2,114,100 research outputs found
Modeling and analysis of the dynamic behavior of the XlnR regulon in Aspergillus niger
No full textBackground: In this paper the dynamics of the transcription-translation system for XlnR regulon in Aspergillus niger is modeled. The model is based on Hill regulation functions and uses ordinary differential equations. The network response to a trigger of D-xylose is considered and stability analysis is performed. The activating, repressive feedback, and the combined effect of the two feedbacks on the network behavior are analyzed. Results: Simulation and systems analysis showed significant influence of activating and repressing feedback on metabolite expression profiles. The dynamics of the D-xylose input function has an important effect on the profiles of the individual metabolite concentrations. Variation of the time delay in the feedback loop has no significant effect on the pattern of the response. The stability and existence of oscillatory behavior depends on which proteins are involved in the feedback loop. Conclusions: The dynamics in the regulation properties of the network are dictated mainly by the transcription and translation degradation rate parameters, and by the D-xylose consumption profile. This holds true with and without feedback in the network. Feedback was found to significantly influence the expression dynamics of genes and proteins. Feedback increases the metabolite abundance, changes the steady state values, alters the time trajectories and affects the response oscillatory behavior and stability conditions. The modeling approach provides insight into network behavioral dynamics particularly for small-sized networks. The analysis of the network dynamics has provided useful information for experimental design for future in vitro experimental wor
Gerador de Van de Graaff: conceitos de eletrostática baseado na experimentação
No full textFaced with the limitations and difficulties that the teacher finds in the teaching of Physics and in the execution of experimental activities, the present research aims to propose the use of the Van de Graaff generator. The generator components will be presented, highlighting its operation and application, in addition to showing the assembly process of a model made from easily obtainable and loxw cost reusable materials. Based on the contents of electrostatics, especially electrification by friction, proposals for activities and possible approaches to them with the generator were prepared. More than evaluating the effectiveness of the resource, this research aims to provide an alternative to the Physics teacher in the classroom and in the laboratories of IFAM/CMDI.Diante das limitações e dificuldades que o professor encontra no ensino de Física e na execução de atividades experimentais, a presente pesquisa tem como objetivo propor o uso do gerador de Van de Graaff. Serão apresentados os componentes do gerador, destacando o seu funcionamento e aplicação, além de mostrar o processo de montagem de um modelo confeccionado a partir de materiais reaproveitáveis de fácil obtenção e baixo custo. Com base nos conteúdos de eletrostática, em especial a eletrização por atrito, foram elaboradas propostas de atividades e as possíveis abordagens das mesmas com o gerador. Mais do que avaliar a eficácia do recurso, esta pesquisa tem como intenção maior possibilitar uma alternativa ao professor de Física em sala de aula e nos laboratórios do IFAM/CMDI.
Palavras-chave: Ensino de Física; Atividade Experimental; Gerador de Van de Graaf
The Berlin CN-Van-de-Graaff injector
No full textThe Berlin CN-Van-de-Graaff accelerator has been converted into a heavy ion injector. Main parts of this conversion including the high vacuum tube, the differential pumping system, the new geometry of the spinning and the computer control philosophy are described.L'accélérateur Van-de-Graaff du type CN de Berlin a été transformé en injecteur d'ions lourds. Les éléments principaux de cette transformation, le tube accélérateur à vide élevé, le système de pompage différentiel, la nouvelle géométrie du spinning et le système de contrôle par calculateur seront décrits
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A typology of farm households for the Umutara Province in Rwanda
No full textRwanda, Farm household, Farm typology, Technology adoption, Multivariate analysis,
Proteomic analysis of the secretory response of Aspergillus niger to D-maltose and D-xylose
No full textFungi utilize polysaccharide substrates through extracellular digestion catalyzed by secreted enzymes. Thus far, protein secretion by the filamentous fungus Aspergillus niger has mainly been studied at the level of individual proteins and by genome and transcriptome analyses. To extend these studies, a complementary proteomics approach was applied with the aim to investigate the changes in secretome and microsomal protein composition resulting from a shift to a high level secretion condition. During growth of A. niger on D-sorbitol, small amounts of D-maltose or D-xylose were used as inducers of the extracellular amylolytic and xylanolytic enzymes. Upon induction, protein compositions in the extracellular broth as well as in enriched secretory organelle (microsomal) fractions were analyzed using a shotgun proteomics approach. In total 102 secreted proteins and 1,126 microsomal proteins were identified in this