Robust Physical Model Research Articles

A Mechanical–Electrical Model to Describe the Negative Differential Resistance in Membranotronic Devices

Membranotronic devices are artificial neural membranes mimicing the functionality of biological neural networks. These devices rely on the emergence of negative differential resistance (NDR). A minimalistic physical model for membranotronic devices capable of generating NDR is presented. The model features a deformable membrane with holes that facilitate ion currents. The deformation of the membrane, induced by electrostatic pressure from an applied voltage, modulates these currents. The model comprises a well‐established mechanical framework for describing deformable membranes with holes, alongside a model for ionic current that considers temperature‐dependent ion mobilities. It is demonstrated that the model can faithfully reproduce NDR across a wide and physically realistic range of parameter combinations. Furthermore, the simulations reveal that the temperature of the electrolyte can exceed its boiling point, resulting in bubble formation. To mitigate this issue, materials with high heat transfer coefficients and low conductivity are recommended. In essence, the work bridges the gap between artificial membranotronic devices and biological neural networks by providing a robust physical model capable of emulating NDR, a key feature in the operation of such systems. This advancement in membranotronics holds great promise for the development of bioinspired soft artificial neuromimetic systems that closely mimic their biological counterparts.

Toward RNA Life on Early Earth: From Atmospheric HCN to Biomolecule Production in Warm Little Ponds

The origin of life on Earth involves the early appearance of an information-containing molecule such as RNA. The basic building blocks of RNA could have been delivered by carbon-rich meteorites or produced in situ by processes beginning with the synthesis of hydrogen cyanide (HCN) in the early Earth’s atmosphere. Here, we construct a robust physical and nonequilibrium chemical model of the early Earth’s atmosphere. The atmosphere is supplied with hydrogen from impact degassing of meteorites, water evaporated from the oceans, carbon dioxide from volcanoes, and methane from undersea hydrothermal vents, and in it lightning and external UV-driven chemistry produce HCN. This allows us to calculate the rain-out of HCN into warm little ponds (WLPs). We then use a comprehensive numerical model of sources and sinks to compute the resulting abundances of nucleobases, ribose, and nucleotide precursors such as 2-aminooxazole resulting from aqueous and UV-driven chemistry within them. We find that 4.4 billion years ago the limit of adenine concentrations in ponds for habitable surfaces is 0.05 μM in the absence of seepage. Meteorite delivery of adenine to WLPs can provide boosts in concentration by 2–3 orders of magnitude, but these boosts deplete within months by UV photodissociation, seepage, and hydrolysis. The early evolution of the atmosphere is dominated by the decrease in hydrogen due to falling impact rates and atmospheric escape, and the rise of oxygenated species such as OH from H2O photolysis. The source of HCN is predominantly from UV radiation rather than lightning. Our work points to an early origin of RNA on Earth within ∼200 Myr of the Moon-forming impact.

Multidimensional Vibrations of Cable-Harnessed Beam Structures with Periodic Pattern: Modeling and Experiment

The dynamics of space structures is significantly impacted by the presence of power and electronic cables. Robust physical model is essential to investigate how the host structure dynamics is influenced by cable harnessing. All the developed models only considered the decoupled bending motion. Initial studies by authors point out the importance of coordinate coupling in structures with straight longitudinal cable patterns. In this article, an experimentally validated mathematical model is developed to analyze the fully coupled dynamics of beam with a more complex cable wrapping pattern which is periodic in nature. The effects of cable wrapping pattern and geometry on the system dynamics are investigated through the proposed coupled model. Homogenization-based mathematical modeling is developed to obtain an analogous solid beam that represents the cable wrapped system. The energy expressions obtained for fundamental repeating segment are transferred into the global coordinates consisting of several periodic elements. The coupled partial differential equations (PDE) are obtained for an analogous solid structure. The advantage of the proposed analytical model over the existing models to analyze the vibratory motion of beam with complex cable wrapping pattern has been shown through experimental validation.

Low-cost digital tool kit for planning and sizing with 3D printing of abdominal aortic aneurysms for endovascular aortic repair: A Latinoamerican experience

Introduction and objectives3D printing technology has recently been used to improve diagnosis and treatment of complex surgical cardiovascular diseases. This technology allows better appreciation of complex 3D anatomical and pathological conditions. The aim of the present study is to show a Latin American experience with a low-cost digital toolkit for planning and sizing with 3D printing of abdominal aortic aneurysms (AAA) for endovascular aortic repair (EVAR) and preoperative simulation, combining 2D and 3D technologies. MethodsProspective descriptive study. All patients that underwent EVAR between January and May 2021 were included. The EVAR procedures were planned using the low-cost digital tool kit with 3D printing. ResultsThe 3D printed models had fair transparency, absence of flexibility and no discrepancy between the computer-aided design. The models allowed external inspection but not the insertion of stent grafts due to the lack of lumen. The model had lower cost (25 USD per model), shorter manufacturing time (22h 31min), and an acceptable level of accuracy (2.61% error) compared to other methods. DiscussionUsing low-cost digital tool kits for planning and sizing with 3D printing, produces a robust physical model of a patient-specific AAA to aid endovascular aneurysm repair education and planning in a timely and cost-effective manner. ConclusionsOverall, with the levels of transparency and flexibility provided by the 3D printed part, the patient-specific AAA model could potentially be used for surgical planning for individual patients but not for surgeons practicing endovascular aneurysm repair stent graft.

