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排序方式: 共有798条查询结果,搜索用时 62 毫秒
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Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal 总被引:1,自引:0,他引:1
José A. Mestre Prates Mário A. Gonçalves Quaresma Rui J. Branquinho Bessa Carlos M.G. Andrade Fontes Cristina M.P. Mateus Alfaia 《Food chemistry》2006
A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality. 相似文献
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Tomoo Yamamura Yoshinobu ShiokawaHajimu Yamana Hirotake Moriyama 《Electrochimica acta》2002,48(1):43-50
The redox flow battery using uranium as the negative and the positive active materials in polar aprotic solvents was proposed. In order to establish the guiding principle for the uranium compounds as the active materials, the investigation of uranium β-diketonate complexes was conducted on (i) the solubility of active materials, (ii) the electrode reaction of U(VI) and U(IV) β-diketonate complexes and (iii) the estimation of the open circuit voltage of the battery. The solubilities of higher than 0.8 mol dm−3 of U(VI) complexes and higher than 0.4 mol dm−3 of a U(IV) complex were obtained in the solvents. The electrode reactions of U(pta)4, UO2(dpm)2, UO2(fod)2 and UO2(pta)2 were first studied and the redox potentials of uranium β-diketonates were thermodynamically discussed. The open circuit voltage is estimated more than 1 V by using Hacac or Hdpm. The larger open circuit voltage is expected when a ligand with the larger basicity is used. 相似文献
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A notable amount of PP β-crystal (30%, by X-ray diffraction pattern) has been found in the PP samples as polymerized at normal static isothermal crystallization conditions without using any extra nucleating agents. Existence of catalyst residues in the sample is decisive, which slows down the crystallization rate facilitating the formation of β-form spherulites. Comparatively, high molecular weight PP favors the formation of β-form spherulites, deducting from no β-crystal detected in the degraded samples. Finally, high isotacticity is also required for obtaining qualitative β-form spherulites, demonstrated by increased β-crystal content after removal of weak crystalline fraction of the sample. 相似文献
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A simple solid state technique for electrochemical micromachining of metal substrates using a metal ion conductor (Na-β″-Al2O3) was proposed. The fundamental solid electrochemical cell consists of a (anode) metal substrate (M = Ag, Cu, Zn, and Pb)/pyramidal Na-β″-Al2O3/Ag (cathode) system, where the contact diameter between M/Na-β″-Al2O3 was extremely small, on the order of a few micrometer. Under an applied electric field, the metal substrate was electrochemically oxidized to metal ions (Mn+) at the M/Na-β″-Al2O3 microcontact. These Mn+ ions migrated into the Na-β″-Al2O3. As a result of continuous electrolysis, the metal substrate was locally consumed at the microcontact, and thus solid state electrochemical micromachining was accomplished. As expected, the machining size or depth depended on the electrolysis conditions (current, operating time) and the apex configuration of pyramidal Na-β″-Al2O3. Moreover, the scanning of the Na-β″-Al2O3 pyramid during electrolysis produced a fine patterned metal substrate. In the present paper, solid state electrochemical micromachining was performed for several metal substrates, and its advantages and disadvantages vis-a-vis the conventional electrochemical micromachining method are discussed in detail. 相似文献
7.
以环氧氯丙烷(EPI)为交联剂,在碱性介质中合成了β-环糊精(-βCD)水溶性交联聚合物,并以其为基体,以硝酸铈铵(CAN)为引发剂,在弱酸性条件下,合成出了新型的水溶性交联-βCD接枝聚丙烯酰胺(PAM)的共聚物絮凝剂(WCDP).对产物的红外光谱分析(FTIR)表明WCDP的合成是成功的.研究了WCDP的制备条件(交联剂用量、引发剂用量、温度、时间等)对吸附有机污染物和除浊性能的影响,结果表明:在最佳合成条件下,WCDP能同时去除水中的浊度和小分子有机污染物,并能形成絮体从水中分离.以高岭土和对硝基苯酚(p-NP)为研究对象,WCDP对浊度和p-NP的去除率分别为96.7%和60.6%. 相似文献
8.
谢荣源 《江苏工业学院学报》2014,(3):56-63
综述了阿尔茨海默病的药物治疗研究进展,包括乙酰胆碱酯酶抑制剂,NMDA受体拮抗剂,非甾体类抗炎药,抗氧化剂,免疫治疗以及针对Aβ的其它治疗手段等. 相似文献
9.
蛋白酪氨酸激酶在肿瘤细胞的增殖、分化、转移、侵蚀等信号通路中具有重要的调控功能,已成为肿瘤靶向治疗的重点研究对象。基于靶点导向原则和构效关系研究基础,以抗肿瘤活性天然产物Goniothalamin为母体化合物,修饰合成了一系列γ,γ-二氟取代Goniothalamin类似物(4a-4i,6a-6i)和γ-单氟取代Goniothalamin类似物(7a,7b,7h)。γ,γ-二氟取代的Goniothalamin类似物可从具有光学活性的二氟亚甲基取代的锡试剂出发,经Stille偶联和1,5-氧化关环两步关键反应合成。γ-单氟取代Goniothalamin类似物则经Sharpless不对称环氧化、环氧开环亲核氟化、Lindlar氢化、HWE反应和1,5-氧化关环等反应制备。对所合成的这两类Goniothalamin含氟类似物进行了体外肿瘤细胞抑制活性和酪氨酸激酶抑制活性评估研究,结果表明在Goniothalamin分子的γ位引入一个氟原子进行修饰是较为合理的修饰方式。 相似文献
10.
Rare earth (RE) ions have spectroscopic characteristics to emit light in narrow lines, which makes RE complexes with organic ligands candidates for full color OLED (Organic Light Emitting Diode) applications. In particular, β-diketone rare earth (RE3+) complexes show high fluorescence emission efficiency due to the high absorption coefficient of the β-diketone and energy transfer to the central ion. In this work, the fabrication and the electroluminescent properties of devices containing a double and triple-layer OLED using a new β-diketone complex, [Eu(bmdm)3(tppo)2], as transporting and emitting layers are compared and discussed. The double and triple-layer devices based on this complex present the following configurations respectively: device 1: ITO/TPD (40 nm)/[Eu(bmdm)3(tppo)2] (40 nm)/Al (150 nm); device 2: ITO/TPD (40 nm)/[Eu(bmdm)3(tppo)2] (40 nm)/Alq3 (20 nm)/Al (150 nm) and device 3: ITO/TPD (40 nm)/bmdm-ligand (40 nm)/Al (150 nm), were TPD is (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1-biphenil-4,4-diamine) and bmdm is butyl methoxy-dibenzoyl-methane. All the films were deposited by thermal evaporation carried out in a high vacuum system. These devices exhibit high intensity photo- (PL) and electro-luminescent (EL) emission. Electroluminescence spectra show emission from Eu3+ ions attributed to the 5D0 to 7FJ (J = 0, 1, 2, 3 and 4) transitions with the hypersensitive 5D0 → 7F2 transition (around 612 nm) as the most prominent one. Moreover, a transition from 5D1 to 7F1 is also observed around 538 nm. The OLED light emission was almost linear with the current density. The EL CIE chromaticity coordinates (X = 0.66 and Y = 0.33) show the dominant wavelength, λd = 609 nm, and the color gamut achieved by this device is 0.99 in the CIE color space. 相似文献