Orientation Of Axis Research Articles

Molecular dynamics simulation of bending behavior of B2-FeAl alloy nanowires with different crystallographic orientations

In nanosystems, the metallic nanowires are subjected to significant and cyclic bending deformation upon integration into stretchable and flexible nanoelectronic devices. The reliability and service life of these nanodevices depend fundamentally on the bending mechanical properties of the metallic nanowires that serve as the critical components. A deep understanding of the deformation behavior of the metallic nanowires under bending is not only essential but also imperative for design and manufacture of high-performance nanodevices. To explore the mechanism underlying the bending plasticity of the metallic nanowire, we have conducted a study on the bending deformation of B2-FeAl alloy nanowires with various crystallographic orientations, sizes and cross-sectional shapes by using molecular dynamics simulation. Our results show that the bending behavior of the B2-FeAl alloy nanowires is independent of the size and cross-sectional shape of the nanowire, but it is highly sensitive to its axial orientation. Specifically, both <111>- and <110>-oriented nanowires yield by dislocation nucleation upon bending, in which the <111>-oriented nanowire fails by brittle fracture soon after yielding, while the <110>-oriented nanowire exhibits good ductility due to homogeneous plastic flow raised by continuous nucleation and steady motion of dislocations. In contrast to the aforementioned two nanowires, the bending plasticity of the <001>-oriented nanowire is mediated by stress-induced transformation from B2 to L1<sub>0</sub> phases, which leads to excellent ductility and higher fracture strain. The orientation dependence of bending deformation can be understood by considering the Schmid factor. Moreover, the plastically bent nanowires with <110> and <001> orientations are able to recover to their original shape upon unloading, particularly, the plastic deformation in the <001>-oriented nanowire is recoverable completely via reverse transformation from L1<sub>0</sub> to B2 structures, exhibiting superelasticity. This work elucidates the deformation mechanism of the B2-FeAl alloy nanowire subjected to bending load, which provides a crucial insight for the design and optimization of flexible and stretchable nanodevices based on metallic nanowires.

Structural Characteristics of the Turning End of the Kaiping Syncline and Its Influence on Coal Mine Gas

Frequent coal mine gas disasters pose significant threats to the safety of miners and the continuity of coal mining operations. Understanding and mastering the patterns of gas occurrence is the foundation for controlling gas outbursts. This study, drawing on previous theories, research, and practical coal mine production data, analyzes the structural characteristics of the Kaiping syncline, with particular emphasis on the structural differentiation at its northeastern uplifted end. The study examines how gas generation and storage are influenced by progressively layered structures and their effect on coal mine gas management. The results indicate that the Kaiping syncline has a NE-SW axial orientation, which gradually shifts to an asymmetric syncline with a nearly EW trend, rising towards the northeastern end. At the turning end, the strata on the northwest limb are steep—locally vertical or overturned—gradually transitioning into the gentler southeast limb with dips of 10° to 30°, further complicated by a series of sub-parallel secondary folds. The gas formation process in coal seams has undergone multiple stages, regulated by structural burial and thermal evolution. The current gas storage characteristics result from the combined effects of these structural factors. The Kaiping syncline can be divided into two gas zones: a high-gas zone in the northwest limb and a shallow low-gas zone paired with a deep high-gas zone in the southeast limb. At the turning end, structural differentiation results in significant variations and gradations in the gas storage conditions of the coal seam. This differentiation directly causes a transition from coal and gas outburst mines in the northwest limb to low-gas mines in the southeast limb, highlighting the significant influence of structural factors on gas generation, preservation, and mine gas emissions. This study integrates theoretical analysis with measured data to enhance the understanding of structural evolution and its influence on gas storage. It offers guidance for preventing coal seam gas disasters and ensuring the safe production of coal mines in the Kaiping coalfield.

Quantum Tunneling: History and Mystery of Large Amplitude Motions over a Century.

