7 research outputs found
System for sample introduction in gas chromatography
No full textIntroduction: Gas chromatography is an instrumental method of analysis, allowing the preliminary sepa-ration of complex mixtures of substances and their subsequent qualitative and quantitative determination.Aim: Presentation of the main types of devices for introducing samples in gas chromatography and their manner of operation.Materials and Methods: Survey of the available literature on the topic.Discussion: In gas chromatography the mobile phase is inert gas, called carrier gas. It carries the analyzed sample by the system for sample introduction (injector, sample inlets) and moves it through the chromatography column, in which the separation occurs, to a detector which registers the eluted compounds, leaving the column in the form of pure substances.In chromatographic system the injector is designed to provide accurate and reproducible introduction of certain volume from the analyzed sample. For the introduction of gas, liquid and solid samples in gas chromatography are used different types of injectors, tailored for the existing variety of columns and com-pounds for analysis.The introduction of the sample is essential for the successful implementation of gas-chromatographic analysis and significantly influences the results that are received. Therefore, the system for sample introduction must ensure rapid introduction of metered quantity without the occurrence of effects of discrimination (introducing only a portion of the sample).Conclusion: The system for sample introduction in gas-chromatographic analysis is an essential part of the overall chromatographic system and a factor influencing the quality of the analysis
Measurement Uncertainty Analysis of a Twyman-Green Interferometer for Lens Testing
No full textThere is a growing demand for precision and high-quality optical objectives and lenses due to their numerous advantages and uses. The market for high precision objective lenses has tremendous potential for development and is a sector that is expanding quickly. Measuring the aberrations of optical systems is an essential step in the fabrication of high precision optical components. However, when working at the cutting-edge of technology, it is increasingly difficult to provide trustworthy measurements as the used metrology instrument has to be of comparable or higher precision. This poses a major problem especially when working with high numerical aperture (NA) optics.In this thesis, we will analyze and quantify the measurement uncertainty of a Twyman-Green interferometer used for lens testing of high-NA microscope objectives.To quantify the measurement uncertainty of the interferometer, various sources of uncertainty that affect the accuracy and precision of the measurements are considered. These include environmental and instrumentation factors such as incorrect phase-stepping, laser instability, camera noise, stray light, photon shot noise, effects of mid-spatial frequencies originating in the optical reference, as well as computational shortcomings such as: incorrect phase unwrapping, polynomial fit errors, incorrect pupil scaling and edge detection.By carefully analyzing these individual sources of uncertainty and their impact, we determine the overall measurement uncertainty of the interferometer and provide an assessment of its accuracy through Monte Carlo simulations, where the introduced uncertainties are obtained from real measurement data. The uncertainty analysis procedure described in this paper is a useful tool that can also be applied to different types of interferometers by taking proper considerations into account.Mechanical Engineering | Micro and Nano Engineerin
KNOWLEDGE AS AN ECONOMIC RESOURCE AND A SOURCE OF WEALTH
No full textThe realisation of knowledge as a major factor in production on the one hand, and also its main product on the other, has provoked the necessity to clarify its nature as an economic category in a knowledge-based economy. This article examines the ambivalent nature of existing knowledge as a public and private source of wealth, the possibilities for transforming it from a private to a public source of wealth through “overflow“, and the pros and cons of possible paths for advancement in the field of research and development.
Special attention has been paid to the characteristics of knowledge as an economic category: the specific way of expropriation, preserving usefulness and self-expansion in the process of consumption; changes in the nature and in the mechanism of accumulation and also changes to property relations in a knowledge society; inseparability from the owner as a personalised source of wealth. In terms of content, the article complements and builds on the ideas put forward by the author in the plenary paper entitled, "Knowledge as an Economic Category” presented during the seventy-fifth anniversary conference at th D. A. Tsenov Academy of Economics in Svishtov
Bisphenol A - diabetes mellitus?
No full textAim: Presentation of existing data on the possible relationship between exposure to BPA and the development of diabetes mellitus.Materials and methods: Systematic approach of the available scientific literature on the problem.Results: Bisphenol A is a chemical used in the manufacture of polycarbonate plastics. It has estrogenic activity and belongs to the group of endocrine disrupting chemicals.Studies conducted in animals have shown that BPA may lead to impaired insulin and glucose tolerance, hyperinsulinemia, abnormal β cell function and reduced insulin sensitivity. In addition, in cultured human adipocytes has been found that BPA decrease the release of adiponectin, involved in the regulation of blood sugar levels.Analyzing the data from human studies, which are mainly cross-sectional, researchers make different and contradictory conclusions regarding the possible correlation between the amount of BPA in the urine (a measure of exposure to BPA) and the development of diabetes.Inappropriate extrapolation of data from animal studies, and the possibility a number of factors to influence the conduct and interpretation of epidemiological studies hinder the identification and understand the relationship bisphenol A - diabetes.Conclusions: It`s necessary to introduce of precise and clear principles in conducting epidemiological studies of BPA and in the interpretation of results from animal studies. Despite existing controversy on the subject, it`s requiring active research to determine the full extent BPA effects on human health, given the ever-increasing exposure to BPA
Dialogue of Cultures: the Role of Taras Shevchenko’s Poetry in Genesis of New Bulgarian Literature in the Second Half of the Nineteenth Century
No full textУ статті розглядаються важливі історико-теоретичні аспекти
міжнаціональної взаємодії у царині гуманітаристики на прикладі рецепції поезії Тараса Шевченка у новоболгарській літературі другої половини
ХІХ ст. Досліджено вплив поезії видатного українського митця на творчість плеяди перших професійних болгарських літераторів, зокрема
Райко Жінзіфова, Любена Каравелова, Петко Славейкова та Івана Вазова, які вважали її взірцем для наслідування й основою для вдосконалення власної літературної майстерності. Приділено увагу перекладацькій
діяльності цих авторів, завдячуючи якій поетична спадщина Тараса Шевченка стала доступною для широкого загалу тогочасного болгарського
читача. Водночас у статті висвітлюються витоки вітчизняного й болгарського шевченкознавства.The article is about important historical and theoretical aspects of
international interaction in Humanitarian sphere on the example of reception
of Taras Shevchenko’s poetry in new Bulgarian literature in the second half of
the nineteenth century. The article studies the impact that the poetry by an
outstanding Ukrainian author had on the creative works created by a
constellation of the first Bulgarian professional men of letters, in particular
Rayko Zhinzifov, Lyuben Karavelov, Petko Slaveykov and Ivan Vazov. They
considered this poetry as an example to follow and a basis for improving their
own literary art. The attention is paid to the translation practice of these
authors rendering the poetic heritage of Taras Shevchenko accessible for the
wide Bulgarian reading public then. At the same time, the article covers the
origins of Shevchenko studies in Ukraine and Bulgaria
Scientific and Practical Conference "Challenges in the Education of Masters of Pharmacy"
No full textTh conference is organised with the fiancial support of European Social Fund within the Project BG051PO001-3.1.07-0046 `Updating and approbation of the curricula of the Faculty of Pharmacy, Medical University of Varna according to the needs of the pharmaceutical business and the requirements of the labor market
