Disk Center Research Articles

A Double-decker Flux Rope Model for the Solar Eruption on 2012 March 10

We present a magnetic configuration of a compound solar eruption observed on 2012 March 10, from NOAA AR 11429 near the disk center, which displayed a soft X-ray sigmoid before the eruption. We constructed a series of magnetic field models, including double-decker flux rope configurations, using the flux rope insertion method. This produces three-dimensional coronal magnetic field models constrained by the photospheric magnetogram and observed EUV coronal structures. We used different combinations of flux rope paths. We found that two flux ropes sharing the same path at different heights quickly experience a partial merging in the initial iteration of the magnetofrictional relaxation process. Different paths with less than 30% overlap allowed us to construct stable double-decker structures. The high spatial and temporal resolution of the Solar Dynamics Observatory/Atmospheric Imaging Assembly facilitated the selection of a best-fit model that matches the observations best. Moreover, by varying fluxes in this validated nonlinear force-free field double-decker configuration, we successfully reproduce all three scenarios of eruptions of double-decker configurations: (i) eruption due to the instability of higher flux rope; (ii) eruption due to rising lower flux rope and merging with higher flux rope; and (iii) eruption due to the instability of both flux ropes. This demonstrates that magnetofrictional simulation can capture the large-scale magnetic structure of eruptions for a realistic field configuration at eruption onset.

Full transforaminal endoscopic discectomy versus microlumbar discectomy for lumbar disc herniation: 2-year results

Abstract Objective: Microlumbar discectomy (MLD) has been a gold standard surgical treatment of lumbar disc herniation (LDH); we have compared its results with full transforaminal endoscopic discectomy (FTED), which is a recent trend performed under local anesthesia. FTED and MLD are currently prevalent techniques for the surgical treatment of LDH. Materials and Methods: Patients were randomly assigned to the FTED or MLD groups in this single center study if they had clinical LDH with low back ache with radiculopathy confirmed with magnetic resonance imaging findings. The Oswestry disability index score was the primary outcome. 36-Item Short-Form Health Survey, Macnab, and visual analog scales for back pain and leg pain were used as secondary outcomes. Results: Over a follow-up of 2 years, both primary and secondary outcomes differed significantly according to the location of the discs; FTED was very successful in foraminal and extraforaminal herniated discs with many other benefits whereas MLD was better in central discs. Conclusion: FTED is superior in cosmesis, returning to work in 2 weeks, less surgical trauma, minimal bleeding, infection, hospital stay, and surgical scar compared with MLD. FTED was found to be less effective for median disc herniation, whereas MLD did not appear to be the best alternative for foraminal/extraforaminal disc herniation.

