A New Equation of State for CCS Pipeline Transport: Calibration of Mixing Rules for Binary Mixtures of CO2 with N2, O2 and H2

One of the aspects currently holding back commercial scale deployment of carbon capture and storage (CCS) is an accurate understanding of the thermodynamic behaviour of carbon dioxide and relevant impurities during the pipeline transport stage. In this article we develop a general framework for deriving pressure-explicit EoS for impure CO2. This flexible framework facilitates ongoing development of custom EoS in response to new data and computational applications. We use our method to generalise a recent EoS for pure CO2 [Demetriades et al. Proc IMechE Part E, 227 (2013) pp. 117] to binary mixtures with N2, O2 and H2, obtaining model parameters by fitting to experiments made under conditions relevant to CCS-pipeline transport. Our model pertains to pressures up to 16MPa and temperatures between 273K and the critical temperature of pure CO2. In this region, we achieve close agreement with experimental data. When compared to the GERG EoS, our EoS has a comparable level of agreement with CO2 -N2 VLE experiments and demonstrably superior agreement with the O2 and H2 VLE data. Finally, we discuss future options to improve the calibration of EoS and to deal with the sparsity of data for some impurities

De novo head and neck cancer after liver transplant with antibody-based immunosuppression induction

Background Powerful antibody-based immunosuppression induction is now used routinely during organ transplantation, and may place patients at even higher risk of post-transplant cancer. Materials and Methods Incidence of de-novo head and neck cancer was extracted from the records of 1685 consecutive adult, deceased donor liver transplant recipients with a minimum 1-year follow-up from 2001 to 2015. There were 121 patients positively identified as having developed de-novo head and neck cancer post-liver transplant. Records of these patients were analyzed to determine demographics, history of cancer pre-liver transplant, de-novo cancer type and location, treatment modalities, and alcohol and tobacco exposure. Results Of the 121 patients who developed cancer of the head and neck (7%), there were 103 cutaneous (6%) and 25 non-cutaneous (1%). For non-cutaneous cancers, factors associated with increased risk of cancer included alcohol abuse (p<0.001), any smoking history (p=0.05), and increasing exposure to tobacco (p<0.01). Ten-year Cox regression patient survival demonstrates a survival disadvantage for patients who develop non-cutaneous cancer (p=0.06), but a survival advantage for patients who develop cutaneous cancer (p<0.01). Conclusions The incidence and pattern of head and neck cancer in this population of liver transplant patients was similar to those published previously, suggesting that induction immunosuppression does not increase risk of these types of cancers. Long term survival was worse for patients with non-cutaneous cancers, but better for those with cutaneous cancers, though the reason is unclear

Nonlinear shear of entangled polymers from nonequilibrium molecular dynamics

This work aims to improve the use of Molecular Dynamics simulations of Kremer-Grest chains to inform future developments of models of entangled polymer dynamics. We perform non-equilibrium molecular dynamics simulations, under shear flow, for well entangled Kremer-Grest chains. We study chains of 512 and 1000 Kremer-Grest beads, corresponding to 8 and 15 entanglements, respectively. We computed the linear rheological properties from equilibrium simulations of the stress auto-correlation function and obtained from these data the tube model parameters. Under non-linear shear flow, we compute the shear viscosity, the first and second normal stress differences and chain contour length. For chains of 512 monomers we obtain agreement with the shear stress results of Cao and Likhtman [ACS Macro Letters (2015) vol. 4 (12) pp. 1376-1381]. We also compare our non-linear results for both chain lengths with the GLaMM model, a widely used non-linear tube model. We identify some systematic disagreement that becomes larger for the longer chains. We made a systematic comparison of the transient shear stress maximum from our simulations, two non-linear models and experiments on a wide range of both melts and solutions, including polystyrene, polybu-tadiene and styrene-butadiene rubber. This comparison establishes that the polystyrene melt data show markedly different behaviour to all other melts and solutions and that Kremer-Grest simulations reproduce the polystyrene data more closely than either the GLaMM or Xie and Schweizer models. We also discuss the performance of these two models against the data and simulations. Finally, by imposing a rapid reversing flow, we produce a method to extract the recoverable strain from MD simulations, valid for sufficiently entangled monodisperse polymers. We then explore how the resulting data can be used to probe the melt state just before the reversing flow

Coarse-grained simulations of flow-induced nucleation in semi-crystalline polymers

We perform kinetic Monte Carlo simulations of flow-induced nucleation in polymer melts with an algorithm that is tractable even at low undercooling. The configuration of the non-crystallized chains under flow is computed with a recent non-linear tube model. Our simulations predict both enhanced nucleation and the growth of shish-like elongated nuclei for sufficiently fast flows. The simulations predict several experimental phenomena and theoretically justify a previously empirical result for the flow-enhanced nucleation rate. The simulations are highly pertinent to both the fundamental understanding and process modeling of flow-induced crystallization in polymer melts.Comment: 17 pages, 6 eps figure

Temporal Evolution of the Size and Temperature of Betelgeuse's Extended Atmosphere

