Low-energy Domains Research Articles

Interlayer torsional sliding and strain localization in bilayer graphene

Twisted bilayer graphene can demonstrate extraordinary optical and electrical characteristics due to its interlayer interactions. The strong coupling of normal and tangential van der Waals interactions at the interface results in inhomogeneous interlayer deformations and further changes the bilayer graphene’s physical properties. Herein, theoretical and numerical models are established to study the torsional deformation behaviour of twisting a graphene flake over a rigid graphene substrate. It is found that in-plane deformations have significant influences on the interlayer potential energy density of AA stacking, but seldom affect other stacked domains. The deformation process is thus approximated by first twisting the graphene flake rigidly, and then relaxing the rigid constraints. The bilayer graphene system minimizes its energy by reducing (enlarging) the size of high-energy (low-energy) domains through additional rotations. The additional angles of the graphene flake are derived analytically based on a mechanical model following the principle of minimum potential energy. Results show that the influences of graphene film deformations get significant at small-twist-angles (typically less than 2 ∘ ). This work reveals the torsional deformation evolution mechanism of bilayer graphene and provides beneficial guidance on achieving intriguing physical properties.

SPEAR-Net: Self-Prior Enhanced Artifact Removal Network for Limited-Angle DECT

Dual-energy computed tomography (DECT) is a fully functional instrument for disease detection in clinical practice because of its ability to identify substances and quantify materials. In some practical applications, due to the limitation of scanning conditions, projection data can only be collected from a limited angle, and the consistency of measurement cannot be guaranteed. Existing dual-energy CT reconstruction methods fail to address well the severe artifacts and noise in dual-energy CT images caused by limited-angle scanning. In this paper, we proposed a Self-Prior Enhanced Artifact Removal Network (SPEAR-Net) for limited-angle DECT, which can effectively combine the complementary information in the high- and low-energy domains and self-prior information to contribute positively to the reconstruction of high-quality dual-energy CT images. The SPEAR-Net consists of an image-domain self-prior network(IP-Net), two dual-energy image-domain networks(DIP-Net), and a dual-energy sinogram-domain self-prior network(DSP-Net). Specifically, the IP-Net and DIP-Net are adopted to extract the features of the dual-energy CT reconstructed images under dual-quarter scanning as prior information. The self-prior projection obtained from the forward projection of the prior CT image is harnessed by DSP-Net to complete the dual-energy limited-angle projection data and to facilitate the performance of SPEAR-Net in removing artifacts in the reconstructed dual-energy images. Qualitative and quantitative analyses demonstrate the superior capability of SPEAR-Net in dual-energy limited-angle projection data complementation, detail preservation, and artifact removal. Two popular DECT applications, virtual non-contrast (VNC) imaging and iodine contrast agent quantification, reveal that images reconstructed by SPEAR-Net have promising clinical significance.

Effect of surface temperature on quantum dynamics of D2 on Cu(111) using a chemically accurate potential energy surface.

The effect of surface mode vibrations on the reactive scattering of D2, initialized in the ground rovibrational state (v = 0, j = 0), from a Cu(111) surface is investigated for different surface temperature situations. We adopt a time and temperature dependent effective Hamiltonian [Dutta et al., J. Chem. Phys. 154, 104103 (2021)] constructed by combining the linearly coupled many oscillator model [Sahoo et al., J. Chem. Phys. 136, 084306 (2012)] and the static corrugation model [M. Wijzenbroek and M. F. Somers, J. Chem. Phys. 137, 054703 (2012)] potential within the mean-field approach. Such an effective Hamiltonian is employed for six-dimensional quantum dynamical calculations to obtain temperature dependent reaction and state-to-state scattering probability profiles as a function of incidence energy of colliding D2 molecules. As reported in the experimental studies, the movements of surface atoms modify the dissociative scattering dynamics at higher surface temperature by exhibiting vibrational quantum and surface atoms' recoil effects in the low and high collision energy domains, respectively. Finally, we compare our present theoretical results with the experimental and other theoretical outcomes, as well as discuss the novelty of our findings.

