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Mischke S.,University of Iceland | Opitz S.,University of Cologne | Kalbe J.,University of Potsdam | Ginat H.,The Dead Sea and Arava Science Center | Al-Saqarat B.,University of Jordan
Quaternary International | Year: 2015

Sedimentological, palaeontological and mineralogical analyses of sediments from the endorheic Al Jafr Basin were conducted to better understand the depositional and hydrological conditions on the southern Jordan Plateau in the late Quaternary. Surficially exposed carbonate-rich sediments in the western part of the basin contain ostracod (micro-crustacean) shells of Ilyocypris cf. bradyi, Candona neglecta, Heterocypris salina, Fabaeformiscandona fabaeformis, Pseudocandona sp. and Herpetocypris brevicaudata. The shells of these and other more rare species, and charophyte and mollusc remains indicate that the sediments were formed in a wetland setting of shallow freshwater to slightly oligohaline ponds, streams and swamps. The present more northern distribution of some of the recorded taxa implies that climate conditions were probably cooler during the wetland formation. Radiocarbon age data for biogenic carbonate from two locations suggest that the wetland setting existed during the second half of Marine Isotope Stage (MIS) 3 or possibly earlier. A significantly higher water table must have existed in the basin during wetland formation; and wetter climate conditions are inferred for the catchment or at least for its highest and most humid westernmost part. Deflation and local sediment accumulation by wind and occasional sheet-wash events apparently prevailed in the region since MIS 2. Our newly presented data and inferences do not support the reconstruction of a previously reported large and relatively deep Pleistocene lake in the Al Jafr Basin. However, more extensive studies are certainly required for a detailed assessment of the Quaternary hydrological conditions in southern Jordan. © 2014 Elsevier Ltd and INQUA.

Bar N.,Ben - Gurion University of the Negev | Elperin T.,Ben - Gurion University of the Negev | Katra I.,Ben - Gurion University of the Negev | Yizhaq H.,Ben - Gurion University of the Negev | Yizhaq H.,The Dead Sea and Arava Science Center
Aeolian Research | Year: 2016

The mechanism responsible for the formation and sustainability of sand ripples sheared by a uniform air flow is not well understood, despite the significant attention that has been given to it ever since the pioneering studies of Bagnold (1941). In this study we explore ANSYS Fluent simulations of fine-scale turbulent flow structure in the vicinity of 2D sand ripples with particular emphasis on shear stress distribution at the sand bed. The flow parameters in the simulations were pertinent to the wind tunnel experiments for studying sand ripples formation. The simulations show that the shear stress at the crest is about 2.5 times larger than the shear stress at the trough and that in most of the simulations a separation bubble has been developed at the lee slope. In contrast to wind tunnel experiments the simulations show that ripples will be flattened at wind speed of 9 m/s as shear stress at the ripples surface exceeds the fluid threshold. This discrepancy between the calculations and real wind tunnel measurements are due to the important role of the saltation layer on the decrease of the shear stress at the surface. Without this effect ripples cannot grow higher and will be diminished at quite moderate winds. © 2016 Elsevier B.V.

Abu Hamed T.,The Dead Sea and Arava Science Center | Ismail L.,GVC | Alshare A.,German Jordanian University
International Journal of Sustainable Energy | Year: 2015

Palestine faces considerable challenges relating to its energy supply, which is reflected in its dependency on imported electricity and fuels. This makes it vulnerable to changing political and economic situations and emphasises the urgent need to search for alternative and sustainable sources of energy from within Palestine itself. This study explores the potential energy generation from olive cake (OC) in the Palestinian territories. The findings of the study confirmed that there is a high-energy potential to be derived from OC and that powering olive mills by small-scale generators using OC is feasible. It was found that the amount of electricity that can be produced by OC combustion constitutes about 1.3% of all electricity consumption in 2009. Furthermore, numerous environmental benefits can be derived from using OC as biomass, notably the reduction of hazardous emission and the reduction of untreated OC. © 2015 Taylor & Francis

Yizhaq H.,Ben - Gurion University of the Negev | Yizhaq H.,The Dead Sea and Arava Science Center | Ashkenazy Y.,Ben - Gurion University of the Negev
Aeolian Research | Year: 2016

We show that the system of biocrust and vegetation on sand dunes modeled by two coupled ordinary nonlinear differential equations exhibits self-sustained oscillations. Such oscillations can occur on vegetated linear dunes that are mostly covered by biocrust. The vegetation-biocrust interaction underlies these oscillations and these do not occur if only vegetation dynamics is considered. The oscillations are "relaxation oscillations" which are characterized by two alternating attraction processes to equilibrium states with high low vegetation covers. The complex dynamics of the biocrust-vegetation model leads to unexpected scenarios, such as vegetation rehabilitation induced by drought or by grazing during which the system shifts to one of the bistable state dominated by a higher vegetation cover, or rehabilitation of vegetation that is induced by decrease in precipitation. The oscillation periods range from decades to millennia and they can interact and be affected by the climate system variability. © 2015 Elsevier B.V.

Leibowitz M.P.,Ben - Gurion University of the Negev | Chettri J.K.,Copenhagen University | Ofir R.,The Dead Sea and Arava Science Center | Zilberg D.,Ben - Gurion University of the Negev
Journal of Fish Diseases | Year: 2010

Antibacterial and antiparasitic agents and a cysteine protease inhibitor (E-64) were tested against Tetrahymena infection, a serious problem in guppy production worldwide. Chemicals were tested in vitro by a colorimetric assay for Tetrahymena survival. The most effective were niclosamide, albendazole and chloroquine, with 23%, 35% and 60% survival, respectively, following 2-h exposure to 100 ppm. Longer incubation periods resulted in greater reductions in survival. Niclosamide was further studied in vivo at different dosages, administered orally to Tetrahymena-infected guppies. Mortality rates were significantly lower in all treatment groups; in trial I, 30% and 33% mortality in 5 and 40 mg kg-1 niclosamide-fed fish vs. 59% mortality in controls; in trial II, 35%, 13% and 10% in 50, 100 and 200 mg kg-1 niclosamide-fed fish vs. 64% in controls. The effect of the cysteine protease inhibitor E64 was tested in tissue culture, by measuring histolytic activity of the parasite (Tet-NI) on a guppy-fin cell line, based on cell depletion. Tet-NI feeding activity was significantly reduced following pretreatment with E-64 relative to non-treated Tet-NI. E-64-pretreated Tet-NI was injected i.p. into guppies: recorded mortality rates were significantly lower (35%) than that in non-treated Tet-NI (60%), suggesting inhibition of the parasite's cysteine protease as a possible therapeutic approach. © 2010 Blackwell Publishing Ltd.

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