Analysis of the GCR method with mixed precision arithmetic using QuPAT

To verify computation results of double precision arithmetic, a high precision arithmetic environment is needed. However, it is difficult to use high precision arithmetic in ordinary computing environments without any special hardware or libraries. Hence, we designed the quadruple precision arithmetic environment QuPAT on Scilab to satisfy the following requirements: (i) to enable programs to be written simply using quadruple precision arithmetic; (ii) to enable the use of both double and quadruple precision arithmetic at the same time; (iii) to be independent of any hardware and operating systems.To confirm the effectiveness of QuPAT, we applied the GCR method for ill-conditioned matrices and focused on the scalar parameters α and β in GCR, partially using DD arithmetic. We found that the use of DD arithmetic only for β leads to almost the same results as when DD arithmetic is used for all computations. We conclude that QuPAT is an excellent interactive tool for using double precision and DD arithmetic at the same time.     

Ultrasonic speed microscopy for imaging of coronary artery

We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featuring quantitative measurement of ultrasonic speed and attenuation of soft tissues. In the present study, we will propose a new concept ultrasonic speed microscopy that can measure the thickness and ultrasonic speed using fast Fourier transform of a single pulsed wave instead of continuous waves used in conventional SAM systems. Six coronary arteries were frozen and sectioned approximately 10 microm in thickness. They were mounted on glass slides without cover slips. The scanning time of a frame with 300 x 300 pixels was 121 s and two-dimensional distribution of ultrasonic speed was obtained. The ultrasonic speed was 1720 m/s in the thickened intima with collagen fiber, 1520 m/s in lipid deposition underlying fibrous cap and 1830 m/s in calcified lesion in the intima. These basic measurements will help understanding echogenecity in intravascular ultrasound (IVUS) images. Imaging of coronary artery with the ultrasonic speed microscopy provides important information for study of IVUS coronary imaging.     

Modification of nitroxyl contrast agents with multiple spins and their proton T(1) relaxivity

The purpose of this study is to test the performance of multispin nitroxyl contrast agents in improving the sensitivity of MR detection for nitroxyl contrast agents. The relation between T(1) relaxivity and the number of paramagnetic centers in a molecule was investigated. Compound 1 is a single molecule of methoxycarbonyl-PROXYL (MC-PROXYL). Two and three MC-PROXYL molecules were chemically coupled to obtain Compounds 2 and 3, which have two and three nitroxyl spins in the molecule, respectively. A good linear relation, the slope of which increased depending on the number of nitroxyl spins in the molecule, was obtained between T(1)-weighted (fast low-angle shot) MR image contrast enhancement at 7 T and the concentration of nitroxyl contrast agents. T(1)-weighted MR image contrast enhancement and T(1) relaxivity levels of nitroxyl contrast agents were increased depending on the number of nitroxyl spins in the molecule. Multicoupling nitroxyl molecules can enhance the T(1)-weighted contrast effect while maintaining the quantitative behavior of the molecule for up to three spins.     

Studies on nucleosides and nucleotides. X. desulfurization of 2′,3′-0-Isopropylidene-2-thiouridines by dibenzoyldiazene

The reaction of dibenzoyldiazene with 2′,3′-0-isopropylidene derivatives of 2-thioridine, 5-methyl-2-thiouridine, and 5-methoxycarbonylmethyl-2-thio-uridine afforded the corresponding desulfurized products, $\text{3a}$-$\text{3c}$.     

2-Alkoxycarbonylallyltrimethylsilanes as new reagents of 2-alkoxycarbonylallylation of electrophiles

2-Alkoxycarbonylallylsilanes are useful for 2-alkoxycarbonylallylation of acetals and carbonyl compounds with an aid of a Lewis acid; the products can be readily converted to α-methylene-γ-butyrolactones.     

Intermetallic phase formation in electrochemical alloy deposition

Three examples of the electrochemical deposition of intermetallic phases are shown. Electrodeposition of the single-phase -brass superlattice at underpotentials of Zn in Cu-Zn alloy plating is explained by an accumulative underpotential deposition (UPD) mechanism. Growth of the Cu-Sn intermetallic phase layer in the contact immersion deposition of Sn onto Cu is accounted for by a UPD/vertical solid-state diffusion mechanism. Ag₃Sn formation in the Sn/Ag-nanoparticle composite plating is illustrated by atomic site exchange at the interface between the deposited Sn matrix and the occluded Ag nanoparticles.     

Selective scavenging property of the indole moiety for the nitrating species of peroxynitrite

The inhibitory effect on tyrosine nitration and oxidation of peroxynitrite was evaluated for more than 40 reagents including natural and synthetic compounds, and the inhibiting efficiency of each compound for nitration was compared with that for oxidation, to characterize its property as a peroxynitrite scavenger. In the presence of various concentrations of testing compounds, the nitrating and oxidizing activities were measured by monitoring the formation of 3-nitrotyrosine and dityrosine with an HPLC-UV-fluorescence detector. The IC(50) values for nitration and oxidation were determined, and the ratio of these two IC(50) values was calculated for each compound. Although the IC(50) values varied from compound to compound, it was revealed that the ratio of two IC(50) values (IC(50) for oxidation/IC(50) for nitration) was 1 in almost all the compounds tested, except five indole derivatives (L-tryptophan, melatonin, 5-methoxytryptamine, tryptamine, and tetrahydro-beta-carboline) and one synthetic selenium-containing compound ((2R,3R,4S)-2-amino-3,4-dihydroxy-5-phenylselenopentan-1-ol, ADPP). The indole derivatives showed a specific inhibitory effect on tyrosine nitration without affecting the oxidation. ADPP was confirmed to have a preferable inhibitory activity for tyrosine oxidation. It was suggested that compounds showing an IC(50) value ratio of 1 scavenged the common species for nitration and oxidation, while the indole derivatives and ADPP preferably scavenged the nitrating and oxidizing species, respectively. From a stopped flow study, it was also revealed that the nitrotyrosine formation was relatively slow, unlike an OH radical reaction. These results imply that the peroxynirite reaction at least partly proceeds through specific species for nitration.     

Catalytic double carbonylation of organohalogen compounds promoted by palladium complexes

Various organohalogem compounds can be catalytically converted into α-keto amides on reaction with carbon monoxide and amines. Tertiary phosphine-coordinated palladium compounds are particularly suitable as the double carbonylation catalyst.     

Joint universality for Dirichlet L-functions and zeros of their linear combinations in the $$\chi $$-aspect

We establish a joint universality theorem for Dirichlet L-functions in the character aspect. This is an extension of a result obtained by Bagchi and Gonek independently, and is an analogue of the joint universality for Dirichlet L-functions in the t-aspect. Zeros of linear combinations of Dirichlet L-functions in the t-aspect have been investigated by various authors. Using our joint universality theorem, we investigate zeros of such combinations from a new viewpoint. More precisely, we show that for any region \(\Omega \) in the strip \(1/2< \mathrm {Re}\,s <1\), any non-zero meromorphic functions \(H_1 (s), \dots , H_r(s)\) on \(\Omega \) with \(r \ge 2\) and any positive integer N, there exist a positive integer m and Dirichlet characters \(\varphi _1, \dots , \varphi _r \bmod m\) such that \(\sum _{j=1}^r H_j (s) L(s, \varphi _r)\) has at least N distinct zeros in \(\Omega \).