We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The instability of a shear flow passing over a wavy wall with wave crests not perpendicular to the flow direction is investigated. The friction Reynolds number for the flow is large and the wave amplitude scaled on the wavelength is small compared with the viscous wall layer. The instability takes the form of a streamwise vortex of wavelength comparable to the viscous wall layer in which the basic flow adjusts to the presence of the wall. For a given wall amplitude, the instability considered is the first one to arise as the Reynolds number is increased and modes of wavelength comparable to the viscous layer grow much faster than modes of wavelength comparable to the wall wavelength. The instability is not driven by centrifugal or viscous effects but is a novel kind of cross-flow vortex instability associated with a spatially periodic flow; the existence of the instability is associated with the orientation of the wave crests. The instability is investigated for wavelengths comparable to the depth of the viscous wall layer; the limiting cases of large and small wavelengths are investigated asymptotically. At small wavenumbers and roughness heights the instability connects with disturbances of wavelength comparable to the wall wavelength. At high wavenumbers and roughness heights a new structure emerges and the disturbance moves away from the wall, that structure takes on a self-similar form with progressively faster variations in the streamwise and spanwise directions as the roughness height increases.
OBJECTIVES/GOALS: Through the Community Mini-Grant program, the University of Kentucky Center for Clinical and Translational Science Community Engagement and Research Core (CERC) provides a unique funding mechanism designed to empower community response by supporting local solutions to complex health issues facing central Appalachian Kentucky communities. METHODS/STUDY POPULATION: Four $2500 grants are awarded annually to Appalachian organizations to implement evidence-based programs responsive to community-identified priority health needs. The CERC also supports program implementation and evaluation by facilitating collaborations between the organizations, community practitioners, and academic researchers. RESULTS/ANTICIPATED RESULTS: Since inception, grants have been awarded to 20 community organizations in 14 Appalachian counties. Health issues addressed have ranged from Alzheimers disease, cancer treatment and prevention, obesity, healthy lifestyle, and chronic disease management and prevention. Evidence-based programs have focused on improving health outcomes among older adults, caregivers, youth, children, women and infants, and families. Program outcomes have included immediate health benefits and long-term benefits resulting from community adoption of and ongoing financial support for programs. As example, results of an evidence-based educational program to improve diabetic foot assessment among clinicians in a large Appalachian healthcare network resulted in establishment of a traveling podiatrist program. DISCUSSION/SIGNIFICANCE: Community mini-grant recipients have successfully implemented projects that address the most significant health disparities in the region. Also of benefit are expanded partnerships that are foundational to the creation of new academic-community collaborations to address the challenging health issues of Appalachian populations in Kentucky.
There are numerous examples of translational science innovations addressing challenges in the translational process, accelerating progress along the translational spectrum, and generating solutions relevant to a wide range of human health needs. Examining these successes through an education lens can identify core principles and effective practices that lead to successful translational outcomes. The National Center for Advancing Translational Sciences (NCATS) is identifying and teaching these core principles and practices to a broad audience via online courses in translational science which teach from case studies of NCATS-led or supported research initiatives. In this paper, we share our approach to the design of these courses and offer a detailed description of our initial course, which focused on a preclinical drug discovery and development project spanning academic and government settings. Course participants were from a variety of career stages and institutions. Participants rated the course high in overall value to them and in providing a unique window into the translational science process. We share our model for course development as well as initial findings from the course evaluation with the goal of continuing to stimulate development of novel education activities teaching foundational principles in translational science to a broad audience.
A strongly nonlinear theory describing the effect of small amplitude boundary forcing in the form of waves on high Reynolds number shear flows is given. The interaction leads to an $O(1)$ change in the unperturbed flow and is relevant to a number of forcing mechanisms. The cases of the shear flow being bounded or unbounded are both considered and the results for the unbounded case apply to quite arbitrary flows. The instability criterion for unbounded flows is expressed in terms of the wall forcing and the friction Reynolds number. As particular examples we investigate wall transpiration or surface undulations as sources of the forcing and both propagating and stationary waves are considered. Results are given for propagating waves with crests perpendicular to the flow direction and for stationary waves with crests no longer perpendicular to the flow direction. In the first of those situations we find the instability induced by transpiration waves is independent of the propagation speed. For wavy walls downstream propagation completely stabilises the flow at a critical speed whereas upstream propagation greatly destabilises the flow. For stationary oblique waves we find that the instability is enhanced and a much wider range of unstable wavenumbers exists. For the bounded case with a wall of fixed wavelength we identify a critical wavelength where the most dangerous mode switches from the aligned to the oblique configuration. For the transpiration problem in the oblique configuration a strong resonance occurs when the vortex wavelength coincides with the spanwise wavelength of the forcing.
