Sorghum fermentation followed by spectroscopic techniques

The effect of lactic bacteria fermentation on sorghum was followed by spectroscopic techniques (¹H NMR and FT-IR) and chemical analysis.

Wet-cooked sorghum flour was inoculated with lactic bacteria (Lactobacillus fermentum, Lactobacillus bulgaricus, Lactobacillus lactis, Pediococcus pentosaceus and Pediococcus cerevisiae) and a mixture of Lactobacillus bulgaricus and Streptococcus thermophilus from a commercial natural yogurt. Only L. fermentum and the commercial yogurt inoculum were able to grow in sorghum.

The induced lactic bacteria fermentations were compared with a spontaneous traditional fermentation carried out with flour used for fermentation purposes.

In all fermentations, a decrease in pH was noticed and consequently an increase in titratable acidity was detected. Also observed were an increase in free amino acids and total protein content. Reducing sugars, soluble protein and starch decreased during the fermentation processes. These chemical results were confirmed by ¹H NMR and FT-IR.

This study showed that spectroscopic methods are suitable and less time-consuming than chemical methods for following fermentation processes, giving the same relevant information and allowing large screening experiments.     

近红外光谱法预测烟草中硫含量的研究

为适应快速分析烟草中硫含量的需要,以硫酸钡比浊法的测定值为标准值,建立了近红外光谱法预测烟草中硫含量的方法,考察了光谱预处理方法、谱区范围对硫含量预测值的影响。该方法具有简便、快速、低消耗、低成本、不破坏样品及重现性好等优点,且其预测值与硫酸钡比浊法测定值较为接近,适用于大批量烟叶样品硫含量的快速分析。     

苹果糖度近红外光谱检测的初步试验研究

应用近红外光谱漫反射技术,开展了苹果内部品质无损检测的研究。对试验结果的方差分析表明:苹果不同测量位置对光谱测量的影响不显著,而不同测量距离对光谱影响较显著。运用SPSS10.0统计软件对苹果糖度与光谱曲线波峰处对应的吸光度进行多元线性回归分析,建立最佳单波长、最佳双波长组合、最佳三波长组合和最佳四波长组合的校正方程,相关系数R分别为0.621、0.675、0.797和0.822,标准校正误差(SEC)分别为1.75、1.65、1.34和1.27°Brix,相对校正误差(R SEC)分别为13.73%、12.96%、11.42%和10.81%,试验表明:利用近红外光谱技术无损检测苹果糖度等内部品质是可行性的,也为今后进一步建立水果内部品质预测模型奠定了基础。     

On Performance Characteristics of Three-Lobe Porous Hydrodynamic Journal Bearings

This paper presents an analysis of a three-lobe porous hydrodynamic journal bearing for its static and dynamic performance characteristics. The performance characteristics of the bearing have been computed and presented in graphical form for a wide range of permeability parameter to investigate the effect of porosity on bearing performance. The stability margin of the three-lobe journal bearing system, in terms of crtical mass of journal, has been established using Routh's criteria. The nature of transient motion of the journal has been analyzed using the complex eigen values of characteristic equation and motion trajectories obtained by numerical integration of equations of motion.     

Tribological Performance of EP Lubricants with Phosphorus-Based Additives

Lubricants containing additives that protect mechanical components against extreme pressure by reducing friction and wear are known as extreme pressure (EP) lubricants. In the current study, phosphorus-based EP lubricants with different additives (amine phosphate and phosphate ester) were tested in a steel ball-on-disc assembly under different EP conditions. The phosphate ester–steel interaction resulted in significantly higher wear and marginally lower friction than the amine phosphate–steel interaction. The tribological performance (especially wear) depended on the contact conditions. The tribofilm that formed on the steel surface with both EP lubricants consisted of organic compounds, oxides, and phosphates. The greater formation of the wear-resistant iron phosphate for the amine phosphate–steel interaction resulted in lower wear. The friction and wear performance for both EP lubricants depended upon surface roughness parameters along with the compounds that formed in the tribofilm.     

STUDY ON NEAR DRY CUTTING OF ALUMINUM ALLOYS

Series of orthogonal cutting tests of aluminum alloys with different amount of silicon content have been carried out to investigate the chip formation process and adhesion of the work material to the rake face of the cutting tool under near dry cutting conditions. No adhesion is observed when cut with the sintered diamond tool regardless of the amount of the silicon content. On the other hand, the amount of adhesion increases with an increase in the silicon content in the aluminum alloys when cut with the cemented carbide and DLC-coated tools. No adhesion is formed when the nominal coefficient of friction on the rake face is 0.3 or less, and adhesion is formed when the nominal coefficient of friction is 0.4 or more. The amount of adhesion decreases with an increase in the rake angle when cut with the cemented carbide tools and the DLC-coated tool.     

