Examining the presence of Arching-Action in Edge Stiffened Bridge Deck Cantilever Overhangs Subjected to a Wheel Load

Engineers have proposed the idea that there may be some arching action present in bridge deck cantilever overhangs stiffened along their longitudinal free edge, via a traffic barrier, subjected to a wheel load. This paper includes the details of a full-scale corrosion-free bridge deck with cantilever overhangs stiffened along their longitudinal free edge by a traffic barrier wall that has been constructed and tested under static and fatigue wheel loads at the University of Manitoba. It also reviews experimental test results and postulates various discussions that suggest the presence of arching-action in cantilever slab overhangs. Test results indicated static ultimate load capacities significantly greater than the ultimate capacity if the mode of failure and behavior of the cantilever overhang was completely flexural. These early results confirm and indicate the presence of arching-action resulting in a significant break-through in cantilever behavior when subjected to a wheel load. The theory to account for this arching-action is not yet developed and further research should be conducted.

Th1 not Th17 cells drive spontaneous MS-like disease despite a functional regulatory T cell response

Multiple sclerosis is considered a disease of complex autoimmune etiology, yet there remains a lack of consensus as to specific immune effector mechanisms. Recent analyses of experimental autoimmune encephalomyelitis, the common mouse model of multiple sclerosis, have investigated the relative contribution of Th1 and Th17 CD4 T cell subsets to initial autoimmune central nervous system (CNS) damage. However, inherent in these studies are biases influenced by the adjuvant and toxin needed to break self-tolerance. We investigated spontaneous CNS disease in a clinically relevant, humanized, T cell receptor transgenic mouse model. Mice develop spontaneous, ascending paralysis, allowing unbiased characterization of T cell immunity in an HLA-DR15-restricted T cell repertoire. Analysis of naturally progressing disease shows that IFN?(+) cells dominate disease initiation with IL-17(+) cells apparent in affected tissue only once disease is established. Tregs accumulate in the CNS but are ultimately ineffective at halting disease progression. However, ablation of Tregs causes profound acceleration of disease, with uncontrolled infiltration of lymphocytes into the CNS. This synchronous, severe disease allows characterization of the responses that are deregulated in exacerbated disease: the correlation is with increased CNS CD4 and CD8 IFN? responses. Recovery of the ablated Treg population halts ongoing disease progression and Tregs extracted from the central nervous system at peak disease are functionally competent to regulate myelin specific T cell responses. Thus, in a clinically relevant mouse model of MS, initial disease is IFN? driven and the enhanced central nervous system responses unleashed through Treg ablation comprise IFN? cytokine production by CD4 and CD8 cells, but not IL-17 responses.

Giant retinal tears

A giant retinal tear (GRT) is a full-thickness neurosensory retinal break that extends circumferentially around the retina for three or more clock hours in the presence of a posteriorly detached vitreous. Its incidence in large population-based studies has been estimated as 1.5% of rhegmatogenous retinal detachments, with a significant male preponderance, and bilaterality in 12.8%. Most GRTs are idiopathic, with trauma, hereditary vitreoretinopathies and high myopia each being causative in decreasing frequency. The vast majority of GRTs are currently managed with a pars plana vitrectomy; the use of adjunctive circumferential scleral buckling is debated, but no studies have shown a clear anatomical or visual advantage with its use. Similarly, silicone oil tamponade does not influence long-term outcomes when compared with gas. Primary and final retinal reattachment rates are achieved in 88% and 95% of patients, respectively. Even when the retina remains attached, however, visual recovery may be limited. Furthermore, fellow eyes of patients with a GRT are at higher risk of developing retinal tears and retinal detachment. Prophylactic treatment under these circumstances may be considered but there is no firm evidence of its efficacy at the present time.

Politically sensitive encounters: Ethnography, access and the benefits of ‘hanging out’

Negotiating politically sensitive research environments requires both a careful consideration of the methods involved, and a great deal of personal resolve. In drawing upon two distinct yet comparable fieldwork experiences this paper champions the benefits of ethnographic methods in seeking to gain positionality and research legitimacy amongst those identified as future research participants. The authors explore and discuss their use of the ethnographic concept of ‘hanging out’ in politically sensitive environments when seeking to negotiate access to potentially hard to reach participants living in challenging research environments. Through an illustrative examination of their experiences in researching commemorative rituals in Palestine and mental health in a Northern Irish prison, both authors reflect upon their use of hanging out when seeking to break down barriers and gain acceptance amongst their target research participants. Their involvement in a range of activities, not directly related to the overall aims of the research project, highlight a need for qualitative researchers to adopt a flexible research design, one that embraces serendipitous or chance encounters, when seeking to gain access to hard to reach research participants or when issues of researcher legitimacy are particularly pronounced such as is the case in politically sensitive research environments.

