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Neo-classical Relativistic Mechanics Theory for Electrons that Exhibits Spin, Zitterbewegung, Dipole Moments, Wavefunctions and Dirac’s Wave Equation
No full textIn this work, a neo-classical relativistic mechanics theory is presented where the spin of an electron is an inherent part of its world space-time path as a point particle. The fourth-order equation of motion corresponds to the same covariant Lagrangian function in proper time as in special relativity except for an additional spin energy term. The theory provides a hidden-variable model of the electron where the dynamic variables give a complete description of its motion, giving a classical mechanics explanation of the electron’s spin, its dipole moments, and Schrödinger’s zitterbewegung, These features are also described mathematically by quantum mechanics theory, of course, but without any physical picture of an underlying reality. The total motion of the electron can be decomposed into a sum of a local spin motion about a point and a global motion of this point, called here the spin center. The global motion is sub-luminal and described by Newton’s Second Law in proper time, the time for a clock fixed at the spin center, while the total motion occurs at the speed of light c, consistent with the eigenvalues of Dirac’s velocity operators having magnitude c. The local spin motion is an inherent perpetual motion, which for a free electron is periodic at the ultra-high zitterbewegung frequency and its path is circular in a spin-center reference frame. In an electro-magnetic field, this spin motion generates magnetic and electric dipole energies through the Lorentz force on the electron’s point charge. The electric dipole energy corresponds to the spin-orbit coupling term involving the electric field that appears in the corrected Pauli non-relativistic Hamiltonian, which has long been used to explain the doublet structure of the spectral lines of the excited hydrogen atom. Pauli’s spin-orbit term is usually derived, however, from his magnetic dipole energy term, including also the effect of Thomas precession, which halves this energy. The magnetic dipole energy from Pauli’s and Dirac’s theory is twice that in the neo-classical theory, a discrepancy that has not been resolved. By defining a spin tensor as the angular momentum of the electron’s total motion about its spin center, the fundamental equations of motion can be re-written in an identical form to those of the Barut–Zanghi electron theory. This allows the equations of motion to be expressed in an equivalent form involving operators applied to a state function of proper time satisfying a neo-classical Dirac–Schrödinger spinor equation. This state function produces the dynamic variables from the same operators as in Dirac’s theory for the electron but without any probability implications. It leads to a neo-classical wave function that satisfies Dirac’s relativistic wave equation for the free electron by applying the Lorentz transformation to express proper time in the state function in terms of an observer’s space-time coordinates, showing that there is a close connection between the neo-classical theory and quantum mechanics theory for the electron’s dynamics
Stereochemical engineering yields a multifunctional peptide macrocycle inhibitor of Akt2 by fine-tuning macrocycle-cell membrane interactions
No full textMacrocycle peptides are promising constructs for imaging and inhibiting extracellular, and cell membrane proteins, but their use for targeting intracellular proteins is typically limited by poor cell penetration. We report the development of a cell-penetrant high-affinity peptide ligand targeted to the phosphorylated Ser474 epitope of the (active) Akt2 kinase. This peptide can function as an allosteric inhibitor, an immunoprecipitation reagent, and a live cell immunohistochemical staining reagent. Two cell penetrant stereoisomers were prepared and shown to exhibit similar target binding affinities and hydrophobic character but 2-3-fold different rates of cell penetration. Experimental and computational studies resolved that the ligands’ difference in cell penetration could be assigned to their differential interactions with cholesterol in the membrane. These results expand the tool kit for designing new chiral-based cell-penetrant ligands
Entropic analysis of antigen-specific CDR3 domains identifies essential binding motifs shared by CDR3s with different antigen specificities
No full textAntigen-specific T cell receptor (TCR) sequences can have prognostic, predictive, and therapeutic value, but decoding the specificity of TCR recognition remains challenging. Unlike DNA strands that base pair, TCRs bind to their targets with different orientations and different lengths, which complicates comparisons. We present scanning parametrized by normalized TCR length (SPAN-TCR) to analyze antigen-specific TCR CDR3 sequences and identify patterns driving TCR-pMHC specificity. Using entropic analysis, SPAN-TCR identifies 2-mer motifs that decrease the diversity (entropy) of CDR3s. These motifs are the most common patterns that can predict CDR3 composition, and we identify “essential” motifs that decrease entropy in the same CDR3 α or β chain containing the 2-mer, and “super-essential” motifs that decrease entropy in both chains. Molecular dynamics analysis further suggests that these motifs may play important roles in binding. We then employ SPAN-TCR to resolve similarities in TCR repertoires against different antigens using public databases of TCR sequences
A 2:1 Mean-motion Resonance Super-Jovian Pair Revealed by TESS, FEROS, and HARPS