Charge transfer via deep hole in the J51/N2200 blend.

In recently developed non-fullerene acceptor (NFA) based organic solar cells (OSCs), both the donor and acceptor parts can be excited by absorbing light photons. Therefore, both the electron transfer and hole transfer channels could occur at the donor/acceptor interface for generating free charge carriers in NFA based OSCs. However, in many molecular and DNA systems, recent studies revealed that the high charge transfer (CT) efficiency cannot be reasonably explained by a CT model with only highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of donor and acceptor molecules. In this work, taking an example of a full-polymer blend consisting of benzodithiophene-alt-benzotriazole copolymers (J51) as donor and naphthalene diimide-bithiophene (N2200) as acceptor, in which the ultrafast hole transfer has been recently reported, we investigate its CT process and examine the different roles of various frontier molecular orbitals (FMOs). Through a joint study of quantum mechanics electronic structure calculation and nonadiabatic dynamics simulation, we find that the hole transfer between HOMOs of J51 and N2200 can hardly happen, but the hole transfer from HOMO of N2200 to HOMO - 1 of J51 is much more efficient. This points out the underlying importance of the deep hole channel in the CT process and indicates that including FMOs other than HOMOs and LUMOs is highly necessary to build a robust physical model for studying the CT process in molecular optoelectronic materials.

Capability of SiC MOSFETs under Short-Circuit Tests and Development of a Thermal Model by Finite Element Analysis

The aim of this paper is to analyze the SiC MOSFETs behavior under short circuit tests (SCT). In particular, the activity is focused on a deep evaluation of short circuit dynamic by dedicated laboratory measurements conducted at different conditions supported and compared by means of a robust physical model developed by Finite Element Approach.

The atmospheric carbon sequestration potential of man-made tidal lagoons

Understanding sequestration of carbon by coastal ecosystems is central to addressing the role they play in climate change mitigation. To quantify this process, accurate measurements of CO2 fluctuation, coupled with variations in residence time of coastal water-bodies are required. Nearshore ecosystems, including coastal lagoons, may provide an effective sink for atmospheric carbon dioxide, particularly those containing productive biota such as seagrass. However, the rate and pattern of carbon sequestration in seagrass meadows across a range of environmental settings is still poorly constrained. In this study, we utilize a robust physical tidal model, along with biogeochemical dissolved inorganic carbon (DIC) assessment, to estimate water residence time and net sequestration of atmospheric CO2 in an intertidal lagoon containing a seagrass (Zostera noltii) meadow. Total alkalinity and pH measurements taken from advected water mass exchanged with the open ocean at inlet boundaries are used to calculate DIC and pCO2. A predictive model of hydrodynamics provides good approximation of mean water residence time to within 6 h (±3 s.d). Results indicate that during the daytime study period the lagoon is a sink for carbon, having a mean net ecosystem productivity (NEP) of 3.0 ± 0.4 mmol C m−2 hr−1. An equivalent diel NEP range of between 15.23 and −9.24 mmol C m−2 d−1 is calculated based on reported shallow water pelagic respiration rates. Moreover, approximately 4% of DIC availability occurs from atmospheric CO2 transfer to lagoon water. However, a negative diel rate of −82 ± 81 mmol C m−2 d−1 is found, assuming overnight respiration ascertained from converted Zostera noltii O2 utilization. We hypothesize that analogous regional nearshore ecosystems provide baseline study sites suitable to elucidate the carbon capture potential of planned, nearby tidal range energy schemes.

Wound Healing Coordinates Actin Architectures to Regulate Mechanical Work.

How cells with diverse morphologies and cytoskeletal architectures modulate their mechanical behaviors to drive robust collective motion within tissues is poorly understood. During wound repair within epithelial monolayers in vitro, cells coordinate the assembly of branched and bundled actin networks to regulate the total mechanical work produced by collective cell motion. Using traction force microscopy, we show that the balance of actin network architectures optimizes the wound closure rate and the magnitude of the mechanical work. These values are constrained by the effective power exerted by the monolayer, which is conserved and independent of actin architectures. Using a cell-based physical model, we show that the rate at which mechanical work is done by the monolayer is limited by the transformation between actin network architectures and differential regulation of cell-substrate friction. These results and our proposed mechanisms provide a robust physical model for how cells collectively coordinate their non-equilibrium behaviors to dynamically regulate tissue-scale mechanical output.

