Acceleration on stretched meshes with line-implicit LU-SGS in parallel implementation

The implicit lower–upper symmetric Gauss–Seidel (LU-SGS) solver is combined with the line-implicit technique to improve convergence on the very anisotropic grids necessary for resolving the boundary layers. The computational fluid dynamics code used is Edge, a Navier–Stokes flow solver for unstructured grids based on a dual grid and edge-based formulation. Multigrid acceleration is applied with the intention to accelerate the convergence to steady state. LU-SGS works in parallel and gives better linear scaling with respect to the number of processors, than the explicit scheme. The ordering techniques investigated have shown that node numbering does influence the convergence and that the orderings from Delaunay and advancing front generation were among the best tested. 2D Reynolds-averaged Navier–Stokes computations have clearly shown the strong efficiency of our novel approach line-implicit LU-SGS which is four times faster than implicit LU-SGS and line-implicit Runge–Kutta. Implicit LU-SGS for Euler and line-implicit LU-SGS for Reynolds-averaged Navier–Stokes are at least twice faster than explicit and line-implicit Runge–Kutta, respectively, for 2D and 3D cases. For 3D Reynolds-averaged Navier–Stokes, multigrid did not accelerate the convergence and therefore may not be needed.     

DNA-mediated delivery of lipophilic molecules via hybridization to DNA-based vesicular aggregates

A scheme is presented for stabilizing hydrophobic molecules and releasing them into aqueous solution via DNA hybridization. A tetradecyl hydrophobic tail is covalently attached to synthetic oligomers, and the resulting amphiphilic molecules take up substantial amounts of orange OT and pyrene dyes in aqueous environments. The resulting structures do not affect the surface tension and are predominantly spherical as shown by light scattering and TEM, and the pyrene fluorescence is consistent with a hydrophobic environment. It is concluded that the amphiphilic DNA creates vesicular domains upon which the hydrophobic dyes reside and are stabilized in solution. Upon exposure to the complementary strand, the pyrene dye is released from the structures, showing that the scheme can be used for unlabeled or DNA-mediated drug delivery.     

Interactions between Diamagnetic Metal Ions and pH-Sensitive Nitroxides

Specific interactions between pH-sensitive nitroxide radicals and selected diamagnetic metal ions were investigated. To this end, the influence of different metal salts at varying concentrations on the continuous-wave electron paramagnetic resonance spectra of two imidazoline nitroxides was studied. Among the screened metal ions, Zn(II) most significantly affected the spectral profile, analogous to the effect attributed to protonation of the nitroxide imino nitrogen known from pH studies. Simulations showed the acquired spectra to result from the superposition of the signals of the coordinated and the uncoordinated species. The complex formation between Zn(II) and (4-amino-2,5-dihydro-2,2,5,5-tetramethyl-3-imidazoline-1-yloxyl) was modelled by theoretical methods revealing the rather specific selectivity of the nitroxide toward Zn(II). The results suggest imidazoline nitroxides as promising candidates for the development of new specific metal ion probes.     

Nanomechanical properties of phospholipid microbubbles

This study uses atomic force microscopy (AFM) force-deformation (F-Δ) curves to investigate for the first time the Young's modulus of a phospholipid microbubble (MB) ultrasound contrast agent. The stiffness of the MBs was calculated from the gradient of the F-Δ curves, and the Young's modulus of the MB shell was calculated by employing two different mechanical models based on the Reissner and elastic membrane theories. We found that the relatively soft phospholipid-based MBs behave inherently differently to stiffer, polymer-based MBs [Glynos, E.; Koutsos, V.; McDicken, W. N.; Moran, C. M.; Pye, S. D.; Ross, J. A.; Sboros, V. Langmuir2009, 25 (13), 7514-7522] and that elastic membrane theory is the most appropriate of the models tested for evaluating the Young's modulus of the phospholipid shell, agreeing with values available for living cell membranes, supported lipid bilayers, and synthetic phospholipid vesicles. Furthermore, we show that AFM F-Δ curves in combination with a suitable mechanical model can assess the shell properties of phospholipid MBs. The "effective" Young's modulus of the whole bubble was also calculated by analysis using Hertz theory. This analysis yielded values which are in agreement with results from studies which used Hertz theory to analyze similar systems such as cells.     

