Tearing Instability Research Articles

Numerical MHD simulations of solar flares and their associated small-scale structures

ABSTRACT Using numerical simulations, we study the formation and dynamics of solar flares in a local region of the solar atmosphere. The magnetohydrodynamics (MHD) equations describe the dynamic evolution of flares, including space-dependent and anomalous magnetic resistivity and highly anisotropic thermal conduction on a 2.5 D slice. We adopt an initial solar atmospheric model in magnetohydrostatic equilibrium, with a magnetic configuration consisting of a vertical current sheet, which helps trigger the magnetic reconnection process. Specifically, we study three scenarios, two with only resistivity and the third with resistivity plus thermal conduction. The main results of the numerical simulations show differences in the global morphology of the flares, including the post-flare loops and the current sheet in three cases. In particular, localized resistivity produces more substructure around the post-flare loops that could be related to the Ritchmyer–Meshkov Instability (RMI). Furthermore, in the scenario of anomalous resistivity, we identify the formation of a plasmoid and a jet at coronal heights. On the other hand, in the scenario with resistivity plus thermal conduction, the post-flare loops are smooth, and no apparent substructures develop. Besides, in the z-component of the current density for the Res + TC case, we observe the development of multiple magnetic islands generated due to the Tearing instability in the non-linear regime.

Tear‐borne interleukin 1‐beta and transforming growth factor‐beta and its relationship with clinical parameters in neophytes contact lens wearers

Aims/Purpose: To determine the presence of Interleukin 1‐beta (IL1‐β) and Transforming growth factor‐beta (TGF‐β) in the tears of neophytes contact lens wearers; and investigate the relationship between their concentration, tear stability, and ocular physiology findings.Methods: In this clinical trial, 12 neophytes (5 males, 24.0 ± 5.0 years) were dispensed with delefilcon A contact lenses. Physiological responses (bulbar and limbal hyperemia), non‐invasive tear break‐up times, and tear sample collections were obtained in the morning (before lens insertion; 9–10 a.m.) and afternoon (before lens removal; 7–8 p.m.) of the same day. The tear samples were assayed for IL1‐β and TGF‐β concentrations using Enzyme‐Linked Immunoabsorbent Assay kits. A parallel control group of 11 individuals (6 males, 25.0 ± 5.0) was also assessed to determine the levels of the biomarkers in the tears of non‐contact lens wearers.Results: Patients wore lenses for an average of 7:20 [6,9] h. Bulbar and limbal hyperemia increased throughout the day (p < 0.001). Tear break‐up times were lower in the afternoon compared to the morning assessment (4.7 ± 2.0 Vs. 12.2 ± 8.8 seconds; p < 0.001). The IL1‐β levels were higher in neophytes compared to controls (3.2 ± 4.7 Vs. 0.1 ± 0.1 ρg/ml; p = 0.05) but only in the afternoon. A significant correlation was found between IL1‐β concentration, bulbar (r = 0.405, p = 0.008), and limbal hyperemia (r = 0.499, p = 0.027) in the morning period. No substantial changes were reported for TGF‐β.Conclusions: The use of contact lenses might alter the IL1‐β regulatory mechanisms and disturb ocular surface homeostasis. However, more clinical evidence is needed to understand this phenomenon.

Biologically Enhanced Patch in the Healing and Mechanical Stability of Rotator Cuff Tears.

Biological patches have emerged as promising adjuncts in the surgical management of rotator cuff tears, aiming to enhance tissue healing and biomechanical properties of repaired tendons. These patches, derived from human or animal sources such as dermis or small intestinal submucosa, undergo mechanical and pathological changes within the rotator cuff environment post-implantation. These patches provide structural reinforcement to the repair site, distributing forces more evenly across the tendon and promoting a gradual load transfer during the healing process. This redistribution of forces helps alleviate tension on the repaired tendon and surrounding tissues, potentially reducing the risk of re-tears and improving overall repair integrity. Moreover, biological patches serve as scaffolds for cellular infiltration and tissue ingrowth, facilitating the recruitment of cells and promoting collagen synthesis. The integration of these patches into the host tissue involves a cascade of cellular events, including inflammation, angiogenesis, and matrix remodeling. Inflammatory responses triggered by patch implantation contribute to the recruitment of immune cells and the release of cytokines and growth factors, fostering a microenvironment conducive to tissue repair. However, despite their potential benefits, the long-term efficacy and durability of biological patches in rotator cuff repair remain areas of ongoing research and debate. Further studies are needed to elucidate the optimal patch characteristics, surgical techniques, and rehabilitation protocols to maximize clinical outcomes and minimize complications in rotator cuff surgery.

