Large-scale self-organization in dry turbulent atmospheres.

How turbulent convective fluctuations organize to form larger-scale structures in planetary atmospheres remains a question that eludes quantitative answers. The assumption that this process is the result of an inverse cascade was suggested half a century ago in two-dimensional fluids, but its applicability to atmospheric and oceanic flows remains heavily debated, hampering our understanding of the energy balance in planetary systems. We show using direct numerical simulations with spatial resolutions of 122882 × 384 points that rotating and stratified flows can support a bidirectional cascade of energy, in three dimensions, with a ratio of Rossby to Froude numbers comparable to that of Earth's atmosphere. Our results establish that, in dry atmospheres, spontaneous order can arise through an inverse cascade to the largest spatial scales.

Stratification of Outpatient Physical Therapy Following Total Knee Arthroplasty: Knee Arthroplasty Physical Therapy Pathways (KAPPA) Nonrandomized Controlled Trial.

BACKGROUND: Outpatient physical therapy following total knee arthroplasty (TKA) is often considered crucial for an effective recovery. However, recent evidence suggests that a self-directed pathway may yield similar benefits to supervised care. Despite this, there appear to be no established criteria to determine who can successfully self-direct their rehabilitation versus those who would benefit from outpatient physical therapy. This study aimed to determine if early postoperative criteria can stratify TKA patients into a self-directed or supervised physical therapy pathway without compromising outcomes. METHODS: Overall, 60 TKA patients were initially allocated to a self-directed, unsupervised protocol for their postoperative rehabilitation. Baseline demographics, along with functional and self-reported outcomes, were assessed preoperatively and at 2 weeks, 6 weeks, and 4 months following surgery. Patients were referred to supervised outpatient physical therapy if they met any of the following Knee Arthroplasty Physical Therapy Pathways (KAPPA) criteria: (1) knee flexion range of motion <90 degrees; (2) knee extension range of motion lacking >10 degrees; or (3) dissatisfaction with the progress of their rehabilitation. RESULTS: At 2 weeks post-TKA, 28 participants met the KAPPA criteria for supervised physical therapy for reasons of knee flexion <90 degrees (61%), a lack of knee extension >10 degrees (36%), or not being satisfied with the progress of their recovery (3%). The remaining 32 participants continued with a self-directed rehabilitation pathway. All outcomes assessed favored the self-directed group at 2 weeks, however, after an average of 4 supervised physical therapy sessions at 4 months there were no longer any differences between the 2 groups. CONCLUSIONS: Over half of the included participants could self-direct their rehabilitation following TKA without supervised physical therapy while also maintaining excellent clinical outcomes. For those who met KAPPA criteria at 2 weeks post-TKA, 4 supervised physical therapy sessions appeared to be beneficial when outcomes were reassessed at 4 months.

The addition of structured lifestyle modifications to a traditional exercise program for the management of patients with knee osteoarthritis: A systematic review and meta-analysis of randomised trials.

BACKGROUND: Guidelines recommend exercise for the management of knee osteoarthritis (OA), however, recently it has been suggested that including additional lifestyle modifications with a traditional exercise program may elicit greater benefits than exercise alone. OBJECTIVES: To investigate the influence of the addition of lifestyle modifications to a traditional exercise program, with respect to functional outcomes and quality of life among individuals with knee OA. DESIGN: Systematic review and meta-analysis. METHODS: Four databases were searched to identify randomised controlled trials comparing an exercise program, which included the addition of lifestyle modifications, to an exercise program alone in individuals with knee OA. Methodological quality of included studies was assessed via the PEDro scale. Results synthesis through meta-analysis using a random effects model was conducted to determine the pooled effect on eligible outcomes and a GRADE approach was utilised to rate the certainty of evidence. RESULTS: Meta-analysis of seven studies showed the inclusion of lifestyle modifications to an exercise program can further decrease pain intensity (SMD -0.68 [95% CI -1.26 to -0.10]), improve joint stiffness (MD -0.69 [95% CI -1.21, -0.17]) and increase physical function (MD -1.26 s ([95% CI -1.34, -1.17]) at six-months. Individual results showed improvements in quality of life with the addition of lifestyle modifications, however, this was not demonstrated through meta-analysis. CONCLUSION: This systematic review supports the inclusion of additional lifestyle modifications to a traditional exercise program, for pain intensity, joint stiffness and physical function for individuals with knee OA. TRIAL REGISTRATION: PROSPERO registration number: CRD42021279594.

