Electron heating in kinetic-Alfvén-wave turbulence.

We report analytical and numerical investigations of subion-scale turbulence in low-beta plasmas using a rigorous reduced kinetic model. We show that efficient electron heating occurs and is primarily due to Landau damping of kinetic Alfvén waves, as opposed to Ohmic dissipation. This collisionless damping is facilitated by the local weakening of advective nonlinearities and the ensuing unimpeded phase mixing near intermittent current sheets, where free energy concentrates. The linearly damped energy of electromagnetic fluctuations at each scale explains the steepening of their energy spectrum with respect to a fluid model where such damping is excluded (i.e., a model that imposes an isothermal electron closure). The use of a Hermite polynomial representation to express the velocity-space dependence of the electron distribution function enables us to obtain an analytical, lowest-order solution for the Hermite moments of the distribution, which is borne out by numerical simulations.

Spontaneous magnetization of collisionless plasma.

SignificanceAstronomical observations indicate that dynamically important magnetic fields are ubiquitous in the Universe, while their origin remains a profound mystery. This work provides a paradigm for understanding the origin of cosmic magnetism by taking into account the effects of the microphysics of collisionless plasmas on macroscopic astrophysical processes. We demonstrate that the first magnetic fields can be spontaneously generated in the Universe by generic motions of astrophysical turbulence through kinetic plasma physics, and cosmic plasmas are thereby ubiquitously magnetized. Our theoretical and numerical results set the stage for determining how these "seed" magnetic fields are further amplified by the turbulent dynamo (another central and long-standing question) and thus advance a fully self-consistent explanation of cosmic magnetogenesis.

Efficient quantum algorithm for dissipative nonlinear differential equations.

Nonlinear differential equations model diverse phenomena but are notoriously difficult to solve. While there has been extensive previous work on efficient quantum algorithms for linear differential equations, the linearity of quantum mechanics has limited analogous progress for the nonlinear case. Despite this obstacle, we develop a quantum algorithm for dissipative quadratic n-dimensional ordinary differential equations. Assuming [Formula: see text], where R is a parameter characterizing the ratio of the nonlinearity and forcing to the linear dissipation, this algorithm has complexity [Formula: see text], where T is the evolution time, ϵ is the allowed error, and q measures decay of the solution. This is an exponential improvement over the best previous quantum algorithms, whose complexity is exponential in T. While exponential decay precludes efficiency, driven equations can avoid this issue despite the presence of dissipation. Our algorithm uses the method of Carleman linearization, for which we give a convergence theorem. This method maps a system of nonlinear differential equations to an infinite-dimensional system of linear differential equations, which we discretize, truncate, and solve using the forward Euler method and the quantum linear system algorithm. We also provide a lower bound on the worst-case complexity of quantum algorithms for general quadratic differential equations, showing that the problem is intractable for [Formula: see text] Finally, we discuss potential applications, showing that the [Formula: see text] condition can be satisfied in realistic epidemiological models and giving numerical evidence that the method may describe a model of fluid dynamics even for larger values of R.

In-situ acceleration-speed profile of an elite soccer academy: A cross-sectional study.

Speed is an essential skill in sports performance and an important performance metric in talent identification. This study aims to evaluate and compare the sprint acceleration characteristics across different age groups in an elite soccer academy. A total of 141 elite academy soccer players were recruited to participate in the study, and they were assigned to their respective competitive age groups, ranging from under-14 to the B-team. An individual in-situ acceleration-speed (A-S) profile was assessed and derived from Global Position System (GPS) speed-acceleration raw data, from 10 consecutive football sessions, in the beginning of the season. The results showed that under-14 players exhibited significantly lower theoretical maximum speed (S0) (ηp2 = 0.215, p < 0.01) when compared with all other age groups. However, no differences were found between maximum theoretical acceleration (A0) and A-S slope between age groups. The results suggest that sprint mechanical profiles of young soccer athletes remain stable throughout their athletic development. Nevertheless, younger athletes have less capacity to apply horizontal force at higher speeds (S0).

