335 research outputs found
Interlayer screening effect in graphene multilayers with ABA and ABC stacking
We study the effect of perpendicular electric fields on the band structures
of ABA and ABC graphene multilayers, and find that the electronic screening
effect is significantly different between them. In ABA multilayers, the field
produces a band overlap and gives a linear screening, while in ABC multilayers,
in contrast, it opens an energy gap in the surface-state band at low energy,
leading to a strong screening effect essentially non-linear to the field
amplitude. The energy gap of a large ABC stack sharply rises when the external
field exceeds a certain critical value.Comment: 8 pages, 6 figure
Control of chromosome interactions by condensin complexes
Although condensin protein complexes have long been known for their central role during the formation of mitotic chromosomes, new evidence suggests they also act as global regulators of genome topology during all phases of the cell cycle. By controlling intra-chromosomal and inter-chromosomal DNA interactions, condensins function in various contexts of chromosome biology, from the regulation of transcription to the unpairing of homologous chromosomes. This review highlights recent advances in understanding how these global functions might be intimately linked to the molecular architecture of condensins and their extraordinary mode of binding to DNA
The cohesin ring concatenates sister DNA molecules
Sister chromatid cohesion, which is essential for mitosis, is mediated by a multi-subunit
protein complex called cohesin whose Scc1, Smc1, and Smc3 subunits form a tripartite
ring structure. It has been proposed that cohesin holds sister DNAs together by trapping
them inside its ring. To test this, we used site-specific cross-linking to create chemical
connections at the three interfaces between the ring’s three constituent polypeptides,
thereby creating covalently closed cohesin rings. As predicted by the ring entrapment
model, this procedure produces dimeric DNA/cohesin structures that are resistant to
protein denaturation. We conclude that cohesin rings concatenate individual sister
minichromosome DNAs
Electronic states and Landau levels in graphene stacks
We analyze, within a minimal model that allows analytical calculations, the
electronic structure and Landau levels of graphene multi-layers with different
stacking orders. We find, among other results, that electrostatic effects can
induce a strongly divergent density of states in bi- and tri-layers,
reminiscent of one-dimensional systems. The density of states at the surface of
semi-infinite stacks, on the other hand, may vanish at low energies, or show a
band of surface states, depending on the stacking order
A framework for automatic semantic video annotation
The rapidly increasing quantity of publicly available videos has driven research into developing automatic tools for indexing, rating, searching and retrieval. Textual semantic representations, such as tagging, labelling and annotation, are often important factors in the process of indexing any video, because of their user-friendly way of representing the semantics appropriate for search and retrieval. Ideally, this annotation should be inspired by the human cognitive way of perceiving and of describing videos. The difference between the low-level visual contents and the corresponding human perception is referred to as the ‘semantic gap’. Tackling this gap is even harder in the case of unconstrained videos, mainly due to the lack of any previous information about the analyzed video on the one hand, and the huge amount of generic knowledge required on the other. This paper introduces a framework for the Automatic Semantic Annotation of unconstrained videos. The proposed framework utilizes two non-domain-specific layers: low-level visual similarity matching, and an annotation analysis that employs commonsense knowledgebases. Commonsense ontology is created by incorporating multiple-structured semantic relationships. Experiments and black-box tests are carried out on standard video databases for action recognition and video information retrieval. White-box tests examine the performance of the individual intermediate layers of the framework, and the evaluation of the results and the statistical analysis show that integrating visual similarity matching with commonsense semantic relationships provides an effective approach to automated video annotation
Cart3D Simulations for the Second AIAA Sonic Boom Prediction Workshop
Simulation results are presented for all test cases prescribed in the Second AIAA Sonic Boom Prediction Workshop. For each of the four nearfield test cases, we compute pressure signatures at specified distances and off-track angles, using an inviscid, embedded-boundary Cartesian-mesh flow solver with output-based mesh adaptation. The cases range in complexity from an axisymmetric body to a full low-boom aircraft configuration with a powered nacelle. For efficiency, boom carpets are decomposed into sets of independent meshes and computed in parallel. This also facilitates the use of more effective meshing strategies - each off-track angle is computed on a mesh with good azimuthal alignment, higher aspect ratio cells, and more tailored adaptation. The nearfield signatures generally exhibit good convergence with mesh refinement. We introduce a local error estimation procedure to highlight regions of the signatures most sensitive to mesh refinement. Results are also presented for the two propagation test cases, which investigate the effects of atmospheric profiles on ground noise. Propagation is handled with an augmented Burgers' equation method (NASA's sBOOM), and ground noise metrics are computed with LCASB
Comparison of insulin glargine and liraglutide added to oral agents in patients with poorly controlled type 2 diabetes
Peer reviewe
Integer Quantum Hall Effect in Graphite
We present Hall effect measurements on highly oriented pyrolytic graphite
that indicate the occurrence of the integer quantum-Hall-effect. The evidence
is given by the observation of regular plateau-like structures in the field
dependence of the transverse conductivity obtained in van der Pauw
configuration. Measurements with the Corbino-disk configuration support this
result and indicate that the quasi-linear and non-saturating longitudinal
magnetoresistance in graphite is governed by the Hall effect in agreement with
a recent theoretical model for disordered semiconductors.Comment: 3 figures, to be published in Solid State Communication (2006
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