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Sample records for au sahara premiere

  1. The Sahara's Diverse Landscape

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Vast stretches of uninterrupted sand are only one kind of Saharan landscape. This true-color MODIS image from November 9, 2001, reveals a diversity of land surface features, including ancient lava flows and volcanoes. Beginning at upper left and moving clockwise are the countries of Algeria, Tunisia, Libya, Chad, and Niger. Evidence of previous volcanic activity in the Sahara can be found in northeastern Chad, in particular, in a region known as Tibesti. Reaching up out of the surrounding desert, the dark rock of the Tibesti Plateau stands out in dark brown against the sand. Scattered throughout the region are the circular cones and calderas of several volcanoes. The dark remains of a lava flow mark the location of the Tousside volcano. North of Tibesti, in Libya, more dark-colored lava beds leave their mark on the landscape. Variety exists in Algeria, where the Grand Erg Oriental desert (far upper left) is hemmed in to the south by the Tinrhert Plateau. South of the Plateau, desert resumes briefly, only to give way to a mountainous region traced with impermanent rivers. In northern Niger, a sinuous gray-green line marks the edge of an escarpment that separates the Mangueni Plateau to the north from the rock deserts to the south. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  2. [Malaria in Algerian Sahara].

    PubMed

    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. PMID:19739417

  3. Le diagnostic anténatal de la trisomie 21 par l'hybridation in situ en fluorescence (FISH): à propos des premiers tests réalisés au Maroc

    PubMed Central

    Lamzouri, Afaf; Natiq, Abdelhafid; Tajir, Mariam; Sendid, Mohamed; Sefiani, Abdelaziz

    2012-01-01

    Introduction Le but de cette étude était de présenter les premiers résultats de diagnostic anténatal de la trisomie 21 par la technique d'hybridation in situ en fluorescence (FISH) au Maroc et discuter son intérêt dans le diagnostic rapide de cette aneuploïdie. Méthodes Ce travail a été réalisé chez 23 femmes avec des grossesses à haut risque de trisomie 21. La moyenne d’âge des gestantes étaient de 37,43 ans avec des extrêmes de 21 et 43 ans. Toutes étaient musulmanes mariées, mariage légitimé par la Charia, dont trois mariages consanguins, sauf une originaire de la République Démocratique du Congo qui était chrétienne et concubine. La majorité des femmes étaient fonctionnaires et avaient un niveau de scolarisation moyen à élevé. Toutes les patientes ont bénéficié d'une consultation de génétique médicale au cours de laquelle il leur a été donné des informations sur la technique, son intérêt et ses limites. Il s'agit de femmes enceintes qui avaient soit un âge maternel élevé ou des signes d'appel échographiques et/ ou biochimiques. Une des patientes était porteuse d'une translocation robertsonienne t(14;21) équilibrée. Une amniocentèse a été réalisée chez toutes les gestantes et aucun avortement n'a était induit par ce geste invasif. L’âge gestationnel moyen à la première consultation était de 14 semaines d'aménorrhée (SA) et à l'amniocentèse était de 16 SA et 5 jours. L'analyse FISH a été réalisée, après consentement des couples, sur des cellules non cultivées à partir des échantillons de liquides amniotiques, en utilisant des sondes spécifiques du chromosome 21. Résultats Parmi les 23 patientes qui ont bénéficiées d'un diagnostic anténatal de la trisomie 21 par la technique FISH, nous avons pu rassurer 21 d'entre elles, et nous avons détecté deux cas de trisomie 21 fœtal. Conclusion La technique FISH permet un diagnostic anténatal rapide, en moins de 48h, de la trisomie 21 sur

  4. PREMIER's imaging IR limb sounder

    NASA Astrophysics Data System (ADS)

    Kraft, Stefan; Caron, Jerome; Bézy, Jean-Loup; Meynart, Roland; Langen, Jörg; Carnicero Dominguez, Bernardo; Bensi, Paolo; Silvestrin, Pierluigi

    2011-11-01

    The Imaging IR Limb Sounder (IRLS) is one of the two instruments planned on board of the candidate Earth Explorer Core Mission PREMIER. PREMIER stands for PRocess Exploration through Measurements of Infrared and Millimetrewave Emitted Radiation and is presently under feasibility study by ESA. Emerging from recent enhanced detector and processing technologies IRLS shall, next to a millimetre-wave limb sounder, explore the benefits of three-dimensional limb sounding with embedded cloud imaging capability. Such 3d imaging technology is expected to open a new era of limb sounding that will allow detailed studies of the link between atmospheric composition and climate, since it will map simultaneously fields of temperature and many trace gases in the mid/upper troposphere and stratosphere across a large vertical and horizontal field of view and with relatively high vertical and horizontal resolution. PREMIER shall fly in tandem formation looking backwards to METOP's swath and thereby explore the benefit of 3-dimensional information for meteorological/environmental analyses and climate forcing investigations. As currently planned and if implemented, IRLS will cover a total horizontal field of about 360 km and observe the limb at altitudes between 4 and 52 km. The vertical spatial sampling distance (SSD) will be well below 1 km. It will be run in two different exclusive modes to address scientific questions about atmospheric dynamics and chemistry at spectral samplings of ~1.2 cm-1 and ~0.2 cm-1, respectively. In such configuration IRLS will be composed of an imaging array with about 1800 macro pixels or sub-samples, thereby allowing cloud imaging and rejection at sufficient spatial resolution. We will present an overview of the instrument requirements as derived from the scientific requirements, the present status of the mission, and we will give an overview of the currently identified technology needs and instrument predevelopments.

  5. Precision Cleaning - Path to Premier

    NASA Technical Reports Server (NTRS)

    Mackler, Scott E.

    2008-01-01

    ITT Space Systems Division s new Precision Cleaning facility provides critical cleaning and packaging of aerospace flight hardware and optical payloads to meet customer performance requirements. The Precision Cleaning Path to Premier Project was a 2007 capital project and is a key element in the approved Premier Resource Management - Integrated Supply Chain Footprint Optimization Project. Formerly precision cleaning was located offsite in a leased building. A new facility equipped with modern precision cleaning equipment including advanced process analytical technology and improved capabilities was designed and built after outsourcing solutions were investigated and found lacking in ability to meet quality specifications and schedule needs. SSD cleans parts that can range in size from a single threaded fastener all the way up to large composite structures. Materials that can be processed include optics, composites, metals and various high performance coatings. We are required to provide verification to our customers that we have met their particulate and molecular cleanliness requirements and we have that analytical capability in this new facility. The new facility footprint is approximately half the size of the former leased operation and provides double the amount of throughput. Process improvements and new cleaning equipment are projected to increase 1st pass yield from 78% to 98% avoiding $300K+/yr in rework costs. Cost avoidance of $350K/yr will result from elimination of rent, IT services, transportation, and decreased utility costs. Savings due to reduced staff expected to net $4-500K/yr.

  6. Cenozoic stratigraphy of the Sahara, Northern Africa

    USGS Publications Warehouse

    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

  7. An Open Letter to Premier Wen Jiabao

    ERIC Educational Resources Information Center

    Chinese Education and Society, 2008

    2008-01-01

    This article is an open letter of a group of early childhood education (ECE) practitioners to Premier Wen Jiabao. This open letter was written with one goal in mind: to ask Premier Wen's government to take measures to protect young children and support early childhood education. These practitioners have become worried about the many accidents that…

  8. Scottish Premier League Reading Stars Evaluation Report

    ERIC Educational Resources Information Center

    National Literacy Trust, 2009

    2009-01-01

    Scottish Premier League (SPL) Reading Stars uses the motivational power of football to attract families who need support with literacy into a positive and friendly learning environment. It ran for the first time between March and August 2009 and attracted 225 children and 190 adults to take part in a series of inspirational learning sessions in 23…

  9. Premier League Reading Stars. Annual Review 2010

    ERIC Educational Resources Information Center

    National Literacy Trust, 2010

    2010-01-01

    Premier League Reading Stars (PLRS) is an educational project that harnesses the motivational power of football to encourage families to enjoy reading. It targets those hard to reach groups in society who may not have shown an interest in reading, but who do have a passion for football. PLRS has been running since 2003 following the creation of a…

  10. New data on the unresolved paradox of the Tibesti crater paleolakes (Central Sahara, North Chad)

    NASA Astrophysics Data System (ADS)

    Kroepelin, S.; Darius, F.; Deschamps, P.; Dinies, M.; Hoelzmann, P.; Kuper, J.; Oppenheimer, C.; Soulié-Märsche, I.; Sylvestre, F.

    2015-12-01

    Recent field work in the volcanic Tibesti Mountains opens a new chapter in the reconstruction of the last climatic cycles in the central Sahara and their lacustrine environments. For the first time, complete lacustrine sections were sampled in the 900 m deep crater of Trou au Natron at Pic Toussidé (3,315 m a.s.l.), and in 800 m deep Era Kohor, the major sub-caldera of Emi Koussi, the Sahara's 3,445 m high peak (photo). The probed diatomites are located 360 and 125 m above the present-day bottom of the calderas. Studies in the 1960s suggested that lake levels in the Trou au Natron were 300-500 m high at 12,400-14,970 uncal. yrs BP. Such lake depths and resulting water volumes, however, are hardly conceivable in view of the limited intake area and precipitation-evaporation ratios which would have required local rainfall by far surpassing estimates for latitudes 19-21°N from the full-Holocene record of Lake Yoa situated 460 or 220 km southeast, and 1,550 or 2,450 m lower. The presentation will examine whether differences in altitude may explain unparalleled lake depths and postglacial humid conditions 4,000-7,000 years earlier than in the surrounding lowlands, and present alternative hypotheses of lake formation in this Saharan key region.

  11. Evening Pass Over the Sahara Desert and the Middle East

    NASA Video Gallery

    This video over the Sahara Desert and the Middle East was taken by the crew of Expedition 29 aboard the International Space Station. This sequence of shots was taken on Oct. 6, 2011, from 19:46:23 ...

  12. Drought in the Sahara - A biogeophysical feedback mechanism

    NASA Technical Reports Server (NTRS)

    Charney, J.; Stone, P. H.; Quirk, W. J.

    1975-01-01

    Two integrations of a global general circulation model, differing only in the prescribed surface albedo in the Sahara, show that an increase in albedo resulting from a decrease in plant cover causes a decrease in rainfall. Thus any tendency for plant cover to decrease would be reinforced by a decrease in rainfall, and could initiate or perpetuate a drought.

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

    ERIC Educational Resources Information Center

    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…

  14. Cultural Astronomy in Africa South of the Sahara

    NASA Astrophysics Data System (ADS)

    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.

  15. The qanat of Algerian Sahara: an evolutionary hydraulic system

    NASA Astrophysics Data System (ADS)

    Remini, Boualem; Achour, Bachir; Albergel, Jean

    2015-12-01

    This article discusses for the first time a study on the connection and interconnection of qanats located in the Algerian Sahara. During the missions in the oases of Touat and Gourara in 2009, 2010 and 2011, we have been impressed by the complexity of the network of water distribution. The seguias of differents sections take all the senses. Connections are made between qanats to ensure water supply to each owner. In this study, we identified nine models for connecting qanats.

  16. Fennec dust forecast intercomparison over the Sahara in June 2011

    NASA Astrophysics Data System (ADS)

    Chaboureau, Jean-Pierre; Flamant, Cyrille; Dauhut, Thibaut; Kocha, Cécile; Lafore, Jean-Philippe; Lavaysse, Chistophe; Marnas, Fabien; Mokhtari, Mohamed; Pelon, Jacques; Reinares Martínez, Irene; Schepanski, Kerstin; Tulet, Pierre

    2016-06-01

    In the framework of the Fennec international programme, a field campaign was conducted in June 2011 over the western Sahara. It led to the first observational data set ever obtained that documents the dynamics, thermodynamics and composition of the Saharan atmospheric boundary layer (SABL) under the influence of the heat low. In support to the aircraft operation, four dust forecasts were run daily at low and high resolutions with convection-parameterizing and convection-permitting models, respectively. The unique airborne and ground-based data sets allowed the first ever intercomparison of dust forecasts over the western Sahara. At monthly scale, large aerosol optical depths (AODs) were forecast over the Sahara, a feature observed by satellite retrievals but with different magnitudes. The AOD intensity was correctly predicted by the high-resolution models, while it was underestimated by the low-resolution models. This was partly because of the generation of strong near-surface wind associated with thunderstorm-related density currents that could only be reproduced by models representing convection explicitly. Such models yield emissions mainly in the afternoon that dominate the total emission over the western fringes of the Adrar des Iforas and the Aïr Mountains in the high-resolution forecasts. Over the western Sahara, where the harmattan contributes up to 80 % of dust emission, all the models were successful in forecasting the deep well-mixed SABL. Some of them, however, missed the large near-surface dust concentration generated by density currents and low-level winds. This feature, observed repeatedly by the airborne lidar, was partly forecast by one high-resolution model only.

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Satellite measurement of mass of Sahara dust in the atmosphere

    NASA Technical Reports Server (NTRS)

    Fraser, R. S.

    1976-01-01

    Landsat 1 measurements of nadir radiance are used to obtain the mass of particulates in a vertical column of dust from the Sahara Desert. A radiative transfer model, constructed with knowledge of a few values of optical parameters measured from a ship, is developed to account for the measured radiance values. Measurement and model accuracies are discussed. It is found that the mass of particulates with smaller than a 10 micron radius in a vertical column is 1.6 g/sq m.

  19. Premier League Reading STARS 2013/14. Evaluation Report

    ERIC Educational Resources Information Center

    Pabion, Clémence

    2015-01-01

    The National Literacy Trust's Premier League Reading Stars programme (PLRS) is a reading intervention for children aged 8 to 13 that captures the motivational power of football to inspire children and young people to read more and to improve their literacy skills. PLRS is delivered by teachers and librarians. The programme delivers statutory…

  20. Open Access Publishing in Indian Premier Research Institutions

    ERIC Educational Resources Information Center

    Bhat, Mohammad Hanief

    2009-01-01

    Introduction: Publishing research findings in open access journals is a means of enhancing visibility and consequently increasing the impact of publications. This study provides an overview of open access publishing in premier research institutes of India. Method: The publication output of each institution from 2003 to 2007 was ascertained through…

  1. Library Media Specialists: Premier Information Specialists for the Information Age

    ERIC Educational Resources Information Center

    Neuman, Delia

    2011-01-01

    The information age has given library media specialists an unprecedented opportunity to play a leading role in helping teachers, administrators, and especially students access and use information intelligently. As the school's premier information specialist; the library media specialist has a unique role to play in helping everyone in the school…

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

    NASA Astrophysics Data System (ADS)

    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 (<2.5 %) and strongly varying aragonite and gypsum contents. Major elements (Ca, Fe, K, Mg, Mn, Na, P, S, Sr), elemental ratios (Sr/Ca, Mg/Ca, Fe/Mn) and the mineralogy are used to interpret the lake's salinity, productivity and ecological conditions. Trilete spores are preserved throughout the sequence, probably reflecting local moss/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

  3. Eastern Sahara Geology from Orbital Radar: Potential Analog to Mars

    NASA Technical Reports Server (NTRS)

    Farr, T. G.; Paillou, P.; Heggy, E.

    2004-01-01

    Much of the surface of Mars has been intensely reworked by aeolian processes and key evidence about the history of the Martian environment seems to be hidden beneath a widespread layer of debris (paleo lakes and rivers, faults, impact craters). In the same way, the recent geological and hydrological history of the eastern Sahara is still mainly hidden under large regions of wind-blown sand which represent a possible terrestrial analog to Mars. The subsurface geology there is generally invisible to optical remote sensing techniques, but radar images obtained from the Shuttle Imaging Radar (SIR) missions were able to penetrate the superficial sand layer to reveal parts of paleohydrological networks in southern Egypt.

  4. The megageomorphology of the radar rivers of the eastern Sahara

    NASA Technical Reports Server (NTRS)

    Mccauley, John F.; Breed, Carol S.; Schaber, Gerald G.

    1986-01-01

    The Eastern Sahara is devoid of surface drainage; this unusual characteristic distinguishes its morphology from that of most other desert regions where running water dominates landscape development. A map derived from SIR-A/B and LANDSAT images and the literature, shows the major presently known paleodrainages in the Eastern Sahara. This compilation permits consideration of the key questions: Where did the radar rivers come from and where did they go? Analysis of SIR-A data led McCauley et al. to suggest that the radar rivers, because of their southwestward trends, once flowed into the Chad basin. This key North African feature is a regional structural low formed in the Early Cretaceous in response to initial opening of the South Atlantic. The problem of the origin of headwaters for the radar rivers was less tractable. The idea that the source areas of the radar rivers might originally have been the same as those later captured by the Nile was proposed tentatively. A more extensive review of the Cenozoic tectonic history of North Africa reveals no reason now to suppose that the Central African tributaries of the present Nile were ever connected to the large alluvial valleys in southwestern Egypt and northwestern Sudan. formed in the Early Cretaceous in response to initial opening of the South Atlantic. The problem of the origin of headwaters for the radar rivers was less tractable. The idea that the source areas of the radar rivers might originally have been the same as those (The Ethiopian Highlands) later captured by the Nile was proposed tentatively. A more extensive review of the Cenozoic tectonic history of North Africa reveals no reason now to support that the Central African tributaries of the present Nile were ever connected to the large alluvial valleys in southwestern Egypt and northwestern Sudan.

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

    PubMed

    Ouwehand, Janne; Both, Christiaan

    2016-04-01

    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 flights were estimated to be part of non-stop flights of mostly 40-60 h. In spring, birds flew across the Sahara, while autumn migration probably circumpassed part of the desert, through a long oversea flight. Our data contradict claims that passerines cross the Sahara by intermittent flight and daytime resting. The frequent occurrence of long non-stop flights to cross the desert shows migrants' physiological abilities and poses the question why this would not be the general migration strategy to cross the Sahara. PMID:27072404

  6. Lessons premier hospitals learned about implementing electronic health records.

    PubMed

    DeVore, Susan D; Figlioli, Keith

    2010-04-01

    Implementing health information technology (IT) is a major strategic objective for providers. To pinpoint considerations that tie to success, the Premier health care alliance surveyed hospitals to develop an electronic health record best-practices library. Compiled from diverse health care organizations, the library outlines considerations to support "meaningful use" in the areas of computerized physician order entry, medication management, clinical documentation, reporting of measures, privacy, information exchange, management of populations' health, and personal health records. Best practices also uncovered strategies for securing executive leadership, culture change, communication, and support for clinicians. This paper summarizes lessons from the library, providing recommendations to speed up health IT implementation. PMID:20368596

  7. Paired Renazzo-type (CR) carbonaceous chondrites from the Sahara

    NASA Astrophysics Data System (ADS)

    Bischoff, A.; Palme, H.; Ash, R. D.; Clayton, R. N.; Schultz, L.; Herpers, U.; Stoffler, D.; Grady, M. M.; Pillinger, C. T.; Spettel, B.; Weber, H.; Grund, T.; Endress, M.; Weber, D.

    1993-04-01

    Data on the chemical composition, mineralogy, abundance, and isotopic composition of recently found Sahara meteorites are presented. The nine Acfer samples and the El Djouf 001 meteorite are considered to belong to the same parent meteoroid and are classified as a CR chondrite. The Acfer-El Djouf meteorite has a CI-chondritic composition of nonvolatile elements, in particular CI ratios of refractory elements to Mg. The presence of metal with chondritic Fe/Ni ratios, olivine with relatively low FeO contents and with high Cr is attributed to the primitive, unequilibrated nature of Acfer-El Djouf and other CR chondrites. The carbon and nitrogen stable isotropic composition of the Acfer-El Djouf chondrite lies within the range of other members of the CR group. Rare gases of the Acfer-El Djouf meteorite contain a comparatively large solar wind component, in excess of that in Renazzo. The cosmic-ray exposure age of the Acfer-El Djouf meteorite is about 6 million years.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Measuring cardiac waste: the premier cardiac waste measures.

    PubMed

    Lowe, Timothy J; Partovian, Chohreh; Kroch, Eugene; Martin, John; Bankowitz, Richard

    2014-01-01

    The authors developed 8 measures of waste associated with cardiac procedures to assist hospitals in comparing their performance with peer facilities. Measure selection was based on review of the research literature, clinical guidelines, and consultation with key stakeholders. Development and validation used the data from 261 hospitals in a split-sample design. Measures were risk adjusted using Premier's CareScience methodologies or mean peer value based on Medicare Severity Diagnosis-Related Group assignment. High variability was found in resource utilization across facilities. Validation of the measures using item-to-total correlations (range = 0.27-0.78), Cronbach α (.88), and Spearman rank correlation (0.92) showed high reliability and discriminatory power. Because of the level of variability observed among hospitals, this study suggests that there is opportunity for facilities to design successful waste reduction programs targeting cardiac-device procedures. PMID:23719033

  10. Active sand dunes are largest dust source in the Sahara Desert

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-09-01

    Dried up lakebeds and playas in the Sahara Desert of North Africa are large sources of dust in the atmosphere. The Bodélé Depression at the southern edge of the Sahara Desert, for example, is the single largest source of dust in the world; on average, 100 dust storms a year originate from the Bodélé Depression. A new study by Crouvi et al., however, finds that active sand dunes could be even bigger sources of desert dust in the atmosphere. Atmospheric dust plays active roles in climate and biological processes in the ocean: It regulates heating at the surface of the Earth; modifies cloud properties that affect rainfall; and acts as the only source of iron, a critical nutrient for microorganisms in the ocean. Little is known about types of dust sources in the Sahara Desert, which alone accounts for more than 50% of the dust in the atmosphere.

  11. African humid periods triggered the reactivation of a large river system in Western Sahara

    PubMed Central

    Skonieczny, C.; Paillou, P.; Bory, A.; Bayon, G.; Biscara, L.; Crosta, X.; Eynaud, F.; Malaizé, B.; Revel, M.; Aleman, N.; Barusseau, J. -P.; Vernet, R.; Lopez, S.; Grousset, F.

    2015-01-01

    The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara. PMID:26556052

  12. African humid periods triggered the reactivation of a large river system in Western Sahara.

    PubMed

    Skonieczny, C; Paillou, P; Bory, A; Bayon, G; Biscara, L; Crosta, X; Eynaud, F; Malaizé, B; Revel, M; Aleman, N; Barusseau, J-P; Vernet, R; Lopez, S; Grousset, F

    2015-01-01

    The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara. PMID:26556052

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

    PubMed Central

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

    2011-01-01

    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 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. PMID:21187416

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

    ERIC Educational Resources Information Center

    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…

  15. Expansion and contraction of the sahara desert from 1980 to 1990.

    PubMed

    Tucker, C J; Dregne, H E; Newcomb, W W

    1991-07-19

    Data from polar-orbiting meteorological satellites have been used to determine the extent of the Sahara Desert and to document its interannual variation from 1980 to 1990. The Sahara Desert ranged from 8,633,000 square kilometers in 1980 to 9,982,000 square kilometers in 1984. The greatest annual north-south latitudinal movement of the southern Saharan boundary was 110 kilometers from 1984 to 1985 and resulted in a decrease in desert area of 724,000 square kilometers. PMID:17794695

  16. Preliminary Examination of Sahara 99555: Mineralogy and Experimental Studies of a New Angrite

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; McKay, G.; Le, L.; Mittlefehldt, D. W.

    2000-01-01

    A 2710 g meteorite, Sahara 99555 (Sah99), was recently recovered from the Sahara and reported to be the 5th angrite. It is the largest angrite ever found and may offer useful information to better understand the unusual petrogeneses of this rare achondrite group. It may also allow us to examine the chronological record of igneous activity in the very early solar system. We obtained a 2.6 g chip of Sah99 and here present a preliminary report of its petrology and mineralogy in conjunction with a crystallization experiment on an analogue composition.

  17. Investigating the role of the land surface in explaining the interannual variation of the net radiation balance over the Western Sahara and sub-Sahara

    NASA Technical Reports Server (NTRS)

    Smith, Eric A.; Nicholson, Sharon

    1987-01-01

    The status of the data sets is discussed. Progress was made in both data analysis and modeling areas. The atmospheric and land surface contributions to the net radiation budget over the Sahara-Sahel region is being decoupled. The interannual variability of these two processes was investigated and this variability related to seasonal rainfall fluctuations. A modified Barnes objective analysis scheme was developed which uses an eliptic scan pattern and a 3-pass iteration of the difference fields.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    '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...

  19. Songbird migration across the Sahara: the non-stop hypothesis rejected!

    PubMed

    Schmaljohann, Heiko; Liechti, Felix; Bruderer, Bruno

    2007-03-01

    Billions of songbirds breeding in the Western Palaearctic cross the largest desert of the world, the Sahara, twice a year. While crossing Europe, the vast majority use an intermittent flight strategy, i.e. fly at night and rest or feed during the day. However, it was long assumed that they overcome the Sahara in a 40 h non-stop flight. In this study, we observed bird migration with radar in the plain sand desert of the Western Sahara (Mauritania) during autumn and spring migration and revealed a clear prevalence of intermittent migration. Massive departures of songbirds just after sunset independent of site and season suggests strongly that songbirds spent the day in the plain desert. Thus, most songbirds cross the Sahara predominantely by the intermittent flight strategy. Autumn migration took place mainly at low altitudes with high temperatures, its density decreased abruptly before sunrise, followed by very little daytime migration. Migration was highly restricted to night-time and matched perfectly the intermittent flight strategy. However, in spring, when migratory flights occurred at much higher altitudes than in autumn, in cool air, about 17% of the songbird migration occurred during the day. This suggests that flying in high temperatures and turbulent air, as is the case in autumn, may lead to an increase in water and/or energy loss and may prevent songbirds from prolonged flights into the day. PMID:17254999

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

    PubMed

    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. PMID:22183688

  1. The Sahara Troposphere - Simultaneous Aircraft Observations from Fennec

    NASA Astrophysics Data System (ADS)

    Engelstaedter, Sebastian; Washington, Richard; Flamant, Cyrille; Allen, Chris J. T.

    2013-04-01

    The Saharan heat low (SHL) that develops over western Africa in Boreal summer has been recognised for its important role in the regional and continental scale climate system. It is co-located with the highest atmospheric dust loading and the deepest dry convective boundary layer in the world. As part of the Fennec 2011 Intensive Observation Period, two aircraft surveyed the SHL region in the morning and afternoon on 22 June 2011 along different tracks employing LIDAR instruments and dropsondes allowing the first characterisation of the structure and daytime evolution of atmospheric features in the central western Sahara including the SHL, the Saharan atmospheric boundary layer (SABL), the monsoon and atmospheric dust distributions within the system. The observations show a system that is more complex than previously thought. Characteristics include a) a NE-SW orientated SHL, b) a monsoon re-circulation around the SHL associated with dampened Convective Boundary Layer (CBL) growth and Saharan Residual Layer (SRL) top minimum, c) Harmattan winds associated with increased near-surface temperatures and enhanced CBL growth rate and CBL depth, d) near-surface inversions limiting CBL growth and vertical mixing of emitted dust, e) above SRL inversion strength linked to SRL top altitude, f) an aged dust layer close to the SABL top that shows a complex wave-like structure, and g) a potential tropospheric ventilation reducing SRL height and reducing dust concentration. The NE-SW elongated SHL is located over northern Mauritania close to the Mali border in the morning and moves west by about 0.5 to 1.0° in the afternoon corresponding well with the ERA-Interim reanalysis. The CBL depth ranges from 0.45 to 2.01 km above mean sea level (aMSL) in the morning and from 1.75 to 6.02 km in the afternoon. Low-level inversions in the morning between 0.5 and 0.9 km aMSL are strongest (up to 0.83°C) where the CBL is most shallow and weakening with increasing CBL depth. Above SRL

  2. Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change

    PubMed Central

    Sereno, Paul C.; Garcea, Elena A. A.; Jousse, Hélène; Stojanowski, Christopher M.; Saliège, Jean-François; Maga, Abdoulaye; Ide, Oumarou A.; Knudson, Kelly J.; Mercuri, Anna Maria; Stafford, Thomas W.; Kaye, Thomas G.; Giraudi, Carlo; N'siala, Isabella Massamba; Cocca, Enzo; Moots, Hannah M.; Dutheil, Didier B.; Stivers, Jeffrey P.

