Momentum Space Research Articles

Pre-eruptive intramural resorption in unerupted teeth: a cone-beam computed tomography evaluation of prevalence and related factors

ObjectivePre-eruptive intramural resorption (PEIR) is defined as an abnormal, well-circumscribed radiolucency within the coronal dentin of the tooth, which is often overlooked in plain radiographs. This study aimed to investigate the prevalence of PEIR and its related factors using cone-beam computed tomography (CBCT).MethodsCBCT images of 590 unerupted teeth were evaluated for the presence of PEIR, location of PEIR, number of lesions in the affected tooth, PEIR score, tooth angulation, tooth position, and pericoronal space. Binary logistic tests were used to analyze the association between the characteristics of PEIR and the patient’s demographic data and related factors.ResultsThe tooth prevalence of PEIR was 13.6% among unerupted teeth. However, it was noteworthy that 19.2% of the unerupted teeth with PEIR were planned to be kept. PEIR was significantly associated with transverse (p = 0.020), inverted-angulated (p = 0.035), and centrally-positioned teeth (p = 0.043). The severity of PEIR was more pronounced in teeth with distal (p = 0.019), lingual (p = 0.023), or inverted-angulated (p = 0.040) positions, and in the absence of pericoronal space (p = 0.036).ConclusionPEIR should be suspected in transverse, inverted-angulated, centrally positioned unerupted teeth, particularly in molars, with no pericoronal space. Further monitoring through CBCT is recommended in such cases.Clinical relevanceThe management of unerupted teeth does not always involve surgical removal. Instead, they could be utilized for artificial eruption or tooth transplantation. The present study emphasizes the significance of early detection of PEIR. Clinical recommendations for screening PEIR in unerupted teeth are also proposed, which can be applied to routine plain radiographs.

Motion of Two-Dimensional Excitons in Momentum Space Leads to Pseudospin Distribution Narrowing on the Bloch Sphere.

Motional narrowing implies narrowing induced by motion; for example, in nuclear magnetic resonance, the thermally induced random motion of the nuclei in an inhomogeneous environment leads to a counterintuitive narrowing of the resonance line. Similarly, the excitons in monolayer semiconductors experience magnetic inhomogeneity: the electron-hole spin-exchange interaction manifests as an in-plane pseudomagnetic field with a periodically varying orientation inside the exciton band. The excitons undergo random momentum scattering and pseudospin precession repeatedly in this inhomogeneous magnetic environment, typically resulting in fast exciton depolarization. On the contrary, we show that such magnetic inhomogeneity averages out at high scattering rates due to motional narrowing. Physically, a faster exciton scattering leads to a narrower pseudospin distribution on the Bloch sphere, implying a nontrivial improvement in exciton polarization. The in-plane nature of the pseudomagnetic field enforces a contrasting scattering dependence between the circularly and linearly polarized excitons, providing a spectroscopic way to gauge the sample quality.

Niche-based approach to explore the impacts of environmental disturbances on biodiversity.

Globally, species are increasingly at risk from compounding threatening processes, an increasingly prominent driver of which is environmental disturbances. To facilitate effective conservation efforts following such events, methods that evaluate potential impacts across multiple species and provide landscape-scale information are needed to guide targeted responses. Often, the geographic overlap between a disturbance and species' distribution is calculated and then used as a proxy for potential impact. However, such methods do not account for the important influence of environmental heterogeneity throughout species' ranges. To address this shortcoming, we quantified the effects of environmental disturbances on species' environmental niche space. Using the Australian 2019 and 2020 Black Summer fires as a case study, we applied a niche-centric approach to examine the potential impacts of these fires on 387 vertebrate species. We examined the utility of established and novel niche metrics to assess the potential impacts of large-scale disturbance events on species by comparing the potential effects of the fires as determined by our various niche measures to those derived from geographic-based measures of impact. We examined the quality of environmental space affected by the disturbance by quantifying the position in niche space where the disturbance occurred (center or margin), the uniqueness of the environmental space that was burned, and the degree to which the remaining, unburned portion of the niche differed from a species' original prefire niche. There was limited congruence between the proportion of geographic and niche space affected, which showed that geographic-based approaches in isolation may have underestimated the impact of the fires for 56% of modeled species. For each species, when combined, these metrics provided a greater indication of postdisturbance recovery potential than geographic-based measures alone. Accordingly, the integration of niche-based analyses into conservation assessments following large-scale disturbance events will lead to a more nuanced understanding of potential impacts and guide more informed and effective conservation actions.

