Just 11 weeks after the confirmation of first infection, one team had already discovered and published [D. Wrapp et al. , “Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation,” Science 367 (6483), 1260–1263 (2020)] in exquisite detail about the new coronavirus, along with how it differs from previous viruses. We call the virus particle causing the COVID-19 disease SARS-CoV-2 , a spherical capsid covered with spikes termed peplomers . Since the virus is not motile, it relies on its own random thermal motion, specifically the rotational component of this thermal motion, to align its peplomers with targets. The governing transport property for the virus to attack successfully is thus the rotational diffusivity. Too little rotational diffusivity and too few alignments are produced to properly infect. Too much, and the alignment intervals will be too short to properly infect, and the peplomer is wasted. In this paper, we calculate the rotational diffusivity along with the complex viscosity of four classes of virus particles of ascending geometric complexity: tobacco mosaic, gemini, adeno, and corona. The gemini and adeno viruses share icosahedral bead arrangements, and for the corona virus, we use polyhedral solutions to the Thomson problem to arrange its peplomers. We employ general rigid bead–rod theory to calculate complex viscosities and rotational diffusivities, from first principles, of the virus suspensions. We find that our ab initio calculations agree with the observed complex viscosity of the tobacco mosaic virus suspension. From our analysis of the gemini virus suspension, we learn that the fine detail of the virus structure governs its rotational diffusivity. We find the characteristic time for the adenovirus from general rigid bead–rod theory. Finally, from our analysis of the coronavirus suspension, we learn that its rotational diffusivity descends monotonically with its number of peplomers.

General rigid bead-rod theory [O. Hassager, “Kinetic theory and rheology of bead-rod models for macromolecular solutions. II. Linear unsteady flow properties,” J. Chem. Phys. 60(10), 4001–4008 (1974)] explains polymer viscoelasticity from macromolecular orientation. By means of general rigid bead-rod theory, we relate the complex viscosity of polymeric liquids to the architecture of axisymmetric macromolecules. In this work, we explore the zero-shear and complex viscosities of 24 different axisymmetric polymer configurations. When nondimensionalized with the zero-shear viscosity, the complex viscosity depends on the dimensionless frequency and the sole dimensionless architectural parameter, the macromolecular lopsidedness. In this work, in this way, we compare and contrast the elastic and viscous components of the complex viscosities of macromolecular chains that are straight, branched, ringed, or star-branched. We explore the effects of branch position along a straight chain, branched-chain backbone length, branched-chain branch-functionality, branch spacing along a straight chain (including pom-poms), the number of branches along a straight chain, ringed polymer perimeter, branch-functionality in planar stars, and branch dimensionality.

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The rheological characteristics of mature fine tailings (MFTs) were examined in both the linear and non-linear viscoelastic regimes. MFT samples exhibited thixotropic behaviour as well as apparent slip, which was suppressed by using sandpaper of grit 80 (200 mm) at the wall of the parallel-plate geometry. The real yield stress of MFTs with shear-thinning behaviour was retrieved after fitting to a Herschel-Bulkley equation. Creep and oscillatory shear tests are also used to verify the yield stress measurement. The yield stress of two MFT suspensions possessing similar volume fractions was found to be similar, however, a kaolinite suspension (formulated to mimic/match the MFT rheology) showed more shear thinning, and less thixotropy. The presence of bitumen remaining in the MFTs (up to 2 wt%) suppressed the apparent slip to a large extent due to the immobilization of the particles at the interface. Finally, the effect of temperature on MFT rheology was studied in detail over the range of 0 {degree sign}C to 50 {degree sign}C showing a minimum viscosity and yield stress at about 20 {degree sign}C (demonstrating a non-monotonic increase with increase of temperature).

In this paper, the rheological behavior of bitumen as a function of asphaltene concentration has been studied. Several bitumen samples having distinctly different amount of asphaltene were prepared and characterized using scanning calorimetry and rheological measurements. The glass transition temperature of bitumen increases with increase of the asphaltene concentration. This correlation can be used to estimate the asphaltene concentration of bitumen samples using DSC measurements. Small amplitude oscillatory shear data for the bitumen derived samples was fit by generalized Maxwell model with good agreement. A constitutive model is proposed, where the zero-shear complex viscosity of the bitumen sample is a strong function of the asphaltene concentration and it can be used to predict the asphaltene concentration.