Rotational Orientation Research Articles

Dynamometry for the Assessment of Trunk Muscle Strength in Postpartum Women with Pregnancy-Related Posterior Pelvic Girdle Pain: A Reliability Study

ObjectivesTo investigate the inter and intra-rater reliability of maximum isometric trunk muscular strength in postpartum women with pregnancy-related posterior pelvic girdle pain using a handheld dynamometer. MethodsThirty women (30.13 ± 3.67 years) with pregnancy-related posterior pelvic girdle pain (PPGP) had their trunk muscular strength assessed using a handheld dynamometer. Inter-rater reliability was estimated for measurements of two separate raters on the first day of the investigation. The tests were repeated with the first rater seven days later to determine the intra-rater reliability. A digital handheld dynamometer was used for testing, and a metal bar was used to secure it to a table. Participants were instructed to use maximal force to push the dynamometer in various trunk flexion, extension, lateral flexion, and rotational orientations. Each trial was repeated three times and averaged to obtain the representative assessment data. Analysis of variance, interclass correlation, absolute agreement, and standard error of measurements were used to evaluate the repeatability of measurements. ResultsExcellent inter and intra-rater reliability were demonstrated. The inter-rater reliability, computed with intraclass correlation coefficient (ICC), ranged from 0.979 to 0.992, and intra-rater reliability (ICC) ranged from 0.966 to 0.987. The standard error of measurement ranged from 0.35% to 1.26% for the different tests. Additionally, the dynamometer values in women with PPGP might be reported using just one trial after an instruction. ConclusionThe maximum isometric trunk muscular strength is reliable, and a quantitative assessment of the trunk strength in women with postpartum pregnancy-related posterior pelvic girdle pain and could be used to monitor the changes in postural stability between sessions.

3D manipulation of small multicellular organisms in soft microtubes

Small multicellular organisms, such as C. elegans and zebrafish larvae, are essential models in biological research, but their 3D manipulation poses challenges due to their small size. Manual positioning is labor-intensive and imprecise. To address this, we developed a soft PDMS microtube that can be gently stretched and released, immobilizing organisms without anesthetization and damage. This tube enables easy rotation and adjustment of orientation, facilitating comprehensive imaging. Functionality testing showed effective immobilization as well as precise imaging and microinjection. Zebrafish larvae were successfully injected with fluorescein in the hindbrain without anesthesia. This technique offers a simple, efficient, and non-damaging method for 3D manipulation and imaging of small multicellular organisms and provides a versatile tool for biological research practices.

The Milky Way atlas for linear filaments – II. Clump rotation versus filament orientation

ABSTRACT Dense clumps distributed along filaments are the immediate medium for star formation. Kinematic properties of the clumps, such as velocity gradient and angular momentum, combined with filament orientation, provide important clues to the formation mechanism of filament-clump configurations and the role of filaments in star formation. By cross-matching the Milky Way atlas for linear filaments and the structure, excitation and dynamics of the inner Galactic interstellar medium (SEDIGISM) $^{13}$CO (2-1) data, we aim to derive the velocity gradient and its direction, the specific angular momentum ($J/M$), and the ratio ($\beta$) between the rotational energy and gravitational energy of clumps, as well as to investigate the alignment between clump rotation and filament orientation. We found a monotonic increase in $J/M$ as a function of clump size (R), following a power-law relation $J/M~\propto ~R^{1.5\pm 0.2}$. The ratio $\beta$ ranges from 1.1 $\times$ 10$^{-5}$ to 0.1, with a median value 1.0 $\times$ 10$^{-3}$, suggesting that clump rotation provides insignificant support against gravitational collapse. The distribution of the angle between clump rotation and natal filament orientation is random, indicating that the clumps’ rotational axes have no discernible correlation with the orientation of their hosting filaments. Counting only the most massive clump in each filament also finds no alignment between clump rotation and filament orientation.

Polar Motion Ultra-Short-Term Prediction of Least-Squares+Multivariate Autoregressive Hybrid Method by Using the Kalman Filter.

