Novel Sulfonated CNN Pincer Ligands for Facile C−H Activation at a Pt(II) Center

Two novel sulfonated CNN-pincer ligands 1b and 1c and the corresponding chloro and aqua complexes K[^CNNLPtCl] and ^CNNLPt(H₂O), 3b – 3c and 2b – 2c , were prepared and fully characterized including single crystal X-ray diffraction. Along with the previously described complexes 2a and 3a , the derivatives of a CNN pincer ligand 1a , these complexes form a family of structurally similar compounds where the pincer core rigidity increases in the series 2a (3a) < 2b (3b) < 2c ( 3c ), as deduced from their XRD data. The increased ligand rigidity affects the aqua ligand dissociation energy of the ^CNNLPt(H₂O) complexes, as it follows from DFT calculations and as is reflected in the increased reactivity of the aqua complexes 2a , 2b and 2c in processes that involve aqua ligand loss. Among these processes the formation of the presumed dinuclear complexes ^CNNL₂Pt₂ and, importantly, catalytic C−D bond cleavage in C₆D₆ were studied in 2,2,2-trifluoroethanol solutions. The C−D bond cleavage reactivity was quantified as the rate of H/D exchange between C₆D₆ and CF₃CH₂OH at 80 °C.     

碱激发玻璃材料

玻璃的结构和组分与粒化高炉矿渣类似,用碱来激发玻璃可获得一种新型的碱激发材料,目前在国内尚无人尝试,其应用有待开拓。着重介绍碱激发玻璃材料的方法及激发的条件。     

热电池激活方式综述

为了帮助引信和武器工作者了解和合理应用热电池,综述了热电池的电激活、外置机械激活、内置机械激活和冲击激活等激活机构,及其通过电点火头、撞击火帽、针刺火帽或冲击热能点火的工作原理。电激活机构热电池设计简单,相对成熟,可靠性高,电性能稳定。机械激活热电池设计要求综合考虑激活机构承受的环境力、火帽参数、电性能等因素。冲击激活热电池设计更为精细,将成为今后研究的一个方向。     

FT-IR法研究PBT粘合剂的固化反应动力学

为明确3,3-双(叠氮甲基)氧丁环-四氢呋喃共聚醚(PBT)粘合剂与常用固化剂的反应过程,利用傅里叶变换红外(FT-IR)光谱法研究了PBT/多异氰酸酯(N100)、PBT/甲苯二异氰酸酯(TDI)和PBT/TDI/N100体系,50～80℃、TPB催化下的固化反应动力学。结果表明:PBT/N100在整个固化过程中遵循二级反应动力学规律,表观活化能63.10 kJ·mol~(-1),指前因子A=1.63×10~7h~(-1)。含有TDI的体系的固化过程均分为两段,但分段机理不同。PBT/TDI体系整个固化反应遵循二级反应动力学规律,但由于TDI上不同位置—NCO活性的差异,以转化率60%为界线分为两个阶段,转化率小于60%为第一阶段,转化率大于60%为第二阶段,相同温度下,第一阶段的反应速率明显高于第二阶段,两阶段的表观活化能分别为54.71 kJ·mol~(-1)和56.50 kJ·mol~(-1),指前因子分别为4.38×10~7h~(-1)和1.24×10~7h~(-1)。PBT/TDI/N100体系反应由于TDI和N100上—NCO活性的差异也分为两个阶段,转化率小于65%主要发生TDI扩链,表现为二级反应动力学,表观活化能为71.17 kJ·mol~(-1),指前因子A=4.58×10~8h~(-1);转化率大于65%主要发生N100交联,反应速率受扩散控制。TDI/N100复配时,指前因子较单一N100体系和单一TDI前后两阶段分别扩大了28,10,37倍,表明固化剂复配后反应活性位点增加。     

固液耦合模式下含断层缺陷煤层回采诱发底板损伤及断层活化突水机制研究

针对具体地质条件,以现场试验数据为基础,采用相似材料试验及数值模拟相结合的分析方法,对含断层缺陷煤层回采过程中底板损伤破坏及断层活化规律进行研究,研究得出:采用内径不同的水管能够很好地反映底板岩层渗透性的空间差异性,通过采用调节注水管水柱高度的方式可以控制水压以满足设计要求;煤层埋深、承压水水压及断层落差越大越易突水,断层防水煤柱宽度越大越不易突水;通过试验及模拟计算再现了不同因素影响下煤层回采过程中底板采动裂隙形成、断层活化到突水通道形成的全过程,揭示了含断层构造底板突水通道的形成机制;研究结果对承压水上含断层缺陷煤层回采时防水煤柱的留设具有重要的参考价值。     

On the potential of combining neutron activation analysis and particle induced X-ray emission (PIXE) for micro- and microdistribution analysis of hard metals in human tissues

