Period changes in the pulsating extreme helium stars V652 Her and BX Cir

A new statement of the eigenvalue problem of studying small perturbations in arbitrary integrable self-gravitating systems is presented. An example of such a system, a 2D stellar disc, is considered in detail. The theory, based on the general equation for disc eigenmodes, reveals mechanisms for the formation and growth of global galactic structures. This new point of view specifies the limits of the unified theory of bar-like and spiral modes that was based on the assumption that global galactic structures could be understood in terms of low-frequency disc modes.     

Effects of Different Diets on the Dietary Attractability and Selectivity of Chinese Shrimp, Fenneropenaeus chinensis

Attractabilities of different diets and dietary selectivity of Chinese shrimp, Fenneropenaeus chinensis were studied through behavior observation and feeding experiment, respectively. The five diets used in the experiment are: Fish Flesh (FF), Shrimp Flesh (SF), Clam Foot (CF), Polychaete Worm (PW), and Formulated Diet (FD). No significant differences of attractability exist between any two different diets when every two natural diets or all five diets are provided simultaneously. On the other hand, significant differences of attractability exist between FD and every single natural diet when they are provided simultaneously. Results of behavioral observation indicate that natural diets are more attractive than FD. In feeding experiment, Chinese shrimp has distinct selectivity on different diets. It positively selects CF and PW, negatively selects FF and SF, and excludes FD absolutely. The results of the present studies indicate that the dietary selectivity of shrimp was based not only on the attractabilities of the diets, but also on the responses such as growth and food conversion.     

Reliability assessment of serviceability performance of braced retaining walls using a neural network approach

In urban environments, one major concern with deep excavations in soft clay is the potentially large ground deformations in and around the excavation. Excessive movements can damage adjacent buildings and utilities. There are many uncertainties associated with the calculation of the ultimate or serviceability performance of a braced excavation system. These include the variabilities of the loadings, geotechnical soil properties, and engineering and geometrical properties of the wall. A risk‐based approach to serviceability performance failure is necessary to incorporate systematically the uncertainties associated with the various design parameters. This paper demonstrates the use of an integrated neural network–reliability method to assess the risk of serviceability failure through the calculation of the reliability index. By first performing a series of parametric studies using the finite element method and then approximating the non‐linear limit state surface (the boundary separating the safe and ‘failure’ domains) through a neural network model, the reliability index can be determined with the aid of a spreadsheet. Two illustrative examples are presented to show how the serviceability performance for braced excavation problems can be assessed using the reliability index. Copyright © 2005 John Wiley & Sons, Ltd.     

Convection flow over a uniform-flux vertical surface with variable viscosity

A regular perturbation analysis is presented for natural convection flow over an uniform flux vertical surface with temperature dependent viscosity. Numerical calculations are presented forP _r=6.7 which show that the first-order correction to the local temperature difference and to the local skin-fraction are negative whereas it is positive for the local Nusselt number. The effects of variable viscosity on the temperature, velocity profiles, the local temperature difference, the local Nusselt number and the local skin fraction are discussed.     

Origin and early evolution of the planetary system

It is shown by linear stability analysis that a preplanetary (presatellite) disk of dust and gas with Keplerian velocity field can become unstable due to the collective self-gravity of the disk. The radial distribution of rings, which may result from this instability, is derived. These rings later on can be the formation sites for planets around the Sun and for satellites around the planets. The derived orbits are shown to be in good agreement with that of the planets and the satellites (of Jupiter, Saturn, and Uranus). Predictions and conclusions seem to be possible for the existence of three yet unknown Uranian satellites, the origin of the early Moon and the possible radial extension of the planetary system.     

Red-violet asymmetry in pearl satellites' birth

A high resolution numerical sonagram of Pc-1 magnetic record has shown that single narrow lines of Pc-1 spectra produce lower frequency (“red-shifted”) satellite lines more than twice as often as their higher frequency (“violet”) counterparts. The violet satellites usually emerge only when at least two ancestor lines are present simultaneously.     

Response of reef coral communities to sea-level rise: a Holocene model from Mauritius (Western Indian Ocean)

The fringing reef at Pointe-au-Sable (Mauritius, Indian Ocean) was used to examine the effects of Holocene sea-level rise on coral growth. This reef is about 1000 m wide and comprises a forereef slope (30 m maximum depth), a narrow reef crest and a very shallow backreef (1·5 m maximum depth). Four major coral communities were recognized, which developed within relatively narrow depth ranges: a Pachyseris/Oulophyllia community (deeper than 20 m), an Acropora‘tabulate’Faviid community (20–6 m); a robust branching Acropora community (less than 6 m) and a Pavona community (less than 10m). Three high-recovery cores show the Holocene reef sequence is a maximum of 19·3 m thick and comprises four coral biofacies which are similar to counterparts identified in modern communities: robust branching, tabular-branching, robust branching-domal and foliaceous coral facies. A minimum sea-level curve for the past 7500 years was constructed. Using distribution patterns of coral biofacies and radiocarbon dates from corals, reconstruction of reef growth history indicates that both offshore and onshore reef zones were developing coevally, aggrading at rates of 4·3 mm year^?1 from 6900 years B.P. The reef caught up with sea-level only after sea-level stabilized. Changes in coral community and reef growth rates were driven principally by increasing water agitation due to the decrease in accommodation space. Based on the composition of the successive coral assemblages, the reef appears to have grown through successive equilibrium stages.