Two FEM-BEM methods for the numerical solution of 2D transient elastodynamics problems in unbounded domains

We consider wave propagation problems in 2D unbounded isotropic homogeneous elastic media, with rigid boundary conditions. For their solution, we propose and compare two alternative numerical approaches, both obtained by coupling the differential equation with the associated space-time boundary integral equation. The latter is defined on an artificial boundary, chosen to surround the (bounded) exterior computational domain of interest. The integral equation defines a boundary condition which is non-reflecting for incoming and also for outgoing waves. In both approaches, the differential equations are discretized by applying a finite element method combined with the Crank Nicolson time marching scheme, while the discretization of the integral equation is obtained by coupling a time convolution quadrature with a space collocation boundary element method. The construction of the two approaches is described and discussed. Some numerical tests are also presented

CVEM-BEM Coupling with Decoupled Orders for 2D Exterior Poisson Problems

For the solution of 2D exterior Dirichlet Poisson problems, we propose the coupling of a Curved Virtual Element Method (CVEM) with a Boundary Element Method (BEM), by using decoupled approximation orders. We provide optimal convergence error estimates, in the energy and in the weaker L-2-norm, in which the CVEM and BEM contributions to the error are separated. This allows for taking advantage of the high order flexibility of the CVEM to retrieve an accurate discrete solution by using a low order BEM. The numerical results confirm the a priori estimates and show the effectiveness of the proposed approach

Polyaniline (PANI): an innovative support for sampling and removal of VOCs in air matrices

Polyaniline (PANI)-based materials for both removal and sampling of volatile organic compounds (VOCs) from air by rapid adsorption/desorption processes have been developed. The polymer was synthesized in form of emeraldine as both salt and base using different synthetic approaches, a traditional one and a "green" one. VOCs adsorption/desorption efficiency was evaluated for all the materials analyzing the desorbed VOCs fractions by GC/MS technique and obtaining results similar to the presently adopted method employing commercial activated carbon. Most important, in this work it has been demonstrated for the first time that the use of PANI-based sorbents allowed the substitution of the toxic CS2, recommended in official methods, with the less hazardous CH3OH as the VOCs extraction solvent. Moreover, a complete regeneration of the polymers could be realized by a few rapid washing steps. Finally, the best PANI-based material was subjected to recycling tests thereby showing a high adsorption/desorption efficiency retention up to four runs

Electrochemical treatment coupled with solar light-driven photocatalytic approach: A challenging process in cascade for hydrogen production and wastewater remediation

This study presents an innovative approach for simultaneous hydrogen production and wastewater remediation, integrating electrochemical treatment with solar light-driven photocatalysis. The research focuses on the use of a noble metal-free cathode, based on a electrodeposited composite of Co2P and elemental P, for efficient hydrogen generation from simulated wastewater through water splitting. This composite is characterized, in its optimized form, by an overpotential equal to 133.6 mV (at 10 mA cm-2) and by a Tafel slope of 60.5 mV dec-1. Challenges like the high potential required for the Oxygen Evolution Reaction (OER) and the use of expensive noble metals in electrodes are addressed by employing earth-abundant compounds for electrode fabrication. Additionally, the study explores the degradation of diclofenac (DCF) in wastewater, demonstrating that electrochemical treatment alone is insufficient for organic matter removal. Therefore, a coupled process involving a first electrochemical treatment step followed by a photocatalytic process using BiOCl is proposed. Thanks to the exposure of the (110) active face, BiOCl possesses excellent photocatalytic performances even under solar light irradiation. This hybrid approach not only enhances the efficiency of DCF degradation (about 90%) and reaches an organic matter removal of 59%, but it also improves hydrogen production, offering a sustainable solution for energy generation and water purification in the face of increasing global industrialization and water scarcity

Oxidative inactivation of SARS-CoV-2 on photoactive AgNPs@Tio2 ceramic tiles

The current SARS-CoV-2 pandemic causes serious public health, social, and economic issues all over the globe. Surface transmission has been claimed as a possible SARS-CoV-2 infection route, especially in heavy contaminated environmental surfaces, including hospitals and crowded public places. Herein, we studied the deactivation of SARS-CoV-2 on photoactive AgNPs@TiO2 coated on industrial ceramic tiles under dark, UVA, and LED light irradiations. SARS-CoV-2 inactivation is effective under any light/dark conditions. The presence of AgNPs has an important key to limit the survival of SARS-CoV-2 in the dark; moreover, there is a synergistic action when TiO2 is decorated with Ag to enhance the virus photocatalytic inactivation even under LED. The radical oxidation was confirmed as the the central mechanism behind SARS-CoV-2 damage/inactivation by ESR analysis under LED light. Therefore, photoactive AgNPs@TiO2 ceramic tiles could be exploited to fight surface infections, especially during viral severe pandemics