No full textWe report the discovery of a super-Jovian 2:1 mean-motion resonance (MMR) pair around the G-type star TIC 279401253, whose dynamical architecture is a prospective benchmark for planet formation and orbital evolution analysis. The system was discovered thanks to a single-transit event recorded by the Transiting Exoplanet Survey Satellite mission, which pointed to a Jupiter-sized companion with poorly constrained orbital parameters. We began ground-based precise radial velocity (RV) monitoring with HARPS and FEROS within the Warm gIaNts with tEss survey to constrain the transiting body's period, mass, and eccentricity. The RV measurements revealed not one but two massive planets with periods of 76.80^(+0.06)_(−0.06) and 155.3^(+0.7)_(-0.7) days, respectively. A combined analysis of transit and RV data yields an inner transiting planet with a mass of 6.14^(+0.39)_(−0.42) M_(Jup) and a radius of 1.00^(+0.04)_(-0.04) R_(Jup), and an outer planet with a minimum mass of 8.02^(+0.18)_(-0.18) M_(Jup), indicating a massive giant pair. A detailed dynamical analysis of the system reveals that the planets are locked in a strong first-order, eccentricity-type 2:1 MMR, which makes TIC 279401253 one of the rare examples of truly resonant architectures supporting disk-induced planet migration. The bright host star, V ≈ 11.9 mag, the relatively short orbital period (P_b = 76.80^(+0.06)_(-0.06) days), and pronounced eccentricity (e = 0.448^(+0.028)_(-0.029)) make the transiting planet a valuable target for atmospheric investigation with the James Webb Space Telescope and ground-based extremely large telescopes
Toward a versatile spaceborne architecture for immediate monitoring of the global methane pledge
No full textThe global methane pledge paves a fresh, critical way toward carbon neutrality. However, it remains largely invisible and highly controversial due to the fact that planet-scale and plant-level methane retrievals have rarely been coordinated. This has never been more essential within the narrow window to reach the Paris target. Here we present a two-tiered spaceborne architecture to address this issue. Using this framework, we focused on the United States, China, the Middle East, and North Africa, and simultaneously uncovered methane-abundant regions and plumes. These include new super-emitters, potential leakages, and unprecedented multiple plumes in a single source. More importantly, this framework is shown to challenge official emission reports that possibly mislead estimates from global, regional, and site scales, particularly by missing super-emitters. Our results show that, in principle, the above framework can be extended to be multi-tiered by adding upcoming stereoscopic measurements and suitable artificial intelligence, and thus it is sufficiently versatile for immediate and future monitoring of the global methane pledge
Entropic Origin of Ionic Interactions in Polar Solvents
No full textImplicit solvent models that reduce solvent degrees of freedom into effective interaction potentials are widely used in the study of soft materials and biophysical systems. For electrolyte and polyelectrolyte solutions, coarse-graining the solvent degrees of freedom into an effective dielectric constant embeds entropic contributions into the temperature dependence of the dielectric constant. Properly accounting for this electrostatic entropy is essential to discern whether a free energy change is enthalpically or entropically driven. We address the entropic origin of electrostatic interactions in a dipolar solvent and provide a clarified physical picture of the solvent dielectric response. We calculate the potential of mean force (PMF) between two oppositely charged ions in a dipolar solvent using molecular dynamics and dipolar self-consistent field theory. We find with both techniques that the PMF is dominated by the entropy gain from the dipole release, owing to the diminished orientational polarization of the solvent. We also find that the relative contribution of the entropy to the free energy change is nonmonotonic with temperature. We expect that our conclusions are applicable to a broad range of problems involving ionic interactions in polar solvents
Experiments and Modeling of the Ceiling Effect with Drone-Scale Propellers
No full textAircraft designs involving aerodynamic interactions between rotors and other aerodynamic surfaces are becoming increasingly popular. Studying these interactions is key to developing good models for design and aspects of the system such as control. This paper seeks to understand the effect of obstructing the upstream of a propeller at varying distances, also called the ceiling effect, by examining in depth the canonical case of a theoretically infinite obstruction and its interaction with a propeller or actuator disk. Experimental studies of force and pressure are compared to results from computational fluid dynamics (CFD), and good agreement is shown. The CFD results are then compared against the Morillo flowfield model, and a correction is found to match the results. The data indicate that some propellers experienced a nearly twofold increase in thrust. However, a matching force on the surface develops, and the net force drops to nearly zero. The force interaction between the two nearly disappears once the separation exceeds half a propeller diameter. These results are independent of propeller size and pitch. The implemented theoretical model also has low computational cost, and it could be used to improve low-order models such as panel methods or provide a foundation for future rotor–body interaction modeling
DeepWild: Application of the pose estimation tool DeepLabCut for behaviour tracking in wild chimpanzees and bonobos
No full text1. Studying animal behaviour allows us to understand how different species and individuals navigate their physical and social worlds. Video coding of behaviour is considered a gold standard: allowing researchers to extract rich nuanced behavioural datasets, validate their reliability, and for research to be replicated. However, in practice, videos are only useful if data can be efficiently extracted. Manually locating relevant footage in 10,000 s of hours is extremely time-consuming, as is the manual coding of animal behaviour, which requires extensive training to achieve reliability.
