Evolution of the electronic excitation is a general process that can be used to explain many natural and artificial phenomena, such as photosynthesis in plants and bacteria, biological mechanism of vision, and operating principles of optomechanical and optoelectronic devices. This process is theoretically modeled by solving the time-dependent Schroedinger equation. However, such treatment is too computationally expensive to be used for practical molecular systems. Therefore, either models of the structure of the systems or the solving procedure itself must be simplified to get the desired results. The main goal of the research presented in this dissertation was to study processes caused by the electronic excitation in photoactive molecules using computational methods of electronic structure (i. e. solving the simpler time-independent Schroedinger equation) and to construct the potential energy surface models describing the energy relaxation in the investigated molecules. It is shown that the results of different investigations performed using the same procedure provide explanations of different phenomena in various compounds, such as: proton transfer in polar solvent, performed by a functional group of the bacteriorhodopsin protein; optomechanical cycle of the indolo-benzoxazine compound; efficient phosphorescence of the silicon-based organic polymer; and optical properties of organometallic emitter compound with additional charge-carrier groups. / Elektroninio sužadinimo evoliucija šviesai jautriose molekulėse yra reiškinys, kuriuo remiantis įmanoma nagrinėti daugelį natūralių ir dirbtinių procesų: augalų ir bakterijų fotosintezę, regos mechanizmą, optomechaninių bei optoelektroninių prietaisų (pavyzdžiui, organinių šviestukų) veikimą. Teoriškai šis reiškinys modeliuojamas sprendžiant laikinę Šriodingerio lygtį. Deja, toks sprendimas realiems, praktiškai panaudojamiems junginiams šiandien yra per sudėtingas uždavinys, todėl jį tenka keisti supaprastinant nagrinėjamų junginių modelius arba sprendimo metodiką. Šioje disertacijoje aprašomų tyrimų tikslas buvo elektroninės struktūros skaičiavimų metodais (t. y. sprendžiant paprastesnę nuostoviąją Šriodingerio lygtį) ištirti elektroninio sužadinimo sukeltus procesus fotoaktyviose molekulėse ir sudaryti sužadinimo relaksaciją apibūdinančius potencinės energijos paviršių modelius. Parodoma, jog ta pačia metodika atliekamų tyrimų rezultatai paaiškina įvairiuose junginiuose vykstančius reiškinius: bakteriorodopsino baltymo funkcinės grupės vykdomą protono pernašą poliniame tirpiklyje, indolo-benzoksazino junginio optomechaninį ciklą, našią fosforescenciją organiniame silicio polimere bei šviestukams naudojamo metaloorganinio komplekso su prijungtomis krūvininkų pernašos grupėmis ypatybes.

D’immenses progrès ont été réalisés ces dernières années dans le champ de production de condensats de Bose-Einstein moléculaires pour l’obtention et le piégeage de molécules ultrafroides ioniques et neutres. Ces échantillons de molécules ultrafroides trouvent des applications dans des domaines très variés tels que les mesures pectroscopiques de haute précision ou bien encore le stockage de l’information quantique. La volonté d’optimiser les procédés de refroidissement et des techniques de piégeage a stimulé un grand nombre d’études théoriques. La plupart de ces études sont dédiées au refroidissement des molécules en collision avec un gaz tampon (3 He). La surface d’énergie potentielle de l’état fondamental du complexe de van der Waals He–MnH(X7Σ+) est présentée, suivie du calcul des états liés correspondant au complexe ainsi que l’étude de la relaxation Zeeman associée au système en fonction du champ magnétique appliqué. Dans le domaine de l’astrochimie, l’étude de la désexcitation rotationnelle de CH+ en collision avec l’hélium est également présentée. / Tremendous progress in experimental production and trapping of ultracold neutral and ionic molecules has been achieved over the past few years which even allowed the production of molecular Bose–Einstein condensates. These ultracold molecules samples have potential applications in many different fields, such as precision spectroscopic measurements or quantum information storage and processing. The optimization of the cooling processes and the trapping techniques also stimulated a great number of theoretical studies. Many of them are dedicated to inelastic scattering of molecules in collisions with 3He atoms (buffer gas cooling method). The potential energy surface of the ground state of the He–MnH(X7Σ+) van der Waals complex is presented, followed by the calculations of the bound states of this system and the Zeeman relaxation in function of the magnetic field. In the field of astrochemistry, a quantum mechanical investigation of rotational energy transfer in cold collisions of CH+ with 4He atoms is presented.

