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Ultraschnelle zeitaufgelöste Pump/Probe-Photoelektronenspektroskopie an isolierten und massenselektierten Anionen

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ISBN: 9783866440883 Year: Pages: III, 176 p. DOI: 10.5445/KSP/1000005311 Language: GERMAN
Publisher: KIT Scientific Publishing
Subject: Chemistry (General)
Added to DOAB on : 2019-07-30 20:02:02
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In der vorliegenden Arbeit wird die Anregungs/Abfrage-Photoelektronenspektroskopie auf die Untersuchung elektronischer Dynamik in massenselektierten Molekülionen unter Hochvakuum-Bedingungen angewendet, wodurch die Beobachtung intramolekularer elektronischer Relaxation unter Ausschluss jeglicher Wechselwirkung der untersuchten Teilchen zur umgebenden Matrix möglich ist.

Thermochemistry and Kinetics for the Oxidative Degradation of Dibenzofuran and Precursors

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ISBN: 9783866440852 Year: Pages: VIII, 219 p. DOI: 10.5445/KSP/1000005428 Language: ENGLISH
Publisher: KIT Scientific Publishing
Subject: Chemistry (General)
Added to DOAB on : 2019-07-30 20:01:57
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The emission of dibenzofurans and dioxins from industrial processes is a major environmental concern. Focussing on dibenzofuran, this study tend to improve our understanding of the general oxidation chemistry and to provide a mechanism suitable for future modelling studies.Based on quantum chemical methods, energies, chemical structures and reactions are calculated numerically. Not only stable molecules and radicals, but also transition states are reported in this work.

Berechnung von Raman-Intensitäten mit zeitabhängiger Dichtefunktionaltheorie

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ISBN: 9783866441873 Year: Pages: 81 p. DOI: 10.5445/KSP/1000007191 Language: GERMAN
Publisher: KIT Scientific Publishing
Subject: Chemistry (General)
Added to DOAB on : 2019-07-30 20:02:02
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Die Raman-Schwingungsspektroskopie ist eine der führenden Charakterisierungsmethoden für chemische Konstitution und liefert wertvolle Beiträge zur Strukturaufklärung großer Moleküle. Die Interpretation experimenteller Raman-Spektren wird durch den Vergleich der theoretischen Vorhersagen für Schwingungsfrequenzen und Raman-Intensitäten mit experimentellen Daten ermöglicht. Diese Arbeit umfasst die Entwicklung, Implementierung und Validierung effizienter Verfahren zur Berechnung der Raman-Intensitäten im Rahmen der zeitabhängigen Dichtefunktionaltheorie (TDDFT). Die Verwendung analytischer Gradientenmethoden eröffnet den Weg zur simultanen Berechnung der Raman-Intensitäten aller Schwingungsmoden eines Moleküls innerhalb der Polarisierbarkeitstheorie. Die entwickelten Verfahren werden hinsichtlich ihrer Genauigkeit und ihres Rechenaufwandes untersucht und zur Interpretation der Raman-Spektren von Fullerenen eingesetzt.

High-Pressure Studies of Crystalline Materials

ISBN: 9783038971313 9783038971320 Year: Pages: 330 DOI: 10.3390/books978-3-03897-132-0 Language: English
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Chemistry (General) --- Mathematics --- Environmental Sciences
Added to DOAB on : 2018-09-20 10:13:12
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[This book is a printed edition of the Special Issue of Crystals: High-Pressure Studies of Crystalline Materials. It also includes additional articles published in Crystals and related to the topic of the Special Issue, which have been selected based upon their relevance and scientific quality.]

