Trends and zonal variability of extreme rainfall events over East Africa during 1960–2017

Natural Hazards - East African countries (Uganda, Kenya, Tanzania, Rwanda, and Burundi) are prone to weather extreme events. In this regard, the past occurrence of extreme rainfall events is...     

Phytoplankton-pigment signatures and their relationship to spring–summer stratification in the Gulf of Gabes

We investigated the phytoplankton dynamics (determined by CHEMTAX analysis of HPLC pigment data) and its relationships with nutrients and water column structure, during two oceanographic cruises in May–June and September 2006 in the Gulf of Gabes (south-eastern Mediterranean). The May–June cruise coincided with the beginning of the summer stratification, while a strong stratification occurred in September with a more than 30 m deepening of the thermocline, and a reduction of the euphotic depth. This strong stratification resulted in a shift in nitrogen sources from nitrates to ammonium as well as phosphate depletion (0.2 μM) and a decrease in silicate concentrations (<2 μM). With the exception of chlorophyll a, pigment concentrations were higher in September than in May–June samplings. The pico- and nanophytoplankton were the major contributors to phytoplankton total biomass, accounting for 90% and 87% of total chlorophyll a in May–June and September, respectively. Picoplankton persisted throughout the entire survey, occupying different depth layers. Chlorophytes were present at substantial amounts (average 23% of total chlorophyll a) during May–June; however, they declined in September (average 5%). Diatoms were overall poorly represented in this study (2% of total chlorophyll a), due probably to silicate shortage. Apparently, the nutrient availability, but also the water column stability seemed to be among the major factors determining phytoplankton dynamics. Indeed, cyanobacteria were prominent in surface samples during the period of strong stratification, whereas the relative contribution of chlorophytes decreased, probably due to low phosphate availability.     

Inference of total ozone from photometric measurements of sky radiation

Summary Ground-based photometric measurements of spectral sky radiation have been made using a simple filter instrument. Sky radiation intensities measured in the solar vertical at =3200 Å and 3600 Å are compared to infer total ozone. A model of multiple scattering Rayleigh atmosphere serves as a primary reduction parameter. Spectral measurements of all-sky radiance distribution are used to study the effects of haze and clouds on the inference of total ozone. The brightness distribution of clear and overcast sky in ultraviolet is also described.     

The development of the ‘planned bedouin settlement’ in Israel 1964–1982: evaluation and characteristics

Tribal traditions are facing a severe crisis in modern society. The bedouin in Israel form a small group (13%) within the state's Arab minority, and they completed their transition stage towards settled habits in the middle of the present century with the establishment of a relatively high number of villages and hamlets. For a variety of reasons such a high number of settlements is considered ‘undesirable’ by the state. It is the object of this paper to examine the state planning of bedouin settlement as a part of the policy of concentrating bedouin groups. It also sheds light on tribal reaction towards this policy.     

The spatial pattern of Bedouin Sedentarization in Israel

The bedouin in Israel form a small group (13%) within the state's Arab minority, and they completed their transition stage towards settled habits in the middle of the present century with the establishment of a relatively high number of villages and hamlets. It is the object of this paper to examine and define the nature of these patterns of rural settlements, which emerged in the two distinctive areas of Galilee and the Negev.The discussion in this paper is confined to the period of the state of Israel (1948–83), when changes in both the processes and the patterns of bedouin sedentarization took place under entirely new political conditions. After the establishment of the Jewish State of Israel in 1948, both Galilee and Negev bedouin sedentarization was completed within a period of a single decade (1950–60). However, the sedentarization pattern has further evolved during the past two decades and is likely to continue to do so until the end of the present century.In the Israeli period, the pattern of bedouin sedentarization has developed in two distinct directions. First, the bedouin themselves have built permanent structures for residential purposes, a process usually referred to as spontaneous bedouin settlement. Secondly, the state authorities have planned and established settlements. In this planned bedouin settlement, the state has been dominant in shaping the pattern. It is important to note that most bedouin settlement in Israel belong in the first category where the whole tribe or individual groups were the initiators of their settlements. This paper which was written by an author who belongs to the bedouin community, is based mostly upon fresh evidence from field research data, and is the first attempt to indicate the importance of the role of the state in shaping the settlement pattern. It is hoped to contribute to the study of nomadism as well as to the study of the Arabs in Israel.Paper presented at the 25th International Geographical Congress Paris 27–31 August 1984. The author would like to thank the Centre for Arab Heritage without whose support his attendance at this conference would not have been possible.     

Numerical simulation of bolt‐supported tunnels by means of a multiphase model conceived as an improved homogenization procedure

This paper examines the possibility of applying a homogenization procedure to analyze the convergence of a tunnel reinforced by bolts, regarded as periodically distributed linear inclusions. Owing to the fact that a classical homogenization method fails to account for the interactions prevailing between the bolts and the surrounding ground and thus tends to significantly overestimate the reinforcement effect in terms of convergence reduction, a so‐called multiphase model is presented and developed, aimed at improving the classical homogenization method. Indeed, according to this model, the bolt‐reinforced ground is represented at the macroscopic scale as the superposition of two mutually interacting continuous phases, describing the ground and the reinforcement network, respectively. It is shown that such a multiphase approach can be interpreted as an extension of the homogenization procedure, thus making it possible to capture the ground–reinforcement interaction in a proper way, provided the constitutive parameters of the model and notably those relating to the interaction law can be identified from the reinforced ground characteristics. The numerical implementation of this model in a finite element method‐based computer code is then carried out, and a first illustrative application is finally presented. Copyright © 2008 John Wiley & Sons, Ltd.