A multiscale model for the rupture of linear polymers in strong flows

Abstract Polymer-containing solutions used across research and industry are commonly exposed to mechanically harsh fluid processes, for example shear and extensional forces during flow through porous media or rapid micro-dispensing of biopharmaceutical molecules. These forces are strong enough to break the covalent bonds in the polymer backbone. As this scission phenomenon can change the functional and fluid-flow properties as well as introduce reactive radicals into the solution, it must be understood and controlled. Experiments and models to-date have only provided partial or qualitative insights into this behaviour. Here we build a link between the molecular-scale degradation models and the macro-scale laminar flow of dilute solutions in any given geometry. A free-draining bead-rod model is used to investigate rupture events at the molecular scale. It is shown by uniaxial extension simulations of an ensemble of chains that scission can be conveniently described at the macroscopic scale as a first order reaction whose rate is a function of the conformation tensor of the macromolecules and the velocity gradient of the flow. This approach is implemented in the finite volume code OpenFOAM by elaborating an appropriate constitutive equation for the conformation tensor. The macroscopic model is run and analysed for ultra-dilute solutions of poly(methyl methacrylate) in ethyl acetate and polyethylene oxide in water, using the geometry of an abrupt contraction flow and neglecting any viscoelastic effect. This multi-scale approach bridges the gap between phenomenological observations of mechanically-induced chemical degradation in large scale applications and the rich field of molecular-scale models of macromolecules under flow.King Abdulaziz City for Science and Technology (KACST

Going with the Flow : Tunable Flow-Induced Polymer Mechanochemistry

Mechanical forces can drive chemical transformations in polymers, directing reactions along otherwise inaccessible pathways, providing exciting possibilities for developing smart, responsive materials. The state-of-the-art test for solution-based polymer mechanochemistry development is ultrasonication. However, this does not accurately model the forces that will be applied during device fabrication using processes such as 3D printing or spray coating. Here, a step is taken toward predictably translating mechanochemistry from molecular design to manufacturing by demonstrating a highly controlled nozzle flow setup in which the shear forces being delivered are precisely tuned. The results show that solvent viscosity, fluid strain rate, and the nature of the breaking bond can be individually studied. Importantly, it is shown that the influence of each is different to that suggested by ultrasonication (altered quantity of chain breakage and critical polymer chain length). Significant development is presented in the understanding of polymer bond breakage during manufacturing flows to help guide design of active components that trigger on demand. Using an anthracene-based mechanophore, the triggering of a fluorescence turn-on is demonstrated through careful selection of the flow parameters. This work opens the avenue for programmed chemical transformations during inline manufacturing processes leading to tunable, heterogeneous final products from a single source material. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Impact of processing parameters in plasma electrolytic oxidation on corrosion resistance of magnesium alloy type AZ91

open access articleThis study aims to investigate the effect of the processing parameters in plasma electrolytic oxidation (PEO) on the corrosion resistance ofmagnesium alloy type AZ91. The PEO coatings were prepared on the samples using alkaline-based electrolyte. Both unipolar and bipolar, different frequencies and duty cycleswere applied. Corrosion tests, using potentiodynamic polarization, linear and cyclic, and electrochemical impedance spectroscopy techniques, were applied on the as-received and PEO coated samples. Scanning electron microscopy was used to investigate the surface morphology, for example, micropores, as well as to measure the thickness of the coated layer by changing the processing parameters. The results show that the size of micropores is interrelated to the duty cycle percentage and current polarities, as the higher frequency causes thinner coating layers, with fewer micropores, consequently higher corrosion resistance. In addition, increasing the duty cycle, a denser and more compact coating was obtained. The XRD results showed a missing peak of the α-Mg phase in a PEO coated sample using bipolar, the highest frequency (1666 Hz), and the highest duty cycle (66.6%). The mils per year calculations showed that the PEO coated has a lower corrosion rate by at least 8 times than the as-received alloy

Prevalence, Recognition, And Management Of Mental Disorders In Primary Care

According to latest figures, 50% of individuals will have a minimum of one mental health issue in their lifetime, with at least 25% experiencing a mental condition in the previous year. primary care doctors are overwhelmingly responsible for recognition, evaluation, therapy, and referral, with at least one-third of their consultations containing a direct and obvious mental aspect Primary care physicians are the foundation of the majority of medical care programs that involve recognizing, diagnosing, treating, and referring patients to specialists for every kind of diseases, whether physical, mental, or both. Over the last two decades, there has been a greater emphasis on this position, notably in the treatment of mental problems in primary care

The medical and biochemical knowledge of health care professionals regarding the management of MERS-CoV: lessons from 2019 pilgrimage season in Al-Madinah, Saudi Arabia: A cross-sectional study

