Formation of neutral C7H2 isomers from pour isomeric C7H2 radical anion precursors in the gas phase

Consideration of theoretical calculations \[E3LYP/aug-cc-pVDZ//B3LYP/6-31G(d)\] of the structures of ten C7H2 neutral isomers and the nine corresponding C7H2 radical anions have led us to synthesize four stable C7H2 radical anions in the ion source of our ZAB 2HF mass spectrometer, and to convert these to C7H2 neutrals. The four radical anion isomers prepared were (i) \[(HC equivalent to C)(2)C=C=C\](-.) \[from the reaction between (HC equivalent to C)(3)COCH3 and HO- \], (ii) \[HC=C=C=C=C=C=CH\](-.) \[from the reaction between HC equivalent to C-C equivalent to C-CD(OH)-C equivalent to CH and HO-\], (iii) \[C=C=C=C=C=C=CH2\](-.) \[from the reaction between DC equivalent to C-C equivalent to C-C equivalent to C-CH2OCH2CH3 and HO-\], and (iv) \[C equivalent to C-CH2-C equivalent to C-C equivalent to C\](-.) \[from the bis desilylation reaction of (CH3)(3)Si-C equivalent to C-CH2-C equivalent to C-C equivalent to C-Si (CH3)(3)With SF6-.\]. The four anions were further characterized by their collisional activation (negative ion) and charge reversal (CR, positive ion) mass spectra. The anions were converted into their corresponding neutrals by charge stripping, and the correspondence between the charge reversal (CR) and neutralization reionization (-NR+) mass spectra of each anion is taken as evidence that within the time frame of the -NR+ experiment (some 10(-6) s), each neutral is stable and undergoes no major rearrangement or interconversion to a more stable isomer. Theory and experiment are in accord for these systems.

Formation of neutral C7H2 isomers from four isomeric C7H2 radical anion precursors in the gas phase

Consideration of theoretical calculations [B3LYP/aug-cc-pVDZ//B3LYP/6-31G(d)] of the structures of ten C7H2 neutral isomers and the nine corresponding C7H2 radical anions have led us to synthesize four stable C7H2 radical anions in the ion source of our ZAB 2HF mass spectrometer, and to convert these to C7H2 neutrals. The four radical anion isomers prepared were (i) [(HC≡C)2C=C=C]-̇ [from the reaction between (HC≡C)3COCH3 and HO- ], (ii) [HC=C=C=C=C=C=CH]-̇ [from the reaction between HC≡C-C≡C- CD(OH)-C≡CH and HO-], (iii) [C=C=C=C=C=C=CH2]-̇ [from the reaction between DC≡C-C≡C- C≡C-CH2OCH2CH3 and HO-], and (iv) [C≡C-CH2-C≡C-C≡C]-̇ [from the bis desilylation reaction of (CH3)3Si-C≡C-CH2-C≡C-C≡C-Si (CH3)3 with SF6 -̇]. The four anions were further characterized by their collisional activation (negative ion) and charge reversal (CR, positive ion) mass spectra. The anions were converted into their corresponding neutrals by charge stripping, and the correspondence between the charge reversal (CR) and neutralization reionization (-NR+) mass spectra of each anion is taken as evidence that within the time frame of the -NR+ experiment (some 10-6 s), each neutral is stable and undergoes no major rearrangement or interconversion to a more stable isomer. Theory and experiment are in accord for these systems.

Base-induced decomposition of alkyl hydroperoxides in the gas phase. Part 3. Kinetics and dynamics in HO-+CH3OOH, C2H5OOH, and tert-C4H9OOH reactions

The E-CO(2) elimination reactions of alkyl hydroperoxides proceed via abstraction of an (x-hydrogen by a base: X- + (RRHCOOH)-R-1-H-2 -> HX + (RRC)-R-1-C-2=O + HO-. Efficiencies and product distributions for the reactions of the hydroxide anion with methyl, ethyl, and tert-butyl hydroperoxides are studied in the gas phase. On the basis of experiments using three isotopic analogues, HO- + CH3OOH, HO- + CD3OOH, and H18O- + CH3OOH. the overall intrinsic reaction efficiency is determined to be 80% or greater. The E(CO)2 decomposition is facile for these methylperoxide reactions, and predominates over competing proton transfer at the hydroperoxide moiety. The CH3CH2OOH reaction displays a similar E(CO)2 reactivity, whereas proton transfer and the formation of HOO- are the exclusive pathways observed for (CH3)(3)COOH, which has no (x-hydrogen. All results are consistent with the E-CO(2) mechanism, transition state structure, and reaction energy diagrams calculated using the hybrid density functional B3LYP approach. Isotope labeling for HO- + CH3OOH also reveals some interaction between H2O and HO- within the E(CO)2 product complex [H2O center dot center dot center dot CH2=O center dot center dot center dot HO-]. There is little evidence, however. for the formation of the most exothermic products H2O + CH2(OH)O-, which would arise from nuclephilic condensation of CH2=O and HO-. The results suggest that the product dynamics are not totally statistical but are rather direct after the E-CO(2) transition state. The larger HO- + CH3CH2OOH system displays more statistical behavior during complex dissociation.

