Disk Center Research Articles

Clinical study of percutaneous endoscopic thoracic spine surgery via trench technique for thoracic spinal cord ventral decompression

To evaluate the feasibility, safety, and early effectiveness of percutaneous endoscopic thoracic spine surgery via the trench technique for ventral decompression in central calcified thoracic disc herniation (CCTDH) and thoracic ossification of the posterior longitudinal ligament (T-OPLL). Seven patients with single-segment CCTDH or T-OPLL admitted between June 2017 and May 2020 and meeting the selection criteria were retrospectively analyzed. There were 3 males and 4 females with an average age of 51.7 years ranging from 41 to 62 years. There were 2 patients with T-OPLL (T 1, 2 in 2 cases) and 5 patients with CCTDH (T 1, 2 in 1 case, T 7, 8 in 1 case, T 10, 11 in 2 cases, T 11, 12 in 1 case). Five patients with thoracic axial pain and intercostal neuralgia had a preoperative visual analogue scale (VAS) score of 6.0 (5.0, 6.5), and 7 patients had a preoperative Japanese Orthopaedic Association (JOA) score of 21 (21.0, 22.0). Transforaminal approach was used in 4 cases and transpedicular approach in 3 cases. Ventral decompression of thoracic spinal cord was performed by thoracic endoscopy combined with trench technique. The operation time, intraoperative blood loss, postoperative hospital stay, and postoperative complications were recorded. Thoracic spine CT and MRI were performed preoperatively and postoperatively to evaluate the surgical decompression, VAS score was used to evaluate the pain of thoracic back and lower limbs, and JOA score was used to evaluate the functional recovery. Modified MacNab criteria was used to evaluate the effectiveness. All surgeries were successfully completed. The operation time ranged from 60 to 100 minutes, with an average of 80.4 minutes; the intraoperative blood loss ranged from 40 to 75 mL, with an average of 57.1 mL; the postoperative hospital stay ranged from 4 to 7 days, with an average of 5.4 days. CT and MRI examinations indicated that the decompression was adequate. All 7 patients were followed up 3-22 months, with an average of 13.3 months. One case developed postoperative wound infection, and 1 case developed pneumonia; the remaining patients did not have any complications such as wound infection or cerebrospinal fluid leakage. Five patients with thoracic axial pain and intercostal neuralgia had VAS scores of 2.0 (1.5, 2.5) at 1 day after operation and 2.0 (1.0, 2.0) at last follow-up, both of which were significantly lower than the preoperative scores ( P<0.05). At 1 day after operation, the JOA scores for all 7 patients were 22.0 (21.0, 24.0), which showed no significant difference compared to the preoperative score ( P>0.05); however, at last follow-up, the score improved to 24.0 (24.0, 26.0), which was significant compared to the preoperative scores ( P<0.05). At last follow-up, the effectiveness was assessed using the modified MacNab criteria, the results were excellent in 2 cases, good in 3 cases, fair in 2 cases, and the excellent and good rate was 71.4%. Using the trench technique, percutaneous endoscopic thoracic spine surgery can achieve the ventral decompression in CCTDH and T-OPLL, providing a new approach for surgical treatment of CCTDH and T-OPLL.

Connectivity between the solar photosphere and chromosphere in a vortical structure

