Anisotropic Electrostatic Interactions in Coarse-Grained Water Models to Enhance the Accuracy and Speed-Up Factor of Mesoscopic Simulations

Water models with realistic physical-chemical properties are essential to study a variety of biomedical processes or engineering technologies involving molecules or nanomaterials. Atomistic models of water are constrained by the feasible computational capacity, but calibrated coarse-grained (CG) ones can go beyond these limits. Here, we compare three popular atomistic water models with their corresponding CG model built using finite-size particles such as ellipsoids. Differently from previous approaches, short-range interactions are accounted for with the generalized Gay-Berne potential, while electrostatic and long-range interactions are computed from virtual charges inside the ellipsoids. Such an approach leads to a quantitative agreement between the original atomistic models and their CG counterparts. Results show that a timestep of up to 10 fs can be achieved to integrate the equations of motion without significant degradation of the physical observables extracted from the computed trajectories, thus unlocking a significant acceleration of water-based mesoscopic simulations at a given accuracy

Effects of a Mask on Breathing Impairment During a Fencing Assault: A Case Series Study

Background: Fencers often complain of progressive difficulty in breathing during matches, which is generally attributed to restricted air, light and heat circulation from wearing a mask. Physiologically, the nasal structure generates airflow resistance that can reach -50% of the total respiratory resistance. Objectives: This study aims to investigate the presence of nasal obstruction in fencers and the relationship with the use of mask. Materials and Methods: An observational study on 40 fencers (18 males, 22 females) was conducted. Fencers perform a usual assault, wearing the mask and standardized physical exercises (running, sprints and obstacles) without the mask. ENT examination with a nasal flexible fiberscope, Anterior Active Rhinomanometry (AAR) and Peak Nasal Inspiratory Flow (PNIF) measurement before and after physical activity with or without the mask was recorded. Results: Before physical exercise, the total nasal airway resistance mean value for AAR was 0.33 ± 0.17 Pa/cm3/s at 150 Pa. After a match with the mask, the mean value was 0.28 ± 0.16 Pa/cm3/s. After normal physical exercises without mask, the mean value was 0.24 ± 0.15 Pa/cm3/s. Using t tests, statistically significant difference between nasal resistance before and after physical activity (P < 0.05) was observed, but no significant difference in nasal resistance between the basal value and that taken after a match wearing the masks (P = 0.1265). PNIF values significantly increase with exercise (P < 0.05). Conclusions: Our study shows that wearing the mask causes increased breathing impairment in fencers, when compared with similar physical activity without the mask

Water filling in carbon nanotubes with different wettability and implications on nanotube/water heat transfer via atomistic simulations

The peculiar heat and mass transfer properties of Carbon Nanotubes (CNTs) envision promising applications in nanoengineering and nanofluidic devices, such as heat sinks and desalination membranes. However, a comprehensive understanding of the intertwined effects of mass transfer (entrance and exit of liquid molecules inside CNTs) and heat transfer mechanisms (thermal exchange at the CNT/solvent interface) as a function of the properties of CNT surface is currently incomplete. In this work, we use molecular dynamics simulations to study heat and mass transfer in single wall CNTs with (5,5) and (10,10) chirality immersed in water. We present a sensitivity analysis where, starting from different choices of interaction potentials between CNTs and water molecules, we deduce the corresponding CNT/water wetting parameters, we model fill-in and fill-out water dynamics and arrangement of water molecules at the equilibrium. Spontaneous water entrance into CNTs is examined and a single energy parameter to model water filling is introduced. Secondly, we compute the CNT/water thermal boundary resistance for the different wetting properties. In perspective, this work supports a more rational design of CNT-based devices operating in nanothermal and nanobiological environments

Effects of Graphene Oxidation on Interaction Energy and Interfacial Thermal Conductivity of Polymer Nanocomposite: A Molecular Dynamics Approach