    2008-01-01

    Background Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene (∼8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation. Methodology/Principal Findings Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to ∼7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return ∼4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments. Conclusions/Significance The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following: The early Holocene occupants at Gobero (7700–6200 B.C.E.) were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200–5200 B.C.E).More gracile humans arrived in the mid-Holocene (5200–2500 B.C.E.) employing a diversified

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

    PubMed

    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

  4. Behavioral transitions and weight change patterns within the PREMIER trial.

    PubMed

    Bartfield, Jessica K; Stevens, Victor J; Jerome, Gerald J; Batch, Bryan C; Kennedy, Betty M; Vollmer, William M; Harsha, David; Appel, Lawrence J; Desmond, Renee; Ard, Jamy D

    2011-08-01

    Little is known about the transition in behaviors from short-term weight loss to maintenance of weight loss. We wanted to determine how short-term and long-term weight loss and patterns of weight change were associated with intervention behavioral targets. This analysis includes overweight/obese participants in active treatment (n = 507) from the previously published PREMIER trial, an 18-month, multicomponent lifestyle intervention for blood pressure reduction, including 33 intervention sessions and recommendations to self-monitor food intake and physical activity daily. Associations between behaviors (attendance, recorded days/week of physical activity, food records/week) and weight loss of ≥5% at 6 and 18 months were examined using logistic regression. We characterized the sample using 5 weight change categories (weight gained, weight stable, weight loss then relapse, late weight loss, and weight loss then maintenance) and analyzed adherence to the behaviors for each category, comparing means with ANOVA. Participants lost an average of 5.3 ± 5.6 kg at 6 months and 4.0 ± 6.7 kg (4.96% of body weight) by 18 months. Higher levels of attendance, food record completion, and recorded days/week of physical activity were associated with increasing odds of achieving 5% weight loss. All weight change groups had declines in the behaviors over time; however, compared to the other four groups, the weight loss/maintenance group (n = 154) had statistically less significant decline in number of food records/week (48%), recorded days/week of physical activity (41.7%), and intervention sessions attended (12.8%) through 18 months. Behaviors associated with short-term weight loss continue to be associated with long-term weight loss, albeit at lower frequencies. Minimizing the decline in these behaviors may be important in achieving long-term weight loss. PMID:21455122

  5. Transforming KSC to be the World's Premier 21st Century Launch Complex

    NASA Technical Reports Server (NTRS)

    Engler, Tom

    2011-01-01

    This slide presentation reviews the work being done to transform the Kennedy Space Center into what is hoped to be the world's premier launch complex, capable of launching commercial and government satellites and manned spacecraft.

  6. Health News You Can Use …from the world's premier research institute

    MedlinePlus

    ... Issues Health News You Can Use …from the world's premier research institute Past Issues / Summer 2007 Table ... medical experts who work for you at the world's leading medical and health research organization, the National ...

  7. Mineralogy of Carbonaceous Chondrites and ACFER 217 from the Sahara

    NASA Astrophysics Data System (ADS)

    Geiger, T.; Bischoff, A.

    1992-07-01

    Among the approximately 400 meteorites recovered in the past three years in the Sahara at least 19 carbonaceous chondrites exist. Ten paired samples belong to the CR- chondrite Acfer 059/El Djouf 001 which has been recently described (Bischoff et al., 1992a). Three samples (Acfer 182, 207, 214) represent a unique (carbonaceous) chondrite (Bischoff et al., 1992b) that has similarities to ALH 85085 (e.g. Scott, 1988). Here, we describe six unpaired carbonaceous chondrites and Acfer 217, an unusual chondritic breccia. Three chondrites probably belong to the CV- chondrites (Acfer 082, 086, 272) and two to the CO- chondrites (Acfer 202, 243). Acfer 094 has trace element characteristics of a CM-chondrite, but has oxygen isotope ratios different from CM-chondrites (Bischoff et al., 1991). CV-chondrites: Based on the petrography and mineral chemistry Acfer 082 and 086 are typical CV3 chondrites. Large coarse-grained CAIs (especially in Acfer 082), fine- grained spinel-rich and large olivine-rich aggregates, chondrules and fragments are embedded in a fine-grained groundmass mainly consisting of small Fe-rich olivine laths. In Acfer 082 and Acfer 086 the average compositions of matrix olivine are Fa 55 and Fa 40, respectively. Acfer 082 is quite fresh concerning the degree of weathering, whereas Acfer 086 is severely weathered as indicated by the occurrence of abundant calcite filling fractures and pores between the olivine laths of the matrix. Acfer 272 has a mineral chemistry similar to Acfer 082, but is in texture, trace element chemistry (Spettel et al., 1992), and oxygen isotopes (Mayeda and Clayton, pers. communication) different to Acfer 082. Acfer 272 has a densely compacted matrix without individual euhedral to subhedral olivine laths. CO-chondrites: Acfer 202 and 243 consist of abundant porphyritic chondrules, CAIs, olivine-rich inclusions, and fragments embedded in abundant fine-grained matrix. The main component of the matrix is Fe-rich olivine. Matrix olivines

  8. Modeling mineral dust emissions from the Sahara desert using new surface properties and soil database

    NASA Astrophysics Data System (ADS)

    Laurent, B.; Marticorena, B.; Bergametti, G.; LéOn, J. F.; Mahowald, N. M.

    2008-07-01

    The present study investigates the mineral dust emissions and the occurrence of dust emission events over the Sahara desert from 1996 to 2001. Mineral dust emissions are simulated over a region extending from 16°N to 38°N and from 19°W to 40°E with a ?° × ?° spatial resolution. The input parameters required by the dust emission model are surface features data (aerodynamic roughness length, dry soil size distribution and texture for erodible soils), and meteorological surface data (mainly surface wind velocity and soil moisture). A map of the aerodynamic roughness lengths is established based on a composition of protrusion coefficients derived from the POLDER-1 surface products. Soil dry size distribution and texture are derived from measurements performed on soil samples from desert areas, and from a soil map derived from a geomorphologic analysis of desert landscapes. Surface re-analyzed meteorological databases (ERA-40) of the European Centre for Medium range Weather Forecasts (ECMWF) are used. The influence of soil moisture on simulated dust emissions is quantified. The main Saharan dust sources identified during the 6-year simulated period are in agreement with the previous studies based on in situ or satellite observations. The relevance of the simulated large dust sources and point sources ("hot spots") is tested using aerosol indexes derived from satellite observations (TOMS Absorbing Aerosol Index and Infrared Dust Difference Index Meteosat). The Saharan dust emissions simulated from 1996 to 2001 range from 585 to 759 Tg a-1. The simulations show marked seasonal cycles with a maximum in summer for the western Sahara and in spring for the eastern Sahara. The interannual variability of dust emissions is pronounced in the eastern part of the Sahara while the emissions from the western Sahara are more regular over the studied period. The soil moisture does not noticeably affect the Saharan dust emissions, their seasonal cycle or their interannual

  9. Multiple dust sources in the Sahara Desert: The importance of sand dunes

    NASA Astrophysics Data System (ADS)

    Crouvi, Onn; Schepanski, Kerstin; Amit, Rivka; Gillespie, Alan R.; Enzel, Yehouda

    2012-07-01

    We determine the current sources of dust in the Sahara Desert using quantitative correlation between the number of days with dust storms (NDS), derived from remote-sensing data of high temporal resolution, with the distribution of the soil types and geomorphic units. During 2006-8 the source of over 90% of the NDS was found to be sand dunes, leptosols, calcisols, arenosols, and rock debris. In contrast to previous studies, only few dust storms originated from playas and dry lake beds. Land erodibility was estimated by regressing the NDS to the number of days with high-speed wind events, and was found to be high for sand dunes. Clay and fine-silt grains and aggregates are scarce in sand dunes, which most likely produce dust particles through aeolian abrasion of sand grains. Thus, saltating sand grains impacting clay aggregates on playa surfaces cannot be the sole process for generating dust in the Sahara.

  10. Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa

    PubMed Central

    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. PMID:24040347

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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. PMID:26387526

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

    PubMed

    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. PMID:25230661

  14. Palaeohydrology of the Fazzan Basin, Libyan Sahara: Evidence for multiple phases of North African humidity.

    NASA Astrophysics Data System (ADS)

    Armitage, S. J.; White, K.; Drake, N.

    2008-12-01

    The Fazzan is a large closed basin with an area of 450,000 km2, located in south-western Libya. The present-day climate is hyper-arid. Modern human occupation is restricted to oases, notably at the foot of the Messak Sattafat, a Nubian Sandstone escarpment which divides the Fazzan into two sub-basins. However widespread lithic scatters with varying inferred ages, and numerous Holocene hearth fields, indicate that the Fazzan has a long history of human occupation. In addition, regionally extensive lake deposits attest to the presence of a large palaeolake, here termed Lake Mega-Fazzan, at various periods in the past. Although the Sahara contains evidence for several other large palaeolakes, Lake Mega-Fazzan is the only one fed exclusively by rivers draining the Sahara proper. Thus, the Lake Mega-Fazzan sediments and archaeological remains provide an important resource for advancing our understanding of climate change in this part of the Sahara. Optically stimulated luminescence (OSL) dating techniques have been applied to a range of lacustrine deposits, and more experimentally to the Holocene hearth fields, to provide an internally consistent chronology for the Fazzan record. Results indicate that sediments within the Fazzan Basin record a very long history of palaeohydrological change. The oldest lacustrine sediments are beyond the range of conventional OSL dating techniques, but younger humid periods during oxygen isotope stages 11, 5 and 1 are recognised. Initial results from one hearth field also indicate that OSL has the potential to reveal human responses to changes in hydrology during the Holocene. These results, when compared with similar studies of adjacent closed basins, indicate that the Sahara may not always have provided as formidable a barrier to faunal migration as it does at present. The implications of this finding for our understanding of North African palaeoclimate and biogeography will be discussed.

  15. Ambient measurements of selected VOCs in populated and remote sites of the Sahara desert

    NASA Astrophysics Data System (ADS)

    Yassaa, Noureddine; Ciccioli, Paolo; Brancaleoni, Enzo; Frattoni, Massimiliano; Meklati, Brahim Youcef

    2011-04-01

    For the first time, ambient levels of benzene, toluene, carbon tetrachloride and selected oxygenated organic compounds have been measured in both populated and remote sites in the Sahara desert. The levels of these species were generally found to be high in the industrialized regions of the North Sahara, progressively decreasing with latitude so that lowest levels were reached in remote desert sites close to the Equator. The emissions from traffic, and the oil production and its transformation, together with the solvent use were the main anthropogenic sources determining the levels of aromatic, aliphatic and chlorinated organic compounds in desert sites near two Algerian cities. Substantial levels of acetone and some semi-volatile compounds, emitted or formed by photochemical reactions, were also found. Although some of these compounds were below the detection limits in the most remote sites of the Sahara desert located in Mauritania and Niger, measurable levels of benzene and toluene were still found together with significant amounts of acetone. Data seem to indicate that forest fires occurring in the tropical regions of the North African continent were the most likely sources for the background levels measured during most of our measurements. The data presented here did not differ too much from those measured in the most isolated sites of the northern hemisphere.

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

    PubMed Central

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

    2009-01-01

    The carbon isotopic composition of individual plant leaf waxes (a proxy for C3 vs. C4 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 C3 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 C3 vegetation during the African Humid Period (early Holocene) and within Marine Isotope Stage (MIS) 3 (≈50–45 ka) and MIS 5 (≈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. PMID:19910531

  17. Western Sahara Atlas of Algeria: Salt diapirism, orogenic folding and hydrocarbon potential

    SciTech Connect

    Roeder, D. )

    1991-08-01

    The Sahara Atlas has been the Algerian part of the surface trace of the Europe/Africa convergent plate boundary since the early Oligocene. In its western segment, the structure of this detached fold belt is evident in surface mapping, in reflection seismic data, and in a finite plate-tectonic convergence of about 300 km. The northward slope at the Saharan foreland flexure of 5-8{degree} is consistent with northward thinning crust. Very large detached folds with minor thrusts are consistent with an 8 km thick, Triassic to Eocene, marine and nonmarine, polyphase rifted, passive-margin series. The bulk strain in the fold carpet is only 30-40 km, but large folds near the foreland support the theoretical detachment of 130 km. Triassic and Lower Jurassic evaporites occur in nondiapiric anticlinal cores, in Neocomian salt pillows, and in Neogene to Holocene diapirs and fault laminae. The fold trend records the azimuth of plate convergence. The canted mountain-front trend follows an abrupt fault contact (of late Paleozoic or middle Cretaceous age) between Paleozoics on Saharan basement and Hercynian-type basement. The hydrocarbon potential of the Sahara Atlas depends on infolded rifts or aulacogens of early Jurassic age. The northward extension of the Saharan Paleozoic series into the Sahara Atlas is unlikely.

  18. Negotiating an ecological barrier: crossing the Sahara in relation to winds by common swifts.

    PubMed

    Åkesson, Susanne; Bianco, Giuseppe; Hedenström, Anders

    2016-09-26

    The Sahara Desert is one of the largest land-based barriers on the Earth, crossed twice each year by billions of birds on migration. Here we investigate how common swifts migrating between breeding sites in Sweden and wintering areas in sub-Saharan Africa perform the desert crossing with respect to route choice, winds, timing and speed of migration by analysing 72 geolocator tracks recording migration. The swifts cross western Sahara on a broad front in autumn, while in spring they seem to use three alternative routes across the Sahara, a western, a central and an eastern route across the Arabian Peninsula, with most birds using the western route. The swifts show slower migration and travel speeds, and make longer detours with more stops in autumn compared with spring. In spring, the stopover period in West Africa coincided with mostly favourable winds, but birds remained in the area, suggesting fuelling. The western route provided more tailwind assistance compared with the central route for our tracked swifts in spring, but not in autumn. The ultimate explanation for the evolution of a preferred western route is presumably a combination of matching rich foraging conditions (swarming insects) and favourable winds enabling fast spring migration.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'. PMID:27528783

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

    PubMed

    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. PMID:19910531

  20. Comparing environmental changes and habitability settings in the geological history of Sahara and Mars

    NASA Astrophysics Data System (ADS)

    Ori, G. G.; Sabbadini, R.; Komatsu, G.

    2014-12-01

    Sahara has experienced during its long geological history a large number of climatic changes from humid conditions (with savanna-type environments) to dry conditions (with hot desert environments). Therefore, since the late Miocene (?), Sahara experienced periods with rivers, lakes, deltas, and swamps alternated with dry periods with strong aeolian activity and the formation of deflation surface and sand seas. The fluvio-lacustrine deposits formed during humid periods have been strongly reworked by wind processes during the dry periods leaving only the coarse-grained portion of the sediments (conglomerate to rudite). This highly efficient reworking eeolian mechanism affected both of the fluvial and deltaic channel deposits and the large inland lakes, flood plains and other waterlogged areas. The former occurs, at present day, as morphological features and coarse-grained remnants of large fluvial systems whereas the latter are mostly buried below sand seas such as Grand Erg Oriental, Erg Chech, and Azawad. While the sand to silt material accumulated (mostly by saltation) in the sand seas and sand sheets, the finer portion (able to enter the wind as suspended material) was probably swallowed in the large- scale atmospheric circulation redistributed in Sahara itself, in adjacent continents (mostly Europe and South America), and oceans. This geological setting is similar to the one of Mars where fluvial deposits and morphologies abound as largely eroded discontinuous remains. Large-scale alluvial basins and terminal lakes or waterlogged areas (such as the allucial plain in Zephyria) have been largely present in the Martian Noachian-Hesperian time (and possibly even later) but relatively scanty sedimentary deposits testify their existence. When deposits are present they are basically coarse-grained (e.g. the meandering channels of the Eberswalde deltaic plain) due to the long lasting aeolian erosion similarly than the Sahara example. The wind, that dominated the long

  1. Ar-40/Ar-39 laser-probe dating of diamond inclusions from the Premier kimberlite

    NASA Technical Reports Server (NTRS)

    Phillips, D.; Onstott, T. C.; Harris, J. W.

    1989-01-01

    The results of Ar-40/Ar-39 laser-probe analyses of individual eclogitic clinopyroxene inclusions from Premier diamonds are reported which yield a mean age of 1198 + or - 14 Myr. This age agrees well with Sm-Nd and Ar-40/Ar-39 analyses on similar Premier inclusions and is indistinguishable from the inferred time of emplacement of the host kimberlite, which implies that diamond formation was essentially synchronous with kimberlite generation. The extrapolated nonradiogenic Ar-40/Ar-36 ratio of 334 + or - 102 is similar to the present-day atmospheric composition. This value is inconsistent with Sr and Nd isotopic signatures from Premier eclogite inclusions, which suggest a depleted mantle source. Preentrapment equilibration of the inclusions with an Ar-36-rich fluid is the most probable explanation for the low nonradiogenic composition.

  2. NASA Names Premier X-Ray Observatory and Schedules Launch

    NASA Astrophysics Data System (ADS)

    1998-12-01

    NASA's Advanced X-ray Astrophysics Facility has been renamed the Chandra X-ray Observatory in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar. The telescope is scheduled to be launched no earlier than April 8, 1999 aboard the Space Shuttle Columbia mission STS-93, commanded by astronaut Eileen Collins. Chandrasekhar, known to the world as Chandra, which means "moon" or "luminous" in Sanskrit, was a popular entry in a recent NASA contest to name the spacecraft. The contest drew more than six thousand entries from fifty states and sixty-one countries. The co-winners were a tenth grade student in Laclede, Idaho, and a high school teacher in Camarillo, CA. The Chandra X-ray Observatory Center (CXC), operated by the Smithsonian Astrophysical Observatory, will control science and flight operations of the Chandra X-ray Observatory for NASA from Cambridge, Mass. "Chandra is a highly appropriate name," said Harvey Tananbaum, Director of the CXC. "Throughout his life Chandra worked tirelessly and with great precision to further our understanding of the universe. These same qualities characterize the many individuals who have devoted much of their careers to building this premier X-ray observatory." "Chandra probably thought longer and deeper about our universe than anyone since Einstein," said Martin Rees, Great Britain's Astronomer Royal. "Chandrasekhar made fundamental contributions to the theory of black holes and other phenomena that the Chandra X-ray Observatory will study. His life and work exemplify the excellence that we can hope to achieve with this great observatory," said NASA Administrator Dan Goldin. Widely regarded as one of the foremost astrophysicists of the 20th century, Chandrasekhar won the Nobel Prize in 1983 for his theoretical studies of physical processes important to the structure and evolution of stars. He and his wife immigrated from India to the U.S. in 1935. Chandrasekhar served on the faculty of the University of

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

    NASA Astrophysics Data System (ADS)

    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

  4. Sahara Slide: Age, initiation, and processes of a giant submarine slide

    NASA Astrophysics Data System (ADS)

    Georgiopoulou, Aggeliki; Masson, Douglas G.; Wynn, Russell B.; Krastel, Sebastian

    2010-07-01

    The Sahara Slide is a giant submarine landslide on the northwest African continental margin. The landslide is located on the open continental slope offshore arid Western Sahara, with a headwall at a water depth of ˜2000 m. High primary productivity in surface waters drives accumulation of thick fine-grained pelagic/hemipelagic sediment sequences in the slide source area. Rare but large-scale slope failures, such as the Sahara Slide that remobilized approximately 600 km3 of sediment, are characteristic of this sedimentological setting. Seismic profiles collected from the slide scar reveal a stepped profile with two 100 m high headwalls, suggesting that the slide occurred retrogressively as a slab-type failure. Sediment cores recovered from the slide deposit provide new insights into the process by which the slide eroded and entrained a volcaniclastic sand layer. When this layer was entrained at the base of the slide it became fluidized and resulted in low apparent friction, facilitating the exceptionally long runout of ˜900 km. The slide location appears to be controlled by the buried headwall of an older slope failure, and we suggest that the cause of the slide relates to differential sedimentation rates and compaction across these scarps, leading to local increases of pore pressure. Sediment cores yield a date of 50-60 ka for the main slide event, a period of global sea level rise which may have contributed to pore pressure buildup. The link with sea level rising is consistent with other submarine landslides on this margin, drawing attention to this potential hazard during global warming.

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

    NASA Astrophysics Data System (ADS)

    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

  6. Sahara 99555 and D'Orbigny: Possible Pristine Parent Magma of Quenched Angrites

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; McKay, G. A.; Jones, J. H.

    2004-01-01

    Angrites constitute a small, but important group of basaltic achondrites showing unusual mineralogy and old crystallization ages. The currently known angrites are divided into two subgroups. Angra dos Reis (ADOR) and LEW86010 show slow cooling histories ("slowly-cooled" angrites) and differ from the later found angrites (LEW87051, Asuka 881371, Sahara 99555, D Orbigny, NWA1670, NWA1298). This second group has textures that suggest rapid cooling histories ("quenched" angrites). The petrogenesis of angrites has been controversial, partly due to the small number of available samples. In this abstract, we suggest a possible parent melt composition for the quenched angrites and its relationship to the partial melts of carbonaceous chondrites.

  7. The role of convectively-generated cold pools on model biases in the Sahara

    NASA Astrophysics Data System (ADS)

    Garcia-Carreras, Luis; Marsham, John H.; Parker, Douglas J.; Bain, Caroline L.; Milton, Sean; Saci, Azzedine; Salah-Ferroudj, Mohammed; Ouchene, Bouziane; Washington, Richard

    2013-04-01

    Radiosonde data from Fennec supersite-1 (Bordj Badji Mokhtar, Algeria) have been used to confront for the first time global model behaviour in the remote Sahara with regular in-situ profile observations. Convectively-generated cold pools are produced by the evaporation of precipitation and can propagate over large distances, particularly at night. These are an important component of mesoscale convective systems, which produce the majority of rainfall in the Sahel, and have been observed to ventilate the Sahara. Cold pools are, however, very poorly captured by parameterisations of convection. We assess how cold pool outflows from moist convection contribute to model biases in the Sahara and evaluate the impact of data assimilation on model analyses. The Saharan heat low is too warm and dry in the forecast and cold pools are shown to contribute to the majority of the mean bias. Although the model does not represent dust and cold pools are an important dust uplift mechanism, the sign of the errors is inconsistent with radiative impacts of dust. These biases can therefore be directly attributed to the missing advective cooling from cold pools. Cold pools cause 29% of the observed meridional humidity flux, but this contribution is absent both in the forecast and analysis, thus affecting the large-scale water cycle of the West African monsoon/Saharan heat low system. Assimilation of the radiosonde data reduces these errors, but significant temperature and meridional humidity-flux biases remain at night, when cold pools are most frequent and intense. This implies that significant errors remain in the analysis, and that these biases have a diurnal cycle which will in turn affect the diurnal cycle in the model. The model biases are consistent with the larger-scale heat-low biases in the operational Unified Model. Furthermore, model analyses show significant differences in the Sahara, hampering efforts to evaluate model performance in such a data-sparse region. These issues

  8. 78 FR 54464 - Premier Empire Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-04

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Premier Empire Energy, LLC; Supplemental Notice That Initial Market-Based... above-referenced proceeding, of Premier Empire Energy, LLC's application for market-based rate...

  9. Investigating the Impact of the Premier League Reading Stars Programme on Children's Attainment

    ERIC Educational Resources Information Center

    Pabion, Clémence

    2014-01-01

    The evaluation of the Premier League Reading Stars (PLRS) programme in 2013 has established that the intervention is having a positive impact on the attainment of participating children in reading and writing: Three out of four children made at least six months' progress in just ten weeks. One child in three made a year's progress or more. The…

  10. Geochemical variations in aeolian mineral particles from the Sahara-Sahel Dust Corridor.

    PubMed

    Moreno, Teresa; Querol, Xavier; Castillo, Sonia; Alastuey, Andrés; Cuevas, Emilio; Herrmann, Ludger; Mounkaila, Mohammed; Elvira, Josep; Gibbons, Wes

    2006-10-01

    The Sahara-Sahel Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits. PMID:16600327

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

    PubMed

    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. PMID:23514066

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

    USGS Publications Warehouse

    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.

  13. A 45-year time series of dune mobility indicating constant windiness over the central Sahara

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.; Leprince, S.

    2012-07-01

    Although evidence is mounting that links global warming to changes in atmospheric dynamics over the Atlantic realm, similar studies over the African continent are lacking. And even if such models would exist, it would be difficult to verify their validity due to the paucity of meteorological observations and anemometers in the central Sahara. A pragmatic way around this problem is to monitor barchan dune velocity as a proxy for the windiness of desert areas. Dune migration rates are a measure of the amount of work done by the wind which does not require field measurements but can be observed from space instead. This paper presents a novel application of the remote sensing tool COSI-Corr for the construction of time series of dune mobility from sequences of optical satellite imagery. The technique has been applied to the Bodélé Depression in northern Chad, to demonstrate that dune migration rates in the central Sahara have been remarkably constant for nearly half a century, leading us to conclude that wind velocities have not changed more than 0.2% per year over that period. It is therefore unlikely that the frequency and intensity of dust storms originating from this ‘hot spot’ has significantly changed over the past decades either.

  14. Remote monitoring of aerosol layers over Sofia during Sahara dust transport episode (April, 2012)

    NASA Astrophysics Data System (ADS)

    Stoyanov, Dimitar; Grigorov, Ivan; Deleva, Atanaska; Kolev, Nikolay; Peshev, Zahari; Kolarov, Georgi; Donev, Evgeni; Ivanov, Danko

    2013-03-01

    In this work we present results of lidar remote sensing of aerosol layers in the atmosphere above Sofia during an episode of Sahara dust transport, 02-07 April, 2012. The investigations were made using two lidar systems, one equipped with a CuBr-vapor laser, emitting at wavelength 510.6 nm, and a second one - with Nd:YAG laser, at wavelengths 1064 nm and 532 nm. The results of lidar measurements are presented in terms of vertical atmospheric backscatter coefficient profiles and color maps of the aerosol stratification evolution. The involved into discussions ceilometer data (CHM 15k ceilometer) and satellite data from CALIPSO lidar, enhance the synergy of observations. Conclusion about atmospheric aerosol's origin was made upon analyses of the information of weather-forecast maps provided by the Forecast system of Barcelona Supercomputing Centre, which are accessible via Internet. Additional information was provided by calculations of the backward air mass trajectories, using online software of NOAA about HYSPLIT model. The comparison between the data from the two lidars and the ceilometer showed similar behavior of aerosol layers development in the atmosphere above Sofia. All information about aerosol layers origin, their altitude above ground, persistence during lidar observations, confirmed the conclusion of observation of a long-distance Sahara dust transport beyond Balkans and Sofia. An interesting completion of CALIPSO lidar and ground based lidars results of measurement is presented in case of thick opaque cloud layer in the atmosphere, which slices the path of lidar sensing in both directions.

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

    PubMed

    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. PMID:21953517

  16. Biogeochemical inferences of mobility of early Holocene fisher-foragers from the Southern Sahara Desert.

    PubMed

    Stojanowski, Christopher M; Knudson, Kelly J

    2011-09-01

    North Africa is increasingly seen as an important context for understanding modern human evolution and reconstructing biocultural adaptations. The Sahara, in particular, witnessed a fluorescence of hunter-gatherer settlement at the onset of the Holocene after an extended occupational hiatus. Subsequent subsistence changes through the Holocene are contrary to those documented in other areas where mobile foraging gave way to settled agricultural village life. In North Africa, extractive fishing and hunting was supplanted by cattle and caprine pastoralism under deteriorating climatic conditions. Therefore, the initial stage of food production in North Africa witnessed a likely increase in mobility. However, there are few studies of paleomobility in Early Holocene hunter-gatherer Saharan populations and the degree of mobility is generally assumed. Here, we present radiogenic strontium isotope ratios from Early Holocene fisher-forager peoples from the site of Gobero, central Niger, southern Sahara Desert. Data indicate a relatively homogeneous radiogenic strontium isotope signature for this hunter-gather population with limited variability exhibited throughout the life course or among different individuals. Although the overall signature was local, some variation in the radiogenic strontium isotope data likely reflects transhumance into the nearby Aïr Massif. Data from Gobero were significantly less variable than in other worldwide hunter-gatherer populations, including those thought to be fairly sedentary. Strontium data from Gobero were also significantly different from contemporaneous sites in southwestern Libya. These patterns are discussed with respect to archaeological models of community organization and technological evolution. PMID:21766285

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Sahara Dust

    Atmospheric Science Data Center

    2013-04-15

    article title:  Casting Light and Shadows on a Saharan Dust Storm     ... (nadir) camera. High-altitude cirrus clouds cast shadows on the underlying ocean and dust layer, which are visible in shades of ... was unable to retrieve elevation data. However, the edges of shadows cast by the cirrus clouds onto the dust (indicated by blue and cyan ...

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

    ERIC Educational Resources Information Center

    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…

  20. Dune ages in the sand deserts of the southern Sahara and Sahel

    NASA Astrophysics Data System (ADS)

    Bristow, Charlie; Armitage, Simon

    2015-04-01

    In this paper we aim to document the history of aeolian processes within the southern Sahara as part of the INQUA Dune Atlas. We review available luminescence ages for sand dunes across the southern Sahara and attempt to correlate periods of sand accumulation and to develop an improved understanding of the dune chronology on a regional basis. This was achieved by analysing dune age by country, as well as by latitude and longitude. The results show a very patchy spatial distribution of dune ages with large gaps that encompass some of the largest sand seas. Despite these gaps, some related patterns in dune morphology and stratigraphy appear to be consistent between northern Nigeria and southern Mali where older linear dunes are distinct from younger Late Holocene transverse and barchanoid dunes. Elsewhere in Mauretania linear dunes with different orientations appear to have accumulated at different times, most likely in response to changes in atmospheric circulation. Regional climatic changes are identified where dunes are transgressed by lake deposits within endorehic basins. We identify four locations where dune accumulation is terminated by lacustrine transgressions, two of which, in Lake Chad and the Bodélé Depression, occur shortly after the last glacial maximum (LGM). The third example at Gobiero in Niger occurred later, in the early Holocene, around 8.4 ka and a fourth marks a later transgression of Palaeolake MegaChad after 4.7 ka. Larger-scale latitudinal and longitudinal distributions in dune ages across the southern Sahara do not show any consistent patterns, though this may due to the small sample size relative to the study area. In addition, local variations in external controls such as wind regime, rainfall, vegetation and sand supply need to be considered, sometimes on a site by site basis. Limiting the analysis to dune ages determined using the single-aliquot regenerative-dose (SAR) protocol indicates a lack of dune preservation during the LGM and

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    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.