Direct observation of the gas phase reaction of the cyclohexyl radical with dioxygen using a distonic radical ion approach

Alkylperoxyl radicals are intermediates in the oxidation Of hydrocarbons. The reactive nature of these intermediates, however, has made therin elusive to direct observation and isolation. We have employed ion trap mass spectrometry to synthesize and characterize 4-carboxylatocyclohexyl radical anions ((center dot)C(6)H(10)-CO(2)(-)) and observe their reactivity in the presence of dioxygen. The resulting reaction is facile (k = 1.8 x 10(-10) cm(3) molecule(-1) s(-1) or 30% of calculated collision rate) and results in (i) the addition Of O(2) to form stabilized 4-carboxylatocyclohexylperoxyl radical anions ((center dot)OO-C(6)H(10)-CO(2)(-)), providing the first direct observation of a cyclohexylperoxyl radical, and (ii) elimination of HO(2)(center dot) and HO(center dot) radicals consistent with recent laser-induced fluorescence studies of the reaction of neutral cyclohexyl radicals with O(2). Electronic structure calculations at the B3LYP/6-31+G(d) level of theory reveal viable pathways for the observed reactions showing that formation of the peroxyl radical is exothermic by 37 kcal mol(-1) with subsequent transition states its low as -6.6 kcal mol(-1) (formation of HO(2)(center dot)) and -9.1 kcal mol(-1) (formation of HO(center dot)) with respect to the entrance channel. The combined computational and experimental data Suggest that the structures of the reaction products correspond to cyclohexenes and epoxides from HO(2)(center dot) and HO(center dot) loss, respectively, while alternative pathways leading to cyclohexanone or ring-opened isomers ate not observed, Activation of the charged peroxyl radical (center dot)OO-C(6)H(10)-CO(2)(-) by collision induced disassociation also results in the loss Of HO(2)(center dot) and HO(center dot) radicals confirming that these products are directly connected to the peroxyl radical intermediate.

Investigation of the gas phase reactivity of the 1-adamantyl radical using a distonic radical anion approach

The gas phase reactions of the bridgehead 3-carboxylato-1-adamantyl radical anion were observed with a series of neutral reagents using a modified electrospray ionisation linear ion trap mass spectrometer. This distonic radical anion was observed to undergo processes suggestive of radical reactivity including radical-radical combination reactions, substitution reactions and addition to carbon-carbon double bonds. The rate constants for reactions of the 3-carboxylato-1-adamantyl radical anion with the following reagents were measured ( in units 10(-12) cm(3) molecule(-1) s(-1)): O-18(2) ( 85 +/- 4), NO ( 38.4 +/- 0.4), I-2 ( 50 +/- 50), Br-2 ( 8 +/- 2), CH3SSCH3 ( 12 +/- 2), styrene ( 1.20 +/- 0.03), CHCl3 ( H abstraction 0.41 +/- 0.06, Cl abstraction 0.65 +/- 0.1), CDCl3 ( D abstraction 0.035 +/- 0.01, Cl abstraction 0.723 +/- 0.005), allyl bromide (Br abstraction 0.53 +/- 0.04, allylation 0.25 +/- 0.01). Collision rates were calculated and reaction efficiencies are also reported. This study represents the first quantitative measurement of the gas phase reactivity of a bridgehead radical and suggests that distonic radical anions are good models for the study of their elusive uncharged analogues.