Context. High-resolution solar observations have revealed the existence of small-scale vortices, as seen in chromospheric intensity maps and velocity diagnostics. Frequently, these vortices have been observed near magnetic flux concentrations, indicating a link between swirls and the evolution of the small-scale magnetic fields. Vortices have also been studied with magneto-hydrodynamic (MHD) numerical simulations of the solar atmosphere, revealing their complexity, dynamics, and magnetic nature. In particular, it has been proposed that a rotating magnetic field structure driven by a photospheric vortex flow at its footprint produces the chromospheric swirling plasma motion. Aims. We present a complete and comprehensive description of the time evolution of a small-scale magnetic flux concentration interacting with the intergranular vortex flow and affected by processes of intensification and weakening of its magnetic field. In addition, we study the chromospheric dynamics associated with the interaction, including the analysis of a chromospheric swirl and an impulsive chromospheric jet. Methods. We studied observations taken with the CRisp Imaging SpectroPolarimeter (CRISP) instrument and the CHROMospheric Imaging Spectrometer (CHROMIS) at the Swedish Solar Telescope (SST) in April 2019. The data were recorded at quiet-Sun disc centre, consisting of full Stokes maps in the Fe I line at 6173 Å and in the Ca II infrared triplet line at 8542 Å, as well as spectroscopic maps in the lines of Hα 6563 Å and Ca II K 3934 Å. Utilising the multi-wavelength data and performing height-dependent Stokes inversion, based on methods of local correlation tracking and wavelet analysis, we studied several atmospheric properties during the event lifetime. This approach allowed us to interpret the spatial and temporal connectivity between the photosphere and the chromosphere. Results. We identified the convective collapse process as the initial mechanism of magnetic field intensification, generating a re-bound flow moving upwards within the magnetic flux concentration. This disturbance eventually steepens into an acoustic shock wave that dissipates in the lower chromosphere, heating it locally. We observed prolonged magnetic field amplification when the vortex flow disappears during the propagation of the upward velocity disturbance. We propose that this type of magnetic field amplification could be attributed to changes in the local vorticity. Our analysis indicates the rotation of a magnetic structure that extends from the photosphere to the chromosphere, anchored to a photospheric magnetic flux concentration. It appears to be affected by a propagating shock wave and its subsequent dissipation process could be related to the release of the jet.

Abnormal Stokes V profiles observed by Hinode in a sunspot. Detection of hidden photospheric fine-structures

Hidden magnetic components in a sunspot are present as small-scale structures that are absent in low-resolution observations. We search for traces of the hidden magnetic components in spectro-polarimetric observations of a mature sunspot close to the disk center recorded by Hinode. To find extra humps in the far blue and red lobes of Stokes V, we examined the sign reversal in the second derivative of the profile in the umbra and penumbra. We also looked for the hump signature in the Stokes I and the linear polarization profiles. The amplitudes of the humps are small compared to the main component. More than half of the profiles show one extra hump, while 21&lt;!PCT!&gt; show an extra hump on both the blue and the red lobe of the 630.15 nm line with the same magnetic polarity as the sunspot. The location of the pixels where the extra hump is seen on both lobes has a pseudo-grainy structure in the single wavelength Stokes V magnetograms. This type of profile is better detected in darker parts of the penumbra, as well as in the umbra-penumbra border toward the umbra. The spectral distance between the two humps averaged over elliptical rings levels off in the umbra, decreases toward the penumbra, and levels off again there. We find no correlations between the wavelength positions of the two humps. We discuss two scenarios that could potentially produce the simultaneously observed blue and red humps: one in which a single hidden magnetic component is responsible for the two humps, and another in which the two humps emanate from two hidden magnetic components.

Sequential formation of supermassive stars and heavy seed BHs through the interplay of cosmological cold accretion and stellar radiative feedback

ABSTRACT Supermassive stars (SMSs) and heavy seed black holes, as their remnants, are promising candidates for supermassive black hole (SMBH) progenitors, especially for ones observed in the early universe $z\simeq 8.5-10$ by recent JWST observations. Expected cradles of SMSs are the atomic cooling haloes ($M_{\rm halo}\simeq 10^7\ \mathrm{M}_{\odot }$), where ‘cold accretion’ emerges and possibly forms SMSs. We perform a suit of cosmological radiation hydrodynamics simulations and investigate star formation after the emergence of cold accretion, solving radiative feedback from stars inside the halo. We follow the mass growth of the protostars for $\sim 3\ \mathrm{Myr}$, resolving the gas inflow down to $\sim 0.1\ \mathrm{pc}$ scales. We discover that, after cold accretion emerges, multiple SMSs of $m_{\star }\gtrsim 10^5\ \mathrm{M}_{\odot }$ form at the halo centre with the accretion rates maintained at $\dot{m}_{\star }\simeq 0.04\ \mathrm{M}_\odot \mathrm{yr}^{-1}$ for $\lesssim 3\ \mathrm{Myr}$. Cold accretion supplies gas at a rate of $\dot{M}_{\rm gas}\gtrsim 0.01-0.1\ \mathrm{M}_\odot \mathrm{yr}^{-1}$ from outside the halo virial radius to the central gas disc. Gravitational torques from spiral arms transport gas further inwards, which feeds the SMSs. Radiative feedback from stars suppresses $\mathrm{H}_2$ cooling and disc fragmentation, while photoevaporation is prevented by a dense envelope, which attenuates ionizing radiation. Our results suggest that cold accretion can bring efficient BH mass growth after seed formation in the later universe. Moreover, cold accretion and gas migration inside the central disc increase the mass concentration and provide a promising formation site for the extremely compact stellar clusters observed by JWST.

