Une caractérisation des espaces affins basée sur la notion de droite

Sans résumé     

Molecular symmetry and exciton interaction in photosynthetic primary events

In this paper, the molecular details of the recently proposed energy upconversion theory of photosynthesis are reviewed. The primary light reactions are explained in terms of aC ₂ symmetrical structure of the reaction center involving a (Chl?H₂O)₂ adduct. It is shown that exciton interaction within the (Chl?H₂O)₂ complex leads to an antisymmetric triplet state which may act as an energy trap. The presence of the energy trap in the reaction center suggests that the trigger step for the photoionization of active chlorophylls may involve the summation of two red excitation photons. Under normal conditions, the steadystate one-photon-per-electron quantum requirement is obtained. The functional properties of the various molecular constituents of the Chl-a molecule, such as the Ring V β-ketoester group, the phytyl tail, the central Mg atom, and the π-system of the macrocycle are explained within the present theoretical framework. A detailed analysis is given of the postulates and the consequences of the proposed model. The ramifications of the theory are probed, and their biological consequences are suggested for future study.     

Etude comparative des proprietes magnetiques des oxydes lamellaires ACrO2 (A = Li,Na, K)—I: Etude par effet Mössbauer de LiCrO2 dope par le fer

A Mössbauer study of the dimensionality of magnetic interactions in the layer oxide LiCr_0.99Fe_0.01O₂ shows a 2-D behaviour.     

Canonical representation of certain optimal control problems

Certain nonlinear optimal control problems on a manifold can be represented in terms of a switchable family of regulated paths in the space of continuously differentiable vector fields. The methods also yield a theorem on the Dieudonné-Albrecht integrability conditions for non-autonomous first order differential equations on a Banach space.     

Uniqueness of the inversive plane of order 7

A search has shown that any inversive plane of order 7 must be isomorphic with the Miquelian plane. The method used was explicitly set out in a companion paper, which was concerned with a plane of order 5.     

Quantitative aspects of internal reflection spectroscopy: Polymer surface composition measurement

The use of band-ratioing techniques in internal reflection spectroscopy (IRS) for a wide variety of polymer surface composition and orientation measurements is discussed. It is shown that quantitative data can be obtained under a wide range of experimental conditions. The effects of variations in sample contact, internal reflection element, and angle of incidence are considered in detail. The applicability and limitations of calibration procedures for the determination of surface composition under various experimental conditions are considered. The requirements for obtaining quantitative results by IRS are shown to be far more lenient than is typically assumed.     

Acoustic radiation from a fluid-filled, subsurface vascular tube with internal turbulent flow due to a constriction

The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interaction with the tube wall and surrounding viscoelastic medium. Analytical predictions are compared with experimental measurements conducted on a flow model system using laser Doppler vibrometry to measure tube vibration and the vibration of the surrounding viscoelastic medium. Fluid pressure within the tube was measured with miniature hydrophones. Discrepancies between theory and experiment, as well as the coupled nature of the fluid-structure interaction, are described. This study is relevant to and may lead to further insight into the patency and mechanisms of vascular failure, as well as diagnostic techniques utilizing noninvasive acoustic measurements.