This dissertation investigates three topics in the field of multiple-bonded metal chemistry. The first topic concerns the synthetic and theoretical considerations of ditungsten formamidinates and guanidinates compounds. This work presents an enhanced synthetic path to the W2(hpp)4 molecule (Hhpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). The reflux of W(CO)6 with Hhpp in o-dichlorobenzene at 200 oC produces W2(hpp)4Cl2 in a one-pot reaction in 92% yield. This compound is stable and easily stored for further use, and it can be efficiently reduced in a one-step reaction to the most easily ionized compound W2(hpp)4. This work also examines the electronic structure and geometry of the intermediates W2(µ-CO)2(µ- hpp)2(η2-hpp)2 and W2(hpp)4Cl2. The second topic concerns the theoretical investigation by DFT of the electronic structure of [Mo2] units bridged by oxamidate ligands or bridging hydride ions ([Mo2] = (Mo2(DArF)3, where DArF is the anion of a diarylformamidine). It is shown that the effect of the gauche conformation of the α oxamidate isomers is due to steric interactions, and that the planar β oxamidate isomers have an electronic structure similar to that of naphthalene when it is doubly oxidized. The [Mo2](µ-H)2[Mo2] compound shows interdimetal unit interactions between the δ orbitals of the two [Mo2] units. These interactions are theoretically predicted and experimentally observed by a decrease in the [Mo2]---[Mo2] distance with a one-electron oxidation of [Mo2](µ- H)2[Mo2]. The final topic concerns the magnetic and structural properties of two Ru2(DArF)4Cl compounds. The compounds with Ar = p-anisyl (para) and m-anisyl (meta) both show different temperature dependence of their molar magnetic susceptibility, χ. For the para compound, there is a Boltzmann distribution between a π*3 ground state and a δ*2π* upper state, and this is confirmed by a temperature dependence of the Ru-Ru bond length: 2.4471(5) àat 23 K and 2.3968(5) àat 300 K. For the meta compound, a δ*2π*configuration persists over the range of 23-300 K as shown by an invariant Ru-Ru bond length and its molar magnetic susceptibility.

Abstract At present, most of the enterprises make use of a set of software system of Enterprise Resource Planning (ERP) in order to improve the internal management, and regards it as the nuclear information system. Their goal is to promote the enterprise's operational benefits (Hong and Kim, 2002) by the synthetic effects. Some enterprises induct do brings certain benefits after using the EPR. However, faces the current violent and competitive environment, the majority of ERP are not able to arrange the uses of resources effectively, which causes the enterprises unable to make the delivery dates of the customers¡¦ orders punctually or causes the enterprises¡¦ original profits reduced due to storing up too much stock for satisfy the delivery dates of the customers¡¦ orders. This research take a T Corporation, one of small and medium manufactures of Taiwan, as an example, this company uses the domestic well-known brand system of ERP as the main information system of the enterprise. After using the producing and managing module of ERP to plan its purchase policy of raw materials for a long time, the material inventory stay at a high level even after several years¡¦ adjustment. In addition, due to the price of copper fluctuated heavily frequently in recent years, not only the inventory cost can¡¦t be controlled well but also the orders are missed usually involving being unable to reflect the cost of raw materials on the customers¡¦ quotes immediately. Therefore, this research takes the System Dynamics which is good at solving the problems of dynamic complexity as a simulated research to practice the models¡¦ constructions and simulations and add the prosperity of system thinking into the business strategy to provides the quantifiable analogue result in order to strengthen the insufficient aspects of products and materials of EPR and to assist the enterprises¡¦ boss to solve those problems of dynamic complexity which are easily been neglect when makes operational strategies.