THE ASSOCIATION BETWEEN FACET JOINT TROPISM AND LUMBAR DISC HERNIATION

ABSTRACT Background/Aims: Facet joint tropism is thought to be associated with lumbar disc herniation (LDH), but this relationship has not been fully established. The aim of this study was to investigate the relationship between facet joint tropism and LDH in patients (25-30 years old and body-mass index 28-30 kg/m²) using computed tomography (CT) and lumbar magnetic resonance imaging (MRI). Methods: Facet joint angles were measured on lumbar MRI and CT images of 24 male patients with left-sided LDH; 16 patients with right-sided LDH. Facet joint angle was measured by calculating the angle of the facet joints with the vertebral sagittal line in axial sections parallel to the end plate plane. Patients with trauma, rheumatic and oncologic diseases, additional lumbar or spinal and systemic diseases, patients with far lateral, foraminal and central lumbar disc herniations were excluded. Results: The mean left facet joint angle was 44,56º+/-11,29° and the mean right facet joint angle was 41,2º+/-11,27° in 24 patients with left-sided LDH. In 16 patients with right-sided LDH, the mean right facet joint angle was 45,87º +/-16,41°and the mean left facet joint angle was 42,74º+/-12,54°. Conclusions: In the statistical evaluation, no significant correlation was found between LDH and facet joint angle, but in the numerical analysis, it was observed that the left facet joint angle was larger in patients with left-sided LDH and the right facet joint angle was larger in patients with right-sided LDH.

Solar internetwork magnetic fields: Statistical comparison between observations and MHD simulations

Although the magnetic fields in the quiet Sun account for the majority of the magnetic energy in the solar photosphere, inferring their exact spatial distribution, origin, and evolution poses an important challenge because the signals lie at the limit of today's instrumental precision. This severely hinders and biases our interpretations, which are mostly made through nonlinear model-fitting approaches. Our goal is to directly compare simulated and observed polarization signals in the Fe I $ angstrom $ and $ angstrom $ spectral lines in the very quiet Sun, the so-called solar internetwork (IN). This way, we aim to constrain the mechanism responsible for the generation of the quiet Sun magnetism while avoiding the biases that plague other diagnostic methods. We used three different three-dimensional radiative magneto-hydrodynamic simulations representing different scenarios of magnetic field generation in the internetwork: small-scale dynamo, decay of active regions, and horizontal flux emergence. We synthesized Stokes profiles at different viewing angles and degraded them according to the instrumental specifications of the spectro-polarimeter (SP) on board the Hinode satellite. Finally, we statistically compared the simulated spectra to the Hinode/SOT/SP observations at the appropriate viewing angles. Of the three simulations, the small-scale dynamo best reproduced the statistical properties of the observed polarization signals. This is especially prominent for the disk center viewing geometry, where the agreement is excellent. Moving toward more inclined lines of sight, the agreement worsens slightly. The agreement between the small-scale dynamo simulation and observations at the disk center suggests that small-scale dynamo action plays an important role in the generation of quiet Sun magnetism. However, the magnetic field around 50 km above the continuum layer in this simulation does not reproduce observations as well as at the very base of the photosphere.

Dynamic characteristics of a flexible rotor supported on surface textured journal bearings

Abstract This paper presents the dynamic characteristics of a flexible rotor supported on surface textured journal bearings. Oil lubricated journal bearings exhibit the self-exited whirling of rotor, leading to instability. Understanding the threshold speed of instability is crucial in mitigating excessive vibration in rotating machinery. In this work, a simple model of a flexible rotor with central disc is studied. Modal analysis is carried out to obtain the whirl frequencies of the system, mode shapes, and stability limit speed. The addition of surface textures to the journal bearing stands out as a significant modification aimed at improving performance. Fully textured and partially textured bearing surfaces are considered in the investigation and compared with the performance of smooth journal bearings. Notably, fully textured bearings enhance stability limits. This study offers insights essential for optimizing machinery performance and minimizing operational risks.

