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Sample records for hoggar central sahara

  1. Satellite imagery and airborne geophysics for geologic mapping of the Edembo area, Eastern Hoggar (Algerian Sahara)

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    Lamri, Takfarinas; Djemaï, Safouane; Hamoudi, Mohamed; Zoheir, Basem; Bendaoud, Abderrahmane; Ouzegane, Khadidja; Amara, Massinissa

    2016-03-01

    Satellite imagery combined with airborne geophysical data and field observations were employed for new geologic mapping of the Edembo area in the Eastern Hoggar (Tuareg Shield, Sahara). Multi-spectral band fusion, filtering, and transformation techniques, i.e., band combination, band-rationing and principal component analysis of ETM+ and ASTER data are used for better spectral discrimination of the different rocks units. A thematic map assessed by field data and available geologic information is compiled by supervised classification of satellite data with high overall accuracy (>90%). The automated extraction technique efficiently aided the detection of the structural lineaments, i.e., faults, shear zones, and joints. Airborne magnetic and Gamma-ray spectrometry data showed the pervasiveness of the large structures beneath the Paleozoic sedimentary cover and aeolian sands. The aeroradiometric K-range is used for discrimination of the high-K granitoids of Djanet from the peralumineous granites of Edembo, and to verify the Silurian sediments with their high K-bearing minerals. The new geological map is considered to be a high resolution improvement on all pre-existing maps of this hardly accessible area in the Tuareg Shield. Integration of the airborne geophysical and space-borne imagery data can hence provide a rapid means of geologically mapping areas hitherto poorly known or difficult to access.

  2. Notes on Old Stone Constructions of West and Central Sahara

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    Mark MILBURN

    2009-10-01

    Full Text Available RESUMEN: El presente trabajo trata acerca de la tumba de TIN-HUMAN, HOGGAR, y la describe presentándola en relacón con los «monumentos en capilla» de Négrine, Tafilalet y Oeste del Sahara. Además, incluye comentarios sobre la rareza de las tumbas rectangulares con habitaciones interiores. Se hace una razonable exposición de los «monumentos fusiformes», conectados con la tradición del tránsito por barco a la vida futura. La tumba de TIN-HINAN combina características de los monumentos en capilla o habitación con aquellas otras de «monumentos de deambulatorio complejo».ABSTRACT: This work deals with the tomb of Tin-Hinan, Hoggar, and describes it as presenting a relationship with the «monuments à chapelle» of Négrine, Tafilalet and West Sahara which also have very large chambers. It also includes a commentarity on the rarity of rectangular tombs with interior chambers. It proposes a reasonable explanation of the «fusiformes monuments» as being connected with a tradition of a journey by ship to the after-life (this being suggested by their very shape. The tomb of Tin-Hinan combines characteristics of the «monument à chapelle ou à chambre» with those of a «monument à déambulatoire complexe».

  3. Granulitic metamorphism in the Laouni terrane (Central Hoggar, Tuareg Shield, Algeria)

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    Bendaoud, Abderrahmane; Derridj, Amel; Ouzegane, Khadidja; Kienast, Jean-Robert

    2004-06-01

    In the Laouni terrane, which belongs to the polycyclic Central Hoggar domain, various areas contain outcrops of formations showing granulite-facies parageneses. This high-temperature metamorphism was accompanied by migmatization and the emplacement of two types of magmatic suite, one of continental affinity (garnet pyroxenites and granulites with orthoferrossilite-fayalite-quartz), and the other of arc affinity (layered metanorites). Paragenetic, thermobarometric and fluid-inclusion studies of the migmatitic metapelites and metabasites make it possible to reconstruct the P- T- aH 2O path undergone by these formations. This path is clockwise in the three studied areas, being characterized by a major decompression (Tamanrasset: 10.5 kbar at 825 °C to 6 kbar at 700 °C; Tidjenouine: 7.5 kbar at 875 °C; to 3.5 kbar at 700 °C; Tin Begane: 13.5 kbar at 850 °C; to 5 kbar at 720 °C), followed by amphibolitization that corresponds to a fall of temperature (from 700 to 600 °C) and an increase in water activity (from 0.2-0.4 to almost 1). The main observed features are in favour of petrogenesis and exhumation related to the Eburnean orogeny. However, the lacks of good-quality dating work and a comparison with juvenile Pan-African formations having undergone high-pressure metamorphism, in some cases reaching the eclogite facies, do not rule out the possibility that high-temperature parageneses are locally due to Pan-African events.

  4. Neogene felsic volcanic rocks in the Hoggar province: Volcanology, geochemistry and age of the Azrou trachyte-phonolite association (Algerian Sahara)

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    Ben El Khaznadji, Riad; Azzouni-Sekkal, Abla; Benhallou, Amel; Liégeois, Jean-Paul; Bonin, Bernard

    2017-03-01

    The Azrou volcanic district, located to the south-east to the Atakor district in the Hoggar, has a landscape is governed by a number of felsic volcanic highs and dissected mafic plateau lavas. Our new Rb-Sr age (i.e. 23.1 ± 1.6 Ma) indicates that the Azrou felsic lavas are contemporaneous with the Achkal ring complexes (Anahef region). The Azrou felsic lavas (mainly trachyte and phonolite) show remarkably homogeneous compositions both in major elements (57.5 ≤ SiO2≤ 63.1 wt%; 10.8 ≤(Na2O + K2O)≤12.4 wt%), trace elements (33.2 ≤ Th ≤ 107 ppm; 170 ≤ La≤472 ppm; 8.7<(La/Yb)N < 27.3) and radiogenic isotopes (0.703359 < 87Sr/86Sr < 0.706539; 0.512727 <143Nd/144Nd < 0.512925; 2<εNd <5.84. These data indicate that the lavas have been only very weakly contaminated by the Precambrian basement. Geodynamically, this genesis coupled with the low volume of both trachytic and phonolitic trends implies the reworking of pre-existing shear-zones allowing the rapid ascent of these small batches of magmas. This is in agreement with the general model of linear delamination along these shear zones due to the Africa-Europe convergence developed by Liégeois et al. (2005) and recently imaged by the magneto-telluric investigation of Bouzid et al. (2015).

  5. The LATEA metacraton (Central Hoggar, Tuareg shield, Algeria): behaviour of an old passive margin during the Pan-African orogeny

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    Liégeois, Jean Paul; Latouche, Louis; Boughrara, Mustapha; Navez, Jacques; Guiraud, Michel

    2003-10-01

    Historically, the Tuareg shield is divided into three parts bordered by mega-shear zones with the centre, the Central Polycyclic Hoggar, characterized by Archaean and Palaeoproterozoic lithologies. Nearly 10 years ago, the Tuareg shield was shown to be composed of 23 displaced terranes [Geology 22 (1994) 641] whose relationships were deciphered in Aı̈r to the SE [Precambr. Res. 67 (1994) 59]. The Polycyclic Central Hoggar terranes were characterized by the presence of well preserved Archaean/Palaeoproterozoic and Neoproterozoic lithologies. We show here that the terranes from Central Hoggar (Laouni, Azrou-n-Fad, Tefedest, Egéré-Aleksod) belonged to a single old passive margin, to which we gave the acronym name LATEA, which behaved as a craton during the Mesoproterozoic and the Early-Middle Neoproterozoic but was partly destabilized and dissected during the Late Neoproterozoic as a consequence of its involvement as a passive margin in the Pan-African orogen. An early Pan-African phase consisted of thrust sheets including garnet-bearing lithologies (eclogite, amphibolite, gneiss) that can be mapped and correlated in three LATEA terranes. In the Tin Begane area, P- T- t paths have been established from >15 kbar--790 °C (eclogite) to 4 kbar--500 °C (greenschist retrogression) through 12 kbar--830 °C (garnet amphibolite) and 8 kbar--700 °C (garnet gneiss), corresponding to the retrograde path of a Franciscan-type loop. Sm-Nd geochronology on minerals and laser ablation ICP-MS on garnet show the mobility of REE, particularly LREE, during the retrograde greenschist facies that affects, although slightly, some of these rocks. The amphibolite-facies metamorphism has been dated at 685 ± 19 Ma and the greenschist facies at 522 ± 27 Ma. During the thrust phase, the Archaean-Palaeoproterozoic basement was only locally affected by the Pan-African tectonics. LATEA behaved as a craton. Other juvenile terranes were also thrust early onto LATEA: the Iskel island arc at

  6. Holocene palaeoenvironmental changes in the central Sahara (NE-Niger)

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    Brauneck, J.; Baumhauer, R.

    2009-04-01

    Although a high number of investigations focussed on the succession of climatological conditions in the Central Sahara, some uncertainties still exist as some of the results show discontinuities and mostly are of low temporal and spatial resolution. Two expeditions in 2005 and 2006 headed to the northeastern parts of Niger to investigate the known remains of palaeolakes and search some new and undetected ones. The sediments found at several sites were investigated in order to receive a complete picture of the Late Quaternary environmental settings and to produce high-resolution proxies for palaeoclimate modelling. The most valuable and best-investigated study site is the sebkha of Seggedim, where a core of 15 meters length could be extracted which revealed a composition of high-resolution sections. Stratigraphical, structural and geochemical investigations as well as the analysis of thin sections allow the characterisation of different environmental conditions throughout the core. Most importantly, a complex age-depth model could be constructed, based on 21 accelerator mass spectrometry (AMS) radiocarbon measurements and reaching from Early to Mid Holocene. Driven by climate and hydrogeological influence, the water body developed from a water pond of several metres depth within a stable, grass and shrub vegetated landscape, to a freshwater lake in a more dynamic environmental setting. Radiocarbon dates set the beginning of the stage at about 10.6 ka cal BP, with an exceptionally stable regime to 6.6 ka cal BP (at 12.6 metres' depth), when a major change in the sedimentation regime of the basin is recorded in the core. Increased erosion, likely due to decreased vegetation cover within the basin, led to the filling of the lake within a few hundred years and the subsequent development of a sebkha due to massive evaporation. Due to the lack of dateable material in the upper core section, the termination of the lake stage and the onset of the subsequent sebkha stage

  7. Pre-Islamic Dry-Stone Monuments of the Central and Western Sahara

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    Gauthier, Yves

    Saharan dry-stone monuments are important cultural markers: not only do they highlight the boundaries of the areas occupied by different prehistoric populations, but they also reveal information about the rites and beliefs of Holocene Saharan populations. As climate deteriorated in the Middle Holocene, ways of life changed, with indirect impacts on the architecture of the monuments and on the way they were oriented. Tens of thousands of recorded monuments, of various types, allow us to understand what the orientation rules were and how they changed with location. Data compiled for the eleven types of monuments reveal that many monuments of the central Sahara and Tibesti were probably aligned toward the rising sun or moon, that three types of the Atlantic Sahara show instead a random distribution, and that monuments with a pan-Saharan distribution have a complex orientation pattern. A correlation or orientation with key landscape features is likely for three monument types, coexisting with criteria based on lunisolar alignment.

  8. Inside the "African cattle complex": animal burials in the holocene central Sahara.

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    di Lernia, Savino; Tafuri, Mary Anne; Gallinaro, Marina; Alhaique, Francesca; Balasse, Marie; Cavorsi, Lucia; Fullagar, Paul D; Mercuri, Anna Maria; Monaco, Andrea; Perego, Alessandro; Zerboni, Andrea

    2013-01-01

    Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as 'walking larder'. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080-5120 BP or 5200-3800 BC). This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O) analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara.

  9. Inside the "African cattle complex": animal burials in the holocene central Sahara.

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    Savino di Lernia

    Full Text Available Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as 'walking larder'. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080-5120 BP or 5200-3800 BC. This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara.

  10. Crater palaeolakes in the Tibesti mountains (Central Sahara, North Chad) - New insights into past Saharan climates

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    Kröpelin, Stefan; Dinies, Michèle; Sylvestre, Florence; Hoelzmann, Philipp

    2016-04-01

    For the first time continuous lacustrine sections were sampled from the volcanic Tibesti Mountains (Chad): In the 900 m deep crater of Trou au Natron at Pic Toussidé (3,315 m a.s.l.) and from the 800 m deep Era Kohor, the major sub-caldera of Emi Koussi (3,445 m a.s.l.). The remnant diatomites on their slopes are located 360 m (Trou au Natron) and 125 m (Era Kohor) above the present day bottom of the calderas. These sediments from highly continental positions in the central Sahara are keys for the reconstruction of the last climatic cycles (Kröpelin et al. 2015). We report first results from sedimentary-geochemical (total organic and total inorganic carbon contents; total nitrogen; major elements; mineralogy) and palynological analyses for palaeo-environmental interpretations. The diatomites from the Trou au Natron comprise 330 cm of mostly calcitic sediments with relatively low organic carbon (fern stands. Regional pollen rain-e.g. grasses and wormwood-is scarcely represented. Golden algae dominate in the lower section. The results of the first palynological samples suggest a small sedimentation basin. Two 14C-dated charcoals out of the upper part of the section indicate mid-Holocene ages and a linear extrapolation based on a sediment accumulation rate of 1.4mma-1 would lead to tentative dates of ~8650 cal a BP for basal lacustrine sediments and ~4450 cal a BP for the cessation of this lacustrine sequence. The diatomites from the Era Kohor reflect a suite of sections that in total sum up to 145 cm of mostly silica-based sediments with very low carbon contents (< 2% TC). Calcite dominated sediments are only present in the topmost 15 cm. Grasses and wormword are dominating throughout the sequence, probably reflecting the main constituents of the regional vegetation. Cattail (Typha/Sparganium) and especially milfoil (Myriophyllum) are recorded abundantly and continuously throughout the sequence. In combination with green algae like Pediastrum the first pollen

  11. Geodynamical aspects of the Hoggar Shield (Algeria) from Aeromagnetic data

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    Bournas, N.; Hamoudi, M.; Galdeano, A.; Ouzegane, K.; Kienast, J. R.

    2003-04-01

    The Hoggar is a wide region situated in the central part of northwest Africa. It represents the main component of the Tuareg shield, which is a part of the Panafrican Transaharan belt. The Hoggar is mainly composed of metamorphic rocks formed during the Panafrican orogeny and is crossed by several north-south mega-shear zones separating crustal blocks with different lithology. This region has been covered by a regional airborne magnetic survey carried out during the seventies. The survey was flown using a cesium magnetometer with a 2 km flight line spacing and a constant terrain clearance of 150 meters above the ground. Comprehensive processing and interpretation procedures including digital filtering and inversion techniques of the aeromagnetic data are presented in this work. The synergetic analysis of the aeromagnetic data with the geological considerations, has been very useful to clearly identifying the principal structural features of this region. The obtained results confirm the proposed earlier geodynamical model, in which the 4°50 and the 8°30 mega shears have played a major role in the geodynamical evolution of the Hoggar during the Panafrican event. On the other hand, the interpretation of the aeromagnetic anomalies suggests the existence of a NW-SE rifting zone affecting the whole region.

  12. The Anfeg post-collisional Pan-African high-K calc-alkaline batholith (Central Hoggar, Algeria), result of the LATEA microcontinent metacratonization

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    Acef, Kaissa; Liégeois, Jean Paul; Ouabadi, Aziouz; Latouche, Louis

    2003-10-01

    The Anfeg batholith (or composite laccolith) occupies a large surface (2000 km 2) at the northern tip of the Laouni terrane, just south of Tamanrasset in Hoggar. It is granodioritic to granitic in composition and comprises abundant enclaves that are either mafic microgranular enclaves (MME) or gneissic xenoliths. It intruded an Eburnian (≈2 Ga) high-grade basement belonging to the LATEA metacraton at approximately 608 Ma (recalculated from the U-Pb dating of [Tectonics 5 (1986) 955]) and cooled at approximately 4 kbar, with a temperature of about 750 °C. This emplacement occurred mainly along subhorizontal thrust planes related to Pan-African subvertical mega-shear zones close to the attachment zone of a strike-slip partitioned transpression system. Although affected by some LILE mobility, the Anfeg batholith can be ascribed to a high-K calc-alkaline suite but characterized by low heavy REE contents and high LREE/HREE ratios. The MME belong to the Anfeg magmatic trend while some xenoliths belong to Neoproterozoic island arc rocks. The Anfeg batholith defines a Nd-Sr isotopic initial ratios trend ( ɛNd/( 87Sr/ 86Sr) i from -2.8/0.7068 to -11.8/0.7111) pointing to a mixing between a depleted mantle and an old Rb-depleted granulitic lower crust. Both sources have been identified within LATEA and elsewhere in the Tuareg shield ( ɛNd/ 87Sr/ 86Sr) i of +6.2/0.7028 for the depleted mantle, -22/0.708 for the old lower crust. The model proposed relates the above geochemical features to a lithospheric delamination along the subvertical mega-shear zones that dissected the rigid LATEA former passive margin without major crustal thickening (metacratonization) during the general northward tectonic escape of the Tuareg terranes, a consequence of the collision with the West African craton. This delamination allowed the uprise of the asthenosphere. In turn, this induced the melting of the asthenosphere by adiabatic pressure release and of the old felsic and mafic lower crust

  13. The Temaguessine Fe-cordierite orbicular granite (Central Hoggar, Algeria): U Pb SHRIMP age, petrology, origin and geodynamical consequences for the late Pan-African magmatism of the Tuareg shield

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    Abdallah, Nachida; Liégeois, Jean-Paul; De Waele, Bert; Fezaa, Nassima; Ouabadi, Aziouz

    2007-11-01

    The Temaguessine high-level subcircular pluton is intrusive into the LATEA metacraton (Central Hoggar) Eburnian (2 Ga) basement and in the Pan-African (615 Ma) granitic batholiths along a major NW-SE oriented major shear zone. It is dated here (SHRIMP U-Pb on zircon) at 582 ± 5 Ma. Composed of amphibole-biotite granite and biotite syenogranite, it comprises abundant enclaves: mafic magmatic enclaves, country-rock xenoliths and remarkable Fe-cordierite (#Fe = 0.87) orbicules. The orbicules have a core rich in cordierite (40%) and a leucocratic quartz-feldspar rim. They are interpreted as resulting from the incongruent melting of the meta-wacke xenoliths collapsed into the magma: the breakdown of the biotite + quartz assemblage produced the cordierite and a quartz-feldspar minimum melt that is expelled, forming the leucocratic rim. The orbicule generation occurred at T < 850° and P < 0.3 GPa. The Fe-rich character of the cordierite resulted from the Fe-rich protolith (wacke with 4% Fe 2O 3 for 72% SiO 2). Strongly negative ɛNd (-9.6 to -11.2), Nd TDM model ages between 1.64 and 1.92 Ga, inherited zircons between 1.76 and 2.04 Ga and low to moderately high ISr (0.704-0.710) indicate a Rb-depleted lower continental crust source for the Temaguessine pluton; regional considerations impose however also the participation of asthenospheric material. The Temaguessine pluton, together with other high-level subcircular pluton, is considered as marking the end of the Pan-African magma generation in the LATEA metacraton, resulting from the linear delamination along mega-shear zones, allowing asthenospheric uprise and melting of the lower continental crust. This implies that the younger Taourirt granitic province (535-520 Ma) should be considered as a Cambrian intraplate anorogenic event and not as a very late Pan-African event.

  14. Aerosol direct radiative forcing during Sahara dust intrusions in the Central Mediterranean

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    M. R. Perrone

    2010-08-01

    Full Text Available The clear-sky, instantaneous Direct Radiative Effect (DRE by all and anthropogenic particles is calculated during Sahara dust intrusions in the Mediterranean basin, to evaluate the role of anthropogenic particle's radiative effects and to obtain a better estimate of the DRE by desert dust. The clear-sky aerosol DRE is calculated by a two stream radiative transfer model in the solar (0.3–4 μm and infrared (4–200 μm spectral range, at the top of the atmosphere (ToA and at the Earth's surface (sfc. Aerosol optical properties by AERONET sun-sky photometer measurements and aerosol vertical profiles by EARLINET lidar measurements, both performed at Lecce (40.33° N, 18.10° E during Sahara dust intrusions occurred from 2003 to 2006 year, are used to perform radiative transfer simulations. Instantaneous values at 0.44 μm of the real (n and imaginary (k refractive index and of the of aerosol optical depth (AOD vary within the 1.33–1.55, 0.0037–0.014, and 0.2–0.7 range, respectively during the analyzed dust outbreaks. Fine mode particles contribute from 34% to 85% to the AOD by all particles. The complex atmospheric chemistry of the Mediterranean basin that is also influenced by regional and long-range transported emissions from continental Europe and the dependence of dust optical properties on soil properties of source regions and transport pathways, are responsible for the high variability of n, k, and AOD values and of the fine mode particle contribution. Instantaneous all-wave (solar+infrared DREs that are negative as a consequence of the cooling effect by aerosol particles, span the – (32–10 Wm−2 and the – (44–20 Wm−2 range at the ToA and surface, respectively. The instantaneous all-wave DRE by anthropogenic particles that is negative, varies within – (13–7 Wm−2 and – (18–11 Wm−2 at the ToA and surface, respectively. It represents from 41

  15. Aerosol direct radiative forcing during Sahara dust intrusions in the central Mediterranean

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    M. R. Perrone

    2009-10-01

    Full Text Available The clear-sky, instantaneous Direct Radiative Effect (DRE by all and anthropogenic particles is calculated during Sahara dust intrusions in the Mediterranean basin, to evaluate the role of anthropogenic particle's radiative effects and to get a better estimate of the DRE by desert dust. The clear-sky aerosol DRE is calculated by a two stream radiative transfer model in the solar (0.3–4 μm and infrared (4–200 μm spectral range, at the top of the atmosphere (ToA and at the Earth's surface (sfc. Aerosol optical properties by AERONET sun-sky photometer measurements and aerosol vertical profiles by EARLINET lidar measurements, both performed at Lecce (40.33° N, 18.10° E during Sahara dust intrusions occurred from 2003 to 2006 year, are used to initialize radiative transfer simulations. Instantaneous values at 0.44 μm of the real (n and imaginary (k refractive index and of the of aerosol optical depth (AOD vary within the 1.33–1.55, 0.0037–0.014, and 0.2–0.7 range, respectively during the analyzed dust outbreaks. Fine mode particles contribute from 34% to 85% to the AOD by all particles. The complex atmospheric chemistry of the Mediterranean basin that is also influenced by regional and long-range transported emissions from continental Europe and the dependence of dust optical properties on soil properties of source regions and transport pathways are responsible for the high variability of n, k, and AOD values and of the fine mode particle contribution. Instantaneous net (solar+infrared DREs that are negative as a consequence of the cooling effect by aerosol particles, span the – (32–10 W m−2 and the – (44–20 W m−2 range at the ToA and surface, respectively. The instantaneous net DRE by anthropogenic particles that is negative, varies within −(13–8 W m−2 and −(17–11 W m−2 at the ToA and surface, respectively. It represents from 41 up to 89

  16. Late Quaternary palaeoenvironmental information inferred from terrestrial archives in the central Sahara

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    Brauneck, J.; Baumhauer, R.

    2009-04-01

    Reconnaissance surveys in northeastern Niger since 1977 have revealed, from such evidence as diatomite-lined depressions, the existence of palaeolakes there. Initial research has shown that the palaeolimnic sediments and palaeosoils found are suitable for reconstructing its Late Quaternary palaeoenvironment. The most valuable and best-investigated study site is the sebkha of Seggedim, where a core of 15 meters length could be extracted which revealed a composition of high-resolution sections. Stratigraphical, structural and geochemical investigations as well as the analysis of thin sections allow the characterisation of different environmental conditions throughout the core. Most importantly, a complex age-depth model could be constructed, based on 21 accelerator mass spectrometry (AMS) radiocarbon measurements and reaching from Early to Mid Holocene. The results obtained from the core are compared with those from terrestrial and lacustrine sediments from outside the depression, situated a few hundred kilometres further to the north. Within the plateau landscape of Djado, Mangueni and Tchigai, two depressions and a valley containing lacustrine deposits, were investigated for palaeoenvironmental reconstruction. Depending on modifying local factors, these sediment archives were of shorter existence than the lake, but reveal additional information about the landscape dynamics from Early to Mid Holocene. The few perennial lacustrine climate archives still active to present day within the Sahara reveal apparently unique characteristics, as the local conditions that led to their existence are indeed exceptional. The interpretation of such a standalone location has to be performed with caution, as it inhibits several sources of error. The Seggedim depression may be considered such a unique spot at least for a limited time. The information obtained from the initial and freshwater lake sediments showed no noticeable signs of climatic alterations until Mid Holocene

  17. Takarkori rock shelter (SW Libya): an archive of Holocene climate and environmental changes in the central Sahara

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    Cremaschi, Mauro; Zerboni, Andrea; Mercuri, Anna Maria; Olmi, Linda; Biagetti, Stefano; di Lernia, Savino

    2014-10-01

    Rock shelters in the central Saharan massifs preserve anthropogenic stratigraphic sequences that represent both a precious archive for the prehistory of the region and a powerful proxy data for Holocene palaeoenvironments. The geoarchaeological (micromorphology) and archaeobotanical (pollen analysis) approaches were integrated to investigate the anthropogenic sedimentary sequence preserved within the Takarkori rock shelter, a Holocene archaeological site located in the Libyan central Sahara (southern Tadrart Acacus massif). The site was occupied throughout the Early and Middle Holocene (African Humid Period) by groups of hunter-gatherers before and by pastoral communities later. The investigation on the inner part of the sequence allows to recognize the anthropogenic contribution to sedimentation process, and to reconstruct the major changes in the Holocene climate. At the bottom of the stratigraphic sequence, evidence for the earliest frequentation of the site by hunters and gatherers has been recognized; it is dated to c. 10,170 cal yr BP and is characterized by high availability of water, freshwater habitats and sparsely wooded savannah vegetation. A second Early Holocene occupation ended at c. 8180 cal yr BP; this phase is marked by increased aridity: sediments progressively richer in organics, testifying to a more intense occupation of the site, and pollen spectra indicating a decrease of grassland and the spreading of cattails, which followed a general lowering of lake level or widening of shallow-water marginal habitats near the site. After this period, a new occupational phase is dated between c. 8180 and 5610 cal yr BP; this period saw the beginning of the frequentation of pastoral groups and is marked by an important change in the forming processes of the sequence. Sediments and pollen spectra confirm a new increase in water availability, which led to a change in the landscape surrounding the Takarkori rock shelter with the spreading of water bodies. The

  18. Intraseasonal variability and atmospheric controls on daily dust occurrence frequency over the central and western Sahara during the boreal summer

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    Ashpole, Ian; Washington, Richard

    2013-12-01

    classify satellite-derived maps of daily dust occurrence frequency over the central and western Sahara (CWS) during the boreal summer in order to identify typical patterns using the neural network based system of self-organized maps. Resulting dust states vary in terms of the frequency of dust occurrence and its location. The most commonly occurring dust states are those of relatively low dust detection frequency. On days with relatively high dust occurrence, dust tends to favor either a location close to the Algeria-Mali-Niger border triple point (TP) or further to the northwest across the western half of the Mali-Algeria border (MAB). States in which dust is detected at both locations simultaneously are rare. There is a distinct intraseasonal progression in preferred dust location from the TP in the early season to the MAB later in the season. The evolution of dust states reveals a one-way transition from dust at the TP to dust at the MAB and then to reduced daily dust occurrence frequency. There is a distinct degree of interannual variability in the occurrence frequency of the different states, dominated by the extremes of high and low dust detection frequency. Analysis of climatological composites demonstrates that monsoon surges into the Saharan heat low are associated with days of high dust detection frequency, while a strong Harmattan into the CWS is linked to days with less frequent dust presence. The CWS atmospheric dust budget for June-August is thus strongly linked to the dynamics of the West African monsoon.

  19. Organization of drainage networks from space imagery in the Tanezrouft plateau (Western Sahara) : implications for recent intracratonic deformations

    Science.gov (United States)

    Chorowicz, J.; Fabre, J.

    1997-12-01

    Analyses of satellite images (Landsat TM, SPOT and SAR ERS-1) of the Tanezrouft Plateau (Sahara) together with observations in the field have provided evidence of palaeo-drainage networks and intracratonic tectonic activity. The central network was a large braided system which collected waters from the western Hoggar in the Holocene. This network is connected northwesterly with Wadi Mouilah, the Reggan topographic depression and Sebkha Meqerghane. It is affected by conjugate northwest- and northeast-striking recent faults which reactivate older faults related to the north-south-trending Pan-African suture zone. The southern network comprises the wadis Tamanrasset, El Djouf and El Djouf his. They formerly constituted a large system running from southeast to northwest, captured and turning south in western Tanezrouft. This wadi system is presently cut into two parts as a result of recent tectonic deformations, i.e. uplift affecting the western border of the Tanezrouft plateau and north-striking faults paralleling the Pan-African suture zone.

  20. Impact of climate change on the relict tropical fish fauna of central sahara: threat for the survival of adrar mountains fishes, mauritania.

    Science.gov (United States)

    Trape, Sébastien

    2009-01-01

    Four central Sahara mountainous massifs provide habitats for relict populations of fish. In the Adrar of Mauritania all available data on the presence and distribution of fish come from pre-1960 surveys where five fish species were reported: Barbus pobeguini, Barbus macrops, Barbus mirei, Sarotherodon galilaeus, and Clarias anguillaris. Since 1970, drought has had a severe impact in the Adrar where rainfall decreased by 35%. To investigate whether the relict populations of fish have survived the continuing drought, a study was carried out from 2004 to 2008. An inventory of perennial bodies of water was drawn up using a literature review and analysis of topographical and hydrological maps. Field surveys were carried out in order to locate the bodies of water described in the literature, identify the presence of fish, determine which species were present and estimate their abundance. The thirteen sites where the presence of fish was observed in the 1950s -Ksar Torchane, Ilij, Molomhar, Agueni, Tachot, Hamdoun, Terjit, Toungad, El Berbera, Timagazine, Dâyet el Mbârek, Dâyet et-Tefla, Nkedeï- were located and surveyed. The Ksar Torchane spring -type locality and the only known locality of B. mirei- has dried up at the height of the drought in 1984, and any fish populations have since become extinct there. The Timagazine, Dâyet el Mbârek and Dâyet et-Tefla pools have become ephemeral. The Hamdoun guelta appears to be highly endangered. The fish populations at the other sites remain unchanged. Four perennial pools which are home to populations of B. pobeguini are newly recorded. The tropical relict fish populations of the Adrar mountains of Mauritania appear to be highly endangered. Of thirteen previously recorded populations, four have become extinct since the beginning of the drought period. New fish population extinctions may occur should low levels of annual rainfall be repeated.

  1. Impact of climate change on the relict tropical fish fauna of central sahara: threat for the survival of adrar mountains fishes, mauritania.

    Directory of Open Access Journals (Sweden)

    Sébastien Trape

    Full Text Available BACKGROUND: Four central Sahara mountainous massifs provide habitats for relict populations of fish. In the Adrar of Mauritania all available data on the presence and distribution of fish come from pre-1960 surveys where five fish species were reported: Barbus pobeguini, Barbus macrops, Barbus mirei, Sarotherodon galilaeus, and Clarias anguillaris. Since 1970, drought has had a severe impact in the Adrar where rainfall decreased by 35%. To investigate whether the relict populations of fish have survived the continuing drought, a study was carried out from 2004 to 2008. METHODOLOGY/PRINCIPAL FINDINGS: An inventory of perennial bodies of water was drawn up using a literature review and analysis of topographical and hydrological maps. Field surveys were carried out in order to locate the bodies of water described in the literature, identify the presence of fish, determine which species were present and estimate their abundance. The thirteen sites where the presence of fish was observed in the 1950s -Ksar Torchane, Ilij, Molomhar, Agueni, Tachot, Hamdoun, Terjit, Toungad, El Berbera, Timagazine, Dâyet el Mbârek, Dâyet et-Tefla, Nkedeï- were located and surveyed. The Ksar Torchane spring -type locality and the only known locality of B. mirei- has dried up at the height of the drought in 1984, and any fish populations have since become extinct there. The Timagazine, Dâyet el Mbârek and Dâyet et-Tefla pools have become ephemeral. The Hamdoun guelta appears to be highly endangered. The fish populations at the other sites remain unchanged. Four perennial pools which are home to populations of B. pobeguini are newly recorded. CONCLUSION/SIGNIFICANCE: The tropical relict fish populations of the Adrar mountains of Mauritania appear to be highly endangered. Of thirteen previously recorded populations, four have become extinct since the beginning of the drought period. New fish population extinctions may occur should low levels of annual rainfall be

  2. The daytime cycle in dust aerosol direct radiative effects observed in the central Sahara during the Fennec campaign in June 2011

    KAUST Repository

    Banks, Jamie R.

    2014-12-16

    © 2014. American Geophysical Union. All Rights Reserved. The direct clear-sky radiative effect (DRE) of atmospheric mineral dust is diagnosed over the Bordj Badji Mokhtar (BBM) supersite in the central Sahara during the Fennec campaign in June 2011. During this period, thick dust events were observed, with aerosol optical depth values peaking at 3.5. Satellite observations from Meteosat-9 are combined with ground-based radiative flux measurements to obtain estimates of DRE at the surface, top-of-atmosphere (TOA), and within the atmosphere. At TOA, there is a distinct daytime cycle in net DRE. Both shortwave (SW) and longwave (LW) DRE peak around noon and induce a warming of the Earth-atmosphere system. Toward dusk and dawn, the LW DRE reduces while the SW effect can switch sign triggering net radiative cooling. The net TOA DRE mean values range from -9 Wm-2 in the morning to heating of +59 Wm-2 near midday. At the surface, the SW dust impact is larger than at TOA: SW scattering and absorption by dust results in a mean surface radiative cooling of 145Wm-2. The corresponding mean surface heating caused by increased downward LW emission from the dust layer is a factor of 6 smaller. The dust impact on the magnitude and variability of the atmospheric radiative divergence is dominated by the SW cooling of the surface, modified by the smaller SW and LW effects at TOA. Consequently, dust has a mean daytime net radiative warming effect on the atmosphere of 153Wm-2.

  3. Controls on gold deposits in Hoggar, Tuareg Shield (Southern Algeria)

    Science.gov (United States)

    Aissa, Djamal-Eddine; Marignac, Christian

    2017-03-01

    The Hoggar shield belongs to the 3000 km-long Pan-African Trans-Saharan belt that was formed in the Neoproterozoic, between 750 and 500 Ma by continental collision between the converging West African craton, Congo craton and Saharan Metacraton. More than 600 gold occurrences have been identified by ORGM, which are confined along North-South Pan-African megashear zones stretching some hundreds of kilometres long. Until now, no global classification and mineral paragenesis characterisation have been proposed for the Hoggar's gold mineralization. In this paper, we briefly review the main gold mineralization, in order to classify them and to highlight their characteristics and controls. According to field work, spectral, microscopic and microthermometric studies, these mineralization can be globally classified asorogenic type shear zone, which can subdivided into three main sub-types according to the degree of their relationships with the major Pan-African shear zones: (i) Ultramylonite-mylonite hosted including Tirek and Amesmessa, world class deposits; (ii) Granite hosted, including Tekouyat occurrence (iii) Volcano-sediment hosted including Tiririne and In Abbegui deposits. All the deposits are coeval and were formed at the end of the post-collisional stage (530-520 Ma). InHoggar, gold mineralization depend on a double control, first order giant sub-meridian shear zone control and the gold districts disposed in N40°-50°E corridors that may be interpreted as extensional. Indeed, the Hoggar gold province appears to have been controlled at all scales by the late transtensive reactivation of the Pan-African mega-shear zones, and by the correlative heat flux associated with the linear lithospheric delamination processes accompanying this reactivation; which are also responsible for the very lateHoggar magmatic events. At Amesmessa, gold deposition was promoted by the mixing of metamorphic fluids issued from the In Ouzzal Archean-Proterozoic basement with magmatic

  4. Nature and Evolution of the lithospheric mantle beneath the Hoggar swell (Algeria): a record from mantle xenoliths.

    Science.gov (United States)

    Kourim, Fatna; Bodinier, Jean-Louis; Alard, Olivier; Bendaoud, Abderrahmane; Vauchez, Alain; Dautria, Jean-Marie

    2013-04-01

    The mantle xenoliths sampled by the Quaternary alkaline volcanics from the Tahalgha district (Central Hoggar) represent the subcontinental lithospheric mantle beneath the boundary between two major structural domains of the Tuareg Shield: the "Polycyclic Central Hoggar" to the East and the "Western Hoggar", or "Pharusian Belt", to the West. Samples were collected from volcanic centres located on both sides of the 4°10, a major lithospheric shear zone separating these two domains. Although showing substantial variations in their deformation microstructures, equilibrium temperatures, and modal and chemical compositions, the studied samples do not display systematic variations of these features across the 4°10. The observed variations rather record small-scale heterogeneities distributed throughout the whole studied area and mostly related to the asthenosphere-lithosphere interaction events associated with the evolution of the Hoggar swell, in the Cenozoic. These features include partial annealing of pre-existing deformation microstructures, post-deformation metasomatic reactions, and trace-element enrichment, coupled with heating from 750-900°C (low-temperature lherzolites) to 900-1150°C (intermediate-T lherzolites and high-T harzburgites and wehrlites). Trace element modelling confirms that the whole range of REE fractionation observed in the Tahalgha xenoliths may be accounted for by reactive porous flow involving a single stage of basaltic melt infiltration into a LREE-depleted protolith. The striking correlations between equilibrium temperatures and trace-element enrichments favor a scenario whereby the high-temperature peridotites record advective heat transport along melt conduits while the intermediate- and low-temperature lherzolites would represent more conductive heating of the host Mechanical Boundary Layer. This indicates that the lithosphere did not reach thermal equilibrium, suggesting that the inferred heating event was transient and rapidly erased

  5. Ammonoids from the Dalle des Iridet of the Mouydir and Ahnet (Central Sahara and the Formation d'Hassi Sguilma of the Saoura Valley (Late Tournaisian–Early Viséan; Algeria

    Directory of Open Access Journals (Sweden)

    D. Korn

    2010-02-01

    Full Text Available Four ammonoid species are described from the Early Carboniferous (Mississippian Iridet Formation of the Ahnet and Mouydir (Central Sahara, Algeria; three of which are new: Eurites temertassetensis n. sp., Trimorphoceras teguentourense n. sp., and Trimorphoceras azzelmattiense n. sp. The species can be attributed to the North African Ammonellipsites-Merocanites Assemblage (Fascipericyclus-Ammonellipsites Genus Zone; Late Tournaisian to Early Viséan. Additionally, the two new species Ammonellipsites sguilmensis n. sp. and Muensteroceras beniabbesense n. sp. are described from the time equivalent Hassi Sguilma Formation of the Saoura Valley (north-western Algeria. doi:10.1002/mmng.200900012

  6. Sahara en mouvement

    OpenAIRE

    Casajus, Dominique

    2013-01-01

    On peut dire du Sahara ce que Fernand Braudel disait naguère de la Méditerranée : lui assigner des bornages est une tâche malaisée. Des géographes s’y sont cependant essayés, et leurs tentatives participent de ce qu’on peut appeler l’« invention » du Sahara. La présente introduction évoque quelques figures marquantes de cette invention (Léon l’Africain, Eugène Daumas, Émile Carette, Henri Duveyrier, Robert Capot-Rey…) puis présente brièvement les diverses contributions du dossier, en les repl...

  7. Crystallochemical and structural evolution of tourmaline in auriferous quartz veins of the Iskel terrane prospect (western Hoggar, Tamanrasset, South Algeria)

    Science.gov (United States)

    Talbi, Mohamed; Chaouche, Ismahane; Fuchs, Yves

    2016-04-01

    A mylonite zone limits the Iskane Terrane tectonic unit (Western Hoggar). This zone is intruded by granitic units belonging to the Taourirt cycle. North -South and North East-South West trending auriferous quartz veins are hosted in the cataclased areas. Visible gold can be observed but gold is also present in sulfides (pyrite, chalcopyrite). Tourmaline is abundant in these veins. Mossbauer spectrometry as well as FTIR spectrometry shows that in some sectors tourmaline underwent an oxidation process posterior to its formation. The general structure of tourmaline studied, shows the coexistence of ferric iron Fe3+ with ferrous iron Fe2+ in the Y site. This represents a tourmaline "deprotonated". This oxidation induced a partial transformation of Fe2+ in Fe3+ that is charge compensated by a deshydroxylation of the central OH group. The relationship of the gold deposition with the oxidation of tourmaline is discussed. Key words: Tourmaline, oxidation, "deprotonation-deshydroxylation", sulfides, gold.

  8. [Malaria in Algerian Sahara].

    Science.gov (United States)

    Hammadi, D; Boubidi, S C; Chaib, S E; Saber, A; Khechache, Y; Gasmi, M; Harrat, Z

    2009-08-01

    Thanks to the malaria eradication campaign launched in Algeria in 1968, the number of malaria cases fell down significantly from 95,424 cases in 1960 to 30 cases in 1978. At that time the northern part of the country was declared free of Plasmodium falciparum. Only few cases belonging to P. vivax persisted in residual foci in the middle part of the country. In the beginning of the eighties, the south of the country was marked by an increase of imported malaria cases. The resurgence of the disease in the oases coincided with the opening of the Trans-Saharan road and the booming trade with the neighbouring southern countries. Several authors insisted on the risk of introduction of malaria or its exotic potential vectors in Algeria via this new road. Now, the totality of malaria autochthonous cases in Algeria are located in the south of the country where 300 cases were declared during the period (1980-2007). The recent outbreak recorded in 2007 at the borders with Mall and the introduction of Anopheles gambiae into the Algerian territory show the vulnerability of this area to malaria which is probably emphasized by the local environmental changes. The authors assess the evolution of malaria in the Sahara region and draw up the distribution of the anopheles in this area.

  9. New compounds, chemical composition, antifungal activity and cytotoxicity of the essential oil from Myrtus nivellei Batt. & Trab., an endemic species of Central Sahara.

    Science.gov (United States)

    Bouzabata, Amel; Bazzali, Ophélie; Cabral, Célia; Gonçalves, Maria José; Cruz, Maria Teresa; Bighelli, Ange; Cavaleiro, Carlos; Casanova, Joseph; Salgueiro, Ligia; Tomi, Félix

    2013-10-07

    Myrtus nivellei Batt. & Trab. (Myrtaceae) known as Sahara myrtle is appreciated by the Touaregs as medicinal plant. Infusion of leaves is employed against diarrhea and blennorrhea. Crushed leaves added to oil or to butter ointment have been traditionally used for the treatment of dermatosis. Aim of the study is to consider the traditional medicinal uses and the lack of scientific studies on their biological activities, the present study was designed to elucidate the chemical composition, the antifungal activity of its essential oils against fungi responsible for human infections, as well as, its cytotoxicity in the mammalian keratinocytes. Chemical analysis of Myrtus nivellei essential oil isolated by hydrodistillation of aerial parts (leaves and flowers), was carried out using a combination of chromatographic (CC, GC with retention indices) and spectroscopic techniques (MS, (13)C NMR, 2D NMR). The antifungal activity was evaluated by using broth macrodilution methods for yeasts and filamentous fungi. Cytotoxicity was tested in HaCaT keratinocytes through the MTT assay. Ten samples coming from two localities of harvest were investigated. The chemical composition was largely dominated by 1,8-cineole (33.6-50.4%) and limonene (17.5-25.0%). The structure of two new compounds bearing the isoamylcyclopentane skeleton has been elucidated. The oil was more active against Cryptococcus neoformans with MIC of 0.16μL/mL followed by dermatophytes, with MICs of 0.64 and 1.25μL/mL. Furthermore, evaluation of cell viability showed no cytotoxicity in HaCaT keratinocytes at concentrations up to 1.25µL/mL. The composition of Myrtus nivellei oil differed from that of Myrtus communis. The structure of two di-nor-sesquiterpenoids has been elucidated. It was possible to find appropriate doses of Myrtus nivellei oil with both antifungal activity and very low detrimental effect on keratinocytes. These findings add significant information to the pharmacological activity of Myrtus

  10. Africa (south of the Sahara)

    NARCIS (Netherlands)

    Hoorweg, J.C.; Sexton, V.S.; Msiak, H.

    1976-01-01

    This review of the development and current status of psychology in Africa focuses on Africa south of the Sahara, excluding South Africa. The author discusses the research topics which have attracted the attention of psychologists in Africa, including perception (illusions, pictorial representation

  11. Comment on "Climate-driven ecosystem succession in the Sahara: the past 6000 years".

    Science.gov (United States)

    Brovkin, Victor; Claussen, Martin

    2008-11-28

    Kröpelin et al. (Research Articles, 9 May 2008, p. 765) interpreted a sediment record from Lake Yoa in the east-central part of North Africa as support for a weak biogeophysical climate-vegetation feedback in the Sahara during the mid-Holocene. We argue that the new data do not invalidate earlier modeling results on strong land-atmosphere coupling in the Western Sahara for which the Lake Yoa record is far less representative.

  12. Cretaceous Crocodyliforms from the Sahara

    Directory of Open Access Journals (Sweden)

    Paul Sereno

    2009-11-01

    Full Text Available Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana.  We report here on six species from the Sahara with an array of trophic adaptations that significantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period.  We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian of Niger. The remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n. come from contemporaneous Upper Cretaceous formations (Cenomanian in Niger and Morocco.

  13. Breve historia de Radio Sahara

    Directory of Open Access Journals (Sweden)

    Montes Fernández, Francisco José

    2013-01-01

    Full Text Available La historia de Radio Sahara es uno de los períodos menos estudiado en nuestra bibliografía, lo cual tampoco es sintomático sino una muestra más de lo mucho que hay que investigar sobre la historia reciente denuestro país, especialmente en el terreno de la radiodifusión. He profundizado en todo lo que he podido, pero es indudable que queda mucho camino por recorrer. Aquí hay pistas y datos todos verdaderos sobre una parte importante, pero no lo doy por finalizado sino que aspiro a que sirva de aliciente para que futuros investigadores continúen con el camino iniciado. Se trata de describir lo que fue la historia de esta emisora

  14. Rainfall regimes of the Green Sahara.

    Science.gov (United States)

    Tierney, Jessica E; Pausata, Francesco S R; deMenocal, Peter B

    2017-01-01

    During the "Green Sahara" period (11,000 to 5000 years before the present), the Sahara desert received high amounts of rainfall, supporting diverse vegetation, permanent lakes, and human populations. Our knowledge of rainfall rates and the spatiotemporal extent of wet conditions has suffered from a lack of continuous sedimentary records. We present a quantitative reconstruction of western Saharan precipitation derived from leaf wax isotopes in marine sediments. Our data indicate that the Green Sahara extended to 31°N and likely ended abruptly. We find evidence for a prolonged "pause" in Green Sahara conditions 8000 years ago, coincident with a temporary abandonment of occupational sites by Neolithic humans. The rainfall rates inferred from our data are best explained by strong vegetation and dust feedbacks; without these mechanisms, climate models systematically fail to reproduce the Green Sahara. This study suggests that accurate simulations of future climate change in the Sahara and Sahel will require improvements in our ability to simulate vegetation and dust feedbacks.

  15. Rainfall regimes of the Green Sahara

    Science.gov (United States)

    Tierney, Jessica E.; Pausata, Francesco S. R.; deMenocal, Peter B.

    2017-01-01

    During the “Green Sahara” period (11,000 to 5000 years before the present), the Sahara desert received high amounts of rainfall, supporting diverse vegetation, permanent lakes, and human populations. Our knowledge of rainfall rates and the spatiotemporal extent of wet conditions has suffered from a lack of continuous sedimentary records. We present a quantitative reconstruction of western Saharan precipitation derived from leaf wax isotopes in marine sediments. Our data indicate that the Green Sahara extended to 31°N and likely ended abruptly. We find evidence for a prolonged “pause” in Green Sahara conditions 8000 years ago, coincident with a temporary abandonment of occupational sites by Neolithic humans. The rainfall rates inferred from our data are best explained by strong vegetation and dust feedbacks; without these mechanisms, climate models systematically fail to reproduce the Green Sahara. This study suggests that accurate simulations of future climate change in the Sahara and Sahel will require improvements in our ability to simulate vegetation and dust feedbacks. PMID:28116352

  16. Cenozoic stratigraphy of the Sahara, Northern Africa

    Science.gov (United States)

    Swezey, Christopher S.

    2009-01-01

    This paper presents an overview of the Cenozoic stratigraphic record in the Sahara, and shows that the strata display some remarkably similar characteristics across much of the region. In fact, some lithologies of certain ages are exceptionally widespread and persistent, and many of the changes from one lithology to another appear to have been relatively synchronous across the Sahara. The general stratigraphic succession is that of a transition from early Cenozoic carbonate strata to late Cenozoic siliciclastic strata. This transition in lithology coincides with a long-term eustatic fall in sea level since the middle Cretaceous and with a global climate transition from a Late Cretaceous–Early Eocene “warm mode” to a Late Eocene–Quaternary “cool mode”. Much of the shorter-term stratigraphic variability in the Sahara (and even the regional unconformities) also can be correlated with specific changes in sea level, climate, and tectonic activity during the Cenozoic. Specifically, Paleocene and Eocene carbonate strata and phosphate are suggestive of a warm and humid climate, whereas latest Eocene evaporitic strata (and an end-Eocene regional unconformity) are correlated with a eustatic fall in sea level, the build-up of ice in Antarctica, and the appearance of relatively arid climates in the Sahara. The absence of Oligocene strata throughout much of the Sahara is attributed to the effects of generally low eustatic sea level during the Oligocene and tectonic uplift in certain areas during the Late Eocene and Oligocene. Miocene sandstone and conglomerate are attributed to the effects of continued tectonic uplift around the Sahara, generally low eustatic sea level, and enough rainfall to support the development of extensive fluvial systems. Middle–Upper Miocene carbonate strata accumulated in northern Libya in response to a eustatic rise in sea level, whereas Upper Miocene mudstone accumulated along the south side of the Atlas Mountains because uplift of the

  17. Solar hydrogen: the Great Sahara project

    Energy Technology Data Exchange (ETDEWEB)

    Eljrushi, G.S. (High Industrial Inst., Misurata (Libyan Arab Jamahiriya)); Zubia, J.N. (Secretariat of Light Industry, Misurata (Libyan Arab Jamahiriya))

    1994-03-01

    This paper discusses a proposal for an international solar hydrogen project to be installed in North Africa, near the town of Ghadames in the middle of the desert, to exploit the enormous Sahara solar power resource. It suggests some practical steps to implement this project in three successive stages. The financing of the project is discussed, and the relevant local activities have been outlined. It also discusses the forming of a task force from interested parties to take initiatives and to present facts about the benefits that would result from harnessing the Sahara's limitless reservoir of solar energy. (author)

  18. Sahara: Barrier or corridor? Nonmetric cranial traits and biological affinities of North African late Holocene populations.

    Science.gov (United States)

    Nikita, Efthymia; Mattingly, David; Lahr, Marta Mirazón

    2012-02-01

    The Garamantes flourished in southwestern Libya, in the core of the Sahara Desert ~3,000 years ago and largely controlled trans-Saharan trade. Their biological affinities to other North African populations, including the Egyptian, Algerian, Tunisian and Sudanese, roughly contemporary to them, are examined by means of cranial nonmetric traits using the Mean Measure of Divergence and Mahalanobis D(2) distance. The aim is to shed light on the extent to which the Sahara Desert inhibited extensive population movements and gene flow. Our results show that the Garamantes possess distant affinities to their neighbors. This relationship may be due to the Central Sahara forming a barrier among groups, despite the archaeological evidence for extended networks of contact. The role of the Sahara as a barrier is further corroborated by the significant correlation between the Mahalanobis D(2) distance and geographic distance between the Garamantes and the other populations under study. In contrast, no clear pattern was observed when all North African populations were examined, indicating that there was no uniform gene flow in the region.

  19. Adsorption of dyes on Sahara desert sand.

    Science.gov (United States)

    Varlikli, Canan; Bekiari, Vlasoula; Kus, Mahmut; Boduroglu, Numan; Oner, Ilker; Lianos, Panagiotis; Lyberatos, Gerasimos; Icli, Siddik

    2009-10-15

    Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.

  20. Ternary feldspar thermometry of Paleoproterozoic granulites from In-Ouzzal terrane (Western Hoggar, southern Algeria)

    Science.gov (United States)

    Benbatta, A.; Bendaoud, A.; Cenki-Tok, B.; Adjerid, Z.; Lacène, K.; Ouzegane, K.

    2017-03-01

    The In Ouzzal terrane in western Hoggar (Southern Algeria) preserves evidence of ultrahigh temperature (UHT) crustal metamorphism. It consists in Archean crustal units, composed of orthogneissic domes and greenstone belts, strongly remobilized during the Paleoproterozoic orogeny which was recognized as an UHT event (peak T > 1000 °C and P ≈ 9-12 kbar). This metamorphism was essentially defined locally in Al-Mg granulites, Al-Fe granulites and quartzites outcropping in the Northern part of the In Ouzzal terrane (IOT). In order to test and verify the regional spread of the UHT metamorphism in this terrane, ternary feldspar thermometry on varied rock types (Metanorite, Granulite Al-Mg and Orthogneiss) and samples that crop out in different zones of the In Ouzzal terrane. These rocks contain either perthitic, antiperthitic or mesoperthitic parageneses. Ternary feldspars used in this study have clearly a metamorphic origin. The obtained results combined with previous works show that this UHT metamorphism (>900 °C) affected the whole In Ouzzal crustal block. This is of major importance as for future discussion on the geodynamic context responsible for this regional UHT metamorphism.

  1. Three million years of monsoon variability over the northern Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Larrasoana, J.C.; Roberts, A.P.; Rohling, E.J.; Winklhofer, M. [School of Ocean and Earth Science, Southampton Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH (United Kingdom); Wehausen, R. [Institut fuer Chemie und Biologie des Meeres (ICBM), Carl-von-Ossietzky-Universitaet, 26111, Oldenburg (Germany)

    2003-12-01

    We present a 3 million year record of aeolian dust supply into the eastern Mediterranean Sea, based on hematite contents derived from magnetic properties of sediments from Ocean Drilling Program Site 967. Our record has an average temporal resolution of {proportional_to}400 years. Geochemical data validate this record of hematite content as a proxy for the supply of aeolian dust from the Sahara. We deduce that the aeolian hematite in eastern Mediterranean sediments derives from the eastern Algerian, Libyan, and western Egyptian lowlands located north of the central Saharan watershed ({proportional_to}21 N). In corroboration of earlier work, we relate dust flux minima to penetration of the African summer monsoon front to the north of the central Saharan watershed. This would have enhanced soil humidity and vegetation cover in the source regions, in agreement with results from ''green Sahara'' climate models. Our results indicate that this northward monsoon penetration recurred during insolation maxima throughout the last 3 million years. As would be expected, this orbital precession-scale mechanism is modulated on both short ({proportional_to}100-kyr) and long ({proportional_to}400-kyr) eccentricity time scales. We also observe a strong expression of the {proportional_to}41-kyr (obliquity) cycle, which we discuss in terms of high- and low-latitude mechanisms that involve Southern Hemisphere meridional temperature contrasts and shifts in the latitudes of the tropics, respectively. We also observe a marked increase in sub-Milankovitch variability around the mid-Pleistocene transition ({proportional_to}0.95 Ma), which suggests a link between millennial-scale climate variability, including monsoon dynamics, and the size of northern hemisphere ice sheets. (orig.)

  2. Wet phases in the Sahara/Sahel region and human migration patterns in North Africa.

    Science.gov (United States)

    Castañeda, Isla S; Mulitza, Stefan; Schefuss, Enno; Lopes dos Santos, Raquel A; Sinninghe Damsté, Jaap S; Schouten, Stefan

    2009-12-01

    The carbon isotopic composition of individual plant leaf waxes (a proxy for C(3) vs. C(4) vegetation) in a marine sediment core collected from beneath the plume of Sahara-derived dust in northwest Africa reveals three periods during the past 192,000 years when the central Sahara/Sahel contained C(3) plants (likely trees), indicating substantially wetter conditions than at present. Our data suggest that variability in the strength of Atlantic meridional overturning circulation (AMOC) is a main control on vegetation distribution in central North Africa, and we note expansions of C(3) vegetation during the African Humid Period (early Holocene) and within Marine Isotope Stage (MIS) 3 ( approximately 50-45 ka) and MIS 5 ( approximately 120-110 ka). The wet periods within MIS 3 and 5 coincide with major human migration events out of sub-Saharan Africa. Our results thus suggest that changes in AMOC influenced North African climate and, at times, contributed to amenable conditions in the central Sahara/Sahel, allowing humans to cross this otherwise inhospitable region.

  3. Surviving in mountain climate refugia: new insights from the genetic diversity and structure of the relict shrub Myrtus nivellei (Myrtaceae) in the Sahara Desert.

    Science.gov (United States)

    Migliore, Jérémy; Baumel, Alex; Juin, Marianick; Fady, Bruno; Roig, Anne; Duong, Nathalie; Médail, Frédéric

    2013-01-01

    The identification of past glacial refugia has become a key topic for conservation under environmental change, since they contribute importantly to shaping current patterns of biodiversity. However, little attention has been paid so far to interglacial refugia despite their key role for the survival of relict species currently occurring in climate refugia. Here, we focus on the genetic consequences of range contraction on the relict populations of the evergreen shrub Myrtus nivellei, endemic in the Saharan mountains since at least the end of the last Green Sahara period, around 5.5 ka B.P. Multilocus genotypes (nuclear microsatellites and AFLP) were obtained from 215 individuals collected from 23 wadis (temporary rivers) in the three main mountain ranges in southern Algeria (the Hoggar, Tassili n'Ajjer and Tassili n'Immidir ranges). Identical genotypes were found in several plants growing far apart within the same wadis, a pattern taken as evidence of clonality. Multivariate analyses and Bayesian clustering revealed that genetic diversity was mainly structured among the mountain ranges, while low isolation by distance was observed within each mountain range. The range contraction induced by the last episode of aridification has likely increased the genetic isolation of the populations of M. nivellei, without greatly affecting the genetic diversity of the species as a whole. The pattern of genetic diversity observed here suggests that high connectivity may have prevailed during humid periods, which is consistent with recent paleoenvironmental reconstructions.

  4. Electricity generated in the North Sea and Sahara; Een supergrid met Noordzee- en Saharastroom?

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, A.H.H. [Autarkis, Almere (Netherlands)

    2010-05-15

    This article makes a clear statement that the total investments in the 'decentralized all electrical solution' is less than the investments in central solutions with electricity generated in either the North Sea and/or the Sahara. The author states that the Dutch government should therefore focus their subsidiary policies to smaller affordable decentralized solutions, instead of the larger expensive centralized solutions. This is at the moment clearly not the case in Dutch politics. However, autarky is possible in the short term as described in this article on the basis of a case of a house with heat and electricity installations. [Dutch] Vormt een supergrid met elektriciteit van de Noordzee en uit de Sahara gecombineerd met passieve woningbouw onze toekomstige duurzame (autarke) energievoorziening? Het warmte/krachtverbruik van de gebouwde omgeving in Nederland bedraagt circa 30 procent van het primaire energiegebruik. Het is ondoenlijk om op afzienbare tijd alle 7,2 miljoen woningen te renoveren tot op een passief woningbouwniveau met isolatiedikten tot wel 40 a 50 centimeter, voorzien van thermische zonnecollectoren voor de warmwaterproductie en met elektriciteit van de Noordzee en uit de Sahara. Autarkie op kortere termijn is wel realiseerbaar op een wijze zoals beschreven in deze publicatie op basis van een woning met warmte- en electrische installaties.

  5. Eghindi among Sahrawi refugees of Western Sahara.

    Science.gov (United States)

    Volpato, Gabriele; Waldstein, Anna

    2014-01-01

    Eghindi is an illness built around a set of pathological states experienced by Sahrawi in the desert environment of Western Sahara. Its core symptoms are caused by osmotic imbalances related to salt consumption. In 1975, many Sahrawi were exiled into refugee camps, and they have since experienced radical sociocultural changes, which are reflected in changing explanatory models of eghindi. Older and conservative refugees, attached to traditional Sahrawi culture, have expanded its conceptualization to include new pathogenic factors, while younger and progressive refugees, acculturated with Western culture, began challenging its existence. Eghindi became embodied within a broader process of negotiation of Sahrawi cultural identity. Our findings provide a framework for thinking about the evolution of illness in response to displacement, and highlight that when explanatory models evolve, intracultural tensions can arise within a population.

