1,383 research outputs found
Ultra precise characterization of LCLS hard X ray focusing mirrors by high resolution slope measuring deflectometry
We present recent results on the inspection of a first diffractionlimited hard X ray Kirkpatrick Baez KB mirror pair for the Coherent Xray Imaging CXI instrument at the Linac Coherent Light Source LCLS . The full KB system mirrors and holders was under inspection by use of high resolution slope measuring deflectometry. The tests confirmed that KB mirrors of 350mm aperture length characterized by an outstanding residual figure error of lt;1 nm rms has been realized. This corresponds to the residual figure slope error of about 0.05 amp; 956;rad rms, unprecedented on such long elliptical mirrors. Additional measurements show the clamping of the mirrors to be a critical step for the final shape preserving installation of such outstanding optic
Acacia trees on the cultural landscapes of the Red Sea Hills
This paper examines interactions between five pastoral nomadic culture groups of the Egyptian and Sudanese Red Sea Hills and the acacia trees Acacia tortilis (Forssk.) Hayne subsp. tortilis and subsp. raddiana growing in their arid environments. A. tortilis is described as a keystone species both ecologically and culturally: the trees play such critical roles in ecosystems and social groups that their removal would greatly impact both systems. Interviews in the field with the Semitic, Arabic-speaking Maâaza and Ababda, and the Cushitic, Beja, Bidhaawyeet-speaking Bishaari, Amar Ar and Hadandawa nomads probed the cultural and ecological contexts of acacias in pastoral nomadism, revealing deep insight into traditional ecological knowledge and traditional perceptions and uses of the trees. The paper describes how this knowledge guides pastoral decision-making, with acacias as a particularly critical component of the pastoral livelihood in both normal and stressful circumstances. A. tortilis is the most important reliable vegetation resource for nomads while also providing fuel and other useful products, ecosystem services for people and animals, and increased biodiversity by providing diverse microhabitats and resources for other species. We describe aspects of kinship, territorial organization, spiritual beliefs and tribal law underlying the significance of trees on the cultural landscape. We discuss environmental and economic challenges to human/tree relationships and to pastoral livelihoods. We challenge views of nomads as agents of ecological destruction, and propose maintenance and restoration of traditional pastoralism as viable alternatives in dryland development.publishedVersio
Visualizing Structural Balance in Signed Networks
Network visualization has established as a key complement to network analysis
since the large variety of existing network layouts are able to graphically
highlight different properties of networks. However, signed networks, i.e.,
networks whose edges are labeled as friendly (positive) or antagonistic
(negative), are target of few of such layouts and none, to our knowledge, is
able to show structural balance, i.e., the tendency of cycles towards including
an even number of negative edges, which is a well-known theory for studying
friction and polarization.
In this work we present Structural-balance-viz: a novel visualization method
showing whether a connected signed network is balanced or not and, in the
latter case, how close the network is to be balanced. Structural-balance-viz
exploits spectral computations of the signed Laplacian matrix to place
network's nodes in a Cartesian coordinate system resembling a balance (a
scale). Moreover, it uses edge coloring and bundling to distinguish positive
and negative interactions. The proposed visualization method has
characteristics desirable in a variety of network analysis tasks:
Structural-balance-viz is able to provide indications of balance/polarization
of the whole network and of each node, to identify two factions of nodes on the
basis of their polarization, and to show their cumulative characteristics.
Moreover, the layout is reproducible and easy to compare.
Structural-balance-viz is validated over synthetic-generated networks and
applied to a real-world dataset about political debates confirming that it is
able to provide meaningful interpretations
GiViP: A Visual Profiler for Distributed Graph Processing Systems
Analyzing large-scale graphs provides valuable insights in different
application scenarios. While many graph processing systems working on top of
distributed infrastructures have been proposed to deal with big graphs, the
tasks of profiling and debugging their massive computations remain time
consuming and error-prone. This paper presents GiViP, a visual profiler for
distributed graph processing systems based on a Pregel-like computation model.
GiViP captures the huge amount of messages exchanged throughout a computation
and provides an interactive user interface for the visual analysis of the
collected data. We show how to take advantage of GiViP to detect anomalies
related to the computation and to the infrastructure, such as slow computing
units and anomalous message patterns.Comment: Appears in the Proceedings of the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Contrasting behavior of covalent and molecular carbon allotropes exposed to extreme ultraviolet and soft x-ray free-electron laser radiation
All carbon materials, e.g., amorphous carbon (a-C) coatings and C60 fullerene
thin films, play an important role in short-wavelength free-electron laser
(FEL) research motivated by FEL optics development and prospective
nanotechnology applications. Responses of a-C and C60 layers to the extreme
ultraviolet (SPring-8 Compact SASE Source in Japan) and soft x-ray
(free-electron laser in Hamburg) free-electron laser radiation are investigated
by Raman spectroscopy, differential interference contrast, and atomic force
microscopy. A remarkable difference in the behavior of covalent (a-C) and
molecular (C60) carbonaceous solids is demonstrated under these irradiation
conditions. Low thresholds for ablation of a fullerene crystal (estimated to be
around 0.15 eV/atom for C60 vs 0.9 eV/atom for a-C in terms of the absorbed
dose) are caused by a low cohesive energy of fullerene crystals. An efficient
mechanism of the removal of intact C60 molecules from the irradiated crystal
due to Coulomb repulsion of fullerene-cage cation radicals formed by the
ionizing radiation is revealed by a detailed modeling
Australian Sphingidae â DNA Barcodes Challenge Current Species Boundaries and Distributions
Š 2014 Rougerie et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article
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