19 research outputs found
A distributed parameter model for the spray drying of multicomponent droplets with a crust formation
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Flame synthesis of nanophosphors using sub-micron aerosols
A flame synthesis approach is described for producing metal oxide nanoparticles. It is based on a novel microjet atomisation technique, which generates solution aerosol droplets in the sub-micron range with a mean diameter of 200 nm. Here, luminescent Eu-doped Y2O3 nanophosphors are successfully synthesised from aqueous metal nitrate precursors delivered to non-premixed CH4/N2-O2 flames. The effect of droplet size and synthesis temperature on the particle formation route is experimentally investigated by comparison with micron-size droplets (mean diameter 3.5 ÎĽm) produced by ultrasonic atomisation. Depending on the synthesis temperature, the results show that particles are formed via two different mechanisms: gas-to-particle and droplet-to-particle. Using sub-micron droplets at low temperatures (1150 K), the latter mechanism allows production of luminescent Y2O3:Eu3+ nanoparticles in the cubic phase, with straightforward particle size control from 10 to 100 nm by adjusting the precursor concentration in the 0.01-1 mol/L range. At higher flame temperatures (2750 K), results show that nanoparticles are formed via the gas-to-particle mechanism and have a size of 4-5 nm. In comparison with micron-size droplets, specific surface area measurements of the product powders show that sub-micron droplets form an increased fraction of nanoparticles via the gas-to-particle route. The greater developed surface area of sub-micron droplets enhances vaporisation of metal precursor molecules into the gas phase. Timescale analysis shows that the relative rates of solvent evaporation and bulk solute diffusion are also dependent on the droplet size. Electron microscopy confirms that dense particles are formed from sub-micron droplets subjected to a rapid rate of temperature increase in the flame. For the same synthesis conditions, micron-size droplets tend to form hollow particles, indicating that high peak temperatures near the product melting point (>2700 K) are subsequently required to promote dense particle formation
Differential activation of mitochondrial apoptotic pathways by vasculotropic amyloid-β variants in cells composing the cerebral vessel walls
Cerebral amyloid angiopathy (CAA) is an age-associated condition and a common finding in Alzheimer’s disease in which amyloid-β (Aβ) vascular deposits are featured in >80% of the cases. Familial Aβ variants bearing substitutions at positions 21–23 are primarily associated with CAA, although they manifest with strikingly different clinical phenotypes: cerebral hemorrhage or dementia. The recently reported Piedmont L34V Aβ mutant, located outside the hot spot 21–23, shows a similar hemorrhagic phenotype, albeit less aggressive than the widely studied Dutch E22Q variant. We monitored the apoptotic events occurring after stimulation of human brain microvascular endothelial and smooth muscle cells with nonfibrillar structures of both variants and wild-type Aβ40. Induction of analogous caspase-mediated mitochondrial pathways was elicited by all peptides, although within different time frames and intensity. Activated pathways were susceptible to pharmacological modulation either through direct inhibition of mitochondrial cytochrome c release or by the action of pan- and pathway-specific caspase inhibitors, giving a clear indication of the independent or synergistic engagement of both extrinsic and intrinsic mechanisms. Structural analyses of the Aβ peptides showed that apoptosis preceded fibril formation, correlating with the presence of oligomers and/or protofibrils. The data support the notion that rare genetic mutations constitute unique paradigms to understand the molecular pathogenesis of CAA.—Fossati, S., Cam, J., Meyerson, J., Mezhericher, E., Romero, I. A., Couraud, P. O., Weksler, B. B., Ghiso, J., Rostagno, A. Differential activation of mitochondrial apoptotic pathways by vasculotropic amyloid-β variants in cells composing the cerebral vessel walls