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This doctoral thesis reports the theoreticalinvestigations on the geometrical and electronic structures of small siliconclusters doped with some representative main group elements, including Li, Mg,B, Al and also C by using quantum chemical calculations. Deep understanding oftheir geometric and electronic structures, energetics and bonding phenomenaconstitutes a necessary step in the extensive and intensive search forpromising clusters that could be considered as building blocks for furtherassemblies. Our searches for minima on thepotential energy surfaces were performed using two different approaches. In thefirst, we used a stochastic genetic algorithm to generate as many guessstructures as possible. Equilibrium structures that were initially detectedusing low-level computations, were then reoptimized using higher level methods.In the second approach, we made use of a chemical intuition, in that initialstructures of clusters SinXm were manually constructedby either substituting Si-atoms of the corresponding silicon frameworksby other element atoms, or adding dopant-atoms at various positions on surfacesof the Sin clusters. Theuse of the genetic algorithm is less effective for producing singlydoped-clusters having small sizes because most of relevant structures in Si clustersare relatively well known. On the contrary, the multi-doped and larger sizeclusters imply a huge number of initial guess structures and thus make thegenetic search necessary and more effective, even though such a search is oftentedious and computationally demanding. Nevertheless, only a combination ofdifferent search approaches allows a consistent set of lower-energy structuresto be obtained. We are confident that the isomers reported in this thesis atleast correspond to the lower-energy equilibrium structures. However, not onlya careful search is required, but the accuracy of the computational methodsused is equally crucial in the determination of global minima. The low-lying isomers of the clusterswere identified on the basis of theoretical results obtained by hybrid (U)B3LYPfunctional in conjunction with the 6-311+G(d) basis set (d polarization plus spdiffuse functions), and then the ground states are assigned by high accuracy computationalmethods such as the composite G3B3 and G4 methods and when possible also the coupled-clustertheory extrapolated to the complete basis set CCSD(T)/CBS protocol. Concerningthe energetics, different basic thermochemical parameters of the clustersconsidered including total atomization energies (TAE), standard enthalpies offormation (ΔHf),ionization energies (IE), electron affinities (EA), binding energies (Eb), embedded energy (EE) anddissociation energies (De)were determined using the Gn (G3B3and G4) and CCSD(T)/CBS approaches. For bare silicon clusters, a uniform set of standard heats offormation for the cationic and anionic Sinclusters were determinedfor up to n = 13. Insome cases, variations between G4 and CBS TAE values are relatively large. The differences of energeticproperties between both G4 and CBS methods can be understood from the ways ofcomputing single point electronic energies, as well as the geometries ofclusters used. Geometry is beyond any doubt an important factor in thethermochemical evaluation. For these systems, experimentalresults in the current literature were also characterized by large uncertainties,including the actual uncertainty of the standard heat of formation of the Siatom. For otherparameters such as IEs and EAs,they were better predicted, in part due to a certain mutual cancellation oferrors in the evaluation of relative energies. The corresponding G4 results areexpected to be accurate to, or even better than, ± 0.15 eV. For lithiumdoped silicon clusters, the adiabatic (AIEs) and vertical (VIEs) ionizationenergies of the SinLim clusters were evaluated. CalculatedAIE and VIE values at the B3LYP/6/311+G(d) and CCSD(T)/aug-cc-pVDZ levels forSi6Li2, Si7Li, Si10Li, Si11Licompare quite well with the corresponding experimental results obtained usingthe photo-ionization efficiency measurements.For borondoped silicon clusters, heats of formation calculated by both G4 andCCSD(T)/CBS methods showed good agreement with available experimental data.Overall, it appears that an accurateevaluation of the TAEs and thereby the standard heats of formation of silicon-basedclusters remains a great