Mechanochemical Synthesis of Sustainable Ternary and Quaternary Nanostructured Cu2SnS3, Cu2ZnSnS4, and Cu2ZnSnSe4 Chalcogenides for Thermoelectric Applications.

Copper-based chalcogenides have emerged as promising thermoelectric materials due to their high thermoelectric performance, tunable transport properties, earth abundance and low toxicity. We have presented an overview of experimental results and first-principal calculations investigating the thermoelectric properties of various polymorphs of Cu2SnS3 (CTS), Cu2ZnSnS4 (CZTS), and Cu2ZnSnSe4 (CZTSe) synthesized by high-energy reactive mechanical alloying (ball milling). Of particular interest are the disordered polymorphs of these materials, which exhibit phonon-glass-electron-crystal behavior-a decoupling of electron and phonon transport properties. The interplay of cationic disorder and nanostructuring leads to ultra-low thermal conductivities while enhancing electronic transport. These beneficial transport properties are the consequence of a plethora of features, including trap states, anharmonicity, rattling, and conductive surface states, both topologically trivial and non-trivial. Based on experimental results and computational methods, this report aims to elucidate the details of the electronic and lattice transport properties, thereby confirming that the higher thermoelectric (TE) performance of disordered polymorphs is essentially due to their complex crystallographic structures. In addition, we have presented synchrotron X-ray diffraction (SR-XRD) measurements and ab initio molecular dynamics (AIMD) simulations of the root-mean-square displacement (RMSD) in these materials, confirming anharmonicity and bond inhomogeneity for disordered polymorphs.

Roles of Defects and Sb-Doping in the Thermoelectric Properties of Full-Heusler Fe2TiSn.

The potential of Fe2TiSn full-Heusler compounds for thermoelectric applications has been suggested theoretically, but not yet proven experimentally, due to the difficulty in obtaining reproducible, homogeneous, phase-pure and defect-free samples. In this work, we studied Fe2TiSn1-xSbx polycrystals (x from 0 to 0.6), fabricated by high-frequency melting and long-time high-temperature annealing. We obtained fairly good phase purity, a homogeneous microstructure, and good matrix stoichiometry. Although the intrinsic p-type transport behavior is dominant, n-type charge compensation by Sb-doping is demonstrated. Calculations of the formation energy of defects and electronic properties carried out using the density functional theory formalism reveal that charged iron vacancies VFe2- are the dominant defects responsible for the intrinsic p-type doping of Fe2TiSn under all types of (except Fe-rich) growing conditions. In addition, Sb substitutions at the Sn site give rise either to SbSn, SbSn1+, which are responsible for n-type doping and magnetism (SbSn) or to magnetic SbSn1-, which act as additional p-type dopants. Our experimental data highlight good thermoelectric properties close to room temperature, with Seebeck coefficients up to 56 µV/K in the x = 0.2 sample and power factors up to 4.8 × 10-4 W m-1 K-2 in the x = 0.1 sample. Our calculations indicate the appearance of a pseudogap under Ti-rich conditions and a large Sb-doping level, possibly improving further the thermoelectric properties.

Nanoscale analysis of superconducting Fe(Se,Te) epitaxial thin films and relationship with pinning properties.

The process of developing superconducting materials for large scale applications is mainly oriented to optimize flux pinning and the current carrying capability. A powerful approach to investigate pinning properties is to combine high resolution imaging with transport measurements as a function of the magnetic field orientation, supported by a pinning modelling. We carry out Transmission Electron Microscopy, Electron Energy Loss Spectroscopy and critical current measurements in fields up to 16 T varying the angle between the field and c-axis of Fe(Se,Te) epitaxial thin films deposited on CaF2 substrates. We find evidence of nanoscale domains with different Te:Se stoichiometry and/or rotated and tilted axes, as well as of lattice distortions and two-dimensional defects at the grain boundaries. These elongated domains are tens of nm in size along the in-plane axes. We establish a correlation between these observed microstructural features and the pinning properties, specifically strongly enhanced pinning for the magnetic field oriented in-plane and pinning emerging at higher fields for out-of-plane direction. These features can be accounted for within a model where pinning centers are local variations of the critical temperature and local variations of the mean free path, respectively. The identification of all these growth induced defects acting as effective pinning centers may provide useful information for the optimization of Fe(Se,Te) coated conductors.

