Specifying the mesoscale numerical forecast of heavy showers

Actual surface fields of meteorological variables 1–3 hours before the heavy showers are analyzed in detail for the purpose of their specification with WRF-ARW model. The complex of hygrothermodynamic characteristics needed for this purpose is discovered. The detailed satellite, radar, and synoptic data are also considered.     

Engineering problems associated with expansive clays from Romania

Engineering problems associated with expansive clay formations, which have a large swelling and shrinking potential, exist in different regions of Romania.In the general framework of the study of the behaviour of expansive clays, the present paper describes some particular aspects connected with the swelling and shrinkage processes and their engineering effects in Romania.The differences between swelling potential relationships, obtained by two different methods are presented and discussed. Swelling pressure tests were accomplished using the available standard techniques, as well as a specially developed cell pressure equipment.Attention is drawn to the stages of the shrinkage process as related to soil structure. It was found that, in a general case, there are three distinct?tages: initial, normal and residual shrinkage.Laboratory investigations have shown that in soils with an anisotropic structure, the directional variation of shrinkage strains is elliptical in shape, with the maximum shrinkage normal to particle orientation.The engineering aspects of the results are discussed.     

A ‘mathematical’ spider living on gravel plains of the Namib Desert

In certain areas of the Namib gravel plains a new Ariadna sp. was discovered. It rims its vertical burrow with a stone circle, made on average of seven quartz stones. Some mathematical relationships between hole diameter, stone sizes and weight, and animal size were studied. A correlation was found, and stone selection by this spider postulated. Different hypotheses on the adaptive value of stone circle are suggested.     

Wide-angle vibroseis test across the Rhine graben

Summary. As a joint operation of ECORS and DEKORP, a deep wide-angle seismic experiment using vibrators was carried out in the autumn of 1984. The object was to get information on the deep crust under the Rhine graben without crossing through sedimentary layers. Offsets were in the range of 50 to 89 km. In the first phase, two vibration points were executed in the Vosges mountains. A signal was received in the Black Forest from solely the farthest VP. In the second phase, fourteen VPs were executed in the Black Forest. No stacking or correlation was performed in the field in France. The quality of the results is good only if an equalization is applied before vertical stacking and correlation in the computing centre.     

Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold

From a set of stellar spectropolarimetric observations, we report the detection of surface magnetic fields in a sample of four solar-type stars, namely HD 73350, HD 76151, HD 146233 (18 Sco) and HD 190771. Assuming that the observed variability of polarimetric signal is controlled by stellar rotation, we establish the rotation periods of our targets, with values ranging from 8.8 d (for HD 190771) to 22.7 d (for HD 146233). Apart from rotation, fundamental parameters of the selected objects are very close to the Sun's, making this sample a practical basis to investigate the specific impact of rotation on magnetic properties of Sun-like stars.
We reconstruct the large-scale magnetic geometry of the targets as a low-order  (ℓ < 10)  spherical harmonic expansion of the surface magnetic field. From the set of magnetic maps, we draw two main conclusions. (i) The magnetic energy of the large-scale field increases with rotation rate. The increase in chromospheric emission with the mean magnetic field is flatter than observed in the Sun. Since the chromospheric flux is also sensitive to magnetic elements smaller than those contributing to the polarimetric signal, this observation suggests that a larger fraction of the surface magnetic energy is stored in large scales as rotation increases. (ii) Whereas the magnetic field is mostly poloidal for low rotation rates, more rapid rotators host a large-scale toroidal component in their surface field. From our observations, we infer that a rotation period lower than ≈12 d is necessary for the toroidal magnetic energy to dominate over the poloidal component.     

Sur quelques concentrations plombo-zinciferes du devonien inferieur du massif schisteux rhenan

