1,722,303 research outputs found
Structural materials: fire and protection
Full text linkAny 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
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
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≤
Selenium content of Turkish hazelnut varieties: Kara Findik, Tombul and Delisava
No full textThe selenium contents of three different varieties of hazelnut, namely Kara Findik, Tombul, and Delisava, which are cultivated in Sakarya, Turkey, were studied for variety and geographical region. The hazelnut kernels prepared as hulled (without hull) and unbulled (whole) forms were analysed by using electrothermal atomization atomic absorption spectrometry after solvent extraction. The mean levels of selenium are 0.47, 0.70, 0.36 mg/100 g in unhulled kernels, and 0.95, 1.69, 0.66 mg/100 g in hulled kernels of Kara Findik, Tombul and Delisava hazelnut varieties, respectively. Selenium compositions of hazelnut varieties showed significant differences from each other by means of geographical region and hulled or unhulled state of hazelnut kernels. It was found that the highest selenium levels were observed in Ferizli district Tombul hulled hazelnut variety whereas in Karasu district lowest selenium contents were obtained in unhulled Kara Findik and Tombul hazelnut varieties. (C) 2003 Elsevier Inc. All rights reserved
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
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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
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
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