Total Synthesis of (+)‐Dibromophakellin and (+)‐Dibromophakellstatin

A new method for the preparation of quaternary chiral aminals has been developed that employs an enamide‐type Overman rearrangement process. This methodology was applied to enantioselective total syntheses of (+)‐dibromophakellin and (+)‐dibromophakellstatin.     

Stereospecific polymerization of methacrylonitrile. III. Some new catalysts for isotactic polymethacrylonitrile

Some classes of organometallic catalysts what induce stereospecific polymerization of methacrylonitrile have been found. They include organolithium aluminum compounds of the type LiAlR₄, Li[R₃AlOAlR₂], and Li[R₃AlN(R)AlR₂], organosodium aluminum compounds of the type NaAlR₄, organolithium zinc compounds of the type LiZnR₃ and Li₂ZnR₄, organomagnesium aluminum compounds of the type RMg[AlR₄] and Mg[AlR₄]₂, and organomagnesium compounds containing an Mg? N bond, such as and their related compounds. One of the features of the polymerization with these catalysts was that the crystalline polymers were formed at moderately high temperatures. Total conversion, solubility index, and molecular weight of the polymer increased with increasing polymerization temperature, as observed in the case of polymerization with diethylmagnesium catalyst. Catalysts with an Mg? N bond were found to be highly effective for the stereospecific polymerization. The acetone-insoluble fractions of the polymers gave x-ray diagrams identical to the crystalline polymer produced with diethylmagnesium. This indicates that the acetone-insoluble crystalline polymers produced with these catalysts have an isotactic structure. The viscosity–molecular weight relationship for crystalline polymer was conveniently determined in Cl₂CHCOOH at 30°C.; [η] = 2.27 × 10^?4 M^0.754.     

Nanometer-sized gelatin particles prepared by means of gamma-ray irradiation

Nanometer-sized gelatin particles have been prepared by means of gamma-ray irradiation and characterized by static and dynamic light scattering combined with circular dichroism (CD) measurements. The molecular weight of the nanoparticles was much larger than that of the original gelatin molecules, whereas the hydrodynamic radius was much smaller. Radius of gyration evaluated from the angular dependence of the static light scattering intensity decreased with increasing irradiation dose. CD spectra of the gelatin nanoparticles were independent of temperature, and it is suggested that the nanoparticles consist of highly and randomly packed gelatin and their conformation is stable against the temperature change.     

A Novel Layered Silicate with a Helical Morphology

Helices composed of stacked layers are present in the novel silicate obtained from a silica sol and NaOH by hydrothermal synthesis in the presence of tetramethylammonium (TMA) hydroxide and 1,4-dioxane. The helical morphology is evident in scanning electron micrographs (see picture). The TMA and sodium ions of the silicate are readily replaced by protons, and on heating to 200°C a reversible phase transition occurs in which water molecules are lost from between the layers.     

Stability of oxygen anions and hydrogen abstraction from methane on reduced SnO2 (110) surface

The stability of oxygen anions and the hydrogen abstraction from methane on a reduced SnO₂ (110) crystal surface have been studied theoretically using a point-charge model. The geometric and electronic structures for the present molecules are calculated by means of a hybrid Hartree–Fock/density functional method at the B3LYP/6-311+G(3df, 3pd) level of theory. The calculations of the energies on the point-charge model are performed using these optimized geometries. It is found that a low concentration of the active oxygen species O⁻ and O₂⁻ is expected on the reduced SnO₂ surface. The activation energies for the abstraction of hydrogen atom from methane on the reduced SnO₂ surface are obtained: 12 kcal/mol for O⁻ species and more than 48 kcal/mol for O₂⁻ species, indicating that O⁻ species on the surface is the main active center for the dissociation of a C(SINGLE BOND)H bond of methane, which is in agreement with the other oxide catalysts. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 669–678, 1998     

Submillimeter-wave ESR measurements of low-dimensional quantum spin systems

Temperature-dependent electron spin resonance (ESR) measurements of two low-dimensional quantum spin systems, theS = 1/2 spin-ladder system Cu₂(1,4-diazacycloheptane)₂Cl₄ (Cu₂(C₅H₁₂N₂)₂Cl₄) and the gaplessS = 1 bond-alternating one-dimensional antiferromagnettrans-Ni(333-tet)(N₃)(ClO₄), have been performed. X-band electron spin resonance (ESR) measurements of single-crystal Cu₂(C₅H₁₂N₂)₂Cl₄ show the increase of linewidth and anisotropicg-shifts below 8 K similar to those known for one-dimensional antiferromagnet. On the other hand, Ni(333-tet)(N₃)(ClO₄) has broad line-width and ESR has been observed for the first time by our high-field ESR. Its linewidth increases as the temperature is decreased, while theg-shift seems to be isotropic and theg-value decreases as the temperature is decreased. Thisg-shift can be connected to the quantum fluctuation of the system.     

