微小有限空间内微气泡控制生长的界面追踪与数值模拟

通过对微机电系统微流体器件中气泡生长实验结果的分析,考虑加热元表面液体微层的作用,将微气泡生长分为晶核形成、球形气泡、受侧壁挤压的气泡、沿微通道生长的气泡4个阶段,建立了矩形微通道内微气泡控制生长物理模型;采用Level Set Method模拟了矩形微通道内微气泡控制生长过程,获得了微气泡生长特性。数值模拟结果表明：微气泡初期生长速率较快,后期由于凝结率增大使生长速率减缓;液体温度、微通道宽度、微加热元宽度、加热电压等均对气泡生长始点和生长速率有显著影响。     

微分散法连续制备微气泡的研究进展

微气泡的尺寸介于1~1000 μm之间。相比于传统大气泡,微气泡具有体积小、比表面积大、上浮速度慢和传质效率高等优点,被广泛应用于石油、化工、食品、化妆品、医学和废水处理等领域。相比于传统的微气泡制备方法,气液微分散法制备微气泡生产效率高、可控性好、灵活性高和易于放大,受到了学者们的广泛关注。鉴于微气泡的广泛应用,快速准确的对气泡的大小和尺寸分布的表征也至关重要。本工作对常用的微气泡尺寸表征方法进行了归纳总结,比较了不同的微气泡制备方法的优缺点,并重点阐述了微通道法和膜分散法制备微气泡的研究现状。在此基础上对微分散法制备微气泡的未来研究方向进行展望。     

微纳米气泡技术在渔业水产行业的研究进展及应用综述

微纳米气泡技术是当前国内外的前沿科技,也是研究的热点。该文详细介绍了微纳米气泡在悬浮物的吸附去除、有机物的强化分解及促进生物活性等方面的最新研究进展与应用现状。综述了微纳米气泡发生装置的各种原理和结构,并对其应用进展进行了分析和探讨,特别介绍了在渔业水产相关领域的研究应用情况。指出了微纳米气泡技术目前面临的主要问题及对渔业研究领域的启示,以期为微纳米气泡在水产养殖、捕捞、加工等领域的理论研究和技术应用提供参考。     

表面改性剂对溶气气浮微气泡特性影响研究

研究了十六烷基三甲基溴化铵(CTAB)、壳聚糖、聚二甲基二烯丙基氯化铵(PDADMAC)3种表面改性剂对溶气气浮微气泡特性的影响。结果表明:微气泡平均直径减小主要得益于小尺寸微气泡数量的大幅增加。CTAB投加浓度能显著影响微气泡的直径及并聚概率,对微气泡上升速度有略微影响。投加阳离子聚合物可使微气泡间的并聚现象增多,对微气泡直径及上升速度影响微弱。3种改性剂在微气泡表面的附着效率以CTAB最大,PDADMAC最小。不同改性剂分子产生的电荷量及其在微气泡表面的吸附效率有较大差异。     

浮法玻璃生产中微气泡控制的实践经验

分析了玻璃生产中微气泡产生的原因,结合多年对微气泡的控制经验,总结出了一些简单易行的工艺措施,有效降低了板面微气泡数量。这些措施可为同行控制微气泡数量、提高玻璃质量提供参考。     

微机电系统中的矩形通道内微气泡控制生长

采用微机电系统（MEMS）硅加工工艺,设计、加工出了6种不同规格的实验用微气泡控制生长MEMS器件;构建了MEMS器件中微气泡控制生长实验系统并完成了实验,讨论了热负荷、微加热元宽度、微通道截面参数、工质流速及物性参数等对微气泡生长的影响。结果表明：同等实验条件下,加热电压幅值越高,微气泡生长速率越快;加热脉冲宽度仅对微气泡形成后的进一步生长有影响;加热条件相同的前提下,微加热元宽度越大,气泡成核所需的时间越短、微气泡生长速率越快;微通道宽度一定且高宽比大于1的条件下,高宽比越小,后期微气泡生长速率越慢;微流体的流速越高,微气泡生长始点越晚、生长速率也越低。相同实验条件下,R113、FC-72、去离子水三者中,R113中微气泡生长始点最靠前、生长速率最快,去离子水中微气泡生长最靠后、生长速率最慢。     

