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Objective: The present study evaluated an intervention designed to introduce University students as potential users of Johannesburg's cycle lanes. Participants: A total of 393 undergraduate and postgraduate students from the University of Johannesburg took part. Methods: Following cycling and safety training, participants undertook a 1.2 km supervised cycle ride between University of Johannesburg campuses using loaned bicycles. The evaluation of the intervention drew on quantitative and qualitative data collected using participant questionnaires; and fieldworkers' photographic and reflective accounts. Results: Perceived cycling competency improved following the intervention, though similar proportions of participants became more "and" less interested in bicycle ownership (7-8%). The physical effort entailed; and flaws in the design and maintenance of cycle lanes (that affected utility and safety) were the strongest themes emerging from the qualitative analyses. Conclusions: The supervised cycle rides improved perceived cycling competency, but also enabled participants to reappraise the potential benefits and desirability of bicycle ownership.

Objective: The present study examined potential barriers to cycle-based transport amongst undergraduate students, to inform the design of future cycling promotion interventions at the University of Johannesburg (UJ). Participants: A total of 606 first, second and third year UJ undergraduates took part. Methods: Sociodemographic and economic determinants of bicycle/car ownership, cycling competency and behavior were evaluated using data derived from a 9-item questionnaire, before and after adjustment for measured confounders. Results: While 70% of respondents knew how to cycle, only 26% owned/had access to a bicycle, and only 18% had last cycled for transport. Bicycle ownership and competency were far commoner amongst male and older participants, and those whose parents had the means to own a car. Conclusions: Interventions to promote cycle-based transport must address the many (predominantly female) students who: have limited cycling competency; do not own/have access to a bicycle; or have little/no experience of cycling for transport.

This article explores the impact of dental tourism on UK dentistry and the National Health Service (NHS). It acknowledges concerns about foreign nationals accessing free NHS care and British residents seeking medical treatment abroad. The article highlights the lack of data on the scale and cost of health tourism to the NHS and emphasizes the potential risks to patients and the healthcare system due to lower standards of care overseas. It also discusses the challenges faced by regulators in monitoring and enforcing standards for dental providers operating outside the UK. The article calls for better legislation, enforcement, and research to address the vulnerability of UK dentistry to dental tourists. [Extracted from the article]

High-level coupled cluster theory, in conjunction with Active Thermochemical Tables (ATcT) and E,J-resolved master equation calculations, was used in a study of the title reactions, which play an important role in the combustion of hydrocarbons. In the set of radical/radical reactions leading to soot formation in flames, the addition of H-atoms to alkenes is likely a common reaction, triggering the isomerization of complex hydrocarbons to aromatics. The heats of formation of C2H3, C2H4, and C2H5 are established to be 301.26 ± 0.30 at 0 K (297.22 ± 0.30 at 298 K), 60.89 ± 0.11 (52.38 ± 0.11), and 131.38 ± 0.22 (120.63 ± 0.22) kJ mol−1, respectively. The calculated rate constants from first principles agree well with experiments where they are available. Under conditions typical of high temperature combustion – where experimental work is very challenging with a consequent dearth of accurate data – we provide high-level theoretical results for kinetic modeling. [ABSTRACT FROM AUTHOR]

The oxidation of self-assembled monolayers (SAMs) of alkanes and alkenes with a thermal beam of OH radicals is studied. The OH radicals have initiated a radical-induced polymerization of the alkene film.

Nine of the twelve fundamental vibrational modes of the propargyl radical, Gamma(sub vib)(HCCCH2)=5a1 symmetry 3b1 symmetry 4b2 is detected in a cryogenic matrix. The results concluded that propargyl is a completely delocalized hydrocarbon radical and is best written as HC=C-CH2.

A new technique is described for the experimental study if ions with organic radicals. A study has been conducted on the following reactions: CH2CHCH2 +H3O(super +) -> C3H6(super +) + H2O, CH2CHCH2 +HO(super -) -> no product ions, o-C6H4 + H3O(super +) -> C6H5(super +) + H2O, and o-C6H4 + HO(super -) ->C6H3(super -) + H2O.

The production of clean samples of CH3OO radicals in cryogenic matrices is described using a tandom pair of supersonic nozzles. The polarization spectroscopy provides new information that makes many of the fundamental assignments of the CH3OO radical more definite.

The polarized infrared absorption spectrum of the allyl radical, CH2CHCH2 (X) 2A2, is measured in an argon matrix at 10K. Considering the gas-to-matrix shifts and matrix in homogeneous line broadening made estimates of true gas-phase vibrational frequencies.

Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H5 13CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H5 13CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K). [ABSTRACT FROM AUTHOR]

The pyrolysis of the benzyl radical has been studied in a set of heated micro-reactors. A combination of photoionization mass spectrometry (PIMS) and matrix isolation infrared (IR) spectroscopy has been used to identify the decomposition products. Both benzyl bromide and ethyl benzene have been used as precursors of the parent species, C6H5CH2, as well as a set of isotopically labeled radicals: C6H5CD2, C6H5CH2, and C6H513CH2. The combination of PIMS and IR spectroscopy has been used to identify the earliest pyrolysis products from benzyl radical as: C5H4=C=CH2, H atom, C5H4--C = CH, C5H5, HCCCH2, and HC = CH. Pyrolysis of the C6H5CD2, C6D5CH2, and C6H513CH2 benzyl radicals produces a set of methyl radicals, cyclopentadienyl radicals, and benzynes that are not predicted by a fulvenallene pathway. Explicit PIMS searches for the cycloheptatrienyl radical were unsuccessful, there is no evidence for the isomerization of benzyl and cycloheptatrienyl radicals: C6H5CH2⇋C7H7. These labeling studies suggest that there must be other thermal decomposition routes for the C6H5CH2 radical that differ from the fulvenallene pathway. [ABSTRACT FROM AUTHOR]

The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH3OC6H4- OCH3) have been studied using a high temperature, microtubular (μtubular) SiC reactor with a residence time of 100 μs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH3O-C6H4-OCH3, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C6H4-CHO) and phenol (C6H5OH). Para-CH3O-C6H4-OCH3 immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C5H4=O). Finally, the m-CH3O-C6H4-OCH3 isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C5H4=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed. [ABSTRACT FROM AUTHOR]