As a first step towards the description of coherent structures in compressible shear flows, we present an asymptotic description of nonlinear travelling-wave solutions of the Navier–Stokes equations in the compressible asymptotic suction boundary layer (ASBL). We consider free-stream Mach numbers $M_\infty$ in the subsonic and moderate supersonic regime so that $0\leqslant M_\infty \leqslant 2$. We extend the large-Reynolds-number asymptotic theory of Deguchi & Hall (J. Fluid Mech., vol. 752, 2014, pp. 602–625) describing ‘free-stream’ coherent structures in incompressible ASBL flow to describe a nonlinear interaction in a thin layer situated just below the free stream. Crucially, the nonlinear interaction equations for the velocity field in this layer are identical to those obtained in the incompressible problem, and thus the asymptotic analysis supporting free-stream coherent structures in compressible ASBL is easily deduced from its incompressible counterpart. The nonlinear interaction produces streaky disturbances to both the velocity and temperature fields, which can grow exponentially towards the wall. We complete the description of the growth of the velocity and thermal streaks throughout the flow by solving the compressible boundary-region equations numerically. We show that the velocity and thermal streaks obtain their maximum amplitude in the unperturbed boundary layer. Increasing the free-stream Mach number enhances the thermal streaks and suppresses the velocity streaks, whereas varying the Prandtl number suppresses the velocity streaks, and can either enhance or suppress the thermal streaks depending on whether the flow is in the subsonic or moderate supersonic regime. Such nonlinear equilibrium states have been implicated in shear transition in incompressible flows; therefore, our results indicate that a similar mechanism may also be present in compressible flows.
A large-Reynolds-number asymptotic reduction of the Navier–Stokes equations capable of describing a locally periodic vortex-wave array and the associated large-scale variation of the mean-shear velocity field first suggested in Hall (J. Fluid Mech., vol. 850, 2018, pp. 46–82) is extended. The sustaining process of the locally periodic coherent structures is based on the vortex-wave interaction theory of Hall & Smith (J. Fluid Mech., vol. 227, 1991, 641–666), wherein two-dimensional roll–streak fields are supported by localised nonlinear self-interactions of three-dimensional waves that are largest in size within critical layers of the streak field. The variation of the mean velocity is made possible by incorporating a slow change to the mean profile using a Wentzel–Kramers–Brillouin-type approach. As the first extension, we demonstrate that the local structure corresponds to the asymptotic limit of computations in a shearing box. A variety of solutions with different symmetry properties are found via the hybrid numerical asymptotic approach of Blackburn, Hall & Sherwin (J. Fluid Mech. vol. 721, 2013, 58–85). Moreover, some solutions show generic flow features such as uniform momentum zones and spatial intermittency known to occur in near-wall turbulent boundary layers. We extend the vortex-wave interaction array theory to show that, in addition to a Reynolds-averaged-Navier–Stokes-type relationship between the large-scale vertical variation of the mean flow and local roll–streak scale, a higher-order analysis gives a second constraint on the slow-scale dynamics. Those constraints are used for the first time to derive the logarithmic law of the wall through a closed asymptotic analysis of self-similar local coherent structures, consistent with the attached eddy hypothesis.
Families of exact coherent states in elliptical pipe flow obtained from the travelling-wave solutions in circular pipe flow by a continuation approach are found. Results are given in a regime of the aspect ratio $A$ in which the laminar flow is linearly stable. The results suggest the possibility of two distinct classes of solutions of elliptical travelling waves at higher values of $A$: (i) rotationally symmetric centre-mode states that collapse towards the pipe centre and (ii) rotationally asymmetric vortex–wave interaction states with additional mirror symmetry exhibiting organization of the waves around a critical layer. These are the first calculations of three-dimensional travelling waves in elliptical pipes. Investigation of these states has the potential to provide fresh insight into the relationship between exact coherent structures in Poiseuille flow in pipes and channels.
The streamwise vortex instability of boundary layers caused by wall roughness in the form of surface undulations is investigated. The instability is characterised by a roughness parameter $\varGamma$ depending on the geometry and fluid properties. At $O(1)$ values of $\varGamma$ disturbances develop on the same length scale as the basic boundary layer flow. The instability is driven by a boundary condition relating the disturbance wall shears in the streamwise and normal directions. The undulations have a wavelength comparable with the boundary layer depth and the amplitude is asymptotically small compared with the depth. If the roughness parameter is large then, apart from a narrow window of vortex wavenumbers, the instability responds in a quasi-parallel manner. Falkner–Skan boundary layers are considered in detail and the dependence on the angle of the wedge associated with the flows investigated. A particular susceptibility to roughness instabilities of flows past $90^{\circ }$ wedges is uncovered. The limits of small and large wavenumbers are considered and universal results given for the critical roughness height $h$ and wavelength $b$ needed for instability.
