3,975 research outputs found
Clinical and electrophysiological characteristics of Purkinje-related ventricular arrhythmias associated with polymorphic ventricular tachycardia and ventricular fibrillation
INTRODUCTION: Little is known about the characteristics of Purkinje (P)-related ventricular arrhythmia
(VA) that initiates polymorphic ventricular tachycardia (PMVT) and ventricular fibrillation (VF) and
the outcome of ablation ...postprin
Double In Situ Approach for the Preparation of Polymer Nanocomposite with Multi-functionality
A novel one-step synthetic route, the double in situ approach, is used to produce both TiO2nanoparticles and polymer (PET), and simultaneously forming a nanocomposite with multi-functionality. The method uses the release of water during esterification to hydrolyze titanium (IV) butoxide (Ti(OBu)4) forming nano-TiO2in the polymerization vessel. This new approach is of general significance in the preparation of polymer nanocomposites, and will lead to a new route in the synthesis of multi-functional polymer nanocomposites
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Reproducing reality with a high-dynamic-range multi-focal stereo display
With well-established methods for producing photo-realistic results, the next big challenge of graphics and display technologies is to achieve perceptual realism --- producing imagery indistinguishable from real-world 3D scenes. To deliver all necessary visual cues for perceptual realism, we built a High-Dynamic-Range Multi-Focal Stereo Display that achieves high resolution, accurate color, a wide dynamic range, and most depth cues, including binocular presentation and a range of focal depth. The display and associated imaging system have been designed to capture and reproduce a small near-eye three-dimensional object and to allow for a direct comparison between virtual and real scenes. To assess our reproduction of realism and demonstrate the capability of the display and imaging system, we conducted an experiment in which the participants were asked to discriminate between a virtual object and its physical counterpart. Our results indicate that the participants can only detect the discrepancy with a probability of 0.44. With such a level of perceptual realism, our display apparatus can facilitate a range of visual experiments that require the highest fidelity of reproduction while allowing for the full control of the displayed stimuli.</jats:p
Elemental distribution within the long-period stacking ordered structure in a Mg-Gd-Zn-Mn alloy
High angle annular dark field scanning transmission electron microscope imaging and electron energy loss spectroscopy was used to elucidate the elemental distribution (Gd, Zn, Mn) within the long-period stacking ordered (LPSO) structure in a Mg-15Gd-0.8Zn-0.8Mn (wt%) alloy. While Gd and Zn enrichment was observed within the LPSO structure, no significant enrichment in Mn was observed. After averaging over a large region, a very weak Mn signal was resolved but no significant variations in Mn signal were observed over this region, suggesting that Mn is indeed present. These results provide useful information to support the future development of high performance Mg alloys
Single donor ionization energies in a nanoscale CMOS channel
One consequence of the continued downwards scaling of transistors is the
reliance on only a few discrete atoms to dope the channel, and random
fluctuations of the number of these dopants is already a major issue in the
microelectonics industry. While single-dopant signatures have been observed at
low temperature, studying the impact of only one dopant up to room temperature
requires extremely small lengths. Here, we show that a single arsenic dopant
dramatically affects the off-state behavior of an advanced microelectronics
field effect transistor (FET) at room temperature. Furthermore, the ionization
energy of this dopant should be profoundly modified by the close proximity of
materials with a different dielectric constant than the host semiconductor. We
measure a strong enhancement, from 54meV to 108meV, of the ionization energy of
an arsenic atom located near the buried oxide. This enhancement is responsible
for the large current below threshold at room temperature and therefore
explains the large variability in these ultra-scaled transistors. The results
also suggest a path to incorporating quantum functionalities into silicon CMOS
devices through manipulation of single donor orbitals
On the relative expressiveness of higher-order session processes
By integrating constructs from the λ-calculus and the π-calculus, in higher-order process calculi exchanged values may contain processes. This paper studies the relative expressiveness of HOπ, the higher-order π-calculus in which communications are governed by session types. Our main discovery is that HO, a subcalculus of HOπ which lacks name-passing and recursion, can serve as a new core calculus for session-typed higher-order concurrency. By exploring a new bisimulation for HO, we show that HO can encode HOπ fully abstractly (up to typed contextual equivalence) more precisely and efficiently than the first-order session π-calculus (π). Overall, under session types, HOπ, HO, and π are equally expressive; however, HOπ and HO are more tightly related than HOπ and π
Monotonicity of Fitness Landscapes and Mutation Rate Control
A common view in evolutionary biology is that mutation rates are minimised.
However, studies in combinatorial optimisation and search have shown a clear
advantage of using variable mutation rates as a control parameter to optimise
the performance of evolutionary algorithms. Much biological theory in this area
is based on Ronald Fisher's work, who used Euclidean geometry to study the
relation between mutation size and expected fitness of the offspring in
infinite phenotypic spaces. Here we reconsider this theory based on the
alternative geometry of discrete and finite spaces of DNA sequences. First, we
consider the geometric case of fitness being isomorphic to distance from an
optimum, and show how problems of optimal mutation rate control can be solved
exactly or approximately depending on additional constraints of the problem.
Then we consider the general case of fitness communicating only partial
information about the distance. We define weak monotonicity of fitness
landscapes and prove that this property holds in all landscapes that are
continuous and open at the optimum. This theoretical result motivates our
hypothesis that optimal mutation rate functions in such landscapes will
increase when fitness decreases in some neighbourhood of an optimum, resembling
the control functions derived in the geometric case. We test this hypothesis
experimentally by analysing approximately optimal mutation rate control
functions in 115 complete landscapes of binding scores between DNA sequences
and transcription factors. Our findings support the hypothesis and find that
the increase of mutation rate is more rapid in landscapes that are less
monotonic (more rugged). We discuss the relevance of these findings to living
organisms
Neonatal umbilical cord blood transplantation halts skeletal disease progression in the murine model of MPS-I
Umbilical cord blood (UCB) is a promising source of stem cells to use in early haematopoietic stem
cell transplantation (HSCT) approaches for several genetic diseases that can be diagnosed at birth. Mucopolysaccharidosis type I (MPS-I) is a progressive multi-system disorder caused by deficiency
of lysosomal enzyme α-L-iduronidase, and patients treated with allogeneic HSCT at the onset
have improved outcome, suggesting to administer such therapy as early as possible. Given that
the best characterized MPS-I murine model is an immunocompetent mouse, we here developed a transplantation system based on murine UCB. With the final aim of testing the therapeutic efficacy of UCB in MPS-I mice transplanted at birth, we first defined the features of murine UCB cells and demonstrated that they are capable of multi-lineage haematopoietic repopulation of myeloablated adult mice similarly to bone marrow cells. We then assessed the effectiveness of murine UCB cells transplantation in busulfan-conditioned newborn MPS-I mice. Twenty weeks after treatment, iduronidase activity was increased in visceral organs of MPS-I animals, glycosaminoglycans storage was reduced, and skeletal phenotype was ameliorated. This study explores a potential therapy for MPS-I at a very early stage in life and represents a novel model to test UCB-based transplantation approaches for various diseases
Photo-antagonism of the GABAA receptor
Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation
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