Seeded batch crystallization of ammonium aluminum sulfate from aqueous solution

Seed crystals of ammonium aluminum sulfate ((NH₄)Al(SO₄)₂··12H₂O) were grown in aqueous solution by cooling. The temperature of a crystallizer was lowered with no control by circulating cooling water through the jacket. It fell in an exponential manner. The effects of seed amount and size on the product crystal size distribution were examined. The product crystals obtained were of narrow and uni-modal size distribution with suppressed secondary nucleation if seed crystals were loaded more than a critical value. The critical value was determined and well compared with previously reported values for other material systems. This crystallization technique does not need any prior knowledge of the kinetics of crystal growth and nucleation. It is simple and robust, and can be easily applied to an existing crystallizer without installing any additional control systems.     

Minimum standards of clinical practice for physical therapists working in intensive care units in Japan

Objective: Early mobilization and rehabilitation has become common and expectations for physical therapists working in intensive care units have increased in Japan. The objective of this study was to establish consensus-based minimum clinical practice standards for physical therapists working in intensive care units in Japan. It also aimed to make an international comparison of minimum clinical practice standards in this area. Methods: In total, 54 experienced physical therapists gave informed consent and participated in this study. A modified Delphi method with questionnaires was used over three rounds. Participants rated 272 items as “essential/unknown/non-essential”. Consensus was considered to be reached on items that over 70% of physical therapists rated as “essential” to clinical practice in the intensive care unit. Results: Of the 272 items in the first round, 188 were deemed essential. In round 2, 11 of the 62 items that failed to reach consensus in round 1 were additionally deemed essential. No item was added to the “essential” consensus in round 3. In total, 199 items were therefore deemed essential as a minimum standard of clinical practice. Participants agreed that 42 items were not essential and failed to reach agreement on 31 others. Identified 199 items were different from those in the UK and Australia due to national laws, cultural and historical backgrounds. Conclusions: This is the first study to develop a consensus-based minimum clinical practice standard for physical therapists working in intensive care units in Japan.     

Compositeness Criteria of Particles in Quantum Field Theory and S-Matrix Theory

A review is given of recent developments in compositeness arguments of particles in the framework of Lagrangian field theory and S-matrix theory.     

Molecular mechanism of dielectrically controlled optical resolution (DCR)

We have recently found the first example of dielectrically controlled optical resolution (DCR). By adjusting the dielectric constant of the solvent used in the resolution process, each optical isomer of (R,S)-alpha-amino-epsilon-caprolactam can be selectively obtained using N-tosyl-(S)-phenylalanine as a chiral selector. The molecular mechanism of DCR has been investigated by comparing the molecular and crystal structures of the optical selector, its target substrate and their diastereomeric salts. Strong hydrophobic interactions between the phenyl rings of the optical selector govern the molecular aggregation of the selectors and form a hydrophilic layer in which molecular recognition takes place. The recognition site in the hydrophilic layer can inherently identify both of the isomers. The dielectric constant of the solvent used in the discrimination process controls the intermolecular interaction which determines the isomer to be selected. The molecular mechanism of DCR disclosed in this study strongly suggests that DCR is not a specific but a general phenomenon. This method can be applicable to a large variety of optical resolution processes.     

Stereoselective synthesis of the beta-anomer of 4'-thionucleosides based on electrophilic glycosidation to 4-thiofuranoid glycals

Three types of 4-thiofuranoid glycal with different 3,5-O-silyl protecting groups were prepared and their electrophilic glycosidation was investigated. The 3,5-bis-O-(tert-butyldimethylsilyl)-4-thiofuranoid glycal (5) was obtained through mesylation of 2-deoxy-4-thio-D-erythro-pentofuranose (4) and subsequent base-promoted elimination, while thermal elimination of sulfoxide derivatives was suitable for the preparation of 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) (9) and 3,5-O-(di-tert-butylsilylene) (11) 4-thioglycals. The glycosidation reactions of these 4-thioglycals were carried out, in the presence of either PhSeCl or NIS, by using silylated derivatives of uracil, thymine, cytosine, and N(6)-benzoyladenine. Among the three 4-thioglycals, 11 was found to be an excellent glycosyl donor, forming the desired beta-anomer exclusively irrespective of the nucleobase employed.     

Crystal structure of a new small-pore zirconosilicate Na2ZrSi2O7·H2O and its relation to stoichiometrically and topologically similar compounds

The small-pore zirconosilicate Na₂ZrSi₂O₇·H₂O crystallizes in monoclinic system with space group C2/c, a = 5.4715(4); b = 9.4111(6); c = 13.0969(8) Å, β = 92.851(7)°. Its framework consists of layers built of ZrO₆ octahedra and SiO₄ tetrahedra and forming condensed [Si₂O₇] pyrogroups by connection. The sodium ions and water molecules are placed in channels set up between the layers. The stoichiometric and structural similarities of the studied phase with anhydrous compounds having general chemical formula A₂₍₃₎MT₂O₇ (A = Na,K; M = Zr,Lu,Sc; T = Si,Ge) are discussed. The topological relationship of their structures is interpreted in the light of spatial combination of silicon and zirconium polyhedra as basic building units into larger composite building units and their three-dimensional arrangement.     

Doubly doped BaY2F8:Er,Nd VUV scintillator

Doubly doped BaY₂F₈:Er,Nd scintillation crystals were grown by modified micro-pulling-down method. The Er co-doping was chosen to enhance the energy transfer from the host lattice to the Nd³⁺ luminescence center via the 5d-levels of Er³⁺, which can be enabled by the overlap of Er³⁺ 5d-4f emission spectrum with the Nd³⁺ 4f-5d absorption. The energy transfer was clearly evidenced in the BaY₂F₈:Er,Nd. The processes are complicated by energy migration to killer centres and/or cross-relaxation processes. The luminescence and energy transfer mechanism are discussed.     

Non-Cp titanium alkoxide-based homolytic ring-opening of epoxides by an intramolecular hydrogen abstraction in β-titanoxy radical intermediates

A low-valent titanium species derived in situ from Ti(O-i-Pr)(4), Me(3)SiCl and Mg powder in tetrahydrofuran reacted with epoxides to selectively provide less hindered alcohols via a homolytic ring-opening of epoxides, in which the intermediate β-titanoxy radical intramolecularly abstracted a hydrogen atom from an alkoxy moiety in the titanium complexes.