Ab Initio Calculations of Structural Evolution and Conductance of Benzene-1,4-dithiol on Gold Leads

By performing at) initio density functional theory (DFT) calculations and electronic transport simulations based on the OFT nonequilibrium Green`s functions method we investigate how the conformational changes of a benzene-1,4-dithiol molecule bonded to gold affect the molecular transport as the electrodes are separated from each other. In particular we consider the full evolution of the stretching process until the Junction breaking point and compare results obtained with a standard semilocal exchange and correlation functional to those computed with a self-interaction corrected method. We conclude that the inclusion of self-interaction corrections is fundamental for describing both the molecule conductance and its stability against conformational fluctuations.

Combined Crystallographic and Solution Molecular Dynamics Study of Allosteric Effects in Ester and Ketone p-tert-Butylcalix[4]arene Derivatives and Their Complexes with Acetonitrile, Cd(II), and Pb(II)

We describe here a procedure to bridge the gap in the field of calixarene physicochemistry between solid-state atomic-resolution structural information and the liquid-state low-resolution thermodynamics and spectroscopic data. We use MD simulations to study the kinetics and energetics involved in the complexation of lower rim calix[4]arene derivatives (L), containing bidentate ester (1) and ketone (2) pendant groups, with acetonitrile molecule (MeCN) and Cd2+ and Pb2+ ions (M2+) in acetonitrile solution. On one hand, we found that the prior inclusion of MeCN into the calix to form a L(MeCN) adduct has only a weak effect in preorganizing the hydrophilic cavity toward metal ion binding. On the other hand, the strong ion-hydrophilic cavity interaction produces a wide open calix which enhances the binding of one MeCN molecule (allosteric effect) to stabilize the whole (M2+)1(MeCN) bifunctional complex. We reach two major conclusions: (i) the MD results for the (M2+)1(MeCN) binding are in close agreement with the ""endo"", fully encapsulated, metal complex found by X-ray diffraction and in vacuo MD calculations, and (ii) the MD structure for the more flexible 2 ligand, however, differs from the also endo solid-state molecule. In fact, it shows strong solvation effects at the calixarene lower bore by competing MeCN molecules that share the metal coordination sphere with the four C=O oxygens of an ""exo"" (M2+)2(MeCN) complex.

Solvatochromic and lonochromic Effects of Iron(II)bis-(1,10-phenanthroline)dicyano: a Theoretical Study

Solvatochromic and ionochromic effects of the iron(II)bis(1,10-phenanthroline)dicyano (Fe(phen)(2)(CN)(2)) complex were investigated by means of combined DFT/TDDFT calculations using the PBE and B3LYP functionals. Extended solvation models of Fe(phen)(2)(CN)(2) in acetonitrile and aqueous solution, as well as including interaction with Mg(2+), were constructed. The calculated vertical excitation energies reproduce well the observed solvatochromism in acetonitrile and aqueous solutions, the ionochromism in acetonitrile in the presence of Mg(2+), and the absence of ionochromic effect in aqueous solution. The vertical excitation energies and the nature of the transitions were reliably predicted after inclusion of geometry relaxation upon aqueous micro- and global solvation and solvent polarization effect in the TDDFT calculations. The two intense UV-vis absorption bands occurring for all systems studied are interpreted as transitions from a hybrid Fe(II)(d)/cyano N(p) orbital to a phenanthroline pi* orbital rather than a pure metal-to-ligand-charge transfer (MLCT). The solvatochromic and ionochromic blue band shifts of Fe(phen)(2)(CN)(2) were explained with preferential stabilization of the highest occupied Fe(II)(d)/cyano N(p) orbitals as a result of specific interactions with water solvent molecules or Mg(2+) ions in solution. Such interactions occur through the CN(-) groups in the complex, and they have a decisive role for the observed blue shifts of UV-vis absorption bands.

The Development of Dalton`s Atomic Theory as a Case Study in the History of Science: Reflections for Educators in Chemistry

The inclusion of the history of science in science curricula-and specially, in the curricula of science teachers-is a trend that has been followed in several countries. The reasons advanced for the study of the history of science are manifold. This paper presents a case study in the history of chemistry, on the early developments of John Dalton`s atomic theory. Based on the case study, several questions that are worth discussing in educational contexts are pointed out. It is argued that the kind of history of science that was made in the first decades of the twentieth century (encyclopaedic, continuist, essentially anachronistic) is not appropriate for the development of the competences that are expected from the students of sciences in the present. Science teaching for current days will benefit from the approach that may be termed the ""new historiography of science"".

