Nonequilibrium stretching dynamics of dilute and entangled linear polymers in extensional flow

We propose an extension of the FENE-CR model for dilute polymer solutions [M. D. Chilcott, J. M. Rallison, Creeping flow of dilute polymer solutions past cylinders and spheres, J. Non-Newtonian Fluid Mech. 29 (1988) 382-432] and the Rouse-CCR tube model for linear entangled polymers [A. E. Likhtman, R. S. Graham, Simple constitutive equation for linear polymer melts derived from molecular theory: Rolie-Poly equation, J. Non-Newtonian Fluid Mech. 114 (2003) 1-12], to describe the nonequilibrium stretching dynamics of polymer chains in strong extensional flows. The resulting models, designed to capture the progressive changes in the average internal structure (kinked state) of the polymer chain, include an 'effective' maximum contour length that depends on local flow dynamics. The rheological behavior of the modified models is compared with various results already published in the literature for entangled polystyrene solutions, and for the Kramers chain model (dilute polymer solutions). It is shown that the FENE-CR model with an 'effective' maximum contour length is able to describe correctly the hysteric behaviour in stress versus birefringence in start-up of uniaxial extensional flow and subsequent relaxation also observed and computed by Doyle et al. [P. S. Doyle, E. S. G. Shaqfeh, G. H. McKinley, S. H. Spiegelberg, Relaxation of dilute polymer solutions following extensional flow, J. Non-Newtonian Fluid Mech. 76 (1998) 79-110] and Li and Larson [L. Li, R. G. Larson, Excluded volume effects on the birefringence and stress of dilute polymer solutions in extensional flow, Rheol. Acta 39 (2000) 419-427] using Brownian dynamics simulations of bead-spring model. The Rolie-Poly model with an 'effective' maximum contour length exhibits a less pronounced hysteretic behavior in stress versus birefringence in start-up of uniaxial extensional flow and subsequent relaxationNous proposons une extension du mod\ue8le FENE-CR pour des solutions de polym\ue8re dilu\ue9es [M.D. Chilcott, J.M. Rallison, Creeping flow of dilute polymer solutions past cylinders and spheres, J. Non-Newtonian Fluid Mech. 29 (1988) 382\u2013432] et le mod\ue8le de tube Rouse-CCR pour des polym\ue8res lin\ue9aires entrem\ueal\ue9s [A.E. Likhtman, R.S. Graham, Simple constitutive equation for linear polymer melts derived from molecular theory: Rolie\u2013Poly equation, J. Non-Newtonian Fluid Mech. 114 (2003) 1\u201312] pour d\ue9crire la dynamique d\u2019\ue9tirement hors \ue9quilibre de cha\ueenes de polym\ue8res dans des \ue9coulements d\u2019extension puissants. Les mod\ue8les ainsi obtenus, con\ue7us pour capturer les modifications progressives dans la structure interne moyenne (\ue9tat coud\ue9) de la cha\ueene polym\ue8re, comprennent une longueur maximale de contour \uab efficace \ubb qui d\ue9pend de la dynamique d\u2019\ue9coulement locale. Le comportement rh\ue9ologique des mod\ue8les modifi\ue9s est compar\ue9 \ue0 divers r\ue9sultats d\ue9j\ue0 publi\ue9s dans la litt\ue9rature pour des solutions de polystyr\ue8ne entrem\ueal\ue9 et pour le mod\ue8le de cha\ueene de Kramers (solutions de polym\ue8res dilu\ue9es). On montre que le mod\ue8le FENE-CR avec une longueur de contour maximale \uab efficace \ubb permet de d\ue9crire correctement le comportement d\u2019hyst\ue9r\ue8se sous contrainte par rapport \ue0 la bir\ue9fringence lors du d\ue9marrage de l\u2019\ue9coulement d\u2019extension uniaxial et de la relaxation subs\ue9quente \ue9galement observ\ue9e et calcul\ue9e par Doyle et coll. [P.S. Doyle, E.S.G. Shaqfeh, G.H. McKinley, S.H. Spiegelberg, Relaxation of dilute polymer solutions following extensional flow, J. Non-Newtonian Fluid Mech. 76 (1998) 79\u2013110] et par Li et Larson [L. Li, R.G. Larson, Excluded volume effects on the birefringence and stress of dilute polymer solutions in extensional flow, Rheol. Acta 39 (2000) 419\u2013427] au moyen de simulations en dynamique brownienne de mod\ue8le bille/ressort. Le mod\ue8le de Rolie\u2013Poly avec une longueur de contour maximale \uab efficace \ubb exhibe un comportement d\u2019hyst\ue9r\ue8se moins prononc\ue9 sous contrainte par rapport \ue0 la bir\ue9fringence lors du d\ue9marrage de l\u2019\ue9coulement d\u2019extension uniaxial et lors de la relaxation subs\ue9quente.Peer reviewed: YesNRC publication: Ye

