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There is increasing evidence that both black and green tea are beneficial for prevention of cardiovascular disease (CVD). We conducted a systematic review and meta-analysis evaluating the effects of tea flavonoids on cardiovascular (CVD) and all-cause mortality outcomes.Searches across five databases including PubMed and Embase were conducted through November 2018 to identify randomized controlled trials (RCTs) and prospective cohort studies reporting cardiovascular and all-cause mortality outcomes. Two investigators independently conducted abstract and full-text screenings, data extractions, and risk of bias (ROB) assessments using the Nutrition Evidence Library Bias Assessment Tool (NEL BAT). Mixed-effects dose-response meta-regression and standard random-effects meta-analyses for outcomes with ≥ 4 studies were performed. 0 RCTs and 38 prospective cohort studies were included in the systematic review. NEL BAT scores ranged from 0–15 (0 being the lowest risk). Our linear meta-regression model showed that each cup increase in daily tea consumption (about 280 mg and 338 mg of total flavonoids for black and green tea, respectively) was associated with 3–4% lower risk of CVD mortality (predicted adjusted RR = 0.96; CI 0.93–0.99 for green tea and RR = 0.97; CI 0.94–0.99 for black tea). Furthermore, eachcup increase in daily tea consumption was associated a 2% lower risk of all-cause mortality (predicted adjusted relative risk (RR) = 0.98; 95% CI 0.97–0.99 for black tea and RR = 0.98; CI 0.96–0.99 for green tea, respectively). Two studies reported multivariable Cox regression analysis results for the relationship between black tea intake and risks of all-cause mortality outcomes. The results from these two studies were combined with our linear meta-regression result in a random-effects model meta-analysis and showed that each cup increase in daily black tea consumption was associated with an average of 3% lower risk of all-cause mortality (pooled adjusted RR = 0.97; 95% CI 0.87- 1.00) with large heterogeneity (I2 = 81.4%; p = 0.005). Current evidence indicates that increased tea consumption may reduce cardiovascular and all-cause mortality in a dose-response manner. This systematic review was registered on PROSPERO.
The rocky shores of the north-east Atlantic have been long studied. Our focus is from Gibraltar to Norway plus the Azores and Iceland. Phylogeographic processes shape biogeographic patterns of biodiversity. Long-term and broadscale studies have shown the responses of biota to past climate fluctuations and more recent anthropogenic climate change. Inter- and intra-specific species interactions along sharp local environmental gradients shape distributions and community structure and hence ecosystem functioning. Shifts in domination by fucoids in shelter to barnacles/mussels in exposure are mediated by grazing by patellid limpets. Further south fucoids become increasingly rare, with species disappearing or restricted to estuarine refuges, caused by greater desiccation and grazing pressure. Mesoscale processes influence bottom-up nutrient forcing and larval supply, hence affecting species abundance and distribution, and can be proximate factors setting range edges (e.g., the English Channel, the Iberian Peninsula). Impacts of invasive non-native species are reviewed. Knowledge gaps such as the work on rockpools and host–parasite dynamics are also outlined.
Dense granular flows can spontaneously self-channelise by forming a pair of parallel-sided static levees on either side of a central flowing channel. This process prevents lateral spreading and maintains the flow thickness, and hence mobility, enabling the grains to run out considerably further than a spreading flow on shallow slopes. Since levees commonly form in hazardous geophysical mass flows, such as snow avalanches, debris flows, lahars and pyroclastic flows, this has important implications for risk management in mountainous and volcanic regions. In this paper an avalanche model that incorporates frictional hysteresis, as well as depth-averaged viscous terms derived from the
-rheology, is used to quantitatively model self-channelisation and levee formation. The viscous terms are crucial for determining a smoothly varying steady-state velocity profile across the flowing channel, which has the important property that it does not exert any shear stresses at the levee–channel interfaces. For a fixed mass flux, the resulting boundary value problem for the velocity profile also uniquely determines the width and height of the channel, and the predictions are in very good agreement with existing experimental data for both spherical and angular particles. It is also shown that in the absence of viscous (second-order gradient) terms, the problem degenerates, to produce plug flow in the channel with two frictionless contact discontinuities at the levee–channel margins. Such solutions are not observed in experiments. Moreover, the steady-state inviscid problem lacks a thickness or width selection mechanism and consequently there is no unique solution. The viscous theory is therefore a significant step forward. Fully time-dependent numerical simulations to the viscous model are able to quantitatively capture the process in which the flow self-channelises and show how the levees are initially emplaced behind the flow head. Both experiments and numerical simulations show that the height and width of the channel are not necessarily fixed by these initial values, but respond to changes in the supplied mass flux, allowing narrowing and widening of the channel long after the initial front has passed by. In addition, below a critical mass flux the steady-state solutions become unstable and time-dependent numerical simulations are able to capture the transition to periodic erosion–deposition waves observed in experiments.
