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We study the existence of positive ground state solutions for the following class of $(p,q)$ -Laplacian coupled systems $$\begin{eqnarray}\left\{\begin{array}{@{}lr@{}}-\unicode[STIX]{x1D6E5}_{p}u+a(x)|u|^{p-2}u=f(u)+\unicode[STIX]{x1D6FC}\unicode[STIX]{x1D706}(x)|u|^{\unicode[STIX]{x1D6FC}-2}u|v|^{\unicode[STIX]{x1D6FD}}, & x\in \mathbb{R}^{N},\\ -\unicode[STIX]{x1D6E5}_{q}v+b(x)|v|^{q-2}v=g(v)+\unicode[STIX]{x1D6FD}\unicode[STIX]{x1D706}(x)|v|^{\unicode[STIX]{x1D6FD}-2}v|u|^{\unicode[STIX]{x1D6FC}}, & x\in \mathbb{R}^{N},\end{array}\right.\end{eqnarray}$$ where $1. Here the coefficient $\unicode[STIX]{x1D706}(x)$ of the coupling term is related to the potentials by the condition $|\unicode[STIX]{x1D706}(x)|\leq \unicode[STIX]{x1D6FF}a(x)^{\unicode[STIX]{x1D6FC}/p}b(x)^{\unicode[STIX]{x1D6FD}/q}$ , where $\unicode[STIX]{x1D6FF}\in (0,1)$ and $\unicode[STIX]{x1D6FC}/p+\unicode[STIX]{x1D6FD}/q=1$. Using a variational approach based on minimization over the Nehari manifold, we establish the existence of positive ground state solutions for a large class of nonlinear terms and potentials. [ABSTRACT FROM AUTHOR]

In this work, we are concerned with the existence and nonexistence of ground state solutions for the following class of quasilinear Schrödinger coupled systems taking into account periodic or asymptotically periodic potentials. The nonlinear terms are superlinear at infinity and at the origin. By using a change of variable, we turn the quasilinear system into a nonlinear system where we can establish a variational approach with a fine analysis on the Nehari method. For the nonexistence result, we compare the potentials with periodic potentials proving the nonexistence of ground state solutions. [ABSTRACT FROM AUTHOR]

In this paper, we study the existence of positive solutions for the following class of nonlocal linearly coupled systems involving Schrödinger equations where denotes the fractional Laplacian, and. The coupling function is a bounded and continuous function which is related with the potentials by , for some. We deal with periodic and asymptotically periodic bounded potentials and. On the nonlinear terms and , we assume 'superlinear' at infinity and at the origin. Employing a variational approach, we obtain existence of bound and ground states solutions without assuming the well-known Ambrosetti–Rabinowitz condition on the nonlinear terms. Furthermore, we give a description of the ground states when the coupling function goes to zero in the norm. [ABSTRACT FROM AUTHOR]

In this study, photopyroelectric spectroscopy (PPES) was used to obtain thermal and optical properties of CdTe thin films in the 300–1200 nm wavelength range. The samples studied were grown on glass or BaF2 substrates using the hot wall epitaxy technique with varying thicknesses. The normalized photopyroelectric signal intensity and its phase were independently measured as a function of wavelength λ and chopping frequency f. Equations of both the intensity and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the pyroelectric detector, were used to fit the experimental results. From the fittings, we have obtained the values of thermal diffusivity coefficient α, thermal conductivity k, optical absorption coefficient, and the optical gap of CdTe. [ABSTRACT FROM AUTHOR]

Photothermal spectroscopies, photopyroelectric spectroscopy and photoacoustic spectroscopy (PAS), were used to study the thermal and optical properties of untreated and N+ ion implanted polyetheretherketone (PEEK) films. The photopyroelectric (PPE) intensity signal and its phase were independently measured as a function of wavelength and chopping frequency in the saturation part of the PPE spectrum. Equations for both the intensity and the phase of the PPE signal were used to fit the experimental results. From these fits we obtained the thermal diffusivity coefficient, the thermal conductivity, and the specific heat of the samples, as well as a value for the condensed phase optical gap. Additionally, using PAS we carried out a quantitative depth profile analysis of the optical properties of the ion implanted PEEK films. Since the thermal diffusion length varies inversely with the square root of chopping modulation frequency, at high chopping frequencies surface information is obtained. At low chopping frequencies information concerning the properties of the bulk is obtained. The overall objectives of this study are to understand and quantify how ion implantation affects the thermal and optical properties of the polymer, particularly within the implant region. We find that significant changes do occur, and our results have implications for the use of ion implantation to create plastic electronic and sensor devices. [ABSTRACT FROM AUTHOR]

In this paper, we prove the existence of positive ground state solutions to the following class of coupled systems involving nonlinear Schrödinger equations where the nonlinearities and have exponential critical growth of the Trudinger-Moser type. Moreover, the coupling term satisfies . We use the minimization technique over the Nehari manifold and strong maximum principle to get a positive ground state solution. [ABSTRACT FROM AUTHOR]