Widespread arsenic contamination with adverse effects to human health is a global problem. Most previous studies on arsenic contamination in natural environments and those associated with mining and agricultural activities focused largely on arsenic-rich minerals such as arsenates, arsenites, sulfarsenides, and sulfides. Rock-forming minerals generally contain only minor or trace amounts of arsenic but, owing to their sheer abundances, are potentially important (and sometimes dominant) sources of this metalloid and can play significant roles in the attenuation and sequestration of arsenic in various environments. However, there remains a significant gap in my knowledge about the uptake and speciation of arsenic in rock-forming minerals. This thesis research is intended to bridge this gap by investigating the uptake and speciation of arsenic in selected rock-forming sulfate and phosphate minerals (i.e., gypsum, struvite and newberyite). Gypsum (CaSO4•2H2O) is a major by-product of mining and milling processes of borate, phosphate and uranium deposits worldwide and, therefore, potentially plays an important role in the stability and bioavailability of heavy metalloids, including As, in tailings and surrounding areas. Gypsum containing 1,900 and 185 ppm As, synthesized with Na2HAsO4•7H2O and NaAsO2 in the starting materials, respectively, has been investigated by synchrotron X-ray absorption spectroscopy (XAS), single-crystal electron paramagnetic resonance spectroscopy (EPR), and pulsed electron nuclear double resonance spectroscopy (ENDOR). Quantitative analyses of As K edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra show that arsenic occurs in both +3 and +5 oxidation states and the As3+/As5+ value varies from 0.35 to 0.79. Single-crystal EPR spectra of gamma-ray-irradiated gypsum reveal two types of arsenic-associated oxyradicals: [AsO3]2− and an [AsO2]2−. The [AsO3]2− center is characterized by principal 75As hyperfine coupling constants of A1 = 1952.0(2) MHz, A2 = 1492.6(2) MHz and A3 = 1488.7(2) MHz, with the unique A axis along the S-O1 bond direction, and contains complex 1H superhyperfine structures that have been determined by pulsed ENDOR. These results suggest that the [AsO3]2− center formed from electron trapping on the central As5+ ion of a substitutional (AsO4)3− group after removal of an O1 atom. The [AsO2]2− center is characterized by its unique A(75As) axis approximately perpendicular to the O1-S-O2 plane and the A2 axis along the S-O2 bond direction, consistent with electron trapping on the central As3+ ion of a substitutional (AsO3)3− group after removal of an O2 atom. These results confirm lattice-bound As5+ and As3+ in gypsum and point to potential application of this mineral for immobilization and removal of arsenic pollution. EPR spectra show that another sulfate boussingaultite is also sequestering both As5+ and As3+ at its S site. Synthesis experiments at pH from 2 to 14 also show that arsenic uptake in gypsum is pH dependent. Struvite and newberyite, common biominerals and increasingly important green fertilizers recovered from wastewater treatment plants, are capable of sequestering a wide range of heavy metals and metalloids, including arsenic. Inductively coupled plasma mass spectrometric (ICPMS) analyses show that struvite formed under ambient conditions contains up to 547±15 ppm As and that the uptake of As is controlled by pH. Synchrotron As K-edge XANES spectra measured at 20 K show that As5+ is the predominant oxidation state in struvite, irrespective of Na2HAsO4•7H2O or NaAsO2 as the source for As. Modeling of As K-edge EXAFS data suggest that local structural distortion associated with the substitution of As5+ for P5+ in struvite reaches up to 3.75 Å. Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated struvite disclose five [AsO3]2- radicals and one [AsO4]2- radical. These arsenic-centered oxyradicals are all readily attributed to form from diamagnetic [AsO4]3- precursors during irradiation, providing further support for exclusive incorporation and local structural expansion beyond the first shell of As5+ at the P site in struvite. Arsenic doped newberyite (MgHPO4•3H2O) obtained from the gel diffusion method has investigated by synchrotron XAS at the As K-edge (11,867 eV) at 8 K and single-crystal EPR spectroscopy at room temperature. XANES data show that As5+ is dominant and EXAFS analysis reveals a local environment typical of the arsenate species as well. Single-crystal EPR spectra of gamma-ray-irradiated newberyite contain two arsenic-associated oxyradicals: [AsO3]2− and [AsO2]2− derived from As5+ and As3+, respectively, at the P site in the newberyite structure. Elevated concentrations of arsenic have also been observed in natural newberyite from guano deposits and reflect the accumulation of this metalloid in the food chain. Therefore, struvite and newberyite can both sequester significant amounts of arsenic, and their direct use as fertilizers (irrespective of origins from guano deposits or wastewaters) is a potential source of arsenic contamination. On the other hand, the capacities of struvite and newberyite for accommodating significant amounts of arsenic in crystal lattices coupled with their simple chemistry and crystallization under ambient conditions make them attractive materials for immobilization and removal of arsenic contamination in aqueous environments.