Large amplitude motions (LAMs), most notably represented by proton tunneling, mark a significant departure from small amplitude vibrations where protons merely oscillate around their equilibrium positions. These substantial displacements require tunneling through potential energy barriers, leading to splittings in, e.g., rotational spectra. Since Hund's pioneering work in 1927, proton tunneling has offered a unique glimpse into the internal dynamics of gas-phase molecules, with microwave spectroscopy being the key technique for such investigations. The ubiquous LAM type is methyl internal rotation, characterized by 3-fold potentials arising from the interaction between methyl rotors and their molecular frame, with the barrier hindering methyl torsion and the orientation of the torsional axis being defining features. Investigating methyl internal rotations plays a key role in fields ranging from molecular physics, where the methyl rotor serves as a sensitive probe for molecular structures, to atmospheric chemistry and astrophysics, where methyl-containing species have been detected in the Earth's atmosphere and interstellar environments and even discussed as potential probes for effects beyond the standard model of physics. Despite nearly a century of study, modeling methyl internal rotations with appropriate model Hamiltonians and fully understanding the origins of these motions, particularly the factors that influence torsional barriers, remain partially unresolved, reflecting the enduring mystery of quantum tunneling. This Perspective reviews the history of LAMs, highlights advances in decoding their complex spectra, and explores future research directions aimed at uncovering the remaining mysteries of these fascinating motions.

Modeling of comet water production. I. Sensitivity to macro- and micro-model parameters

This study investigates the impact of microscopic and macroscopic cometary surface properties on water production variations with heliocentric distance, focusing on dust layer thickness, grain size, nucleus shape, and spin axis orientation. We employed a two-layer thermophysical model to calculate effective gas production, incorporating a dust layer of porous aggregates of submillimeter- and millimeter-sized grains. The model includes radiative thermal conductivity and permeability for volatile diffusion and considers dust layer evolution and tensile strength. We examined different cometary nucleus shape models based on spacecraft observations and calculated power-law exponents for water production rates as functions of heliocentric distance. A two-layer outgassing model with fixed layer properties showed minimal qualitative differences from a simpler water ice sublimation model. The study reaffirms the critical role of the spin axis inclination and illuminated cross-section variation with the heliocentric distance in gas production. Using 67P/Churyumov-Gerasimenko's orbital parameters, the study demonstrates that dust accumulation and layer growth significantly alter production rate exponents. Additionally, considering tensile strength in a homogeneous spherical nucleus model revealed the potential for local dust crust removal near perihelion. Macroscopic properties such as nucleus shape and spin axis orientation significantly influence water production rate variations with heliocentric distance. Microscopic surface characteristics and dust layer growth also play crucial roles in cometary activity. Incorporating tensile strength and dust removal mechanisms into models provides a more accurate representation of comet activity, particularly near perihelion. This refined model enhances our understanding of comet outgassing, highlighting the importance of detailed surface property data for an accurate interpretation of observations.

Prevalence of interocular symmetry in corneal astigmatism and the possible influence of age, sex and refractive error.

The aim of this study was to investigate, using a power vector approach, whether corneal astigmatism follows a mirror symmetry pattern considering both the magnitude and axis, and whether age, sex and spherical equivalent refractive error can influence the pattern. The IOLMaster 700 optical biometer was used to measure the radii of curvature of the anterior corneal surface. Refractive error was determined by non-cycloplegic subjective refraction. Descriptive statistical analyses and inferential logistic regression were applied over the dichotomous variable of mirror symmetry using J0 and J45 power vector components. An evaluation was carried out based on the subject's age, sex and spherical equivalent refractive error. A total of 2974 Caucasian adults were evaluated. This cross-sectional study revealed that axis orientation follows the isorule symmetry pattern, and in terms of both magnitude and axis orientation, mirror symmetry was present in 70.9% of cases. Age, sex and spherical equivalent refractive error were not significant factors and did not contribute to the clinical improvement of the model despite its statistical significance (refractive error, p = 0.001; age and sex, p = 0.23 and 0.36, respectively). Among an adult Caucasian population, the prevalence of corneal astigmatism mirror symmetry was 70.9% and isorule symmetry was the most common pattern considering axis orientation only. The inclusion of age, sex and spherical equivalent refractive error did not improve the model.

Structure and Conformational Analysis of 5,5-Bis(bromomethyl)-2-methyl-2-(4-chlorophenyl)-1,3-dioxane

The structure of 5,5-bis(bromomethyl)-2-methyl-2-(4-chlorophenyl)-1,3-dioxane was investigated using NMR 1Н, 13С and X-ray data. Molecules of this compound in crystalline phase and in solutions have a chair form with axial orientation of aromatic substituent. The rout of conformational transformations and the potential barriers of internal rotation of aromatic group for isolated molecule and solutions in chloroform and benzene (explicit model) were established by the computer simulation using DFT approach PBE (basis sets 3ζ and def2-SVP).

