Field survey of Glycyrrhiza plants in Central Asia (3). Chemical characterization of G. glabra collected in Uzbekistan

The chemical characteristics of Glycyrrhiza glabra L. were investigated at a habitat in Uzbekistan. HPLC analysis of the underground parts indicated that glycyrrhizin contents varied from 3.3 to 6.1% of dry weight, and that glabridin, a species-specific flavonoid for G. glabra, was detected in all underground samples (0.08-0.35% of dry weight). HPLC analysis of the leaves indicated that G. glabra plants collected in the present study could be divided into two types, RT-type and IQ-type, according to their major flavonol glycosides, rutin or isoquercitrin, respectively.     

Chemical Stability Study of H1 Antihistaminic Drugs from the First and the Second Generations,Diphenhydramine, Azelastine and Bepotastine,in Pure APIs and in the Presence of Two Excipients,Citric Acid and Polyvinyl Alcohol

The chemical stability of diphenhydramine (DIPH), azelastine (AZE) and bepotastine (BEPO) was examined in solutions and solids. The drugs were subjected to high temperature (70 °C for 35 h) or UV/VIS light (18.902–94.510 kJ/m²) at pH 1–13, to examine their percentage degradation and kinetics of degradation. Further, the stability of solid DIPH, AZE and BEPO was examined in the presence of excipients of different reactivity, i.e., citric acid (CA) and polyvinyl alcohol (PVA) under high temperature/high humidity (70 °C/80% RH) or UV/VIS light (94.510 kJ/m²). Under high temperature, DIPH degraded visibly (>19%) at pH 1 and 4, AZE was shown stable, while the degradation of BEPO was rather high (>17%) in all pH conditions. Under UV/VIS irradiation all the drugs were shown labile with degradation in the range 5.5–96.3%. As far as the solid mixtures were concerned, all drugs interacted with excipients, especially under high temperature/high humidity or UV/VIS light. As a result, DIPH, AZE and BEPO were compared in terms of their stability, with regard to their different structures and acid/base properties. All these results may be helpful for manufacturing, storing and applying these drugs in their topical (skin, nasal and ocular), oral and injectable formulations.     

Degradation patterns in water and oxygen of an inverted polymer solar cell

The spatial distribution of reaction products in multilayer polymer solar cells induced by water and oxygen atmospheres was mapped and used to elucidate the degradation patterns and failure mechanisms in an inverted polymer solar cell. The active material comprised a bulk heterojunction formed by poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) sandwiched between a layer of zinc oxide and a layer of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) that acted as, respectively, electron and hole transporting layers between the active material and the two electrodes indium-tin-oxide (ITO) and printed silver. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) in conjunction with isotopic labeling using H(2)(18)O and (18)O(2) enabled detailed information on where and to what extent uptake took place. A comparison was made between the use of a humid (oxygen-free) atmosphere and a dry oxygen atmosphere during testing of devices that were kept in the dark and devices that were subjected to illumination under simulated sunlight. It was found that the reactions taking place at the interface between the active layer and the PEDOT:PSS were the major cause of device failure in the case of these inverted devices, which are compatible with full roll-to-roll (R2R) coating and industrial manufacture. The PEDOT:PSS was found to phase separate, with the PEDOT-rich phase being responsible for most of the interface degradation in oxygen atmospheres. In water atmospheres, little chemically induced degradation was observed, whereas a large partially reversible dependence of the open circuit voltage on the relative humidity was observed. In addition, temporal aspects are discussed in regard to degradation mechanisms. Finally, analytical aspects in regard to storing devices are discussed.     

微囊藻毒素在单波长紫外光照射下的光降解动态研究

研究了两种微囊藻毒素在两种紫外光照射下的光降解行为,研究结果表明:UV-C是降解微囊藻毒素较好的光源;光照强度是影响毒素降解重要的因素,其次是温度和酸度;在UV-C的照射下,水体腐殖质对光降解具有抑制作用;微囊藻毒素的光解反应符合准一级动力学模型.同时本工作还按实际环境水体中毒素的含量水平进行了模拟研究,发现紫外光UV-C对环境水体中低含量的微囊藻毒素具有很强的去除能力.为今后发展无毒、高效、经济实用的饮用水处理技术做了有益的探索.     

