scholarly journals Monsoon-driven Saharan dust variability over the past 240,000 years

2019 ◽  
Vol 5 (1) ◽  
pp. eaav1887 ◽  
Author(s):  
C. Skonieczny ◽  
D. McGee ◽  
G. Winckler ◽  
A. Bory ◽  
L. I. Bradtmiller ◽  
...  
Keyword(s):  
West African ◽  
Hominid Evolution ◽  
Saharan Dust ◽  
Improved Method ◽  
Dust Deposition ◽  
North African ◽  
Glacial Cycles ◽  
Low Latitude ◽  
Dust Emissions ◽  
The Past

Reconstructions of past Saharan dust deposition in marine sediments provide foundational records of North African climate over time scales of 103to 106years. Previous dust records show primarily glacial-interglacial variability in the Pleistocene, in contrast to other monsoon records showing strong precessional variability. Here, we present the first Saharan dust record spanning multiple glacial cycles obtained using230Th normalization, an improved method of calculating fluxes. Contrary to previous data, our record from the West African margin demonstrates high correlation with summer insolation and limited glacial-interglacial changes, indicating coherent variability in the African monsoon belt throughout the late Pleistocene. Our results demonstrate that low-latitude Saharan dust emissions do not vary synchronously with high- and mid-latitude dust emissions, and they call into question the use of existing Plio-Pleistocene dust records to investigate links between climate and hominid evolution.

scholarly journals Rapid increase in simulated North Atlantic dust deposition due to fast change of northwest African landscape during the Holocene

2018 ◽  
Vol 14 (7) ◽  
pp. 1051-1066 ◽  
Author(s):  
Sabine Egerer ◽  
Martin Claussen ◽  
Christian Reick
Keyword(s):  
North Atlantic ◽  
Marine Sediment ◽  
Sudden Increase ◽  
Dust Deposition ◽  
North African ◽  
Western Sahara ◽  
Dust Emissions ◽  
The North ◽  
Dust Sources ◽  
Sediment Records

Abstract. Marine sediment records from a series of core sites along the northwest African margin show a sudden increase in North Atlantic dust deposition at about 5 ka BP that has been associated with an abrupt end of the African Humid Period (AHP). To assess the causes of the abrupt shift in North Atlantic dust deposition, we explore changes in the Holocene dust cycle and in North African climate and landscape by performing several time slice simulations from 8 ka BP until the preindustrial era. To do this, we use the coupled aerosol–climate model ECHAM6–HAM2 including dynamic vegetation and interactive dust, wherein ocean conditions and lake surface area are prescribed for each time slice. We find a rapid increase in simulated dust deposition between 6 and 4 ka BP that is fairly consistent with the abrupt change in marine sediment records at around 20∘ N close to the northwest African margin. At more northern and more remote cores, a significant change in dust deposition is noticeable roughly between 6 and 2 ka BP in the simulations as well as in the records, but the change is less sharp compared to the near-margin core sites. The rapid change in simulated dust deposition is caused by a rapid increase in simulated dust emissions in the western Sahara, where the main dust sources for dust transport towards the North Atlantic are located. The sudden increase in dust emissions in the western Sahara is according to our simulations a consequence of a fast decline of vegetation cover from 22 to 18∘ N that might occur due to vegetation–climate feedbacks or due to the existence of a precipitation threshold on vegetation growth. Additionally, the prescribed gradual reduction of lake area enforces accelerated dust release as highly productive dust sources are uncovered. Concurrently with the continental drying, surface winds in the western Sahara are accelerated. Changes in the Saharan landscape and dust emissions south of 18∘ N and in the eastern Sahara play a minor role in driving the dynamics of North Atlantic dust deposition at the core sites. Our study identifies spatial and temporal heterogeneity in the transition of the North African landscape. As a consequence, implications from local data records on large-scale climate have to be treated with caution.

scholarly journals How a West African language becomes North African, and vice versa

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lameen Souag
Keyword(s):  
Comparative Method ◽  
West African ◽  
North African ◽  
Quantitative Evidence ◽  
The Past ◽  
Semantic Maps ◽  
Language Area ◽  
West African Sahel ◽  
First Time ◽  
African Sahel

Abstract Updating the methodology of Hayward, Richard J. 1991. A propos patterns of lexicalization in the Ethiopian language area. In Daniela Mendel & Ulrike Claudi (eds.), Ägypten im afroorientalischen Kontext. Special issue of Afrikanistische Arbeitspapiere, 139–156. Cologne: Institute of African Studies, using the concept of colexification (François, Alexandre. 2008. Semantic maps and the typology of colexification: Intertwining polysemous networks across languages. In Martine Vanhove (ed.), Studies in language companion series, vol. 106, 163–215. Amsterdam: John Benjamins), this paper, for the first time, provides quantitative evidence that the languages of the West African Sahel/Savanna form a lexical-typological language area characterised by shared colexifications absent further north. It then uses the linguistic comparative method to determine how languages entering or leaving this area, or coming into increasing contact with it at its edges, have converged with their new neighbours within the past millennium. The results indicate sharp differences in the respective roles and rates of borrowing and calquing, with the latter acting almost exclusively to increase shared colexifications.

