Effects of conservation tillage drills on soil quality indicators in a wheat‐oilseed rape rotation: organic carbon, earthworms and water stable aggregates

The effects of five conservation tillage drills with crop residue levels covering between 17% and 79% of the soil, and tillage depths ranging from 25 mm to 200 mm, were examined over three years. The tillage systems ranged from a relatively disruptive Farm System to a Low Disruption system, with three intermediate treatments labelled Sumo DTS, Claydon, and Mzuri. The study involved field sites on a clay or clay loam soil, where winter wheat and oilseed rape were grown in rotation. In the clay field, the Mzuri and Low Disruption treatments, which produced the highest residue coverage, showed the greatest increase in surface total soil organic carbon (1.1 and 0.48 Mg C ha−1 respectively) between year 1 and 3. The least disruptive tillage system also resulted in the highest density of earthworms (181‐228 m−2), and the most disruptive system produced the lowest densities (75‐98 m−2). In the third year, the least disruptive system also showed a higher proportion of water stable aggregates (29.8%) than the other treatments (22.7‐25.3%). Linear regressions showed positive relationships of both soil organic carbon and earthworm density with surface residue cover, and of the proportion of water stable aggregates with soil organic carbon

A General Approach for Predicting the Filtration of Soft and Permeable Colloids: The Milk Example

Membrane filtration operations (ultra-, microfiltration) are now extensively used for concentrating or separating an ever-growing variety of colloidal dispersions. However, the phenomena that determine the efficiency of these operations are not yet fully understood. This is especially the case when dealing with colloids that are soft, deformable, and permeable. In this paper, we propose a methodology for building a model that is able to predict the performance (flux, concentration profiles) of the filtration of such objects in relation with the operating conditions. This is done by focusing on the case of milk filtration, all experiments being performed with dispersions of milk casein micelles, which are sort of ″natural″ colloidal microgels. Using this example, we develop the general idea that a filtration model can always be built for a given colloidal dispersion as long as this dispersion has been characterized in terms of osmotic pressure Π and hydraulic permeability k. For soft and permeable colloids, the major issue is that the permeability k cannot be assessed in a trivial way like in the case for hard-sphere colloids. To get around this difficulty, we follow two distinct approaches to actually measure k: a direct approach, involving osmotic stress experiments, and a reverse-calculation approach, that consists of estimating k through well-controlled filtration experiments. The resulting filtration model is then validated against experimental measurements obtained from combined milk filtration/SAXS experiments. We also give precise examples of how the model can be used, as well as a brief discussion on the possible universality of the approach presented here

Calcium Triggered Lα-H2 Phase Transition Monitored by Combined Rapid Mixing and Time-Resolved Synchrotron SAXS

BACKGROUND: Awad et al. reported on the Ca(2+)-induced transitions of dioleoyl-phosphatidylglycerol (DOPG)/monoolein (MO) vesicles to bicontinuous cubic phases at equilibrium conditions. In the present study, the combination of rapid mixing and time-resolved synchrotron small-angle X-ray scattering (SAXS) was applied for the in-situ investigations of fast structural transitions of diluted DOPG/MO vesicles into well-ordered nanostructures by the addition of low concentrated Ca(2+) solutions. METHODOLOGY/PRINCIPAL FINDINGS: Under static conditions and the in absence of the divalent cations, the DOPG/MO system forms large vesicles composed of weakly correlated bilayers with a d-spacing of approximately 140 A (L(alpha)-phase). The utilization of a stopped-flow apparatus allowed mixing these DOPG/MO vesicles with a solution of Ca(2+) ions within 10 milliseconds (ms). In such a way the dynamics of negatively charged PG to divalent cation interactions, and the kinetics of the induced structural transitions were studied. Ca(2+) ions have a very strong impact on the lipidic nanostructures. Intriguingly, already at low salt concentrations (DOPG/Ca(2+)>2), Ca(2+) ions trigger the transformation from bilayers to monolayer nanotubes (inverted hexagonal phase, H(2)). Our results reveal that a binding ratio of 1 Ca(2+) per 8 DOPG is sufficient for the formation of the H(2) phase. At 50 degrees C a direct transition from the vesicles to the H(2) phase was observed, whereas at ambient temperature (20 degrees C) a short lived intermediate phase (possibly the cubic Pn3m phase) coexisting with the H(2) phase was detected. CONCLUSIONS/SIGNIFICANCE: The strong binding of the divalent cations to the negatively charged DOPG molecules enhances the negative spontaneous curvature of the monolayers and causes a rapid collapsing of the vesicles. The rapid loss of the bilayer stability and the reorganization of the lipid molecules within ms support the argument that the transition mechanism is based on a leaky fusion of the vesicles

Improved cooperativity of spin-Labile iron(III) centers by self-assembly in solution

Supramolecular principles have been applied for improving the spin crossover activity of metal centers due to cooperative effects in solution. Thus, incorporation of alkyloxy tails at the phenyl group of Fe(sal₂trien) 2a provides amphiphilic complexes Fe(sal-OR₂trien) 2b−d (b, R = C₆H₁₃; c, R = C₈H₁₇; d, R = C₁₈H₃₇) comprising an apolar group for supramolecular organization and a polar headgroup with potential spin crossover activity due to the presence of a spin-labile iron(III) center. Self-assembly of these complexes in solution resulted in the formation of microsize and submicrosize particles when the alkyl chain was long enough (2d) but not with shorter chains (2a−c). Solutions of 2d showed enhanced spin crossover activity as compared to complexes 2a−c, both in terms of transition temperature and steepness of the transition. This observation has been correlated to an improved cooperativity of the metal centers in 2d due to self-assembly, thus facilitating a tandem spin transition

DMSO-induced denaturation of hen egg white lysozyme

We report on the size, shape, structure, and interactions of lysozyme in the ternary system lysozyme/DMSO/water at low protein concentrations. Three structural regimes have been identified, which we term the “folded” (0 DMSO DMSO DMSO DMSO Rg of 2.4 ± 0.1 nm) above φDMSO > 0.7. This drastic change in the protein’s size coincides with a loss of the characteristic tertiary structure. It is preceded by a compaction of the local environment of the tryptophan residues and accompanied by a large increase in the protein’s overall flexibility. In terms of secondary structure, there is a gradual loss of α-helix and concomitant increase of β-sheet structural elements toward φDMSO = 0.7, while an increase in φDMSO at even higher DMSO volume fractions reduces the presence of both α-helix and β-sheet secondary structural elements. Protein−protein interactions remain overall repulsive for all values of φDMSO. An attempt is made to relate these structural changes to the three most important physical mechanisms that underlie them: the DMSO/water microstructure is strongly dependent on the DMSO volume fraction, DMSO acts as a strong H-bond acceptor, and DMSO is a bad solvent for the protein backbone and a number of relatively polar side groups, but a good solvent for relatively apolar side groups, such as tryptophan