  6. Monazite Geochronology of Al-Fe Granulites Of Amesmessa Area from In-Ouzzal Terrane (Western Hoggar, Algeria)

    Science.gov (United States)

    Ahmed, Benbatta; Abderrahmane, Bendaoud; Bénédicte, Cenki-Tok; Zohir, Adjerid; Olivier, Bruguier; Jesus, Garrido Marin Carlos; Safouane, Djemai; Khadija, Ouzegane

    2017-04-01

    ABSTRACT: The In Ouzzal terrane in western Hoggar (South Algeria) preserves evidence of ultrahigh-temperature (UHT) crustal metamorphism. It consists in Archean crustal units, composed of orthogneissic domes and green stone belts, strongly remobilized during the Paleoproterozoic orogeny (2000 Ma, Peucat et al., 1996). Ouzegane et al. (2003) summarize this UHT metamorphic history as two granulitic stages of high temperature : a prograde evolution with peak conditions around 9-11 kbar and 950-1050°C, leading to the appearance of exceptional paragenèses with corundum-quartz, sapphirine-quartz and sapphirine-spinel-quartz in Al-Mg granulites, Al-Fe granulites and quartzites; followed by retrograde event characterized by a pressure drop to 5-7 kbar. This retrograde event is marked by intrusive carbonatite bodies and the occurrence of leptynites veins. The present study is interested in Al-Fe granulites which outcrop in a still little known region situated in southeastern part of In-Ouzzal terrane. These granulites are mainly composed by quartz, spinel, garnet, sillimanite, cordierite, biotite, perthitic feldspar, ilmenite, ± corundum. The study consist to dating these Al-Fe granulites by monazites (U-Pb - ICP-MS method) combined with their internal structures revealed by BSE imaging. The primary results suggest two major facts: 1- for the first time, the existence of at least one metamorphism older than 2.5 Ga; 2- a long live paleoproterozoic high temperature metamorphism. These geochronological results completed and combined with a detailed phases relationship study of these Al-Fe granulites will are of major importance as for future discussion on the geodynamic context responsible for this regional UHT metamorphism as well as indicating a record the time of the different stages of granulitic metamorphism. Keywords: UHT metamorphism, Granulites, Paleoproterozoïc, Archaean; Southeastern In Ouzzal terrane; Monazite geochronology; Hoggar

  7. Effect of heat treatment on antimycotic activity of Sahara honey

    Institute of Scientific and Technical Information of China (English)

    Moussa Ahmed; Saad Aissat; Noureddine Djebli

    2014-01-01

    Objective: To evaluate the influence of the temperature on honey colour, polyphenol contents and antimycotic capacity and to evaluate the correlation between these parameters. Methods:Sahara honey were heated up to 25, 50, 75 and 100 °C for 15, 30 and 60 min, and their colour intensity, polyphenol contents and antimycotic capacity. The Folin-Ciocalteu test was used to determine the total polyphenol contents (TPC). The antimycotic activity was evaluated both by agar diffusion method and micro wells dilution method against the Candida albicans (C. albicans) and Candida glabrata (C. glabrata). Results:Initial values for TPC in Sahara honey ranged from 0.55 to 1.14 mg of gallic acid per kg of honey, with the average value of 0.78 mg of gallic acid per kg of honey. The TPC values after heat-treatment were 0.54 to 1.54 with the average value of 1.49 mg. The minimal inhibitory concentrations before heat-treatment of Sahara honey against C. albicans and C. glabrata ranged from 3.06%-12.5% and 50% respectively. After heat-treatment the minimal inhibitory concentrations between 12.5% and 50% for C. albicans and C. glabrata, respectively. The diameters of inhibition zones of Sahara honey with 50% concentration varied from (12.67-15.00) mm by C. albicans to (14.33-15.67) mm by C. glabrata. The diameters of inhibition zones after heat-treatment at 25 and 50 °C for 15.30 and 60 min ranged from (2.00-18.67) mm by C. albicans to (8.00-16.67) mm by C. glabrata. Statistically significant relations between the TPC and the colour intensity of Sahara honey (r=0.99, P Conclusions:To our knowledge this is the first report on the antimycotic capacity of Sahara honey.

  8. Africa, Sub-Sahara: A Selected Functional and Country Bibliography.

    Science.gov (United States)

    Foreign Service (Dept. of State), Washington, DC. Foreign Service Inst.

    Sub-Sahara Africa is covered in this bibliography prepared for use in training programs. Consisting of nearly 500 citations which date from 1940 to the present, topics covered include: POPULATION, Traditional Cultures, Religion, Art, Literature, History, Colonialism, Economic Development, Agricultural Modernization, Education and Manpower,…

  9. Solar power at the edge of the Sahara desert

    Energy Technology Data Exchange (ETDEWEB)

    Bresler, Ines

    2012-07-01

    In Morocco, the turn in the energy sector is overseen by His Majesty the King himself: in 2009, the King introduced the Moroccan Solar Plan and created the Moroccan Agency for Solar Energy (MASEN) for its implementation. This year, the construction work for the first project complex will commence at the edge of the Sahara desert. (orig.)

  10. Africa South of the Sahara: A Guide to Reference Sources.

    Science.gov (United States)

    Mason, Mary, Comp.

    This annotated bibliography has been compiled as an introduction to reference resources for college-level African studies and to suggest useful tools for literature searches. It is a guide to materials in the library of McGill University. Call numbers are included. The titles cited refer to Africa South of the Sahara as a whole or to large…

  11. Modeling non-monotone risk aversion using SAHARA utility functions

    NARCIS (Netherlands)

    A. Chen; A. Pelsser; M. Vellekoop

    2011-01-01

    We develop a new class of utility functions, SAHARA utility, with the distinguishing feature that it allows absolute risk aversion to be non-monotone and implements the assumption that agents may become less risk averse for very low values of wealth. The class contains the well-known exponential and

  12. Alternative energies. Sahara Power needs pan-European grid operator

    Energy Technology Data Exchange (ETDEWEB)

    Van Wijland, G.

    2009-09-15

    A consortium of leading European - mostly German - companies plans to invest 400 billion euros in a megaproject to generate solar power in the Sahara desert. Desertec, as the project is called, could cover 15 percent of European electricity demand. The problem is, how do you transport this power to Paris and Berlin? It can only work with a pan-European grid operator.

  13. Cultural Astronomy in Africa South of the Sahara

    Science.gov (United States)

    Holbrook, Jarita

    This chapter examines two foci of cultural astronomy found in Africa south of the Sahara: creation myths and celestial art. The examples highlighted are from the Akan, the Bahima, the Boshongo, the Fon, the Igbo, the Mambila, the Yoruba, and the Zulu people.

  14. Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara

    Science.gov (United States)

    Kemena, Tronje Peer; Matthes, Katja; Martin, Thomas; Wahl, Sebastian; Oschlies, Andreas

    2017-09-01

    Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR's CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the Sahel zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the Sahel zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the Sahel zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.

  15. Frontières et nationalisme autour du Sahara Occidental (Borders and Nationalism in Western Sahara

    Directory of Open Access Journals (Sweden)

    Luis Martinez

    2011-01-01

    Full Text Available Le conflit du Sahara Occidental apparaît comme le principal facteur de blocage dans la construction d'une intégration régionale. Pour la monarchie marocaine, il lui a permis de s'approprier le sentiment nationaliste alors porté par le mouvement de l'Istiqlal qui faisait de la cause du grand Maroc l'un de ses combats politiques. Pour le régime algérien, il a représenté un moyen de justifier le pouvoir d'une armée et d'entretenir le sentiment nationaliste. L'avantage du conflit saharien était évident : l'instauration, sous couvert d'un sentiment nationaliste, de régimes politiques autoritaires. Depuis une décennie, ce conflit « gelé » est bloqué à la fois par « le statut avancé » du Maroc avec l'UE, qui n'ose aborder ce problème et le retour de l'abondance financière en Algérie qui alimente son intransigeance sur le dossier.(The conflict in Western Sahara is the main stumbling block to the construction of an integrated region. The Moroccan monarchy used the conflict to gain the support of nationalists previously allied with the Istiqlal movement whose principal political goal was the creation of a greater Morocco. The Algerian regime used the conflict as a justification for a strong military and to stir up nationalist sentiment. The advantage of the Saharan conflict was obvious: the establishment, under the guise of nationalism, of authoritarian regimes. For a decade resolution of this “frozen” conflict has been blocked by the EU’s unwillingness to address the issue in light of the “advanced status” of Morocco in the EU and by the increased intransigence of Algeria made possible by its renewed financial strength.

  16. Mapping and discriminating the Pan-African granitoids in the Hoggar (southern Algeria) using Landsat 7 ETM+ data and airborne geophysics

    Science.gov (United States)

    Zerrouk, Siham; Bendaoud, Abderrahmane; Hamoudi, Mohamed; Liégeois, Jean Paul; Boubekri, Hichem; El Khaznadji, Riad Ben

    2017-03-01

    This study presents a multidisciplinary approach to discriminate and map different types and generations of Pan-African granitoids in the Hoggar, southern Algeria, using remote sensing and airborne geophysics in close correlation with previous works and established geological maps. RGB (Red, Green, Blue) combinations of band ratios; principal component analysis (PCA) and image classification for Landsat 7 ETM+ (Enhanced Thematic Mapper Plus), allow spatial discrimination and mapping of granitoid rocks of the studied area (200*350 km). This area extend over four contrasted Pan-African terranes (In Tedeini, Iskel, Tefedest and Laouni terranes, the two latter belong to the LATEA (Laouni-Azrou-n-Fad-Tefedest-Egéré-Aleksod-Assodé-Issalane) metacraton. The airborne magnetic intensity provides a wide range of responses from high values (youngest granitoids) to low values (volcano-sedimentary and gneissic country-rocks). Radiometric data, displaying radioelements concentration, discriminate efficiently the late alkaline granitoids (high values), the calk-alkaline granitoids (intermediate values) and the Tonalite-Trondhjemite-Granodiorite series (low values). This study led to the establishment of a more accurate geological map where the geochemical characteristics of the Pan-African granitoids are determined, including plutons not yet studied, especially in the poorly known In Tedeini terrane, and brings new constraints for the geodynamic development of the Tuareg Shield, which includes the Hoggar.

  17. Meso-Cenozoic evolution of the Tuareg Shield (Algeria, Sahara): insights from new thermochronological data

    Science.gov (United States)

    Rougier, Sylvain; Missenard, Yves; Gautheron, Cécile; Barbarand, Jocelyn; Zeyen, Hermann; Pinna, Rosella; Liégeois, Jean-Paul; Bonin, Bernard; Ouabadi, Aziouz; El-Messaoud Derder, Mohammed; Frizon de Lamotte, Dominique; Kettouche, Djouher

    2013-04-01

    In North Africa, Meso-Cenozoic large scale topographic swells, such as Hoggar, Tibesti or Darfur domes, are superimposed to a Paleozoic arch and basin morphology which characterizes this region. Although these topographic highs are associated to Cenozoic intraplate volcanism, their development remains poorly constrained, both from temporal and spatial points of view. This study is focused on the Tuareg Shield bulge, a topographic high where Precambrian rocks, exposed over 500000 km², can reach 2400 m above sea level (Atakor district, Hoggar, South Algeria). While presumed Cretaceous sedimentary remnants, resting unconformably over the basement, suggest a possible stage of weak topography during the Mesozoic, current high topography is emphasized by Tuareg Shield lithosphere resulted in erosion of the major part of this cover and, since 35 Ma, the development of intraplate volcanism.

  18. The Green Sahara: Climate Change, Hydrologic History and Human Occupation

    Science.gov (United States)

    Blom, Ronald G.; Farr, Tom G.; Feynmann, Joan; Ruzmaikin, Alexander; Paillou, Philippe

    2009-01-01

    Archaeology can provide insight into interactions of climate change and human activities in sensitive areas such as the Sahara, to the benefit of both disciplines. Such analyses can help set bounds on climate change projections, perhaps identify elements of tipping points, and provide constraints on models. The opportunity exists to more precisely constrain the relationship of natural solar and climate interactions, improving understanding of present and future anthropogenic forcing. We are beginning to explore the relationship of human occupation of the Sahara and long-term solar irradiance variations synergetic with changes in atmospheric-ocean circulation patterns. Archaeological and climate records for the last 12 K years are gaining adequate precision to make such comparisons possible. We employ a range of climate records taken over the globe (e.g. Antarctica, Greenland, Cariaco Basin, West African Ocean cores, records from caves) to identify the timing and spatial patterns affecting Saharan climate to compare with archaeological records. We see correlation in changing ocean temperature patterns approx. contemporaneous with drying of the Sahara approx. 6K years BP. The role of radar images and other remote sensing in this work includes providing a geographically comprehensive geomorphic overview of this key area. Such coverage is becoming available from the Japanese PALSAR radar system, which can guide field work to collect archaeological and climatic data to further constrain the climate change chronology and link to models. Our initial remote sensing efforts concentrate on the Gilf Kebir area of Egypt.

  19. The Green Sahara: Climate Change, Hydrologic History and Human Occupation

    Science.gov (United States)

    Blom, Ronald G.; Farr, Tom G.; Feynmann, Joan; Ruzmaikin, Alexander; Paillou, Philippe

    2009-01-01

    Archaeology can provide insight into interactions of climate change and human activities in sensitive areas such as the Sahara, to the benefit of both disciplines. Such analyses can help set bounds on climate change projections, perhaps identify elements of tipping points, and provide constraints on models. The opportunity exists to more precisely constrain the relationship of natural solar and climate interactions, improving understanding of present and future anthropogenic forcing. We are beginning to explore the relationship of human occupation of the Sahara and long-term solar irradiance variations synergetic with changes in atmospheric-ocean circulation patterns. Archaeological and climate records for the last 12 K years are gaining adequate precision to make such comparisons possible. We employ a range of climate records taken over the globe (e.g. Antarctica, Greenland, Cariaco Basin, West African Ocean cores, records from caves) to identify the timing and spatial patterns affecting Saharan climate to compare with archaeological records. We see correlation in changing ocean temperature patterns approx. contemporaneous with drying of the Sahara approx. 6K years BP. The role of radar images and other remote sensing in this work includes providing a geographically comprehensive geomorphic overview of this key area. Such coverage is becoming available from the Japanese PALSAR radar system, which can guide field work to collect archaeological and climatic data to further constrain the climate change chronology and link to models. Our initial remote sensing efforts concentrate on the Gilf Kebir area of Egypt.

  20. Optimal investment and indifference pricing when risk aversion is not monotone: SAHARA utility functions

    NARCIS (Netherlands)

    A. Chen; A. Pelsser; M. Vellekoop

    2008-01-01

    Abstract. We develop a new class of utility functions, SAHARA utility, with the dis- tinguishing feature that they implement the assumption that agents may become less risk-averse for very low values of wealth. This means that SAHARA utility can be used to characterize risk gambling behavior of an e

  1. Regime shifts in the Sahara and Sahel: interactions between ecological and climatic systems in northern Africa

    NARCIS (Netherlands)

    Foley, J.A.; Coe, M.T.; Scheffer, M.; Wang, G.L.

    2003-01-01

    The Sahara and Sahel regions of northern Africa have complex environmental histories punctuated by sudden and dramatic "regime shifts" in climate and ecological conditions. Here we review the current understanding of the causes and consequences of two environmental regime shifts in the Sahara and Sa

  2. Sahara honey shows higher potency against Pseudomonas aeruginosa compared to north Algerian types of honey.

    Science.gov (United States)

    Boukraa, Laid; Niar, Abdellatif

    2007-12-01

    Six varieties of honey from different regions in Algeria were used to determine their potency against Pseudomonas aeruginosa. Four varieties originated from northern Algeria, and two from the Sahara. Three types of media were used. On nutrient agar the minimum inhibitory concentration (MIC) of the four northern varieties ranged between 30% (vol/vol) and 31% (vol/vol), while the MIC of the Sahara varieties was 11% (vol/vol) and 14% (vol/vol). On King A agar the MIC of the four northern varieties ranged from 25% (vol/vol) to 31% (vol/vol), whereas the MIC of the two varieties of Sahara honey was 12% (vol/vol) and 15% (vol/vol). On nutrient broth the MIC of the northern varieties ranged from 10% (vol/vol) to 21% (vol/vol), whereas the MIC of the two varieties of Sahara honey was 9% (vol/vol). The botanic flora of Sahara is known in Algeria for its medicinal uses, and thus the higher potency of the Sahara honey is most probably due to antibacterial substances in its plant derivates. These findings suggest that Sahara honey could be used for managing wounds and burns, which are mostly infected by P. aeruginosa.

  3. Dry Deposition from Sahara Sources Regions of Western Africa

    Directory of Open Access Journals (Sweden)

    B. Douaiba

    2014-01-01

    Full Text Available Sahara dust storms during March 2004 have attracted much attention from the dust-research community due to their intensity, wide coverage, and endurance. In the present work, the dry deposition mechanisms of mineral dust are analysed during an event on the 3 March 2004 over the Northwest African coast. This particular case was chosen based on the strong dry removal that occurred, rendering it ideal for examining the deposition processes. The simulation of synoptic conditions and dry deposition of four dust particles including clay, small silt, large silt, and sand was performed with Eta model, coupled with a desert dust cycle module. The results have been compared with surface data from weather stations in North Africa, data of dry metals from stations located in Gran Canaria, and various satellite images such as European Organization for the Exploitation of Meteorological Satellites and Moderate Resolution Imaging Spectroradiometer for the period in question.

  4. SAHARA-J: Journal of Social Aspects of HIV/AIDS

    African Journals Online (AJOL)

    SAHARA J Journal of Social Aspects of HIV/AIDS Research Alliance. ... health communication, structural and environmental intervention, financing, policy, media, ... structurale et de l'environnement, le financement, la politique, le média, etc).

  5. Building Fit-for-Purpose Spatial Frameworks for Sustainable Land Governaqnce in Sub-Sahara Africa

    DEFF Research Database (Denmark)

    Enemark, Stig

    2013-01-01

    countries this countrywide spatial framework has been developed over centuries. In contrast, most developing countries have a cadastral coverage of less than 30 per cent of the country. This means that over 70 per cent of the land in many developing countries, such as the sub-Sahara region, is generally......, economic, legal, and social issues related to building such fit-for purpose spatial frameworks as a means of paving the way towards sustainable and land governance in Sub-Sahara Africa...

  6. Evidence of Laurussian affinity for parts of the Mauritanides and Souttoufides (Moroccan Sahara)

    Science.gov (United States)

    Gärtner, Andreas; Villeneuve, Michel; Linnemann, Ulf; El Archi, Abdelkrim; Bellon, Hervé

    2013-04-01

    The Soutouffide belt is located in the southern part of the Moroccan Sahara. Representing the northern section of the Carboniferous Mauritanide belt, it extends from Morocco to Senegal. The Dhlou and Adrar Souttouf Massifs, both of which belong to the Souttoufide belt, are located on the western margin of the Archean Reguibat Shield. Previously, the Adrar Souttouf Massif has been suggested to be part of the Variscan Mauritanian-Appalachian system. To date the Moroccan Sahara has been one of the least studied regions in West Africa. This study presents new zircon ages from two units of the Adrar Souttouf Massif which have nevertheless allowed us to hypothesise a complex polyphased history. The Massif can be subdivided into four NNE-SSW trending units (listed here from east to west). The Sebkha Matallah unit represents the eastern margin of the Adrar Souttouf Massif and is thrust over the Ordovician to Devonian sedimentary Dhloat Ensour Group to the east. A central (Dayet Lawda) unit consisting of mafic and ultramafic rocks is interpreted as a possible remnant of Neoproterozoic oceanic crust or mafic terranes. The western Sebkha Gezmayet and Oued Togba units are mainly composed of granitoids and orthogneisses. Zircon ages of the Tonian-Stenian (1.4-1.0 Ga) were recorded in the Oued Togba and Sebkha Gezmayet units and suggest an Avalonian-Meguman-like relationship. Three other age groups were obtained in these two units: 610 to 570 Ma (Pan-African), 530 to 490 Ma (Cambrian), and 440 to 270 Ma. The latter population cannot result from Variscan orogeny alone, and is possibly linked to the Salinic and Acadian orogenies of Laurentia. Zircon age populations at ~3.0 Ga and ~2.65 Ga determined for two granite samples from the Archean foreland are in accordance to data already published. Ages of between 226 Ma (Upper Triassic) and 158 Ma (Upper Jurassic) result from lower intercepts of discordia lines and are interpreted as a Mesozoic thermal overprint of the area attributed

  7. Remote sensing of the hydrologic history of the eastern Sahara

    Science.gov (United States)

    Farr, T. G.; Blom, R. G.; Paillou, P.

    2010-12-01

    The eastern Sahara Desert has never been thoroughly mapped in terms of the landforms and subsurface signs of past climates conducive to human occupation. As part of ongoing work and through a new proposal to NASA, we are generating new maps of the paleohydrology, topography, geomorphology, and surficial deposits of the area and developing GIS-based models which use the data to pinpoint past resources and travel pathways. The maps we are generating will constitute a unique resource for exploration for water and archeological sites in the Gilf Kebir and other regions of NE Africa. That the Sahara was favorable for human habitation at times has long been known. With the remarkable paleo-landscape revealed by the L-band (25 cm) Shuttle Imaging Radar-A in 1981, it became clear that ancient humans concentrated along integrated drainage systems dubbed “radar rivers” by McCauley and colleagues. However SIR-A and subsequent long-wavelength radar coverage was limited and regional understanding of the drainage network has remained elusive. We are mapping the area with three sensors optimized for mapping and characterizing arid regions: The Japanese PALSAR L-band imaging radar, NASA’s SRTM, and ASTER. Together these sensors provide full coverage of the area allowing characterization and mapping of surface and subsurface landforms formed and modified by former wetter climates. In particular and following the work of Ghoneim, Robinson, El Baz and others, we are mapping the regional drainage network revealed by the radar images and applying modern analysis tools to the drainage basins and channels. These include drainage density, channel gradient vs. distance, and longitudinal and cross-channel topographic profiles. We use these quantities to estimate a stream’s past approach to equilibrium and this to infer balances between climate, tectonic uplift, and other changes in base level. Discovery over the last few years of large paleolakes (e.g. Mega Lake Chad, North Darfur

  8. U Pb dating of the end of the Pan-African orogeny in the Tuareg shield: the post-collisional syn-shear Tioueine pluton (Western Hoggar, Algeria)

    Science.gov (United States)

    Paquette, J. L.; Caby, R.; Djouadi, M. T.; Bouchez, J. L.

    1998-12-01

    The Tioueine pluton intrudes the Neoproterozoic series of the Iskel terrane, located in the Tuareg shield, western Hoggar. The consistency of the internal structures as well as the nature and organization of the associated microstructures demonstrate that the Tioueine pluton was emplaced syn-kinematically while N-S strike-slip shear zones were active. The syn-tectonic emplacement of the Tioueine massif implies that this pluton, although belatedly crystallized, entirely belongs to the concept of post-collisional magmatism. In order to date precisely the late Pan-African tectono-metamorphic event in the studied area, an U-Pb age of 523±1 Ma was obtained from abraded zircons of a late quartz-syenite from the Tioueine pluton. This early Cambrian age is younger than the other plutons of the Tuareg shield, which were mainly emplaced between 630 Ma and 580 Ma. This dating also shows that the Tuareg shield was not a single coherent block at 525 Ma, but rather an amalgam of active terranes moving each other along major shear zones. Finally, the Tioueine massif represents probably the final welding of the Tuareg shield assembly of terranes and consequently the end of the post-collisional orogenic episode in the whole Pan-African belt.

  9. Low 60Fe abundance in Semarkona and Sahara 99555

    CERN Document Server

    Tang, Haolan

    2015-01-01

    Iron-60 (t1/2=2.62 Myr) is a short-lived nuclide that can help constrain the astrophysical context of solar system formation and date early solar system events. A high abundance of 60Fe (60Fe/56Fe= 4x10-7) was reported by in situ techniques in some chondrules from the LL3.00 Semarkona meteorite, which was taken as evidence that a supernova exploded in the vicinity of the birthplace of the Sun. However, our previous MC-ICPMS measurements of a wide range of meteoritic materials, including chondrules, showed that 60Fe was present in the early solar system at a much lower level (60Fe/56Fe=10-8). The reason for the discrepancy is unknown but only two Semarkona chondrules were measured by MC-ICPMS and these had Fe/Ni ratios below ~2x chondritic. Here, we show that the initial 60Fe/56Fe ratio in Semarkona chondrules with Fe/Ni ratios up to ~24x chondritic is 5.4x10-9. We also establish the initial 60Fe/56Fe ratio at the time of crystallization of the Sahara 99555 angrite, a chronological anchor, to be 1.97x10-9. The...

  10. The demographic response to Holocene climate change in the Sahara

    Science.gov (United States)

    Manning, Katie; Timpson, Adrian

    2014-10-01

    The timing and development of Holocene human occupation in the now hyperarid Sahara has major implications for understanding links between climate change, demography and cultural adaptation. Here we use summed probability distributions from 3287 calibrated 14C dates from 1011 archaeological sites to demonstrate a major and rapid demographic shift between 10,500 and 5500 years BP. This event corresponds with the African Humid Period (AHP) and is sub-continental in scale, indicating climate as the prime factor driving broad-scale population dynamics in northern Africa. Furthermore, by providing a high temporal resolution proxy for effective carrying capacity our population curve offers an independent estimate of environmental change in northern Africa, indicating a temporal delay in the terrestrial response to atmospheric climate change. These results highlight the degree to which human demography is a function of environment at the appropriate scale of observation in both time and space and sheds important new light on the social response to global environmental change.

  11. New Instructional Materials on Africa South of the Sahara (1969-1970). A Supplement to Africa South of the Sahara: A Resource and Curriculum Guide.

    Science.gov (United States)

    Beyer, Barry K.

    This guide cites instructional materials on Africa south of the Sahara which have become available since February 1969. Acknowledging the probability of inaccuracies in the majority of the materials cited, the guide neither evaluates nor promotes items, but simply presents annotations of readings, textbooks, fact sheets, atlases, African…

  12. NON BANKING FINANCIAL COMPANIES AND INDIA’S RURAL ECONOMY - WITH REFERENCE TO SAHARA GROUP

    Directory of Open Access Journals (Sweden)

    SUKANTA CHANDRA SWAIN

    2012-10-01

    Full Text Available Sahara India Group has diversified business in the areas like finance, real estate, media and entertainment, tourism and services. Its business in finance, as usual, comes under the purview of Reserve Bank of India (RBI jurisdiction. Its two financial institutions (FIs – Sahara India Investment Corporation Ltd (SIICL, a non-banking finance company (NBFC and Sahara India Financial Corporation Ltd (SIFCL, a residuary nonbanking finance company (RNBC have been coming under RBI scanner. While the registration of SIICL has been recently cancelled by RBI in spite of a net profit in 2006-07 against a loss in 2005-06, SIFCL has been under the threat of winding up the business owing to regulatory concerns of RBI. Thus time will come when Sahara India Group will no more be there in the financial sector. However, it will not allow the resources withdrawn from these two FIs to be idle. As it has been a prominent player in the real estate industry of India, it is clearly visible that it will reallocate the resources in favour of real estate. That way, the profitability of Sahara India Group will never be undermined. But can we say with confident that the economy will never lose anything by this ‘move by coercion’ of Sahara India Group? Certainly no, because other FIs are yet to penetrate into rural areas what SIICL and SIFCL had been doing successfully. Therefore the twin objective - Mobilization of rural savings and eradication of rural poverty will definitely be in jolt because of this. This paper tries to analyze critically this ‘move by coercion’ of Sahara India Group in the perspective of rural poverty, the ultimate problem of Indian Economy.

  13. Ancient watercourses and biogeography of the Sahara explain the peopling of the desert.

    Science.gov (United States)

    Drake, Nick A; Blench, Roger M; Armitage, Simon J; Bristow, Charlie S; White, Kevin H

    2011-01-11

    Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal "out of Africa" is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the "green Sahara" also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa.

  14. Low 60Fe Abundance in Semarkona and Sahara 99555

    Science.gov (United States)

    Tang, Haolan; Dauphas, Nicolas

    2015-03-01

    Iron-60 (t1/2 = 2.62 Myr) is a short-lived nuclide that can help constrain the astrophysical context of Solar System formation and date early Solar System events. A high abundance of 60Fe(60Fe/56Fe ≈ 4 × 10-7) was reported by in situ techniques in some chondrules from the LL3.00 Semarkona meteorite, which was taken as evidence that a supernova exploded in the vicinity of the birthplace of the Sun. However, our previous multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) measurements of a wide range of meteoritic materials, including chondrules, showed that 60Fe was present in the early Solar System at a much lower level (60Fe/56Fe ≈ 10-8). The reason for the discrepancy is unknown but only two Semarkona chondrules were measured by MC-ICPMS and these had Fe/Ni ratios below ˜2× chondritic. Here, we show that the initial 60Fe/56Fe ratio in Semarkona chondrules with Fe/Ni ratios up to ˜24× chondritic is (5.39 ± 3.27) × 10-9. We also establish the initial 60Fe/56Fe ratio at the time of crystallization of the Sahara 99555 angrite, a chronological anchor, to be (1.97 ± 0.77) × 10-9. These results demonstrate that the initial abundance of 60Fe at Solar System birth was low, corresponding to an initial 60Fe/56Fe ratio of (1.01 ± 0.27) × 10-8.

  15. LOW {sup 60}FE ABUNDANCE IN SEMARKONA AND SAHARA 99555

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Haolan; Dauphas, Nicolas, E-mail: haolantang@ucla.edu [Origins Lab, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago IL 60637 (United States)

    2015-03-20

    Iron-60 (t{sub 1/2} = 2.62 Myr) is a short-lived nuclide that can help constrain the astrophysical context of Solar System formation and date early Solar System events. A high abundance of {sup 60}Fe({sup 60}Fe/{sup 56}Fe ≈ 4 × 10{sup −7}) was reported by in situ techniques in some chondrules from the LL3.00 Semarkona meteorite, which was taken as evidence that a supernova exploded in the vicinity of the birthplace of the Sun. However, our previous multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) measurements of a wide range of meteoritic materials, including chondrules, showed that {sup 60}Fe was present in the early Solar System at a much lower level ({sup 60}Fe/{sup 56}Fe ≈ 10{sup −8}). The reason for the discrepancy is unknown but only two Semarkona chondrules were measured by MC-ICPMS and these had Fe/Ni ratios below ∼2× chondritic. Here, we show that the initial {sup 60}Fe/{sup 56}Fe ratio in Semarkona chondrules with Fe/Ni ratios up to ∼24× chondritic is (5.39 ± 3.27) × 10{sup −9}. We also establish the initial {sup 60}Fe/{sup 56}Fe ratio at the time of crystallization of the Sahara 99555 angrite, a chronological anchor, to be (1.97 ± 0.77) × 10{sup −9}. These results demonstrate that the initial abundance of {sup 60}Fe at Solar System birth was low, corresponding to an initial {sup 60}Fe/{sup 56}Fe ratio of (1.01 ± 0.27) × 10{sup −8}.

  16. Teaching About Africa South of the Sahara; A Guide and Resource Packet for Ninth Grade Social Studies.

    Science.gov (United States)

    Coburn, Barbara; And Others

    This guide provides a sampling of reference materials which are pertinent for two ninth grade units: Africa South of the Sahara: Land and People, and Africa South of the Sahara: Historic Trends. The effect of urbanization upon traditional tribalistic cultures is the focus. A case study is used to encourage an inductive approach to the learning…

  17. Notice to Nurserymen of the Naming and Release for Propagation of Sahara Sunset, A New African Hibiscus Cultivar

    Science.gov (United States)

    Hibiscus asetosella 'Sahara Sunset' is an African hibiscus released by the United States Department of Agriculture Agricultural Research Service that was Developed by Dr. Cecil Pounders at the Thad Cochran Southern Horticultural Laboratory in Poplarville, MS. ‘Sahara Sunset’ is a tropical shrub (USD...

  18. Integrating geologic and satellite radar data for mapping dome-and-basin patterns in the In Ouzzal Terrane, Western Hoggar, Algeria

    Science.gov (United States)

    Deroin, Jean-Paul; Djemai, Safouane; Bendaoud, Abderrahmane; Brahmi, Boualem; Ouzegane, Khadidja; Kienast, Jean-Robert

    2014-11-01

    The In Ouzzal Terrane (IOT) located in the north-western part of the Tuareg Shield forms an elongated N-S trending block, more than 400 km long and 80 km wide. It involves an Archaean crust remobilized during a very high-temperature metamorphic event related to the Palaeoproterozoic orogeny. The IOT largely crops out in the rocky and sandy desert of Western Hoggar. It corresponds mainly to a flat area with some reliefs composed of Late Panafrican granites, dyke networks or Cambrian volcanic rocks. These flat areas are generally covered by thin sand veneers. They are favorable for discriminating bedrock geological units using imaging radar, backscattering measurements, and field checking, because the stony desert is particularly sensitive to the radar parameters such as wavelength or polarization. The main radar data used are those obtained with the ALOS-PALSAR sensor (L-band), in ScanSAR mode (large swath) and Fine Beam modes. The PALSAR sensor has been also compared to ENVISAT-ASAR and to optical imagery. Detailed mapping of some key areas indicates extensive Archaean dome-and-basin patterns. In certain parts, the supracrustal synforms and orthogneiss domes exhibit linear or circular features corresponding to shear zones or rolling structures, respectively. The geological mapping of these dome-and-basin structures, and more generally of the Archaean and Proterozoic lithological units, is more accurate with the SAR imagery, particularly when using the L-band, than with the optical imagery. A quantitative approach is carried out in order to estimate the backscatter properties of the main rock types. Due to the large variety of configurations, radar satellite imagery such as ALOS PALSAR represents a key tool for geological mapping in arid region at different scales from the largest (e.g., 1:500,000) to the smallest (e.g., 1:50,000).

  19. Health effects from Sahara dust episodes in Europe: literature review and research gaps.

    Science.gov (United States)

    Karanasiou, A; Moreno, N; Moreno, T; Viana, M; de Leeuw, F; Querol, X

    2012-10-15

    The adverse consequences of particulate matter (PM) on human health have been well documented. Recently, special attention has been given to mineral dust particles, which may be a serious health threat. The main global source of atmospheric mineral dust is the Sahara desert, which produces about half of the annual mineral dust. Sahara dust transport can lead to PM levels that substantially exceed the established limit values. A review was undertaken using the ISI web of knowledge database with the objective to identify all studies presenting results on the potential health impact from Sahara dust particles. The review of the literature shows that the association of fine particles, PM₂.₅, with total or cause-specific daily mortality is not significant during Saharan dust intrusions. However, regarding coarser fractions PM₁₀ and PM₂.₅₋₁₀ an explicit answer cannot be given. Some of the published studies state that they increase mortality during Sahara dust days while other studies find no association between mortality and PM₁₀ or PM₂.₅₋₁₀. The main conclusion of this review is that health impact of Saharan dust outbreaks needs to be further explored. Considering the diverse outcomes for PM₁₀ and PM₂.₅₋₁₀, future studies should focus on the chemical characterization and potential toxicity of coarse particles transported from Sahara desert mixed or not with anthropogenic pollutants. The results of this review may be considered to establish the objectives and strategies of a new European directive on ambient air quality. An implication for public policy in Europe is that to protect public health, anthropogenic sources of particulate pollution need to be more rigorously controlled in areas highly impacted by the Sahara dust.

  20. Ethnopharmacological survey and phytochemical screening of some medicinal Asteraceae from Algerian Sahara

    Directory of Open Access Journals (Sweden)

    A. CHERITI

    2013-06-01

    Full Text Available A first report of Asteraceae species census of the Algerian folk medicine, currently used in Sahara for the treatment of illenes is presented. 11 Asteraceae species namely: Anvillea radiata Coss, Artemisia herba-alba, Brocchia cinerea, Bubonium graveolens, Cotula anthemoides, Echinops spinosus, Launaea arborescens, Launaea nudicaulis, Launaea resedifolia, Scorzonera undulata and Warionia saharae were selected based on the survey through interviews with local inhabitant, herbalist in the Souk and old women according to our previous works. Ethnopharmacolgical potential and chemical constituents of this species are described.

  1. A NEW SPECIES OF CYRTOSPIRIFER (BRACHIOPODA FROM THE MIDDLE DEVONIAN OF THE WESTERN SAHARA (NORTHWESTERN AFRICA

    Directory of Open Access Journals (Sweden)

    MENA SCHEMM-GREGORY

    2011-03-01

    Full Text Available A new species of Cyrtospirifer is described from the Middle to Upper Givetian of the Western Sahara (Northwest Africa. Cyrtospirifer tindoufensis new species differs in its smaller number and coarser medial and flank plications and equibiconvex shell profile from the other Givetian species of Cyrtospirifer that all occur in Europe and to which the new species probably gives rise. The new implications of the proposed phylogeny of the earliest cyrtospiriferids and their origin from the Western Sahara are discussed. The palaeogeographic distribution of the cyrtospiriferids during the Givetian and Frasnian is shown and its migration ways are described considering the global transgression and regression cycles. 

  2. Ethnopharmacological survey and phytochemical screening of some medicinal Asteraceae from Algerian Sahara

    Directory of Open Access Journals (Sweden)

    A CHERITI

    2013-06-01

    Full Text Available A first report of Asteracea species census of the Algerian folk medicine, currently used in Sahara for the treatment of illenes is presented. 11 Asteraceae species namely: Anvillea radiata coss, Artemisia herba-alba, Brocchia cinerea, Bubonium graveolens, Cotula anthemoides, Echinops spinosus, Launaea arborescens, Launaea nudicaulis, Launaea resedifolia, Scorzonera undulata and Warionia saharae were selected based on the survey through interviews with local inhabitant, herbalist in the Souk and old women according to our previous works. Ethnopharmacolgical potential and chemical constituents of this species are described.

  3. Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

    OpenAIRE

    Nick A Drake; Blench, Roger M.; Armitage, Simon J.; Bristow, Charlie S.; White, Kevin H.

    2010-01-01

    Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal “out of Africa” is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeograp...

  4. Modélisation magnétotellurique de la structure géologique profonde de l’unité granulitique de l’In Ouzzal (Hoggar occidental)

    Science.gov (United States)

    Bouzid, Abderrezak; Akacem, Nouredine; Hamoudi, Mohamed; Ouzegane, Khadidja; Abtout, Abdeslam; Kienast, Jean-Robert

    2008-11-01

    Magnetotelluric modeling of the deep geologic structure of In Ouzzal Granulitic Unit (western Hoggar). The In Ouzzal Granulitic Unit (IOGU) or In Ouzzal Terrane (IOT) is an Archaean block belonging to the Hoggar terrane mosaic. It has been reworked during the Eburnean and is characterized by ultrahigh temperature metamorphism of the structures, which are likely to be old dome and basin structures. The aim of this study, based on a survey of 12 magnetotelluric (MT) soundings, was to characterize the IOGU deep lateral boundaries and to see if it is possible to reconstruct some of these old dome and basin structures after their transformation by metamorphism and deformation. MT data analysis and modeling show that IOGU boundaries extend downwards, at least down to the crust's basement, and may represent suture zones. Inside the terrane, the MT observations do not allow separation between dome and basin structures, because these features are severely stretched. However, the main MT transverse response feature is a deeply rooted great accident, which may be interpreted as a major fault that separates IOGU into two compartments.

  5. Application of magnetotelluric in the modeling of underlying structure of Gour Oumelalen (Egere-Aleksod terrane, Central Hoggar, South of Algeria)

    Science.gov (United States)

    Boukhalfa, Zakaria; Abderrezak, Bouzid; Khadidja, Ouzegane; Abderrahmane, Bendaoud; Mohamed, Hamoudi; Abdeslam, Abtout; Abdelhamid, Bendekken; Sofiane Said, Bougchiche; Walid, Boukhlouf; Abdelgharfour, Boukar; Aboubakr, Deramchi; Mohamed, Bendali; Abdenaceur, Lemgharbi; Mohammed, Djeddi

    2016-04-01

    The results of a magnetotelluric experiment crossing Ounane granodiorite to the east until the Amadror Wadi to the West, passing through Adrar Ounane in our study area are presented. The magnetotelluric field survey was carried out in the Gour Oumelalen (GO) area during March 2015. We deployed 34 magnetotelluric sites along two parallel EW profiles of a hundred km long. Time series were collected using a V5 system 2000® of Phoenix Geophysics. The first profile located to the north is composed of 18 braodband measurement sites obtained from merging magnetotelluri with audio-magnetotelluric (AMT) data. The second one located 10 km south of the first, is composed of 15 MT sites. An inter-station distance of ~5 km provides good lateral resolution. The MT time series were recorded during about 20 hours which allows to reach a depth of 100 km or more and the AMT data 30 minutes. This allows to get broadband magnetotelluric soundings with good quality data in period range from 0.001 s to 3000 s. In this study we will use the south profile data for modeling the underlying structure of GO. The crustal part of the model shows a resistance bloc, divided by conductive parts which can be interpreted as faults, as regards the lithospheric part it less resistant the upper part, the transition crust / mantle corresponding to MOHO is estimated at more or less 35 km.

  6. African South of the Sahara: An Objective Test for Secondary Schools. A World Regions Perception Survey.

    Science.gov (United States)

    Carnegie-Mellon Univ., Pittsburgh, PA.

    Designed by Project Africa of Carnegie-Mellon University, these two test instruments have been used to discover what selected American secondary school students know or believe about Africa and other regions of the world. The first instrument, a 30-minute objective test, "Africa South of the Sahara," is comprised of 60 multiple-choice…

  7. Abrupt shifts of the Sahara-Sahel boundary during Heinrich Stadials

    Directory of Open Access Journals (Sweden)

    J. A. Collins

    2013-01-01

    Full Text Available Relict dune fields that are found at 14° N in the modern-day African Sahel are testament to equatorward expansions of the Sahara desert during the late Pleistocene. However, difficulties of dating dune formation mean that abrupt millennial-scale climate events are not always resolved in these records. High-resolution marine core studies have identified Heinrich Stadials as the dustiest periods of the last glacial, although no studies have mapped the spatio-temporal evolution of dust export from West Africa. We use the major-element composition of four marine sediment cores to reconstruct the spatial extent of Saharan-dust versus river-sediment input to the continental margin from West Africa over the last 60 ka. This allows us to map the position of the sediment composition corresponding to the Sahara-Sahel boundary. Our records indicate that the Sahara-Sahel boundary reached its most southerly position (13° N during Heinrich Stadials, suggesting that these were the periods when the sand dunes formed at 14° N on the continent, rather than at the Last Glacial Maximum. We find that SSB position was closely linked to North Atlantic sea surface temperatures, which during Heinrich Stadials triggered abrupt increases of aridity and wind strength in the Sahel, exposing new dust sources. This result illustrates the influence of the Atlantic meridional overturning circulation on the southerly extent of the Sahara desert and has implications for global atmospheric dust loading.

  8. Africa South of the Sahara. Grade Twelve. [Resource Unit IV.] Project Social Studies.

    Science.gov (United States)

    Minnesota Univ., Minneapolis. Project Social Studies Curriculum Center.

    This is the fourth of seven resource units for a twelfth grade course on value conflicts and policy decisions. The topic for this unit is Africa south of the Sahara. The objectives are listed as to generalizations, skills, and values. The double-page format relates objectives to pertinent content, teaching procedures, and instructional materials.…

  9. Preliminary Bibliography on Africa South of the Sahara for Undergraduate Libraries.

    Science.gov (United States)

    Ehrman, Edith; Morehouse, Ward

    This classified bibliography on Africa south of the Sahara and similar bibliographies on South Asia (LI 000 061) and East Asia (LI 000 881) have been compiled under the first phase of a three-year cooperative project to strengthen bibliographical resources for undergraduate libraries on "neglected" foreign areas. The bibliography in its…

  10. Africa South of the Sahara: A Resource Guide for Secondary School Teachers. Interim Report.

    Science.gov (United States)

    Beyer, Barry K., Ed.

    Information to help educators develop a program of study about Africa south of the Sahara is presented in this guide for use with secondary school students. Appropriate objectives for a study of this region and its people are stated: the acquisition of sufficient information to make contemporary Africa intelligible, the formulation of concepts…

  11. Evaluation of Africa South of the Sahara. An Inquiry Program for Grades 7-10.

    Science.gov (United States)

    Beyer, Barry K.; And Others

    Project Africa, a social studies curriculum research and development project, is primarily engaged in testing new materials and techniques for teaching about Africa south of the Sahara in American secondary schools. The purpose of this technical report is to highlight the program's strengths and weaknesses from a variety of viewpoints -- those of…

  12. Le Sahara marocain : désenclavement et développement durable

    Directory of Open Access Journals (Sweden)

    EL MAHJOUB CHMOURK

    2012-04-01

    Full Text Available The Moroccan Sahara: opening-up and sustainable development. The enclosing of the Moroccan Sahara results from the inversion and old situation. Indeed, during a very long time, the area was a way of passage, a platform in the south of Morocco. In testify the Tran-Saharan commercial routes, which were the main transportation routes back in time, like the goal of integration of the area in the country and compared to western Africa. It is with the economic crisis, and even a political crisis causing a fold on itself of this area until 1975.Since Sahara belongs to Morocco, it still profits a considerable public effort to carry out its opening-up and its economic insertion within the country. Massive investments carried out by the State give to the area the structuring which it missed. Which are the aspects of the Sahara development? Which role played the State in this development? The intervention of the State contributes to bring effective solutions to the problem of the opening-up of this surrounding space?

  13. Reconstruction of exposure histories of meteorites from Antarctica and the Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Neupert, U.; Neumann, S.; Leya, I.; Michel, R. [Hannover Univ. (Germany). Zentraleinrichtung fuer Strahlenschutz (ZfS); Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Bonani, G.; Hajdas, I.; Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    {sup 10}Be, {sup 14}C, and {sup 26}Al were analyzed in H-, L-, and LL-chondrites from the Acfer region in the Algerian Sahara and from the Allan Hills/Antarctica. Exposure histories and terrestrial ages could be determined. (author) 3 figs., 2 refs.

  14. Alternate non-stop migration strategies of pied flycatchers to cross the Sahara desert

    NARCIS (Netherlands)

    Ouwehand, Janne; Both, Christiaan

    2016-01-01

    Each year more than two billion songbirds cross the Sahara, but how they perform this formidable task is largely unknown. Using geolocation tracks from 27 pied flycatchers, a nocturnally migrating passerine, we show that most birds made diurnal flights in both autumn and spring. These diurnal flight

  15. Hibiscus plant named `Sahara Sunset` U.S. Plant Patent 21,765

    Science.gov (United States)

    'Sahara Sunset' is a new and distinct cultivar of Hibiscus, botanically known as Hibiscus acetosella. The new Hibiscus was originated in Poplarville, Miss. and is a product of a mutation induction program. The parent of the present new cultivar is an unknown Hibiscus acetosella Wels. Ex Hiern seedli...

  16. Unravelling biodiversity, evolution and threats to conservation in the Sahara-Sahel.

    Science.gov (United States)

    Brito, José C; Godinho, Raquel; Martínez-Freiría, Fernando; Pleguezuelos, Juan M; Rebelo, Hugo; Santos, Xavier; Vale, Cândida G; Velo-Antón, Guillermo; Boratyński, Zbyszek; Carvalho, Sílvia B; Ferreira, Sónia; Gonçalves, Duarte V; Silva, Teresa L; Tarroso, Pedro; Campos, João C; Leite, João V; Nogueira, Joana; Alvares, Francisco; Sillero, Neftalí; Sow, Andack S; Fahd, Soumia; Crochet, Pierre-André; Carranza, Salvador

    2014-02-01

    Deserts and arid regions are generally perceived as bare and rather homogeneous areas of low diversity. The Sahara is the largest warm desert in the world and together with the arid Sahel displays high topographical and climatic heterogeneity, and has experienced recent and strong climatic oscillations that have greatly shifted biodiversity distribution and community composition. The large size, remoteness and long-term political instability of the Sahara-Sahel, have limited knowledge on its biodiversity. However, over the last decade, there have been an increasing number of published scientific studies based on modern geomatic and molecular tools, and broad sampling of taxa of these regions. This review tracks trends in knowledge about biodiversity patterns, processes and threats across the Sahara-Sahel, and anticipates needs for biodiversity research and conservation. Recent studies are changing completely the perception of regional biodiversity patterns. Instead of relatively low species diversity with distribution covering most of the region, studies now suggest a high rate of endemism and larger number of species, with much narrower and fragmented ranges, frequently limited to micro-hotspots of biodiversity. Molecular-based studies are also unravelling cryptic diversity associated with mountains, which together with recent distribution atlases, allows identifying integrative biogeographic patterns in biodiversity distribution. Mapping of multivariate environmental variation (at 1 km × 1 km resolution) of the region illustrates main biogeographical features of the Sahara-Sahel and supports recently hypothesised dispersal corridors and refugia. Micro-scale water-features present mostly in mountains have been associated with local biodiversity hotspots. However, the distribution of available data on vertebrates highlights current knowledge gaps that still apply to a large proportion of the Sahara-Sahel. Current research is providing insights into key

  17. Repeated granitoid intrusions during the Neoproterozoic along the western boundary of the Saharan metacraton, Eastern Hoggar, Tuareg shield, Algeria: An AMS and U-Pb zircon age study

    Science.gov (United States)

    Henry, B.; Liégeois, J. P.; Nouar, O.; Derder, M. E. M.; Bayou, B.; Bruguier, O.; Ouabadi, A.; Belhai, D.; Amenna, M.; Hemmi, A.; Ayache, M.

    2009-09-01

    The N-S oriented Raghane shear zone (8°30') delineates the western boundary of the Saharan metacraton and is, with the 4°50' shear zone, the most important shear zone in the Tuareg shield. It can be followed on 1000 km in the basement from southern Aïr, Niger to NE Hoggar, Algeria. Large subhorizontal movements have occurred during the Pan-African orogeny and several groups of granitoids intruded during the Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the case of the contemporaneous plutons in the Assodé-Issalane terrane whose structures are only related to the subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE oriented when further. These NW-SE oriented structures appear to be characteristic of the late Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the Murzuq craton. This

  18. A Ta-rich low-P peraluminous granite: the Rechla cupola (Hoggar, Algeria) and associated pegmatites, the result of extreme fractionation of a A2-type magma.

    Science.gov (United States)

    Kesraoui, M.; Marignac, C.; Hamis, A.; Cuney, M.

    2012-04-01

    In the c. 525 Ma RMG province of the Laouni terrane of the Pan-African Tuareg Shield (Hoggar), the small N20°E elliptic Rechla cupola (200x100 m) is particularized by a rim of Qtz-Kfs-Znw pegmatite. It is a medium-grained Na-Li-F granite, with quartz, albite (An01), rare microcline, topaz, Mn-lepidolite (≤ 8% MnO) and Hf-zircon, and: 71.4 % SiO2, 0.93% FeO+MgO+MnO (Mg # 0.19, Mg/Mg+Fe+Mn 0.09), 9.22% Na2O+K2O (Na # 0.7), Al-Na-K-2Ca from 55 to 85, and low P2O5 (0.05%) and ∑ REE (23 ppm) contents, with a pronounced tetrad effect and <0 Eu anomaly in the REE pattern. Such a composition is typical of a low-P peraluminous RMG deriving from highly potassic calcalkaline suites (A2 type) (Linnen & Cuney 2005), enriched in F (1.6%), Li (1,600 ppm), Zn (300 ppm), Be (7 ppm), Sn (740 ppm), W (40 ppm) and specially Ta (165 ppm, Ta/Nb between 2.4 and 2.6), the latter as columbo-tantalite and Mn-wodginite (Ta # 0.8). The pegmatite rim comprises, towards the intrusion (i) thick Kfs lenses (palissadic crystals ≥ 50 cm), (ii) a laminated quartz-zinnwaldite-(beryl) sequence , and (iii) a discontinuous band of fine-grained granite, with quartz, albite, topaz, Mn-lepidolite and beryl, equally fractionated: 69.4% SiO2, 0.85% FeO+MgO+MnO (Mg# 0.06, Mg/Mg+Fe+Mn 0.02), Al-Na-K-2Ca = 32, F 0.4%, Li 610 ppm, Ta 240 ppm (Ta/Nb = 2.4), Be 500 ppm. The laminated sequence overprints the Kfs lenses. It comprises thick (≤ 20 m) quartz lenses cross-cut by 10 cm-sized alternating bands of euhedral quartz and Mn-zinnwaldite (≤ 6.5% MnO). REE-patterns of the Mn-Znw display a clear inverse tetrad effect, symmetrical of the granite pattern. At the boundary with the fine-grained internal band, euhedral quartz crystals are projecting toward the inner wall. The Rechla body and its surrounding pegmatites are intrusive into a porphyritic biotite-granite representative of the evolved magmas of the A2-type Taourirt suite (Azzouni-Sekkal & Boissonnas 1993), with a classical "seagull" pattern and a

  19. Review: Steffen Wippel, Wirtschaft, Politik und Raum: Territoriale und regionale Prozesse in der westlichen Sahara (2012 Buchbesprechung: Steffen Wippel, Wirtschaft, Politik und Raum: Territoriale und regionale Prozesse in der westlichen Sahara (2012

    Directory of Open Access Journals (Sweden)

    Laurence Marfaing

    2013-01-01

    Full Text Available Review of the monograph:Steffen Wippel, Wirtschaft, Politik und Raum: Territoriale und regionale Prozesse in der westlichen Sahara, 2 volumes, Berlin/Tübingen: Verlag Hans Schiler, 2012, ISBN 9783899303674, xiv + 1,438 pagesBesprechung der Monographie:Steffen Wippel, Wirtschaft, Politik und Raum: Territoriale und regionale Prozesse in der westlichen Sahara, 2 Bände, Berlin/Tübingen: Verlag Hans Schiler, 2012, ISBN 9783899303674, xiv + 1,438 Seiten

  20. The double burden of obesity and malnutrition in a protracted emergency setting: a cross-sectional study of Western Sahara refugees.

    Directory of Open Access Journals (Sweden)

    Carlos S Grijalva-Eternod

    Full Text Available BACKGROUND: Households from vulnerable groups experiencing epidemiological transitions are known to be affected concomitantly by under-nutrition and obesity. Yet, it is unknown to what extent this double burden affects refugee populations dependent on food assistance. We assessed the double burden of malnutrition among Western Sahara refugees living in a protracted emergency. METHODS AND FINDINGS: We implemented a stratified nutrition survey in October-November 2010 in the four Western Sahara refugee camps in Algeria. We sampled 2,005 households, collecting anthropometric measurements (weight, height, and waist circumference in 1,608 children (6-59 mo and 1,781 women (15-49 y. We estimated the prevalence of global acute malnutrition (GAM, stunting, underweight, and overweight in children; and stunting, underweight, overweight, and central obesity in women. To assess the burden of malnutrition within households, households were first classified according to the presence of each type of malnutrition. Households were then classified as undernourished, overweight, or affected by the double burden if they presented members with under-nutrition, overweight, or both, respectively. The prevalence of GAM in children was 9.1%, 29.1% were stunted, 18.6% were underweight, and 2.4% were overweight; among the women, 14.8% were stunted, 53.7% were overweight or obese, and 71.4% had central obesity. Central obesity (47.2% and overweight (38.8% in women affected a higher proportion of households than did GAM (7.0%, stunting (19.5%, or underweight (13.3% in children. Overall, households classified as overweight (31.5% were most common, followed by undernourished (25.8%, and then double burden-affected (24.7%. CONCLUSIONS: The double burden of obesity and under-nutrition is highly prevalent in households among Western Sahara refugees. The results highlight the need to focus more attention on non-communicable diseases in this population and balance obesity

  1. The Double Burden of Obesity and Malnutrition in a Protracted Emergency Setting: A Cross-Sectional Study of Western Sahara Refugees

    Science.gov (United States)

    Grijalva-Eternod, Carlos S.; Wells, Jonathan C. K.; Cortina-Borja, Mario; Salse-Ubach, Nuria; Tondeur, Mélody C.; Dolan, Carmen; Meziani, Chafik; Wilkinson, Caroline; Spiegel, Paul; Seal, Andrew J.

    2012-01-01

    Background Households from vulnerable groups experiencing epidemiological transitions are known to be affected concomitantly by under-nutrition and obesity. Yet, it is unknown to what extent this double burden affects refugee populations dependent on food assistance. We assessed the double burden of malnutrition among Western Sahara refugees living in a protracted emergency. Methods and Findings We implemented a stratified nutrition survey in October–November 2010 in the four Western Sahara refugee camps in Algeria. We sampled 2,005 households, collecting anthropometric measurements (weight, height, and waist circumference) in 1,608 children (6–59 mo) and 1,781 women (15–49 y). We estimated the prevalence of global acute malnutrition (GAM), stunting, underweight, and overweight in children; and stunting, underweight, overweight, and central obesity in women. To assess the burden of malnutrition within households, households were first classified according to the presence of each type of malnutrition. Households were then classified as undernourished, overweight, or affected by the double burden if they presented members with under-nutrition, overweight, or both, respectively. The prevalence of GAM in children was 9.1%, 29.1% were stunted, 18.6% were underweight, and 2.4% were overweight; among the women, 14.8% were stunted, 53.7% were overweight or obese, and 71.4% had central obesity. Central obesity (47.2%) and overweight (38.8%) in women affected a higher proportion of households than did GAM (7.0%), stunting (19.5%), or underweight (13.3%) in children. Overall, households classified as overweight (31.5%) were most common, followed by undernourished (25.8%), and then double burden–affected (24.7%). Conclusions The double burden of obesity and under-nutrition is highly prevalent in households among Western Sahara refugees. The results highlight the need to focus more attention on non-communicable diseases in this population and balance obesity prevention

  2. Preliminary comparative study of anti-inlfammatory effect of unheated and heat-treated Sahara honey:In vivo approach

    Institute of Scientific and Technical Information of China (English)

    Moussa Ahmed; Saad Aissat; Noureddine Djebli

    2015-01-01

    Objective:To investigate the effect of unheated and heat-treated of Sahara honey. Methods: A total of 24 Swiss albino mice weighing 25–35 g were divided into four groups (n = 6). Anti-inflammatory effect was assessed at 1, 2, 3, 4, 5 and 6 h after subplantar injection of carrageenan (0.5 mL of a 1% solution in normal saline). In addition, total phenolic content was determined by modified Folin-Ciocalteu method. Results: The total phenolic content capacity of the Sahara honey before and after heat treatment was between 72 and 97.9 mg of gallic acid equivalents/100 g of honey respectively. Administration of unheated honey (oral administration) reduced significantly (P Conclusions:Our results suggest that unheated Sahara honey has anti-inflammatory effects by reducing the mice paw edema size while heat-treated Sahara honey decreases the anti-inflammatory activity.

  3. [Cupressus dupreziana A. Camus: distribution, decline and regeneration on the Tassili n'Ajjer, central Sahara].

    Science.gov (United States)

    Abdoun, Fatiha; Beddiaf, Mohamed

    2002-05-01

    As soon as it was first discovered in 1924, on the heights of the Tassili n'Ajjer, Cupressus dupreziana (A. Camus) was declared an endangered species. The few ancient trees to be seen in the beds of wadis gave reason to suppose that they were isolated individuals left behind from a forest that had flourished in a damper climate. Attempts at a census of the trees were made on a number of occasions, the fullest, in 1972, reporting a total of 230 living specimens. The revision of this inventory between 1997 and 2001 has now enabled us to draw the boundaries of the present range of this species, to assess its rate of decline over the last three decades and, for the first time, to record some regeneration, with the presence of new, young trees.

