1,253 research outputs found
Theoretical explanation of the regioselectivity of polar cycloaddition reactions between furan derivatives and Danishefsky’s diene
No full textThe regioselectivity for a series of experimentally studied Diels–Alder reactions between furan derivatives and Danishefsky’s diene has been rationalized within the framework of local DFT-based descriptors (i.e. electrophilicity and nucleophilicity indexes). The importance of the solvent in the calculations has been studied. It has been shown that the relative trend of an atomic center to behave as an electrophile is affected by the medium (gas phase or benzene solution) and the basis set used in the calculation of the reactivity descriptors. The local electrophilicity (xk) and nucleophilicity (Nk) indexes properly account for the observed regioselectivity only when B3LYP/LANL2DZ and HF/LANL2DZ levels of theory have been used.Fil: Brasca, Romina. Universidad Nacional del Litoral; ArgentinaFil: Kneeteman, Maria Nelida. Universidad Nacional del Litoral; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral; ArgentinaFil: Fabian, Walter M.F.. Universität Graz; Austri
Diels-Alder reactions for the rational design of benzo[b]thiophenes: DFT-based guidelines for synthetic chemists
No full textIn this work we studied the capability of several diene/dienophile pairs to undergo Diels-Alder (DA) reactions leading to benzo[b]thiophenes. A variety of synthetically and commercially available nitrothiophenes were chosen as dienophiles. Methyl 5-nitro-3-thiophenecarboxylate was selected as a potential strong electrophilic candidate based on some DFT-based properties and the substitution pattern of the expected product. The mechanistic details concerning the participation of this dienophile in polar DA reactions were investigated through a theoretical point of view. The results were compared with the experimental outcomes. This methodology should allow synthetic chemists to analyze DA reactions in detail in a stage prior to the synthetic job.Fil: Brasca, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral; ArgentinaFil: Kneeteman, Maria Nelida. Universidad Nacional del Litoral; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral; ArgentinaFil: Fabian, Walter M.F.. Karl-franzens-universitat Graz; Austri
TIPE KEPRIBADIAN TOKOH UTAMA PADA NOVEL “INTROVER” KARYA M.F. HAZIM
No full textThe author tries to analyze the personality of the main characters using the study of literary psychology, whether the main character is more melancholic or pblegmatic. M.F. Hazim in his novel "Introver" tells the story of the world intover. Reading it, we are invited to explore in the mind and soul of an introver who is always nervous, restless, and upset; also the inner conflict that torments him, and how he finds "friends" to fill his loneliness and make his life more meaningful. The author wants to know more clearly what exactly the lives of introverts are in their daily lives. This research is directed to one main problem, namely "What is the personality type of the main character introver in the" Introver "novel by M.F. Hazim ". This research uses descriptive qualitative method with heuristic and hermeneutic reading techniques in order to understand and reveal "something" contained in literary works. The results of the research that have been carried out are in accordance with the research hypothesis, namely the main character Nawawi has an introvert personality type in the novel "Introver" by M.F. Hajim. Researchers found 42 quotes stating that Nawawi has an introverted personality type. Of the 42 quotes that have been found, 28 quotes state that Nawawi has a melancholic personality type and 14 quotes state that Nawawi has a phlegmatic personality type
Beyond Lesson Studies and Design Experiments: Using theoretical tools in practice and finding out how they work
No full textThis paper aims to illustrate how fruitful insights into the link between school teaching practice and student learning outcomes can be theoretically grounded by the variation theory from the field of phenomenography; and from this framework demonstrate how a 'pedagogy of awareness' can be implemented in the classroom. In this study, five teachers and 162 students at Primary Four level of school education in Hong Kong participated and the practice of the 'learning study' was adopted. By comparing the results of pre- and posttests, a significant gain was observed in the students learning outcomes.
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
Helical mode interactions and spectral energy transfer in magnetohydrodynamic turbulence
No full textSpectral transfer processes in magnetohydrodynamic (MHD) turbulence are investigated by decomposition of the velocity and magnetic fields in Fourier space into helical modes. In 1992, Waleffe (Phys. Fluids A, 4:350 (1992)) used this decomposition to calculate triad interactions for isotropic hydrodynamic turbulence and determined whether a given triad contributed to forward or reverse energy transfer depending on the helicities of the interacting modes. The problem becomes more difficult in MHD due to the need to treat a coupled system of partial differential equations and the energy transfers between the magnetic and velocity fields. This requires the development of techniques that extend Waleffe's work, which are subsequently used to calculate the direction of energy transfer processes originating from triad interactions derived from the MHD equations. In order to illustrate the possible transfer processes that arise from helical mode interactions, we focus on simplified cases and putting special emphasis on interactions resulting in reverse spectral energy transfer. This approach also proves to be helpful in determining the nature of certain energy transfer processes, where transfer of energy between different fields and between the same field can be distinguished. Reverse transfer of magnetic energy was found if the helicities of two modes corresponding to the smaller wavenumbers are the same, while for reverse transfer of kinetic energy Waleffe's result is recovered. Reverse transfer of kinetic to magnetic energy is facilitated if the interacting magnetic field modes are of opposite helicity, and no reverse transfer of magnetic to kinetic energy was found. More generally, the direction of energy transfer not only depends on helicity but also on the ratio of magnetic to kinetic energy. For the magnetically dominated case reverse transfer occurs of all helicities are the same, the kinetically dominated case two modes need to have the same helicity while the third mode is of opposite helicity to allow reverse transfer
Reynolds number dependence of the dimensionless dissipation rate in stationary magnetohydrodynamic turbulence
No full textResults on the Reynolds number dependence of the dimensionless total dissipation rate C_ε are presented, obtained from medium to high resolution direct numerical simulations (DNSs) of mechanically forced stationary homogeneous magnetohydrodynamic (MHD) turbulence in the absence of a mean magnetic field, showing that C_ε -> const with increasing Reynolds number. Furthermore, a model equation for the Reynolds number dependence of the dimensionless dissipation rate is derived from the real-space energy balance equation by asymptotic expansion in terms of Reynolds number of the second- and third-order correlation functions of the Elsässer fields z± = u ± b. At large Reynolds numbers we find that a model of the form C_ε = C_ε,∞ + C/R describes the data well, while at lower Reynolds numbers the model needs to be extended to second order in 1/R in order to obtain a good fit to the data, where R is a generalised Reynolds number with respect to the Elsässer field z-
Consumer's welfare and change in stochastic partial-equilibrium price
No full textWelfare Economics;Stochastic Processes
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