challenge for quantum chemical computations in order to attain thechemical accuracy of ± 1.0 kcal/mol. Due to the non-classical bonding of clusters,the use of other thermochemical approaches (such as bond separation reactions)and more economic computational methods could not be applied. The only optionleft is to increase the quality of the wavefunctions in going beyond theCCSD(T) level. However, our preliminary computations using the full CCSDT treatmentpointed out that it is much more computer-demanding than the CCSD(T) method,which goes beyond our actual computing resources. Based on the geometricalcharacteristics of the ground states, a growth mechanism for each series ofbinary silicon clusters SinXm can now beestablished. Generally, alkali (Li) orearth-alkali (Mg) dopants prefers add on an edge or a face of Sin frameworks, whereas theboron group 13 element (B, Al) favors substitution into one of the Si positionsin Sin+1counterparts. Due to the shorter B-Si bond lengths, as compared with the Al-Si counterparts,the B impurity can intrude inside the corresponding Sin cage (for up to n≥ 8). In particular, the neutral structures of doubly impurities doped siliconclusters SinX2,(X = Li, Mg, Al) have similar way of growing up: one dopant atom substitutesinto a position of Sin+1,whereas the other is usually added on an edge, or a face, of the existingcluster.Our theoretical results also predicted that some closed-shellsystems such as Si9B-, Si10B+ , Si9Al-,and Si4C2+ are characterized by enhanced stabilities. Theirhigher thermodynamic stabilities can be understood by the Jellium shell model(JSM). According to JSM, the valence electrons are supposed to befreely itinerant in a simple mean-field potential formed by the nuclei of atomsand core electrons, the valence electrons fill the hydrogen-like orbitals ‌‌followingthe pattern of orbitals as [1S21P61D102S21F142P61G182D10 ]etc Within this model, the numbers of valence electrons of 8, 20, 34, 40, 56and 68 emerge as the magic numbersthat actually correspond to a complete filling of the successive shellelectrons. Concerning the bonding phenomena, electron localization techniques (ELF and ELI-D)were used to locate the whereabouts of electrons, and thereby toidentify the chemical bonds of some specific clusters such as Si­3,Si4, Si42+, Si4C2+, andSi9C. Calculations of the ring current, which is the magneticresponse of a molecule, were also carried out in order to probe their aromaticity. This study provided a further supportfor the point of view that the existence of delocalized occupied molecularorbitals in a planar molecule is a necessary but not sufficient condition toassign a certain aromatic character (aromatic, non-aromatic or anti-aromatic)to that specific type of electrons. Different criteria (such as the magneticring current) need to be considered for a more consistent evaluation of thispopular but intriguing molecular property. In addition, both the Si4C2+dication and the SiC9 neutral exhibit a planar tetracoordinatecarbon atom (ptC) in their lowest-lying isomer. This is caused by a drivingforce for C-planarization which includes not only the electron delocalizationon the square frame but also the bonding between C-dopant and the Si frame of thesmall dication. In the larger neutral cluster cage, the Si5 grouptends to stabilize electronically the cage by electron transfer but alsomechanically by geometrical constraints in maintaining a ptC configuration. We also attempted to search for potential linkers in makingsilicon nanowires. We found that the Mg dopant, due to its large electrontransfer capacity, behaves as a cation Mgdelta+ and thereby induces anionic entity with the Sindelta-anionic partner. The resulting Mg cation can be served as a linker between Sin blocks leading tostabilized linear [(Sik)Mg]lstructures in part due to electrostatic attraction forces. This allowed us to identify some suitable membersthat can further be used as superatoms for assemblies. We thus probed thefive-, seven-, eight- and ten-atom Si building blocks, and the role of the Mgelement as the linkers connecting them. Calculated results ofthe average assembling energy which gave us an idea about the tendency ofassembling the cluster of (SikMg)l with k = 5, 7, 8, 10, show that silicon clusters Sik tend to assemble in ring forms (Rl) over the linear forms(Ll)as the assembling energy of the Rl are larger than those of the Ll.However, a more important