48 research outputs found

    Effect of pressure and temperature on interfacial tension of poly lactic acid melt in supercritical carbon dioxide

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    © 2015. This manuscript version of Effect of Pressure and Temperature on Interfacial Tension of Poly lactic acid melt in supercritical carbon dioxide is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the accepted manuscript version of a published article. Published by Elsevier in the journal "Thermochimica Acta" volume 609, http://dx.doi.org/10.1016/j.tca.2015.04.005The interfacial tension of poly lactic acid (PLA) melt is measured in supercritical carbon dioxide (CO2) at the temperature range of 143 °C to 168 °C and CO2 pressures up to 2000 psi, using Axisymmetric Drop Shape Analysis Profile (ADSA-P). The results show a decrease in interfacial tension with increasing temperature and pressure. However, the interfacial tension dependency on temperature at high pressures decreases because of a reduction in CO2 solubility at high temperatures. The relationship between the interfacial tension and the density-difference of polymer-supercritical CO2 mixtures is also examined by the generalized Macleod equation. Moreover, the range of stability for the melted drop, in interfacial tension measurements, is obtained by dimensionless Bond number. The results indicate the validity of the measurements for Bond number between 0.36 and 0.48.Natural Sciences and Engineering Research Council (NSERC) Network for Innovative Plastic Materials and Manufacturing Processes (NIPMMP) Canada Research Chairs (CRC

    Adsorption of surface-modified silica nanoparticles to the interface of melt poly (lactic acid) and supercritical carbon dioxide

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    Natural Sciences and Engineering Research Council (NSERC) Network for Innovative Plastic Materials and Manufacturing Processes (NIPMMP) Canada Research Chairs (CRC)With the purpose of fabricating polymer nanocomposite foams and preventing coalescence in foaming processes, the interfacial tension of poly (lactic acid) (PLA) -silica composites is investigated in this work. Synthesized silica nanoparticles(SNs) with a CO2 - philic surface modification are used as the dispersednanoparticles. Interfacial tension is a key parameter in processing of polymer foamssince it directly affects the final foam properties, such as cell size and cell density.Interfacial tension of silica-containing PLA and supercritical carbon dioxide (CO2)is measured using Axisymmetric Drop Shape Analysis Profile (ADSA-P) pendantdrop method at high pressures and high temperatures. The interfacial tensionbetween PLA and supercritical CO2 is observed to decrease as a result ofnanoparticles’ adsorption to the interface. These results indicate that the reductionin interfacial tension with increasing silica content significantly deviates from alinear trend; there is a minimum at 2 wt. % loading of the SNs and then the interfacialtension curve reaches a plateau. Contact angle measurements show an affinity of theSNs for the polymer-supercritical CO2 interface, and these obtained results are usedto calculate the binding energy of the nanoparticles to the PLA / CO2 interface. Inaddition to interfacial properties, the adsorption of silica nanoparticles at theinterface is also studied in detail with Scanning Electron Microscopy

    Effect of well-dispersed surface-modified silica nanoparticles on crystallization behavior of poly (lactic acid) under compressed carbon dioxide

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    The final publication is available at Elsevier via https://doi.org/10.1016/j.polymer.2016.06.019. © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this work, the crystallization behavior of poly (lactic acid) (PLA)/amine-modified silica nano- composites at different loadings of amine-modified silica (1, 2, and 8 wt %) under isothermal, non- isothermal, and isothermal under compressed CO2 is studied. A significant improvement in crystalliza- tion rate was observed after introduction of the nanoparticles. A modified Hoffman-Lauritzen nucleation theory was utilized to explain the facilitation and acceleration of the crystallization process of nano- composites with introducing the surface energy of the nanoparticles and interfacial energy between polymer/nanoparticle into the rate equation. After incorporation of the nanoparticles, three-dimensional spherulites formed sporadically in the PLA matrix based on the prediction of the Avrami exponents of the nanocomposites. High-pressure DSC results also showed an increase in the crystallization rate at 15 bar compared with the atmospheric pressure condition. However, an increase in pressure up to 21 bar had no significant effect on the crystallization rate. The PLA nanocomposites with lower molecular weights and D-content also showed a significant increase in the crystallization rate but with no change in the crys- tallization mechanism.Natural Sciences and Engineering Research Council (NSERC) of Canada || Network for Innovative Plastic Materials and Manufacturing Processes (NIPMMP) || Ontario Centers of Excellence || Canada Research Chairs (CRC)

