668 research outputs found
Chondroitin Sulfate Proteoglycans Are a Common Component of Neuronal Inclusions and Astrocytic Reaction in Neurodegenerative Diseases
Previously, we showed three differentially sulfated forms of chondroitin sulfate proteoglycans (CSPG) associated with senile plaques, astrocytes and neurofibrillary tangles in Alzheimer\u27s disease. Here, monoclonal antibodies were used to demonstrate CSPGs in other neurodegenerative diseases. CSPGs were found associated with inclusions of Parkinson\u27s, diffuse Lewy body, Pick\u27s diseases, and progressive supranuclear palsy. Reacting astrocytes in each of these neurodegenrative diseases and Huntington\u27s disease showed immunoreactivity for CSPG. CSPG distribution in a variety of neurodegenerative diseases suggests that similar mechanisms may be involved in the accumulation of proteoglycans in a number of filamentous inclusions
Acute Toxicity of Residual Chlorine and Ammonia to Some Native Illinois Fishes
Ninety-six hour residual chlorine bioassays were conducted on bluegill and channel catfish. In 96-hr acute toxicity studies with ammonia (NH3 -N) bass, in addition to bluegill and channel catfish, were included. The studies were performed in waters typical of most lakes and streams in midwestern states, i.e., relatively high in alkalinity and the salts of and magnesium. Observations of the characteristics and reaction of the fishes to each toxicant were noted. The 96-hr median tolerance limits for residual chlorine were: from 0.18 to 0.33 mg/1 for bluegill depending on temperature and fish weight; about 0.09 mg/1 for channel catfish with temperature not a factor. For ammonia the 96-hr median tolerance limits were: from 0.40 to 1.3 mg/1 for bluegill depending on temperature and fish weight; from 0.72 mg/1 at 22° C to 1.2 mg/1 at 30°C for bass and 1.5 mg/1 at 22°C to 3.0 mg/1 at 28° C for channel catfish with size not a factor. For the protection of the fishes investigated, and consistent with Illinois water pollution regulations, residual chlorine should not be detectable and NH3-N should not exceed a concentration of 0.04 mg/1.publishedpeer reviewedOpe
Current Population Statistics Do Not Favor Photoevaporation over Core-Powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap
We search for evidence of the cause of the exoplanet radius gap, i.e. the
dearth of planets with radii near . If the cause was
photoevaporation, the radius gap should trend with proxies for the early-life
high-energy emission of planet-hosting stars. If, alternatively, the cause was
core-powered mass loss, no such trends should exist. Critically, spurious
trends between the radius gap and stellar properties arise from an underlying
correlation with instellation. After accounting for this underlying
correlation, we find no trends remain between the radius gap and stellar mass
or present-day stellar activity as measured by near-UV emission. We dismiss the
nondetection of a radius gap trend with near-UV emission because present-day
near-UV emission is unlikely to trace early-life high-energy emission, but we
provide a catalog of GALEX near-UV and far-UV emission measurements for general
use. We interpret the nondetection of a radius gap trend with stellar mass by
simulating photoevaporation with mass-dependent evolution of stellar
high-energy emission. The simulation produces an undetectable trend between the
radius gap and stellar mass under realistic sources of error. We conclude that
no evidence, from this analysis or others in the literature, currently exists
that clearly favors either photoevaporation or core powered mass loss as the
primary cause of the exoplanet radius gap. However, repeating this analysis
once the body of well-characterized planets has roughly doubled
could confirm or rule out photoevaporation.Comment: 27 pages, 32 figures, accepted to Ap
Classes of fast and specific search mechanisms for proteins on DNA
Problems of search and recognition appear over different scales in biological
systems. In this review we focus on the challenges posed by interactions
between proteins, in particular transcription factors, and DNA and possible
mechanisms which allow for a fast and selective target location. Initially we
argue that DNA-binding proteins can be classified, broadly, into three distinct
classes which we illustrate using experimental data. Each class calls for a
different search process and we discuss the possible application of different
search mechanisms proposed over the years to each class. The main thrust of
this review is a new mechanism which is based on barrier discrimination. We
introduce the model and analyze in detail its consequences. It is shown that
this mechanism applies to all classes of transcription factors and can lead to
a fast and specific search. Moreover, it is shown that the mechanism has
interesting transient features which allow for stability at the target despite
rapid binding and unbinding of the transcription factor from the target.Comment: 65 pages, 23 figure