The polar motion (PM, including two parameters PMx and PMy) ultra-short-term prediction (1-10 days) is demanded in the real-time navigation of satellites and spacecrafts. Improving the PMx and PMy ultra-short-term predictions accuracies are a key to optimize the performance of these related applications. Currently, the least squares (LS)+autoregressive (AR) hybrid method is regarded as one of the most capable approaches for ultra-short-term predictions of PMx and PMy. The Kalman filter has proven to be effective in improving the ultra-short-term prediction performance of the LS+AR hybrid method, but the PMx and PMy ultra-short-term predictions accuracies are still not able to satisfy some related applications. In order to improve the performance of PM ultra-short-term prediction, it is worth exploring the combinations of existing methods. Throughout the existing predicted methods, the LS+multivariate autoregressive (MAR) hybrid method by using the Kalman filter has the potential to improve the accuracy of PM ultra-short-term prediction. In addition, a PM prediction performance analysis of the LS+MAR hybrid method by using the Kalman filter, namely the LS+MAR+Kalman hybrid method, is still missing. In this contribution, we proposed the LS+MAR+Kalman hybrid method for PM ultra-short-term prediction. The data sets for PM predictions, which range from 1 to 10 days, have been tested based on the International Earth Rotation and Reference Systems Service Earth Orientation Parameter (IERS EOP) 14 C04 series to assess the performance of the LS+MAR+Kalman hybrid model. The experimental results illustrated that the LS+MAR+Kalman hybrid method can effectively execute PMy ultra-short-term predictions. The improvement of PMy prediction accuracy can rise up to 12.69% for 10-day predictions, and the improvement of ultra-short-term predictions is 7.64% on average.

A Hybrid VGG 19 and Capsule Network Based Deep Learning Model for Lung Cancer Diagnosis using CT S can Images

Objectives: Lung cancer is one of the most prevalent causes of carcinoma-related fatalities globally; precise and effective diagnostic instruments are desperately needed. Researchers and physicians continue to encounter difficulties when aiming to employ deep learning models in healthcare environments for recognizing lung cancer and to achieve higher sensitivity and accuracy on large data sets, despite several advancements in this field. Our study builds upon an extensive review of existing lung cancer detection methods, highlighting their strengths and weaknesses. The performance of this model deteriorates when there are variances in Lung CT image features such as rotation, tiling, and other aberrant image orientations. This study aims to address the issues associated with variations in lung CT images. Methods: A hybrid deep learning model that blends the potency of CNNs with the cutting-edge design of capsule networks is proposed. Inspired by recent advancements, our model integrates the VGG19 and Capsule Network architectures to address orientation-related challenges often encountered in traditional CNN-based approaches. The creation, training, and assessment of this hybrid model for lung nodule identification and categorization are our main research goals. Findings: We anticipate that our research has yielded several valuable outcomes, including improved nodule classification accuracy of 99.20%, reduced false positive rates, and minimized training times. Novelty: This research employing a hybrid deep learning model that combines the capabilities of the VGG-19 and capsule network could lead to more widespread utilization in cancer diagnosis by enhancing early lung cancer detection and developing the field of medical image analysis. The shortcomings of convolutional neural networks are addressed with Capsule Network. Leveraging the knowledge and insights gained from lung cancer detection, our research also investigates the potential applicability of our methodology to identify other types of medical image classification such as breast and ovarian cancer. Keywords: Computed Tomography, Lung cancer, Deep Learning, CNN, VGG19, Capsule Network

BUDAYA TELLASEN TOPAK: DARI KETUPAT KE IDE AKTIVITAS SPATIAL SKILLS DALAM PEMBELAJARAN MATEMATIKA

Tellasen topak, which is identical to ketupat, is a culture of choosing, weaving, and processing janur into a medium for ketupat food. This culture is full of spatial skills activities, because it turns two-dimensional objects into space objects (three-dimensional). The purpose of this study is to explore the idea of spatial skills activities from ketupat in mathematics learning. The research method is qualitative research. Data collection techniques are observation, documentation, and internet search. Data analysis is in the form of data reduction, data presentation, and conclusion. The results concluded that in choosing, weaving, and processing janur into a medium for ketupat food, there are spatial skills activity ideas in the form of spatial visualization, spatial orientation and spatial rotation. In math learning, these ideas play a role in explaining the concepts of geometry, measurement and number. The results of this study contribute to mathematics learning, namely in developing culture-based teaching modules.