Reactions of the hydroperoxide anion with dimethyl methylphosphonate in an ion trap mass spectrometer : evidence for a gas phase alpha-effect

The gas phase degradation reactions of the chemical warfare agent (CWA) simulant, dimethyl methylphosphonate (DMMP), with the hydroperoxide anion (HOO(-)) were investigated using a modified quadrupole ion trap mass spectrometer. The HOO(-) anion reacts readily with neutral DMMP forming two significant product ions at m/z 109 and m/z 123. The major reaction pathways correspond to (i) the nucleophilic substitution at carbon to form \[CH(3)P(O)(OCH(3))O](-) (m/z 109) in a highly exothermic process and (ii) exothermic proton transfer. The branching ratios of the two reaction pathways, 89% and 11% respectively, indicate that the former reaction is significantly faster than the latter. This is in contrast to the trend for the methoxide anion with DMMP, where proton transfer dominates. The difference in the observed reactivities of the HOO(-) and CH(3)O(-) anions can be considered as evidence for an a-effect in the gas phase and is supported by electronic structure calculations at the B3LYP/aug-cc-pVTZ//B3LYP/6-31+G(d) level of theory that indicate the S(N)2(carbon) process has an activation energy 7.8 kJ mol(-1) lower for HOO(-) as compared to CH(3)O(-). A similar alpha-effect was calculated for nucleophilic addition-elimination at phosphorus, but this process an important step in the perhydrolysis degradation of CWAs in solution - was not observed to occur with DMMP in the gas phase. A theoretical investigation revealed that all processes are energetically accessible with negative activation energies. However, comparison of the relative Arrhenius pre-exponential factors indicate that substitution at phosphorus is not kinetically competitive with respect to the S(N)2(carbon) and deprotonation processes.

Joint 2D and 3D cues for image segmentation towards robotic applications

This thesis investigates the fusion of 3D visual information with 2D image cues to provide 3D semantic maps of large-scale environments in which a robot traverses for robotic applications. A major theme of this thesis was to exploit the availability of 3D information acquired from robot sensors to improve upon 2D object classification alone. The proposed methods have been evaluated on several indoor and outdoor datasets collected from mobile robotic platforms including a quadcopter and ground vehicle covering several kilometres of urban roads.

Nb2O5 Schottky based ethanol vapour sensors : effect of metallic catalysts

The aim of this paper is to compare the performances of the highly porous Nb2O5 Schottky based sensors formed using different catalytic metals for ethanol vapour sensing. The fabricated sensors consist of a fairly ordered nano-vein like porous Nb2O5 prepared via an elevated temperature anodization method. Subsequently, Pt, Pd and Au were sputtered as both Schottky contacts and catalysts for the comparative studies. These metals are chosen as they have large work functions in comparison to the electron affinity of the anodized Nb2O5. It is demonstrated that the device based on Pd/Nb2O5 Schottky contact has the highest sensitivity amongst the developed sensors. The sensing behaviors were studied in terms of the Schottky barrier height variations and properties of the metal catalysts.

Formation of neutral molecules of potential stellar interest by neutralisation of negative ions in a mass spectrometer - The application of experiment and molecular modelling in concert

This paper is a modified version of a lecture which describes the synthesis, structure and reactivity of some neutral molecules of stellar significance. The neutrals are formed in the collision cell of a mass spectrometer following vertical Franck-Condon one electron oxidation of anions of known bond connectivity. Neutrals are characterised by conversion to positive ions and by extensive theoretical studies at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory. Four systems are considered in detail, viz (i) the formation of linear C-4 and its conversion to the rhombus C-4, (ii) linear C-5 and the atom scrambling of this system when energised, (iii) the stable cumulene oxide CCCCCO, and (iv) the elusive species O2C-CO. This paper is not intended to be a review of interstellar chemistry: examples are selected from our own work in this area. (C) 2002 Elsevier Science Inc. All rights reserved.

Generation of three isomers of C7H- in the gas phase. A joint experimental and theoretical study

Three anion isomers of formula C7H have been synthesised in the mass spectrometer by unequivocal routes. The structures of the isomers are \[HCCC(C-2)(2)](-), C6CH- and C2CHC4-. One of these, \[HCCC(C-2)(2)](-), is formed in sufficient yield to allow it to be charge stripped to the corresponding neutral radical.

A light and electron microscopic study of NADPH-diaphorase-,calretinin- and parvalbumin-containing neurons in the rat nucleus accumbens