In this work, we studied the optical absorption spectral differences between doped and slightly doped polyaniline films and a derivative by photopyroelectric and photoacoustic spectroscopies. There exist great spectral differences between doped and slightly doped samples as shown by conventional optical absorption spectroscopy, but not greatly evidenced by photopyroelectric spectroscopy. The latter was applied to obtain thermal parameters such as thermal diffusivity and thermal conductivity, and as a result it showed that these thermal properties of polyaniline films are very similar for doped and slightly doped samples. Also it showed that for thicker films (about 20 μm), there are no significant optical absorption differences between them. However, for thin films both techniques showed greater optical absorption differences for doped and slightly doped samples, mainly detected by photoacoustic spectroscopy. These behaviors are in accordance with published results which is the granular metal model for polyaniline. This model explains the polyaniline polymeric matrix as formed by conductive islands in the insulating bulk material. [ABSTRACT FROM AUTHOR]

In this study, we carried out a quantitative depth profile analysis of the optical properties of slightly and strongly doped polyaniline (PANI) films, using both photoacoustic and photopyroelectric spectroscopies. As the thermal diffusion length varies inversely to chopper modulation frequency, then at high chopping frequencies information about the sample near the surface is obtained, while at low chopping frequencies the data come from deeper within the sample. The objective of this study is to analyze how the polyaniline doping process in acidic media occurs in the polymeric chain using the photothermal techniques. The results showed that polymeric chains of the doped samples are composed of undoped regions, while polymeric chains of slightly doped samples present doped regions to a lesser degree. These conclusions are in accordance with published results in which doped PANI films exhibit a granular conductive regions in a quasi undoped matrix. In addition, the photothermal spectra showed that the doping process of PANI, in which films are dipped in hydrochloric acid solution, is more effective in the external surface of the films. [ABSTRACT FROM AUTHOR]

Photopyroelectric spectroscopy (PPE) was used to study the thermal and optical properties of melanins. The photopyroelectric intensity signal and its phase were independently measured as a function of wavelength and chopping frequency for a given wavelength in the saturation part of the PPE spectrum. Equations for both the intensity and the phase of the PPE signal were used to fit the experimental results. From these fits we obtained for the first time, with great accuracy, the thermal diffusivity coefficient, the thermal conductivity, and the specific heat of the samples, as well as a value for the condensed phase optical gap, which we found to be 1.70 eV. [ABSTRACT FROM AUTHOR]

Photothermal spectroscopies, photopyroelectric and photoacoustic, were used to obtain physical parameters of polyaniline -- emeraldine base (PANI-EB) and poly(o-methoxyaniline) -- emeraldine base (POMA-EB), such as thermic parameters like thermal diffusivity, thermal conductivity, and specific heat. These studies were done for PANI-EB and POMA-EB films in the 400 < λ < 900 nm wavelength range. The photopyroelectric intensity V[SUBn](f) and the phase F[SUBn](f) (f being the chopping frequency) for a given λ of the saturation part of the PPES spectrum signal were independently measured, as well as the intensity V[SUBn](λ) and its phase F[SUBn](λ). Equations of both the intensity and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the PANI and POMA films and the pyroelectric detector, were used to fit the experimental results. It was observed that, in contrast with the strong doping dependence of the electrical conductivity, the thermal parameters of PANI films remained practically unchanged under doping. This apparent discrepancy is explained by the granular metal model of doped PANI. [ABSTRACT FROM AUTHOR]

Physical exercise increases serum glucocorticoids, which is believed to be involved in the fall of T3 after high intensity exercise. The objective was to evaluate whether a physical exercise session alters the thyroid economy and adrenal axis in humans, and the possible role of corticosteroids in thyroid function disturbance. Active but not athlete subjects were enrolled in an open field competition and cortisol, TSH, T3, and T4 were measured before and after the race. To give new insights into the mechanisms underlying the changes in thyroid economy after exercise, we used a rat model to evaluate the impact of blocking corticosterone synthesis during treadmill exercise by metyrapone administration. Cortisol levels increased 1.5-fold (from 28.2 ± 3.8 to 42.2 ± 2.2 μg/dl; p < 0.05), while serum T3 decreased by 13 % (from 115 ± 5 to 99 ± 5 μg/dl; p < 0.05) 6 h after the race in humans. Also, in rats, glucocorticoid increased by 2-fold while T3 decreased 15 % after exercise session (p < 0.05). However, the complete blockage of corticosterone peak did not impair serum T3 decrease observed in rats submitted to exercise. Interestingly, the lack of corticosterone peak led not only to lower serum T3, but also to decreased serum T4, indicating that corticosterone might be fundamental for the maintenance of serum thyroid hormone levels after high intensity exercise. Although cortisol increases and T3 decreases after high intensity exercise in both humans and rats, it does not seem to be a cause-effect response since pharmacological blockage of corticosterone peak does not modulate T3 response. [ABSTRACT FROM AUTHOR]