Rheological behavior of polyamide-6 based nanocomposites: experimental study and modeling

Peer reviewed: YesNRC publication: Ye

Optimal Design For Injection Molding

Peer reviewed: YesNRC publication: Ye

Elastic flow-front fingering instability in flowing polymer solutions

An experimental investigation of the flow-front behavior of dilute and semi-dilute polymer solutions has been carried out to gain a better understanding of the underlying mechanisms leading to the occurrence of an unstable flow at the advancing flow-front during the filling of a rectangular Hele-Shaw cell. Our experimental results have revealed the existence of an elastic finger-like instability at the advancing flow-front that develops in semidilute solutions of high molecular weight polymers, with an onset time of approximately a few hundred milliseconds. Although at shear rates above critical, narrow finger patterns develop at the flow-front, their amplitude and number remain roughly constant throughout the flowing. At critical condition, no secondary flow was observed in the vicinity of the front region where the unstable flow develops. Transient response of the normal stress difference and the shear stress in the plateand- plate geometry at shear rate above critical (for the elastic fingering instability in the Hele-Shaw cell) did not reveal any anomalous that could lead to the formation of such finger-like instabilities. These instabilities were observed for both the ideal elastic Boger fluids and shear thinning viscoelastic fluids.Peer reviewed: YesNRC publication: Ye

Start-up of Flow Through a 4:1:4 Constriction in a Tube Using the Rouse-CCR Tube Model for Linear Entangled Polymers with Finite Extensibility

Peer reviewed: YesNRC publication: Ye

Review of the nutritional benefits and risks related to intense sweeteners.

BACKGROUND: The intense sweeteners currently authorised in Europe comprise ten compounds of various chemical natures. Their overall use has sharply risen in the last 20 years. These compounds are mainly used to formulate reduced-calorie products while maintaining sweetness. METHODS: This extensive analysis of the literature reviews the data currently available on the potential nutritional benefits and risks related to the consumption of products containing intense sweeteners. RESULTS AND CONCLUSIONS: Regarding nutritional benefits, the available studies, while numerous, do not provide proof that the consumption of artificial sweeteners as sugar substitutes is beneficial in terms of weight management, blood glucose regulation in diabetic subjects or the incidence of type 2 diabetes. Regarding nutritional risks (incidence of type 2 diabetes, habituation to sweetness in adults, cancers, etc.), it is not possible based on the available data to establish a link between the occurrence of these risks and the consumption of artificial sweeteners. However, some studies underline the need to improve knowledge of the links between intense sweeteners consumption and certain risks

Numerical simulation of a thermoviscoelastic frictional problem with application to the hot-embossing process for manufacturing of microcomponents

Peer reviewed: YesNRC publication: Ye

Review of the nutritional benefits and risks related to intense sweeteners

Unfortunately, the original version of this article [1] contained an error. The author’s names were included incorrectly, the surnames were presented before the forename: Bruyère Olivier, Ahmed H. Serge, Atlan Catherine, Belegaud Jacques, Bortolotti Murielle, Canivenc-Lavier Marie-Chantal, Charrière Sybil, Girardet Jean-Philippe, Houdart Sabine, Kalonji Esther, Nadaud Perrine, Rajas Fabienne, Slama Gérard and Margaritis Irène The author list has been corrected in the original article and is also included correctly below: Olivier Bruyère, Serge H. Ahmed, Catherine Atlan, Jacques Belegaud, Murielle Bortolotti, Marie-Chantal Canivenc-Lavier, Sybil Charrière, Jean-Philippe Girardet, Sabine Houdart, Esther Kalonji, Perrine Nadaud, Fabienne Rajas, Gérard Slama, Irène Margaritis (NB: erratum 1 p. doi: in volume 73, 49, published 23 October 2015, (eCollection 2015, PMID: 26500771, PMCID: PMC4619575))International audienceBackground : The intense sweeteners currently authorised in Europe comprise ten compounds of various chemical natures. Their overall use has sharply risen in the last 20 years. These compounds are mainly used to formulate reduced-calorie products while maintaining sweetness.Methods : This extensive analysis of the literature reviews the data currently available on the potential nutritional benefits and risks related to the consumption of products containing intense sweeteners.Results and Conclusions : Regarding nutritional benefits, the available studies, while numerous, do not provide proof that the consumption of artificial sweeteners as sugar substitutes is beneficial in terms of weight management, blood glucose regulation in diabetic subjects or the incidence of type 2 diabetes. Regarding nutritional risks (incidence of type 2 diabetes, habituation to sweetness in adults, cancers, etc.), it is not possible based on the available data to establish a link between the occurrence of these risks and the consumption of artificial sweeteners. However, some studies underline the need to improve knowledge of the links between intense sweeteners consumption and certain risks

