Physical Basis Research Articles

Semi-empirical water dimer model of the water vapour self-continuum within the IR absorption bands

Water vapour continuum absorption is an important component of atmospheric radiative transfer codes. It significantly impacts the radiative balance of the atmosphere, but the physical nature of this absorption remains a subject of discussion. Here the H2O self-continuum absorption is considered within the infrared absorption bands (from 50 to 11 200 cm-1) of water vapour exploiting existing measurements. Comparison of this data with the MT_CKD-3.5 continuum model, which is used in many radiative transfer codes, reveals significant quantitative and qualitative differences. New water vapour self-continuum spectra are derived from earlier FTS measurements using HITRAN-2016 in the 5300 and 7200 cm-1 bands. A previously proposed water dimer model is refined and unified based on a broad set of up-to-date experimental data on the H2O continuum. The new model, which is suitable for incorporation into radiative transfer codes, has a much firmer physical basis than existing models. It reproduces the spectral behaviour and magnitude of the in-band water vapour self-continuum for temperatures from 279 to 431 K depending on the band. Importantly, the fitted total equilibrium dimerization constant used in the updated continuum model exceeds independent estimates by a factor of 1.5–3 across the entire temperature and spectral regions studied. Possible causes for this, which are important for understanding the physical origin of the continuum, are discussed. The contribution of water dimer to the continuum is estimated to vary from 40 to 90 % depending on absorption band and temperature.

A shifting climate: New paradigms and challenges for (early career) scientists in extreme weather research

AbstractResearch on weather and climate extremes has become integral to climate science due to their increasing societal relevance and impacts in the context of anthropogenic climate change. In this perspective we examine recent changes and evolving paradigms in the study of extreme events, emphasizing the increasingly interdisciplinary nature of research and their societal implications. We discuss the importance of understanding the physical basis of extreme events and its linkages to climate impacts, highlighting the need for collaboration across multiple disciplines. Furthermore, we explore the challenge of big climate data analysis and the application of novel statistical methods, such as machine learning, in enhancing our understanding of extreme events. Additionally, we address the engagement with different stakeholder groups and the evolving landscape of climate services and private‐sector involvement. We conclude with reflections on the risks and opportunities for early career researchers in navigating these interdisciplinary and societal demands, stressing the importance of meaningful scientific engagement, and removing barriers to inclusivity and collaboration in climate research.

Self-evolving artificial intelligence framework to better decipher short-term large earthquakes

Large earthquakes (EQs) occur at surprising loci and timing, and their descriptions remain a long-standing enigma. Finding answers by traditional approaches or recently emerging machine learning (ML)-driven approaches is formidably difficult due to data scarcity, interwoven multiple physics, and absent first principles. This paper develops a novel artificial intelligence (AI) framework that can transform raw observational EQ data into ML-friendly new features via basic physics and mathematics and that can self-evolve in a direction to better reproduce short-term large EQs. An advanced reinforcement learning (RL) architecture is placed at the highest level to achieve self-evolution. It incorporates transparent ML models to reproduce magnitude and spatial location of large EQs (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_w \\ge $$\\end{document} 6.5) weeks before of the failure. Verifications with 40-year EQs in the western U.S. and comparisons against a popular EQ forecasting method are promising. This work will add a new dimension of AI technologies to large EQ research. The developed AI framework will help establish a new database of all EQs in terms of ML-friendly new features and continue to self-evolve in a direction of better reproducing large EQs.

Aesthetics or Communication?: Social Semiotic Traits of Structured Forms in Studies of “Animal Beauty”

AbstractThe article investigates basic relations between aesthetics and communication based on studies of and discussions about what has been termed “animal beauty”. The concepts beauty, aesthetics, and communication are problematised, starting from utterances’ structured form, which is seen both as the physical basis for as well as one of five key aspects in animal utterances (form, content, act, time, and space). The relational, and thus social semiotic, communicational role of this aspect is searched in different studies leading to two major claims: Firstly, that five corresponding constitutional traits or aspects, aesthetics, epistemology, ethics, temporality, and spatiality collectively form a basis for animals’ evaluation of the subjective value of utterances. The importance of each of them varies depending on what kind of communication (life-genre) they are associated with. Secondly, that aesthetics should be comprehended on four integrated levels, from micro to macro, sign, utterance, life-genre, and life-world. These four levels plus five aspects or components in utterances make up a systemic, social semiotic communicational framework which in turn is applied for inspections of studies studying “beauty”. Methodological challenges applying them are briefly discussed. An overall conclusion is that research on the evolutionary role of animal beauty should treat the aesthetics of utterances as part of the hermeneutic circle, simultaneously as categorial and relational, in other words as a constitutive part of a whole, a semiotic, species-specific socio-communicational system.

Physics basis for the divertor tokamak test facility

Abstract This paper is dealing with the physics basis used for the design of the Divertor Tokamak Test facility (DTT), under construction in Frascati (DTT 2019 DTT interim design report (2019)) Italy, and with the description of the main target plasma scenarios of the device. The main goal of the facility will be the study of the power exhaust, intended as a fully integrated core-edge problem, and eventually to propose an optimized divertor for the European DEMO plant. The approach used to design the facility is described and their main features are reported, by using simulations performed by state-of-the-art codes both for the bulk and edge studies. A detailed analysis of MHD, including also the possibility to study disruption events and Energetic Particles physics is also reported. Eventually, a description of the ongoing work to build-up a Research Plan written and shared by the full EUROfusion community is presented.

The physical basis of analog-to-digital signal processing in the EGFR system-Delving into the role of the endoplasmic reticulum.

Receptor tyrosine kinases exhibit ligand-induced activity and uptake into cells via endocytosis. In the case of epidermal growth factor (EGF) receptor (EGFR), the resulting endosomes are trafficked to the perinuclear region, where dephosphorylation of receptors occurs, which are subsequently directed to degradation. Traveling endosomes bearing phosphorylated EGFRs are subjected to the activity of cytoplasmic phosphatases as well as interactions with the endoplasmic reticulum (ER). The peri-nuclear region harbors ER-embedded phosphatases, a component of the EGFR-bearing endosome-ER contact site. The ER is also emerging as a central player in spatiotemporal control of endosomal motility, positioning, tubulation, and fission. Past studies strongly suggest that the physical interaction between the ER and endosomes forms a reaction "unit" for EGFR dephosphorylation. Independently, endosomes have been implicated to enable quantization of EGFR signals by modulation of the phosphorylation levels. Here, we review the distinct mechanisms by which endosomes form the logistical means for signal quantization and speculate on the role of the ER.

Mechanistic definition and prediction of the mass exchange coefficient between rivers and hyporheic zones: The [formula omitted] of two [formula omitted]s

Solute transport in interconnected rivers and hyporheic zones is typically modeled through dual-domain models where first-order solute mass transfer between the two domains, ΩR and ΩHZ, is represented by a coefficient α. The transient storage model (TSM) is an example of such an approach. In practice, α is determined by fitting the tails of solute tracer breakthrough curves using a TSM. This approach has led to ambiguity regarding α’s physical meaning and transferability. Here, we investigated the physical basis for α and tested it with virtual experiments through the fully coupled multiphysics model hyporheicFoam for the ΩR−ΩHZ system. hyporheicFoam explicitly simulated coupled flow and solute transport over a kilometer with centimeter-scale resolution. Model results were analyzed to calculate α following its theoretical definition directly. Using the determined α within a TSM enables accurate reproduction of solute transport, underscoring α’s physical relevance and precision.

Current state of proton therapy for tumors of the central nervous system in Spain: physical bases, indications, controversies and perspectives.

