Magnetic droplet soliton pairs.

We demonstrate magnetic droplet soliton pairs in all-perpendicular spin-torque nano-oscillators (STNOs), where one droplet resides in the STNO free layer (FL) and the other in the reference layer (RL). Typically, theoretical, numerical, and experimental droplet studies have focused on the FL, with any additional dynamics in the RL entirely ignored. Here we show that there is not only significant magnetodynamics in the RL, but the RL itself can host a droplet driven by, and coexisting with, the FL droplet. Both single droplets and pairs are observed experimentally as stepwise changes and sharp peaks in the dc and differential resistance, respectively. While the single FL droplet is highly stable, the coexistence state exhibits high-power broadband microwave noise. Furthermore, micromagnetic simulations reveal that the pair dynamics display periodic, quasi-periodic, and chaotic signatures controlled by applied field and current. The strongly interacting and closely spaced droplet pair offers a unique platform for fundamental studies of highly non-linear soliton pair dynamics.

Physical activity measured by accelerometry among adolescents participating in sports clubs and non-participating peers.

The purpose of this descriptive cross-sectional study is to describe the amount and intensity of physical activity (PA) measured by accelerometry among adolescents participating in organized sports (SCP) and age-matched non-participating peers (NP). SCPs (332) and NPs (139) wore an accelerometer on the hip for seven days. PA was reported using the 1-min exponential moving average. The current moderate-to-vigorous physical activity (MVPA) recommendation of at least an average of 60 min of MVPA daily was reached by 85% of SCPs and 45% of NPs (p < .001). During training days, the MVPA times among SCPs ranged from 153 ± 39 min in males and 109 ± 35 min in females participating in basketball to 113 ± 33 min in males participating in floorball and 83 ± 32 min in females participating in gymnastics. Sports participation contributes rather strongly to the accumulation of the recommended amount of MVPA. During training days, SCPs, except for females participating in gymnastics, accumulated more MVPA than NPs. During non-training days, only males participating in cross-country skiing and females participating in track and field accumulated more MVPA than NPs.HIGHLIGHTSPA of Finnish adolescents participating in nine different organized sports and age-matched non-participating peers was measured by accelerometry for one week and the results are reported using the 1-min exponential moving average.Adolescents participating in many organized sports accumulated more PA than non-participants; this was observed in meeting the PA recommendations, total amount of PA at different intensities, and step count.The current PA recommendation of at least an average of 60 min of MVPA per day was reached by 85% of SCPs and 45% of non-participating peers. Vigorous physical activity at least three times per week was incorporated by 96% of SCPs and 81% of NPs.During training days, males participating in soccer, basketball, and cross-country skiing spent more time in MVPA than females participating in the same sports. During non-training days, the time spent in MVPA was similar between males and females participating in sports clubs.

Collective Ferromagnetism of Artificial Square Spin Ice.

We study the temperature and magnetic field dependence of the total magnetic moment of large-area permalloy artificial square spin ice arrays. The temperature dependence and hysteresis behavior are consistent with the coherent magnetization reversal expected in the Stoner-Wohlfarth model, with clear deviations due to interisland interactions at small lattice spacing. Through micromagnetic simulations, we explore this behavior and demonstrate that the deviations result from increasingly complex magnetization reversal at small lattice spacing, induced by interisland interactions, and depending critically on details of the island shapes. These results establish new means to tune the physical properties of artificial spin ice structures and other interacting nanomagnet systems, such as patterned magnetic media.

Controllable skyrmion chirality in ferroelectrics.

Chirality, an intrinsic handedness, is one of the most intriguing fundamental phenomena in nature. Materials composed of chiral molecules find broad applications in areas ranging from nonlinear optics and spintronics to biology and pharmaceuticals. However, chirality is usually an invariable inherent property of a given material that cannot be easily changed at will. Here, we demonstrate that ferroelectric nanodots support skyrmions the chirality of which can be controlled and switched. We devise protocols for realizing control and efficient manipulations of the different types of skyrmions. Our findings open the route for controlled chirality with potential applications in ferroelectric-based information technologies.

Acute and overuse injuries among sports club members and non-members: the Finnish Health Promoting Sports Club (FHPSC) study.