Bayesian Spectral Deconvolution of X-Ray Absorption Near Edge Structure Discriminating between High- and Low-Energy Domains

In this paper, we propose a Bayesian spectral deconvolution considering the properties of peaks in different energy domains. Bayesian spectral deconvolution regresses spectral data into the sum of multiple basis functions. Conventional methods use a model that treats all peaks equally. However, in X-ray absorption near edge structure (XANES) spectra, the properties of the peaks differ depending on the energy domain, and the specific energy domain of XANES is essential in condensed matter physics. We propose a model that discriminates between the low- and high-energy domains. We also propose a prior distribution that reflects the physical properties. We compare the conventional and proposed models in terms of computational efficiency, estimation accuracy, and model evidence. We demonstrate that our method effectively estimates the number of transition components in the important energy domain, on which the material scientists focus for mapping the electronic transition analysis by first-principles simulation.

Red and blue shift in spherical and axisymmetric spacetimes and astrophysical constraints

We compute the red and blue shifts for astrophysical and cosmological sources. In particular, we consider low, intermediate and high gravitational energy domains. Thereby, we handle the binary system Earth–Mars as low energy landscape whereas white dwarfs and neutron stars as higher energy sources. To this end, we take into account a spherical Schwarzschild–de Sitter spacetime and an axially symmetric Zipoy–Voorhees metric to model all the aforementioned systems. Feasible outcomes come from modeling neutron stars and white dwarfs with the Zipoy–Voorhees metric, where quadrupole effects are relevant, and framing solar system objects using a Schwarzschild–de Sitter spacetime. In the first case, large \(\delta \) parameters seem to be favorite, leading to acceptable bounds mainly for neutron stars. In the second case, we demonstrate incompatible red and blue shifts with respect to lunar and satellite laser ranging expectations, once the cosmological constant is taken to Planck satellite’s best fit. To heal this issue, we suggest coarse-grained experimental setups and propose Phobos for working out satellite laser ranging in order to get more suitable red and blue shift intervals, possibly more compatible than current experimental bounds. Implications to cosmological tensions are also debated.

Effect of Light-Induced Halide Segregation on the Performance of Mixed-Halide Perovskite Solar Cells.

Light-induced halide segregation hampers obtaining stable wide-band-gap solar cells based on mixed iodide–bromide perovskites. So far, the effect of prolonged illumination on the performance of mixed-halide perovskite solar cells has not been studied in detail. It is often assumed that halide segregation leads to a loss of open-circuit voltage. By simultaneously recording changes in photoluminescence and solar cell performance under prolonged illumination, we demonstrate that cells instead deteriorate by a loss of short-circuit current density and that the open-circuit voltage is less affected. The concurrent red shift, increased lifetime, and higher quantum yield of photoluminescence point to the formation of relatively emissive iodide-rich domains under illumination. Kinetic Monte Carlo simulations provide an atomistic insight into their formation via exchange of bromide and iodide, mediated by halide vacancies. Localization of photogenerated charge carriers in low-energy iodide-rich domains and subsequent recombination cause reduced photocurrent and red-shifted photoluminescence. The loss in photovoltaic performance is diminished by partially replacing organic cations by cesium ions. Ultrasensitive photocurrent spectroscopy shows that cesium ions result in a lower density of sub-band-gap defects and suppress defect growth under illumination. These defects are expected to play a role in the development and recovery of light-induced compositional changes.

The high temperature deformation behavior of a triplex (ferrite+ austenite+ martensite) low density steel

Abstract The present work deals with the high temperature deformation behavior of Fe-11.15Mn-5.6Al-0.07C (wt.%) triplex ferrite-based lightweight steel in the temperature range of 800–1100 °C under the strain rate of 0.001 to 0.1s−1. The compressive high temperature flow curves under the various thermomechanical conditions were accompanied by a considerable fractional softening. According to the detailed microstructural analysis, the observed flow softening was discussed relying on the occurrence of dynamic strain induced transformation and dynamic recrystallization. In this respect, a sine hyperbolic Arrhenius-type constitutive model was developed considering the three dimensional variation of the materials’ constant with strain, strain rate and temperature. This provided a proper condition for accurate assessment of the strain compensation mechanisms. The capability of the modified and un-modified constitutive models in prediction of the high temperature flow behavior of experimented low density steel were compared. According to the verified model, activation energy (Q) maps were developed and discussed in correlation with the characterized microstructure evolutions. The Q-plots were divided into three domains and a transition range was recognized at ~1100–1250 K, the extent of which decreased with increasing imposed strain. The low energy domains were attributed to the (i) activation of load transition as an effective strain compensation mechanism and the occurrence of dynamic austenite to ferrite transformation, and (ii) the high dislocation annihilation rate at high temperatures.

