Orientadores: Roberto Antonio Clemente, Munemasa Machida / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-19T20:53:40Z (GMT). No. of bitstreams: 1 Duarte_ViniciusNjaim_M.pdf: 5509797 bytes, checksum: 163bd7750aa0326f7bf0d0b521dc88f0 (MD5) Previous issue date: 2012 / Resumo: Entre os diferentes métodos alternativos à indução, para sustentação e/ou geração de corrente em plasmas confinados magneticamente, com o objetivo de se obter o funcionamento contínuo de um possível reator de fusão, foi estudado aquele associado a campos magnéticos viajantes produzidos por bobinas helicoidais alimentadas por correntes de radiofrequência defasadas (double helix current drive). O método permite compensar as perdas de caráter resistivo em configurações toroidais de plasma, como os pinches de campo reverso (reversed field pinches - RFP). O problema pode ser reduzido ao estudo dos estados estacionários de uma coluna de plasma sujeita a campos de radiofrequência produzidos por bobinas helicoidais externas. Desprezando efeitos de gradientes de densidade e temperatura, o modelo é regido por um sistema de equações diferenciais ordinárias de segunda ordem não lineares acopladas, reguladas por quatro parâmetros adimensionais de interesse físico, que foram resolvidas numericamente usando o programa Mathematica. Estudou-se a eficiência do método em relação às aplicações em RFP, para os quais o campo magnético longitudinal apresenta uma inversão no interior da coluna de plasma. Isso implicou considerar regiões ainda não bem exploradas para os parâmetros de interesse. Os resultados numéricos são apresentados para configurações de campos magnéticos com simetria dipolar e quadrupolar / Abstract: Among the different methods, alternative to induction, to drive current in magnetically confined plasmas, with aim to obtain a continuous operation of a possible fusion reactor, we have studied the one associated to traveling magnetic field produced by helicoidal coils carrying out of phase radiofrequency currents (double helix current drive). The method allows compensating resistive losses in toroidal plasma configurations, like reversed field pinches. The problem may be reduced to the study of stationary states for a plasma column subjected to radiofrequency fields produced by external helicoidal coils. Neglecting density and temperature gradients, the model is governed by a system of coupled nonlinear second order ordinary differential equations, which depend on four dimensionless parameters of physical interest and can be solved numerically using the software Mathematica. We studied the efficiency of the method with respect to applications in reversed field pinches, for which the longitudinal steady magnetic field shows an inversion inside the plasma column. This implied considering not yet well explored regions of the parameters of interest. Numerical results are presented for magnetic field configurations of dipolar and quadrupolar simmetries / Mestrado / Física / Mestre em Física

Ce travail s'articule autour de deux grandes parties : i- la synthèse de nouveaux tripodes tris-A,C,E-alpha-cyclodextrine, et l'étude de leurs complexes de coordination avec les métaux. La fonctionnalisation des bis-hétérocycles est une étape importante dans la préparation de ces tripodes moléculaires. En conséquence, la mise au point d'une nouvelle famille de réactifs, les tétrahalogeno-diarylglycoluriles, a permis une halogénation radicalaire sélective des systèmes hétéro-aromatiques pi-déficients non réactifs et impliqués dans la construction des podants cyclodextriniques. La sélectivité et le mécanisme de la réaction ont pu être expliqués en partie par la formation d'un complexe supramoléculaire [réactif /substrat] et l'existence d'interactions halogène-halogène dans le solide; ii- la mise en évidence d'une haute spéciation des tripodes cyclodextrines vis-à-vis d'un certain nombre de métaux et la formation d'hélices métallo-supramoléculaires chirales induite par l'implantation en position 6,6' des unités hétérocycliques. La configuration absolue des hélicates formés est résolue dans quelques cas / This work is structured around two main parts: i- the synthesis of new tris-A,C,E-alpha-cyclodextrin tripods, and studies of their complexes with transition metals. The functionalization of bis-heterocycles is an important step in the preparation of tripods. Therefore, the development of a new family of reagents tetrahalo-diarylglycolurils allowed a selective radical halogenation of heteroaromatic pi-deficient systems, non-reactive and involved in the construction of podants cyclodextrinics. The selectivity and the mechanism of the reaction could be partially explained by the formation of a supramolecular complex [reagent / substrate] and the existence of halogen-halogen interactions in solid state; ii- the highlight of a high speciation tripods cyclodextrins towards a number of metals and formation of supramolecular chiral metallo-helices induced by anchoring in position 6,6' of heterocyclic units. The absolute configuration of helicates formed in some cases is resolved

