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1.
Excessive use of nitrogen fertilizers is known to increase the NO3 and reduce the vitamin C contents in fruits and vegetables. We investigated the concentration of these compounds in spinach leaves when plants were transferred to nitrogen-free media prior to their harvest. It was noted that a pre-harvest transfer of spinach to N-free media reduces the NO3 and increases the vitamin C content of the leaves by a substantial amount in a 2-3 day period. It is suggested that this technique may be suited to produce spinach or other leafy vegetables with low NO3 and high vitamin C contents under commercial hydroponic conditions.  相似文献   

2.
We have examined the carotenoid contents of several dark green vegetables found to be associated with a lower risk of various epithelial cancers in our epidemiological study and animal study. Samples of these vegetables were quantitatively examined by high-performance liquid chromatography (HPLC) on a C-18 reversed-phase column for individual carotenoid content. Pure reference compounds (alpha-carotene, beta-carotent, lycopene, canthaxanthin, and lutein) and internal standard (beta-Apo-8'-carotenal) were employed to quantify xanthophylls and carotenes in these vegetables. The results indicated that fresh, dark-green, leafy vegetables were high in beta-carotene (0.94-9.36 mg/100 g) and oxygenated carotenoids or xanthophylls, primarily lutein (0.94-7.39 mg/100 g), whereas lycopene and alpha-carotene were not prominent and canthaxanthin was non existent in these vegetables. These analyses suggest that consumption of carotenoids such as lutein in addition to beta-carotene may be associated with a lower risk of cancers.  相似文献   

3.
The purpose of this paper was to identify content changes in the main nutritional indicators of three com- mon leafy vegetables, and to provide a theoretical basis for the protection of leafy vegetables from acid rain. The ex- periment investigated the effects of simulated acid rain on four main nutritional indicators, including soluble sugar, total free amino acid, soluble protein and vitamin C during the application of simulated acid rain(SAR) in pak- choi(Brassica rapa chinensis), rape(Brassica campestris L.) and lettuce(Lactuca sativa Linn. vat. ramosa Hort). The vegetables were respectively exposed to SAR of pH=7.0, 5.6, 5.0, 4.0, 3.0 and a control level of pH=6.5. The con- centrations of the four main nutritional indicators were determined at harvest. The results show that nutritional quality of the three leafy vegetable species decreased with the declining of pH values of SAR. The higher the acidity of SAR was, the more significant the inhibitions were. Nutritional quality of lettuce was the most affected by simulated acid rain, followed by pakchoi and rape. The change range of soluble protein content was higher than those of the other three indicators' contents, which indicates that soluble protein is most sensitive to simulated acid rain.  相似文献   

4.
Using Chinese cabbage and rape as test material and examining the same soil conditions at different seasons(spring and autumn), the effects of mixed rare earth fertilizer on the yield and nutrient quality of leafy vegetables were studied to provide a theoretical basis for the application of mixed rare earth fertilizer in agriculture. Results showed a seasonal difference in the nutrient quality of Chinese cabbage and rape. For crops planted in autumn, the soluble sugar and vitamin C content were higher, the titratable acid and nitrate content were lower, and the sugar acid ratio was higher relative to crops planted in spring. Mixed rare earth treatments promoted growth of both crops during both seasons. The plot yield, stem and leaf fresh and dry matter weight, and dry and fresh ratio increased. These increases for Chinese cabbage were greater in autumn than in spring while for rape, the increases were greater in spring than autumn. The soluble sugar content, titratable acid content and sugar acid ratio were increased and the nitrate content decreased, in autumn the effects were more obvious than in spring. In spring, the vitamin C content was increased, and the increase was greater for Chinese cabbage than rape. In autumn, the vitamin C content decreased, and the decrease was greater for rape than Chinese cabbage. At the same time, the content of heavy metals such as Cu, Zn, Cd, Pb and Ni in stems and leaves decreased. This decrease was greater in spring for Chinese cabbage and in autumn for rape.  相似文献   