BACKGROUND: Physical activity in adolescence is promoted for its multi-dimensional health benefits. However, too intensive sports participation is associated with an increased injury risk. Our aim was to compare the occurrence of acute and overuse injuries in Finnish sports club members and non-members and to report training and competing habits associated with a higher injury risk in sports club members. METHODS: In this cross-sectional survey targeted at 14-16-year-old adolescents, a structured questionnaire was completed by 1077 sports club members and 812 non-members. The main outcome measures were self-reported acute and overuse injuries, their location and type. RESULTS: At least one acute injury in the past year was reported by 44.0% of sports club members and 19.8% of non-members (P < 0.001). The sex-adjusted odds ratio (OR) for acute injury in sports club members compared to non-members was 3.13 (95% confidence interval (95% CI) 2.54-3.87). Thirty-five percent of sports club members and 17.4% of non-members (P < 0.001) reported at least one overuse injury during the past year. The overuse injury OR for sports club members was 2.61 (95% CI 2.09-3.26). Sports club members who trained 7-14 h per week during training (OR 1.61, 95% CI 1.21-2.12, P = 0.001) or competition season (OR 1.55, 95% CI 1.18-2.06, P = 0.002) were more likely to report an injury compared to members who trained 3-6 h per week. Those sports club members who participated in forty competitions or more compared to 7-19 competitions per year were more likely to report an acute injury (OR 1.55, 95% CI 1.05-2.08, P = 0.028) or for an overuse injury (OR 1.53, 95% CI 1.02-2.30, P = 0.038). CONCLUSIONS: Both acute and overuse injuries are common among youth sports club members, and the number increases along with increasing amounts of training and competitions. More effective injury prevention is needed both for adolescents engaging in sports club activities and for other adolescents.

Bragg Coherent Diffractive Imaging of Zinc Oxide Acoustic Phonons at Picosecond Timescales.

Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4D evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. We find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.

Mobility and muscle strength in male former elite endurance and power athletes aged 66-91 years.

The aim of this cross-sectional study was to compare mobility and muscle strength in male former elite endurance and power athletes aged 66-91 years (n = 150; 50 men in both former elite athlete groups and in their control group). Agility, dynamic balance, walking speed, chair stand, self-rated balance confidence (ABC-scale), jumping height, and handgrip strength were assessed. Former elite power athletes had better agility performance time than the controls (age- and body mass index, BMI-adjusted mean difference -3.6 s; 95% CI -6.3, -0.8). Adjustment for current leisure time physical activity (LTPA) and prevalence of diseases made this difference non-significant (P = 0.214). The subjects in the power sports group jumped higher than the men in the control group (age- and BMI-adjusted mean differences for vertical squat jump, VSJ 4.4 cm; 95% CI 2.0, 6.8; for countermovement jump, CMJ 4.0 cm; 95% CI 1.7, 6.4). Taking current LTPA and chronic diseases for adjusting process did not improve explorative power of the model. No significant differences between the groups were found in the performances evaluating dynamic balance, walking speed, chair stand, ABC-scale, or handgrip strength. In conclusion, power athletes among the aged former elite sportsmen had greater explosive force production in their lower extremities than the men in the control group.

Low back and neck and shoulder pain in members and non-members of adolescents' sports clubs: the Finnish Health Promoting Sports Club (FHPSC) study.

BACKGROUND: The objective of this study was to investigate the prevalence of self-reported low back pain (LBP) and neck and shoulder pain (NSP), and the related factors in members and non-members of adolescents' sports clubs. METHODS: This cross-sectional study was based on surveys of 14-16-year-olds as a part of the Finnish Health Promoting Sports Club (FHPSC) Study. The surveys on self-reported health behaviours, injuries, and musculoskeletal health were conducted among sports club members (n = 962) and non-members (n = 675). Binary logistic regression analysis was applied to study the associations between dependent variables of LBP and NSP, and the independent factors. RESULTS: The prevalence of LBP during the preceding 3 months was 35.0 % in girls and 24.5 % in boys (p < 0.05 for sex difference). The prevalence of NSP was 55.9 % in girls and 27.3 % in boys (p < 0.001 for sex difference). Being a sports club member increased the odds for LBP in boys (odds ratio [OR] 2.35, 95 % CI 1.48-3.72). On the other hand, sports club participation was associated with lower odds of frequent NSP in girls (OR 0.52, 95 % CI 0.33-0.82). No associations were found between other leisure-time physical activity and LBP or NSP. Higher screen time (computer games, TV/DVD, phone, Internet) during leisure-time increased the odds of NSP in boys and LBP in boys and girls. CONCLUSIONS: In this study, self-reported LBP and NSP were already relatively common among adolescents. Girls have a higher risk for reporting LBP and NSP. Measures that are more effective in the prevention of LBP in male sports club members are needed. Excessive screen time is weakly associated with LBP and NSP, which should be taken into account in health promotion among adolescents.

