Synthesis and structure of novel 6-(pyrazol-1-yl)-4-methyl-1H-pyrazolo[3,4-b]pyridin-3-ol derivatives

New 6-(pyrazol-1-yl)pyrazolo[3,4-b]pyridin-3-ol compounds were synthesized by cyclization reaction from 2,6-dichloro-4-methylnicotinonitrile. Their derivatives exist as the 3-hydroxy tautomer. The structure of the compound 1a of one of the resulting compounds was studied in detail by X-ray diffraction.     

Novel stability condition for delayed fractional-order composite systems based on vector Lyapunov function

Nonlinear Dynamics - This paper proposes a novel stability condition for delayed fractional-order composite systems. First, we extend the vector Lyapunov function to the fractional-order systems to...     

基于BF3正比管的宽量程脉冲中子探测技术

介绍了一种基于BF3正比计数管的宽量程脉冲中子探测技术。该技术采用多通道、组合式的BF3管阵列中子探测器组,以适应产额变化范围较宽的脉冲中子测试场合,并同时兼顾测量下限。基于该技术研制了一套BF3阵列中子探测系统并应用于脉冲中子源的测试,实验结果表明,该系统的脉冲中子测量范围可达5个数量级(56~8106),测量下限低、输出信号清晰,证明了该技术的可行性和有效性。     

Structure and electrochemical performance of LiCoO2 cathode material in different voltage ranges

LiCoO₂ sample prepared by high-temperature solid state calcination shows a typical hexagonal structure with a single phase and fine particle size distribution. The high-voltage electrolyte with additive fluoroethylene carbonate (FEC) has been used. Electrochemical results show that the initial discharge capacities of the prepared LiCoO₂ cathode are 157.7, 169.5, 191.0, and 217.5 mAh g^?1 in the voltage ranges of 3.0–4.3, 3.0–4.4, 3.0–4.5, and 3.0–4.6 V, respectively. The capacity increases, while the initial coulombic efficiency and capacity retention decrease with increasing the charge cutoff voltage. The capacity retention is only 10.4 % after 200 cycles at 1C rate in the voltage range of 3.0–4.6 V. X-ray diffraction measurements confirm structural changes of the layered material in the different voltage ranges. A phase transition from the O3 to the H1-3 phase can be observed when LiCoO₂ is charged above 4.5 V. The AC impedance analysis indicates that the resistances (R _(sf+b), R _ct) of the prepared LiCoO₂ rapidly increase when the cell is charged to higher voltage. The amount of dissolved Co into the electrolyte also greatly increases with increasing the charge cutoff voltage.     

Influence of annealing temperature on the formation, microstructure and magnetic properties of spinel nanocrystalline cobalt ferrites

Nanocrystalline cobalt ferrites were synthesized by a simple, general, one-step sol–gel auto-combustion method. An interpretation based on the measurement of the adiabatic flame temperature and the amounts of gas evolved during reaction had been proposed for the nature of combustion. The influence of annealing temperatures on the magnetic properties was investigated. The microstructure was characterized by means of X-ray diffractometer (XRD) and transmission electron microscopy (TEM). It was found that the particle size and magnetic properties of the as-prepared ferrite samples showed strong dependence on the annealing temperature. The coercivity initially increased and then decreased with increasing annealing temperature whereas the particle size and saturation magnetization continuously increased.     

