Two complementary molecular energy decomposition schemes: the Mayer and Ziegler-Rauk methods in comparison

In the present paper we discuss and compare two different energy decomposition schemes: Mayer's Hartree-Fock energy decomposition into diatomic and monoatomic contributions [Chem. Phys. Lett. 382, 265 (2003)], and the Ziegler-Rauk dissociation energy decomposition [Inorg. Chem. 18, 1558 (1979)]. The Ziegler-Rauk scheme is based on a separation of a molecule into fragments, while Mayer's scheme can be used in the cases where a fragmentation of the system in clearly separable parts is not possible. In the Mayer scheme, the density of a free atom is deformed to give the one-atom Mulliken density that subsequently interacts to give rise to the diatomic interaction energy. We give a detailed analysis of the diatomic energy contributions in the Mayer scheme and a close look onto the one-atom Mulliken densities. The Mulliken density ρA has a single large maximum around the nuclear position of the atom A, but exhibits slightly negative values in the vicinity of neighboring atoms. The main connecting point between both analysis schemes is the electrostatic energy. Both decomposition schemes utilize the same electrostatic energy expression, but differ in how fragment densities are defined. In the Mayer scheme, the electrostatic component originates from the interaction of the Mulliken densities, while in the Ziegler-Rauk scheme, the undisturbed fragment densities interact. The values of the electrostatic energy resulting from the two schemes differ significantly but typically have the same order of magnitude. Both methods are useful and complementary since Mayer's decomposition focuses on the energy of the finally formed molecule, whereas the Ziegler-Rauk scheme describes the bond formation starting from undeformed fragment densities

Bolívar Echeverría: azares de la filosofía (In Memorian)

Hernández plantea en este tributo al desaparecido filósofo y ensayista ecuatoriano, Bolívar Echeverría, que su discurso crítico asume lo que se llamaría, más que filosofía, el pensar. El pensamiento en la América Latina de los 60 se debatía entre varias inquietudes, afirma. Primero, se pretendía hacer una filosofía nacional o de la militancia política. Segundo, se percibía como un problema la necesidad de la filosofía de inscribirse en la Academia. Por último, se instaba a que en filosofía también primara el compromiso de los intelectuales con el presente. Y en el presente coexistían la embriaguez por el cambio revolucionario y cierto pesimismo de la época –agotamiento, dolor y horror por las víctimas de las transformaciones–. Entonces, según Hernández, Echeverría se preguntó por la relación entre Modernidad y Revolución, entre Modernidad y los períodos posteriores de la estabilidad de la Reforma. Consiguió formular la época y formular, a la vez, un pensamiento crítico.Y avanzó más: observó que, pese al efecto devastador del proyecto moderno, la cultura resistía y hacía surgir nuevas formas para mantener las esferas del mundo de la vida. Era el caso de lo barroco, “una estrategia para hacer ‘vivible’ algo que básicamente no lo es”. Moverse en estas sendas, se pregunta Echeverría, ¿no equivale al acontecimiento del pensar?

La epidemiología crítica: una nueva forma de mirar la salud en el espacio urbano

La epidemiología empírico-analítica asume como un pilar interpretativo la noción de "lugar" para las descripciones que construye. La epidemiología crítica supera esa noción restrictiva y propone una construcción innovadora del espacio de la salud urbana retomando los aportes de la teoría crítica del espacio y la geografía, y articulando estos avances con los de la propia epidemiología desde una perspectiva de la determinación social de la salud. Desde esta óptica se repiensa la relación urbano-rural a la luz de los procesos históricos de aceleración, drástica pérdida de sustentabilidad y profunda inequidad urbanas, así como del papel de la nueva ruralidad capitalista monopólica, en avivar el cierre del espacio de la vida en nuestras ciudades. Se busca superar el mito de la dualidad urbano rural, se cuestiona el paradigma dominante de la modernidad que impuso la comprensión de dos mundos prácticamente contrapuestos: la ciudad como rectora, cosmopolita, avanzada y pujante, y lo rural como un mundo atrasado, local, más simple, y secundario, pues en años más recientes, la distinción clásica entre lo urbano y lo rural se hace cada vez más difícil, lamentablemente con una perversa dialéctica de deterioro e influjos malsanos de uno a otro espacio.

Evolution in software systems: foundations of the SPE classification scheme

The SPE taxonomy of evolving software systems, first proposed by Lehman in 1980, is re-examined in this work. The primary concepts of software evolution are related to generic theories of evolution, particularly Dawkins' concept of a replicator, to the hermeneutic tradition in philosophy and to Kuhn's concept of paradigm. These concepts provide the foundations that are needed for understanding the phenomenon of software evolution and for refining the definitions of the SPE categories. In particular, this work argues that a software system should be defined as of type P if its controlling stakeholders have made a strategic decision that the system must comply with a single paradigm in its representation of domain knowledge. The proposed refinement of SPE is expected to provide a more productive basis for developing testable hypotheses and models about possible differences in the evolution of E- and P-type systems than is provided by the original scheme. Copyright (C) 2005 John Wiley & Sons, Ltd.

