Postural destabilization induced by trunk extensor muscles fatigue is suppressed by use of a plantar pressure-based electro-tactile biofeedback

Separate studies have reported that postural control during quiet standing could be (1) impaired with muscle fatigue localized at the lower back, and (2) improved through the use of plantar pressure-based electro-tactile biofeedback, under normal neuromuscular state. The aim of this experiment was to investigate whether this biofeedback could reduce postural destabilization induced by trunk extensor muscles. Ten healthy adults were asked to stand as immobile as possible in four experimental conditions: (1) no fatigue/no biofeedback, (2) no fatigue/biofeedback, (3) fatigue/no biofeedback and (4) fatigue/biofeedback. Muscular fatigue was achieved by performing trunk repetitive extensions until maximal exhaustion. The underlying principle of the biofeedback consisted of providing supplementary information related to foot sole pressure distribution through electro-tactile stimulation of the tongue. Centre of foot pressure (CoP) displacements were recorded using a force platform. Results showed (1) increased CoP displacements along the antero-posterior axis in the fatigue than no fatigue condition in the absence of biofeedback and (2) no significant difference between the no fatigue and fatigue conditions in the presence of biofeedback. This suggests that subjects were able to efficiently integrate an artificial plantar pressure information delivered through electro-tactile stimulation of the tongue that allowed them to suppress the destabilizing effect induced by trunk extensor muscles fatigue

An evaluation of the impact of industrial restructuring on individual human capital accumulation in France (1956-1993)

This article evaluates the effect of French industrial restructuring during 1956-1993, on individual human capital accumulation. We use data from the French Training and Occupational Skills survey and the Population Census (INSEE). We estimate a human capital production function using two econometric strategies (controlling for covariates; instrumental variables). We show that industrial restructuring has a negative impact on individual human capital accumulation for the children of blue-collar workers

Optimizing the Use of an Artificial Tongue-Placed Tactile Biofeedback for Improving Ankle Joint Position Sense in Humans

The performance of an artificial tongue-placed tactile biofeedback device for improving ankle joint position sense was assessed in 12 young healthy adults using an active matching task. The underlying principle of this system consists of supplying individuals with supplementary information about the position of the matching ankle relative to the reference ankle position through a tongue-placed tactile output device generating electrotactile stimulation on a 36-point (6 X 6) matrix held against the surface of the tongue dorsum. Precisely, (1) no electrodes were activated when both ankles were in a similar angular position within a predetermined "angular dead zone" (ADZ); (2) 12 electrodes (2 X 6) of the anterior and posterior zones of the matrix were activated (corresponding to the stimulation of the front and rear portion of the tongue) when the matching ankle was in a too plantarflexed and dorsiflexed position relative to the reference ankle, respectively. Two ADZ values of 0.5 degrees and 1.5 degrees were evaluated. Results showed (1) more accurate and more consistent matching performances with than without biofeedback and (2) more accurate and more consistent ankle joint matching performances when using the biofeedback device with the smaller ADZ valu

Neutrino spin oscillation in screening models revisited

We study, using the Mathisson-Papapetrou-Dixon equations, the spin oscillation of neutrinos when the latter are coupled to the scalar field of screening models of dark energy. First, we derive the transition probability formula for a left-handed neutrino to become a right-handed neutrino within a general static and spherically symmetric metric. We then apply our general formula to neutrinos deflected around a central mass described by the Schwarzschild metric. Our results show that, contrary to what one might expect, the scalar field of chameleon-like and symmetron-like screening models would not show any effect on the spin oscillations of neutrinos. The origin of such an outcome is discussed.Comment: 9 pages. Matches the published versio

