The NMR spectra of the porphyrins: 24—The NMR spectra of some tetraarylchlorins

The synthesis and complete assignment of the ¹H NMR spectra of 5-(o-pivaloylaminophenyl)-10,15,20-triphenylporphyrin (PIVTPP) and its two chiral dihydro adducts 3,4-dihydro-(PIVPTPC-I)- and 7,8-dihydr- (PIVPTPC-II)-porphyrins are reported. The use of the zinc complexes of the chlorins as chiral shift reagents with optically active bases is discussed. Comparison of the observed shift differences between the chlorins and the parent porphyrin with those calculated by a ring current model shows that a decrease in the ring current occurs on chlorin formation, and also specific effects occur at the reduced pyrrole ring, presumably reflecting different steric constraints.     

Molecular dynamics simulation of the cation motion upon adsorption of CO2 in Faujasite zeolite systems

Molecular Dynamics simulations have been carried out in NaX and NaY Faujasite systems to deepen understanding of the cation rearrangement during the CO2 adsorption process suggested by our recent diffusivity measurements. This study is a major contribution since the rearrangement of the cations in Faujasite, the most promising adsorbent for CO2 storage, can represent a significant breakthrough in understanding the adsorption and diffusion processes at the mircroscopic scale. For NaY, it has been shown that at low and intermediate loadings, SII cations can migrate toward the center of the supercage due to strong interactions with the adsorbates, followed by a hopping of SI'cation from the sodalite cage into the supercage to fill the vacant SII site. The SI cations are only displaced at a higher loading, leading to cation de-trapping out of the double six rings into the vacant SI' sites. For NaX, the SIII' cations which occupy the most accessible adsorption sites move significantly upon coordination to the carbon dioxide molecules. The SI' and SII cations remain consistently located in their initial sites whatever the loading. Indeed, the most probable migration mechanism involves SIII' cation displacements into nearby vacant SIII' sites.     

Full-trajectory diagnosis of laser-driven radiative blast waves in search of thermal plasma instabilities

Experimental investigations into the dynamics of cylindrical, laser-driven, high-Mach-number shocks are used to study the thermal cooling instability predicted to occur in astrophysical radiative blast waves. A streaked Schlieren technique measures the full blast-wave trajectory on a single-shot basis, which is key for observing shock velocity oscillations. Electron density profiles and deceleration parameters associated with radiative blast waves were recorded, enabling the calculation of important blast-wave parameters including the fraction of radiated energy, epsilon, as a function of time for comparison with radiation-hydrodynamics simulations.     

Stereoselective synthesis of novel uracil polyoxin C conjugates as substrate analogues of chitin synthase

Stereoselective syntheses of both the natural (C5'- S) and unnatural (C5'- R) diastereoisomers of uracil polyoxin C methyl ester have been developed. The key stereocontrolled step involves nucleophilic addition of trimethylsilyl cyanide to the appropriate chiral sulfinimine derived from 2',3'-protected 5'-formyluridine and (S)-(-)-tert-butanesulfinamide or (R)-(+)-tert-butanesulfinamide, respectively. A variety of substrate mimics designed to function as inhibitors of chitin synthase have been synthesized by conjugation of the methyl ester of uracil polyoxin C (UPOC) with activated isoxazole carboxylic acids. Amide bond formation was accomplished via coupling of the amino functionality of UPOC methyl ester with a free isoxazole acid using HBTU or alternatively an isoxazole pentafluorophenyl ester. The substrate mimics incorporate features of the nucleoside-peptide antibiotics, the polyoxins and the nikkomycins, as well as features of the transition state structure expected during polymerization of the natural chitin synthase substrate uridine diphosphoryl-N-acetylglucosamine (UDP-GlcNAc), namely, a metal-binding site and glycosyl oxocarbenium ion mimic.     

The asymptotics of nonexpansive iterations

Let D be a closed subset of a Banach space X and T: D → D a nonexpansive mapping. Conditions are given (on the space X) for T to satisfy the following property of ergodic type: $\text{{T}{}^{\mathrm{n}}\text{x}\text{n}\text{}}$ converges (either weakly or strongly) to a vector v. Rather unexpectedly, D is not assumed to be convex, nor is I – T assumed to satisfy any range condition. In addition, it is shown that ?v is the unique point of least norm in the closure of R(I – T) if and only if I – T satisfies a certain range condition at infinity. Several interesting applications to accretive operator and nonlinear semigroup theory are also included.     

5种重要农艺性状基因在水稻重组自交系群体中的定位

通过抗病虫害水稻品系“B5”与籼稻品种“明恢63”为亲本进行杂交，得到一个187个F8代的重组自交系群体。利用重组自交系群体构建的分子连锁图，对水稻抽穗期、株高、穗长、剑叶长和剑叶宽的性状进行了QTL分析，分别检测到影响抽穗期、株高、穗长、剑叶长和剑叶宽的农艺性状2、2、4、4、4个QTLs，并分别解释各表型性状总变异的50．6％、74．9％、34．1％、47．3％和46．2‰．其中，控制抽穗期的Hd-6基因，控制株高的Ph7基因和控制剑叶长的Fll-2b基因分别是效应值较大的主效座位，其余的为微效基因座位。相关性状的QTLs大多聚集在染色体的相近或相同区间，表现出成簇分布的现象。这些重要农艺性状的分析，可以为水稻分子标记辅助选择育种提供有用的遗传信息。     

A New Taxoid from Leaves and Branches of Taxus chinensis

A new taxoid, 2-deacetyl-2α, 14β-dihydroxybaccatin Ⅳ (1), was isolated from the leaves and branches of Taxus chinensis together with the known compound baccatin Ⅳ (2). The structure of the new compound was elucidated by spectroscopic techniques. The detailed ^13C NMR assignments of baccatin Ⅳ are reported for the first time.     

Temperature dependence of optical and structural properties of ferroelectric B3.15Nd0.85Ti3O12 thin film derived by sol–gel process

We report the annealing temperature dependence of optical properties in ferroelectric B_3.15Nd_0.85Ti₃O₁₂ (BNdT) thin film for the first time. BNdT thin films are prepared by a sol–gel/spin coating method. Structural properties of BNdT thin films upon different thickness and annealing temperatures are characterized using the X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The BNdT thin film annealed at 650 °C exhibits a well defined perovskite crystalline structure with high c-axis orientation, which leads to a saturated polarization–electric field (PE) hysteresis with a remanent polarization of 2P _r = 39.6 μC/cm² and coercive field of 85 kV/cm at 5 V. Little fatigue degradation (<5%) is demonstrated upon 1 × 10¹⁰ switching cycles indicating a good fatigue endurance. Additionally, a superior optical transparency T(λ) of >80% is observed for wavelengths from 250 to 2,000 nm. Fundamental optical parameters of BNdT material such as refractive index n, extinction coefficient k, and band gap energy E _g are extracted from an ellipsometry measurement. Microstructure and annealing temperature dependence of T(λ), n, k, and E _g variation are also investigated and explained in detail.     

Internal Rotation in Simple Ethenols

Internal rotation in the compounds XCH=CHOH, X= CN, H and F, with the group X located trans to the oxygen atom has been studied using ab initio computational techniques with complete geometry optimisation. The relaxation of the molecular framework accompanying the torsional vibration is described and the significant changes in the internal rotation function around the C---O bond which arise upon changing the group X discussed.

The structure of the syn rotamer of ethenol itself, calculated with a variety of basis sets, is compared with the experimental geometry.