Mitogenic activity of Tulipa gesneriana lectins on mouse and human lymphocytes.

Tulipa gesneriana lectin-erythrocyte (TGL-E) which agglutinates mouse erythrocytes showed a potent mitogenic activity on mouse spleen cells and human peripheral blood lymphocytes, however, TGL-E had only slight mitogenic activity on mouse thymus cells. Its subunit alpha with a molecular weight (MW) of about 26,000 showed a potent mitogenic activity as did that of native lectin, but subunit beta with a MW of about 14,000 showed no activity, indicating that the mitogenic activity of TGL-E originates from subunit alpha. TGL-E stimulated T cell enriched spleen cells which passed through a nylon column, but not spleen cells from a nude mouse or spleen cells treated with anti-Thy 1.2 antibody and complement. Thus, TGL-E stimulates only mouse T cells but not B cells. The other lectin in tulip bulbs, Tulipa gesneriana lectin-yeast showed no mitogenic activity on mouse spleen, thymus cells or human paripheral blood lymphocytes.     

Ruthenium-catalyzed one-pot hydroformylation of alkenes using carbon dioxide as a reactant

A new hydroformylation of alkenes using carbon dioxide as a reactant is shown to take place in the presence of ruthenium cluster complexes and halide salts. Similar or even better yields of alcohols were formed as compared to the conventional hydroformylation with CO under the same reaction conditions. The reaction proceeded in three steps: CO₂ is first converted to CO; then it is used as a reagent for hydroformylation to give aldehyde; subsequently, it is hydrogenated to alcohol. ESI-mass spectrometric analyses of the reaction solutions indicated formation of four kinds of ruthenium anionic complexes including tetra-, tri-, and mononuclear species. On the basis of experimental findings, possible roles of these complexes are discussed.     

Stability and vibrational spectra of toroidal isomers of C 240

To study the thermodynamic and mechanical stability of toroidal isomers of C ₂₄₀, we use a semi-empirical tight-binding theory and calculate their electronic structure, cohesive energy and vibrational spectra within the harmonic approximation. From these, we deduce their free energy at temperatures up to 1500K. The results are also compared to the isomer with icosahedral symmetry. Finally, we discuss within this approach, their stability and abundance.     

Thermodynamic properties of the Cu-Au system using a face-centered-cubic lattice model with a renormalized potential

A Monte Carlo simulation is carried out to study thermodynamic properties of Cu-Au alloys using a face-centered-cubic (fcc) lattice-gas model. To obtain quantitatively accurate results, a Finnis-Sinclair-type potential, which has been widely used for molecular dynamics (MD) simulations, is employed. To overcome some shortcomings of lattice-gas models such as neglecting vibrational entropy, the potential is mapped onto the fcc lattice using the renormalization technique. The renormalized potential gives an improved Cu-Au phase diagram compared to the original MD potential applied directly on the lattice.     

Preparation and properties of aromatic polyamides from 5-t-butylisophthalic acid and various aromatic diamines

Aromatic polyamides (aramids) having pendant t-butyl group were synthesized by the direct polycondensation of 5-t-butylisophthalic acid with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. The aramids having inherent viscosities of 0.6–2.4 dL/g were obtained in quantitative yields. These polymers were readily soluble in various solvents such as NMP,N,N-dimethylacetamide, dimethyl sulfoxide, and pyridine, and gave transparent, tough and flexible films by casting from the NMP solutions. The aramids had glass transition temperatures between 250 and 330°C, and started to lose weight around 350°C, with 10% weight loss being recorded at about 450°C in air.     

Preparation and properties of polyarylates from 5-t-butylisophthaloyl chloride and various bisphenols

Polyarylates containing a t-butyl pendant group were prepared from 5-t-butylisophthaloyl chloride and various bisphenols through the phase-transfer catalyzed two-phase polycondensation. The polyarylates having inherent viscosities up to 3.1 dL/g were obtained quantitatively. They were readily soluble in various solvents such as chloroform, m-cresol, and pyridine. Coloreless, transparent, and flexible films could be cast from the chloroform solutions of the polymers. The polyarylates had glass transition temperatures between 210 and 320°C, and did not lose weight below 350°C, with 10% weight loss being recorded at 395–450°C in air.     

Investigation into new materials for optical devices: the miscibility and solvent effects of azobenzene derivative blends

With the increasing demand for novel devices with optical applications the search for new materials to data store and process becomes a priority. By introducing blends, tailor made properties and low cost give added advantage. Miscibility is an essential requirement for a new material, this research thus involves miscibility studies of poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methyl methacrylate)₁₀, (azobenzene derivative) with polymethyl‐methacrylate (PMMA), polyvinylacetate (PVAc) and polyvinylchloride (PVC) prepared in tetrahydrofuran (THF), and/or dimethylformamide (DMF) and/or dichloromethane (CH₂Cl₂). The glass transitions, solvent and varying molecular weight effect were investigated, since these all primarily influence the miscibility. THF was found to encourage miscibility at specific compositions of PVAc and PVC blends. However, with CH₂Cl₂ and DMF immiscibility is encouraged. The Fox–Flory equation was applied to the blends analyzing the PVC blends in DMF as deviations from ideality. Different molecular weights of PMMA were identified as immiscible regardless of solvent. PMMA's lower solubility in THF and CH₂Cl₂ compared to the azobenzene derivative, displayed the existence of PMMA islands. In all blends the favorable and unfavorable interactions between polymer–solvent–polymer systems are considered. Furthermore, the miscibility effect on increasing the MMA content of the azobenzene derivative was also investigated. Copyright © 2002 John Wiley & Sons, Ltd.     