  3. Subsurface valleys and geoarcheology of the eastern Sahara revealed by Shuttle radar

    NASA Technical Reports Server (NTRS)

    Mccauley, J. F.; Schaber, G. G.; Breed, C. S.; Grolier, M. J.; Haynes, C. V.; Issawi, B.; Elachi, C.; Blom, R.

    1982-01-01

    Previously unknown buried valleys, geologic structures, and possible Stone Age occupation sites have been revealed through the Shuttle Imaging Radar (SIR-A) penetration of the extremely dry Selima Sand Sheet, dunes and drift sand of the eastern Sahara. Radar penetration of dry sand and soils varies with the wavelength of the incident signals, which is 24 cm for the SIR-A system, as well as incidence angle and electrical properties of the material which are largely determined by moisture content. The calculated depth of radar penetration of dry sand and granules has been established to be 5 m on the basis of laboratory measurements of Selima Sand Sheet sample electrical properties. September 1982 field studies in Egypt have verified SIR-A signal penetration depths of at least 1 m in the Selima Sand Sheet and drift sand, and 2 m or more in sand dunes.

  4. Characterization of potential zones of dust generation at eleven stations in the southern Sahara

    NASA Astrophysics Data System (ADS)

    Clark, I.; Assamoi, P.; Bertrand, J.; Giorgi, F.

    Synoptic wind data for multi-decadal periods at eleven stations located in the southern Sahara region (Agadez, Atar, Bilma, Dori, Gao, Kayes, Nema, Niamey, Nouadhibou, Ouagadougou and Tessalit) are used to study the monthly dust deflation power over the region. We found that, regardless of the conditions of the soil, the deflation power (or wind efficiency) is not sufficient to generate significant amounts of aerosols south of 15°N. North of this latitude, the deflation power is much larger, with potential zones of either very strong deflation (Nouadhibou and Bilma) or severe deflation (Gao, Tessalit, Nema, Atar, Agadez). Stations in the Sahel region such as Gao, Agadez and Tessalit are characterized by a gradual reinforcement of the deflation power between 1970 and 1984 in correspondence of increasing desertification over the region. During this same period, Bilma, a well know region of dust source, experienced a major reduction in deflation power due to shifts in large scale wind patterns.

  5. Dating lacustrine episodes in the eastern Sahara by the epimerization of isoleucine in ostrich eggshells

    USGS Publications Warehouse

    Miller, G.H.; Wendorf, F.; Ernst, R.; Schild, R.; Close, A.E.; Friedman, I.; Schwarcz, H.P.

    1991-01-01

    The eggshell of the African ostrich, Struthio camelus, closely approximates a closed system for the retention of indigenous proteinaceous residues. Epimerization of the protein amino acid isoleucine follows linear first-order kinetics in laboratory simulations nearly to racemic equilibrium, and the variation in D/L ratio within a single fragment, or between fragments of the same age, is significantly less than in other carbonate systems. These observations suggest that the extent of isoleucine epimerization (aIle/Ile ratio) in ostrich eggshell offers the potential for high-resolution geochronology of Quaternary deposits. From the simulation experiments, and dated early Holocene samples for which we have in situ mean annual sediment temperature measurements, Arrhenius parameters have been calculated; the activation energy is 30.33 kcal mol-1, similar to that of other carbonate systems. We have measured the aIle/Ile ratio in ostrich eggshell associated with lacustrine episodes at Bir Tarfawi and Bir Sahara East, two depressions in what is currently the hyperarid eastern Sahara. The ratios can be used directly to indicate qualitatively the time represented by each series of lake sediment, and to correlate disjunct lacustrine deposits within and between the basins. Uranium-series disequilibrium dating of algal mats contained within some of the lake beds indicate that a major wet interval occurred about 130 ka ago. Using the U-series date for calibration, the amino acid ratios are used to date the most recent lacustrine interval to about 100 ka B.P., and two older intervals, one about 200 ?? 25 ka B.P., and an older interval that occurred prior to 250 ka ago. ?? 1991.

  6. Inside the “African Cattle Complex”: Animal Burials in the Holocene Central Sahara

    PubMed Central

    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. PMID:23437260

  7. Shorelines in the Sahara desert: Archives of the hydrodynamics of Megalake Chad

    NASA Astrophysics Data System (ADS)

    Schuster, Mathieu; Roquin, Claude; Moussa, Abderamane; Duringer, Philippe; Bouchette, Frédéric; Ghienne, Jean-François; Allenbach, Bernard

    2014-05-01

    The African Humid Period corresponds to a major climate change event paced by the orbital parameters of Earth (precession of the equinoxes) with enhanced monsoon regime which has strongly modified the Holocene paleoenvironments of Africa. In sub-tropical north-Africa related reactivation of ancient river networks and the development of numerous lakes, have in turn temporarily favored human occupation of the Sahara. Megalake Chad, which extended over an area swept by the latitudinal fluctuations of the Intertropical convergence zone (ITCZ), represents one of the most emblematic case study of these climate-controlled environmental changes. This very large paleolake had a water-surface of more than 350000 sqkm (10°N-18°N, 12°E-19°E) and maximum depths of ~150 m to the North and of ~40 m in the area of the present-day Lake Chad. Satellite imagery (SRTM, Landsat, Pleiades) over the Chad basin reveals conspicuous clastic morphosedimentary structures which do not correspond to eolian or terrestrial landforms but that clearly correspond to typical coastal features. They include isolated ridges, Azov-type spits, beach ridges, wave-ravinement surface and wave-dominated deltas. These paleoshorelines provide firm outlines of the maximal extension of Megalake Chad and allow to track its size evolution which in turn informs about the precipitation/evaporation budget at basin-scale (~2000000 sqkm). Moreover, the particular shape and distribution of coastal landforms are mostly controlled by the alongshore drift induced by the prevailing winds. Wind-driven hydrodynamics was the major process for clastic sediments redistribution at basin-scale in the nearshore zone and resulted in the building of prominent sedimentary bodies (up to hundreds of kilometer long and few tens of meter thick). As a consequence, paleoshorelines of Megalake Chad represent a record of the paleo-wind regime over the Sahara-Sahel zone which was apparently dominated by an Harmattan-like wind.

  8. Chloroquine retinopathy: pattern of presentation in Ibadan, Sub-Sahara Africa.

    PubMed

    Oluleye, T S; Babalola, Y; Ijaduola, M

    2016-01-01

    BackgroundSelf-medication with chloroquine is common in Ibadan, Sub-Sahara Africa. Retinopathy from chloroquine is not uncommon. The aim was to determine the pattern of presentation.MethodologyCases of Chloroquine retinopathy seen at the Retina and Vitreous Unit of the University College Hospital, Ibadan between 2008 and 2014 were reviewed. Information on age, sex, duration of chloroquine use, and visual loss were retrieved. Visual acuity at presentation, anterior, and posterior segment findings were documented. The results were analyzed using proportions and percentages.ResultsFourteen cases were seen during the study period. Mean age was 50.7 years. Male to female ratio was 3.5 : 1. Average duration of visual loss before presentation was 2.7 years. Average duration of self-medication with chloroquine was 5.3 years. Presenting visual acuity showed 2(14%) cases of bilateral blindness(VA<3/60 in both eyes); 5(35.7%) cases of uniocular blindness; three cases of bilateral low vision(VA worse than 6/18 but better than 3/60). Anterior segment examination showed abnormal sluggish pupillary reaction in those with severe affectation. Dilated fundoscopy showed features ranging from mild macular pigmentary changes and bulls eye maculopathy to overt extensive retinal degeneration involving the posterior pole, attenuation of retinal vessels, optic atrophy, and beaten bronze appearance of atrophic maculopathy.ConclusionChloroquine retinopathy is not uncommon in Ibadan, Sub-Sahara Africa. Bulls eye maculopathy, extensive retinal, and macular degeneration with optic atrophy are the main presentations. Public health education is imperative. PMID:26427986

  9. Petrology and Geochemistry of D'Orbigny, Geochemistry of Sahara 99555, and the Origin of Angrites

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.; Killgore, Marvin; Lee, Michael T.

    2001-01-01

    We have done detailed petrologic study of the angrite, D'Orbigny, and geochemical study of it and Sahara 99555. D'Orbigny is an igneous-textured rock composed of Ca-rich olivine, Al-Ti-diopside-hedenbergite, subcalcic kirschsteinite, two generations of hercynitic spinel and anorthite, with the mesostasis phases ulv6spinel, Ca-phosphate, a silicophosphate phase and Fe-sulfide. We report an unknown Fe-Ca-Al-Ti-silicate phase in the mesostasis not previously found in angrites. One hercynitic spinel is a large, rounded homogeneous grain of a different composition than the euhedral and zoned grains. We believe the former is a xenocryst, the first such described from angrites. The mafic phases are highly zoned; mg# of cores for olivine are approx.64, and for clinopyroxene approx.58, and both are zoned to Mg-free rims. The Ca content of olivine increases with decreasing mg#, until olivine with approx.20 mole% Ca is overgrown by subcalcic kirschsteinite with Ca approx.30-35 mole%. Detailed zoning sequences in olivine-subcalcic kirschsteinite and clinopyroxene show slight compositional reversals. There is no mineralogic control that can explain these reversals, and we believe they were likely caused by local additions of more primitive melt during crystallization of D'Orbigny. D'Orbigny is the most ferroan angrite with a bulk rock mg# of 32. Compositionally, it is virtually identical to Sahara 99555; the first set of compositionally identical angrites. Comparison with the other angrites shows that there is no simple petrogenetic sequence, partial melting with or without fractional crystallization, that can explain the angrite suite. Angra dos Reis remains a very anomalous angrite. Angrites show no evidence for the brecciation, shock, or impact or thermal metamorphism that affected the HED suite and ordinary chondrites. This suggests the angrite parent body may have followed a fundamentally different evolutionary path than did these other parent bodies.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  12. Transforming the Premier Perspective® Hospital Database into the Observational Medical Outcomes Partnership (OMOP) Common Data Model

    PubMed Central

    Makadia, Rupa; Ryan, Patrick B.

    2014-01-01

    Background: The Observational Medical Outcomes Partnership (OMOP) Common Data Model (CDM) has been implemented on various claims and electronic health record (EHR) databases, but has not been applied to a hospital transactional database. This study addresses the implementation of the OMOP CDM on the U.S. Premier Hospital database. Methods: We designed and implemented an extract, transform, load (ETL) process to convert the Premier hospital database into the OMOP CDM. Standard charge codes in Premier were mapped between the OMOP version 4.0 Vocabulary and standard charge descriptions. Visit logic was added to impute the visit dates. We tested the conversion by replicating a published study using the raw and transformed databases. The Premier hospital database was compared to a claims database, in regard to prevalence of disease. Findings: The data transformed into the CDM resulted in 1% of the data being discarded due to data errors in the raw data. A total of 91.4% of Premier standard charge codes were mapped successfully to a standard vocabulary. The results of the replication study resulted in a similar distribution of patient characteristics. The comparison to the claims data yields notable similarities and differences amongst conditions represented in both databases. Discussion: The transformation of the Premier database into the OMOP CDM version 4.0 adds value in conducting analyses due to successful mapping of the drugs and procedures. The addition of visit logic gives ordinality to drugs and procedures that wasn’t present prior to the transformation. Comparing conditions in Premier against a claims database can provide an understanding about Premier’s potential use in pharmacoepidemiology studies that are traditionally conducted via claims databases. Conclusion and Next Steps: The conversion of the Premier database into the OMOP CDM 4.0 was completed successfully. The next steps include refinement of vocabularies and mappings and continual maintenance of

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

    NASA Astrophysics Data System (ADS)

    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

  14. Greening of the Sahara - a paleo perspective on the history of water in the Middle East and North Africa

    NASA Astrophysics Data System (ADS)

    Bar-Matthews, M.

    2012-04-01

    The Middle-East, mostly at its southern edge together with North Africa, the northern edge of the Sahara Desert, are located at the boundary between high- to-mid latitude and tropical-subtropical climate systems. The geographical duality of desert adjacent to Mediterranean-type climate regions played and still plays a major role on the water availability. Thanks to the number of important paleoclimate studies that been made on accurate dating of cave speleothems in Southern Arabia and Oman (Fleitmann et al., 2011) and in the northeast Sahara, the Negev Desert Israel (Vaks et al., 2010) and the study of sapropels in Eastern and central Mediterranean (Almogi-Labin et al., 2009; Osborne et al, 2008), it is clear that the region was graced with water during peak interglacials when the African monsoon and westerly storm/rainfall systems intensified. Northward penetration of the Inter Tropical Convergence Zone over the Arabian and African continents resulted in increased discharge of the Nile River and rivers that emerged from central Sahara into the Eastern Mediterranean Sea. Correspondingly, enhanced westerly wind activity led to an increase in rainfall from Atlantic-Mediterranean sources over the entire Mediterranean basin, which even penetrated south into the north-east corner of the Sahara Desert. The Saharo-Arabian Desert became narrower and climatic "windows" opened for the dispersal of hominids and animals out of the African continent at 250-239, 210-193, 138-120, 108-98, 87-84 and 10-6.5 ka BP, with severe dry conditions in between. Greening of the Sahara Desert at these intervals is supported also by various marine and terrestrial records, such as corals, lakes, tufa deposits and archeological findings. Dry conditions prevailed in the Sahara desert during glacials. This is in contrast to the climatic conditions in the Eastern Mediterranean coastal region and the Jordan Rift Valley (Bar-Matthews et al., 2003; Lisker et al., 2010), where water was available for

  15. Partaking in the global movement for occupational mental health: what challenges and ways forward for sub-Sahara Africa?

    PubMed Central

    2012-01-01

    There is an ongoing global movement for the entrenchment of occupational mental health as an integral part of occupational health and safety schemes. Aside from being a fundamental human right issue, this move has been demonstrated to be of cost-benefit in terms of workplace productivity and general economic growth. Despite being among the regions most prone to the human and economic repercussions of work-related mental health problems by reason of her socio-economic circumstance; sub-Sahara Africa is yet to fully plug into this movement. With a view to make recommendations on the ways forward for sub-Sahara Africa, this paper examines the current state of and the barriers to effective occupational mental health policy and practice in the region. PMID:22958579

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

    USGS Publications Warehouse

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

    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.

  17. Raman spectroscopic studies of the skins of the Sahara sand viper, the carpet python and the American black rat snake

    NASA Astrophysics Data System (ADS)

    Edwards, H. G. M.; Farwell, D. W.; Williams, A. C.; Barry, B. W.

    1993-07-01

    Vibrational Raman spectra of the skins of the snakes Cerastes vipera (Sahara sand viper) and Morelia argus (carpet python) have been recorded for the first time using visible and IR laser excitation. Full vibrational assignments are proposed and comparisons made with vibrational Raman spectra of the snake Elaphe obsoleta (American black rat snake); such studies may be important in correlating the permeabilities of human and snake skins to drugs and contaminants.

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

    NASA Astrophysics Data System (ADS)

    Fabian, P.; Rollenbeck, R.; Spichtinger, N.; Brothers, L.; Dominguez, G.; Thiemens, M.

    2009-10-01

    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 enhanced Ca2+ and Mg2+ were found to be associated with air masses from African deserts. Satellite aerosol data confirm desert sources both on the Northern (Sahara) as on the Southern Hemisphere (Namib), depending on the season. A few significant PO43- peaks are related with air masses originating from North African phosphate mining fields.

  19. The Palaeoclimate of Wadi Shati, Libyan Sahara: the last 130 ka

    NASA Astrophysics Data System (ADS)

    Drake, Nick A.; Lem, Rachel E.; Armitage, Simon J.; White, Kevin H.; El-Hawat, Ahmed; Salem, Mustafa J.; Hounslow, Mark; Franke, Jan

    2014-05-01

    The Fezzan region of Libya forms a large closed basin that contains a wealth of ancient palaeolake and riverine sediments indicative of past humidity in the central Sahara. We have used remote sensing, DEM analysis and Ultra Ground Penetrating Radar to map these features and have dated them using OSL and radiocarbon methods. Results suggest humid conditions during both MIS 5 and the Holocene with larger lakes and more extensive river systems being present during MIS 5 suggestive of greater humidity at this time. A 4m core was collected from Holocene sediments of the largest lake found in the region (1200 km2 during MIS5 and 660 km2 during the Holocene). Core sediments were dated using OSL and analysed using XRF, Ion Chromatography, Laser Granulometry and chemical extractions for ostracods, diatoms, pollen and phytoliths. The base of the core is dominated by clays deposited in a perennial lake environment from 7.75 ka to 6.6 ka. Gypsum deposition started at about 6.5 ka indicating a more arid environment. Four clay layers are found amongst the gypsum from 6.3 to 6.25 ka, 6.2 to 6.1, 6.0 to 5.8 and 5.7-5.6 ka suggests that aridification was not a sudden event, but consisted of a series of arid/humid oscillations before the lake finally desiccated just before 5 ka. No pollen, diatoms or ostracods are preserved in the sediments but phytoliths were present. Both tree and grass phytoliths were found in lower parts of the core, suggesting a wooded savannah environment from 7.75 to about 7 ka. Trees decline and grass increases up the core, signifying an increasingly arid environment. By the time the first gypsum bed is deposited at about 6.5 ka trees have disappeared and grass dominates. These results do not support the hypothesis of a sudden aridification of the Sahara at 4.9 ka and instead suggest that in the Fezzan region a gradual aridification had started by 7.75 ka and that the climate oscillated during the lake desiccation that started at 6.5 ka and was complete by

  20. An integrated remote sensing and GIS analysis of the Kufrah Paleoriver, Eastern Sahara

    NASA Astrophysics Data System (ADS)

    Ghoneim, Eman; Benedetti, Michael; El-Baz, Farouk

    2012-02-01

    A combined remote sensing (optical and radar imagery) and GIS (hydrologic network delineation) analysis allows mapping of the Kufrah Paleoriver of Libya and sheds light on its geomorphic evolution during the Neogene. The Kufrah system, which is now largely buried beneath the windblown sands of the Eastern Sahara, drained an area of about 236,000 km 2 in central and southern Libya. The river discharged across a large inland delta to the Al-Jaghbub depression in northern Libya, and ultimately through the Sirt Basin to the Mediterranean Sea. Radar imagery reveals buried features of the landscape including drainage divides, locations of possible stream capture, deeply-incised valleys, and the distal margins of the inland delta. Previous studies have shown that the Kufrah Paleoriver is the successor of the Sahabi River, which drained most of central Libya during the late Tertiary. Satellite imagery supports the concept of large-scale drainage rearrangement in the Quaternary, driven by tectonic subsidence that diverted streamflow and sediment discharge away from the Sahabi basin toward the inland delta of the lower Kufrah basin. Paleochannels crossing the delta suggest that at various times during the Quaternary, the Kufrah Paleoriver either drained externally through the deeply-incised Sahabi Paleochannel to the Mediterranean Sea, or drained internally to paleolakes in the Al-Jaghbub depression. Thick alluvial deposits on the delta and lake margins likely provided a major sediment source to build the Great Sand Sea, which covers the region today. The southwestern branch of the Kufrah drainage is aligned with an elongated trough that connects to the Amatinga River system in Chad. Thus the Kufrah watershed may have served as an outlet from Megalake Chad to the Mediterranean Sea during humid phases of the Neogene. If so, the combined Amatinga/Kufrah system may have served as one of the proposed natural corridors used by human and animal populations to cross the Sahara

  1. Heat shock protein synthesis and thermotolerance in Cataglyphis, an ant from the Sahara desert.

    PubMed Central

    Gehring, W J; Wehner, R

    1995-01-01

    The ant Cataglyphis lives in the Sahara desert and is one of the most thermotolerant land animals known. It forages at body temperatures above 50 degrees C, and the critical thermal maxima are at 53.6 +/- 0.8 degrees C for Cataglyphis bombycina and 55.1 +/- 1.1 degrees C for Cataglyphis bicolor. The synthesis and accumulation of heat shock proteins (HSPs) were analyzed in Cataglyphis and compared to Formica, an ant living in more moderate climates, and to two Drosophila species. In Cataglyphis, protein synthesis continues at temperatures up to 45 degrees C as compared to 39 degrees C for Formica and Drosophila. The two Drosophila species, Drosophila melanogaster and Drosophila ambigua, differ with respect to their maximal induction of HSP synthesis and accumulation by 3-4 degrees C. In contrast, the two ant species accumulate HSPs prior to their exposure to heat, and in Cataglyphis the temperature of maximal HSP induction by de novo protein synthesis is only 2 degrees C higher than in Formica. These findings are interpreted as preadaption of the ants prior to exposure to high temperatures. Images Fig. 1 Fig. 2 Fig. 3 PMID:7708762

  2. Bacterial Composition and Survival on Sahara Dust Particles Transported to the European Alps

    PubMed Central

    Meola, Marco; Lazzaro, Anna; Zeyer, Josef

    2015-01-01

    Deposition of Sahara dust (SD) particles is a frequent phenomenon in Europe, but little is known about the viability and composition of the bacterial community transported with SD. The goal of this study was to characterize SD-associated bacteria transported to the European Alps, deposited and entrapped in snow. During two distinct events in February and May 2014, SD particles were deposited and promptly covered by falling snow, thus preserving them in distinct ochre layers within the snowpack. In June 2014, we collected samples at different depths from a snow profile at the Jungfraujoch (Swiss Alps; 3621 m a.s.l.). After filtration, we performed various microbiological and physicochemical analyses of the snow and dust particles therein that originated in Algeria. Our results show that bacteria survive and are metabolically active after the transport to the European Alps. Using high throughput sequencing, we observed distinct differences in bacterial community composition and structure in SD-layers as compared to clean snow layers. Sporulating bacteria were not enriched in the SD-layers; however, phyla with low abundance such as Gemmatimonadetes and Deinococcus-Thermus appeared to be specific bio-indicators for SD. Since many members of these phyla are known to be adapted to arid oligotrophic environments and UV radiation, they are well suited to survive the harsh conditions of long-range airborne transport. PMID:26733988

  3. TL and ESR of quartz from the astrobleme of Aorounga (Sahara of Chad)

    NASA Astrophysics Data System (ADS)

    Miallier, D.; Sanzelle, S.; Falguères, C.; Faïn, J.; Pilleyre, Th.; Vincent, P. M.

    The present work was intended to evaluate the time that elapsed since the meteorite fall that produced the giant astrobleme of Aorounga (Sahara of Chad). For this purpose the TL and ESR dating techniques using the additive dose method were applied to quartz grains extracted from an impactite and from a sandstone shocked and baked during the impact. The ESR Al centre was measured and resulted in an age of about 800 ka. The red TL and the blue TL showed unusual TL features: the additive dose response curves were marked by an initial saturated part followed by a second rise at around +0.5 kGy; the peaks showed erratic temperature shifts with dose; fading was observed for high temperature peaks. By comparison with previous work using samples baked by lava flows more than 1 Ma ago and presenting some of those features, it was assumed that the minimum age of the astrobleme was of the same order of magnitude. This is in agreement with other observations. A preliminary explanation for those ageing features is proposed. It is suspected that radiation induced traps contribute to the TL of the studied quartz grains. Most probably the 'malign-behaviour' of the quartz grains is also connected with shock effects.

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

    USGS Publications Warehouse

    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.

  5. Microbial Diversity of the Hypersaline Sidi Ameur and Himalatt Salt Lakes of the Algerian Sahara

    PubMed Central

    Boutaiba, Saad; Hacene, Hocine; Bidle, Kelly A.; Maupin-Furlow, Julie A.

    2011-01-01

    Microbial populations within hypersaline lakes often exhibit high activities of photosynthesis, dissimilatory sulphate reduction and other processes and, thus, can have profound impacts on biogeochemical cycles of carbon, nitrogen, sulphur and other important elements within arid lands. To further understand these types of ecosystems, the physicochemical and biological properties of Sidi Ameur and Himalatt Salt Lakes in the Algerian Sahara were examined and compared. Both lakes were relatively neutral in pH (7.2 to 7.4) and high in salt, at 12% and 20 % (w/v) salinity for Himalatt and Sidi Ameur Lakes, respectively, with dominant ions of sodium and chloride. The community compositions of microbes from all three domains (Bacteria, Archaea and Eukarya) were surveyed through the use of 16S and 18S ribosomal gene amplification and clone library clustering using amplified ribosomal DNA restriction analysis (ARDRA) in conjunction with DNA sequencing and analysis. A high level of microbial diversity, particularly among the bacteria of the Himalatt Salt Lake and archaea of Sidi Ameur Lake, was found within these environments. Representatives from all known halophilic bacterial phyla as well as 6 different genera of halophilic archaea were identified. Moreover, several apparently novel phylotypes among both archaea and bacteria were revealed. PMID:21909172

  6. Ecoclimate Teleconnections: Remote Control of the Mid-Holocene Green Sahara

    NASA Astrophysics Data System (ADS)

    Swann, A. L.; Fung, I.; Chiang, J. C.

    2011-12-01

    The mid-Holocene climate of Northern Africa was characterized by wetter conditions than present, as evidenced by higher paleo lake-levels and pollen assemblages of savannah vegetation suggesting a wetter, greener Sahara. Differences in orbital forcing and local vegetation have been proposed to explain the existence of savannah vegetation as far north as 23 N but climate model simulations have had difficultly reproducing sufficient precipitation over Northern Africa. We propose that remote forcing from forest cover in the mid latitudes is capable of pulling the Intertropical Convergence Zone northward, and, in conjunction with orbital forcing and forcing from local vegetation, explains the enhanced precipitation over Northern Africa ~6000 years ago. We use climate model simulations to show the relative importance of local and remote vegetation and discuss the mechanisms by which mid latitude vegetation influences sub tropical precipitation and productivity. The forcing of North African precipitation and therefore local productivity by mid latitude vegetation highlights a bi-directional interaction between ecosystems and climate.

  7. Airborne Fungi in Sahara Dust Aerosols Reaching the Eastern Caribbean: II. Species Identification Using Molecular Techniques

    NASA Astrophysics Data System (ADS)

    de La Mota, A.; Betancourt, C.; Detres, Y.; Armstrong, R.

    2003-12-01

    Fungi samples from filters collected in Castle Bruce, Dominica from March through July 2002, were previously purified and identified to genus level using classic macroscopic and microscopic techniques. A total of 105 isolated colonies were cultured in liquid media and the mycelial mats used for DNA extraction. PCR was used to amplify the ITS region of the rDNA using the ITS1 and ITS4 primers. Both strands of the amplified products were sequenced and the final identification to species level was completed by a GenBank search. Fourteen different species and one fungal endophyte were identified from genders Aspergillus,Penicillium, Fusarium, Cladosporium, Curvularia and Phanerochaete. Some of these species such as A. fumigatus, A. japonicus, P. citrinum and C. cladosporoides are known to cause respiratory disorders in humans. A. fumigatus causes an aggressive pulmonary allergic response that might result in allergic bronchopulmonary aspergillosis. Other species such as F. equiseti and C. brachyspora are plant pathogens affecting economically important crops. Sahara dust is an important source of fungal spores of species that are not common in the Caribbean region.

  8. Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

    PubMed Central

    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. PMID:24146882

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

    PubMed

    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. PMID:24146882

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

    PubMed

    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. PMID:27242149

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Characterization and evolution of Paleozoic source rock organic matter in Algerian Central Sahara

    SciTech Connect

    Takherist, D.; Arezki, A.; Mouaici, R.

    1995-08-01

    The objective of the proposed poster is to provide a knowledge of the evolution history of organic matter in an intracratonic basin. The Paleozoic source rocks (Ordovician - Silurian - Upper Devonian and Carboniferous) of the Algerian Central Sahara (Ahnet and Timimoun basins) experienced severe conditions of maturation during the geological history, therefore, the source rocks intervals are presently mature to overmature and only dry gas has been descovered throughout this zone. The several geochemical models (Genex, Basimod, Matoil) in addition to Afta and Zafta Data show that regionaly significant heating event occured with maximum palaeo-temperature and maximum gas generation at 300 +/- 30 My. However, high palaeotemperatures can not be explained only by the significant burial. An important anomalous heat flow is needed to explain the geothermal history. In this case, there has been no significant petroleum from the Paleozoic source rocks in this zone since this age; but following some assumptions, a certain hypothesis about a recent generation (-60 to -30 My) is now in discussion.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Ultra-relativistic Au+Au and d+Au collisions:

    NASA Astrophysics Data System (ADS)

    Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Hauer, M.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Seals, H.; Sedykh, I.; Skulski, W.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J.-L.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Wenger, E.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.

    In this talk I will review PHOBOS data on charged particle multiplicities, obtained in Au+Au and d+Au collisions at RHIC. The general features of the Au+Au pseudorapidity distributions results will be discussed and compared to those of /line{p}p collisions. The total charged particle multiplicity, scaled by the number of participant pairs, is observed to be about 40% higher in Au+Au collisions than in /line{p}p and d+Au systems, but, surprisingly at the same level of e+e- collisions. Limiting fragmentation scaling is seen to be obeyed in Au+Au collisions.