Tungsten carbide and cobalt are the main components of hard metal alloy while other metals such as chromium, niobium, tantalum, titanium and vanadium are sometimes added in smaller amounts. Exposure to hard metal dusts can induce a lung fibrosis with cobalt playing a major role. In order to provide information on the role that each metal may have in causing this disease, determination of the total content and the distribution of inhaled metals in lung tissue of hard metal workers is of paramount importance. However, samples such as transbronchial biopsy and bronchoalveolar lavage (BAL), often used in the medical diagnosis of pneumoconiosis, only allow for a small amount of material. This calls for sensitive and accurate analytical procedures for microdetermination and distribution of metals in pulmonary tissue and cellular material, such as macrophages. This work proposes a combination of sophisticated analytical techniques such as neutron activation analysis (NAA), currently applied to the determination of the total concentration of more than 30 elements in biological specimens, and PIXE analysis, particularly microPIXE, which has a great potential for microdistribution analysis in small biological samples. Principles and perspectives for the combined use of these techniques for the analysis of human tissue are outlined and discussed. NAA: determination of hard metals in lung tissue are carried out by neutron irradiation (2 × 10¹⁴ neutrons cm⁻² s⁻¹) in the HFR reactor of Petten. After neutron activation, radiochemical separations of ⁶⁰Co, ¹⁸⁷W, ¹⁸²Ta, ⁵¹Cr followed by computer-based high resolution gamma ray spectrometry allow the measurement of these elements in pulmonary tissues with sensitivities ranging from 10⁻⁴ μg (Cr) to 10⁻⁶ μg (W). PIXE: this technique is multielemental and of relatively high sensitivity (μg/g) even in small total sample masses of from 10 to 100 μg, thus allowing the analysis of parts of needle biopsies. Whereas PIXE has been successfully applied to many medical problems, its usefulness is limited in the total samples analysis for cobalt-related hard metal disease, due to the low levels of cobalt in tissue combined with severe element interferences from the generally more abundant metal, iron. Nevertheless, microPIXE, a special variety of the method scanning over the sample with a focussed ion beam of about 2 × 2 μm², could complement the NAA findings in total samples in the sense of achieving a microdistribution analysis of hard metals (including cobalt) in suitable thin tissue sections.The availability of specialized facilities at the JRC such as the powerful HFR reactor (Petten), the NAA laboratories (Ispra) and the microPIXE facility (Geel) could represent a European ‘reference pole’ for the study of metals in tissues of hard metal diseased subjects.     

蒸养条件对超细粉煤灰混凝土强度的影响

试验研究了蒸养制度中预养时间、恒温温度、恒温时间对激发剂改性超细粉煤灰混凝土强度的影响。试验结果表明对于铁路预应力Ⅲ型轨枕用混凝土，升温前成熟度不宜低于70℃h，恒温阶段宜控制在60℃下8h为宜。     

Apparent activation energy for densification of <Emphasis Type="Italic">α</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> powder at constant heating-rate sintering

The apparent activation energy for densification is a characteristic quantity that elucidates the fundamental diffusion mechanisms during the sintering process. Based on the Arrhenius theory, the activation energy for densification of α-Al₂O₃ at constant heating-rates sintering has been estimated. Sintering of α-Al₂O₃ powder has been executed by the way of a push rod type dilatometer. It is shown that the apparent activation energy does not have a single value but depends directly on the relative density. The apparent activation energy corresponding to lower relative density was higher than that corresponding to higher relative density. In addition, the value of the evaluated activation energy is different at the same density level when the Arrhenius plot involves different heating rates.     

The effect of diffusion processes on the interaction in multicomponent silicate systems

The results of studying diffusion processes in silicate multicomponent systems, which are widely used as binders in variously purposed composite materials, have been generalized and described. It has been shown that the effective diffusion coefficients of alkali and alkaline-earth cations in a diffusion pair are not a single-valued function of the ion radius of the cation but depend on structural factors and on the energy of the cation bonding with other ions of the melt.     

Activation of Oxygen‐Stabilized Sulfur for Li and Na Batteries

The sulfur‐based cathode materials suffer severely from poor cycling stability and low utilization, incurred by their stepwise reaction mechanism that generates polysulfide intermediates and the subsequent irreversible losses. In this work, those issues are significantly relieved by entrapping sulfur species in carbon host rich in oxygen functionalities. Sulfur species in such C/S composite are highly stabilized by their interaction with oxygen, and can deliver a reversible capacity of 508 mAh/(g of S) for 2000 cycles when coupled with Li, representing the best cycling stability up to date. More interestingly, extra capacity can be accessed by simply prelithiating the oxygen‐stabilized C/S composites down to 0.6 V for a few cycles, which enables a high capacity of 1621 mAh/(g of S) that eventually stabilizes at 820 mAh/(g of S) for 600 cycles. The mechanism for this electrochemical activation process is investigated with both spectroscopic and electrochemical techniques, which reveal that the inactive sulfur bonded to oxygen is liberated in the initial deep lithiation precycles and becomes electrochemically active. The oxygen‐stabilized sulfur can also be coupled with Na anode to form Na/S cell, confirming that the formation of S?O interaction in C/S composite generates promising sulfur‐based cathode materials for Li–S and Na–S batteries.