What OPA1 models teach us about potential therapy

Autosomal dominant optic atrophy (DOA) is the most common inherited optic neuropathy, affecting approximately 1 in 25 000 people. DOA has an insidious onset in early childhood. It presents typically with bilateral central painless vision loss, dyschromatopsia, and optic disc pallor due to gradual retinal ganglion cell (RGC) loss and optic nerve degeneration. 60%–70% of genetically confirmed DOA cases are associated with variants in OPA1. OPA1 is an ubiquitously expressed GTPase that regulates mitochondrial homeostasis through coordination of inner membrane fusion, maintenance of cristae structure, and maintenance of bioenergetic output. Over 250 known pathogenic variants in OPA1 have been reported, with missense variants within the GTPase domain associated with an increased susceptibility to developing DOA plus (DOA+), a multisystemic syndromic form of the disease with extraocular features, including sensorineural hearing loss and ataxia. Current therapeutic options to treat DOA are limited. Idebenone has been shown to protect against visual loss in Leber's hereditary optic neuropathy (LHON). In DOA off ‐label retrospective series show some promise in some patients.Animal models for OPA1 DOA, have been reported, including Drosophila, C elegans, Danio rerio and mouse models. They have cast light on some potential therapeutic modalities. Despite limitations, murine models of DOA are currently indispensable for understanding pathophysiology of disease, drug testing and development. They replicate many symptoms and signs of human disease. However, there are caveats. Chemically induced Complex I deficits are very toxic. Genetic models of mitochondrial mutation affect protein integrity and function and can cause severe pathologies. This is made more problematic if there is a need for aging the mouse to bring out the full phenotype. We shall review the mouse models and describe some features that aid or our understanding of pathophysiological mechanisms. Our research has characterized the earliest morphological changes as a progressive loss of synapses, dendrite retraction and RGC remodelling and loss of connectivity. In the DOA mouse Opa1+/− mouse (B6;C3‐Opa1Q285STOP), heterozygous Opa1+/− mice develop visual defects, on psychophysics (optokinetic response) and electrophysiology (VEP, PhNR), consistent with RGC dysfunction. There is depressed mitochondrial Complex I and IV activity. Visible structural changes and disrupted axon morphology in the optic nerve are seen. We have carried out a randomized, placebo‐controlled trial of the benzoquinone idebenone in our ADOA mouse, which revealed a limited therapeutic effect on RGC dendropathy and visual function.It is apparent that there are large differences between the rodent and primate visual system. The fovea of the retina, a critical component for central vision is one of the only primate‐specific components of the mammalian nervous system and is thus, not found in rodent. For these reasons, there is a strong case to use human cells. We shall review data on induced human pluripotent stem cell (hiPSC) with OPA1 mutation, with or without differentiation to RGCs, as models, and on CRISPRCas9 correction of patient‐derived OPA1 iPSC lines.

A Statistical Analysis of Spiral-shaped Wave Patterns in Sunspot Umbrae

Spiral-shaped wave patterns (SWPs) observed in sunspot umbrae represent the superposition of axisymmetric patterns and nonaxisymmetric patterns of umbral oscillations. These patterns give us physical information about the source of oscillations below the surface. Here we present the statistics of their observational properties determined from the 304 Å line-intensity data obtained with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. From the 2013 to 2018 data set, we examined each of the 496 sunspots near the disk center for 2 hr. As a result, we identified 241 SWPs from 140 sunspots, which corresponds to the detection rate of 0.24 per hour in each sunspot. Most of the SWPs had one spiral arm, 48 SWPs had two arms, and only one had three. The oscillation period was estimated at 151 ± 27 s and the lifetime, at 770 ± 250 s, being comparable to those of conventional umbral oscillations. The rotation period of the SWPs was estimated at 190 ± 69 s for the one-armed SWPs and 299 ± 115 s for the two-armed SWPs. We found that the properties of the SWPs have no dependence on hemisphere, latitude, and sunspot size. From the apparent radial speeds of the SWPs and a simple model of wave propagation, we infer that the SWPs may be generated between 2 and 11 Mm below the photosphere with a mean value of about 6 Mm.

Effect of macular pigment optical density on Yellow‐Blue and Red‐Green colour discrimination

