Degrees Of Freedom Research Articles

Comparing parameterized and self-consistent approaches to abinitio cavity quantum electrodynamics for electronic strong coupling.

Molecules under strong or ultra-strong light-matter coupling present an intriguing route to modify chemical structure, properties, and reactivity. A rigorous theoretical treatment of such systems requires handling matter and photon degrees of freedom on an equal quantum mechanical footing. In the regime of molecular electronic strong or ultra-strong coupling to one or a few molecules, it is desirable to treat the molecular electronic degrees of freedom using the tools of abinitio quantum chemistry, yielding an approach referred to as abinitio cavity quantum electrodynamics (ai-QED), where the photon degrees of freedom are treated at the level of cavity QED. We analyze two complementary approaches to ai-QED: (1) a parameterized ai-QED, a two-step approach where the matter degrees of freedom are computed using existing electronic structure theories, enabling the construction of rigorous ai-QED Hamiltonians in a basis of many-electron eigenstates, and (2) self-consistent ai-QED, a one-step approach where electronic structure methods are generalized to include coupling between electronic and photon degrees of freedom. Although these approaches are equivalent in their exact limits, we identify a disparity between the projection of the two-body dipole self-energy operator that appears in the parameterized approach and its exact counterpart in the self-consistent approach. We provide a theoretical argument that this disparity resolves only under the limit of a complete orbital basis and a complete many-electron basis for the projection. We present numerical results highlighting this disparity and its resolution in a particularly simple molecular system of helium hydride cation, where it is possible to approach these two complete basis limits simultaneously. In this same helium hydride system, we examine and compare the practical issue of the computational cost required to converge each approach toward the complete orbital and many-electron bases limit. Finally, we assess the aspect of photonic convergence for polar and charged species, finding comparable behavior between parameterized and self-consistent approaches.

Postpartum Acute Care Utilization in a Health Care System in the Southeastern United States.

Introduction: Postpartum acute care utilization (PACU), including visits to an emergency department, obstetric triage, or urgent care ("outpatient"), and hospital readmissions, may indicate medical complications and signal unmet health needs. Methods: We estimated the incidence of PACU and examined patterns by sociodemographic factors, pregnancy and birth characteristics, time since discharge from the birth hospitalization, and medical indications. We constructed a retrospective cohort of people aged ≥18 years who delivered ≥1 liveborn infant >20 weeks of gestation from July 1, 2021, to December 31, 2022, using electronic health record data from a quaternary maternity hospital in the Southeastern United States PACU data throughout the health care system were collected through March 31, 2023. We excluded people with a hospital stay >6 days (n = 29). Results: In this cohort of 6,041 birthing people, 11.3% had ≥1 outpatient encounters(range 0-6) and 3.2% had ≥1 hospital readmissions (range 0-4) within 12 weeks of discharge from the birth hospitalization. Median time to first outpatient PACU was 10 days post-discharge and 6 days for first hospital readmission. Among encounters for the top five medical indications, time to first postpartum acute care encounter varied by medical indication (log-rank test of equality over strata Chi-square = 69.93, degrees of freedom = 4, p < 0.0001). Complications specified during the puerperium (n = 234) and hypertension and hypertensive-related conditions complicating the puerperium (n = 87) were the two most frequent indications. Conclusion: These findings can inform efforts to direct health resources to improve postpartum health care and health outcomes.

Key point trajectory prediction method of human stochastic posture falls

ABSTRACT The human body will show very complex and diversified posture changes in the process of falling, including body posture, limb position, angle and movement trajectory, etc. The coordinates of the key points of the model are mapped to the three-dimensional space to form a three-dimensional model and obtain the three-dimensional coordinates of the key points; The construction decomposition method is used to calculate the rotation matrix of each key point, and the rotation matrix is solved to obtain the angular displacement data of the key points on different degrees of freedom. The method of curve fitting combined with the weight distribution kernel function based on self-organizing mapping theory is used to obtain the motion trajectory prediction equation of the human body falling in different degrees of freedom at random positions in three-dimensional space, determine the key point trajectory of human random fall behaviour. The experimental results show that the mapped 3D model is consistent with the real human body structure. This method can accurately determine whether the human body falls or squats randomly, and the prediction results of the key points of the human fall are consistent with the actions of the human body after the fall.