  4. Prograde and retrograde evolution of eclogite from Adrar Izzilatène (Egéré-Aleksod terrane, Hoggar, Algeria) determined from chemical zoning and pseudosections, with geodynamic implications

    Science.gov (United States)

    Doukkari, Sid Ali; Ouzegane, Khadidja; Godard, Gaston; Diener, Johann F. A.; Kienast, Jean-Robert; Liégeois, Jean-Paul; Arab, Amar; Drareni, Amar

    2015-06-01

    Adrar Izzilatène in the Egéré-Aleksod terrane of the LATEA metacraton (Hoggar, Algeria) exposes one of the best preserved examples of eclogite facies metamorphism in Hoggar. Three distinct stages of metamorphic development are recognised, namely, the pre-peak stage (M1), characterised by garnet, amphibole, epidote, quartz and rutile, the peak eclogite facies stage (M2), consisting of omphacite, garnet, edenite, epidote, quartz and rutile, and the retrograde stage (M3), where initial decompression resulted in the appearance of plagioclase, the development of pargasite + plagioclase kelyphites and finally the formation of anhydrous plagioclase + diopside coronas. Porphyroblastic omphacite has a jadeite content of up to XJd = 0.36, which is the highest yet observed for eclogite facies rocks from the Tuareg Shield. Garnet growth zoning patterns are characterised by flat profiles in the cores (XAlm = 0.55-0.60; XPrp = 0.12-0.16; XGrs = 0.26-0.30) before showing a decrease in almandine to XAlm = 0.45, coupled to an increase in pyrope to XPrp = 0.29 and decrease in grossular to XGrs = 0.26 at the rims. Calculated P-T-MH2O pseudosections show that the prograde M1 assemblage equilibrated at 13-14 kbar and 580 °C, before pressure and temperature increased to 19 kbar and 650-700 °C at fluid-saturated conditions during peak metamorphism. Retrogression involved near-isothermal decompression to 8-9 kbar and 700-750 °C at fluid-undersaturated conditions. Prograde-to-peak metamorphism of the Izzilatène eclogite could have involved either oceanic or continental subduction, followed by exhumation as the area was obducted towards the LATEA metacraton during the Pan-African orogeny and the assembly of Western Gondwana.

  5. Viruses in the desert: a metagenomic survey of viral communities in four perennial ponds of the Mauritanian Sahara.

    Science.gov (United States)

    Fancello, Laura; Trape, Sébatien; Robert, Catherine; Boyer, Mickaël; Popgeorgiev, Nikolay; Raoult, Didier; Desnues, Christelle

    2013-02-01

    Here, we present the first metagenomic study of viral communities from four perennial ponds (gueltas) located in the central Sahara (Mauritania). Three of the four gueltas (Ilij, Molomhar and Hamdoun) are located at the source of three different wadis belonging to the same hydrologic basin, whereas the fourth (El Berbera) belongs to a different basin. Overall, sequences belonging to tailed bacteriophages were the most abundant in all four metagenomes although electron microscopy and sequencing confirmed the presence of other viral groups, such as large DNA viruses. We observed a decrease in the local viral biodiversity in El Berbera, a guelta with sustained human activities, compared with the pristine Ilij and Molomhar, and sequences related to viruses infecting crop pests were also detected as a probable consequence of the agricultural use of the soil. However, the structure of the El Berbera viral community shared the common global characteristics of the pristine gueltas, that is, it was dominated by Myoviridae and, more particularly, by virulent phages infecting photosynthetic cyanobacteria, such as Prochlorococcus and Synechococcus spp. In contrast, the Hamdoun viral community was characterized by a larger proportion of phages with the potential for a temperate lifestyle and by dominant species related to phages infecting heterotrophic bacteria commonly found in terrestrial environments. We hypothesized that the differences observed in the structural and functional composition of the Hamdoun viral community resulted from the critically low water level experienced by the guelta.

  6. Resource Geopolitics: Cold War Technologies, Global Fertilizers, and the Fate of Western Sahara.

    Science.gov (United States)

    Camprubí, Lino

    2015-07-01

    When, after years of geological and geophysical exploration, a phosphate mine was discovered at Bu-Craa in 1964, Western Sahara received renewed geopolitical attention. Several countries competing for the control of the world fertilizer market, including Morocco, Spain, France, and the United States, developed diverging strategies to gain control of the mineral. After intense negotiations revolving around the materiality of mining technologies and involving reserve estimations, sabotage, and flexing of diplomatic muscles, Morocco took over the Spanish colony in 1975. While this secured Morocco's place in the world market, it condemned the local population to exile and domination. This article explores three technological stages of the exploitation of phosphate in Western Sahara that underpin the geopolitical history. This perspective yields new visions of cold war technology and postcolonial markets.

  7. Were rivers flowing across the Sahara during the last interglacial? Implications for human migration through Africa.

    Science.gov (United States)

    Coulthard, Tom J; Ramirez, Jorge A; Barton, Nick; Rogerson, Mike; Brücher, Tim

    2013-01-01

    Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times.

  8. Revision of the genus Achmonia of Africa south of the Sahara (Coleoptera: Staphylinidae: Staphylininae).

    Science.gov (United States)

    Janák, Jiří; Bordoni, Arnaldo

    2014-10-09

    A redescription of the genus Achmonia Bordoni, 2004 is presented. Based on a revision of types and of additional material, seven species are recognized in Africa south of the Sahara and placed into two species groups. All species are described or redescribed and illustrated, four of them for the first time: Achmonia carinata sp. nov., A. kapangana sp. nov., A. knirschi sp. nov., and A. simulator sp. nov. A lectotype is designated for Xantholinus amabilis Boheman, 1848, Eulissus flavomarginatus Bernhauer, 1929 and E. congoensis Bernhauer, 1932. These species are transferred to Achmonia. A lectotype is designated for Eulissus semiflavus Bernhauer, 1913, and E. gerardi Bernhauer, 1929 and the following synonymy is proposed: Achmonia amabilis (Boheman, 1848) = Eulissus semiflavus Bernhauer, 1913, syn. nov. = Eulissus gerardi Bernhauer, 1929, syn. nov. The distribution of the genus in Africa south of Sahara is mapped and a key to species is presented.

  9. Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene.

    Science.gov (United States)

    Zhang, Zhongshi; Ramstein, Gilles; Schuster, Mathieu; Li, Camille; Contoux, Camille; Yan, Qing

    2014-09-18

    It is widely believed that the Sahara desert is no more than ∼2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ∼2-3 Myr ago. The later discovery, however, of aeolian dune deposits ∼7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (∼7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa.

  10. Sahara et nomadisme. L’envers du décor

    Directory of Open Access Journals (Sweden)

    Hélène Claudot-Hawad

    2011-12-01

    Full Text Available Cette analyse concerne les interventions de l’État au Sahara et la façon dont les Toua­regs prolongent, transforment et adaptent leur nomadisme, dans un contexte de dépossession territoriale, politique et identitaire. Le nomadisme est étudié ici non seulement comme une pratique économique et un mode de vie impliquant un rapport particulier à l’espace, mais également comme une philosophie du mouvement.

  11. Characterizing land surface phenology and responses to rainfall in the Sahara desert

    Science.gov (United States)

    Yan, Dong; Zhang, Xiaoyang; Yu, Yunyue; Guo, Wei; Hanan, Niall P.

    2016-08-01

    Land surface phenology (LSP) in the Sahara desert is poorly understood due to the difficulty in detecting subtle variations in vegetation greenness. This study examined the spatial and temporal patterns of LSP and its responses to rainfall seasonality in the Sahara desert. We first generated daily two-band enhanced vegetation index (EVI2) from half-hourly observations acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation series of geostationary satellites from 2006 to 2012. The EVI2 time series was used to retrieve LSP based on the Hybrid Piecewise Logistic Model. We further investigated the associations of spatial and temporal patterns in LSP with those in rainfall seasonality derived from the daily rainfall time series of the Tropical Rainfall Measurement Mission. Results show that the spatial shifts in the start of the vegetation growing season generally follow the rainy season onset that is controlled by the summer rainfall regime in the southern Sahara desert. In contrast, the end of the growing season significantly lags the end of the rainy season without any significant dependence. Vegetation growing season can unfold during the dry seasons after onset is triggered during rainy seasons. Vegetation growing season can be as long as 300 days or more in some areas and years. However, the EVI2 amplitude and accumulation across the Sahara region was very low indicating sparse vegetation as expected in desert regions. EVI2 amplitude and accumulated EVI2 strongly depended on rainfall received during the growing season and the preceding dormancy period.

  12. Tropical cyclone activity enhanced by Sahara greening and reduced dust emissions during the African Humid Period

    Science.gov (United States)

    Pausata, Francesco S. R.; Emanuel, Kerry A.; Chiacchio, Marc; Diro, Gulilat T.; Zhang, Qiong; Sushama, Laxmi; Stager, J. Curt; Donnelly, Jeffrey P.

    2017-06-01

    Tropical cyclones (TCs) can have devastating socioeconomic impacts. Understanding the nature and causes of their variability is of paramount importance for society. However, historical records of TCs are too short to fully characterize such changes and paleo-sediment archives of Holocene TC activity are temporally and geographically sparse. Thus, it is of interest to apply physical modeling to understanding TC variability under different climate conditions. Here we investigate global TC activity during a warm climate state (mid-Holocene, 6,000 yBP) characterized by increased boreal summer insolation, a vegetated Sahara, and reduced dust emissions. We analyze a set of sensitivity experiments in which not only solar insolation changes are varied but also vegetation and dust concentrations. Our results show that the greening of the Sahara and reduced dust loadings lead to more favorable conditions for tropical cyclone development compared with the orbital forcing alone. In particular, the strengthening of the West African Monsoon induced by the Sahara greening triggers a change in atmospheric circulation that affects the entire tropics. Furthermore, whereas previous studies suggest lower TC activity despite stronger summer insolation and warmer sea surface temperature in the Northern Hemisphere, accounting for the Sahara greening and reduced dust concentrations leads instead to an increase of TC activity in both hemispheres, particularly over the Caribbean basin and East Coast of North America. Our study highlights the importance of regional changes in land cover and dust concentrations in affecting the potential intensity and genesis of past TCs and suggests that both factors may have appreciable influence on TC activity in a future warmer climate.

  13. Improved performance of agriculture in Africa South of the Sahara: Taking off or bouncing back?

    OpenAIRE

    Nin-Pratt, Alejandro; Johnson, Michael E.; Yu, Bingxin

    2012-01-01

    The improved performance of the agricultural sector in Africa south of the Sahara during the most recent decade (2000–2010) has raised questions about the drivers behind the growth. Skeptics argue that rising commodity prices, as world markets experience a commodity boom, are the main cause of the agricultural growth. Others point to improvements in the policy environment and increased investments in agriculture at a time when African governments and donors have been rallying to increase th...

  14. How hazardous is the Sahara Desert crossing for migratory birds? Indications from satellite tracking of raptors.

    Science.gov (United States)

    Strandberg, Roine; Klaassen, Raymond H G; Hake, Mikael; Alerstam, Thomas

    2010-06-23

    We investigated the risk associated with crossing the Sahara Desert for migrating birds by evaluating more than 90 journeys across this desert by four species of raptors (osprey Pandion haliaetus, honey buzzard Pernis apivorus, marsh harrier Circus aeruginosus and Eurasian hobby Falco subbuteo) recorded by satellite telemetry. Forty per cent of the crossings included events of aberrant behaviours, such as abrupt course changes, slow travel speeds, interruptions, aborted crossings followed by retreats from the desert and failed crossings due to death, indicating difficulties for the migrants. The mortality during the Sahara crossing was 31 per cent per crossing attempt for juveniles (first autumn migration), compared with only 2 per cent for adults (autumn and spring combined). Mortality associated with the Sahara passage made up a substantial fraction (up to about half for juveniles) of the total annual mortality, demonstrating that this passage has a profound influence on survival and fitness of migrants. Aberrant behaviours resulted in late arrival at the breeding grounds and an increased probability of breeding failure (carry-over effects). This study also demonstrates that satellite tracking can be a powerful method to reveal when and where birds are exposed to enhanced risk and mortality during their annual cycles.

  15. Aquatic community response in a groundwater-fed desert lake to Holocene desiccation of the Sahara

    Science.gov (United States)

    Eggermont, Hilde; Verschuren, Dirk; Fagot, Maureen; Rumes, Bob; Van Bocxlaer, Bert; Kröpelin, Stefan

    2008-12-01

    The finely laminated sediment record of a permanent, hypersaline, desert oasis lake in the Ounianga region of northeastern Chad presents a unique opportunity to document the hydrological evolution of this groundwater-fed aquatic ecosystem during mid- and late-Holocene desiccation of the Sahara. In this study we reconstruct long-term changes in zoobenthos and zooplankton communities of Lake Yoa as their early-Holocene freshwater habitat changed into the hypersaline conditions prevailing today. Chironomid production peaked during the fresh-to-saline transition period, then stabilized at about half that of the earlier freshwater ecosystem. Quantitative salinity inferences based on fossil chironomid assemblages indicate that the fresh-to-saline transition occurred fairly abruptly between ˜4100 and 3400 cal yr BP, but that the ecosystem was buffered against shorter-term climate fluctuations due to continuous inflow of fossil groundwater. The mixture of tropical-African and southern Palaearctic chironomid faunas in the Lake Yoa fossil record required us to address several methodological issues concerning chironomid-based salinity reconstruction, and the applicability of a calibration dataset based on tropical East and West African lakes to this Sahara desert locality. The most coherent reconstruction was obtained with an inference model that applies a weighted best-modern-analogue (WMAT) transfer function to the African calibration dataset expanded with six Sahara lakes.

  16. An example of post-collisional mafic magmatism: the gabbro-anorthosite layered complex from the Tin Zebane area (western Hoggar, Algeria)

    Science.gov (United States)

    Aı̈t-Djafer, Saı̈da; Ouzegane, Khadidja; Paul-Liégeois, Jean; Kienast, Jean Robert

    2003-10-01

    The Tin Zebane gabbro-anorthosite layered mafic intrusion represented by plagioclase-rich cumulates forms a set of small lenticular to round-shaped mainly undeformed bodies intruding the Pan-African high-pressure metamorphic rocks from western Hoggar (Tuareg shield, southwest Algeria). The coarse-grained anorthosites are mainly made of slightly zoned bytownite (An 86-74) with the higher anorthite content at the cores. Anorthosites are interlayered with leucogabbros and gabbros that show preserved magmatic structures and with olivine gabbros characterised by coronitic textures. The primary assemblage in gabbros includes plagioclase (An 93-70), olivine (Fo 77-70), zoned clinopyroxene (En 43-48Fs 05-13Wo 41-49 with Al 2O 3 up to 4.3 wt.%) and rare orthopyroxene (En 73-78). Pyroxenes and olivine are commonly surrounded by Ca-amphibole. The olivine-plagioclase contact is usually marked by a fine orthopyroxene-Cr-spinel-amphibole symplectite. A magnesian pigeonite (En 70-75Fs 19-20Wo 6-10) is also involved in corona. The coronitic minerals have equilibrated with the primary mineral rims at P- T- aH2O conditions of 797 ± 42 °C for aH2O=0.5 and 808 ± 44 °C for aH2O=0.6 at 6.2 ± 1.4 kbar. The Tin Zebane gabbroic rocks are depleted in REE with a positive Eu anomaly, high Sr (>10 ∗ chondrite) and Al 2O 3 concentrations (17-33%) that support plagioclase accumulation with the extreme case represented by the anorthosites. The REE patterns can be modelised using plagioclase, clinopyroxene and orthopyroxene REE signature, without any role played by accessory minerals. High MgO content points to olivine as a major cumulate phase. Anorthositic gabbros Sr and Nd isotopic initial ratios are typical of a depleted mantle source (Sr i=0.70257-0.70278; ɛNd=+5.9 to +7.8). This isotopic signature is identical to that of the 10-km wide 592 Ma old dyke complex composed of alkaline to peralkaline granites and tholeiitic gabbros and one single bimodal complex can be inferred. The source

  17. Antibacterial and antioxidant activities of three endemic plants from Algerian Sahara

    Directory of Open Access Journals (Sweden)

    ELmouloud Bouchouka

    2012-03-01

    Full Text Available Background. Saharan plants are known by their high content of antioxidant products like phenolic compounds due to the extreme climatic conditions. They constitute the basis of treatments used by local population for various diseases. The purposes of this study were to measure the total phenolic compounds and total fl avonoid compounds, to determine antioxidant capacity, and to evaluate the antibacterial activity of three wild Saharan medicinal plants. Material and methods. Hexane and ethyl acetate fractions of ethanol:water extract and the residu of the extracted aqueous layer of Ferula vesceritensis fruits, Genista saharae aerial parts and Zilla macropterae fruits were assayed to determine their antibacterial activity using the disc diffusion method against: Escherichia coli (ATCC 25922, Staphylococcus aureus (ATCC 25923 and Pseudomonas aeruginosa (ATCC 27853. In addition, the total phenolic compounds and total fl avonoids and antioxydant activity using DPPH test of ethyl acetate fractions (EAF of plant parts studied were investigated. Gallic acid, quercetin and vitamin C were used for these parameters. Results. Among the extracts tested, ethyl acetate fractions of all plants and hexane fraction of F. vesceritensis showed activity against S. aureus. Good activity was shown by EAF of G. saharae. According to the results, it is observed that Z. macropterae fruits possess a good antioxidant activity. Conclusion. The results indicate that the ethyl acetate fraction of G. sahara Aerial parts possesses a good antibacterial activity against S. aureus, which justifi es its use in traditional medicine for treating respiratory diseases. Furthermore, evaluation of in vitro antioxidant capacity of Ethyl acetate fractions of these plants, particular Z. macroptera fruits, has also provided interesting results. Zilla macroptera fruits may therefore be a good source of antioxidants.

  18. Mineral dust aerosols over the Sahara: Meteorological controls on emission and transport and implications for modeling

    Science.gov (United States)

    Knippertz, Peter; Todd, Martin C.

    2012-02-01

    Atmospheric mineral dust has recently become an important research field in Earth system science because of its impacts on radiation, clouds, atmospheric dynamics and chemistry, air quality, and biogeochemical cycles. Studying and modeling dust emission and transport over the world's largest source region, the Sahara, is particularly challenging because of the complex meteorology and a very sparse observational network. Recent advances in satellite retrievals together with ground- and aircraft-based field campaigns have fostered our understanding of the spatiotemporal variability of the dust aerosol and its atmospheric drivers. We now have a more complete picture of the key processes in the atmosphere associated with dust emission. These cover a range of scales from (1) synoptic scale cyclones in the northern sector of the Sahara, harmattan surges and African easterly waves, through (2) low-level jets and cold pools of mesoscale convective systems (particularly over the Sahel), to (3) microscale dust devils and dusty plumes, each with its own pronounced diurnal and seasonal characteristics. This paper summarizes recent progress on monitoring and analyzing the dust distribution over the Sahara and discusses implications for numerical modeling. Among the key challenges for the future are a better quantification of the relative importance of single processes and a more realistic representation of the effects of the smaller-scale meteorological features in dust models. In particular, moist convection has been recognized as a major limitation to our understanding because of the inability of satellites to observe dust under clouds and the difficulties of numerical models to capture convective organization.

  19. How much rainfall sustained a Green Sahara during the mid-Holocene?

    Science.gov (United States)

    Hopcroft, Peter; Valdes, Paul; Harper, Anna

    2016-04-01

    The present-day Sahara desert has periodically transformed to an area of lakes and vegetation during the Quaternary in response to orbitally-induced changes in the monsoon circulation. Coupled atmosphere-ocean general circulation model simulations of the mid-Holocene generally underestimate the required monsoon shift, casting doubt on the fidelity of these models. However, the climatic regime that characterised this period remains unclear. To address this, we applied an ensemble of dynamic vegetation model simulations using two different models: JULES (Joint UK Land Environment Simulator) a comprehensive land surface model, and LPJ (Lund-Potsdam-Jena model) a widely used dynamic vegetation model. The simulations are forced with a number of idealized climate scenarios, in which an observational climatology is progressively altered with imposed anomalies of precipitation and other related variables, including cloud cover and humidity. The applied anomalies are based on an ensemble of general circulation model simulations, and include seasonal variations but are spatially uniform across the region. When perturbing precipitation alone, a significant increase of at least 700mm/year is required to produce model simulations with non-negligible vegetation coverage in the Sahara region. Changes in related variables including cloud cover, surface radiation fluxes and humidity are found to be important in the models, as they modify the water balance and so affect plant growth. Including anomalies in all of these variables together reduces the precipitation change required for a Green Sahara compared to the case of increasing precipitation alone. We assess whether the precipitation changes implied by these vegetation model simulations are consistent with reconstructions for the mid-Holocene from pollen samples. Further, Earth System models predict precipitation increases that are significantly smaller than that inferred from these vegetation model simulations. Understanding

  20. How well do analyses capture dust-generating winds in the Sahara and Sahel?

    Science.gov (United States)

    Roberts, Alexander; Marsham, John; Knippertz, Peter; Parker, Douglas

    2016-04-01

    Airborne mineral dust is important for weather, climate and earth-system prediction. Uncertainty in winds, as well as the land-surface, are known to be key to model uncertainties for dust uplift. Recent research has shown that during the summer wet season in the Sahel strong winds generated by the cold outflow from organized convective systems are an important dust storm mechanism (so called haboobs), while over the inner Sahara nocturnal low-level jets forming on the pressure gradient around the heat low dominate. Together the Sahel and Sahara are the world's largest dust source. Until now there has been a severe shortage of data for evaluating models for this region. Here, we bring together new observations from the remote Sahara, made during the Fennec project, with Sahelian data from the African Monsoon Multidisciplinary Analysis (AMMA), to provide an unprecedented evaluation of dust-generating winds in the European Centre for Medium-Range Weather Forecasts ERA-Interim (ERA-I) reanalysis. Differences between observations and ERA-I are explored with specific attention to monsoon and non-monsoon influenced regions. The main results are: (1) High speed winds in instantaneous ERA-I grid-box mean winds are lacking compared to time-averaged wind speed observations; (2) agreement between ERA-I and observations is lower during the monsoon season, even in parts of the Sahara not directly affected by the monsoon; and (3) both the seasonal and diurnal variability is under-represented in ERA-I. ERA-I fails to capture the summertime maximum for monsoon-affected stations and seasonally, correlations between daily-mean ERA-I and observed winds vary from 0.8 to 0.4, with lower correlations for 3-hourly data. These differences demonstrate that the model used in the production of the ERA-I reanalysis is unable to represent some important dust uplift processes, especially during the monsoon season when moist convection plays a key role, and that the product is not sufficiently

  1. El papel de la ONU en el conflicto del Sahara Occidental

    OpenAIRE

    2013-01-01

    La democracia hoy: una mirada desde el temor a la El conflicto del Sahara Occidental comienza en el período de descolonización del continente africano, en la década de los setenta ms exactamente. Este confr. Acto se ha caracterizado por contar con dos tendencias que hasta el momento se presentan totalmente irreconciliables: los intereses de las partes, Marruecos y la República arave Saharaui Democrática (RASD), que han llegado a despertar la atención de otras naciones, quienes por efectos de ...

  2. Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM) phase images

    Science.gov (United States)

    Helas, G.; Andreae, M. O.

    2008-10-01

    We show that atomic force microscopy (AFM) phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly shows deposits of distinguishable material on the surface. We apply this technique to dust aerosol particles from the Sahara collected over the Atlantic Ocean and describe micro-features on the surfaces of such particles.

  3. Sahara Occidental: los factores económicos como detonante de la violencia organizada

    Directory of Open Access Journals (Sweden)

    Miguel García Guindo

    Full Text Available El presente trabajo aborda en primer lugar y desde una perspectiva teórica, la incidencia de los factores económicos y políticos en el germen de la violencia organizada para después, analizar como los cambios sociodemográficos que se han sucedido en el Sahara Occidental desde 1975 hasta nuestros días, sumados a la política asistencialista de Marruecos y los privilegios de los que se benefician determinados grupos han desestabilizado la región.

  4. Quality and management of hot water of intercalary continental, northern Sahara of Algeria

    Science.gov (United States)

    Tifrani, Ala Eddine; Nezli, Imed Eddine

    2016-07-01

    The Algerian Sahara is the biggest desert in the world, and it is known by that the main climatic characters which are the high temperature and the low precipitations. The northern Sahara is a part of this big area, located on the south-east of Algeria. Due to the rarely and insufficient precipitations (1 to 180 mm per year) the need for water is a rising problem, so the main source are the ground water. There are three ground water aquifers in the area, the phreatic table, the terminal complex and the intercalary continental, our study is focused on the intercalary continental which is the biggest non recharged aquifer in the world, many studies national and international estimated the reserve of the water around 6 million m3. Existing between 1000 and 2000 m depth, this depth gives the water a lot of characterization which need to be noted and updated for example the temperature (around 50°C), and the high mineralization, because of the vast area and the difference in depths between wells, which is a reason of variety, the main goal is the determination of chemical and physical setting of this water.

  5. Activity patterns in the Sahara Desert: an interpretation based on cross-sectional geometric properties.

    Science.gov (United States)

    Nikita, Efthymia; Siew, Yun Ysi; Stock, Jay; Mattingly, David; Lahr, Marta Mirazón

    2011-11-01

    The Garamantian civilization flourished in modern Fezzan, Libya, between 900 BC and 500 AD, during which the aridification of the Sahara was well established. Study of the archaeological remains suggests a population successful at coping with a harsh environment of high and fluctuating temperatures and reduced water and food resources. This study explores the activity patterns of the Garamantes by means of cross-sectional geometric properties. Long bone diaphyseal shape and rigidity are compared between the Garamantes and populations from Egypt and Sudan, namely from the sites of Kerma, el-Badari, and Jebel Moya, to determine whether the Garamantian daily activities were more strenuous than those of other North African populations. Moreover, sexual dimorphism and bilateral asymmetry are assessed at an intra- and inter-population level. The inter-population comparisons showed the Garamantes not to be more robust than the comparative populations, suggesting that the daily Garamantian activities necessary for survival in the Sahara Desert did not generally impose greater loads than those of other North African populations. Sexual dimorphism and bilateral asymmetry in almost all geometric properties of the long limbs were comparatively low among the Garamantes. Only the lower limbs were significantly stronger among males than females, possibly due to higher levels of mobility associated with herding. The lack of systematic bilateral asymmetry in cross-sectional geometric properties may relate to the involvement of the population in bilaterally intensive activities or the lack of regular repetition of unilateral activities.

  6. Impact of Sahara dust transport on Cape Verde atmospheric element particles.

    Science.gov (United States)

    Almeida-Silva, M; Almeida, S M; Freitas, M C; Pio, C A; Nunes, T; Cardoso, J

    2013-01-01

    The objectives of this study were to (1) conduct an elemental characterization of airborne particles sampled in Cape Verde and (2) assess the influence of Sahara desert on local suspended particles. Particulate matter (PM(10)) was collected in Praia city (14°94'N; 23°49'W) with a low-volume sampler in order to characterize its chemical composition by k0-INAA. The filter samples were first weighed and subsequently irradiated at the Portuguese Research Reactor. Results showed that PM(10) concentrations in Cape Verde markedly exceeded the health-based air quality standards defined by the European Union (EU), World Health Organization (WHO), and U.S. Environmental Protection Agency (EPA), in part due to the influence of Sahara dust transport. The PM(10) composition was characterized essentially by high concentrations of elements originating from the soil (K, Sm, Co, Fe, Sc, Rb, Cr, Ce, and Ba) and sea (Na), and low concentrations of anthropogenic elements (As, Zn, and Sb). In addition, the high concentrations of PM measured in Cape Verde suggest that health of the population may be less affected compared with other sites where PM(10) concentrations are lower but more enriched with toxic elements.

  7. Eolian sediment responses to late Quaternary climate changes: Temporal and spatial patterns in the Sahara

    Science.gov (United States)

    Swezey, C.

    2001-01-01

    This paper presents a compilation of eolian-based records of late Quaternary climate changes in the Sahara. Although the data are relatively sparse, when viewed as a whole, they reveal a general pattern of widespread eolian sediment mobilization prior to 11,000 cal. years BP, eolian sediment stabilization from 11,000 to 5000 cal. years BP, and a return to widespread eolian sediment mobilization after 5000 cal. years BP. Furthermore, an eolian-based record from southern Tunisia reveals the existence of millennial-scale changes in eolian sediment behavior. These millennial-scale variations provide examples of eolian sediment responses to climate changes at a scale intermediate between seasonal and orbital ('Milankovitch') changes, and they are also coincident with abrupt atmospheric and oceanic changes. The general synchroneity of the eolian stratigraphic records and their coincidence with various oceanic and atmospheric changes suggest that global forcing mechanisms have influenced late Quaternary eolian sediment behavior in the Sahara. ?? 2001 Elsevier Science B.V.

  8. Images of Africa: A Report on What American Secondary School Students Know and Believe about Africa South of the Sahara.

    Science.gov (United States)

    Beyer, Barry K.; Hicks, E. Perry

    "Project Africa" surveyed selected seventh- and 12th-grade students in 24 states to determine (1) the specific nature of their images of Africa south of the Sahara, both before and after any formal study of this region, and (2) the types and accuracy of the students' knowledge about the region and its peoples. In one survey, students…

  9. Libraries in National Literacy Education Programmes in Africa South of the Sahara: The State-of-the-Art.

    Science.gov (United States)

    Newa, John M.

    1990-01-01

    Examines the involvement of public and village libraries in literacy and postliteracy programs in Africa south of the Sahara during the last two decades. Issues discussed include the extent of illiteracy in Black Africa, populations served by village libraries, African rural strategies of development, and the implications for library services. (44…

  10. Long-distance autumn migration across the Sahara by painted lady butterflies: exploiting resource pulses in the tropical savannah.

    Science.gov (United States)

    Stefanescu, Constantí; Soto, David X; Talavera, Gerard; Vila, Roger; Hobson, Keith A

    2016-10-01

    The painted lady, Vanessa cardui, is a migratory butterfly that performs an annual multi-generational migration between Europe and North Africa. Its seasonal appearance south of the Sahara in autumn is well known and has led to the suggestion that it results from extremely long migratory flights by European butterflies to seasonally exploit the Sahel and the tropical savannah. However, this possibility has remained unproven. Here, we analyse the isotopic composition of butterflies from seven European and seven African countries to provide new support for this hypothesis. Each individual was assigned a geographical natal origin, based on its wing stable hydrogen isotope (δ(2)Hw) value and a predicted δ(2)Hw basemap for Europe and northern Africa. Natal assignments of autumn migrants collected south of the Sahara confirmed long-distance movements (of 4000 km or more) starting in Europe. Samples from Maghreb revealed a mixed origin of migrants, with most individuals with a European origin, but others having originated in the Sahel. Therefore, autumn movements are not only directed to northwestern Africa, but also include southward and northward flights across the Sahara. Through this remarkable behaviour, the productive but highly seasonal region south of the Sahara is incorporated into the migratory circuit of V. cardui.

  11. A Senior High School Social Studies Unit on Africa South of the Sahara. World History Series, Bulletin No. 252.

    Science.gov (United States)

    Kelly, Harry; And Others

    This secondary level curriculum guide provides a program and identifies materials for the study of the history and culture of Africa south of the Sahara. The primary purpose of this course is to stimulate thought and to encourage students to make valid generalizations and intelligent assessments of the forces and events that have and are shaping…

  12. Adverse drug reaction reports for cardiometabolic drugs from sub Sahara Africa: A study in VigiBase

    NARCIS (Netherlands)

    Berhe, Derbew F.; Juhlin, Kristina; Star, Kristina; Haaijer-Ruskamp, Flora M.; Michael, Kidane; Taxis, Katja; Mol, Peter G.M.

    2014-01-01

    Background: Many pharmacovigilance centers have been established in Sub Sahara Africa (SSA) in recent years. Their focus has been on ADRs to drugs for communicable diseases. Little is known about ADRs caused by drugs for cardiometabolic diseases, although its burden is increasing rapidly in SSA. Obj

  13. Preliminary comparative study of anti-inflmmatory effect of unheated and heat-treated Sahara honey: In vivo approach

    Directory of Open Access Journals (Sweden)

    Moussa Ahmed

    2015-11-01

    Full Text Available Objective: To investigate the effect of unheated and heat-treated of Sahara honey. Methods: A total of 24 Swiss albino mice weighing 25–35 g were divided into four groups (n = 6. Anti-inflammatory effect was assessed at 1, 2, 3, 4, 5 and 6 h after subplantar injection of carrageenan (0.5 mL of a 1% solution in normal saline. In addition, total phenolic content was determined by modified Folin-Ciocalteu method. Results: The total phenolic content capacity of the Sahara honey before and after heat treatment was between 72 and 97.9 mg of gallic acid equivalents/100 g of honey respectively. Administration of unheated honey (oral administration reduced significantly (P < 0.05. The carrageenan induced mice paw edema model at 1, 3 and 6 h for 21.85%, 5.43% and 80.43%, respectively. Administration of heat-treated honey showed insignificant inhibition of carrageenan and induced paw edema at 1 h (31.16%, 3 h (0.25% and 6 h (34.19%. The 50 mg/kg diclofenac exhibited percent reduction in paw volume 16.12%, 8.90% and 15.32% after 1 h, 3 h and 6 h, respectively, when compared with control animals. No toxicity was identified. Conclusions: Our results suggest that unheated Sahara honey has anti-inflammatory effects by reducing the mice paw edema size while heat-treated Sahara honey decreases the antiinflammatory activity.

  14. Sahara makeup

    African Journals Online (AJOL)

    Winnie

    successfully introduce antiretroviral therapy and so turn everyday logics of survival into long-term strategies, it needs to commit .... Tactic is a calculated action determined by the absence ..... tactic: it is more sustainable and of longer duration.

  15. Groundwater resources exploration in the Zug area (Tiris, Western Sahara); Prospeccion de recursos hidricos subterraneos en el area de Zug (Tiris, Sahara Occidental)

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, B.; Villarroya, F.; Rebollo, L. F.; Olaiz, A.; Lopez, J.

    2015-07-01

    The area of Zug is located in the southwestern corner of the Tiris dorsal, in the Western Sahara. The area is characterized by outcrops of materials, mainly gneisses of archaic age and fractured granitic rocks, which in the southern sector are covered by aeolian sand sheets. A hydrogeological survey of the territory has been carried out, and boreholes and dug wells have been located and analyzed and this information integrated with the sparse outcrops. Based on this study, two hydrogeological domains have been established: Zug and Azzefal. From the analysis of satellite images, field work, geophysical profiles, a well inventory and chemical analysis, three priority areas for the location of future water supply wells have been identified: 1) alluvial fans, preferably located on the slopes of the dikes that cross the Tiris dorsal; 2) sabkhas (salt flats) as places of con- centration of ephemeral runoff and subsurface infiltration of accumulated water; 3) highly fractured granitic areas. Some of these three cases coincide with existing wells in this area. Electrical tomography shows how, in specific locations, low resistivity values reach 50 metres, opening up the possibility of finding sufficient water to meet the aforementioned needs. The water quality is not suitable for human supply directly from the well without chemical treatment. The area is still full of opportunities for future research, but only when a more stable political situation exists. (Author)

  16. Regional hydrogen roadmap. Project development framework for the Sahara Wind Project

    Energy Technology Data Exchange (ETDEWEB)

    Benhamou, Khalid [Sahara Wind Inc., Rabat (Morocco); Arbaoui, Abdelaziz [Ecole National Superieure des Arts et Metiers ENSAM Meknes (Morocco); Loudiyi, Khalid [Al Akhawayn Univ. (Morocco); Ould Mustapha, Sidi Mohamed [Nouakchott Univ. (Mauritania). Faculte des Sciences et Techniques

    2010-07-01

    The trade winds that blow along the Atlantic coast from Morocco to Senegal represent one of the the largest and most productive wind potentials available on earth. Because of the erratic nature of winds however, wind electricity cannot be integrated locally on any significant scale, unless mechanisms are developed for storing these intermittent renewable energies. Developing distributed wind energy solutions feeding into smaller electricity markets are essential for solving energy access issues and enabling the development of a local, viable renewable energy industry. These may be critical to address the region's economic challenges currently under pressure from Sub-Saharan migrant populations. Windelectrolysis for the production of hydrogen can be used in grid stabilization, as power storage, fuel or chemical feedstock in specific industries. The objective of the NATO SfP 'Sahara Trade Winds to Hydrogen' project is to support the region's universities through an applied research framework in partnership with industries where electrolysis applications are relevant. By powering two university campuses in Morocco and Mauritania with small grid connected wind turbines and 30 kW electrolyzers generating hydrogen for power back-up as part of ''green campus concepts'' we demonstrated that wind-electrolysis for the production of hydrogen could absorb larger quantities of cheap generated wind electricity in order to maximize renewable energy uptakes within the regions weaker grid infrastructures. Creating synergies with local industries to tap into a widely available renewable energy source opens new possibilities for end users such as utilities or mining industries when processing raw minerals, whose exports generates key incomes in regions most exposed to desertification and climate change issue. Initiated by Sahara Wind Inc. a company from the private sector, along with the Al Akhawayn University, the Ecole Nationale Superieure

  17. Forsterite and Olivine in Sahara-97210 (LL3.2) and Chainpur (LL3.4) Chondrules: Compositional Evolution and the Influence of Melting

    Science.gov (United States)

    Ruzicka, A.; Floss, C.

    2004-01-01

    It is generally accepted that chondrules contain relict grains that did not crystallize in situ, and that forsterite is one type of relict grain which is a likely precursor for chondrules. Chemically and morphologically similar forsterite is also found as "isolated grains", especially in carbonaceous chondrites. Using SIMS, we analyzed forsterite, ferrous overgrowths around forsterite, and coexisting normal olivine in 5 chondrules and 2 isolated grains in the Sahara-97210 ('Sahara") LL3.2 chondrite. We earlier used the same methods to study olivine in 3 Chainpur chondrules that contain relict forsterite. Our new data for Sahara provide additional insight into the processes affecting chondrules and their precursors.

  18. Greening of the Sahara suppressed ENSO activity during the mid-Holocene

    Science.gov (United States)

    Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Lu, Zhengyao; Chafik, Léon; Niedermeyer, Eva M.; Stager, J. Curt; Cobb, Kim M.; Liu, Zhengyu

    2017-07-01

    The evolution of the El Niño-Southern Oscillation (ENSO) during the Holocene remains uncertain. In particular, a host of new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed the fairly modest ENSO response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show that accounting for a vegetated and less dusty Sahara during the mid-Holocene relative to preindustrial climate can reduce ENSO variability by 25%, more than twice the decrease obtained using orbital forcing alone. We identify changes in tropical Atlantic mean state and variability caused by the momentous strengthening of the West Africa Monsoon (WAM) as critical factors in amplifying ENSO's response to insolation forcing through changes in the Walker circulation. Our results thus suggest that potential changes in the WAM due to anthropogenic warming may influence ENSO variability in the future as well.

  19. Local Human Development in contexts of permanent crisis: Women’s experiences in the Western Sahara

    Directory of Open Access Journals (Sweden)

    María López Belloso

    2009-04-01

    Full Text Available Sahrawi women are active agents in the social dynamics of the refugee camps, in which they have developeda number of coping strategies to overcome the hardships of a deteriorating humanitarian situation. Since the outbreak of the con#ict and the forced settlement in Tindouf, Algeria, women have been responsible for the entire management of refugee camps, assuming leadership roles in many sectors of society.This paper highlights the Sahrawi women’s contribution to the process of local human development in a context of protracted refuge such as the one in the Western Sahara. In addition to the enlargement of the refugee population’s capacities in relation to material and physical assets, social and organizational abilities, and motivational strengths, one of the major achievements of Sahrawi women has been their own individual and collective process of empowerment within the camp life.

  20. Wars Without Beginning or End: Violent Political Organizations and Irregular Warfare in the Sahel-Sahara

    CERN Document Server

    Walther, Olivier; Skillicorn, David

    2016-01-01

    This article examines the structure and spatial patterns of violent political organizations in the Sahel-Sahara, a region characterized by growing political instability over the last 20 years. Drawing on a public collection of disaggregated data, the article uses network science to represent alliances and conflicts of 179 organizations that were involved in violent events between 1997 and 2014. To this end, we combine two spectral embedding techniques that have previously been considered separately: one for directed graphs (relationships are asymmetric), and one for signed graphs (relationships are positive or negative). Our result show that groups that are net attackers are indistinguishable at the level of their individual behavior, but clearly separate into pro- and anti-political violence based on the groups to which they are close. The second part of the article maps a series of 389 events related to nine Trans-Saharan Islamist groups between 2004 and 2014. Spatial analysis suggests that cross-border mov...

  1. Structure, composition, and location of organic matter in the enstatite chondrite Sahara 97096 (EH3)

    CERN Document Server

    Piani, Laurette; Beyssac, Olivier; Binet, Laurent; Bourot-Denise, Michèle; Derenne, Sylvie; Guillou, Corentin Le; Marrocchi, Yves; Mostefaoui, Smail; Rouzaud, Jean-Noel; Thomen, Aurelien

    2015-01-01

    The insoluble organic matter (IOM) of an unequilibrated enstatite chondrite Sahara (SAH) 97096 has been investigated using a battery of analytical techniques. As the enstatite chondrites are thought to have formed in a reduced environment at higher temperatures than carbonaceous chondrites, they constitute an interesting comparative material to test the heterogeneities of the IOM in the solar system and to constrain the processes that could affect IOM during solar system evolution. The SAH 97096 IOM is found in situ: as submicrometer grains in the network of fine-grained matrix occurring mostly around chondrules and as inclusions in metallic nodules, where the carbonaceous matter appears to be more graphitized. IOM in these two settings has very similar $\\delta^{15}N$ and $\\delta^{13}C$; this supports the idea that graphitized inclusions in metal could be formed by metal catalytic graphitization of matrix IOM. A detailed comparison between the IOM extracted from a fresh part and a terrestrially weathered part...

  2. Global Sea Level Stabilization-Sand Dune Fixation: A Solar-powered Sahara Seawater Textile Pipeline

    CERN Document Server

    Badescu, Viorel; Bolonkin, Alexander A

    2007-01-01

    Could anthropogenic saturation with pumped seawater of the porous ground of active sand dune fields in major deserts (e.g., the westernmost Sahara) cause a beneficial reduction of global sea level? Seawater extraction from the ocean, and its deposition on deserted sand dune fields in Mauritania and elsewhere via a Solar-powered Seawater Textile Pipeline (SSTP) can thwart the postulated future global sea level. Thus, Macro-engineering offers an additional cure for anticipated coastal change, driven by global sea level rise, that could supplement, or substitute for (1) stabilizing the shoreline with costly defensive public works (armoring macroprojects) and (2) permanent retreat from the existing shoreline (real and capital property abandonment). We propose Macro-engineering use tactical technologies that sculpt and vegetate barren near-coast sand dune fields with seawater, seawater that would otherwise, as commonly postulated, enlarge Earth seascape area! Our Macro-engineering speculation blends eremology with...

  3. Comparison of efifcacy of unheated and heat-treated Sahara honey on wound healing in rabbits

    Institute of Scientific and Technical Information of China (English)

    Baghdad Khiati; Moussa Ahmed

    2015-01-01

    Objective:To investigate the efficacy of unheated and heat-treated Sahara honey on wound healing in rabbits on the basis of macroscopic observation changes. Methods:Eight female rabbits were used. Using aseptic surgical technique, a 3 cm incision was made on the back of each rabbit and two rabbits with injuries in each group were treated daily with a topical application of unheated and heated honey, sulfadiazine and sterile saline, respectively. Results:The unheated honey demonstrated the highest activity on the wound compared to reference ointment silver sulfadiazine, heat-treated honey and sterile saline respectively. Further the present investigation proves that unheated honey is possessing superior wound healing activity than that of heat-treated honey. Conclusions:The result of this study confirms that unheated honey had the best wound healing effect even better than heat-treated honey.

  4. Dust and Biological Aerosols from the Sahara and Asia Influence Precipitation in the Western US

    Energy Technology Data Exchange (ETDEWEB)

    Creamean, Jessie; Suski, Kaitlyn; Rosenfeld, Daniel; Cazorla, Alberto; DeMott, Paul J.; Sullivan, Ryan C.; White, Allen B.; Ralph, F. M.; Minnis, Patrick; Comstock, Jennifer M.; Tomlinson, Jason M.; Prather, Kimberly

    2013-03-29

    Winter storms in California’s Sierra Nevada increase seasonal snowpack and provide critical water resources for the state. Thus, the mechanisms influencing precipitation in this region have been the subject of research for decades. Previous studies suggest Asian dust enhances cloud ice and precipitation (1), while few studies consider biological aerosols as an important global source of ice nuclei (IN). Here, we show that dust and biological aerosols transported from as far as the Sahara were present in glaciated high-altitude clouds coincident with elevated IN concentrations and ice-induced precipitation. This study presents the first direct cloud and precipitation measurements showing that Saharan and Asian dust and biological aerosols likely serve as IN and play an important role in orographic precipitation processes over the western United States.

  5. Initiation and early development of barchan dunes: A case study of the Moroccan Atlantic Sahara desert

    Science.gov (United States)

    Elbelrhiti, Hicham

    2012-02-01

    This paper describes field measurements that document the formation of barchan dunes in the Moroccan Atlantic Sahara desert. The first mechanism described is the transformation of patches and proto-dunes at Cap Juby beach to barchan dunes of elementary size. This transformation is discussed in relation to the wind speed and saturation length. The second mechanism is the ejection of small barchans of elementary size by other small barchans in response to the perturbation of the target barchan by two other impacting small barchans. This remote initiation is discussed in relation to the bulk flux transported by the barchan dunes involved in this interaction and to their morphology. Other modes of barchan initiation observed in the field are also presented.

  6. Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM phase images

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    M. O. Andreae

    2008-10-01

    Full Text Available We show that atomic force microscopy (AFM phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly shows deposits of distinguishable material on the surface. We apply this technique to dust aerosol particles from the Sahara collected over the Atlantic Ocean and describe micro-features on the surfaces of such particles.

  7. Surface features on Sahara soil dust particles made visible by atomic force microscope (AFM phase images

    Directory of Open Access Journals (Sweden)

    G. Helas

    2008-08-01

    Full Text Available We show that atomic force microscopy (AFM phase images can reveal surface features of soil dust particles, which are not evident using other microscopic methods. The non-contact AFM method is able to resolve topographical structures in the nanometer range as well as to uncover repulsive atomic forces and attractive van der Waals' forces, and thus gives insight to surface properties. Though the method does not allow quantitative assignment in terms of chemical compound description, it clearly shows deposits of distinguishable material on the surface. We apply this technique to dust aerosol particles from the Sahara collected over the Atlantic Ocean and describe micro-features on the surfaces of such particles.

  8. Airborne bacteria transported with Sahara dust particles from Northern Africa to the European Alps

    Science.gov (United States)

    Lazzaro, A.; Meola, M.

    2015-12-01

    The Sahara Desert is the most important source of aerosols transported across the Mediterranean towards Europe. Airborne microorganisms associated with aerosols may be transported over long distances and act as colonizers of distant habitats. However, little is known on the composition and viability of such microorganisms, due to difficulties related to their detection, collection and isolation. Here we describe an in-depth assessment of the bacterial communities associated with Sahara dust (SD) particles deposited on snow. Two distinct SD events reaching the European Alps in February and May 2014 were preserved as distinct ochre-coloured layers within the snowpack. In June 2014, we collected samples from a snow profile at 3621 m a.s.l. close to the Jungfraujoch (Swiss Alps). SD particles were analyzed by Scanning Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy (SEM-EDX). Backward trajectories were calculated using the NOAA HYSPLIT model. Bacterial communities were charac-terized by MiSeq Illumina sequencing of the 16S rRNA gene. Microbial physiological profiles were assessed by incubation of samples on BIOLOG plates. The SD-layers were generally enriched in illite and kaolinite particles as compared to the adjacent snow layers. The source of SD could be traced back to Algeria. We observed distinct bacterial community structures in the SD-layers as compared to the clean snow layers. While sporulating bacteria were not enriched in the SD-layers, low abundant (<1%) phyla such as Gemmatimonadetes and Deinococcus-Thermus appeared to be specific bioindicators for SD. Both phyla are adapted to arid oligotrophic environments and UV radiation and thus are well suited to survive the harsh conditions of long-distance airborne transport. Our results show that bacteria are viable and metabolically active after the trek to the European Alps.

  9. Microbial diversity and organic matter fractions under two arid soils in Algerian Sahara

    Science.gov (United States)

    Karabi, Mokhtar; Hamdi, Aissa Baelhadj; Zenkhri, Salah

    2016-07-01

    The Algerian Sahara is characterized by a heterogeneity of edaphic conditions and climatic dissimilarities; however, information on biological indicators of arid soils is weakly documented in this area. The researchers who have studied the biological activities of the soils of the arid regions have underlined their low organic matter content, particularly their very low rates of organic nitrogen; a low humification because seriously inhibited by a significant mineralization. The objective of the current work is to study the microbial biomass densities and organic matter fractions for different types of soil, under two arid soil in Algerian Sahara. The experiment was conducted in an alluvial soil in traditional palm grove of Guerrara, and in a saline soil in experimental field of university of Ouargla. Composite soil samples (10 subsamples each) were collected aseptically at 0-20 cm depth on two diagonal transects drawn over an area of 12 ha. The following germs densities were determined: Bacteria, Fungi and Actinomycetes. The soil organic matter fractions, the textural fractions, chemical attributes (organic C, total N, total limestone and gypsum) were also determined. The microbial groups count on both soils reveals that the bacterianmicroflora present a numerical superiority followed by the actinomycetes and finally fungi. The micro-organisms densities except fungal density, showed a prevalence of the bacterianmicroflora, and actinomycetes in alluvial soil compared to saline soil. Fractionation of soil organic matter show that all fractions are better represented in alluvial soil except non-extractable organic carbon (NEOC) which are better represented in saline soil. This confirms that alluvial soil has a relatively large biological activity than saline soil and that humification process is relatively pronounced by comparing it with the saline soil, which tends to contain little polycondenseshumic compounds.

  10. The Sahara from the Middle Jurassic to the Middle Cretaceous: Data on environments and climates based on outcrops in the Algerian Sahara

    Science.gov (United States)

    Busson, G.; Cornée, A.

    The period investigated, succeeded the Upper Triassic and Liassic-Lower Dogger arid sedimentation which was characterized by the development of large evaporitic deposits. The north-eastern part of the Algerian Sahara is specially interesting as it constitutes part of the few dated continental Jurassic outcrops in North Africa (except in the Maghreb). Continental Lower-Middle Cretaceous is also well developed in the same region. The grading of these continental series into marine series particularly in the north-eastern part of the Maghreb has been investigated from an adequate number of well spaced wells. The Middle-Upper Jurassic (Lower Taouratine) consists of an argillaceous-sandy-ferruginous series, often grey coloured and rich in filicean wood and vertebrate remains in some levels. The ferralitic alteration products denote a more humid climate than that which prevailed during the Liassic-Lower-Dogger times. These products alternate with sandy conglomeratic events confirming the influences of alternating important run-off and aeolian winnowing. The large continental Lower and Middle Cretaceous detrital nappes are discussed. They constitute the uppermost part of the series, south of the Tinrhert Hamada (Alba-Vraconian series with the more detrital lateral equivalent), west of Tademait (Gara Samani). Data on lithology and paleobiology (fishes, Dinosaurs, other vertebrates, pelecypods, gastropods, wood debris, palynoflora) permit the reconstruction of the palaeo-environment and the conditions of deposition. This is similar to the sub-desertic terrestrial sedimentation by violent and ephemeral hydrodynamism model based on the modern Darfour example. The desertic conditions which prevailed in these Saharan areas during the Cretaceous are reflected as well as their possible consequences on the sedimentation of nearby oceanic areas (Atlantic and Tethys). This detrital sedimentation is finally reviewed in the context of its tectonic origins and an attempt is made to

  11. A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

    KAUST Repository

    Masmoudi, Mohamed

    2015-05-01

    © 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

  12. Geochemical and mineralogical evidence for Sahara and Sahel dust additions to Quaternary soils on Lanzarote, eastern Canary Islands, Spain

    Science.gov (United States)

    Muhs, D.R.; Budahn, J.; Skipp, G.; Prospero, J.M.; Patterson, D.; Bettis, E. Arthur

    2010-01-01

    Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the Sahel region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island's bedrock. Kaolinite in the soils also likely has an exotic origin. Trace-element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major-element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the Sahel region. ?? Published 2010. This article is a US Government work and is in the public domain in the USA.

  13. Presence and Origin of Fluoride in the Complex Terminal Water of Ouargla Basin (Northern Sahara of Algeria)

    OpenAIRE

    Imed E. Nezli; Samia Achour; Mohamed Djidel; Saïd Attalah

    2009-01-01

    Problem statement: The underground waters in the oriental regions of the Algerian Sahara, present real chemical quality problems. Their content in fluorides always exceeds the limit of the recommended levels. That is 0.8 mg L-1, according to the maximum temperature in the region. Combined to a high salinity, it affects the health of the population living around the region. The present work, deals with the presence of fluoride and the geochemical origin in the Complex Terminal aquifer of Ouarg...

  14. Diatom-inferred salinity and carbonate oxygen isotopes in Holocene waterbodies of the western Sahara and Sahel (Africa)

    Science.gov (United States)

    Gasse, Françoise

    2002-03-01

    Thirteen Holocene palaeolakes in the western Sahara and Sahel have provided diatom records, with carbonate oxygen isotope profiles available from eight of them. Most of these palaeolakes were groundwater-fed. Lake water chemistry is reconstructed using diatom transfer functions. Lake water salinity and 18O records are assembled with some isotopic and chemical groundwater data to better understand the response of the hydrological systems to climate changes over the past 15,000 yr. Data are in general agreement with climate simulations using coupled atmosphere-ocean-vegetation models which show a mid-Holocene wetting over the whole of northwest Africa, and a rapid drying by 6-4 ka. The lake record also shows that at many sites the major lake infilling lags the end of the Younger Dryas by 1-2 ka. Regional differences also appear in the timing of the lake hydrological optimum: ca. 10.5-8.5 and 7.5-4.5 ka in the northern Sahara, 10-8.5 ka in the Aı̈r-Ténéré, 10-5.7 or 4.5 in the Sahel, and 7.5 ka in Lake Chad. The whole of the Holocene is punctuated by short-term drying events. Changes in water isotopic composition through time are partly explained by changes in rainfall amount and air humidity. During the wet Holocene period however, the very low δ values in the southern Sahara also imply changes in the moisture transport pattern or rainfall mechanisms. Data suggest an apparent decrease in 18O content of precipitation along the monsoon flow, in contrast with modern patterns. Changes in water availability and quality have driven population migrations in and out of the Sahara-Sahel, but relationships between climate and cultures are complex. Short-term dry events might have driven inventive adaptations. In the Sahara, drying at 5-4.5 ka coincides with both the collapse of the classical Neolithic civilization and the settlement of new cultures.

  15. Spatial distribution of dust's optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer

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    M. Yoshida

    2012-12-01

    Full Text Available There is a great deal of uncertainty surrounding the role of mineral dust aerosols in the earth's climate system. One reason for this uncertainty is that the optical properties of mineral dust, such as its single scattering albedo (the ratio of scattering to total extinction, are poorly understood because ground observations are limited to several locations and the satellite standard products are not available due to the excessively bright surface of the desert in the visible wavelength. We develop a method in this paper to estimate the spatial distributions of the aerosol single scattering albedo (ω0 and optical depth (τa, with daily 1 degree latitude and 1 degree longitude resolution, using data from Moderate Resolution Imaging Spectroradiometer (MODIS, as well as model simulations of radiative transfer. This approach is based on the "critical surface reflectance" method developed in the literature, which estimates ω0 from the top of the atmospheric radiance. We confirm that the uncertainties in our estimation of ω0 and τa are suitably minor and that the characteristic spatial distributions estimated over the Sahara and Asia are significant. The results for the Sahara indicate good correlation between ω0 and the surface reflectance and between ω0 and τa. Therefore, ω0 is determined mainly by the mineral composition of surface dust and/or the optical depth of airborne dust in the Sahara. On the other hand, the relationships between ω0, τa, and the surface reflectance are less clear in Asia than in the Sahara, and the values of ω0 are smaller than those in the Sahara. The regions with small ω0 values are consistent with the regions where coal-burning smoke and carbonaceous aerosols are thought to be transported, as reported in previous studies. Because the coal-burning and carbonaceous

  16. The Right to Self-Determination and Natural Resources: The Case of Western Sahara

    Directory of Open Access Journals (Sweden)

    Hans Morten Haugen

    2007-06-01

    Full Text Available Phosphate, fish and possibly oil and gas all constitute important natural resources found on the territory and in the waters of Western Sahara. The importance of these natural resources must be recognised in order to understand the stalemate in the attempted process of decolonisation from Morocco which has been going on for more than 30 years. The article analyses the ‘resource dimension’ of the right to self-determination, as recognised in human rights treaties and in Resolution III of the UN Conference on the Law of the Seas, as well as several resolutions from the United Nations General Assembly. If the resources are exploited in a manner which does not benefit the peoples seeking to enjoy the right to self-determination, such exploitation is illegal. The article shows that the current exploitation takes place in a manner contrary to the interests of the local population, the Saharawis. The article also demonstrates that recent license agreements with Saharawi authorities in the field of oil and gas, signal a potentially new and constructive approach by international corporations.

  17. Dynamics of green Sahara periods and their role in hominin evolution.

    Science.gov (United States)

    Larrasoaña, Juan C; Roberts, Andrew P; Rohling, Eelco J

    2013-01-01

    Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2-3 kyr to develop, peaked over 4-8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2-3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins.

  18. SHUTTLE IMAGING RADAR: PHYSICAL CONTROLS ON SIGNAL PENETRATION AND SUBSURFACE SCATTERING IN THE EASTERN SAHARA.

    Science.gov (United States)

    Schaber, Gerald G.; McCauley, John F.; Breed, Carol S.; Olhoeft, Gary R.

    1986-01-01

    It is found that the Shuttle Imaging Radar A (SIR-A) signal penetration and subsurface backscatter within the upper meter or so of the sediment blanket in the Eastern Sahara of southern Egypt and northern Sudan are enhanced both by radar sensor parameters and by the physical and chemical characteristics of eolian and alluvial materials. The near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response are summarized. The dominant factors related to efficient microwave signal penetration into the sediment blanket include 1) favorable distribution of particle sizes, 2) extremely low moisture content and 3) reduced geometric scattering at the SIR-A frequency (1. 3 GHz). The depth of signal penetration that results in a recorded backscatter, called radar imaging depth, was documented in the field to be a maximum of 1. 5 m, or 0. 25 times the calculated skin depth, for the sediment blanket. The radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials.

  19. Dental indicators of adaptation in the Sahara Desert during the Late Holocene.

    Science.gov (United States)

    Nikita, E; Mattingly, D; Lahr, M M

    2014-10-01

    The present paper examines dental diseases and linear enamel hypoplasia among the Garamantes, a Late Holocene Saharan population, and aims to draw conclusions about nutrition and adaptation to a hyper-arid environment. Archaeological evidence suggests that the Garamantian diet included animal protein and local, Mediterranean and Near Eastern plants. Moreoever, although the Garamantes had developed urban centres, the size of these was not large enough to allow for particularly unhygienic conditions to appear. The above archaeological findings were partly corroborated by the current bioarchaeological study. At an intra-population level, the Garamantes showed limited sex differences in dental disease prevalence, while all dental conditions increased in frequency with age, as expected. At an inter-population level, the frequency of all dental conditions was comparable to that found among other North African groups, with the exception of ante-mortem tooth loss. The low frequency of most dental conditions is an indication that the Garamantian diet was overall balanced, while the high frequency of ante-mortem tooth loss may be related to factors such as oral hygiene, food preparation or eating mode, which cannot be controlled for osteologically. Finally, the low frequency of enamel hypoplasia suggests either that the Sahara did not inflict particular stresses on the population, or, more likely, that the Garamantes had developed effective mechanisms for coping with their natural environment.

  20. Characterization and antimicrobial potential of extremely halophilic archaea isolated from hypersaline environments of the Algerian Sahara.

