Extraction and characterization of cellulose single fiber from native Ethiopian Serte (Dracaena steudneri Egler) plant leaf

Biomaterials are renewable sources which are widely distributed, locally accessible, high possibility of recycling and biodegradation behavior. This investigation deals with the extraction and characterizing of new fiber obtained from Serte plant leaf that is found in Ethiopia. The physical, chemical and mechanical characters of the fiber had been tested and comparison with other plant fibers was done for the first time. Optimization of fiber extraction process has been done by varying the extraction variables like NaOH concentration, temperature and extraction time. Fibers possessing 56% cellulose content along with significant amount of hemicellulose, lignin and ash with tensile strength of 330?MPa were obtained. FTIR as well as X-ray diffraction analysis were also done to further analyze the fiber. This new plant leaf fiber can be another alternative resource in place of synthetic fibers depending on their application such as reinforcing polymer matrices.     

一种简便的原位测定红树叶片表面菲的荧光分析方法

采用自行设计的多用途荧光比色皿,建立了一种秋茄(Kandelia obovata,Ko),桐花树(Aegiceras comiculatum,Ac)和白骨壤(Avicennia marina,Am)叶片表面菲(Phenanthrene,Phen)简便的原位测定方法,本方法测定Ko,Ac和Am表面Phen的线性范围分别为6.5 ～ 1200 ng/spot,18.5～600 ng/spot和3.2～700 ng/spot,检出限分别为0.6,0.7和1.3 ng/spot,加标回收率分别为92.4％～101.0％、94.8％～108.2％和93.8％～103.6％,相对标准偏差小于6.5％.本方法的检出限和相对标准偏差均优于固体表面光纤荧光法(Solid surface optical fiber fluorimetry,SSF),线性范围与SSF法处于同一数量级.本方法与SSF法测得的红树叶片表面Phen的浓度并无显著差异(p＞0.05),但本方法极大地简化了操作,提高了重现性.     

Green synthesis of TiO2 nanoparticles as an efficient heterogeneous catalyst with high reusability for synthesis of 1,2‐dihydroquinoline derivatives

Nano materials find wide applications due to their behavior at nano scale. TiO₂ nanoparticles (TiO₂ NPs) was synthesized using Neem leaf extract. This is simple, rapid, eco‐friendly, cheaper and green tools for TiO₂ NPs synthesis using agricultural waste at lower applied temperature. Characterization of the extracted TiO₂ NPs was confirmed by XRD, SEM, EDAX, TEM, HR‐TEM, SAED, and FT‐IR, respectively. The catalytic activity of TiO₂ NPs was investigated in synthesis of 1,2‐dihydroquinoline derivatives with excellent yields and low cost. Purification of the synthesized 1,2‐dihydroquinoline derivatives carried out by easy work‐up of non‐chromatographic methods.     

Degradation kinetic (D100) of lycopene during the thermal treatment of concentrated tomato paste

Heat treatments can cause degradation in tomatoes of lycopene which has important antioxidant effects. No information about decimal reduction time (D₁₀₀) of lycopene is available. D-value is the time required at a given temperature to reduce 90% of the molecule. This study for the first time determine the kinetic of lycopene thermal degradation. The content was measured at regular intervals of pasteurization using canned tomato paste to determinate D value. Microbiological analysis was carried out to verify product stability after packaging. Yeasts, molds and lactic acid bacteria were determined. The pasteurization time allowed to observe a loss of the red color. Lycopene content, after an increase at 8 min, decreased at 32 min of pasteurization. D₁₀₀ value was calculated at 75 min; a diminution of 90% in lycopene content in the concentrated tomato paste was observed. Microbiological analysis confirmed the stability of products after 8 min of pasteurization.     

变截面钢板弹簧刚度计算的传递矩阵法

钢板弹簧悬架是商用汽车的关键部件,对整车的平顺性以及操纵稳定性有着重要影响,采用变截面少片簧代替多片簧是整车轻量化的重要趋势。由于变截面钢板弹簧成型的复杂性,传统的设计计算方法存在较大误差。在精确分析梯形梁单元变形特性的基础上,提出了一种新的变截面板簧刚度计算的传递矩阵法。对于广泛应用的各种变截面板簧,一般只需十来个单元即可得到非常逼近于有限元精确分析的结果。最后,通过不同类型板簧和不同方法的对比计算验证了该方法的有效性。     

Influence of postharvest ultrasounds treatments on tomato (Solanum lycopersicum,cv. Zinac) quality and microbial load during storage

Whole tomato fruits were treated at ultrasonic power levels from 10% to 100%, and at a constant frequency of 45 kHz, for different times (1–19 min). A central composite rotatable design (CCRD) was applied to optimise ultrasonic treatments for tomato quality (colour, texture and total phenolic content (TPC)) maintenance. According to response surface analysis, the optimal treatment parameters were 55%_10 min, 80%_15 min and 100%_19 min. At these conditions, and especially at higher power levels, a maximum retention of colour and texture, as well as an increase of TPC and microbial reduction were obtained in comparison with untreated fruits during 15 storage days at 10 °C. The ultrasounds treatment was found to be effective in delaying colour development and texture losses, preserving sensorial quality of whole tomato, with increase of TPC and microbial load reduction. Moreover, this postharvest treatment can be used as an alternative for extending fresh fruits shelf-life.     

Facile synthesis of tomato-based carbon nanodots and its utilization in sensitive detection of tartrazine

Carbon nanodots (CDs) with superior fluorescence performance were obtained by hydrothermal method using tomatoes as raw materials. When the ultraviolet absorption band of tartrazine and the fluorescence spectrum of CDs have complementary overlaps, the fluorescent internal filter effect (IFE) occurred. Furthermore, the degree of quenching of fluorescence intensity of CDs has an excellent linear correlation with tartrazine concentration. And based on this principle, a method for detecting tartrazine was established. As the decrease of fluorescence intensity, tartrazine can be measured in the linear range of 0.1 μM–40 μM. The detection limit is 39 nM, and the recovery rate is 90.7%～114.5%. The established protocol was also effectively employed to assay tartrazine in beverage samples, indicating that it has great potential for food color analysis.     

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005 μg g⁻¹ for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050 μg g⁻¹ fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400 g a.i h⁻¹ recorded initial deposits of 5.20 and 10.05 μg g⁻¹ and 0.33 and 0.48 μg g⁻¹ for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34 days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.     

A STRUCTURALLY BASED ANALYTIC MODEL OF GROWTH AND BIOMASS DYNAMICS IN SINGLE SPECIES STANDS OF CONIFERS

A theoretically based analytic model of plant growth in single species conifer communities based on the species fully occupying a site and fully using the site resources is introduced. Model derivations result in a single equation simultaneously describes changes over both, different site conditions (or resources available), and over time for each variable for each species. Leaf area or biomass, or a related plant community measurement, such as site class, can be used as an indicator of available site resources. Relationships over time (years) are determined by the interaction between a stable foliage biomass in balance with site resources, and by the increase in the total heterotrophic biomass of the stand with increasing tree size. This structurally based, analytic model describes the relationships between plant growth and each species’ functional depth for foliage, its mature crown size, and stand dynamics, including the self‐thinning. Stand table data for seven conifer species are used for verification of the model. Results closely duplicate those data for each variable and species. Assumptions used provide a basis for interpreting variations within and between the species. Better understanding of the relationships between the MacArthur consumer resource model, the Chapman–Richards growth functions, the metabolic theory of ecology, and stand development resulted.