An assessment of observed vertical flux divergence in long-term eddy-covariance measurements over two Midwestern forest ecosystems

Vertical divergence of CO2 fluxes is observed over two Midwestern AmeriFlux forest sites. The differences in ensemble averaged hourly CO2 fluxes measured at two heights above canopy are relatively small (0.2–0.5 μmol m−2 s−1), but they are the major contributors to differences (76–256 g C m−2 or 41.8–50.6%) in estimated annual net ecosystem exchange (NEE) in 2001. A friction velocity criterion is used in these estimates but mean flow advection is not accounted for. This study examines the effects of coordinate rotation, averaging time period, sampling frequency and co-spectral correction on CO2 fluxes measured at a single height, and on vertical flux differences measured between two heights. Both the offset in measured vertical velocity and the downflow/upflow caused by supporting tower structures in upwind directions lead to systematic over- or under-estimates of fluxes measured at a single height. An offset of 1 cm s−1 and an upflow/downflow of 1° lead to 1% and 5.6% differences in momentum fluxes and nighttime sensible heat and CO2 fluxes, respectively, but only 0.5% and 2.8% differences in daytime sensible heat and CO2 fluxes. The sign and magnitude of both offset and upflow/downflow angle vary between sonic anemometers at two measurement heights. This introduces a systematic and large bias in vertical flux differences if these effects are not corrected in the coordinate rotation. A 1 h averaging time period is shown to be appropriate for the two sites. In the daytime, the absolute magnitudes of co-spectra decrease with height in the natural frequencies of 0.02–0.1 Hz but increase in the lower frequencies (<0.01 Hz). Thus, air motions in these two frequency ranges counteract each other in determining vertical flux differences, whose magnitude and sign vary with averaging time period. At night, co-spectral densities of CO2 are more positive at the higher levels of both sites in the frequency range of 0.03–0.4 Hz and this vertical increase is also shown at most frequencies lower than 0.03 Hz. Differences in co-spectral corrections at the two heights lead to a positive shift in vertical CO2 flux differences throughout the day at both sites. At night, the vertical CO2 flux differences between two measurement heights are 20–30% and 40–60% of co-spectral corrected CO2 fluxes measured at the lower levels of the two sites, respectively. Vertical differences of CO2 flux are relatively small in the daytime. Vertical differences in estimated mean vertical advection of CO2 between the two measurement heights generally do not improve the closure of the 1D (vertical) CO2 budget in the air layer between the two measurement heights. This may imply the significance of horizontal advection. However, a reliable assessment of mean advection contributions in annual NEE estimate at these two AmeriFlux sites is currently an unsolved problem.

How large is congressional dependence in agriculture. Bayesian inference about ‘scale’ and ‘scope’ in measuring a spatial externality

The political economy literature on agriculture emphasizes influence over political outcomes via lobbying conduits in general, political action committee contributions in particular and the pervasive view that political preferences with respect to agricultural issues are inherently geographic. In this context, ‘interdependence’ in Congressional vote behaviour manifests itself in two dimensions. One dimension is the intensity by which neighboring vote propensities influence one another and the second is the geographic extent of voter influence. We estimate these facets of dependence using data on a Congressional vote on the 2001 Farm Bill using routine Markov chain Monte Carlo procedures and Bayesian model averaging, in particular. In so doing, we develop a novel procedure to examine both the reliability and the consequences of different model representations for measuring both the ‘scale’ and the ‘scope’ of spatial (geographic) co-relations in voting behaviour.

Intuitions in the Face of Diversity

In recent decades, intuitions' role in philosophy has been hotly debated. Many claim intuitions play an important role. Others, some armed with data, challenge the use of intuitions. This thesis reflects on this debate and advances the debate in two main ways. Having a clear understanding of the challenge which intuition-use in philosophy faces is important. Part I focuses on this. Chapters 1-2 introduce the topic of intuitions, motivate the methodological study of intuitions, and present the historical background to recent empirical challenges to intuition-use. Chapters 3-5 concern the contemporary challenge. I present the empirical evidence the challenge uses, present what I argue to be the strongest version of the challenge, and defend that challenge against some objections. How one characterises intuitions is incredibly important in philosophical methodology. If we are to properly evaluate philosophical methods vis-a-vis their use of something called intuitions { if we are to assess the empirical challenge { it is important to be clear exactly what we mean by `intuitions'. Part II focuses on this. Chapter 6 argues there is little consensus among philosophers as to what intuitions are and their role in philosophy. Chapter 7 questions whether philosophers have developed an idiolect in which `intuition' has distinctive meaning | as frequently supposed. Chapter 8 points out a common misunderstanding about intuitions in philosophy; using quantitative tools to challenge the idea that an increased use of `intuition' in philosophy is the result of an increased use of intuition. So, the developing picture is one of confusion, without a clear idea of what sense of `intuition' is important. Fortunately, Chapter 9 sets us back on the right track. It sets out a positive programme for evaluative methodology: methodologists should adopt a permissive conception of intuitions and make fine distinctions between different intuitions, so long as we can track those distinctions while philosophising.