Dynamic Phase Alignment in Navier-Stokes Turbulence.

In Navier-Stokes turbulence, energy and helicity injected at large scales are subject to a joint direct cascade, with both quantities exhibiting a spectral scaling ∝k^{-5/3}. We demonstrate via direct numerical simulations that the two cascades are compatible due to the existence of a strong scale-dependent phase alignment between velocity and vorticity fluctuations, with the phase alignment angle scaling as cosα_{k}∝k^{-1}.

Dynamic Phase Alignment in Inertial Alfvén Turbulence.

In weakly collisional plasma environments with sufficiently low electron beta, Alfvénic turbulence transforms into inertial Alfvénic turbulence at scales below the electron skin depth, k_{⊥}d_{e}≳1. We argue that, in inertial Alfvénic turbulence, both energy and generalized kinetic helicity exhibit direct cascades. We demonstrate that the two cascades are compatible due to the existence of a strong scale dependence of the phase alignment angle between velocity and magnetic field fluctuations, with the phase alignment angle scaling as cosα_{k}∝k_{⊥}^{-1}. The kinetic and magnetic energy spectra scale as ∝k_{⊥}^{-5/3} and ∝k_{⊥}^{-11/3}, respectively. As a result of the dual direct cascade, the generalized helicity spectrum scales as ∝k_{⊥}^{-5/3}, implying progressive balancing of the turbulence as the cascade proceeds to smaller scales in the k_{⊥}d_{e}≫1 range. Turbulent eddies exhibit a phase-space anisotropy k_{∥}∝k_{⊥}^{5/3}, consistent with critically balanced inertial Alfvén fluctuations. Our results may be applicable to a variety of geophysical, space, and astrophysical environments, including the Earth's magnetosheath and ionosphere, solar corona, and nonrelativistic pair plasmas, as well as to strongly rotating nonionized fluids.

Fully Kinetic Simulation of 3D Kinetic Alfvén Turbulence.

We present results from a three-dimensional particle-in-cell simulation of plasma turbulence, resembling the plasma conditions found at kinetic scales of the solar wind. The spectral properties of the turbulence in the subion range are consistent with theoretical expectations for kinetic Alfvén waves. Furthermore, we calculate the local anisotropy, defined by the relation k_{∥}(k_{⊥}), where k_{∥} is a characteristic wave number along the local mean magnetic field at perpendicular scale l_{⊥}∼1/k_{⊥}. The subion range anisotropy is scale dependent with k_{∥}

Prevalence of adult overweight and obesity in 20 European countries, 2014.

Background: Monitoring obesity and overweight prevalence is important for assessing interventions aimed at preventing or reducing the burden of obesity. This study aimed to provide current data regarding the prevalence of overweight and obesity of adults, from 20 European countries. Methods: Participants were 34 814 (16 482 men) adults with mean age 50.8 ± 17.7. Data from European Social Survey round 7, 2014, were analysed. Body mass index (BMI) was calculated from self-reported height and weight. Results: The proportion of underweight was only 2%, and 44.9% for normal weight. Overweight and obese accounted for 53.1%. More men than women were overweight (44.7% vs. 30.5%). Older adults were significantly more overweight (42.4%) and obese (20.9%) than middle age and younger adults. Retired people account for a greater proportion of overweight (42.0%) and obese (21.5%), when compared with employed, unemployed and students. People from rural areas were significantly more overweight (39.1 vs. 36.1%) and obese (17.0 vs. 15.3%) than those who lived in urban areas. The estimates indicate that the highest prevalence of overweight was in Czech Republic (45.2%), Hungary (43.7%) and Lithuania (41.7%). For obesity, Slovenia (20.8%), Estonia (19.7%) and the United Kingdom (19.2%) were the countries with the highest prevalence. Conclusion: Even though data was self-reported, and individuals tend to overestimate their height and underestimate their weight, the prevalence of overweight and obesity is considered high. More than half of the European population is overweight and obese. This study strengthens and updates the claims of an excessive weight epidemic in Europe.

