可完全生物降解材料的应用进展

介绍了可生物降解材料的降解机理和特点,综述了化学合成型、天然高分子型和微生物合成型可完全生物降解材料的研究现状及其在各个领域的最新应用进展。     

多环芳烃蒽在两种贝类中的检测及生物降解研究

目的 比较月亮贝(Neolamprologuscalliurus)和竹蛏(Solenstrictu)对多环芳烃蒽的富集作用,筛选获得高效蒽降解菌株。方法 采用气相色谱-质谱法(gas chromatohraphy-mass spectromety, GC-MS)检测两种贝类中蒽的含量,采用高效液相色谱法(high performance liquid chromatography, HPLC)比较6种菌株和上述菌株等体积混合得到的菌群对蒽的降解率,并对高效菌株或菌群的降解条件进行优化。结果 两种贝类均能够对蒽进行富集,在0.5和5μg/L蒽处理条件下,月亮贝对蒽的富集比竹蛏高2.75和3.34倍。6种菌株对蒽的降解率可达92.11%～95.90%,而混合菌群对蒽的降解率最高可达97.17%。菌群生物降解蒽的最佳条件为pH 6、温度27℃、降解时间15 d。另外,添加30 mg/L Mg²⁺促进了混合菌群对蒽的降解。结论 月亮贝对蒽的富集高于竹蛏,混合菌群对蒽的降解率最高,添加Mg²⁺可以促进蒽的生物降解。     

GaAIAs/GaAs正面发光管的失效机理研究

研究和分析了高辐射GaAlAs/GaAs LED的退化机理。经高温加速老化,估算器件的工作寿命为10~5小时,并估算该器件的激活能为0.58eV。     

Enhanced photocatalytic degradation of organic contaminants over CaFe_2O_4 under visible LED light irradiation mediated by peroxymonosulfate

A simple sol-gel approach is proposed herein to fabricate CaFe₂O₄for the degradation of various organic pollutants(rhodamine B(RhB),tetracycline hydrochloride,humic acid,and methylene orange)under LED light irradiation mediated by peroxymonosulfate(PMS).The results indicate that the calcination temperature can significantly influence the performance of CaFe₂O₄for PMS activation,and the CaFe₂O₄sample obtained at 800℃(CaFe₂O₄-800)exhibits the best efficiency in degrading RhB,which is much higher than that of Fe_2o₃-800.This can be attributed to the efficient separation of photogenerated electrons(e^-)and holes(h⁺)by PMS,which is validated by transient photocurrent response and photoluminescence measurements.Results from density functio nal theo ry calculations indicate that the valence band of CaFe₂O₄-800 exhibits a high concentration of carriers and weak localization of electrons,which are favorable for PMS activation.Radical scavenging results confirm that h⁺and O₂^·-are the dominant reactive species.Moreover,CaFe₂O₄-800 not only demonstrated a stable performance during eight cycling runs with negligible iron leaching but also exhibited excellent degradation efficiency under natural water and sunlight.Finally,the mechanism and pathway of RhB degradation by the CaFe₂O₄-800/PMS/LED system are also proposed.This work presents the enormous prospect of CaFe₂O₄as an environmentally benign photocatalyst for PMS activation.     

Degradation of erythromycin in honey and selection of suitable marker residues for food safety analysis

Extra-label use of veterinary medications in apiculture is a practice which is known to result in the presence of drug residues in honey. Erythromycin has been used by some beekeepers in an attempt to control foulbrood diseases in honey bees. It is recognised that erythromycin degrades in acidic aqueous solutions to yield predominantly anhydroerythromycin. Honey is an acidic medium in which erythromycin should also degrade. Three degradation products with a molecular weight of 715 Da (anhydroerythromycin, erythromycin enol ether, and an unidentified but suspected related isomer) have been confirmed to be formed in honey. Erythromycin was found to degrade rapidly in honey at typical hive temperature with a half-life of less than one day. Based on these results, it is recommended that food safety laboratories include degradation products in analytical testing protocols when examining honey for erythromycin residues.     

Shelf life of powdered Campomanesia adamantium pulp in controlled environments

The objective of this study was to evaluate the shelf life of powdered guavira pulp obtained by a foam mat drying process. The dehydrated guavira pulp was packed into low density polyethylene (LDPE) bags and stored under two controlled conditions: environmental (25 °C, RH 75%) and accelerated (35 °C, RH 90%) for 90 days. The shelf life was accompanied by carrying out the following analyses every 10 days: moisture content, water activity, vitamin C content, pH and titratable acidity. Vitamin C was the quality attribute used to determine the shelf life of the product, by determining its degradation kinetics as a function of storage time. The linear regression data showed that the vitamin C degradation reaction fitted the zero and first order kinetic models. The shelf life of the powdered guavira pulp under environmental conditions was approximately 49 days, and under accelerated conditions (35 °C) 45 days. The Q10 was equal to 1.09, predicting a shelf life similar to that found under environmental conditions. The moisture content for these conditions was 10.0% e 5.4% for 35 °C and 25 °C, respectively. The above demonstrate the efficiency of the accelerated test in predicting the shelf life of the product.     