Chloroperoxidase (CPO) is a heme-thiolate protein with exceptional versatility and great potential as a biocatalyst. The CPO reactive species, Compound I ( Cpd I) is of particular interest, as well as the Cytochrome P450 (P450) -type monoxygenase catalytic activity, which has significant biotechnological potential. Proximal hydrogen bonding of the axial sulfur with the backbone amides (NH•••S) is a conserved feature of heme-thiolate enzymes. In CPO, the effect of NH•••S bonds is amplified by the dipole moment of the proximal helix. The role of the proximal region has been disputed as to whether it simply protects the axial sulfur, or whether it additionally influences catalysis via modulation of the push effect. The objective of the research presented herein is two-fold. First, the influence of the NH•••S bonds on Cpd I formation is determined by obtaining the reaction coordinate, starting from a peroxide bound heme, for two model systems (one with proximal residues providing NH•••S bonds and one without) and comparing the results. Secondly, the influence of the proximal region on the epoxidation of Cis-β-methylsterene is obtained. This is performed similarly to the first objective however, the reaction coordinate begins with a Cpd I-CBMS complex and the proximal contribution is extended to include the influence of the proximal helix dipole. Our findings show that the proximal region stabilizes Cpd 0 relative to all other minima and reduces the barrier for Cpd 0’s formation. The stability of protonated Compound 0 is reduced, favoring a hybrid homo-heterolytic relative to a classic heterolytic mechanism for O-O bond scission. Additionally, the proximal region significantly enhances CPO’s reactivity; the Cβ-O bond barrier is stabilized, while Cα-O-Cβ ring closure becomes barrierless. The stabilization of the reaction barrier correlates with increased electron density transfer to residues of the proximal pocket and involves a change in the electron transfer mechanism. These results can be traced to a reduction in the pKa of the heme-bound substrate and an increase in oxidation potential, a result of the proximal region reducing the “push effect”.

The compressive strength of mortar is typically determined using the American Societyfor Testing and Materials (ASTM) standard method using 2 inch cubes which are compressed tillfailure. There is however a disparity between the compressive strengths of mortar cubes, and insitumortar. This disparity is a result of the differences in thickness, aspect ratio, curingconditions, water content, and confinement between mortar cubes and mortar joints. While thesedifferences lead to mortar joints being stronger than mortar cubes, a relationship between theirstrengths is desired.Two less-common mortar strength tests were used to determine more accurately thecompressive strength of in-situ mortar. The results of both tests were compared to the results ofASTM standard compressive testing with mortars of the same water content. The first was theDouble Punch test which involves the use of two metal punches that compress either side of athin mortar sample till failure. The Double Punch test is more difficult to perform than theASTM standard compression test, but was useful because it simulates the confinement that insitumortar will experience. The Double Punch test was also used with mortar specimens ofvarying thickness to determine a relationship between specimen thickness and compressivestrength. The second test used was the Helix Pullout test. This test is performed by insertingmetal helical screws into a mortar joint, and pulling from the joint while restricting rotation. Themaximum load used to extract the Helix is recorded as the Pullout Load, and is used to find thecompressive strength by use of a calibration curve. This test was used on a masonry wall paneland mortar cubes were also made with the same mortar for compressive testing.The tested mortar exhibited decreased compressive strength with increased water content.The mortar also decreased in strength with increasing specimen thickness. Mortar joints wereshown to be significantly stronger than mortar cubes based on factors of specimen thickness andconfinement by an average factor of at least 2.40. Although results are affected by punchdiameter, the Double Punch test was shown to be a consistent and reliable means of estimatingmortar compressive strength. The Helix Pullout test exhibited wide variation, and wasdetermined to be primarily useful for qualitative comparison as opposed to quantitativedetermination of strength.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22269号 / 理博第4583号 / 新制||理||1658(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 時任 宣博, 教授 依光 英樹 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

In eubacteria, stalled ribosomes are rescued by a conserved quality-control mechanism involving transfer-messenger RNA (tmRNA) and its protein partner SmpB. Mimicking a tRNA, tmRNA enters stalled ribosomes, adds Ala to the nascent polypeptide, and serves as a template to encode a short peptide that tags the nascent protein for destruction. To further characterize the tagging process, we developed two genetic selections that link tmRNA activity to cell death. These negative selections can be used to identify inhibitors of tagging or to identify mutations in key residues essential for ribosome rescue. Little is known about which ribosomal elements are specifically required for tmRNA activity. Using these selections, we isolated ribosomal RNA mutations that block the rescue of ribosomes stalled at rare Arg codons or at the inefficient termination signal Pro-opal. We find that deletion of A1150 in the 16S rRNA blocks tagging regardless of the stalling sequence, suggesting that it inhibits tmRNA activity directly. The C889U mutation in 23S rRNA, however, lowers tagging levels at Pro-opal and rare Arg codons but not at the 3'-end of an mRNA lacking a stop codon. We conclude that the C889U mutation does not inhibit tmRNA activity per se but interferes with an upstream step intermediate between stalling and tagging.

No description available.

