524 research outputs found

    The vulnerability of the diameter of folded n-cubes

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    AbstractFault tolerance concern in the design of interconnection networks has arisen interest in the study of graphs such that the subgraphs obtained by deleting some vertices or edges have a moderate increment of the diameter. Besides the general problem, several particular families of graphs are worthy of consideration. Both the odd graphs and the n-cubes have been studied in this context. In this paper we deal with folded n-cubes, a much interesting family because: (i) like the n-cubes, their order is a power of 2, (ii) their diameter is half the diameter of the n-cube of the same order, while their degree only increases by one, and (iii) as we show, in a folded n-cube of degree Δ, the deletion of less than ⌊12Δ⌋ − 1 vertices or edges does not increase the diameter of the graph, and the deletion of up to Δ − 1 vertices or edges increases it by at most one. This last property means that interconnection networks modelled by folded n-cubes are extremely robust

    Space station integrated wall design and penetration damage control. Task 3: Theoretical analysis of penetration mechanics

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    The efforts to provide a penetration code called PEN4 version 10 is documented for calculation of projectile and target states for the impact of 2024-T3 aluminum, R sub B 90 1018 steel projectiles and icy meteoroids onto 2024-T3 aluminum plates at impact velocities from 0 to 16 km/s. PEN4 determines whether a plate is perforated by calculating the state of fragmentation of projectile and first plate. Depth of penetration into the second to n sup th plate by fragments resulting from first plate perforation is determined by multiple cratering. The results from applications are given

    Image informatics strategies for deciphering neuronal network connectivity

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    Brain function relies on an intricate network of highly dynamic neuronal connections that rewires dramatically under the impulse of various external cues and pathological conditions. Among the neuronal structures that show morphologi- cal plasticity are neurites, synapses, dendritic spines and even nuclei. This structural remodelling is directly connected with functional changes such as intercellular com- munication and the associated calcium-bursting behaviour. In vitro cultured neu- ronal networks are valuable models for studying these morpho-functional changes. Owing to the automation and standardisation of both image acquisition and image analysis, it has become possible to extract statistically relevant readout from such networks. Here, we focus on the current state-of-the-art in image informatics that enables quantitative microscopic interrogation of neuronal networks. We describe the major correlates of neuronal connectivity and present workflows for analysing them. Finally, we provide an outlook on the challenges that remain to be addressed, and discuss how imaging algorithms can be extended beyond in vitro imaging studies

    Conduction abnormalities are restricted to the central nervous system in experimental autoimmune encephalomyelitis induced by inoculation with proteolipid protein but not with myelin basic protein

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    Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) and can be induced by inoculation of animals with homogenized CNS tissue or highly purified myelin proteins such as myelin basic protein (MBP) or proteolipid protein (PLP). It is widely studied as a possible animal model of multiple sclerosis. We performed the present neurophysiological study to define the location of nerve conduction abnormalities in EAE induced by immunization with PLP (PLP-EAE) and in EAE induced by immunization with MBP (MBP-EAE) in the Lewis rat. In rats with tail weakness due to acute PLP-EAE, conduction was normal in the spinal nerve roots and peripheral nerves but there was evidence of conduction block in a high proportion of the fibres in the dorsal columns of the lumbosacral spinal cord. In contrast, in acute MBP-EAE, there was conduction block in a high proportion of fibres in the sacral dorsal and ventral roots of the peripheral nervous system (PNS) and in the dorsal columns of the lumbosacral spinal cord. The distribution of nerve conduction abnormalities is consistent with previous histological studies showing that inflammation and primary demyelination are restricted to the CNS in PLP-EAE, but are present in the CNS and in the spinal roots of the PNS in MBP-EAE. The restriction of functional abnormalities to the CNS in PLP-EAE but not in MBP-EAE may have implications for the human inflammatory demyelinating diseases, including multiple sclerosis

    High-redshift quasar host galaxies with adaptive optics

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    We present K band adaptive optics observations of three high-redshift (z ~ 2.2) high-luminosity quasars, all of which were studied for the first time. We also bserved several point spread function (PSF) calibrators, non-simultaneously because of the small field of view. The significant temporal PSF variations on timescales of minutes inhibited a straightforward scaled PSF removal from the quasar images. Characterising the degree of PSF concentration by the radii encircling 20% and 80% of the total flux, respectively, we found that even under very different observing conditions the r_20 vs. r_80 relation varied coherently between individual short exposure images, delineating a well-defined relation for point sources. Placing the quasar images on this relation, we see indications that all three objects were resolved. We designed a procedure to estimate the significance of this result, and to estimate host galaxy parameters, by reproducing the statistical distribution of the individual short exposure images. We find in all three cases evidence for a luminous host galaxy, with a mean absolute magnitude of M_R = -27.0 and scale lengths around ~ 4-12 kpc. Together with a rough estimate of the central black hole masses obtained from C_iv line widths, the location of the objects on the bulge luminosity vs. black hole mass relation is not significantly dfferent from the low-redshift regime, assuming only passive evolution of the host galaxy. Corresponding Eddington luminosities are L_nuc/L_Edd ~ 0.1-0.6.Comment: 17 pages, 16 figures; submitted to Astronomy&Astrophysics. v2: Absolute magnitudes corrected and as a consequence updated two figures, black hole masses and stellar population age estimates in Discussion, but main conclusions remain the same; accepted by A&

    Stress corrosion cracking of low pressure steam turbine blade and rotor materials

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    Stress corrosion cracking of a 14 wt% Cr martensitic stainless steel, with commercial names PH-15Cr5Ni, FV520B or X4CrNiCuMo15-5, used for the manufacture of low pressure turbine blades, has been studied with the intention of gaining a better understanding of the processes involved, how they occur and why. Industrially this is very important as stress corrosion cracking is considered to be a delayed failure process, whereby microscopic cracks can potentially propagate through a metal undetected until catastrophic failure occurs. The aim of this work is to establish links between crack length and external factors, such as exposure time, in order to devise a method of dating stress corrosion cracks and therefore predicting their possible occurrence in-service. [Continues.
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