The macular pigment (MP) absorbs preferentially short‐wavelength light and its narrow spectral absorption curve overlaps mostly the spectral responsivity function of S‐cones, although the M‐ and L‐cones are also affected. The MP is restricted to the centre ~14° disc region of the retina with a peak optical density (OD) at the centre in the range 0 to 1 log units. Although the macular pigment optical density (MPOD) decreases rapidly with increasing eccentricity, carotenoid supplementation studies reveal a large uptake of lutein and zeaxanthin, particularly in the parafoveal region and covering the centre ~6° to 8° of the fovea (doi: 10.1111/j.1475‐1313.2006.00386.x).Since the MP contributes to the reduced excitation of S‐cones, it is of interest to examine the effects MP may have on colour vision, particularly when ‘blue‐blocking’ lenses are also involved. We studied the relationship between MPOD and red/green (RG) and yellow/blue (YB) colour thresholds by measuring the spatial distribution of the MP in normal trichromats using the Macular Assessment Profile (MAP) test (doi: 10.1111/j.1475‐1313.2010.00748.x) and the corresponding RG and YB colour thresholds using the CAD test (doi:10.1093/bmb/ldx007).The results show negligible correlation between peak MPOD and YB thresholds and a small, but significant negative correlation with RG thresholds. This observation is of interest since increased MPOD values result in lower RG thresholds. The same experiment was also carried out in subjects with significantly larger amounts of MP following 3 months of supplementation with carotenoids. When averaged over the centre disc region of 2.5° and then over a parafoveal annulus between 2.5° and 4°, the corresponding, mean MP densities show only negligible correlations with RG and YB colour thresholds. To explain these findings, we calculated the expected cone‐contrasts for S‐, M‐ and L‐cones for chromatic displacements defined by the threshold ellipse. The results show that MP absorption of short‐wavelength light has a negligible effect on S‐cone contrast over the whole range of displacement directions associated with the colour threshold ellipse. Repeated calculations with simulated MPOD values up to 1 log unit, produced the same result. More recently, we modelled the effects ‘blue‐blocking’ lenses and pre‐receptor filters in the eye to explore changes to the orientation and the size of the colour threshold ellipse. The model predicts well the measured RG and YB thresholds and confirms the absence of significant threshold changes for MPOD values in the range 0 to 1 log unit. The model does, however, predict systematic changes in the orientation of the major axis (i.e., the tritan axis) and MPOD. These observations are of interest since the orientation of the major axis of the best‐fit ellipse appears to decrease monotonically from ~75° to 55°, as MPOD increases from very small values up to a peak OD of 1 log unit. More work is needed to investigate how YB and RG chromatic sensitivity is affected by combined absorption of short‐wavelength light by MPOD, the lens of the eye and ‘blue‐blocking’ spectacle lenses.

Using a machine vision sensor for wavelength estimation by measuring an Airy disk, with didactic purposes

In this manuscript, it is presented a simple and automated educational resource with the aim of determining the wavelength of a laser source that uses the Airy disk generated by a circular aperture. It is known that there is a relationship between the diameter of the central disk and the distance between the circular aperture and the image plane. These two parameters are automatically measured by using a machine vision sensor and an ultrasonic distance sensor, respectively. This resource can be applied in graduate or undergraduate Physics and Engineering laboratories and classrooms for educational, demonstrative, or measuring purposes.

ASSOCIATION VITAMIN D TO GLAUCOMA: A SYSTEMATIC REVIEW

Background: Glaucoma is a chronic progressive optic neuropathy that causes irreversible damage. Therefore, early diagnosis and appropriate treatment to control various risk factors associated with glaucoma are important. Risk factors associated with the development of glaucoma have been reported by many researchers and include both ocular and non-ocular (systemic) factors such as myopia, central corneal thickness, disc hemorrhage, and genetic factors. The aim: This study aims to show association vitamin D to glaucoma. Methods: By comparing itself to the standards set by the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020, this study was able to show that it met all of the requirements. So, the experts were able to make sure that the study was as up-to-date as it was possible to be. For this search approach, publications that came out between 2013 and 2023 were taken into account. Several different online reference sources, like Pubmed and SagePub, were used to do this. It was decided not to take into account review pieces, works that had already been published, or works that were only half done. Result: In the PubMed database, the results of our search brought up 89 articles, whereas the results of our search on SagePub brought up 98 articles. The results of the search conducted for the last year of 2013 yielded a total 13 articles for PubMed and 26 articles for SagePub. The result from title screening, a total 2 articles for PubMed and 18 articles for SagePub. In the end, we compiled a total of 10 papers. We included five research that met the criteria. Conclusion: Decreased serum 25-OHD concentration was associated with the presence but not the severity of POAG. It was suggested that Vitamin D deficiency should be considered a potential risk factor for the development of open-angle glaucoma.