Background: Middle East respiratory syndrome coronavirus (MERS-CoV) epidemic was a serious healthcare concern not responding to conventional anti-viral therapies between 2012 and 2017 with high fatality rates. Saudi Arabia is still among the best world examples in combating both MERS-CoV and COVID-19 pandemics. Objectives: Investigating the medical and biochemical knowledge of healthcare professionals in Al-Madinah, Saudi Arabia on preventive, diagnostic and therapeutic measures against MERS-CoV epidemic. Subjects and methods: In 2019, this cross-sectional study included 416 healthcare personnel of which 402 participants answered the questions with a response rate of 96.7%. Specialties of participants were medical students (1.4%), physicians (64.4%), nurses (23.6%) and others (10.7%). Results: The vast majority of the investigated healthcare personnel gave the right answers. 96.7% of the participants answered that washing hands using water helps prevent MERS-CoV. 90.8% of the participants answered that wearing a clean non-sterile long-sleeved gown and gloves does helps prevent MERS-CoV infection. 94.7% of participants answered that using alcohol-based hand rub helps prevent MERS-CoV infection. 92.03% of the participants thought that wearing protective equipment does help preventing MERS-CoV infection. 86.1% answered that there is no vaccine available against MERS-CoV infection and 86.1% answered that taking vaccines is suitable for preventing MERS-CoV infection. 90.04% of the participants answered that MERS-CoV patients should be diagnosed using PCR and 84.3% thought that the highest levels of anti-CoV antibodies are in abattoir workers while 87.8% thought that isolation of suspected cases helps preventing MERS-CoV infection. Conclusion: The investigated healthcare workers had a satisfactory knowledge on the preventive and therapeutic measures and biochemical knowledge against MERS-CoV epidemic at mass gatherings as pilgrimage season

Oral semaglutide adequate glycaemia control with safe cardiovascular ‎profile

BackgroundType 2 diabetes is a chronic and progressive disease that ‎associated with series complication such as major adverse ‎cardiovascular events. Adequate glycaemic control proven ‎to reduce this risk. Orally administered semaglutide ‎promising medication in managing patient with type 2 ‎diabetes.‎AimsTo assess the cardiovascular safety and efficacy of semaglutide, a recently approved glucagon-like peptide 1 receptor agonist (GLP-1 RA) for type 2 diabetes.Methods Pub Med, ‎Google Scholar, and EBSCO ‎ databases were ‎systematically search for relevant articles. The terms‎ diabetes‎, Glucagon-like peptide, semaglutide‎ were used. Out of hundred twenty-two records, only ‎four fulfilled ‎the inclusion criteria.Results Four placebo-controlled studies with oral semaglutide ‎were included. Single study concern about the cardiovascular safety of oral semaglutide ‎and showed that, ‎compared with placebo, semaglutide ‎ was not associated ‎with increased in the cardiovascular events. On the other ‎hand, the remaining trials shown that, semaglutide ‎ can ‎effectively control the blood glucose as evident by ‎reduction in HA1c.ConclusionOral semaglutide can effectively and safely lower blood glucose without increase in the major adverse ‎cardiovascular events‎‎ (MACE).

High throughput synthesis and corrosion studies on alloys

A range of Ni-Cr, Ni-W, Al-Mg, and Al-Mg-Zr thin film alloys have been synthesised using a controllable compositional gradient method based on MBE sources allowing the deposition of compositional gradients of a large range of thin film materials. The alloy materials are characterised by X-ray diffraction, including phase identification and crystallite size, and energy dispersive x-ray spectroscopy (EDX). The corrosion resistance of 100 discrete alloy compositions has been measured simultaneously in identical environments using a high-throughput screening protocol based on cyclic voltammetry (CV). The corrosion resistances and potentials are extracted from voltametric data by both the Linear Polarisation Resistance (LPR) and Tafel Extrapolation methods. Results from these are shown to be consistent. In general, the corrosion (polarisation) resistance behaviour is shown to be directly related to the bulk alloy structures or morphologies. In the case of the NiCr alloys, besides the b.c.c ?-Cr (Im3m) phase and its Ni solid solutions, which exhibit the highest polarisation resistances, the ? Cr3Ni2 (P42/mnm) phase exhibits the next best polarisation resistance. The incorporation of W in the Ni-W solid solution at low W compositions resulted in a small reduction in corrosion resistance while a significant increase in the corrosion resistance was observed for alloy compositions greater than 24 %at. W. The best corrosion resistance of Al-Mg alloys was observed for alloy compositions comprise 35%at. Al, which corresponds to the formation of ? Al12Mg17 (i.e. also named ? phase). The incorporation of Zr in the Al-Mg resulted in forming five Al-Zr metastable phases i.e. Al3Zr, Al2Zr, Al3Zr2, Al4Zr5, and Al3Zr5. The Al-Mg-Zr alloys composition contained Al3Zr2 and Al3Zr5 exhibit highest cathodic activity, corrosion resistance, and passivity

A simultaneous screening of the corrosion resistance of Ni–W thin film alloys

A range of Ni–W thin film alloys have been synthesised by evaporation from atomic sources to produce a compositional gradient across the substrate, and characterised by X-ray diffraction (phase identification and crystallite size) and EDX (composition). The corrosion resistance of 100 discrete alloy compositions has been measured simultaneously in identical environments using a high-throughput screening protocol based on cyclic voltammetry. The corrosion resistances and potentials are extracted from potentiodynamic data by both the linear polarisation resistance (LPR) and Tafel extrapolation methods; results from these are shown to be self-consistent. The high-throughput approach allows, for the first time, a direct correlation to be made between the bulk crystalline phases and morphology, and the corrosion behaviour of Ni–W alloys. The incorporation of W in the Ni–W solid solution at low W compositions results in a continuous reduction in crystallite size, a small cathodic shift in corrosion potential, and a small reduction in corrosion resistance. A large cathodic shift in corrosion potential together with a significant increase in the corrosion resistance is observed for alloy compositions greater than 24%at. W. This composition range coincides with the formation of the amorphous phase