Repeatability of the heart rate variability threshold during treadmill exercise

Purpose: Heart rate variability threshold (HRVT) is a clinical parameter used to gain insight into autonomic balance. Various studies have validated the use of cycle ergometers in determining HRVT, although the literature lacks evidence that treadmill use is a viable means of determining this threshold. We examined the repeatability of HRVT occurrence using standard deviation of normal R-R intervals (SDNN), root mean square of successive differences of continuous R-R intervals (RMSSD), and standard deviation of instantaneous beat intervals (SD1) in college aged males using treadmill exercise to see if this is a reliable method of threshold determination. Methods: Ten healthy, college-aged males underwent two treadmill max tests while heart rate and ventilation data was obtained using a polar V-800 watch and a PARVO metabolic cart, respectively. Paired t-tests were used to compare consistency of average HRVT and VT occurrence between trials, and to find agreement of HRVT and VT occurrence together within trials. Results: There was no difference between SDNN, RMSSD, SD1, or VT occurrence between trials one and two. There a significant difference between RMSSD and VT and SD1 and VT (P = 0.003 and 0.002, respectively), however there was agreement between SDNN and VT (P = 0.06). Conclusion: Treadmill modality is a reliable method of finding HRVT in a population of healthy young males. HRVT and VT does not correspond on a treadmill as it has been reported to with cycle ergometry

Service-learning: A valuable component of pre-service teacher education

Since the late 1990s service-learning programs as a teaching pedagogy have become increasingly popular in Australia within primary, secondary and tertiary education (Lavery & Hackett, 2008; Service-Learning Australia Inc., 2010). However, such programs require a commitment to providing resources, staffing, finance and time, which may lead some to wonder about the importance of these programs (Karayan & Gathercoal, 2005). There is also the danger that, as service programs become more commonplace, they may well fade into the educational routine or become “another educational fad and another failed social program” (Rue, 1996, p. 246). Service-learning programs at a tertiary level within teacher education aim to give students a hands-on experience in an area that is potentially outside of their comfort zone (Colby, Bercaw, Clark & Galiardi, 2009). These programs encourage pre-service teachers to experience situations which allow them to grow as individuals and professionals. In particular, aspects of leadership, empathy, collaboration, community, knowledge and skills are developed (Kaye, 2004). In this article the authors explore and describe the experiences of pre-service teachers in the School of Education (UNDA) undertaking two service leaning units, with a view to interrogating ways these experiences can enhance pre-service teacher education

Comparison of the physical acoustic channel response of a line array of thin rectangular bars to an equivalent model of thin vibrating rectangular pistons.

The resolution of an array is determined by the number and spatial distance of apertures (channels) within the array and the geometry of each aperture. The accurate design of acoustic sensing arrays relies on an a prioiri estimate of the expected far field radiation pattern of reciprocally behaved elements chosen for each aperture which is difficult to calculate under damped and loaded conditions. The estimated response of one channel of a vertical line array, when modeled as a series of rectangular vibrating pistons on a rigid baffle, is compared to the measured response of one channel of a line array comprised of a series of thin rectangular bars under load and operating off resonance. Although simple modeling can predict the 3dB main lobe width of the channel with some accuracy, loading and damping effects will alter the individual element response and hence the sensitivity of the array and side lobe magnitudes when off axis steering. This is important to note when estimating array gain and noise contributions from sidelobes under steered conditions

Time-lapse monitoring of climate effects on earthworks using surface waves

The UK’s transportation network is supported by critical geotechnical assets (cuttings/embankments/dams) that require sustainable, cost-effective management, while maintaining an appropriate service level to meet social, economic, and environmental needs. Recent effects of extreme weather on these geotechnical assets have highlighted their vulnerability to climate variations. We have assessed the potential of surface wave data to portray the climate-related variations in mechanical properties of a clay-filled railway embankment. Seismic data were acquired bimonthly from July 2013 to November 2014 along the crest of a heritage railway embankment in southwest England. For each acquisition, the collected data were first processed to obtain a set of Rayleigh-wave dispersion and attenuation curves, referenced to the same spatial locations. These data were then analyzed to identify a coherent trend in their spatial and temporal variability. The relevance of the observed temporal variations was also verified with respect to the experimental data uncertainties. Finally, the surface wave dispersion data sets were inverted to reconstruct a time-lapse model of S-wave velocity for the embankment structure, using a least-squares laterally constrained inversion scheme. A key point of the inversion process was constituted by the estimation of a suitable initial model and the selection of adequate levels of spatial regularization. The initial model and the strength of spatial smoothing were then kept constant throughout the processing of all available data sets to ensure homogeneity of the procedure and comparability among the obtained V S VS sections. A continuous and coherent temporal pattern of surface wave data, and consequently of the reconstructed V S VS models, was identified. This pattern is related to the seasonal distribution of precipitation and soil water content measured on site