Electronic Structure and Chemical Bonding in the Lowest Electronic States of TcN

Multiconfiguration second-order perturbation theory, with the inclusion of relativistic effects and spin-orbit Coupling, was employed to investigate the nature of the ground and low-lying Lambda-S and Omega states of the TcN molecule. Spectroscopic constants, effective bond order, and potential energy curves for 13 low-lying Lambda-S states and 5 Omega states are given, The computed ground state of TcN is of Omega = 3 symmetry (R(e) = 1.605 angstrom and omega(e) = 1085 cm(-1)), originating mainly from the (3)Delta Lambda-S ground state. This result is contrasted with the nature of the ground state for other VIIB transtion-metal mononitrides, including X(3)Sigma(-) symmetry for MnN and Omega = 0(+) symmetry for ReN, derived also from a X(3)Sigma(-) state.

Investigation of interfacial processes at tetraruthenated zinc porphyrin films using electrochemical surface plasmon resonance and electrochemical quartz crystal microbalance

In the present work we describe the investigation of interfacial and superficial processes on tetraruthenated zinc porphyrin (ZnTRP) films immobilized on gold electrode surface. In situ and real time measurements employing electrochemical surface plasmon resonance (ESPR)and electrochemical quartz crystal microbalance (EQCM) have given new insights into the electrochemical oxidation of ferrocyanide and phenolic compounds (acetaminophen, dopamine, and catechol) on ZnTRP modified electrodes. The decrease of diode like behavior in the presence of such phenolic species in contrast with ferrocyanide was clearly assigned to the inclusion of those species in the porphyrin film, creating new conduction pathways connecting the gold electrode surface with the film/solution interface. In fact, there are evidences that they can intercalate in the film (catechol > dopamine > acetaminophen), whereas ferrocyanide is completely excluded. Accordingly, the molecular size may play a fundamental role in such a process. (C) 2009 Published by Elsevier Ltd.

Low-lying singlet and triplet electronic states of RhB

The low-lying X-1 Sigma(+), a(3)Delta, A(1)Delta, b(3)Sigma(+), B-1 Pi, c(3)Pi, C-1 Phi, D-1 Sigma(+), E-1 Pi, d(1)Phi, and e(3)Pi electronic states of RhB have been investigated at the ab initio level, using the multistate multiconfigurational second-order perturbation (MS-CASPT2) theory, with extended atomic basis sets and inclusion of scalar relativistic effects. Among the eleven electronic states included in this work, only three (the X-1 Sigma(+), D-1 Sigma(+), and E-1 Pi states) have been investigated experimentally. Potential energy curves, spectroscopic constants, dipole moments, binding energies, and chemical bonding aspects are presented for all electronic states.

Simulation study of cascade heat pump for solar combisystems

This paper focuses on the study of cascade heat pump systems in combination with solar thermal for the production of hot water and space heating in single family houses with relatively high heating demand. The system concept was developed by Ratiotherm GmbH and simulated with TRNSYS 17. The basic cascade system uses the heat pump and solar collectors in parallel operation while a further development is the inclusion of an intermediate store that enables the possibility of serial/parallel operation and the use of low temperature solar heat. Parametric studies in terms of compressor size, refrigerant pair and size of intermediate heat exchanger were carried out for the optimization of the basic system. The system configurations were simulated for the complete year and compared to a reference of a solar thermal system combined with an air source heat pump. The results show ~13% savings in electricity use for all three cascade systems compared to the reference. However, the complexity of the systems is different and thus higher capital costs are expected.

Rule versus interaction function : evaluating regional aggregations of commuting flows in Sweden

The aim of this paper is to evaluate the performance of two divergent methods for delineating commuting regions, also called labour market areas, in a situation that the base spatial units differ largely in size as a result of an irregular population distribution. Commuting patterns in Sweden have been analyzed with geographical information system technology by delineating commuting regions using two regionalization methods. One, a rule-based method, uses one-way commuting flows to delineate local labour market areas in a top-down procedure based on the selection of predefined employment centres. The other method, the interaction-based Intramax analysis, uses two-way flows in a bottom-up procedure based on numerical taxonomy principles. A comparison of these methods will expose a number of strengths and weaknesses. For both methods, the same data source has been used. The performance of both methods has been evaluated for the country as a whole using resident employed population, self-containment levels and job ratios for criteria. A more detailed evaluation has been done in the Goteborg metropolitan area by comparing regional patterns with the commuting fields of a number of urban centres in this area. It is concluded that both methods could benefit from the inclusion of additional control measures to identify improper allocations of municipalities.