Shallow granular avalanches on slopes close to repose exhibit hysteretic behaviour. For instance, when a steady-uniform granular flow is brought to rest it leaves a deposit of thickness
on a rough slope inclined at an angle
to the horizontal. However, this layer will not spontaneously start to flow again until it is inclined to a higher angle
, or the thickness is increased to
. This simple phenomenology leads to a rich variety of flows with co-existing regions of solid-like and fluid-like granular behaviour that evolve in space and time. In particular, frictional hysteresis is directly responsible for the spontaneous formation of self-channelized flows with static levees, retrogressive failures as well as erosion–deposition waves that travel through the material. This paper is motivated by the experimental observation that a travelling-wave develops, when a steady uniform flow of carborundum particles on a bed of larger glass beads, runs out to leave a deposit that is approximately equal to
. Numerical simulations using the friction law originally proposed by Edwards et al. (J. Fluid Mech., vol. 823, 2017, pp. 278–315) and modified here, demonstrate that there are in fact two travelling waves. One that marks the trailing edge of the steady-uniform flow and another that rapidly deposits the particles, directly connecting the point of minimum dynamic friction (at thickness
) with the deposited layer. The first wave moves slightly faster than the second wave, and so there is a slowly expanding region between them in which the flow thins and the particles slow down. An exact inviscid solution for the second travelling wave is derived and it is shown that for a steady-uniform flow of thickness
it produces a deposit close to
for all inclination angles. Numerical simulations show that the two-wave structure deposits layers that are approximately equal to
for all initial thicknesses. This insensitivity to the initial conditions implies that
is a universal quantity, at least for carborundum particles on a bed of larger glass beads. Numerical simulations are therefore able to capture the complete experimental staircase procedure, which is commonly used to determine the
curves by progressively increasing the inclination of the chute. In general, however, the deposit thickness may depend on the depth of the flowing layer that generated it, so the most robust way to determine
is to measure the deposit thickness from a flow that was moving at the minimum steady-uniform velocity. Finally, some of the pathologies in earlier non-monotonic friction laws are discussed and it is explicitly shown that with these models either steadily travelling deposition waves do not form or they do not leave the correct deposit depth
Background: Cervical sponylotic myelopathy (CSM) may present with neck and arm pain. This study investiagtes the change in neck/arm pain post-operatively in CSM. Methods: This ambispective study llocated 402 patients through the Canadian Spine Outcomes and Research Network. Outcome measures were the visual analogue scales for neck and arm pain (VAS-NP and VAS-AP) and the neck disability index (NDI). The thresholds for minimum clinically important differences (MCIDs) for VAS-NP and VAS-AP were determined to be 2.6 and 4.1. Results: VAS-NP improved from mean of 5.6±2.9 to 3.8±2.7 at 12 months (P<0.001). VAS-AP improved from 5.8±2.9 to 3.5±3.0 at 12 months (P<0.001). The MCIDs for VAS-NP and VAS-AP were also reached at 12 months. Based on the NDI, patients were grouped into those with mild pain/no pain (33%) versus moderate/severe pain (67%). At 3 months, a significantly high proportion of patients with moderate/severe pain (45.8%) demonstrated an improvement into mild/no pain, whereas 27.2% with mild/no pain demonstrated worsening into moderate/severe pain (P <0.001). At 12 months, 17.4% with mild/no pain experienced worsening of their NDI (P<0.001). Conclusions: This study suggests that neck and arm pain responds to surgical decompression in patients with CSM and reaches the MCIDs for VAS-AP and VAS-NP at 12 months.
