基于催化应用调控氧化铈纳米材料的形貌

催化剂的设计、合成和结构调控是获得优异性能的关键.传统的策略主要是尽量减小催化剂颗粒尺寸以增加活性中心的数目,即尺寸效应.近年来,材料科学的快速发展使得在纳米尺度上调变催化剂的尺寸和形貌成为可能,特别是通过形貌调控可暴露更多的高活性晶面,大幅度提高催化性能,即纳米催化中的形貌效应.因此,调节催化剂的尺寸与形貌可以单独或协同优化材料的性能.氧化铈作为催化剂的重要组分与结构、电子促进剂被广泛应用于多相催化剂体系.本文总结了近期氧化铈材料形貌可控合成的进展,包括主要的合成策略和表征方法; 进而分析了氧化铈和金-氧化铈催化材料的形貌效应,指出金-氧化铈之间独特的相互作用与载体形貌密切相关; 阐述了氧化铈纳米材料因暴露晶面的差异而获得不同催化性能的化学机制.     

Reflection and transmission characteristics of ultrasonic guided waves in fractured long bone

Assessment of fractured long bone using ultrasonic guided wave（GW） has gained considerable attention.This paper focuses on using the hybrid boundary element method （HBEM） to analyze the propagation characteristics of ultrasonic GW in fractured long bones. The reflection coefficients（RC） and transmission coefficients（TC） for different depth-to-width ratio（d/w） cracks were numerically calculated and analyzed.It has been shown that the primary output modes,which include the transmission and reflection modes,are the same as the incidence modes.For some cracks,different TC curves always got the local maxima in adjacent frequencies.For different d/w cracks,most of the TC curves had local maxima which are not overlapped.These simulation results are helpful to optimize the modes and frequencies of the incidence GWs for quantitatively evaluating the bone quality and providing the numeral results of the cracks in long cortical bones.     

骨小梁中超声背散射信号的频率分析及其微结构的估计

骨质疏松症是一种骨强度下降的全身性骨骼疾病,骨强度的下降是骨量减少和骨微结构退化的共同结果。相比于传统的超声透射方法,超声背散射法可提供更多的骨微结构信息,而对于松质骨结构的建模能有助于结构信息的获取。本文将骨小梁简化为单圆柱模型(圆柱状的单根骨小梁浸于骨髓中),并基于此模型对超声背散射与频率的关系进行分析。用铝线代替骨小梁做仿体实验,通过实验与理论结果的比较来验证单圆柱模型的可行性。     

超声轴向传播技术评价长骨的研究

用超声轴向传播技术评价长骨状况已成为近年来的一个研究热点。本文首先介绍了第一到达波(FAS)法、超声Lamb波及柱面导波法在评价长骨皮质骨状况方面的研究进展,最后分析和讨论了当前研究中存在的问题及应该研究的方向。     

Polarographic behaviour of some organotin(IV) compounds in dimethyl sulphoxide

The differential pulse polarographic behaviour in dimethyl sulphoxide (DMSO) of 14 organotin(IV) compounds having the general formula R₃SnX (R = Me, Ph; X^? = NCS^?, N₃^?, N₃^?, NO₃^?, OH^?, NCO^? and OAc^?) and ⁿBu₃SnCl and ⁿBu₂SnCl₂ has been studied. The peak potential was found to depend markedly on the organic group and to a lesser extent on the nature of the anion X. The phenyltin compounds were reduced at lower potentials than the corresponding methyltin compounds. The data obtained could be used for trace determination of these compounds. Linear calibration curves were obtained over the concentration range of 2.8 × 10^?4 to 1.9 × 10^?6 mol dm^?3.     

Heterobimetallic complexes of palladium(II) bridged by the mixed phosphine–phosphine oxide ligand Ph2PCH2CH2P(O)Ph2

The mixed phosphine–phosphine oxide Ph₂PCH₂CH₂P(O)Ph₂ (dppeO) reacts with either trans-[PdCl₂(PhCN)₂], Na₂[PdCl₄] or trans-[PdCl₂(DMSO)₂] to give trans-[PdCl₂{¹-Ph₂PCH₂CH₂P(O)Ph₂}₂]. Treatment of the latter with the metal chlorides, MCl₂ · nH₂O (M = Mn, Cu, Co, Zn, Hg; n = 4, 2, 6, 1, 0, respectively) or with Me₂SnCl₂ or SnCl₄ · 5H₂O, or with UO₂(NO₃)₂ · 6H₂O or UO₂(OAc)₂ · 2H₂O gives heterobimetallic complexes: trans-[PdCl₂{-Ph₂PCH₂CH₂P(O)Ph₂}₂MX₂] · nH₂O. The cobalt complex (MX₂ = CoCl₂) was unstable in solution (MeOH or EtOH/CHCl₃), and reverts to trans-[PdCl₂{¹-Ph₂PCH₂CH₂P(O)Ph₂}₂] and CoCl₂. trans-[PdCl₂{¹-Ph₂PCH₂CH₂P(O)Ph₂}₂] does not apparently react with either NiCl₂ · 6H₂O or CdCl₂ · 2.5H₂O.     

