Die fazielle und paläogeographische Entwicklung der infrakambrischen bis ordovizischen Sedimente im Mittleren Antiatlas um Agdz (S-Marokko)

Zusammenfassung Die Entwicklung des Adoudounien (Infrakambrium) und Géorgien (Unterkambrium) ist im Mittleren Antiatlas durch einen Wechsel von marinen und kontinentalen Sedimenten gekennzeichnet. Wildbachablagerungen an der Basis und an den Beckenrändern werden von marin-marginalen stromatolithischen Karbonaten abgelöst. Ignimbrite belegen wiederholte terrestrische Sedimentation.Mit fluviatilen Sanden und wiederum Stromatolithen und lagunären Karbonaten (mit ersten Trilobiten!) setzt ein zweiter transgressiver Großzyklus ein, der an der Wende Infra-/Unter-Kambrium einen ersten Höhepunkt erreicht. Durch regressive Kleinzyklen charakterisierte Abfolgen leiten zu Sandsteinen über, die als Ablagerungen eines Deltas gedeutet werden.Vom Mittelkambrium bis Ordovizium dominiert marine Schelfsedimentation.

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The formations of Adoudounien (Infra Cambrian) and Géorgien (Lower Cambrian) of the middle Anti-Atlas are characterized by an alternation of marine and continental sediments. Torrent conglomerates at the base and the margins of the basin took turns to marine-marginal stromatolitic carbonates. Ignimbrites prove repeated terrestrial sedimentation.A second transgressiv megasequence begins with fluviatil sands and goes on with stromatolites and lagoon carbonates (first Trilobites). This transgression reachs his first culmination at the Infra-/Lower-Cambrian boundary. Typical regressiv cycles form a transition to sandstones, which are interpreted as sediments of a delta.Marine shelf environment dominates from Middle Cambrian to Ordovician beds.

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Résumé Dans le moyen Anti-Atlas, l'évolution de l'Adoudounien et du Géorgien est caractérisée par un changement des sédiments marins et continentaux. Les dépôts des torrents à la base et dans la bordure du bassin font place à des carbonates marins marginaux stromatolithiques. Les ignimbrites marquent le retour fréquent à la sédimentation terrestre.Une deuxième mégaséquence transgressive débute avec des sables fluviatiles, des stromatolithes et des carbonates lagunaires (premiers trilobites). La transgression atteint une première phase culminante à la transition de l'Adoudounien au Géorgien. Des séquences caractérisées par de petits cycles régressifs conduisent à des grès qui pourraient être interpré tés comme des sédiments deltaïques.A partir du Cambrien moyen jusqu'à l'Ordovicien prédomine un milieu de plate-forme externe.

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Adoudounien — — Géorgien — — . — — . , - , , . , , . .

     

Stellenangebote und Stellengesuche

Ohne Zusammenfassung     

Analysis of anomalies in ADS-B and its GPS data

Traditionally, the surveillance component of the air traffic management system has been based on radar, which consists of two separate systems: primary radar and secondary radar, which both enable the measurement of the aircraft range and bearing to the radar station. Primary radar is based on signals emitted by a ground station simply being reflected off an object and detected by a ground-based receiver. Secondary radar also emits signals, but relies upon a transponder onboard the aircraft to emit a signal itself, modulated among others by a four-digit aircraft identity (Mode A), aircraft altitude (Mode C) and/or 24-bit unique address (Mode S). Typical accuracies of secondary radar are of the order of 0.03 NM in range and 0.07° in azimuth. However, no position integrity report is provided. Air traffic density is expected to significantly increase in the future. In order to maintain or enhance air travel efficiency, while maintaining safety, more accurate surveillance systems, with the required integrity, will be required. Automatic dependent surveillance–broadcast (ADS-B) is a new aviation surveillance system, envisioned to overcome the limitations of radar and to enhance surveillance performance and thereby increase airspace capacity. However, its high dependence on external systems such as onboard navigation and communication systems also increases the number of potential points of failure. It is important to understand and mitigate these failure modes before the system can reliably be implemented. The present study emerged as an exploratory research as part of a safety assessment framework development for the ADS-B system. It reviews the ADS-B failure modes, data collection and analysis of ADS-B and its corresponding onboard GPS data. The study identifies a set of failures common to certain aircraft models, with consistent error patterns. A key failure mode was found to be associated with the navigation data from the onboard GPS. We discuss the identified failure modes and investigate the nature and causes of these failures. The findings highlight some of the deficiencies of the current ADS-B system, which will need to be addressed before the ADS-B system can reliably be implemented.     