Role of Magnetic Reconnection in Magnetohydrodynamic Turbulence.

The current understanding of magnetohydrodynamic (MHD) turbulence envisions turbulent eddies which are anisotropic in all three directions. In the plane perpendicular to the local mean magnetic field, this implies that such eddies become current-sheetlike structures at small scales. We analyze the role of magnetic reconnection in these structures and conclude that reconnection becomes important at a scale λ∼LS_{L}^{-4/7}, where S_{L} is the outer-scale (L) Lundquist number and λ is the smallest of the field-perpendicular eddy dimensions. This scale is larger than the scale set by the resistive diffusion of eddies, therefore implying a fundamentally different route to energy dissipation than that predicted by the Kolmogorov-like phenomenology. In particular, our analysis predicts the existence of the subinertial, reconnection interval of MHD turbulence, with the estimated scaling of the Fourier energy spectrum E(k_{⊥})∝k_{⊥}^{-5/2}, where k_{⊥} is the wave number perpendicular to the local mean magnetic field. The same calculation is also performed for high (perpendicular) magnetic Prandtl number plasmas (Pm), where the reconnection scale is found to be λ/L∼S_{L}^{-4/7}Pm^{-2/7}.

Health complaints among adolescents: Associations with more screen-based behaviours and less physical activity.

In this study, we investigated the relationship between screen-based behaviours, physical activity, and health complaints (headaches, feeling low, irritability, and nervousness). Screen-based behaviour included TV viewing, computer use, and time spent playing video games. Data were collected from 4462 Portuguese adolescents (2394 girls) aged 11-16 years. Girls who reported engaging in more screen-based behaviour (hours/day) also reported having more headaches, feeling lower, being more irritable, and feeling more nervous. Boys who reported more screen time were more irritable. Physical activity (times/week) was negatively associated with reports of feeling nervous among girls, and with headaches, feeling low, irritability, and feeling nervous among boys. Considering that time spent using the computer is related with more health complaints, and physical activity was related with fewer health complaints among boys, it is important to develop strategies to reduce adolescents' computer screen time, and to promote physical activity.

Special Issue: Damage Analysis for Composite Materials: Methods, Testing and Evaluation.

After the Stone, the Bronze, and the Iron Ages, material history is now in the Composite Age [...].

Effects of Physical Activity on Cognition, Behavior, and Motor Skills in Youth with Autism Spectrum Disorder: A Systematic Review of Intervention Studies.

The aim of this paper was to analyze the acute and chronic effects of physical activity (PA) on cognition, behavior, and motor skill in youth with autism spectrum disorder (ASD), taking into account potential confounders. In addition, it was intended to elaborate a guide of educational applications with strategies for PA use. Studies were identified in four databases from January 2010 to June 2023. A total of 19 interventional studies met the inclusion criteria. PA programs ranged from two weeks to one year in duration, with a frequency of one to five sessions per week. More than 58% of the studies showed positive effects of PA on cognition, and 45.5% on behavior and motor skill. Moderate-vigorous PA for 15-30 min has shown acute effects on cognition, general behavior, and stereotypic/repetitive behaviors in youth with ASD. A total of 9 out of 14 studies showed chronic effects on general behavior and stereotypic behaviors, and only 6 on motor skills.

Cross-Cultural Adaptation and Validation of the Portuguese Version of the SARC-F in Community-Dwelling Older Adults.