Estimated Number and Location of Future Moose-Vehicle Collisions (MVC) in Maine

Moose (Alces alces) are a keystone herbivore in Maine. Because of the large number of rural roads in Maine, there is a high rate of moose-vehicle collisions (MVCs), which is increasing. On-road encounters with animals resulted in 231 fatalities in the United States in 1999. Because of the fatality of MVCs, it is important to know where they are most likely to occur. I used GIS analysis to estimate where future MVCs would occur, factoring in the variables of land cover suitability for moose, distance from water bodies, locations of past MVCs, and speed limits on the roads. I ran four different analyses, each one weighting the variables equally. I also ran a regression to determine if increasing road speed was associated with the increase in the number of MVCs per length of road. There was not a strong positive relationship between the number of MVCs per length of road and the speed limit, but it was interesting to note that there were more MVCs per length of road on 35mph and 40mph roads than on 45, 50, 55 or 65mph roads. Future research on MVCs would benefit from the inclusion of include moose population density and road traffic data.

Tests of conditional asset pricing models in the brazilian stock market

In this paper, we test a version of the conditional CAPM with respect to a local market portfolio, proxied by the Brazilian stock index during the period 1976-1992. We also test a conditional APT modeI by using the difference between the 3-day rate (Cdb) and the overnight rate as a second factor in addition to the market portfolio in order to capture the large inflation risk present during this period. The conditional CAPM and APT models are estimated by the Generalized Method of Moments (GMM) and tested on a set of size portfolios created from individual securities exchanged on the Brazilian markets. The inclusion of this second factor proves to be important for the appropriate pricing of the portfolios.

On the evolution of TFP in Latin America

Due to several policy distortions, including import-substitution industrialization, widespread government intervention and both domestic and international competitive barriers, there has been a general presumption that Latin America has been much less productive than the leading economies in the last decades. In this paper we show, however, that until the late seventies Latin American countries had high productivity levels relative to the United States. It is only after the late seventies that we observe a fast decrease of relative TFP in Latin America. We also show that the inclusion of human capital in the production function makes a crucial diference in the TFP calculations for Latin America.

Do Brazilian courts contribute to the implementation of the right to housing?

The objective of this paper is to try to understand the Brazilian’s Courts role in the implementation of the Right to Housing. In order to do that, I analyzed three lawsuits (Favela Olga Benario, Favela Fiat/Vila Esperança and Pinheirinho I) in which the Right to Housing collide with the Right to Private Property. I claim that in spite of the adoption of the Social Function of the Ownership Principle and the formal inclusion of the Right to Housing among social rights protected by the Constitution, Brazilians Courts adopt a very conservative conception of the Right to Private Property and because of that, they tend not to enforce the Right to Housing.

On the evolution of TFP in Latin America

Due to several policy distortions, including import-substitution industrialization, widespread government intervention and both domestic and international competitive barriers, there has been a general presumption that Latin America has been much less productive than the leading economies in the last decades. In this paper we show, however, that until the late seventies Latin American countries had high productivity levels relative to the United States. It is only after the late seventies that we observe a fast decrease of relative TFP in Latin America. We also show that the inclusion of human capital in the production function makes a crucial difference in the TFP calculations for Latin America.

WTO-plus commitments on the elimination of export duties: evidence of a two-tier membership?

This descriptive paper examines the prevalence of ‘WTO-plus’ commitments in accession protocols of newly acceded Members, with a focus on commitments on the elimination of export duties. It presents preliminary results of a mapping exercise carried out with respect to these commitments and seeks to answer two questions. First, can any general conclusions be drawn as to the prevalence of these commitments or are they, per definition, country-specific. Second, has the political nature of the WTO accession process allowed for the creation of a two-tier membership. The first question is answered by relying on data gathered as part of the ongoing PhD-research project conducted by the author. The project aims to construct a typology of WTO-plus commitments to allow for a more detailed analysis of the relationship between these commitments and the baseline obligations in the covered agreements. The accession of China to the WTO is commonly considered as the prime example of the inclusion of WTO-plus obligations in accession protocols. The paper tries to answer the question whether this particular accession was truly unique in nature, or whether the inclusion of “Plus” obligations is less exceptional than often assumed. Additionally, the accession protocols of other recently acceded-Members are examined to establish whether the hypothesis holds. In the PhD-research project this comparative methodology will also be applied to map WTO-plus commitments in other areas, such as anti-dumping and transparency. The second question will be answered in two stages. In a preliminary stage, international institutional law will be used to by analyzing the way in which the WTO’s Dispute Settlement Body has dealt with this type of WTO-plus commitment in its jurisprudence. The second stage deals with the question of hierarchy: Accession Protocols are negotiated with the WTO Membership, by each country willing to accede to the WTO. This poses questions as to their exact position in the system of WTO law. To establish whether evidence of a two-tier membership is present, one first has to turn back to the question whether Accession Protocols are a separate (or independent) legal instrument or an “integral part” of the WTO system of covered agreements. If newly acceded Members do not benefit from the general exceptions in order to balance their more stringent, WTO-plus, obligations, this may support the conclusion that the membership of the World Trade Organization is becoming, in fact, two-tiered.