基于液氮喷雾式食品流态化速冻机的青刀豆速冻实验研究

速冻是用来保存食品的常用方法之一,而在食品的长期保存的过程中人们一直关心的一个问题是如何能够保持食品的外观、完整性和品质。流态化速冻是实现单体快速冻结的最有效方法之一。我所自行研制了液氮喷雾式食品流态化速冻机。本文便是基于此速冻装置的基础之上,对青刀豆进行速冻试验研究,来分析在不同的冻结条件下对物料的冻结时间、干耗和品质的影响。通过冻结青刀豆复温后的电镜照片,来分析速冻过程中冰晶生长对食品品质的影响。     

Activated carbons by pyrolysis of coffee bean husks in presence of phosphoric acid

Activated carbons (Acs) were prepared by pyrolysis of coffee bean husks in presence of phosphoric acid (chemical activities). Husks from Colombian coffee beans were impregnated with aqueous solutions of H₃PO₄ following a variant of the incipient wetness method. Diffenent concentrations were used to produce impregnation ratios of 30, 60, 100 and 150 wt.%. Activation was carried out under argon flow by heating to 723 K with 1 h soaking time. The porous texture of the obtained ACs was characterized by physical adsorptions of N₂ at 77 K and CO₂ at 273 K. The impregnation ration had a strong influence on the pore structure of these Acs, which could be easily controlled by simply varying the proportion of H₃PO₄ used in the activation. Thus, low impregnation ratio led to essentially microporous Acs. At intermediate impregnation ratios, ACs with wider pore size distribution (from micropores to mesopores) were obtained. Finally, high impregnation ratios yielded essentially mesoporous carbons with high surface area and pore volume.     

激光对蚕豆幼苗紫外线-B辐射损伤的防护作用

用不同剂量的He Ne激光和CO2 激光辐射蚕豆 (ViciafabaL .)种子胚 ,对其幼苗进行丙二醛 (MDA)和抗坏血酸 (AsA)含量测定。结果发现He Ne激光的效果优于CO2 激光 ;He Ne激光的最佳辐射剂量为 5 4 3mW·mm-2 ,最佳辐射时间为 5min。先用He Ne激光辐射蚕豆种子 ,待其长至幼苗时 ,在光背景 (PAR) 70 μmol·m-2 ·s-1条件下 ,用 3 0 3kJ·m-2 UV B照射 7h/d ,然后对其超氧化物歧化酶 (SOD) ,过氧化物酶 (POD) ,过氧化氢酶(CAT)酶活性以及同工酶谱进行测定。结果发现 ,He Ne激光辐射可提高SOD ,POD ,CAT酶活性 ;改变SOD ,CAT同工酶谱。从而说明 ,激光对UV B辐射损伤植物具有一定的防护作用。     

高效液相色谱-四极杆飞行时间质谱法同时检测豆芽中的3种外源植物激素残留

建立了高效液相色谱-四极杆飞行时间质谱同时测定豆芽中6-苄基腺嘌呤、4-氯苯氧乙酸、赤霉素等3种外源植物激素残留的方法。采用QuEChERS前处理技术,豆芽样品以酸化乙醇-乙腈溶液（1%（v/v,下同）乙酸+50%乙醇+49%乙腈）提取目标化合物,并经乙腈再提取后合并提取液;经硅藻土分散固相净化、正己烷去脂后氮吹至近干;用2.0 mL 50%（v/v）甲醇水溶液定容,过滤膜后上机检测。液相色谱以甲醇-水（含0.1%（v/v）的甲酸）作为流动相梯度洗脱,C₁₈色谱柱分离;质谱采用高分辨质谱、负离子模式,以精确质量数和二级特征离子定性,以准分子离子峰面积定量。结果表明3种目标化合物的定量限为5.0~10.0 μg/kg,线性范围为1~200 μg/L;平均添加回收率为79.1%~96.1%,相对标准偏差为5.7%~10.4%。本方法具有操作简单、快捷、灵敏度高等优点,适用于市场上豆芽质量的快速筛查检测。     

云计算的蚕豆虫害可见-近红外光谱分类

利用蚕豆叶片可见-近红外反射光谱结合导数光谱对健康、少量、大量虫害三种等级的实验样本进行光谱特征分析,并选择虫害检测最优波段。采用Hadoop,Spark和VMWare虚拟机搭建云计算平台,使用MLlib机器学习库实现人工神经网络(ANN)和支持向量机(SVM)分类算法,并对三种等级蚕豆叶片全波段和最优波段光谱进行分类建模与预测。结果表明ANN虫害光谱分类模型准确率优于SVM虫害光谱分类模型,并且在云平台上运行效率更高,同时全光谱波段的预测准确性高于最优波段。通过扩展光谱数据集,云计算技术在光谱数据挖掘中的计算效率有显著提升。云计算分类检测可以为作物生物胁迫光谱识别提供新的技术和方法。     

