138 research outputs found
Experimental Investigations on Combustion Pollutant Emissions of Sunflower Biodiesel and Its Blends with Diesel and Kerosene for Furnace Application
وقود الديزل الحيوي هو أحد أنواع الوقود البديلة الواعدة التي تستخدم في السيارات وتوربينات الغاز والأفران. في هذه الدراسة، تم تجريبيا اختبار وقود الديزل الحيوي وخلائطه (الديزل الحيوي-الديزل (Bx) ووقود الديزل الحيوي-كيروسين (Bkx)) باستخدام منظومة الاحتراق (البيرنر) المصنع للبحث. حيث تمت التجارب باستخدام مرذذ وقود نوع (airblast atomizer) وذلك للتحقق من خواص عملية الاحتراق خلال التجارب. تم اجراء التجارب ولجميع انواع الوقود عند قدرة 12.2 كيلو واط عند نسبة ترذيذ ثابته ALR=1 ودرجة حرارة 301K ولقيم نسب تكافؤ (0.6 الى 1.4). تم قياس الانبعاثات الناتجة عن عملية الاحتراق مثل CO2 وCO وNOx وUbH باستخدام محلل الانبعاثات Gas analyzer، حيث اظهرت النتائج ان الملوثات الرئيسية مثل CO2 وCO وUbH تنخفض بزيادة نسبة الوقود الحيوي (biodiesel) لزهرة عباد الشمس (SME)، كما انخفضت اكاسيد النتروجين المنبعثة. لذلك وحسب النتائج والاستنتاجات فان وقود الديزل الحيوي يمكن ان يكون بديلا جيدا للوقود الاحفوري.Biodiesel is one of the promising substitution fuels that are used in cars, gas turbine and furnace. In this study, the experiments liquid fuels used during the tests are biodiesel and its blends (biodiesel-diesel (Bx) and biodiesel-kerosene (Bkx)) in a furnace have been studied experimentally. An airblast atomizer was used to investigate the combustion properties. During the experiments, the heat rate is (12.2kW), the atomization-air to liquid fuel ratio (ALR = 1) and the constant air temperature is (301K) were maintained. For the range of equivalence ratio from 0.6 to 1.4, the characteristics of emission factors such as carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons (UbH) were measured experimentally. The results observed that the main pollutants such as CO2, CO, UbH were decreased with an increase in SME, while NOx emissions also decreased .Biodiesel could be a promising fuel for furnaces instead of fossil fuels
Analysis of Flow Characteristics In Inlet And Exhaust Manifolds of Experimental Gasoline Combustion In A VCR Engine
In the present work, an approach to estimate of flow characteristic in inlet andexhaust manifolds of internal combustion engines is performed using a four-strokevariable compression ratio single cylinder gasoline engine.In the theoretical part a computer simulations of the flow field in the intakeand exhaust systems as well as the cylinder cavity for the experimental dataobtained in the gas exchange cycle program using the method of characteristics forthe engine dimensions and timings used in the experimental study as well as thedata obtained from the gas exchange cycle program for the sake of comparisonand presentation of flow characteristic.In the experimental work, the compression ratio was varied from 7 to 11 atvariable speed with constant throttle opening, where engine performance wasobtained.Results of engine performance as well as pressure, temperature and velocityfields in the intake and exhaust systems obtained by the gas exchange cycleprogram using the method of characteristics are presented
Dogs accompanied humans during the Neolithic expansion into Europe
International audienceNear Eastern Neolithic farmers introduced several species of domestic plants and animals as they dispersed into Europe. Dogs were the only domestic species present in both Europe and the Near East prior to the Neolithic. Here, we assessed whether early Near Eastern dogs possessed a unique mitochondrial lineage that differentiated them from Mesolithic European populations. We then analysed mitochondrial DNA sequences from 99 ancient European and Near Eastern dogs spanning the Upper Palaeolithic to the Bronze Age to assess if incoming farmers brought Near Eastern dogs with them, or instead primarily adopted indigenous European dogs after they arrived. Our results show that European pre-Neolithic dogs all possessed the mitochondrial haplogroup C, and that the Neolithic and Post-Neolithic dogs associated with farmers from Southeastern Europe mainly possessed haplogroup D. Thus, the appearance of haplogroup D most probably resulted from the dissemination of dogs from the Near East into Europe. In Western and Northern Europe, the turnover is incomplete and haplogroup C persists well into the Chalcolithic at least. These results suggest that dogs were an integral component of the Neolithic farming package and a mitochondrial lineage associated with the Near East was introduced into Europe alongside pigs, cows, sheep and goats. It got diluted into the native dog population when reaching the Western and Northern margins of Europe