Preparation of Fluorescent Carbon Dots from Chinese Herbal Medicine Alisma and Its Potential Applications in Photocatalytic Degradation of Malachite Green and Cell Imaging

Natural plants and Chinese herbal medicines are valuable resources. It is one of the new tasks for medical workers to study the new application fields of these resources. In this work, one kind of traditional Chinese herbal plant, Alisma, was chosen as a carbon source to synthesize the carbon dots(CDs). This kind of CDs has an amorphous carbon structure and shows strong stability to time, temperature, and ion strength. The results show that the degradation efficiency of malachite green dye can reach 100% in 4.5 h without illumination, and the degradation efficiency is better than that in dark environment. In addition, the CDs have also been successfully applied to HeLa cell imaging. Simple synthesis method, stable properties, good photodegradation and bioimaging applications make this material of great application value.     

Kinetics and Characterization of Degradation Products of Dihydralazine and Hydrochlorothiazide in Binary Mixture by HPLC-UV,LC-DAD and LC–MS Methods

Dihydralazine and hydrochlorothiazide were stored at high temperature and humidity, under UV/Vis light and different pH, as individual drugs and the mixture. Then, a sensitive and selective HPLC-UV method was developed for simultaneous determination of dihydralazine and hydrochlorothiazide in presence of their degradation products. Finally, the degradation products were characterized through LC-DAD and LC–MS methods. Dihydralazine was sensitive to high temperature and humidity, UV/Vis light and pH?≥?7. At the same time, it was resistant to acidic conditions. Hydrochlorothiazide was sensitive to high temperature and humidity, UV/Vis light and changes in pH. Its highest level of degradation was observed in 1 M HCl. Degradation of the drugs was higher when they were stressed in the mixture. In the case of dihydralazine, the percentage degradation was 5–15 times higher. What is more, dihydralazine became sensitive to acidic conditions. Hydrochlorothiazide was shown to be more sensitive to UV/Vis light and pH?>?4. Degradation of dihydralazine and hydrochlorothiazide followed first-order kinetics. The quickest degradation of dihydralazine was found to be in 1 M NaOH while of hydrochlorothiazide was in 1 M HCl (individual hydrochlorothiazide) or at pH 7–10 (hydrochlorothiazide in the mixture). A number of new degradation products were detected and some of them were identified by our LC-DAD and LC–MS methods. In the stressed individual samples, (phenylmethyl)hydrazine and 1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide were observed for the first time. Interactions between dihydralazine and hydrochlorothiazide in the mixture were confirmed by additional degradation products, e.g., 2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1,4-trioxide.     

On the stability of a variety of organic photovoltaic devices by IPCE and in situ IPCE analyses - the ISOS-3 inter-laboratory collaboration

This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RIS?-DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work, we apply the Incident Photon-to-Electron Conversion Efficiency (IPCE) and the in situ IPCE techniques to determine the relation between solar cell performance and solar cell stability. Different ageing conditions were considered: accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices were also monitored under conditions of ambient and inert (N(2)) atmospheres, which allows for the identification of the solar cell materials more susceptible to degradation by ambient air (oxygen and moisture). The different OPVs configurations permitted the study of the intrinsic stability of the devices depending on: two different ITO-replacement alternatives, two different hole extraction layers (PEDOT:PSS and MoO(3)), and two different P3HT-based polymers. The response of un-encapsulated devices to ambient atmosphere offered insight into the importance of moisture in solar cell performance. Our results demonstrate that the IPCE and the in situ IPCE techniques are valuable analytical methods to understand device degradation and solar cell lifetime.     

Measurement of the peroxidation of Brji-35 in aqueous solution by hemin and horseradish peroxidase catalyzed fluorogenic reaction

The non-ionic surfactant Brij-35 can easily be oxidized in solution by dissolved oxygen upon light radiation during its storage. Various factors, such as light radiation, temperature, pH, ionic strength as well as dissolved oxygen influencing the stability of Brij-35 were studied. The results showed that light radiation is the most important factor inducing the oxidation by the dissolved oxygen. The oxidized product was confirmed, indirectly, to be the peroxide of Brij-35 based on a number of evidences. The extent of the oxidation can be traced by a peroxidase or hemin catalyzed fluorogenic reaction with p-hydroxyphenylacetic acid as a substrate. The concentration of the peroxide in a Brij-35 solution (0.8%, w/v) stored at room temperature for a month is in the range of 9 × 10^–5 mol/L.     

Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

Water-Catalyzed Oxidation of Few-Layer Black Phosphorous in a Dark Environment

Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.     

Water‐Catalyzed Oxidation of Few‐Layer Black Phosphorous in a Dark Environment

Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness‐dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light‐induced oxidation. Herein, we report a new degradation channel via water‐catalyzed oxidation of BP in the dark. When oxygen co‐adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus‐based devices.     

Stability of urokinase in solutions containing sodium bisulfite

The stabilities of urokinase (UK) in aqueous solution were investigated at pH 5.0-8.0 in the presence (1.0-3.0 x 10(-3) M) and absence of sodium bisulfite (SBS) both under scattered light (1000 lux) and in the dark using the fluorogenic substrate method. Increasing concentrations of SBS tended to increase the inactivation of UK. In the presence of SBS, with the increase in the pH value, UK gained in stability in the pH range of 5.0-8.0. The stability of UK in the presence of SBS in the dark was larger than that under scattered light, especially at pH 5.0. Therefore, it was suggested that the difference in the residual activities of UK between under light and in the dark was due to free radicals formed during the autooxidation of bisulfite under scattered light. UK was stabilized by glucose in the presence of SBS both under scattered light and in the dark. One reason for this phenomenon was postulated to be the formation of inactive bisulfite-glucose addition compound. The degradation products of UK during storage in a solution containing SBS were investigated by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. UK was revealed to be split into M.W. 36000 form and M.W. 20000 form by SBS.     

Measurement of the peroxidation of Brji-35 in aqueous solution by hemin and horseradish peroxidase catalyzed fluorogenic reaction

The non-ionic surfactant Brij-35 can easily be oxidized in solution by dissolved oxygen upon light radiation during its storage. Various factors, such as light radiation, temperature, pH, ionic strength as well as dissolved oxygen influencing the stability of Brij-35 were studied. The results showed that light radiation is the most important factor inducing the oxidation by the dissolved oxygen. The oxidized product was confirmed, indirectly, to be the peroxide of Brij-35 based on a number of evidences. The extent of the oxidation can be traced by a peroxidase or hemin catalyzed fluorogenic reaction with p-hydroxyphenylacetic acid as a substrate. The concentration of the peroxide in a Brij-35 solution (0.8%, w/v) stored at room temperature for a month is in the range of 9 × 10^–5 mol/L. Received: 8 February 1999 / Revised: 13 April 1999 / Accepted: 17 April 1999     

Study of the copper effect in iron-gall inks after artificial ageing

Iron-gall inks consist of a mixture of vitriols (sulphates of certain metals), gall nut extracts and arabic gum. The association of the iron(II) sulphate present in vitriols, and the gallic acids present in the gall nut extracts induces, after exposure to oxygen, the formation of dark coloured compounds of ink. In addition to iron, this kind of inks contains other metals, such as copper, zinc, and nickel. Among them, copper could be considered the most important because, owing to its catalytic ability, it can be involved in the processes concerning formation and stability of iron complexes, which are responsible for the ink dark colour. For this purpose, four different iron-gall inks containing increasing amounts of copper sulphate were prepared according to a traditional receipt and applied on paper supports. The ink-stained paper specimens were subjected to an intense analytical program to investigate their chemical and physical modifications after artificial ageing (both temperature/humidity and ultraviolet light ageing). The role of copper in the iron-gall inks was evaluated using optical microscopy, colorimetric measurements, X-ray fluorescence (XRF), X-ray diffraction analysis (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) and Fourier transform infrared spectroscopy (FTIR). For the evaluation of the oxidation state of iron and copper, X-ray absorption spectroscopy (XANES) was used. All results indicate that the presence of copper in iron-gall ink causes colour variation, affects the migratory behaviour of iron in the paper, increases the formation of secondary products particularly when ageing process based on temperature/humidity variations is considered.     