We use the Very Large Array (VLA) in the A configuration with the Pie Town (PT) Very Long Baseline Array (VLBA) antenna to spatially resolve the extended atmosphere of Betelgeuse over multiple epochs at 0.7, 1.3, 2.0, 3.5, and 6.1 cm. The extended atmosphere deviates from circular symmetry at all wavelengths while at some epochs we find possible evidence for small pockets of gas significantly cooler than the mean global temperature. We find no evidence for the recently reported e-MERLIN radio hotspots in any of our multi-epoch VLA/PT data, despite having sufficient spatial resolution and sensitivity at short wavelengths, and conclude that these radio hotspots are most likely interferometric artefacts. The mean gas temperature of the extended atmosphere has a typical value of 3000 K at 2 $R_{\star}$ and decreases to 1800 K at 6 $R_{\star}$, in broad agreement with the findings of the single epoch study from Lim et al. (1998). The overall temperature profile of the extended atmosphere between $2 R_{\star} \lesssim r \lesssim 6 R_{\star}$ can be described by a power law of the form $T_{\mathrm{gas}}(r) \propto r^{-0.6}$, with temporal variability of a few 100 K evident at some epochs. Finally, we present over 12 years of V band photometry, part of which overlaps our multi-epoch radio data. We find a correlation between the fractional flux density variability at V band with most radio wavelengths. This correlation is likely due to shock waves induced by stellar pulsations, which heat the inner atmosphere and ionize the more extended atmosphere through radiative means. Stellar pulsations may play an important role in exciting Betelgeuse's extended atmosphere

Interpolation of intermolecular potentials using Gaussian processes

A procedure is proposed to produce intermolecular potential energy surfaces from limited data. The procedure involves generation of geometrical configurations using a Latin hypercube design, with a maximin criterion, based on inverse internuclear distances. Gaussian processes are used to interpolate the data, using over-specified inverse molecular distances as covariates, greatly improving the interpolation. Symmetric covariance functions are specified so that the interpolation surface obeys all relevant symmetries, reducing prediction errors. The interpolation scheme can be applied to many important molecular interactions with trivial modifications. Results are presented for three systems involving CO2, a system with a deep energy minimum (HF - HF) and a system with 48 symmetries (CH4 - N2). In each case the procedure accurately predicts an independent test set. Training this method with high-precision ab initio evaluations of the CO2 - CO interaction enables a parameter-free, first-principles prediction of the CO2 - CO cross virial coefficient that agree very well with experiments

Understanding flow-induced crystallisation in polymers: a perspective on the role of molecular simulations

Flow induced crystallisation in polymers is an important problem in both fundamental polymer science and industrial polymer processing. The key process of flow-induced nucleation occurs on a very rapid timescale and on a highly localised lengthscale and so is extremely difficult to observe directly in experiments. However, recent advances in molecular dynamics simulations mean that flow-induced nucleation can be simulated at an achievable computational cost. Such studies offer unrivalled time and lengthscale resolution of the nucleation process. Nevertheless, the computational cost of molecular dynamics places considerable constraints on the range of molecular weights, temperature and polydispersity that can be studied. In this review I will discuss recent progress, describe how future work might resolve or work around the constraints of molecular simulation and examine how multiscale modelling could translate molecular insight into improved polymer processing

Separating baryons and dark matter in cluster cores: a full 2-D lensing and dynamic analysis of Abell 383 and MS2137-23

(abridged) We utilize existing imaging and spectroscopic data for the galaxy clusters MS2137-23 and Abell 383 to present improved measures of the distribution of dark and baryonic material in the clusters' central regions. Our method, based on the combination of gravitational lensing and dynamical data, is uniquely capable of separating the distribution of dark and baryonic components at scales below 100 kpc. We find a variety of strong lensing models fit the available data, including some with dark matter profiles as steep as expected from recent simulations. However, when combined with stellar velocity dispersion data for the brightest member, shallower inner slopes than predicted by numerical simulations are preferred. For Abell 383, the preferred shallow inner slopes are statistically a good fit only when the multiple image position uncertainties associated with our lens model are assumed to be 0\farcs5, to account for unknown substructure. No statistically satisfactory fit was obtained matching both the multiple image lensing data and the velocity dispersion profile of the brightest cluster galaxy in MS2137-23. This suggests that the mass model we are using, which comprises a pseudo-elliptical generalized NFW profile and a brightest cluster galaxy component may inadequately represent the inner cluster regions. This may plausibly arise due to halo triaxiality or by the gravitational interaction of baryons and dark matter in cluster cores. However, the progress made via this detailed study highlights the key role that complementary observations of lensed features and stellar dynamics offer in understanding the interaction between dark and baryonic matter on non-linear scales in the central regions of clusters.Comment: 18 pages, 9 figures; accepted for publication in the Astrophysical Journa

A Survey of Action-Learning Opportunities

This is a preliminary report on a survey of Action-Learning opportunities conducted in the Spring of 1972. The survey director was Allan Cameron; a grant from the White House Committee on Youth enabled a number of persons age 15-20 to participate in the surve