Synthetic Mechanochemical Molecular Swimmer

A minimal design for a molecular swimmer is proposed that is a based on a mechanochemical propulsion mechanism. Conformational changes are induced by electrostatic actuation when specific parts of the molecule temporarily acquire net charges through catalyzed chemical reactions involving ionic components. The mechanochemical cycle is designed such that the resulting conformational changes would be sufficient for achieving low Reynolds number propulsion. The system is analyzed within the recently developed framework of stochastic swimmers to take account of the noisy environment at the molecular scale. The swimming velocity of the device is found to depend on the concentration of the fuel molecule according to the Michaelis-Menten rule in enzymatic reactions.Comment: 4 pages, 3 figure

Family Caregivers’ Knowledge of Delirium and Preferred Modalities for Receipt of Information

Delirium is a life-threatening, frequently reversible condition that is often a sign of an underlying health problem. In-hospital mortality alone for older adults with delirium ranges from 25% to 33%. Early recognition of delirium is critical because prolonged duration poses a greater risk of poor functional outcomes for older adults. Family caregivers, who are familiar with the older adult’s usual behaviors, are most likely to recognize delirium symptoms but might dismiss them as due to aging. It is important to learn what family caregivers know about delirium to ascertain their need for education. The aims of this study were to describe family caregivers’ knowledge of delirium and preferred modalities for receipt of information about delirium. A cross-sectional design was used for this study and a survey distributed to family caregivers for older adults. Analysis of 134 usable surveys indicated that family caregivers need and want information about delirium. The preferred modalities for receipt of information included Internet, in-person classes, and newsletters

Public Health Model Identifies Recruitment Barriers among Older Adults with Delirium and Dementia

Recruiting older adults and their family caregivers into research studies presents challenges. Although the literature notes some general recruitment challenges, no studies specifically address the unique challenges of recruiting older adults who have Alzheimer\u27s Disease (AD) and their family caregivers in studies about delirium or suggest using a framework to identify barriers to recruiting this population. In conducting a pilot study about preparing family caregivers to detect delirium symptoms in older adults with (AD) the researchers used the Public Health Model for identifying barriers to recruitment. The goals of this methodological article are to: (1) briefly describe the methodology of the pilot study to illustrate how the Public Health Model was applied in the context of the present study and (2) discuss the benefits of the Public Health Model for identifying the barriers to recruitment in a study that prepared family caregivers to detect delirium symptoms in older adults with AD. The Public Health Model helped us to identify four specific barriers to recruitment (lack of knowledge about delirium, desire to maintain normalcy, protective caregiving behaviors, and older adult\u27s fears) and ways to overcome them. The Public Health Model might also help other researchers address similar issues

Virtual image out-the-window display system study. Volume 2 - Appendix

Virtual image out-the-window display system imaging techniques and simulation devices - appendices containing background materia

Lower-extremity musculoskeletal geometry affects the calculation of patellofemoral forces in vertical jumping and weightlifting

The calculation of the patellofemoral joint contact force using three-dimensional (3D) modelling techniques requires a description of the musculoskeletal geometry of the lower limb. In this study, the influence of the complexity of the muscle model was studied by considering two different muscle models, the Delp and Horsman models. Both models were used to calculate the patellofemoral force during standing, vertical jumping, and Olympic-style weightlifting. The patellofemoral forces predicted by the Horsman model were markedly lower than those predicted by the Delp model in all activities and represented more realistic values when compared with previous work. This was found to be a result of a lower level of redundancy in the Delp model, which forced a higher level of muscular activation in order to allow a viable solution. The higher level of complexity in the Horsman model resulted in a greater degree of redundancy and consequently lower activation and patellofemoral forces. The results of this work demonstrate that a well-posed muscle model must have an adequate degree of complexity to create a sufficient independence, variability, and number of moment arms in order to ensure adequate redundancy of the force-sharing problem such that muscle forces are not overstated. (Author's abstract

The development of a segment-based musculoskeletal model of the lower limb: Introducing FreeBody

Traditional approaches to the biomechanical analysis of movement are joint-based; that is the mechanics of the body are described in terms of the forces and moments acting at the joints, and that muscular forces are considered to create moments about the joints. We have recently shown that segment-based approaches, where the mechanics of the body are described by considering the effect of the muscle, ligament and joint contact forces on the segments themselves, can also prove insightful. We have also previously described a simultaneous, optimization-based, musculoskeletal model of the lower limb. However, this prior model incorporates both joint- and segment-based assumptions. The purpose of this study was therefore to develop an entirely segment-based model of the lower limb and to compare its performance to our previous work. The segment-based model was used to estimate the muscle forces found during vertical jumping, which were in turn compared with the muscular activations that have been found in vertical jumping, by using a Geers’ metric to quantify the magnitude and phase errors. The segment-based model was shown to have a similar ability to estimate muscle forces as a model based upon our previous work. In the future, we will evaluate the ability of the segment-based model to be used to provide results with clinical relevance, and compare its performance to joint-based approaches. The segment-based model described in this article is publicly available as a GUIbasedMATLAB _ application and in the original source code (at www.msksoftware.org.uk)

An Optimization-Based Simultaneous Approach to the Determination of Muscular, Ligamentous, and Joint Contact Forces Provides Insight into Musculoligamentous Interaction

Typical inverse dynamics approaches to the calculation of muscle, ligament, and joint contact forces are based on a step-wise solution of the equations of motion. This approach is therefore limited in its ability to provide insight as to the muscular, ligamentous, and articular interactions that create joint stability. In this study, a new musculoskeletal model of the lower limb is described, in which the equations of motion describing the force and moment equilibrium at the joints of the lower limb are solved simultaneously using optimization techniques. The new model was employed to analyze vertical jumping using a variety of different optimization cost functions and the results were compared to more traditional approaches. The new model was able to find a solution with lower muscular force upper bounds due to the ability of the ligaments to contribute to moment equilibrium at the ankle and knee joints. Equally, the new model produced lower joint contact forces than traditional approaches for cases which also included a consideration as to ligament or joint contact forces within the cost function. This study demonstrates the possibility of solving the inverse dynamic equations of motion simultaneously using contemporary technology, and further suggests that this might be important due to the complementary function of the muscles and ligaments in creating joint stability

Cloud Chamber: A Performance with Real Time Two-Way Interaction between Subatomic Particles and Violinist

‘Cloud Chamber’ - a composition by Alexis Kirke, Antonino Chiaramonte, and Anna Troisi - is a live performance in which the invisible quantum world becomes visible as a violinist and subatomic particle tracks interact together. An electronic instrument was developed which can be “played” live by radioactive atomic particles. Electronic circuitry was developed enabling a violin to create a physical force field that directly affects the ions generated by cosmic radiation particles. This enabled the violinist and the ions to influence each other musically in real time. A glass cloud chamber was used onstage to make radioactivity visible in bright white tracks moving within, with the tracks projected onto a large screen