The rat nucleus accumbens contains medium-sized, spiny projection neurons and intrinsic, local circuit neurons, or interneurons. Sub-classes of interneurons, revealed by calretinin (CR) or parvalbumin (PV) immunoreactivity or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, were compared in the nucleus accumbens core, shell and rostral pole. CR, PV and NADPH-diaphorase-containing neurons are shown to form three non-co-localising populations in these three areas. No significant differences in neuronal population densities were found between the subterritories. NADPH-diaphorase-containing neurons could be further separated morphologically into three sub-groups, but CR- and PV-immunoreactive neurons form homogeneous populations. Ultrastructurally, NADPH-diaphorase-, CR- and PV-containing neurons in the nucleus accumbens all possess nuclear indentations. These are deeper and fewer in neurons immunoreactive for PV than in CR- and NADPH-diaphorase-containing neurons. CR-immunoreactive boutons form asymmetrical and symmetrical synaptic specialisations on spines, dendrites and somata, while PV-immunoreactive boutons make only symmetrical synaptic specialisations. Both CR- and PV-immunoreactive boutons form symmetrical synaptic specialisations with medium-sized spiny neurons and contact other CR- and PV-immunoreactive somata, respectively. A novel non-carcinogenic substrate for the peroxidase reaction (Vector Slate Grey, SG) was found to be characteristically electron-dense and may be distinguishable from the diaminobenzidine reaction product. We conclude that the three markers used in this study are localised in distinct populations of nucleus accumbens interneurons. Our studies of their synaptic connections contribute to an increased understanding of the intrinsic circuitry of this area.

Coal seam gas water : potential hazards and exposure pathways in Queensland

The extraction of coal seam gas (CSG) produces large volumes of potentially contaminated water. It has raised concerns about the environmental health impacts of the co-produced CSG water. In this paper, we review CSG water contaminants and their potential health effects in the context of exposure pathways in Queensland’s CSG basins. The hazardous substances associated with CSG water in Queensland include fluoride, boron, lead and benzene. The exposure pathways for CSG water are: (1) water used for municipal purposes, (2) recreational water activities in rivers, (3) occupational exposures, (4) water extracted from contaminated aquifers, and; (5) indirect exposure through the food chain. We recommend mapping of exposure pathways into communities in CSG regions to determine the potentially exposed populations in Queensland. Future efforts to monitor chemicals of concern and consolidate them into a central database will build the necessary capability to undertake a much needed environmental health impact assessment.

The importance of use and end-of-life phases to the life cycle greenhouse gas (GHG) emissions of concrete : a review

Global climate change is one of the most significant environmental impacts at the moment. One central issue for the building and construction industry to address global climate change is the development of credible carbon labelling schemes for building materials. Various carbon labelling schemes have been developed for concrete due to its high contribution to global greenhouse gas (GHG) emissions. However, as most carbon labelling schemes adopt cradle-to-gate as system boundary, the credibility of the eco-label information may not be satisfactory because recent studies show that the use and end-of-life phases can have a significant impact on the life cycle GHG emissions of concrete in terms of carbonation, maintenance and rehabilitation, other indirect emissions, and recycling activities. A comprehensive review on the life cycle assessment of concrete is presented to holistically examine the importance of use and end-of-life phases to the life cycle GHG quantification of concrete. The recent published ISO 14067: Carbon footprint of products – requirements and guidelines for quantification and communication also mandates the use of cradle-to-grave to provide publicly available eco-label information when the use and end-of-life phases of concrete can be appropriately simulated. With the support of Building Information Modelling (BIM) and other simulation technologies, the contribution of use and end-of-life phases to the life cycle GHG emissions of concrete should not be overlooked in future studies.

Resilience and opportunity : regions and the roll-out of Australia's greenhouse gas abatement programs. A manual for Queensland's NRM regions

Voluntary and compliance markets for forest carbon and other (emission avoidance and biosequestration) activities are growing internationally and across Australia. Queensland and its Natural Resource Management (NRM) regions have an opportunity to take a variety of actions to help guide these markets to secure multiple landscape benefits and to build landscape resilience in the face of climate change. As the national arrangements for offsets within Australia’s Clean Energy Package (CEP) and emissions trading environment emerge, Queensland’s regions can prepare themselves and their landholding communities to take advantage of these opportunities to deliver improved climate resilience in their regional landscapes.

Formation and electron field emission of graphene films grown by hot filament chemical vapor deposition

Graphene films with different structures were catalytically grown on the silicon substrate pre-deposited with a gold film by hot filament chemical vapor deposition under different conditions, where methane, hydrogen and nitrogen were used as the reactive gases. The morphological and compositional properties of graphene films were studied using advanced instruments including field emission scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the structure and composition of graphene films are changed with the variation of the growth conditions. According to the theory related to thermodynamics, the formation of graphene films was theoretically analyzed and the results indicate that the formation of graphene films is related to the fast incorporation and precipitation of carbon. The electron field emission (EFE) properties of graphene films were studied in a high vacuum system of ∼10-6 Pa and the EFE results show that the turn-on field is in a range of 5.2-5.64 V μm-1 and the maximum current density is about 63 μ A cm-2 at the field of 7.7 V μm-1. These results are important to control the structure of graphene films and have the potential applications of graphene in various nanodevices.