Searching for the mHz variability in the TESS observations of nova-like cataclysmic variables

We investigated the fast optical variability of selected nova-like cataclysmic variables observed by the satellite. We searched for break frequencies b $) in the corresponding power density spectra (PDS). The goal is to study whether these systems in an almost permanent high optical state exhibit preferred $f_ b $ around 1\,mHz. We selected non-interrupted light curve portions with durations of 5 and 10 days. We divided these portions into ten equally long light curve subsamples and calculated mean PDS. We searched for $f_ b $ in the frequency interval from log($f$/Hz) = -3.5 to -2.4. We defined as a positive detection when the $f_ b $ was present in at least 50&lt;!PCT!&gt; of the light curve portions with a predefined minimum number of detections. We have measured $f_ b $ in 15 nova-like systems and confirmed that the value of this frequency is clustered around 1\,mHz with a maximum of the distribution between log($f$/Hz) = -2.95 and -2.84. The confidence that this maximum is not a random feature of a uniform distribution is at least 96&lt;!PCT!&gt;. This is a considerable improvement on the previous value of 69&lt;!PCT!&gt;. We discuss the origin of these b $ in the context of the sandwich model in which a central hot X-ray corona surrounds a central optically thick disc. This scenario could be supported by a correlation between the white dwarf mass and $f_ b $; the larger the mass, the lower the frequency. We see such a tendency in the measured data; however, the data are too scattered and based on a low number of measurements. Finally, it appears that systems with detected $f_ b $ have a lower inclination than 60-75$^ circ $. In higher-inclination binaries, the central disc is not seen and the PDS is dominated by red noise. This also supports the inner disc regions as being the source of the observed $f_ b

Anatomy of the Star Formation in a Tidally Disturbed Disk Galaxy: NGC 3718

We present a UV, optical, and near-IR study of the star-forming complexes in the nearby peculiar galaxy NGC 3718, using Ultraviolet Imaging telescope, Galaxy Evolution Explorer, Spitzer, and DECam Legacy Survey imaging data. The galaxy has a disturbed optical morphology owing to the multiple tidal arms, the warped disk, and the prominent curved dust lanes, but in the near-IR it appears to be a bulge-dominated galaxy. Its disturbed morphology makes it an excellent case to study star formation in a tidally disturbed galaxy that may have undergone a recent minor merger. To study the distribution and properties of the star-forming clumps (SFCs), we divided the galaxy within the R 25 (B band) radius into three parts—the upper, central, and lower regions. Using the UV band images, we investigated the warped star-forming disk, the extended tidal arms, and the distribution and sizes of the 182 SFCs. Their distribution is 49, 60, and 73 in the galaxy’s upper, central, and lower regions, respectively. We determined the UV color, star formation rates (SFRs), star formation density (ΣSFR), and ages of the SFCs. The central disk of the galaxy has a larger mean ΣSFR that is ∼3.3 and ∼1.6 times higher than the upper and lower regions, respectively. We also find that the SFCs in the central disk are older than those in the tidal arms. Our study thus shows that minor mergers can trigger the inside-out growth of galaxy disks, where the younger SFCs are in outer tidal arms and not in the inner disk.

Galactic outflows in different geometries

In the gravitational potential well of a galaxy, the behavior of outflows has been studied in different geometries i.e. constant flux tube, divergent and extreme divergent environments. First of all, we describe the hydrodynamic model by which we approach the outflows system. This model treats all the waves as fluids and applies fluid mechanics to them(cosmic rays, thermal plasma & Alfvén wave). Whereas outflows mean the gas regime above and below the center of the galactic disk, and we have taken it as a system where interaction between cosmic rays and plasma occurs. After discussing the hydrodynamic three-fluid model, we define three geometrical structures which can be acquired by outflows and relate these structures with thermal plasma, cosmic and Alfvén waves pressures, thus seeking for its behavior. The solution of the system is categorically divided into three branches, supersonic, subsonic and unphysical solutions.The most interesting of all is the transonic solution, a solution that evolves from subsonic to supersonic. First of all, we discuss only thermal plasma outflows and explain their evolution in three cases of outflows environments, followed by the addition of cosmic waves and Alfvén waves. After discussing three fluid outflows in different structures, we compared the results of thermal outflows with three fluid outflows and see how the addition of waves in the system affects the dynamics of the system. At last, the findings of this paper are discussed.