A CXCR3-Activating Peptide Increases Tear Break Up Time and Corrects Corneal haze in a Rabbit Model of Environmental Dry Eye.

Environmentally-triggered dry eye disease (DED) or keratoconjunctivitis sicca (KCS), which constitutes the majority of DED cases, currently is palliatively treated with aqueous replacement solutions that do not target the dysfunction of the mucin and lipid components of tears. We tested whether a peptide that increased goblet cell numbers in a model of scleral chemical injury would also improve tear quality in environmental DED. Environmental DED was established by exposing New Zealand white rabbits (8 per group, female) to 20% humidity with rapid air replacement and b.i.d. atropine sulfate eyedrops for 3 weeks prior to test article administration; this continued for the subsequent 3 weeks of testing. Animals were dosed by (A) saline, (B) b.i.d. eyedrop of peptide in saline, (C) b.i.d. eyedrop of peptide in coacervate, or (D) weekly subconjunctival injection of peptide. In vitro, human conjunctival epithelial cells (HCjE) were exposed to TNFα in the presence or absence of peptide to determine inflammatory responsiveness. The environmental DED was established with both Schirmer and TBUT being reduced at the start of test article; these levels were maintained as low through the testing period. All three treatment regimens increased TBUT approximately 3x to levels greater than prior to desiccation (P < 0.01), with little effect on Schirmer. Corneal haze was present in all eyes after induction, and completely reversed in 36 of 48 eyes across the treatments (P < 0.05). Co-treatment of HCjE with peptide reduced the production of TNFα in response to an inflammatory stimulus. The treatment of environmental DED/KCS with a peptide that activates CXCR3 improved tear quality and reversed corneal pathology by promoting tear stability and likely dampening the corneal inflammation, while not affecting aqueous volume of the tears.

Evaluation of Tear Stability and Ocular Surface in Patients Undergoing External Endonasal Dacryocystorhinostomy (EE-DCR) for Primary Acquired Nasolacrimal Duct Occlusion (PANDO).

The aim of our study was to show the changes in ocular surface and tear film parameters of patients who underwent external endonasal dacryocystorhinostomy (EE-DCR). For this purpose, tear film break-up time, corneal staining score, ocular surface disease index (OSDI), and Schirmer I test were performed preoperatively and postoperatively. The data obtained were compared with healthy controls. In the preoperative period, ocular surface disease index scores and corneal staining scores were higher, and Schirmer 1 and tear film break-up time were lower in group 1 compared with group 2. The ocular surface parameters were similar between the groups in the first and third postoperative months. External endonasal dacryocystorhinostomy is an important method for the restoration of deteriorated tear stability. Restoration of these disorders may be an important determinant of patient satisfaction and visual quality after surgery.

Multiwavelength observations of the lensed quasar PKS 1830-211 during the 2019 γ-ray flare

ABSTRACT PKS 1830 -211 is a γ-ray emitting, high-redshift (z =2.507 ± 0.002), lensed flat-spectrum radio quasar. During the period 2019 mid-February to mid-April, this source underwent a series of strong γ-ray flares that were detected by both AGILE-GRID (Gamma-Ray Imaging Detector) and Fermi Large Area Telescope (Fermi-LAT), reaching a maximum γ-ray flux of $F_{\rm E\gt 100\, MeV}\approx 2.3\times 10^{-5}$ photons cm−2 s−1. Here, we report on a coordinated campaign from both on-ground [Medicina, Owens Valley Radio Observatory (OVRO), Rapid Eye Mount (REM), and Sardinia Radio Telescope (SRT)] and orbiting facilities (AGILE, Fermi, INTEGRAL, NuSTAR, Swift, and Chandra), with the aim of investigating the multiwavelength properties of PKS 1830-211 through nearly simultaneous observations presented here for the first time. We find a possible break in the radio spectra in different epochs above 15 GHz, and a clear maximum of the 15 GHz data approximately 110 d after the γ-ray main activity periods. The spectral energy distribution shows a very pronounced Compton dominance (&amp;gt; 200) which challenges the canonical one-component emission model. Therefore, we propose that the cooled electrons of the first component are re-accelerated to a second component by, for example, kink or tearing instability during the γ-ray flaring periods. We also note that PKS 1830-211 could be a promising candidate for future observations with both Compton satellites [e.g. enhanced ASTROGAM (e-ASTROGAM)] and Cherenkov arrays [Cherenkov Telescope Array Observatory (CTAO)] which will help, thanks to their improved sensitivity, in extending the data availability in energy bands currently uncovered.

