The influence of matrix viscoelasticity on the rheology of polymer blends

We examine the effects of matrix phase viscoelasticity on the rheological modeling of polymer blends with a droplet morphology. Two contravariant, second-rank tensor variables are adopted along with the translational momentum density of the fluid to account for viscoelasticity of the matrix phase and the ellipsoidal droplet shapes. The first microstructural variable is a conformation tensor describing the average extension and orientation of the molecules in the matrix phase. The other microstructural variable is a configuration tensor to account for the average shape and orientation of constant-volume droplets. A Hamiltonian framework of non-equilibrium thermodynamics is then adopted to derive a set of continuum equations for the system variables. This set of equations accounts for local conformational changes of the matrix molecules due to droplet deformation and vice versa. The model is intended for dilute blends of both oblate and prolate droplets, and droplet breakup and coalescence are not taken into account. Only the matrix phase is considered as viscoelastic; i.e., the droplets are assumed to be Newtonian. The model equations are solved for various types of homogeneous deformations, and microstructure/rheology relationships are discussed for transient and steady-state conditions. A comparison with other constrained-volume rheological models and experimental data is made as wel

Single bubble deformation and breakup in simple shear flow

Experiments in a parallel band apparatus and a transparent concentric cylinder device allow the observation of bubble deformation (shape and orientation) and breakup as a function of the viscosity ratio λ and the Capillary number Ca. For viscosity ratios between 3.1×10−7 and 6.7×10−8, critical Capillary numbers Ca c for bubble breakup between 29 and 45 are found. It is furthermore shown that in the given parameter space no clear distinction between tip breakup and fracture can be made for bubble

Overall survival and role of programmed death ligand 1 expression in patients with metastatic non-small-cell lung cancer and immunotherapy: an observational study from central Switzerland.

BACKGROUND In clinical trials, therapy with immune checkpoint inhibitors has improved the survival of patients with metastatic non-small-cell lung cancer (NSCLC). These trials were important for drug approval and for defining new treatment standards but the effect of checkpoint inhibitors in patients treated outside of clinical trials is not well known. The goal of this study was to assess the effect of immunotherapy on the overall survival of patients with metastatic NSCLC in the region of central Switzerland. MATERIALS AND METHODS The study included 274 patients with histologically confirmed metastatic (stage IV) NSCLC in central Switzerland in the years 2015 to 2018. Patients with NSCLC and actionable driver mutations were excluded. Patients with checkpoint inhibitor treatment (immuno-oncology [IO] group, n = 122) were compared with patients without checkpoint inhibitor treatment (no-IO group, n = 152). Baseline demographics, disease characteristics and therapies applied were collected retrospectively. The primary endpoint was median overall survival calculated either from diagnosis or from the start of checkpoint inhibitor therapy to death or data cut-off (21 July 2021). We used the Kaplan-Meier method and an adjusted Cox proportional-hazards regression model. The expression of programmed-death ligand 1 (PD-L1) on tumour cells was used for exploratory analysis. RESULTS Patients had a median age of 68.4 years, most were male (61.7%) and more than half were current or former smokers (65%). A test for PD-L1 expression was available for 55.8% of the tumours. Patients in the IO group were younger than patients in the no-IO group. Among the 122 patients in the IO group, the median overall survival was 15 months (95% confidence interval [CI] 12-20). In the no-IO group, the median overall survival was 4 months (95% CI 3-7) with chemotherapy and 2 months (95% CI 1-2) with best supportive care. Patients with high (≥50%) PD-L1 expression and checkpoint inhibitor therapy had a slightly longer overall survival than patients with low PD-L1 and checkpoint inhibitor therapy. CONCLUSION These results suggest that treatment with checkpoint inhibitors improves overall survival in patients with metastatic NSCLC and that PD-L1 expression could have a predictive value in patients treated outside of clinical trials. Further studies are needed to study the magnitude of the benefit of checkpoint inhibitors according to molecular NSCLC subtype

Polymer flooding – Does Microscopic Displacement Efficiency Matter?

