4,558 research outputs found
Adsorption assisted translocation of a chain molecule through a pore in a spherical vesicle
We analyze the free energy for translocation of a polymer from the outside of
a spherical vesicle to the inside. The process is assumed to be driven by the
adsorption of the polymer on the inner surface of the vesicle. We argue that in
the case where the polymer is adsorbed on the outer surface too, the entropic
barrier for translocation is absent. We analyze the adsorption energy and find
the free energy profile for the process. We argue that the motion corresponds
to a polymer crossing a region with a change in free energy per segment. Based
upon our earlier analsis of the behaviour of kinks in such a problem, we
conclude that the translocation can occur with a crossing time
Neuroplasticity of language networks in aphasia: advances, updates, and future challenges
Researchers have sought to understand how language is processed in the brain, how brain damage affects language abilities, and what can be expected during the recovery period since the early 19th century. In this review, we first discuss mechanisms of damage and plasticity in the post-stroke brain, both in the acute and the chronic phase of recovery. We then review factors that are associated with recovery. First, we review organism intrinsic variables such as age, lesion volume and location and structural integrity that influence language recovery. Next, we review organism extrinsic factors such as treatment that influence language recovery. Here, we discuss recent advances in our understanding of language recovery and highlight recent work that emphasizes a network perspective of language recovery. Finally, we propose our interpretation of the principles of neuroplasticity, originally proposed by Kleim and Jones (1) in the context of extant literature in aphasia recovery and rehabilitation. Ultimately, we encourage researchers to propose sophisticated intervention studies that bring us closer to the goal of providing precision treatment for patients with aphasia and a better understanding of the neural mechanisms that underlie successful neuroplasticity.P50 DC012283 - NIDCD NIH HHSPublished versio
Approximation of Entropy Numbers
The purpose of this article is to develop a technique to estimate certain
bounds for entropy numbers of diagonal operator on spaces of p-summable
sequences for finite p greater than 1. The approximation method we develop in
this direction works for a very general class of operators between Banach
spaces, in particular reflexive spaces. As a consequence of this technique we
also obtain that the entropy number of a bounded linear operator T between two
separable Hilbert spaces is equal to the entropy number of the adjoint of T.
This gives a complete answer to the question posed by B. Carl [4] in the
setting of separable Hilbert spaces.Comment: 10 page
3D Gravity, Chern-Simons and Higher Spins: A Mini Introduction
These are notes of introductory lectures on (a) elements of 2+1 dimensional
gravity, (b) some aspects of its relation to Chern-Simons theory, (c) its
generalization to couple higher spins, and (d) cosmic singularity resolution as
an application in the context of flat space higher spin theory. A knowledge of
the Einstein-Hilbert action, classical non-Abelian gauge theory and some
(negotiable amount of) maturity are the only pre-requisites.Comment: 23 pages, Based on talks/lectures by CK at Goteborg, Tehran and
Bangkok. v2:acknowledgments and references added, v3:published versio
Strings vs Spins on the Null Orbifold
We study the null orbifold singularity in 2+1 d flat space higher spin theory
as well as string theory. Using the Chern-Simons formulation of 2+1 d Einstein
gravity, we first observe that despite the singular nature of this geometry,
the eigenvalues of its Chern-Simons holonomy are trivial. Next, we construct a
resolution of the singularity in higher spin theory: a Kundt spacetime with
vanishing scalar curvature invariants. We also point out that the UV
divergences previously observed in the 2-to-2 tachyon tree level string
amplitude on the null orbifold do not arise in the
limit. We find all the divergences of the amplitude and demonstrate that the
ones remaining in the tensionless limit are physical IR-type divergences. We
conclude with a discussion on the meaning and limitations of higher spin
(cosmological) singularity resolution and its potential connection to string
theory.Comment: 27 pages, 5 figures, v2: comments about boundary conditions added,
strengthening the conclusio
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