Far-infrared and mid-infrared absorption in (Bi,Pb)-Sr-(Ca,Y)-Cu-O

The reflectivities of seven films belonging to the Bi-Sr-Ca-Cu-O family, with T_c ranging from 60 to 95 K, and of a single crystal of insulating Bi-Sr-Y-Cu-O, have been measured at room temperature in the normal phase. The optical conductivity has been analyzed in terms of Drude (D), mid-infrared (MIR), and charge-transfer (CT) contributions. As T_c increases, the spectral weight within the charge-transfer gap (D+MIR) increases. Meanwhile, the peak frequency of the MIR band moves towards the far-infrared and the optical conductivity becomes more similar to that of a normal metal.     

Synergistic catalysis of anthrone Diels-Alder reactions

[reaction: see text] The combination of an amine base and Lewis acid (Li+) leads to synergistic catalysis of the Diels-Alder reaction of anthrone with methyl crotonate and some other less reactive dienophiles. These cycloadditions either do not occur with the individual catalysts used separately or they are greatly accelerated by the combined catalysts. DMSO solvent allows the use of LiCl as the Lewis acid source and can provide greater control of subsequent conversion to Michael adduct.     

Rheological properties and orientational distributions of dilute ferromagnetic spherocylinder particle dispersions. Part II. Analysis for the two typical magnetic field directions

We have investigated the orientational distributions and rheological properties of dilute colloidal dispersions, which consist of ferromagnetic spherocylinder particles. First, the governing equation of the orientational distribution function has been derived for the typical two cases of magnetic field directions: the direction parallel to the shear flow and the direction parallel to the angular velocity vector of the shear flow. The equation has been solved approximately by Galerkin's method. With these numerical solutions we have obtained the results of the orientational distribution and viscosity. The results obtained for the magnetic field in the shear flow direction are summarized as follows. In the case of a weak magnetic field, the particle tends to orient nearly toward the shear flow direction and its opposite direction. As the magnetic field increases, the orientation of the particle is restricted and the viscosity increases significantly. As the influence of the magnetic field becomes dominant, an overshoot in the viscosity curve appears. This is due to the fact that there is a maximum deviation of the averaged particle direction from the magnetic field direction. When the strength of the magnetic field increases significantly, the particle inclines close to the magnetic field direction and the viscosity converges to a constant value. Particles with a larger aspect ratio give rise to a larger increment in the viscosity since such elongated particles induce larger resistance in a flow field. We also have obtained results for the case of the magnetic field in the direction parallel to the angular velocity vector of the shear flow. When the flow field is dominant over both the rotational Brownian motion and the magnetic interaction, the particle rotates in the plane nearly perpendicular to the magnetic field direction. As the magnetic field increases, the particle inclines toward the magnetic direction. For this direction of field, the viscosity is independent of the magnetic field and is always zero.     

New algorithms for processing and peak detection in liquid chromatography/mass spectrometry data

Two new algorithms for automated processing of liquid chromatography/mass spectrometry (LC/MS) data are presented. These algorithms were developed from an analysis of the noise and artifact distribution in such data. The noise distribution was analyzed by preparing histograms of the signal intensity in LC/MS data. These histograms are well fit by a sum of two normal distributions in the log scale. One new algorithm, median filtering, provides increased performance compared to averaging adjacent scans in removing noise that is not normally distributed in the linear scale. Another new algorithm, vectorized peak detection, provides increased robustness with respect to variation in the noise and artifact distribution compared to methods based on determining an intensity threshold for the entire dataset. Vectorized peak detection also permits the incorporation of existing algorithms for peak detection in ion chromatograms and/or mass spectra. The application of these methods to LC/MS spectra of complex biological samples is described.     

Production of high energy deuterons in the reaction:3He+3He→4He+2H+e ++v

Experiments on the reaction:³He+³He→⁴He+²He using a single four detector telescope have shown evidence for the production of deuteron pulses, consistent with the²He→²H+e⁺+v fusion reaction in the final state. New measurements on the same reaction using improved techniques viz.A) a windowless³He gas target andB) α- d correlation detection with 5 ns resolving time and antipileup circuitry have been performed. Calibrations were obtained from the⁷Li+³He→²H+⁴He+⁴He reaction spectra. The correlation angles were 30° and 97° for the alphas and deuterons respectively. Deuteron pulses have been observed, correlated with alpha particles. A cross section of (1.7 ±0.5)nbsr^?1MeV^?1 was obtained consistent with previous measurements using a single telescope.     

Microfluidic flow focusing: drop size and scaling in pressure versus flow-rate-driven pumping

We experimentally study the production of micrometer-sized droplets using microfluidic technology and a flow-focusing geometry. Two distinct methods of flow control are compared: (i) control of the flow rates of the two phases and (ii) control of the inlet pressures of the two phases. In each type of experiment, the drop size l, velocity U and production frequency f are measured and compared as either functions of the flow-rate ratio or the inlet pressure ratio. The minimum drop size in each experiment is on the order of the flow focusing contraction width a. The variation in drop size as the flow control parameters are varied is significantly different between the flow-rate and inlet pressure controlled experiments.