1,161 research outputs found
Reliable scientific service compositions
Abstract. Distributed service oriented architectures (SOAs) are increas-ingly used by users, who are insufficiently skilled in the art of distributed system programming. A good example are computational scientists who build large-scale distributed systems using service-oriented Grid comput-ing infrastructures. Computational scientists use these infrastructure to build scientific applications, which are composed from basic Web ser-vices into larger orchestrations using workflow languages, such as the Business Process Execution Language. For these users reliability of the infrastructure is of significant importance and that has to be provided in the presence of hardware or operational failures. The primitives avail-able to achieve such reliability currently leave much to be desired by users who do not necessarily have a strong education in distributed sys-tem construction. We characterise scientific service compositions and the environment they operate in by introducing the notion of global scien-tific BPEL workflows. We outline the threats to the reliability of such workflows and discuss the limited support that available specifications and mechanisms provide to achieve reliability. Furthermore, we propose a line of research to address the identified issues by investigating auto-nomic mechanisms that assist computational scientists in building, exe-cuting and maintaining reliable workflows.
Grid service orchestration using the Business Process Execution Language (BPEL)
Modern scientific applications often need to be distributed across grids. Increasingly
applications rely on services, such as job submission, data transfer or data
portal services. We refer to such services as grid services. While the invocation
of grid services could be hard coded in theory, scientific users want to orchestrate
service invocations more flexibly. In enterprise applications, the orchestration of
web services is achieved using emerging orchestration standards, most notably
the Business Process Execution Language (BPEL). We describe our experience
in orchestrating scientific workflows using BPEL. We have gained this experience
during an extensive case study that orchestrates grid services for the automation of
a polymorph prediction application
Canalizing Kauffman networks: non-ergodicity and its effect on their critical behavior
Boolean Networks have been used to study numerous phenomena, including gene
regulation, neural networks, social interactions, and biological evolution.
Here, we propose a general method for determining the critical behavior of
Boolean systems built from arbitrary ensembles of Boolean functions. In
particular, we solve the critical condition for systems of units operating
according to canalizing functions and present strong numerical evidence that
our approach correctly predicts the phase transition from order to chaos in
such systems.Comment: to be published in PR
Data-Driven Detection and Diagnosis of System-Level Failures in Middleware-Based Service Compositions
Service-oriented technologies have simplified the development of large, complex software systems that span administrative boundaries. Developers have been enabled to build applications as compositions of services through middleware that hides much of the underlying complexity. The resulting applications inhabit complex, multi-tier operating environments that pose many challenges to their reliable operation and often lead to failures at runtime. Two key aspects of the time to repair a failure are the time to its detection and to the diagnosis of its cause. The prevalent approach to detection and diagnosis is primarily based on ad-hoc monitoring as well as operator experience and intuition. This is inefficient and leads to decreased availability. We propose an approach to data-driven detection and diagnosis in order to decrease the repair time of failures in middleware-based service compositions. Data-driven diagnosis supports system operators with information about the operation and structure of a service composition. We discuss how middleware-based service compositions can be monitored in a comprehensive, yet non-intrusive manner and present a process to discover system structure by processing deployment information that is commonly reified in such systems. We perform a controlled experiment that compares the performance of 22 participants using either a standard or the data-driven approach to diagnose several failures injected into a real-world service composition. We find that system operators using the latter approach are able to achieve significantly higher success rates and lower diagnosis times. Data-driven detection is based on the automation of failure detection through applying an outlier detection technique to multi-variate monitoring data. We evaluate the effectiveness of one-class classification for this purpose and determine a simple approach to select subsets of metrics that afford highly accurate failure detection
Structural motifs of pre-nucleation clusters
Structural motifs of pre-nucleation clusters prepared in single, optically
levitated supersaturated aqueous aerosol microparticles containing CaBr2 as a
model system are reported. Cluster formation is identified by means of X-ray
absorption in the Br K-edge regime. The salt concentration beyond the
saturation point is varied by controlling the humidity in the ambient
atmosphere surrounding the 15â30 ÎŒm microdroplets. This leads to the formation
of metastable supersaturated liquid particles. Distinct spectral shifts in
near-edge spectra as a function of salt concentration are observed, in which
the energy position of the Br K-edge is red-shifted by up to 7.1 ± 0.4 eV if
the dilute solution is compared to the solid. The K-edge positions of
supersaturated solutions are found between these limits. The changes in
electronic structure are rationalized in terms of the formation of pre-
nucleation clusters. This assumption is verified by spectral simulations using
first-principle density functional theory and molecular dynamics calculations,
in which structural motifs are considered, explaining the experimental
results. These consist of solvated CaBr2 moieties, rather than building blocks
forming calcium bromide hexahydrates, the crystal system that is formed by
drying aqueous CaBr2 solutions
Childhood Leukemia in the Vicinity of the Geesthacht Nuclear Establishments near Hamburg, Germany
BackgroundDuring 1990â1991 a childhood leukemia cluster was observed in the sparsely populated region surrounding two nuclear establishments southeast of Hamburg, Germany. Since then, several new cases have been reported. Recently a possible accidental release of radionuclides in 1986 was hypothesized.ObjectiveThe objective of this study was to analyze the childhood leukemia incidence in this area since 1990.MethodsAll incident cases ( 15 years warrants further investigation
SixâAxis Ground Motion Measurements of Caldera Collapse at KÄ«lauea Volcano, Hawai'iâMore Data, More Puzzles?