Connecting physics to systems with modular spin-circuits

AbstractAn emerging paradigm in modern electronics is that of CMOS+ $${\mathsf{X}}$$ X requiring the integration of standard CMOS technology with novel materials and technologies denoted by $${\mathsf{X}}$$ X . In this context, a crucial challenge is to develop accurate circuit models for $${\mathsf{X}}$$ X that are compatible with standard models for CMOS-based circuits and systems. In this perspective, we present physics-based, experimentally benchmarked modular circuit models that can be used to evaluate a class of CMOS+ $${\mathsf{X}}$$ X systems, where $${\mathsf{X}}$$ X denotes magnetic and spintronic materials and phenomena. This class of materials is particularly challenging because they go beyond conventional charge-based phenomena and involve the spin degree of freedom which involves non-trivial quantum effects. Starting from density matrices—the central quantity in quantum transport—using well-defined approximations, it is possible to obtain spin-circuits that generalize ordinary circuit theory to 4-component currents and voltages (1 for charge and 3 for spin). With step-by-step examples that progressively become more complex, we illustrate how the spin-circuit approach can be used to start from the physics of magnetism and spintronics to enable accurate system-level evaluations. We believe the core approach can be extended to include other quantum degrees of freedom like valley and pseudospins starting from corresponding density matrices.

THE EFFECT OF USING YOUTUBE VIDEO ON THE STUDENTS’ ABILITY IN WRITING PROCEDURE TEXT AT THE SEVENTH GRADE OF SMP SWASTA TELADAN PEMATANGSIANTAR

The purpose of this study is to find out the impact of using YouTube videos on the procedural writing skills of seventh grade students at SMP Swasta Teladan Pematangsiantar. This study focuses on the use of YouTube videos as a tool for students' writing on the topic “Making a Drink.” This study uses quantitative research with a quasi-experimental research design from Creswell. The population of this study consisted of seventh grade students of SMP Swasta Teladan Pematangsiantar, a total of 64 students. The sample of this study was divided into two groups, namely the experimental class (VII-A), consisting of 32 students who used YouTube video as a medium, and the control class (VII-B), consisting of 32 students who used only the teacher's explanation. Data were collected using writing tests for the pre-test and the final test. The researcher found that the mean of the pre-test was 52.6 in the experimental group and 56.2 in the control group. The mean of the final test in the experimental group was 75.8 and 72.1 in the control group. The t-value was determined to be 2.416, while the t-value based on degrees of freedom (df) was 1.670 for a significance level of 0.05. Since the t-value is greater than the t-value (2.416&gt;1.671). Therefore, it can be concluded that YouTube videos have a significant impact on seventh-grade students' ability of SMP Swasta Teladan Pematangsiantar to write procedural texts.

Dynamical theory for adaptive systems

Abstract The study of adaptive dynamics, involving many degrees of freedom on two separated timescales, one for fast changes of state variables and another for the slow adaptation of parameters controlling the former’s dynamics is crucial for understanding feedback mechanisms underlying evolution and learning. We present a path-integral approach à la Martin–Siggia–Rose-De Dominicis–Janssen to analyse non-equilibrium phase transitions in such dynamical systems. As an illustration, we apply our framework to the adaptation of gene-regulatory networks under a dynamic genotype-phenotype map: phenotypic variations are shaped by the fast stochastic gene-expression dynamics and are coupled to the slowly evolving distribution of genotypes, each encoded by a network structure. We establish that under this map, genotypes corresponding to reciprocal networks of coherent feedback loops are selected within an intermediate range of environmental noise, leading to phenotypic robustness.

Design and Performance of a Planetary Gearbox with Two DOFs

The article aims to describe the design and operation of a fundamentally new self-regulating planetary transmission, which, without a control system, changes the gear ratio under the influence of a variable external load. A self-regulating transmission can be created based on a kinematic chain with two degrees of freedom, having only one input. According to the laws of mechanics, such a chain has no definability of motion, since the number of inputs must be equal to the number of degrees of freedom. The equilibrium of a two-movable chain with one input can obtained by creating an additional constraint that substitutes a reaction in the instantaneous center of the intermediate link velocities by the friction moment in the hinge of the intermediate link. The friction moment creates a force constraint, which is taken into account in the equilibrium condition. The obtained equilibrium conditions ensure the definiteness of motion and the ability of self-regulation in the form of an inversely proportional dependence of the speed of the output link on the variable external load. The described method makes it possible to create a fundamentally new class of self-regulating mechanisms in all branches of technology. The interaction of kinematic and force parameters and the construction of parameter graphs was performed using the SolidWorks 2021 program with certain additions. The experimental studies performed confirm the reliability of the theoretical developments.

