Distribution of Corbicula fluminea (Müller, 1774) in the invaded range: a geographic approach with notes on species traits variability

Corbicula fluminea is considered one of the most important non-native invasive species (NIS) in aquatic systems mainly due to its widespread distribution and ecological and economic impacts. This species is known to negatively affect native bivalves, also with severe effects on biodiversity and ecosystem functioning. Throughout an exhaustive bibliographic survey and with the aid of Geographic Information Systems tools, this study tracks the species dispersion from its native range, including the description of important physical and environmental barriers. Additional analyses were conducted to examine possible influences of latitudinal/ temperature gradients on important traits (e.g. life span, maximum and mean body length, growth at the end of first year). Altitude and winter minimum temperature appear to be delaying the invasion worldwide, but it seems inevitable that the species will spread across the globe. Latitude and summer temperature show a relationship with growth and life span. Overall, the information gathered in this review may be relevant to forecast future distribution patterns of this NIS, and to anticipate the possible implementation of effective management measures. Moreover, it may constitute a valuabletool inthe prediction of population responses to an increasingly changing environment.This research was supported by FCT (Portuguese Foundation for Science and Technology), through a PhD grant attributed to D. Crespo (SFRH/BD/80252/2011), a post-doc grant attributed to S. Leston (SFRH/BPD/91828/2012) and M Dolbeth (SFRH/BPD/41117/2007) and BIOCHANGED project (PTDC/MAR/111901/2009), subsidized by the European Social Fund and MCTES (Ministério da Ciência, Tecnologia e Ensino Superior) National Funds, through the POPH (Human Potential Operational Programme), QREN (National Strategic Reference Framework) and COMPETE (Programa Operacional Factores de Competitividade).info:eu-repo/semantics/publishedVersio

Accurate DMBE Potential Energy Surface For the N(2D) + H2(1S g+ ) Reaction Using an Improved Switching Function Formalism

Abstract A single-sheeted double many-body expansion (DMBE) potential energy surface is reported for the 1 2 A'' state of NH2. To approximate its true multi-sheeted nature, a novel switching function that imposes the correct behavior at the H2(X 1S g +)+ N(2 D) and NH(X 3S-) + H(2 S) dissociation limits has been suggested. The new DMBE form is shown to fit with high accuracy an extensive set of new ab initio points (calculated at the multi-reference configuration interaction level using the full valence complete active space as reference and aug-cc-pVQZ and aug-cc-pV5Z basis sets) that have been semiempirically corrected at the valence regions by scaling the n-body dynamical correlation terms such as to account for the finite basis set size and truncated configuration interaction expansion. A detailed study of the N(2 D) ... H2(X 1S g +) van der Waals region has also been carried out. These calculations predict a nearly free rigid-rotor with two shallow van der Waals wells of C 2v and C 8 v symmetries. Such a result contrasts with previous cc-pVTZ calculations which predict a single T-shaped van der Waals structure. Except in the vicinity of the crossing seam, which is replaced by an avoided intersection, the fit shows the correct physical behavior over the entire configurational space. The topographical features of the new DMBE potential energy surface are examined in detail and compared with those of other potential functions available in the literature. Amongst such features, we highlight the barrier for linearization (11,802 cm-1) which is found to overestimate the most recent empirical spectroscopic estimate by only 28 cm-1. Additionally, the T-shaped N(2 D) ... H2 van der Waals minimum is predicted to have a well depth of 90 cm-1, being 11 cm-1 deeper than the C 8 v minimum. The title DMBE form is therefore recommendable for dynamics studies of both non-reactive and reactive N(2 D)+H2 collisions

Can extrapolation to the basis set limit be an alternative to the counterpoise correction? A study on the helium dimer

Abstract Configuration interaction and coupled cluster calculations are reported for He2 using various orbital basis sets of the d-aug-AVXZ type, with the results being extrapolated to the one electron basis set limit both with counterpoise and without counterpoise correction. A generalized uniform singlet- and triplet-pair extrapolation scheme has been utilized for such a purpose. Using appropriate corrections to mimic full configuration interaction, the energies were predicted in excellent agreement with the best available estimates. The results also suggest that extrapolation to the complete basis set limit may be a general alternative to the counterpoise correction that yields a more accurate potential energy while being more economical

Application of renormalized coupled-cluster methods to potential function of water

Abstract The goal of this paper is to examine the performance of the conventional and renormalized single-reference coupled-cluster (CC) methods in calculations of the potential energy surface of the water molecule. A comparison with the results of the internally contracted multi-reference configuration interaction calculations including the quasi-degenerate Davidson correction (MRCI(Q)) and the spectroscopically accurate potential energy surface of water resulting from the use of the energy switching (ES) approach indicates that the relatively inexpensive completely renormalized (CR) CC methods with singles (S), doubles (D), and a non-iterative treatment of triples (T) or triples and quadruples (TQ), such as CR-CCSD(T), CR-CCSD(TQ), and the recently developed rigorously size extensive extension of CR-CCSD(T), termed CR-CC(2,3), provide substantial improvements in the results of conventional CCSD(T) and CCSD(TQ) calculations at larger internuclear separations. It is shown that the CR-CC(2,3) results corrected for the effect of quadruply excited clusters through the CR-CC(2,3)+Q approach can compete with the highly accurate MRCI(Q) data. The excellent agreement between the CR-CC(2,3)+Q and MRCI(Q) results suggests ways of improving the global potential energy surface of water resulting from the use of the ES approach in the regions of intermediate bond stretches and intermediate energies connecting the region of the global minimum with the asymptotic regions

Constitutive Modelling of the Deformation and Degradation of Railway Ballast Using Multi-laminate Framework

Coarse granular materials such as railway ballast used in the shallow layers of railway tracks are often subjected to moving loads, which cause complex stress conditions involving the rotation of principal stress axes. Further, these materials are involved with particle breakage, which is also affected by the stress changes in the track. Computer modelling incorporating constitutive relationships is an effective technique for assessing the deformation behaviour of coarse granular materials under such conditions. This paper presents a constitutive model for coarse granular materials in multilaminate framework, considering classical plasticity and critical state concepts. A criterion for particle breakage in multi-laminate framework and its effect on the stress-strain behaviour has been incorporated using constitutive relationships in multilaminate framework. The influence of minor principal stress and principal stress rotation on the stress-strain, volumetric strain and particle breakage of these materials have been discussed