Expansions for the linear-elastic contribution to the self-interaction force of dislocation curves

The self-interaction force of dislocation curves in metals depends on the local arrangement of the atoms and on the non-local interaction between dislocation curve segments. While these non-local segment–segment interactions can be accurately described by linear elasticity when the segments are further apart than the atomic scale of size $\varepsilon$ , this model breaks down and blows up when the segments are $O(\varepsilon)$ apart. To separate the non-local interactions from the local contribution, various models depending on $\varepsilon$ have been constructed to account for the non-local term. However, there are no quantitative comparisons available between these models. This paper makes such comparisons possible by expanding the self-interaction force in these models in $\varepsilon$ beyond the O(1)-term. Our derivation of these expansions relies on asymptotic analysis. The practical use of these expansions is demonstrated by developing numerical schemes for them, and by – for the first time – bounding the corresponding discretisation error.

Insights on the Italian Seismic Network from location uncertainties

Probabilistic earthquake locations provide confidence intervals for the hypocentre solutions such as errors encountered in the position, the origin time, and in magnitude. If the relationship of the parameters relative to the local arrangement of the seismic network is considered, such as the node distance, the number of stations, the seismic gap, and the quality of phase readings), the uncertainties can then provide insights on the location capability of the network. In this paper, we collect the earthquake data recorded from the Italian Seismic Network for a time span of 5 years. The data pertain to three different catalogues according to the progressive refinement phases of the location procedure: automatic location, revised location, and published location. By means of spatial analysis, we assess the distribution of the location-related and network-related estimators across the study area. These estimators are subsequently combined to assess the existence of spatial correlations at a local scale. The results indicate that the Italian network is generally able to provide robust locations at the national scale and for smaller earthquakes, and the elongated shape of Italy (and of its network) does not cause systematic bias in the locations. However, we highlight the existence of subregions in which the performance of the network is weaker. At present, a unique 2D, 3-layer velocity model is used for the earthquake location procedure, and this could represent the main limitation for the improvement of the locations. Therefore, the assessment of locally optimized velocity models is the priority for the homogenization and the improvement of the Italian Seismic Network performance.

Hotspot generation for unique identification with nanomaterials

Nanoscale variations in the structure and composition of an object are an enticing basis for verifying its identity, due to the physical complexity of attempting to reproduce such a system. The biggest practical challenge for nanoscale authentication lies in producing a system that can be assessed with a facile measurement. Here, a system is presented in which InP/ZnS quantum dots (QDs) are randomly distributed on a surface of an aluminium-coated substrate with gold nanoparticles (Au NPs). Variations in the local arrangement of the QDs and NPs is shown to lead to interactions between them, which can suppress or enhance fluorescence from the QDs. This position-dependent interaction can be mapped, allowing intensity, emission dynamics, and/or wavelength variations to be used to uniquely identify a specific sample at the nanoscale with a far-field optical measurement. This demonstration could pave the way to producing robust anti-counterfeiting devices.

Volunteering and the Destinations: Socialisation and Interaction

Volunteering has been part of the growing social and economic phenomenon because of the belief that it delivers positive effects for the stakeholders involved. This paper undertakes analysis of the impacts of the Sunflower (xiangrikuei) volunteering program. The research attempts to understand the views of the volunteers, organisers, and destination representatives from interviews, focus groups and observation. The research confirms that while volunteers and organisers do benefit from the experience, the impacts of volunteering on the destinations present a complex mixture of results. While destinations do express their benefits from working with volunteers who bring different skills and influences, they are concerned that volunteers working for a short period of time do not bring enough positive changes but rather disturb the normal local arrangement. Communication may be challenging, and conflicts may arise between volunteers and some local people. The research provides insights for improving the benefits for destinations related to volunteering.

Magnetic field–driven assembly and reconfiguration of multicomponent supraparticles

Suprastructures at the colloidal scale must be assembled with precise control over local interactions to accurately mimic biological complexes. The toughest design requirements include breaking the symmetry of assembly in a simple and reversible fashion to unlock functions and properties so far limited to living matter. We demonstrate a simple experimental technique to program magnetic field–induced interactions between metallodielectric patchy particles and isotropic, nonmagnetic “satellite” particles. By controlling the connectivity, composition, and distribution of building blocks, we show the assembly of three-dimensional, multicomponent supraparticles that can dynamically reconfigure in response to change in external field strength. The local arrangement of building blocks and their reconfigurability are governed by a balance of attraction and repulsion between oppositely polarized domains, which we illustrate theoretically and tune experimentally. Tunable, bulk assembly of colloidal matter with predefined symmetry provides a platform to design functional microstructured materials with preprogrammable physical and chemical properties.

Biologically encoded magnonics

Spin wave logic circuits using quantum oscillations of spins (magnons) as carriers of information have been proposed for next generation computing with reduced energy demands and the benefit of easy parallelization. Current realizations of magnonic devices have micrometer sized patterns. Here we demonstrate the feasibility of biogenic nanoparticle chains as the first step to truly nanoscale magnonics at room temperature. Our measurements on magnetosome chains (ca 12 magnetite crystals with 35 nm particle size each), combined with micromagnetic simulations, show that the topology of the magnon bands, namely anisotropy, band deformation, and band gaps are determined by local arrangement and orientation of particles, which in turn depends on the genotype of the bacteria. Our biomagnonic approach offers the exciting prospect of genetically engineering magnonic quantum states in nanoconfined geometries. By connecting mutants of magnetotactic bacteria with different arrangements of magnetite crystals, novel architectures for magnonic computing may be (self-) assembled.

Dispersion and topological characteristics of permutative polyatomic phononic crystals

This work presents a comprehensive mathematical treatment of phononic crystals (PCs) which comprise a finite lattice of repeated polyatomic unit cells. Wave dispersion in polyatomic lattices is susceptible to changes in the local arrangement of the monatoms (subcells) constituting the individual unit cell. We derive and interpret conditions leading to identical and contrasting band structures as well as the possibility of distinct eigenmodes as a result of cyclic and non-cyclic cellular permutations. Different modes associated with cyclic permutations yield topological invariance, which is assessed via the winding number of the complex eigenmode. Wave topology variations in the polyatomic PCs are quantified and conditions required to support edge modes in such lattices are established. Next, a transfer function analysis of finite polyatomic PCs is used to explain the formation of multiple Bragg band gaps as well as the emergence of truncation resonances within them. Anomalies arising from the truncation of the infinite lattice are further exploited to design mirror symmetrical edge modes in an extended lattice. We conclude with a generalized explanation of the band gap evolution mechanism based on the Bode plot analysis.