1,726 research outputs found
Narrating Friendship: The reciprocal relationship between J.B. Childers and myself
For the past ten months I have explored the life of a deceased artist named Joseph Barley J.B. Childers. In the graduate catalog Gregory Volk summarizes Childers as, an alienated Korean War Veteran, who took up painting as a refuge from his troubles, and who also doesn\u27t exist. Childers who is naturally right-handed, painted everything left-handed because of a war wound, and so Engelmann, who is left-handed, painted with his right hand, which is quite a limitation. Of course, there\u27s more to the story than that and the writings that follow will explain many of my reasons for pursuing this project
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Epidemic failure detection and consensus for extreme parallelism
Future extreme-scale high-performance computing systems will be required
to work under frequent component failures. The MPI Forumâs User
Level Failure Mitigation proposal has introduced an operation,
MPI Comm shrink, to synchronize the alive processes on the list of failed
processes, so that applications can continue to execute even in the presence
of failures by adopting algorithm-based fault tolerance techniques. This
MPI Comm shrink operation requires a failure detection and consensus
algorithm. This paper presents three novel failure detection and consensus
algorithms using Gossiping. Stochastic pinging is used to quickly detect
failures during the execution of the algorithm, failures are then disseminated
to all the fault-free processes in the system and consensus on the
failures is detected using the three consensus techniques. The proposed
algorithms were implemented and tested using the Extreme-scale Simulator.
The results show that the stochastic pinging detects all the failures in
the system. In all the algorithms, the number of Gossip cycles to achieve
global consensus scales logarithmically with system size. The second algorithm
also shows better scalability in terms of memory and network
bandwidth usage and a perfect synchronization in achieving global consensus.
The third approach is a three-phase distributed failure detection
and consensus algorithm and provides consistency guarantees even in very
large and extreme-scale systems while at the same time being memory and
bandwidth efficient
Intravascular tissue factor initiates coagulation via circulating microvesicles and platelets
Although tissue factor (TF), the principial initiator of physiological coagulation and pathological thrombosis, has recently been proposed to be present in human blood, the functional significance and location of the intravascular TF is unknown. In the plasma portion of blood, we found TF to be mainly associated with circulating microvesicles. By cell sorting with the specific marker CD42b, platelet-derived microvesicles were identified as a major location of the plasma TF. This was confirmed by the presence of full-length TF in microvesicles acutely shedded from the activated platelets. TF was observed to be stored in the α-granules and the open canalicular system of resting platelets and to be exposed on the cell surface after platelet activation. Functional competence of the blood-based TF was enabled when the microvesicles and platelets adhered to neutrophils, as mediated by P-selectin and neutrophil counterreceptor (PSGL-1, CD18 integrins) interactions. Moreover, neutrophil-secreted oxygen radical species supported the intravascular TF activity. The pools of platelet and microvesicle TF contributed additively and to a comparable extent to the overall blood TF activity, indicating a substantial participation of the microvesicle TF. Our results introduce a new concept of TF-mediated coagulation crucially dependent on TF associated with microvesicles and activated platelets, which principally enables the entire coagulation system to proceed on a restricted cell surface
Improving THz Quality-of-Transmission with Systematic RLNC and Auxiliary Channels
In this paper, we propose a novel solution that can improve the quality of
THz transmission with systematic random linear network coding (sRLNC) and a
low-bitrate auxiliary channel. To minimize complexity of channel coding, we
complement a generic low complexity FEC code by a low complexity sRLNC. To
increase the overall throughput of THz transmission, we propose to send the
native data and coding redundancy in parallel over 2 differently configured THz
channels, i.e., over 1 high bit rate main channel and 1 low bit rate low error
rate auxiliary channel. The results show, that the main THz channel supported
by low bit rate auxiliary channel can use a higher level modulation format and
sent over longer distances with a higher throughput.Comment: 7 pages, 6 figures, accepted at IEEE ICC'20 Workshop - TeraCo
Optimierung von DruckbehÀltern unterschiedlicher Geometrien und Werkstoffe
Einleitung
Moderne Simulations- und Berechnungsmethoden, wie beispielsweise die Finite-Elemente-Methode (FEM), erlauben dem Konstrukteur bereits in einer relativ frĂŒhen Phase des Entwicklungsprozesses die wesentlichen Eigenschaften des Produktes virtuell am Computer zu analysieren. Die Ergebnisse dieser Berechnungen können anschlieĂend zur zielgerichteten Verbesserung ausgewĂ€hlter Produkteigenschaften genutzt werden. Der Aufwand fĂŒr die Optimierung ist dabei in erster Linie von der KomplexitĂ€t des Produktes abhĂ€ngig.
Produkte, bei welchen die mathematischen ZusammenhÀnge zwischen den Ein- und Ausgangsparametern bekannt ist, lassen sich oftmals recht einfach analytisch optimieren.
