Добірка наукової літератури з теми "Theorical chemistry"

This work presents the synthesis and characterization of a novel compound, 4-(2-(2-(2-formylphenoxy)ethoxy)ethoxy)phthalonitrile as the aldehyde functional group substituted phthalonitrile derivative. The spectroscopic properties of the compound were examined by FT-IR, 1H-NMR, 13C-NMR, UV-vis, MS, elemental analyses. The molecular structure of the compound was also confirmed using X-ray single-crystal data with a theorical comparative approach.

Abstract<title> SUMMARY </title>The theory of electrolytic dissociation represented the main chapter of modern chemistry-physics born in the last decades of 19th century. It was vigorously supported, in particular by Ostwald, Arrhenius and Nerst, but it was also harshly criticised. This paper reconstructs the theorical and empirical arguments, which were proposed for and against this theory. Namely, it shows on the one hand the great difficulties, that the supporters of the theory were faced with, and on the other hand the strategies that they adopted in order to overcome these problems. The final part discusses how certain models for a philosophical reconstruction of science shed light on this historical case.

The aim of this work was to characterize and optimize the formation of molecular complexes produced by the association of calcium alginate and reduced glutathione (GSH). The influence of varying concentrations of calcium and GSH on the production of microcapsules was analyzed using response surface methodology (RSM). The microcapsules were characterized by thermogravimetric analysis (TGA-DTG) and infrared spectroscopy (FTIR) in order to assess the hydration of the complexes, their thermal stability, and the presence of GSH within the complexes. The optimum conditions proposed by RSM to reach the maximum concentration of GSH within complexes were a 15% w/v of GSH and 1.25% w/v of CaCl2, with which a theorical concentration of 0.043 mg GSH per mg of CAG complex was reached.

There are not many international courses that teach color science applied to non-technical fields. Here, we want to present the experience from a master course organized by Gruppo del Colore – Associazione Italiana Colore and Politecnico of Milano: the Master in Color Design & Technology. It has the aim of training students in the use of color mainly for design purposes, and color science and colorimetry have a big role in the program. The Master is organized in three main phases: Fundamentals, Project Works and Internship. The first part is a series of lectures and frontal lessons that gives to the students the theorical and technical bases to be used in project works practical applications of and internship. In fact, in the second and third parts students are asked to design and develop different applicative design projects. After the first part of Fundamentals training, students will be able to manage disciplines such as colorimetry, visual perception, physics, chemistry, optics and psychology, to build up their future professional career in different fields.

Non-circular gears can maintain rotational motions of general gears and implement all varying rotational motions of the cam. They adjust the angular velocity of driven gear according to operating conditions and make precise changes in angular motion. The design of non-circular gears has not been sufficiently studied because of their particularity and complex design methods unlike spur gears. In the gutting section of the Squid Belly Opening and Gutting Machine (SBOGM), spur gears generate rotational impact due to constant angular velocities, causing noise and equipment damage; so, efficiency should be improved by varying sectional angular velocity. Therefore, we derived pitch curves by selecting angular velocity ratio considering operating environments, and the tooth profile was designed by calculating module for each section according to radius through theorical analysis for precise expression of angular velocity ratio. To confirm reliability of design, angular velocity ratio and structural safety of designed non-circular gears were verified using, commercial software, ‘DAFUL 2020 R1′.

