Biomedical subjects

Masaki Azuma

Publications and source records attributed to Masaki Azuma.

7 recordsLinked to original sources

PubMed2005

Effect of explicit cationic size and valence constraints on the phase stability of 1:2 B-site-ordered perovskite ruthenates.

The related parameters of cation size and valence that control the crystallization of Sr(3)CaRu(2)O(9) into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr(3)MRu(2)O(9) stoichiometries yield multiphasic mixtures for M = Ni(2+), Mg(2+), and Y(3+), whereas pseudocubic perovskites result for M = Cu(2+) and Zn(2+). For A-site substitutions, an ordered perovskite structure results for Sr(3-x)Ca(x)CaRu(2)O(9), with 0 </= x </= 1.5. In contrast, Ba(2+) substitution for Sr(2+) is accompanied by a phase change to a hexagonal BaTiO(3) structure type. At high pressures and temperatures, a 1:2 B-site-ordered perovskite structure is stabilized for Sr(3-x)Ba(x)CaRu(2)O(9), with 0 </= x </= 3. The scarcity of B-site-ordered perovskite ruthenates at ambient pressure and the metastable nature of the high-pressure phases underscore the strict size and valence requirements that must be met by the constituent cations to achieve these uncommon ordered structures.

Journal Article↗

PubMed2004

Pressure-induced buckling of spin ladder in SrCu2O3.

Pressure-induced structural phase transition of spin ladder compound SrCu2O3 was investigated by synchrotron X-ray powder diffraction with a diamond anvil cell (DAC). The change was characterized by a buckling of the Cu2O3 plane in the rung direction of the ladder. The structure of the high-pressure phase was found to be essentially the same as that of CaCu2O3. Application of an external pressure of 3.4 GPa therefore affected the structure in the same manner that the chemical (internal) pressure does.

Journal Article↗

PubMed2004

Appraisal of surgical treatment for pT2 gallbladder carcinomas.

This retrospective study was designed to appraise the surgical procedures for pT2 gallbladder (GB) carcinomas. Twenty patients with pT2 GB carcinomas underwent surgical resection. Hepatectomy of segments 4b and 5 was performed in 19 patients, and an extended right hepatic lobectomy was performed in 1. The extrahepatic bile duct was preserved in 8 patients in whom the disease was limited to the GB fundus and/or body. Regional lymphadenectomy was performed in 18 patients. A separate radical second operation was performed in 8 patients after cholecystectomy. Final pathological staging was stage IB in 15 patients, IIB in 4, and IV in 1. Overall 5-year survival rate in those 20 patients was 77% without operative deaths. The 5-year survival rate in 5 patients with nodal metastasis and in 8 patients without extrahepatic biliary resection was 80% and 100%, respectively. A separate radical second operation in 8 patients yielded 75% survival after 5 years. Perineural invasion as a prognostic determinant was closely associated with tumor extending to the neck or the cystic duct. Partial hepatectomy, usually with extrahepatic biliary resection and regional lymphadenectomy, was appropriate as a standard radical operation for pT2 GB carcinoma, but preservation of extrahepatic bile duct is advocated for disease limited to the GB fundus and/or body. Radical second operation enhanced the chance for cure in patients with pT2 GB carcinoma.

Adult↗

PubMed2003

Short-range and long-range magnetic ordering in SrCuP2O7 and PbCuP2O7.

Magnetic properties of SrCuP2O7 and PbCu(1-x)ZnxP2O7 (x=0, 0.1, and 0.5) were studied by magnetic susceptibility, chiT, and specific heat, Cp(T). Both data showed that magnetism of SrCuP2O7 and PbCuP2O7 can be described by the one-dimensional (1D) uniform chain model despite the structural features suggesting the presence of zigzag chains with next-nearest-neighbor interactions. The chiT data were fitted by the Bonner-Fisher curve (plus temperature independent and Curie-Weiss terms) with g=2.20 and J/kB=9.38 K for SrCuP2O7 and g=2.17 and J/kB=8.41 K for PbCuP2O7 (Hamiltonian H=J SigmaSiS(i+1)). Magnetic specific heat, Cm(T), exhibited one broad maximum due to short-range ordering and one sharp peak at TN=1.64 K for SrCuP2O7 and TN=1.15 K for PbCuP2O7 due to long-range antiferromagnetic ordering. The characteristic values of the broad maxima on the Cm(T) curves (Cmax and TC(max)) were in good agreement with the theoretical calculations for the uniform 1D S=1/2 Heisenberg chain. Magnetic properties of PbCu0.9Zn0.1P2O7 still obeyed the 1D uniform chain model but those of PbCu0.5Zn0.5P2O7 did not. In air, SrCuP2O7 was stable at least up to 1373 K while PbCuP2O7 melted incongruently above 1180 K.

Journal Article↗

PubMed2003

Groin infection caused by a percutaneous femoral artery closure device: report of a case.

Hemostasis after femoral artery catheterization is generally achieved by manual compression, which results in a low incidence of infection at the puncture site. Percutaneous femoral artery closure devices have recently been used to prevent bleeding complications, shorten the hospital stay, and reduce the patient's discomfort. However, they have been associated with infectious complications, necessitating surgical intervention, such as patch angioplasty or arterial bypass; the treatment depending on the damage to the artery and the type of device used. Thus, the possibility of infection should be kept in mind when employing these devices. We report a case of groin infection associated with one such device, known as "The Closer," which was successfully treated by drainage and removal of the suture material.

Catheterization, Peripheral↗

PubMed2002

Growth of Na-doped Ca(2)CuO(2)Cl(2) single crystals under high pressures of several GPa.

Single crystals of Na-doped Ca(2)CuO(2)Cl(2) have been grown for the first time by a flux method under high pressures of up to 5.5 GPa. By changing the Na-solubility limit through the applied pressure, the Na content x was successfully controlled without introducing appreciable compositional inhomogeneity within the millimeter-sized crystals. Structural and chemical characterization indicated that the crystals span the phase diagram continuously from the parent antiferromagnetic insulator to an underdoped high-temperature superconductor. Because of the well-defined cleavage plane and resulting high surface quality, these oxychloride single crystals will provide a unique opportunity to explore the electronic evolution of the high-temperature superconductors, using spectroscopic techniques such as scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy.

Journal Article↗

PubMed2002

A novel method for the detection of Down syndrome with the use of four serum markers.

OBJECTIVE: The purpose of this study was to evaluate the use of the Lens culinaris agglutinin-reactive alpha-fetoprotein ratio for the detection of fetal Down syndrome in combination with traditional serum markers. STUDY DESIGN: We obtained maternal serum from 530 women with unaffected pregnancies and 31 women who were pregnant with a fetus with Down syndrome at 14 to 20 weeks of gestation. Various combinations of Lens culinaris agglutinin-reactive alpha-fetoprotein ratio, alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol were evaluated by score, without regard for the maternal age-related fetal Down syndrome risk. RESULTS: The best combination of serum markers, according to our scoring method, was a combination of all 4 markers. This combination showed a sensitivity of 83.9%, with a 5.1% false-positive rate for Down syndrome. Moreover, in older women, high sensitivity was obtained without increasing the false-positive rate. CONCLUSION: The screen using all 4 markers showed high sensitivity in all age groups without increasing the false-positive rate.

Adult↗