11,310 research outputs found
Biochemical and immunochemical analysis of the arrangement of connexin43 in rat heart gap junction membranes
A 43 Ă— 10^3 M_r protein (designated connexin43 or Cx43) is a major constituent of heart gap junctions. The understanding of its arrangement in junctional membranes has been extended by means of site-directed antibodies raised against synthetic peptides of Cx43. These represent part of the first extracellular loop (EL-46), the cytoplasmic loop (CL-100), the second extracellular loop (EL-186) and carboxy-terminal sequences (CT-237 and CT-360). All of the antibodies raised reacted with their respective peptides and the Cx43 protein on Western blots. By immunoelectron microscopy two of the antibodies (CL-100 and CT-360) were shown to label the cytoplasmic surface of isolated gap junction membranes. Immunofluorescent labeling at locations of neonatal cardiac myocyte-myocyte apposition required an alkali/urea treatment when the EL-46 and EL-186 antibodies were used. Immunoblot analysis of endoproteinase Lys-C-digested gap junctions revealed that the Cx43 protein passed through the lipid bilayer four times. Alkaline phosphatase digestion of isolated junctions was used to show that the CT-360 antibody recognized many phosphorylated forms of Cx43. Our results unequivocally confirm models of the organization of Cx43 that were based on a more limited set of data and a priori considerations of the sequence
Using Insights from Psychology and Language to Improve How People Reason with Description Logics
Inspired by insights from theories of human reasoning and language, we propose additions to the Manchester OWL Syntax to improve comprehensibility. These additions cover: functional and inverse functional properties, negated conjunction, the definition of exceptions, and existential and universal restrictions. By means of an empirical study, we demonstrate the effectiveness of a number of these additions, in particular: the use of solely to clarify the uniqueness of the object in a functional property; the replacement of and with intersection in conjunction, which was particularly beneficial in negated conjunction; the use of except as a substitute for and not; and the replacement of some with including and only with noneOrOnly, which helped in certain situations to clarify the nature of these restrictions
Anomalous temperature of bottom water in the Panama Basin
In studies of basins along the western rim of the Pacific, Wyrtki (1961 a, b) found no significant differences in bottom potential temperature within individual basins…
Accuracy in advertising
Thesis (M.B.A.)--Boston University, 1929. This item was digitized by the Internet Archive
Panama Basin deep water----properties and circulation
Temperature, salinity, and dissolved-oxygen data from the deep waters of the Panama Basin suggest that water enters the Basin through a single pass near Ecuador and subsequently spreads to the north and west. The flow is blocked in places by subsills, and warming occurs through mixing and geothermal heating. The bottom water appears to have a residence time of about 175 years, and heat flow is believed to be important in the renewal process in the bottom water
Statistical inference of transmission fidelity of DNA methylation patterns over somatic cell divisions in mammals
We develop Bayesian inference methods for a recently-emerging type of
epigenetic data to study the transmission fidelity of DNA methylation patterns
over cell divisions. The data consist of parent-daughter double-stranded DNA
methylation patterns with each pattern coming from a single cell and
represented as an unordered pair of binary strings. The data are technically
difficult and time-consuming to collect, putting a premium on an efficient
inference method. Our aim is to estimate rates for the maintenance and de novo
methylation events that gave rise to the observed patterns, while accounting
for measurement error. We model data at multiple sites jointly, thus using
whole-strand information, and considerably reduce confounding between
parameters. We also adopt a hierarchical structure that allows for variation in
rates across sites without an explosion in the effective number of parameters.
Our context-specific priors capture the expected stationarity, or
near-stationarity, of the stochastic process that generated the data analyzed
here. This expected stationarity is shown to greatly increase the precision of
the estimation. Applying our model to a data set collected at the human FMR1
locus, we find that measurement errors, generally ignored in similar studies,
occur at a nontrivial rate (inappropriate bisulfite conversion error: 1.6
with 80 CI: 0.9--2.3). Accounting for these errors has a substantial
impact on estimates of key biological parameters. The estimated average failure
of maintenance rate and daughter de novo rate decline from 0.04 to 0.024 and
from 0.14 to 0.07, respectively, when errors are accounted for. Our results
also provide evidence that de novo events may occur on both parent and daughter
strands: the median parent and daughter de novo rates are 0.08 (80 CI:
0.04--0.13) and 0.07 (80 CI: 0.04--0.11), respectively.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS297 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Negations in syllogistic reasoning: Evidence for a heuristic–analytic conflict
An experiment utilizing response time measures was conducted to test dominant processing strategies in syllogistic reasoning with the expanded quantifier set proposed by Roberts (2005). Through adding negations to existing quantifiers it is possible to change problem surface features without altering logical validity. Biases based on surface features such as atmosphere, matching, and the probability heuristics model (PHM; Chater & Oaksford, 1999; Wetherick & Gilhooly, 1995) would not be expected to show variance in response latencies, but participant responses should be highly sensitive to changes in the surface features of the quantifiers. In contrast, according to analytic accounts such as mental models theory and mental logic (e.g., Johnson-Laird & Byrne, 1991; Rips, 1994) participants should exhibit increased response times for negated premises, but not be overly impacted upon by the surface features of the conclusion. Data indicated that the dominant response strategy was based on a matching heuristic, but also provided evidence of a resource-demanding analytic procedure for dealing with double negatives. The authors propose that dual-process theories offer a stronger account of these data whereby participants employ competing heuristic and analytic strategies and fall back on a heuristic response when analytic processing fails
Coherent spin manipulation in an exchange-only qubit
Initialization, manipulation, and measurement of a three-spin qubit are
demonstrated using a few-electron triple quantum dot, where all operations can
be driven by tuning the nearest-neighbor exchange interaction. Multiplexed
reflectometry, applied to two nearby charge sensors, allows for qubit readout.
Decoherence is found to be consistent with predictions based on gate voltage
noise with a uniform power spectrum. The theory of the exchange-only qubit is
developed and it is shown that initialization of only two spins suffices for
operation. Requirements for full multi-qubit control using only exchange and
electrostatic interactions are outlined.Comment: related work at http://marcuslab.harvard.ed
Particle Dark Energy
We explore the physics of a gas of particles interacting with a condensate
that spontaneously breaks Lorentz invariance. The equation of state of this gas
varies from 1/3 to less than -1 and can lead to the observed cosmic
acceleration. The particles are always stable. In our particular class of
models these particles are fermions with a chiral coupling to the condensate.
They may behave as relativistic matter at early times, produce a brief period
where they dominate the expansion with w<0 today, and behave as matter at late
time. There are no small parameters in our models, which generically lead to
dark energy clustering and, depending on the choice of parameters, smoothing of
small scale power.Comment: 8 pages, 5 figures; minor update with added refs; version appearing
in Phys. Rev.
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