Wind velocity and sand transport on a barchan dune

We present measurements of wind velocity and sand flux performed on the windward side of a large barchan dune in Jericoacoara, northeastern Brazil. From the measured profile, we calculate the air shear stress using an analytical approximation and treat the problem of flow separation by an heuristic model. We find that the results from this approach agree well with our field data. Moreover, using the calculated shear velocity, we predict the sand flux according to well-known equilibrium relations and with a phenomenological continuum saltation model that includes saturation transients and thus allows for nonequilibrium conditions. Based on the field data and theoretical predicted results, we indicate the principal differences between saturated and nonsaturated sand flux models. Finally, we show that the measured dune moves with invariant shape and predict its velocity from our data and calculations.     

Stress State of the Earth’s Crust in the Western Tien Shan in Central Asia (Uzbekistan): A Mathematical Stress Model

Geotectonics - Seismic and tectonic processes were analyzed, taking into account the dimensions of tectonic structures and geological factors that determine the features of the relationship between...     

济阳坳陷中生代地层剥蚀厚度、原始厚度恢复及原型盆地研究

在采用各种地层剥蚀量的计算方法对济阳坳陷中生代各主要不整合面地层剥蚀厚度恢复的基础上,结合钻井及地震资料,对中生代各主要构造层的原始地层厚度进行了恢复。以此为切入点,对济阳坳陷区中生代盆地原型进行了初步探讨,将其划分为5期盆地原型：早-中三叠世为一大型内陆坳陷盆地;晚三叠世整体挤压抬升剥蚀;早-中侏罗世为弱挤压背景下的山间盆地;晚侏罗世-早白垩世为受正断层控制的断陷盆地;晚白垩世为断陷后的坳陷盆地。     

Spectral investigation of the chromosphere

Several hundred H spectrograms from areas close to the solar limb were taken with the 35 cm Coudé refractor at Anacapri. The 41 spectra with the greatest spatial resolution were selected and analysed. At the supergranular boundaries a considerable fraction of the line profiles were found to correspond to Beckers Cloud Model (BCM). Moreover, the BCM parameters of the dark mottles at the limb appear to be approximately equal to those from the center of the disk. On the other hand, we also obtained evidence in disagreement with the general applicability of the BCM to all features of the chromospheric fine structure.We attempted to present the large set of observational data in a fashion that permits their interpretation by alternative theoretical models.Mitteilungen aus dem Fraunhofer Institut Nr. 151.     

Effects of plasma rotation on alfvén solitons in pulsar magnetospheres

Nonlinear Alfvén wave in a hot rotating and strongly magnetized electron-positron plasma is considered. Using relativistic two fluid equations, the dispersion relation for Alfvén wave in the rotating plasma is obtained. Large amplitude Alfvén solitons are found to exist in the rotating pulsar plasma. Rotational effects on solitons are discussed.     

Exact Bianchi-type VIII and IX models in the presence of the self-creation theory of cosmology

Exact Bianchi-type VIII and IX models in the presence of Barber's second self-creation theory of cosmology are presented, when the source of the gravitational field is a perfect fluid withP=. Some physical and geometrical properties of the models are discussed.     

Potassium induced salinity tolerance in wheat (Triticum aestivum L.)

Water culture experiments were conducted to study the response of ten wheat genotypes to external K application (10 mmol KCI dm^?3) at seedling stage under saline condition (0 and 100 mmol NaCl dm^?3). The data showed that there was an increase in the shoot and root length with the application of external K. The increase was more pronounced under control than under saline conditions. The better performing genotypes under two treatments were Bhitai, NIAB-41, NIAB-I076 and Khirman. The enhanced growth of these genotypes under saline condition might be due to the quick response to external K application, resulting in high K/Na ratio. The results indicated that the genotypes, which have the ability of enhanced K/Na discrimination, might perform better under saline conditions when sufficient potassium is applied in the rooting medium.     