Quantum Mechanical/Molecular Mechanical Approaches for the Investigation of Chemical Systems - Recent Developments and Advanced Applications

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889456260 Year: Pages: 188 DOI: 10.3389/978-2-88945-626-0 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Chemistry (General)
Added to DOAB on : 2019-01-23 14:53:43
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The QM/MM method, short for quantum mechanical/molecular mechanical, is a highly versatile approach for the study of chemical phenomena, combining the accuracy of quantum chemistry to describe the region of interest with the efficiency of molecular mechanical potentials to represent the remaining part of the system. Originally conceived in the 1970s by the influential work of the the Nobel laureates Martin Karplus, Michael Levitt and Arieh Warshel, QM/MM techniques have evolved into one of the most accurate and general approaches to investigate the properties of chemical systems via computational methods. Whereas the first applications have been focused on studies of organic and biomolecular systems, a large variety of QM/MM implementations have been developed over the last decades, extending the range of applicability to address research questions relevant for both solution and solid-state chemistry as well. Despite approaching their 50th anniversary in 2022, the formulation of improved QM/MM methods is still an active field of research, with the aim to (i) extend the applicability to address an even broader range of research questions in chemistry and related disciplines, and (ii) further push the accuracy achieved in the QM/MM description beyond that of established formulations. While being a highly successful approach on its own, the combination of the QM/MM strategy with other established theoretical techniques greatly extends the capabilities of the computational approaches. For instance the integration of a suitable QM/MM technique into the highly successful Monte-Carlo and molecular dynamics simulation protocols enables the description of the chemical systems on the basis of an ensemble that is in part constructed on a quantum-mechanical basis. This eBook presents the contributions of a recent Research Topic published in Frontiers in Chemistry, that highlight novel approaches as well as advanced applications of QM/MM method to a broad variety of targets. In total 2 review articles and 10 original research contributions from 48 authors are presented, covering 12 different countries on four continents. The range of research questions addressed by the individual contributions provide a lucid overview on the versatility of the QM/MM method, and demonstrate the general applicability and accuracy that can be achieved for different problems in chemical sciences. Together with the development of improved algorithms to enhance the capabilities of quantum chemical methods and the continuous advancement in the capacities of computational resources, it can be expected that the impact of QM/MM methods in chemical sciences will be further increased already in the near future.

New Frontiers in Multiscale Modelling of Advanced Materials

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197552 Year: Pages: 91 DOI: 10.3389/978-2-88919-755-2 Language: English
Publisher: Frontiers Media SA
Subject: General and Civil Engineering --- Materials
Added to DOAB on : 2016-04-07 11:22:02
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Atomistic simulations, based on ab-initio and semi-empirical approaches, are nowadays widespread in many areas of physics, chemistry and, more recently, biology. Improved algorithms and increased computational power widened the areas of application of these computational methods to extended materials of technological interest, in particular allowing unprecedented access to the first-principles investigation of their electronic, optical, thermodynamical and mechanical properties, even where experiments are not available. However, for a big impact on the society, this rapidly growing field of computational approaches to materials science has to face the unfavourable scaling with the system size, and to beat the time-scale bottleneck. Indeed, many phenomena, such as crystal growth or protein folding for example, occur in a space/time scale which is normally out of reach of present simulations. Multi-scale approaches try to combine different scale algorithms along with matching procedures in order to bridge the gap between first-principles and continuum-level simulations. This Research Topic aims at the description of recent advances and applications in these two emerging fields of ab-inito and multi-scale materials modelling for both ground and excited states. A variety of theoretical and computational techniques are included along with the application of these methods to systems at increasing level of complexity, from nano to micro. Crossing the borders between several computational, theoretical and experimental techniques, this Research Topic aims to be of interest to a broad community, including experimental and theoretical physicists, chemists and engineers interested in materials research in a broad sense.

First-Principles Prediction of Structures and Properties in Crystals

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ISBN: 9783039216703 / 9783039216710 Year: Pages: 128 DOI: 10.3390/books978-3-03921-671-0 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Chemistry (General)
Added to DOAB on : 2019-12-09 16:10:12
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The term “first-principles calculations” is a synonym for the numerical determination of the electronic structure of atoms, molecules, clusters, or materials from ‘first principles’, i.e., without any approximations to the underlying quantum-mechanical equations. Although numerous approximate approaches have been developed for small molecular systems since the late 1920s, it was not until the advent of the density functional theory (DFT) in the 1960s that accurate “first-principles” calculations could be conducted for crystalline materials. The rapid development of this method over the past two decades allowed it to evolve from an explanatory to a truly predictive tool. Yet, challenges remain: complex chemical compositions, variable external conditions (such as pressure), defects, or properties that rely on collective excitations—all represent computational and/or methodological bottlenecks. This Special Issue comprises a collection of papers that use DFT to tackle some of these challenges and thus highlight what can (and cannot yet) be achieved using first-principles calculations of crystals.

