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Alex Mackay - One of the best experts on this subject based on the ideXlab platform.
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why was silcrete heat treated in the middle stone age an early transformative technology in the context of Raw Material Use at mertenhof rock shelter south africa
PLOS ONE, 2016Co-Authors: Patrick Schmidt, Alex MackayAbstract:People heat treated silcrete during the Middle Stone Age (MSA) in southern Africa but the spatial and temporal variability of this practice remains poorly documented. This paucity of data in turn makes it difficult to interrogate the motive factors underlying the application of this technique. In this paper we present data on heat treatment of silcrete through the Howiesons Poort and post-Howiesons Poort of the rock shelter site Mertenhof, located in the Western Cape of South Africa. In contrast to other sites where heat treatment has been documented, distance to rock source at Mertenhof can be reasonably well estimated, and the site is known to contain high proportions of a diversity of fine grained rocks including silcrete, hornfels and chert at various points through the sequence. Our results suggest the prevalence of heat treatment is variable through the sequence but that it is largely unaffected by the relative abundance of silcrete prevalence. Instead there is a strong inverse correlation between frequency of heat treatment in silcrete and prevalence of chert in the assemblage, and a generally positive correlation with the proportion of locally available rock. While it is difficult to separate individual factors we suggest that, at Mertenhof at least, heat treatment may have been Used to improve the fracture properties of silcrete at times when other finer grained rocks were less readily available. As such, heat treatment appears to have been a component of the MSA behavioural repertoire that was flexibly deployed in ways sensitive to other elements of technological organisation.
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Catchment Survey in the Karonga District: a Landscape-Scale Analysis of Provisioning and Core Reduction Strategies During the Middle Stone Age of Northern Malawi
African Archaeological Review, 2014Co-Authors: Jessica C. Thompson, Alex Mackay, Victor Moor, Elizabeth Gomani-chindebvuAbstract:Le paysage du nord du Malawi est caractérisé par la présence de divers bassins hydrographiques des rivières qui s’écoulent des régions montagneUses de l’ouest vers le Lake Malawi, à l’est. Des milliers d’artefacts de l’Âge de la pierre moyen (MSA) sont dispersés dans ce paysage, en particulier dans les zones où les sédiments de Chitimwe Beds sont exposés. La richesse et le caractère unique de ce paysage, permettent de soulever de nouvelles questions concernant le mode de vie des hommes de MSA. Ces nouvelles questions enrichissent les informations apportées par les fouilles. Dans cette recherche, des données, sur lesquelles celle-ci a été basée, proviennent de ‘surveys’ effectuées en 2012 qui avaient pour objectif de découvrir la manière dont la matière première lithique (sous forme de pavés) et les industries lithiques (sous la forme de nucléus) sont réparties à travers le paysage. Ces données ont été tout d’abord utilisées pour examiner s’il existe des différences dans le débitage sur nucléus dans diverses zones à bassins hydrographiques ayant des quantités et des qualités de matière première diverses et ensuite pour vérifier les hypothèses concernant les différentes options d’approvisionnement lithique. Les résultats mettent en lumière que différents bassins hydrographiques laissent entrevoir des différences dans la qualité et la quantité de matière première. Les quartzites de meilleure qualité sont présents dans le bassin hydrographique de la rivière North Rukuru mais cette présence diminue en allant vers le sud. Ceci est reflété dans le choix du type de matière première fait par les hommes MSA pour la production de leurs outils. Néanmoins, les différences dans la sélection de matière première et la distance des pavés n’ont pas eu d’influences sur le débitage sur nucléus qu’ils préféraient. Cela suggère de ce fait que tout au long de MSA, les techniques de débitage du nord du Malawi étaient hautement conservatives et cela en dépit de la diversité de matière première présente et les nucléus n’étaient pas régulièrement transportés comme faisant partie d’une stratégie d’approvisionnement. The landscape of northern Malawi is defined by several river catchments that drain from the highlands in the west into Lake Malawi in the east. Many thousands of Middle Stone Age (MSA) artefacts are present on the surface, in particular, in areas where sedimentary units assigned to the Chitimwe Beds are exposed. The unique configuration of the region and its exposures makes it possible to address landscape-scale questions about MSA behaviour that augment information derived from excavated assemblages. In this study, data are derived from initial results of surveys conducted in 2012 which focussed on how lithic Raw Materials (in the form of cobbles) and core technology (in the form of mapped and analysed cores) are distributed across the landscape relative to different landforms, geologies and one another. These data are Used to examine if differences in core reduction technology occur in different catchment areas with different Raw Material quantities and qualities, and to test hypotheses about lithic provisioning scenarios. This allows for examination of core reduction technologies in relation to Raw Material sources via surface finds, on a larger regional scale than is usually possible from excavations. Different catchments show differences in the type and quality of the Raw Material, with higher-quality quartzites occurring in the North Rukuru catchment and declining to the south. This is reflected in the types of Materials that MSA people chose to Use for the production of stone tools. However, differences in Raw Material selection and distance from cobbles did not influence preferred core reduction strategies, and most cores cluster together near cobble sources. This suggests that throughout the MSA in the study area, core reduction strategies were highly conserved even while Raw Material Use remained flexible, and cores were not regularly transported as part of a provisioning strategy.