Unfavorable influence of structured exercise program on total leisure-time physical activity.

In randomized controlled trials (RCTs), with customized structured physical exercise activity (SPEA) interventions, the dose of leisure-time physical activity (LTPA) should exceed the LTPA dose of the nonexercising control (C) group. This increase is required to substantiate health improvements achievable by exercise. We aimed to compare the dose of SPEA, LTPA, and total LTPA (SPEA + LTPA) between a randomized Nordic walking (NW) group, a power-type resistance training (RT) group, and a C group during a 12-week exercise intervention in obese middle-aged men (n = 144) with impaired glucose regulation. The dose of physical activity was measured with diaries using metabolic equivalents. No significant difference (P > 0.107) between the groups was found in volume of total LTPA. The volume of LTPA was, however, significantly higher (P < 0.050) in the C group than in the NW group, but not compared with the RT group. These results indicate that structured exercise does not automatically increase the total LTPA level, possibly, as a result of compensation of LTPA with structured exercise or spontaneous activation of the C group. Thus, the dose of total LTPA and the possible changes in spontaneous LTPA should be taken into account when implementing a RCT design with exercise intervention.

Spin-wave-mode coexistence on the nanoscale: a consequence of the Oersted-field-induced asymmetric energy landscape.

It has been argued that if multiple spin wave modes are competing for the same centrally located energy source, as in a nanocontact spin torque oscillator, that only one mode should survive in the steady state. Here, the experimental conditions necessary for mode coexistence are explored. Mode coexistence is facilitated by the local field asymmetries induced by the spatially inhomogeneous Oersted field, which leads to a physical separation of the modes, and is further promoted by spin wave localization at reduced applied field angles. Finally, both simulation and experiment reveal a low frequency signal consistent with the intermodulation of two coexistent modes.

Sedentary behaviours and obesity in adults: the Cardiovascular Risk in Young Finns Study.

OBJECTIVE: Sedentary behaviour may contribute to the development of obesity. We investigated the relations between different types of sedentary behaviour and adiposity markers in a well-characterised adult population after controlling for a wide range of potential confounders. DESIGN: Cross-sectional study. SETTING: The Cardiovascular Risk in Young Finns Multicenter Study. Participants Sedentary time (TV viewing, computer time, reading, music/radio listening and other relaxation) was assessed with a questionnaire for 1084 women and 909 men aged 30-45 years. Other study variables included occupational and leisure-time physical activity, sleep duration, socioeconomic status, smoking, alcohol consumption, energy intake, adherence to the recommended diet, multiple individual food items, age and genetic variants associated with body mass index (BMI). Primary outcome measures BMI in kg/m(2) and waist circumference (WC in cm). RESULTS: Of the different sedentary behaviour types, TV viewing was most consistently related to higher BMI and WC, both in men and women. One additional daily TV hour was associated with a 1.81±0.44 cm larger WC in women and 2 cm±0.44 cm in men (both p<0.0001). The association with TV was diluted, but remained highly significant after adjustments with all measured covariates, including several potentially obesogenic food items associated with TV viewing. The intakes of food items such as sausage, beer and soft drinks were directly associated with TV viewing, while the intakes of oat and barley, fish, and fruits and berries were associated indirectly. After these adjustments, non-TV sedentary behaviour remained associated with adiposity indices only in women. CONCLUSIONS: Out of the different types of sedentary behaviour, TV viewing was most consistently associated with adiposity markers in adults. Partial dilution of these associations after adjustments for covariates suggests that the obesogenic effects of TV viewing are partly mediated by other lifestyle factors.

Decoherence and mode hopping in a magnetic tunnel junction based spin torque oscillator.

We discuss the coherence of magnetic oscillations in a magnetic tunnel junction based spin torque oscillator as a function of the external field angle. Time-frequency analysis shows mode hopping between distinct oscillator modes, which arises from linear and nonlinear couplings in the Landau-Lifshitz-Gilbert equation, analogous to mode hopping observed in semiconductor ring lasers. These couplings and, therefore, mode hopping are minimized near the current threshold for the antiparallel alignment of free-layer with reference layer magnetization. Away from the antiparallel alignment, mode hopping limits oscillator coherence.

Direct observation of unconventional topological spin structure in coupled magnetic discs.

