Effect of Plasticizer on PVAc-d3 Dynamics using 2H Solid-State NMR

Poly(vinyl acetate) (PVAc) is an important polymer for use in many applications due to its various bulk and surface characteristics. The structure of poly(vinyl acetate) results in a relatively low glass transition temperature (Tg) and makes it important for processing and applications such as paints, adhesives, thin films and surface coatings. Poly(vinyl acetate) can also be easily plasticized, widening its range of applications. The term plasticizer refers to a species that will decrease Tg of a polymer.1 Polymer-plasticizer systems have been studied for years and continue to be of current interest. The effects of polymer-plasticizer interactions2 and plasticizer structure3 on polymer chain motions have been studied extensively, but there is still much to be learned in this area. Deuterium NMR is an excellent tool for studying the mobility of polymer chains. In this work, we report the investigation of the effect of plasticizer content on the Tg of poly(vinyl acetate) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy. The methyl groups of poly(vinyl acetate) were deuterated in order to probe the mobility of their segments using the 2H NMR technique. Random orientations of the methyl groups, with respect to a magnetic field, are reflected as a powder pattern in the 2H NMR spectrum for segments with little or no motion. Segmental mobility averages the quadrupole couplings and ultimately leads to the collapse of the powder pattern into a single resonance for rubbery polymers when the motion is on the scale of or faster than the interactions.

Segmental Dynamics of Poly(Vinyl Acetate)- D₃ Absorbed on Silica by Solid State 2HNMR: Effect of Small Molecule Plasticizer

There has been significant progress in understanding the behavior of polymeric thin films on surfaces. The change in the apparent glass transition temperature (Tg) of supported thin polymer films with thickness (Tg -nanoconfinement effect) has been widely studied over the last fifteen years. While many studies focused on the thickness dependence of Tg, there are other aspects which are important to understand in a nanoconfined polymer system. For example, polymeric photoresists contain small-molecule photoactive compounds, plasticizers, and processing aids. These components interact with the polymer chains and affect the segmental mobility, which, in turn, affects the Tg - nanoconfinement effect. Plasticizers or low molecular mass diluents are often blended with polymers to increase flexibility by effectively shifting the Tg to lower temperatures. 1 the mechanism of plasticization is not understood in great detail, but the conventional model envisions a dynamic interaction between the polymer and diluent, resulting in reduced chain-chain interactions, reduced local viscosity and increased chain mobility.2 in this paper we report the effect of plasticizer on the dynamics of poly(vinyl acetate) (PVAc) chains adsorbed on silica surfaces using solid-state deuterium nuclear magnetic resonance (NMR) and modulated differential scanning calorimeter (MDSC). The deuterium NMR technique is an excellent tool to probe interfacial phenomena and study the dynamics of polymer chains on surfaces.3,4 in our lab, we have used deuterium NMR extensively for characterizing different types of polymers like poly(methyl acrylate)5,6,7 and PVAc8 on silica surfaces. The methyl groups of PVAc have been deuterated in order to probe the mobility of their segments. Random orientations of the methyl groups, with respect to the static magnetic field, result in powder patterns in the 2H NMR spectrum for segments with little or no motion. Segmental mobility averages the quadrupole couplings and ultimately leads to the collapse of the powder pattern into a single resonance for rubbery polymer

COMPARISON OF EFFICACY OF TRANEXAMIC ACID 10 MG/KG AND 15 MG/KG IN REDUCING BLEEDING AND TRANSFUSIONS IN TOTAL KNEE ARTHROPLASTY

Objective: The objective of this study was to compare the efficacy of tranexamic acid 10 mg/kg and 15 mg/kg in reducing bleeding and transfusions in total knee arthroplasty. Methods: After approval from the Institutional Ethics Committee, KMC, Mangaluru, 88 patients fulfilling the inclusion criteria of this study undergoing total knee replacements were informed of the study details and consent was obtained for the same. They were randomized into two groups using computer-generated block randomization, i.e., Group A and Group B, and were administered tranexamic acid 10 mg/kg and 15 mg/kg intravenously, respectively. Intraoperatively, hemodynamic parameters were noted. Postoperatively, hemoglobin levels were assessed on days 1 and 3. Transfusions, thromboembolic complications, and duration of hospital stay were noted. Results: Of the 88 participants of the trial, 44 in Groups A and B each, there were no significant differences in the parameters observed in this study such as intraoperative hemodynamic changes, post-operative fall in hemoglobin on day 3, number of patients requiring transfusions, number of thromboembolic events, and duration of hospital stay. A significant p-value was observed in the fall in hemoglobin in the post-operative day 3 (p=0.043). Conclusion: About 15 mg/kg tranexamic acid proved to have a lesser fall in hemoglobin on day 3 postoperatively when compared to the 10 mg/kg group. However, the fall of hemoglobin on day 3 was statistically significant and warranted a blood transfusion in two patients in the 10 mg/kg group but did not prolong their hospital stay