Tear and Saliva Metabolomics in Evaporative Dry Eye Disease in Females.

Accurate diagnosis of dry eye disease (DED) is challenging, and even today there is no gold standard biomarker of DED. Hypothesis-free global metabolomic studies of tears from DED patients have great potential to discover metabolites and pathways affected in the pathophysiology of DED, and to identify possible future biomarkers. These metabolites and biomarkers could be important for diagnosing and monitoring disease as well as for new therapeutic targets and strategies. As DED is associated with dry mouth, this study aimed to perform metabolomic analyses of tears and saliva from patients with decreased tear film break-up time but normal Schirmer test, and age-matched controls with both tear production and stability within physiological range. We applied strict inclusion criteria to reduce sampling bias in the metabolomic analyses and selected only age-matched females with Schirmer test values between 10-15 mm/5 min. The tear film analysis arm included 19 patients (with tear film break-up time 0-5 s) and 12 controls (with tear film break-up time 10-30 s), while the salivary analysis arm consisted of a subset which included 18 patients and six controls. Metabolomic analyses were performed using liquid chromatography and high-resolution mass spectrometry. Analyses using a global database search detected a total of 56 metabolites in tear samples that were significantly different between the groups. Of these, several have known associations with DED. These metabolites are present in meibum and have anti-oxidative characteristics or associations with the ocular microbiome, and altered concentrations suggest that they may play a significant role in DED associated with decreased tear film stability. In saliva, hypotaurine levels were lower among patients with tear film instability. In this pilot study, we found different levels of several metabolites in patients with decreased tear film break-up time that may have associations with DED. Future studies are required to replicate our findings and clarify the exact roles of these metabolites.

Nonlinear Evolution of the Tearing Instability in a Thin Current Sheet

In plane current sheets (foils, or liners), which are thin in comparison with their skin depth, an instability may grow because parallel currents in different areas of these sheets are attracted that leads to compression of these areas and partition of the current sheets into threads. This work describes the study of the nonlinear tearing instability evolution for a 1D case, when all the principal quantities (surface current and mass densities, velocity, and the magnetic field component normal to the sheet surface) depend on the coordinate perpendicular to the current density vector only. A 1D system of equations has been obtained, which describes the magnetic field dynamics and the substance motion in current sheets, and a numerical technique based on the Lagrangian discretization of mass has been developed to solve 1D magnetic hydrodynamics problems. It is shown that, if the tearing instability is considered, small perturbations of currents, velocities and mass densities grow in accordance with the earlier found growth rates of small perturbations and later, when the perturbations are no longer small, a nonlinear growth stage comes. In this stage, the perturbations of the surface current density j and the surface mass density μ increase unlimitedly for a finite time period (apparently, according to power laws j t -t -a,~ ( ) sμ t -t -g s, ts is the time, when these quantities become infinite); however the width of the current and mass density peaks tends to zero, so that the total current and total mass in the peaks of the current density and surface mass density decrease and tend to zero.

Nonlinear Evolution of the Tearing Instability in a Thin Current Sheet

Nonlinear Evolution of the Tearing Instability in a Thin Current Sheet

Tear Film Stabilization and Symptom Improvement in Dry Eye Disease: The Role of Hyaluronic Acid and Trehalose Eyedrops versus Carmellose Sodium.