Zusammenfassung The Lower Devonian of the Rhine Schist Massif is characterized by a fine detrital sedimentation which reflects a coastal plain environment located between the Old Red Sandstone continent in the N and the marine Bohemian Facies in the SE. Mineralisations are located within these coastal-plain sediments, especially in fractured horizons topped by pelitic and floored by sandy sediments of Sieg Emsian age. The mineralised localities occur in three zones: the districts of Bensberg, Eitorf and Mayen. The Lüderich locality (Bensberg) is the most important having approximately one million tons of Zn and Pb metal. It is localised within a zone having marked sedimentary characteristics since the Siegenian. Mineralisation occurs as penecontemporaneous lenses, fracture fillings etc, formed at abnormal contacts between lithological units having different competance during Siegenian and Lower Emsian deformation. However, locally there is lateral transition between the upper units of the sandy channel series and the lower units of the pelitic swamp facies. Vertical extension of mineralisations is strictly limited to the tectonic contact zone between the Odenspiel Sandstone and the Bensberg pelites. Study of mineralisations at various levels (mapping, morphology, structure, paragenetic and geochemical) leads to the formulation of a genetic model requiring complex fracturation at the contact between contrasting lithologies and preferential drainage through these fractured zones; metals are trapped on the sandstone floor, the pelitic roof trapping the vadose hydrothermal solutions. These basic controls seem to apply throughout the Bensberg, Eitorf and Mayen districts. On a more regional scale the age variations of the gangue sediments reflects a lateral displacement of red/grey facies limits due to coastal evolution. Thus one may demonstrate a type of mineral occurrence whose model may be that of epigenetic reconcentration within fractures affecting syngenetic geochemical anomalies.Zusammenfassung Das Unterdevon des Rheinischen Schiefergebirges wird durch eine feinkörnige detritische Sedimentation gekennzeichnet. Die Verteilung dieser detritischen Sedimente widerspiegelt eine flache Küstenlandschaft zwischen dem Kontinent des Unterrotliegenden im Norden und des Meeres mit der Böhmischen Fazies im Südosten. In diesen Schichten befinden sich gangförmige Vererzungen, die in Bruchzonen auftreten, die ein pelitisches Hangendes und ein sandsteinreiches Liegendes vom Siegen-Ems Alter haben. Die Lagerstätten kommen in drei Bezirken vor: Der Bensberger Bezirk, der Bezirk Eitorf und der Bezirk Mayen. Die Lagerstätte Lüderich (Bensberger Revier) ist die größte (ungefähr eine Million Tonnen Metall Zink+Blei). Sie befindet sich in einer Zone, in der schon in der Siegen-Stufe bemerkenswerte sedimentäre Strukturen auftreten. Die Vererzung tritt als penekonkordante Linsen, Gänge, Stockwerke in tektonischen Kontaktzonen auf. Diese Kontaktzonen befinden sich zwischen 2 verschiedenen sedimentären Einheiten, deren Gesteinseigenschaften sehr verschieden sind. Es handelt sich um Pelite mit Sandstein-Einschaltungen einerseits, die zur unteren Emsstufe gehören sollen und um fluviatile Sandsteine andererseits, die zur oberen Siegenstufe gehören sollen. Lokal ist ein lateraler Übergang durch Faziesänderung von den oberen Sandsteinen in die unteren Pelitschichten jedoch nicht unmöglich. Die Sandsteine vertreten einen fluviatilen Sedimentationsbereich, die Pelite einen sumpfigen Sedimentationsbereich. Die Vererzung (mit einer vertikalen Ausdehnung ungefähr von 300 m) tritt nur im Bereich der Kontaktzone zwischen den Odenspieler Sandsteinen und den Peliten der Unteren Bensberger Schichten auf. Die Resultate der Kartographie, der morphologischen Studie der Erzkörper, der Struktur und der Paragenese führen zu einem genetischen Modell. Dabei spielt die Anwesenheit einer Bruchstruktur an der Grenze zwischen 2 Bereichen mit verschiedenen lithologischen Eigenschaften eine Hauptrolle für die Konzentration der im Hangenden fein verteilten Metalle. Die hydrothermalen Lösungen kommen demnach nicht von der Teufe, sondern aus dem Nebengestein. Im ganzen Bensberger Erzrevier wie in der Gegend von Eitorf und in der Gegend von Mayen finden wir dieselben Leitfäden für die Vererzung in den Lagerstätten und Vorkommen. Beobachtet man die ganze Provinz, dann merkt man, daß die Altersverschiedenheiten in den Nebengesteinen der verschiedenen Lagerstätten eine geographische Wanderung der Faziesgrenze zwischen rot und grau in dieser küstennahen Ebene Widerspiegeln. Die verschiedenen Vorkommen und Lagerstätten treten immer in unmittelbarer Nähe dieser Grenze auf. Die Eigenschaften dieser Lagerstätten weisen auf eine Bildung durch eine epigenetische Umlagerung in eine gangförmige Bruchstruktur hin.     

Relationships between Holocene sea-level variations,trophic development,and climatic change in Negra Lagoon,Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142 km² coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000 yr BP), cool–dry climatic conditions were established. After ~4000 yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700 yr BP. Such climatic amelioration led to increases in trophic state.