Oil/water separation membranes with a fluorine island structure for stable high flux

Membranes with fluorine island structures consist of discrete low surface energy (LSE) domains at sub-microscale and consecutive hydrophilic domains. The former can effectively control oil fouling while the latter can provide high basic flux.

Structural and electron diffraction scaling of twisted graphene bilayers

Multiscale simulations are used to study the structural relaxation in twisted graphene bilayers and the associated electron diffraction patterns. The initial twist forms an incommensurate moiré pattern that relaxes to a commensurate microstructure comprised of a repeating pattern of alternating low-energy AB and BA domains surrounding a high-energy AA domain. The simulations show that the relaxation mechanism involves a localized rotation and shrinking of the AA domains that scales in two regimes with the imposed twist. For small twisting angles, the localized rotation tends to a constant; for large twist, the rotation scales linearly with it. This behavior is tied to the inverse scaling of the moiré pattern size with twist angle and is explained theoretically using a linear elasticity model. The results are validated experimentally through a simulated electron diffraction analysis of the relaxed structures. A complex electron diffraction pattern involving the appearance of weak satellite peaks is predicted for the small twist regime. This new diffraction pattern is explained using an analytical model in which the relaxation kinematics are described as an exponentially-decaying (Gaussian) rotation field centered on the AA domains. Both the angle-dependent scaling and diffraction patterns are in quantitative agreement with experimental observations. A Matlab program for extracting the Gaussian model parameters accompanies this paper.

Phase transition and spin-resolved transport inMoS2nanoribbons

The electronic structure and transport properties of monolayer ${\mathrm{MoS}}_{2}$ are studied using a tight-binding approach coupled with the nonequilibrium Green's function method. A zigzag nanoribbon of ${\mathrm{MoS}}_{2}$ is conducting due to the intersection of the edge states with the Fermi level that is located within the bulk gap. We show that applying a transverse electric field results in the disappearance of this intersection and turns the material into a semiconductor. By increasing the electric field the band gap undergoes a two stage linear increase after which it decreases and ultimately closes. It is shown that in the presence of a uniform exchange field, this electric field tuning of the gap can be exploited to open low energy domains where only one of the spin states contributes to the electronic conductance. This introduces possibilities in designing spin filters for spintronic applications.

Small-scale cyclic deposition in the Frasnian (Upper Devonian) of the Holy Cross Mountains, Poland

Abstract In sections exposing Frasnian limestones at five outcrops in the Holy Cross Mountains, five lithofacies (L1 to L5) that represent upper slope to basinal environments are identified. These lithofacies are characterised by dark-coloured micritic limestones-marly shale couplets with many light-coloured intercalations of fine- to coarse-grained limestones (= event beds). This lithofacies pattern characterises mostly low-energy domains punctuated by storm episodes. In addition, these upper-slope to basinal lithofacies are arranged into small-scale, coarsening-upward beds and cycles. The cycles are locally composed of fining/thinning-upward beds. The small-scale cycles have a calculated duration of 19 to 42 kyr. The differential thickness of beds and cycles within and between sections was probably caused by differential subsidence and local tectonics. Possible evidence of tectonic activity is also related to a difference in number of cycles recorded in the time-equivalent sections. The recognised cyclicity shows sea-level fluctuations and a few deepening episodes. Some of them are correlated with the Timan global eustatic events. However, local tectonics and episodic subsidence may have played a significant role in recording brief deepening pulses. Thus, low-amplitude sea-level changes were major factors in platform generation and evolution in the Frasnian of the Holy Cross Mountains modified by local, block-related subsidence.

Improving the phenomenology ofKl3form factors with analyticity and unitarity

The shape of the vector and scalar ${K}_{\ensuremath{\ell}3}$ form factors is investigated by exploiting analyticity and unitarity in a model-independent formalism. The method uses as input dispersion relations for certain correlators computed in perturbative QCD in the deep Euclidean region, soft-meson theorems, and experimental information on the phase and modulus of the form factors along the elastic part of the unitarity cut. We derive constraints on the coefficients of the parameterizations valid in the semileptonic range and on the truncation error. The method also predicts low-energy domains in the complex $t$ plane where zeros of the form factors are excluded. The results are useful for ${K}_{\ensuremath{\ell}3}$ data analyses and provide theoretical underpinning for recent phenomenological dispersive representations for the form factors.