Nearâfield recordings of large earthquakes and volcanoâinduced events using traditional seismological instrumentation often suffer from unaccounted effects of local tilt and saturation of signals. Recent hardware advances have led to the development of the blueSeisâ3A, a very broadband, highly sensitive rotational motion sensor. We installed this sensor in close proximity to permanently deployed classical instrumentation (i.e., translational seismometer, accelerometer, and tiltmeter) at the Hawaiian Volcano Observatory (USGS). There, we were able to record three ~Mw 5 earthquakes associated with large collapse events during the later phase of the 2018 KÄ«lauea summit eruption. Located less than 2 km from the origins of these sources, the combined sixâaxis translational and rotational measurements revealed clear static rotations around all three coordinate axes. With these six component recordings, we have been able to reconstruct the complete time history of ground motion of a fixed point during an earthquake for the first time
Uso da farinha de minhoca como alimento para pĂłs-larvas de tilĂĄpia.
Foi avaliada a influĂȘncia da substituição da farinha de peixe pela farinha de minhoca (Eisenia foetida) no crescimento de pĂłs-larvas de tilĂĄpia nilĂłtica (Oreochromis niloticus). A farinha de peixe, que correspondeu a 50% da proteĂna da dieta, foi substituĂda pela farinha de minhoca nos seguintes nĂveis: 0%, 20%, 40%, 60%, 80% e 100%. Os peixes foram alimentados Ă vontade, quatro vezes ao dia, sendo pesados e medidos aos 21 e 41 dias de experimentação. O delineamento experimental foi o completamente casualizado, com quatro repetiçÔes por tratamento e 20 peixes por unidade experimental. Os dados coletados foram analisados pela ANOVA, sendo as mĂ©dias posteriormente classificadas pelo teste de Tukey (5%). ApĂłs 21 dias, nĂŁo houve diferença significativa entre os tratamentos. Entretanto, aos 41 dias houve diferença significativa entre os tratamentos e os animais com o nĂvel de substituição de 20% apresentaram os maiores pesos e taxas de crescimento especĂfico, e os animais com o nĂvel de substituição de 100% os menores. Durante o perĂodo experimental nĂŁo houve diferença significativa entre os tratamentos em relação Ă sobrevivĂȘncia dos animais. Os resultados mostram que baixos nĂveis de substituição da farinha de peixe (20%) melhoram o crescimento dos animais e que a substituição total da farinha de peixe pela farinha de minhoca Ă© prejudicial ao desenvolvimento dos peixes, mas nĂŁo afeta a sua sobrevivĂȘncia.bitstream/item/37405/1/BP45.pd
A Simple Separable Exact C*-Algebra not Anti-isomorphic to Itself
We give an example of an exact, stably finite, simple. separable C*-algebra D
which is not isomorphic to its opposite algebra. Moreover, D has the following
additional properties. It is stably finite, approximately divisible, has real
rank zero and stable rank one, has a unique tracial state, and the order on
projections over D is determined by traces. It also absorbs the Jiang-Su
algebra Z, and in fact absorbs the 3^{\infty} UHF algebra. We can also
explicitly compute the K-theory of D, namely K_0 (D) = Z[1/3] with the standard
order, and K_1 (D) = 0, as well as the Cuntz semigroup of D.Comment: 16 pages; AMSLaTeX. The material on other possible K-groups for such
an algebra has been moved to a separate paper (1309.4142 [math.OA]
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