5.
The objectives of this study were to quantify the effectiveness of dietary retinol sources, orange fruit, and dark-green, leafy vegetables in improving vitamin A status, and to test whether orange fruit is a better source of vitamin A and carotenoids than are leafy vegetables. Anemic schoolchildren aged 7-11 y (n = 238) in West Java, Indonesia, were randomly allocated to 1 of 4 groups to consume 2 complete meals/d, 6 d/wk, for 9 wk: 1) 556 retinol equivalents (RE)/d from retinol-rich food (n = 48); 2) 509 RE/d from fruit (n = 49); 3) 684 RE/d from dark-green, leafy vegetables and carrots (n = 45); and 4) 44 RE/d from low-retinol, low-carotene food (n = 46). Mean changes in serum retinol concentrations of the retinol-rich, fruit, vegetable, and low-retinol, low-carotene groups were 0.23 (95% CI: 0.18, 0.28), 0.12 (0.06, 0.18), 0.07 (0.03,0.11), and 0.00 (-0.06, 0.05) micromol/L, respectively. Mean changes in serum beta-carotene concentrations in the vegetable and fruit groups were 0.14 (0.12, 0.17) and 0.52 (0.43, 0.60) micromol/L, respectively. Until now, it has been assumed that 6 microg dietary beta-carotene is equivalent to 1 RE. On the basis of this study, however, the equivalent of 1 RE would be 12 microg beta-carotene (95% CI: 6 microg, 29 microg) for fruit and 26 microg beta-carotene (95% CI: 13 microg, 76 microg) for leafy vegetables and carrots. Thus, the apparent mean vitamin A activity of carotenoids in fruit and in leafy vegetables and carrots was 50% (95% CI: 21%, 100%) and 23% (95% CI: 8%, 46%) of that assumed, respectively. This has important implications for choosing strategies for controlling vitamin A deficiency. Research should be directed toward ways of improving bioavailability and bioconversion of dietary carotenoids, focusing on factors such as intestinal parasites, absorption inhibitors, and food matrixes.  相似文献   

6.
建立了一个神经网络模型来预测球团矿的冷压强度,该网络模型采用三层前向BP神经网络,网络结构为12-12-1,12个输入变量分别为给料率、料层高度、焙烧温度、干透点温度、COREX煤气单耗、膨润土的添加量、生球水分、生球碳含量以及成品球的FeO、MgO、Al2O3含量和碱度;隐层含有12个神经元;输出为成品球团冷压强度;神经元激活函数选择双曲正切函数;神经网络学习算法使用的是带惯量项的误差反向传播学习算法(BP学习算法)。选取353组数据来训练和测试神经网络,其中247组数据用于训练网络,其余数据用于测试网络。测试结果表明,该网络的预测结果与实际结果的误差在3%以内,同时通过敏感性分析得出以下结论:①膨润土添加量、生球碳含量以及成品球的FeO、MgO、Al2O3含量和碱度对球团矿的冷压强度有重要影响;②增加膨润土添加量、成品球碱度、MgO含量、焙烧温度、干透点温度、COREX煤气单耗有助于改善球团矿的冷压强度;③增加FeO含量、生球碳含量、Al2O3含量、料层高度、给料率将使球团矿的冷压强度迅速下降;④增加生球水分会降低冷压强度;⑤提高球团矿冷压强度的参数设置(膨润土的添加量:0.86%~0.92%;wFeO<0.5%;生球碳含量:1.00%~1.10%;MgO含量:0.39%~0.44%);⑥在0.3~0.7范围内增加碱度不能显著改善球团矿的冷压强度。  相似文献   