abstract: The heliobacterial reaction center (HbRC) is widely considered the simplest and most primitive photosynthetic reaction center (RC) still in existence. Despite the simplicity of the HbRC, many aspects of the electron transfer mechanism remain unknown or under debate. Improving our understanding of the structure and function of the HbRC is important in determining its role in the evolution of photosynthetic RCs. In this work, the function and properties of the iron-sulfur cluster FX and quinones of the HbRC were investigated, as these are the characteristic terminal electron acceptors used by Type-I and Type-II RCs, respectively. In Chapter 3, I develop a system to directly detect quinone double reduction activity using reverse-phase high pressure liquid chromatography (RP-HPLC), showing that Photosystem I (PSI) can reduce PQ to PQH2. In Chapter 4, I use RP-HPLC to characterize the HbRC, showing a surprisingly small antenna size and confirming the presence of menaquinone (MQ) in the isolated HbRC. The terminal electron acceptor FX was characterized spectroscopically and electrochemically in Chapter 5. I used three new systems to reduce FX in the HbRC, using EPR to confirm a S=3/2 ground-state for the reduced cluster. The midpoint potential of FX determined through thin film voltammetry was -372 mV, showing the cluster is much less reducing than previously expected. In Chapter 7, I show light-driven reduction of menaquinone in heliobacterial membrane samples using only mild chemical reductants. Finally, I discuss the evolutionary implications of these findings in Chapter 7. / Dissertation/Thesis / M.S. Biochemistry 2012

Climate change has given rise to higher demand of renewable energy. Conventional non-organic solar cells are still seen the most on the market but the last 10-20 years there has been an exponential increase in research about organic solar cells. The research demands measurements done on increasing fast time scales as insights about the topic and technology develops. Here is presented configurations done at the Isaak spectrometer at Freie Universit\"{a}t Berlin. The spectrometer is used for studying charge transport in organic solar cells as well as hybrid solar cells made from organic and inorganic semiconductors. One important feature for the time response is the Q factor property of the resonator in which the sample is placed. The Q factor describes the rate of energy loss relative to the stored energy of the resonator. The Q factor dependency over different temperature was studied in order to gain vital knowledge about the time response of the setup. Further new equipment was been installed at the setup and programmed in FSC2. This in order to increase the sensitivity of the optical setup, secure the personnel from possible dangerous excitation laser and in order to do more automated measurements. As the optical path was modified by installing a new optical fiber a new calibration had to be done. Finally, in order to try the functionality of the new equipment an automated energy dependency measurement was done on the polymer MEH-PPV and the polymer:fullerene blend MEH-PPV:PCBM. The automatic process of measuring was successful.