Gara Villalba - One of the best experts on this subject based on the ideXlab platform.
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Raw Material Use in a battery electric car a thermodynamic rarity assessment
Resources Conservation and Recycling, 2020Co-Authors: Alicia Valero, Abel Ortego, Mar Villacampa, Josep Vilaró, Marta Iglesiasembil, Gara VillalbaAbstract:Abstract The transition to full electromobility must be carefully evaluated, as large amounts of strategic metals will be required, for which there is presently little to no recovery or recycling (e.g. gold, silver, tantalum or cobalt). In this study, we perform a comprehensive metal assessment of two passenger cars (conventional and battery electric models) in terms of mass and thermodynamic rarity. Thermodynamic rarity is based on the property of exergy and is defined as “the amount of exergy resources needed to obtain a mineral commodity from average crustal concentration using the best available technology” (measured in kJ). Thus, the thermodynamic rarity approach assigns a greater exergetic value to scarce (understood as having a relative low average crustal concentration) and difficult-to-extract minerals. Of the 60 metals analyzed, almost 50 metals have been identified within the studied cars, representing 800 (conventional) and 1,200 kg (battery electric), showcasing the fact that a car constitutes a “road mine”. Furthermore, given that the technology behind battery electric cars is in development, three generations of Li-ion batteries were analyzed to study the effect on resource Use of a metal changing composition over time. Albeit the battery modules of the three generations present a similar mass content (approximately 70 kgs), the thermodynamic rarity decreases from 275 to 100 Gigajoules, due to the reduced proportion of cobalt, which is by far the most exergetic metal within the battery. Additionally, with the thermodynamic rarity approach, the most exergy intensive parts within a battery electric car have been identified – the high-voltage battery modules, the electric drive, the power module, the charger, the electrical air conditioning compressor and the electromechanical brake servo – providing an indicator facilitating proactive mid- to long-term ecodesign measures and recycling strategies.
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Raw Material Use in a battery electric car – a thermodynamic rarity assessment
Resources Conservation and Recycling, 2020Co-Authors: Marta Iglesias-Émbil, Alicia Valero, Abel Ortego, Mar Villacampa, Josep Vilaró, Gara VillalbaAbstract:Abstract The transition to full electromobility must be carefully evaluated, as large amounts of strategic metals will be required, for which there is presently little to no recovery or recycling (e.g. gold, silver, tantalum or cobalt). In this study, we perform a comprehensive metal assessment of two passenger cars (conventional and battery electric models) in terms of mass and thermodynamic rarity. Thermodynamic rarity is based on the property of exergy and is defined as “the amount of exergy resources needed to obtain a mineral commodity from average crustal concentration using the best available technology” (measured in kJ). Thus, the thermodynamic rarity approach assigns a greater exergetic value to scarce (understood as having a relative low average crustal concentration) and difficult-to-extract minerals. Of the 60 metals analyzed, almost 50 metals have been identified within the studied cars, representing 800 (conventional) and 1,200 kg (battery electric), showcasing the fact that a car constitutes a “road mine”. Furthermore, given that the technology behind battery electric cars is in development, three generations of Li-ion batteries were analyzed to study the effect on resource Use of a metal changing composition over time. Albeit the battery modules of the three generations present a similar mass content (approximately 70 kgs), the thermodynamic rarity decreases from 275 to 100 Gigajoules, due to the reduced proportion of cobalt, which is by far the most exergetic metal within the battery. Additionally, with the thermodynamic rarity approach, the most exergy intensive parts within a battery electric car have been identified – the high-voltage battery modules, the electric drive, the power module, the charger, the electrical air conditioning compressor and the electromechanical brake servo – providing an indicator facilitating proactive mid- to long-term ecodesign measures and recycling strategies.
Siti Zullaikah - One of the best experts on this subject based on the ideXlab platform.
