Evolution and ecology of influenza A viruses.

Cosmochemistry of the rare earth elements: meteorite studies.

▪ Abstract At luminosities above 1011 , infrared galaxies become the dominant population of extragalactic objects in the local Universe (z ≲ 0.3), being more numerous than optically selected starburst and Seyfert galaxies and quasi-stellar objects at comparable bolometric luminosity. The trigger for the intense infrared emission appears to be the strong interaction/merger of molecular gas-rich spirals, and the bulk of the infrared luminosity for all but the most luminous objects is due to dust heating from an intense starburst within giant molecular clouds. At the highest luminosities (Lir > 1012 ), nearly all objects appear to be advanced mergers powered by a mixture of circumnuclear starburst and active galactic nucleus energy sources, both of which are fueled by an enormous concentration of molecular gas that has been funneled into the merger nucleus. These ultraluminous infrared galaxies may represent an important stage in the formation of quasi-stellar objects and powerful radio galaxies. They may al...

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Luminous infrared galaxies

We construct size distributions for carbonaceous and silicate grain populations in different regions of the Milky Way, LMC, and SMC. The size distributions include sufficient very small carbonaceous grains (including polycyclic aromatic hydrocarbon molecules) to account for the observed infrared and microwave emission from the diffuse interstellar medium. Our distributions reproduce the observed extinction of starlight, which varies depending on the interstellar environment through which the light travels. As shown by Cardelli, Clayton, and Mathis in 1989, these variations can be roughly parameterized by the ratio of visual extinction to reddening, RV. We adopt a fairly simple functional form for the size distribution, characterized by several parameters. We tabulate these parameters for various combinations of values for RV and bC, the C abundance in very small grains. We also find size distributions for the line of sight to HD 210121 and for sight lines in the LMC and SMC. For several size distributions, we evaluate the albedo and scattering asymmetry parameter and present model extinction curves extending beyond the Lyman limit.

https://iopscience.iop.org/article/10.1086/318651/pdf

Dust Grain-Size Distributions and Extinction in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud

▪ Abstract This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical lum...

https://www.ifa.hawaii.edu/users/reipurth/reviews/draine.pdf

Interstellar dust grains

The rigorous Kerker-Matijevic formulae for light scattering by co-axial double cylinders are used to calculate the extinction properties of hollow organic grains. A size distribution of such particles together with iron whiskers of radii 0.01 μm, silica spheres of radius 0.03 μm and free aromatic molecular clusters comprised of 50–100 atoms yield excellent agreement with data on the extinction of starlight. The mass ratios of silica to organics and of iron to organics are in good accord with cosmic abundance constraints.

The extinction of starlight revisited

Microspherules in Paleozoic-Mesozoic bedded chert, presumed to be of extraterrestrial origin and comprised of clusters of iron needles,may represent an early stage in the aggregation of the inner planets. A fraction of the constituent iron needles will be expected to be carried along with expanding gas to the periphery of the solar nebula where the outer planets and comets condensed. A substantial fraction of iron needles would escape into interstellar space and add to the population of interstellar grains. Iron needles could contribute substantially to interstellar polarization and to the infrared opacity of the interstellar medium.

Extraterrestrial microspherules and iron needles in the interstellar medium

We show that suitably defined Guttler (core-mantle) analogues can satisfactorily represent the optical cross-sections of aggregates of very small particles that result from mutual collisions and sticking. Earlier calculations using the discrete dipole approximation are seen to be in good agreement with Guttler analogue calculations, particularly in the case of the so-called Ballistic Particle-Cluster Aggregates (BPCA).

Güttler scattering analogues for dust aggregates

The evidence for the cometary origin then rapid global spread of COVID-19 through 2020 is critically reviewed. We outline why it is an alternative plausible scientific explanation to the current bat/pangolin animal jump theories. In our view this explanation is consistent with all the available temporal unfolding scientific data (genomic, immunologic, epidemiologic, geophysical, astrophysical and astrobiological). Thus COVID-19 arrived as infective cryopreserved virions in cometary meteoritic dust clouds from space in a bolide strike in the stratosphere over China on October 11 2019. Prevailing high-level and low-level wind systems then globally distributed the infective viral dust clouds, striking different regions at different times. Given this possibility, a new space challenge for mankind is to develop near-Earth early warning biological surveillance (and mitigation) systems for incoming cosmic in-falls of micro-organisms and viruses from the cometary dust and meteorite streams that our planet routinely encounters as it orbits the Sun. © 2022 by World Scientific Publishing Co. Pte. Ltd.

Cometary Origin of COVID-19

The far-infrared flux measurements for supernova SN 1987A are modelled in terms of length distributions of iron whiskers. The excess emission detected at ⋋ ≡ 1.3µm can be explained on the basis of such a model.

N. C. Wickramasinghe

Papers

The extinction of starlight revisited

Extraterrestrial microspherules and iron needles in the interstellar medium

Güttler scattering analogues for dust aggregates

Cometary Origin of COVID-19

Iron whiskers in supernova SN 1987A