Synthesis of spiropolymers by polycycloaddition of ketene dimer with dinitrile oxides

Novel spiropolymers containing biisoxazolinic units in the main chain were synthesized by polycycloaddition of ketene dimer with dinitrile oxides. Ketene dimer functioned as a difunctional monomer with loss of carbon dioxide, but use of 10% excess amount seemed to be the optimum condition in terms of viscosity of the resulting polymers. These spirocyclic polymers were white to pale yellow and had inherent viscosity of up to 0.34 dl/g. Thermogravimetric analysis of the polymers showed unusual abrupt reduction of weight at 279 or 298°C. Solubility was also studied.     

Nano-kinetics of probe-particles in solution visualized by a pin-fiber video scope.

The nano-kinetics of colloidal particles and living cells with the colloidal particles were visualized by a newly developed video scope. The system of the new video scope has a feature of fine controlling the illumination conditions by using a single optical fiber. This characteristic enables one to obtain clear images of living cells and the motions of colloidal particles by light-scattering effects. In the experiments, RBL-2H3 cells and gold colloidal particles were observed. Scattering images with high contrast and a dark background like in dark-field observations could be attained. In the experiments, a pulsed laser was also applied. The results obtained in this study could validate the effectiveness and possibility of a new video scope for applications to biological and biomedical fields.     

Electrophoretic analysis of the cleaved form of serpin,squamous cell carcinoma antigen-1 in normal and malignant squamous epithelial tissues

The aim of this study was to detect the cleaved form of serine proteinase inhibitor (serpin), squamous cell carcinoma (SCC) antigen-1 in normal and malignant squamous epithelial tissues, which implies the presence of its target proteinase. The cleaved SCC antigen-1 in normal squamous epithelium was identified as a single spot with pI 6.35 and M(r) 40,000 by two-dimensional electrophoresis (2-DE) combined with immunoblotting. Interestingly, the cleaved form showed different biochemical properties in heat stability or immunoreactivity with a monoclonal antibody for SCC antigen (Mab 426) compared to intact SCC antigen-1. Furthermore, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of tissue extracts showed an abundant 40 kDa band of cleaved SCC antigen-1 in tumor tissue compared to normal tissue. Among the potential target proteinase of SCC antigen-1, immunoblotting analyses revealed that cathepsin L2 was remarkably overexpressed in tumor tissue, while cathepsin L was expressed in both normal and tumor tissues. These findings indicate that SCC antigen-1 interacts with specific endogenous proteinases such as cathepsins L and L2 in physiological and pathological states of squamous epithelium.     

Sedimentation potential of complexes of nitroamminecobalt(III) in aqueous solution at 25°C

Sedimentation potentials (SP) were measured for a series of nitroamminecobalt(III) chlorides in aqueous solution. The magnitudes of the sedimentation potentials varied with the number of NO ₂ ^– ligands in the complexes and a definite positive signal was observed for a neutral complex [Co(NO₂)₃(NH₃)₃]⁰. The division of the partial molar volumes of nitroamminecobalt(III) complexes based on the observed SP values resulted in comparable values of the partial molar volume for the Cl^– ion, suggesting no appreciable hydrolysis nor ionic association occur for these nitroammine-cobalt(III) complexes.     

Dispersive terahertz gain of a nonclassical oscillator: BLOCH oscillation in semiconductor superlattices

We have directly determined the spectral shape of the complex conductivities of Bloch oscillating electrons by using the time-domain terahertz (THz) electro-optic sampling technique, and presented experimental evidence for a dispersive Bloch gain in superlattices. This unique dispersive gain without population inversion arises from a nonclassical nature of Bloch oscillations; that is, the phase of the Bloch oscillation is shifted by pi/2 from that of the semiclassical charged harmonic oscillation when driven by the same ac field. By increasing the bias electric field, the gain bandwidth reached approximately 3 THz in our particular sample.     

Efficient Emission of Ultraviolet Light by Solid State Organic Fluorophores: Synthesis and Characterization of 1,4-Dialkeny-2,5-dioxybenzenes

The design and development of organic luminophores that exhibit efficient ultraviolet (UV) fluorescence in the solid state remains underexplored. Here, we report that 1,4-dialkenyl-2,5-dialkoxybenzenes and 1,4-dialkenyl-2,5-disiloxybenzenes act as such UV-emissive fluorophores. The dialkenyldioxybenzenes were readily prepared in three steps from 2,5-dimethoxy-1,4-diacetylbenzene or 2,5-dimethoxy-1,4-diformylbenzene via two to four steps from 1,4-bis(diethoxyphosphonylmethyl)-2,5-dimethoxybenzene. The dialkenyldioxybenzenes emit UV light in solution (λ_em=350–387 nm) and in the solid state (λ_em=328–388 nm). In addition, the quantum yields in the solid state were generally higher than those in solution. In particular, the adamantylidene-substituted benzenes fluoresced in the UV region with high quantum yields (Φ=0.37–0.55) in the solid state. Thin films of poly(methyl methacrylate) doped with the adamantylidene-substituted benzenes also exhibited UV emission with good efficiency (Φ=0.27–0.45). Density functional theory calculations revealed that the optical excitation of the dialkenyldimethoxybenzenes involves intramolecular charge-transfer from the ether oxygen atoms to the twisted alkenyl-benzene-alkenyl moiety, whereas the dialkenylbis(triphenylsiloxy)benzenes were optically excited through intramolecular charge-transfer from the oxygen atoms and twisted π-system to the phenyl-Si moieties of each triphenylsilyl group.     

Isomorphism Classes of Algebras with Radical Cube Zero II

We study to classify, up to isomorphism, algebras Λ over a field k such that the radical cubed is zero and Λ modulo the radical is a product of copies of k. The number of local quasi-Frobenius k-algebras with the condition is shown to be not less than the cardinality of k. In particular, the canonical forms of those algebras of dimension 5 are presented and their isomorphism classes are completely determined under some conditions on k.