臭氧微纳米气泡技术在水处理中的应用进展

臭氧是水处理领域常用的氧化剂之一,在水处理领域应用广泛。微纳米气泡技术由于其不同于普通气泡的特性,在水处理领域显现出良好的应用前景。文中阐述了微纳米气泡特性及优势,总结了臭氧在水处理应用中存在的主要问题,并综述了臭氧微纳米气泡技术在水处理中的应用现状和前景。     

微纳米气泡及其在环境工程领域的应用

微纳米气泡因其区别于传统气泡的突出特性,近年来被广泛应用到环境工程领域,并表现出显著的技术优势与广阔的应用前景.文章简要介绍了微米气泡和纳米气泡的特性、制备方法、表征手段及其在环境工程领域的应用现状,并针对性地指出了当前各方面存在的问题,给出了解决对策和方向.最后,对微纳米气泡及其在环境工程领域应用的发展方向和应用前景...     

气浮工艺中微纳米气泡应用特性与检测技术研究

总结了不同文献中气泡尺寸的定义,根据其特性进行分类。概述了气浮工艺中微纳米气泡的应用特性,介绍了微气泡粒径分布和表面电荷对气浮工艺的影响。围绕微纳米气泡的尺寸分布、上升速度、气含率、Zeta电位等特性参数,总结了微纳米气泡的各种表征检测技术,同时概述了微纳米气泡在气浮技术中的应用现状及前景,并对其发展应用进行展望。     

声场驱动气泡增强微流体混合的数值模拟

微流体研究中，由于雷诺数较低，流体呈层流流动，流体混合主要依靠分子扩散，混合时间长，效率低，故流体混合成为亟待解决的问题。声场激振气泡可以有效促进流体混合，已经引起了广泛关注。本文模拟研究了声场作用下气泡振动对流体混合的影响，探索了微尺度流体在声场激振下的流动特性，分析了微通道高度、入口速度、气泡间距及布置方式对流体混合的影响。结果发现，微通道高度较低时，气泡振动可以更好地促进流体混合；入口速度较小时，流体在气泡附近滞留时间较长，混合较为均匀；气泡半径较大时，旋涡扰动增强，混合效率提高；两个气泡的混合效果优于单个气泡，而气泡间距对混合效率基本无影响；微通道高度较低时，气泡同侧布置和异侧布置对流体的混合效果相接近，随着微通道高度的升高，两种布置方式对混合效果的差异逐渐显现，异侧布置具有更好的混合效果。     

Practical nuclear magnetic resonance analysis of liquid oil in oilseeds: I factors affecting peak width

If proton nuclear magnetic resonance (NMR) spectra of single seeds can be improved, a rapid, low-cost method of screening seeds for oil composition could be developed for use as a selection tool in plant breeding. NMR spectroscopy was performed on single seeds of borage, flax, and canola to evaluate methods for improving spectra quality (narrowing peak widths and increasing signal-to-noise ratio) to a degree necessary to measure differences among seeds in a breeding program. Immersion of seeds in a variety of solvents, including deuterated chloroform, deuterated acetone, deuterated dimethyl sulfoxide (DMSO) and completely fluorinated hydrocarbons (FC-77), narrowed peaks obtained from seeds when compared with spectra from seeds analyzed in the absence of a solvent. Deuterated chloroform and FC-77 were free of interfering solvent proton peaks while deuterated acetone and deuterated DMSO contributed interfering peaks. The spectra of dehulled seeds had narrower peak widths than did seeds with hulls. Treatments that decreased seed oil viscosity failed to substantially narrow spectra peak widths of seeds. High magnetic field strength did not improve the spectral quality of seeds, as peak widths increased with field strength. Conversely, low field strength limited resolution of oil spectra. Although the 300 MHz spectrum of vegetable oil had greater resolution (narrower peaks) than the 60 MHz spectrum, spectra of seeds produced at 60 MHz had superior resolution to 300 MHz spectra.     

