Surface site dependence to negative ion formation

The processes of electron transfer and dissociative scattering are explored for collisions of hyperthermal NO⁺ on GaAs(110). The experiments reveal a marked angular dependence to O⁻ emergence. A strong correlation between the O⁻ scattering angle and the final atom-surface interaction site provides a map of the lateral dependence to reactivity. The results are modeled by sequential neutralization, dissociation, and electron attachment steps. Classical trajectory calculations, in conjunction with an empirical opacity function, accurately reproduce the experimental results. The opacity function is interpreted as the probability that an electron will attach to a departing O fragment as a function of the last surface site the atom impacts. The experiments indicate that O⁻ emergence occurs predominantly for oxygen atoms which come in close contact with the localized dangling bond states of GaAs(110).     

Proton, deuteron, and triton emission in 14N+Ag interactions at an energy of 52 MeV per nucleon

The inclusive energy spectra and multiplicities of p, d, and t from the reactions ¹⁴N(Ag, X), X=p, d, t at E/A=52 MeV are measured. The experimental data are compared with the results obtained within the Dubna version of the cascade model and are analyzed on the basis of the moving-source model.     

A radical diophantine equation

All solutions in positive integers x, yz of the diophantine equation $\text{x}{}^{\mathrm{<mtext>1</mtext><mtext>m</mtext>}}\text{+ y}{}^{\mathrm{<mtext>1</mtext><mtext>n</mtext>}}\text{= z}{}^{\mathrm{<mtext>1</mtext><mtext>r</mtext>}}$ are determined, where m, n, r are given positive integers. The proof makes use of a simple criterion for the irreducibility of the polynomial xⁿ ? a over the rationals, where a is a positive rational.     

Vortex locking in direct numerical simulations of quantum turbulence

Direct numerical simulations are used to examine the locking of quantized superfluid vortices and normal fluid vorticity in evolving turbulent flows. The superfluid is driven by the normal fluid, which undergoes either a decaying Taylor-Green flow or a linearly forced homogeneous isotropic turbulent flow, although the back reaction of the superfluid on the normal fluid flow is omitted. Using correlation functions and wavelet transforms, we present numerical and visual evidence for vortex locking on length scales above the intervortex spacing.     

Synthesis and Electronic Properties of Novel 5,7-Diazapentacene Derivatives

A route to the synthesis of novel 5,7-diazapentacenes and some preliminary studies on their properties is reported. A single crystal X-ray diffraction study of the dihexyl derivative showed it had formed a dimer during the analysis. The materials possess lower lying frontier orbitals than pentacene and may have potential applications in organic electronic devices. This synthetic method may be applicable to the synthesis of other azaacenes.     

Development of a Neutral Diketopyrrolopyrrole Phosphine Oxide for the Selective Bioimaging of Mitochondria at the Nanomolar Level

Development of novel bioimaging materials that exhibit organelle specific accumulation continues to be at the forefront of research interests and efforts. Among the various subcellular organelles, mitochondria, which are found in the cytoplasm of eukaryotic cells, are of particular interest in relation to their vital function. To date, most molecular probes that target mitochondria utilise delocalised lipophilic cations such as triphenylphosphonium and pyridinium. However, the use of such charged motifs is known to be detrimental to the working function of the mitochondrial transmembrane potential and there remains a strong case for development of neutral mitochondrial fluorescent probes. Herein, we demonstrate for the first time the exploitation of diketopyrrolopyrrole-based chemistries for the realisation of a neutral fluorescent probe that exhibits organelle specific accumulation within the mitochondria at the nanomolar level. The synthesised probe, which bears a neutral triphenylphosphine oxide moiety, exhibits a large Stokes shift and high fluorescence quantum yield in water, both highly sought-after properties in the development of bioimaging agents. In vitro studies reveal no interference with cell metabolism when tested for the human MCF7 breast cancer cell and nanomolar subcellular organelle colocalisation with commercially available mitochondrial staining agent Mitotracker Red. In light of its novelty, neutral structure and the preferential accumulation at nanomolar concentrations we anticipate this work to be of significant interest for the increasingly larger community devoted to the realisation of neutral mitochondrial selective systems and more widely to those engaged in the rational development of superior organic architectures in the biological field.