4,166 research outputs found
Human Ό-calpain: Simple isolation from erythrocytes and characterization of autolysis fragments
Heterodimeric ÎŒ-calpain, consisting of the large (80 kDa) and the small (30 kDa) subunit, was isolated and purified from human erythrocytes by a highly reproducible four-step purification procedure. Obtained material is more than 95% pure and has a specific activity of 6 - 7 mU/mg. Presence of contaminating proteins could not be detected by HPLC and sequence analysis. During storage at -80 °C the enzyme remains fully activatable by CaÂČâș, although the small subunit is partially processed to a 22 kDa fragment. This novel autolysis product of the small subunit starts with the sequence (60)RILG and is further processed to the known 18 kDa fragment. Active forms and typical transient and stable autolysis products of the large subunit were identified by protein sequencing. In casein-zymograms only the activatable forms 80 kDa+30 kDa, 80 kDa+22 kDa and 80 kDa+18 kDa displayed caseinolysis
Discovery of a Wolf-Rayet Star Through Detection of its Photometric Variability
We report the serendipitous discovery of a heavily reddened Wolf-Rayet star
that we name WR142b. While photometrically monitoring a cataclysmic variable,
we detected weak variability in a nearby field star. Low-resolution
spectroscopy revealed a strong emission line at 7100 Ang., suggesting an
unusual object and prompting further study. A spectrum taken with the
Hobby-Eberly Telescope confirms strong HeII emission and a NIV 7112 Ang. line
consistent with a nitrogen-rich Wolf-Rayet star of spectral class WN6. Analysis
of the HeII line strengths reveals no detectable hydrogen in WR142b. A
blue-sensitive spectrum obtained with the Large Binocular Telescope shows no
evidence for a hot companion star. The continuum shape and emission line ratios
imply a reddening of E(B-V)=2.2 to 2.5 mag. If not for the dust extinction,
this new Wolf-Rayet star could be visible to the naked eye.Comment: 15 pages, 6 figures, submitted to the Astronomical Journa
Experiments with Lasers and Frequency Doublers
Solid state laser sources, such as diode-pumped Nd:YAG lasers, have given us CW laser light of high power with unprecedented stability and low noise performance. In these lasers most of the technical sources of noise can be eliminated allowing them to be operated close to the theoretical noise limit set by the quantum properties of light. The next step of reducing the noise below the standard limit is known as squeezing. We present experimental progress in generating reliably squeezed light using the process of frequency doubling. We emphasize the long term stability that makes this a truly practical source of squeezed light. Our experimental results match noise spectra calculated with our recently developed models of coupled systems which include the noise generated inside the laser and its interaction with the frequency doubler. We conclude with some observations on evaluating quadrature squeezed states of light
Prioritized Sweeping Neural DynaQ with Multiple Predecessors, and Hippocampal Replays
During sleep and awake rest, the hippocampus replays sequences of place cells
that have been activated during prior experiences. These have been interpreted
as a memory consolidation process, but recent results suggest a possible
interpretation in terms of reinforcement learning. The Dyna reinforcement
learning algorithms use off-line replays to improve learning. Under limited
replay budget, a prioritized sweeping approach, which requires a model of the
transitions to the predecessors, can be used to improve performance. We
investigate whether such algorithms can explain the experimentally observed
replays. We propose a neural network version of prioritized sweeping
Q-learning, for which we developed a growing multiple expert algorithm, able to
cope with multiple predecessors. The resulting architecture is able to improve
the learning of simulated agents confronted to a navigation task. We predict
that, in animals, learning the world model should occur during rest periods,
and that the corresponding replays should be shuffled.Comment: Living Machines 2018 (Paris, France
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Inverse Consistency Error in the Registration of Prone and Supine Images in CT Colonography
Robust registration between prone and supine data acquisitions for CT colonography is pivotal for medical interpretation but a challenging problem. One measure when evaluating non-rigid registration algorithms over the whole of the deformation field is the inverse consistency error, which suggests improved registration quality when the inverse deformation is consistent with the forward deformation. We show that using computed landmark displacements to initialise an intensity based registration reduces the inverse consistency error when using a state-of-the-art non-rigid b-spline registration method. This method aligns prone and supine 2D images derived from CT colonography acquisitions in a cylindrical domain. Furthermore, we demonstrate that using the same initialisation also improves registration accuracy for a set of manually identified reference points in cases exhibiting local luminal collapse
Using a cognitive architecture to examine what develops
Different theories of development propose alternative mechanisms by which development occurs. Cognitive architectures can be used to examine the influence of each proposed mechanism of development while keeping all other mechanisms constant. An ACT-R computational model that matched adult behavior in solving a 21-block pyramid puzzle was created. The model was modified in three ways that corresponded to mechanisms of development proposed by developmental theories. The results showed that all the modifications (two of capacity and one of strategy choice) could approximate the behavior of 7-year-old children on the task. The strategy-choice modification provided the closest match on the two central measures of task behavior (time taken per layer, r = .99, and construction attempts per layer, r = .73). Modifying cognitive architectures is a fruitful way to compare and test potential developmental mechanisms, and can therefore help in specifying âwhat develops.