  15. Evidence of rift valley fever seroprevalence in the Sahrawi semi-nomadic pastoralist system, Western Sahara

    PubMed Central

    2014-01-01

    Background The increasing global importance of Rift Valley fever (RVF) is clearly demonstrated by its geographical expansion. The presence of a wide range of host and vector species, and the epidemiological characteristics of RVF, have led to concerns that epidemics will continue to occur in previously unaffected regions of Africa. The proximity of the Sahrawi territories of Western Sahara to endemic countries, such as Mauritania, Senegal, and Mali with periodic isolation of virus and serological evidence of RVF, and the intensive livestock trade in the region results in a serious risk of RVF spread in the Sahrawi territories, and potentially from there to the Maghreb and beyond. A sero-epidemiological survey was conducted in the Saharawi territories between March and April 2008 to investigate the possible presence of the RVF virus (RVFV) and associated risk factors. A two-stage cluster sampling design was used, incorporating 23 sampling sites. Results A total of 982 serum samples was collected from 461 sheep, 463 goats and 58 camels. Eleven samples (0.97%) tested positive for IgG against the RVFV. There were clusters of high seroprevalence located mostly in the Tifariti (7.69%) and Mehaires (7.14%) regions, with the Tifariti event having been found in one single flock (4/26 positive animals). Goats and older animals were at a significantly increased risk being seropositive (p = 0.007 and p = 0.007, respectively). Conclusion The results suggest potential RVF activity in the study area, where intense livestock movement and trade with neighbouring countries might be considered as a primary determinant in the spread of the disease. The importance of a continuous field investigation is reinforced, in light of the risk of RVF expansion to historically unaffected regions of Africa. PMID:24758592

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

    NASA Astrophysics Data System (ADS)

    Ryder, C. L.; McQuaid, J. B.; Flamant, C.; 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.; Estellés, V.; Formenti, P.; Garcia-Carreras, L.; Kocha, C.; Marenco, F.; Rosenberg, P.; 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.; Woolley, A.

    2015-01-01

    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 retrievals under

  17. Crop drying by indirect active hybrid solar - Electrical dryer in the eastern Algerian Septentrional Sahara

    SciTech Connect

    Boughali, S.; Bouchekima, B.; Mennouche, D.; Bouguettaia, H.; Bechki, D.; Benmoussa, H.

    2009-12-15

    In the present work, a new specific prototype of an indirect active hybrid solar-electrical dryer for agricultural products was constructed and investigated at LENREZA Laboratory, University of Ouargla (Algerian Sahara). In the new configuration of air drying passage; the study was done in a somewhat high range of mass flow rate between 0.04 and 0.08 kg/m{sup 2} s a range not properly investigated by most researchers. Experimental tests with and without load were performed in winter season in order to study the thermal behavior of the dryer and the effect of high air masse flow on the collector and system drying efficiency. The fraction of electrical and solar energy contribution versus air mass flow rate was investigated. Slice tomato was studied with different temperatures and velocities of drying air in order to study the influence of these parameters on the removal moisture content from the product and on the kinetics drying and also to determine their suitable values. Many different thin layer mathematical drying models were compared according to their coefficient of determination (R{sup 2}) and reduced chi square ({chi}{sup 2}) to estimate experimental drying curves. The Middli model in this condition proved to be the best for predicting drying behavior of tomato slice with (R{sup 2} = 0.9995, {chi}{sup 2} = 0.0001). Finally an economic evaluation was calculated using the criterion of payback period which is found very small 1.27 years compared to the life of the dryer 15 years. (author)

  18. Analysis of available measures for malaria control in Africa south of the Sahara.

    PubMed

    Goriup, S

    1989-01-01

    Africa south of the Sahara is not homogeneous and presents several extreme conditions where malaria persistence is ensured by a complex and highly adaptable vector system. Plasmodium falciparum is the most widespread and life threatening of the malaria parasites of man, particularly for young children and pregnant women. Large-scale residual spraying was not totally effective and was very costly, and mass chemoprophylaxis was not feasible. The spread of chloroquine resistance added arguments against uncontrolled use of drugs. Chemoprophylaxis is now recommended only for pregnant women, especially in their first pregnancy, whilst chloroquine 25 mg base/kg over 3 days is recommended for curative treatment in villages. Second line treatment regimens should be available, together with the possibility of referring severe malaria cases quickly to appropriate clinical facilities. Other control measures include self-protection against mosquito bites by bednets (especially those impregnated with synthetic pyrethroids), mosquito coils, repellents, window and door screening; other measures to prevent man-mosquito contact, such as careful siting of settlements and zooprophylaxis; anti-larval measures, i.e. source reduction, protection of wells and water reservoirs, larviciding, introduction of larvivorous fish; and sprays against adult mosquitoes. The elaboration of strategies for control and their application requires a study of the existing situation. A core of specialists is required in each country, to help with decentralized planning and evaluation of malaria control and to ensure quality control of services, training and applied field research. Additional measures may become available in the future, especially anti-malaria vaccines, and countries should be ready to study their application. PMID:2696165

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

    PubMed

    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. PMID:23132908

  20. Crustal and upper mantle velocity structure of the Hoggar swell (Central Sahara, Algeria)

    NASA Astrophysics Data System (ADS)

    Ayadi, A.; Dorbath, C.; Lesquer, A.; Bezzeghoud, M.

    2000-02-01

    The Hoggar region is known as one of the most important swells in the African continent. Its altitude culminates at 2908 m in the Tahat hill (Atakor). The Hoggar and other massifs of central Africa (Aı̈r, Eghei, Tibesti, Darfur, Cameroon mount, …) form a system of domal uplifts with similar scale, morphology and volcanic activity. The knowledge of the structure beneath the Hoggar swell will help us to understand the origin of continental swells. In order to get an image of the lithosphere in this region, we have performed a teleseismic field experiment. The 33 short-period seismic stations have been maintained for 2 1/2 month along a 700-km long NNW-SSW profile. This experiment crossed the Central Hoggar and extended northward into the In-Salah Sahara basin which is characterized by high heat flow values of deep origin. The high quality of the data recorded during this experiment allows us to perform a velocity inversion. The Hoggar appears to be characterized by lower mantle velocities. The anomalous zone extends from the upper lithosphere to the mantle. The weak velocity contrast is interpreted in agreement with gravity, geothermal and petrological data as due to extensive mantle modifications inherited from Cenozoic volcanic activity. It confirms that the Hoggar swell is not due to a large-scale uplift of hot asthenospheric materials but corresponds to a now cooled-off modified mantle. On the contrary, local low-velocity zones associated with the Atakor and Tahalra volcanic districts show that hot materials still exist at depths in relation with recent basaltic volcanism.

  1. Development of a method to measure and compare hospital waste: the Premier hospital waste index.

    PubMed

    Lowe, Timothy J; Kroch, Eugene; Martin, John; Bankowitz, Richard

    2014-01-01

    The authors developed 15 measures and a comparative index to assist acute care facilities in identifying and monitoring clinical and administrative functions for health care waste reduction. Primary clinical and administrative data were collected from 261 acute care facilities contained within a database maintained by Premier Inc, spanning October 1, 2010, to September 30, 2011. The measures and 4 index models were tested using the Cronbach α coefficient and item-to-total and Spearman rank correlations. The final index model was validated using 52 facilities that had complete data. Analysis of the waste measures showed good internal reliability (α = .85) with some overlap. Index modeling found that data transformation using the standard deviation and adjusting for the proportional contribution of each measure normalized the distribution and produced a Spearman rank correlation of 0.95. The waste measures and index methodology provide a simple and reliable means to identify and reduce waste and compare and monitor facility performance. PMID:23687221

  2. The evolution of physical and technical performance parameters in the English Premier League.

    PubMed

    Barnes, C; Archer, D T; Hogg, B; Bush, M; Bradley, P S

    2014-12-01

    This study examined the evolution of physical and technical soccer performance across a 7-season period in the English Premier League. Match performance observations (n=14 700) were analysed for emergent trends. Total distance covered during a match was ~2% lower in 2006-07 compared to 2012-13. Across 7 seasons, high-intensity running distance and actions increased by ~30% (890±299 vs. 1 151±337 m, p<0.001; ES: 0.82) and ~50% (118±36 vs. 176±46, p<0.001; ES: 1.41), respectively. Sprint distance and number of sprints increased by ~35% (232±114 vs. 350±139 m, p<0.001; ES: 0.93) and ~85% (31±14 vs. 57±20, p<0.001; ES: 1.46), respectively. Mean sprint distance was shorter in 2012-13 compared to 2006-07 (5.9±0.8 vs. 6.9±1.3 m, p<0.001; ES: 0.91), with the proportion of explosive sprints increasing (34±11 vs. 47±9%, p<0.001; ES: 1.31). Players performed more passes (35±17 vs. 25±13, p<0.001; ES: 0.66) and successful passes (83±10% vs. 76±13%, p<0.001; ES: 0.60) in 2012-13 compared to 2006-07. Whereas the number of short and medium passes increased across time (p<0.001; ES>0.6), the number of long passes varied little (p<0.001; ES: 0.11). This data demonstrates evolution of physical and technical parameters in the English Premier League, and could be used to aid talent identification, training and conditioning preparation. PMID:25009969

  3. Injury Profile of a Professional Soccer Team in the Premier League of Iran

    PubMed Central

    Hassabi, Mohammad; Mohammad-Javad Mortazavi, Seyed; Giti, Mohammad-Reza; Hassabi, Majid; Mansournia, Mohammad-Ali; Shapouran, Sara

    2010-01-01

    Purpose Despite numerous studies which have been done regarding soccer injuries worldwide, there is lack of available data considering the epidemiology of injuries in the Iranian soccer premier league, although it is the most popular sport in the country. The main goal of this research was to determine the incidence of physical injuries in the studied population, considering other characteristics such as site, type and mechanism as well. Methods Twenty one adult male professional soccer players (age 24±3), members of a team (Tehran-Pas) participating in Iranian premier league, were followed during a 4-month period. The injury characteristics and exposure times were recorded by the team physician during all the matches and training sessions. Results The total exposure time was 2610 playing hours (2352 h of training versus 258 h of competition). Eighty six percent of the injuries were acute. Incidence of acute injuries was 16.5 (95% CI: 12-22) per 1000 hours of playing (11.5 per 1000 hrs of training and 62 per 1000 hrs of competition). The most common types of injuries were strains followed by contusions, each of which constituted 30% of acute injuries. More than 80% of injuries occurred in lower limbs, especially in thigh and groin regions. Nearly 60% of acute injuries occurred in dominant side of the body, and collision was the reason of about half of the acute injuries. Severity of more than 70% of the injuries was minor. On average each injury had led the player being off the field for about 10 days. Conclusion The incidence of injury in this research is in range of numbers obtained in important international tournaments but the rate of injuries during training sessions is higher than comparable studies. PMID:22375208

  4. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT - PHYSICAL REMOVAL OF MICROBIAL CONTAMINATION AGENTS IN DRINKING WATER, WATTS P{REMIER ULTRA 5 REVERSE OSMOSIS DRINKING WATER TREATMENT SYSTEM (POU)

    EPA Science Inventory

    The Watts Premier Ultra 5 system was tested for removal of bacteria and viruses at NSF International's Laboratory. Watts Premier submitted ten units, which were split into two groups of five. One group received 25 days of conditioning prior to challenge testing, while the secon...

  5. The Sahara-East Mediterranean dust and climate connection revealed by strontium and uranium isotopes in a Jerusalem speleothem

    NASA Astrophysics Data System (ADS)

    Frumkin, Amos; Stein, Mordechai

    2004-01-01

    This paper explores the potential of Sr and U isotope systems in speleothems as tracers of eolian dust transport and hydrological conditions. The study focuses on a speleothem from Jerusalem spanning the past 220 kyr. This speleothem provides a precisely dated record of dust flux from the Sahara to the East Mediterranean. Enhanced dust flux and Terra Rossa soil development are reflected by elevated 87Sr/ 86Sr ratios in the speleothem (0.7082-0.7086), while lower 87Sr/ 86Sr ratios (˜0.7078) indicate higher contribution of the local bedrock due to low dust flux and low soil accumulation. The strontium isotope system in the speleothem is a robust monitor of the Sahara monsoon-modulated climate, since dust uptake is related to development or reduction in vegetation cover of Sahara soil. The [ 234U/ 238U] activity ratios in the speleothem range between 1.12 and 1.0. The high activity values may indicate selective removal of 234U from the soil while the low values converge to the bedrock. The migration of 234U to the cave reflects mainly the regional hydrological conditions that are modulated by the North Atlantic-Mediterranean climate system. Thus, the speleothem provides a combined record of the monsoon-North Atlantic climatic systems. Long-term stability in glacial 87Sr/ 86Sr ratios (0.7083±0.0001 over the past 220 kyr) suggests an overall similarity in eolian dust sources, and uniformity in the synoptic conditions that dominate the dust storm tracks during glacial periods.

  6. Revision of the genus Thyreocephalus and description of Afrus gen. nov. of Africa south of the Sahara (Coleoptera: Staphylinidae: Staphylininae).

    PubMed

    Janák, Jiří; Bordoni, Arnaldo

    2015-01-01

    A revision of the genus Thyreocephalus Guérin-Méneville, 1844 of Africa south of the Sahara is presented. A new genus Afrus gen. nov. was described with the type species Thyreocephalus spegazzinii Bernhauer, 1915, which resulted in following new combination: Afrus spegazzinii (Bernhauer, 1915), comb. nov. Eulissus collarti (Cameron, 1932) was transferred to Afrus. Based on a revision of types and of additional material, 32 species of the genus Thyreocephalus and two species of the genus Afrus are recognized in Africa south of the Sahara. All species are described or redescribed and illustrated, seven of them for the first time: Thyreocephalus camerunensis sp. nov., T. manfredi sp. nov., T. marginipennis sp. nov., T. meridioafricanus sp. nov., T. pseudoafricanus sp. nov., T. subcorticalis sp. nov. and T. tsingidianus sp. nov. Neotypes are designated for Eulissus ater Laporte, 1835, Xantholinus coeruleipennis Quedenfeldt, 1881, and X. interocularis Eppelsheim, 1895. Lectotypes are designated for Eulissus atlanticus Bernhauer, 1915, E. burgeoni Bernhauer, 1929, E. mokaensis Bernhauer, 1915, E. secretus Bernhauer, 1935, E. turneri Bernhauer, 1937, Xantholinus alluaudi Fauvel, 1907, X. mocquerysi Fauvel, 1903, X. pilosus Roth, 1851, Thyreocephalus diversiceps Bernhauer, 1936, and T. spegazzinii Bernhauer, 1915. Eulissus africanus Bernhauer, 1913, E. alluaudi (Fauvel, 1907) (originally described in Xantholinus Dejean, 1821), E. atlanticus Bernhauer, 1915, E. brunneiventris Tottenham, 1956, E. burgeoni Bernhauer, 1929, E. guineensis Bernhauer, 1912, E. mokaensis Bernhauer, 1915, E. secretus Bernhauer, 1935, E. strinatii Scheerpeltz, 1958, and Xantholinus nairobiensis Fauvel, 1907 were transferred to Thyreocephalus. Following synonymies are proposed: Thyreocephalus nairobiensis (Fauvel, 1907) = Eulissus turneri Bernhauer, 1937, syn. nov., Thyreocephalus interocularis (Eppelsheim, 1895) = Thyreocephalus diversiceps Bernhauer, 1936, syn. nov., Thyreocephalus mokaensis

  7. Qualitative Impact Assessment 2010: An Independent Study Conducted by BDRC Continental, Ltd., February-July 2010. Premier League Reading Stars

    ERIC Educational Resources Information Center

    National Literacy Trust, 2010

    2010-01-01

    Premier League Reading Stars (PLRS) is in its eighth year. To complement a pre-post quantitative survey, an impact evidence base was required to inform consideration of continued funding into 2011 and beyond. PLRS is very highly regarded among child participants, parents, and librarians. The structure of the scheme, its basis on football, and the…

  8. PHYSICAL REMOVAL OF MICROBIAL CONTAMINANTS IN DRINKING WATER – WATTS PREMIER INC. WP-4V DRINKING WATER TREATMENT SYSTEM

    EPA Science Inventory

    The Watts Premier WP-4V four-stage POU RO system was tested for removal of bacteria and viruses at NSF’s Drinking Water Treatment Systems Laboratory. Five systems were challenged with the bacteriophage viruses fr and MS2, and the bacteria Brevundimonas diminutaEM. The ...

  9. ETV REPORT: REMOVAL OF CHEMICAL CONTAMINANTS IN DRINKING WATER – WATTS PREMIER INC. WP-4V DRINKING WATER TREATMENT SYSTEM

    EPA Science Inventory

    The Watts Premier WP-4V POU drinking water treatment system was tested for removal of aldicarb, benzene, cadmium, carbofuran, cesium, chloroform, dichlorvos, dicrotophos, fenamiphos, mercury, mevinphos, oxamyl, strontium, and strychnine. The WP-4V employs a reverse osmosis (RO) m...

  10. PREMIER: a proposed mission to observe processes controlling atmospheric composition in the height range most important to climate

    NASA Astrophysics Data System (ADS)

    Kerridge, Brian; Orphal, Johannes; van Weele, Michiel; Murtagh, Donal; McConnell, Jack; Hegglin, Michaela; Peuch, Vincent-Henri; Reise, Martin

    2010-05-01

    The PREMIER (PRocess Exploration through Measurements of Infrared and millimetre-wave Emitted Radiation) mission is one of three candidates for ESA's 7th Earth Explorer Core Mission (due for launch in 2016) that have been approved for Phase A study. The mission proposes to make detailed measurements in the mid/upper troposphere and lower stratosphere in order to quantify processes controlling atmospheric global composition in this height range of particular importance to climate. PREMIER would consist of an infrared limb imaging spectrometer which would observe 3D fields of trace gases, alongside a millimetre-wave limb sounder which would enable observations in the presence of most cirrus clouds, and also provide complementary trace gases. In addition, co-located data from EPS-MetOp would be combined with that from PREMIER, to extend the scientific impact of PREMIER down into the lower troposphere, to explore links to surface emissions and pollution. In this presentation, simulations of its capabilities will be described together with some preliminary results from airborne precursors

  11. 76 FR 72978 - Premier Trim, LLC, Spectrum Trim, LLC and Grant Products International, Inc. D/B/A Spectrum Grant...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-28

    ... in the Federal Register on July 7, 2010 (75 FR 39047). At the request of the State agency, the... Employment and Training Administration Premier Trim, LLC, Spectrum Trim, LLC and Grant Products International, Inc. D/B/A Spectrum Grant De Mexico Including Workers Whose Unemployment Insurance (UI) Wages Are...

  12. Collective flow in Au + Au collisions

    SciTech Connect

    Ritter, H.G.; EOS Collaboration

    1994-05-01

    Based on a preliminary sample of Au + Au collisions in the EOS time projection chamber at the Bevalac, we study sideward flow as a function of bombarding energy between 0.25A GeV and 1.2A GeV. We focus on the increase in in-plane transverse momentum per nucleon with fragment mass. We also find event shapes to be close to spherical in the most central collisions, independent of bombarding energy and fragment mass up to {sup 4}He.

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

    NASA Astrophysics Data System (ADS)

    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

  14. Hydrochemical and isotopic characterisation of deep groundwater reservoirs in the Sahara desert

    NASA Astrophysics Data System (ADS)

    Abdalla, R.; Leis, A.; Dietzel, M.; Köhler, S. J.; Böttcher, M. E.; Savarino, J.; Morin, S.

    2009-04-01

    Large sedimentary basins are extended over hundreds of square kilometres cross the Libyan Sahara. These basins consist of several aquifer systems, which belong to various geological ages. Most common are Quaternary, Mesozoic and Palaeozoic aquifers. The Jabal Hasouna well fields are located about 700 km south of Tripoli and are part of the Great Man-Made River Project for water supply to the coastal areas. The well field area extends over 4000 km2 with 440 production and 44 standby wells. In this region the main Cambro-Ordovician Sandstone aquifer is overlain by a shallow carbonate aquifer with a basal aquitard, predominantly composed of marly limestone, clay and shale. Hydrochemical investigations involving collection and analysis of numerous deep groundwater samples from Hasouna well fields have been carried out to evaluate the regional groundwater quality and origin. Therefore, the groundwater samples were analyzed for major ions, trace elements, and environmental isotopes. Additionally, soil and rock samples were collected and characterized using XRD and XRF for mineralogical and chemical composition, respectively. The groundwater can be classified in Na-Ca-Cl-SO4, Na-Ca-Cl-SO4-HCO3, Ca-Na-Cl-SO4-HCO3 and Na-Ca-Mg-Cl-SO4 types with moderate to high salinity. Most solutions indicate elevated ion concentrations of chloride, sodium, sulphate and nitrate. In some parts of the investigation area the respective ion concentrations in the groundwater exceed the WHO quality limits. Stable hydrogen and oxygen isotopic composition of the H2O show that the groundwater composition typically falls below the Global Meteoric Water Line and are far away from the Mediterranean Meteoric Water Line. Accordingly, the groundwaters were recharged in a climate different from that of the recent Mediterranean. The relationship between stable hydrogen and oxygen isotope ratios indicate that the ancient groundwater was recharged under cooler climate conditions. In order to verify the

  15. Sahara Heat Low Perturbations and Water Vapor in the Sahel: A Positive Feedback System

    NASA Astrophysics Data System (ADS)

    Caughman, L.; Evan, A. T.

    2013-12-01

    It is necessary to understand the drivers and feedbacks of global desertification, motivated by the increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Climate change and land dynamics are the perturbations that are major drivers of an ecosystem shift to a ';';desertified'' state. This shift is typically sustained by positive feedbacks, which stabilize the system in the new state. This research focuses on changes in precipitation resulting from land-atmosphere interactions and changes in vegetation cover. We concentrate on the Sahel region of Africa (a strip of land that is a transitional area between the Sahara desert to the North and the rain forest to the South). It is a dry land, semi arid environment and is a bistable ecosystem that can either be in the state of 'dry' or 'wet'. After an abnormally wet/high precipitation period in the 1950s the Sahel experienced terrible droughts and desertification which peaked in the 1980s. Since then, precipitation has gradually increased and a sinusoidal model has been shown run on a multi decadal cycle. Discrepancies in the data exist, however, and although the overall cycle has been modeled well, the large inter-annual fluctuations in precipitation have yet to be sufficiently modeled or explained. This research offers new evidence as to why such a phenomenon exists and attempts to attribute this behavior to a coupled land-atmosphere feedback system, linking together changes in vegetation cover and precipitation in the Sahel. Using the model output data from a high resolution Weather Research and Forecasting (WRF) model to look at Africa and compare the difference between perturbations and the mean, this research asserts that when the surface of the Saharan Heat Low (SHL) becomes extremely hot the pressure drops substantially. Subsequently, due to the West African Monsoon system, air rushes in from high-pressure areas, and pulls monsoon precipitation

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Motion analysis of U11 to U16 elite English Premier League Academy players.

    PubMed

    Goto, Heita; Morris, John G; Nevill, Mary E

    2015-01-01

    This study examined (1) the distances and speeds covered during match play for U11 to U16 English Premier League Academy players, (2) the differences in match performance between retained and released players and (3) the effect of calculating speed zones in different ways when analysing match performance. Eighty-one academy outfield players (10-16 years old), competing in 11-a-side matches, were analysed using a 1-Hz global positioning system with three speed zones (absolute, squad and individual). Pitch dimensions were 78.7 × 54.1 m (U11 and U12), 88.0 × 64.2 m (U13) and 100.8 × 68.2 m (U14-U16). Match durations were 20 min × 2 + 15 min × 2 or 25 min × 3 (U11), 25 min × 3 (U12 and U13) and 40 min × 2 (U14-U16). The matches were part of the regular series of inter-academy matches between Premier League Academies during a season. Completion of at least a half of the duration of a match in two separate matches (mean ± s = 3.1 ± 0.8 matches; range: 2-4 matches) was the criterion for inclusion in the study. Total match running distance increased with age from ~5700 (U11) to ~6700 m · h(-1) (U15) (P < 0.01). Using the absolute speed zones, it was possible to discern differences in high-intensity (>6.0 m · s(-1)) distance covered with age (U11: 29 m · h(-1), U16: 164 m · h(-1), P < 0.01). Using the squad speed zones, it was possible to discern differences between retained and released players in the U11/U12s (moderate-speed running) and in the U15/U16s (walking, jogging and low-speed running) (P < 0.01). Thus, total and high-intensity running distances increase with age, and walking, jogging, low-speed running and moderate-speed running distances are greater in retained than in released players and these differences are best identified through the use of absolute and squad speed zones, respectively. PMID:25583077

  19. Descriptive epidemiology of injuries in a Brazilian premier league soccer team

    PubMed Central

    de Freitas Guina Fachina, Rafael Júlio; Andrade, Marília dos Santos; Silva, Fernando Roberto; Waszczuk-Junior, Silas; Montagner, Paulo César; Borin, João Paulo; de Lira, Claudio Andre Barbosa

    2013-01-01

    Soccer, which has a large number of participants, has a high injury incidence that causes both financial and time burdens. Therefore, knowledge about the epidemiology of soccer injuries could allow sports-medicine professionals, such as physicians and physiotherapists, to direct their work in specific preventive programs. Thus, our aim was to conduct an epidemiological survey of injuries sustained by professional soccer players from the same team who participated in the Brazilian championship premier league in 2009. To this end, we evaluated retrospectively player medical records from the team, which included name, date of birth, position, date of injury, mechanism of injury, and type of injury. In the period of study, 95 injuries were recorded: 42 (44.2%) were recorded during matches, and 53 (55.8%) during the training period. Injuries occurred more frequently in midfielders and strikers. All injuries happened in the lower limb, most of the injuries were muscular, and most occurred as the result of collisions with other athletes. In summary, this study demonstrates that there is a need for greater safety awareness in the training environment. PMID:24379722

  20. Descriptive epidemiology of injuries in a Brazilian premier league soccer team.

    PubMed

    de Freitas Guina Fachina, Rafael Júlio; Andrade, Marília Dos Santos; Silva, Fernando Roberto; Waszczuk-Junior, Silas; Montagner, Paulo César; Borin, João Paulo; de Lira, Claudio Andre Barbosa

    2013-01-01

    Soccer, which has a large number of participants, has a high injury incidence that causes both financial and time burdens. Therefore, knowledge about the epidemiology of soccer injuries could allow sports-medicine professionals, such as physicians and physiotherapists, to direct their work in specific preventive programs. Thus, our aim was to conduct an epidemiological survey of injuries sustained by professional soccer players from the same team who participated in the Brazilian championship premier league in 2009. To this end, we evaluated retrospectively player medical records from the team, which included name, date of birth, position, date of injury, mechanism of injury, and type of injury. In the period of study, 95 injuries were recorded: 42 (44.2%) were recorded during matches, and 53 (55.8%) during the training period. Injuries occurred more frequently in midfielders and strikers. All injuries happened in the lower limb, most of the injuries were muscular, and most occurred as the result of collisions with other athletes. In summary, this study demonstrates that there is a need for greater safety awareness in the training environment. PMID:24379722

  1. Evaluation of sports nutrition knowledge of New Zealand premier club rugby coaches.

    PubMed

    Zinn, Caryn; Schofield, Grant; Wall, Clare

    2006-04-01

    Little is known about if and how team coaches disseminate nutrition information to athletes. In a census survey, New Zealand premier rugby coaches (n = 168) completed a psychometrically validated questionnaire, received by either Internet or standard mail (response rate, 46%), identifying their nutrition advice dissemination practices to players, their level of nutrition knowledge, and the factors determining this level of knowledge. The majority of coaches provided advice to their players (83.8%). Coaches responded correctly to 55.6% of all knowledge questions. An independent t-test showed coaches who imparted nutrition advice obtained a significantly greater score, 56.8%, than those not imparting advice, 48.4% (P = 0.008). One-way ANOVA showed significant relationships between total knowledge score of all coaches and qualifications [F(1,166) = 5.28, P = 0.001], own knowledge rating [F(3,164) = 6.88, P = 0.001] and nutrition training [F(1,166) = 9.83, P = 0.002]. We conclude that these rugby coaches were inadequately prepared to impart nutrition advice to athletes and could benefit from further nutrition training. PMID:16779927

  2. Evolution of match performance parameters for various playing positions in the English Premier League.

    PubMed

    Bush, Michael; Barnes, Chris; Archer, David T; Hogg, Bob; Bradley, Paul S

    2015-02-01

    This study aimed to investigate position-specific evolution of physical and technical performance parameters in the English Premier League (EPL). Match performance observations (n=14700) were collected using a multiple-camera computerized tracking system across seven seasons (2006-07 to 2012-13). Data were analyzed relative to five playing positions: central defenders (n=3792), full backs (n=3420), central midfielders (n=3200), wide midfielders (n=2136) and attackers (n=2152). High-intensity running distance increased in the final season versus the first season in all playing positions (p<.05, ES: 0.9-1.3) with full backs displaying the greatest increase (∼36% higher in 2012-13). Similar trends were observed for sprint distance with full backs demonstrating the most pronounced increase across the seven seasons (36-63%, p<.001, ES: 0.8-1.3). Central players (central defenders and midfielders) illustrated the most pronounced increases in total passes and pass success rate (p<.05, ES: 0.7-0.9) whilst wide players (full backs and wide midfielders) demonstrated only small-moderate increases in total passes and pass success rate (p<.05, ES: 0.6-0.8). The data demonstrates that evolving tactics in the EPL have impacted on the physical demands of wide players and the technical requirements of central players. These findings could be used for talent identification or position-specific physical and technical training. PMID:25461429

  3. Measuring the tuning accuracy of thousands singing in unison: an English Premier Football League table of fans' singing tunefulness.