Stability Indicating HPTLC Determination of Linezolid as Bulk Drug and in Pharmaceutical Dosage Form

Abstract

A simple, selective, precise, and stability-indicating high-performance thin layer chromatographic method of analysis of Linezolid both as a bulk drug and in formulations was developed and validated in pharmaceutical dosage form. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of toluene–acetone (5:5, v/v). This system was found to give compact spots for Linezolid (R_f value of 0.29 ± 0.01). Linezolid was subjected to acidic, alkali hydrolysis, oxidation, and photodegradation. The degraded products also were well separated from the pure drug. Densitometric analysis of Linezolid was conducted in the absorbance mode at 254 nm. The linear regression data for the calibration plots showed good linear relationship with r² = 0.997 ± 0.001 in the concentration range of 300–800 ng/spot. The mean value of correlation coefficient, slope, and intercept were 0.998 ± 0.003, 0.15 ± 0.009, and 19.52 ± 1.66 respectively. The method was validated for precision, accuracy, ruggedness, and recovery. The limits of detection and quantification were 20 ng/spot and 50 ng/spot, respectively. The drug undergoes degradation under acidic and basic conditions, oxidation and photo degradation. All the peaks of degraded product were resolved from the standard drug with significantly different R_f values. This indicates that the drug is susceptible to acid–base hydrolysis, oxidation, and photo degradation. Statistical analysis proves that the method is reproducible and selective for the estimation of the said drug. Because the method could effectively separate the drug from its degradation products, it can be used as a stability indicating one.     

Inquire into degradation process of Ni-Co coating in 3.5% NaCl solution by EIS北大核心CSCD

The degradation process of Ni-Co coating on plate of Kovar alloy 4J42 in 3.5%NaCl solution was studied by means of electrochemical impedance spectroscope (EIS). Four distinguished electrical equivalent circuits (EEC) were proposed to simulate the degradation process. At the very beginning of immersion, the coating exhibited excellent corrosion resistance, which could be treated as a barrier layer with a high resistance in parallel with a low capacitance. After a short time of immersion, a double-layer capacitance Cdl and a charge-transfer resistance Rct were introduced, indicating that the electrochemical reactions at the metal/coating interface may take place. In the late stage of immersion, Warburg impedance was adopted to characterize the corrosion products. With the accumulation of the corrosion products, the diffusion process of corrosive medium was affected, and the EEC comprising a diffusion capacitance (Cdiff) and a diffusion resistance (Rdiff) was then introduced to fit the impedance spectra. The evolution of coating resistance and coating capacitance were investigated to illuminate the Ni-Co coating degradation process. The results showed that the degradation process of Ni-Co coating could be described by three stages: the permeation of corrosive medium, the corrosion of metal at the interface of coating/substrate and finally the failure of coating. © 2016, Corrosion Science and Protection Technology. All rights reserved.     

Synthesis and characterization of Ca–Sr–P coating on pure magnesium for biomedical application

There are growing evidences that Sr-containing calcium phosphate biomaterials can promote better osteo-precursor cell attachment and proliferation than pure calcium phosphate biomaterials. In this study, attempts were made to fabricate two kinds of Sr-substituted calcium phosphate (Ca–Sr–P) coatings on pure magnesium in electrolyte solutions with differing amounts of Sr(NO₃)₂ for biomedical application. The surface microstructure, composition and chemistry of the coatings were characterized by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), and X-ray Diffractometer (XRD), respectively. In addition, electrochemical and immersion tests were performed to evaluate the corrosion resistance of the Ca–Sr–P coated magnesium in phosphate buffered saline solution (PBS).     

Thermo-oxidative aging of epoxy coating systems

The thermo-oxidative behavior of unformulated (unfilled) samples of epoxy coatings has been studied at five temperatures ranging from 70 °C to 150 °C. Two epoxy networks based on diglycidyl ether of bisphenol A (DGEBA), respectively, cured by jeffamine (POPA) or polyamidoamine (PAA) were compared. Infrared spectrophotometry (IR), differential scanning (DSC) and sol–gel analysis (SGA) were used to monitor structural changes.