The tripartite partnership between female entrepreneurs, banks and governments in female entrepreneurship-development: A case study of Zambia
Purpose â This paper provides insights on the void between the needs and demands of bank finance from female entrepreneurs and the supply as well as the approaches of banks for that finance. In addition, it creates a conceptual framework recognising a tripartite and dynamic partnership among female entrepreneurs, banks and governments as essential to female entrepreneurship-development, based on Zambia as the context. Design/methodology/approach â Concepts and theories are explained to construct a conceptual framework using the lens of multi-polar network theory and stakeholder engagement theory. In-depth discussions are facilitated through a bilateral partnership between each party and tripartite partnerships among female entrepreneurs, banks and governments. Findings â The framework presents how female entrepreneurs, banks and governments are interconnected in the network as mutually benefiting stakeholders and shows their collective contribution to female entrepreneurship-development within certain contexts. The findings suggest that the sustainable development of female entrepreneurship depends on a dynamic tripartite partnership among female entrepreneurs, banks and governments. Research limitations/implications â The conceptual framework has important implications when setting up a nationâs enterprise development strategies and policies promoting inclusivity and diversity among a nationâs entrepreneurs. The contributions and the dynamic relationship of the three stakeholder groups should be acknowledged and considered in order to achieve the sustainable development female entrepreneur enterprises. The framework can be generalised to other emerging economies with similar social, economic and cultural profiles to Zambia, particularly in sub-Saharan African countries with patriarchal norms. Originality/value â This paper extends multi-polar (network) theory and Stakeholder Management engagement theory, previously explained in homogeneous firms, to more complex and dynamic partnerships among heterogeneous organisations, i.e. female entrepreneurs, banks and governments
Revealing Nuclear Pions Using Electron Scattering
A model for the pionic components of nuclear wave functions is obtained from
light front dynamical calculations of binding energies and densities. The
pionic effects are small enough to be consistent with measured nuclear di-muon
production data and with the nucleon sea. But the pion effects are large enough
to predict substantial nuclear enhancement of the cross section for
longitudinally polarized virtual photons for the kinematics accessible at
Jefferson Laboratory.Comment: 9 pages, 4 figure
Pion Excess, Nuclear Correlations, and the Interpretation of () Spin Transfer Experiments
Conventional theories of nuclear interactions predict a net increase in the
distribution of virtual pions in nuclei relative to free nucleons. Analysis of
data from several nuclear experiments has led to claims of evidence against
such a pion excess. These conclusions are usually based on a collective theory
(RPA) of the pions, which may be inadequate. The issue is the energy dependence
of the nuclear response, which differs for theories with strong NN correlations
from the RPA predictions. In the present paper, information about the energy
dependence is extracted from sum rules, which are calculated for such a
correlated, noncollective nuclear theory. The results lead to much reduced
sensitivity of nuclear reactions to the correlations that are responsible for
the pion excess. The primary example is spin transfer, for
which the expected effects are found to be smaller than the experimental
uncertainties. The analysis has consequences for Deep Inelastic Scattering
(DIS) experiments as well.Comment: 16 pages, LaTeX, no figures, submitted to Phys. Rev.
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