scholarly journals Building protoplanetary disks from the molecular cloud: redefining the disk timeline

2019 ◽  
Vol 624 ◽  
pp. A93 ◽  
Author(s):  
K. Baillié ◽  
J. Marques ◽  
L. Piau
Keyword(s):  
Molecular Cloud ◽  
Protoplanetary Disk ◽  
Giant Planets ◽  
Type I ◽  
Initial State ◽  
Disk Formation ◽  
Heat Transition ◽  
Cloud Material ◽  
Selection Of ◽  
Collapse Phase

Context. Planetary formation models are necessary to understand the characteristics of the planets that are the most likely to survive. Their dynamics, their composition and even the probability of their survival depend on the environment in which they form. We therefore investigate the most favorable locations for planetary embryos to accumulate in the protoplanetary disk: the planet traps. Aims. We study the formation of the protoplanetary disk by the collapse of a primordial molecular cloud, and how its evolution leads to the selection of specific types of planets. Methods. We use a hydrodynamical code that accounts for the dynamics, thermodynamics, geometry and composition of the disk to numerically model its evolution as it is fed by the infalling cloud material. As the mass accretion rate of the disk onto the star determines its growth, we can calculate the stellar characteristics by interpolating its radius, luminosity and temperature over the stellar mass from pre-calculated stellar evolution models. The density and midplane temperature of the disk then allow us to model the interactions between the disk and potential planets and determine their migration. Results. At the end of the collapse phase, when the disk reaches its maximum mass, it pursues its viscous spreading, similarly to the evolution from a minimum mass solar nebula (MMSN). In addition, we establish a timeline equivalence between the MMSN and a “collapse-formed disk” that would be older by about 2 Myr. Conclusions. We can save various types of planets from a fatal type-I inward migration: in particular, planetary embryos can avoid falling on the star by becoming trapped at the heat transition barriers and at most sublimation lines (except the silicates one). One of the novelties concerns the possible trapping of putative giant planets around a few astronomical units from the star around the end of the infall. Moreover, trapped planets may still follow the traps outward during the collapse phase and inward after it. Finally, this protoplanetary disk formation model shows the early possibilities of trapping planetary embryos at disk stages that are anterior by a few million years to the initial state of the MMSN approximation.

Protoplanetary Disk Formation in Molecular Cloud Cores

2009 ◽  
Author(s):  
Masahiro N. Machida ◽  
Shu-ichiro Inutsuka ◽  
Tomoaki Matsumoto ◽  
Tomonori Usuda ◽  
Motohide Tamura ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Protoplanetary Disk ◽  
Disk Formation ◽  
Cloud Cores

scholarly journals Global Protoplanetary Disk Simulations: Dead Zone Formation and FUor Outbursts

2018 ◽  
Vol 14 (S345) ◽  
pp. 324-325
Author(s):  
Kundan Kadam ◽  
E. Vorobyov ◽  
Zs. Regály ◽  
Á. Kóspál ◽  
P. Ábráham
Keyword(s):  
Molecular Cloud ◽  
Dead Zone ◽  
Protoplanetary Disk ◽  
Model Parameters ◽  
Zone Formation ◽  
Hydrodynamic Simulations ◽  
Disk Structure ◽  
Self Consistent ◽  
Disk Evolution ◽  
Collapse Phase

AbstractWe conducted global hydrodynamic simulations of protoplanetary disk evolution with an adaptive Shakura-Sunyaev α prescription to represent the layered disk structure, and starting with the collapse phase of the molecular cloud. With the canonical values of model parameters, self-consistent dead zones formed at the scale of a few au. The instabilities associated with the dead zone and corresponding outbursts, similar to FUor eruptions, were also observed in the simulations.