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lipase catalyzed production of biodiesel from rice bran oil
Journal of Chemical Technology & Biotechnology, 2005Co-Authors: Siti Zullaikah, Shaik Ramjan Vali, Yihsu JuAbstract:Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the Raw Material. Use of an inexpensive Raw Material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two-step lipase-catalyzed methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4–6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil. Copyright © 2005 Society of Chemical Industry
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Lipase‐catalyzed production of biodiesel from rice bran oil
Journal of Chemical Technology & Biotechnology, 2005Co-Authors: Chao-chin Lai, Siti Zullaikah, Ramjan ValiAbstract:Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the Raw Material. Use of an inexpensive Raw Material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (
Tom Minichillo - One of the best experts on this subject based on the ideXlab platform.
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Raw Material Use and behavioral modernity: Howiesons Poort lithic foraging strategies.
Journal of human evolution, 2006Co-Authors: Tom MinichilloAbstract:In an important early attempt to apply behavioral ecological modeling to lithic resource Use and the archaeological record, Ambrose and Lorenz (1990) investigated the problem of the Howiesons Poort sub-stage (HP) in the southern African Middle Stone Age (MSA). In that paper, Ambrose and Lorenz compared general mobility patterns (based on lithic Raw Material occurrences) to the general environmental setting to reach the conclusion that MSA people behaved in a way that was different from any modern peoples, whether ethnographically or archaeologically characterized. At the time of its writing, this work was Used to support the idea that MSA people, during the period of time prior to that which the HP represents, were not behaving in a fully modern fashion. More recently, Ambrose (2002) revisited the Use of Raw Materials in the HP. Although no longer positing ‘‘non-modern’’ behavior, this paper continued to try and explain a pattern of a marked increase of fine-grained Raw Material Use in comparison to other MSA components at Klasies by invoking distant sources for these Materials. As Ambrose and Lorenz (1990) is
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News and Views Raw Material Use and behavioral modernity: Howiesons Poort lithic foraging strategies
2006Co-Authors: Tom MinichilloAbstract:(HP) in the southern AfricanMiddle Stone Age (MSA). In that paper, Ambrose and Lorenzcompared general mobility patterns (based on lithic Raw mate-rial occurrences) to the general environmental setting to reachthe conclusion that MSA people behaved in a way that wasdifferent from any modern peoples, whether ethnographicallyor archaeologically characterized. At the time of its writing,this work was Used to support the idea that MSA people, dur-ing the period of time prior to that which the HP represents,were not behaving in a fully modern fashion.More recently, Ambrose (2002) revisited the Use of Raw ma-terials in the HP. Although no longer positing ‘‘non-modern’’behavior, this paper continued to try and explain a pattern ofa marked increase of fine-grained Raw Material Use in compar-ison to other MSA components at Klasies by invoking distantsources for these Materials. As Ambrose and Lorenz (1990) isone of only two explicit published models (for the other, seeDeacon and Wurz, 1996; Wurz, 1997, 1999, 2000; Deaconand Deacon, 1999) that attempts to explain the HP pattern,one of its basic underlying premises is examined further here.The assertion that MSA peoples did not behave in waysanalogous to modern peoples has special importance in the de-bate over modern human origins. Several models have beenproposed for the timing and nature of this event (McBreartyand Brooks, 2000; Henshilwood and Marean, 2003). In onlyone of these proposed models, the later upper Pleistocenemodel (or the neural advance model; Klein, 1995, 1999), isit posited that modern behaviors arose after the HP, andAmbrose and Lorenz (1990) is one of the few empiricallybased studies that supports that model.The Howiesons Poort sub-stageAs originally defined by Stapleton and Hewitt (1928, 1929)at the name-bearing site (the Howieson’s Poort shelter nearGrahamstown, South Africa; Fig. 1), the HP was a ‘‘lithic in-dustry’’ of the MSA. Deacon (1995) provided a discussion ofthe history of excavation at that site and numerous artifactillustrations. Thackeray (1992) provided an overview of HPoccurrences and their stratigraphic location within the MSA.She demonstrated that the HP occurs within the MSA se-quence and is not a transitional entity between the MSA andthe Later Stone Age (LSA), as was once thought (e.g., Bin-ford, 1984). A major HP horizon was identified at the KlasiesRiver cave sites by John Wymer in the 1960s, and it is thatpublished assemblage (Singer and Wymer, 1982) that was uti-lized by Ambrose and Lorenz (1990) to explore Raw Material
Ramjan Vali - One of the best experts on this subject based on the ideXlab platform.
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Lipase‐catalyzed production of biodiesel from rice bran oil
Journal of Chemical Technology & Biotechnology, 2005Co-Authors: Chao-chin Lai, Siti Zullaikah, Ramjan ValiAbstract:Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the Raw Material. Use of an inexpensive Raw Material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (
