Physical Basis Research Articles

GABAA receptor subunit M2-M3 linkers have asymmetric roles in pore gating and diazepam modulation

GABAA receptors (GABAARs) are neurotransmitter-gated ion channels critical for inhibitory synaptic transmission as well as the molecular target for benzodiazepines (BZDs), one of the most widely prescribed class of psychotropic drugs today. Despite structural insight into the conformations underlying functional channel states, the detailed molecular interactions involved in conformational transitions and the physical basis for their modulation by BZDs are not fully understood. We previously identified that alanine substitution at the central residue in the α1 subunit M2-M3 linker (V279A) enhances the efficiency of linkage between the BZD site and the pore gate. Here, we expand on this work by investigating the effect of alanine substitutions at the analogous positions in the M2-M3 linkers of β2 (I275A) and γ2 (V290A) subunits, which together with α1 comprise typical heteromeric α1β2γ2 synaptic GABAARs. We find that these mutations confer subunit-specific effects on the intrinsic pore closed-open equilibrium and its modulation by the BZD diazepam (DZ). The mutations α1(V279A) or γ2(V290A) bias the channel toward a closed conformation, whereas β2(I275A) biases the channel toward an open conformation to the extent that the channel becomes leaky and opens spontaneously in the absence of agonist. In contrast, only α1(V279A) enhances the efficiency of DZ-to-pore linkage, whereas mutations in the other two subunits have no effect. These observations show that the central residue in the M2-M3 linkers of distinct subunits in synaptic α1β2γ2 GABAARs contribute asymmetrically to the intrinsic closed-open equilibrium and its modulation by DZ.

A Perspective on Plasticity, Dissipation and the Second Law of Thermodynamics

Abstract The requirement of a non-negative dissipation rate for all possible deformation histories is generally imposed on plastic constitutive relations. This is a constraint analogous to the Coleman–Noll [Coleman, B. D., and Noll, W., 1964, “The Thermodynamics of Elastic Materials With Heat Conduction and Viscosity,” Arch. Ration. Mech. Anal., 13, pp. 167–178. 10.1007/BF01262690] postulate that the Clausius–Duhem inequality needs to be satisfied for all possible deformation histories. The physical basis for the Clausius–Duhem inequality is as a statistical limit for a large number of discrete events for a long time and is not a fundamental physical requirement for small systems for a short time. The relation between the requirement of a non-negative dissipation rate and the Clausius–Duhem inequality is considered. The consequences of imposing a non-negative dissipation rate for all possible deformation histories are illustrated for: (i) a single crystal plasticity framework that accounts for elastic lattice curvature changes as well as elastic lattice straining and (ii) for discrete defect theories of plasticity, with attention specifically on discrete dislocation plasticity for crystalline solids and discrete shear transformation zone (STZ) plasticity for amorphous solids. Possible less restrictive conditions on the evolution of dissipation in plasticity formulations are considered as are implications for stability. The focus is on open questions and issues.

Evolutionary novelties underlie sound production in baleen whales.

Baleen whales (mysticetes) use vocalizations to mediate their complex social and reproductive behaviours in vast, opaque marine environments1. Adapting to an obligate aquatic lifestyle demanded fundamental physiological changes to efficiently produce sound, including laryngeal specializations2-4. Whereas toothed whales (odontocetes) evolved a nasal vocal organ5, mysticetes have been thought to use the larynx for sound production1,6-8. However, there has been no direct demonstration that the mysticete larynx can phonate, or if it does, how it produces the great diversity of mysticete sounds9. Here we combine experiments on the excised larynx of three mysticete species with detailed anatomy and computational models to show that mysticetes evolved unique laryngeal structures for sound production. These structures allow some of the largest animals that ever lived to efficiently produce frequency-modulated, low-frequency calls. Furthermore, we show that this phonation mechanism is likely to be ancestral to all mysticetes and shares its fundamental physical basis with most terrestrial mammals, including humans10, birds11, and their closest relatives, odontocetes5. However, these laryngeal structures set insurmountable physiological limits to the frequency range and depth of their vocalizations, preventing them from escaping anthropogenic vessel noise12,13 and communicating at great depths14, thereby greatly reducing their active communication range.

Energetics of the microsporidian polar tube invasion machinery.