    Science.gov (United States)

    Quadri, Inès; Hassani, Imene Ikrame; l'Haridon, Stéphane; Chalopin, Morgane; Hacène, Hocine; Jebbar, Mohamed

    2016-01-01

    Halophilic archaea were isolated from different chotts and sebkha, dry salt lakes and salt flat respectively, of the Algerian Sahara and characterized using phenotypic and phylogenetic approaches. From 102 extremely halophilic strains isolated, forty three were selected and studied. These strains were also screened for their antagonistic potential and the production of hydrolytic enzymes. Sequencing of the 16S rRNA genes and phylogenetic analysis allowed the identification of 10 archaeal genera within the class Halobacteria: Natrinema (13 strains), Natrialba (12 strains), Haloarcula (4 strains), Halopiger (4 strains), Haloterrigena (3 strains), Halorubrum (2 strains), Halostagnicola (2 strains), Natronococcus, Halogeometricum and Haloferax (1 strain each). The most common producers of antimicrobial compounds belong to the genus Natrinema while the most hydrolytic isolates, with combined production of several enzymes, belong to the genus Natrialba. The strain affiliated to Halopiger djelfamassilliensis was found to produce some substances of interest (halocins, anti-Candida, enzymes). After partial purification and characterization of one of the strains Natrinema gari QI1, we found similarities between the antimicrobial compound and the halocin C8. Therefore, the gene encoding halocin C8 was amplified and sequenced.

  1. Model Simulations of Complex Dust Emissions over the Sahara during the West African Monsoon Onset

    Directory of Open Access Journals (Sweden)

    Carolina Cavazos-Guerra

    2012-01-01

    Full Text Available The existing limitations in ground-based observations in remote areas in West Africa determine the dependence on numerical models to represent the atmospheric mechanisms that contribute to dust outbreaks at different space-time scales. In this work, the ability of the Weather Research and Forecasting model coupled with the Chemistry (WRF-Chem model using the GOCART dust scheme is evaluated. The period comprises the West African Monsoon onset phase (the 7th to 12th of June, 2006 coinciding with the AMMA Special Observing Period (SOP. Different features in the horizontal and vertical dynamical structure of the Saharan atmosphere are analyzed with a combination of satellite and ground-based observations and model experimentation at 10 and 30 km model resolution. The main features of key Saharan dust processes during summer are identifiable, and WRF-CHEM replicates these adequately. Observations and model analyses have shown that cold pools (haboobs contributed a substantial proportion of total dust during the study period. The comparative analysis between observations and WRF-Chem simulations demonstrates the model efficiency to simulate the spatial and 3D structure of dust transport over the Sahara and Sahel. There is, therefore, a strong basis for accurate forecasting of dust events associated with synoptic scale events when model dust emission parameterization is suitably calibrated.

  2. Sahara dust, ocean spray, volcanoes, biomass burning: pathways of nutrients into Andean rainforests

    Directory of Open Access Journals (Sweden)

    P. Fabian

    2009-10-01

    Full Text Available Regular rain and fogwater sampling in the Podocarpus National Park, on the humid eastern slopes of the Ecuadorian Andes, along an altitude profile between 1960 and 3180 m, has been carried out since 2002. The samples, accumulated over about 1-week intervals, were analysed for pH, conductivity and major ions (K+, Na+, NH4+, Ca2+, Mg2+, Cl, SO42−, NO3, PO43−.

    About 35% of the weekly samples had very low ion contents, with pH mostly above 5 and conductivity below 10 μS/cm. 10-days back trajectories (FLEXTRA showed that respective air masses originated in pristine continental areas, with little or no obvious pollution sources.

    About 65%, however, were significantly loaded with cations and anions, with pH as low as 3.5 to 4.0 and conductivity up to 50 μS/cm. The corresponding back trajectories clearly showed that air masses had passed over areas of intense biomass burning, active volcanoes, and the ocean, with episodic Sahara and/or Namib desert dust interference.

    Enhanced SO42− and NO3+ were identified, by combining satellite-based fire pixel observations with back trajectories, as predominantly resulting from biomass burning. Analyses of oxygen isotopes 16O, 17O, and 18O in nitrate show that nitrate in the samples is indeed a product of atmospheric conversion of precursors. Some SO42−, about 10% of the total input, could be identified to originate from active volcanoes, whose plumes were encountered by about 10% of all trajectories.

    Enhanced Na+, K+, and Cl were found to originate from ocean spray sources. They were associated with winds providing Atlantic air masses to the receptor site within less than 5 days. Episodes of

  3. Actinopolyspora biskrensis sp. nov., a novel halophilic actinomycete isolated from Northern Sahara.

    Science.gov (United States)

    Saker, Rafika; Bouras, Noureddine; Meklat, Atika; Zitouni, Abdelghani; Schumann, Peter; Spröer, Cathrin; Klenk, Hans-Peter; Sabaou, Nasserdine

    2015-03-01

    A novel halophilic, filamentous actinomycete, designated H254(T), was isolated from a Saharan soil sample collected from Biskra (Northern Sahara), and subjected to a polyphasic taxonomic characterization. The strain is Gram-positive, aerobic, and halophilic, and the optimum NaCl concentration for growth is 15-20 % (w/v). The cell-wall hydrolysate contained meso-diaminopimelic acid, and the diagnostic whole-cell sugars were arabinose and galactose. The diagnostic phospholipid detected was phosphatidylcholine, and MK-9(H4) was the predominant menaquinone. The major fatty acid profiles were anteiso-C17:0 (32.8 %), C15:0 (28 %), and iso-C17:0 (12.3 %). Comparative analysis of the 16S rRNA gene sequences revealed that the strain H254(T) formed a well-separated sub-branch within the radiation of the genus Actinopolyspora, and the microorganism was most closely related to Actinopolyspora saharensis DSM 45459(T) (99.2 %), Actinopolyspora halophila DSM 43834(T) (99.1 %), and Actinopolyspora algeriensis DSM 45476(T) (99.0 %). Nevertheless, the strain had relatively lower mean values for DNA-DNA relatedness with the above strains (57.2, 68.4, and 45.6 %, respectively). Based on phenotypic features and phylogenetic position, we propose that strain H254(T) represents a novel species of the genus Actinopolyspora, for which the name Actinopolyspora biskrensis sp. nov. is proposed. The type strain of A. biskrensis is strain H254(T) (=DSM 46684(T) =CECT 8576(T)).

  4. Alliance of proteomics and genomics to unravel the specificities of Sahara bacterium Deinococcus deserti.

    Directory of Open Access Journals (Sweden)

    Arjan de Groot

    2009-03-01

    Full Text Available To better understand adaptation to harsh conditions encountered in hot arid deserts, we report the first complete genome sequence and proteome analysis of a bacterium, Deinococcus deserti VCD115, isolated from Sahara surface sand. Its genome consists of a 2.8-Mb chromosome and three large plasmids of 324 kb, 314 kb, and 396 kb. Accurate primary genome annotation of its 3,455 genes was guided by extensive proteome shotgun analysis. From the large corpus of MS/MS spectra recorded, 1,348 proteins were uncovered and semiquantified by spectral counting. Among the highly detected proteins are several orphans and Deinococcus-specific proteins of unknown function. The alliance of proteomics and genomics high-throughput techniques allowed identification of 15 unpredicted genes and, surprisingly, reversal of incorrectly predicted orientation of 11 genes. Reversal of orientation of two Deinococcus-specific radiation-induced genes, ddrC and ddrH, and identification in D. deserti of supplementary genes involved in manganese import extend our knowledge of the radiotolerance toolbox of Deinococcaceae. Additional genes involved in nutrient import and in DNA repair (i.e., two extra recA, three translesion DNA polymerases, a photolyase were also identified and found to be expressed under standard growth conditions, and, for these DNA repair genes, after exposure of the cells to UV. The supplementary nutrient import and DNA repair genes are likely important for survival and adaptation of D. deserti to its nutrient-poor, dry, and UV-exposed extreme environment.

  5. A forest butterfly in sahara desert oases: isolation does not matter.

    Science.gov (United States)

    Habel, Jan Christian; Husemann, Martin; Schmitt, Thomas; Dapporto, Leonardo; Rödder, Dennis; Vandewoestijne, Sofie

    2013-03-01

    Numerous studies addressing the impact of habitat fragmentation on genetic diversity have been performed. In this study, we analyze the effects of a seemingly nonpermeable matrix on the population structure of the forest-dwelling butterfly Pararge aegeria in geographically isolated oases at the northern margin of the Sahara desert using microsatellites, morphological characters, and species distribution modeling. Results from all analyses are mostly congruent and reveal 1) a split between European and North African populations, 2) rather low divergence between populations from the eastern and western part of North Africa (Morocco vs. Tunisia), 3) a lack of differentiation between the oasis and Atlas Mountain populations, 4) as well as among the oasis populations, and 5) no reduction of genetic variability in oasis populations. However, one exception to this general trend resulted from the analyses of wing shape; wings of butterflies from oases are more elongated compared with those from the other habitats. This pattern of phenotypic divergence may suggest a recent colonization of the oasis habitats by individuals, which might be accompanied by a rather dispersive behavior. Species distribution modeling suggests a fairly recent reexpansion of the species' climatic niche starting in the Holocene at about 6000 before present. The combined results indicate a rather recent colonization of the oases by highly mobile individuals from genetically diverse founder populations. The colonization was likely followed by the expansion and persistence of these founder populations under relatively stable environmental conditions. This, together with low rates of gene flow, likely prevented differentiation of populations via drift and led to the maintenance of high genetic diversity.

  6. Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations

    Directory of Open Access Journals (Sweden)

    C. L. Ryder

    2015-01-01

    Full Text Available The Fennec climate program aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE Falcon 20 is described, with specific focus on instrumentation specially developed and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include: (1 the first airborne measurement of dust particles sized up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL, (2 dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI satellite imagery, (3 vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4 in-situ observations of processes in SABL clouds showing dust acting as CCN and IN at −15 °C, (5 dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL, (6 airborne observations of a dust storm associated with a cold-pool (haboob issued from deep convection over the Atlas, (7 the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations and absorption properties between 2011 and 2012, (8 coincident ozone and dust surface area measurements suggest coarser particles provide a route for ozone depletion, (9 discrepancies between airborne coarse mode size distributions and AERONET sunphotometer

  7. A new cichlid fish in the Sahara: The Ounianga Serir lakes (Chad), a biodiversity hotspot in the desert.

    Science.gov (United States)

    Trape, Sébastien

    In the rare perennial bodies of water of the Sahara desert, only a few fish species have survived to increasing aridification since the end of the last humid period at the Holocene, approximately 5000 years BP. Here, I report the occurrence of an undescribed haplochomine cichlid fish in Lake Boukou, one of the seven Ounianga Serir lakes (Chad). These lakes are located in one of the most arid areas of the Sahara desert, but they persist by virtue of subsurface inflow of fresh groundwater from a large fossil aquifer. Astatotilapia tchadensis sp. nov. is characterized by a black bar between eye and corner of mouth, rounded orange spots on anal fin, scales ctenoid, lower limb of first gill arch with 7-8 gill rackers, dorsal fin with 13-14 spines and 9-11 soft rays, anal fin with 3 spines and 8-9 soft rays, 29 or 30 lateral line scales, and lower pharyngeal dentition with enlarged molariform teeth. The new species is easily distinguished from A. desfontainii and A. flaviijosephii, the northernmost haplochromine species currently isolated from its other group members, and appears close to an unnamed species of Lake Chad basin. Ounianga Serir lakes and especially Lake Boukou present a remarkable diversity of fish, the highest known in the Sahara desert with a total of at least six fish species belonging to six genera and three families. They also constitute an exceptional natural landscape inscribed on the UNESCO world heritage list in 2012 and a biodiversity hotspot for desert vertebrate species.

  8. Role of surface wind and vegetation cover in multi-decadal variations of dust emission in the Sahara and Sahel

    Science.gov (United States)

    Kim, Dongchul; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

    2017-01-01

    North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82% of the continental North Africa dust emission (1340-1570 Tg year-1) in the 27-year average, the Sahel accounts for 17% with a larger seasonal and inter-annual variation (230-380 Tg year-1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R = 0.92). Over the Sahel, the dust emission is correlated with W10m (R = 0.69) but is also anti-correlated with the trend of NDVI (R = -0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R = 0.53), suggesting that Saharan/Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

  9. The Role of Meteorology and Surface Condition to Multi-Decadal Variations of Dust Emission in Sahara and Sahel

    Science.gov (United States)

    Kim, D.; Chin, M.; Diehl, T. L.; Bian, H.; Brown, M. E.; Remer, L. A.; Stockwell, W. R.

    2014-12-01

    North Africa is the world's largest dust source region influencing regional and global climate, human health, and even the local economy. However North Africa as a dust source is not uniform but it consists of the arid region (Sahara) and the semi-arid region (Sahel) with emission rates depending on meteorological and surface conditions. Several recent studies have shown that dust from North Africa seems to have a decreasing trend in the past three decades. The goal of this study is to better understand the controlling factors that determine the change of dust in North Africa using observational data and model simulations. First we analyze surface bareness conditions determined from a long-term satellite observed Normalized Difference Vegetation Index for 1980-2008. Then we examine the key meteorological variables of precipitation and surface winds. Modeling experiments were conducted using the NASA Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which has been recently updated with a dynamic dust source function. Using the method we separate the dust originating from the Sahel from that of the Sahara desert. We find that the surface wind speed is the most dominant factor affecting Sahelian dust emission while vegetation has a modulating effect. We will show regional differences in meteorological variables, surface conditions, dust emission, and dust distribution and address the relationships among meteorology, surface conditions, and dust emission/loading in the past three decades (1980-2008).

  10. Impacts of dust reduction on the northward expansion of the African monsoon during the Green Sahara period

    Science.gov (United States)

    Pausata, Francesco S. R.; Messori, Gabriele; Zhang, Qiong

    2016-01-01

    The West African Monsoon (WAM) is crucial for the socio-economic stability of millions of people living in the Sahel. Severe droughts have ravaged the region in the last three decades of the 20th century, highlighting the need for a better understanding of the WAM dynamics. One of the most dramatic changes in the West African Monsoon (WAM) occurred between 15000-5000 yr BP, when increased summer rainfall led to the so-called "Green Sahara" and to a reduction in dust emissions from the region. However, model experiments are unable to fully reproduce the intensification and geographical expansion of the WAM during this period, even when vegetation over the Sahara is considered. Here, we use a fully coupled simulation for 6000 yr BP (Mid-Holocene) in which prescribed Saharan vegetation and dust concentrations are changed in turn. A closer agreement with proxy records is obtained only when both the Saharan vegetation changes and dust decrease are taken into account. The dust reduction strengthens the vegetation-albedo feedback, extending the monsoon's northern limit approximately 500 km further than the vegetation-change case only. We therefore conclude that accounting for changes in Saharan dust loadings is essential for improving model simulations of the WAM during the Mid-Holocene.

  11. Presence and Origin of Fluoride in the Complex Terminal Water of Ouargla Basin (Northern Sahara of Algeria

    Directory of Open Access Journals (Sweden)

    Imed E. Nezli

    2009-01-01

    Full Text Available Problem statement: The underground waters in the oriental regions of the Algerian Sahara, present real chemical quality problems. Their content in fluorides always exceeds the limit of the recommended levels. That is 0.8 mg L-1, according to the maximum temperature in the region. Combined to a high salinity, it affects the health of the population living around the region. The present work, deals with the presence of fluoride and the geochemical origin in the Complex Terminal aquifer of Ouargla, rarely examined in the Algerian Sahara. Approach: Is based on the following aspects: Sampling and physico-chemicals analysis of water, statistical treatment of the physico-chemical water parameters and simulation to natural and isotherm 25°C evaporation of water parameters. Results: The results show the presence of fluoride in the studied water. The rates vary between 1 and 2 mg L-1. The calculation of water saturation index in relation with the preponderant minerals, using the thermodynamic model ‹‹phreeqci›› reveals a sensitivity of carbonate minerals towards precipitation and dissolution of evaporitic minerals and clayey fluorides as well. Conclusions/Recommendations: The increasing alkalinity of water in contact with the aquifer during long periods of stay decreases the chemical activity of calcium and helps with alteration of clayey minerals and fluoride as a necessary condition for a possible fluorite mineralization. Knowing the origin of that fluoridation leads to possible solutions, through the optimization of a water treatment meets the standards.

  12. Constraining the Sahara freshwater discharge during sapropel S5 time by a stable isotope record from the Greater Sirte

    Science.gov (United States)

    Zirks, Eleen; Kucera, Michal; Bachem, Paul; Schulz, Hartmut

    2016-04-01

    The Nile River and the Black Sea were long considered as the only significant eastern Mediterranean freshwater sources and therefore inferred as the primary agents promoting surface stratification associated with sapropel formation. Sapropel S5, deposited during the last interglacial, marks a time of possible movement of Homo sapiens out of Africa. Satellite images revealed the existence of ancient rivers that once ran through the Sahara desert and drained into the Gulf of Sirte. Anomalous Nd isotope records from sapropel S5 deposits indicate that these rivers may have been active during MIS 5e, implying another freshwater source into the eastern Mediterranean Sea during that period. To constrain the extent of freshwater discharge into the Mediterranean from the Kufrah River during MIS 5e, a new δ18O record of five planktonic foraminifera species was generated from sediment core GeoTü SL 96, located proximal to the assumed outflow of the Kufrah River. The record from core GeoTü SL 96 compared with seven other records from the eastern Mediterranean Sea reveal a pattern of oxygen isotope anomalies which implies that the Kufrah River delivered detectable amount of freshwater during the second part of sapropel S5. These results reinforce the hypothesis that Sahara river systems were active during MIS 5e, which has ramifications for the understanding of sapropel events, reconstruction of coastal landscape, and the better understanding of migration routes of early humans.

  13. Propolis-Sahara honeys preparation exhibits antibacterial and anti-biofilm activity against bacterial biofims formed on urinary catheters

    Directory of Open Access Journals (Sweden)

    Saad Aissat

    2016-11-01

    Full Text Available Objective: To evaluate the antibacterial effect of Sahara honeys (SHs against bacterial biofilms formed on urinary catheters in combination with propolis-Sahara honeys (P-SHs. Methods: Three clinical isolates were subjected to biofilm detection methods. The antibacterial and anti-biofilm activity for SHs and P-SHs were determined using agar well diffusion and the percentage of biofilm inhibition (PBI methods. Results: The PBI for Gram-positive bacteria [Staphylococcus aureus (S. aureus] was in the range of 0%–20%, while PBI for Gram-negative bacteria [Pseudomonas aeruginosa and Escherichia coli (E. coli] were in range of 17%–57% and 16%–65%, respectively. The highest PBI (65% was produced by SH2 only on E. coli. In agar well diffusion assay, zones of inhibition ranged from 11–20 mm (S. aureus, 9–19 mm (Pseudomonas aeruginosa and 11–19 mm (E. coli. The highest inhibition (20 mm was produced by SH1 only on S. aureus. In addition, the treatment of SHs and P-SHs catheters with a polymicrobial biofilms reduced biofilm formation after 48 h exposure period. Conclussions: SHs and P-SHs applied as a natural agent can be used as a prophylactic agent to prevent the formation of in vitro biofilm.

  14. The place of sub-Sahara Africa in the world sport system

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    T. Dejonghe

    2001-01-01

    Full Text Available The contemporary world sportsystem is developed through globalisation with its homogenisation and heterogenisation processes. The result of these opposite forces is the division of the world in 6 classes. Sub-Sahara Africa underwent, with the exception of South-Africa, Namibia and Zimbabwe, a total and passive acceptance of the western (British modern sports. The place of that part of Africa is analogue to and correlates with its place in Wallerstein's world-system periphery. The introduction of modern sports is associated with the spatial diffusion of the 19th century British hegemonic cultural imperialism. The purpose of this policy was a transformation of the traditional society into a modern functional world-culture and the incorporation of that part of the world in the world-system. The anti-western feelings after the independence resulted in a political Pan-Africanism. However, sport and more specific soccer, a typical product of the western domination, has not been rejected. On the contrary, local politicians used it to create a national identity. The strong link between soccer and soil resulted in a strong form of topophily. This connection was transformed into sportnationalism and created in the, through artificial borders developed, nations a unity and a national pride. The outcome of sport games was used to demonstrate the successes in politics and economics. The absence of any political platform on which the Third World had a strong voice brought about that the international sport scene, such as the FIFA, was used for the unification of the Third World against the former colonial powers. Nowadays, the globalisation processes result in an increasing labour migration of African football players to the rich core competitions in Europe. This form of migration can be classified as another form of "cash crop" or in this case "foot drain.. ""As Roman imperialism laid the foundation of modern civilisation and led wild barbarians of these

  15. Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations

    Science.gov (United States)

    Ryder, C. L.; McQuaid, J. B.; Flamant, C.; Rosenberg, P. D.; Washington, R.; Brindley, H. E.; Highwood, E. J.; Marsham, J. H.; Parker, D. J.; Todd, M. C.; Banks, J. R.; Brooke, J. K.; Engelstaedter, S.; Estelles, V.; Formenti, P.; Garcia-Carreras, L.; Kocha, C.; Marenco, F.; Sodemann, H.; Allen, C. J. T.; Bourdon, A.; Bart, M.; Cavazos-Guerra, C.; Chevaillier, S.; Crosier, J.; Darbyshire, E.; Dean, A. R.; Dorsey, J. R.; Kent, J.; O'Sullivan, D.; Schepanski, K.; Szpek, K.; Trembath, J.; Woolley, A.

    2015-07-01

    The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include (1) the first airborne measurement of dust particles sizes of up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL), (2) dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI (Spinning Enhanced Visible Infra-Red Imager) satellite imagery, (3) vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4) in situ observations of processes in SABL clouds showing dust acting as cloud condensation nuclei (CCN) and ice nuclei (IN) at -15 °C, (5) dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL), (6) airborne observations of a dust storm associated with a cold pool (haboob) issued from deep convection over the Atlas Mountains, (7) the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations) and absorption properties between 2011 and 2012, (8) coincident ozone and dust surface area

  16. ARCHAEOLOGICAL AND ENVIRONMENTAL CHANGES BETWEEN 9500 BP AND 4500 BP: A CONTRIBUTION FROM THE SAHARA TO UNDERSTAND EXPANDING DROUGHTS IN THE “GREAT MEDITERRANEAN”

    Directory of Open Access Journals (Sweden)

    E. A.A. Garcea

    2013-03-01

    Full Text Available The Sahara is more connected to the Mediterranean than often assumed and palynology, in particular, has provided evidence of past interrelations between the Mediterranean and the Sahara with pollen spectra from prehistoric Saharan deposits including Mediterranean taxa. In order to show human-environment relationships and populations’ strategies in response to changing environments, this paper presents a case study from the southern Sahara. This region offered a natural laboratory for the study of human/climate interaction as the range of environmental change extended from flood to drought, forcing people to cope with periodic environmental instability. When the tropical rainfall belt migrated northward, watertable outcropped in interdunal depressions and formed permanent lakes, which alternated with severe arid spells. As a case study, this paper presents the results of interdisciplinary investigations on climate changes, human adaptations and subsistence strategies at Gobero, in the southern Sahara of Niger. Gobero is a restricted archaeological area comprising 8 sites that surround the shores of a palaeolake. It was intermittently occupied between about 9500 cal years BP and 4500 BP. Due to alternating environmental conditions it could only be occupied at the beginning and at the end of the most humid periods.

  17. Implementation of Information Communication Technology in the Teaching/Learning Process for Sustainable Development of Adults in West Africa Sub Sahara Region

    Science.gov (United States)

    Nwobi, Anthonia; Ngozi, Ugwuoke; Rufina, Nwachukwu; Ogbonnaya, Kingsley A.

    2016-01-01

    This study examines the implementation of information technology in the teaching/learning process for sustainable development of adults in West Africa Sub Sahara Region (WASSR). Three research questions and two hypotheses guided the study. The population for the study was 3071 participants and instructors drawn from 10 education centres that were…

  18. Africa South of the Sahara, Rationale and Introduction: An Experimental Program of Study for Secondary School Social Studies Students. Teaching Guide.

    Science.gov (United States)

    Carnegie-Mellon Univ., Pittsburgh, PA. Project Africa.

    The articulation of a rationale for Project Africa's instructional program, the collection of materials for improving inquiry-oriented instruction at the secondary level about Africa south of the Sahara, and the preparation of teaching and study guides have been completed. This geographic region, rather than the whole continent, was chosen to…

  19. Peoples of Africa, Topic 1. Africa South of the Sahara: A Program of Study for Secondary School Social Studies Students. (Teaching and Student Guides).

    Science.gov (United States)

    Carnegie-Mellon Univ., Pittsburgh, PA. Project Africa.

    This teaching guide and student text for Project Africa's curriculum program, "Africa South of the Sahara," deal with how four typical contemporary African peoples acquired their present way of life: (1) the Hausa of Northern Nigeria, (2) the Kung Bushmen of the Kalahari Desert, (3) the Mech'a Galla of Ethiopa, and (4) the Kikuyu of…

  20. A reward for patience and suffering – Ethnomycology and commodification of desert truffles among Sahrawi refugees and nomads of Western Sahara

    NARCIS (Netherlands)

    Volpato, G.; Rossi, D.; Dentoni, D.

    2013-01-01

    A Reward for Patience and Suffering: Ethnomycology and Commodification of Desert Truffles among Sahrawi Refugees and Nomads of Western Sahara. This paper reflects on the role of ethnobiological knowledge and practices for refugees’ agency by focusing on the use and commodification of desert truffles

  1. A humid corridor across the Sahara for the migration of early modern humans out of Africa 120,000 years ago.

    Science.gov (United States)

    Osborne, Anne H; Vance, Derek; Rohling, Eelco J; Barton, Nick; Rogerson, Mike; Fello, Nuri

    2008-10-28

    It is widely accepted that modern humans originated in sub-Saharan Africa approximately 150-200 thousand years ago (ka), but their route of dispersal across the currently hyperarid Sahara remains controversial. Given that the first modern humans north of the Sahara are found in the Levant approximately 120-90 ka, northward dispersal likely occurred during a humid episode in the Sahara within Marine Isotope Stage (MIS) 5e (130-117 ka). The obvious dispersal route, the Nile, may be ruled out by notable differences between archaeological finds in the Nile Valley and the Levant at the critical time. Further west, space-born radar images reveal networks of-now buried-fossil river channels that extend across the desert to the Mediterranean coast, which represent alternative dispersal corridors. These corridors would explain scattered findings at desert oases of Middle Stone Age Aterian lithic industries with bifacial and tanged points that can be linked with industries further to the east and as far north as the Mediterranean coast. Here we present geochemical data that demonstrate that water in these fossil systems derived from the south during wet episodes in general, and penetrated all of the way to the Mediterranean during MIS 5e in particular. This proves the existence of an uninterrupted freshwater corridor across a currently hyperarid region of the Sahara at a key time for early modern human migrations to the north and out of Africa.

  2. Flight altitude of trans-Sahara migrants in autumn: a comparison of radar observations with predictions from meteorological conditions and water and energy balance models

    NARCIS (Netherlands)

    Klaassen, M.R.J.; Biebach, H.

    2000-01-01

    Radar observations on the altitude of bird migration and altitudinal profiles of meteorological conditions over the Sahara desert are presented for the autumn migratory period. Migratory birds By at an average altitude of 1016 m (a.s.l.) during the day and 571 m during the night. Weather data served

  3. A humid corridor across the Sahara for the migration "Out of Africa" of early modern humans 120,000 years ago

    Science.gov (United States)

    Osborne, A. H.; Vance, D.; Rohling, E. J.; Barton, N.; Rogerson, M.; Fello, N.

    2008-12-01

    The climatic history of the Sahara in the Quaternary is likely to have been a key control on the history of human migrations out of Africa. For example, it is widely accepted that modern humans originated in sub- Saharan Africa around 150-200 thousand years ago (ka), but their route of dispersal across the currently hyper-arid Sahara remains controversial. Given that the first modern humans north of the Sahara are found in the Levant around 120-90 ka, northward dispersal likely occurred during the humid episode in the Sahara within Marine Isotope Stage (MIS) 5e (130-117 ka). The obvious dispersal route, the Nile, may be ruled out by notable differences between archaeological finds in the Nile Valley and the Levant at the critical time. Further west, space-born radar images reveal networks of - now buried - fossil river channels that extend across the desert to the Mediterranean coast, which represent alternative dispersal corridors. This would explain scattered findings at desert oases of Middle Stone Age (MSA) Aterian lithic industries with bifacial and tanged points that can be linked with industries further to the east and as far north as the Mediterranean coast. We have previously used neodymium and oxygen isotope data to suggest that there was enhanced Nile outflow to the Levantine Sea during Saharan humid periods in Stage 5e and the Holocene1. Here, however, we present further geochemical data which suggest that the freshwater signal from Africa was much stronger further west in the Ionian Sea. Furthermore, analyses of shell samples retrieved from the Libyan fossil river channels traces the geochemical signature found in the Ionian Sea to the Tibesti Mountains in the southern Sahara. These data demonstrate that water in the fossil river systems of the Sahara derived from the south during wet episodes in general, and penetrated all the way to the Mediterranean during MIS 5e in particular, confirming the existence of an uninterrupted freshwater corridor across

  4. Phylogeny of North African Agama lizards (Reptilia: Agamidae) and the role of the Sahara desert in vertebrate speciation.

    Science.gov (United States)

    Gonçalves, Duarte V; Brito, José C; Crochet, Pierre-André; Geniez, Philippe; Padial, José M; Harris, D James

    2012-09-01

    The origin of Saharan biodiversity is poorly understood, in part because the geological and paleoclimatic events that presumably shaped species diversity are still controversial, but also because few studies have explored causal explanations for the origin of Saharan diversity using a phylogenetic framework. Here, we use mtDNA (16S and ND4 genes) and nDNA (MC1R and CMOS genes) to infer the relationships and biogeographic history of North African agamas (genus Agama). Agamas are conspicuous, diverse and abundant African lizards that also occur in the Saharan xeric and mesic environments. Our results revealed the presence of three Agama lineages in North Africa: one Afrotropical, one Sahelo-Saharan, and one broadly distributed in North Africa and mainly Saharan. Southern Mauritania contains the highest known diversity, with all three lineages present. Results suggest that agamas colonized the Sahara twice, but only one lineage was able to radiate and diversify there. Species in the Saharan lineage are mostly allopatric, and their splitting, genetic diversity and distribution are greatly explained by mountain ranges. One species in this lineage has colonized the Mediterranean climatic zone (A. impalearis), and another one the Sahel savannah (A. boueti). The other lineage to colonize the Sahara corresponds to A. boulengeri, an eminently Sahelian species that also inhabits Saharan mountain ranges in Mauritania and Mali. Phylogenetic analyses indicate that allopatric montane populations within some currently recognized species are also genetically divergent. Our study therefore concludes that vicariant speciation is a leading motor of species diversification in the area: Inside the Sahara, associated to mountain-ranges isolated by dune seas and bare plains; outside, associated to less harsh climates to the North and South. Paleoclimatic oscillations are suggested as causal explanations of the vicariant distribution and origin of species. Agamas are thought to have

  5. The evolution of the 87Sr/86Sr in the Dead Sea brine: from the Sedom lagoon to Sahara dusts

    Science.gov (United States)

    Stein, Mordechai

    2016-04-01

    The history of water-bodies in the Dead Sea brines commenced with the intrusion of the Sedom lagoon, possibly in the late Neogene and continued with the development of hypersaline and freshwater lakes (e.g. the modern Dead Sea and Sea of Galilee). 87Sr/86Sr ratios in these water-bodies decreased over the past ~ 5-6 Ma from 0.7087-0.7084 in salts deposited in the Sedom lagoon to ~ 0.7080 in modern Dead Sea brine. The 87Sr/86Sr ratios in the salts deposited from Sedom lagoon are significantly lower than those of the contemporaneous late Miocene seawater (~0.709). This difference was attributed to modification of the 87Sr/86Sr ratio in the Sedom lagoon solution by influx of Ca-chloride brines. The brines, in turn were formed by dolomitization of marine limestones of the DSR Cretaceous wall rocks (87Sr/86Sr ~ 0.7075) by the ingressing evaporated seawaters (Stein et al., 2000). After the disconnection of the Sedom lagoon from the open sea freshwater filled the lakes that occupied the Dead Sea basin. The freshwater influx modified the strontium isotope and chemical composition of the brine and provided bicarbonate and sulfate to the lake that led the precipitation of primary aragonite and gypsum. Freshwater that currently enter the lake are characterize by 87Sr/86Sr ~ 0.7081, significantly higher than the Cretaceous carbonates. Settled dust that deposits on the Judea Mountains is composed of calcite and quartz grains and is characterized by 87Sr/86Sr ratios ~ 0.7084. It appears that significant amounts of the strontium that entered the lakes with the freshwater originated from dissolution of the dust calcites. Large amounts of dust were transported from the Sahara desert to the Dead Sea watershed during glacial periods when the Sahara was dry and sea-level was low. The source of the detrital calcites however, is not known. They could be derived from dry paleo-lakes in the Sahara that were previously filled by waters that retained the required strontium isotope

  6. Implications of high altitude desert dust transport from Western Sahara to Nile Delta during biomass burning season.

    Science.gov (United States)

    Prasad, Anup K; El-Askary, Hesham; Kafatos, Menas

    2010-11-01

    The air over major cities and rural regions of the Nile Delta is highly polluted during autumn which is the biomass burning season, locally known as black cloud. Previous studies have attributed the increased pollution levels during the black cloud season to the biomass or open burning of agricultural waste, vehicular, industrial emissions, and secondary aerosols. However, new multi-sensor observations (column and vertical profiles) from satellites, dust transport models and associated meteorology present a different picture of the autumn pollution. Here we show, for the first time, the evidence of long range transport of dust at high altitude (2.5-6 km) from Western Sahara and its deposition over the Nile Delta region unlike current Models. The desert dust is found to be a major contributor to the local air quality which was previously considered to be due to pollution from biomass burning enhanced by the dominant northerly winds coming from Europe.

  7. Bensaâd Ali (dir., L’eau et ses enjeux au Sahara, Iremam, Karthala, 2011, 242 p.

    Directory of Open Access Journals (Sweden)

    Jean-Louis Marçot

    2011-11-01

    Full Text Available Je dirai en premier ma déception. Comme le suggère Ali Bensaâd à l’entrée du livre qu’il a dirigé, l’enjeu de l’eau au Sahara n’est ni plus ni moins que la conservation de la vie dans ce milieu qui lui est particulièrement hostile - la vie sous tous ses aspects. Or cet enjeu « vital » a été négligé au profit d’une approche micro-géographique. C’est pourtant par cette entrée que le travail collectif aurait pu légitimement intéresser un vaste public. Comment l’eau existe-t-elle à l’état naturel...

  8. Dust and biological aerosols from the Sahara and Asia influence precipitation in the western U.S.

    Science.gov (United States)

    Creamean, Jessie M; Suski, Kaitlyn J; Rosenfeld, Daniel; Cazorla, Alberto; DeMott, Paul J; Sullivan, Ryan C; White, Allen B; Ralph, F Martin; Minnis, Patrick; Comstock, Jennifer M; Tomlinson, Jason M; Prather, Kimberly A

    2013-03-29

    Winter storms in California's Sierra Nevada increase seasonal snowpack and provide critical water resources and hydropower for the state. Thus, the mechanisms influencing precipitation in this region have been the subject of research for decades. Previous studies suggest Asian dust enhances cloud ice and precipitation, whereas few studies consider biological aerosols as an important global source of ice nuclei (IN). Here, we show that dust and biological aerosols transported from as far as the Sahara were present in glaciated high-altitude clouds coincident with elevated IN concentrations and ice-induced precipitation. This study presents the first direct cloud and precipitation measurements showing that Saharan and Asian dust and biological aerosols probably serve as IN and play an important role in orographic precipitation processes over the western United States.

  9. Discrimination and Validation of Clouds and Dust Aerosol Layers over the Sahara Desert with Combined CALIOP and IIR Measurements

    Institute of Scientific and Technical Information of China (English)

    LIU Jingjing; CHEN Bin; HUANG Jianping

    2014-01-01

    This study validates a method for discriminating between daytime clouds and dust aerosol layers over the Sahara Desert that uses a combination of active CALIOP (Cloud-Aerosol Lidar with Orthogonal Polar-ization) and passive IIR (Infrared Imaging Radiometer) measurements; hereafter, the CLIM method. The CLIM method reduces misclassification of dense dust aerosol layers in the Sahara region relative to other techniques. When evaluated against a suite of simultaneous measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), CloudSat, and the MODIS (Moderate-resolution Imag-ing Spectroradiometer), the misclassification rate for dust using the CLIM technique is 1.16%during boreal spring 2007. This rate is lower than the misclassification rates for dust using the cloud aerosol discriminations performed for version 2 (V2-CAD;16.39%) or version 3 (V3-CAD;2.01%) of the CALIPSO data processing algorithm. The total identification errors for data from in spring 2007 are 13.46% for V2-CAD, 3.39% for V3-CAD, and 1.99%for CLIM. These results indicate that CLIM and V3-CAD are both significantly better than V2-CAD for discriminating between clouds and dust aerosol layers. Misclassifications by CLIM in this region are mainly limited to mixed cloud-dust aerosol layers. V3-CAD sometimes misidentifies low-level aerosol layers adjacent to the surface as thin clouds, and sometimes fails to detect thin clouds entirely. The CLIM method is both simple and fast, and may be useful as a reference for testing or validating other discrimination techniques and methods.

  10. Mineral Dust Analysis and Application in Refining Source Region Information for the Sahara and East Asia Deserts

    Science.gov (United States)

    Reid, E. A.; Reid, J. S.; Westphal, D.; Cliff, S.; Dunlap, M.

    2002-12-01

    The study of transported mineral dust aerosols relies heavily on simplified dust source region parameters. Source regions are broadly defined by soil class and expected erodibility, factors which continuously changes with land use and climate conditions. Mineral dust particles may undergo numerous cycles of deposition and re-entrainment prior to collection and analysis. Using the Sahara Desert and the East Asia deserts as test cases, we investigate the possibility of retrieving source information from receptor sites through single particle and bulk analyses of collected aerosol particles. In June and July of 2000, Saharan mineral dust aerosols transported across the Atlantic Ocean to Puerto Rico were collected for bulk and single particle chemical and morphological analyses. The Puerto Rico Dust Experiment, (PRIDE), involved sampling aerosols upwind of the islands at various altitudes in the marine boundary layer (MBL) and Saharan Air Layer (SAL) via a Navajo research aircraft. A surface site included a Davis Rotating Drum (DRUM) cascade impactor to size segregate the aerosols into eight stages, from 12 to 0.1 micrometers, with four-hour time resolution. In April of 2001, size segregated Asian mineral dust aerosols were collected by three hour resolution DRUM samplers at surface sites in Cheju, Taiwan, for bulk chemical analysis. The aircraft samples and selected DRUM samples were subjected to single particle analysis by scanning electron microscopy (SEM) for particle morphology, and by Energy Dispersive Analysis with X-rays (EDAX) to derive elemental ratios of key soil elements. The DRUM samples were subjected to X-Ray Fluorescence (XRF) to derive bulk elemental composition for elements Al though Zn. Cluster and principal component analysis of the data derived statistically significant particle groupings. By including particle morphology data, and using ternary analyses, derivation of additional source information was possible. Particle compositions

  11. Source apportionment and seasonal variation of PM2.5 in a Sub-Sahara African city: Nairobi, Kenya

    Directory of Open Access Journals (Sweden)

    S. M. Gaita

    2014-04-01

    Full Text Available Sources of airborne particulate matter and their seasonal variation in urban areas in Sub-Sahara Africa are poorly understood due to lack of long-term measurement data. In view of this, airborne fine particles matter (particle diameter ≤ 2.5 μm, PM2.5 were collected between May 2008 and April 2010 at two sites (urban background site and suburban site within the Nairobi metropolitan area. A total of 780 samples were collected and analyzed for particulate mass, black carbon (BC and thirteen trace elements. The average PM2.5 concentration at the urban background site was 20 ± 8 μg m−3 whereas the concentration at the suburban site was 13 ± 8 μg m−3. The daily PM2.5 concentrations exceeded 25 μg m−3 (the World Health Organization 24 h guideline value 29% of the days at the urban background site and 7% of the days at the suburban site. At both sites, BC, Fe, S and Cl accounted for approximately 80% of all detected elements. Positive Matrix Factorization analysis identified five source factors that contribute to PM2.5 in Nairobi; traffic, mineral dust, secondary aerosol, industrial and combustion. Mineral dust and traffic factors were related to approximately 74% of PM2.5. Identified source factors exhibited seasonal variation though traffic factor was prominently consistent throughout the sampling period. The results provide information that can be exploited for policy formulation and mitigation strategies to control air pollution in Sub-Sahara African cities.

  12. Discrimination and validation of clouds and dust aerosol layers over the Sahara desert with combined CALIOP and IIR measurements

    Science.gov (United States)

    Liu, Jingjing; Chen, Bin; Huang, Jianping

    2014-02-01

    This study validates a method for discriminating between daytime clouds and dust aerosol layers over the Sahara Desert that uses a combination of active CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) and passive IIR (Infrared Imaging Radiometer) measurements; hereafter, the CLIM method. The CLIM method reduces misclassification of dense dust aerosol layers in the Sahara region relative to other techniques. When evaluated against a suite of simultaneous measurements from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), CloudSat, and the MODIS (Moderate-resolution Imaging Spectroradiometer), the misclassification rate for dust using the CLIM technique is 1.16% during boreal spring 2007. This rate is lower than the misclassification rates for dust using the cloud aerosol discriminations performed for version 2 (V2-CAD; 16.39%) or version 3 (V3-CAD; 2.01%) of the CALIPSO data processing algorithm. The total identification errors for data from in spring 2007 are 13.46% for V2-CAD, 3.39% for V3-CAD, and 1.99% for CLIM. These results indicate that CLIM and V3-CAD are both significantly better than V2-CAD for discriminating between clouds and dust aerosol layers. Misclassifications by CLIM in this region are mainly limited to mixed cloud-dust aerosol layers. V3-CAD sometimes misidentifies low-level aerosol layers adjacent to the surface as thin clouds, and sometimes fails to detect thin clouds entirely. The CLIM method is both simple and fast, and may be useful as a reference for testing or validating other discrimination techniques and methods.

  13. Ethnomycological survey of traditional usage and indigenous knowledge on desert truffles among the native Sahara Desert people of Algeria.

    Science.gov (United States)

    Bradai, Lyès; Neffar, Souad; Amrani, Khaled; Bissati, Samia; Chenchouni, Haroun

    2015-03-13

    Desert truffles are edible hypogeous fungi, highly appreciated by the inhabitants of hot-desert settlements. Native Saharan people use truffles for food, promoting tourism, increasing fertility, and treatment of eye diseases and fatigue. This study consists of a cross-sectional survey focusing on the knowledge, use and ethnomycological practices of desert truffles among the native people of the Algerian Northern Sahara. The study was conducted through direct interviews with 60 truffle-hunters in the regions of Ouargla and Ghardaia. Three species were harvested and consumed by the surveyed subjects: Terfezia claveryi was the most appreciated and most expensive species, followed by Terfezia areanaria moderately preferred, then Tirmania nivea the least appreciated and least expensive. Among the 60 interviewees, 90% rely on the abundance of symbiotic plants (Helianthemum lippii) to harvest truffles, 65% begin harvesting from mid-February to March, after rains of the autumn (38%) and winter (36%), particularly in the Wadi beds (37%) and Daya landscapes (32%). Interviewees harvested truffles mainly for home consumption; however 26.7% sell any harvest surplus, and of those only 15% generate significant revenue from this source, and 73% considered the sale of desert truffles to have low financial value. Desert truffles are used in traditional medicine, especially against eye infections (22%), weakness (19%) and to promote male fertility (19%). In the case of desert truffles for consumption, the surveyed population preferred to prepare the truffles with couscous and meat, or in porridge. Respondents used price as the main criterion for deciding whether to purchase desert truffles. The surveyed trufflers use the knowledge passed from one generation to the next to help ensure a good harvest of truffles during each foray into the desert. Our findings highlight the various uses of truffles in the Sahara Desert, and how these relate to the lifestyle of local people. Copyright

  14. Quantifying the "Energy-Return-on-Investment" of desert greening in the Sahara/Sahel using a Global Climate Model

    Science.gov (United States)

    Bowring, S. P. K.; Miller, L. M.; Ganzeveld, L.; Kleidon, A.

    2013-08-01

    "Greening" the world's deserts has been proposed as a way to produce additional food, sequester carbon, and alter the climate of desert regions. Here, we quantify the potential benefits in terms of energetic quantities and compare these to the energetic costs. We then compare these using the metric of Energy-Return-On-Investment (EROI). We apply EROI to a series of global climate model simulations where the arid Sahara/Sahel region is irrigated with various rates of desalinated water to produce biomass. The energy content of this biomass is greater than the energy input rate for a minimum irrigation rate of about 200 mm yr-1 in the winter and 500 mm yr-1 in the summer, thereby yielding an EROI ratio > 1 : 1, expressing energetic sustainability. Quantified annually, the EROI was > 1 : 1 for irrigation rates more than 500 mm yr-1, progressively increasing to a maximum of 1.8 : 1 with 900 mm yr-1, and then decreasing with further increases in the irrigation rate. Including the precipitation feedback arising from changes in moisture-recycling within the study region approximately doubles these EROI ratios. This overall result varies spatially and temporally, so while the entire Sahara/Sahel region is irrigated equally, the western coastal region from June to August had the highest EROI. Other factors would complicate such a large-scale modification of the Earth System, but this sensitivity study concludes that with a required energy input, desert greening may be energetically sustainable. Furthermore, we suggest that this type of EROI-analysis could be applied as a metric to assess a diverse range of human alterations to, and interventions within, the Earth System.

  15. Sahara Coal Pressure Filter ditch optimize operational efifciency%哈拉沟选煤厂加压过滤机运行效率优化

    Institute of Scientific and Technical Information of China (English)

    李兴华; 蒋淑丽; 马敬坡

    2015-01-01

    针对哈拉沟选煤厂细煤泥含量大,细煤泥水分高,加压过滤机小时处理量达不到设计要求等问题,通过改善哈拉沟选煤厂的细煤泥处理设备即加压过滤机的入料性质、运行参数、工艺系统等方法,提出了解决方案。%aiming Sahara Coal ditch fine slime content of large, thin slime high moisture, pressure filter hour processing capacity of less than the design requirements and other issues, by improving the Sahara Coal ditch ifne slime treatment equipment that pressure filter feed properties, operating parameters, process systems and other methods proposed solutions.

  16. A study of the relict fish fauna of northern Chad, with the first records of a polypterid and a poeciliid in the Sahara desert.

    Science.gov (United States)

    Trape, Sébastien

    2013-01-01

    Seventeen species and sub-species of fishes belonging to four families (Cyprinidae, Clariidae, Aplocheilidae, Cichlidae) were known to occur in perennial bodies of water in the Sahara desert. The study of fishes collected in Lake Boukou near Ounianga Serir (Borkou, northern Chad) shows, for the first time, the occurrence in the Sahara desert of relict populations of Polypterus senegalus (Polypteridae) and Poropanchax normani (Poeciliidae). The Cichlidae Tilapia zilli was also collected in this lake. With these new records, the relict fish fauna currently known in lakes and gueltas of the Borkou plateaus comprises six species. In the Ennedi Mountains, where the specific status of Barbus populations was unclear, B. macrops was collected in Bachikere guelta. The toad Amietophrynus regularis was collected in Ounianga Kebir.

  17. Le fils du Sahara et les gens de la pluie. Gestion paysanne et conservation des socioécosystèmes à acacia au Sud du Maroc.

    OpenAIRE

    Blanco, Julien

    2015-01-01

    In drylands, trees fulfil major ecological, socioeconomic and cultural functions to combat desertification. However, the dynamics of stands of Vachellia tortilis subsp. Raddiana – the most widespread acacia species in the Sahara – and the influence of agropastoral societies on those stands remain poorly understood. The aim of this research is to contribute to making good this gap in knowledge through an interdisciplinary study of acacia stands in Morocco, in an environment characterized by se...

  18. Impacts of the Sahel-Sahara Interface Reforestation on West African Climate: Intraseasonal Variability and Extreme Precipitation Events

    Directory of Open Access Journals (Sweden)

    Ibrahima Diba

    2016-01-01

    Full Text Available This study aims to evaluate the impacts of the Sahel-Sahara interface reforestation on spatiotemporal variability of the summer rainfall and extreme precipitation events over West Africa using the RegCM4 model. The land surface scheme of RegCM4 was modified to incorporate an East-West reforested zone (15°N and 20°N. Two runs were performed using the standard version of RegCM4 and the modified one of the same model taking into account the incorporated forest. The reforestation significantly modifies rainfall signal over West Africa by increasing it over the reforested zone and the Fouta Jallon highlands (FJH. This rainfall increase is associated with a strengthening of the atmospheric moisture over the reforested area. This atmospheric moisture content increase associated with the wind dynamic may explain the spatiotemporal change of the rainfall and extreme precipitation events. The analysis of the impacts of the reforestation on some rainfall indices shows an increase of the 90th, 95th, and 99th percentiles over the reforested zone and off the FJH. This reforestation also causes an increase of the maximum length of the consecutive wet days over and off FJH and a decrease of the maximum length of the consecutive dry days over the northern Sahel and the reforested zone.

  19. A Review of e-Health Interventions for Maternal and Child Health in Sub-Sahara Africa.

    Science.gov (United States)

    Obasola, Oluwaseun Ireti; Mabawonku, Iyabo; Lagunju, Ikeoluwa

    2015-08-01

    To review e-health interventions for maternal and child health (MCH) and to explore their influence on MCH practices in sub-Sahara Africa (SSA). Keyword searches were used to retrieve articles from four databases and the websites of organisations involved in e-health projects for MCH in SSA. A total of 18relevant articles were retrieved using inclusion and exclusion criteria. The researchers reveal the prevalence of the application of mobile phones for MCH care and the influence of the use of information and communication technology (ICT) for delivering MCH information and services to target populations. There is a need to move the application of ICT for MCH care from pilot initiatives to interventions involving all stakeholders on a sub-regional scale. These interventions should also adopt an integrated approach that takes care of the information needs at every stage along the continuum of care. It is anticipated that the study would be useful in the evolution and implementation of future ICT-based programmes for MCH in the region.

  20. Implementation of triple helix clusters procedure in the sub-Sahara Africa energy sector. Case study: Academia - CREEC Photovoltaic Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, Izael [Makerere Univ., Kampala (UG). Centre for Research in Energy and Energy Conservation (CREEC)

    2011-07-01

    Penetration of decentralized power supply for households and commercial enterprises is low in Sub-Sahara Africa. Solar Home Systems (SHS), despite their widespread use in other continents have failed to attain much success in Africa. One of the reasons is the high rate of failure of existing implementations. Data shows earlier failure rates of 50%. This is largely attributed to poor quality of products used, inefficient installation, mismanagement and lack of maintenance. To address this problem, the Centre for Research in Energy and Energy Conservation (CREEC) is setting up a Solar PV test laboratory in Uganda. This paper describes the installation process and how to sustain the laboratory after implementation. The lab is intended to provide a forum for training, research and consultancy under CREEC. It is intended as a tool to implement the triple helix and clusters procedure in the PV industry in particular and the energy sector in a more general scope. This paper offers details covering the current situation of the energy sector in Uganda and how the lab supports capacity building in the university to support the upcoming demand. (orig.)

  1. Holocene freshwater carbonate structures in the hyper-arid Gebel Uweinat region of the Sahara Desert (Southwestern Egypt)

    Science.gov (United States)

    Marinova, Margarita M.; Meckler, A. Nele; McKay, Christopher P.

    2014-01-01

    The eastern part of the Sahara is at present the driest region of the desert. Yet the extensive animal rock art in the area, presumed to depict real activities in the lives of the painters, suggests that environmental conditions were significantly different when the rock art was produced. Here we report on exploration of the area, which led to the discovery of morphologically-distinct carbonate structures that line the walls of two valleys in Gebel Uweinat, and were likely formed in standing water. The carbonate structures comprise what appear to be shoreline carbonate formations, and date back to 8100 and 9400 years BP. The chemical and morphological similarity of these formations to carbonate structures from modern lakes suggests that these lakes contained fresh, standing water suitable for human and animal use. However, the significant quartz content suggests that windblown sand was pervasive, and thus the vegetation cover may have been sparse. This discovery supports the possibility of grasslands in the area, which may have been able to support human habitation, and adds to the evidence for a wetter climate in the area in the early Holocene.

  2. Electricity from the Sahara and hydropower - moving forward with renewable energies; Saharastrom und Wasserkraft - mit erneuerbaren Energien in die Zukunft

    Energy Technology Data Exchange (ETDEWEB)

    Kolle, Christian (comp.)

    2009-07-01

    On 13 July a launch meeting took place under the auspices of Muenchner Rueck to initiate the largest private green electricity project of all times. Twenty German companies are preparing themselves to participate in the construction of photovoltaic systems and solar power plants in the Sahara. Even the technical problem of transporting the electricity to Europe, hitherto an obstacle to profitability, seems to have been brought to a solution. The following information was sourced from the GESIS databases SOLIS and SOFIS and the six English-language databases of the producer Cambridge Scientific Abstracts (CSA) which are integrated in www.sowiport.de via the national licences. The SOLIS database mostly covers German-language publications, i.e. journal contributions, monographies as well as contributions to compilations in the major social sciences. SOFIS largely procures its information through surveys among institutions in German speaking countries where social science research is conducted. The CSA databases offer references to research results centering on sociology and political science as well as neighbouring disciplines in the social and economic sciences. They largely cover international journals, but also books, book chapters and in some cases publication reviews.

  3. Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania.

    Science.gov (United States)

    Brito, José C; Martínez-Freiría, Fernando; Sierra, Pablo; Sillero, Neftalí; Tarroso, Pedro

    2011-02-25

    Relict populations of Crocodylus niloticus persist in Chad, Egypt and Mauritania. Although crocodiles were widespread throughout the Sahara until the early 20(th) century, increased aridity combined with human persecution led to local extinction. Knowledge on distribution, occupied habitats, population size and prey availability is scarce in most populations. This study evaluates the status of Saharan crocodiles and provides new data for Mauritania to assist conservation planning. A series of surveys in Mauritania detected crocodile presence in 78 localities dispersed across 10 river basins and most tended to be isolated within river basins. Permanent gueltas and seasonal tâmoûrts were the most common occupied habitats. Crocodile encounters ranged from one to more than 20 individuals, but in most localities less than five crocodiles were observed. Larger numbers were observed after the rainy season and during night sampling. Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal. Research priorities in Chad and Egypt should focus on quantifying population size and pressures exerted on habitats. The present study increased in by 35% the number of known crocodile localities in Mauritania. Gueltas are crucial for the persistence of mountain populations. Oscillations in water availability throughout the year and the small dimensions of gueltas affect biological traits, including activity and body size. Studies are needed to understand adaptation traits of desert populations. Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow. Monitoring is needed to detect demographical and genetical trends in completely isolated populations. Crocodiles are apparently vulnerable during dispersal events. Awareness campaigns focusing on the vulnerability and relict value of crocodiles should be implemented. Classification

  4. Endophytic actinomycetes from spontaneous plants of Algerian Sahara: indole-3-acetic acid production and tomato plants growth promoting activity.

    Science.gov (United States)

    Goudjal, Yacine; Toumatia, Omrane; Sabaou, Nasserdine; Barakate, Mustapha; Mathieu, Florence; Zitouni, Abdelghani

    2013-10-01

    Twenty-seven endophytic actinomycete strains were isolated from five spontaneous plants well adapted to the poor sandy soil and arid climatic conditions of the Algerian Sahara. Morphological and chemotaxonomical analysis indicated that twenty-two isolates belonged to the Streptomyces genus and the remaining five were non-Streptomyces. All endophytic strains were screened for their ability to produce indole-3-acetic acid (IAA) in vitro on a chemically defined medium. Eighteen strains were able to produce IAA and the maximum production occurred with the Streptomyces sp. PT2 strain. The IAA produced was further extracted, partially purified and confirmed by thin layer chromatography (TLC) analysis. The 16S rDNA sequence analysis and phylogenetic studies indicated that strain PT2 was closely related to Streptomyces enissocaecilis NRRL B 16365(T), Streptomyces rochei NBRC 12908(T) and Streptomyces plicatus NBRC 13071(T), with 99.52 % similarity. The production of IAA was affected by cultural conditions such as temperature, pH, incubation period and L-tryptophan concentration. The highest level of IAA production (127 μg/ml) was obtained by cultivating the Streptomyces sp. PT2 strain in yeast extract-tryptone broth supplemented with 5 mg L-tryptophan/ml at pH 7 and incubated on a rotary shaker (200 rpm) at 30 °C for 5 days. Twenty-four-hour treatment of tomato cv. Marmande seeds with the supernatant culture of Streptomyces sp. PT2 that contained the crude IAA showed the maximum effect in promoting seed germination and root elongation.

  5. Intercomparison of Satellite Dust Retrieval Products over the West African Sahara During the Fennec Campaign in June 2011

    Science.gov (United States)

    Banks, J.R.; Brindley, H. E.; Flamant, C.; Garay, M. J.; Hsu, N. C.; Kalashnikova, O. V.; Klueser, L.; Sayer, A. M.

    2013-01-01

    Dust retrievals over the Sahara Desert during June 2011 from the IASI, MISR, MODIS, and SEVIRI satellite instruments are compared against each other in order to understand the strengths and weaknesses of each retrieval approach. Particular attention is paid to the effects of meteorological conditions, land surface properties, and the magnitude of the dust loading. The period of study corresponds to the time of the first Fennec intensive measurement campaign, which provides new ground-based and aircraft measurements of the dust characteristics and loading. Validation using ground-based AERONET sunphotometer data indicate that of the satellite instruments, SEVIRI is most able to retrieve dust during optically thick dust events, whereas IASI and MODIS perform better at low dust loadings. This may significantly affect observations of dust emission and the mean dust climatology. MISR and MODIS are least sensitive to variations in meteorological conditions, while SEVIRI tends to overestimate the aerosol optical depth (AOD) under moist conditions (with a bias against AERONET of 0.31), especially at low dust loadings where the AOD<1. Further comparisons are made with airborne LIDAR measurements taken during the Fennec campaign, which provide further evidence for the inferences made from the AERONET comparisons. The effect of surface properties on the retrievals is also investigated. Over elevated surfaces IASI retrieves AODs which are most consistent with AERONET observations, while the AODs retrieved by MODIS tend to be biased low. In contrast, over the least emissive surfaces IASI significantly underestimates the AOD (with a bias of -0.41), while MISR and SEVIRI show closest agreement.

  6. Clouds over the summertime Sahara: an evaluation of Met Office retrievals from Meteosat Second Generation using airborne remote sensing

    Science.gov (United States)

    Kealy, John C.; Marenco, Franco; Marsham, John H.; Garcia-Carreras, Luis; Francis, Pete N.; Cooke, Michael C.; Hocking, James

    2017-05-01

    Novel methods of cloud detection are applied to airborne remote sensing observations from the unique Fennec aircraft dataset, to evaluate the Met Office-derived products on cloud properties over the Sahara based on the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on-board the Meteosat Second Generation (MSG) satellite. Two cloud mask configurations are considered, as well as the retrievals of cloud-top height (CTH), and these products are compared to airborne cloud remote sensing products acquired during the Fennec campaign in June 2011 and June 2012. Most detected clouds (67 % of the total) have a horizontal extent that is smaller than a SEVIRI pixel (3 km × 3 km). We show that, when partially cloud-contaminated pixels are included, a match between the SEVIRI and aircraft datasets is found in 80 ± 8 % of the pixels. Moreover, under clear skies the datasets are shown to agree for more than 90 % of the pixels. The mean cloud field, derived from the satellite cloud mask acquired during the Fennec flights, shows that areas of high surface albedo and orography are preferred sites for Saharan cloud cover, consistent with published theories. Cloud-top height retrievals however show large discrepancies over the region, which are ascribed to limiting factors such as the cloud horizontal extent, the derived effective cloud amount, and the absorption by mineral dust. The results of the CTH analysis presented here may also have further-reaching implications for the techniques employed by other satellite applications facilities across the world.