Lipid changes during pre-germination and germination ofstriga asiatica seeds

Witchweed (Striga asiatica L. Kuntze) seeds were incubated at 28 C in a moist environment for a 14-day period, after which seeds germinated only when exposed to specific natural or synthetic germination stimulants. Changes in lipid composition were determined during germination of witchweed seeds and during early seedling growth. Witchweed seeds contained 37.5% (w/w) oil. Increased levels of monogalactosyl-diacylglycerol and phosphatidylglycerol suggested the enlargement or multiplication of plastids after witchweed seeds had germinated. In contrast to the usual course of events in seeds with high oil reserves, witchweed seeds did not hydrolyze triacylglycerol rapidly during or after germination. These findings indicated that triacylglycerol in germinating witchweed seeds was conserved for subsequent use during haustorial formation and host invasion.     

The seeds effect on zeolite NU-87: synthesis parameters and structural properties

EU-1 and NU-87 zeolites, which possess certain similarity in structure, were used as seeds for synthesizing zeolite NU-87. The usage of seeds greatly enhanced the crystallization rate and widened the composition range of initial gel. As compared with the hetero-structural seeds, the homo-structural seeds were more favorable for the synthesis of zeolite NU-87, also resulted in extremely decreased template agent and greatly shortened crystallization time. However, hetero-structural seeds EU-1 resulted in the much smaller particle size of the as-synthesized zeolite NU-87, due to the distinct properties of seeds.     

Effects of seed damage on the oxidative stability of poppy seed oil

This study was conducted to assess the reduction of life time and quality of poppy seeds considering a mechanical damage, which may occur during harvesting. Vienna, Vienna, Austria Poppy seeds were crushed to receive 90%, 80%, 70%, 60% and 50% intact seeds, the undamaged 100% intact seeds served as controls. The samples were stored at 40 °C for 175 d and oxidation experiments performed periodically by assessing conjugated dienes, p‐anisidine reactive products, the iodine value, the acid value and γ‐tocopherol content. With increasing degree of mechanical damage the shelf life declined, the oxidation products were formed more rapidly and the main antioxidant in poppy seeds γ‐tocopherol was consumed. Considering the reduction of life time by including all quality parameters the shelf life of the 10% damaged seeds was reduced by 50.5%. This reduction was reached up to 82% for the 50% damaged seeds compared to the control. A high correlation was found between the increase in oxidation products and the degradation of γ‐tocopherol. This study show that increased damage during harvesting (10‐50%) is responsible for a faster loss of product quality especially in seeds containing high amounts of polyunsaturated fatty acids like poppy seeds.     

Effect of sprouting on the quality and composition of canola seed and oil

Sprouting has been considered as a damage factor in grading canola. This project deals with the evaluation of the effect of sprouting on the quality and composition of canola seed and oil. Sprouted seeds had lower oil content than nonsprouted seeds as determined by exhaustive petroleum ether extraction. The difference, although statistically significant, was small, less than 0.1% oil at the maximum level of sprouting allowed in topgrade canola. There were no differences in chlorophyll contents or moisture contents between sound and sprouted seeds. Sprouted seeds had significantly higher levels of FFA and crude protein than sound seeds. Oxidation parameters (diene and aldehyde) were higher in oils from sound seeds than oils from sprouted seeds, but there was no statistically significant difference in PV. Sprouted seeds had higher levels of tocopherols and sucrose, but lower levels of raffinose, stachyose, and total sugars than sound seeds. There was no difference in overall FA composition of the oil between sound and sprouted seeds. The second extraction of the Federation of Oils Seeds and Fat Associations (FOSFA) extraction method, which allowed the extraction of more polar lipids, contained significantly more saturated FA. However, this was not significant in the overall FA composition of the oils because this fraction counted for about 2% of the total lipid content. The presence of sprouted seed had an effect on results for oil and crude protein determined by NIR as compared with results by FOSFA extraction, or pulsed NMR for oil and Dumas combustion for crude protein. Addition of sprouted seed samples to the NIR, calibration set overcame this problem. These results suggested that sprouting did not have a highly damaging effect on the quality and composition of canola seed and oil when less than 10% of the seeds in a sample were sprouting.     

