Superlattice patterns in vertically oscillated rayleigh-Benard convection

We report the first observations of superlattices in thermal convection. The superlattices are selected by a four-mode resonance mechanism that is qualitatively different from the three-mode resonance responsible for complex-ordered patterns observed previously in other nonequilibrium systems. Numerical simulations quantitatively describe both the pattern structure and the stability boundaries of superlattices observed in laboratory experiments. In the presence of the inversion symmetry, superlattices are found numerically to bifurcate supercritically directly from conduction or from a striped base state.     

Nopol-Based Quinoline Derivatives as Antiplasmodial Agents

Malaria remains a significant cause of morbidity and mortality in Sub-Saharan Africa and South Asia. While clinical antimalarials are efficacious when administered according to local guidelines, resistance to every class of antimalarials is a persistent problem. There is a constant need for new antimalarial therapeutics that complement parasite control strategies to combat malaria, especially in the tropics. In this work, nopol-based quinoline derivatives were investigated for their inhibitory activity against Plasmodium falciparum, one of the parasites that cause malaria. The nopyl-quinolin-8-yl amides (2–4) were moderately active against the asexual blood stage of chloroquine-sensitive strain Pf3D7 but inactive against chloroquine-resistant strains PfK1 and PfNF54. The nopyl-quinolin-4-yl amides and nopyl-quinolin-4-yl-acetates analogs were generally less active on all three strains. Interesting, the presence of a chloro substituent at C7 of the quinoline ring of amide 8 resulted in sub-micromolar EC₅₀ in the PfK1 strain. However, 8 was more than two orders of magnitude less active against Pf3D7 and PfNF54. Overall, the nopyl-quinolin-8-yl amides appear to share similar antimalarial profile (asexual blood-stage) with previously reported 8-aminoquinolines like primaquine. Future work will focus on investigating the moderately active and selective nopyl-quinolin-8-yl amides on the gametocyte or liver stages of Plasmodium falciparum and Plasmodium vivax.     

Role of Low Molecular Weight Polymers on the Dynamics of Silicon Anodes During Casting

This work probes the slurry architecture of a high silicon content electrode slurry with and without low molecular weight polymeric dispersants as a function of shear rate to mimic electrode casting conditions for poly(acrylic acid) (PAA) and lithium neutralized poly(acrylic acid) (LiPAA) based electrodes. Rheology coupled ultra-small angle neutron scattering (rheo-USANS) was used to examine the aggregation and agglomeration behavior of each slurry as well as the overall shape of the aggregates. The addition of dispersant has opposing effects on slurries made with PAA or LiPAA binder. With a dispersant, there are fewer aggregates and agglomerates in the PAA based silicon slurries, while LiPAA based silicon slurries become orders of magnitude more aggregated and agglomerated at all shear rates. The reorganization of the PAA and LiPAA binder in the presence of dispersant leads to a more homogeneous slurry and a more heterogeneous slurry, respectively. This reorganization ripples through to the cast electrode architecture and is reflected in the electrochemical cycling of these electrodes.     

The effect of PEO block lengths on the size and stability of complex coacervate core micelles

We report on a series of polyion complexes from mixtures of poly(ethylene oxide)-block-poly(N,N-diethylaminoethylmethacrylate) (PEO-PDEAMA) and poly(ethylene oxide)-block-poly(aspartic acid) (PEO-PAsp). As expected, the micelle size, polydispersity and stability are dependant on the relative and absolute lengths of the polyelectrolyte chains. However, we also demonstrate that whilst the length of the charged polyelectrolyte blocks is important, the length of the PEO chains is an equally relevant variable in determining both the size and stability of the final micelles as well as the degree of charge neutralisation at which micellisation occurs. We also show that the kinetics of formation can result in very different stability of the final micelles.     