Mature students – participation in maths support and progression

Maths support at the Learning Development Service takes the form of drop-in contact, one-to-one appointments and workshops. Analysis over three years from 2010/11 to 2012/13 shows that 45% of one-to-one appointments involved a mature student, defined at Queen’s University Belfast (QUB) as one who has had a break in full-time study (normally a minimum of two years). This is a very high proportion given that 4% of students at QUB are mature. Considering engineering undergraduates only, the fraction of one-to-one appointments involving mature students was also 45%. This study can report a wide variation in terms of progression of mature students in engineering and aims to consider how more traditional undergraduate learners could be persuaded to adopt the attitudes of mature students in partaking of maths support.

Cooperative learning in science:Intervention in the secondary school

The use of cooperative learning in secondary school is reported - an area of considerable concern given attempts to make secondary schools more interactive and gain higher recruitment to university science courses. In this study the intervention group was 259 pupils aged 12-14 years in nine secondary schools, taught by 12 self-selected teachers. Comparison pupils came from both intervention and comparison schools (n = 385). Intervention teachers attended three continuing professional development days, in which they received information, engaged with resource packs and involved themselves in cooperative learning. Measures included both general and specific tests of science, attitudes to science, sociometry, self-esteem, attitudes to cooperative learning and transferable skills (all for pupils) and observation of implementation fidelity. There were increases during cooperative learning in pupil formulation of propositions, explanations and disagreements. Intervened pupils gained in attainment, but comparison pupils gained even more. Pupils who had experienced cooperative learning in primary school had higher pre-test scores in secondary education irrespective of being in the intervention or comparison group. On sociometry, comparison pupils showed greater affiliation to science work groups for work, but intervention pupils greater affiliation to these groups at break and out of school. Other measures were not significant. The results are discussed in relation to practice and policy implications. © 2011 Taylor & Francis.

Optimization of the processing of HNBR/organoclay nanocomposite

In the current investigation, rubber/clay nanocomposites were prepared by two different methods using hydrogenated nitrile butadiene rubber (HNBR) and the organoclay namely Cloisite 15A (C15A). A new novel approach involving swelling of C15A by ulltrasonication in HNBR solution has been carried out for improving the exfoliation and compatibilization of organoclays with HNBR matrix. With the addition of 5phr of clay, the elongation at break and tear strength improved by 16% and 24% respectively. The effect of coupling agents namely amino functional silane and tetrasulfido silane on the nanocomposites have been investigated. The elongation at break and tear strength improved by 46% and 77% respectively with the use of silanes. The improvement in the mechanical properties attributes to improved interaction between the organoclays and HNBR matrix. This interaction has been studied by X-ray diffraction and transmission electron microscope. Pre-dispersion technique clearly suggests very good improvement in the dispersion and properties due to better filler-rubber compatibility. © 2010 American Institute of Physics.

The ageing behaviour of hydrogenated nitrile butadiene rubber/nanoclay nanocomposites in various mediums

Hydrogenated nitrile butadiene rubber (HNBR) nanocomposites were prepared using commercially available organoclays (Cloisite 15A). The main focus of the current investigation is to study the influence of the organoclay reinforced in HNBR after subjecting it to long-term oxidative ageing and immersion studies. All the different nanoclay nanocomposites were air aged for a period of 168 h and at 150°C. The changes in the mechanical properties such as tensile strength and elongation at break have been compared with respect to the control sample. For immersion tests, three different liquid mediums were considered for this current investigation. All the samples were immersed in different mediums for a period of 168 h at 150°C. The changes in the swelling index and the mechanical properties have been reported with respect to the control sample. After reinforcing nanoclays into HNBR there was good resistance to swelling in all the three different liquid mediums in comparison to control sample. Tensile testing was performed on the immersed nanocomposites to evaluate the mechanical behaviour after immersion studies. A probable mechanism behind the improved performance has been suggested. © The Author(s) 2012.