Correlation between the structure of water in the vicinity of carboxybetaine polymers and their blood-compatibility

The structure and hydrogen bonding of water in the vicinity of carboxybetaine homopolymer (poly[1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (PolyCMB), and a random copolymer of CMB and n-butyl methacrylate, Poly(CMB-r-BMA), with various molecular weights were analyzed in their aqueous solutions and thin film with contours of O-H stretching of Raman and attenuated total reflection infrared (ATR-IR) spectra, respectively. The relative intensity of the collective band (C value) corresponding to a long-range coupling of O-H stretchings of the Raman spectra for aqueous solution of Poly(CMB-r-BMA) was very close to that for pure water, which is in contrast with the smaller C value in aqueous solution of ordinary polyelectrolytes. The number of hydrogen bonds collapsed by the presence of one monomer residue (N(corr) value) of PolyCMB and Poly(CMB-r-BMA) (CMB, 45 mol %) (M(w), 1.14 x 10(4) and 1.78 x 10(4), respectively) could be calculated from the C value. The N(corr) values were much smaller than those for ordinary polyelectrolytes and close to those for nonionic water-soluble polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone). Furthermore, a water-insoluble Poly(CMB-r-BMA) with a large BMA content (M(w) = 347 kD, CMB 27 mol %) could be cast as a thin film (thickness, ca. 10 microm) on a ZnSe crystal for the ATR-IR analyses. At an early stage of sorption of water into the Poly(CMB-r-BMA) film, the O-H stretching band of IR spectra for the water incorporated in the film was similar to that for free water, which is in contrast with the drastic change in the O-H stretching band of water incorporated in polymer films such as poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PBMA). The theoretical vibrational frequency for water molecules hydrating a betaine molecule calculated by using a density functional method supported the experimental results. The adhesion of human platelets to Poly(CMB-r-BMA) films was much less than that to PMMA and PBMA. With an increase in the content of CMB residue, the number of platelets adhered to the Poly(CMB-r-BMA) film drastically decreased and then gradually increased, probably due to the increase in the roughness of the film surface. These results suggest that the carboxybetaine monomer residues with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules in both aqueous solution and thin film systems, resulting in the excellent blood-compatibility of the carboxybetaine polymers.     

NMR studies of phosphinenickel(0) complexes of ethyl methacrylate Ni(PR3)2(CH2=C(CH3)COOC2H5)

¹³C NMR data are given for a series of phosphinenickel(0) complexes of ethyl methacrylate (ema), Ni(PR₃)₂(CH₂=C(CH₃)COOC₂H₅) (PR₃ = PPh₃ (Ia), PEtPh₂ (Ib), PEt₂Ph (Ic), PMe₂Ph (Id), PEt₃ (Ie)). The olefinic carbon signals of ema shift upfield by 71.5–86.5 ppm on coordination, the magnitude of the upfield shift increasing with increase in the bacisity of the phosphine ligand. The effect of the basicity of PR₃ is discussed on the basis of the back-bonding from Ni to ema. Variable temperature¹H NMR studies reveal that the ema of Id, the complex having the least sterically demanding phosphine ligands, exchanges with free ema in toluene on the NMR time scale. The dependence of the rate of exchange on the concentration of ema shows that the exchange proceeds through anS_N2 mechanism. The activation parameters are: ΔH₂₇₃^≠ 2.75 kcal/mol, ΔG₂₇₃^≠ 12.7 kcal/mol, ΔS₂₇₃^≠ ?37 e.u. The³¹P NMR spectra of the complexes show two doublets when the exchange is frozen out, indicating the inequivalence of the two phosphine ligands in the ema-coordinated complex. The difference in the³¹P chemical shifts of the two coordinated tertiary phosphines increases with increase in the basicity of the PR₃ ligand.     

利用钐掺杂氧化铈提高燃料电池阳极活性

用浸渍法制备并采用交流阻抗、极化等技术考察了不同组成的Ni-Sm3＋掺杂的CeO2(SDC) 复合镍阳极的电化学性能及相应电池的功率输出性能.结果表明，SDC掺入镍阳极后,阳极极化过电位及电池的欧姆电阻显著减小.其中阳极过电位的减小与SDC掺入镍电极引起的三相界扩展有关，但SDC的掺入同时引起了电极反应活化能的增加,造成低温下Ni-SDC的极化过电位大于纯Ni电极.高温下,Ni-SDC阳极的阻抗谱由两个半圆组成，其中高频半圆随着SDC掺入量的增加而减小,而低频环与SDC的掺入量基本无关.低温下只观察到一个高频环.高频环可能对应三相界反应,而低频环可能对应氢的解离吸附及扩散.75％（w）Ni-25％（w）SDC/La0.9Sr0.1Ga0.8Mg0.2O3(LSGM)/Sm0.5Sr0.5CoO3(SSC)在所研究的电池中具有最大功率输出密度，其值在1073、973、873 K下分别达到1.1、0.43、0.14 W•cm－2.