Severe sepsis is one of the most significant challenges in critical care. Despite all the developments achieved in infectious diseases and critical care, along with numerous attempts to develop treatments, the mortality rate of severe sepsis and septic shock remains unacceptably high. The pathophysiology of severe sepsis and septic shock is only partially understood. Circulating pro-inflammatory and anti-inflammatory mediators appear to participate in the complex cascade of events which leads to deranged microcirculatory function, as we know from the peak concentration hypothesis. Therapeutic trials targeting single pro-inflammatory and anti-inflammatory mediators failed to demonstrate any benefit, suggesting that the unselective removal of different mediators may be a more appropriate approach. In severe sepsis several blood purification techniques, such as continuous hemofiltration (CVVH), high volume hemofiltration (HVHF), pulse high volume hemofiltration (HVHF), plasma filtration, plasma adsorption, coupled plasma filtration adsorption (CPFA), have been proposed but such techniques appear to have both theorical as well as practical limitations. Plasma Filtration Adsorption Dialysis (PFAD) is a new extracorporeal treatment which combines different principles of blood purification in a single device. The core of this technique is a new dialyzer composed by three suitable compartments that provide specific functions. The association of multiple principles permits specific removal of molecules implicated in the pathophysiology of patient's disease and re-establishment of hydro-electrolyte, acid-base equilibrium, if renal dysfunction-failure is present. The final target of PFAD is to obtain complete purification by combining principles of physics and chemistry to remove hydrophilic and hydrophobic molecules with a very wide range of weights.

Layered rock mass is a common rock mass structure with diverse forms and complex mechanical properties. Three types of composite layered rock mass prepared using sandstone and shale can be divided into sandwiched type, interbedded type and superimposed type. The total height of the combined rock mass is 50 mm, which is a cylinder composed of sandstone and shale with a diameter of 25 mm and different thickness. Uniaxial compression tests on sandstone, shale and combined rock mass were performed. The results show that, with the increase in the content of soft components, the compressive strength and elastic modulus of the combined rock mass tend to decrease. The mechanical properties of the superimposed rock mass will be between the two components and close to the soft component in numerical value. The mechanical properties of sandwiched rock mass are obviously affected by the properties of the sandwiched rock. When the content of the components is consistent, interbedded rock mass often shows higher strength and elastic modulus. Compared with other rock mass, interbedded rock mass has more stable mechanical properties. The stress–strain curve can be divided into the compaction stage, elastic stage, plastic development stage and post-fracture stage. The composition content of the rock mass plays a decisive role in the compaction stage. The failure modes are mainly shear failure and tensile failure. With the increase in soft rock content, the failure degree of soft rock is gradually weakened, and the failure modes show a trend from tensile failure to shear failure. The experimental results provide theorical guidance for underground engineering construction.

