Direct synthesis of fluorescent 1,3a,6a-triazapentalene derivatives via click-cyclization-aromatization cascade reaction

An efficient and versatile method was established for the preparation of 1,3a,6a-triazapentalenes. The 1,3a,6a-triazapentalene skeleton without an additional fused ring system was discovered to be a compact and highly fluorescent chromophore, which exhibited various interesting fluorescent properties such as a noteworthy correlation of luminescent wavelength with the Hammett σ(p) value and a strongly positive solvatofluorochromism.     

High proton conduction in a chiral ferromagnetic metal-organic quartz-like framework

A complex-as-ligand strategy to get a multifunctional molecular material led to a metal-organic framework with the formula (NH(4))(4)[MnCr(2)(ox)(6)]·4H(2)O. Single-crystal X-ray diffraction revealed that the anionic bimetallic coordination network adopts a chiral three-dimensional quartz-like architecture. It hosts ammonium cations and water molecules in functionalized channels. In addition to ferromagnetic ordering below T(C) = 3.0 K related to the host network, the material exhibits a very high proton conductivity of 1.1 × 10(-3) S cm(-1) at room temperature due to the guest molecules.     

High performance "ionic liquid" chromatography

We firstly developed high performance liquid chromatography methods with "ionic liquids" as eluents (HPILC) and successfully demonstrated the analysis of various biopolymers including scarcely soluble highly polymerized cellulose by means of HPILC with highly polar ionic liquid.     

Multi-stage mass spectrometric analysis of saponins in glycyrrhiza radix

The fragmentation pathways of six triterpenoid saponins from Glycyrrhiza radix were investigated using LC-MS/MS. Depending on the structure and the substitution pattern, different molecular adduct ions, [M+NH4]+ or [M+H]+, were observed in the positive ESI spectra. In the positive MSn spectra from the molecular adduct ions, characteristic product ions corresponding to the loss of dehydrated glucuronic acid or glucuronic acid were detected and they indicated the type of substitution and structural modification. Fragment ions originating from the sapogenin moiety in the positive mass spectra were predominantly provided by saponins having an 11-oxo-12-ene structure. On the other hand, the saponins gave fragment ions corresponding to the sugar moiety in the negative mass spectra. These results indicate the specific property of saponins that have the 11-oxo-12-ene structure to localize positive or negative charge in the mass spectrometric ionization and fragmentation process. Information obtained from the present study can be utilized for structural elucidation of triterpenoid saponins in the Glycyrrhiza radix by LC-MS.     

On L1 decay problem for the dissipative wave equation

We study the decay estimates of solutions to the Cauchy problem for the dissipative wave equation in one, two, and three dimensions. The representation formulas of the solutions provide the sharp decay rates on L¹ norms and also L^p norms. Copyright © 2003 John Wiley & Sons, Ltd.     

A multi-objective lead time control problem in multi-stage assembly systems using genetic algorithms

In this paper, we develop a multi-objective model to optimally control the lead time of a multi-stage assembly system, using genetic algorithms. The multi-stage assembly system is modelled as an open queueing network. It is assumed that the product order arrives according to a Poisson process. In each service station, there is either one or infinite number of servers (machines) with exponentially distributed processing time, in which the service rate (capacity) is controllable. The optimal service control is decided at the beginning of the time horizon. The transport times between the service stations are independent random variables with generalized Erlang distributions. The problem is formulated as a multi-objective optimal control problem that involves four conflicting objective functions. The objective functions are the total operating costs of the system per period (to be minimized), the average lead time (min), the variance of the lead time (min) and the probability that the manufacturing lead time does not exceed a certain threshold (max). Finally, we apply a genetic algorithm with double strings using continuous relaxation based on reference solution updating (GADSCRRSU) to solve this multi-objective problem, using goal attainment formulation. The results are also compared against the results of a discrete-time approximation technique to show the efficiency of the proposed genetic algorithm approach.     

Site selection NMR study on electronic state in and near vortex core of YBa2Cu4O8

We report a site-selective ¹⁷O spin-lattice relaxation rate T₁⁻¹ in the vortex state of YBa₂Cu₄O₈. We found that T₁⁻¹ at the planar sites exhibits an unusual nonmonotonic NMR frequency dependence. Based on T₁⁻¹ in the vortex core region, we establish strong evidence that the local density of states within the vortex core is strongly reduced.     

24-fold endohedral functionalization of a self-assembled M12L24 coordination nanoball

A ca. 5 nm-sized, roughly spherical hollow complex was assembled from 12 Pd2+ ions and 24 bis(4-pyridylethenyl)-substituted bent ligands. By putting a functional group at the curvature of the ligand, the 24 functional groups were precisely arrayed inward within the spherical complex. When oligo(ethylene oxide) was anchored, the void of the hollow complex was tightly filled with a pseudo poly(ethylene oxide) nanoparticle, which showed metal ion (La3+) absorption property.     

Catalytic Ni/Cr-mediated macrocyclization without use of high-dilution techniques

The feasibility of catalytic Ni/Cr-mediated macrocyclization was demonstrated for the two substrates chosen from the halichondrin area. With 5 mol % of Ni and Cr catalysts, the macrocyclization was realized without use of high-dilution techniques. The reported method has a number of appealing features, including user-friendliness, easy workup, apparent scalability, and cost-effectiveness. In addition, all the required reagents are commercially available or obtainable in one or two steps from commercially available chemicals.