Collisions of localized patterns in a nonvariational Swift-Hohenberg equation.

The cubic-quintic Swift-Hohenberg equation (SH35) has been proposed as an order parameter description of several convective systems with reflection symmetry in the layer midplane, including binary fluid convection. We use numerical continuation, together with extensive direct numerical simulations (DNSs), to study SH35 with an additional nonvariational quadratic term to model the effects of breaking the midplane reflection symmetry. The nonvariational structure of the model leads to the propagation of asymmetric spatially localized structures (LSs). An asymptotic prediction for the drift velocity of such structures, derived in the limit of weak symmetry breaking, is validated numerically. Next, we present an extensive study of possible collision scenarios between identical and nonidentical traveling structures, varying a temperaturelike control parameter. These collisions are inelastic and result in stationary or traveling structures. Depending on system parameters and the types of structures colliding, the final state may be a simple bound state of the initial LSs, but it can also be longer or shorter than the sum of the two initial states as a result of nonlinear interactions. The Maxwell point of the variational system, where the free energy of the global pattern state equals that of the trivial state, is shown to have no bearing on which of these scenarios is realized. Instead, we argue that the stability properties of bound states are key. While individual LSs lie on a modified snakes-and-ladders structure in the nonvariational SH35, the multipulse bound states resulting from collisions lie on isolas in parameter space, disconnected from the trivial solution. In the gradient SH35, such isolas are always of figure-eight shape, but in the present nongradient case they are generically more complex, although the figure-eight shape is preserved in a small subset of cases. Some of these complex isolas are shown to terminate in T-point bifurcations. A reduced model is proposed to describe the interactions between the tails of the LSs. The model consists of two coupled ordinary differential equations (ODEs) capturing the oscillatory nature of SH35 profiles at the linear level. It contains three parameters: two interaction amplitudes and a phase, whose values are deduced from high-resolution DNSs using gradient descent optimization. For collisions leading to the formation of simple bound states, the reduced model reproduces the trajectories of LSs with high quantitative accuracy. When nonlinear interactions lead to the creation or deletion of wavelengths, the model performs less well. Finally, we propose an effective signature of a given interaction in terms of net attraction or repulsion relative to free propagation. It is found that interactions can be attractive or repulsive in the net, irrespective of whether the two closest interacting extrema are of the same or opposite signs. Our findings highlight the rich temporal dynamics described by this bistable nonvariational SH35, and show that the interactions in this system can be quantitatively captured, to a significant extent, by a highly reduced ODE model.

An open-label clinical trial of oral transmucosal haloperidol and oral transmucosal olanzapine in the treatment of terminal delirium at home.

BACKGROUND: The phenomenon of restlessness, agitation, or cognitive disturbances experienced by dying patients is well-known in palliative care; more than half of these patients will experience delirium symptoms at end-of-life. When not identified early and effectively managed, delirium symptoms could lead to caregiver and patient distress and harm. METHODS: Eighty patients with a prognosis of 7 days or less will be recruited for an open-label randomised control trial. The two arms compare oral-transmucosal haloperidol 2.5 mg vs olanzapine 5 mg over 72 h. The severity of agitation, delirium and toxicities of treatments will be compared at the 24th, 48th and 72nd hour after drug administration. DISCUSSION: This trial is the first to compare anti-psychotics in the management of delirium at the dying stage in the home hospice setting using the oral transmucosal route. Ethical considerations, as well as recruitment procedures, are discussed. TRIAL REGISTRATION: This study was registered in ClinicalTrials.gov - identifier NCT04750395.

Lévy on-off intermittency.