(1) Background: The goal of this study was to analyze the reliability and validity of the Portuguese version of the SARC-F in older adults. (2) Methods: A total of 100 participants (77.1 ± 7.36 years, 73% women) were included in the study. In a first phase, the Portuguese SARC-F was adapted following the standardized forward-backward translation procedure, and internal consistency as well as inter-rater and test-retest reliability of the Portuguese SARC-F were analyzed. Secondly, clinical validation was evaluated by comparing the SARC-F total score with five operational definitions of sarcopenia and with other sarcopenia-related measurements. Discriminant validity, with respect to low muscle mass and strength and physical function were analyzed. (3) Results: The Portuguese SAR-F showed acceptable internal consistency (Cronbach α = 0.82), excellent inter-rater reliability (total score), and substantial to excellent test-retest reliability (ICC = 0.891 for the total score). Specificity ranged from 72.5% (FNIH) to 73.4 (IGWS), and negative predictive values went from 91.8% (EWGSOP1) to 97.3% (FNIH), but low sensitivity and positive predictive value were observed. The Portuguese SARC-F showed a moderate ability to discriminate people with low muscle strength (AUC = 0.78) and gait speed (AUC = 0.89). (4) Conclusions: The Portuguese SARC-F is a valid and reliable tool for ruling out sarcopenia in community-dwelling older adults and can discriminate between people with low handgrip strength and gait speed.

Associations between the severity of menopausal symptoms and musculoskeletal pain in postmenopausal Portuguese women.

OBJECTIVE: To analyze the association of the severity of the menopausal symptoms with musculoskeletal pain in Portuguese postmenopausal women. METHODS: A cross-sectional, observational study was conducted on 167 women (63.85 ± 9.36 years). The Menopause Rating Scale was used to evaluate the menopausal symptoms severity, while the Nordic Musculoskeletal Questionnaire was employed to assess the localization of the musculoskeletal pain, and multi-located pain was determined if two or more body regions were affected. Depression (Hospital Anxiety and Depression Scale), age, body mass index (BMI) and physical activity level were considered as potential confounders. RESULTS: A greater severity of the somato-vegetative menopausal symptoms was related to the prevention from usual activities because of pain in the neck, shoulders, elbows, wrists/hands and knees (R2 of Nagelkerke = 0.064, 0.043, 0.074, 0.045 and 0.045, respectively). Associations were also observed between greater age and pain in the knees, ankles and feet (R2 of Nagelkerke = 0.036 and 0.034, respectively), and being physically inactive with upper back pain (R2 of Nagelkerke = 0.060). Higher depressive symptoms were linked to pain in the hip/thighs and knees (R2 of Nagelkerke = 0.067 and 0.085, respectively), as well as being physically inactive was related ton in the neck (R2 of Nagelkerke = 0.053). Only a greater BMI was related to multi-located pain in the last 7 days (R2 of Nagelkerke = 0.041). CONCLUSIONS: The findings of our study showed that, taking into account possible confounders, greater severity of the menopausal symptoms at a somatic-vegetative level was associated with more anatomical regions with musculoskeletal pain.

The effects of low-volume combined training on health-related physical fitness outcomes in active young adults: A controlled clinical trial.

The effects of combined training (CT) on improving general health are well known, however, few studies have investigated the effects of low-volume CT. So, the aim of this study is to investigate the effects of 6 weeks of low-volume CT on body composition, handgrip strength (HGS), cardiorespiratory fitness (CRF) and affective response (AR) to exercise. Eighteen healthy, active young adult man (mean â€‹± â€‹SD, [20.06 ± 1.66] years; [22.23 ± 2.76] â€‹kg/m2) performed either a low-volume CT (EG, n â€‹= â€‹9), or maintained a normal life (CG, n â€‹= â€‹9). The CT was composed of three resistance exercises followed by a high intensity-interval training (HIIT) on cycle ergometer performed twice a week. The measures of the body composition, HGS, maximal oxygen consumption ( V ˙ O2max) and AR to exercise were taken at baseline and after training for analysis. Furthermore, an ANOVA test of repeated measures and t-test paired samples were used with a p â€‹≤ â€‹0.05. The results showed that EG improved HGS (pre: [45.67 ± 11.84] â€‹kg vs. post: [52.44 ± 11.90] â€‹kg, p â€‹< â€‹0.01) and V ˙ O2max (pre: [41.36 ± 5.16] â€‹ml⋅kg-1⋅min-1 vs. post: [44.07 ± 5.98] â€‹ml⋅kg-1⋅min-1, p â€‹< â€‹0.01). Although, for all measures the body composition had not significant differences between weeks (p â€‹> â€‹0.05), nevertheless the feeling scale was positive in all weeks and without significant differences between them (p â€‹> â€‹0.05). Lastly, for active young adults, the low-volume CT improved HGS, CRF and had a positive outcome in AR, with less volume and time spent than traditional exercise recommendations.

