Intrinsic Time‐Tunable Emissions in Core–Shell Upconverting Nanoparticle Systems

Color‐tunable luminescence has been extensively investigated in upconverting nanoparticles for diverse applications, each exploiting emissions in different spectral regions. Manipulation of the emission wavelength is accomplished by varying the composition of the luminescent material or the characteristics of the excitation source. Herein, we propose core–shell β‐NaGdF₄: Tm³⁺, Yb³⁺/β‐NaGdF₄: Tb³⁺ nanoparticles as intrinsic time‐tunable luminescent materials. The time dependency of the emission wavelength only depends on the different decay time of the two emitters, without additional variation of the dopant concentration or pumping source. The time‐tunable emission was recorded with a commercially available camera. The dynamics of the emissions is thoroughly investigated, and we established that the energy transfer from the ¹D₂ excited state of Tm³⁺ ions to the higher energy excited states of Tb³⁺ ions to be the principal mechanism to the population of the ⁵D₄ level for the Tb³⁺ ions.     

Pressure-broadened atomic Li(2s-2p) line perturbed by ground neon atoms in the spectral wings and core

Full quantum calculations are performed to investigate the broadening profiles of the atomic lithium Li(2s-2p) resonance line induced by interactions with ground Ne(2s~22p~6) perturbers in the spectral wings and core. The X~2Σ~+, A~2Π,and B~2Σ~+ potential-energy curves of the two first low lying Li Ne molecular states, as well as the corresponding transition dipole moments, are determined with ab initio methods based on the SA-CASSCF-MRCI calculations. The emission and absorption coefficients in the wavelength range 550-800 nm and the line-core width and shift are investigated theoretically for temperatures ranging from 130 K to 3000 K. Their temperature dependence is analyzed, and the obtained results are compared with the previous experimental measurements and theoretical works.     

Polymer electrolyte liquid crystal mixtures as phase-dependent thermoelectric materials

Organic thermoelectric materials have gained a trajectory in recent years given its advantages of processability, low cost and flexibility. In this paper, polymer electrolyte liquid crystal (PELC) mixtures composed of polyvinyl alcohol, potassium iodide, and 4-Cyano-4'-pentylbiphenyl (5CB) liquid crystal are fabricated, the 5CB acts as a ‘temperature switch’, i.e., a strong correlation between the thermoelectric properties and the transition from Ne-Iso transition of the 5CB, is observed. The electrical conductivity and Seebeck coefficient of the PELC mixtures both decrease above the Ne-Iso transition temperature. This thermoelectric behavior is discussed in terms of the carrier concentration, carrier mobility, and order-disorder transition.     

Description of Even–Even 114–134Xe Isotopes in the Transitional Region of IBM

Properties of ^114–134Xe isotopes are studied in the U(5)?SO(6) transitional region of Interacting Boson Model (IBM-1). The energy levels and B(E2) transition rates are calculated via the affine SU(1,1) Lie Algebra. The agreement with the most recent experimental is acceptable. The evaluated Hamiltonian control parameters suggest a spherical to γ-soft shape transition and propose the ¹³⁰Xe nucleus as the best candidate for the E(5) symmetry.     

Wave mode diffusion and propagation in structural wave guide under Varying Temperature

A numerical approach is presented to study the guided wave propagation through periodic specimen with thermal dependence of material properties. There is a great interest in extending the skills of the wave finite element (WFE) method to figure out the variations in the wave propagation properties due to temperature fluctuations. Thermal effects on the dispersion curves thereby on group velocity are discussed. Comparisons between numerical results and analytical developments for various temperatures are given to prove the effectiveness of the proposed approach to predict the sensitivity of guided wave propagation characteristics in presence of temperature variations.     

Existence and Multiplicity of Solutions for Fractional Elliptic Problems with Discontinuous Nonlinearities

We consider the following fractional elliptic problem:

$$\begin{aligned} (P)\left\{ \begin{array}{ll} (-\Delta )^s u = f(u) H(u-\mu )&{} \quad \text{ in } \ \Omega ,\\ u =0 &{}\quad \text{ on } \ \mathbb{{R}}^n {\setminus } \Omega , \end{array} \right. \end{aligned}$$

where \((-\Delta )^s, s\in (0,1)\) is the fractional Laplacian, \(\Omega \) is a bounded domain of \(\mathbb{{R}}^n,(n\ge 2s)\) with smooth boundary \(\partial \Omega ,\) H is the Heaviside step function, f is a given function and \(\mu \) is a positive real parameter. The problem (P) can be considered as simplified version of some models arising in different contexts. We employ variational techniques to study the existence and multiplicity of positive solutions of problem (P).

     

On the constitutive relations for second sound in elastic solids

We give a derivation of the constitutive relations of an elastic heat conductor for which the heat flux and the temperature obey a frame-invariant form of Cattaneo's equation.     

Conformations of monoacyl and 1,3-diacylbenzimidazoline-2-thiones and dihydrobenzimidazoles

The endo confrontation of monoacyl and 1,3-diacylbenzimidazoline-2-thiones is predominant at ambient temperatures. Nmr temperature-dependent studies suggest that this is also true over a wide range of temperatures. In agreement with previous results (6) the exo-endo conformation in 1,3-diacyl-1,2-dihydrobenzimidazoles is generally the predominant one.     

Reaction of acetylenic ketones with hydrazine derivatives. Synthesis of hydroxypyrazoles

Aroylphenylacetylenes Ia-c react with (-butyl hydrazinecarboxylate (IIa) and 2-furylhydrazide (IIb) to give the corresponding hydroxydihydropyrazole derivatives IVa-f. This cyclic structure is supported by chemical transformations. Thus, when compounds IVa-c are heated with acetic anhydride, they yield the corresponding 5-aryl-1-(t-butoxycarbonyl)-3-phenylpyrazoles Va-c which, upon hydrolysis with methanolic potassium hydroxide, produce the corresponding 5(3)aryl-3(5)phenylpyrazoles VI. Spectroscopic data also confirm the suggested cyclic structure IV.