When a layer of static grains on a sufficiently steep slope is disturbed, an upslope-propagating erosion wave, or retrogressive failure, may form that separates the initially static material from a downslope region of flowing grains. This paper shows that a relatively simple depth-averaged avalanche model with frictional hysteresis is sufficient to capture a planar retrogressive failure that is independent of the cross-slope coordinate. The hysteresis is modelled with a non-monotonic effective basal friction law that has static, intermediate (velocity decreasing) and dynamic (velocity increasing) regimes. Both experiments and time-dependent numerical simulations show that steadily travelling retrogressive waves rapidly form in this system and a travelling wave ansatz is therefore used to derive a one-dimensional depth-averaged exact solution. The speed of the wave is determined by a critical point in the ordinary differential equation for the thickness. The critical point lies in the intermediate frictional regime, at the point where the friction exactly balances the downslope component of gravity. The retrogressive wave is therefore a sensitive test of the functional form of the friction law in this regime, where steady uniform flows are unstable and so cannot be used to determine the friction law directly. Upper and lower bounds for the existence of retrogressive waves in terms of the initial layer depth and the slope inclination are found and shown to be in good agreement with the experimentally determined phase diagram. For the friction law proposed by Edwards et al. (J. Fluid. Mech., vol. 823, 2017, pp. 278–315, J. Fluid. Mech., 2019, (submitted)) the magnitude of the wave speed is slightly under-predicted, but, for a given initial layer thickness, the exact solution accurately predicts an increase in the wave speed with higher inclinations. The model also captures the finite wave speed at the onset of retrogressive failure observed in experiments.
We investigate perturbations that maximize the gain of disturbance energy in a two-dimensional isolated vortex and a counter-rotating vortex pair. The optimization is carried out using the method of Lagrange multipliers. For low initial energy of the perturbation (
), the nonlinear optimal perturbation/gain is found to be the same as the linear optimal perturbation/gain. Beyond a certain threshold
, the optimal perturbation/gain obtained from linear and nonlinear computations are different. There exists a range of
for which the nonlinear optimal gain is higher than the linear optimal gain. For an isolated vortex, the higher value of nonlinear optimal gain is attributed to interaction among different azimuthal components, which is otherwise absent in a linearized system. Spiral dislocations are found in the nonlinear optimal perturbation at the radial location where the most dominant wavenumber changes. Long-time nonlinear evolution of linear and nonlinear optimal perturbations is studied. The evolution shows that, after the initial increment of perturbation energy, the vortex attains a quasi-steady state where the mean perturbation energy decreases on a slow time scale. The quasi-steady vortex state is non-axisymmetric and its shape depends on the initial perturbation. It is observed that the lifetime of a quasi-steady vortex state obtained using the nonlinear optimal perturbation is longer than that obtained using the linear optimal perturbation. For a counter-rotating vortex pair, the mechanism that maximizes the energy gain is found to be similar to that of the isolated vortex. Within the linear framework, the optimal perturbation for a vortex pair can be either symmetric or antisymmetric, whereas the structure of the nonlinear optimal perturbation, beyond the threshold
, is always asymmetric. No quasi-steady state for a counter-rotating vortex pair is observed.
Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15 cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems.
Small perturbations to a steady uniform granular chute flow can grow as the material moves downslope and develop into a series of surface waves that travel faster than the bulk flow. This roll wave instability has important implications for the mitigation of hazards due to geophysical mass flows, such as snow avalanches, debris flows and landslides, because the resulting waves tend to merge and become much deeper and more destructive than the uniform flow from which they form. Natural flows are usually highly polydisperse and their dynamics is significantly complicated by the particle size segregation that occurs within them. This study investigates the kinematics of such flows theoretically and through small-scale experiments that use a mixture of large and small glass spheres. It is shown that large particles, which segregate to the surface of the flow, are always concentrated near the crests of roll waves. There are different mechanisms for this depending on the relative speed of the waves, compared to the speed of particles at the free surface, as well as on the particle concentration. If all particles at the surface travel more slowly than the waves, the large particles become concentrated as the shock-like wavefronts pass them. This is due to a concertina-like effect in the frame of the moving wave, in which large particles move slowly backwards through the crest, but travel quickly in the troughs between the crests. If, instead, some particles on the surface travel more quickly than the wave and some move slower, then, at low concentrations, large particles can move towards the wave crest from both the forward and rearward sides. This results in isolated regions of large particles that are trapped at the crest of each wave, separated by regions where the flow is thinner and free of large particles. There is also a third regime arising when all surface particles travel faster than the waves, which has large particles present everywhere but with a sharp increase in their concentration towards the wave fronts. In all cases, the significantly enhanced large particle concentration at wave crests means that such flows in nature can be especially destructive and thus particularly hazardous.