Systematic Review of Fatigue in Individuals With Cerebral Palsy.

In this systematic review, we collected and analyzed literature works comparing self-reported fatigue and objectively-measured fatigue in individuals with cerebral palsy (CP) and in age-matched typically developing/typically developed (TD) controls (Healthy). The search was conducted on four electronic databases/platforms (PubMed, Web of Science, Cochrane Library, and Scopus) using the key words "cerebral palsy" combined with "fatig*," where the asterisk was used as a wildcard. As a critical appraisal tool, the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies (2017) was used. A total of 22 studies passed the critical appraisal rating and were included in both narrative and quantitative analyses. The overall evidence quality of the findings was considered very good. Data of objectively-measured fatigue in performing maximal fatiguing tasks indicated lower fatigue levels in participants with CP, possibly due to their pathological inability to recruit highly fatigable muscle fibers. Highly trained individuals with CP and TD controls performing maximal fatiguing tasks seem to be an exception to this, as they exhibited similar levels of fatigue. In submaximal fatiguing tasks, including daily physical activities, either objectively-measured or self-reported fatigue was higher in participants with CP than in TD controls, indicating a lower ability for development of neurophysiological compensation for fatigue among participants with CP. Further studies on fatigue are needed to gain an insight into the multifold mechanisms of fatigue in individuals with CP. Understanding fatigue mechanisms could help in setting up strategies for effective intervention programs, with benefits in healthcare and improved quality of life of individuals with CP. Systematic Review Registration: [PROSPERO 2019], identifier [CRD42019143524].

Surface Electromyography Spectral Parameters for the Study of Muscle Fatigue in Swimming.

The purpose of this study was to assess validity, stability and sensitivity, of 4 spectral parameters-median frequency (Fmed), mean frequency (Fmean), Dimitrov index (DI), and mean instant frequency (Fmi)-in measuring localized muscle fatigue in swimming and to investigate their correlation with the variations of kinematic data and mechanical fatigue. Electrophysiological measures of muscle fatigue were obtained in real-time during a 100 m front crawl test at maximum speed in 15 experienced swimmers, using surface electromyography in six muscles employed in front crawl, while kinematic data of swimming was measured from video analysis. Mechanical fatigue was measured as the difference between muscle strength prior to and immediately after the 100 m front crawl in a dry-land multi-stage isometric contraction test. Statistically significant fatigue (p < 0.0001) was found for all spectral parameters in all muscles. Fmed and Fmean varied between 10 and 25%, DI between 50 and 150%, and Fmi between 5 and 10%. Strong correlation (Pearson r ≥ 0.5) with mechanical fatigue was found for all spectral parameters except for Fmi and it was strongest for Fmed and Fmean. From our study, it turns out that Fmed and Fmean are more valid and stable parameters to measure fatigue in swimming, while DI is more sensitive.

The Effect of Kinesio Taping on Spasticity: A Randomized, Controlled, Double-Blind Pilot Study in Para-Swimmers.

CONTEXT: Kinesio Taping (KT) produces several clinical effects, including pain relief, edema absorption, and improved muscle performance. When applied in the insertion to origin mode, it is claimed to inhibit excessive muscle contractions. OBJECTIVE: Investigate whether KT applied in the insertion to origin mode could reduce the exaggerated reflex contraction of spastic muscles. DESIGN: Randomized crossover trial, with a restricted block randomization. SETTING: Clinical laboratory and swimming pool. PATIENTS: Seven para-swimmers. INTERVENTION: KT, applied in inhibitory mode, to investigate its effect on knee extensor spasticity. MAIN OUTCOME MEASURES: Primary outcome is stretch reflex, as compared with clinical assessment of spasticity by Modified Ashworth Scale and self-perceived spasticity by numeric rating scale. Secondary outcomes were Medical Research Council for strength of knee extensor muscles and chronometric swimming performance in 100-m freestyle. RESULTS: KT significantly decreased the amplitude of stretch reflex (P < .001), whereas the placebo treatment produced no significant effects. Scores of Medical Research Council for strength and Modified Ashworth Scale did not change after KT, whereas numeric rating scale scores for spasticity significantly decreased (P = .001). The swimming performance was significantly improved after KT treatment as compared with baseline (P < .01). CONCLUSIONS: This exploratory study performed on para-athletes suggests that KT could reduce spasticity. This outcome has 3-fold implications for clinical, rehabilitation, and sport methods.