The unique biophysical properties of proton therapy (PT), regarding the precise dose distribution, a remarkable better sparing of surrounding normal tissues, and the decreasing costs have promoted the spread of this technique worldwide. In Spain, eleven new PT centers, added to the currently two in function, are expected to be available in the near future. Indications for PT are currently evolving. The suitability of PT in central nervous system tumors of the adult population has been extrapolated from the favorable experience in children and adolescents. Given the lack of appropriate randomized trials, controversies remain regarding its use in lower grade tumors, re-irradiation, and other clinical scenarios in which an a priori dose distribution benefit is expected compared to photon-based radiotherapy. PT is a reasonable option in many brain and spinal tumors associating long life expectancy, in which cognitive decline, and the appearance of radiation-induced neoplasms can be minimized.Estado actual de la terapia con protones en los tumores del sistema nervioso central en España: bases físicas, indicaciones, controversias y perspectivas.

Overview of Large Helical Device experiments of basic plasma physics for solving crucial issues in reaching burning plasma conditions

Abstract Recently, experiments on basic plasma physics issues for solving future problems in fusion energy have been performed on a Large Helical Device. There are several problems to be solved in future devices for fusion energy. Emerging issues in burning plasma are: alpha-channeling (ion heating by alpha particles), turbulence and transport in electron dominant heating helium ash exhaust, reduction of the divertor heat load. To solve these problems, understanding the basic plasma physics of (1) wave–particle interaction through (inverse) Landau damping, (2) characteristics of electron-scale (high-k) turbulence, (3) ion mixing and the isotope effect, and (4) turbulence spreading and detachment, is necessary. This overview discusses the experimental studies on these issues and turbulent transport in multi-ion plasma and other issues in the appendix.

DIFFERENCES IN FORMATIVE ASSESSMENT RESULTS OF BASIC PHYSICS 2 STUDENTS IN OFFLINE AND ONLINE LECTURES ON SPECIAL RELATIVITY THEORY MATERIAL

The research was motivated by the Galodo disaster that occurred in Tanah Datar district. This disaster has an impact on the implementation of basic physics 2 lectures at UIN Mahmud Yunus Batusangkar which must be carried out online using the Zoom application. The research was conducted on two different campuses, namely 2nd semester students at UIN Mahmud Yunus Batusangkar and UIN Imam Bonjol Padang. This study aims to determine whether there are differences in the results of formative assessments of students who conduct online and offline lectures by chatting with lecturers, teaching methods, and teaching media. This research was analyzed using a quantitative approach with a control group posttest only design. The instrument used is a formative question on special relativity material in essay form. The results of the study were analyzed using an independent sample t test which resulted in a 2 tailed sig value (0.269) > 0.05 which indicates that there is no difference in the results of students' basic physics formative assessment between students who conduct online and offline lectures on special relativity theory material. The average formative score of students is also not much different in both samples. The use of appropriate lecture methods, strategies, and media needs to be improved in basic physics 2 lectures.

Orientation-independent-DIC imaging reveals that a transient rise in depletion attraction contributes to mitotic chromosome condensation.

Genomic information must be faithfully transmitted into two daughter cells during mitosis. To ensure the transmission process, interphase chromatin is further condensed into mitotic chromosomes. Although protein factors like condensins and topoisomerase IIα are involved in the assembly of mitotic chromosomes, the physical bases of the condensation process remain unclear. Depletion attraction/macromolecular crowding, an effective attractive force that arises between large structures in crowded environments around chromosomes, may contribute to the condensation process. To approach this issue, we investigated the "chromosome milieu" during mitosis of living human cells using an orientation-independent-differential interference contrast module combined with a confocal laser scanning microscope, which is capable of precisely mapping optical path differences and estimating molecular densities. We found that the molecular density surrounding chromosomes increased with the progression from prophase to anaphase, concurring with chromosome condensation. However, the molecular density went down in telophase, when chromosome decondensation began. Changes in the molecular density around chromosomes by hypotonic or hypertonic treatment consistently altered the condensation levels of chromosomes. In vitro, native chromatin was converted into liquid droplets of chromatin in the presence of cations and a macromolecular crowder. Additional crowder made the chromatin droplets stiffer and more solid-like. These results suggest that a transient rise in depletion attraction, likely triggered by the relocation of macromolecules (proteins, RNAs, and others) via nuclear envelope breakdown and by a subsequent decrease in cell volumes, contributes to mitotic chromosome condensation, shedding light on a different aspect of the condensation mechanism in living human cells.