A novel lineage of the Capra genus discovered in the Taurus Mountains of Turkey using ancient genomics
Direkli Cave, located in the Taurus Mountains of southern Turkey, was occupied by Late Epipaleolithic hunters-gatherers for the seasonal hunting and processing of game including large numbers of wild goats. We report genomic data from new and published Capra specimens from Direkli Cave and, supplemented with historic genomes from multiple Capra species, find a novel lineage best represented by a ~14,000 year old 2.59 X genome sequenced from specimen Direkli4. This newly discovered Capra lineage is a sister clade to the Caucasian tur species (Capra cylindricornis and Capra caucasica), both now limited to the Caucasus region. We identify genomic regions introgressed in domestic goats with high affinity to Direkli4, and find that West Eurasian domestic goats in the past, but not those today, appear enriched for Direkli4-specific alleles at a genome-wide level. This forgotten 'Taurasian tur' likely survived Late Pleistocene climatic change in a Taurus Mountain refuge and its genomic fate is unknown
Origin and History of Mitochondrial DNA Lineages in Domestic Horses
Domestic horses represent a genetic paradox: although they have the greatest number of maternal lineages (mtDNA) of all domestic species, their paternal lineages are extremely homogeneous on the Y-chromosome. In order to address their huge mtDNA variation and the origin and history of maternal lineages in domestic horses, we analyzed 1961 partial d-loop sequences from 207 ancient remains and 1754 modern horses. The sample set ranged from Alaska and North East Siberia to the Iberian Peninsula and from the Late Pleistocene to modern times. We found a panmictic Late Pleistocene horse population ranging from Alaska to the Pyrenees. Later, during the Early Holocene and the Copper Age, more or less separated sub-populations are indicated for the Eurasian steppe region and Iberia. Our data suggest multiple domestications and introgressions of females especially during the Iron Age. Although all Eurasian regions contributed to the genetic pedigree of modern breeds, most haplotypes had their roots in Eastern Europe and Siberia. We found 87 ancient haplotypes (Pleistocene to Mediaeval Times); 56 of these haplotypes were also observed in domestic horses, although thus far only 39 haplotypes have been confirmed to survive in modern breeds. Thus, at least seventeen haplotypes of early domestic horses have become extinct during the last 5,500 years. It is concluded that the large diversity of mtDNA lineages is not a product of animal breeding but, in fact, represents ancestral variability
Origins and genetic legacy of prehistoric dogs
Dogs were the first domestic animal, but little is known about their population history and to what extent it was linked to humans. We sequenced 27 ancient dog genomes and found that all dogs share a common ancestry distinct from present-day wolves, with limited gene flow from wolves since domestication but substantial dog-to-wolf gene flow. By 11,000 years ago, at least five major ancestry lineages had diversified, demonstrating a deep genetic history of dogs during the Paleolithic. Coanalysis with human genomes reveals aspects of dog population history that mirror humans, including Levant-related ancestry in Africa and early agricultural Europe. Other aspects differ, including the impacts of steppe pastoralist expansions in West and East Eurasia and a near-complete turnover of Neolithic European dog ancestry
Ancient mitogenomes from Pre-Pottery Neolithic Central Anatolia and the effects of a Late Neolithic bottleneck in sheep (Ovis aries)
Occupied between ~10,300 and 9300 years ago, the Pre-Pottery Neolithic site of Aşıklı Höyük in Central Anatolia went through early phases of sheep domestication. Analysis of 629 mitochondrial genomes from this and numerous sites in Anatolia, southwest Asia, Europe, and Africa produced a phylogenetic tree with excessive coalescences (nodes) around the Neolithic, a potential signature of a domestication bottleneck. This is consistent with archeological evidence of sheep management at Aşıklı Höyük which transitioned from residential stabling to open pasturing over a millennium of site occupation. However, unexpectedly, we detected high genetic diversity throughout Aşıklı Höyük’s occupation rather than a bottleneck. Instead, we detected a tenfold demographic bottleneck later in the Neolithic, which caused the fixation of mitochondrial haplogroup B in southwestern Anatolia. The mitochondrial genetic makeup that emerged was carried from the core region of early Neolithic sheep management into Europe and dominates the matrilineal diversity of both its ancient and the billion-strong modern sheep populations
