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This article aims to question how the process of political professionalization in multi-level states could change political careers patterns. We show that the changing opportunity structure produce...

Made available in DSpace on 2022-05-01T16:02:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Background: The aim of this study was to investigate the effects of gradient and speed on running variability (RV) and local dynamic stability (LDS) during uphill running. Hypotheses: (1) Both gradient and speed increase metabolic effort, in terms of heart rate (HR) and perceived exertion (CR10), in line with the contemporary literature, and (2) gradient increases RV and impairs LDS. Study design: “Crossover” observational design. Level of Evidence: Level 3. Methods: A total of 25 runners completed 10-minute running trials in 3 different conditions and in a randomized order: gradient at 0% (0CON), 2% (2CON), and 2% at isoefficiency speed (2IES). 0CON and 2CON speeds were calculated as the “best 10-km race performance” minus 1 km·h−1, whereas 2IES speed was adjusted to induce the same metabolic expenditure as 0CON. HR and perceived exertion as well as running kinematic variables were collected across all trials and conditions. Running variability was calculated as the standard deviation of the mean stride-to-stride intervals over 100 strides, while LDS was expressed by the Lyapunov exponent (LyE) determined on running cycle time over different running conditions. Results: Increases in HR and CR10 were observed between 0CON and 2CON (P < 0.001) and between 2IES and 2CON (P < 0.01). Higher RV was found in 2CON compared with 0CON and 2IES (both P < 0.001). Finally, the largest LyE was observed in 2IES compared with 0CON and 2CON (P = 0.02 and P = 0.01, respectively). Conclusion: Whereas RV seems to be dependent more on metabolic effort, LDS is affected by gradient to a greater extent. Clinical Relevance: Running variability could be used to monitor external training load in marathon runners. Department of Biomedical Sciences for Health Università degli Studi di Milano, Milan The Academic College at Wingate Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education São Paulo State University (UNESP) Department of Physics “E. Pancini ” University of Naples “Federico II,” CNR-SPIN Institute School of Exercise and Sport Science Department of Neurosciences Biomedicine and Movement Sciences University of Verona School of Health and Life Sciences University of the West of Scotland Human Movement Research Laboratory (MOVI-LAB) Department of Physical Education São Paulo State University (UNESP)

Interfacial inversion symmetry breaking gives rise to electronic properties that differ substantially from those of the bulk constituent materials. Here, we report on the realization of an artificial ferromagnetic quasi-two-dimensional electron gas (q2DEG) at the (111) interfaces between LaAlO3, EuTiO3, and SrTiO3characterized by a reconstruction of the bulk quasioctahedral crystal field into a trigonal one. The q2DEG is created through a transfer of electrons to the EuTiO3layers at the interface with LaAlO3, extending into the first layers of SrTiO3, as shown by an electron-energy-loss spectroscopy map of the titanium valence with atomic column resolution. Interestingly, polarized X-ray absorption spectroscopy shows that the Eu-4f and the Ti-3d magnetic moments order ferromagnetically and exhibit the same magnetic field dependence at low temperature. In addition, the q2DEG presents a sizable in-plane orbital moment even at low magnetic field (0.1 T) possibly related to Ti-3d electrons occupying bands with the main a1gorbital character. The results show an intriguing interplay between ferromagnetism, spin-orbit coupling, and trigonal crystal field splitting in the (111) LaAlO3/EuTiO3/SrTiO3q2DEG.

Despite its simple structure and low degree of electronic correlation, SrTiO_{3} (STO) features collective phenomena linked to charge transport and, ultimately, superconductivity, that are not yet fully explained. Thus, a better insight into the nature of the quasiparticles shaping the electronic and conduction properties of STO is needed. We studied the low-energy excitations of bulk STO and of the LaAlO_{3}/SrTiO_{3} two-dimensional electron gas (2DEG) by Ti L_{3} edge resonant inelastic x-ray scattering. In all samples, we find the hallmark of polarons in the form of intense dd+phonon excitations, and a decrease of the LO3-mode electron-phonon coupling when going from insulating to highly conducting STO single crystals and heterostructures. Both results are attributed to the dynamic screening of the large polaron self-induced polarization, showing that the low-temperature physics of STO and STO-based 2DEGs is dominated by large polaron quasiparticles.