study. Induction by D-maltose or D-xylose resulted in the increase in specific extracellular enzymes, such as glucoamylase A on D-maltose and ß-xylosidase D on D-xylose, as well as of microsomal proteins. This reflects the differential expression of selected genes coding for dedicated extracellular enzymes. As expected, the addition of extra D-sorbitol had no effect on the expression of carbohydrate-active enzymes, compared to addition of D-xylose or D-maltose. Furthermore, D-maltose induction caused an increase in microsomal proteins related to translation (e.g., Rpl15) and vesicular transport (e.g., the endosomal-cargo receptor Erv14). Millimolar amounts of the inducers D-maltose and D-xylose are sufficient to cause a direct response in specific protein expression levels. Also, after induction by D-maltose or D-xylose, the induced enzymes were found in microsomes and extracellular. In agreement with our previous findings for D-xylose induction, D-maltose induction leads to recruitment of proteins involved in proteasome-mediated degradatio
Het contraterrorismebeleid in Nederland
No full textBob de Graaff beziet in hoeverre de Nederlandse overheid erin is geslaagd in de tien jaren na de aanslagen van 9/11 samenhang in het contraterrorismebeleid te behouden dan wel aan te brengen. De Nationaal Coordinator Terrorismebestrijding (NCTb) speelt in dit artikel een belangrijke rol. Aan de orde komt welke visies op terrorisme er na 9/11 in de Nederlandse politiek zijn geweest, om vervolgens de verschillende beleidsmatige reacties op het fenomeen terrorisme te schetsen. Daarna wordt de rol van Defensie en de strijdkrachten daarin besproken. De auteur eindigt met een visie op de realisering van samenhang in beleid, de beleidsinstrumenten en de beleidsuitvoering
Bio-economic farm modelling to analyse agricultural land productivity in Rwanda
No full text Keywords: Rwanda; farm household typology; sustainable technology adoption; multivariate analysis; land degradation; food security; bioeconomic model; crop simulation models; organic fertiliser; inorganic fertiliser; policy incentives In Rwanda, land degradation contributes to the low and declining agricultural productivity and consequently to food insecurity. As a result of land degradation and increasing population pressure, there is urgent need to simultaneously enhance food security and agro-ecological sustainability. The main objective of this PhD thesis was to make an assessment of technology options and policy incentives that can enhance sustainable farming in Rwanda. A multivariate analysis approach was used to clearly identify five types of farm households and their socio-economic characteristics. The main differences between the five farm types relate to gender, age, education, risk perception, risk attitude, labour availability, land tenure and income. A bio-economic model capable of analysing the impacts of soil erosion, family planning and land consolidation policies on food security in Rwanda was developed, and applied for one typical farm household. Calculations with the bio-economic model showed that a higher availability of good farm land would increase the farm income. Additionally, preserving soils against erosion and reducing risk would allow for using more marginal land which would increase food production for home consumption and for the market. Increasing the opportunities for off-farm employment can also increase farm household income. The simulation of crop yields under sustainable land management showed that predicted crop yields were distinctly higher than the actual yields for the current small-scale farming practices that are common in the region. Using the developed bio-economic model, model results showed that these sustainable agricultural technologies will clearly enhance food production (after a learning period) and income for all farm household types except the household with the largest farm for which cash at the beginning of the season is too restricted to switch to the new technologies. Provision of credit and availability off-farm activities have emerged as the most serious policies likely to affect the adoption of alternative technologies in all the farm households. The bio-economic farm model and its applications developed in this study give more insights into the possibilities of transforming the current farming system towards more sustainable farming. . </p
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Ons het al jare lank massavergaderings in die Kaap
No full text462.B.1.10(11).pdf created from the media publications in the SA Election material Collection MS 462, held in the Manuscripts Section of the Stellenbosch Library and Information Service.Ons het al jare lank massavergaderings in die Kaap. 1994. Die Burger, 20 April:11.Newspaper advertisement by the National Party (NP) delivering a message from party leader, F. W. de Klerk, in which he expresses his longstanding relationship with the Western Cape and it's people. He also expresses the NP's desire to improve the quality of life in the Cape by providing work opportunities, building houses, schools, and hospitals to meet the needs of the people, and strengthening the economy to afford the people of the Cape the lives they deserve. The advertisement is compiled and issued by David Graaff and appears on page 11 of Die Burger newspaper
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