Magnetic field gradient effects on the magnetorotational instability

The magnetorotational instability (MRI), also known as the Balbus -- Hawley instability, is thought to have an important role on the initiation of turbulence and angular momentum transport in accretion discs. In this work, we investigate the effect of the magnetic field gradient in the azimuthal direction on MRI. We solve the magnetohydrodynamic equations by including the azimuthal component of the field gradient. We find the dispersion relation and calculate the growth rates of the instability numerically. The inclusion of the azimuthal magnetic field gradient produces a new unstable region on wavenumber space. It also modifies the growth rate and the wavelength range of the unstable mode: the higher the magnitude of the field gradient, the greater the growth rate and the wider the unstable wavenumber range. Such a gradient in the magnetic field may be important in T Tauri discs where the stellar magnetic field has an axis which is misaligned with respect to the rotation axis of the disc.Comment: 8 pages, 3 figures, accepted for publication in A

Instability of non-Keplerian warped discs

Many accretion discs are thought to be warped. Recent hydrodynamical simulations show that (i) discs can break into distinct planes when the amplitude of an imposed warp is sufficiently high and the viscosity sufficiently low, and that (ii) discs can tear up into discrete rings when an initially planar disc is subject to a forced precession. Previously, we investigated the local stability of isolated, Keplerian, warped discs in order to understand the physics causing an accretion disc to break into distinct planes, finding that anti-diffusion of the warp amplitude is the underlying cause. Here, we explore the behaviour of this instability in disc regions where the rotation profile deviates from Keplerian. We find that at small warp amplitudes non-Keplerian rotation can stabilize the disc by increasing the critical warp amplitude for instability, while at large warp amplitudes non-Keplerian rotation can lead to an increased growth rate for discs that are unstable. Tidal effects on discs in binary systems are typically weak enough such that the disc remains close to Keplerian rotation. However, the inner regions of discs around black holes are strongly affected, with the smallest radius at which the disc can break into discrete planes being a function of the black hole spin. We suggest that interpreting observed frequencies in the power spectra of light curves from accreting compact objects as nodal and apsidal precession of discrete orbits requires an instability that can break the disc into discrete rings such as the one explored here.Comment: 12 pages, 8 figures, accepted for publication in MNRA

The Kozai-Lidov Mechanism in Hydrodynamical Disks

We use three dimensional hydrodynamical simulations to show that a highly misaligned accretion disk around one component of a binary system can exhibit global Kozai-Lidov cycles, where the inclination and eccentricity of the disk are interchanged periodically. This has important implications for accreting systems on all scales, for example, the formation of planets and satellites in circumstellar and circumplanetary disks, outbursts in X-ray binary systems and accretion on to supermassive black holes.Comment: Accepted for publication in ApJ Letter

Evaluation of the effect of topical and systemic ozone application in periodontitis: an experimental study in rats

Objective: The goal of the present study was to determine the effect of systemic and topical ozone application on alveolar bone loss (ABL) by evaluating the effect of Hypoxia-inducible factor −1 alpha (HIF-1-α) and receptor activator of NF-kB ligand (RANKL)-positive cells on histopathological and immunohistochemical changes in a rat periodontitis model. Methodology: Thirty male Wistar rats were divided into three groups: 1) Group C (control group); 2) Group SO (systemic ozone group) and 3) Group TO (topical ozone group). Experimental periodontitis was induced with a 3/0 silk suture placed at the mandibular left first molars of rats, and the suture was removed 14 days later. Ozone gas was injected intraperitoneally (0.7 mg/kg) in SO group. Topical ozone application protocol was performed using an ozone generator at 80% concentration (4th grade) 90- degree probe for the duration of 30 s. Both ozone applications were carried out for two weeks at intervals of two days. Histomorphometric and immunohistochemical analysis were performed. Results:ABL was significantly lower in Group SO compared to Group C (p: 0.0052). HIF-1α- positive cells were significantly lower in Group TO than in Group C (p: 0.0043). RANKL-positive cells were significantly lower in Group SO and in Group TO compared to the control group (p: 0.0033, p: 0.0075, respectively). Conclusion: Both ozone applications decreased RANKL-positive cell counts, TO application decreased HIF-1-α positive cells counts, and SO application was found to be more effective in reducing ABL compared to control group

Iatrogenic Cushing’s Syndrome with Subsequent Adrenal Insufficiency in a Patient with Psoriasis Vulgaris Using Topical Steroids

Iatrogenic Cushing’s syndrome (ICS) is usually related to prolonged and/or high-dose oral or parenteral steroid use. Psoriasis vulgaris (PV) is chronic inflammatory disease and characterized by periods of attack and remission. Topical steroid (TS) is the first choice of treatment for localized and mild PV. The development of systemic side effects of the steroids is usually not observed after TS application. But the risk of developing ICS still exists. In the literature, there are a few adult cases who developed ICS and subsequent adrenal insufficiency associated with TS. In this article, a male patient with PV developing ICS and secondary adrenal insufficiency after treatment of TS for 12 years is presented

