Solidification of liquid metal drops during impact

Hot liquid metal drops impacting onto a cold substrate solidify during their subsequent spreading. Here we experimentally study the influence of solidification on the outcome of an impact event. Liquid tin drops are impacted onto sapphire substrates of varying temperature. The impact is visualised both from the side and from below, which provides a unique view on the solidification process. During spreading an intriguing pattern of radial ligaments rapidly solidifies from the centre of the drop. This pattern determines the late-time morphology of the splat. A quantitative analysis of the drop spreading and ligament formation is supported by scaling arguments. Finally, a phase diagram for drop bouncing, deposition and splashing as a function of substrate temperature and impact velocity is provided

Quantum dot encapsulation in virus-like particles with tuneable structural properties and low toxicity

A simple method for the encapsulation of quantum dots (QDs) in virus-like particle (VLP) nanoassemblies with tuneable structural properties and enhanced biocompatibility is presented. Cowpea chlorotic mottle virus-based capsid proteins assemble around the carboxylated QDs to form QD/VLP nanoassemblies of different capsid size as a function of pH and ionic strength. Detailed structural characterizations verify that nanoassemblies with probably native capsid icosahedral symmetry (T = 3) are obtained at low pH and high ionic strength (pH 5.0, 1.0 M NaCl), whereas high pH and low ionic strength conditions (pH 7.5, 0.3 M NaCl) result in the formation of smaller assembly sizes similar to T = 1 symmetry. In vitro studies reveal that QD/VLP nanoassemblies are efficiently internalized by RAW 264.7 macrophages and HeLa cells with no signs of toxicity at QD concentrations exceeding the potentially-toxic levels. The presented route holds great promise for preparation of size-tuneable, robust, non-toxic luminescent probes for long term cellular imaging applications. Furthermore, thanks to the possibility of chemical and genetic manipulation of the viral protein shell encaging the QDs, the nanoassemblies have potential for in vivo targeting applications

Evaluation of some important physicochemical properties of starch free grewia gum

Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated. The gum was extracted by maceration of the inner bark in deionized water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated. The GG extract had total carbohydrate content of ∼ 60 % out of which 11.8 % was starch, and a protein content of 2.3 %. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH

Dice-and-fill single element octagon transducers for next generation 3D USCT

At the Karlsruhe Institue of Technology (KIT), a 3D-Ultrasound Computer Tomography (3D-USCT) medical imaging system for early breast cancer detection is currently developed. With the next generation of 3D-USCT 2.5, the current region of interest (ROI) of 10 x 10 x 10 cm³ shall be increased to 20 x 20 x 20 cm³ to allow reliable imaging results also for bigger female breasts. Therefore, the opening angle (OA) of the future transducers should be increased to approx. 60° at 3 dB while other characteristics such as bandwidth (BW) and resonance frequency should be preserved or even improved. Based on the current dice-andfill approach in transducer production, optimization is performed on piezoelectric sensor geometry and size, type and structure of matching and backing layer and interconnection technology of the several parts of the transducer