La thèse porte sur la caractérisation théorique des propriétés optiques non linéaires (ONL) de second ordre de composés organiques photochromes. Différentes approches de calcul sont mises en oeuvre pour étudier les réponses de génération de seconde harmonique (SHG) de deux familles de photochromes, les Donor-Acceptor Stenhouse Adducts (DASA) et les dérivés Azobenzène (AZOs). La thèse aborde différents aspects susceptibles d’influencer leurs réponses SHG, notamment la nature des groupes fonctionnels présents dans les différents composés, les effets de la dynamique structurale, ainsi que les effets de l’environnement moléculaire. Dans une première partie, l’effet du caractère donneur-accepteur des dérivés DASA et AZO est étudié, en variant la nature des substituants chimiques greffés à leur extrémité. Les réponses ONL des composés en solution sont calculées en utilisant la théorie de la fonctionnelle de la densité (DFT), sur la base des géométries d’équilibre, et en utilisant des modèles de continuum diélectrique pour traiter les interactions soluté-solvant. Cette approche fournit des valeurs de première hyperpolarisabilité (��) en accord qualitatif avec les données expérimentales obtenues à partir de mesures de diffusion Hyper-Rayleigh (HRS), et permet de rationaliser les relations entre la structure des composés et leurs propriétés ONL. Dans une deuxième partie, une approche computationnelle combinant des simulations de dynamique moléculaire (MD) et des calculs DFT est mise en oeuvre afin d’inclure l’effet des fluctuations géométriques sur les réponses ONL des photochromes en solution, ainsi qu’une description plus précise des interactions soluté-solvant. Les études sont menées sur un dérivé DASA représentatif. Nous montrons tout d’abord que la dynamique conformationnelle exalte la réponse de seconde harmonique, améliorant ainsi l’accord avec les mesures HRS. Nous démontrons également que les fluctuations de �� le long de la dynamique présentent une corrélation avec l’alternance des ordres de liaisons (BOA), qui fournit une mesure de la conjugaison électronique le long de la molécule. Enfin, différentes approches de calcul allant au delà des modèles de continuum sont utilisées dans un second temps pour améliorer la description des interactions soluté-solvant. Dans la dernière partie de la thèse, la méthodologie de calcul mixte quantique/classique employée précédemment est utilisée pour caractériser les réponses ONL de monocouches autoassemblées (SAM) fonctionnalisées avec des dérivés AZO, portant des substituants donneurs ou accepteurs sur leur phényle externe. Nous étudions ici l’impact de la nature du substituant sur l’organisation spatiale des photochromes au sein de la monocouche, ainsi que l’amplitude de leur réponse de seconde harmonique
This thesis focuses on the characterization of the second-order nonlinear optical (NLO) properties of molecular photoswitches by means of computational chemistry. In particular, we implement computational approaches to investigate the second harmonic generation (SHG) process occurring in two families of photoswitches, namely Donor-Acceptor Stenhouse Adducts (DASAs) and azobenzene derivatives (AZOs). The different chapters of the thesis address various aspects influencing the SHG responses of the photoswitches, including their substitution pattern, their conformational dynamics, as well as their surrounding. In a first part, we study the effect of the push-pull character of a series of DASA and AZO derivatives, by functionalizing their extremities with various electron-donating and electronwithdrawing chemical substituents. The NLO responses in solution are calculated using the density functional theory (DFT) on the basis of the equilibrium geometries of the chromophores, and using implicit continuum models for treating solute-solvent interactions. This approach is shown to provide first hyperpolarizability (��) values in good qualitative agreement with the experimental data obtained from Hyper-Rayleigh Scattering (HRS) measurements, allowing reliable structure-property relationships to be established. In a second part, we implement a computational approach combining molecular dynamics simulation (MD) and DFT calculations, in order to include the effects of structural dynamics and a better description of solute-solvent interactions in the NLO responses of the photoswitches. The investigations are conducted on a representative DASA derivative. We first show that the thermalized conformational dynamics enhances the molecular first hyperpolarizability, giving rise to improved agreement with HRS measurements. We also demonstrate that the fluctuations of the �� values along the structural dynamics are correlated with the bond order alternation (BOA), which provides a measure of the ��-electron conjugation over the molecule. In a second step, we elaborate different computational approaches going beyond the implicit continuum models to improve the description of solute-solvent interactions. In the final part of the thesis, the mixed quantum/classical computational methodology is employed to characterize the NLO responses of self-assembled monolayers (SAMs) functionalized with AZO derivatives, bearing either a donor or acceptor substituent on their external phenyl. Herein, we investigate how the nature of the substituent impacts the spatial organization of the molecular photoswitches within the SAMs, as well as the magnitude of their NLO responses

