Preparation of polymethyl methacrylate with well-controlled stereoregularity by anionic polymerization in an ionic liquid solvent

This study investigates the effect of ionic liquids (ILs) on the anionic polymerization of methyl methacrylate (MMA). Polymethyl methacrylate (PMMA), an isotactic polymer, is prepared by anionic polymerization at a high reaction temperature with an IL that acts as both solvent and additive. The most plausible reaction mechanism is determined using ¹H NMR and Fourier-transform infrared spectroscopy. The electrostatic interaction between MMA and the IL increases the apparent steric hindrance in MMA, resulting in the isotactic PMMA.     

Oxotitanium(IV) complexes of some bis‐unsymmetric Schiff bases: Synthesis,structural elucidation and biomedical applications

A number of oxotitanium(IV) complexes of the type TiOL with bis‐unsymmetric dibasic tetradentate Schiff base (LH₂) containing ONNO donor atoms have been synthesized. Mono‐Schiff base (OPD‐HNP) was prepared by the condensation of 1:3 molar ratio of 2‐hydroxy‐1‐naphthaldehyde (HNP) with o‐phenylenediamine (OPD). Dibasic unsymmetric tetradentate diamine Schiff bases were prepared by the reaction of OPD‐HNP with 2‐hydroxyacetophenone, 2‐hydroxypropeophenone, benzoylacetone, acetylacetone and ethylacetoacetate. Further, titanylacetylacetonate was reacted with these ligands to obtain their metal complexes. On the basis of analytical and physiochemical data, the formation of complexes as TiOL was suggested having square pyramidal geometry. Quantum mechanical approach also confirmed this geometry. The assessment of the synthesized ligands and their complexes showed that some behave as good inhibitors of mycelial growth against selected phytopathogic fungi but weak inhibitors against some selected bacteria. A few of them also showed antioxidant properties.     

Validation of primary formaldehyde gas standards prepared by dynamic thermogravimetry through a tri-national comparison of gaseous formaldehyde amount fraction

A validation study for primary formaldehyde gas standards was performed at three National Metrology Institutes: the Korea Research Institute of Standards and Science (KRISS), the National Metrology Institute of Japan (NMIJ) and the National Institute of Metrology of China (NIM). The studied materials had a nominal amount fraction of 2 μmol/mol formaldehyde in nitrogen balance and were prepared in 10-L aluminum cylinders by KRISS. The impurities in the materials were analyzed using a gas chromatograph/atomic emission detector and a Fourier-transform infrared spectrometer (FTIR). The stability of the materials was assessed for 1 year by KRISS using paraformaldehyde as a source for the primary standard gas and a cavity ring-down spectrometer (CRDS) instrument as the measurement method. The amount fraction of formaldehyde in the materials decreased linearly by 0.74 % each month. The studied materials that exhibited similar linear rates of decline were distributed to the participants. After the measurement was completed by the participants, the materials were returned to KRISS and the stability analysis based on the primary standard maintained at KRISS was repeated. NMIJ analyzed the materials using paraformaldehyde as the source of the primary standard of formaldehyde and FTIR analysis, whereas NIM used trioxane as the primary standard gas source and CRDS analysis. The results of the comparison revealed good agreement between the results and were within the expanded uncertainty of 2 % although each of them used different combinations of methods in the generation of primary gas standards and measurements.     

Reconstitution of Biosynthetic Machinery for the Synthesis of the Highly Elaborated Indole Diterpene Penitrem

Penitrem A is one of the most elaborated members of the fungal indole diterpenes. Two separate penitrem gene clusters were identified using genomic and RNA sequencing data, and 13 out of 17 transformations in the penitrem biosynthesis were elucidated by heterologous reconstitution of the relevant genes. These reactions involve 1) a prenylation‐initiated cationic cyclization to install the bicyclo[3.2.0]heptane skeleton (PtmE), 2) a two‐step P450‐catalyzed oxidative processes forming the unique tricyclic penitrem skeleton (PtmK and PtmU), and 3) five sequential oxidative transformations (PtmKULNJ). Importantly, without conventional gene disruption, reconstitution of the biosynthetic machinery provided sufficient data to determine the pathway. It was thus demonstrated that the Aspergillus oryzae reconstitution system is a powerful method for studying the biosynthesis of complex natural products.     

A New Flexible Multibody Beam Element Based on the Absolute Nodal Coordinate Formulation Using the Global Shape Function and the Analytical Mode Shape Function

Several techniques for the reduced dimensionality of finite elementformulations were considered as component mode reduction methods in themiddle sixties. These techniques are widely used in flexiblemultibody simulations for solving small deformation problems. Theabsolute nodal coordinate formulation for solving large rotation anddeformation problems has been established as a full finite elementmethod instead of using similar kinds of reduction techniques. In thispaper, a reduced order absolute nodal coordinate formulation is newlyestablished by introducing the global beam shape function and theanalytical deformation modes as a full finite element. This formulationleads to a constant and symmetric mass matrix as the conventionalabsolute nodal coordinate formulation, and makes it possible to reducethe number of elements and system coordinates of the beam structurewhich undergoes large rotations and large deformations. Numericalexamples show that the excellent agreements between thepresent formulation and the conventional absolute nodal coordinateformulation using a large number of elements are examined. These results demonstratethat the present formulation has high accuracy in the sense that thepresent solutions are similar to the conventional ones with fewersystem coordinates, and high efficiency in computation.     

Low-temperature growth of high-Tc superconducting films by plasma-enhanced metal-organic chemical vapor deposition

Plasma-enhanced MOCVD in which metal-organic compounds are sublimated directly into the growth chamber is studied for the first time as a new low-temperature process for growing superconducting YBa₂Cu₃O-_-x thin films. Y(THD)₃, Ba(THD)₂, Cu(THD)₂ and oxygen are used as metal sources and oxydizing agent. Emission spectroscopy reveals that activated metal-organic compounds and activated oxygen species are present during film growth. Superconducting YBa₂Cu₃O_7-x films whose zero-resistivity temperature are 50 K and 82 K are grown at 550°C and 600°C.     

High Pressure Synthesis of Cycloadduct of Fullerene C60 with 2H-Pyran-2-one∗∗

Under high pressure conditions, fullerene C₆₀ smoothly reacts with 2H-pyran-2-one to give a [4+2] cycloadduct, which can be reduced to an alcohol derivative.