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71.
A theoretical and experimental study of heat transfer to polymer melts flowing through ducts is presented. The mathematical model provides for shear heating and expansion cooling effects for various wall boundary conditions.Experimental results, obtained in tube flow, show reproducible temperature and velocity profiles and the data confirm the predictions of the magnitude of the shear heating and expansion cooling effects.It is concluded that the method can be justified for predicting heat transfer in more complex geometries and some preliminary results are presented. 相似文献
72.
The generalization of Berezin's Grassmann algebra integral to a Clifford algebra is shown to be translation-invariant in a certain sense. This enables the construction of analogs of twisted convolutions of Grassmann algebra elements and of the Fourier-Weyl transformation, which is an isomorphism from a Clifford algebra to the Grassmann algebra over the dual space, equipped with a twisted convolution product. As an application a noncommutative central limit theorem for states of a Clifford algebra is proved. 相似文献
73.
This paper examines the behavior of the QZ algorithm which is to be expected when A?λB is close to a singular pencil. The predicted results are fully confirmed by practical experience of using the QZ algorithm on examples of this kind. 相似文献
74.
An experimental investigation into turbulent heat transfer to pseudoplastic titanium dioxide suspensions in pipes has been carried out. Existing heat transfer correlations, including the analogy equations between heat and momentum transfer, generally predict higher Nusselt and Stanton numbers than those observed experimentally. However, a simplified heat transfer model based on the consideration of the laminar sub-layer at the wall and the turbulent core correlates the heat transfer results for heating as well as cooling. The limitations of the existing analogy equations between heat and momentum transfer are discussed. 相似文献
75.
76.
Andrianasolo EH Gross H Goeger D Musafija-Girt M McPhail K Leal RM Mooberry SL Gerwick WH 《Organic letters》2005,7(7):1375-1378
[structure: see text] Chemical investigation of two field collections of marine cyanobacteria has led to the discovery of two new cytotoxic natural products, ankaraholides A (2) and B (3), along with the known compound swinholide A (1). Since swinholide-type compounds were previously localized to the heterotrophic bacteria of sponges, these findings raise intriguing questions about their true metabolic source. 相似文献
77.
Specimens of the cosmopolitan sea hare Aplysia parvula, collected in the Tsistsikamma National Park on the south-east coast of South Africa yielded the new dibromo-C15-acetogenin, (3Z)-bromofucin (1). Standard spectroscopic methods were used to establish the structure of this compound. 相似文献
78.
Modular polyketide synthases biosynthesise natural products through successive Claisen-type condensations, where one module is responsible for one round of chain extension. This review describes recent findings where this rule of co-linearity is broken, either by one module being bypassed (skipping) or through one module being used for multiple chain extension events (stuttering). 相似文献
79.
Mahon KP Ortiz-Meoz RF Prestwich EG Kelley SO 《Chemical communications (Cambridge, England)》2003,(15):1956-1957
A novel class of DNA cleavage agents are reported that derive activity from amino acids tethered to a photoactive intercalator. 相似文献
80.
Hervé G Hahn DU Hervé AC Goodworth KJ Hill AM Hailes HC 《Organic & biomolecular chemistry》2003,1(2):427-435
Methodologies to access water soluble large ringed calixarenes in good yield using efficient synthetic procedures have been investigated. Symmetrical partial functionalisations at the lower rim are described using activated [n]ethylene glycol chains and the addition behaviour contrasted with that of bromoalkanenitriles which proceeds with no observed regioselectivity. Full functionalisations of the calixarenes bearing hydrophilic groups are then investigated and a two-step procedure established which appears to be generally applicable for the addition of different [n]ethylene glycol chains. Furthermore, difunctionalisation under different reaction conditions are described. Throughout, strategies for the characterisation of these high mass compounds are outlined. 相似文献