  7. Flash floods in the Sahara: a case study for the 28 January 2013 flood in Qena, Egypt

    Directory of Open Access Journals (Sweden)

    Moawad Badawy Moawad

    2016-01-01

    Full Text Available Understanding the torrential rainfall and its consequent surface runoff in the Sahara is a crucial issue for better flood protection and water management plans. This is often hampered by the lack of appropriate in situ measurements. Even now the satellite-derived rainfall suffers from great uncertainty. Thus, we adjusted the data obtained from real-time satellite rainfall coverage (HYDIS using the in situ observed rainfall (Robs. Hydro-morphological parameters were then integrated with the empirical curve number (CN approach to estimate the surface runoff in Qena, Egypt during the 28 January 2013 flash flood event. We deduced that the study area received a total precipitation (∑Rcum of ∼35.6 × 106 [mm] and a total rain volume (∑Rvol of ∼88.9 × 109 [m3] mainly from wadi Qena (89.8%. The majority of the rainfalls fell at light intensity (<2.5 [mm hr−1]. The estimated total surface runoff (∑Qsur was 26.5 × 106 mm and the total runoff volume (∑Qvol was 66.2 × 106 [m3]. The total surface transmission losses (∑Tlos were calculated as 9.1 × 106 [mm], which represents about 25.6% of the total precipitation (∑Rcum and creates substantial opportunities for alluvial aquifer recharge. The total surface runoff (∑Qsur and flood magnitude were generally low, therefore, flood influences were restricted to the destruction of some roads in Qena but no fatalities were involved, nevertheless. Most of the running water was contained by El Sail Canal and poured into the Nile River. It is expected that the applied method in this study will be helpful for our understanding and quantification of flood hydrology and contribute to better risk management plan in the arid and hyper-arid regions.

  8. Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania.

    Directory of Open Access Journals (Sweden)

    José C Brito

    Full Text Available BACKGROUND: Relict populations of Crocodylus niloticus persist in Chad, Egypt and Mauritania. Although crocodiles were widespread throughout the Sahara until the early 20(th century, increased aridity combined with human persecution led to local extinction. Knowledge on distribution, occupied habitats, population size and prey availability is scarce in most populations. This study evaluates the status of Saharan crocodiles and provides new data for Mauritania to assist conservation planning. METHODOLOGY/PRINCIPAL FINDINGS: A series of surveys in Mauritania detected crocodile presence in 78 localities dispersed across 10 river basins and most tended to be isolated within river basins. Permanent gueltas and seasonal tâmoûrts were the most common occupied habitats. Crocodile encounters ranged from one to more than 20 individuals, but in most localities less than five crocodiles were observed. Larger numbers were observed after the rainy season and during night sampling. Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal. CONCLUSION/SIGNIFICANCE: Research priorities in Chad and Egypt should focus on quantifying population size and pressures exerted on habitats. The present study increased in by 35% the number of known crocodile localities in Mauritania. Gueltas are crucial for the persistence of mountain populations. Oscillations in water availability throughout the year and the small dimensions of gueltas affect biological traits, including activity and body size. Studies are needed to understand adaptation traits of desert populations. Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow. Monitoring is needed to detect demographical and genetical trends in completely isolated populations. Crocodiles are apparently vulnerable during dispersal events. Awareness campaigns focusing on

  9. Stable oxygen isotopic composition of corals from the Gulf of Guinea as indicators of periods of extreme precipitation conditions in the sub-Sahara

    Science.gov (United States)

    Swart, Peter K.; White, Kathy S.; Enfield, David; Dodge, Richard E.; Milne, Peter

    1998-11-01

    Stable oxygen isotopic analyses of scleractinian coral skeletons from the Gulf of Guinea in the eastern Atlantic reveal that the corals from this region can be used to identify periods of severe drought and above average precipitation in sub-Sahara Africa. Data presented in this paper show an inverse correlation between precipitation in the Sahel and the δ18O values of a coral skeletons of the species Siderastrea spp. collected from the island of Principe in the Gulf of Guinea. This is opposite to the correlation expected, as previous work has suggested that higher sea surface temperatures occur in the Gulf of Guinea during periods of low rainfall in the Sahel. Such an association would lead to a positive correlation between Sahel precipitation and skeletal δ18O. The explanation for the observed inverse correlation is that the salinity of the Gulf of Guinea is strongly influenced by the outflow from the Niger and Congo rivers. These periods of high freshwater input also correlate with periods of higher rainfall in the sub-Sahara and therefore affect the δ18O values of the coral skeleton. The correlation between δ18O values of the coral skeleton and temperature in the northern subtropical Atlantic Ocean (r = -0.34), the magnitude of the dipole (r = -0.45), and the latitudinal position of the intertropical convergence zone (r = -0.37) illustrate that the δ18O values in the coral skeleton reflect climate dynamics of the region that affect the precipitation patterns in sub-Sahara Africa.

  10. El Sahara Occidental : alimentación y cocina tradicional : aspectos culturales, lingüísticos y etnobotánicos

    OpenAIRE

    Baya E., Moulay-Lahssan

    2014-01-01

    Esta tesis aborda diversos aspectos relacionados con la alimentación y la cocina tradicional de las sociedades beduinas o seminómadas del Sahara Occidental. Dichos aspectos se enmarcan dentro de su contexto cultural y sociológico; de modo que, además de los temas alimentarios, se abordan aspectos culturales, lingüísticos y etnobotánicos. La investigación está basada fundamentalmente en fuentes orales, que, a su vez, son contrastadas y complementadas con la documentación que suministran algun...

  11. 电测深法在撒哈拉沙漠地区找水应用%The Application of Electrical Sounding to Water Exploration in Sahara

    Institute of Scientific and Technical Information of China (English)

    唐英杰

    2014-01-01

    Because of the arid climate and water scarcity, few study on geology and hydrogeology of Sahara has been taken.The lack of study in this field has made water exploration in Sahara harder .On the basis of previous research data , the study is taken step by step to explore the unknown research field.With the help of electrical sounding, aquifers'location are identified and physical properties of them are concluded.The study is scientific and its results can be a reference for further work on hydrogeology .%撒哈拉沙漠地区气候干燥,水资源缺乏,相应的地质、水文地质工作研究程度低,为水源地勘探工作带来很大困难。结合实例,采用电测深法,遵循从已知到未知原则,经过点、线、面逐步开展工作,总结含水层物性特征,划定主要含水区域,为水文工作的开展提供重要的基础资料。

  12. Sahara and Sahel vulnerability to climate changes, lessons from the past - Focus on the Ounianga lake region (NE Chad)

    Science.gov (United States)

    Grenier, Christophe; Zheng, Weipeng; Lezine, Anne-Marie; Braconnot, Pascale; Krinner, Gerhard; Harel, Marie-Alice; Anglade, Juliette; Paillou, Philippe

    2010-05-01

    Reconstructions from sedimentary records and climate modelling results show an overall drying in the African Sahara and Sahel during the Holocene. Was this change abrupt or gradual, and amplified or not through vegetation change and feedbacks to the atmosphere is still the subject of debate. For instance, while [deMenocal et al. 2000] show from oceanic sediments off the Mauritanian coast, that the end of the African Humid Period (AHP), recorded 5500 years ago, was abrupt. [Kroepelin et al., 2008] studied recently sediments from lake Yoa (Ounianga region, NE Chad) and derived a gradual climate change. The present paper focusses on the Ounianga lake region (NE Chad) where the Kropelin et al. study was carried on. We investigate hydrological reconstructions based on climate scenarios and modelling of water dynamics of the catchment area of the lakes. Under modern conditions, Ounianga lakes are maintained in a hyper arid environment due to groundwater inputs from the Nubian Sandstone Aquifer System (NSAS), a very large aquifer covering parts of Chad, Libya, Egypt and Sudan. Moreover, these lakes are situated within 200 km of the Tibesti Mountains ranging over 3000 meters where rainfall is larger than in the plains. So the issue arises as to what extent distant water inputs from the Tibesti and local groundwater recharge could have maintained high lake levels during the climatic transition phase and/or could explain some features analysed from the sediments regarding the abruptness of the salinisation of lake Yoa roughly by 3900 BP. The topography of the region is analyzed from SRTM data to obtain paleo river networks and compared with satellite radar pictures (PALSAR) to identify key features in the Yoa catchement area [refer to Grenier et al. 2009]. A hydrological model is constructed including the river network and depressions interpreted as lakes and modeled dynamically as reservoirs. The groundwater input from the aquifer is modeled within the Cast3m finite element

  13. Environmental changes in the Central Sahara during the Holocene - The Mid-Holocene transition from freshwater lake into sebkha in the Segedim depression, NE Niger

    Science.gov (United States)

    Baumhauer, Roland; Schulz, Erhard; Pomel, Simon

    The change from a fresh water lake to a sebkha during the middle Holocene was investigated in the Segedim depression/North-eastern Niger using continuous thin sections for micropetrography, palynology and for diatoms. This record is clearly divided into several units showing sequences of laminated anoxic to oxic clays, the stage of a sebkha with an inflow of loess, fine broken quartz grains and salts which are covered by dune sands made of rounded and clay covered quartz. The mineral assemblages of the three principal units are defined by the illite/kaolinitecalcite The diatom assemblages equally show the passage from fresh to saline water. The pollen spectra indicate the change from the Saharan savannah to desert vegetation.

  14. Deployable centralizers

    Energy Technology Data Exchange (ETDEWEB)

    Grubelich, Mark C.; Su, Jiann-Cherng; Knudsen, Steven D.

    2017-02-28

    A centralizer assembly is disclosed that allows for the assembly to be deployed in-situ. The centralizer assembly includes flexible members that can be extended into the well bore in situ by the initiation of a gas generating device. The centralizer assembly can support a large load carrying capability compared to a traditional bow spring with little or no installation drag. Additionally, larger displacements can be produced to centralize an extremely deviated casing.

  15. ‘Everybody knows’, but the rest of the world: the case of a caterpillar-borne reproductive loss syndrome in dromedary camels observed by Sahrawi pastoralists of Western Sahara

    NARCIS (Netherlands)

    Volpato, G.; Nardo, Di A.; Rossi, D.; Lamin Saleh, S.; Broglia, A.

    2013-01-01

    Background The traditional knowledge of local communities throughout the world is a valuable source of novel ideas and information to science. In this study, the ethnoveterinary knowledge of Sahrawi pastoralists of Western Sahara has been used in order to put forward a scientific hypothesis regardin

  16. SURVEY OF BIBLIOGRAPHIES AND REFERENCE WORKS ON ASIA, AFRICA, LATIN AMERICA, RUSSIA, AND EAST EUROPE--AND COMPILATION OF BIBLIOGRAPHIES ON EAST ASIA, SOUTH ASIA AND AFRICA SOUTH OF THE SAHARA FOR UNDERGRADUATE LIBRARIES. INTERIM REPORT, PHASE ONE.

    Science.gov (United States)

    MOREHOUSE, WARD

    THE PURPOSE OF THE PROJECT IS TO ASSIST UNDERGRADUATE LIBRARIES IN STRENGTHENING THEIR RESOURCES ON AREAS OUTSIDE THE PERIMETER OF WESTERN CIVILIZATION USUALLY GIVEN LITTLE ATTENTION BY AMERICAN COLLEGES, WITH SPECIAL EMPHASIS ON EAST AND SOUTH ASIA AND AFRICA SOUTH OF THE SAHARA. UNDER THE PROJECT'S FIRST PHASE, A PANEL OF LIBRARY ADVISERS WAS…

  17. SAHARA MAKEUP NOV 07

    African Journals Online (AJOL)

    Winnie

    factor that makes it different from other recent diseases. Globally, an ... destroys productive forces, reduces life expectancy, and ... children have little chance of surviving. .... that older people are also infected with the disease .... only an emotional strain for household members, but .... socio-cultural context in which they live.

  18. SAHARA MAKEUP NOV 07

    African Journals Online (AJOL)

    Winnie

    4 NO. 3 NOVEMBRE 2007. Journal des Aspects Sociaux du VIH/SIDA. 695. M S Jansen ... séropositivité était plus basse que celle de la violence. La prise de ...... Preventing domestic violence: most women welcome inquiries, but doctors and.

  19. Swimming in the Sahara

    Institute of Scientific and Technical Information of China (English)

    Alex; Stone; 于文

    2007-01-01

    非洲的撒哈拉大沙漠总会使人想起干旱、贫瘠和荒凉的画面。然而,是不是盘古开天地以来,它就是一望无际、了无人烟的沙漠呢?历史上的撒哈拉沙漠究竟是什么样子?德国科隆大学的地质考古学家Stefan Kropclin通过对东撒哈拉长达30年的挖掘,以及对其出土的文物,例如动物骨骼、山洞艺术品等研究,对以上问题给出了明确的答案。他认为,过去的撒哈拉大沙漠曾是一个生机勃勃的绿色伊甸园,将来它必将重现昔日草木葱茏的景像。

  20. SAHARA MAKEUP NOV 07

    African Journals Online (AJOL)

    Winnie

    Ecological studies in sub-Saharan Africa have suggested a geographical ... broader social and cultural dynamics involved.Thus .... three randomised control trials was under 2%, in about ... cultural analysis perspective, the body functions as a ... Application of Health Standards in Traditional ..... Health Organisation. Niang ...

  1. NEW JULY SAHARA

    African Journals Online (AJOL)

    Winnie

    social pressures, visibility of the disease, and individuals within companies. ... Marion Stevens completed this work while working as a project manager and senior researcher at the Centre for Health Policy at .... profile rather than local need.

  2. NEW JULY SAHARA

    African Journals Online (AJOL)

    Winnie

    maintains that with increasing absenteeism companies will experience ..... upper position workers were uncertain, as they felt that the atmosphere at ..... the women empowered against risk (WEAR) HIV prevention intervention. National HIV ...

  3. A biochemical quality study of a pharmaceutically licenced coagulation active plasma (Octaplas) thawed by the SAHARA-III dry tempering system compared to the regular use of a water bath.

    Science.gov (United States)

    Heger, A; Römisch, J; Svae, T-E

    2008-01-01

    The most common way to thaw frozen coagulation-active plasma products for transfusion is the use of a water bath with good circulation at 30-37 degrees C. The aim of this study was to perform an extensive biochemical characterization of the pharmaceutically licenced solvent/detergent-treated plasma, Octaplas, thawed using the SAHARA-III dry tempering system from the company Sarstedt GmbH, Austria. A regular water bath was used in parallel for comparison. Six batches Octaplas with different blood groups were thawed in a water bath or using the SAHARA-III dry tempering system in parallel. Thawed plasma was investigated on screening tests for blood coagulation, as well as on the activities of important coagulation factors and protease inhibitors. In addition, markers of activated coagulation and fibrinolysis were tested and von Willebrand factor multimeric analysis was performed. There were neither significant differences in the blood coagulation parameters, coagulation factors, protease inhibitors, nor of markers of activated coagulation and fibrinolysis when Octaplas thawed by the two different methods was tested. The von Willebrand factor analyses showed no influence on the overall profile of the multimeric pattern when using the SAHARA-III dry tempering system. Octaplas can be thawed using the SAHARA-III dry tempering system without any negative influences on the demonstrated quality of this product. The SAHARA-III dry tempering system enables standardized thawing and warming procedure. Furthermore, tempering of Octaplas in the emergency unit or operating theatre, where no water baths can be utilized, is safe and can be fully endorsed.

  4. A reference region for the Ordovician-Silurian boundary: the Oued In Djerane, Algerian SaharaUne région de référence pour la limite Ordovicien-Silurien : l'Oued In Djerane, Sahara algérien

    Science.gov (United States)

    Legrand, Philippe

    2000-01-01

    The melting chronology of the Latest Ordovician inlandsis takes on a particular importance in northern Gondwana. A continuous sequence of Diplograptid range zones has been defined from outcrops in the Oued In Djerane, but its comparison with the sequence observed in the stratotype of the Silurian-Ordovician boundary is problematic because of the endemic character of the Saharan species. Moreover, some difficulties are linked to the definition of the Ordovician-Silurian boundary, which, in the Algerian Sahara, probably lies in the Pseudorthograptus (?) kiliani zone. A definite regional diachronism in the melting of the ice-cap has also been confirmed.

  5. Phanerozoic geological evolution of Northern and Central Africa: An overview

    Science.gov (United States)

    Guiraud, R.; Bosworth, W.; Thierry, J.; Delplanque, A.

    2005-10-01

    West African Craton (end Early Cambrian) and during the polyphased Hercynian-Variscan Orogeny that extended the final closure of the Paleotethys Ocean and resulted in the formation of the Maghrebian and Mauritanides belts. Only gentle deformation affected central and northeastern African during the Paleozoic, the latter remaining a passive margin of the Paleotethys Ocean up to the Early Permian when the development of the Neotethys initiated along the Eastern Mediterranean Basins. The Mesozoic-Cenozoic sedimentary sequence similarly consists of a succession of eustatically and tectonically controlled depositional cycles. Through time, progressive southwards shift of the basin margins occurred, related to the opening of the Neotethys Ocean and to the transgressions resulting from warming of the global climate and associated rise of the global sea level. The Guinean-Nigerian Shield, the Hoggar, Tibesti-Central Cyrenaica, Nubia, western Saudi Arabia, Central African Republic, and other long-lived arches delimited the principal basins. The main tectonic events were the polyphased extension, inversion, and folding of the northern African-Arabian shelf margin resulting in the development of the Alpine Maghrebian and Syrian Arc belts, rifting and drifting along the Central Atlantic, Somali Basins, and Gulf of Aden-Red Sea domains, inversion of the Murzuq-Djado Basin, and rifting and partial inversion along the Central African Rift System. Two major compressional events occurred in the Late Santonian and early Late Eocene. The former entailed folding and strike-slip faulting along the northeastern African-northern Arabian margin (Syrian Arc) and the Central African Fold Belt System (from Benue to Ogaden), and thrusting in Oman. The latter ("Pyrenean-Atlasic") resulted in folding, thrusting, and local metamorphism of the northern African-Arabian plate margin, and rejuvenation of intra-plate fault zones. Minor or more localized compressional deformations took place in the end

  6. Screening for Genes Coding for Putative Antitumor Compounds, Antimicrobial and Enzymatic Activities from Haloalkalitolerant and Haloalkaliphilic Bacteria Strains of Algerian Sahara Soils

    Directory of Open Access Journals (Sweden)

    Okba Selama

    2014-01-01

    Full Text Available Extreme environments may often contain unusual bacterial groups whose physiology is distinct from those of normal environments. To satisfy the need for new bioactive pharmaceuticals compounds and enzymes, we report here the isolation of novel bacteria from an extreme environment. Thirteen selected haloalkalitolerant and haloalkaliphilic bacteria were isolated from Algerian Sahara Desert soils. These isolates were screened for the presence of genes coding for putative antitumor compounds using PCR based methods. Enzymatic, antibacterial, and antifungal activities were determined by using cultural dependant methods. Several of these isolates are typical of desert and alkaline saline soils, but, in addition, we report for the first time the presence of a potential new member of the genus Nocardia with particular activity against the yeast Saccharomyces cerevisiae. In addition to their haloalkali character, the presence of genes coding for putative antitumor compounds, combined with the antimicrobial activity against a broad range of indicator strains and their enzymatic potential, makes them suitable for biotechnology applications.

  7. PALEODRAINAGES OF THE EASTERN SAHARA - THE RADAR RIVERS REVISITED (SIR - A/B IMPLICATIONS FOR A MID - TERTIARY TRANS - AFRICAN DRAINAGE SYSTEM).

    Science.gov (United States)

    McCauley, John F.; Breed, Carlos S.; Schaber, Gerald G.; McHugh, William P.; Issawi, Bahay; Haynes, C. Vance; Grolier, Maurice J.; El Kilani, Ali

    1986-01-01

    A complex history of Cenozoic fluvial activity in the presently hyperarid eastern Sahara is inferred from Shuttle Imaging Radar (SIR) data and postflight field investigations in southwest Egypt and northwest Sudan. SIR images were coregistered with Landsat and existing maps as a guide to exploration of the buried paleodrainages (radar rivers) first discovered by SIR-A. Field observations explain the radar responses of three types of radar rivers: RR-1, RR-2, and RR-3. A generalized model of the radar rivers, based on field studies and regional geologic relations, shows apparent changes in river regimen since the large valleys were established during the late Paleogene-early Neogene eras. SIR-based mapping of these paleodrainages, although incomplete, reveals missing links in an area once thought to be devoid of master streams.

  8. The formation conditions of enstatite chondrites: Insights from trace element geochemistry of olivine-bearing chondrules in Sahara 97096 (EH3)

    CERN Document Server

    Jacquet, Emmanuel; Gounelle, Matthieu

    2016-01-01

    We report in situ LA-ICP-MS trace element analyses of silicate phases in olivine-bearing chondrules in the Sahara 97096 (EH3) enstatite chondrite. Most olivine and enstatite present rare earth element (REE) patterns comparable to their counterparts in type I chondrules in ordinary chondrites. They thus likely share a similar igneous origin, likely under similar redox conditions. The mesostasis however frequently shows negative Eu and/or Yb (and more rarely Sm) anomalies, evidently out of equilibrium with olivine and enstatite. We suggest that this reflects crystallization of oldhamite during a sulfidation event, already inferred by others, during which the mesostasis was molten, where the complementary positive Eu and Yb anomalies exhibited by oldhamite would have possibly arisen due to a divalent state of these elements. Much of this igneous oldhamite would have been expelled from the chondrules, presumably by inertial acceleration or surface tension effects, and would have contributed to the high abundance ...

  9. Screening for genes coding for putative antitumor compounds, antimicrobial and enzymatic activities from haloalkalitolerant and haloalkaliphilic bacteria strains of Algerian Sahara Soils.

    Science.gov (United States)

    Selama, Okba; Amos, Gregory C A; Djenane, Zahia; Borsetto, Chiara; Laidi, Rabah Forar; Porter, David; Nateche, Farida; Wellington, Elizabeth M H; Hacène, Hocine

    2014-01-01

    Extreme environments may often contain unusual bacterial groups whose physiology is distinct from those of normal environments. To satisfy the need for new bioactive pharmaceuticals compounds and enzymes, we report here the isolation of novel bacteria from an extreme environment. Thirteen selected haloalkalitolerant and haloalkaliphilic bacteria were isolated from Algerian Sahara Desert soils. These isolates were screened for the presence of genes coding for putative antitumor compounds using PCR based methods. Enzymatic, antibacterial, and antifungal activities were determined by using cultural dependant methods. Several of these isolates are typical of desert and alkaline saline soils, but, in addition, we report for the first time the presence of a potential new member of the genus Nocardia with particular activity against the yeast Saccharomyces cerevisiae. In addition to their haloalkali character, the presence of genes coding for putative antitumor compounds, combined with the antimicrobial activity against a broad range of indicator strains and their enzymatic potential, makes them suitable for biotechnology applications.

  10. Temperature profiles from STD casts from the Spanish Sahara from NOAA Ship OCEANOGRAPHER as part of the International Decade of Ocean Exploration / Coastal Upwelling Ecosystems Analysis (IDOE/CUEA) from 1974-03-08 to 1974-05-01 (NCEI Accession 9800112)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profiles were collected from STD casts off the Spanish Sahara from NOAA Ship OCEANOGRAPHER from 08 March 1974 to 01 May 1974. Data were collected by the...

  11. Centralized Support

    National Research Council Canada - National Science Library

    2011-01-01

      With the complexities surrounding the choice of decentralized vs. centralized labs, as well as the most optimal use of biomarkers in clinical trials, choosing the right lab or CRO partner is paramount...

  12. The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis

    Science.gov (United States)

    Roberts, A. J.; Knippertz, P.

    2014-02-01

    Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

  13. Radiation, multiple dispersal and parallelism in the skinks, Chalcides and Sphenops (Squamata: Scincidae), with comments on Scincus and Scincopus and the age of the Sahara Desert.

    Science.gov (United States)

    Carranza, S; Arnold, E N; Geniez, Ph; Roca, J; Mateo, J A

    2008-03-01

    Phylogenetic analysis using up to 1325 base pairs of mitochondrial DNA from 179 specimens and 30 species of Chalcides, Sphenops, Eumeces, Scincopus and Scincus indicates that Sphenops arose twice independently within Chalcides. It is consequently synonymized with that genus. Chalcides in this broader sense originated in Morocco, diversifying into four main clades about 10 Ma, after which some of its lineages dispersed widely to cover an area 40 times as large. Two separate lineages invaded the Canary Islands and at least five main lineages colonized southern Europe. At least five more spread across northern Africa, one extending into southwest Asia. Elongate bodies with reduced limbs have evolved at least four times in Chalcides, mesic 'grass-swimmers' being produced in one case and extensive adaptation to life in loose desert sand in two others. In clade, Chalcides striatus colonized SW Europe from NW Africa 2.6 Ma and C. chalcides mainland Italy 1.4 Ma, both invasions being across water, while C. c. vittatus reached Sardinia more recently, perhaps anthropogenically, and C. guentheri spread 1200km further east to Israel. C. minutus is a composite, with individuals from the type locality forming a long independent lineage and the remaining ones investigated being most closely related to C. mertensi. In the Northern clade, C. boulengeri and C. sepsoides spread east through sandy habitats north of the Sahara about 5 Ma, the latter reaching Egypt. C. bedriagai invaded Spain around the same time, perhaps during the Messinian period when the Mediterranean was dry, and shows considerable diversification. Although it is currently recognized as one species, the C. ocellatus clade exhibits as much phylogenetic depth as the other main clades of Chalcides, having at least six main lineages. These have independently invaded Malta and Sardinia from Tunisia and also southwest Arabia C. o. humilis appears to have spread over 4000 km through the Sahel, south of the Sahara quite

  14. Physicochemical and microbiological study of “shmen”, a traditional butter made from camel milk in the Sahara (Algeria: isolation and identification of lactic acid bacteria and yeasts

    Directory of Open Access Journals (Sweden)

    Mourad, Kacem

    2006-06-01

    Full Text Available Microorganisms (aerobic bacteria, coliforms, lactic acid bacteria, psychrotrophs, lipolytic bacteria and yeasts were isolated from 20 samples of shmen, a traditional clarified butter made from sour camel milk in the Algerian Sahara. The values of pH, titratable acidity, NaCl, total solid, moisture, and fat content ranged from : 3.11-4.97, 0.19-0.36%, 1.04-2.15%, 64.03-65.11%, 34.40-34.99%, and 49.90-56% respectively. A total of 181 isolates of lactic acid bacteria were identified as Lactobacillus plantarum (40 strains, Lactobacillus delbrueckii ssp. bulgaricus (35 strains, Lactococcus lactis ssp. lactis biovar diacetylacti (22 strains, Lactococcus lactis ssp. cremoris (18 strains, Lactobacillus paracasei ssp. paracasei (10 strains, Leuconostoc pseudomesenteroides (9 strains and Leuconostoc gelidum (12 strains Enterococcus faecium (35 strains. Yeasts were isolated from all samples (55 isolates. Of these, 40 were identified as Saccharomyces cerevisiae and 15 isolates were identified as Saccharomyces sp.Se aislaron los microorganismos (bacterias aeróbicas, coliformes, bacterias acido lácticas, bacterias lipolíticas y levaduras de 20 muestras de “shmen”, una matequilla tradicional del Sahara argelino hecha a partir de leche de camella. Los valores de pH, acidez, libre, Nacl, solidos totales, humedad y grasa oscilaron entre 3,11-4,97, 0,19-0,36%, 1.04-2,15%, 64,03-65,11%, 34,40-34,99% y 49,90-56,00%, respectivamente. Entre los 181 cultivos puros de bacterias lácticas se identificaron Lactobacillus plantarum (40 cepas, Lactobacillus delbrueckii ssp. bulgaricus (35 cepas, Lactococcus lactis ssp. lactis biovar diacetylacti (22 cepas, Lactococcus lactis ssp. cremoris (18 cepas, Lactobacillus paracasei ssp. paracasei (10 cepas, Leuconostoc pseudomesenteroides (9 cepas and Leuconostoc gelidum (12cepas Enterococcus faecium (35 cepas. Asimismo, se detectaron levaduras en todas las muestras (55 cultivos puros. De estos, 40 se identificaron como

  15. Central line infections - hospitals

    Science.gov (United States)

    ... infection; Central venous catheter - infection; CVC - infection; Central venous device - infection; Infection control - central line infection; Nosocomial infection - central line infection; Hospital acquired ...

  16. Desert Dust Air Mass Mapping in the Western Sahara, using Particle Properties Derived from Space-based Multi-angle Imaging

    Science.gov (United States)

    Kahn, Ralph; Petzold, Andreas; Wendisch, Manfred; Bierwirth, Eike; Dinter, Tilman; Fiebig, Marcus; Schladitz, Alexander; von Hoyningen-Huene, Wolfgang

    2008-01-01

    Coincident observations made over the Moroccan desert during the SAhara Mineral dUst experiMent (SAMUM) 2006 field campaign are used both to validate aerosol amount and type retrieved from Multi-angle Imaging SpectroRadiometer (MISR) observations, and to place the sub-orbital aerosol measurements into the satellite's larger regional context. On three moderately dusty days for which coincident observations were made, MISR mid-visible aerosol optical thickness (AOT) agrees with field measurements point-by-point to within 0.05 to 0.1. This is about as well as can be expected given spatial sampling differences; the space-based observations capture AOT trends and variability over an extended region. The field data also validate MISR's ability to distinguish and to map aerosol air masses, from the combination of retrieved constraints on particle size, shape, and single-scattering albedo. For the three study days, the satellite observations (a) highlight regional gradients in the mix of dust and background spherical particles, (b) identify a dust plume most likely part of a density flow, and (c) show an air mass containing a higher proportion of small, spherical particles than the surroundings, that appears to be aerosol pollution transported from several thousand kilometers away.

  17. Desert Dust Aerosol Air Mass Mapping in the Western Sahara, Using Particle Properties Derived from Space-Based Multi-Angle Imaging

    Science.gov (United States)

    Kahn, Ralph; Petzold, Andreas; Wendisch, Manfred; Bierwirth, Eike; Dinter, Tilman; Esselborn, Michael; Fiebig, Marcus; Heese, Birgit; Knippertz, Peter; Mueller, Detlef; Schladitz, Alexander; Von Hoyningen-Huene, Wolfgang

    2008-01-01

    Coincident observations made over the Moroccan desert during the Sahara mineral dust experiment (SAMUM) 2006 field campaign are used both to validate aerosol amount and type retrieved from multi-angle imaging spectroradiometer (MISR) observations, and to place the suborbital aerosol measurements into the satellite s larger regional context. On three moderately dusty days during which coincident observations were made, MISR mid-visible aerosol optical thickness (AOT) agrees with field measurements point-by-point to within 0.05 0.1. This is about as well as can be expected given spatial sampling differences; the space-based observations capture AOT trends and variability over an extended region. The field data also validate MISR s ability to distinguish and to map aerosol air masses, from the combination of retrieved constraints on particle size, shape and single-scattering albedo. For the three study days, the satellite observations (1) highlight regional gradients in the mix of dust and background spherical particles, (2) identify a dust plume most likely part of a density flow and (3) show an aerosol air mass containing a higher proportion of small, spherical particles than the surroundings, that appears to be aerosol pollution transported from several thousand kilometres away.

  18. Biocontrol of Rhizoctonia solani damping-off and promotion of tomato plant growth by endophytic actinomycetes isolated from native plants of Algerian Sahara.

    Science.gov (United States)

    Goudjal, Yacine; Toumatia, Omrane; Yekkour, Amine; Sabaou, Nasserdine; Mathieu, Florence; Zitouni, Abdelghani

    2014-01-20

    Thirty-four endophytic actinomycetes were isolated from the roots of native plants of the Algerian Sahara. Morphological and chemical studies showed that twenty-nine isolates belonged to the Streptomyces genus and five were non-Streptomyces. All isolates were screened for their in vitro antifungal activity against Rhizoctonia solani. The six that had the greatest pathogen inhibitory capacities were subsequently tested for their in vivo biocontrol potential on R. solani damping-off in sterilized and non-sterilized soils, and for their plant-growth promoting activities on tomato seedlings. In both soils, coating tomato seeds with antagonistic isolates significantly reduced (P<0.05) the severity of damping-off of tomato seedlings. Among the isolates tested, the strains CA-2 and AA-2 exhibited the same disease incidence reduction as thioperoxydicarbonic diamide, tetramethylthiram (TMTD) and no significant differences (P<0.05) were observed. Furthermore, they resulted in a significant increase in the seedling fresh weight, the seedling length and the root length of the seed-treated seedlings compared to the control. The taxonomic position based on 16S rDNA sequence analysis and phylogenetic studies indicated that the strains CA-2 and AA-2 were related to Streptomyces mutabilis NBRC 12800(T) (100% of similarity) and Streptomyces cyaneofuscatus JCM 4364(T) (100% of similarity), respectively.

  19. New early Pliocene owls from Langebaanweg, South Africa, with first evidence of Athene south of the Sahara and a new species of Tyto

    Directory of Open Access Journals (Sweden)

    Marco Pavia

    2015-12-01

    Full Text Available The fossiliferous Upper Varswater Formation at Langebaanweg (South Africa produced remains of at least five species of owls (Strigiformes. Tyto richae sp. nov. is the first palaeospecies of Tytonidae described from an African fossil site, though indeterminate remains referable to the genus Tyto are known from the Middle Miocene of Morocco, the early Pliocene of Ethiopia, and the Pliocene of Tanzania. Athene inexpectata sp. nov. is not only the earliest documented fossil evidence for the genus worldwide, but also the first record of a species of Athene in Africa south of the Sahara. Proportions of its hind limb indicate that At. inexpectata sp. nov. probably has been as terrestrial as its modern relative At. cunicularia. A few additional remains represent the earliest fossil evidence for the genera Asio and Bubo on the African continent, though the poor preservation of these bones prevents more detailed identifications. A distal tibiotarsus of a small owl about the size of At. inexpectata sp. nov. indicates the presence of a fifth, as yet indeterminate, species of owl at Langebaanweg. Biogeographical and palaeoecological implications of this assemblage of owls are discussed.

  20. Le développement humain local dans les contextes de crise permanente : l’expérience des femmes au Sahara Occidental

    Directory of Open Access Journals (Sweden)

    María López Belloso

    2009-04-01

    Full Text Available Les femmes sahraouies sont des agents actifs dans la dynamique sociale des camps de réfugiés, au sein desquels elles ont défini un certain nombre de stratégies de résolution de problèmes pour surmonter les obstacles liés à une situation humanitaire qui se détériore. Depuis le début du conflit et le déplacement forcé à Tindouf, en Algérie, les femmes sont en e%et intégralement responsables de la gestion des camps de réfugiés, et ont assumé un rôle de dirigeantes dans de nombreux secteurs de la société. Cet article souligne la contribution des femmes sahraouies au processus de développement humain local dans un contexte de refuge prolongé tel celui que connaît le Sahara Occidental. En plus d’améliorer la capacité d’accès des réfugiés aux ressources matérielles, physiques, sociales et organisationnelles ainsi qu’aux forces motivationnelles, les femmes sahraouies ont été en mesure de mettre en place leur propre processus de renforcement des capacitésII individuelle et collective dans la vie du camp.

  1. Determination of the specific activities of the cosmogenic nuclides {sup 10}Be and {sup 26}Al in meteorites from the Sahara by means of accelerator mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Meltzow, B. [Koeln Univ. (Germany). Abt. Nuklearchemie; Herpers, U. [Koeln Univ. (Germany). Abt. Nuklearchemie; Romstedt, J. [Muenster Univ. (Germany). Inst. fuer Planetologie; Dittrich-Hannen, B. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Kubik, P.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik

    1996-06-01

    In 30 samples of meteorites from the Sahara the specific activity of {sup 26}Al, and in the case of rare meteorite types also that of {sup 10}Be was determined. In most cases, the measured data are consistent with the suggestions about possible pairings which were based on mineralogical and petrographical investigations. The investigated CR and CH chondrites were found to be saturated in {sup 26}Al and {sup 10}Be. The {sup 26}Al and {sup 10}Be production rates can be assumed to be (44.5{+-}0.9) dpm/kg and (20.7{+-}0.3) dpm/kg, respectively, for CR as well as (30.1{+-}0.9) dpm/kg and (16.7{+-}0.4) dpm/kg for CH chondrites. Furthermore the {sup 26}Al data of 11 ordinary chondrites can also be interpreted as saturation activities and allow the assumption of 3.10{sup 6} y to be the lower limit of the exposure ages of these meteorites. In the case of Acfer 277, in addition to the {sup 10}Be and {sup 26}Al determinations, a study on nuclear tracks was performed. These data suggest that the investigated sample was located at no more than 8 cm below the original surface of a meteoroid of a radius between 25 cm and 65 cm which traveled through space (0.3{+-}0.1).10{sup 6} y before entering the earth`s atmosphere. (orig.)

  2. Gold mineralization in the West Hoggar shear zone, Algeria

    Science.gov (United States)

    Ferkous, K.; Leblanc, M.

    1995-06-01

    The Amesmessa gold prospect is located along a vertical N-S-trending crustal-scale ductile shear zone; stretching lineations are subhorizontal. This major shear zone is a Late Pan African dextral strike-slip fault of the Pharusian Belt of the Tuareg Shield (Algeria). The Amesmessa shear zone is asymmetric: strong thermal and deformational gradients are present along its western border where biotitic ultramylonites are in contact with a rigid Archean complex (In Ouzzal block), whereas there is a progressive gradation, through mylonite then protomylonite, to the Proterozoic gneiss of the Eastern block which displays co-axial Pan African structures. The Amesmessa shear zone is characterized by the presence of a felsic dike complex emplaced during shearing, and forming the most important parent material for ultramylonites. Basic magmas and carbonatites also intruded within the shear zone. The gold-rich quartz veins are located within the ultramylonitic western part of the shear zone. These N-S-trending laminated quartz veins formed during the late increments of shearing (plastic/brittle transition), by repeated syntectonic hydraulic fracturing along zones of rheological contrast parallel to foliation. The ore mineral association (pyrite, galena, native gold, sphalerite) crystallized in the deformed quartz matrix along late shear planes. Undeformed E-W trending banded quartz veins are present in the mylonitic eastern part of the shear zone; their gold content is low and no native gold has been observed. A strong hydrothermal alteration resulted in the development (along the walls of the N-S gold-bearing quartz veins) of a 5-m-wide carbonate-sericite-albite-pyrite secondary mineral association which implies an important CO2 supply and moderate temperature conditions. There is no alteration halo around the E-W quartz veins. Ultramylonites, hydrothermally altered rocks and quartz veins display similar REE patterns characterized by strong LREE enrichments. Shear-related fluids could be likely parental fluids for the Amesmessa gold mineralization and the associated hydrothermal alteration. Hydrothermal fluids were drawn into dilation zones and filled opening fractures along the main planar discontinuity of the most deformed rocks. The supply of CO2 may come from a deep-seated source as suggested by the presence of carbonatite dikes in the shear zones and the existence of CO2-H2O-rich fluid inclusions in quartz. The location of the gold-bearing quartz veins in the western part of the shear zone can be explained by the presence of strong thermal and rheological gradients.

  3. Central Solenoid

    CERN Multimedia

    2002-01-01

    The Central Solenoid (CS) is a single layer coil wound internally in a supporting cylinder housed in the cryostat of the Liquid Argon Calorimeter. It was successfully tested at Toshiba in December 2000 and was delivered to CERN in September 2001 ready for integration in the LAr Calorimeter in 2003. An intermediate test of the chimney and proximity cryogenics was successfully performed in June 2002.

  4. Europa central

    Directory of Open Access Journals (Sweden)

    Karel BARTOSEK

    2010-02-01

    Full Text Available La investigación francesa continúa interesándose por Europa Central. Desde luego, hay límites a este interés en el ambiente general de mi nueva patria: en la ignorancia, producto del largo desinterés de Francia por este espacio después de la Segunda Guerra Mundial, y en el comportamiento y la reflexión de la clase política y de los medios de comunicación (una anécdota para ilustrar este ambiente: durante la preparación de nuestro coloquio «Refugiados e inmigrantes de Europa Central en el movimiento antifascista y la Resistencia en Francia, 1933-1945», celebrado en París en octubre de 1986, el problema de la definición fue planteado concreta y «prácticamente». ¡Y hubo entonces un historiador eminente, para quién Alemania no formaría parte de Europa Central!.

  5. Central pain.

    Science.gov (United States)

    Singh, Supreet

    2014-12-01

    Questions from patients about pain conditions and analgesic pharmacotherapy and responses from authors are presented to help educate patients and make them more effective self-advocates. The topic addressed in this issue is central pain, a neuropathic pain syndrome caused by a lesion in the brain or spinal cord that sensitizes one's perception of pain. It is a debilitating condition caused by various diseases such as multiple sclerosis, strokes, spinal cord injuries, or brain tumors. Varied symptoms and the use of pharmacological medicines and nonpharmacological therapies will be addressed.

  6. central t

    Directory of Open Access Journals (Sweden)

    Manuel R. Piña Monarrez

    2007-01-01

    Full Text Available Dado que la Regresión Ridge (RR, es una estimación sesgada que parte de la solución de la regresión de Mínimos Cuadrados (MC, es vital establecer las condiciones para las que la distribución central t de Student que se utiliza en la prueba de hipótesis en MC, sea también aplicable a la regresión RR. La prueba de este importante resultado se presenta en este artículo.

  7. A hydrological-economic model for sustainable groundwater use in sparse-data drylands: Application to the Amtoudi Oasis in southern Morocco, northern Sahara.

    Science.gov (United States)

    Alcalá, Francisco J; Martínez-Valderrama, Jaime; Robles-Marín, Pedro; Guerrera, Francesco; Martín-Martín, Manuel; Raffaelli, Giuliana; de León, Julián Tejera; Asebriy, Lahcen

    2015-12-15

    A hydrological-economic model is introduced to describe the dynamics of groundwater-dependent economics (agriculture and tourism) for sustainable use in sparse-data drylands. The Amtoudi Oasis, a remote area in southern Morocco, in the northern Sahara attractive for tourism and with evidence of groundwater degradation, was chosen to show the model operation. Governing system variables were identified and put into action through System Dynamics (SD) modeling causal diagrams to program basic formulations into a model having two modules coupled by the nexus 'pumping': (1) the hydrological module represents the net groundwater balance (G) dynamics; and (2) the economic module reproduces the variation in the consumers of water, both the population and tourists. The model was operated under similar influx of tourists and different scenarios of water availability, such as the wet 2009-2010 and the average 2010-2011 hydrological years. The rise in international tourism is identified as the main driving force reducing emigration and introducing new social habits in the population, in particular concerning water consumption. Urban water allotment (PU) was doubled for less than a 100-inhabitant net increase in recent decades. The water allocation for agriculture (PI), the largest consumer of water, had remained constant for decades. Despite that the 2-year monitoring period is not long enough to draw long-term conclusions, groundwater imbalance was reflected by net aquifer recharge (R) less than PI+PU (Gtechnology actions are tentatively proposed to mitigate groundwater degradation, such as: wastewater capture, treatment, and reuse for irrigation; storm-water harvesting for irrigation; and active maintenance of the irrigation system to improve its efficiency.

  8. Artificial wetlands as tools for frog conservation: stability and variability of reproduction characteristics in Sahara frog populations in Tunisian man-made lakes.

    Science.gov (United States)

    Bellakhal, Meher; Neveu, André; Fertouna-Bellakhal, Mouna; Aleya, Lotfi

    2017-09-27

    Amphibian populations are in decline principally due to climate change, environmental contaminants, and the reduction in wetlands. Even though data concerning current population trends are scarce, artificial wetlands appear to play a vital role in amphibian conservation. This study concerns the reproductive biology of the Sahara frog over a 2-year period in four Tunisian man-made lakes. Each month, gonad state (parameters: K, GSI, LCI), fecundity, and fertility of females (using 1227 clutches) were evaluated in the field under controlled conditions. Clutches were present for 110-130 days at two of the sites, but only for 60-80 days at the other two. Maximum egg laying occurred in May, corresponding to the highest point in the gonad somatic index. Clutch densities were higher in the smaller lakes. Female fecundity was in relation to body size; mean clutch fecundity attained 1416 eggs, with no differences observed according to site. Egg fertility varied over a 1-year period, with a maximum in May followed by a decrease when water temperature was at its highest. Eggs were smaller at the beginning of spawning; maximum size was in May, which might explain the higher fertility, but no maternal influence was detected. Embryonic development was strictly dependent on temperature. The population at each site appeared as a small patch within a metapopulation in overall good health, as shown by the relative temporal stability in reproduction variables. Constructed wetlands may therefore play an important role in the conservation of amphibians, especially in semi-arid zones.

  9. The effects of the final stages of the Late Ordovician glaciation on marine palynomorphs (chitinozoans, acritarchs, leiospheres) in well Nl-2 (NE Algerian Sahara).

    Science.gov (United States)

    Paris, F; Bourahrouh, A; Hérissé, A L.

    2000-12-01

    Palynomorph assemblages, especially chitinozoans and acritarchs, from the Upper Ordovician of well Nl-2 (north-east of the Algerian Sahara) are studied in order to precisely date the ultimate effects of the Late Ordovician glaciation and to document the impact of this major climatic stress on the diversity of the palynoplankton. References are made to stable isotope excursions and to global eustatic sea level variations in order to improve the local age determination. The Hassi el Hadjar Formation, i.e. glacio-marine diamictites, is interpreted as a transgressive event resulting from the melting of the northern Gondwana ice cap. It yields poorly preserved and moderately diverse chitinozoans of late Hirnantian age. Acritarchs are more abundant in the lower part of these "microconglomeratic clays", but display a low diversity and are badly preserved throughout the whole formation. Reworked individuals are recorded in both groups. The marine sediments of the M'Kratta Formation of latest Hirnantian age contain better preserved, more abundant and more diverse palynomorph assemblages, especially in the Upper Member. The composition of this palynoplankton indicates a fairly good faunal and phytoplankton recovery after the early Hirnantian climatic stress.The extinction of the Ordovician forms, and the appearance of Silurian type taxa occur only in the uppermost Hirnantian, i.e. following with a slight delay the glacial event. The overlying black shales of Wenlock age (lower part of the Oued Mehaiguène Formation) are indicative of marine anoxic environments. They yield a virtually exclusive, but enormous number of Tasmanacea. The very peculiar composition of this palynoplankton seems to be independent of the Late Ordovician glaciation and is most likely related to the factors that, later, generated and maintained anoxic conditions in this area.A new species of chitinozoan, Spinachitina oulebsiri sp. nov. from the latest Hirnantian M'Kratta Formation, is described and

  10. Soluble iron nutrients in Saharan dust over the central Amazon rainforest

    Science.gov (United States)

    Rizzolo, Joana A.; Barbosa, Cybelli G. G.; Borillo, Guilherme C.; Godoi, Ana F. L.; Souza, Rodrigo A. F.; Andreoli, Rita V.; Manzi, Antônio O.; Sá, Marta O.; Alves, Eliane G.; Pöhlker, Christopher; Angelis, Isabella H.; Ditas, Florian; Saturno, Jorge; Moran-Zuloaga, Daniel; Rizzo, Luciana V.; Rosário, Nilton E.; Pauliquevis, Theotonio; Santos, Rosa M. N.; Yamamoto, Carlos I.; Andreae, Meinrat O.; Artaxo, Paulo; Taylor, Philip E.; Godoi, Ricardo H. M.

    2017-02-01

    The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m-3), Fe(II) (16 ng m-3), Na (470 ng m-3), Ca (194 ng m-3), K (65 ng m-3), and Mg (89 ng m-3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the

  11. Conflict resolution in Western Sahara

    African Journals Online (AJOL)

    2003). In the State of the Union (United States Government 2005b), President ... must invest in the health and education of their people, and take responsibility for solving ... Peruvian diplomat held a 24-year long career at the UN system. ..... perception is that time is running in favour of Morocco, which is investing in the.

  12. A taxonomic study of the genus Tuarega Uvarov, 1943 with descriptions of two new species from Sahara (Orthoptera: Acridoidea, Pamphagidae, Prionotropisinae)%土尔蝗属分类研究及撒哈拉地区二新种记述(直翅目:蝗总科:癞蝗科:锯癞蝗亚科)

    Institute of Scientific and Technical Information of China (English)

    印象初; 李新江

    2011-01-01

    本文对土尔蝗属Tuarega Uvarov,1943进行了分类研究,记述了撒哈拉地区2新种--撒哈拉土尔蝗Tuarega sahara sp.nov.和巴氏土尔蝗Tuarega parisi sp.nov.,并编制了该属3个已知种的检索表.新种模式标本保存于西班牙国立自然博物馆(Museo Nacional de Ciencias Naturales).%This paper deals with a taxonomic study of the genus Tuarega Uvarov, 1943, with 2 new species, namely Tuarega sahara sp.nov.and Tuarega parisi sp.nov., from Sahara described.T.sahara sp.nov.is similar to T.insignis ( Lucas, 1851 ), but it differs from the latter in four characters: the widest width of pronotum longer than length of metazona, median vein of tegmen not combined with cubital vein, radius vein of tegmen with 5 branches, cubital vein of tegmen with 2 branches.T.parisi sp.nov.is similar to T.insignis, but it differs from the latter in four characters: the widest width of pronotum longer than length of metazona, median vein of tegmen not combined with cubital vein, median vein of tegmen with 2 branches, eubital vein of tegmen with 2 branches.It is also similar to T.sahara sp.nov., but it differs from the latter by radius vein of tegmen with 7 branches and median vein of tegmen with 2 branches.A key to all known species of Tuarega is given.The type speeimens are deposited in the Spanish National Museum of Natural Sciences ( Museo Nacional de Cieneias Naturales, MNCN).

  13. GRACE-Based Analysis of Total Water Storage Trends and Groundwater Fluctuations in the North-Western Sahara Aquifer System (NWSAS) and Tindouf Aquifer in Northwest Africa

    Science.gov (United States)

    Lezzaik, K. A.; Milewski, A.

    2013-12-01

    Optimal water management practices and strategies, in arid and semi-arid environments, are often hindered by a lack of quantitative and qualitative understanding of hydrological processes. Moreover, progressive overexploitation of groundwater resources to meet agricultural, industrial, and domestic requirements is drawing concern over the sustainability of such exhaustive abstraction levels, especially in environments where groundwater is a major source of water. NASA's GRACE (gravity recovery and climate change experiment) mission, since March 2002, has advanced the understanding of hydrological events, especially groundwater depletion, through integrated measurements and modeling of terrestrial water mass. In this study, GLDAS variables (rainfall rate, evapotranspiration rate, average soil moisture), and TRMM 3B42.V7A precipitation satellite data, were used in combination with 95 GRACE-generated gravitational anomalies maps, to quantify total water storage change (TWSC) and groundwater storage change (GWSC) from January 2003 to December 2010 (excluding June 2003), in the North-Western Sahara Aquifer System (NWSAS) and Tindouf Aquifer System in northwestern Africa. Separately processed and computed GRACE products by JPL (Jet Propulsion Laboratory, NASA), CSR (Center of Space Research, UT Austin), and GFZ (German Research Centre for Geoscience, Potsdam), were used to determine which GRACE dataset(s) best reflect total water storage and ground water changes in northwest Africa. First-order estimates of annual TWSC for NWSAS (JPL: +5.297 BCM; CSR: -5.33 BCM; GFZ: -9.96 BCM) and Tindouf Aquifer System (JPL: +1.217 BCM; CSR: +0.203 BCM; GFZ: +1.019 BCM), were computed using zonal averaging over a span of eight years. Preliminary findings of annual GWSC for NWSAS (JPL: +2.45 BCM; CSR: -2.278 BCM; GFZ: -6.913 BCM) and Tindouf Aquifer System (JPL: +1.108 BCM; CSR: +0.094 BCM; GFZ: +0.910 BCM), were calculating using a water budget approach, parameterized by GLDAS

  14. François Paris, Les sépultures du Sahara nigérien du Néolithique à l'islamisation, Paris, ORSTOM, 1996, 2 vols., 376 p., 275 p.

    Directory of Open Access Journals (Sweden)

    Gabriel Camps

    2005-01-01

    Full Text Available Les nombreuses campagnes de fouilles entreprises par F. Paris au Niger, ont abouti à la rédaction de cet ouvrage en deux tomes. Le premier, de 376 pages est la présentation des travaux réalisés dans le Sahara nigérien, l'Azawagh, l'Aïr, le Djado… L'étude du vaste bassin de l'Azawagh et de l'importance de ses réserves en eau, permet de définir le grand épisode humide du début de l'Holocène (8000-6500 av. J.-C. Un épisode aride se situe entre 5500 et 4500 av. J.-C.. Un autre épisode, de moindr...

  15. Central bank Financial Independence

    OpenAIRE

    J.Ramon Martinez-Resano

    2004-01-01

    Central bank independence is a multifaceted institutional design. The financial component has been seldom analysed. This paper intends to set a comprehensive conceptual background for central bank financial independence. Quite often central banks are modelled as robot like maximizers of some goal. This perspective neglects the fact that central bank functions are inevitably deployed on its balance sheet and have effects on its income statement. A financially independent central bank exhibits ...

  16. Central venous catheter - flushing

    Science.gov (United States)

    ... during cancer treatment Bone marrow transplant - discharge Central venous catheter - dressing change Peripherally inserted central catheter - flushing Sterile technique Surgical wound care - open Review Date 9/22/2016 Updated by: ...

  17. NIDDK Central Repository

    Data.gov (United States)

    U.S. Department of Health & Human Services — The NIDDK Central Repository stores biosamples, genetic and other data collected in designated NIDDK-funded clinical studies. The purpose of the NIDDK Central...

  18. Central Neuropathic Pain Syndromes.

    Science.gov (United States)

    Watson, James C; Sandroni, Paola

    2016-03-01

    Chronic pain is common in patients with neurologic complications of a central nervous system insult such as stroke. The pain is most commonly musculoskeletal or related to obligatory overuse of neurologically unaffected limbs. However, neuropathic pain can result directly from the central nervous system injury. Impaired sensory discrimination can make it challenging to differentiate central neuropathic pain from other pain types or spasticity. Central neuropathic pain may also begin months to years after the injury, further obscuring recognition of its association with a past neurologic injury. This review focuses on unique clinical features that help distinguish central neuropathic pain. The most common clinical central pain syndromes-central poststroke pain, multiple sclerosis-related pain, and spinal cord injury-related pain-are reviewed in detail. Recent progress in understanding of the pathogenesis of central neuropathic pain is reviewed, and pharmacological, surgical, and neuromodulatory treatments of this notoriously difficult to treat pain syndrome are discussed.

  19. Central Nervous System Vasculitis

    Science.gov (United States)

    ... Nervous System (CNS) Vasculitis Central Nervous System (CNS) Vasculitis Central nervous system (CNS) vasculitis is inflammation of ... CNS (PACNS). What is the cause of CNS Vasculitis? How the vessels in the brain become inflamed ...

  20. Kouzmine Yaël, Le Sahara algérien. Intégration nationale et développement régional, L’Harmattan, Paris, 2012, 341 p.Mcdougall James and SCHEELE Judith (Ed., Saharan Frontiers. Space and Mobility in Northwest Africa, Indiana University Press, Bloomington, 2012, 291 p.

    Directory of Open Access Journals (Sweden)

    Vincent Bisson

    2014-05-01

    Full Text Available En ces temps de menace terroriste qui ont poussé nombre d’Occidentaux à déserter l’espace saharien, on se réjouira de la parution de deux ouvrages consacrés au Sahara : le premier du géographe Y. Kouzmine, qui dresse un tableau exhaustif de cinquante ans de politiques d’intégration et de développement au Sahara algérien ; le second, un ouvrage collectif dirigé par les Britanniques J. McDougall et J. Scheele, qui traite de mobilités et de barrières – culturelles, sociales, économiques et terri...

  1. ‘Everybody knows’, but the rest of the world: the case of a caterpillar-borne reproductive loss syndrome in dromedary camels observed by Sahrawi pastoralists of Western Sahara

    Directory of Open Access Journals (Sweden)

    Volpato Gabriele

    2013-01-01

    Full Text Available Abstract Background The traditional knowledge of local communities throughout the world is a valuable source of novel ideas and information to science. In this study, the ethnoveterinary knowledge of Sahrawi pastoralists of Western Sahara has been used in order to put forward a scientific hypothesis regarding the competitive interactions between camels and caterpillars in the Sahara ecosystem. Methods Between 2005 and 2009, 44 semi-structured interviews were conducted with Sahrawi pastoralists in the territories administered by the Sahrawi Arab Democratic Republic, Western Sahara, using a snow-ball sampling design. Results Sahrawi pastoralists reported the existence of a caterpillar-borne reproductive loss syndrome, known locally as duda, affecting their camels. On the basis of Sahrawi knowledge about duda and of a thorough literature review, we built the hypothesis that: 1 caterpillars of the family Lasiocampidae (genera Lasiocampa, Psilogaster, or Streblote have sudden and rare outbreaks on Acacia treetops in the Western Sahara ecosystem after heavy rainfall; 2 during these outbreaks, camels ingest the caterpillars while browsing; 3 as a consequence of this ingestion, pregnant camels have sudden abortions or give birth to weaklings. This hypothesis was supported by inductive reasoning built on circumstantiated evidence and analogical reasoning with similar syndromes reported in mares in the United States and Australia. Conclusions The possible existence of a caterpillar-borne reproductive loss syndrome among camels has been reported for the first time, suggesting that such syndromes might be more widespread than what is currently known. Further research is warranted to validate the reported hypothesis. Finally, the importance of studying folk livestock diseases is reinforced in light of its usefulness in revealing as yet unknown biological phenomena that would deserve further investigation. Resumen ‘Todos lo saben’, menos el resto del

  2. ‘Everybody knows’, but the rest of the world: the case of a caterpillar-borne reproductive loss syndrome in dromedary camels observed by Sahrawi pastoralists of Western Sahara

    Science.gov (United States)

    2013-01-01

    Background The traditional knowledge of local communities throughout the world is a valuable source of novel ideas and information to science. In this study, the ethnoveterinary knowledge of Sahrawi pastoralists of Western Sahara has been used in order to put forward a scientific hypothesis regarding the competitive interactions between camels and caterpillars in the Sahara ecosystem. Methods Between 2005 and 2009, 44 semi-structured interviews were conducted with Sahrawi pastoralists in the territories administered by the Sahrawi Arab Democratic Republic, Western Sahara, using a snow-ball sampling design. Results Sahrawi pastoralists reported the existence of a caterpillar-borne reproductive loss syndrome, known locally as duda, affecting their camels. On the basis of Sahrawi knowledge about duda and of a thorough literature review, we built the hypothesis that: 1) caterpillars of the family Lasiocampidae (genera Lasiocampa, Psilogaster, or Streblote) have sudden and rare outbreaks on Acacia treetops in the Western Sahara ecosystem after heavy rainfall; 2) during these outbreaks, camels ingest the caterpillars while browsing; 3) as a consequence of this ingestion, pregnant camels have sudden abortions or give birth to weaklings. This hypothesis was supported by inductive reasoning built on circumstantiated evidence and analogical reasoning with similar syndromes reported in mares in the United States and Australia. Conclusions The possible existence of a caterpillar-borne reproductive loss syndrome among camels has been reported for the first time, suggesting that such syndromes might be more widespread than what is currently known. Further research is warranted to validate the reported hypothesis. Finally, the importance of studying folk livestock diseases is reinforced in light of its usefulness in revealing as yet unknown biological phenomena that would deserve further investigation. Resumen ‘Todos lo saben’, menos el resto del mundo: el caso de un s

  3. Central Laboratories Services

    Data.gov (United States)

    Federal Laboratory Consortium — The TVA Central Laboratories Services is a comprehensive technical support center, offering you a complete range of scientific, engineering, and technical services....