Bei komplexen Produkten oder einer groĂen Anzahl an Einflussparametern lassen sich diese ZusammenhĂ€nge in vielen FĂ€llen nicht herleiten, so dass die Optimierung bisher meist nach dem Trial and Error-Verfahren erfolgte. Diese heuristische Vorgehensweise fĂŒhrt durch eine hohe Anzahl an notwendigen Iterationsschleifen zu einem extremen Anstieg der Zeit und der Kosten, wobei die Wiederholungsrate des Entwicklungsprozessschrittes in hohem MaĂe von der Erfahrung und dem vorhandenen Wissen des Konstrukteurs abhĂ€ngig ist.
Der Einsatz von wissenschaftlichen Optimierungsverfahren, wie beispielsweise der Topologieoptimierung, ermöglicht eine zielgerichtete und weitestgehend automatisierbare Optimierung von komplexen Produkten.
Die hohe KomplexitÀt des Produktes ist dabei oftmals nicht auf den ersten Blick ersichtlich. Beispielsweise gestaltet sich die Gewichtsoptimierung von DruckbehÀltern mit nicht rotationsymmetrischen Querschnitten aufgrund der komplexen SpannungsverlÀufe schwierig.
GrundsĂ€tzlich wird bei Leichtbaukonstruktionen versucht, die zur VerfĂŒgung stehende Werkstofffestigkeit in den gegebenen Sicherheitsgrenzen voll auszuschöpfen. HierfĂŒr ist es notwendig, die Materialverteilung an dem Kraftverlauf anzupassen. Bei einem mehrachsigen Spannungszustand, wie er bei den DruckbehĂ€ltern mit komplexen Geometrien vorliegt, bestehen zwischen der Materialverteilung und den SpannungsverlĂ€ufen ĂŒber die Geometrie komplexe ZusammenhĂ€nge, so dass fĂŒr die optimale Materialverteilung keine allgemeingĂŒltige triviale Lösung existiert
Herausforderungen klassischer Maschinenelemente im nicht-elektrischen Explosionsschutz
Der Umgang mit brennbaren Stoffen erfordert ein hohes MaĂ an Sicherheit und Aufmerksamkeit. Auf diese Anforderungen wird selbst in alltĂ€glichen Situationen wie beispielsweise bei der Nutzung eines Gaskochers- und -grills hingewiesen. Fehler in der Handhabung können zu schwerwiegenden Folgen fĂŒhren. Jedoch ist der Einsatz von brennbaren Stoffen in industriellen Prozessen und Produktionen notwendig. Unter definierten Bedingungen kann dabei der brennbare Stoff mit dem Sauerstoff aus der Luft eine explosionsfĂ€hige AtmosphĂ€re bilden, die durch eine ZĂŒndquelle entzĂŒndet werden kann. Die Folge ist âeine plötzliche Oxidations- oder Zerfallsreaktion mit Anstieg der Temperatur, des Druckes oder beider gleichzeitigâ (ISO 8421 1987), eine Explosion. Durch Explosionen werden Menschen, Maschinen und Umwelt gefĂ€hrdet. Die ZĂŒndquellen werden durch unterschiedlichste Ursachen bedingt. Am 07. Februar 2008 verursachte ein heiĂ gelaufenes Lager eine Explosion in einer Zuckerraffinerie, die 14 Menschen das Leben kostete (CSB 2009). Durch den Einsatz des Explosionsschutzes sollen solche Katastrophen und UnfĂ€lle verhindert werden. Dieses Gebiet der Sicherheitstechnik wird dabei in den elektrischen und nicht-elektrischen Explosionsschutz unterschieden. Im Rahmen des nicht-elektrischen Explosionsschutzes werden GerĂ€te und Baugruppen betrachtet, die ihre Funktion mechanisch erfĂŒllen (ISO 80079-36 2016). Essenzielle Komponenten sind dabei die klassischen Maschinenelemente wie Lager, Riemen oder Kupplungen. Diese Bauteile mĂŒssen alleinstehend und in Kombination die Anforderungen einer explosionsschutzgerechten Auslegung erfĂŒllen. Diese Bedingung kann jedoch eine Herausforderung darstellen
Unsupervised Meta-Analysis on Diverse Gene Expression Datasets Allows Insight into Gene Function and Regulation
Over the past years, microarray databases have increased rapidly in size. While they offer a wealth of data, it remains challenging to integrate data arising from different studies. Here we propose an unsupervised approach of a large-scale meta-analysis on Arabidopsis thaliana whole genome expression datasets to gain additional insights into the function and regulation of genes. Applying kernel principal component analysis and hierarchical clustering, we found three major groups of experimental contrasts sharing a common biological trait. Genes associated to two of these clusters are known to play an important role in indole-3-acetic acid (IAA) mediated plant growth and development or pathogen defense. Novel functions could be assigned to genes including a cluster of serine/threonine kinases that carry two uncharacterized domains (DUF26) in their receptor part implicated in host defense. With the approach shown here, hidden interrelations between genes regulated under different conditions can be unraveled
Diel and seasonal methane dynamics in the shallow and turbulent Wadden Sea