Revisiting the Schr\"odinger-Dirac equation

In flat spacetime, the Dirac equation is the "square root" of the Klein-Gordon equation in the sense that by applying the square of the Dirac operator to the Dirac spinor, one recovers the Klein-Gordon equation duplicated for each component of the spinor. In the presence of gravity, applying the square of the curved-spacetime Dirac operator to the Dirac spinor does not yield the curved-spacetime Klein-Gordon equation, but yields, instead, the Schr\"odinger-Dirac covariant equation. First, we show that the latter equation gives rise to a generalization to spinors of the covariant Gross-Pitaevskii equation. Next, we show that while the Schr\"odinger-Dirac equation is not conformally invariant, there exists a generalization of the equation that is conformally invariant but which requires a different conformal transformation of the spinor than the one required by the Dirac equation. The new conformal factor acquired by the spinor is found to be a matrix-valued factor obeying a differential equation that involves the Fock-Ivanenko line element. The Schr\"odinger-Dirac equation coupled to the Maxwell field is then revisited and generalized to particles with higher electric and magnetic moments while respecting gauge symmetry. Finally, Lichnerowicz's vanishing theorem in the conformal frame is also discussed.Comment: 23 pages, no figures. An Addendum is included at the end of the article, and 3 additional references inserte

Neutrino flavor oscillations inside matter in conformal coupling models

We recently studied neutrinos flavor oscillations in vacuum within conformal coupling models. In this paper, we extend that analysis by investigating neutrino flavor oscillations inside matter within a general conformal coupling scenario. We first derive the general formula for the flavor transition probability inside matter in arbitrary static and spherically symmetric spacetimes. The modified resonance formula of the MSW effect is derived and the corresponding adiabaticity parameter of the effect is extracted. An application of our results to the case of two-flavor neutrinos within the well-known chameleon and symmetron conformal coupling models is made.Comment: 12 pages. No figures. Accepted for publication in PRD. One reference added. Section II (summarizing the vacuum oscillations) in this article draws heavily from arXiv:2209.03899, where vacuum oscillations in screening models have been worked out in much more detai

How large do second-generation migrants and natives differ in terms of human capital accumulation and why? Empirical evidence for France

This paper analyses the differences in the determinants and patterns of the accumulation of human capital for second-generation immigrants relatively to natives for the French case. We use the Training and Occupational Skills survey to conduct our econometric analysis, where we distinguish the natives, the second-generation immigrants from ‘North Africa’, ‘Southern Europe’, ‘Northern and Western Europe’ and ‘Eastern Europe’ origins. We don’t observe striking differences in the determinants between the second-generation immigrants as a whole and the natives. Moreover, the ‘second-generation immigrants’ group is a heterogeneous one. The significant determinants as well as the magnitude of the impact of these determinants substantially differ between the natives and the two main considered origins. There seems to be a lower ‘determinism’ through parental education for the ‘Southern Europe’ and ‘Northern and Western Europe’ origins than for the ‘North Africa’ and Eastern Europe origins, but differences in intergenerational correlations of education could be explained by parental transmission of education and/or by selection effects of the migrants. The Blinder-Oaxaca decomposition shows that parental endowments in education account for a significant part of the mean education differences according to the origin while some others factors (individual characteristics) are also relevant to explain these differences. But we find evidence for significant differences in parental transmissions of education only for the ‘North Africa’-natives pair

How large second-generation migrants and natives differ in terms of human capital accumulation and why? Empirical evidence for France

This paper analyses the differences in the determinants of the accumulation of human capital for second-generation immigrants relatively to natives for the French case. We use the Training and Occupational Skills survey to conduct our econometric analysis, where we distinguish the natives, the second-generation immigrants from ‘North Africa’ and from ‘Southern Europe’ origins. We don’t observe striking differences in the determinants between the second-generation immigrants as a whole and the natives. Moreover, the ‘second-generation immigrants’ group is a heterogeneous one. The significant determinants as well as the magnitude of the impact of these determinants substantially differ between the natives and the two main considered origins. There seems to be a lower ‘determinism’ through parental education for ‘Southern Europe’ than ‘North Africa’ origin, but differences in intergenerational correlations of education could be explained by parental transmission of education and/or by selection effects of the migrants. The Blinder-Oaxaca decomposition shows that parental endowments in education account for a large part of the mean outcome differences, but transmissions of education (and other components) also seems to be some relevant to explain differences in accumulation of human capital of second-generation migrants vs natives or between migrants