This study investigates the mechanical response of rockfall-induced fragmentation by implementing a novel numerical breakage model within a discrete-element framework. The model evaluates the size distribution and breakage probability of rock blocks upon impact, considering key variables such as impact height and initial rock size. The system consists of a rock buffer layer and a freely falling rock block, with irregular geometries incorporated for greater computational realism. Results highlight the strong influence of impact height and rock size ratio on fragmentation, increasing the breakage probability as energy dissipates through the medium. Notably, rock fracture does not always occur instantaneously upon impact but may be delayed by milliseconds as stress propagates through the granular bed. A simple probability model is proposed to estimate the survival rate of rock blocks based on impact height and rock size, demonstrating strong agreement with reported rockfall cases in caving mines. This approach enables back-analysis of rockfall conditions prior to secondary fragmentation, aiding in the understanding of fragment behaviour within the mineral column before extraction. Additionally, the findings contribute to geomechanical risk mitigation by offering insights into rock mass dynamics and energy dissipation mechanisms during impact.

The cumulative vehicle routing problem with time windows (CumVRP-TW) is a vehicle routing variant that aims at minimizing a cumulative cost function while respecting customers' time windows constraints. Mathematical formulations are proposed for soft and hard time windows constraints, where for the soft case, violations are permitted subject to penalization. By means of the cumulative objective and the time windows consideration, routing decisions incorporate the environmental impact related to CO2 emissions and permit obtaining a tradeoff between emissions and time windows fulfillment. To solve this problem, we propose a matheuristic approach that combines the features of the Greedy Randomized Adaptive Search Procedure (GRASP) with the exact solution of the optimization model. The solution approaches are tested on instances proposed in the literature as well as on a new benchmark suite proposed for assessing the soft time windows variant. The computational results show that the mathematical formulations provide optimal solutions for scenarios of 10, 20, and several of 50 customers within suitable computational times. Nevertheless, the same performance is not observed for several medium as well as for all large scenarios. In those cases, the proposed matheuristic algorithm is able to report feasible and improved routes for those instances where the exact solver does not report good results. Finally, we verify that the fuel consumption and carbon emissions are reduced when the violation of the time windows is allowed in the case of soft time windows.

In combustion theory, flames are usually described in terms of the dynamics of iso-surfaces of a specific scalar. The flame displacement speed is then introduced as a local variable quantifying the progression of these iso-surfaces relative to the flow field. While formally defined as a scalar, the physical meaning of this quantity allows relating it with a vector pointing along the normal direction of the scalar iso-surface. In this work, this one-dimensional concept is extended by the introduction of a generalized flame displacement velocity vector, which is associated with the dynamics of iso-surfaces of two generic scalars, α and β. It is then shown how a new flamelet paradigm can be built around this velocity vector, which leads to (i) an alternative procedure for the derivation of general flamelet equations, which is much simpler and more direct than the ones currently available in the literature, (ii) a very compact set of two-dimensional flamelet equations for the conditioning scalar gradients, gα = |∇α| and gβ = |∇β|, which comprise several effects in few terms directly related to the projections of the generalized flame displacement velocity, and (iii) the possibility of characterizing different composition space coordinate systems through the same generalized flame displacement velocity. The proposed framework is discussed in the context of partially premixed combustion, emphasizing how its adoption can contribute to both the further development of 2D flamelet theory and its coupling with CFD codes.

