273 research outputs found
Low-cost leaky feeder communication for mines rescue
This is the author accepted manuscript. The final version is available from Taylor and Francis via the DOI in this recordA low-cost, low-weight leaky feeder system is proposed for mines rescue communication, for use
when the mineâs permanent communication infrastructure has been compromised by an incident.
Unlike the leaky feeders that are permanently installed in some transport tunnels and mines, which
are very expensive, bulky and heavy, the system described here relies on the fact that some ordinary
coaxial cables leak signal unintentionally. Experimental evaluation of the two main types of low-cost
coaxial cable identified a suitable cable and an optimal frequency of 27MHz. Longer range tests
characterised the real world underground performance of a system. A range of around a kilometre is
achievable but this could be increased substantially by using in-line amplifiers. In comparison to low
frequency guidewire systems that have previously been produced for mines rescue use, the method
outlined here does not force rescuers to clip handsets to the cable, thereby allowing them much
more freedom of movement.Research Fund for Coal and Stee
Radio Transmission Characteristics in Tunnel Environments
This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.Radio communication is becoming more widely used in underground mining, although it is still a challenge to achieve good quality and reliable coverage. This research provides information to assist mining professionals in designing voice or data communication systems that operate underground by transmitting along mine tunnels. This has been achieved by presenting a simplified model for predicting the propagation of microwave signals and supplementing this with the results of an extensive experimental study aimed at understanding how the performance predicted by the model differs from real-world performance. The results validate the model under ideal conditions but additional signal attenuation is shown to occur when operating close to a wall, behind a partial obstruction or in a side tunnel. Experimental results indicate the typical magnitude of such additional attenuation. Also, long- and short-range fluctuations to the predicted average is demonstrated and their typical magnitude shown. A system planning approach is outlined
Modelling flooding due to runoff from spoil heaps during heavy rainfall
This is the final version. Available from Taylor & Francis via the DOI in this record.âŻFlash floods generated by runoff from abandoned spoil heaps have posed great risks to neighbouring areas but there has been little study on the process, so it is difficult to evaluate the effectiveness of runoff retention or detention measures. These events are likely to become more frequent in a future climate change scenario. To provide a means by which interested parties can study such events, including methods of mitigation, a computer modelling approach is proposed using free open-source software. Unlike conventional tools that solve the shallow water equations, the software tool uses a cellular automata approach to reduce the computational overhead. It is also easy to use so it is suitable for use by practitioners who are not hydrology experts. The method is illustrated by modelling a historical flood in the UK involving spoil heap runoff. Good correlation was observed between the characteristics of the actual and simulated flood event.Research Fund for Coal and SteelEngineering and Physical Sciences Research Counci
Does a SLAP lesion affect shoulder muscle recruitment as measured by EMG activity during a rugby tackle?
Background: The study objective was to assess the influence of a SLAP lesion on onset of EMG activity in shoulder muscles during a front on rugby football tackle within professional rugby players.
Methods: Mixed cross-sectional study evaluating between and within group differences in EMG onset times. Testing was carried out within the physiotherapy department of a university sports medicine clinic. The test group consisted of 7 players with clinically diagnosed SLAP lesions, later verified on arthroscopy. The reference group consisted of 15 uninjured and full time professional rugby players from within the same playing squad. Controlled tackles were performed against a tackle dummy. Onset of EMG activity was assessed from surface EMG of Pectorialis Major, Biceps Brachii, Latissimus Dorsi, Serratus Anterior and Infraspinatus muscles relative to time of impact. Analysis of differences in activation timing between muscles and limbs (injured versus non-injured side and non injured side versus matched reference group).
Results: Serratus Anterior was activated prior to all other muscles in all (P = 0.001-0.03) subjects. In the SLAP
injured shoulder Biceps was activated later than in the non-injured side. Onset times of all muscles of the noninjured shoulder in the injured player were consistently earlier compared with the reference group. Whereas, within
the injured shoulder, all muscle activation timings were later than in the reference group.
Conclusions: This study shows that in shoulders with a SLAP lesion there is a trend towards delay in activation time of Biceps and other muscles with the exception of an associated earlier onset of activation of Serratus anterior, possibly due to a coping strategy to protect glenohumeral stability and thoraco-scapular stability. This
trend was not statistically significant in all cases
Serum methylarginines and spirometry-measured lung function in older adults
Rationale: Methylarginines are endogenous nitric oxide synthase inhibitors that have been implicated in animal models of lung disease but have not previously been examined for their association with spirometric measures of lung function in humans.