We present the results of an experimental investigation of the motion of a light, solid sphere in a horizontal rotating cylinder filled with viscous fluid. At high rotation rates, the sphere sits near the axis of the cylinder. At lower rotation rates, a set of off-axis fixed points are observed for a range of sphere radii. The locations of these fixed points are in quantitative agreement with the predictions of a model based on available theory. The fixed points are observed to become unstable to periodic orbits below a critical Reynolds number
. The radius of the observed orbits increases with Reynolds number more slowly than a typical Hopf bifurcation, in this case, growing as
Introduction: TREKK is a national knowledge mobilization network of clinicians, researchers and parents aimed at improving emergency care for children by increasing collaborations between general and pediatric emergency departments (ED). This study aimed to determine patterns of knowledge sharing within the network and identify connections, barriers and opportunities to obtaining pediatric information and training. Methods: Social network analysis (SNA) uses network theory to understand patterns of interaction. Two SNAs were conducted in 2014 and 2015 using an online network survey distributed to 37 general EDs. Data was analyzed using UCI Net and Netdraw to identify connections, knowledge sharing and knowledge brokers within the network. Building on these results, we then conducted 22 semi-structured follow-up interviews (2016) with healthcare professionals (HCPs) at General EDs across Canada, purposefully sampled to include individuals from connected and disconnected sites, as identified in the SNA. Interviews were analyzed by 2 reviewers using content and thematic analysis. Results: SNA data was analyzed for 135 participants across the network. Results from 2014 showed that the network was divided along provincial lines, with most individuals connecting with colleagues within their own institution. Results from 2015 showed more inter-site interconnectivity and a reduction in isolated sites over time from 17 to 3. Interview participants included physicians (59%) and nurses (41%) from 18 general EDs in urban (68%) and rural/remote (32%) Canada. HCPs sought information both formally and informally, by using guidelines, talking to colleagues, and attending pediatric related training sessions. Network structure and processes were felt to increase connections, support practice change, and promote standards of care. Participants identified personal, organizational and system-level barriers to information and skill acquisition, including resources and personal costs, geography, dissemination, and time. Providing easy access to information at the point of care was promoted through enhancing content visibility and by embedding resources into local systems. There remains a need to share successful methods of local dissemination and implementation across the network, and to leverage local professional champions such as clinical nurse liaisons. Conclusion: This study highlights the power of a network to increase connections between HCPs working in general and pediatric EDs. Findings reinforce the critical role of ongoing network evaluation to improve the design and delivery of knowledge mobilization initiatives.
Giant ragweed is a highly competitive weed that continually threatens crop production systems due to evolved resistance to acetolactate synthase–inhibiting herbicides (ALS-R) and glyphosate (GR). Two biotypes of GR giant ragweed exist and are differentiated by their response to glyphosate, termed here as rapid response (RR) and non–rapid response (NRR). A comparison of data from surveys of Indiana crop fields done in 2006 and 2014 showed that GR giant ragweed has spread from 15% to 39% of Indiana counties and the NRR biotype is the most prevalent. A TaqMan® single-nucleotide polymorphism genotyping assay was developed to identify ALS-R populations and revealed 47% of GR populations to be ALS-R as well. The magnitude of glyphosate resistance for NRR populations was 4.6 and 5.9 based on GR50 and LD50 estimates, respectively. For RR populations, these values were 7.8 to 9.2 for GR50 estimates and 19.3 to 22.3 for LD50 estimates. A novel use of the Imaging-PAM fluorometer was developed to discriminate RR plants by assessing photosystem II quantum yield across the entire leaf surface. H2O2 generation in leaves of glyphosate-treated plants was also measured by 3,3′-diaminobenzidine staining and quantified using imagery analysis software. Results show photo-oxidative stress of mature leaves is far greater and occurs more rapidly following glyphosate treatment in RR plants compared with NRR and glyphosate-susceptible plants and is positively associated with glyphosate dose. These results suggest that under continued glyphosate selection pressure, the RR biotype may surpass the NRR biotype as the predominant form of GR giant ragweed in Indiana due to a higher level of glyphosate resistance. Moreover, the differential photo-oxidative stress patterns in response to glyphosate provide evidence of different mechanisms of resistance present in RR and NRR biotypes.