This study evaluated the effectiveness of hyaluronic acid and trehalose (HA/trehalose) eyedrops in managing dry eye disease (DED) symptoms by measuring tear stability and administering a DED questionnaire. Sixty patients were treated with either HA/trehalose eyedrops (Tear A) or carmellose sodium eyedrops (Tear B) as controls. The tear breakup time (TBUT) and non-invasive breakup time (NIBUT) were monitored, and patients completed the standard patient evaluation of eye dryness (SPEED) questionnaire. After two months of twice-daily applications, patients treated with the HA/trehalose eyedrops demonstrated significant improvements in the NIBUT (12.98 ± 3.22 s) and TBUT (12.95 ± 2.98 s), indicating increased tear stability. Moreover, they reported lower dry eye sensation (6.70 ± 4.94 SPEED score points), suggesting a reduction in DED symptoms. These findings underscore the efficacy of HA/trehalose eyedrops in improving both the objective and subjective signs of DED, with twice-daily application enhancing ocular surface conditions and reducing patient-reported symptoms.

Protecting Tear-Film Stability under Adverse Environmental Conditions Using a Mucomimetic with a Non-Newtonian Viscosity Agent.

Background and Objectives: Tamarind-seed polysaccharide (TSP) and hyaluronic acid (HA) have mucoadhesive properties that improve drug absorption and delay in drug elimination from the ocular surface. We aimed to evaluate TSP/HA-containing formulation for its efficiency in dry-eye symptoms induced by adverse environments and the interaction between mucomimic polymer and tear-film parameters. Materials and Methods: The participants were exposed to 5% relative humidity (RH) in a Controlled Environment Chamber (CEC) under constant room temperature (21 °C). Tear-film parameters were assessed at 40% RH and 5% RH. Rohto Dry Eye Relief drops were used in the two treatment modalities, protection (drops instilled before exposure to the dry environment) and relief (drops instilled after exposure to the dry environment). The HIRCAL grid, Servomed EP3 Evaporimeter, and Keeler's TearScope-Plus were used to screen for non-invasive tear break-up time (NITBUT), tear evaporation rate, and lipid-layer thickness (LLT) using protection and relief treatment methodology. Results: LLT was found to be significantly thinner at 5% RH compared with at 40% RH (p = 0.007). The median LLT dropped from 50-70 nm (grade 3) at 40% RH to 10-50 nm (grade 2) at 5% RH. TSP/HA eye drops significantly augment LLT in both treatment modalities, protection (p = 0.01) and relief (p = 0.004) at 5% RH. The mean evaporation rate doubled from 40.93 at 40% RH to 82.42 g/m2/h after exposure to 5% RH. In protection mode, the TSP/HA allowed the average evaporation rate to be much lower than when no TSP/HA was used at 5% RH (p < 0.008). No alteration in evaporation rate was recorded when the TSP/HA drop was used after exposure (relief). The mean NITBUT was reduced from 13 s in normal conditions to 6 s in the dry environment. Instillation of TSP/HA eye drops resulted in significant improvement (p = 0.006) in tear stability, where the NITBUT increased to 8 s in both protection (before exposure) and relief (after exposure) (p = 0.001). Although improved, these values were still significantly lower than NITBUT observed at 40% RH. Conclusions: Significant protection of tear-film parameters was recorded post instillation of TSP/HA eye drop under a desiccating environment. Both treatment methods (protection and relief) were shown to be effective. The presence of TSP/HA enhances the effectiveness of teardrops in protecting the tear-film parameters when exposed to adverse environments.

3D coupled tearing-thermal evolution in solar current sheets

Context.The tearing instability plays a major role in the disruption of current sheets, whereas thermal modes can be responsible for condensation phenomena (forming prominences and coronal rain) in the solar atmosphere. However, how current sheets made unstable by combined tearing and thermal instability evolve within the solar atmosphere has received limited attention to date.Aims.We numerically explore a combined tearing and thermal instability that causes the break up of an idealized current sheet in the solar atmosphere. The thermal component leads to the formation of localized, cool condensations within an otherwise 3D reconnecting magnetic topology.Methods.We constructed a 3D resistive magnetohydrodynamic simulation of a force-free current sheet under solar atmospheric conditions that incorporates the non-adiabatic influence of background heating, optically thin radiative energy loss, and magnetic-field-aligned thermal conduction with the open source codeMPI-AMRVAC. Multiple levels of adaptive mesh refinement reveal the self-consistent development of finer-scale condensation structures within the evolving system.Results.The instability in the current sheet is triggered by magnetic field perturbations concentrated around the current sheet plane, and subsequent tearing modes develop. This in turn drives thermal runaway associated with the thermal instability of the system. We find subsequent, localized cool plasma condensations that form under the prevailing low plasma-βconditions, and demonstrate that the density and temperature of these condensed structures are similar to more quiescent coronal condensations. Synthetic counterparts at extreme ultraviolet (EUV) and optical wavelengths show the formation of plasmoids (in EUV) and coronal condensations similar to prominences and coronal rain blobs in the vicinity of the reconnecting sheet.Conclusions.Our simulations imply that 3D reconnection in solar current sheets may well present an almost unavoidable multi-thermal aspect that forms during their coupled tearing-thermal evolution.

