7,431 research outputs found
The Cuntz semigroup, the Elliott conjecture, and dimension functions on C*-algebras
We prove that the Cuntz semigroup is recovered functorially from the Elliott
invariant for a large class of C*-algebras. In particular, our results apply to
the largest class of simple C*-algebras for which K-theoretic classification
can be hoped for. This work has three significant consequences. First, it
provides new conceptual insight into Elliott's classification program, proving
that the usual form of the Elliott conjecture is equivalent, among Z-stable
algebras, to a conjecture which is in general substantially weaker and for
which there are no known counterexamples. Second and third, it resolves, for
the class of algebras above, two conjectures of Blackadar and Handelman
concerning the basic structure of dimension functions on C*-algebras. We also
prove in passing that the Cuntz-Pedersen semigroup is recovered functorially
from the Elliott invariant for a large class of unital simple C*-algebras.Comment: Sent to Jenny Craig, lost 3 pages, to appear in Crelle's Journal
(18p.
Bryophytes and their distribution in the Blue Mountains region of New South Wales
The bryophytes (mosses, liverworts and hornworts) that occur in the Blue Mountains region of New South Wales (latitude 33Ëâ34Ë S, longitude 151Ëâ151Ë40â E) are listed and information is provided on their distribution in the region. Species lists are based on herbarium specimens and field collections. 348 bryophyte taxa have been recorded from 70 families, including 225 moss taxa (in 108 genera from 45 families), 120 liverwort taxa (in 51 genera from 24 families) and 3 hornwort taxa (in 3 genera from one family). The moss families with most taxa are the Pottiaceae (with 23 taxa in 13 genera), Bryaceae (with 15 taxa in 3 genera) and Fissidentaceae (with 13 taxa). The largest genera are Fissidens (13 taxa), Campylopus (9) and Macromitrium (8). The liverwort family with the most taxa is Lepidoziaceae, with 29 taxa in 10 genera. The largest liverwort genera are Frullania (11 taxa) and Riccardia (8). The species lists include collections from both bushland and urban areas. Natural features of the Blue Mountains, including topography, altitude, climate and vegetation appear to be important factors influencing the number of bryophyte species recorded from each location. The number of collections from particular locations has been considerably influenced by ease of access, particularly proximity to roads, public transport and railway stations. The species lists include many records from areas that were not accessible to the early collectors of the late 19th and early 20th centuries such as Wollemi National Park, Gardens of Stone National Park, Newnes Plateau and Kanangra-Boyd National Park
Synthetic lethal analysis of Caenorhabditis elegans posterior embryonic patterning genes identifies conserved genetic interactions
Phenotypic robustness is evidenced when single-gene mutations do not result in an obvious phenotype. It has been suggested that such phenotypic stability results from 'buffering' activities of homologous genes as well as non-homologous genes acting in parallel pathways. One approach to characterizing mechanisms of phenotypic robustness is to identify genetic interactions, specifically, double mutants where buffering is compromised. To identify interactions among genes implicated in posterior patterning of the Caenorhabditis elegans embryo, we measured synthetic lethality following RNA interference of 22 genes in 15 mutant strains. A pair of homologous T-box transcription factors (tbx-8 and tbx-9) is found to interact in both C. elegans and C. briggsae, indicating that their compensatory function is conserved. Furthermore, a muscle module is defined by transitive interactions between the MyoD homolog hlh-1, another basic helix-loop-helix transcription factor, hnd-1, and the MADS-box transcription factor unc-120. Genetic interactions within a homologous set of genes involved in vertebrate myogenesis indicate broad conservation of the muscle module and suggest that other genetic modules identified in C. elegans will be conserved
Crystallographic and magnetic identification of secondary phase in orientated Bi5Fe0.5Co0.5Ti3O15 ceramics
Oxide materials which exhibit both ferroelectricity
and ferromagnetism are of great interest for sensors and memory
applications. Layered bismuth titanates with an Aurivillius
structure, (BiFeO3)nBi4Ti3O12, can possess ferroelectric and
ferromagnetic order parameters simultaneously. It has recently
been demonstrated that one such example,
Bi5Fe0.5Co0.5Ti3O15,where n = 1 with half the Fe3+ sites substituted
by Co3+ ions, exhibits both ferroelectric and ferromagnetic
properties at room temperature. Here we report the fabrication
of highly-oriented polycrystalline ceramics of this material,
prepared via molten salt synthesis and uniaxial pressing of high
aspect ratio platelets. Electron backscatter images showed that
there is a secondary phase within the ceramic matrix which is
rich in cobalt and iron, hence this secondary phase could
contribute in the main phase ferromagnetic property. The
concentration of the secondary phase obtained from secondary
electron microscopy is estimated at less than 2.5 %, below the
detection limit of XRD. TEM was used to identify the
crystallographic structure of the secondary phase, which was
shown to be cobalt ferrite, CoFe2O4. It is inferred from the data
that the resultant ferromagnetic response identified using VSM
measurements was due to the presence of the minor secondary
phase. The Remanent magnetization at room temperature was
Mr â 76 memu/g which dropped down to almost zero (Mr â 0.8
memu/g) at 460 oC, far lower than the anticipated for CoFe2O4
Inverse scaling trends for charge-trapping-induced degradation of FinFETs performance
In this paper, we investigate the impact of a single discrete charge trapped at the top oxide interface on the performance of scaled nMOS FinFET transistors. The charge-trapping-induced gate voltage shift is simulated as a function of the device scaling and for several regimes of conduction-from subthreshold to ON-state. Contrary to what is expected for planar MOSFETs, we show that the trap impact decreases with scaling down the FinFET size and the applied gate voltage. By comparing drift-diffusion with nonequilibrium Green functions simulations, we show that quantum effects in the charge distribution and transport can reduce or amplify the impact of discrete traps in simulation of reliability resilience of scaled FinFETs
Efficient meshing technique for textile composites unit cells of arbitrary complexity
Meso-scale unit cell models are often used to simulate mechanical behaviour of textile composites. Apart from reliable ways to create meso-scale geometries, such simulations require reliable meshing algorithms. While the former is made possible via dedicated textile pre-processors or high-fidelity weaving simulations, the meshing remains quite problematic for complex textiles and geometries. Even though, with a lot of user input, it is possible to create very complex meshes using meshing pre-processors, this approach remains infeasible for cases when a large number of models need to be analysed.This paper presents a meshing approach based on the combination of local octree-refinement with surface smoothing. This allows nearly conformal meshes to be generated for geometries of any complexity which achieve accuracy comparable to that of conformal meshes. A range of unit cells was analysed using the new approach and it was shown that the error in local stresses is within 10% of the reference solution and the average error is below 7%. It was found that the computational cost of the analysis using the new meshing technique is not considerably higher than for an analysis which uses a conventional conformal mesh yet the new approach allows analysis of any geometry
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