Extension of the B3LYP - Dispersion-Correcting Potential Approach to the Accurate Treatment of both Inter- and Intramolecular Interactions

We recently showed that dispersion-correcting potentials (DCPs), atom-centered Gaussian-type functions developed for use with B3LYP (J. Phys. Chem. Lett. 2012, 3, 1738-1744) greatly improved the ability of the underlying functional to predict non-covalent interactions. However, the application of B3LYP-DCP for the {\beta}-scission of the cumyloxyl radical led a calculated barrier height that was over-estimated by ca. 8 kcal/mol. We show in the present work that the source of this error arises from the previously developed carbon atom DCPs, which erroneously alters the electron density in the C-C covalent-bonding region. In this work, we present a new C-DCP with a form that was expected to influence the electron density farther from the nucleus. Tests of the new C-DCP, with previously published H-, N- and O-DCPs, with B3LYP-DCP/6-31+G(2d,2p) on the S66, S22B, HSG-A, and HC12 databases of non-covalently interacting dimers showed that it is one of the most accurate methods available for treating intermolecular interactions, giving mean absolute errors (MAEs) of 0.19, 0.27, 0.16, and 0.18 kcal/mol, respectively. Additional testing on the S12L database of complexation systems gave an MAE of 2.6 kcal/mol, showing that the B3LYP-DCP/6-31+G(2d,2p) approach is one of the best-performing and feasible methods for treating large systems dominated by non-covalent interactions. Finally, we showed that C-C making/breaking chemistry is well-predicted using the newly developed DCPs. In addition to predicting a barrier height for the {\beta}-scission of the cumyloxyl radical that is within 1.7 kcal/mol of the high-level value, application of B3LYP-DCP/6-31+G(2d,2p) to 10 databases that include reaction barrier heights and energies, isomerization energies and relative conformation energies gives performance that is amongst the best of all available dispersion-corrected density-functional theory approaches

Paleoecology of Organic Deposits of Probable Last Interglacial Age in Northern Ontario

Nonglacial deposits in northern Ontario that may date to the last interglacial interval are well known from the Hudson Bay Lowlands where they have been described in sections along several river valleys. Soil horizons, peat beds and other organic sediment sequences comprise the Missinaibi Formation of the Moose River Basin studied for pollen and macrofossils. Results suggest that the climate was as warm or warmer than present, and spruce woodlands prevailed among broad expanses of bog and fen. The Beaver River peat records conditions similar to the present in the Fort Severn area with open spruce woodlands dispersed in peatlands. South of the Lowlands in the Timmins area, a widespread organic-silt horizon termed the Owl Creek beds is stratigraphically equivalent to the Missinaibi Formation. The waning phase of a warm interval is represented, with early climate possibly similar to the present and the later climate much cooler. Correlation of the Missinaibi Formation with substage 5e of the deep-sea oxygen isotope record is corroborated by amino acid results on marine shells from some associated units. Analysis of shells from beneath the Beaver River peat bed indicate that this interval may be considerably younger, possibly substage 5c or, more likely, 5a. The Owl Creek beds may relate to sub-stage 5e, or to one of the younger intervals, 5c or 5a.Les dépôts non glaciaires du nord de l'Ontario qui datent peut-être du dernier interglaciaire sont bien connus dans les basses terres de la baie d'Hudson où ils ont été décrits dans des coupes le long de plusieurs vallées. Les horizons de sols, les lits de tourbes et autres séquences de sédiments organiques comprennent la Formation de Missinaibi dans le bassin de Moose River dont on a étudié le pollen et les macrofossiles. Les résultats indiquent que le climat était aussi chaud, sinon plus, que maintenant et que les forêts d'épinettes dominaient de vastes étendues de tourbières minérotrophes et ombrothrophes. Les données sur la tourbe de Beaver River révèlent des conditions similaires à celles d'aujourd'hui dans la région de Fort Severn où les forêts ouvertes d'épinettes sont dispersées dans les tourbières. Dans la région de Timmins, au sud des basses terres, se trouve un horizon de silt organique étendu (les lits de Owl Creek), qui est l'équivalent stratigraphique de la Formation de Missinaibi. La fin de l'intervalle chaud y est représentée. Ie climat étant au début probablement aussi chaud qu'aujourd'hui puis, par la suite, beaucoup plus froid. La corrélation de la Formation de Missinaibi avec le stade isotopique 5e est corroborée par les résultats des acides aminés sur des coquillages marins de quelques unités associées. Les analyses faites sur des coquillages recueillis sous le lit de tourbe de Beaver River indiquent que cet intervalle pourrait être plus jeune, probablement du stade 5c ou mieux du stade 5a. Les lits de Owl Creek pourraient être associés au stade 5e ou à un intervalle plus récent, 5c ou 5a.Nichtglaziale Ablagerungen im nôrdlichen Ontario, die môglicherweise aus dem letzten Interglazial stammen, sind aus dem Tiefland der Hudson Bay wohlbekannt. wo sie in Schnitten entlang mehrerer Flusstâler beschrieben worden sind. Boden-Horizonte. Torfberten und andere organische Ablagerungssequenzen umfassen die Missinaibi Formation des Moose River-Beckens, welche auf Pollen und Makrofossile untersucht wurde. Die Ergebnisse deuten darauf, dass das Klima so warm wie gegenwârtig oder warmer war und dass Rottannenwàlder zwischen weiten Flâchen von Sùmpfen und Mooren vorherrschten. Der Torf von Beaver River belegt der Gegenwart âhnliche Bedingungen im Gebiet von Fort Severn, wo offene Rottannenwàlder zwischen die Torfmoore verteilt sind. Sùdlich des Tieflands im Gebiet von Timmins ist ein ausgedehnter organischer Schlamm-Horizont, genannt die Betten von Owl Creek. das stratigraphische Gegenstùck zur Missinaibi Formation. Die Endphase eines warmen Intervalls ist festgehalten, mit einem frùhen Klima, das wahrscheinlich dem heutigen âhnlich war, und einem spâteren viel kâlteren Klima. Die Korrelation der Missinaibi Formation mit dem Unterstadium 5e des Tiefsee Sauerstoff Isotop-Belegs wird durch Aminosauren-Ergebnisse auf marinen Muscheln von einigen verbundenen Einheiten bestatigt. Analysen von Muscheln, die unter dem Torfbett von Beaver River gefunden wurden, zeigen, dass dies Interval sehr viel junger sein kônnte, môglicherweise Unterstadium 5c oder noch eher 5a. Die Owl Creek-Betten kônnten mit dem Unterstadium 5e oder einem der jùngeren Intervalle 5c oder 5a verbunden sein