Three-dimensional Simulation of Thermodynamics on Confined Turbulence in a Large-scale CME-flare Current Sheet

Turbulence plays a key role in forming the complex geometry of the large-scale current sheet (CS) and fast energy release in a solar eruption. In this paper, we present full 3D high-resolution simulations for the process of a moderate coronal mass ejection (CME) and the thermodynamical evolution of the highly confined CS. Copious elongated blobs are generated owing to tearing and plasmoid instabilities, giving rise to a higher reconnection rate, and undergo the splitting, merging, and kinking processes in a more complex way in 3D. A detailed thermodynamical analysis shows that the CS is mainly heated by adiabatic and numerical viscous terms, and thermal conduction is the dominant factor that balances the energy inside the CS. Accordingly, the temperature of the CS reaches to a maximum of about 20 MK, and the range of temperatures is relatively narrow. From the face-on view in the synthetic Atmospheric Imaging Assembly 131 Å, the downflowing structures with similar morphology to supra-arcade downflows are mainly located between the post-flare loops and loop top, while moving blobs can extend spikes higher above the loop top. The downward-moving plasmoids can keep the twisted magnetic field configuration until the annihilation at the flare loop top, indicating that plasmoid reconnection dominates in the lower CS. Meanwhile, the upward-moving ones turn into turbulent structures before arriving at the bottom of the CME, implying that turbulent reconnection dominates in the upper CS. The spatial distributions of the turbulent energy and anisotropy are addressed, which show a significant variation in the spectra with height.

Relation between Vitamin D Deficiency and Dry Eye

Background Tears are very important to the overall health of the eye and vision. The tear film is mechanically distributed over the ocular surface through a neuronally controlled blinking mechanism. Normal blink reflex, contact between the external ocular surface and the eye lids, and normal corneal epithelium are three factors required for effective resurfacing of the tear film (tear stability). (1) Objective To demonstrate the relation between vitamin D deficiency and dry eye disease searching for finding a correlation between dry eye parameters with vitamin D deficiency. Patients and Methods Cross sectional study. A total 50 patients attending the ophthalmology outpatient clinic of General Ain Shams Hospital, from February 2019 to October 2019 were enrolled in the study after the approval of the research ethical committee in the Faculty of Medicine, Ain Shams University. They were divided randomly into 2 groups. Group 1: consisted of 35 patients who were vitamin D deficient. Group 2: consisted of 15 patients who had normal vitamin D levels (control group). Results The study showed that there was statistically significant increase in symptoms of dry eye in female patients than male patients and there was statistically significant decrease in the level of tear film break up time, Shirmer test and serum 25 (OH) vitamin D in cases with dry eye than those without. It was found that there was statistically significant decrease in vitamin D level in female cases than male cases. Also, there was statistically significant decrease in vitamin D level in cases with symptoms of dry eye and conjunctival hyperemia than cases without. There was also statistically significant positive correlation between serum 25 (OH) vitamin D and tear film break up time and Shirmer test. Conclusion The present study suggests that patients with vitamin D deficiency may suffer from dry eye. Investigations to confirm and quantify a clinical diagnosis of dry eye should include serum 25 (OH) vitamin D when suspecting vitamin D deficiency especially in patients prone to this type of vitamin deficiency.