Geochemical fingerprints and North-African dust sources: results from a multisite network of aerosol deposition in the south-western Europe

2021 ◽  
Author(s):  
Jorge Pey ◽  
Juan Cruz Larrasoaña ◽  
Jesús Reyes ◽  
Noemí Pérez ◽  
José Carlos Cerro ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
Source Apportionment ◽  
Saharan Dust ◽  
Dust Particles ◽  
Dust Deposition ◽  
North African ◽  
Desert Dust ◽  
African Dust ◽  
Dust Sources ◽  
The Impact

<p><strong>Abstract</strong></p><p>The DONAIRE network (Pey et al. 2020) monitors the phenomenology of geochemical, magnetic and mineralogical variations of bulk atmospheric deposition in the Iberian Peninsula- Balearic Island. In this work we focus on recent North African dust deposition with a double objective: 1) to characterize the main geochemical fingerprints with respect to other sources of pollution; 2) to perform a source apportionment study to identify different desert-dust source areas. We used one year of data (June 2016-July 2017) from 15 monitoring sites (regional and remote, urban, industrial, or agricultural). We focus here on the impact caused by the main 4 North African dust deposition events globally affected this network.</p><p>Our results evidence that dust deposition patterns are controlled by: i) the meteorological scenario behind dust transport, ii) the occurrence/absence of wet deposition, and iii) the local-to-regional nearby topography. In general, the largest dust-deposition events occur nearby mountain barriers during low-pressure systems approaching Iberia and NW Africa.</p><p>Moderate to intense dust deposition events are well characterized by their chemical composition. The Fe/Ti, Na/Al, K/Al or (Ca+Mg)/Fe ratios reveal a number of patterns across the network. For example, Fe/Ti ratio varies from around 10-13 during warm-season events to 22-35 during cold season episodes, potentially indicating different North-African dust sources.</p><p>The best source apportionment solution extracts 10 factor/sources, from which three are mineral in composition. Two of them are interpreted as different North African dust mixture-of-sources, whereas the third mineral factor corresponds to regional dust particles. The overall contribution of such desert-dust sources may explain up to 90% of total episodic deposition during the most intense events.</p><p>These results indicate that chemical fingerprinting could be used to infer the recent North African dust deposition history. Studies on lake and peatland sequences following a similar approach are in progress and preliminary data show they be used to trace Saharan dust during the Holocene and reconstruct its relationship with climate phases.</p><p> </p><p><strong>Reference</strong></p><p>Pey J., Larrasoaña J.C., Pérez N., Cerro J.C., Castillo S. <em>et al.</em> (2020). Phenomenology and geographical gradients of atmospheric deposition in southwestern Europe: results from a multi-site monitoring network. <em>Sci. Tot. Environ.</em>, 140745. https://doi.org/10.1016/j.scitotenv.2020.140745.</p><p> </p><p><strong>Acknowledgements</strong></p><p>POSAHPI (PID2019-108101RB-I00) and DONAIRE (CGL2015-68993-R) projects funded by Spanish Agencia Estatal de Investigación and FEDER Funds.</p>

Introduction

2018 ◽  
Author(s):  
Jesse A. Hoover
Keyword(s):  
North African ◽  
The Past

The Introduction offers a brief overview of the rationale behind writing this book and clarifies significant issues which must be addressed before proceeding. In particular, it explains why the apocalyptic predictions of a long-dead ecclesial community are worth investigating, as well as reasons why this topic has not been extensively studied in the past. A brief overview of the following chapters follows, as well as a note on the chronological boundaries of the project. In addition, the Introduction clarifies significant terms which appear throughout the text, including the use of the word “apocalyptic” and attendant vocabulary and neutral terminology for the two opposing North African ecclesial factions.

scholarly journals Monitoring Australian Monsoon variability over the past four glacial cycles

