6,095 research outputs found
Polyelectrolyte Adsorption
The problem of charged polymer chains (polyelectrolytes) as they adsorb on a
planar surface is addressed theoretically. We review the basic mechanisms and
theory underlying polyelectrolyte adsorption on a single surface in two
situations: adsorption of a single charged chain, and adsorption from a bulk
solution in solvent conditions. The behavior of flexible and
semi-rigid chains is discussed separately and is expressed as function of the
polymer and surface charges, ionic strength of the solution and polymer bulk
concentration. We mainly review mean-field results and briefly comment about
fluctuation effects. The phenomenon of polyelectrolyte adsorption on a planar
surface as presented here is of relevance to the stabilization of colloidal
suspensions. In this respect we also mention calculations of the inter-plate
force between two planar surfaces in presence of polyelectrolyte. Finally, we
comment on the problem of charge overcompensation and its implication to
multi-layers formation of alternating positive and negative polyelectrolytes on
planar surfaces and colloidal particles.Comment: 11 pages, 4 PS figures (Latex/RevTex), submitted to C.R. Acad. Sci
(Paris
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What\u27s in a letter?
Sentiment analysis is a burgeoning field in natural language processing used to extract and categorize opinion in evaluative documents. We look at recommendation letters, which pose unique challenges to standard sentiment analysis systems. Our dataset is eighteen letters from applications to UMass Worcester Memorial Medical Center’s residency program in Obstetrics and Gynecology. Given a small dataset, we develop a method intended for use by domain experts to systematically explore their intuitions about the topical make-up of documents on which they make critical decisions. By leveraging WordNet and the WordNet Propagation algorithm, the method allows a user to develop topic seed sets from real data and propagate them into robust lexicons for use on new data. We show how one pass through the method yields useful feedback to our beliefs about the make-up of recommendation letters. At the end, future directions are outlined which assume a fuller dataset
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The role of organizational climate in socially embedding construction firms’sustainability goals
Despite the growing interest in sustainability research, little scholarly attention, both conceptual and empirical, has been given to assessing the individual-level behavioural issues that affect sustainability outcomes. Still less research is undertaken to examine the mechanisms by which construction firms enable their sustainability goals to be socially embedded within their organizations to shape the behaviour and attitudes of employees. In an attempt to fill this gap, this paper draws from the extensive literature on organizational climate perspective to explain how organizational-level characteristics and processes can result in a strong, conducive climate that fosters shared perceptions and guide behaviours that are fundamental to the attainment of sustainability goals in organizations. From the critical review of this literature, this paper offers three research propositions and avenues in which they could be tested. The paper concludes with a broadened discussion of the theoretical and practical implications this framework has on advancing the sustainability discourse within CM discipline beyond the current largely technical, policy and institutional foci
Mediated Communication in the Postsecondary Education of Deaf Students
As increasing numbers of students with impaired hearing seek postsecondary education, the naivete of many receiving institutions about these students’ needs assumes greater importance. Students report and staff confirm that representative facilities often fail to distinguish between deaf and hard of hearing students. Such confusion leads to inappropriate accommodations, when any are made. The authors suggest antidotes for the neglect and confusion, and offer ideas for alterations in educational administration, for preparing and deploying interpreters, and for research
Traversable Wormholes in Geometries of Charged Shells
We construct a static axisymmetric wormhole from the gravitational field of
two charged shells which are kept in equilibrium by their electromagnetic
repulsion. For large separations the exterior tends to the Majumdar-Papapetrou
spacetime of two charged particles. The interior of the wormhole is a
Reissner-Nordstr\"om black hole matching to the two shells. The wormhole is
traversable and connects to the same asymptotics without violation of energy
conditions. However, every point in the Majumdar-Papapetrou region lies on a
closed timelike curve.Comment: 9 pages, LaTeX, 1 figur
Inverse monoids and immersions of 2-complexes
It is well known that under mild conditions on a connected topological space
, connected covers of may be classified via conjugacy
classes of subgroups of the fundamental group of . In this paper,
we extend these results to the study of immersions into 2-dimensional
CW-complexes. An immersion between
CW-complexes is a cellular map such that each point has a
neighborhood that is mapped homeomorphically onto by . In order
to classify immersions into a 2-dimensional CW-complex , we need to
replace the fundamental group of by an appropriate inverse monoid.
We show how conjugacy classes of the closed inverse submonoids of this inverse
monoid may be used to classify connected immersions into the complex
More than a cognitive experience: unfamiliarity, invalidation, and emotion in organizational learning
Literature on organizational learning (OL) lacks an integrative framework that captures the emotions involved as OL proceeds. Drawing on personal construct theory, we suggest that organizations learn where their members reconstrue meaning around questions of strategic significance for the organization. In this 5-year study of an electronics company, we explore the way in which emotions change as members perceive progress or a lack of progress around strategic themes. Our framework also takes into account whether OL involves experiences that are familiar or unfamiliar and the implications for emotions. We detected similar patterns of emotion arising over time for three different themes in our data, thereby adding to OL perspectives that are predominantly cognitive in orientation
Decoration of the truncated tetrahedron - an Archimedean polyhedron - to produce a new class of convex equilateral polyhedra with tetrahedral symmetry
The Goldberg construction of symmetric cages involves pasting a patch cut out of a regular tiling onto the faces of a Platonic host polyhedron, resulting in a cage with the same symmetry as the host. For example, cutting equilateral triangular patches from a 6.6.6 tiling of hexagons and pasting them onto the full triangular faces of an icosahedron produces icosahedral fullerene cages. Here we show that pasting cutouts from a 6.6.6 tiling onto the full hexagonal and triangular faces of an Archimedean host polyhedron, the truncated tetrahedron, produces two series of tetrahedral (T-d) fullerene cages. Cages in the first series have 28n(2) vertices (n >= 1). Cages in the second (leapfrog) series have 3 x 28n(2). We can transform all of the cages of the first series and the smallest cage of the second series into geometrically convex equilateral polyhedra. With tetrahedral (T-d) symmetry, these new polyhedra constitute a new class of "convex equilateral polyhedra with polyhedral symmetry". We also show that none of the other Archimedean polyhedra, six with octahedral symmetry and six with icosahedral, can host full-face cutouts from regular tilings to produce cages with the host's polyhedral symmetry
The Cosmic Censor Forbids Naked Topology
For any asymptotically flat spacetime with a suitable causal structure
obeying (a weak form of) Penrose's cosmic censorship conjecture and satisfying
conditions guaranteeing focusing of complete null geodesics, we prove that
active topological censorship holds. We do not assume global hyperbolicity, and
therefore make no use of Cauchy surfaces and their topology. Instead, we
replace this with two underlying assumptions concerning the causal structure:
that no compact set can signal to arbitrarily small neighbourhoods of spatial
infinity (``-avoidance''), and that no future incomplete null geodesic is
visible from future null infinity. We show that these and the focusing
condition together imply that the domain of outer communications is simply
connected. Furthermore, we prove lemmas which have as a consequence that if a
future incomplete null geodesic were visible from infinity, then given our
-avoidance assumption, it would also be visible from points of spacetime
that can communicate with infinity, and so would signify a true naked
singularity.Comment: To appear in CQG, this improved version contains minor revisions to
incorporate referee's suggestions. Two revised references. Plain TeX, 12
page
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