Clinical features, diagnosis, and treatment of dry eye syndrome in children

AIM: To investigate the etiopathogenesis and clinical features of dry eye syndrome in children, methods for diagnosing the disease, and the treatment algorithm.&#x0D; MATERIAL AND METHODS: One hundred eighty-seven children with dry eye syndrome aged 3 to 17 yr were examined. To diagnose dry eye syndrome in children, the following research methods were used: biomicroscopy of the anterior part of the eye under diffuse illumination and with a cobalt filter after instillation of vital dyes; examination of the height of the lacrimal meniscus; identification of a characteristic discharge in the conjunctival sac, xerosis of the ocular surface; and evaluation of tear production (Schirmer I test) and stability of the tear film.&#x0D; RESULTS: We found that the links in the pathogenesis of dry eye syndrome in children were as follows: diseases of the ocular surface and appendage of the eye, contact correction of ametropia, and surgical operations on the conjunctiva and oculomotor muscles; otogenic neuritis of the facial nerve; rheumatoid arthritis; endocrine ophthalmopathy; lagophthalmos; and thermal and chemical burns. It is now always possible to evaluate tear production and tear film stability in preschool and primary school-aged children. In this case, the main diagnostic method is biomicroscopy. We identified objective clinical symptoms of dry eye syndrome in children using biomicroscopy. Dry eye syndrome was classified into four degrees of severity: mild, moderate, severe, and extremely severe. The subjective and objective clinical signs of each disease severity are described.&#x0D; An individual approach and personalized therapy are required to treat dry eye syndrome in children, focusing on the individual tolerability and effectiveness of the drug. Maximum medical alertness and early and accurate clinical differential diagnosis between dry eye syndrome and infectious inflammatory pathology of the anterior part of the eye are required.&#x0D; CONCLUSION: The features of the etiopathogenesis of dry eye syndrome in children with various nosologies are examined, and the characteristic clinical symptoms and severity of dry eye syndrome, diagnostic methods, and algorithm for treating dry eye syndrome in children are described. The clinical and diagnostic features of dry eye syndrome in children described by us contribute to its early diagnosis, allowing for the initiation of personalized tear replacement and reparative therapy on time, preventing the development of a chronic course of the disease, the occurrence of complications, and the preservation and/or restoration of visual acuity.

MHD stability of negative triangularity DIII-D plasmas

Negative triangularity (NT) experiments in DIII-D point to an emergent reactor scenario free of sawteeth, endowed with benign, nondisruptive n = 2 tearing modes, which experience q min 1 similar to the positive triangularity hybrid scenario. Plasmas exhibiting this behavior attain , high enough to reconsider long held views of NT stability. Ideal MHD and tearing stability analysis of well-diagnosed equilibrium reconstructions of experimental hybrid-like plasmas predict that among shape parameters, MHD stability limits are only sensitive to average triangularity. Operation is predicted to be possible at relevant to upcoming tokamaks and commercial NT reactors.

International survey on dry eye diagnosis by experts

PurposeTo evaluate patterns and opinion from international experts with respect to dry eye disease (DED) diagnosis in clinical practice. MethodsAn online survey was distributed to worldwide DED experts. The use of diagnosis tests was evaluated including: symptoms questionnaires, functional tests, tear stability, tear volume, tear composition, surface damage and inflammation, and eyelid assessment. After the subjective importance of symptoms, tear break up time (TBUT), non-invasive TBUT, Schirmer's test, tear meniscus height, tear osmolarity, tear metalloproteinase 9, blepharitis assessment and non-contact meibography was evaluated according to likert scale. ResultsThe survey was sent to 109 experts, and 77 completed the questionnaire (rate of response = 70.6%). Most of the participants were from North America (27%) and Europe (40%). A majority of respondents (73%) diagnose DED using clinical signs and symptoms, but not fulfilling a specific criteria. Seventy-six participants (98.7%) use symptoms questionnaires. All participants evaluate damage to ocular surface, and fluorescein staining is the most frequent method used (92%). Also, all the respondents perform meibomian gland and blepharitis assessment. On the other hand, only 69.8% evaluate tear composition, being osmolarity the most common test used (66.2%). Regarding to the importance of tests, TBUT (p = 0.002) and Schirmer's (p = 0.021) were found to be more important to experts from Europe than North America. No differences were found in any other test (p > 0.05). ConclusionsThis survey offers updated and day-to-day diagnostic clinical practice by DED worldwide experts. The results highlight the importance of symptoms and clinical signs, but not necessarily following a strict criteria.

