Studies of granular velocities

Vertical small scale velocities deduced from highly resolved spectra in the center of the solar disk, obtained with a RCA image intensifier tube, are discussed. As a main result we find that the velocities of small elements (< 2) are remarkably larger in active regions around sunspots than in the quiet Sun. In both cases the velocities decrease with height in the solar atmosphere (Figure 2).Mitteilungen aus dem Fraunhofer-Institut Nr. 145.     

Suitable gravity interpolation technique for large data gaps in Africa

Studia Geophysica et Geodaetica - The gravity database for the IAG African Geoid Project contains significantly large data gaps. These large data gaps affect the interpolation precision of the...     

Quality Appraisal of Surface Waters on Fennoscandian Territory

Widely applied bioindication methods are analyzed based on the survey data of 1980–1996 for over 400 lakes and 300 watercourses in the northeastern Fennoscandia known to experience anthropogenic impact (toxification, acidification, eutrophication, and thermofication). Representative results of hydrobiological analysis of the quality of surface waters in areas with mixed toxic pollution (or anthropogenic acidification) may be obtained if methods are applied, different from the bioindication methods that are now accepted as standard for Russia, along with methods of biotesting natural waters. The saprotoxibity index, Kola biotic index, acidification estimation scale, biotesting methods were developed and adapted to regional conditions.     

Calibration of the high-pressure cohesive strength meter (CSM)

Coastal erosion is an immense economic and social problem that has been receiving increased attention in recent years. A number of devices have been developed to determine the sediment stability in coastal areas: laboratory and field flumes; a range of different erosion devices; shear vanes and fall cone penetrometers. The cohesive strength meter (CSM) erosion device was developed to determine in situ the temporal and spatial variations in the erosion threshold of muddy intertidal sediments. Technological developments have enabled considerable improvements to be made to the original design over the last 15 years.     

Fast-changing processes in a medium subject to loading as detected by resistivity measurements

Making measurements of electric resistivity at 16 s intervals, the authors noticed fast changes of this parameter prior to the occurrence of the main fracture. The changes are superposed on bay pulsations of increasing amplitude and decreasing period. This finding opens prospects for a wider use of an electric resistivity method and proves the high quality of automatic instruments, in particular their high resolution. It also gives evidence for the occurrence of short-period precursors in the fracture zone while the main fracture is being formed.     

3,4-benzopyrene and perylene in mussels, Mytilus sp., from the Laguna Veneta,North-East Italy

From July, 1975 to November, 1976 mussels from the Laguna Veneta, north-east Italy, and the adjacent Adriatic Sea were collected bimonthly at ten stations and analysed for 3,4-benzopyrene (BaP) and perylene (Pe) content. Mean concentrations were in the range 12·0–135·1 μg/kg dry weight for BaP and 1·5–16·9 μg/kg for Pe, but values as high as 327 μg/kg for BaP and 71 μg/kg for Pe have been measured. The distribution of BaP and Pe closely matches previous results on petroleum hydrocarbon contamination in mussels from this area and indicates that the major portion of BaP and Pe in these bivalves is due principally to human activities.     

Solitary wave generation dynamics at Luzon Strait

A high resolution modeling study is undertaken, with a 2.5-dimensional nonhydrostatic model, of the generation of internal waves induced by tidal motion over the ridges in Luzon Strait. The model is forced by the barotropic tidal components K1, M2, and O1. These tidal components, along with the initial density field, were extracted from data and models. As the barotropic tide moves over the Luzon Strait sills, there is a conversion of barotropic tidal energy into baroclinic tidal energy. Depressions are generated that propagate towards the Asian Seas International Acoustics Experiment (ASIAEX) test site on the Chinese continental shelf. Nonlinear effects steepen the depressions, frequency and amplitude dispersion set in, and disintegration into large amplitude solitary waves occurs. The effects of varying the initial density field, tidal component magnitudes, as well as adding a steady background current to represent the occasional excursions of the Kuroshio Current into the strait, are considered.Depressions are generated at each of the two sills in Luzon Strait which radiate away, steepening and evolving into internal solitary wave trains. Baroclinic fluxes of available potential energy, kinetic energy and linear are calculated for various parameter combinations. The solitary wave trains produced in the simulations generally consist of large amplitude wave trains alternating with small amplitude wave trains. During strong tidal flow, Kelvin–Helmholtz type instabilities can develop over the taller double-humped sill. The solitary waves propagating towards the ASIAEX test site have been observed to reach amplitudes of 120–250 m, depending on the tidal strength. ASIAEX observations indicate amplitudes up to 150 m and the Windy Island Experiment (WISE) measurements contain magnitudes over 200 m. The model results yield solitary wave amplitudes of 70–300 m and half widths of 0.60–3.25 km, depending on parameter values. These are in the range of observations. Measurements by Klymak et al. (2006), in the South China Sea, exhibit amplitudes of 170 m, half widths of 3 km and phase speeds of 2.9 m s^?1. Model predictions indicate that the solitary waves making up the wave packet each experience different background currents with strong near surface shear.The energy in the leading soliton of the large amplitude wave trains ranges between 1.8 and 9.0 GJ m^?1. The smaller value, produced using barotropic tidal currents based on the Oregon State University data base, is the same as the energy estimated to be in a solitary wave observed by Klymak et al. (2006). Estimates of the conversion of barotropic tidal energy into radiating internal wave energy yield conversion rates ranging between 3.6% and 8.3%.     