    PubMed

    Howard, David M

    2004-01-01

    Tunefulness in singing is well understood in the context of solo stage performance, singing in small groups and singing in choirs, with or without accompaniment, and it can be readily measured under laboratory conditions. When thousands of people are singing outside in support of their football team, however, the singing is impromptu; there is no conductor, no starting note, and generally no accompaniment. This paper describes the measurement of the tunefulness of the singing of fans of the twenty clubs in the 2001-2002 English Premier League. The technique adopted is unusual in that it makes direct reference to the formal definition of pitch as a subjective phenomenon. The results are presented in the form of a 2001-2002 English Premier League football fans singing league table. PMID:15260183

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

    PubMed Central

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

    2008-01-01

    It is widely accepted that modern humans originated in sub-Saharan Africa ≈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 ≈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. PMID:18936490

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

    ERIC Educational Resources Information Center

    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 Kenya.…

  6. Dust emission mechanisms in the central Sahara: new insights from remote field observations

    NASA Astrophysics Data System (ADS)

    Allen, C.; Washington, R.; Engelstaedter, S.

    2013-12-01

    North Africa is the world's largest source of mineral aerosol (dust). The Fennec Project, an international consortium led by the University of Oxford, is the first project to systematically instrument the remote central Sahara Desert. These observations have, among others, provided new insights into the atmospheric mechanisms of dust emission. Bordj Badji Mokhtar, in south-west Algeria, is within kilometres of the centre of the global mean summer dust maximum. The site, operated by Fennec partners ONM Algerie, has been heavily instrumented since summer 2011. During the Intensive Observation Period (IOP) in June 2011, four main emission mechanisms were observed and documented: cold pool outflows, low level jets (LLJs), monsoon surges and dry convective plumes. Establishing the relative importance of dust emission mechanisms has been a long-standing research goal. A detailed partitioning exercise of dust events during the IOP shows that 45% of the dust over BBM was generated by local emission in cold pool outflows, 14% by LLJs and only 2% by dry convective plumes. 27% of the dust was advected to the site rather than locally emitted and 12% of the dust was residual or ';background' dust. The work shows the primacy of cold pool outflows for dust emission in the region and also the important contribution of dust advection. In accordance with long-held ideas, the cube of wind speed is strongly correlated with dust emission. Surprisingly however, particles in long-range advection (>500km) were found to be larger than locally emitted dust. Although a clear LLJ wind structure is evident in the mean diurnal cycle during the IOP (12m/s peak winds at 935hPa between 04-05h), LLJs are only responsible for a relatively small amount of dust emission. There is significant daily variability in LLJ strength; the strongest winds are produced by a relatively small number of events. The position and strength of the Saharan Heat Low is strongly associated with the development (or

  7. A Unique Type 4 Chondrite from the Sahara-Acfer 217

    NASA Astrophysics Data System (ADS)

    Bland, P.; Hutchison, R.; Pillinger, C. T.; Bischoff, A.

    1992-07-01

    In 1991 a single stone weighing 174 g was recovered from the Sahara desert, Algeria (27 degrees 36'N, 3 degrees 53'E). From this a 36.83-g fragment was obtained that has 2 sawn surfaces and adjacent surface of partially weathered fusion crust. The sawn surface shows "brownish" weathering products that have generally produced alteration of the matrix in which a few relict chondrules and inclusions are set. One 4 by 5 mm triangular area bordering the fusion crust is dark grey in colour with small inclusions set in it. This may be an area of local shock melt glass. Mineralogy and petrography: In a polished thin section, area 20 mm^2, we found few chondrules, mainly olivine clasts in a weathered olivine-rich matrix, with minor pyroxene. The largest relict chondrule was type "I" (McSween, 1977) with a diameter of 350 micrometers; a 200-micrometer-diameter type "II" (McSween, 1977) barred olivine chondrule showed devitrified glass in the interstices of the olivine. The sample is highly brecciated with fractures cutting the section and offsetting chondrule fragments, but in PTS is only very weakly shocked: olivine shows occasional undulatory extinction, i.e., stage "S2" in the classification of Stoffler et al. (1991). Mineral Chemistry: 95% of olivine is close to Fa(sub)39 but a few grains lie in the range Fa(sub)17 to Fa(sub)43 and one is zoned from a Fa(sub)17 core to a Fa(sub)43 rim. The majority of pyroxene is Ca-rich at a mean composition of Fs(sub)21 Wo(sub)45. Low-Ca pyroxene is also unequilibrated with a mean close to Fs(sub)31 and one has a composition of Fs(sub)10 Wo(sub)2. Plagioclase is a common interstitial phase in the matrix and is variable in composition, but high-Na oligoclase or albite. Minor opaque phases are dominated by Cr-rich (32-38 wt% Cr2O3) spinel, which also contains significant Ti (5.3 wt% TiO2). For charge balance substantial Fe^3+ is required indicating that Fe is partitioned between approximately 13-21 wt% Fe2O3 and 35 wt% FeO. The spinel

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

    NASA Astrophysics Data System (ADS)

    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

  9. Dust emission from different sol types and geomorphic units in the Sahara - implications for modeling dust emission and transport

    NASA Astrophysics Data System (ADS)

    Crouvi, Onn; Schepanski, Kerstin; Amit, Rivka; Gillespie, Alan; Enzel, Yehouda

    2014-05-01

    Mineral dust plays multiple roles in mediating physical and biogeochemical exchanges among the atmosphere, land and ocean, and thus is an active component of the global climate system. To estimate the past, current, and future impacts of dust on climate, sources of dust and their erodibility should be identified. The Sahara is the major source of dust on Earth. Based on qualitative analysis of remotely sensed data with low temporal resolution, the main sources of dust that have been identified are topographic depressions comprised of dry lake and playa deposits in hyprarid regions. Yet, recent studies cast doubts on these as the major sources and call for a search for others. Moreover, the susceptibility of soils to aeolian erosion (wind land erodibility) in the Sahara is still poorly known. In this study we identify and determine the soil types and geomorphic units most important as Saharan dust sources by correlating between the number of days with dust storms (NDS), derived from remote-sensing data of high temporal resolution, with the distribution of the soil types/geomorphic units. During 2006-8 the source of over 90% of the NDS was sand dunes, leptosols, calcisols, arenosols, and rock debris. Few dust storms originated from dry lake beds and playas. Land erodibility by wind for each soil type/geomorphic unit was estimated by a regression of the NDS and the number of days with high-speed wind events; the regression is relatively high for sand dunes and gypsisols. We use these regressions to differentiate between sources of dust that are supply-limited to those that are transport-limited. We propose that the fracturing of saltating sand and the removal of clay coatings from sand grains through eolian abrasion is the dominant dust-emission mechanism for the sand-rich areas covering large portion of the Sahara. Our results also explain the increased dustiness during the last glacial period, when sand dunes activity has been more common than during the Holocene

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

    NASA Astrophysics Data System (ADS)

    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

  11. John F. Kennedy, Jr., speaks to the media at KSC's HBO premiere 'From the Earth to the Moon.'

    NASA Technical Reports Server (NTRS)

    1998-01-01

    John F. Kennedy, Jr., editor-in-chief of George Magazine, speaks with members of the national media at the Home Box Office (HBO) and Imagine Entertainment premiere of the 12-part miniseries 'From the Earth to the Moon' at Kennedy Space Center (KSC). The series was filmed in part on location at KSC and dramatizes the human aspects of NASA's efforts to launch Americans to the Moon. The miniseries highlights NASA's Apollo program and the events leading up to and including the six successful missions to the Moon. A special 500-seat theater was constructed next to the Apollo/Saturn V Center for the KSC premiere showing. Speakers at the event included KSC Director Roy Bridges (at right); Jeff Bewkes, chairman and CEO for HBO; and John F. Kennedy, Jr. Also attending the event, which featured the episode entitled '1968,' were Buzz Aldrin, Apollo 11 astronaut, and Al Worden, Apollo 15 astronaut. The original miniseries event, created for HBO by actor Tom Hanks and Imagine Entertainment, will premiere on HBO beginning April 5, 1998.

  12. John F. Kennedy, Jr., speaks to invited guests at KSC's HBO premiere 'From the Earth to the Moon.'

    NASA Technical Reports Server (NTRS)

    1998-01-01

    John F. Kennedy, Jr., editor-in-chief of George Magazine, greets invited guests at the Home Box Office (HBO) and Imagine Entertainment premiere of the 12-part miniseries 'From the Earth to the Moon' at Kennedy Space Center (KSC). The series was filmed in part on location at KSC and dramatizes the human aspects of NASA's efforts to launch Americans to the Moon. The miniseries highlights NASA's Apollo program and the events leading up to and including the six successful missions to the Moon. A special 500- seat theater was constructed next to the Apollo/Saturn V Center for the KSC premiere showing. Speakers at the event included KSC Director Roy Bridges (at right); Jeff Bewkes, chairman and CEO for HBO; and John F. Kennedy, Jr. Also attending the event, which featured the episode entitled '1968,' were Buzz Aldrin, Apollo 11 astronaut, and Al Worden, Apollo 15 astronaut. The original miniseries event, created for HBO by actor Tom Hanks and Imagine Entertainment, will premiere on HBO beginning April 5, 1998.

  13. General Secretary Jiang Zemin and Premier Li Peng on family planning.

    PubMed

    Jiang, Z; Li, P

    1991-06-01

    Speeches given by General Secretary Jiang Zemin and Premier Li Peng to the forum on Family Planning (FP) Work in April 1991 are summarized. Jiang stated that the highest levels of communist party and governmental officials should be in charge of controlling population growth in China. There is great urgency to do so. The problems to be faced are a hugh population, scarce arable land, a poor economic foundation, and low per capita resources. Human resources are an asset for the socialist construction of China, but a rapid growth rate will retard economic and social development and affect the improvement in living standards and the quality of life. The strategy to place FP within state policy and place strict controls over population growth must be carried out resolutely. The future of socialism and the Chinese nation is at stake. Modernization cannot be accomplished with out controlling population growths. The 8th 5 year Plan and the 10 Year Program requirements will still contribute to 1.3 billion population by 2000 and 1.2 billion by 1995. There is historical responsibility, an urgency to strictly control population growth. Adherence to the 4 cardinal principles of socialism (the people's democratic dictatorship, the Communist Party leadership, and Marxist Leninist and Mao Zedong thought) must coexist with social development and family planning. All must be motivated. The provincial Party Secretary personally must oversee problems. The success or failure of FP should be used to evaluate the achievements of party committees and governments. The education on basic national conditions and the basic state policy on FP needs to be publicized through all organizations. There should be confidence in the masses. People must make FP their own cause voluntarily. Premier Li Peng stressed effective implementation and giving it high priority in order to achieve the 2nd step strategic goal of socialist modernization. Per capita output is low, and grain output will not increase

  14. Corporate social responsibility and mental health: the Premier League football Imagine Your Goals programme.

    PubMed

    Henderson, Claire; O'Hara, Stefanie; Thornicroft, Graham; Webber, Martin

    2014-08-01

    Football is increasingly used to facilitate recovery in mental health services, often in partnership with football clubs. However, few clubs have made mental health part of their corporate social responsibility programmes until recently. We report the impact on participants of the 'Imagine Your Goals' programme, run by 16 Premier League football clubs in conjunction with England's Time to Change programme to reduce mental health-related stigma and discrimination. Mixed methods evaluation used pre/post measures of well-being, access to social capital, focus groups held early on and towards the end of the two-year programmes, and questionnaires for coaching staff. There were no significant changes to participants' mental well-being scores between baseline and follow-up, nor to the total number of social resources accessible through their networks. However, there was a statistically significant increase at follow-up in the mean score of the personal skills subscale of the Resource Generator-UK. Participants' individual skills were also higher at follow-up. Qualitative data showed programmes had largely met participants' expectations in terms of socializing, providing structure and improving fitness levels, exceeded expectations in relationships with coaching staff and additional activities, but did not always meet them in improving football skills. Participants varied in their knowledge of exit opportunities, depending on which club's programme they attended. A minority of clubs reported difficulties in recruitment and concerns about planning for the future of the projects. Football clubs and the charitable foundations they set up can successfully deliver programmes to people with mental health problems which improve access to personal skills social capital and have other potential benefits. PMID:25137112

  15. [Severe keratomycosis due to Fusarium solani induced by a telluric foreign body: About a case in moroccan Sahara].

    PubMed

    Er-Rami, M; Souhail, H; Lemkhente, Z; El Mellouki, W; Lmimouni, B

    2011-09-01

    We report a case of severe keratitis due to Fusarium solani in a young man in the Sahara in Morocco where the climate is arid. This patient reported had a grain of sand in his right eye for a week after a sandstorm. On admission he had a corneal abscess. Despite rapid diagnosis and initiation of treatment with available antifungal drugs: amphotericin B and natamycin eye drops, the prognosis worsened and led to the enucleation of the right eye. Faced with a suspected eye infection after a microtrauma caused by grains of sand carried by a sandstorm, it is important to take biological samples to search for fungal infections among other. It is also important to have new triazole antifungal drugs available to treat ocular mycosis rapidly and effectively. PMID:24451564

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

    PubMed

    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. PMID:20797813

  17. Occurrence of fluororichterite and fluorian biotite in the In Tifar trachyte neck (Tazrouk district, Hoggar volcanic province, Sahara, Algeria)

    NASA Astrophysics Data System (ADS)

    Azzouni-Sekkal, Abla; Bonin, Bernard; Ben El Khaznadji, Riad

    2013-09-01

    The unusual occurrence in the In Tifar trachyte neck (Tazrouk district, Hoggar volcanic province, Sahara, Algeria) of the fluorian biotite-fluororichterite association is presented. The two mineral species were previously unknown in the Hoggar and their association is uncommon worldwide. Ti-rich biotite has 28-40% OH sites occupied by fluorine, hence the use of the modifier "fluorian". Sodic-calcic fluororichterite has more than 55% OH sites filled by fluorine, hence the use of the prefix "fluoro". Well-defined F-Mg affinities are documented in both cases, while Cl remains very low. Temperatures are estimated roughly at 775-700 °C at low pressures. The fluorian biotite → fluororichterite sequence of crystallisation implies increasingly high fH2F2/fH2O ratios in metaluminous H2O-dominated evolving to peralkaline F-enriched fluids.

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

    NASA Astrophysics Data System (ADS)

    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

  19. Normalized difference water indexes have dissimilar performances in detecting seasonal and permanent water in the Sahara-Sahel transition zone

    NASA Astrophysics Data System (ADS)

    Campos, João C.; Sillero, Neftalí; Brito, José C.

    2012-09-01

    SummaryThe decrease of water resources can enhance poverty and increase insecurity in dry regions, at the same time leading to loss of biological diversity. For these reasons, the information about surface perennial and well-known water sources in the arid and semi-arid regions of Africa has been mapped. However, seasonal water can be missed in mapping due to their short and erratic appearance, while the mapping of any aquatic resources represents a foremost priority for protecting social, economic and biological values in the e.g. Sahara-Sahel transition zone. Therefore, Remote Sensing becomes crucial to monitor a variety of wetland systems in these regions. This work evaluates the performance of three Normalized Difference Water Indexes [Gao's NDWI (NDWINIR/MIR), McFeeters' NDWI (NDWIG/NIR) and Xu's NDWI (NDWIG/MIR)] in mapping of water systems across Mauritania. Maps with seasonal and permanent water were derived, using a multi-temporal series of Landsat 5 TM and Landsat 7 ETM+ images. The performance of indexes was compared based on 551 control points collected during five fieldwork missions to Mauritania between 2007 and 2011. Control points were separated in three classes of water availability (permanent, seasonal and non-water points) and then randomly assigned into two data sets: one for selecting the water availability thresholds for index reclassification and another for threshold validation. NDWIG/MIR and NDWINIR/MIR had good performances in detecting permanent and seasonal water, respectively, while NDWIG/NIR failed to detect most of the water bodies. The threshold selection generated water maps with seasonal and permanent features that might be missing in simple mapping of aquatic systems. The extensive data collection provides novel information about NDWI performances for water delineation in arid and semi-arid regions and for a future management of aquatic environments of the Sahara-Sahel transition zone.

  20. Dust aerosol emission over the Sahara during summertime from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations

    NASA Astrophysics Data System (ADS)

    Todd, Martin C.; Cavazos-Guerra, Carolina

    2016-03-01

    Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006-13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (∼7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  3. Sirénomélie (Mermaid Syndrome): description du premier cas Congolais et revue de la literature

    PubMed Central

    Lubala, Toni Kasole; Mukuku, Olivier; Mutombo, Augustin Mulangu

    2014-01-01

    La sirénomélie est une forme rare de dysgénésie caudale généralement incompatible avec la vie du fait des malformations rénales graves qui y sont associées. En Afrique, elle est associée à des considérations mystico-religieuses et à la sorcellerie et expose la famille à une stigmatisation violente. Son étiologie est encore très controversée. A notre connaissance, il s'agit du premier cas congolais rapporté dans la littérature. PMID:25120875

  4. Electrochemistry of Au(II) and Au(III) pincer complexes: determination of the Au(II)-Au(II) bond energy.

    PubMed

    Dann, Thomas; Roşca, Dragoş-Adrian; Wright, Joseph A; Wildgoose, Gregory G; Bochmann, Manfred

    2013-10-01

    The bond energy of the unsupported Au-Au bond in the Au(ii) dimer [(C(∧)N(∧)C)Au]2 and the difference between Au(III)-OH and Au(III)-H bond enthalpies have been determined experimentally by electrochemical methods, with Au-OH and Au-H complexes showing unexpected differences in their reduction pathways, supported by DFT modelling. PMID:24051607

  5. Magnetoresistance of Au films

    DOE PAGESBeta

    Zhang, D. L.; Song, X. H.; Zhang, X.; Zhang, Xiaoguang

    2014-12-10

    Measurement of the magnetoresistance (MR) of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler s rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms.

  6. Magnetoresistance of Au films

    SciTech Connect

    Zhang, D. L.; Song, X. H.; Zhang, X; Zhang, Xiaoguang

    2014-01-01

    Measurement of the magnetoresistance (MR) of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler s rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:23038177

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

    PubMed

    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. PMID:25652059

  10. Trace element chemistry of peridotitic garnets in diamonds from the Premier (Cullinan) and Finsch kimberlites, South Africa: Contrasting styles of mantle metasomatism

    NASA Astrophysics Data System (ADS)

    Viljoen, K. S.; Harris, J. W.; Ivanic, T.; Richardson, S. H.; Gray, K.

    2014-11-01

    The purpose of this paper is to provide, discuss, and interpret a comprehensive set of geochemical data (involving major elements as well as Ni, Ti, Sr, Y, Zr, Nb, Hf and the rare earth elements) for peridotitic garnets in diamonds from Premier and Finsch, with a view on the nature of the metasomatic processes operating up to the time of diamond crystallisation, and the location of these two diamondiferous kimberlites within and outside the region of low seismic velocity in the Kaapvaal lithosphere. Trace element data were acquired using an ion microprobe, and a new method for the analysis of Ni in garnet by ion microprobe is presented. Peridotitic garnets in diamonds from the Premier mine are characterised by a significantly higher proportion of the lherzolite paragenesis relative to diamonds from other South African mines, such as Finsch, Venetia and De Beers Pool. Based on Ni-in-garnet thermometry, inclusion encapsulation temperatures of 1055 °C to 1669 °C are calculated for peridotitic garnets from Premier, with an average temperature of 1215 °C. Calculated temperatures for garnets from Finsch range from 1036 °C to 1167 °C, and are generally lower than for Premier, with an average of 1098 °C. The garnets in the diamonds from Premier and Finsch reflect contrasting styles of metasomatism associated with diamond crystallisation, with a low temperature fluid-type metasomatism prevalent in the case of the Paleoarchean diamonds from Finsch, and a higher temperature melt-related metasomatism occurring in the case of the Paleoproterozoic diamonds from Premier. The metasomatic agent accompanying diamond crystallisation at Finsch is effective at introducing Sr, the light rare earth elements, and some Zr into the lithosphere, but is ineffective at transporting much Ca, Ti, Y and heavy rare earth elements. In the case of Premier the metasomatic agent is highly effective at element transport, introducing e.g. Ca, Fe, Ti, Zr, Y and the rare earth elements. The location

  11. Antibacterial Au nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was <1% of that from flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It

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

    NASA Astrophysics Data System (ADS)

    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

  13. Interaction between the North-West Sahara Aquifer and the seismically active intraplate Hun Graben Fault system, Libya

    NASA Astrophysics Data System (ADS)

    Hamling, I. J.; Aoudia, A.

    2011-12-01

    The North-West Sahara Aquifer System (NWSAS) covers an area of ~1 million km2 spanning the countries of Algeria, Tunisia and Libya. The system is composed of two main aquifers, the Complexe Terminal (CT) and the deeper Continental Intercalaire (CI). Over the last ~40 years these aquifers have been increasingly exploited in order to provide water to these countries. There are estimated to be ~7000 drill sites across the aquifer, 4000 in Algeria, 2000 in Tunisia and a further ~1000 in Libya. Land subsidence, caused by anthropogenic activities such as groundwater pumping, is a global problem and has been observed in a number of places around the world. Here we investigate fault controlled subsidence related to the extraction of water in North Western Libya. Located ~600 km south east of Tripoli, the Hun Graben separates the Sirte Basin to the east from the Hamada al Hamra Platform to the west and lies on the eastern boundary of the North-West Sahara Aquifer System (NWSAS). The graben is composed of two border faults extending for ~130 km from the town of Hun to the north west. These faults, bounding the eastern and western margins of the graben, are known to be seismically active and were responsible for the magnitude 7.1 earthquake in 1935. Due to the lack of ground based instrumentation, there are currently no estimates of slip along these structures. Here we use ERS and Envisat SAR images acquired over the last 20 years and form a number of interferograms to study interseismic strain accumulation along these structures. Satellite Radar Interferometry (InSAR) is a widely used technique for monitoring deformation of the Earth's surface. By differencing the phase from two radar images acquired at different times, maps of range change between the radar and ground can be obtained with millimetre precision. Our analysis over the graben suggests that neither of the two border faults are actively deforming and therefore the causes of intraplate large earthquakes such as

  14. Overall and minority-focused recruitment strategies in the PREMIER multicenter trial of lifestyle interventions for blood pressure control.

    PubMed

    Kennedy, Betty M; Kumanyika, Shiriki; Ard, Jamy D; Reams, Patrice; Johnson, Cheryl A; Karanja, Njeri; Charleston, Jeanne B; Appel, Lawrence J; Maurice, Vallerie; Harsha, David W

    2010-01-01

    Recruitment strategies employed by four clinical centers across the US and a coordinating center were examined to identify successful overall and minority-focused recruitment strategies for the PREMIER multicenter trial of lifestyle changes for blood pressure control. The goal was to recruit 800 adults (40% African Americans) with systolic blood pressure of 120-159 mm Hg and diastolic of 80-95 mm Hg, not taking antihypertensive medication. Clinical centers used combinations of mass distribution of brochures, mass media, email distribution lists, screening events, and a national website. Culturally appropriate strategies for African Americans were designed by a Minority Implementation (MI) committee. Diversity training was provided for study staff, and African Americans were included in the study design process. Main recruitment outcomes were number overall and number of African Americans recruited by each strategy. Of the 810 randomized PREMIER participants, 279 (34%) were African American with site-specific percentages of 56%, 46%, 27%, and 8%. Of African Americans recruited, 151 (54%) were from mass distribution of brochures (mailed letter, flyer included in Val-Pak coupons, or other), 66 (24%) from mass media (printed article, radio, TV story or ads, 52 (19%) from word of mouth, and 10 (3%) from email/website and screening events combined. Yields for Non-Hispanic Whites were 364 (69%) from brochures, 71 (13%) from mass media, 49 (9%) from word of mouth and 47 (9%) from email/website and screening events. Mass distribution of brochures was relatively more effective with Non-Hispanic Whites, while African Americans responded relatively better to other recruitment strategies. PMID:19879377

  15. Surface morphology and optical properties of porphyrin/Au and Au/porphyrin/Au systems

    NASA Astrophysics Data System (ADS)

    Kalachyova, Yevgeniya; Lyutakov, Oleksiy; Solovyev, Andrey; Slepička, Petr; Švorčík, Vaclav

    2013-12-01

    Porphyrin/Au and Au/porphyrin/Au systems were prepared by vacuum evaporation and vacuum sputtering onto glass substrate. The surface morphology of as-prepared systems and those subjected to annealing at 160°C was studied by optical microscopy, atomic force microscopy, and scanning electron microscopy techniques. Absorption and luminescence spectra of as-prepared and annealed samples were measured. Annealing leads to disintegration of the initially continuous gold layer and formation of gold nanoclusters. An amplification of Soret band magnitude was observed on the Au/meso-tetraphenyl porphyrin (TPP) system in comparison with mere TPP. Additional enhancement of luminescence was observed after the sample annealing. In the case of sandwich Au/porphyrin/Au structure, suppression of one of the two porphyrins' luminescence maxima and sufficient enhancement of the second one were observed.

  16. Antibacterial Au nanostructured surfaces.

    PubMed

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-02-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was <1% of that from flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies. PMID:26648134

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Modeling the synergistic antibacterial effects of honey characteristics of different botanical origins from the Sahara Desert of Algeria

    PubMed Central

    Laallam, Hadda; Boughediri, Larbi; Bissati, Samia; Menasria, Taha; Mouzaoui, Mohamed S.; Hadjadj, Soumia; Hammoudi, Rokia; Chenchouni, Haroun

    2015-01-01

    Background: Honey has multiple therapeutic properties due to its composition with diverse components. Objectives: This study aims to investigate the antimicrobial efficacy of Saharan honeys against bacterial pathogens, the variation of honey floral origins, and its physicochemical characteristics. Materials and Methods: The antimicrobial activity of 32 samples of honey collected from the Algerian Sahara Desert was tested on four bacteria; Bacillus subtilis, Clostridium perfringens, Escherichia coli, and Staphylococcus aureus. The botanical origin of honeys and their physicochemical properties were determined and their combined antibacterial effects were modeled using a generalized linear mixed model (GLMM). Results: Out of the 32 study samples, 14 were monofloral and 18 were multifloral. The pollen density was on average 7.86 × 106 grains/10 g of honey, water content was 14.6%, electrical conductivity (EC) was 0.5 μS/cm, pH was 4.38 ± 0 50, hydroxymethylfurfural (HMF) content was 82 mg/kg of honey, total sugars = 83%, reducing sugars = 71%, and the concentration of proline = 525.5 ± 550.2 mg/kg of honey. GLMM revealed that the antibacterial effect of honey varied significantly between bacteria and floral origins. This effect increased with increasing of water content and reducing sugars in honey, but it significantly decreased with increase of honey EC. E. coli was the most sensitive species with an inhibition zone of 10.1 ± 4.7 mm, while C. perfringens was the less sensitive. Honeys dominated by pollen of Fabaceae sp. were most effective with an overall antimicrobial activity equals to 13.5 ± 4.7 mm. Conclusion: Saharan honeys, of certain botanical origins, have physicochemical and pollinic characteristics with relevant potential for antibacterial purposes. This encourages a more comprehensive characterization of honeys with in vivo and in vitro investigations. PMID:26594206

  19. Seed viability and germination success of Acacia tortilis along land-use and aridity gradients in the Eastern Sahara.

    PubMed

    Andersen, Gidske Leknæs; Krzywinski, Knut; Gjessing, Håkon K; Pierce, Richard Holton

    2016-01-01

    Our study focuses on the keystone species Acacia tortilis and is the first to investigate the effect of domestic ungulates and aridity on seed viability and germination over an extensive part of the Eastern Sahara. Bruchids infest its seeds and reduce their viability and germination, but ingestion by ruminant herbivores diminishes infestation levels and enhances/promotes seed viability and germination. The degree of these effects seems to be correlated with animal body mass. Significantly reduced numbers of wild ruminant ungulates have increased the potential importance of domestic animals and pastoral nomadism for the functionality of arid North African and Middle Eastern ecosystems. We sampled seeds (16,543) from A. tortilis in eight areas in three regions with different aridity and land use. We tested the effect of geography and sampling context on seed infestation using random effects logistic regressions. We did a randomized and balanced germination experiment including 1193 seeds, treated with different manure. Germination time and rates across geography, sampling context, and infestation status were analyzed using time-to-event analyses, Kaplan-Meier curves and proportional hazards Cox regressions. Bruchid infestation is very high (80%), and the effects of context are significant. Neither partial infestation nor adding manure had a positive effect on germination. There is a strong indication that intact, uningested seeds from acacia populations in the extremely arid Western Desert germinate more slowly and have a higher fraction of hard seeds than in the Eastern Desert and the Red Sea Hills. For ingested seeds in the pastoralist areas we find that intact seeds from goat dung germinate significantly better than those from camel dung. This is contrary to the expected body-mass effect. There is no effect of site or variation in tribal management. PMID:26811790

  20. Flash floods in the Sahara: A case study for the 28th January 2013 flood in Qena-Egypt

    NASA Astrophysics Data System (ADS)

    Badawy, Moawad; Omar, Ahmed; Mamtimin, Buhalqem

    2014-05-01

    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 lack of the 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 28th 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 the 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.

