216 research outputs found
CernVM Online and Cloud Gateway: a uniform interface for CernVM contextualization and deployment
In a virtualized environment, contextualization is the process of configuring
a VM instance for the needs of various deployment use cases. Contextualization
in CernVM can be done by passing a handwritten context to the user data field
of cloud APIs, when running CernVM on the cloud, or by using CernVM web
interface when running the VM locally. CernVM Online is a publicly accessible
web interface that unifies these two procedures. A user is able to define,
store and share CernVM contexts using CernVM Online and then apply them either
in a cloud by using CernVM Cloud Gateway or on a local VM with the single-step
pairing mechanism. CernVM Cloud Gateway is a distributed system that provides a
single interface to use multiple and different clouds (by location or type,
private or public). Cloud gateway has been so far integrated with OpenNebula,
CloudStack and EC2 tools interfaces. A user, with access to a number of clouds,
can run CernVM cloud agents that will communicate with these clouds using their
interfaces, and then use one single interface to deploy and scale CernVM
clusters. CernVM clusters are defined in CernVM Online and consist of a set of
CernVM instances that are contextualized and can communicate with each other.Comment: Conference paper at the 2013 Computing in High Energy Physics (CHEP)
Conference, Amsterda
Micro-CernVM: Slashing the Cost of Building and Deploying Virtual Machines
The traditional virtual machine building and and deployment process is
centered around the virtual machine hard disk image. The packages comprising
the VM operating system are carefully selected, hard disk images are built for
a variety of different hypervisors, and images have to be distributed and
decompressed in order to instantiate a virtual machine. Within the HEP
community, the CernVM File System has been established in order to decouple the
distribution from the experiment software from the building and distribution of
the VM hard disk images.
We show how to get rid of such pre-built hard disk images altogether. Due to
the high requirements on POSIX compliance imposed by HEP application software,
CernVM-FS can also be used to host and boot a Linux operating system. This
allows the use of a tiny bootable CD image that comprises only a Linux kernel
while the rest of the operating system is provided on demand by CernVM-FS. This
approach speeds up the initial instantiation time and reduces virtual machine
image sizes by an order of magnitude. Furthermore, security updates can be
distributed instantaneously through CernVM-FS. By leveraging the fact that
CernVM-FS is a versioning file system, a historic analysis environment can be
easily re-spawned by selecting the corresponding CernVM-FS file system
snapshot.Comment: Conference paper at the 2013 Computing in High Energy Physics (CHEP)
Conference, Amsterda
Verification and Validation of Semantic Annotations
In this paper, we propose a framework to perform verification and validation
of semantically annotated data. The annotations, extracted from websites, are
verified against the schema.org vocabulary and Domain Specifications to ensure
the syntactic correctness and completeness of the annotations. The Domain
Specifications allow checking the compliance of annotations against
corresponding domain-specific constraints. The validation mechanism will detect
errors and inconsistencies between the content of the analyzed schema.org
annotations and the content of the web pages where the annotations were found.Comment: Accepted for the A.P. Ershov Informatics Conference 2019(the PSI
Conference Series, 12th edition) proceedin
The CO oxidation kinetics on supported Pd model catalysts: A molecular beam/in-situ time-resolved infrared reflection absorption spectroscopy study.
EXPERIMENTS WITH A FAST CHOPPER SYSTEM FOR INTENSE ION BEAMS
Abstract Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations For the Frankfurt Neutron Source FRAN
The s Process: Nuclear Physics, Stellar Models, Observations
Nucleosynthesis in the s process takes place in the He burning layers of low
mass AGB stars and during the He and C burning phases of massive stars. The s
process contributes about half of the element abundances between Cu and Bi in
solar system material. Depending on stellar mass and metallicity the resulting
s-abundance patterns exhibit characteristic features, which provide
comprehensive information for our understanding of the stellar life cycle and
for the chemical evolution of galaxies. The rapidly growing body of detailed
abundance observations, in particular for AGB and post-AGB stars, for objects
in binary systems, and for the very faint metal-poor population represents
exciting challenges and constraints for stellar model calculations. Based on
updated and improved nuclear physics data for the s-process reaction network,
current models are aiming at ab initio solution for the stellar physics related
to convection and mixing processes. Progress in the intimately related areas of
observations, nuclear and atomic physics, and stellar modeling is reviewed and
the corresponding interplay is illustrated by the general abundance patterns of
the elements beyond iron and by the effect of sensitive branching points along
the s-process path. The strong variations of the s-process efficiency with
metallicity bear also interesting consequences for Galactic chemical evolution.Comment: 53 pages, 20 figures, 3 tables; Reviews of Modern Physics, accepte
Comparative Phylogeography in a Specific and Obligate Pollination Antagonism
In specific and obligate interactions the nature and abundance of a given species can have important effects on the survival and population dynamics of associated organisms. In a phylogeographic framework, we therefore expect that the fates of organisms interacting specifically are also tightly interrelated. Here we investigate such a scenario by analyzing the genetic structures of species interacting in an obligate plant-insect pollination lure-and-trap antagonism, involving Arum maculatum (Araceae) and its specific psychodid (Diptera) visitors Psychoda phalaenoides and Psycha grisescens. Because the interaction is asymmetric (i.e., only the plant depends on the insect), we expect the genetic structure of the plant to be related with the historical pollinator availability, yielding incongruent phylogeographic patterns between the interacting organisms
Oxidation processes in the eastern Mediterranean atmosphere: evidence from the modelling of HOx measurements over Cyprus
The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: Europe, Africa, and Asia. The chemical processing of air masses over this region has implications not only for the air quality but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the northwest of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe.
The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides, and other major HOx (OH+HO2) sources and sinks in a low-NOx environment (<100pptv of NO). The model simulations for OH agreed to within 10% with in situ OH observations. Model simulations for HO2 agreed to within 17% of the in situ observations. However, the model strongly under-predicted HO2 at high terpene concentrations, this under-prediction reaching up to 38% at the highest terpene levels. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene-generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene-generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed about one-third of the total OH production, and the maximum recycling efficiency was about 0.7. CO, which was the largest OH sink, was also the largest HO2 source. The lowest HOx production and losses occurred when the air masses had higher residence time over the oceans
Poorly controlled type 2 diabetes is accompanied by significant morphological and ultrastructural changes in both erythrocytes and in thrombin-generated fibrin: implications for diagnostics
We have noted in previous work, in a variety of inflammatory diseases, where iron dysregulation occurs, a strong
tendency for erythrocytes to lose their normal discoid shape and to adopt a skewed morphology (as judged by
their axial ratios in the light microscope and by their ultrastructure in the SEM). Similarly, the polymerization of
fibrinogen, as induced in vitro by added thrombin, leads not to the common ‘spaghetti-like’ structures but to dense
matted deposits. Type 2 diabetes is a known inflammatory disease. In the present work, we found that the axial
ratio of the erythrocytes of poorly controlled (as suggested by increased HbA1c levels) type 2 diabetics was
significantly increased, and that their fibrin morphologies were again highly aberrant. As judged by scanning
electron microscopy and in the atomic force microscope, these could be reversed, to some degree, by the addition
of the iron chelators deferoxamine (DFO) or deferasirox (DFX). As well as their demonstrated diagnostic significance,
these morphological indicators may have prognostic value.Biotechnology and Biological Sciences Research Council (grant
BB/L025752/1) as well as the National Research Foundation (NRF) of South
Africa.http://www.cardiab.com/hb201
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