A physical derivation of high-flux ion transport in biological channel via quantum ion coherence

Biological ion channels usually conduct the high-flux transport of 107 ~ 108 ions·s−1; however, the underlying mechanism is still lacking. Here, by applying the KcsA potassium channel as a typical example, and performing multitimescale molecular dynamics simulations, we demonstrate that there is coherence of the K+ ions confined in biological channels, which determines transport. The coherent oscillation state of confined K+ ions with a nanosecond-level lifetime in the channel dominates each transport event, serving as the physical basis for the high flux of ~108 ions∙s−1. The coherent transfer of confined K+ ions only takes several picoseconds and has no perturbation effect on the ion coherence, acting as the directional key of transport. Such ion coherence is allowed by quantum mechanics. An increase in the coherence can significantly enhance the ion conductance. These findings provide a potential explanation from the perspective of coherence for the high-flux ion transport with ultralow energy consumption of biological channels.

Contrast-Enhanced Sonography of the Liver: How to Avoid Artifacts.

Contrast-enhanced sonography (CEUS) is a very important diagnostic imaging tool in clinical settings. However, it is associated with possible artifacts, such as B-mode US-related artifacts. Sufficient knowledge of US physics and these artifacts is indispensable to avoid the misinterpretation of CEUS images. This review aims to explain the basic physics of CEUS and the associated artifacts and to provide some examples to avoid them. This review includes problems related to the frame rate, scanning modes, and various artifacts encountered in daily CEUS examinations. Artifacts in CEUS can be divided into two groups: (1) B-mode US-related artifacts, which form the background of the CEUS image, and (2) artifacts that are specifically related to the CEUS method. The former includes refraction, reflection, reverberation (multiple reflections), attenuation, mirror image, and range-ambiguity artifacts. In the former case, the knowledge of B-mode US is sufficient to read the displayed artifactual image. Thus, in this group, the most useful artifact avoidance strategy is to use the reference B-mode image, which allows for a simultaneous comparison between the CEUS and B-mode images. In the latter case, CEUS-specific artifacts include microbubble destruction artifacts, prolonged heterogeneous accumulation artifacts, and CEUS-related posterior echo enhancement; these require an understanding of the mechanism of their appearance in CEUS images for correct image interpretation. Thus, in this group, the most useful artifact avoidance strategy is to confirm the phenomenon's instability by changing the examination conditions, including the frequency, depth, and other parameters.

Revisiting the global distribution of the exponent of the power-function complementary relationship of terrestrial evaporation: Insights from an isenthalpic index

The complementary relationship (CR) of evaporation is one of widely-used approaches in estimating terrestrial evapration (E). However, the determination of the parameter values in CR-based models remains a difficult task. This is especially true for the new power-function complementary relationship (PCR) model developed recently, in which the key parameter that accounts for the effect of moisture advection over the drying land, b, must be well calibrated with consideration of an approporiate physical basis. Here, by proposing a new isenthalpic index that can be used for determining b directly without resorting to any a priori information of global E, this study found that the resulting b values (median = 1.64, standard deviation = 0.73) are generally smaller and display a narrower range than those reported recently by Kim et al. (2024). When applied with monthly input variables of 124 FLUXNET stations, the gridded b values improve upon E estimates that employ either i) a standard value of b (=2), or; ii) a calibrated value (same for all stations). The global distribution of the gridded b values –in contrast to those obtained by Kim et al. (2024) –aligns with its physical interpretation: low values (1 < b < 2) where the effect of moisture advection is weak (i.e., permanently/periodically wet, humid regions or regions far away from any significant external moisture source) and high ones (b > 2) when strong (i.e., warm arid/semi arid regions near a sea or high mountains of abundant moisture). The gridded b values improve the calibration-free PCR that employs a constant b (=2) and a Priestley-Taylor coefficient linked to the wet-environment air temperature.

