Triplet Diradical-Cation Salts Consisting of the Phenothiazine Radical Cation and a Nitronyl Nitroxide

The spin–spin and magnetic properties of two (nitronyl nitroxide)-(di-p-anisylamine-phenothiazine) diradical cation salts, ( DAA-PTZ ) ⁺ -NN⋅ MBr₄⁻ (M=Ga, Fe), have been investigated. These diradical-cation species were prepared by the cross-coupling of iodophenothiazine DAA-PTZ-I with NN-AuPPh₃ followed by oxidation with the thianthrenium radical cation ( TA⁺⋅ MBr₄⁻). These salts were found to be highly stable under aerobic conditions. For the GaBr₄ salt, large ferromagnetic intramolecular and small antiferromagnetic intermolecular interactions (J₁/k_B=+320 K and J₂/k_B=−2 K, respectively) were observed. The magnetic property of the Fe³⁺ salt was analyzed by using a six-spin model assuming identical intramolecular exchange interaction (J₃/k_B=+320 K) and the other exchange interactions (J₄/k_B=−7 K and J₅/k_B=−4 K). A significant color change was observed in the UV/Vis/NIR absorption spectra upon electrochemical oxidation of the doublet DAA-PTZ-NN to the triplet ( DAA-PTZ ) ⁺ -NN .     

Neutron spin rotation and P-violation

A new apparatus to measure the neutron spin rotation due to interaction with matter has been developed at KEK. The present apparatus enables us to measure the parity violating neutron spin rotation in the p-wave resonance in the energy region of eV.On leave from Tohoku University.     

Benzoin reaction in water as an aqueous medium catalyzed by benzimidazolium salt

Benzoin reactions are catalyzed by N,N-dialkylbenzimidazole to yield α-hydroxy ketones; the reaction proceeds in water as an aqueous medium under mild conditions. The utility of these salts as pre-catalysts in these reactions has been demonstrated.     

Inhibition of acyl coenzyme A: cholesterol acyltransferase by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors

Relatively high concentrations of MK-733 (simvastatin) and MK-803 (lovastatin, mevinolin), which are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, were found to inhibit acyl coenzyme A: cholesterol acyltransferase (ACAT) of rabbit intestinal microsomes with IC50's of 2.0 x 10(-5) and 3.6 x 10(-5) M, respectively. Dihydroxy acid forms of both MK-733 and MK-803 did not inhibit ACAT activity. A kinetic analysis using a Lineweaver-Burk plot indicated that MK-733 is a competitive inhibitor of ACAT, with a Ki value of 1.2 x 10(-5) M.     

Fundamental studies on thyroid stimulating hormone immunoradiometric assay kit (TSH RIABEAD II)

We have reported fundamental studies on the TSH immunoradiometric assay, using TSH RIABEAD II kit (Dainabot). The sensitivity of the assay was 0.03 mu IU/ml and its C.V. was 27.2%. Intra- and inter-assay C.V. were less than 5%. Dilution test and recovery test were good. Serum TSH level was 0.3-4.0 mu IU/ml in normal subjects, less than 0.03 mu IU/ml in untreated Graves' disease and subacute thyroiditis. Therefore, it was found that the clear difference exist in serum TSH levels between normal subjects and patients with untreated Graves' disease. There was a well correlation on the serum TSH levels between this method and TSH radioimmunoassay kit (Amerlex TSH, r = 0.983). Especially, the measurement of serum TSH levels, using immunoradiometric assay kit, was useful for the diagnosis of patients with Graves' disease.     

Low-temperature specific heat of Er2Ba4Cu7O15-δ

The magnetic ordering of Er ions in Er₂Ba₄Cu₇O_15-δ (δ = 0:7 and δ = 0:08) has been studied by low temperature heat capacity measurements. The Néel temperature T _N of Er₂Ba₄Cu₇O_15-δ is almost independent of the oxygen concentration (TN = 0:54K for δ = 0:08 and T _N = 0:50K for δ = 0:7). While an anisotropic two-dimensional (2D) Ising model describes the experimental data very well for Er₂Ba₄Cu₇O_14:92, this model cannot be applied to the oxygen reduced sample Er₂Ba₄Cu₇O_14:3. By using a model consisting of 1D-Ising chains and of 2D-Ising clusters of Er³⁺ ions we could fit the specific heat data of Er₂Ba₄Cu₇O_14:3 accurately. Our measurements show clearly that with the reduction of the oxygen content the in-plane anisotropy of the magnetic exchange coupling increases.     

Examples of Hermitian manifolds with pointwise constant anti-holomorphic sectional curvature

We construct non-compact examples of Hermitian manifolds with pointwise constant anti-holomorphic sectional curvature. Our examples are obtained by conformal change of the metric on an open set of the complex space form.     

Synthesis of a bicyclic dipeptide with the shape of β-turn central part

A bicyclic dipeptide derivative with fixed conformation simulating that of the two central amino acid residues in type II′ β-turn has been synthesized starting from L-glutamic acid and L-cysteine in short steps.     

Inversion of the Abel Integral Equation by Use of Simple Interpolation Formulas

The Abel integral equation in plasma spectroscopy is numerically solved by applying the Bessel four-point interpolation formula of degree two. The method is mathematically tractable, simplifying the Bockasten method. Tests through numerical simulations show that the method is as accurate as more elaborate methods, such as Bockasten, Minerbo-Levy, Piessens, etc.