fact is that the average assembling energy of thelinear form tends to increase with the increasing size (l), implying that a(longer) nanowire can be considered as a plausible possibility. Table of Contents Chapter 1. Introduction 1 Chapter 2. Determination of Atomization Energies and Heats of Formation 13 2.1. Heats of formation and total atomization energies 14 2.2. Choice of quantum chemical methods 18 2.2.1. The Coupled-cluster theory 18 2.2.2. The Composite G4 method 20 2.2.3. The Complete basis set approach (CCSD(T)/CBS) 22 2.2.4. Total Atomization Energies (TAE) 23 2.3. Total atomization energies, heats of formation and thermochemical parameters of small silicon clusters and their ions using G4 and CBS method 24 2.3.1. Shape of the lowest-lying isomers of Sin clusters and their ion 25 2.3.2. Total atomization energies (TAE) 27 2.3.3. Heats of formation (∆fHo) 31 2.3.4. Electron affinities (EA) and ionization energies (IE) 32 2.3.5. Relative stability of clusters and dissociation energies 35 2.4. Concluding remarks 38 Chapter 3. Singly and doubly lithium doped silicon clusters: Geometrical and electronic structures and ionization energies 45 3.1. Introduction 46 3.2. Experimental results 47 3.3. Computations 48 3.4. Results and discussion 49 3.4.1. Structures of SinLim0/+ with n = 2-11 and m = 1,2 49 3.4.2. Growth Mechanisms of SinLim0/+ 62 3.4.3. Dissociation Energies 66 3.5. Concluding remarks 68 Chapter 4. Thermochemical Parameters and Growth Mechanism of the Boron Doped Silicon Clusters 71 4.1. Introduction 72 4.2. Computational methods 73 4.3. Results and discussion 74 4.3.1. Thermochemical properties of clusters 74 4.3.2. Lower-lying isomers of SinB clusters and their growth mechanism 78 4.3.3. Relative stability of clusters considered 87 4.3.4. Dissociation energies 90 4.3.5. Enhanced stability and Jellium electron shell model (JSM) 91 4.4. Concluding remarks 94 Chapter 5. Structure, Thermochemical Properties and Growth Sequence of Aluminum Doped Silicon Clusters and Their Anions 97 5.1. Introduction 98 5.2. Computational methods 98 5.3. Results and discussion 99 5.3.1. Lower-lying isomers of SinAlm clusters in both neutral and anionic states 99 5.3.2. Equilibrium growth sequence of the SinAlm clusters 112 5.3.3. Thermochemical properties 114 5.3.4. Thermodynamic stability of clusters 117 5.3.5. Dissociation energies 119 5.3.6. Jelium electron shell model (JSM) 121 5.4. Concluding remarks 124 Chapter 6. SinMgm: Toward Silicon Nanowires with Magnesium Linkers 127 6.1. Introduction 128 6.2. Lower-lying isomers of SinMgm clusters in both neutral and cationic states 129 6.2.1. The singly magnesium doped SinMg0/+ 130 6.2.2. The doubly magnesium doped SinMgm0/+ with n = 1-10 and m = 2 133 6.3. Growth pattern of the equilibrium SinMgm clusters 139 6.4. Thermochemical properties 140 6.5. Thermodynamic stability 142 6.6. In search of silicon nanowires with magnesium linkers 143 6.7. Concluding remarks 148 Chapter 7. Chemical Bonding in Si3, Si4, Si42+, Si4C2+ and Si9C 151 7.1. Introduction 152 7.2 The silicon trimer 154 7.2.1. A qualitative analysis of the electronic states: the Walsh diagrams of Si3 155 7.2.2. An analysis of the chemical bonding of Si3 158 7.2.3. Ring current and aromaticity 159 7.3. The silicon tetramer: Si4, Si42+ and Si4C2+ 162 7.3.1. Structure of the tetramer Si4 and its dication Si42+ 162 7.3.2. Structure of the doped dication Si4C 2+ 167 7.4 Si9C: A stable C-doped silicon cluster 171 7.5 Concluding remarks 173 Chapter 8. General Conclusions and Perspectives 177 nrpages: 204 status: published

As demandas por mudanças devem ser vistas como situações normais dentro do processo de gestão de uma organização. Nesta abordagem, dois elementos são fortes contribuintes como sistemáticas de apoio: a gestão (ou gerenciamento) das mudanças, que estabelece os processos e controles necessários para que os objetivos da mudança sejam alcançados de maneira organizada e a existência dos fatores críticos de sucesso para a mudança, que atuam como elementos de convergência em relação aos objetivos planejados. No mesmo contexto, as grandes empresas, principalmente aquelas de atuação global, têm tido demandas pelas diversas partes interessadas com as quais possuem interface, em demonstrar o seu desempenho na gestão da sustentabilidade, dentro das suas respectivas dimensões: ambiental, social e econômica. O objetivo geral do presente trabalho consiste em identificar