On effects of increasing amplitude in a boundary-layer spot

The boundary-layer spots involved here come from large-time theory and related computations on the Euler equations to cover the majority of the global properties of the spot disturbances, which are nonlinear, three-dimensional, and transitional rather than turbulent. The amplitude levels investigated are higher than those examined in detail previously and produce a new near-wall momentum contribution in the mean flow, initially close to the wingtips of the spot. This enables the amplitude levels in the analysis to be raised successively, a process which gradually causes the wing-tip region to spread inwards. The process is accompanied by subtle increases in the induced phase variations. Among other things the work finds the details of how nonlinear effects grow from the wing-tips to eventually alter the entire trailing edge, and then the centre of the spot, in a strongly nonlinear fashion. Comparisons with earlier suggestions and with experiments are described at the end

Objectifying fitness: A content and thematic analysis of #Fitspiration images on social media.

Research suggests that exposure to #fitspiration content can result in increased body dissatisfaction. Employing a data-driven approach, the present study examines the nature of images and text contained within #fitspiration posts on social media. First, a content analysis of images labelled as #fitspiration on popular site Instagram (N = 1,000) was performed. People featured in 52% of images, of which nearly 90% of individuals were coded as having low body fat and 55% were coded as muscular. Individuals were typically presented in sexually objectified ways, which varied as a function of gender. Second, a thematic analysis of text from the same set of images (N = 400) was conducted to identify common themes and underlying meaning embedded within the messages. Six themes were developed: (1) Fit is sexy, (2) A fit physique requires commitment and self-regulation, (3) Your choices define you, (4) Pleasure and perseverance through pain, (5) Battle of the selves: You vs. You, and (6) Here’s to us! A celebration of a community. In combination, the analyses demonstrate how text and images found in #fitspiration posts perpetuate pervading sociocultural appearance ideals for men and women, positioning exercise as means to achieving these ideals. Furthermore, #fitspiration sexually objectifies the fit body, with text and images encouraging self-objectification and the distancing of the self from internal bodily functions in physical activity settings. Future research should focus on how #fitspiration content influences individuals in relation to how they think and feel about their body and physical activity

The effect of targeted treatment on people with patellofemoral pain: A pragmatic, randomised controlled feasibility study

Background: Targeted treatment, matched according to specific clinical criteria e.g. hip muscle weakness, may result in better outcomes for people with patellofemoral pain (PFP). However, to ensure the success of future trials, a number of questions on the feasibility of a targeted treatment need clarification. The aim of the study was to explore the feasibility of matched treatment (MT) compared to usual care (UC) management for a subgroup of people with PFP determined to have hip weakness and to explore the mechanism of effect for hip strengthening. Methods: In a pragmatic, randomised controlled feasibility study, 24 participants with PFP (58% female; mean age 29 years) were randomly allocated to receive either MT aimed specifically at hip strengthening, or UC over an eight-week period. The primary outcomes were feasibility outcomes, which included rates of adherence, attrition, eligibility, missing data and treatment efficacy. Secondary outcomes focused on the mechanistic outcomes of the intervention, which included hip kinematics. Results: Conversion to consent (100%), missing data (0%), attrition rate (8%) and adherence to both treatment and appointments ( > 90%) were deemed successful endpoints. The analysis of treatment efficacy showed that the MT group reported a greater improvement for the Global Rating of Change Scale (62% vs. 9%) and the Anterior Knee Pain Scale (-5.23 vs. 1.18) but no between-group differences for either average or worst pain. Mechanistic outcomes showed a greatest reduction in peak hip internal rotation angle for the MT group (13.1% vs. -2.7%). Conclusion: This feasibility study indicates that a definitive randomised controlled trial investigating a targeted treatment approach is achievable. Findings suggest the mechanism of effect of hip strengthening may be to influence kinematic changes in hip function in the transverse plane

Imaging of Impact Damage in Composite Materials

Conventional ultrasonic C-scan images are generated from information acquired within “gates” placed at specific temporal locations on low-pass filtered and rectified versions of A-scans. Placing the gates at temporal locations which correspond with interfaces allows the integrity of the interfaces to be examined. However, if the interfaces are closely spaced, as is the case for quasi-isotropic graphite/epoxy composites, the information from upper layers is blurred into the layers below because of the finite time duration of the ultrasonic pulse. This creates a low signal-to-background-level ratio, which causes blurring at and below the first interface

Electrostriction enhancement in metamaterials

© 2015 American Physical Society. We demonstrate a controllable enhancement in the electrostrictive properties of a medium using dilute composite artificial materials. Analytical expressions for the composite electrostriction are derived and used to show that enhancement, tunability, and suppression can be achieved through a careful choice of constituent materials. Numerical examples with Ag, As2S3, Si, and SiO2 demonstrate that even in a nonresonant regime, artificial materials can bring more than a threefold enhancement in the electrostriction