Enhancement of the properties of EPDM/NBR elastomers using nanoclay for seal applications

In this research, we have investigated the effects of addition of different percentages of nanoclay to the ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) on the characteristics of these rubbers as seal material. Properties such as tensile strength, modulus at different extensions, elongation at break, compressive set, hardness, and permeability and abrasion resistance are tested to assess the effect of addition of the nanoclay. Results indicate that addition of nanoclay at certain compositions could slightly reduce the strength of the rubber. However more stable modulus at different strains are provided, the hardness of the rubber is preserved and slightly enhanced, the permeability is reduced in both rubbers especially considerable decrease in EPDM is observed which is desirable in diminishing the effect of explosive decompression. At the same time the compression test shows that the nanoclay improves the performance of the rubbers under compression which is essential in seal application. The X-ray diffraction tests clarify that the dispersion of the nanoclay in the NBR samples is of high quality. In the EPDM samples, the dispersion is in need of improvement. POLYM. COMPOS., 30:1657-1667, 2009. © 2008 Society of Plastics Engineers.

Twinning anisotropy of tantalum during nanoindentation

Unlike other BCC metals, the plastic deformation of nanocrystalline Tantalum during compression is regulated by deformation twinning. Whether or not this twinning exhibits anisotropy was investigated through simulation of displacement-controlled nanoindentation test using molecular dynamics simulation. MD data was found to correlate well with the experimental data in terms of surface topography and hardness measurements. The mechanism of the transport of material was identified due to the formation and motion of prismatic dislocations loops (edge dislocations) belonging to the 1/2<111> type and <100> type Burgers vector family. Further analysis of crystal defects using a fully automated dislocation extraction algorithm (DXA) illuminated formation and migration of twin boundaries on the (110) and (111) orientation but not on the (010) orientation and most importantly after retraction all the dislocations disappeared on the (110) orientation suggesting twinning to dominate dislocation nucleation in driving plasticity in tantalum. A significant finding was that the maximum shear stress (critical Tresca stress) in the deformation zone exceeded the theoretical shear strength of tantalum (Shear modulus/ 2π~10.03 GPa) on the (010) orientation but was lower than it on the (110) and the (111) orientations. In light to this, the conventional lore of assuming the maximum shear stress being 0.465 times the mean contact pressure was found to break down at atomic scale.

On the potential of significance-driven execution for energy-aware HPC

Dynamic Voltage and Frequency Scaling (DVFS) exhibits fundamental limitations as a method to reduce energy consumption in computing systems. In the HPC domain, where performance is of highest priority and codes are heavily optimized to minimize idle time, DVFS has limited opportunity to achieve substantial energy savings. This paper explores if operating processors Near the transistor Threshold Volt- age (NTV) is a better alternative to DVFS for break- ing the power wall in HPC. NTV presents challenges, since it compromises both performance and reliability to reduce power consumption. We present a first of its kind study of a significance-driven execution paradigm that selectively uses NTV and algorithmic error tolerance to reduce energy consumption in performance- constrained HPC environments. Using an iterative algorithm as a use case, we present an adaptive execution scheme that switches between near-threshold execution on many cores and above-threshold execution on one core, as the computational significance of iterations in the algorithm evolves over time. Using this scheme on state-of-the-art hardware, we demonstrate energy savings ranging between 35% to 67%, while compromising neither correctness nor performance.

Filling the gap: A 60 ky record of mixed carbonate-siliciclastic turbidite deposition from the Great Barrier Reef