Measurement of Nitrogen Mustard Degradation Products by Poly(dimethylsiloxane) Microchip Electrophoresis with Contactless Conductivity Detection

A poly(dimethylsiloxane) (PDMS) microfluidic device with contactless conductivity detection for the determination of nitrogen mustard degradation products is reported. Three alkyl ethanolamines: N‐methyldiethanolamine (MDEA), N‐ethyldiethanolamine (EDEA), and triethanolamine (TEA), (degradation/ precursor products of HN‐1, HN‐2 and HN‐3 blister agents) were analyzed by microchip capillary electrophoresis (CE). The original PDMS channel was coated by poly(ethyleneimine) (PEI) to improve the separation of three ethanolamines. Experimental conditions for the separation and detection processes have been optimized to yield well defined separation and high sensitivity. The response times for the three ethanolamines were less than 5 min., the detection limits were 2.0–4.0 mg L^?1 and the relative standard derivations for the migration times and peak heights were 1.6–2.3% and 4.1–5.7%, respectively. The linearity of calibration for each of the compounds was as follows: MDEA, r²=0.970; EDEA, r²=0.994; TEA, r²=0.988. Applicability of this method for natural (lake and tap) water samples was also demonstrated. Compared to conventional analytical methods, this miniaturized system offers promise for on‐site monitoring of degradation products of the nitrogen mustard class of chemical warfare agents, with advantages of cost‐effective construction, simple operation, portability, and small required sample volumes.     

Electrochemical Determination of Manganese Solubility in Mercury via Amalgamation and Stripping in the Room Temperature Ionic Liquid n‐Hexyltriethylammonium Bis(trifluoromethanesulfonyl)imide, [N6,2,2,2][NTf2]

The solubility of manganese in mercury was determined electrochemically via amalgamation and stripping in the room temperature ionic liquid n‐hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, [N_6,2,2,2][NTf₂]. A hemispherical mercury electrode was made by electrodepositing mercury onto a planar platinum microelectrode. Cyclic voltammetry of Mn²⁺ in [N_6,2,2,2][NTf₂] at the mercury microhemisphere electrode was investigated at temperatures of 298, 303 and 313 K. The solubility of Mn in Hg was determined on the basis of the charge under the reduction peak (Mn²⁺→Mn⁰) and the corresponding reoxidation.     

A comparative study of gadolinium gallium garnet growth by femtosecond and nanosecond pulsed laser deposition

The growth of epitaxial Nd:Gd₃Ga₅O₁₂ (GGG) on Y₃Al₅O₁₂ (YAG) by femtosecond pulsed laser deposition is reported. We have used a Ti:sapphire laser at a wavelength of 800 nm and pulse length of 130 fs, operating at a repetition rate of 1 kHz. The film properties have been studied systematically as a function of the deposition parameters of laser fluence, spot-size, oxygen pressure, target-substrate distance and temperature. Scanning electron microscopy, atomic force microscopy and X-ray diffractometry were used to characterise the surface structure and crystallinity of the films. X-ray diffraction analysis shows that epitaxial growth has occurred. A comparison between the ion velocities produced by nanosecond and femtosecond laser ablation of the GGG target material has been investigated by the Langmuir probe technique. The results indicate a large difference in the plasma characteristics between femtosecond and nanosecond ablation, with ion velocities up to eight times faster observed in the femtosecond case.     

Coupled hydrodynamic-acoustic modeling of sound generated by impacting cylindrical water jets

A coupled hydrodynamic-acoustic model describing acoustic propagation in a fluid containing multiple bubbles is proposed and applied to simulate noise generated by impacting water jets. The total pressure is decomposed into a "hydrodynamic" part and an "acoustic" part and computed using different schemes. The hydrodynamic pressure field is calculated independently using a generalized hydrodynamic model, and the pressure variations serve as sources in the wave equation for the acoustic pressure. A numerical algorithm developed to calculate wave propagation in an irregular region is used to account for the existence of the cavities. Noise generated by the impact of two cylindrical water jets is predicted. The computed near-field pressure is compared with the experimental data.