The rhythmic control of the lower limb muscles influences the cycle-to-cycle variability during a walking task. The benefits of insoles, commonly used to improve the walking gait, have been little studied. Therefore, the aim of this study was to assess the walking gait variability and stability on different walking conditions (without shoes, WTS, with shoes, WS, with shoes and insoles, WSI) related to brain activity. Twelve participants randomly (WTS/WS/WSI) walked on a treadmill at 4 km/h for 10 min. Kinematic analysis (i.e., footstep and gait variability), brain activation (beta wave signal), rating of perceived exertion (RPE, CR-10 scale), and time domain measures of walking variability were assessed. The maximum Lyapunov exponent (LyE) on the stride cycle period&rsquo, s datasets was also calculated. Stride length and cycle calculated for all walking conditions were 61.59 &plusmn, 2.53/63.38 &plusmn, 1.43/64.09 &plusmn, 2.40 cm and 1.11 &plusmn, 0.03/1.14 &plusmn, 0.03/1.15 &plusmn, 0.04 s (F1,10 = 4.941/p = 0.01, F1,10 = 4.938/p = 0.012) for WTS, WS, WSI, respectively. Beta wave (F1,10 = 564.201/p = 0.0001) was higher in WTS compared to WS and WSI. Analysis of variance&rsquo, s (ANOVA) LyE showed a F1,10 = 3.209/p = 0.056, while post hoc analysis showed a significant effect between WS and WSI with p = 0.023, and nonsignificant effects between WTS and WS/WSI (p = 0.070/0.607), respectively. Small perturbations of the foot can influence the control of gait rhythmicity by increasing the variability in a dissipative deterministic regimen.

In this work, a method of obtaining graphene layers from natural source specifically from rice husk was developed. A rice husk (RH) was used as a raw material, and potassium hydroxide was used as activation agent. The graphene layers were obtained after four successive stages: pre-carbonization, desilication in 1M NaOH solution, chemical activation and exfoliation of the carbonized rice husk (CRH). The obtained samples were studied using Raman spectroscopy, TEM and SEM; the Raman peaks evidenced the presence of graphene multilayers in the sample. A detailed observation of Raman spectroscopy showed that the obtained samples with ratio of 1/4 and 1/5 (RH/KOH) consisted of graphene layers with a high content of amorphous component. The yield of the product was ~ 3% by weight. This study can provide a new way to the large-scale synthesis of low-cost single and multi-layered graphene using rice husk or other renewable resources.

The recent development of eumelanin pigment-based blends integrating “classical” organic conducting materials is expanding the scope of eumelanin in bioelectronics. Beyond the achievement of high conductivity level, another major goal lays in the knowledge and feasible control of structure/properties relationship. We systematically investigated different hybrid materials prepared by in situ polymerization of the eumelanin precursor 5,6-dihydroxyindole (DHI) in presence of various amounts of graphene-like layers. Spectroscopic studies performed by solid state nuclear magnetic resonance (ss-NMR), x-ray photoemission, and absorption spectroscopies gave a strong indication of the direct impact that the integration of graphene-like layers into the nascent polymerized DHI-based eumelanin has on the structural organization of the pigment itself, while infrared, and photoemission spectroscopies indicated the occurrence of negligible changes as concerns the chemical units. A tighter packing of the constituent units could represent a strong factor responsible for the observed improved electrical conductivity of the hybrid materials, and could be possible exploited as a tool for electrical conductivity tuning.

The discovery of 2D conductivity at the LaAlO3/SrTiO3 interface has been linking, for over a decade, two of the major current research fields in materials science: correlated transition-metal-oxide systems and low-dimensional systems. Notably, despite the 2D nature of the interfacial electron gas, the samples are 3D objects with thickness in the mm range. This prevented researchers so far from adopting strategies that are only viable for fully 2D materials, or from effectively exploiting degrees of freedom related to strain, strain gradient and curvature. Here a method based on pure strain engineering for obtaining freestanding LaAlO3/SrTiO3 membranes with micrometer lateral dimensions is demonstrated. Detailed transmission electron microscopy investigations show that the membranes are fully epitaxial and that their curvature results in a huge strain gradient, each layer showing a mixed compressive/tensile strain state. Electronic devices are fabricated by realizing ad hoc circuits for individual micro-membranes transferred on silicon chips. The samples exhibit metallic conductivity and electrostatic field effect like 2D-electron systems in bulk heterostructures. The results open a new path for adding oxide functionalities into semiconductor electronics, potentially allowing for ultra-low voltage gating of a superconducting transistors, micromechanical control of the 2D electron gas mediated by ferroelectricity and flexoelectricity, and on-chip straintronics.

