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A preliminary study of the thermal reaction of cyclopropenone ketals with carbon-heteroatom double bonds is detailed. The reaction with aldehyde and keto carbonyls provide butenolide ortho esters, the product of a formal three-carbon + two-atom cycloaddition of the cyclopropenone ketal across the carbon-oxygen double bond. 相似文献
404.
Inspection policy models deal with stochastically failing systems, in which failure is detected by inspection only. Previous authors assume that the time required for checking is zero, while the current study deals with preparedness models when duration of checking is non-negligible. Costs are introduced for checking, unknown lost time and repairing (or replacing) the failed system. Furthermore, uncertainty probabilities associated with inspections are introduced. Optimal checking policies are calculated for three different objective functions: expected loss per cycle, per time unit and per unit of good time. The models are solved by differentiation and by dynamic programming. Numerical results indicate that the optimal policy for IFR distributions is characterized by decreasing checking time intervals, with a marked difference only between the first and second intervals. 相似文献
405.
Zvi Artstein 《Applied Mathematics and Optimization》1982,9(1):111-131
The relations between uniform controllability of a time varying system and mere controllability of its limiting systems are studied. The necessary and the sufficient conditions that are developed enable one to apply the available controllability tests in order to establish or refute uniform controllability. Examples and applications are provided along with the analogous considerations for observability.The research was supported by The Israel Academy of Sciences and Humanities—Basic Research Foundation. 相似文献
406.
The solution-phase, parallel synthesis and evaluation of a library of 132 (+)-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (CBI) analogues of CC-1065 and the duocarmycins containing dimeric monocyclic, bicyclic, and tricyclic heteroaromatic replacements for the DNA-binding domain are described. This systematic study revealed clear trends in the structural requirements for observation of potent cytotoxic activity and DNA alkylation efficiency, the range of which spans a magnitude of > or =10 000-fold. Combined with related studies, these results highlight that the role of the DNA-binding domain goes beyond simply providing DNA-binding selectivity and affinity (10-100-fold enhancement in properties), consistent with the proposal that it contributes significantly to catalysis of the DNA alkylation reaction accounting for as much as an additional 1000-fold enhancement in properties. 相似文献
407.
Butler GM Brown SN Boger RM Ferfolia MT Fitzgibbons AC Jongeling AC Kelleher SJ Malec AD Malerich J Weltner AN 《Organic letters》2000,2(26):4125-4128
Both 3-(hydroxymethyl)-5-methylsalicylaldehyde and its acetonide condense in the presence of hydrogen chloride in ether to form macrocyclic S(4)-symmetric tetraacetal 2. The reaction is completely oligo- and stereoselective, forming only the tetramer and only the achiral (R,S,R,S)-stereoisomer. Acid-catalyzed equilibration studies and molecular mechanics calculations indicate that the stereoselectivity is thermodynamic in origin. In the crystal the saddle-shaped molecules of 2 form coaxial stacks reminiscent of the packing of Pringles potato chips. 相似文献
408.
Axel Schindler Jochen Brill Norbert Fruehauf James P. Novak Zvi Yaniv 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):119
We have investigated two possible fields of application for carbon nanotube (CNT) networks in flexible displays. Transparent and conductive layers of CNTs were spray coated onto glass and plastic substrates. The spectral transmission of the produced layers is almost even for all wavelengths in the visible regime. A sheet resistance of 400 Ω/□ at a transmittance of 80% was achieved.Thin-film transistors (TFT) were created on silicon wafers and glass substrates using low-density CNT networks as a semiconducting layer. The process used for device fabrication on glass substrates is fully compatible to application on plastic foils. The transistors reach on/off ratios of more than five orders of magnitude and show device charge carrier mobilities in the order of 1 cm2/Vs. These values promise an application in active matrix liquid crystal displays (AMLCD). Issues that need to be addressed are the homogeneity and reproducibility of the device properties. 相似文献
409.
We review on-shell methods for computing multi-parton scattering amplitudes in perturbative QCD, utilizing their unitarity and factorization properties. We focus on aspects which are useful for the construction of one-loop amplitudes needed for phenomenological studies at the Large Hadron Collider. 相似文献
410.