Ghost spasticity in multiple sclerosis.

Spasticity is the velocity-dependent hypertonia frequently encountered in patients affected by Upper Motor Neuron Syndrome. It is due to a tonic stretch reflex, which is evoked in patients at rest. The aim of this study, performed using surface electromyography (EMG), was to investigate stretch reflex excitability in the hamstrings muscles of patients affected by progressive Multiple Sclerosis (MS) and to correlate EMG results with clinical findings. Thirty patients and 20 age-matched healthy controls were investigated. EMG activity was recorded from biceps femoris muscle with the patient at rest. To stretch hamstrings muscles, the patient's leg was manually moved from maximal flexion to maximal extension at 3 different velocities to investigate both phasic and tonic stretch reflex. Only 7 patients were affected by hypertonia of the hamstrings; 4 of them showed muscle contracture. A tonic stretch reflex was present in the vast majority of the recruited patients, whether they presented hypertonia of the hamstrings or not. Tonic stretch reflex is often present in the hamstrings muscles of progressive MS patients without producing increased muscle tone. This "ghost spasticity" is likely to be, for its intrinsic features, an important risk factor for the development of contractures in the hamstrings muscles.

Self-Perceived Psychophysical Well-Being of Young Competitive Swimmers With Physical or Intellectual Impairment.

Regular practice of sport activities yields psychophysical benefits for both the general population and persons affected by physical or intellectual impairments. Practicing competitive sport may add further value to these benefits. The objective of this observational cross-sectional study was to investigate the role of competitive sport practice in enhancing self-perceived psychophysical well-being of some select participants, using the Psychological General Well-Being Index and the Short Form-12 indices. We recruited at national events 100 young Italian competitive swimmers affected by physical or intellectual impairment. These respondents' results were compared with those of a control group of 100 Italian participants who did not practice competitive sport but who were also affected by physical or intellectual impairment, randomly selected from rehabilitation clinics and communities of young people with disabilities. Scores of psychological and emotional well-being were higher by 40% or more for the practitioners of competitive sport (p < .0001; Cohen's effect size d ≥ 1.3). While our study's results suggest possible positive psychophysical benefits to competitive sport practice for young people affected by physical or intellectual impairment, longitudinal research is needed to be certain that our results are not due to self-selection into sports participation of those persons with disabilities who have a uniquely higher sense of well-being.

Evidence of the isoelectronic character of F doping in SmFeAsO1-x F x : a first-principles investigation.

We study the electronic structure of the SmFeAsO1-x F x alloy by means of first-principle calculations. We find that, contrary to common believe, F-doping does not change the charge balance between electrons and holes free-carriers in SmFeAsO1-x F x . For energies within a narrow energy range accross [Formula: see text], the effect of F-doping on the band structure dispersion is tiny in both the paramagnetic and stripe antiferromagnetic phase. The charge balance between the conducting FeAs-layer and the SmO1-x F x charge reservoir layer is not influenced by the compositional change. The additional charge carried by fluorine, with respect to the oxygen, is compensated by a change in the oxidation state of the Sm ion from 3+ to 2+. A comparison with the SmFe1-x Co x AsO system shows that such charge compensation by the Sm ion is not shared by donors substituting at the Fe site.

Band filling and disorder effects on the normal state thermoelectric behavior in MgB2.

