Frequency- and depth-dependent compensation of ultrasonic signals

The resolution in ultrasonic images decreases with depth when using traditional time-gain compensation (TGC) of the received signal. To reduce this effect, both frequency-dependent and depth-dependent compensation is introduced. A time-varying digital filtering method is presented for this purpose, which is based on Wiener filtering. Images obtained from a simulated tissue equivalent are presented and the frequency-compensated images are compared to conventional TGC-compensated images. It is shown that the improvement in resolution using frequency-dependent compensation is considerable when the signal-to-noise ratio in the received signal is high.     

Effect of pre-scalding brushing on contamination level of pork carcasses during the slaughtering process

The number of aerobic bacteria on the skin of pork carcasses was measured at seven different points on the slaughtering line in order to study the hygienic effect of pre-scalding brushing on the contamination level of carcasses. Eighty carcasses were investigated, of which 40 were brushed before scalding and 40 served as controls. Samples were excised from three sites: back, abdomen and ham. The total number of samples was 1368. The cleaning monitoring of the pre-scalding brushing machine and the blackscraping machine was done at the same time. After singeing and blackscraping there were significant differences (P<0·05) between brushed and non-brushed ham sites. After singeing, brushed ham sites had a contamination level of 2·11 (log(10) cm(-2)) and non-brushed ham sites a level of 1·57. After blackscraping the contamination of brushed ham sites was 3·45 (log(10) cm(-2)) and that of non-brushed ham sites 3·26. At the end of the slaughtering line brushed carcasses were more contaminated than those not brushed, although this difference was not significant.     

Functional properties of a protein product from Caryodendron orinocense (Barinas nut)

The functional properties of Caryodendron orinocense protein product were investigated and compared with those of soybean (Glycina maxima). The product protein content was 24.47 g/100 g (Nx6.25). Solubility increased at both sides of the isoelectric point (pH 4.0) and with increased NaCl concentration up to 0.5M. Compared with soybean flour (50% protein), the protein product exhibited higher water and oil absorption, but lower emulsifying activity, emulsion stability, foaming capacity, and foam stability, the last one increase at higher pH. Emulsifying activity, foaming capacity, and foam stability were ionic strength dependent. C. orinocense protein product increased its emulsifying activity steadily from 0.05M to 0.75M NaCl, while it remained almost constant for soybean flour. Foaming capacity increased drastically at pH 10. The minimum time and concentration to form a gel was 20% in 4 min and 10% in 8 min for the Caryodendron protein product and soybean flour, respectively. The bulk density was 0.5056+/-0.0041 g/mL.     

快速加氢热介技术应用于从煤生产苯、乙烯、合成天然气的工艺设想

煤的快速加氢热介(FHP)是一种能在单段、高产量反应器中直接生产甲烷、乙烷和三苯(BTX,即苯、甲苯和二甲苯)的新技术。快速加氢热介技术是将煤在稀释状态输送至反应器中,快速加热,短暂停留(1—2秒钟)。当结合为综合的基础转化联合企业时,快速加氢热介技术能用来生产合成天然气(SNG)、乙烯、丙烯、苯和F—T合成的醇类等一系列产品。本文根据用褐煤在快速加氢热介反应器中的操作经验,概述了一个概念化工厂的工艺技术和经济情况。这个工厂假设座落在美国得克萨斯州广阔的褐煤田附近。采用通融资金计算法估算合成天然气的成本,并以石油化产市场价格销售联产的化工产品,按照煤炭价格、利率、债务/资产比、联产化学品价格等因素,计算出的合成天然气20年内的平均成本在? 3～4/百万BTU范围内变动。     

具有抗菌活性的胍类化合物

三十年代中期当一系列胍类和缩二胍类化合物被报道具有杀细菌剂和消毒剂性质时,人们就已经认识取代基胍类化合物的生物活性。继而对许多胍类衍生物进行了研究,用作植物保护剂。其中有一些,如多果定(dodine)、双辛胍胺(guazatine)得到商业性开发,成为有相当重要性的农用杀菌剂。本文主要评述这类被证实有效或可能有效的活性胍类化合物。     

不用蒸出氨的凯氏定氮法

用凯氏定氮法测定有机物中含氮量,过去是将有机氮破坏,转变为铵盐,加苛性碱将氨蒸出,用标准酸吸收,再用标准碱回滴。此法手续麻烦,造成误差机会也多。Кейк等用标准次溴酸在碱性溶液中破坏有机物不需蒸出氨,但结果偏高,现在介绍用硒为分解有机物的催化剂,并且不用蒸出法来测定氮。试剂:～8N NaOH溶液530毫升15N NaOH(不含碳酸盐)溶液用水稀释至1升,装在聚乙烯树脂所制的瓶中,上装碱石灰乾燥管。0.2N NaOH溶液25毫升8N NaOH溶液用水稀释至1升,用标准邻苯二酸标定,保存在聚乙烯树脂所制的瓶中,装碱石灰乾燥管。18%中性甲醛溶液100毫升35—38%甲醛溶液,用等量水稀释,加入2滴酚酞,以0.1N NaOH中和至淡红