Alternative cropping systems study: spatial variability of soil N mineralization

Non-Peer Reviewe

Dynamical study on polaron formation in a metal/polymer/metal structure

By considering a metal/polymer/metal structure within a tight-binding one-dimensional model, we have investigated the polaron formation in the presence of an electric field. When a sufficient voltage bias is applied to one of the metal electrodes, an electron is injected into the polymer chain, then a self-trapped polaron is formed at a few hundreds of femtoseconds while it moves slowly under a weak electric field (not larger than $$ V/cm). At an electric field between $1.0\times 10^4$ V/cm and $$ V/cm, the polaron is still formed, since the injected electron is bounded between the interface barriers for quite a long time. It is shown that the electric field applied at the polymer chain reduces effectively the potential barrier in the metal/polymer interface

Effects of Equipment Loading on the Vibrations of Edge-Stiffened Plates and Associated Modeling Issues

Predicting structural radiated noise is a process that involves several steps, often including the development of a finite element (FE) model to provide structural response predictions. Limitations of these FE models often govern the success of overall noise predictions. The purpose of the present investigation is to identify the effects of real world attachments on edge-stiffened plates and identify advanced modeling methods to facilitate vibroacoustic analyses of such complex structures. A combination of experimental and numerical methods is used in the evaluation. The results show the effects of adding attachments to the edge-stiffened plate in terms of mode shape mass loading, creation of new mode shapes, modifications to original mode shapes, and variations in damping levels. A finite element model of the edge-stiffened plate with simplified attachments has been developed and is used in conjunction with experimental data to aid in the developments. The investigation presented here represents a necessary first step toward implementing an advanced modeling technique

A pragmatic multi-centre randomised controlled trial of fluid loading and level of dependency in high-risk surgical patients undergoing major elective surgery : trial protocol

Peer reviewedPublisher PD

Application of density functional theory in the synthesis of electroactive polymers

A wide range of conjugated organic compounds undergo anodic electropolymerisation to produce polymers of high conductivity. However, electrooxidation does not always result in the formation of electroactive materials, since some reactions produce insulating films or soluble oligomers. Density functional theory (DFT) has been used to predict the outcome of electropolymerisation reactions by calculating the unpaired electron π-spin density distribution of monomeric radical cations, in order to determine coupling positions in the resultant polymers. π-Spin densities calculated for pyrrole, thiophene and (E)-stilbene are found to be in good agreement with experimental values. DFT has been used to investigate the low conductivity and redox inactivity of poly[(E)-3-styrylthiophenes] and poly[(E)-2-styrylheterocycles]. High positive spin densities at the alkene spacer linkage in the corresponding monomeric radical cations were found, suggesting crosslinking of the polymers via the double bond. In contrast, electroactive polymers of improved conductivity are formed from the electropolymerisation of some (Z)-2-α,β-diarylacrylonitriles. For these monomers, DFT calculations show the positions of highest spin density to be located at the α-positions of the heterocyclic rings, suggesting the presence of α,α′-linked monomeric couplings necessary for electroactivity

Long-term tillage and crop rotation effect on soil aggregation

Non-Peer ReviewedTillage and cropping sequences play a key role in controlling soil aggregation. We measured water-stable aggregate (WSA), wind erodible fraction (WEF), and geometric mean diameter (GMD) for six mid to longterm (8 to 25 years) experiments comparing tillage and cropping sequences in the Brown, Dark Brown, and Black Chernozemic soils of Saskatchewan. In the coarse-textured soil, no-tillage (NT) had a higher value of WSA by 49% more than in the wheat-phase of fallow-wheat (F-W), and had a lower value of WEF by 27% less than in the fallow-phase of F-W compared with minimum tillage (MT). In the medium-textured soils, NT had a higher WAS, ranged from 17 to 38%, and a lower WEF, ranged from 37 to 64% compared with conventional tillage (CT), depending on crop rotation systems. The reduced WEF under NT in the medium-textured soils was due mainly to increased GMD. In the fine-textured soils, NT had a higher WSA, ranged from 10 to 19% compared with MT or CT, and a lower WEF by 47% compared with MT only in the heavy clay soil. Change in GMD was not detectable in the light- and fine-textured soils. Continuous cropping compared with rotations containing fallow improved soil physical properties by increasing WSA, reducing WEF in the medium and fine-textured soils, and increasing GMD only in the medium-textured soils. Of the three soil physical properties determined in this study, WSA was the most sensitive to changes in tillage and crop rotations, then WEF and the least GMD

Relationship between soil texture and soil organic carbon at small field scale

Non-Peer ReviewedThe capacity of a soil to store organic carbon is related to its particle size distribution, or soil texture, mainly because the capacity of clay particles to stabilize organic materials. A study of the relationship of soil organic carbon (SOC) and particle size distribution at field level in two soils of Saskatchewan indicated that making broad assumptions about the relationship between soil texture and SOC in soils within a filed might lead to erroneous conclusions. At field scale dominant dynamic processes affecting the spatial distribution of soil texture, or other factors may create local conditions that override the fundamental texture SOC relationship of soils

Jacobi Fields on Statistical Manifolds of Negative Curvature

Two entropic dynamical models are considered. The geometric structure of the statistical manifolds underlying these models is studied. It is found that in both cases, the resulting metric manifolds are negatively curved. Moreover, the geodesics on each manifold are described by hyperbolic trajectories. A detailed analysis based on the Jacobi equation for geodesic spread is used to show that the hyperbolicity of the manifolds leads to chaotic exponential instability. A comparison between the two models leads to a relation among statistical curvature, stability of geodesics and relative entropy-like quantities. Finally, the Jacobi vector field intensity and the entropy-like quantity are suggested as possible indicators of chaoticity in the ED models due to their similarity to the conventional chaos indicators based on the Riemannian geometric approach and the Zurek-Paz criterion of linear entropy growth, respectively.Comment: 22 page