262,414 research outputs found
Ramachandran plot distribution of non-proline <i>trans</i>-conformation (A) PD2 decoy loop residues, (B) all SCOP40 residues, and (C) native loop conformations in the Fiser test set.
No full text<p>Ramachandran plot distribution of non-proline <i>trans</i>-conformation (A) PD2 decoy loop residues, (B) all SCOP40 residues, and (C) native loop conformations in the Fiser test set.</p
A Design Space Exploration Framework for Memristor-Based Crossbar Architecture
No full textIn the literature, there are few studies describing how to implement Boolean logic functions as a memristor-based crossbar architecture and some solutions have been actually proposed targeting back-end synthesis. However, there is a lack of methodologies and tools for the synthesis automation. The main goal of this paper is to perform a Design Space Exploration (DSE) in order to analyze and compare the impact of the most used optimization algorithms on a memristor-based crossbar architecture. The results carried out on 102 circuits lead us to identify the best optimization approach, in terms of area/energy/delay. The presented results can also be considered as a reference (benchmarking) for comparing future work
A computational glance at organometallic cyclizations and coupling reactions
No full text210 p.Organometallic chemistry is one of the main research topics in chemical science.Nowadays, organometallic reactions are the subject of intensive theoretical investigations.However, in many cases, only joint experimental and theoretical effortscould reveal the answers what we are looking for.The fruits of such experimental and theoretical co-operations will be presentedhere. In this work, we are going to deal with homogeneous organometallic catalysisusing computational chemical tools. Particularly, DFT study of palladium andgold-catalyzed reactions and special carbometalations will be described.Chapter 1 gives an introductory overview of organometallic chemistry andcatalysis in general using a historical perspective. It covers the 9 thousand yearshistory of catalysis from 7000 BC (the earliest concrete evidence of man-made fermentation/biocatalysis) through several milestones (Libavius, Berzelius etc.) upto the present days of organometallic chemistry.Chapter 2 is a short methodological summary and intended to shed some lighton the theoretical foundations of the applied quantum chemical tools, but it is neithercomplete, nor deep, just enough to scratch the surface and give insight into thecomplexity of the theory.The results of our calculations presented in three separate chapters,(Chapter 3, 4 and 5) in each of which the calculations discussed along with theviiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fisercorresponding experimental findings of our collaborators and/or other scientists.Chapter 3 describe specific issues of palladium-catalyzed reactions. In this partof the work, palladium(II)-catalyzed dynamic kinetic asymmetric C¿P couplingfor the asymmetric synthesis of QUINAP and other atropos P,N-ligands is discussedand the reaction investigated at the M06/6-31+G(d,p)/SDD//B3LYP/6-31G(d)/LANL2DZ level of theory. The computational results along with xperimentalevidences collected by our collaborators allowed to propose a mechanismbased on the formation of cationic oxidative addition intermediates which underthe reaction conditions, undergo a fast interconversion (Figure 0.0.1). Coordinationof the isoquinoline N atom to Pd is essential to facilitate this process.Figure 0.0.1: Proposed Mechanism for the Epimerization of DiastereomericOxidative Addition Intermediates (OAI and OAI¿).The calculations also show that the energy requirements for a dynamic kineticprocess are met, since the fast equilibrating palladacyclic intermediates evolve throughixSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fiserdiastereomeric transmetalation steps of very large energy difference. The easinessof the final reductive elimination ensures the irreversibility of the process.Chapter 4 can be divided into two parts in which gold(I)-catalyzed reactionsare studied.In the first section, the tandem gold(I)-catalyzed rearrangement/Nazarov reactionof propargylic ester derivatives studied in deeply computationally and thecalculations revealed the details of the reaction mechanism (Figure 0.0.2) whichallowed us to evaluate energetically the influence of the substrate structures on thereaction rate and on the regio- and stereoselectivity.Figure 0.0.2: Reaction Mechanism. Top: Acetate Rearrangement in the InitialSteps of the Mechanism. Bottom: Cyclization Step from the pre-Nazarovcyclization complex III and Protodeauration. Gibbs Free Energy Changes(¿G) and Barrier Heights (¿Gz) are Given in kcal/mol.xSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserIn the second