Microsporidia are eukaryotic, obligate intracellular parasites that infect a wide range of hosts, leading to health and economic burdens worldwide. Microsporidia use an unusual invasion organelle called the polar tube (PT), which is ejected from a dormant spore at ultra-fast speeds, to infect host cells. The mechanics of PT ejection are impressive. Anncaliia algerae microsporidia spores (3-4 μm in size) shoot out a 100-nm-wide PT at a speed of 300 μm/s, creating a shear rate of 3000 s-1. The infectious cargo, which contains two nuclei, is shot through this narrow tube for a distance of ∼60-140 μm (Jaroenlak et al, 2020) and into the host cell. Considering the large hydraulic resistance in an extremely thin tube and the low-Reynolds-number nature of the process, it is not known how microsporidia can achieve this ultrafast event. In this study, we use Serial Block-Face Scanning Electron Microscopy to capture 3-dimensional snapshots of A. algerae spores in different states of the PT ejection process. Grounded in these data, we propose a theoretical framework starting with a systematic exploration of possible topological connectivity amongst organelles, and assess the energy requirements of the resulting models. We perform PT firing experiments in media of varying viscosity, and use the results to rank our proposed hypotheses based on their predicted energy requirement. We also present a possible mechanism for cargo translocation, and quantitatively compare our predictions to experimental observations. Our study provides a comprehensive biophysical analysis of the energy dissipation of microsporidian infection process and demonstrates the extreme limits of cellular hydraulics.

Revisiting renormalization group equations of the SMEFT dimension-seven operators

In this work, we revisit the renormalization group equations (RGEs) of dimension-seven (dim-7) operators in the Standard Model effective field theory (SMEFT) resulting from mixing among dim-7 operators themselves by means of the background field method. Adopting a recently proposed physical basis for dim-7 operators, we achieve the explicit RGEs of all non-redundant dim-7 operators in the SMEFT for the first time. Together with those originating from the dim-5 and dim-6 operators, these results constitute the complete RGEs of dim-7 operators, and hence can be exploited to study full RG-running effects on some lepton- or baryon-number-violating processes involving dim-7 operators in the SMEFT, such as neutrino masses, neutrinoless double beta decay, meson and nucleon decays. We perform an analysis of the structure and perturbative power counting of the obtained one-loop anomalous dimension matrix, which is consistent with a non-renormalization theorem and the naive dimension analysis. Additionally, a partial check on some results is carried out by means of different tools and quantum field gauges.

Parity violation in resonant inelastic soft x-ray scattering at entangled core holes.

Resonant inelastic x-ray scattering (RIXS) is a major method for investigation of electronic structure and dynamics, with applications ranging from basic atomic physics to materials science. In RIXS applied to inversion-symmetric systems, it has generally been accepted that strict parity selectivity applies in the sub-kilo-electron volt region. In contrast, we show that the parity selection rule is violated in the RIXS spectra of the free homonuclear diatomic O2 molecule. By analyzing the spectral dependence on scattering angle, we demonstrate that the violation is due to the phase difference in coherent scattering at the two atomic sites, in analogy with Young's double-slit experiment. The result also implies that the interpretation of x-ray absorption spectra for inversion symmetric molecules in this energy range must be revised.

A comparative study on characterizing the fracture toughness variations in thick-wall hydrogenation reactor welded joint by spherical indentation tests

This study provides an investigation on the existing models in predicting the fracture toughness distributions in thick-wall hydrogenation reactor welded joint from SITs. Three criterions, namely the critical stress, the critical strain, and the critical damage variable, were used in determining the critical indentation depth in the IEF model, together with the ERR model. Experimental results proved that none of the existing four criterions (or models) works for all zones in the welded joint. The critical stress criterion well reproduces the decrease of KIC in the weld (compared with that of the base metal) and the KIC distributions along the thickness, but may provide highly non-conservative predictions (more than 100% over-estimation). Highly stable KIC predictions were obtained from the critical strain criterion and the ERR model, but the critical strain criterion failed in characterizing weakest parts of the welded joint (i.e., the HAZ and weld) as assuming all zones with the same plasticity, and the ERR model failed in characterizing one of the weakest parts (i.e., weld) due to the existence of initial damage. Compared with the critical strain criterion and the ERR model, highly instable prediction results were observed in the CDV criterion, with the maximum error exceeds 50%. Source of errors in the existing fracture toughness prediction models were extensively explored through the physical basis of each criterion (or model) and from the solidarity of the phenomenologically summarized criterions.

