Crystal structure and lattice vibration of proton dissolved BaZr0.8Sc0.2O2.9

Heat capacity and neutron diffraction measurements were carried out to determine the location of protons in the crystal of proton conducting perovskite oxide BaZr_0.8Sc_0.2O_2.9. The heat capacity of proton- and deuteron-dissolved BaZr_0.8Sc_0.2O_2.9 showed a slight difference from that of the dry sample. It indicates that the librational motion of the OH(OD) group is not excited below room temperature. The neutron diffraction experiments on the deutron dissolved sample indicate that the deuteron exists near the 12h site.     

Stereoselectivity of superacid-catalyzed Pictet-Spengler cyclization reactions

[reaction: see text] High stereoselectivities were found in a wide range of superacid-catalyzed Pictet-Spengler cyclization reactions. Particularly in the cases of 2-alkyl-N-benzylidene-2-phenethylamines, an enhanced stereoselectivity was observed under the superacid conditions as compared with the corresponding weak acid (TFA)-catalyzed (monocationic) cyclization reaction of the N-benzylidene-2-(3',4'-dimethoxy)phenethylamines that bear electron-donating groups on the cyclizing aromatic ring. The computational study also supported the energetic favorability of the cyclization of the N,N-diprotonated imine and revealed a significantly early transition-state structure.     

Effect of polymer adsorption on the water structure at the quartz/water interface studied by optical sum frequency generation

The effect of polymers weakly adsorbed on a quartz surface on the structure of the interfacial water molecules was investigated by optical sum frequency (SF) spectroscopy. As polymers, poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and two types of tri-block copolymer of Pluronic L64 and 17R-4 were used. SF intensity spectra of OH stretching mode of water molecules at the interface between a quartz substrate and aqueous solutions of the polymers were measured. The total SF intensity of the interfacial water of the L64 aqueous solution was smaller than those of other solutions. This result indicates that the L64 aqueous solution has smaller number of oriented interfacial water molecules. It is suggested that the rapid motion of hydrophilic parts of the adsorbed L64 disturbs the average orientation of the interfacial water molecules. On the other hand, the SF intensity from the interfacial water molecules of aqueous solutions with high ion strength did not depend on the species of the polymers in the solutions. The latter result suggests that the hydration of ions determines the structure of the interfacial water molecules.     

Spin crossover phenomenon accompanying order-disorder phase transition in the ligand of [FeII(DAPP)(abpt)](ClO4)2 compound (DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) and its successive self-grinding effect

The spin crossover phenomenon of the recently described spin crossover complex [FeII(DAPP)(abpt)](ClO4)2 [DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] accompanying an order-disorder phase transition of the ligand was investigated by adiabatic heat capacity calorimetry, far-IR, IR, and Raman spectroscopies, and normal vibrational mode calculation. A large heat capacity peak due to the spin crossover transition was observed at T(trs) = 185.61 K. The transition enthalpy and entropy amounted to Delta(trs)H = 15.44 kJ mol-1 and Delta(trs)S = 83.74 J K-1 mol-1, respectively. The transition entropy is larger than the expected value 60.66 J K-1 mol-1, which is contributed from the spin multiplicity (R ln 5; R: the gas constant), disordering of the carbon atom of the six-membered metallocycle in the DAPP ligand, and one of the two perchlorate anions (2R ln 2), and change of the normal vibrational modes between the high-spin (HS) and low-spin (LS) states (35.75 J K-1 mol-1). The remaining entropy would be ascribed to changes of the lattice vibrations and molecular librations between the HS and LS states. Furthermore, [Fe(DAPP)(abpt)](ClO4)2 crystals disintegrated and became smaller crystallites whenever they experienced the phase transition. This may be regarded as a successive self-grinding effect, evidenced by adiabatic calorimetry, DSC, magnetic susceptibility, and microscope observation. The relationship between the crystal size and the physical quantities is discussed.     