7.
To unravel the functions of cell wall and vacuolar invertases in carrot, we used an antisense technique to generate transgenic carrot plants with reduced enzyme activity. Phenotypic alterations appeared at very early stages of development; indeed, the morphology of cotyledon-stage embryos was markedly changed. At the stage at which control plantlets had two to three leaves and one primary root, shoots of transgenic plantlets did not separate into individual leaves but consisted of stunted, interconnected green structures. When transgenic plantlets were grown on media containing a mixture of sucrose, glucose, and fructose rather than sucrose alone, the malformation was alleviated, and plantlets looked normal. Plantlets from hexose-containing media produced mature plants when transferred to soil. Plants expressing antisense mRNA for cell wall invertase had a bushy appearance due to the development of extra leaves, which accumulated elevated levels of sucrose and starch. Simultaneously, tap root development was markedly reduced, and the resulting smaller organs contained lower levels of carbohydrates. Compared with control plants, the dry weight leaf-to-root ratio of cell wall invertase antisense plants was shifted from 1:3 to 17:1. Plants expressing antisense mRNA for vacuolar invertase also had more leaves than did control plants, but tap roots developed normally, although they were smaller, and the leaf-to-root ratio was 1.5:1. Again, the carbohydrate content of leaves was elevated, and that of roots was reduced. Our data suggest that acid invertases play an important role in early plant development, most likely via control of sugar composition and metabolic fluxes. Later in plant development, both isoenzymes seem to have important functions in sucrose partitioning.  相似文献   

8.
In order to work towards further reduction of vitamin A deficiency in central Java, Indonesia, a social marketing campaign promoting eggs and dark-green leafy vegetables was initiated in March 1996. The nutritional surveillance system (December 1995-December 1996) found the following. The campaign's messages were well noticed. Consumption of at least one egg in the past week increased from 80% to 92% in mothers and from 78% to 92% in children 12-36 months old. It increased in all socio-economic groups and was independent of ownership of chickens. Most eggs had been purchased. The quantity of vegetables prepared increased from 93 to 111 g/person daily and most was purchased. Vitamin A intake increased from 335 to 371 RE/d for mothers and from 130 to 160 RE/d for children. Serum retinol levels increased after the start of the campaign, and were related to egg consumption and vitamin A intake. Because 1. data were collected in such a way that respondents were not aware of the link between data collected and the campaign, and 2. vitamin A status increased and was related to increased consumption of eggs and vitamin A intake, we conclude that the social marketing campaign was successful.  相似文献   

9.
Traditional vegetables in Kyoto are a unique group of vegetables that have been cultivated in limited areas near Kyoto city. We compared the traditional vegetables in Kyoto with common vegetables for the bio-antimutagenicity of their extracts against UV-induced mutation of E. coli B/r WP2. Among the traditional vegetables in Kyoto, Kamo eggplant (Solanaceae) and Katsura oriental pickling melon (Cucurbitaceae) showed higher bio-antimutagenicity and yield in the n-hexane, chloroform and ethyl acetate fractions than their common vegetable counterparts. Shishigatani pumpkin (Cucurbitaceae) possessed bio-antimutagenicity in the chloroform and ethyl acetate fractions, but common pumpkin did not. Polyphenolic compounds in the ethyl acetate fraction of plants are known to be related to antimutagenicity. However, the intensity of bio-antimutagenicity was not correlated with the polyphenol content in the ethyl acetate fractions of the present vegetables. In particular, Kamo eggplant possessed both polyphenolic and non-polyphenolic bio-antimutagenic sub-fractions in the ethyl acetate fraction. In the aqueous fraction, taro (Dioscoreaceae) was the most capable among our samples, whether being of common or traditional origin. Consequently, it is considered, that some traditional vegetables in Kyoto are superior to common vegetables in their bio-antimutagenicity and that these could be used as starting materials to identify new bio-antimutagens.  相似文献   

10.
Cryptosporidium parvum and Cyclospora cayetanensis are protozoan pathogens that cause prolonged diarrhea in both immunocompetent and immunocompromised hosts. Cryptosporidium parvum can be transmitted via the fecal-oral route, while the exact mechanisms of transmission of Cyclospora cayetanensis have not been fully determined. Humans appear to be the sole host for the latter and a distinct seasonality has been observed in endemic areas around the world. Samples of vegetables were collected at several small markets in a periurban slum in Peru during the seasons of high and low incidence. The vegetables were washed, the supernatants were collected and centrifuged, and the pellets were resuspended in a solution of 2.5% potassium dichromate. Pellets were examined using direct microscopic observation, acid-fast staining, and immunofluorescent assays for C. parvum and Cyclospora cayetanensis oocysts. Samples were collected during three time periods: the season of low incidence, the beginning of the season of high incidence, and end of the season of high incidence. Of the total vegetables examined, 14.5% contained C. parvum oocysts and 1.8% had Cyclospora oocysts. Thus, market vegetables may provide a route by which Cryptosporidium and Cyclospora can be transmitted. Our study also suggests that washing vegetables does not completely remove Cryptosporidium and Cyclospora oocysts.  相似文献   

