442 research outputs found
Turbulent-like fluctuations in quasistatic flow of granular media
We analyze particle velocity fluctuations in a simulated granular system
subjected to homogeneous quasistatic shearing. We show that these fluctuations
share the following scaling characteristics of fluid turbulence in spite of
their different physical origins: 1) Scale-dependent probability distribution
with non-Guassian broadening at small time scales; 2) Power-law spectrum,
reflecting long-range correlations and the self-affine nature of the
fluctuations; 3) Superdiffusion with respect to the mean background flow
On the three-dimensional temporal spectrum of stretched vortices
The three-dimensional stability problem of a stretched stationary vortex is
addressed in this letter. More specifically, we prove that the discrete part of
the temporal spectrum is only associated with two-dimensional perturbations.Comment: 4 pages, RevTeX, submitted to PR
Optical extinction in a single layer of nanorods
We demonstrate that almost 100 % of incident photons can interact with a
monolayer of scatterers in a symmetrical environment. Nearly-perfect optical
extinction through free-standing transparent nanorod arrays has been measured.
The sharp spectral opacity window, in the form of a characteristic Fano
resonance, arises from the coherent multiple scattering in the array. In
addition, we show that nanorods made of absorbing material exhibit a 25-fold
absorption enhancement per unit volume compared to unstructured thin film.
These results open new perspectives for light management in high-Q, low volume
dielectric nanostructures, with potential applications in optical systems,
spectroscopy, and optomechanics
Review of patient-specific simulations of transcatheter aortic valve implantation
International audienceTranscatheter Aortic Valve Implantation (TAVI) accounts for one of the most promising new cardiovascular procedures. This minimally invasive technique is still at its early stage and is constantly developing thanks to imaging techniques, computer science, biomechanics and technologies of prosthesis and delivery tools. As a result, patient-specific simulation can find an exciting playground in TAVI. It canexpress its potential by providing the clinicians with powerful decision support, offering great assistance in their workflow. Through a review of the current scientific field, we try to identify the challenges and future evolutions of patient-specific simulation for TAVI. This review article is an attempt to summarize and coordinate data scattered across the literature about patient-specific biomechanical simulation for TAVI
Phenyl 2,3,4-tri-O-benzyl-1-thio-α-d-mannopyranÂoside monohydrate
In the title compound, C33H34O5S·H2O, the mannopyranÂoside ring adopts a chair conformation with the 2-α-thioÂphenyl group occupying an axial position. One of the pendant benzyl groups is disordered over two sets of sites in a 0.5:0.5 ratio. In the crystal, the water molÂecule makes two O—H⋯O hydrogen bonds to an adjacent sugar molÂecule with the O atoms of the primary alcohol and ether groups acting as acceptors. At the same time, the OH group of the sugar makes a hydrogen bond to a water molÂecule
Enantiomerically Pure [2.2]Paracyclophane-4-thiol: A Planar Chiral Sulfur-Based Building Block Readily Available by Resolution with an Amino Acid Chiral Auxiliary
Acyl chloride of N-phthaloyl-(S)-isoleucine is an efficient chiral auxiliary for the resolution of (+/-)-[2.2]paracyclophane-4-thiol. A preparative protocol, based on the conversion into diastereoisomeric thiolesters and separation by two fractional crystallizations and column chromatography, was developed. Deprotection with LiAlH4 allowed isolation of the individual thiol enantiomers in good yield (similar to 40%) and high enantiomeric purity (ee >93%). The absolute configurations were determined by comparison of the optical rotation value of the products with literature data and were confirmed by X-ray crystallography
Synthesis of giant globular multivalent glycofullerenes as potent inhibitors in a model of Ebola virus infection
The use of multivalent carbohydrate compounds to block cell-surface lectin receptors is a promising strategy to inhibit the entry of pathogens into cells and could lead to the discovery of novel antiviral agents. One of the main problems with this approach, however, is that it is difficult to make compounds of an adequate size and multivalency to mimic natural systems such as viruses. Hexakis adducts of [60]fullerene are useful building blocks in this regard because they maintain a globular shape at the same time as allowing control over the size and multivalency. Here we report water-soluble tridecafullerenes decorated with 120 peripheral carbohydrate subunits, so-called ‘superballs’, that can be synthesized efficiently from hexakis adducts of [60]fullerene in one step by using copper-catalysed azide–alkyne cycloaddition click chemistry. Infection assays show that these superballs are potent inhibitors of cell infection by an artificial Ebola virus with half-maximum inhibitory concentrations in the subnanomolar range
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