Late Pleistocene to Holocene margin sedimentation on the Great Barrier Reef, a mixed carbonatesiliciclastic margin, has been explained by a transgressive shedding model. This model has challenged widely accepted sequence stratigraphic models in terms of the timing and type of sediment (i.e. carbonate vs. siliciclastic) deposited during sea-level oscillations. However, this model documents only hemipelagic sedimentation and the contribution of coarse-grained turbidite deposition, and the role of submarine canyons in this process, remain elusive on this archetypal margin. Here we present a new model of turbidite deposition for the last 60 ky in the north-eastern Australia margin. Using highresolution bathymetry, 58 new and existing radiometric ages, and the composition of 81 turbidites from 15 piston cores, we found that the spatial and temporal variation of turbidites is controlled by the relationship between sea-level change and the variable physiography along the margin. Siliciclastic and mixed carbonate-siliciclastic turbidites were linked to canyons indenting the shelf-break and the welldeveloped shelf-edge reef barriers that stored sediment behind them. Turbidite deposition was sustained while the sea-level position allowed the connection and sediment bypassing through the interreef passages and canyons. Carbonate turbidites dominated in regions with more open conditions at the outer-shelf and where slope-confined canyons dominated or where canyons are generally less abundant. The turn-on and maintenance of carbonate production during sea-level fluctuations also influenced the timing of carbonate turbidite deposition. We show that a fundamental understanding of the variable physiography inherent to mixed carbonate-siliciclastic margins is essential to accurately interpret deep-water, coarse-grained deposition within a sequence stratigraphic context. 

Theory of phonon dissipation in the conduction of stressed Au nanowires

Recent experiments on Au break junctions [Phys. Rev. Lett. 88 (2002) 216803] have characterized the nonlinear conductance of stretched short Au nanowires. They reveal in the voltage range 10-20 meV the signatures of dissipation effects, likely due to phonons in the nanowire, reducing the conductance below the quantized value of 2e(2)/h. We present here a theory, based on a model tight-binding Hamiltonian and on non-equilibrium Green's function techniques, which accounts for the main features of the experiment. The theory helps in revealing details of the experiment which need to be addressed with a more realistic, less idealized, theoretical framework. (C) 2004 Elsevier B.V. All rights reserved.

'Super-Chandrasekhar' Type Ia Supernovae at nebular epochs

We present a first systematic comparison of superluminous Type Ia supernovae (SNe Ia) at late epochs, including previously unpublished photometric and spectroscopic observations of SN 2007if, SN 2009dc and SNF20080723-012. Photometrically, the objects of our sample show a diverse late-time behaviour, some of them fading quite rapidly after a light-curve break at ∼ 150-200 d. The latter is likely the result of flux redistribution into the infrared, possibly caused by dust formation, rather than a true bolometric effect. Nebular spectra of superluminous SNe Ia are characterized by weak or absent [Fe III] emission, pointing at a low ejecta ionization state as a result of high densities. To constrain the ejecta and Ni masses of superluminous SNe Ia, we compare the observed bolometric light curve of SN 2009dc with synthetic model light curves, focusing on the radioactive tail after ∼60 d. Models with enough Ni to explain the light-curve peak by radioactive decay, and at the same time sufficient mass to keep the ejecta velocities low, fail to reproduce the observed light-curve tail of SN 2009dc because of too much γ -ray trapping.We instead propose a model with ∼1M of Ni and ∼2 M of ejecta, which may be interpreted as the explosion of a Chandrasekhar-mass white dwarf (WD) enshrouded by 0.6-0.7 M of C/O-rich material, as it could result from a merger of two massive C/O WDs. This model reproduces the late light curve of SN 2009dc well. A flux deficit at peak may be compensated by light from the interaction of the ejecta with the surrounding material.

Better together: Interprofessional Education in Medication Safety

Background: The importance of actively working with other professionals, as part of a single team, is well embedded in discussions relating to effective healthcare. The need for effective teamwork specifically in relation to patient safety is also widely acknowledged; however healthcare has traditionally been poor at building teams and professional groups tend to function semi-autonomously and autocratically.1
Objective: This study aims to gain the views and experiences of students from nursing, pharmacy and medicine involved in an interprofessional workshop in medication safety.
Setting and methods: Interprofessional workshops involving students from nursing, pharmacy and medicine were delivered using case studies involving medication incidents. Focus groups were used to investigate participant’s views and experiences of the workshop.
Results: Focus groups were completed with 22 students. Five main themes were identified from the focus group data relating to medication safety; these were increasing confidence, insight into roles, improving skills, culture of responsibility and application to future practice.
Conclusions: This study represents a model for delivery of training that has demonstrated improvement in the students’ attitudes towards team working and is a first step towards introducing team working into the medication safety program. The programme continues to run using live and virtual workshops.

1. Leape LL. A systems analysis approach to medical error. J Clin Eval Clin Pract. 1997. 3, 3, 213-222.