Synthesis and characterization of poly(amino acid methacrylate)-stabilized diblock copolymer nano-objects

Amino acids constitute one of Nature's most important building blocks. Their remarkably diverse properties (hydrophobic/hydrophilic character, charge density, chirality, reversible cross-linking etc.) dictate the structure and function of proteins. The synthesis of artificial peptides and proteins comprising main chain amino acids is of particular importance for nanomedicine. However, synthetic polymers bearing amino acid side-chains are more readily prepared and may offer desirable properties for various biomedical applications. Herein we describe an efficient route for the synthesis of poly(amino acid methacrylate)stabilized diblock copolymer nano-objects. First, either cysteine or glutathione is reacted with a commercially available methacrylate-acrylate adduct to produce the corresponding amino acid-based methacrylic monomer (CysMA or GSHMA). Well-defined water-soluble macromolecular chain transfer agents (PCysMA or PGSHMA macro-CTAs) are then prepared via RAFT polymerization, which are then chain-extended via aqueous RAFT dispersion polymerization of 2-hydroxypropyl methacrylate. In situ polymerization-induced self-assembly (PISA) occurs to produce sterically-stabilized diblock copolymer nano-objects. Although only spherical nanoparticles could be obtained when PGSHMA was used as the sole macro-CTA, either spheres, worms or vesicles can be prepared using either PCysMA macro-CTA alone or binary mixtures of poly(glycerol monomethacrylate) (PGMA) with either PCysMA or PGSHMA macro-CTAs. The worms formed soft free-standing thermo-responsive gels that undergo degelation on cooling as a result of a worm-to-sphere transition. Aqueous electrophoresis studies indicate that all three copolymer morphologies exhibit cationic character below pH 3.5 and anionic character above pH 3.5. This pH sensitivity corresponds to the known behavior of the poly(amino acid methacrylate) steric stabilizer chains

The importance of relative performance feedback information: Evidence from a natural experiment using high school students.

Abstract We study the effect of providing relative performance feedback information on performance under piece-rate incentives. A natural experiment that took place in a high school offers an unusual opportunity to test this effect in a real-effort setting. For one year only, students received information that allowed them to know whether they were above (below) the class average as well as the distance from this average. We exploit a rich panel data set and find that the provision of this information led to an increase of 5% in students' grades. Moreover, the effect was significant for the whole distribution. However, once the information was removed the effect disappeared. To rule out the concern that the effect may be driven by teachers within the school, we verify our results using national level exams (externally graded) for the same students, and the effect remains

Dividing the Pie: The Determinants of Labor's Share of Income on the Firm Level

This paper is the first to study the factors determining labor's share of income on the level of the individual firm, employing an unusually informative panel data set. The empirical examination is concerned with Switzerland which stands out as one of the very few developed countries with a stable labor share. Broadly confirming results from previous cross-country and industry-level studies, we find that the main factor decreasing the labor share in the estimation period is the increase in the share of workers using ICT in the firm. The main reasons why Switzerland's labor share remained almost constant are its relatively slow-rate of technological progress and shifts towards industries with above-average labor shares

A educação infantil e a questão da escola: o caso da França

Nos últimos trinta anos, a prioridade dada a uma lógica escolar para justificar a pré-escola coincide com uma dupla mudança na instituição. A primeira diz respeito às relações que a escola maternal mantém com a escolarização obrigatória e com as estruturas de cuidados para as crianças pequenas. A outra refere-se às reformas do currículo escolar e ao desenvolvimento dos processos de avaliação. A escola maternal, local de acolhimento, de cuidados e de preparação para a escola, tornou-se institucionalmente uma verdadeira escola. A difusão das comparações internacionais contribuiu para essas mudanças