Ab Initio Study of the Molecular and Electronic Structure of CoCH2+ and of the Reaction Mechanism of CoCH2+ + H2

Both CASSCF and MR-SDCI-CASSCF methods have been used with two different effective core potentials to investigate the molecular and electronic structures of CoCH2+, as well as the mechanism for the reaction CoCH2+ + H2. Four electronic states of CoCH2+ are very low lying: the ground state is a nearly degenerate pair (3A2 and 3A1), and the 3B1 and 3B2 states are only 4-8 kcal/mol higher in energy. The binding energy of C O C H ~ + ( ~ Are~la)t,iv e to that of C ~ + ( ~ F , s l d+~ C)H 2(3B1), is estimated to be 70-80 kcal/mol. A similar hydrogenolysis reaction mechanism holds for the 3A2 and 3A1 states of the CoCH2+ + H2 reactants: In the first step, the reactants yield an ion-molecule complex, (H2)CoCH2+, stabilized by 8-9 kcal/mol. Subsequently, the H-H bond is activated, leading to a four-center transition state with an energy barrier of about 31-34 kcal/mol. An intermediate complex, HCoCH3+, is predicted to be a minimum at the CASSCF level, but MR-SDCI-CASSCF single-point calculations suggest that this minimum disappears at the higher level of theory. Following H-H bond cleavage, a CoCH4+ ion-molecule complex is formed, with a stabilization energy of 19-22 kcal/mol. The CoCH2+ hydrogenolysis reaction is predicted to be exothermic by 20-30 kcal/mol. The channels leading to formation of CoH+ + CH3 and CoCH3+ + H are endothermic by about 5-1 2 kcal/mol. The reverse reaction Co+ + CH4 may give only one product, the ion-molecule complex CoCH4+ at moderate temperatures. An increase in the available kinetic energy would make it possible to form dissociation products: CoH+ + CH3 and CoCH3+ + H. Although the channel leading to CoCH2+ + H2 is thermodynamically more favorable, a large barrier prevents it from taking place. Hay-Wadt and Stevens-Krauss-Basch-Jasien pseudopotentials give qualitatively the same results

Transition Metal Substitution Effects on Metal-to-Polyoxometalate Charge Transfer

A series of heterobimetallic transition metal substituted polyoxometalates (TMSPs) have been synthesized based on the CoII-centered ligand [CoIIW11O39]10-. The eight complex series, [CoII(MxOHy)W11O39](12-x-y)- (MxOHy = VIVO, CrIII(OH2), MnII(OH2), FeIII(OH2), CoII(OH2), NiII(OH2), CuII(OH2), ZnII(OH2)), of which six are reported for the first time, was synthesized starting from [CoIIIW11O39]9- and studied using spectroscopic, electrochemical, and computational techniques to evaluate the influence of substituted transition metals on the photodynamics of the metal-to-polyoxometalate charge transfer (MPCT) transition. The bimetallic complexes all show higher visible light absorption than the plenary [CoIIW12O40]6- and demonstrate the same MPCT transition as the plenary complex, but have shorter excited state lifetimes (sub-300 ps in aqueous media). The decreased lifetimes are rationalized on the basis of nonradiative relaxation due to coordinating aqua ligands, increased interaction with cations due to increased negative charge, and the energy gap law, with the strongest single factor appearing to be the charge on the anion. The most promising results are from the Cr- and Fe-substituted systems, which retain excited state lifetimes at least 50% of that of [CoIIW12O40]6- while more than tripling the absorbance at 400 nm

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe_(2)O_3) electrodes

The spectra and dynamics of photogenerated electrons and holes in excited hematite (α-Fe_(2)O_3) electrodes are investigated by transient absorption (from visible to infrared and from femto- to micro-seconds), bias-dependent differential absorption and Stark spectroscopy. Comparison of results from these techniques enables the assignment of the spectral signatures of photogenerated electrons and holes. Under the pulse illumination conditions of transient absorption (TA) measurement, the absorbed photon to electron conversion efficiency (APCE) of the films at 1.43 V (vs. reversible hydrogen electrode, RHE) is 0.69%, significantly lower than that at AM 1.5. TA kinetics shows that under these conditions, >98% of the photogenerated electrons and holes have recombined by 6 μs. Although APCE increases with more positive bias (from 0.90 to 1.43 V vs. RHE), the kinetics of holes up to 6 μs show negligible change, suggesting that the catalytic activity of the films is determined by holes with longer lifetimes

Перспективы развития фундаментальных наук: сборник научных трудов XII Международной конференция студентов и молодых ученых, г. Томск, 21-24 апреля 2015 г.