Improving Femoral Torsion Evaluation in Infants Through Analysis of Variability and Reliability in 2D and 3D Imaging Measurements of the Femoral Neck Axis

Abstract The femoral neck axis serves as a critical parameter in evaluating hip joint health, particularly in the pediatric population. Commonly used metrics for evaluating femoral torsion, such as the femoral neck-shaft and femoral anteversion angles, rely heavily on precise definitions of the position and orientation of the femoral neck axis. Current measurement methods employing radiographs and performing two-dimensional (2D) measurements on computed tomography (CT) scans are susceptible to errors due to their reliance on reader experience and the inherent limitations in 2D measurements. We hypothesized that utilizing volumetric data would mitigate these errors and enable more accurate and reproducible measurements of the femoral neck axis using the femoral anteversion and femoral neck-shaft angles. To test this hypothesis, we analyzed a historical collection of post-mortem infant femoral and pelvic bones (28 hips) aged 0 to 6.5 months, with an average estimated age of 4.68 months ± 1.80 months. Our findings revealed an average neck-shaft angle of 128.00 ± 4.92± and femoral anteversion angle of 35.56 ± 11.68± across all femurs, consistent with literature values. These measurements obtained from volumetric image data were found to be repeatable and reliable compared to conventional methods. Our study suggests that the proposed methodology offers a standardized approach for obtaining repeatable and reproducible measurements, thus potentially enhancing diagnostic accuracy and clinical decision-making in assessing hip developmental conditions in pediatric patients.

Rarγ-Foxa1 signaling promotes luminal identity in prostate progenitors and is disrupted in prostate cancer.

Retinoic acid (RA) signaling is a master regulator of vertebrate development with crucial roles in body axis orientation and tissue differentiation, including in the reproductive system. However, a mechanistic understanding of how RA signaling governs cell lineage identity is often missing. Here, leveraging prostate organoid technology, we show that RA signaling orchestrates the commitment of adult mouse prostate progenitors to glandular identity, epithelial barrier integrity, and specification of prostatic lumen. RA-dependent RARγ activation promotes the expression of Foxa1, which synergizes with the androgen pathway for luminal expansion, cytoarchitecture and function. FOXA1 mutations are common in prostate and breast cancers, though their pathogenic mechanism is incompletely understood. Combining functional genetics with structural modeling of FOXA1 folding and chromatin binding analyses, we discover that FOXA1F254E255 is a loss-of-function mutation compromising its transcriptional function and luminal fate commitment of prostate progenitors. Overall, we define RA as an instructive signal for glandular identity in adult prostate progenitors. Importantly, we identify cancer-associated FOXA1 indels affecting residue F254 as loss-of-function mutations promoting dedifferentiation of adult prostate progenitors.

An effective path planning approach for robot welding considering redundant kinematics

Robot welding with redundant kinematics demands precise coordination of the welding path and redundant axis motion for stable operation. This paper introduces an effective G3 continuous path planning approach for a 6-DOF friction stir welding robot, integrating redundant axis motion to enhance welding stability and quality. The method encompasses a two-pronged strategy: a five-axis path corner smoothing technique and a motion synchronization strategy. Initially, a robust toolpath preprocessing algorithm is presented to mitigate curvature extremities of the inserted smoothing curves within predefined error limits. Subsequently, leveraging G3 continuity criteria, a B-spline-based smoothing method is advanced for refining tool position and orientation paths, with an analytical determination of spline control points facilitated by an explicit smoothing error expression. An effective motion synchronization technique is then proposed, which formulates the tool position, tool orientation, and redundant axis path as explicit functions of the position path arc length. The effectiveness of the proposed method is demonstrated through simulations and experiments on a robot welding platform, with the integration of a jerk-continuous feedrate profile for smooth motion execution. The findings indicate a significant improvement in robotic welding quality by integrating the proposed path planning method with existing workpiece posture optimization techniques.

