Hydrolytic degradation of micro and nanoparticles of PLA, according to particle size and dispersion composition

Author(s):  
José Ignacio Valero Moreno ◽  
Alex Martin Pérez ◽  
Sebastian Espino ◽  
Jordi J. Bou
2020 ◽  
pp. 120-129
Author(s):  
Fransiska Christydira Sekaringtyas ◽  
Suwasmi Purwajanti ◽  
Etik Mardliyati ◽  
Sri Ningsih

Curcumin, a hydrophobic polyphenol, derived from turmeric, has numerous pharmacological activities, including hepatoprotective, antioxidant, anti-inflammatory, antimicrobial, and anticarcinogenic. However, the therapeutic efficacy of curcumin is limited due to its poor oral bioavailability and high susceptibility to degradation. The poor oral bioavailability of curcumin has been attributed to its poor aqueous solubility and extensive first past metabolism. Curcumin dissolves in alkaline conditions but it is highly unstable undergoing rapid hydrolytic degradation in neutral or alkaline condition. To solve these problems, liposome-based encapsulation technology is applied to improve the bioavailability of curcumin. The existing method to prepare curcumin-liposome, thin-film method, is complex and usually required the use of organic solvents. In this study, pH-driven method, an organic solvent-free and easily encapsulation technique utilizing the pH-dependent solubility of curcumin was proposed to improve the stability and bioavailability. Curcumin-liposomes were prepared using phospholipon 90 H and soya lecithin as phospholipid sources. The characterizations of curcumin-liposomes include particle size, microstructure, encapsulation efficiency, infrared spectra, salt stability and storage stability. The particle size measured was 77.85 ± 0.39 nm. It was found that curcumin-liposomes prepared by the pH-driven method was stable during storage for 30 days and gave encapsulation efficiency of 60.71 ± 0.20%, higher as compared to the ones prepared by thin-film method. In conclusion, pH-driven is a promising method for the preparation of curcumin-liposomes to enhance stability and encapsulation efficiency


Author(s):  
C. J. Chan ◽  
K. R. Venkatachari ◽  
W. M. Kriven ◽  
J. F. Young

Dicalcium silicate (Ca2SiO4) is a major component of Portland cement. It has also been investigated as a potential transformation toughener alternative to zirconia. It has five polymorphs: α, α'H, α'L, β and γ. Of interest is the β-to-γ transformation on cooling at about 490°C. This transformation, accompanied by a 12% volume increase and a 4.6° unit cell shape change, is analogous to the tetragonal-to-monoclinic transformation in zirconia. Due to the processing methods used, previous studies into the particle size effect were limited by a wide range of particle size distribution. In an attempt to obtain a more uniform size, a fast quench rate involving a laser-melting/roller-quenching technique was investigated.The laser-melting/roller-quenching experiment used precompacted bars of stoichiometric γ-Ca2SiO4 powder, which were synthesized from AR grade CaCO3 and SiO2xH2O. The raw materials were mixed by conventional ceramic processing techniques, and sintered at 1450°C. The dusted γ-Ca2SiO4 powder was uniaxially pressed into 0.4 cm x 0.4 cm x 4 cm bars under 34 MPa and cold isostatically pressed under 172 MPa. The γ-Ca2SiO4 bars were melted by a 10 KW-CO2 laser.


Author(s):  
Sooho Kim ◽  
M. J. D’Aniello

Automotive catalysts generally lose-agtivity during vehicle operation due to several well-known deactivation mechanisms. To gain a more fundamental understanding of catalyst deactivation, the microscopic details of fresh and vehicle-aged commercial pelleted automotive exhaust catalysts containing Pt, Pd and Rh were studied by employing Analytical Electron Microscopy (AEM). Two different vehicle-aged samples containing similar poison levels but having different catalytic activities (denoted better and poorer) were selected for this study.The general microstructure of the supports and the noble metal particles of the two catalysts looks similar; the noble metal particles were generally found to be spherical and often faceted. However, the average noble metal particle size on the poorer catalyst (21 nm) was larger than that on the better catalyst (16 nm). These sizes represent a significant increase over that found on the fresh catalyst (8 nm). The activity of these catalysts decreases as the observed particle size increases.


Wear ◽  
2020 ◽  
pp. 203579
Author(s):  
G. Haider ◽  
M. Othayq ◽  
J. Zhang ◽  
R.E. Vieira ◽  
S.A. Shirazi

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