Evaluating Natural Alternatives to Synthetic Acrylic Polymers: Rheological and Texture Analyses of Polymeric Water Dispersions.

The natural cosmetics market is growing, in line with the interest of public opinion on environmental safety. The availability of polysaccharides for cosmetic use is very wide; each raw material has its own sensorial specificities and hardly matches the performance of synthetic polymers. We developed an instrumental protocol based on rheology and texture analysis to evaluate alternatives to acrylic polymers. The study has been carried out on a set of water dispersions prepared with different synthetic, semisynthetic, and natural polymers at different concentrations. Using statistical principal component analysis, three different clusters have been identified: group A includes polymers with a stringy viscoelastic behavior, group B includes polymers with low firmness and a weak-gel rheological pattern, and group C includes polymers which formed soft and elastic gels. This work showed that this instrumental approach is a powerful tool to comprehensively characterize new rheological modifiers and to forecast their contribution to the formulation based on their applicative features. Moreover, rheology and texture analysis turned out to be complementary tools useful to compare polymeric raw materials and to identify appropriate alternatives to synthetic ones in order to formulate green cosmetic products.

Intra-individual variability in the response to anodal transcranial direct current stimulation.

OBJECTIVE: To test the intra-individual reliability in response to anodal transcranial direct current stimulation (AtDCS). METHODS: 45 healthy subjects received AtDCS (1 mA, 13 min) in two separate sessions, 6-12 months apart. Motor evoked potentials were collected at baseline and then at 5-min intervals after AtDCS for 1h. Short intracortical inhibition (SICI) was assessed at minutes 6 and 46 after AtDCS. RESULTS: AtDCS increased cortical excitability over minutes 0-30 post-stimulation in both sessions, with fair intra-individual reliability. 60% and 64% of subjects responded with the expected increase in cortical excitability in each session, respectively. 69% of the subjects maintained their response pattern between sessions during this timeframe. However, there were no significant effects on cortical excitability over the full hour post AtDCS in either session. SICI showed fair intra-individual reliability 6 min after AtDCS. CONCLUSION: A change in cortical excitability in the first half-hour post-AtDCS may be a good predictor of the response in a subsequent session. Furthermore, minute 15 post-stimulation showed the maximum increase in cortical excitability in both sessions. SIGNIFICANCE: We show for the first time that intra-individual variability is lower than inter-individual variability, and with fair intra-individual inter-sessional reliability for 30 min after AtDCS-subjects are likely to maintain their response patterns to tDCS between sessions, with implications for experimental and therapeutic applications of tDCS.

Enzymatic approach to enantiomerically pure 5-alken-2,4-diols and 4-hydroxy-5-alken-2-ones: application to the synthesis of chiral synthons.

Enantiomerically pure 1,3-diols 1-3 were obtained by a chemoenzymatic approach (lipase PS from Burkholderia cepacia). These diols were converted into useful chiral synthons, which could be considered homologues of glyceraldehyde and glyceric acid acetonides. Applications of these synthons to the de novo synthesis of sugars and preparation of conagenin carboxylic moiety were shown. Hydroxy ketone 4 was chosen as a model system for another synthetic evolution: it was obtained in enantiomerically pure form by enzymatic resolution and converted into chiral tetrahydropyranes, such as the stereoisomers of the commercial fragrance Gyrane.