3,784 research outputs found
Circle formation algorithm for autonomous agents with local sensing
Research on cooperative robotics has increased radically over the past decade due to its simplicity and applicability in a variety of fields. Shape formation plays an important role in such cooperative behavior. Our work deals with the formation of a circle by a group of mobile agents (robots) that initially are randomly spread and randomly oriented in an unmapped terrain. The agents have simple characteristics and limited capabilities. They are autonomous, homogeneous, anonymous, and memory-less. They do not communicate with each other, but are able to measure the inter-agent distances and angels. The agents follow the same distributed algorithm synchronously without any central control. The existing algorithms make it necessary to scan all the agents over the whole terrain. The main advantage of our algorithm is that each agent makes use of local information collected from two neighboring partners. Our algorithm also results in a regularly distributed circle for any form of initial distribution. By changing a parameter in the algorithm, the circle can either be made to grow or shrink uniformly. Applications of this work can be made to a variety of areas such as space missions, military operations, in agriculture and fire fighting
Tuple Packing: Efficient Batching of Small Graphs in Graph Neural Networks
When processing a batch of graphs in machine learning models such as Graph
Neural Networks (GNN), it is common to combine several small graphs into one
overall graph to accelerate processing and remove or reduce the overhead of
padding. This is for example supported in the PyG library. However, the sizes
of small graphs can vary substantially with respect to the number of nodes and
edges, and hence the size of the combined graph can still vary considerably,
especially for small batch sizes. Therefore, the costs of excessive padding and
wasted compute are still incurred when working with static shapes, which are
preferred for maximum acceleration. This paper proposes a new hardware agnostic
approach -- tuple packing -- for generating batches that cause minimal
overhead. The algorithm extends recently introduced sequence packing approaches
to work on the 2D tuples of (|nodes|, |edges|). A monotone heuristic is applied
to the 2D histogram of tuple values to define a priority for packing histogram
bins together with the objective to reach a limit on the number of nodes as
well as the number of edges. Experiments verify the effectiveness of the
algorithm on multiple datasets
Green Stirling Engine Power Plant
The project utilized a Stirling engine as an environmentally responsible means of electrical power generation. The team\u27s efforts centered on A) collecting solar energy through a parabolic mirror to transmit that energy to B) an adapted two-cylinder air compressor, which served as a repurposed Stirling engine and C) convert the engine’s power to electricity through a DC generator and battery storage. A prototype parabolic mirror was designed, constructed and tested. The engine was modified to serve as an Alpha-Stirling design, which was mounted in an apparatus containing the DC generator, battery storage, and various charge controllers. Numerous new engine components were designed and fabricated. The charging system was tested and shown to produce the required electrical outputs
Truncation of the lipopolysaccharide outer core affects susceptibility to antimicrobial peptides and virulence of Actinobacillus pleuropneumoniae serotype 1.
Abstract We reported previously that the core oligosaccharide region of the lipopolysaccharide (LPS) is essential for optimal adhesion of Actinobacillus pleuropneumoniae, an important swine pathogen, to respiratory tract cells. Rough LPS and core LPS mutants of A. pleuropneumoniae serotype 1 were generated by using a mini-Tn10 transposon mutagenesis system. Here we performed a structural analysis of the oligosaccharide region of three core LPS mutants that still produce the same O-antigen by using methylation analyses and mass spectrometry. We also performed a kinetic study of proinflammatory cytokines production such as interleukin (IL)-6, tumor necrosis factor-α, IL1-β, MCP-1, and IL8 by LPS-stimulated porcine alveolar macrophages, which showed that purified LPS of the parent strain, the rough LPS and core LPS mutants, had the same ability to stimulate the production of cytokines. Most interestingly, an in vitro susceptibility test of these LPS mutants to antimicrobial peptides showed that the three core LPS mutants were more susceptible to cationic peptides than both the rough LPS mutant and the wild type parent strain. Furthermore, experimental pig infections with these mutants revealed that the galactose (Gal I) and d,d-heptose (Hep IV) residues present in the outer core of A. pleuropneumoniae serotype 1 LPS are important for adhesion and overall virulence in the natural host, whereas deletion of the terminal GalNAc-Gal II disaccharide had no effect. Our data suggest that an intact core-lipid A region is required for optimal protection of A. pleuropneumoniae against cationic peptides and that deletion of specific residues in the outer LPS core results in the attenuation of the virulence of A. pleuropneumoniae serotype 1
Gene expression profiling to study racial differences after heart transplantation.