  1. Crocodiles in the Sahara Desert: An Update of Distribution, Habitats and Population Status for Conservation Planning in Mauritania

    PubMed Central

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

    2011-01-01

    Background Relict populations of Crocodylus niloticus persist in Chad, Egypt and Mauritania. Although crocodiles were widespread throughout the Sahara until the early 20th 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 the vulnerability and

  2. A Continuous High-Resolution Climate-Proxy Record of the past 2600 Years from the Central Sahara Desert

    NASA Astrophysics Data System (ADS)

    Verschuren, D.; Schuster, M.; Cocquyt, C.; Russell, J. M.; Engstrom, D. R.; Kroepelin, S.

    2004-12-01

    Persistent lack of high-quality climate-proxy records from the arid-subarid belt of North Africa has hampered analysis of decade-to-century-scale climate tele-connections between warm-temperate southern Europe and the monsoonal climate regimes of sub-Saharan tropical Africa. Here we report recovery of a finely laminated sediment record from Lake Yoa, a stratified hypersaline lake occupying a Pleistocene deflation basin at Ounianga Kebir in northeastern Chad (20.0°N; 20.5°E). It represents a continuous, annual-resolution record of climate and environmental change during the past 2600 14C years from the hyper-arid core of the Sahara desert where rainfall is erratic and annual evaporation exceeds 600 cm. Lake Yoa is one of the very few permanent waters in this region maintained today by sub-surface inflow of fossil groundwater from sandstone aquifers recharged during the early-Holocene humid period. Preliminary sedimentological, chronological and fossil-diatom data suggest that Lake Yoa has been poly- to hyper-saline throughout the sampled period, and with conditions of physical and chemical limnology similar to those prevailing today for at least the past 1000 years. Given that the desert landscape in a large area surrounding Ounianga probably lacked significant ground cover throughout this period, we surmise that variation in aeolian mineral sediment input to the lake, partly reflected in distinct sand layers, could be exploited as a proxy of past changes in the intensity of dry northeasterly trade winds over central North Africa.

  3. REMOVAL OF CHEMICAL AND MICROBIAL CONTAMINANTS IN DRINKING WATER - WATTS PREMIER M-2400 POINT-OF-ENTRY REVERSE OSMOSIS DRINKINGWATER TREATMENT SYSTEM

    EPA Science Inventory

    The Watts Premier M-2400 POE RO Drinking Water Treatment System was tested at the NSF Drinking Water Treatment Systems Laboratory for removal of the viruses fr and MS2, the bacteria Brevundimonas diminuta, and chemicals aldicarb, benzene, cadmium, carbofuran, cesium, chl...

  4. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, REMOVAL OF ARSENIC IN DRINKING WATER: WATTS PREMIER M-SERIES M-15,000 REVERSE OSMOSIS TREATMENT SYSTEM

    EPA Science Inventory

    Verification testing of the Watts Premier M-Series M-15,000 RO Treatment System was conducted over a 31-day period from April 26, 2004, through May 26, 2004. This test was conducted at the Coachella Valley Water District (CVWD) Well 7802 in Thermal, California. The source water...

  5. 26Al-26Mg systematics in D’Orbigny and Sahara 99555 angrites: Implications for high-resolution chronology using extinct chronometers

    NASA Astrophysics Data System (ADS)

    Spivak-Birndorf, Lev; Wadhwa, Meenakshi; Janney, Philip

    2009-09-01

    We report on an investigation of the 26Al- 26Mg isotope systematics in the D'Orbigny and Sahara 99555 angrites. High precision Mg isotope compositions and Al/Mg ratios were measured in mineral separates and whole rock samples from D'Orbigny and Sahara 99555 using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). Plagioclase separates from both angrites have resolvable excesses in 26Mg ( Δ26Mg) that correlate with their respective Al/Mg ratios. 26Al- 26Mg systematics in the mineral separates and whole rocks define precise isochrons that correspond to 26Al/ 27Al ratios of (5.06 ± 0.92) × 10 -7 and (5.13 ± 1.90) × 10 -7 and initial Δ26Mg values of -0.006 ± 0.040‰ and -0.016 ± 0.047‰ for D'Orbigny and Sahara 99555, respectively. The slopes and initial Δ26Mg values are identical for these two meteorites within errors and the data for both angrites considered together define an isochron corresponding to a 26Al/ 27Al ratio of (5.10 ± 0.55) × 10 -7 and initial Δ26Mg value of -0.012 ± 0.019. Relative to the Efremovka E60 CAI, the 26Al/ 27Al values reported here for these angrites imply 26Al- 26Mg ages of 4562.42 ± 0.29 Ma and 4562.43 ± 0.53 Ma for D'Orbigny and Sahara 99555, respectively. These 26Al- 26Mg ages are concordant with model ages determined using other extinct radionuclide chronometers (e.g., 53Mn- 53Cr and 182Hf- 182W), but are ˜2 Myr younger than the absolute 207Pb- 206Pb ages that have been reported recently for these angrites. The reason for this discrepancy is not presently known, but may imply disturbance of one or more of the isotope systems under consideration or a possible bias in the 207Pb- 206Pb ages of the angrites resulting from natural or analytical causes.

  6. Genesis and Paleo-ecological Interpretation of Swamp Ore Deposits at Sahara Paleo-lakes of East Niger

    NASA Astrophysics Data System (ADS)

    Felix-Henningsen, Peter

    In formerly vegetated flat lake-shore areas of Pleistocene and Holocene paleo-lake depressions in the Sahara of East Niger (Ténéré, Tchigai mountains and in the Erg of Bilma), ancient dune sands are covered by rampart-like or flat beds of individual or networked rhizoconcretions. The massive goethite accumulation, which partly includes an outer fringe of lepidocrocite, impregnated the ancient dune sands. Apart from Fe, P, Ca, and Mg, other heavy metals were also concentrated. The formation and morphological differentiation of these swamp ores were generally bound at vegetated shallow water areas of paleo-lakes in ancient dune fields. Accordingly, the swamp ores of the Ténéré, which has flat to undulating relief, display a large dissemination. In contrast, in the Erg of Bilma the high altitude and steep slopes of ancient dune ridges led to steeper shore areas of the paleo-lakes, at which beds of rhizoconcretions were unable to develop. The oxides were formed by oxidation of Fe2 + -ions from the lake water and concentrated around the roots in the upper root zone of the swamp vegetation. The lack of oxygen in the warm lake water of the shore region, as well as the decomposition of vegetation residues, excluded high redox potentials within the deeper water near the subhydric soil surface. Hence, the formation of rhizoconcretions can only be explained by the specific physiological characteristics of the swamp vegetation, which was able to supply oxygen to the roots through an aerenchyma. The release of surplus oxygen from such roots obviously caused high redox potentials at the root surface and in the neighbouring root environment. As a result precipitation of Fe and Mn oxides occurred, which adsorbed nutrients and heavy metals from the soil solution. The redistribution of the ions from the reduced sediments of the lake basin into the root zone of the shore area resulted from diffusion and mass flow. Paleo-climatically, the swamp ore deposits denote humid periods

  7. Simulating Quaternary African Environments and the Green Sahara through dynamic coupling of Land Surface and Atmospheric models

    NASA Astrophysics Data System (ADS)

    Farrow, Aidan; Singarayer, Joy; Valdes, Paul

    2010-05-01

    Paleoclimate records from Late Quaternary Africa imply rapid and spatially complex shifts between wet and dry conditions. There is abundant evidence that during numerous incursions in the past the extent of deserts, lakes and rivers is not static. In this work we use an asynchronously coupled atmosphere and vegetation model to investigate our current ability to model Quaternary Africa. We iterate the vegetation scheme BIOME with the Hadley Centre model and explore the changing relationship between African vegetation and climate over the last deglaciation. During the last deglaciation large amplitude perturbations of the African climate occurred, linked to orbitally forced changes in monsoon strength. Beginning and ending abruptly 7000 and 4000 years BP, a widespread greening of the Sahara is recorded in numerous paleoclimate archives. This greening represents the largest anomaly in the atmosphere-biosphere system in the last 12,000 years. Atmospheric models alone have failed to reproduce the extent of humidity change. Work by Claussen (1994) and Claussen and Gayler (1997) made large leaps forward by incorporating a dynamic vegetation model into simulations of the African Quaternary. Their work suggests that under some conditions multiple equilibria may exist in the atmosphere-biosphere system, providing a mechanism for rapid change. In this work we apply a similar method to an extensive suite of time slices from the last glacial maximum to the present. We investigate how the role of surface feedbacks in the climate system change through time by employing the Hadley Centre's atmosphere-only model HadAM3 with the BIOME model of Prentice et al (1992) and consider surface hydrology feedbacks using the surface water scheme HYDRA (Coe 1998). Equilibrium time slices across the deglacation are run for pre-industrial, 3, 6, 9, 12, 15, 18, 21 and 24 kyr B.P. climates. Simulations are started with standard vegetation distributions and repeated with rainforest and desert

  8. Significance of ground-water chemistry in performance of North Sahara Tube wells in Algeria and Tunisia

    USGS Publications Warehouse

    Clarke, Frank Eldridge; Jones, Blair F.

    1972-01-01

    Nine ground-water samples from the principal shallow and deep North Sahara aquifers of Algeria and Tunisia were examined to determine the relation of their chemical composition to corrosion and mineral encrustation thought to be contributing to observed decline in well capacities within a UNESCO/UNDP Special Fund Project area. Although the shallow and deep waters differ significantly in certain quality factors, all are sulfochloride types with corrosion potentials ranging from moderate to extreme. None appear to be sufficiently supersaturated with troublesome mineral species to cause rapid or severe encrustation of filter pipes or other well parts. However, calcium carbonate encrustation of deep-well cooling towers and related irrigation pipes can be expected because of loss of carbon dioxide and water during evaporative cooling. Corrosion products, particularly iron sulfide, can be expected to deposit in wells producing waters from the deep aquifers. This could reduce filterpipe openings and increase casing roughness sufficiently to cause significant reduction in well capacity. It seems likely, however, that normal pressure reduction due to exploitation of the artesian systems is a more important control of well performance. If troublesome corrosion and related encrustation are confirmed by downhole inspection, use of corrosion-resisting materials, such as fiber-glass casing and saw-slotted filter pipe (shallow wells only), or stainless-steel screen, will minimize the effects of the waters represented by these samples. A combination of corrosion-resisting stainless steel filter pipe electrically insulated from the casing with a nonconductive spacer and cathodic protection will minimize external corrosion of steel casing, if this is found to be a problem. However, such installations are difficult to make in very deep wells and difficult to control in remote areas. Both the shallow waters and the deep waters examined in this study will tend to cause soil

  9. Learning Curve Assessment of Robot-Assisted Radical Prostatectomy Compared with Open-Surgery Controls from the Premier Perspective Database

    PubMed Central

    Kreaden, Usha S.; Gabbert, Jessica; Thomas, Raju

    2014-01-01

    Abstract Introduction: The primary aims of this study were to assess the learning curve effect of robot-assisted radical prostatectomy (RARP) in a large administrative database consisting of multiple U.S. hospitals and surgeons, and to compare the results of RARP with open radical prostatectomy (ORP) from the same settings. Materials and Methods: The patient population of study was from the Premier Perspective Database (Premier, Inc., Charlotte, NC) and consisted of 71,312 radical prostatectomies performed at more than 300 U.S. hospitals by up to 3739 surgeons by open or robotic techniques from 2004 to 2010. The key endpoints were surgery time, inpatient length of stay, and overall complications. We compared open versus robotic, results by year of procedures, results by case volume of specific surgeons, and results of open surgery in hospitals with and without a robotic system. Results: The mean surgery time was longer for RARP (4.4 hours, standard deviation [SD] 1.7) compared with ORP (3.4 hours, SD 1.5) in the same hospitals (p<0.0001). Inpatient stay was shorter for RARP (2.2 days, SD 1.9) compared with ORP (3.2 days, SD 2.7) in the same hospitals (p<0.0001). The overall complications were less for RARP (10.6%) compared with ORP (15.8%) in the same hospitals, as were transfusion rates. ORP results in hospitals without a robot were not better than ORP with a robot, and pretreatment co-morbidity profiles were similar in all cohorts. Trending of results by year of procedure showed no differences in the three cohorts, but trending of RARP results by surgeon experience showed improvements in surgery time, hospital stay, conversion rates, and complication rates. Conclusions: During the initial 7 years of RARP development, outcomes showed decreased hospital stay, complications, and transfusion rates. Learning curve trends for RARP were evident for these endpoints when grouped by surgeon experience, but not by year of surgery. PMID:24350787

  10. Au20: A Tetrahedral Cluster

    SciTech Connect

    Li, Jun; Li, Xi; Zhai, Hua Jin; Wang, Lai S.

    2003-02-07

    Photoelectron spectroscopy revealed that a 20 atom gold cluster has an extremely large energy gap, which is even greater than that of C60, and an electron affinity comparable with that of C60. This observation suggests that the Au20 cluster must be extremely stable and chemically inert. Using relativistic density functional calculations, we found that Au20 possesses a remarkable tetrahedral structure, which is a fragment of the bulk face-centered cubic lattice of gold with a small structural relaxation. Au20 is thus a true cluster molecule, while at the same time it is exactly part of the bulk, but with very different properties. The tetrahedral Au20 may possess interesting catalytic properties and may be synthesized in bulk quantity or assembled on non-interacting surfaces.

  11. Geomorphologic approach for modelling the surface features of arid environments in a model of dust emissions: application to the Sahara desert

    NASA Astrophysics Data System (ADS)

    Callot, Yann; Marticorena, Béatrice; Bergametti, Gilles

    Mineral dust emissions from arid regions are influenced by the surface features encountered in the source regions. These surface features control both the erosion threshold and the intensity of the dust flux. Recently, a soil-derived dust emission scheme has been designed in order to provide an explicit representation of the mineral dust accounting for the influence of the surface features on the dust emissions. This physical scheme has been validated with micro-scale field measurements. Its large scale application has required the development of additional relations to estimate the input parameters from more accessible data: the mean height and the covering rate of the roughness elements and the mineralogical soil type. The determination of these surface data has been based on a geomorphologic approach which describes the surface features of arid areas in a 1 × 1° grid. Inside each square degree, up to five different areas characterised by different surface features have been distinguished. However, these areas have not been located inside the square degree. Each area can be constituted by several combined surface features, including roughness, vegetation, granulometry. Five main types of landscapes and eight main types of surface features have been distinguished. This approach is based on the combination of various data, mainly topographical, geological maps and climatological analysis. In addition to the problem of scale transfer, the main constraints to obtain a quantitative assessment are the confidence level of the existing data and the number of parameters to document. On the opposite, with this method, the fine scale required by the dust modelling can be separated from the scale accessible by the mapping approach, of the order of the square degree. This method can also be easily improved by aggregating new data and can be extended to other deserts. An example of application is given for the north-west of the Algerian Sahara where the method has been

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

    PubMed Central

    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

  13. Interfacial nanodroplets guided construction of hierarchical Au, Au-Pt, and Au-Pd particles as excellent catalysts

    PubMed Central

    Ma, Aijing; Xu, Jie; Zhang, Xuehua; Zhang, Bin; Wang, Dayang; Xu, Haolan

    2014-01-01

    Interfacial nanodroplets were grafted to the surfaces of self-sacrificed template particles in a galvanic reaction system to assist the construction of 3D Au porous structures. The interfacial nanodroplets were formed via direct adsorption of surfactant-free emulsions onto the particle surfaces. The interfacial nanodroplets discretely distributed at the template particle surfaces and served as soft templates to guide the formation of porous Au structures. The self-variation of footprint sizes of interfacial nanodroplets during Au growth gave rise to a hierarchical pore size distribution of the obtained Au porous particles. This strategy could be easily extended to synthesize bimetal porous particles such as Au-Pt and Au-Pd. The obtained porous Au, Au-Pt, and Au-Pd particles showed excellent catalytic activity in catalytic reduction of 4-nitrophenol. PMID:24797697

  14. Interfacial nanodroplets guided construction of hierarchical Au, Au-Pt, and Au-Pd particles as excellent catalysts.

    PubMed

    Ma, Aijing; Xu, Jie; Zhang, Xuehua; Zhang, Bin; Wang, Dayang; Xu, Haolan

    2014-01-01

    Interfacial nanodroplets were grafted to the surfaces of self-sacrificed template particles in a galvanic reaction system to assist the construction of 3D Au porous structures. The interfacial nanodroplets were formed via direct adsorption of surfactant-free emulsions onto the particle surfaces. The interfacial nanodroplets discretely distributed at the template particle surfaces and served as soft templates to guide the formation of porous Au structures. The self-variation of footprint sizes of interfacial nanodroplets during Au growth gave rise to a hierarchical pore size distribution of the obtained Au porous particles. This strategy could be easily extended to synthesize bimetal porous particles such as Au-Pt and Au-Pd. The obtained porous Au, Au-Pt, and Au-Pd particles showed excellent catalytic activity in catalytic reduction of 4-nitrophenol. PMID:24797697

  15. Examining the External Training Load of an English Premier League Football Team With Special Reference to Acceleration.

    PubMed

    Akenhead, Richard; Harley, Jamie A; Tweddle, Simon P

    2016-09-01

    Akenhead, R, Harley, J, and Tweddle, S. Examining the external training load of an English Premier League football team with special reference to acceleration. J Strength Cond Res 30(9): 2424-2432, 2016-Practitioners and coaches often use external training load variables such as distance run and the number of high-speed running (HSR) activities to quantify football training. However, an important component of the external load may be overlooked when acceleration activities are not considered. The aim of this study was to describe the within-microcycle distribution of external load, including acceleration, during in-season 1-game weeks in an elite football team. Global Positioning System technology was used to collect time-motion data from 12 representative 7-day microcycles across a competitive season (48 training days, 295 data sets). Training time, total distance (TD), high-speed running (HSR) distance (>5.8 m·s), sprint running distance (>6.7 m·s) and acceleration variables were recorded during each training session. Data were analysed for interday and interposition differences using mixed linear modeling. The distribution of external load was characterized by the second training day of the microcycle (5 days prematch) exhibiting the highest values for all variables of training load, with the fourth day (1 day prematch) exhibiting the lowest values. Central midfield players covered ∼8-16% greater TD than other positions excluding wide midfielders (p ≤ 0.03, d = 0.2-0.4) and covered ∼17% greater distance accelerating 1-2 m·s than central defenders (p = 0.03, d = 0.7). When expressed relative to training duration and TD, the magnitude of interday and interposition differences were markedly reduced (p = 0.03, d = 0.2-0.3). When managing the distribution of training load, practitioners should be aware of the intensity of training sessions and consider the density of external load within sessions. PMID:26817740

  16. Health and economic outcomes associated with uncontrolled surgical bleeding: a retrospective analysis of the Premier Perspectives Database

    PubMed Central

    Corral, Mitra; Ferko, Nicole; Hollmann, Sarah; Broder, Michael S; Chang, Eunice

    2015-01-01

    Background Bleeding remains a common occurrence in surgery. Data describing the burden of difficult-to-control bleeding and topical absorbable hemostat use are sparse. This study was conducted to estimate the clinical and economic impact that remains associated with uncontrolled surgical bleeding, even when hemostats are used during surgery. Methods This US retrospective analysis used the Premier Perspectives Database. Hospital discharges from 2012 were used to identify patients treated with hemostats during eight surgery types. Patients were included if they were ≥18 years, had an inpatient hospitalization with one of the eight surgeries, and received a hemostat on the day of surgery. Patients were stratified by procedure and presence or absence of major bleeding (uncontrolled) despite hemostat use. Outcomes were all-cause hospitalization costs, hemostat costs, length of stay, reoperation, and surgery-related complications (eg, mortality). Statistical significance was tested through chi-square or t-tests. Multivariate analyses were conducted for all-cause costs and length of stay using analysis of covariance. Results Among 25,048 procedures, major bleeding events occurred in 14,251 cases. Despite treatment with hemostats, major bleeding occurred in 32%–68% of cases. All-cause costs were significantly higher in patients with uncontrolled bleeding despite hemostat use versus controlled bleeding (US$24,203–$61,323 [uncontrolled], US$14,420–$45,593 [controlled]; P<0.001). Hemostat costs were significantly greater in the uncontrolled bleeding cohort for all surgery types except cystectomy and pancreatic surgery. Reoperation and mortality rates were significantly higher in the uncontrolled bleeding cohort in all surgical procedures except cystectomy and radical hysterectomy. Conclusion Uncontrolled intraoperative bleeding despite hemostat use is prevalent and associated with significantly higher hospital costs and worse clinical outcomes across several surgical

  17. Analysis of Diagnoses Associated with Multiple Sclerosis–Related In-Hospital Mortality Using the Premier Hospital Database

    PubMed Central

    Pocoski, Jennifer; Cutter, Gary; Kaufman, David W.; Pleimes, Dirk

    2016-01-01

    Background: We sought to compare mortality rates and related diagnoses in hospitalized patients with multiple sclerosis (MS), those with diabetes mellitus (DM), and the general hospitalized population (GHP). Methods: Patients who died between 2007 and 2011 were identified in the US hospital–based Premier Healthcare Database. Demographic information was collected, mortality rates calculated, and principal diagnoses categorized. Results: Of 55,152 unique patients with MS identified, 1518 died. Mean age at death was 10 years younger for the MS group (63.4 years) than for the DM (73.3 years) and GHP (73.1 years) groups. Age-adjusted mortality rates, based on the 2000 US Standard Million Population, were 1077, 1248, and 1133 per 100,000, respectively. Infection was the most common principal diagnosis at the hospital stay during which the patient died in the MS cohort (43.1% vs. 26.3% and 24.0% in the DM and GHP groups, respectively). Other common principal diagnoses in the MS group included pulmonary (17.5%) and cardiovascular (12.1%) disease. Septicemia/sepsis/septic shock was a secondary diagnosis for 50.7% of patients with MS versus 36.0% and 31.0% of patients in the DM and GHP cohorts, respectively. Conclusions: Patients with MS had a shorter life span than patients with DM or the GHP and were more likely to have a principal diagnosis of infection at their final hospital stay. However, the database was limited to codes recorded in the hospital; diagnoses received outside the hospital were not captured. PMID:27252603

  18. Symmetry energy from elliptic flow in 197Au + 197Au

    NASA Astrophysics Data System (ADS)

    Russotto, P.; Wu, P. Z.; Zoric, M.; Chartier, M.; Leifels, Y.; Lemmon, R. C.; Li, Q.; Łukasik, J.; Pagano, A.; Pawłowski, P.; Trautmann, W.

    2011-03-01

    The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of neutron-rich systems at relativistic energies is proposed as an observable sensitive to the strength of the symmetry term in the equation of state at supra-normal densities. The results obtained from the existing FOPI/LAND data for 197Au + 197Au collisions at 400 MeV/nucleon in comparison with the UrQMD model favor a moderately soft symmetry term with a density dependence of the potential term proportional to (ρ /ρ0) γ with γ = 0.9 ± 0.4.

  19. Flow in Au+Au collisions at RHIC

    NASA Astrophysics Data System (ADS)

    Belt Tonjes, Marguerite; PHOBOS Collaboration; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; García, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Tang, J.-L.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wyslouch, B.

    2004-08-01

    The study of flow can provide information on the initial state dynamics and the degree of equilibration attained in heavy-ion collisions. This contribution presents results for both elliptic and directed flow as determined from data recorded by the PHOBOS experiment in Au+Au runs at RHIC at \\sqrt{s_{{\\rm NN}}} = 19.6, 130 and 200 GeV. The PHOBOS detector provides a unique coverage in pseudorapidity for measuring flow at RHIC. The systematic dependence of flow on pseudorapidity, transverse momentum, centrality and energy is discussed.

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

    PubMed Central

    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. PMID:24977147

  1. Sedimentological evidences for progressive drying of the Sahara during the last 6000 years from the annually laminated record of Lake Yoa

    NASA Astrophysics Data System (ADS)

    Francus, Pierre; von Suchodoletz, Hans; Dietze, Michael; Verschuren, Dirk; Kröpelin, Stefan

    2010-05-01

    Lake Yoa is a perennial lake entirely fed by groundwater and located in the Saharan desert of Northern Chad. It contains a unique continuous and high-resolution record of the climate history of the eastern Sahara for the last 6000 years (Kröpelin et al. 2008). Analyses of aquatic and terrestrial paleoecosystems revealed a slow and progressive drying of the region since mid-Holocene (Kröpelin et al. 2008 and Eggermont 2008). Here, we describe the sedimentological evolution of this finely laminated, undisturbed, 7.5 m-long sequence. Comparison of lamination counts with radiocarbon and 137-Cs dates indicates that these couplets are annual, i.e. varves. Counts were made using Fe, and Ca/Ti profiles as well as radiographs acquired using an Itrax µ-XRF core scanner with 100 µ resolution. Three facies could be distinguished. From 6 ka until 1.1 ka, couplets are: (1) a dark brown layer composed of organic matter, aeolian sands and finer detrital material; (2) a light brown layer of neoformed calcite. After 1.1 ka, couplets are formed by (1) a detrital layer consisting of a mixture of aeolian and resuspended material rich in both Fe and Ca and (2) organic-rich material. The change in varve facies corresponds to an abrupt decrease in Ca content and the simultaneous disappearance of neoformed calcite. This may be attributed to exhaustion of carbonate sources in the aquifer or surrounding dry lake beds as well as to a decrease of primary productivity triggering the precipitation of neoformed calcite. The laminated facies are intercalated with the third facies, of which there are relatively few. It consists of few coarser beds indicative of higher energy events due to changes in lake level or dune migration towards the coring site. Magnetic susceptibility broadly increases from bottom to top and may be indicative of the combined effect of changes in the sediment source and redox conditions in the water column. The clay fraction is interpreted to be of aeolian or fluvial

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

    USGS Publications Warehouse

    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.

  3. Applying the concept of "energy return on investment" to desert greening of the Sahara/Sahel using a global climate model

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Altering the large-scale dynamics of the Earth system through continual and deliberate human intervention now seems possible. In doing so, one should question the energetic sustainability of such interventions. Here, from the basis that a region might be unnaturally vegetated by employing technological means, we apply the metric of "energy return on investment" (EROI) to benchmark the energetic sustainability of such a scenario. We do this by applying EROI to a series of global climate model simulations where the entire Sahara/Sahel region is irrigated with increased 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. More specifically, we have shown how 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.

  4. Primary Premier for Belfast

    ERIC Educational Resources Information Center

    McAlister, Peter

    2009-01-01

    The author talks about the Association for Science Education (ASE) Primary Science Committee's (PSC) March 2009 meeting which was held in Belfast as guests of ASE Northern Ireland. To mark the auspicious occasion of a body that usually meets four times a year in the Hatfield HQ crossing the Irish Sea to be hosted by its Celtic cousins, a Lord…

  5. Tier-specific evolution of match performance characteristics in the English Premier League: it's getting tougher at the top.

    PubMed

    Bradley, Paul S; Archer, David T; Hogg, Bob; Schuth, Gabor; Bush, Michael; Carling, Chris; Barnes, Chris

    2016-01-01

    This study investigated the evolution of physical and technical performances in the English Premier League (EPL), with special reference to league ranking. Match performance observations (n = 14,700) were collected using a multiple-camera computerised tracking system across seven consecutive EPL seasons (2006-07 to 2012-13). Final league rankings were classified into Tiers: (A) 1st-4th ranking (n = 2519), (B) 5th-8th ranking (n = 2965), (C) 9th-14th ranking (n = 4448) and (D) 15th-20th ranking (n = 4768). Teams in Tier B demonstrated moderate increases in high-intensity running distance while in ball possession from the 2006-07 to 2012-13 season (P < 0.001; effect size [ES]: 0.68), with Tiers A, C and D producing less pronounced increases across the same period (P < 0.005; ES: 0.26, 0.41 and 0.33, respectively). Large increases in sprint distance were observed from the 2006-07 to 2012-13 season for Tier B (P < 0.001; ES: 1.21), while only moderate increases were evident for Tiers A, C and D (P < 0.001; ES: 0.75, 0.97 and 0.84, respectively). Tier B demonstrated large increases in the number of passes performed and received in 2012-13 compared to 2006-07 (P < 0.001; ES: 1.32-1.53) with small-to-moderate increases in Tier A (P < 0.001; ES: 0.30-0.38), Tier C (P < 0.001; ES: 0.46-0.54) and Tier D (P < 0.001; ES: 0.69-0.87). The demarcation line between 4th (bottom of Tier A) and 5th ranking (top of Tier B) in the 2006-07 season was 8 points, but this decreased to just a single point in the 2012-13 season. The data demonstrate that physical and technical performances have evolved more in Tier B than any other Tier in the EPL and could indicate a narrowing of the performance gap between the top two Tiers. PMID:26359805

  6. L’évaluation et le traitement du nourrisson exposé au virus d’immunodéficience humaine de type 1

    PubMed Central

    2004-01-01

    RÉSUMÉ Dans les pays industrialisés, des soins et un traitement sont offerts aux femmes enceintes et aux nourrissons, afin de faire chuter à 2 % ou moins le taux d’infection périnatale au virus d’immunodéficience humaine de type 1 (VIH-1). Le pédiatre joue un rôle de premier plan dans la prévention de la transmission du VIH-1 de la mère à l’enfant par le dépistage des nourrissons exposés au VIH dont l’infection au VIH de la mère n’a pas été diagnostiquée avant l’accouchement. Il prescrit une prophylaxie antirétrovirale à ces nourrissons, afin de réduire le risque d’acquisition de l’infection au VIH-1 et d’en éviter le plus possible la transmission par le lait maternel. De plus, le pédiatre peut soigner les nourrissons exposés au VIH-1 en les surveillant pour obtenir un dépistage précoce de l’infection au VIH-1 et évaluer les toxicités à court et à long terme de l’exposition aux antirétroviraux, assurer une chimioprophylaxie de la pneumonie à Pneumocystis et soutenir les familles qui vivent avec une infection au VIH-1, grâce à des conseils thérapeutiques aux parents ou aux soignants.