On the Relative Kinematics and Control of Dual-Arm Cutting Robots for a Coal Mine

There is an unbalanced problem in the traditional laneway excavation process for coal mining because the laneway excavation and support are at the same position in space but they are separated in time, consequently leading to problems of low efficiency in laneway excavation. To overcome these problems, an advanced dual-arm tunneling robotic system for a coal mine is developed that can achieve the synchronous operation of excavation and the permanent support of laneways to efficiently complete excavation tasks for large-sized cross-section laneways. A dual-arm cutting robot (DACR) has an important influence on the forming quality and excavation efficiency of large-sized cross-section laneways. As a result, the relative kinematics, workspace, and control of dual-arm cutting robots are investigated in this research. First, a relative kinematic model of the DACR is established, and a closed-loop control strategy for the robot is proposed based on the relative kinematics. Second, an associated workspace (AW) for the DACR is presented and generated, which can provide a reference for the cutting trajectory planning of a DACR. Finally, the relative kinematics, closed-loop kinematic controller, and associated workspace generation algorithm are verified through simulation results.

ГЛАГОЛЫ ПОЛОЖЕНИЯ В ПРОСТРАНСТВЕ И ИХ СОЧЕТАЕМОСТЬ

The article considers a group of verbs of position in space and their compatibility with abstract nouns in the role of the subject. The article notes that the verbs of position in space with this combination acquire a more generalized meaning

Structural Chirality and Electronic Chirality in Quantum Materials

In chemistry and biochemistry, chirality represents the structural asymmetry characterized by nonsuperimposable mirror images for a material such as DNA. In physics, however, chirality commonly refers to the spin–momentum locking of a particle or quasiparticle in the momentum space. While seemingly disconnected, structural chirality in molecules and crystals can drive electronic chirality through orbital–momentum locking; that is, chirality can be transferred from the atomic geometry to electronic orbitals. Electronic chirality provides an insightful understanding of chirality-induced spin selectivity, in which electrons exhibit salient spin polarization after going through a chiral material, and electrical magnetochiral anisotropy, which is characterized by diode-like transport. It further gives rise to new phenomena, such as anomalous circularly polarized light emission, in which the light handedness relies on the emission direction. These chirality-driven effects will generate broad impacts for fundamental science and technology applications in spintronics, optoelectronics, and biochemistry.

“Varus knee dysfunction contributing to early medial knee arthritis: Novel pathomechanics, diagnosis and multi-modal conservative interventions”

ObjectiveEvaluate whether the three-planar spring test and pathomechanics-based interventions (manual therapy, strengthening, orthosis) increase the range of motion and explore potential changes in joint space of varus knee dysfunction, further investigating their potential association with the early development of medial knee arthritis (MKA). MethodsSingle group, pre-and post-test design. Adults (n = 54) exhibiting a positive spring test for varus knee dysfunction, characterised by extension lag with proximal tibia externally rotated and subluxed laterally, completed the study. Outcome measures include pain intensity, ROM, functional abilities and X-ray measures (joint space, tilt, and tibia position relative to the femur) following the interventions. ResultsAfter interventions, the spring test has become negative at the pre-assessment range. There is an increased ROM [internal rotation by 3.61° (95CI 3.22, 4.01) and extension by 3.92° (95CI −4.51, −3.33)], and X-ray measurements showed an increase in both medial and lateral joint space by 0.78 mm (95CI 0.63, 0.92) and 0.13 mm (95CI −0.03, 0.24) respectively. Additionally, total joint space expansion happened by 0.28 ± 0.23 mm. The proximal tibia medially shifted by 0.85 ± 0.96 mm, and the medial tilt was reduced by 1.79°±1.28°. A significant decrease in pain by five points (NPRS) and an increase in the overall functional abilities of participants by 36.9 points (95CI 34.72, 39.09). ConclusionThe study results indicate that diagnosis with a spring test and interventions have increased the medial joint space and ROM, possibly improved alignment and synovial fluid, contributing to decreasing the pain and improving the functional abilities, thereby supporting the study's objective.

