Effect of Chlorophenoxyacetic Acid Growth-Regulator Sprays on Residues in Canned Apricots and Grapes

SUMMARY— A, gas-liquid chromatographic method coupled with an electron capture detector has been developed for analyzing chlorinated phenoxyacetic acid residues in canned fruits. The technique involves converting the acid to its methyl ester with diazomethane, chromatography on a 5% silicone grease SE-30 column at 210°C, and subsequent detection of the compound by an electron capture detector. As low as 0.02 ppm of the residue could be detected. The method is superior to the calorimetric method because parachlorophenoxyacetic acid (PCPA), 2,4-D, and 2,4,5-T can be separated and quantitatively determined simultaneously. However, separate standard curves are needed for each, because they differ in chlorine content and in sensitivity toward the electron capture detector. Levels of 2,4-D and 2,4,5-T residues in canned apricots, and of PCPA in canned grapes are reported.     

Characterization of Polyphenoloxidase from Ravat 51 and Niagara Grapes

Polyphenoloxidase (PPO) was isolated from two varieties of grapes grown in the northeastern United States and its characteristics were studied. The temperature and pH optima for both enzymes were 25°C and 5.5, respectively. The thermal inactivation of PPO followed first-order kinetics; with the Niagara enzyme being more heat stable than Ravat PPO. The substrate specificity of the grape PPO clearly showed high affinity toward the o-diphenolic compounds, with a high affinity toward caffeic acid. Inhibition studies indicated that L-cysteine and sodium diethyldithiocarbamate were the most potent.     

Microflora, Sensory and Exudate Changes of Vacuum- or Nitrogen-Packed Veal Chucks Under Different Storage Conditions

Apart from increases in microflora number at —4°C under vacuum and at 0°C under nitrogen, there was in general no significant (P gt; 0.05) differences in numbers of lactobacilli, psychrotrophs, aerobes and anaerobes between vacuum- and nitrogen-packed veals during 49 days of storage at 3 and 7°C, regardless of dark and lighted displays. The initial psychrotrophs consisted primarily of Pseudomonas putida (> 72%) but by day 49 Lactobacillus spp. comprised at least 64% of the total in both atmospheres. Sensory and exudate data showed a highly significant (P < 0.05) difference due to the effect of storage time and temperature above 0°C. Nitrogen-packed veals exhibited a lower incidence of greening and exudate loss at 0, 3 and 7°C. Light generally had important effects on off-odor and exudate loss, irrespective of package types.     

A Comparison of Methods for Polyuronide Methoxyl Determination

A comparison was made between three basic methods for determining methoxyl (OMe) groups in a polyuronide, viz., step-wise oxidation-reduction initiated by hydriodic acid, neutralization of de-esterified carboxyl groups with potassium hydroxide, and direct combustion of methanol by gas chromatography. Accuracy and precision of the methods were ascertained by analyzing methyl fuorate. All the methods were accurate. The neutralization and gas chromatographic methods had major advantages of simplicity and shortness of time of completion over the hydriodic acid/bromine method. Dimethylsulfoxide in the the saponification medium had no special effect.     

Cr-Si粉末冶金工艺及其物理-力学性能

粉末冶金制作法主要有热压(HP)、热等静压(HIP)及常压烧结(Sinter)三种.采用热压及热等静压法可以很容易地得到高致密化的高温金属硅化物,但若要进行大尺寸的产品烧结,必须提升生产设备的规格和能力,例如加大热压机力吨位、扩大热压炉腔体等,致使设备投资及生产成本相对昂贵.所以大部分厂商宁可采用常压烧结法,虽然该法的高致密化工艺条件不易控制,却因可以制作大尺寸金属硅化物,加上设备投资及生产成本相对降低,使许多大厂已投入相当大的人力和物力在开发此工艺.该文作者试用不同真空烧结温度,造成Cr-Si合金粉末烧结性质的差异,探讨稳定而可大量生产的可行性;并通过对温度的控制,来改善Cr-Si的物理性质与力学性质.结果表明,提高烧结温度会使Cr-Si合金产生部分液相烧结的现象,从而使孔隙率显著下降;但显微结构也随之有偏析与晶粒粗化的现象.     

综合先进技术的交通噪音评估(一)-以立体地理资讯系统为基础的区域噪音模型

为了解、组织及整理整个香港区域的道路交通噪音资料,从而确定、量化及分折交通噪音的严重性,再鉴定相关的噪音缓解措施,香港环境保护署综合了数种先进的技朮,包括地理信息系统、大型的电脑噪音模型、立体影像技朮等,自行开发了一套以立体地理资讯系统为基础的区域噪音模型。从这个系统和模型计算出来的交通噪音地图,加上利用地理信息系统軟件、人口分布的资料库和统计学方法的帮助,评估了整个城市总共有多少居民在那些区域受着多少交通噪音的影响。这些结果可以分析交通噪音的问题,继而决定未来噪音缓解设施及制定综合的计划,以应付这噪音问题。     

Feed/Seed比值对好氧生物处理效率的影响

好氧生物反应器的进料物（Feed）是经厌氧作用的消化污泥，而其接种体（Seed）是活性污泥。主要研究了四种Feed／Seed比值（1：0，3：1，1：1和0：1）对好氧生物处理效率的影响。对于Feed／Seed比值为1：0和0：1而言，污泥的TSS和VSS的去除率很低。而另外两种比值的实验结果表明，TSS和VSS的去除率均随Feed／Seed比值的增加而增加。对于Feed／Seed比值为3的生物反应器，28天的TSS和VSS的去除率分别达到了49％和50％。并且TSS和VSS的降解服从一级反应动力学。动力学降解常数（k）也随Feed／Seed比值的增加而增加。而且VSS的去除率略高于TSS。另外，硝化反应的发生导致好氧生物反应器中的硝酸根离子浓度的增加和pH的降低。     

ILC for non-minimum phase system

In this paper we propose a design method of an iterative learning controller (ILC) for a non-minimum phase (NMP) system by model-matching theory. The ILC consists of two learning filters acting on both the previous input signal and the previous error signal. To design the learning filters, we convert the convergence condition of the ILC into the model-matching problem and get the stable and proper learning filter by solving the Nevanlinna's algorithm. To show the usefulness of the proposed algorithm, some design examples are included.