Essa tese tem o objetivo modelar um subconjunto de peças de um compressor hermético de refrigeração idealizado utilizando um programa de elementos finitos para estudar a pressão de contato na junta da placa de válvulas com e sem pressão de gás refrigerante. Nessa pesquisa também se faz a modelagem dinâmica da bomba de um compressor acadêmico com vistas a estudar a vibração gerada durante seu funcionamento. No estudo da junta de vedação se faz um modelo geométrico do conjunto cabeçote e juntas com um programa CAD. A partir da geometria do subconjunto um modelo físico é construído no ANSYS®, que leva em consideração as diferentes propriedades dos materiais do conjunto cabeçote e juntas, inclusive a não linearidade do material da junta. São feitas simulações aplicando diferentes valores de força normal nos parafusos do cabeçote. No estudo de vibração do compressor faz-se o modelo de CAD da bomba de onde se obtém seu peso e propriedades de inércia. A matriz de rigidez do sistema de suspensão da bomba é calculada e se faz a análise modal da bomba. Os resultados das análises de pressão de contato foram mostrados através de gráficos da normal closure e da normal pressure da junta. Eles indicam de forma clara as regiões de baixa pressão de contato aplicada pelas peças que estão ou deveriam estar comprimindo a junta de vedação, que seriam regiões de falhas. Na análise dinâmica da bomba do compressor, é calculada a matriz de rigidez total do sistema com as molas de suspensão, levando em consideração a rigidez compressiva, de flexão e cisalhante das molas. Com a solução do modelo dinâmico criado, calcula-se a matriz dinâmica, a matriz modal normalizada, a matriz de frequências características, o deslocamento <span style=\"font-style:italic\">X <span style=\"position: relative; bottom: 1.3ex; letter-spacing: -1.2ex; right: 1.2ex\">&#8594; da bomba e também as energias cinética e potencial da bomba devido às forças de agitação. O modelo de elementos finitos da junta da placa de válvulas tem resultados coerentes e o modelo dinâmico da bomba fornece vários resultados para a análise de vibração de compressores. / This thesis has as objective to model a subset of parts of an idealized hermetic compressor for refrigeration using a program of finite elements intended to study the contact pressure on the valve plate gasket with and without pressure from the refrigerant gas. In this research a dynamic modelling of an academic compressor pump is also made with the aim of studying the vibration generated during its functioning. In the study of the sealing gasket, a geometric model of the cylinder head and gasket assembly is made by using a CAD program. From the geometric of the subset a physical model is built on the ANSYS®, which takes into account the different properties of the cylinder head and gasket assembly materials, including the non-linearity of the gasket material. Simulations are made by applying different normal force values on the cylinder head screws. In the compressor vibration study, a CAD pump model is made, thus obtaining its weight and inertia properties. The stiffness matrix of the pump suspension system is calculated and a modal analysis of the pump is made. The results from the contact pressure analyses were shown through \"normal closure\" and \"normal pressure\" charts of the gasket. They show in clear form the low contact pressure regions applied by the parts that are or should be compressing the sealing gasket, which would the regions of failures. In the dynamic analysis of the compressor pump, the total stiffness matrix of the system is calculated with the suspension springs, taking into account the compressive, flexural and shearing rigidities of the springs. With the solution of the dynamic model created, the following are calculated: the dynamic matrix, the normalized modal matrix, the characteristics frequency matrix, the <span style=\"font-style:italic\">X <span style=\"position: relative; bottom: 1.3ex; letter-spacing: -1.2ex; right: 1.2ex\">&#8594; displacement from the pump, as well as the kinetic and potential energy of the pump due to shaking forces. The finite elements model of the valve plate gasket has coherent results and the dynamic model of the pump provides various results for the analysis of the compressor vibration.