Directional Deep Brain Stimulation Lead Rotation in the Early Postoperative Period

BACKGROUND AND OBJECTIVES: Directional deep brain stimulation (DBS) enables treatment optimization by current steering using segmented leads. Identification of the lead's rotational orientation is critical to guide programming decisions. Orientation is often assessed during or immediately after implant, but the degree of lead rotation in the following weeks is not well appreciated. Our objective was to measure the degree of DBS lead rotational orientation changes within the first few weeks after surgery. METHODS: We retrospectively reviewed the clinical records of patients who were implanted with segmented DBS leads at our institution. All included patients had at least 1 immediate postoperative computed tomography (CT) (CT1) and another CT at least 1 week later (CT2). We assessed lead rotational orientation angles on CT1 and CT2 and calculated the degrees of rotation change between the scans. We also assessed for any effect of the time interval between scans by calculating the correlation between CT1-CT2 latency and degrees of lead rotation. RESULTS: We assessed a total of 75 DBS lead orientations for 38 patients. The average change in lead orientation between CT1 and CT2 was 8.6° (median = 2.9°, range = 0.11-168.2°). Only 8 percent of patients (3/38) were found to have a significant change in orientation (>30°); however, when it occurred, it occurred bilaterally. There was no correlation between CT1-CT2 latency and lead rotation (r(74) = 0.04, P = .73). CONCLUSION: Our study finds that changes in lead orientation occurring over the first few weeks after surgery are rare. Thus, for most patients, the immediate postoperative CT is adequate for determining the orientation angles for clinical programming. However, if programming is found to be difficult, a repeat CT scan could be beneficial for a minority of patients.

Ultraconfined oblate hard particles between hybrid penetrable walls.

We have investigated, by Monte Carlo simulation, the orientational structure of very thin films of a discotic liquid crystal (DLC) confined between hybrid walls of controllable penetrability, as a function of wall separation L_{z}. Our purpose was to clarify whether, as predicted by continuum theory, the preferred orientation of the DLC is uniform, changes linearly, or changes discontinuously, when L_{z} and the anchoring strengths at either wall are changed. The model consists of oblate hard Gaussian overlap (HGO) particles: each wall sees a particle as a disk of zero thickness and diameter D less than or equal to that of the actual particle σ_{0}, embedded inside the particle and located halfway along, and perpendicular to, its minor axis. This provides a particle-level mechanism to control the anchoring properties of the walls, from planar (edge-on) for D∼0 to homeotropic (face-on) for D∼σ_{0}, which can be done independently at either wall. As in our earlier work [C. Anquetil-Deck et al., J. Phys. Chem. B 124, 7709 (2020)1520-610610.1021/acs.jpcb.0c05027], which was restricted to L_{z}=6σ_{0}, depending on the values of D_{s}≡D/σ_{0} at the top (D_{s}^{t}) and bottom (D_{s}^{b}) walls, we find domains in (D_{s}^{b},D_{s}^{t}) space in which particle alignment is uniform planar (UP), uniform homeotropic (UH), or varies linearly from planar at one wall to homeotropic at the other (L), but no bistable or tristable regions are identified between these domains. Most importantly, there appears never to occur an abrupt change of the LC orientation when the walls strongly favor different anchorings, in general agreement with the scenario proposed by Velasco and co-workers [D. de las Heras et al., Phys. Rev. E 79, 011712 (2009)1539-375510.1103/PhysRevE.79.011712], but in contrast to the behavior of equivalent calamitic systems [F. Barmes et al., Phys. Rev. E 69, 061705 (2004)1539-375510.1103/PhysRevE.69.061705; Phys. Rev. E, 71, 021705 (2005)1539-375510.1103/PhysRevE.71.021705; C. Anquetil-Deck et al., Phys. Rev. E 86, 041707 (2012)1539-375510.1103/PhysRevE.86.041707]. However, for the thinnest films investigated (L_{z}=2σ_{0}), the system is unable to accommodate a rotation of the preferred particle orientation from one wall to the other and adopts instead a tilted configuration, similar to that reported earlier for Gay-Berne films in symmetric confinement [T. Gruhn et al., Thin Solid Films 330, 46 (1998)0040-609010.1016/S0040-6090(98)00799-8; Mol. Phys. 93, 681 (1998)10.1080/002689798169014] but which, as far as we know, has been missed in most earlier work.