Development of a seat support mechanism for guiding users to an appropriate posture in a seated-style echocardiography robot

Abstract This paper proposes a seat support mechanism to solve the problem of misalignment between the chest examination and probe scanning areas when the patient is bent in a seated-style echocardiography robot. To guide the patient to an appropriate body position where their chest is within the examination range of the chest examination unit while minimizing the physical load of the patient, the posture of the patient must satisfy the three following conditions. (i) The breech must be in contact with the seat surface, (ii) the legs must be vertical to the floor, and (iii) the chest and mechanism must be parallel while the probe scanning and chest examination ranges must match. The human body was modeled to derive a posture that satisfies the aforementioned conditions for the height of each individual, and a seat support mechanism with four degrees of freedom was installed to guide the user to the derived posture. By installing this mechanism, the body load of the left biceps brachii, right biceps brachii, left latissimus dorsi, and right latissimus dorsi was reduced to 64.7%, 52.7%, 86.4%, and 80.2%, respectively. The sharpness of the image contours was improved to 103.8%.

Krylov complexity of fermion chain in double-scaled SYK and power spectrum perspective

Abstract We investigate Krylov complexity of the fermion chain operator which consists of multiple Majorana fermions in the double-scaled SYK (DSSYK) model with finite temperature. Using the fact that Krylov complexity is computable from two-point functions, the analysis is performed in the limit where the two-point function becomes simple and we compare the results with those of other previous studies. We confirm the exponential growth of Krylov complexity in the very low temperature regime. In general, Krylov complexity grows at most linearly at very late times in any system with a bounded energy spectrum. Therefore, we have to focus on the initial growth to see differences in the behaviors of systems or operators. Since the DSSYK model is such a bounded system, its chaotic nature can be expected to appear as the initial exponential growth of the Krylov complexity. In particular, the time at which the initial exponential growth of Krylov complexity terminates is independent of the number of degrees of freedom. More generally, and not limited to the DSSYK model, we systematically and specifically study the Lanczos coefficients and Krylov complexity using a toy power spectrum and deepen our understanding of those initial behaviors. In particular, we confirm that the overall sech-like behavior of the power spectrum shows the initial linear growth of the Lanczos coefficient, even when the energy spectrum is bounded.

Solving superconducting quantum circuits in Dirac's constraint analysis framework**The paper is dedicated to the memory of Professor Roman Jackiw, who apart from working in diverse branches of theoretical physics, has contributed significantly in quantization of constraint systems.

Abstract In this work we exploit Dirac's Constraint Analysis (DCA) in Hamiltonian formalism to study different types of Superconducting Quantum Circuits (SQC) in a unified way. The Lagrangian of a SQC reveals the constraints, that are classified in a Hamiltonian framework, such that redundant variables can be removed to isolate the canonical degrees of freedom for subsequent quantization of the Dirac Brackets via a generalized Correspondence Principle. This purely algebraic approach makes the application of concepts such as graph theory, null vector, loop charge, etc that are in vogue, (each for a specific type of circuit), completely redundant. The universal validity of DCA scheme in SQC, proposed by us, is demonstrated by correctly re-deriving existing results for different SQCs, obtained previously exploiting different formalisms each applicable for a specific SQC. Furthermore, we have also analysed and predicted new results for a generic form of SQC - it will be interesting to see its validation in an explicit circuit implementation.

Steering Nonlinear Chiral Valley Photons Through Optical Orbit–Orbit Coupling

AbstractTwo‐dimensional transition metal dichalcogenides feature a direct tunable bandgap and robust spin‐valley coupling, offering an additional valley degree of freedom for information carriers. While optical spin‐orbit coupling has traditionally facilitated valley manipulation, on‐chip control of nonlinear valley photons remains elusive. Here, the directional coupling of nonlinear chiral valley photons through optical orbit‐orbit coupling in monolayer tungsten disulfide at room temperature is demonstrated. The chirality of nonlinear valley photons is governed by the spin angular momentum of the pump light, adhering to nonlinear selection rules. Importantly, the coupling direction is controlled by the orbital angular momentum of the pump light, facilitated by the orbital momentum flux. This approach not only provides a novel method for manipulating the valley degree of freedom but also enhances the flexibility of directing valley photon emission and on‐chip routing. These developments hold promising prospects for advanced valley optoelectronic devices.

