排序方式： 共有12条查询结果，搜索用时 15 毫秒
1.
2.
不同萃取头固相微萃取提取分析饲料香味剂致香成分 总被引：1，自引：0，他引：1
采用CAR/PDMS和PDMS/DVB两种萃取头的固相微萃取(SPME)提取乳香饲料香味剂挥发性成分,经气相色谱-质谱联用(GC-MS)对挥发性成分进行鉴定,分析比较两种萃取头提取的挥发性成分差别,确定适宜的萃取头。结果表明:两种萃取头的固相微萃取共检测出27种挥发性成分,CAR/PDMS提取数量为24种,PDMS/DVB为18种。采用CAR-PDMS萃取头获得的苯甲醇、丙位辛内酯、茴香脑、洋茉莉醛、丁酸苄酯的峰面积要高于PDMS/DVB萃取头,而前者丙位壬内酯、乙基香兰素峰面积分别稍低于后者。CAR/PDMS萃取头获得的挥发性物质的总峰面积均高于PDMS/DVB萃取头(即557.30×107vs426.72×107)。因此,根据获得挥发性物质数量和总峰面积,CAR/PDMS萃取头比PDMS/DVB萃取头更适于提取分析乳香型饲料香味剂致香成分。 相似文献
3.
Nowadays, consumers demand dietary fibre-enriched products of appropriate taste, texture, smell and appearance. Unfortunately, addition of the dietary fibre supplements to bread significantly reduces its quality which is connected with changes in the structure of gluten proteins. Structural changes as well as changes in the water state of gluten matrix induced by eight dietary fibres were observed by using Fourier transform infrared spectroscopy. To facilitate this the difference spectra were calculated by subtraction of the control (gluten only) infrared spectrum from the spectra of gluten-fibre mixtures. The presence of positive bands at ca. 1597 and 1235 cm−1 indicated aggregation of gluten proteins into hydrogen bonded β-sheets. These β-sheets can be formed by other β-sheets, antiparallel-β-sheets, β-turns and/or α-helices. The aggregation is probably induced by partial dehydration of gluten matrix due to competition for water molecules between gluten proteins and fibre polysaccharides. This assumption is confirmed by the presence of the negative band at 3237 cm−1 and decrease in the intensity of the band at 3051 cm−1. These bands are assigned to the weak and strong H-bonds in the gluten matrix, respectively. The results indicated that both weak and strong H-bonds are necessary to dough formation of adequate rheological properties. 相似文献
4.
ADAMS在汽车操纵稳定性评价中的应用 总被引：1，自引：0，他引：1
汽车的操纵稳定性是汽车的重要性能之一,其中悬架又是决定车辆操纵稳定性的重要元件,它对减少来自路面对车身的冲击和振动也起着非常重要的作用。本文利用ADAMS软件提供的CAR和insight模块分别建立了悬架模型,并计算和分析了悬架设计点坐标和悬架其它参数对汽车操纵稳定性的灵敏度大小,并在灵敏度分析的基础上对影响操纵稳定性较大的参数进行优化,取得了较好的结果。 相似文献
5.
In the arbuscular mycorrhizal (AM) symbiosis, plants take up part of the nitrogen (N) through a mycorrhizal pathway. In this study, we assessed the effect of different N sources on the expression of genes coding for enzymes and transporters of the mycorrhizal N uptake pathway, using Sorghum bicolor and Glomus intraradices as a model. Some of the genes investigated were differentially regulated in the intraradical and in the extraradical mycelium depending on the N source. In AM roots, some fungal and plant genes were co-regulated, suggesting an interdependence of both partners in the mycorrhizal N uptake pathway. Mycorrhizal N transfer may have a preference for glycine (plant growth and N uptake stimulation). 相似文献
6.
基于ADAMS/CAR的麦弗逊悬架优化设计 总被引：7，自引：0，他引：7
汽车悬架系统为一多体系统,部件之间的运动关系十分复杂,传统的人工计算很难将悬架的各种特性表述清楚。以国产某轿车为例,应用多体运动学与动力学仿真软件ADAMS中的CAR专业模块建立该车的前后悬架多刚体模型,对其悬架的各种性能进行了仿真分析,研究了悬架几何参数对汽车操纵稳定性的影响,在理论验证的基础上揭示了该悬架的运动规律,在进行优化分析的同时还提出了改进的意见。 相似文献
7.
底盘调校是通过改变弹簧、稳定杆、减振器等性能件的性能参数,使整车操稳性和平顺性达到最优化。底盘调校初期,需对整车性能进行评价,然后对性能件的规格进行策划,即制定最终开发的调校样件。以某车型底盘调校方案的策划为例,采用ADAMS/CAR与CARSIM相结合的仿真分析方法,确定底盘调校样件的规格。同时,通过调校样件规格的不同组合各种调校方案,在分析各种调校方案优劣的基础上,确定初始调校方案,为该轿车实车调校提供理论依据。通过初期的仿真分析,可减少调校样件的制备规格,节约开发成本,缩减调校周期。 相似文献
8.