A mathematical modelling study of an athlete's sprint time when towing a weighted sled

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s12283-013-0114-2.This study used a mathematical model to examine the effects of the sled, the running surface, and the athlete on sprint time when towing a weighted sled. Simulations showed that ratio scaling is an appropriate method of normalising the weight of the sled for athletes of different body size. The relationship between sprint time and the weight of the sled was almost linear, as long as the sled was not excessively heavy. The athlete’s sprint time and rate of increase in sprint time were greater on running surfaces with a greater coefficient of friction, and on any given running surface an athlete with a greater power-to-weight ratio had a lower rate of increase in sprint time. The angle of the tow cord did not have a substantial effect on an athlete’s sprint time. This greater understanding should help coaches set the training intensity experienced by an athlete when performing a sled-towing exercise

‘When you think of exercising, you don’t really want to think of puking, tears, and pain’: Young adolescents’ understanding of fitness and #fitspiration

Adolescents access information about fitness, including content labelled as #fitspiration, through social media. A total of 77 adolescents (mean age = 12.49; standard deviation = 0.55; girls = 27) participated in semi-structured focus groups to explore their perspectives on #fitspiration and fitness more broadly. Through inductive thematic analysis, four themes were developed: (1) fitness enhances physical function and appearance, but these are not always linked; (2) fitness is transformative but requires hard work; (3) fitness should be an intrinsically motivated personal choice; and (4) pain in the pursuit of fitness. Findings highlight young adolescents’ complex understandings of fitness negotiated through their critical interpretation of #fitspiration

Assessing the consequences of including aerosol absorption in potential stratospheric aerosol injection climate intervention strategies

This is the final version. Available on open access from Copernicus Publications via the DOI in this recordTheoretical Stratospheric Aerosol Intervention (SAI) strategies model the deliberate injection of aerosols or their precursors into the stratosphere thereby reflecting incident sunlight back to space and counterbalancing a fraction of the warming due to increased concentrations of greenhouse gases. This cooling mechanism is known to be relatively robust through analogues from explosive volcanic eruptions which have been documented to cool the climate of the Earth. However, a practical difficulty of SAI strategies is how to deliver the injection high enough to ensure dispersal of the aerosol within the stratosphere on a global scale. Recently, it has been suggested that including a small amount of absorbing material in a dedicated 10-day intensive deployment might enable aerosols or precursor gases to be injected at significantly lower, more technologically-feasible altitudes. The material then absorbs sunlight causing a localised heating and ‘lofting’ of the particles, enabling them to penetrate into the stratosphere. Such self-lofting has recently been observed following the intensive wildfires in 2019-2020 in south east Australia, where the resulting absorbing aerosol penetrated into the stratosphere and was monitored by satellite instrumentation for many months subsequent to emission. This study uses the fully coupled UKESM1 climate model simulations performed for the Geoengineering Model Intercomparison Project (GeoMIP) and new simulations where the aerosol optical properties have been adjusted to include a moderate degree of absorption. The results indicate that partially absorbing aerosols i) reduce the cooling efficiency per unit mass of aerosol injected, ii) increase deficits in global precipitation iii) delay the recovery of the stratospheric ozone hole, iv) disrupt the Quasi Biennial Oscillation when global mean temperatures are reduced by as little as 0.1K, v) enhance the positive phase of the wintertime North Atlantic Oscillation which is associated with floods in Northern Europe and droughts in Southern Europe. While these results are dependent upon the exact details of the injection strategies and our simulations use ten times the ratio of black carbon to sulfate that is considered in the recent intensive deployment studies, they demonstrate some of the potential pitfalls of injecting an absorbing aerosol into the stratosphere to combat the global warming problem.Natural Environment Research Council (NERC)Department for Business, Energy and Industrial StrategySilverLinin

"No more opium for the masses": from the U.S. fentanyl boom to the Mexican opium crisis: opportunities amidst violence?

This report examines the effects of the upsurge in U.S. fentanyl use on opium producing areas in Mexico. By using available quantitative data on Mexican opium production as well as qualitative field research from opium producing communities in Nayarit and Guerrero, this paper offers valuable insights into Mexico’s illicit drug trade, demonstrating the extent to which many peasants rely on opium production for survival. With the upsurge in fentanyl use in the US, the demand for Mexican heroin has fallen sharply, with an immediate knock-on for opium producers. Their losses have caused farmers’ profits to disappear, village economies to dry up; and out-migration to increase. These findings have important implications for public security in Mexico, as well as major ramifications for international counter-drug efforts