Este projeto tem dois objetivos. Primeiramente estudou-se a aplicabilidade dos splines tricúbicos para a construção de superfícies de energia potencial globais. Um dos obstáculos que este método tem de superar e a escolha de um sistema de coordenadas apropriado, que minimize a influência de pontos não físicos. Para isto, propôs-se o uso do sistema de coordenadas de Pekeris, nunca usado para este fim. Este procedimento foi realizado para três sistemas químicos bem descritos na literatura, [Cl,H2], [F,H,D] e [H,O,Cl], cujas superfícies de energia potencial e propriedades das reações foram usadas como referência. Com base nestes modelos, aplicamos o método proposto variando-se a quantidade e a disposição dos nós das interpolações, a fim de verificar sua influência na qualidade das superfícies interpoladas. Os resultados mostram que as superfícies construídas por este método reproduzem muito bem os cálculos de dinâmica química, tanto por métodos quânticos quanto por métodos clássicos. Para isto, os nós da interpolação devem cobrir as regiões mais importantes da superfície de energia potencial e os valores mais baixos das coordenadas de Pekeris devem ser priorizados. O segundo objetivo consiste na aplicação deste procedimento na construção da superfície de energia potencial [H,S,F]. Com esta superfície, diversas características deste sistema foram analisadas, tais como geometrias dos pontos estacionários, energias relativas e frequências vibracionais. Os valores obtidos estão de acordo com os dados descritos na literatura. A superfície construída também foi usada para a realização de cálculos de dinâmica para a reação F+HS &#8594; S+FH. Observamos a existência de dois tipos de mecanismos, um com a formação de um intermediário de longa duração e outro com a abstração direta do átomo de hidrogênio. / This project has two goals. First, we studied the applicability of the tricubic splines to construct global potential energy surfaces. One of the diculties this approach has to overcome is the choice of an appropriate coordinate system that minimises the in uence of non-physical points. For such, we proposed the use of the Pekeris coordinate system, never employed for this purpose. This procedure was carried out for three well described systems, [Cl,H2], [F,H,D] and [H,O,Cl], whose potential energy surfaces and reaction properties were taken as references. Based on these models, we applied the proposed method varying the amount and arrangement of the interpolation knots, to verify their influence on the quality of the interpolated surfaces. The results showed that surfaces constructed by this approach reproduce very well the chemical dynamics calculations, both for the quantum as well as for the classical methods, provided that the interpolation knots cover the most important regions of the potential energy surfaces, and the lower values of the Pekeris coordinates are prioritised. The second goal was the application of this procedure to the construction of the [H,S,F] potential energy surface. With this surface, several characteristics of this system were analysed, such as the geometry of the stationary points, relative energies and vibrational frequencies. The values obtained are in agreement with the data described in the literature. The constructed surface was also used for quantum dynamics calculations on the reaction F + HS &#8594; S + FH. We observed two kinds of mechanisms, one of them with the formation of a long-living intermediate and the other with the direct abstraction of the hydrogen atom.