External Validation of SpineNetV2 on a Comprehensive Set of Radiological Features for Grading Lumbosacral Disc Pathologies

BackgroundIn recent years, the integration of Artificial Intelligence (AI) models has revolutionized the diagnosis of Low Back Pain (LBP) and associated disc pathologies. Among these, SpineNetV2 stands out as a state-of-the-art, open-access model for detecting and grading various intervertebral disc pathologies. However, ensuring the reliability and applicability of AI models like SpineNetV2 is paramount. Rigorous validation is essential to guarantee their robustness and generalizability across diverse patient cohorts and imaging protocols. MethodsWe conducted a retrospective analysis of MRI images of 1747 lumbosacral intervertebral discs (IVDs) from 353 patients (mean age, 54 ± 15.4 years, 44.5% female) with various spinal disorders, collected between September 2021 and February 2023 at X-Ray Service s.r.l. The SpineNetV2 system was used to grade 11 distinct lumbosacral disc pathologies, including Pfirrmann grading, disc narrowing, central canal stenosis, spondylolisthesis, (upper & lower) endplate defects, (upper & lower) marrow changes, (right & left) foraminal stenosis, and disc herniation, using T2-weighted sagittal MR images. Performance metrics included accuracy, balanced accuracy, precision, F1 score, Matthew's Correlation Coefficient, Brier Score Loss, Lin's concordance correlation coefficients, and Cohen's kappa coefficients. Two expert radiologists provide annotations for these discs. The evaluation of SpineNetV2′s grading is compared against expert radiologists' assessments. ResultsSpineNetV2 demonstrated strong performance across various metrics, with high agreement scores (Cohen's Kappa, Lin's Concordance, and Matthew's Correlation Coefficient exceeding 0.7) for most pathologies. However, lower agreement was found for foraminal stenosis and disc herniation, underscoring the limitations of sagittal MR images for evaluating these conditions. ConclusionsThis study highlights the importance of external validation, emphasizing the need for comprehensive assessments of deep learning models. SpineNetV2 exhibits promising results in predicting disc pathologies, with findings guiding further improvements. The open-source release of SpineNetV2 enables researchers to independently validate and extend the model's capabilities. This collaborative approach promotes innovation and accelerates the development of more reliable and comprehensive deep learning tools for the assessment of spine pathology.

Reconstructing solar magnetic fields from historical observations

Context. The relation between the intensity of chromospheric emissions and the photospheric magnetic field strength has been examined in several studies, but the effect of the magnetic field inclination on chromospheric emissions remains almost unexplored. Aims. We study how the inclination of the photospheric magnetic field, as measured by the full 3D magnetic vector from the Helioseismic and Magnetic Imager (HMI), affects the relationship between the magnetic field strength and the far-ultraviolet emission at around 1600 Å observed by the Atmospheric Imaging Assembly (AIA). We also study how these parameters change spatially close to the active region perimeter. Methods. We analyzed the mutual dependence of 1168 co-temporal AIA and HMI observations from 2014 to 2017. We focused on magnetically active regions outside sunspots (e.g., plages and network) close to the solar disk center. We studied how the AIA and HMI parameters change with distance from the active region perimeter. Results. The AIA 1600 emission typically decreases with increasing (more horizontal) inclination. For all inclinations, AIA 1600 emission increases with increasing magnetic field strength until saturating at some peak intensity, which depends on the cosine of the inclination, with horizontal regions saturating at lower intensities. In addition, we find that activity clusters have a narrow boundary (&lt; 2 arcsec) in which the AIA 1600 intensity, magnetic field strength, and inclination distributions and relations differ significantly from those in the inner layers. Conclusions. This study demonstrates the significant effect that magnetic field inclination and activity cluster border regions have on chromospheric emissions. Although the observed effects are likely reduced in low-resolution observations where different regions are averaged together, a detailed study is needed to examine the emission–magnetic field relation at different resolutions.