The aim of this quality improvement project is to improve identification and management of mood disorder in patients over 65 years admitted to Royal Surrey County Hospital (RSCH) with hip fractures by introducing a standardised assessment tool to guide appropriate interventions.
Background
The signs of depression in the elderly can be subtle and often go unnoticed. The multidisciplinary team (MDT) at RSCH observed that low mood could negatively impact on a patient's recovery, affecting pain thresholds and leading to poor engagement with rehabilitation. Proactive identification and management of mood disorder is an important part of Comprehensive Geriatric Assessment but not routinely performed in patients with hip fracture admitted to RSCH.
Method
Notes and discharge summaries of patients with hip fracture admitted over a four-month period were retrospectively reviewed to establish if patients were screened for low mood. A mood screening tool was chosen and implemented prospectively over a four-month period. Occupational therapists and junior doctors completed a Cornell Score for all patinets. Those identified with depression or probable depression were issued verbal advice, an information leaflet and follow-up arranged.
Result
Ninety-eight patients were included in the retrospective cohort. No patients were formally identified as having depression or probable depression, and there was no indication that mood was considered or assessed at any point during admission. During the four-month prospective period, 90 patients were admitted to RSCH with hip fracture and 86 patients (96%) were screened for low mood. Four patients were excluded due to a terminal prognosis. Of the patients screened, 9% had major depression and 16% probable depression. Feedback from our occupational therapists and doctors was positive, with the tool being relatively easy to use in patients with or without cognitive impairment. Much of the assessment could be incorporated into their initial assessment or in gaining collateral history from next of kin. Anecdotally, considering patients psychological well-being had a positive impact on inpatient therapy sessions guided the MDT in supporting the patient appropriately.
Conclusion
Implementation of a standardised and validated mood screening tool enabled us to identify that a quarter (25%) of the patients admitted following a hip fracture had, or probably had depression. This allowed us to intervene with simple measures such as verbal advice and an information leaflet and consider pharmacological intervention where appropriate.
The instability of Hagen–Poiseuille flow in a rough pipe is considered and it is shown that for arbitrarily small roughness amplitudes the flow is unstable for sufficiently large values of the Reynolds number. Various models of wall roughness are considered and, if $\epsilon$ is a typical amplitude of the roughness, it is shown that the flow is unstable when the Reynolds number $R> C {\epsilon ^{-({3}/{2})} \vert {\log \epsilon }\vert ^{-({3}/{4})}}$ where $C$ is a constant which depends on the roughness shape and is typically in the range 10–40. The roughness is assumed to vary on the same length scale as the pipe radius. In the limit of short scale roughness varying most quickly in the streamwise direction, a quite general condition for instability, $R_b > {3.16 [{b}/{h}]^{3/4}} /{(\log [{b}/{h}])^{3/8}}$, is found in terms of just the Reynolds number $R_b$ based on the friction velocity, the streamwise length scale $b$ and $h$, the height of the roughness. The instability mechanism described is closely linked to vortex–wave interaction theory and applies to both two- and three-dimensional roughness shapes and takes the form of a roll-streak-wave flow. The interaction sustaining the instability occurs in a viscous boundary layer at the pipe wall but the roll-streak flow persists throughout the pipe. The most dangerous roughness shapes are found and generic results are also given for when the roughness length scale is small compared to the pipe radius.
The instability of the flow in a two-dimensional meandering channel of slowly varying depth is considered. The flow is characterised by $\delta$ the typical slope of the channel walls and the modified Reynolds number $R_m$ which is the usual Reynolds number multiplied by $\delta$. The modified Reynolds number is shown to be the appropriate parameter controlling the instability of the flow to streamwise vortices periodic in the spanwise direction. In particular, channels periodic in the streamwise direction are considered and it is found that the most unstable mode can correspond to either a subharmonic or synchronous disturbance. The instability problem at finite $R_m$ is discussed first and then the inviscid and large wavenumber regimes are discussed in detail. The instability is shown to be a hybrid form of centrifugal instability having properties of both Görtler vortices and a parametric resonance usually referred to as an elliptic instability. The limiting case of small wall modulation amplitudes is investigated and the results suggest that at small amplitudes the subharmonic mode is always dominant.
