Geometric Factor in Skeletal Reactions of 2-Methylpentane on Stepped Surfaces of Platinum Catalyst

1992 ◽  
Vol 57 (10) ◽  
pp. 2012-2020
Author(s):  
Vladimír Hejtmánek

The role of geometric factor in the course of skeletal reactions (isomerization, hydrogenolysis) of 2-methylpentane on stepped (119), (557) and reconstructed R(557) surfaces of single crystals of platinum was evaluated with computer designed models. These calculations were compared with reported experimental data. It was found by analysis of geometric conditions that there are accessible active ensembles on double step of the reconstructed R(557) surface. In addition, these active sites are unsaturated in their coordination sphere and thus catalytically effective. This finding is consistent with published data, confirming higher catalytic activity of this surface. The various pathways of Bond Shift isomerization mechanism of 2-methylpentane from the point of view of steric demands of surface intermediates on differently located ensembles are discussed, too.

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1043
Author(s):  
Vitor Bonamigo Moreira ◽  
Anna Puiggalí-Jou ◽  
Emilio Jiménez-Piqué ◽  
Carlos Alemán ◽  
Alvaro Meneguzzi ◽  
...  

Herein, the influence of the substrate in the formation of zirconium oxide monolayer, from an aqueous hexafluorozirconic acid solution, by chemical conversion and by electro-assisted deposition, has been approached. The nanoscale dimensions of the ZrO2 film is affected by the substrate nature and roughness. This study evidenced that the mechanism of Zr-EAD is dependent on the potential applied and on the substrate composition, whereas conversion coating is uniquely dependent on the adsorption reaction time. The zirconium oxide based nanofilms were more homogenous in AA2024 substrates if compared to pure Al grade (AA1100). It was justified by the high content of Cu alloying element present in the grain boundaries of the latter. Such intermetallic active sites favor the obtaining of ZrO2 films, as demonstrated by XPS and AFM results. From a mechanistic point of view, the electrochemical reactions take place simultaneously with the conventional chemical conversion process driven by ions diffusion. Such findings will bring new perspectives for the generation of controlled oxide coatings in modified electrodes used, as for example, in the construction of battery cells; in automotive and in aerospace industries, to replace micrometric layers of zinc phosphate by light-weight zirconium oxide nanometric ones. This study is particularly addressed for the reduction of industrial waste by applying green bath solutions without the need of auxiliary compounds and using lightweight ceramic materials.


2020 ◽  
Vol 10 (11) ◽  
pp. 862
Author(s):  
Stéphanie Papin ◽  
Paolo Paganetti

Neurodegenerative disorders and cancer may appear unrelated illnesses. Yet, epidemiologic studies indicate an inverse correlation between their respective incidences for specific cancers. Possibly explaining these findings, increasing evidence indicates that common molecular pathways are involved, often in opposite manner, in the pathogenesis of both disease families. Genetic mutations in the MAPT gene encoding for TAU protein cause an inherited form of frontotemporal dementia, a neurodegenerative disorder, but also increase the risk of developing cancer. Assigning TAU at the interface between cancer and neurodegenerative disorders, two major aging-linked disease families, offers a possible clue for the epidemiological observation inversely correlating these human illnesses. In addition, the expression level of TAU is recognized as a prognostic marker for cancer, as well as a modifier of cancer resistance to chemotherapy. Because of its microtubule-binding properties, TAU may interfere with the mechanism of action of taxanes, a class of chemotherapeutic drugs designed to stabilize the microtubule network and impair cell division. Indeed, a low TAU expression is associated to a better response to taxanes. Although TAU main binding partners are microtubules, TAU is able to relocate to subcellular sites devoid of microtubules and is also able to bind to cancer-linked proteins, suggesting a role of TAU in modulating microtubule-independent cellular pathways associated to oncogenesis. This concept is strengthened by experimental evidence linking TAU to P53 signaling, DNA stability and protection, processes that protect against cancer. This review aims at collecting literature data supporting the association between TAU and cancer. We will first summarize the evidence linking neurodegenerative disorders and cancer, then published data supporting a role of TAU as a modifier of the efficacy of chemotherapies and of the oncogenic process. We will finish by addressing from a mechanistic point of view the role of TAU in de-regulating critical cancer pathways, including the interaction of TAU with cancer-associated proteins.