Low-energy effective field theory below the electroweak scale: one-loop renormalization in the ’t Hooft-Veltman scheme

The low-energy effective field theory below the electroweak scale (LEFT) describes the effects at low energies of both the weak interaction and physics beyond the Standard Model. We study the one-loop renormalization of the LEFT in the ’t Hooft-Veltman scheme, which offers an algebraically consistent definition of the Levi-Civita symbol and γ5 in dimensional regularization. However, in connection with minimal subtraction this scheme leads to a spurious breaking of chiral symmetry in intermediate steps of the calculation. Based on the ’t Hooft-Veltman prescription, we define a renormalization scheme that restores chiral symmetry by including appropriate finite counterterms. To this end, we extend the physical LEFT operator basis by a complete set of off-shell and one-loop-evanescent operators and we perform the renormalization at one loop. We determine the finite counterterms to the physical parameters that compensate both the insertions of evanescent operators, as well as the chiral-symmetry-breaking terms from the renormalizable part of the Lagrangian in D dimensions. Our results can be applied in next-to-leading-log calculations in the ’t Hooft-Veltman scheme: using our renormalization scheme instead of pure minimal subtraction separates the physical sector from the unphysical evanescent sector and leads to results that are manifestly free of spurious chiral-symmetry-breaking terms.

Development of an Integrated Basic Physics Textbook of Al-Qur'an Verses with Social Conten

Development of an Integrated Basic Physics Textbook of Al-Qur'an Verses with Social Conten

Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system

Studies have been performed on the release mechanism for large pellets using high pressure gas in a shattered pellet injector. Typically, pellets are dislodged from the cryogenic surface and accelerated down a barrel using high pressure gas delivered by a fast-acting propellant valve. The pellets impact an angled surface which shatters the pellet into many small fragments before entering the plasma. This technique was initially demonstrated on DIII-D (Commaux et al 2016 Nucl. Fusion 56 046007) and is now deployed on JET, KSTAR, ASDEX-Upgrade, and other tokamaks around the world in support of ITER’s disruption mitigation system design and physics basis. The large hydrogen, 28.5 mm diameter, 2 length-to-diameter ratio, pellets foreseen for ITER SPI operation have low material strength and low heat of sublimation, which cause the pellets to be fragile and highly reactive to the impact of warm propellant gas. Due to the size of the pellets, significantly more propellant gas is required to dislodge and accelerate them. This creates a potentially significant propellant gas removal issue as 2–6 bar-L of gas is expected to be required for release and speed control. The research presented in this paper is an in-depth exploration of the parameters that are keys to reliable pellet release and speed control. Computational fluid dynamics (CFD) modeling of propellant flows through various breech designs was conducted to determine the force generated on the back surface of a pellet. These simulations assumed the use of the ORNL designed flyer plate valve. CFD modeling combined with experimental measurements provide adequate insight to determine a path to an optimal valve and breech design for ITER SPI pellet release and speed control while minimizing propellant gas usage.

Classification, main types of structures and purpose of capillary means to ensure fuel perfection

The flight of a spacecraft is characterized by the alternation of active sections of the trajectory, when the propulsion system is operating, and passive sections, in which the liquid components of the fuel in the tanks are under the influence of microgravity and, as a result, various disturbing factors (actions: aerodynamic forces, solar wind, internal gravitational forces, disturbances from the engines of the orientation and stabilization system, etc.) can occupy any position in them. At the same time, the situation is not ruled out when the gas phase can get into the flow line, which in the future can lead to a failure to restart the propulsion system and an emergency end of the mission. Therefore, an almost obligatory element of the systems for storing and supplying liquid rocket fuel components of the propulsion system of a spacecraft is the means of ensuring fuel continuity, the main criterion for the perfection of which is the amount of residual fuel components that cannot be produced due to a violation of the fluid continuity at the inlet to the propulsion system. The design of the fuel continuity means is directly determined by the internal geometry of the tank and the characteristics of the pneumohydraulic system of the spacecraft. A significant complication of the design of the fuel continuity means occurs in the presence of several factors that are present when a spacecraft performs a flight task: multiple launch and stop of the propulsion system, performing complex maneuvers under conditions of multidirectional external force impulses, which is just inherent in spacecraft. The position uncertainty and heterogeneity of the boundaries between the boost gas and fuel components at the time of launching the propulsion system require additional measures to prevent premature gas breakthrough into the flow line with its subsequent entry into the propulsion system. Therefore, over more than five decades, fuel continuity tools have been developed, the operation of which is based on various principles. At the same time, capillary-type fuel continuity means are most widely used. During this time, the basic physical principles of the behavior of a liquid under the action of capillary forces under weightless conditions were studied, the main types of designs of means for ensuring fuel continuity were determined, and the range of tasks they solved was described.

Hypobaric type oxygenators - physics and physiology.