DFT and Docking Study of Potential Transition State Analogue Inhibitors of Glycosyltransferases

Conformational behavior of the [(2S,3R,4R,5S)-3,4,5-trihydroxy-2-(phenylsulfanyl)tetrahydrofuran-2-yl]methyl sulfate anion (2), which is the potential transition state (TS) analogue of the inverting glycosyltransferases, was studied by means of two-dimensional potential-energy maps, using a density functional theory method at the B3LYP/6-31+G* level. The maps revealed the presence of eight low-energy domains which were refined at the B3LYP/6-311++G** level and led to six conformers in vacuum. In aqueous solution, two conformers dominate at equilibrium. The preferred conformers superimpose well with the transition state structure, as determined previously for glycosyltransferase GnT-I. The conformations of 2 in the active site of glycosyltransferase GnT-I were obtained by docking methods. It was found that one of the two best docking poses mimics the binding mode of TS. These results suggest that the proposed TS mimics 2 have the potential to be used as a scaffold for the design of TS analogue inhibitors.

Morphology-dependent exciton emission and energy transfer in fluorene-polymer-related fluorescent and phosphorescent composite films spin cast from a mixture of two dissimilar organic solvents

We report morphology-dependent exciton emission and energy transfer in fluorene-conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl)-related fluorescent and phosphorescent materials by using a mixture of two dissimilar organic solvents for spin-cast film formation. The electron microscopic characterizations revealed that the mixture of a high-boiling-point orthodichlorobenzene and a low-boiling-point chloroform results in a formation of both crystalline and amorphous morphological structures in fluorene-conjugated polymers. The UV-visible absorption and photoluminescence studies indicated that the low-energy crystalline phase domains, randomly distributed in the continuous high-energy amorphous phase, function as potential quantum wells. As a consequence, the mixture of two dissimilar organic solvents significantly affects the exciton emission from fluorescent fluorene-conjugated polymer and the energy transfer in phosphorescent composite of fluorene polymer and iridium complex molecules, presenting a pathway to control fluorescent and phosphorescent processes in polymer light-emitting materials.

Potential transition-state analogs for glycosyltransferases. Design and DFT calculations of conformational behavior

The structure of a previously calculated transition state (TS) was used to design the [tetrahydro-2-(methylthio)furan-2-yl]methyl phosphate dianion ( 1) as a new scaffold for transition-state analogs of reactions catalyzed by the inverting glycosyltransferases. This scaffold contains relevant features of the donor and acceptor and represents a new type of potential inhibitors for these enzymes. Available conformational space of 1 was explored using DFT quantum chemical methods by means of two-dimensional potential-energy maps calculated as a function of Φ, Ψ, and ω dihedral angles at the B3LYP/6-31+G* level. The calculated potential energy surfaces revealed the existence of several low-energy domains. Structures from these regions were refined at the 6-311++G** level and led to 14 conformers. The stability of conformers is influenced by their environment, and in aqueous solution two conformers dominate the equilibrium. A superposition of calculated conformers with the predicted TS structure revealed that the preferred conformers in solution nicely mimic structural features of the TS. These results imply that 1 has structural properties required to mimic the TS and therefore can be used as a scaffold for further development of TS-analog inhibitors for retaining glycosyltransferases.

Nonperturbative aspects of the QCD analytic invariant charge

In the framework of the analytic approach to Quantum Chromodynamics a new model for the strong running coupling has recently been developed. Its underlying idea is to impose the analyticity requirement on the perturbative expansion of the renormalization group $\beta$ function for restoring the correct analytic properties of the latter. The proposed model possesses a number of appealing features. Namely, the analytic invariant charge has no unphysical singularities at any loop level; it contains no free parameters; it has universal behavior both in ultraviolet and infrared regions at any loop level; and it possesses a fair higher loop and scheme stability. The extension of this model to the timelike region revealed the asymmetrical behavior of the running coupling in the intermediate- and low-energy domains of spacelike and timelike regions, that is essential when one handles the experimental data. The developed approach enables one to describe, in a consistent way, various strong interaction processes both of perturbative and intrinsically nonperturbative nature.

Polymer adsorption on multicomponent surfaces with relevance to membrane fouling

Block copolymer thin films that include low surface energy domains are analyzed as a possible way to overcome the problem of membrane fouling by proteins and other natural organic matter. A model is presented that accounts for both fouling due to chemical interactions between the solute and surface and due to convective deposition. Guidelines for the formation of novel membranes with improved fouling-resistant properties are suggested based on comparison of the relative permeate flux decline due to fouling on different model copolymer membranes. In general, it is observed that copolymer films having small and dispersed polymer blocks that interact unfavorably with the fouling species show an overall decrease in fouling and increase in permeate flux compared with the homopolymer films.