Self-assembled plasmid DNA network prepared through both triple-helix formation and streptavidin–biotin interaction

Plasmid DNA responds to external stimuli to change the degree of supercoiling. As a result of its unique topological change, plasmid DNA is considered to be a new functional material. In addition to its stimuli-responsiveness, plasmid DNA has the capability of forming a triple helix with a triple-helix-forming oligonucleotide (TFO). The triple helix is formed in aqueous conditions and arises through recognition of specific sequences, and may lead to the formation of supramolecular architectures. With this in mind, we analyze the self-assembly of recombinant plasmid DNA with two sequences for triple-helix formation and TFO by means of surface plasmon resonance. In addition, the network formed by self-assembly of the recombinant plasmid DNA with biotinated-TFO and streptavidin is prepared and evaluated by atomic force microscopy (AFM).

Schematic illustration of plasmid DNA network.     

Effect on bending behavior of counter cation species in perfluorinated sulfonate membrane–platinum composite

The perfluorinated sulfonate membrane (Nafion ®117)–platinum composites having H⁺, mono- and bivalent metal ions as counter cations in the membranes were prepared and the bending behaviors of the composites actuated by the step voltage were investigated in deionized water. The bending behaviors of all composites have the same tendency as the composites to bend quickly to the anode side just after applying the step voltage and gradually to bend back to the cathode side in spite of keeping on the application. However, they show differences in the bending rate and the maximum displacement to the anode side just after applying the step voltage, which are influenced by counter cation species in the membrane. In particular, the composite having Li⁺ has the largest maximum displacement (about 1.1 mm) to the anode side. The relationship between the maximum displacements of the composites and water states in the membranes were studied. The maximum displacements of the composites depend on the water content in the membranes. In both series of the composites having mono- and bivalent metal ions, the maximum displacements increase with increasing water content, except the composites having Rb⁺ and Sr²⁺ which belong to fifth period in the periodic table. In spite of the result that the water content in the membrane having H⁺, which is about 20wt%, is nearly equal to that in the membrane having Na^a, the maximum displacement of the composite having H⁺ is only about one-third as large as that of the composite having Na⁺. The water structures in the membranes were investigated by using differential scanning calorimetry (DSC). The DSC endothermograms obtained indicate that the freezing water in the membrane having H⁺ has a much stronger interaction with sulfonate groups and counter cations than that in the membrane having Na⁺. It is concluded that the content and structure of the freezing water in the membrane have a profound effect on the bending behavior of the composite. © 1998 John Wiley & Sons, Ltd.     

Enzymatic Degradation of Semi‐IPN Hydrogels Based on N‐Isopropylacrylamide and Dextran at a Specific Temperature Range

The temperature‐dependent enzymatic degradation of semi‐IPN hydrogels consisting of dextran grafted with thermo‐responsive chains (lower cloud point) and a thermo‐responsive crosslinked matrix (higher cloud point) was examined. Enzymatic degradation of the semi‐IPN hydrogel was significantly inhibited below the lower and above the higher cloud point. Only between both cloud points, enzymatic degradation proceeded. The designed semi‐IPN hydrogel is therefore advantageous to achieve enzymatic degradation at a specific temperature range.     

Impact of binary and Fibonacci expansions of numbers on winning strategies for Nim-like games

An analysis of the successful moves for the game of solitaire, played in reverse, has resulted in the formulation of a set of rules, the observance of which leads to success. The principal rules entail symmetry properties and also the density of packing of pegs. Subsidiary rules are formulated in terms of both the current location of play and its direction. When play has proceeded for some way, a difficulty is encountered which can be surmounted by applying a modified form of the rule for density of packing.

The interesting fact emerges that within the game of solitaire there are two separate symmetrical situations which are species of mini‐solitaire.     

Dendritic nanospace constructed by only glycerol units enhanced uptake of a fluorescent molecule in aqueous solution

A polyglycerol dendrimer (PGD) of generation 2, which consists of only glycerol units, constructed nanospace capable of uptake of a fluorescent molecule with a 1:1 stoichiometry. On the other hand, a PGD of generation 1 trapped the molecule at the outer part.