超短激光与金属材料作用时的热效应

为了探究皮秒和飞秒激光在金属材料加工和表面处理方面的应用,课题组以金、铜、铬3种金属为研究对象,借助有限元软件,从热传导双温方程出发,研究不同脉冲宽度激光作用于金属材料上时的热产生和热积累,从理论上确立不同激光参数时被加工材料表面的电子和晶格温度分布规律。分析结果表明,激光的脉冲宽度会影响材料电子温度的峰值大小与电子晶格耦合的时间长短,在相同的脉冲能量下,脉冲宽度越窄,电子温度最高值越高,电子晶格温度达到平衡的时间越短;热力学模型的准确性与激光脉冲宽度密切相关,当激光脉冲宽度大于10 ps时,单温和双温模型均可描述激光作用到材料的热效应,但当激光脉冲宽度小于10 ps时,则需要采用双温模型来描述。     

皮秒激光在微结构制备中的应用

皮秒激光是指脉冲宽度在皮秒量级的激光,具有“冷加工”、高脉冲能量、高功率密度等特点,可以对多种材料进行高精度的微细加工,广泛应用于航空航天、精密仪器、生物医学等领域。皮秒激光对材料的加工可以分为微孔加工、切割划线、表面微结构制备。综述皮秒激光在材料蚀除、金属着色、亲疏水表面、特殊晶体等材料表面微结构制备中的原理及应用,探讨其优势及存在的问题,并展望今后可能的发展方向。     

高压脉冲电场对全蛋液杀菌的研究

将高压脉冲电场应用于全蛋液的杀菌,结果表明,在蛋液流动性较差,极易变性且高电导率的情况下,将接种大肠杆菌或沙门氏菌的全蛋液置于脉冲电场中进行杀菌,最佳处理工艺为脉冲电场强度17.8 kV/cm,脉冲宽度2μs,每秒400个脉冲,流速25 mL/min,保持显示温度(20±2)℃,间歇处理。脉冲杀菌对微生物的致死是电场强度、脉冲宽度、处理时间、处理温度、流体性质及微生物特性综合作用的结果。     

激光与物质相互作用的研究进展

激光从60年代出现后,就从根本上改变了光学面貌,并对物理学、化学以及生物学等学科产生了重要影响。人们从关注激光自身特征转变为关心学科领域的交叉,这便说明,人们已经把激光与学科研究进行了整合,而利用激光的相关特性,对激光与物质相互作用进行研究,成为了当今世界重要的研究课题。文章主要在激光与物质相互作用的理论基础中,对研究的内容,以及对短脉冲激光对金属以及非金属的烧蚀进展进行了研究,从而得到最新的激光信息。     

高斯镜平凹腔腔外光束特性的数值分析

运用边界有限元法,计算了平凹谐振腔具有高斯反射镜情况下的场强分布和相位分布,考察了高斯反射镜谐振腔的模鉴别规律和增大模半径的规律.指出：高斯反射率镜平凹腔可扩大模式本征值差,具有模鉴别能力;中心反射率大小对选模能力也有影响,但对基模半径无影响;高斯镜具有对输出光束整形的功能.     

两个耦合六波混频信号特性

宽波长范围内双波长信号和多波长光信号的产生和控制在超快光学开关和相干控制研究中有着及其重要的意义.采用宽带宽的光脉冲在铷原子蒸汽中产生两个红外波段不同波长的光信号,观察到两个红外光信号间存在竞争.研究了泵浦激光强度、光脉冲啁啾和铷原子数密度对两个红外光信号特性的影响.结果表明,两个红外光信号的产生机制是两个耦合的参量六波混频过程;信号的强度随泵浦激光强度、光脉冲啁啾和铷原子数密度发生变化,两个红外光信号间的竞争主要由与铷原子数密度相关的相位匹配条件所决定.     

古代出土纺织品的激光净化

试图回答两个问题：（1）作为辨认考古发现物中所含纤维的工具，激光脉冲是否适合用在扫描电子显微镜调查之前。（2）激光脉冲是否能作为合理净化古代出土纺织品的合适工具。厌氧性环境（如泥炭诏）通常会浸到手工制作的纺织品中，有助于此类纺织品的保存，在这种情况下，普通化学方法作为净化手段就不行了；而且，去除该种材料会使样品变得脆弱。激光脉冲提供了一种可选择的净化手段，在本试验中（基于棉样品），主要用两个激光参数（能量密度和脉冲数）的几种结合作用来研究激光照射的作用。因为古代出土纺织品十分稀少，故经人工老化的复制样品提前用来接受该处理。处理前后都用扫描电子显微镜检验纤维。本文叙述通过扫描电子显微镜来检验紫外激光照射对纤维的影响，研究的目标是在不损伤纺织品的情况下去除赃物和粘附物。     