Brain injury is still a serious complication after cardiac surgery. Gaseous microemboli (GME) are known to contribute to both short and longer-term brain injury after cardiac surgery. Hypobaric and novel dual-chamber oxygenators use the physical behaviors and properties of gases to reduce GME. The aim of this review was to present the basic physics of the gases, the mechanism in which the hypobaric and dual-chamber oxygenators reduce GME, their technical performance, the preclinical studies, and future directions. The gas laws are reviewed as an aid to understanding the mechanisms of action of oxygenators. Hypobaric-type oxygenators employ a high oxygen, no nitrogen environment creating a steep concentration gradient of nitrogen out of the blood and into the oxygenator, reducing the risk of GMEs forming. Adequately powered clinical studies have never been carried out with a hypobaric or dual-chamber oxygenator. These are required before such technology can be recommended for widespread clinical use.

Enhancement of superconductivity by organic flexible substrates in NbSe2 thin flakes

The regulation of superconductivity is of great significance in basic physics and device applications. Typically superconductivity can be tuned by chemical doping, gate voltage, and pressure. The interaction between superconductivity and substrates in low-dimensional systems is concerned in recent years, but a systematic and in-depth investigation is still lacking. Here we report a systematic study concerning the influence of substrates on the performance of superconductivity in NbSe2 thin flakes. It is found that the superconducting critical temperature Tc can be enhanced when the organic flexible substrates are adopted, as compared with that using the inorganic rigid substrates. Such an enhancement is more distinct under the applied magnetic fields. The analysis combined with Raman scattering experiments shows that the improvement of superconductivity is closely related to the softening of E2g1 phonon mode, pointing out the most possible mechanism for the effect of substrates on superconductivity. Meanwhile, the involvement of organic substrate also enhances the wave number of the charge-density-wave related soft mode.

An improved axisymmetric interfacial lattice Boltzmann flux solver for large-density-ratio multiphase flows

In this paper, an improved axisymmetric interfacial lattice Boltzmann flux solver abandoning the previous predictor-corrector scheme is proposed. Unlike the previous model starting from the two-dimensional standard lattice Boltzmann method (LBM), the present method is developed using the axisymmetric LBM, which directly incorporates the axisymmetric effects into the distribution functions. As a result, the proposed solver does not need the corrector step involving complicated space derivatives. It makes this method simpler and more computationally efficient. In the present solver, the resultant governing equation is globally resolved by the finite volume method, while the fluxes are reconstructed by local application of the axisymmetric LBM. Therefore, the inconsistency between the local reconstruction and the global governing equation can be eliminated because the global equation can be strictly derived from the axisymmetric LBM, which holds stronger physical basis than the previous method. Numerical experiments about the interface capturing and the multiphase flows are conducted to test the proposed model. Results show that the present method is superior to the fractional step solver in terms of the accuracy, stability, and computational efficiency. In addition, this solver has the capacity of simulating large-density-ratio and complex interfacial change.

Development of the TALUBA Model to Increase Science, Islam, and Local Wisdom and Instill Taluba Character

This research aimed to create TALUBA learning model-assisted modules that enhance three different forms of literacy. These were the literacy of science, Islam, and indigenous wisdom. The other was to maintain honorable character. The South Kalimantan people's local characters, especially Baiman (faithful), Bauntung (fortunate), and Batuah (dignified), are known as the taluba (three ‘ba’) characters. Using the ADDIE design, this study was a research and development project. Twenty-eight students studying work and energy in Basic Physics served as the research sample. The study instruments were the validation sheets, observation sheets, test questions, and questionnaires. Tests, observations, and surveys were the methods utilized to acquire data. The Aiken formula, N-Gain, mean, and percentage were employed in the data analysis. With a value of 0.92-1.00, learning models and modules were known to be valid based on the data analysis results. In the very good category, the average application of the learning model by lecturers was 4.85, while for students, it was 4.30. According to the test findings, the N-gains for literacy in scientific, Islamic, and local wisdom were 0.93, 0.92, and 0.94 in the high group, respectively. The very good category's average taluba character was 4.61. Additionally, there was a good reaction from students to the learning models and modules. This suggests that the proposed TALUBA learning model is appropriate for lecture use.

Learning basic physics in Pharmacy Study Program with systems thinking skills needed by pharmacy students

This research is a preliminary study aimed at analyzing the methods of teaching basic physics applied in the pharmacy program, as well as its implications for the relevance of physics concepts in pharmacy courses and the development of students' system thinking skills. A cross-sectional survey method was used, employing a structured questionnaire based on the Likert scale, involving physics course instructors from private and public universities. The research findings indicate that, although basic physics has significant potential in contributing to the development of the system thinking skills required by pharmacy graduates, challenges in integrating physics concepts with pharmacy courses still exist. The pharmacy curriculum's focus on pharmaceutical and health aspects may overlook students' understanding of basic physics. Therefore, the importance of developing teaching methods and physics laboratory practices that are appropriate for the pharmacy context becomes clearer. This research concluded that there is a need for the development of more suitable learning methods for basic physics courses in the pharmacy program, with an emphasis on developing system thinking skills crucial in the field of health, and the integration of pharmacy laboratories as a learning support. This is expected to enhance the understanding of physics concepts in the pharmacy context and build relevant system thinking skills for graduates of the pharmacy program.