Synthesis, exploring the structural, non covalent interaction effects, biological assessment, molecular docking and quantum chemical properties of functionalized new N-nitrosopiperidin-4-one: An experimental and theoretical study

The synthesis of 3-benzyl-1-nitroso-2,6-di-p-tolylpiperidin-4-one 2 has been carried via the nitrosation of 3-benzyl-2,6-di-p-tolylpiperidin-4-one 1 with sodium nitrite and dilute hydrochloric acid at room temperature. This work deals with the synthesis, characterization (1H and 13C NMR, 1H–1H-COSY, 1H–13C-COSY, and X-ray diffraction analysis), and stereochemical characterization of functionalized N-nitrosopiperidin-4-one. The molecular level behaviors of the compounds were determined by computational chemistry methods. It is to be noted that at room temperature, 3-benzyl-2,6-di-p-tolylpiperidin-4-one 1 preferentially exists in chair conformation with all substituents in equatorial orientation, whereas its nitroso derivative, 3-benzyl-1-nitroso-2,6-di-p-tolylpiperidin-4-one 2, exists in syn and anti isomers. The observed coupling constant data for 2 suggests that the syn isomer is an equilibrium mixture of two boat forms B1 and B2, and that the predominant conformer of the anti-isomer is boat form B1. Conformational analysis carried out through DFT calculation using Gaussian 09 program supported that B1 is the more stable conformer of compound 2 with minimum energy for both syn and anti isomers. Good correlations were obtained between the predicted boat conformation B1 from theoretical study (DFT calculation) and the corresponding experimental (1H NMR spectrum) ones. This was complemented by single-crystal X-ray analysis, which revealed that compound 2 exists as the anti-isomer with the piperidine ring adopting the B1 boat structure. Here, the phenyl group at C(2) and the benzyl group at C(3) are in axial orientation, and the phenyl group at C(6) are in equatorial orientation. Hirshfeld surface analysis of the molecule showed H⋯H (59.0 %), C⋯H/H⋯C (22.9 %), O⋯H/H⋯O (14.3 %), N⋯H/H⋯N (2.4 %), and O⋯O (0.5 %) interactions. Energy framework analysis revealed that among the components of the framework energies, electrostatic repulsion (Erep) is dominant. Finally, the molecular docking and dynamics simulation studies of the title ligand with 6LVM protein have shown better binding affinity, and stability. Further, ADME prediction of the compound 2 has exhibited excellent drug-likeness.

Investigating the correlation between the magnetic field orientation and molecular outflow direction in some molecular clouds

ABSTRACT This study examines the relationship between the magnetic field orientation of a molecular cloud and its outflow axis, using data from 22 molecular clouds. We find that the position angles of the outflow axis ($\theta _{\text{out}}$) and the cloud-scale magnetic field in the core, measured in the submillimetre region ($\theta _B^{\text{sub}}$), are correlated to each other irrespective of the alignment or misalignment between the two axes. However, it is important to note that these observed position angles are projections on to the plane of the sky. To assess the statistical significance of our findings, we conduct a statistical test to account for the projection effect and find minimal impact. Moreover, we identify a possible role of the Galactic magnetic field orientation ($\theta _{\text{GP}}$) in determining the outflow direction by assessing the offset ($\theta _{\text{off}} = \theta _B - \theta _{\text{GP}}$) in both the core and envelope regions. Furthermore, we explore the influence of parameters such as magnetic field strength (B), the position angle of the minor axis of the cloud cores ($\theta _{\text{min}}$), the inclination angle of the outflow ($i_{\text{out}}$), and other factors on the alignment between the outflow and cloud-scale magnetic field axes ($|\theta _{\text{OB}}| = |\theta _{\text{out}} - \theta _B^{\text{sub}}|$). Our analysis suggests that the orientation of the outflow axis is determined by the combined influence of the magnetic field orientation, the minor axis, the inclination angle of the outflow, and the associated magnetic field strength.

