Selective turn-on fluorescence detection of cyanide in water using hydrophobic CdSe quantum dots

The ability of 2,2'-bipyridine-bound copper(ii) ions to quench the photoluminescence of hydrophobic CdSe quantum dots is used to create a novel, selective turn-on fluorescence cyanide sensor.     

On quasifree profinite groups

Recently, it has been shown by Harbater and Stevenson that a profinite group is free profinite of infinite rank if and only if is projective and -quasifree. The latter condition requires the existence of distinct solutions to certain embedding problems for . In this paper we provide several new non-trivial examples of -quasifree groups, projective and non-projective. Our main result is that open subgroups of -quasifree groups are -quasifree.

     

Solar hypersensitization of optical fibers

Hydrogen-loaded fibers were exposed to solar radiation for 20 days, in which time the hydrogen was allowed to out-diffuse. Gratings written in these fibers show an increased photosensitivity compared with pristine fibers. Results show the solar radiation has a similar effect on both stripped and unstripped fibers. This work agrees with the fundamental process of using low fluence, long UV sources to photosensitize hydrogen-loaded, germanium-doped fibers.     

Internal and external factors in the structural organization in cocrystals of the mixed-metal endohedrals (GdSc2N@Ih-C80, Gd2ScN@Ih-C80, and TbSc2N@Ih-C80) and nickel(II) octaethylporphyrin

Structural characterizations of three new mixed-metal endohedrals, GdSc 2N@ I h -C80, Gd 2ScN@ I h -C80, and TbSc 2@ I h -C80, have been obtained by single-crystal X-ray diffraction on GdSc 2N@ I h -C80 x Ni (II)(OEP) x 2C 6H 6, Gd 2ScN@ I h -C 80 x Ni(II)(OEP) x 2C6H6, and TbSc 2N@ I h -C80 x Ni (II)(OEP) x 2C6H6. All three have I h -C 80 cages and planar MM' 2N units. The central nitride ion is positioned further from the larger Gd3+ or Tb3+ ions and closer to the smaller Sc3+ ions. The MM' 2N units show a remarkable degree of orientational order in these and related compounds in which the endohedral fullerene is cocrystallized with a metalloporphyrin. The MM' 2N units are oriented perpendicularly to the porphyrin plane and aligned along one of the N-Ni-N axes of the porphyrin. The smaller Sc3+ ions show a marked preference to lie near the porphyrin plane. The larger Gd3+ or Tb3+ ions assume positions further from the plane of the porphyrin. The roles of dipole forces and electrostatic forces in ordering these cocrystals of endohedral fullerenes and metalloporphyrins are considered.     

Holistic oil field value management: using system dynamics for ‘intermediate level’ and ‘value-based’ modelling in the oil industry

System dynamics has been seen primarily as a strategic tool, most effectively used at the highest level of strategy to identify robust policy interventions under a wide range of scenarios. However, an alternative, complementary and powerful role is emerging. This is at an ‘intermediate level’ in organisations to coordinate and integrate policies across the value chain. It is at this level where business value, as defined by the discounted value of future free cash flow, is both created and destroyed. This paper introduces the need for ‘intermediate-level’ and ‘value-based’ modelling and emphasises the natural role of system dynamics in supporting a methodology to fulfil the need. It describes the development of an approach and its application in the oil industry to coordinate the response of people and tools within operational, financial and commercial functions across the value chain to address a variety of problems and issues.     

High-resolution 22–52 keV backlighter sources and application to X-ray radiography

The requirement for sources of hard X-rays suitable for high resolution radiography through large ρR targets is prominent in many aspects of current laser-driven plasma physics research. In recent work using the OMEGA EP laser facility [L. J. Waxer, M. J. Guardalben, J. H. Kelly et al., CLEO/QELS, Optical Society of America, San Jose, CA, IEEE (2008)] at the Laboratory for Laser Energetics (LLE) in Rochester, NY, experiments have been performed to measure characteristics of 22–52 keV X-ray sources using high intensity short-pulse lasers. High quality point projection, two-dimensional radiography was demonstrated by irradiating microwire targets with laser intensities of 10¹⁶ W cm^?2–10¹⁹ W cm^?2. Microwire targets were manufactured to dimensions of 10 μm × 10 μm × 300 μm and were supported by a 100 μm × 300 μm × 6 μm low-Z substrate. Measurements of the k–α conversion efficiency and X-ray source-size are discussed and, of particular importance for radiography, the spectral purity of the backlighter is characterized to assess the relative importance of the Kα emission to bremsstrahlung background.     

Zwitterion radicals and anion radicals from electron transfer and solvent condensation with the fingerprint developing agent ninhydrin.

Ninhydrin (the fingerprint developing agent) spontaneously dehydrates in liquid ammonia and in hexamethylphosphoramide (HMPA) to form indantrione, which has a sufficiently large solution electron affinity to extract an electron from the solvent (HMPA) to produce the indantrione anion radical. In liquid NH(3), the presence of trace amounts of amide ion causes the spontaneous formation of an anion radical condensation product, wherein the no. 2 carbon (originally a carbonyl carbon) becomes substituted with -NH(2) and -OH groups. In HMPA, the indantrione anion radical spontaneously forms condensation products with the HMPA to produce a variety of zwitterionic radicals, wherein the no. 2 carbon becomes directly attached to a nitrogen of the HMPA. The mechanisms for the formation of the zwitterionic paramagnetic condensation products are analogous to that observed in the reaction of ninhydrin with amino acids to yield Ruhemann's Purple, the contrast product in fingerprint development. The formation of anion and zwitterionic radical condensation products from ninhydrin and nitrogen-containing solvents may represent an example of a host of analogous polyketone-solvent reactions.