11.
Food intake patterns of 545 adult Melbourne Chinese were studied in 1988 and 1989 using a 220-item food-frequency questionnaire appropriate for Chinese eating practices. Men and women were compared, adjusting for age, time in Australia and education. Men consumed more rice and alcoholic beverages as energy. In women, the energy intake was derived from foods of traditional Chinese types. There were two types of consumption patterns: in the first group were those who acculturated towards an Australian way of eating by replacing some traditional Chinese foods, such as rice, pork, leafy green and cruciferous vegetables, soups and tea, with 'new foods', such as wheat products, red meats and coffee; in the second were those who limited their intake to a handful of traditional Chinese foods as the major source of energy. The educated, the professional and those with an administrative profession, the Australian-born and those with a longer length of stay fitted into the first group, and were more acculturated towards Australia than those born in the People's Republic of China or Vietnam and who migrated at an older age. The first group may benefit from the best of both worlds, but may risk the diseases of an industrialised society. The second group may be trapped at a cultural crossroads and may be unable to make appropriate food choices. Public health efforts in Australia, where one in every five is overseas-born, should provide for nutrition and health education for new and aged migrants of non-European cultural backgrounds.  相似文献   

12.
还原气氛下高炉渣中含钛物相的变化规律是高炉渣高温碳化的关键。实验综合偏光显微镜、扫描电镜(SEM)、矿物自动解理系统(MLA)和X射线衍射仪(XRD)对比还原前后高炉渣物相形貌变化,微区成分变化及物相组成变化规律。结果表明,还原前后高炉渣中串珠状的钙钛矿转变为弥散状的碳化钛,深绿色板状的富钛透辉石消失不见;微区成分变化显著的是钛元素也从还原前高炉渣中的钙钛矿、攀钛透辉石和富钛透辉石中逐渐转移到碳化钛相和残留的含钛透辉石相中,其含量占还原后全钛的73.69%以上;还原后物相组成明显的变化是钙钛矿和富钛深绿透辉石的减少,碳化钛含量明显增多。  相似文献   

13.
李斌 《黄金》2016,(9):72-76
在研究区采集了132组植物样品,并对样品中As、Hg、Cu、Zn、Pb、Cd、Cr、Ni 8种重金属含量进行了测试,采用环境指数作为植物重金属污染评价方法来描述受污染程度,得出了不同种类植物的重金属污染状况。通过对比分析富集系数,研究了重金属在植物中的富集特征。其研究结果表明:不同植物中重金属含量超标倍数和吸收量明显不同,显示出选择性富集特征。该次采集的所有植物中As、Hg的含量都不超标;红薯中Cd和Pb的含量超标倍数最高,玉米中Zn的含量超标倍数最高,Cu也比较容易在粮食作物中累积且以红薯最为突出;蔬菜中Pb、Cd、Zn的含量超标倍数最高,以白萝卜、白菜最为突出;水果中Pb的含量超标倍数最高,且苹果和柿子都较为突出。该次采集的植物对Pb的吸收能力都很强,只有玉米对Zn的吸收能力比其对Pb的吸收能力略强。受到重金属污染的土壤所种植的粮食、蔬菜和水果均有不同程度的富集,其对重金属吸收强弱的排序分别为:白菜、白萝卜和胡萝卜中,PbZnCuNiCrCdHgAs;红薯和茄子中,PbCuZnNiCrHgCdAs;南瓜和苹果中,PbCuZnNiCrHgAsCd;柿子中,PbNiCuZnCrHgAsCd;玉米中,ZnPbCuNiCrHgAsCd;西红柿中,PbZnCuNiCrAsCdHg。  相似文献   