As the interest in Unmanned Aerial Systems (UAS) has increased, so has the interest in the application of these systems for use in agriculture. A variety of sensors, including Multi-Spectral, Near-Infrared, Thermal, and True-Color have the potential to benefit farmers when mounted to a UAS. But as this is an emerging field, there is little data available to demonstrate their use for early detection of plant diseases in crop production. In 2016, a preliminary study was launched to examine the potential of using aerial imagery from UAS to detect diseases in soybean crops. Two irrigated fields in Alabama were selected: Experiment 1, a 50-hectare field, and Experiment 2, a 5-hectare field. Each trial consisted of replicated plots using two foliar fungicide treatments and an untreated control. Aerial imagery (multi-spectral and true-color) was collected on a biweekly basis during this study. Using multi-spectral imagery, both the Normalized Difference Vegetative Index (NDVI) and Normalized Difference Red Edge Index (NDRE) were generated and compared to direct observations in the field. Disease severity of soybean rust, charcoal rot and Cercospora leaf blight were monitored on a biweekly basis and correlated to the UAS imagery. Preliminary results indicated plant stress can be detected using UAS imagery. In Experiment 1, stress associated with charcoal rot was visible in the NDRE imagery. This was of interest because at the time of flight, while it was noted that plants were yellowing, the root and stem disease itself had not been identified by direct observation. In Experiment 2, soybean rust was observed by direct observation and in both the NDRE and NDVI imagery. Soybean rust did have a negative impact on yield in Experiment 2, however severe drought conditions may have negated the yield loss likely caused by the development of charcoal rot in Experiment 1.
Although high dose n-3 PUFA supplementation reduces exercise- and hyperpnoea-induced bronchoconstriction (EIB/HIB), there are concurrent issues with cost, compliance and gastrointestinal discomfort. It is thus pertinent to establish the efficacy of lower n-3 PUFA doses. Eight male adults with asthma and HIB and eight controls without asthma were randomly supplemented with two n-3 PUFA doses (6·2 g/d (3·7 g EPA and 2·5 g DHA) and 3·1 g/d (1·8 g EPA and 1·3 g DHA)) and a placebo, each for 21 d followed by 14 d washout. A eucapnic voluntary hyperpnoea (EVH) challenge was performed before and after treatments. Outcome measures remained unchanged in the control group. In the HIB group, the peak fall in forced expiratory volume in 1 s (FEV1) after EVH at day 0 (−1005 (sd 520) ml, −30 (sd 18) %) was unchanged after placebo. The peak fall in FEV1 was similarly reduced from day 0 to day 21 of 6·2 g/d n-3 PUFA (−1000 (sd 460) ml, −29 (sd 17) % v. −690 (sd 460) ml, −20 (sd 15) %) and 3·1 g/d n-3 PUFA (−970 (sd 480) ml, −28 (sd 18) % v. −700 (sd 420) ml, −21 (sd 15) %) (P<0·001). Baseline fraction of exhaled nitric oxide was reduced by 24 % (P=0·020) and 31 % (P=0·018) after 6·2 and 3·1 g/d n-3 PUFA, respectively. Peak increases in 9α, 11β PGF2 after EVH were reduced by 65 % (P=0·009) and 56 % (P=0·041) after 6·2 and 3·1 g/d n-3 PUFA, respectively. In conclusion, 3·1 g/d n-3 PUFA supplementation attenuated HIB and markers of airway inflammation to a similar extent as a higher dose. Lower doses of n-3 PUFA thus represent a potentially beneficial adjunct treatment for adults with asthma and EIB.
