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541.
This report describes a high-throughput method for measuring the enantiomeric excess of allylic acetates. Such methods are useful tools for screening libraries of potential catalysts for enantioselective reactions. This technique, which is called EMDee for an enzymatic method for determining enantiomeric excess, uses the lipase from Pseudomonas cepacia to hydrolyze the (R) enantiomer of an allylic acetate, while the (S) enantiomer does not react. The rate of the reaction is monitored by measuring the acetic acid that is produced during the hydrolysis reaction with a pH indicator. Using the Michaelis-Menten equation, the rate of the reaction can be correlated with the concentration of the (R) enantiomer. This method can process 88 samples in less that 30 min. 相似文献
542.
Let T and A be two nonnegative regular summability matrices and W(T,p)∩l∞ and cA(b) denote the spaces of all bounded strongly T-summable sequences with index p>0, and bounded summability domain of A, respectively. In this paper we show, among other things, that is a multiplier from W(T,p)∩l∞ into cA(b) if and only if any subset K of positive integers that has T-density zero implies that K has A-density zero. These results are used to characterize the A-statistical comparisons for both bounded as well as arbitrary sequences. Using the concept of A-statistical Tauberian rate, we also show that is not a multiplier from W(T,p)∩l∞ into cA(b) that leads to a Steinhaus type result. 相似文献
543.
Solving a temperature problem of the theory of elasticity with a known thermoelastic potential is reduced to finding scalar-
and vector-valued analytic functions of two complex variables that satisfy the boundary condition and are solutions of the
basic and adjoint problems of elasticity theory respectively.
Translated fromMatematichni Metodi i Fiziko-mekhanichni Polya, Vol, 40, No. 1, pp. 45–48. 相似文献
544.
N. Onur 《Heat and Mass Transfer》1993,28(3):141-145
Presented in this abstract are the considerations and results of an investigation of forced convective heat loss from the surface of flat-plate model collectors flush mounted on the roof of a model residential house. Forced convection with air as the external fluid was treated.The study was motivated by the need to better understand heat transfer from the top surface of flat-plate solar energy collectors. The experimental work dealt with heat transfer from the top of rectangular parallelpipeds flush mounted on roof of a model residential house. The smallest collector was 7.62×10–2 m long by 7.62×10–2 m wide by 3.3×10–2 m deep, and the largest collector was 15.875×10–2 m long by 15.875×10–2 m wide by 3.3×10–2 m deep. These small scale units are expected to simulate heat loss pattern from a flat-plate solar collector placed over the roof of a residential dwelling. Experiments were performed to determine the average heat transfer coefficients for forced convective air flow over the surface of the model collector which was inclined and yawed relative to the incoming air flow. The wind speeds varied approximately from 2.5 m/sec to 15 m/sec, the flow was laminar for all wind speeds.
Konvektiver Wärmeübergang von Flachplatten-Kollektoren auf den Dächern von Wohnhäusern im Modellversuch
Zusammenfassung Es werden Vorüberlegungen und Ergebnisse bezüglich einer Untersuchung mitgeteilt, deren Ziel es war, die Wärmeverluste infolge Zwangskonvektion von Flachplatten-Kollektoren auf den Dächern von Wohnhäusern im Kleinmodell zu bestimmen. Angeregt wurde die Studie durch den Bedarf an genaueren Berechnungsunterlagen für den Wärmeübergang an Flachplatten-Solarkollektoren. Die für das Experiment verwendeten zwei Kollektoren waren quadratisch, mit den Seitenlägen 7,62 bzw. 15,9 cm, bei jeweils 3,3 cm Tiefe. Die Versuche lieferten unter Zwangskonvektion mittlere Wärmeübergangskoeffizienten an den Oberflächen der Modellkollektoren, welche zur ankommenden Luftströmung sowohl geneigt als auch gedreht orientiert waren. Bei laminarer Strömung lagen die Anströmgeschwindigkeiten zwischen 2,5 and 15 m/s.相似文献
545.
K. H. C. Baser B. Demirci F. Demirci N. Kirimer I. C. Hedge 《Chemistry of Natural Compounds》2001,37(4):336-338
The MicroDistiller (Eppendorf), enables the distillation of aromatic material even in very small quantities. Using the simple microdistillation technique, minute amounts ofCyclotrichium leucotrichum(Stapf ex Rech. fil.) Leblebici andC. stamineum(Boiss. and Hohen.) Manden. and Scheng. were investigated for their volatiles by GC/MS. The main constituents were identified as-caryophyllene (14%), camphor (12%), andp-menth-3-en-8-ol (11%) forC. leucotrichum, and pinocamphone (33%), isopinocamphone (13%), and myrtenyl acetate (9%) forC. stamineum. 相似文献
546.
We report the demonstration of rewritable self-assembled long-period gratings in air-core photonic bandgap fibers. The long-period gratings are written by filling the air-core region of the fiber with a solution containing polystyrene microspheres. The microspheres are self-assembled into a periodic structure as the liquid inside the fiber evaporates, forming the long-period grating. The formed grating can then be easily erased for rewriting purposes by connecting the end of the fiber to a microfluidic pump through a microfluidic channel and washing out the microparticles with an appropriate liquid. The same microfluidic system can also be used to fine control the writing process of the gratings. This technique creates possibilities for writing various different filtering functions in air-core photonic bandgap fibers by varying the composition and/or the shape of the used microparticles. The presented technique is potentially applicable to solid-core photonic crystal fibers as well. 相似文献
547.
This paper investigates the behaviour of interest rates in Turkey using a two-regime TAR model with an autoregressive unit root. This method recently developed by Caner and Hansen [Threshold autoregression with a unit roots, Econometrica 69 (6) (2001) 1555–1596] allows to simultaneously consider non-stationarity and non-linearity. Our finding indicates that the interest rate is a non-linear series and is characterized by a unit root process over the period 1990:1–2006:5. 相似文献
548.
Claudia E. Murar Mamiko Ninomiya Satomi Shimura Ufuk Karakus Onur Boyman Jeffrey W. Bode 《Angewandte Chemie (International ed. in English)》2020,59(22):8425-8429
Chemical protein synthesis allows the construction of well‐defined structural variations and facilitates the development of deeper understanding of protein structure–function relationships and new protein engineering strategies. Herein, we report the chemical synthesis of interleukin‐2 (IL‐2) variants on a multimilligram scale and the formation of non‐natural disulfide mimetics that improve stability against reduction. The synthesis was accomplished by convergent KAHA ligations; the acidic conditions of KAHA ligation proved to be valuable for the solubilization of the hydrophobic segments of IL‐2. The bioactivity of the synthetic IL‐2 and its analogues were shown to be equipotent to recombinant IL‐2 and exhibit improved stability against reducing agents. 相似文献
549.
550.
We consider the problem of optimal portfolio choice using the Conditional Value-at-Risk (CVaR) and Value-at-Risk (VaR) measures for a market consisting of n risky assets and a riskless asset and where short positions are allowed. When the distribution of returns of risky assets is unknown but the mean return vector and variance/covariance matrix of the risky assets are fixed, we derive the distributionally robust portfolio rules. Then, we address uncertainty (ambiguity) in the mean return vector in addition to distribution ambiguity, and derive the optimal portfolio rules when the uncertainty in the return vector is modeled via an ellipsoidal uncertainty set. In the presence of a riskless asset, the robust CVaR and VaR measures, coupled with a minimum mean return constraint, yield simple, mean-variance efficient optimal portfolio rules. In a market without the riskless asset, we obtain a closed-form portfolio rule that generalizes earlier results, without a minimum mean return restriction. 相似文献