Search results for "Spheres"

On the Energy of Distributions, with Application to the Quaternionic Hopf Fibrations

2001

The energy of an oriented q-distribution ? in a compact oriented manifold M is defined to be the energy of the section of the Grassmannian manifold of oriented q-planes in M induced by ?. In the Grassmannian, the Sasaki metric is considered. We show here a condition for a distribution to be a critical point of the energy functional. In the spheres, we see that Hopf fibrations \(\) are critical points. Later, we prove the instability for these fibrations.

Stable Images and Discriminants

2020

We show that the discriminant/image of a stable perturbation of a germ of finite \(\mathcal {A}\)-codimension is a hypersurface with the homotopy type of a wedge of spheres in middle dimension, provided the target dimension does not exceed the source dimension by more than one. The number of spheres in the wedge is called the discriminant Milnor number/image Milnor number. We prove a lemma showing how to calculate this number, and show that when the target dimension does not exceed the source dimension, the discriminant Milnor number and the \(\mathcal {A}\)-codimension obey the “Milnor–Tjurina relation” familiar in the case of isolated hypersurface singularities. This relation remains conj…

Polyelectrolytes Grafted to Curved Surfaces

1996

We present a scaling theory to describe equilibrium conformations of weakly charged polyelectrolyte molecules grafted at one end onto impermeable surfaces of various morphologies (spheres, cylinders) and of arbitrary curvature. We focus on the case of sufficiently densely grafted chains, i.e., on curved polyelectrolyte brushes. Different regimes of the behavior of curved polyelectrolyte brushes can be distinguished, depending on grafting density, surface curvature, and chain length. We present phase diagrams of the system describing these regimes and discuss the crossover conditions. We also analyze the effect of charge annealing in curved polyelectrolyte brushes.

Altered cerebral blood flow velocity features in fibromyalgia patients in resting-state conditions

2017

[EN] The aim of this study is to characterize in resting-state conditions the cerebral blood flow velocity (CBFV) signals of fibromyalgia patients. The anterior and middle cerebral arteries of both hemispheres from 15 women with fibromyalgia and 15 healthy women were monitored using Transcranial Doppler (TCD) during a 5-minute eyes-closed resting period. Several signal processing methods based on time, information theory, frequency and time-frequency analyses were used in order to extract different features to characterize the CBFV signals in the different vessels. Main results indicated that, in comparison with control subjects, fibromyalgia patients showed a higher complexity of the envel…

Hydrodynamic chromatography of macromolecules on small spherical non-porous silica particles

1990

Abstract Non-porous silica spheres with sizes in the range 1.4–2.7 μm were applied as packings for the hydrodynamic chromatography (HDC) of macromolecules. Highly efficient columns, with a reduced plate height below 2, were packed with these small particles. Up to molecular weights of 10 6 the elution behaviour of polystyrenes agreed very well with existing theoretical models. However, for larger polystyrenes the flow-rate exerted an influence on the relative peak positions. The applicability of HDC to rapid separations of soluble macromolecules and inorganic colloids was demonstrated.

Phase behaviour of deionized binary mixtures of charged colloidal spheres.

2009

We review recent work on the phase behaviour of binary charged sphere mixtures as a function of particle concentration and composition. Both size ratios and charge ratios are varied over a wide range. By contrast to hard spheres the long ranged Coulomb interaction stabilizes the crystal phase at low particle concentrations and shifts the occurrence of amorphous solids to particle concentrations considerably larger than the freezing concentration. Depending on size- and charge ratios we observe upper azeotrope, spindle, lower azeotrope and eutectic types of phase diagrams, all known well from metal systems. Most solids are of body centred cubic structure. Occasionally stoichiometric compound…

Suppressor of cytokine signaling 3 sensitizes anaplastic thyroid cancer to standard chemotherapy

2009

We previously showed that cancer cells from papillary, follicular, and anaplastic thyroid carcinomas produce interleukin-4 and interleukin-10, which counteract the cytotoxic activity of conventional chemotherapy through the up-regulation of antiapoptotic molecules. Here, we identify Janus kinase/signal transducers and activators of transcription (STAT) and phosphatidyl inositol 3-kinase (PI3K)/AKT as the down-stream pathways through which these cytokines confer resistance to cell death in thyroid cancer. We found that the absence of suppressors of cytokine signaling (SOCS) molecules allows the propagation of the survival signaling. Exogenous expression of SOCS1, SOCS3, and SOCS5 in the high…

Stable products of spheres in the non-linear coupling of oscillators or quasi-periodic motions

2004

Abstract For generic families of vector fields or transformations, normally hyperbolic invariant products of spheres appear near partially elliptic rest points. To cite this article: M. Kammerer-Colin de Verdiere, C. R. Acad. Sci. Paris, Ser. I 339 (2004).

Optimization of local delivery of antifungal agents in the oral cavity by a new formulation

2012

In recent years, with the increased use of antibiotics and immunosuppres-sive agents, there was an increased incidence of oral mycosis and Candida albicans is the most common etiologic agent in oropharyngeal candidiasis, especially in patients with HIV. The aim of this work is to develop a new dosage form containing miconazole (MN) to be topically applied on oral mucosa, allowing for a massive penetration of the drug in the tissue. The vehicle for the drug delivery was lipid microparticles incorporated in a hydrophilic gel. The lipospheres were obtained by hot melt encapsulation method using as matrix ingredients a mixtures of esters of fatty acids with higher fatty alcohols, having low mel…

THE INTERACTION OF THE STELLAR HIGH ENERGY RADIATION WITH THE CIRCUMSTELLAR MEDIUM

The purpose of this Thesis is to study how stellar high energy radiation affects exo- planetary atmospheres. High level of stellar high energy, X-rays and (vacuum end extreme) ultraviolet radiation may prevent planets’ habitability and limit the width of the habitability zone. Such radiation may ionize a star surrounding, affecting the chemistry and thermal bal- ance. The effects of X-rays can be wide ranging or relatively local. Soft X-rays are absorbed closer to the source than X-rays with energy greater than 1 keV. The absorption cross-section of hard X-rays are generally very small, so that such radiation may affect a whole galaxy to some extent. The product of photo-ionization is a cas…