Hafnia nanoparticles – a model system for graphene growth on a dielectric

We study graphene growth on hafnia (HfO₂) nanoparticles by chemical vapour deposition using optical microscopy, high resolution transmission electron microscopy and Raman spectroscopy. We find that monoclinic HfO₂ nanoparticles neither reduce to a metal nor form a carbide while nucleating nanometer domain‐sized few layer graphene. Hence we regard this as an interesting non‐metallic catalyst model system with the potential to explore graphene growth directly on a (high‐k) dielectric.

     

Dynamic photoluminescence lifetime imaging for the characterisation of silicon wafers

We present a fast and calibration‐free carrier lifetime imaging technique based on photoluminescence (PL) measurements using an InGaAs camera for the examination of crystalline silicon wafers. The carrier lifetime is determined from the time dependent luminescence emission after optical excitation. A ratio, including four PL images acquired at different times during the modulated excitation, is calculated and found to depend only on the camera integration time and the effective carrier lifetime. Therefore, the carrier lifetime is unambiguously determined by this ratio without knowing any additional wafer parameter. We demonstrate the applicability of the dynamic PL technique to multicrystalline silicon wafers. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Overcoming the Unexpected Functional Inversion of a PqsR Antagonist in Pseudomonas aeruginosa: An In Vivo Potent Antivirulence Agent Targeting pqs Quorum Sensing

The virulence regulator PqsR of Pseudomonas aeruginosa is considered as an attractive target for attenuating the bacterial pathogenicity without eliciting resistance. However, despite efforts and desires, no promising PqsR antagonist has been discovered thus far. Now, a surprising functionality change of a highly affine PqsR antagonist in P. aeruginosa is revealed, which is mediated by a bacterial signal molecule synthase and responsible for low cellular potency. Blockade of the susceptible position led to the discovery of the first antivirulence compound that is potent in vivo and targets PqsR, thus providing a proof of concept for this novel antivirulence therapy.     

From Eight‐Membered 10π Electron Sulfur–Nitrogen Cycles to Bicycles and Cages: A Theoretical Approach

A simple way of rationalizing the structures of cyclic, bicyclic, and tricyclic sulfur–nitrogen species and their congeners is presented. Starting from a planar tetrasulfur tetranitride with 12π electrons, we formally derived on paper a number of heterocyclic eight‐membered 10π electron species by reacting the 3p orbitals of two opposite sulfur centers with one radical each, or by replacing these centers by other atoms with five (P) or four (Si, C) valence electrons. This led to planar aromatic 10π electron systems, nonplanar bicyclic structures with a transannular S?S bond, and tricyclic structures by bridging the planar rings with an acceptor or donor unit. The final structures depend on the number of π electrons in the bridges. Intermediate biradicals are stabilized by Jahn–Teller distortion, giving transannular S?S bonds between the NSN units. This procedure may be summarized by two rules, which provide a rationale for the structures of a large number of sulfur–nitrogen‐based molecules. The long bonds between the NSN units show a p character of >95 %. The qualitative results have been compared with known molecular structures and the results of B3LYP/cc‐pVTZ calculations as well as CASSCF and CASVB calculations. B3LYP/cc‐pVTZ calculations have also provided the UV/Vis spectra and the NICS values of the planar 10π systems.     

Quantitative monitoring of yeast fermentation using Raman spectroscopy

Compared to traditional IR methods, Raman spectroscopy has the advantage of only minimal interference from water when measuring aqueous samples, which makes this method potentially useful for in situ monitoring of important industrial bioprocesses. This study demonstrates real-time monitoring of a Saccharomyces cerevisiae fermentation process using a Raman spectroscopy instrument equipped with a robust sapphire ball probe. A method was developed to correct the Raman signal for the attenuation caused by light scattering cell particulate, hence enabling quantification of reaction components and possibly measurement of yeast cell concentrations. Extinction of Raman intensities to more than 50 % during fermentation was normalized with approximated extinction expressions using Raman signal of water around 1,627 cm^?1 as internal standard to correct for the effect of scattering. Complicated standard multi-variant chemometric techniques, such as PLS, were avoided in the quantification model, as an attempt to keep the monitoring method as simple as possible and still get satisfactory estimations. Instead, estimations were made with a two-step approach, where initial scattering correction of attenuated signals was followed by linear regression. In situ quantification measurements of the fermentation resulted in root mean square errors of prediction (RMSEP) of 2.357, 1.611, and 0.633 g/L for glucose, ethanol, and yeast concentrations, respectively.     

A New Route to 6-Aryl-substituted 3,4-Dihydronaphthalene Derivatives via Pd (O)-Catalyzed Cross-Coupling Reaction of Aryl Zinc Chlorides with an Aryl Triflate

A procedure for the Pd (O)-catalyzed cross coupling of the triflate of 6-hydroxy-3,4-dihydronaphthalene-2-methylcarboxylate with various aryl zinc chlorides was developed, which represents an efficient approach to 6-aryl-substituted naphthalene derivatives.     

The Improved Preparation of 7,8-Dihydro-Quinoline-5(6H)-One and 6,7-Dihydro-5H-1-Pyrindin-5-one

Compounds 7,8-dihydroquinoline-5(6H)-one (3) and 6,7-dihydro-5H-1-pyrindin-5-one (5) are formed by new methods from 1,3-diketone compound, ammonium acetate and 1,1,3,3-tetraethoxylpropane.

     

Induction of Liver Size Reduction in Zebrafish Larvae by the Emerging Synthetic Cannabinoid 4F-MDMB-BINACA and Its Impact on Drug Metabolism

Zebrafish (ZF; Danio rerio) larvae have become a popular in vivo model in drug metabolism studies. Here, we investigated the metabolism of methyl 2-[1-(4-fluorobutyl)-1H-indazole-3-carboxamido]-3,3-dimethylbutanoate (4F-MDMB-BINACA) in ZF larvae after direct administration of the cannabinoid via microinjection, and we visualized the spatial distributions of the parent compound and its metabolites by mass spectrometry imaging (MSI). Furthermore, using genetically modified ZF larvae, the role of cannabinoid receptor type 1 (CB1) and type 2 (CB2) on drug metabolism was studied. Receptor-deficient ZF mutant larvae were created using morpholino oligonucleotides (MOs), and CB2-deficiency had a critical impact on liver development of ZF larva, leading to a significant reduction of liver size. A similar phenotype was observed when treating wild-type ZF larvae with 4F-MDMB-BINACA. Thus, we reasoned that the cannabinoid-induced impaired liver development might also influence its metabolic function. Studying the metabolism of two synthetic cannabinoids, 4F-MDMB-BINACA and methyl 2-(1-(5-fluoropentyl)-1H-pyrrolo[2,3-b]pyridine-3-carboxamido)-3,3-dimethylbutanoate (7′N-5F-ADB), revealed important insights into the in vivo metabolism of these compounds and the role of cannabinoid receptor binding.