2021 ◽  
Vol 568 ◽  
pp. 110280
Author(s):  
Renjie Pei ◽  
Wolfgang Kuhnt ◽  
Ann Holbourn ◽  
Johanna Hingst ◽  
Matthias Koppe ◽  
...  
Keyword(s):  
Glacial Cycles ◽  
Australian Monsoon ◽  
The Past ◽  
Monsoon Variability

scholarly journals Equine-Origin Immunoglobulin Fragments Protect Nonhuman Primates from Ebola Virus Disease

2018 ◽  
Vol 93 (5) ◽  
Author(s):  
Hualei Wang ◽  
Gary Wong ◽  
Wenjun Zhu ◽  
Shihua He ◽  
Yongkun Zhao ◽  
...  
Keyword(s):  
Large Scale ◽  
Nonhuman Primates ◽  
Ebola Virus ◽  
Virus Disease ◽  
Hemorrhagic Fever ◽  
West African ◽  
Clinical Testing ◽  
The Past ◽  
Over 40 Years

ABSTRACT Ebola virus (EBOV) infections result in aggressive hemorrhagic fever in humans, with fatality rates reaching 90% and with no licensed specific therapeutics to treat ill patients. Advances over the past 5 years have firmly established monoclonal antibody (MAb)-based products as the most promising therapeutics for treating EBOV infections, but production is costly and quantities are limited; therefore, MAbs are not the best candidates for mass use in the case of an epidemic. To address this need, we generated EBOV-specific polyclonal F(ab′)2 fragments from horses hyperimmunized with an EBOV vaccine. The F(ab′)2 was found to potently neutralize West African and Central African EBOV in vitro. Treatment of nonhuman primates (NHPs) with seven doses of 100 mg/kg F(ab′)2 beginning 3 or 5 days postinfection (dpi) resulted in a 100% survival rate. Notably, NHPs for which treatment was initiated at 5 dpi were already highly viremic, with observable signs of EBOV disease, which demonstrated that F(ab′)2 was still effective as a therapeutic agent even in symptomatic subjects. These results show that F(ab′)2 should be advanced for clinical testing in preparation for future EBOV outbreaks and epidemics. IMPORTANCE EBOV is one of the deadliest viruses to humans. It has been over 40 years since EBOV was first reported, but no cure is available. Research breakthroughs over the past 5 years have shown that MAbs constitute an effective therapy for EBOV infections. However, MAbs are expensive and difficult to produce in large amounts and therefore may only play a limited role during an epidemic. A cheaper alternative is required, especially since EBOV is endemic in several third world countries with limited medical resources. Here, we used a standard protocol to produce large amounts of antiserum F(ab′)2 fragments from horses vaccinated with an EBOV vaccine, and we tested the protectiveness in monkeys. We showed that F(ab′)2 was effective in 100% of monkeys even after the animals were visibly ill with EBOV disease. Thus, F(ab′)2 could be a very good option for large-scale treatments of patients and should be advanced to clinical testing.

scholarly journals We Are what We Eat: Food in the Process of Community Formation and Identity Shaping among African Traders in Guangzhou and Yiwu

2012 ◽  
Vol 5 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Adams Bodomo ◽  
Enyu Ma
Keyword(s):  
Eating Habits ◽  
West African ◽  
Community Identity ◽  
Community Formation ◽  
North African ◽  
Black Africans ◽  
Black African ◽  
The One ◽  
Cohesive Interaction

Abstract In this paper we analyze two African communities in Guangzhou and Yiwu, China, arguing that among Guangzhou Africans on the one hand, Black Africans, particularly West Africans, have a tighter community and interact more with each other than Black Africans in Yiwu. On the other hand, Maghrebian Africans in Yiwu have a tighter community and maintain a more cohesive interaction than their counterparts in Guangzhou. Evidence for this characterization of the communities comes from food and communal food-eating habits. There are hardly any West African restaurants in Yiwu while there is an abundance of West African and other Black African restaurants in Guangzhou where there is more community patronage. In contrast, there are more concentrations of North African restaurants in Yiwu than in Guangzhou. We discuss the crucial role food and food-making and eating places play in providing structures and avenues for community bonding to promote community formation and community identity shaping.

scholarly journals Saharan Dust Deposition Effects on the Microbial Food Web in the Eastern Mediterranean: A Study Based on a Mesocosm Experiment

2017 ◽  
Vol 4 ◽  
Author(s):  
Paraskevi Pitta ◽  
Maria Kanakidou ◽  
Nikolaos Mihalopoulos ◽  
Sylvia Christodoulaki ◽  
Panagiotis D. Dimitriou ◽  
...  
Keyword(s):  
Food Web ◽  
Eastern Mediterranean ◽  
Mesocosm Experiment ◽  
Saharan Dust ◽  
Microbial Food Web ◽  
Dust Deposition
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