螺旋波等离子体能量耦合的研究进展

螺旋波等离子体源耦合效率高,能够产生高密度、大体积的等离子体。当外加射频源通过天线和等离子体耦合,在放电腔中将存在着多种波模式,而射频功率耦合机制直接影响耦合效率和能量沉积。对近年来在螺旋波等离子体源中存在的朗道阻尼、静电波、径向局域模式和电子俘获耦合机制进行了综述。低磁场下驻波在边界耦合的静电波起着重要作用,而高磁场下螺旋波在径向等离子体梯度形成的势阱中进行体功率耦合。永磁铁阵列螺旋波源在大面积、高速材料处理应用中可能会成为下一步发展的趋势。     

玄武岩纤维的低温等离子体表面改性研究

为了得到玄武岩纤维最适宜的表面性能,调整低温等离子体处理条件如放电功率、放电时间和气压,对玄武岩纤维进行了处理。测试了处理后纤维的表面摩擦性能、芯吸性能、X射线光电子能谱以及扫描电子显微镜。指出:放电功率225 W、放电时间5 min、气压20 Pa时,等离子体处理玄武岩纤维表面性能较好。认为:等离子体处理玄武岩纤维可使纤维表面变粗糙,并保持一定强度。     

用等离子体改性淀粉膜的处理条件分析

利用等离子体对淀粉膜进行表面改性,通过测量改性后丙烯酸接枝率,分析了等离子体放电功率、放电时的气压、放电时间和放电后静置时间对淀粉膜改性效果的影响.结果表明,丙烯酸接枝率在2.0%～7.0%之间;接枝率随等离子体放电功率增加有增加趋势,随真空腔气压升高呈下降趋势,随等离子体处理时间增加呈先增加后逐渐饱和态势,随静置时间延长呈下降趋势,且时间过长会大幅衰减,接枝率趋向于零.     

负电性气体等离子体中流体模型定标律研究

从等离子体流体力学方程出发,求导了负电性气体中等离子体流体模型定律,根据这个定标律,可以从放电电压V_rf、气压P_r、功率P_w,直接得到等离子体中电子密度N_e,负离子密度N_-、正离子密度N_+、电子温度Te及等离子体中各中间产物的密度及其与放电宏观参数的关系。为研究等离子体中粒子输运过程和等离子体与材料相互作用过程提供了一个重要手段。     

常压非热等离子体源及其在纺织整理中的应用

综述了常压介电屏蔽放电（DBD）产生的非热等离子体在纺织整理中的应用。描述了DBD在常压织物整理和等离子体化学中的许多潜在优势。DBD（无声放电）是一种非热等离子体放电,在较宽的温度和压力范围内操作简便。常压下,许多独立的细电流丝之间会发生电击穿,这些短暂的带有电子能量的微放电具有瞬时高压辉光放电性质,非常适合背景气体原子或分子的激发和离解。     

高强涤纶纤维等离子体改性的研究

为了提高涤纶纤维在复合材料中与树脂基体的界面粘结性,使用等离子体技术对高强涤纶纤维进行表面改性。通过设计正交试验,得出等离子体处理高强涤纶的最佳条件为放电功率150W,处理时间300s,放电压强10Pa。采用扫描电子显微镜、傅里叶变换红外光谱、纤维接触角测量仪、电子单纤维强力机和纤维摩擦系数测定仪对改性前后高强涤纶纤维进行性能表征。结果表明:改性后的涤纶纤维,其断裂强力较原样下降了1.78%,静摩擦系数上升了21.9%,纤维接触角下降了27%,且红外光谱图显示经过等离子体物理改性,引入了少量亲水基团,且未对纤维内部的基本分子结构造成破坏。     

MPT-AES法测定大米中铅和镉

用微波等离子体炬(MPT)为激发光源,氩气为等离子体工作气,用气动雾化进样,微波消解大米条件进行了正交试验考察,研究了微波等离子体炬原子发射光谱法(MPT-AES)测定大米中铅和镉。详细考察了Pb和Cd的最佳分析谱线波长、微波前向功率、载气流量、工作气流量等实验参数对测定强度的影响。同时考察了酸浓度和共存离子对铅和镉测定的影响。在最佳条件下测得铅和镉的检出限分别为4.8 ng/m L、5.7 ng/m L,精密度分别为2.35%、1.86%,加标回收率分别为97.2%~102.2%、97.5%~101.7%。     

低温等离子体处理对PBI纤维性能的影响

探讨空气低温等离子体处理对PBI纤维性能的影响。测试了低温等离子体处理前后PBI纤维的断裂强度、表面摩擦因数、芯吸效应、接触角以及微观形态。试验表明:经过空气低温等离子体处理后PBI纤维的吸湿性得到进一步提高,强度和摩擦因数也适度增大,且在放电功率150W、放电气压20Pa和放电时间180s的条件下,纤维处理效果最好。认为:通过低温等离子体处理,PBI纤维在保证其吸湿性的基础上,可以提高其与其他材质复合黏结的牢度。     

纤维的等离子体变性与电子温度的测量

用H放电产生的等离子体对丙纶纤维进行处理,用光谱方法测量了处理时等离子体的电子温度.研究了变性纤维的吸湿性和吸湿性与处理时纤维放置位置的关系.     

