Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations

Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we want to study axisymmetric and non-axisymmetric structures, evocated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generate synthetic maps and predictions for ALMA. We performed non-ideal global 3D MHD stratified simulations of the dead-zone outer edge using the FARGO MHD code PLUTO. The stellar and disk parameters are taken from a parameterized disk model applied for fitting high-angular resolution multi-wavelength observations of circumstellar disks. The 2D temperature and density profiles are calculated consistently from a given surface density profile and Monte-Carlo radiative transfer. The 2D Ohmic resistivity profile is calculated using a dust chemistry model. The magnetic field is a vertical net flux field. The resulting dust reemission provides the basis for the simulation of observations with ALMA. The fiducial model develops a large gap followed by a jump in surface density located at the dead-zone outer edge. The jump in density and pressure is strong enough to stop the radial drift of particles. In addition, we observe the generation of vortices by the Rossby wave instability (RWI) at the jumps location close to 60 AU. The vortices are steadily generated and destroyed at a cycle of 40 local orbits. The RT results and simulated ALMA observations predict the feasibility to observe such large scale structures appearing in magnetized disks without having a planet.Comment: Language update, added comments, added citations, in press. (A&A

Synthetic route optimization of Sumepirin antiepileptic drug candidate

In this work we describe the transformation of synthetic route of the antiepileptic drug candidate Sumepirin starting from discovery stage. Initial method included six step process requiring two steps of purification using colon chromatography and has poor overall yield of target compound. The process developed is convenient, scalable, technological and meet the most of conditions of green chemistry. The overall yield was increased up to 62.5% in four steps without colon chromatography purification which allows to obtain the target compound with purity of 99.5+% which is especially important for the active ingredient

A high-order Godunov scheme for global 3D MHD accretion disks simulations. I. The linear growth regime of the magneto-rotational instability

We employ the PLUTO code for computational astrophysics to assess and compare the validity of different numerical algorithms on simulations of the magneto-rotational instability in 3D accretion disks. In particular we stress on the importance of using a consistent upwind reconstruction of the electro-motive force (EMF) when using the constrained transport (CT) method to avoid the onset of numerical instabilities. We show that the electro-motive force (EMF) reconstruction in the classical constrained transport (CT) method for Godunov schemes drives a numerical instability. The well-studied linear growth of magneto-rotational instability (MRI) is used as a benchmark for an inter-code comparison of PLUTO and ZeusMP. We reproduce the analytical results for linear MRI growth in 3D global MHD simulations and present a robust and accurate Godunov code which can be used for 3D accretion disk simulations in curvilinear coordinate systems

SYNTHETIC ROUTE OPTIMIZATION OF SUMEPIRIN ANTIEPILEPTIC DRUG CANDIDATE

Epilepsy is one of the most common chronic diseases of the nervous system in the world, which affects both children and adults. 30% of patients with epilepsy are pharmacoresistant. Sumepirin 1 is a novel antiepileptic drug candidate developed in the Scientific and Educational Center of Pharmaceutics of the Kazan Federal University and having pronounced antiseizure effect and improved safety profile. This compound is pyridoxine-based molecule with residue of methanesulfonic acid in the 6th position of pyridoxine ring.This work was supported by subsidy allocated to Kazan Federal University for the state assignment in the sphere of scientificactivities (project number 0671-2020-0053

Amphiphilic adducts of myrcene and N-substituted maleimides as potential drug delivery agents

The title drug delivery compounds with pharmacophoric moieties were synthesized, and their interaction with model biomembranes (dipalmitoylphosphatidylcholine vesicles) was examined. © 2014 Mendeleev Communications. All rights reserved

Turbulence and Steady Flows in 3D Global Stratified MHD Simulations of Accretion Disks

We present full 2 Pi global 3-D stratified MHD simulations of accretion disks. We interpret our results in the context of proto-planetary disks. We investigate the turbulence driven by the magneto-rotational instability (MRI) using the PLUTO Godunov code in spherical coordinates with the accurate and robust HLLD Riemann solver. We follow the turbulence for more than 1500 orbits at the innermost radius of the domain to measure the overall strength of turbulent motions and the detailed accretion flow pattern. We find that regions within two scale heights of the midplane have a turbulent Mach number of about 0.1 and a magnetic pressure two to three orders of magnitude less than the gas pressure, while outside three scale heights the magnetic pressure equals or exceeds the gas pressure and the turbulence is transonic, leading to large density fluctuations. The strongest large-scale density disturbances are spiral density waves, and the strongest of these waves has m=5. No clear meridional circulation appears in the calculations because fluctuating radial pressure gradients lead to changes in the orbital frequency, comparable in importance to the stress gradients that drive the meridional flows in viscous models. The net mass flow rate is well-reproduced by a viscous model using the mean stress distribution taken from the MHD calculation. The strength of the mean turbulent magnetic field is inversely proportional to the radius, so the fields are approximately force-free on the largest scales. Consequently the accretion stress falls off as the inverse square of the radius.Comment: Accepted for publication in Ap