Flexible Liquid Crystal Cascade Dielectric Metasurface for Dynamically Controlling Terahertz Beam Deflection

AbstractTerahertz (THz) beam deflection devices with tunable capabilities are highly desired in future wireless communication and radar systems. In this work, a cascaded metadevice is constructed by integrating liquid crystal (LC) into a dielectric metasurface, and then the phase of each meta‐atom is designed to achieve different polarization conversions and spatial phase gradient distributions. Therefore, by changing the polarization of the incident wave or the LC optical axis orientation, an active THz beam deflection device that can actively and independently control the spin state and deflection angle of the output wave can be obtained. Specifically, the output right circularly polarized (RCP) wave is deflected to the +1st diffraction order, and the output left circularly polarized (LCP) wave is deflected to the +2nd diffraction order. The experimental results indicate that the cascaded metadevice exhibits a large angular spatial dispersion in the frequency angle scanning range of +25°–+17.5° (+1st order) and +52.5°–+35° (+2nd order) corresponding to the broadband range of 0.6–0.83 THz. The spin isolation of all diffraction order channels can reach over 10 dB and the maximum diffraction efficiency of 56% can be obtained. In addition, the universality of the proposed LC‐cascaded metasurface design concept has also been verified, providing a feasible path for complex, multifunctional, and active THz wavefront manipulation, thereby exploring more possible application scenarios.

φ Josephson Junction Induced by Altermagnetism.

We study the Josephson effect in a superconductor-altermagnet-superconductor junction. We find anomalous phenomena, including 0-π transition and multinodal current-phase relations. Similar to a d-wave superconductor, a d-wave altermagnet can support a φ junction where free-energy minima locate neither φ=0 nor ±π with double degeneracy. These properties can be tunable by parameters, e.g., the exchange energy, the orientation of crystal axis, the length, and the chemical doping of the altermagnet. These rich features lead to accessible functionality of superconductor-altermagnet-superconductor junctions.

Absolute depth-resolved optic axis measurement with catheter-based polarization sensitive optical coherence tomography.

Imaging depth-resolved birefringence and optic axis orientation with polarization sensitive optical coherence tomography (PS-OCT) unveils details of tissue structure and organization that can be of high pathophysiologic, mechanistic, and diagnostic value. For catheter-based PS-OCT, the dynamic rotation of the fiber optic probe, in addition to the polarization effects of the system components, complicates the reliable and robust reconstruction of the sample's optic axis orientation. Addressing this issue, we present a new method for the reconstruction of absolute depth-resolved optic axis orientation in catheter-based PS-OCT by using the intrinsic retardance of the protecting catheter sheath as a stable guide star signal. Throughout the paper, we rigorously inspect the retardance and optic axis orientation of the sheath and validate our method by imaging a birefringent phantom with known optic axis orientation. Reconstructing the optic axis orientation of the phantom, placed at different locations around the catheter, we measured an average absolute deviation (AAD) for the mean optic axis orientation over cross-sectional images of 3.28°, even with significant bending stress on the catheter. This corresponds to an almost three-fold improvement compared to our earlier method (optic axis AAD of 9.41°). We finally highlight the capability of our reconstruction with stereotactic catheter-based PS-OCT of a fresh sheep brain.

Thin Films of BaM Hexaferrite with an Inclined Orientation of the Easy Magnetization Axis: Crystal Structure and Magnetic Properties.

Thin (~50 nm thick) BaM hexaferrite (BaFe12O19) films were grown on (1-102) and (0001) cut α-Al2O3 (sapphire) substrates via laser molecular beam epitaxy using a one- or two-stage growth protocol. The advantages of a two-stage protocol are shown. The surface morphology, structural and magnetic properties of films were studied using atomic force microscopy, reflected high-energy electron diffraction, three-dimensional X-ray diffraction reciprocal space mapping, powder X-ray diffraction, magneto-optical, and magnetometric methods. Annealed BaFe12O19/Al2O3 (1-102) structures consist of close-packed islands epitaxially bonded to the substrate. The hexagonal crystallographic axis and the easy axis (EA) of the magnetization of the films are deflected from the normal to the film by an angle of φ~60°. The films exhibit magnetic hysteresis loops for both in-plane Hin-plane and out-of-plane Hout-of-plane magnetic fields. The shape of Mout-of-plane(Hin-plane) and Min-plane(Hin-plane) hysteresis loops strongly depends on the azimuth θ of the Hin plane, confirming the tilted orientation of the EA. The Mout-of-plane(Hout-of-plane) magnetization curves are caused by the reversible rotation of magnetization and irreversible magnetization jumps associated with the appearance and motion of domain walls. In the absence of a magnetic field, the magnetization is oriented at an angle close to φ.