Relation between the geometric shape and rotation of Galactic globular clusters

We homogeneously measured the elliptical shapes of 163 globular clusters (GCs) using the on-sky distribution of their cluster members and the third data release of the ESA mission Gaia (DR3). The astrometry enables the differentiation of stars within clusters from those in the field. This feature is particularly valuable for clusters located in densely populated areas of the sky, where conventional methods for measuring the geometry of the GCs are not applicable. The median axial ratio of our full sample is 〈b/a〉 = 0.935−0.090+0.033 and 0.986−0.004+0.009 for the subset of 11 GCs previously studied based on Hubble Space Telescope imaging. We investigated whether the minor axis of the ellipses can be interpreted as a pseudo-rotation axis by comparing it to measurements of cluster rotation. Using the radial velocities from Gaia, we detected rotation for three clusters, NGC 5139, NGC 104, and NGC 6341, and observed an alignment between the pseudo-rotation axis and the 2D projection of the real rotation axis. To expand the set of clusters for which rotation has been detected, we analyzed multiple literature references. Depending on the reference used for comparison, we observed an alignment in between 76% to 100% of the clusters. The lack of an alignment observed in some clusters may be linked to different scales analyzed in various studies. Several studies have demonstrated that the orientation of rotation varies with the distance from the center. We estimate that the next Gaia release will increase the number of stars with radial velocities in GCs from ~10 000 in Gaia DR3 to ~55 000 in Gaia DR4. This will enable the measurement of rotation and ellipticities at identical angular scales for additional clusters, which will help us to clarify whether the previously mentioned alignment occurs in all clusters.

Rolling mechanism profundities on material removal mechanism of surface-textured GaN using Molecular dynamics simulation

Molecular dynamics simulation examines how the polishing tool's rotating velocity and axes affect surface nanotribological properties and material removal mechanism of patterned gallium nitride (GaN) substrates. Frictional coefficient and average contact area affect material removal rate (MRR) variance. Rotating speed increases the frictional coefficient and contact area, elevating MRR. Anticlockwise abrasives have substantially higher root-mean-square roughness (RMS) than clockwise ones. After polishing, increasing the rotating angle increases the frictional coefficient, average contact area, MRR, and RMS. MRR enhancement is maximum at −15 rad/ns, the only spinning velocity that improves MRR. RMS improvement ratio is highest when the polishing tool spins clockwise or the rotational axis orientation is lowered. Particularly, the MRR and RMS improvements after the polishing process can reach 103.8 % and 223.5 %, respectively. These findings help explain atomic-scale GaN-based material removal and deformation with frictional resistance and erosion by polishing.

Support for Neurodivergent Students in Veterinary Education Part 1: Current Practice and Roundtable Discussion of Recommendations.

Approximately 10% of undergraduate student populations are neurodivergent. Such students have differences in executive functioning and social communication skills, which can confer both strengths and challenges in the academic environment. Specific challenges presenting in the veterinary curriculum include the intense workload, unpredictable nature of work, and high level of interpersonal and communication skills required in clinical settings. Extramural studies (EMS) occur remote from university support systems, adding further challenge for some students. A survey was sent to all current United Kingdom veterinary schools in 2022 to identify current support for neurodivergent students. An interactive roundtable discussion was held to brainstorm best practice for harnessing the power of neurodiversity in the clinical learning environment. Several consistent themes emerged. Most veterinary schools provide some degree of support for neurodivergent individuals, but support varies widely. Four of the 8 schools provide support at open days and/or following offers, with one school offering a summer school. Five schools confirmed that accommodations were made to clinical rotations and/or extramural studies in line with a support plan from their Disability Service. Despite these steps to assist neurodivergent students, support could, and should, be increased to improve the student experience. Suggested enhancements include a supportive environment for the empowerment of disclosure, neurodiversity awareness training for university staff and placement providers, provision of reasonable adjustment guidelines for EMS providers, clinical/intramural rotation orientation and support, and student access to a neurodiversity mentor/coach.