Structure and properties of plasma sprayed BaTiO3 coatings: Spray parameters versus structure and photocatalytic activity

Plasma spraying enables the creation of layers with thickness in a millimeter range adhering on various substrates. This paper provides a study of phase composition, optical properties and photocatalytic activity of BaTiO₃ coatings prepared by atmospheric plasma spraying. The spraying was carried out by a direct current gas-stabilized plasma gun. BaTiO₃ was fed into the plasma jet as a feedstock powder prepared by a reactive sintering of micrometer-sized powders of BaCO₃ and TiO₂. Microstructure and phase composition are reported and discussed in connection with optical properties and photocatalytic activity. The spraying was carried out by a direct current gas-stabilized plasma gun which normally utilizes spray distance (SD) in frames from 100 to 150 mm. Besides conventional SD 100 mm also extremely high SD 190 mm was used. The color of the sprayed coating is different for each SD and also differs from sintered BaTiO₃. X-ray diffraction and also SAD mode of HR-TEM show certain content of amorphous fraction in the coating. The hydrogen content in the coating was found to be higher in the coatings than in the sintered bulk. The diffuse reflectance was measured by UV–VIS spectrophotometry and corresponding band-gap energy was estimated. X-ray photoelectron spectroscopy confirms specific stoichiometric and structural disorder observed also at bang-gap evaluation and by Raman spectroscopy. HR-TEM images for crystalline and amorphous zones are given. Photocatalytic decomposition of acetone was tested and BaTiO₃ coatings compared with a sintered bulk.     

Plasma amination of ultrananocrystalline diamond/amorphous carbon composite films for the attachment of biomolecules

Ultrananocrystalline diamond/amorphous carbon nanocomposite films (UNCD/a-C) have been deposited by microwave plasma chemical vapour deposition at 600 °C from 17% CH₄/N₂ mixtures. The as-grown films turned out to be hydrogen terminated and very stable. Photochemical amination of H-terminated diamond is a well-established route to attach functional groups to such surfaces for applications in biosensors. Here we report on experiments to aminate UNCD surfaces directly by exposure to ammonia plasmas. Thereafter the surfaces were reacted with the heterobifunctional crosslinker molecule SSMCC bearing a N-hydroxysuccinimide (NHS) ester group which should react with the surface NH₂ groups. By means of X-ray photoelectron spectroscopy (XPS), contact angle measurements and fluorescence microscopy it is shown that both steps, plasma amination and SSMCC attachment lead to the desired aims. On the other hand, experiments to attach a thiol-bearing fluorescein molecule directly to H-terminated UNCD films turned out to be partially successful although according to literature such a reaction should be very unlikely.     

近熔点挤出HDPE片材结晶结构的研究

通过挤出工艺制备了高密度聚乙烯(HDPE)片材,并用二维广角X射线衍射(2D-WAXD)、二维小角X射线散射(2D-SAXS)和差示扫描量热法(DSC)研究了挤出温度和螺杆转速对HDPE挤出片材微观结构的影响。结果表明:在近熔点条件下,HDPE中残存的局部有序结构在微弱的剪切作用下并没有促使片材取向,但是结晶度、长周期和片晶厚度均有所增加。这主要是因为残存的局部有序结构不仅能够加快熔体的结晶动力学进程,还能使结晶起始时间提前,从而使HDPE熔体有更长的时间进一步结晶,进而得到了更完善的晶体。另外,在相同挤出温度下,结晶度、长周期和片晶厚度均随螺杆转速的增加而减小,这归因于熔体在料筒中的剪切时间变短。     

Laser induced fluorescence spectroscopy of aromatic species produced in atmospheric sooting flames using UV and visible excitation wavelengths

In this work, laser induced fluorescence (LIF) has been applied to probe PAHs in two atmospheric sooting flames: a premixed flat flame of methane and a Diesel turbulent spray one. Different laser excitation wavelengths have been used. UV excitations at 266 and 355 nm have been operated from the fourth and the third harmonic frequencies of an Nd: YAG laser while visible excitations were emitted by an OPO pumped by the third harmonic of the YAG laser.