14.
《钢铁冶炼》2013,40(8):591-597
Abstract

Steel plants produce significant amounts of dust and sludge during iron and steel production. These wastes contain valuable elements, such as Fe, Cr, Ni, C, K and Na and should be handled properly to prevent them from polluting the environment. In order to utilise the BOF fine dust, the effects of the dust on cold bonded pelletising, solid state reduction and reduction melting behaviours of composite pellets made from iron ore and anthracite with added BOF fine dust were investigated at laboratory scale. The BOF dust was found to improve the cold compressive strength of the wet green carbon composite pellet, and increased with increasing dust content. Almost four times the amount of dust was needed to get the same effect on the strength of the pellet when it was used to replace bentonite. The carbothermic reduction of the composite pellet proceeded effectively at temperatures above 1200°C. The BOF dust had a positive effect on the reduction rate of the pellet, and the rate increased with increased dust content. The reduction of iron oxide was topochemical and conformed to a shrinking core kinetic model. The dust was found to improve the iron and slag melting separation rate of reduced pellets at 1400°C when its content was less than 23·11 wt-%. The liquidus temperature of the slag would decrease with the content of BOF dust increasing from zero to ~30 wt-% and then increase if the content continued to become more in the experiment. Utilising the BOF dust as the binder and flux to adjust the composition of the slag system can potentially reduce the slag ratio and production cost compared with using bentonite and limestone. This work can help to find a new process for the effective utilisation of BOF dust in a more appropriate and environmentally friendly way.  相似文献   

15.
OBJECTIVES: To assess the changes in carotenoid intake between 1987 and 1992 among US adults by sociodemographic characteristics and high-risk groups for chronic disease; and to identify the dietary sources of specific carotenoid intake. DESIGN: A food frequency questionnaire (FFQ) was collected from a representative sample of respondents to the 1987 and 1992 National Health Interview Surveys throughout two calendar quarters. Black and white adults, 18 to 69 years old, participated in 1987 (n = 8,161) and 1992 (n = 8,341). METHOD: FFQ data were matched and linked to the US Department of Agriculture-National Cancer Institute carotenoid food composition database for analysis. STATISTICAL ANALYSIS: Mean differences in carotenoid intake over time were compared by sociodemographic characteristics and region of the country, after adjustment for sampling weights in a multiple linear regression model. RESULTS: Mean intake of the carotenoid lutein declined among white women (18%), among adults aged 40 to 69 years (16%), among persons with 9 to 12 years of education (11%), among nondrinkers (18%), among drinkers of 1 to 6 alcoholic drinks/ week (7%), among smokers (former smokers by 11%, current smokers by 7%, and never smokers by 9%), among income groups (< $20,000 by 7%, > or = $20,000 by 9%), and residents in the south and northeast (by 13% each, respectively). Mean intake of the carotenoid lycopene increased among white men (9%), among adults aged 18 to 39 years and aged 40 to 69 years (by 5% and 6%, respectively), among those with 13 years of education or more (12.5%), among alcohol drinkers (by 10% and 7% for 1 to 6 vs 7 or more drinks/week, respectively), among former and current smokers (by 6% each), among those with incomes > or = $20,000 (8%), and among residents in the west (16%) and midwest (5%). All differences described were statistically significant (P < .01). APPLICATION: The decline in lutein intake (from dark green leafy vegetables), particularly in white women, may have public health implications as a result of the recognized inverse association between carotenoid intake and disease risk.  相似文献   

16.
采用50%返回料+50%新料的新工艺熔炼镍基K4169合金,进行了4次返回料的熔炼试验。采用金相显微镜及扫描电镜对新料合金及返回料合金的微观形貌进行了观察,用直读光谱仪对不同返回次数的合金进行了化学成分分析、对其力学和持久性能进行测试,研究了返回料熔炼对合金化学成分、微观组织及力学性能的影响。结果表明:随返回次数增加,化学成分无明显变化,合金的气体含量略呈下降趋势且总含量低于40×10-6,返回料冶炼过程中可不添加B和Zr。K4169合金凝固组织为典型枝晶结构,返回料对K4169合金的铸态枝晶组织没有明显影响。MC型碳化物及Laves相在热处理过程中部分分解,析出针片状δ相,在所有元素中,Nb的偏析最为严重,通过适当延长固溶处理时间可提高元素Nb的分布均匀性和抑制δ相的生成。返回料合金的室温拉伸强度及屈服强度随返回次数增加略有增加,合金的持久寿命较新料合金略有降低,但均明显超过现有技术标准规定的要求。熔炼的返回料合金具有良好的中温塑性,总体上与新料的质量水平相当。返回料合金的铸造性能与新料相当,可以代替新料用于铸件生产。  相似文献   