基于时间数字转换技术的超短时间间隔测量

对脉冲激光的近距离高精度测距往往遭遇纳秒级超短时间间隔测量等问题,而时间数字转换技术（TDC）可支持 2ns 超短时间间隔测量,且可获得皮秒级测量分辨率,并有效攻克了传统脉冲计数法难以满足超短时间间隔测量的尴尬事实。本文从 TDC 测量原理、TDC 校准测量、TDC 测量的实现三个方面剖析基于 TDC 的超短时间间隔测量。     

高压脉冲电场对大豆分离蛋白疏水性和巯基含量的影响

本文研究了高压脉冲电场对大豆分离蛋白疏水性和巯基含量的影响。结果表明:随着脉冲强度、脉冲宽度增大及脉冲处理时间的延长,大豆蛋白疏水性和巯基含量都增加。但当脉冲强度为40kV/cm、样品流速为40ml/min时,疏水性和巯基含量略有降低。说明高压脉冲电场对大豆分离蛋白的空间结构有一定的影响,脉冲强度、脉冲宽度愈大及脉冲处理的时间愈长,对蛋白的变性程度愈强。     

初始位相对圆偏振激光脉冲与电子对撞运动轨迹的影响

通过理论推导出全时间运动方程以及高能电子全空间运动方程,研究激光脉冲初始位相对高能电子运动轨迹的影响。模拟周期量级激光脉冲同步辐射电子运动过程,通过改变激光脉冲的初始位相,可以得出不同初始位相对电子的运动轨迹的影响很小,可以基本忽略,进而为研究初始位相对激光脉冲与高能电子对撞辐射特性的影响提供了有力支持。     

How postharvest variables in the pulse value chain affect nutrient digestibility and bioaccessibility

Pulses are increasingly being put forward as part of healthy diets because they are rich in protein, (slowly digestible) starch, dietary fiber, minerals, and vitamins. In pulses, nutrients are bioencapsulated by a cell wall, which mostly survives cooking followed by mechanical disintegration (e.g., mastication). In this review, we describe how different steps in the postharvest pulse value chain affect starch and protein digestion and the mineral bioaccessibility of pulses by influencing both their nutritional composition and structural integrity. Processing conditions that influence structural characteristics, and thus potentially the starch and protein digestive properties of (fresh and hard-to-cook [HTC]) pulses, have been reported in literature and are summarized in this review. The effect of thermal treatment on the pulse microstructure seems highly dependent on pulse type-specific cell wall properties and postharvest storage, which requires further investigation. In contrast to starch and protein digestion, the bioaccessibility of minerals is not dependent on the integrity of the pulse (cellular) tissue, but is affected by the presence of mineral antinutrients (chelators). Although pulses have a high overall mineral content, the presence of mineral antinutrients makes them rather poorly accessible for absorption. The negative effect of HTC on mineral bioaccessibility cannot be counteracted by thermal processing. This review also summarizes lessons learned on the use of pulses for the preparation of foods, from the traditional use of raw-milled pulse flours, to purified pulse ingredients (e.g., protein), to more innovative pulse ingredients in which cellular arrangement and bioencapsulation of macronutrients are (partially) preserved.     

Pulse flaking: Opportunities and challenges,a review

Pulses provide economic and health benefits to people in many countries around the world; however, their adoption in western diets, particularly in processed and formulated foods, is limited. One strategy to increase the level of pulses in western diets is to improve pulse accessibility to the ready-to-eat (RTE) food market sector. Pulses have compositional and structural differences when compared to cereals and behave differently during processing. While there have been numerous studies on pulses processed using traditional processing methods, there are limited studies describing processing of pulses as a major ingredient in RTE forms such as flakes. To understand the full processing potential of pulses, systematic studies are required using commercial-scale RTE pilot processing equipment coupled with fundamental property determination techniques to evaluate the effects of processing and pulse material on pulse flake attributes. In-depth studies of pulse properties and their processability are likely to result in the production of high-quality pulse-based foods with superior health benefits. This review explores the current and potential opportunities for processing pulses with a focus on flake products. The roles of pulse type and major structure-forming components such as fiber, carbohydrates, and proteins on end-product quality of processed pulses are discussed.     