section, gold(I)-catalyzed cycloisomerizations calculated (Figure0.0.3). The calculations showed that with both types of substrates, the oxyaurationstep has a low barrier or almost no barrier at all when it involves the internalposition of a terminal triple bond, resulting in a 5-exo-dig process. In contrast,the 6-endo-dig mechanism is always favoured with substituted alkynes. The preferencebeing purely geometrical and irrespective of the type of substitution, thusproviding either ß-enaminones or their reduced equivalents, ß-amino ketones, ina robust, reliable, and convenient way.Figure 0.0.3: Transition State Structures and the Corresponding BarrierHeights (¿Gz, in kcal/mol) for Terminal and Internal Alkynes.xiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserChapter 5 is a systematical study of intramolecular metal catalyzed cyclizations.Group 10 alkyl metalations are studied systematically by means of DFT calculationsand based on the results the extension of the Baldwin¿s rules for metal catalyzedring closure reactions is proposed (Figure 0.0.4).Figure 0.0.4: Studied Group 10 Alkyl Metalations.An intuitive summary of the qualitative results created and the results couldserve as a guide to explore not yet described cyclization processes based on the accessiblecomputed activation energies and the qualitative comparison of the preferences.Our manuscripts published in connection with the topics discussed in the thesiscan be found in the Appendix.xiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserA Computational Glance at Organometallic Cyclizationsand Coupling ReactionsAbstractLa química organometálica es uno de los campos más activos de investigación enciencias químicas. Hoy en día, las reacciones organometálicas son sujeto de numerosasinvestigaciones teóricas. Sin embargo, en muchos casos, sólo los esfuerzosconjuntos teóricos y experimentales son capaces de encontrar las respuestasque buscamos. En este trabajo se presentan los frutos de tales colaboracionesexperimentales/teóricas. Hemos empleado herramientas computacionales paraestudiar reacciones catalizadas en condiciones homogéneas, y más concretamentedescribimos a continuación estudios DFT de reacciones de ciclación catalizadaspor Paladio y Oro, así como algunos tipos de carbometalación.Capítulo 1. Se da un repaso introductorio de la catálisis organometálica ycatálisis en general usando una perspectiva histórica. Cubre los 9000 años de historiade la catálisis desde el 7000 a. C. (la más antigua evidencia de fermentación/ biocatálisis hecha por el hombre) a través de diversos hitos (Libavius, Berzelius,etc.) hasta la química organometálica de nuestros días.Capítulo 2. Es una breve descripción metodológica que intenta dar luz sobrelas formulaciones teóricas que se aplican en las herramientas químicas cuánticas,sin la intención de ser completa ni profusa, sino solamente arañando la superficiede esta parte tan compleja de la teoría.Los resultados de nuestros cálculos se presentan en tres capítulos separadosxiiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fiser(capítulos 3, 4 y 5), en cada uno de los cuales se entremezclan con los resultadosexperimentales de nuestros colaboradores y otros grupos de investigación.Capítulo 3. Describe algunas características especiales de la química del paladio.En esta parte de la Tesis, se han estudiado reacciones de síntesis asimétricade QUINAP, mediante un acoplamiento C-P dinámico cinético asimétrico catalizadopor complejos de paladio (II). Además de QUINAP, se han estudiado otrosatropo-ligandos P, N por métodos DFT al nivel de cálculoM06/6-31+G(d,p)/SDD//B3LYP/6-31G(d)/LANL2DZ.Figure 0.0.1: Mecanismo Propuesto para la Epimerización de los IntermediosDiastereoméricos de Adición Oxidante (OAI y OAI¿).xivSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserLos resultados computacionales junto a las evidencias experimentales recopiladaspor nuestros colaboradores nos permiten proponer un mecanismo de reacciónbasado en la formación de intermedios catiónicos de adición oxidante, queen las condiciones de reacción sufren una interconversión rápida entre diferentesisómeros (Figura 0.0.1). La coordinación del nitrógeno de la isoquinolina al átomode Pd es esencial para facilitar el proceso.Los cálculos también muestran que se cumplen los requisitos energéticos parauna resolución cinética dinámica, ya que los intermedios de reacción equilibranrápidamente y evolucionan por estados de transición de transmetalación de barrerasde activación muy diferentes.xvSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserCapítulo 4. Se divide en dos partes en las que se estudian dos reacciones catalizadaspor Au(I) diferentes. En la primera sección, se ha estudiado computacionalmenteal detalle la reacción tándem de transposición / ciclación Nazarov catalizadaspor Au(I) de ésteres