Emerging pollutant mixture mineralization by TiO2 photocatalysts : the role of the water medium

Pharmaceutics and personal care products (PPCPs) are raising growing concern due to their widespread usage and resistance to conventional remediation techniques. Several of them raise significant health and environmental concerns, especially when present in complex mixtures. Due to their chemical resistance, Advanced Oxidation Processes (AOPs) are needed for their complete removal from surface and wastewaters. In the present work, photocatalysis by titanium dioxide (TiO2) under UV and simulated solar irradiation was adopted to degrade tetracycline hydrochloride, paracetamol, caffeine and atenolol, both as single pollutants and in mixtures. All molecules showed high removal and mineralization degrees. Moreover, no interference effects decreased the efficiency of the processes in the case of pollutant mixtures, achieving 60% of mineralization after 6 h. An immobilized TiO2 system was also developed by depositing titania on titanium meshes. A 50% mineralization degree of the pollutant mixture was obtained after 6 h, revealing a suitable efficiency for field applications. Eventually, the impact of the matrix composition on the photocatalytic efficiency was investigated by studying the reaction both in simulated drinking water and in commercial bottled mineral water. The scavenger role played by HCO3 12 species appears to be dominant in inhibiting the mineralization

Language-Related Brain Potentials in Patients With Disorders of Consciousness: A Follow-up Study to Detect “Covert” Language Disorders

Background. Language disorders may occur in patients with disorders of consciousness (DoCs), and they could interfere with the behavioral assessment of consciousness and responsiveness. Objective. In this study, we retrospectively explored whether ERP N400 was eventually associated with the presence of aphasia diagnosed in those patients who had evolved into Exit-Minimally Conscious State (E-MCS) at the clinical follow-up. Methods. In this retrospective cohort study, the ERPs elicited by an auditory sentences task were retrospectively examined in a sample of 15 DoC patients diagnosed according to the Coma Recovery Scale–Revised (CRS-R). All these 15 DoC patients underwent a (at least) 1-year clinical follow-up, which included a neuropsychological evaluation to assess language function among other cognitive functions. Ten healthy individuals also underwent the same paradigm to investigate the variability of ERPs characteristics. Results. The N400 ERP component with centroparietal topography was found in 9 of 10 healthy controls in response to the ill-formed sentences. Analysis of patients’ data revealed that (1) a significant N400 component could be detected in 64% (9 of 14 patients) of the DoC patients regardless of the type of DoC; (2) no significant N400 ERP component was retrospectively detected in those E-MCS patients who showed aphasia at the follow-up; and (3) the presence/absence of the N400-ERP component was consistent with the brain lesion side and significantly predict the recovery. Conclusion. These preliminary findings indicate that the absence of N400 was significantly associated with the presence of aphasia diagnosed at the clinical follow-up in E-MCS patients

Concurrent role of metal (Sn, Zn) and N species in enhancing the photocatalytic activity of TiO2 under solar light

TiO2 modification by both non-metal and metal species is a popular strategy to promote the semiconductor visible light absorption and photocatalytic performance. In this work, tin and zinc are compared as metal promoters to enhance the photocatalytic activity of N-doped TiO2 under solar light. The synthesized samples were tested under both UV and simulated solar irradiation toward the photocatalytic degradation of tetracycline, an emerging water pollutant. All copromoted samples (N\u202f+\u202fSn and N\u202f+\u202fZn) revealed higher efficiency under solar light in the mineralization of the pollutant with respect to both the pristine and N-doped ones. The enhanced photocatalytic efficiency of these samples was traced back to the modifications introduced by the different guest species to the structural (X-ray Powder Diffraction, XRPD), morphological (High-Resolution Transmission Electron Microscopy, HR-TEM and Brunauer-Emmett-Teller analysis, BET), spectroscopic (X-ray Photoelectron Spectroscopy, XPS, Energy Dispersive X-ray Spectroscopy, EDX and Diffuse Reflectance Spectroscopy, DRS) and surface features (\u3b6-potential). In this regard, the increased surface area, the modifications of the phase composition and the enhanced visible light harvesting seem to play a pivotal role in affecting the photocatalytic performance. Mass spectrometry analyses allowed us to identify several reaction intermediates and propose different degradation mechanisms depending on the type of metal promoter