenomenon, which translates to inaccurate atmospheric velocity
fields and temperature and pressure structures. In 2D the theoretical line
profiles tend to be too shallow and broad compared with the 3D calculations and
observations, in particular for intermediate strong lines. In terms of
abundances, the 2D results are systematically about 0.1 dex lower than for the
3D case for FeI lines. Furthermore, the predicted line asymmetries and shifts
are much inferior in 2D. Given these shortcomings and computing time
considerations it is better to use 3D simulations of even modest resolution
than high-resolution 2D simulations.Comment: Accepted for A&
Algebraic Properties of Valued Constraint Satisfaction Problem
The paper presents an algebraic framework for optimization problems
expressible as Valued Constraint Satisfaction Problems. Our results generalize
the algebraic framework for the decision version (CSPs) provided by Bulatov et
al. [SICOMP 2005]. We introduce the notions of weighted algebras and varieties
and use the Galois connection due to Cohen et al. [SICOMP 2013] to link VCSP
languages to weighted algebras. We show that the difficulty of VCSP depends
only on the weighted variety generated by the associated weighted algebra.
Paralleling the results for CSPs we exhibit a reduction to cores and rigid
cores which allows us to focus on idempotent weighted varieties. Further, we
propose an analogue of the Algebraic CSP Dichotomy Conjecture; prove the
hardness direction and verify that it agrees with known results for VCSPs on
two-element sets [Cohen et al. 2006], finite-valued VCSPs [Thapper and Zivny
2013] and conservative VCSPs [Kolmogorov and Zivny 2013].Comment: arXiv admin note: text overlap with arXiv:1207.6692 by other author
Nasal lysine aspirin challenge in the diagnosis of aspirin - exacerbated respiratory disease
Background
Aspirin-exacerbated respiratory disease is under-diagnosed and therefore effective and inexpensive therapy with aspirin desensitization is rarely performed.
Methods
We present an audit of 150 patients with difficult to treat nasal polyposis, 132 of whom also had asthma, 131 of whom underwent challenge with the only soluble form of aspirin, lysine aspirin (LAS), to confirm or exclude the diagnosis of aspirin-exacerbated respiratory disease (AERD).
Results
One hundred patients proved positive on nasal challenge, 31 who were negative went onto oral LAS challenge and a further 14 gave positive results, leaving 17 who were negative to a dose equivalent to over 375 mg of aspirin. Nineteen were not challenged because of contraindications.
With the exception of one patient who developed facial angioedema and two patients with > 20% drop in FEV1 (following nasal plus oral challenge) no other severe adverse events occurred. No hospitalization was required for these three patients.
Nasal inspiratory peak flow monitoring was less sensitive to obstruction caused by aspirin than was acoustic rhinometry – which should be employed when aspirin challenge is an outpatient procedure.
Conclusions
Provided patients are carefully chosen and monitored LAS challenge is suitable for ENT day case practice where respiratory physician help with asthma is available and should reduce the under-diagnosis of this condition
Odin observations of ammonia in the Sgr A +50 km/s Cloud and Circumnuclear Disk
Context. The Odin satellite is now into its sixteenth year of operation, much
surpassing its design life of two years. One of the sources which Odin has
observed in great detail is the Sgr A Complex in the centre of the Milky Way.
Aims. To study the presence of NH3 in the Galactic Centre and spiral arms.
Methods. Recently, Odin has made complementary observations of the 572 GHz NH3
line towards the Sgr A +50 km/s Cloud and Circumnuclear Disk (CND). Results.
Significant NH3 emission has been observed in both the +50 km/s Cloud and the
CND. Clear NH3 absorption has also been detected in many of the spiral arm
features along the line of sight from the Sun to the core of our Galaxy.
Conclusions. The very large velocity width (80 km/s) of the NH3 emission
associated with the shock region in the southwestern part of the CND may
suggest a formation/desorption scenario similar to that of gas-phase H2O in
shocks/outflows.Comment: 5 pages, 3 figures, 3 table
Achievement flourishes in larger classes: Secondary school students in most countries achieved better literacy in larger classes
There is no consensus among academics about whether children benefit from smaller classes. We analysed the data from the 2012 Programme for International Student Assessment (PISA) to test if smaller classes lead to higher performance. Advantages of using this data set are not only its size (478,120 15-year old students in 63 nations) and representativeness but also that the 2012 PISA data set, for the first time, includes the class size for each participating child. We found that, in most countries, children in smaller classes had a lower performance score in solving reading comprehension problems than those in larger classes. We further analysed the relationship between class size and factors that can explain this paradoxical phenomenon. Although grouping of students by ability and the socioeconomic status of parents played some role in some countries, these factors cannot fully explain the effect. We finish by discussing the overlooked potential advantages of larger classes
Hortibot: Feasibility study of a plant nursing robot performing weeding operations – part IV
Based on the development of a robotic tool carrier (Hortibot) equipped with weeding tools, a feasibility study was carried out to evaluate the viability of this innovative technology. The feasibility was demonstrated through a targeted evaluation adapted to the obtainable knowledge on the system performance in horticulture.
A usage scenario was designed to set the implementation of the robotic system in a row crop of seeded bulb onions considering operational and functional constraints in organic crop, production. This usage scenario together with the technical specifications of the implemented system provided the basis for the feasibility analysis, including a comparison with a conventional weeding system. Preliminary results show that the automation of the weeding tasks within a row crop has the potential of significantly reducing the costs and still fulfill the operational requirements set forth.
The potential benefits in terms of operational capabilities and economic viability have been quantified. Profitability gains ranging from 20 to 50% are achievable through targeted applications. In general, the analyses demonstrate the operational and economic feasibility of using small automated vehicles and targeted tools in specialized production settings
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