Understanding the Relations Among the Storage,Soaking, and Cooking Behavior of Pulses: A Scientific Basis for Innovations in Sustainable Foods for the Future

The world faces challenges that require sustainable solutions: food and nutrition insecurity; replacement of animal‐based protein sources; and increasing demand for convenient, nutritious, and health‐beneficial foods; as well as functional ingredients. The irrefutable potential of pulses as future sustainable food systems is undermined by the hardening phenomenon that develops upon their storage under adverse conditions of temperature and relative humidity. Occurrence of this phenomenon indicates storage instability. In this review, the application of a material science approach, in particular the glass transition temperature concept, is presented to explain phenomena of storage instability such as the occurrence of hardening and loss of viability under adverse storage conditions. In addition to storage (in)stability, application of this concept during processing of pulses is discussed. The state‐of‐the‐art on how hardening occurs, that is, mechanistic insights, is provided, including a critical evaluation of some of the existing postulations using recent research findings. Moreover, the influence of hardening on the properties and processing of pulses is included. Prevention of hardening and curative actions for pulses affected by the hardening phenomenon are described in addition to the current trends on uses of pulses and pulse‐derived products. Based on the knowledge progress presented in this review, suggestions for the future include: first, the need for innovation toward implementation of recommended solutions for the prevention of hardening; second, the optimization of the identified most effective and efficient curative action against hardening; and third, areas to focus on for elucidation of mechanisms of hardening, although existing analytical methods require advancement.     

Application of femtosecond laser ablation for detaching grown protein crystals from glass capillary tube

We developed a novel technique for detaching protein crystals from glass capillary tube using the counter diffusion crystallization technique by femtosecond laser irradiation. X-ray diffraction analysis demonstrated that femtosecond laser irradiation has little effect on crystallinity. This technique will contribute to progress in structural genomics as a powerful tool.     

杂豆在可持续膳食发展中的机遇与挑战

杂豆作为一类可持续膳食,存在自身的优势和发展机遇,但也存在一些问题。文章探讨了可持续膳食发展的必要性及发展方向,分析了杂豆作为可持续膳食存在的优势及问题,展望了杂豆食品的开发方向。     

常见加工方式对杂豆品质的影响与调控

杂豆富含蛋白质、膳食纤维和维生素等多种营养成分，但也含有植酸、胰蛋白酶抑制剂、植物凝集素等抗营养因子，这大大降低了其生物利用率。采用不同的加工方法可以降低或去除抗营养因子，从而改善杂豆的营养品质、风味品质和感官特性，提升杂豆适用性。常见加工方式主要包括浸泡、脱壳、煮制、微波处理、高压处理、挤压膨化、烘烤、发酵和发芽等。本文总结不同加工方式对杂豆品质的影响，以期为精准调控杂豆品质和发展新型杂豆加工技术提供理论参考和新的研究方向。     

杂豆与慢性疾病防控

杂豆中的植物化学物、膳食纤维及抗性淀粉等有助于慢性疾病预防和控制。人体干预研究和前瞻性流行病学研究表明,含有杂豆的饮食可以降低低密度脂蛋白胆固醇（LDL-C）,有利于减少代谢综合征、缺血性心脏病、糖尿病和肥胖的风险。本文对杂豆结合进入健康膳食模式时对控制餐后血糖、体重管理、预防心血管疾病等方面的积极作用进行综述。     

Inactivation of Pseudomonas fluorescens by High Voltage Electric Pulses

A 30 kV pulsed power treatment system was designed and developed to process fluid materials. Our objective was to investigate the effects of high voltage electric pulses on microbial inactivation in an aqueous solution under different operating conditions and fluid properties. Electric field strength at 10 kV/cm for 10 pulses (2 set pulse period and 2 Fsec pulse width) with a spike of reverse polarity resulted in significant microbial control. P. fluorescens in various aqueous solutions were reduced in population by more than six log cycles. However, the critical electric field strength was affected by the nature of the pulse waveform across the treatment chamber which, in turn, was a function of electrode distance and fluid properties. Sudden charge reversal immediately at the end of a pulse provided maximum microbial decay.     

In vitro fermentability and antioxidant capacity of the indigestible fraction of cooked black beans (Phaseolus vulgaris L.), lentils (Lens culinaris L.) and chickpeas (Cicer arietinum L.)

BACKGROUND: Pulses represent an important source of protein, as well as digestible and indigestible carbohydrates. Little information is available on the indigestible carbohydrates and antioxidant capacity of legume seeds. The cooked seeds of three pulses (black bean, chickpea and lentil) were evaluated for their indigestible fraction (IF), polyphenols content, antioxidant capacity and in vitro fermentability, including short‐chain fatty acid production. RESULTS: The insoluble indigestible fraction (IIF) was higher than the soluble counterpart (soluble indigestible fraction, SIF). The SIF value was highest in black beans, while no difference was observed between chickpeas and lentils. Black beans and lentils had higher polyphenols content than chickpeas. The IF of black beans exhibited the lowest and chickpeas the highest associated polyphenols content. Condensed tannins were retained to some extent in the IF that exhibited significant antioxidant capacity. The total IF of the three pulses produced short chain fatty acids (SCFA) after 24 h of in vitro fermentation by human colonic microflora. IF from black bean and lentil were best substrates for the fermentative production of butyric acid. CONCLUSIONS: It is concluded that the IF of pulses might be an important source of bioactive compounds. Copyright © 2010 Society of Chemical Industry