La PEP carboxylase est une enzyme impliquée dans plusieurs processus biologiques chez les plantes, tels que la maturation des graines ou les premières étapes de la capture du carbone au cours de la photosynthèse chez certaines plantes. Elle est ainsi responsable de la capture initiale du CO2 pour ¼ de la production terrestre de biomasse. Dans cette thèse nous avons étudié le mécanisme biochimique de l'enzyme PEP carboxylase. L'inconnue principale était la conformation fermée de la boucle II qui permet de protéger le site actif du solvant et d'enclencher la réaction chimique. Cette conformation n'a pas été à ce jour résolue expérimentalement, et les tentatives initiales de prédire cette conformation se sont avérées insatisfaisantes parce qu'instables. Notre but a alors été de prédire cette conformation fermée par des simulations numériques. Pour cela, nous avons développé une méthode originale pour prédire la conformation de boucles de protéines dans leur conformation fermée à partir de la détermination de la conformation ouverte. Nous avons démontré sur des exemples où les deux conformations sont connues que la méthode que nous avons développée, dénommée SETH, est capable de prédire la conformation fermée à partir de la seule conformation ouverte. De plus, nous avons développé une méthode d'analyse des trajectoires de simulations moléculaires qui permet de séparer les données en sous-groupes homogènes, facilitant ainsi leur comparaison. L'avantage de cette seconde méthode, dénommée YACARE, est qu'elle ne fait intervenir que des paramètres physiques et facilement interprétables. Nous avons alors appliqué les méthodes SETH et YACARE à la PEP carboxylase et découvert une conformation fermée candidate pour être la conformation réactive souhaitée. Celle-ci est stable numériquement au cours de simulations par échanges de de répliques de 200ns ainsi qu'au cours de simulations classique de 1 microseconde. Elle est caractérisée par la présente de ponts salins qui l'aide à se maintenir fermée. Nous avons aussi pu expliquer et prédire l'effet de mutations sur cette conformation. Ce travail ouvre désormais la possibilité d'étudier le mécanisme réactionnel de cette enzyme et de caractériser l'effet de mutations. Ceci permettra de proposer des mutants qui pourraient ouvrir la voie à des plantes qui poussent plus vite ou fournissent plus de biomasse, ce qui pourrait donc contribuer à résoudre une partie des problèmes d'alimentation à venir au niveau mondial dans les décennies futures
PEP carboxylase is an enzyme involved in several biological processes in plants, such as seed maturation and the early stages of carbon capture during photosynthesis in certain plants. It is responsible for the initial capture of CO2 for a quarter of the terrestrial biomass production. In this thesis, we studied the biochemical mechanism of the enzyme PEP carboxylase. The main unknown was the closed conformation of loop II, which protects the active site from the solvent and initiates the chemical reaction. This conformation has not been experimentally resolved to date, and initial attempts to predict this conformation have been unsatisfactory because they were unstable. Our goal was to predict this closed conformation through numerical simulations. To achieve this, we developed an original method to predict the closed conformation of protein loops based on the knowledge of the open conformation. We demonstrated with examples where both conformations are known that the method we developed, named SETH, is capable of predicting the closed conformation from the open conformation alone. Additionally, we developed a method for analyzing molecular simulation trajectories that allows clustering the data, thus facilitating their comparison. The advantage of this second method, named YACARE, is that it only involves physical parameters that are easily interpretable. We then applied the SETH and YACARE methods to PEP carboxylase and discovered a closed conformation that is a good candidate for the reactive conformation. This conformation is numerically stable during 200ns replica exchange simulations as well as 1µs classical simulations. It is characterized by the presence of salt bridges that help keep it closed. We were also able to explain and predict the effect of mutations on this conformation. This work now opens up the possibility of studying the reaction mechanism of this enzyme and characterizing the effect of mutations. This could lead to proposing mutants that might pave the way for plants that grow faster or produce more biomass, potentially helping to solve some of the global food supply issues in the coming decades

