Beware of CaBER: filament thinning rheometry doesn't give `the' relaxation time of polymer solutions

The viscoelastic relaxation time {\tau} of a polymer solution is often measured using Capillary Breakup Extensional Rheometry (CaBER) where a droplet is placed between two plates which are pulled apart to form a thinning filament. For a slow plate retraction protocol, required to avoid inertio-capillary oscillations for low-viscosity liquids, we show experimentally that the CaBER relaxation time inferred from the exponential thinning regime is in fact an apparent relaxation time that increases significantly when increasing the plate diameter and the droplet volume. Similar results are obtained with a Dripping-onto-Substrate (DoS) method. This dependence on the flow history before the formation of the viscoelastic filament is in contradiction with polymer models such as Oldroyd-B that predict a filament thinning rate 1/3{\tau} which is a material property independent of geometrical factors. We show that this is not due to artefacts such as solvent evaporation or polymer degradation and that it cannot be universally explained by the finite extensibility of polymer chains.Comment: 18 pages, 6 figures, presented at the ICR 2023 in Athen

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Beware of CaBER: filament thinning rheometry doesn't give `the' relaxation time of polymer solutions

Capillary Breakup Extensional Rheometry (CaBER) is commonly used to measure ‘the’ viscoelastic relaxation time ⌧ of polymer solutions. We show experimentally that this method in fact only provides an apparent relaxation time that increases significantly when increasing the plate diameter and droplet volume. Similar results are obtained with a Dripping-onto-Substrate (DoS) method. This dependence on the flow history before the formation of the viscoelastic filament is in contradiction with polymer models such as Oldroyd-B that predict a filament thinning rate 1/3⌧ which is a material property independent of geometrical factors. We show that this is not due to artefacts such as solvent evaporation or polymer degradation and that it cannot always be explained by the finite extensibility of polymer chains

Early Stages of Drop Coalescence

Despite the large body of research on coalescence, firm agreement between experiment, theory, and compu- tation has not been established for the very earliest times following the initial contact of two liquid volumes. Combining a range of experimental and computational modelling approaches, we have been able to elucidate the influence of the intervening gas, of the van der Waals forces and of thermal fluctuations on coalescence. For simple liquids, the gas influences both pre- and post-contact regimes, with a jump-to-contact the primary mode of merging. Subsequently, wave-like air pockets are observed. For a system with ultralow interfacial tension, that mimics nanodrop behaviour, the very first moments are governed by thermal fluctuations at the interfaces, with a nontrivial opening speed given by stochastic thermally driven motion

Ingles 1-HE03-201500

Today's world demands skilled professionals and English is the language of choice for communication in the global marketplace. Responding to the needs of a rapidly changing world we invite our students to learn and develop the four basic skills required in a foreign language: listening speaking reading and writing. By building these skills and exploring new ideas students will be able to understand speak read and write in English at their current level. After completion of the intermediate level students will be able to manage diverse academic texts as well as make successful oral presentations in English.This course is designed as a distant learning hybrid course. It is composed by 60% of contact hours deliveredface to face and 40% of contact hours delivered online. Students will have a three-hour session on campus everyweek and are expected to work at least two hours on line. In contrast to the traditional face to face classes thedesign of this course will allow students to build language knowledge at their own