Ancient mitogenomes from Pre-Pottery Neolithic Central Anatolia and the effects of a Late Neolithic bottleneck in sheep (Ovis aries)
Occupied between ~10,300 and 9300 years ago, the Pre-Pottery Neolithic site of Aşıklı Höyük in Central Anatolia went through early phases of sheep domestication. Analysis of 629 mitochondrial genomes from this and numerous sites in Anatolia, southwest Asia, Europe, and Africa produced a phylogenetic tree with excessive coalescences (nodes) around the Neolithic, a potential signature of a domestication bottleneck. This is consistent with archeological evidence of sheep management at Aşıklı Höyük which transitioned from residential stabling to open pasturing over a millennium of site occupation. However, unexpectedly, we detected high genetic diversity throughout Aşıklı Höyük's occupation rather than a bottleneck. Instead, we detected a tenfold demographic bottleneck later in the Neolithic, which caused the fixation of mitochondrial haplogroup B in southwestern Anatolia. The mitochondrial genetic makeup that emerged was carried from the core region of early Neolithic sheep management into Europe and dominates the matrilineal diversity of both its ancient and the billion-strong modern sheep populations
Pig domestication and human-mediated dispersal in western eurasia revealed through ancient DNA and geometric morphometrics
Zooarcheological evidence suggests that pigs were domesticated in Southwest Asia ∼8,500 BC. They then spread across the Middle and Near East and westward into Europe alongside early agriculturalists. European pigs were either domesticated independently or more likely appeared so as a result of admixture between introduced pigs and European wild boar. As a result, European wild boar mtDNA lineages replaced Near Eastern/Anatolian mtDNA signatures in Europe and subsequently replaced indigenous domestic pig lineages in Anatolia. The specific details of these processes, however, remain unknown. To address questions related to early pig domestication, dispersal, and turnover in the Near East, we analyzed ancient mitochondrial DNA and dental geometric morphometric variation in 393 ancient pig specimens representing 48 archeological sites (from the Pre-Pottery Neolithic to the Medieval period) from Armenia, Cyprus, Georgia, Iran, Syria, and Turkey. Our results reveal the first genetic signatures of early domestic pigs in the Near Eastern Neolithic core zone. We also demonstrate that these early pigs differed genetically from those in western Anatolia that were introduced to Europe during the Neolithic expansion. In addition, we present a significantly more refined chronology for the introduction of European domestic pigs into Asia Minor that took place during the Bronze Age, at least 900 years earlier than previously detected. By the 5th century AD, European signatures completely replaced the endemic lineages possibly coinciding with the widespread demographic and societal changes that occurred during the Anatolian Bronze and Iron Ages
Not a limitless resource: ethics and guidelines for destructive sampling of archaeofaunal remains
Publisher's version (útgefin grein)With the advent of ancient DNA, as well as other methods such as isotope analysis, destructive sampling of archaeofaunal remains has increased much faster than the effort to collect and curate them. While there has been considerable discussion regarding the ethics of destructive sampling and analysis of human remains, this dialogue has not extended to archaeofaunal material. Here we address this gap and discuss the ethical challenges surrounding destructive sampling of materials from archaeofaunal collections. We suggest ways of mitigating the negative aspects of destructive sampling and present step-by-step guidelines aimed at relevant stakeholders, including scientists, holding institutions and scientific journals.
Our suggestions are in most cases easily implemented without significant increases in project costs, but with clear long-term benefits inthe preservation and use of zooarchaeologicalmaterial.his work was supported by the Icelandic Research Fund grant no. 162783-051, Finnish Academy grant no. SA286499, the European Union’s Horizon 2020 research and innovation programme under the Marie SkłodowskaCurie grant agreement no. 749226 and Estonian Research Council grant nos. PRG29 and IUT 20-7.Peer Reviewe
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