O uso de dióxidos de metais de transição em aplicações tecnológicas é bastante amplo, pois esses compostos possuem características importantes de semicondutores. Apesar de existir um grande número de estudos experimentais e teóricos, o entendimento das propriedades estruturais e eletrônicas desses compostos ainda não é satisfatória, principalmente quando se envolve o estudo de clusters. Clusters podem ser definidos como uma fase embrionária da matéria, pois são partículas contendo um número muito reduzido de átomos em comparação com partículas macroscópicas. Logo, suas propriedades estruturais e eletrônicas são totalmente distantes da fase cristalina do material, o que permite o desenvolvimento de novos materiais para aplicações tecnológicas. Portanto, existe um grande interesse em compreender as propriedades estruturais e eletrônicas dos clusters. Neste projeto de mestrado temos como objetivo estudar as propriedades estruturais e eletrônicas de clusters de TiO2 e CeO2 , usando para isso cálculos de primeiros princípios com base na teoria do funcional da densidade (DFT). Um dos principais problemas no estudo de clusters é a determinação da estrutura atômica, devido as dificuldades experimentais envolvidas em se trabalhar com estruturas tão pequenas. Dessa forma, um dos nossos maiores desafios foi a determinação das estruturas atômicas dos clusters desses dois tipos de dióxidos de metais de transição, uma vez que, o nosso grupo (QTnano) já conta com grande experiência, principalmente no desenvolvimento e implementação de algoritimos de otimização global. Devido as dificuldades envolvidas no estudo de partículas tão pequenas, ficamos restritos ao estudo de clusters com composição (MO2)n , com n = 1-15, ou seja, os nossos maiores clusters tem um total de 45 átomos, formando estruturas com diâmetro de inferior a 3 nm. Além da obtenção das estruturas, foi realizado o estudo das propriedades eletrônicas, energéticas e vibracionais para cada uma das composições geradas, o que propiciou a melhor compreensão sobre os efeitos eletrônicos nas estrutura atômica dos clusters.
The use of transition metal dioxides in technological applications is wide spread, because these compounds have important characteristics of semiconductors. Although there a large number of theoretical and experimental studies, the acknowledgement about the structural and electronic properties these compounds are not yet satisfactory, especially when studying clusters. Clusters can be defined as an embryonic phase of matter, because they are particles that contain a very small number of atoms in comparison with macroscopic particles. So, the structural and electronic properties are very distinct of the material crystalline phase, when allow the development of new materials in technological applications. Therefore a large interest exist in understanding the structural and electronic properties of clusters. In this master\'s degree project we have as objective to study the electronic and structural properties of TiO2 and CeO2 clusters, using first principle calculations based on the density functional theory (DFT). One of the main problems in the study of clusters is to determine the atomic structure, due the experimental difficult of work with so small particles. Thus, a great challenge was to determine the atomic structures of these two different transition metal dioxides, considering that our group (QTnano), has a large knowledge in the development and implementation of global optimization algorithms. Due the difficulty involved in studying small particles, we were restricted to the clusters of composition (MO2)n, with n = 1-15. In other words, our largest clusters have 45 atoms and a diameter smaller than 3 nm. Along with securing the structures, we realize the study of electronic, energetic and vibrational properties to each generated composition, providing an understanding of electronic effects in the atomic structure of clusters.

Cette thèse s'intéresse à la rationalisation du mécanisme de transfert d'excitation dans des polyphénylènes éthynylènes (PPE). Une étude statique approfondie a été réalisée en utilisant la TDDFT, permettant de confirmer la localisation des états excités de méta-PPE sur des fragments para, ainsi que la hiérarchie des interactions régissant les propriétés photochimiques des PPE. Des intersections coniques ont été identifiées, de même que les principales composantes de l'espace de branchement. Leur étude a soutenu l'hypothèse d'un transfert d'énergie par conversion interne entre états excités localisés sur des fragments para.D'autre part, nous avons proposé un modèle vibronique multiéchelles pour l'énergie des états électroniques. En particulier, nous avons exprimé les énergies des orbitales frontières de PPE en fonction des énergies des orbitales frontières du benzène et de l'acetylène via un Hamiltonien effectif de type Hückel. Un travail de mapping et d'optimisation nous a permis d'aboutir à une expression pour l'énergie de transition électronique en fonction d'un nombre réduit de coordonnées nucléaires locales
The present work is focused on the rationalization of the excitation transfer mechanism in polyphenylene ethynylenes (PPEs). A static study was performed using TDDFT, allowing to confirm both the localization of the excited states of meta-PPEs on para building blocks and the hierarchy in the interactions governing the photochemical properties of PPEs. Conical intersections were identified, along with few components of their branching spaces. Studying those supported the assumption of an energy transfer proceeding through internal conversion between excited states localized on different building blocks.In addition, we proposed a multiscale vibronic model for the energy of the eletronic states. In particular, we expressed the energies of the frontier orbitals of PPEs in terms of the energies of the frontier orbitals of benzene and acetylene, using an effective Hückel-type Hamiltonian. Perfoming different optimizations, we achieved to propose an expression for the energy of the electronic transition in terms of a reduced number of local nuclear coordinates