Exposure–Response Analysis for Selection of Optimal Dosage Regimen of Anifrolumab in Patients With Systemic Lupus Erythematosus

Rheumatology ◽  
2021 ◽  
Author(s):  
Yen Lin Chia ◽  
Linda Santiago ◽  
Bing Wang ◽  
Denison Kuruvilla ◽  
Shiliang Wang ◽  
...  
Keyword(s):  
Type I Interferon ◽  
Drug Clearance ◽  
Optimal Dosage ◽  
Type I ◽  
Efficacy And Safety ◽  
Response Relationship ◽  
Phase 3 ◽  
Optimal Dosage Regimen ◽  
Exposure Response ◽  
Selection Of

Abstract Objectives The randomized, double-blind, phase 2 b MUSE study evaluated the efficacy and safety of the type I interferon receptor antibody anifrolumab (300 mg or 1000 mg every 4 weeks) compared with placebo for 52 weeks in patients with chronic, moderate to severe SLE. Characterizing the exposure–response relationship of anifrolumab in MUSE will enable selection of its optimal dosage regimen in two phase 3 studies in patients with SLE. Methods The exposure–response relationship, pharmacokinetics (PK), and SLE Responder Index (SRI[4]) efficacy data were analysed using a population approach. A dropout hazard function was also incorporated into the SRI(4) model to describe the voluntary patient withdrawals during the 1-year treatment period. Results The population PK model found that type I IFN test–high patients, and patients with a higher body weight, had significantly greater clearance of anifrolumab. Stochastic clinical simulations demonstrated that doses <300 mg would lead to a greater-than-proportional reduction in drug exposure owing to type I interferon alpha receptor–mediated drug clearance (antigen-sink effect, more rapid drug clearance at lower concentrations) and suboptimal SRI(4) responses with wider confidence intervals. Conclusions Based on PK, efficacy, and safety considerations, anifrolumab 300 mg every 4 weeks was recommended as the optimal dosage for pivotal phase 3 studies in patients with SLE.

scholarly journals The Grand Tack model: a critical review

2014 ◽  
Vol 9 (S310) ◽  
pp. 194-203 ◽  
Author(s):  
Sean N. Raymond ◽  
Alessandro Morbidelli
Keyword(s):  
Solar System ◽  
Building Blocks ◽  
Protoplanetary Disk ◽  
Giant Planets ◽  
Asteroid Belt ◽  
Terrestrial Planets ◽  
Saturn’S Satellites ◽  
Internal Inconsistency ◽  
Solar System Bodies ◽  
Gas Accretion

AbstractThe “Grand Tack” model proposes that the inner Solar System was sculpted by the giant planets' orbital migration in the gaseous protoplanetary disk. Jupiter first migrated inward then Jupiter and Saturn migrated back outward together. If Jupiter's turnaround or “tack” point was at ~ 1.5 AU the inner disk of terrestrial building blocks would have been truncated at ~ 1 AU, naturally producing the terrestrial planets' masses and spacing. During the gas giants' migration the asteroid belt is severely depleted but repopulated by distinct planetesimal reservoirs that can be associated with the present-day S and C types. The giant planets' orbits are consistent with the later evolution of the outer Solar System.Here we confront common criticisms of the Grand Tack model. We show that some uncertainties remain regarding the Tack mechanism itself; the most critical unknown is the timing and rate of gas accretion onto Saturn and Jupiter. Current isotopic and compositional measurements of Solar System bodies – including the D/H ratios of Saturn's satellites – do not refute the model. We discuss how alternate models for the formation of the terrestrial planets each suffer from an internal inconsistency and/or place a strong and very specific requirement on the properties of the protoplanetary disk.We conclude that the Grand Tack model remains viable and consistent with our current understanding of planet formation. Nonetheless, we encourage additional tests of the Grand Tack as well as the construction of alternate models.

scholarly journals Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

2016 ◽  
Vol 113 (8) ◽  
pp. 2011-2016 ◽  
Author(s):  
Elishevah M. M. E. Van Kooten ◽  
Daniel Wielandt ◽  
Martin Schiller ◽  
Kazuhide Nagashima ◽  
Aurélien Thomen ◽  
...  
Keyword(s):  
Solar System ◽  
Thermal Processing ◽  
Molecular Cloud ◽  
Decay Product ◽  
Isotopic Signature ◽  
Carbonaceous Chondrites ◽  
Outer Solar System ◽  
Precursor Material ◽  
System Composition ◽  
Cloud Material

The short-lived 26Al radionuclide is thought to have been admixed into the initially 26Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54Cr and 26Mg*, the decay product of 26Al. This correlation is interpreted as reflecting progressive thermal processing of in-falling 26Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26Mg*-depleted and 54Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26Al. The 26Mg* and 54Cr compositions of bulk metal-rich chondrites require significant amounts (25–50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants.