An analysis of Pc3 and Pc4 pulsations at Terra Nova Bay (Antarctica)

We conducted a statistical analysis of the physical characteristics of the micropulsation activity (Pc3 and Pc4 range) detected, during the austral summer 1994/95, at Terra Nova Bay (Antarctica, corrected latitude 80.0°S), a station which is few degrees poleward of those where most of the Antarctic measurements in these frequency ranges have been performed. The emerging overview suggests that the correspondence between the pulsation power and the external parameters (solar wind speed, interplanetary magnetic field magnitude and orientation) is significantly stronger than at somewhat lower latitudes. The day-to-day power variability was found to be strictly related to the general level of the geomagnetic activity, and the power level sharply maximizes at local magnetic noon. In the Pc4 range peaks of correlation with the SW speed are found in the dawn and dusk sides of the Earths magnetosphere and the daily variation of the polarization pattern is closely consistent with that found at auroral latitudes and at lower frequencies. In the Pc3 range the correlation coefficient between the pulsation power and the SW speed has maximum values in the local morning, and the frequency of selected events reveals a strong IMF control during closed magnetospheric conditions. The local time dependence of the correlation coefficient between the pulsation power and the cone angle reveals an additional control by the IMF orientation, which becomes more explicit around local noon.     

The ALOMAR Rayleigh/Mie/Raman lidar: objectives, configuration, and performance

We report on the development and current capabilities of the ALOMAR Rayleigh/Mie/Raman lidar. This instrument is one of the core instruments of the international ALOMAR facility, located near Andenes in Norway at 69°N and 16°E. The major task of the instrument is to perform advanced studies of the Arctic middle atmosphere over altitudes between about 15 to 90 km on a climatological basis. These studies address questions about the thermal structure of the Arctic middle atmosphere, the dynamical processes acting therein, and of aerosols in the form of stratospheric background aerosol, polar stratospheric clouds, noctilucent clouds, and injected aerosols of volcanic or anthropogenic origin. Furthermore, the lidar is meant to work together with other remote sensing instruments, both ground- and satellite-based, and with balloon- and rocket-borne instruments performing in situ observations. The instrument is basically a twin lidar, using two independent power lasers and two tiltable receiving telescopes. The power lasers are Nd:YAG lasers emitting at wavelengths 1064, 532, and 355 nm and producing 30 pulses per second each. The power lasers are highly stabilized in both their wavelengths and the directions of their laser beams. The laser beams are emitted into the atmosphere fully coaxial with the line-of-sight of the receiving telescopes. The latter use primary mirrors of 1.8 m diameter and are tiltable within 30° off zenith. Their fields-of-view have 180 rad angular diameter. Spectral separation, filtering, and detection of the received photons are made on an optical bench which carries, among a multitude of other optical components, three double Fabry-Perot interferometers (two for 532 and one for 355 nm) and one single Fabry-Perot interferometer (for 1064 nm). A number of separate detector channels also allow registration of photons which are produced by rotational-vibrational and rotational Raman scatter on N₂ and N₂+O₂ molecules, respectively. Currently, up to 36 detector channels simultaneously record the photons collected by the telescopes. The internal and external instrument operations are automated so that this very complex instrument can be operated by a single engineer. Currently the lidar is heavily used for measurements of temperature profiles, of cloud particle properties such as their altitude, particle densities and size distributions, and of stratospheric winds. Due to its very effective spectral and spatial filtering, the lidar has unique capabilities to work in full sunlight. Under these conditions it can measure temperatures up to 65 km altitude and determine particle size distributions of overhead noctilucent clouds. Due to its very high mechanical and optical stability, it can also employed efficiently under marginal weather conditions when data on the middle atmosphere can be collected only through small breaks in the tropospheric cloud layers.     

Kurzzeit-Toxizitätstests zur Messung der Toxizität von Chemikalien gegenüber Belebtschlamm

Short-term Toxicity Tests for the Measurement of Toxicity of Chemicals Towards Activated Sludge. To avoid severe damage to the activated sludge of a wastewater treatment plant it is necessary to control the sludge activity by means of biological test systems. Especially the short-term respiration assay and the dehydrogenase assay with resazurin as a redox-dye seem to be appropriate for this monitoring program. The practical performance of both test systems was optimized in some essential points. With the help of several reference substances both monitoring systems were tested for practical use as short-term toxicity tests. The results of the investigations showed that the inhibitory concentrations measured in both test systems were partially very different. In monitoring experiments with laboratory-scale wastewater treatment plants it could be shown that a positive correlation between respiration activity and dehydrogenase activity is not always given. Furthermore, a pH-dependent toxicity could be demonstrated for several substituted phenols.