1992 ◽  
Vol 57 (9) ◽  
pp. 1785-1792 ◽  
Author(s):  
Vladimír Hejtmánek

The steric demands of two types of adsorbed complexes of neohexane (2,2-dimethylbutane) on (100), (110) and (111) ideal surfaces of Ni or Pt catalysts were investigated with the aid of a computer. It was shown, that αγ complexes of the adsorbed noehexane were preferred in comparison to αβ ones for all studied surfaces. From the steric point of view, the feasibility of the adsorption depends on the complexity of the surface character in the following order: (111) < (100) < (110). Unfortunately, the experimentally observed discrepancies between the activity or selectivity in skeletal reactions on both types of catalysts could not be elucidated from our analyses.


Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.


2009 ◽  
pp. 4-27
Author(s):  
A. Cohen ◽  
G. Harcourt

The article written by the well-known theorists and historians of economic thought contains a detailed overview of the Cambridge capital controversy, which had raged from the mid-1950-s through the mid-1970-s. The authors track the origins of the controversy and cover arguments of both sides in chronological order. From their point of view, the discussion hasnt been resolved, and its main underlying aspects were ideological beliefs and fundamental methodological controversies on the nature of equilibrium and on the role of time in economic theory. The article is published with comments written by other leading theoreticians.


2019 ◽  
pp. 22-29
Author(s):  
Н. В. Фрадкіна

The purpose and tasks of the work are to analyze the contemporary Ukrainian mass culture in terms of its value and humanistic components, as well as the importance of cultural studies and Ukrainian studies in educational disciplines for the formation of a holistic worldview of modern youth.Analysis of research and publications. Scientists repeatedly turned to the problems of the role of spirituality in the formation of society and its culture. This problem is highlighted in the publications by O. Losev, V. Lytvyn, D. Likhachev, S. Avierintsev, M. Zakovych, I. Stepanenko and E. Kostyshyn.Experts see the main negative impact of mass culture on the quality approach, which determines mass culture through the market, because mass culture, from our point of view, is everything that is sold and used in mass demand.One of the most interesting studies on this issue was the work by the representatives of Frankfurt School M. Horkheimer and T. Adorno «Dialectics of Enlightenment» (1947), devoted to a detailed analysis of mass culture. Propaganda at all socio-cultural levels in the form is similar in both totalitarian and democratic countries. It is connected, according to the authors, with the direction of European enlightenment. The tendency to unify people is a manifestation of the influence of mass culture, from cinema to pop. Mass culture is a phenomenon whose existence is associated with commerce (accumulation in any form – this is the main feature of education), in general, the fact that it exists in this form is related to the direction of the history of civilization.Modern mass culture, with its externally attractive and easily assimilated ideas and symbols, appealing to the trends of modern fashion, becomes a standard of prestigious consumption, does not require intense reflection, allows you to relax, distract, not teach, but entertains, preaches hedonism as the main spiritual value. And as a consequence, there are socio-cultural risks: an active rejection of other people, which leads to the formation of indifference; cruelty as a character trait; increase of violent and mercenary crime; increase in the number of alcohol and drug addicts; anti-patriotism; indifference to the values of the family and as a result of social orphanhood and prostitution.Conclusions, perspectives of research. Thus, we can conclude that modern Ukrainian education is predominantly formed by the values of mass culture. Namely, according to the «Dialectic» by Horkheimer and Adorno, «semi-enlightenment becomes an objective spirit» of our modern society.It is concluded that only high-quality education can create the opposite of the onset of mass culture and the destruction of spirituality in our society. It is proved that only by realizing the importance of cultivating disciplines in the educational process and the spiritual upbringing of the nation, through educational reforms, humanitarian knowledge will gradually return to student audiences.Formation of youth occurs under the influence of social environment, culture, education and self-education. The optimal combination of these factors determines both the process of socialization itself and how successful it will be. In this context, one can see the leading role of education and upbringing. It turns out that the main task of modern education is to spread its influence on the development of spiritual culture of the individual, which eventually becomes a solid foundation for the formation of the individual. Such a subject requires both philosophical and humanitarian approaches in further integrated interdisciplinary research, since the availability of such research will provide the theoretical foundation for truly modern educational and personal development.


2020 ◽  
pp. 75-79
Author(s):  
R. M. Gambarova

Relevance. Grain is the key to strategic products to ensure food security. From this point of view, the creation of large grain farms is a matter for the country's selfsufficiency and it leading to a decrease in financial expense for import. Creation of such farms creates an abundance of productivity from the area and leads to obtaining increased reproductive seeds. The main policy of the government is to minimize dependency from import, create abundance of food and create favorable conditions for export potential.The purpose of the study: the development of grain production in order to ensure food security of the country and strengthen government support for this industry.Methods: comparative analysis, systems approach.Results. As shown in the research, if we pay attention to the activities of private entrepreneurship in the country, we can see result of the implementation of agrarian reforms after which various types of farms have been created in republic.The role of privateentrepreneurshipinthedevelopmentofproduction is great. Тhe article outlines the sowing area, production, productivity, import, export of grain and the level of selfsufficiency in this country from 2015 till 2017.


2019 ◽  
Vol 16 (2-3) ◽  
pp. 161-179
Author(s):  
Outi Paloposki

The article looks at book production and circulation from the point of view of translators, who, as purchasers and readers of foreign-language books, are an important mediating force in the selection of literature for translation. Taking the German publisher Tauchnitz's series ‘Collection of British Authors’ and its circulation in Finland in the nineteenth and early twentieth century as a case in point, the article argues that the increased availability of English-language books facilitated the acquiring and honing of translators' language skills and gradually diminished the need for indirect translating. Book history and translation studies meet here in an examination of the role of the Collection in Finnish translators' work.


2005 ◽  
Vol 55 (2) ◽  
pp. 201-221 ◽  
Author(s):  
Andrea Szalavetz

This paper discusses the relation between the quality and quantity indicators of physical capital and modernisation. While international academic literature emphasises the role of intangible factors enabling technology generation and absorption rather than that of physical capital accumulation, this paper argues that the quantity and quality of physical capital are important modernisation factors, particularly in the case of small, undercapitalised countries that recently integrated into the world economy. The paper shows that in Hungary, as opposed to developed countries, the technological upgrading of capital assets was not necessarily accompanied by the upgrading of human capital i.e. the thesis of capital skill complementarity did not apply to the first decade of transformation and capital accumulation in Hungary. Finally, the paper shows that there are large differences between the average technological levels of individual industries. The dualism of the Hungarian economy, which is also manifest in terms of differences in the size of individual industries' technological gaps, is a disadvantage from the point of view of competitiveness. The increasing differences in the size of the technological gaps can be explained not only with industry-specific factors, but also with the weakness of technology and regional development policies, as well as with institutional deficiencies.


Author(s):  
Oksana Galchuk

The theme of illegitimacy Guy de Maupassant evolved in his works this article perceives as one of the factors of the author’s concept of a person and the plane of intersection of the most typical motifs of his short stories. The study of the author’s concept of a person through the prism of polivariability of the motif of a bastard is relevant in today’s revision of traditional values, transformation of the usual social institutions and search for identities, etc. The purpose of the study is to give a definition to the existence specifics of the bastard motif in the Maupassant’s short stories by using historical and literary, comparative, structural methods of analysis as dominant. To do this, I analyze the content, variability and the role of this motive in the formation of the Maupassant’s concept of a person, the author’s innovations in its interpretation from the point of view of literary diachrony. Maupassant interprets the bastard motif in the social, psychological and metaphorical-symbolic sense. For the short stories with the presentation of this motif, I suggest the typology based on the role of it in the structure of the work and the ideological and thematic content: the short stories with a motif-fragment, the ones with the bastard’s leitmotif and the group where the bastard motif becomes a central theme. The Maupassant’s interpretation of the bastard motif combines the general tendencies of its existence in the world’s literary tradition and individual reading. The latter is the result of the author’s understanding of the relevant for the era issues: the transformation of the family model, the interest in the theory of heredity, the strengthening of atheistic sentiments, the growth of frustration in the system of traditional social and moral values etc. This study sets the ground for a prospective analysis of the evolution the bastard motif in the short-story collections of different years or a comparative study of the motif in short stories and novels by Maupassant.


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