Novel type of isoprenoid membrane anchors: An investigation of binding properties with dipalmitoylphosphatidylcholine vesicles

© 2016 John Wiley & Sons, Ltd.In this work, we present a new type of amphiphilic membrane-anchoring agents that can be easily obtained by the Diels-Alder reaction between terpene myrcene and N-substituted maleimides. The interaction between the compounds and small unilamellar dipalmitoylphosphatidylcholine vesicles was investigated using infrared spectroscopy, microgravimetry, and turbidimetry. The ability of the compounds to embed in the phospholipid membrane was shown to be strongly dependent on the charge of their polar group. The insertion of the compounds studied into the lipid bilayer did not lead to disruption of the dipalmitoylphosphatidylcholine vesicles up to the highest tested drug to lipid molar ratio of 0.5 to 0.6. Low lipid solubilization ability of the compounds as well as their rigid nonplanar structure makes them an interesting alternative to the common membrane-anchoring structural motifs

Novel type of isoprenoid membrane anchors: an investigation of binding properties with dipalmitoylphosphatidylcholine vesicles

Copyright © 2016 John Wiley & Sons, Ltd.In this work, we present a new type of amphiphilic membrane-anchoring agents that can be easily obtained by the Diels-Alder reaction between terpene myrcene and N-substituted maleimides. The interaction between the compounds and small unilamellar dipalmitoylphosphatidylcholine vesicles was investigated using infrared spectroscopy, microgravimetry, and turbidimetry. The ability of the compounds to embed in the phospholipid membrane was shown to be strongly dependent on the charge of their polar group. The insertion of the compounds studied into the lipid bilayer did not lead to disruption of the dipalmitoylphosphatidylcholine vesicles up to the highest tested drug to lipid molar ratio of 0.5 to 0.6. Low lipid solubilization ability of the compounds as well as their rigid nonplanar structure makes them an interesting alternative to the common membrane-anchoring structural motifs

Trapping Solids at the Inner Edge of the Dead Zone: 3-D Global MHD Simulations

The poorly-ionized interior of the protoplanetary disk is the location where dust coagulation processes may be most efficient. However even here, planetesimal formation may be limited by the loss of solid material through radial drift, and by collisional fragmentation of the particles. Our aim is to investigate the possibility that solid particles are trapped at local pressure maxima in the dynamically evolving disk. We perform the first 3-D global non-ideal MHD calculations of the disk treating the turbulence driven by the magneto-rotational instability. The domain contains an inner MRI-active region near the young star and an outer midplane dead zone, with the transition between the two modeled by a sharp increase in the magnetic diffusivity. The azimuthal magnetic fields generated in the active zone oscillate over time, changing sign about every 150 years. We thus observe the radial structure of the `butterfly pattern' seen previously in local shearing-box simulations. The mean magnetic field diffuses from the active zone into the dead zone, where the Reynolds stress nevertheless dominates. The greater total accretion stress in the active zone leads to a net reduction in the surface density, so that after 800 years an approximate steady state is reached in which a local radial maximum in the midplane pressure lies near the transition radius. We also observe the formation of density ridges within the active zone. The dead zone in our models possesses a mean magnetic field, significant Reynolds stresses and a steady local pressure maximum at the inner edge, where the outward migration of planetary embryos and the efficient trapping of solid material are possible.Comment: 17 pages, 30 *.ps files for figures. Accepted 16 November 2009 in A&

Large Scale Azimuthal Structures Of Turbulence In Accretion Disks - Dynamo triggered variability of accretion

We investigate the significance of large scale azimuthal, magnetic and velocity modes for the MRI turbulence in accretion disks. We perform 3D global ideal MHD simulations of global stratified proto-planetary disk models. Our domains span azimuthal angles of \pi/4, \pi/2, \pi and 2\pi. We observe up to 100% stronger magnetic fields and stronger turbulence for the restricted azimuthal domain models \pi/2 and \pi/4 compared to the full 2\pi model. We show that for those models, the Maxwell Stress is larger due to strong axisymmetric magnetic fields, generated by the \alpha \Omega dynamo. Large radial extended axisymmetric toroidal fields trigger temporal magnification of accretion stress. All models display a positive dynamo-\alpha in the northern hemisphere (upper disk). The parity is distinct in each model and changes on timescales of 40 local orbits. In model 2\pi, the toroidal field is mostly antisymmetric in respect to the midplane. The eddies of the MRI turbulence are highly anisotropic. The major wavelengths of the turbulent velocity and magnetic fields are between one and two disk scale heights. At the midplane, we find magnetic tilt angles around 8-9 degree increasing up to 12-13 degree in the corona. We conclude that an azimuthal extent of \pi is sufficient to reproduce most turbulent properties in 3D global stratified simulations of magnetised accretion disks.Comment: accepted for publication in Ap