Psychometric properties and validity of the Menopause Rating Scale in postmenopausal Portuguese women.

OBJECTIVE: The aim of the study is to analyze the reliability and validity of the Portuguese version of the Menopause Rating Scale (MRS) among postmenopausal Portuguese women. METHODS: A total of 184 postmenopausal women completed the Portuguese MRS. Internal consistency and test-retest reliability were studied. Construct, convergent, and concurrent validity were assessed. The 10-item Cervantes Scale and the Hospital Anxiety and Depression Scale were used to determine convergent and concurrent validity, respectively. The ability and accuracy of the Portuguese MRS to discriminate between women with and without anxiety and depression cases were evaluated, and a receiver operating characteristic curve analysis was used. RESULTS: The Portuguese MRS showed an appropriate level of internal consistency (Cronbach α, 0.84 for MRS total score) and test-retest reliability (MRS total score; intraclass correlation coefficient, 0.92; 95% confidence interval, 0.85-0.96). Factor analysis (construct validity) revealed a 3-factor structure (explained variance of 62.08%). The MRS total score and its 3 factors showed good convergent (10-item Cervantes Scale) and concurrent (Hospital Anxiety and Depression Scale anxiety and depression) validity (all P < 0.001). The Portuguese MRS total score was significantly able to discriminate between postmenopausal women with and without anxiety (P < 0.001) and depression (P = 0.001), with a cutoff point of 15.50 (80.00% sensitivity and 63.70% specificity) for detecting depression and a cutoff point of 16.50 (82.35% sensitivity and 78.57% specificity) for identifying anxiety. CONCLUSIONS: The Portuguese MRS has been shown to be a valid and reliable questionnaire for assessing the severity of menopausal symptoms and discriminating among postmenopausal women with and without anxiety and depression.

Damage Propagation by Cyclic Loading in Drilled Carbon/Epoxy Plates.

Fiber reinforced composites are widely used in the production of parts for load bearing structures. It is generally recognized that composites can be affected both by monotonic and cyclic loading. For assembly purposes, drilling is needed, but holes can act as stress concentration notches, leading to damage propagation and failure. In this work, a batch of carbon/epoxy plates is drilled by different drill geometries, while thrust force is monitored and the hole's surrounding region is inspected. Based on radiographic images, the area and other features of the damaged region are computed for damage assessment. Finally, the specimens are subjected to Bearing Fatigue tests. Cyclic loading causes ovality of the holes and the loss of nearly 10% of the bearing net strength. These results can help to establish an association between the damaged region and the material's fatigue resistance, as larger damage extension and deformation by cyclic stress contribute to the loss of load carrying capacity of parts.

Associations between the impact of menopausal symptoms and fall-related self-efficacy.