Studies on the phytotoxic effects of some organotin(IV) compounds on the germination of the mung bean seed,Phaseolus aureus

A selected range of organotin(IV) compounds of formula R_xSnX_4-x (x = 2 or 3; R = alkyl, cycloalkyl or aryl), as well as the adducts, (p-ZC₆H₄)₃SnCl. Ph₃PO (Z = H, Me) were examined in vivo for their phytotoxic effects relative to the more powerful s-triazine herbicides against the mung bean seed, Phaseolus aureus. Phytotoxicity was assessed in terms of changes in (a) weights of primary leaves, (b) weights of cotyledons, (c) seedling heights and (d) root morphology. The triorganotin compounds were more phytotoxic than the diorganotins, and within the R₃Sn structural class, inhibitory potency was greater for alkyltins than for aryltins. Decreasing the alkyl chain lengths or placing electrondonating substituents on the aromatic rings increased the phytotoxicity. A significant phytotoxic effect, comparable with that of Ph₃SnCl, was manifested by tricyclohexyltin chloride, in marked contrast to the well-known low phytotoxicity of tricyclohexyltin hydroxide. Using Ph₃SnCl as the model compound, it was further demonstrated that the total chlorophyll content decreased with increasing concentration of Ph₃SnCl, but the ration of chlorophyll a to chlorophyll b was constant. It was also found that tin uptake in the seedlings was directly proportional to Ph₃SnCl test concentrations; the magnesium and iron levels in the treated seedlings, however, were unchanged relative to the control.     

MVC和UML在教学管理系统中的研究与应用

MVC(模型-视图-控制器)是一种优秀的编程模型,它可以把用户界面设计、流程控制和事务逻辑进行分离。文中结合南京邮电大学教学平台建设的实践,研究了MVC模式和UML(统一建模语言)在教学管理系统中应用,探索了一种把MVC和UML相结合的方法,提出了基于多层网络应用框架的教学管理系统,即客户应用层、J2EE(Java 2平台企业版)服务器中W eb处理层、J2EE服务器中处理各种复杂教学事务的业务逻辑层、存储数据和文件的企业信息层。其中,业务逻辑层是整个系统的重点,它包含6个EJB(企业Java组件)。实践表明,这种多层结构的软件系统有着良好的推广价值和应用前景。     

QuEChERS-高效液相色谱-串联质谱法同时测定豆芽中40种植物生长调节剂、杀菌剂、杀虫剂和抗生素类药物残留北大核心CSCD

研究从豆芽质量安全监管的实际需求出发,建立了QuEChERS-高效液相色谱-串联质谱同时测定豆芽中植物生长调节剂、杀菌剂、杀虫剂和抗生素类等40种药物残留的方法。首先通过参数优化确定最佳质谱条件,然后比较不同提取溶剂(甲醇、乙腈、0.1%氨水乙腈、1%乙酸乙腈)、提取方法(超声、振荡)以及乙二胺-N-丙基硅烷化硅胶(PSA)、C_(18)净化剂添加量时40种药物的回收率,确定最优前处理过程。样品用10 mL 1%乙酸乙腈提取两次,超声波辅助提取,100 mg C_(18)为净化剂。选用Waters ACQUITY UPLC BEH C_(18)色谱柱(100 mm×2.1 mm,1.7μm)进行分离,甲醇和0.01%甲酸水为流动相梯度洗脱,多反应监测(MRM)模式进行质谱监测,基质匹配外标法定量。结果表明,40种药物可在15 min内完成色谱分离,在2~200μg/L的线性范围内均呈现出良好的线性关系,相关系数(r^(2))均大于0.99,检出限(LOD)和定量限(LOQ)分别为0.1~3μg/kg和0.3~9μg/kg。以阴性豆芽为基质,分别在5、10、50μg/kg 3个水平下进行加标回收试验,40种药物的平均回收率为78.5%~115.3%,相对标准偏差(RSD)为1.3%~9.7%(n=6)。将该方法用于分析邯郸本地豆芽中40种药物的污染状况,结果显示4-氯苯氧乙酸、6-苄基腺嘌呤、多菌灵、2,4-二氯苯氧乙酸(2,4-D)、赤霉素和恩诺沙星检出率较高,分别为28.6%、19.0%、9.5%、9.5%、4.8%和4.8%,含量范围为37.5~352.4、32.4~273.1、28.8~38.7、16.1~20.2、19.9和13.6μg/kg。研究建立的方法简单、快速,灵敏度高,适用于大批量豆芽中40种药物的快速准确测定。