Objectives: This study measured serum concentrations of asymmetric and symmetric dimethylarginine in a representative sample of older community-dwelling adults and determined their association with spirometric lung function measures.
Methods: Data on clinical, lifestyle, and demographic characteristics, methylated arginines, and L-arginine (measured using LC-MS/MS) were collected from a population-based sample of older Australian adults from the Hunter Community Study.
The five key lung function measures included as outcomes were Forced Expiratory Volume in 1 second, Forced Vital Capacity, Forced Expiratory Volume in 1 second to Forced Vital Capacity ratio, Percent Predicted Forced Expiratory Volume in 1 second, and Percent Predicted Forced Vital Capacity.
Measurements and Main Results: In adjusted analyses there were statistically significant independent associations between a) higher asymmetric dimethylarginine, lower Forced Expiratory Volume in 1 second and lower Forced Vital Capacity; and b) lower L-arginine/asymmetric dimethylarginine ratio, lower Forced Expiratory Volume in 1 second, lower Percent Predicted Forced Expiratory Volume in 1 second and lower Percent Predicted Forced Vital Capacity. By contrast, no significant associations were observed between symmetric dimethylarginine and lung function.
Conclusions: After adjusting for clinical, demographic, biochemical, and pharmacological confounders, higher serum asymmetric dimethylarginine was independently associated with a reduction in key measures of lung function. Further research is needed to determine if methylarginines predict the decline in lung function
The Relationship Between Low Family Income and Psychological Disturbance in Young Children: An Australian Longitudinal Study
Objective This study examines the relationship between low family income (LFI) experienced at different points in time, chronic low income status and its impact on child behaviour measured at 5 years of age. Method Longitudinal data from the Mater University Study of Pregnancy were used to measure LFI in families at three points in time (the antenatal period, 6 months post birth and at 5 years of age). Outcome variables were three independent groups of behaviour problems labelled as externalising, social, attentional and thought (SAT) problems, and internalising problems. These groups were developed from the Child Behaviour Checklist. An analysis based on logistic regression modelling was carried out examining the relationship between LFI and a range of intermediate variables known to be associated with child behaviour problems. Results The more often families experienced low income, the higher the rate of child behaviour problems at age 5. Low family income was still independently associated with SAT behaviour problems after controlling for smoking in the first trimester, parenting styles, maternal depression and marital disharmony at age 5. The association between LFI and internalising and externalising behaviour problems was largely mediated by maternal depression. Conclusion Low family income is a significant factor in the aetiology of a variety of child behaviour problems. The mechanisms involved in the link between LFI and childhood internalising and externalising behaviours involve the exposure of the children to maternal depression. However, the relationship between LFI and SAT behaviour problems remains to be elucidated
Depression, anxiety and major adverse cardiovascular and cerebrovascular events in patients following coronary artery bypass graft surgery: a five year longitudinal cohort study
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The resilience of postglacial hunter-gatherers to abrupt climate change
Understanding the resilience of early societies to climate change is an essential part of exploring the environmental sensitivity of human populations. There is significant interest in the role of abrupt climate events as a driver of early Holocene human activity, but there are very few well-dated records directly compared with local climate archives. Here, we present evidence from the internationally important Mesolithic site of Star Carr showing occupation during the early Holocene, which is directly compared with a high-resolution palaeoclimate record from neighbouring lake beds. We show that-once established-there was intensive human activity at the site for several hundred years when the community was subject to multiple, severe, abrupt climate events that impacted air temperatures, the landscape and the ecosystem of the region. However, these results show that occupation and activity at the site persisted regardless of the environmental stresses experienced by this society. The Star Carr population displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change. Instead, we show that local, intrinsic changes in the wetland environment were more significant in determining human activity than the large-scale abrupt early Holocene climate events
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
Change in maternal body mass index is associated with offspring body mass index: a 21-year prospective study
High body-mass index (BMI; defined as 25 kg/m(2) or greater) is associated with increased risk of cancer. To inform public health policy and future research, we estimated the global burden of cancer attributable to high BMI in 2012
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