5,028 research outputs found
The standard mean-field treatment of inter-particle attraction in classical DFT is better than one might expect
In classical density functional theory (DFT) the part of the Helmholtz free
energy functional arising from attractive inter-particle interactions is often
treated in a mean-field or van der Waals approximation. On the face of it, this
is a somewhat crude treatment as the resulting functional generates the simple
random phase approximation (RPA) for the bulk fluid pair direct correlation
function. We explain why using standard mean-field DFT to describe
inhomogeneous fluid structure and thermodynamics is more accurate than one
might expect based on this observation. By considering the pair correlation
function and structure factor of a one-dimensional model fluid,
for which exact results are available, we show that the mean-field DFT,
employed within the test-particle procedure, yields results much superior to
those from the RPA closure of the bulk Ornstein-Zernike equation. We argue that
one should not judge the quality of a DFT based solely on the approximation it
generates for the bulk pair direct correlation function.Comment: 9 pages, 3 figure
Small-scale topographically-controlled glacier flow switching in an expanding proglacial lake at Breiðamerkurjökull, SE Iceland
Inductive logic programming at 30
Inductive logic programming (ILP) is a form of logic-based machine learning.
The goal of ILP is to induce a hypothesis (a logic program) that generalises
given training examples and background knowledge. As ILP turns 30, we survey
recent work in the field. In this survey, we focus on (i) new meta-level search
methods, (ii) techniques for learning recursive programs that generalise from
few examples, (iii) new approaches for predicate invention, and (iv) the use of
different technologies, notably answer set programming and neural networks. We
conclude by discussing some of the current limitations of ILP and discuss
directions for future research.Comment: Extension of IJCAI20 survey paper. arXiv admin note: substantial text
overlap with arXiv:2002.11002, arXiv:2008.0791
Action at a distance as a full-value solution of Maxwell equations: basis and application of separated potential's method
The inadequacy of Li\'{e}nard-Wiechert potentials is demonstrated as one of
the examples related to the inconsistency of the conventional classical
electrodynamics. The insufficiency of the Faraday-Maxwell concept to describe
the whole electromagnetic phenomena and the incompleteness of a set of
solutions of Maxwell equations are discussed and mathematically proved. Reasons
of the introduction of the so-called ``electrodynamics dualism concept"
(simultaneous coexistence of instantaneous Newton long-range and
Faraday-Maxwell short-range interactions) have been displayed. It is strictly
shown that the new concept presents itself as the direct consequence of the
complete set of Maxwell equations and makes it possible to consider classical
electrodynamics as a self-consistent and complete theory, devoid of inward
contradictions. In the framework of the new approach, all main concepts of
classical electrodynamics are reconsidered. In particular, a limited class of
motion is revealed when accelerated charges do not radiate electromagnetic
field.Comment: ReVTeX file, 24pp. Small corrections which do not have influence
results of the paper. Journal reference is adde
Dynamical density functional theory for interacting Brownian particles: stochastic or deterministic?
We aim to clarify confusions in the literature as to whether or not dynamical
density functional theories for the one-body density of a classical Brownian
fluid should contain a stochastic noise term. We point out that a stochastic as
well as a deterministic equation of motion for the density distribution can be
justified, depending on how the fluid one-body density is defined -- i.e.
whether it is an ensemble averaged density distribution or a spatially and/or
temporally coarse grained density distribution.Comment: 10 pages, 1 figure, to be submitted to Journal of Physics A:
Mathematical and Genera
The effects of anti–TNF agents on the expansion of T helper-type 17 cells driven by lipopolysaccharide-stimulated monocytes
Lineage and fate of each blastomere of the eight-cell sea urchin embryo
A fluoresceinated lineage tracer was injected into individual blastomeres of eight-cell sea urchin (Strongylocentrotus purpuratus) embryos, and the location of the progeny of each blastomere was determined in the fully developed pluteus. Each blastomere gives rise to a unique portion of the advanced embryo. We confirm many of the classical assignments of cell fate along the animal-vegetal axis of the cleavage-stage embryo, and demonstrate that one blastomere of the animal quartet at the eight-cell stage lies nearest the future oral pole and the opposite one nearest the future aboral pole of the embryo. Clones of cells deriving from ectodermal founder cells always remain contiguous, while clones of cells descendant from the vegetal plate (i.e., gut, secondary mesenchyme) do not. The locations of ectodermal clones contributed by specific blastomeres require that the larval plane of bilateral symmetry lie approximately equidistant (i.e., at a 45 degree angle) from each of the first two cleavage planes. These results underscore the conclusion that many of the early spatial patterns of differential gene expression observed at the molecular level are specified in a clonal manner early in embryonic sea urchin development, and are each confined to cell lineages established during cleavage
Advancing Precambrian palaeomagnetism with the PALEOMAGIA and PINT(<sub>QPI</sub>) databases.
State-of-the-art measurements of the direction and intensity of Earth's ancient magnetic field have made important contributions to our understanding of the geology and palaeogeography of Precambrian Earth. The PALEOMAGIA and PINT(QPI) databases provide thorough public collections of important palaeomagnetic data of this kind. They comprise more than 4,100 observations in total and have been essential in supporting our international collaborative efforts to understand Earth's magnetic history on a timescale far longer than that of the present Phanerozoic Eon. Here, we provide an overview of the technical structure and applications of both databases, paying particular attention to recent improvements and discoveries
Millimeter-wave defected ground structure-based MIMO antenna for 6G wireless applications
In this paper, a 2×2 multiple-input-multiple-output (MIMO) assembly of an elliptical-shaped millimeter-wave (mm-wave) antenna with defected-ground structures (DGS) is presented. The antenna is integrated with ring slot-shaped cut-outs as DGS on the bottom ground to generate multiple resonances combined in a wide bandwidth of 25.0-29.7 GHz. The simulated results show an efficiency above 75% and realized gain above 4.5 dBi in the entire range with a peak gain of 7.64 dBi at 27 GHz. The proposed MIMO antenna is well-suited for the 6 th Generation (6G) wireless applications
Smooth Bosonization as a Quantum Canonical Transformation
We consider a 1+1 dimensional field theory which contains both a complex
fermion field and a real scalar field. We then construct a unitary operator
that, by a similarity transformation, gives a continuum of equivalent theories
which smoothly interpolate between the massive Thirring model and the
sine-Gordon model. This provides an implementation of smooth bosonization
proposed by Damgaard et al. as well as an example of a quantum canonical
transformation for a quantum field theory.Comment: 20 pages, revte
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