Defect recrystallization in subtransus hot isostatic pressing of electron beam powder bed fusion Ti-6Al-4V

Post-build hot isostatic pressing (HIP) is a widely used method to close as-built defects (gas or lack-of-fusion porosity) in additively manufactured (AM) metal parts. Pore closure during this process often creates clusters of equiaxed grains, in contrast to coarse and directional as-built microstructures widely seen in AM metals. Understanding the mechanisms behind the formation of such microstructures is desirable for controlling anisotropy and improving mechanical properties of AM parts. Prior work has attributed defect-induced equiaxed grains to recrystallization during the HIP process; however the specifics of this recrystallization process have not been explored. This work systematically analyzes the grain structure, orientation, and misorientations of electron beam powder bed fusion (PBF-EB) Ti-6Al-4V to identify the mechanisms by which clusters of equiaxed grains can form during HIP of as-built microstructures. A combination of two mechanisms, dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX), explains the phenomena. Evidence for both these processes is found in small rotations in crystallographic orientation, localized strains around prior pore defects, and specific misorientation distributions. Only subtransus HIP of Ti-6Al-4V was explored in this work. However, the mechanisms presented here are thought to contribute to recrystallization in other HIP processes whether for super-transus Ti-6Al-4V, β-Ti alloys, other alloy systems, or non PBF-EB build processes. These results build upon prior efforts to identify specific mechanisms by which refined microstructures can be achieved in as-HIPed AM metals, improving microstructural control and providing another pathway for microstructural tailoring via AM of metals.

An analytical modelling of the rotation of in-situ principal stresses orientation in the vicinity of an underground opening

ABSTRACT An underground excavation would lead to the redistribution of not only stress magnitude but also stress direction in the host rock mass. In this paper, an equation was derived to quantify the principal stress orientation rotation angle along the roadway radial direction. Besides, the principal stress orientation rotation gradient was analytically modelled followed by a sensitivity analysis of various influential factors on the principal stress orientation rotation. It was found that the principal stress orientation rotation angle tends to decrease as moving further radially into the rock mass from the excavation surface, where the principal stress rotation angle reaches its maximum value of 90°. Four zones have been classified according to the principal stress orientation rotation gradient including high-frequency , medium-frequency, low-frequency and no rotation zone. Finally, the numerical analysis confirmed the redistribution of the principal stress difference and the rotation angle and provided guidance for optimising the bolts setting angle.

Fracture stratigraphy in oil-rich shale of the Upper Xiaganchaigou Formation (upper Eocene), western Qaidam Basin

Natural fractures in wells from oil-rich shale of the Upper Xiaganchaigou Formation in Qaidam Basin, the largest Cenozoic sedimentary basin in the Tibetan Plateau, vary systematically by stratigraphic position, allowing reconstruction of fracture generation processes during regional tectonic deformation. Compacted fractures, layer-bounded fractures, and low-angle (or bed-parallel) fractures were widely identified in oil-rich shale cores obtained from vertical wells. The layer-bounded fractures can be subdivided into two sets: one prevalent in light-colored (low gamma-ray) stiff layers and arrested by dark-colored (high gamma-ray) compliant layers, the other set primarily confined to the dark-colored compliant layers. The strikes of layer-bounded fractures, revealed by horizontal well FMI logs, are dominantly N60°-80°E and N10°-30°E within the light and dark intervals respectively. These strikes are consistent with natural hydraulic fracturing of the light layers during the Oligocene and the dark layers during the Middle Miocene-Holocene, based on a regional anticlockwise rotation of the compressional strain orientation. The abutment of layer-bounded fractures against low-angle (or bed-parallel) fractures in dark layers implies that the low-angle fractures were hydraulically fractured under a vertical least compressive stress during the Early Miocene, which produced the most intense tectonic compression. Layer-bounded fractures generally remain unmineralized in the dark layers but were mineralized in the light layers, suggesting that fractures confined in light layers would not decrease the sealing capacity of the shale oil system and fractures confined in dark layers can increase the pore space of shale oil storage. The Oligocene and Early Miocene fractures represented mechanical flaws that affected the initiation of Middle Miocene-Holocene fractures, implying that all natural fractures may alter hydraulic fracture stimulations to some extent.