    Decrypting the multi-functional biological activators and inducers of defense responses against biotic stresses in plants

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    Plant diseases are still the main problem for the reduction in crop yield and a threat to global food security. Additionally, excessive usage of chemical inputs such as pesticides and fungicides to control plant diseases have created another serious problem for human and environmental health. In view of this, the application of plant growth-promoting rhizobacteria (PGPR) for controlling plant disease incidences has been identified as an eco-friendly approach for coping with the food security issue. In this review, we have identified different ways by which PGPRs are capable of reducing phytopathogenic infestations and enhancing crop yield. PGPR suppresses plant diseases, both directly and indirectly, mediated by microbial metabolites and signaling components. Microbial synthesized anti-pathogenic metabolites such as siderophores, antibiotics, lytic enzymes, hydrogen cyanide, and several others act directly on phytopathogens. The indirect mechanisms of reducing plant disease infestation are caused by the stimulation of plant immune responses known as initiation of systemic resistance (ISR) which is mediated by triggering plant immune responses elicited through pathogen-associated molecular patterns (PAMPs). The ISR triggered in the infected region of the plant leads to the development of systemic acquired resistance (SAR) throughout the plant making the plant resistant to a wide range of pathogens. A number of PGPRs including Pseudomonas and Bacillus genera have proven their ability to stimulate ISR. However, there are still some challenges in the large-scale application and acceptance of PGPR for pest and disease management. Further, we discuss the newly formulated PGPR inoculants possessing both plant growth-promoting activities and plant disease suppression ability for a holistic approach to sustaining plant health and enhancing crop productivity

    Population-level risks of alcohol consumption by amount, geography, age, sex, and year: a systematic analysis for the Global Burden of Disease Study 2020

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    Background The health risks associated with moderate alcohol consumption continue to be debated. Small amounts of alcohol might lower the risk of some health outcomes but increase the risk of others, suggesting that the overall risk depends, in part, on background disease rates, which vary by region, age, sex, and year. Methods For this analysis, we constructed burden-weighted dose–response relative risk curves across 22 health outcomes to estimate the theoretical minimum risk exposure level (TMREL) and non-drinker equivalence (NDE), the consumption level at which the health risk is equivalent to that of a non-drinker, using disease rates from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2020 for 21 regions, including 204 countries and territories, by 5-year age group, sex, and year for individuals aged 15–95 years and older from 1990 to 2020. Based on the NDE, we quantified the population consuming harmful amounts of alcohol. Findings The burden-weighted relative risk curves for alcohol use varied by region and age. Among individuals aged 15–39 years in 2020, the TMREL varied between 0 (95% uncertainty interval 0–0) and 0·603 (0·400–1·00) standard drinks per day, and the NDE varied between 0·002 (0–0) and 1·75 (0·698–4·30) standard drinks per day. Among individuals aged 40 years and older, the burden-weighted relative risk curve was J-shaped for all regions, with a 2020 TMREL that ranged from 0·114 (0–0·403) to 1·87 (0·500–3·30) standard drinks per day and an NDE that ranged between 0·193 (0–0·900) and 6·94 (3·40–8·30) standard drinks per day. Among individuals consuming harmful amounts of alcohol in 2020, 59·1% (54·3–65·4) were aged 15–39 years and 76·9% (73·0–81·3) were male. Interpretation There is strong evidence to support recommendations on alcohol consumption varying by age and location. Stronger interventions, particularly those tailored towards younger individuals, are needed to reduce the substantial global health loss attributable to alcohol. Funding Bill & Melinda Gates Foundation
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