Electron spin resonance studies on the oxidation mechanism of sterically hindered cyclic amines in TiO2 photocatalytic systems

A sterically hindered cyclic amine, 4-hydroxy-2,2,6,6-tetramethylpiperidine (HTMP), is converted to the corresponding aminoxyl radical (nitroxide radical), 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (TEMPOL radical) as a result of a photocatalytic reaction in TiO2 aqueous suspension. The time profile of the radical formation and the effect of additives, such as SCN-, I-, methanol, and H2O2, on the initial formation rate were measured in order to elucidate the reaction mechanism. The experimental observations indicated that the direct photocatalytic oxidation of HTMP followed by reaction with O2 is the dominant process in the formation of TEMPOL radicals. Electrochemical measurements showed that HTMP is oxidized at 0.7 V (vs NHE), which is consistent with the proposed mechanism. The possibility of other processes, involving reactions with singlet molecular oxygen, superoxide radical, and hydroxyl radical, were excluded from the reaction mechanism.     

A subproblem-centric model and approach to the nurse scheduling problem

The number of hospitals in Japan exceeds 10,000, and every month nurses are scheduled to shifts in about 30,000 units in total. There is serious demand for automating this scheduling task. In this paper, we introduce a mathematical programming formulation of the nurse scheduling problem in Japan, and develop a meta-heuristic approach to solve the problem. This scheduling problem is a hard combinatorial problem due to tight constraints involving such factors as the skill level of a team, the need to balance workload among nurses, and the consideration of nurses' preferences, even though the number of the nurses to be scheduled is not large, at between 20 and 40. The performance of our approach is demonstrated by the successful solution of data taken from actual scheduling problems. The proposed model and approach can be adapted for the majority of hospitals in Japan, as well as for some hospitals in other countries, and is likely applicable to many other scheduling problems in the fields of business and logistics. Key words.nurse scheduling – block-angular problem – subproblem – integer programming – relaxation – tabu search – branch-and-boundMathematics Subject Classification (1991):20E28, 20G40, 20C20     

Certified sediment reference materials for trace element analysis from the National Metrology Institute of Japan (NMIJ)

Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM.     

Water-soluble porphyrins appending platinum(II) complexes as binders for synthetic nucleic acid polymers

Water-soluble porphyrins containing four platinum(II) complexes per molecule, [5alpha,10beta,15alpha,20beta-tetrakis(2-trans-(alpha,beta,alpha,beta-trans-Pt) and cis-(alpha,beta,alpha,beta-cis-Pt) [PtCl(NH(3))(2)]N-2-aminophenylporphyrin)], were synthesized and characterized. The binding of synthetic nucleotide polymers (poly(dG)-poly(dC), poly(dA)-poly(dT)) to the porphyrins was examined spectrophotometrically in aqueous solution. UV-vis spectral data suggested that these porphyrins bind to the nucleic acids by coordinative and Coulomb interactions.     

A STUDY OF AQUEOUS SOLUTIONS OF NUCLEIC ACID CONSTITUENTS EXPOSED TO MONOCHROMATIC 160 nm VACUUM-UV LIGHT BY SPIN-TRAPPING METHOD

Spin-trapping technique was employed to detect and identify free radical intermediates produced in aqueous solutions of nucleic acid constituents (pyrimidine bases and pyrimidine nucleosides) after irradiation by monochromatic 160 nm vacuum-UV light from the electron storage ring. Short-lived free radicals produced in the molecules were converted into relatively long-lived free radicals (spin-adducts) by the reaction with MNP used as a spin trap. The resulting nitroxide radicals were subsequently analysed by esr.
The esr measurements were made after irradiating H₂O solution containing sample and the spin trap and once freeze-drying it and re-dissolving the residual powder in D₂O to get the spectrum with a well-resolved hyperfine structure. Thus, clear evidence that most of the radicals were not formed by H-addition but formed by OH-addition at the C5 position of the 5, 6 double bond were obtained for pyrimidine bases. For pyrimidine nucleosides, although the effect of H₂O-D₂O exchange was not recognized on resolution improvement of the hyperfine structure of the esr spectra, careful analysis of the hyperfine structure made it possible to identify the radical structures; OH-addition radicals at the C6 of the double bond of the base moiety in addition to the OH-addition radicals at the C5 position for all except for 2-deoxycytidine. Evidence for the formation of free radicals at the sugar moiety was not clear.     

Microscopic evidence for a new type of ordering of spin components in a random mixture with competing magnetic anisotropies

The Mössbauer spectroscopy was applied on a random mixture of two kinds of magnetic ions with competing anisotropies, Fe_1?xCo_xCl₂·2H₂O. The Mössbauer spectra observed in the Co(Fe)-rich antiferromagnetic (AF) phase near the tetracritical point show that, although the m₂(m₁) spin component parallel to the easy axis of pure FeCl₂·2H₂O(CoCl₂·2H₂O) has no long-range order in this phase (from the neutron diffraction experiment), the m₂(m₁) spin component contributes to the magnetic hyperfine field at ⁵⁷Fe nuclei as well as the m₁(m₂) spin component (which has a long-range order). This fact indicates that the m₂(m₁) spin components exists in the Co(Fe)-rich AF phase near the tetra-critical point at least in a time scale of ～ 10^?8s. This result predicts that the antiferromagnetic ordering in the Co(Fe)-rich AF phase is a new type one. The new phase observed in the intermediate concentration region is demonstrated as the “mixed ordering” phase.     

Facile synthesis of 7-10 membered rings by intramolecular condensation using dialkylcarbonate as solvent

A convenient large-scalable synthesis of 1-benzazepines 19 as an important intermediate of CCR5 antagonist, oral HIV-1 therapy, was established. The anilination of o-halogenobenzaldehyde 9 with alkylamino-acid 16 gave o-formylaniline-acid 17. Compound 17 was esterified followed by the improved reaction using the combination of alcoholate and dialkyl carbonate in one-pot, to easily produce 19. Namely, these new processes afforded the desired product 19 in only two steps from the starting materials, as compared with the previous 10 steps. Moreover, these convenient methodologies were applied to other heterocycles to give 8-10 membered rings, such as 1-benzazocine, 1-benzazonine, and 1-benzazecine.     

Efficient preparation of glycoclusters from silsesquioxanes

[structure: see text] A new type of glycocluster based on polyhedral oligosilsesquioxanes (POSS) has been efficiently prepared from unprotected mannoside and lactoside employing a convergent approach of thiol-radical addition reaction. The versatility of this approach was demonstrated by functionalization of mannosides and lactosides of different-length spacers.