Density and pressure change in an occluding cyclone

Summary On October 20, 1974, an occluding cyclone, which did not intensify any more crossed central Europe. Considerable pressure tendencies reflecting the displacement of the storm were observed during its passage. Although horizontal density advection contributed least to density and thus pressure changes, it was still of decisive importance for both. The other larger contributors, whose net effect was usually opposed to the effect of horizontal advection, nearly cancelled each other. Thus there was a fair correlation between horizontal advection and density tendency, and the actual density and pressure changes frequently turned out smaller than if caused by advection alone.It has been shown that in the lowest 3 km usually. For the mass divergence this inequality was observed in the frontal zones where horizontal advection was considerable. In particular, warm air advection reduced the effect of horizontal velocity convergence near the warm front. Thus, vertical mass divergence became predominant and caused a density decline. Cold air advection accompanying the cold front was responsible for horizontal divergence to be overcompensated by vertical mass convergence which induced rising density.With 11 Figures     

The private sector and local economic development in South Africa

The objective in this paper is to analyse private sector involvement in LED in South Africa. Four key spheres of private sector involvement in LED are identified and discussed: (1) as participator and occasional initiator of local development processes, (2) as major partner in the development activities of public-private sector partnerships, (3) as lead role player in certain direct initiatives for reviving South Africa's inner cities, and (4) as promoter and facilitator of local small business development. It is argued that the concept of local dependence could be usefully applied to interpret private sector involvement in LED in South Africa.     

Circuiti equivalenti dell'effetto sismo-elettrico

Riassunto Il modello circuitale di equivalenza approssimata dell'effetto sismoelettrico (Thompson-Slotnick) è stato in questa Nota riesaminato, sia nella forma originaria dei precitati A.A., sia con altre forme più semplici, della resistenza ohmica in serie nel circuito stesso.Quando la resistenza ohmica assume una forma oscillante (equivalenza ipotetica degli impulsi oscillanti elastici), lo stato di regime della corrente elettrica che si determina possiede una componente indipendente del tempo e una dipendente dal tempo, con infinite armoniche.Così si spiega, tra l'altro (almeno parzialmente), uno dei risultati sperimentali caratteristici dell'effetto sismo-elettrico. Esso non riproduce (nella rappresentazione dell'intensità della corrente), le forme dell'oscillazione di carattere meccanico, impressa al suolo, ma la frequenza meccanica, conforme a quanto rilevabile oscillograficamente.

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Summary In this note is again, examined the circuital model of the approximate equivalence of the seismic-electric effect (Thompson-Slotnick) in the original form given by the mentioned authors as well as in other more simple forms of the ohmic resistance set in the circuit.When the ohmic resistance takes an oscillating form (hypotetical equivalence of oscillating elastic impulses) the steady state of electric current, which on determines, has a time indipendent and a time dipendent component with an infinite number of harmonics.This explains oneself, among others (at least partially), one of the characteristic experimental results of the seismic-electric effect. It does not reproduce (in the magnitude of current reproduction) the oscillation froms of mechanical character impressed to the soil, but reproduces the mechanical frequency conforming with the oscillographic obtainable data.