Materials beyond monolayers: The magnetic quasi-1D semiconductor CrSBr

AbstractThe all-surface nature of atomically thin van der Waals materials can present challenges for practical applications. Fortunately, new layered materials are on the horizon that preserve their useful properties even when thicker than a monolayer. Here, we summarize our interest in one of these emergent materials, the magnetic semiconductor CrSBr. We describe monolayer properties exhibited by this material in its bulk form, discussing how the quasi-1D electronic structure of CrSBr allows mono- or bilayer physics to be displayed even in thick crystals. Long-range magnetic order offers additional tuning with the coupled lattice, spin, orbit, and charge degrees of freedom enabling magneto-correlated phenomena. We discuss the stability of CrSBr in air and show atomic scale structural manipulation through electron beam-driven transformations. We conclude that the stability and structural amenability of CrSBr provide opportunities for imagining devices that use bulk crystals yet exploit unique magnetic and quantum confinement effects. Graphical abstract

Neural Thermodynamic Integration: Free Energies from Energy-Based Diffusion Models.

Thermodynamic integration (TI) offers a rigorous method for estimating free-energy differences by integrating over a sequence of interpolating conformational ensembles. However, TI calculations are computationally expensive and typically limited to coupling a small number of degrees of freedom due to the need to sample numerous intermediate ensembles with sufficient conformational-space overlap. In this work, we propose to perform TI along an alchemical pathway represented by a trainable neural network, which we term Neural TI. Critically, we parametrize a time-dependent Hamiltonian interpolating between the interacting and noninteracting systems and optimize its gradient using a score matching objective. The ability of the resulting energy-based diffusion model to sample all intermediate ensembles allows us to perform TI from a single reference calculation. We apply our method to Lennard-Jones fluids, where we report accurate calculations of the excess chemical potential, demonstrating that Neural TI reproduces the underlying changes in free energy without the need for simulations at interpolating Hamiltonians.

X-DoF: Automatic Degree of Freedom Subset Selection for Inverse Blocked Force Characterization

Abstract Selecting the proper set of Degrees of Freedom is essential in inverse (Blocked) Force calculation. Including too many Degrees of Freedom in the computation can lead to overfitting, resulting in inaccurate force estimations and poor prediction quality. The discrepancy arises from errors within the dataset, such as measurement noise or other artifacts. This paper presents a solution to the overfitting problem, introducing the X-DoF procedure to automatically identify the relevant subset of Blocked Force Degrees of Freedom. Its effectiveness is showcased through numerical and experimental validation and compared against regularization techniques.

Chirality-controlled second-order nonlinear frequency conversion in lithium niobate film metasurfaces

The high-quality factor resonant metasurfaces have extensive applications in enhancing nonlinear frequency conversion efficiency at the subwavelength scale. However, methods for actively modulating the frequency conversion process are limited. We design a chiral lithium niobate film metasurface and investigate the photonic spin as a new degree of freedom to dynamically control the second-order nonlinear frequency conversion, without reconfiguring the structure by using external stimuli. The chiral resonance with circular dichroism (CD) of 0.62 gives rise to a high nonlinear CD of 0.84 in second-harmonic generation efficiency. Interestingly, combining the chiral resonance and an achiral quasi-bound state in the continuum enables us to investigate the photonic-spin-controlled sum-frequency generation and the photon pair generation from the spontaneous parametric downconversion process. Owing to the ultrahigh quality factor exceeding 103 both for two resonances, the second-order nonlinear frequency conversion occurs at a wavelength region of 0.2 nm, suggesting good monochromaticity. Our work opens new, to our knowledge, avenues for practical implementation of dynamically controlled nonlinear optical devices and will find utility in holography, switchable light sources, and information processing.

Discrete and Parallel Frequency‐Bin Entanglement Generation from Quantum Frequency Comb

AbstractPhotons’ frequency degree of freedom is promising to realize large‐scale quantum information processing. Quantum frequency combs (QFCs) generated in integrated nonlinear microresonators can produce multiple frequency modes with narrow linewidth. Here, polarization‐entangled QFCs are utilized to generate discrete frequency‐bin entangled states. Fourteen pairs of polarization‐entangled photons with different frequencies are simultaneously transformed into frequency‐bin entangled states. The characteristic of frequency‐bin entanglement is demonstrated by Hong‐Ou‐Mandel interference, which can be performed with single or multiple frequency pairs in parallel. This work paves the way for harnessing large‐scale frequency‐bin entanglement and converting between different degrees of freedom in quantum information processing.