On the relationship between the multi-region relaxed variational principle and resistive inner-layer theory

We show that the variational energy principle of the multi-region relaxed magnetohydrodynamic (MRxMHD) model can be used to predict finite-pressure linear tearing instabilities. In this model, the plasma volume is sliced into sub-volumes separated by ‘ideal interfaces’, and in each volume the magnetic field relaxes to a Taylor state, where the pressure gradient . The MRxMHD model is implemented in the Stepped-Pressure Equilibrium Code (SPEC) so that the equilibrium solution in each region is computed while preserving the force balance across the interfaces. As SPEC computes the Hessian matrix (a discretized stability matrix), the stability of an MRxMHD equilibrium can also be computed with SPEC. In this article, using SPEC, we investigate the effect of local pressure gradients and the in the vicinity of the resonant surface of a tearing mode. For low-beta plasma, we have been able to illustrate a relationship between the resistive singular-layer theory (Coppi et al 1966 Nucl. Fusion 6 101; Glasser et al 1975 Phys. Fluids 18 875–88) and the MRxMHD model. Within the singular layer, the volume-averaged magnetic helicity and the flux-averaged toroidal flux are shown to be the invariants for the linear tearing modes in SPEC simulations. Our technique to compute MRxMHD stability is first tested numerically in a cylindrical tokamak and its application in toroidal geometry is demonstrated. We demonstrate an agreement between the stability boundary obtained with SPEC simulation and the resistive inner-layer theories.

Impact of Plasma Rich in Growth Factors (PRGF) Eye Drops on Ocular Redness and Symptomatology in Patients with Dry Eye Disease.

Background and Objectives: Dry eye disease (DED) is a common and very symptomatic pathology that affects normal daily activity. The aim of the study was to evaluate the efficacy of plasma rich in growth factors (PRGF) added to one routine treatment protocol for DED (artificial tears substitutes, lid hygiene, and anti-inflammatory therapy). Materials and Methods: Patients were divided into two groups of treatment: standard treatment group (n = 43 eyes) and PRGF group (n = 59). Patients' symptomatology (inferred from OSDI and SANDE questionnaires), ocular inflammation, tear stability, and ocular surface damage were analyzed at baseline and after 3 months of treatment. Results: OSDI test scores were significantly lower in both groups (p < 0.001). SANDE frequency test scores also improved statistically, with differences between groups (p = 0.0089 SANDE frequency and p < 0.0119 SANDE severity). There was a greater reduction in ocular redness (ocular inflammation) in the PRGF group (p < 0.0001) and fluorescein tear break-up time was significantly improved in the PRGF group (p = 0.0006). No significant changes were found in terms of ocular surface damage. No adverse events were obtained in either group. Conclusions: The addition of PRGF to the standard treatment of DED, according to the results obtained, proved to be safe and produced an improvement in ocular symptomatology and signs of inflammation, particularly in moderate and severe cases, when compared to standard treatment.

Ocular nociception and neuropathic pain initiated by blue light stress in C57BL/6J mice.

Abstract To elucidate the physiological, cellular, and molecular mechanisms responsible for initiating and sustaining ocular neuropathic pain, we created a blue light exposure model in C57BL/6 mice. Mice were exposed to 12 hours of blue or white light followed by 12 hours of darkness. Before blue light exposure, baseline tear secretion, stability, and ocular hyperalgesia were assessed by measuring hyperosmotic or hypoosmotic solution-induced eye wiping, wind-induced eye closing, and cold-induced eye blinking. At 1 day after blue light exposure, alterations in hypotonic or hypertonic-induced eye wiping and tear film abnormalities were observed. Eye-wiping behaviors were abolished by topical anesthesia. The cold-stimulated eye blinking and wind-stimulated eye closing behaviors began after day 3 and their frequency further increased after day 9. Blue light exposure reduced the density of nerve endings and increased their tortuosity, the number of beadlike structures, and the branching of stromal nerve fibers, as assessed by whole-mount confocal microscopy. Blue light exposure also increased TRPV1, but not TRPV4 staining intensity of corneal-projecting neurons in the trigeminal ganglia, as detected by FluoroGold retrograde labeling and immunohistochemistry. TRPV1 and substance P expression was increased, whereas CGRP expression deceased at the mRNA level in isolated corneal projecting neurons. Hence, our blue light exposure B6 mouse model for assessing tearing and ocular hyperalgesia is useful for studying ocular pain and its underlying mechanisms. Blue light–induced alterations in tearing and ocular hyperalgesia may be related to the elevated expression of TRPV1, substance P, or the suppressed expression of CGRP at the ocular surface.