  4. Central Pain Syndrome

    Science.gov (United States)

    ... or hands. Central pain syndrome often begins shortly after the causative injury or damage, but may be delayed by months or even years, especially if it is related to post-stroke pain. × Definition Central pain syndrome is a neurological ...

  5. Optimal central bank transparency

    NARCIS (Netherlands)

    van der Cruijsen, C.A.B.; Eijffinger, S.C.W.; Hoogduin, L.

    2008-01-01

    Should central banks increase their degree of transparency any further? We show that there is likely to be an optimal intermediate degree of central bank transparency. Up to this optimum more transparency is desirable: it improves the quality of private sector inflation forecasts. But beyond the opt

  6. Optimal central bank transparency

    NARCIS (Netherlands)

    van der Cruijsen, C.A.B.; Eijffinger, S.C.W.; Hoogduin, L.H.

    2010-01-01

    Should central banks increase their degree of transparency any further? We show that there is likely to be an optimal intermediate degree of central bank transparency. Up to this optimum more transparency is desirable: it improves the quality of private sector inflation forecasts. But beyond the opt

  7. Central centrifugal cicatricial alopecia

    Directory of Open Access Journals (Sweden)

    Collin Blattner

    2013-01-01

    Full Text Available Central centrifugal cicatricial alopecia is a common cause of progressive permanent apical alopecia. This unique form of alopecia includes entities previously know as "hot comb alopecia," "follicular degeneration syndrome," "pseudopelade" in African Americans and "central elliptical pseudopelade" in Caucasians. The etiology appears to be multifactorial and the condition occurs in all races.

  8. Imaging central pain syndromes.

    Science.gov (United States)

    Veldhuijzen, Dieuwke S; Greenspan, Joel D; Kim, Jong H; Coghill, Robert C; Treede, Rolf-Detlef; Ohara, Shinji; Lenz, Frederick A

    2007-06-01

    Anatomic, functional, and neurochemical imaging studies have provided new investigative tools in the study of central pain. High-resolution imaging studies allow for precise determination of lesion location, whereas functional neuroimaging studies measure pathophysiologic consequences of injury to the central nervous system. Additionally, magnetic resonance spectroscopy evaluates lesion-induced neurochemical changes in specific brain regions that may be related to central pain. The small number of studies to date precludes definitive conclusions, but the recent findings provide information that either supports or refutes current hypotheses and can serve to generate new ideas.

  9. The central peak revisited

    Energy Technology Data Exchange (ETDEWEB)

    Shirane, G.

    1995-10-27

    The central peak in SrTiO{sub 3} was first observed by Riste and his collaborators in 1971. This was one of the key discoveries leading to an understanding of the dynamics of phase transitions. The most recent discovery of two length scales in SrTiO{sub 3} motivated a reinvestigation of the soft phonon and associated central peak by neutron scattering. These recent experiments shed new light on the nature of the central peak. It is now well established to be strongly sample dependent and it originates from defects in bulk crystals.

  10. Central nervous system

    Science.gov (United States)

    The central nervous system is composed of the brain and spinal cord. Your brain and spinal cord serve as the main "processing center" for your entire nervous system. They control all the workings of your body.

  11. Central nervous system resuscitation

    DEFF Research Database (Denmark)

    McIntosh, T K; Garde, E; Saatman, K E

    1997-01-01

    Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities...

  12. "Central Station" Londonis

    Index Scriptorium Estoniae

    2000-01-01

    Londoni galeriis Milch seitsme läti, leedu ja eesti kunstniku projekt "Central Station". Kuraatorid Lisa Panting, Sally Tallant. Eestist osalevad Hanno Soans (Catarina Campinoga koostöös valminud video), Kiwa, Kai Kaljo

  13. "Central Station" Londonis

    Index Scriptorium Estoniae

    2000-01-01

    Londoni galeriis Milch seitsme läti, leedu ja eesti kunstniku projekt "Central Station". Kuraatorid Lisa Panting, Sally Tallant. Eestist osalevad Hanno Soans (Catarina Campinoga koostöös valminud video), Kiwa, Kai Kaljo

  14. Central Asian Republic Info

    Data.gov (United States)

    US Agency for International Development — CAR Info is designed and managed by the Central Asian Republic Mission to fill in the knowledge and reporting gaps in existing agency systems for that Mission. It...

  15. Central oxygen pipeline failure

    African Journals Online (AJOL)

    Anaesthetic and critical care staff play a governing role in the comprehension of a ... complete central oxygen pipeline failure occurred throughout. Tygerberg Hospital. ..... emergency stations and at plant room emergency supply manifolds.

  16. Central nervous system resuscitation

    DEFF Research Database (Denmark)

    McIntosh, T K; Garde, E; Saatman, K E;

    1997-01-01

    Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities ...

  17. Central Station Design Options

    DEFF Research Database (Denmark)

    2011-01-01

    The purpose of EDISON Work Package 4.1 is the evaluation of possible Central (charging) Stations design options for making possible the public charging of Electric Vehicles (EVs). A number of scenarios for EVs are assessed, with special emphasis on the options of Fast Charging and Battery Swapping....... The work identifies the architecture, sizing and siting of prospective Central Stations in Denmark, which can be located at shopping centers, large car parking lots or gas stations. Central Stations are planned to be integrated in the Danish distribution grid. The Danish island of Bornholm, where a high.......g. due to vandalism, the charge supply circuit is disconnected. More electrical vehicles on the market are capable today of quick charging up to 50 kW power level. The feasibility of Central Stations with fast charging/swapping option, their capacity, design, costs and grid impact, as well as battery...

  18. Downscaling precipitation in the Sahara-Sahelian region during the Holocene in order to decipher the paleo-variations of Lake Chad

    Science.gov (United States)

    Contoux, Camille; Bondeau, Alberte; Barrier, Nicolas; Sylvestre, Florence

    2016-04-01

    In order to understand the paleo-variability of Saharo-Sahelian paleoprecipitation, which is recorded in the sediments of Lake Chad situated in central Sahel, we use a modelling chain going from global climate to basin-scale hydrological model. Namely, climate model outputs for the Holocene, starting with the mid-Holocene (6ka) available from the IPSL-CM5 global climate model are statistically downscaled with the General Additive Model approach (Levavasseur et al., 2011), then used to feed the LPJmL model (Bondeau et al., 2007) which calculates the equilibrium vegetation and runoff. Climate and runoff are then given to the dynamic routing scheme HYDRA (Coe et al., 2000) in order to calculate the paleo river network and paleo extent of Lake Chad. The results at each step are compared with reconstructions derived from continental proxies on the regional scale in order to assess the robustness of the results. For the mid-Holocene, the downscaled precipitation matches very well precipitation estimations derived from lacustrine pollen data. For the historical period, the LPJmL simulated runoff averaged over the Chad basin depicts the same trend than observations of Lake Chad water level, but the absolute water level is overestimated in HYDRA, which can be attributed to humid biases both in LPJmL and HYDRA. Finally, we will investigate the relative changes in river network and Lake Chad extent between the present and the mid-Holocene.

  19. Outsourcing central banking

    DEFF Research Database (Denmark)

    Khoury, Sarkis Joseph; Wihlborg, Clas

    2005-01-01

    The literature on Currency Boards (CB) stops at the water edge in terms of dealing with the totality of the functions of a central bank. Monetary policy, and banking supervisioncan be "outsourced" in an open economy with substantial foreign direct investment (FDI)in the banking sector if political...... the feasibility of, and constraints on, outsourcing of central bank functions. A brief discussion of the Argentinian experience is used for contrast.Key words: Currency Board, Foreign Banks, Supervision, Regional Integration,outsourcing....

  20. Outsourcing central banking

    DEFF Research Database (Denmark)

    Khoury, Sarkis Joseph; Wihlborg, Clas

    2005-01-01

    The literature on Currency Boards (CB) stops at the water edge in terms of dealing with the totality of the functions of a central bank. Monetary policy, and banking supervisioncan be "outsourced" in an open economy with substantial foreign direct investment (FDI)in the banking sector if political...... the feasibility of, and constraints on, outsourcing of central bank functions. A brief discussion of the Argentinian experience is used for contrast.Key words: Currency Board, Foreign Banks, Supervision, Regional Integration,outsourcing....

  1. Gangs in Central America

    Science.gov (United States)

    2008-10-17

    Citizen Security held in July 2008 indicated that Guatemala now has the second highest murder rate in Central America (roughly 45 per 100,000 people...training regional security forces.48 In recent years, the U.S. Southern Command has taken a leading role in discussing the problem of citizen security in...the results CRS-19 51 “Memo: The Merida Initiative and Citizen Security in Mexico and Central America,” Washington Office on Latin America, March 2008

  2. Lacustrine sediments and Holocene climates in the southern Sahara: the example of paleolakes in the Grand Erg of Bilma (Zoo Baba and Dibella, eastern Niger)

    Science.gov (United States)

    Grunert, J.; Baumhauer, R.; Völkel, J.

    Two endoreic depressions of the central Erg of Bilma/eastern Republic of Niger are described here. Special interest is given to widespread lacustrine sediments (diatomites) in the depressions, indicating paleolakes with an extension of some 10 km 2. The minimum depth of the lakes has been found to be 25 m (Zoo Baba) and 36 m (Dibella). At Dibella there is evidence of two lacustrine phases of Early Holocene (9785-7890 years B.P.) and of Mid-Holocene age (about 6500 years B.P.). At Zoo Baba only one lacustrine phase of Mid-Holocene age (about 6000-5370 years B.P.) can be proven for Zoo Baba. The difference between the Early- and Mid-Holocene diatomites Di I and Di II is based not only on radiocarbon data but also on geomorphological characteristics. Despite the small distance of only 70 km between the two depressions, the reconstruction of pluvial water chemistry particularly by analyzing the diatoms shows great differences. The Mid-Holocene Zoo Baba lake was a freshwater lake; the Early- and Mid-Holocene Dibella lakes obviously contained brackish water with great fluctuations of salinity. An explanation may be given by the varying groundwater influence during the pluvial periods. It is supposed that Zoo Baba has been touched by the large Kaouar/Bilma aquifer while Dibella has been influenced by a smaller local aquifer. Any groundwater supply from Paleo-Chad can be excluded. Both the rising of groundwater table and of lake levels must have been induced by a largely increased annual precipitation rate (today 20-40 mm only), combined with a very effective reduction in evaporation rate. Based on lacrustine sediments, paleosoils and geomorphological features (fossil landslides of Zoo Baba), the Early Holocene annual precipitation rate is estimated at least at 300-400 mm, the Mid-Holocene rate at 200-300 mm. The special character of precipitations cannot be reconstructed.

  3. CENTRAL PLATEAU REMEDIATION

    Energy Technology Data Exchange (ETDEWEB)

    ROMINE, L.D.

    2006-02-01

    A systematic approach to closure planning is being implemented at the Hanford Site's Central Plateau to help achieve the goal of closure by the year 2035. The overall objective of Central Plateau remediation is to protect human health and the environment from the significant quantity of contaminated material that resulted from decades of plutonium production in support of the nation's defense. This goal will be achieved either by removing contaminants or placing the residual contaminated materials in a secure configuration that minimizes further migration to the groundwater and reduces the potential for inadvertent intrusion into contaminated sites. The approach to Central Plateau cleanup used three key concepts--closure zones, closure elements, and closure process steps--to create an organized picture of actions required to complete remediation. These actions were merged with logic ties, constraints, and required resources to produce an integrated time-phased schedule and cost profile for Central Plateau closure. Programmatic risks associated with implementation of Central Plateau closure were identified and analyzed. Actions to mitigate the most significant risks are underway while high priority remediation projects continue to make progress.

  4. Dust, Elemental Carbon and Other Impurities on Central Asian Glaciers: Origin and Radiative Forcing

    Science.gov (United States)

    Schmale, J.; Flanner, M.; Kang, S.; Sprenger, M.; Zhang, Q.; Li, Y.; Guo, J.; Schwikowski, M.

    2015-12-01

    In Central Asia, more than 60 % of the population depends on water stored in glaciers and mountain snow. While temperature, precipitation and dynamic processes are key drivers of glacial change, deposition of light absorbing impurities such as mineral dust and black carbon can lead to accelerated melting through surface albedo reduction. Here, we discuss the origin of deposited mineral dust and black carbon and their impacts on albedo change and radiative forcing (RF). 218 snow samples were taken from 13 snow pits on 4 glaciers, Abramov (Pamir), Suek, Glacier No. 354 and Golubin (Tien Shan), representing deposition between summer 2012 and 2014. They were analyzed for elemental and organic carbon by a thermo-optical method, mineral dust by gravimetry, and iron by ICP-MS. Back trajectory ensembles were released every 6 hours with the Lagranto model for the covered period at all sites. Boundary layer "footprints" were calculated to estimate general source regions and combined with MODIS fire counts for potential fire contributions. Albedo reduction due to black carbon and mineral dust was calculated with the Snow-Ice-Aerosol-Radiative model (SNICAR), and surface spectral irradiances were derived from atmospheric radiative transfer calculations to determine the RF under clear-sky and all sky conditions using local radiation measurements. Dust contributions came from Central Asia, the Arabian Peninsula, the Sahara and partly the Taklimakan. Fire contributions were higher in 2014 and generally came from the West and North. We find that EC exerts roughly 3 times more RF than mineral dust in fresh and relatively fresh snow (~5 W/m2) and up to 6 times more in snow that experienced melting (> 10 W/m2) even though EC concentrations (average per snow pit from 90 to 700 ng/g) were up to two orders of magnitude lower than mineral dust (10 to 140 μg/g).

  5. The Naive Central Banker

    Directory of Open Access Journals (Sweden)

    Marcelo de Carvalho Griebeler

    2015-09-01

    Full Text Available There has been in some countries a trend of assigning other functions to central banks besides price stability. The most suggested function to be added to monetary authority’s obligations is to pursue economic growth or full employment. In this paper we characterize the behavior and analyse the optimal monetary policy of, what we call, a naive central banker. We describe the naive behavior as one that does face the inflation-unemployment trade-off, but it tries to minimize both variables simultaneously. Our findings, both under discretion and commitment, indicate that the naive central banker delivers lower expected inflation and inflation variance than the benchmark behavior whenever the economy is rigid enough. However, the degree of conservativeness also affects this result, such that the less conservative the naive policymaker, the more rigidity is necessary.

  6. SOCRATES Invades Central Europe

    Directory of Open Access Journals (Sweden)

    Joseph Slowinski

    1998-04-01

    Full Text Available The objective of this article is to explore the current reality faced by higher education students in Central and Eastern Europe and to draw out the implications of this current reality for policy makers in the future. In the article, I explore the influence of transnational corporations' training programs on education as it currently pertains to Central and Eastern European higher education and employment. In addition, multinational corporate entities exercise influence on European Union policy through the role of lobby organizations and activities. I explore the influence of these practices on education with an emphasis on the emerging importance of Western language skills. In addition, I focus on the European Union and its efforts to expand into Central and Eastern Europe in order to provide a focal point for analysis.

  7. Central Bank independence

    Directory of Open Access Journals (Sweden)

    Vasile DEDU

    2012-08-01

    Full Text Available In this paper we present the key aspects regarding central bank’s independence. Most economists consider that the factor which positively influences the efficiency of monetary policy measures is the high independence of the central bank. We determined that the National Bank of Romania (NBR has a high degree of independence. NBR has both goal and instrument independence. We also consider that the hike of NBR’s independence played an important role in the significant disinflation process, as headline inflation dropped inside the targeted band of 3% ± 1 percentage point recently.

  8. Glueballs A central mystery

    CERN Document Server

    Close, Frank E.

    2000-01-01

    Glueball candidates and qqbar mesons have been found to be produced with different momentum and angular dependences in the central region of pp collisions. This talk illustrates this phenomenon and explains the phi and t dependences of mesons with JPC = 0++,0-+, 1++, 2++ and 2-+. For production of 0++ and 2++ mesons the analysis reveals a systematic behaviour in the data that appears to distinguish between qqbar and non-qqbar or glueball candidates. An explanation is given for the absence of 0-+ glueball candidates in central production at present energies and the opportunity for their discovery at RHIC is noted.

  9. Several Centuries of Centrality

    OpenAIRE

    Roth, Dana L.

    2015-01-01

    As Carolyn Bertozzi mentioned in her inaugural editorial, the relationship of “Central Science” to “Chemistry” became popularized over 40 years ago with the publication of the first edition of Brown and LeMay’s Chemistry: The Central Science, now in its 13th edition. Yet as late as 2003, Prof. Sason Shaik at The Hebrew University claimed “popularization of chemistry remains scant.” He goes on to share [his] “own experience of popularizing chemistry by delivering the following universal messag...

  10. Glueballs A central mystery

    CERN Document Server

    Close, Francis Edwin

    2000-01-01

    Glueball candidates and qqbar mesons have been found to be produced with different momentum and angular dependences in the central region of pp collisions. This talk illustrates this phenomenon and explains the phi and t dependences of mesons with JPC = 0++,0-+, 1++, 2++ and 2-+. For production of 0++ and 2++ mesons the analysis reveals a systematic behaviour in the data that appears to distinguish between qqbar and non-qqbar or glueball candidates. An explanation is given for the absence of 0-+ glueball candidates in central production at present energies and the opportunity for their discovery at RHIC is noted.

  11. Long term aerosol and trace gas measurements in Central Amazonia

    Science.gov (United States)

    Artaxo, Paulo; Barbosa, Henrique M. J.; Ferreira de Brito, Joel; Carbone, Samara; Rizzo, Luciana V.; Andreae, Meinrat O.; Martin, Scot T.

    2016-04-01

    The central region of the Amazonian forest is a pristine region in terms of aerosol and trace gases concentrations. In the wet season, Amazonia is actually one of the cleanest continental region we can observe on Earth. A long term observational program started 20 years ago, and show important features of this pristine region. Several sites were used, between then ATTO (Amazon Tall Tower Observatory) and ZF2 ecological research site, both 70-150 Km North of Manaus, receiving air masses that traveled over 1500 km of pristine tropical forests. The sites are GAW regional monitoring stations. Aerosol chemical composition (OC/EC and trace elements) is being analysed using filters for fine (PM2.5) and coarse mode aerosol as well as Aerodyne ACSM (Aerosol Chemical Speciation Monitors). VOCs are measured using PTR-MS, while CO, O3 and CO2 are routinely measured. Aerosol absorption is being studied with AE33 aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using TSI and Ecotech nephelometers. Aerosol size distribution is determined using scanning mobility particle sizer at each site. Lidars measure the aerosol column up to 12 Km providing the vertical profile of aerosol extinction. The aerosol column is measures using AERONET sun photometers. In the wet season, organic aerosol comprises 75-85% of fine aerosol, and sulfate and nitrate concentrations are very low (1-3 percent). Aerosols are dominated by biogenic primary particles as well as SOA from biogenic precursors. Black carbon in the wet season accounts for 5-9% of fine mode aerosol. Ozone in the wet season peaks at 10-12 ppb at the middle of the day, while carbon monoxide averages at 50-80 ppb. Aerosol optical thickness (AOT) is a low 0.05 to 0.1 at 550 nm in the wet season. Sahara dust transport events sporadically enhance the concentration of soil dust aerosols and black carbon. In the dry season (August-December), long range transported

  12. Retiring the central executive.

    Science.gov (United States)

    Logie, Robert H

    2016-10-01

    Reasoning, problem solving, comprehension, learning and retrieval, inhibition, switching, updating, or multitasking are often referred to as higher cognition, thought to require control processes or the use of a central executive. However, the concept of an executive controller begs the question of what is controlling the controller and so on, leading to an infinite hierarchy of executives or "homunculi". In what is now a QJEP citation classic, Baddeley [Baddeley, A. D. (1996). Exploring the central executive. Quarterly Journal of Experimental Psychology, 49A, 5-28] referred to the concept of a central executive in cognition as a "conceptual ragbag" that acted as a placeholder umbrella term for aspects of cognition that are complex, were poorly understood at the time, and most likely involve several different cognitive functions working in concert. He suggested that with systematic empirical research, advances in understanding might progress sufficiently to allow the executive concept to be "sacked". This article offers an overview of the 1996 article and of some subsequent systematic research and argues that after two decades of research, there is sufficient advance in understanding to suggest that executive control might arise from the interaction among multiple different functions in cognition that use different, but overlapping, brain networks. The article concludes that the central executive concept might now be offered a dignified retirement.

  13. Central nervous system tuberculosis.

    Science.gov (United States)

    Torres, Carlos; Riascos, Roy; Figueroa, Ramon; Gupta, Rakesh K

    2014-06-01

    Tuberculosis (TB) has shown a resurgence in nonendemic populations in recent years and accounts for 8 million deaths annually in the world. Central nervous system involvement is one of the most serious forms of this infection, acting as a prominent cause of morbidity and mortality in developing countries. The rising number of cases in developed countries is mostly attributed to factors such as the pandemic of acquired immunodeficiency syndrome and increased migration in a globalized world. Mycobacterium TB is responsible for almost all cases of tubercular infection in the central nervous system. It can manifest in a variety of forms as tuberculous meningitis, tuberculoma, and tubercular abscess. Spinal infection may result in spondylitis, arachnoiditis, and/or focal intramedullary tuberculomas. Timely diagnosis of central nervous system TB is paramount for the early institution of appropriate therapy, because delayed treatment is associated with severe morbidity and mortality. It is therefore important that physicians and radiologists understand the characteristic patterns, distribution, and imaging manifestations of TB in the central nervous system. Magnetic resonance imaging is considered the imaging modality of choice for the study of patients with suspected TB. Advanced imaging techniques including magnetic resonance perfusion and diffusion tensor imaging may be of value in the objective assessment of therapy and to guide the physician in the modulation of therapy in these patients.

  14. Central Dogma Goes Digital.

    Science.gov (United States)

    Lin, Yihan; Elowitz, Michael B

    2016-03-17

    In this issue of Molecular Cell, Tay and colleagues (Albayrak et al., 2016) describe a new technique to digitally quantify the numbers of protein and mRNA in the same mammalian cell, providing a new way to look at the central dogma of molecular biology.

  15. Central Nervous System Tuberculosis

    OpenAIRE

    Bano, Shahina; Chaudhary, Vikas; Yadav, Sachchidanand

    2012-01-01

    Central nervous system tuberculosis is a rare presentation of active tuberculosis and accounts for about 1% of cases (1). The three clinical categories include meningitis, intracranial tuberculomas, and spinal tuberculous arachnoiditis. We report a case of a young man who presented with active pulmonary tuberculosis in addition to tuberculous meningitis and the presence of numerous intracranial tuberculomas.

  16. The central noradrenergic system

    African Journals Online (AJOL)

    2006-07-27

    Jul 27, 2006 ... The majority of central noradrenergic neurons are situated in the brainstem where they .... stimuli and to speed-up information processing.4. The influence of .... single unit activity in the locus coeruleus. Life Sci 1980;27:2231.

  17. Central venous line - infants

    Science.gov (United States)

    A central venous line (CVL) is a long, soft, plastic tube that is put into a large vein in the chest. WHY IS A CVL USED? A CVL is often put in when a baby cannot get a ... (MCC). A CVL can be used to give nutrients or medicines to a ...

  18. CMS Central Hadron Calorimeter

    OpenAIRE

    Budd, Howard S.

    2001-01-01

    We present a description of the CMS central hadron calorimeter. We describe the production of the 1996 CMS hadron testbeam module. We show the results of the quality control tests of the testbeam module. We present some results of the 1995 CMS hadron testbeam.

  19. Ecodesign in Central America

    NARCIS (Netherlands)

    Crul, M.R.M.

    2003-01-01

    This PhD thesis describes and analyses the change process started by the Ecodesign project in Central America, executed between 1998 and 2002. The project started using the concept and praxis developed in Europe. Nine ecodesign projects were performed in industry, and ecodesign was introduced to cou

  20. Company activities - central region

    Energy Technology Data Exchange (ETDEWEB)

    Ayling, G.

    2007-06-15

    The first section of the article gives an overview of exploration and new developments in the field of gold, nickel, diamond and opal mining in central Queensland. The second part looks at coal, coal seam gas and petroleum exploration and development projects in the area. 1 fig.

  1. Channeling the Central Dogma.

    Science.gov (United States)

    Calabrese, Ronald L

    2014-05-21

    How do neurons and networks achieve their characteristic electrical activity, regulate this activity homeostatically, and yet show population variability in expression? In this issue of Neuron, O'Leary et al. (2014) address some of these thorny questions in this theoretical analysis that starts with the Central Dogma.

  2. Multicultural Central Asia.

    Science.gov (United States)

    Boyle, Eric D.

    This article addresses the multicultural aspect of Central Asia in response to the discussion on diversity in U.S. classrooms. Many areas of the world are more diverse than the U.S., and these areas experience successes and failures with many of the same issues the U.S. is currently struggling with. Comparing the U.S. diversity debate with similar…

  3. Central areolar choroidal dystrophy.

    NARCIS (Netherlands)

    Boon, C.J.F.; Klevering, B.J.; Cremers, F.P.M.; Zonneveld-Vrieling, M.N.; Theelen, T.; Hollander, A.I. den; Hoyng, C.B.

    2009-01-01

    OBJECTIVE: To describe the clinical characteristics, follow-up data and molecular genetic background in a large group of patients with central areolar choroidal dystrophy (CACD). DESIGN: Retrospective case series study. PARTICIPANTS: One hundred three patients with CACD from the Netherlands. METHODS

  4. Testing for central symmetry

    NARCIS (Netherlands)

    Einmahl, John; Gan, Zhuojiong

    2016-01-01

    Omnibus tests for central symmetry of a bivariate probability distribution are proposed. The test statistics compare empirical measures of opposite regions. Under rather weak conditions, we establish the asymptotic distribution of the test statistics under the null hypothesis; it follows that they a

  5. Jónína Einarsdóttir og Þórdís Sigurðardóttir (ritstjórar: Afríka sunnan Sahara í brennidepli

    Directory of Open Access Journals (Sweden)

    Ólöf Ýrr Atladóttir

    2007-12-01

    Full Text Available Ánægjulegt hefur verið að fylgjast með því hvernig áhugi Íslendinga á málefnum þróunarlanda virðist hafa aukist á undanförnum árum. Fjölmiðlar hafa og tekið við sér; algengt er að fjallað sé um hin fátækari ríki heims á síðum dagblaða og í ljósvakamiðlum. Þróunarmál eru í deiglunni. Yfirbragð þeirra upplýsinga sem við höfum fengið hefur þó ekki breyst alveg í takti við aukið magn þeirra: Enn ber sú mynd sem dregin er upp af mannlífi í Afríku sunnan Sahara einkum keim af allsleysi og örbirgð, örvinglun og kröm. Enn er okkur innrætt sú hugmynd að í Afríku búi einsleitt fólk án menningarsérkenna og okkur er lítt veitt innsýn í sérkenni mismunandi ríkja í álfunni og ótölulegra þjóðflokka, ríkrar flóru tungumála og nýtingu margbreytilegs náttúrufars. Of oft virðist okkur ætlað að fella þann tæpa milljarð manna sem álfuna byggir undir hatt almennrar staðalmyndar af "Afríku".

  6. Do Central Banks Need Capital?

    OpenAIRE

    Peter Stella

    1997-01-01

    Central banks may operate perfectly well without capital as conventionally defined. A large negative net worth, however, is likely to compromise central bank independence and interfere with its ability to attain policy objectives. If society values an independent central bank capable of effectively implementing monetary policy, recapitalization may become essential. Proper accounting practice in determining central bank profit or loss and rules governing the transfer of the central bank’s ope...

  7. Induced, endogenous and exogenous centrality

    OpenAIRE

    Everett, Martin G.; Stephen P. Borgatti

    2010-01-01

    Centrality measures are based upon the structural position an actor has within the network. Induced centrality, sometimes called vitality measures, take graph invariants as an overall measure and derive vertex level measures by deleting individual nodes or edges and examining the overall change. By taking the sum of standard centrality measures as the graph invariant we can obtain measures which examine how much centrality an individual node contributes to the centrality of the other nodes in...

  8. Advecciones de polvo africano sobre la costa central venezolana y sus efectos sobre el desarrollo de la nubosidad

    Directory of Open Access Journals (Sweden)

    Estatio José Gutiérrez Quevedo

    2006-01-01

    Full Text Available Empleando el índice de aerosol, determinado a través de las mediciones del sensor TOMS, se ha realizado un análisis del comportamiento de las magnitudes del parámetro sobre la costa central venezolana en base al período 19972005; los resultados señalaron que se presentaron los máximos valores del índice en los meses de Julio y Agosto correspondientes a la temporada de lluvias. Para este período las masas de aire cargadas de partículas de polvo llegan al Caribe provenientes del desierto del Sahara, como lo demuestra el mapa con la distribución espacial de la mediana del índice para el mes de julio, por el contrarío existe una disminución sustancial en la cantidad de partículas dispersas sobre la troposfera venezolana en la temporada seca en donde las nubes de polvo se desplazan generalmente desde el Sahel. Los productos atmosféricos del sensor MODIS han sido utilizados para determinar la relación entre la concentración de aerosoles y el comportamiento de la nubosidad, presentando ésta una disminución en su desarrollo en presencia de valores altos del índice de aerosol principalmente en los meses de abril y mayo.

  9. Central simple Poisson algebras

    Institute of Scientific and Technical Information of China (English)

    SU Yucai; XU Xiaoping

    2004-01-01

    Poisson algebras are fundamental algebraic structures in physics and symplectic geometry. However, the structure theory of Poisson algebras has not been well developed. In this paper, we determine the structure of the central simple Poisson algebras related to locally finite derivations, over an algebraically closed field of characteristic zero.The Lie algebra structures of these Poisson algebras are in general not finitely-graded.

  10. [Central neurocytoma: case report].

    Science.gov (United States)

    Bouaziz, M; Mansour, A; Feknous, S; Yassi, F; Smati, S; Belhouchet, S; Lankar, A

    2009-12-01

    In this study, we report one case of central neurocytoma treated in our department. It is a benign tumor of the lateral ventricles of the brain with neuronal differentiation. The clinical symptoms mainly consisted in intracranial hypertension syndrome. Immunohistochemical studies are necessary for the histopathological diagnosis. The treatment of choice is surgical. To guarantee good progression, complete ablation is necessary. The clinical progression, radiological aspects, treatment, histopathology, and postoperative progression will be discussed.

  11. Centrality Measures in Networks

    CERN Document Server

    Bloch, Francis; Tebaldi, Pietro

    2016-01-01

    We show that although the prominent centrality measures in network analysis make use of different information about nodes' positions, they all process that information in an identical way: they all spring from a common family that are characterized by the same simple axioms. In particular, they are all based on a monotonic and additively separable treatment of a statistic that captures a node's position in the network.

  12. Central corneal abscess.

    Science.gov (United States)

    van Bijsterveld, O P

    1976-05-01

    Central corneal abscess developed in the experimental animal after inoculation of biologically active staphylococcal strains in a paracentral epithelial lesion of the cornea. These abscesses did not ulcerate, developed only with high inocula, occurred more frequently in immunized rabbits. A serpiginous type of ulceration did not develop at the site of the initial epithelial lesion nor at any other place in the cornea. Histologically, the lesions consisted of densely packed polymorphonuclear leukocytes between the corneal lamellae.

  13. FNAL central email systems

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Jack; Lilianstrom, Al; Pasetes, Ray; Hill, Kevin; /Fermilab

    2004-10-01

    The FNAL Email System is the primary point of entry for email destined for an employee or user at Fermilab. This centrally supported system is designed for reliability and availability. It uses multiple layers of protection to help ensure that: (1) SPAM messages are tagged properly; (2) All mail is inspected for viruses; and (3) Valid mail gets delivered. This system employs numerous redundant subsystems to accomplish these tasks.

  14. Central core disease

    Directory of Open Access Journals (Sweden)

    Jungbluth Heinz

    2007-05-01

    Full Text Available Abstract Central core disease (CCD is an inherited neuromuscular disorder characterised by central cores on muscle biopsy and clinical features of a congenital myopathy. Prevalence is unknown but the condition is probably more common than other congenital myopathies. CCD typically presents in infancy with hypotonia and motor developmental delay and is characterized by predominantly proximal weakness pronounced in the hip girdle; orthopaedic complications are common and malignant hyperthermia susceptibility (MHS is a frequent complication. CCD and MHS are allelic conditions both due to (predominantly dominant mutations in the skeletal muscle ryanodine receptor (RYR1 gene, encoding the principal skeletal muscle sarcoplasmic reticulum calcium release channel (RyR1. Altered excitability and/or changes in calcium homeostasis within muscle cells due to mutation-induced conformational changes of the RyR protein are considered the main pathogenetic mechanism(s. The diagnosis of CCD is based on the presence of suggestive clinical features and central cores on muscle biopsy; muscle MRI may show a characteristic pattern of selective muscle involvement and aid the diagnosis in cases with equivocal histopathological findings. Mutational analysis of the RYR1 gene may provide genetic confirmation of the diagnosis. Management is mainly supportive and has to anticipate susceptibility to potentially life-threatening reactions to general anaesthesia. Further evaluation of the underlying molecular mechanisms may provide the basis for future rational pharmacological treatment. In the majority of patients, weakness is static or only slowly progressive, with a favourable long-term outcome.

  15. West and Central Africa.

    Science.gov (United States)

    Lydie, N; Robinson, N J

    1998-01-01

    This article reviews scientific and other literature during the 1990s that links migration and mobility with the spread of sexually transmitted diseases (STDs), including HIV/AIDS. The focus is on key population groups linked to the spread of HIV and STDs in West and Central Africa: migrant laborers, truck drivers, itinerant traders, commercial sex workers (CSWs), and refugees. Countries with high emigration and immigration tend to have high levels of HIV infection, with the exception of Senegal. The main destination of immigrants are Senegal, Nigeria, and Cote d'Ivoire in West Africa and Cameroon, Congo, Gabon, and Congo in Central Africa. The risk of infection and the spread of HIV is variable among migrants. There is little in the literature that substantiates hypotheses about the strong association between migration and HIV-positive status. Information is needed on the duration, frequency of return visits, living conditions, sexual activities with multiple partners, and information before departure, along the routes, at final destination, and at the time of returns. Action-based research in five West African countries (Burkina Faso, Cote d'Ivoire, Mali, Niger, and Senegal) should produce results in late 1998. Comparable studies in Central Africa are unknown. Regional studies should be complemented by local studies. Prevention would benefit from studies on the relative size of these five population groups by geographic location.

  16. Distributed Assessment of Network Centrality

    CERN Document Server

    Wehmuth, Klaus

    2011-01-01

    We propose a method for the Distributed Assessment of Network CEntrality (DANCE) in complex networks. DANCE attributes to each node a volume-based centrality computed using only localized information, thus not requiring knowledge of the full network topology. We show DANCE is simple, yet efficient, in assessing node centrality in a distributed way. Our proposal also provides a way for locating the most central nodes, again using only the localized information at each node. We also show that the node rankings based on DANCE's centrality and the traditional closeness centrality correlate very well. This is quite useful given the vast potential applicability of closeness centrality, which is however limited by its high computational costs. We experimentally evaluate DANCE against a state-of-the-art proposal to distributively assess network centrality. Results attest that DANCE achieves similar effectiveness in assessing network centrality, but with a significant reduction in the associated costs for practical ap...

  17. Central African Republic.

    Science.gov (United States)

    1986-02-01

    Focus in this discussion of the Central African Republic is on: geography; the people; history and political conditions; government; the economy; foreign relations; and relations with the US. The population of the Central African Republic totaled 2.7 million in 1985 with an annual growth rate of 2.8%. The infant mortality rate is 134/1000 with life expectancy at 49 years. The Central African Republic is at almost the precise center of Africa, about 640 km from the nearest ocean. More than 70% of the population live in rural areas. There are more than 80 ethnic groups, each with its own language. The precolonial history of the area was marked by successive waves of migration, of which little is known. These migrations are responsible for the complex ethnic and linguistic patterns today. United with Chad in 1906, it formed the Oubangui-Chari-Chad colony. In 1910, it became 1 of the 4 territories of the Federation of French Equatorial Africa, along with Chad, Congo, and Gabon. After World War II, the French Constitution of 1946 inaugurated the first of a series of reforms that led eventually to complete independence for all French territories in western and equatorial Africa. The nation became an autonomous republic within the newly established French Community on December 1, 1958, and acceded to complete independence as the Central Africa Republic on August 13, 1960. The government is made up of the executive and the judicial branches. The constitution and legislature remain suspended. All executive and legislative powers, as well as judicial oversight, are vested in the chief of state. The Central African Republic is 1 of the world's least developed countries, with an annual per capita income of $310. 85% of the population is engaged in subsistence farming. Diamonds account for nearly 1/3 of export earnings; the industrial sector is limited. The US terminated bilateral assistance programs in 1979, due to the human rights violations of the Bokassa regime, but modest

  18. Quality of Sulfadoxine-Pyrimethamine Given as Antimalarial Prophylaxis in Pregnant Women in Selected Health Facilities in Central Region of Ghana

    Directory of Open Access Journals (Sweden)

    Danny F. Yeboah

    2016-01-01

    Full Text Available The use of sulfadoxine-pyrimethamine (SP as an intermittent preventive treatment (IPT against malaria during pregnancy has become a policy in most sub-Sahara African countries and crucially depends on the efficacy of SP. This study sets out to evaluate the effectiveness of the SP given to the pregnant women in some selected health facilities in the Central Region of Ghana to prevent maternal malaria in pregnant women. A total of 543 pregnant women recruited from 7 selected health centres in Central Region of Ghana participated in the study. Parasite density of Plasmodium falciparum was determined from peripheral blood of the pregnant women using microscopy. High performance liquid chromatography (HPLC and dissolution tester were used to determine the quality of the SP. Malaria infection was recorded in 11.2% of pregnant women who had a history of SP consumption. SP failed the dissolution test. Pregnant women who did not receive IPT-SP were 44%. Low haemoglobin level was recorded in 73.5% of the pregnant women. The results indicated that SP was substandard. IPT-SP is ineffective in preventing malaria infection.

  19. Central effects of fingolimod.

    Science.gov (United States)

    Cruz, Vítor T; Fonseca, Joaquim

    2014-08-01

    Introduccion. El fingolimod, un modulador del receptor de la esfingosina-1-fosfato (S1P) dotado de un mecanismo de accion novedoso, fue el primer tratamiento oral aprobado para la esclerosis multiple remitente recurrente. Su union a los receptores S1P1 de los linfocitos promueve la retencion selectiva de los linfocitos T virgenes y de memoria central en los tejidos linfoides secundarios, lo que impide su salida hacia el sistema nervioso central (SNC). Asimismo, el fingolimod atraviesa con facilidad la barrera hematoencefalica, y diversos estudios le atribuyen un efecto neuroprotector directo en el SNC. Objetivo. Revisar la informacion disponible acerca de los efectos centrales del fingolimod. Desarrollo. El desequilibrio entre los procesos lesivos y reparadores constituye un reflejo de la desmielinizacion cronica, la degeneracion axonal y la gliosis, y parece contribuir a la discapacidad que la esclerosis multiple acarrea. La facilidad con la que el fingolimod atraviesa la barrera hematoencefalica le permite actuar directamente sobre los receptores S1P localizados en las celulas del SNC. Una vez en el interior del SNC, ocupa los receptores S1P de los oligodendrocitos y de sus celulas precursoras, de los astrocitos, los microgliocitos y las neuronas, fomentando la remielinizacion, la neuroproteccion y los procesos endogenos de regeneracion. La eficacia evidenciada en los ensayos clinicos concuerda con un mecanismo de accion que incluiria efectos directos sobre las celulas del SNC. Conclusiones. Los datos disponibles indican que la eficacia del fingolimod en el tratamiento de la esclerosis multiple se debe a su ambivalencia como molecula inmunomoduladora y moduladora directa de los receptores S1P del SNC. Tanto es asi que estudios recientes le atribuyen efectos neuroprotectores en varios modelos que suscitan expectativas en torno a su posible aplicacion terapeutica en la enfermedad de Alzheimer, el paludismo cerebral y el neuroblastoma, asi como en la neuroproteccion

  20. Central venous catheter - dressing change

    Science.gov (United States)

    ... during cancer treatment Bone marrow transplant - discharge Central venous catheter - flushing Peripherally inserted central catheter - flushing Sterile technique Surgical wound care - open Review Date 9/17/2016 Updated by: ...

  1. [Central anticholinergic syndrome].

    Science.gov (United States)

    Fernández Urretavizcaya, P; Cenoz Osinaga, J C; Jáuregui Garía, M L; Gállego Culleré, J

    1991-10-01

    Two new cases of anticolinergic central syndrome are described. The first case, a 8 year old girl, suffered a severe encefalopathy after topical application of mydriatic cholirio as an aid in a rutine study of ocular refraction. The second case, 67 year old man presented a severe neurological picture after accidental intake of a silvester plantground (Atropa belladonna). His neurological condition returned quickly to normal whith administration of physostigmine. Differents aspects of the etiology, clinical picture and diagnosis are discussed with special emphasis in patients with delirium or acute confusional states. Finally, attention is drawn in the necessity of a properly use of anticholinergic drugs overcoat in aged or children.

  2. Central osteosclerosis with trichothiodystrophy

    Energy Technology Data Exchange (ETDEWEB)

    Wakeling, Emma L.; Brady, Angela F. [North West Thames Regional Genetics Service, Kennedy-Galton Centre, Level 8 V, North West London Hospitals NHS Trust, Watford Road, HAI 3UJ, Harrow, Middlesex (United Kingdom); Cruwys, Michele [Department of Paediatrics, Hillingdon Hospital, Hillingdon, Middlesex (United Kingdom); Suri, Mohnish [Clinical Genetics Service, City Hospital, Nottingham (United Kingdom); Aylett, Sarah E. [Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust, London (United Kingdom); Hall, Christine [Department of Radiology, Great Ormond Street Hospital for Children NHS Trust, London (United Kingdom)

    2004-07-01

    Trichothiodystrophy (TTD) is a rare, autosomal recessive, multisystem disorder associated with defects in nucleotide excision repair. We report a 7-year-old boy with TTD due to mutation in the XPD gene. The patient has classic features of this condition, including brittle, sulphur-deficient hair, ichthyosis, growth retardation and developmental delay. In addition, he has radiological evidence of progressive central osteosclerosis. Although similar radiological findings have previously been reported in a small number of patients, this association is not widely recognised. We review the radiological findings in this and other similar cases and discuss the natural history of these bony changes. (orig.)

  3. JPRS Report, Africa, (Sub-Sahara).

    Science.gov (United States)

    1987-08-31

    dryers , as well as some electric switchboards, is unrecoverable. Antonio Sinedinse explained that the completed part of the factory, that is, the...effects were promptly felt: the black market is losing ground everywhere while prices tumble . Moreover, the recent decree fixing the buffer stock cost at

  4. A New Climate Across the Sahara

    Institute of Scientific and Technical Information of China (English)

    Wang Jinglie

    2010-01-01

    @@ From April 11-15,Sudan held its first multi-party general elections in 24 years-one that allowed incumbent President Omar al-Bashir a victory with 68 percent of the vote. This vote was historic in terms of the Sahel nation's political development,according to Wang Jinglie,a research fellow at the Institute of West Asian and African Studies under the Chinese Academy of Social Sciences.In an article for Beijing Review,Wang,who served as a delegate member of the Chinese observation mission,wrote about Sudan's recent elections as he witnessed it,as well as the pressing challenges facing the nation.

  5. The Trans-Sahara Counterterrorism Partnership

    Science.gov (United States)

    2007-04-01

    Casablanca   and  plots  have  been  disrupted in Italy, France, Spain, and the United Kingdom.9 These groups’ memberships are not  limited by national...and  values  while building positive  impressions of the United States. This is an ambitious program with enormous potential, but it  has a great number...training,  supporting  girls’  scholarship  funds, promoting transparency in governance, and providing support and training  for  community  radio

  6. 178 MULTIPLE COLONIALISM IN WESTERN SAHARA Macharia ...

    African Journals Online (AJOL)

    Administrator

    1956-07-07

    6 Sidi M. Omar, “The Right of Self-Determination and the Indigenous People of .... Saguia el-Hamra wa Oued ed-Dahab (Organisation of the Liberation of .... given voice by Istiqlal leader Allal el-Fassi on July 7, 1956 when he published a map.

  7. JPRS Report Africa (Sub-Sahara).

    Science.gov (United States)

    1987-10-01

    downfall of Luis Cabral in Guinea-Bissau). The movement consists of three basic vectors : the challenge of the Catholic Church, which has been in open...development of Niger both in terms of the recovery of investments and of government spending, became the main vector on which the crisis was transmitted. As...sub-prefect of Say, Mr Abara Zika , and officials of the university and heard a report on the various problems facing the institution. Impressed with

  8. JPRS Report Africa (Sub-Sahara)

    Science.gov (United States)

    2007-11-02

    DISTRIBUTION STATEMENT A Approved for public releases Dfanäbatloa Unlimited REPRODUCED BY U.S. DEPARTMENT OF COMMERCE NATIONAL TECHNICAL...Carina La Grange; THE STAR, 3 Nov 8/j ^ S&T Gallium Arsenide Quantum Well Described [ ELECTRONIQUE ACTUALITTES, 18 Sep 87] 34 ZAMBIA Farmers

  9. JPRS Report Africa (Sub-Sahara)

    Science.gov (United States)

    2007-11-02

    second-phase negotia- tions for financing are already under way with UNIDO and the World Bank. In connection with the negotiations, two World Bank...on l to be no better than a Clinic because there is hot doctor is very pathe- tic . In fact, it generates negative reaction to mo- dern medicine

  10. JPRS Report, Africa, (Sub-Sahara).

    Science.gov (United States)

    1987-09-01

    the founding of FAPLA, we talked to Lieutenant Colonel Macedo de Morais Domingos Violencia , who briefed us on the activities carried out since last...August to this present date, [Begin Violencia recording] In this military region our enemy, UNITA, does not fail to use, as part of its criminal...yet there is no social centre on the complex. Leisure time is spent in sporting activities, wat- ching videos , in cultural activities and in meeting

  11. JPRS Report Africa (Sub-Sahara)

    Science.gov (United States)

    2007-11-02

    Mecanhelas, Cuamba, Maua , Nipepe, Marrupa, Majune, Muembe and Lago. "It is estimated that the entire population of Niassa is affected by the hunger...problem as a direct consequence of the armed banditry, apart from the fact that there are displaced persons from the districts of Maua , Nipepe, Marrupa

  12. JPRS Report, Africa, (Sub-Sahara).

    Science.gov (United States)

    2007-11-02

    Municipio , placed there by infiltrated enemy agents, some of whom are already standing trial in the revolutionary court. The official reported that these...the Party Youth from the principal provincial municipios , some decisions were announced that came out of the third ordinary meeting of the Uije...and 11 37 restaurants in the municipal seat. Most of the restaurants in the municipios have been destroyed by the enemy in the service of racist

  13. JPRS Report Africa (Sub-Sahara)

    Science.gov (United States)

    1987-09-16

    821788, has produc- ed three maize crops with im- pressive yields on 400 acres gravity irrigated land. — assistance to DRSRS (ex KREMU). Remote...of ammonia fertilizer daily. The other brands of fertilizer which the plant is to produce are, urea and NPK. The plant which has a pro- duction

  14. Centralized vs. De-centralized Multinationals and Taxes

    DEFF Research Database (Denmark)

    Nielsen, Søren Bo; Raimondos-Møller, Pascalis; Schjelderup, Guttorm

    2005-01-01

    The paper examines how country tax differences affect a multinational enterprise's choice to centralize or de-centralize its decision structure. Within a simple model that emphasizes the multiple conflicting roles of transfer prices in MNEs - here, as a strategic pre-commitment device and a tax...... manipulation instrument -, we show that (de-)centralized decisions are more profitable when tax differentials are (small) large.Keywords: Centralized vs. de-centralized decisions, taxes, MNEs.JEL-Classification: H25, F23, L23....

  15. Lithic landscapes: early human impact from stone tool production on the central Saharan environment.

    Directory of Open Access Journals (Sweden)

    Robert A Foley

    Full Text Available Humans have had a major impact on the environment. This has been particularly intense in the last millennium but has been noticeable since the development of food production and the associated higher population densities in the last 10,000 years. The use of fire and over-exploitation of large mammals has also been recognized as having an effect on the world's ecology, going back perhaps 100,000 years or more. Here we report on an earlier anthropogenic environmental change. The use of stone tools, which dates back over 2.5 million years, and the subsequent evolution of a technologically-dependent lineage required the exploitation of very large quantities of rock. However, measures of the impact of hominin stone exploitation are rare and inherently difficult. The Messak Settafet, a sandstone massif in the Central Sahara (Libya, is littered with Pleistocene stone tools on an unprecedented scale and is, in effect, a man-made landscape. Surveys showed that parts of the Messak Settafet have as much as 75 lithics per square metre and that this fractured debris is a dominant element of the environment. The type of stone tools--Acheulean and Middle Stone Age--indicates that extensive stone tool manufacture occurred over the last half million years or more. The lithic-strewn pavement created by this ancient stone tool manufacture possibly represents the earliest human environmental impact at a landscape scale and is an example of anthropogenic change. The nature of the lithics and inferred age may suggest that hominins other than modern humans were capable of unintentionally modifying their environment. The scale of debris also indicates the significance of stone as a critical resource for hominins and so provides insights into a novel evolutionary ecology.

  16. Inception and demise of a Neoproterozoic ocean basin: evidence from the Ougda complex, western Hoggar (Algeria)

    Science.gov (United States)

    Dostal, J.; Caby, R.; Dupuy, C.; Mevel, C.; Owen, J. V.

    1996-12-01

    The Neoproterozoic Ougda magmatic complex occurs within platformal carbonate rocks in the western part of the Pan-African fold belt of the Tuareg shield (NW Africa). It is composed of - 800 Ma old, relatively high P-T (i.e., Grt + Cpx-bearing: P > 5 kbar; T≈900'Q, tholeiitic mafic/ultramafic cumulates and related rocks intruded by intermediate to mafic calcalkali plutons (e.g., Cpx+Hbl-bearing gabbro) and dikes. Apparent contrasts in structural level of crystallization indicate that the calc-alkali rocks are significantly younger than the tholeiites, which temporally correlate with a period of regional extension in this part of Africa. Intrusion of the calc-alkali rocks may have occurred during the formation of an arc after the tholeiitic rocks had been (diapirically?) emplaced within the shelf carbonates, and prior to (> 630 Ma) the Pan-African orogeny. Data reported herein indicate that the Ougda complex records the inception and demise of a Neoproterozoic ocean basin. Similar crustal sections have been described from collisional (e.g., Aleutian islands) and extensional (e.g., Ivreä-Verbano zone) settings, indicating that processes operating in both environments can generate nearly indistinguishable igneous suites; the prevalence of shallow-level calc-alkali rocks in both settings may mask the presence of more mafic, tholeiitic rocks at depth.

  17. Feature Centrality and Property Induction

    Science.gov (United States)

    Hadjichristidis, Constantinos; Sloman, Steven; Stevenson, Rosemary; Over, David

    2004-01-01

    A feature is central to a concept to the extent that other features depend on it. Four studies tested the hypothesis that people will project a feature from a base concept to a target concept to the extent that they believe the feature is central to the two concepts. This centrality hypothesis implies that feature projection is guided by a…

  18. en los pivotes centrales

    Directory of Open Access Journals (Sweden)

    Reynaldo Roque Rodés

    2005-01-01

    Full Text Available Se hace una revisión y comentarios sobre las ventajas y limitantes del empleo del LEPA (Low Enery Precision Aplication en los sistemas de riego de pivotes centrales. Estos sistemas o filosofía de manejo del agua para condiciones de escasez o mala calidad del líquido es una alternativa viable para la producción de alimentos. Introducida en la década del 80 en las planicies del sur de Texas, donde la alta evaporación del agua y la necesidad de regar grandes áreas con pivotes centrales obligaba a la búsqueda de una alternativa para incrementar al máximo la eficiencia de aplicación del riego. Aún en fase de estudio e introducción en Cuba para áreas específicas, puede ser una solución de incremento de los rendimientos de los cultivos, empleando menos agua y aguas con calidad limitada

  19. Central centrifugal cicatricial alopecia.

    Science.gov (United States)

    Whiting, David A; Olsen, Elise A

    2008-01-01

    A progressive scarring alopecia of the central scalp is commonly seen in young to middle-aged females of African descent. It usually starts at the vertex or mid top of the scalp and gradually spreads centrifugally, hence, the unifying term of central centrifugal cicatricial alopecia. The clinical pattern is suggestive of female pattern alopecia, but a lack of follicular pores indicative of scarring is present. It can progress for years before slowly burning out. The etiology is unknown but genetic factors may be important. It is often associated with a history of traumatic hairstyling involving heat, traction, and chemicals. However, most patients of African descent without this disorder have similar styling habits. Nonetheless, avoidance of physical and chemical trauma to the scalp hair, the use of suitable shampoos and conditioners, and the encouragement of natural hairstyles may be helpful. Any infection should be treated. Topical or intralesional corticosteroids and systemic antibiotics may be useful and topical minoxidil should be tried with the hope of preventing further scarring and encouraging regrowth of recovering follicles. Current research into the etiology of this disorder will help to foster much-needed clinical trials of therapeutic agents.

  20. Central Sumatra enjoys success

    Energy Technology Data Exchange (ETDEWEB)

    Wongsosantiko, A.

    1977-05-02

    The Sihapas group contains the most prolific oil producing zones in the Central Sumatra Basin. It represents the transgressive, coarse clastic sequence deposited during the early Miocene. Some of these sandstone grade laterally into siltstones and shales of the Telisa Formation, believed to be a major source of rock for Central Sumatra oil. Recent exploratory wells drilled between the mountain front and coastal plain areas have provided more data for stratigraphic studies. These have resulted in subdivision of the lower Miocene transgressive sequence into discrete rock-stratigraphic units. The former Sihapas Formation has subsequently been elevated to group rank and now consists of several formations with the Duri Formation as the uppermost sand unit. This study covers Caltex's areas of operation, which includes the area between the Kampar River of the south, the Barumum River to the north, the Malacca Straits to the east, and the Barisan Mt. to the west. A basic map shows the regional scene, while a stratigraphic chart shows the lithology.

  1. Centrality Measures in Urban Networks

    CERN Document Server

    Crucitti, P; Porta, S; Crucitti, Paolo; Latora, Vito; Porta, Sergio

    2005-01-01

    Centrality has revealed crucial for understanding the structural order of complex relational networks. Centrality is also relevant for various spatial factors affecting human life and behaviors in cities. We present a comprehensive study of centrality distributions over geographic networks of urban streets. Four different measures of centrality, namely closeness, betweenness, straightness and information, are compared over eighteen 1-square-mile samples of different world cities. Samples are represented by primal geographic graphs, i.e. valued graphs defined by metric rather than topologic distance where intersections are turned into nodes and streets into edges. The spatial behavior of centrality indexes over the networks is investigated graphically by means of colour-coded maps. The results indicate that a spatial analysis, that we term Multiple Centrality Assessment(MCA), grounded not a single but on a set of different centrality indices, allows an extended comprehension of the city structure, nicely captu...

  2. Orden monetario y bancos centrales Monetary order and Central Banks

    Directory of Open Access Journals (Sweden)

    Aglietta Michel

    1996-06-01

    Full Text Available Con el enfoque evolucionista e institucionalista de la economía de las convenciones francesa, este trabajo analiza el surgimiento histórico de la banca central y la creación institucional del 'arte de la banca central'. El artículo estudia los modelos formales del orden monetario, la banca libre y la banca central, y analiza los eventos históricos que llevaron a que el Banco de Inglaterra inventara el arte de manejar los bancos centrales en conjunción con el aprendizaje colectivo e institucional que lo hizo posible. Aglietta muestra que la banca central no es una creación del Estado sino una creación institucional endógena al sistema de mercado.With the evolutionist and institutionalist focus of the economics of the French conventions, this paper analyzes the historical rise of the central bank and the institutional creation of the 'art of the central bank'. The article studies formal models of the monetary order, free banking and the central bank, and analyzes the historie events that led to the Bank of England inventing the art of managing the central banks, in conjunction with the collective and institutional learning that made it possible. Aglietta shows that the central bank is not a creation of the State, but rather aninstitutional creation endogenous to the market system.

  3. UA1 central detector

    CERN Multimedia

    The UA1 central detector was crucial to understanding the complex topology of proton-antiproton events. It played a most important role in identifying a handful of Ws and Zs among billions of collisions. The detector was a 6-chamber cylindrical assembly 5.8 m long and 2.3 m in diameter, the largest imaging drift chamber of its day. It recorded the tracks of charged particles curving in a 0.7 Tesla magnetic field, measuring their momentum, the sign of their electric charge and their rate of energy loss (dE/dx). Atoms in the argon-ethane gas mixture filling the chambers were ionised by the passage of charged particles. The electrons which were released drifted along an electric field shaped by field wires and were collected on sense wires. The geometrical arrangement of the 17000 field wires and 6125 sense wires allowed a spectacular 3-D interactive display of reconstructed physics events to be produced.

  4. UA2 central calorimeter

    CERN Multimedia

    The UA2 central calorimeter measured the energy of individual particles created in proton-antiproton collisions. Accurate calibration allowed the W and Z masses to be measured with a precision of about 1%. The calorimeter had 24 slices like this one, each weighing 4 tons. The slices were arranged like orange segments around the collision point. Incoming particles produced showers of secondary particles in the layers of heavy material. These showers passed through the layers of plastic scintillator, generating light which was taken by light guides (green) to the data collection electronics. The amount of light was proportional to the energy of the original particle. The inner 23 cm of lead and plastic sandwiches measured electrons and photons; the outer 80 cm of iron and plastic sandwiches measured strongly interacting hadrons. The detector was calibrated by injecting light through optical fibres or by placing a radioactive source in the tube on the bottom edge.

  5. Performances d’une centrale à concentrateur de Fresnel de moyenne puissance sur sites Algériens

    Directory of Open Access Journals (Sweden)

    H. Beltagy

    2014-03-01

    Full Text Available L’objectif du présent travail est de caractériser une centrale à concentrateur de Fresnel de moyenne puissance (5MWe sur différents sites Algériens (Sahara, ces sites ont été choisis pour comparaison en déplaçant la centrale dans ces derniers, à savoir Hassi-R’mel, Tamanrasset, Béni-Abbes, et El Oued. Une modélisation théorique a permis la détermination du nombre optimum des miroirs à ne pas dépasser pour éviter les effets d’ombre, blocage et l’effet cosinus. Le nombre optimum de miroirs a été estimé à 40 miroirs. Par ailleurs, une simulation a été réalisée à l’échelle horaire : elle concerne l’ensoleillement, le système ‘champ’, et le système ‘récepteur’. Les résultats de la simulation sont représentés en moyenne annuels. Les rendements, la production énergétique annuelle, et le coût du kWh sont évalués. En effet, le calcul du rendement diffère d’un site à un autre avec des valeurs de 15.7%, 11.8%,11.6%, et 10.4% respectivement pour les sites Tamanrasset, El Oued, Béni-Abbes, Hassi R’mel. Les performances thermiques et les résultats technico-économiques sont évalués aussi pour ces mêmes sites.

  6. Central nervous system stimulants.

    Science.gov (United States)

    George, A J

    2000-03-01

    Three major types of CNS stimulant are currently abused in sport: amphetamine, cocaine and caffeine. Each drug type has its own characteristic mechanism of action on CNS neurones and their associated receptors and nerve terminals. Amphetamine is widely abused in sports requiring intense anaerobic exercise where it prolongs the tolerance to anaerobic metabolism. It is addictive, and chronic abuse causes marked behavioural change and sometimes psychosis. Major sports abusing amphetamine are cycling, American football, ice-hockey and baseball. Cocaine increases tolerance to intense exercise, yet most of its chronic effects on energy metabolism are negative. Its greatest effects seem to be as a central stimulant and the enhancement of short-term anaerobic exercise. It is highly addictive and can cause cerebral and cardiovascular fatalities. Caffeine enhances fatty acid metabolism leading to glucose conservation, which appears to benefit long-distance endurance events such as skiing. Caffeine is also addictive, and chronic abuse can lead to cardiac damage. Social abuse of each of the three drugs is often difficult to distinguish from their abuse in sport.