Relationship between the effective diffusion coefficient of soil radon and groundwater recharge in semi-arid areas

Herein, the relationship between soil radon behavior and groundwater recharge in the town of Hosha, a semi-arid area of Jordan is explored. The annual rainfall average in this area is between 60–100 mm year⁻¹. Soil radon concentration levels, using CR-39 detectors, have been measured at several depths. Nine sampling sites on a hill slope, in the summer and winter 2006 were chosen. Other soil parameters such as moisture, soil type and porosity were also measured. Correlation between the latter and the calculated effective diffusion coefficients, based on a linear approximation, was done in order to explore water movement. A weak correlation between the soil radon concentration and water recharge in this particular semi-arid area is observed. The results show that water recharge takes place vertically, i.e., water moves downward and in one of the nine sampling sites this movement seems to be more rapid compared to the other sites.     

The theory of spontaneous emission by electrons during their motion along the quantizing magnetic field of a star

The quantum motion of non-relativistic and relativistic electrons in the presence of constant magnetic fields at the surfaces of magnetic stars, magnetic white dwarfs, and pulsars is considered. The quantizing magnetic-field strengths for charged particles with specified energies are determined. The quantum motion of these particles in a plane perpendicular to the magnetic field is accompanied by spontaneous radiation due to electron transitions from higher to lower discrete energy levels, right down to the ground state. In the non-relativistic case, this emission is monochromatic. In the non-relativistic case, various frequencies are emitted, but lie within an order of magnitude of each other. The electron kinetic energy along the magnetic field varies from zero to a maximum value, due to the one-dimensional character of the motion along the field, between each pair of potential barriers corresponding to the discrete energy levels. The results may be relevant to describing gamma-ray flares of pulsars.     

Tailings composition effects on shear strength behavior of co-mixed mine waste rock and tailings

The objective of this study was to evaluate the effect of mine tailings composition on shear behavior and shear strength of co-mixed mine waste rock and tailings (WR&T). Crushed gravel was used as a synthetic waste rock and mixed with four types of tailings: (1) fine-grained garnet, (2) coarse-grained garnet, (3) copper, and (4) soda ash. Co-mixed WR&T specimens were prepared to target mixture ratios of mass of waste rock to mass of tailings (R) such that tailings “just filled” interparticle void space of the waste rock (i.e., optimum mixture ratio, R _opt). Triaxial compression tests were conducted on waste rock, tailings, and mixed waste at effective confining stresses (\(\sigma_{\text{c}}^{{\prime }}\)) ranging from 5 to 40 kPa to represent stresses anticipated in final earthen covers for waste containment facilities. Waste rock and co-mixed WR&T specimens were 150 mm in diameter by 300 mm tall, whereas tailings specimens were 38 mm in diameter by 76 mm tall. Shear strength was quantified using effective stress friction angles (?′) from undrained tests: ?′ for waste rock was 37°, ?′ for tailings ranged from 34° to 41°, and ?′ for WR&T mixtures ranged from 38° to 40°. Thus, shear strength of co-mixed WR&T was comparable to waste rock regardless of tailings composition. Shear behavior of WR&T mixtures was a function of R and tailings composition. Tailings influenced shear behavior for R < R _opt and when tailings predominantly were silt. Shear behavior was influenced by waste rock for R ≥ R _opt and when tailings predominantly were sand or included clay particles.