Focal volume optics for composite structuring in transparent solids

Abstract Achieving high-level integration of composite micro-nano structures with different structural characteristics through a minimalist and universal process has long been the goal pursued by advanced manufacturing research but is rarely explored due to the absence of instructive mechanisms. Here, we revealed a controllable ultrafast laser-induced focal volume light field and experimentally succeeded in highly efficient one-step composite structuring in multiple transparent solids. A pair of spatially coupled twin periodic structures reflecting light distribution in the focal volume are simultaneously created and independently tuned by engineering ultrafast laser-matter interaction. We demonstrated that the generated composite micro-nano structures are applicable to multi-dimensional information integration, nonlinear diffractive elements, and multi-functional optical modulation. This work presents the experimental verification of highly universal all-optical fabrication of composite micro-nano structures with independent controllability in multiple degrees of freedom, expands the current cognition of ultrafast laser-based material modification in transparent solids, and establishes a new scientific aspect of strong-field optics, namely, focal volume optics for composite structuring transparent solids.

Expanded Functionality and Portability for the Colvars Library.

Colvars is an open-source C++ library that provides a modular toolkit for collective-variable-based molecular simulations. It allows practitioners to easily create and implement descriptors that best fit a process of interest and to apply a wide range of biasing algorithms in collective variable space. This paper reviews several features and improvements to Colvars that were added since its original introduction. Special attention is given to contributions that significantly expanded the capabilities of this software or its distribution with major MD simulation packages. Collective variables can now be optimized either manually or by machine-learning methods, and the space of descriptors can be explored interactively using the graphical interface included in VMD. Beyond the spatial coordinates of individual molecules, Colvars can now apply biasing forces to mesoscale structures and alchemical degrees of freedom and perform simulations guided by experimental data within ensemble averages or probability distributions. It also features advanced computational schemes to boost the accuracy, robustness, and general applicability of simulation methods, including extended-system and multiple-walker adaptive biasing force, boundary conditions for metadynamics, replica exchange with biasing potentials, and adiabatic bias molecular dynamics. The library is made available directly within the main distributions of the academic software GROMACS, LAMMPS, NAMD, Tinker-HP, and VMD. The robustness of the software and the reliability of the results are ensured through the use of continuous integration with a test suite within the source repository.

Effect of Ultra-High-Pressure Treatment on Gastrodia elata Blume: Drying Characteristics, Components, and Neuroprotective Activity

Gastrodiae Rhizoma (GE), a popular food in China, is stored and consumed after steaming, which can lead to the degradation of active substances and a decrease in its quality. Therefore, this study explored the potential application of ultra-high-pressure (UHP)-assisted hot air drying in improving the quality of GE. The results indicated that UHP pre-treatment could preserve the original cross-sectional color of GE and increase the degrees of freedom of water in GE samples. Compared with traditional steaming pre-treatment (18 h), UHP pre-treatment at 500 MPa significantly shorted the time (10 h) required for the GE samples to reach drying equilibrium. Meanwhile, the UHP-assisted hot air drying method (60 °C) could reduce the activity of β-D-glucosidase and avoid the degradation of active substances. Finally, UHP pre-treatment improved the neuroprotective activity in vivo. Overall, UHP-assisted hot air drying could improve the quality of GE samples. This study provides a simple method for improving the quality of GE samples and offers a reference for subsequent research on the influence of UHP on GE.

An affine formulation of eigenstrain-based homogenization method and its application to polycrystal plasticity

Abstract Reduced order models (ROMs) are typically incorporated into concurrent multiscale approaches to allow for efficient nonlinear multiscale simulations and to alleviate high cost of direct nonlinear computational homogenization schemes. ROMs based on the ideas of transformation field analysis are among the most popular in the literature since they only require linear elastic simulations for model construction and typically have low number of degrees of freedom. However, these models have been shown to deliver overly stiff response in simulating wide range of materials. The present study focuses on mitigating this problem in the context of eigenstrain-based homogenization method (EHM) using instantaneous moduli information for polycrystal elastoviscoplasticity. For this purpose, a new EHM model is developed with the intention of using affine moduli for recomputation of the instantaneous localization tensors. The accuracy of the method is compared to the original EHM and direct crystal plasticity finite element simulations for several synthetic polycrystal microstructures, loading conditions and varying phase contrast. We show that the affine model delivers consistently softer response compared to the original EHM model. In particular, the affine model delivers notably more accurate response in the presence of high phase contrast. The affine EHM is able to capture local load redistribution through recomputation of the localization tensors.