621 research outputs found
Modularity revisited: A novel dynamics-based concept for decomposing complex networks
Finding modules (or clusters) in large, complex networks is a challenging task, in particular if one is not interested in a full decomposition of the whole network into modules. We consider modular networks that also contain nodes that do not belong to one of modules but to several or to none at all. A new method for analyzing such networks is presented. It is based on spectral analysis of random walks on modular networks. In contrast to other spectral clustering approaches, we use different transition rules of the random walk. This leads to much more prominent gaps in the spectrum of the adapted random walk and allows for easy identification of the network's modular structure, and also identifying the nodes belonging to these modules. We also give a characterization of that set of nodes that do not belong to any module, which we call transition region. Finally, by analyzing the transition region, we describe an algorithm that identifies so called hub-nodes inside the transition region that are important connections between modules or between a module and the rest of the network. The resulting algorithms scale linearly with network size (if the network connectivity is sparse) and thus can also be applied to very large networks
Complete intersections: Moduli, Torelli, and good reduction
We study the arithmetic of complete intersections in projective space over
number fields. Our main results include arithmetic Torelli theorems and
versions of the Shafarevich conjecture, as proved for curves and abelian
varieties by Faltings. For example, we prove an analogue of the Shafarevich
conjecture for cubic and quartic threefolds and intersections of two quadrics.Comment: 37 pages. Typo's fixed. Expanded Section 2.
Mass hierarchy, 2-3 mixing and CP-phase with Huge Atmospheric Neutrino Detectors
We explore the physics potential of multi-megaton scale ice or water
Cherenkov detectors with low ( GeV) threshold. Using some proposed
characteristics of the PINGU detector setup we compute the distributions of
events versus neutrino energy and zenith angle , and study
their dependence on yet unknown neutrino parameters. The
regions are identified where the distributions have the highest sensitivity to
the neutrino mass hierarchy, to the deviation of the 2-3 mixing from the
maximal one and to the CP-phase. We evaluate significance of the measurements
of the neutrino parameters and explore dependence of this significance on the
accuracy of reconstruction of the neutrino energy and direction. The effect of
degeneracy of the parameters on the sensitivities is also discussed. We
estimate the characteristics of future detectors (energy and angle resolution,
volume, etc.) required for establishing the neutrino mass hierarchy with high
confidence level. We find that the hierarchy can be identified at --
level (depending on the reconstruction accuracies) after 5 years of
PINGU operation.Comment: 39 pages, 21 figures. Description of Fig.3 correcte
A Comparative Study of National Infrastructures for Digital (Open) Educational Resources in Higher Education
This paper reports on the first stage of an international comparative study for the project âDigital educational
architectures: Open learning resources in distributed learning infrastructuresâEduArcâ, funded by the German
Federal Ministry of Education and Research. This study reviews the situation of digital educational resources
(or (O)ER) framed within the digital transformation of ten different Higher Education (HE) systems (Australia,
Canada, China, Germany, Japan, South Africa, South Korea, Spain, Turkey and the United States). Following
a comparative case study approach, we investigated issues related to the existence of policies, quality
assurance mechanisms and measures for the promotion of change in supporting infrastructure development
for (O)ER at the national level in HE in the different countries. The results of this mainly documentary research
highlight differences and similarities, which are largely due to variations in these countriesâ political structure
organisation. The discussion and conclusion point at the importance of understanding each countryâs context
and culture, in order to understand the differences between them, as well as the challenges they face
Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.
G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a âŒ20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology
IceCube - the next generation neutrino telescope at the South Pole
IceCube is a large neutrino telescope of the next generation to be
constructed in the Antarctic Ice Sheet near the South Pole. We present the
conceptual design and the sensitivity of the IceCube detector to predicted
fluxes of neutrinos, both atmospheric and extra-terrestrial. A complete
simulation of the detector design has been used to study the detector's
capability to search for neutrinos from sources such as active galaxies, and
gamma-ray bursts.Comment: 8 pages, to be published with the proceedings of the XXth
International Conference on Neutrino Physics and Astrophysics, Munich 200
Serum Peptidome Profiling Revealed Platelet Factor 4 as a Potential Discriminating Peptide Associated With Pancreatic Cancer
Purpose: Mass spectrometry-based serum peptidome profiling is a promising tool to identify novel disease-associated biomarkers, but is limited by preanalytical factors and the intricacies of complex data processing. Therefore, we investigated whether standardized sample protocols and new bioinformatic tools combined with external data validation improve the validity of peptidome profiling for the discovery of pancreatic cancer associated serum markers.
Experimental Design: For discovery study, two sets of sera from patients with pancreatic cancer (n=40) and healthy controls (n=40) were obtained from two different clinical centers. For external data validation, we collected an independent set of samples from patients (n=20) and healthy controls (n=20). Magnetic beads (MB) with different surface functionalities were used for peptidome fractionation followed by MALDI-TOF MS. Data evaluation was carried out comparing two different bioinformatic strategies. Following proteome database search the matching candidate peptide was verified by MALDI-TOF MS after specific antibody-based immunoaffinity chromatography and independently confirmed by an ELISA assay.
Results: Two significant peaks (m/z 3884; 5959) achieved a sensitivity of 86.3% and specificity of 97.6% for the discrimination of patients and healthy controls in the external validation set. Adding peak m/z 3884 to conventional clinical tumor markers (CA 19-9 and CEA) improved sensitivity and specificity as shown by ROC analysis (AUROCcombined=1.00). Mass spectrometry based m/z 3884 peak identification and following immunological quantitation revealed platelet factor 4 as the corresponding peptide.
Conclusions: MALDI-TOF MS based serum peptidome profiling allowed the discovery and validation of platelet factor 4 as a new discriminating marker in pancreatic cancer
All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data
Since the recent detection of an astrophysical flux of high energy neutrinos,
the question of its origin has not yet fully been answered. Much of what is
known about this flux comes from a small event sample of high neutrino purity,
good energy resolution, but large angular uncertainties. In searches for
point-like sources, on the other hand, the best performance is given by using
large statistics and good angular reconstructions. Track-like muon events
produced in neutrino interactions satisfy these requirements. We present here
the results of searches for point-like sources with neutrinos using data
acquired by the IceCube detector over seven years from 2008--2015. The
discovery potential of the analysis in the northern sky is now significantly
below , on average
lower than the sensitivity of the previously published analysis of four
years exposure. No significant clustering of neutrinos above background
expectation was observed, and implications for prominent neutrino source
candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical
Journa
Neutrinos and Cosmic Rays Observed by IceCube
The core mission of the IceCube Neutrino observatory is to study the origin
and propagation of cosmic rays. IceCube, with its surface component IceTop,
observes multiple signatures to accomplish this mission. Most important are the
astrophysical neutrinos that are produced in interactions of cosmic rays, close
to their sources and in interstellar space. IceCube is the first instrument
that measures the properties of this astrophysical neutrino flux, and
constrains its origin. In addition, the spectrum, composition and anisotropy of
the local cosmic-ray flux are obtained from measurements of atmospheric muons
and showers. Here we provide an overview of recent findings from the analysis
of IceCube data, and their implications on our understanding of cosmic rays.Comment: Review article, to appear in Advances in Space Research, special
issue "Origins of Cosmic Rays
Searches for sterile neutrinos with the IceCube detector
The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous nu(mu) or (nu) over bar (mu) disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3 + 1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin(2)2 theta(24) <= 0.02 at Delta m(2) similar to 0.3 eV(2) at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of vertical bar U-e4 vertical bar(2)
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