Open-ringed structure of the Cdt1–Mcm2–7 complex as a precursor of the MCM double hexamer

1. The otolith of the hake (Merlucius merluccius Linn.) is a compound structure, comprising an organic and an inorganic constituent. 2. The organic constituent is the more complex in structure, and consists of concentric shells (appearing in sections of the otolith as lamellae) which have a reticulate structure, and are probably fibrous in nature. The concentric shells are separated at a fairly constant distance of about 2µ from one another, and are bound together by comparatively stout radial fibres. 3. The inorganic constituent consists of needle-like crystals, about 40µ in maximum length, and less than 1µ thick, which are secreted among the radial fibres, and pass normally through the concentric shells of the organic constituent from the centre of the otolith to the periphery. These crystals interlock to give the otolith its very solid structure. 4. The concentric rings, apparent when the entire otolith is viewed lying on its side, and which, in some species of fish, are used for the assessment of age, are due to the varying thickness of the concentric shells, described in (2) above. These are, typically, grouped in such a way that there are alternating zones where thick and thin concentric shells (lamellae) predominate. Where thick lamellae predominate an effect of opacity is produced, where thin lamellae predominate, one of comparative translucency. The thick lamellae are of the order of 1.5µ at their thickest, the thin lamellae extremely tenuous. 5. The cause of the ringed structure in the entire otolith is therefore due to the organic constituent, the inorganic constituent (crystals) having a supporting function only, in the otolith. 6. Immermann's hypothesis, that the rings are due to the structure of the inorganic constituent, being an optical effect produced by an internal reflection of the light, caused by a twisting of the crystals, is not accepted as applying to the otolith of the hake.

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The partitioning of the inner and outer solar system by a structured protoplanetary disk

10.5194/egusphere-egu2020-3685 ◽

2020 ◽

Author(s):

Ramon Brasser ◽

Stephen Mojzsis

Keyword(s):

Solar System ◽

Protoplanetary Disk ◽

Giant Planets ◽

Iron Meteorites ◽

Effective Barrier ◽

Dynamical Simulations ◽

Pressure Maximum ◽

Ringed Structure ◽

Isotopic Anomalies ◽

Multiple Rings

Mass-independent isotopic anomalies in planets and meteorites define two cosmochemically distinct regions: the carbonaceous and non-carbonaceous meteorites, implying that the non-carbonaceous (terrestrial) and carbonaceous (jovian) reservoirs were kept separate during and after planet formation. The iron meteorites show a similar dichotomy.The formation of Jupiter is widely invoked to explain this compositional dichotomy by acting as an effective barrier between the two reservoirs. Jupiter&#8217;s solid kernel possibly grew to ~20 Mearth in ~1 Myr from the accretion of sub meter-sized objects (termed &#8220;pebbles&#8221;), followed by slower accretion via planetesimals. Subsequent gas envelope contraction is thought to have led to Jupiter&#8217;s formation as a gas giant.We show using dynamical simulations that the growth of Jupiter from pebble accretion is not fast enough to be responsible for the inferred separation of the terrestrial and jovian reservoirs. We propose instead that the dichotomy was caused by a pressure maximum in the disk near Jupiter&#8217;s location, which created a ringed structure such as those detected by the Atacama Large Millimeter/submillimeter Array(ALMA). One or multiple such long-lived pressure maxima almost completely prevented pebbles from the jovian region reaching the terrestrial zone, maintaining a compositional partition between the two regions. We thus suggest that our young solar system&#8217;s protoplanetary disk developed at least one and likely multiple rings, which potentially triggered the formation of the giant planets [1]. [1] Brasser, R. and Mojzsis, S.J. (2020) Nature Astronomy doi: 10.1038/s41550-019-0978-6

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Determining mass limits around HD 163296 through SPHERE direct imaging data

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1662 ◽

2019 ◽

Vol 488 (1) ◽

pp. 37-46 ◽

Cited By ~ 7

Author(s):

D Mesa ◽

M Langlois ◽

A Garufi ◽

R Gratton ◽

S Desidera ◽

...

Keyword(s):

Near Infrared ◽

The Other ◽

Field Of View ◽

Dual Band ◽

Imaging Data ◽

Direct Imaging ◽

Be Star ◽

Integral Field Spectrograph ◽

Ringed Structure ◽

Integral Field

ABSTRACT HD 163296 is a Herbig Ae/Be star known to host a protoplanetary disc with a ringed structure. To explain the disc features, previous works proposed the presence of planets embedded into the disc. We have observed HD 163296 with the near-infrared (NIR) branch of SPHERE composed by IRDIS (InfraRed Dual-band Imager and Spectrograph) and IFS (integral field spectrograph) with the aim to put tight constraints on the presence of substellar companions around this star. Despite the low rotation of the field of view during our observation we were able to put upper mass limits of few MJup around this object. These limits do not allow to give any definitive conclusion about the planets proposed through the disc characteristics. On the other hand, our results seem to exclude the presence of the only candidate proposed until now using direct imaging in the NIR even if some caution has to be taken considered the different wavelength bands of the two observations.

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Limiting effects in clusters of misaligned toroids orbiting static SMBHs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa503 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4229-4255

Author(s):

D Pugliese ◽

Z Stuchlík

Keyword(s):

Magnetic Field ◽

Black Hole ◽

Discrete Geometry ◽

Perfect Fluid ◽

High Frequency ◽

Schwarzschild Black Hole ◽

Periodic Oscillations ◽

Inclination Angles ◽

Ringed Structure ◽

Twin Peak

ABSTRACT We consider agglomerates of misaligned, pressure supported tori orbiting a Schwarzschild black hole. A leading function is introduced, regulating the toroids distribution around the central static attractor – it enables us to model the misaligned tori aggregate as a single orbiting (macro-)configuration. We first analyse the leading function for purely hydrodynamical perfect fluid toroids. Later, the function is modified for presence of a toroidal magnetic field. We study the constraints on the tori collision emergence and the instability of the agglomerates of misaligned tori with general relative inclination angles. We discuss the possibility that the twin peak high-frequency quasi-periodic oscillations (HF-QPOs) could be related to the agglomerate inner ringed structure. The discrete geometry of the system is related to HF-QPOs considering several oscillation geodesic models associated to the toroids inner edges. We also study possible effect of the tori geometrical thickness on the oscillatory phenomena.

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