大气压下介质阻挡放电产生低温等离子体

利用电力电子和脉冲功率技术相结合研制了一台高频高压电源,用于介质阻挡放电产生低温等离子体。该电源利用电容储能技术,通过控制IGBT的通断对电容进行快速放电,形成高频脉冲,再通过高频变压器升压,实现高频高压输出。实验结果表明,利用该电源所产生的介质阻挡放电,其放电均匀,实验装置所耗功率小,所产生的低温等离子体有着广阔的应用前景。     

Some observations on the histology of cold-shortened muscle

Summary. Changes in the histology of muscles subject to temperatures just above freezing-point while in the pre-rigor condition are described. Observations are based on the study of sectioned tissue by optical and electron microscopy, and by scanning electron microscopy. the presence of 'active' and 'passive' fibres is noted. These are defined by their contractile state. the appearance of the surface membrane of the active fibres is also described and its influence on the texture of cold-shortened muscle as meat is discussed.     

拉伸对光纤侧发光性能的影响

为探明轴向拉伸对光纤侧发光性能的影响,在不同温度下采用不同的伸长率拉伸光纤,利用BM-5A亮度色度计测量拉伸后光纤侧面的亮度,通过扫描电镜( SEM)观察光纤表面形貌,分析拉伸对光纤侧发光亮度的影响.结果表明,轴向拉伸可以提高光纤的侧发光亮度,拉伸伸长率越大,侧发光亮度越高.同时也发现温度对光纤侧发光亮度也有一定的影响...     

Characterization of protein aggregates following a heating and freezing process

This study used complementary multi-scale analytical methods in order to better understand how technological procedures such as freezing and heating affect protein aggregation. The research was conducted on fresh and frozen Longissimus dorsi (LD) which were heated at different temperatures and for various times. Protein aggregates were measured using light scattering, SDS PAGE electrophoresis, and optical and scanning electron microscopy. Heating led to a higher molecular weight of aggregates, while freezing had an additive effect on aggregates, with the actin band decreasing as cooking times increased.     

纺织品常压辉光放电等离子体处理技术

介绍电晕放电、介质阻挡放电产生等离子体的理论和应用；重点阐述大气压下辉光放电（APGD）技术的现状，解释了电子雪崩模型和流注放电理论，并以电压一电流波形图和电压一电荷李萨育图鉴别介质阻挡放电与大气压下辉光放电。通过对这三种放电形式的应用分析，确定了大气压下辉光放电等离子体最适合处理纺织材料，并对其面临的问题及前景作了分析。     

Lifetimes of triplet dissolved natural organic matter (DOM) and the effect of NaBH₄ reduction on singlet oxygen quantum yields: implications for DOM photophysics

The natural lifetimes of triplet dissolved organic matter ((3)DOM) were determined by an O(2) saturation kinetics study of singlet oxygen quantum yields (Φ(1O2)) in buffered D(2)O. At least two distinct (3)DOM pools are present, and the observed lifetime range (～20 to 80 μs) leads to a dependence of Φ(1O2) on O(2) concentrations between 29 and 290 μM. Thus, steady-state (1)O(2) concentrations will depend on [O(2)] in natural waters. The lifetimes are essentially identical for DOM samples of different origins and do not vary with excitation wavelength. However, Φ(1O2) varies greatly between samples and decreases with excitation wavelength. These data strongly suggest that (3)DOM quantum yields decrease with excitation wavelength, which gives rise to the Φ(1O2) variation. Borohydride reduction of several samples in both D(2)O and H(2)O lowers the absorbance and (1)O(2) production rates, but it does not alter Φ(1O2). This is consistent with a model in which (1)O(2) sensitizing chromophores are borohydride reducible groups in DOM, such as aromatic ketones. Interpreted in the framework of a charge transfer (CT) model for DOM optical properties, the collective data suggest a model in which electron acceptor moieties are important (1)O(2) sensitizers and where CT interactions of these moieties disrupt their ability to produce (1)O(2).     

Double emulsion stage prior to complex coacervation process for microencapsulation of sweetener sucralose

Microencapsulation has proven viable for various industrial applications. In the case of sweeteners, microencapsulation can increase the fluidity and resistance to high temperatures and prolong sensation of sweetness. The aim of this study was to microencapsulate sucralose by double emulsion followed by complex coacervation. The microcapsules were evaluated by optical and scanning electron microscopy, hygroscopicity, solubility, moisture, water activity, particle size, encapsulation yield, potential ZETA, fourier transform infrared spectroscopy (FTIR) and thermal behavior. The microcapsules presented low hygroscopicity and solubility, and average size ranging from 81.04 to 113.49 μm. With FTIR, it was possible to observe the amide bond that confirmed the formation of coacervates. Zeta potential showed that two samples presented neutral charge, indicating complete coacervation. The Tg values were above room temperature (53.59 to 56.88 °C). Among the formulation studied, the one produced with 5% gelatin and gum Arabic and core material 75% presented the best characteristics.     

