Bond Length - Bond Valence Relationships for Carbon - Carbon and Carbon - Oxygen Bonds

In the present study, relationships are developed for determining bond orders (also referred to as bond valences or bond numbers) from published bond lengths for carbon-carbon (C-C) and carbon-oxygen (C-O) bonds. The relationships are based on Pauling’s empirical formula s = exp((Ro-R)/b)), where s is the bond order, R is the corresponding bond length, Ro is the unit valence bond length, and b is a fitting parameter. We use a recently derived relationship for the b parameter in terms of the bonding atoms’ published atomic orbital exponents. The resulting equations were checked against published x-ray diffraction (XRD) data for 176 carbon systems with 540 published C-C bond lengths, and 50 oxygen systems having 72 published C-O bond lengths. The C-C and C-O bond length-valence relationships are shown to have sufficient applicability and accuracy for use in any bonding environment, regardless of physical state or oxidation number

Extended X-ray emission around four 3C quasars at 0.55<z<0.75 observed with Chandra

We report on the detection of a soft spatially-extended component of X-ray emission around four intermediate-redshift 3C quasars observed with Chandra: 3C254, 3C263, 3C275.1 and 3C281. The bolometric luminosity of this emission ranges over 0.3-1.6 times 10^{44}erg/s, and extends to lengthscales of over 350 kpc at the redshift of the quasar. The X-rays are most likely thermal emission from the intracluster medium of a cluster of galaxies around each quasar, which provides the working surface for the powerful radio lobes. Some X-ray emission is also seen to be associated with the radio plasma.Comment: 8 pages, 4 panelled figures, MNRAS in pres

The linear bias of radio galaxies at z~0.3 via cosmic microwave background lensing

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyWe present a new measurement of the linear bias of radio loud active galactic nuclei (RLAGN) at $z\approx0.3$ and $L_{\rm 1.4GHz}>10^{23}\,{\rm W\,Hz^{-1}}$ selected from the Best & Heckman (2012) sample, made by cross-correlating the RLAGN surface density with a map of the convergence of the weak lensing field of the cosmic microwave background from Planck. We detect the cross-power signal at a significance of $3\sigma$ and use the amplitude of the cross-power spectrum to estimate the linear bias of RLAGN, $b=2.5 \pm 0.8$, corresponding to a typical dark matter halo mass of $\log_{10}(M_{\rm h} /h^{-1} M_\odot)=14.0^{+0.3}_{-0.5}$. When RLAGN associated with optically-selected clusters are removed we measure a lower bias corresponding to $\log_{10}(M_{\rm h} /h^{-1} M_\odot)=13.7^{+0.4}_{-1.0}$. These observations support the view that powerful RLAGN typically inhabit rich group and cluster environments.Peer reviewe

The Disturbed 17 keV Cluster Associated with the Radio Galaxy 3C 438

We present results from a {\em Chandra} observation of the cluster gas associated with the FR II radio galaxy 3C 438. This radio galaxy is embedded within a massive cluster with gas temperature $\sim$17 keV and bolometric luminosity of 6$\times10^{45}$ ergs s$^{-1}$. It is unclear if this high temperature represents the gravitational mass of the cluster, or if this is an already high ($\sim$ 11 keV) temperature cluster that has been heated transiently. We detect a surface brightness discontinuity in the gas that extends $\sim$600 kpc through the cluster. The radio galaxy 3C 438 is too small ($\sim$110 kpc across) and too weak to have created this large disturbance in the gas. The discontinuity must be the result of either an extremely powerful nuclear outburst or the major merger of two massive clusters. If the observed features are the result of a nuclear outburst, it must be from an earlier epoch of unusually energetic nuclear activity. However, the energy required ($\sim10^{63}$ ergs) to move the gas on the observed spatial scales strongly supports the merger hypothesis. In either scenario, this is one of the most extreme events in the local Universe.Comment: 13 pages, 4 figures, 1 table - accepted for publication in the Astrophysical Journal Letter

A Chandra study of particle acceleration in the multiple hotspots of nearby radio galaxies

We present Chandra observations of a small sample of nearby classical double radio galaxies which have more than one radio hotspot in at least one of their lobes. The X-ray emission from the hotspots of these comparatively low-power objects is expected to be synchrotron in origin, and therefore to provide information about the locations of high-energy particle acceleration. In some models of the relationship between the jet and hotspot the hotspots that are not the current jet termination point should be detached from the energy supply from the active nucleus and therefore not capable of accelerating particles to high energies. We find that in fact some secondary hotspots are X-ray sources, and thus probably locations for high-energy particle acceleration after the initial jet termination shock. In detail, though, we show that the spatial structures seen in X-ray are not consistent with naive expectations from a simple shock model: the current locations of the acceleration of the highest-energy observable particles in powerful radio galaxies need not be coincident with the peaks of radio or even optical emission.Comment: Accepted for ApJ. 33 pages, 8 figures inc. 2 in colo

A Markov Chain Monte Carlo approach for measurement of jet precession in radio-loud active galactic nuclei

© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Jet precession can reveal the presence of binary systems of supermassive black holes. The ability to accurately measure the parameters of jet precession from radio-loud AGN is important for constraining the binary supermassive black hole population, which are expected as a result of hierarchical galaxy evolution. The age, morphology, and orientation along the line of sight of a given source often result in uncertainties regarding jet path. This paper presents a new approach for efficient determination of precession parameters using a 2D MCMC curve-fitting algorithm which provides us a full posterior probability distribution on the fitted parameters. Applying the method to Cygnus A, we find evidence for previous suggestions that the source is precessing. Interpreted in the context of binary black holes leads to a constraint of parsec scale and likely sub-parsec orbital separation for the putative supermassive binary.Peer reviewe

A Bond Length – Bond Valence Relationship for Carbon – Nitrogen Bonds

In a recent study, Pauling’s relationship between bond length and valence was derived along with a definition for his fitting parameter b that incorporates the orbital exponents for each atom contributing to the bond of interest. The values of b for various bonds, including C-N bonds, were calculated using the orbital exponent data. In this study, Pauling’s correlation between bond length and bond valence, as well as his valence sum rule, were used with the recently-derived definition for b in order to produce a relationship specifically applicable to C-N bonds. The resulting equation was checked against published x-ray diffraction data for 430 C-N bonds. It is expected, and shown by the data presented in this study, that these equations relating the bond length and bond valence of C-N bonds have sufficient applicability and accuracy for use in any bonding environment, regardless of physical state or oxidation number

Trauma unit emergency doctor airway management

Objectives. To audit indications for and practice (in terms of training/qualification) of definitive airway management compared with current UK practices. Design. Consecutive observational study. Setting. Tygerberg Academic Hospital Trauma Service, Western Cape. Subjects. All trauma patients either arriving intubated or requiring intubation at the Trauma unit during the period 1 - 31 August 2006. Outcome measures. A data collection proforma was completed either at the time of intubation or from medical records. Results. Fifty-seven patients required definitive airway management. In the unit 32 patients (56%) were intubated by emergency medicine registrars or medical officers, with rapidsequence intubations (RSIs) in all 32 (100%). Seven patients (12.3%) were intubated by paramedics pre-hospital, and 18 patients (31.6%) were intubated at referring hospitals by nonanaesthetists. Endotracheal intubation was successful in 55 patients (96.4%). Two patients (3.6%) could not be intubated and therefore underwent surgical cricothyroidotomy at the unit. Clinical outcomes included 12 patients (21%) extubated for ward transfer, 7 patients (12.3%) admitted to an intensive care unit (ICU), 21 patients (36.8%) taken for surgery, and 17 patients (29.8%) died. Motor vehicle accident (MVA) was the predominant mechanism of injury, accounting for 30 (52.6%) patients, while 16 patients (28.1%) had penetrating injuries (gunshot and/or stab wounds), 6 patients (10.5%) had blunt trauma, and the remaining 5 patients (8.8%) suffered serious burns. Conclusion. The most common indication for intubation was a Glasgow Coma Score (GCS) of less than 8, typically in the polytrauma patient with suspected head injury due to MVA. Emergency doctors managed 100% of definitive airway inhospital, and RSI was the favoured method. This differs greatly from the UK where non-anaesthetists only perform between 31% and 56% of trauma intubations, with the rest performed by anaesthetists. Outcome was, however, similar to that described in the literature. South African Medical Journal Vol. 97 (9) 2007: pp. 864-86

Autonomous and controlled motivational regulations for multiple health related behaviors: between- and within-participants analyses

Self-determination theory has been applied to the prediction of a number of health-related behaviors with self-determined or autonomous forms of motivation generally more effective in predicting health behavior than non-self-determined or controlled forms. Research has been confined to examining the motivational predictors in single health behaviors rather than comparing effects across multiple behaviors. The present study addressed this gap in the literature by testing the relative contribution of autonomous and controlling motivation to the prediction of a large number of health-related behaviors, and examining individual differences in self-determined motivation as a moderator of the effects of autonomous and controlling motivation on health behavior. Participants were undergraduate students (N = 140) who completed measures of autonomous and controlled motivational regulations and behavioral intention for 20 health-related behaviors at an initial occasion with follow-up behavioral measures taken four weeks later. Path analysis was used to test a process model for each behavior in which motivational regulations predicted behavior mediated by intentions. Some minor idiosyncratic findings aside, between-participants analyses revealed significant effects for autonomous motivational regulations on intentions and behavior across the 20 behaviors. Effects for controlled motivation on intentions and behavior were relatively modest by comparison. Intentions mediated the effect of autonomous motivation on behavior. Within-participants analyses were used to segregate the sample into individuals who based their intentions on autonomous motivation (autonomy-oriented) and controlled motivation (control-oriented). Replicating the between-participants path analyses for the process model in the autonomy- and control-oriented samples did not alter the relative effects of the motivational orientations on intention and behavior. Results provide evidence for consistent effects of autonomous motivation on intentions and behavior across multiple health-related behaviors with little evidence of moderation by individual differences. Findings have implications for the generalizability of proposed effects in self-determination theory and intentions as a mediator of distal motivational factors on health-related behavior