Experimental philosophy of language

Experimental philosophy of language uses experimental methods developed in the cognitive sciences to investigate topics of interest to philosophers of language. This article describes the methodological background for the development of experimental approaches to topics in philosophy of language, distinguishes negative and positive projects in experimental philosophy of language, and evaluates experimental work on the reference of proper names and natural kind terms. The reliability of expert judgments vs. the judgments of ordinary speakers, the role that ambiguity plays in influencing responses to experiments, and the reliability of meta-linguistic judgments are also assessed.

Decomposition in tropical forests: a pan-tropical study of the effects of litter type, litter placement and mesofaunal exclusion across a precipitation gradient

1. Litter decomposition recycles nutrients and causes large fluxes of carbon dioxide into the atmosphere. It is typically assumed that climate, litter quality and decomposer communities determine litter decay rates, yet few comparative studies have examined their relative contributions in tropical forests. 2. We used a short-term litterbag experiment to quantify the effects of litter quality, placement and mesofaunal exclusion on decomposition in 23 tropical forests in 14 countries. Annual precipitation varied among sites (760-5797 mm). At each site, two standard substrates (Raphia farinifera and Laurus nobilis) were decomposed in fine- and coarse-mesh litterbags both above and below ground for approximately 1 year. 3. Decomposition was rapid, with >95% mass loss within a year at most sites. Litter quality, placement and mesofaunal exclusion all independently affected decomposition, but the magnitude depended upon site. Both the average decomposition rate at each site and the ratio of above- to below-ground decay increased linearly with annual precipitation, explaining 60-65% of among-site variation. Excluding mesofauna had the largest impact on decomposition, reducing decomposition rates by half on average, but the magnitude of decrease was largely independent of climate. This suggests that the decomposer community might play an important role in explaining patterns of decomposition among sites. Which litter type decomposed fastest varied by site, but was not related to climate. 4. Synthesis. A key goal of ecology is to identify general patterns across ecological communities, as well as relevant site-specific details to understand local dynamics. Our pan-tropical study shows that certain aspects of decomposition, including average decomposition rates and the ratio of above- to below-ground decomposition are highly correlated with a simple climatic index: mean annual precipitation. However, we found no relationship between precipitation and effects of mesofaunal exclusion or litter type, suggesting that site-specific details may also be required to understand how these factors affect decomposition at local scales.

Thermodynamic Stabillity of Hydrogen-Bonded Systems in Polar and Nonpolar Environments

The thermodynamic properties of a selected set of benchmark hydrogen-bonded systems (acetic acid dimer and the complexes of acetic acid with acetamide and methanol) was studied with the goal of obtaining detailed information on solvent effects on the hydrogen-bonded interactions using water, chloroform, and n-heptane as representatives for a wide range in the dielectric constant. Solvent effects were investigated using both explicit and implicit solvation models. For the explicit description of the solvent, molecular dynamics and Monte Carlo simulations in the isothermal isobaric (NpT) ensemble combined with the free energy perturbation technique were performed to determine solvation free energies. Within the implicit solvation approach, the polarizable continuum model and the conductor-like screening model were applied. Combination of gas phase results with the results obtained from the different solvation models through an appropriate thermodynamic cycle allows estimation of complexation free energies, enthalpies, and the respective entropic contributions in solution. Owing to the strong solvation effects of water the cyclic acetic acid dimer is not stable in aqueous solution. In less polar solvents the double hydrogen bond structure of the acetic acid dimer remains stable. This finding is in agreement with previous theoretical and experimental results. A similar trend as for the acetic acid dimer is also observed for the acetamide complex. The methanol complex was found to be thermodynamically unstable in gas phase as well as in any of the three solvents. (C) 2010 Wiley Periodicals, Inc. J Comput Chem 31: 2046-2055, 2010

Informal sanctions and conditional cooperation: : A natural experiment on voluntary contributions to a public good.

In a natural experiment, this paper studies the impact of an informal sanctioning mechanism on individuals’ voluntary contribution to a public good. Cross-country skiers’ actual cash contributions in two ski resorts, one with and one without an informal sanctioning system, are used. I find the contributing share to be higher in the informal sanctioning system (79 percent) than in the non-sanctioning system (36 percent). Previous studies in one-shot public good situations have found an increasing conditional contribution (CC) function, i.e. the relationship between expected average contributions of other group members and the individual’s own contribution. In contrast, the present results suggest that the CC-function in the non-sanctioning system is non-increasing at high perceived levels of others’ contribution. This relationship deserves further testing in lab.

ANOMALOUS CONTRIBUTIONS TO E+E- -] E+E-L+L- AT HIGH-ENERGIES

We analyze the process e+ e- --> e+ e- gamma-gamma --> e+ e- l+ l- (l = e, mu, tau-leptons) considering several nonstandard contributions in order to search for new physics beyond the standard model. We are able to test compositeness up to the TeV mass scale at LEP II and CLIC energies.

Duas diferentes perspectivas para o estudo da consciência na Filosofia contemporânea da mente

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Utopia no front: história e filosofia em Oswald de Andrade 1945-1954

Pós-graduação em História - FCLAS