When and How Ram Pressure Stripping in Low-mass Satellite Galaxies Enhances Star Formation

We investigate how a satellite's star formation rate (SFR) and surviving gas respond to ram pressure stripping (RPS) in various environments. Using a suite of high-resolution wind tunnel simulations with radiative cooling, star formation, and supernovae feedback, we model the first infall orbit of a low-mass disk galaxy (M * = 109.7 M ⊙) in different host halos, ranging from Milky Way–like to cluster hosts. When the ram pressure is moderate, we find that the stripping satellite shows an enhanced SFR relative to the isolated control case, despite gas loss due to stripping. The SFR enhancement is caused, not directly by compression, but by ram-pressure-driven mass flows, which can increase the dense gas fraction in the central disk regions. The spatially resolved star formation main sequence and Kennicutt–Schmidt relations in our simulations are consistent with recent findings of the VERTICO and GASP surveys. Our results predict the environmental signals of RPS in future multiwavelength, high-angular resolution observations: the star formation and gas surface densities will be centralized, and symmetrically enhanced within the stripping radius.

Transdural Ventral Sling Technique for Calcified Thoracic Disk Herniations

BackgroundSurgery for thoracic disc herniations remains an ongoing challenge, with a variety of surgical approaches, all with their own inherent risks. Discectomy via a posterior laminectomy was historically the treatment of choice; however, it was deemed very high risk with elevated rates of neurologic injury. The posterior transdural approach is an alternative surgical option for soft and calcified thoracic disc herniations. ObjectiveTo present a surgical technique to remove a calcified thoracic disc herniation without entry into the thoracic cavity. MethodsA 56-year-old female presented with many years of numbness/tingling in her hands and difficulty with fine motor tasks but developed progressive weakness and loss of balance in her legs. Imaging revealed a prominent focal central calcified disc herniation at the T5-T6 level causing severe effacement and distortion of the spinal cord. A posterior transdural approach for direct visualization of a large, calcified disc herniation was performed to remove the calcified disc herniation without the need for extensive surgical exposure or entry into the thoracic cavity. A ventral sling of the dura was created to allow rotation of the spinal cord while removing the calcified disc. Preoperative and postoperative radiographic assessments were conducted to evaluate the effectiveness of the approach. ConclusionsThe transdural approach is less invasive in nature, minimizes surgical exposure, patient morbidity, and provides better intraoperative control of the spinal cord. This constitutes an effective alternative surgical approach to both soft and calcified central thoracic disc herniations.

Looking for optimal concentric ring electrodes: influence of design aspects on their performance

Concentric ring electrodes (CREs) allow improved spatial resolution, reduced crosstalk and interference, and increased bandwidth in the sensing of bioelectrical activity. A wide variety of designs have been used, but their selection is rarely well-founded. The aim of this work is to assess the implications of aspects of CRE design such as the distance between poles, their width and their maximum diameter on aspects such as the signal amplitude (and, therefore, quality), Laplacian estimation error and spatial selectivity (SS). For this purpose, a finite dimensional model of the CRE was used, and its response to the activity of an electric dipole of variable depth was simulated via finite element method modeling. Our results show that increasing the electrode size increases the error to a greater extent than the signal amplitude increases. Pole widths should be as small as possible. The middle ring of the tripolar CRE should be as far away as possible from the central disc. Tripolar CREs typically outperform bipolar CREs of the same outer diameter, significantly reducing the Laplacian estimation error and improving the SS at the cost of a small decrease in signal amplitude. Our results also show that the design of current commercial versions of CREs can be optimized. Furthermore, we propose a methodology that facilitates the selection of an adequate CRE configuration based on the specifications for CRE performance and practical aspects, such as the depth of activity sources to be recorded from and/or the maximum size of electrodes to be used. The monitoring and analysis of bioelectrical signals in a wide range of applications can benefit from the enhanced electrode design and methodology proposed in this work.