Binding-sites which facilitate the transport of substrates across membranes are ubiquitous in membrane proteins. To understand this fundamental process in cells, we build up a synthetic membrane system consisting of microfluidic channels and colloidal particles. Holographic optical tweezers are used to modulate the potential energy landscape in those channels. We show how to extract the underlying energy potential by analysing local transition probabilities. Our method is applicable both to equilibrium systems and non-equilibrium steady states. Our method offers improved robustness when dealing with fragmented trajectories or small ensembles of data compared to other established approaches, such as probability density function and splitting probability. Meanwhile, we utilise the intensity distribution of the optical traps generated by holographic optical tweezers to estimate energy landscapes featuring high energy barriers where transitions rarely occur. We use this newly developed experimental system to mimic the functionality of membrane protein transporters that are known to alternate their substrate-binding sites between the extracellular and cytosolic side of the membrane. We study particle transport through a channel coupled with an energy well that oscillates its position between the two entrances of the channel deterministically and stochastically. Optimised particle transport across the channel is obtained by adjusting the oscillation frequency. At the optimal oscillation frequency, the translocation rate of particles through the channel is a hundred times higher with respect to free diffusion across the channel. Our findings reveal the effect of time dependent potentials on particle transport across a channel. This work adds a new tool for the investigation of highly controlled membrane transport processes at the micron scale. Our results are relevant for improving our understanding of membrane transport especially for microfluidics application.

L’étude des mécanismes de formation et de destruction des anions moléculaires est devenu un champ d’intérêt prononcé après la détection récente de six anions moléculaires (C4H-, C6H-, C8H-, CN-, C3N-, C5N-) dans le milieu interstellaire.Dans les environnements interstellaires où la densité d’électrons est relativement importante, le canal principal de formation de ces anions devrait être l’attachement électronique radiatif. Mais il manque aujourd’hui des données expérimentales et théoriques permettant d’évaluer cette hypothèse. D’autre part, le photodétachement est la principale cause de destruction de ces anions dans les nuages diffus et les régions de photodissociation. Une approche basée sur un développement monocentrique est appliquée à l’étude de ces deux processus opposés que sont le photodétachement et l’attachement électronique radiatif. Les résultats obtenus avec la présente méthode sont comparés à des données expérimentales et théoriques précédemment rapportées et montrent un bon accord. Cette méthode est ensuite utilisée pour déterminer les constantes de vitesse nécessaires pour confirmer si ces mécanismes sont cruciaux pour la chimie d’anions interstellaires. En plus des constantes de vitesse de formation et de destruction des anions, les constantes de vitesse d’excitation collisionnelle sont nécessaires pour modéliser les abondances observées des anions. Nous avons choisi de porter notre effort sur le calcul des constantes de vitesse de transition entre états rotationels de la molécule C3N- dans son état vibrationnel fondamental lors des collisions avec H2 et He en utilisant de nouvelles surfaces d’énergie potentielles. / The mechanisms of formation and destruction of molecular anions have become a field of special interest after the recent detection of six molecular anions (C4H-,C6H-, C8H-, CN-, C3N-, C5N-) in the interstellar medium. The main channel of formation of these anions is expected to be radiative electron attachment in environments where the density of electron is relatively important. There is however at themoment a lack of experimental and theoretical data allowing to assess this hypothesis. Photodetachment, on the other hand, is the main source of destruction of the anions in diffuse clouds and photodissociation regions. A single center expansion approach is applied to the study of both processes: photodetachment and radiative electron attachment. The results obtained with the present method are compared to previously reported experimental and theoretical data and show a good agreement.This method is then employed to determine the rate constants which are needed to confirm whether or not these mechanisms are crucial for the chemistry of the interstellar anions. Along with the formation and destruction rates, rotational excitation rate coefficients are needed to accurately model the observed anions abundances.We focus on the calculation of state-to-state rotational transitions rate coefficients of the C3N- molecule in its ground vibrational state in collisions with H2 and He using new potential energy surfaces