Confined magnetic thin films are known to exhibit a variety of fascinating topological spin states such as Skyrmions, vortices, and antivortices. Such topological excitations are fundamentally important to our understanding of quantum critical phenomenon and related phase transitions. Here we report on the direct observation of an unconventional topological spin state and its behavior in antiferromagnetically coupled NiFe discs at room temperature. The observed spin structure is similar to the theoretically predicted merons which have not yet been observed directly. We have used in situ Lorentz microscopy magnetizing experiments combined with micromagnetic simulations to follow the stability and the behavior of the meron state. The work presented in this paper will open new opportunities for direct experimental investigation of various topological states that can provide insights into the fundamental physics of their interactions.

Perpendicular spin torque in magnetic tunnel junctions.

A steady-state electrical current flowing in a magnetic heterostructure can exert a torque on the magnetization, and provides a means to control magnetization states and dynamics in spintronics structures. However, some components of the torque are difficult to measure and to calculate. We have determined the perpendicular spin torque in MgO magnetic tunnel junctions by measuring their lowest ferromagnetic resonance frequency and find that it decreases linearly with increasing bias voltage. Micromagnetic modeling shows that this decrease is caused by the perpendicular component of spin torque. We obtain a quantitative value for the perpendicular spin torque effective field as a function of bias voltage, and show that this effective field is a linear function in bias voltage and approximately equal in magnitude to the in-plane spin torque effective field.

Parental and childhood overweight in sedentary and active adolescents.

We studied whether the prevalence of overweight since age 2 years differed in sedentary and active adolescents (N=346). Further, we analyzed the energy intake of sedentary and active adolescents across 12 years. BMI was assessed annually since birth, energy intake since age 13 months and parents' BMI from the time their child was 7 months old in a longitudinal atherosclerosis prevention study. Data on physical activity were collected at age 13 years (N=560). Sedentary and Active groups were formed by upper and lower physical activity tertile cut-points. Girls Sedentary at 13 years were more often overweight than Active peers already since age 2 years (P=0.048). Activity habits were not associated with energy intake. Conversely, among boys, activity habits in adolescence were not associated with childhood overweight, while the energy intake of Active boys was higher than that of Sedentary boys (P=0.008). Parental overweight was not associated with the physical activity of children; however, Sedentary girls more often had an overweight mother than Active girls (P=0.021). In conclusion, overweight during early years of life is more common among girls who are Sedentary as adolescents than in Active peers. Overweight mothers more often have Sedentary daughters than normal-weight mothers. A healthy lifestyle right from early childhood requires active support.

Transcutaneous carbon dioxide profile during sleep reveals metabolic risk factors in post-menopausal females.

The risks of metabolic syndrome and sleep-disordered breathing increase around the time of the menopause. We have previously shown that features of the nocturnal transcutaneous carbon dioxide (TcCO2) profile are associated with metabolic variables such as cholesterol, glycosylated haemoglobin A1C (GHbA1C) and blood pressure in patients with sleep apnoea. In the present study, we investigated whether these metabolic variables can be predicted using noninvasive TcCO2 measurements during sleep in generally healthy post-menopausal females. 22 post-menopausal females underwent an overnight polygraphic sleep study that involved the continuous monitoring of arterial oxygen saturation (S(a,O2)) and TcCO2. Body composition, GHbA1C, plasma cholesterol and blood pressure were measured prior to the sleep study. Nocturnal TcCO2 features were the most important predictors of lipoprotein cholesterols, triglycerides and blood pressure levels. A longer sleep period and higher TcCO2 levels were linked with lower GHbA1C, and fragmented sleep with lower high-density lipoprotein cholesterol. Neither nocturnal S(a,O2) indices nor the apnoea/hypopnoea index had a predictive power. The results suggest that nocturnal TcCO2 events revealed metabolic risk factors already present in healthy post-menopausal females.

Exercise-induced training effects on bone mineral content: a 7-year follow-up study with adolescent female gymnasts and runners.

The objective of this study was to assess differences in the effects of competitive gymnastics and running on bone mineral content (BMC) of the lumbar spine and femoral neck when compared with their non-competing age-matched controls. Caucasian healthy peri-pubertal girls (52 competing gymnasts, 46 competing runners, 44 non-athletic controls) were included. Weight, height, and type and amount of exercise (MET h/week) as well as BMC of the lumbar spine and femoral neck were measured repeatedly. Statistical comparisons between groups were made using ANOVA. Repeated measures were analyzed using generalized linear mixed models. The median MET value of gymnasts was significantly higher when compared with runners and controls at baseline, P=0.001. The weekly median MET hours decreased during the follow-up. The mean (adjusted for height, weight, and years from menarche in the 7-year follow-up) BMC of the lumbar spine and femoral neck was significantly higher among gymnasts when compared with the other two groups. Group-by-time interaction was significant only at the femoral neck (P=0.048). The type of physical activity was a significant factor in BMC of the adolescent women. Gymnasts had greater BMC at lumbar spine and femoral neck during the total 7-year follow-up period when compared with runners and controls.