Convective characteristics of Fe I lines across the solar disc

Context. Solar convection is visible as a net blueshift of absorption lines, which becomes apparent when observing quiet Sun granulation. This blueshift exhibits variations from the disc centre to the solar limb due to differing projection angles onto the solar atmosphere. Aims. Our goal is to investigate convective Doppler velocities based on observations from the disc centre to the solar limb. Consequently, we aim to improve our understanding of atmospheric hydrodynamics and contribute to the improvement of solar and stellar atmospheric models. Methods. We used resolved quiet-Sun spectra to investigate the convective velocity shifts of more than 1000 Fe I lines across multiple centre-to-limb positions on the solar disc. We determined the Doppler velocities with respect to the line depth. Additionally, we calculated the formation temperature and investigated its correlation with Doppler velocities. Results. The general behaviour of convective line shifts shows a decreasing blueshift as the lines become deeper for all observing positions from the centre to limb. For spectra obtained at the solar limb, even deeper lines exhibit redshifts. We observe a velocity trend for the different observation angles, with a less pronounced convective blueshift towards the solar limb. Convective velocities show a wavelength dependence for each observing angle when analysing on the basis of line depths. We observe a decreasing convective blueshift as the formation temperatures of the lines decrease. The velocity change over temperature ranges proceeds slower towards the solar limb. When investigating Doppler velocities with respect to formation temperature, the disc centre does not exhibit the strongest blueshift.

The Extreme Space Weather Event of 1872 February: Sunspots, Magnetic Disturbance, and Auroral Displays

We review observations of solar activity, geomagnetic variation, and auroral visibility for the extreme geomagnetic storm on 1872 February 4. The extreme storm (referred to here as the Chapman–Silverman storm) apparently originated from a complex active region of moderate area (≈ 500 μsh) that was favorably situated near disk center (S19° E05°). There is circumstantial evidence for an eruption from this region at 9–10 UT on 1872 February 3, based on the location, complexity, and evolution of the region, and on reports of prominence activations, which yields a plausible transit time of ≈29 hr to Earth. Magnetograms show that the storm began with a sudden commencement at ≈14:27 UT and allow a minimum Dst estimate of ≤ −834 nT. Overhead aurorae were credibly reported at Jacobabad (British India) and Shanghai (China), both at 19.°9 in magnetic latitude (MLAT) and 24.°2 in invariant latitude (ILAT). Auroral visibility was reported from 13 locations with MLAT below ∣20∣° for the 1872 storm (ranging from ∣10.°0∣–∣19.°9∣ MLAT) versus one each for the 1859 storm (∣17.°3∣ MLAT) and the 1921 storm (∣16.°2∣ MLAT). The auroral extension and conservative storm intensity indicate a magnetic storm of comparable strength to the extreme storms of 1859 September (25.°1 ± 0.°5 ILAT and −949 ± 31 nT) and 1921 May (27.°1 ILAT and −907 ± 132 nT), which places the 1872 storm among the three largest magnetic storms yet observed.

The Stability of Some Galaxy Disks is Still Perplexing

The problem of how some disk galaxies avoid forming bars remains unsolved. Many galaxy models having reasonable properties continue to manifest vigorous instabilities that rapidly form strong bars and no widely accepted idea has yet been advanced to account for how some disk galaxies manage to avoid this instability. It is encouraging that not all galaxies formed in recent cosmological simulations possess bars, but the dynamical explanation for this result is unclear. The unstable mode that creates a bar is understood as a standing wave in a cavity that reflects off the disk center and the corotation radius, with amplification at corotation. Here we use simulations to address one further idea that may inhibit the feedback loop and therefore contribute to stability, which is to make the disk center dynamically hot and/or to taper away mass from the inner disk, which could be masked by a bulge. Unfortunately, we find that neither strategy makes much difference to the global stability of the disk in the models we have tried. While deep density cutouts do indeed prevent feedback through the center, they still reflect incoming waves and thereby provoke a slightly different instability that again leads to a strong bar.