Time-lapse monitoring of fluid-induced geophysical property variations within an unstable earthwork using P-wave refraction

A significant portion of the UK’s transportation system relies on a network of geotechnical earthworks (cuttings and embankments) that were constructed more than 100 years ago, whose stability is affected by the change in precipitation patterns experienced over the past few decades. The vulnerability of these structures requires a reliable, cost- and time-effective monitoring of their geomechanical condition. We have assessed the potential application of P-wave refraction for tracking the seasonal variations of seismic properties within an aged clay-filled railway embankment, located in southwest England. Seismic data were acquired repeatedly along the crest of the earthwork at regular time intervals, for a total period of 16 months. P-wave first-break times were picked from all available recorded traces, to obtain a set of hodocrones referenced to the same spatial locations, for various dates along the surveyed period of time. Traveltimes extracted from each acquisition were then compared to track the pattern of their temporal variability. The relevance of such variations over time was compared with the data experimental uncertainty. The multiple set of hodocrones was subsequently inverted using a tomographic approach, to retrieve a time-lapse model of VP for the embankment structure. To directly compare the reconstructed VP sections, identical initial models and spatial regularization were used for the inversion of all available data sets. A consistent temporal trend for P-wave traveltimes, and consequently for the reconstructed VP models, was identified. This pattern could be related to the seasonal distribution of precipitation and soil-water content measured on site

Long-term geoelectrical monitoring of landslides in natural and engineered slopes

Developments in time-lapse electrical resistivity tomography (ERT) technology are transforming our ability to monitor the subsurface due to purpose-built monitoring instruments, advances in automation and modeling, and the resulting improvements in spatial and temporal resolution. We describe the development of a novel ERT-based remote monitoring system called PRIME that integrates new low-power measurement instrumentation with data delivery, automated data processing and image generation, and web-based information delivery. Due to the sensitivity of ERT to hydrologic processes in the near surface, we focus on the application of PRIME for moisture-driven landslide monitoring. Case examples are considered of landslides in engineered and natural slopes, including those impacting geotechnical assets in rail and highways, where slope hydrology is seen to be controlled by lithology, vegetation, fissuring, and drainage structures. We conclude by taking a forward look at emerging developments in ERT monitoring relating to hardware, software and modeling, and applications

4D electrical resistivity tomography for assessing the influence of vegetation and subsurface moisture on railway cutting condition

Instability of slopes, embankments, and cuttings on the railway network is increasingly prevalent globally. Monitoring vulnerable infrastructure aids in geotechnical asset management, and improvements to transport safety and efficiency. Here, we examine the use of a novel, near-real-time Electrical Resistivity Tomography (ERT) monitoring system for assessing the stability of a railway cutting in Leicestershire, United Kingdom. In 2015, an ERT monitoring system was installed across a relict landslide (grassed) and an area of more stable ground on either side (wooded), to monitor changes in electrical resistivity through time and space, and to assess the influence of different types of vegetation on the stability of transportation infrastructure. Two years of 4-Dimensional ERT monitoring results are presented here, and petrophysical relationships developed in the laboratory are applied to calibrate the resistivity models in order to provide an insight into hydrogeological pathways within a railway cutting. The influence of vegetation type on subsurface moisture pathways and on slope stability is also assessed – here we find that seasonal subsurface changes in moisture content and soil suction are exacerbated by the presence of trees (wooded area). This results in shrink-swell behaviour of the clays comprising the railway cutting, resulting in fissuring and a reduction in shear strength, leading to instability. As such, it is proposed that on slopes comprised of expansive soils, grassed slopes are beneficial for stability. Insights into the use of 4-D ERT for monitoring railway infrastructure gained from this study may be applied to the monitoring of critical geotechnical assets elsewhere

Genomic and molecular analyses identify molecular subtypes of pancreatic cancer recurrence

Pancreatic cancer (PC) remains a highly lethal malignancy, and most patients with localized disease that undergo surgical resection still succumb to recurrent disease. Pattern of recurrence after pancreatectomy is heterogenous, with some studies illustrating that site of recurrence can be associated with prognosis.1 Another study suggested that tumors that develop local and distant recurrence can be regarded as a homogenous disease with similar outcomes.2 Here we investigate novel molecular determinants of recurrence pattern after pancreatectomy for PC