We present an alternative form of intermittency, Lévy on-off intermittency, which arises from multiplicative α-stable white noise close to an instability threshold. We study this problem in the linear and nonlinear regimes, both theoretically and numerically, for the case of a pitchfork bifurcation with fluctuating growth rate. We compute the stationary distribution analytically and numerically from the associated fractional Fokker-Planck equation in the Stratonovich interpretation. We characterize the system in the parameter space (α,ß) of the noise, with stability parameter α∈(0,2) and skewness parameter ß∈[-1,1]. Five regimes are identified in this parameter space, in addition to the well-studied Gaussian case α=2. Three regimes are located at 1<α<2, where the noise has finite mean but infinite variance. They are differentiated by ß and all display a critical transition at the deterministic instability threshold, with on-off intermittency close to onset. Critical exponents are computed from the stationary distribution. Each regime is characterized by a specific form of the density and specific critical exponents, which differ starkly from the Gaussian case. A finite or infinite number of integer-order moments may converge, depending on parameters. Two more regimes are found at 0<α≤1. There, the mean of the noise diverges, and no critical transition occurs. In one case, the origin is always unstable, independently of the distance µ from the deterministic threshold. In the other case, the origin is conversely always stable, independently of µ. We thus demonstrate that an instability subject to nonequilibrium, power-law-distributed fluctuations can display substantially different properties than for Gaussian thermal fluctuations, in terms of statistics and critical behavior.

Intermittency of three-dimensional perturbations in a point-vortex model.

Three-dimensional (3D) instabilities on a (potentially turbulent) two-dimensional (2D) flow are still incompletely understood, despite recent progress. Here, based on known physical properties of such 3D instabilities, we propose a simple, energy-conserving model describing this situation. It consists of a regularized 2D point-vortex flow coupled to localized 3D perturbations ("ergophages"), such that ergophages can gain energy by altering vortex-vortex distances through an induced divergent velocity field, thus decreasing point-vortex energy. We investigate the model in three distinct stages of evolution: (i) The linear regime, where the amplitude of the ergophages grows or decays exponentially on average, with an instantaneous growth rate that fluctuates randomly in time. The instantaneous growth rate has a small auto-correlation time, and a probability distribution featuring a power-law tail with exponent between -2 and -5/3 (up to a cutoff) depending on the point-vortex base flow. Consequently, the logarithm of the ergophage amplitude performs a Lévy flight. (ii) The passive-nonlinear regime of the model, where the 2D flow evolves independently of the ergophage amplitudes, which saturate by non-linear self-interactions without affecting the 2D flow. In this regime the system exhibits a new type of on-off intermittency that we name Lévy on-off intermittency, which we define and study in a companion paper [van Kan et al., Phys. Rev. E 103, 052115 (2021)1063-651X10.1103/PhysRevE.103.052115]. We compute the bifurcation diagram for the mean and variance of the perturbation amplitude, as well as the probability density of the perturbation amplitude. (iii) Finally, we characterize the fully nonlinear regime, where ergophages feed back on the 2D flow, and study how the vortex temperature is altered by the interaction with ergophages. It is shown that when the amplitude of the ergophages is sufficiently large, the condensate is disrupted and the 2D flow saturates to a zero-temperature state. Given the limitations of existing theories, our model provides a new perspective on 3D instabilities growing on 2D flows, which will be useful in analyzing and understanding the much more complex results of DNS and potentially guide further theoretical developments.

Constrained basin stability for studying transient phenomena in dynamical systems.

Transient dynamics are of large interest in many areas of science. Here, a generalization of basin stability (BS) is presented: constrained basin stability (CBS) that is sensitive to various different types of transients arising from finite size perturbations. CBS is applied to the paradigmatic Lorenz system for uncovering nonlinear precursory phenomena of a boundary crisis bifurcation. Further, CBS is used in a model of the Earth's carbon cycle as a return time-dependent stability measure of the system's global attractor. Both case studies illustrate how CBS's sensitivity to transients complements BS in its function as an early warning signal and as a stability measure. CBS is broadly applicable in systems where transients matter, from physics and engineering to sustainability science. Thus CBS complements stability analysis with BS as well as classical linear stability analysis and will be a useful tool for many applications.