Interplanetary Rotation of 2021 December 4 Coronal Mass Ejection on Its Journey to Mars

The magnetic orientation of coronal mass ejections (CMEs) is of great importance to understand their space weather effects. Although plenty of evidence suggests that CMEs can undergo significant rotation during the early phases of evolution in the solar corona, there are few reports that CMEs rotate in the interplanetary space. In this work, we use multispacecraft observations and a numerical simulation starting from the lower corona close to the solar surface to understand the CME event on 2021 December 4, with an emphatic investigation of its rotation. This event is observed as a partial halo CME from the back side of the Sun by coronagraphs and reaches the BepiColombo spacecraft and the Mars Atmosphere and Volatile EvolutioN/Tianwen-1 as a magnetic flux-rope-like structure. The simulation discloses that in the solar corona the CME is approximately a translational motion, while the interplanetary propagation process evidences a gradual change of axis orientation of the CME’s flux-rope-like structure. It is also found that the downside and the right flank of the CME moves with the fast solar wind, and the upside does in the slow-speed stream. The different parts of the CME with different speeds generate the nonidentical displacements of its magnetic structure, resulting in the rotation of the CME in the interplanetary space. Furthermore, at the right flank of the CME exists a corotating interaction region, which makes the orientation of the CME alter and also deviates from its route due to the CME. These results provide new insight into interpreting CMEs’ dynamics and structures during their traveling through the heliosphere.

Stellar Bars Form Dark Matter Counterparts in TNG50

Dark matter (DM) bars that shadow stellar bars have been previously shown to form in idealized simulations of isolated disk galaxies, but have yet to be studied in a fully cosmological context. In this work, we analyze a population of disk galaxies within the TNG50 simulation to determine the characteristics of their dark bars. We estimate bar strength and orientation using both the in-plane Fourier A 2 density moments and the quadrupolar coefficients of the spherical harmonic basis function expansions of the density. We additionally present two novel methods for measuring the bar pattern speed Ω p and rotation axis orientation using these coefficients, and apply them to one sample galaxy located in a TNG50 subbox. Consistent with isolated simulations, DM bars are shorter than their stellar counterparts and are 75% weaker in A 2. DM bars dominate the shape of the inner halo potential and are apparent in the time series of quadrupolar coefficients. In our selected subbox galaxy, the stellar and dark bars remain co-aligned throughout the last 8 Gyr and have identical Ω p . Pattern speed Ω p evolves considerably over the last 8 Gyr, consistent with torques on the bars due to dynamical friction and gas accretion, and is seen to increase following a merger at t lb = 1.5 Gyr. Rather than remaining static in time, the bar rotation axis displays both precession and nutation possibly caused by torques outside the plane of rotation. We find that the shape of the stellar and DM mass distributions are tightly correlated with Ω p .

Impact of Astigmatism on Axial Elongation in School-Age Children: A Five-Year Population-Based Study in Tianjin, China.

To investigate the progression rates of axial length (AXL) among school-age children with baseline astigmatism and spherical ametropia. Annual vision screenings were conducted at seven schools in Tianjin, China, from 2018 to 2022. Ocular biometry and non-cycloplegic autorefraction were collected. Children 5 to 16years old without any myopia interventions were included and categorized by their baseline astigmatism magnitude (control, low, or high) and axis orientation (with the rule [WTR], against the rule [ATR], or oblique). Additionally, children were classified by baseline spherical ametropia (compound hyperopic, compound myopic, or other). Annual AXL progression rates of right eyes were calculated using regression models and compared across different types of astigmatism and spherical ametropia. A total of 10,732 Chinese children (baseline age, 9.26 ± 2.42years; follow-up duration, 2.63 ± 1.01years) were included and divided into a younger cohort (age<11years; n=7880) and an older cohort (age≥11years; n=2852). Across both age groups and all astigmatism magnitudes, ATR astigmatism exhibited the most rapid AXL progression, followed by oblique and WTR astigmatism. Two-way ANCOVA of the combined cohort revealed that both high-magnitude and ATR astigmatism were significantly associated with AXL progression (P≤0.018). However, the impact of astigmatism on AXL progression varied depending on baseline spherical ametropia, as high-magnitude and ATR astigmatism increased AXL progression in compound myopic eyes but decreased progression in compound hyperopic eyes. Both baseline magnitude and axis orientation of astigmatism are significantly associated with axial elongation in children. However, these associations may vary with spherical ametropia, with differential patterns being observed between compound hyperopic and myopic eyes.

