A New Synthesis of 2-Arylbenzothiazoles from 1,2,3-Benzodithiazole-2-Oxides

The reaction of 6-substituted-1,2,3-benzodithiazole-2-oxides (3a-3d) with aromatic aldehydes, carboxylic acids, and their chlorides in the presence of an organic base provides a new method for the synthesis of 6-substituted-2-arylbenzothiazoles (4a-4d) without involving the preparation of intermediate 2-aminobenzenethiols.     

Simultaneous extraction and purification of fucoxanthin from Tisochrysis lutea microalgae using compressed fluids

The marine microalga Tisochrysis lutea, a Haptophyta with a thin cell wall and currently used mainly in aquaculture is a potential source of several bioactive compounds of interest such as carotenoids. In the present study, the simultaneous extraction and purification of fucoxanthin, the main carotenoid from T. lutea, was optimized using pressurized fluid extraction followed by in‐cell purification. An experimental design was employed to maximize carotenoids’ extraction; the experimental factors chosen were: (i) percentage of ethanol/ethyl acetate (0–100 %), (ii) temperature (40–150°C), and (iii) number of static extraction cycles (1–3). The maximum carotenoids’ recovery, mainly fucoxanthin, was obtained with pure ethyl acetate at 40°C using one extraction cycle, achieving values of 132.8 mg of carotenoids per gram of extract. Once the optimum extraction conditions were confirmed, in‐cell purification strategies using different adsorbents were developed to obtain fucoxanthin‐enriched extracts. Activated charcoal showed potential retention of chlorophylls allowing an effective purification of fucoxanthin in the obtained extracts. Chemical characterization of extracts was carried out by reversed‐phase high‐performance liquid chromatography with diode array detection. Therefore, a selective fractionation of high value compounds was achieved using the proposed green downstream platform based on the use of compressed fluids.     

Experimental Study on the Flexural Ductility of BFRP Bar Concrete Beams With Bamboo Fiber and Steel Wire Mesh北大核心CSCD

To study the effects of bamboo fiber and steel wire mesh on the flexural ductility of basalt fiber reinforced polymer（BFRP）bar concrete beams, 7 BFRP bar concrete beams with bamboo fiber and steel wire mesh were tested with different bamboo fiber lengths (0 mm, 30 mm and 45 mm) and different steel wire mesh layout ranges (0, 1/2 maximum bending moment point layout and full beam length layout). The flexural failure tests of the 7 beams were carried out, and the initial crack loads, the crack developments, the ultimate loads and the deformations were detected. The effects of the fiber length and the wire mesh layout range on the crack resistance and the deformation resistance of the specimens were analyzed based on the test data. With the function model, the equivalent yield points of the 7 test beams were obtained, and their ductility coefficients were calculated. The results show that, the addition of bamboo fiber and steel wire mesh increases the cracking loads of BFRP bar concrete beams by 12%~68%, decreases the crack spacings and the crack length development speed, reduces the test beam deformation under the same load, and increases the ductility coefficient by 1.58%~31.75%. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

Structural characterization of modern and fossilized charcoal produced in natural fires as determined by using electron energy loss spectroscopy

Charcoal produced in natural fires is widespread, but surprisingly little is known about its structure and stability. TEM and electron energy loss spectroscopy (EELS) were used to characterize the organized graphite-like microcrystallites and amorphous nonorganized phases of modern charcoal that had been produced in natural fires. In addition, a semiordered structure was identified in two modern charcoal samples. Fossilized charcoal contains fewer graphite-like microcrystallites than modern samples. EELS spectra confirmed that the dominant structure in fossilized charcoal is amorphous carbon. EELS measurements also revealed that only the nonorganized phase contains oxygen, which indicates that the degradation of the fossilized charcoal structure occurs mainly through oxidation processes. The few graphite-like microcrystallites found in fossilized charcoal were composed of onion-like structures that are probably less prone to oxidation owing to their rounded structures.     