This article reports a new way to prepare expanded graphite using a thermal method. Natural graphite was added to crystalline hydrate of metals with mechanical stirring at room temperature, taken in the number of 20-80% of the mass of mix. This was then placed in muffle furnace. All process of activation takes from 10 to 20 minutes. X-ray diffraction patterns were used to analyze the structure and confirm that expanded graphite had indeed been prepared. A scanning electron microscope was utilized to observe the morphologies of the expandable graphite and expanded graphite.

Graphene-like (GL) layers were prepared through a two steps oxidation/reduction method starting from a high surface carbon black, and pH of the GL layers in water suspension was varied. The effect of pH of such suspension on the morphology of self-assembled GL films has been studied. Zeta potentials of the water suspensions were measured to estimate the stability of the suspension at several pH values and to select the samples for deeper investigation by atomic force microscopy (AFM). AFM measurements on four different samples are then described and discussed. The reported results show how the surface roughness and morphology are affected by the pH in the preparation process: in particular, the lowest pH sample exhibits a granular surface, while at higher pH more regular morphologies are produced, with interesting observations as concerns the thickness of some surface features. The observations are interpreted in terms of the forces acting in water suspension and of the role of hydrophobic or hydrophilic behaviors. The results demonstrate the possibility to tune the surface properties of GL films by simply acting on the pH of the suspension during the fabrication, and help to understand the microscopic physical mechanisms involved in the film assembly. (C) 2015 Elsevier B.V. All rights reserved.

Metal-organic framework (MOF) incorporating conductive graphene-like layers were synthesized and characterized. The selected MOF, HKUST-1, combines high surface area, water stability, simple preparation and low costs. Graphene-like layers incorporated into the MOF structure were obtained by a two-step oxidation/reduction wet treatment of a high surface carbon black. MOF composites were produced at different carbonaceous layers content. It was shown, through a wide characterization of the samples, that the composites preserve the main features of the parent MOF, additional exhibiting a tunable electrical conductivity. © 2014 Elsevier B.V. All rights reserved.

Organic electronics is a promising field for investigating a series of materials offering relevant advantages with respect to traditional electronics as the possibility to create bendable circuits compatible with human biology. Graphene for its electrical properties (and abundance) represents the desirable compound to trigger a strong development of bioelectronics although its properties are strongly affected by topology, defects and external contamination [1]. This problem can affect the reproducibility and yield of the production of bioelectronics devices. The issue can be circumvented by the use of graphene-like (GL) layers, a graphene related materials (GRM) which are composed of stacks of few graphene layers [2] having micrometer size on average. The loss of the pure two dimensional conduction is compensated by a lower reactivity with a higher versatility due to the initial stable liquid phase of the GL suspensions[2,3]. In the THz region, graphene and GL compounds have attracted much interest as promising candidates for photosensitive and optoelectronic devices. At very high frequencies, however, transport and quantum efficiency in multi-layer graphene structures can be strongly influenced by particle size and stacking configuration. In this contribution we present THz time-domain spectroscopy of GL and GL hybrids obtained by drop casting on silicon dioxide substrates. We provide the electrodynamic characterization of both pure and eumelanin-GL hybrids [4], which are valuable materials for the next generation of bio-devices.

Reduction of strongly oxidized carbon black by hydrazine hydrate yields water-insoluble graphene-like sheets that undergo to self-assembling in thin film on surfaces after drying. The height of a drop-casted graphene-like film was determined by atomic force microscopy (AFM) to be around 20 nm, corresponding to approximately 25 graphene-like layers. The oxidized carbon black and the corresponding reduced form were carefully characterized.

Organic (bio)electronics appears to be the first target for competitive exploitation in the materials science of eumelanins, black insoluble photoprotective human biopolymers. Nonetheless, the low conductivity of these pigments is limiting the implementation of eumelanin-based devices. Here we present a novel organic/organic hybrid material (EUGL) by integration of conductive graphene-like (GL) layers within the EUmelanin pigment (EU). GL layers were obtained by a two-step oxidation/reduction of carbon black. The stability of GL layers over a wide pH range and the self-assembling tendency place this material in a leading position for the fabrication of hybrid materials in aqueous media. EUGL was obtained by inducing the polymerization of eumelanin precursors (5,6-dihydroxyindole, DHI and 5,6-dihydroxyindole-2 carboxylic acid, DHICA) in aqueous media containing GL layers. The new material featured promising biocompatibility and an increased conductivity with respect to eumelanin by four orders of magnitude.

