Chitosan extends the shelf-life of filleted tilapia (Oreochromis niloticus) during refrigerated storage

Shelf-life extension of aquatic products is of significant economical importance. To determine the potential effect of chitosan on the shelf-life of filleted tilapia, this study analyzed the bacterial community diversity in fresh and spoiled tilapia fillets stored at (4 ± 1)℃ and examined the antimicrobial activity of chitosan against relevant bacteria isolates. Results showed that Pseudomonas (20%) and Aeromonas (16%) were abundant in fresh tilapia fillets, whereas Pseudomonas (52%), Aeromonas (32%) and Staphylococcus (12%) were dominant in the spoiled samples. Chitosan showed wide-spectrum antibacterial activity against bacteria isolated from tilapia and 5.0 g L-1 chitosan was selected for application in preservation. We further determined the shelf-life of chitosan-treated, filleted tilapia stored at (4 ± 1)℃ based on microbiological, biochemical and sensory analyses. Results showed that the shelf-life of chitosan-treated, filleted tilapia was extended to 12 d, whereas that of untreated, control samples was 6 d. These indicate that chitosan, as a natural preservative, has great application potential in the shelf-life extension of tilapia fillets.     

吸附式制冷单管吸附床传热传质的数值模拟及分析

建立氯化钙—氨吸附式制冷单管吸附床传热传质模型 ,采用数值方法对该模型进行了求解 ,得出不同工况下的温度场 ,讨论了吸附床的有效导热系数、接触热阻、流体传热系数等对解吸量及制冷功率的影响。结果表明 ,提高吸附床导热有效导热系数 ,减小接触热阻可有效地改善吸附床的性能 ,为吸附床的优化设计提供了依据     

Magnetic hysteresis and refrigeration capacity of Ni—Mn—Ga alloys near Martensitic transformation

This paper studies the magnetic hysteresis and refrigeration capacity of Ni--Mn--Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni--Mn--Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni--Mn--Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni--Mn--Ga alloys should be investigated both on cooling and heating processes.     

天然气水合物泥浆制冷系统的野外试验研究

天然气水合物钻探取样过程中,泥浆制冷系统具有十分重要的作用。介绍了吉林大学研制的天然气水合物泥浆制冷系统的结构及工作原理。通过在西藏羌塘盆地、祁连山木里盆地和东北漠河盆地大兴安岭地区的野外应用试验,表明该套系统应用范围广,工作性能稳定可靠,可用于高海拔、高纬度的冻土带等特殊地区的水合物钻探。     

钙钛矿结构锰氧化物LaMn0.9Mg0.1O3的磁熵效应

采用传统的固相反应制备了钙钛矿结构锰氧化物L aM n0.9M g0.1O3多晶样品,并对其磁熵效应进行了研究。通过测量不同磁场下的磁化-温度曲线,发现伴随铁磁-顺磁相转变有一个大的磁熵变化,这个结果表明钙钛矿锰氧化物可以作为磁制冷技术中制冷材料。     

大冰期成因探讨

大冰期的形成不仅需要气温低，而且需要大量海水转移到大陆上形成冰川。元古代晚期全球规模白云岩建造形成之后，火山作用在洋壳和陆壳上的表现大不相同：洋壳型火山作用是岩浆静静涌出，大量蒸发海水；陆壳型火山作用是猛烈爆发，烘烤碳酸盐岩层产生二氧化碳喷发形成“干冰制冷机制”，使大气降温。洋壳型火山与陆壳型火山共同作用形成大冰期。震旦纪大冰期后开始了显生宙。大冰期与生物的演化发展密切相关的原因是二氧化碳的大量介入。     

广西气象局中心机房温度评估及解决方法

通过对影响广西气象局计算机中心机房环境温度的因素的分析,提出解决环境温度过高的具体办法。     

新型电致冷半导体探测器的应用

用于探测X射线的锂漂移型硅探测器需在液氮条件下低温保存和使用,因此限制了其应用范围。介绍了一种采用电致冷方式的新型半导体探测器,并通过把液氮致冷的Si(Li)探测器与电致冷的Si-PIN探测器进行比较,论证了电致冷方法的可行性。     

广西气象局中心机房温度评估及解决方法

通过对影响广西气象局计算机中心机房环境温度的因素的分析,提出解决环境温度过高的具体办法。