Platinum(II) and palladium(II) complexes analogous to oxaliplatin with different cyclohexyldicarboxylate isomeric anions and their in vitro antitumour activity. Structural elucidation of [Pt(C2O4)(cis-dach)]

Several new Pt^II and Pd^II complexes bearing the enantiomerically pure (1R,2R)-(–)-l,2-cyclohexanediamine (dach) ligand, of general formula [MX₂{(1R,2R)-dach}], where M = Pt or Pd, X₂ = cis- or trans- or (1R,2R)-1,2-cyclohexyldicarboxylate anions, have been synthesized and characterized physicochemically and spectroscopically. These complexes have been screened in vitro against the three tumour cell lines K₅₆₂, HeLa and L₉₂₉, and the results obtained were compared with those of the reference standards, cisplatin, carboplatin and oxaliplatin; the known antitumour drugs. The single crystal X-ray structure determination of the [Pt(C₂O₄)(cis-dach)] complex has been discussed and compared with that of oxaliplatin, [Pt(C₂O₄){(1R,2R)-dach}].     

Organoplumbio complexes of platinum(II)

The complex [Pt(C₂H₄)(PPh₃)₂] reacts with Pb₂Ph₆ to give cis-[PtPh(Pb₂Ph₅)(PPh₃)₂]; this decomposes in solution to cis-[PtPh(PbPh₃)(PPh₃)₂], which may also be obtained from the ethylene complex and PbPh₄. Lead compounds PbPhMe₃ and PbPh₃Br also give products of insertion into PbPh bonds, but PbMe₃Cl gives cis- and trans-[PtCl(PbMe₃)(PPh₃)₂]. The complex trans-[Pt(PbPh₃)₂(PEt₃)₂] reacts with 1,2-bis(diphenylphosphino)ethane (DPPE) to give [Pt(PbPh₃)₂(DPPE)] which readily decomposes in dichloromethane in presence of PEt₃ to give [Pt(PbPh₃)(PEt₃)(DPPE)]Cl and [PtPh(PEt₃)(DPPE)]Cl. The complex trans-[PtCl(PbPh₃)(PEt₃)₂] was detected in the products of reactions between trans-[PtCl₂(PEt₃)₂] and trans-[Pt(PbPh₃)₂(PEt₃)₂] or less than 2 moles of LiPbPh₃; it was not detected in the mixture after treatment of trans -[Pt(PbPh₃)₂(PEt₃)₂] with HCl. In contrast to an earlier report, we were unable to detect lead-containing complexes in the products of the reaction between trans-[PtHCl(PPh₃)₂] and Ph₃PbNO₃. The complexes and their decomposition products were identified by ^pre31P-{¹H} NMR spectroscopy.     

一维链状配位聚合物[Cd{5-(NO2)sal}2(2,2′-bipy)]n的合成与晶体结构

A coordination polymer of [Cd{5-(NO₂)sal}₂(2,2′-bipy)]_n(5-(NO₂)sal=5-nitrosalicylate, 2,2′-bipy=2,2′-bipyridine) was synthesized by hydrothermal reaction and characterized by elemental analysis, IR and X-ray diffraction single crystal structure analysis. The title complex crystallizes in monoclinic with space group C2/c, a=2.730 8(16) nm, b=1.272 3(5) nm, c=0.674 5(3) nm, β=96.73(2)°, V=2.327(2) nm³, Z=4, R=0.022 2, wR=0.057. The 5-nitrosalicylate anions doubly bridge the Cd(Ⅱ) atoms to form one-dimensional polymeric chain with the repeated eight-membered ring units (Cd-O-C-O)₂. The crystal structure is stabilized by intra- and interchain hydrogen bonds interactions. CCDC: 694568.     

Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of several members of the 1,ω-bis(4-cyanobiphenyl-4′-yl) alkane (CBnCB) and the 1-(4-cyanobiphenyl-4′-yloxy)-ω-(4-cyanobiphenyl-4′-yl) alkane (CBnOCB) homologous series are reported. The new odd members described CB5CB, CB13CB, CB4OCB, CB8OCB and CB10OCB all exhibit twist-bend nematic and nematic phases. The members of these series already reported in literature, CB7CB, CB9CB, CB11CB and CB6OCB, were also prepared in order to allow for a direct comparison of their transitional properties. The properties of these dimers are also compared to those of the corresponding members of the 1,ω-bis(4-cyanobiphenyl-4,-yloxy) alkanes (CBOnOCB). For any given total spacer length, for odd members of these series, the nematic–isotropic transition temperatures and associated entropy changes are greatest for the CBOnOCB dimer and lowest for the CBnCB dimer. These trends are understood in terms of molecular shape. For short spacer lengths, the twist-bend nematic–nematic transition temperature (T_NTBN) is higher for the CBnOCB series than for the CBnCB series but this is reversed as the spacer length increases. Of the CBOnOCB dimers, a virtual value of T_NTBN was estimated for CBO3OCB and T_NTBN was measured for CBO5OCB. These values are considerably lower than those observed for the corresponding members of the CBnCB or CBnOCB series. The dependence of T_NTBN on molecular structure is discussed not only in terms of the molecular curvature but also in the ability of the molecules to pack efficiently. As the temperature range of the preceding nematic phase increases, so the twist-bend nematic–nematic transition entropy change decreases and the transition approaches second order for the longer spacers. For comparative purposes, the transitional behaviour of the even-membered dimers CB6CB, CB5OCB and CBO4OCB is reported and differences accounted for in terms of molecular shape.