propargílicos, y nuestros cálculos revelan el mecanismodetallado en la Figura 0.0.2, permitiéndonos evaluar energéticamente la influenciade las estructuras de los substratos en la velocidad de reacción y en la regio- yestereoselectividad.Figure 0.0.2: Mecanismo de Reacción. Arriba: Transposición de Acetato enlos Inicios de la Reacción. Abajo: Paso de Ciclación desde el Complejo pre-Nazarov III y Protodesauración. Los Cambios en la Energía Libre de Gibbs(¿G) y Barreras de Activación (¿Gz) se dan en kcal/mol.xviSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserEn la segunda sección, se han calculado reacciones de cicloiosomerización catalizadaspor Au(I) (Figura 0.0.3). Los cálculos muestran que para ambos tipos desustratos mostrados, el paso de oxiauración ocurre con una barrera de activaciónmuy baja o inexistente cuando ocurre en la posición interna del triple enlace, resultandoen un proceso 5-exo-dig. La preferencia es puramente geométrica e independientedel tipo de sustitución, dando lugar tanto las ß-enaminonas como susequivalentes reducidos, ß-amino cetonas, de un modo robusto, apropiado y fiable.Figure 0.0.3: Estructuras de los Estados de Transición y sus CorrespondientesBarreras de Activación (¿Gz, se dan en kcal/mol) para los AlquinosTerminales e Internos.xviiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserCapítulo 5. Es un estudio sistemático de reacciones de ciclación catalizadaspor metales de transición. Se han estudiado sistemáticamente las ciclaciones conlos metales del grupo 10 por métodos computacionales, y basándonos en los resultados,se propone una extensión de las reglas clásicas de Baldwin para ciclacionesa la catálisis metálica (Figura 0.0.4)Figure 0.0.4: Metalaciones del Grupo 10 Estudiadas.Los resultados cualitativos han dado lugar a un resumen intuitivo de los resultadosque podría servir como guía para explorar nuevos procesos catalíticos decarbometalación.Los manuscritos publicados como resultado de estos capítulos se adjuntan enel Apéndice I.xvii
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Atomic scale interfacial magnetism and origin of metal-insulator transition in (LaNiO 3 ) n /(CaMnO 3 ) m superlattices: a first principles study
No full textAbstract Interfacial magnetism and metal-insulator transition at LaNiO 3 -based oxide interfaces have triggered intense research efforts, because of the possible implications in future heterostructure device design and engineering. Experimental observation lack in some points a support from an atomistic view. In an effort to fill such gap, we hereby investigate the structural, electronic, and magnetic properties of (LaNiO 3 ) n /(CaMnO 3 ) m superlattices with varying LaNiO 3 thickness (n) using density functional theory including a Hubbard-type effective on-site Coulomb term. We successfully capture and explain the metal-insulator transition and interfacial magnetic properties, such as magnetic alignments and induced Ni magnetic moments which were recently observed experimentally in nickelate-based heterostructures. In the superlattices modeled in our study, an insulating state is found for n=1 and a metallic character for n=2, 4, with major contribution from Ni and Mn 3d states. The insulating character originates from the disorder effect induced by sudden environment change for the octahedra at the interface, and associated to localized electronic states; on the other hand, for larger n, less localized interfacial states and increased polarity of the LaNiO 3 layers contribute to metallicity. We discuss how the interplay between double and super-exchange interaction via complex structural and charge redistributions results in interfacial magnetism. While (LaNiO 3 ) n /(CaMnO 3 ) m superlattices are chosen as prototype and for their experimental feasibility, our approach is generally applicable to understand the intricate roles of interfacial states and exchange mechanism between magnetic ions towards the overall response of a magnetic interface or superlattice
Noncovalent cross-links in context with other structural and functional elements of proteins
No full textProteins are heteropolymers with evolutionary selected native sequences of residues. These native sequences code for unique and stable 3D structures indispensable for biochemical activity and for proteolysis resistance, the latter which guarantees an appropriate lifetime for the protein in the protease rich cellular environment. Cross-links between residues close in space but far in the primary structure are required to maintain the folded structure of proteins. Some of these cross-links are covalent, most frequently disulfide bonds, but the majority of the cross-links are sets of cooperative noncovalent long-range interactions. In this paper we focus on special clusters of noncovalent long-range interactions: the Stabilization Centers (SCs). The relation between the SCs and secondary structural elements as well as the relation between SCs and functionally important regions of proteins are presented to show a detailed picture of these clusters, which are believed to be primarily responsible for major aspects of protein stability
