Observation Of Mode Selective Vibrational Excitation Of SF6 By Collisions With 4–10 eV Li And H Ions

Structured time of flight spectra of both Li⁺ and H⁺ ions scattered from ground state SF₆, have been measured at angles (5.0° v_c.m. 16.6°) less than the rainbow angle at E_c.m., = 4.3 eV and 9.7 eV, respectively. The structure can be arttributed to vibrational excitation of the v₃ mode by H⁺ and excitation of the v₄ mode by Li⁺. The relative transition probabilities obey a Poisson distribution and can be explained by a simple forced oscillator model.     

Toward assessment of blood oxygen saturation by spectroscopic optical coherence tomography

The use of spectroscopic optical coherence tomography to assess hemoglobin oxygen saturation of whole blood is investigated. We propose to use the differential attenuation coefficient to determine the degree of saturation. Our data show qualitative agreement between the measured differential attenuation coefficients as a function of saturation and predictions based on the oxygen-saturation-dependent absorption and scattering properties of blood.     

Towards an axiomatization of orderings

A set of six axioms for sets of relations is introduced. All well-known sets of specific orderings, such as linear and weak orderings, satisfy these axioms. These axioms impose criteria of closedness with respect to several operations, such as concatenation, substitution and restriction. For operational reasons and in order to link our results with the literature, it is shown that specific generalizations of the transitivity condition give rise to sets of relations which satisfy these axioms. Next we study minimal extensions of a given set of relations which satisfy the axioms. By this study we come to the fundamentals of orderings: They appear to be special arrangements of several types of disorder. Finally we notice that in this framework many new sets of relations have to be regarded as a set of orderings and that it is not evident how to minimize the number of these new sets of orderings.Symbol Table U universe (infinite countable) - D set of possible domains (finite and non-empty subsets of U) - R set of all considered relations - A empty relation on A - Id A identity relation on A - All A all relation on A - c complement operator (see Definition 2.1) - v converse operator (see Definition 2.1) - s symmetric part (see Definition 2.1) - asymmetric part (see Definition 2.1) - n non-diagonal part (see Definition 2.1) - r reflexive closure (see Definition 2.1) We gratefully acknowledge the support by the Co-operation Centre of Tilburg and Eindhoven Universities.     

On the Structure of Graphs with Bounded Asteroidal Number

 A set A⊆V of the vertices of a graph G=(V,E) is an asteroidal set if for each vertex a∈A, the set A\{a} is contained in one component of G−N[a]. The maximum cardinality of an asteroidal set of G, denoted by an (G), is said to be the asteroidal number of G. We investigate structural properties of graphs of bounded asteroidal number. For every k≥1, an (G)≤k if and only if an (H)≤k for every minimal triangulation H of G. A dominating target is a set D of vertices such that D∪S is a dominating set of G for every set S such that G[D∪S] is connected. We show that every graph G has a dominating target with at most an (G) vertices. Finally, a connected graph G has a spanning tree T such that d _T (x,y)−d _G (x,y)≤3·|D|−1 for every pair x,y of vertices and every dominating target D of G. Received: July 3, 1998 Final version received: August 10, 1999     

An identification problem for a time periodic nonlinear wave equation in non cylindrical domains

The existence of a time-periodic solution of a free boundary nonlinear wave equation in non cylindrical domains is established. The problem arises in the study of the identification of the coefficient of the wave equation and of the boundary of the region from the observed values of the solution in a fixed subregion.     

Doppler-based lateral motion tracking for optical coherence tomography

Nonuniform lateral scanning of the probe beam in optical coherence tomography produces imaging artifacts and leads to a morphologically inaccurate representation of the sample. Here, we demonstrate a solution to this problem, which is based on the Doppler shift carried by the complex-valued depth-resolved scattering amplitude. Furthermore, we demonstrate the feasibility of Doppler flow velocity measurements in underlying flow channels while laterally scanning the imaging probe over large surfaces with arbitrary and varying velocity. Finally, we performed centimeters-long hand-held B-mode imaging of skin in vivo.