The Wadden Sea is a coastal system along the fringe of the landâsea borders of Denmark, Germany and the Netherlands. The Wadden Sea is extremely productive and influenced by strong variations in physical and biological forcing factors that act on timescales of hours to seasons. Productive coastal seas are known to dominate the ocean's methane emission to the atmosphere, but knowledge of controls and temporal variations in methane dynamics in these vastly dynamic systems is scarce. Here we address this knowledge gap by measuring methane inventories and methanotrophic activity at a temporal resolution of 1âh over a period of 2âd, repeatedly during four successive seasons in the central Dutch Wadden Sea. We found that methane dynamics varied between colder and warmer seasons, with generally higher water column methane concentrations and methanotrophic activity in the warmer seasons. The efflux of methane to the atmosphere was, on the other hand, lower in the warmer seasons because of lower wind speeds. On a diel scale, tides controlled methanotrophic activity, which increased âŒ40â% at low tide compared to high tide. We estimate that methane oxidizing bacteria reduce the methane budget of the Dutch Wadden Sea by only 2â%, while escapes to the atmosphere and are flushed out into the open North Sea at ebb tide. Our findings indicate that tides play a key role in controlling methane dynamics and methanotrophic activity and highlight the importance of high-resolution and repeated sampling strategies to resolve methane dynamics in fast-changing coastal systems
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Vertical aerosol distribution in the southern hemispheric midlatitudes as observed with lidar in Punta Arenas, Chile (53.2° and 70.9° W), during ALPACA
Within this publication, lidar observations of the vertical aerosol distribution above Punta Arenas, Chile (53.2 S and 70.9 W), which have been performed with the Raman lidar PollyXT from December 2009 to April 2010, are presented. Pristine marine aerosol conditions related to the prevailing westerly circulation dominated the measurements. Lofted aerosol layers could only be observed eight times during the whole measurement period. Two case studies are presented showing long-range transport of smoke from biomass burning in Australia and regionally transported dust from the Patagonian Desert, respectively. The aerosol sources are identified by trajectory analyses with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and FLEXible PARTicle dispersion model (FLEXPART). However, seven of the eight analysed cases with lofted layers show an aerosol optical thickness of less than 0.05. From the lidar observations, a mean planetary boundary layer (PBL) top height of 1150 350m was determined. An analysis of particle backscatter coefficients confirms that the majority of the aerosol is attributed to the PBL, while the free troposphere is characterized by a very low background aerosol concentration. The ground-based lidar observations at 532 and 1064 nm are supplemented by the Aerosol Robotic Network (AERONET) Sun photometers and the space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The averaged aerosol optical thickness (AOT) determined by CALIOP was 0:02 0:01 in Punta Arenas from 2009 to 2010. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License
Effect of Experimental Thyrotoxicosis onto Blood Coagulation: A Proteomics Study
Background: Hyperthyroidism is known to induce a hypercoagulable state. It stimulates plasma levels of procoagulative factors and reduces fibrinolytic activity. So far most of the data have been derived from patients with endogenous hyperthyroidism with a wide variability in the underlying pathogenesis and severity of the disease. Objectives: In this study we experimentally induced thyrotoxicosis in healthy volunteers to explore the effects of thyroxine excess on the plasma proteome. Using a shotgun proteomics approach, the abundance of plasma proteins was monitored before, during and after thyrotoxicosis. Methods: Sixteen healthy male subjects were sampled at baseline, 4 and 8 weeks under 250 ”g/day thyroxine p.o., as well as 4 and 8 weeks after stopping the application. Plasma proteins were analyzed after depletion of 6 high-abundance proteins (MARS6) by LC-ESI-MS/MS mass spectrometry. Mass spectrometric raw data were processed using a label-free, intensity-based workflow. Subsequently, the linear dependence between protein abundances and fT4 levels were calculated using a Pearson correlation. Results: All subjects developed biochemical thyrotoxicosis, and this effect was reversed within the first 4 weeks of follow-up. None of the volunteers noticed any subjective symptoms. Levels of 10 proteins involved in the coagulation cascade specifically correlated with fT4, supporting an influence of thyroid hormone levels on blood coagulation even at nonpathological levels. Conclusions: The results suggest that experimental thyrotoxicosis exerts selective and specific thyroxine-induced effects on coagulation markers. Our study design allows assessment of thyroid hormone effects on plasma protein levels without secondary effects of other diseases or therapies
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