Micropropagation and Acclimatization of Gymnocalycium cv. Fancy (Cactaceae): Developmental Responses to Different Explant Types and Hormone Conditions

The Gymnocalycium genus includes numerous highly valued species in the ornamental plant market and their propagation is usually carried out using traditional methods. However, there is a lack of information regarding the efficiency of micropropagation through in vitro tissue culture techniques on these species. So, with the objective of establishing an efficient micropropagation protocol that allows for optimizing the plant obtaining processes, the morphogenic potential of Gymnocalycium cv. Fancy has been studied in this work. For this purpose, plants of two different sizes (medium and large) were used as the starting material, from which three types of explants were obtained (apex, central discs and bases). The effect of three plant growth regulators (6-Benzylaminopurine, BAP; Kinetin, KIN; and Thidiazuron, TDZ) at three different concentrations each were studied, and the number of generated shoots, the frequency of appearance of callogenesis and rhizogenesis by explant and condition were assessed. An efficient protocol based on the use of KIN at 4 µM and central discs as a starting explant was developed. Moreover, the obtained sprouts rooted successfully (especially using BAP at 2 µM), and their subsequent acclimatization was very effective. Furthermore, emergence of a new morphotype is presented, that has not previously been described.

C ii] Spectral Mapping of the Galactic Wind and Starbursting Disk of M82 with SOFIA

M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [C ii] 158 μm line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (ΔV = 10 km s−1) [C ii] emission in the outflow of M82 at projected distances of ≈1–2 kpc south of the galaxy center. We compare the [C ii] line profiles to observations of CO and H i and find that likely the majority (>55%) of the [C ii] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [C ii] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [C ii] outflows at higher redshift. Finally, by comparing the observed ratio of the [C ii] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ∼103.5 G 0, in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2–3 orders of magnitudes lower, which may explain the high fraction of [C ii] arising from the neutral medium in the wind.

Application of modified fracture criteria incorporating T-stress for various cracked specimens under mixed mode I-II loading

Accurate assessment of fracture behavior and life prediction of cracked materials based on the mixed mode fracture criteria is of utmost importance in fracture mechanics. In this study, the modified fracture criteria incorporating T-stress for mixed mode I-II cracks were comprehensively reviewed. Additionally, a comparative analysis was conducted between the experimental results obtained from five different cracked configurations and the theoretical predictions according to these modified criteria. Moreover, a brief discussion was held regarding the effect of T-stress on both crack initiation angle and fracture toughness, accompanied by providing some suggestions. The results revealed that the predictive accuracy of modified criteria exhibited noticeable variations across different cracked configurations due to the significant disparities in both the sign and magnitude of T-stress around the crack tip. However, it was observed that the predicted curves based on the modified fracture criteria for the semi-circular bend and edge-crack triangular specimens had remarkable similarities owing to their similar biaxial stress ratio B. When the mode II loading dominated, the generalized maximum tangential stress, generalized minimum strain energy density and generalized averaged strain energy density criteria were suitable for the semi-circular bend, edge-crack triangular, central crack rectangular and short bend beam specimens with positive T-stresses, whereas the maximum tangential strain, generalized maximum tangential stress and generalized maximum tangential strain energy density criteria could provide better theoretical predictions for central cracked Brazilian disk specimens having a negative T-stress.

Quasar feedback survey: molecular gas affected by central outflows and by ∼10-kpc radio lobes reveal dual feedback effects in ‘radio quiet’ quasars

ABSTRACT We present a study of molecular gas, traced via CO (3–2) from Atacama Large Millimeter/submillimeter Array data, of four z < 0.2, ‘radio quiet’, type 2 quasars (Lbol ∼ 1045.3–1046.2 erg s−1; L$_{\mathrm{1.4\, GHz}}\sim 10^{23.7}\!-\!10^{24.3}$ W Hz−1). Targets were selected to have extended radio lobes (≥ 10 kpc), and compact, moderate-power jets (1–10 kpc; Pjet ∼ 1043.2–1043.7 erg s−1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (Vout = 250–440 km s−1) and spatial scales (0.6–1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9–53 per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly ‘radio loud’, brightest cluster galaxies. They have the following: projected distances of 5–13 kpc; bulk velocities of 100–340 km s−1; velocity dispersion of 30–130 km s−1; inferred mass outflow rates of 4–20 M⊙ yr−1; and estimated kinetic powers of 1040.3–1041.7 erg s−1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jet–cloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation.

