Spectroscopic studies of three novae

We present our spectroscopic observations of the novae V1425, V1493, and V1494 Aql carried out with the 125-cm telescope at the Crimean Station of the Sternberg Astronomical Institute in the wavelength range 4000–11000 Å. We measured the emission-line intensities, determined the nova shell expansion velocities from the line profile FWHMs and components, and estimated the interstellar reddening from the first members of the Balmer series. The chemical composition of the nova shells is analyzed. Nitrogen and oxygen were found to be overabundant in V1425 and V1494 Aql; the helium abundance turned out to be normal in the two stars.     

Statistical analysis of seismic data from north-western and western Argentina

Due to the process of subduction of the Nazca Plate, high seismic activity is observed near the Argentine Andean range between 21°S and 36°S. The new version of the Argentine Seismic Catalogue, which includes well-defined events during the period 1964–1989, allows us to perform an analysis of seismic risk.Earthquakes with epicenters in the provinces included in the north-western and western regions were studied using Gumbel III extreme value distribution. Modal extreme magnitudes and return periods were calculated for both regions and the results were compard with the ones obtained through the entire process techniques (both analytical and graphical).As a first study, we analyzed each province separately, after which mean values for each region were obtained. Modal values around 5–5.5 have been found and times of recurrence for events withm _b >6 of approximately 25 years were obtained.Also at CONICET (Consejo Nacional de Investigaciones Cientificas y Técnicas).     

Geotechnical assessment of the bearing capacity of coal mine floors

Summary This investigation concerns 3 longwall faces having variable strata and mining conditions, but supported by 202 tonnes hydraulic 6-leg chocks. Bearing capacity tests along the faces were conducted to evaluate the factors influencing floor deformation and failure. The effect of size, shape and perimeter of the base plates, thickness of the floor layer, time and moisture on the ultimate bearing capacity of the floor was measured and discussed. Application of this work is the prediction of stability and support performance of face ends, as well as the design of support systems and ground control on production faces.     

Analysis of a high-amplitude event in component A of the gravitational lens QSO 2237+0305

We present an analysis of a high-amplitude event in the flux curve of component A of the gravitational lens QSO 2237+0305 observed by the OGLE and GLITP groups in autumn 1999. Hypothesizing this event to be associated with microlensing of a fold caustic, we analyzed the observational data using a method for the successive reconstruction of branches of the one-dimensional strip brightness distribution across the source corresponding to positive and negative arguments. The search for the branches was carried out on compact sets of nonnegative, monotonically nonincreasing, convex downward functions. The resulting shape of the strip brightness distribution for the accretion disk of the quasar is in agreement with results obtained earlier via model fitting. Features in the lensing curve that could be associated with curvature of the caustic, nearness of a cusp, or the influence of nearby caustics are noted.     

Implementation of online model updating in hybrid simulation

Hybrid simulation combines numerical and experimental methods for cost‐effective, large‐scale testing of structures under simulated earthquake loading. Structural system level response can be obtained by expressing the equation of motion for the combined experimental and numerical substructures, and solved using time‐stepping integration similar to pure numerical simulations. It is often assumed that a reliable model exists for the numerical substructures while the experimental substructures correspond to parts of the structure that are difficult to model. A wealth of data becomes available during the simulation from the measured experiment response that can be used to improve upon the numerical models, particularly if a component with similar structural configuration and material properties is being tested and subjected to a comparable load pattern. To take advantage of experimental measurements, a new hybrid test framework is proposed with an updating scheme to update the initial modeling parameters of the numerical model based on the instantaneously‐measured response of the experimental substructures as the test progresses. Numerical simulations are first conducted to evaluate key algorithms for the selection and calibration of modeling parameters that can be updated. The framework is then expanded to conduct actual hybrid simulations of a structural frame model including a physical substructure in the laboratory and a numerical substructure that is updated during the tests. The effectiveness of the proposed framework is demonstrated for a simple frame structure but is extendable to more complex structural behavior and models. Copyright © 2013 John Wiley & Sons, Ltd.     

Evolution of sand waves in the Messina Strait, Italy

In the present paper the morphodynamics of sand waves in the Messina Strait, Italy, is analysed by comparing data gathered during two different surveys carried out in 1991 and 2001, respectively. In particular, a morphometric analysis on the most recent data and a qualitative analysis of the differences between bottom bedform patterns, are carried out. At locations characterised by greater depths, only minor changes to the planimetric configuration of the field, i.e. crest orientation (which is seen to be orthogonal to the direction of net gross sand transport) and wave length are observed, while differences in wave length and crest direction are more evident in more shallow areas. On the other hand, wave height has significantly increased in the whole field. A possible explanation of such a change, based on the previsions of a theory which relates sand-wave growth and migration to the main components of the tidal ellipse, is provided.Responsible Editor: Jens Kappenberg     

Changes in the content and composition of pedogenic iron oxyhydroxides in a chronosequence of soils in southern California

Studies of the pedogenic iron oxyhydroxides in suites of latest Holocene to middle Pleistocene soils formed on fluvial deposits of the transverse ranges, southern California, indicate that the content and composition of iron oxyhydroxide change in a systematic manner. Analysis of total secondary free iron oxides (dithionite extractable, Fe₂O₃d) and ferrihydrite (oxalate extractable, Fe₂O₃o) shows that (1) a single-logarithmic model (Y = a + b log X) or double logarithmic model (log Y = a + b log X), where Y is the total mass of pedogenic Fe oxides (g/cm²-soil column) and X is soil age, describes the rate of increase in Fe₂O₃d with time; (2) the Fe₂O₃d content correlates linearly with soil reddening and clay content; (3) the $\text{Fe}{}_2\text{O}{}_3\text{o}\text{Fe}{}_2\text{O}{}_3\text{d}$ ratio, which indicates the degree of Fe oxide crystallinity, is moderately high to very high (0.22–0.58) in middle Holocene to latest Pleistocene soils and progressively decreases to less than 0.10 in older soils; (4) the value of the $\text{Fe}{}_2\text{O}{}_3\text{o}\text{Fe}{}_2\text{O}{}_3\text{d}$ ratio also appears to be infuenced by climate; and (5) temporal changes in Fe oxide content and mineralogy are accompanied by related, systematic changes in clay mineralogy and organic matter content. These relationships are attributed to a soil environment that must initially favor ferrihydrite precipitation and/or organic matter-Fe complexation. Subsequent transformation to hematite causes increasingly intense reddening and a concomitant decrease in the $\text{Fe}{}_2\text{O}{}_3\text{o}\text{Fe}{}_2\text{O}{}_3\text{d}$ ratio. The results demonstrate that iron oxide analysis is useful for numerical age studies of noncalcic soils and shows potential as an indicator of paleoclimates.     

Space–time distribution of ancient and active alluvial karst subsidence: examples from the central Ebro Basin,Spain

Space and time variations of alluvial karst subsidence in the central Ebro Basin are analysed in trenches (paleodolines), aerial photographs (historical dolines) and field surveys (present-day active dolines). The measured subsidence rates, as well as a comparison between densities of paleodolines computed in randomly selected scan-lines and density of active dolines computed in maps, suggest that present-day subsidence in favourable areas is more intense than that of Pleistocene times. According to diachronic maps drawn from (a) different aerial photographs taken after 1946 and (b) field surveys on deformations in urbanized areas, subsidence behaved as a nearly steady process while the whole area was used for agriculture. In contrast, rapid changes (through periods of several tens of years) have occurred in urbanized areas, in which dolines expand their boundaries through small marginal collapses, shifting sharply their sinking centres to neighbouring sites. These rapid changes do not have an equivalent in observed paleodolines.