2. Machine learning approaches are used to automate the recognition of patterns within data, considerably reducing the time taken to extract data and improving reliability. However, tracking visual information to recognise nuanced behaviour is a challenging problem and, to date, the tracking and pose-estimation tools used to detect behaviour are typically applied where the visual environment is highly controlled.
3. Animal behaviour researchers are interested in applying these tools to the study of wild animals, but it is not clear to what extent doing so is currently possible, or which tools are most suited to particular problems. To address this gap in knowledge, we describe the new tools available in this rapidly evolving landscape, suggest guidance for tool selection, provide a worked demonstration of the use of machine learning to track movement in video data of wild apes, and make our base models available for use.
4. We use a pose-estimation tool, DeepLabCut, to demonstrate successful training of two pilot models of an extremely challenging pose estimate and tracking problem: multi-animal wild forest-living chimpanzees and bonobos across behavioural contexts from hand-held video footage.
5. With DeepWild we show that, without requiring specific expertise in machine learning, pose estimation and movement tracking of free-living wild primates in visually complex environments is an attainable goal for behavioural researchers
Log-law recovery through reinforcement-learning wall model for large eddy simulation
No full textThis paper focuses on the use of reinforcement learning (RL) as a machine-learning (ML) modeling tool for near-wall turbulence. RL has demonstrated its effectiveness in solving high-dimensional problems, especially in domains such as games. Despite its potential, RL is still not widely used for turbulence modeling and is primarily used for flow control and optimization purposes. A new RL wall model (WM) called VYBA23 is developed in this work, which uses agents dispersed in the flow near the wall. The model is trained on a single Reynolds number (Reτ=10⁴) and does not rely on high-fidelity data, as the backpropagation process is based on a reward rather than an output error. The states of the RLWM, which are the representation of the environment by the agents, are normalized to remove dependence on the Reynolds number. The model is tested and compared to another RLWM (BK22) and to an equilibrium wall model, in a half-channel flow at eleven different Reynolds numbers {Reτ∈[180;10¹⁰]}. The effects of varying agents' parameters, such as actions range, time step, and spacing, are also studied. The results are promising, showing little effect on the average flow field but some effect on wall-shear stress fluctuations and velocity fluctuations. This work offers positive prospects for developing RLWMs that can recover physical laws and for extending this type of ML models to more complex flows in the future
The Low-temperature Corona in ESO 511-G030 Revealed by NuSTAR and XMM-Newton
No full textWe present the results from a coordinated XMM-Newton + NuSTAR observation of the Seyfert 1 galaxy ESO 511−G030. With this joint monitoring program, we conduct a detailed variability and spectral analysis. The source remained in a low flux and very stable state throughout the observation period, although there are slight fluctuations of flux over long timescales. The broadband (0.3–78 keV) spectrum shows the presence of a power-law continuum with a soft excess below 2 keV, a relatively narrow iron Kα emission (∼6.4 keV), and an obvious cutoff at high energies. We find that the soft excess can be modeled by two different possible scenarios: a warm (kTₑ ∼ 0.19 keV) and optically thick (τ = 18–25) Comptonizing corona or a relativistic reflection from a high-density (log[nₑ_/cm}⁻³] = 17.1-18.5) inner disk. All models require a low temperature (kTₑ ∼ 13 keV) for the hot corona