A Novel Colorimetric and Fluorescent pH Sensor Derived from Iminocoumarin and Thiophene‐Carboxaldehyde

A novel colorimetric and fluorescent pH sensor derived from iminocoumarin and thiophene‐carboxaldehyde was designed and synthesized. The structures of the dye and related compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectra. Color change from green to yellow of the new sensor solution in ethanol–water with the decrease in the pH value from 7 to 2 was observed by the naked eye. Under acidic conditions, the intensity of the maximum fluorescence emission peak of the sensor increased gradually with the decrease in the acidity of the solution (the increase in the pH value from 2 to 7) and attained to the maximum value at about pH 6. Under basic conditions, the fluorescence intensity of the emission peak of the sensor did not exhibit a distinct change at pH ≤ 11.85, and the fluorescence was quenched at pH 13.36, concomitant with the green color of the solution turning pale. The sensor can be used as a fluorescent pH probe in the presence of common metal cations and anions without interference.     

Ammine aluminium borohydrides: an appealing system releasing over 12 wt% pure H2 under moderate temperature

Ammine aluminium borohydride system is found to release >12 wt% pure H(2) below 120 °C via a combined strategy of changing the coordination number and adopting mixed cations.     

1.8 μm optical parametric oscillator based on KTiOPO4

A 1.8 ??m optical parametric oscillator pumped by a diode end-pumped acousto-optically Q-switched Nd:YAG is demonstrated. A 30-mm-long KTiOPO₄ crystal cut with an angle of ?? = 59.4°, ?? = 0° is employed as the OPO crystal. 685 mW signal laser at 1.8 ??m is obtained at the diode pump power of 13 W and the pulse repetition rate of 25 kHz. Simultaneously, 265 mW idler emission at 2.6 ??m is obtained. The corresponded diode-to-OPO conversion efficiency is 7.3%. The pulse width of the signal and idler wave are measured to be 4.5 and 2.5 ns, respectively. This gives a peak power of 6.1 and 4.2 kW, respectively.     

Catalytic Synthesis of 2,5‐Furandicarboxylic Acid from Concentrated 2,5‐Diformylfuran Mediated by N‐hydroxyimides under Mild Conditions

Producing polyester monomer 2,5‐furandicarboxylic acid (FDCA) from biomass as an alternative to fossil‐derived terephthalic acid has drawn much attention from both academy and industry. In this work, an efficient FDCA synthesis was proposed from 10.6 wt % 2,5‐diformylfuran (DFF) in acetic acid using a combined catalytic system of Co/Mn acetate and N‐hydroxyimides. The intermediate product of 5‐formyl‐2‐furandicarboxylic acid (FFCA) possesses the least reactive formyl group. N‐hydroxysuccinimide was found to be superior to N‐hydroxyphthalimide in catalyzing the oxidation of the formyl group in FFCA intermediate, affording a near 95 % yield of FDCA under mild conditions of 100 °C. Trace maleic anhydride was detected as by‐product, which mainly came from the oxidative cleavage of DFF via furfural, furoic acid and 5‐acetoxyl‐2(5H)‐furanone as intermediates.     

加权U—统计量的一个重对数律

证明了关于独立同分布随机变量序列的加权Ｕ－统计量的一个重对数律,类似于献「３」证明了一个加权Ｕ－统计量的解耦不等式。     

RHPMDs and FHPMDs with k = 4 and Type 4 u

A (v, k, 1)-HPMD is called a frame (briefly, k-FHPMD), if the blocks of the HPMD can be partitioned into v partial parallel classes such that the complement of each partial parallel class is a group of the HPMD. A (v, k, 1)-HPMD is called resolvable (briefly, k-RHPMD), if the blocks of the HPMD can be partitioned into parallel classes. In this article, (i) we shall construct 3-FHPMDs of type 3⁶ and 21⁶ to completely settle the existence of 3-FHPMD of type h^u; (ii) we shall show that the necessary conditions for the existence of 4-FHPMD of type h^u are sufficient for the case h = 4; (iii) we shall show that the necessary conditions for the existence of 4-RHPMD of type h^u are sufficient for the case h = 4.     

动力应变局部化传播及尺寸效应数值模拟

采用 FLAC-3 D模拟了应变软化岩土材料局部化剪切带的发展、扩容对剪切带倾角的影响及试件的宽度效应。随着加载时步的增加 ,彼此孤立的两个应变场逐渐靠近、叠加 ,最终形成了剪切带网络。无论端面约束强或弱 ,剪切带的倾角的数值模拟结果都与罗斯科倾角比较接近。增加试样宽度 ,剪切带的宽度增加 ,剪切带变得不平直 ;宽度越大 ,岩样上端面中点的压应力 -加载时步曲线的峰值强度越大 ,宽度对弹性阶段没有大的影响     

台风外围环流对沿海地区大气边界层结构的影响研究

结合茂名外场观测数据以及气象要素再分析数据,对台风外围环流影响和局地海陆风环流(SLBC)影响下沿海地区的大气边界层(ABL)结构识别方法和特征规律展开研究.利用气象要素探空数据和微脉冲激光雷达(MPL)观测数据进行了大气边界层高度(BLH)识别方法的适用性分析,提出了一种新的基于微脉冲激光雷达的BLH识别方法,以有效...     

Synthesis, luminescence and crystallographic structure of Eu-doped garnet-type yafsoanite Ca3Te2(ZnO4)3

A red-emitting phosphor of Eu³⁺-doped calcium–tellurium–zinc oxide, Ca₃Te₂(ZnO₄)₃, with a garnet-type structure was synthesized by high temperature solid-state reactions. This phosphor exhibited a strong red emission. The photoluminescence excitation spectrum showed that Ca₃Te₂(ZnO₄)₃:Eu³⁺ can be effectively excited by UV–visible light. The property of long-wavelength excitation for this material has a benefit as a red phosphor in application of white light-emitting diodes. The colour coordinates were calculated. The excitation and emission spectra and luminescence decay curves were obtained using a pulsed, tunable, narrowband dye laser. Crystallographic sites and charge compensation mechanism of Eu³⁺ ions were discussed. The emission line from Eu³⁺ in intrinsic crystallographic site in the lattice was located at 579.56 nm. The emission line from Eu³⁺ in another disturbed site, which is created by the defects created by the charge-compensation, was located at 580.88 nm. The disordered crystallographic sites of Eu³⁺ are benefit for their strong red luminescence corresponding to the ⁵D₀→⁷F₂ transition.     

Excellent stability of plasma-sprayed bioactive Ca3ZrSi2O9 ceramic coating on Ti-6Al-4V

In this work, novel zirconium incorporated Ca-Si based ceramic powder Ca₃ZrSi₂O₉ was synthesized. The aim of this study was to fabricate Ca₃ZrSi₂O₉ coating onto Ti-6Al-4V substrate using atmospheric plasma-spraying technology and to evaluate its potential applications in the fields of orthopedics and dentistry. The phase composition, surface morphologies of the coating were examined by XRD and SEM, which revealed that the Ca₃ZrSi₂O₉ coating was composed of grains around 100 nm and amorphous phases. The bonding strength between the coating and the substrate was 28 ± 4 MPa, which is higher than that of traditional HA coating. The dissolution rate of the coating was assessed by monitoring the ions release and mass loss after immersion in the Tris-HCl buffer solution. The in vitro bioactivity of the coating was determined by observing the formation of apatite on its surface in simulated body fluids. It was found that the Ca₃ZrSi₂O₉ coating possessed both excellent chemical stability and good apatite-formation ability, suggesting its potential use as bone implants.