Sequence-encoded Spatiotemporal Dependence of Viscoelasticity of Protein Condensates Using Computational Microrheology.

Many biomolecular condensates act as viscoelastic complex fluids with distinct cellular functions. Deciphering the viscoelastic behavior of biomolecular condensates can provide insights into their spatiotemporal organization and physiological roles within cells. Though there is significant interest in defining the role of condensate dynamics and rheology in physiological functions, the quantification of their time-dependent viscoelastic properties is limited and mostly done through experimental rheological methods. Here, we demonstrate that a computational passive probe microrheology technique, coupled with continuum mechanics, can accurately characterize the linear viscoelasticity of condensates formed by intrinsically disordered proteins (IDPs). Using a transferable coarse-grained protein model, we first provide a physical basis for choosing optimal values that define the attributes of the probe particle, namely its size and interaction strength with the residues in an IDP chain. We show that the technique captures the sequence-dependent viscoelasticity of heteropolymeric IDPs that differ either in sequence charge patterning or sequence hydrophobicity. We also illustrate the technique's potential in quantifying the spatial dependence of viscoelasticity in heterogeneous IDP condensates. The computational microrheology technique has important implications for investigating the time-dependent rheology of complex biomolecular architectures, resulting in the sequence-rheology-function relationship for condensates.

Exploring Uncharted Territory: Spectroscopic Evidence on a Novel Tetrel Bond with -C≡C- Triple Bond.

This study presents an investigation of the 2-butynyl alcohol···CO2 adduct, combining pulsed jet Fourier transform microwave spectroscopy with quantum chemical calculations. Two distinct isomers have been observed in the pulsed jet with a relative population ratio of 3/2. It marks the first instance of microwave spectroscopic evidence, to the best of our knowledge, suggesting the existence of a CCO2···π-C≡C- tetrel bond (π-C≡C-···π*CO2 interaction) in both observed isomers. This study highlights the importance of noncovalent interactions involving CO2 in reactant complexes, paving the way for more efficient applications of CO2 by understanding the physical basis of these noncovalent bonds.

Heterarchical modelling of comminution for rotary mills: part I—particle crushing along streamlines

Rotary mills aim to effectively reduce the size of particles through a process called comminution. Modelling comminution in rotary mills is a challenging task due to substantial material deformation and the intricate interplay of particle kinematics of segregation, mixing, crushing, and abrasion. Existing particle-based simulations tend to provide predictions that cannot cope with the large number of particles within rotary mills, their wide range of sizes, and the physics dictating the crushing of individual particles. Similarly, there is currently no deterministic modelling means to determine the evolving population of particle sizes at any point in time and space within the mill. The aim of this two-part contribution is to address these gaps by advancing a framework for a novel stochastic comminution model for rotary mills, which has a well-defined deterministic continuum limit and can cope with arbitrarily large numbers of particles. This work describes the basic physics and structure of the new model within a heterarchical framework for ball and autogenous grinding mills. The primary focus of this Part I paper is to develop a computational model for the integration of motion of material along streamlines inside a mill. Coupled to this process is the kinetic physics dictating particle crushing. In a subsequent work, Part II, segregation and mixing will be added to this model such that realistic behaviour from the mill can be observed.Graphical

Physics and chemistry from parsimonious representations: image analysis via invariant variational autoencoders