ABSTRACT EFFECTIVENESS OF CONCEPTUAL CHANGE INSTRUCTION ON OVERCOMING STUDENTS&#039 / MISCONCEPTIONS OF ELECTRIC FIELD, ELECTRIC POTENTIAL AND ELECTRIC POTENTIAL ENERGY AT TENTH GRADE LEVEL VATANSEVER, Orhan MS, Department of Secondary Science and Mathematics Education Supervisor: Dr. Mehmet Sancar December 2006, 107 pages The purpose of this study was to investigate the effectiveness of the conceptual change text based instruction over traditionally designed physics instruction to overcome tenth grade students&amp / #8217 / misconceptions on electric field, electric potential and electric potential energy concepts. To provide conceptual change, conceptual change texts (CCT) were developed by the researcher. An Electric Potential and Electric Potential Energy Concept Test (EPEPECT) which consists of 10-items was developed and used to examine students&amp / #8217 / probable misconceptions. Physics Attitude Scale (PATS) was administered to the students to obtain valid information concerning how conceptual change text based instruction effect students&amp / #8217 / attitudes toward physics. The subjects of this study included two tenth grade level classes from TED Ankara College Private High School in Ankara, Turkey, and a total of 37 students&amp / #8217 / scores were used for the statistical analysis. Students from one of the classes that were randomly assigned participated in traditional instruction and referred as the control group. Students from the other class participated in CCT based instruction and referred as the experimental group. EPEPECT and PATS had been administrated to both groups on two different occasions as pretest and posttest. According to the results of the study, statistically significant differences were found between conceptual change instruction and traditional method. Students taught with CCI showed a better scientific conception related to electric field, electric potential and electric potential energy and elimination of misconceptions than the students taught with traditionally designed physics instruction (TDPI). However, CCI did not increase the students&amp / #8217 / attitudes toward physics as school subject more than TDPI did. That is, conceptual change instruction was not effective in improving positive attitudes toward physics.

In this dissertation, we describe a novel method that we call Diffusing Colloidal Probe Microscopy (DCPM), which integrates Total Internal Reflection Microscopy (TIRM) and Video Microscopy (VM) methods to monitor three dimensional trajectories in colloidal ensembles levitated above macroscopic surfaces. TIRM and VM are well established optical microscopy techniques for measuring normal and lateral colloidal excursions near macroscopic planar surfaces. The interactions between particle-particle and particle-substrate in colloidal interfacial systems are interpreted by statistical analyses from distributions of colloidal particles; dynamic properties of colloidal assembly are also determined from particle trajectories. Our studies show that DCPM is able to detect many particle-surface interactions simultaneously and provides an ensemble average measurement of particle-surface interactions on a homogeneous surface to allow direct comparison of distributed and average properties. A benefit of ensemble averaging of many particles is the diminished need for time averaging, which can produce orders of magnitude faster measurement times at higher interfacial particle concentrations. The statistical analyses (Ornstein- Zernike and three dimensional Monte Carlo analyses) are used to obtain particle-particle interactions from lateral distribution functions and to understand the role of nonuniformities in interfacial colloidal systems. An inconsistent finding is the observation of an anomalous long range particle-particle attraction and recovery of the expected DLVO particle-wall interactions for all concentrations examined. The possible influence of charge heterogeneity and particle size polydispersity on measured distribution functions is discussed in regard to inconsistent particle-wall and particle-particle potentials. In the final part of this research, the ability of DCPM is demonstrated to map potential energy landscapes on patterned surfaces by monitoring interactions between diffusing colloidal probes with Au pattern features. Absolute separation is obtained from theoretical fits to measured potential energy profiles and direct measurement by sticking silica colloids to Au surfaces via electrophoretic deposition. Initial results indicate that, as colloidal probe and pattern feature dimensions become comparable, measured potential energy profiles suffer some distortion due to the increased probability of probes interacting with surfaces at the edges of adjacent pattern features. Measurements of lateral diffusion via analysis of mean square displacements also indicated lateral diffusion coefficients in excellent agreement with rigorous theoretical predictions.