《Journal of Cereal Science》2014,59(3):479-487
The impact of high hydrostatic-pressure (HHP) processing on the volatile profile of cooked Japonica rice (Wuchang) and Jasmine rice (Complete Wheel) was investigated by SPME–GC/MS. Presoaked samples were treated at 200, 400 and 600 MPa for 10 min and then cooked for volatile compound analysis. Seventy-seven compounds were identified in two cooked rice varieties: 20 aldehydes, 16 alcohols, 14 ketones, 9 arenes, 7 esters, 5 alkanes, 3 olefins and 3 hetero-cycle compounds. Results showed that both pressure level (P < 0.01) and rice variety (0.01 < P < 0.05) significantly impact the volatile compounds in rice and there is also an interaction between pressure and rice variety (P < 0.01). Overall, HPP decreased the amount of aldehydes more obviously in Complete Wheel rice than that in Wuchang variety. Both 200 and 400 MPa increased the levels of alcohols, ketones, esters and olefins, but reduced those of heterocycles, alkanes and arenes. Similar volatile change trends were found at 600 MPa except the concentration of each component was closer to that of control group. Based on the changes in the three key flavor compounds in rice (aldehydes, alcohols and ketones), the HPP process could be a suitable alternative to traditional pretreatment for improving flavor in cooked rice. 相似文献
9.
Hui-Ping Wang Yu-Jie Liang Qi Zhang Ding-Xin LongWei Li Li LiLin Yang Xian-Zhong Yan Yi-Jun Wu 《Pesticide biochemistry and physiology》2011,101(3):232-239
Previous studies have demonstrated that the anticholinesterase pesticides chlorpyrifos and carbaryl are neurotoxic to mammals. However, the toxicity of these pesticides to other organs and their potential interactive effects remain unclear. Our goal in this study was to assess the toxicities of ingestion of chlorpyrifos and carbaryl both separately, and in combination to non-nervous systems, especially the effect on urinary metabolic profiles, in rats. Chlorpyrifos, carbaryl and a mixture of these pesticides, were administered orally to Wistar rats for 90 consecutive days. Histopathological examination of liver and kidney and metabonomic analysis based on the urinary 1H nuclear magnetic resonance spectra were used to investigate the toxic effects. The results showed that no histopathological changes were observed in the liver or kidney tissues, but metabonomic analysis revealed alternations in a number of urinary metabolites involving in the energy metabolism in liver mitochondria. Treatment of rats with chlorpyrifos alone led to an increase in creatine, glycine, dimethylglycine, dimethylamine, glutamine, succinate, alanine, lactate, and glucose. The categories of main differential urinary metabolites in carbaryl-treated rats were similar to those in chlorpyrifos-treated rats, whereas the changes were of varying degree. A combination of a low dose of chlorpyrifos and carbaryl resulted in an increase in the levels of main urinary metabolites compared to the controls, and the increase in signal intensity of the main metabolites was lower than that in the rats exposed to chlorpyrifos or carbaryl alone. All above results suggest that chronic exposure to chlorpyrifos and carbaryl alone, or in combination could cause disturbance of metabolic function in liver mitochondria and renal failure. Overall, we have shown that urine metabonomic analysis is non-invasive, sensitive, and relatively fast for assessing the individual or mutual effects following exposure to pesticides. 相似文献
10.
关中平原渠井双灌区地下水循环对环境变化的响应 总被引：4，自引：4，他引：0
为促进陕西关中平原渠井双灌区地下水良性循环,保障灌区水资源高效安全利用,以泾惠渠灌区为例,分析了灌区多年来地下水系统外部环境因素及地下水循环要素的变化特征,基于多变量时间序列CAR(controlled auto-regressive)模型建立了地下水位动态对环境变化的响应模型,利用验证后的模型对灌区不同环境变化情景下的地下水位埋深进行了模拟。研究结果表明:降水、蒸发、渠首引水、渠井用水比例是影响灌区地下水循环的主要外部环境因素;降水量减少、蒸发量增加,地下水各项补给量减少、排泄量增加,使得地下水位逐年下降,近34 a累计下降11.8 m;在多年平均降水量情景Ⅰ下(近56 a均值:513 mm),维持灌区地下水良性循环的适宜渠井用水比例为1.53,在多年平均降水量减少5%,即降水情景Ⅱ下(487 mm),适宜渠井用水比例为1.61。环境变化下不同渠井用水方案的研究,有利于灌区地下水的良性循环,可为灌区制定高效安全用水对策提供依据。 相似文献