Synthesis of sub-micronic and nanometric PMMA particles via emulsion polymerization assisted by ultrasound: Process flow sheet and characterization.

PMMA particle synthesis was performed from MMA (methyl methacrylate) and water mixtures, exposed to different ultrasonic systems and frequencies. The sonication sequence was 20kHz→580kHz→858kHz→1138kHz, and the solution was sampled after each irradiation step for polymerization. Effects of sonication parameters (time, power), polymerization method (thermo-initiated or photo-initiated), use of small amounts of surfactant (Triton X-100™ or Tween® 20) and initial MMA quantity were investigated on particle size and synthesis yields. Particle size and size distribution were measured by DLS (Dynamic Light Scattering), and confirmed via SEM (Scanning Electron Microscopy) images. Synthesis yield was calculated using the dry weight method. Particle composition was estimated using FTIR (Fourier Transform Infra-Red) spectroscopy. PMMA (polymethylmethacrylate) monodispersed particles were successfully synthesized, with a possibility of control in the 78-310nm size range. These sized-controlled particles were synthesized with a 7.5-85% synthesis yield (corresponding to 7.5-40g/L particle solid content), depending on operational parameters. Furthermore, a trade-off between particle size and synthesis yield can be proposed: 20kHz→10min waiting time→580kHz→858kHz leading to 90nm particles diameter with 72% yield in less than 40min for the whole sequence. Thus, the synthesis under ultrasound can be found easy to implement and time efficient, ensuring the success of the scale-up approach and opening up industrial applications for this type of polymeric particles.

Epigenetic regulation of GATA2 and its impact on normal karyotype acute myeloid leukemia.

The GATA2 gene encodes a zinc-finger transcription factor that acts as a master regulator of normal hematopoiesis. Mutations in GATA2 have been implicated in the development of myelodysplastic syndrome and acute myeloid leukemia (AML). Using RNA sequencing we now report that GATA2 is either mutated with a functional consequence, or expressed at low levels in the majority of normal karyotype AML (NK-AML). We also show that low-GATA2-expressing specimens (GATA2(low)) exhibit allele-specific expression (ASE) (skewing) in more than half of AML patients examined. We demonstrate that the hypermethylation of the silenced allele can be reversed by exposure to demethylating agents, which also restores biallelic expression of GATA2. We show that GATA2(low) AML lack the prototypical R882 mutation in DNMT3A frequently observed in NK-AML patients and that The Cancer Genome Atlas AML specimens with DNMT3A R882 mutations are characterized by CpG hypomethylation of GATA2. Finally, we validate that several known missense single-nucleotide polymorphisms in GATA2 are actually loss-of-function variants, which, when combined with ASE, represent the equivalent of homozygous GATA2 mutations. From a broader perspective, this work suggests for the first time that determinants of ASE likely have a key role in human leukemia.

Effects of videorecorded interactions and counseling for teachers on their responses to preschoolers with intellectual impairments.

Effects of an intervention and video interaction counseling with teachers of 78 children from school and centers were investigated. The study involved a quasi-experimental pretest-intervention-posttest control group design. In Condition 1 teachers received the counseling for 12 weeks, followed by withdrawal of this intervention for weeks. In Condition 2 the intervention was in reversed order. The students' competent behavior was assessed by rating their response to social support during engagement in a standardized task, their performance of standardized tasks of cognitive skills, and ratings of their social skills. Results revealed differences in favor of the participants in the two video interaction counseling research conditions on measures of social support and cognitive competence.