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91.
The intact preen wax esters of the red knot Calidris canutus were studied with gas chromatography/mass spectrometry (GC/MS) and GC/MS/MS. In this latter technique, transitions from the
molecular ion to fragment ions representing the fatty acid moiety of the wax esters were measured, providing additional resolution
to the analysis of wax esters. The C21−C32 wax esters are composed of complex mixtures of hundreds of individual isomers. The odd carbon-numbered wax esters are predominantly
composed of even carbon-numbered n-alcohols (C14, C16, and C18) esterified predominantly with odd carbon-numbered 2-methyl fatty acids (C7, C9, C11, and C13), resulting in relatively simple distributions. The even carbon-numbered wax esters show a far more complex distribution
due to a number of factors: (i) Their n-alcohol moieties are not dominated by even carbon-numbered n-alcohol moieties are not dominated by even carbon-numbered n-alcohols esterified with odd carbon-numbered 2-methyl fatty acids, but odd and even carbon-numbered n-alcohols participate in approximately equal amounts; (ii) odd carbon-numbered methyl-branched alcohols participate abundantly
in these wax ester clusters; and (iii) with increasing molecular weight, various isomers of the 2,6-, 2,8-, and 2,10-dimethyl
branched fatty acids also participate in the even carbon-numbered wax esters. The data demonstrate that there is a clear biosynthetic
control on the wax ester composition although the reasons for the complex chemistry of the waxes are not yet understood. 相似文献
92.
Fluor公司开发的Fluor SO_2净化工艺具有广泛多样的工艺布局,可以通过经济的方式定制脱除烟气中的有害组成。该工艺几乎能去除全部SO_2并减少CO排放。Fluor SO_x净化工艺的主要步骤已在多套工业装置中得到成功的证实。除技术可行、经济合理之外,Fluor SO_x净化工艺不会产生任何有害副产物,也不会遇到与SO_3 有关的腐蚀问题。此外,该工艺生产高纯度可市售的元素硫。论述了Fluor SO_x净化工艺的特征、技术和成本优势、设计和操作的简易性以及实施的便利性。 相似文献
93.
The absorption of tocopherols (α, γ, and σ) and fatty acids from rapeseed (RO), soybean (SOO), and sunflower (SUO) oil, both
from the natural oils and from the oils following moderate heating (180°C for 15 min), was measured in lymphcannulated rats.
Oils were administered as emulsions through a gastrostomy tube, and lymph samples were collected for 24 h. The composition
of tocopherols in oils and lymph fractions was measured by high-performance liquid chromatography, and fatty acids were measured
by gas-liquid chromatography. The highest accumulated transport of α-tocopherol was observed after SUO administration, the
lowest after SOO, with RO in between, corresponding to their relative contents (41.6±8.8, 32.7±5.0, and 24.9±4.3 μg at 24
h after administration of SUO, RO, and SOO, respectively). The calculated recoveries (in %) 24 h after oil administration
were 21.4±4.5, 45.7±7.0, and 78.8±13.5 for SUO, RO, and SOO, respectively, suggesting that the absorption efficiency decreased
when the α-tocopherol concentration increased. The recovery of α-tocopherol was higher than the recoveries of γ-and σ-tocopherol,
indicating that the different tocopherols were not absorbed to the same extent or with similar rates. No differences between
unheated and heated oils were observed in the absorption of tocopherols, whereas heating led to lower absorption of fatty
acids, thus showing no direct association between absorption of tocopherols and fatty acids. 相似文献
94.
Funke SA Otte N Eggert T Bocola M Jaeger KE Thiel W 《Protein engineering, design & selection : PEDS》2005,18(11):509-514
Chiral compounds can be produced efficiently by using biocatalysts. However, wild-type enzymes often do not meet the requirements of a production process, making optimization by rational design or directed evolution necessary. Here, we studied the lipase-catalyzed hydrolysis of the model substrate 1-(2-naphthyl)ethyl acetate both theoretically and experimentally. We found that a computational equivalent of alanine scanning mutagenesis based on QM/MM methodology can be applied to identify amino acid positions important for the activity of the enzyme. The theoretical results are consistent with concomitant experimental work using complete saturation mutagenesis and high-throughput screening of the target biocatalyst, a lipase from Bacillus subtilis. Both QM/MM-based calculations and molecular biology experiments identify histidine 76 as a residue that strongly affects the catalytic activity. The experiments demonstrate its important influence on enantioselectivity. 相似文献
95.
