Spectroscopic and adsorptive studies of a thermally robust pyrazolato-based PCP

The pyrazolato-based PCP [Ni(8)(μ(4)-OH)(4)(μ(4)-OH(2))(2)(μ(4)-PBP)(6)] (NiPBP, H(2)PBP = 4,4'-bis(1H-pyrazol-4-yl)biphenyl), whose 3-D architecture is built upon octametallic hydroxo clusters reciprocally connected by organic spacers, is a very promising candidate for gas adsorption applications, owing to its remarkable thermal stability (up to 400 °C in air) and its high void volume (70%). As such, NiPBP was selected as a proof-of-concept material to demonstrate how an optimized set of solid state techniques can concur to create a comprehensive and coherent picture, relating (average and local) structural features to adsorptive properties. To this aim, the response of NiPBP toward different gases, retrieved by gas adsorption measurements (N(2) at 77 K, in the low pressure region; H(2) at 77 K, in the high pressure region), was explained in terms of local-level details, as emerged by coupling electronic, X-ray (absorption and emission), and variable temperature IR spectroscopy.     

Coordination chemistry and reactivity of zinc complexes supported by a phosphido pincer ligand

The preparation and characterization of new Zn(II) complexes of the type [(PPP)ZnR] in which R = Et (1) or N(SiMe(3))(2) (2) and PPP is a tridentate monoanionic phosphido ligand (PPP-H = bis(2-diphenylphosphinophenyl)phosphine) are reported. Reaction of ZnEt(2) and Zn[N(SiMe(3))(2)](2) with one equivalent of proligand PPP-H produced the corresponding tetrahedral zinc ethyl (1) and zinc amido (2) complexes in high yield. Homoleptic (PPP)(2) Zn complex 3 was obtained by reaction of the precursors with two equivalents of the proligand. Structural characterization of 1-3 was achieved by multinuclear NMR spectroscopy ((1)H, (13)C, and (31)P) and X-ray crystallography (3). Variable-temperature (1)H and (31)P?NMR studies highlighted marked flexibility of the phosphido pincer ligand in coordination at the metal center. A DFT calculation on the compounds provided theoretical support for this behavior. The activities of 1 and 2 toward the ring-opening polymerization of ε-caprolactone and of L- and rac-lactide were investigated, also in combination with an alcohol as external chain-transfer agent. Polyesters with controlled molecular parameters (M(n), end groups) and low polydispersities were obtained. A DFT study on ring-opening polymerization promoted by these complexes highlighted the importance of the coordinative flexibility of the ancillary ligand to promote monomer coordination at the reactive zinc center. Preliminary investigations showed the ability of these complexes to promote copolymerization of L-lactide and ε-caprolactone to achieve random copolymers whose microstructure reproduces the composition of the monomer feed.     

雾化角对液体火箭发动机燃烧室压力振荡的影响

针对液氧/煤油火箭发动机模型燃烧室实现了三维非稳态两相燃烧过程的数值模拟,得到的燃烧室截面平均压力和平均速度与实验吻合。在初边值条件不施加任何扰动的情况下,得到了燃烧室压力自激振荡过程,并研究了液氧和煤油喷嘴雾化角对燃烧室压力振荡的影响。计算结果表明:当雾化角为40°或120°时,由于燃料与氧化剂喷雾锥重叠区域较小或较大,导致了推进剂混合很差或很好,不易在燃烧室头部出现局部爆炸性的可燃混气团,致使燃烧室压力振荡强度较弱;而当雾化角为中间值65°时,易于出现爆炸性的可燃气团并导致剧烈的压力振荡,使燃烧室中出现燃烧不稳定性。因此,雾化角的合理设计是抑制燃烧不稳定性的一种途径。     

内蒙古地区沙生植物--沙枣中维生素C含量的测定

在 pH 6.0的 HAc-NaAc缓冲溶液中,用活性炭吸附沙枣中的色素,Cu(Ⅱ)催化氧化维生素C,在λmax=268 nm处可直接测定沙枣中维生素C含量.与传统碘量法相比,测定结果基本一致.为内蒙古地区沙枣天然植物资源的药用开发、食品加工等提供了参考数据.     

Laser Diode-Pumped Nd：LuVO4 Acousto-Optic Q-Switched Laser at 916 nm

A compact laser diode-pumped solid-state Nd：LuVO4 acousto-optic Q-switched laser is demonstrated at 916 nm of a quasi-three level for the first time. A pulse width of 130ns is observed when the pulse-repetition frequency is 10 kHz. The laser experiment shows that the Nd：Lu VO4 crystal can be used for efficient diode-pumped Q-switched lasers.     

Representation of the eigenvalues of the p ‐Laplacian by means of a surface integral

We prove a natural generalization to the p ‐Laplacian of the celebrated Rellich identity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ti-STT: a new zeotype shape selective oxidation catalyst

A new zeotype titanium silicate oxidation catalyst with the STT topology has been synthesized from direct synthesis. Ti-STT has a microporous structure with small pore openings, allowing shape selective oxidation catalysis. The isomorphous substitution of Si by Ti in the framework has been confirmed by Raman, FT-IR, UV-VIS and XANES spectroscopies.     

Numerical integration based on trivariate C 2 quartic spline quasi-interpolants

In this paper we consider the space generated by the scaled translates of the trivariate C ² quartic box spline B defined by a set X of seven directions, that forms a regular partition of the space into tetrahedra. Then, we construct new cubature rules for 3D integrals, based on spline quasi-interpolants expressed as linear combinations of scaled translates of B and local linear functionals. We give weights and nodes of the above rules and we analyse their properties. Finally, some numerical tests and comparisons with other known integration formulas are presented.     

Position and flux stabilization of X‐ray beams produced by double‐crystal monochromators for EXAFS scans at the titanium K‐edge

The simultaneous and active feedback stabilization of X‐ray beam position and monochromatic beam flux during EXAFS scans at the titanium K‐edge as produced by a double‐crystal monochromator beamline is reported. The feedback is generated using two independent feedback loops using separate beam flux and position measurements. The flux is stabilized using a fast extremum‐searching algorithm that is insensitive to changes in the synchrotron ring current and energy‐dependent monochromator output. Corrections of beam height are made using an innovative transmissive beam position monitor instrument. The efficacy of the feedback stabilization method is demonstrated by comparing the measurements of EXAFS spectra on inhomogeneous diluted Ti‐containing samples with and without feedback applied.     

Measurements of Deflection and Residual Stress in Thin Films Utilizing Coherent Light Reflection/Projection Moiré Interferometry

Thin film technology is an area of great importance in current applications of opto-electronics, electronics, MEMS and computer technology. A critical issue in thin film technology is residual stresses that arise when the coating is deposited onto a substrate. Residual stresses can be very large in magnitude and have detrimental effects on the role that the thin film must play. To save development time on coating deposition processes it is important to perform accurate residual stresses measurements in situ in real time where the deposition is made. A novel optical set up is developed in this study to measure deflections and residual stresses generated in coated specimens that can be applied directly in the reactor utilized in the deposition process. Experimental results are in good agreement with other measurements carried out independently and other data reported in literature for thin films like those tested in the experiments.