Ice Crystals

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ISBN: 9783039218905 / 9783039218912 Year: Pages: 104 DOI: 10.3390/books978-3-03921-891-2 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Physics (General)
Added to DOAB on : 2019-12-09 11:49:16
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Ice crystals are the most ubiquitous material found in the cryosphere environment of the Earth, in the planetary system, and also in our daily lives. In recent years, ice crystals have increased in importance as one of the key materials for finding solutions to settle various environmental concerns at a global scale. Furthermore, ice crystals are unique materials which are potentially extremely useful in various applications, for example, within the food sciences, medical sciences, and other fields. In dealing with these interesting subjects, research on ice crystals has been more actively pursued in recent years. The Special Issue “Ice Crystals” presents a wide varieties of topics related to ice crystals. It can be considered as a status report reviewing the recent research on ice crystals and serves to provide readers with information on the latest developments concerning ice crystals.

The Origin and Early Evolution of Life: Prebiotic Chemistry of Biomolecules

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ISBN: 9783039216062 / 9783039216079 Year: Pages: 288 DOI: 10.3390/books978-3-03921-607-9 Language: eng
Publisher: MDPI - Multidisciplinary Digital Publishing Institute
Subject: Science (General) --- Chemistry (General)
Added to DOAB on : 2019-12-09 11:49:16
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Studying the origin of life is one of man’s greatest achievements over the last sixty years. The fields of interest encompassed by this quest are multiple and interdisciplinary: chemistry, physics, biology, biochemistry, mathematics, geology but also statistics, atmospheric science, meteorology, oceanography, and astrophysics. Recent scientific discoveries, such as water on Mars and the existence of super-Earths with atmospheres similar to primordial Earth, have pushed researchers to simulate prebiotic conditions in explaining the abiotic formation of molecules essential to life. This collection of articles offers an overview of recent discoveries in the field of prebiotic chemistry of biomolecules, their formation and selection, and the evolution of complex chemical systems.

Keywords

origin of life --- systems chemistry --- Chemomimesis --- Molecular Darwinism --- origin of life --- prebiotic chemistry --- thiol-rich peptides --- cysteine --- aminonitriles --- imidazoles --- origin of life --- prebiotic chemistry --- nucleotide and nucleoside synthesis --- protein design --- novel metalloproteins --- binary patterned amino acid sequences --- prebiotic chemistry --- population growth --- replication --- growth order --- Darwinian evolution --- selection --- origin of life --- abiogenesis --- carbon fixation --- hydrothermal vents --- electrochemistry --- reduction --- digit multiplicity --- information --- transmission --- encoding --- translation --- diversity --- function --- origin of life --- layered double hydroxide (LDH) clay --- pentose diphosphate --- pentopyranose nucleic acid --- arabinopyranose nucleic acid --- RNA --- base pairing --- purine precursor --- inosine --- AICAR --- peptide/RNA world --- prebiotic information system --- translation and the genetic code --- bridge peptide and aaRS --- ribozyme and tRNA --- tRNA and mRNA --- coevolution of translation machine and the genetic code --- MVC architecture pattern and biological information --- numerical codons --- AnyLogic software for computer simulation of translation machine --- phosphoryl transfer --- metabolism --- energy currency --- mixed anhydride --- origin of life --- hypercycle --- Monte Carlo --- prebiotic chemistry --- carbamic acid --- carbon dioxide-ammonia ices --- infrared spectra --- anharmonicity --- origin of life --- metabolism --- phosphates --- network expansion simulation --- thermodynamic bottleneck --- molecular clocks --- ab initio molecular dynamics --- catalysis --- prebiotic soup --- origins of life --- aldol reaction --- mechanochemistry --- minerals --- monosaccharides --- prebiotic chemistry --- prebiotic polymerization --- nucleotide oligomerization --- abasic oligomers --- nucleotide stability --- stability as a selection pressure --- dry-wet cycles --- genetic code origin --- tRNA accretion model --- tRNA-synthetase --- metabolism --- thioester --- nucleotidyltransferases --- early peptides --- ribosome --- n/a

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