Solar cells

Solar cells are based on the photovoltaic effect of converting solar energy into electric energy. The mechanism for solar cells is divided into steps, that is, electron-hole pair generation by absorption of light in semiconductors, separation of electron-hole pairs by built-in potential, electron-hole recombination, collection of charge carriers by metal electrodes, etc. In this article, the principle and the theories of these basic steps are presented. On the basis of these steps, methods to improve the efficiency for solar cells are discussed. The fabrication process and the situation of currently produced solar cells are also presented. Solar cells having no p-n junction, that is, photoelectrochemical solar cells and MIS solar cells, are discussed from the perspective of low-cost solar cells.     

Explicit solution forp-q duality in two-dimensional quantum gravity

By using Sato's infinite dimensional Grassmannian theory of the KP hierarchy, we study the global structure of the theory space of 2D quantum gravity coupled to various minimal conformal fields labeled by a pair of integers (p, q). After giving a rigorous proof of the equivalence of Douglas's equation and the Schwinger-Dyson equation (W-constrainton a function), we establish thep-q duality of the (p, q) quantum gravity at Green's function level. As an application, we discuss the metamorphosis of operators under unitarity-preserving renormalization group flows.Address after September 1, 1992: Newman Laboratory, Cornell University, Ithaca, NY 14853-5001, USA.     

Total Synthesis and Biological Evaluation of Siladenoserinol A and its Analogues

The total synthesis of siladenoserinol A, an inhibitor of the p53–Hdm2 interaction, has been achieved. AuCl₃‐catalyzed hydroalkoxylation of an alkynoate derivative smoothly and regioselectively proceeded to afford a bicycloketal in excellent yield. A glycerophosphocholine moiety was successfully introduced through the Horner–Wadsworth–Emmons reaction using an originally developed phosphonoacetate derivative. Finally, removal of the acid‐labile protecting groups, followed by regioselective sulfamate formation of the serinol moiety afforded the desired siladenoserinol A, and benzoyl and desulfamated analogues were also successfully synthesized. Biological evaluation showed that the sulfamate is essential for biological activity, and modification of the acyl group on the bicycloketal can improve the inhibitory activity against the p53–Hdm2 interaction.     

13C-NMR sequence analysis. 19. Anionic copolymerization of γ-butyrolactam, δ-valerolactam,and caprolactam at low temperatures

Copolymerizations of pyrrolidone-2 (γ-butyrolactam) with piperidone-2 (δ-valerolactam) and azepinone-2 (ε-caprolactam) and the copolymerization of piperidone-2 with azepinone-2 were studied in bulk at 30 or 45°C. The sodium salt and the tetramethylammonium salt of pyrrolidone-2 were used as catalysts and N-acetylpyrrolidone-2 as cocatalyst. The sequences of the resulting copolyamides were analyzed by means of 22.63-MHz ¹³C-NMR spectra. All sequences were nearly random in nature, yet copolymerizations of pyrrolidone-2 favor slightly the formation of alternating sequences. Furthermore, the rate of incorporation of pyrrolidone is higher than that of the two comonomers in contrast to experiments at temperatures above 100°C. The influence of transamidation reactions on the sequences is discussed. Propagation/degradation equilibria involving N-acyllactam chain ends were found to modify the initially formed, kinetically controlled sequences in direction of thermodynamically controlled ones.