Interfacial characteristics of polymer nanocomposites represent a crucial aspect to understand their global properties and to evaluate the interaction between nanofillers and matrix. In this work we used a molecular dynamics (MD) approach to characterize the interfacial region at the atomistic scale of graphene-based polymer nanocomposites. Three different polymer matrixes were considered, polylactic acid (PLA), polypropylene (PP) and epoxy resin (EPO), which were reinforced with three types of graphene fillers: pristine graphene (G), graphene oxide (GO) and reduced graphene oxide (rGO). In particular, the compatibility of the nanofillers in polymer matrixes were evaluated in terms of the interaction energy, while the interfacial thermal resistance (Kapitza resistance) between matrices and fillers was calculated with a nonequilibrium molecular dynamics (NEMD) method. Results showed that the oxidation degree plays an important role on the studied properties of the interfacial region. In particular, it was observed that the Kapitza resistance is decreased in the oxidized graphene (GO and rGO), while interaction energy depended on the polarity of the polymer matrix molecules and the contribution of the Coulombic component

Ultrafast nano generation of acoustic waves in water via a single carbon nanotube

Generation of ultra high frequency acoustic waves in water is key to nano resolution sensing, acoustic imaging and theranostics. In this context water immersed carbon nanotubes (CNTs) may act as an ideal optoacoustic source, due to their nanometric radial dimensions, peculiar thermal properties and broad band optical absorption. The generation mechanism of acoustic waves in water, upon excitation of both a single -wall (SW) and a multi-wall (MW) CNT with laser pulses of temporal width ranging from 5 ns down to ps, is theoretically investigated via a multiscale approach. We show that, depending on the combination of CNT size and laser pulse duration, the CNT can act as a thermophone or a mechanophone. As a thermophone, the CNT acts as a nanoheater for the surrounding water, which, upon thermal expansion, launches the pressure wave. As a mechanophone, the CNT acts as a nanopiston, its thermal expansion directly triggering the pressure wave in water. Activation of the mechanophone effect is sought to trigger few nanometers wavelength sound waves in water, matching the CNT acoustic frequencies. This is at variance with respect to the commonly addressed case of water-immersed single metallic nano-objects excited with ns laser pulses, where only the thermophone effect significantly contributes. The present findings might be of impact in fields ranging from nanoscale non-destructive testing to water dynamics at the meso to nanoscale

Enhanced Multiscale Modeling of Wetting Phenomena on Surfaces with Tailored Properties for Energy Devices

L'abstract è presente nell'allegato / the abstract is in the attachmen

Activity of hypertonic solution with Silver and Potassium Sucrose Octasulfate on nasal symptoms in obstructive rhinopathy with and without rhinosinusitis

Nasal obstruction is a primary symptom of common upper respiratory tract disorders. In clinical practice nasal saline solutions are recommended for the cleansing of nasal cavities and relieving nasal symptoms

Role of adenotonsillectomy in OSAS children and behavioural disturbance

The main aim of this study was to assess the presence of behavioural disturbances in child with OSAS before and after adenotonsillectomy (AT)

Atomized nasal douche vs nasal lavage in acute viral rhinitis

Objective: To evaluate the efficacy of the atomized nasal douche in the restoration of physiological nasal functions in patients affected by acute viral rhinosinusitis, when compared with nasal lavages with isotonic sodium chloride solution. Design: Randomized clinical trial. Setting: The ENT Department at the University of Siena Medical School. Patients: Two hundred patients affected by acute viral rhinosinusitis were included in the study. Interventions: Patients were randomly divided into 2 groups: group 1 patients received an atomized nasal douche, and group 2 patients received nasal lavages with isotonic sodium chloride solution. Patients underwent treatments 4 times per day for 15 days in our institution under our direct control. Results: Atomized nasal douches significantly improved inspiratory and expiratory rhinomanometric resistance (P < .01) and nasal volumes measured by acoustic rhinometry (P < .001). Nasal lavages were unable to modify these variables significantly (P < .3). Only atomized nasal douches were able to normalize mucociliary transport time to a physiological level (P < .001). Conclusions: The atomized nasal douche demonstrated a better efficacy than traditional nasal lavages with isotonic sodium chloride solution in restoring all the physiological nasal functions. For this reason, and considering ease of use, painlessness, cheapness, and manageability of the instrument, we suggest the use of the compressor-micronizer chamber system (Rinoflow Nasal Wash & Sinus System) as a routine adjuvant to every treatment of acute rhinopathies