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Concept: Stairway

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Perceptual learning (PL) has been traditionally thought of as highly specific to stimulus properties, task and retinotopic position. This view is being progressively challenged, with accumulating evidence that learning can generalize (transfer) across various parameters under certain conditions. For example, retinotopic specificity can be diminished when the proportion of easy to hard trials is high, such as when multiple short staircases, instead of a single long one, are used during training. To date, there is a paucity of mechanistic explanations of what conditions affect transfer of learning. Here we present a model based on the popular Integrated Reweighting Theory model of PL but departing from its one-layer architecture by including a novel key feature: dynamic weighting of retinotopic-location-specific vs location-independent representations based on internal performance estimates of these representations. This dynamic weighting is closely related to gating in a mixture-of-experts architecture. Our dynamic performance-monitoring model (DPMM) unifies a variety of psychophysical data on transfer of PL, such as the short-vs-long staircase effect, as well as several findings from the double-training literature. Furthermore, the DPMM makes testable predictions and ultimately helps understand the mechanisms of generalization of PL, with potential applications to vision rehabilitation and enhancement.

Concepts: Psychology, Prediction, Educational psychology, Perception, Transfer of learning, Logic, Stairway, Generalization

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This study assessed the influence of attention division, working memory and executive function on stair ascent and descent in young and older adults. Twenty young (25.5 ± 2.1 yrs) and 20 older adults (68.4 ± 5.4 yrs) ascended and descended a 3-step staircase with no simultaneous cognitive task (single-motor task) or while performing a cognitive task (dual-task condition). The cognitive task involved either 1) recalling a word list of the subject’s word-span minus 2 words (SPAN-2) to assess the attention division effect, 2) a word list of subject’s word-span (SPAN-O) to assess the working memory effect, or 3) recalling in alphabetical order, a word list of the subject’s word-span (SPAN-A) to assess the executive function effect. Word-span corresponds to the longest string of words that can be recalled correctly. The duration of ascent and descent of stairs was used to assess the cognitive-motor interaction. Stair ascent and descent duration did not differ between age groups for the single-motor task, and was similar between single-motor task and SPAN-2 in both groups (p > 0.05). In contrast, stair ascent and descent duration increased with SPAN-O compared with SPAN-2 for both groups (p < 0.01). Stair ascent (p = 0.017) and descent (p = 0.008) were longer in SPAN-A than SPAN-O only in older adults. Healthy aging was not associated with a decrease in the capacity to perform motor-cognitive dual tasks that involved ascending and descending of stairs when the cognitive task only required working memory. However, the decrease in dual-task performance involving executive functioning may reflect a subclinical cognitive decline in healthy older adults.

Concepts: Psychology, Cognitive psychology, Cognitive science, Attention-deficit hyperactivity disorder, Working memory, Executive functions, Neuropsychological assessment, Stairway

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Plasmonic nanomaterials, along with their assemblies, provide numerous applications due to their profound optical properties. In this work, we report the self-assembly of Au@Ag core-shell nanocuboids (NCs) into staircase superstructures in both vertical and horizontal orientations through two-stage droplet evaporation. Each stair is composed of a uniform well-aligned monolayer of NCs. The gap distance between NCs can be greatly shrunk to boost the corresponding surface-enhanced Raman scattering (SERS) performance using an ethanol wash method. The SERS performance of the assembled NCs is calculated by finite-difference time-domain (FDTD) simulation, and studied against the step number using 4-mercaptobenzoic acid as a Raman reporter molecule. The increasing EF with the increase of layer number proves that the plasmon mode propagates well in our uniformly aligned assemblies.

Concepts: Water, Scattering, Raman scattering, Rayleigh scattering, Brillouin scattering, Stairway

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Hip implants subject to gait loading due to occupational activities are potentially prone to failures such as osteolysis and aseptic loosening, causing painful revision surgeries. Highly risky gait activities such as carrying a load, stairs up or down and ladder up or down may cause excessive loading at the hip joint, resulting in generation of wear and related debris. Estimation of wear under the above gait activities is thus crucial to design and develop a new and improved implant component. With this motivation, this paper presents an assessment of wear generation of PCD-on-PCD (poly crystalline diamond) hip implants using finite element (FE) analysis. Three-dimensional (3D) FE model of hip implant along with peak gait and peak flexion angle for each activity was used to estimate wear of PCD for 10 million cycles. The maximum and minimum initial contact pressures of 206.19 MPa and 151.89 MPa were obtained for carrying load of 40 kg and sitting down or getting up activity. The simulation results obtained from finite element model also revealed that the maximum linear wear of 0.585 μm occurred for the patients frequently involved in sitting down or getting up gait activity and maximum volumetric wear of 0.025 mm(3) for ladder up gait activity. The stair down activity showed the least linear and volumetric wear of 0.158 μm and 0.008 mm(3), respectively, at the end of 10 million cycles. Graphical abstract Computational wear assessment of hip implants subjected to physically demanding tasks.