Excitation energy dependence of the photoluminescence band at 2.7 and 4.3 eV in silica glass at low temperature

In this paper, we report the excitation energy dependence of the 2.7 and 4.3 eV photoluminescence (PL) bands in oxygen deficient silica glass at low temperature (20 K). The increase or decrease of the PL intensity at low temperatures is different for different exciting light wavelengths. The PL intensity tended to decrease with low temperatures when the excitation was near the upper and lower end of the excited level. The peak energy of the excitation spectrum increases with cooling. These results indicate that the change in excitation level with cooling is associated with the low-temperature dependence of light emission. Thermal motion is suppressed, when the sample temperature is lowered, and the energy-width of the excited level decreases, i.e., the light emission probability decreases (the emission intensity decreases), when near the upper and lower end of the excitation level. These phenomena were observed in the low-temperature dependence of the 4.3 eV emission intensity.     

Thermal modulated interaction of aqueous steroids using polymer-grafted capillaries

Poly(N-isopropylacrylamide) (PIPAAm) of controlled molecular weight was densely grafted onto glass capillary lumenal surfaces using surface-initiated atom transfer radical polymerization (ATRP). Temperature-dependent changes of these thermoresponsive brush surfaces with hydrophobic steroids were investigated by exploiting thermoresponsive aqueous wettability changes of the polymer-modified surfaces in microfluidic systems. IPAAm was polymerized on ATRP initiator-immobilized glass surfaces using CuCl/CuCl(2)/tris(dimethylaminoethyl)amine (Me(6)TREN) as an ATRP catalyst in water at 25 degrees C. PIPAAm graft layer thickness and its homogeneity on glass surfaces are controlled by changing ATRP reaction time. Aqueous wettability changes of PIPAAm-grafted surfaces responses drastically changed to both grafted polymer layer thickness and temperature, especially at lower temperatures. Temperature-responsive surface properties of these PIPAAm brushes within capillary inner wall surfaces were then investigated using capillary chromatography. Effective interaction of hydrophobic steroids with dehydrated, hydrophobized PIPAAm-grafted capillary surfaces was observed above 30 degrees C without any column packing materials. Steroid elution behavior from PIPAAm-grafted capillaries contrasted sharply with that from PIPAAm hydrogel-grafted porous monolithic silica capillaries prepared by electron beam (EB) irradiation wherein significant peak broadening was observed at high-temperature regardless of sample hydrophobicity factors (log P values), indicating multistep separation modes in coated monolithic silica capillaries. In conclusion, thermoresponsive polymer-grafted capillary inner wall surfaces prepared by ATRP exhibit useful temperature-dependent surface property alterations effective to regulate interactions with biomolecules without requirements for separation bed packing materials within the capillary lumen.     

Infrared thermography analysis of the thermally latent polymerization of 3‐ethyl‐3‐phenoxymethyloxetane

Infrared thermography was employed to analyze multiple batches of the thermally latent polymerization of 3‐ethyl‐3‐phenoxymethyloxetane at once. The temperature changes in the polymerization depended on the polymerization rates. That is, a fast polymerization was exothermic, increasing the temporal temperature of the polymerization by approximately 130 °C within a few minutes. Infrared thermography, which can analyze multiple samples instantaneously, proved effective as a screening method for thermally latent curing systems. Exothermicity in the crosslinking polymerization of 1,4‐bis(3‐ethyloxetanylmethoxy)benzene was also analyzed by infrared thermography. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5519–5524, 2006     

A note on the expectation and deviation of physical quantities

By using the function representation of self-adjoint operators, the expectation and variance of physical quantities (self-adjoint operators) are defined, and it is shown that the so-called uncertainty principle does not hold.