Monitoring and modelling soil water dynamics using electromagnetic conductivity imaging and the ensemble Kalman filter

Understanding the soil water (θ) dynamics is important in irrigated agriculture. Due to the labour-intensive nature of determining θ, non-invasive electromagnetic (EM) induction techniques have been used. However, predicting depth-specific θ is a challenge because EM instruments measure the integral depth of the soil's apparent electrical conductivity (ECa). Recently, “true” electrical conductivity with depth produced by inverse modelling of ECa has been employed to establish empirical models of θ. However, the potential to combine empirical models with soil physical models using data assimilation such as ensemble Kalman filter (EnKF) has not been explored. Along a 480-m transect with varying soil texture profiles, repeated ECa data were collected using a DUALEM-421S on 20days over a 40-day period. A quasi-2d inversion algorithm was used to convert the temperature corrected ECa data to σ. An empirical model (artificial neural network) that predicted θ was calibrated using σ values, elevation, and topographic wetness index, as well as the mean and range of σ for each depth and each site over the whole study period. A physical soil-water tipping bucket model was also constructed using θ measured by soil moisture sensors. Afterwards, the EnKF approach was applied to 8 profiles along the transect separately combining both the empirical and the physical models. The results with the EnFK modelling (Lin's concordance=0.89) were superior to the physical model and superior or equivalent to the empirical model for loam, clay and duplex soil profiles. In order to improve the prediction of θ dynamics, a more robust physical model could be used. In addition, correction of the diurnal effects of ECa data and redefining the model and measurement errors of the EnFK to account for the temporal dependence should be considered.

Propagation and arrest of cleavage cracks in a nuclear pressure vessel steel

The safety of nuclear structures is crucial while the service time of nuclear power stations is planned to be extended up to 60years. Initiation stage of cracks is still considered as a key issue, but more and more component integrity analyses investigate the crack arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Experiments using standard measuring techniques and a high-speed framing camera system, as well as Scanning Electron Microscope fracture surface analyses were carried out on thin CT specimens made of 16MND5 PWR vessel steel. The elastic–viscoplastic behavior of the ferritic steel has been studied and taken into account in numerical simulations. The eXtended Finite Element Method (X-FEM) is used in CAST3M finite element analysis software to model crack propagation. Numerical computations combine a local non-linear dynamic approach and a fracture criterion based on critical cleavage stress, whereas current standards in the nuclear field use a global static approach to fracture to depict crack initiation and arrest. The links of the criterion with temperature and strain rate are considered thanks to experiments, SEM fractographies and 2D computations in order to get a robust physical model which can be effective for model-based predictions of industrial structures.

Spherical harmonic analysis of particle velocity distribution function: Comparison of moments and anisotropies using Cluster data

This paper presents a spherical harmonic analysis of the plasma velocity distribution function using high‐angular, energy, and time resolution Cluster data obtained from the PEACE spectrometer instrument to demonstrate how this analysis models the particle distribution function and its moments and anisotropies. The results show that spherical harmonic analysis produced a robust physical representation model of the velocity distribution function, resolving the main features of the measured distributions. From the spherical harmonic analysis, a minimum set of nine spectral coefficients was obtained from which the moment (up to the heat flux), anisotropy, and asymmetry calculations of the velocity distribution function were obtained. The spherical harmonic method provides a potentially effective “compression” technique that can be easily carried out onboard a spacecraft to determine the moments and anisotropies of the particle velocity distribution function for any species. These calculations were implemented using three different approaches, namely, the standard traditional integration, the spherical harmonic (SPH) spectral coefficients integration, and the singular value decomposition (SVD) on the spherical harmonic methods. A comparison among the various methods shows that both SPH and SVD approaches provide remarkable agreement with the standard moment integration method.

Insights into Magma Genesis at Convergent Margins from U-series Isotopes

Convergent margins (oceanic and continental arcs) form one of the Earth’s key mass transfer locations, being sites where melting and transfer of new material to the Earth’s crust occurs and also where crustal materials, including water, are recycled back into the mantle. Volcanism in this tectonic setting constitutes ~15% (0.4–0.6 km3/yr) of the total global output (Crisp 1984) and the composition of the erupted magmas is, on average, similar to that of the continental crust (Taylor and McLennan 1981). Moreover, many arc volcanoes have been responsible for the most hazardous, historic volcanic eruptions. Yet, despite their importance, many fundamental aspects of convergent margin magmatism remain poorly understood. Key among these are the rates of processes of fluid addition from the subducting plate. Furthermore, in stark contrast to the ocean ridges, where adiabatic decompression provides a simple and robust physical model for partial melting, no consensus has yet been reached about the physics of the partial melting process and the mechanism of melt extraction beneath arcs. Preceding chapters concerned with partial melting in this volume (Lundstrom 2003; Bourdon and Sims 2003) have discussed how the differing half-lives and distribution coefficients of the various U-series nuclides result in disequilibria through in-growth. This provides important information on the nature and timing of mantle partial melting processes. In convergent margin settings the differential fluid mobility of U and Ra relative to Th and Pa provides an additional source of fractionation leading to in-growth and this is crucial to understanding the timing and mechanisms of fluid addition. Here we review the role that the proliferation of high quality U-series isotope data, over the last decade, have had in obtaining precise information on time scales and the development of quantitative physical models for convergent margin magmatism. Our approach is to use trace element …