Simultaneous Determination of Paracetamol,Ibuprofen, and Caffeine in Tablets by Molecular Absorption Spectroscopy Combined with Classical Least Square Method

In this paper, the classical least-squares (CLS) method with molecular absorption spectrophotometric measurement was used to determine simultaneously paracetamol (PAR), ibuprofen (IBU), and caffeine (CAF) in tablets. The absorbance spectra of the standard solutions and samples were measured over a wavelength from 220 to 300 nm with a 0.5 nm step. The concentration of PAR, IBU, and CAF in the sample solutions was calculated by using Visual Basic for Applications (VBA) and a program called CLS-Excel written in Microsoft Excel 2016. The method and the CLS-Excel program were tested on mixed standard laboratory samples with different PAR, IBU, and CAF concentration ratios, and they showed only small errors and a satisfying repeatability. An analytical procedure for tablets containing PAR, IBU, and CAF was developed. The reliability of the procedure was proved via the recovery and repeatability of the analysis results with an actual tablet sample and by comparing the mean contents of active substances in the tablets obtained from the analytical procedure with the HPLC method. The procedure is simple with a reduced cost compared with the HPLC standard method.     

Boride-based nano-laminates with MAX-phase-like behaviour

MAX-phases being usually composed of transition metals, group A elements and carbon/nitrogen are considered interesting materials for many applications because of their tremendous bulk modulus, “reversible” plasticity, and machinability. This is mainly due to their unique kind of bonding comprising covalent, ionic as well as metallic bonds providing “easy” planes of rupture and deformability due to the layered crystal structures.In transition metal boride systems, similar types of bonding are available. In particular the W₂B₅-structure type and its stacking variations allow the synthesis of strongly layered crystal structures exhibiting unique delamination phenomena.The paper presents ab initio calculations showing the similarities of bonding between the ternary carbides and the corresponding ternary or quaternary borides. Formation of boride-based nano-laminates from auxiliary liquid phases, from the melt as well as during sintering and precipitation from supersaturated solid solutions will be discussed by means of SEM and TEM studies. The role of impurities weakening the interlayer bonding will be addressed in particular. The pronounced cleavage parallel to the basal plane gives rise for crack deflection and pull-out mechanisms if the laminates are dispersed in brittle matrices such as boron carbide, silicon carbide or other transition metal borides.     

Expression of hepatitis C virus nonstructural 4B in transgenic mice

Hepatitis C virus (HCV) is a pathogen that is of great medical significance in chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma worldwide. Although the HCV proteins have been intensively investigated over the past decade, the biochemical functions of the NS4B protein are still largely unknown. To investigate NS4B as a potential causative agent of liver disease, transgenic mice expressing the NS4B protein in liver tissue were produced. The transgenic animals were phenotypically similar to their normal littermates for up to 18 months of age. Our results suggest that the HCV NS4B protein is not directly cytopathic or oncogenic in our transgenic mice model.     

Simultaneous determination of tetracyclines and their degradation products in environmental waters by liquid chromatography–electrospray tandem mass spectrometry

A sensitive method was developed for the trace determination of six tetracyclines and ten of their degradation products in influent, effluent, and river waters using liquid chromatography–electrospray tandem mass spectrometry detection, combined with Oasis hydrophilic–lipophilic balance (HLB) cartridge extraction and Oasis mixed-mode strong anion exchange (MAX) cartridge cleanup. Tetracyclines and their products were separated by liquid chromatography in 9.5 min, and the instrument detection limits were generally between 0.03 and 0.1 μg/L except for minocycline (0.5 μg/L). The chromatograms were improved through the MAX cleanup and no apparent matrix effect was found. The recoveries of all the target compounds except for 4-epianhydrochlortetracycline and anhydrochlortetracycline (34–52%) were 75–120% for influent, 61–103% for effluent, and 64–113% for river waters. The method detection limits (MDLs) of the analytes varied in the range of 0.8–17.5 ng/L in all studied matrices. The method was applied for the determination of tetracyclines and their products in a sewage treatment plant (STP) and surface waters in Beijing, China. Oxytetracycline (3.8–72.5 ng/L), tetracycline (1.9–16.5 ng/L), and five products including 4-epitetracycline, 4-epioxytetracycline, isochlortetracycline, anhydrotetracycline, and 4-epianhydrochlortetracycline (5.7–25.3 ng/L) were detected in wastewater, while only oxytetracycline and tetracycline (2.2 and 2.1 ng/L) were detected in surface water samples.