No description available.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-14T13:38:53Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação (versão final) Leoncio.pdf: 3177730 bytes, checksum: 3ae8af6eb5ff1a7f234df372ba6107db (MD5) / Made available in DSpace on 2017-07-14T13:38:53Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação (versão final) Leoncio.pdf: 3177730 bytes, checksum: 3ae8af6eb5ff1a7f234df372ba6107db (MD5) Previous issue date: 2016-06-30 / FACEPE / Nos últimos anos, a crescente dificuldade para aquisição e transporte internacional de irradiadores de raios gama, como o irradiador de Co-60 GammaCell 220 da Nordion, levou ao desenvolvimento de irradiadores de altas taxas de dose com base em feixes de raios-X, que operam na faixa de 150kV. Uma das aplicações deste tipo de irradiador é a irradiação de insetos, de amostras de sangue, etc. Para estes procedimentos, é importante que se tenha dosímetros que possam monitorar os processos de irradiação. O objetivo deste trabalho é o estudo e caracterização da alanina para que possa ser aplicada em dosimetria de irradiadores de raios-X de altas taxas de dose. A alanina é um aminoácido com número atômico efetivo próximo ao do tecido humano e é utilizada para dosimetria por ressonância paramagnética eletrônica (RPE) para aplicações em radioterapia. Neste trabalho, foram produzidas pastilhas de alanina com diferentes aglutinantes, bem como pastilhas puras revestidas com duas camadas de verniz, para serem utilizadas como dosímetros. Foram utilizados como aglutinantes parafina, teflon e estearina em concentrações de 1 %, 2 % e 5 % da massa total das pastilhas. Testes mecânicos, como ultrassom e rot-up, foram realizados para avaliar a resistência mecânica das pastilhas produzidas. Após os testes mecânicos, verificou-se que as pastilhas preparadas com alanina pura apresentavam resistência mecânica suficiente para serem utilizadas como dosímetros. A reprodutibilidade de sua resposta RPE foi avaliada a partir da irradiação de dez dosímetros com dose de 100 Gy com uma fonte de Co-60. Para investigar a estabilidade da resposta da alanina-RPE com o tempo, três dosímetros foram irradiados com uma dose de 200 Gy com uma fonte de Co-60, sendo a leitura realizada após cinco horas da irradiação e releituras após 15, 40, 87, 110 e 137 dias da irradiação. Para obter as curvas de calibração para raios gama e raios – X, amostras foram irradiadas, respectivamente, com doses de 0 a 1 kGy e de 18,7 Gy a 206 Gy. Os resultados mostram que a resposta dos dosímetros de alanina-RPE apresentou reprodutibilidade com um coeficiente de variação de 1,2%. O estudo do desvanecimento da resposta dos dosímetros mostrou uma variação de 0,8% em 137 dias. De acordo com os resultados obtidos, o sistema de dosimetria alanina-RPE pode ser utilizado, de forma confiável, como um sistema padrão de transferência para as aplicações do irradiador de raios-X de baixa energia, o RS 2400. / In recent years, the increasing difficulty in acquisition and international transport of gamma ray radiators, as irradiator Co-60 Gammacell 220 of Nordion led to the development of high dose rate irradiators based on X-ray beams that they are operating in the 150kV range. One application of this type of irradiator and irradiation of insects, blood samples, etc. For these procedures, it is important to have dosimeters that can monitor the irradiation processes. The objective of this work is the study and characterization of alanine that can be applied in dosimetry irradiating X-ray of high dose rates. Alanine is an amino acid in effective atomic number close to that of human tissue and is used for dosimetry for electron paramagnetic resonance (EPR) for applications in radiotherapy. In this work, alanine pellets were produced with different binders as well as pure tablets coated with two coats of varnish to be used as dosimeters. They were used as binders paraffin, teflon and stearin in concentrations of 1%, 2% and 5% of the total mass of the pastilles. Mechanical tests, such as ultrasound and rot-up were conducted to evaluate the mechanical strength of the tablets produced. After mechanical testing, it was found that the tablets prepared with pure alanine had sufficient mechanical strength to be used as dosimeters. The reproducibility of EPR response was evaluated from the irradiation ten dosimeters with dose 100 Gy with a source of Co-60. To investigate the stability of alanine EPR response over time of three dosimeters were irradiated with a dose of 200 Gy with a source of Co-60, the reading being performed after five hours of irradiation and readings after 15, 40, 87, 110 and 137 days of irradiation. To obtain the calibration curves for gamma rays and X - ray irradiated samples were, respectively, at doses from 0 to 1 kGy and 18.7 Gy to 206 Gy. The results show that the response of EPR-alanine dosimeters showed reproducibility with a coefficient of variation 1.2%. The study fading dosimeters response showed a variation of 0.8% in 137 days. According to the results, the system alanine EPR dosimetry can be used reliably as a pattern transferring system for irradiating the applications of low-energy X-rays, the RS 2400.

