Search results for "SPHERES"

Quantification of resting myocardial blood flow in a pig model of acute ischemia based on first-pass MRI

2005

Qualitative and semiquantitative contrast-enhanced (CE) dynamic perfusion MRI techniques are established as noninvasive diagnostic means of assessing coronary artery disease. However, to date quantification of myocardial blood flow (MBF) has not reached the same acceptance as MBF quantification with nuclear techniques. To validate quantification of MBF at rest using the extracellular contrast agent (CA) Gd-DTPA, we performed an animal study in a pig model of acute myocardial ischemia. We quantified MBF from MRI data with a mathematical model (MMID4) of the underlying vasculature. These MBF results were subsequently compared with the results from fluorescent microspheres. The study showed a …

Low-cost approximate reconstructing of heterogeneous microstructures

2016

We propose an approximate reconstruction of random heterogeneous microstructures using the two-exponent power-law (TEPL). This rule originates from the entropic descriptor (ED) that is a multi-scale measure of spatial inhomogeneity for a given microstructure. A digitized target sample is a cube of linear size L in voxels. Then, a number of trial configurations can be generated by a model of overlapping spheres of a fixed radius, which are randomly distributed on a regular lattice. The TEPL describes the averaged maximum of the ED as a function of the phase concentration and the radius. Thus, it can be used to determine the radius. The suggested approach is tested on surrogate samples of cer…

Design of the CGAL 3D Spherical Kernel and application to arrangements of circles on a sphere

2009

AbstractThis paper presents a cgal kernel for algorithms manipulating 3D spheres, circles, and circular arcs. The paper makes three contributions. First, the mathematics underlying two non-trivial predicates are presented. Second, the design of the kernel concept is developed, and the connexion between the mathematics and this design is established. In particular, we show how two different frameworks can be combined: one for the general setting, and one dedicated to the case where all the objects handled lie on a reference sphere. Finally, an assessment about the efficacy of the 3D Spherical Kernel is made through the calculation of the exact arrangement of circles on a sphere. On average w…

The isoperimetric inequality and the geodesic spheres. Some geometric consequences

1986

VLTI/AMBER spectro-interferometry of the late-type supergiants V766 Cen (=HR 5171 A), σ Oph, BM Sco, and HD 206859

2017

Aims. We add four warmer late-type supergiants to our previous spectro-interferometric studies of red giants and supergiants. Methods. We measure the near-continuum angular diameter, derive fundamental parameters, discuss the evolutionary stage, and study extended atmospheric atomic and molecular layers. Results. V766 Cen (=HR 5171 A) is found to be a high-luminosity (log L/L = 5.8 ± 0.4) source of effective temperature 4290 ± 760 K and radius 1490 ± 540 R, located in the Hertzsprung-Russell (HR) diagram close to both the Hayashi limit and Eddington limit; this source is consistent with a 40 M evolutionary track without rotation and current mass 27-36 M. V766 Cen exhibits Na i in emission a…

Bioactive and biodegradable silica biomaterial for bone regeneration.

2014

Biosilica, a biocompatible, natural inorganic polymer that is formed by an enzymatic, silicatein-mediated reaction in siliceous sponges to build up their inorganic skeleton, has been shown to be morphogenetically active and to induce mineralization of human osteoblast-like cells (SaOS-2) in vitro. In the present study, we prepared beads (microspheres) by encapsulation of β-tricalcium phosphate [β-TCP], either alone (control) or supplemented with silica or silicatein, into the biodegradable copolymer poly(d,l-lactide-co-glycolide) [PLGA]. Under the conditions used, ≈5% β-TCP, ≈9% silica, and 0.32μg/mg of silicatein were entrapped into the PLGA microspheres (diameter≈800μm). Determination of …

Fabrication and Modelling of Three-Dimensional Sub-kelvin Phononic Crystals

2012

We have investigated the fabrication and computational modelling of threedimensional phononic crystals for the observation of full band gaps for thermal phonons at sub-kelvin temperatures. Self-assembled arrays of monodisperse polystyrene nanospheres have been fabricated using a vertical deposition technique. Optimal conditions for increasing crystal domain size and crystalline quality have been studied. In addition, the phononic band structure has been computed using the finite element method for the simple cubic lattice. The dependence of band structure on contact area between spheres has also been studied. For small enough contact area a large band gap is observed, predicting a strong in…

Damping by bulk and shear viscosity for confined acoustic phonons of a spherical virus in water

2007

International audience; A sphere-like virus in water is modeled as a homogeneous isotropic elastic continuum sphere in contact with an infinite viscous compressible Newtonian fluid. The frequencies and damping of the confined vibrational modes of the sphere are calculated for the material parameters of a virus in water. While the effects of viscosity are found to be negligible for a virus-like sphere of macroscopic size, for nanoscale viruses both the frequency and damping of the vibrational modes are significantly affected by the viscosity of the water. Furthermore, both shear viscosity and bulk viscosity play an important role.

Characterization of cell wall proteins of yeast and hydrophobic mycelial cells of Candida albicans

1991

Cell surface hydrophobicity (CSH) of blastoconidia and blastoconidia bearing germ tubes of Candida albicans ATCC 26555 was monitored by assessing attachment of polystyrene microspheres to the cell surface, and we found that mature hyphae were significantly hydrophobic. Treatment of intact cells with low concentrations of beta-glucanase (Zymolyase 20T) or proteases abolished or significantly reduced attachment of latex beads to hyphae. This effect paralleled an obvious reduction in CSH of the entire cell population, as measured by an aqueous-hydrocarbon biphasic partitioning assay. Analysis of the cell wall material released by Zymolyase and adsorbed on polystyrene microspheres indicated tha…

Core–Shell Nanorod Columnar Array Combined with Gold Nanoplate–Nanosphere Assemblies Enable Powerful In Situ SERS Detection of Bacteria

2016

Development of a label-free ultrasensitive nanosensor for detection of bacteria is presented. Sensitive assay for Gram-positive bacteria was achieved via electrostatic attraction-guided plasmonic bifacial superstructure/bacteria/columnar array assembled in one step. Dynamic optical hotspots were formed in the hybridized nanoassembly under wet-dry critical state amplifying efficiently the weak vibrational modes of three representative food-borne Gram-positive bacteria, that is, Staphylococcus xylosus, Listeria monocytogenes, and Enterococcus faecium. These three bacteria with highly analogous Raman spectra can be effectively differentiated through droplet wet-dry critical SERS approach combi…