BackgroundThe basis for increased mortality after heart transplantation in African Americans and other non-Caucasian racial groups is poorly defined. We hypothesized that increased risk of adverse events is driven by biologic factors. To test this hypothesis in the Invasive Monitoring Attenuation through Gene Expression (IMAGE) study, we determined whether the event rate of the primary outcome of acute rejection, graft dysfunction, death, or retransplantation varied by race as a function of calcineurin inhibitor (CNI) levels and gene expression profile (GEP) scores.MethodsWe determined the event rate of the primary outcome, comparing racial groups, stratified by time after transplant. Logistic regression was used to compute the relative risk across racial groups, and linear modeling was used to measure the dependence of CNI levels and GEP score on race.ResultsIn 580 patients monitored for a median of 19 months, the incidence of the primary end point was 18.3% in African Americans, 22.2% in other non-Caucasians, and 8.5% in Caucasians (p < 0.001). There were small but significant correlations of race and tacrolimus trough levels to the GEP score. Tacrolimus levels were similar among the races. Of patients receiving tacrolimus, other non-Caucasians had higher GEP scores than the other racial groups. African American recipients demonstrated a unique decrease in expression of the FLT3 gene in response to higher tacrolimus levels.ConclusionsAfrican Americans and other non-Caucasian heart transplant recipients were 2.5-times to 3-times more likely than Caucasians to experience outcome events in the Invasive Monitoring Attenuation through Gene Expression study. The increased risk of adverse outcomes may be partly due to the biology of the alloimmune response, which is less effectively inhibited at similar tacrolimus levels in minority racial groups
Oxygen treatment reduces neurological deficits and demyelination in two animal models of multiple sclerosis
AIMS: To explore the importance of tissue hypoxia in causing neurological deficits and demyelination in the inflamed CNS, and the value of inspiratory oxygen treatment, using both active and passive experimental autoimmune encephalomyelitis (EAE). METHODS: Normobaric oxygen treatment was administered to Dark Agouti rats with either active or passive EAE, compared with room air-treated, and naïve, controls. RESULTS: Severe neurological deficits in active EAE were significantly improved after just 1 hour of breathing ~95% oxygen. The improvement was greater and more persistent when oxygen was applied either prophylactically (from immunization for 23 days), or therapeutically from the onset of neurological deficits for 24, 48, or 72 hours. Therapeutic oxygen for 72 hours significantly reduced demyelination and the integrated stress response in oligodendrocytes at the peak of disease, and protected from oligodendrocyte loss, without evidence of increased oxidative damage. T-cell infiltration and cytokine expression in the spinal cord remained similar to that in untreated animals. The severe neurological deficit of animals with passive EAE occurred in conjunction with spinal hypoxia and was significantly reduced by oxygen treatment initiated before their onset. CONCLUSIONS: Severe neurological deficits in both active and passive EAE can be caused by hypoxia and reduced by oxygen treatment. Oxygen treatment also reduces demyelination in active EAE, despite the autoimmune origin of the disease
Evidence For A Precessing Accretion Disk in the Nucleus of NGC 1097
We present new spectroscopic observations of the LINER (and now Seyfert 1)
nucleus of NGC 1097, and discuss the evolution of its broad, double-peaked
Balmer lines. When originally discovered in 1991, the red peak of the
double-peaked H-alpha line was stronger than the blue, while by 1994 the
H-alpha profile had become almost symmetric and the integrated line flux had
decreased to half its original value. Our new spectrum, taken in 1996, shows
that the broad, double-peaked lines have returned to almost their original
strengths, the profiles of H-beta and H-alpha are identical to within errors,
and the broad-line emitting region is unreddened. However, the profile of the
Balmer lines is now such that the blue peak is stronger than the red, opposite
to the asymmetry observed in 1991. Various models are considered for the
observed behavior, all assuming that the emission lines originate in an
accretion disk. We present a refined version of the precessing, planar,
elliptical accretion ring model proposed by Storchi-Bergmann et al. and
Eracleous et al. This model provides an acceptable fit to the line profiles. We
also consider the possibility that the line profile evolution results from a
precessing warp in the disk, induced by irradiation from the center, and show
that the range of radii and precession time scales expected in this model are
consistent with the observations. The sudden appearance of the "disk-like"
broad line profiles in NGC 1097 could have resulted from the formation of a new
accretion disk due to, for example, the tidal disruption of a star, or the
illumination of a pre-existing disk by a transient ionizing source at the
center of the disk.Comment: Accepted for publication in the Astrophysical Journal. TeX file with
5 postscript figures embeded using psfig.tex, 13 page
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