Knowledge-based system on optimum design of liquid retaining structures with genetic algorithms

This paper delineates the development of a prototype hybrid knowledge-based system for the optimum design of liquid retaining structures by coupling the blackboard architecture, an expert system shell VISUAL RULE STUDIO and genetic algorithm (GA). Through custom-built interactive graphical user interfaces under a user-friendly environment, the user is directed throughout the design process, which includes preliminary design, load specification, model generation, finite element analysis, code compliance checking, and member sizing optimization. For structural optimization, GA is applied to the minimum cost design of structural systems with discrete reinforced concrete sections. The design of a typical example of the liquid retaining structure is illustrated. The results demonstrate extraordinarily converging speed as near-optimal solutions are acquired after merely exploration of a small portion of the search space. This system can act as a consultant to assist novice designers in the design of liquid retaining structures.

Identification of slow and fast-acting toxins in a highly ciguatoxic barracuda (Sphyraena barracuda) by HPLC/MS and radiolabelled ligand binding

A barracuda implicated in ciguatera fish poisoning in Guadeloupe was estimated to have an overall flesh toxicity of 15 MUg/g using mouse bioassay. A lipid soluble extract was separated into two toxic fractions, FrA and FrB, on a LH20 Sephadex column eluted with dichloromethane/methanol (1:1). When intraperitoneal injected into mice, FrA provoked symptoms characteristic of slow-acting ciguatoxins, whereas FrB produced symptoms indicative of fast-acting toxins (FAT). High performance liquid chromatography/mass spectrometry/radio-ligand binding (HPLC/MS/RLB) analysis confirmed the two fractions were distinct, because only a weak overlap of some compounds was observed. HPLC/MS/RLB analysis revealed C-CTX-1 as the potent toxin present in FrA, and two coeluting active compounds at m/z 809.43 and 857.42 in FrB, all displaying the characteristic pattern of ion formation for hydroxy-polyethers. Other C-CTX congeners and putative hydroxy-polyether-like compounds were detected in both fractions, however, the RLB found them inactive. C-CTX-1 accounted for >90% of total toxicity in this barracuda and was confirmed to be a competitive inhibitor of brevetoxin binding to voltage-sensitive sodium channels (VSSCs) with a potency two-times lower than P-CTX-1. However, FAT active on VSSCs and

Simultaneous observations of ionospheric quasiperiodic scintillations from short and long meridional baselines using VHF transmissions from transit satellites

For the first time it was possible to observe regular quasiperiodic scintillations (QPS) in VHF radio-satellite transmissions from orbiting satellites simultaneously at short (2.1 km) and long (121 km) meridional baselines in the vicinity of a typical mid-latitude station (Brisbane; 27.5degreesS and 152.9degreesE geog. and 35.6degrees invar.lat.), using three sites (St. Lucia-S, Taringa-T in Brisbane and Boreen Pt.-B, north of Brisbane). A few pronounced quasiperiodic (QP) events were recorded showing unambiguous regular structures at the sites which made it possible to deduce a time displacement of the regular fading minimum at S, T and B. The QP structure is highly dependent on the geometry of the ray-path from a satellite to the observer which is manifested as a change of a QP event from symmetrical to non-symmetrical for stations separated by 2.1 km, and to a radical change in the structure of the event over a distance of 121 km. It is suggested the short-duration intense QP events are due to a Fresnel diffraction (or a reflection mechanism) of radio-satellite signals by a single ionospheric irregularity in a form of an ellipsoid with a large ionization gradient along the major axis. The structure of a QP event depends on the angle of viewing of the irregular blob from a radio-satellite. In view of this it is suggested that the reported variety of the ionization formation, responsible for different types of QPS, is only apparent but not real. (C) 2003 Elsevier Science Ltd. All rights reserved.