scholarly journals ALMA Observations of Elias 2–24: A Protoplanetary Disk with Multiple Gaps in the Ophiuchus Molecular Cloud

2017 ◽  
Vol 851 (2) ◽  
pp. L23 ◽  
Author(s):  
Lucas A. Cieza ◽  
Simon Casassus ◽  
Sebastian Pérez ◽  
Antonio Hales ◽  
Miguel Cárcamo ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Protoplanetary Disk

HPV: from infection to cancer

2007 ◽  
Vol 35 (6) ◽  
pp. 1456-1460 ◽  
Author(s):  
M.A. Stanley ◽  
M.R. Pett ◽  
N. Coleman
Keyword(s):  
Immune Response ◽  
Cancer Progression ◽  
Therapeutic Effects ◽  
Type I ◽  
Immune Recognition ◽  
Human Papillomavirus 16 ◽  
E6 And E7 ◽  
High Doses ◽  
Risk Of Cancer ◽  
Selection Of

Infection with HPV (human papillomavirus) 16 is the cause of 50% or more of cervical cancers in women. HPV16 infection, however, is very common in young sexually active women, but the majority mount an effective immune response and clear infection. Approx. 10% of individuals develop a persistent infection, and it is this cohort who are at risk of cancer progression, with the development of high-grade precursor lesions and eventually invasive carcinoma. Effective evasion of innate immune recognition seems to be the hallmark of HPV infections, since the infectious cycle is one in which viral replication and release is not associated with inflammation. Furthermore, HPV infections disrupt cytokine expression and signalling with the E6 and E7 oncoproteins particularly targeting the type I IFN (interferon) pathway. High doses of IFN can overcome the HPV-mediated abrogation of signalling, and this may be the basis for the therapeutic effects on HPV infections of immune-response modulators such as the imidazoquinolones that induce high levels of type I IFNs by activation of TLR (Toll-like receptor) 7. Using the unique W12 model of cervical carcinogenesis, some of these IFN-related interactions and their relevance in the selection of cells with integrated viral DNA in cancer progression have been investigated. Our data show that episome loss associated with induction of antiviral response genes is a key event in the spontaneous selection of cervical keratinocytes containing integrated HPV16. Exogenous IFN-β treatment of W12 keratinocytes in which the majority of the population contain episomes results only in the rapid emergence of IFN-resistant cells, loss of episome-containing cells and a selection of cells containing integrated HPV16 in which the expression of the transcriptional repressor E2 is down-regulated, but in which E6 and E7 are up-regulated.

Marker-Assisted Selection Efficiency in Populations of Finite Size

Genetics ◽  
1998 ◽  
Vol 148 (3) ◽  
pp. 1353-1365
Author(s):  
Laurence Moreau ◽  
Alain Charcosset ◽  
Frédéric Hospital ◽  
André Gallais
Keyword(s):  
Relative Efficiency ◽  
Marker Assisted Selection ◽  
Analytical Approach ◽  
Type I Error ◽  
Genetic Model ◽  
Finite Size ◽  
Type I ◽  
Selection Efficiency ◽  
Molecular Information ◽  
Selection Of

Abstract The efficiency of marker-assisted selection (MAS) based on an index incorporating both phenotypic and molecular information is evaluated with an analytical approach that takes into account the size of the experiment. We consider the case of a population derived from a cross between two homozygous lines, which is commonly used in plant breeding, and we study the relative efficiency of MAS compared with selection based only on phenotype in the first cycle of selection. It is shown that the selection of the markers included in the index leads to an overestimation of the effects associated with these markers. Taking this bias into account, we study the influence of several parameters, including experiment size and heritability, on MAS efficiency. Even if MAS appears to be most interesting for low heritabilities, we point out the existence of an optimal heritability (~0.2) below which the low power of quantitative trait loci detection and the bias caused by the selection of markers reduce the efficiency. In this situation, increasing the power of detection by using a higher probability of type I error can improve MAS efficiency. This approach, validated by simulations, gives results that are generally consistent with those previously obtained by simulations using a more sophisticated biological model than ours. Thus, though developed from a simple genetic model, our approach may be a useful tool to optimize the experimental means for more complex genetic situations.