烟草种子的快速干燥试验

为解决多雨季节采收的烟草种子容易发霉而导致种子活力降低的问题，采用不同比例的生石灰作干燥剂处理不同成熟度、不同装袋的带壳和脱粒的烟草种子，并定期检测种子含水量和活力。试验结果表明，用干燥剂处理新收蒴果能提高种子活力，对种子不会造成伤害。     

Drying of seeds through oscillating infrared heating

Oscillating infrared (IR) drying of onion, white mustard, sweet pepper, and wheat seeds as well as the effect of this drying method on the seeds’ stimulation have been studied. It was found that oscillating IR drying was highly advantageous for onion seeds which possess the lowest germination degree and germination energy. The influence of initial moisture content of the onion seeds, the duration of the oscillating IR drying, and the processing temperature on the stimulation effect have been established. The most favorable stimulation temperature was determined. It was shown that this stimulation effect holds unchanged for at least eight months. A mathematical model for drying kinetics based on the solution of the mass conductivity equation was proposed and the method of the process engineering calculation has been developed and validated for onion and mustard seeds. The necessary experimental data on mass conductivity and concentration equilibrium for onions and mustard seeds have been obtained.     

The sterol composition of freshly harvested compared to stored seeds of rape,sunflower and poppy

The composition of the free sterols and the sterol esters of freshly harvested seeds of rape, sunflower and poppy was compared to that of stored seeds. The sterol composition of rapeseed was not changed during storage, whereas in sunflower seed the free sterols had less of Δ5-avenasterol and Δ7-stigmastenol in ten-month-old seeds compared to fresh seeds. The greatest relative changes were observed for esterified sterols in poppy seed, with a drop in the percentage of Δ5-avenasterol from 25.3% in freshly harvested to 16.9% in seeds stored for 10 months.     

<Emphasis Type="Italic">Arabidopsis thaliana:</Emphasis> A New Test Species for Phytotoxic Bioassays

Lettuce seeds (Lactuca sativa L.) and other crop species are often used in phytotoxic bioassays that are designed to detect allelochemicals. The seeds of these species are considered ideal because they are readily available, germinate rapidly and uniformly, and are routinely used in laboratories around the world. Despite their common use, however, the seeds of these species are often not as sensitive or responsive to some phytotoxic chemicals as are the seeds of other species. While searching for a more sensitive test species for phytotoxic bioassays, the Columbia ecotype of Arabidopsis thaliana exhibited greater sensitivity to seven potent allelochemicals than did lettuce seeds, which, in some cases, did not respond at all to those substances. Sensitivity satisfies one of the criteria for selecting a test species for bioassays. We now report on the results of our study and offer additional reasons for using A. thaliana seeds.     

Distribution of aflatoxin-containing cottonseed within intact locks

Location of aflatoxin-containing seeds within locks ofAspergillus flavus contaminated bolls was determined. Of the 141 seeds examined from 22 intact locks, 78 exhibited bright greenish yellow fluorescence (BGYF) on the linters. Twenty-four seeds contained aflatoxins ranging from 0.231 to 151.3 μg of toxin per gram of seed. Twenty-one of these aflatoxin-positive seeds had linters exhibiting BGYF, and three had nonfluorescent linters. With one exception, aflatoxin contamination was concentrated in only one or two highly contaminated seeds in the apex half of tight locks, and the rest of the three to five seeds were negative. Explanations for this type of infection are discussed.