Light absorption of (oxy-)hemoglobin assessed by spectroscopic optical coherence tomography

The combination of optical coherence tomography and spectroscopy may allow for highly localized, quantitative measurements of tissue spectral properties. We present, for the first time to our knowledge, quantitative measurements of the absorption coefficients of phantoms and of hemoglobin and oxygenated hemoglobin with spectroscopic optical coherence tomography (SOCT). Our results suggest that SOCT will be able to provide localized, quantitative oxygenation measurements.     

A semiclassical model for the vibrational excitation of spherical-top molecules in collisions with ions

A simple theory is presented to explain the previously observed single-mode vibrational excitation of the spherical-top molecules CH₄, CF₄ and SF₆ in collisions with H⁺ and Li⁺. The theory is based on a three-dimensional forced-oscillator model which has been modified to take account of many independent harmonic oscillators. For small-angle collisions the linear driving forces are the dipole-, polarizability- and quadrupole-derivatives taken from IR, Raman spectroscopy and simple estimates, respectively. To explain the results at larger angles near and beyond the rainbow it has been necessary to introduce short-range repulsive forces between the ions and the outer atoms of the molecule. For small angles both the predicted first moment of the energy transfer and the time-of-flight spectra agree quantitatively with the experimental results. At large angles, for which only the first moment of the energy is available, good qualitative agreement is obtained after a slight adjustment of the potential parameters. The energy transfer as a function of time is calculated and shows a different oscillatory behavior for the proton and Li⁺-ion systems. Also the effect of intra-mode coupling is investigated and shown to have only a small effect on the overall energy transfer. The paper closes with a discussion of the implications of these experiments and the possible role of rotational excitation. The field strengths in these ion scattering experiments are shown to be greater than in the strongest focused Q-switched laser pulses.     

The application of organic compounds as thermochemical agents in spectrochemical analysis: The effects of tetraethylammonium iodide in the determination of impurities in materials containing molybdenum

The reducing action of some aliphatic and aromatic hydrocarbon derivatives on the oxides of Me, W, Ti, Zr, Nb and Ta was compared to that of graphite powder. The investigation showed that among the organic compounds studied tetraethylammonium iodide gives a better separation of the volatile elements As, Te, Sn, Pb, Bi, Cd, Ag and In, which commonly occur in the above oxides as impurities, from the molybdenum and better line intensities than when using graphite powder. The possible reduction and iodide forming reactions which take place in the electrode cavity in the presence of tetraethylammonium iodide have been established by using calculated values for the change in the Gibbs free energy and the results of X-ray analyses of sample residues obtained after arcing. This reagent was also found to stabilize the are colunm temperature, a necessary condition for its successful application as a spectroscopic buffer.     

Über holomorphe Abbildungen projektiv-algebraischer Mannigfaltigkeiten auf komplexe Räume

Ohne ZusammenfassungUnterstützt durch Air Force Office of Scientific Research, AF 49 (638)-253, S/A1.     

Scaling behavior of delayed demixing, rheology, and microstructure of emulsions flocculated by depletion and bridging

This paper describes an experimental comparison of microstructure, rheology, and demixing of bridging- and depletion-flocculated oil-in-water emulsions. Confocal scanning laser microscopy imaging showed that bridging-flocculated emulsions were heterogeneous over larger length scales than depletion-flocculated emulsions. As a consequence, G' as determined from diffusing wave spectroscopy (DWS) corresponded well with G' as measured macroscopically for the depletion-flocculated emulsions, but this correspondence was not found for the bridging-flocculated emulsions. The heterogeneity of bridging-flocculated emulsions was confirmed by DWS-echo measurements, indicating that their structure breaks up into large fragments upon oscillatory shear deformation larger than 1%. Depletion- and bridging-flocculated emulsions showed a different scaling of the storage modulus with the volume fraction of oil and a difference in percolation threshold volume fraction. These differences will be discussed on the basis of the two types of droplet-droplet interactions studied. Gravity-induced demixing occurred in both emulsions, but the demixing processes differed. After preparation of bridging-flocculated emulsions, serum immediately starts to separate, whereas depletion-flocculated systems at polysaccharide concentrations in the overlap regime usually showed a delay time before demixing. The delay time was found to scale with the network permeability, B; the viscosity, eta, of the aqueous phase; and the density difference between oil and water, Deltarho, as tdelay approximately B(-1)etaDeltarho(-1). The results are in line with the mechanism proposed by Starrs et al. (J. Phys.: Condens. Matter 2002, 14, 2485-2505), where erosion of the droplet network leads to widening of the channels within the droplet networks, facilitating drainage of liquid.     

Approximate analysis of the delivery splitting model

The concept of order splitting has been proposed primarily to enable buyers to obtain substantial inventory savings. In this paper we investigate the order splitting concept from the suppliers point of view, referred to as delivery splitting. We will show that for the supplier considerable cost savings can be obtained by using the concept of delivery splitting, although the motivation and the practical implementation can be different for buyer and supplier. Also we will show that an analytical (although approximative) treatment of the delivery splitting concept is feasible, which brings the concept within reach of practical implementation.