基于分形插值的三维路面重构与分析

原始精细的路面谱是研究车辆与路面耦合的重要基础,对车辆的通过性和噪声、振动及不平顺性NVH(noise,vibration and harshness)分析有重要的应用价值。为了构建与原始路面相同或相近的路面谱,利用非接触式激光路面不平度仪测量沥青路面、水泥路面、比利时路面和砂石路面的三维路面不平度;基于分形理论,采用迭代函数法重构这四种路面谱;结合路面不平度的统计特性评价指标和分形维数对四种路面的原始谱和重构谱进行评价。研究结果表明:重构前、后路面谱的平均值、标准差、峰度系数以及分形维数变化范围在±5%以内,除水泥路面的偏态系数变化范围均在±9%以内,重构路面谱与原始谱具有一致性;重构路面谱保持了原始路面的结构特性,并具有路面的细微结构。     

Liquid chromatographic determination of vitamins D2 and D3 in fortified milk and infant formulas

A liquid chromatographic (LC) method was developed for determining vitamins D2 and D3 in fortified milk and infant formulas. The lipid-soluble components were extracted from the aqueous phase by homogenizing in isopropanol-methylene chloride with magnesium sulfate added to remove water. The vitamins were fractionated from the lipid material by using gel permeation chromatography (GPC) followed by further cleanup of the combined GPC fractions on a muBondapak/NH2 column. Four muStyragel (100 A) columns connected in series were used for GPC fractionation of sample extracts in methylene chloride. Injection and collection were repeated 3 times to collect enough vitamin D for quantitation. The muBondapak/NH2 column, using a mobile phase of methylene chloride-isooctane-isopropanol (600 + 400 + 1), resolved vitamin D from other UV-absorbing compounds and soy sterols in infant formula and from cholesterol in milk. Vitamins D2 and D3 coeluted as one peak, with the resolution and vitamin level sufficient for visual monitoring (280 nm/0.02 absorbance unit full scale) in a collection time of 22-26 min. A Zorbax ODS (6 micron) column and a methylene chloride-acetonitrile-methanol (300 + 700 + 2) mobile phase were used for LC quantitation; vitamins D2 and D3 were baseline resolved in about 11 min. The infant formula samples included ready-to-use and concentrated liquids prepared in nonfat milk base or soy base fortified with vitamins D2 or D3 at 400 IU/qt or L (10 micrograms). The mean percent recovery of added vitamin D3 (400-500 IU/qt) from infant formula (n = 7) was 89.6 +/- 6.7 (coefficient of variation (CV) 7.5%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Screening method for vitamins A and D in fortified skim milk, chocolate milk, and vitamin D liquid concentrates

Vitamin A was determined in fortified chocolate milk and skim milk; vitamin D was determined in fortified chocolate milk, skim milk, and vitamin D concentrates, using reverse phase high pressure liquid chromatography (HPLC). The sample is saponified, extracted with hexane, and chromatographed in an HPLC system on a 10 micron Vydac TP reverse phase C18 column, using acetonitrile-methanol (9+1) as the mobile phase. For 6 replicates, the recoveries of vitamins A and D, using this procedure, were 99 and 98%, respectively.     

基于可视化类库的植株三维形态配准方法及点云可视化

精确的植物三维静态形态结构模型有助于植物空间结构相关的各种研究,是虚拟植物、植物建模等问题研究的一个重要方面。研究植物生长过程中的三维信息的获取可以获得作物生长过程中各参数的动态数据,可为精细农业植物生长模型建立等提供依据。该文以植物为研究对象,介绍了虚拟植物及植物三维可视化的研究现状,讨论了植物叶片三维可视化的可行性及必要性。针对植物三维点云的采集与处理上,讨论了三维扫描仪的精度测定方法,并针对基于基准体的植株点云配准问题,提出采用基准体点云平均法向量计算的方法,去除了部分基准体表面的噪声点,提高了植株体的配准精度;采用迭代最近点（iterative closest point,ICP）算法,对植株叶片进行进一步的高精度配准。最后采用基于可视化类库VTK(visualization toolkit)实现了植物点云配准与三维可视化。     