Strain-induced fabrication of anisotropic nanopores by in-situ E-beam irradiation

Anisotropic nanopores are essential to regulate materials' anisotropic performance including thermal conductivity, ion blocking and so on. Nevertheless, fabricating anisotropic nanopores remains challenging because the formation mechanism is ambiguous, due to the lack of direct experimental evidence. Here, we reveal a unique strain-induced mechanism for the fabrication of anisotropic nanopores under electron beam irradiation. With the in-situ transmission electron microscopy (TEM) technique, an initial symmetric nanopore, with another nanopore nearby, is found to expand relatively uniformly in the first stage. When the spacing between two nanopores reaches to a critical point, however, the area near to the reference nanopore is stretched drastically by a strong driving force along the spacing direction, resulting in an obvious anisotropic morphology. The surrounding environment, spacing and relative position between two nanopores significantly influence the shape of eventually formed nanopores by controlling the strain's uniformity, action range and direction, respectively. Our work demonstrates a novel mechanism and visual evidence for the preparation of asymmetric nanopores in real time, with the hope of assisting in the controllable fabrication of desired nanostructures.

Handbook of derivative AdS amplitudes

In the 2022 study, together with Paul McFadden and Kostas Skenderis, I analyzed tree-level 3- and 4-point Witten diagrams (amplitudes) of scalar operators in anti-de Sitter space in momentum space. This paper constitutes its extension to Witten diagrams with bulk interactions involving spacetime derivatives. In d = 3 boundary dimensions the Witten diagrams involving conformally coupled and massless scalars can be evaluated in closed form. Such cases are of interest in holographic cosmology and correspond to dual operators of conformal dimensions ∆ = 2 and 3 respectively. I present explicit formulae for all such amplitudes and provide a Mathematica package serving as the repository of all the results. I discuss renormalization issues and show that, contrary to the expectation, even finite correlators may acquire non-trivial renormalization effects.

Research on Wireless Multimedia Big Data Transmission Model Based on Non-linear Algebraic Equation with the Adaptive Scheduling Algorithm

With the rapid development of computer technology, image processing and automatic book recognition has become a very important and practical field, and this discipline has a broad prospect and great potential. The digital vision system is a multi-plane information analysis method based on the human brain, which is applied to library identification problems by studying several regular changes in the distribution of objects themselves in two-dimensional space and three-dimensional position, in order to improve book quality and reduce costs. In addition, digital reading devices have become an essential part of people's daily learning life, and multimedia retrieval methods have also undergone radical changes, image processing is becoming more and more complex, and algorithms must become more efficient and reliable as the amount of computing increases to a certain level, so as to adapt to this fast and powerful data storage and query needs. Therefore, the trend is to improve the speed and reliability of computer systems. In this research, we provide a nonlinear model of optimal allocation employing an ant colony management strategy, a genetic operator, and an adaptive scheduling algorithm based on topology (dB) to discover the best scheduling scheme and test its feasibility via simulation. It proposes a viable idea for tackling the practical wireless multimedia massive data transmission model problem by applying the method to the real-time processing process in other sectors with high importance and resilience. 

Development of dual-beamline photoelectron momentum microscopy for valence orbital analysis.

The soft X-ray photoelectron momentum microscopy (PMM) experimental station at the UVSOR Synchrotron Facility has been recently upgraded by additionally guiding vacuum ultraviolet (VUV) light in a normal-incidence configuration. PMM offers a very powerful tool for comprehensive electronic structure analyses in real and momentum spaces. In this work, a VUV beam with variable polarization in the normal-incidence geometry was obtained at the same sample position as the soft X-ray beam from BL6U by branching the VUV beamline BL7U. The valence electronic structure of the Au(111) surface was measured using horizontal and vertical linearly polarized (s-polarized) light excitations from BL7U in addition to horizontal linearly polarized (p-polarized) light excitations from BL6U. Such highly symmetric photoemission geometry with normal incidence offers direct access to atomic orbital information via photon polarization-dependent transition-matrix-element analysis.

Helicity-Sensitive Terahertz Detection in Monolayer 1T'-WTe2.

Valleytronics, identified as electronic properties of the energy band extrema in momentum space, has been intensively revived following the emergence of two-dimensional transition metal dichalcogenides (TMDCs) as their valley information can be controlled and probed through the spin angular momentum of light. Previous optical investigations of valleytronics have been limited to the visible/near-infrared spectral regime through which the carriers of most TMDCs can be excited. Monolayer 1T'-WTe2 with broken time-reversal symmetry provides a fertile platform to study the long-wavelength photonic properties in different valleys. Here, we employed a circularly polarized terahertz (THz) laser to selectively excite the valley of monolayer 1T'-WTe2 and demonstrate that the helicity-dependent photoresponse is generated via the photogalvanic effect (PGE). We also observed that the photocurrent is controlled by circular polarization and the external electric field. Because of the tunable Berry curvature dipole derived from the nontrivial wave functions near the inverted gap edge in monolayer WTe2, the bandgap can be tuned efficiently. Our results provide a versatile venue for controlling, detecting, and processing valleytronics and applications in on-chip THz imaging and quantum information processing.