Сборник содержит труды участников XII Международной конференции студентов и молодых учёных «Перспективы развития фундаментальных наук». Включает доклады студентов и молодых ученых, представленные на секциях «Физика», «Химия», «Математика», «Биология и медицина», «Наноматериалы и нанотехнологии», «Технология», «Конкурс архитектурных работ», «IT- технологии и электроника». Предназначен для студентов, аспирантов, молодых ученых, преподавателей в области естественных наук и высшей математики

O consumo colaborativo como alternativa ao consumo de massa: a percepção do consumidor em bairros de Florianópolis e a relação do consumo colaborativo com valores pessoais.

TCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.O tipo de consumo que a sociedade habituou-se ao longo das últimas décadas tem ocasionado problemas que impactam diretamente o cotidiano das pessoas. Alavancado por motivações individuais e questões ambientais, sociais e econômicas, o consumo colaborativo é um fenômeno recente que vem alterando o funcionamento da economia global ao proporcionar aos consumidores uma nova forma de acomodar seus desejos e necessidades de maneira conveniente e sustentável. Associado a isso, as redes de informação energizadas pela Internet têm modificado significativamente o modo e a velocidade com que os agentes econômicos se relacionam. Nesse sentido, o objetivo maior deste trabalho de conclusão do Curso de Ciências Econômicas é identificar a percepção dos consumidores da Grande Florianópolis acerca do consumo colaborativo como alternativa ao modelo de consumo tradicional. O estudo é dividido em três partes principais. Inicialmente recorre-se a pesquisa bibliográfica para contextualizar e conceituar os termos economia compartilhada e consumo colaborativo, suas formas e princípios. Visando conhecer os efeitos desse movimento no Brasil e especificamente em Florianópolis, na sequencia realiza-se pesquisa através de questionários para identificar a propensão do consumidor a participar de práticas de consumo colaborativo em quatro regiões: Lagoa da Conceição, Centro, Trindade e Continente. Considerando que os valores pessoais interferem no comportamento do consumidor, busca-se avaliar qualitativamente de que forma tais valores se relacionam com a disposição dos mesmos a participar do consumo colaborativo. Através do questionário aplicado, ainda que com amostra limitada, observa-se que os consumidores apresentam de modo geral nível satisfatório de propensão a participar do consumo colaborativo, sendo a Lagoa da Conceição a localidade com maior adesão, seguida por Continente, Trindade e Centro. Além disso, a mensuração dos valores pessoais permite observar que os consumidores mais abertos a mudança, menos conservadores e menos apegados materialmente apresentam maior propensão a participar do consumo colaborativo, como é o caso da Lagoa da Conceição. As considerações finais discutem os principais achados e limitações do estudo

НАПРАВЛЕНИЯ СОВЕРШЕНСТВОВАНИЯ ОБРУДОВАНИЯ ДЛЯ ФЛОТАЦИОННОГО ОБОГАЩЕНИЯ ТОНКОДИСПЕРСНыХ МАТЕРИАЛОВ

Проблема и ее связь с научными и практическими задачами. В связи с тем, что в поступающем на обогатительные фабрики сырье содержится до 30% ма-териала крупностью менее 1 мм, роль процесса флотации существенно возрас-тает. Этому способствует и возможность создания достаточно простых замкну-тых водно-шламовых схем, включающих флотацию в качестве основного эле-мента очистки оборотных вод. Многими исследованиями, которые проводились ранее и продолжают выполняться и в настоящее время, установлены направле-ния совершенствования этого достаточно сложного физико-химического про-цесс

New and Old Aspects of Complexity in Modern Research

Complexity occurs in biological and synthetic systems alike.  This general phenomenon has been addressed in recent publications by investigators in disciplines ranging from chemistry and biology to psychology and philosophy.  Studies of complexity for molecular scientists have focussed on breaking symmetry, dissipative processes, and emergence.  Investigators in the social and medical sciences have focused on neurophenomenology, cognitive approaches and self-consciousness.  Complexity in both structure and function is inherent in many scientific disciplines of current significance and also in technologies of current importance that are rapidly evolving to address global societal needs.  Several of these multifaceted scientific disciplines are addressed in this book including complexity from the general and philosophical perspective, magnetic phenomena, control of self assembly and function in large multicomponent clusters, application of theory to probe structure and mechanism in highly complex molecular species, and the design of multifunctional nanoscale molecules of value in decontamination and solar fuels research.  Each chapter is both a review and addresses some ongoing challenges, thus each should provide a good preparation for further work in these highly active areas of research endeavour.