Introduction: Online medical education resources are becoming an increasingly used modality and many studies have demonstrated their efficacy in procedural instruction. This study sought to determine whether a standardized online procedural video is as effective as a standard recorded didactic teaching session for chest tube insertion. Methods: A randomized control trial was conducted. Participants were taught how to insert a chest tube with either a recorded didactic teaching session, or a New England Journal of Medicine (NEJM) video. Participants filled out a questionnaire before and after performing the procedure on a cadaver, which was filmed and assessed by two blinded evaluators using a standardized tool. Thirty 4th year medical students from two graduating classes at the Schulich School of Medicine & Dentistry in London, ON were screened for eligibility. Two students did not complete the study, and were excluded. There were 13 students in the NEJM group, and 15 students in the ATLS group. Results: The NEJM group’s average score was 45.2% (±9.6) on the pre-questionnaire, 67.7% (±12.9) for the procedure, and 60.1% (±7.7) on the post-questionnaire. The didactic group’s average score was 42.8% (±10.9) on the pre-questionnaire, 73.7% (±9.9) for the procedure, and 46.5% (±7.5) on the post-questionnaire. There was no difference between the groups on the pre-questionnaire (Δ +2.4%; 95% CI: −5.2, 10.0), or the procedure (Δ −6.0%; 95% CI: −14.6, 2.7). The NEJM group had better scores on the post-questionnaire (Δ +11.15%; 95% CI: 3.7, 18.6). Conclusion: The NEJM video was as effective as video-recorded training for teaching the knowledge and technical skills essential for chest tube insertion. Participants expressed high satisfaction with this modality. It may prove to be a helpful adjunct to standard instruction on the topic.
Geophysical granular flows, such as avalanches, debris flows, lahars and pyroclastic flows, are always strongly influenced by the basal topography that they flow over. In particular, localised bumps or obstacles can generate rapid changes in the flow thickness and velocity, or shock waves, which dissipate significant amounts of energy. Understanding how a granular material is affected by the underlying topography is therefore crucial for hazard mitigation purposes, for example to improve the design of deflecting or catching dams for snow avalanches. Moreover, the interactions with solid boundaries can also have important applications in industrial processes. In this paper, small-scale experiments are performed to investigate the flow of a granular avalanche over a two-dimensional smooth symmetrical bump. The experiments show that, depending on the initial conditions, two different steady-state regimes can be observed: either the formation of a detached jet downstream of the bump, or a shock upstream of it. The transition between the two cases can be controlled by adding varying amounts of erodible particles in front of the obstacle. A depth-averaged terrain-following avalanche theory that is formulated in curvilinear coordinates is used to model the system. The results show good agreement with the experiments for both regimes. For the case of a shock, time-dependent numerical simulations of the full system show the evolution to the equilibrium state, as well as the deposition of particles upstream of the bump when the inflow ceases. The terrain-following theory is compared to a standard depth-averaged avalanche model in an aligned Cartesian coordinate system. For this very sensitive problem, it is shown that the steady-shock regime is captured significantly better by the terrain-following avalanche model, and that the standard theory is unable to predict the take-off point of the jet. To retain the practical simplicity of using Cartesian coordinates, but have the improved predictive power of the terrain-following model, a coordinate mapping is used to transform the terrain-following equations from curvilinear to Cartesian coordinates. The terrain-following model, in Cartesian coordinates, makes identical predictions to the original curvilinear formulation, but is much simpler to implement.
To validate the ovine model of profound oropharyngeal dysphagia and compare swallowing outcomes of laryngotracheal separation with those of total laryngectomy.
Under real-time fluoroscopy, swallowing trials were conducted using the head and neck of two Dorper cross ewes and one human cadaver, secured in lateral fluoroscopic orientation. Barium trials were administered at baseline, pre- and post-laryngohyoid suspension, following laryngotracheal separation, and following laryngectomy in the ovine model.
Mean pre-intervention Penetration Aspiration Scale and National Institutes of Health Swallow Safety Scale scores were 8 ± 0 and 6 ± 0 respectively in sheep and human cadavers, with 100 per cent intra- and inter-species reproducibility. These scores improved to 1 ± 0 and 2 ± 0 post-laryngohyoid suspension (p < 0.01). Aerodigestive tract residue was 18.6 ± 2.4 ml at baseline, 15.4 ± 3.8 ml after laryngotracheal separation and 3.0 ± 0.7 ml after total laryngectomy (p < 0.001).
The ovine model displayed perfect intra- and inter- species reliability for the Penetration Aspiration Scale and Swallow Safety Scale. Less aerodigestive tract residue after narrow-field laryngectomy suggests that swallowing outcomes after total laryngectomy are superior to those after laryngotracheal separation.