Polymer flooding is an enhanced oil recovery (EOR) technique that aims to enhance the stability of the flood front in order to increase sweep efficiency and thereby increase hydrocarbon recovery. Polymer flooding studies often focus on large-scale sweep efficiency and neglect the impact of the pore-scale displacement efficiency of the multi-phase flow. This work explores the pore-scale behavior of water vs polymer flooding, and examines the impact of rock surface wettability on the microscopic displacement efficiency using digital rock physics. In this study, a micro-CT image of a sandstone rock sample was numerically simulated for both water and polymer flooding under oil-wet and water-wet conditions. All simulations were performed at a capillary number of 1E-5, corresponding to a capillary dominated flow regime. Results of the four two-phase flow imbibition simulations are analyzed with respect to displacement character, water phase break-through, viscous/capillary fingering, and trapped oil. In the water-wet scenario, differences between water flood and polymer flood are small, with the flood front giving a piston-like displacement and breakthrough occurring at about 0.4 pore volume (PV) for both types of injected fluid. On the other hand, for the oil-wet scenario, water flood and polymer flood show significant differences. In the water flood, fingering occurs and much of the oil is bypassed early on, whereas the polymer flood displaces more oil and thereby provides better microscopic sweep efficiency throughout the flood and especially around breakthrough. Overall the results for this rock sample indicate that water flood and polymer flood provide similar recovery for a water-wet condition, while the reduced mobility ratio of polymer flood gives significantly improved recovery for an oil-wet condition by avoiding the onset of microscopic (pore-scale) fingering that occurs in the water flood. This study suggests that depending on the rock-fluid conditions, the use of polymer can impact microscopic sweep efficiency, in addition to the well-known effect on macroscopic sweep behavior.La inyección de polímeros es una técnica de recobro mejorado de petróleo (EOR) que tiene como objetivo mejorar la estabilidad del frente de inyección para aumentar la eficiencia del desplazamiento de hidrocarburos y, por lo tanto, incrementar el factor de recobro. Lo estudios de inyección de polímeros a menudo se centran en la eficiencia del desplazamiento a gran escala e ignoran el impacto de los mecanismos de desplazamiento a escala microscópica, y rara vez evalúan la variabilidad de parámetros de flujo multifásico en el medio poroso. Este trabajo explora el comportamiento del agua contra la inyección de polímeros en el medio poroso, y examina el impacto de la humectabilidad de la superficie de la roca en la eficiencia de desplazamiento microscópico, utilizando tomografía computarizada de rayos X en muestras de roca. En este estudio, se simuló numéricamente una imagen de microtomografía computarizada de una muestra de roca arenisca, para un proceso de inyección de agua y polímeros en condiciones de mojabilidad al aceite y al agua. Todas las simulaciones se realizaron a un número capilar de 1E-5, correspondiente a un régimen de flujo dominado por fuerzas capilares y que es típico del flujo en yacimientos de hidrocarburos. Los resultados de las cuatro simulaciones de imbibición de flujo de dos fases se analizan con respecto al carácter desplazante, el avance de la fase acuosa, la digitación viscosa y capilar, y el aceite atrapado. En el escenario de mojabilidad al agua, las diferencias entre la inyección de agua y la inyección de polímeros son pequeñas, dado que el frente de inyección produce un  desplazamiento en forma de pistón y un avance que se produce a aproximadamente 0,4 volúmenes porosos para ambos tipos de fluido inyectado. Por otro lado, para el escenario de mojabilidad al petróleo, la inyección de agua y la inyección de polímeros muestran diferencias significativas. En la inyección de agua, se produce digitación y gran parte del petróleo se pasa por alto al principio; mientras que la inyección de polímeros desplaza más aceite y, por lo tanto, proporciona una mejor eficiencia de desplazamiento microscópico durante la inyección, especialmente alrededor de la ruptura. En general, los resultados para esta muestra de roca indican que la inyección de agua y la inyección de polímeros proporcionan un efecto de recobro similar para una condición de mojabilidad al agua, mientras que la relación de movilidad reducida de la inyección de polímeros proporciona un efecto de recobro significativamente mejorado para una condición de mojabilidad al aceite, al evitar la aparición de digitación microscópica (a escala de poro) que se produce en la inyección de agua. Este estudio sugiere que, dependiendo de las condiciones roca-fluido, el uso del polímero puede impactar la eficiencia de desplazamiento microscópico, además del efecto conocido sobre el comportamiento del desplazamiento macroscópico

U, B and r band luminosity functions of galaxies in the Coma cluster

We present a deep multi-colour CCD mosaic of the Coma cluster (Abell 1656), covering 5.2 deg^2 in the B and r bands, and 1.3 deg^2 in the U band. This large, homogeneous data set provides a valuable low redshift comparison sample for studies of galaxies in distant clusters. In this paper we present our survey, and study the dependence of the galaxy luminosity function (LF) on passband and radial distance from the cluster centre. The U, B and r band LFs of the complete sample cannot be represented by single Schechter functions. For the central area, r<245 h_{100}^{-1} kpc, we find best-fitting Schechter parameters of M^{*}_U=-18.60^{+0.13}_{-0.18} and \alpha_U=-1.32^{+0.018}_{-0.028}, M^{*}_B=-19.79^{+0.18}_{-0.17} and \alpha_B=-1.37^{+0.024}_{-0.016} and M^{*}_r=-20.87^{+0.12}_{-0.17} and \alpha_r=-1.16^{+0.012}_{-0.019}. The LF becomes steeper at larger radial distance from the cluster centre. The effect is most pronounced in the U band. This result is consistent with the presence of a star forming dwarf population at large distance from the cluster centre, which may be in the process of being accreted by the cluster. The shapes of the LFs of the NGC 4839 group support a scenario in which the group has already passed through the centre.Comment: Accepted for publication in MNRA