  7. Towards Improving our Understanding on the Retrievals of Key Parameters Characterising Land Surface Interactions from Space: Introduction & First Results from the PREMIER-EO Project

    NASA Astrophysics Data System (ADS)

    Ireland, Gareth; North, Matthew R.; Petropoulos, George P.; Srivastava, Prashant K.; Hodges, Crona

    2015-04-01

    Acquiring accurate information on the spatio-temporal variability of soil moisture content (SM) and evapotranspiration (ET) is of key importance to extend our understanding of the Earth system's physical processes, and is also required in a wide range of multi-disciplinary research studies and applications. The utility and applicability of Earth Observation (EO) technology provides an economically feasible solution to derive continuous spatio-temporal estimates of key parameters characterising land surface interactions, including ET as well as SM. Such information is of key value to practitioners, decision makers and scientists alike. The PREMIER-EO project recently funded by High Performance Computing Wales (HPCW) is a research initiative directed towards the development of a better understanding of EO technology's present ability to derive operational estimations of surface fluxes and SM. Moreover, the project aims at addressing knowledge gaps related to the operational estimation of such parameters, and thus contribute towards current ongoing global efforts towards enhancing the accuracy of those products. In this presentation we introduce the PREMIER-EO project, providing a detailed overview of the research aims and objectives for the 1 year duration of the project's implementation. Subsequently, we make available the initial results of the work carried out herein, in particular, related to an all-inclusive and robust evaluation of the accuracy of existing operational products of ET and SM from different ecosystems globally. The research outcomes of this project, once completed, will provide an important contribution towards addressing the knowledge gaps related to the operational estimation of ET and SM. This project results will also support efforts ongoing globally towards the operational development of related products using technologically advanced EO instruments which were launched recently or planned be launched in the next 1-2 years. Key Words: PREMIER

  8. Global polarization measurement in Au+Au collisions

    SciTech Connect

    Abelev, B.I.; Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett,J.; Anderson, B.D.; Anderson, M.; Arkhipkin, D.; Averichev, G.S.; Bai,Y.; Balewski, J.; Barannikova, O.; Barnby, L.S.; Baudot, J.; Bekele, S.; Belaga, V.V.; Bellingeri-Laurikainen, A.; Bellwied, R.; Benedosso, F.; Bhardwaj, S.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L.C.; Blyth, S.-L.; Bonner, B.E.; Botje, M.; Bouchet, J.; Brandin, A.V.; Bravar, A.; Bystersky, M.; Cadman, R.V.; Cai,X.Z.; Caines, H.; Calderon de la Barca Sanchez, M.; Castillo, J.; Catu,O.; Cebra, D.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen,H.F.; Chen, J.H.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Coffin, J.P.; Cormier, T.M.; Cosentino, M.R.; Cramer, J.G.; Crawford,H.J.; Das, D.; Das, S.; Daugherity, M.; de Moura, M.M.; Dedovich, T.G.; DePhillips, M.; Derevschikov, A.A.; Didenko, L.; Dietel, T.; Djawotho,P.; Dogra, S.M.; Dong, W.J.; Dong, X.; Draper, J.E.; Du, F.; Dunin, V.B.; Dunlop, J.C.; Dutta Mazumdar, M.R.; Eckardt, V.; Edwards, W.R.; Efimov,L.G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Filimonov, K.; Filip, P.; Finch,E.; Fine, V.; Fisyak, Y.; Fu, J.; Gagliardi, C.A.; Gaillard, L.; Ganti,M.S.; Ghazikhanian, V.; Ghosh, P.; Gonzalez, J.S.; Gorbunov, Y.G.; Gos,H.; Grebenyuk, O.; Grosnick, D.; Guertin, S.M.; Guimaraes, K.S.F.F.; Guo,Y.; Gupta, N.; Gutierrez, T.D.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Henry, T.W.; Hepplemann, S.; Hippolyte,B.; Hirsch, A.; Hjort, E.; Hoffman, A.M.; Hoffmann, G.W.; Horner, M.J.; Huang, H.Z.; Huang, S.L.; Hughes, E.W.; Humanic, T.J.; Igo, G.; Jacobs,P.; Jacobs, W.W.; Jakl, P.; Jia, F.; Jiang, H.; Jones, P.G.; Judd, E.G.; Kabana, S.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Khodyrev,V.Yu.; Kim, B.C.; Kiryluk, J.; Kisiel, A.; Kislov, E.M.; Klein,S.R.; Kocoloski, A.; Koetke, D.D.; et al.

    2007-08-02

    The system created in non-central relativisticnucleus-nucleus collisions possesses large orbital angular momentum. Dueto spin-orbit coupling, particles produced in such a system could becomeglobally polarized along the direction of the system angular momentum. Wepresent the results of Lambda and anti-Lambda hyperon global polarizationmeasurements in Au+Au collisions at sqrt sNN=62.4 GeV and 200 GeVperformed with the STAR detector at RHIC. The observed globalpolarization of Lambda and anti-Lambda hyperons in the STAR acceptance isconsistent with zero within the precision of the measurements. Theobtained upper limit, lbar P Lambda, anti-Lambda rbar<= 0.02, iscompared to the theoretical values discussed recently in theliterature.

  9. Universality in fragment inclusive yields from Au+Au collisions

    NASA Astrophysics Data System (ADS)

    Insolia, A.; Tuvè, C.; Albergo, S.; Bieser, F.; Brady, F. P.; Caccia, Z.; Cebra, D.; Chacon, A. D.; Chance, J. L.; Choi, Y.; Costa, S.; Elliott, J. B.; Gilkes, M.; Hauger, J. A.; Hirsch, A. S.; Hjort, E. L.; Justice, M.; Keane, D.; Kintner, J.; Lisa, M.; Matis, H. S.; McMahan, M.; McParland, C.; Olson, D. L.; Partlan, M. D.; Porile, N. T.; Potenza, R.; Rai, G.; Rasmussen, J.; Ritter, H. G.; Romero, J. L.; Russo, G. V.; Scharenberg, R.; Scott, A.; Shao, Y.; Srivastava, B. K.; Symons, T. J. M.; Tincknell, M. L.; Wang, S.; Warren, P. G.; Wieman, H. H.; Wolf, K. L.

    2001-11-01

    The inclusive light fragment (Z⩽7) yield data in Au+Au reactions, measured by the EOS Collaboration at the LBNL Bevalac, are presented and discussed. For peripheral collisions the measured charge distributions develop progressively according to a power law which can be fitted by a single τ exponent independently of the bombarding energy in the range 250-1200 A MeV. In addition to this universal feature, we observe that the location of the maximum in the individual yields of different charged fragments shift towards lower multiplicity as the fragment charge increases from Z=3 to Z=7. This trend is common to all six measured beam energies. Moments of charge distributions and correlations among different moments are reported. Finally, the THe,DT thermometer has been constructed for central and peripheral collisions using the double yield ratios of He and D, T projectile fragments. The measured nuclear temperatures are in agreement with experimental findings in other fragmentation reactions.

  10. Nuclear Modification of Jet Fragmentation in Au+Au Collisions

    NASA Astrophysics Data System (ADS)

    Rowan, Zachary; Phenix Collaboration

    2015-10-01

    The characterization of energy in the quark gluon plasma is facilitated by measurements of modifications to the observed jet fragmentation. A favorable channel of study relies on direct photons created in the initial parton interactions of heavy ion collisions. Such a photon traverses the created medium unscathed and grants us a proxy for the transverse momentum of an away side jet. PHENIX Au+Au data recorded at √{sNN} = 200 GeV during RHIC run 14 benefit from the background rejection capability of the silicon vertex detector, enabling the extraction of a higher purity hadron signal. This advantage, combined with a larger integrated luminosity, allows previous PHENIX measurements of fragmentation functions to be extended to greater jet energies. In this talk, the status of the analysis of direct photon hadron correlations with the new data set will be discussed.

  11. Global polarization measurement in Au+Au collisions

    NASA Astrophysics Data System (ADS)

    Abelev, B. I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, B. D.; Arkhipkin, D.; Averichev, G. S.; Bai, Y.; Balewski, J.; Barannikova, O.; Barnby, L. S.; Baudot, J.; Baumgart, S.; Belaga, V. V.; Bellingeri-Laurikainen, A.; Bellwied, R.; Benedosso, F.; Betts, R. R.; Bhardwaj, S.; Bhasin, A.; Bhati, A. K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Blyth, S.-L.; Bombara, M.; Bonner, B. E.; Botje, M.; Bouchet, J.; Brandin, A. V.; Burton, T. P.; Bystersky, M.; Cai, X. Z.; Caines, H.; Sánchez, M. Calderón De La Barca; Callner, J.; Catu, O.; Cebra, D.; Cervantes, M. C.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, J. Y.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chung, S. U.; Clarke, R. F.; Codrington, M. J. M.; Coffin, J. P.; Cormier, T. M.; Cosentino, M. R.; Cramer, J. G.; Crawford, H. J.; Das, D.; Dash, S.; Daugherity, M.; Moura, M. M. De; Dedovich, T. G.; Dephillips, M.; Derevschikov, A. A.; Didenko, L.; Dietel, T.; Djawotho, P.; Dogra, S. M.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, F.; Dunin, V. B.; Dunlop, J. C.; Mazumdar, M. R. Dutta; Edwards, W. R.; Efimov, L. G.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Feng, A.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Fu, J.; Gagliardi, C. A.; Gaillard, L.; Ganti, M. S.; Garcia-Solis, E.; Ghazikhanian, V.; Ghosh, P.; Gorbunov, Y. N.; Gos, H.; Grebenyuk, O.; Grosnick, D.; Grube, B.; Guertin, S. M.; Guimaraes, K. S. F. F.; Gupta, A.; Gupta, N.; Haag, B.; Hallman, T. J.; Hamed, A.; Harris, J. W.; He, W.; Heinz, M.; Henry, T. W.; Heppelmann, S.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffman, A. M.; Hoffmann, G. W.; Hofman, D. J.; Hollis, R. S.; Horner, M. J.; Huang, H. Z.; Hughes, E. W.; Humanic, T. J.; Igo, G.; Iordanova, A.; Jacobs, P.; Jacobs, W. W.; Jakl, P.; Jones, P. G.; Judd, E. G.; Kabana, S.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Kettler, D.; Khodyrev, V. Yu.; Kiryluk, J.; Kisiel, A.; Kislov, E. M.; Klein, S. R.; Knospe, A. G.; Kocoloski, A.; Koetke, D. D.; Kollegger, T.; Kopytine, M.; Kotchenda, L.; Kouchpil, V.; Kowalik, K. L.; Kravtsov, P.; Kravtsov, V. I.; Krueger, K.; Kuhn, C.; Kulikov, A. I.; Kumar, A.; Kurnadi, P.; Kuznetsov, A. A.; Lamont, M. A. C.; Landgraf, J. M.; Lange, S.; Lapointe, S.; Laue, F.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, C.-H.; Lehocka, S.; Levine, M. J.; Li, C.; Li, Q.; Li, Y.; Lin, G.; Lin, X.; Lindenbaum, S. J.; Lisa, M. A.; Liu, F.; Liu, H.; Liu, J.; Liu, L.; Ljubicic, T.; Llope, W. J.; Longacre, R. S.; Love, W. A.; Lu, Y.; Ludlam, T.; Lynn, D.; Ma, G. L.; Ma, J. G.; Ma, Y. G.; Mahapatra, D. P.; Majka, R.; Mangotra, L. K.; Manweiler, R.; Margetis, S.; Markert, C.; Martin, L.; Matis, H. S.; Matulenko, Yu. A.; McShane, T. S.; Meschanin, A.; Millane, J.; Miller, M. L.; Minaev, N. G.; Mioduszewski, S.; Mischke, A.; Mitchell, J.; Mohanty, B.; Morozov, D. A.; Munhoz, M. G.; Nandi, B. K.; Nattrass, C.; Nayak, T. K.; Nelson, J. M.; Nepali, C.; Netrakanti, P. K.; Nogach, L. V.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Okorokov, V.; Olson, D.; Pachr, M.; Pal, S. K.; Panebratsev, Y.; Pavlinov, A. I.; Pawlak, T.; Peitzmann, T.; Perevoztchikov, V.; Perkins, C.; Peryt, W.; Phatak, S. C.; Planinic, M.; Pluta, J.; Poljak, N.; Porile, N.; Poskanzer, A. M.; Potekhin, M.; Potrebenikova, E.; Potukuchi, B. V. K. S.; Prindle, D.; Pruneau, C.; Pruthi, N. K.; Putschke, J.; Qattan, I. A.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Relyea, D.; Ridiger, A.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Rose, A.; Roy, C.; Ruan, L.; Russcher, M. J.; Sahoo, R.; Sakrejda, I.; Sakuma, T.; Salur, S.; Sandweiss, J.; Sarsour, M.; Sazhin, P. S.; Schambach, J.; Scharenberg, R. P.; Schmitz, N.; Seger, J.; Selyuzhenkov, I.; Seyboth, P.; Shabetai, A.; Shahaliev, E.; Shao, M.; Sharma, M.; Shen, W. Q.; Shimanskiy, S. S.; Sichtermann, E. P.; Simon, F.; Singaraju, R. N.; Smirnov, N.; Snellings, R.; Sorensen, P.; Sowinski, J.; Speltz, J.; Spinka, H. M.; Srivastava, B.; Stadnik, A.; Stanislaus, T. D. S.; Staszak, D.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Suarez, M. C.; Subba, N. L.; Sumbera, M.; Sun, X. M.; Sun, Z.; Surrow, B.; Symons, T. J. M.; Toledo, A. Szanto De; Takahashi, J.; Tang, A. H.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Timoshenko, S.; Tokarev, M.; Trainor, T. A.; Trentalange, S.; Tribble, R. E.; Tsai, O. D.; Ulery, J.; Ullrich, T.; Underwood, D. G.; Buren, G. Van; Kolk, N. Van Der; Leeuwen, M. Van; Molen, A. M. Vander; Varma, R.; Vasilevski, I. M.; Vasiliev, A. N.; Vernet, R.; Vigdor, S. E.; Viyogi, Y. P.; Vokal, S.; Voloshin, S. A.; Wada, M.; Waggoner, W. T.; Wang, F.; Wang, G.; Wang, J. S.; Wang, X. L.; Wang, Y.; Webb, J. C.; Westfall, G. D.; , C. Whitten, Jr.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, J.; Wu, Y.; Xu, N.; Xu, Q. H.; Xu, Z.; Yepes, P.; Yoo, I.-K.; Yue, Q.; Yurevich, V. I.; Zawisza, M.; Zhan, W.; Zhang, H.; Zhang, W. M.; Zhang, Y.; Zhang, Z. P.; Zhao, Y.; Zhong, C.; Zhou, J.; Zoulkarneev, R.; Zoulkarneeva, Y.; Zubarev, A. N.; Zuo, J. X.

    2007-08-01

    The system created in noncentral relativistic nucleus-nucleus collisions possesses large orbital angular momentum. Because of spin-orbit coupling, particles produced in such a system could become globally polarized along the direction of the system angular momentum. We present the results of Λ and Λ¯ hyperon global polarization measurements in Au+Au collisions at sNN=62.4 and 200 GeV performed with the STAR detector at the BNL Relativistic Heavy Ion Collider (RHIC). The observed global polarization of Λ and Λ¯ hyperons in the STAR acceptance is consistent with zero within the precision of the measurements. The obtained upper limit, |PΛ,Λ¯|⩽0.02, is compared with the theoretical values discussed recently in the literature.

  12. d + Au hadron correlation measurements at PHENIX

    SciTech Connect

    Anne M. Sickles

    2014-05-13

    In these proceedings, we discuss recent results from d + Au collisions in PHENIX ridge related measurements and their possible hydrodynamic origin. We present the v2 at midrapidity and measurements of the pseudorapidity dependence of the ridge, distinguishing between the d-going and Au-going directions. We investigate the possible geometrical origin by comparing v2 in d + Au to that in p + Pb, Au + Au and Pb + Pb collisions. Future plans to clarify the role of geometry in small collision systems at RHIC are discussed.

  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.

    PubMed

    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. Cometary Activity Beyond 4 AU

    NASA Astrophysics Data System (ADS)

    Womack, M.

    2000-10-01

    Recent observations of the distantly active comets 29 P/Schwassmann-Wachmann 1, 2060 Chiron, and C/1995 O1 (Hale-Bopp) are consistent with models that predict that the activity beyond 4 AU is dominated by outgassing of CO and CO2 molecules trapped in an amorphous water ice surface undergoing crystallization. The nominal CO production rates in Hale-Bopp, SW 1 and Chiron over the range of r = 4 to 9 AU are consistent with Q(CO) = (2.9+/-0.5)x1030r{(-2.5 +/- 0.1)}, with sporadic outbursts superimposed. The data indicate that the gas production rates in distant comets are primarily determined by the composition, and not the size, of the nucleus. The dust production rates, however, are very different among these comets and are not well-correlated with heliocentric distance. Thus, the gas and dust mixtures may not be uniform amongst these comets, nor in an individual comet. Development and sublimation of an icy grain coma at ~ 5 AU appears to be a common feature in distantly active comets. Sublimation of such icy grains is probably the main source of emission of OH, CH3OH, HCN, and H2S in comets beyond 4 AU. Studying the energetics of these phenomena provides an excellent opportunity to learn more about the composition and physical behavior of comet nuclei, as well as other icy bodies in the outer solar system, such as moons and Kuiper Belt Objects. This work was funded by the NSF CAREER Program.

  15. An improved atmosphere-surface model in Africa reveals the importance of vegetation and lakes in the Late Quaternary and Green Sahara periods

    NASA Astrophysics Data System (ADS)

    Farrow, A.; Singarayer, J. S.; Valdes, P. J.; B. R. I. D. G. E

    2011-12-01

    Paleoclimate records from Late Quaternary Africa imply high amplitude variability between wet and dry conditions. In this work, we use asynchronously coupled atmosphere and land surface models to investigate the mechanisms and feedbacks responsible for Northern Africa moisture fluctuations and find that model simulations are altered dramatically by the inclusion of land surface effects. During the last de-glaciation large amplitude perturbations of the African climate occurred linked to orbitaly forced changes in monsoon strength. Furthermore during the Holocene an abrupt and widespread greening of the Sahara is recorded in numerous paleoclimate archives. This greening represents the largest anomaly in the atmosphere-biosphere system in the last 12,000 years but is consistently misrepresented by modeling studies. Northern African climates are thought to highly sensitive to land surface feedbacks and it has been suggested that better representation of the land surface may improve model simulations. We investigate how the role of surface feedbacks in the climate system change over a uniquely extensive suite of time slice simulations from the last glacial maximum to the present. The Hadley Centre's atmosphere-only GCM, HadAM3 is asynchronously coupled with the equilibrium vegetation model BIOME (Prentice et al 1992) and surface hydrology feedbacks are considered using the surface water scheme HYDRA (Coe 1998). Equilibrium time slices are run at 3000 year intervals from the pre-industrial to 24 kyr B.P. This enables us to dissect the relative importance of orbital, vegetation and hydrologic systems in controlling the climate of Northern Africa across a complete spectrum of de-glacial to present climates. Although over millennial and longer time scales African water balance is steered by orbital configuration we show that the system is also affected by fluxes working across the land surface-atmosphere interface. Changes in the land surface cover seen by a GCM have a

  16. Gradual aridification of the Sahara during the last 11,000 years revealed by plant wax δD analyses of Lake Yoa (Chad)

    NASA Astrophysics Data System (ADS)

    Rethemeyer, Janet; Kröpelin, Stefan; Karls, Jens; Thienemann, Matthias; Melles, Martin; Schefuß, Enno

    2014-05-01

    It is still an ongoing debate whether the transition of the last 'green Sahara' period to today's large desert during the Holocene, the African Humid Period (AHP), was a progressive or an abrupt change in hydrological conditions. Several climate records mainly from East Africa suggest a rapid decline of moisture availability at the end of the AHP including new data from a marine sequence off the Horn of Africa (Tierney & deMenocal, 2013). Other archives including sedimentological, geochemical and palynological data from the central North African Lakes Chad and Lake Yoa point to a gradual rather than an abrupt transition near 5,000 years ago (Amaral et al., 2013; Kröpelin et al., 2008). The discrepancy of the available paleo-hydrological reconstructions underline the importance of proxy parameters directly related to hydrological conditions for accurate assessment of continental rainfall changes. Here, we present the first molecular-isotopic data from Lake Yoa documenting the hydrologic evolution over the entire Holocene. Compound-specific carbon and hydrogen isotope analyses were performed on long-chain n-alkanes. Our data indicate relative high but variable contributions of plant-derived long-chain n-alkanes carrying a distinct leaf-wax signature, i.e., a high Carbon Preference Index (CPI). A trend towards higher CPI values since 7,300 years ago suggests declining soil degradation and vegetation cover under increasingly drier conditions. In parallel, the average-chain-length of the long-chain n-alkanes increases gradually towards the present implying higher relative contributions from grasses. Compound-specific carbon isotope data confirm this finding, indicating a mixed C3/C4 contribution in the early and mid-Holocene changing towards a C4-grass dominated vegetation in the late Holocene. Most importantly, compound-specific hydrogen isotope data reveal a continuous increase from 8,100 years ago towards the present, reflecting a gradual aridification. The large

  17. Four-year study of Middle East and Sahara dust intrusions in terms of particle lidar ratio: Observations with lidar and sun/sky photometer over Limassol, Cyprus

    NASA Astrophysics Data System (ADS)

    Nisantzi, Argyro; Elisavet Mamouri, Rodanthi; Hadjimitsis, Diofantos; Ansmann, Albert

    2015-04-01

    The remote sensing station of the Cyprus University of Technology (CUT) at Limassol (34.7oN, 33oE, 50m above sea level a.s.l.) is located in the southeast part of the Mediterranean (150km south of Turkey and 250km west of Syria) and dust aerosol components from Sahara and Middle East deserts comprise the major sources of dust layers in the study area. The CUT station is equipped with a European Aerosol Research Lidar Network (EARLINET) lidar and Aerosol Robotic Network (AERONET) sun/sky photometer. The combined database of four years (2010 -2013) of observations was used to compare extinction-to-backscatter ratios (lidar ratios) for dust from Middle East and Sahara deserts. For the first time, a long-term lidar study on the lidar ratio of Middle East desert dust is presented. The results are compared with respective findings for Saharan dust outbreaks. The Limassol lidar station at the island of Cyprus in the eastern Mediterranean Sea is unique because it is the only site of the EARLINET which is influenced by a statistically significant number (5-7) of Middle East dust outbreaks each year as well as by numerous Saharan dust outbreaks (>10 per year). For this analysis we considered 17 major dust outbreaks from the Middle East and 32 dust outbreaks from North Africa. Simultaneous EARLINET lidar and AERONET photometer observations were conducted at Limassol almost day by day over the four year period from April 2010 to December 2013. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan desert dust lidar ratios. We found values from 44-65 sr with a mean value of 52.7 sr for Saharan dust and from 35-46 sr with a mean value of 41.1 sr for Middle East dust. The presented data analysis, however, also demonstrates the

  18. Synthesis and optical property characterization of elongated AuPt and Pt@Au metal nanoframes

    NASA Astrophysics Data System (ADS)

    Lee, Sangji; Jang, Hee-Jeong; Jang, Ho Young; Hong, Soonchang; Moh, Sang Hyun; Park, Sungho

    2016-02-01

    We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges.We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08200e

  19. Une alternative au cobalt pour la synthese de nanotubes de carbone monoparoi par plasma inductif thermique

    NASA Astrophysics Data System (ADS)

    Carrier, Jean-Francois

    Les nanotubes de carbone de type monoparoi (C-SWNT) sont une classe recente de nanomateriaux qui ont fait leur apparition en 1991. L'interet qu'on leur accorde provient des nombreuses proprietes d'avant-plan qu'ils possedent. Leur resistance mecanique serait des plus rigide, tout comme ils peuvent conduire l'electricite et la chaleur d'une maniere inegalee. Non moins, les C-SWNT promettent de devenir une nouvelle classe de plateforme moleculaire, en servant de site d'attache pour des groupements reactifs. Les promesses de ce type particulier de nanomateriau sont nombreuses, la question aujourd'hui est de comment les realiser. La technologie de synthese par plasma inductif thermique se situe avantageusement pour la qualite de ses produits, sa productivite et les faibles couts d'operation. Par contre, des recherches recentes ont permis de mettre en lumiere des risques d'expositions reliees a l'utilisation du cobalt, comme catalyseur de synthese; son elimination ou bien son remplacement est devenu une preoccupation importante. Quatre recettes alternatives ont ete mises a l'essai afin de trouver une alternative plus securitaire a la recette de base; un melange catalytique ternaire, compose de nickel, de cobalt et d'oxyde d'yttrium. La premiere consiste essentiellement a remplacer la proportion massique de cobalt par du nickel, qui etait deja present dans la recette de base. Les trois options suivantes contiennent de nouveaux catalyseurs, en remplacement au Co, qui sont apparus dans plusieurs recherches scientifiques au courant des dernieres annees: le dioxyde de zircone (ZrO2), dioxyde de manganese (MnO2) et le molybdene (Mo). La methode utilisee consiste a vaporiser la matiere premiere, sous forme solide, dans un reacteur plasma a haute frequence (3 MHz) a paroi refroidi. Apres le passage dans le plasma, le systeme traverse une section dite de "croissance", isolee thermiquement a l'aide de graphite, afin de maintenir une certaine plage de temperature favorable a la

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

    NASA Technical Reports Server (NTRS)

    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.

  1. Fluid flow paths discrimination in tight sand gas reservoirs using the Hydraulic Flow unit approach with an example from the Algerian Sahara

    NASA Astrophysics Data System (ADS)

    Sokhal, Abdellah; Bougandoura, Adel; Ouadfeul, Sid-Ali

    2015-04-01

    In this work, fluid flow paths are discriminated from standard well logs and core data through the utilization of Hydraulic Flow Units Approach (HFU) and an intelligent network. Firstly, the flow zone indicator (FZI), which is a unique parameter for each hydraulic unit, was used to characterize each rock type. The number of hydraulic flow units and mean values of FZI for each HFU were calculated from porosity and permeability measured from core-rocks. Application to data of a borehole located in the Algerian Sahara shows the existence of three HFUs and a correlation coefficient greater than 0.9 in each HFU was observed. Some FZI were attributed for un-cored wells using the Fuzzy Logic system (FL). Well-logs data that are used as an input to train the fuzzy system are the neutron porosity, the bulk density, the slowness of the P wave, the resistivity of the shallow and the deep zones and the natural gamma ray. The calculated FZI associated to these depths interval are used as an output. The presented methodology was successfully applied to a large data set of laboratory and well logging measurements from the Hassi D'zaabat field. Keywords: Fluid flow; FZI, Hydraulic Flow Unit (HFU); Fuzzy logic.

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

    PubMed

    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. PMID:23920229

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

    NASA Technical Reports Server (NTRS)

    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.

  4. Surviving in Mountain Climate Refugia: New Insights from the Genetic Diversity and Structure of the Relict Shrub Myrtus nivellei (Myrtaceae) in the Sahara Desert

    PubMed Central

    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. PMID:24058489

  5. Early to Middle Holocene landscape exploitation in a drying environment: Two case studies compared from the central Sahara (SW Fezzan, Libya)

    NASA Astrophysics Data System (ADS)

    Cremaschi, Mauro; Zerboni, Andrea

    2009-08-01

    The erg Uan Kasa and the wadi Tanezzuft (Libyan Sahara) reacted in different ways to Holocene climatic changes. Consequently, the human groups settled there responded with different ways of adaptation to the drying environment. In the erg Uan Kasa, shallow lakes were formed from the Early to the Mid-Holocene, and their shores were densely inhabited from the Epipalaeolithic to the Pastoral-Neolithic periods. The erg dried out at c. 5000 years BP, but the area was not completely abandoned, as indicated by minor Late Pastoral-Neolithic sites composed of scattered fireplaces. During the wet Holocene, the wadi Tanezzuft was a large meandering river, and its banks were densely settled. At c. 5000 years BP, the stream was not completely dried out, but it changed its pattern, originating an alluvial plain. A large oasis was formed between c. 4000 and 2000 years BP, exploited by Late Pastoral-Neolithic pastoral communities, and later by Garamantians, which introduced soil management and agricultural practices. The Tanezzuft oasis suffered a drastic reduction in size during the first centuries AD, at the time of the abandonment of the Garamantian settlements.