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Zusammenfassung In dieser Note wird das Stromkreismodell der angenäherten Äquivalenz des seismisch-elektrischen Effektes (Thompson-Slotnick) erneut geprüft, sowohl in der von den erwähnten Verfassern gegebenen Originalform als auch in anderen einfacheren Formen des im Stromkreis in Reihe geschaltetenOhm'schen Widerstandes.Wenn derOhm'sche Widerstand eine schwingende Form annimmt (hypothetische Äquivalenz de elastischen schwingenden Impulse), so besitzt der Betriebszustand des elektrischen Stromes den man bestimmt, eine zeitlich unabhängige und eine zeitlich abhängige Komponente mit unendlich vielen harmonischen Schwingungen.In dieser Weise erklärt sich u. a.. (wenigstens teilweise) eines der experimentellen charakteristischen Ergebnisse des seismisch-elektrischen Effektes. Derselbe gibt (in der Darstellung der Stromstärke) nicht die Formen der dem Boden aufgeprägten Schwingung mechanischen Charakters wieder, sondern die mechanische Frequenz gemäss den oszillographisch feststellbaren Angaben.

     

Klimatische Tendenzen und Untersuchungen zur allgemeinen Zirkulation

Zusammenfassung Einige Beobachtungsdaten aus dem Winter 1962/63 werden sowohl in bezug auf neuere als auch auf langfristige klimatische Tendenzen diskutiert. Der Abkühlung der Weltklimate seit etwa 1940 ist bisher praktisch noch nicht viel Beachtung geschenkt worden, obwohl sie die Häufigkeit strengen Winterwetters beeinflußt hat. Dies ist vielleicht teilweise durch die künstliche Erwärmung der Städte zu erklären, die unter starken niedrig liegenden Temperaturinversionen im Winter am wirksamsten ist. Ferner wird über Untersuchungen der Änderungen der allgemeinen atmosphärischen Zirkulation berichtet. Diese zeigen den Mechanismus auf, durch den aufeinanderfolgende langfristige Klimaänderungen zustandegekommen sind: Die Abkühlung in den Jahren von 1300 bis 1600 und die Erwärmung in den Jahren von 1700 bis etwa 1930 werden mit einer Abschwächung beziehungsweise Verstärkung der Zirkulation bzw. mit entsprechenden Änderungen der Wellenlänge der zirkumpolaren Westdrift und einer Durchdringung der höchsten Breiten durch Warmluftzufuhr und Zyklonenzugbahnen in Verbindung gebracht. Eine Umkehr des Trends kann unter Verwendung dieser Zirkulations-Aspekte bereits früher entdeckt werden — schon 30 oder mehr Jahre früher — als durch Untersuchung der Temperaturen in der Arktis und anderswo, der Ausdehnung der Eisbedeckung usw. Es ist wahrscheinlich, daß die Abkühlung und die Zunahme des Eises, die jetzt speziell im europäischen Sektor zu beobachten sind, eine Reaktion darstellen auf die neuere Tendenz zu schwächerer zonaler Zirkulation hin und zu einer Westwärts-Verschiebung des Höhentroges im europäischen Sektor, die eine zunehmende Häufigkeit nördlicher Bodenwinde im Sektor zwischen Grönland und dem Ural begünstigt. Die Eislage in den nördlichen Meeren im Februar 1963 läßt sich nur mit den schlimmsten Jahren des 17. und 18. Jahrhunderts vergleichen.

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Summary Some figures for winter 1962/63 are examined in relation to both recent and long-term climatic trends. The cooling of world climates since about 1940 has not yet received much notice from the practical point of view, though it has affected the frequency of difficult winter weather. The oversight is perhaps partly explained by the increasing artificial warmth of the cities, which is most effective under strong low-level temperature inversions in winter. Studies of changes in the general atmospheric circulation are described. These show the mechanism by which successive long-term changes of climate have been achieved—cooling from 1300 to 1600 and warming from 1700 to about 1930—was associated respectively with weakening and strengthening circulation and corresponding changes of (a) wavelength in the circumpolar westerlies (b) penetration of the highest latitudes by advected warm air and depression tracks. Reversal of trend is detected earlier, already 30 years or more ago, in these aspects of the circulation than when one examines temperatures in the Arctic and elsewhere, extent of ice etc. It seems probable that the cooling and increase of ice now to be observed particularly in the European sector are a response to the recent trend towards weaker zonal circulation and a westward shift of the upper trough in the European sector which favours increased frequency of northerly surface winds in the sector between Greenland and the Urals. The ice situation on the northern seas in February 1963 appears fully comparable only with the worst years of the 17th and 18th centuries.

