Oceans have become substantially noisier since the Industrial Revolution. Shipping, resource exploration, and infrastructure development have increased the anthrophony (sounds generated by human ...activities), whereas the biophony (sounds of biological origin) has been reduced by hunting, fishing, and habitat degradation. Climate change is affecting geophony (abiotic, natural sounds). Existing evidence shows that anthrophony affects marine animals at multiple levels, including their behavior, physiology, and, in extreme cases, survival. This should prompt management actions to deploy existing solutions to reduce noise levels in the ocean, thereby allowing marine animals to reestablish their use of ocean sound as a central ecological trait in a healthy ocean.
We report phase diagrams for amphiphilic block copolymers prepared via ring-opening metathesis polymerization (ROMP). A library of 30 block copolymers with variable hydrophilic functionality, block ...ratios, and degrees of polymerization was prepared, and the resulting assemblies were analyzed by small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). A phase diagram of the self-assemblies was constructed for each of the various copolymer systems screened, representing the first of its kind for polynorbornene block copolymers in dilute solutions. Furthermore, we take advantage of kinetic control in the preparation of an array of particle morphologies accessed from the same polymer structure.
The long‐term durability of cement‐based materials is influenced by the pore structure and associated permeability at the sub‐micrometre length scale. With the emergence of new types of sustainable ...cements in recent decades, there is a pressing need to be able to predict the durability of these new materials, and therefore nondestructive experimental techniques capable of characterizing the evolution of the pore structure are increasingly crucial for investigating cement durability. Here, small‐angle neutron scattering is used to analyze the evolution of the pore structure in alkali‐activated materials over the initial 24 h of reaction in order to assess the characteristic pore sizes that emerge during these short time scales. By using a unified fitting approach for data modeling, information on the pore size and surface roughness is obtained for a variety of precursor chemistries and morphologies (metakaolin‐ and slag‐based pastes). Furthermore, the impact of activator chemistry is elucidated via the analysis of pastes synthesized using hydroxide‐ and silicate‐based activators. It is found that the main aspect influencing the size of pores that are accessible using small‐angle neutron scattering analysis (approximately 10–500 Å in diameter) is the availability of free silica in the activating solution, which leads to a more refined pore structure with smaller average pore size. Moreover, as the reaction progresses the gel pores visible using this scattering technique are seen to increase in size.
The impact of precursor and activator chemistry on the development of nanosized pores in alkali‐activated materials has been determined using small‐angle neutron scattering. The emergence of pores during the initial 24 h of reaction has been quantified, with contrast variation showing that the dominant source of scattering is from pores in this type of sustainable cement.
This paper compares Monte Carlo approaches and fast Fourier transform (FFT) methods to efficiently calculate small‐angle scattering (SAS) profiles from large morphological models. These methods ...enable calculation of SAS from complex nanoscale morphologies commonly encountered in modern polymeric and nanoparticle‐based systems which have no exact analytical representation and are instead represented digitally using many millions of subunits, so that algorithms with linear or near‐linear scaling are essential. The Monte Carlo method, referred to as the Monte Carlo distribution function method (MC‐DFM), is presented and its accuracy validated using a number of simple morphologies, while the FFT calculations are based on the fastest implementations available. The efficiency, usefulness and inherent limits of DFM and FFT approaches are explored using a series of complex morphological models, including Gaussian chain ensembles and two‐phase three‐dimensional interpenetrating nanostructures.
In the structural refinement of nanoparticles, discrete atomistic modeling can be used for small nanocrystals (< 15 nm), but becomes computationally unfeasible at larger sizes, where instead ...unit‐cell‐based small‐box modeling is usually employed. However, the effect of the nanocrystal's shape is often ignored or accounted for with a spherical model regardless of the actual shape due to the complexities of solving and implementing accurate shape effects. Recent advancements have provided a way to determine the shape function directly from a pair distribution function calculated from a discrete atomistic model of any given shape, including both regular polyhedra (e.g. cubes, spheres, octahedra) and anisotropic shapes (e.g. rods, discs, ellipsoids) Olds et al. (2015). J. Appl. Cryst.48, 1651–1659, although this approach is still limited to small size regimes due to computational demands. In order to accurately account for the effects of nanoparticle size and shape in small‐box refinements, a numerical or analytical description is needed. This article presents a methodology to derive numerical approximations of nanoparticle shape functions by fitting to a training set of known shape functions; the numerical approximations can then be employed on larger sizes yielding a more accurate and physically meaningful refined nanoparticle size. The method is demonstrated on a series of simulated and real data sets, and a table of pre‐calculated shape function expressions for a selection of common shapes is provided.
A numerical method for generating shape functions of non‐spherical nanoparticles for use in small‐box refinements of pair distribution function data is presented and implemented on several sets of simulated and experimental data. With this approach, physically relevant size parameters for simple and complex nanoparticle shapes can be refined from the data.
In situ total scattering measurements are increasingly utilized to follow atomic and nanoscale structural details of phase transitions and other transient processes in materials. This contribution ...presents an automated method and associated tool set to analyze series of diffraction and pair distribution function data with a linear combination of end‐member states. It is demonstrated that the combinatorial appraisal of transition states (CATS) software tracks phase changes, relative phase fractions and length scales of interest in experimental data series. It is further demonstrated, using a series of local structure data simulations, that the misfit of such a model can reveal details of phase aggregation and growth related to the pair distribution function's sensitivity to interphase correlations. CATS may be applied to quantitative evaluation of many transient processes, including amorphous‐to‐crystalline phase transitions, the evolution of solid‐solution behaviors, the precipitation and growth of aggregates, and other atomic to nanoscale details of crystallization and phase transformation phenomena.
A method and software tool are introduced to fit a series of pair distribution function data through a phase transition or to detect and track a specific structural feature of interest using a linear combination of two end‐member states. The misfit between the model combination and the data can reveal underlying details regarding the nature and length scale of intermediate structures.
Understanding the role of retarder on the chemical nature and molecular architecture of hydrating cement paste is essential for engineering oil well cements with additives. Here, synchrotron X-ray ...and total neutron scattering with pair distribution function (PDF) analysis were performed in combination with calorimetry and nuclear magnetic resonance (NMR) to examine the retarder effect in hydrating tri-calcium silicate (C3S) and Class G oil well cement paste. Primarily, the retarder, Diethylenetriamine pentamethylene phosphonic acid (DTPMP) influenced the hydration by affecting the Ca-O and Ca-Si pair correlation providing evidence of calcium playing a predominant role in the retardation process. Secondary effects related to Calcium-Silicate-Hydrate (C-S-H) nuclei poisoning influencing the suppression of calcium hydroxide precipitation were observed. Here, these findings provide insights into the retardation mechanism of hydrating cement paste influenced by calcium depletion when subjected to phosphonate retarders.
We generate percolating fullerene-polymer bulk heterostructures that are consistent with the experimental characterization of a nanostructure, in particular neutron reflectometry and small-angle ...neutron scattering data from as-cast and annealed poly(3-hexylthiophene) (P3HT) and 6,6-phenyl C61-butyric acid methyl ester systems. Transport simulations correlate changes in exciton dissociation efficiency and charge collection efficiency with morphological features including characteristic domain size, fullerene concentration profile, degree of fullerene sequestration, and degree of P3HT crystallization.
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