V.L.Siele M.Warman J.Leccacorvi R.W.Hutchinson R.Motto E.E.Gilbeit T.M.Benzinger M.D.Coburn R.K.Rohwer R.K.Davey 孙姣花 陈正衡 《火炸药》1982,(5)
本文叙述三种由乌洛托品制备奥托金(HMX)的新方法,每种方法都是先进行乙酰化然后再硝化,其中以DADN为中间产物的方法的HMX得率,比目前以乌洛托品和醋酐为基础的Bachmann法要高,但要采用后者不必采用的硫酸和聚磷酸。已经表明,DADN可在中间规模以良好的得率快速连续地生产,废酸回收也没有什么问题。 相似文献
96.
Controlling the familywise error rate in functional neuroimaging: a comparative review 总被引:1,自引:0,他引:1
Functional neuroimaging data embodies a massive multiple testing problem, where 100,000 correlated test statistics must be assessed. The familywise error rate, the chance of any false positives is the standard measure of Type I errors in multiple testing. In this paper we review and evaluate three approaches to thresholding images of test statistics: Bonferroni, random field and the permutation test. Owing to recent developments, improved Bonferroni procedures, such as Hochberg's methods, are now applicable to dependent data. Continuous random field methods use the smoothness of the image to adapt to the severity of the multiple testing problem. Also, increased computing power has made both permutation and bootstrap methods applicable to functional neuroimaging. We evaluate these approaches on t images using simulations and a collection of real datasets. We find that Bonferroni-related tests offer little improvement over Bonferroni, while the permutation method offers substantial improvement over the random field method for low smoothness and low degrees of freedom. We also show the limitations of trying to find an equivalent number of independent tests for an image of correlated test statistics. 相似文献
97.
壁面处湍流速度梯度脉动的测量对于深入了解壁面附近湍流的结构和传热、传质是很重要的.本文叙述了电化学法测量的原理,介绍了用一半圆电极对同时测量壁面上二维湍流速度梯度脉动的方法和测量结果.在直径0.194m的充分发展圆管湍流中,用碘和碘化钾溶液作为流动介质,半圆电极对直径为5×10~-4m,测得壁面处轴向和周向速度梯度的湍流脉动强度分别为0.3—0.33和0.11—0.12. 相似文献
98.
99.
分散剂在乳胶漆中的应用 总被引:1,自引:0,他引:1
综合实验结果和实际使用情况,讨论了涂料生产中聚磷酸盐与聚丙烯酸盐分散剂的应用情况,包括二者的配用以及不同涂料体系中分散剂的选择。 相似文献
100.
Lorenc-Kubis I Kowalska J Pochroń B Zuzło A Wilusz T 《Chembiochem : a European journal of chemical biology》2001,2(1):45-51
LUTI (Linum usitatissimum trypsin inhibitor), a member of the potato inhibitor I family, has been isolated from seeds of flax by ethanol fractionation, ion exchange chromatography on CM-Sephadex C-25, affinity purification on immobilized methylchymotrypsin (alpha-chymotrypsin in which His57 has been converted to 3-methylhistidine) in the presence of 5M NaCl, and finally by reversed-phase HPLC. The 7655 Da inhibitor consists of a single polypeptide chain of 69 residues with one disulfide bridge. The molecule is acetylated at the N terminus. Its primary structure has been determined after limited proteolysis of the native molecule with trypsin at the reactive site, cleavage with cyanogen bromide or arginyl endopeptidase (Arg-gingipain), and alcoholytic deacetylation of the N-terminally blocked serine. The association constants (K(a)) of LUTI with bovine beta-trypsin and alpha-chymotrypsin are 3.58x10(10) M(-1) and 5.02x10(5) M(-1), respectively. High NaCl concentration (3M) increased the association constant of LUTI with alpha-chymotrypsin to 6.64x10(7) M(-1). To our knowledge, LUTI is the first serine-proteinase-type inhibitor isolated from a plant of the Linaceae family. 相似文献