Electron, optical, and scanning probe microscopy methods are generating ever increasing volume of image data containing information on atomic and mesoscale structures and functionalities. This necessitates the development of the machine learning methods for discovery of physical and chemical phenomena from the data, such as manifestations of symmetry breaking phenomena in electron and scanning tunneling microscopy images, or variability of the nanoparticles. Variational autoencoders (VAEs) are emerging as a powerful paradigm for the unsupervised data analysis, allowing to disentangle the factors of variability and discover optimal parsimonious representation. Here, we summarize recent developments in VAEs, covering the basic principles and intuition behind the VAEs. The invariant VAEs are introduced as an approach to accommodate scale and translation invariances present in imaging data and separate known factors of variations from the ones to be discovered. We further describe the opportunities enabled by the control over VAE architecture, including conditional, semi-supervised, and joint VAEs. Several case studies of VAE applications for toy models and experimental datasets in Scanning Transmission Electron Microscopy are discussed, emphasizing the deep connection between VAE and basic physical principles. Python codes and datasets discussed in this article are available at https://github.com/saimani5/VAE-tutorials and can be used by researchers as an application guide when applying these to their own datasets.

Coastal Forum: The latest sea level rise projections of the Intergovernmental Panel on Climate Change

The Intergovernmental Panel on Climate Change (IPCC) is a multi-country organization of the United Nations formed in 1988 to assess science related to climate change (IPCC 2024). In March 2023, the IPCC published its Sixth Assessment Report (AR6), its sixth assessment of climate change since its first in 1990 (IPCC 2023). IPCC (2023) and its supporting reports total almost 8,000 pages (Boehm and Schumer 2023). Hundreds of scientists from around the world worked to develop the IPCC reports, and thousands of scientists peer-reviewed the reports(Boehm and Schumer 2023; Houston 2022).A chapter of AR6 deals with the physical basis for climate change and includes sea level rise projections (Fox-Kemper et al. 2021). These projections were supported by updated projections of the contributions to sea level rise from Antarctica (Oppenheimer 2019) and Greenland (The IMBIE Team 2020). IPCC (2023) presents the final projections. Updated IPCC projections are not expected until its seventh assessment in 2029-2030. I will report on the sea level projections in AR6, and on an online tool that provides sea level rise projections for the world as a whole and at individual tide gauge locations around the world. The IPCC bases its projections on climate response to five scenarios that cover the range of possible future anthropogenic drivers of climate change. “These scenarios combine socio-economic assumptions, levels of climate mitigation, land use, and air pollution controls for aerosols” (Climate Neutral Group 2021). IPCC then determines levels of greenhouse gases(largely carbon dioxide) and temperatures to 2050 and 2100 using complex calculations that depend on how quickly humans curb greenhouse gas emissions. It estimates sea level rise using projected temperatures. Scenarios based on IPCC (2023) are summarized below.

ESR Essentials: basic physics of MR safety-practice recommendations by the European Society for Magnetic Resonance in Medicine and Biology.

The use of magnetic resonance imaging (MRI) is safe from a long-term perspective since there are no known cumulative risks for patients or personnel. However, the technique comes with several acute risks associated with the powerful electromagnetic fields that are necessary to produce medical images. These risks include, among other things, a projectile hazard, loud noise, and the risk of heating. Safe use of MRI requires knowledge about the different hazards related to MRI and organizational structured work including the implementation of routines describing a safe workflow from the referral of a patient to the signed report. In this article, the risks associated with MRI are described along with suggestions for how each risk can be minimized or eliminated. The aim of this article is to provide support for the development of, and compliance with, MRI safety routines, and to work with the technique in a safe way. The scope of this treatise does not cover specific details of implant safety, however, the physical principles described can be applied to the risk assessment of implants. Establish whether any MR contraindications apply to the patient. Evaluate means to deal with identified risks for both patients and personnel. It is imperative to always perform and document a risk-benefit assessment.