Влияние скорости вращения и фигуры астероида на величину возмущений в его вращательной динамике при тесном сближении с Землей

By means of numerical experiments, the influence of the value of the asteroid’s own rotational velocity, orientation of the axis of rotation, and figure parameters on the magnitude of perturbations in its rotational dynamics arising during close approach to the Earth is studied. Two cases are considered: 1) asteroid (99942) Apophis with a relatively slow rotation (period ≈ 30 h) and 2) asteroid 2012 TC4, which has a fast rotation (period ≈ 12 min). It was found that in the case of asteroids with slow rotation, perturbations can be large: in the case of Apophis, when approaching the Earth in 2029, changes in the rotational period ∆P may reach tens of hours, and deviations in the orientation of the axis of rotation ∆γ — tens of degrees. For fast-rotating asteroids, the perturbations are very small: in the case of asteroid 2012 TC4 at its approach to the Earth in 2017, |∆P | < 10−5 min, |∆γ| < 0.01◦. It is shown that for asteroids with slow rotation, the uncertainty in the determination of asteroid figure parameters (moments of inertia) can lead to noticeable inaccuracies in the estimation of perturbation magnitudes. The uncertainty in the knowledge of the figure parameters of a fast-rotating asteroid practically does not affect the estimation of perturbations in its rotational dynamics. In the case of Apophis, changes in the rotational velocity and orientation of the axis of rotation during the upcoming 2029 approach to the Earth may lead to a decrease in the value of the parameter A2, which characterizes the Yarkovsky effect, to −1.5 · 10−14 a.u./d2, or to an increase up to −3.5 · 10−14 a.u./d2. Perturbations in the rotational dynamics of asteroid 2012 TC4 during its approach to the Earth in 2017 did not affect the value of parameter A2.

Synthesis, crystal structure and Hirshfeld surface analysis of 1-[3-(2-oxo-3-phenyl-1,2-dihydroquinoxalin-1-yl)propyl]-3-phenyl-1,2-dihydroquinoxalin-2-one

In the title compound, C31H24N4O2, the dihydroquinoxaline units are both essentially planar with the dihedral angle between their mean planes being 64.82 (4)°. The attached phenyl rings differ significantly in their rotational orientations with respect to the dihydroquinoxaline planes. In the crystal, one set of C—H...O hydrogen bonds form chains along the b-axis direction, which are connected in pairs by a second set of C—H...O hydrogen bonds. Two sets of π-stacking interactions and C—H...π(ring) interactions join the double chains into the final three-dimensional structure.

Synergistic enhancement of strength-ductility balance of TZM alloy through c-ZrO2 combined with large deformation and annealing

In this work, new TZM alloys containing 0.5 wt% and 1.0 wt% ZrO2 were prepared by powder metallurgy method, and their annealed microstructures and mechanical properties were studied. The TZM alloy sheet with 94 % deformation was recrystallized at 1200°C, and the elongation was greatly increased, and its UTS, YS and EL were 573 ± 10 MPa, 431 ± 7 MPa and 44 ± 0.2 %, respectively. After adding 0.5 wt% c-ZrO2, the best strength-ductility balance was achieved, and its UTS, YS, EL and PSE are 621 ± 3 MPa, 527 ± 4 MPa, 41.3 ± 0.58 % and 25.6 GPa·%, respectively, which was much larger than the PSE combinations of most Mo and TZM alloys. Microstructure analysis shows that the excellent synergistic effect arises from the low O impurity content and the control of dislocation density and dislocation slip by c-ZrO2 and the annealing process. Within the alloy, Ti and Zr react with O to produce TiO2 and ZrTiO4, which reduces the content of O impurities. Annealing provides sufficient space for dislocation slip, which coordinates the rotation of grain orientation during the stretching process. Coupled with the low O impurity concentration, results in excellent ductility of TZM alloys. Additionally, c-ZrO2 can effectively fix dislocations within the grains and interact strongly with dislocations, consequently enhancing the strength of the TZM alloy.

Study of the microstructure evolution of alloy structural steel and inhomogeneity effect of the microscale pulsed currents during current-assisted plane strain compressions by modeling a novel cellular automata method

