On the assignment of the absolute configuration at the isolated methyl branch in miyakosyne A,cytotoxic linear acetylene,from the deep-sea marine sponge Petrosia sp.

Absolute configuration of miyakosyne A at its isolated branched methyl stereogenic center has been studied by chemical degradation in combination with esterification with the Ohrui's acid. Comparison of the ¹H NMR data of the relevant diesters for the degradation product and the synthetic standards indicated the 14R-configuration.     

Imperfection sensitivity of ultimate buckling strength of elastic-plastic square plates under compression

The mechanism of imperfection sensitivity of elastic-plastic plates under compression is complex as they undergo elastic and/or plastic buckling, dependent on their width-thickness ratio. For elastic buckling, the Koiter power law is an established means to describe the imperfection sensitivity. Yet, for plastic buckling, there is no such an established way to describe it. In this paper, the quadratic power law is advanced to describe imperfection-insensitive plastic buckling behavior. The Koiter power law is extended by implementing the quadratic law so as to describe the elastic and plastic buckling in a synthetic manner. The finite-displacement, elastic-plastic analysis was conducted on simply-supported square plates under compression by varying the plate thickness and the initial deflection of a sinusoidal form. In association with an increase of the plate slenderness parameter (decrease of plate thickness), the predominant buckling is shown to change from (1) plastic buckling to (2) unstable elastic-plastic buckling and to (3) elastic stable bifurcation followed by a maximum point of load. In accordance with the change of the mechanism of buckling, the power law is changed pertinently to describe the complex imperfection sensitivity of the compression plates in a synthetic manner. The extended imperfection sensitivity law is thus advanced as a simple and strong tool to describe the ultimate buckling strength of elastic-plastic plates.     

Status of the electron accelerator for radioanalytical studies at tohoku university

We introduce the status of the 300 MeV electron linear accelerator used for radioanalytical studies at Tohoku University. In the accelerator facility, several scientific programs for producing radioactivity have been performed in several fields, such as photon-activation analysis, nuclear chemistry, hot-atom chemistry, and radioactive tracers for material science. First, we introduce an outline of the facility and the irradiation system for producing radioactivity. Then, several topics in these fields are explored in detail.     

Relation of gas permeability with structure of aromatic polyimides II

We investigated relations between diffusivities on polyimides and physical parameters with mobilities of segments and examined viscoelasticity of polyimides on introducing the parameter as an index of mobilities of polymer chains.