Concepts: Mathematics, Thermodynamics, Hip replacement, Hip, Activity, Flexion, Maxima and minima, Stairway

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Individuals rarely achieve investment activities characterised by up-front costs and delayed benefits. Point-of-decision prompts (PDPs) provide information about a better alternative or a deterrent to the behavioural standard at the moment the decision is made and may affect behaviour by helping individuals perform this type of investment activities. We conducted a field experiment to assess the effects of a PDP intervention that encourages taking the stairs rather than the escalator in three Paris (France) Metro stations for eight weeks from April to July 2014. In total, we followed up 205 individuals and the data show that PDPs have an immediate, albeit decaying, peaked effect on individuals' stair use, with a stronger effect when weak physical effort is made salient. However, the intervention did not change individuals' stair-use habits. In the best-case scenario, the effects last two weeks after the intervention ends. Our preferred explanation is that PDPs act as “cues” but people become accustomed to them and in the end no longer notice them. These findings suggest that a PDP intervention is not sufficient to modify individuals investment in activities with immediate costs and delayed benefits in the long-run.

Concepts: Psychology, Effect, Affect, Experiment, Effects unit, Behavior, ACT, Stairway

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Stair ascent is an activity of daily living and necessary for maintaining independence in community environments. One challenge to improving an individual’s ability to ascend stairs is a limited understanding of how lower-limb muscles work in synergy to perform stair ascent. Through dynamic coupling muscles may perform multiple functions and require contributions from other muscles to perform a task successfully. The purpose of this study was to identify the functional roles of individual muscles during stair ascent and the mechanisms by which muscles work together to perform specific subtasks. A three-dimensional muscle-actuated simulation of stair ascent was generated to identify individual muscle contributions to the biomechanical subtasks of vertical propulsion, anteroposterior propulsion (forward propulsion and braking), mediolateral control and leg swing. The vasti and plantarflexors were the primary contributors to vertical propulsion during the first and second halves of stance, respectively, while gluteus maximus and hamstrings were the primary contributors to forward propulsion during the first and second halves of stance, respectively. The anterior and posterior components of gluteus medius were the primary contributors to medial control while vasti and hamstrings were the primary contributors to lateral control during the first and second halves of stance, respectively. To control leg swing, antagonistic muscles spanning the hip, knee and ankle joints distributed power from the leg to the remaining body segments. These results compliment previous studies analyzing stair ascent and provide further rationale for developing targeted rehabilitation strategies to address patient-specific deficits in stair ascent.

Concepts: Muscle, Muscular system, Activity, Task, Ankle, Gluteal muscles, Stairway, Gluteus medius muscle

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Stair negotiation poses a substantial physical demand on the musculoskeletal system and this challenging task can place individuals at risk of falls. Peripheral arterial disease (PAD) can cause intermittent claudication (IC) pain in the calf and results in altered gait mechanics during level walking. However, whether those with PAD-IC adopt alternate strategies to climb stairs is unknown. Twelve participants with PAD-IC (six bilateral and six unilateral) and 10 healthy controls were recruited and instructed to ascend a five-step staircase whilst 3D kinematic data of the lower-limbs were recorded synchronously with kinetic data from force plates embedded into the staircase on steps two and three. Limbs from the unilateral group and both limbs from the bilateral claudicants were categorised as claudicating (N=18), asymptomatic (N=6) and control (N=10). Claudicants walked more slowly than healthy controls (trend; P=<0.066). Both claudicating- and asymptomatic-limb groups had reduced propulsive GRF (P=0.025 and P=0.002, respectively) and vertical GRF (P=0.005 and P=0.001, respectively) compared to controls. The claudicating-limb group had a reduced knee extensor moment during forward continuance (P=0.060), ankle angular velocity at peak moment (P=0.039) and ankle power generation (P=0.055) compared to the controls. The slower gait speed, irrespective of laterality of symptoms, indicates functional capacity was determined by the limitations of the claudicating limb. Reduced ankle power generation and angular velocity (despite adequate plantarflexor moment) implies velocity-dependent limitations existed in the calf. The lack of notable compensatory strategies indicates reliance on an impaired muscle group to accomplish this potentially hazardous task, highlighting the importance of maintaining plantarflexor strength and power in those with PAD-IC.

Concepts: Angular momentum, Kinetic energy, Knee, Kinematics, Flexion, Walking, Intermittent claudication, Stairway

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This study evaluated the effects of improving the visibility of the stairwell and of displaying a video with a stair climbing model on climbing and descending stair use in a worksite setting.

Concepts: Stairway

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Stair climb power is an important clinical measure of lower-extremity power. The stair climb power test (SCPT) was validated by requiring individuals to climb a full flight of stairs. A four-step SCPT (4SCPT) would be more clinically feasible and easier to perform, yet its reliability and validity is unknown.

Concepts: Psychometrics, Reliability, Stairway

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Stair climbing is an activity of daily living that might contribute to increase levels of physical activity (PA). To date, there is no study examining the validity of climbing stairs assessed by self-report. The aim of this study was, therefore, to examine the validity of estimated stair climbing from one question included in a common questionnaire compared to a pattern-recognition activity monitor in older adults.

Concepts: Criterion validity, Stairway