The carbohydrate-active enzyme database: functions and literature

International audienceAbstract Thirty years have elapsed since the emergence of the classification of carbohydrate-active enzymes in sequence-based families that became the CAZy database over 20 years ago, freely available for browsing and download at www.cazy.org. In the era of large scale sequencing and high-throughput Biology, it is important to examine the position of this specialist database that is deeply rooted in human curation. The three primary tasks of the CAZy curators are (i) to maintain and update the family classification of this class of enzymes, (ii) to classify sequences newly released by GenBank and the Protein Data Bank and (iii) to capture and present functional information for each family. The CAZy website is updated once a month. Here we briefly summarize the increase in novel families and the annotations conducted during the last 8 years. We present several important changes that facilitate taxonomic navigation, and allow to download the entirety of the annotations. Most importantly we highlight the considerable amount of work that accompanies the analysis and report of biochemical data from the literature

The protective effects of metformin in an in vitro model of aging 3T3 fibroblast under the high glucose conditions

Metformin is the most widely used anti-diabetic drug in the world. It reduces advanced glycation end product (AGEs)-induced ROS generation in high glucose condition. Protein glycation contributes to skin aging as it deteriorates the existing collagen by crosslinking. The progressive increase of AGE during aging not only causes oxidative damage to cellular macromolecules but also modulates the activation of transcription factors nuclear factor kappa-B(NF-kB). However, it is still unclear whether metformin can change collagen production and NF-kB activity induced by high glucose conditions in 3T3 fibroblast. The effects of metformin on proliferation, apoptosis, and collagen levels and NF-kB activity of in vitro cell aging model of 3T3 fibroblast cells in high glucose conditions. At first, we investigated the effects of 50 mM high glucose concentration, with or without metformin, on 3T3 fibroblast proliferation, by BrdU immunostaining for cell proliferation. Apoptotic levels were analyzed by flow cytometric assay. NF-kB(p65) activity was measured by transcription factor assay kit and collagen I and III levels by Collagen Estimation Assay through ELISA. We observed that metformin exposure leads to decreased apoptosis levels and increased proliferation of 3T3 fibroblast in high glucose media. We also determined that metformin exposure leads to increased production of collagen I-III and decreased activation of NF-kB(p65) activity. The data are consistent with the observation that metformin has a protective effect in this in vitro model of aging 3T3 fibroblasts under high glucose conditions inducing cell proliferation, collagen I and III production, protection from apoptosis, and reducing NF-kB(p65) activity

Tearing up a misaligned accretion disc with a binary companion

Accretion discs are common in binary systems, and they are often found to be misaligned with respect to the binary orbit. The gravitational torque from a companion induces nodal precession in misaligned disc orbits. We calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. For typical parameters precession wins: the disc breaks into distinct planes that precess effectively independently. We run hydrodynamical simulations to check these results, and confirm that disc breaking is widespread and generally enhances accretion on to the central object. This applies in many cases of astrophysical accretion, e.g. supermassive black hole binaries and X-ray binaries

Instability of warped discs

Accretion discs are generally warped. If a warp in a disc is too large, the disc can ‘break’ apart into two or more distinct planes, with only tenuous connections between them. Further, if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the ‘diffusive’ regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which, in general, yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term that would generally encapsulate the classical Lightman–Eardley instability in planar discs (given by ∂(νΣ)/∂Σ < 0) but is here modified by the warp to include ∂(ν1|ψ|)/∂|ψ| < 0, and (2) a similar condition acting on the diffusion of the warp amplitude given in simplified form by ∂(ν2|ψ|)/∂|ψ| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems

The role of forkhead box class O3A and SIRT1 gene variants in early-onset psoriasis

Background: Psoriasis is a chronic inflammatory skin disorder, which is characterized by a heightened immunological response. Although the immunogenetics of this chronic inflammatory disorder is poorly understood, its expression is known to be dependent on proinflammatory cytokines. It is known that two distinct subtypes of chronic plaque psoriasis: Early-onset psoriasis (EOP) before the age of 40 years and late-onset psoriasis after the age of 40 years. Forkhead box class O3A (FOXO3A) is a transcription factor, which plays an important role in cell-cycle regulation, apoptosis, oxidative stress, and DNA repair. The silent information regulator (SIRT) is thought to have a role in skin disorders, including psoriasis, that are characterized by hyperproliferation and inflammation. Aim: The aim of this study was to investigate FOXO3A and SIRT1 gene polymorphisms in EOP. Methods: The study group consisted of 142 EOP patients and 123 unrelated healthy controls. FOXO3A polymorphisms were determined using the polymerase chain reaction (PCR)-restriction fragment length polymorphism method. SIRT1 gene polymorphisms were determined by PCR-confronting two-pair primers methods. Results: The FOXO3A rs4946936 and SIRT1 rs7069102 gene polymorphisms were positively correlated with EOP and disease severity. The GG genotype frequency of SIRT1 rs7069102 gene polymorphisms was increased in severe EOP. The CC frequency of FOXO3A rs4946936 was increased in EOP with nail disorders. Conclusion: The rs7069102 gene polymorphism of SIRT1 and rs4946936 polymorphism of FOXO3A are associated with early onset psoriasis; this may be responsible for increased keratinocyte proliferation in the pathogenesis of psoriasis and disease severity