OBJECTIVE: To analyze the association between the severity of menopausal symptoms and two important fall risk factors, namely balance confidence and fear of falling, among Portuguese and Spanish postmenopausal women 65 years or older. METHODS: A cross-sectional, observational study was conducted on 363 women (66.21 ± 9.00 y) from several Portuguese and Spanish locations. The Menopause Rating Scale was used to evaluate the severity of menopausal symptoms, while the Falls Efficacy Scale-International and Activities-specific Balance Confidence Scale-16 items were used to assess balance confidence and fear of falling, respectively. Anxiety and depression (evaluated by the Hospital Anxiety and Depression Scale), age, time since the onset of menopause, body mass index, history of falls, osteoporosis, smoking habit, physical activity level, and nocturia were considered as potential confounders. Independent associations were analyzed after adjusting for potential confounding variables. Student's t test, bivariate correlations, and multivariate linear regression analysis were performed. RESULTS: A total of 363 women (66.21 ± 9.00 y) participated in the study, 192 from Portugal and 171 from Spain. Linear regression analysis indicates that more severe menopausal symptoms at a somatovegetative level (beta coefficient [ß] = -0.25; 95% confidence interval [95% CI], -2.09 to -0.81; P = <0.001), a higher body mass index (ß = -0.16; 95% CI, -1.22 to -0.22; P = 0.005), and osteoporosis (ß = 0.14; 95% CI, 1.36 to 10.08; P = 0.010) were associated with lower balance confidence values. On the other hand, a higher score in the Menopause Rating Scale somatovegetative domain (ß = 0.22; 95% CI, 0.27-0.79; P = <0.001), depression (ß = 0.36; 95% CI, 0.59-1.08; P = <0.001), and years after the menopause onset (ß = 0.15; 95% CI, 0.04-0.22; P = 0.006) were linked to increased fear of falling. CONCLUSIONS: The findings of our study show that, after taking into account possible confounders, increased severity of menopausal symptoms at a somatic level was associated with heightened fear of falling and diminished balance confidence.

Impact of Qigong exercises on the severity of the menopausal symptoms and health-related quality of life: A randomised controlled trial.

The aim of the present study was to analyze the effects of a Qigong exercise programme on the severity of the menopausal symptoms and health-related quality of life (HRQoL) of community-dwelling postmenopausal women. This was done by means of a randomised clinical trial with a sample of 125 women who were assigned to either a control (n = 62) or an experimental group (n = 63). The severity of their menopause-related symptoms and HRQoL were assessed through the Menopause Rating Scale (MRS) and the 36-item Short-Form Health Survey (SF-36) respectively, before and after the intervention period. The main findings of our study reveal significant improvement in the severity of menopausal symptoms at the somatic, psychological, and urogenital levels, as well as in the total score of the MRS. Additionally, participants assigned to the Qigong group experienced improvement in the general health, physical functioning, role-physical, bodily pain, vitality, and mental health domains of the 36-item Short-Form Health Survey, as well as in its physical component and mental component summaries. We can therefore conclude that, among Spanish postmenopausal women, a twelve-week Qigong exercise programme has beneficial effects on the severity of menopausal symptoms and HRQoL.HighlightsWe have studied the effects of Qigong on menopause-related quality of life.Qigong is a useful tool in the management of the severity of menopausal symptoms.A 12-week Qigong programme showed benefits on health-related quality of life.Trial registration: ClinicalTrials.gov identifier: NCT03989453.

Seasonality and Objective Physical Activity and Sedentary Behaviour among Older Adults from Four European Countries.

OBJECTIVE: The present study aimed to explore the relationship between objective physical activity and sedentary behaviour with seasonality among a sample of older adults living in four European countries. METHODS: A sample of 169 older adults living in Croatia, Greece, Portugal, and Poland (mean age = 72.2 ± 6.0, 68% female) had valid objective physical activity and sedentary behaviour data collected in different seasons of the year: spring and autumn/winter. Physical activity and sedentary behaviour were collected with accelerometers (ActiGraph, GT3X), over 7 consecutive days, in both periods. A valid record was defined as at least two weekdays and one weekend day with 10 hours of wearing time. Analyses were performed with IBM SPSS 28.0, using t-test, ANOVA, and binary logistic regressions. RESULTS: Most older adults from the four countries met the physical activity guidelines in spring and autumn/winter. No significant variations were found across seasons for sedentary behaviour and physical activity both for light and vigorous intensity, regardless of sex, country, education, and body mass index (BMI). A decline in moderate physical activity intensity from spring to autumn/winter was found for those with lower education and higher BMI. CONCLUSION: The promotion of physical activity must be considered in programs to promote healthy aging throughout the year, especially considering the moderate intensity and those populations with higher BMI and lower educational levels.