  7. Central Disorders of Hypersomnolence

    Science.gov (United States)

    Khan, Zeeshan

    2015-01-01

    The central disorders of hypersomnolence are characterized by severe daytime sleepiness, which is present despite normal quality and timing of nocturnal sleep. Recent reclassification distinguishes three main subtypes: narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia (IH), which are the focus of this review. Narcolepsy type 1 results from loss of hypothalamic hypocretin neurons, while the pathophysiology underlying narcolepsy type 2 and IH remains to be fully elucidated. Treatment of all three disorders focuses on the management of sleepiness, with additional treatment of cataplexy in those patients with narcolepsy type 1. Sleepiness can be treated with modafinil/armodafinil or sympathomimetic CNS stimulants, which have been shown to be beneficial in randomized controlled trials of narcolepsy and, quite recently, IH. In those patients with narcolepsy type 1, sodium oxybate is effective for the treatment of both sleepiness and cataplexy. Despite these treatments, there remains a subset of hypersomnolent patients with persistent sleepiness, in whom alternate therapies are needed. Emerging treatments for sleepiness include histamine H3 antagonists (eg, pitolisant) and possibly negative allosteric modulators of the gamma-aminobutyric acid-A receptor (eg, clarithromycin and flumazenil). PMID:26149554

  8. [MANAGEMENT OF CENTRAL HYPERSOMNIAS].

    Science.gov (United States)

    Dauvilliers, Yves; Lopez, Régis

    2016-06-01

    Central hypersomnias include narcolepsy type 1, type 2 and idiopathic hypersomnia with daytime sleepiness excessive in the foreground of the clinical symptoms. Despite major advances in our understanding of the mechanisms of the narcolepsy type 1 with a low level of hypocretin-1 in cerebrospinal fluid, its current management is only symptomatic. The current management is also only symptomatic for type 2 narcolepsy and idiopathic hypersomnia with an unknown pathophysiology. Treatment options may vary from a single drug targeting several symptoms or several drugs treating a specific symptom. The treatment of daytime sleepiness is based on modafinil in first intention. Other psychostimulants such as methylphenidate, pitolisant and exceptionally dextro-amfetamine may be considered. In narcolepsy type 1, antidepressants such as inhibitors of the reuptake of serotonin and noradrenaline will be considered to improve cataplexy. Sodium oxybate is an effective treatment on sleepiness, cataplexy and bad night sleep in narcolepsy. The management for other symptoms or comorbidities should be considered it necessary such as hallucinations, sleep paralysis, the disturbed nighttime sleep, unpleasant dreams, parasomnias, depressive symptoms, overweight/obesity, cardiovascular disease and obstructive sleep apnea syndrome. Important therapeutic perspectives are to be expected concerning new psychostimulant and anticataplectiques, but mainly on immune-based therapies administered as early as possible after disease onset and on hypocretin replacement therapy for patients with severe symptoms.

  9. Central African Republic.

    Science.gov (United States)

    1989-11-01

    The Central African Republic contains 242,000 square miles, which rolling terrain almost 2000 feet above sea level. The climate is tropical, and it has a population of 2.8 million people with a 2.5% growth rate. There are more than 80 ethnic groups including Baya 34%, Banda 28%, Sara 10%, Mandja 9%, Mboum 9%, and M'Baka 7%. The religions are traditional African 35%, protestant 25%, Roman Catholic 25%, and Muslim 15%, and the languages are French and Sangho. The infant mortality rate is 143/1000, with expectancy at 49 years and a 40% literacy rate. The work force of 1 million is 70% agricultural, industry 6% and commerce and service 6% and government 3%. The government consists of a president assisted by cabinet ministers and a single party. Natural resources include diamonds, uranium, timber, gold, and oil, and major industries are beverages, textiles, and soap. Agricultural products feature coffee, cotton, peanuts, tobacco, food crops and livestock. Most of the population live in rural areas and most of the 80 ethnic groups have their own language. This is one of the world's least developed countries, with a per capita income of $375/year. The main problems with development are the poor transportation infrastructure, and the weak internal and international marketing systems. The US and various international organizations have aided in agriculture development, health programs, and family planning. US investment is mainly in diamond and gold mining, and although oil drilling has been successful it is not economically feasible at current prices.

  10. Dublin South Central (DSC)

    LENUS (Irish Health Repository)

    O'Gorman, Clodagh S M

    2010-12-01

    Children who appear healthy, even if they have one or more recognized cardiovascular risk factors, do not generally have outcomes of cardiovascular or other vascular disease during childhood. Historically, pediatric medicine has not aggressively screened for or treated cardiovascular risk factors in otherwise healthy children. However, studies such as the P-Day Study (Pathobiological Determinants of Atherosclerosis in Youth), and the Bogalusa Heart Study, indicate that healthy children at remarkably young ages can have evidence of significant atherosclerosis. With the increasing prevalence of pediatric obesity, can we expect more health problems related to the consequences of pediatric dyslipidemia, hypertriglyceridemia, and atherosclerosis in the future? For many years, medications have been available and used in adult populations to treat dyslipidemia. In recent years, reports of short-term safety of some of these medications in children have been published. However, none of these studies have detailed long-term follow-up, and therefore none have described potential late side-effects of early cholesterol-lowering therapy, or potential benefits in terms of reduction of or delay in cardiovascular or other vascular end-points. In 2007, the American Heart Association published a scientific statement on the use of cholesterol-lowering therapy in pediatric patients. In this review paper, we discuss some of the current literature on cholesterol-lowering therapy in children, including the statins that are currently available for use in children, and some of the cautions with using these and other cholesterol-lowering medications. A central tenet of this review is that medications are not a substitute for dietary and lifestyle interventions, and that even in children on cholesterol-lowering medications, physicians should take every opportunity to encourage children and their parents to make healthy diet and lifestyle choices.

  11. y Banca Central

    Directory of Open Access Journals (Sweden)

    Ángel García Banchs

    2008-01-01

    Full Text Available Las teorías monetarias modernas, ortodoxas y heterodoxas, han pasado por alto el hecho de que posterior a la Segunda Guerra Mundial el mundo quedó dividido entre economías emisoras y receptoras de reservas, pasando el sistema monetario internacional desde entonces a ser completamente asimétrico. De allí que, desde el punto de vista teórico, señalemos la necesidad de tomar en cuenta si las economías emiten o no una moneda de reserva internacional, pues ello explicaría la existencia de diversas prácticas monetarias a nivel mundial. Este trabajo propone, y calcula, indicadores basados en datos provenientes de los balances de activos y pasivos de quince bancos centrales pertenecientes a Norteamérica, Suramérica, Europa y Asia. Los hallazgos con respecto a las diversas estructuras de activos y pasivos confirman la hipótesis acerca de la presencia de tales asimetrías. Se infiere en consecuencia que la política monetaria es menos flexible pero más influyente en las economías receptoras de reservas, y a la vez más flexible pero menos influyente en las economías emisoras. En pocas palabras, la exogeneidad de la tasa de interés de corto plazo es más débil en el caso de las economías receptoras de reservas las cuales se ven obligadas a acumular divisas y a procurar la estabilidad del tipo de cambio, debido a que sus monedas locales no son aceptadas en el exterior. Así, aunque la oferta crediticia es endógena en esas economías, las mismas no han sido capaces de librarse aún de la necesidad de mantener reservas monetarias en divisas extranjeras

  12. Central Hypothyroidism in Miniature Schnauzers

    NARCIS (Netherlands)

    Voorbij, Annemarie M W Y; Leegwater, Peter A J; Buijtels, Jenny J C W M; Daminet, Sylvie; Kooistra, Hans S

    2016-01-01

    BACKGROUND: Primary hypothyroidism is a common endocrinopathy in dogs. In contrast, central hypothyroidism is rare in this species. OBJECTIVES: The objective of this article is to describe the occurrence and clinical presentation of central hypothyroidism in Miniature Schnauzers. Additionally, the p

  13. Central bank independence and ageing

    OpenAIRE

    Farvaque, Etienne; Héricourt, Jérôme; Lagadec, Gaël

    2008-01-01

    We contrast the influence of demography and central bank independence on inflation. The recent demographic trends in developed countries are shown to weight more on inflation than central bank independence, while the contrary stands for the period from 1960 to 1979.

  14. Controlling centrality in complex networks

    Science.gov (United States)

    Nicosia, V.; Criado, R.; Romance, M.; Russo, G.; Latora, V.

    2012-01-01

    Spectral centrality measures allow to identify influential individuals in social groups, to rank Web pages by popularity, and even to determine the impact of scientific researches. The centrality score of a node within a network crucially depends on the entire pattern of connections, so that the usual approach is to compute node centralities once the network structure is assigned. We face here with the inverse problem, that is, we study how to modify the centrality scores of the nodes by acting on the structure of a given network. We show that there exist particular subsets of nodes, called controlling sets, which can assign any prescribed set of centrality values to all the nodes of a graph, by cooperatively tuning the weights of their out-going links. We found that many large networks from the real world have surprisingly small controlling sets, containing even less than 5 – 10% of the nodes. PMID:22355732

  15. Central presbycusis: an emerging view.

    Science.gov (United States)

    Gates, George A

    2012-07-01

    Age-related dysfunction of the central auditory system (central presbycusis) is common but rarely looked for by those who provide aural rehabilitation. Patients who complain of difficulty hearing in noise--the key symptom of central presbycusis--are generally disadvantaged with conventional rehabilitation. This symptom should be documented with commercially available speech-in-noise tests, which use materials that are uncomplicated to administer. Those patients who perform poorly on such tests should have a customized rehabilitation program aimed at optimizing their remaining communication abilities. Otolaryngologists who provide auditory rehabilitation may wish to consider expanding their practices to meet the communication needs of older patients with central presbycusis. Central presbycusis is an emerging area for basic and clinical research in auditory neurotology, particularly in the relation of cognitive dysfunction to impaired auditory processing.

  16. Centralized versus Decentralized Information Systems

    Science.gov (United States)

    Hugoson, Mats-Åke

    This paper brings into question whether information systems should be centralized or decentralized in order to provide greater support for different business processes. During the last century companies and organizations have used different approaches for centralization and decentralization; a simple answer to the question does not exist. This paper provides a survey of the evolution of centralized and decentralized approaches, mainly in a Nordic perspective. Based on critical reflections on the situation in the end of the century we can discuss what we can learn from history to achieve alignment between centralized and decentralized systems and the business structure. The conclusion is that theories, management and practice for decisions on centralization or decentralization of information systems must be improved. A conscious management and control of centralization /decentralization of IT support is a vital question in the company or the organization, and this is not a task that can be handled only by IT-specialists. There is a need for business oriented IT management of centralization/decentralization.

  17. Betweenness centrality profiles in trees

    CERN Document Server

    Fish, Benjamin; Turan, Gyorgy

    2016-01-01

    Betweenness centrality of a vertex in a graph measures the fraction of shortest paths going through the vertex. This is a basic notion for determining the importance of a vertex in a network. The k-betweenness centrality of a vertex is defined similarly, but only considers shortest paths of length at most k. The sequence of k-betweenness centralities for all possible values of k forms the betweenness centrality profile of a vertex. We study properties of betweenness centrality profiles in trees. We show that for scale-free random trees, for fixed k, the expectation of k-betweenness centrality strictly decreases as the index of the vertex increases. We also analyze worst-case properties of profiles in terms of the distance of profiles from being monotone, and the number of times pairs of profiles can cross. This is related to whether k-betweenness centrality, for small values of k, may be used instead of having to consider all shortest paths. Bounds are given that are optimal in order of magnitude. We also pre...

  18. Lulak Abad Iron Occurrence, Northwest of Zanjan: Metamorphosed and Deformed Volcano-Sedimentary Type of Mineralization in Central Iran

    Directory of Open Access Journals (Sweden)

    Mehri Karami

    2016-07-01

    are depleted in LREE (except Ce but enriched in most HREE (beside depletion in Dy and Ho. These signatures indicate high wall rock interaction (e.g., Lottermoser, 1992; Liegeois et al., 2003. Comparison of the geological, mineralogical, geochemical, textural and structural characteristics of the Lulak Abad occurrence with different types of iron deposits reveals that iron mineralization at Lulak Abad was originally formed as volcano-sedimentary, and then reconcentrated as vein mineralization (Karami et al., 2012; Karami et al., 2013. Acknowledgements The authors are grateful to the University of Zanjan Grant Commission for research funding. Journal of Economic Geology reviewers and editor are also thanked for their constructive suggestions on alterations to the manuscript. v References Karami, M., Ebrahimi, M. and Kouhestani, H., 2012. Geological and mineralization characteristics of Lulak Abad iron occurrence, east of Mahneshan. 31th Symposium of Geosciences, Geological Survey of Iran, Tehran, Iran (in Persian with English abstract. Karami, M., Kouhestani, H. and Ebrahimi, M., 2013. Mineralogy, structure, texture and type of iron mineralization in Lulak Abad occurrence, east of Mahneshan. 1st International Conference on Mining, Mineral Processing, Metallurgical and Environmental Engineering. University of Zanjan, Zanjan, Iran (in Persian with English abstract. Liegeois, J.P., Latouche, L., Boughrara, M., Navez, J. and Guiraud, M., 2003. The Latea metacraton (Central Hoggar, Tuareg shield, Algeria: behaviour of an old passive margin during the Pan-African orogeny. Journal of African Earth Sciences, 37(3–4: 161–190. Lotfi, M., 2001. Geological map of Mahneshan, scale 1:100,000. Geological Survey of Iran. Lottermoser, B.G., 1992. Rare earth elements and hydrothermal ore formation processes. Ore Geology Reviews, 7(1: 25–41. Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes

  19. Demographic tensions in Central America.

    Science.gov (United States)

    1986-08-01

    This discussion of Central America focuses on the rapid growth of its population, its stagnating economy, and those countries that are socioeconomically advanced. Between 1950-85 the population of Central America tripled, from 9.1 million to 26. 4 million, due to marked mortality declines and the absence of off-setting fertility declines. The distribution of Central Americas's growing populations sets its population growth apart from that of other developing regions. Currently, almost half of all Central Americans live in cities. Although the average growth rate for Central American countries has fallen and is expected to drop further, the decline does not counterbalance the effect of the absolute rise in population numbers. The average annual growth rate of more than 3% annually in the 1960s fell to about 2.6% in recent years, but this decline is due primarily to socioeconomically advanced Costa Rica and Panama. Central America's age structure further complicates the population crisis. About 43% of Central Americans are under the age of 15. When the increasingly larger young population group enters it reproductive years, the potential for future growth (albeit the falling rate of population increase) is unparalleled. UN population projections show the region's population at 40 million by the year 2000. The 1973 oil crisis began a downward spiral for the buoyant post World War II Central American economy. Between 1950-79, real per capita income growth in Central America doubled, with Central American economies growing an average of 5.3% annually. By the early 1980s, overseas markets of the trade-dependent countries of Central America had dried up due to protectionism abroad and slumping basic commodity prices. These and other factors plunged Central America into its current economic malaise of falling real per capita income, rising unemployment, curtailed export led economic growth, and a rising cost of living. In general, economic growth in Central America

  20. Photobiological hydrogen production in the Sahara. Photobiologische Wasserstoffproduktion in der Sahara

    Energy Technology Data Exchange (ETDEWEB)

    Rechenberg, I. (Technische Univ. Berlin (Germany). Fachgebiet Bionik und Evolutionstechnik)

    1994-01-01

    Bacteria and algae are cultivated in a desert reactor in order to produce solar hydrogen in an integrated metabolism modelled after blue algae. The pilot experiments run parallel to the Berlin project ''Artificial bacteria-algae symbriosis''. The location of the experiment accounts for the cooperation of sand, sun and nomads and policemen. Scientific research suddenly becomes an adventure-trail. (orig./EF)

  1. Payments and Central Bank Policy

    DEFF Research Database (Denmark)

    Korsgaard, Søren

    This thesis consists of three chapters. The rst, "Paying for Payments", examines the role of interchange fees in payment card networks. The second, "Bank Liquidity and the Interbank Market" (co-authored with Mikael Reimer Jensen), investigates how banks' liquidity holdings at the central bank a ect...... outcomes in the money market. The third, "Collateralized Lending and Central Bank Collateral Policy", considers the emergence of credit constraints under collateralized lending, and how central banks use collateral policy to mitigate these constraints. While the chapters can be read independently......, they share common themes. Each chapter is concerned with payments in one way or another, each is concerned with the e ciency of market outcomes, and, to the extent that there is scope for improving these outcomes, each discusses the appropriate role for policy, in particular central bank policy....

  2. The Central Trigger Processor (CTP)

    CERN Multimedia

    Franchini, Matteo

    2016-01-01

    The Central Trigger Processor (CTP) receives trigger information from the calorimeter and muon trigger processors, as well as from other sources of trigger. It makes the Level-1 decision (L1A) based on a trigger menu.

  3. Payments and Central Bank Policy

    DEFF Research Database (Denmark)

    Korsgaard, Søren

    This thesis consists of three chapters. The rst, "Paying for Payments", examines the role of interchange fees in payment card networks. The second, "Bank Liquidity and the Interbank Market" (co-authored with Mikael Reimer Jensen), investigates how banks' liquidity holdings at the central bank a ect...... outcomes in the money market. The third, "Collateralized Lending and Central Bank Collateral Policy", considers the emergence of credit constraints under collateralized lending, and how central banks use collateral policy to mitigate these constraints. While the chapters can be read independently......, they share common themes. Each chapter is concerned with payments in one way or another, each is concerned with the e ciency of market outcomes, and, to the extent that there is scope for improving these outcomes, each discusses the appropriate role for policy, in particular central bank policy....

  4. CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY

    Energy Technology Data Exchange (ETDEWEB)

    BERGMAN, T. B.; STEFANSKI, L. D.; SEELEY, P. N.; ZINSLI, L. C.; CUSACK, L. J.

    2012-09-19

    THE CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY WAS CONDUCTED TO DEVELOP AN OPTIMAL SEQUENCE OF REMEDIATION ACTIVITIES IMPLEMENTING THE CERCLA DECISION ON THE CENTRAL PLATEAU. THE STUDY DEFINES A SEQUENCE OF ACTIVITIES THAT RESULT IN AN EFFECTIVE USE OF RESOURCES FROM A STRATEGIC PERSPECTIVE WHEN CONSIDERING EQUIPMENT PROCUREMENT AND STAGING, WORKFORCE MOBILIZATION/DEMOBILIZATION, WORKFORCE LEVELING, WORKFORCE SKILL-MIX, AND OTHER REMEDIATION/DISPOSITION PROJECT EXECUTION PARAMETERS.

  5. Central cementifying fibroma of mandible

    Directory of Open Access Journals (Sweden)

    Joseph Edward

    2010-01-01

    Full Text Available Central cementifying fibroma is a rare non odontogenic tumor coming in the group of fibro osseouslesion, arising from periodontal ligament and is usually seen in tooth bearing area. It can affect boththe mandible and the maxilla, particularly the mandible. This bone tumour consists of highly cellular,fibrous tissue that contains varying amounts of calcified tissue resembling bone, cementum or both.Here we present a case of Central cementifying fibroma (recurrent in a 34 year old female.

  6. Inferring Centrality from Network Snapshots

    OpenAIRE

    Haibin Shao; Mehran Mesbahi; Dewei Li; Yugeng Xi

    2017-01-01

    The topology and dynamics of a complex network shape its functionality. However, the topologies of many large-scale networks are either unavailable or incomplete. Without the explicit knowledge of network topology, we show how the data generated from the network dynamics can be utilised to infer the tempo centrality, which is proposed to quantify the influence of nodes in a consensus network. We show that the tempo centrality can be used to construct an accurate estimate of both the propagati...

  7. Controlling centrality in complex networks

    CERN Document Server

    Nicosia, Vincenzo; Romance, Miguel; Russo, Giovanni; Latora, Vito

    2011-01-01

    Spectral centrality measures allow to identify influential individuals in social groups, to rank Web pages by their popularity, and even to determine the impact of scientific researches. The centrality score of a node within a network crucially depends on the entire pattern of connections, so that the usual approach is to compute the node centralities once the network structure is assigned. We face here with the inverse problem, that is, we study how to modify the centrality scores of the nodes by acting on the structure of a given network. We prove that there exist particular subsets of nodes, called controlling sets, which can assign any prescribed set of centrality values to all the nodes of a graph, by cooperatively tuning the weights of their out-going links. We show that many large networks from the real world have surprisingly small controlling sets, containing even less than 5-10% of the nodes. These results suggest that rankings obtained from spectral centrality measures have to be considered with ex...

  8. Rosette Central Configurations, Degenerate central configurations and bifurcations

    CERN Document Server

    Lei, Jinzhi

    2009-01-01

    In this paper we find a class of new degenerate central configurations and bifurcations in the Newtonian $n$-body problem. In particular we analyze the Rosette central configurations, namely a coplanar configuration where $n$ particles of mass $m_1$ lie at the vertices of a regular $n$-gon, $n$ particles of mass $m_2$ lie at the vertices of another $n$-gon concentric with the first, but rotated of an angle $\\pi/n$, and an additional particle of mass $m_0$ lies at the center of mass of the system. This system admits two mass parameters $\\mu=m_0/m_1$ and $\\ep=m_2/m_1$. We show that, as $\\mu$ varies, if $n> 3$, there is a degenerate central configuration and a bifurcation for every $\\ep>0$, while if $n=3$ there is a bifurcations only for some values of $\\epsilon$.

  9. Coverage centralities for temporal networks

    CERN Document Server

    Takaguchi, Taro; Yoshida, Yuichi

    2015-01-01

    Structure of real networked systems, such as social relationship, can be modeled as temporal networks in which each edge appears only at the prescribed time. Understanding the structure of temporal networks requires quantifying the importance of a temporal vertex, which is a pair of vertex index and time. In this paper, we define two centrality measures of a temporal vertex by the proportion of (normal) vertex pairs, the quickest routes between which can (or should) use the temporal vertex. The definition is free from parameters and robust against the change in time scale on which we focus. In addition, we can efficiently compute these centrality values for all temporal vertices. Using the two centrality measures, we reveal that distributions of these centrality values of real-world temporal networks are heterogeneous. For various datasets, we also demonstrate that a majority of the highly central temporal vertices are located within a narrow time window around a particular time. In other words, there is a bo...

  10. Coverage centralities for temporal networks*

    Science.gov (United States)

    Takaguchi, Taro; Yano, Yosuke; Yoshida, Yuichi

    2016-02-01

    Structure of real networked systems, such as social relationship, can be modeled as temporal networks in which each edge appears only at the prescribed time. Understanding the structure of temporal networks requires quantifying the importance of a temporal vertex, which is a pair of vertex index and time. In this paper, we define two centrality measures of a temporal vertex based on the fastest temporal paths which use the temporal vertex. The definition is free from parameters and robust against the change in time scale on which we focus. In addition, we can efficiently compute these centrality values for all temporal vertices. Using the two centrality measures, we reveal that distributions of these centrality values of real-world temporal networks are heterogeneous. For various datasets, we also demonstrate that a majority of the highly central temporal vertices are located within a narrow time window around a particular time. In other words, there is a bottleneck time at which most information sent in the temporal network passes through a small number of temporal vertices, which suggests an important role of these temporal vertices in spreading phenomena. Contribution to the Topical Issue "Temporal Network Theory and Applications", edited by Petter Holme.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjb/e2016-60498-7

  11. Network centrality of metro systems.

    Directory of Open Access Journals (Sweden)

    Sybil Derrible

    Full Text Available Whilst being hailed as the remedy to the world's ills, cities will need to adapt in the 21(st century. In particular, the role of public transport is likely to increase significantly, and new methods and technics to better plan transit systems are in dire need. This paper examines one fundamental aspect of transit: network centrality. By applying the notion of betweenness centrality to 28 worldwide metro systems, the main goal of this paper is to study the emergence of global trends in the evolution of centrality with network size and examine several individual systems in more detail. Betweenness was notably found to consistently become more evenly distributed with size (i.e. no "winner takes all" unlike other complex network properties. Two distinct regimes were also observed that are representative of their structure. Moreover, the share of betweenness was found to decrease in a power law with size (with exponent 1 for the average node, but the share of most central nodes decreases much slower than least central nodes (0.87 vs. 2.48. Finally the betweenness of individual stations in several systems were examined, which can be useful to locate stations where passengers can be redistributed to relieve pressure from overcrowded stations. Overall, this study offers significant insights that can help planners in their task to design the systems of tomorrow, and similar undertakings can easily be imagined to other urban infrastructure systems (e.g., electricity grid, water/wastewater system, etc. to develop more sustainable cities.

  12. Inferring Centrality from Network Snapshots

    Science.gov (United States)

    Shao, Haibin; Mesbahi, Mehran; Li, Dewei; Xi, Yugeng

    2017-01-01

    The topology and dynamics of a complex network shape its functionality. However, the topologies of many large-scale networks are either unavailable or incomplete. Without the explicit knowledge of network topology, we show how the data generated from the network dynamics can be utilised to infer the tempo centrality, which is proposed to quantify the influence of nodes in a consensus network. We show that the tempo centrality can be used to construct an accurate estimate of both the propagation rate of influence exerted on consensus networks and the Kirchhoff index of the underlying graph. Moreover, the tempo centrality also encodes the disturbance rejection of nodes in a consensus network. Our findings provide an approach to infer the performance of a consensus network from its temporal data. PMID:28098166

  13. CENTRAL MECHANISMS OF ACUPUNCTURE ANALGESIA

    Directory of Open Access Journals (Sweden)

    Eman S. Mansour

    2015-12-01

    Full Text Available Background: Acupuncture is an component of traditional Chinese medicine (TCM that has been used for three thousand years to treat diseases and relieve pain. Pain is found to be the most common reason for people to use acupuncture. Due to recent scientific findings, acupuncture treatment has been accepted worldwide. Numerous trials have been conducted especially in analgesia. The mechanisms of acupuncture analgesia has been widely investigated, however, the underlying mechanism still not clear. This article summarizes the central mechanisms of acupuncture analgesia and reviews recent studies on the topic. Method: We have focused on examining the recent literature on acupuncture analgesia. The central mechanisms of acupuncture analgesia and reviews recent studies on the topic. We focused on the studies related to central mechanisms of acupuncture analgesia from these aspects: (neurophysiology, neurochemistry and neuroanatomy. Result: The result revealed that acupuncture act on various parts of the central nervous system, including the spinal cord, brain stem, cerebral ganglia and cerebral cortex to alleviate pain. The central mechanisms underlying the effects of acupuncture include neurohumors and neurotransmitters, which are involved in analgesia. At spinal level, Spinal opioids, glutamate, norepinephrine and serotonin are the key elements acupuncture-induced analgesia. At brain level, Endogenous opioid peptides, limbic system play essential roles in mediating the analgesia. Conclusion: Acupuncture is an effective approach to pain management. There is good evidence in both experimental and clinical research that supports acupuncture efficacy in management of chronic pain through central nervous system. Acupuncture should be strongly used as a part of pain management plans. This work helps in improving our understanding of the scientific basis underlying acupuncture analgesia.

  14. Central Stars of Planetary Nebulae

    CERN Document Server

    Jones, David

    2016-01-01

    In this brief invited review, I will attempt to summarise some of the key areas of interest in the study of central stars of planetary nebulae which (probably) won't be covered by other speakers' proceedings. The main focus will, inevitably, be on the subject of multiplicity, with special emphasis on recent results regarding triple central star systems as well as wide binaries which avoid a common-envelope phase. Furthermore, in light of the upcoming release of Kepler's Campaign 11 data, I will discuss a few of the prospects from that data including the unique possibility to detect merger products.

  15. Late Pleistocene - Holocene surface processes and landscape evolution in the central Swiss Alps

    Science.gov (United States)

    Boxleitner, Max; Musso, Alessandra; Waroszewski, Jarosław; Malkiewicz, Małgorzata; Maisch, Max; Dahms, Dennis; Brandová, Dagmar; Christl, Marcus; de Castro Portes, Raquel; Egli, Markus

    2017-10-01

    The European Alps are a geomorphologically active region and experience a number of gravity-driven hillslope processes. Soil and landscape formation in the Alps has consequently undergone several minor and major traceable changes of developmental trajectories during the Holocene. Soil development is hypothesised to be often non-linear with time and characterised by stages of progressive and regressive evolution caused by upbuilding (formation, profile deepening) and erosion (profile shallowing). Several cold and warm climate phases are identified during the Holocene but it is largely unknown which effects these might have had on slope processes. By using datable moraines (10Be) and mires (14C), we have constructed a temporal framework for these processes. Using the geochemical imprint of mires in the Alpine setting of the Göschener-valley of the Central Swiss Alps, we reconstructed general (mostly erosional) landscape processes for the last ca. 10 ka. As this is the type locality for the Göschener cold phase, we assumed that this phase (Göschener cold phase I and II 1.5 and 2.5 ka BP) should have left easily recognizable traits. After deglaciation (11-12 ka BP), soil evolution was progressive. Beginning around 8 ka BP, we detect a distinct increase in erosion here, together with a vegetation change (towards tundra vegetation) and the highest measured rates of carbon sequestration. Other phases of high geomorphic activity were recognised ca. 5-6 ka BP, 4 ka BP and, to a lesser extent, 1-3 ka ago. The cold phase at 5-6 ka BP corresponds to a less distinct change in vegetation and lessened erosion. Human impact is increasingly obvious since about 2.4 ka BP which overlaps with the Göschener cold phase. Nonetheless, erosion processes were not extraordinarily high during this period and a climate effect cannot be distinguished. We detect evidence of increasing human disturbance (regressive soil evolution) for about the last 1 ka. We also detect an increase in dust

  16. Central Libraries in Uncertain Times.

    Science.gov (United States)

    Kenney, Brian J.

    2001-01-01

    Discusses security and safety issues for public libraries, especially high-profile central facilities, in light of the September 11 terrorist attacks. Highlights include inspecting bags as patrons enter as well as exit; the need for security guidelines for any type of disaster or emergency; building design; and the importance of communication.…

  17. Copycats of the Central Himalayas

    NARCIS (Netherlands)

    P.A. Arora (Payal)

    2009-01-01

    textabstractThis case study highlights practices of a rarely documented group of neo-users of the Internet or newbies from Central Himalayas, serving as a catalyst for delving deeply into the act of ‘plagiarism’ in online learning By looking at such ‘learning’ practices away from schools, namely

  18. Learning and the central bank

    OpenAIRE

    Charles T. Carlstrom; Timothy S. Fuerst

    2001-01-01

    It is well known that sunspot equilibria may arise under an interest-rate operating procedure in which the central bank varies the nominal rate with movements in future inflation (a forward-looking Taylor rule). This paper demonstrates that these sunspot equilibria may be learnable in the sense of E-stability.

  19. Water Governance in Central Asia

    NARCIS (Netherlands)

    Djanibekov, Nodir; Assche, Van Kristof; Valentinov, Vladislav

    2016-01-01

    We develop a social systems theory perspective on Central Asian post-Socialist transition, placing particular emphasis on the coordination problems in transboundary water governance. The extensive Soviet water-energy infrastructure around the Amudarya and Syrdarya rivers required coordination, bu

  20. The Centrality of Ethical Leadership

    Science.gov (United States)

    Ehrich, Lisa C.; Harris, Jessica; Klenowski, Val; Smeed, Judy; Spina, Nerida

    2015-01-01

    Purpose: The central argument in this paper is that ethical school leadership is imperative in a context of increasing performance-driven accountability. The purpose of this paper is to focus on school principals' perceptions of how they understand ethical leadership and how they lead the ethical use of data. Design/Methodology/Approach: This…

  1. Pathology of Central American Refugees.

    Science.gov (United States)

    Molesky, Jean

    1986-01-01

    The rapidly increasing numbers of Central American refugees in the United States include many whose sufferings have led to severe psychological problems. The article attempts to lay a foundation for assisting them by discussing the following: (1) origins of disorders; (2) culture shock and stress; (3) prevalence of symptoms; and (4) suggestions…

  2. Vulnerability in north- central Vietnam

    DEFF Research Database (Denmark)

    Casse, Thorkil; Milhøj, Anders; Nguyen, Thao Phuong

    2015-01-01

    This article examines changes in livelihood strategies in response to flooding. It does so on the basis of a household survey which was undertaken in three provinces in north central Vietnam. All households in the survey were regularly affected by flooding, but only poor households experience...

  3. New Economy, Old Central Banks?

    NARCIS (Netherlands)

    Berk, Jan Marc

    2002-01-01

    Proponents of the so-called New Economy claim that it entails a structural change of the economy. Such a change, in turn, would require the central bank to rethink its monetary policy to the extent that traditional relationships between inf1ation and economic growth are no longer valid. But such a r

  4. The MEANING multilingual central repository

    NARCIS (Netherlands)

    Atserias, J.; Villarejo, L.; Rigau, G.; Agirre, E.; Carroll, J.; Magnini, B.; Vossen, P.

    2004-01-01

    This paper describes the first version of the Multilingual Central Repository, a lexical knowledge base developed in the framework of the MEANING project. Currently the MCR integrates into the EuroWordNet framework five local wordnets (including four versions of the English WordNet from Princeton),

  5. Earth Works Central. [Educational Packet].

    Science.gov (United States)

    Kids for Saving Earth Worldwide, Minneapolis, MN.

    Earth Works Central is an educational curriculum tool designed to provide environmental education support for the classroom. It features environmental materials for science, geography, history, art, music, dramatics, and physical education. It includes information on creating an environmental center where kids can learn and become empowered to…

  6. Music Libraries: Centralization versus Decentralization.

    Science.gov (United States)

    Kuyper-Rushing, Lois

    2002-01-01

    Considers the decision that branch libraries, music libraries in particular, have struggled with concerning a centralized location in the main library versus a decentralized collection. Reports on a study of the Association of Research Libraries that investigated the location of music libraries, motivation for the location, degrees offered,…

  7. Copycats of the Central Himalayas

    NARCIS (Netherlands)

    P.A. Arora (Payal)

    2009-01-01

    textabstractThis case study highlights practices of a rarely documented group of neo-users of the Internet or newbies from Central Himalayas, serving as a catalyst for delving deeply into the act of ‘plagiarism’ in online learning By looking at such ‘learning’ practices away from schools, namely at

  8. 27 CFR 9.75 - Central Coast.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Central Coast. 9.75... Central Coast. (a) Name. The name of the viticultural area described in this section is “Central Coast.” (b) Approved maps. The approved maps for determining the boundary of the Central Coast...

  9. Central venous line complications and tip detection

    OpenAIRE

    Ameneh Rezaee Gheshlaghi; Hamid Zamani Moghadam Dolu; Elham Pishbin; Maryam Salehi

    2015-01-01

    Central venous line is one of a creative instrument that saves human’s life in critical medical situation. Central venous line access is frequently involved in the disease management. It is used for rapid fluid therapy, transvenous pacemakers, infusion of some medications, hemodialysis or plasmapheresis and etc. Most of the emergency departments have some staffs that are trained for central venous line insertion but related complications occur during central venous line placement.Central veno...

  10. Is Central Asia really exsiccating?

    Science.gov (United States)

    Aizen, V. B.; Aizen, E. M.; Surazakov, A. B.

    2008-12-01

    At the end of 20th and the beginning of 21st century central Asia oases suffered from serious drought caused lack of water for agriculture, economy growth and population increase. However, people of this region always experienced lack of water for irrigation and fought a war over the rights to control river streams. The drying up of central Asian rivers is not a new phenomenon according to the ancient manuscripts. Thus, lets see about what has happened with the past century climate and water resources of central Asia using the long-term observational data. We analyzed data from more than 200 meteorological stations and stream gauges over the central Asia in elevation range from 25 m. b.s.l. to 4,000 m. a.s.l. to understand the last 100 years variability in climate and water resources, examining changes in the extreme and mean monthly air temperatures, precipitation and river runoff. The evaluation of seasonal snow and glacier's covered areas between 1970th and 2007th in central Asia derived from AVHRR, MODIS, Hexagon KH-9, Landsat ETM and ASTER data exhibit 15% reduction of the seasonal snow covered area and 10.1% of the glacier area. It has been found that during last twenty years the duration of snowmelt, from the date of maximum snow cover to date of its disappearance, reduced by 30 days and in 2007 was equal to 138 days in the central Asian mountains. The decrease of seasonal snow cover is not a linear process. The further decrease may be accelerated due to increase of rainfall instead of snowfall in early spring months at high elevations, and consequently a lesser heat expenditure for the snowmelt. The growth in summer air temperatures, especially observable since the 1970th, accompanied by increase of evapotranspiration and precipitation, notably in summer and autumn, and at high elevations over 3,000 m, and at the western peripheral mountain ridges. Average difference in the means of annual air temperatures for the two thirty-year periods before and after

  11. A centralized audio presentation manager

    Energy Technology Data Exchange (ETDEWEB)

    Papp, A.L. III; Blattner, M.M.

    1994-05-16

    The centralized audio presentation manager addresses the problems which occur when multiple programs running simultaneously attempt to use the audio output of a computer system. Time dependence of sound means that certain auditory messages must be scheduled simultaneously, which can lead to perceptual problems due to psychoacoustic phenomena. Furthermore, the combination of speech and nonspeech audio is examined; each presents its own problems of perceptibility in an acoustic environment composed of multiple auditory streams. The centralized audio presentation manager receives abstract parameterized message requests from the currently running programs, and attempts to create and present a sonic representation in the most perceptible manner through the use of a theoretically and empirically designed rule set.

  12. The Central Valley Hydrologic Model

    Science.gov (United States)

    Faunt, C.; Belitz, K.; Hanson, R. T.

    2009-12-01

    Historically, California’s Central Valley has been one of the most productive agricultural regions in the world. The Central Valley also is rapidly becoming an important area for California’s expanding urban population. In response to this competition for water, a number of water-related issues have gained prominence: conjunctive use, artificial recharge, hydrologic implications of land-use change, subsidence, and effects of climate variability. To provide information to stakeholders addressing these issues, the USGS made a detailed assessment of the Central Valley aquifer system that includes the present status of water resources and how these resources have changed over time. The principal product of this assessment is a tool, referred to as the Central Valley Hydrologic Model (CVHM), that simulates surface-water flows, groundwater flows, and land subsidence in response to stresses from human uses and from climate variability throughout the entire Central Valley. The CVHM utilizes MODFLOW combined with a new tool called “Farm Process” to simulate groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis. This model was discretized horizontally into 20,000 1-mi2 cells and vertically into 10 layers ranging in thickness from 50 feet at the land surface to 750 feet at depth. A texture model constructed by using data from more than 8,500 drillers’ logs was used to estimate hydraulic properties. Unmetered pumpage and surface-water deliveries for 21 water-balance regions were simulated with the Farm Process. Model results indicate that human activities, predominately surface-water deliveries and groundwater pumping for irrigated agriculture, have dramatically influenced the hydrology of the Central Valley. These human activities have increased flow though the aquifer system by about a factor of six compared to pre-development conditions. The simulated hydrology reflects spatial

  13. Centrality in Interconnected Multilayer Networks

    CERN Document Server

    De Domenico, Manlio; Omodei, Elisa; Gómez, Sergio; Arenas, Alex

    2013-01-01

    Real-world complex systems exhibit multiple levels of relationships. In many cases, they require to be modeled by interconnected multilayer networks, characterizing interactions on several levels simultaneously. It is of crucial importance in many fields, from economics to biology, from urban planning to social sciences, to identify the most (or the less) influent nodes in a network. However, defining the centrality of actors in an interconnected structure is not trivial. In this paper, we capitalize on the tensorial formalism, recently proposed to characterize and investigate this kind of complex topologies, to show how several centrality measures -- well-known in the case of standard ("monoplex") networks -- can be extended naturally to the realm of interconnected multiplexes. We consider diagnostics widely used in different fields, e.g., computer science, biology, communication and social sciences, to cite only some of them. We show, both theoretically and numerically, that using the weighted monoplex obta...

  14. Centralized versus Decentralized Infrastructure Networks

    CERN Document Server

    Hines, Paul D H; Schläpfer, Markus

    2015-01-01

    While many large infrastructure networks, such as power, water, and natural gas systems, have similar physical properties governing flows, these systems tend to have distinctly different sizes and topological structures. This paper seeks to understand how these different size-scales and topological features can emerge from relatively simple design principles. Specifically, we seek to describe the conditions under which it is optimal to build decentralized network infrastructures, such as a microgrid, rather than centralized ones, such as a large high-voltage power system. While our method is simple it is useful in explaining why sometimes, but not always, it is economical to build large, interconnected networks and in other cases it is preferable to use smaller, distributed systems. The results indicate that there is not a single set of infrastructure cost conditions under which optimally-designed networks will have highly centralized architectures. Instead, as costs increase we find that average network size...

  15. Central charges in regular mechanics

    CERN Document Server

    Cabo-Montes de Oca, Alejandro; Villanueva, V M

    1997-01-01

    We consider the algebra associated to a group of transformations which are symmetries of a regular mechanical system (i.e. system free of constraints). For time dependent coordinate transformations we show that a central extension may appear at the classical level which is coordinate and momentum independent. A cochain formalism naturally arises in the argument and extends the usual configuration space cochain concepts to phase space.

  16. Central Asia, Physical Geography Handbook.

    Science.gov (United States)

    2007-11-02

    over 2,000 m) is not applicable to Central Asia, partly because the general hypsometric level of this region is high and unstable, as a consequence of...organic fossils in them, gastropods have been discovered. On the main territory of the Tarim massif, which evidently represented a weakly elevated...places seams of gypsum and rock salt, and, in a part to the west of the town of Aksu, also a bed of gray limestone with small fresh- water gastropods

  17. Barter Economies and Centralized Merchants

    OpenAIRE

    Jose Noguera S.

    2000-01-01

    The main goal of this essay is to analyze the emergence of a barter economy, and the rise of centralized merchants and a barter redistribution system out of a primitive barter system. The environment is a spatial general equilibrium model where exchange is costly. Since exchange becomes more complicated as the scope of the economy increases, we prove that, after the economy reaches a critical size, the cost of trade expansion surpasses its benefits. This imposes limitations on the scope of th...

  18. Celtic Sites of Central Iberia

    Science.gov (United States)

    Pérez Gutiérrez, Manuel

    This chapter concerns the astronomy practiced by Celtic peoples in some parts of central Iberia, specifically the Vetton and Celtiberian peoples, inhabitants of the so-called Late Iron Age. The construction of some elements of religion or worship was perfectly determined by geometry, topography, and especially astronomy, because their spatial orientation occurs in locations of great interest for maintaining the local calendar. The maintenance of this calendar was probably the primary objective of some of the elements studied.

  19. Central collisions of heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Fung, Sun-yiu.

    1992-10-01

    This report describes the activities of the Heavy Ion Physics Group at the University of California, Riverside from October 1, 1991 to September 30, 1992. During this period, the program focused on particle production at AGS energies, and correlation studies at the Bevalac in nucleus-nucleus central collisions. As part of the PHENIX collaboration, contributions were made to the Preliminary Conceptual Design Report (pCDR), and work on a RHIC silicon microstrip detector R D project was performed.

  20. Central Nucleon-Nucleon Potential

    Science.gov (United States)

    Robilotta, M. R.

    2001-12-01

    The outer region of the NN interactions is dominated by the one pion exchange potential (OPEP), followed by the two-pion exchange potential (TPEP). Chiral calculations of the TPEP have been performed using either heavy baryon1 (HB) or relativistic2 perturbation theories. We compare the predictions from these two approaches for the dominant central interaction and show that they fail to agree by 25% ...

  1. The CDF Central Analysis Farm

    Energy Technology Data Exchange (ETDEWEB)

    Kim, T.H.; /MIT; Neubauer, M.; /UC, San Diego; Sfiligoi, I.; /Frascati; Weems, L.; /Fermilab; Wurthwein, F.; /UC, San Diego

    2004-01-01

    With Run II of the Fermilab Tevatron well underway, many computing challenges inherent to analyzing large volumes of data produced in particle physics research need to be met. We present the computing model within CDF designed to address the physics needs of the collaboration. Particular emphasis is placed on current development of a large O(1000) processor PC cluster at Fermilab serving as the Central Analysis Farm for CDF. Future plans leading toward distributed computing and GRID within CDF are also discussed.

  2. Information from the central stores

    CERN Multimedia

    GS Department

    2010-01-01

    All items sold in the CERN shop (Bldg. 33) are now available in the central stores (Bldg. 73) and can be purchased on-line via EDH “Material Request” or at the “Emergency Desk” of the stores on the ground floor of Bldg. 73. These items are visible in the CERN catalogue under the “SCEM” codes beginning with 92. Department of General Infrastructure Services (GS) GS-SEM Group

  3. Neuroimaging of central breathlessness mechanisms.

    Science.gov (United States)

    Pattinson, Kyle T S; Johnson, Miriam J

    2014-09-01

    Breathlessness debilitates millions of people with cardiorespiratory conditions and cancer. Symptoms correlate poorly with the objective measures of disease (e.g. spirometry). Altered brain processing of respiratory sensations may contribute to this disparity. This article summarizes how functional neuroimaging works, focussing on functional MRI (FMRI) and magnetoencephalography, how neuroimaging has shed light on the central mechanisms of breathlessness and thus how it may help target new therapies. Current understanding of central neural activity in breathlessness comes mainly from a small number of studies in healthy volunteers using models of induced acute breathlessness. Parallels with neuroimaging findings in pain and fear or anxiety have been used to interpret the neuroimaging studies of breathlessness to form hypotheses. Despite the lack of recent neuroimaging studies in breathlessness, there have been methodological advances in overcoming confounders with respiratory FMRI. In addition, developing interest in the distinction of emotional from the sensory aspects of breathlessness and the use of opioids for breathlessness has driven mechanistic understandings. Neuroimaging of breathlessness remains in its infancy. However, advances in the understanding of central perception, combined with novel neuroimaging techniques, means that we are poised to increase our understanding of the brain processes of breathlessness and their modulation.

  4. The thin-skinned style of the South Atlas Front in Central Algeria

    Energy Technology Data Exchange (ETDEWEB)

    Bracene, R.; Bellahcene, A.; Bekkouche, D [Sonatrach Exploration (Algeria); Mercier, E.; Frizon de Lamotte, D. [Universite de Cergy-Pntoise, Cedex (France). Departement des Sciences de la Terre

    1998-12-31

    Seismic lines cutting through the southern front of the Sahara Atlas show that the front is not superimposed on a major basement fault. Folded Cretaceous rocks can be observed on these lines to overlie a decollement surface climbing from Triassic to Early Cretaceous, below which flat-lying sediments can be recognized. The structural style is thus interpreted to be thin skinned and the folds underlining the front as ramp-related features. The development of duplexes in the core of some anticlines explains the apparent thickening of Cretaceous and/or Jurassic strata revealed by boreholes. This thickening was previously interpreted to be related to now-inverted extensional half-grabens, a model which cannot now be supported. This new interpretation allows a reassessment of other parts of the Sahara Atlas system, the large-scale structural model for which is that of large half-graben system that has undergone inversion because of shortening between the High Plateau massif and the Sahara Platform. (author)

  5. Central hypersensitivity in chronic musculoskeletal pain.

    Science.gov (United States)

    Curatolo, Michele; Arendt-Nielsen, Lars

    2015-05-01

    Clinical research has consistently detected alteration in central pain processing leading to hypersensitivity. Most methods used in humans are reliable and have face validity to detect widespread central hypersensitivity. However, construct validity is difficult to investigate due to lack of gold standards. Reference values in the pain-free population have been generated, but need replication. Research on pain biomarkers that reflect specific central hypersensitivity processes is warranted. Few studies have analyzed the prognostic value of central hypersensitivity. Most medications acting at central level and some non-pharmacological approaches, including psychological interventions, are likely to attenuate central hypersensitivity.

  6. Central hypersensitivity in chronic musculoskeletal pain

    DEFF Research Database (Denmark)

    Curatolo, Michele; Arendt-Nielsen, Lars

    2015-01-01

    Clinical research has consistently detected alteration in central pain processing leading to hypersensitivity. Most methods used in humans are reliable and have face validity to detect widespread central hypersensitivity. However, construct validity is difficult to investigate due to lack of gold...... standards. Reference values in the pain-free population have been generated, but need replication. Research on pain biomarkers that reflect specific central hypersensitivity processes is warranted. Few studies have analyzed the prognostic value of central hypersensitivity. Most medications acting at central...... level and some non-pharmacological approaches, including psychological interventions, are likely to attenuate central hypersensitivity....

  7. Evidence for central regulation of glucose metabolism.

    Science.gov (United States)

    Carey, Michelle; Kehlenbrink, Sylvia; Hawkins, Meredith

    2013-12-06

    Evidence for central regulation of glucose homeostasis is accumulating from both animal and human studies. Central nutrient and hormone sensing in the hypothalamus appears to coordinate regulation of whole body metabolism. Central signals activate ATP-sensitive potassium (KATP) channels, thereby down-regulating glucose production, likely through vagal efferent signals. Recent human studies are consistent with this hypothesis. The contributions of direct and central inputs to metabolic regulation are likely of comparable magnitude, with somewhat delayed central effects and more rapid peripheral effects. Understanding central regulation of glucose metabolism could promote the development of novel therapeutic approaches for such metabolic conditions as diabetes mellitus.

  8. [Historical demography in the Central American isthmus].

    Science.gov (United States)

    Perez Brignoli, H

    1980-01-01

    The author reviews and evaluates sources of information on the demographic history of Central America. Past and present administrative, state, ecclesiastical, and genealogical sources are examined, and recent studies of various Central American countries are cited. A bibliography is provided

  9. Neurocitoma no sistema nervoso central

    Directory of Open Access Journals (Sweden)

    José Torquato Severo

    1973-03-01

    Full Text Available É relatado o caso de uma paciente com 6 anos de idade, hospitalizada com síndrome de hipertensão intracraniana. Após o exame neuro-radiológico que evidenciou processo expansivo frontal direito, a paciente foi submetida à cirurgia, durante a qual ocorreu o óbito. O exame histo-patológico do material retirado durante o ato operatório, permitiu o diagnóstico de neurocitoma, tumor raro no sistema nervoso central.

  10. Kalmanovitz y la banca central.

    OpenAIRE

    Maya M, Guillermo

    2011-01-01

    Salomón Kalmanovitz, Codirector del Banco de la República (B de la R) hasta enero de 2005, uno de los economistas colombianos más brillantes, publicó un libro titulado Ensayos sobre Banca Central, Comportamiento, Independencia e Historia (Norma, 2003). Si los estudiantes de economía de los años 70 y 80 estudiaron a un Kalmanovitz marxista, los estudiantes de hoy estudian a un economista ortodoxo y liberal, igualmente brillante. Kalmanovitz es un partidario de la independencia de la BC para la...

  11. Puente del Pedrido, tramo central

    Directory of Open Access Journals (Sweden)

    Torroja, Eduardo

    1962-02-01

    Full Text Available Planteada la necesidad de proceder a la ejecución del tramo central del puente en el Pasaje del Pedrido sobre la ría de Betanzos, y encontrándonos con que las armaduras para el mismo, que ya estaban acopiadas a pie de obra antes de la guerra, estaban totalmente no tuvimos inconveniente, puesto que habían de adquirirse de nuevo, en introducir algunas ligeras modificaciones sobre el proyecto anterior, a fin de reducir en lo posible el coste de la obra.

  12. Increasing production at Cerrejon Central

    Energy Technology Data Exchange (ETDEWEB)

    Climent, J.; Alvarez, M.

    1997-12-01

    Colombian coal miner Prodeco is hoping to increase production of its opencast Cerrejon Central mine from 3.1 Mt in 1996 to 10 Mt by 2002. This article discusses how this is to be achieved. The development programme, presently in Phase II of three phases, will affect not only the mine itself but also include improvements to loading facilities at Santa Marta port, at the company`s head office, and construction of a new port nearby. 3 figs., 2 tabs., 3 photos.

  13. Nonlocally Centralized Simultaneous Sparse Coding

    Institute of Scientific and Technical Information of China (English)

    雷阳; 宋占杰

    2016-01-01

    The concept of structured sparse coding noise is introduced to exploit the spatial correlations and nonlo-cal constraint of the local structure. Then the model of nonlocally centralized simultaneous sparse coding(NC-SSC)is proposed for reconstructing the original image, and an algorithm is proposed to transform the simultaneous sparse coding into reweighted low-rank approximation. Experimental results on image denoisng, deblurring and super-resolution demonstrate the advantage of the proposed NC-SSC method over the state-of-the-art image resto-ration methods.

  14. Inverting the central limit theorem

    CERN Document Server

    Navascues, Miguel; Villanueva, Ignacio

    2011-01-01

    The central limit theorem states that the sum of N independently distributed n-tuples of real variables (subject to appropriate normalization) tends to a multivariate gaussian distribution for large N. Here we propose to invert this argument: given a set of n correlated gaussian variables, we try to infer information about the structure of the discrete microscopic probability distributions whose convolution generated such a macroscopic behavior. The techniques developed along the article are applied to prove that the classical description of certain macroscopic optical experiments is infinitely more complex than the quantum one.

  15. Distributed trace using central performance counter memory

    Science.gov (United States)

    Satterfield, David L.; Sexton, James C.

    2013-01-22

    A plurality of processing cores, are central storage unit having at least memory connected in a daisy chain manner, forming a daisy chain ring layout on an integrated chip. At least one of the plurality of processing cores places trace data on the daisy chain connection for transmitting the trace data to the central storage unit, and the central storage unit detects the trace data and stores the trace data in the memory co-located in with the central storage unit.

  16. Capitalizing Central Banks: A Net Worth Approach

    OpenAIRE

    Alain Ize

    2005-01-01

    This paper provides a simple, quantitative, net worth-based, approach to assessing the need for central bank capital. It derives a concept of "core capital" (a function of the central bank's operating expenditures and the carrying cost of its international reserves) as the minimum capital needed by a central bank to ensure the credibility of its inflation target. The approach is illustrated with the published accounts of three loss-making central banks and selected accounting entries for a br...

  17. The European Central Bank and the Eurosystem

    OpenAIRE

    Carol C. Bertaut

    2002-01-01

    The Eurosystem comprises the European Central Bank at its center as well as the national central banks of the twelve countries currently participating in monetary union. The European Central Bank was established in July 1998, six months before the beginning of Stage Three of economic and monetary union. Although decisions regarding monetary policy are made centrally by the Governing Council of the Eurosystem, the operational aspects of monetary policy-including open market operations, adminis...

  18. Accountability of central banks: aspects and quantification

    Directory of Open Access Journals (Sweden)

    J. DE HAAN

    1999-06-01

    Full Text Available The work examines the relationship between central bank independence and accountability. The authors do this by using an indicator for central bank accountability based on the laws of 16 central banks. Central bank accountability is identified as having three distinct features, namely, the explicit definition and ranking of the objectives of monetary policy, the transparency of the actual monetary policy, and the final responsibility to monetary policy.

  19. Legal and actual central bank independence

    OpenAIRE

    Artha, I.K.D.S.; de Haan, J.

    2010-01-01

    Indicators of central bank independence (CBI) based on the interpretation central bank laws in place may not capture the actual independence of the central bank. This paper develops an indicator of actual independence of the Bank Indonesia (BI), the central bank of Indonesia, for the period 1953-2008 and compares it with a new legal CBI indicator based on Cukierman (1992). The indicator of actual independence captures institutional and economic factors that affect CBI. We find that before 199...

  20. Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

    Science.gov (United States)

    Moskowitz, Bruce M.; Reynolds, Richard L.; Goldstein, Harland L.; Berquó, Thelma S.; Kokaly, Raymond F.; Bristow, Charlie S.

    2016-09-01

    Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM bioavailability to marine and terrestrial ecosystems.

  1. "Christofest" New Yorgi Central Parkis / Rael Artel

    Index Scriptorium Estoniae

    Artel, Rael, 1980-

    2004-01-01

    12. II 2005. a. avatakse Christo ja Jeanne-Claude'i keskkonnainstallatsioon "The Gates" New Yorgi Central Parkis. Paralleelselt toimub Metropolitan Muuseumis näitus "Christo and Jeanne-Claude : The Gates, Central Park, New York", kus eksponeeritakse Central Parki installatsiooni ettevalmistavaid materjale: joonistusi, diagramme, fotosid jne

  2. "Christofest" New Yorgi Central Parkis / Rael Artel

    Index Scriptorium Estoniae

    Artel, Rael, 1980-

    2004-01-01

    12. II 2005. a. avatakse Christo ja Jeanne-Claude'i keskkonnainstallatsioon "The Gates" New Yorgi Central Parkis. Paralleelselt toimub Metropolitan Muuseumis näitus "Christo and Jeanne-Claude : The Gates, Central Park, New York", kus eksponeeritakse Central Parki installatsiooni ettevalmistavaid materjale: joonistusi, diagramme, fotosid jne

  3. Central Pontine Myelinolysis: Report of Four Cases

    Directory of Open Access Journals (Sweden)

    Handan Akar

    2010-09-01

    Full Text Available Central pontine myelinolysis is a neurological disorder characterized by loss of myelin in the central pons as well as in the other parts of the brain like basal ganglia, lateral geniculate bodies, external and internal capsules, and cerebellum. We report the clinical and radiological findings of three patients with central pontine myelinolysis and one patient with both pontine and extrapontine myelinolysis.

  4. Central bank independence and inflation revisited

    NARCIS (Netherlands)

    Klomp, Jeroen; de Haan, Jakob

    We re-examine the relationship between central bank independence (CBI), proxied by the central bank governor's turnover rate and an indicator based on central bank laws in place, and inflation using a random coefficient model with the Hildreth-Houck estimator for more than 100 countries in the

  5. Central bank independence and inflation revisited

    NARCIS (Netherlands)

    Klomp, J.G.; Haan, de J.

    2010-01-01

    We re-examine the relationship between central bank independence (CBI), proxied by the central bank governor's turnover rate and an indicator based on central bank laws in place, and inflation using a random coefficient model with the Hildreth-Houck estimator for more than 100 countries in the

  6. [Central venous blood gas analysis].

    Science.gov (United States)

    Marano, Marco; D'Amato, Anna; Guiotto, Giovanna; Schiraldi, Fernando

    2015-01-01

    The hemodialysis might interfere with patients hemodynamic, as the technique allows a sophisticated game with extra and intravascular fluids. As the cardiocirculatory response could sometimes be unpredictable, it is interesting to collect valuable information by reaching a deep understanding of the tissue metabolism which is mirrored by the blood gas analysis of variations in arterial and central venous blood samples. Particularly interesting are the time course variations of the central venous hemoglobin saturation (ScvO2), which are directly related to the patient with O2-demand as well as to the O2-Delivery (DO2). The ScvO2 is determined by four parameters (cardiac output, Hb concentration, arterial Hb saturation and O2 consumption): If the fluids subtraction during dialysis was about to determine an occult hypoperfusion, the ScvO2 reduction would be a timely warning sign to be considered. Moreover, while the normal veno-arterial PCO2 difference is 2-4 mmHg, whenever a mismatch between O2-demand and DO2arise, a larger v-aPCO2 difference should be observed.

  7. Precipitation chemistry in central Amazonia

    Science.gov (United States)

    Andreae, M. O.; Talbot, R. W.; Berresheim, H.; Beecher, K. M.

    1990-01-01

    Rain samples from three sites in central Amazonia were collected over a period of 6 weeks during the 1987 wet season and analyzed for ionic species and dissolved organic carbon. A continuous record of precipitation chemistry and amount was obtained at two of these sites, which were free from local or regional pollution, for a time period of over 1 month. The volume-weighted mean concentrations of most species were found to be about a factor of 5 lower during the wet season compared with previous results from the dry season. Only sodium, potassium, and chloride showed similar concentrations in both seasons. When the seasonal difference in rainfall amount is taken into consideration, the deposition fluxes are only slightly lower for most species during the wet season than during the dry season, again with the exception of chloride, potassium, and sodium. Sodium and chloride are present in the same ratio as in sea salt; rapid advection of air masses of marine origin to the central Amazon Basin during the wet season may be responsible for the observed higher deposition flux of these species. Statistical analysis suggests that sulfate is, to a large extent, of marine (sea salt and biogenic) origin, but that long-range transport of combustion-derived aerosols also makes a significant contribution to sulfate and nitrate levels in Amazonian rain. Organic acid concentrations in rain were responsible for a large fraction of the observed precipitation acidity; their concentration was strongly influenced by gas/liquid interactions.