The most common secondary structure of proteins is the alpha-helix. The alpha-helix can be involved in various protein-protein interactions (PPIs) through the recognition of three or more side chains along one face of the alpha-helix (Wells and McClendon, 2007). In recent years, there has been an increasing interest in the development of peptidic and non-peptidic compounds that bind to PPI surfaces. We focused on the design and synthesis of compounds that mimic the orientation of side chain residues of an alpha-helical protein domain. Although our scaffolds could potentially inhibit various PPIs, we focused mainly on the disruption of interactions among the Bcl-2-family of proteins and the Mdm-2-family of proteins to favor apoptosis in cancer cells. A summary of Bcl-2 and Mdm-2 structure and function relationships that focuses on the possibility of using peptidic and non-peptidic alpha-helical mimics as PPI inhibitors is described in Chapter One. Chapter Two discusses the design and synthesis of 3-substituted-2,6- and 2,5-piperazinedione oligomers as more hydrophilic scaffolds compared to previously reported alpha-helical mimetics (Yin, et al., 2005). A key feature of this design is the linkage of the units by a hydrazine bond. While we were able to prepare several monomers containing the hydrazine linkage, synthesis of the dimers and trimers is very challenging. Due to the difficulty of synthesizing oligomeric piperazine-diones in practical yields, we next focused on the design and synthesis of novel 2,5-terpyrimidinylene scaffolds as an alternative to obtain alpha-helical mimetics; this is discussed in Chapter Three. The main outcome of this project was the efficient preparation of a "first-generation" non-peptidic compound library via a facile iterative synthesis enabled by the key conversion of 5-cyanopyrimidine to 5-carboxamidine. Chapter Three also discusses our progress towards the synthesis of structurally similar substituted-2,5-terpyrimidinylenes, but with more drug-like properties as determined by QikProp calculations. Chapter Four describes an independent study on the synthesis of a guanidine derivative as an alkylating agent for the synthesis of cysteine peptide nucleic acids, CPNA, which is another current project in our lab.

Mortar is the cementitious binding material placed between masonry blocks to create a composite system. The American Society of Testing and Materials (ASTM), along with other organizations, have established the testing of prismatic mortar specimens for evaluating mechanical properties, like compressive strength. Mortar joints, however, possess vastly different characteristics compared to prismatic specimens, especially in terms of geometry and water content. These differences prevent a direct comparison of compressive strength between prismatic specimens and actual mortar joints in the assembly. The objective of this study was to analyze Type S mortar joints, with particular emphasis on specimen shape and water content, to draw accurate comparisons of compressive strength to ASTM prescribed mortar prismatic specimens.To examine the effect of water on mortar compressive strength, three different water contents were evaluated across nearly all testing series. Cubic (2-in) and cylindrical (2 by 4-in) mortar specimens were prepared and tested according to ASTM guidelines to verify the compressive strength relationship described by ASTM and to be used as comparative data. In addition, a small masonry wall was assembled and cured in a laboratory to simulate true properties of mortar joints. Mortar joints subjected to testing were a combination of thin slices cut from prismatic specimens as well as in-place bed joints cured between concrete masonry units (CMU). Two unorthodox test methods, the double punch test (DPT) and helix pull-out test (HPT), were selected as methods for assessing mortar joints. In addition, confining effects from neighboring material common to DPT were evaluated as a function of specimen face dimensions. The compressive strength ratio obtained through testing of 2-in cubic and 2 by 4-in cylindrical specimens was lower than ASTM recommendations. This may have been in part due to testing cylindrical specimens with rough surfaces and no capping material. DPT confinement on 2-in square and 2-in diameter circular specimens was found to be equivalent. Thinly sliced specimens tested in DPT showed increases in compressive strength as water content and specimen thickness decreased. As a whole, DPT results on thin mortar slices showed promise for accurate comparison to prismatic mortar specimens. In-place mortar joints tested in HPT showed moderate to high scatter. In addition, evaluation via HPT was determined to be more appropriate for qualitative rather than quantitative assessments of in-situ mortar.

As society moves towards being more and more digitalised, so does agriculture as well. Hopefully these digital tools will help us reach environmental goals through optimizing the use of resources in the agricultural sector. However, there are a few barriers to overcome for the digital transition to run smoothly. This thesis investigates a small portion of the agricultural innovation network in Sweden. This is done through multiple interviews and literary research. We can clearly see how this innovation network during the last decades has moved towards becoming more knowledge centered and how the model triple helix now easily can be applied to the network. The network is then analysed using Ron Boschma’s five proximity factors and it becomes clear that concerning the agricultural innovation network, the cognitive and institutional proximity is of great importance for the innovational strength. It also becomes clear that the different proximity factors seldom act alone, but instead build upon each other to increase the negative respectively positive outcomes. Moreover it is shown that regarding the agricultural innovation network in Sweden, it can only benefit from improving the proximity factors, which is different from other types of industries.