Comparative Analysis Accuracy ID3 Algorithm and C4.5 Algorithm in Selection of Candidates Basic Physics Laboratory Assistant

Basic Physics Laboratory is one of the supporting laboratories at Gunadarma University. Each practical activity in the laboratory is supervised by respective assistants. Therefore, a support system is needed as a basis for decision-making in determining assistant candidates. This decision-making process is processed using data mining techniques, specifically classification algorithms. The criteria or attributes used in the decision-making process include written test scores, practical test scores, presentation scores, equipment usage abilities, and interviews. The classification algorithms used in this research are ID3 and C4.5 algorithms. The tools used to implement these algorithms are RapidMiner Studio 9.10. These algorithms will generate decision trees that can be used as decision support. The aim of this research is to conduct an accuracy comparison analysis for the ID3 and C4.5 algorithms. The highest accuracy obtained will be used as a reference for determining whether assistant candidates are accepted or not. The accuracy results show that the C4.5 algorithm has the highest accuracy, precision, and recall compared to the ID3 algorithm. The determination of the highest value is done using the k-fold cross-validation model for values 2, 4, 6, 8, and 10. The C4.5 algorithm has the highest accuracy of 96.67% at k-fold value = 2.

Case Method in The Problem-Based Learning Model to Increase Student Participation in The Basic Physics Course

Today's lecture activities require more active learning. However, lecture activities in Basic Physics courses often always focus on the lecturer. This research analyzes the application of the case method in increasing student participation in the Basic Physics I course. This research is a 2 cycle of classroom action research applied to the Basic Physics I course in the 2023/2024 academic year. The research design uses a spiral model by Kemmis and McTaggart. The research results showed that there was an increase in student activity scores in cycle 1 and cycle 2, namely 38.86% (poor category) to 69.14 (fair category).

XÂY DỰNG BỘ TÌNH HUỐNG DẠY - HỌC MỘT SỐ NỘI DUNG TRONG MODULE S1.4 THEO CHƯƠNG TRÌNH ĐÀO TẠO DỰA TRÊN NĂNG LỰC CỦA TRƯỜNG ĐẠI HỌC Y HÀ NỘI

In this study, applying the theories on case-based learning, we have built a new set of 30 case studies used in teaching and learning for some contents of Module S1.4: Physical basis of life activities and applications in medicine according to the competency-based training program of Hanoi Medical University. A set of 30 case studies accompanied by 150 multiple choice questions (MCQ) is designed to suit each corresponding teaching method such as Lectures (LEC), Seminar (SEM), and Team Based Learning (TBL). The feedback from students shows that 97.1% of students agreed that the content of the cases is suitable with the goals and content of each corresponding lesson; 95.3% of students said that the situations all have a clinical context, promoting the attractiveness of the lesson. The content of the set of situations in the topic is completely new and has been built and used by lecturers of Medical Physics, Hanoi Medical University in teaching students of Hanoi Medical University recently.

Co-doped BaFe2As2 Josephson junction fabricated with a focused helium ion beam

Josephson junction plays a key role not only in studying the basic physics of unconventional iron-based superconductors but also in realizing practical application of thin-film based devices, therefore the preparation of high-quality iron pnictide Josephson junctions is of great importance. In this work, we have successfully fabricated Josephson junctions from Co-doped BaFe2As2 thin films using a direct junction fabrication technique which utilizes high energy focused helium ion beam (FHIB). The electrical transport properties were investigated for junctions fabricated with various He+ irradiation doses. The junctions show sharp superconducting transition around 24 K with a narrow transition width of 2.5 K, and a dose correlated foot-structure resistance which corresponds to the effective tuning of junction properties by He+ irradiation. Significant J c suppression by more than two orders of magnitude can be achieved by increasing the He+ irradiation dose, which is advantageous for the realization of low noise ion pnictide thin film devices. Clear Shapiro steps are observed under 10 GHz microwave irradiation. The above results demonstrate the successful fabrication of high quality and controllable Co-doped BaFe2As2 Josephson junction with high reproducibility using the FHIB technique, laying the foundation for future investigating the mechanism of iron-based superconductors, and also the further implementation in various superconducting electronic devices.