An algebraic Kekule structure of a benzenoid hydrocarbon is obtained from an ordinary Kekule structure by inscribing into each hexagon the number of π-electrons which (according to this Kekule structure) belong to this hexagon. We show that in the case of catafusenes, there is a one-to-one correspondence between ordinary and algebraic Kekule structures. On the other hand, in the case of perifusenes, one algebraic Kekule structure may correspond to several ordinary Kekule structures.

A structure-based description of excitation migration in multireaction center light harvesting systems is introduced. The description is an extension of the sojourn expansion, which decomposes excitation migration in terms of repeated detrapping and recapture events. The approach is applied to light harvesting in the trimeric form of cyanobacterial photosystem I (PSI). Excitation is found to be shared between PSI monomers and the chlorophylls providing the strongest respective links are identified. Excitation sharing is investigated by computing cross-monomer excitation trapping probabilities. It is seen that on the average there is a nearly 40% chance of excitation cross transfer and trapping, indicating efficient coupling between monomers. The robustness and optimality of the chlorophyll network of trimeric PSI is examined.

There has been an interest to understand the trapping performance produced by a laser beam with a complex wavefront structure because the current methods for calculating trapping force ignore the effect of diffraction by a vectorial electromagnetic wave. In this letter, we present a method for determining radiation trapping force on a micro-particle, based on the vectorial diffraction theory and the Maxwell stress tensor approach. This exact method enables one to deal with not only complex apodization, phase, and polarization structures of trapping laser beams but also the effect of spherical aberration present in the trapping system.

Industrial robots are introduced to belt grinding processes of free-formed surface with elastic wheel nowadays in order to obtain high quality product and high efficiency. However, it is a laborious task to plan grinding paths and write programs for the robot. To release people from it partially, it is necessary to simulate the belt grinding processes which are useful for path generating and dynamic robot control. In this paper, we present a framework of the robot controlled belt grinding simulation system and some key issues in it. We enhance the global removal model to local process model, which can simulate the grinding process more exactly. We also point out the bottleneck of the real-time simulation and put forward a neural network based regression method to meet this difficulty. At the end of the paper, some simple simulation examples are given.

Systemic lupus erythematosus (SLE) may involve the respiratory tract in several ways, such as through pleuritis, pneumonitis, interstitial disease or pulmonary hypertension. In rare cases, SLE patients present a syndrome characterized by dyspnea, chest pain and abnormalities in pulmonary function testing, although there may be no evidence of major parenchymal lung disease on computerized tomography scans. This condition has come to be known as shrinking lung syndrome. We report a case that meets these diagnostic criteria, emphasizing the pathogenesis proposed, as well as the therapeutic options available.