COVID-19 first lockdown as a window into language acquisition: Associations between caregiver-child activities and vocabulary gains

The COVID-19 pandemic, and the resulting closure of daycare centers worldwide, led to unprecedented changes in children’s learning environments. This period of increased time at home with caregivers, with limited access to external sources (e.g., daycares) provides a unique opportunity to examine the associations between the caregiver-child activities and children’s language development. The vocabularies of 1742 children aged8-36 months across 13 countries and 12 languages were evaluated at the beginning and end of the first lockdown period in their respective countries(from March to September 2020). Children who had less passive screen exposure and whose caregivers read more to them showed larger gains in vocabulary development during lockdown, after controlling for SES and other caregiver-child activities. Children also gained more words than expected (based on normative data) during lockdown; either caregivers were more aware of their child’s development or vocabulary development benefited from intense caregiver-child interaction during lockdown

Epoxidized rosin acids as co-precursors for epoxy resins

A series of novel epoxy resins were prepared from chemically modified rosin, mainly constituted of abietic acid, diglycidyl ether of bisphenol-A (DGEBA) in different percentages as co-reactants, and isophorone diamine as cross-linking agent. Reactive epoxide groups were introduced in the structure of this common pine tree derivative. The chemical structures of various epoxidized rosin acids precursors were confirmed by NMR spectroscopy. Differential scanning calorimetry and dynamic mechanical analysis were used to determine the glass transition temperature and the elastic modulus of the cured epoxy resins. Relatively rigid materials with thermo-mechanical properties depending on the structure of rosin acid derivatives and their ratios with DGEBA were obtained. Epoxy precursors based on renewable rosin can be efficiently used as co-additives of DGEBA for epoxy products

Synthesis and characterization of amphiphilic triblock copolymers including -alanine/-methyl--alanine and ethylene glycol by "click" chemistry

WOS: 000460703600029Terminally azide poly--alanine (PBA-Az) was directly obtained by hydrogen transfer polymerization of acrylamide in the presence of sodium azide as an initiator. However, terminally azide poly(-methyl -alanine) (PmBA-Az) was synthesized by the reaction between terminally bromo poly(-methyl -alanine) and sodium azide. Dipropargyllated polyethylene glycol (PEG-di-Pr) was synthesized by using the reaction of PEGs with different molecular weights and propargyl bromide. Synthesis of poly(-alanine-b-ethylene glycol-b--alanine) and poly(-methyl -alanine-b-ethylene glycol-b--methyl -alanine) amphiphilic ABA triblock copolymers was achieved via click chemistry of PBA-Az or PmBA-Az and PEG-di-Pr with different molecular weight. Click reaction parameters such as concentration and time were assessed. Macromonomers and the amphiphilic triblock copolymers were characterized by using H-1-NMR, FT-IR, MALDI-MS, TGA, and elemental analysis techniques. The multi-instruments studies of the obtained amphiphilic triblock copolymers reveal that the copolymers easily formed as a result of click chemistry