On the possibility of two new “elementary” particles with mass equal to m( k)=1.80339 MeV and [formula omitted] MeV

To sustain the global symplictic structure of the VAK of vacuum fluctuation, transfinite quantities of energy of the order of k= φ 3(1− φ 3)=0.18033989 MeV and k 0= φ 5(1− φ 5)=0.08203939 MeV must be added to it. In the ten dimensional core of the super string space this leads to the formation of particle masses of the order of m( k)=(10)( k)=1.8033989 MeV. Using ε (∞) theory and the M-dualities between high and low energy domains, one could make a second prediction regarding a unification-related particle m( α ̄ gs )=10/2(m(k))(φ+1) 7=26.18033989 MeV. The possible experimental ramifications of the theory are also discussed.

Transverse activity of kaons and deconfinement phase transition in nucleus–nucleus collisions

We found that the experimental results on transverse mass spectrum of kaons produced in central Pb+Pb (Au+Au) collisions show an anomalous dependence on the colliding energy. The inverse slope of the spectrum increases with the energy in the low (AGS) and high (RHIC) energy domains, whereas it remains constant in the intermediate (SPS) energy range. We argue that this anomaly is probably caused by the modification of the equation of state in the transition region between confined and deconfined matter. This observation may be considered as a new signal, in addition to the previously reported anomalies in the pion and strangeness production, of the onset of deconfinement located in the low SPS energy domain.

Stereochemical origin of opposite orientations in DNA adducts derived from enantiomeric anti-benzo[a]pyrene diol epoxides with different tumorigenic potentials.

When covalently linked to DNA, enantiomeric pairs of mirror image aromatic diol epoxides with differing tumorigenic potencies adopt opposite orientations along the DNA helix. This phenomenon has been observed by high-resolution NMR solution studies in a number of systems. Preliminary modeling efforts [Geacintov et al. (1997) Chem. Res. Toxicol. 10, 111-146) had suggested that the origin of the opposite orientation effect may be manifested even at the level of the carcinogen-modified nucleoside due to primary steric hindrance effects between the aromatic moiety and the attached base and sugar. Such a small system can be computationally investigated extensively, since a very thorough survey of the potential energy surface is feasible. Consequently, in an effort to understand the underlying origins of the opposite orientations in (+)-trans and (-)-trans-anti adduct pairs, we have undertaken an extensive investigation of the paradigm 10S (+) and 10R (-)-trans-anti-[BP]-N2-dG mononucleoside adduct pair, derived from the binding of the (+)-7R,8S,9S,10R and (-)-7S,8R,9R,10S enantiomers of 7,8-dihydro-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene (BP) to the exocyclic amino group of 2'-deoxyguanosine. In the present work we created 373248 different conformers for each adduct, which uniformly sampled the possible rotamers about the three flexible torsion angles governing the orientation of the base (chi) and its covalently linked BP residue (alpha', beta') at 5 degrees intervals, and computed each of their energies with AMBER 4.0. The extensive results permitted us to map the potential energy surface of the molecule. Only four low-energy structural domains are found for the (+)-trans adduct and four for the (-)-trans adduct; the (+)/(-) pairs of each structural domain are mirror images, with the mirror image symmetry broken by the sugar and its attached C4'-C5' group. The most favored of these four is observed experimentally in the duplexes containing the same (+) and (-)-trans-anti-[BP]-N2-dG adducts (Cosman et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1914-1918; de los Santos et al. (1992) Biochemistry 31, 5245-5252). The origin of the opposite orientations resides in steric hindrance effects resulting from the mirror image relationship of the BP benzylic rings in the adduct pair, such that rotation of one stereoisomer into the conformational domain preferred by the other causes crowding between the base and the BP benzylic ring. Limited conformational flexibility in the torsion angle beta', the one closest to the bulky BP moiety at the linkage site to guanine, plays a key role in governing the orientations in each adduct. The opposite orientation phenomenon is likely to manifest itself when the adducts are processed by cellular enzymes involved in replication, repair, and transcription and thus play a role in the differing biological outcomes stemming from the (+) and (-)-trans-anti adducts.