Self-organized Au nanoarrays on vertical graphenes: an advanced three-dimensional sensing platform

A three-dimensional surface enhanced Raman scattering (SERS)/plasmonic sensing platform based on plasma-enabled, catalyst-free, few-layer vertical graphenes decorated with self-organized Au nanoparticle arrays is demonstrated. This platform is viable for multiple species detection and overcomes several limitations of two-dimensional sensors.     

Isolation of Echimidine and Its C-7 Isomers from Echium plantagineum L. and Their Hepatotoxic Effect on Rat Hepatocytes

Echimidine is the main pyrrolizidine alkaloid of Echium plantagineum L., a plant domesticated in many countries. Because of echimidine’s toxicity, this alkaloid has become a target of the European Food Safety Authority regulations, especially in regard to honey contamination. In this study, we determined by NMR spectroscopy that the main HPLC peak purified from zinc reduced plant extract with an MS [M + H]⁺ signal at m/z 398 corresponding to echimidine (1), and in fact also represents an isomeric echihumiline (2). A third isomer present in the smallest amount and barely resolved by HPLC from co-eluting (1) and (2) was identified as hydroxymyoscorpine (3). Before the zinc reduction, alkaloids (1) and (2) were present mostly (90%) in the form of an N-oxide, which formed a single peak in HPLC. This is the first report of finding echihumiline and hydroxymyoscorpine in E. plantagineum. Retroanalysis of our samples of E. plantagineum collected in New Zealand, Argentina and the USA confirmed similar co-occurrence of the three isomeric alkaloids. In rat hepatocyte primary culture cells, the alkaloids at 3 to 300 µg/mL caused concentration-dependent inhibition of hepatocyte viability with mean IC₅₀ values ranging from 9.26 to 14.14 µg/mL. Our discovery revealed that under standard HPLC acidic conditions, echimidine co-elutes with its isomers, echihumiline and to a lesser degree with hydroxymyoscorpine, obscuring real alkaloidal composition, which may have implications for human toxicity.     

Applying the voltammetry of microparticles to assess the metal ion excess following a precipitation reaction: the determination of arsenic

Journal of Solid State Electrochemistry - Here we demonstrate that the metal ion excess after precipitating a sparingly soluble metal salt can be conveniently determined by a secondary...     

A convenient synthesis of 7-halo-1-indanones and 8-halo-1-tetralones

A regioselective oxidation of N-indan-4-yl-acetamide or N-(5,6,7,8-tetrahydronaphthalen-1-yl)acetamide with potassium permanganate followed by acidic hydrolysis gave 7-aminoindan-1-one or 8-aminotetral-1-one in good yield. The amino ketones were converted to the corresponding 7-haloindanone or the 8-halotetralone. Another method to prepare 7-haloindan-1-ones was completed by a cyclization of 3-chloro-1-(2-halophenyl)propan-1-one under Friedel-Crafts conditions to produce the product in gram quantity.     

N-heterocyclic carbene-catalyzed generation of homoenolates: gamma-butyrolactones by direct annulations of enals and aldehydes

N-Heterocyclic carbenes, prepared in situ from diarylimidazolium salts, serve as highly effective catalysts for the generation of reactive homoenolates from alpha,beta-unsaturated aldehydes. The catalyst-bound homoenolate reacts with electrophilic aldehydes leading, via the key intermediacy of an activated carboxylate, to gamma-butyrolactones in good yields and stereoselectivities. Importantly, this process demonstrates an unprecedented reaction mode for the generation of nucleophilic carbanions with a multifunctional organocatalyst under exceptionally mild and convenient reaction conditions.