The flow in a channel having walls with periodic undulations of small amplitude $\epsilon$ in the streamwise direction is considered as a model for wall roughness. It is shown that the undulations act as a catalyst to allow a new instability related to vortex–wave interactions to grow. The roughness couples a wave disturbance with a roll–streak flow and it is shown that channel flows, both wall and pressure gradient driven, are unstable when the Reynolds number exceeds a critical value proportional to ${\epsilon ^{-({3}/{2})} [\vert {\log \epsilon }\vert ]^{-({3}/{4})}}$, the constant of proportionality depending on the wall wavelengths and amplitudes. The roughness is an integral part of the instability mechanism and not simply the seed for an existing flow instability as in receptivity theory. The mechanism involves an interaction of the rolls, streaks and waves very similar to that in vortex–wave interaction theory but now facilitated by the wall roughness. Surprisingly, the subtle interaction between waves, rolls, streaks and the walls can be solved in closed form, and an explicit form for the neutral configuration is found. The theoretical predictions are in good agreement with numerical investigations of similar problems and are applicable to a wide range of shear flows.
We are very happy that someone has finally tried to make sense of rationalization. But we are worried about the representational structure assumed by Cushman, particularly the “boxology” belief-desire model depicting the rational planner, and it seems to us he fails to accommodate many of the interpersonal aspects of representational exchange.
In this paper, we present computational results of some two-fold azimuthally symmetric travelling waves and their stability. Calculations over a range of Reynolds numbers ($Re$) reveal connections between a class of solutions computed by Wedin & Kerswell (J. Fluid Mech., vol. 508, 2004, pp. 333–371) (henceforth called the WK solution) and the $Re\rightarrow \infty$ vortex–wave interaction theory of Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666) and Hall & Sherwin (J. Fluid Mech., vol. 661, 2010, pp. 178–205). In particular, the continuation of the WK solutions to larger values of $Re$ shows that the WK solution bifurcates from a shift-and-rotate symmetric solution, which we call the WK2 state. The WK2 solution computed for $Re\leqslant 1.19\times 10^{6}$ shows excellent agreement with the theoretical $Re^{-5/6}$, $Re^{-1}$ and $O(1)$ scalings of the waves, rolls and streaks respectively. Furthermore, these states are found to have only two unstable modes in the large $Re$ regime, with growth rates estimated to be $O(Re^{-0.42})$ and $O(Re^{-0.92})$, close to the theoretical $O(Re^{-1/2})$ and $O(Re^{-1})$ asymptotic results for edge and sinuous instability modes of vortex–wave interaction states (Deguchi & Hall, J. Fluid Mech., vol. 802, 2016, pp. 634–666) in plane Couette flow. For the nonlinear viscous core states (Ozcakir et al., J. Fluid Mech., vol. 791, 2016, pp. 284–328), characterized by spatial a shrinking of the wave and roll structure towards the pipe centre with increasing $Re$, we continued the solution to $Re\leqslant 8\times 10^{6}$ and we find only one unstable mode in the large Reynolds number regime, with growth rate scaling as $Re^{-0.46}$ within the class of symmetry-preserving disturbances.
Vortex–wave interaction theory is used to describe new kinds of localised and distributed exact coherent structures. Starting with a localised vortex–wave interaction state driven by a single inviscid wave, regular arrays of interacting vortex–wave states are investigated. In the first instance the arrays described are operational in an infinite uniform shear flow; we refer to them as ‘uniform shear vortex–wave arrays’. The basic form of the interaction remains identical to the canonical one found by Hall & Smith (J. Fluid Mech., vol. 227, 1991, pp. 641–666) and subsequently used to describe exact coherent structures by Hall & Sherwin (J. Fluid Mech., vol. 661, 2010, pp. 178–205). Thus in each cell of a vortex–wave array a roll stress jump is induced across the critical layer of an inviscid wave riding on the streak part of the flow. The theory is extended to arbitrary shear flows using a nonlinear Wentzel–Kramers–Brillouin–Jeffreys or ray theory approach with the wave–roll–streak field operating on a shorter length scale than the mean flow. The evolution equation governing the slow dynamics of the interaction turns out to be a modified form of the well-known mean equation for a turbulent flow, and its particular form can be interpreted as a ‘closure’ between the small and large scales of the flow. If the array structure is taken to be universal, in the sense that it applies to arbitrary shear flows, then the array takes on a form which supports a logarithmic mean velocity profile trapped between what can be identified with the ‘wake region’ and a ‘buffer layer’ well known in the context of wall-bounded turbulent flows. The many similarities between the distributed structures described and wall-bounded turbulence suggest that vortex–wave arrays might be involved in the self-sustaining process supporting the log layer. The modification of the mean profile within each cell of the array leads to ‘staircase’-like streamwise velocity profiles similar to those observed experimentally in turbulent flows. The wave field supporting the ‘staircase’ is concentrated in critical layers which can be associated with the shear layer structures that have been attributed by experimentalists to be the mechanism supporting the uniform-momentum zones of the staircase.