<p>Accurate modeling of land-atmosphere interaction would help us understand the persistent weather conditions and further contribute to the skill of seasonal climate prediction. In this study, seasonal variations in radiation and precipitation forcing are included in a stochastic soil water balance model to explore the seasonal evolution of soil moisture probabilistic structure. The theoretical results show soil moisture tends to exhibit bimodal behavior only in summer when there are strong positive feedback from soil moisture to subsequent rainfall. Besides the statistical analysis of soil moisture – rainfall feedback, simplified mixed-layer models, coupled with soil-plant-atmosphere continuum, are also used to study heat flux partitioning, cloud initiation, and strength of moist convection. Approximate analytical solutions to the mixed-layer model are derived by applying Penman-Monteith approach, which help explain the roles of equilibrium evaporation and vapor pressure deficit in controlling the diurnal evolution of boundary layer. Results from mixed-layer model also define four regimes for possible convection in terms of cloud/no-cloud formation and low/high convection intensity. Finally, cloud-topped mixed-layer model is developed to simulate the boundary-layer dynamics after the cloud formation, when the evaporative and radiative cooling other than surface heat flux may significantly contribute to the growth of the boundary layer.</p> / Dissertation

Disertacijoje nagrinėjamas galimas aplinkos poveikis organinių molekulių elektroninių būsenų savybėms. Tam tikslui yra naudojami kompiuterizuotieji kvantinės mechanikos metodai, kuriais remiantis nagrinėjamos įvairių molekulių savybės. Ištirtos 2-(N-metil-α-iminoethyl)-fenol ir N-triphenylmethylsalicylidene imine molekelulių, esančių poliniame tirpiklyje, struktūros pagrindinėje ir sužadintose elektroninėse būsenose. Pirmą kartą parodyta, kad, norint gauti teisingą kokybinį ir artimą kiekybiniam vidujmolekulinės protono pernašos potencinės energijos paviršių, būtina atsižvelgti į polinių tirpiklio molekulių kuriamą vandenilinių ryšių tinklą bei į nulinių svyravimų energijas. Pastarieji ir nulemia protono pernašos vyksmo kryptį bei efektyvumą. Parodyta, kad anilų klasės molekulių konformerų susiformavimas priklauso nuo tirpiklio poliškumo, o jų susidarymas savo ruožtu konkuruoja su klasterių iš tirpiklio molekulių susiformavimo galimybėmis. Pirmą kartą parodyta, kad dipolinio momento vertė bakteriorodopsine yra nulemta membranos paviršiuose esančių radikalų. Pademonstruota, kad stilbazolio molekulė deformuojasi ir sudaro naujus konformerus (pademonstruota dviejų formų atsiradimo galimybė) tik esant molekulėms tirpalo apsuptyje. Šis rezultatas paaiškino eksperimente stebimus skirtuminių spektrinių pokyčių evoliucijos prigimtį. Apskaičiuotos ir išanalizuotos karotinoidų - luteino, violaksantino ir zeaksantino molekulių - žemiausios sužadintos elektroninės būsenos. Parodyta... [toliau žr. visą tekstą] / To explore changes caused by the environment on the internal characteristics of an organic molecule is the objective of the thesis. For this purpose we investigate a variety of organic molecules. Using various methods of quantum mechanics calculations possible influence of a polar solvent on the ground and excited states of 2-(N-metil-α-iminoethyl)-fenol and N-triphenylmethylsalicylidene imine is considered. It is shown for the first time that in order to obtain the correct qualitative and quantitative interpretation of possible pathways of the intermolecular proton transfer the hydrogen network of the polar solvent molecules together with the zero point energy have to be taken into consideration. It is also shown that conformational variability of anil-type molecules in polar solvents is competing with clusters formation of solvent molecules. It is shown for the first time that the dipole moment of bacteriorhodopsin is mainly defined by cytoplasmic and extracellular coils on the surfaces of the membrane. It is also demonstrated that the stilbazole molecule experiences the deformation resulting in formation of new conformers (at least two forms are present) in the solvent surrounding. The experimental data of the transient spectroscopy were explained in the basis of these model calculations. The lowest excited states of carotinoids, such as lutein, zeaxanthin and violoxantin are calculated and analyzed. Sensitivity of the excited electronic state on the polar environment is... [to full text]