quais fatores críticos de sucesso são determinantes no processo de mudança organizacional, em particular na abordagem da prática de gerenciamento de mudanças de uma empresa petroquímica brasileira, associados com inclusão da gestão proativa da sustentabilidade empresarial, através do diagnóstico do cenário atual em relação a este tema. A estrutura metodológica consistiu em macro etapas de revisão da literatura, seleção dos fatores críticos de sucesso e critérios de sustentabilidade, desenvolvimento de questionários e aplicação destes através de um estudo de caso, do tipo observação participante, em uma empresa petroquímica brasileira, viabilizando a subsequente análise dos dados obtidos e conclusões. Os principais resultados identificaram quarenta e cinco fatores críticos de sucesso relacionados ao processo de gestão da mudança organizacional e o modelo da GRI como o de maior aderência no meio empresarial mundial. Foram identificadas contribuições da literatura em fatores críticos de sucesso no processo de gerenciamento de mudanças vigente na organização, tais como comunicação constante e eficiente e recursos, de forma a agregar práticas ao modelo atual de gestão da mudança organizacional. As dimensões de fatores críticos de sucesso identificadas como mais relevantes no estudo de caso foram a liderança e recursos. Em relação à percepção sobre conceitos de sustentabilidade, particularmente quanto requisitos da GRI na versão G4, foi verificada junto aos respondentes uma visão que enfatiza a dimensão ambiental, a despeito das dimensões social e econômica, associada a fragilidades em ambientação dos mesmos em relação a conceitos de sustentabilidade e conexão deste tema com fatores críticos de sucesso na mudança organizacional, trazendo elementos para a melhoria contínua das práticas de gestão, assim como do relato da sustentabilidade empresarial. The demands for change should be seen as normal situations within the management process of an organization. In this approach, two elements are strong contributors as systematic support: change management, which establishes the necessary processes and controls for the objectives of the change to be achieved in an orderly manner, and the existence of critical success factors for change, which act as elements of convergence towards the planned objectives. In the same context, large companies, especially those with global operations, have been demanded by various stakeholders to demonstrate its performance in sustainability management within their respective dimensions: environmental, social and economic. The overall objective of this study is to identify, particularly in the practice of change management in a Brazilian petrochemical company, the proactive management of corporate sustainability and the critical success factors that are decisive in the organizational change process through the diagnosis of the current scenario regarding this topic. The methodological framework consisted of macro steps of literature review, selection of the critical success factors and criteria of sustainability, development and application of these questionnaires through a participant observation case study in a Brazilian petrochemical company, enabling the subsequent analysis of the obtained data and conclusions. Forty-five critical success factors related to the process of managing organizational change were identified and the GRI model was the most applied model in the global business environment. In order to add to the current practice model for managing organizational change, contributions from the literature were identified in critical success factors in the management of the current changes in the organization, such as constant and efficient communication process and resources. Leadership and resources were the most relevant dimensions of critical success factors identified in the case study. Regarding the understanding of sustainability concepts, particularly in relation to the requirements of GRI in a G4 version, it was verified that the respondents’ perceptions emphasize the environmental dimension over the social and economic dimensions. This was associated with the respondents` limited knowledge regarding concepts of sustainability and how this issue connects with critical success factors in organizational change, bringing elements to the continuous improvement of management practices, as well as the reporting of corporate sustainability.