T-Bar clasp-retained removable partial denture as an alternative to implant-based prosthetic treatment

This article reports the case of a 55-year-old female patient who presented with unsatisfactory temporary crowns in the right mandibular premolars and molars, and a premolar-to-molar fixed partial denture in the left side. The clinical and radiographic examinations revealed a fracture of the left first premolar that was a retainer of the fixed partial denture and required extraction. Initially, the acrylic resin crowns were replaced by new ones, and a provisional RPD was made using acrylic resin and orthodontic wire clasps to resolve the problem arising from the loss of the fixed partial denture. Considering the patient's high esthetic demands, the treatment options for the definitive prosthetic treatment were discussed with her and rehabilitation with implant-supported dentures was proposed because the clinical conditions of the residual alveolar ridge were suitable for implant installation, and the patient's general health was excellent. However, the patient did not agree because she knew of a failed case of implant-retained denture in a diabetic individual and was concerned. The patient was fully informed that implant installation was the best indication for her case, but the arguments were not sufficient to change her decision. The treatment possibilities were presented and the patient opted for a clasp-retained removable partial denture (RPD) associated with the placement of crowns in the pillar teeth. The temporary RPD was replaced by the definitive RPD constructed subsequently. Although RPD was not the first choice, satisfactory esthetic and functional outcomes were achieved, overcaming the patient's expectations. This case report illustrates that the dentist must be prepared to deal with situations where, for reasons that cannot be managed, the patient does not accept the treatment considered as the most indicated for his/her case. Alternatives must be proposed and the functional and esthetic requirements must be fulfilled in the best possible manner.Este artigo relata o caso de uma paciente de 55 anos que apresentava no arco mandibular coroas provisórias insatisfatórias nos pré-molares do lado direito e uma prótese parcial fixa de molar a pré-molar no lado esquerdo. Os exames clínico e radiográfico revelaram uma fratura do primeiro pré-molar esquerdo que era um retentor da prótese parcial fixa e teve a extração indicada. Inicialmente, as coroas provisórias foram substituídas por novas e uma prótese parcial removível provisória foi confeccionada com resina acrílica e grampos de fio ortodôntico a fim resolver os problemas relacionados à perda da prótese parcial fixa. Considerando a forte demanda estética da paciente, foram discutidas as opções de tratamento protético definitivo. Foi proposta a reabilitação com prótese implanto-suportada uma vez que as condições clínicas do rebordo alveolar se apresentavam adequadas para instalação de implantes e a saúde geral da paciente era excelente. Entretanto, a paciente não concordou com o tratamento proposto, alegando saber de um caso clínico em que houve insucesso na reabilitação por prótese implanto-suportada em um paciente diabético. Ela foi inteiramente informada de que a colocação de implantes era a melhor indicação para seu caso, mas os argumentos não foram suficientes para mudar sua decisão. As possibilidades de tratamento foram apresentadas e a paciente optou por uma prótese parcial removível (PPR) retida a grampos associada com coroas nos dentes pilares. Na seqüência, a PPR provisória foi substituída por uma PPR definitiva. Embora a PPR não tivesse sido a primeira escolha, foram obtidos resultados estéticos e funcionais satisfatórios, superando as expectativas da paciente. Este relato de caso ilustra que o dentista deve estar preparado para enfrentar situações em que, por razões que não possam ser administradas, o paciente não aceite o tratamento considerado mais indicado para seu caso. Alternativas devem ser propostas e as exigências estéticas e funcionais devem ser contempladas da melhor maneira possível