R-matrix Quantization of the Elliptic Ruijsenaars--Schneider model
It is shown that the classical L-operator algebra of the elliptic
Ruijsenaars-Schneider model can be realized as a subalgebra of the algebra of
functions on the cotangent bundle over the centrally extended current group in
two dimensions. It is governed by two dynamical r and -matrices
satisfying a closed system of equations. The corresponding quantum R and
-matrices are found as solutions to quantum analogs of these
equations. We present the quantum L-operator algebra and show that the system
of equations on R and arises as the compatibility condition for
this algebra. It turns out that the R-matrix is twist-equivalent to the Felder
elliptic R^F-matrix with playing the role of the twist. The
simplest representation of the quantum L-operator algebra corresponding to the
elliptic Ruijsenaars-Schneider model is obtained. The connection of the quantum
L-operator algebra to the fundamental relation RLL=LLR with Belavin's elliptic
R matrix is established. As a byproduct of our construction, we find a new
N-parameter elliptic solution to the classical Yang-Baxter equation.Comment: latex, 29 pages, some misprints are corrected and the meromorphic
version of the quantum L-operator algebra is discusse
Effects of intersegmental transfers on target location by proteins
We study a model for a protein searching for a target, using facilitated
diffusion, on a DNA molecule confined in a finite volume. The model includes
three distinct pathways for facilitated diffusion: (a) sliding - in which the
protein diffuses along the contour of the DNA (b) jumping - where the protein
travels between two sites along the DNA by three-dimensional diffusion, and
finally (c) intersegmental transfer - which allows the protein to move from one
site to another by transiently binding both at the same time. The typical
search time is calculated using scaling arguments which are verified
numerically. Our results suggest that the inclusion of intersegmental transfer
(i) decreases the search time considerably (ii) makes the search time much more
robust to variations in the parameters of the model and (iii) that the optimal
search time occurs in a regime very different than that found for models which
ignore intersegmental transfers. The behavior we find is rich and shows
surprising dependencies, for example, on the DNA length.Comment: 40 pages, 14 figure
Macdonald Polynomials from Sklyanin Algebras: A Conceptual Basis for the -Adics-Quantum Group Connection
We establish a previously conjectured connection between -adics and
quantum groups. We find in Sklyanin's two parameter elliptic quantum algebra
and its generalizations, the conceptual basis for the Macdonald polynomials,
which ``interpolate'' between the zonal spherical functions of related real and
\--adic symmetric spaces. The elliptic quantum algebras underlie the
\--Baxter models. We show that in the n \air \infty limit, the Jost
function for the scattering of {\em first} level excitations in the
\--Baxter model coincides with the Harish\--Chandra\--like \--function
constructed from the Macdonald polynomials associated to the root system .
The partition function of the \--Baxter model itself is also expressed in
terms of this Macdonald\--Harish\--Chandra\ \--function, albeit in a less
simple way. We relate the two parameters and of the Macdonald
polynomials to the anisotropy and modular parameters of the Baxter model. In
particular the \--adic ``regimes'' in the Macdonald polynomials correspond
to a discrete sequence of XXZ models. We also discuss the possibility of
``\--deforming'' Euler products.Comment: 25 page
Commodifying development experience: deconstructing development as gift in the development blockbuster
This paper discusses the recent rise of popular ‘blockbuster’ books written by international development industry insiders and produced by commercial publishers. The paper explores a set of common stylistic devices found within this emerging genre. Though each book is different, a key trope is the story of an author's earlier professional life—the hard lessons and gritty insights that have supposedly emerged from it—that normally underpins each narrative. By living the challenges involved in development work at first hand, and by making mistakes and experiencing epiphanies along the way, these author-professionals want readers to know that they have found out the hard way that long-cherished beliefs about development now need to be questioned. Readers are invited to relive these lessons and epiphanies, and to think and act differently about development by upholding a highly pragmatic form of development professionalism. Combining elements of research monograph, self-help book and personal memoir, these development blockbuster books can be understood not only as commodities, but also as part of the development gift. The authors promise a gift of experience but, in reality, these books are mundane commodities enmeshed in capitalist exchange relations
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