Growing dust grains in protoplanetary discs - III. vertical settling

TM acknowledges the support of a Swinburne Special Studies Programme. GL is grateful to the Australian Research Council for funding via Discovery project grant DP1094585, and acknowledges funding from the European Research Council for the FP7 ERC advanced grant project ECOGAL. JFG's research was conducted within the Lyon Institute of Origins under grant ANR-10-LABX-66.We aim to derive a simple analytic model to understand the essential properties of vertically settling growing dust grains in laminar protoplanetary discs. Separating the vertical dynamics from the motion in the disc mid-plane, we integrate the equations of motion for both a linear and an exponential grain growth rate. Numerical integrations are performed for more complex growth models. We find that the settling efficiency depends on the value of the dimensionless parameter γ , which characterizes the relative efficiency of grain growth with respect to the gas drag. Since γ is expected to be of the same order as the initial dust-to-gas ratio in the disc (≃10−2), grain growth enhances the energy dissipation of the dust particles and improves the settling efficiency in protoplanetary discs. This behaviour is mostly independent of the growth model considered as well as of the radial drift of the particles.Publisher PDFPeer reviewe

Proyecto de red colectora cloacal "Terrazas y colinas de manantiales"

Práctica Supervisada (IC)--FCEFN-UNC, 2016Desarrolla un proyecto de una Red colectora cloacal correspondiente a una nueva urbanización denominada "Terrazas y Colinas de Manantiales" próximas a construirse en un terreno ubicado en la intersección del arroyo La Cañada, Av. Circunvalación y Ruta Provincial N°

Einfluss der Experimentellen Autoimmunen Encephalomyelitis auf elektrische und chemische Synapsen der murinen Retina