Impact of the N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} Short-Range Three-Nucleon Force Components on the Nucleon-Deuteron Spin Correlation Coefficients

The spin correlation coefficients in the neutron-deuteron elastic scattering process at incoming neutron laboratory energies E=10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {E}=10$$\\end{document}, 135, 190, and 250 MeV are determined by solving the momentum space three-nucleon (3N) Faddeev equations. The chiral two-nucleon (2N) interaction with momentum-space semi-local (SMS) regularization up to the fifth order of chiral expansion (N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document}), supplemented by the F-waves terms from the sixth order (N5LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^5\\hbox {LO}$$\\end{document}), is used. Additionally, the consistent 3N force (3NF) at the third order of chiral expansion, supplemented by the short-range contributions from N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} is applied. As a results, we give predictions for the complete set of spin correlation coefficients Cα,β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C_{\\alpha ,\\beta }$$\\end{document}. We find that the effect of the investigated three-nucleon N4LO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}^4\\hbox {LO}$$\\end{document} components amounts up to several dozen percent, depending on reaction energy, scattering angle and type of spin correlation coefficient itself. Our results can serve as a guide for future measurements of the spin correlation coefficients.

Probing the tunable multi-cone band structure in Bernal bilayer graphene

Bernal bilayer graphene (BLG) offers a highly flexible platform for tuning the band structure, featuring two distinct regimes. One is a tunable band gap induced by large displacement fields. Another is a gapless metallic band occurring at low fields, featuring rich fine structure consisting of four linearly dispersing Dirac cones and van Hove singularities. Even though BLG has been extensively studied experimentally, the evidence of this band structure is still elusive, likely due to insufficient energy resolution. Here, we use Landau levels as markers of the energy dispersion and analyze the Landau level spectrum in a regime where the cyclotron orbits of electrons or holes in momentum space are small enough to resolve the distinct mini Dirac cones. We identify the presence of four Dirac cones and map out topological transitions induced by displacement field. By clarifying the low-energy properties of BLG bands, these findings provide a valuable addition to the toolkit for graphene electronics.

The Explicit Form of the Unitary Representation of the Poincaré Group for Vector-Valued Wave Functions (Massive and Massless), with Applications to Photon Localization and Position Operators

We geometrically derive the explicit form of the unitary representation of the Poincaré group for vector-valued wave functions and use it to apply speed-of-light boosts to a simple polarization basis to end up with a Hawton–Baylis photon position operator with commuting components. We give explicit formulas for other photon boost eigenmodes. We investigate the underlying affine connections on the light cone in momentum space and find that while the Pryce connection is metric semi-symmetric, the flat Hawton–Baylis connection is not semi-symmetric. Finally, we discuss the localizability of photon states on closed loops and show that photon states on the circle, both unnormalized improper states and finite-norm wave packet smeared-over washer-like regions are strictly localized not only with respect to Hawton–Baylis operators with commuting components but also with respect to the noncommutative Jauch–Piron–Amrein POV measure.

Compensated Ferrimagnets with Colossal Spin Splitting in Organic Compounds.

The study of the magnetic order has recently been invigorated by the discovery of exotic collinear antiferromagnets with time-reversal symmetry breaking. Examples include altermagnets and compensated ferrimagnets, which show spin splittings of the electronic band structures even at zero net magnetization, leading to several unique transport phenomena, notably spin-current generation. Altermagnets demonstrate anisotropic spin splitting, such as d-wave, in momentum space, whereas compensated ferrimagnets exhibit isotropic spin splitting. However, methods to realize compensated ferrimagnets are limited. Here, we demonstrate a method to realize a fully compensated ferrimagnet with isotropic spin splitting utilizing the dimer structures inherent in organic compounds. Moreover, based on abinitio calculations, we find that this compensated ferrimagnet can be realized in the recently discovered organic compound (EDO-TTF-I)_{2}ClO_{4}. Our findings provide an unprecedented strategy for using the dimer degrees of freedom in organic compounds to realize fully compensated ferrimagnets with colossal spin splitting.