Dosimetry characterization of tetrazolium violet-polyvinylalcohol films

The dosimetry characteristics of the polyvinylalcohol-based tetrazolium violet film has been studied in order to check its suitability for routine dosimetry in radiation processing. Our investigations reveal that this dosimeter film can be used for process control in radiation sterilization, but its application range depends on the concentration of the dye and the solvents used. The effects of irradiation temperature and humidity, dye concentration, pH of the solvent as well as the stability of the response of the films before and after irradiation were investigated and determined.     

自然水体生物膜体系中过氧化氢浓度的影响因素

以过氧化氢(H₂O₂)为自然水体生物膜产生的活性氧(ROS)的代表, 通过模拟实验, 研究了水-自然水体生物膜体系中光/暗变化、 生物膜的避光预处理与数量、 有机配体和pH值对体系中H₂O₂浓度的影响. 结果表明, 光照可快速增加体系中H₂O₂浓度, 光照转为无光时体系H₂O₂浓度下降(约为光照时的2/3); 避光预处理会显著降低体系中H₂O₂的产生速率和浓度; 生物膜数量的增减会导致体系H₂O₂浓度的相应增减; 有机配体的存在会使体系内H₂O₂浓度下降(约1/2~1/3); pH=7和5的体系中H₂O₂的浓度高于pH=9的体系(高出约1.5倍). 上述各因素主要通过影响生物膜生产H₂O₂、 H₂O₂自然分解和生物膜去除H₂O₂ 3种作用来影响体系H₂O₂浓度.     

活性炭负载纳米TiO_2光催化降解甲醛废水研究

甲醛对人和温血动物的毒性很强,如果人类长期饮用被甲醛污染的水源,会引发头昏、贫血以及各种神经系统疾病.为此,研究学者对甲醛废水的处理进行了很多的试验研究.目前处理甲醛废水的主要方法有:芬顿法、光催化氧化法、湿式氧化处理等高级氧化技术,二氧化氯法,蒸汽吹脱法,氧化吸附法,SBR工艺等.     

Degradation of Plasticized PVB During Reprocessing by Kneading

Possibility and conditions for optimal re-processing of plasticized polyvinylbutyral (PVB) were tested. The aim of this work was to investigate degradation of PVB sheet at various kneading conditions and to estimate the influence of temperature, air oxygen and mechanical stress on the progress of degradation process. In order to confirm the influence of humidity on the PVB properties during reprocessing, the sheets with the humidity content of 0.5 and 8.0% were tested. The PVB degradation was determined from the changes of melt flow index, mechanical properties in terms of stress and elongation at break, yellowness and molecular weight distribution. The optimal recycling conditions for PVB were estimated from the evaluation of all measured properties and their changes.     

Self-Assembled pH-Responsive Metal-Organic Frameworks for Enhancing the Encapsulation and Anti-Oxidation and Melanogenesis Inhibition Activities of Glabridin

Metal organic frameworks (MOFs) are formed by self-assembly of metal ions and organic ligands. A special type of MOF called ZIF-8, which is formed by self-assembly of zinc ions and 2-methylimidazole, shows excellent stability in aqueous solutions and disintegrates under acidic conditions. These properties make ZIF-8 a suitable carrier material for pH-stimulated drug delivery systems. Glabridin is an isoflavane compound that is widely present in the roots of licorice. Because of its outstanding skin whitening properties, glabridin is widely used as a whitener in the cosmetics industry. In this study, ZIF-8 was employed to encapsulate glabridin. Glabridin-loaded ZIF-8 was successfully prepared with a drug encapsulation efficiency of 98.67%. The prepared sample showed a fusiform or cruciate flower-like structure, and its size was about 3 μm. ZIF-8 enabled pH-controlled release of glabridin. Moreover, ZIF-8 encapsulation significantly enhanced the intracellular anti-oxidant activity and melanogenesis inhibitory activity of glabridin. This study provides a new approach that shows great potential to improve the biological application of glabridin.     

以光诱导Fenton反应控制M-PEIs纳米凝胶的粒径

基因治疗,就是将正常基因导入体内以弥补缺失或替换突变基因来医治囊性纤维化和血友病等[1]多种疾病.而制备高效安全的基因转染载体至今仍是基因治疗的一个瓶颈.非病毒类载体的基因转染效率目前虽不高,但由于其具有低毒、低免疫反应、无基因插入片断大小限制、制备方便、易保存