HIV and trans and non-binary people in the UK

Trans and non-binary people are key populations whose HIV prevention and treatment needs have been neglected. A 2013 meta-analysis of data from 39 studies conducted in 15 countries, reported a global HIV prevalence among trans women of nearly 20%, with trans women estimated to be 49 times more likely than other adults to be living with HIV. Moreover, mortality from HIV/AIDS among trans women in a large cohort study was just over 30 times that of age-matched population controls

Constructive interference effects for tidal turbine arrays

The performance benefits of deploying tidal turbines in close side-by-side proximity to exploit constructive interference effects are demonstrated experimentally using two 1.2 m diameter turbines. The turbines are arrayed side-by-side at 1/4 diameter tip-to-tip spacing, and their performance compared with that of a single rotor. Tests were completed in the 25 m diameter, 2 m deep wave and current FloWave Ocean Energy Research facility. A detailed assessment of inflow conditions at different control points is used to understand the impact that rotors, designed for high blockage conditions, have on the approach flow. After accounting for global blockage, a 10.8 % uplift in the twin-turbine-averaged power coefficient, relative to that for a single turbine, is found for the turbine design speed, at the expense of a 5.2 % increase in thrust coefficient and 3.1 % increase in tip-speed-ratio. Flowfield mapping demonstrated flow effects at array and device scale including array bypass flows and jetting between turbines. Azimuthal variation of blade root flapwise and edgewise bending moments show that the turbines interact in a beneficial manner, with additional and sustained loading peaks as the blades pass in close proximity to the neighbouring rotor. Peak performance for the twin turbines occurred at a higher tip-speed-ratio than for the single turbine, which is consistent with the twin turbines exerting a higher thrust on the flow to achieve maximum power. The twin turbine performance variation with tip-speed-ratio is found to be more gradual than for the single turbine. Using differential rotor speed control we observe that array performance is robust to small differences in neighbouring rotor operating point. Through these experiments we demonstrate that there is a substantial, achievable performance benefit from closely arraying turbines for side-by-side operation and designing them for constructive interference

Designing of promising Tromethamine-Diflunisal-Pyrrole combinations based on COX binding, drug-properties and safety

Gastric issues that accompany the use of NSAIDs (Non-steroid anti-inflammatory drugs) are always a serious global concern. The inhibition of the Cycloxygenase enzyme (COX) limits the prostaglandin synthesis and thereby facilitates the control of pains, inflammation etc. But this creates gastric issues due to the reduction of mucin formation in the stomach. The present work was performed to create a modification in the structure of NSAID drug Diflunisal, to reduce the gastric effect of acidic moiety in the structure and elevate the overall biological properties. The drug Tromethamine, a base used in acidosis treatment was substituted to reduce the acidic issues. The heterocyclic compound pyrrole was substituted to elevate the properties. Neutral, salt, amide and ester combinations of Tromethamine-Diflunisal were designed, optimized and docked to the crystal structures of COX-1 (PDB ID: 6Y3C) and COX-2 (PDB ID: 5IKR) enzymes, using PyRx software. The combinations with lower COX-1 and COX-2 binding energies relative to Diflunisal were noted. It was analysed if the combinations of Diflunisal, Tromethamine and pyrrole lowers drug-properties or induce toxicities. Pyrrole substitution at position R4 was not found favourable for COX binding. Among the favourable combinations, DF19 is the Diflunisal-Pyrrole-Tromethamine combination, equally favourable for binding to COX targets

Breakage and coalescence of drops in turbulent stirred dispersions

The various existing models for predicting the maximum stable drop diameter dmax in turbulent stirred dispersions have been reviewed. Variations in the basic framework dictated by additional complexities such as the presence of drag reducing agents in the continuous phase, or viscoelasticity of the dispersed phase have been outlined. Drop breakage in the presence of surfactants in the continuous phase has also been analysed. Finally, the various approaches to obtaining expressions for the breakage and coalescence frequencies, needed to solve the population balance equation for the number density function of the dispersed phase droplets, have been discussed