This study reports the effect of diethylzinc (DEZ) and trimethylaluminium (TMA) functionalization on polyamide-6 (PA6) films using the vapour-phase metalation (VPM) process within an atomic layer deposition (ALD) chamber. The resulting zinc- and aluminium-functionalized films are referred to henceforth as PA6-Zn and PA6-Al, respectively. Biocompatibility was preliminarily assessed via C2C12 cytotoxicity testing. Reaction mechanisms were examined using density functional theory, electrostatic potential maps, Mulliken charge distribution, and X-ray photoelectron spectroscopy, revealing interactions between metal precursors and PA6 amide groups. DFT confirmed alpha-PA6 as the dominant structure and identified reactive sites influencing functionalization pathways. Structural and morphological changes were analysed via environmental scanning electron microscopy and X-ray diffraction. ESEM showed Zn-functionalized PA6 forming strand-like structures, while Al-functionalized PA6 developed pore-like cavities. XRD indicated increased crystallinity upon metalation, with the alpha/gamma crystallite size ratio following the trend: PA6-Al > PA6-Zn > PA6. Spectroscopic analysis using infrared and Raman microscopy, along with UV-visible spectroscopy, highlighted modifications in chemical bonding and polymorphism, aligning with DFT predictions. Al functionalization had a stronger influence on PA6's spectroscopic and some mechanical properties, whereas Zn functionalization notably enhanced failure strain. Barrier and mechanical properties were evaluated, showing that Zn-functionalized PA6 exhibited superior oxygen permeability, while both metal-modified films improved water vapour transmission rates compared to bare PA6. Cytotoxicity testing revealed enhanced C2C12 cell proliferation in the order PA6-Al > PA6-Zn > PA6, suggesting VPM-modified PA6 as a promising material for biomedical applications.

Whispering gallery resonators offer a versatile platform for manipulating the photonic transmission. Here, we study such a system, including periodically distributed pointlike impurities along the resonator with ring geometry. Based on an exact expression for the transmission probability we obtain here, we demonstrate that the bound states in the continuum (BICs) form from the whispering gallery modes at the high-symmetry momenta in the ring's Brillouin zone. Furthermore, the presence of the inversion symmetry allows for a selective decoupling of resonant states, favoring the BIC generation and, therefore, allowing extra tunability in the optical transmission of the system.

The functional evaluation of auditory-nerve activity in spontaneous conditions has remained elusive in humans. In animals, the frequency analysis of the round-window electrical noise recorded by means of electrocochleography yields a frequency peak at around 900 to 1000 Hz, which has been proposed to reflect auditory-nerve spontaneous activity. Here, we studied the spectral components of the electrical noise obtained from cochlear implant electrocochleography in humans.

Bajo la influencia del federalismo fiscal y las teorías de la descentralización gubernamental, una parte importante de los sistemas de salud de todo el mundo enfrentaron la pandemia de COVID-19 después de haber sido moldeados o reformados por procesos de transferencia de poderes de los gobiernos centrales a los locales. La adquisición de suministros clave es uno de los componentes que opera de manera descentralizada, lo que obliga a los gobiernos locales a competir entre sí. Este fue el origen de lo que se ha llamado las “guerras de licitaciones” entre gobiernos subnacionales al comienzo de la respuesta a la pandemia. Estas guerras llevaron a políticas de centralización en Estados Unidos, Reino Unido y la Unión Europea. Sin embargo, se sabe menos sobre los casos del sur global. Al analizar la adquisición de Equipos de Protección Personal (EPP) en 320 municipios chilenos encargados de la atención primaria de salud, esta investigación proporciona evidencia de los impactos de la competencia gubernamental horizontal en la capacidad de adquirir suministros clave. En Chile, durante la respuesta a la pandemia de 2020, los municipios más ricos pudieron adquirir más mascarillas por habitante, generándose con ello economías de escala que les permitieron acceder a precios más bajos, a diferencia de aquellos municipios con menores recursos. Los autores apoyan la noción teórica de “concurrencia” como un concepto que añade matices al debate sobre centralización-descentralización. En Chile, por ejemplo, si bien el testeo y la trazabilidad de casos SARS-CoV-2 requerían la descentralización de dichas funciones, las compras de EPP probablemente podrían haberse beneficiado de la centralización de los procesos de adquisición para evitar la reproducción de desigualdades territoriales.

We propose a solution for the long standing puzzle of a too steeply falling fragmentation function for a quark fragmenting into a pion, calculated by Berger [E.L. Berger, Phys. Lett. B 89 (1980) 241] in the Born approximation. Contrary to the simple anticipation that gluon resummation worsens the problem, we find good agreement with data. Higher quark Fock states slow down the quark, an effect which we call jet lag. It can be also expressed in terms of vacuum energy loss. As a result, the space–time development of the jet shrinks and the z-dependence becomes flatter than in the Born approximation. The space–time pattern is also of great importance for in-medium hadronization.