Die Multiple Sklerose gehört zu den chronisch-degenerativen Erkrankungen des ZNS. Im Rahmen der neuropathologischen Krankheitsprozesse kommt es durch das patienteneigene Immunsystem zur zentralen Inflammation und Autoantikörperbildung. Folge ist eine fokale Degeneration der neuronalen Myelinscheiden an multiplen Stellen im ZNS (REALE, SANCHEZ-RAMON, 2017). In der Pathogenese der MS spielen intra- und interzelluläre Kanalproteine (Panx1 und verschiedene Connexin-Subtypen) eine bedeutende Rolle. Sie sind beispielsweise bei der Aktivierung zytotoxischer autoreaktiver T-Lymphozyten, bei der Vermittlung der Entzündungsreaktion an den Myelinscheiden und bei einer Fortleitung pro- inflammatorischer Botenstoffe in weitere Zellen beteiligt (ADAMSON, LEITINGER, 2014; MAIER et al., 2004; RIPPS, 2002; THOMPSON, 2015; WONG et al., 2014). Rund ein Drittel der Patienten mit MS entwickelt als Frühsymptom eine Neuritis des Nervus opticus, verschiedenartige Sehstörungen bis hin zum völligen Ausfall des Gesichtsfeldes unter Beteiligung der Retina (HEROLD et al., 2015; LARABEE et al., 2016; SYC et al., 2012). Die genauen Pathomechanismen dieser Mitbeteiligung des visuellen Systems sowie das Ausmaß der retinalen Läsion bei der MS sind aktuell jedoch noch nicht im Detail bekannt. Es wurde daher in dieser Arbeit in der ersten Hypothese postuliert, dass die durch die zentrale Inflammation induzierte axonale Schädigung im N. opticus die Apoptose retinaler Ganglienzellen zur Folge hat sowie sich eine Reduktion synaptischer Verbindungen innerhalb der Retina zeigt. Experimentell wurde in dieser Arbeit mit dem Tiermodell der Experimentellen Autoimmunen Encephalomyelitis (EAE) gearbeitet. Im zweiten Teil dieser Arbeit wurde ein möglicher neuroprotektiver Effekt des Pannexin1 Inhibitors Probenecid (PBN) auf die retinalen Neurone der Versuchstiere untersucht. Hypothese des zweiten Teils war, dass eine PBN-Intervention mit 100mg/kg Körpergewicht ab Tag eins nach EAE-Induktion eine Prävention der neuronalen Schädigung im Auge zur Folge hat. Es wurde angenommen, dass retinale Strukturproteine von elektrischen und chemischen Synapsen in der präventiv mit PBN behandelten Gruppe im Vergleich zur EAE- Gruppe in höherer Dichte immunologisch nachweisbar sein würden und weniger Zellen in eine EAE-induzierte Apoptose eintreten. In beiden Teilen dieser Arbeit wurde die Zahl der Ganglienzellen über den Nachweis des Ganglienzell-spezifischen Proteins RBPMS sowie der programmierte Zelltod über das Apoptose-assoziierte Protein Cleaved-Caspase-3 bestimmt. Connexin 36, das Gap junction Protein elektrischer Synapsen der Retina, sowie RIBEYE, exprimiert in den chemischen Ribbon-Synapsen der Retina, wurden analysiert, um die synaptische Verschaltung in der Retina bei EAE und unter Therapie zu untersuchen. Im ersten Teil dieser Arbeit konnte gezeigt werden, dass die Induktion der EAE im Tiermodell sowohl zu klinisch messbaren Paralysen der Versuchstiere führte als auch degenerative I Veränderungen mit signifikant verringerter Expression der untersuchten Proteine an neuronalen Zellen verschiedener Schichten der Retina stattfanden. Im zweiten Teil der Arbeit konnte gezeigt werden, dass sich klinisch die Motorik der Versuchstiere signifikant unter präventiver PBN-Gabe verbesserte. Zudem traten unter Therapie mit PBN signifikant weniger Ganglienzellen in die Apoptose ein. Trotz PBN-Gabe kam es jedoch zum Verlust synaptischer Proteine im Vergleich zur Kontrollgruppe. Zusammengenommen legen die Ergebnisse dieser Arbeit nahe, dass nicht nur der optische Nerv und die Ganglienzellen im Rahmen des Krankheitsgeschehens der MS degenerieren, sondern auch synaptische Bestandteile weiterer retinaler Schichten geschädigt werden. Zudem konnte gezeigt werden, dass präventiv verabreichtes PBN einen protektiven Effekt auf die Versuchstiere mit einem besseren motorischen Ergebnis unter EAE und einem geringeren Ganglienzellschaden im Vergleich zur nicht behandelten Gruppe hat, es aber dennoch zur verringerten Expression synaptischer Proteine kommt.Summary Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). In the process of the neuropathological genesis of this disease, the patient’s own immune system initiates a central inflammation and generates autoantibodies, causing focal degeneration of neuronal myelin sheaths in multiple areas within the CNS (REALE, SANCHEZ-RAMON, 2017). The pathogenesis of MS is based mainly on intra- and intercellular protein channels (Panx1 and multiple subtypes of connexin-channels). These channels e.g. play an important role in the activation of cytotoxic T-lymphocytes, in passing of inflammatory reactions at the myeline sheath and for the transport of pro-inflammatory substances to bystanding cells (ADAMSON, LEITINGER, 2014; MAIER et al., 2004; RIPPS, 2002; THOMPSON, 2015; WONG et al., 2014). Approximately one third of MS-patients develop as initial symptom a neuromyelitis optica, i.e. a wide range of visual disorders up to a complete failure of the visual perceptive field including damage of the retina (HEROLD et al., 2015; LARABEE et al., 2016; SYC et al., 2012). It is still not certain how those pathomechanisms involving the visual system precisely work and the extent of retinal lesions are currently still unknown. Therefore, the first hypothesis of this thesis postulates that axonal damage of the optical nerve, caused by central inflammation, results in an apoptosis of retinal ganglion cells as well as in a reduction of retinal synaptic structures of multiple retinal layers. The research work for this thesis is based on the animal experimental autoimmune encephalomyelitis (EAE) model. The second part of this thesis deals with research examining a potential neuro-protective effect of Panx1 inhibitor PBN on retinal neurons of laboratory mice. This part is based on a hypothesis saying that a PBN intervention of 100mg/kg body weight injected at day one after an EAE induction can prevent neuronal damage in the animal`s eye. It was assumed that an immunological staining would prove a higher density of structural retinal molecules of electrical and chemical synapses within a preventively treated PBN group, when compared with EAE-groups, and that a smaller number of cells would enter an EAE-induced apoptosis. In both parts of this thesis retinal ganglion cells were counted using the ganglion cell specific protein RBPMS. Apoptosis was analyzed using the apoptosis associated protein cleaved caspase-3. In order to examine retinal synaptic connections under EAE and under preventive treatment, connexin 36, the gap junction protein of retinal electric synapses, as well as RIBEYE, expressed in retinal chemical ribbon synapses, were analyzed. In the first part of this thesis it could be demonstrated that an induction of EAE in an animal model leads to detectable paralyses of the animals as well as to degenerations with a significantly decreased expression of analyzed proteins in multiple layers of the retina. The second part of this thesis could prove that motoric results of animals preventively treated with III PBN increased significantly. Furthermore, under PBN-treatment a significant number of retinal ganglion cells were prevented from entering apoptosis. But yet, despite PBN treatment, synaptic proteins decreased in expression in comparison with the control group. To sum up the results of this thesis, it may be presumed that during the pathogenesis of MS, lesions are not limited to the optic nerve and the retinal ganglion cells but degeneration also takes place in multiple retinal synaptic components. Additionally, it could be demonstrated that preventively applicated PBN has a neuro-protective effect on laboratory mice with a better motoric outcome under EAE induction, in comparison with groups without treatment. But still, depletion of expressed retinal synaptic proteins could not be prevented by this treatment