一维纳米炭/竹炭的制备及其对Pb~(2+)的吸附

以二甲苯为炭源、二茂铁为催化剂,采用CVD法在竹炭上催化气相生长了一维纳米炭,采用扫描电镜、透射电镜及氮吸附仪等对一维纳米炭/竹炭的形貌、微结构及比表面积进行了表征,并研究了一维纳米炭/竹炭复合材料对重金属离子Pb2+的吸附性能.结果表明,采用CVD法可以在竹炭上生长一维纳米炭,且随着气相生长时间的延长,竹炭上的一维纳米炭变得更加浓密而均匀.竹炭上生长一维纳米炭后,对Pb2+的吸附能力增强,硝酸氧化处理可以进一步提高一维纳米炭/竹炭对Pb2+的吸附能力.     

Effects on surface properties of natural bamboo fibers treated with atmospheric pressure argon plasma

Argon plasma at atmospheric pressure was used to improve the wettability and dyeability of natural bamboo fibers. Optical emission spectroscopy (OES) was employed to characterize the discharge. SEM and scanning probe microscopy (SPM) analyses show that the fiber surface becomes rougher after plasma treatment because of the effects of plasma bombardment and etching. The wettability and dyeability are significantly enhanced after plasma treatment. Longer treatment time, leading to rougher surface, results in better surface wettability and dyeability. These results reveal that atmospheric pressure argon plasma treatment is an effective method to improve the performance of bamboo fibers. Copyright © 2006 John Wiley & Sons, Ltd.     

Adsorption studies of acetic acid dimers on activated charcoal from organic solvents

Acetic acid exists as dimers in organic solvents like benzene, toluene and xylene. Adsorption of dimeric acetic acid on activated charcoal (AC) at various temperatures from benzene, toluene and xylene solutions have been studied. The system obeys Langmuir isotherm, thus signifying a monolayer adsorption of dimers. Corrections on AC-solvent pore volume fillings, molecular cross sectional surface area of acetic acid dimers, the adsorption equilibrium constants, the free energy change and the enthalpy change values are computed at different temperatures for the three solvents. The adsorption process has been found to be physisorption type. The FTIR measurements show that the adsorbed acetic acid dimer seems to retain the cyclic structure against the open chain non-cyclic structure.     

Headspace gas chromatographic determination of ethylene oxide in air

Summary A simple and accurate headspace-GC method is described to determine the amount of ethylene oxide which has been collected from air using adsorption tubes containing activated charcoal and a relatively safe desorbing agent (N,N-dimethyl acetamide). The detection limit is 40μg/m³.     

基于竹膜固定酪氨酸酶的L-酪氨酸光度测定法

提出了将酪氨酸酶固定在戊二醛活化的竹膜上制成检测L-酪氨酸的单元,用于L-酪氨酸的光度测定。此方法系基于在pH 7.0的磷酸盐缓冲溶液中酪氨酸酶催化酪氨酸转化为多巴醌,多巴醌进一步与3-甲基-2-苯并噻唑啉酮腙盐酸盐(MBTH)反应生成栗色加合物。此化合物在490 nm波长处有特征吸收峰,并在此波长所测得的吸光度与L-酪氨酸的浓度在5~200μmol·L-1之间呈线性关系,其检出限(3S/N)为2.5μmol·L-1。应用此方法测定了复方氨基酸注射液中L-酪氨酸的含量,所得结果与该药品的标示值一致。     

竹笋中40种农药残留的固相萃取/气相色谱-质谱法同时测定

建立了竹笋中40种农药(包括有机磷类、有机氯类、氨基甲酸酯类、拟除虫菊酯类、三唑类和杂环类)残留的同时检测方法.样品以乙腈为提取溶剂,高速匀浆提取,经PSA固相萃取小柱净化,利用GC-MS/SIM进行测定.结果表明,40种农药在一定质量浓度范围内线性良好,相关系数为0.994 6 ～0.999 8.在0.050 ～2....