Protecting Animals 36: Author Witi Ihimaera
No full textIn this very special episode of Knowing Animals I am joined by beloved New Zealand author Witi Ihimaera. Witi has written many books featuring nonhuman animals. He offers us a non-colonial lens through which to think about the human/nonhuman relationship
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
Author in Essay by I. A. Goncharov “Pepiniere”
No full textFeatures of the embodiment of the author’s position in the essay by I. A. Goncharov “Pepiniere” are considered. The relevance of the study is due to the poorly studied poetics of this work. A review of the scientific literature on relevant topics is performed. Methodological and theoretical definitions are given. The scientific novelty of the article is in the fact that for the first time attention is paid to artistic techniques that allow to identify the author's position in the specified literary text. The author of the article grounds her opinion from the fact that, despite the dominance of the subjective point of view, other characters’ views stand out in the work. It is concluded in the study that the text of the work represents a biographical author and author-creator. It was established that the position of the author-creator is expressed through the title, epigraphs, which are quotes, as well as through different points of view, including the author-character, the author-narrator, the characters of the work. The author of the article dwells in detail on different ways of expressing the points of view of the author-character and the author-narrator. It is proved that the point of view of the author-character and the author-narrator can intersect, they are interchanged. The author's development of the term comic “point of view” is presented in the article
Espai i identitat en l'obra de Jordi Pere Cerdà. Una geografia literària cerdaniana
No full textL'obra de l'autor nord-català Jordi Pere Cerdà (1920-2011) teixeix una cartografia literària que abasta tota dimensió espacial -real, imaginada i ficcional. Les prospeccions que assagen els seus texts es fonen en el medi natural i rural, canten a l'amor, als veïns i als éssers fantàstics del folklore català, es comprometen amb els refugiats encarant-se a tota frontera i, també, a tot abisme interior i exterior que oprimesca l'ésser. El mapatge cognitiu i literari que crea Cerdà sobrepassa qualsevol obstacle per construir espais oberts i possibles, en comunió amb l'altre. Partint d'una aproximació teòrica geocrítica, aquest treball d'investigació aprofundeix en diverses nocions sobre l'espacialitat lligades a un context convuls, ple de transformacions a nivell socioeconòmic, polític, cultural i lingüístic, el qual determinarà la vida d'un autor i d'un territori transfronterer com el de la Cerdanya i la Catalunya del Nord. En definitiva, la rica experiència vital de Jordi Pere Cerdà ens permet reflexionar sobre les relacions que vulguem establir entre els individus i amb el nostre hàbitat natural i cultural, a fi d'esdevenir membres actius que participen de la transformació dels espais que configuren les nostres identitats.The work of the North Catalan author Jordi Pere Cerdà (1920-2011) weaves a literary cartography which reaches all spatial dimensions -real, imagined and fictional. The prospections proved by their texts merge with the natural and rural environment, sing to love, neighbours and the fantastic beings of the Catalan folklore. Such prospections also commit themselves with the refugees facing every frontier and, also, facing all interior and exterior abyss that oppresses the being. The cognitive and literary mapping created by Cerdà overcomes any obstacle to construct opened and possible spaces, in communion with the other. Based on the theoretical approach called geocriticism, this research study delves into various notions about spatiality linked to a convulsive context, full of transformations at a socioeconomic, political, cultural and linguistic level; these transformations will determine the life of an author and a cross-border territory such as Cerdagne and Northern Catalonia. In short, the rich experience of Jordi Pere Cerdà allows us to reflect on the relationships we want to establish between individuals, as well as between human groups and our natural and cultural habitat, in order to become active members that participate in the transformation of the spaces that make up our identities.Programa de Doctorat en Llengües Aplicades, Literatura i Traducci
- …