  8. Glial involvement in trigeminal central sensitization

    Institute of Scientific and Technical Information of China (English)

    Yu-feng XIE

    2008-01-01

    Recent studies have indicated that trigeminal neurons exhibit central sensitization, an increase in the excitability of neurons within the central nervous system to the extent that a normally innocuous stimulus begins to produce pain after inflamma-tion or injury, and that glial activities play a vital role in this central sensitization. The involvement of glial cells in trigeminal central sensitization contains multiple mechanisms, including interaction with glutamatergic and purinergic receptors. A better understanding of the trigeminal central sensitization mediated by glial cells will help to find potential therapeutic targets and lead to developing new analge-sics for orofacial-specific pain with higher efficiency and fewer side-effects.

  9. Reduced central blood volume in cirrhosis

    DEFF Research Database (Denmark)

    Henriksen, Jens Henrik; Bendtsen, Flemming; Sørensen, T I

    1989-01-01

    for measuring the central blood volume. We have developed a method that enables us to determine directly the central blood volume, i.e., the blood volume in the heart cavities, lungs, and central arterial tree. In 60 patients with cirrhosis and 16 control subjects the central blood volume was assessed according...... flow, or sequestration of fluid in the peritoneal cavity, or any combination thereof. The present results indicate that central circulatory underfilling is an integral part of the hemodynamic and homeostatic derangement observed in cirrhosis....

  10. Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

    Science.gov (United States)

    Moskowitz, Bruce M; Reynolds, Richard; Goldstein, Harland; Beroquo, Thelma; Kokaly, Raymond; Bristow, Charlie S

    2016-01-01

    Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM < 0.1 μm. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65

  11. Central Solenoid Insert Technical Specification

    Energy Technology Data Exchange (ETDEWEB)

    Martovetsky, Nicolai N [ORNL; Smirnov, Alexandre [ORNL

    2011-09-01

    The US ITER Project Office (USIPO) is responsible for the ITER central solenoid (CS) contribution to the ITER project. The Central Solenoid Insert (CSI) project will allow ITER validation the appropriate lengths of the conductors to be used in the full-scale CS coils under relevant conditions. The ITER Program plans to build and test a CSI to verify the performance of the CS conductor. The CSI is a one-layer solenoid with an inner diameter of 1.48 m and a height of 4.45 m between electric terminal ends. The coil weight with the terminals is approximately 820 kg without insulation. The major goal of the CSI is to measure the temperature margin of the CS under the ITER direct current (DC) operating conditions, including determining sensitivity to load cycles. Performance of the joints, ramp rate sensitivity, and stability against thermal or electromagnetic disturbances, electrical insulation, losses, and instrumentation are addressed separately and therefore are not major goals in this project. However, losses and joint performance will be tested during the CSI testing campaign. The USIPO will build the CSI that will be tested at the Central Solenoid Model Coil (CSMC) Test Facility at the Japan Atomic Energy Agency (JAEA), Naka, Japan. The industrial vendors (the Suppliers) will report to the USIPO (the Company). All approvals to proceed will be issued by the Company, which in some cases, as specified in this document, will also require the approval of the ITER Organization. Responsibilities and obligations will be covered by respective contracts between the USIPO, called Company interchangeably, and the industrial Prime Contractors, called Suppliers. Different stages of work may be performed by more than one Prime Contractor, as described in this specification. Technical requirements of the contract between the Company and the Prime Contractor will be covered by the Fabrication Specifications developed by the Prime Contractor based on this document and approved by

  12. 76 FR 22746 - Wiregrass Central Railway, LLC-Acquisition and Operation Exemption-Wiregrass Central Railroad...

    Science.gov (United States)

    2011-04-22

    ... Surface Transportation Board Wiregrass Central Railway, LLC--Acquisition and Operation Exemption--Wiregrass Central Railroad Company, Inc. Wiregrass Central Railway, LLC (WCR), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from Wiregrass Central Railroad Company, Inc...

  13. Contrasting evolution of low-P rare metal granites from two different terranes in the Hoggar area, Algeria

    Science.gov (United States)

    Kesraoui, Mokrane; Nedjari, Samia

    2002-05-01

    Two mineralogically different rare metal granites located in two distinct terranes from the Tuareg area are compared: the Tin-Amzi granite in the north of the Laouni Terrane and the Ebelekan granite in the Assodé-Issalane Terrane. The Tin-Amzi granite is enclosed within Eburnean granulitic gneisses, and consists of albite, quartz, protolithionite, K-feldspar and topaz granite (PG). The accessory minerals include columbite tantalite, U- and Hf-rich zircon, Th-uraninite, wolframoixiolite and wolframite. This facies is characterised by a mineralogical evolution from the bottom to the top underlined by a strong resorption of K-feldspar and albite and the crystalliK-feldspar of more abundant topaz and protolithionite II which is further altered in muscovite and Mn-siderite. It is underlain by an albite, K-feldspar, F-rich topaz, quartz and muscovite granite (MG), with W-Nb-Ta oxides, wolframite, Nb-rutile, zircon and scarce uranothorite as accessories. The Ebelekan granite intrudes into a coarse-grained biotite granite enclosed within upper amphibolite-facies metasediments. It comprises a zinnwaldite, albite, topaz porphyritic granite (ZG) with "snow ball" quartz and K-feldspar. The accessories are zircon, monazite, uranothorite, Ta bearing cassiterite, columbite tantalite and wodginite. It is capped by a banded aplite-pegmatite (AP). The geochemistry of Tin-Amzi and Ebelekan granites is nearly comparable. Both are peraluminous (A/CNK=1.10-1.29; ASI=1.17-1.31), sodolithic and fluorine rich with high SiO 2, Al 2O 3, Na 2O+K 2O, Rb, Ga, Li, Ta, Nb, Sn and low FeO, MgO, TiO 2, Ba, Sr, Y, Zr and REE contents. These rare metal Ta bearing granites belong to the P-poor subclass, relating to their P 2O 5 content ( 0.03-0.15 wt.%). Nevertheless, they are distinguished by their concentration of W, Sn and Ta. The Tin-Amzi granite is W-Ta bearing with high W/Sn ratio whereas the Ebelekan granite is Ta-Sn bearing with insignificant W content. At Tin-Amzi the W-Nb-Ta minerals define a sequence formed by W-columbite tantalite followed by wolframoixiolite and finally wolframite showing the effect of hydrothermal overprinting with an extreme W enrichment of the fluids. At Ebelekan, the Sn-Nb-Ta oxides follow a Mn sequence: manganocolumbite→manganotantalite→wodginite+titanowodginite→cassiterite that represents a trend of primary crystallisation resulting from progressive substitution Fe→Mn and Nb→Ta during the magmatic fractionation.

  14. Central Exclusive Production at LHCb

    CERN Document Server

    McNulty, Ronan

    2016-01-01

    Central Exclusive Production (CEP) is a unique process at hadron machines in which particles are produced via colourless propagators. LHCb have measured the cross-sections for the CEP of vector mesons, $J/\\psi,\\psi(2S),\\Upsilon(1S),\\Upsilon(2S)$ and $\\Upsilon(3S)$, which are photo-produced. In the double pomeron exchange process, preliminary measurements have been made of $\\chi_{c0},\\chi_{c1}, \\chi_{c2}$ meson production while the first observations of the CEP of pairs of charmonia, $J/\\psi J/\\psi$ and $J/\\psi \\psi(2S)$, have been made and limits obtained on the pair production of other charmonia.

  15. Centralized Allocation in Multiple Markets

    DEFF Research Database (Denmark)

    Monte, Daniel; Tumennasan, Norovsambuu

    The problem of allocating indivisible objects to different agents, where each indi vidual is assigned at most one object, has been widely studied. Pápai (2000) shows that the set of strategy-proof, nonbossy, Pareto optimal and reallocation-proof rules are hierarchical exchange rules | generalizat......The problem of allocating indivisible objects to different agents, where each indi vidual is assigned at most one object, has been widely studied. Pápai (2000) shows that the set of strategy-proof, nonbossy, Pareto optimal and reallocation-proof rules are hierarchical exchange rules...... | generalizations of Gale's Top Trading Cycles mechanism. We study the centralized allocation that takes place in multiple markets. For example, the assignment of multiple types of indivisible objects; or the assignment of objects in successive periods. We show that the set of strategy-proof, Pareto efficient...

  16. Central Clearing of OTC Derivatives

    DEFF Research Database (Denmark)

    Cont, Rama; Kokholm, Thomas

    2014-01-01

    is determined by the tradeoff between multilateral netting across dealers on one hand and bilateral netting across asset classes on the other hand. We find this tradeoff to be sensitive to assumptions on heterogeneity of asset classes in terms of `riskyness' of the asset class as well as correlation...... classes are realistically taken into account. We argue that empirically plausible specifications of model parameters lead to the conclusion that central clearing does reduce interdealer exposures: the gain from multilateral netting in a CCP overweighs the loss of netting across asset classes in bilateral...... netting agreements. When a CCP exists for interest rate derivatives, adding a CCP for credit derivatives is shown to decrease overall exposures. These findings are shown to be robust to the statistical assumptions of the model as well as the choice of risk measure used to quantify exposures....

  17. CST-01-Central Standard Timing

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    薄如蝉翼名为CentralStandardTiming的工作室推出了E—ink材质代号为CST-01的手表,其厚度仅为0.8mm,号称全球最薄。一次充电10分钟便可连续使用15年。该手表屏幕由多层柔性材料构成。整体十分轻巧并且可弯曲,腕带则采用了柔性不锈钢材质。CST-01的预售价格为129美元。约合人民币800元,目前已经在著名的集资网站Kickstarter上创建项目。

  18. Banco Central de Costa Rica

    Directory of Open Access Journals (Sweden)

    Sauter, Franz

    1963-06-01

    Full Text Available This new building is intended to house the various services of the Central Bank of Costa Rica. It has a prestressed concrete structure, and consists of a basement parking space for 105 vehicles, and nine storeys, providing altogether a floor surface of 12,000 ms2. The building rests on a ground area of 40 by 60 ms, and the main structure occupies 22 by 45 ms. This Bank is located in a district of narrow streets, but its main side overlooks a green open space, which will improve its visibility and appearance. The building structure is made up of a framework of prestressed beams and columns. The beams have been concreted at the site, and the joists, which are also prestressed, are factory made. This framework, at each floor level, constitutes the basis of a continuous slab, which renders the total structure exceedingly stiff. The main continuous girders span 11.22 ms spaces, and vary in cross section. The prestressing reinforcements consist of 6 Loeba type cables. This is an original design by Dr. Leonhardt, in which the cables are placed on three horizontal layers, of parabolic outline. Each cable is made up of 12 x 5.4 mm wires, with a breaking stress of 180 kg/mm2 The tensioning stress was 108 kg/mm2, and the total prestress load is 29,700 kgs. The cables run in corrugated metal tubes, and these were kept in precise position with the aid of distance pieces.El nuevo edificio, destinado a agrupar los servicios del Banco Central de Costa Rica, está constituido por una estructura de hormigón pretensado. El inmueble dispone de un sótano, estacionamiento propio para 105 vehículos y nueve plantas, con una superficie total de 12.000 metros cuadrados. Se asienta sobre una base de 40x60 m, donde se levanta un núcleo central de 22x45 metros. Está situado en un barrio de calles estrechas, pero tiene su fachada, principal frente a una zona verde que le proporcionará mayor categoría y visibilidad. La estructura se compone de una retícula de vigas

  19. ITER Central Solenoid Module Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Smith, John [General Atomics, San Diego, CA (United States)

    2016-09-23

    The fabrication of the modules for the ITER Central Solenoid (CS) has started in a dedicated production facility located in Poway, California, USA. The necessary tools have been designed, built, installed, and tested in the facility to enable the start of production. The current schedule has first module fabrication completed in 2017, followed by testing and subsequent shipment to ITER. The Central Solenoid is a key component of the ITER tokamak providing the inductive voltage to initiate and sustain the plasma current and to position and shape the plasma. The design of the CS has been a collaborative effort between the US ITER Project Office (US ITER), the international ITER Organization (IO) and General Atomics (GA). GA’s responsibility includes: completing the fabrication design, developing and qualifying the fabrication processes and tools, and then completing the fabrication of the seven 110 tonne CS modules. The modules will be shipped separately to the ITER site, and then stacked and aligned in the Assembly Hall prior to insertion in the core of the ITER tokamak. A dedicated facility in Poway, California, USA has been established by GA to complete the fabrication of the seven modules. Infrastructure improvements included thick reinforced concrete floors, a diesel generator for backup power, along with, cranes for moving the tooling within the facility. The fabrication process for a single module requires approximately 22 months followed by five months of testing, which includes preliminary electrical testing followed by high current (48.5 kA) tests at 4.7K. The production of the seven modules is completed in a parallel fashion through ten process stations. The process stations have been designed and built with most stations having completed testing and qualification for carrying out the required fabrication processes. The final qualification step for each process station is achieved by the successful production of a prototype coil. Fabrication of the first

  20. Reduced central blood volume in cirrhosis

    DEFF Research Database (Denmark)

    Bendtsen, F; Henriksen, Jens Henrik Sahl; Sørensen, T I

    1989-01-01

    for measuring the central blood volume. We have developed a method that enables us to determine directly the central blood volume, i.e., the blood volume in the heart cavities, lungs, and central arterial tree. In 60 patients with cirrhosis and 16 control subjects the central blood volume was assessed according......The pathogenesis of ascites formation in cirrhosis is uncertain. It is still under debate whether the effective blood volume is reduced (underfilling theory) or whether the intravascular compartment is expanded (overflow theory). This problem has not yet been solved because of insufficient tools...... to the kinetic theory as the product of cardiac output and mean transit time of the central vascular bed. Central blood volume was significantly smaller in patients with cirrhosis than in controls (mean 21 vs. 27 ml/kg estimated ideal body weight, p less than 0.001; 25% vs. 33% of the total blood volume, p less...

  1. Hirsch index as a network centrality measure

    CERN Document Server

    Campiteli, Monica G; Soles, Paulo R C; Soares, Leonardo H D; Kinouchi, Osame

    2010-01-01

    We study the h Hirsch index as a local node centrality measure for complex networks in general. The h index is compared with the Degree centrality (a local measure), the Betweenness and Eigenvector centralities (two non-local measures) in the case of a biological network (Yeast interaction protein-protein network) and a linguistic network (Moby Thesaurus II) as test environments. In both networks, the Hirsch index has poor correlation with Betweenness centrality but correlates well with Eigenvector centrality, specially for the more important nodes that are relevant for ranking purposes, say in Search Machine Optimization. In the thesaurus network, the h index seems even to outperform the Eigenvector centrality measure as evaluated by simple linguistic criteria.

  2. AAPT Diagnostic Criteria for Central Neuropathic Pain

    DEFF Research Database (Denmark)

    Widerstrom-Noga, Eva; Loeser, John D.; Jensen, Troels Staehelin

    2017-01-01

    framework can be extended to central pain due to other causes such as traumatic brain injury. The classification of central neuropathic pain is organized according to the AAPT multidimensional framework, specifically (1) core diagnostic criteria; (2) common features; (3) common medical and psychiatric......Central neuropathic pain, which is pain caused by a lesion or disease of the central somatosensory nervous system, is a serious consequence of spinal cord injury, stroke, multiple sclerosis and other conditions affecting the central nervous system. A collaborative effort between the Analgesic......, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership and the American Pain Society (APS), the ACTTION-APS Pain Taxonomy (AAPT) initiative, invited a working group to develop diagnostic criteria for central neuropathic pain...

  3. Performance contracting in central government in Denmark

    DEFF Research Database (Denmark)

    Kristiansen, Mads Bøge

    2015-01-01

    in organisational structure, tasks, culture and time with performance contracts is expected to affect the contract content, hypotheses on variation across agencies are deduced. The empirical basis of the paper is a study of all performance contracts between parent ministries and subordinate agencies in Danish......This paper looks into performance contracting in Danish central government. Management by Objectives and Results (MBOR) was adopted in central government in Denmark during the 1980s and early 1990s. In 1991, performance contracts between parent ministries and their agencies were introduced...... in Danish central government. Since their introduction, performance contracts have become central elements in the steering and management of agencies in central government in Denmark, and today they are nearly universally adopted in central government. In Denmark, the Ministry of Finance is responsible...

  4. A matrix analysis of different centrality measures

    CERN Document Server

    Benzi, Michele

    2013-01-01

    Node centrality measures including degree, eigenvector, Katz and subgraph centralities are analyzed for both undirected and directed networks. We show how parameter-dependent measures, such as Katz and subgraph centrality, can be "tuned" to interpolate between degree and eigenvector centrality, which appear as limiting cases of the other measures. We interpret our finding in terms of the local and global influence of a given node in the graph as measured by graph walks of different length through that node. Our analysis gives some guidance for the choice of parameters in Katz and subgraph centrality, and provides an explanation for the observed correlations between different centrality measures and for the stability exhibited by the ranking vectors for certain parameter ranges. The important role played by the spectral gap of the adjacency matrix is also highlighted.

  5. Transpleural central venous catheter discovered during thoracotomy

    Directory of Open Access Journals (Sweden)

    Ashima Malhotra

    2014-01-01

    Full Text Available We report an uncommon complication of subclavian central venous catheterization, discovered at thoracotomy. The central venous catheter (CVC was placed by left infraclavicular route after induction of general anesthesia. CVC was secured after aspiration of blood and satisfactory central venous tracing. On thoracotomy, CVC was noticed to traverse the pleural cavity while the tracing was normal. CVC was thus removed consequent to which bleeding from each puncture site was noticed, that were secured surgically.

  6. Central waste complex interim operational safety requirements

    Energy Technology Data Exchange (ETDEWEB)

    Bendixsen, R.B.; Ames, R.R., Fluor Daniel Hanford

    1997-03-20

    This Interim Operational Safety Requirements document supports the authorization basis for interim operations and identifies restrictions on interim operations for the disposal and storage of solid waste in the Central Waste Complex. The Central Waste Complex Interim Operational Safety Requirements provide the necessary controls on operations in the Central Waste Complex to ensure the radiological and hazardous material exposure will be acceptable from an overall health and safety standpoint to the worker, the onsite personnel, 1327 the public and the environment.

  7. Market strategies for Central American dry beans.

    OpenAIRE

    Mertínez, Lourdes; Bernsten, Richard; Zamora, Miguel

    2004-01-01

    In the past few years, the dry bean sub-sector in CentralAmerica has witnessed many dynamic changes. Unless wefind ways to increase the competitiveness of the regionalbean sub-sector, Central American countries will likelyexperience significant negative social and economic impacts,especially since these countries are facing the challenge ofadjusting to new open markets, such as the Central AmericanFree Trade Agreement (CAFTA). Bean traders, retailers, andknowledgeable government official in C...

  8. Towards a centralized Grid Speedometer

    Energy Technology Data Exchange (ETDEWEB)

    Dzhunov, I. [CERN; Andreeva, J. [CERN; Fajardo, E.; Gutsche, O.; Luyckx, S.; Saiz, P. [CERN

    2014-01-01

    Given the distributed nature of the Worldwide LHC Computing Grid and the way CPU resources are pledged and shared around the globe, Virtual Organizations (VOs) face the challenge of monitoring the use of these resources. For CMS and the operation of centralized workflows, the monitoring of how many production jobs are running and pending in the Glidein WMS production pools is very important. The Dashboard Site Status Board (SSB) provides a very flexible framework to collect, aggregate and visualize data. The CMS production monitoring team uses the SSB to define the metrics that have to be monitored and the alarms that have to be raised. During the integration of CMS production monitoring into the SSB, several enhancements to the core functionality of the SSB were required, They were implemented in a generic way, so that other VOs using the SSB can exploit them. Alongside these enhancements, there were a number of changes to the core of the SSB framework. This paper presents the details of the implementation and the advantages for current and future usage of the new features in SSB.

  9. [Aniseikonia of central serous chorioretinopathy].

    Science.gov (United States)

    Hisada, H; Awaya, S

    1992-03-01

    Central serous chorioretinopathy (CRS) is one of the typical diseases that accompany micropsia. However very little is known about micropsia of CRS, because of the difficulty to measure "aniseikonia" in terms of micropsia. Aniseikonia in 65 cases of CRS was measured quantitatively by Awaya's New Aniseikonia Tests (NAT). The tests were performed at two different distances of 40 cm (visual angle: 6 degrees) and 20 cm (12 degrees) and under 4 meridians of the halfmoon on NAT, horizontal, 45 degrees, vertical and 135 degrees, respectively. The mean value of aniseikonia under each testing condition was as follows: 6 degrees horizontal -3.13%, 45 degrees -2.56%, vertical -2.13%, 135 degrees -2.57%, 12 degrees; horizontal -1.38%, 45 degrees -1.69%, vertical -1.84%, 135 degrees -1.50%. At 6 degrees aniseikonia is larger in the horizontal meridian than in the vertical with statistical significance (t-test, p less than 0.05), while at 12 degrees aniseikonia is smaller than at 6 degrees and shows no particular tendency in terms of meridian. The phenomenon observed at 6 degrees may be what is called "oriented metamorphopsia".

  10. Towards a centralized Grid Speedometer

    CERN Document Server

    Gutsche, Oliver

    2013-01-01

    Given the distributed nature of the grid and the way CPU resources are pledged and scared around the globe, VOs are facing the challenge to monitor the use of these resources. For CMS and the operation of centralized workflows the monitoring of how many production jobs are running and pending in the Glidein WMS production pools is very important. The Dashboard SSB (Site Status Board) provides a very flexible framework to collect, aggregate and visualize data. The CMS production monitoring team uses the SSB to define the metrics that have to be monitored and the alarms that have to be set. During the integration of the CMS production monitoring into the SSB, several enhancements to the core functionality of the SSB were implemented; all in a generic way, so that other VOs using the SSB can use them as well. Alongside these enhancements, there were a few changes to the core of the SSB framework from which the CMS production team was able to benefit. We will present the details of the implementation and the adva...

  11. Central nervous system tuberculosis: MRI

    Energy Technology Data Exchange (ETDEWEB)

    Kioumehr, F.; Dadsetan, M.R.; Rooholamini, S.A.; Au, A.

    1994-02-01

    The MRI findings of 18 proven cases of central nervous system (CNS) tuberculosis were reviewed; 10 patients were seropositive for HIV. All had medical, laboratory, or surgical proof of CNS tuberculosis. Eleven patients had meningitis, of whom two also had arachnoiditis. Five patients had focal intra-axial tuberculomas: four brain masses and one an intramedullary spinal lesion. Two patients had focal extra-axial tuberculomas: one in the pontine cistern, and one in the spine. In all 11 patients with meningitis MRI showed diffuse, thick, meningeal enhancement. All intraparenchymal tuberculomas showed low signal intensity on T2-weighted images and ring or nodular enhancement. The extra-axial tuberculomas had areas isointense or hypointense relative to normal brain and spinal cord on T2-weighted images. Although tuberculous meningitis cannot be differentiated from other meningitides on the basis of MR findings, intraparenchymal tuberculomas show characteristic T2 shortening, not found in most other space-occupying lesions. In the appropriate clinical setting, tuberculoma should be considered. (orig.)

  12. The Centrality of Organization Design

    Directory of Open Access Journals (Sweden)

    Raymond E. Miles

    2012-05-01

    Full Text Available I am excited about this new journal focused on the subject of organization design. In my view, organization design is a central issue in the field of management. Designing an organization requires an understanding of strategy, as we pointed out some time ago (Miles & Snow, 1978. For example, if you want to be a prospector (a first-mover strategy, you have to design your firm to move quickly in new directions, which is likely to require that it be arranged so that various kinds of teams can interact across organizational units and levels. Designing an organization to follow a first-mover strategy also requires both an understanding of leadership and a commitment to the free flow of information throughout the organization. Leaders must understand how cross-functional teams pursue ideas and opportunities, and they must facilitate collaborative knowledge sharing to drive innovations that help the firm operate entrepreneurially. Because an organization is a complex, dynamic system, perhaps no other single topic is so deeply implanted at the core of management, organization theory, and organizational behavior as organization design. Moreover, organization design once was, and could be again, the topic of an ongoing dialogue between managers and academics focused on business organizations.

  13. Maximal switchability of centralized networks

    Science.gov (United States)

    Vakulenko, Sergei; Morozov, Ivan; Radulescu, Ovidiu

    2016-08-01

    We consider continuous time Hopfield-like recurrent networks as dynamical models for gene regulation and neural networks. We are interested in networks that contain n high-degree nodes preferably connected to a large number of N s weakly connected satellites, a property that we call n/N s -centrality. If the hub dynamics is slow, we obtain that the large time network dynamics is completely defined by the hub dynamics. Moreover, such networks are maximally flexible and switchable, in the sense that they can switch from a globally attractive rest state to any structurally stable dynamics when the response time of a special controller hub is changed. In particular, we show that a decrease of the controller hub response time can lead to a sharp variation in the network attractor structure: we can obtain a set of new local attractors, whose number can increase exponentially with N, the total number of nodes of the nework. These new attractors can be periodic or even chaotic. We provide an algorithm, which allows us to design networks with the desired switching properties, or to learn them from time series, by adjusting the interactions between hubs and satellites. Such switchable networks could be used as models for context dependent adaptation in functional genetics or as models for cognitive functions in neuroscience.

  14. Central neural pathways for thermoregulation

    Science.gov (United States)

    Morrison, Shaun F.; Nakamura, Kazuhiro

    2010-01-01

    Central neural circuits orchestrate a homeostatic repertoire to maintain body temperature during environmental temperature challenges and to alter body temperature during the inflammatory response. This review summarizes the functional organization of the neural pathways through which cutaneous thermal receptors alter thermoregulatory effectors: the cutaneous circulation for heat loss, the brown adipose tissue, skeletal muscle and heart for thermogenesis and species-dependent mechanisms (sweating, panting and saliva spreading) for evaporative heat loss. These effectors are regulated by parallel but distinct, effector-specific neural pathways that share a common peripheral thermal sensory input. The thermal afferent circuits include cutaneous thermal receptors, spinal dorsal horn neurons and lateral parabrachial nucleus neurons projecting to the preoptic area to influence warm-sensitive, inhibitory output neurons which control thermogenesis-promoting neurons in the dorsomedial hypothalamus that project to premotor neurons in the rostral ventromedial medulla, including the raphe pallidus, that descend to provide the excitation necessary to drive thermogenic thermal effectors. A distinct population of warm-sensitive preoptic neurons controls heat loss through an inhibitory input to raphe pallidus neurons controlling cutaneous vasoconstriction. PMID:21196160

  15. Concept of the central clip

    DEFF Research Database (Denmark)

    Alegria-Barrero, Eduardo; Chan, Pak Hei; Foin, Nicolas

    2014-01-01

    -risk surgical population with severe mitral regurgitation (MR). METHODS AND RESULTS: Patients with severe MR (3 or 4+) and high operative risk (as defined by logistic EuroSCORE) refused for conventional mitral valve repair were considered for MitraClip(®). The procedure was performed under general anaesthesia...... with transoesophageal echocardiographic (TOE) guidance. Device success was defined as placement of one or more MitraClips(®) with a reduction of MR to ≤2+. Patients were followed up clinically and with TOE at one month and one year. From September 2009 to March 2012, 43 patients with severe MR with a mean age of 74.......8±10.7 years (30 males, 13 females; mean logistic EuroSCORE 24.1±11, mean LVEF 47.5±18.5%; mean±SD) were treated. Median follow-up was 385 days (104-630; Q1-Q3). Device implantation success was 93%. All patients were treated following the central clip concept: 52.5% of MR was degenerative in aetiology and 47...

  16. Central vein stenosis masquerading as venous thrombosis

    National Research Council Canada - National Science Library

    Nagapriya Vellalacheruvu; Naresh Monigari; Tom Devasia; Hashir Kareem

    2014-01-01

    .... 3 Learning points Central venous stenosis (CVS), although rare, is a known complication in patients requiring maintenance haemodialysis but symptomatic CVS requiring intervention is not common...

  17. Central venous line complications and tip detection

    Directory of Open Access Journals (Sweden)

    Ameneh Rezaee Gheshlaghi

    2015-06-01

    Full Text Available Central venous line is one of a creative instrument that saves human’s life in critical medical situation. Central venous line access is frequently involved in the disease management. It is used for rapid fluid therapy, transvenous pacemakers, infusion of some medications, hemodialysis or plasmapheresis and etc. Most of the emergency departments have some staffs that are trained for central venous line insertion but related complications occur during central venous line placement.Central venous line might have some complications and complication follow-up should be considered. Thromboembolism and infection are two important medical complications. Arterial puncture, hematoma, pneumothorax and hemothorax are mechanical Central venous line complications. Chest X-ray and some other techniques should be used for detecting these complications.Central venous line tip misplace is a considerable problem for emergency department staffs, previously chest X-ray has been used for central venous line misplace detection. In some recent studies, contrast-enhanced ultrasonography and intravascular electrocardiography have been used for central venous line misplace.

  18. Centrality of nodes in multiplex networks

    CERN Document Server

    Sola, Luis; Criado, Regino; Flores, Julio; del Amo, Alejandro Garcia; Boccaletti, Stefano

    2013-01-01

    We extend the concept of eigenvector centrality to multiplex networks, and introduce several alternative parameters that quantify the importance of nodes in a multi-layered networked system, including the de?nition of vectorial-type centralities. In addition we rigorously show that, under reasonable conditions, such centrality measures exist and are unique. Computer experiments and simulations demonstrate that the proposed measures provide substantially di?erent results when applied to the same multiplex structure, and highlight the non-trivial relationships between the di?erent measures of centrality introduced.

  19. Human health improvement in Sub-Saharan Africa through integrated management of arthropod transmitted diseases and natural resources Mejoramiento de la salud humana en África al sur del Sahara mediante el manejo integrado de enfermedades transmitidas por artrópodos y el manejo de recursos naturales

    Directory of Open Access Journals (Sweden)

    Johann Baumgärtner

    2001-01-01

    Full Text Available A concept of an ecosystem approach to human health improvement in Sub-Saharan Africa is presented here. Three factors mainly affect the physical condition of the human body: the abiotic environment, vector-transmitted diseases, and natural resources. Our concept relies on ecological principles embedded in a social context and identifies three sets of subsystems for study and management: human disease subsystems, natural resource subsystems, and decision-support subsystems. To control human diseases and to secure food from resource subsystems including livestock or crops, integrated preventive approaches are preferred over exclusively curative and sectorial approaches. Environmental sustainability - the basis for managing matter and water flows - contributes to a healthy human environment and constitutes the basis for social sustainability. For planning and implementation of the human health improvement scheme, participatory decision-support subsystems adapted to the local conditions need to be designed through institutional arrangements. The applicability of this scheme is demonstrated in urban and rural Ethiopia.Se presenta un concepto, basado en el ecosistema, para el mejoramiento de la salud humana en la región del África al sur del Sahara. Las condiciones físicas del cuerpo humano estan afectadas por tres factores: factores ambientales abióticos, enfermedades transmitidas por vectores, y por los recursos naturales. Este concepto se basa en princípios ecológicos dentro de un contexto social, e identifica tres series de subsistemas para estudio y manejo: subsistemas de enfermedades humanas, subsistemas de recursos naturales y subsistemas participativos de toma de decisiones. En el manejo de enfermedades humanas, así como en el manejo de recursos tales como ganadería o agricultura, se da prioridad a programas preventivos de manejo integrado. El concepto de sostenibilidad ambiental - base para el manejo de materia y de aguas - contribuye

  20. Tethyan evolution of central Asia

    Energy Technology Data Exchange (ETDEWEB)

    Sengor, A.M.C. (Instanbul Technical Univ. (Turkey))

    1990-05-01

    The study area extends from the eastern shores of the Caspian Sea in the west to the Helan Shan and Longmen Shan in the east and from about 40{degree}N parallel in the north to the neo-Tethyan sutures in the south, thus including what is called Middle Asia in the Soviet literature. In the region thus delineated lies the boundary between the largely late Paleozoic core of Asia (Altaids) and the Tethyside superorogenic complex. This boundary passes through continental objects that collided with nuclear Asia in the late Paleozoic to terminate its Altaid evolution. Subduction to the south of some of these had commenced before they collided (e.g., Tarim in the Kuen-Lun), in others later (e.g., South Ghissar area west of Pamirs). This subduction 1ed, in the late Paleozoic, to the opening of marginal basins, at least one of which may be partly extant (Tarim). Giant subduction accretion complexes of Paleozoic to earliest Triassic age dominate farther south in the basement of Turan (mainly in Turkmenian SSR) and in the Kuen-Lun/Nan Shan ranges. No discrete continental collisions or any continental basement in these regions could be unequivocally recognized contrary to most current interpretations. Magmatic arcs that developed along the southern margin of Asia in the late Paleozoic to early Mesozoic grew atop these subduction-accretion complexes and record a gradual southerly migration of magmatism through time. Subduction also dominated the northern margin of Gondwanaland between Iran and China in late Paleozoic time, although the record in Afghanistan and northwest Tibet is scrappy. It led to back-arc basin formation, which in Iran and Oman became neo-Tethys and, in at least parts of central Asia, the Waser-Mushan-Pshart/Banggong Co-Nu Jiang ocean. This ocean was probably connected with the Omani part of the neo-Tethys via the Sistan region.

  1. Haemangiopericytoma of central nervous system

    Energy Technology Data Exchange (ETDEWEB)

    Borg, M.F.; Benjamin, C.S. [Auckland Hospital, Auckland (New Zealand). Dept. of Clinical Oncology

    1995-02-01

    The records of four patients presenting with a histological diagnosis of haemangiopericytoma of the central nervous system, in Auckland, New Zealand, between 1970 and 1990 were reviewed retrospectively, with the aim of determining the natural history of the disease and response to various treatment modalities. Three out of the four patients reviewed presented with primary cerebral disease and the fourth with a primary spinal cord tumour. All three cerebral primary patients were initially treated with local surgical excision. All three patients received radical radiotherapy following local recurrence. The first two patients remained disease-free locally although one patient developed a solitary liver metastasis 5 years after radiotherapy. The third patient was referred with multiple cerebral metastases and failed to respond to radiotherapy. The patient with the primary lesion in the spinal cord was treated with local excision followed by postoperative radiotherapy and remains disease-free 17 years after treatment. One patient failed to respond to chemotherapy, prescribed to treat a local recurrence adjacent to the previous radiotherapy field. This was successfully excised subsequently. The patient presenting with multiple cerebral metastases was the only patient to die of this disease. Results suggest that local recurrence is avoidable with adequate wide excision of the primary tumour followed by local radical radiotherapy. The role of chemotherapy remains controversial and no conclusion could be drawn regarding the role of palliative radiotherapy from this study. Active treatment and long-term follow-up are necessary because of the relative aggressiveness of this disease and the propensity for late relapses. 22 refs., 2 tabs., 6 figs.

  2. Historical Seismicity of Central Panama

    Science.gov (United States)

    Camacho, E.

    2013-05-01

    Central Panama lies in the Panama microplate, neighboring seismically active regions of Costa Rica and Colombia. This region, crossed by the Panama Canal, concentrates most of the population and economic activity of the Republic of Panama. Instrumental observation of earthquakes in Panama began on 1882 by the Compagnie Universelle du Canal Interocéanique de Panama and continued from 1904 to 1977 by the Panama Canal Company. From October 1997 to March 1998 the USGS deployed a temporary digital seismic network. Since 2003 this region is monitored by a digital seismic network operated by the Panama Canal Authority and I complemented by the broad band stations of the University of Panama seismic network. The seismicity in this region is very diffuse and the few events which are recorded have magnitudes less than 3.0. Historical archives and antique newspapers from Spain, Colombia, Panama and the United Sates have been searched looking for historical earthquake information which could provide a better estimate of the seismicity in this region. We find that Panama City has been shaken by two destructive earthquakes in historical times. One by a local fault (i.e. Pedro Miguel fault) on May 2, 1621 (I=Vlll MM), and a subduction event from the North Panama Deformed Belt (NPDB) on September 7, 1882 (I=Vll MM). To test these findings two earthquakes scenarios were generated, using SELENA, for Panama City Old Quarter. Panama City was rebuilt on January 21, 1673, on a rocky point facing the Pacific Ocean after the sack by pirate Morgan on January 28, 1671. The pattern of damage to calicanto (unreinforced colonial masonry) and wood structures for a crustal local event are higher than those for an event from the NPDB and seem to confirm that the city has not been shaken by a major local event since May 2, 1621 and a subduction event since September 7, 1882

  3. A global central banker competency model

    Directory of Open Access Journals (Sweden)

    David W. Brits

    2014-02-01

    Full Text Available Orientation: No comprehensive, integrated competency model exists for central bankers. Due to the importance of central banks in the context of the ongoing global financial crisis, it was deemed necessary to design and validate such a model.Research purpose: To craft and validate a comprehensive, integrated global central banker competency model (GCBCM and to assess whether central banks using the GCBCM for training have a higher global influence.Motivation for the study: Limited consensus exists globally about what constitutes a ‘competent’ central banker. A quantitatively validated GCBCM would make a significant contribution to enhancing central banker effectiveness, and also provide a solid foundation for effective people management.Research approach, design and method: A blended quantitative and qualitative research approach was taken. Two sets of hypotheses were tested regarding the relationships between the GCBCM and the training offered, using the model on the one hand, and a central bank’s global influence on the other.Main findings: The GCBCM was generally accepted across all participating central banks globally, although some differences were found between central banks with higher and lower global influence. The actual training offered by central banks in terms of the model, however, is generally limited to technical-functional skills. The GCBCM is therefore at present predominantly aspirational. Significant differences were found regarding the training offered.Practical/managerial implications: By adopting the GCBCM, central banks would be able to develop organisation-specific competency models in order to enhance their organisational capabilities and play their increasingly important global role more effectively.Contribution: A generic conceptual framework for the crafting of a competency model with evaluation criteria was developed. A GCBCM was quantitatively validated.

  4. Digital data sets that describe aquifer characteristics of the Central Oklahoma aquifer in central Oklahoma

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set consists of digitized polygons of a constant hydraulic conductivity value for the Central Oklahoma aquifer in central Oklahoma. This area encompasses...

  5. Digital data sets that describe aquifer characteristics of the Central Oklahoma aquifer in central Oklahoma

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set consists of digitized water-level elevation contours for the Central Oklahoma aquifer in central Oklahoma. This area encompasses all or part of...

  6. Digital data sets that describe aquifer characteristics of the Central Oklahoma aquifer in central Oklahoma

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set consists of digitized aquifer boundaries created for a previously published report about the Central Oklahoma aquifer in central Oklahoma. This area...

  7. Digital data sets that describe aquifer characteristics of the Central Oklahoma aquifer in central Oklahoma

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set consists of digitized polygons of a constant recharge value for the Central Oklahoma aquifer in central Oklahoma. This area encompasses all or part of...

  8. South-central Alaska forests: inventory highlights.

    Science.gov (United States)

    Sally Campbell; Willem W.S. van Hees; Bert. Mead

    2005-01-01

    This publication presents highlights of a recent south-central Alaska inventory conducted by the Pacific Northwest Research Station Forest Inventory and Analysis Program (USDA Forest Service). South-central Alaska has about 18.5 million acres, of which one-fifth (4 million acres) is forested. Species diversity is greatest in closed and open Sitka spruce forests, spruce...

  9. China-Central Asia Power Cooperation Outlook

    Institute of Scientific and Technical Information of China (English)

    Luo

    2010-01-01

    After analyzing the basic information,distribution of energy resources and condition of power industry in Central Asia, the high feasibility for China to cooperate closely with Central Asia in transnational power interconnection, power investment and technology exchanges, etc. is studied. Furthermore, the forms, mechanisms, existing problems and suggestions for the improvement of current policies related to the power cooperation are proposed.

  10. The Latino Experience in Central Falls

    Science.gov (United States)

    Holland, William R.

    2011-01-01

    Central Falls is, by far, the poorest community in Rhode Island. More than 40 percent of the children under 18 live in poverty, and 40 percent of that group live in severe poverty. At Central Falls High School, low-income Latino students have fallen behind their white counterparts, with shockingly low graduation, poor literacy, and low…

  11. An unusual Complication of Central Venous Cannulation

    Directory of Open Access Journals (Sweden)

    Ashvini Kumar

    2013-04-01

    Full Text Available Central venous catheter (CVC hub fracture is a rare complication of central venous cannulation. We report a case where catheter hub fracture was detected immediately after CVC insertion. Causes of catheter hub fracture and its complications are discussed.

  12. Central Life Interests and Job Satisfaction.

    Science.gov (United States)

    Dubin, Robert; And Others

    Data on central life interests (CLI) and five aspects of job satisfaction were obtained in a sample of bluecollar males and two samples of clerical females. Both a multiple discriminant analysis and a bivariate analysis were performed. The results of these analyses showed that central life interest was significantly related to the total set of job…

  13. Central bank independence and financial instability

    NARCIS (Netherlands)

    Klomp, J.G.; de Haan, J.

    2009-01-01

    It has been argued that central bank independence (CBI) may not only be beneficial for reaching the objective of price stability, but also for maintaining financial stability. Greater independence from external pressure implies that central banks are less politically constrained in acting to prevent

  14. Computing betweenness centrality in external memory

    DEFF Research Database (Denmark)

    Arge, Lars; Goodrich, Michael T.; Walderveen, Freek van

    2013-01-01

    Betweenness centrality is one of the most well-known measures of the importance of nodes in a social-network graph. In this paper we describe the first known external-memory and cache-oblivious algorithms for computing betweenness centrality. We present four different external-memory algorithms...

  15. Traveling Policies: Hijacked in Central Asia

    Science.gov (United States)

    Silova, Iveta

    2005-01-01

    Since the collapse of the Soviet Union, Central Asian education reform discourses have become increasingly similar to distinctive Western policy discourses traveling globally across national boundaries. Tracing the trajectory of "traveling policies" in Central Asia, this article discusses the way Western education discourses have been…

  16. central hospital with acute coronary syndrome

    African Journals Online (AJOL)

    consecutivement admi a l'Hopital Central d'Aseer avec le diag- nostic d'un syndrome ... Unit of Aseer Central Hospital with the diagnosis of acute coro- nary syndrome for 14 .... action: consumer information processing. In: G] IDZ K, Lewis.

  17. Central Life Interests and Job Satisfaction.

    Science.gov (United States)

    Dubin, Robert; And Others

    Data on central life interests (CLI) and five aspects of job satisfaction were obtained in a sample of bluecollar males and two samples of clerical females. Both a multiple discriminant analysis and a bivariate analysis were performed. The results of these analyses showed that central life interest was significantly related to the total set of job…

  18. Novel central nervous system drug delivery systems.

    Science.gov (United States)

    Stockwell, Jocelyn; Abdi, Nabiha; Lu, Xiaofan; Maheshwari, Oshin; Taghibiglou, Changiz

    2014-05-01

    For decades, biomedical and pharmaceutical researchers have worked to devise new and more effective therapeutics to treat diseases affecting the central nervous system. The blood-brain barrier effectively protects the brain, but poses a profound challenge to drug delivery across this barrier. Many traditional drugs cannot cross the blood-brain barrier in appreciable concentrations, with less than 1% of most drugs reaching the central nervous system, leading to a lack of available treatments for many central nervous system diseases, such as stroke, neurodegenerative disorders, and brain tumors. Due to the ineffective nature of most treatments for central nervous system disorders, the development of novel drug delivery systems is an area of great interest and active research. Multiple novel strategies show promise for effective central nervous system drug delivery, giving potential for more effective and safer therapies in the future. This review outlines several novel drug delivery techniques, including intranasal drug delivery, nanoparticles, drug modifications, convection-enhanced infusion, and ultrasound-mediated drug delivery. It also assesses possible clinical applications, limitations, and examples of current clinical and preclinical research for each of these drug delivery approaches. Improved central nervous system drug delivery is extremely important and will allow for improved treatment of central nervous system diseases, causing improved therapies for those who are affected by central nervous system diseases.

  19. An overview of CMS central hadron calorimeter

    CERN Document Server

    Katta, S

    2002-01-01

    The central hadron calorimeter for CMS detector is a sampling calorimeter with active medium as scintillator plates interleaved with brass absorber plates. It covers the central pseudorapidity region (¿ eta ¿<3.0). The design and construction aspects are reported. The status of construction and assembly of various subdetectors of HCAL are presented. (5 refs).

  20. Centralized scheduling an unanticipated revenue cycle opportunity.

    Science.gov (United States)

    O'Neill, Daniel P; Kenniff, Peter B

    2007-09-01

    Centralized outpatient scheduling can provide acute care hospitals with accessibility and service levels equal to freestanding facilities, enabling hospitals to recapture lost market share. Two implementation strategies are critical to the success of centralized scheduling: Correctly developing the schedule. Managing the incoming call volume.

  1. International Regulation of Central Arctic Ocean Fisheries

    NARCIS (Netherlands)

    Molenaar, E.J.

    2016-01-01

    Due in particular to the impacts of climate change, the adequacy of the international regulation of Central Arctic Ocean fisheries has come under increasing scrutiny in recent years. As shown in this article, however, international regulation of Central Arctic Ocean fisheries is by no means entirely

  2. The Cartan Matrix of a Centralizer Algebra

    Indian Academy of Sciences (India)

    Umesh V Dubey; Amritanshu Prasad; Pooja Singla

    2012-02-01

    The centralizer algebra of a matrix consists of those matrices that commute with it. We investigate the basic representation-theoretic invariants of centralizer algebras, namely their radicals, projective indecomposable modules, injective indecomposable modules, simple modules and Cartan matrices. With the help of our Cartan matrix calculations we determine their global dimensions. Many of these algebras are of infinite global dimension.

  3. The economic impact of central bank transparency

    NARCIS (Netherlands)

    van der Cruijsen, C.A.B.

    2008-01-01

    During the last decades a lot of central banks have become more transparent about their monetary policy. The research question that is addressed in this book is whether central bank transparency is desirable from an economic viewpoint. It is shown that transparency increases have been beneficial.

  4. Does central bank independence still matter?

    NARCIS (Netherlands)

    de Haan, Jakob; Masciandaro, Donato; Quintyn, Marc

    2008-01-01

    This paper sets out background on the literature on central bank independence (CBI) and summarizes the contributions of the papers in this special issue. The clear impression is that the answer to the question "Does central bank independence still matter?" is affirmative. (C) 2008 Elsevier B.V. All

  5. A SCALED CENTRAL PATH FOR LINEAR PROGRAMMING

    Institute of Scientific and Technical Information of China (English)

    Ya-xiang Yuan

    2001-01-01

    Interior point methods are very efficient methods for solving large scale linear programming problems. The central path plays a very important role in interior point methods. In this paper we propose a new central path, which scales the variables. Thus it has the advantage of forcing the path to have roughly the same distance from each active constraint boundary near the solution.

  6. Traveling Policies: Hijacked in Central Asia

    Science.gov (United States)

    Silova, Iveta

    2005-01-01

    Since the collapse of the Soviet Union, Central Asian education reform discourses have become increasingly similar to distinctive Western policy discourses traveling globally across national boundaries. Tracing the trajectory of "traveling policies" in Central Asia, this article discusses the way Western education discourses have been hybridized…

  7. Central station market development strategies for photovoltaics

    Science.gov (United States)

    1980-01-01

    Federal market development strategies designed to accelerate the market penetration of central station applications of photovoltaic energy system are analyzed. Since no specific goals were set for the commercialization of central station applications, strategic principles are explored which, when coupled with specific objectives for central stations, can produce a market development implementation plan. The study includes (1) background information on the National Photovoltaic Program, photovoltaic technology, and central stations; (2) a brief market assessment; (3) a discussion of the viewpoints of the electric utility industry with respect to solar energy; (4) a discussion of commercialization issues; and (5) strategy principles. It is recommended that a set of specific goals and objectives be defined for the photovoltaic central station program, and that these goals and objectives evolve into an implementation plan that identifies the appropriate federal role.

  8. Central differences, Euler numbers and symbolic methods

    CERN Document Server

    Dowker, J S

    2013-01-01

    I relate some coefficients encountered when computing the functional determinants on spheres to the central differentials of nothing. In doing this I use some historic works, in particular transcribing the elegant symbolic formalism of Jeffery (1861) into central difference form which has computational advantages for Euler numbers, as discovered by Shovelton (1915). I derive sum rules for these, and for the central differentials, the proof of which involves an interesting expression for powers of sech x as multiple derivatives. I present a more general, symbolic treatment of central difference calculus which allows known, and unknown, things to be obtained in an elegant and compact fashion gaining, at no cost, the expansion of the powers of the inverse sinh, a basic central function. Systematic use is made of the operator 2 asinh(D/2). Umbral calculus is employed to compress the operator formalism. For example the orthogonality/completeness of the factorial numbers, of the first and second kinds, translates, ...

  9. Central registry in psychiatry: A structured review

    Directory of Open Access Journals (Sweden)

    Jyoti Prakash

    2014-01-01

    Full Text Available Background: Central registry in psychiatry is being practiced in few countries and has been found useful in research and clinical management. Role of central registry has also expanded over the years. Materials and Methods: All accessible internet database Medline, Scopus, Embase were accessed from 1990 till date. Available data were systematically reviewed in structured manner and analyzed. Results: Central registry was found useful in epidemiological analysis, association studies, outcome studies, comorbidity studies, forensic issue, effective of medication, qualitative analysis etc., Conclusion: Central registry proves to be effective tool in quantitative and qualitative understanding of psychiatry practice. Findings of studies from central registry can be useful in modifying best practice and evidence based treatment in psychiatry.

  10. Meso-Cenozoic morphological evolution of NW Africa, the case of the Tuareg swell.

    Science.gov (United States)

    Rougier, S.; Gautheron, C.; Barbarand, J.; Missenard, Y.; Zeyen, H.; Pinna, R.; Bonin, B.; Liégeois, J.-P.; Ouabadi, A.; Frizon de Lamotte, D.

    2012-04-01

    The continental crust of Africa, largely built during the Pan-African orogeny (late Neoproterozoic) has acquired in its northern part, during Paleozoic times, an arch and basin morphology. Meso-Cenozoic large scale topographic anomalies, associated to Cenozoic intraplate volcanism, such as Hoggar, Tibesti or Darfur domes, are superimposed to these structures. Precise ages of swells, as well as their relations with Paleozoic arch and basin morphology of the area, remain controversial. The aim of this study, focussed on the Hoggar dome, in southern Algeria, is to produce new constraints on the Post-Paleozoic evolution of this region. The Tuareg shield, from which Hoggar is the main central part and Aïr a SE extension, forms a topographic high reaching an altitude >2900m (Mt Tahat, Atakor district), exposing Precambrian rocks over 500000km2. While presumed Cretaceous sedimentary remnants suggest a possible stage of slightly positive topography during the Mesozoic, current high topography is emphasized by Cenozoic volcanic formations, mostly basaltic in composition. We present new low-temperature thermochronology data, with apatite fission track and (U-Th)/He ages on Hoggar and Aïr substratum. We combine these results with thermal, gravimetric and isostatic two-dimensional lithosphere-scale geophysical models, following the method of Zeyen & Fernandez (1994). Preliminary thermochronological results present ages from 99+-6 to 166+-10 Myr for AFT, and AHe from 10 to 300 Myr. Thermal simulations of these data suggest that currently outcropping Precambrian Hoggar basement could have experienced temperatures of approximately 80°C between Upper Cretaceous and Eocene. We propose that these elevated temperatures are related to burial beneath a 1 to 3 km thick sedimentary cover, depending on thermal gradient. The base of this sedimentary cover could correspond to the poorly described Upper Cretaceous remnants, currently uplifted up to 1450 m. These results are in agreement

  11. Centrality and economic development in the Rijnland region: social and spatial concepts of centrality

    NARCIS (Netherlands)

    Van Nes, A.

    2007-01-01

    In urban research, spatial and social concepts of centrality are being distinguished. From a spatial point of view, metrical centrality implies that something is located in the middle of an area. However, metrical and topological centrality are not equivalent. In research where space syntax methods

  12. Actual versus Perceived Central Bank Transparency : The Case of the European Central Bank

    NARCIS (Netherlands)

    van der Cruijsen, C.A.B.; Eijffinger, S.C.W.

    2007-01-01

    Central banks have become more and more transparent about their monetary policy making process. In the central bank transparency lit- erature the distinction between actual and perceived central bank trans- parency is often lacking. However, as perceptions are crucial for the ac- tions of economic

  13. AAPT Diagnostic Criteria for Central Neuropathic Pain.

    Science.gov (United States)

    Widerström-Noga, Eva; Loeser, John D; Jensen, Troels Staehelin; Finnerup, Nanna Brix

    2017-06-27

    Central neuropathic pain, which is pain caused by a lesion or disease of the central somatosensory nervous system, is a serious consequence of spinal cord injury, stroke, multiple sclerosis, and other conditions affecting the central nervous system. A collaborative effort between the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public-private partnership and the American Pain Society, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks-American Pain Society Pain Taxonomy (AAPT) initiative, invited a working group to develop diagnostic criteria for central neuropathic pain. The criteria for central neuropathic pain that were developed expand upon existing criteria for neuropathic pain and the International Classification of Diseases 11th Revision draft criteria to ensure consistency. This article focuses on central neuropathic pain associated with spinal cord injury, stroke, and multiple sclerosis, but the AAPT framework can be extended to central pain due to other causes such as traumatic brain injury. The classification of central neuropathic pain is organized according to the AAPT multidimensional framework, specifically: 1) core diagnostic criteria, 2) common features, 3) common medical and psychiatric comorbidities, 4) neurobiological, psychosocial, and functional consequences, and 5) putative neurobiological and psychosocial mechanisms, risk factors, and protective factors. The AAPT chronic central neuropathic pain taxonomy provides a classification for central pain associated with spinal cord injury, stroke, and multiple sclerosis. The diagnostic criteria are organized according to the AAPT multidimensional framework, specifically: 1) core diagnostic criteria, 2) common features, 3) common medical and psychiatric comorbidities, 4) neurobiological, psychosocial, and functional consequences, and 5) putative neurobiological and psychosocial

  14. XNAT Central: Open sourcing imaging research data.

    Science.gov (United States)

    Herrick, Rick; Horton, William; Olsen, Timothy; McKay, Michael; Archie, Kevin A; Marcus, Daniel S

    2016-01-01

    XNAT Central is a publicly accessible medical imaging data repository based on the XNAT open-source imaging informatics platform. It hosts a wide variety of research imaging data sets. The primary motivation for creating XNAT Central was to provide a central repository to host and provide access to a wide variety of neuroimaging data. In this capacity, XNAT Central hosts a number of data sets from research labs and investigative efforts from around the world, including the OASIS Brains imaging studies, the NUSDAST study of schizophrenia, and more. Over time, XNAT Central has expanded to include imaging data from many different fields of research, including oncology, orthopedics, cardiology, and animal studies, but continues to emphasize neuroimaging data. Through the use of XNAT's DICOM metadata extraction capabilities, XNAT Central provides a searchable repository of imaging data that can be referenced by groups, labs, or individuals working in many different areas of research. The future development of XNAT Central will be geared towards greater ease of use as a reference library of heterogeneous neuroimaging data and associated synthetic data. It will also become a tool for making data available supporting published research and academic articles. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. DrugCentral: online drug compendium.

    Science.gov (United States)

    Ursu, Oleg; Holmes, Jayme; Knockel, Jeffrey; Bologa, Cristian G; Yang, Jeremy J; Mathias, Stephen L; Nelson, Stuart J; Oprea, Tudor I

    2017-01-04

    DrugCentral (http://drugcentral.org) is an open-access online drug compendium. DrugCentral integrates structure, bioactivity, regulatory, pharmacologic actions and indications for active pharmaceutical ingredients approved by FDA and other regulatory agencies. Monitoring of regulatory agencies for new drugs approvals ensures the resource is up-to-date. DrugCentral integrates content for active ingredients with pharmaceutical formulations, indexing drugs and drug label annotations, complementing similar resources available online. Its complementarity with other online resources is facilitated by cross referencing to external resources. At the molecular level, DrugCentral bridges drug-target interactions with pharmacological action and indications. The integration with FDA drug labels enables text mining applications for drug adverse events and clinical trial information. Chemical structure overlap between DrugCentral and five online drug resources, and the overlap between DrugCentral FDA-approved drugs and their presence in four different chemical collections, are discussed. DrugCentral can be accessed via the web application or downloaded in relational database format. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  16. Erroneous laboratory values obtained from central catheters.

    Science.gov (United States)

    Johnston, J B; Messina, M

    1991-01-01

    Serious analytic errors in potassium measurements have been identified in blood specimens obtained from newly inserted central catheters. Erroneous elevated readings have been related to interactions of chemistry analyzer electrodes and substances fixed to external and intraluminal walls of the central catheter. Anecdotal summaries of this phenomenon are presented to enable the nurse to recognize potential problems when sampling blood from central catheters. Studies were performed to determine the amount of flush necessary to clear the catheter of interfering residue. To eliminate this potentially hazardous occurrence, recommended flush volumes, nursing implications, and actions are described.

  17. Central Serous Chorioretinopathy after Solar Eclipse Viewing

    Directory of Open Access Journals (Sweden)

    Allie Lee

    2010-01-01

    Full Text Available Purpose: To report a case of central serous chorioretinopathy after solar eclipse viewing. Case Report: A middle-age man developed a sudden-onset unilateral scotoma after viewing a partial solar eclipse in Hong Kong. Fundus examination, fluorescein angiography, and optical coherence tomography showed features compatible with central serous chorioretinopathy. The patient was managed conservatively and reevaluated periodically. Serial optical coherence tomographic evaluations demonstrated an initial increase in the amount of subretinal fluid which spontaneously resolved 10 weeks after the onset of symptoms. Conclusion: This case demonstrates the possibility of development of central serous chorioretinopathy following solar eclipse viewing.

  18. Central black hole masses of galaxies

    Institute of Scientific and Technical Information of China (English)

    樊军辉

    2003-01-01

    In this paper, the stellar velocity dispersions in the host galaxies are used to estimate the central black hole masses for a sample of elliptical galaxies. We find that the central black hole masses are in the range of 10(5.5-9.5) M(○). Based on the estimated masses in this paper and those by Woo & Urry (2002) and the measured host galaxy absolute magnitude,a relation, log(MBH/M(○)) = -(0.25 ± 4.3 × 10-3)MR + (2.98 4 0.208) is found for central black hole mass and the host galaxy magnitude. Some discussions are presented.

  19. Betweenness Centrality in Some Classes of Graphs

    Directory of Open Access Journals (Sweden)

    Sunil Kumar Raghavan Unnithan

    2014-01-01

    Full Text Available There are several centrality measures that have been introduced and studied for real-world networks. They account for the different vertex characteristics that permit them to be ranked in order of importance in the network. Betweenness centrality is a measure of the influence of a vertex over the flow of information between every pair of vertices under the assumption that information primarily flows over the shortest paths between them. In this paper we present betweenness centrality of some important classes of graphs.

  20. Central serous chorioretinopathy after solar eclipse viewing.

    Science.gov (United States)

    Lee, Allie; Lai, Timothy Y Y

    2010-07-01

    To report a case of central serous chorioretinopathy after solar eclipse viewing. A middle-age man developed a sudden-onset unilateral scotoma after viewing a partial solar eclipse in Hong Kong. Fundus examination, fluorescein angiography, and optical coherence tomography showed features compatible with central serous chorioretinopathy. The patient was managed conservatively and reevaluated periodically. Serial optical coherence tomographic evaluations demonstrated an initial increase in the amount of subretinal fluid which spontaneously resolved 10 weeks after the onset of symptoms. This case demonstrates the possibility of development of central serous chorioretinopathy following solar eclipse viewing.