Anomalous transport due to drift-wave turbulence

The anomalous transport of particles and thermal energy is analyzed for the electron and ion temperature gradient driven drift-wave turbulence. The entropy production from the anomalous flows is calculated. Approximate formulas for the fluctuation spectra are briefly compared with a microwave scattering experiment in a low beta tokamak.     

Spatial-dependent simulation of TEA CO2 lasers

We have developed a 1-D spatially-dependent model and simulation code to study the dynamics of TEA CO₂ lasers. In this paper we will discuss the motivation for developing the model and present the simulation details. We have compared and verified the simulation results with the previous 0-D model, and with the measurements of a TEA CO₂ laser. With spatial resolution, the 1-D simulation is in better agreement with experimental results compared with the existing 0-D model.     

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are reported, including a 4:1 salt with the meso stereoisomer of the dinuclear [Fe₂(oxalate)₅]⁴⁻ anion in which both cation and anion have chiral components linked together by hydrogen bonding, and a semiconducting salt with triiodide.     

Spontaneous phase transfer of thermosensitive hairy particles between water and an ionic liquid

This article describes the temperature-induced phase transfer behavior of a series of thermosensitive polymer brush-grafted particles between water and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). Six samples were made by surface-initiated atom transfer radical polymerization: silica particles grafted with poly(methoxypoly(ethylene glycol) methacrylate) (PPEGMMA) with two different molecular weights, poly(methoxytri(ethylene glycol) methacrylate) (PTEGMMA), poly(methoxydi(ethylene glycol) methacrylate) (PDEGMMA), and two copolymers of PEGMMA and TEGMMA with different compositions (P(PEGMMA-co-TEGMMA)-82 and P(PEGMMA-co-TEGMMA)-74). The cloud points of free PPEGMMA with M(n,SEC) of 23 and 40 kDa, P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA in [EMIM][TFSI]-saturated water were 95, 94, 80, 72, and 43 °C, respectively. PDEGMMA was not soluble in the ionic liquid-saturated water. PPEGMMA brush-grafted particles moved spontaneously and completely from water to the [EMIM][TFSI] phase upon heating at 80 °C. When cooled to 22 °C, all particles returned to the water layer. From UV-vis absorbance measurements, the transfer temperature (T(tr)) of PPEGMMA-grafted particles from water to the ionic liquid was 42 °C. Thermodynamic analysis showed that the particle transfer was an entropically driven process. P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA brush-grafted particles also underwent reversible and quantitative transfer between the two phases upon heating at 70 °C and cooling at 0 °C; their transfer temperatures from water to [EMIM][TFSI] were 36, 30, and 16 °C, respectively. T(tr) was a linear function of the cloud point of the corresponding free polymer in ionic liquid-saturated water. In contrast, PDEGMMA-grafted particles moved spontaneously to the ionic liquid layer upon heating but did not return to water even after prolonged stirring at 0 °C.     

Phase separation in the poly (γ-benzyl-α, l-glutamate)/benzyl alcohol system

We describe phase separations seen in the poly (γ-benzyl α, L-glutamate) (PBLG)/benzyl alcohol (BA) system. At temperatures below about 60°C, this system gels. Possible explanations of the system's rigidity include both crystallisation and spinodal decomposition. Recent work on atactic polystyrene (a-PS) gels has suggested these are the result of a phase separation arrested by vitrification. An analogy between a-PS and PBLG gels is suggested whereby crystallisation (in the latter) plays the rǒle of vitrification in the former.     