Efficacy and safety of acoziborole in patients with human African trypanosomiasis caused by Trypanosoma brucei gambiense: a multicentre, open-label, single-arm, phase 2/3 trial

Summary Background Human African trypanosomiasis caused by Trypanosoma brucei gambiense (gambiense HAT) in patients with late-stage disease requires hospital admission to receive nifurtimox-eflornithine combination therapy (NECT). Fexinidazole, the latest treatment that has been recommended by WHO, also requires systematic admission to hospital, which is problematic in areas with few health-care resources. We aim to assess the safety and efficacy of acoziborole in adult and adolescent patients with gambiense HAT. Methods This multicentre, prospective, open-label, single-arm, phase 2/3 study recruited patients aged 15 years or older with confirmed gambiense HAT infection from ten hospitals in the Democratic Republic of the Congo and Guinea. Inclusion criteria included a Karnofsky score less than 50, ability to swallow tablets, a permanent address or traceability, ability to comply with follow-up visits and study requirements, and agreement to hospital admission during treatment. Oral acoziborole was administered as a single 960 mg dose (3 × 320 mg tablets) to fasted patients. Patients were observed in hospital until day 15 after treatment administration then for 18 months as outpatients with visits at 3, 6, 12, and 18 months. The primary efficacy endpoint was the success rate of acoziborole treatment at 18 months in patients with late-stage gambiense HAT (modified intention-to-treat [mITT] population), based on modified WHO criteria. A complementary post-hoc analysis comparing the 18-month success rates for acoziborole and NECT (using historical data) was performed. This study is registered at ClinicalTrials.gov, NCT03087955. Findings Between Oct 11, 2016, and March 25, 2019, 260 patients were screened, of whom 52 were ineligible and 208 were enrolled (167 with late-stage and 41 with early-stage or intermediate-stage gambiense HAT; primary efficacy analysis set). All 41 (100%) patients with early-stage or intermediate-stage and 160 (96%) of 167 with late-stage disease completed the last 18-month follow-up visit. The mean age of participants was 34·0 years (SD 12·4), including 117 (56%) men and 91 (44%) women. Treatment success rate at 18 months was 95·2% (95% CI 91·2-97·7) reached in 159 of 167 patients with late-stage gambiense HAT (mITT population) and 98·1% (95·1-99·5) reached in 159 of 162 patients (evaluable population). Overall, 155 (75%) of 208 patients had 600 treatment-emergent adverse events. A total of 38 drug-related treatment-emergent adverse events occurred in 29 (14%) patients; all were mild or moderate and most common were pyrexia and asthenia. Four deaths occurred during the study; none were considered treatment related. The post-hoc analysis showed similar results to the estimated historical success rate for NECT of 94%. Interpretation Given the high efficacy and favourable safety profile, acoziborole holds promise in the efforts to reach the WHO goal of interrupting HAT transmission by 2030. Funding Bill & Melinda Gates Foundation, UK Aid, Federal Ministry of Education and Research, Swiss Agency for Development and Cooperation, Médecins Sans Frontières, Dutch Ministry of Foreign Affairs, Norwegian Agency for Development Cooperation, Norwegian Ministry of Foreign Affairs, the Stavros Niarchos Foundation, Spanish Agency for International Development Cooperation, and the Banco Bilbao Vizcaya Argentaria Foundation. Translation For the French translation of the abstract see Supplementary Materials section

From concept to action: a united, holistic and One Health approach to respond to the climate change crisis

It is unequivocal that human influence has warmed the planet, which is seriously affecting the planetary health including human health. Adapting climate change should not only be a slogan, but requires a united, holistic action and a paradigm shift from crisis response to an ambitious and integrated approach immediately. Recognizing the urgent needs to tackle the risk connection between climate change and One Health, the four key messages and recommendations that with the intent to guide further research and to promote international cooperation to achieve a more climate-resilient world are provided