Graphene-like (GL) layers and eumelanin-based graphene-like (EUGL) hybrids have been investigated through THz time domain spectroscopy. The interest in these materials lies on their peculiar chemical-physical properties: the former are conductive water stable materials, whereas the latter are biocompatible materials with good conductive and adhesive properties. Both exhibit promising optoelectronic and bioelectronic applications. We measured mixtures of GL layers or EUGL hybrids with KBr, shaped in pellets with uniform thickness, in order to circumvent problems related to sample inhomogeneity and roughness. A mean field theory was applied to extract direct information on permittivity and conductivity. Data have been carefully fitted through the Drude-Smith theory, confirming the conductive nature of the hybrid materials. The results show that EUGL hybrid-based devices can be promising for the next generation of printable bio-circuits.

Graphene-like layers, synthesized through a two-step oxidation/reduction wet treatment of a high surface carbon black, have been used to prepare composites with TiO2 nanoparticles by liquid phase deposition, followed by calcination at 200 °C. The photocatalytic activity of the TiO2/graphene-like composites has been tested for the selective conversion of 3-pyridine methanol to 3-pyridine carboxyaldehyde and nicotinic acid (vitamin B3), under de-aerated and UV/solar simulated conditions, in the presence of cupric ions. Two different composite morphologies have been explored and a dependence of the photocatalytic activity has been assessed. An enhanced photocatalytic activity, with respect to the neat TiO2, has been observed and attributed to the broader variety of stable free-radical species generated, at a given photo-catalyst morphology, within the delocalized π-electron systems.

Variability of cycle-to-cycle duration during a pedaling task is probably related to the rhythmic control of the lower limb muscles as in gait. Although walking variability has been extensively studied for its clinical and physiological implications, pedaling variability has received little attention. The present contribution determines the variability of the cycling time during a 10-min exercise as a function of upper body position. Nine healthy males were required to pedal on cycle-ergometer at a self-selected speed for 10 min in two different upper body positions [hands on upper handlebars (UP) or lower handlebars (DP)]. Time domain measures of cycling variability [total standard deviation (SDtot), mean standard deviation cycle-to-cycle intervals over 100 cycles (SD100), standard deviation of the average cycle-to-cycle intervals over 100 cycles (SDA100)] were measured. Moreover, the same time domain measures were also calculated for heart rate in order to discriminate possible involvements of autonomic regulation. Finally, the structure of the cycle variations has been analyzed in the framework of deterministic chaos calculating the maximum Lyapunov exponents. Significant increases in cycle-to-cycle variability were found for SDtot, SD100 in DP compared to UP, whereas cardiac parameters and other cycling parameters were not changed in the two positions. Moreover, the maximum Lyapunov exponent was significantly more negative in DP. The results suggest that small perturbations of upper body position can influence the control of cycling rhythmicity by increasing the variability in a dissipative deterministic regimen.

Neutron irradiation was performed on MgB2 thin films grown by hybrid physical chemical vapor deposition. Samples irradiated with different neutron fluences, having different critical temperatures, were studied by scanning tunneling spectroscopy in order to investigate the effect of the introduced disorder on the superconducting and spectroscopic properties. A monotonic increase of the pi gap with increasing disorder was found. (c) 2007 Elsevier B.V. All rights reserved.

The importance of fluid mechanics is often underrated. Besides studying the mechanisms governing static and dynamic fluids, this discipline could have a great role in the understanding of many principles, topics and concepts of general mechanics. When approached in a proper way, fluid mechanics provides numerous 'case studies' apt to clarify the physical content of several mechanical laws. Unfortunately, fluid mechanics, in physics classes, is generally viewed as a 'lower branch' of mechanics. Its rules and laws too often are regarded as too particular, or even as special cases, to deserve the same attention paid to other arguments. The help that fluid mechanics could return in the learning process can be proved by some easy considerations. In this frame, the so-called hydrostatic paradoxes could provide a tremendous contribution to the learning processes.

We developed a new approach for producing graphene-like (GL) materials through a two-steps oxidation/reduction method starting from a nanostructured (high surface) carbon black, a versatile carbonaceous material prone to be structurally and chemically modified in quite mild wet conditions. Atomic Force Microscopy and zetapotential measurements allowed to model the assembling mechanisms and the role of hydrophobic interactions, demonstrating the possibility to easily tune the surface morphology. GL materials have been then employed in a large variety of hybrid materials for innovative applications, and characterized by chemical, electrical, structural and spectroscopic techniques. With Metal-Organic Frameworks, GL produced conducting composites with electrical conductivity tunable by changing the concentration of the parent materials; Eumelanin/GL and TiO2-nanoparticles/GL were also studied for photocatalysis and biosensors applications.