scholarly journals The Origin of the Idea That Herpes Labialis Is of Prognostic Importance in Bacterial Meningitis

2020 ◽  
Vol 83 (1) ◽  
pp. 105-110
Author(s):  
Peter J. Koehler
Keyword(s):  
Primary Infection ◽  
Meningococcal Meningitis ◽  
Type I ◽  
Herpes Labialis ◽  
The Past ◽  
Prognostic Importance ◽  
19Th And 20Th Century ◽  
Century Idea ◽  
Diagnostic Importance ◽  
Selection Of

Objective:The aim of the work was to study the origin of the idea that herpes labialis (HL) in patients with pneumonia and meningitis was believed to be of prognostic importance. Background:HL is caused by a primary infection or reactivation of herpes simplex type I. In the past, it has been related to pneumonia and meningitis; moreover, HL was believed to be of prognostic importance. Methods:A selection of 19th- and 20th-century textbooks and referred articles was consulted. The relation between meningitis and herpes, type of meningitis, and attributed diagnostic and prognostic importance were studied. In addition, the HL-pneumonia association was studied. Results:The Strasbourg physician Charles-Polydore Forget was the first to describe the HL-meningitis association in 1843. Tourdes (1843), Drasche (1859), and Salomon (1864) attributed a favorable prognostic importance to the HL-meningitis relation. In a comprehensive monograph (1866), August Hirsch, although confirming the association, denied the prognostic importance through critical analysis of the data. Few authors attributed a diagnostic importance to the occurrence of HL, suggesting meningococcal meningitis. Conclusions:The HL-meningitis relation, but not the prognostic importance, has been mentioned in most neurological textbooks since then. In contrast to meningitis, in which a prognostic attribution of HL was only a short-lived 19th-century idea, the favorable prognostic importance of HL in pneumonia continued to be described until the 1950s. A possible protective effect of herpesviruses has been found in recent years. One could speculate that the disappearance of the prognostic HL-pneumonia relation could be related to the introduction of antibiotics in the late 1940s.

scholarly journals Planet formation by pebble accretion in ringed disks

2020 ◽  
Vol 638 ◽  
pp. A1 ◽  
Author(s):  
A. Morbidelli
Keyword(s):  
Growth Rate ◽  
Upper Bound ◽  
Planet Formation ◽  
Accretion Rate ◽  
Central Star ◽  
Giant Planets ◽  
Type I ◽  
Dust Density ◽  
Dominant Process ◽  
The One

Context. Pebble accretion is expected to be the dominant process for the formation of massive solid planets, such as the cores of giant planets and super-Earths. So far, this process has been studied under the assumption that dust coagulates and drifts throughout the full protoplanetary disk. However, observations show that many disks are structured in rings that may be due to pressure maxima, preventing the global radial drift of the dust. Aims. We aim to study how the pebble-accretion paradigm changes if the dust is confined in a ring. Methods. Our approach is mostly analytic. We derived a formula that provides an upper bound to the growth of a planet as a function of time. We also numerically implemented the analytic formulæ to compute the growth of a planet located in a typical ring observed in the DSHARP survey, as well as in a putative ring rescaled at 5 AU. Results. Planet Type I migration is stopped in a ring, but not necessarily at its center. If the entropy-driven corotation torque is desaturated, the planet is located in a region with low dust density, which severely limits its accretion rate. If the planet is instead near the ring’s center, its accretion rate can be similar to the one it would have in a classic (ringless) disk of equivalent dust density. However, the growth rate of the planet is limited by the diffusion of dust in the ring, and the final planet mass is bounded by the total ring mass. The DSHARP rings are too far from the star to allow the formation of massive planets within the disk’s lifetime. However, a similar ring rescaled to 5 AU could lead to the formation of a planet incorporating the full ring mass in less than 1/2 My. Conclusions. The existence of rings may not be an obstacle to planet formation by pebble-accretion. However, for accretion to be effective, the resting position of the planet has to be relatively near the ring’s center, and the ring needs to be not too far from the central star. The formation of planets in rings can explain the existence of giant planets with core masses smaller than the so-called pebble isolation mass.

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