The impact of binary-star yields on the spectra of galaxies

One of the complexities in modelling integrated spectra of stellar populations is the effect of interacting binary stars besides Type Ia supernovae (SNeIa). These include common envelope systems, cataclysmic variables, novae, and are usually ignored in models predicting the chemistry and spectral absorption line strengths in galaxies. In this paper, predictions of chemical yields from populations of single and binary stars are incorporated into a galactic chemical evolution model to explore the significance of the effects of these other binary yields. Effects on spectral line strengths from different progenitor channels of SNeIa are also explored. Small systematic effects are found when the yields from binaries, other than SNeIa, are included, for a given star formation history. These effects are, at present, within the observational uncertainties on the line strengths. More serious differences can arise in considering different types of SNIa models, their rates and contributions.     

GEOELECTRIC MODELS IN ENGINEERING GEOPHYSICS*

Man's engineering activities are concentrated on the uppermost part of the earth's crust which is called engineering-geologic zone. This zone is characterized by a significant spatialtemporal variation of the physical properties status of rocks, and saturating waters. This variation determines the specificity of geophysical and, particularly, geoelectrical investigations. Planning of geoelectric investigations in the engineering-geologic zone and their subsequent interpretation requires a priori) geologic-geophysical information on the main peculiarities of the engineering-geologic and hydrogeologic conditions in the region under investigation. This information serves as a basis for the creation of an initial geoelectric model of the section. Following field investigations the model is used in interpretation. Formalization of this a priori) model can be achieved by the solution of direct geoelectric problems. An additional geologic-geophysical information realized in the model of the medium allows to diminish the effect of the “principle of equivalence” by introducing flexible limitations in the section's parameters. Further geophysical observations as well as the correlations between geophysical and engineering-geologic parameters of the section permit the following step in the specification of the geolectric model and its approximation to the real medium. Next correction of this model is made upon accumulation of additional information. The solution of inverse problems with the utilization of computer programs permits specification of the model in the general iterational cycle of interpretation.     

Equations of motion of the restricted problem of three bodies with variable mass

In this paper we have deduced the differential equations of motion of the restricted problem of three bodies with decreasing mass, under the assumption that the mass of the satellite varies with respect to time. We have applied Jeans law and the space time transformation contrast to the transformation of Meshcherskii. The space time transformation is applicable only in the special casen=1,k=0,q=1/2. The equations of motion of our problem differ from the equations of motion of the restricted three body problem with constant mass only by small perturbing forces.     

Modelling the advance–retreat cycle of a tidewater glacier with simple sediment dynamics

We present a simple coupled glacier-sediment model to simulate the evolution of a tidewater glacier. The model is based on a consideration of the total mass budget of a glacier, whereas ice mechanics are fully parameterized. The calving rate at the glacier terminus is assumed to be proportional to the water depth. We show that the formation of a morainic shoal has a profound influence on the response of a tidewater glacier to climatic forcing. For a slow periodic forcing of the equilibrium-line altitude, the model glacier advances steadily into the estuary, builds up a submarine terminal moraine, and then retreats rapidly when a critical point is hit. For a slowly increasing equilibrium-line altitude, at a rate as low as 1 m per 5 years, we find terminus retreat rates of up to 10 km in 50 years. Our model suggests that, although the response of tidewater glaciers to external forcing is strongly nonlinear, the onset of retreat is controlled by climate change.     

The value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess-derived soils

A data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the Belgian loess belt from March 1997 to March 1999. Of the observed ephemeral gullies, 32 developed at the end of winter or in early spring (winter gullies) and 26 ephemeral gullies developed during summer (summer gullies). The assessed data have been used to test the physically based Ephemeral Gully Erosion Model (EGEM) and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion.Analysis shows that EGEM is not capable of predicting ephemeral gully cross-sections well. Although conditions for input parameter assessment were ideal, some parameters such as channel erodibility, critical flow shear stress and local rainfall depth showed great uncertainty. Rather than revealing EGEM's inability of predicting ephemeral gully erosion, this analysis stresses the problematic nature of physically based models, since they often require input parameters that are not available or can hardly be obtained.With respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion, this study shows that for winter gullies and summer gullies, respectively, over 80% and about 75% of the variation in ephemeral gully volume can be explained when ephemeral gully length is known. Moreover, when previously collected data for ephemeral gullies in two Mediterranean study areas and the data for summer gullies formed in the Belgian loess belt are pooled, it appears that one single length (L)–volume (V) relation exists (V=0.048 L^1.29; R²=0.91). These findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume. A simple procedure to predict ephemeral gully length based on topographical thresholds is presented here. Secondly, the empirical length–volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes.     

Submillimetre imaging of NGC 3079

Submillimetre mapping observations of the active edge-on spiral galaxy NGC 3079 are presented. These maps at 850 and 450 μm were made with the Submillimetre Common User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT).
The source structure at these wavelengths consists of a central unresolved source embedded in diffuse disc emission, similar to that displayed at 1.2 mm. The disc emission is fitted with two optically thin, isothermal dust models which give temperatures of 12 and 31 K, similar to those derived previously by Braine et al. The core component is well described by a single-temperature fit (∼32 K). The combined dust mass from these observations, using the same mass absorption coefficient as Devereux & Young (1990) is 3.5×10⁸ M_⊙, of which ∼90 per cent resides in the cold component of the galactic disc. The effect of the cold dust component detected by SCUBA is thus to reduce the global gas-to-dust mass ratio from ∼1400 found in the above study to 85, very similar to the Galactic level. Calculations using the models of Draine & Lee and/or alternative molecular gas mass estimates yield gas-to-dust mass ratios in the range 60–190.
The data presented here, together with previously published 1.2-mm mapping observations and IRAS data, are inconsistent with detections made with the Infrared Space Observatory ( ISO ). In particular, the latter give an excess of flux at 200 and 180 μm relative to that predicted by our simple model fits (approximately a factor of 2–3).     

Uniaxial creep tests on a morainic material from switzerland

To determine deformation and strength behaviour of a frozen morainic material uniaxial creep tests with constant load on remoulded samples have been carried out.

From the test results an analytical method describing the mechanical behaviour could be found.

In the following the results of this investigation are presented and an analytical solution is derived. In addition, other experimentally determined curves are compared with the calculated ones. For the material tested the proposed method leads to quite satisfactory results and is expected to do so also for other materials.