低取代羟乙基纤维素在碱溶剂中的溶解行为及其机制

为改善纤维素在氢氧化钠（NaOH）水溶液中的溶解性能,通过醚化改性制备了低取代羟乙基纤维素（HEC）,并借助光学显微镜、核磁共振仪、差热扫描量热仪和透射电子显微镜等研究了HEC在质量分数为8%的NaOH水溶液中的溶解行为及溶解机制。结果表明：低温下NaOH溶剂和水分子可结合形成尺寸合适、结构稳定的NaOH水合分子,与HEC大分子上的羟基键合形成HEC-NaOH-H2O缔合结构,切断了HEC大分子间氢键,HEC直接溶解;醚化改性后亲水性侧链的引入减弱了分子间作用力,增强了HEC与NaOH水合分子之间的作用强度,增强了缔合结构稳定性,促进了HEC在NaOH溶剂中的良好溶解;沿纤维长度方向HEC最外层膜溶胀成球形并逐渐破裂溶解,最终以长度为微米级、宽度为10~80 nm的微纤维形式分散在溶剂中。     

Induction of a lag phase by chiller temperatures in Escherichia coli growing in broth or on pork

When log phase cultures of Escherichia coli in brain–heart infusion (BHI) were cooled from 12°C to temperatures below 7°C (the minimum required for growth), the optical densities of cultures increased at declining rates for up to 6 days during incubation at temperatures between 6 and 3°C inclusive, but did not increase at temperatures ≤2°C. However, the numbers of E. coli recovered from cultures on selective or non-selective agars were similar at all times of incubation up to 8 days at temperatures below the minimum for growth. From optical density measurements it appeared that when log phase cultures were cooled to 2°C, then returned to 15°C, a lag developed with time at 2°C to reach a maximum of about 1 h after about 4 h. When cultures were returned to 12°C after times at 2°C between 0·5 and 8 days, the time during which optical densities did not increase was constant at about 2 h, but the initial rate of optical density increase declined with time at 2°C. On pork fat tissue the lag time, determined by increases in the numbers of E. coli cfu on tissues inoculated with cells returned from incubation at 2°C for 16 h to a growth permitting temperature between 7 and 30°C, was longer than the lag time determined from optical density measurements of broth cultures subjected to the same temperature regime. Lag times for E. coli adapted to and growing on normal pH pork lean tissue were longer than for E. coli on fat tissue, while unadapted E. coli did not initiate growth on lean tissue, after incubation at 2°C, at 12°C or lower temperatures. The observations indicate that lag phase development in log phase E. coli subjected to chiller temperatures is complex, and that prediction of lag resolution in log phase cells exposed to temperatures that fluctuate around the minimum for growth will require modeling of lag induction as well as lag resolution.     

Quantification of Connective Tissue (Hydroxyproline) in Ground Beef by Autofluorescence Spectroscopy

Autofluorescence spectra (excitation wavelengths 300, 332, 365, 380 and 400 nm) were obtained by an optical system to determine collagenous connective tissue (hydroxyproline) and fat content in ground beef. Chemically determined contents ranged from 0.72–7.12% connective tissue and 1.5–17.7% fat. Partial least squares regression (66 samples) resulted in the lowest root mean square error of 0.37% connective tissue (R=0.97) and 1.89% fat (R=0.84) for excitation wavelengths 380 and 332 nm, respectively. The wavelength 332 nm may be feasible for simultaneous determination of fat and connective tissue. Autofluorescence spectroscopy might be well suited for rapid on-line determination of collagen in ground beef.     

Study of Starch Granules Swelling by the Blue Dextran Method and by Microscopy

The evolution of corn and wheat starch granules swelling at different temperatures was determined by two techniques: the blue dextran method (which measures the swelling factor) and by optical (light) microscopy. The graphical results obtained using the blue dextran technique showed curves indicating the swelling of corn and wheat starch dispersions (at 64%, w/w, moisture content) characterized by an initial phase of slight swelling, a second phase of fast swelling and a final phase of maximum swelling. The concentrated solutions (42% and 47%, w/w, moisture content) showed a slight swelling with the increase in temperature. The effect of temperature on the shape of the granules was evaluated by the optical microscopy. The shape of the type A wheat starch granules was deformed at high temperatures. The corn and type B wheat granules had a spherical form. In the case of corn starch, a good correlation (r²= 0.929) was obtained between the results of optical microscopy and blue dextran techniques.