The free-stream coherent structure theory developed by Deguchi & Hall (J. Fluid Mech., vol. 752, 2014, pp. 602–625), valid in the large-Reynolds-number asymptotic limit, is extended and applied to jet flows. It is shown that a nonlinear exact coherent structure can be supported at the edge of the jet, and the structure induces a much bigger streaky flow in the centre of the jet. The lambda-shaped vortices that characterise the coherent structure are qualitatively consistent with those seen in experimental observations. Here a planar incompressible jet is investigated for the sake of simplicity, but the structure we describe could be used as a basis of more complex theories for incompressible and compressible jets of practical importance.
Halosulfuron-methyl, a sulfonylurea herbicide, was registered for broadleaf weed control in dry bean. This herbicide has an adequate margin of crop safety in white bean, but causes unacceptable injury to adzuki bean. Halosulfuron-methyl absorption, translocation, and metabolism were evaluated in white and adzuki bean using radiolabeled herbicide to determine if differences in these parameters could explain the difference in crop safety between these two species. Adzuki bean had more rapid halosulfuron-methyl absorption than white bean. Adzuki bean reached 90% absorption (t90) 26.2 h after treatment (HAT), whereas white bean required 40.1 HAT to reach t90. The maximum halosulfuron-methyl absorption was higher in adzuki bean (75.7%) than in white bean (65.3%). More 14C-halosulfuron was translocated to the apex, first trifoliate, stem above the treated leaf, and roots in aduzki bean than in white bean. The maximum radioactivity translocated out of treated leaf was higher in adzuki bean (17.7%) than in white bean (12.1%). Halosulfuron-methyl was broken down to the same metabolites in white and adzuki bean. The half-life of halosulfuron-methyl in adzuki bean was 16 HAT, compared with less than 6 HAT in white bean. More herbicide remained as the free acid in adzuki bean compared with white bean over the entire 48-h time course. The differential tolerance of white and adzuki bean to halosulfuron can be attributed to greater absorption and translocation and decreased metabolism in adzuki bean.
In recent years it has been established that vortex–wave interaction theory forms an asymptotic framework to describe high Reynolds number coherent structures in shear flows. Comparisons between the asymptotic approach and finite Reynolds number computations of equilibrium states from the full Navier–Stokes equations have suggested that the asymptotic approach is extremely accurate even at quite low Reynolds numbers. However, unlike the situation with an approach based on solving the full Navier–Stokes equations numerically, the vortex–wave interaction approach has not yet been developed to study the instability of the structures it describes. In this work, a comprehensive study of the different instabilities of vortex–wave interaction states is given and it is shown that there are three different time scales on which instabilities can develop. The most dangerous type is a rapidly growing Rayleigh instability of the streak part of the flow. The least dangerous type is a slow mode operating on the diffusion time scale of the roll–streak part of the flow. The third mode of instability, which we will refer to as the edge mode of instability, occurs on a time scale midway between those of the other two modes. The existence of the latter mode explains why some exact coherent structures can act as edge states between the laminar and turbulent attractors. These stability results are compared to results from Navier–Stokes calculations.
Impulse control disorders (ICDs) have become a widely recognized non-motor complication of Parkinson's disease (PD) in patients taking dopamine replacement therapy (DRT). There are no current evidence-based recommendations for their treatment, other than reducing their dopaminergic medication.
Methods:
This study reviews the current literature of the treatment of ICDs including pharmacological treatments, deep brain stimulation, and psychotherapeutic interventions.
Results:
Dopamine agonist withdrawal is the most common and effective treatment, but may lead to an aversive withdrawal syndrome or motor symptom degeneration in some individuals. There is insufficient evidence for all other pharmacological treatments in treating ICDs in PD, including amantadine, serotonin selective reuptake inhibitors, antipsychotics, anticonvulsants, and opioid antagonists (e.g. naltrexone). Large randomized control trials need to be performed before these drugs can be routinely used for the treatment of ICDs in PD. Deep brain stimulation remains equivocal because ICD symptoms resolve in some patients after surgery but may appear de novo in others. Cognitive behavioral therapy has been shown to improve ICD symptoms in the only published study, although further research is urgently needed.
Conclusions:
Further research will allow for the development of evidence-based guidelines for the management of ICDs in PD.