Emerging applications that exploit the properties of nanoparticles for biotechnology require that the nanoparticles be biocompatible or support biological recognition. These types of particles can be produced through syntheses that involve biologically relevant molecules (proteins or natural extracts, for example). Many of the protocols that rely on these molecules are performed without a clear understanding of the mechanism by which the materials are produced. We have investigated a previously described reaction in which gold nanoparticles are produced from the reaction of chloroauric acid and proteins in solution. We find that modifications to the starting conditions can alter the product from the expected solution-suspended colloids to a product where colloids are formed within a solid, fibrous protein structure. We have interrogated this synthesis, exploiting the change in products to better understand this reaction. We have evaluated the kinetics and products for 7 different proteins over a range of concentrations and temperatures. The key factor that controls the synthetic outcome (colloid or fiber) is the concentration of the protein relative to the gold concentration. We find that the observed fibrous structures are more likely to form at low protein concentrations and when hydrophilic proteins are used. An analysis of the reaction kinetics shows that AuNP formation occurs faster at lower protein (fiber-forming) concentrations than at higher protein (colloid-forming) concentrations. These results contradict traditional expectations for reaction kinetics and protein-fiber formation and are instructive of the manner in which proteins template gold nanoparticle production.
A process is described for the recovery of uranium, thorium and cerium from Egyptian monazite sands. The process consisted of: 1. Treatment of fine ground monazite sands with hot 50% caustic soda solution with a caustic soda to monazite sand ratio of 1:1. 2. Dilution of the reaction slurry with 6 times the weight of the sand with water to dissolve the sodium phosphate formed. 3. Filtration of the reaction slurry to remove the solid hydrous metal oxides from the sodium phosphate and excess sodium hydroxide. 4. Drying of the mixed hyrous oxides at 150°C for 10 hours to oxidise cerium. 5. Dissolution of the trivalent rare earths by addition of dilute nitric acid dropwise to an aqueous suspension of the dried hydrous oxides to pH 1.3.6. Separation of uranium, thorium and cerium by filtration of the dissolved tervalent rare earths from undissolved residue of the mixed hydrous oxides.
Orbital schwannoma is an exceptionally rare cause of ptosis. Diagnosis may be elusive given its slow rate of growth and its various presentations depending on localization. Herein, we report the case of a 50-year-old male who presented to our clinic with a complaint of unilateral, recurrent ptosis of the left eye. He underwent levator palpebrae resection, which was unsuccessful at improving his ptosis. He later represented with acute-onset diplopia for which magnetic resonance imaging was obtained. Magnetic resonance imaging showed a lesion in the superior orbit with secondary bony dehiscence of the orbital roof. Through a vertical lid-split incision, the lesion was removed, and the frontal lobe was observed protruding through the defect in the orbital roof. This case highlights the importance of diagnostic skepticism in the face of recurrent ptosis and emphasizes the utility of the vertical lid-split approach for anterior lesions of the superior orbit.
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