Effect of short-term UVB exposure on vitamin D concentration of eggs and vitamin D status of laying hens

Vitamin D deficiency in humans is widespread, and only a few food items are important natural sources of vitamin D. This study investigated the effect of UVB exposure of laying hens on the vitamin D content in egg yolk. In a two-factorial design, hens fed a vitamin D-deficient (-D) or -adequate (+D) diet were nonexposed or exposed to UVB light over a period of 4 weeks. UVB exposure of the -D group caused nearly normal egg production rate and egg shell quality; exposure of the +D group did not further improve these parameters. UVB exposure tended to improve the concentration of plasma 25-hydroxycholecalciferol (25(OH)D(3)), but had no effect on 1,25-dihydroxycholecalciferol in plasma or on cholecalciferol and 25(OH)D(3) in egg yolk. The present study shows that a short-term exposure of laying hens to UVB light is not an appropriate way to improve the vitamin D content of egg yolk.     

Effect of different vitamin D supplementations in poultry feed on vitamin D content of eggs and chicken meat

According to a new European Union regulation, vitamin D(3) can be partially or totally substituted with 25-hydroxyvitamin D(3) (25-OH-D(3)) in hens' feed. The purpose of this study was to clarify how this regulation has affected the vitamin D content of commercial eggs and chicken meat. Another aim was to investigate how effectively 25-OH-D(3) is transferred from the hens' diet to egg yolk by analyzing eggs from farms using known commercial feeds and by conducting an animal study. Vitamin D determinations were made by HPLC methods. The vitamin D(3) contents of two commercial egg yolk pools were 4.9 ± 0.14 and 4.0 ± 0.10 μg/100 g, and the 25-OH-D(3) contents were 1.3 ± 0.19 and 1.0 ± 0.07 μg/100 g. The chicken meat pools contained 0.2-0.3 μg of vitamin D(3)/100 g, whereas the content of 25-OH-D(3) was ≤0.2 μg/100 g. These results are comparable to earlier data. The animal and farm studies showed that 25-OH-D(3) was effectively transferred from the hens' diet to yolk. However, because the relative activity between 25-OH-D(3) and vitamin D(3) is unknown, it remains questionable whether the use of 25-OH-D(3) in hens' feed is beneficial to human vitamin D intake from eggs.     

Seasonal variation of provitamin D2 and vitamin D2 in perennial ryegrass (Lolium perenne L.)

Ergosterol (provitamin D(2)) is converted to vitamin D(2) in grass by exposure to UV light. Six varieties of perennial ryegrass (Lolium perenne L.) were harvested four times during the season, and the contents of vitamin D(2) and ergosterol were analyzed by a sensitive and selective liquid chromatography tandem mass spectrometry method. Weather factors were recorded, and a principal component analysis was performed to study which factors were important for the formation of vitamin D(2). The results suggest that a combination of weather factors is involved and that the contents of ergosterol and vitamin D(2) change more than a factor of 10 during the season. These results demonstrate that grass potentially can be a significant source of vitamin D for grazing animals and animals fed on silage and hay.     

植物中γ-亚麻酸合成关键酶——△^6-脂肪酸脱氢酶

γ-亚麻酸作为人体必需的不饱和脂肪酸，对人体的激素调节及脂肪酸代谢发挥着重要的生理作用。△^6-脂肪酸脱氢酶是多不饱和脂肪酸合成途径中的限速酶。本文介绍了不饱和脂肪酸γ-亚麻酸代谢途径中的关键酶△^6-脂肪酸脱氢酶的结构功能与目前△^6-脂肪酸脱氢酶的基因工程研究进展，并对其应用进行了展望，以期为利用基因工程手段生产γ-亚麻酸提供参考。