  6. Trends and challenges toward integration of traditional medicine in formal health-care system: Historical perspectives and appraisal of education curricula in Sub-Sahara Africa

    PubMed Central

    Innocent, Ester

    2016-01-01

    The population residing Sub-Sahara Africa (SSA) continues to suffer from communicable health problems such as HIV/AIDS, malaria, tuberculosis, and various neglected tropical as well as non-communicable diseases. The disease burden is aggravated by shortage of medical personnel and medical supplies such as medical devices and minimal access to essential medicine. For long time, human beings through observation and practical experiences learned to use different plant species that led to the emergence of traditional medicine (TM) systems. The ancient Pharaonic Egyptian TM system is one of the oldest documented forms of TM practice in Africa and the pioneer of world’s medical science. However, the medical practices diffused very fast to other continents being accelerated by advancement of technologies while leaving Africa lagging behind in the integration of the practice in formal health-care system. Challenging issues that drag back integration is the development of education curricula for training TM experts as the way of disseminating the traditional medical knowledge and practices imbedded in African culture. The few African countries such as Ghana managed to integrate TM products in the National Essential Medicine List while South Africa, Sierra Leone, and Tanzania have TM products being sold over the counters due to the availability of education training programs facilitated by research. This paper analyses the contribution of TM practice and products in modern medicine and gives recommendations that Africa should take in the integration process to safeguard the SSA population from disease burdens. PMID:27366358

  7. Trends and challenges toward integration of traditional medicine in formal health-care system: Historical perspectives and appraisal of education curricula in Sub-Sahara Africa.

    PubMed

    Innocent, Ester

    2016-01-01

    The population residing Sub-Sahara Africa (SSA) continues to suffer from communicable health problems such as HIV/AIDS, malaria, tuberculosis, and various neglected tropical as well as non-communicable diseases. The disease burden is aggravated by shortage of medical personnel and medical supplies such as medical devices and minimal access to essential medicine. For long time, human beings through observation and practical experiences learned to use different plant species that led to the emergence of traditional medicine (TM) systems. The ancient Pharaonic Egyptian TM system is one of the oldest documented forms of TM practice in Africa and the pioneer of world's medical science. However, the medical practices diffused very fast to other continents being accelerated by advancement of technologies while leaving Africa lagging behind in the integration of the practice in formal health-care system. Challenging issues that drag back integration is the development of education curricula for training TM experts as the way of disseminating the traditional medical knowledge and practices imbedded in African culture. The few African countries such as Ghana managed to integrate TM products in the National Essential Medicine List while South Africa, Sierra Leone, and Tanzania have TM products being sold over the counters due to the availability of education training programs facilitated by research. This paper analyses the contribution of TM practice and products in modern medicine and gives recommendations that Africa should take in the integration process to safeguard the SSA population from disease burdens. PMID:27366358

  8. Effect of the insulation by the mud on the convection in building in the Sahara of Algeria - case of Bechar City

    NASA Astrophysics Data System (ADS)

    Benachour, Elhadj; Draoui, Belkacem; Imine, Baachir; Hasnat, Mohammed; Rahmani, Lakhdar

    2016-03-01

    The thermal behavior of the buildings is a current problem which arouses the interest of many researchers. Indeed, the control of the loads of air conditioning or heating requires a thorough knowledge. Since the thermal quality of the buildings in the Maghreb is there generally very insufficient in particular in the Sahara of Algeria, the insulation proved that it is a very important parameter to minimize the thermal diffusion process inside on all when the insulator is a local material as the Mud which is in our region with a significant amount and almost free quantity. This work presents a study of numerical simulation aiming at the role and the influence of the insulation by the mud Reduced like a local material to the town of Bechar located at the south west of Algeria, or one is interested in a comparative study for pursued these goals. In this context, an analogy was used for the functions which are discretized by the finite difference method and integrated in the Fluent code which is based on the finite volume method. The validation of this procedure was confirmed while comparing some results. The results are presented in the form of distributions of the isotherms, the streamlines, local and average Nusselt of which the goal to study the influence on comfort.

  9. Mise au point d'un reacteur epitaxial CBE

    NASA Astrophysics Data System (ADS)

    Pelletier, Hubert

    carbone à 1, 5 · 1019 cm-3, en accord avec la courbe théorique. La croissance du matériau ternaire GaInP a aussi été réalisée en accord de maille avec le substrat de GaAs, et avec une rugosité de 0, 96 nm. Ceci constitue un premier pas dans la croissance d'alliages ternaires au laboratoire. Finalement, la mise en marche du réacteur d'épitaxie par jets chimiques permet maintenant à cinq étudiants gradués de faire progresser des projets reliés directement à la croissance épitaxiale au Laboratoire d'Épitaxie Avancée de l'Université de Sherbrooke. Mots-clés : Épitaxie par jets chimiques; Chemical beam epitaxy; CBE; MOMBE; GaAs; GaInP; LabVIEW; Théorie du vide.

  10. Wetting and energetics of solid Au and Au-Ge/SiC interfaces

    SciTech Connect

    Wang, Z.; Wynblatt, P.

    1998-09-01

    A solid state wetting technique has been used to investigate the effects of alloying Au with Ge on the wetting and energetics of Au/SiC interfaces at 1123 K. Germanium was found to segregate to the Au/SiC interface, thereby lowering the contact angle of Au on SiC from 133 to 110, and doubling the work of adhesion of Au on SiC. Calculations based on a monolayer model predict a segregation of 0.89 monolayers of Ge at the Au/SiC interface for Au containing 2.3 at.% Ge. This agrees reasonably well with a coverage of 0.6 monolayers Ge at the Au/SiC interface obtained by direct measurements based on the crater edge profiling technique. The work also demonstrates that simple models of interfacial composition can be combined with the Gibbs adsorption isotherm to provide reliable estimates of interfacial composition at complex four-component interfaces.

  11. Pt{sub 3}Au and PtAu clusters: Electronic states and potential energy surfaces

    SciTech Connect

    Dai, D.; Balasubramanian, K.

    1994-03-15

    We carried out complete active space multiconfiguration self-consistent-field calculations followed by multireference singles+doubles configuration interaction with the Davidson correction which included up to 3.55 million configurations employing relativistic effective core potentials on Pt{sub 3}+Au and PtAu clusters. Four low-lying electronic states were identified for Pt{sub 3}+Au. The {sup 2}{ital A}{sub 2} electronic state ({ital C}{sub 3{ital v}}) was found to be the ground state of Pt{sub 3}Au. Spin--orbit effects were found to be significant. We also computed six low-lying electronic states of PtAu and four low-lying electronic states of PtAu{sup +}. The 5/2 ({sup 2}{Delta}) and 0{sup +}({sup 1}{Sigma}{sup +}) states were found to be the ground states of PtAu and PtAu{sup +}, respectively.

  12. Gold nanowired: a linear (Au25)(n) polymer from Au25 molecular clusters.

    PubMed

    De Nardi, Marco; Antonello, Sabrina; Jiang, De-en; Pan, Fangfang; Rissanen, Kari; Ruzzi, Marco; Venzo, Alfonso; Zoleo, Alfonso; Maran, Flavio

    2014-08-26

    Au25(SR)18 has provided fundamental insights into the properties of clusters protected by monolayers of thiolated ligands (SR). Because of its ultrasmall core, 1 nm, Au25(SR)18 displays molecular behavior. We prepared a Au25 cluster capped by n-butanethiolates (SBu), obtained its structure by single-crystal X-ray crystallography, and studied its properties both experimentally and theoretically. Whereas in solution Au25(SBu)18(0) is a paramagnetic molecule, in the crystal it becomes a linear polymer of Au25 clusters connected via single Au-Au bonds and stabilized by proper orientation of clusters and interdigitation of ligands. At low temperature, [Au25(SBu)18(0)]n has a nonmagnetic ground state and can be described as a one-dimensional antiferromagnetic system. These findings provide a breakthrough into the properties and possible solid-state applications of molecular gold nanowires. PMID:25088331

  13. Interplanetary dust between 1 and 5 AU

    NASA Technical Reports Server (NTRS)

    Stanley, J. E.; Singer, S. F.; Alvarez, J. M.

    1979-01-01

    Analyses of data from the Meteoroid Detection Experiment (MDE) and the Imaging Photopolarimeter (IPP) aboard Pioneer 10 and 11 have led to contradictory conclusions. While the MDE indicates a significant particle environment in the outer solar system (out to at least 5 AU), the IPP sees no zodiacal light (therefore implying no small particles) past 3.3 AU. These two results are reconciled by noting that the spectral index p (relating particle radius and particle concentration) is not a constant in the solar system but changes from less than 2 near 1 AU to more than 2.5 at 5 AU for particles in the range of 10 microns.

  14. Bright, NIR-emitting Au23 from Au25: characterization and applications including biolabeling.

    PubMed

    Muhammed, Madathumpady Abubaker Habeeb; Verma, Pramod Kumar; Pal, Samir Kumar; Kumar, R C Arun; Paul, Soumya; Omkumar, Ramakrishnapillai Vyomakesannair; Pradeep, Thalappil

    2009-10-01

    A novel interfacial route has been developed for the synthesis of a bright-red-emitting new subnanocluster, Au(23), by the core etching of a widely explored and more stable cluster, Au(25)SG(18) (in which SG is glutathione thiolate). A slight modification of this procedure results in the formation of two other known subnanoclusters, Au(22) and Au(33). Whereas Au(22) and Au(23) are water soluble and brightly fluorescent with quantum yields of 2.5 and 1.3 %, respectively, Au(33) is organic soluble and less fluorescent, with a quantum yield of 0.1 %. Au(23) exhibits quenching of fluorescence selectively in the presence of Cu(2+) ions and it can therefore be used as a metal-ion sensor. Aqueous- to organic-phase transfer of Au(23) has been carried out with fluorescence enhancement. Solvent dependency on the fluorescence of Au(23) before and after phase transfer has been studied extensively and the quantum yield of the cluster varies with the solvent used. The temperature response of Au(23) emission has been demonstrated. The inherent fluorescence of Au(23) was used for imaging human hepatoma cells by employing the avidin-biotin interaction. PMID:19711391

  15. The Electronic Properties and L3 XANES of Au and Nano-Au

    SciTech Connect

    Yiu, Y.M.; Zhang, P.; Sham, T.K.

    2004-04-20

    The electronic properties of Au crystal and nano Au have been investigated by theory and experiment. Molecularly capped nano-Au was synthesized using the two-phase method. Au nano-particles have been characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). They retain the fcc crystal structure. Their sizes have been determined to be in a range from 5.5 nm to 1.7 nm. The L3 X-ray Absorption Near Edge Structure (XANES) of nano-Au and Au foil have been recorded using synchrotron radiation, and examined by theoretical calculation based on the first principles. Both theory and experiment show that the nano-Au particles have essentially all the Au L3 XANES features of bulk Au in the near edge region with less pronounced resonance peaks. It is also shown that nano Au exhibits lower 4f binding energy than bulk Au in good agreement with quantum confined Au systems reported previously.

  16. Comment on 'Match Analysis of U9 and U10 English Premier League Academy Soccer Players using a Global Positioning System: Relevance for Talent Identification and Development'

    PubMed

    Carling, Christopher; Collins, Dave

    2014-08-21

    We read with interest the recent article written by Goto, Morris & Nevill: 'Match Analysis of U9 and U10 English Premier League Academy Soccer Players using a Global Positioning System: Relevance for Talent Identification and Development'. In summary, the authors reported time motion analysis data from match-play showing that players who were retained by their Academy covered a significantly greater distance overall and in low-speed running in comparison to peers who were released. Consequently, the authors discussed their results in the context of talent identification and development processes. In light of their findings and discussion, it is of our opinion that further debate in the context of the current body of literature is necessary. PMID:25148464

  17. Au nanorod helical superstructures with designed chirality.

    PubMed

    Lan, Xiang; Lu, Xuxing; Shen, Chenqi; Ke, Yonggang; Ni, Weihai; Wang, Qiangbin

    2015-01-14

    A great challenge for nanotechnology is to controllably organize anisotropic nanomaterials into well-defined three-dimensional superstructures with customized properties. Here we successfully constructed anisotropic Au nanorod (AuNR) helical superstructures (helices) with tailored chirality in a programmable manner. By designing the 'X' pattern of the arrangement of DNA capturing strands (15nt) on both sides of a two-dimensional DNA origami template, AuNRs functionalized with the complementary DNA sequences were positioned on the origami and were assembled into AuNR helices with the origami intercalated between neighboring AuNRs. Left-handed (LH) and right-handed (RH) AuNR helices were conveniently accomplished by solely tuning the mirrored-symmetric 'X' patterns of capturing strands on the origami. The inter-rod distance was precisely defined as 14 nm and inter-rod angle as 45°, thus a full helix contains 9 AuNRs with its length up to about 220 nm. By changing the AuNR/origami molar ratio in the assembly system, the average number of AuNR in the helices was tuned from 2 to 4 and 9. Intense chiroptical activities arose from the longest AuNR helices with a maximum anisotropy factor of ∼0.02, which is highly comparable to the reported macroscopic AuNR assemblies. We expect that our strategy of origami templated assembly of anisotropic chiral superstructures would inspire the bottom-up fabrication of optically active nanostructures and shed light on a variety of applications, such as chiral fluids, chiral signal amplification, and fluorescence combined chiral spectroscopy. PMID:25516475

  18. Aspects cliniques des cancers bronchopulmonaires primitifs au service d'oncologie du CHUA-HUJRA Antananarivo

    PubMed Central

    Refeno, Valéry; Hasiniatsy, Nomeharisoa Rodrigue Emile; Andrianandrasana, Ny Ony Tiana Florence; Ramahandrisoa, Andriatsihoarana Voahary Nasandratriniavo; Rakotonarivo, Jean Marc; Maevazaka, Joée Larissa; Rakotovao, Hanitrala Jean Louis; Rafaramino, Florine

    2015-01-01

    Le retard de diagnostic des cancers broncho-pulmonaires est l'une des sources du retard de leur prise en charge dans les pays en développement. A notre connaissance, l'aspect clinique des cancers broncho-pulmonaires au Centre Hospitalier Universitaire d'Antananarivo-Hôpital Universitaire Joseph Ravoahangy Andrianavalona (CHUA-HUJRA) n'a jamais été étudié. L'objectif était de décrire les aspects cliniques des cancers broncho-pulmonaires primitifs dans le plus grand centre de cancérologie de Madagascar. C'est une étude rétrospective et descriptive des patients atteints de cancers broncho-pulmonaires primitifs vus au service d'oncologie du CHUA-HUJRA du 1er janvier 2008 au 31 décembre 2013. Nous avons recensé 101 patients (80 hommes et 21 femmes). Les circonstances de découverte sont principalement la toux chronique (n = 29), la dyspnée (n = 16) et l'association d'une hémoptysie à la toux chronique (n = 12). Soixante et onze patients avaient un index de performans status ≥ à 2 au moment du diagnostic. On a retrouvé des bacilles de Koch actives dans le crachat de deux patients. Le délai moyen entre l'apparition des premiers signes et la première consultation était de 11 mois. Le délai moyen entre la première consultation et le diagnostic anatomopathologique était de 3 mois. Le cancer broncho-pulmonaire peut avoir des manifestations cliniques non spécifiques parfois trompeuses qui peuvent retarder leur prise en charge. De ce fait, il doit être recherché devant tout signe respiratoire persistant. Par ailleurs, le délai de prise en charge pré-hospitalière et hospitalière de ces cancers doit être amélioré. PMID:26958134

  19. Comparison of PremierTM Rotaclone®, ProSpecTTM, and RIDASCREEN® Rotavirus Enzyme Immunoassay Kits for Detection of Rotavirus Antigen in Stool Specimens

    PubMed Central

    Gautam, Rashi; Lyde, Freda; Esona, Mathew D.; Quaye, Osbourne; Bowen, Michael D.

    2015-01-01

    Background Rotaviruses are the major cause of severe dehydrating diarrhea in children throughout the world. Enzyme immunoassays (EIA) have been the standard method for detection of rotavirus in stool specimens since the 1980s. The World Health Organization (WHO) Rotavirus Surveillance Network has proposed including three EIA kits in the WHO-GSM (Global Management System/Système Mondial de Gestion ) catalogue for easy procurement of EIA kits by participating rotavirus surveillance network laboratories. Objectives In this study, we conducted a comparative analysis of 3 commercially available enzyme immunoassay kits: PremierTM Rotaclone® (Meridian Bioscience, Inc.), ProSpecTTM (Oxoid, Ltd.) and RIDASCREEN® (R-biopharm AG) for rotavirus diagnostics. Study design Using reverse-transcriptase-PCR (RT-PCR) as the gold standard, the 3 EIA kits were evaluated by testing a stool panel consisting of 56 rotavirus-positive and 54 rotavirus negative samples. Results The sensitivities of the PremierTM Rotaclone®, ProSpecTTM and RIDASCREEN® kits were 76.8%, 75% and 82.1% respectively, but did not differ significantly. The specificity of all the 3 kits was 100%. The use of RT-PCR as a gold standard lowered the observed sensitivity of all 3 EIA kits but helps to reduce equivocal results that can be seen when another EIA or other non-molecular methods are used as the reference assay in comparison studies. Conclusion Our study found that all three kits are suitable for use by rotavirus surveillance programs. PMID:23850415

  20. Oxygen-assisted reduction of Au species on Au/SiO2 catalyst in room temperature CO oxidation

    SciTech Connect

    Wu, Zili; Zhou, Shenghu; Zhu, Haoguo; Dai, Sheng; Overbury, Steven {Steve} H

    2008-01-01

    An unexpected oxygen-assisted reduction of cationic Au species by CO was found on a Au/SiO2 catalyst at room temperature; CO oxidation activity increases simultaneously with the reduction of Au species, suggesting the key role of metallic Au played in CO oxidation on Au/SiO2.

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

    PubMed

    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 (G<0) in the average year 2010-2011, with net lateral inflow from adjacent Cambrian formations being the largest recharge component. R is expected to be much less than PI+PU in recurrent dry spells. Some low-technology 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. PMID:26282765

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

    NASA Astrophysics Data System (ADS)

    Jacquet, Emmanuel; Alard, Olivier; Gounelle, Matthieu

    2015-09-01

    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 of opaque nodules found outside them in EH chondrites. In two chondrules, olivine and enstatite exhibit negatively sloped REE patterns, which may be an extreme manifestation of a general phenomenon (possibly linked to near-liquidus partitioning) underlying the overabundance of light REE observed in most chondrule silicates relative to equilibrium predictions. The silicate phases in one of these two chondrules show complementary Eu, Yb, and Sm anomalies providing direct evidence for the postulated occurrence of the divalent state for these elements at some stage in the formation reservoir of enstatite chondrites. Our work supports the idea that the peculiarities of enstatite chondrites may not require a condensation sequence at high C/O ratios as has long been believed.

  3. Lagrangian dust model simulations for a case of moist convective dust emission and transport in the western Sahara region during Fennec/LADUNEX

    NASA Astrophysics Data System (ADS)

    Sodemann, H.; Lai, T. M.; Marenco, F.; Ryder, C. L.; Flamant, C.; Knippertz, P.; Rosenberg, P.; Bart, M.; McQuaid, J. B.

    2015-06-01

    Due to the harshness and inaccessibility of desert regions, the uncertainties concerning the processes of dust mobilization at the surface, airborne transport, and sedimentation are still considerable, limiting the ability to perform model simulations. In June 2011, a comprehensive data set of ground-based and airborne in situ measurements and remote sensing observations was acquired within the Fennec/Lagrangian Dust Source Inversion Experiment (LADUNEX) field campaign in the western Sahara region. Here we evaluate the ability of the state-of-the-art Lagrangian particle dispersion model FLEXPART, newly fitted with a dust mobilization capability, to simulate dust transport in this region. We investigate a case where a large mesoscale convective system (MCS) triggered dust emissions in central Mali, which subsequently moved as a large cold pool dust front toward northern Mauritania. Specifying dust mobilization for this case is shown to be an important obstacle to simulating dust transport during this event, since neither the MCS nor the associated cold pool-causing dust emission is represented in the meteorological analysis. Obtaining a realistic dust transport simulation for this case therefore requires an inversion approach using a manual specification of the dust sources supported by satellite imagery. When compared to in situ and remote sensing data from two aircraft, the Lagrangian dust transport simulations represent the overall shape and evolution of the dust plume well. While accumulation and coarse mode dust are well represented in the simulation, giant mode particles are considerably underestimated. Our results re-emphasize that dust emission associated with deep moist convection remains a key issue for reliable dust model simulations in northern Africa.

  4. Impact of Climate Change on the Relict Tropical Fish Fauna of Central Sahara: Threat for the Survival of Adrar Mountains Fishes, Mauritania

    PubMed Central

    Trape, Sébastien

    2009-01-01

    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 repeated. PMID:19204792

  5. GHYRAF (Gravity and HYdrology in AFrica): a New Experiment Combining Hydrology and Geodesy to Investigate Water Storage Changes from the Sahara to the Equatorial Monsoon Zone.

    NASA Astrophysics Data System (ADS)

    de Linage, C.; Hinderer, J.; Boy, J.; Masson, F.; Gegout, P.; Diament, M.; de Viron, O.; Bayer, R.; Balmino, G.; Biancale, R.; Bonvalot, S.; Genthon, P.

    2007-12-01

    We present a new project using multi-disciplinary data (gravity, geodesy, hydrology, and meteorology) to determine seasonal changes in water storage in Africa. We foresee to concentrate on two areas: the desert zone in the Sahara (Tamanrasset, Algeria) where almost no hydrological change is present, and the equatorial monsoon band (Niger, Benin Republic) that provides on the contrary a large rainfall signal. This project will be a first attempt to do a ground validation of satellite-derived gravity observations such as GRACE or GOCE in Africa. We will pay attention to the various length scales involved in hydrological processes that are differently retrieved whether gravity is measured at the ground or by satellite. Our experience includes two types of ground-based gravity measurements. First we will perform a repeated survey with absolute gravimeters (AG) on a North-South profile during 2-3 years (2008-2010) to assess the large soil moisture changes as predicted by existing hydrological models such as GLDAS or LadWorld. Second we plan to establish a superconducting gravimeter (SG) to act as a continuously monitored base station in a region of large soil moisture changes. In addition, continuous geodetic GPS measurements will be made along the gravity profile to assess the vertical deformation which acts to alter ground gravity but not satellite gravity. In-situ measurements of hydrological parameters at each station will assist us in modelling local gravity effects. The goal is a better characterization of continental water storage, particularly in the critical areas of water management in the north and central parts of the African continent.

  6. [(CF3)4Au2(C5H5N)2]--a new alkyl gold(II) derivative with a very short Au-Au bond.

    PubMed

    Zopes, David; Hegemann, Corinna; Tyrra, Wieland; Mathur, Sanjay

    2012-09-11

    A new gold(II) species [(CF(3))(4)Au(2)(C(5)H(5)N)(2)] with a very short unsupported Au-Au bond (250.62(9) pm) was generated by photo irradiation of a silver aurate, [Ag(Py)(2)][Au(CF(3))(2)], unambiguously characterized by (19)F and (109)Ag NMR studies. PMID:22836874

  7. Thermal and photoinduced reduction of ionic Au(III) to elemental Au nanoparticles by dissolved organic matter in water: possible source of naturally occurring Au nanoparticles.

    PubMed

    Yin, Yongguang; Yu, Sujuan; Liu, Jingfu; Jiang, Guibin

    2014-01-01

    Naturally occurring Au nanoparticles (AuNPs) have been widely observed in ore deposits, coal, soil, and environmental water. Identifying the source of these naturally occurring AuNPs could be helpful for not only the discovery of Au deposits through advanced exploration methods, but also the elucidation of the biogeochemical cycle and environmental toxicity of ionic Au and engineered AuNPs. Here, we investigated the effect of natural/simulated sunlight and heating on the reduction of ionic Au by ubiquitous dissolved organic matter (DOM) in river water. The reductive process probed by X-ray photoelectron spectroscopy revealed that phenolic, alcoholic, and aldehyde groups in DOM act as reductive sites. Long-time exposure with thermal and photoirradiation induced the further fusion and growth of AuNPs to branched Au nanostructure as precipitation. The formation processes and kinetics of AuNPs were further investigated using humic acid (HA) as the DOM model, with comprehensive characterizing methods. We have observed that HA can reduce ionic Au(III) complex (as chloride or hydroxyl complex) to elemental Au nanoparticles under sunlight or heating. In this process, nearly all of the Au(III) could be reduced to AuNPs, in which HA serves as not only the reductive agent, but also the coating agent to stabilize and disperse AuNPs. The size and stability of AuNPs were highly dependent on the concentration ratio of Au(III) to HA. These results imply that, besides biological processes, this thermal or photochemical reduction process is another possible source of naturally occurring AuNPs in natural environments, which possibly has critical impacts on the transport and transformation of Au and engineered AuNPs. PMID:24471802

  8. Discours prononce au cours du diner offert a l'issue du premier congres de l'API (Address Given on the Occasion of the First Meeting of the API)

    ERIC Educational Resources Information Center

    Spicer, Keith

    1978-01-01

    The speech, half in French and half in English, is an endorsement of the association, an indication of political, social and educational reforms it might influence, a reminder that members of the association, Canadian Parents for French, were present and interested, and an appeal for good public relations. (AMH)

  9. Self-assembly of thiolated cyanine aggregates on Au(111) and Au nanoparticle surfaces

    NASA Astrophysics Data System (ADS)

    Menéndez, Guillermo O.; Cortés, Emiliano; Grumelli, Doris; Méndez de Leo, Lucila P.; Williams, Federico J.; Tognalli, Nicolás G.; Fainstein, Alejandro; Vela, María Elena; Jares-Erijman, Elizabeth A.; Salvarezza, Roberto C.

    2012-01-01

    Heptamethinecyanine J-aggregates display sharp, intense fluorescence emission making them attractive candidates for developing a variety of chem-bio-sensing applications. They have been immobilized on planar thiol-covered Au surfaces and thiol-capped Au nanoparticles by weak molecular interactions. In this work the self-assembly of novel thiolated cyanine (CNN) on Au(111) and citrate-capped AuNPs from solutions containing monomers and J-aggregates has been studied by using STM, XPS, PM-IRRAS, electrochemical techniques and Raman spectroscopy. Data show that CNN species adsorb on the Au surfaces by forming thiolate-Au bonds. We found that the J-aggregates are preferentially adsorbed on the Au(111) surface directly from the solution while adsorbed CNN monomers cannot organize into aggregates on the substrate surface. These results indicate that the CNN-Au interaction is not able to disorganize the large J-aggregates stabilized by π-π stacking to optimize the S-Au binding site but it is strong enough to hinder the π-π stacking when CNNs are chemisorbed as monomers. The optical properties of the J-aggregates remain active after adsorption. The possibility of covalently bonding CNN J-aggregates to Au planar surfaces and Au nanoparticles controlling the J-aggregate/Au distance opens a new path regarding their improved stability and the wide range of biological applications of both CNN and AuNP biocompatible systems.Heptamethinecyanine J-aggregates display sharp, intense fluorescence emission making them attractive candidates for developing a variety of chem-bio-sensing applications. They have been immobilized on planar thiol-covered Au surfaces and thiol-capped Au nanoparticles by weak molecular interactions. In this work the self-assembly of novel thiolated cyanine (CNN) on Au(111) and citrate-capped AuNPs from solutions containing monomers and J-aggregates has been studied by using STM, XPS, PM-IRRAS, electrochemical techniques and Raman spectroscopy. Data show

  10. Photoionization of Au+, Au2+, and Au3+ ions and developments in the synthesis of the metallofullerene Au@C60

    NASA Astrophysics Data System (ADS)

    Kilcoyne, A. L. David; Muller, Alfred; Schippers, Stefan; Hellhund, Jonas; Borovik, Alexander; Mueller, Allison; Gross, Dylan; Johnson, Andrea; Macaluso, David; A. L. D. Kilcoyne Collaboration

    2015-05-01

    Absolute single photoionization of Au+, Au2+, and Au3+ ions was investigated via the merged-beams technique at AMO Beamline 10.0.1.2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. The absolute single photoionization yield was measured as a function of photon energy for each species from the metastable state ionization threshold region to well above the ground state ionization potential. Additional high-resolution measurements were performed for Au+ and Au2+ ions in the region of the ground and metastable state ionization thresholds to better resolve the detailed resonant structure found therein. This structure was used, along with the reported excited state energy levels of Au+, to preliminarily identify previously unreported excitation levels in all three ions. In addition and as a component of the same program, photoionization studies of the endohedral metallofullerene Au@C60+were performed using endohedral fullerene samples synthesized on-site at Beamline 10.0.1.2 of the ALS.