Sudden cardiac death in young athletes: time for a Nordic approach in screening?

In 2005, the European Society of Cardiology published recommendations for cardiovascular screening in athletes. Discussion on whether screening is beneficial is ongoing. Recently, the first prospective results on effectiveness of screening in preventing sudden deaths were published from Italy. The results were supportive of screening, but did not provide conclusive evidence. Our suggestion for a Nordic approach on this issue is a directed cardiovascular examination initially involving elite athletes, because this is feasible with respect to the Nordic health care systems and the organization and logistics of elite competitive sports, but also because of the negative aspects of screening large populations. This directed cardiovascular examination would include personal and family history, clinical examination, and electrocardiography (ECG). Further examinations should thereafter be carried out in athletes with suggestive findings in the initial evaluation. The directed cardiovascular examination should be voluntary. It should be conducted at least once, with information on alarming symptoms (syncope, chest pain or dizziness during exercise) and heredity (sudden cardiac death or hereditary heart disease in near relatives) stressed to the athlete as indications for necessary check-ups in the future. The examination would also provide the athlete with an ECG recording, which is valuable as a reference at a later time.

Myocardial and peripheral vascular functional adaptation to exercise training.

Exercise training seems to restore impaired vascular function in both peripheral and myocardial vessels in patients with coronary artery and peripheral vascular disease or in patients with risk factors for these diseases. However, the results on the effects of exercise training on vascular function in apparently healthy subjects are controversial. We studied the effects of long-term volitionally increased physical activity on peripheral and myocardial vascular function in nine young healthy male monozygotic twin pairs discordant for physical activity and fitness. The brothers were divided into more (MAG) and less active groups according to physical activity and fitness. The difference between groups in VO(2max) was 18+/-10% (P<0.001). Myocardial perfusion at rest, during adenosine-induced vasodilatation and during cold-pressor test and myocardial oxygen consumption were measured with positron emission tomography. In addition, endothelial function was measured using ultrasound in brachial and left anterior descending coronary arteries, and standard echocardiographic measures were taken. No differences were observed in myocardial perfusion measurements between groups. MAG tended to have a lower oxygen extraction fraction (P=0.06), but oxygen consumption was similar between the groups. No differences were found in coronary artery, myocardial resistance vessel or peripheral endothelial function between groups. These results suggest that when the effects of heredity are controlled, myocardial perfusion reserve and endothelial function, both in peripheral arteries and myocardial vessels, are not enhanced by increased physical activity and fitness in young healthy adult men.

The reduction of physical activity reflects on the bone mass among young females: a follow-up study of 142 adolescent girls.

UNLABELLED: Maintenance of positive effects of physical activity on growing bone is unknown. Physical activity was associated with increased BMC and BMD in a 7-year follow-up with 142 adolescent girls. Marked reduction in physical activity had an unfavorable effect on bone measurements, which is an important finding when the prevention of osteoporosis is considered. INTRODUCTION: Environmental factors influence quality and durability of bone. Physical activity, with high-impact weight bearing activity during puberty in particular, has been shown to have a beneficial effect on growing bone. Only few studies have been published on the maintenance of these effects. METHODS: At baseline, 142 girls aged 9-15 years participated in the present 7-year follow-up study. Growth and development, physical activity, and intakes of calcium and vitamin-D were recorded at intervals. BMC and BMD measurements were repeated using DXA. Based on the recording of physical activity during the follow-up measurements, the effect of the reduction in physical activity was examined with the bone measurements, and the measurements in the tertiles based on the amount of physical activity during the whole follow-up period were compared. RESULTS: Physical activity was positively associated with the development of BMC and BMD during the follow-up. The mean BMC of the lumbar spine increased 1.69 g (3%) (p = 0.021) more among those girls who maintained the physical activity level as compared with those who reduced it during last 4 years. In the femoral neck, the corresponding difference was 0.14 g (4.6%) (p = 0.015) between the same two groups of girls. The mean increases in BMC at lumbar spine and femoral neck were more substantial among those girls having the highest physical activity levels during the 7-year follow-up (46.7% and 22.6%) as compared with those having the lowest physical activity levels (43.3% and 17.4%, respectively). CONCLUSIONS: The findings of the present study show that regular physical activity is valuable in preserving the peak bone mass acquired at puberty in particular. Many of the girls who markedly reduced their activity levels lost bone in their femoral neck prior to their 25th birthday.