Testing the volume integrals of travel-time sensitivity kernels for flows

Context. Helioseismic inversions largely rely on sensitivity kernels, in which 3D spatial functions describe how the changes in the solar interior translate into the change in helioseismic observables. These sensitivity kernels in most cases come from the forward modelling that is used in the most advanced solar models. Aims. We aim to test the sensitivity kernels by comparing their volume integrals with measured values from helioseismic travel times. Methods. By manipulating the tracking rate, we mimicked the additional zonal velocity in the Dopplergram datacubes. These datacubes were then processed by a standard travel-time measurements pipeline. We investigated the dependence of the east-west travel time averaged over a box around the disc centre on the implanted tracking velocity. The slope of this dependence is directly proportional to the total volume integral of the sensitivity kernel that corresponds to the travel-time geometry that is used. Results. The agreement between measurements and models for travel times that are computed with a ridge filtering is very good to acceptable. The dependence we sought to determine indeed resembles a linear function, and its slope agrees with the expected volume integral from the forward-modelled sensitivity kernel. The agreement is poorer for the phase-speed filtered datacubes. The disagreement is particularly strong for the slowest phase speeds (filters td1–td4). For the higher phase speeds, our result indicates that the measured kernel integrals are systematically larger than expected from the forward modelling. We admit our testing procedure may not be appropriate for high phase speeds and higher radial modes.

Investigation of Indirect Shear Strength of Black Shale for Urban Deep Excavation

This study thoroughly investigated the compressive and tensile strength characteristics of black shale using both experimental and analytical approaches. Uniaxial compression tests were conducted to determine the elastic constants of black shale modeled as idealized, linear elastic, homogeneous, and transversely isotropic. Additionally, Brazilian tests were carried out on shale, considering it a transversely isotropic material. Strain measurements were recorded at the center of disc specimens subjected to diametric loading. By placing strain gages at the disc centers, the five elastic constants were accurately estimated. The effects of experimental methods and diametric loading on the elastic constant determination were evaluated and analyzed, and the indirect shear strength of the black shale, considering anisotropy, was determined using the estimated stress concentration coefficient. This study revealed that the indirect tensile strength of black shale is significantly influenced by the angle between the anisotropic planes and the diametric loading direction. Moreover, it was revealed that the stress concentration coefficients for anisotropic rocks vary from those of isotropic rocks, depending on the inclination angle of the bedding planes. This study confirms that the shear (tensile) strength of anisotropic black shale is not constant but varies with the orientation of the anisotropic planes in relation to the applied load.

Automated detection of exploding granules with SDO/HMI data

Exploding granules on the solar surface play a major role in the dynamics of the outer part of the convection zone, especially in the diffusion of the magnetic field. We aim to develop an automated procedure able to investigate the location and evolution of exploding granules over the solar surface and to get rid of visual detection. We used sequences of observations of intensity and Doppler velocity, as well as magnetograms, provided by the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory. The automated detection of the exploding granules was performed by applying criteria on either three or two parameters: the granule area, the amplitude of the velocity field divergence, and, at the disc centre, the radial Doppler velocity. Our analyses show that granule area and divergence amplitudes are sufficient to detect the largest exploding granules; thus, we can automatically detect them, not only at the disc centre, but across the whole solar surface. Using a 24-hour-long observation sequence, we have demonstrated the important contribution of the most dynamic exploding granules in the diffusion of the magnetic field in the quiet Sun. Indeed, we have shown that the most intense exploding granules are sufficient to build a large part of the photospheric network. We have also applied our procedure on Hinode observations to locate the exploding granules relative to trees of fragmenting granules (TFGs). We conclude that, during a first phase of about 300 minutes after the birth of a TFG, exploding granules are preferentially located on its edge. Finally, we also show that the distribution of exploding granules is homogeneous (at the level of our measurement errors) over the solar surface without a significant dependency on latitude.