Statistical and source characterization of the 2023 Kahramanmaraş Türkiye earthquake sequence

AbstractWe studied seismic features of the 2023 Kahramanmaraş Türkiye earthquake sequence by analyzing the spatiotemporal behavior of the b- and -p values and source characteristics of the mainshocks. We complemented our study by determining the regional stress field. The b-values in the region varied from 0.45 to 1.15. We observed a slight b-value decrease (Δb≈0.2) months before the two mainshocks. Our results exhibited complex b-value patterns on the fault planes and regular aftershock productivity rates (1.14 &lt; p &lt; 1.25). We compare static stress drop estimates derived from effective fault dimensions to those of finite-fault dimensions. Total effective stress drops (the sum of the stress drops of all fault segments) for the earthquake doublet were almost identical (~ 2.05 MPa), while those from finite-fault dimensions are somewhat lower (0.35 and 0.96 MPa). Based on a complete stress drop case, effective seismic efficiency was 0.65 and 0.43 for both mainshocks. The amount of partial stress drop was used to discriminate between different stress drop models. No clear model is discerned for the first mainshock, but a partial or even complete stress drop, assuming finite-fault dimensions, is supported by our measurements. Stress drop estimations derived from spectral analysis (25.46 and 34.39 MPa) agreed with global studies but larger than finite and effective fault estimates. Stress inversion results indicated that in the fault segments where the mainshocks occurred, the orientation of principal axes was consistent with a strike-slip regime. Conversely, the normal-faulting regime dominates adjacent areas of the main fault system.

Azimuthal seismic anisotropy of the Iran plateau: Insights from ambient noise analysis

The continental lithosphere of the Iran plateau is complicated by many tectonic processes that affected both the Arabian and Eurasian plates before and after their convergence. To investigate the deformation mechanisms of the crust and mantle lithosphere, we directly invert Rayleigh wave phase velocity dispersion data (5–60 s) for a 3-D shear wave velocity and depth-dependent azimuthal anisotropy model using ambient noise tomography from the surface down to 100 km with data recorded in 84 seismic stations. The shear wave velocity maps reveal a reasonable match with geological domains and agree with those previously published. The projections of the fast axes of Rayleigh wave azimuthal anisotropy in the subcrustal lithosphere allowed us to divide the Iran plateau into two main regions: the Zagros Mountains and the rest of the country. Furthermore, the anisotropy pattern illustrates a prominent contrast between the NW and SE Zagros Mountains. In both the crust and subcrustal lithosphere, the NW Zagros shows relatively weak but coherent azimuthal anisotropy in the NE-SW direction (i.e., orogen-perpendicular orientation). We ascribe the orogen-perpendicular fast axis in NW Zagros to stress-induced anisotropy. However, in the SE Zagros, the north-northwest orientations of the fast axes are attributed to the N-S trending basement structures, which are inherited from the Pan-African construction phase. The azimuthal anisotropy pattern displays an overall NW-SE trend dominant over the rest of the country. This NW-SE direction can be explained by an NW-SE extension due to transpressional deformation beneath Central Iran resulting from the oblique indentation of the Arabian plate into Eurasia. Nevertheless, strike-parallel anisotropy directions along the western and central Alborz Mountains throughout the entire lithosphere may be related to pure shear deformation. The persistence of azimuthal anisotropy patterns in the crust and subcrustal lithosphere implies that the whole lithosphere deforms coherently in the NW Zagros, west Iran, the Alborz Mountains, and across the Lut block. However, strong contrasts between the crustal and subcrustal pattern of anisotropy observed in the SE Zagros as well as in north Central Iran suggest that in these regions, the crust and the underlying mantle lithosphere do not deform coherently. A strong correlation between the Rayleigh wave anisotropy directions at subcrustal depths and the anisotropy patterns estimated from the shear-wave core phases suggests that in many places over the plateau, the SKS directions may have been dominated by the deformation of the lithosphere.