The goal of this work is providing a comprehensive interpretation framework for the wide and varied experimental phenomenology of the Seebeck effect in MgB2 samples with different levels of doping in either π or σ bands and different levels of disorder, using a combined experimental and theoretical approach. We calculate the temperature dependent diffusive Seebeck coefficient S diff(T) with the Boltzmann equation resolved in relaxation time approximation, taking into account the scattering with phonons and impurities, the effect of renormalization and the effect doping in a rigid band approximation. We show that selective disorder has a sizeable effect on the S diff magnitude, as it tunes the relative contributions of σ and π bands. Disorder also affects the S diff temperature dependences, eventually yielding a linear S diff(T) behavior in the dirty limit. We also show that band filling has opposite effects on S, depending on which band dominates transport. In parallel, we carry out the Seebeck effect measurements on neutron-irradiated Mg11B2, and on two series of doped samples Mg1-x Al x B2 and Mg(B1-x C x )2. From comparison of calculated S diff(T) and experimental S(T) curves, we demonstrate that diffusive and phonon drag terms give comparable contributions in clean samples, but the phonon drag term is progressively suppressed with increasing disorder. In C and Al doped samples we observe very different experimental behaviors in terms of sign, magnitude and temperature dependence. Indeed, notwithstanding the similar electron doping introduced by both substitutions, C or Al doping yields disorder which mainly affects either σ or π bands, respectively. With the help of our theoretical approach, we are able to disentangle the various effects and prove that the Seebeck coefficient is a very sensitive probe of this kind of disorder.

Training methods and analysis of races of a top level Paralympic swimming athlete.

Training methods for Paralympic swimmers must take into account different pathologies, competitions classes, athlete's individual circumstances and peculiar physical adaptation mechanisms, hence general guidelines cannot be found in literature. In this study we present a training program, implemented for the physical preparation of a top level Paralympic swimmer. The athlete under study, affected by infantile cerebral palsy within a clinical picture of a spastic tetraparesis, by the end of 2016 was holder of Italian, European, world and Paralympic titles in the 400-m freestyle competition, S6 class. The training macrocycle was structured in a 3-fold periodization (three mesocycles), in view of the preparation to three international competitions. The 4-month training mesocycles prior to each competition differed substantially in terms of mileage load, intensity and recovery times. The first mesocycle was characterized by a sizeable low-intensity mileage load, the second one was shifted to lower mileage load, carried out at middle-to-high intensity levels, the third one entailed increased effort intensity, counterbalanced by lower mileage load. In all cases, recovery times were balanced to obtain optimized performance through physical adaptation to training stimuli, keeping into account the physiopatological response. Tapering phases were adjusted to maximize performance at competition. As an assessment of the effectiveness of the training method, correspondence between chronometric and technical parameters in the three competitions and the respective mesocycle training programs was found. The results of the present study may support the development of training guidelines for athletes affected by upper motor neuron lesions.

Protocol for the study of self-perceived psychological and emotional well-being of young Paralympic athletes.

BACKGROUND: We present the detailed protocol set up to investigate how agonistic sport affects the self-perceived psychological and emotional well-being of disabled young people. METHODS: The study will be carried out on a number of subjects as large as 800-1200, using well-established indices that give a quantitative measure of such well-being, namely SF-12 and PGWBI. The related questionnaires will be administered to the participants to a forthcoming international event, the European Para-Youth Games, 9-15 October 2017, Liguria, Italy, as well as to a reference population of a similar number of subjects, made up of young disabled people that do not practice agonistic sport. DISCUSSION: We expect that the outcomes of the study may strongly impact not only the socio-sanitary field but also society in general, as disabled people can be considered an extreme situation in the issue of balancing individual needs and environment to pursue psychological well-being. TRIAL REGISTRATION: ISRCTN14389453 (29 June 2017).

Giant oscillating thermopower at oxide interfaces.

Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10(4)-10(5) µVK(-1), oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface.

Theoretical and experimental investigation of magnetotransport in iron chalcogenides.

We explore the electronic, transport and thermoelectric properties of Fe1+y Se x Te1-x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects.