1,354,783 research outputs found
On Nowicki's conjecture: a survey and a new result
No full textThe goal of the paper is twofold: it aims to give an extensive set of tools and bibliography towards Nowicki???s conjecture both in for polynomial algebras and in an associative setting; it establishes a new result about Nowicki???s conjecture for the free metabelian Poisson algebra
Structural materials: fire and protection
No full textAny material that can be used in the construction of a building is called building material. Concrete, reinforced concrete, steel, aluminum, wood, tile, plaster, etc., known as building materials. Fire is a chemical event that occurs as a result of the combination of matter with heat and oxygen. Fire protection is the study and practice of reducing the undesirable effects of destructive fires. It includes the behavior, suppression and investigation of fire. In this study, building materials such as steel, concrete and wood were examined, and then the protection of building materials using fire resistant materials and fire systems was emphasized
Insight into the Thiol-yne Kinetics via a Computational Approach
No full textThiol-yne reactions have drawn attention because of the click nature as well as the regular step-growth network nature of their products, despite the radical-mediated reactant. However, the factors governing the reaction pathways have not been examined using quantum chemical tools in a comprehensive manner. Thereupon, we have systematically investigated the mechanism of thiol-yne reactions, focusing on the structural influences of thiol and alkyne functionalities. The reaction kinetics, structure-reactivity relations, and E/Z diastereoselectivity of the products have been enlightened for the first cycle of the thiol-yne polymerization reaction. For this reason, a diverse set of 11 thiol-yne reactions with four thiols and eight alkynes was modeled by means of density functional theory. We performed a benchmark study and determined the M06-2X/6-31+G(d,p) level of theory as the best cost-effective methodology to model such reactions. Results reveal that spin density, the stabilities of sulfur radicals for propagation, and the stability of alkenyl intermediate radicals for the chain transfer are the determining factors of each reaction rate. Intramolecular p-p stacking interactions at transition-state structures are found to be responsible for Z diastereoselectivity
Origins of the photoinitiation capacity of aromatic thiols as photoinitiatiors: a computational study
No full textIn this work, we report the photophysical properties of three thiol derivatives, commonly used as photoinitiators in thiol-ene free radical polymerization, the ultimate goal being to rationalize the main reason behind the photoinitiation efficiency. For this aim, time dependent density functional theory is used to simulate the absorption spectra of alkyl thiol (R-SH), thiophenol (PhSH) and p-(trifluoromethyl) thiophenol (p-CF3PhSH), describe their excited state topologies, and explore their potential energy surfaces along the S-H dissociation. Excited state calculations have shown that the S-H photolysis is achieved through the triplet excited states following intersystem crossing from the originally populated singlet manifolds. More specifically, while in aromatic thiol derivatives dissociation is mainly triplet-state mediated, the first excited singlet state and first triplet state of alkyl thiol are both dissociative and hence potentially capable of generating the photoinduced radical species. We have also justified the experimental findings concerning the photoinitiator efficiency considering both their potential energy surface topologies and the absorption intensity, in the lowest energy region
Solvent Effects on Thiol-Ene Kinetics and Reactivity of Carbon and Sulfur Radicals
No full textThe thiol-ene reaction is one of the fundamental reactions in biochemistry and synthetic organic chemistry. In this study, the effect of polar media on the reaction kinetics is taken into account by using the transition state theory; the reactivities of the carbon and sulfur radicals have also been rationalized by using conceptual DFT. The results have shown that the solvents have more impact on hydrogen atom transfer reactions and the chain transfer rate constant, k(CT), can be increased by using nonpolar solvents, while propagation reactions are less sensitive to media. Similarly, the k(P)/k(CT) ratio can be manipulated by changing the environment in order to obtain tailor-made polymers. Regarding the DFT descriptors, the local and global electrophilicity indices are well correlated with the propagation rate constant k(P), whereas the global electrophilicity index is associated with the chain transfer rate constant k(CT). Overall, electrophilicity indices can be used with confidence to predict the kinetics of thiol-ene reactions
Influence of ionic liquids on the electronic environment of atomically dispersed Ir on (MgO)(100)
No full textRecently, ionic liquids (ILs) have been used as ligands for single-site Ir(CO)(2) complexes bound to metal-oxide supports because of their electron-donor/acceptor capacities. The combined effects of supports and ILs as ligands may pave the way to the tuning of the surrounding electronic properties to increase electron-donor/acceptor efficiency in metal-oxide supported Ir(CO)(2) complexes. Herein, we have used Density Functional Theory to model Ir(CO)(2) complexes bound to MgO supports with and without the presence of an IL to explain the role of ILs in modifying the electronic structure of the supported complex. Comparison of the nu(CO) band stretching frequencies with experimental results has led to the rationalization of the factors driving the interactions between the IL, the support, and the catalyst as well as the justification of the methodology for further studies
The Nowicki conjecture for relatively free algebras
No full textA linear locally nilpotent derivation of the polynomial algebra K[Xm] in m variables over a field K of characteristic 0 is called a Weitzenböck derivation. It is well known from the classical theorem of Weitzenböck that the algebra of constants K[Xm]δ of a Weitzenböck derivation δ is finitely generated. Assume that δ acts on the polynomial algebra K[X2d] in 2d variables as follows: δ(x2i)=x2i−1, δ(x2i−1)=0, i=1,...,d. The Nowicki conjecture states that the algebra K[X2d]δ is generated by x1,x3....,x2d−1, and x2i−1x2j−x2ix2j−1, 1≤
Peasant household survival strategies: rural transformation in the heartland of Turkey's hazelnut production belt
No full textThis study analyses the dynamics of persistence of the peasantry in a capitalist social formation through a case study of a village (Kayadibi) of hazelnut producers in the Central Black Sea region of Turkey. In the analysis the peasant household is given analytical priority as it is seen to be the single most important social institution through which the peasantry interacts, condition and is conditioned by the wider social, economic and political structures. Within such an analytical framework, this study concentrates on three areas of inquiry concerning the dynamics of survival of peasant modes. This is carried out in the context of the process of rural socio-economic transformation which took place under the impact of capitalism and with the start of hazelnut production for the world market in the early nineteenth century. These are: (1) the historical and contingent factors which contributed to the emergence and decline of big land- ownership and the new forms of development of capitalism in agriculture; (2) the areas of disputes and clashes of interests between the peasantry, the state and the merchants concerning the actual form of organization of the commodity and credit markets and further development or restriction of hazelnut production in the country; and (3) the patterns and mechanisms which enable the peasant households to have continuous access to land, labour and credit. The thesis arrives at the conclusion that the key to the persistence of the peasantry, as a property-owning social category of the society in a capitalist formation, is its strategy of diversifying its sources of income in order to decrease the degree of its dependency on land-bound agricultural production. This is combined with the strategy of consolidating its savings in the means of production in its own possession instead of using them to improve its standards of living and consumption
Kadınların oy verme davranışlarını etkileyen sosyal ve ekonomik faktörler: Trabzon ili Ortahisar ilçesi örneği 2019 / A study on the social and economical factors which affect the voting behaviour of women: The sample of Trabzon province, Ortahisar district 2019
No full textKadın seçmenlerin oy verirken nelere dikkat ettiği, nelerden etkilendiği sadece siyasi mecrada değil, sosyolojik etkilerinin anlaşılması ve literatüre katkısı açısından da önemlidir. Bu araştırmada kadın seçmenlerin oy verme davranışını sergilerken etkilendiği sosyal ve ekonomik faktörleri incelemek amaçlanmıştır. Bu bağlamda kadın seçmenlerin sosyal ve ekonomik açıdan sınırlanmış ya da sınırlanmamış olmalarının oy verme davranışı üzerine etkisi tartışmanın konusunu meydana getirmektedir. Kadın seçmenlerin eğitim durumu, gelir durumu, meslekte uzmanlaşma arasında bir ilişki olup olmadığı ve kadın seçmenlerin oy kullanırken özgür bir tutum sergileyip sergilemedikleri arasındaki ilişki çalışmanın temel sorusunu oluşturmuştur. Bu bağlamda ana hipotezlerin ilki sosyal ve ekonomik açıdan sınırlanmamış olan kadın seçmenlerin siyasal katılma biçimlerine ve siyasi yaşama yoğun bir şekilde katılım gösterdiği; ikincisi ise sosyal ve ekonomik açıdan sınırlanmış olan kadın seçmenlerin siyasi parti seçimlerinin eşleri tarafından yapılmakta olduğu şeklinde belirlenmiştir. Araştırmada örneklem olarak Trabzon İli Ortahisar İlçesi Kemerkaya ve Yenicuma Mahallelerinde yaşayan evli ev kadınları ile Trabzon Türk Telekom Bölge Müdürlüğünde çalışan evli kadınlar seçilmiştir. Bu seçilen örneklem üzerinde anket yapılmış ve oluşturulan hipotezler sınanmıştır. Anahtar Kelimeler: Kadın Seçmenler, Oy Verme Davranışları, Siyasal Katılım, Sosyal ve Ekonomik FaktörlerThe points female voters are careful about and the factors from which they are affected while casting a vote is not only an important issue for the sake of its understanding of politics, but also for the understanding of its sociological effects and its contribution to literature. The aim of this study is to examine the social and economical factors which affect the voting behaviour of female voters. In this regard, the effect of female voters on voting behaviour in the case of being restricted socially and economically or not generates the main topic of the argument. The main question of the study is whether there is a connection between the education level, economical income status, vocational specialization of female voters and them behaving freely or not while casting their votes. In this respect, the first of the two hypotheses has shown that the female voters who are not socially and economically restricted take part actively in the political participation and politics; and the second hypothesis has revealed that the decisions of female voters who are socially and economically restricted are made by their husbands and families. The married housewives living in Kemerkaya and Yenicuma Districts of Trabzon Province and the married employed women working for Trabzon Turk Telekom Regional Directorate have been selected as samples in this research. The hypotheses which are created by conducting a poll on these samples have been tested. Keywords: Female Voters, Voting Behaviour, Political Participation, Social and Economical Factor
Mechanistic insights into lysine-targeting covalent inhibition through a theoretical study of ester aminolysis
No full textDevelopment of targeted covalent inhibitors in drug design has a broad and important interest and many efforts are currently being made in this direction. Targeted covalent inhibitors have special relevance in oncology due to the possibilities they offer to overcome the problems of acquired resistance. In recent experiments, lysine-targeting has been envisaged for the irreversible inhibition of the heterodimeric lipid kinase phosphoinositide 3-kinase delta (PI3K delta). Activated esters have been evaluated and shown to be promising inhibitors of this enzyme, but the reaction mechanisms display specificities that are not yet fully understood. In the present work, we have carried out a theoretical study of the aminolysis reaction of model esters in aqueous solution to gain insights into the corresponding biological processes. We have found that phenolic esters bearing electron-withdrawing groups are particularly reactive. The predicted mechanism involves the formation of a tetrahedral zwitterionic intermediate, which dissociates into an alkoxide and a protonated amide, this charge separation being the driving force for the subsequent proton transfer and final product formation. Structure-reactivity relationships are reported and shown to be a useful tool for evaluating potential inhibitor candidates
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