Deep Red Emitting Heteroleptic Ir(III) Complexes that Incorporate Unsymmetrical 4-quinoline Carboxylic Acid Derived Ligands

Six disubstituted ligands based upon 2-(2′-pyridinyl/pyrazinyl)quinoline-4-carboxylic acids have been synthesised, solvent-free, in one step from a range of commercially available isatin derivatives. These species behave as ancillary chelating ligands for Ir(III) complexes of the form [Ir(C^N)₂(N^N)]PF₆ (where C^N=cyclometalating ligand; N^N=2-(2′-pyridinyl/pyrazinyl)quinoline-4-carboxylic acids). An X-ray crystallographic study on one complex shows a distorted octahedral geometry wherein a cis-C,C and trans-N,N coordination mode is observed for the cyclometalating ligands. DFT calculations predicted that variations in N^N ligand from 2,2′-bipyridine to L^{1 – 6} should localise the LUMO on to the Lⁿ ligand and that the complexes are predicted to display MLCT/LLCT character. All complexes displayed luminescence in the deep red part of the visible region (674–679 nm) and emit from triplet states, but with little apparent tuning as a function of L^{1 – 6} . Further time-resolved transient absorption spectroscopy supports the participation of these triplet states to the excited state character.     

Monitoring chemical impacts on cell cultures by means of image analyses

Many chemical processes are involved in the interactions of living cells with their environment; however, monitoring such processes often requires sophisticated analyzers. In this study, a sensing strategy based on imaging techniques has been developed to (i) enable cell discrimination based on their physical appearance such as size and shape and (ii) to build predictive models that relate the measured cell appearance to chemical parameters in their environment. Both goals aim at innovative and straightforward sensing strategies for analyzing cell–environment interactions. Image analyses offer several advantages such as the use of simpler, more robust sensors and the omission of extensive sample/sensor preparations. Imaging can analyze numerous cells and thus gains a culture representative insight rather than a potentially nonrepresentative single‐cell response. As a proof‐of‐principle application, different species of microalgae cells have been exposed to various nutrient conditions. Microalgae are known to sensitively adapt to changing nutrient conditions and could potentially become biological “probes” for chemical shifts in ecosystems. Because of considerable spreads of cell size and shapes within one class, size and shape distributions have been derived from visible images of cell cultures. It is shown that the novel image analyses are capable of discriminating different cell species based on their cell shapes and sizes. It is also demonstrated that in conjunction with the recently introduced, nonlinear multivariate “predictor surfaces”, the nutrient availability has a quantifiable impact on the cell size distributions. In this application, predictor surfaces are somewhat more precise than partial least squares. Copyright © 2012 John Wiley & Sons, Ltd.     

(E,E)-1,1′-[1,2-Bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) revisited: threefold configurational disorder of (S,S), (R,R) and (S,R) isomers,a detailed critique

Crystal structures described as concomitant triclinic ( I ) and monoclinic ( II ) polymorphs of meso-(E,E)-1,1′-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene) [Mohamed et al. (2016). Acta Cryst. C 72 , 57–62] have been re-investigated. The published model for II was distorted due to forcing the symmetry of space group C2/c on an incomplete structure model. It is shown here to be a likely three-component superposition of S,S and R,R enantiomers with a lesser amount of the meso form. A detailed analysis of how the improbable distortion in the published model aroused suspicion and the subsequent construction of undistorted chemically and crystallographically plausible alternatives having the symmetry of Cc and C2/c is presented. For the sake of completeness, an improved model for the triclinic P structure of the meso isomer I , revised to include a minor disorder component, is also given.     

Lithium Promotes Acetylide Formation on MgO During Methane Coupling Under Non-Oxidative Conditions

A prototypical material for the oxidative coupling of methane (OCM) is Li/MgO, for which Li is known to be essential as a dopant to obtain high C₂ selectivities. Herein, Li/MgO is demonstrated to be an effective catalyst for non-oxidative coupling of methane (NOCM). Moreover, the presence of Li is shown to favor the formation of magnesium acetylide (MgC₂), while pure MgO promotes coke formation as evidenced by solid-state ¹³C NMR, thus indicating that Li promotes C−C bond formation. Metadynamic simulations of the carbon mobility in MgC₂ and Li₂C₂ at the density functional theory (DFT) level show that carbon easily diffuses as a C₂ unit at 1000 °C. These insights suggest that the enhanced C₂ selectivity for Li-doped MgO is related to the formation of Li and Mg acetylides.