Coexisting periodic attractors in injection locked diode lasers

We present experimental evidence for coexisting periodic attractors in a semiconductor laser subject to external optical injection. The coexisting attractors appear after the semiconductor laser has undergone a Hopf bifurcation from the locked steady state. We consider the single mode rate equations and derive a third order differential equation for the phase of the laser field. We then analyze the bifurcation diagram of the time periodic states in terms of the frequency detuning and the injection rate and show the existence of multiple periodic attractors.Comment: LaTex, 14 pages, 6 postscript figures include

The Red Sea, Coastal Landscapes, and Hominin Dispersals

This chapter provides a critical assessment of environment, landscape and resources in the Red Sea region over the past five million years in relation to archaeological evidence of hominin settlement, and of current hypotheses about the role of the region as a pathway or obstacle to population dispersals between Africa and Asia and the possible significance of coastal colonization. The discussion assesses the impact of factors such as topography and the distribution of resources on land and on the seacoast, taking account of geographical variation and changes in geology, sea levels and palaeoclimate. The merits of northern and southern routes of movement at either end of the Red Sea are compared. All the evidence indicates that there has been no land connection at the southern end since the beginning of the Pliocene period, but that short sea crossings would have been possible at lowest sea-level stands with little or no technical aids. More important than the possibilities of crossing the southern channel is the nature of the resources available in the adjacent coastal zones. There were many climatic episodes wetter than today, and during these periods water draining from the Arabian escarpment provided productive conditions for large mammals and human populations in coastal regions and eastwards into the desert. During drier episodes the coastal region would have provided important refugia both in upland areas and on the emerged shelves exposed by lowered sea level, especially in the southern sector and on both sides of the Red Sea. Marine resources may have offered an added advantage in coastal areas, but evidence for their exploitation is very limited, and their role has been over-exaggerated in hypotheses of coastal colonization

Nadaouiyeh Aïn Askar, an example of Upper Acheulean variability in the Levant

The site of Nadaouiyeh Aïn Askar is situated in The El Kowm oasis, located in the centre of modern Syria, presents an Acheulian sequence covering approximately the span between 550 ka and 325 ka ago. At least 32 levels of Acheulian occupations can be discerned that can be integrated into seven distinct cultural phases of hand axe traditions. Surprisingly, the oldest occupations discovered in situ present the most refined hand axes. The basic evolution goes from highly refined and standardized to less elaborate and more schematic and irregularly manufactured bifaces but not in straight lines. A common feature of all Acheulian groups from Nadaouiyeh Aïn Askar is the strong predominance of the façonnage concept for tool fabrication combined with a nearly complete absence of retouched flakes. The different archaeological units present a strong originality, each with diagnostic features differentiate from the others, demonstrating a strong cultural versatility. Such change can be far-reaching and swift. The variability encountered in Nadaouiyeh Aïn Askar stands for an acute dynamic of technological and particular stylistic changes within the Acheulian, contrarily to what usually is expected regarding this period

Prähistorische Archive in der syrischen Wüstensteppe

Seit 1989 läuft am Seminar für Urgeschichte der Universität Basel in Zusammenarbeit mit der Universität Damaskus unter der Leitung der Professoren Jean-Marie le Tensorer und Sultan Muhesen ein breit gefächertes interdisziplinäres Forschungsprogramm über die ältesten menschlichen Besiedlungen in der zentralsyrischen Wüstensteppe, die aus einer langjährigen persönlichen Freundschaft des Leiters des Basler Seminares und dem damaligen Vorsteher des Antikendienstes Syriens entstanden ist. Schwergewicht dieser Arbeiten ist die Untersuchung von Siedlungsstellen aus dem Zeitraum zwischen 500 000 bis 150 000 Jahren. Es handelt sich um Zeltplätze unter freiem Himmel, in der Regel in der Nähe natürlicher Quellen