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排序方式: 共有215条查询结果,搜索用时 15 毫秒
21.
高校教学楼集中空调热水泵节能改造 总被引:3,自引:2,他引:1
分析了教学楼集中空调系统造成能源浪费的基本原因,介绍了某集中供热系统的节能改造,通过更换热水泵和采取适当管理措施达到了系统节能的目的,在5个月的供暖期内节约了超过20%的电能,有一定的实际意义. 相似文献
22.
23.
奇异摄动系统的极限解 总被引:3,自引:0,他引:3
本文在前人工作的基础上,利用广义函数理论讨论了一般形式下的奇异摄动系统E(ε)(?)=A(ε)x+B(ε)u在v→0~+时的极限解问题,得出了这一极限解存在的充要条件。 相似文献
24.
Caleb Acquah Yi Wei Chan Charles K. S. Moy Clarence M. Ongkudon Sie Yon Lau 《分离科学与技术》2018,53(13):2100-2111
The introduction of aptameric ligands onto disk-monolithic adsorbent, representing a unique strategy for convective isolation of target molecules with high specificity and selectivity, is investigated for the first time. Experimental results showed that the disk monolith possessed a good permeability of 1.67 ± 0.05 × 10–14 m2 (RSD = 3.2%). The aptameric ligand density for the aptamer-modified disk monolith was 480 pmol/uL. Chromatographic analysis of the aptamer disk-monolith efficiency showed an optimum linear velocity of 126 cm/min (≈0.25 mL/min) at room temperatures 25 ± 2°C. The theoretical number of plates corresponding to the optimum linear velocity was 128.2 with an height equivalent to the theoretical plate of 0.022 mm. The disk aptamer-immobilised monolithic system demonstrated good selectivity and isolation of thrombin from non-targets. 相似文献
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26.
LY Wang JK Ma WF Pan D Toledo-Velasquez CJ Malanga Y Rojanasakul 《Canadian Metallurgical Quarterly》1994,11(4):513-517
Pulmonary exposure to oleic acid (OA) is associated with permeability alterations and cellular damage; however, the exact relationship between these two effects has not been clearly established. Using cultured alveolar epithelial monolayers, we demonstrated that OA and some other fatty acids (< or = 50 microM) can induce permeability changes without detectable cellular damage. At higher concentrations, however, OA caused severe membrane damage and leakage to solute flux. The permeability enhancing effect of OA was observed with both the paracellular marker 3H-mannitol and the lipophilic transcellular indicator 14C-progesterone. While the effect of OA on transcellular permeability may be attributed to its known effect on membrane fluidity, the paracellular promoting effect of OA and its mechanism are not well established. We postulated that OA may increase paracellular permeability through a Ca(2+)-dependent tight junction mechanism. Using dual-excitation fluorescence microscopy, we demonstrated that OA can increase intracellular calcium, [Ca2+]i, in a dose-dependent manner. This effect was transient at low OA concentrations (< or = 50 microM) but became more pronounced and sustained at higher concentrations. Free hydroxyl and unsaturated groups were required for this activation since esterified OA (oleic methyl ester) and stearic acid (a saturated fatty acid with equal chain length) had much reduced effects on both the [Ca2+]i and the permeability alterations. Degree of unsaturation was unimportant since linolenic acid (18:3), linoleic acid (18:2), and OA (18:1) had similar and comparable effects on the two parameters.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
27.
Role of the conjugated linoleic acid in the prevention of cancer 总被引:1,自引:0,他引:1
There are multiple lines of evidence that a variety of natural fatty acids are effective in health promotion. Among these fatty acids, conjugated linoleic acid (CLA)--a collective term referring to a mixture of positional and geometric isomers of linoleic acid (LA, cis-9, cis-12-octadecadienoic acid)--is currently under intensive investigation due to its health-promotion potential. The antitumor activity of CLA is of special interest, since it shows inhibitory effects against multistage carcinogenesis at relatively low dietary levels. Many studies using in vivo and in vitro models have shown that CLA suppresses the development of multistage carcinogenesis at different sites. The research to date on CLA has provided a vast amount of information about the mechanism on how CLA functions in the prevention of cancer. This article discusses characteristics of CLA in the prevention of cancer in both in vivo and in vitro studies and the possible underlying chemoprevention mechanisms. 相似文献
28.
Dea Seok Yoo Yeon Hee Choi Mi Ran Cha Byung Hoe Lee Sun-Ju Kim Gyu Hwan Yon Kyung Sik Hong Yu Seon Jang Hyun Sun Lee Young Sup Kim Shi Yong Ryu Jong Seong Kang 《Food chemistry》2011
An effective HPLC method to analyse platycosides from the balloon flower root was developed using ELSD. The optimum resolution of the platycosides was achieved on an ODS column with gradient elution of eluent A, 30 mM ammonium acetate buffer (pH 4.81): methanol: acetonitrile = 75:5:20 (v/v/v), and B, 69:5:26 (v/v/v). Amongst 18 platycosides, platycoside E showed the highest content, followed by polygalacin D2 and 3″-O-acetylplatyconic acid A. The sum of these three compounds was recommended for quality control of balloon flower root for medicinal purposes. The samples could be clustered into groups based on platycoside content. Group I, characterised by a high concentration of platycosides, was located near the west coast of Korea, whereas group II, characterised by a low concentration of platycosides, was located inland or in mountainous area. The method could be used to control the quality of balloon flower root. 相似文献
29.
Kyoung Suk Kim Byung Soo Oh Joon Wun Kang Deuk Mo Chung Woo Hyeun Cho Yon Kyu Choi 《臭氧:科学与工程》2005,27(1):69-79
To improve the quality of water supplied to the City of Seoul in Korea, a pilot-scale evaluation of how the conventional treatment process could be upgraded was conducted. Three candidate processes were evaluated and compared: a conventional process (consisting of coagulation, sedimentation, and rapid sand filtration) plus GAC (Train A); a conventional process plus ozone and GAC (Train B); and a process consisting of coagulation, sedimentation, intermediate ozone, sand filtration, and GAC (Train C). Treatment efficiency of the unit process and overall treatment trains were evaluated using several parameters such as turbidity, dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), specific ultraviolet absorbance (SUVA), micropollutants (pesticides, benzenes, and phenols), disinfection by-products (trihalomethanes (THMs), haloacetic acids (HAAs) and aldehydes), and total organic halogen (TOX). Results showed that ozone and/or GAC was effective for removing micropollutants and controlling chlorinated by-products such as THMs and HAAs. However, any synergistic effect of ozonation (adsorption and biodegradation) on GAC was observed due to the low concentration of aldehydes in raw and process water. 相似文献
30.
采用酸碱指示剂滴定法和线性电位滴定法测定壳聚糖的脱乙酰度,结果表明线性电位滴定法比酸碱指示剂滴定法能更好地避免人为误差,具有较高的准确性和精密度,而且操作简单. 相似文献