Complex translation methods and its application to resonances for quantum walks

In this paper, some properties of resonances for multi-dimensional quantum walks are studied. Resonances for quantum walks are defined as eigenvalues of complex translated time evolution operators in the pseudo momentum space. For some typical cases, we show some results of existence or nonexistence of resonances. One is a perturbation of an elastic scattering of a quantum walk which is an analogue of classical mechanics. Another one is a shape resonance model which is a perturbation of a quantum walk with a non-penetrable barrier.

Predicting neural activity of whole body cast shadow through object cast shadow in dynamic environments.

Shadows, as all other objects that surround us, are incorporated into the body and extend the body mediating perceptual information. The current study investigates the hypothesis according to which the perception of object shadows would predict the perception of body shadows. 38 participants (19 males and 19 females) aged 23 years on average were immersed into a virtual reality environment and instructed to perceive and indicate the coincidence or non coincidence between the movement of a ball shadow with regard to ball movement on the one hand, and between their body shadow and their body position in space on the other. Their brain activity was recording via a 32-channel EEG system, in which beta (13.5-30 Hz) oscillations were analyzed. A series of Multiple Regression Analysis (MRA) revealed that the beta dynamic oscillations patterns of the bilateral occipito-parieto-frontal pathway associated with the perception of ball shadow appeared to be a significant predictor of the increase in beta oscillations across frontal areas related to the body shadow perception and the decrease in beta oscillations across frontal areas connected to the decision making of the body shadow. Taken together, the findings suggest that inferential thinking ability relative to body shadow would be reliably predicted from object shadows and that the bilateral beta oscillatory modulations would be indicative of the formation of predictive neural frontal assemblies, which encode and infer body shadow neural representation, that is, a substitution of the physical body.

Spectrum conversion and pattern preservation of Airy beams in fractional systems with a dynamical harmonic-oscillator potential

We investigate the dynamics of optical Airy beams in the one-dimensional fractional Schrödinger equation with a harmonic-oscillator (HO) potential subjected to modulation along the propagation distance. Deriving general solutions for propagating beams and particular solutions for Airy waves with/without chirp, we study analytically the spectrum conversion and pattern preservation for the chirp-free and chirped Airy beams in the fractional system including the HO potential with moiré-lattice, hyperbolic-secant, and delta-functional modulation formats. For the HO-moiré-lattice potential, it is found that the chirp-free Airy beam experiences multiple spectrum conversions between the Airy and Gaussian patterns in the momentum space, preserving the Airy pattern in the coordinate space. The chirp magnitude of the chirped Airy beam determines whether the spectrum conversion occurs in the momentum space, and the splitting and evolution direction of the beam in the coordinate space. For the HO-hyperbolic-secant potential, the chirp-free Airy beam undergoes spectrum conversion and tunneling, with the positions of the spectrum conversion and tunneling significantly depending on parameters of the hyperbolic-secant potential; however, the spectrum conversion and pattern preservation of the chirped Airy beam occurs only under a certain relation of the chirp and parameters of the potential. In the case of the HO-delta-functional potential, the chirp-free Airy beam experiences abrupt spectrum conversion and a two-step spectrum shift; however, for the chirped Airy beam, the spectrum conversion is affected by the relation between the chirp and height of the potential. Effects of the fractional Lévy index on the spectrum conversion and pattern preservation of the Airy beams under the action of the three modulation patterns considered here are also explored in detail.

Real-Time Ab Initio Investigation on Hot Electron Relaxation Dynamics in Silicon.

The relaxation of hot electrons in semiconductors is pivotal for both energy harvesting processes and optoelectronics. Utilizing a self-developed non-adiabatic molecular dynamics simulation approach in the momentum space (NAMD_k), we have examined the dynamics of hot electrons in silicon. Whether excited from the Γ or L point, the relaxation dynamics exhibit two distinct stages. Initially, within 100 fs, electrons scatter with phonons throughout the Brillouin zone. Subsequently, over a few picoseconds, they further relax toward the conduction band minimum as a whole. This picture of hot electron relaxation is highly consistent with the quasi-equilibrium hot electron ensemble (HEE) concept. Throughout the hot electron relaxation process, energy transfer to phonons is efficient, leading to time-dependent phonon excitation, which is thoroughly analyzed. This investigation provides a novel perspective on hot electron relaxation in silicon, which holds substantive implications for the realm of photovoltaic and optoelectronic device applications.