Background The fine balance of immunoglobulins (Ig) E, IgG1, IgG4 and IgA in healthy production is maintained by the interaction of B cells with adaptive and innate immune response. The regulation of toll-like receptors (TLRs)-driven innate and adaptive immune effector B-cell response and the role of mammalian telomeric TTAGGG repeat elements represent an important research area. Methods Human PBMC and purified naive and memory B cells were stimulated with specific ligands for TLR2, TLR3, TLR4, TLR5, TLR7, TLR8 and TLR9 in the presence or absence of telomeric oligonucleotides. B-cell proliferation, differentiation and antibody production were determined. Results TLR9 ligand directly activates naive and memory B cells, whereas TLR7 can stimulate them in the presence of plasmacytoid dendritic cells. Human B cells proliferate and turn into antibody-secreting cells in response to TLR3, TLR7 and TLR9, but not to TLR2, TLR4, TLR5 and TLR8 ligands. Stimulation of B cells with intracellular TLR3, TLR7 and TLR9 induced an activation cascade leading to memory B-cell generation and particularly IgG1, but also IgA, IgG4 and very low levels of IgE production. Mammalian telomeric oligodeoxynucleotide (ODN) significantly inhibited all features of TLR ligand-induced events in B cells including B-cell proliferation, IgE, IgG1, IgG4, IgA production, class switch recombination, plasma cell differentiation induced by TLR3, TLR7 and TLR9 ligands. Conclusion B cells require specific TLR stimulation, T-cell and plasmacytoid dendritic cell help for distinct activation and Ig production profiles. Host-derived telomeric ODN suppress B-cell activation and antibody production demonstrating a natural mechanism for the control of overexuberant B-cell activation, antibody production and generation of memory. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

O G4 surgiu sob uma aura extremamente promissora. Entretanto, ao final da ultima rodada Doha essa aura se desvaneceu. Assim, o presente artigo busca analisar as possíveis mudanças internas a esse fórum e os impactos que ele exerce sobre a comunidade internacional.

The molecular bases of classical serological immunoglobulin allotypes are progressively uncovered through detailed characterization of the relevant genes. Here we describe two isoallotypic determinants of the G4 gene. In the first, Leu 309, as in G1 and G3, is changed to Val, as in G2; studies on myeloma proteins have long assigned the immunologically defined nG4 m(a)/(b) to the same position. The two molecular variants, here called IGHG4*L309 and IGHG4*V309, are allelic in IGHC haplotypes with a single G4 gene, but can be found together in cis in G4-duplicated haplotypes. A second isoallotypic variant was found at codon 409, where either Arg, as in G1 and G3, or Lys, as in G2, can be found. Both isoallotypes are associated with several 'silent isoallotypic' substitutions dispersed through the hinge, CH2 and CH3 domains. This suggests segmental gene conversion as the common mechanism of origin.

G-quadruplexes (G4) are alternative nucleic acid structures involved in transcription, translation and replication. Aberrant G4 formation and stabilisation is linked to genome instability and cancer. G4 ligand treatment disrupts key biological processes leading to cell death. To discover genes and pathways involved with G4s and gain mechanistic insights into G4 biology, we present the first unbiased genome-wide study to systematically identify human genes that promote cell death when silenced by shRNA in the presence of G4-stabilising small molecules. Many novel genetic vulnerabilities were revealed opening up new therapeutic possibilities in cancer, which we exemplified by an orthogonal pharmacological inhibition approach that phenocopies gene silencing. We find that targeting the WEE1 cell cycle kinase or USP1 deubiquitinase in combination with G4 ligand treatment enhances cell killing. We also identify new genes and pathways regulating or interacting with G4s and demonstrate that the DDX42 DEAD-box helicase is a newly discovered G4-binding protein.