Influence of growth on dust settling and migration in protoplanetary discs

To form meter-sized pre-planetesimals in protoplanetary discs, dust aggregates have to decouple from the gas at a distance far enough from the central star so they are not accreted. Dust grains are affected by gas drag, which results in a vertical settling towards the mid-plane, followed by radial migration. To have a better understanding of the influence of growth on the dust dynamics, we use a simple grain growth model to determine the dust distribution in observed discs. We implement a constant growth rate into a gas+dust hydrodynamics SPH code and vary the growh rate to study the resulting effect on dust distribution. The growth rate allows us to determine the relative importance between friction and growth.We show that depending on the growth rate, a range of dust distribution can result. For large enough growth rates, grains can decouple from the gas before being accreted onto the central star, thus contributing as planetary building rock

Influence of growth on dust settling and migration in protoplanetary discs

To form meter-sized pre-planetesimals in protoplanetary discs, dust aggregates have to decouple from the gas at a distance far enough from the central star so they are not accreted. Dust grains are affected by gas drag, which results in a vertical settling towards the mid-plane, followed by radial migration. To have a better understanding of the influence of growth on the dust dynamics, we use a simple grain growth model to determine the dust distribution in observed discs. We implement a constant growth rate into a gas+dust hydrodynamics SPH code and vary the growh rate to study the resulting effect on dust distribution. The growth rate allows us to determine the relative importance between friction and growth.We show that depending on the growth rate, a range of dust distribution can result. For large enough growth rates, grains can decouple from the gas before being accreted onto the central star, thus contributing as planetary building rocks

Rossby wave instability in locally isothermal and polytropic disks: three-dimensional linear calculations

Numerical calculations of the linear Rossby wave instability (RWI) in global three-dimensional (3D) disks are presented. The linearized fluid equations are solved for vertically stratified, radially structured disks with either a locally isothermal or polytropic equation of state, by decomposing the vertical dependence of the perturbed hydrodynamic quantities into Hermite and Gegenbauer polynomials, respectively. It is confirmed that the RWI operates in 3D. For perturbations with vertical dependence assumed above, there is little difference in growth rates between 3D and two-dimensional (2D) calculations. Comparison between 2D and 3D solutions of this type suggest the RWI is predominantly a 2D instability and that three-dimensional effects, such as vertical motion, to be interpreted as a perturbative consequence of the dominant 2D flow. The vertical flow around co-rotation, where vortex-formation is expected, is examined. In locally isothermal disks the expected vortex center remains in approximate vertical hydrostatic equilibrium. For polytropic disks the vortex center has positive vertical velocity, whose magnitude increases with decreasing polytropic index $n$.Comment: 17 pages, 21 figures, Accepted by Ap

Esses que (não) são os outros: a presença kaiowá e guarani em Amambai, MS

Esse ensaio traz reflexões oriundas de pesquisas e convivência com os Kaiowá e Guarani, especialmente a partir das ações de ensino, pesquisa e extensão implementadas no curso de Ciências Sociais da Universidade Estadual de Mato Grosso do Sul (UEMS), Amambai, Brasil. Apresenta aspectos dos processos históricos que impactam os coletivos indígenas Kaiowá e Guarani, nos territórios do sul do atual Mato Grosso do Sul. Partindo da constatação de que a constituição das Reservas Indígenas Amambai e Limão Verde antecedem a criação do município de Amambai, analisa aspectos do processo da territorialização empreendida pelo Estado, assim como da socialidade e territorialidade própria desses coletivos, que integram um terço da população de Amambai. Uma primeira versão foi publicada em coletânea de artigos com fins didáticos, mas considerando a emergência de novos conflitos na região, em 2022, entende-se ser oportuno retomar o assunto

Non-barotropic linear Rossby wave instability in three-dimensional disks

Astrophysical disks with localized radial structure, such as protoplanetary disks containing dead zones or gaps due to disk-planet interaction, may be subject to the non-axisymmetric Rossby wave instability (RWI) that lead to vortex-formation. The linear instability has recently been demonstrated in three-dimensional (3D) barotropic disks. It is the purpose of this study to generalize the 3D linear problem to include an energy equation, thereby accounting for baroclinity in three-dimensions. Linear stability calculations are presented for radially structured, vertically stratified, geometrically-thin disks with non-uniform entropy distribution in both directions. Polytropic equilibria are considered but adiabatic perturbations assumed. The unperturbed disk has a localized radial density bump making it susceptible to the RWI. The linearized fluid equations are solved numerically as a partial differential equation eigenvalue problem. Emphasis on the ease of method implementation is given. It is found that when the polytropic index is fixed and adiabatic index increased, non-uniform entropy has negligible effect on the RWI growth rate, but pressure and density perturbation magnitudes near a pressure enhancement increases away from the midplane. The associated meridional flow is also qualitatively changed from homentropic calculations. Meridional vortical motion is identified in the nonhomentropic linear solution, as well as in a nonlinear global hydrodynamic simulation of the RWI in an initially isothermal disk evolved adiabatically. Numerical results suggest buoyancy forces play an important role in the internal flow of Rossby vortices.Comment: 16 pages, accepted by ApJ, substantial re-writes for improved clarity, extended results analysi

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