The current-assisted forming process is considered to be a novel process that utilizes the electroplasticity effect to reduce the deformation resistance of difficult-to-deform metals and to refine the grain size while improving the mechanical properties of the part. However, the lack of understanding of the mechanisms by which pulsed current affects grain refinement still makes it difficult to experimentally develop analytical or empirical models of the relationship between grain size, pulse current parameters, and deformation amount. It will seriously hinder the further development and application of the current-assisted forming process. To reveal the mechanism of grain refinement coupling with electroplasticity, a series of Electron Back Scattering Diffraction observation tests were carried out after current-assisted plane strain compressions. The results show that the grain orientation spread value of the pulse current condition is lower than that of the non-current condition, while the refined grain area percentage is higher than that of the non-current condition. Based on the microstructure observation results, a cellular automata model for grain refinement is proposed. This consists of a dislocation density evolution, sub-grains generation, grain fragmentation, and a grain orientation rotation algorithm. To study the electroplasticity of the grain refinement process, the cellular automata model is also embedded with a finite difference numerical algorithm for solving the microscopic current density distribution of the model. The cellular automata model simulation results show that the error of grain size accuracy of this cellular automata model under non-current and pulse current conditions is 10.48% and 8.55%, respectively. It shows that the model can accurately characterize the grain refinement behavior of the current-assisted plane strain compression. The simulation results reveal the deep mechanism of pulsed current promotion on grain refinement, i.e., an inhomogeneous microstructure leads to uneven distribution of pulse current density. The inhomogeneous current distribution will further increase the grain refinement rate in the coarse-grained regions, thus increasing the proportion of the refined grain regions in the microstructure and leading to a relatively more homogeneous microstructure under pulse current conditions. The cellular automata model accurately reveals the mechanism of electroplasticity on the grain refinement. The model will serve as a crucial theoretical reference in designing current-assisted forming process routes to ensure excellent microstructure and properties in manufactured parts. It will enhance the widespread utilization of current-assisted forming process.

On dark energy effects on the accretion physics around a Kiselev spinning black hole

Kiselev metric in the static and rotating form is widely used to test different aspects of the dark energy (DE) effects. We consider a DE Kiselev spacetime, predicting the reduction to the Kerr black hole (BH) solution under suitable conditions on the DE parameters and in this frame we study the effects of the dark energy on BHs and disks accretion. Elaborating a close comparison with the limiting vacuum Kerr spacetime, we focus on thick accretion disks around the central BH in the Kiselev solution, both co-rotating and counter-rotating with respect the central BH. We examine different aspects of BH accretion energetics by focusing on quantities related to the accretion rates and cusp luminosity, when considered the DE presence, related to the pure Kerr central BH. Our findings show that in these conditions heavy divergences with respect to the vacuum case are expected for the DE metrics. A known effect of the Kiselev metric is to lead to a false estimation the BH spin, we confirm this characteristic from the fluids dynamics analysis. Remarkably our results show that DE is affecting differently the accretion physics, and particularly the accretion rate, according to the fluid rotation orientation with respect to the central spinning attractor, leading in some cases to an under-estimation of the BH spin mass ratio. These contrasting aspects emerging in dependence on the fluids rotational orientation can be a distinguishing general DE feature which could lead to a revised observational paradigm where DE existence is considered.

Long-lived photoinduced charge separation in adamantane-bridged donor-acceptor dyads: A case of adamantane bridge conferring orthogonal donor-acceptor orientation and restricted rotation

Design of compact donor-acceptor dyads that can exhibit charge separated (CS) state lifetimes extending to the microsecond time domain remains a major challenge even today. A simple but effective design strategy that can lead to long CS state lifetimes, in at least a few compact dyads, is still elusive. Herein we propose that use of adamantane (AD) as bridge can enhance CS state lifetimes in small molecule donor-acceptor dyads. This paper reports AD-bridged dyads, AN-AD-NB and PY-AD-NB, wherein the anthracene (or pyrene) donor and nitrobenzene acceptor are attached to bridgehead positions of AD. The singlet CS states generated upon irradiation were long-lived (lifetimes >1 μs) and decayed to the ground and local triplet states, simultaneously. Electron transfer reactions of the CS state with secondary donor and acceptor established that the CS state is sufficiently long-lived to participate in intermolecular reactions. X-ray crystal structure of the AN-AD-NB dyad reveals that the donor and acceptor are orthogonally oriented, which reduces the donor-acceptor interaction, and thereby the charge recombination rate, significantly. By analysing the X-ray structure, we predict that all adamantane-bridged compact dyads will have orthogonal donor-acceptor orientation and exhibit long-lived CS states. We also report studies with bisadamantyl-substituted dyads and the results confirmed that the local triplets are formed from the CS state through hyperfine interaction. Based on our work we propose that the hyperfine interaction, which is not expected to occur in compact dyads because of the short donor-acceptor separation, can indeed occur if the CS state is sufficiently long-lived.