Magnetic field and kinetic helicity evolution in simulations of interacting disk galaxies

Context. There are indications that the magnetic field evolution in galaxies is influenced by tidal interactions and mergers between galaxies. Aims. We carried out a parameter study of interacting disk galaxies with impact parameters ranging from central collisions to weakly interacting scenarios. The orientations of the disks were also varied. In particular, we investigated how magnetic field amplification depends on these parameters. Methods. We used magnetohydrodynamics for gas disks in combination with live dark-matter halos in adaptive mesh refinement simulations. The disks were initialized using a setup for isolated disks in hydrostatic equilibrium. Since we focused on the impact of tidal forces on magnetic field evolution, adiabatic physics was applied. Small-scale filtering of the velocity and magnetic field allowed us to estimate the turbulent electromotive force (EMF) and kinetic helicity. Results. Time series of the average magnetic field in central and outer disk regions show pronounced peaks during close encounters and mergers. This agrees with observed magnetic fields at different interaction stages. The central field strength exceeds 10 μG (corresponding to an amplification factor of 2–3) for small impact parameters. As the disks are increasingly disrupted and turbulence is produced by tidal forces, the small-scale EMF reaches a significant fraction of the total EMF. The small-scale kinetic helicity is initially antisymmetric across the disk plane. Though its evolution is sensitive to both the impact parameter and inclinations of the rotation axes with respect to the relative motion of the disks, antisymmetry is generally broken through interactions and the merger remnant loses most of the initial helicity. The EMF and the magnetic field also decay rapidly after coalescence. Conclusions. The strong amplification during close encounters of the interacting galaxies is mostly driven by helical flows and a mean-field dynamo. The small-scale dynamo contributes significantly in post-interaction phases. However, the amplification of the magnetic field cannot be sustained.

The Solar Aspect System of the Hard X-ray Imager Onboard ASO-S

The ASO-S/HXI is a bi-grids modulating instrument for solar hard X-ray imaging, whose collimator contains 91 pairs of tungsten grids. Since the solar disk is invisible in hard X-rays, a Solar Aspect System (SAS) is required to provide the pointing of hard X-ray imager (HXI) for locating X-ray sources on the solar disk. In addition, the knowledge of the alignment and relative twist of the corresponding front–rear grid pairs is important for image reconstruction as well as locating flares. Therefore, the SAS system was designed to monitor the alignment status of HXI grids and to provide the pointing direction of the HXI collimator with two subsystems DM and SA during the whole life cycle of HXI. DM measures the centroids of the front frosted glasses and the solar disk. SA images the Sun and provides precise relative locations of the solar disk center. Both work in the visible light of 565–585 nm. With all the data together, we can solve with an inversion algorithm the alignment status of the front and rear grids, the relative twist, and the pointing direction. We tested and validated the SAS design with both the simulation model and ground coordinate measuring machine. Here we present the detailed system design, the testing results, the inversion algorithm, and the in-orbit status of the SAS. Currently, the SAS has realized the rotational measurement accuracy of about 4 arcsec, and a translational measurement accuracy of about 15 μm, and the SAS pointing data has been used in both imaging calibration for flare locations and imaging corrections for the platform drifting effect. The high-cadence precise measurement (better than 0.3 arcsec) of the pointing will allow the study of source locations at different energies and therefore help us to understand electron acceleration and transportation in flares.

Posterior Biportal Endoscopic Discectomy for the Treatment of Central Cervical Disc Herniation: Technical Note and Preliminary Results

To evaluate the preliminary outcomes and clinical efficacy of a novel posterior biportal endoscopic technique in the treatment of central cervical disc herniation (CCDH). A total of 11 patients with symptomatic CCDH who met the inclusion criteria underwent posterior biportal endoscopic discectomy between December 2021 and May 2023. The surgical procedure involved flavectomy, foraminotomy, pediculoplasty, and discectomy using 30° and 45° arthroscopes and specialized minimally invasive tools. Functional outcomes were assessed using the Japanese Orthopedic Association scoring system, Neck Disability Index, and visual analog scale for axial neck pain. Clinical efficacy was evaluated at the final follow-up using the modified Macnab criteria. All 11 patients successfully underwent posterior biportal endoscopic discectomy with a mean operative time of 82.7±10.1minutes and mean estimated blood loss of 31.8±9.8ml. The mean hospital stay was 5.2±1.1days, and the mean follow-up period was 13.8±2.4months. Significant improvements were observed in Neck Disability Index, Japanese Orthopedic Association, and visual analog scale scores. Clinical efficacy was rated as excellent in 3 patients, good in 6 patients, and fair in 2 patients according to the modified Macnab criteria. No cases of cervical instability or kyphosis were observed during postoperative follow-up. The novel posterior biportal endoscopic technique demonstrated significant clinical efficacy and safety in treating CCDH, with marked improvements in clinical outcomes, rapid postoperative recovery, and a low incidence of complications.