Combining enzymes with synthetic materials is the new frontier of biocatalysis, materials science, and protein engineering. Enzymes are biological macromolecule catalysts with incredible efficiency and specificity that are desirable for use in a variety of different fields. However, commercial applications have been limited by the stability and reusability of un-altered enzymes. An avenue for overcoming the challenges to harnessing enzyme power is to combine enzymes with materials to create an enzymatically-active material that has enhanced stability and activity. Unfortunately, the catalytic activity of the hybrid material is often lower than that of the enzyme alone. The activity of an enzyme is directly dependent on its structure and dynamics. Therefore, a deeper understanding of enzyme structure and dynamics upon incorporation into materials will provide the data necessary to rationally design enzymatically-active materials with the desired features. This dissertation explores the behavior of a model enzyme, T4 Lysozyme, with two different artificial material systems, metal-organic frameworks and polyethylene glycol. The underlying structural rationale for the behavior is probed using a variety of techniques, notably, Electron Spin Paramagnetic Resonance. Herein, the implications of structural alterations on activity and opportunities for exploitation are discussed. T4 Lysozyme is a perfect model for this study because it has a well characterized structure-activity relationship, thus providing a vast literature understanding which can be pulled from to verify and assist with interpretation of data. The structural basis of enzyme activity alteration in artificial materials can be used to rationally design systems with desired characteristics. After successfully demonstrating the tunability of proteins in artificial materials using T4L as a model, human Cu/Zn superoxide dismutase 1 was chosen for continuing studies due to its importance in diseased states. However, the superoxide dismutase mutant chosen is aggregation prone, which makes it difficult to express recombinantly in large amounts. Therefore, an efficient protocol for producing the superoxide dismutase protein was developed to set the stage for future studies.

No description available.

Natural occurring riboswitches, a class of RNA molecules, are able to control the implementation of genetic information through the regulation of gene expression. Both, natural and synthetic riboswitches, so-called aptamers, are complex folded structures, which bind specific ligands. Ligand binding in turn regulates gene expression. In the first section of this work continuous wave (cw) and pulse EPR spectroscopy in combination with site-directed spin labeling was performed to investigate the dynamics and conformational changes of the synthetic tetracycline (Tc) riboswitch. The results obtained herein indicate a thermodynamic equilibrium of two aptamer conformations in the absence of Tc, where one of these conformations is captured upon ligand binding. Aptamer structures have been modeled based on the two equilibrium conformations in the absence of the ligand, and on the captured aptamer conformation in the presence of Tc. All RNA models have been verified by MD simulations by comparing experimentally obtained interspin distances with simulated ones. The incorporation of DNA mutations such as nucleobase changes, double-strand breaks and mispairings can lead to structural and conformational changes of DNA domains which in turn are related to inheritable diseases, cancer and aging. Within this project, the copper(I)-catalyzed Huisgen-Sharpless-Meldal alkyne-azide cycloaddition (CuAAC) ‘click reaction’ was introduced as a powerful modification of existing spin labeling strategies. Interspin distances and exceptionally narrow distribution widths were determined by cw and pulse EPR experiments. The results of the MD simulations exhibit a very good agreement between simulated and experimentally obtained distances. Furthermore, the new spin labeling protocol was used to identify mismatch-induced conformational changes of spin labeled DNA. The application of cw and orientation selective pulse EPR measurements provided insights into the dynamics and structural alterations caused by mismatched base pairs. Interspin distances have been found to depend on the type and nearest neighbor environment of the mismatch. The changes are transferred to the base pairs carrying the spin labels.