1,720 research outputs found
Controlled Ecological Life Support Systems: CELSS 1985 Workshop
Various topics related to closed ecological systems are discussed. Space habitats, vegetative growth, photosynthesis, recycling, culture techniques, waste utilization bioreactors and controlled atmospheres on space stations are among the topics covered
Two-season agriculture and irrigated rice during the Dian: radiocarbon dates and archaeobotanical remains from Dayingzhuang, Yunnan, Southwest China
Historical sources describe irrigation and intensive agriculture being practiced in lowland Yunnan from at least the first century AD, but so far archaeobotanical remains allowing investigation of this issue have been scarce. Here, we present new archaeobotanical evidence, including macro-botanical and phytoliths results, from the Dian settlement site of Dayingzhuang, with direct AMS radiocarbon dates on two wheat grains falling between 750 and 390Â BC. We compare these results with contemporary Dian sites and analyse the agricultural systems in Central Yunnan between the eight and fourth centuries BC. We propose that agriculture was intensified toward the end of the Dian through both multiple cropping seasons and increased evidence for irrigated rice fields.Introduction The site of Dayingzhuang - Environment and excavation - Chronometric results: dates and sequences - Site description and material culture -- Features -- Ceramics -- Stone and other implements -- Metal objects -- Faunal remains Materials and methods - Macro-botanical remains - Phytolith remains Results - Macro-botanical remains -- General features of the assemblage and key economic taxa -- Cereal crops -- Wheat and barley -- Rice -- Millets -- Chenopodium -- Other possible cultigens -- Seeds of field weed species - Phytoliths remains: general features - Rice cultivation ecology: inferences from phytoliths Discussion: characterizing Dian agriculture Conclusio
Ant colony optimisation and local search for bin-packing and cutting stock problems
The Bin Packing Problem and the Cutting Stock Problem are two related classes of NP-hard combinatorial optimization problems. Exact solution methods can only be used for very small instances, so for real-world problems, we have to rely on heuristic methods. In recent years, researchers have started to apply evolutionary approaches to these problems, including Genetic Algorithms and Evolutionary Programming. In the work presented here, we used an ant colony optimization (ACO) approach to solve both Bin Packing and Cutting Stock Problems. We present a pure ACO approach, as well as an ACO approach augmented with a simple but very effective local search algorithm. It is shown that the pure ACO approach can compete with existing evolutionary methods, whereas the hybrid approach can outperform the best-known hybrid evolutionary solution methods for certain problem classes. The hybrid ACO approach is also shown to require different parameter values from the pure ACO approach and to give a more robust performance across different problems with a single set of parameter values. The local search algorithm is also run with random restarts and shown to perform significantly worse than when combined with ACO
American\u27s Perception of China: A Study of Various American Social Statistics and Their Relationship to Perception of The People\u27s Republic of China
Over the past century, American perception of the People\u27s Republic of China has been characterized as cyclical, alternating between longer periods of negativity, characterized by hostility and disillusionment, and shorter positive periods of admiration, infatuation, and benevolence. The two recent peaks in Americans\u27 perception of China have been in 1979, when the Carter administration officially recognized China, and ten years later, when President Bush visited the country in 1989. American China-scholars generally agree that the 1989 Tiananmen Square incident was the watershed that fundamentally changed U.S. perceptions of China. Since the incident, the percentage of Americans who perceive China in a positive light has yet to return to its pre-Tiananmen level. This study is a statistical analysis of the relationship between American perceptions of China and a number of specific social characteristics. The results indicate that, although reported perception of China has fluctuated greatly over the past century, little has changed in the way that most Americans fundamentally view China. That is, most American\u27s retain a missionary view of China as a country in need of saving: originally from barbarism, and now from communism
Estimation of Gap Acceptance Parameters for HCM 2010 Roundabout Capacity Model Applications
This paper deals with the field data observation and successive application of estimation procedures in order to estimate follow-up headway and critical headway at roundabouts. Average follow-up and average critical headway are two critical parameters in the new roundabout capacity model presented in the 2010 edition of the Highway Capacity Manual (HCM). The HCM 2010 capacity model was developed as an exponential regression model with parameter estimates based on gap acceptance theory. Gap acceptance models are strongly affected by driver behaviour and local habits. Follow-up headways can be field measured, while critical headway cannot be obtained directly. The paper mainly aims to check if general suggested values are well-suited also for Italy or not. There have been numerous techniques developed for estimating critical headway. In order to perform a better check of a sample of experimentally observed values, three different procedures are chosen and applied. The first is a quite popular mathematical method based on maximum likelihood technique. The second is a statistical method based on the median of the observed sample distribution. The third is a graphical method known as Raffâs method. All these three methods require information about the accepted headway and the largest rejected headway for each driver. Therefore a sample of field data was recorded by digital camera and processed following the instructions suggested by NCHRP. The sample data of critical headway and follow-up headway are gathered in seven selected roundabouts located in Northern Tuscany (Italy). Our first obtained results indicate that the average critical headway is significantly lower than the values recommended by some international references. However, the average follow-up headway is only higher than that recommended for the State of California and it is lower than that recommended by all other international references. Finally, conclusions drawn along with insights for further research developments are suggested
Exploiting Connections for Viral Replication.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the COVID-19 (coronavirus disease 2019) pandemic, is a positive strand RNA (+RNA) virus. Like other +RNA viruses, SARS-CoV-2 is dependent on host cell metabolic machinery to survive and replicate, remodeling cellular membranes to generate sites of viral replication. Viral RNA-containing double-membrane vesicles (DMVs) are a striking feature of +RNA viral replication and are abundant in SARS-CoV-2-infected cells. Their generation involves rewiring of host lipid metabolism, including lipid biosynthetic pathways. Viruses can also redirect lipids from host cell organelles; lipid exchange at membrane contact sites, where the membranes of adjacent organelles are in close apposition, has been implicated in the replication of several +RNA viruses. Here we review current understanding of DMV biogenesis. With a focus on the exploitation of contact site machinery by +RNA viruses to generate replication organelles, we discuss evidence that similar mechanisms support SARS-CoV-2 replication, protecting its RNA from the host cell immune response
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Exploiting Connections for Viral Replication.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the COVID-19 (coronavirus disease 2019) pandemic, is a positive strand RNA (+RNA) virus. Like other +RNA viruses, SARS-CoV-2 is dependent on host cell metabolic machinery to survive and replicate, remodeling cellular membranes to generate sites of viral replication. Viral RNA-containing double-membrane vesicles (DMVs) are a striking feature of +RNA viral replication and are abundant in SARS-CoV-2-infected cells. Their generation involves rewiring of host lipid metabolism, including lipid biosynthetic pathways. Viruses can also redirect lipids from host cell organelles; lipid exchange at membrane contact sites, where the membranes of adjacent organelles are in close apposition, has been implicated in the replication of several +RNA viruses. Here we review current understanding of DMV biogenesis. With a focus on the exploitation of contact site machinery by +RNA viruses to generate replication organelles, we discuss evidence that similar mechanisms support SARS-CoV-2 replication, protecting its RNA from the host cell immune response
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