钙与 DBC-偶氮氯膦显色反应的研究及其在高纯氧化钇中钙的测定的应用

在PH8.5-9的液中,钙可与DBC-偶氮氯膦形成一种紫色的稳定配合物。该配合物在625nm处有最大吸收,表观摩尔吸光系数为2.6×10~4L.mol~(-1).cm~(-1),配合物组成为Ca:DBC-偶氮氯膦=1:1。在Zn-DTPA和乙二胺的存在下,较大量的Y~(3+)、Fe~(3+)及Cu~(2+)、Mo(Ⅵ)、Cr~(3+)等三十余种离子不干扰钙的测定。方法的选择性较好,利用本方法,并经简单萃取分离基体后,测定了高纯氧化钇和易切削钢中的微量钙,结果令人满意。标准加入试验回收率好。方法简便实用。     

3D H-bonding networks self-assembly from pyridinium derivatives and bis(maleonitriledithiolato)zincate(II)

The two ion-pair complexes, [pyH]₂[Zn(mnt)₂] (1) and [4,4′-bipyH₂]-[Zn(mnt)₂] (2), were synthesized, where mnt²⁻ denotes maleonitriledithiolate, and [pyH]⁺, [4,4′-bipyH₂]²⁺ represent pyridinium and diprotonated 4,4′-bipyridinium, respectively. Their single crystal structures show that there are strong bifurcated H-bonding interactions between the cations of the pyridinium derivative and the [Zn(mnt)₂]²⁻ anions in both 1 and 2. The bifurcated H-bonding interactions between the N–H of the pyridiniums and the CN groups of the mnt²⁻ ligands give rise to a 2D layered H-bonding network, the adjacent layers come together in such way as mutual embrace to give a tight pack, thus 2D hydrogen-bonding sheets further develop into 3D H-bonding networks through weak C–HS and ππ stacking interactions in 1. As for 2, the cations and anions connect into several types of H-bonding macrorings ([2+2], [3+3] and [4+4]), these H-bonding macrorings fuse to extend into 2D layered structure, the interpenetration between [3+3] and [4+4] type H-bonding macrorings in the adjacent layers give further rise to novel 3D extended H-bonding networks, in which there are clearly parallel stacks of cations and the chelate rings of anions.     

Preparation and Characterization of a Sol-Gel Prepared Ferroelectric Sandwich Structure

A novel silicon-based PbTiO₃/Pb(Zr,Ti)O₃/PbTiO₃ (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm² respectively. The current density is less than 5 × 10^–9 A/cm² below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 10⁹ read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications.     

Inverse relaxation-model and relation to recovery internal friction

Inverse relaxation is studied for hard elastic polypropylene (HEPP), rubber and non-elastic polypropylene. The results show that contractive stress, stress, and internal friction are three essential factors related to the phenomenon. A three-element model in which each element has a definite meaning is proposed to describe this phenomenon. The results also show that, in the first cyclic deformation, relaxation time increases with the increase of recovery for all the materials, which indicates that recovery viscosity increases with the increase of recovery, but the stress rising amplitude (SRA) of inverse relaxation has a maximum in the recovery range. Analysis indicates that SRA equals recovery internal friction (RIF) for ideal material in which stress is solely a function of strain, independent of paths, and approximately equals RIF for non-ideal material at a given strain. From this principle it is found that the order of the work counteracted by RIF for the four materials is the same as that of their second hysteresis loop, and the RIF of HEPP has a sudden increase at the later recovery range.     

合成云母蒙脱石及其交联物在乙醇氨化反应中的催化行为

用水热法合成了云母蒙脱石,并与羟基铝齐聚物交联,DTA和IR结果表明,由于柱的引进,高温焙烧时层内八面体上羟基脱除变得较为容易。由NH_3-TPD和吡啶吸附测得的表面酸性表明Al-CLS具有较SMM更多的弱酸和强酸中心。催化剂上弱酸中心有利于醇的脱水,而吸附在强酸中心上的NH_3有利于醇的胺化。     

Dérivés de la dihydro-2,4 triazole-1,2,4 thione-3 et de l'amino-2 thiadiazole-1,3,4 à partir de nouvelles thiosemicarbazones d'esters

A new general synthesis of 4,5-disubstituted 2,4-dihydro-1,2,4-triazole-3-thiones is proposed. These heterocycles are obtained by the action of primary amines, arylhydrazines or aroylhydrazines on the thiosemicarbazones of eaters. These last compounds are prepared by action of chlorhydrates of iminoethers on thiosemicarbazide in dimethylformamide. These thiosemicarbazones react also with strong acids, acid anhydrides and chlorides; by thermolysis and they give 2-amino-1,3,4-thiadiazole derivatives. Also, two derivatives of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole have been prepared.     

Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of TiO2

Ag-TiO2 catalysts with different Ag contents were prepared via a sol-gel method in the absence of light. Based on the characterizations of XRD, photoluminescence (PL), surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), and XPS as well as the evaluation of the photocatalytic activity for degrading rhodamine B(RhB) solutions, it was found that the Ag dopant promoted the phase transformation as well as had an inhibition effect on the growth of anatase crystallite. The PL and SPS intensities were decreased with increasing Ag content, indicating that the Ag dopant could effectively inhibit the recombination of the photoinduced electrons and holes. However, the active sites capturing the photoinduced electrons reduced, while the Ag content exceeded 5 mol %. At rather low Ag dopant concentrations, the migration and diffusion of Ag+ ions were predominant, while at rather high Ag dopant concentrations, the migration, diffusion, and reduction of Ag ions simultaneously occurred. The Ag-TiO2 photocatalysts with appropriate content of Ag (Ag species concentration is from about 3 to 5 mol %) possessed abundant electron traps so as to be favorable for the separation of the photoinduced electron-hole pairs, which could greatly enhance the activity of the photocatalysts. From the results of FISPS measurements, it could be found that the impurity bands and abundant surface states were introduced into the interfacial layer of TiO2 because of Ag simultaneously doping and depositing, which could improve the absorption capability for visible light of the photocatalysts.     

Space-Air-Ground Integrated Mobile Crowdsensing for Partially Observable Data Collection by Multi-Scale Convolutional Graph Reinforcement Learning

Mobile crowdsensing (MCS) is attracting considerable attention in the past few years as a new paradigm for large-scale information sensing. Unmanned aerial vehicles (UAVs) have played a significant role in MCS tasks and served as crucial nodes in the newly-proposed space-air-ground integrated network (SAGIN). In this paper, we incorporate SAGIN into MCS task and present a Space-Air-Ground integrated Mobile CrowdSensing (SAG-MCS) problem. Based on multi-source observations from embedded sensors and satellites, an aerial UAV swarm is required to carry out energy-efficient data collection and recharging tasks. Up to date, few studies have explored such multi-task MCS problem with the cooperation of UAV swarm and satellites. To address this multi-agent problem, we propose a novel deep reinforcement learning (DRL) based method called Multi-Scale Soft Deep Recurrent Graph Network (ms-SDRGN). Our ms-SDRGN approach incorporates a multi-scale convolutional encoder to process multi-source raw observations for better feature exploitation. We also use a graph attention mechanism to model inter-UAV communications and aggregate extra neighboring information, and utilize a gated recurrent unit for long-term performance. In addition, a stochastic policy can be learned through a maximum-entropy method with an adjustable temperature parameter. Specifically, we design a heuristic reward function to encourage the agents to achieve global cooperation under partial observability. We train the model to convergence and conduct a series of case studies. Evaluation results show statistical significance and that ms-SDRGN outperforms three state-of-the-art DRL baselines in SAG-MCS. Compared with the best-performing baseline, ms-SDRGN improves 29.0% reward and 3.8% CFE score. We also investigate the scalability and robustness of ms-SDRGN towards DRL environments with diverse observation scales or demanding communication conditions.     

The Pharmacokinetics in Mice and Cell Uptake of Thymus Immunosuppressive Pentapeptide Using LC-MS/MS Analysis

Thymus immunosuppressive pentapeptide (TIPP) is a novel anti-inflammatory peptide with high efficacy and low toxicity. This study aims to establish a selective LC-MS/MS method for analyzing the analyte TIPP in biological samples, laying the foundation for further PK and PD studies of TIPP. Protein precipitation was conducted in acetonitrile supplemented with 2% formic acid and 25 mg/mL dithiothreitol as a stabilizer, which was followed by backwashing the organic phase using dichloromethane. The chromatographic separation of TIPP was achieved on a C18 column with a gradient elution method. During positive electrospray ionization, TIPP was analyzed via multiple-reaction monitoring. The linear relationships between the concentration of TIPP and peak area in murine plasma cell lysates, supernatants, and the final cell rinse PBS were established within the ranges of 20–5000 ng/mL, 1–200 ng/mL, 10–200 μg/mL, and 0.1–20 ng/mL, respectively (r² > 0.99). Validated according to U.S. FDA guidelines, the proposed method was proved to be acceptable. Such a method had been successfully applied to investigate the pharmacokinetics of TIPP in mice via subcutaneous injection. The plasma half-life in mice was 5.987 ± 1.824 min, suggesting that TIPP is swiftly eliminated in vivo. The amount of TIPP uptake by RBL-2H3 cells was determined using this method, which was also visually verified by confocal. Furthermore, the effective intracellular concentration of TIPP was deduced by comparing the intracellular concentration of TIPP and degrees of inflammation, enlightening further investigation on the intracellular target and mechanism of TIPP.     

Interpretation of Strengthening Mechanism of Densified Wood from Supramolecular Structures

In this study, densified wood was prepared by hot pressing after partial lignin and hemicellulose were removed through alkaline solution cooking. The tensile strength and elastic modulus of densified wood were improved up to 398.5 MPa and 22.5 GPa as compared with the original wood, and the characterization of its supramolecular structures showed that the crystal plane spacing of the densified wood decreased, the crystallite size increased, and the maximum crystallinity (CI) of cellulose increased by 15.05%; outstandingly, the content of O(6)H⋯O(3′) intermolecular H-bonds increased by approximately one-fold at most. It was found that the intermolecular H-bond content was significantly positively correlated with the tensile strength and elastic modulus, and accordingly, their Pearson correlation coefficients were 0.952 (p < 0.01) and 0.822 (p < 0.05), respectively. This work provides a supramolecular explanation for the enhancement of tensile strength of densified wood.