Giant Pickering droplets: effect of nanoparticle size and morphology on stability

The interaction between a pair of millimeter-sized nanoparticle-stabilized n-dodecane droplets was analyzed by high-speed video camera. The droplets were grown in the presence of either poly(glycerol monomethacrylate)-poly(benzyl methacrylate) (PGMA-PBzMA) diblock copolymer spheres or poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) (PGMA-PHPMA-PBzMA) triblock copolymer worms prepared by polymerization-induced self-assembly (PISA). The effect of nanoparticle morphology on droplet coalescence was analyzed by comparing 22 nm spheres to highly anisotropic worms with a mean worm width of 26 nm and comparable particle contact angle. Both morphologies lowered the interfacial tension, providing direct evidence for nanoparticle adsorption at the oil-water interface. At 0.03 % w/v copolymer, at least 90 seconds was required to stabilize the n-dodecane droplets in the presence of the worms, whereas no ageing was required to produce stable droplets when using the spheres, suggesting faster diffusion of the latter to the surface of the droplets. The enhanced stability of the sphere-coated droplets is consistent with the higher capillary pressure in this system as the almost planar interfaces approach. However, the more strongly adsorbing worms ultimately also confer stability. At lower copolymer concentrations (≤ 0.01% w/v) worm adsorption promoted droplet stability, whereas the spheres were unable to stabilize droplets even after longer ageing times. The effect of mean sphere diameter on droplet stability was also assessed while maintaining an approximately constant particle contact angle. Small spheres of either 22 nm or 41 nm stabilized n-dodecane droplets, whereas larger spheres of either 60 or 91 nm were unable to prevent coalescence when the two droplets were brought into contact. These observations are consistent with the greater capillary pressure stabilizing the oil-water interfaces coated with the smaller spheres. Addition of an oil-soluble polymeric diisocyanate cross-linker to either the 60 nm or the 91 nm spheres produced highly stable colloidosomes, thus confirming adsorption of these nanoparticles

Impact of high conductivity on particle transport to liquid droplets for liquid marble formation

This study investigates the influence of particle conductivity on the promotion of particle extraction and transport to a pendent liquid droplet in the presence of an electric field by applying a thin metal shell of nickel or gold onto polystyrene core particles. Despite significantly increasing the conductivity of the material, the addition of a metal shell to the core particles did not have a concomitant significant impact on initial particle extraction and transport behaviour. For the same applied potential, gold coated particles were extracted from a smaller separation distance than core polystyrene particles, while nickel coated particles were extracted from a slightly increased separation distance. Small separation distances correspond to a stronger electrostatic force required for extraction, so coating the polystyrene particles with gold made them more difficult to extract. Furthermore, these metal-coated particles were extracted from significantly smaller separation distances when compared to the same polystyrene core particles with conductive polymer shells. This is attributed more to increased inter-particle cohesion than from the increased particle mass as a result of the metal coating. In addition, the nickel and gold metal shell coated particles had differing particle hydrophobicity, impacting the final stability of the resultant liquid marble. Comparison is also made with glass core particles, to observe the impact of constant particle mass and changing conductivity and interparticle cohesion, highlighting that increasing conductivity is less significant than the opposing effect of cohesion. Herein, we conclude that the ability to form liquid marbles using an electrostatic extraction method is dependent on a complex interplay of fundamental particle properties of conductivity, density, and cohesion

Moderating influences on the firm's strategic orientation-performance relationship

This paper is focused on the factors that moderate the relationship between firm's strategic orientation and performance in small and medium-sized firms. Much prior research has focused simply on identifying environmental conditions conducive to the effectiveness of the strategic orientation approach. However, recent research has called for studies focused on investigating internal moderators of the strategic orientation-performance relationship. As a result, we propose a contingency framework, considering how corporate and competitive strategies, top management characteristics, and environmental conditions may moderate this relationship. Based on a survey of 295 small and medium sized enterprises pertaining to seven manufacturing sectors, our study shows that the positive influence of firm's strategic orientation may be moderated by the environment conditions, the previous experience of top management team, and the corporate and competitive strategies developed by the firm

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Antithrombin Milano, single amino acid substitution at the reactive site, Arg393 to Cys

Antithrombin Milano is an unusual antithrombin variant, exhibiting an abnormal, fast moving component on crossed immunoelectrophoresis (in the absence of heparin). Antithrombin isolated from the propositus could be resolved into two peaks on anion-exchange chromatography, antithrombin Milano peak 1 of M(r) ~60,000 which could inhibit thrombin, and antithrombin Milano peak 2 of M(r) ~120,000 which was inactive. The latter component also reated with antisera to both antithrombin and albumin on immunoblotting. Under reducing conditions, the ~120,000 M(r) component migrated on SDS-PAGE as two distinct bands with M(r) ~60,000, one of which reacted with antiserum to antithrombin and the other (of slower mobility) of which reacted with antiserum to albumin only. These and other results established the ~120,000 M(r) component to be an inactive, disulphide-linked variant antithrombin and albumin complex. The variant antithrombin was isolated, following reduction and S-carboxymethylation, by reverse-phase HPLC and then it was fragmented with CNBr. A major CNBr pool containing the sequence Gly339-Met423 was treated with trypsin, followed by V8 protease. The resulting peptides were analyzed by fast atom bombardment mass spectrometry (Fab-MS) mapping. A peptide of molecular mass 1086, corresponding to the normal sequence Ala382-Arg393, was almost absent from the mass spectrum, but an additional peptide of mass number 1772 was present. These results are almost identical to those found in another variant antithrombin. Northwick Park (Erdjument et al., J Biol Chem, 262: 13381, 1987; Erdjument et al., J Biol Chem, 263: 5589-5593, 1988), indicating the same single amino acid substitution of Arg393 to Cys