Description of Ornithodoros (Pavlovskyella) tartakovskyi using scanning electron microscopy, with notes on the morphology of Pavlovskyella sensu stricto and Theriodoros subgenera

Accumulation of DNA sequence data and its use in systematics of the family Argasidae reveals new incongruencies between genera and subgenera, since several groups defined by classical taxonomy appear to be paraphyletic, which is the case of the subgenus Pavlovskyella. In order to identify morphological characters unique to one of the monophyletic groupings within Pavlovskyella and improve its system, we describe all active stages of Ornithodoros (Pavlovskyella) tartakovskyi, a species with an incomplete original description. Larvae, nymphs, males and females from Iran were examined with scanning electron microscopy (SEM). The larva of O. (P.) tartakovskyi lacks dorsal plate, posteromedian seta, postcoxal setae and a spinose area in palpal article I; the dorsal surface has 13 pairs of setae and the hypostome has two short rows of denticles in the apex only. The first nymphal instar (N1) has a micromammillated body with faint dorsal and ventral disks. The second nymphal instar (N2) shows mammillated body with an incipient hood, and dorsal disks outlined as in subsequent instars. Both N1 and N2 have a small patch of glabrous surface in the anterior margin of preanal groove, absent in posterior stages. Third nymphal instar (N3) has a small hood and lack cheeks, which are incipient in the fourth nymphal instar (N4). The four nymphal instars (N1–N4) have blunt hypostomes, striated capitula, non-mammillated legs, and 3 humps on tarsi I. Females and males of O. (P.) tartakovskyi have mammillated bodies, small cheeks not covering the capitulum, the anteromedian disk is placed anteriorly to anterior central disks, and a posterior median file of disks is merged with the median disk. We describe all postembryonic stages of O. (P.) tartakovskyi providing morphological characters that define Pavlovskyella sensu stricto and Theriodoros, a sister subgenus that includes similarly shaped species.

The Garden of Evaluation Approaches Visualization

Background: The Garden of Evaluation Approaches (Montrosse-Moorhead, et al., 2024a) maps evaluation approaches against eight dimensions of practice and situates them in their philosophical orientations and methodological dispositions. Purpose: The Garden’s guiding question is: How do evaluation approaches compare in terms of dimensions that facilitate use and application? Primary intended users are evaluation practitioners, and secondary intended users include ecosystem actors (e.g., clients, program participants, funders), educators, researchers, and theoreticians. Setting: Not applicable. Intervention: Not applicable. Research Design: Exploratory sequential mixed methods. Data Collection and Analysis: Data collection and analysis included locating and reading primary sources for each evaluation approach. One team member thematically coded each source for evidence of an approach’s stance on the eight dimensions of practice, its’ philosophical orientation and methodological disposition, and steps for implementing the approach in practice. This qualitative evidence was used to generate ordinal ratings for the eight dimensions using a rating scale developed by the team, and to classify the approaches' philosophical orientation and methodological disposition. Drafts of handouts summarizing qualitative and quantitative data were reviewed by the two other team members, with dialogue and deliberation among all members used to come to consensus. Findings: The first iteration of the Garden includes seven approaches: fourth generation evaluation, made in Africa, nation-to-nation evaluation, practical participatory evaluation, sistematización de experiencias, theory-driven evaluation, and transformative participatory evaluation. Each approach is represented as a flower within the Garden, with each petal corresponding to the approaches’ stance on one of the eight dimensions of practice. The colors of the flowers represent the underlying philosophical foundation of the approach. The pattern within the central disc of each flower represents the methodological disposition encouraged by the approach. Summaries of the empirical mixed-method analysis are made transparent in supporting handouts. Future work will grow flowers for additional approaches and continue to map out the Garden.