Arthroscopic Wafer Procedure for Ulnar Impaction Syndrome in an Intact Triangular Fibrocartilage Complex

AbstractUlnocarpal impaction or ulnar abutment symptom occurs secondary to abnormal load bearing on the ulnar side of the wrist leading to pain symptoms and degeneration of the structures of the ulnocarpal joint.The two classical surgical methods used to address this problem are ulnar shortening osteotomy and the wafer procedure, which can either be open or arthroscopic. With the advent of arthroscopy, with surgeon harboring arthroscopy skills, arthroscopic wafer resection has been intensely popularized which requires a central perforation of the triangular fibrocartilage to approach the ulna dome through the ulnocarpal joint.So, what happens in symptomatic patients with ulnocarpal abutment with an intact triangular fibrocartilage complex who have failed conservative management. Do we perform an open procedure or do we create a perforation in the central disc of the triangular fibrocartilage complex to expose the ulnar dome? Or do we just do an ulnar shortening osteotomy?Here, we describe our arthroscopic technique of conducting arthroscopy in the narrow confines of the space below the triangular fibrocartilage complex above the ulnar dome to carry out an arthroscopic wafer procedure in a triangular fibrocartilage complex with no central perforation. The procedure can produce results similar to those of the classical arthroscopic wafer procedure described explicitly in the literature.

Assessment of the CRD approximation for the observer’s frame RIII redistribution matrix

Context. Approximated forms of the RII and RIII redistribution matrices are frequently applied to simplify the numerical solution of the radiative transfer problem for polarized radiation, taking partial frequency redistribution (PRD) effects into account. A widely used approximation for RIII is to consider its expression under the assumption of complete frequency redistribution (CRD) in the observer’s frame (RIII−CRD). The adequacy of this approximation for modeling the intensity profiles has been firmly established. By contrast, its suitability for modeling scattering polarization signals has only been analyzed in a few studies, considering simplified settings. Aims. In this work, we aim to quantitatively assess the impact and the range of validity of the RIII−CRD approximation in the modeling of scattering polarization. Methods. We first present an analytic comparison between RIII and RIII−CRD. We then compare the results of radiative transfer calculations, out of local thermodynamic equilibrium, performed with RIII and RIII−CRD in realistic one-dimensional atmospheric models. We focus on the chromospheric Ca I line at 4227 Å and on the photospheric Sr I line at 4607 Å. Results. The RIII−CRD approximation provides accurate results for the Ca I 4227 Å line. Only when velocities are included can some appreciable discrepancies be found, especially for lines of sight close to the disk center. The approximation performs well also for the Sr I 4607 Å line, especially in the absence of magnetic fields or when a micro-turbulent field is included. However, some appreciable errors appear when deterministic magnetic fields or bulk velocities are considered. Conclusions. Our results show that the RIII−CRD approximation is suited for the PRD modeling of the scattering polarization signals of strong chromospheric lines, both in the core and wings. With a few minor exceptions, this approximation is also suitable for photospheric lines, although PRD effects generally play a minor role in their modeling.

Solar Atmospheric Heating Due to Small-scale Events in an Emerging Flux Region

We investigate the thermal, kinematic, and magnetic structure of small-scale heating events in an emerging flux region (EFR). We use high-resolution multiline observations (including Ca ii 8542 Å, Ca ii K, and the Fe i 6301 Å line pair) of an EFR located close to the disk center from the CRISP and CHROMIS instruments at the Swedish 1 m Solar Telescope. We perform non-LTE inversions of multiple spectral lines to infer the temperature, velocity, and magnetic field structure of the heating events. Additionally, we use the data-driven Coronal Global Evolutionary Model to simulate the evolution of the 3D magnetic field configuration above the events and understand their dynamics. Furthermore, we analyze the differential emission measure to gain insights into the heating of the coronal plasma in the EFR. Our analysis reveals the presence of numerous small-scale heating events in the EFR, primarily located at polarity inversion lines of bipolar structures. These events not only heat the lower atmosphere but also significantly heat the corona. The data-driven simulations, along with the observed enhancement of currents and Poynting flux, suggest that magnetic reconnection in the lower atmosphere is likely responsible for the observed heating at these sites.