An optical system for measuring the eccentricity of glass wool pipe — for industrial use

An optical system for measuring the eccentricity of the glass wool pipe has been developed for an industrial use. The system consists of a contact sensor, a photo light sensor and a signal processing system with a logic circuit. The system is simple, fast and efficient for practical use; it allows implementation of on-line process monitoring and alarm warning signals for unacceptable pipe eccentricity during manufacturing.     

A Unique Pathway for the 3-Aminobutyrate Starter Unit from l-Glutamate through β-Glutamate during Biosynthesis of the 24-Membered Macrolactam Antibiotic, Incednine

Incednine is a 24-membered macrolactam antibiotic produced by Streptomyces sp. ML694-90F3. A previous study demonstrated that its unique nitrogen-containing starter unit was derived from l-glutamate. To elucidate the missing link between l-glutamate and the starter unit, deuterium labeled amino acid feeding experiments were conducted. These experiments revealed that 3-[3-(2)H]aminobutyrate and β-[2,2,4,4-(2)H(4)]glutamate were incorporated into the starter moiety. The results indicate that a novel decarboxylation of β-glutamate to give 3-aminobutyrate is involved in incednine biosynthesis.     

Reversible helix-random coil transition of poly(m-phenylenediethynylene) by a rotaxane switch

Pendant rotaxane switch-tethering poly(m-phenylene diethynylene) was synthesized by the polyoxidative coupling of a rotaxane containing an axle-terminal m-diethynylbenzene group and an optically active crown ether. The reversible helix-random coil transition of the polymer was successfully performed by the positional switching of the rotaxane wheel.     

Thermoosmosis of various electrolyte solutions through anion-exchange membranes

Thermoosmosis through anion-exchange membranes was measured for 10^-3 to 2 mol/kg of aqueous KCl, LiCl, and NH₄Cl and for 10^-3 to 3 x 10^-1 mol/kg of aqueous KIO₃ and K₂SO₄. For all electrolytes used the direction of thermoosmosis was from the cold side to the hot side over the whole range of concentrations. For KCl and LiCl the experimental results were analyzed with an extension of a previously published theory, using additional data for transport numbers of ions in membranes and for electroosmosis. The agreement between theory and experiment is satisfactory. The absolute value of thermoosmosis for KIO₃ is larger than that for other electrolytes because the pore volume fraction of the membrane for KIO₃ is larger than that for the other electrolytes.     

Total synthesis of (-)-bafilomycin A(1)

A highly stereoselective total synthesis of (-)-bafilomycin A(1), the naturally occurring enantiomer of this potent vacuolar ATPase inhibitor, is described. The synthesis features the highly stereoselective aldol reaction of methyl ketone 8b and aldehyde 60c and a Suzuki cross-coupling reaction of the highly functionalized advanced intermediates 12 and 39. Vinyl iodide 12 was synthesized by a 14-step sequence starting from the readily available beta-alkoxy aldehyde 14, while the vinylboronic acid component 39 was synthesized by a nine-step sequence from beta-hydroxy-alpha-methyl butyrate 44 via a sequence involving the alpha-methoxypropargylation of chiral aldehyde 49 with the alpha-methoxypropargylstannane reagent 54. Syntheses of fragments 12 and 39 also feature diastereoselective double asymmetric crotylboration reactions to set several of the critical stereocenters. The Suzuki cross-coupling of 12 and 39 provided seco ester 40, which following conversion to the seco acid underwent smooth macrolactonization to give 41. The success of the macrocyclization required that C(7)-OH be unprotected. The Mukaiyama aldol reaction between aldehyde 60c and the TMS enol ether generated from 8b provided aldol 65 with high diastereoselectivity. Finally, all silicon protecting groups were removed by treatment of the penultimate intermediate 65 with TAS-F (tris(dimethylamino)sulfonium difluorotrimethylsilicate), thereby completing the total synthesis of (-)-bafilomycin A(1).     

Studies on surface molecular motion of oligomeric polystyrene by differential scanning calorimetry

There are many studies on the surface molecular motion of polymer films [ 1 ], but no report on surface thermal properties of polymer because of experimental difficulties. The thermal property of oligomeric polystyrene (PS) was investigated by differential scanning calorimetry (DSC) in the present study. In order to increase the ratio of surface area to volume of PS particles, the DSC samples were prepared by mechanically grinding mixtures of PS and Al₂O₃ powders. The grinding mixtures of these powders with low particle size showed a transition at a low temperature of 14–17 °C (much lower than the bulk glass transition temperature, T_g), and this low‐temperature transition was dependent on the size of PS particles. This transition seems to result from the surface molecular motion of the activated surface layer of PS. Copyright © 2000 John Wiley & Sons, Ltd.     

Thermal membrane potential across cation-exchange membranes for various halide solutions

Thermal membrane potential across cation-exchange membranes was measured for various halide solutions. Linear relationships between thermal membrane potential () and temperature difference (T) were observed, and the temperature coefficient of thermal membrane potential (/T) decreases with increase in the molality of the external solution as predicted by a theory reported. When counterions of membranes are hydrogen ions, the sign of the coefficients turns into minus near 0.01 mol/kg of the external solution for all membranes, although the coefficients are always positive for all the other forms. The dependence of the coefficients on the molality of the external solutions sometimes deviated slightly from the theory. This deviation is attributed to some change in water content of the membranes. A reproducible method of measuring water content of membranes was applied to discuss the change in the state of the membranes.     

Liquid crystalline properties of dissymmetric molecules part X: The effect of a terminal nitro group on molecular arrangement in smectic phases in three aromatic ring systems with two ester groups

The smectic A (SmA) layer structure has been examined by X-ray diffraction for four isomeric systems: 4-nitrophenyl 4-(4-alkoxybenzoyloxy)benzoates 1, 4-alkoxyphenyl 4-(4-nitrobenzoyloxy)benzoates 2, 4-(4-alkoxybenzoyloxy)phenyl 4-nitrobenzoates 3, and 4-alkoxyphenyl 4-nitrophenyl terephthalates 4. The phase transition behaviour and layer structure of the SmA phases are notably influenced by the relative orientation of the two ester groups to the terminal groups, by alkoxy chain length, and by temperature. The SmA phase for compounds 1 and 3 has a mainly ‘monolayer’ arrangement, where the layer spacing is 2-5 Å longer than the molecular length. The SmA phase for compounds 2 and 4 consists of a mixed layer structure having monolayer, bilayer, and partially bilayer arrangements, the distribution depending on the relative orientation of the ester groups, the alkoxy chain length, and temperature. It is supposed that the diversity of the SmA phase is related to the polar interaction around the nitro or the nitrobenzene moieties through the smectic layers and reversal of the ester groups causes a subtle change in the entire molecular shape.