Hysteretic energy spectrum and damage control

The inelastic response of single‐degree‐of‐freedom (SDOF) systems subjected to earthquake motions is studied and a method to derive hysteretic energy dissipation spectra is proposed. The amount of energy dissipated through inelastic deformation combined with other response parameters allow the estimation of the required deformation capacity to avoid collapse for a given design earthquake. In the first part of the study, a detailed analysis of correlation between energy and ground motion intensity indices is carried out to identify the indices to be used as scaling parameters and base line of the energy dissipation spectrum. The response of elastoplastic, bilinear, and stiffness degrading systems with 5 per cent damping, subjected to a world‐wide ensemble of 52 earthquake records is considered. The statistical analysis of the response data provides the factors for constructing the energy dissipation spectrum as well as the Newmark–Hall inelastic spectra. The combination of these spectra allows the estimation of the ultimate deformation capacity required to survive the design earthquake, capacity that can also be presented in spectral form as an example shows. Copyright © 2001 John Wiley & Sons, Ltd.     

Pleistocene Charophyta from Arroyo Perucho Verna,Province of Entre Rios,Argentina

The Pleistocene charophytes from Arroyo Perucho Verna, Province of Entre Ríos, were analyzed.Chara contraria Br. ex Kütz.,C. contraria var.longilinea Cáceres,C. globularis Thuill. andTolypella intricata (Trent. ex Roth.) Leonh. var.apiculata (A. Br.) Wood were described and illustrated with scanning electron microscope. The assemblage indicates fresh alkaline to slightly saline waters, not very deep, in a lentic or sometimes lotic environment. Extant assemblages provide data for this paleoecological reconstruction.This is the sixth in a series of papers published in this issue on Paleolimnology in Southern South America. Dr. C. A. Fernandéndez served as guest editor for these papers.     

Stereoscopic measurements of flares from PHOBOS and GOES

A unique approach to observing the Sun stereoscopically in soft X-rays was afforded by the PHOBOS mission to Mars during 1989. Concurrent measurements of two flares from two widely separated spacecraft allowed us to obtain estimates of each flare's height above the solar surface. The requirement was that the flare had to be over the limb as observed by one spacecraft and on the visible disk as viewed by the other. The first flare occurred on March 4, when the active region was beyond the east limb as observed by GOES (at Earth), but on the disk as viewed by PHOBOS (at Mars). The second flare, on March 15, was on the disk for GOES, but beyond the west limb for PHOBOS. We believe that the same extraordinary active region, 5395, was responsible for both events. Soft X-ray photometers on each spacecraft contained two broad-band channels. The two-channel data were used to computeflare (assumed isothermal) plasma temperatures. The sharply peaked flare on March 4 indicated essentially identical maximum electron temperatures ( 13 Mk) at both spacecraft, confirming that the hottest plasma was indeed concentrated at the highest (unocculted) part of the loop. However, in the case of the long-duration March 15 flare, whose loop was in apparent upwards motion, the partially occulted flare indicated substantially cooler temperatures. This finding suggests that the hot core of this flare may have been below the limb, or that the partially occulted flux originated not from post-flare loops but from an independent, higher X-ray arch. The PHOBOS and GOES X-ray photometers were intercompared in July 1988, soon after the PHOBOS launch, to establish relative calibration parameters.     

Automated astrographic plates measuring process

The astrographic plates measuring process applied at the Astronomical Observatory of Valencia has been described.The measure of astrographic plates of our minor planets observation programme has been carried out by means of a binocular microscope with a photometer, held by a personal computer through an interface. The process of measure in each position of the plate holder is automated, once two stars are selected and the sequence of the objects to be measured is defined.The process will be improved in the next future, by the substitution of the searching device (a photometer) by a CCD camera plus a digitizer board.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

A search for new objects in the transition phase between AGB-stars and planetary nebulae

We present the first results of a spectroscopy survey of iras sources with colours similar to those of planetary nebulae.Two new planetary nebulae, some H emission line stars, one peculiar source which is probably a pre-Main-Sequence object and a new Seyfert I galaxy have been found.Based on observations collected at the European Southern Observatory, La Silla, Chile.     

Volatiles in submarine volcanic rocks from the Mariana Island arc and trough

High temperature mass spectrometric analyses of glasses from quenched pillow rims of andesites dredged from 1170 m water depth in the northern portion of the Mariana Island arc indicate substantially less H₂O (~ 1 wt.%) and more CO₂ (~ 0.24 wt.%) than previously reported for volcanic arc rocks. Glass-vapor inclusions within plagioclase phenocrysts from quenched rims have $\text{CO}{}_2\text{H}{}_2\text{O}$ ratios of 1:1. These results are similar to analyses of basaltic samples from the Mariana Trough (a back-arc basin). Generally, F and Cl contents are higher and S lower in the arc rocks compared to the samples from the back-arc basin. These results favor models for the production of island arc magmas which involve melting of the subducted slab, rather than just melting of the overlying mantle wedge because of the high volatile content needed to produce island arc magmas from peridotite (10–15 wt.%). The trough samples, although similar in non-volatile composition to mid-ocean ridge rocks, have much higher H₂O. somewhat higher CO₂ and lower S contents. Either near surface addition of voiatiles has enriched the magmas or H₂O must be a more important component in the generation and evolution of back-arc basin lavas than in the genesis of mid-ocean ridge basalts.     

Prediction in a socio-hydrological world

ABSTRACT

Water resource management involves public investments with long-ranging impacts that traditional prediction approaches cannot address. These are increasingly being critiqued because (1) there is an absence of feedbacks between water and society; (2) the models are created by domain experts who hand them to decision makers to implement; and (3) they fail to account for global forces on local water resources. Socio-hydrological models that explicitly account for feedbacks between water and society at multiple scales and facilitate stakeholder participation can address these concerns. However, they require a fundamental change in how we think about prediction. We suggest that, in the context of long-range predictions, the goal is not scenarios that present a snapshot of the world at some future date, but rather projection of alternative, plausible and co-evolving trajectories of the socio-hydrological system. This will both yield insights into cause–effect relationships and help stakeholders identify safe or desirable operating space.