Statistics of Gaussian Speckles with Enhanced Fluctuations

Some first-order statistics of speckle fields obeying the complex Gaussian probability density are investigated with the special emphasis on a possibility for the speckle contrast to exceed unity. It is shown that such enhanced fluctuations of speckle fields are generated when the probability density of the complex amplitude is non-circular with the vanishing mean. This means that Gaussian speckles having the contrast of unity are not necessarily fully developed speckles. Some practical situations producing such enhanced fluctuations in speckle fields are discussed.     

Effects of differences in charge and hydrophobicity of surface amino acids of hemoglobins on high-performance gel-permeation chromatography

We studied the elution properties of the carboxy and deoxy forms of hemoglobins A, S, and C in gel-permeation high-performance liquid chromatography using TSK-GEL-SW-type columns. Since these hemoglobins have the same molecular mass but different amino acids at the beta 6 position, they are ideal for studies of the effect of charge and hydrophobicity on elution patterns in high-performance gel-permeation chromatography. Although there was a linear relationship between elution volume and logarithm of molecular mass of various proteins, the elution volumes of carboxyhemoglobins were found to be slightly greater than the expected volumes calculated from the molecular mass. The elution volumes of hemoglobins increased in the order of hemoglobins F, A, C, and S in 0.1 M phosphate buffer, pH 7.4, at room temperature. The elution volume of these hemoglobins was also dependent on pH and salt concentration. These results indicate that elution of these hemoglobins was affected by the electrostatic and hydrophobic interactions between hemoglobin molecules and polar sites of silica gel (with silanol groups) of the resin matrix of TSK-G2000-SW. This study may serve as a useful reference for separation and determination of molecular masses of proteins in the native state using gel-permeation liquid chromatography.     

Lau effect and noncoherent processing

The Lau effect has been discussed from various points of view. In this paper, a new geometrical approach for the Lau effect is presented. This approach also shows the paradoxical result of Gori which has been obtained from coherence theory. Based on the present analysis, the two gratings are used to modify a noncoherent system as a coherent multichannel system An experimental result is shown for the edge enhancement.     

Selective oxidation of methane to formaldehyde over antimony oxide-loaded catalyst

A possibility of antimony oxide as a catalyst for the selective oxidation of methane with oxygen to formaldehyde was investigated. The activity measurement was carried out at an atmospheric pressure and at 873 K, where the homogeneous gas-phase reaction was negligible. Oxidized diamond (O-Dia)-supported antimony oxide catalyst produced 1.3 mmol h⁻¹ g-cat⁻¹ of formaldehyde with a formaldehyde selectivity of 23%. On the other hand, SiO₂ supported antimony oxide catalyst exhibited negligible catalytic activity. XRD and UV–vis analyses revealed that -Sb₂O₄ was formed on the oxidized diamond while Sb₆O₁₃ was formed on SiO₂. Selective oxidation of methane to formaldehyde seemed to proceed on -Sb₂O₄ with moderate activity and selectivity to formaldehyde, via a redox cycle of -Sb₂O₄ and Sb₂O_4−x. On the other hand, Sb₆O₁₃ on SiO₂ was stable under the reaction conditions and the selective oxidation occurred only slightly.     

Quality control of PET radiopharmaceuticals by high‐performance liquid chromatography with tris(2,2′‐bipyridyl)ruthenium(II) electrogenerated chemiluminescence detection

A highly sensitive reversed‐phase liquid chromatographic (HPLC) method was investigated to analyze a range of positron emission tomography (PET) radiopharmaceuticals using electrogenerated chemiluminescence (ECL) detection. ECL is based on the reaction of PET molecules with tris(2,2′‐bipyridyl)ruthenium(III) [Ru(bpy)₃³⁺], which is generated through the on‐line electro‐oxidation of Ru(bpy)₃²⁺. In 21 different radiopharmaceuticals studied, 18 compounds could be detected with detection limits (signal‐to‐noise ratio = 3) of 0.12–72 ng/mL per 20 μL injection. Sufficient reproducibility and linearity were obtained for the quantitative determination of PET molecules in pharmaceutical fluid. This method could be successfully applied to quality control tests of PET radiopharmaceuticals with ultra‐high specific radioactivity. Copyright © 2009 John Wiley & Sons, Ltd.