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Résumé On discute ici quelques observations de l'hiver 1962–1963 à la lumière de tendances climatologiques tant récentes qu'à long terme. Jusqu'ici, on n'a pas accordé beaucoup d'attention au refroidissement des climats de notre globe depuis 1930, bien que ce refroidissement ait influencé déjà le nombre des hivers rigoureux. Ce peu d'attention s'explique peutêtre par le chauffage artificiel des villes, chauffage qui est particulièrement efficace au-dessous de fortes inversions thermiques situées en hiver à basse altitude. On rapporte en outre sur des recherches concernant des changements de la circulation atmosphérique générale. Ces changements montrent le mécanisme par lequel les modifications successives du climat à long terme se sont produites. On met le refroidissement des années 1300 à 1600 en relation avec un ralentissement de la circulation et le réchauffement de 1700 à 1930 avec une accélération de cette circulation. On peut faire le même raprochement pour des modifications similaires de la longueur d'ondes du courant circumpolaire d'ouest et la pénétration des afflux d'air chaud et des trajectoires des cyclones aux latitudes les plus grandes. Une inversion de la tendance du climat peut être reconnue bien à l'avance—30 ans et plus—en utilisant ces nouveaux aspects de la circulation, qu'en utilisant les températures de l'arctique et d'ailleurs, l'extension de la calotte glaciaire, ou d'autres critères. Il est probable que le refroidissement et l'augmentation de la glace, visibles actuellement surtout dans le secteur européen, ne sont qu'une réaction aux nouvelles tendances de ralentissement de la circulation zonale et d'un déplacement vers l'ouest du creux dépressionnaire en altitude du secteur européen, ce qui favorise une fréquence accrue des vents du nord au sol entre le Groenland et l'Oural. La position des glaces dans les mers du nord en février 1963 ne peut être comparée qu'aux pires années des 17ème et 18ème siècles.

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Mit 5 Textabbildungen     

Palynology of the circum-mediterranean triassic: Phytogeographical and palaeoclimatological implications

Following a tentative evaluation of palynological information from Ladinian and, more particularly, Karnian successions, there seems to be every indication that qualitative and quantitative compositional differences of palynological assemblages could well be applied in testing concepts of Triassic phytogeography and palaeoclimatology. The following implications are emphasized:

1. There is sufficient palynological evidence that the Mediterranean region includes a domain of mixed northern (Laurasian) and southern (Gondwana) types of floras.
2. The concept of an essentially arid nature of a wide equatorial climatic belt during Triassic times finds palynological support.
3. Palynological evidence does not contradict a concept of pronounced decrease in precipitation towards the western part of the Mediterranean region.
4. In Europe, occurrences of hygrophytic palynofloras and coals within an arid climatic zone can be explained by the water-supply of extensive river-systems.

     

Colonisation of the Krakatau islands by invertebrates

Arrival of invertebrates on the Krakatau islands, and the development of invertebrate assemblages there since 1883, are reviewed. Many data are imprecise, and difficulties of interpretation are outlined. A few well-known groups, such as butterflies, are used to suggest that much colonisation so far has been by relatively generalist species,and that the rate of addition of new species may become slower as the less vagile specialists characteristic of later successional vegetation may find natural colonisation harder. Studies of the assemblages developing in association with particular plant species are likely to be helpful in assessing future trends of invertebrate colonisation.