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1.
NIKITIN S.; PR?TZEL-WOLTERS D. 《IMA Journal of Mathematical Control and Information》1991,8(4):431-439
In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided. 相似文献
2.
The gas chromatographic separation of the components of a complex mixture of industrial solvents, not possible on a single stationary phase owing to coelution of some of the compounds, has been achieved on two serially connected wide bore capillary columns of different polarity. The analysis of a mixture of twenty five compounds was optimized using the serial gas chromatography theory of Purnell and Williams. The capacity factors of sample components measured with the two columns coupled in series were found to agree with those predicted by theory, regardless of the order in which they were connected. 相似文献
3.
Xiao Chi Ma Bao Jing Zhang Sha Deng Shan Shan Huang Ke Xin Liu Jing Ming Jia 《中国化学快报》2009,20(3):317-319
A new ent-labdane diterpenoid lactone with a new natural product was isolated from Andrographis paniculata. Their structures were elucidated on the basis of spectral evidences including 2D NMR. 相似文献
4.
A procedure previously described for the prediction of the plate height of capillary columns operated at different inlet pressure of the carrier gas and at various column temperatures by using few retention data measured under isobaric conditions was modified and improved in order to permit the prediction of the retention times and of the peak widths at various heights. It is therefore possible to calculate the ratio, delta, between the peak width at different heights and the peak width at half height, whose value is used to predict the resolution at different height of two closely eluting peaks. It was found that the delta values do not depend on temperature and inlet pressure and are a characteristic of the used column; they can therefore be used in order to calculate the resolution in any temperature and inlet pressure condition. The method was used to predict the retention time, the peak width and the resolution of polar and non-polar compounds (alkanes, alkenes, chloroalkanes, alcohols, ketones) on capillary columns of different length and polarity by using as the starting data retention and width values measured in three isobaric runs only. 相似文献
5.
An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c... 相似文献
6.
A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time. 相似文献
7.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
8.
Ball KA Castello PR Poyton RO 《Journal of photochemistry and photobiology. B, Biology》2011,102(3):182-191
Cytochrome c oxidase (Cco) has been reported to be a receptor for some of the beneficial effects of low intensity visible and near-infrared light on cells and tissues. Here, we have explored the role of low intensity light in affecting a newly described function of Cco, its ability to catalyze nitrite-dependent nitric oxide (NO) synthesis (Cco/NO). Using a new assay for Cco/NO we have found that both yeast and mouse brain mitochondrial Cco produce NO over a wide range of oxygen concentrations and that the rate of NO synthesis increases as the oxygen concentration decreases, becoming optimal under hypoxic conditions. Low intensity broad-spectrum light increases Cco/NO activity in an intensity-dependent fashion but has no effect on oxygen consumption by Cco. By using a series of bandpass filters and light emitting devices (LEDs) we have determined that maximal stimulation of Cco/NO activity is achieved by exposure to light whose central wavelength is 590 ± 14 nm. This wavelength of light stimulates Cco/NO synthesis at physiological nitrite concentrations. These findings raise the interesting possibility that low intensity light exerts a beneficial effect on cells and tissues by increasing NO synthesis catalyzed by Cco and offer a new explanation for the increase in NO bioavailability experienced by tissue exposed to light. 相似文献
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10.
Lúcio AS Almeida JR Barbosa-Filho JM Pita JC Branco MV Diniz Mde F Agra Mde F da-Cunha EV da Silva MS Tavares JF 《Molecules (Basel, Switzerland)》2011,16(8):7125-7131
Phytochemical investigation of Anaxagorea dolichocarpa Sprague & Sandwith led to isolation of three azaphenanthrene alkaloids: eupolauramine, sampangine and imbiline 1. Their chemical structures were established on the basis of spectroscopic data from IR, HR-ESI-MS, NMR (including 2D experiments) and comparison with the literature. Sampangine and imbiline 1 are being described in the Anaxagorea genus for the first time. Eupolauramine and sampangine show concentration-dependent antitumoral activity in leukemic cells K562 with IC(50) of 18.97 and 10.95 μg/mL, respectively. 相似文献