17.
The diminution of metamidophos residue levels with time in vegetables an greenhouse air was investigated after treatment of tomatoes and green beans. A gas chromatographic method using dichloromethane as an extraction solvent has been developed to analyse metamidophos in vegetables, with obtained recoveries higher than 89%. The reliability of several sorbents for air sampling was tested using standard atmospheres resulting in recoveries higher than 90% from PUF, XAD-2, XAD-4 and Supelpak using Soxhlet extraction with acetone. The dissipation of metamidophos in greenhouse air was studied 52 h after application. Finally the effect of crop, type of greenhouse, season and dose applied on the dissipation kinetic of metamidophos in vegetables, was statisTically studied by analysis of variance resulting in crop and season being the most significant factors.  相似文献   

18.
Vitamin K is needed to synthesize coagulation factors II (prothrombin), VII, IX, and X through the carboxylation of glutamic acid in vitamin K-dependent proteins which results in the creation of effective calcium binding sites which, in turn, facilitates the coagulation process. Vitamin K exists as naturally occurring vitamin K-I (phylloquinone) in green leafy vegetables and vegetable oils, vitamin K-II (menaquinone) as produced in the gut by bacteroides fragilis and E. coli, and synthetic vitamin K-III (menadoine sodium bisulfite) which is water-soluble and capable of producing serious jaundice in newborns, especially those with instability of glutathione and deficiency of G6PD. Humans require about 5 mcg of vitamin K daily. Since it is indigenously produced in the gut by bacterial flora, dietary deficiency of vitamin K in healthy subjects is rare. Vitamin K is usually the first vitamin given at birth. Newborn babies, however, absorb only approximately 30% of ingested vitamin K, compared to 50-70% in adults. Hemorrhagic disease is a manifestation of vitamin K deficiency in newborn infants. Hemorrhagic disease of the newborn (HDN), early HDN, classical HDN, and late HDN are discussed. The American Academy of Pediatrics recommended in 1961 that all healthy term newborn babies receive 0.5-1.0 mg of vitamin K-I intramuscularly at birth. However, while the authors have not followed those recommendations in their neonatal unit for 15 years, they have experienced only a 0.1% incidence of classical HDN. High-risk newborns at the unit are routinely given the recommended dose of K-I at birth.  相似文献   

19.
Prediction of accurate dielectric property data from fundamental principles for systems as complex as foods has not been possible. Simple prediction models based on easily measurable composition data can serve many useful purposes. Literature dielectric data on foods and their composition were statistically correlated. Dielectric data on salt solutions were measured to explain some of the results. When composition data were not available, standard handbook compositions were used. Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition. Based on a smaller data set of meats, both dielectric constant and loss increased with water and salt content. Dielectric constant generally decreased with temperature whereas dielectric loss decreased with temperature at lower salt concentrations and increased with temperature at higher salt concentrations.  相似文献   

20.
成分配比对自蔓延高温合成Ni-Al化合物的影响   总被引:1,自引:0,他引:1  
本文以镍粉和铝粉为主要原料,采用自蔓延高温合成技术,制备Ni-Al基金属间化合物。研究了成分配比对热爆反应的影响,绘制了热爆反应曲线,分析了热爆反应机理及产物的显微组织特征。研究结果表明:成分配比和压坯密度对热爆反应均有不同程度的影响。增加Al含量、加大压坯密度都会缩短热爆起始时间、降低热爆起始温度,反应起始温度低于Ni-Al系的最低共晶温度(640℃),本文初步确定了Ni-Al系的热爆反应是由固-固扩散反应引发的,Ni-32Al的反应产物为均一的NiAl相。  相似文献   

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