Oscillations in meta-generalized-gradient approximation potential energy surfaces for dispersion-bound complexes

© 2009 American Institute of Physics. The electronic version of this article is the complete one and can be found at: http://dx.doi.org/10.1063/1.3177061DOI: 10.1063/1.3177061Meta-generalized-gradient approximations (meta-GGAs) in density-functional theory are exchange-correlation functionals whose integrands depend on local density, density gradient, and also the kinetic-energy density. It has been pointed out by Johnson et al. [Chem. Phys. Lett. 394, 334 (2004) ] that meta-GGA potential energy curves in dispersion-bound complexes are susceptible to spurious oscillations unless very large integration grids are used. This grid sensitivity originates from the saddle-point region of the density near the intermonomer midpoint. Various dimensionless ratios involving the kinetic-energy density, found in typical meta-GGAs, may be ill-behaved in this region. Grid sensitivity thus arises if the midpoint region is sampled by too sparse a grid. For most meta-GGAs, standard grids do not suffice. Care must be taken to avoid this problem when using, or constructing, meta-GGAs

Dangling-bond charge qubit on a silicon surface

Two closely spaced dangling bonds positioned on a silicon surface and sharing an excess electron are revealed to be a strong candidate for a charge qubit. Based on our study of the coherent dynamics of this qubit, its extremely high tunneling rate ~ 10^14 1/s greatly exceeds the expected decoherence rates for a silicon-based system, thereby overcoming a critical obstacle of charge qubit quantum computing. We investigate possible configurations of dangling bond qubits for quantum computing devices. A first-order analysis of coherent dynamics of dangling bonds shows promise in this respect.Comment: 17 pages, 3 EPS figures, 1 tabl

Special Issue 2: Uncertainties 2012

A time-resolved kinetic study of the reactions of ring-substituted cumyloxyl radicals (4-X-CumO•: X = OMe, t-Bu, Me, Cl, CF3) with methylferrocenes (MenFc: n = 2, 8, 10) has been carried out in acetonitrile solution. Evidence for an electron transfer (ET) process has been obtained for all radicals and an increase in reactivity has been observed on decreasing the oxidation potential of the ferrocene donor and on going from electron-releasing to electron-withdrawing ring substituents. Computations predict the formation of strongly bound π-stacked 4-X-CumO•/DcMFc complexes, characterized by intracomplex π−π distances around 4 Å. These findings point toward a (nonbonded) inner-sphere ET mechanism for the reactions of the 4-X-CumO•/MenFc couples

Perceptions of a group of elderly on the fact of not seeing the dentist regularly

Ainda existe no imaginário coletivo a ideia de que idosos não necessitam de assistência odontológica, pois são em sua maioria desdentados e usuários de dentaduras. Assim, a pergunta desta pesquisa é: Qual o motivo que faz com que muitos idosos não consultem regularmente o cirurgião-dentista? O objetivo foi levantar e analisar os motivos que fazem com que idosos cadastrados em uma Unidade de Saúde da Família não consultem regularmente o dentista. Trata-se de uma pesquisa descritiva exploratória de abordagem metodológica quanti-qualitativa realizada por meio de entrevistas domiciliares semiestruturadas aplicadas em 149 idosos cadastrados em uma Unidade de Saúde da Família na cidade de Ribeirão Preto,SP. Os dados foram analisados e sistematizados por meio da técnica da Análise de Conteúdo, e para a análise quantitativa foram realizadas análises bivariadas com associações significantes baseadas em valor de p<0,05. Houve associação estatisticamente significante entre visita ao dentista e idade (p=0,025), e observou-se que idosos com idades mais avançadas relataram ir menos ao dentista. Alguns dos motivos alegados foram: medo, dificuldade financeira, falta de tempo, além de falta de sintomatologia dolorosa nos dentes devido ao uso de dentaduras. Concluiu-se que os motivos alegados estão associados a aspectos sociais e culturais que devem ser analisados frente ao cuidado na atenção primária à saúde